EFFECT OF DIFFERING LENGTHS OF SPA THERAPY ON OSTEOARTHRITIS PATIENTS

合集下载

TA Luft and EN ISO 15848-1

Emission measurements of industrial valves according to TA Luft and EN ISO 15848-1 As the title suggests, in this article Professor Dr.-Ing Alexander Riedl looks into the implications of measuring emissions according to TA Luft and EN ISO 15848-1 and points out some important conclusions.Professor Dr.-Ing. Alexander Riedl, University of Applied Sciences Muenster, GermanyTA LuftInasmuch as they relate to Germany,the “T echnische Anleitung zur Reinhaltung der Luft”(T echnical Guidelines for Air Pollution Control,or TA Luft for short and referred to hereinafter as TA Luft) [1] are like a law in character.Among other things,they pursue the objective of reducing emissions with gasket systems as normally used in the chemicals andpetrochemical industries.TA Luft onlygives guidelines in respect of compliancewith permissible leakage limits and refersto regulations which define basicconditions for inspections.For shutoffand regulating valves,this affects VDI(Association of German Engineers)Guideline 2440 [2],which may beregarded as state-of-the-art from a legalperspective.VDI 2440Guideline VDI 2440 refers to averagegas-like emissions for differing gasketsystems but these are not upper limits(see Table 1).Table 1 – Average gaseous emissions (leakage) and valve gaskets [1] Gasket system Leakage related to the average sizeof the gasket [mg/(s x m)] Stuffing box with packing 1.0Stuffing box with cup leather, O-ring0.1Stuffing box with packing, stuffing box with cup leather,0.01O-Ring (with "TA Air Certificate" according toVDI 2440, Section 3.3.1.3)Metallic bellows, sealed0.01Metallic bellows, sealed (with flat gasket possessing0.001a TA Luft Certificate according to VDI 2440)Stuffing box with packing and sealing medium/suction,No emissionmetallic bellows, welded on both sides(technically leak-proof)VDI 2440 refers to the use of high-quality metallic bellows with adownstream safety stuffing box orequivalent gasket systems as aparticularly effective means of reducingemissions.In other words,metallicbellows and so-called “equivalent gasketsystems”are established as conforming toTA Luft.This means that only these kindsof gasket systems may be used in Germany on shutoff and regulating valves when a TA Luft medium is subsidised.Gasket systems may be regarded as equivalent if they fulfil the following conditions:(1) The construction of the gasket systemcan be expected to permit itsregulation function under operatingconditions.(2) Compliance with specific leakage ratewith reference to the average size ofthe gasket,from 10-4mbar x l/(s x m)at temperatures of less than 250°Cand from 10-2mbar x l/(s x m) attemperatures on the gasket system ofgreater than 250°C is proven at thefirst inspection.No specific explanation is given on construction under (1) as to why this guideline is difficult to understand.On the other hand,the determination of a leakage rate to be complied with under (2) for all gaskets except metallic bellows is crucial in order to get valves that fulfil the conditions of this certificate onto the market.Guideline VDI 2440 describes a testing procedure with which the above-mentioned certificate can be shown.The ancillary conditions here are:(1) testing medium:helium;(2) testing pressure:nominal pressure;(3) testing temperature:permissibleoperating temperature;(4) before the test,a representativenumber of switching cycles is carriedout depending on the operatingconditions (switching rate);(5) test:with static and movingspindle/shaft;(6) leak rate:leakage resulting after atleast 24-hour admission flow withhelium under the given testingconditions.If the leak in (6) is less than 10-4mbar xl/(s x m) (up to 250°C) or 10-2mbar xl/(s x m) (over/the same as 250°C),thevalve may be regarded as TA Luftcompliant and may be used with TA Luftmedia.EN ISO 15848-1ISO norm EN ISO 15848-1 [3] has beenvalid since 2006.It refers exclusively tovalves and describes,independent of theguidelines of TA Luft and VDI 2440respectively,detailed tests fordetermining leakage and the creepbehaviour of valves.The norm wasdeveloped under the overall control ofthe CEN/TC 69 “Industrial Valves”Committee.The norm distinguishesbetween the following parameters:(1) 3 grades of imperviousness for thespindle/shaft;(2) a grade of imperviousness for thebody gasket;(3) 2 testing media (helium and methane);(4) 3 grades of firmness;(5) 5 grades of temperature;and1 distinction between shutoff andregulating valves.Table 2 [3] shows the following grades ofimperviousness for die spindle and theshaft:Table 2 – Grade of imperviousness/leakage areasGrade Measured leakage Remarksrate mg/(s x m)A Typically achieved with bellows gaskets or an equivalent (helium only)≤10-6spindle/shaft gasket system for swivel valves.B≤10-4Typically achieved with packing on a PTFE basisor elastomer packing.C≤10-2Typically achieved with packing on the basis offlexible graphite.The required imperviousness for the bodygasket,measured using the sniffing method,may not exceed 50 ppmv (1 ppmv = 1cm3x /m3).In respect of the media,the normis not intended to achieve anycomparability,but less leakage may beexpected than with helium.However,thisstatement requires testing.The leakage testsare conducted both at room temperatureand at maximum operating temperature,taking cycles of differing lengths.The gasketconnection may only be re-tightened to alimited extent.At the moment the author does not knowwhether any European country or the EUhas adopted the norm in order to convertthe limits described here into national orEuropean law.Through the preciseguidelines,however,it is expected that thiswill be carried out within the foreseeablefuture.The same applies to the stability andtemperature grades described below.The shutoff and regulating valves differ bystability grades,but the classification to agrade of stability is given by the number ofcycles in which a certain grade ofimperviousness (see T able 1) has not beenexceeded.With the shutoff valves the normassumes a maximum cycle of 2500 andwith the regulating valves,a maximumcycle of 105 cycles.Differences aredescribed in three grades of firmnessshown in T able 3 below.H EADINGF UGITIVE E MISSION C ONTROLComparison of regulationsThe guidelines in EN ISO 15848-1 are very precise and easy to understand.It is important to note here that clear guidelines are given in respect of the testing procedure.As well,the subdivision into grades of stability,imperviousness and temperature are significant in order to also enable the users of valves to differentiate between them.The same applies to the subdivision into shutoff (low number of expected cycles) and regulating valves (high number of expected cycles).The TA Luft and Guideline VDI 2440give a maximum permissible leakage as the only criterion which may not be exceeded;however,the marginal conditions (cycle etc.) are not clearly defined.In addition,the construction requirement which allows it to function according to the purpose for which it was built,is not really a clear guideline.But what is important is the question of the usefulness of EN ISO 15848-1 for verifying TA Luft.If we compare the degree of leakage in the ISO norm with the guidelines of TA Luft/VDI 2440,we arrive at the following interrelationship [4]:T =temperature of the gases (K)X =leakage rate (mbar x l/s)Y =leakage rate (mg/m x s)Note:the dependence of the leakage on the temperature of the gas is not taken into account in EN ISO 15848-1.Accordingly,the conversion factor for leaks at room temperature,taking into account the relationship to the size of the spindle/shaft,is:Y = 0,164 .X (2)Y = leakage [mg/(s x m)]X = leakage [mbar x l/(s x m)]If one takes into account the fact that,according to TA Luft,the average size of the sealing material for inspecting the leakage is the determining factor and that,by contrast,EN ISO 15848-1includes the size of the spindle/shaft,we arrive at the following interrelationship:Y dm = 0,164 D + d X d (3)Y dm = leakage according to VDI 2440,in relation to the average size of the gasket [mg/(s x m)]X d =leakage according to EN ISO15848-1,in relation to the diameter of the spindle/shaft [mbar x l/(s x m)]D =outside diameter of the sealingelement (corresponds to theinterior diameter of the body) [mm]D =exterior diameter of thespindle/shaft [mm].In most cases this probably means that,on achieving grade B imperviousness according to EN ISO 15848-1,the guidelines of TA Luft are probably also fulfilled.The same applies toimperviousness grade C at temperatures of over 250°C.Essentially,it may be assumed that EN ISO 15848-1 constitutes a tightening of the criteria in contrast to TALuft/VDI2440,as more temperature cycles can be carried out with the ISO-Norm.Table 3 – Stability grade for shutoff and regulating valvesTypeStability gradeCycle Temperature cyclesC015002Regulating valveC021,5003C032,5004CC120,0002Regulating valveCC260,0003CC3100,0004Table 4 – Grade of temperatureGrade of temperature (t-196°C)(t-46°C)(tRT)(t 200°C)(t 400°C)Temperature-196°C-46°CAtmospheric 200°C400°CtemperatureThe testing temperatures are subdivided into five grades and an area of -29°C x 40°C is given for room temperature (see Table 4).M • f Y =R•T•π•DX (1)where:D =average gasket diameter (m)f =conversion factor (=100) (mg x Pax m 3/g x mbar x l)M =molecular mass (g/mol)R =general gas constant (8,314)(J/mol x K)2d Literature[1] TA Luft:T echnical Guidelines for Air Pollution Control (TA Luft).Heymanns Verlag,Cologne,2002.[2]VDI 2440:Reducing Emissions from Mineral Oil Refineries.Beuth Verlag,Berlin,2000.[3] DIN EN ISO 15848-1:Industrial Valves - Measuring,T esting and Qualification Procedures for Escaping Emissions - Part 1:A Classification System andQualification Procedures for the T esting the Design of Valves.Beuth Verlag,Berlin,2006.[4] D.Bathen,C.Hummelt,J.Meisel:Emissions on Flanged Joints.Vulkan Verlag,Essen,2000.。

替加氟红外

J.At.Mol.Sci.doi:10.4208/jams.032510.042010a Vol.1,No.3,pp.201-214 August2010Theoretical Raman and IR spectra of tegafur andcomparison of molecular electrostatic potentialsurfaces,polarizability and hyerpolarizability oftegafur with5-ﬂuoro-uracil by density functionaltheoryOnkar Prasad∗,Leena Sinha,and Naveen KumarDepartment of Physics,University of Lucknow,Lucknow,Pin Code-226007,IndiaReceived25March2010;Accepted(in revised version)20April2010Published Online28June2010Abstract.The5-ﬂuoro-1-(tetrahydrofuran-2-yl)pyrimidine-2,4(1H,3H)-dione,also knownas tegafur,is an important component of Tegafur-uracil(UFUR),a chemotherapy drugused in the treatment of cancer.The equilibrium geometries of”Tegafur”and5-ﬂuoro-uracil(5-FU)have been determined and analyzed at DFT level employing the basis set6-311+G(d,p).The molecular electrostatic potential surface which displays the activitycentres of a molecule,has been used along with frontier orbital energy gap,electricmoments,ﬁrst static hyperpolarizability,to interpret the better selectivity of prodrugtegafur over the drug5-FU.The harmonic frequencies of prodrug tegafur have alsobeen calculated to understand its complete vibrational dynamics.In general,a goodagreement between experimental and calculated normal modes of vibrations has beenobserved.PACS:31.15.E-,31.15.ap,33.20.TpKey words:prodrug,polarizability,hyperpolarizability,frontier orbital energy gap,molecular electrostatic potential surface.1IntroductionThe use of a prodrug strategy increases the selectivity and thus results in improved bioavailability of the drug for its intended target.In case of chemotherapy treatments,the reduction of adverse effects is always of paramount importance.The prodrug whichis used to target the cancer cell has a low cytotoxicity,prior to its activation into cytotoxic form in the cell and hence there is a markedly lower chance of it”attacking”the healthy∗Corresponding author.Email address:prasad onkar@lkouniv.ac.in(O.Prasad)/jams201c 2010Global-Science Press202O.Prasad,L.Sinha,and N.Kumar/J.At.Mol.Sci.1(2010)201-214 non-cancerous cells and thus reducing the side-effects associated with the chemothera-peutic agents.Tegafur,a prodrug and chemically known as5-ﬂuoro-1-(tetrahydrofuran-2-yl)pyrimidine-2,4(1H,3H)-dione,is an important component of’Tegafur-uracil’(UFUR), a chemotherapy drug used in the treatment of cancer,primarily bowel cancer.UFUR is a ﬁrst generation Dihydro-Pyrimidine-Dehydrogenase(DPD)inhibitory Flouropyrimidine drug.UFUR is an oral agent which combines uracil,a competitive inhibitor of DPD,with the5-FU prodrug tegafur in a4:1molar ratio.Excess uracil competes with5-FU for DPD, thus inhibiting5-FU catabolism.The tegafur is taken up by the cancer cells and breaks down into5-FU,a substance that kills tumor cells.The uracil causes higher amounts of 5-FU to stay inside the cells and kill them[1–4].The present communication deals with the investigation of the structural,electronic and vibrational properties of tegafur due to its biological and medical importance inﬁeld of cancer treatment.The structure and harmonic frequencies have been determined and analyzed at DFT level employing the basis set6-311+G(d,p).The optimized geometry of tegafur and5-FU and their molecular properties such as equilibrium energy,frontier orbital energy gap,molecular electrostatic potential energy map,dipole moment,polar-izability,ﬁrst static hyperpolarizability have also been used to understand the properties and activity of the drug and prodrug.The normal mode analysis has also been carried out for better understanding of the vibrational dynamics of the molecule under investi-gation.2Computational detailsGeometry optimization is one of the most important steps in the theoretical calculations. The X-ray diffraction data of the tegafur monohydrate and the drug5-FU,obtained from Cambridge Crystallographic Data Center(CCDC)were used to generate the initial co-ordinates of the prodrug tegafur and drug5-FU to optimize the structures.The Becke’s three parameter hybrid exchange functionals[5]with Lee-Yang-Parr correlation func-tionals(B3LYP)[6,7]of the density functional theory[8]and6-311+G(d,p)basis set were chosen.All the calculations were performed using the Gaussian03program[9].TheFigure1:Optimized structure of Tegafur and5-ﬂuoro-uracil at B3LYP/6-311+G(d,p).O.Prasad,L.Sinha,and N.Kumar/J.At.Mol.Sci.1(2010)201-214203Figure2:Experimental and theoretical Raman spectra of Tegafur.model molecular structure of prodrug tegafur and drug5-FU are given in the Fig.1.Pos-itive values of all the calculated vibrational wave numbers conﬁrmed the geometry to be located on true local minima on the potential energy surface.As the DFT hybrid B3LYP functional tends to overestimate the fundamental normal modes of vibration,a scaling factor of0.9679has been applied and a good agreement of calculated modes with ex-perimental ones has been obtained[10,11].The vibrational frequency assignments have been carried out by combining the results of the Gaussview3.07program[12],symmetry considerations and the VEDA4program[13].The Raman intensities were calculated from the Raman activities(Si)obtained with the Gaussian03program,using the following relationship derived from the intensity theory of Raman scattering[14,15]I i=f(v0−v i)4S iv i{1−exp(−hc v i/kT)},(1)where v0being the exciting wave number in cm−1,v i the vibrational wave number of i th normal mode,h,c and k universal constants and f is a suitably chosen common nor-malization factor for all peak intensities.Raman spectra has been calculated according to the spectral database for organic compounds(SDBS)literature,using4880˚A as excit-ing wavelength of laser source with200mW power[16].The calculated Raman and IR spectra have been plotted using the pure Lorentzian band shape with a band width of FWHM of3cm−1and are shown in Fig.2and Fig.3,respectively.204O.Prasad,L.Sinha,and N.Kumar/J.At.Mol.Sci.1(2010)201-214Figure3:Experimental and theoretical IR spectra of Tegafur.The density functional theory has also been used to calculate the dipole moment, mean polarizability<α>and the totalﬁrst static hyperpolarizabilityβ[17,18]are given as for both the molecules in terms of x,y,z components and are given by following equationsµ=(µ2x+µ2y+µ2z)1/2(2)<α>=13αxx+αyy+αzz,(3)βTOTAL=β2x+β2y+β2z1/2=(βxxx+βxyy+βxzz)2+(βyyy+βyxx+βyzz)2+(βzzz+βzxx+βzyy)21/2.(4)Theβcomponents of Gaussian output are reported in atomic units and therefore the calculated values are converted into e.s.u.units(1a.u.=8.3693×10−33e.s.u.).O.Prasad,L.Sinha,and N.Kumar/J.At.Mol.Sci.1(2010)201-214205 3Results and discussion3.1Geometric structureThe electronic structure of prodrug tegafur and the drug5-FU have been investigated, in order to assess the effect of introduction ofﬁve-membered ring having an electron withdrawing carbonyl group to the drug5-FU for better selectivity of target cancer cells. The optimized molecular structures with the numbering scheme of the atoms are shown in Fig. 1.The ground state optimized parameters are reported in Table1.Theﬁve-membered ring in case of tegafur adopts an envelope conformation,with the C(14)atom, acting as theﬂap atom,deviating from the plane through the remaining four carbon atoms.The C-C and C-H bond lengths ofﬁve-membered rings lie in the range1.518˚A ∼1.556˚A and1.091˚A∼1.096˚A respectively.The endocyclic angles ofﬁve-membered ring lie between103.50to108.00whereas there is a sharp rise in the endohedral angle values(129.1◦)at N(6)atom and sharp fall in the angle values(111.3◦)at C(8)atom in the six-membered hetrocyclic ring.The C(7)=O(2)/C(8)=O(3)/C(12)=O(4)bond lengths are equal to1.217/1.211/1.202˚A and are found to be close to the standard C=O bond length(1.220˚A).These calculated bond length,bond angles are in full agreement with those reported in[19,20].The skeleton of tegafur molecule is non-planar while the5-FU skeleton is planar.The optimized parameters agree well with the work reported by Teobald et al.[21].The angle between the hetrocyclic six-membered ring plane andﬁve-membered ring plane represented byζ(N(5)-C(11)-C(15)-C(12))is calculated at126.1◦.It is seen that most of the bond distances are similar in tegafur and5-FU molecules,al-though there are differences in molecular formula.In the six-membered ring all the C-C and C-N bond distances are in the range1.344∼1.457˚A and1.382∼1.463˚A.Accord-ing to our calculations all the carbonyl oxygen atoms carry net negative charges.The signiﬁcance of this is further discussed in terms of its activity in the next section.Table1:Parameters corresponding to optimized geometry at DFT/B3LYP level of theory for Tegafur and5-FUParameters Tegafur5-FUGround state energy(in Hartree)-783.639204-514.200506Frontier orbital energy gap(in Hartree)0.185850.19593Dipole moment(in Debye) 6.43 4.213.2Electronic propertiesThe frontier orbitals,HOMO and LUMO determine the way a molecule interacts with other species.The frontier orbital gap helps characterize the chemical reactivity and ki-netic stability of the molecule.A molecule with a small frontier orbital gap is more po-larizable and is generally associated with a high chemical reactivity,low kinetic stability206O.Prasad,L.Sinha,and N.Kumar/J.At.Mol.Sci.1(2010)201-214 and is also termed as soft molecule[22].The frontier orbital gap in case of prodrug tega-fur is found to be0.27429eV lower than the5-FU molecule.The HOMO is the orbital that primarily acts as an electron donor and the LUMO is the orbital that largely acts as the electron acceptor.The3D plots of the frontier orbitals HOMO and LUMO,electron density(ED)and the molecular electrostatic potential map(MESP)for both the molecules are shown in Fig.4and Fig.5.It can be seen from theﬁgures that,the HOMO is almost distributed uniformly in case of prodrug except the nitrogen atom between the two car-bonyl groups but in case of5-FU the HOMO is spread over the entire molecule.Homo’s of both the molecules show considerable sigma bond character.The LUMO in case of tegafur is found to be shifted mainly towards hetrocyclic ring and the carbonyl group ofﬁve-membered ring and shows more antibonding character as compared to LUMO of 5-FU in which the spread of LUMO is over the entire molecule.The nodes in HOMO’s and LUMO’s are placed almost symmetrically.The ED plots for both molecules show a uniform distribution.The molecular electrostatic potential surface MESP which is a plot of electrostatic potential mapped onto the iso-electron density surface,simultaneously displays molecular shape,size and electrostatic potential values and has been plotted for both the molecules.Molecular electrostatic potential(MESP)mapping is very use-ful in the investigation of the molecular structure with its physiochemical property rela-tionships[22–27].The MESP map in case of tegafur clearly suggests that each carbonyl oxygen atom of theﬁve and six-membered rings represent the most negative potential region(dark red)but theﬂuorine atom seems to exert comparatively small negative po-tential as compared to oxygen atoms.The hydrogen atoms attached to the six andﬁve-membered ring bear the maximum brunt of positive charge(blue region).The MESP of tegafur shows clearly the three major electrophyllic active centres characterized by red colour,whereas the MESP of the5-FU reveals two major electrophyllic active centres,the ﬂuorine atom seems to exert almost neutral electric potential.The values of the extreme potentials on the colour scale for plotting MESP maps of both molecules have been taken same for the sake of comparison and drawing the conclusions.The predominance of green region in the MESP surfaces corresponds to a potential halfway between the two extremes red and dark blue colour.From a closer inspection of various plots given in Fig. 4and Fig.5and the electronic properties listed in Table1,one can easily conclude how the substitution of the hydrogen atom by theﬁve-membered ring containing an electron withdrawing carbonyl group modiﬁes the properties of the drug5-FU.3.3Electric momentsThe dipole moment in a molecule is an important property that is mainly used to study the intermolecular interactions involving the non bonded type dipole-dipole interactions, because higher the dipole moment,stronger will be the intermolecular interactions.The calculated value of dipole moment in case of tegafur is found to be quite higher than the drug5-FU molecule and is attributed due to the presence of an extra highly electron withdrawing carbonyl group.The calculated dipole moment for both the molecules areO.Prasad,L.Sinha,and N.Kumar/J.At.Mol.Sci.1(2010)201-214207Table2:Polarizability data/a.u.for Tegafur at DFT/B3LYP level of theoryPolarizability TegafurαXX173.315αXY-2.494αYY111.365αXZ-4.149αYZ0.399αZZ92.930<α>125.870Table3:Allβcomponents andβTotal for Tegafur calculated at DFT/B3LYP level of theoryPolarizability TegafurβXXX-54.9411βXXY-57.5539βXYY-13.4605βYYY95.0387βXXZ31.8370βXYZ9.2943βYYZ-22.0880βXZZ57.6657βYZZ-21.7419βZZZ-37.3655βTotal(e.s.u.)0.2808×10−30also given in Table1.The lower frontier orbital energy gap and very high dipole moment for the tegafur are manifested in its high reactivity and consequently higher selectivity for the target carcinogenic/tumor cells as compared to5-FU(refer to Table1).According to the present calculations,the mean polarizability of tegafur(125.870/ a.u.,refer to Table2)is found signiﬁcantly higher than5-FU(66.751/a.u.calculated at the same level of theory as well as same basis set).This is related very well to the smaller frontier orbital gaps of tegafur as compared to5-FU[22].The different components of polarizability are reported in the Table2.Theﬁrst static hyperpolarizabilityβcalculated value is found to be appreciably lowered in case of tegafur(0.2808x10−30e.s.u.,refer to Table3)as compared to5-FU(0.6218x10−30e.s.u.calculated at B3LYP/6-311+G(d,p)). Table3presents the different components of static hyperpolarizability.In addition,βval-ues do not seem to follow the same trend asαdoes,with the frontier orbital energy gaps. This behavior could be explained by a poor communication between the two frontier or-bitals of tegafur.Although the HOMO is almost distributed uniformly in case of tegafur208O.Prasad,L.Sinha,and N.Kumar/J.At.Mol.Sci.1(2010)201-214Figure4:Plots of Homo,Lumo and the energy gaps in Tegafur and5-FU.Figure5:Total Density and MESP of Tegafur and5-FU.but the LUMO is found to be shrunk and shifted mainly towards hetrocyclic ring and the carbonyl group ofﬁve-membered ring and shows more antibonding character than the LUMO of5-FU.It may thus be concluded that the higher”selectivity”of the prodrug tegafur as compared to the drug5-FU may be attributed due to the higher dipole mo-ment and lower values of frontier energy band gap coupled with the lowerﬁrst static hyperpolarizability.3.4Vibrational spectral analysisAs the molecule has no symmetry,all the fundamental modes are Raman and IR active. The66fundamental modes of vibrations of tegafur are distributed among the functional and theﬁnger print region.The experimental and computed vibrational wave num-O.Prasad,L.Sinha,and N.Kumar/J.At.Mol.Sci.1(2010)201-214209 bers,their IR and Raman intensities and the detailed description of each normal mode of vibration of the prodrug tegafur,carried out in terms of their contribution to the total potential energy are given in Table4.The calculated Raman and IR spectra of prodrugTable4:Theoretical and experimental a wave numbers(in cm−1)of TegafurExp a Exp a Calc.Calc.Calc.Calc.Assignment of dominantIR Raman(Unscaled(Scaled IR Raman modes in order of Wave no.Wave no.Wave no.Wave no.Intensity Intensity decreasing potentialin cm−1in cm−1in cm−1)in cm−1)energy distribution(PED)3426-3592347779.8317.38υ(N-H)(100)3076310032193115 3.0919.49υ(C-H)R(99)3033-3117301714.2012.97υas methylene(C-H)(82)30333004310730079.8732.29υas methylene(C-H)(90)-29763097299818.5945.83υas methylene(C-H)(80)--3065296720.6530.88υs methylene(C-H)(96)--305029527.8416.11υ(C-H)pr(98)--3044294610.2419.02υs methylene(C-H)(91)2911-3033293624.9745.77υs methylene(C-H)(84)1721-183********.637.65υ(C12=O)pr(90)1693172317821725461.2581.78υ(C8=O)R(72)1668170717661709871.67 3.93υ(C7=O)R(66)165816611701164776.0842.39υ(C9-C10)(66)+β(H17-C10-C9)(11)14711473151114628.71 2.05sc CH2(93)14661469149314457.829.82sc CH2(87)140014381467142042.97 1.93υ(N5-C)10)(23)+β(N5-C10-C9)(13) +υ(N6-C8)(11)+β(N5-C11-H18)(10)140014031450140320.857.15sc(CH2)(88)13621367141913738.94 3.78β(H16-N6-C7)(52)+υ(C=O)R(20) +β(H17-C10-N5)(11)135613401393134971.90 4.40β(H18-C11-N5)(35) +β(H16-N6-C7)(13)1339-138********.7460.20β(H17-C10-C9)(21)+υ(C9-C10)(14) +υ(N5-C10)(13)+υ(N6-C7)(12)--1343130010.26 1.21methylene(C14)wag(62)+methylene(C15)twisting(13)--1337129414.487.82methylene(C15)wag(56)+methylene(C14)twisting(16)1264126113071266 4.21 1.73methylene(C13)wag(56)+methylene(C14),(C15)twisting(16)1264-12991257 1.958.16Methylene twisting(60)1231-12671225199.09 4.95β(H17-C10-N5)(23)+methylene(C13)twisting(15) +υ(N5-C10)(10)1187-1244120485.739.03Ring deformation1179119912281189 4.29 1.65Methylene twisting(40) +(C11-H18)wag(35)--1193115522.238.09methylene(C13)wag(10) +β(H17-C10-C9)(10)210O.Prasad,L.Sinha,and N.Kumar/J.At.Mol.Sci.1(2010)201-214(continued)Exp a Exp a Calc.Calc.Calc.Calc.Assignment of dominantIR Raman(Unscaled(Scaled IR Raman modes in order of Wave no.Wave no.Wave no.Wave no.Intensity Intensity decreasing potentialin cm−1in cm−1in cm−1)in cm−1)energy distribution(PED)1115-11681131134.60 4.73β(H23-C15-C11)(21) +β(H22-C13-C14)(18)β(H16-N6-C7)(17)1115-11571120 5.9920.48υ(N6-C7)(30)+υ(N5-C10)(16) +methylene twisting(14)1065104510621028 3.60 4.26υ(C-C)pr(28)+β(H18-C11-C12)(13) +methylene twisting(11)1087-1126109020.609.14υ(C-C)pr(35)+β(C12-C13-C14)(12) --10139808.56 6.79υ(C-C)pr(54)+methylene wag(25)941942965934 2.79 1.53υ(C-C)pr(20)+β(H18-C11-C15)(17) +methylene twisting(10)9139219268970.27 6.28methylene rocking(33) +υ(C-C)pr(11)--916886 4.1310.06υ(C-C)pr(59)867-896868 2.20 5.99C-H out of plane Ring wag(79)840-8868570.48 4.53β(H16-N6-C7)(20)+β(H17-C10-C9)(13)+methylene(C13)rocking(13) +methylene(C14)twisting(11)--82780011.31 6.48methylene rocking(69)77378281578950.9325.00β(C10-N5-C7)(27)+β(C9-C10-N5)(16) +υ(F-C)(11)749-760736 5.940.73βout(O-C-N)(78)--75473052.72 2.02βout(O-C-N)(77)+(N-H)wag(10) --746722 5.537.78Ring Breathing mode(51)687704728705 1.7330.18methylene rocking(39) +β(O2-C7-N6)(18)-6466686479.5512.38β(O-C-N)(45)+β(F-C-C)(11) -64665863742.75 2.90(N-H)wag(90)608-6266069.55 2.91β(C-C-C)Pr(18)+β(O-C-C)Pr(18) +(N-H)wag(12)--58256320.4212.86βout(C-C-C)Pr(17)+β(C8-N6-C7)(12) +β(C9-C10-N5)(10)542-550532 2.497.84βout(C-C-C)Pr(31)+β(O-C-C)Pr(15)48249051850110.7119.07β(O-C-C)Pr(32)+Pr torsional mode(12) +Ring Tors.mode(12)430-4694548.9916.04Pr tors.mode(31)+β(N-C-N)(23) +β(N5-C10-C9)(10)-421418405 2.01 1.44Pr tors.mode(29)+Ring Tors.mode(17)--4103967.608.21Ring Tors.mode(54)(continued)Exp a Exp a Calc.Calc.Calc.Calc.Assignment of dominant IR Raman(Unscaled(Scaled IR Raman modes in order ofWave no.Wave no.Wave no.Wave no.Intensity Intensity decreasing potential in cm−1in cm−1in cm−1)in cm−1)energy distribution(PED)-38138937719.530.39β(O2-C7-N6)(22)+Ring Tors.(21) Tors.(O4-C11-C13-C12)(12)-352364352 3.228.17Tors.(F1-C8-C10-C9)(59) +Tors.(O3-N6-C9-C8)(10)-319312302 1.680.76β(C10-C9-F1)(26)+β(C8-N6-C7)(18) +β(C10-N5-C11)(29)+β(C10-N5-C7)(12)--2872787.10 4.57Ring Tors.(24)+βout(C10-C9-F1)(22) +β(C15-C11-N5)(20)--2432360.17 1.90Pr tors.mode(32)+Ring Tors.(30) +βout(C10-C9-F1)(12)--230223 1.08 1.61Pr tors.mode(30) +β(C10-N5-C11)(29)--166160 4.74 3.08Ring Tors.(64)--152147 2.75 4.58Pr tors.mode(20)+Tors.(C15-C11-N5-C7)(19)+Ring Tors(10)+β(C10-N5-C11)(10)--1281230.78 3.22Tors.(C15-C11-N5-C7)(35)+Ring Tors.(33)+Pr tors.mode(17)--7471 1.78 1.29Tors.(C14-C15-C11-N5)(61) +β(C11-N5-C10)(10)--6159 1.36 1.94Ring Tors.(36)+Tors.(C15-C11-N5-C7)(35)--4543 1.18 1.74Tors.(C11-C7-C10-N5)(67) +Tors.(C12-C11-N5-C7)(11)The experimental IR and Raman data have been taken from http://riodb01.ibase.aist.go.jp/sdbs website.Note:υ:stretching;υs:symmetric stretching;υas:asymmetric stretching;β:in plane bending;βout:out of plane bending;Tors:torsion;sc:scissoring;ωag:wagging;Pr:Five-membered ring;Ring:Hetroaromatic six-membered ring tegafur agree well with the experimental spectral data taken from the Spectral Database for Organic Compounds(SDBS)[16].3.4.1N-H vibrationsThe N-H stretching of hetrocyclic six-membered ring of tegafur is calculated at3477 cm−1.As expected,this is a pure stretching mode and is evident from P.E.D.table con-tributing100%to the total P.E.D.,and is assigned to IR wave number at3426cm−1.The discrepancy in the calculated and experimental N-H stretching wave number is due to the intermolecular hydrogen bonding.The mode calculated at637cm−1represents the pure N-H wagging mode which is assigned well with the peak at646cm−1in Raman spectra.3.4.2C-C and C-H vibrationsC-C stretching are observed as mixed modes in the frequency range1600cm−1to980 cm−1for tegafur with general appearance of C-H and C-C stretching modes and are in good agreement with experimentally observed frequencies.C-C stretches are calcu-lated to be1090,980,934and886cm−1.The functional group region in aromatic het-rocyclic compounds exhibits weak multiple bands in the region3100∼3000cm−1.The six-membered ring stretching vibrations as well as the C-H symmetric and asymmet-ric stretching vibrations of methylene group in tegafur are found in the region3125to 2925cm−1.In the present investigation,the strengthening and contraction of C-H bond C(10)-H(17)=108.147pm in hetrocyclic six-membered ring may have caused the C-H stretching peak to appear at3115cm−1having almost100%contribution to total P.E.D. in calculation.This C-H stretching vibration is assigned to the3076cm−1IR spectra. The calculated peaks at3017,3007,2998cm−1and2967cm−1are identiﬁed as methylene asymmetric and symmetric stretching vibrations with more than80%contribution to the total P.E.D.are matched moderately and have been assigned at3033cm−1in the IR and at3004and2976cm−1in Raman spectra respectively.The calculated peaks in the frequency range1475∼1400cm−1of tegafur correspond methylene scissoring modes with more than85%contribution to the total P.E.D.are as-signed at1471/1473and1466/1469cm−1in the IR/Raman spectra.Methylene wagging calculated at1300cm−1(62%P.E.D.),1294and1266cm−1(56%P.E.D.each),show con-siderable mixing with methylene twisting mode,whereas dominant twisting modes are calculated at1257cm−1and1189cm−1with60%and40%contribution to P.E.D.The mode calculated at897,800and705cm−1are identiﬁed as methylene rocking with their respective33%,69%and39%contribution to the total P.E.D.3.4.3Ring vibrationsThe calculated modes at868cm−1and722cm−1represent the pure six-membered ring wagging and breathing modes.As expected the skeletal out of plane deformations/ the torsional modes appear dominantly below the600cm−1.The mode calculated at 789cm−1represent mixed mode with(C-C-N)and(C-N-C)in-plane bending and F-C stretching and corresponds to Raman/IR mode at782/773cm−1.The experimental wave number at646cm−1in Raman spectra is assigned to the in-plane(O-C-N)and(F-C-C) bending at647cm−1.3.4.4C=O vibrationsThe appearance of strong bands in Raman and IR spectra around1700to1880cm−1show the presence of carbonyl group and is due to the C=O stretch.The frequency of the stretch due to carbonyl group mainly depends on the bond strength which in turn depends upon inductive,conjugative,ﬁeld and steric effects.The three strong bands in the IR spectra at 1721,1693and1668cm−1are due to C=O stretching vibrations corresponding to the three C=O groups at C(12),C(8)and C(7)respectively in tegafur.These bands are calculatedat1771,1725and1709cm−1.The discrepancy between the calculated and the observed frequencies may be due to the intermolecular hydrogen bonding.4ConclusionsThe equilibrium geometries of tegafur and5-FU and harmonic frequencies of tegafur molecule under investigation have been analyzed at DFT/6-311+G(d,p)level.In general, a good agreement between experimental and calculated normal modes of vibrations has been was observed.The skeleton of optimized tegafur molecule is non-planar.The lower frontier orbital energy gap and the higher dipole moment values make tegafur the more reactive and more polar as compared to the drug5-FU and results in improved target cell selectivity.The molecular electrostatic potential surface andﬁrst static hyperpolarizabil-ity have also been employed successfully to explain the higher activity of tegafur over its drug5-FU.The present study of tegafur and the corresponding drug in general may lead to the knowledge of chemical properties which are likely to improve absorption of the drug and the major metabolic pathways in the body and allow the modiﬁcation of the structure of new chemical entities(drug)for the improved bioavailability. Acknowledgments.We would like to thank Prof.Jenny Field for providing the crystal data of Tegafur and5-FU from Cambridge Crystallographic data centre(CCDC),U.K. and Prof.M.H.Jamroz for providing his VEDA4software.References[1]L.W.Li,D.D.Wang,D.Z.Sun,M.Liu,Y.Y.Di,and H.C.Yan,Chinese Chem.Lett.18(2007)891.[2] D.Engel, A.Nudelman,N.Tarasenko,I.Levovich,I.Makarovsky,S.Sochotnikov,I.Tarasenko,and A.Rephaeli,J.Med.Chem.51(2008)314.[3]Z.Zeng,X.L.Wang,Y.D.Zhang,X.Y.Liu,W H Zhou,and N.F.Li,Pharmaceutical Devel-opment and Technology14(2009)350.[4]ura,A Azucena,C Carmen,and G Joaquin,Therapeutic Drug Monitoring25(2003)221.[5] A.D.Becke,J.Chem.Phys.98(1993)5648.[6] C.Lee,W.Yang,and R.G.Parr,Phys.Rev.B37(1988)785.[7] B.Miehlich,A.Savin,H.Stoll,and H.Preuss,Chem.Phys.Lett.157(1989)200.[8]W.Kohn and L.J.Sham,Phys.Rev.140(1965)A1133.[9]M.J.Frisch,G.W.Trucks,H.B.Schlegel,et al.,Gaussian03,Rev.C.01(Gaussian,Inc.,Wallingford CT,2004).[10] A.P.Scott and L.Random,J.Phys.Chem.100(1996)16502.[11]P.Pulay,G.Fogarasi,G.Pongor,J.E.Boggs,and A.Vargha,J.Am.Chem.Soc.105(1983)7037.[12]R.Dennington,T.Keith,lam,K.Eppinnett,W.L.Hovell,and R.Gilliland,GaussView,Version3.07(Semichem,Inc.,Shawnee Mission,KS,2003).[13]M.H.Jamroz,Vibrational Energy Distribution Analysis:VEDA4Program(Warsaw,Poland,2004).[14]G.Keresztury,S.Holly,J.Varga,G.Besenyei,A.Y.Wang,and J.R.Durig,Spectrochim.Acta49A(1993)2007.[15]G.Keresztury,Raman spectroscopy theory,in:Handbook of Vibrational Spectroscopy,Vol.1,eds.J.M.Chalmers and P.R.Grifﬁth(John Wiley&Sons,New York,2002)pp.1.[16]http://riodb01.ibase.aist.go.jp/sdbs/(National Institute of Advanced Industrial Scienceand Technologys,Japan)[17] D.A.Kleinman,Phys,Rev.126(1962)1977.[18]J.Pipek and P.Z.Mezey,J.Chem.Phys.90(1989)4916.[19]dd,Introduction to Physical Chemistry,third ed.(Cambridge University Press,Cam-bridge,1998).[20] F.H.Allen,O.Kennard,and D.G.Watson,J.Chem.Soc.,Perkin Trans.2(S1)(1987)12.[21] B.Blicharska and T.Kupka,J.Mol.Struct.613(2002)153.[22]I.Fleming,Frontier Orbitals and Organic Chemical Reactions(John Wiley and Sons,NewYork,1976)pp.5-27.[23]J.S.Murray and K.Sen,Molecular Electrostatic Potentials,Concepts and Applications(El-sevier,Amsterdam,1996).[24]I.Alkorta and J.J.Perez,Int.J.Quant.Chem.57(1996)123.[25] E.Scrocco and J.Tomasi,Advances in Quantum Chemistry,Vol.11(Academic Press,NewYork,1978)pp.115.[26] F.J.Luque,M.Orozco,P.K.Bhadane,and S.R.Gadre,J.Phys.Chem.97(1993)9380.[27]J.Sponer and P.Hobza,Int.J.Quant.Chem.57(1996)959.。

调脂治疗逆转冠脉斑块

Nissen SE, et al. JAMA 2006; 295: 1556–65.
瑞舒伐他汀40mg目前未在中国注册；瑞舒伐他汀目前在中国的适应症为治疗高脂血症；瑞舒伐他汀在中国未注册逆转动脉粥样硬化及斑块的适应症。
主要终点（通过 IVUS 评估的两项终点）：所评估的整段动脉中动脉粥样硬化病变体积百分比（PAV）的变化病情最严重的 10mm 节段中动脉粥样硬化病变总体积（TAV）变化
Study of Coronary Atheroma by InTravascular Ultrasound: Effect of Rosuvastatin Versus AtorvastatiN 冠状动脉粥样斑块的血管内超声研究：瑞舒伐他汀和阿托伐他汀的效果比较
有效期至2012年11月
01
02
研究假设：只有在强效降低LDL-C基础之上，同时升高HDL-C达到一定水平才能真正逆转动脉粥样硬化斑块
LDL-C
HDL-C
TC
LDL-C/HDL-C ratio
Apo A1
* p<0.001 for difference from baseline values. Wilcoxon signed rank test
ASTEROID研究主要终点：中位数PAV的变化
-0.9
-0.8
-0.7
-0.6
-0.5
SATURN研究他汀治疗后血脂参数的变化瑞舒伐他汀阿托伐他汀
Nicholls SJ et al. New Eng J. Med. 2011: DOI: 10.1056/NEJMoa1110874
†组间比较；*与基线比较
P<0.001*
P<0.001*

(英文,图示详细、实用)去除地环干扰的方法

AŒ 30, 2008Electrical noise and mitigation - Part 3: Shielding and grounding (cont filtering harmonicsThis excerpt from the book "Practical Grounding, Bonding, Shielding and Protection" concludes with a look at the shielded isolation transformer, ze reference grounds and signal transport ground planes, and the generation of in electrical systems and how they can be filtered.By G Vijayaraghavan, MarkBrown, Malcolm BarnesShielding and Surge Protection" by ordering fr and using offer code 92[Part 1begins by defining electrical noise, examreasons for its generation and looking at ways toits effects. Part 2looks at earth loop as a causethe ways in which noise can enter a signal cablcontrol, and shielding.]8.10 Shielded isolation transformerA shielded transformer is a two-winding transfusually delta"star connected and serves the fopurposes:∙Voltage transformation from the distribu voltage to the equipment's utilization voltage.∙Converting a 3-wire input power to a 4-wire output thereby deriving a stable neutral for the power supply wiring going to sensitive equ ∙Keeping third and its multiple harmonics away from sensitive equi allowing their free circulation in the delta winding.∙Softening of high-frequency noise from the input side by the natural i of the transformer, particularly true for higher frequency of noise the reactance becomes more as the frequency increases.∙Providing an electrostatic shield between the primary and the sec windings thus avoiding transfer of surge/impulse voltages passinginter-winding capacitance.Figure 8.27 shows the principle involved in a shielded transformer. The construction of the transformer is such that the magnetic core forms the innermost layer, followed by the secondary winding, the electrostatic shield made of a conducting material (usually copper) and finally the primary winding.Figure 8.27Principle of a shielded two winding transformerFigure 8.28 shows this detail.Figure 8.28Construction of a shielded two-winding transformerIt can be seen that the high-frequency surge is conducted to ground through the capacitance between the primary winding (on the left) and the shield, which is connected to ground. Besides the shield, the magnetic core, the neutral of the secondary winding and the grounding wire from the electronic equipment are all terminated to a ground bar, which in turn, is connected to the power supply ground/building ground. It is also important that the primary wiring to and secondary wiring from the isolation transformer are routed through separate trays/conduits. If this is not done, the inter-cable capacitances may come into play negating the very purpose of the transformer.Figure 8.29 shows the proper way for an isolation transformer to be wired. Note that the AC power supply wiring and the secondary wiring from the transformer are taken through separate conduits. Also, the common ground connection of the isolation transformer serves as the reference ground for the sensitive loads. The AC system ground electrode connection is taken through a separate metal conduit. If these methods are not followed and wiring/earth connections are done incorrectly, noise problems may persist in spite of the isolation transformer.Figure 8.29Wiring/earthing of a shielded two-winding transformer8.11 Avoidance of earth loopWe discussed earlier in this chapter about the earth loop being a primary mechanism of noise injection into sensitive signal circuits. One of the important noise mitigation measures is therefore the avoidance of ground loops altogether. We have also seen in the previous chapters that while keeping a separate ground for the sensitive equipment may resolve noise issues, it is an unsatisfactory solution from the safety point of view.The correct approach is therefore to keep a common electronic ground but bond it firmly with the power system ground at the source point. Figure 8.30 shows an installation with a ground loop problem.Figure 8.30Ground loop problemHere, the main computer system (bottom) and its user terminal are shown connected to the power circuit (including ground wiring) at two different points. A communication cable runs between the computer and its terminal. A ground loop is thus formed with the length of communication cable and the ground wire acting together in series.Figure 8.31 shows one way in which this loop can be tackled, by bringing the two power and ground connections together to outlets at a single point.Figure 8.31Solution to the ground loop problemThis arrangement may not be feasible or practical to adopt. What is really possibleis to introduce additional impedance in the ground loop so that the high-frequency noise prefers to take another low-impedance path and diverts itself away from the communication path. This is the principle behind the use of a longitudinal (or 'balun') transformer. Figure 8.32 demonstrates the action of this method.Figure 8.32Use of a 'balun' transformer for noise mitigation8.12 Use of insulated ground (IG) receptacleThe IG receptacles are used in situations where we wish to avoid the mixing of sensitive equipment ground and the building power system ground at all points except the power source (say, the secondary of the shielded isolation transformer) thus avoiding ground loops from forming. Figure 8.33 shows such a receptacle.Figure 8.33An exploded view of IG receptacleThe receptacle frame has a separate ground connection, which is bonded to the general ground system through the metallic conduit to ensure safe conditions. But the grounding wire from the sensitive equipment is an insulating wire, which runs through the conduit directly to the ground point of the source. Figure 8.34 illustrates such a connection.Figure 8.34Grounding while using an IG receptacle8.13 Zero signal reference grid and signal transport ground planeFrom the foregoing, it will be clear that correct ground connection is a key factor for error-free operation of sensitive equipment and elimination of ground loops to the best possible extent is of extreme importance.A practical way in which the above can be achieved is by using the support structures of the raised floor (which are common in computer installations and control rooms) as a ground grid called the zero signal reference grid (ZSRG). The grid is formed by the support structures of the raised floor usually arranged as 2 ft square tiles. Copper conductor of #4 AWG size is clamped to the structures forming a grid. All signal grounds of the sensitive equipment and enclosures of the equipment are connected to this grid by short grounding leads.The grid itself is connected to the power ground through more than one conductor. It is ideal to place the isolation transformer also on this grid and connect the secondary neutral point to the reference grid. Figure 8.35 shows the construction of a ZSRG installation.Figure 8.35Zero signal reference ground using a cavity floorWhen communication cables are used to interconnect two sensitive equipment, use of a signal transport ground plane (STGP) is recommended. This is a copper foil or a GI sheet on which the communication cable is placed so that it is shielded from electrostatic transfer of noise.Metallic cable trays on which a cable is placed and clamped close to it can also serve as an STGP. Within the same room the STGP can be bonded to the ZSRG at one or more points. When a cable runs between installations in different parts of a building, it will be necessary to have individual ZSRGs in each area and also ensure that the STGP is bonded at either end to these grids. In case balun transformers are also used on the signal cable, noise will be further reduced. Figure 8.36 shows such an installation.Figure 8.36Use of signal transport ground planeUse of ZSRG has an added bonus too. It provides numerous parallel grounding paths and thus avoids resonance situation. Resonance happens when the length of a ground lead coincides with quarter wavelength of the noise frequency (or 3/4, 1 1/4, etc.) causing the earth lead to act as an open circuit to these frequencies. With multiple ground paths, this is unlikely to happen.A judicious mix of ZSRG, shielded transformer and STGP used appropriately will go a long way in avoiding grounding related noise problems.Raised floor-supporting structure as a signal reference grid:∙Bolted down stringers (struts between supporting posts) assure low electrical resistance joints.∙Isolation from building steel except via computer system earthing conductors, conductor to computer systems central earthing point and to power source earth.∙Ideal floor height for crawling access is 30 in. less than 18 in. restricts airflow. For larger computer rooms, install firewall separation barriers to confine fire and Halon extinguishing gas.8.13.1 Self-resonance effect in grounding/bonding conductorsWhen dealing with grounding of power system conductors, we are concerned with the ground circuit resistance. But when dealing with circuits with high-frequency signals, it becomes necessary to consider the impedance of the grounding conductor. The grounding electrode conductors (the conductors that connect a system to the ground electrode) exhibit distributed capacitance and inductance in the length of the conductor. A particular conductor may resonate at a certain frequency (or it multiples) and may thus behave like an open-circuited conductor (refer Figure 8.37).Figure 8.37Impedance variation of a typical grounding electrode conductorIt is therefore advisable that grounding circuits of such systems be connected usingmultiple conductors with different lengths so that the combined grounding system does not resonate as a whole for any frequency. The ZSRG thus fulfills this need by providing multiple ground paths of differing lengths so that the ground path always has low impedance for any signal frequency (refer Figure 8.38).Figure 8.38Effective grounding by ZSRG8.14 Harmonics in electrical systemsThe subject of harmonics is not directly related to this course, except that it is also a contributory factor in electrical noise. It also causes several other problems in power circuit components such as motors, transformers and capacitor banks.A load that is purely resistive has the same wave shapes for voltage and current. Both are normally pure sinusoids. Most induction motors fed directly from AC mains also behave in a similar manner except that they draw some reactive load as well. The current waveform is still sinusoidal (see Figure 8.39).Figure 8.39Voltage and current waveforms of an induction motorHowever, the current waveform gets distorted when power electronic devices are introduced in the system to control the speed of motors. These devices chop off partLet us see how these shunt filters function. We can use acomputer to show what happens as harmonics are filtered froma distorted wave. The example chosen is a 120° square wavecurrent with a 10° commutation time; a typical line currentwaveform for a DC motor drive and for many AC drives.Here is the square wave before any filtering. The distortionfactor is 26% not too pretty a waveform (Figure 8.41a). Nowlet us take out the fifth harmonic.This may not look a whole lot better, but the distortionfactor is down from 26 to 18%, so things are improving(Figure 8.41b). Now let us take out the seventh as well.Things are actually looking better now. We can see the sinewave starting to emerge. Distortion factor is down to 11%(Figure 8.41c). Next, we take out the eleventh.Still no beauty queen, but the distortion factor is now only8% (Figure 8.41d). Let us add in the final element and removethe thirteenth harmonic.This is our final current waveform (Figure 8.41e). Thedistortion factor is 6%, so we are putting a reasonablecurrent into the utility. Of course, the significance ofthis current waveform to the voltage distortion would dependon the source impedance and the current level.Figure 8.41Reduction of harmonics by filtersHigher-frequency harmonics can be propagated by the powerconductors acting as antennae and appear as induced noisevoltages in nearby signal circuits.It is not possible to prevent harmonic currents altogether. But they can be prevented from flowing through the entire system by providing a separate low-impedance path for them. This is done by the use of adequately rated series tuned circuits consisting of a reactor and capacitor, which have equal impedance at a specific harmonic frequency.Several such tuned banks (one for each harmonic frequency) will be needed to totally divert all harmonics away from the system. However, for practical reasons, only a few of the lower order harmonics with larger magnitudes are filtered out, which is adequate to provide substantial reduction of harmonic content.Figure 8.41 shows how a filter might remove the high-frequency components and how the wave shape might appear as the removal takes place. A full treatment of this subject is beyond the scope of this book.8.15 SummaryIn this chapter, we have dealt with electrical noise in detail and the ways in which noise finds a path into sensitive signal circuits. We learnt the various methods by which noise can be reduced by avoiding shields, by separating the cabling, by using shielding transformers, by eliminating earth loops and by using zero signal reference grounds and signal transport ground planes. We also briefly dealt with the generation of harmonics and how they can be filtered.Printed with permission from Butterworth Heinemann。

快速制备Cf

第27卷第1期粉末冶金材料科学与工程2022年2月V ol.27 No.1 Materials Science and Engineering of Powder Metallurgy Feb. 2022DOI:10.19976/ki.43-1448/TF.2021083快速制备C f/SiC复合材料的组织与力学性能王洋，李国栋，于士杰，姜毅(中南大学粉末冶金国家重点实验室，长沙410083)摘要：以SiC粉末、醇溶性酚醛树脂粉末以及炭纤维毡、炭纤维无纬布为原料，采用料浆刷涂−针刺−温压固化−高温碳化工艺，在料浆中酚醛树脂的体积分数分别为10%和15%、温压固化压力分别为8 MPa和20 MPa条件下制备C f/SiC多孔预制体，然后通过化学气相渗透法沉积SiC，快速制备C f/SiC陶瓷基复合材料。

观察和分析复合材料的形貌和组织结构，测定材料的密度、孔隙率、抗弯强度和断裂韧性等性能。

结果表明：料浆中的酚醛树脂体积分数较低时，C f/SiC复合材料的性能较好，并且随固化压力增加而提高。

在酚醛树脂体积分数为10%、温压固化压力为20 MPa条件下得到开孔隙率为13.1%的高致密C f/SiC复合材料，该材料的基体较致密，且纤维束和基体之间基本没有孔隙；当材料受到外加载荷时，通过纤维拔出、纤维脱粘和裂纹偏转来提高复合材料的强度和韧性，断裂方式为假塑性断裂，抗弯强度和断裂韧性都较高，分别为570 MPa和18.6 MPa∙m1/2。

关键词：C f/SiC复合材料；料浆针刺；化学气相渗透；抗弯强度；断裂韧性中图分类号：TB332文献标志码：A 文章编号：1673-0224(2022)01-92-10Microstructure and mechanical properties ofrapid prepared C f/SiC compositesAll Rights Reserved.WANG Yang, LI Guodong, YU Shijie, JIANG Yi(State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China)Abstract: C f/SiC ceramic matrix composites were prepared byslurry brushing-needle punching-warm pressure curing-high temperature carbonization proces using SiC powders, alcohol-soluble phenolic resin powders, carbon fiber felt andcarbon fibers weft free cloth as raw materials. The C f/SiC porous preform was prepared by slurry brush coating, puncture,temperature pressure curing and high temperature carbonization. The volume fraction of phenolic resin in the slurry wasrespectively 10% and 15%, and temperature and pressure curing pressures was 8 MPa and 20 MPa, respectively. Andthen SiC was deposited by chemical vapor infiltration method to quickly prepare C f/SiC ceramic matrix composites. Themorphology and microstructure of the materials were observed and analyzed. The properties such as density, porosity,bending strength and fracture toughness of the materials were measured. The results show that the properties of C f/SiCcomposites are better when the volume fraction of phenolic resin in the slurry is low, and the properties increase with theincrease of curing pressure. When the volume fraction of phenolic resin was 10% and the curing pressure was 20 MPa, ahigh density C f/SiC composite with open porosity of 13.1% is obtained. The matrix of C f/SiC composite was relativelycompact, and there was almost no pores between the fiber bundles and the matrix. When the composite was subjected tothe applied load, the strength and toughness of the composite were improved by fiber pulling out, fiber debonding andcrack deflection. The fracture mode of the composite was pseudoplastic fracture, with the highest bending strength andfracture toughness of 570 MPa and 18.6 MPa·m1/2, respectively.Keywords: C f/SiC composites; slurry needling; chemical vapor infiltration; bending strength; fracture toughness基金项目：轻质高强结构材料国家重点实验室基金资助项目收稿日期：2021−09−16；修订日期：2021−10−29通信作者：李国栋，教授，博士。

第二讲语言迁移与对比分析假说

第二讲语言迁移与对比分析假说（Language Transfer and Contrastive Analysis Hypothesis）对儿童而言，他们从对母语一片空白到流利表达，一语习得是个虽然复杂但是相对快速的过程。

过了儿童时期，再来学习一门新的语言，似乎就没有母语那么简单，这个过程相比之下显得极其困难，而且绝少能够达到精通与流利的程度。

成人学习者往往花费数年时间，才能够达到儿童在四五岁时轻而易举就可以达到的语言熟练程度。

过了儿童期，无论成人如何努力，二语习得似乎都很难达到类似母语的水平。

二语习得者经常困惑于这样的问题：成人二语学习者与儿童一语学习者的差异、成人的二语学习效果为何如此糟糕、成人的二语学习与儿童的一语学习路径是否一致、成人的二语学习如何达到高效，等等。

对于二语习得领域的这些核心议题，虽然一些学者已经关注了很长时间，不过第二语言习得仍然是一个新的领域。

从1940年代至今，学界一直试图运用许多理论研究人类如何学习第二语言，从行为主义学习模式，到近来认知视角的输入与互动假说，不一而足。

如今，第二语言习得领域的诸多论题，大多植根于早期的语言学、心理学、社会学以及教学论的研究进展，从本章开始，我们试图探究第二语言习得研究的理论基础，这种基础的构建大致从20世纪50年代开始，而这正是对语言学习进行理论研究的时期。

一、理论背景语言迁移一直是应用语言学、第二语言习得和语言教学领域有争议的论题。

其理论基础就是对比分析理论假说。

对比分析理论假说主要是基于行为主义心理学与结构主义语言学的背景，在20世纪50-60年代盛于一时，余脉迄今未歇。

在20世纪50-60年代，第二语言习得的理论探索绝对是语言教学实践的附属，从19世纪的教学革新运动开始，语言教学只能适应于学习过程的观念深入人心。

当时语言学理论体系里，索绪尔仍然居于统治地位，乔姆斯基的生成语法理论还在摇篮之中。

“the conviction that language systems considered fo a finite set of ‘patterns’or ‘structures’which acted as models……for the production of an infinite number of similary constructed sentences;the belief that repetition and practice resulted in the formation of accurate and fluent foreign language habits; a methodology which set out to teach ‘the basics’before encouraging learners to communicate their own thoughts and ideas”.对比分析假说理论的首创者Charles Fries (1945)就提出假设：语言教学的最终目的是建立一套习惯，在此过程中，人们倾向于把母语及其文化的形式、意义以及分布迁移到目的语及其文化之中。

On the Effect of the Internal Friction of Fluids on the Motion of Pendulums

ON THE EFFECT OF THE INTERNAL FRICTION OF FLUIDS ON THE MOTION OF PENDULUMSSir George Gabriel Stokes[Read December 9, 1850.][From the Transactions of the Cambridge Philosophical Society, Vol. IX. p. [8]Reprinted in Mathematical and Physical Papers, Sir George Gabriel Stokes and Sir J. Larmor, Vol. 3, 1880-1905]T HE great importance of the results obtained by means of the pendulum has induced philosophers to devote so much attention to the subject, and to perform the experiments with such a scrupulous regard to accuracy in every particular, that pendulum observations may justly be ranked among those most distinguished by modern exactness. It is unnecessary here to enumerate the different methods which have been employed, and the several corrections which must be made, in order to deduce from the actual observations the result which would correspond to the ideal case of a simple pendulum performing indefinitely small oscillations in vacuum. There is only one of these corrections which bears on the subject of the present paper, namely, the correction usually termed the reduction to a vacuum. On account of the inconvenience and expense attending experiments in a vacuum apparatus, the observations are usually made in air, and it then becomes necessary to apply a small correction, in order to reduce the observed result to what would have been observed had the pendulum been swung in a vacuum. The most obvious effect of the air consists in a diminution of the moving force, and consequent increase in the time of vibration, arising from the buoyancy of the fluid. The correction for buoyancy is easily calculated from the first principles of hydrostatics, and formed for a considerable time the only correction which it was thought necessary to make for reduction to a vacuum. But in the year 1828 Bessel, in a very important memoir in which he determined by a new method the length of the seconds' pendulum, pointed out from theoretical considerations the necessity of taking account of the inertia of the air as well as of its buoyancy. The numerical calculation of the effect of the inertia forms a problem of hydrodynamics which Bessel did not attack; but he concluded from general principles that a fluid, or at any rate a fluid of small density, has no other effect on the time of very small vibrations of a pendulum than that it diminishes its gravity and increases its moment of inertia. In the case of a body of which the dimensions are small compared with the length of the suspending wire, Bessel represented the increase of inertia by that of a mass equal to k times the mass of the fluid displaced, which must be supposed to be added to the inertia of the body itself. This factor k be determined experimentally for a sphere a little more than two inches in diameter, swung in air and in water. The result for air, obtained in a rather indirect way, was k = 0.9459, which value Bessel in a subsequent paper increased to 0.956. A brass sphere of the above size having been swung in water with two different lengths of wire in succession gave two values of k, differing a little from each other, and equal to only about two-thirds of the value obtained for air.The attention of the scientific world having been called to the subject by the publication of Bessel's memoir, fresh researches both theoretical and experimental soon appeared. In order to examine the effect of the air by a more direct method than that employed by Bessel, a large vacuum apparatus was erected at the expense of the Board of Longitude, and by means of this apparatus Captain (now Colonel) Sabine determined the effect of the air on the time of vibration of a particular invariable pendulum. The results of the experiments are contained in a memoir read before the Royal Society in March 1829, and printed in the Philosophical Transactions for that year. The mean of eight very consistent experiments gave 1.655 as the factor by which for that pendulum the old correction for buoyancy must be multiplied in order to give the whole correction on account of the air. A very remarkable fact was discovered in the course of these experiments. While the effects of air at the atmospheric pressure and under a pressure of about half an atmosphere were found to be as nearly as possible proportional to the densities, it was found that the effect of hydrogen at the atmospheric pressure was much greater, compared with the effect of air, than corresponded with its density. In fact, it appeared that the ratio of the effects of hydrogen and air on the times of vibration was about 1 to 5 1/4, while the ratio of the densities is only about 1 to 13. In speaking of this result Colonel Sabine remarks, "The difference of this ratio from that shewn by experiment is greater than can well be ascribed to accidental error in the experiment, particularly as repetition produced results almost identical. May it not indicate an inherent property in the elastic fluids, analogous to that of viscidity in liquids, of resistance to the motion of bodies passing through them, independently of their density ? a property, in such case,possessed by air and hydrogen gas in very different degrees; since it would appear from the experiments that the ratio of the resistance of hydrogen gas to that of air is more than double the ratio following from their densities. Should the existence of such a distinct property of resistance, varying in the different elastic fluids, be confirmed by experiments now in progress with other gases, an apparatus more suitable than the present to investigate the ratio in which it is possessed by them, could scarcely be devised: and the pendulum, in addition to its many important and useful purposes in general physics, may find an application for its very delicate, but, with due precaution, not more delicate than certain, determinations, in the domain of chemistry." Colonel Sabine has informed me that the experiments here alluded to were interrupted by a cause which need not now be mentioned, but that as far as they went they confirmed the result of the experiments with hydrogen, and pointed out the existence of a specific action in different gases, quite distinct from mere variations of density.Our knowledge on the subject of the effect of air on the time of vibration of pendulums has received a most valuable addition from the labours of the late Mr Baily, who erected a vacuum apparatus at his own house, with which he performed many hundreds of careful experiments on a great variety of pendulums. The experiments are described in a paper read before the Royal Society on the 31st of May 1832. The result for each pendulum is expressed by the value of n, the factor by which the old correction for buoyancy must be multiplied in order to give the whole effect of the air as deduced from observation. Four spheres, not quite 1 1/2 inch in diameter, gave as a mean n = 1.864, while three spheres, a little more than 2 inches in diameter, gave only 1.748. The latter were nearly of the same size as those with which Bessel, by a different method, had obtained k = 0.946 or 0.956, which corresponds to n = 1.946 or 1.956. Among the "Additional Experiments " in the latter part of Baily's paper, is a set in which the pendulums consisted of plain cylindrical rods. With these pendulums it was found that n regularly increased, though according to an unknown law, as the diameter of the rod decreased. While a brass tube 1 1/2 inch in diameter gave n equal to about 2.3, a thin rod or thick wire only 0.072 inch in diameter gave for n a value as great as 7.530.Mathematicians in the meanwhile were not idle, and several memoirs appeared about this time, of which the object was to determine from hydrodynamics the effect of a fluid on the motion of a pendulum. The first of these came from the pen of the celebrated Poisson. It was read before the French Academy on the 22nd of August 1831, and is printed in the 11th Volume of the Memoirs. In this paper, Poisson considers the case of a sphere suspended by a fine wire, and oscillating in the air, or in any gas. He employs the ordinary equations of motion of an elastic fluid, simplified by neglecting the terms which involve the square of the velocity; but in the end, in adapting his solution to practice, be neglects, as insensible, the terms by which alone the action of an elastic differs from that of an incompressible fluid, so that the result thus simplified is equally applicable to fluids of both classes. He finds that when insensible quantities are neglected n = 1.5, so that the mass which we must suppose added to that of the pendulum is equal to half the mass of the fluid displaced. This result does not greatly differ from the results obtained experimentally by Bessel in the case of spheres oscillating in water, but differs materially from the result he bad obtained for air. It agrees pretty closely with some experiments which bad been performed about fifty years before by Dubuat, who bad in fact anticipated Bessel in shewing that the time of vibration of a pendulum vibrating in a fluid would be affected by the inertia of the fluid as well as by its density. Dubuat's labours on this subject had been altogether overlooked by those who were engaged in pendulum experiments; probably because such persons were not likely to seek in a treatise on hydraulics for information connected with the subject of their researches. Dubuat had, in fact, rather applied the pendulum to hydrodynamics than hydrodynamics to the pendulum.In the Philosophical Magazine for September 1833, p. 185, is a short paper by Professor Challis, on the subject of the resistance to a ball pendulum, After referring to a former paper, in which he had shewn that no sensible error would be committed in a problem of this nature by neglecting the compressibility of the fluid even if it be elastic, Professor Challis, adopting a particular hypothesis respecting the motion, obtains 2 for the value of the factor n for such a pendulum. This mode of solution, which is adopted in several subsequent papers, has given rise to a controversy between Professor Challis and the Astronomer Royal, who maintains the justice of Poisson's result.In a paper read before the Royal Society of Edinburgh on the 16th of December 1833, and printed in the 13th Volume of the Society's Transactions, Green has determined from the common equations of fluid motion the resistance to an ellipsoid performing small oscillations without rotation. The result is expressed by a definite integral; but when two of the principal axes of the ellipsoid become equal, the integral admits of expression in finite terms, by means of circular or logarithmic functions. When the ellipsoid becomes a sphere, Green's result reduces itself to Poisson's.In a memoir read before the Royal Academy of Turin on the 18th of January 1835, and printed in the 37th Volume of the memoirs of the Academy, M. Plana has entered at great length into the theory of the resistance of fluids to pendulums. This memoir contains, however, rather a detailed examination of various points connected with the theory, than the determination of the resistance for any new form of pendulum. The author first treats the case of an incompressible fluid, and then shews that the result would be sensibly the same in the case of an elastic fluid. In the case of a ball pendulum, the only one in which a complete solution of the problem is effected, M. Plana's result agrees with Poisson's.In a paper read before the Cambridge Philosophical Society on the 29th of May 1843, and printed in the 8th Volume of the Transactions, p. 105*, 1 have determined the resistance to a ball pendulum oscillating within a concentric spherical envelope, and have pointed out the source of an error into which Poisson had fallen, in concluding that such an envelope would have no effect . When the radius of the envelope becomes infinite, the solution agrees with that which Poisson had obtained for the case of an unlimited mass of fluid. I have also investigated the increase of resistance due to the confinement of the fluid by a distant rigid plane. The same paper contains likewise the calculation of the resistance to a long cylinder oscillating in a mass of fluid either unlimited, or confined by a cylindrical envelope, having the same axis as the cylinder in its position of equilibrium. In the case of an unconfined mass of fluid, it appeared that the effect of inertia was the same as if a mass equal to that of the fluid displaced were distributed along the axis of the cylinder, so that n = 2 in the case of a pendulum consisting of a long cylindrical rod. This nearly agrees with Baily's result for the long 1 ½-inch tube ; but, on comparing it with the results obtained with the cylindrical rods, we observe the same sort of discrepancy between theory and observation as was noticed in the case of spheres. The discrepancy is, however, far more striking in the present case, as might naturally have been expected, after what had been observed with spheres, on account of the far smaller diameter of the solids employed.* [Ante, Vol. 1. p. 179.]A few years ago Professor Thomson communicated to me a very beautiful and powerful method which he had applied to the theory of electricity, which depended on the consideration of what he called electrical images. The same method, I found, applied, with a certain modification, to some interesting problems relating to ball pendulums. It enabled me to calculate the resistance to a sphere oscillating in presence of a fixed sphere, or within a spherical envelope, or the resistance to a pair of spheres either in contact, or connected by a narrow rod, the direction of oscillation being, in all these cases, that of the line joining the centres of the spheres. The effect of a rigid plane perpendicular to the direction of motion is of course included as a particular case. The method even applies, as Professor Thomson pointed out to me, to the uncouth solid bounded by the exterior segments of two intersecting spheres, provided the exterior angle of intersection be a submultiple of two right angles. A set of corresponding problems, in which the spheres are replaced by long cylinders, may be solved in a similar manner. These results were mentioned at the meeting of the British Association at Oxford in 1847, and are noticed in the volume of reports for that year, but they have not yet been published in detail.The preceding are all the investigations that have fallen under my notice, of which the object was to calculate from hydrodynamics the resistance to a body of given form oscillating as a pendulum. They all proceed on the ordinary equations of the motion of fluids. They all fail to account for one leading feature of the experimental results, namely, the increase of the factor n with a decrease in the dimensions of the body. They recognize no distinction between the action of different fluids, except what arises from their difference of density.In a conversation with Dr Robinson about seven or eight years ago on the subject of the application of theory to pendulums, he noticed the discrepancy which existed between the results of theory and experiment relating to a ball pendulum, and expressed to me his conviction that the discrepancy in question arose from the adoption of the ordinary theory of fluid motion, in which the pressure is supposed to be equal in all directions. He also described to me a remarkable experiment of Sir James South's which be had witnessed. This experiment has not been published, but Sir James South has kindly allowed me to mention it. When a pendulum is in motion, one would naturally have supposed that the air near the moving body glided past the surface, or the surface past it, which comes to the same thing if the relative motion only be considered, with a velocity comparable with the absolute velocity of the surface itself. But on attaching a piece of gold leaf to the bottom of a pendulum, so as to stick out in a direction perpendicular to the surface, and then setting the pendulum in motion, Sir James South found that the gold leaf retained its perpendicular position just as if the pendulum had been at rest ; and it was not till the gold leaf carried by the pendulum had been removed to some distance from the surface, that it began to lag behind. Thisexperiment shews clearly the existence of a tangential action between the pendulum and the air, and between one layer of air and another. The existence of a similar action in water is clearly exhibited in some experiments of Coulomb's which will be mentioned in the second part of this paper, and indeed might be concluded from several very ordinary phenomena, Moreover Dubuat, in discussing the results of his experiments on the oscillations of spheres in water, notices a slight increase in the effect of the water corresponding to an increase in the time of vibration, and expressly attributes it to the viscosity of the fluid.Having afterwards occupied myself with the theory of the friction of fluids, and arrived at general equations of motion, the same in essential points as those which had been previously obtained in a totally different manner by others, of which, however, I was not at the time aware, I was desirous of applying, if possible, these equations to the calculation of the motion of some kind of pendulum. The difficulty of the problem is of course materially increased by the introduction of internal friction, but as I felt great confidence in the essential parts of the theory, I thought that labour would not be ill-bestowed on the subject. I first tried a long cylinder, because the solution of the problem appeared likely to be simpler than in the case of a sphere. But after having proceeded a good way towards the result, I was stopped by a difficulty relating to the determination of the arbitrary constants, which appeared as the coefficients of certain infinite series by which the integral of a certain differential equation was expressed. Having failed in the case of a cylinder, I tried a sphere, and presently found that the corresponding differential equation admitted of integration in finite terms, so that the solution of the problem could be completely effected. The result, I found, agreed very well with Baily's experiments, when the numerical value of a certain constant was properly assumed ; but the subject was laid aside for some time. Having afterwards attacked a definite integral to which Mr Airy bad been led in considering the theory of the illumination in the neighbourhood of a caustic, I found that the method which I had employed in the case of this integral* would apply to the problem of the resistance to a cylinder, and it enabled me to get over the difficulty with which I bad before been baffled. I immediately completed the numerical calculation, so far as was requisite to compare the formulae with Baily's experiments on cylindrical rods, and found a remarkably close agreement between theory and observation. These results were mentioned at the meeting of the British Association at Swansea in 1848, and are briefly described in the volume of reports for that year.The present paper is chiefly devoted to the solution of the problem in the two cases of a sphere and of a long cylinder, and to a comparison of the results with the experiments of Baily and others. Expressions are deduced for the effect of a fluid both on the time and on the arc of vibration of a pendulum consisting either of a sphere, or of a cylindrical rod, or of a combination of a sphere and a rod. These expressions contain only one disposable constant, which has a very simple physical meaning, and which I propose to call the index of friction of the fluid. This constant we may conceive determined by one observation, giving the effect of the fluid either on the time or on the arc of vibration of any one pendulum of one of the above forms, and then the theory ought to predict the effect both on the time and on the arc of vibration of all such pendulums. The agreement of theory with the experiments of Baily on the time of vibration is remarkably close. Even the rate of decrease of the are of vibration, which it formed no part of Baily's object to observe, except so far as was necessary for making the small correction for reduction to indefinitely small vibrations, agrees with the result calculated from theory as nearly a& could reasonably be expected under the circumstances.* [Ante, Vol. II. p. 328.]It follows from theory that with a given sphere or cylindrical rod the factor n increases with the time of vibration. This accounts in a good measure for the circumstance that Bessel obtained so large a value of k for air, as is shewn at length in the present paper; though it unquestionably arose in a great degree from the increase of resistance due to the close proximity of a rigid plane to the swinging ball.I have deduced the value of the index of friction of water from some experiments of Coulomb's on the decrement of the are of oscillation of disks, oscillating in water in their own plane by the torsion of a wire. When the numerical value thus obtained is substituted in the expression for the time of vibration of a sphere, the result agrees almost exactly with Bessel's experiments with a sphere swung in water.The present paper contains one or two applications of the theory of internal friction to problems which are of some interest, but which do not relate to pendulums. The resistance to a sphere moving uniformly in a fluid may be obtained as a limiting case of the resistance to a ball pendulum, provided the circumstances be such that the square of the velocity may be neglected. The resistance thus determined proves to be proportional, for a given fluid and a given velocity, not to the surface, but to the radius of the sphere; and therefore the accelerating force of theresistance increases much more rapidly, as the radius of the sphere decreases, than if the resistance varied as the surface, as would follow from the common theory. Accordingly, the resistance to a minute globule of water falling through the air with its terminal velocity depends almost wholly on the internal friction of air. Since the index of friction of air is known from pendulum experiments, we may easily calculate the terminal velocity of a globule of given size, neglecting the part of the resistance which depends upon the square of the velocity. The terminal velocity thus obtained is so small in the case of small globules such as those of which we may conceive a cloud to be composed, that the apparent suspension of the clouds does not seem to present any difficulty. Had the resistance been determined from the common theory, it would have been necessary to suppose the globules much more minute, in order to account in this way for the phenomenon. Since in the case of minute globules falling with their terminal velocity the part of the resistance depending upon the square of the velocity, as determined by the common theory, is quite insignificant compared with the part which depends on the internal friction of the air, it follows that were the pressure equal in all directions in air in the state of motion, the quantity of water which would remain suspended in the state of cloud would be enormously diminished. The pendulum thus, in addition to its other uses, affords us some interesting information relating to the department of meteorology.The fifth section of the first part of the present paper contains an investigation of the effect of the internal friction of water in causing a series of oscillatory waves to subside. It appears from the result that in the case of the long swells of the ocean the effect of friction is insignificant, while in the case of the ripples raised by the wind on a small pool, the motion subsides very rapidly when the disturbing force ceases to act.PART I.ANALYTICAL INVESTIGATION.SECTION I.Adaptation of the general equations to the case of the fluid surrounding a body which oscillates as a pendulum. General laws which follow from the form of the equations. Solution of the equations in the case of an oscillating plane.1. IN a paper "On the Theories of the Internal Friction of Fluids in Motion, &c.*,'' which the society did me the honour to publish in the 8th Volume of their Transactions, I have arrived at the following equations for calculating the motion of a fluid when the internal friction of the fluid itself is taken into account, and consequently the pressure not supposed equal in all directions: with two more equations which may be written down from symmetry. In these equations u, v, w, are the components of the velocity along the rectangular axes of x, y, z; X, Y, Z are the components of the accelerating force ; p is the pressure, t the time, ρ the density, and µ a certain constant depending on the nature of the fluid.The three equations of which (1) is the type are not the general equations of motion which apply to a heterogeneous fluid when internal friction is taken into account, which are those numbered 10 in my former paper, but are applicable to a homogeneous incompressible fluid, or to a homogeneous elastic fluid subject to small variations of density, such as those which accompany sonorous vibrations. It must be understood to be included in the term homogeneous that the temperature is uniform throughout the mass, except so far as it may be raised or lowered by sudden condensation or rarefaction in the case of an elastic fluid. The general equations contain the differential coefficients of the quantity µwith respect to x, y, and z; but the equations of the form (1) are in their present shape even more general than is required for the purposes of the present paper.* [Ante. Vol. I. p. 75.]These equations agree in the main with those which had been previously obtained, on different principles, by Navier, by Poisson, and by M. de Saint-Venant, as I have elsewhere observed*. The differences depend only on the coefficient of the last term, and this term vanishes in the case of an incompressible fluid, to which Navier bad confined his investigations.The equations such as (1) in their present shape are rather complicated, but in applying them to the case of a pendulum they may be a good deal simplified without the neglect of any quantities which it would be important to retain. In the first place the motion is supposed very small, on which account it will be allowable to neglect the terms which involve the square of the velocity. In the second place, the nature of the motion that we have got to deal with is such that the compressibility of the fluid has very little influence on the result, so that we may treat the fluid as incompressible, and consequently omit the last terms in the equations. Lastly, the forces X, Y, Z are in the present case the components of the force of gravity, and if we writeFor p, we may omit the terms X, Y, Z.If z' be measured vertically downwards from a horizontal plane drawn in the neighbourhood of the pendulum, and if g be the force of gravity, ∫ (Xdx + Ydy + Zdz) = gx', the arbitrary constant, or arbitrary function of the time if it should be found necessary to suppose it to be such, being included in Π. The part of the whole force acting on the pendulum which depends on the terms Π+ gρ z'is simply a force equal to the weight of the fluid displaced, and acting vertically upwards through the centre of gravity of the volume.* Report on recent researches in Hydrodynamics. Report of the British Association for 1846, p. 16. [Ante, Vol. I.p. 182.]When simplified in the manner just explained, the equations such as (1) becomewhich, with the equation of continuity,are the only equations which have to be satisfied at all points of the fluid, and at all instants of time.In applying equations (2) to a particular pendulum experiment, we may suppose µconstant ; but in order to compare experiments made in summer with experiments made in winter, or experiments made under a high barometer with experiments made under a low, it will be requisite to regard µ as a quantity which may vary with the temperature and pressure of the fluid. As far as the result of a single experiment*, which has been already mentioned, performed with a single elastic fluid, namely air, justifies us in drawing such a general conclusion, we may assert that for a given fluid at a given temperature µ varies as ρ +.2. For the formation of the equations such as (1), 1 must refer to my former paper; but it will be possible, in a few words, to enable the reader to form a clear idea of the meaning of the constant µ.Conceive the fluid to move in planes parallel to the plane of xy, the motion taking place in a direction parallel to the axis of y. The motion will evidently consist of a sort of continuous sliding, and the differential coefficient。

安捷伦Hi-Plex配体交换柱使用说明不完全翻译

Agilent Hi-Plex Ligand Exchange Columns安捷伦Hi-Plex配体交换柱Installation Column Connections安装色谱柱Hi-Plex columns are supplied with industry standard end fittings. Only compatible nuts and ferrules should be used. Nuts should be tightened finger tight and then 1/4 turn using a wrench. To avoid loosening column end fittings, wrenchesmust be used only on the outer column end fitting, marked A in Figure 1. Hi-Plex色谱柱提供行业标准端配件。

只能使用相容的螺母和套圈。

一般用用手指拧紧后再用扳手拧紧1/4圈。

为避免松动柱端配件，扳手只能在外柱端配件上使用，标有A在图1中。

Figure 1. Wrench surface.图1.扳手表面。

Alternatively, the appropriate PEEK “Fingertight” fitting can be used, ensuring that there is no dead volume between the tube and the end fitting bottom.另外，适当的PEEK“Fightertight”配件可以使用，确保没有管和接头底部之间无死体积。

Shipping Eluent运输洗脱液Hi-Plex columns are supplied containing UHP water. Columns are securely sealed with end caps which must ALWAYS be replaced when the column is disconnected from the system to prevent the column from drying out.提供的Hi-Plex色谱柱包含UHP水。

英语ppt

文章例句赏析
7)The coefficient of uniformity (CU) is calculated according to the Christiansen (1942) method by(论文常用表达语句，表达方式比较固定化，要灵活掌握)
Vi V CU 1001 nV
文章例句赏析
4)The results indicated that mean sprinkler irrigation depths ranged from 45.5 to 51.4 mm and from 21.3 to 25.9 mm for 15 and30 m /h system speeds, respectively. (并列结构写法)Mean coefficient of uniformity (CU) values for the same speeds ranged from 89.4% to 92.6% and 88.9% to 95.1%, respectively.
文章例句赏析
9)Increasing irrigation uniformity can improve irrigation efficiency by preventing deep percolation and surface runoff due to over irrigation. (语句整体简洁紧凑，没有一个词是浪费的，有种说不出的逻辑美感)
文章例句赏析
11）The system speed and the nozzle height were adjustable with a maximum possible speed of 50 m /h and a 1.90 m nozzle height above ground with nozzle spacings ranging from 1.45 to 1.55 m（with短语做补语解释说明前面的句子，比较常用，自己写写不成这样。）系统移动最大移动速度为50m/h, 喷头离地面最大高度为1.9m，喷头的间距为1.45m到1.55m。

TPO20阅读解析-Passage2

Q1正确答案：C解析：momentous“重要的，重大的”，所以very important正确。

从单词本身看，意思上应该跟moment相关，“时刻的”，A和D明显不合文意。

原句提到这些变化对于本地稀疏的人口有什么影响，“常规的”影响明显不正确，答案是C。

Q2正确答案：B解析：EXCEPT题，排除法。

A/C/D都在第一段第一句中提到了，只有B没有提到，所以答案是B。

Q3正确答案：D解析：指代题，需要沿着提到的内容往前看，前一句提到由于农业和城镇的发展，人口成千上万，紧接着提到this change，说这个变化指的就是人口的增长，所以答案是D。

Q4正确答案：B解析：exploit“开采，开发，利用”，所以B的utilize正确。

原句提到当地人怎么样自然景观，之后举了很多例子，有放牧有打猎等等，都是在利用自然环境，所以是“利用”。

C“定居”和D“改善”都不正确；A选项不选，后面的例子说明不只是探索，所以答案是B。

Q5正确答案：A解析：根据这些例子找定位，提到定居点里包含很多通过贸易获得的外来物品，诸如……，所以列举的这些东西都是外来品，A是正确答案。

BCD都未提及。

Q6正确答案：D解析：cramped“局促的，狭窄的，难懂的”，所以confined正确。

原句提到在公元前9500年，一个村子的人都在一个什么样的住处里，根据句义，这里强调的是比较小，所以其他的都不合文意。

而且extend刚好和confine是相反的意思，所以D是答案。

Q7正确答案：D解析：Abu Hureyra做关键词定位至第一句的后半句和第二句的前半句，一直在说AH，接着往下看，提到接下来的1500年里，他们所在的地方气候温暖，种子丰富，所以答案是D，C与原文相反；A和B选项的内容在此并未提及。

Q8正确答案：C解析：shift“转变，转换，倒班”，所以最接近的答案是change。

原句提到漂浮的样品使得植物学家研究植物集群习惯的什么就好像在显微镜下看风景一样，风景是会变的，所以答案是change。

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)。

Limitations Of This Study
Limitations noted by the researchers were firstly, a lack of longitudinal follow-up to establish whether the results lasted after treatment and secondly, the lack of a control group. •
PENNY ROBERTSHAWE Vaht M, Birkenfeldt R, Übner M. An evaluation of the effect of differing lengths of spa therapy upon patients with osteoarthritis (OA). Complementary Therapies in Clinical Practice 2008;14:60-64.
233
Copyright of Journal of the Australian Traditional-Medicine Society is the property of Australian TraditionalMedicine Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
Joumal of the Australian Traditional-Medicine Society December 2008 Volume 14 Issue 4
Research Review
EFFECT O F DIFFERING LENGTHS O F SPA THERAPY O N
OSTEOARTHRITIS P A T I E N T S
Method
Two hundred and ninety-six OA patients took part in this study. All participants were assessed for OA of the knee, hip or hand according to the American College of Rheumatology criteria. Participants were given the choice to join a 6 day spa treatment group or a 12 day spa treatment group. Two hundred and thirty-five participants (57 male, 178 female) chose to be in the 6 day group, and 61 participants (18 males, 43 females) elected to be in the 12 day group. Participants in the 6 day group were a mean age of 64.3 years, and those in the 12 day group were a mean age of 66.2 years. Both groups received daily spa therapies that consisted of alternating treatments over two consecutive days. Treatments on Day 1 consisted of either a paraffin-ozokerite treatment which involved having the paraffm ozokerite wrapped around the affected areas for a deep heating effect, or a mud treatment which was applied to the whole body. These treatments took 15 minutes. On Day 2, participants received either a pearl bath which involved sitting in a warm bath with air bubbles or an underwater massage involving the participant sitting in a bath with submerged water jets massaging joints and muscles. These treatments took 10-15 minutes. Days 1 and 2 alternated until the end of the study period (6 or 12 days). Participants also undertook 20 minutes of daily therapeutic exercise in the gym and 30 minutes of swimming pool exercises. They also received 20 minute massages each day.
Conclusion
The researchers concluded that study demonstrated that the intensity of elinical symptoms deereased in both groups. This meant that the therapy was effective in both groups of patients suffering from OA.
Pain was also assessed at the beginning and end of the study period by a 10 cm visual analogue scale (VAS) with 0 cm representing 'no pain' and 10 cm representing 'worst possible pain'. All participants completed these two measurements. Two hundred and twenty-nine participants who suffered knee and hip OA completed the Lequesne Index at the beginning and end of the study period. The results indicate the clinical severity of an OA sufferer's pain and categorises it into a (I) mild (II) moderate (III) severe (IV) very severe (V) extremely severe.
Measurements
The Health Assessment Questionnaire Disability Index (HAQ-DI) was used at the beginning of the study. This questionnaire assesses difficulty with daily activities such as dressing, eating and walking as well as pain severity.
Aim Of This Study
T
his study was conducted to determine the length of time required to obtain symptom relief for osteoarthritis (OA) through composite spa therapy.
Results
The mean HAQ-DI results for all participants showed that none of them were severely limited when it came to managing daily activities. Of those participants with knee OA (64%) and hip OA (19%), 37% complained of additional joint pain. Both groups showed similar levels of pain and disability prior to the study commencement. Participants who completed the Lequesne Index, and who were categorised between levels III and V, decreased their levels of severity by more than one point in 36.3% of cases post-intervention. This index also decreased by more than two points in 62.2% in the total 6 day group, and 72.7% in the total 12 day group post-intervention. VAS scores decreased from pre-intervention to post-intervention by more than one point in 78.7% of participants in the 6 day group and 79.6% in the 12 day group.