Natural Variation in the Promoter of GSE5 Contributes to Grain Size Diversity in Rice译文及感悟

Adaptation and Survival in Natural Selection Adaptation and survival in natural selection is a fascinating and complex process that has been shaping the diversity of life on Earth for millions of years. From the smallest microorganisms to the largest mammals, every living organism has evolved through the mechanism of natural selection to better suit its environment and increase its chances of survival. This process has led to the incredible diversity of life that we see today, with each species uniquely adapted to its specific niche in the ecosystem.One of the key aspects of adaptation and survival in natural selection is the concept of genetic variation. Genetic variation refers to the diversity of genes within a population, which is essential for natural selection to occur. Without genetic variation, there would be no raw material for evolution to work with, and species would not be able to adapt to changing environmental conditions. Genetic variation can arise through a variety of mechanisms, including mutations, genetic recombination, and gene flow between different populations. These mechanisms create the diversity of traits within a population, some of which may confer a survival advantage in certain environments.Another important aspect of adaptation and survival in natural selection is the role of environmental pressures. The environment plays a crucial role in shaping the traits of a species, as individuals with traits that are better suited to their environment are more likely to survive and reproduce. For example, in a harsh desert environment, individuals with traits that allow them to conserve water and tolerate high temperatures are more likely to survive and pass on their genes to the next generation. Over time, this can lead to the evolution of specific adaptations that are well suited to the unique challenges of the desert environment.In addition to genetic variation and environmental pressures, the concept of fitness is central to understanding adaptation and survival in natural selection. Fitness refers to the ability of an individual to survive and reproduce in its environment, and is ultimately what drives the process of natural selection. Individuals with traits that increase their fitness are more likely to pass on their genes to the next generation, leading to the spread of thoseadvantageous traits within the population. As a result, the population as a whole becomes better adapted to its environment, increasing its chances of survival.It is important to note that adaptation and survival in natural selection is not a perfect or predetermined process. Evolution does not have a specific goal or endpoint, and the traits that increase an individual's fitness in one environment may be detrimental in another. Additionally, environmental conditions are constantly changing, which means that what is advantageous today may not be advantageous tomorrow. As a result, natural selection is an ongoing and dynamic process, with species constantly adapting to new challenges and opportunities in their environment.From a human perspective, the concept of adaptation and survival in natural selection can be both awe-inspiring and humbling. The incredible diversity of life on Earth, and the myriad ways in which species have adapted to their environments, is a testament to the power of natural selection. It is a reminder of the interconnectedness of all living things, and the delicate balance that exists within ecosystems. At the same time, it serves as a stark reminder of the fragility of life, and the constant struggle for survival that is inherent to all living organisms.In conclusion, adaptation and survival in natural selection is a fundamental process that has shaped the diversity of life on Earth. Through genetic variation, environmental pressures, and the concept of fitness, species have evolved and adapted to their environments over millions of years. From a human perspective, this process is both inspiring and humbling, serving as a reminder of the interconnectedness and fragility of life. As our understanding of natural selection continues to grow, so too does our appreciation for the incredible diversity and resilience of the natural world.。

a r X i v :a s t r o -p h /0302555v 1 26 F eb 2003Draft version February 2,2008Preprint typeset using L A T E X style emulateapj v.04/03/99THE NATURE OF THE UV/X-RAY ABSORBER IN PG 2302+029Bassem M.Sabra &Fred HamannDepartment of Astronomy,University of Florida,Gainesville,FL 32611Buell T.JannuziNational Optical Astronomy Observatory,950North Cherry Ave.,Tuscon,AZ 85719Ian M.GeorgeJoint Center for Astrophysics,Department of Physics,University of Maryland,Baltimore County,1000Hilltop Circle,Baltimore,MD 21250Laboratory for High Energy Astrophysics,Code 662,NASA/Goddard Space Flight Center,Greenbelt,MD20771Joseph C.ShieldsDepartment of Physics &Astronomy,Ohio University,Athens,OH 45701Accepted for Publication in the Astrophysical JournalABSTRACTWe present Chandra X-ray observations of the radio-quiet QSO PG 2302+029.This quasar has a rare system of ultra-high velocity (−56,000km s −1)UV absorption lines that form in an outflow from the active nucleus (Jannuzi et al.2003).The Chandra data indicate that soft X-ray absorption is also present.We perform a joint UV and X-ray analysis,using photoionization calculations,to detemine the nature of the absorbing gas.The UV and X-ray datasets were not obtained simultaneously.Nonetheless,our analysis suggests that the X-ray absorption occurs at high velocities in the same general region as the UV absorber.There are not enough constraints to rule out multi-zone models.In fact,the distinct broad and narrow UV line profiles clearly indicate that multiple zones are present.Our preferred estimates of the ionization and total column density in the X-ray absorber (log U =1.6,N H =1022.4cm −2)over predict the O VI λλ1032,1038absorption unless the X-ray absorber is also outflowing at ∼56,000km s −1,but they over predict the Ne VIII λλ770,780absorption at all velocities.If we assume that the X-ray absorbing gas is outflowing at the same velocity of the UV-absorbing wind and that the wind is radiatively accelerated,then the outflow must be launched at a radius of ≤1015cm from the central continuum source.The smallness of this radius casts doubts on the assumption of radiative acceleration.Subject headings:galaxies:active—quasars:absorption lines—quasars:individual(PG 2302+029)—X-rays:galaxies1.INTRODUCTIONX-ray absorption in quasars provides a powerful tool to study QSO environments.The signatures of this absorp-tion are typically the suppression of soft X-rays and /or the presence of absorption edges from O VII and O VIII near 0.8keV (Reynolds 1997;George et al.1998).The strength of these features depends mainly on the degree of ionization and total column density.The relationship of the X-ray absorber to other components of the quasar environs,especially the UV absorbing gas,is not well un-derstood.A natural question is whether these features originate in the same gas.The best-known intrinsic UV absorption lines in QSOs are the broad absorption lines (BALs),but recent work has shown that some of the observed narrow absorption lines (NALs)and “mini-BALs”are also intrinsic to QSO environments (Barlow,Hamann &Sargent 1997;Hamann et al.1997a and 1997b).These features can have velocity shifts comparable to the BALs (up to −51,000km s −1in one confirmed case;Hamann et al.1997b)but the narrow line widths (from <100km s −1to a few thousand km s −1)require outflows with much smaller line-of-sight velocity dispersions.BALs,mini-BALs,and intrinsic NALs are each rare in QSO spectra,but the outflows that cause them might be common if,as expected,the gas covers asmall fraction of the sky as seen from the central source.Among Seyfert 1galaxies,50%show intrinsic UV absorp-tion (Crenshaw et al.1999),and there is also a one-to-one correlation between the detection of X-ray absorption in Seyfert 1galaxies and the appearance of intrinsic UV ab-sorption lines (Crenshaw et al.1999).In QSOs,X-ray absorption is much rarer (Laor et al.1997).Brandt,Laor,&Wills (2000)showed that QSOs with BALs are all significantly weaker soft X-ray sources than comparable-luminosity QSOs without BALs.Posi-tive X-ray detections of BALQSOs (e.g.,Mathur,Elvis,&Singh 1995;Green et al.2001;Sabra &Hamann 2001;Gallagher et al.2002)reveal large absorbing columns ofN H ∼>1023cm −2.QSOs with weaker intrinsic UV ab-sorption lines,e.g.,the NALs and mini-BALs,appear to have systematically weaker X-ray absorption (Brandt et al.2000).However,more work is needed to characterize the X-ray absorption in quasars with different types/strengths of UV absorption.Studies of X-ray absorbers in quasars,especially in relation to the UV absorption lines,will have profound impact on our knowledge of quasar wind prop-erties,such as the acceleration mechanism,outflow geom-etry,wind launch radius,and mass loss rate (e.g.,Mathur et al.1995;Murray,Chiang,&Grossman 1995;Hamann 1998;Sabra &Hamann 2001).For example,it is difficult to radiatively accelerate an outflow with a large column12density,unless it is launched from the inner most regions of the accretion disk.In this paper we will discuss Chandra X-ray observations of the QSO PG2302+029.This object shows a system of intrinsic UV absorption lines that have a velocity shift of −56,000km s−1(Jannuzi et al.1996)with respect to the systemic velocity of the QSO(z ems=1.044).The system consists of NALs(F W HM≈330km s−1)at z=0.7016 and a“mini-BAL”system(F W HM≈3300km s−1)at z=0.695(Jannuzi et al.1996;1998).It is also character-ized by being an X-ray faint source with an HEAO-1A-2flux upper limit at2keV of4×10−12erg s−1cm−2(Della Ceca et al.1990).Our aim is to determine the proper-ties of the X-ray spectrum,search for signs of absorption, and define the relationship between the UV and X-ray ab-sorbing gas.We also discuss the location of the absorber, and the potential implications of high-velocity X-ray ab-sorption for the wind dynamics.If the X-ray and UV absorbers are the same,then the−56,000km s−1velocity shift of the UV absorption lines in PG2302+029is poten-tially resolvable with the Advanced Imaging Spectrometer (ACIS),given sharp features and adequate signal-to-noise ratio.2.OBSERVATIONS AND DATA REDUCTIONWe observed PG2302+029with Chandra using ACIS on7January2000.We used the most recent(2Novem-ber2000)re-processed data released by the Chandra X-ray Center for our analysis.Nofiltering for high background or bad aspect times was required because the light curves did not show anyflare-ups in the count rate and the aspect solution,the pattern by which the telescope was dithered to distribute the incoming photons over different pixels to minimize pixel-to-pixel variation,did not have any out-lying points.We performed data extraction and calibra-tion using version1.4of the Chandra Interactive Analysis of Observations(CIAO).We created the response matrix and ancillary responsefiles using calibration data provided when the chip temperature during observations was−120◦C.We extracted the source counts from a circular region of radius of5′′while the background region was an annu-lus with radii between10′′and20′′,both centered on the position of PG2302+029.The position of PG2302+029 (α(J2000)=23h04m44s,δ(J2000)=+03◦11′46′′),as de-termined from the ACIS image,coincides to within∼1′′with the optical position of the source reported in Schnei-der et al.(1992).We obtained a total of391±21counts in an exposure time of48ksec across the observed energy range∼0.4−4.0keV.3.ANALYSIS AND RESULTSWe bin the spectrum to have at least30counts/bin and use XSPEC(Arnaud1996)to perform the analysis.The low count rate indicates that X-ray absorption may be present.We,therefore,considerfits to the data that in-clude an X-ray continuum attentuated through an ionized X-ray absorber.Neutral X-ray absorption can be ruled out because the UV spectra do not contain any low-ionization metal lines that can be identified with the NAL and/or mini-BAL systems discussed in this paper(Jannuzi et al. 1996;Jannuzi et al.2003).We model the ionized ab-sorbers using the photoionization code CLOUDY(Ferland et al.1998)assuming solar abundances.We use this code to generate grids of absorbed continua in the following way:The incident continuum is a piece-wise powerlaw,fν∝ν−α,(Zheng et al.1997;Laor et al.1997;Telfer et al.2002)and is displayed in Figure1. The far-UV part of the spectrum is characterized by the2-point spectral indexαox,which relates theflux densities at 2500˚A and2keV:αox=0.384log(fν(2500˚A)/fν(2keV)). We use the B magnitude of16.3for PG2302+029to anchor the spectral energy distribution(SED)at2500˚A, taking into account the appropriate k−correction(Green 1996).Consequently,the X-rayflux density is specified throughαox.We stepαox from1.6to2.2in increments of0.2.This effectively gives us4different unabsorbed spectra representing4possible intrinsic SEDs from the quasar’s central engine,leading to4different intrinsic X-ray luminosities(cf.Figure1).Each SED is then attenu-ated through an ionized absorber.The amount of absorp-tion largely depends on the intrinsic total hydrogen col-umn density,N H(cm−2),and the ionization parameter, U,defined as the ratio of the density of hydrogen ioniz-ing photons to that of hydrogen particles(H0+H+).For each of our4SEDs,we create a grid of attenuated continua by calculating ionized absorbers on a grid of U and N H. Therefore,for every SED,there will be a grid of absorbed X-ray spectra identified by the(U,N H)combinations of the absorber through which they were transmitted. XSPEC incorporates aχ2minimization scheme that al-lows us tofind the bestfitting attenuated continuum to the X-ray spectrum of PG2302+029.We note that all our X-rayfits include attenuation by a Galactic columndensity of N Gal.H=5×1020cm−2(Lockman&Savage 1995)and the presence of an emission line with a Gaus-sian profile at∼3keV(probably Fe Kαat the redshift of the QSO).The significance of the Fe Kαdetection is clearly very low,given just391counts(see Figure2),but we include it in ourfits because the line is plausibly present and it improves theχ2results.We adjust the properties of the best Fe Kαfit—normalization(1.7×10−6photon s−1 cm−2keV−1),width(0.3keV),and energy(2.9keV)—by hand afterfinding the bestfit for the continuum in other parts of the spectrum.Our scheme also allows us to place the intrinsic absorber at any redshift we want.Naturally, we choose to place it either at the systemic redshift of the QSO,z XAbs=z QSO≈1,or at the redshift of the UV absorption lines,z Xabs=z UV abs≈0.7.For a specific absorber redshift and for each of our4 grids corresponding to the4intrinsic SEDs,wefit the data,with U and N H as free parameters,and note the value of the lowest reducedχ2,χ2ν,possible for that par-ticular SED,and henceαox,and z.Upon comparison be-tween the8χ2νvalues,wefind that the lowestχ2ν≈1,was that for the SED with intrinsicαox=2.0,corresponding to a far-UV/X-ray slope ofαEUV=2.4,for both z=0.7 and1.0.The rest of the SEDs are rejected at the95% confidence level,regardless of the amount of intrinsic ab-sorption.The need for intrinsic absorption is illustrated in Figure 2,where we show the X-ray spectrum of PG2302+029 together with best possiblefits,for the continuum with αox=2.0,with no intrinsic absorption(upper panel),and with an ionized absorber at z=0.7(lower panel).Clearly,3 thefit that includes intrinsic ionized absorption is muchbetter than the one that does not.In particular,the un-absorbed spectrumfits the data well at high energies,butit substantially over predicts the counts in soft X-rays.AnX-ray absorber naturally lowers the soft X-rayflux to themeasured values.Figure3shows overplots of the67%,90%,and99%confidence contours fromfitting the data for the casewhere the X-ray absorber is at the emission redshift,z XAbs=z QSO(solid contours),and where the X-ray ab-sorber matches the UV absorber redshift,z XAbs=z UV abs(dotted contours).For the z XAbs=z QSO case wefindwhilethat N H=1022.8±0.2cm−2and log U=2.2+0.1−0.2for the z XAbs=z UV abs,N H=1022.4±0.1cm−2andlog U=1.6±0.3,where all errors are at the90%con-fidence level.Theχ2νin both cases is∼1,and thereforethefits do not constrain the redshift of thte X-ray ab-sorber.Note that these results were derived assuming afixed X-ray powerlaw index ofαx=0.9.We did not ex-plore other X-ray spectral slopes because the data qualityis not sufficient to constrain additional free parameters.4.DISCUSSION4.1.Intrinsic X-ray BrightnessOurfinding in Section3that the intrinsicαox is2.0forPG2302+029deserves more attention.It has been knownthat there is a correlation between the optical luminosityat2500˚A of a quasar and its intrinsicαox(e.g.,Yuan et al.1998and references therein).The relation shows a widescatter in the distribution.The averageαox for radio quietQSOs,such as PG2302+029(Kellerman et al.1989),is1.7(Yuan et al.1998;Vignali,Brandt,&Schneider2003).PG2302+029,withαox=2.0and Lν(2500˚A)≈1031.8ergs−1Hz−1,is still consistent with the scatter in the Lν−αoxdistribution discussed in Yuan et al.(1998),although it is∼102.0−1.74given an equivalent width,we calculated the resulting ionic column density,the one shown in Figure4.We assumed that the mini-BAL is due to a single transition.The os-cillator strength of this transition is the sum of the two oscillator strengths of the doublet.The rest wavelength of the single transition is the oscillator-strength-weighted av-erage of the rest wavelengths of the doublet lines.A more appropriate method would be to use the prescription pre-sented in Junkkarinen,Burbidge,&Smith(1983)where an effective optical depth is calculated at every point across the line profile taking into account the combined contri-butions of the lines in the doublet.Upon experimentation with the STIS C IV mini-BALs,we found that the differ-ence between the two methods is∼30%,within the mea-surements errors involved and making minimal difference in Figure4.While weak low-ionization UV absorption lines are seen at the redshift of the quasar and may be of a different na-ture than the NALs and mini-BALs we are discussing here (Jannuzi et al.1998),high-ionization UV absorption lines are absent at this redshift.Moreover,there is no Lyman break,at any redshift,in the UV spectrum,and hence the total hydrogen column density in a low-ionization/neutral absorbing component is not high enough to lead to any observable effects on the X-ray spectrum.Our bestfit to the X-ray absorber at z Xabs=z QSO over predicts the OVI line absorption at this redshift.In particular,the pre-dicted OVI column density at this redshift,1015.6cm−2, would lead to an equivalent width of∼9˚A and∼3˚A in the observed frame if the lines have a Doppler param-eter of b≈2000km s−1and b≈200km s−1,like the high-velocity mini-BALs and NALs,respectively.These features should be detectable at∼>7σin the FOS and STIS spectra.Their absence suggests that the X-ray absorber is not at the quasar systemic velocity.Note that these results do not depend on our assumption of solar metallicity,as long as the relative metal abundances are roughly in their solar ratios.The X-ray absorption is dominated by metal ions,and we use ourfits to that to predict the strength of the metal lines in the UV.The relative abundance of hydrogen,therefore,is not a significant factor.Another important constraint on the UV–X-ray rela-tionship comes from the Ne VIII column densities(Figure 5).The Ne VIII lines are at770and780˚A,within the spectral coverage of the STIS observations but not the FOS.The fact that they are high-ionization lines implies that they are good tracers of the X-ray gas.Our best fits to the X-ray data predict Ne VIII column densities of∼1016.5cm−2if z Xabs=z QSO and∼1017.2cm−2if z Xabs=z UV abs.For Doppler parameters appropriate for the mini-BALs or NALs,b≈2000km s−1or b≈200km s−1,respectively,wefind that the Ne VIII column densities predicted by the X-rays should produce easily measurable UV lines(∼>40σ),corresponding to observed frame equiv-alent widths of∼40˚A or∼3˚A respectively.However, there is no Ne VIII absorption detected at either redshift. There are several possible explanations for the appar-ent discrepancies.First,the absorber overall is complex and time variable.The complexity is evident from the distinct UV kinematic components,e.g.,the NALs and mini-BALs.Also,the column densities derived from the UV lines do not define an isolated location in the log U versus log N H plane(Fig.4),suggesting that the NAL and mini-BAL regions both have multiple zones(with differ-ent values of U and N H).Third,as we have noted above, the NALs and mini-BALs both varied between the1994 and1998HST observations(Jannuzi2002),and neither of those measurements was simultaneous with the X-ray data obtained in2000.Finally,the true uncertainties in U and N H of the X-ray absorber are likely to be larger than shown in Figure3.Those results are based onfits that fixed the underlying continuum shape.Letting both the continuum shape and absorber properties vary in thefit would clearly lead to more uncertain results−although, without pursuing that option,it is not clear if the the pre-dicted Ne VIII absorption could be as low as the upper limit from the UV spectrum.Another complication is that the UV lines may be af-fected by partial coverage.If the absorbing gas does not fully cover the background light source,as we have as-sumed above,then there can be unabsorbed lightfilling in the bottoms of the UV line troughs and the column densities inferred from the lines will be only lower limits. Studies of other sources show that the coverage fraction can differ between ions and vary with velocity(across the line profiles)in the same ion(Hamann et al.1997,Bar-low&Sargent1997,Barlow,Sargent&Hamann1997). Our column density estimates all assume100%coverage. We can determine from the doublet ratios of the NALs that those lines are not optically thick absorption masked by partial coverage,i.e.,their derived column densities should be reasonable(section4.2).Moreover,we have no diagnostic of partial coverage for the mini-BALs.We must therefore keep in mind that their derived column densities are,strictly speaking,only lower limits.Similarily,the line strengths predicted from the X-ray column densities,e.g. for O VI and Ne VIII above,are lower limits because of the assumption of100%coverage in the X-rayfits.In summary,the strengths of most of the UV lines are consistent with the X-ray measurements,if the X-ray and UV absorbers are outflowing at the same speed.The ab-sence of high-ionization absorption lines at the quasar’s redshift argues for the UV and X-ray absorbers occuring in the same general region at high velocity.However,the X-ray observations overpredict the high-ionization UV lines of Ne VIII at all velocities.Simultaneous UV and X-ray observations are needed to probe the UV–X-ray relation-ship further.4.3.Wind DynamicsIf we assume the X-ray absorbing gas is outflowing with the UV absorber,then we can use the outflow velocity de-termined from the UV lines together with the X-ray mea-sured total hydrogen column density to test the viability of radiative acceleration of the wind.Hamann(1998)found that the terminal velocity(v terminal)of a radiatively accel-erated wind is related(cf.equation3of Hamann1998)to the total luminosity of the quasar,the mass of its central blackhole,the total column density of the wind(N H),the radius at which it is launched(R launch),and the fraction (f L)of incident continuum energy absorbed or scattered by the wind along an average line of sight.For BALs,Hamann(1998)estimated that f L could be on the order of a few tenths.However,the narrower and shallower lines in PG2302+029will intercept less con-5tinuumflux.Moreover,lower column densities compared to BALflows imply that reprocessing overall is less ef-ficient.We,therefore,assume that f L≤0.1for our present analysis.We also adopt representative values of the blackhole mass,108M⊙,and luminosity,1046erg s−1, which is the Eddington luminosity associated with that mass.We assume that v terminal=56,000km s−1and N H=2.34×1022cm−2.These values are the outflow velocity of the UV lines(Jannuzi et al.1996)and the column density we determined from the X-rays if the ab-sorber is at z=0.7(see end of section3).Substituting all these numbers into equation(3)of Hamann(1998),wefind that the launch radius is≤1015cm≈100R Schwarzchild. Therefore,if the wind is radiatively accelerated,it must be launched very near to the black hole.The mass loss rate implied by this radius is≤0.1Q M⊙yr−1,where Q is the global covering factorΩ/4π(Hamann &Brandt2002,in preparation).The density of theflow at this launch radius should be n H∼>1011cm−3,if it is photoionized with log U=1.6appropriate for the X-ray absorber(see Hamann&Brandt2002for explicit equa-tions).4.4.Geometry and Physical ModelsThe small launch radius required for a high-velocity X-ray absorber may be problematic for models of the out-flow in PG2302+029.For comparison,this maximum launch radius is much smaller than the nominal radius of the broad emission line region for a quasar of the same luminosity(R BLR≈2×1018cm,based on reverberation studies,e.g.,Kaspi et al.2000).On the other hand,the size of the X-ray continuum source is∼1014cm(e.g., Peterson1993),an order of magnitude smaller than the launch radius derived above.Given the small launch ra-dius,it seems likely that the X-ray absorber is either not radiatively accelerated,or not outflowing at the same high speed as the UV lines.In either case,the absence of high-ionization UV absorp-tion near the systemic velocity places another important constraint on wind models.If it is a steady-stateflow, then the acceleration must occur in a region that does not intersect our sightline to the continuum source.Models of outflows that lead to such UV lines have been discussed by Murray et al.(1995),Murray&Chiang(1995),and Elvis (2000).In these scenarios,the wind is initially perpen-dicular to the accretion disk.As itflows farther from the disk,the radiation pressure accelerating it bends andflares in the radial direction.Oblique lines of sight then could pass through the bent part of the wind,thus explaining the absence of zero-velocity absorption.The models mentioned in the previous paragraph dif-fer in subtle ways.Murray et al.(1995)described a case in which the X-ray absorber is at rest.Its function is to shield the UV gas from soft X-rays and prevent it from be-coming highly ionized,in which case resonant line driving would not be effective.Another variant of this scheme is the possibility of a self-shielding wind(Murray&Chiang 1995;Elvis2000).The X-ray and UV absorption arise in the same outflowing gas.The high column density of the wind requires a small launch radius,although probably larger than the radius we derive in section4.3.5.CONCLUSIONSWe presented Chandra X-ray observations of the radio-quiet QSO PG2302+029and demonstrated the presence of soft X-ray absorption in its spectrum.Older UV spec-tra of this quasar have been used to identify the presence of rarely observed ultra-high velocity(−56,000km s−1) absorption lines consistent with this quasar containing a remarkable outflow from its active nucleus(Jannuzi et al. 1996,Jannuzi et al.2003).Using photoionization models and the combined X-ray and UV data sets we have investi-gated the possible physical properties of the gas producing the X-ray and UV absorption.We suggest that the X-ray absorption also occurs at high velocities in the same gen-eral region as the UV absorber.There are not enough con-straints to rule out multi-zone models.Multi-zone mod-els are required if the distinct broad and narrow UV line profiles are both intrinsic to the QSO.The properties of the X-ray and UV absorption,as inferred from the data, are consistent with each other,if the X-ray absorbing gas is outflowing with the UV absorber.However,the X-ray data over predict the strength of the high-ionization UV lines of Ne VIII at all velocities.If we assume the X-ray absorbing gas is in an outflow with the same velocity as the gas producing the UV-absorbing wind and that such winds are radiatively accelerated,then the outflow must be started at a radius of≤1015cm from the central source of the radiation.Acknowledgements:We wish to acknowledge support through Chandra grants GO0-1123X and GO0-1157X. BTJ acknowledges support from the National Science Foundation through their support of the National Op-tical Astronomy Observatory,which is operated by the Association of Universities for Research in Astronomy, Inc.(A.U.R.A.)under cooperative agreement with the National Science Foundation and from NASA through a grant to proposal GO-07348.01-A from the Space Tele-scope Science Institute,which is operated by A.U.R.A., Inc.,under NASA contract NAS5-26555REFERENCESArnaud,K. A.1996,Astronomical Data Analysis Software and Systems V,eds.Jacoby G.and Barnes J.,p17,ASP Conf.Series volume101Barlow,T.A.,&Sargent,W.L.W.1997,AJ,113,136Barlow,T.A.,Hamann,F.,&Sargent,W.L.W.1997,ASP Conf.Ser.,128,13Brandt,W.N.,Laor,A.,&Wills,B.J.2000,ApJ,528,637 Crenshaw, D.M.,Kraemer,S. 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The dotted,dashed,long-dashed,and dash dotted lines correspond toαox=1.6,1.8,2.0,and2.2,respectively.8Fig.2.—X-ray spectrum of PG2302+029.Upper Panel:with no intrinsic absorption.Lower Panel:ionized absorber at z≈0.7.In both casesαox=2.09Fig.3.—Confidence contours,67%,90%,and99%,levels for X-rayfits.Solid-line contours are for z Xabs=z QSO,while dashed-line ones are for z XAbs=z UV abs.。

Clinical Nutrition(2003)22(4):415–421r2003Elsevier Ltd.All rights reserved.doi:10.1016/S0261-5614(03)00098-0SPECIAL ARTICLEESPEN Guidelines for Nutrition Screening2002J.KONDRUP,n S.P.ALLISON,y M.ELIA,z B.VELLAS,z M.PLAUTH yn Rigshospitalet University Hospital Copenhagen,Denmark,y Queen’s Medical Centre,Nottingham,UK,z University of Southampton, Southampton,UK,z University Hospital Centre,T oulouse,France,y Community Hospital Dessau,Germany(Correspondence to:JK, Nutrition Unit^5711,Rigshospitalet University,9Blegdamsvej,2100Copenhagen,Denmark)AbstractöAim:T o provide guidelines for nutrition risk screening applicable to di¡erent settings(community,hospital, elderly)based on published and validated evidence available until June2002.Note:These guidelines deliberately make reference to the year2002in their title to indicate that this version is based on the evidence available until2002and that they need to be updated and adapted to current state of knowledge in the future. In order to reach this goal the Education and Clinical Practice Committee invites and welcomes all criticism and sugges-tions(button for mail to ECPC chairman).r2003Elsevier Ltd.All rights reserved.Key words:Nutritional Assessment;malnutrition;hos-pital;communityBackgroundAbout30%of all patients in hospital are under-nourished.A large part of these patients are under-nourished when admitted to hospital and in the majority of these,undernutrition develops further while in hospital(1).This can be prevented if special attention is paid to their nutritional care.Other features of the patient’s primary disease are screened routinely and treated(e.g.dehydration,blood pressure,fever),and it is unacceptable that nutritional problems causing significant clinical risk are not identified.Neglect is also beginning to have medico-legal consequences,since an increasing number of cases of nutritional neglect are being brought to the courts.There is every reason, therefore,for hospitals and healthcare organizations to adopt a minimum set of standards in this area. However,the lack of a widely accepted screening system which will detect patients who might benefit clinically from nutritional support is commonly seen as a major limiting factor to improvement.It is the purpose of this document to give simple guidelines as to how undernutrition,or risk for develop-ment of undernutrition,can be detected,by proposing a set of standards which are practicable for general use in patients and clients within present healthcare resources. Purpose of screeningThe purpose of nutritional screening is to predict the probability of a better or worse outcome due to nutritional factors,and whether nutritional treatmentis likely to influence this.Outcome from treatment may be assessed in a number of ways:1.Improvement or at least prevention of deteriorationin mental and physical function2.Reduced number or severity of complications ofdisease or its treatment.3.Accelerated recovery from disease and shortenedconvalescence.4.Reduced consumption of resources, e.g.length ofhospital stay and other prescriptions.The nutritional impairment identified by screening should therefore be relevant to these aims and outcomes and may vary according to circumstances,e.g.age or type of illness.In the community,undernutrition,with or without chronic disease,may be the primary factor determining the mental or physical function of an individual,whereas in hospital or in a nursing home, disease factors assume a greater importance with disease-associated undernutrition assuming an important albeit secondary role.Screening in the community can therefore be focused primarily on nutritional variables based on the results of semi-starvation studies such as those of Ancel Keys and his colleagues in1950(2).In hospitals,other aspects of disease need to be considered in combination with purely nutritional measurements in order to deter-mine whether nutritional support is likely to be beneficial.Randomized controlled trials of nutritional support in particular disease groups may therefore provide important evidence on which to base our criteria of nutritional risk.Methodological considerationsThe usefulness of screening tools can be evaluated by a number of methods.The predictive validity is of major importance,i.e.that the individual identified to beat 415risk by the method is likely to obtain a health benefit from the intervention arising from the results of the screening.This can be obtained in various ways,as described for the individual screening tools below.The screening tool must also have a high degree of content validity,i.e.considered to include all relevant components of the problem it is meant to solve.This is usually achieved by involving representatives of those who are going to use it in the process of designing the tool.It must additionally have a high reliability,i.e little inter-observer variation.It must also be practical, i.e.those who are going to use the tool mustfind it rapid,simple and intuitively purposeful.It should not contain redundant information,rmation about vomiting or dysphagia is unnecessary when dietary intake is part of the screening.The etiology of reduced dietary intake belongs to asssessment(see below)or is incorporated into the nutrition care plan.Several other aspects of evaluating screening tools are described in an analysis of44nutritional screening tools(3). Finally,a screening tool should be linked to specified protocols for action, e.g.referral of those screened at risk to an expert for more detailed assessment and care plans.Screening leads to nutritional careHospital and healthcare organizations should have a policy and a specific set of protocols for identifying patients at nutritional risk,leading to appropriate nutritional care plans:an estimate of energy and protein requirements including posssible allowance for weight gain,followed by prescription of food,oral supple-ments,tube feeding or parenteral nutrition,or a combination of these.It is suggested that the following course of action be adopted.1.Screening This is a rapid and simple processconducted by admitting staff or community health-care teams.All patients should be screened on admission to hospital or other institutions.The outcome of screening must be linked to defined courses of action:a.The patient is not at risk,but may need to bere-screened at specified intervals,e.g.weeklyduring hospital stay.b.The patient is at risk and a nutrition plan isworked out by the staff.c.The patient is at risk,but metabolic orfunctional problems prevent a standard planbeing carried out.d.There is doubt as whether the patient is at risk.In the two latter cases,referral should be made to an expert for more detailed assessment.2.Assessment.This is a detailed examination ofmetabolic,nutritional or functional variables by an expert clinician,dietitian or nutrition nurse.It isa longer process than screening which leads to anappropriate care plan considering indications, possible side-effects,and,in some cases,special feeding techniques.It is based,like all diagnosis, upon a full history,examination and,where appropriate,laboratory investigations.It will in-clude the evaluation or measurement of the func-tional consequences of undernutrition,such as muscle weakness,fatigue and depression.It involves consideration of drugs that the patient is taking and which may be contributing to the symptoms,and of personal habits such as eating patterns and alcohol intake.It includes gastrointestinal assessment, including dentition,swallowing,bowel function, etc.It necessitates an understanding of the inter-pretation of laboratory tests,e.g.plasma albumin which is more likely to be a measure of disease severity than of malnutrition per se.Calcium, magnesium and zinc levels may be important,and in some cases laboratory measurement of micro-nutrient levels may be appropriate.3.Monitoring and outcome.A process of monitoringand defining outcome should be in place.The effectiveness of the care plan should be monitored by defined measurements and observations,such as recording of dietary intake,body weight and function,and a schedule for detecting possible side-effects.This may lead to alterations in treatment during the natural history of the patient’s condition.munication.Results of screening,assessmentand nutrition care plans should be communicated to other healthcare professionals when the patient is transferred,either back into the community or to another institution.When patients are transferred from the community to hospital or vice versa,it is important that the nutritional data and future care plans be communicated.5.Audit.If this process is carried out in a systematicway,it will allow audit of outcomes which may inform future policy decisions.Although this document will focus mainly on the process of screening,this cannot be considered in isolation and must be linked to the pathway of care described above.Components of nutritional screeningScreening tools are designed to detect protein and energy undernutrition,and/or to predict whether under-nutrition is likely to develop/worsen under the present and future conditions of the patient/client.Therefore, screening tools embody the following four main principles:1.What is the condition now?Height and weight allowcalculation of body mass index(BMI).Normal range 20–25,obesity430,borderline underweight18.5–20, undernutrition o18.5.In cases where it is not possible416ESPENGUIDELIN ESto obtain height and weight,e.g.in severely ill patients,a useful surrogate may be mid-arm circumference,measured with a tape around the upper arm midway between the acromion and the olecranon.This can be related to centiles of tables for that particular population,age and sex.1BMI may be less useful in growing children and adolescents,and in the very elderly.Nevertheless,the BMI provides the best generally accepted measure of weight for height.2.Is the condition stable?Recent weight loss is obtainedfrom the patient’s history,or,even better,from previous measurements in medical records.More than5%involuntary weight loss over3months,is usually regarded as significant.This may reveal undernutrition which was not discovered by1.,e.g.weight loss in obesity,and may also predict further nutritional deterioration depending on3and4.3.Will the condition get worse?This question may beanswered by asking whether food intake has been decreased up to the time of screening,and if so by approximately how much and for how long.Con-firmatory measurements can be made of the patient’s food intake in hospital or by food diary.If these are found to be less than the patient’s requirements with normal intake,then further weight loss is likely.4.Will the disease process accelerate nutritional deteriora-tion?In addition to decreasing appetite,the disease process may increase nutritional requirements due to the stress metabolism associated with severe disease(e.g.major surgery,sepsis,multitrauma),causingnutritional status to worsen more rapidly,or to develop rapidly from fairly normal states of(1–3)above. Variables1–3should be included in all screening tools,while4is relevant mainly to hospitals.In screening tools,each variable should be given a score, thereby quantifying the degree of risk and allowing a direct link to a defined course of action.Screening tools recommended by ESPENThe community:MUST for adults(see appendix)The purpose of the MUST system is to detect under-nutrition on the basis of knowledge about the associa-tion between impaired nutritional status and impaired function(5).It was primarily developed for use in the community,where serious confounders of the effect of undernutrition are relatively rare.Evaluation.The predictive validity of MUST in the community is based on previous and new studies of the effect of semi-starvation/starvation on mental and physical function in healthy volunteers concurrent validity with other tools,and utilisation of health care resources.The new series of studies describe the impair-ment of function as a results of various extents of weight loss,with various rates of weight loss,from various initial nutritional statures(low or high BMI)(6).It has been documented to have a high degree of relia-bility(low inter-observer variation)with a k=0.88À1.00. Its content validity has been assured by involving a multidisciplinary working group in its preparation.Its practicability has been documented in a number of studies in different community regions in the UK(5)(Table1). The tool has recently been extended to other health care settings,including hospitals,where again it has been found to have excellent inter-rater reliability,concurrent validity with other tools,and predictive validity(length of hospital stay,mortality in elderly wards,and discharge destination in orthopaedic patients).The hospital:NRS-2002(see appendix)The purpose of the NRS-2002system is to detect the presence of undernutrition and the risk of developing undernutrition in the hospital setting(4).It contains the nutritional components of MUST,and in addition,a grading of severity of disease as a reflection of increased nutritional requirements.It includes four questions as a pre-screening for departments with few at risk patients. With the prototypes for severity of disease given,it is meant to cover all possible patient categories in a hospital.A patient with a particular diagnosis does not always belong to the same category.A patient with cirrhosis,for example,who is admitted to intensive care because of a severe infection,should be given a score of 3,rather than1.It also includes old age as a risk factor, based on RCTs in elderly patients(4)(Table2). Evaluation.Its predictive validity has been documented by applying it to a retrospective analysis of128RCTs of nutritional support which showed that RCTs with patients fullfilling the risk criteria had a higher likelihood of a positive clinical outcome from nutritional support than RCTs of patients who did not fulfill these criteria (4).In addition,it has been applied prospectively in a controlled trial with212hospitalized patients selected according to this screening method,which showed a reduced length of stay among patients with complications in the intervention group(when adjusted for occurrence of operation and death).2Its content validity was maximized by involving an ESPENad hoc working group under the auspices of the ESPENEducational and Clinical Practice Committee in the literature based validation.It has also been used by nurses and dietitians in a2years’implementation study in three hospitals (local,regional and university hospital)in Denmark(7),1Data on simultaneous measurements of BMI and mid-arm circum-ference have not been published in a form that allows comparison of cut-off points for these measurements.An analysis of RCTs,in whichmean values BMI were given together with mean values of mid-arm circumference,suggested that a mid-arm circumference o25cm corresponds to a BMI o20.5(4).The data did not allow for distinguishing between lower cut-off points for BMI.2The trial was completed in April2002and a manuscript is in preparation by N.Johansen et al.A copy is available upon request (kondrup@rh.dk)CLINICAL NUTRITION417which indicated that staff and investigators seldomly disagreed about a patient’s risk status.Its reliability was validated by inter-observer variation between a nurse,a dietitian and a physician with a k=0.67.Its practicability was shown by thefinding that99%of750newly admitted patients could be screened.The incidence of at-risk patients was about20%(7).The elderly:MNAThe purpose of MNA is to detect the presence of undernutrition and the risk of developing undernutrition among the elderly in home-care programmes,nursing homes and hospitals.The prevalence of undernutrition among the elderly may reach significant levels(15–60%) under these circumstances(8).The screening methods mentioned above will detect undernutrition among many elderly patients,but for the frail elderly the MNA screening is more likely to identify risk of developing undernutrition,and undernutrition at an early stage, since it also includes physical and mental aspects that frequently affect the nutritional status of the elderly,as well as a dietary questionnaire.It is in fact a combination of a screening and an assessment tool,since the last part of the form(not reproduced here)is a more detailed exploration of the items in thefirst part of the form. Evalution.The predictive validity of MNA has been evaluated by demonstrating its association with adverse health outcome(9),social functioning(10),mortality (11,12)and a higher rate of visits to the general practitioner(13).In a randomized trial of elderly at risk according to MNA,those given oral supplements increased body weight,but not grip strength(14),and in another similar(but small)randomized trial of elderly in a nursing home,the intervention group increased dietary intake but no functional or clinical outcome data were reported(15).The content validity has not been reported.The reliability(inter-observer variation)was estimated,with a k=0.51(8).The MNA takes o10min to complete and its practicability has been shown by its use in a large number of studies,see(8).ChildrenA universally accepted screening tool for children is not yet available(although guidelines are in preparation under the Chairmanship of Professor Bert Koletzko, Munich).It is already standard practice among paedia-tricians to maintain height and weight charts,allowing calculation of growth velocity which is high-sensitive to nutritional status.Pubertal development is also im-paired during undernutrition.Other screening systemsIn their recent guidelines,the ASPENboard of directors stated that no screening system has been validated with respect to clinical outcome(16).They also suggested that,in the absence of an outcomes validated approach,a combination of clinical and biochemical parameters should be used to assess the presence of malnutrition. They suggest using the subjective global assessment,SGA (17),which classifies patients subjectively on the basis of data obtained from history and physical examination, since this system has been validated in several ways other than with respect to clinical outcome,e.g.inter-observer variation.However,the lack of a direct connection between the observations and the classification of patients leaves the tool more complex and less focused than desired for rapid screening purposes.An analysis of a total of44screening tools for use in hospital and the community(3)indicated that tools were published with insufficient details regarding their intended use and method of derivation,and with an inadequate assessment of their effectiveness.No one tool satisfied a set of criteria regarding scientific merit. The present recommendations by ESPENmay share some of these short-comings,but in view of the massive neglect of nutritional problems in health institutions, and the explicit lack of generally accepted screening tools,the predictive validity given above is considered sufficient to provide a practical and reasonable ap-proach in the light of present knowledge.These recommendations may need to be modified in the light of future experience.Predictive validity vs meta-analyses of treatmentThe predictive validity reported here needs to be commented upon in relation to recent meta-analyses, or systematic reviews.Such analyses suggest that nutritional support by the enteral or oral route improves functional capacity and clinical outcome,and reduces length of stay and mortality,e.g.(18,19).In a recent meta-analysis of studies employing parenteral nutrition (20),it was pointed out that there are inadequate data to assess the efficacy of parenteral nutrition in patients who are severely undernourished,who have highly catabolic disease processes,or who cannot be provided with enteral nutrition for several weeks.These are in fact the patients who most commonly receive supportive par-enteral nutrition now-a-days,and for ethical reasons, there will probably not be randomized trials available in the future either.The majority of studies available deal with the grey area of patients who are less under-nourished/not undernourished and/or are mildly–mod-erately catabolic.With these studies at hand,it was difficult to identify clinical conditions where parenteral nutrition would be clinically effective(20).However,the literature analysis mentioned above(4)suggests that parenteral nutrition is clinically effective in studies of patients who rather more than just fulfill the criteria for being nutritionally at risk.Furthermore,nutrients known to be essential for healthy humans are also essential for patients,and therefore the required documentation is not to confirm418ESPENGUIDELIN ESthe essentiality of nutrients among patients,but rather to define when a certain form of nutritional support is more beneficial than leaving the patient to develop nutritional deficiences.Therefore,meta-analyses and systematic reviews of nutritional support are too simplistic,if performed by analogy with treatment using a new drug.Finally,a nutritional care plan in most cases will involve food,oral supplements,tube feeding and parenteral nutrition,often used interchangeably in the same patient,whereas the majority of randomized trials,and meta-analyses,have dealt with studies of single modality treatments.The predictive validity of a screen-ing tool therefore cannot be directly based on meta-analyses available at present.References1.McWhirter J P,Pennington C R.Incidence and recognition of malnutrition in hospital.BMJ 1994;308:945–9482.Keys A,Brozek J,Henschel A et al.The Biology of Human Starvation.Minneapolis:University of Minnesota Press;1950:703–748&819and 9183.Jones J M.The methodology of nutritional screening and assess-ment tools.J Hum Nutr Diet 2002;15:59–714.Kondrup J,Rasmussen H H,Hamberg O et al.Nutritional Risk Screening (NRS 2002):a new method based on an analysis of controlled clinical trials.Clin Nutr 2003;22:321–3365.Malnutrition Advisory Group (MAG).MAG—guidelines for Detection and Management of Malnutrition.British Association for Parenteral and Enteral Nutrition,2000,Redditch,UK6.Elia M.Personal communication7.Kondrup J,Johansen N,Plum L M et al.Incidence of nutritional risk and causes of inadequate nutritional care in hospitals.Clin Nutr 2002;21:461–4688.Vellas B,Guigoz Y,Garry P J et al.The Mini NutritionalAssessment (MNA)and its use in grading the nutritional state of elderly patients.Nutrition 1999;15:116–1229.Beck A M,Ovesen L,Osler M.The ‘Mini Nutritional Assessment’(MNA)and the ‘Determine Your Nutritional Health’Checklist (NSI Checklist)as predictors of morbidity and mortality in an elderly Danish population.Br J Nutr 1999;81:31–3610.Griep M I,Mets T F,Collys K et al.Risk of malnutrition inretirement homes elderly persons measured by the ‘mini-nutritional assessment’.J Gerontol A Biol Sci Med Sci 2000;55:M57–pan B,di Castri A,Plaze J M et al.Epidemiological studyof malnutrition in elderly patients in acute,sub-acute and long-term care using the MNA.J Nutr Health Aging 1999;3:146–15112.Gazzotti C,Albert A,Pepinster A et al.Clinical usefulness of themini nutritional assessment (MNA)scale in geriatric medicine.J Nutr Health Aging 2000;4:176–8113.Beck A M,Ovesen L,Schroll M.A six months’prospective follow-up of 65+-y-old patients from general practice classified according to nutritional risk by the Mini Nutritional Assessment.Eur J Clin Nutr 2001;55:1028–1033uque S,Arnaud Battandier F,Mansourian R et al.Protein-energy oral supplementation in malnourished nursing-home residents.A controlled trial.Age Ageing 2000;29:51–5615.Beck A M,Ovesen L,Schroll M.Home-made oral supplement asnutritional support of old nursing home residents,who areundernourished or at risk of undernutrition based on the MNA.A pilot trial.Aging Clin Exp Res 2002;14:212–21516.ASPENBoard of directors.Guidelines for the use of parenteral,enteral nutrition in adult and pediatrc care.J Parenter Enteral Nutr 2002;26:9SA–12SA17.Detsky A S,McLaughlin J R,Baker J P et al.What is subjectiveglobal assessment of nutritional status?J Parenter Enteral Nutr 1987;11:8–1318.Potter J,Langhorne P,Roberts M.Routine protein energy supple-mentation in adults:systematic review.BMJ 1998;317:495–50119.Stratton R J,Green C J,Elia M E.Disease Related Malnutrition:An Evidence-based Approach to Treatment.CAB International,Oxford,UK,200320.Koretz R L,Lipman T O,Klein S.AGA technical review onparenteral nutrition.Gastroenterology 2001;121:970–1001Can be adapted for special circumstances (e.g.when weight and height cannot be measured or when there are fluid disturbances)using specified alternative measurements including subjective criteria.It also identifies obesity (BMI 430kg/m 2).AppendixMalnutrition Universal Screening Tool (MUST)for adultsCLINICAL NUTRITION 419420ESPENGUIDELIN ESNutritional Risk Screening(NRS2002)CLINICAL NUTRITION421 r。

单元知识滚动练Unit 4 复习强化Ⅰ.单词拼写1．He felt the rough surface of the rock cutting into his knees.2．He can’t decide which candidate he should vote in the next election.3．The club has created an exciting atmosphere for gaming and recreation(娱乐)．4．The young couple were busy filling their new house with some furniture(家具)．5．It is natural that one might question the motives(动机) of some politicians.6．Our manager ordered us to have a thorough cleaning that weekend.7．The young man is genuine，so you can rely on him to help you out.8．The woman entered the room and put a blanket(毯子) over the little baby.Ⅱ.单句语法填空9．Strengthening our emotional endurance(endure) is vital for a happy life.10．As a qualified(qualify) new employee，he was highly thought of in the company. 11．I’m afraid that I can’t finish the work assigned(assign) to me within three days. 12．The little boy burst into tears when he found his favorite toy crushed(crush)．13．The old man was so kind that he adopted the child abandoned(abandon) by his parents. 14．To be honest，I’m not sure whether the results have any practical application(apply)．15．Fortunately(fortunate)，the two boys were saved by the local villagers.Unit 5 巩固落实Ⅲ.单词拼写16．The present situation is complicated(复杂的)，so you’d better leave here.17．The farmers had to depend on the barren(贫瘠的) field in the past.18．The girl spent much time polishing the article before handing it in.19．If your son fails in the contest，you’d better comfort him in time.20．They were working hard in order not to miss the deadline(最后期限)．21．When she turned around，she saw her mother’s blank(没表情的) eyes.22．The fact is that the woman has been awaiting her husband all the time.23．It is better for you to talk about that matter when he is in a good mood.Ⅳ.单句语法填空24．Our monitor is sympathetic(sympathy) and he often helps the poor classmates. 25．After the accident，she left the city with a sorrowful(sorrow) heart.26．Having read the text many times，he found it really hard to recite(recite)．27．The leader will pay a visit to a team made(make) up of over 200 people.28．They turned to one another with the same expression of comprehension(comprehend) and relief.29．It was cruel of the general to put some innocent(innocence) soldiers into prison.30．There is a large variation(vary) in the amount of sleep people feel happy with.Ⅴ.完成句子31．He was the first person to question racial prejudice in this town.他是这个镇上第一个对种族偏见提出质疑的人。

《中国癌症杂志》2020年第30卷第9期 CHINA ONCOLOGY 2020 Vol.30 No.9656·论　著·欢迎关注本刊公众号基金项目：国家自然科学基金（81101483）；河北省自然科学基金重点项目（H2017209233）； 唐山市科技创新团队培养计划（14130225B ）。

通信作者：张　志　E-mail: zhi1969@膜辅助蛋白CD46 rs1970530遗传变异对肝癌发病风险的影响徐珊珊1，宋琴琴1，仵红娇2，付　宁2，车玲玉2，金　敏1，刘　冲1，韩素桂3，张雪梅2，张　志11.华北理工大学附属唐山市工人医院肿瘤科，河北 唐山 063000；2.华北理工大学生命科学学院，河北 唐山 063210；3.华北理工大学附属唐山市人民医院核医学检验科，河北 唐山 063000［摘要］ 背景与目的：膜辅助蛋白CD 46可保护宿主细胞免受补体依赖的细胞毒性作用，研究表明，CD46可能作为肝细胞癌（hepatocellular carcinoma ，HCC ）患者的潜在生物标志物。

探讨CD 46基因表达及启动子区遗传变异与HCC 发病风险的关系。

方法：通过基因表达谱交互分析（gene expression profiling interactive analysis ，GEPIA ）在线网站分析HCC 组织和正常肝组织CD46表达的差异；2011—2015年在华北理工大学附属唐山市工人医院和华北理工大学附属唐山市人民医院经病理学检查确诊且未经放化疗的240例HCC 患者作为病例组，对照组为同时期入院体检的500名健康人群。

采用聚合酶链反应-限制性片段长度多态性分析（polymerase chain reaction-restriction fragment length polymorphism ，PCR-RFLP ）法进行基因分型，检测两组基因型频率和等位基因频率，评估CD 46 rs1970530遗传变异与HCC 发病风险的关系。

As a high school student, Ive always been fascinated by the diversity of nature, and one of the most common yet intriguing subjects of this fascination is the humble carrot. The carrot, with its distinct shape and vibrant color, is not just a staple in many diets but also a symbol of health and vitality. Let me take you on a journey through my observations and experiences with this root vegetable.Growing up, I remember the first time I saw a carrot in our garden. It was a warm summer day, and I was helping my father with the gardening chores. As we pulled back the soil, the sight of those orange treasures peeking through the earth was nothing short of magical. The carrots were not all uniform some were long and slender, while others were stubby and thick. This natural variation in shape sparked my curiosity.The typical carrot shape is a conical one, with a wider base and a tapered top, which tapers to a point. This shape is not only aesthetically pleasing but also serves a practical purpose. The wide base allows the carrot to anchor itself firmly in the soil, while the tapered top makes it easier for the plant to push through the earth as it grows. This is a testament to natures efficiency in design.One of the most striking features of a carrot is its color. Most people are familiar with the bright orange hue that is almost synonymous with the vegetable. However, did you know that carrots can come in a variety of colors including purple, yellow, red, and white? The vibrant orange we commonly associate with carrots is due to the presence of betacarotene, a pigment that our bodies convert into vitamin A. This not only adds to thecarrots nutritional value but also contributes to its striking appearance.In school, we learned about the importance of carrots in history and culture. For instance, during World War II, the British government promoted the consumption of carrots to improve night vision, a myth that was propagated to hide the use of radar technology. This story illustrates the deeprooted significance of carrots in our collective consciousness.Moreover, the shape and color of carrots have also found their way into art and literature. From the whimsical carrotshaped top hat worn by the Mad Hatter in Alice in Wonderland to the symbolic use of carrots in paintings to represent health and prosperity, the carrots influence extends beyond the kitchen.In terms of taste, the texture of a carrot is firm yet crisp, and its flavor is subtly sweet. When cooked, the texture becomes tender, and the natural sugars caramelize, enhancing its sweetness. This versatility makes carrots a popular ingredient in various dishes, from salads to stews and even desserts.My personal experience with carrots has been quite enriching. I remember the excitement of harvesting carrots from our garden, washing off the dirt, and biting into the fresh, crunchy vegetable. It was a simple pleasure that brought me closer to nature and taught me to appreciate the beauty of our natural world.In conclusion, the carrot, with its distinct shape, color, and versatility, ismore than just a root vegetable. It is a symbol of health, a piece of history, and a source of culinary delight. As I continue to explore the world around me, I am reminded of the simple yet profound lessons that can be learned from the humble carrot.。

托福考试 复习托福阅读TPO10(试题+答案+译文)第2篇:Variations in the Climate托福阅读原文One of the most difficult aspects ofdeciding whether current climatic events reveal evidence of the impact of humanactivities is that it is hard to get a measure of what constitutes the naturalvariability of the climate. We know that over the past millennia the climatehas undergone major changes without any significant human intervention. We alsoknow that the global climate system is immensely complicated and thateverything is in some way connected, and so the system is capable offluctuating in unexpected ways. We need therefore to know how much the climatecan vary of its own accord in order to interpret with confidence the extent towhich recent changes are natural as opposed to being the result of humanactivities.Instrumental records do not go back farenough to provide us with reliable measurements of global climatic variabilityon timescales longer than a century. What we do know is that as we includelonger time intervals, the record shows increasing evidence of slow swings inclimate between different regimes. T o build up a better picture offluctuationsappreciably further back in time requires us to use proxy records.Over long periods of time, substances whosephysical and chemical properties change with the ambient climate at the timecan be deposited in a systematic way to provide a continuous record of changesin those properties overtime, sometimes for hundreds or thousands of years.Generally, the layering occurs on an annual basis, hence the observed changesin the records can be dated. Information on temperature, rainfall, and otheraspects of the climate that can be inferred from the systematic changes inproperties is usually referred to as proxy data. Proxy temperature records havebeen reconstructed from ice core drilled out of the central Greenland ice cap,calcite shells embedded in layered lake sediments in Western Europe, oceanfloor sediment cores from the tropical Atlantic Ocean, ice cores from Peruvianglaciers, and ice cores from eastern Antarctica. While these records providebroadly consistent indications that temperature variations can occur on aglobal scale, there are nonetheless some intriguing differences, which suggestthat the pattern of temperature variations in regional climates can also differsignificantly from each other.What the proxy records make abundantlyclear is that there have beensignificant natural changes in the climate overtimescales longer than a few thousand years. Equally striking, however, is therelative stability of the climate in the past 10,000 years (the Holoceneperiod).To the extent that the coverage of theglobal climate from these records can provide a measure of its truevariability, it should at least indicate how all the natural causes of climatechange have combined. These include the chaotic fluctuations of the atmosphere,the slower but equally erratic behavior of the oceans, changes in the landsurfaces, and the extent of ice and snow. Also included will be any variationsthat have arisen from volcanic activity, solar activity, and, possibly, humanactivities.One way to estimate how all the variousprocesses leading to climate variability will combine is by using computermodels of the global climate. They can do only so much to represent the fullcomplexity of the global climate and hence may give only limited informationabout natural variability. Studies suggest that to date the variability incomputer simulations is considerably smaller than in data obtained from theproxy records.In addition to the internal variability ofthe global climate system itself, there is the added factor of externalinfluences, such as volcanoes andsolar activity. There is a growing body ofopinion that both these physical variations have a measurable impact on theclimate. Thus we need to be able to include these in our deliberations. Somecurrent analyses conclude that volcanoes and solar activity explain quite aconsiderable amount of the observed variability in the period from theseventeenth to the early twentieth centuries, but that they cannot be invokedto explain the rapid warming in recent decades.托福阅读试题1.According to paragraph 1, which of thefollowing must we find out in order to determine the impact of human activitiesupon climate?A.The major changes in climate over thepast millenniaB.The degree to which the climate variesnaturallyC.The best method for measuring climaticchangeD.The millennium when humans began tointerfere with the climate2.According to paragraph 2, an advantage ofproxy records overinstrumental records is thatA.they are more-reliable measures ofclimatic variability in the past centuryB. they provide more-accurate measures oflocal temperaturesC.they provide information on climatefluctuations further back in timeD.they reveal information about the humanimpact on the climate3.Which of the sentences below bestexpresses the essential information in the highlighted sentence in thepassage(Paragraph 3)? Incorrect choices change the meaning in important ways orleave out essential information.A.Because physical and chemical propertiesof substances are unchanging, they are useful records of climate fluctuationsover time.B.For hundreds or thousands of years,people have been observing changes in the chemical and physical properties of substancesin order to infer climate change.C. Because it takes long periods of timefor the climate to change, systematic changes in the properties of substancesare difficult to observe.D.Changes in systematically depositedsubstances that are affected by climate can indicate climate variations overtime.4.According to paragraph 3, scientists areable to reconstruct proxy temperature records byA.studying regional differences intemperature variationsB.studying and dating changes in theproperties of substancesC. observing changes in present day climateconditionsD.inferring past climate shifts fromobservations of current climatic changes5.The word “striking” in thepassage(Paragraph 4)is closest in meaning toA.noticeableB.confusingC. trueD. unlikely6.Accordingto paragraphs 3 and 4, proxydata have suggested all of the following about theclimate EXCEPT:A.Regional climates may change overtime.B.The climate has changed very little inthe past 10,000 years.C.Global temperatures vary more thanregional temperatures.D. Important natural changes in climatehave occurred over large timescales.7.The word “erratic” in thepassage(Paragraph 5)is closest in meaning toA.dramaticB. importantC. unpredictablemon8.All of the following are mentioned inparagraph 5 as natural causes of climate change EXCEPTA. atmospheric changesB. the slow movement of landmassesC. fluctuations in the amount of ice andsnowD.changes in ocean activity9.According to paragraph 6, which of thefollowing is true of computer models of the global climate?A.The information they produce is stilllimited.B.They are currently most useful inunderstanding past climatic behaviors.C.They allow researchers to interpret thedata obtained from proxy records.D.They do not provide information aboutregional climates.10.The word “deliberations”(Paragraph 7)inthe passage is closest in meaning toA. recordsB.discussionsC.resultsD. variations11.The word “invoked”(Paragraph 7)in thepassage is closest inmeaning toA.demonstratedB.called uponC. supportedD. expected12.What is the author's purpose inpresenting the information in paragraph 7?A. To compare the influence of volcanoesand solar activity on climate variability with the influence of factorsexternal to the global climate systemB.To indicate that there are other types ofinfluences on climate variability in addition to those previously discussedC.To explain how external influences onclimate variability differ from internal influencesD.To argue that the rapid warming of Earthin recent decades cannot be explained13. Look at the four squares [■] thatindicate where the following sentence could be added to the passage. Wherewould the sentence best fit? Indeed, the contribution of volcanoes and solaractivity would more likely have been to actually reduce the rate of warmingslightly.In addition to the internal variability ofthe global climate system itself, there is the added factor of externalinfluences, such as volcanoes and solar activity. ■【A】There is agrowing body of opinion that both these physical variations have a measurableimpact on the climate. ■【B】Thus we need to be able to include these in our deliberations. ■【C】Some currentanalyses conclude that volcanoes and solar activity explain quite aconsiderable amount of the observed variability in the period from theseventeenth to the early twentieth centuries, but that they cannot be invokedto explain the rapid warming in recent decades. ■【D】14. Directions: An introductory sentencefor a brief summary of the passage is provided below. Complete the summary byselecting the THREE answer that express the most important ideas in thepassage.Some sentences do not belong in the summary because they express ideasthat not presented in the passage or are minor ideas in the passage. Thisquestion is worth 2 points.A number of different and complex factorsinfluence changes in the global climate over long periods of time.A.In the absence of instrumental records,proxy data allow scientists to infer information about past climates.B. Scientists see a consistent pattern inthe global temperature variations that have occurred in the past.puter models are used to estimate howthe different causes of climate variability combine to account for the climatevariability that occurs.D.Scientists have successfully separatednatural climate variation from changes related to human activities.E. Scientists believe that activitiesoutside the global climate system, such as volcanoes and solar activity mayhave significant effects on the system.F.Scientistshave concluded that human activity accounts for the rapid global warming inrecent decades.托福阅读答案1.以human activities做关键词定位至第一句，说在判断人类对气候的影响之前必须断定自然的影响，所以B正确。