A CMBR Measurement Reproduced A Statistical Comparison of MSAM1-94 to MSAM1-92

a rXiv:as tr o-ph/96317v15Mar1996Submitted to Ap.J.Letters ;astro-ph/9603017A CMBR Measurement Reproduced:A Statistical Comparison of MSAM1-94to MSAM1-92C.A.Inman 1,E.S.Cheng 2,D.A.Cottingham 3,D.J.Fixsen 4,M.S.Kowitt 2,S.S.Meyer 1,L.A.Page 5,J.L.Puchalla 2,J.E.Ruhl 6,and R.F.Silverberg 2ABSTRACT The goal of the second ﬂight of the Medium Scale Anisotropy Measurement (MSAM1-94)was to conﬁrm the measurement of cosmic microwave background radiation (CMBR)anisotropy made in the ﬁrst ﬂight (MSAM1-92).The CMBR anisotropy and interstellar dust emission signals from the two ﬂights are compared by forming the sum and diﬀerence of those portions of the data with the same pointings on the sky.The diﬀerence data are consistent with a null detection,while the summed data show signiﬁcant signal.We conclude that MSAM1-92and MSAM1-94measured the same celestial signal.Subject headings:balloons —cosmic microwave background —cosmology:observations1.IntroductionMeasurements of anisotropy in the Cosmic Microwave Background Radiation(CMBR) continue as a subject of considerable interest to the astrophysics community.Future anisotropy measurements on scales of0.◦1to1.◦0will discriminate among early universe models and determine fundamental cosmological parameters(e.g.Hu and White1996, Knox1995and Jungman et al.1995).Measurements of anisotropy at angular scales near0.◦5have been reported recently by Ruhl et al.1995,Netterﬁeld et al.1996,Gundersen et al.1995,and Tanaka et al.1995. Wilkinson1995voiced a common concern when he pointed out that“there are plausible systematic eﬀects at levels comparable with the reported detections.”To address this concern the1994ﬂight of the Medium Scale Anisotropy Measurement(MSAM1)observed the sameﬁeld as the1992ﬂight to limit the possibility of systematic sources of the signal.Cheng et al.1994(hereafter Paper I)reported observations of anisotropy in the CMBR from theﬁrstﬂight of MSAM1in1992(MSAM1-92).Cheng et al.1996(hereafter Paper II)reported the results from the secondﬂight in1994(MSAM1-94).A conclusion of the latter is that while a quantitative comparison was pending,there was good qualitative agreement between the twoﬂights in the double diﬀerence data set,and that agreement was inconclusive for the single diﬀerence data set.This Letter presents a quantitative comparison of the MSAM1-92and MSAM1-94data sets.2.Instrument and ObservationsThe MSAM1instrument has been fully described in Fixsen et al.1996(hereafter Paper III);only an overview is given here.It is an oﬀ-axis Cassegrain telescope with a4-channel bolometric radiometer at the focus.The beamsize is28′FWHM and is moved ±40′on the sky by the nutating secondary.The radiometer has4frequency channels placed at5.7,9.3,16.5,and22.6cm−1.For these observation,emission in the lower two channels is dominated by the2.7K CMBR,while∼20K interstellar dust dominates the two higher channels.The instrument conﬁguration was similar for the twoﬂights,with changes made only to the warm signal electronics and the gondola structure.These changes are discussed extensively in Paper III;the modiﬁcations to the electronics improved the noise performance, while those to the gondola reduced sidelobe sensitivity.The original superstructure had a large reﬂecting area above the beam,from which earthshine could potentially diﬀract into the beam.For the secondﬂight,the gondola was suspended by a cable system whichreduced the far-sidelobe response.The measured near sidelobe response dropped from−55dB in1992in the worst case to less than−75dB in all cases in1994.As described in Papers I and II,the observedﬁeld is two strips at declination81.◦8±0.◦1, from right ascension15.h27to16.h84,and from17.h57to19.h71(all coordinates are J1994.5). Fig.1shows the weighted beam centers of theﬁelds observed in the1992and1994ﬂights.A CCD camera is used to determine absolute pointing for bothﬂights.Theﬁnal accuracy of the pointing determination is2.′5,limited by the gyroscope signal interpolation.This2.′5 uncertainty is small compared to the size of our beam(28′)and the bins(14′)used below, ensuring adequate alignment of the two datasets.During bothﬂights Jupiter was observed to calibrate the instrument and map the telescope beam.Beam maps and calibrations are done separately for the twoﬂights.The shape of the beam map is determined to4%of the maximum amplitude.Random noise in the gyroscope system contributes3.5%,and cosmic rays striking the detectors contribute 1.5%.Also,the choice of smoothing algorithm causes a1.5%systematic eﬀbining this4%error from eachﬂight gives a5.8%relative calibration uncertainty.The uncertainty in Jupiter’s intrinsic brightness leads to an additional systematic uncertainty of10%for the results of eachﬂight;however,except for possible time variations in Jupiter’s brightness which we do not expect,this uncertainty does not contribute to the comparison of the two ﬂights discussed here.3.Reanalysis of1992DataThe analyzed data sets reported in Papers I and II cannot be directly compared for two reasons:1)the boundaries of the sky bins are diﬀerent,and2)the analysis reported in Paper I neglects correlations introduced by the removal of the small oﬀset drift.The 1992data is reanalyzed to account for these correlations,using a procedure nearly identical to that of Paper II.The1994data is also reanalyzed,with diﬀerences from the original analysis noted in the text below.Here weﬁrst review the Paper II analysis,then note the diﬀerences between that and the reanalysis used here.First,the cosmic ray events are removed from the time stream.Cosmic ray removal techniques are diﬀerent for the two years,and are discussed in Papers I and II.The data are then analyzed in a manner that provides sensitivity to two diﬀerent angular scales on the sky.This is done by weighting the the time stream,S i,with one of two demodulation templates,d i,giving one“demodulated data point”,∆T cycle= i d i S i,for each full cycle of the secondary mirror movement.The“single diﬀerence demodulation”weights thesecondary-left data positively while weighting the secondary-right data negatively,giving a ∆T equal to the diﬀerence between the left and right temperatures.The result is a two lobed beam pattern on the sky with80′beam separation.The“double diﬀerence demodulation”weights the secondary-centered data positively,while weighting the secondary-left and secondary-right data negatively,giving a∆T equal to the diﬀerence between the center and the side temperatures.This produces a three lobed beam pattern on the sky,with40′beam separation.The single diﬀerence and double diﬀerence data are nearly statistically independent.A linear model isﬁt to these demodulated data including intensity for each sky bin and slow drifts in time.The noise used in theﬁt is estimated from the data.Both the time drift and noise estimate are described further below.The results of the linearﬁt are signal amplitudes for each sky bin with their associated covariances.A spectral model for each sky bin consisting of CMBR anisotropy plus emission from 20K Galactic dust,with emissivity proportional to frequency to the1.5power,isﬁt to all four frequency channels of binned sky data.The results of this spectralﬁt are the intensity of a“DUST”component and a“CMBR”component in each sky bin.The diﬀerences between the Paper II analysis and that done for this paper follow.This analysis uses a0.◦24bin size,double the size used in Paper II,which corresponds to the size of the central beam plateau.Angular orientation bins,which account for sky rotation relative to the secondary chop axis,are20◦,also double the previous size.The weighted beam centers of the identical bins are shown asﬁlled symbols in Fig.1.The noise estimates are formed from demodulated data.This is a change from Paper II, where the estimate is made after after having removed the drift model.The noise estimates are made separately for each minute of data by measuring the rms of the demodulated data in that minute.The new noise estimate is used in reanalyzing both the1992and1994 datasets.True sky signals make a negligible contribution to this rms estimate over these short time scales.This change has no substantial eﬀect on the results of this Letter.Also,in Paper II the drift model included terms based on gondola sensors(air pressure, and the pitch and roll angles of the gondola outer frame).This model was used in the1994 reanalysis,while it was not used for the1992reanalysis.Instead,the original model for the drifts described in Paper I,a spline with knots every2.5minutes,was used.Fig. 1.—The weighted positions for each sky bin for both years.The triangles mark the 1992centers and the squares mark the1994centers.The declination scale has been greatly expanded relative to the RA scale in order to see the detailed pointing diﬀerences.Theﬁlled symbols are the weighted centers for the bins used in the comparison( δ =81◦50′).The bin boundaries(every0.◦24,or0.h11)in RA are not shown.The declination bin boundaries (every0.◦24)are marked by the horizontal lines.The angular orientation is ignored in this plot,but is not in our analysis.The vertical beam proﬁle is plotted in the hatched region.Note that at this declination,every hour of RA corresponds to about2◦.parisonWe compare the signal measured at each point on the sky as measured in the twoﬂights,not just the rms levels of the sky signal found in each data set.In the1994ﬂight, we attempted to observe the identical swath of sky observed in the1992ﬂight.As can be seen in Fig.1,which is extremely enlarged in declination relative to right ascension,the 1994ﬂight was low by about10′.To enable direct comparison,only the data from those bins which fall into the center declination bin is used.After this selection∼50%of the data is retained.The data from the1992ﬂight is diﬀerenced from that of the1994ﬂight to form a diﬀerence data set,92−94.Similarly,the two data sets are summed to form a sum data set,92+94.This is done for each demodulation and for both CMBR and DUST.To allow for diﬀering oﬀsets in the twoﬂights,a weighted mean is removed from each dataset.The covariance matrix,V ij,for both the sum and diﬀerence sets is the sum of the masked1992 and1994covariance matrices.There is no cross term because theﬂights have independent noise.The signiﬁcance of any detected signal in the sum or diﬀerence is tested with aχ2 statistic,χ2±=ij (92±94)i V−1ij(92±94)j.Theχ2and degrees of freedom,and the cumulative probability,P(χ2),for the comparison is shown in Table1.P is the probability of getting a value ofχ2at or above the observed value,under the assumption that there is no signal in the data.This should be the case for the diﬀerence data,where the common sky signal should cancel.To check the eﬀect of the relative calibration uncertainty onχ2,the1994dataset is rescaled by±6%and the value ofχ2recalculated.In all cases|∆χ2|≤2.A Kolmogorov-Smirnov(KS)test(Press et al.1992)of the92−94probabilities(.04, .22,.41,and.91)gives a74%probability that these are drawn from a uniform distribution from0to1.Based on this,we conclude that the92−94data in both the single and double diﬀerence demodulations for both the CMBR and DUST components is consistent with no observed signal.A KS test of the92+94probabilities(2×10−12,2×10−8,4×10−7,and1×10−4) gives a7×10−4probability that these are drawn from a uniform distribution from0to1. From this,together with the extremely lowχ2probabilities themselves,we see that there are statistically signiﬁcant signals in all four92+94datasets.This result,combined with the absence of such signals in the92−94datasets,enables us to conclude that the signals observed during the twoﬂights are common,and therefore present on the sky.parison of1992and1994Data SetsType Data Setχ2/DOF PSingle DiﬀerenceDouble Diﬀerence5.ConclusionsThe same region of the sky was observed in the1992and1994ﬂights to conﬁrm the detection of a celestial signal.It is clear from the statistical analysis that the same sky signal is measured in these twoﬂights.We conclude that at the level of our signal, our measurements are likely to be free from signiﬁcant contamination from time-varying systematics such as sidelobe pickup or atmospheric contamination.In addition to our own conﬁrmation of the MSAM1-92results,the Saskatoon experiment has recently observed this section of sky at lower frequencies,36GHz to46GHz (Netterﬁeld et al.1996).They have compared their signal with the double diﬀerence CMBR signal from Paper I,andﬁnd good agreement.This result,spanning nearly a decade in frequency,is strong evidence that we are observing CMBR anisotropies rather than some other astrophysical foreground source.We would like to thank E.Magnier,R.Rutledge,L.Knox,and A.Goldin for useful conversations.The research was supported by the NASA Oﬃce of Space Science, Astrophysics Division through grants NTG50720and50908and RTOP188-44.REFERENCESCheng,E.S.et al.1994,ApJ,422,L37.Cheng,E.S.et al.1996,ApJ,456,L71.Fixsen,D.J.et al.1996,ApJ.submitted,preprint astro-ph/9512006.Gundersen,J.O.et al.1995,ApJ,443,L57.Hu,W.and White,M.1996,ApJ.submitted,preprint astro-ph/9602019.Jungman,G.,Kamionkowski,M.,Kosowsky,A.,and Spergel,D.1995,Phys.Rev.D.submitted,preprint astro-ph/9512139.Knox,L.1995,Phys.Rev.D,52,4307.Netterﬁeld,C.B.,Devlin,M.J.,Jarosik,N.,Page,L.,and Wollack,E.J.1996,ApJ.submitted,preprint astro-ph/9601197.Press,W.H.,Teukolsky,S.A.,Vetterling,W.T.,and Flannery,B.P.1992.Numerical Recipes in FORTRAN:The Art of Scientiﬁc Computing.Cambridge UniversityPress,Cambridge,2nd edition.Ruhl,J.E.,Dragovan,M.,Platt,S.R.,Kovac,J.,and Novak,G.1995,ApJ,453,L1. Tanaka,S.T.et al.1995,ApJ.submitted,preprint astro-ph/9512067.Wilkinson,D.1995.A Warning Label for Cosmic Microwave Background Anisotropy Experiments.In Astbury,A.et al.,editors,Particle Physics and Cosmology,Proceedings of the Ninth Lake Louise Winter Institute,page110,Singapore.World Scientiﬁc.。

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REV. DE CIÊNCIA & TECNOLOGIA, Piracicaba, v. 11, n. 21, p. 1-73, jan./jun. 2003.R EVISTA DE C IÊNCIA& T ECNOLOGIA • 211COMISSÃO EDITORIALN IVALDO L EMOS C OPPINI – presidente (Engenharia de Produção) K LAUS S CHÜTZER (Engenharia Mecânica)N ELSON C ARVALHO M AESTRELLI (Gestão da Produção)N IVALDI C ALONEGO JÚNIOR (Ciência da Computação)SÔNIA M ARIA M ALMONGE (Engenharia Química)COMITÊ CIENTÍFICOB ERT L AUWERS (Katholieke Universiteit Leuven –Bélgica)C ARLOS A LBERTO G ASPARETTO (Facens/Unicamp –ESTEVAL project partners.– Feature Based Integrated Design Environment.Identiﬁcation of interdependencies between manufacturing features.Unsuitable ﬁnishing quality (Schützer et al., 1999).After considering several possibilities, which could result in this poor surface quality cutting tool geometry , clamping and balancing of the tool system, technological parameters and machining set-ups, it was realized, that the problem came from the CNC of the machine tool, which was incapable of processing the NC program as fast as the feed rate deﬁned in the NC program. So the machine reaches the point refereed in one line of the program and the information to move the tool to the next point was not processed yet, then the machine had to wait a couple of milliseconds to start moving again.This incompatibility between the feed rate deﬁned in the NC program and the processing time of the CNC results in two different situations according to the CNC used:poor surface quality – the CNC tries to move the machine at the programmed feed rate, but it can-Improper surface finishingThe workpiece used and the ﬁnishing tool path.The roughing and semi-ﬁnishing operations were accomplished using exactly the same technological parameters and cutting strategies for all workpieces.The comparison analysis was done only during the ﬁnishing operation and the same technological para-meters, cutting strategies and tools were used in both cases. The ﬁnishing operation was distinguished by the methodology of interpolation. The trajectory of the ﬁnishing tool path is shown in ﬁgure 3. For this operation it was used a 10 mm ball end mill tool at 10000 rpm and the programmed feed rate was 2000 mm/min.YSISThe results of the machining experiments considering the NC program size, the time required to exe-cute the program and the surface quality in terms of roughness and superﬁcial texture were compared and the conclusions are presented below.NC Program SizesThe table 2 presents the ﬁnishing programs sizes calculated for both methods. It proves that less infor-mation are required to describe tool paths by the circular/linear method, thus reducing the program size byMETHOD P ROGRAM SIZE N UMBER586 kbCircular/linear83 kb• V. 11, Nº 21 – pp. 29-36Regions where the feed rate as reduced.2000 mm/min660 mm/min 1500 mm/min700 mm/min2000 mm/minRoughness AnalysisIt was used a digital Surftest Equipment to obtain the Ra and Rz parameters. It was analyzed the same areas for all workpieces. Practically, there are not differences between the roughness parameters for both interpolation methods.Surface T exture AnalysisIt was possible to visually verify the differences between the surfaces of both methods. The circular/ linear workpieces are smoother than the linear ones. The ﬁgure 5 shows this texture.Irregular surface texture Regular surface textureBesides those transversal marks at the workpiece machined by the linear interpolation, this method also gives a deﬁcient quality in the longitudinal direction, as it is seen in the next photos taken by a CCD camera connected in an microscopy.Figure 6 was taken using a microscopy with magniﬁcation 10x of the linear part. The vertical marks are the cusp heights left by the ball end mill tool. The steps-over of the tool path is on the horizontal direc-Fig. 6. Uneven cusps from a linear workpiece.Fig. 7. Even cusps from a circular/linear workpieceIn linear interpolation method is possible to see uneven cusp heights, what can difﬁcult drastically the hand ﬁnishing afterwards. This problem is not seen at the workpieces milled by the circular/linear method, as shown in ﬁgure 7. It happens due to the more constant cutting movements.In this method, the cusps height are much more uniform, what can help the manual ﬁnishing afterwards, by decreasing this process time, and improving the accuracyCONCLUSIONThe High Speed Cutting T echnology can be attractively applied in die and mould manufacturing, among others applications. However, there are several other technologies in the process chain that must be considered to support an efﬁcient HSC process.R EVISTA DE C IÊNCIA & T ECNOLOGIA • V. 11, Nº 21 – pp. 29-36。

离子色谱测定唾液葡萄糖含量方法的建立及评估

•论著•离子色谱测定唾液葡萄糖含量方法的建立及评估徐春I窦倩2汪诗文2章子锋？戴庆2'解放军总医院第三医学中心内分泌科，北京1()()()39；2国家纳米科学中心，中国科学院卓越中心，中国科学院纳米光子材料与器件重点实验室，北京10()190徐春和窦倩对本文有同等贡献通信作者：戴庆，Email：***************,电话：************【摘要】目的建立用离子色谱测定唾液中葡萄糖浓度的方法。

方法利用热变性法去除唾液中的蛋白质，以CarboPac PA20(3x30mm)作为保护柱.CarboPac PA20(3xl50mm)作为分析柱进行离子色谱分析。

以超纯水(A),250mmol/L NaOH溶液(B),500mmol/L NaAc(C)为淋洗液进行梯度洗脱，采用脉冲安培检测器检测”结果本方法在0.04-0.12mgn.范围内具有较好的线性关系，线性相关系数^.9967:葡萄糖的检出限是0.002mg/L；重复性测量相对标准偏差(RSD)的平均值为0.75%,加标冋收率平均值为103.07%0结论本方法操作简便、灵敏度高、准确性好、结果稳定，可用于唾液中葡萄糖含量的测定。

【关键词】离子色谱；唾液；筍萄糖；糖尿病；无创检测基金项目：中国科学院科技服务网络计划(STS计划)(K町-STS-ZDTP-063)；国家重点研发计划(2016YFA0201600)DOI：10.3760/.l15807-20200623-00194Establishment,evaluation,and determination of saliva glucose concentration by ion chromatography XuChun1,Dou Qian2,Wang Shiwen2,Zhang Zifeng2,Dai Qing2'Department of Endocrinology,3rd Medical Center,PLA General Hospital,Beijing100039,China;2CAS Key Laboratory of Nanophotonic Materials(uid Devices,CAS Center for Excellence in Na/ioscience,National Center forNanoscience and Technology,Beijing100190,ChinaXu Chun and Dou Qian contributed equally to this articleCorresponding author:Dili Qing,Email:***************,Tel:************[Abstract]Objective To establish an analytical method for measuring the concentration of glucose insaliva by ion chromatography.Methods The proteins in saliva were removed by thermal denaturation method,CarboPac PA20(3x30mm)was used as a protective column and CarboPac PA20(3x150mm)was used as ananalytical column for ion chromatography analysis.Gradient elution was carried out with A：ultra-pure water,B:250mmol/L NaOH solution and C:500tnmol/L NaAc solution.Pulsed ampere detector was used for detection.Results This method had a good linear relationship in the range of0.04to0.12mg/L,with a linear relation coefficient of0.9967.The detection limit of glucose was2|xg/L,the mean value of the relative standard deviation(RSD)of the repeatability measurement was0.75%,and the average spike recovery was103.07%.Conclusion Thismethod is simple,sensitive,accurate and stable,and can be used for the detennination of glucose concentration insaliva.[Key words]Ion chromatography;Saliva;Glucose;Diabetes;Non-invasive detectionFund program：Science and Technology Service Network Plan of Chinese Academy of Sciences(STS Plan)(KFJ-STS-ZDTP-063);National Key Research and Development Plan(2016YFA0201600)DOI：10.3760/.l15807-20200623-00194唾液由唾液腺(腮腺、颌下腺、舌下腺、小涎腺)分泌，在口腔内起帮助消化、湿润和保护黏膜的作用。

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a selection of measurement results -回复

a selection of measurement results -回复选定主题：[一组测量结果]第一步：引言（100-150字）本文将深入探讨一组测量结果，并逐步回答与其相关的问题。

我们将以科学准确性为基础，以合理推理和相关证据为支撑，共同探究这些测量结果的意义和可能的解释。

第二步：概述测量结果（150-200字）首先，让我们简要介绍这组测量结果。

这些结果涉及多个领域，包括物理学、生物学和经济学等。

我们收集了各种实验和调查数据，这些数据对于我们理解和解决当前问题至关重要。

本文将对其中一些测量结果进行详细分析和解释，以便更好地理解它们的含义。

第三步：重要测量结果的详细分析（800-1000字）接下来，我们将深入分析一些关键的测量结果，以便更好地理解它们。

我们将选择几个代表性的结果，涵盖不同领域，以获得更全面的认识。

首先，让我们考虑一项物理学实验的结果。

该实验旨在测量重力加速度，以确定地球表面的重力场强度。

通过精确地测量时间和物体的自由落体运动，我们得出了一个平均值，并计算了其误差范围。

这些结果对于我们理解地球的物理特性和基本常数非常重要，以及对于未来的科学研究和技术应用有着深远的影响。

接着，我们转向生物学领域的一个测量结果。

通过对一群人进行健康调查和评估，我们得出了一个关于肥胖率的统计数据。

这些数据显示了不同年龄组和性别之间的肥胖率差异，并提供了对这一全球问题的见解。

通过这些结果，我们可以加深对肥胖症的根源和其潜在健康影响的理解，并为制定预防措施和干预政策提供依据。

最后，让我们来看一个经济学领域的测量结果。

通过对某个国家的经济指标进行调查和收集，我们得到了一组有关就业率、通货膨胀率和经济增长率的数据。

这些结果对于政策制定者和经济学家来说至关重要，因为它们可以揭示经济的整体健康状况和趋势，进而帮助他们制定适当的政策和措施来促进经济发展。

通过这些详细分析，我们可以更好地理解这组测量结果的重要性和意义。

Apparatus and method for determining the amount of

专利名称：Apparatus and method for determining the amount of entrapped gas in a material发明人：Charles E. Lee,John D. Della-Santina申请号：US09/132630申请日：19980811公开号：US06082174A公开日：20000704专利内容由知识产权出版社提供摘要：An entrapped gas measuring apparatus includes a reservoir housing with a reservoir which is adapted to receive a material sample and to expand according to an expansion of the material sample when a negative pressure is applied externally to the reservoir. A parameter indicating the change in volume of the reservoir during the expansion, such as the actual change of volume of the reservoir or a change in position of a moveable wall which at least in part defines the reservoir, is detected by a detector. A processor coupled to the detector is used to determine the amount of entrapped gas based upon the detected parameter. The amount of entrapped gas determined by the processor may be the percent volume of the entrapped gas in relation to the overall volume of the sample, or may be the actual volume of the entrapped gas in the sample. Based at least in-part upon the measured amount of entrapped gas within the sample, the processor is further adapted to determine at least one of: percent volume of the substrate in the sample in relation to the overall volume of the sample; actual volume of the substrate in the sample; or density of the sample or substrate within the sample. The entrapped gas measuring apparatus may be used to produce a material having a known amount of entrapped gas by: making a first material according to a first method andwhich has a first amount of entrapped gas; applying a negative pressure to the sample such that the sample expands from a first volume to a second volume; detecting a parameter which is indicative of the change of sample volume under the applied negative pressure; comparing the detected parameter with a predetermined range for the parameter; and, if the detected parameter is not within the predetermined range, making a second material according to a second method which has a second amount of entrapped gas that is within the predetermined range.申请人：BENCHTOP MACHINE AND INSTRUMENT, INC.代理人：James C. Peacock III,John P. O'Banion更多信息请下载全文后查看。

fluorescence quantitative analysis -回复

fluorescence quantitative analysis -回复"Fluorescence quantitative analysis" refers to a technique used to measure the concentration of a substance by examining its fluorescence properties. This technique is commonly employed in various scientific fields such as chemistry, biology, and environmental science. In this article, we will explore the principles behind fluorescence quantitative analysis, the instruments used, and some applications of this technique.1. Introduction to Fluorescence:Fluorescence is a phenomenon exhibited by certain substances when they absorb light at a specific wavelength and emit light at a longer wavelength. This emission of light is called fluorescence. It occurs due to the excitation of electrons in the atoms or molecules of the substance.2. Principles of Fluorescence Quantitative Analysis: Fluorescence quantitative analysis is based on the principle that the intensity of fluorescence emitted by a substance is directly proportional to its concentration. This principle forms the basis for detecting and measuring the concentration of various substances.3. Instrumentation for Fluorescence Quantitative Analysis:a. Fluorometers: Fluorometers are the primary instruments used for fluorescence quantitative analysis. They consist of a light source, filters to select the excitation and emission wavelengths, and a detector to measure the emitted light.b. Fluorescence Microscopes: Fluorescence microscopes combine traditional microscopy with fluorescence detection. They allow for the visualization and quantification of fluorescently labeled samples.c. Flow Cytometers: Flow cytometers employ fluorescence to analyze individual cells or particles in a solution. They can measure multiple parameters simultaneously, providing detailed information about the sample.4. Process of Fluorescence Quantitative Analysis:a. Selection of fluorophore: The first step involves choosing a suitable fluorophore that exhibits fluorescence properties when bound to the target substance.b. Calibration Curve: A calibration curve is constructed by measuring the fluorescence intensity at different known concentrations of the target substance. This curve establishes therelationship between fluorescence intensity and concentration. c. Sample Preparation: The sample is prepared by incorporating the fluorophore into the solution containing the substance to be quantified.d. Excitation and Emission: The sample is excited with a specific wavelength of light, and the emitted fluorescence is detected and measured.e. Comparison with Calibration Curve: The fluorescence intensity of the sample is compared with the calibration curve to determine its concentration.5. Applications of Fluorescence Quantitative Analysis:a. Biochemical Assays: Fluorescence quantitative analysis is widely used in biochemical assays to determine the concentration of biomolecules such as DNA, proteins, and enzymes.b. Drug Discovery: Researchers use fluorescence quantitative analysis to screen potential drug candidates and study their interactions with target molecules.c. Environmental Monitoring: This technique is utilized to measure the concentration of pollutants in water and air, facilitating environmental monitoring and assessment.d. Medical Research: Fluorescence quantitative analysis helpsdiagnose diseases and monitor their progression by quantifying specific biomarkers in biological samples.In conclusion, fluorescence quantitative analysis is a versatile technique that enables precise and sensitive measurements of substance concentrations. It finds extensive applications in various scientific fields and continues to contribute to advancements in research and analysis.。

msa 计量型计数型英语

msa 计量型计数型英语The MSA (Measurement, Selection, and Analysis) method is a type of statistical analysis that focuses on measuring and analyzing data to make decisions. This method is commonly used in research and business to determine the effectiveness of a particular process or to identify trends and patterns in data. MSA involves the use of various statistical tools and techniques to quantify and evaluate the variability and accuracy of measurements.On the other hand, the Counting method is a type of statistical analysis that focuses on the frequency of occurrences of specific events or items within a given data set. This method is often used to track the number of defects, errors, or occurrences of a particular eventwithin a process. Counting methods can help identify areas for improvement and track the progress of process changes over time.In English:MSA (Measurement, Selection, and Analysis)方法是一种统计分析方法，其重点是测量和分析数据以做出决策。

The Galactic Center Magnetosphere

a r X i v :a s t r o -p h /0701050v 1 2 J a n 2007The Galactic Center MagnetosphereMark MorrisDepartment of Physics &Astronomy,University of California,Los Angeles,CA 90095-1547,USA E-mail:morris@ Abstract.The magnetic ﬁeld within a few hundred parsecs of the center of the Galaxy is an essential component of any description of that region.The ﬁeld has several pronounced observational manifestations:1)morphological structures such as nonthermal radio ﬁlaments (NTFs)–magnetic ﬂux tubes illuminated by synchrotron emission from relativistic electrons –and a remarkable,large-scale,helically wound structure,2)relatively strong polarization of thermal dust emission from molecular clouds,presumably resulting from magnetic alignment of the rotating dust grains,and 3)synchrotron emission from cosmic rays.Because most of the NTFs are roughly perpendicular to the Galactic plane,the implied large-scale geometry of the magnetic ﬁeld is dipolar.Estimates of the mean ﬁeld strength vary from tens of microgauss to ∼a milligauss.The merits and weaknesses of the various estimations are discussed here.If the ﬁeld strength is comparable to a milligauss,then the magnetic ﬁeld is able to exert a strong inﬂuence on the dynamics of molecular clouds,on the collimation of a Galactic wind,and on the lifetimes and bulk motions of relativistic particles.Related to the question of ﬁeld strength is the question of whether the ﬁeld is pervasive throughout the central zone of the Galaxy,or whether its manifestations are predominantly localized phenomena.Current evidence favors the pervasive model.1.Introduction The magnetic ﬁeld at the center of the Galaxy (hereafter,the ”ﬁeld”)has been studied with a wide variety of techniques for over 20years,and while there is some consensus that thepredominant,global geometry within the central 200-300parsecs is poloidal,the discussion at this workshop has emphasized that there is no universal agreement on the strength of the ﬁeld and on the extent to which the ﬁeld strength varies from one place to another.In this review,I summarize the evidence characterizing the various points of view.Earlier reviews of the Galactic center magnetic ﬁeld have described many of the central points that have been known for some time [1,2,3,4,5,6],but recent observations have added considerably to the information that can be brought to bear on this discussion.The primary probe of the large-scale ﬁeld has been radio observations of polarized,ﬁlamentary structures which,while typically <0.5pc in width,are tens of parsecs in length.The strong radio polarization,and the occasional ﬁlamentary counterpart at X-ray wavelengths [7]indicate that the emission is synchrotron radiation,and the position angle of the polarization,once corrected for Faraday rotation,conﬁrms that the magnetic ﬁeld lies along the ﬁlaments [8,9,10,11].The almost invariant curvature of the ﬁlaments,and their absence of distortion in spite of clear interactions with the highly turbulent interstellar medium,led Yusef-Zadeh &Morris (1987[12],see also [5])to note that the implied rigidity of the ﬁlaments requires a ﬁeld strength on theorder of a milligauss,which is surprisingly large,given the scale of these structures.The orientation of the most prominent NTFs is roughly perpendicular to the Galactic plane, as illustrated in Figure1,a schematic diagram depicting allﬁlaments identiﬁed in theλ20-cm VLA survey by Yusef-Zadeh et al.(2004[13]).Because the individualﬁlaments deﬁne the localﬁeld direction,the ensemble ofﬁlaments has been interpreted in terms of a predominantly dipolarﬁeld,extending at least200pc along the Galactic plane[14].The deviations from perfect verticality of many of theﬁlaments can be ascribed to a global divergence of theﬁeld above and below the Galactic plane.The short,nonconformingﬁlaments are discussed in§2.3(and[15]).Figure1.Schematic map showing the radioﬁlaments catalogued by Yusef-Zadeh et al.(2004, [13])in the course of theirλ20-cm survey of the Galactic center.Quite a diﬀerent probe of the magneticﬁeld is provided by mid-and far-IR observations of thermal dust emission from magnetically aligned dust grains.The rotation axes of dust grains align with the magneticﬁeld by dissipative torques[16],leading to a net polarization of the thermal emission such that the E-vector is perpendicular to the magneticﬁeld.This probe, however,is strongly dominated by dense,warm clouds,so it is quite diﬀerent from the NTFs, which sample theﬁeld in the intercloud medium occupying most of the volume of the Galactic center.The magneticﬁeld implied by the polarized dust emission is parallel to the Galactic plane[17,18,19,20,21],and thus perpendicular to the large-scale intercloudﬁeld revealed by the NTFs.The perhaps surprising orthogonality of these two systems can be understood in terms of the tidal shear suﬀered by molecular clouds inhabiting the central molecular zone (CMZ).Any portion of a molecular cloud located a distance R gc pc from the Galactic center, and having a density less than104cm−3[75pc/R gc]1.8is subject to such shear[22,23],so cloud envelopes tend to get stretched into tidal streams that may subtend a large angle at the Galactic center(e.g.,[24]).Any magneticﬁeld within the clouds–presumablyﬂux-frozen to the partially ionized molecular gas–will thus be deformed into an azimuthal conﬁguration,with theﬁeldlines oriented predominantly along the direction of the shear[17].There is little evidence that the cloud and inter-cloud environments are magnetically coupled to each other in any signiﬁcant way,as might have been expected if theﬁeld lines were anchored to the cloud layer,and if the rotation of the cloud layer thus imposes a global twist upon the verticalﬁeld[25,26].The most prominent NTFs show very little deformation where they pass through the Galactic plane and interact with gas in the CMZ(e.g.,[12]).Some case can be made that Faraday rotation measurements are consistent with the geometry of a twisted,large-scale ﬁeld([6],and references therein),but these data remain too sparse to draw anyﬁrm conclusions.If,as the evidence does indicate,the magneticﬁeld is not anchored in the CMZ,then it is either anchored in the essentially non-rotating Galactic halo or beyond,or it arcs back to the Galactic plane at relatively large radii and is anchored there.In either case,theﬁeld lines do not rotate with the CMZ,and the molecular clouds move through theﬁeld with a large relative velocity.This gives rise to an induced v×B electricﬁeld at cloud surfaces(10−4B(mG)V/cm) which can accelerate particles,drive currents and contribute to the cloud heating[27,28].The residence time of clouds in the Galactic center is a few hundred million years as a result of angular momentum loss resulting from both dynamical friction and magnetic drag[29,2,30], so it is not clear how clouds forming at the outside edge of the CMZ[31]will retain any magnetic contact with their surroundings as they migrate inwards through the verticalﬁeld.Any original connection between the cloud and extra-cloudﬁelds could have pinched oﬀduring the inward migration,leaving the clouds magnetically isolated.If typical cloud lifetimes are less than the inspiral times of clouds,presumably because clouds are sheared in the tidalﬁeld,then the situation is more complex,but these comments can still apply to sheared cloud streams and the new clouds that reform as the streams interact with each other.The remainder of this review focuses on several topics of current interest–both observational and theoretical–and culminates in a description of what I think are some of the most important open questions.2.Uniformity of the Galactic Center Field2.1.Pressure Conﬁnement of Magnetic StructuresRegardless of the magneticﬁeld strength,the pressure of the interstellar medium in the CMZ is very large compared to the Galactic disk[32].A hot diﬀuse gas(T∼108K,n∼0.04cm−3) that pervades much of the volume of the Galactic center[33,34,35]has a pressure of6x 10−10dynes cm−2,and is in approximate pressure equilibrium with the warm(∼150K,low-density molecular medium[36,37],if the velocity dispersion of∼20km s−1is used to calculate a turbulent pressure.This pressure is at least two orders of magnitude higher than is characteristic of the Galactic disk.The magneticﬁeld,on the other hand,has a pressure of4x10−8B(mG)2 dynes cm−2.Consequently,if the magneticﬁeld strength in observed magneticﬁeld structures is∼a milligauss,then those structures are not conﬁned,and would expand and disappear on a short time scale.This consideration led to the argument that a milligauss magneticﬁeld must be pervasive throughout the CMZ[38];the strong and extended magneticﬁeld would then provide its own support.In this view,the NTFs are then simply illuminated magneticﬂux tubes into which relativistic electrons have been injected,and along which the electrons are constrained to ﬂow[1].A ring current at the outer edge of the CMZ,or distributed over some range of radii there,is required to generate and conﬁne the overall dipoleﬁeld[5].2.2.Models of Localized Magnetic StructuresThe alternative to a strong,pervasiveﬁeld is that the NTFs represent localized peaks in the magneticﬁeld strength.A force-free magneticﬁeld conﬁguration might be considered as a way of tying a local current to a local enhancement of the magneticﬁeld strength[39,40],but unless the overall conﬁguration is pressure conﬁned,it will be transient and short-lived.A recent suggestion by Boldyrev&Yusef-Zadeh[41]is that the NTF’s are localized structures of milligaussﬁeld strength conﬁned by the eﬀective pressure of large-scale turbulence in the Galactic center.In their model,the turbulent cells expulse theﬁeld,and concentrate it in regions between the cells.However,while theﬁeld will indeed diﬀuse out of a zone of strong turbulence,the turbulence itself is generally accompanied by the generation of newﬁeld at a rate at least as fast as the rate of outward diﬀusion.Consequently,while this mechanism raises the interesting possibility that the geometry of the boundaryﬁeld might be diﬀerent from that within the turbulent zones because of the interactions of theﬁeld emanating from the diﬀerent zones,it is not obvious how this mechanism would lead to a relative enhancement of theﬁeld strength at those boundaries.Furthermore,the turbulence in this model must be organized in such a way that the resulting magneticﬁlaments are predominantly vertical.This places a strong constraint on the overall helicity distribution of plasma motions in the Galactic center. Numerical models that address these concerns are needed to assess this model further.While other models for localized structures have been proposed[42,43,44],they lack the generality needed to account for the population and the orientations of theﬁlaments.2.3.Signiﬁcance of the Short Radio Streaks?One relatively recentﬁnding that has called the notion of a pervasive,uniformﬁeld into question is a population of short radioﬁlaments,or streaks,that occupy much of the same Galactic longitude range as the prominent NTFs[14,45,15].These structures are largely included in ﬁgure1.They diﬀer in three ways from the long-known,prominent NTFs:(i)They are quite short,∼0.1pc.(ii)Their surface brightness is typically about1/4that of the prominent NTFs.(iii)They appear to be more or less randomly oriented,and thus do not conform to the global verticality of the prominent NTFs.This point has been raised as an argument against a globally ordered,dipole magneticﬁeld.Given these pronounced diﬀerences,one could argue that the radio streaks represent a diﬀerent population with a separate origin,such as localized oblique shock structures,or strong local deformations of the large-scaleﬁeld as a result of some local,energetic disturbance.It is premature to conclude that they are inconsistent with a predominantly ordered,large-scale dipoleﬁeld.Further study of these features is warranted to determine whether they diﬀer systematically from the prominent NTFs in other ways as well,such as in terms of spectral index and polarization properties,and whether they are connected to other interstellar structures in the same way that the prominent NTFs are.2.4.Dynamical ConsequencesAs mentioned above,a pervasive,dipoleﬁeld exerts a magnetic drag force on clouds moving through it,enhancing the rate at which they spiral inwards.If suﬃciently strong,theﬁeld can also collimate winds and energetic particles that emanate from the center,creating a chimney eﬀect.This is consistent with observations of extended columnar radio features in nearby,radio-bright galactic nuclei[46,47,48],although the extent to which the energetic winds in such galaxies have been collimated by the magneticﬁeld,as opposed to the back pressure of their stratiﬁed interstellar gas layers,has not been settled.Recent work by Belmont et al.[34]has shown that at least the hydrogen in the hot,diﬀuse gas at the Galactic center is unbound,so a thermal galactic wind is implied.A dipole magnetic ﬁeld can collimate this wind to an extent that depends on theﬁeld strength,so observations of the large-scale morphology of thermal X-ray emission from the hot gas will be a useful probe of both the wind and the magneticﬁeld.Cosmic rays will also be conﬁned by a pervasive,verticalﬁeld.This has two important consequences:ﬁrst,the residence time for cosmic rays in the Galactic center will be relatively short(a few×105yr)compared to that in the Galactic disk(a few×106yr),because the constraint that cosmic rays diﬀuse primarily along theﬁeld lines implies,in the Galactic center, that they diﬀuse directly away from the Galactic plane,whereas in the Galactic disk,they are largely trapped by the azimuthalﬁeld.This relatively short residence time implies a much smaller cosmic ray density than one might infer from the volume rate of supernovae alone.This is consistent with the fact that the high-energyγ-ray emission intensity across the CMZ does not have a peak comparable in its contrast to the peak in the total column density of gas[49,50]. Second,the longitudinal diﬀusion of cosmic rays,especially electrons,would be suppressed by a pervasive verticalﬁeld.Such diﬀusion–for protons–is assumed in a recent model for the extended TeV emission observed by HESS invoking a single source of high-energy cosmic rays [51,52];this model is probably inconsistent with the presence of a strong,pervasive,vertical ﬁeld.ments on Arguments for a Weak Field3.1.The Minimum Energy AssumptionA number of researchers have estimated the strength of the Galactic center magneticﬁeld using the minimum energy assumption,also referred to as”equipartition”,applied to observations of synchrotron emission from relativistic particles(e.g.,[60]).This assumption can be applied to a medium in which energy exchange takes place between particles andﬁelds on time scales much less than the energy loss times of particles or theﬁeld generation time from macroscopic particle dynamics.This can,for example,describe environments characterized by isotropic turbulence and tangledﬁelds,such as the hot spots in the lobes of double radio source galaxies.However,it is quite generally inapplicable to the Galactic center,except perhaps in very local environments in which energetic events have recently occurred.The striking large-scale order of the Galactic center magneticﬁeld implies that its energy content is not responding in any signiﬁcant way to localﬂuid motions or relativistic particle dynamics.The relativistic particles are responding to theﬁeld,but the reverse is not true.The energy content of the Galactic centerﬁeld is far greater than that of the emitting particles,and thus theﬁeld strength can be much larger than the equipartition value.3.2.Zeeman MeasuresThe most compelling measure ofﬁeld strength would be a direct measure via the Zeeman eﬀect. Zeeman measures have indeed been made in Galactic center clouds in lines of both H and OH [53,54,55,56,57],with the result that,where any signiﬁcant Zeeman signal is seen at all,it implies aﬁeld strength on the order of a milligauss or larger.However,there are only a few places where a signiﬁcant Zeeman signal has been detected.(We do not include in these comments the Zeeman measures deduced from1720-MHz OH masers around Sgr A East and the circumnuclear disk,which giveﬁeld strengths of3-5mG[58,59],because such masers presumably arise from locally compressed gas,and may therefore not be representative of the magneticﬁeld on large scales.)One strong selection eﬀect in Zeeman measures is that the extremely broad lines of Galactic center clouds make detection of the Zeeman splitting very diﬃcult unless theﬁeld strength exceeds∼1mG.Two other points must be considered when interpreting Zeeman measurements:ﬁrst,they apply largely to the magneticﬁeld within clouds or at the surfaces of clouds.As the above discussion indicates,the magneticﬁeld geometry in clouds is not necessarily related to the large-scale intercloudﬁeld.Second,the Zeeman eﬀect measures only the mean line-of-sight component of theﬁeld,so if there areﬁeld reversals along the line of sight,or if theﬁeld direction changes across the radiotelescope beam,then there is signiﬁcant averaging and dilution of the Zeemansignal.In any case,even if Zeeman measures were able to provide insight into the strength of the intercloudﬁeld,the line-of-sight restriction makes it diﬃcult to draw conclusions about a largely vertical dipoleﬁeld.Further Zeeman measurements,not only of H and OH with improved sensitivity and spatial resolution,but also of other molecules that probe denser regions,will be very important for achieving a more complete understanding of the Galactic centerﬁeld.3.3.Synchrotron LifetimesOne argument that has been raised against a pervasiveﬁeld of milligauss strength is that the synchrotron lifetime of the electrons responsible for the nonthermal radio emission is relatively short,∼105years for electrons responsible for the330-MHz radio emission arising from the central4◦×2◦diﬀuse nonthermal source[60].So the supernova rate in the CMZ(or in the Galactic and nuclear bulges above it,since not much less than half of the relativistic electrons created in a supernova will diﬀuse along theﬁeld lines and reach the Galactic plane)must be somewhat larger than1per105yrs if supernovae alone are to account for the uniformity of the synchrotron emission.The rate of only Type Ia supernovae in the Galactic bulge has been estimated at30per105yrs,[61],and in the nuclear bulge(deﬁned in[62,63])it is about20 per105yrs,so allowing also for core collapse supernovae,the particle production rate seems abundantly suﬃcient,even if no particles diﬀuse to the Galactic center from the rest of the Galaxy[64],and if there is no particle reacceleration process operating.The synchrotron lifetimes of electrons responsible for the5-GHz radio emission from the NTFs is only∼104years,so if they diﬀuse along theﬁeld lines at the Alfv´e n speed,2200km s−1 B(mG)/n(cm−3)1/2,then the net distance they can travel before losing an appreciable amount of energy is∼20pc×B(mG)/n(cm−3)1/2,somewhat shorter than the length of the longest ﬁlaments(60pc).(The Alfv´e n speed is assumed because the diﬀusion is usually limited by scattering of the streaming particles oﬀof Alfv´e n waves propagating along theﬁeld lines).So far,observations indicate that the radio spectral index has no noticeable variation along the length of theﬁlaments(e.g.,[10]).Consequently,if the relativistic electrons are produced at a speciﬁc location along them,then the synchrotron lifetime may present a problem unless theﬁeld strength is substantially less than a milligauss.Two possible alternatives warrant consideration:ﬁrst that the diﬀusion along theﬁeld lines is much faster than the relatively slow rate assumed here because the magneticﬁeld is much more rigid and smooth than in most situations where the Alfv´e n speed is invoked.Second,a reacceleration process may take place along theﬁlaments via shocks,wave dissipation,or reconnection,in analogy with the reacceleration processes needed to account for the persistence of highly relativistic particles in extragalactic jet sources,in spite of their synchrotron and Compton losses.4.The Double Helix NebulaA potential new probe of the Galactic center magneticﬁeld was recently revealed at24µm with the Spitzer Space Telescope[65].At a distance of∼100pc toward positive Galactic latitude from the Galactic center,a nebula having the form of an intertwined double helix extends over at least50pc,with its long axis oriented approximately perpendicular to the Galactic plane (Figure2).This feature was interpreted as a torsional Alfv´e n wave propagating away from the Galactic center along the magneticﬁeld,and driven by the rotation of the circumnuclear gas disk (CND).The few-parsec scale of the CND matches the width of the nebula,and the wavelength of the torsional wave,19pc,corresponds to the∼104-year rotation period of the CND if the Alfv´e n speed is103km s−1.This speed,in turn,constrains the magneticﬁeld to have a strength of0.5n1/2mG in the context of this hypothesis,where n is the hydrogen density in the medium through which the wave propagates.The density is not known,but for values of the magnetic ﬁeld ranging from0.1to1mG,a plausible density is found:n=0.04-4cm−3.The presence of two strands has been attributed to an apparent”dumbbell”asymmetry of the driving disk(see[65]);the magneticﬁeld threading the disk is concentrated into two diametrically opposed density maxima.A potential weakness of the torsional wave hypothesis is that the wave cannot yet be followed all the way down to its hypothetical source,the CND.However,this also raises the question of why the double helix is visible in theﬁrst place;its mid-infrared emission is most likely thermal emission from dust,so the visibility of the nebula at its present location presumably requires that the wave has levitated charged dust grains.Because of variable conditions at the base of the wave over the past105years(indeed,the CND is a rather disturbed,non-equilibrated disk [5]),such dust may not have been continuously available to highlight the wave.This may also help explain why a similar nebula is not present on the opposite side of the CND.An alternative scenario for understanding the Double Helix feature is that it be connected in some way with the linear radioﬁlaments of the Galactic Center Radio Arc.If the Northern extension of the Arc[66]is followed and extrapolated to Galactic latitudes beyond0.5◦(seeﬁg 20b of[13]),then it coincides approximately with the long axis of the Double Helix.However, there is no continuous connection in the radio maps between the linearﬁlaments and the Double Helix,and the only radio emission associated with the Double Helix lies outside the mid-IR strands(w,personal communication).There is so far no explanation for how a long bundle of linear,nonthermalﬁlaments could culminate in helically wound,thermal structures. Whether or not the CND hypothesis for the Double Helix is valid,further study of this feature should provide valuable insight into the Galactic center magneticﬁeld.5.Open QuestionsThe questions that seem now to be the most compelling for guiding near-future research on the Galactic center magneticﬁeld,besides those already mentioned above,are the following:•Whether or not the central verticalﬁeld is more or less uniform,how and where does it merge with the azimuthalﬁeld of the Galactic disk?•If the Galactic center magnetosphere is deﬁned as the region in which nonthermal radio ﬁlaments are observed,then its outer edge roughly coincides with the edge of the CMZ, with the Galaxy’s inner inner Lindblad resonance,and with the transition from X1to X2 gas orbits in the bar.What is the interplay between these phenomena,at this critical juncture in the Galaxy?•Can high-resolution observations be used to obtain more detail on the points of interaction between cloud and intercloudﬁelds?This may best be done with a combination of radio and far-infrared polarization measurements.•What process produces the relativistic particles that illuminate the NTFs via their synchrotron emission?•At the moment,we lack consensus on the power source for the108K gas occupying much of the volume of the nuclear bulge.Can we appeal to the stirring that takes place as clouds move through theﬁeld,leaving magnetosonic and Alfv´e n waves in their wake?Or can the energy be supplied by magneticﬁeld line annihilation of new verticalﬁeld constantly migrating inwards from the rest of the Galaxy?•What is the origin of the poloidalﬁeld?Dynamo models have been hard-pressed to produce a dipoleﬁeld like that observed,and a promising possibility is that the centralﬁeld represents protogalacticﬁeld that has been concentrated over the history of the Galaxy by mass inﬂow[67].Now is a propitious time to take these models to the next stage of sophistication.AcknowledgmentsI gratefully acknowledge stimulating discussions with Steve Cowley.Figure2.The Double Helix Nebula,observed with the MIPS instrument on the Spitzer Space Telescope[65].This structure was also seen at shorter wavelengths,3.6-8µm,with the IRAC camera on Spitzer.References[1]Morris,M.1990,in IAU Symp.No.140:Galactic and Intergalactic Magnetic Fields,eds:R.Beck,P.Kronberg,and R.Wielebinski,Dordrecht:Kluwer,p.361[2]Morris,M.1994,in The Nuclei of Normal Galaxies:Lessons from the Galactic Center,NATO ASI Series C:Vol.445,eds:R.Genzel and A.I.Harris,Dordrecht:Kluwer,p.185[3]Morris,M.1996,in IAU Symp.No.169:Unsolved Problems in the Milky Way,eds:L.Blitz&PJ Teuben,Dordrecht:Kluwer,p.247[4]Morris,M.1998,in IAU Symp.No.184:The Central Regions of the Galaxy and Galaxies,ed:Y.Sofue,Dordrecht:Kluwer,p.331[5]Morris,M.&Serabyn,E.1996,Ann.Rev.Astron.Ap.34,645[6]Novak,G.2005,in Magnetic Fields in the Universe:From Laboratory and Stars to Primordial Structures,eds:E.M.de Gouveia Dal Pino,G.Lugones,&zarian,New 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