Prediction of LSND effect as a sterile perturbation of the bimaximal texture for three acti

合集下载

有关经济地理实证方面的计量成就及欠缺

Rev World Econ(2011)147:567–592DOI10.1007/s10290-011-0092-zO R I G I N A L P A P E RThe empirics of economic geography:how to drawpolicy implications?Pierre-Philippe CombesPublished online:6March2011ÓKiel Institute2011Abstract Using both reduced-form and structural approaches,the spectrum of policy recommendations that can be drawn from empirical economic geography is pretty large.Reduced-form approaches allow the researchers to consider many variables that impact on regional disparities,as long as they are careful about interpretation and endogeneity issues.Structural approaches have the opposite advantages.Less issues can be simultaneously addressed,but one can be more precise in terms of which intuitions are considered and the underlying mechanisms and effects at work.Many regional policy issues remain unanswered,opening some interesting future lines of research.Keywords Agglomeration economiesÁRegional policyÁStructural estimationÁInstrumental variablesJEL Classiﬁcation R12ÁR23Paper prepared for the VII Annual Elsnit Conference hosted by the Kiel Institute for the World Economy,under the sponsorship and co-organisation of the Inter-American Development Bank(IDB), ments from Rolf Langhammer,Harmen Lehment,Elsnit conference participants and a referee were appreciated.The presentation of empirical approaches in economic geography and their limits(Sects.2.1and3.1)borrows some elements from Combes et al.Economic Geography,The Integration of regions and Nations,Princeton University Press,2008.Financial support from IDB and CNRS is gratefully acknowledged.bes(&)GREQAM-University of Aix-Marseille,Marseille,Francee-mail:ppcombes@univmed.frURL:http://www.vcharite.univ-mrs.fr/pp/combes/besInternational Trade and Regional Economics Programme,Centre for Economic Policy Research,London,United Kingdombes 1IntroductionIn their book,Fujita et al.(1999)called for the emergence of empirical contributions to assess the relevance of new economic geography models.Ten years later,quite a few papers have shown that such models are not rejected by the real data.Moreover,these papers emphasise the role of certain variables,such as the real market potential,that are extremely relevant empirically to explain regional development.Beyond such conclusions,we try here to assess the policy implications to be drawn from this empirical material,the limits to such exercises and the directions research could take to better enlighten the regional policy debate.We start in Sect.2by describing an empirical literature whose roots are older than new economic geography models,but which has beneﬁted from renewed interest with this emphasis on the need for empirical assessment of regional development models.Typically,this literature seeks to determine which character-istics of a region enhance its productivity or growth.We show that advances in econometric methods and the availability of individual data sets has allowed signiﬁcant progress in the precision and robustness of conclusions,and therefore on the policy implications that can be drawn.We then review in Sect.3the more structural empirical literature,sticking closely to new economic geography models, and we illustrate how it can be used to derive relevant policy implications.In both cases,we conclude that empirical studies speciﬁcally designed to deal with policy issues are still the exception and we propose possible lines of research in such a direction.2Reduced-form approaches and the optimal characteristics of regionsIn recent years,interest in the empirical evaluation of new economic geography models has in turn revived interest in the literature estimating the magnitude of agglomeration economies,which is older and with fairly different theoretical roots. To assess the empirical relevance of these reduced-form approaches,weﬁrst describe their theoretical background,deﬁne the empirical assumptions and how they are dealt with.Then we move to possible policy implications of the results obtained and to possible extensions that would enlarge the policy scope of such approaches.This concerns the existence of an optimal size,and more generally industrial composition,of regions,the links between trade and regional disparities, and the possible role of regional subsidies.2.1Theoretical background and estimation strategiesMaybe even more than in otherﬁelds,reduced-form empirical approaches in economic geography need to have their theoretical background clariﬁed.Otherwise, it is very difﬁcult to interpret the results obtained and to assess whether missing variables or endogeneity issues arise.The literature we review in this sectionﬁts into the following very simple framework.This is not really a model,but it sheds light on the relationship between productivity and the industrial characteristics ofthe region of interest.It assumes that a ﬁrm j operates under constant marginal cost in region r and industry s .Its output y j depends,on the one hand,on the capital k j and labour l j it uses,along with its level of technology A j and average labour efﬁciency s j ,and,on the other hand,on intermediate consumptions,c j ,which are made explicit here to match the data that usually concern value added.The production function is assumed to be given by y j ¼Min A j k a j s j l j ÀÁ1Àa ;c j b;where a 20;1 ½and b [0are two technological parameters.Firm j ’s proﬁt can be written as:p j ¼X bp jb y jb Àv j c j Àw j l j Àr j k j ;where y jb is the quantity exported to area b and p jb is the price set for region b ,net of trade costs (if any)borne by the ﬁrm.The term v j denotes the marginal cost of intermediate consumption,w j denotes the wage and r j denotes the cost of other inputs.Firm j ’s proﬁt reduces to:p j ¼p j y j Àw j l j Àr j k j ;where p j ¼P b p jb y jby jÀb v j is the average income per unit produced by the ﬁrm,net of trade and intermediate consumption costs.With such a speciﬁcation,p j y j rep-resents value added,the magnitude usually provided in data sets.The ﬁrst-order conditions for proﬁt maximisation under perfect competition on both goods and inputs markets reduces tow j ¼ð1Àa Þa ðÞa =ð1Àa Þs j p j A j r aj !1=ð1Àa Þ;ð1Þwhich serves as the basis for the estimation.Alternatively,one can work on total factor productivity,which is given byp j y j k j l j¼p j A j s 1Àa j ð2ÞEquations 1and 2can be used to summarise most economic geography effects.Typically,productivity (wages or total factor productivity)is high in a region if the region beneﬁts from technology or labour efﬁciency pure externalities that make A j or s j high.But wage and total factor productivity are also high if market access is good relatively to the degree of competition,which translates into high prices net of trade costs,p j .Finally,ﬁrm j may also beneﬁt from Marshallian externalities working through local input markets.If the access to inputs (or intermediate consumption)is good,translating into low r j (or v j ),then wages and total factor productivity are also high.All these effects can be read in the reverse direction.Productivity is low if pure congestion effects dominate in the region,which lowers A j or s j ,if market access is bad—either because competition is strong or becauseThe empirics of economic geography:how to draw policy implications?569markets are located far away (which implies a low p j )—or if access to inputs is bad (high r j or v j ,due to high land prices for example).Economic geography models are much richer than the present framework.They provide micro-foundations to all market-based effects,typically working through p j and r j in fully-ﬂedged models under imperfect competition and equilibrium as general as possible.To ground theoretically reduced-form approaches in economic geography,there is no need to go much further than that,however.Taking the example of the impact of density on productivity,the following wage equation is typically estimatedlog w rs ¼a þb log den r þe rs ;ð3Þwhere w rs is the average wage in region r and sector s ,den r ¼emp r =sup r corresponds to the total number of employees (or population)in region r (emp r )divided by land area (sup r )and e rs is an error term representing unexplained productivity.Typical values for elasticity b are between 0.02and 0.09.When density is doubled,wages increase by 2b À1ÀÁÂ100,i.e.,between 2and 7%according to standard estimates.Density gaps between regions at the ﬁrst and third quartile can be as high as a factor of 15,even within the same country,in which case the productivity gap is higher than 50%.A value added/total factor productivity equation can also be estimated,generally extended to a framework that does not assume a constant marginal cost,typicallylog p rs y rs ¼a s log k rs þa 0s log l rs þb log den r þe rsRelating these speciﬁcations to the theoretical framework implies that the assumption made is log s j p j A j r a j!1=ð1Àa Þðr ;s Þ264375¼b log den r þe rs or log s j p j A j ÀÁðr ;s Þ!¼b log den r þe rs ;the left-hand side of these equations corresponding to logarithm of the average over all ﬁrms located in region r and operating in sector s .Note ﬁrst that the impact of density on productivity works through either A j ;s j ;p j ,or r j ,which means that the channel of agglomeration economies (technology,labour efﬁciency,goods or inputs prices)is not identiﬁed.Second,only the total net effect of density is identiﬁed,negative effects being possibly offset by positive effects,and vice versa.Still,and as described below,the impact of density increases on productivity can be crucial from the policy point of view,making such estimations important.Whereas local productivity is usually explained at the industrial level,s ,density is not an industry-speciﬁc variable.It reﬂects what are called ‘‘inter-industry’’(or ‘‘urbanisation’’)externalities,which are the effects of the overall characteristics of the region that do not depend on s .Other proxies for inter-industry externalities that besare normally included in such regressions are the overall size(land-area or total employment)of the local economy and local industrial diversity,which measures the role of the distribution of activity across local industries,typically using a Herﬁndhal index on local industrial shares.Recently,in relation to those more structural studies presented in Sect.3below,a simple market potential variable has often been introduced to measure the role of the proximity to dense markets other than the local one.Typically,Harris’(1954)potential given byMP r¼logXu¼r den u d ruwhere d ru is the distance between r and u,is often used.This is an external market potential,own-region density not being included since its effect is evaluated separately.The second important question this literature tackles relates to the role of local industry characteristics.This concerns externalities operating within the industry, called‘‘intra-industry’’(or‘‘localisation’’)externalities.The most standard intra-industry externalities proxy is the degree of specialisation of the region in the industry,measured by its share in the local economy.The average size ofﬁrms, which can capture the magnitude of intra-ﬁrm economies of scale,is also sometimes considered.The last variable consists in the share of professionals in the local labour force of the industry evaluates the possible role that such workers can play as a conduit of technological spillovers.1There is another reason to control,more generally,for the skills composition of the labour force.In local productivity,it is important to isolate those effects that really result from local externalities from more direct differences in labour efﬁciency across occupations.Not properly controlling for the uneven spatial distribution of occupations,some regions could appear more productive even if there is no local externality,simply due to the fact that they host more skilled people.While it is interesting to understand why the distribution of skills is uneven, a question to which we return below,the literature proposes strategies to quantify the presence of local externalities separately from this composition effect of local labour markets.Finally,this literature acknowledges the fact that local endowments,in a broad sense,do differ across regions,which affects productivity,again possibly independently from the presence of agglomeration economies.Typically,one would like to control for private and public capital local endowments(research centres,universities,transport infrastructure),physical geography(access to coast, river,central location,etc.)and for the quality of local institutions or the level of available technology,these last two being more relevant in the context of developing countries(including China).Clarifying the theoretical framework as we have just done is important for an accurate interpretation of the results.It is also necessary to assess whether econometric estimates may suffer from endogeneity biases.Typically,ordinary least squares(OLS)estimates assume that no explanatory variable is correlated with the 1See Rosenthal and Strange(2004)for a review.The empirics of economic geography:how to draw policy implications?571bes residuals.In Eq.3,this means that the co-variance between density and the residual is zero.There are two sources of endogeneity,missing variables and reverse causality,which we illustrate here in the case of density but which concern almost all the variables that this literature considers.Possible missing variables are numerous.Some industries are more productive than others at the national level and simultaneously over-represented in the densest areas.This is also the case of the local endowments that increase productivity.If such variables are omitted from the regression,the effect of the density,interpreted as a presence of local externalities,is over-estimated,since it captures effects not directly reﬂecting agglomeration economies.Density economies can also be under-estimated if one omits from the regression local amenities(cultural goods,leisure facilities,etc.)that are also positively correlated with density.Indeed,Roback (1982)underlines that amenities attract people to cities,thereby increasing land prices,encouragingﬁrms to substitute labour for land in the production process, thus reducing the marginal productivity of labour.Reverse causality arises when people and/orﬁrms choose their location according to their returns,directly linked to the local productivity.In this case, productivity shocks unobserved by the econometrician(e.g.,local government choosing an efﬁcient policy,a climate event decreasing efﬁciency)but observed by people and/orﬁrms become correlated to density due to endogenous location choices,thus biasing OLS estimates.Fortunately,both sources of bias can be circumvented.One strategy consists in introducing all available control variables,as long as they are consistent with the theoretical framework.If panel data are available,ﬁxed-effect strategies can be adopted,for instance to control for aggregate effects such as the nation-wide industry-speciﬁc ones.Fixed effects,in this case individual,can also be used to address the role of individual skills,as proposed by Combes et al.(2008).The second strategy relies on instrumentation.The aim is toﬁnd instrumental variables correlated with the possibly endogenous explanatory variables,typically density, but not with productivity shocks.One then replaces the endogenous explanatory variables in the regression by their predictor according to the instruments.As proposed for instance by Ciccone and Hall(1996),the literature typically uses historical variables,for instance local density many decades before the years for which the model is bes et al.(2010)also propose using instruments based on the nature of soils,which could be a determinant of very early human settlements.Because of the inertia of location patterns,both families of instruments remain correlated to current density,whereas they have little chance of being correlated with current productivity shocks.Finally,natural experiments that affect density or market-potential exogenously can be also used to identify their causal effect on productivity.For instance,Hanson(1996,1997)uses Mexico’s trade liberalisation,Redding and Strum(2008)use the division of Germany after the Second World War,although in a more structural context than those presented in bes et al.(2011)detail all these issues related to the identiﬁcation of agglomeration economies.Finally,instead of assessing the impact of local characteristics on productivity,an older literature studies the possible dynamic effects of these characteristics,i.e.,their impact on local growth.This approach isThe empirics of economic geography:how to draw policy implications?573 described in Combes et al.(2008).However,studying its policy implications,which are furthermore blurred by the weak links with theory,is beyond the scope of this paper.2.2Policy implicationsWe now turn to the possible policy implications that can be drawn from reduced-form estimations.Although some clear messages are sometimes obtained,the absence of a real objective to provide policy recommendations in this literature is striking.This is underlined by both the lack of policy-oriented interpretation of existing results towards this line and the partial inappropriateness of the strategy used.2.2.1How to gain more from density?Clearly,the main outcome of this literature consists in the characterisation of the optimal characteristics of the regions,in terms of both overall size and industrial composition.For instance,the positive effect of density on productivity that is always obtained in such estimations clearly implies that increasing the size of regions induces productivity gains.It is,however,difﬁcult to evaluate the magnitude of these gains precisely.For a country like France,a doubling of density leads to a productivity gain of2%at the lower bound,but almost5%at the upper bound,depending on the controls introduced and,more importantly,on whether the endogenous quality(skills)and quantity(number)of the labour force are controlled for.Typically,controlling for the endogeneity of density reduces its impact by20%,while taking individual skills properly into account divides the estimation of agglomeration economies by a factor of2.This makes quite a large difference for the policy-maker thinking about improving the productivity of local ﬁrms and workers by increasing density.Such differences in estimates are partly related to an interpretational issue that is rarely commented.The2%obtained for France corresponds to the density elasticity controlled for both skills and endogeneity.Doubling employment density increases the productivity of any worker by2%independently of the composition of the labour force(but keeping the industrial structure constant).Now,on aggregate grounds,when one doubles the density in a region,one can simultaneously match the current regional skills composition,and the gain is2%for all workers in the region.But one can also match the skill composition of the regions that are twice as large,biased towards higher skills.In this case,one must consider the total effect of density,i.e.,not only the2%corresponding to the direct effect,but also the extra gains due to the presence of more skilled workers,resulting in a total increase in regional average productivity of around4%.Since density is endogenous,the policy-maker can also expect increased productivity to attract even more people to the region.This will have a positive feed-back effect on productivity,which will increase by a further1%point,hence the total5%effect mentioned above.This discussion raises a second issue about how a policy-maker can increase the size of a region.The comparative static exercise we have just described correspondsbes to the compulsory displacement of(preferably skilled)populations.Clearly,that is not very realistic.The policy-maker must use endogenous market incentives for moving to larger cities,but little is known about these incentives.Typically, although one can control for the endogeneity of density,the equation relating people’s location choices to the characteristics of the region has not been estimated yet.This means that the tools that could allow a policy-maker to attract more workers to larger regions have not yet been characterised in a framework consistent with the estimation of agglomeration economies.Furthermore,this should be done for each skill level separately if one wants to control the skills composition of the region’s new immigrants.At one extreme,it might well be that people refuse to move to large regions in any greater numbers than at present,and the policy-maker will fail to increase the size of the region.At the other extreme,one can also reasonably imagine that people are sensitive to housing and land prices,meaning that changing land use legislation could be an effective way to inﬂuence the regional size.Again,the problem is that no quantiﬁcation of the migration determinants consistent with the agglomeration economies estimation is available.Note that the estimation of agglomeration economies also implicitly assumes that the degree of congestion of local infrastructure remains the same.For this to hold, land development would have to take place simultaneously with the increase in regional density.Typically,local transport infrastructure,schools,health services, etc.will have to be built.Obviously,such costs can be covered by taxes on productivity gains(and are netted out of the above estimates of the density impact), but the current empirical economic geography literature has very little to say about how this can be implemented and the effort it represents.In other words,2%is only a net gain,corresponding to a x?2%gross gain and a x%loss.Whether x is large or small,which has not yet been assessed by the literature,can make some difference to the magnitude of the tax policy to be implemented simultaneously with the local density increase.In the same vein,it is worth stressing that the whole discussion in this section is only about possible productivity gains from changes in the region’s characteristics. Unfortunately,given the current state of the empirical literature,broader conclu-sions about the impact of regional size,or any other local characteristics,on the total welfare of the economy cannot be proposed.This requires the productivity gains and therefore income gains from agglomeration for the representative consumer to be weighed against the costs of agglomeration borne by the consumer,typically the impact of the region’s characteristics on his cost of living.Very little is known empirically in this area;there is for instance no consensual estimate for the elasticity of housing or land prices to city size.Typically,if workers were mobile enough for their indirect utilities(income minus the cost of living)to equalise across regions, the elasticity of productivity with respect to density would also identify the impact of city size on the cost of living.There would be no welfare gain for the representative consumer from increasing city size,even if productivity increased. However,as presented in Combes et al.(2005a)using a diagrammatic approach, this type of conclusion relies on a number of crucial assumptions,regarding the inter-regional and inter-sectoral mobility of workers,their possible differentiation in terms of skills,the magnitude of trade costs for goods,the nature of competition,theThe empirics of economic geography:how to draw policy implications?575 way new cities can be built and so on.This prevents us from providing aﬁrm empirical answer to policy-makers regarding the overall welfare effects of city characteristics.2.2.2What are the optimal size and number of regions?Given the log-linear form assumed for the positive impact of density on productivity,one single region of the largest possible size would maximise the overall productivity of the economy.However,this makes little sense in reality and has to be qualiﬁed from both the theoretical and empirical perspectives.One of the conclusions of the theoretical literature on systems of cities(from Henderson1974) states that,for each city,there exists a size that maximises productivity(and then an optimal number of cities in the economy,generally different from one).City size increases productivity but at a decreasing marginal rate,a peak is reached and then productivity declines with city size.The peak may depend on other characteristics of the city and therefore be different for all of them.Estimating it over a cross-section of cities,or regions,can thus prove to be difﬁcult,and further complicated by endogeneity issues like those discussed in the previous section.Beyond such problems,it is surprising that empirical speciﬁcations assume a monotonously increasing effect of density,which prevents any inference about the fact that regions are too large or too small with respect to the size that maximises productivity.The study by Au and Henderson(2006),who focus on Chinese cities,is one of the rare exceptions that attempt at addressing these questions.China is an interesting case study,because of the country’s rapid overall expansion and the presence of institutional constraints on internal migration.Both in a structural setting,in the spirit of those described below,and in reduced-form speciﬁcations,Au and Henderson(2006)ﬁnd that the impact of city size on output per worker is indeed bell-shaped,implying the existence of a size for each city that maximises its output per worker.They also show that it depends on the city characteristics,in particular its composition in terms of manufacturing employment relative to services.The main conclusion reached,which is striking,is that Chinese cities are in general too small to maximise productivity.Between50and60%of the cities have a size signiﬁcantly below the productivity peak,while only about2%are signiﬁcantly above.Among the cities that are too small,the median productivity loss is modest, around17%.However,it reaches28%at theﬁrst quartile and at least69%for10% of the cities.According to the authors,these undersized Chinese cities are explained by restrictions on migration.Given the higher productivity they observe in cities, their intuition is that wages there should be higher,and that this difference should not be fully offset by higher goods and housing prices.Migration,if permitted by the authorities,should take place,thereby increasing city size.However,a location choices equation to determine whether such mobility will take place is not estimated,so this remains hypothetical.Moreover,even if such migration went in the right direction,one should not forget that the market outcome rarely corresponds to the social optimum in economic geography.The question of how to reach this optimum,i.e.how to induce more migration than obtained through market forces(if the market outcome is insufﬁcient)remains.besA last issue concerns the impact on other regions of increasing the size of a region.In the absence of foreign immigration or an increase in fertility rates,the growth of one region’s population can only arise at the expense of other regions.If density,and therefore productivity,increase in one region,they will both decrease elsewhere.This means that the optimal policy for a region may be different from the optimal policy at the national level,a standard policy issue when studying regional policies that is clearly present in this case.Beyond the optimal size of each region,the question therefore arises of the optimal total number of large regions.Although largely studied from the theoretical point of view,there is,to the best of our knowledge,no empirical assessment of this issue.The difﬁculty lies in the fact that current speciﬁcations do not involve much of the rest of the economy.The productivity of a region depends on the characteristics of this region only and not on those of other regions(apart from the market potential variable,which is further discussed below).A general equilibrium model of regional trade would make all regions inter-dependent and should therefore be the starting point of the analysis.Typically,an experiment such as increasing the density of a region would have not only the direct,positive effect on its productivity we have just discussed but also indirect and possibly negative effects on the productivity of other regions.It might then be possible to determine the optimal spatial allocation of employment between regions.Still,we are clearly far from having a setting allowing for all of this,and this makes it a possibly interesting future line of research.The previous discussion focused on the role of density/overall size of the region. Similar issues arise for most other explanatory variables considered in the reduced-form speciﬁcations.Generally,the impact of own-industry size(specialisation)is positive.In France,it is around0.02,meaning that increasing the share of an industry by10%,increases productivity by0.2%.Specialisation elasticities can reach0.04in high-tech industries or business services.First,how can a policy-maker increase the local share of a speciﬁc industry?To answer this question,one ﬁrst needs to estimate the determinants of newﬁrms’location choices.Aﬁrst step in this direction is proposed by Combes et al.(2004),who estimate simultaneously(in a VAR model)the determinants of the growth of existingﬁrms and of the creation of newﬁrms in a region.It is typically obtained that some local characteristics that favour the latter may hinder the former.However,this remains to be further investigated.Second,one cannot increase the share of all industries at the same time within the same region.Moreover,as for density,it is probable that if specialisation in a given industry increases in one region,it will decrease in others.The optimal number of regions in the economy where a given industry is present is a question that this literature does not answer.Another issue speciﬁc to specialisation is its possible hysteresis effect.Some researchers hypothesise that specialisation could have a positive impact on regional growth in periods where the industry expands nationally,but a negative one when it contracts.In this case,the optimal policy would depend on the period when it is applied,which can create time inconsistency.For example,increasing specialisation may be efﬁcient in the short run but induce losses in the long run.。

个体差异和群际偏差

Individual differences and intergroup bias:Divergent dynamics associated with prejudice and stereotypingAnna-Kaisa Newheiser ⇑,John F.DovidioYale University,New Haven,CT,USAa r t i c l e i n f o Article history:Received 8November 2011Received in revised form 23February 2012Accepted 29February 2012Available online 24March 2012Keywords:Stereotyping PrejudiceNeed for StructureRight-Wing Authoritarianism Intergroup contact EntitativityGroup perceptiona b s t r a c tAlthough the study of intergroup bias has attracted substantial empirical interest within personality and social psychology,distinctions among types of bias,primarily prejudice and stereotyping,are often not fully considered.However,stereotyping and prejudice are conceptually and empirically distinct phenom-ena.We investigated how individual-difference variables distinctively predict stereotyping and preju-dice,and examined the differential antecedents,dynamics,and consequences of these forms of intergroup bias.Personal Need for Structure predicted stereotyping,and Right-Wing Authoritarianism and intergroup contact predicted prejudice.In addition,stereotyping and prejudice had divergent dynamics with perceptions of out-groups’entitativity (i.e.,out-groups’perceived unity,coherence,and internal organization).Speciﬁcally,entitativity mediated the relationship between Personal Need for Structure and stereotyping.In contrast,prejudice mediated the relationships of both Right-Wing Author-itarianism and intergroup contact with entitativity.Implications for theory and research on the predic-tors and dynamics of intergroup bias are discussed.Ó2012Elsevier Ltd.All rights reserved.1.IntroductionThe study of intergroup bias has attracted substantial empirical interest,both historically and currently (Duckitt,2010).Although much of the focus in the past 30years has been on the ‘‘universal-ity of bias,’’emphasizing fundamental cognitive (Hamilton,1979)and motivational (Tajfel &Turner,1979)processes,considering individual differences in bias remains an important topic in inter-group relations (Duckitt,2010).Moreover,although both prejudice and stereotyping are integral forms of intergroup bias,it is impor-tant to recognize that they are conceptually distinct:Whereas pre-judice primarily involves evaluations of an out-group,stereotyping entails a more cognitive attribution of speciﬁc characteristics to group members (Dovidio,Hewstone,Glick,&Esses,2010).In addi-tion,prejudice and stereotyping are only modestly related empiri-cally (meta-analytic r =.25;Dovidio,Brigham,Johnson,&Gaertner,1996)and have different antecedents (Pettigrew &Tropp,2006)and consequences (Talaska,Fiske,&Chaiken,2008).The present research directly examined the divergent dynamics associated with prejudice and stereotyping in two ways.First,we investigated the role of individual differences as distinctive predictors of preju-dice and stereotyping.Second,we studied differential relationships with perceptions of entitativity ,deﬁned as the extent to which groups are perceived to have the nature of real entities (Campbell,1958)and to possess unity,coherence,and organization (Hamilton &Sherman,1996).Prejudice is typically conceptualized as a category-based evalu-ative response to a group and its members,whereas stereotyping involves perceptions of group members’shared characteristics (Amodio &Devine,2006).Based on this conceptual distinction,we considered speciﬁc dimensions of individual differences that we expected to differentially predict prejudice and stereotyping.Because stereotyping involves processing information about groups (Hamilton,1979),the ways in which people process infor-mation in general are particularly relevant.Indeed,individual dif-ferences in Personal Need for Structure (Neuberg &Newsom,1993),the extent to which people organize their thinking and activities in simple,unambiguous ways (see also Kruglanski &Webster,1996),is a well-established predictor of stereotyping.By contrast,Right-Wing Authoritarianism,which indexes adher-ence to conventional norms,uncritical submission to authority,and aggression toward norm-violators (Altemeyer,1981),relates to basic evaluative responses and is among the strongest individ-ual-difference predictors of prejudice (Van Hiel &Mervielde,2005).We also examined the role of an experiential factor,inter-group contact,that is a robust predictor of intergroup attitudes (i.e.,prejudice).Contact with out-group members under optimal conditions (including equal status,cooperation,and friendship po-tential)is reliably negatively associated with prejudice (Brown &Hewstone,2005;Pettigrew &Tropp,2006).Accordingly,in the0191-8869/$-see front matter Ó2012Elsevier Ltd.All rights reserved./10.1016/j.paid.2012.02.024⇑Corresponding author.Address:Department of Psychology,Yale University,2Hillhouse Avenue,New Haven,CT 06511,USA.Tel.:+12035779815.E-mail address:anna-kaisa.newheiser@ (A.Newheiser).present research,we examined individual differences in Personal Need for Structure,Right-Wing Authoritarianism,and intergroup contact as predictors of intergroup biases.Complementing and extending prior work that has concen-trated on divergence in the predictors of stereotyping and preju-dice,we also considered potential differences in terms of more proximal associations with out-groups’perceived entitativity. Entitativity is typically conceptualized as an antecedent of bias (e.g.,Gaertner&Schopler,1998).In particular,a substantial body of evidence demonstrates that perceptions of greater entitativity increase stereotyping(e.g.,Crawford,Sherman,&Hamilton, 2002;Rydell,Hugenberg,Ray,&Mackie,2007;Spencer-Rodgers, Hamilton,&Sherman,2007).High perceived entitativity is an important antecedent of stereotyping because the attribution of stereotypical traits may occur only when the group is sufﬁciently homogeneous for perceivers to believe that group members indeed share common characteristics(Hamilton,2007;Hewstone& Hamberger,2000;Ryan,Judd,&Park,1996).Perceptions of entitativity are also associated with prejudice (e.g.,Roets&Van Hiel,2011a).However,relative to the well-researched relationship between entitativity and stereotyping, considerably less is known about the entitativity–prejudice relationship.In previous work(Newheiser,Tausch,Dovidio,& Hewstone,2009),we proposed that high perceived entitativity may represent a consequence of prejudice.People justify prejudice by perceiving out-groups as threatening(Pereira,Vala,&Costa-Lopes,2010),and because high-entitativity groups are distinctively threatening(Dasgupta,Banaji,&Abelson,1999),perceiving greater entitativity in out-groups may aid such justiﬁcation.Consistent with this reasoning,in a path modeling analysis we found support for a model in which prejudice predicted entitativity over the re-verse model,in which entitativity predicted prejudice(Newheiser et al.,2009).Entitativity is also plausibly associated with individual differ-ences that predict forms of intergroup bias.For instance,inter-group contact enhances perceived out-group variability(Voci& Hewstone,2003),thus potentially reducing perceived entitativity. Entitativity may be positively associated with Right-Wing Author-itarianism because authoritarianism entails a belief in rigid group cohesion(Altemeyer,1981).Need for structure has been shown to be positively associated with perceptions of entitativity(Roets &Van Hiel,2011a,2011b).In an attempt to synthesize prior work that has typically exam-ined prejudice,stereotyping,and perceived entitativity separately, in the present research we proposed and tested speciﬁc hypotheses regarding divergent relationships among intergroup biases,entit-ativity,and individual difference predictors of intergroup orienta-tions.Participants completed measures of Personal Need for Structure,Right-Wing Authoritarianism,intergroup contact,ste-reotyping,prejudice,and perceived entitativity.We chose Muslims as the target group because Islamophobia represents a prominent form of contemporary bias(Sheridan,2006).We predicted that Personal Need for Structure would be the primary predictor of ste-reotyping and that entitativity would be a key mediating link in this process.In contrast,based on our previous work(Newheiser et al.,2009),we anticipated that Right-Wing Authoritarianism and intergroup contact would predict prejudice and entitativity, and that prejudice would mediate entitativity’s relationships with both Right-Wing Authoritarianism and intergroup contact.Weﬁrst examined these hypotheses separately for stereotyping and preju-dice.However,we also employed path analysis in order to test all hypothesized relationships simultaneously.This strategy allowed us to,ﬁrst,fully consider the distinction between prejudice and stereotyping,and,second,to provide an overall understanding of the structure of the interrelationships among individual differ-ences and intergroup biases.2.Method2.1.ParticipantsOne hundred and sixty-one non-Muslim students(85women; mean age=21.73,SD=3.64,range:18–35)participated in return for a chance to win a gift certiﬁcate.2.2.Procedure and measuresParticipants were recruited through email advertisements and completed measures online.We orthogonally counterbalanced the order of the predictors and the criterion variables;there were no order effects.Personal Need for Structure(PNS)was assessed with an11-item scale(Neuberg&Newsom,1993;1=strongly disagree to 7=strongly agree;a=.86).Items included‘‘I don’t like situations that are uncertain’’and‘‘I enjoy the exhilaration of being in unpre-dictable situations’’(reverse-scored).Right-Wing Authoritarianism was assessed with20items from the30-item Right-Wing Authoritarianism scale(Altemeyer,1998; 1=strongly disagree to7=strongly agree;a=.91).The20items were selected on the basis of having the strongest item-total corre-lations,within the constraints that half of the items were reverse-scored and that sentiments of authoritarian submission, authoritarian aggression,and conventionalism were invoked equally(B.Altemeyer,personal communication,November2004). Items included‘‘The‘old-fashioned ways’and‘old-fashioned val-ues’still show the best way to live’’and‘‘Our country needs free thinkers who will have the courage to defy traditional ways,even if this upsets many people’’(reverse-scored).As a2-item measure of intergroup contact(Islam&Hewstone, 1993),participants indicated how much contact(1=none at all to7=a great deal)they have with Muslims‘‘just chatting to peo-ple’’and‘‘over all social situations.’’The items were highly corre-lated,r(159)=.72,p<.001,and were averaged into a single index.As a6-item index of perceived entitativity(Lickel et al.,2000), participants estimated(1=not at all to7=extremely;a=.81)the frequency with which Muslims interact with one another,the importance Muslims attach to being Muslim,the degree to which Muslims qualify as a real group,Muslims’similarity,and the de-gree to which Muslims share common goals and common out-comes to daily events.Prejudice against Muslims was measured with a15-item scale (Leibold&Kühnel,2006;1=strongly disagree to7=strongly agree; a=.84).Items included‘‘Islam is a backward religion’’and‘‘Islam has created an admirable culture’’(reverse-scored).Stereotyping of Muslims was assessed via ratings of the extent to which a series of traits applied to Muslims,developed through pre-testing conducted in two stages(as recommended by Stangor& Lange,1994).In theﬁrst stage,36non-Muslim students(Pilot Sam-ple1;33women;mean age=19.56,SD=1.23)generated traits that came to mind when thinking of Muslims.We selected the se-ven most commonly listed positive and negative traits from the free responses provided by Pilot Sample1(place high value on hon-or;very religious;loyal;disciplined;family-oriented;against women’s rights;follow rules strictly).In the second pretesting stage,these se-ven stereotypical traits,together with six positive non-stereotypi-cal traits(enthusiastic;serene;joyful;attentive;optimistic;curious), and six negative non-stereotypical traits(nervous;unimaginative; distressed;unreliable;childish;snobbish)were presented to an inde-pendent sample of92non-Muslim students(Pilot Sample2;79 women;mean age=18.91years,SD=1.58).In Pilot Sample2, Muslims were rated higher(1=does not apply at all to7=extremely applicable)on stereotypical traits(M=5.63,SD=0.77,a=.80)thanA.-K.Newheiser,J.F.Dovidio/Personality and Individual Differences53(2012)70–7471on non-stereotypical positive traits(M=3.75,SD=0.73,a=.71), t(91)=18.34,p<.001,or non-stereotypical negative traits (M=3.00,SD=0.73,a=.69),t(91)=23.93,p<.001,conﬁrming that the traits freely generated by Pilot Sample1were perceived as stereotypical of Muslims by Pilot Sample2.Accordingly,participants in the main study rated the extent to which the seven stereotypical and seven non-stereotypical positive and negative traits(attentive,optimistic,curious,enthusiastic,child-ish,snobbish,and unreliable)applied to Muslims(1=does not apply at all to7=extremely applicable).We averaged the ratings of the stereotypical(a=.86)and non-stereotypical traits(a=.64). Regressing the stereotypical trait ratings on the non-stereotypical trait ratings,we obtained the residuals and employed them as theﬁnal stereotyping measure(see Correll,Judd,Park,&Witten-brink,2010).This strategy allowed us to isolate the extent to which participants attributed stereotypical traits to Muslims from the ex-tent to which they attributed any trait to Muslims,thus represent-ing participants’tendency to stereotype Muslims over and above their tendency to agree that the non-stereotypical traits also ap-plied to Muslims.Importantly,because some of the non-stereotyp-ical traits were negative,attributing these traits to Muslims plausibly represents a form of prejudice;adjusting for these ratings thus also allowed us to isolate stereotyping from a potential expression of prejudice(see Wittenbrink,Judd,&Park,1997).3.ResultsMeans,standard deviations,and intercorrelations are presented in Table1.Prior research has suggested that intergroup contact, Right-Wing Authoritarianism,and Personal Need for Structure may have some joint effects as predictors of intergroup biases (e.g.,Dhont&Van Hiel,2009;Hodson,Harry,&Mitchell,2009). Preliminary analyses,however,revealed no interactions among the predictors in the present work.Given the large body of litera-ture showing separate effects for these predictors and the absence of moderation effects in the present study,our analyses focused on the simultaneous main effects of these variables.3.1.Interrelationships with prejudiceTo examine the relationships associated with prejudice,we con-ducted a series of linear regression analyses.Speciﬁcally,we tested the hypotheses that Right-Wing Authoritarianism and intergroup contact would predict prejudice,and that prejudice would mediate the relationships of both Right-Wing Authoritarianism and inter-group contact with entitativity.Indeed,as expected,Right-Wing Authoritarianism,b=.29,p<.001,and intergroup contact, b=À.21,p=.005,predicted prejudice.Right-Wing Authoritarian-ism also predicted entitativity,b=.26,p=.001;the association be-tween intergroup contact and entitativity approached signiﬁcance, b=À.12,p=.117.When prejudice was included as a predictor in the latter analysis,it signiﬁcantly predicted entitativity,b=.23,p=.004,accompanied with a reduction in the strength of the rela-tionship between entitativity and Right-Wing Authoritarianism, b=.19,p=.016,and entitativity and intergroup contact,b=À.07, p=.353.We used bootstrapping(5000resamples)to test the two pre-dicted mediated relationships in a single model(as recommended by Hayes&Preacher,submitted for publication;see also Preacher &Hayes,2008).An indirect effect can be interpreted to signiﬁ-cantly differ from zero with95%conﬁdence when its bootstrap conﬁdence interval does not contain zero.As hypothesized,preju-dice mediated both the RWA–entitativity relationship,M=.08, SE=.03,95%conﬁdence interval[.02,.15],and the intergroup contact–entitativity relationship,M=À.04,SE=.02,p=.001,95% conﬁdence interval[À.07,À.01].3.2.Interrelationships with stereotypingTo examine the relationships associated with stereotyping,we again conducted a series of linear regression analyses,testing the hypotheses that Personal Need for Structure would predict entit-ativity and stereotyping and that entitativity would mediate the PNS–stereotyping relationship.Indeed,as expected,Personal Need for Structure predicted both entitativity,b=.20,p=.009,and ste-reotyping,b=.19,p=.018.When entitativity was included as a predictor in the latter analysis,it signiﬁcantly predicted stereotyp-ing,b=.40,p<.001,accompanied with a reduction in the strength of the PNS–stereotyping relationship,b=.11,p=.151.Bootstrap-ping(5000resamples)conﬁrmed that,as hypothesized,entitativity mediated the PNS–stereotyping relationship,M=.08,SE=.04,95% conﬁdence interval[.02,.16].3.3.Supplementary analyses:simultaneous test of all interrelationshipsHaving provided support for our predictions with separate anal-yses for prejudice and stereotyping,we next sought to assess the complete pattern of hypothesized interrelationships among the variables in a single analysis.For this purpose,we employed path analysis.We note that our data were cross-sectional and inferences about directions of causality should thus be interpreted cautiously. In this analysis,we derived estimates with the maximum likeli-hood procedure and using covariance matrices as input.We used the v2test,the comparativeﬁt index(CFI),the root mean square error of approximation(RMSEA),and the standardized root mean square residual(SRMR)to assess modelﬁt.Goodﬁt is indicated by a nonsigniﬁcant v2,v2/df ratio62or3,CFI P.95,RMSEA6.06, p-close>.05,and SRMR6.08(Carmines&McIver,1981;Hu& Bentler,1998,1999;Kline,2005).In the hypothesized model,inter-group contact and Right-Wing Authoritarianism predicted preju-dice,Personal Need for Structure and prejudice predicted entitativity,and Personal Need for Structure,prejudice,and entit-ativity predicted stereotyping(see Fig.1).The model achievedTable1Means,standard deviations,and intercorrelations.M SD1234561.Intergroup contact 3.12 1.25–.04.13À.11À.20*À.19*2.Right-Wing Authoritarianism 2.170.83––.24**.25**.28***.083.Personal Need for Structure 3.950.93–––.20**.10.19*4.Perceived entitativity 4.430.93––––.30***.42***5.Prejudice 3.030.85–––––.36***6.Stereotyping0.000.89––––––*p<.05.**p<.01.***p<.001.72 A.Newheiser,J.F.Dovidio/Personality and Individual Differences53(2012)70–74acceptableﬁt,v2(5)=10.43,p=.064,v2/df=2.09,CFI=.94, RMSEA=.08,p-close=.186,SRMR=.05.All indirect effects were signiﬁcant,p s6.015.In order to further corroborate the hypothesized model,we also sought to demonstrate that it achieved relatively betterﬁt com-pared to alternatives.We tested an alternative model in which intergroup contact and Right-Wing Authoritarianism predicted prejudice,Personal Need for Structure predicted stereotyping and entitativity,stereotyping predicted entitativity and prejudice,and entitativity predicted prejudice.Importantly,the two models had the same degrees of freedom and were structurally equivalent in terms of intergroup contact and Right-Wing Authoritarianism only predicting prejudice and Personal Need for Structure only predict-ing stereotyping and entitativity.Relative to the hypothesized model,this model achieved poorerﬁt,v2(5)=16.29,p=.006,v2/ df=3.26,CFI=.88,RMSEA=.12,p-close=.035,SRMR=.07.We also tested an alternative model in which intergroup contact, Right-Wing Authoritarianism,and Personal Need for Structure pre-dicted entitativity,which predicted both prejudice and stereotyp-ing.This model conceptualized entitativity as a proximal antecedent of intergroup biases(following prior work;e.g.,Spen-cer-Rodgers et al.,2007),and also achieved poorerﬁt relative to the hypothesized model,v2(7)=33.40,p<.001,v2/df=4.77, CFI=.72,RMSEA=.15,p-close=.001,SRMR=.09.Finally,to address the issue that both stereotyping and entit-ativity are associated with groups’perceived homogeneity,we con-ducted all analyses reported above using a5-item entitativity measure that excluded the item assessing Muslims’similarity. The results did not change in any instance,indicating that the pat-tern was not dependent on perceived homogeneity.4.DiscussionThe present research investigated the distinctive qualities of stereotyping and prejudice in terms of the individual differences that predict them,as well as in terms of their relationships with perceptions of out-group entitativity.We found that an individ-ual-difference factor related to conventionalism(Right-Wing Authoritarianism)and an experiential factor(intergroup contact) predicted prejudice,whereas individual differences in cognitive orientations(Personal Need for Structure and entitativity)pre-dicted stereotyping.Thus,we extended previous work,which has generally considered which individual differences best predict intergroup bias by testing how Right-Wing Authoritarianism and Personal Need for Structure differentially predict prejudice and ste-reotyping,over and above the potent,well-established effect of intergroup contact.Recognizing the distinct natures of prejudice and stereotyping,rather than treating them as similar forms of bias,illuminates the divergent ways in which individual differ-ences relate to intergroup biases.We also extended prior work by considering the differential downstream processes associated with prejudice and stereotyping, speciﬁcally in terms of their associations with out-groups’per-ceived entitativity.Prior studies have characterized entitativity both as a predictor(Roets&Van Hiel,2011a;Spencer-Rodgers et al.,2007)and as a potential consequence(Newheiser et al., 2009)of intergroup biases,suggesting that entitativity provides a fruitful perspective for understanding the distinction between pre-judice and stereotyping.Indeed,we found evidence supporting a conceptualization of entitativity as an antecedent of stereotyping. With regard to prejudice,we found support for the reverse relation-ship,showing that prejudice emerged as a predictor of entitativity. Theseﬁndings suggest that entitativity’s function may vary among forms of bias.Our results may help explain theﬁnding that whereas prejudice is more efﬁciently reduced when affective rather than cognitive factors are targeted(Pettigrew&Tropp, 2008),stereotype change instead occurs when people see greater variability in the out-group(Hewstone&Hamberger,2000; Rothbart&John,1985).Ourﬁnding that perceived entitativity is a key mediator of stereotyping further highlights the importance of interventions targeting individual differences in cognitive orientations in efforts to undermine stereotyping.Entitativity’s differential dynamics with prejudice and stereo-typing further suggest that its meaning may differ across contexts. For example,entitativity may crystallize perceptions of homogene-ity into attributions of stereotypical traits to out-group members (Crawford et al.,2002),or help rationalize prejudice by character-izing an out-group as an agentic entity with means to pursue goals that are potentially at odds with one’s own.These distinctions may help explain theﬁnding that entitativity can be judged either in terms of a group’s shared characteristics or in terms of its dynamic functioning(Brewer,Hong,&Li,2004;Rutchick,Hamilton,&Sack, 2008),suggesting that whereas prejudice reduction interventions may beneﬁt from targeting agency-based beliefs,attempts to re-duce stereotyping may require targeting similarity-based beliefs.In conclusion,ourﬁndings extend prior work by simultaneously examining the dynamics among intergroup biases,individual dif-ferences,and group perception.Explicitly considering the distinct roles of individual differences in different facets of intergroup bias allows for a more complete understanding of the antecedents of stereotyping and prejudice(see also Roets&Van Hiel,2011c).Inte-grating the study of individual difference predictors of intergroup bias with research on group perception may thus hold unique po-tential for understanding the perpetuation of group-based conﬂict.AcknowledgementsThis work was partially supported by a National Science Foun-dation Graduate Research Fellowship awarded to Anna Newheiser. We thank Elze Ufkes and Jojanneke van der Toorn for their valuable feedback on drafts of this paper.A.-K.Newheiser,J.F.Dovidio/Personality and Individual Differences53(2012)70–7473ReferencesAltemeyer, B.(1981).Right-wing authoritarianism.Winnipeg,MB:University of Manitoba Press.Altemeyer, B.(1998).The other authoritarian personality.In M.Zanna(Ed.).Advances in experimental social psychology(Vol.30,pp.47–92).San Diego,CA: Academic Press.Amodio,D.M.,&Devine,P.G.(2006).Stereotyping and evaluation in implicit race bias:Evidence for independent constructs and unique effects on behavior.Journal of Personality and Social Psychology,91,652–661.Brewer,M.B.,Hong,Y.,&Li,Q.(2004).Dynamic entitativity:Perceiving groups as actors.In V.Yzerbyt,C.Judd,&O.Corneille(Eds.),The psychology of group perception:Perceived variability,entitativity,and essentialism(pp.25–38).New York,NY:Psychology Press.Brown,R.,&Hewstone,M.(2005).An integrative theory of intergroup contact.In M.Zanna(Ed.).Advances in experimental social psychology(Vol.37,pp.255–343).San Diego,CA:Academic Press.Campbell,D.T.(1958).Common fate,similarity,and other indices of the status of aggregates of persons as social entities.Behavioral Science,3,14–25. Carmines,E.G.,&McIver,J.P.(1981).Analyzing models with unobserved variables: Analysis of covariance structures.In G.W.Bohmstedt&E.F.Borgatta(Eds.), Social measurement(pp.65–115).Thousand Oaks,CA:SAGE.Correll,J.,Judd,C.M.,Park,B.,&Wittenbrink,B.(2010).Measuring prejudice, stereotypes,and discrimination.In J.F.Dovidio,M.Hewstone,P.Glick,&V.M.Esses(Eds.),The SAGE handbook of prejudice,stereotyping,and discrimination (pp.45–62).Thousand Oaks,CA:SAGE Publications.Crawford,M.T.,Sherman,S.J.,&Hamilton,D.L.(2002).Perceived entitativity, stereotype formation,and the interchangeability of group members.Journal of Personality and Social Psychology,83,1076–1094.Dasgupta,N.,Banaji,M.R.,&Abelson,R.P.(1999).Group entitativity and group perception:Associations between physical features and psychological judgment.Journal of Personality and Social Psychology,77,991–1003.Dhont,K.,&Van Hiel,A.(2009).We must not be enemies:Interracial contact and the reduction of prejudice among authoritarians.Personality and Individual Differences,46,172–177.Dovidio,J.F.,Brigham,J.C.,Johnson,B.T.,&Gaertner,S.L.(1996).Stereotyping, prejudice,and discrimination:Another look.In C.N.Macrae,C.Stangor,&M.Hewstone(Eds.),Stereotypes and stereotyping(pp.276–322).New York,NY: Guilford.Dovidio,J.F.,Hewstone,M.,Glick,P.,&Esses,V.M.(2010).The SAGE handbook of prejudice,stereotyping and discrimination.Thousand Oaks,CA:SAGE Publications.Duckitt,J.(2010).Historical overview.In J.F.Dovidio,M.Hewstone,P.Glick,&V.M.Esses(Eds.),The SAGE handbook of prejudice,stereotyping and discrimination (pp.29–44).Thousand Oaks,CA:SAGE Publications.Gaertner,L.,&Schopler,J.(1998).Perceived ingroup entitativity and intergroup bias:An interconnection of self and others.European Journal of Social Psychology, 28,963–980.Hamilton, D.L.(1979).A cognitive-attributional analysis of stereotyping.In L.Berkowitz(Ed.).Advances in experimental social psychology(Vol.12,pp.53–84).San Diego,CA:Academic Press.Hamilton, D.L.(2007).Understanding the complexities of group perception: Broadening the domain.European Journal of Social Psychology,37,1077–1101. Hamilton,D.L.,&Sherman,S.J.(1996).Perceiving persons and groups.Psychological Review,103,336–355.Hayes,A.F.,&Preacher,K.J.(submitted for publication).Indirect and direct effects of a multicategorical causal agent in statistical mediation analysis.Available from /public/hp2011.pdf.Hewstone,M.,&Hamberger,J.(2000).Perceived variability and stereotype change.Journal of Experimental Social Psychology,36,103–124.Hodson,G.,Harry,H.,&Mitchell,A.(2009).Independent beneﬁts of contact and friendship on attitudes toward homosexuals among authoritarians and highly identiﬁed heterosexuals.European Journal of Social Psychology,39,509–525. Hu,L.T.,&Bentler,P.M.(1998).Fit indices in covariance structure modeling: Sensitivity to underparameterized model misspeciﬁcation.Psychological Methods,3,424–453.Hu,L.,&Bentler,P.M.(1999).Cutoff criteria forﬁt indexes in covariance structure analysis:Conventional criteria versus new alternatives.Structural Equation Modeling,6,1–55.Islam,M.R.,&Hewstone,M.(1993).Dimensions of contact as predictors of intergroup anxiety,perceived out-group variability,and out-group attitude:An integrative model.Personality and Social Psychology Bulletin,19,700–710.Kline,R.B.(2005).Principles and practice of structural equation modeling(2nd ed.).New York:Guilford.Kruglanski,A.W.,&Webster,D.M.(1996).Motivated closing of the mind:‘‘Seizing’’and‘‘freezing’’.Psychological Review,103,263–283.Leibold,J.,&Kühnel,S.(2006).Islamophobie:Differenzierung tut not.In W.Heitmeyer(Ed.).Deutsche Zustände,Folge4(pp.135–155).Frankfurt am Main, Germany:Suhrkamp.Lickel,B.,Hamilton,D.L.,Wieczorkowska,G.,Lewis,A.,Sherman,S.J.,&Uhles,A.N.(2000).Varieties of groups and the perception of group entitativity.Journal of Personality and Social Psychology,78,223–246.Neuberg,S.L.,&Newsom,J.T.(1993).Personal Need for Structure:Individual differences in the desire for simple structure.Journal of Personality and Social Psychology,65,113–131.Newheiser,A.,Tausch,N.,Dovidio,J.F.,&Hewstone,M.(2009).Entitativity and prejudice.Examining their relationship and the moderating effect of attitude certainty.Journal of Experimental Social Psychology,45,920–926.Pereira,C.,Vala,J.,&Costa-Lopes,R.(2010).From prejudice to discrimination:The legitimizing role of perceived threat in discrimination against immigrants.European Journal of Social Psychology,40,1231–1250.Pettigrew,T.F.,&Tropp,L.R.(2006).A meta-analytic test of intergroup contact theory.Journal of Personality and Social Psychology,90,751–783.Pettigrew,T. F.,&Tropp,L.R.(2008).How does intergroup contact reduce prejudice?Meta-analytic tests of three mediators.European Journal of Social Psychology,38,922–934.Preacher,K.J.,&Hayes,A.F.(2008).Asymptotic and resampling strategies for assessing and comparing indirect effects in multiple mediator models.Behavior Research Methods,40,879–891.Roets, A.,&Van Hiel, A.(2011a).The role of need for closure in essentialist entitativity beliefs and prejudice:An epistemic needs approach to racial categorization.British Journal of Social Psychology,50,52–73.Roets,A.,&Van Hiel,A.(2011b).Item selection and validation of a brief,15-item version of the Need for Closure Scale.Personality and Individual Differences,50, 90–94.Roets,A.,&Van Hiel,A.(2011c).Allport’s prejudiced personality today:Need for closure as the motivated cognitive basis of prejudice.Current Directions in Psychological Science,20,349–354.Rothbart,M.,&John,O.P.(1985).Social categorization and behavioral episodes:A cognitive analysis of the effects of intergroup contact.Journal of Social Issues,41, 81–104.Rutchick,A.M.,Hamilton,D.L.,&Sack,J.D.(2008).Antecedents of entitativity in categorically and dynamically construed groups.European Journal of Social Psychology,38,905–921.Ryan,C.S.,Judd,C.M.,&Park,B.(1996).Effects of racial stereotypes on judgments of individuals:The moderating role of perceived group variability.Journal of Experimental Social Psychology,32,71–103.Rydell,R.J.,Hugenberg,K.,Ray,D.,&Mackie,D.M.(2007).Implicit theories about groups and stereotyping:The role of group entitativity.Personality and Social Psychology Bulletin,33,549–558.Sheridan,L.P.(2006).Islamophobia pre-and post-September11th,2001.Journal of Interpersonal Violence,21,317–336.Spencer-Rodgers,J.,Hamilton,D.L.,&Sherman,S.J.(2007).The central role of entitativity in stereotypes of social categories and task groups.Journal of Personality and Social Psychology,92,369–388.Stangor,C.,&Lange,J.E.(1994).Mental representations of social groups:Advances in understanding stereotypes and stereotyping.In M.Zanna(Ed.).Advances in experimental social psychology(Vol.26,pp.357–416).San Diego,CA:Academic Press.Tajfel,H.,&Turner,J.C.(1979).An integrative theory of intergroup conﬂict.In W.G.Austin&S.Worchel(Eds.),The social psychology of intergroup relations (pp.33–48).Monterey,CA:Brooks/Cole.Talaska,C.A.,Fiske,S.T.,&Chaiken,S.(2008).Legitimating racial discrimination: Emotions,not beliefs,best predict discrimination in a meta-analysis.Social Justice Research,21,263–296.Van Hiel, A.,&Mervielde,I.(2005).Authoritarianism and social dominance orientation:Relationships with various forms of racism.Journal of Applied Social Psychology,35,2323–2344.Voci, A.,&Hewstone,M.(2003).Intergroup contact and prejudice against immigrants in Italy:The mediational role of anxiety and the moderational role of group salience.Group Processes and Intergroup Relations,6,37–54. Wittenbrink,B.,Judd,C.M.,&Park,B.(1997).Evidence for racial prejudice at the implicit level and its relationship with questionnaire measures.Journal of Personality and Social Psychology,72,262–274.74 A.Newheiser,J.F.Dovidio/Personality and Individual Differences53(2012)70–74。

考研英语阅读应具备的五大能力

考研英语阅读应具备的五大能力考研英语阅读应具备的五大能力【摘要】考研阅读的重要性不言而喻，不仅占分多，而且得分难。

接下来就来谈谈考研阅读需要具备五大能力，各位同学可做参考。

携手2016大纲解析人第一时间解大纲，点击免费报名。

单词能力其实非常多阅读题目，最终归结到底与单词相互关联。

经典的例子如：例1：2003年第一篇Wild Bill Donovan would have loved the Internet.The American spymaster who built the Office of Strategic Services in the World War II and later laid the roots for the CIA was fascinated with information.Donovan believed in using whatever tools came to hand in the “great game” of espionage- spying as a “profession.” These days the Net, which has already re-made such everyday pastimes as buying books and sending mail, is reshaping Donovan’s vocation as well.21. The emergence of the Net has ________.[A] received support from fans like Donovan[B] remolded the intelligence services[C] restored many common pastimes[D] revived spying as a profession【解析】这道题定位在最后一句，由于Bill Donovan的职业（vocation）就是情报服务，所以说到底本题考察了re-made是否能和restore同意替换，reshape是否能和remold同意替换。

低叶酸、维生素B12营养在阿曼儿童新诊断为自闭症是常见的

Applied nutritional investigationLow folate and vitamin B12nourishment is common in Omani children with newly diagnosed autismYahya M.Al-Farsi M.D.,D.Sc.a ,Mostafa I.Waly M.P.H.,Ph.D.b ,g ,Richard C.Deth Ph.D.c ,Marwan M.Al-Sharbati Ph.D.d ,Mohamed Al-Shafaee M.D.a ,Omar Al-Farsi M.Sc.a ,Maha M.Al-Khaduri M.D.e ,Ishita Gupta M.Sc.f ,Amanat Ali Ph.D.b ,Maha Al-Khalili M.Sc.a ,Samir Al-Adawi Ph.D.d ,Nathaniel W.Hodgson Ph.D.c ,Allal Ouhtit M.Ph.,Ph.D.f ,*aDepartment of Family Medicine and Public Health,College of Medicine and Health Sciences,Sultan Qaboos University,Muscat,Sultanate of Oman bDepartment of Food Science and Nutrition,College of Agriculture and Marine Sciences,Sultan Qaboos University,Muscat,Sultanate of Oman cDepartment of Pharmaceutical Sciences,Northeastern University,Boston,Massachusetts,USA dDepartment of Behavioral Medicine,College of Medicine and Health Sciences,Sultan Qaboos University,Muscat,Sultanate of Oman eDepartment of Obstetrics and Gynecology,College of Medicine and Health Sciences,Sultan Qaboos University,Muscat,Sultanate of Oman fDepartment of Genetics,College of Medicine and Health Sciences,Sultan Qaboos University,Muscat,Sultanate of Oman gDepartment of Nutrition,High Institute of Public Health,Alexandria University,Alexandria,Egypta r t i c l e i n f oArticle history:Received 24March 2012Accepted 5September 2012Keywords:Autism FolateMethylation Nutrition OmanVitamin B12a b s t r a c tObjective:Arab populations lack data related to nutritional assessment in children with autism spectrum disorders (ASDs),especially micronutrient de ﬁciencies such as folate and vitamin B12.Methods:To assess the dietary and serum folate and vitamin B12statuses,a hospital-based case –control study was conducted in 80Omani children (40children with ASDs versus 40controls).Results:The ASD cases showed signi ﬁcantly lower levels of folate,vitamin B12,and related parameters in dietary intake and serum levels.Conclusion:These data showed that Omani children with ASDs exhibit signi ﬁcant de ﬁciencies in folate and vitamin B12and call for increasing efforts to ensure suf ﬁcient intakes of essential nutrients by children with ASDs to minimize or reverse any ongoing impact of nutrient de ﬁciencies.Ó2013Elsevier Inc.All rights reserved.IntroductionA survey of the available literature suggests that nutritional and dietary interventions are considered routine treatment for developmental disorders including autism [1,2].However,the study and implementation of such measures have been limited to the industrialized and af ﬂuent countries of North America and Western Europe,with few exceptions [3,4].Developing coun-tries,and especially Arab countries,lack relevant data because autism is not a common theme of research [5].Autism spectrum disorders (ASDs)are neurodevelopmental disorders commonly characterized by debilitating and intran-sigent symptoms in three categories:dif ﬁculties with reciprocalsocial interactions,impaired communication skills,and disturbed emotional functioning that often manifests as stereo-typical and non-goal –directed behaviors [6].Oman,an Arab country located on the southern tip of the Arabian Peninsula adjacent to the Asian and African continents with a population nearing 3.5million,presents fertile ground to explore the nutritional and dietary de ﬁcits in children with developmental disorders [7].In Oman,a preliminary epidemio-logic survey has suggested that 0.14per 1000Omani children (0–14y old)have ASDs [8].Issues of child welfare are generally a signi ﬁcant concern for domestic social policy.Oman,like other emerging economies,is witnessing the co-occurrence of undernutrition and obesity in its population [9].Evidence also suggests that the country has yet to overcome persistent malnutrition.Alasfoor et al.[10]reported that,nationwide,approximately 7%of children exhibit wasting,11%exhibit stunting,and 18%were classi ﬁed as underweight.A more recent study replicating that study has suggested that these indices of malnutrition may be even higher [11].However,these studies limited their sample selection to preschool childrenThis study was supported by the Internal Grant Fund (IG/AGR/Food/10/01)and His Majesty ’s Strategic Fund (SR/MED/FMCO/11/01),College of Medicine and Health Sciences,Sultan Qaboos University.A research grant from the Autism Research Institute provided partial support for this study.*Corresponding author.Tel.:þ96-8-2414-3464;fax:þ96-8-2441-3300.E-mail address:aouhtit@.om (A.Ouhtit).0899-9007/$-see front matter Ó2013Elsevier Inc.All rights reserved./10.1016/j.nut.2012.09.014Contents lists available at ScienceDirectNutritionjo urnal homepag e:www.nutritNutrition 29(2013)537–541in mainstream education.Thus,children with ASDs were unlikely to be accounted for by these assessments of malnutri-tion indices because such children are unlikely to be enrolled in mainstream schools in Oman[12].To address the potential data gap regarding children with developmental disorders,Al-Farsi et al.[13]examined the nutritional status of128children with ASDs in Oman and found that approximately9%of the partici-pants were malnourished according to the indices of under-weight,wasting,and stunting.There is evidence that the variation in levels of two important nutrients,folate and vitamin B12[14–16],is strongly relevant for ASD.These two nutrients have been suggested to play a vital role in cognitive functions [17]similar to those often found to be disturbed in children with ASDs[14,18–20].Building on these emerging data showing that Arab pop-ulations tend to have folate and vitamin B12deﬁciencies,we initially conducted a preliminary study on screening the folate and vitamin B12status and we reported that a low status of these two vitamins was associated with hyperhomocysteinemia in Omani autistic children[21].In the present study,we performed a more comprehensive investigation and compared dietary and serum folate and vitamin B12statuses between children with ASDs and control subjects matched for age,gender,ethnicity,and sociodemographic status.Materials and methodsThe present case–control study was designed to determine the differential variation in folate or vitamin B12levels in preschool-age Omani children(3–5y old)with and without diagnosed ASDs.The study was conducted from December 2009to August2010at Sultan Qaboos University Hospital(SQUH),the main referral hospital for all autism cases in Oman.ParticipantsThe study participants included80Omani children(40ASD cases and40 control subjects of overall similar age and gender).The study was approved by the medical research ethics committee of Sultan Qaboos University.All caregivers of the participants provided their informed consent to be included in the study.Ascertainment of an ASD diagnosis was made according to the Childhood Autism Rating Scale[22],which was developed using gold-standard criteria based on the Diagnostic and Statistical Manual of Mental Disorders,Fourth Edition, Text Revision[23].Accordingly,all participants fulﬁlled the eligibility for a diag-nosis of an ASD,exhibiting symptoms within the triad of typical autistic traits: communication impairment,social deﬁcits,and ritualistic interests.Control subjects were randomly selected from eligible outpatients at the Department of Child Health at SQUH.Eligible subjects included children3to5y old who were not known to have any overt neurodevelopmental or behavioral disturbances and were not previously or currently considered malnourished.Eligible diag-noses included trauma,routine physical examination,dental problems,and dermatologic problems.Study protocolEach participant’s mother was interviewed one on one.The interview questions were designed to elicit information regarding the child’s develop-mental milestones,sociodemographic background,and dietary history including vitamin supplementation,in addition to other risk factors that might indicate a predisposition to autism,including pregnancy complications,preterm delivery, breast-feeding,and a family history of autism.To overcome the problem of reverse causality d that autistic children might have changed their dietary habits after diagnosis d only recently diagnosed cases were included,for which the dietary intake questionnaire was administered within10to14d of conﬁrming the diagnosis.The retrospective dietary intake of folate and vitamin B12was ascertained using the Reduced Dietary Questionnaire of Block et al.[24],which is a semiquantitative tool to gauge food intake frequency.The psychometric properties of the Reduced Dietary Questionnaire were found to be adequate for the present cohort.Ina food diary,the participants’mothers were asked to report the food items the child had consumed during the year preceding the study and whether they had changed their diet from their usual routine during the previous6mo.Subsequently,all food diaries were analyzed using standard computer-assisted procedures(ESHA Research,Salem,OR,USA).Laboratory measurementsBlood samples were collected from each of the40cases and40controls matched for age,sex,and weight(withinÆ0.5kg)to estimate the levels of serum folate and vitamin B12.For blood sampling,10mL of venous blood was collected from the median cubital vein.Blood samples were drawn into a plain tube by venipuncture.After centrifugation,the serum was transferred to a micro-centrifuge tube and stored atÀ80 C before the folate and vitamin B12 measurements.We used the AxSYM Instrument(Abbott Diagnostics,Worcester,Massachu-setts)for the quantitative determination of serum levels of folate and vitamin B12.The cutoff values were3to20ng/mL for folate and250to1250pg/mL for vitamin B12.Hypersegmented neutrophils on the peripheral blood smear were deﬁned approximately as more than5%of neutrophils with at leastﬁve lobes or more than1%of neutrophils with at least six lobes.Serum levels of homocysteine and methionine were measured using high-performance liquid chromatography and electrochemical detection.Serum samples were blown with nitrogen and10m L was injected into an ESA CoulArray high-performance liquid chromatographic system with a BDD analytical cell electrochemical detector system(model5040)equipped with an Agilent Eclipse XDB-C8(3Â150mm,3.5m m)reverse-phase C8column.A dual mobile phase gradient elution was used,consisting of a mobile phase containing sodium phosphate25mmol/L and1-octanesulfonic acid1.4mmol/L,adjusted to pH2.65 with phosphoric acid,with the second mobile phase containing50%acetonitrile. The system was run at aﬂow rate of0.6mL/min at ambient temperature with the following gradients:0to9min0%B,9to19min50%B,and19to30min50%B. Peak area analysis was provided by CoulArray3.06software(ESA,Chelmsford, Massachusetts)based on the standard curves generated for each compound. Statistical analysesChi-square analyses were used to evaluate the statistical signiﬁcance of differences among portions of the categorical data.The non-parametric Fisher exact test(two-tailed)was used instead of the chi-square test for small samples where the expected frequency was less than5in any of the2Â2table cells. Unpaired Student’s t test was used to ascertain any signiﬁcant differences between the mean values of two continuous variables,and the Mann–Whitney test was used for non-parametric tests.The odds ratios(ORs)for ASDs were computed for the bottom and middle thirds compared with the top third of folate and vitamin B12concentrations based on the distributions in the control group. The ORs and95%conﬁdence intervals(CIs)obtained from logistic regression modeling were taken as measurements of association between ASD and levels of folate and vitamin B12.All statistical analyses were performed using SAS9.1(SAS Institute,Cary,NC,USA);a cutoff P value<0.05was the threshold of statistical signiﬁcance for all tests.ResultsEighty children,including40cases and40controls,were analyzed.The age was identical in cases and controls.Selected sociodemographic characteristics of all subjects at the time of enrollment in the study are listed in Table1.In the two groups, most participant families lived in urban areas.The groups were also comparable in the distribution of maternal age,mother’s occupation,and family pared with the control group,mothers of participants in the case group tended to have higher illiteracy rates and folic acid supplementation during pregnancy and a higher consumption of fortiﬁedﬂour and bread; however,these differences were not statistically signiﬁcant (P>0.05).Our results showed that children with ASD had consistently lower levels of folate and vitamin B12in their diet and in their serum(Table2).The level of homocysteine was signiﬁcantly increased in ASD cases by68%(P¼0.004),whereas the level of methionine was signiﬁcantly decreased by15%(P¼0.05; Table2).Because homocysteine is the substrate for the folate-and vitamin B12-dependent enzyme methionine synthase and methionine is the product,these results are indicative of a func-tional deﬁcit in methionine synthase activity in children withY.M.Al-Farsi et al./Nutrition29(2013)537–541 538ASD in Oman,consistent with lower serum levels of its vitamin cofactors.Table 3lists the ORs and 95%CIs for ASD by tertile of folate and vitamin B12levels after adjusting for age,gender,and other socioeconomic variables.The OR for being in the ASD group among subjects with folate levels in the lowest tertile compared with those in the highest tertile was 1.7(95%CI 0.3–5.2).The OR for being in the ASD group among subjects with vitamin B12levels in the lowest tertile compared with those in the highest tertiles was 1.6(95%CI 0.8–8.3).A statistically signi ﬁcant trend toward membership in the ASD group was found in participants in the lowest tertiles for folate and vitamin B12(P <0.01,P ¼0.04,respectively).DiscussionThe present study shows that there is a differential variation in two nutrients,folate and vitamin B12,in Omani children with ASD compared to those de ﬁned as control subjects.A signi ﬁcant decrease was found in the mean values of dietary and serum levels of folate and vitamin B12between children with and those without ASD.A decrease in the activity of methionine synthase,for which folate and vitamin B12are required cofactors,was observed,indicating that their dietary and serum de ﬁcits have functional consequences.On the whole,the present data suggest pervasive and persistent de ﬁciencies of folate and vitamin B12in the studied children with ASD.Even in the general population,the prevalence of folate and vitamin B12de ﬁciencies in Oman is unknown.However,several reports have indicated that folate and vitamin B12de ﬁciencies may be common in Arab populations generally [25].A study that compared an Arab population with its Western Europe coun-terpart showed that the dietary intake of folate in Arab men and women was below the recommended nutrient intakes [26].Another study from Israel showed de ﬁciencies in folate and vitamin B12in Arab patients with Alzheimer ’s disease [27].Our previous study showed that folate de ﬁciency was associated with adult type 2diabetes in Oman [28].Folate de ﬁciency has been implicated in the manifestation of various clinical disorders [28].Folate de ﬁciency is characterized by hypersegmentation of neutrophils,megaloblastosis,and anemia.Megaloblastic anemia can be masked by concurrent iron-de ﬁciency anemia or thalassemia.Folate de ﬁciency has been shown to arrest children ’s development,even in the absence of anemia [29].Serum folate concentration,although typically low in patients with folate-de ﬁcient megaloblastic anemia,is primarily a re ﬂection of a short-term folate balance.The World Health Organization has recommended empiric treatment for severely malnourished children with folate de ﬁ-ciency [30].In Oman,prompt treatment of folate de ﬁciency should be routinely prioritized for children with ASDs.Children with autism or a pervasive developmental disorder-not other-wise speci ﬁed exhibit selective eating habits and very often exhibit feeding dif ﬁculties [31,32].Children with autism also exhibit greater dif ﬁculties with feeding and at meal times compared with non-autistic children [33,34].Parents of autistic children ﬁnd it dif ﬁcult to feed their children,probably because of pica,a disorder in which children tend to be picky eaters,prefer to eat non-edible objects,and resist consuming solid food [34].Although the underlying mechanisms are not very well understood,some autistic children tend to have motor delays resulting in dif ﬁculties while eating and swallowing,whereas some have gastrointestinal problems (constipation or diarrhea)resulting in an aversion to food [35].De ﬁciencies in various nutrients have been reported to be associated with autism,including but not limited to vitamin D [36],calcium and vitamin E [37],and vitamins B6,B9,and B12.One possible explanation for the relation between folate and/or vitamin B12de ﬁciencies and ASD involves DNA hypomethylation [38].Vitamin B12de ﬁciency has been shown to occur in vegetarians and children who are breast-fed by vegetarian mothers [39,40].Table 1Values are presented as number (percentage)or mean ÆSD.Table 2Comparison of dietary and serum folate and vitamin B12levels and their relatedTable 3Odds ratios and 95%con ﬁdence intervals for autism spectrum disorder by CI,con ﬁdence interval;OR,odds ratio*Tertiles based on the distribution of the controls.Y.M.Al-Farsi et al./Nutrition 29(2013)537–541539An existing vitamin B12deﬁciency is known to inhibit the release of vitamin B12found in subsequently consumed food,which may be another factor contributing to the predicament of children with ASDs[41].Vitamin B12deﬁciency has been shown to precipitate megaloblastic anemia,atrophic glossitis,neuropathy,and demy-elination of the central nervous system[42].The fact that vitamin B12deﬁciency has been linked to several neurologic disorders is further evidence of its vital importance[43].The question remains as to whether such adverse effects of vitamin deﬁciency may also be observed in children with ASDs.The present study implies that increased intakes of several vitamins and essential nutrients should be promoted.Feeding difﬁculties in autism can be allevi-ated through the supplementation of essential nutrients such as vitamins B6and B12,which has been recommended by some studies[44].In addition,anecdotal and clinical evidence supports a more active role by health care professionals in the case of nutritional deﬁciencies in autistic children because problems are sometimes overlooked owing to picky eating being a common problem in neurotypical and autistic children around the age when autism is usually diagnosed(reviewed by Rempel et al.[45]).In general,Oman has been highly proactive with such initiatives.National supplementation programs targeting micronutrient deﬁciencies were started two decades ago.In 1990,a supplementation program began providing all pregnant women with a daily dose of folic acid5mg and iron200mg throughout the course of their pregnancies[46].In1997,another national program was initiated to fortify relevant food consumed in the country with folic acid5mg/kg and iron30ppm[47].Both programs have been reasonably successful.In1993,it was found that97%of all pregnant women attending health centers had received the supplements,although their compliance rate with the supplementation recommendations had reached77%[48].In 2004,a national survey showed that the initiative for folate fortiﬁcation inﬂour and bread had achieved81%coverage of all households in Oman,with an averageﬂour consumption of116 g/person per day[46].The question remains as to whether such a proactive initiative has reversed known folate and vitamin B12 deﬁciencies in Omani children with autism.From the present data,compared with the control group,children with autism showed signiﬁcantly decreased levels of folate and vitamin B12 in their dietary intake and serum.Therefore,concerted effort needs to be directed toward such a vulnerable population.Several limitations of this study must be acknowledged.First, the participants were drawn from a clinical population,namely those seeking consultation at an urban tertiary care unit.It is well known that those seeking care at a hospital are not necessarily a suitable proxy for the community at large.Therefore, community studies with a broader sampling would be prereq-uisite to generalizing the presentﬁndings.Second,although most of the measurements used were objective,psychosocial histories and demographic information were narrated by the participants’caregivers.It is not clear whether any unidentiﬁed confounders exist owing to any possible bias of this approach. Third,the present study was restricted to children of preschool age with ASD;therefore,the present results should be inter-preted within the conﬁnes of this age group.Fourth,although the present study indicates a greater folate and vitamin B12deﬁ-ciency in children with ASD compared with control subjects,the observed association is not temporal and therefore does not establish a causal link.It remains unclear whether the observed deﬁciencies are a consequence of pathologic processes central to developmental disorders or a compensatory adaptation.The condition of the ASD cases may have rendered them incapable of following dietary guidelines with respect to the nutrients investigated,or under-consumption may have been secondary to the primary pathologic processes inherent in developmental disorders such as ASD.In summary,the present study showed that Omani children with ASDs exhibit signiﬁcant deﬁciencies in folate and vitamin B12compared with their non-ASD counterparts,deﬁning a nutritional basis for this pervasive developmental disorder in Oman.Ourﬁndings underscore the importance of mobilizing available health and educational resources to ensure the sufﬁ-cient intake of relevant trace elements and other essential nutrients by children with ASDs and to minimize or reverse any ongoing impact of nutrient deﬁciencies.Further studies of this type should be encouraged to translate the presentﬁndings into appropriate policy recommendations.References[1]Mart ıLF.Effectiveness of nutritional interventions on the functioning ofchildren with ADHD and/or ASD.An updated review of research evidence.Bol Asoc Med P R2010;102:31–42.[2]Johnson M,Ostlund S,Fransson G,KadesjöB,Gillberg C.Omega-3/omega-6fatty acids for attention deﬁcit hyperactivity disorder:a randomized placebo-controlled trial in children and adolescents.J Atten Disord 2009;12:394–401.[3]Tang B,Piazza CC,Dolezal D,Stein MT.Severe feeding disorder andmalnutrition in2children with autism.J Dev Behav Pediatr2011;32:264–7.[4]Xia W,Zhou Y,Sun C,Wang J,Wu L.A preliminary study on nutritionalstatus and intake in Chinese children with autism.Eur J Pediatr 2010;169:1201–6.[5]AﬁﬁMM.Mental health publications from the Arab world cited in PubMed,1987–2002.East Mediterr Health J2005;1:319–28.[6]Greenspan SI,Brazelton TB,Cordero J,Solomon R,Bauman ML,Robinson R,et al.Guidelines for early identiﬁcation,screening,and clinical manage-ment of children with autism spectrum disorders.Pediatrics 2008;121:828–30.[7]Central Intelligence Agency.The world factbook:Oman.Available at:https:///library/publications/the-world-factbook/geos/mu.html.Accessed August1,2011.[8]Al-Farsi YM,Al-Sharbati MM,Al-Farsi OA,Al-Shafaee MS,Brooks DR,Waly MI.Brief report:prevalence of autistic spectrum disorders in the Sultanate of Oman.J Autism Dev Disord2011;41:821–5.[9]Musaiger AO.Overweight and obesity in the eastern Mediterranean region:can we control it?East Mediterr Health J2004;10:789–93.[10]Alasfoor D,Elsayed MK,Al-Qasmi AM,Malankar P,Sheth M,Prakash N.Protein–energy malnutrition among preschool children in Oman:results ofa national survey.East Mediterr Health J2007;13:1022–30.[11]Alasfoor D,Mohammed AJ.Implications of the use of the new WHO growthcharts on the interpretation of malnutrition and obesity in infants and young children in Oman.East Mediterr Health J2009;15:890–8.[12]Profanter A.Facing the challenges of children and youth with specialabilities and needs on the fringes of Omani society.Child Youth Serv Rev 2009;31:8–15.[13]Al-Farsi YM,Al-Sharbati MM,Waly MI,Al-Farsi OA,Al Shafaee MA,Deth RC.Malnutrition among preschool-aged autistic children in Oman.Res Autism Spectrum Disord2011;5:1549–52.[14]Schmidt RJ,Hansen RL,Hartiala J,Allayee H,Schmidt LC,Tancredi DJ,et al.Prenatal vitamins,one-carbon metabolism gene variants,and risk for autism.Epidemiology2011;22:476–85.[15]James SJ,Melnyk S,Fuchs G,Reid T,Jernigan S,Pavliv O,et al.Efﬁcacy ofmethylcobalamin and folinic acid treatment on glutathione redox status in children with autism.Isr J Clin Nutr2009;89:425–30.[16]Moretti P,Sahoo T,Hyland K,Bottiglieri T,Peters S,del Gaudio D,et al.Cerebral folate deﬁciency with developmental delay,autism,and response to folinic acid.Neurology2005;64:1088–90.[17]Fafouti M,Paparrigopoulos T,Liappas J,Mantouvalos V,Typaldou R,Christodoulou G.Mood disorder with mixed features due to vitamin B(12) and folate deﬁciency.Gen Hosp Psychiatry2002;24:106–9.[18]Adams JB,Audhya T,McDonough-Means S,Rubin RA,Quig D,Geis E,et al.Nutritional and metabolic status of children with autism vs.neurotypical children,and the association with autism severity.Nutr Metab2011;8:34.[19]Lowe TL,Cohen DJ,Miller S,Young JG.Folic acid and B12in autism andneuropsychiatric disturbances of childhood.J Am Acad Child Adolesc Psychiatry1981;20:104–11.[20]Coelho D,Suormala T,Stucki M,Lerner-Ellis JP,Rosenblatt DS,Newbold RF,et al.Gene identiﬁcation for the cblD defect of vitamin B12metabolism.N Engl J Med2008;358:1454–64.Y.M.Al-Farsi et al./Nutrition29(2013)537–541 540[21]Ali A,Waly MI,Al-Farsi YM,Al-Sharbati MM,Essa MM,Deth RC.Hyper-homocysteinemia among Omani autistic children:a case control study.Acta Biochim Pol2011;58:547–51.[22]Schopler E,Reichler RJ,DeVellis RF,Daly K.Toward objective classiﬁcationof childhood autism:Childhood Autism Rating Scale(CARS).J Autism Dev Disord1980;10:91–103.[23]Diagnostic and statistical manual of mental disorders.4th ed,text rev.Washington,DC:American Psychiatric Association;2000.[24]Block G,Hartman AM,Naughton D.A reduced dietary questionnaire:development and validation.Epidemiology1990;1:58–64.[25]Moussa NA,Awad MO,Yahya TM.Pernicious anaemia and neurophysio-logical studies in Arabs.Int J Clin Pract2000;54:152–4.[26]Herrmann W,Obeid R,Jouma M.Hyperhomocysteinemia and vitamin B-12deﬁciency are more striking in Syrians than in Germans d causes and implications.Atherosclerosis2003;166:143–50.[27]Hirsch S,de la Maza P,Barrera G,Gatt a s V,Petermann M,Bunout D.TheChileanﬂour folic acid fortiﬁcation program reduces serum homocysteine levels and masks vitamin B-12deﬁciency in elderly people.J Nutr 2002;132:289–91.[28]Al-Maskari MY,Waly MI,Ali A,Al-Shuaibi YS,Ouhtit A.Folate and vitaminB12deﬁciency and hyperhomocysteinemia promote oxidative stress in adult type2diabetes.Nutrition2012;28:e23–6.[29]Shakur YA,Choudhury N,Hyder SM,Zlotkin SH.Unexpectedly high earlyprevalence of anaemia in6-month-old breast-fed infants in rural Bangladesh.Publ Health Nutr2010;13:4–11.[30]World Health Organization.Preparation and use of food based dietaryguidelines.WHO technical series880.Geneva:World Health Organization;1998.[31]Ahearn WH,Castine T,Nault K,Green G.An assessment of food acceptancein children with autism or pervasive developmental disorder-not other-wise speciﬁed.J Autism Dev Disord2001;31:505–11.[32]Palmer S,Ekvall S.Pediatric nutrition in developmental disorders.Springﬁeld,IL:CC Thomas’;1978.[33]Schreck KA,Williams K.Food preferences and factors inﬂuencing foodselectivity for children with autism spectrum disorders.Res Dev Disabil 2006;27:353–63.[34]Nadon G,Feldman DE,Dunn W,Gisel E.Mealtime problems in childrenwith autism spectrum disorder and their typically developing siblings:a comparison study.Autism2011;15:98–113.[35]Emond A,Emmett P,Steer C,Golding J.Feeding symptoms,dietarypatterns,and growth in young children with autism spectrum disorders.Pediatrics2010;126:e337–42.[36]Kocovska E,Fernell E,Billstedt E,Minnis H,Gillberg C.Vitamin D andautism:clinical review.Res Dev Disabil2012;33:1541–50.[37]Herndon AC,DiGuiseppi C,Johnson SL,Leiferman J,Reynolds A.Does nutri-tional intake differ between children with autism spectrum disorders and children with typical development?J Autism Dev Disord2009;39:212–22.[38]Piyathilake CJ,Macaluso M,Alvarez RD,Chen M,Badiga S,Siddiqui NR,et al.Ahigher degree of LINE-1methylation in peripheral blood mononuclear cells,a one-carbon nutrient related epigenetic alteration,is associated with a lowerrisk of developing cervical intraepithelial neoplasia.Nutrition2011;27:513–9.[39]Gammon CS,von Hurst PR,Coad J,Kruger R,Stonehouse W.Vegetarianism,vitamin B12status,and insulin resistance in a group of predominantly overweight/obese South Asian women.Nutrition2012;28:20–4.[40]Fadyl H,Inoue bined B12and iron deﬁciency in a child breast-fed bya vegetarian mother.J Pediatr Hematol Oncol2007;29:74.[41]Chatthanawaree W.Biomarkers of cobalamin(vitamin B12)deﬁciency andits application.J Nutr Health Aging2011;15:227–31.[42]Reynolds E.Vitamin B12,folic acid,and the nervous ncet Neurol2006;5:949–60.[43]Haapamäki J,Roine RP,Turunen U,FärkkiläMA,Arkkila PE.Increased riskfor coronary heart disease,asthma,and connective tissue diseases in inﬂammatory bowel disease.J Crohn Dis Colitis2011;5:41–7.[44]Hjiej H,Doyen C,Couprie C,Kaye K,Contejean Y.Substitutive and dieteticapproaches in childhood autistic disorder:interests and limits.Encephale 2008;34:496–503.[45]Rempel GR,Blythe C,Rogers LG,Ravindran V.The process of familymanagement when a baby is diagnosed with a lethal congenital condition.J Fam Nurs2012;18:35–64.[46]Alasfoor DH,AlRassasi B,Rajab H.National food based dietary guidelinesfor Oman d a technical report.Muscat:Department of Nutrition,Ministry of Health;2007.[47]Grosse SD,Waitzman NJ,Romano PS,Mulinare J.Reevaluating the beneﬁtsof folic acid fortiﬁcation in the United States:economic analysis,regulation, and public health.Am J Publ Health2005;95:1917–22.[48]Sayers GM,Hughes N,Scallan E,Johnson Z.A survey of knowledge and useof folic acid among women of childbearing age in Dublin.J Publ Health Med1997;19:328–32.Y.M.Al-Farsi et al./Nutrition29(2013)537–541541。

英语同等学力人员申请硕士学位试卷及答案指导(2025年)

2025年同等学力人员申请硕士学位英语自测试卷及答案指导一、口语交际（共10分）第一题Conversation:A: Hi Jacob, how are you?B: Hi Anna, I’m doing pretty well, thanks. How about you?A: I’m doing great. I was just thinking about the upcoming group project. We need to split the work.B: Sure, no problem. What tasks do you think we should work on?A: Well, I was considering the research part since I have experience in that area.B: That sounds fair. I’ll take care of the writing part then. Let’s set up a meeting to discuss the specifics later.A: Definitely. I’ll send out the meeting invite next week.1、What is the purpose of their conversation?a)Planning a meetingb)Discussing the division of laborc)Complaining about the workloadd)Introducing new members to the teame)Sharing personal health updatesAnswer: b2、Whom is Anna talking to?a)Her family memberb)Her colleaguec)Her friendd)Her professore)Her clientAnswer: b3、What task is Anna considering for herself?a)Writingb)Presentingc)Researchd)Editinge)DesigningAnswer: c4、What task is Jacob taking care of?a)Researchb)Writingc)Presentationd)Editinge)DesigningAnswer: b5、What will Anna do after the conversation?a)Call Jacobb)Send out a meeting invitec)Finish the project aloned)Cancel the projecte)Ask for more tasksAnswer: b第二题A conversation between two friends, Alice and Bob, about their study plans and university life.Alice: Hi, Bob! It’s been a while since we last studied together. Are you still preparing for the postgraduate entrance exam?Bob: Hi, Alice! Yes, I am. I’m really excited to enter graduate school. How about you? Have you made any progress on your studies?Alice: Yes, I’ve been working hard. I’m particularly focused on preparing for the TOEFL exam as it’s a requirement for my pro gram. Last week, I attended a preparation class and I wanted to discuss it with you.Bob: That’s great! What do you think of the class?Alice: I found it quite helpful. The instructor explained the format and strategies for each section. We even had a little practice session at the end.Bob: Nice! I heard about the class. Do you think it covered everything important?Alice: Yeah, I think it did. They even provided some sample questions andanswered our doubts. I was able to improve my speaking skills, which is essential for my program.Bob: Speaking skills are indeed crucial. By the way, is there anything you want to improve the most?Alice: Definitely my writing. It’s really challenging for me. I struggle to organize my thoughts and write coherently. So, any tips you can give me would be appreciated.Bob: Sure, I can help with that. First, try to practice writing short essays on a regular basis. It’ll help you get used to the structure and vocabulary required for academic writing.1.What topic did Alice discuss with Bob about her study plan?A) The postgraduate entrance examB) The TOEFL examC) The preparation class for the postgraduate entrance examD) The challenges she faces in her writing2.How does Alice feel about the preparation class she attended?A) She thinks it’s a waste of time.B) She thinks it’s quite helpful.C) She thinks it’s not informative enough.D) She thinks it’s too difficult for her.3.What kind of assistance does Alice seek regarding her writing improvement?A) Reading tipsB) Speaking tipsC) Writing tipsD) Vocabulary tips4.What does Bob suggest Alice do to improve her writing?A) Practice reading a lotB) Practice writing short essays regularlyC) Focus solely on spoken EnglishD) Take a proofreading course5.What is one aspect of the TOEFL exam that Alice needs to improve on?A) Listening skillsB) Reading skillsC) Writing skillsD) All of the aboveAnswers:1.B2.B3.C4.B5.C二、词汇-选择填空（本大题有10小题，每小题1分，共10分）1、In today’s fast-paced world, staying healthy requires a__________balance of physical exercise, a nutritious diet, and mental well-being.A. perfectB. perfectibleC. perfectiveD. perfectible答案：A解析：选项A “perfect” 意为“完美的”，符合题意。

监督字典学习

α∈Rk

It is well known in the statistics, optimization, and compressed sensing communities that the ℓ1 penalty yields a sparse solution, very few non-zero coefﬁcients in α, although there is no explicit analytic link between the value of λ1 and the effective sparsity that this model yields. Other sparsity penalties using the ℓ0 regularization2 can be used as well. Since it uses a proper norm, the ℓ1 formulation of sparse coding is a convex problem, which makes the optimization tractable with algorithms such as those introduced in [16, 17], and has proven in practice to be more stable than its ℓ0 counterpart, in the sense that the resulting decompositions are less sensitive to small perturbations of the input signal x. Note that sparse coding with an ℓ0 penalty is an NP-hard problem and is often approximated using greedy algorithms. In this paper, we consider a setting, where the signal may belong to any of p different classes. We ﬁrst consider the case of p = 2 classes and later discuss the multiclass extension. We consider a n m training set of m labeled signals (xi )m i=1 in R , associated with binary labels (yi ∈ {−1, +1})i=1 . Our goal is to learn jointly a single dictionary D adapted to the classiﬁcation task and a function f which should be positive for any signal in class +1 and negative otherwise. We consider in this paper two different models to use the sparse code α for the classiﬁcation task: (i) linear in α: f (x, α, θ ) = wT α + b, where θ = {w ∈ Rk , b ∈ R} parametrizes the model. (ii) bilinear in x and α: f (x, α, θ ) = xT Wα + b, where θ = {W ∈ Rn×k , b ∈ R}. In this case, the model is bilinear and f acts on both x and its sparse code α. The number of parameters in (ii) is greater than in (i), which allows for richer models. Note that one can interpret W as a linear ﬁlter encoding the input signal x into a model for the coefﬁcients α, which has a role similar to the encoder in [18] but for a discriminative task. A classical approach to obtain α for (i) or (ii) is to ﬁrst adapt D to the data, solving

D o e s D i v i d e n d Po l i c y D r i v e E a rn i n g s股利分配盈余平滑20143AH

Accounting Horizons American Accounting Association Vol.28,No.3DOI:10.2308/acch-50764 2014pp.501–528Does Dividend Policy Drive EarningsSmoothing?Nan Liu and Reza EspahbodiSYNOPSIS:This paper examines the earnings-smoothing behavior of dividend-payingfirms.We show that dividend-paying firms engage in more earnings smoothing than non-payers through both real activities and accrual choices.More specifically,dividend-paying firms with positive(negative)pre-managed earnings changes engage in moredownward(upward)earnings management than non-payers.Additional tests suggestthat the results are driven by dividend-related incentives and not the differences in theeconomic characteristics of dividend-paying firms,are robust to alternative measures ofearnings management,and are not due to spurious correlation.We also show thatearnings smoothing,in part,explains the higher earnings persistence of dividend-payingfirms.These findings are consistent with a firm’s dividend policy having an incrementalimpact on earnings-smoothing behavior.Keywords:earnings smoothing;dividend policy;real earnings management;accruals management;earnings persistence.JEL Classiﬁcations:M41;G35.INTRODUCTIONS urvey evidence indicates that dividend-payingﬁrms have a strong desire to maintain their historical dividend policy and that they target both dividend level and dividend payout ratio (Lintner1956;Baker and Powell2000;Baker,Veit,and Powell2001;Brav,Graham, Harvey,and Michaely2005).The importance of maintaining historical dividend level and payout ratio is supported by empirical research that shows a large negative stock market reaction to unexpected dividend decreases or omission and the stock market’s perception of the valueNan Liu is an Assistant Professor at Indiana University and Reza Espahbodi is a Professor at Washburn University.We appreciate the helpful comments from Lawrence Brown,Hassan Espahbodi,Lixin Huang,Siva Nathan,and Arianna Pinello.Also appreciated are the helpful suggestions from the participants at a Georgia State University workshop and the2012American Accounting Association Annual Meeting.We are grateful for the suggestions and guidance from Paul Grifﬁn(co-editor)and two anonymous reviewers.The remaining errors are ours.Submitted:April2012Accepted:March2014Published Online:March2014Corresponding author:Nan LiuEmail:liunan@501relevance of dividends (Aharony and Swary 1980;Healy and Palepu 1988;Ghosh and Woolridge 1989;Kallapur 1994;Grullon,Michaely,and Swaminathan 2002).When earnings change relative to the prior year,maintaining the dividend level leads to a change in the dividend payout ratio,while maintaining the payout ratio necessitates a change in the dividend level.‘‘Reducing variation in the change in earnings ’’(hereafter,earnings smoothing)can reduce the ﬂuctuations in the dividend payout ratio and allow the ﬁrm to avoid changing its dividend level.We thus argue that earnings smoothing is more important for dividend-paying ﬁrms than for other ﬁrms,and that they engage in more downward (upward)earnings management than non-payers in years of positive (negative)pre-managed earnings change to maintain their dividend policy.To test our argument,we regress our measures of earnings management on a dichotomous variable coded as 1(0)for dividend-paying ﬁrms (non-payers),pre-managed earnings change,and their interaction.In our regressions,we control for various factors that potentially affect ﬁrms’incentives to manage earnings and for differences in the life-cycle stage and ﬁnancial characteristics of dividend-paying ﬁing a sample of ﬁrm years obtained from Compustat’s ExecuComp database over the 18-year period 1992–2009,we ﬁnd that,while on average ﬁrms engage in earnings smoothing,dividend-paying ﬁrms engage in more earnings smoothing than non-payers through both real activities and accrual choices.We then run two separate regressions—one for ﬁrm years with positive and one for ﬁrm years with negative pre-managed earnings change—to determine if both upward and downward earnings management are at play.We ﬁnd that dividend-paying ﬁrms with positive (negative)pre-managed earnings change manage earnings down (up)more than non-payers.Our results are robust to alternative measures of earnings management,and are not due to spurious correlation.We conduct three additional tests to ensure that the results are driven by dividend-related incentives and not the differences in the economic characteristics of dividend-paying ﬁrms.First,we regress our measure of total earnings management on change in dividend policy and our control variables and ﬁnd that dividend-paying ﬁrms engage in signiﬁcantly less smoothing in years when they change their dividend level or payout ratio than in years when they do not.Second,using Chi-square tests we show that dividend-paying ﬁrms make less of a change in their dividend level and payout ratio in years when they report a small change in earnings (less than one percent)than in years when they do not.Third,because regular repurchasers are likely to have generally similar characteristics as regular dividend-paying ﬁrms,but do not have dividend-related incentives (Skinner and Soltes 2011),we repeat our tests using ﬁrms that make regular repurchases but do not pay dividends as a control group and ﬁnd that dividend-paying ﬁrms smooth earnings to a greater extent than repurchasers.The results of these three tests conﬁrm our ﬁnding that dividend policy drives earnings smoothing.Finally,we test whether the greater degree of earnings smoothing of the dividend-paying ﬁrms is,in part,responsible for their documented higher earnings persistence (e.g.,Skinner and Soltes 2011)by developing two models.The ﬁrst model replicates prior results to conﬁrm that dividend-paying ﬁrms have more persistent earnings.The second model modiﬁes the ﬁrst by breaking out current earnings into pre-managed earnings and earning management.The results support the conjecture that earnings smoothing,in part,drives the higher earnings persistence of dividend-paying ﬁrms.Overall,the results of our analyses are consistent with the notion that dividend-paying ﬁrms seek to smooth reported earnings to maintain their dividend policy,and indicate that earnings smoothing is more important for dividend-paying ﬁrms than for other ﬁrms.Our study makes several contributions to the literature.First,the study’s ﬁndings extend our understanding of dividend-policy driven earnings management.Kasanen,Kinnunen,and Niskanen (1996)document that Finnish ﬁrms manage earnings upward to report earnings high enough to pay out dividends in response to pressure from large institutional shareholders.Daniel,Denis,and Naveen (2008)ﬁnd that dividend level threshold drives upward accruals management when502Liu andEspahbodi Accounting HorizonsSeptember 2014pre-managed earnings fall short of last year’s dividends.We expand on Daniel et al.(2008)by(1) measuring earnings management relative to last year’s earnings,not last year’s dividends,and(2) showing that dividend policy drives earnings management in both directions.1Thus,our results provide further support to survey and empirical evidence about the importance of maintaining dividend policy.Second,prior studies on dividend-policy driven earnings management only examine accrual-based earnings management.Earnings are affected by the sum of real activities management and accruals management.Cohen and Zarowin(2010)and Zang(2012)ﬁnd that ﬁrms manage earnings through real activities in addition to,or as a substitute to,accrual-based activities.Zang(2012)in fact argues that real activities manipulation occurs during theﬁscal year. At the end of the year,managers adjust the level of accrual-based earnings management based on the outcome of real activities manipulation.If managers use real activities management in addition to,or as a substitute to,accrual-based earnings management,examining only one earnings management technique at a time cannot explain the overall effect of earnings management activities (Fields,Lyz,and Vincent2001;Zang2012).By documenting that both real activities and accrual choices are at play,therefore,we provide additional evidence on dividend-policy driving earnings management.Third,and as important,we provide evidence that the greater earnings persistence of dividend-payingﬁrms that previous studies document(e.g.,Skinner and Soltes2011)is in part driven by earnings management,as conjectured by Dechow,Ge,and Schrand(2010b).That is,we show that dividend-payingﬁrms have greater earnings persistence than non-payers,partially because they smooth earnings to a greater extent to maintain their dividend policy.Thisﬁnding has implications for studies that examine the earnings quality of dividend-payingﬁrms.Finally,professional standards require the auditor to plan and perform the audit to obtain reasonable assurance about whether theﬁnancial statements are free of material misstatement, whether caused by errors or fraud.Our research suggests the company’s dividend policy as a risk factor(in the form of incentive or pressure to manipulate earnings)for the auditor to consider. Conversations with two partners at Big4accountingﬁrms conﬁrm that while auditors typically look to understand whether‘‘earnings pressures’’exist that may provide management with the incentive and attitude to undertake inappropriate behavior(including the smoothing of earnings), they have not speciﬁcally thought about the company’s dividend policy driving such behavior.We proceed as follows.The second section discusses related research and develops our hypothesis.In the third section,we describe our data and methodology.The fourth section analyzes the association between dividend policy and earnings smoothing.Theﬁfth section examines whether the results are in fact driven by dividend policy.We evaluate the association between earnings smoothing and earnings persistence of dividend-payingﬁrms in the sixth section.The results of supplemental tests are reported in the seventh section.Finally,the eighth section concludes.RELATED LITERATURE AND HYPOTHESIS DEVELOPMENTEarnings Management LiteratureWe focus on three sets of studies that relate to our research questions.Theﬁrst set examines the upward real and accruals earnings management to meet or beat important earnings benchmarks, such as positive earnings level,positive earnings change,analyst forecast,and prior year’s 1Measuring earnings smoothing relative to last year’s earnings will only smooth the dividend payout ratio if dividend levels remain constant across time.We believe this is a reasonable assumption.Does Dividend Policy Drive Earnings Smoothing?503Accounting Horizons September2014dividends (Burgstahler and Dichev 1997;Degeorge,Patel,and Zeckhauser 1999;Burgstahler and Eames 2006;Roychowdhury 2006;Daniel et al.2008).We add to this literature by demonstrating that earnings smoothing is more important for dividend-paying ﬁrms than for other ﬁrms.Another set of studies explores upward and downward earnings management to smooth earnings.Graham,Harvey,and Rajgopal (2005)ﬁnd that 97percent of the surveyed executives prefer smooth earnings,and 78percent of the surveyed executives admit to giving up economic value in exchange for smooth earnings.Empirical studies have documented various means through which ﬁrms smooth their reported earnings, e.g.,deferring or accelerating research and development expenses (R&D)(Perry and Grinaker 1994)and using accounting rules for valuing retained interest from securitizations (Dechow,Myers,and Shakespeare 2010a ).Empirical studies also have documented varying incentives for earnings smoothing.For example,Bergstresser and Philippon (2006)and Cheng and Warﬁeld (2005)ﬁnd that accruals management is more pronounced in the presence of higher levels of stock-based incentives;and J.Gaver,K.Gaver,and Austin (1995)show that managers manipulate earnings to maximize bonus compensation.Our paper contributes to this subset of literature by providing evidence that dividend policy has an incremental effect on earnings smoothing.Finally,the third set of studies relates to earnings persistence of dividend-paying ﬁrms.Healy and Palepu (1988)ﬁnd that dividend-initiating ﬁrms show more persistent earnings than dividend-omitting ﬁrms,suggesting there is less need for earnings management.Chen,Shevlin,and Tong (2007)ﬁnd evidence that the initiation of,and increase in,dividend payments is associated with investors perceiving earnings to be of higher quality.Skinner and Soltes (2011)also document higher earnings persistence for dividend-paying ﬁrms.While the above studies document that the earnings of dividend-paying ﬁrms is more persistent,they do not investigate whether earnings management contributes to the higher earnings persistence.As Dechow et al.(2010b ,351)conjecture,the earnings of dividend-paying ﬁrms may be more persistent because these ﬁrms engage in more extensive earnings smoothing.By showing that earnings smoothing is at least partially responsible for the documented greater earnings persistence of dividend-paying ﬁrms,we provide empirical support for this conjecture.2Dividends LiteratureIn his pioneering survey of 28well-established companies,Lintner (1956)ﬁnds that managers are reluctant to cut dividends and they target long-term payout ratios when making dividend decisions.Twenty-six out of the 28sample companies had a speciﬁc target payout ratio that did not change over long periods of time.Many survey studies have been conducted since Lintner’s.Baker,Farrelly,and Edelman (1985)and Baker and Powell (1999)survey chief ﬁnancial ofﬁcers of New York Stock Exchange ﬁrms and ﬁnd that managers generally agree that their ﬁrms should avoid making dividend changes that might soon be reversed,and that their ﬁrms should have target payout ratios.Baker and Powell (2000)and Baker et al.(2001)ﬁnd that the desire to maintain a given dividend payout ratio is a moderately important factor relative to dividend level in determining dividend policy,and about half of the responding ﬁrms have explicit target payout ratios.Brav et al.(2005)investigate payout policies in the 21st century.Their analysis indicates that about 90percent of dividend-paying ﬁrms have a strong desire to avoid dividend reductions and to 2This evidence provides empirical support to what is implied from the ﬁnding of Francis,LaFond,Olsson,and Schipper (2004)that earnings persistence is positively associated with earnings smoothness,meaning any earnings ﬁgure that is smoother will also be more persistent.And,that since the reported earnings for dividend-paying ﬁrms are smoothed relative to pre-managed earnings (and to a greater extent than for non-dividend-paying ﬁrms),they should be relatively more persistent than pre-managed earnings (and to a greater extent than for non-dividend-paying ﬁrms).504Liu andEspahbodi Accounting HorizonsSeptember 2014smooth dividend streams from year to year.Eighty-four percent of the executives try to maintain consistency with historical dividend policies.Brav et al.’s(2005)analysis shows that maintaining dividend level is the main variable in deciding dividend policy,and payout ratio is of secondary importance.It also shows that managers believe that dividend decisions convey information to the market and that dividend reductions have negative consequences.3Overall,the results of survey studies suggest thatﬁrms target both dividend level and dividend payout ratio.The survey results also suggest that managers believe that dividend policy is value-relevant.The importance of maintaining historical dividend policy is supported by empirical research that shows a large negative stock market reaction to unexpected dividend decreases or omission (Aharony and Swary1980;Healy and Palepu1988;Ghosh and Woolridge1989;Grullon et al. 2002)and the stock market’s perception of the value relevance of dividends.In relation to the latter, Kallapur(1994)ﬁnds that,after controlling for earnings persistence and riskiness,and riskless interest rates,the earnings response coefﬁcient increases as aﬁrm’s payout ratio gets larger.The results of these empirical studies suggest that dividends constitute implicit contracts between shareholders and management and,as such,managers have strong incentives to smooth earnings to maintain the dividend level and payout ratio.By documenting that dividend-payingﬁrms engage in more earnings smoothing,we provide support to survey and empirical evidence about the importance of maintaining dividend policy.Hypothesis DevelopmentPrior studies on earnings managementﬁnd thatﬁrms,in general,have incentives to manage earnings downward when pre-managed earnings exceed last year’s earnings and upward when pre-managed earnings fall short of last year’s earnings(Bartov1993;Perry and Grinaker1994;Graham et al.2005;Dechow et al.2010a).We hypothesize that earnings smoothing is more important for dividend-payingﬁrms and that dividend-payingﬁrms engage in more downward,as well as upward,earnings management than non-payers.The intuition for our hypothesis is as follows.Survey and empirical studies(presented above)suggest that dividend-payingﬁrms have a strong desire to maintain their historical dividend policy and they target both dividend level and payout ratio.In years of positive pre-managed earnings change,maintaining the dividend level would lead to a decrease in the payout ratio.And,maintaining the payout ratio would require the ﬁrm to increase its dividend level,raising the benchmark for future periods.Manipulating earnings downward,therefore,helps dividend-payingﬁrms to maintain(avoid changing)their dividend level and payout ratio.On the other hand,in years of negative pre-managed earnings change,maintaining the dividend level would lead to an increase in the payout ratio.And,maintaining the payout ratio would require theﬁrm to decrease its dividend level,exposing theﬁrm to a potential negative stock market reaction.Manipulating earnings upward,therefore,helps dividend-payingﬁrms to maintain their dividend level and payout ratio.Relative to non-payers,then,we expect dividend-payingﬁrms to have incremental incentives to smooth reported earnings due to the desire to maintain their dividend level and dividend payout 3Mukherjee(2009,157)concludes:‘‘Researchers consistently report that abnormal return of a dividend-change announcement is of the same sign as the sign of the dividend change.Although researchers have advanced several hypotheses to explain this phenomenon,two highly researched and competing hypotheses are the cash ﬂow signaling hypothesis and the free cashﬂow hypothesis.According to the cashﬂow signaling hypothesis,the stock price moves in the same direction as the dividend change because dividend changes convey information about theﬁrm’s future growth opportunities.The free cashﬂow hypothesis suggests that price reacts favorably to the announcement of a dividend increase because dividend increase reduces the agency cost of free cashﬂow.Similarly,the stock price reacts negatively to an announcement of reduced dividends because the potential for overinvestment increases.’’Does Dividend Policy Drive Earnings Smoothing?505Accounting Horizons September2014ratio.Further,both downward and upward earnings management should be at play.That is,dividend-paying ﬁrms with positive (negative)pre-managed earnings change are expected to engage in more downward (upward)earnings management than non-payers.Several earnings management studies (e.g.,Burgstahler and Dichev 1997;Cohen and Zarowin 2010;Zang 2012)show that ﬁrms use real activities in addition to,or in lieu of,accrual choices to manage earnings.Managers may rather manipulate earnings through real activities because real activities manipulation is less likely to draw auditor or regulator scrutiny (Dechow and Skinner 2000;Graham et al.2005;Roychowdhury 2006;Cohen and Zarowin 2010).On the other hand,managers would likely not know the impact of real activities manipulation on earnings until the end of the ﬁscal year,at which time they may have to adjust the level of accruals (Cohen and Zarowin 2010;Zang 2012).The costs associated with real activities manipulation may also create an incentive for managers to use accruals manipulation instead (Cohen and Zarowin 2010).We thus expect dividend-paying ﬁrms to use both accruals and real activities to smooth earnings.Formally stated,our hypothesis is:H:Dividend-paying ﬁrms engage in more earnings smoothing than non-payers through realactivities and accruals.DATA AND METHODOLOGYAppendix A describes the variables used in this study.Like Daniel et al.(2008),our sample consists of all publicly traded ﬁrms in Compustat’s ExecuComp database,because it includes managerial compensation data,which have been shown to be important determinants of earnings management.Our study,however,spans over the period 1992to 2009,whereas Daniel et al.’s (2008)covers the period 1992–2005.We limit the sample to ﬁrms with sufﬁcient annual data to calculate the variables listed in Appendix A.Consistent with prior literature,we omit ﬁrms in regulated industries and ﬁnancial institutions (Roychowdhury 2006;Daniel et al.2008).To control for outliers,we delete ﬁrm years with dividends at the extreme 99th percentile levels and all the other variables at the 1st and 99th percentiles of their respective distributions (Burgstahler and Dichev 1997;Dechow,Kothari,and Watts 1998;Dechow,Richardson,and Tuna 2003).Also,to estimate normal levels of cash ﬂows,production costs,discretionary expenditures,and accruals,we require at least eight observations in each two-digit SIC industry for each year (Cohen,Dey,and Lys 2008;Cohen and Zarowin 2010).Our ﬁnal sample includes 13,826ﬁrm years.Because earnings is affected by both real activities and accrual choices,we deﬁne total earnings management as the sum of real earnings management and abnormal total accruals.Prior studies (Roychowdhury 2006;Cohen and Zarowin 2010)consider three measures of real earnings management:abnormal cash ﬂows,abnormal production costs,and abnormal discretionary expenditures.We deﬁne real earnings management as the negative of the sum of abnormal cash ﬂows and abnormal discretionary expenditures so that a higher value suggests more upward earnings management (Cohen and Zarowin 2010).We do not include abnormal production costs in our measure of real earnings management for our main tests because,as stated in Cohen and Zarowin (2010,9),the same activities that lead to abnormally high production costs also lead to abnormally low CFO;thus,adding abnormal production costs leads to double counting.44However,to be consistent with Cohen and Zarowin (2010)and Zang (2012),we also measure real earnings management as the sum of abnormal production cost and negative of abnormal discretionary expenditures.As another sensitivity test,we measure real earnings management as the negative of abnormal cash ﬂows for the reasons stated in in the ‘‘Supplemental Tests ’’section.The results of both tests are discussed in the ‘‘Supplemental Tests ’’section.506Liu andEspahbodi Accounting HorizonsSeptember 2014To estimate normal cashﬂows,normal production costs,and normal discretionary expenditures,we use the models developed by Dechow et al.(1998)and implemented in other earnings management papers(Roychowdhury2006;Cohen et al.2008;Cohen and Zarowin2010; Zang2012).Normal total accruals is estimated using the cross-sectional model of Jones(1991)and adjusting forﬁnancial performance because Kothari,Leone,and Wasley(2005)ﬁnd that it is important to control forﬁrm performance when estimating discretionary accruals.5Speciﬁcally,we develop the following four regressions:CFO t=Assets tÀ1¼a0ð1=Assets tÀ1Þþa1ðSales t=Assets tÀ1Þþa2ðD Sales t=Assets tÀ1Þþ´e t:ð1ÞPROD t=Assets tÀ1¼a0ð1=Assets tÀ1Þþa1ðSales t=Assets tÀ1Þþa2ðD Sales t=Assets tÀ1Þþa3ðD Sales tÀ1=Assets tÀ1Þþ´e t:ð2ÞDISX t=Assets tÀ1¼a0ð1=Assets tÀ1Þþa1ðSales tÀ1=Assets tÀ1Þþ´e t:ð3ÞTA t=Assets tÀ1¼a0ð1=Assets tÀ1Þþa1ðD Sales t=Assets tÀ1Þþa2ðPPE t=Assets tÀ1Þþa3ðIBEI t=Assets tÀ1Þþ´e t:ð4ÞIn the above regressions,CFO is cashﬂow from operations as reported on the statement of cashﬂows;Assets is total assets;Sales is total revenues;PROD is production costs,deﬁned as the sum of cost of goods sold and change in the inventory;DISX is discretionary expenditures,deﬁned as the sum of advertising expenses,R&D expenses,and selling,general and administrative expenses(SG&A);IBEI is income before extraordinary items;TA is total accruals,deﬁned as IBEI less CFO;and PPE is property,plant,and equipment.Each regression is estimated separately for each two-digit SIC industry for each year.The abnormal cashﬂows,abnormal production costs(APROD),abnormal discretionary expenditures,and abnormal total accruals(ATA)are computed as the difference between the actual values and the normal levels predicted(i.e.,they are the residuals)from Regressions(1)through (4).6Abnormal cashﬂows and abnormal discretionary expenditures are multiplied byÀ1(and denoted as ACFO and ADISX,respectively)so that a higher value in all cases indicates greater upward earnings management.We deﬁne real earnings management as the sum of ACFO and ADISX,and total earnings management(TEM)as ACFO plus ADISX plus ATA.Our hypothesis examines whether dividend-payingﬁrms engage in more earnings smoothing than non-payers through real activities and accruals management.It is tested using the following regression:5Since previous research has shown that measures of abnormal accruals are more likely to be misspeciﬁed for ﬁrms with extreme levels of performance(Dechow,Sloan,and Sweeney1995)and for fast growingﬁrms (McNichols2000;Dechow et al.2003),we re-estimate total accruals using change in sales;property,plant,and equipment;cashﬂow from operations;and book-to-market ratio as independent variables.The results are qualitatively the same.6Abnormal operating cashﬂows can be the result of real activities to manage earnings(as discussed above)or opportunistic classiﬁcation of cashﬂows within the Statement of Cash Flows.Both activities result in‘‘abnormal cashﬂows,’’even though classiﬁcation shifting has no effect on reported earnings,which is what we intend to measure.That is,classifying an investing cashﬂow as if it were operating,or vice versa,would affect reported operating cashﬂows but would have no effect on reported earnings.Any misclassiﬁcations create noise and bias our results againstﬁnding a signiﬁcant difference in earnings smoothing behavior between payers and non-payers.Further,misclassiﬁcations do not affect other measures of real earnings management:ADISX and APROD.We thank the reviewer who brought this point to our attention.Does Dividend Policy Drive Earnings Smoothing?507Accounting Horizons September2014EM ¼b 0þb 1DP þb 2PMEC þb 3PMEC ÃDP þb 4STOCK þb 5BONUSþb 6PMEC ÃSTOCK þb 7PMEC ÃBONUS þb 8BTM þb 9SIZE þb 10LEV þb 11REþb 12AGE þb 13GROWTH þb 14CAPX þb 15INDYR þe :ð5ÞEM is the earnings management proxy,and is initially deﬁned as TEM to capture the total effects of real activities and accruals management.To shed light on whether dividend-paying ﬁrms engage in income smoothing through real activities,accrual-based activities,or both,and in the case of real activities,whether they do so through revenues or costs,we also estimate the above regression,deﬁning EM as ACFO,APROD,ADISX,or ATA.7The independent variables in Regression (5)are as follows.DP is the dividend-paying ﬁrm dummy,which equals 1if the ﬁrm pays dividends in both the prior year and the current year,and 0otherwise;it is included to control for any systematic difference between payers and non-payers.8PMEC is pre-managed earnings change,and equals earnings change minus the earnings management proxy:TEM,ACFO,APROD,ADISX,or ATA .The rest of the variables are intended to control for factors that inﬂuence management’s incentives to manage earnings and for differences in the life-cycle stage and ﬁnancial characteristics of dividend-paying ﬁrms.Stock incentive ratio (STOCK )and bonus (BONUS )control for compensation incentives for chief ﬁnancial ofﬁcers and chief executive ofﬁcers (Bergstresser and Philippon 2006;Cohen et al.2008;Jiang,Petroni,and Wang 2010).As with Daniel et al.(2008),we also control for growth opportunities (BTM ),ﬁrm size (SIZE ),leverage (LEV ),and retained earnings (RE ).Further,since prior research (e.g.,Healy and Palepu 1988;Grullon et al.2002;Skinner and Soltes 2011)has established that the life-cycle stage and ﬁnancial characteristics of dividend-paying ﬁrms differ from non-payers,9we add age (AGE ),sales growth (GROWTH ),and capital expenditures (CAPX )to our regression (Anthony and Ramesh 1992;Tian,Collins,and Hribar 2009).Two-digit SIC and year dummies (INDYR )are also included in the regression.Evidence of earnings smoothing would be provided by a negative coefﬁcient on PMEC,and evidence that dividend-paying ﬁrms engage in more earnings smoothing would be provided by a negative coefﬁcient on PMEC ÃDP .All p-values reported are calculated using two-tailed tests,unless indicated otherwise.RESULTSThe descriptive statistics for our sample and the correlation coefﬁcients among the earnings management measures are reported in Table 1.In Panel A,we report the descriptive statistics for the dividend-paying ﬁrms and non-payers separately.Similar to Daniel et al.(2008),about 50percent of the whole sample are dividend-paying ﬁrms (6,791over 13,826),and the average dividends paid is about $100million (not reported in the table).While the average dividend-paying ﬁrm has over $4.7billion in sales and $4.5billion in assets,the average non-payer ﬁrm has less than $1.7billion in sales and $1.6billion in assets.Dividend-paying ﬁrms are also more proﬁtable than non-payers 7Reporting results for the three individual measures of real earnings management (ACFO,APROD,and ADISX )would also avoid possible dilution of the potentially different implications of the three individual variables for earnings by using an aggregated earnings management measure (Cohen and Zarowin 2010,9).8Non-payers include ﬁrms that paid dividends in prior year but not in the current year,and vice versa .To address the concern that this classiﬁcation of ﬁrms as payers and non-payers may have driven the results,we re-run our regression using a new sample excluding these ﬁrms (Daniel et al.2008).Our results hold using this new sample.9Because of differences in the dividend-paying ﬁrms’life-cycle stage and ﬁnancial characteristics,any abnormal accruals or cash ﬂows are likely to have the effect of smoothing earnings regardless of whether managers are using discretion in their accounting choices,or real activities.Also,these differences in ﬁnancial characteristics can affect the beneﬁts and costs—unrelated to dividends—of managing earnings.We are thankful to one of the reviewers for bringing these issues up and for suggesting tests to address them.508Liu andEspahbodiAccounting HorizonsSeptember 2014。

ò á êúD Y× × óò ú úD ò ìêì

C e n t r u m v o o r W i s k u n d e e n I n f o r m a t i c aPNAProbability, Networks and AlgorithmsProbability, Networks and AlgorithmsAn image retrieval system based on adaptive waveletliftingP.J. Oonincx, P.M. de ZeeuwR EPORT PNA-R0208 M ARCH 31, 2002CWI is the National Research Institute for Mathematics and Computer Science. It is sponsored by the Netherlands Organization for Scientific Research (NWO).CWI is a founding member of ERCIM, the European Research Consortium for Informatics and Mathematics. CWI's research has a theme-oriented structure and is grouped into four clusters. Listed below are the names of the clusters and in parentheses their acronyms.Probability, Networks and Algorithms (PNA)Software Engineering (SEN)Modelling, Analysis and Simulation (MAS)Information Systems (INS)Copyright © 2001, Stichting Centrum voor Wiskunde en InformaticaP.O. Box 94079, 1090 GB Amsterdam (NL)Kruislaan 413, 1098 SJ Amsterdam (NL)Telephone +31 20 592 9333Telefax +31 20 592 4199ISSN 1386-3711CWIP.O.Box94079,1090GB Amsterdam,The NetherlandsPatrick.Oonincx,Paul.de.Zeeuw@cwi.nl1.I NTRODUCTIONContent-based image retrieval(CBIR)is a widely used term to indicate the process of retrieving desired images from a large collection on the basis of features.The extraction process should be automatic(i.e. no human interference)and the features used for retrieval can be either primitive(color,shape,texture) or semantic(involving identity and meaning).In this paper we conﬁne ourselves to grayscale images of objects against a background of texture.This class of images occurs for example in various databases created for the combat of crime:stolen objects[21],tyre tracks and shoe sole impressions[1].In this report we restrict ourselves to the following problem.Given an image of an object(a so-called query)we want to identify all images in a database which contain the same object irrespective of translation,rotation or re-sizing of the object,lighting conditions and the background texture.One of the most classical approaches to the problem of recognition of similar images is by the use of moment invariants[11].This method is based on calculating moments in both the-and-direction of the image density function up to a certain order.Hu[11]has shown that certain homogeneous polynomials of these moments can be used as statistical quantities that attain the same values for images that are of the same class,i.e.,that can be obtained by transforming one single original image(afﬁne transforms and scaling).However,this method uses the fact that such images consists of a crisp object against a neutral background.If the background contains‘information’(noise,environment in a picture)the background should be the same for all images in one class and should also be obtained from one background using the same transformations.In general this will not be the case.The kind of databases we consider in this paper consists of classes of different objects pasted on different background textures.To deal with the problem of different backgrounds one may use someﬁltering process as a preprocessing step.In Do et al.[7]the wavelet transform modulus maxima is used as such preprocessing step.To measure the(dis)similarity between images,moments of the set of maxima points are determined(per scale)and subsequently Hu’s invariants are computed.Thus,each image is indexed by a vector in the wavelet maxima moment space.By its construction,this vector predominantly represents shapes.In this report we propose to bring in adaptivity by using different waveletﬁlters for smooth and unsmooth parts of the image.Theﬁlters are used in the context of the(redundant)lifting scheme[18].The degree2of”smoothness”is determined by measuring the relative local variance(RLV),which indicates whether locally an image behaves smoothly or not.Near edges low order predictionﬁlters are activated which lead to large lifting detail coefﬁcients along thin curves.At backgrounds of texture high order predictionﬁlters are activated which lead to negligible detail coefﬁcients.Moments and subsequently moment invariants are computed with respect to these wavelet detail coefﬁcients.With the computation of the detail coefﬁcients a certain preprocessing is required to make the method robust for shifts over a non-integer number of gridpoints.Further we introduce the homogeneity condition which means that we demand a homogeneous change in the elements of a feature vector if the image seen as a density distribution is multiplied by a scalar.The report is organized as follows.In Sections2and3we discuss the lifting scheme and its adaptive version.Section4is devoted to the topic of afﬁne invariances of the coefﬁcients obtained from the lifting scheme.In Section5the method of moment invariants is recapitulated.The homogeneity condition is in-troduced which leads to a normalization.Furthermore,the mathematical consequences for the computation of moments of functions represented byﬁelds of wavelet(detail)coefﬁcients are investigated.Section6 discusses various aspects of theﬁnal retrieval algorithm,including possible metrics.Numerical results of the algorithm for a synthetic database are presented in Section7.Finally,some conclusions are drawn in Section8.2.T HE L IFTING S CHEMEThe lifting scheme as introduced by Sweldens in1997,see[18],is a method for constructing wavelet transforms that are not necessarily based on dilates and translates of one function.In fact the construction does not rely on the Fourier transform which makes it also suitable for functions on irregular grids.The transform also allows a fully in-place calculation,which means that no auxiliary memory is needed for the computations.The idea of lifting is based on splitting a given set of data into two subsets.In the one-dimensional case this can mean that starting with a signal the even and odd samples are collected into two new signals,i.e.,,where and,for all.The next step of the lifting scheme is to predict the value of given the sequence.This prediction uses a prediction operator acting on.The predicted value is subtracted from yielding a ‘detail’signal.An update of the odd samples is needed to avoid aliassing problems.This update is performed by adding to the sequence,with the update operator.The lifting procedure can also be seen as a2-bandﬁlter bank.This idea has been depicted in Figure1.The inverse lifting scheme can/.-,()*+/.-,()*+/.-,()*+/.-,()*+/.-,()*+Figure1:The lifting scheme:splitting,predicting,updating.immediately be found by undoing the prediction and update operators.In practice,this comes down in Figure1to simply changing each into a and vice versa.Compared to the traditional wavelet transform the sequence can be regarded as detail coefﬁcients of the signal.The updated sequence can be regarded as the approximation of at a coarse ing again as input for the lifting scheme yields detail and approximation signals at lower resolution levels.We observe that every discrete wavelet transform can also be decomposed into a ﬁnite sequence of lifting steps[6].To understand the notion of vanishing moments in terms of the prediction and update operators,we com-pare the lifting scheme with a two-channelﬁlter bank with analysisﬁlters(lowpass)and(highpass) and synthesisﬁlters and.Such aﬁlter bank has been depicted in Figure2.Traditionally we say that a389:;?>=<89:;?>=</.-,()*+89:;?>=<89:;?>=<Figure2:Classical2-band analysis/synthesisﬁlter bank.ﬁlter bank has primal and vanishing moments ifandwhere denotes the space of all polynomial sequences of order.Given theﬁlter operators and, the correspondingﬁlters and can be computed by(2.1)(2.2)where and denote theﬁlter sequences of the operators and respectively.In[12]Kovacevic and Sweldens showed that we can always use lifting schemes with primal vanishing moments and dual vanishing moments by taking for a Nevilleﬁlter of order with a shift and for half the adjoint of a Nevilleﬁlter of order and shift,see[17].Example2.1We take and.With these operators we getTheﬁlter bank has only one vanishing moment.The lifting transform corresponds in this example to the Haar wavelet transform.Example2.2For more vanishing moments,i.e.,smoother approximation signals,we takeThese Nevilleﬁlters give rise to a2-channelﬁlter bank with2primal and4dual vanishing moments. The lifting scheme can also be used for higher dimensional signals.For these signals the lifting scheme consists of channels,where denotes the absolute value of the determinant of the dilation matrix,that is used in the corresponding discrete wavelet transform.In each channel the signal is translated along one of the coset representatives from the unit cell of the corresponding lattice,see[12]. The signal in theﬁrst channel is then used for predicting the data in all other channels by using possible different prediction operators.Thereafter theﬁrst channel is updated using update operators on the other channels.Let us consider an image as a two-dimensional signal.An important example of the lifting scheme applied to such a signal is one that involves channels().We subdivide the lattice on which the signal has been deﬁned into two sets on quincunx grids,see Figure3.This division is also called ”checkerboard”or”red-black”division.The pixels on the red spots()are used to predict the samples on the black spots(),while updating of the red spots is performed by using the detailed data on the black spots.An example of a lifting transform with second order prediction and updateﬁlters is given by4Figure3:A rectangular grid composed of two quincunx grids.order200000040000060008Table1:Quincunx Nevilleﬁlter coefﬁcientsThe algorithm using the quincunx lattice is also known as the red-black wavelet transform by Uytterhoeven and Bultheel,see[20].In general can be written as(2.3) with a subset of mod and,a set of coefﬁcients in. In this case a general formula for reads(2.4)with depending on the number of required primal vanishing moments.For several elements in the coefﬁcients attain the same values.Therefore we take these elements together in subsets of, i.e.,(2.5)Table1indicates the values of all,for different values of(2through8)when using quincunx Nevilleﬁlters,see[12],which are theﬁlters we use in our approach.We observe that and so a44tapsﬁlter is used as prediction/update if the requiredﬁlter order is8.For an illustration of the Nevilleﬁlter of order see Figure4.Here the numbers,correspond to the values of theﬁlter coefﬁcients as given in and respectively at that position.The left-handﬁlter can be used to transform a signal deﬁned on a quincunx grid into a signal deﬁned on a rectangular grid,the right-hand ﬁlter is the degrees rotated version of the left-handﬁlter and can be used to transform a signal from a rectangular grid towards a quincunx grid.We observe that the quincunx lattice yields a non separable2D-wavelet transform,which is also sym-metric in both horizontal and vertical direction.Furthermore,we only need one prediction and one update operator for this2D-lifting scheme,which reduces the number of computations.The prediction and update operators for the quincunx lattice do also appear in schemes for other lattices, like the standard2D-separable lattice and the hexagonal lattice[12].The algorithm for the quincunx lattice can be extended in a rather straightforward way for these two other well-known lattices.5111122222222111122222222Figure 4:Neville ﬁlter of order :rectangular (left)and quincunx (right)Figure 5illustrates the possibility of the use of more than channels in the lifting scheme.Herechannels are employed,using a four-colour division of the 2D-lattice.It involves (interchange-able)prediction steps.Each of the subsets with colours ,and respectively,is predicted by application of a prediction ﬁlter on the subset with colour .Figure 5:Separable grid (four-colour division).3.A DAPTIVE L IFTINGWhen using the lifting scheme or a classical wavelet approach,the prediction/update ﬁlters or wavelet/scaling functions are chosen in a ﬁxed fashion.Generally they can be chosen in such way that a signal is approximated with very high accuracy using only a limited number of coefﬁcients.Discontinuities mostly give rise to large detail coefﬁcients which is undesirable for applications like compression.For our purpose large detail coefﬁcients near edges in an images are desirable,since they can be identiﬁed with the shape of objects we want to detect.However,they are undesirable if such large coefﬁcients are related to the background of the image.This situation occurs if a small ﬁlter is used on a background of texture that contains irregularities locally.In this case a large smoothing ﬁlter gives rise to small coefﬁcients for the background.These considerations lead to the idea of using different prediction ﬁlters for different parts of the signal.The signal itself should indicate (for example by means of local behavior information)whether a high or low order prediction ﬁlter should be used.Such an approach is commonly referred to as an adaptive approach.Many of these adaptive approaches have been described already thoroughly in the literature,e.g.[3,4,8,13,19].In this paper we follow the approach proposed by Baraniuk et al.in [2],called the space-adaptive approach.This approach follows the scheme as shown in Figure 6.After splitting all pixels of a given image into two complementary groups and (red/black),thepixels inare used to predict the values in .This is done by means of a prediction ﬁlter acting on ,i.e.,.In the adaptive lifting case this prediction ﬁlter depends on local information of the image pixels .Choices for may vary from high to low order ﬁlters,depending on the regularity of the image locally.For the update operator,we choose the update ﬁlter that corresponds to the prediction ﬁlter with lowest order from all possible to be chosen .The order of the update ﬁlter should be lower or equal to the order of the prediction ﬁlter as a condition to provide a perfect reconstruction ﬁlter bank.As with the classical wavelet ﬁlter bank approach,the order of the prediction ﬁlter equals the number of dual vanishing6/.-,()*+/.-,()*+Figure6:Generating coefﬁcients via adaptive liftingmoments while the order of the updateﬁlter equals the number of primal vanishing moments,see[12].The above leads us to use a second order Nevilleﬁlter for the update step and an th order Nevilleﬁlter for the prediction step,where.In our application the reconstruction part of the lifting scheme is not needed.In[2],Baraniuk et al.choose to start the lifting scheme with an update operator followed by an adaptively chosen prediction operator.The reason for interchanging the prediction and update operator is that this solves stability and synchronization problems in lossy coding applications.We will not discuss this topic in further detail,but only mention that they took for theﬁlters of and the branch of the Cohen-Daubechies-Feauveau(CDF)ﬁlter family[5].The order of the predictionﬁlter was chosen to be,,or,depending on the local behavior of the signal.Theﬁlter orders of the CDFﬁlters in their paper correspond to theﬁlter orders of the Nevilleﬁlters we are using in our approach.Relative local variance We propose a measure on which the decision operator in the2D adaptive lifting scheme can be based on,namely the relative local variance of an image.This relative local variance(RLV) of an image is given byrlv var(3.1) with(3.2) For the window size we take,since with this choice all that are used for the prediction of contribute to the RLV for,even for the8th order Nevilleﬁlter.When the RLV is used at higher resolution levels weﬁrst have to down sample the image appropriately.Theﬁrst time the predictionﬁlter is applied(to the upper left pixel)we use the8th order Nevilleﬁl-ter on the quincunx lattice as given in Table1.For all other subsequent pixels to be predicted,we ﬁrst compute rlv.Then quantizing the values of the RLV yields a decisionmap indicating which predictionﬁlter should be used at which positions.Values above the highest quantizing level induce a 2nd order Nevilleﬁlter,while values below the lowest quantizing levels induce an8th order Nevilleﬁl-ter.For the quantizing levels we take multiples of the mean of the RLV.Test results have shown that rlv rlv rlv are quantizing levels that yield a good performance in our application.In Figure7we have depicted an image(left)and its decision map based on the RLV(right).4.A FFINE I NVARIANT L IFTINGAlthough both traditional wavelet analysis and the lifting scheme yield detail and approximation coefﬁ-cients that are localised in scale and space,they are both not translation invariant.This means that if a signal or image is translated along the grid,its lifting coefﬁcients may not be just be given by a translation of the original coefﬁcients.Moreover,in general the coefﬁcients will attain values in the same range of the original values(after translation),but they will be totally different.7a) original image b) decision map (RLV)Figure7:An object on a wooden background and its rel.local variance(decision map):white=8th order, black=2nd order.For studying lifting coefﬁcients of images a desirable property would also be invariance under reﬂections and rotations.However,for these two transformations we have to assumeﬁrst that the values of the image on the grid points is not affected a rotation or reﬂection.In practice,this means that we only consider reﬂections in the horizontal,the vertical and the diagonal axis and rotations over multiples of.4.1Redundant LiftingFor the classical wavelet transform a solution for translation invariance is given by the redundant wavelet transform[15],which is a non-decimated wavelet(at all scales)transform.This means that one gets rid of the decimation step.As a consequence the data in all subbands have the same size as the size as the input data of the transform.Furthermore,at each scaling level,we have to use zero padding to theﬁlters in order to keep the multiresolution analysis consistent.Not only more memory is used by the redundant transform,also the computing complexity of the fast transform increases.For the non-decimated transform computing complexity is instead of for the fast wavelet transform.Whether the described redundant transform is also invariant under reﬂections and rotations depends strongly on theﬁlters(wavelets)themselves.Symmetry of theﬁlters is necessary to guarantee certain rotation and reﬂection invariances.This is a condition that is not satisﬁed by many well-known wavelet ﬁlters.The redundant wavelet transform can also be translated into a redundant lifting scheme.In one dimension this works out as follows.Instead of partitioning a signal into and we copy to both and.The next step of the lifting scheme is to predict by(4.1) The predictionﬁlter is the sameﬁlter as used for the non-redundant case,however now it depends on the resolution level,since at each level zero padding is applied to.This holds also for the updateﬁlters .So,the update step reads(4.2)For higher dimensional signals we copy the data in all channels of the usedﬁlter bank. Next the-channel lifting scheme is applied on the data,using zero padding for theﬁlters at each resolu-8................ ........Figure8:Tree structure of the-channel lifting scheme.tion level.Remark,that for each lifting step in the redundant-channel lifting scheme we have to store at each scaling level times as much data as in the non-redundant scheme,see Figure8.We observe that in our approach Nevilleﬁlters on a quincunx lattice are used.Due to their symmetry properties,see Table1,the redundant scheme does not only guarantee translation invariance,but also invariance under rotations over multiples of and reﬂections in the horizontal,vertical and diagonal axis is assured.Invariance under other rotations and reﬂections can not be guaranteed by any prediction and updateﬁlter pair,since the quincunx lattice is not invariant under these transformations.4.2An Attempt to Avoid Redundancy:Fixed Point LiftingAs we have seen the redundant scheme provides a way ofﬁnding detail and approximation coefﬁcients that are invariant under translations,reﬂections and rotations,under which the lattice is also invariant.Due to its redundancy this scheme is stable in the sense that it treats all samples of a given signal in the same way.However redundancy also means additional computational costs and perhaps even worse additional memory to store the coefﬁcients.Therefore we started searching for alternative schemes that are also invariant under the described class of afﬁne transformation.Although we did not yet manage to come up with an efﬁcient stable scheme,we would like to stretch the principal idea behind the building blocks of such approach.In the sequel we will only use the redundant lifting scheme as described in the preceding section.Before we start looking for possible alternative schemes we examine why the lifting scheme is not translation invariant.Assume we have a signal that is analysed with an-band lifting scheme. Then after one lifting step we have approximation data and detail data.Whether one sample,is determined to become either a sample of or a sample ofdepends only on its position on the lattice and the way we partition the lattice into groups.Of course, this partitioning is rather arbitrary.The more channels we use the higher the probability is that for aﬁxed partitioning one sample that was determined to be used for predicting other samples,will become a sample of after translating.Following Figure8it is clear that any sample,can end up after lifting steps in ways,either in approximation data at level or in detail data at some level.The idea of the alternative scheme we propose here is to partition a signal not upon its position on the lattice but upon its structure.This means that for each individual signal we indicate aﬁxed point for which we demand that it will end up in the approximation data after lifting steps.If this point can be chosen independent of its coordinates on the lattice,the lifting scheme based on this partitioning will then translation invariant.For higher dimensional signals we can also achieve invariance under the other discussed afﬁne transformations,however then we have toﬁx more points,depending on the number ofchannels.In our approach the quincunx lattice is used and thereforeﬁxing one approximation sample on scales will immediatelyﬁx the partitioning of all other samples on the quincunx lattice at scale. As a result theﬁxed point lifting scheme is invariant under translations,rotations and reﬂections that leave the quincunx lattice invariant.In the sequel of this chapter we will only discuss the lifting scheme for for the quincunx lattice.Although the proposedﬁxed point lifting scheme may seem to be a powerful tool for afﬁne invariant lifting,it will be hard to deal with in practice.The problem we will have to face is how to choose aﬁxed point in every image.In other words we have toﬁnd a suitable decision operator that adds to every a unique,itsﬁxed point,i.e.,If we demand to depend only on and not on the lattice(coordinate free)it will be hard toﬁnd such that is well deﬁned.This independence of the coordinates is necessary for rotation invariances.However, this is not the only difﬁculty we have to face.Stability of the scheme is an other problem.If for some reason aﬁxed point has been wrongly indicated,for example due to truncation errors,the whole scheme might collapse down.Although we cannot easily solve the problem of determining incorrectﬁxed points we can increase the stability of the scheme by not imposing that at each scale should be an index number of the coarse scale data after zero padding.Instead of this procedure we rather determine aﬁxed point for both the original signal()and for the coarse scale data(at each scale.Then we impose that should be used for prediction in the th lifting step,for and with.Furthermore,stability may be increased by using decision operators that generate a set ofﬁxed points.However,since no stable method (uniform decision operator)is available yet,we will use the redundant lifting scheme in our approach and do not work out the idea ofﬁxed point lifting here at this moment.5.M OMENT I NVARIANTSAt the outset of this section we give a brief introduction into the theory of statistical invariants for imag-ing purposes,based on centralized moments.Traditionally,these features have been widely used in pat-tern recognition applications to recognize the geometrical shapes of different objects[11].Here,we will compute invariants with respect to the detail coefﬁcients as produced by the wavelet lifting schemes of Sections2–4.We use invariants based on moments of the coefﬁcients up to third order.We show how to construct a feature vector from the obtained wavelet coefﬁcients at several scales It is followed by proposals for normalization of the moments to keep them in comparable range.5.1Introduction and recapitulationWe regard an image as a density distribution function,the Schwartz class.In order to obtain translation invariant statistics of such we use central moments of for our features.The order central moment of is given by(5.1) with the center of massand(5.2)Computing the centers of mass and of yieldsand bining this with(5.1)showsi.e.,the central moments are translation invariant.We also require that the features should be invariant under orthogonal transformations(rotations).For deriving these features we follow[11]using a method with homogeneous polynomials of order.These are given by(5.3) Now assume that the variables are obtained from other variables under some linear transformation,i.e.,then is an algebraic invariant of weight if(5.4) with the new coefﬁcients obtained after transforming by.For orthogonal transformations we have and therefore is invariant under rotations ifParticularly we have from[11],that if is an algebraic invariant,then also the moments of order have the same invariant,i.e.,(5.5) From this equation2functions of second order can be derived that are invariant under rotations,see[11]. For we have the invariantsandIt was also shown that these two functions are also invariant under reﬂections,which can be a useful property for identifying reﬂected images.Since the way of deriving these invariants may seem a bit technical and artiﬁcial,we illustrate with straightforward calculus that and are indeed invariant under rotations.The invariance under reﬂections is left to the reader,since showing this follows the same calculations.We consider the rotated distribution functionand the corresponding invariants and,which are and but now based on moments calculated from.So what we have to show is that and.It follows from(5.1)and(5.2)that if and only ifwith and.Obviously this holds true,considering the trigonometric rule .To do the same for we also have to introduce and.Because we have to take products of integrals that deﬁne,we cannot use and in both integrals.As for we can now derive from(5.1)and(5.2)that if and only ifWe simplify the right-hand side term by term.Theﬁrst term,that is related to becomes The second term(related to)becomesAdding these two terms gives uswhich demonstrates that indeed also is invariant under rotations.Similar calculus shows that invariance under reﬂections also holds.From Equation(5.5)four functions of third order and one function of both second and third order can be derived that are invariant under both rotations and reﬂecting,namelyandwithThe last polynomial that is invariant under both rotations and reﬂections consists of both second and third order moments and is given bywith and as above.To these six invariants we can add a seventh one,which is only invariant under rotations and changes sign under reﬂections.It is given bySince we want to include reﬂections as well in our set of invariant transformations we will use instead of in our approach.From now on,we will identify with.We observe that all possible linear combinations of these invariants are invariant under proper orthogonal transformations and translations.Therefore we can call these seven invariants also invariant generators.。

路西法效应英语

路西法效应英语The Lucifer Effect refers to the psychological phenomenon where individuals exhibit extreme and harmful behavior when placed in certain situations. This term was coined by social psychologist Philip Zimbardo, who conducted the famous Stanford Prison Experiment in 1971. The study involved college students role-playing as guards and prisoners in a simulated prison environment. The experiment was meant to last for two weeks but had to be terminated after only six days due to the extreme and abusive behavior displayed by the "guards" towards the "prisoners."The findings from the Stanford Prison Experiment shed light on the power of situational and systemic influences on individual behavior. Zimbardo argued that the dynamics of the prison environment, including the power differentials, dehumanization, and lack of oversight, led the participants to engage in acts of cruelty and aggression that they wouldn't have exhibited under normal circumstances. This demonstrated how ordinary people can betransformed into perpetrators of evil given the right setof circumstances.The implications of the Lucifer Effect extend beyond the confines of the experiment and have been used to explain various real-world events and phenomena. For example, ithas been invoked to understand the behavior of soldiers in war, the actions of individuals in positions of authority, and the dynamics of abusive relationships. The concept highlights the importance of considering the impact ofsocial and environmental factors when trying to comprehend and address harmful behavior.In addition to its applicability in understanding individual behavior, the Lucifer Effect also hasimplications for social institutions and policies. By recognizing the power of situational forces in shaping behavior, it becomes crucial to design systems and environments that minimize the potential for abuse and harm. This could involve implementing oversight mechanisms, promoting a culture of empathy and respect, and fostering conditions that empower individuals to resist negative influences.路西法效应是指当个体置身于特定情境时表现出极端和有害行为的心理现象。

药学通识英语试题及答案

药学通识英语试题及答案一、选择题（每题2分，共20分）1. Which of the following is not a primary function of drugs?A. DiagnosisB. TreatmentC. PreventionD. Rehabilitation答案：A2. The term "pharmacology" refers to the study of:A. The effects of drugs on living organismsB. The synthesis of new drugsC. The distribution of drugs in the marketD. The legal regulations of drugs答案：A3. The most common route of drug administration is:A. OralB. IntravenousC. IntramuscularD. Topical答案：A4. Which of the following is a side effect of a drug?A. The intended therapeutic effectB. An effect that is harmful and unintendedC. The effect of the drug on a different organD. The effect of the drug on a different disease答案：B5. The half-life of a drug refers to:A. The time it takes for the drug to be completely eliminated from the bodyB. The time it takes for the drug's concentration to decrease by halfC. The time it takes for the drug to reach its maximum concentrationD. The time it takes for the drug to be absorbed into the bloodstream答案：B6. The bioavailability of a drug is:A. The percentage of the drug that is absorbed into the bloodstreamB. The percentage of the drug that is excreted unchangedC. The percentage of the drug that is metabolized by theliverD. The percentage of the drug that is stored in the fat tissues答案：A7. The therapeutic index of a drug is an indicator of:A. The drug's effectivenessB. The drug's safetyC. The drug's cost-effectivenessD. The drug's duration of action答案：B8. A drug's pharmacokinetics involves the study of:A. How the body affects the drugB. How the drug affects the bodyC. How the drug is synthesizedD. How the drug is regulated by the government答案：A9. The first-pass metabolism refers to:A. The metabolism of a drug after it is absorbed into the bloodstreamB. The metabolism of a drug before it enters the bloodstreamC. The metabolism of a drug after it is excreted from the bodyD. The metabolism of a drug after it is distributed to the tissues答案：B10. The term "drug interaction" refers to:A. The combined effect of two or more drugsB. The effect of one drug on the action of another drugC. The effect of a drug on the patient's behaviorD. The effect of a drug on the patient's diet答案：B二、填空题（每题2分，共20分）1. The study of the effects of drugs on living organisms is called __________.答案：pharmacology2. The intended therapeutic effect of a drug is known as its __________.答案：pharmacological effect3. The process by which a drug is absorbed into the bloodstream is called __________.答案：absorption4. A drug that is taken orally and then undergoes metabolism in the liver before entering the bloodstream is subject to__________.答案：first-pass metabolism5. The time it takes for the drug's concentration to decrease by half is known as the drug's __________.答案：half-life6. The percentage of the drug that is absorbed into the bloodstream is referred to as the drug's __________.答案：bioavailability7. The study of how the body affects the drug is known as the pharmacokinetics of the drug, while the study of how the drug affects the body is known as the __________.答案：pharmacodynamics8. A drug's safety is indicated by its __________.答案：therapeutic index9. The combined effect of two or more drugs is known as a__________.答案：drug interaction10. The unintended harmful effect of a drug is called a(n)__________.答案：side effect三、简答题（每题10分，共40分）1. Explain the difference between the pharmacokinetics and pharmacodynamics of a drug.答案：Pharmacokinetics is the study of how the body affects the drug, including absorption, distribution, metabolism, and excretion. Pharmacodynamics, on the other hand, is the study of how the drug affects the body, including the drug's mechanism of action and its effects on physiological functions.2. Describe the significance of a drug's half-life inclinical practice.答案：The half-life of a drug is significant in clinical practice as it determines the frequency of drug administration. A shorter half-life may require more frequent dosing, while a longer half-life allows for less frequent dosing. It also。

1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。

Institute of Theoretical Physics, Warsaw University Ho˙ za 69, PL–00–681 Warszawa, Poland
Abstract As a contribution to the hypothesis of mixing of three active neutrinos with, at least, one sterile neutrino, we report on a simple 4 × 4 texture whose 3 × 3 part arises from the √ popular bimaximal texture for three active neutrinos νe , νµ , ντ , where c12 = 1/ 2 = s12 , √ c23 = 1/ 2 = s23 and s13 = 0. Such a 3 × 3 bimaximal texture is perturbed through a rotation in the 14 plane, where ν4 is the extra neutrino mass state induced by the
<
Uith c14 = cos θ14 and s14 = sin θ14 (note that in Eq. (2) only s12 , s23 and s14 of all sij 1
c14 0 0 0 0 0 −s14 0 1

2 1 4 2 2 2 2 sin2 2θLSND = 2 s14 and ∆m2 LSND = |∆m41 |, while sin 2θsol = c14 and ∆msol = ∆m21 as
for the possible LSND eﬀect. In fact, with the use of our 4 × 4 texture we predict that

notation used for a generic Cabibbo–Kobayashi–Maskawa–type matrix [6] (if the LSND eﬀect is ignored, the upper bound |s13 | ∼ 0.1 follows from the negative result of Chooz reactor experiment [7]). Going out from the form (1), we propose in the 4 × 4 texture the following mixing matrix: √ √ c14 / 2 1/ 2 0 0 s14 √ 0 0 − c / 2 1 / 2 1 / 14 √2 = 1 0 c14 /2 −1/2 1/ 2 0 c14 −s14 0 0 √ s14 / 2 −s14 /2 (2) s14 /2 c14
IFT–01/03
Prediction of LSND eﬀect as a ”sterile” perturbation of the bimaximal texture for three active neutrinos∗
´ likowski Wojciech Kro
arXiv:hep-ph/0102016v2 7 Feb 2001
2 1 4 −3 we predict that sin2 2θatm = 1 (1 + c2 14 ) ∼ 0.95 and sin 2θLSND = 2 s14 ∼ 5 × 10 , and 2 2 sterile neutrino νs which becomes responsible for the LSND eﬀect. Then, with m2 1 ≃ m2
2 −7 ∆m2 eV2 if e.g. the LOW solar solution is applied. 21 = ∆msol ∼ 10
2 2 2 2 2 in addition ∆m2 atm = ∆m32 and ∆mLSND = |∆m41 |, where c14 = sin 2θsol ∼ 0.9 and
solution [1] is accepted; then we predict sin2 2θatm ∼ 0.95 and sin2 2θLSND ∼ 5 × 10−3 . In the popular 3 × 3 bimaximal texture the mixing matrix has the form [4]
1 2 c14 m1 + s2 14 m4 + m2 , 2 1 2 −Meτ = − √ c2 14 m1 + s14 m4 − m2 , 2 2 1 1 2 Mτ τ = c m1 + s2 14 m4 + m2 + m3 = Mee + Mµτ , 2 2 14 1 1 2 c m1 + s2 − 14 m4 + m2 − m3 , 2 2 14 1 − √ c14 s14 (m1 − m4 ) , 2 1 1 −Mτ s = c14 s14 (m1 − m4 ) = − √ Mes , 2 2 2 s14 m1 + c2 m . 14 4
2 2 2 2 2 2 where by deﬁnition m2 1 ≤ m2 ≤ m3 and either m4 ≤ m1 or m3 ≤ m4 . Then, due to the
formula Mαβ =
i
∗ Uαi mi Uβi we obtain
Mee = Meµ = Mµµ = Mµτ = Mes = Mµs = Mss =
(5)
Of course, M † = M −1 and also M ∗ = M . From Eqs. (5) we ﬁnd that √ √ Mee − Meµ 2 + Mss Mee − Meµ 2 − Mss = ± 2 2 √ = Mee + Meµ 2 , m3 = Mµµ + Mµτ
2 2 , + 2Mes
m1,4 or m4,1 m2
(6)
if m4 ≤ m1 or m1 ≤ m4 , respectively, and 2
(2c14 s14 )2 =
Obviously, m1 + m2 + m3 + m4 = Mee + Mµµ + Mτ τ + Mss as Mee = Mµµ − Mµτ and Mµµ = Mτ τ . Due to the mixing of four neutrino ﬁelds described in Eq. (3), neutrino states mix according to the form
2 2 2 2 (1 + c2 well as sin2 2θatm = 1 14 ) and ∆matm = ∆m32 , if m1 ≃ m2 (and both are diﬀerent 2
2 2 2 −7 enough from m2 eV2 if e.g. the LOW solar 3 and m4 ). Here, c14 ∼ 0.9 and ∆m21 ∼ 10
0 1 0 0
with i, j = 1, 2, 3, 4 , i < j are nonzero).The unitary transformation describing the mixing of four neutrinos να = νe , νµ , ντ , νs is inverse to the form να =
PACS numbers: 12.15.Ff , 14.60.Pq , 12.15.Hh .
February 2001
∗
Supported in part by the Polish State Committee for Scientiﬁc Research (KBN).
The present status of experimental data for atmospheric νµ ’s as well as solar νe ’s favours oscillations between three conventional neutrinos νe , νµ , ντ only [1]. However, the problem of the third neutrino mass-square diﬀerence, related to the possible LSND eﬀect for accelerator νµ ’s, is still actual [2], stimulating a further discussion about mixing of these three active neutrinos with, at least, one hypothetical sterile neutrino νs (although such a sterile neutrino is not necessarily able to explain the LSND eﬀect [3]). As a contribution to this discussion, we report in this note on a simple 4 × 4 texture for three active and one sterile neutrinos, νe , νµ , ντ and νs , whose 3 × 3 part arises from the popular bimaximal texture [4] working grosso modo in a satisfactory way for solar νe ’s and atmospheric νµ ’s if the LSND eﬀect is ignored. Such a 3 × 3 bimaximal texture is perturbed [5] by the sterile neutrino νs inducing one extra neutrino mass state ν4 and so, becoming responsible