1-4μm Photometry of Two Sites of Massive Star Formation Preliminary Results

Differences between China and Westin Response to ‘’Sexy photo-gate’’KZchia Jennifer spoke about the incident for the first time by callin g the photo theft “a sex crime.”Recently, more than a hundred Hollywood actress’ private photos, and with many containing nudity were posed online.This event is similar to EdisonChen’s‘’sexy photo-gate’’ incident that happened several years ago in China, but it leads to totally different responses in this two society. In America, it is a sex crime. In China, it is sex scandal.Why is there such a difference? The following is my view1、Acceptances of barenessIn the west, from ancient Greece to contemporary, nude has never been a big problem. Whether Venus's breast or David’s penis, it’s open and aboveboard, not sheltered, regarded as beautiful and classic.In China, the nakedness causes enormous anxiety in the crowd. Tides of criticism come like atomic bomb explodes or bunch of houses collapse.Viewer evaluations are in a contrary too. People in China tend to consider the incident as cynical and gloat, while Westerners think it is the invasion of privacy, feel more pity on that.2、Ways of looking at SexWesterners have a relatively positive attitude toward sex , it is normal and no constrain, but in China, when it comes to sex, most people feel embarrassing , even have belittled and mocked attitude toward that.The different extent of social public opinion response affects the evaluations of people in the country. In China, when there is such a buzz topic, lots of people rise and attack, and cause a great disturbance eventually. In the west, they will be in understatement at first, listen patiently and don’t seem surprised, then announced their comments.In conclusion, different views and mindsets between Chinese and Western, lead to different reactions to the ‘’sexy photo-gate’’. “It’s my body, and it should be my choice”, “if who viewed the pictures should cower with shame”. Jennifer Lawrence’s speak is resolute and brave. And to us, we should all have great reflections on ourselves.。

a r X i v :0803.1019v 1 [a s t r o -p h ] 7 M a r 2008Draft version March 7,2008Preprint typeset using L A T E X style emulateapj v.10/09/06THE DISK POPULATION OF THE CHAMAELEON I STAR-FORMING REGION 1K.L.Luhman 2,L.E.Allen 3,P.R.Allen 2,R.A.Gutermuth 3,L.Hartmann 4,E.E.Mamajek 3,S.T.Megeath 5,P.C.Myers 3,and G.G.F azio 3Draft version March 7,2008ABSTRACTWe present a census of circumstellar disks in the Chamaeleon I star-forming ing the Infrared Array Camera and the Multiband Imaging Photometer onboard the Spitzer Space Telescope ,we have obtained images of Chamaeleon I at 3.6,4.5,5.8,8.0,and 24µm.To search for new disk-bearing members of the cluster,we have performed spectroscopy on objects that have red colors in these data.Through this work,we have discovered four new members of Chamaeleon I with spectral types of M4,M6,M7.5,and L0.The first three objects are highly embedded (A J ∼5)and reside near known protostars,indicating that they may be among the youngest low-mass sources in the cluster (τ<1Myr).The L0source is the coolest known member of Chamaeleon I.Its luminosity implies a mass of 0.004-0.01M ⊙,making it the least massive brown dwarf for which a circumstellar disk has been reliably detected.To characterize the disk population in Chamaeleon I,we have classified the infrared spectral energy distributions of the 203known members that are encompassed by the Spitzer images.Through these classifications,we find that the disk fraction in Chamaeleon I is roughly constant at ∼50%from 0.01to 0.3M ⊙.These data are similar to the disk fraction of IC 348,which is a denser cluster at the same age as Chamaeleon I.However,the disk fraction at M 1M ⊙is significantly higher in Chamaeleon I than in IC 348(65%vs.20%),indicating longer disk lifetimes in Chamaeleon I for this mass range.Thus,low-density star-forming regions like Chamaeleon I may offer more time for planet formation around solar-type stars than denser clusters.Subject headings:accretion disks –planetary systems:protoplanetary disks –stars:formation —stars:low-mass,brown dwarfs —stars:pre-main sequence1.INTRODUCTIONLow-mass stars and brown dwarfs are important sites for studies of planet formation because most stars in the galaxy are low-mass stars while brown dwarfs offer an opportunity to explore planet formation in an extreme environment.Planet formation around low-mass stars and brown dwarfs can be investigated through obser-vations of their primordial circumstellar disks.These observations are most easily performed at mid-infrared (IR)wavelengths (λ∼5-20µm)because this wavelength range provides the best combination of contrast of the disk relative to stellar photosphere,disk brightness,and sensitivity of available telescopes.Molecular clouds that contain ongoing star formation1Based on observations performed with the Magellan Tele-scopes at Las Campanas Observatory,Gemini Observatory,and the Spitzer Space Telescope .Gemini Observatory is operated by AURA under a cooperative agreement with the NSF on behalf of the Gemini partnership:the NSF (United States),the Parti-cle Physics and Astronomy Research Council (United Kingdom),the National Research Council (Canada),CONICYT (Chile),the Australian Research Council (Australia),CNPq (Brazil)and CON-ICET (Argentina).Spitzer is operated by the Jet Propulsion Labo-ratory (JPL),California Institute of Technology under NASA con-tract 1407.Support for this work was provided by NASA through contract 1256790issued by JPL.Support for the IRAC instrument was provided by NASA through contract 960541issued by JPL.2Department of Astronomy and Astrophysics,The Penn-sylvania State University,University Park,PA 16802;kluh-man@.3Harvard-Smithsonian Center for Astrophysics,Cambridge,MA 02138.4Department of Astronomy,The University of Michigan,Ann Arbor,MI 48109.5Department of Physics and Astronomy,The University of Toledo,Toledo,OH 43606.(τ 5Myr)are the natural laboratories for obser-vations of circumstellar disks.Among these regions,Chamaeleon I is arguably the best site for studying disks around low-mass stars and brown dwarfs.It is one of the nearest star-forming regions to the Sun (d =160-170pc,Whittet et al.1997;Wichmann et al.1998;Bertout et al.1999),making its low-mass mem-bers relatively bright.The cluster is young enough that it retains a significant population of primordial disks,but it is old enough that most of its members are no longer highly obscured by dust (A V 5).Because of the relatively low extinction,optical wavelengths are accessible for the spectral classification of the stellar population (Comer´o n et al.2004;Luhman 2004a,refer-ences therein)and for measuring diagnostics of accre-tion (Mohanty et al.2005;Muzerolle et al.2005).Op-tical and near-IR imaging and spectroscopic surveys of Chamaeleon I have produced an extensive census of the stellar and substellar cluster members (Luhman 2007).In particular,this census is unbiased in terms of disks,which is essential for measuring the prevalence of disks.With ∼200known members at masses of 0.01-1M ⊙,Chamaeleon I is sufficiently rich for a statistical anal-ysis of disks around low-mass stars and brown dwarfs.This region is also well-suited for observations of disks at mid-IR wavelengths.The stellar population is sparse enough that current mid-IR telescopes can resolve indi-vidual members,while compact enough for deep imaging of a large fraction of the cluster in a reasonable amount of time.In addition,the cloud exhibits relatively little nebulosity and extended emission at mid-IR wavelengths,which enables accurate photometry of the faint,low-mass members.2Luhman et al.Several studies have searched for evidence of disks in Chamaeleon I through near-and mid-IR photome-try.During pointed observations of known members,Glass (1979)and Jayawardhana et al.(2003)obtained photometry in the JHKL bands (1.2,1.6,2.2,3.4µm)for 17and 15members with spectral types as late as M4and M8,ing a similar set of filters,G´o mez &Kenyon (2001)and Kenyon &G´o mez (2001)performed wide-field imaging of a 0.5deg 2field that en-compassed a large fraction of the Chamaeleon I cloud.Photometry at wavelengths longward of the L -band of-fers more reliable detections of disks because of the bet-ter contrast of cool circumstellar dust relative to warmer stellar photopsheres.To obtain data of this kind for known young stars in Chamaeleon I and to search for new disk-bearing members of the cluster,Baud et al.(1984)observed Chamaeleon I with the Infrared Astronomical Satellite (IRAS )at 12,25,60,and 100µm.They de-tected 70sources,half of which are cluster members.A mid-IR survey with better sensitivity and spatial resolu-tion was later conducted with the Infrared Space Obser-vatory (ISO ,Nordh et al.1996;Persi et al.2000),which provided photometry for 99known members,including a brown dwarf with a spectral type near M8(Natta &Testi 2001;Apai et al.2002).Mid-IR imaging also has been performed toward smaller areas surrounding the three most prominent reflection nebulae in the Chamaeleon I cloud using IRAS (Assendorp et al.1990;Prusti et al.1991)and ISO (Lehtinen et al.2001).The Spitzer Space Telescope (Werner et al.2004)is currently the most advanced telescope operating at mid-IR wavelengths.Because of its high spatial resolution,excellent sensitivity,and large field of view,Spitzer is proficient at identifying disk-bearing members of young clusters (Allen et al.2004;Gutermuth et al.2004;Megeath et al.2004;Muzerolle et al.2004).This capability has been widely utilized through Spitzer surveys of nearby star-forming regions and young associations (τ 10Myr),including Taurus (Hartmann et al.2005;Luhman et al.2006;Guieu et al.2007),Perseus (Luhman et al.2005b;Lada et al.2006;Jørgensen et al.2006;Muench et al.2007;Rebull et al.2007;Gutermuth et al.2007),Lupus (Allen et al.2007),Serpens (Harvey et al.2006,2007;Winston et al.2007),σOri (Hern´a ndez et al.2007;Caballero et al.2007;Zapatero Osorio et al.2007;Scholz &Jayawardhana 2007),λOri (Barrado y Navascu´e s et al.2007),Orion OB1b (Hern´a ndez et al.2006),ηCha (Megeath et al.2005),Chamaeleon II (Young et al.2005;Allers et al.2006;Porras et al.2007),NGC 2362(Dahm &Hillenbrand 2007),Upper Sco (Carpenter et al.2006;Scholz et al.2007),Tr 37,and NGC 7160(Sicilia-Aguilar et al.2006).Extensive Spitzer imaging has been performed in Chamaeleon I as well.Some of these data have been used to examine the properties of the disk population of Chamaeleon I (Luhman et al.2005b;Damjanov et al.2007),identify low-mass brown dwarfs with disks (Luhman et al.2005a,c),and search for outflows (Bally et al.2006).In this paper,we present a comprehensive census of disks in Chamaeleon I using most of the Spitzer imagesbetween3.6and 24µm that have been obtained in this region.We begin by describing the collection and analysis of the Spitzer images (§2)and the identificationof new disk-bearing members of the cluster with these data (§3).We then use the Spitzer photometry of the known members of the cluster to investigate the global properties of the disk population of Chamaeleon I (§4).2.INFRARED IMAGES 2.1.ObservationsFor our census of the disk population in Chamaeleon I,we use images at 3.6,4.5, 5.8,and 8.0µm obtained with Spitzer ’s Infrared Array Camera (IRAC;Fazio et al.2004a)and images at 24µm obtained with the Multi-band Imaging Photometer for Spitzer (MIPS;Rieke et al.2004).The fields of view are 5.2′×5.2′and 5.4′×5.4′for IRAC and the 24µm channel of MIPS,respectively.The cameras produce images with FWHM=1.6-1.9′′from 3.6to 8.0µm and FWHM=5.9′′at 24µm.In this paper,we consider all IRAC and MIPS 24µm observations that have been performed within a radius of 3◦from α=11h 07m 00s ,δ=−77◦10′00′′(J2000)with the exception of the recently executed Legacy pro-gram of L.Allen,which has a program identification (PID)of 30574.These data were obtained through IRAC Guaranteed Time Observations (GTO)for PID=6,36,and 37(G.Fazio),IRAC and IRS GTO for PID=30540(G.Fazio,J.Houck),IRS GTO for PID=40302(J.Houck),Director’s Discretionary Time for PID=248(S.Mohanty),and Legacy programs for PID=139,173(N.Evans),and 148(M.Meyer).The characteristics of the IRAC and MIPS images are summarized in Tables 1and 2,respectively.The boundaries of these images are indi-cated in the maps of Chamaeleon I in Figure 1.2.2.Data ReductionInitial processing of the IRAC images was performed with the Spitzer Science Center (SSC)S14.0.0pipeline.The resulting Basic Calibrated Data (BCD)images were automatically treated for bright source artifacts (jailbar,pulldown,muxbleed,and banding)with customized ver-sions of IDL routines developed by the IRAC instru-ment team (Hora et al.2004;Pipher et al.2004).Mo-saicking of the treated BCDs was performed using R.Gutermuth’s WCSmosaic IDL package,which includes the following features:a redundancy-based cosmic ray detection and rejection algorithm;frame-by-frame dis-tortion correction,derotation,and subpixel offsetting in a single transformation (to minimize data smoothing);and on-the-fly background matching.WCSmosaic was built with heavy dependence on the FITS and WCS ac-cess and manipulation procedures provided by the IDL Astronomy Users Library (Landsman et al.1993).We selected a plate scale of 0.86′′pixel −1for the reduced IRAC mosaics,which is the native scale divided by√Disk Population of Chamaeleon I3in the4.5µm image for areas that were imaged by both channels.Similarly,we rejected STARFIND detections at4.5µm that did not have a corresponding detection at 3.6µm.For the data at5.8and8.0µm,we retained only the sources that were detected in the3.6and4.5µm im-ages,respectively.We marked the sources produced by these criteria on the images and removed remaining spu-rious detections through visual inspection.We measured aperture photometry for the IRAC and MIPS sources using the IRAF task PHOT.We adopted zero point magnitudes(ZP)of19.670,18.921,16.855, 17.394,and15.119in the3.6,4.5,5.8,8.0,and24µm bands,where M=−2.5log(DN/sec)+ZP(Reach et al. 2005;Engelbracht et al.2007).For IRAC,we used an aperture radius of4pixels and inner and outer radii of4and5pixels,respectively,for the sky annu-lus.For MIPS,we adopted radii of3,3,and4pix-els for the aperture and the inner and outer bound-aries of the sky annulus,ing bright,iso-lated stars in the IRAC and MIPS images,we mea-sured aperture corrections between our adopted aper-tures and the larger ones employed by Reach et al.(2005) and Engelbracht et al.(2007).For the MIPS data,we combined our aperture correction with the one estimated by Engelbracht et al.(2007)between their aperture and an infinite one.The total aperture corrections applied to our measurements are0.18,0.17,0.23,0.48,and 0.8mag for3.6,4.5,5.8,8.0,and24µm,respectively. Smaller apertures(and the appropriate aperture correc-tions)were used for sources that were near other stars, including the known members Hn21W and E,the new member2MASS J11062942−7724586and its candidate companion Cha J11062788−7724543,and the new mem-ber2MASS J11084296−7743500,which is close to the protostar IRN.Our quoted photometric errors include the Poisson errors in the source and background emis-sion and the2%and4%uncertainties in the calibra-tions of IRAC and MIPS,respectively(Reach et al.2005; Engelbracht et al.2007).The errors do not include an additional error of±0.05mag due to location-dependent variations in the IRAC calibration.To illustrate the detection and completeness limits of the IRAC data,we consider the two shallow maps (AOR=3960320,3651328)and two of the three deep maps(AOR=3955968,12620032)that are centered on the northern and southern subclusters.The total expo-sure times at a given position in these maps are20.8and 968s,respectively.For each exposure time andfilter,we estimate the completeness limit by measuring the magni-tude at which the logarithm of the number of sources as a function of magnitude departs from a linear slope and begins to turn over.Based on the distributions of IRAC magnitudes,which are shown in Figure2,we arrive at completeness limits of16.25,16.25,14.25,and13.5for the short exposures and17.0,16.75,16.0,and15.25for the long exposures at3.6,4.5,5.8,and8.0µm,respec-tively.The estimates for the short exposures are con-firmed by the comparisons of the histograms for the short and long exposures in Figure2.The improvement in the completeness limits from the short exposures to the long ones is smaller at3.6and4.5µm than at5.8and8.0µm because the short exposures at3.6and4.5µm are already near the depth at which source confusion begins to reduce completeness(Fazio et al.2004b).Thus,the complete-ness limits of the longer exposures at3.6and4.5µm do not scale with√4Luhman et al.2MASS J11081204−7622124,falls outside of the bound-aries of the color-color diagram in Figure3.Three of the nonmembers,2MASS J11085651−7645154,2MASS J11105185−7642259,and2MASS J11105353−7726389, were identified as candidates because they exhibited ex-cesses in preliminary photometric measurements that were used for selecting candidates for spectroscopy.How-ever,upon further data analysis,we found that those ap-parent excesses were caused by contamination from cos-mic rays,and that the sources do not exhibit excesses in ourfinal photometry.For this reason,these three objects are excluded from Figure3.3.2.Spectroscopy of Candidates3.2.1.ObservationsWe performed optical and near-IR spectroscopy on nine of the candidate members of Chamaeleon I that were selected in§3.1using the Low Dispersion Survey Spec-trograph(LDSS-3)on the Magellan II Telescope and the Gemini Near-Infrared Spectrograph(GNIRS)at Gem-ini South Observatory.The GNIRS observations were conducted through program GS-2005A-C-13.Table3 summarizes the observing runs and instrument config-urations for the spectra.In Table4,we indicate the night on which each new member was observed.We also observed known late-type members of Chamaeleon I for comparison to the candidates,obtaining LDSS-3spec-tra of OTS44and Cha J11091363−7734446and GNIRS spectra of T50,Hn12W,Cha Hα11,and CHSM17173. The procedures for the collection and reduction of the LDSS-3and GNIRS spectra were similar to those de-scribed by Luhman(2004c)and Luhman et al.(2004), respectively.3.2.2.NonmembersOur spectroscopic targets are fainter than most of the known members of Chamaeleon I in the IRAC bands,which indicates that they should be low-mass stars or brown dwarfs if they are members of the clus-ter.Among the17candidates observed spectroscopi-cally by Luhman(2007)and in this work,13sources do not exhibit the molecular absorption bands that char-acterize cool,low-mass objects.They also lack the hy-drogen emission lines that are often seen in young stars with disks.Therefore,we classify these candidates as nonmembers.The spectral classifications of eight of these nonmembers were presented by Luhman(2004a). The remainingfive sources(Cha J11081724−7631107, Cha J11083029−7733067,Cha J11084006−7627085,Cha J11090876−7626234,Cha J11120546−7631376)are clas-sified as<M0based on the absence of molecular absorp-tion bands.3.2.3.New Member in Optical SampleThe remaining four candidates do show late-type spectral features and evidence of membership in Chamaeleon I.One of these candidates is in the LDSS-3sample and the other three objects are in the GNIRS sample.Wefirst discuss the source observed by LDSS-3,Cha J11070768−7626326(hereafter Cha1107−7626). The optical spectrum of this candidate is shown in Fig-ure4.The most obvious feature of this spectrum is the strong Hαemission line.The equivalent width of the line is uncertain because the surrounding contin-uum is weak and poorly measured,but it appears to have a value of several hundred angstroms.The line is clearly stronger than the emission observed in active late-typefield dwarfs(Gizis et al.2002)and indicates the presence of accretion.The Hαemission and the mid-IR excess emission together demonstrate the youth of Cha1107−7626,and thus we conclude that it is a mem-ber of Chamaeleon I.To measure its spectral type,we have compared Cha1107−7626to optically-classified late-type mem-bers of Chamaeleon I and other star-forming regions (Luhman2004a,2007)as well as standardfield dwarfs (Kirkpatrick et al.1999).The results of our classifi-cation are illustrated in Figure4,where we compare Cha1107−7626to the young late-type objects KPNO4, OTS44,and Cha J11091363−7734446and the L0field dwarf2MASS J03454316+2540233(Kirkpatrick et al. 1999).KPNO4and OTS44have optical spectral types of M9.5(Brice˜n o et al.2002;Luhman2007)and Cha J11091363−7734446was classified as≥M9with IR spectra(Luhman2007).We now classify the lat-ter as M9.5±0.5based on the similarity to KPNO4 and OTS44in the optical data in pared to the three young M9.5objects,Cha1107−7626ex-hibits weaker TiO and VO absorption,which suggests a later spectral type.Indeed,its spectrum agrees bet-ter with the L0field dwarf,as shown in Figure4.Be-cause the transition from M to L types is defined by the disappearance of TiO absorption at7000-7200˚A (Kirkpatrick et al.1999),we need a spectrum with a higher signal-to-noise ratio at those wavelengths to definitively classify Cha1107−7626as L-type.However, given that its spectrum agrees significantly better with L0than M9.5,we tentatively classify it as L0.The comparison of Cha1107−7626to thefield dwarf in Figure4indicates that it has negligible extinction (A J 0.3).By combining its J-band magnitude with a bolometric correction for L0(Dahn et al.2002)and a distance modulus of6.05(Luhman2008),we estimate a bolometric luminosity of3.3×10−4L⊙.At this luminos-ity,Cha1107−7626is tied with Cha J11083040−7731387 (Luhman2007)as the least luminous known member of Chamaeleon I.To estimate the mass of Cha1107−7626,we begin by examining its position on the Hertzsprung-Russell(H-R)diagram.To do this,we must convert the spectral type of Cha1107−7626to an effective temperature.In our previous studies of young late-type objects,we have performed conversions of this kind with the temperature scales from Luhman(1999)and Luhman et al.(2003), which spanned M1to M9.The former scale was designed to produce coevality for the components of the young quadruple system GG Tau(K7-M7.5)on the model isochrones from Baraffe et al.(1998).Luhman et al. (2003)adjusted that scale at M8and M9to improve the coevality between the coolest members of Taurus and IC348and the members at earlier types.The resulting scale was then extrapolated to M9.25and M9.5as cooler objects were discovered in Taurus and Chamaeleon I (Brice˜n o et al.2002;Luhman et al.2004;Luhman2007). For the purposes of this study,we continue this extrap-olation to L0for Cha1107−7626,arriving at a value ing this temperature and our luminosityDisk Population of Chamaeleon I5estimate,we have placed Cha1107−7626on the H-R di-agram in Figure5.We have included all other known low-mass members of Chamaeleon I(Luhman2007)as well as the three new members that we have found with GNIRS(§3.2.4).Four of the previously known mem-bers have formal spectral types of≥M9because they were classified through H2O absorption bands,and the variation of these bands with optical spectral type is un-known for young objects later than M9.5.However,the strengths of the H2O bands in these objects do agree with those of OTS44and KPNO4,which have optical types of M9.5.Thus,it is likely that they have spectral types near M9.5.The cluster sequence for Chamaeleon I in Figure5 is parallel to the model isochrones for members earlier than M8,which is expected since the adopted temper-ature scale was designed to produce coevality for the GG Tau system.However,the sequence does not remain parallel to the isochrones at later types.Most mem-bers earlier than M8appear between the isochrones for 1and10Myr,while the coolest brown dwarfs,includ-ing Cha1107−7626,are bracketed by10and100Myr. It is unlikely that these old ages are valid.For in-stance,the lifetimes of molecular clouds are too short (τ<10Myr,Hartmann,Ballesteros-Paredes,&Bergin 2001)for the Chamaeleon I clouds to have undergone star formation across such an extended period of time. In addition,objects with ages of10-100Myr would have dispersed from the cloud long ago.Instead,the old isochronal ages are probably a reflection of errors in the adopted temperature scale and/or the evolution-ary models.If the models are valid,then the temper-ature scale for young objects at M9-L0must be much cooler than the adopted one,which is already cooler than the scale measured forfield dwarfs(Kirkpatrick 2005).Significant errors are probably present in both the temperature scale,which is unconstrained at the latest types,and the predicted effective temperatures,which are sensitive to various details of the models,such as the treatment of convection(Baraffe et al.2002).Com-pared to effective temperature,bolometric luminosity appears to be less sensitive to model uncertainties,at least for ages ofτ 1Myr(Baraffe et al.2002),and is easier to measure.Therefore,we have chosen to esti-mate the mass of Cha1107−7626from its luminosity. If we assume that it has an age in the range of val-ues exhibited by the stellar members of Chamaeleon I (τ=1-6Myr,Luhman2007),then we arrive at a mass of0.004-0.01M⊙for Cha1107−7626based on the luminosities predicted by Burrows et al.(1997)and Chabrier et al.(2000).Zapatero Osorio et al.(2007) and Scholz&Jayawardhana(2007)have reported detec-tions of disks for brown dwarfs at comparable masses in theσOri cluster using IRAC data.However,because of the very large uncertainties in the5.8and8.0µm photometry in those studies(0.3-0.5mag),their detec-tions of excess emission have low significance.Thus, Cha1107−7626is the least massive brown dwarf that has definitive evidence for a circumstellar disk.3.2.4.New Members in Infrared SampleIn the GNIRS sample,the three candidates that show evidence of membership in Chamaeleon I are2MASS J11084296−7743500,2MASS J11062942−7724586,and 2MASS J11070369−7724307(hereafter2M1108−7743, 2M1106−7724,2M1107−7724).The near-IR spectra of these objects exhibit strong H2O absorption bands, which indicates that they are low-mass stars or brown dwarfs rather than galaxies.High levels of reddening in their spectra demonstrate that they are notfield stars in the foreground of the cluster and they are too bright to be backgroundfield dwarfs.We also detect emission in H21-0S(1)at2.12µm in2M1108−7743,which is a signature of very young stars.Finally,the spectral features that are sensitive to surface gravity in our data,such as the shape of the H-and K-band continua(Lucas et al.2001; Luhman et al.2004;Kirkpatrick et al.2006),are incon-sistent withfield dwarfs and giants.Instead,the spectra of2M1108−7743,2M1106−7724,and2M1107−7724 agree well with known cluster members observed with GNIRS in terms of the gravity-sensitive features.Based on these properties and the presence of mid-IR ex-cess emission,we classify these sources as members of Chamaeleon I.To measure the spectral types of2M1108−7743, 2M1106−7724,and2M1107−7724,we have compared their H2O and atomic absorption features to those of the optically-classified members of Chamaeleon I that we observed with GNIRS.To facilitate this comparison, we dereddened the spectra of the new members to give them the same slopes as the known members.We also smoothed the spectra to a low resolution when compar-ing the broad H2O absorption bands.The dereddened, smoothed versions of the spectra are shown in Figure6. Each object is compared to the young standards that pro-vide the closest match to the strength of the H2O absorp-tion.Through this comparison and a similar analysis of the atomic absorption lines,we classify2M1108−7743, 2M1106−7724,and2M1107−7724as M4±1,M6±1, and M7.5±1,respectively.These spectral types corre-spond to masses of∼0.3,0.1,and0.04M⊙,respec-tively,according to the theoretical evolution models of Baraffe et al.(1998)and Chabrier et al.(2000)and the temperature scale of Luhman et al.(2003)for ages of a few Myr.The process of dereddening the near-IR spectra of 2M1108−7743,2M1106−7724,and2M1107−7724to match the young standards,which have little if any ex-tinction(Luhman2007),produces extinction estimates of A J=5.6,5.6,and4.7,respectively.It is not surpris-ing that these objects are highly obscured given their locations.2M1108−7743is only14′′from the protostar IRN while the other two sources are within the group of embedded stars near Cederblad110.Spitzer and2MASS images of2M1106−7724,2M1107−7724,and the proto-stars in Cederblad110are shown in Figure7.Based on their high levels of extinction and their close proximity to known protostars,2M1108−7743,2M1106−7724,and 2M1107−7724may be the youngest known low-mass members of the cluster.By combining our extinction estimates for these sources with their H and K s mag-nitudes,the appropriate bolometric corrections,and the distance of Chamaeleon I,we arrive at luminosities of 0.053,0.035,and0.020L⊙,respectively.Because the H-and K-band spectra for these sources do not show any evidence of continuum veiling,these luminosity estimates should be uncontaminated by disk emission.The spectral types,extinctions,luminosities,member-6Luhman et al.ship evidence,and near-IR photometry for the four new members of Chamaeleon I are provided in Table4.The IRAC and MIPS photometry for these sources are pre-sented in the tabulation of Spitzer data for all known members of the cluster in§4.1.The IRAC and MIPS measurements for the13nonmembers are listed in Ta-ble5.3.3.Remaining CandidatesIn the previous section,we obtained spectra for a small sample of the candidate disk-bearing members of Chamaeleon I that were identified in§3.1with Figure3. To investigate the nature of the remaining candidates,we compare them to the known cluster members in Spitzer color-magnitude and color-color diagrams in Figure8. Many of the candidates are as red as the reddest known members,indicating that they are protostellar if they are members.In addition,bonafide members are likely to be brown dwarfs given that nearly all of the candidates are fainter than the stellar members of the cluster,although stars with edge-on disks can also appear very faint.For instance,Cha J11081938−7731522has a stellar mass ac-cording to its spectral type,but it is the faintest and reddest known member in[3.6]and[3.6]−[24],respec-tively,which is explained by the presence of an edge-on disk(Luhman2007).However,rather than brown dwarfs or stars with edge-on disks,the vast majority of the can-didates are probably galaxies.We can refine our sample of candidate members and remove some of the galaxy contaminants by apply-ing additional criteria.The initial sample of candi-dates was defined by colors of[3.6]−[4.5]>0.15 and[5.8]−[8.0]>0.3.However,the sources with [3.6]−[4.5] 0.7and[5.8]−[8.0] 1.2within that sample have colors that differ significantly from those of all known members of Chamaeleon I,as shown in Fig-ure3.These objects can be rejected as likely galax-ies.Because galaxy contamination increases with fainter magnitudes,brighter candidates are less likely to be galaxies.The probability of membership is also higher for candidates that are close to known members of Chamaeleon I.By applying these criteria,we have iden-tified the most promising candidate disk-bearing mem-bers,which are listed in Table6.The brightest candi-date,2MASS J11085367−7521359,is probably a solar-mass star if it is associated with Chamaeleon I.The magnitudes of the remaining candidates are indicative of brown dwarfs.As noted in Table6,some of the candi-dates may be class I sources or companions to known members.The new member2M1106−7724and the candidate Cha J11062788−7724543could comprise the youngest low-mass binary system discovered to date.In addition to revealing new candidate members of Chamaeleon I,our mid-IR measurements provide con-straints on the membership of sources that have been previously cited as possible members.In a census of Chamaeleon I,Luhman(2004a)assigned membership to a few objects that lacked spectroscopic classifica-tion but that exhibited mid-IR excess emission.One of these objects is ISO13(Nordh et al.1996;Persi et al. 2000).The near-IR counterpart for ISO13was not pos-itively identified in previous studies because of uncer-tainties in the coordinates measured with ISO.Based on a comparison of the photometry from ISO to mea-surements from IRAC for sources in the vicinity of the ISO coordinates,we conclude that ISO13corresponds to 2MASS J11025579−7724304.For this source,we mea-sure magnitudes of13.87,13.68,12.68,9.87,and6.54at 3.6,4.5,5.8,8.0,and24µm,respectively.When we com-bine these data with photometry from the Two-Micron All-Sky Survey(2MASS,Skrutskie et al.2006),wefind that the colors of ISO13are relatively blue at1-5µm but become very red at8and24µm.These colors are incon-sistent with those of known members of Chamaeleon I,as illustrated by the position of ISO13in the IRAC color-color diagram in Figure3.Therefore,we remove ISO13 from our list of members of Chamaeleon I because it is probably a galaxy.Luhman(2004a)included ISO206in a list of candidate members based on an apparent excess at6.7µm in photometry from ISO.However,mid-IR ex-cess emission is not present in the IRAC data for this source.As a result,there is no longer any reason to con-sider ISO206as a possible member.Finally,Persi et al. (2001)identified three candidate class I brown dwarfs in the vicinity of Cederblad110through the presence of near-IR excess emission.In our IRAC data,wefind that one of these candidates,NIR72,is a patch of nebulosity rather than a stellar source while the other two objects, NIR84and NIR89,do not exhibit excess emission,and thus are not class I sources.pleteness for Members with DisksWe now use our mid-IR data to examine the com-pleteness of the current census of disk-bearing members of Chamaeleon I.We consider only the areas that have been imaged in all four bands of IRAC,which encompass 170of the229known members of the cluster.Within these areas,156members have photometric errors less than0.1mag in all IRAC bands,while the remaining14 known members lack accurate photometry in at least one band because they are saturated,extended,too close to a brighter star,or below the detection limit of all four bands(Cha-MMS1).Thus,the photometric criteria that we used for selecting candidate members with disks in §3.1recover all known members with disks in the areas with4-band coverage with the exception of the brightest stars,faint companions,and the youngest protostars.As a result,our sample of candidates should be complete for disk-bearing members in the same range of magnitudes and extinctions exhibited by the known stellar popula-tion.To quantify the completeness limits of this candi-date sample,we have plotted the photometric complete-ness limits at8µm for the shortest and longest expo-sures in the color-magnitude diagram in Figure8(§2.2). Meanwhile,to evaluate the completeness of the current census of confirmed members with disks,we consider the remaining candidates that lack spectroscopy.As shown in Figure8,only one candidate is present in the magni-tude range of young stars in Chamaeleon I([3.6] 12), which is in Table6.Thus,the current census is nearly complete for stars with disks in thefields imaged by all four bands of IRAC,which encompass most of the Chamaeleon I cloud(Figure1).Our survey is not com-plete for brown dwarfs with disks,as indicated by the large number of candidates lacking spectroscopy in Fig-ure8.However,based on optical and near-IR surveys, the census of substellar cluster members(both with and without disks)is complete for specificfields and ranges。

外刊精读让马拉松变得更环保导读：似乎在世界各地，每个主要的大城小镇都会举办年度马拉松比赛。

成千上万的参赛运动员要经受艰难的体能考验，跑完42.1 公里的赛程。

和其它大型比赛一样，马拉松比赛也会产生大量的碳足迹。

数千人乘坐飞机前来参赛或观赛，观众和运动员留在赛道的食物垃圾、包装袋、礼品袋等等。

本期《外刊精读》讨论相关部门针对马拉松比赛所采取的各项环保措施。

一、语篇泛读Even if you’re a couch potato like me, you’ll know the benefits of running - pounding the pavements, working up a sweat, burning off some calories and generally keeping fit. But if you’re a real fitness junkie, the ultimate running challenge is to take part in a marathon.It seems every major city and town aro und the world hosts an annual marathon, with thousands of athletes running a gruelling 42.1 kilometers. Whilst many runners’ motivation is to beat their personal best and cross the finishing line without collapsing, they’re also doing it for a good cause– to generate funds for charity. But like other major events, the marathon also generates a massive carbon footprint. Thousands travel - some by plane - to the location, and waste from food packaging and goody bags gets left behind by spectators and runners. For example, during the London Marathon in 2018, 47,000plastic bottles were collected, although some were recycled.This is becoming a big issue for cities –how to host a worthwhile event, encouraging people to exercise and help charities, whilst protecting the environment? Several cities have developed formal plans to reduce their environmental impact and promote sustainable ideas. One event in Wales, for example, introduced recycling for old running kit and ethically sourced the race t-shirts.It’s something that this year’s London Marathon tried to tackle by reducing the number of drink stations on the running route, giving out water in paper cups and offering some drinks in edible seaweed capsules. They also trialed new bottle belts made from recycled plastic so 700 runners could carry water bottles with them during their run. London Marathon event director Hugh Brasner told the三、测试与练习阅读课文并回答问题。

Predicting paleoelevation of Tibet and the Himalaya from N18O vs.altitude gradients in meteoric water across theNepal HimalayaCarmala N.Garzione a Y*,Jay Quade b,Peter G.DeCelles b,Nathan B.English ba Department of Earth and Environmental Sciences,University of Rochester,Rochester,NY14627,USAb Department of Geosciences,University of Arizona,Tucson,AZ85721,USAReceived26May2000;received in revised form3August2000;accepted8September2000AbstractThe N18O value of meteoric water varies with elevation,providing a means to reconstruct paleoelevation if the N18O values of paleowater are known.In this study,we determined the N18O values of water(N18O mw)from small tributaries along the Seti River and Kali Gandaki in the Nepal Himalaya.We found that N18O mw values decrease with increasing altitude for both transects.N18O mw vs.altitude along the Kali Gandaki in west-central Nepal fit a second order polynomial curve,consistent with increasing depletion of18O with increasing elevation,as predicted by a Rayleigh-type fractionation process.This modern N18O mw vs.altitude relationship can be used to constrain paleoelevation from the N18O values of Miocene^Pliocene carbonate(N18O c)deposited in the Thakkhola graben in the southern Tibetan Plateau. Paleoelevations of3800þ480m to5900þ350are predicted for the older Tetang Formation and4500þ430m to 6300þ330m for the younger Thakkhola Formation.These paleoelevation estimates suggest that by V11Ma the southern Tibetan Plateau was at a similar elevation to modern.ß2000Elsevier Science B.V.All rights reserved.Keywords:O-18/O-16;altitude;streams;surface water;Nepal;Himalayas1.IntroductionAltitude across the topographic front of the Himalaya increases from approximately200m in the Gangetic foreland basin to8000+m at the tallest peaks.North of the high Himalaya, the Tibetan Plateau has an average elevation s5000m[1].Understanding when and how the Himalaya and Tibet attained their current eleva-tions is important for evaluating the e¡ects of high topography on south Asian ecology,regional and global climate,and ocean chemistry[2^8]. Previous work has demonstrated that oxygen isotopes of lacustrine and paleosol carbonate can be used as a gauge of paleoelevation(e.g., [9^11])because they are partially determined by the N18O value of meteoric water(N18O mw),which is largely dependent on elevation.As a vapor mass rises in elevation,it expands and cools,caus-0012-821X/00/$^see front matterß2000Elsevier Science B.V.All rights reserved. PII:S0012-821X(00)00252-1ing rainout,and producing lower N18O mw values at progressively higher elevation.Modern world-wide gradients of N18O mw(Vienna Standard Mean Ocean Water(VSMOW))vs.altitude fall in a range from30.1x to31.1x/100m,with a global mean gradient of30.26x/100m[12]. Oxygen isotopic partitioning trends generally¢t Rayleigh-type fractionation models[13,14],com-plicated by processes such as evapotranspiration and vertical mixing in a cloud system(e.g., [15,16]).The N18O values of carbonate(N18O c)from Ti-bet and the Himalaya are potentially useful for understanding the development of high elevation on the plateau.Carbonate from the Thakkhola graben on the southern Tibetan Plateau yield N18O c(Vienna Peedee belemnite(VPDB))values between316x and323x,consistent with for-mation at very high elevation[11].However,pa-leoelevation reconstructions rely on knowledge of the N18O mw vs.altitude relationship,which is sparsely documented in the Himalaya.Two stud-ies of river waters in India report linear gradients of N18O mw vs.altitude of30.19x/100for the headwaters of the Ganges between300and 3000m[17]and30.14x/100m for surface waters in the Gaula river catchment in Kumaun, India between915and2150m[18].Another study of thermal waters determined a range of 0.2to0.3x/100[19].In this study,we measured N18O values of small streams along two transects across the Himalayan orogen in Nepal,from the foothills to the Tibetan Plateau(Fig.1).Our ob-jective is to determine an empirical relationship for the modern N18O mw vs.altitude gradient and to compare it to the paleocarbonate record from the Tibetan Plateau to understand the elevation history of the plateau.We chose these transects because they provide a N^S pro¢le across the Hi-malaya and southern Tibet,allowing sampling along elevation gradients across the approximate trajectory of rainfall as it moves over the Hima-layan range.Streams more closely represent mete-oric water compositions of average annual rainfall if sampled during the dry season when ground-water dominates the stream water budget,because groundwater contains a mixture of rainfall throughout the annual cycle[20,21].Although maintaining rain collection stations across the Hi-malayan fold-thrust belt would provide better es-timates of average meteoric water composition, sampling stream water is much more feasible.2.Geology2.1.Himalayan fold^thrust belt and southernTibetan PlateauThe Himalayan fold^thrust belt in Nepal con-sists of four regional lithotectonic packages sepa-rated by major fault zones.The northern bound-ary of the fold^thrust belt is the Indus suture zone (Fig.1A),which sutures the Eurasian and Indian plates[22,23].South of the suture zone lies the Tibetan Himalaya,which consists of Cambrian^ Eocene sedimentary rocks of the Tethyan Series that are incorporated into numerous south-verg-ing thrust sheets[23^25].The southern boundary of the Tibetan Himalaya is the South Tibetan detachment system,a system of north-dipping, normal-sense detachment faults that juxtapose the Tethyan Series against Greater Himalayan rocks[24,26].Greater Himalayan rocks consist of late Proterozoic to early Paleozoic[27,28]para-gneisses,orthogneisses,and schists that were metamorphosed to amphibolite grade during the Cenozoic orogenic event.These rocks have been thrust southward along the Main Central thrust system upon lower to upper greenschist grade metasedimentary rocks of the Lesser Himalayan zone[29^31].Lesser Himalayan rocks,which con-sist of early to middle Proterozoic passive margin sequences have been thrust southward along the Main Boundary thrust system.The frontal,Sub-himalayan zone of the fold^thrust belt comprises an imbricate thrust system in Neogene foreland basin deposits of the Siwalik Group.The kinematic history of the Himalayan fold^ thrust belt followed a generally southward pro-gression of emplacement of the major thrust sys-tems[31^33].Tibetan thrusts were active mainly during Eocene and Oligocene time[23,25],and produced regional Barrovian metamorphism of underlying Greater Himalayan rocks[34].Ther-mochronologic data from Greater HimalayanC.N.Garzione et al./Earth and Planetary Science Letters183(2000)215^229 216rocks suggest rapid cooling during late Oligocene^early Miocene time,presumably during emplace-ment of the Main Central thrust system (e.g.,[35,36]).At about the same time,the South Tibe-tan detachment system became active (e.g.,[36,37]).Since middle Miocene time the deforma-tion front has migrated southward into the Lesser Himalayan and Subhimalayan zones [38,39].Esti-mates of regional shortening rates in the Hima-layan fold^thrust belt in Nepal during the Neo-gene [39^41]and the Paleogene [33]are similar to modern rates of shortening determined by space geodetic measurements [42].Observations that (1)crustal thickening su¤cient to drive Barrovian metamorphism in Greater Himalayan rocks was underway during Eocene and Oligocene time and (2)the Himalayan foreland basin has been ¢lled above sea level since at least late OligocenetimeFig.1(continued).Fig.1.(A)General tectonic map of the southern Tibetan Plateau and Nepal Himalaya.Hachures are north-south striking normal faults.Lines with ball and stick ornaments are South Tibetan Detachment system (STDS).Barbed lines are Main Central thrust (MCT)and Main Boundary thrust (MBT).Thakkhola graben is shown.Boxes show locations of study areas detailed in 1B and 1C.(B)Map of the Seti River showing tributary sample localities.(C)Map of the Kali Gandaki showing tributary sample localities.Small sampled tributaries are shown as medium gray and large tributaries sampled in the Thakkhola graben are shown as light gray.C.N.Garzione et al./Earth and Planetary Science Letters 183(2000)215^229217Table 1Oxygen isotopic data and elevation information for sampled tributaries along the Seti River and Kali Gandaki Sample name Tributary/riverSampling elevation Tributary elevation range N 18O(VSMOW)N D (VSMOW)(m)(m)(x )(x )Seti River 42Gadpai Gad 23502740310.4310.533Ramus Khola 20403110310.530Panai Gad 177********.227Lisni Khola 1710140039.726Unnamed 159090039.124Talkoti Gad 1460150038.414Dungri Khola 131090039.712Dil Gad 1220130039.539.59Jidear Gad 1130205039.36Juili Gad91090038.849Nayagari Khola 820145037.754Dhung Gad 720155037.858Rori Gad 61090037.459Kali Gad 570100037.761Unai Gad 530100037.763Gandi Gad 490105037.766Bheri Khola 430105037.269Chairo Khola 370145036.8Kali Gandaki 99kg9Unnamed 39001850317.53128317.499kg8Unnamed 38001450318.399kg10Giling Khola 3750250317.499kg11Qumona Khola 37002200320.599kg12Unnamed l37001550319.3314399kg6Samar Khola 36701800317.6312899kg16Ghechang Khola 35502450319.899kg15Puyon Khola 35002000318.599kg1Ghidiya Khola 34501800317.7311399kg18Yak Khola 34102350318.8313999kg13Kali Gandaki 3300*319.599kg14Tsarang Khola 33002500321.299kg17Tange Khola 32802450319.199kg5Unnamed 32502000317.597kg1Kali Gandaki 3000*318.299kg3Kali Gandaki 3000*319.599kg2Narsing Khola 29602750318.899kg4Chele Khola 29602750317.599kg20Panda Khola 28002500316.599kg22Unnamed 27501700315.7311599kg21Unnamed 2700600313.799kg23Unnamed26001000311.237699kg24Yamkin Khola 25001400313.439299kg25Unnamed25001400312.899kg26Largung Khola 24401800312.238499kg27Unnamed 23001800313.099kg28Kaiku Khola 20002300311.938299kg29Ghasa Khola 185********.299kg30Unnamed18001600312.0384C.N.Garzione et al./Earth and Planetary Science Letters 183(2000)215^229218[43,33],suggest that the Himalayan fold^thrust belt attained high elevations by Oligocene time.2.2.Thakkhola grabenThakkhola graben is located in north-central Nepal,on the southern edge of the Tibetan Pla-teau,between the South Tibetan Detachment sys-tem and the Indus Suture zone(Fig.1A).The Kali Gandaki drains the southern Tibetan Plateau in this region,£owing southward along the axis of the graben and through the fold^thrust belt to the Himalayan foreland basin.The Thakkhola graben is bound by faults to the east and west,with Tethyan Series rocks in its footwalls[44].Basin-¢ll deposits are exposed between3000and4200m in the basin.Two depositional sequences,sepa-rated by an angular unconformity,make up the basin¢ll[45,46].The older Tetang Formation(up to230m thick)crops out in the southeastern part of the basin and consists of£uvial deposits that grade into lacustrine deposits toward the top of the section.Magnetostratigraphic data suggest an age of V11to10.5Ma for the onset of deposi-tion of the Tetang Formation[11].The overlying Thakkhola Formation(up to1000m thick)is exposed throughout the basin and consists of al-luvial fan deposits along the western basin-bound-ing fault,and£uvial and lacustrine deposits in the central and eastern parts of the basin.The pres-ence of C4vegetation reconstructed from the soil carbonate record of the Thakkhola Formation constrains its age to67Ma[11].Paleocurrent indicators suggest southward axial drainage since the beginning of Thakkhola Formation deposi-tion[46].More recently,the Kali Gandaki has incised through at least1000m of basin¢ll,into Cretaceous Tethyan Series rocks.Several cycles of Pleistocene deposition within the incised valley indicate that the basin has experienced multiple phases of Pleistocene damming and incision [45,47,48]3.Hydrology and meteorology of the Himalaya and southern TibetMost rainfall in the Himalaya and southernTable1(continued)Sample name Tributary/river Sampling elevation Tributary elevation range N18O(VSMOW)N D(VSMOW)(m)(m)(x)(x)99kg31Rupse Khola17002300311.499kg32Dana Khola14001550310.036899kg33Bhalu Khola135********.6310.799kg34Unnamed1240106039.636799kg35Thado Khola11401540310.799kg36Beg Khola1040184039.836899kg37Unnamed87021039.599kg48Hulandi Khola85550039.099kg49Unnamed82033039.236799kg40Dundure Khola80032039.636899kg42Buchchha Khola790121039.436799kg38Damuwa Khola760114039.637099kg41Luha Khola72078039.899kg43Phoksin Khola720128039.799kg45Unnamed72018038.799kg39Malyandi Khola68092039.399kg50Unnamed66016038.799kg44Unnamed62016038.299kg47Unnamed62066038.836299kg51Unnamed48022038.1360Data for each location appear in order from highest to lowest sampling elevation.Tributary elevation range(m)is the number of meters of elevation above the sampling elevation over which the tributary£ows.Seti River tributary data also appear in[52].C.N.Garzione et al./Earth and Planetary Science Letters183(2000)215^229219Tibet occurs during the summer monsoon.Rain stations at New Delhi,Kathmandu,and Lhasa record more than 85%of annual precipitation from May to September,during the summer mon-soon [49].The monthly average discharge of ma-jor rivers that £ow southward out of the fold^thrust belt increases by an order of magnitude during the summer monsoon [50].Precipitation varies greatly between the Himalaya and Tibet as a result of the high Himalayan rainshadow (Fig.2B).South of the high Himalaya,across the central Nepal fold^thrust belt,the mean an-nual rainfall is between V 100and 500cm/yr,whereas north of the high Himalaya,in the Thak-khola graben,rainfall is 640cm/yr [50].The Kali Gandaki and Seti River £ow south-ward through the Himalayan fold^thrust belt,joining the Ganges River system in the foreland.These rivers drain the southern edge of the Tibe-tan Plateau,north of the South Tibetan Detach-ment system and south of the Indus Suture zone.A drainage pro¢le along the Kali Gandaki [51]has a large nick point associated with the Main Central thrust and high Himalaya (Fig.2A).To a large extent,this steep stream gradient is a result of the more resistant rock types in the Greater Himalaya.4.Sampling and analytical methodsEighteen tributaries to the Seti River (Fig.1B)and 46tributaries to the Kali Gandaki (Fig.1C)were sampled during foot traverses in March^April 1998and late September^October 1999,re-spectively.We collected during the dry season in order to sample base-level £ows,which give a closer approximation of mean annual preci-pitation [20,21].Generally,we sampled tribut-aries that £ow perennially over an elevation range of 62000m (henceforth termed `small tributa-ries')for the N 18O mw vs.altitude transect.Tribu-taries with perennial £ow over an elevation range s 2000m we term `large tributaries.'We sampled both large and small tributaries north of Jomsom along the Kali Gandaki traverse,in order to char-acterize the complete range of modern N 18O mw values in the Thakkhola graben.In the ¢eld,water samples were sealed in 15ml polyethylene bottles.Samples were transported and stored in darkness and refrigerated during storage prior to analysis.Elevations were deter-mined with a Garmin Model 45GPS unit and cross-checked with 1:25,000to 1:125,000topo-graphic maps for accuracy along the Kali Ganda-ki.Elevations were determined from 1:63360scale maps along the Seti River.For oxygen isotope analysis,5ml of water was equilibrated with CO 2at 16³C for 8h.Gasses were analyzed on a Finnegan MAT Delta gas-ra-tio mass spectrometer.Precision was þ0.07x for N 18O of ¢ve replicate pairs of water.Twenty-seven internal standards run during the time of analysis yielded standard deviations þ0.05.On the basis of these data,the overall external preci-sion was 6þ0.1x (1c ).All water results are presented inVSMOW.Fig.2.Elevation pro¢les,tributary N 18O values,and rainfall pro¢le across the Kali Gandaki drainage plotted against dis-tance from source of the Kali Gandaki.(A)Elevation pro¢le of the Kali Gandaki is shown as shaded region and average crest elevation is shown as black line (from [51].Tributary N 18O values are plotted at location of sampling along the Kali Gandaki.Principle bedrock provinces:Tethyan Series (TS),Greater Himalaya (GH),Lesser Himalaya (LH),and fault systems:South Tibetan Detachment System (STDS),Main Central Thrust (MCT).(B)Average annual precipita-tion across the Kali Gandaki drainage pro¢le (from [51]).C.N.Garzione et al./Earth and Planetary Science Letters 183(2000)215^2292205.Results 5.1.Seti transectTributaries to the Seti River were sampled be-tween 365and 2350m (Table 1and Fig.3).N 18O mw plotted against altitude yields a best-¢t line with a slope of 30.18x /100m,with a re-gression coe¤cient (R 2)of 0.85(n =18).We sampled from Jiuli Gad (6)north to Gadpai Gad (42),and then from Nayagari Khola (49)south to Chairo Khola (69^just o¡of map)(Fig.1B).The ¢rst samples (6,9,12,and 14)were collected prior to several large rainfall events.The ¢rst rainfall event lasted V 12h and raised the water level in the Seti River substan-tially.After rainfall 1,the ¢rst tributary sampled upstream (24)had a N 18O value 1.3x higher than the last downstream tributary (14),sampled just before the storm (Fig.3).This suggests that rain-fall run-o¡had higher N 18O values than base-level £ow,and is consistent with measurements of high-er N 18O values for winter/spring rainfall compared to summer monsoon rainfall in the Himalaya [53].Over several days of water sampling subsequent to rainfall 1,N 18O mw values declined as run-o¡decreased.Rainfall 2,which lasted V 8h,alsocaused an increase in tributary N 18O values (Fig.3).During collection of the ¢nal set of samples below Jiuli Gad (49^69),no rainfall events oc-curred.The addition of rainfall with high N 18O values to upstream tributaries (24^42)decreases the gradient of N 18O vs.altitude estimated for far-western Nepal.Excluding these data,a linear regression through tributaries from 365to 1310m yields a best-¢t line with a slope of 30.29x /100m and R 2=0.92(n =12)(Fig.3).At the 95%con-¢dence limit,the slope varies between 30.23x /100m and 30.35x /100m and the y -intercept between 35.4x and 36.4x .5.2.Kali Gandaki transectTributaries to the Kali Gandaki and Tinau Khola (just south of the eastward bend in the Kali Gandaki)were sampled between elevations of 480and 3900m.(Fig.1C).We sampled both large and small tributaries north of Kagbeni,in the Thakkhola graben,to characterize the full range of N 18O values of river water.Tributaries of the Thakkhola graben,sampled between 2960and 3900m,yield N 18O values ranging from 315.7x to 321.2x (Table 1and Fig.1C).Small tributaries have higher N 18O values (315.7x to 319.3x )than large tributaries sampled at the same elevations (316.5x and 321.2x ),because the larger tributaries have catchment areas that reach higher elevations and therefore carry a greater proportion of high ele-vation precipitation (Fig.4).Large tributaries in-crease the scatter in the data,producing a spuri-ous N 18O mw vs.altitude gradient and are therefore excluded from the N 18O mw vs.altitude regression.We determined N D values from 20water sam-ples,representing the full range of elevations,so that we could evaluate the possibility of kinetic evaporation e¡ects as moisture moves northward beyond the high Himalaya onto the Tibetan Pla-teau.A linear regression through the data produ-ces a local meteoric water line of:N D 7X 59Æ0X 14 N 18O 5X 67Æ1X 91yielding an R 2=0.99.The excellent line-¢t to a slope of V 8indicates that there are nosigni¢cantFig.3.N 18O vs.altitude for tributaries sampled along the Seti River in far-western Nepal during March/April 1998.Rainfalls 1and 2show the ¢rst samples collected after rain-fall events.The positive shift in tributary N 18O values subse-quent to rainfall events indicates that spring rainfall is rela-tively more positive than base-level £ow.See text for discussion of regression lines.C.N.Garzione et al./Earth and Planetary Science Letters 183(2000)215^229221kinetic evaporation e¡ects during rainfall in the arid region north of the high Himalaya.Tributary N 18O values plotted next to the Kali Gandaki stream pro¢le indicate there is a strong correlation between oxygen isotopic fractionation and local sampling elevation (Fig.2A).Where the Kali Gandaki stream gradient is steeper,N 18O mw values decrease more rapidly.The correlation be-tween the Kali Gandaki gradient and tributary N 18O values suggests that elevation changes are the dominant cause of rainout and that the N 18O value of small tributaries represents rainfall at lo-cal elevations,rather than at high elevations on the surrounding peaks (black line,Fig.2A).Even in the arid region north of the high peaks,the decrease in tributary N 18O values re£ects the Kali Gandaki stream gradient,which suggests that the e¡ects of evaporation are negligible.A plot of N 18O values of tributaries vs.altitude yields a best-¢t line with a slope of 30.29x /100m and R 2=0.93(n =38)(Fig.5).One data point (99kg23)falls signi¢cantly above the line.This data point ¢ts the local meteoric water line,which indicates that disequilibrium evaporation process-es are not responsible for the high value.Possible causes of the higher N 18O value are that the stream water has undergone equilibrium evapora-tion or the stream carries a greater proportion of winter rainfall than other sampled tributaries.A second order polynomial provides a better ¢t to the data (R 2=0.96)(Fig.5),yielding the following relationship:N 18O 34X 02U 1037Æ1X 26U 1037 h 2 3 0X 0012Æ0X 0005 h 3 8X 02Æ0X 462Sample 99kg23has been omitted from the regres-sion because it is clearly anomalous,and it signi¢-cantly modi¢es the best-¢t curve.We choose a second order polynomial ¢t because it allows for variation from pure Rayleigh fractionation,present in the data,that can result from processes such as evapotranspiration and mixing of vapor masses.Two minor rainfall events occurred in the late afternoon between Larjung and Beni (Fig.5).On both afternoons,drizzle fell over a 2^3h period and stream discharge increased.Little scatter in the data between Larjung and Beni indicates that these events did not signi¢cantly modify trib-utary N 18O values.This suggests that tributary discharge during the months after the monsoon season is dominated by groundwater discharge of monsoonrainfall.Fig.5.N 18O vs.altitude for tributaries sampled along the Kali Gandaki and Tinau Khola in west-central Nepal during September/October 1999.Only those tributaries with perenni-al £ow over an elevation range of 62000m are plotted in the arid region north of the high Himalaya.Line ¢t is shown in gray,and second order polynomial ¢t inblack.Fig.4.N 18O vs.altitude for all tributaries sampled along the Kali Gandaki and Tinau Khola in west-central Nepal during September/October rge tributaries (s 2000m eleva-tion range)north of Jomsom are shown as open squares and all other tributaries are shown as ¢lled bels for tributaries north of Jomsom indicate the tributary elevation range.More negative N 18O values of large tributaries indicate they carry a greater proportion of high-elevation precipita-tion.C.N.Garzione et al./Earth and Planetary Science Letters 183(2000)215^2292226.Discussion6.1.Mean rainfall elevation in tributary drainagebasins Tributaries carry meteoric water that fell over a range of elevations in the drainage basin.The elevation of sampling is lower than the average elevation of the drainage basin and N 18O values therefore re£ect higher elevation rainfall than the rainfall at the elevation of sampling.For this rea-son,the y -intercept of the Kali Gandaki regres-sion (38x )is more negative than the N 18O value of mean annual precipitation in the modern Hi-malayan foreland (Fig.5).We assume that the N 18O value at New Delhi (elevation =212m,N 18O =35.81,weighted mean [53])is a represen-tative value of precipitation in the foreland source region.We can estimate and correct for the di¡er-ence between sampling elevation and the average elevation of the drainage basin by determining the di¡erence in elevation that yields a curve that ¢ts both New Delhi rainfall and N 18O values of Kali Gandaki tributaries (Fig.6).At an elevation dif-ference of 1000m,the best-¢t polynomial has ay -intercept of 36.0x ,approaching the value for New Delhi rainfall.Above 1000m there is no signi¢cant change in the y -intercept of the best-¢t second order polynomial.An elevation di¡er-ence of 1000m between sampling elevation and average elevation of the drainage basin seems rea-sonable given that the streams we sampled source water over a range of elevations from 160to 2300m above the sampling elevation (Table 1).The second order polynomial that ¢ts New Delhi pre-cipitation and de¢nes a 1000m elevation di¡er-ence above the sampling elevations is de¢ned by:N 18O 32X 61U 1037Æ0X 84U 1037 h 2 30X 0013Æ0X 0005 h 3 6X 00Æ0X 693(termed `Kali Gandaki relationship').Tributaries of the Seti River fall within the range of scatter of the Kali Gandaki data,assuming an average ele-vation of rainfall 600m above the sampling ele-vation (Fig.7).The di¡erence in the apparent average elevation of rainfall probably resulted from a greater proportion of more positive win-ter/spring rainfall in Seti River tributaries because there were anomalously large rainfall events dur-ing our sampling.However this is di¤cult to re-solve because the sample set is small and repre-sents a narrow range of elevations.6.2.N 18O vs.altitude relationshipThe Kali Gandaki transect provides the best constraints on the regional N 18O mw vs.altitude relationship because it covers the largest range of elevations,and tributary N 18O values did not experience perturbations from rainfall events.Rainout by a Rayleigh fractionation process pre-dicts that N 18O mw will become increasingly more negative with each rainout event.The second or-der polynomial ¢t to the N 18O mw vs.altitude rela-tionship for Kali Gandaki tributaries displays this depletion and is consistent with a Rayleigh-type fractionation process.Rowley and Pierrehumbert used atmospheric thermodynamic relations,based on relative humidity and temperature,in a Ray-leigh-type fractionation model to predict the oxy-gen isotopic composition of rainfall withincreas-Fig.6.N 18O vs.altitude for Kali Gandaki tributaries cor-rected for the di¡erence between sampling elevation and average rainfall elevation.Diamonds show N 18O values of tributaries at the sampling elevation.Note the y -value at 200m (approximate elevation of the Gangetic foreland)does not equal the average annual rainfall at New Delhi (N 18O =35.81x ,weighted mean [53])in the foreland.Squares show N 18O values of tributaries at 1000m higher than the sam-pling elevation.The best-¢t second order polynomial to both the New Delhi value and elevation-corrected data is shown.See text for discussion.C.N.Garzione et al./Earth and Planetary Science Letters 183(2000)215^229223ing elevation in the tropics [54].Data presented here provide an empirical relationship that can be compared with the model of Rowley and Pierre-humbert.By setting the y -intercept to 0x ,the Kali Gandaki relationship can be compared to their model or any region with di¡erent source moisture values (Fig.7).The agreement between our data and the model of Rowley and Pierre-humbert is striking.All of the small tributaries we sampled along the Kali Gandaki (except 99kg23)fall within þ1.5x of the Kali Gandaki relationship (Fig.7).We therefore take þ1.5x as the range of error in the y-axis of the relationship.This yields errors in elevation estimates of less than þ560m for regions over 3000m.6.3.Modern meteoric water vs.the carbonaterecord The modern N 18O mw vs.altitude relationship can be used to reconstruct the paleoelevation dur-ing carbonate formation.A variety of factors in-£uence the N 18O values of carbonate,such as the N 18O mw ,evaporation,diagenetic e¡ects,and tem-perature of calcite/aragonite precipitation.Diage-netic processes can be gauged independently through petrographic observations and by analyz-ing diagenetic carbonate to determine the isotopic composition of diagenetic £uids.The degree of fractionation as a result of evaporation is di¤cultto quantify.In lacustrine carbonate deposits rela-tive changes in evaporation can be assessed using changes in Mg/Ca ratios and by comparing per-cent aragonite to percent paring dif-ferent types of carbonate can help in determining whether one type has been enriched in 18O by evaporation or other processes.Oxygen isotopic fractionation between calcite and water (K c Àw )depends on the temperature of calcite precipitation:1000ln K c Àw 2X 78 106T 32 32X 894where the fractionation factor K c Àw =(18O/16O)c /(18O/16O)w and T is absolute temperature [55].Assumptions must be made about average annual temperature and the season of carbonate precip-itation in order to use this equation to calculate N 18O mw .An uncertainty of þ10³C only introdu-ces an error of þ2.3x to the N 18O mw estimate 1,which is minor compared to the degree of frac-tionation associated with changes in elevation.Garzione et al.[11]inferred that the Thakkhola graben in the southern Tibetan Plateau has been at an elevation similar to modern since the onset of deposition in the graben,based on very low N 18O c values from lacustrine and paleosol carbo-nate in the Late Miocene^Pliocene basin ¢ll (data available in EPSL Online Background Data-set 2)[11].A range of paleoelevations can be esti-mated from these carbonates using the Kali Gan-daki relationship.Today the average annual temperature of Lo Manthang,in northern Thak-khola graben is 6³C 3(3750m above sea level)[57].In lacustrine systems,the averageannualFig.7.The Kali Gandaki relationship (black line)compared to the N 18O/altitude model of Rowley and Pierrehumbert [54](crosses)and elevation-corrected data from the Kali Gandaki and Seti River transects.See text for discussion.1We use the equation of Friedman and O'Neil [55]instead of the more recently published equation by Kim and O'Neil [56]to better compare calculated meteoric water values to past studies that use the Friedman and O'Neil ing the Kim and O'Neil equation would produce calculated mete-oric water values up to 0.4x lower,which would increase paleoelevation estimates by up to V 100m.2http://www.elsevier.nl/locate/epsl,mirror site:/locate/epsl3Mean of average monthly maximum and minimum temper-atures from data available between 1974and 1994.C.N.Garzione et al./Earth and Planetary Science Letters 183(2000)215^229224。

小学上册英语第2单元期末试卷英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.The ______ thrives in tropical climates.2.What is the capital of Colombia?A. BogotáB. MedellínC. CaliD. Cartagena3.My friend has a pet ______ (仓鼠) that loves to run.4.The _______ of a wave can be increased by adding energy.5.What is the capital of Peru?A. LimaB. CuscoC. ArequipaD. TrujilloA6.I like to wear my __________ when it’s cold outside. (手套)7.What do you call the person who teaches you in school?A. DoctorB. TeacherC. ChefD. EngineerB8.I saw a _______ hopping in the meadow (我在草地上看到一只_______).9.What is the process of changing liquid into gas called?A. CondensationB. EvaporationC. FreezingD. BoilingB10.The clouds are ________ in the sky.11.What do we call the time when it rains heavily?A. DroughtB. StormC. FloodD. ShowerB12.The __________ (历史的动力) fuels change.13.What do you call the sweet food made from chocolate and peanuts?A. SnickersB. Reese'sC. M&MsD. Peanut Butter CupsB14.The __________ (道路) leads to the park.15.The _______ (狗) is always loyal to its owner.16.The teacher is very ________.17.I enjoy making ________ (美味的食物) for family.18.The ________ (社会结构) varies between regions.19.What do we call a person who repairs cars?A. MechanicB. DriverC. PilotD. EngineerA20.I like to share my stories with my toy ________ (玩具名称).21.Renaissance artists include Leonardo da Vinci and __________ (米开朗基罗).22. A bear can stand on its ________________ (后腿).23.Which animal is known for its long neck?A. ElephantB. GiraffeC. LionD. ZebraB24.The _______ provides food and shelter for wildlife.25.The park is ___. (fun)26.I have a wonderful _____ (朋友).27.The ancient Greeks invented the _______ to measure time. (日晷)28.I found a ________ under the couch.29.The _____ (香味) of lavender is calming.30.What type of animal is a parrot?A. MammalB. FishC. ReptileD. BirdD31.I enjoy making ________ (拼贴画) in art class.32.The _______ plays a vital role in our environment.33.My sister enjoys __________ (画画) in her free time.34.What is 14 + 6?A. 18B. 19C. 20D. 21A35.My dog loves to eat _______ (狗粮).36.What do you call a collection of short stories published together?A. AnthologyB. NovelC. CompilationD. CollectionA37.The unit of measurement for mass is called a ______.38.I love to listen to ________ while I study.39.We are going to ______ (celebrate) my birthday.40.What is the name of the famous ancient city in Ethiopia?A. AxumB. LalibelaC. GondarD. All of the above41.The ________ (茎) transports nutrients.42.I see a rainbow after the ______. (rain)43.Substances that speed up chemical reactions without being consumed are called _____ (catalysts).44.Which day comes after Monday?A. SundayB. TuesdayC. WednesdayD. ThursdayB45.The __________ (历史的连贯性) is key to comprehension.46.What is the capital city of Mexico?A. CancunB. GuadalajaraC. Mexico CityD. Tijuana47.They are _____ (playing) badminton.48.We have a ______ (快乐的) family tradition for special occasions.49.Salt forms when an acid reacts with a ________.50. A _______ is a substance that can accept protons in a reaction.51. A herbal tea can be made from dried ______ (草).52.The ________ (农业) is crucial for feeding people.53.I like to _______ (与朋友见面).54.I can ___ (skip) rope very well.55.What is the main source of energy for plants?A. WaterB. SoilC. SunlightD. AirCbustion reactions require fuel and _____.57.What do we call the day of the week after Wednesday?A. MondayB. TuesdayC. ThursdayD. FridayC58.What is the capital city of Slovenia?A. LjubljanaB. MariborC. CeljeD. Kranj59.I saw a _______ (小鹿) grazing peacefully.60.I can climb ______ trees.61.The _______ can be a wonderful subject for photography.62. A _____ (colloid) is a mixture where tiny particles are dispersed but not settled.63.The ____ is often seen sharing food with its friends.64.What do we call the phenomenon of water droplets falling from the sky?A. RainB. SnowC. SleetD. HailA65.The chemical formula for water is ______.66.How many sides does an octagon have?A. 6B. 7C. 8D. 967.My uncle is a ____.68.I love to _______ (研究) new topics.69.The _____ (种植者) cares for the plants in the garden.70.What do you call the past tense of "go"?A. GoneB. WentC. GoD. GoingB71.What do we call the science of studying plants?A. BotanyB. ZoologyC. EcologyD. AnthropologyA72.What do we call the process of water soaking into the ground?A. InfiltrationB. EvaporationC. TranspirationD. CondensationA73.The capital of Slovakia is __________.74.The _____ (生物多样性) of plants is vital for ecosystems.75.The __________ is a famous area known for its coffee production.76.I have a toy _______ that dances and sings songs.77.Which holiday is celebrated on December 25th?A. HalloweenB. ThanksgivingC. ChristmasD. New YearC78.The stem of a plant supports its ______ and transports nutrients. (植物的茎支持其叶子并运输养分。

2025年河北省英语中考仿真试卷与参考答案一、听力部分（本大题有20小题，每小题1分，共20分）1、You will hear a short conversation between two students about their plans for the weekend. Listen to the conversation and choose the correct option.Conversation:“Hey Tom, what are you up to this weekend?”“I’m planning to visit the new art exhibition downtown. How about you, Sarah?”“I’ll probably just catch up on some reading at home.”Question: What is Tom planning to do?A)Visit a friend.B)Go to an art exhibition.C)Catch up on some reading.Answer: B) Go to an art exhibition.Explanation: In the dialogue, Tom explicitly states that he’s planning to visit the new art exhibition downtown, making option B the correct answer.2、Listen to a short weather forecast and determine what the weather will be like tomorrow afternoon in the city center.Forecast:“Good evening, folks. Looking ahead to tomorrow, we can expect mostly sunny skies in the morning, but clouds will start rolling in by noon. By mid-afternoon, there’s a high chance of showers in the city center and surrounding areas.”Question: What will the weather be like tomorrow afternoon in the city center?A)Sunny all day.B)Cloudy with a chance of showers.C)Rainy from morning till night.Answer: B) Cloudy with a chance of showers.Explanation: The forecast indicates that while the morning will be mostly sunny, by mid-afternoon there is a high chance of showers in the city center, which matches option B.This section tests the students’ ability to comprehend spoken English and extract specific information from a conversation and a forecast.3、What are the speakers discussing?A)The weather forecast for the next week.B)The importance of exercise for health.C)The latest movie releases.Answer: B) The importance of exercise for health.Explanation: The conversation between the two speakers focuses on the benefits of regular exercise and how it contributes to overall health, which indicates that the topic is related to exercise and not weather or movies.4、How does the woman suggest the man improve his productivity at work?A)By taking longer breaks.B)By working longer hours.C)By organizing his workspace.Answer: C) By organizing his workspace.Explanation: The woman advises the man to organize his workspace to improve his efficiency and productivity, suggesting that a cluttered or disorganized environment might be hindering his work performance.5、You will hear a short conversation between two friends. Listen carefully and choose the best answer to the following question.Question: What is the man’s favorite sport?A. BasketballB. FootballC. TennisD. None of the aboveAnswer: C. TennisExplanation: In the conversation, the man says, “I really enjoy playing tennis. It’s my favorite sport.” Therefore, the correct answer is C. Tennis.6、You will hear a news report about a recent event. Listen carefully and answer the following question.Question: What happened during the event?A. A fire broke out at the shopping center.B. A group of people gathered for a protest.C. An accident occurred on the highway.D. A festival was held in the park.Answer: B. A group of people gathered for a protest.Explanation: The news report states, “Today, a group of p eople gathered in the city center to protest against the new policy.” Therefore, the correct answer is B. A group of people gathered for a protest.7.Listen to the following dialogue and choose the best answer to the question.A. They are discussing a book.B. They are planning a trip.C. They are comparing their diets.Answer: BExplanation: The dialogue focuses on the speakers’ plans for their upcoming vacation, which indicates they are planning a trip.8.Listen to the following passage and answer the question.Question: What is the main purpose of the passage?A. To describe a new product.B. To provide information about a famous person.C. To explain the benefits of exercise.Answer: CExplanation: The passage discusses the various health benefits of regular physical activity, making option C the correct answer. The other options are not supported by the content of the passage.9、You will hear a conversation between two friends, Tom and Lucy. Listen carefully and choose the best answer to the question.What is the main topic of their conversation?A. Tom’s new job.B. Lucy’s birthday party.C. Tom’s weekend plans.Answer: BExplanation: The conversation is mainly about Lucy’s birthday par ty. They discuss the location, time, and activities planned for the party.10、You will hear a short passage about climate change. Listen carefully and answer the question.Which of the following is NOT mentioned in the passage?A. The increase in global temperatures.B. The melting of polar ice caps.C. The rise in sea level.Answer: BExplanation: The passage mentions the increase in global temperatures, the rise in sea level, and the negative effects of climate change. However, the melting of polar ice caps is not mentioned in the passage.11.You will hear a short conversation between two students about their weekend plans. Listen carefully and choose the best answer to the question.What does the woman plan to do on Saturday?A)Visit her grandparents.B)Go shopping.C)Study for an exam.D)Travel to another city.Answer: C) Study for an exam.Explanation: The woman mentions that she has a big exam coming up on Monday, which suggests that her weekend plans include studying.12.You will hear a news report about a new health initiative in a major city. Listen carefully and answer the following question.What is the main goal of the new initiative?A)To reduce traffic congestion.B)To promote healthy eating habits.C)To increase public awareness about mental health.D)To encourage more people to walk or cycle to work.Answer: B) To promote healthy eating habits.Explanation: The news report states that the initiative aims to provide more fresh food options in urban areas and educate residents about the importance of a balanced diet.13.You will hear a short conversation between two friends about their weekend plans. Listen carefully and answer the question.Question: What does Mark plan to do this weekend?A) Go hikingB) Visit his grandparentsC) Stay at home and relaxAnswer: CExplanation: In the conversation, Mark says, “I think I’ll just stay at homethis weekend and relax. I’ve been really busy lately.”14.You will hear a radio announcement about the weather forecast for the next three days. Listen carefully and answer the question.Question: What will the weather be like on Tuesday?A) Sunny with a high of 75°FB) Rainy with a low of 50°FC) Cloudy with a high of 65°FAnswer: AExplanation: The radio announcement states, “On Tuesday, we’ll have a sunny day with a hi gh of 75 degrees Fahrenheit.”15.You will hear a conversation between two friends discussing their weekend plans. Listen and answer the following question.Question: What does Sarah plan to do on Saturday afternoon?A) Go shoppingB) Watch a movieC) Visit a museumD) Go for a hikeAnswer: B) Watch a movieExplanation: In the conversation, Sarah mentions, “I’m thinking of watching a new movie at the cinema on Saturday afternoon.” Therefore, the correct answer is B) Watch a movie.16.Listen to a short passage about a famous author and answer the followingquestion.Question: What is the author known for?A) Writing a popular mystery novelB) Writing a science fiction novelC) Writing a historical fiction novelD) Writing a fantasy novelAnswer: C) Writing a historical fiction novelExplanation: The passage states, “The author, known for her historical fiction novels, has won numerous awards for her captivating storytelling.” Therefore, the correct answer is C) Writing a historical fiction novel.17.Listen to the following conversation and choose the best answer.A. The man is asking for directions to the library.B. The woman is looking for a book about history.C. The man is helping the woman find the nearest post office.D. The woman is inquiring about the opening hours of the museum.Answer: BExplanation: The woman mentions that she needs a book about history, which indicates that she is looking for a book related to that subject.18.Listen to the following news report and answer the question.What is the main topic of the news report?A. A new shopping center opening soon.B. A severe storm hitting the city.C. A famous singer performing in the city.D. A new law passed to improve traffic conditions.Answer: BExplanation: The news report discusses a severe storm that has hit the city, including details about the weather and the impact it has had on local residents. This indicates that the main topic is the storm itself.19.You will hear a conversation between two friends at a bookstore. Listen to the conversation and answer the following question.Question: What book is the woman looking for?A) A science fiction novel.B) A history book.C) A cookbook.D) A mystery novel.Answer: C) A cookbook.Explanation: The woman mentions that she needs a cookbook for her new cooking class, which indicates that she is looking for a cookbook.20.You will hear a short lecture about the effects of climate change on wildlife. Listen to the lecture and answer the following question.Question: What is one of the main effects of climate change mentioned in the lecture?A) Increased number of polar bears.B) Decline in bee populations.C) Enhanced plant growth in deserts.D) Increase in the salinity of freshwater lakes.Answer: B) Decline in bee populations.Explanation: The lecture discusses how climate change is affecting various species, and it specifically mentions the decline in bee populations due to changes in their habitats and food sources.二、阅读理解（30分）Title: The Birth of a New SpeciesReading Passage:In the small town of Greenfield, scientists have made an extraordinary discovery. For years, the local wildlife had been changing, and the townsfolk had noticed that the animals seemed to be evolving at an unprecedented rate. The town’s most famous naturalist, Dr.Evelyn Carter, decided to investigate this phenomenon. After months of research, she and her team uncovered the secret: a previously undiscovered mineral, known as “Evolium,” found deep within the town’s forest, was causing the animals to evolve rapidly.Dr. Carter’s findings were groundbreaking. The mineral seemed to stimulate the animals’ DNA, leading to genetic mutations that enhanced their physical and cognitive abilities. The most remarkable of these mutations was the appearance of a new species of bird, which Dr. Carter named the “Greenfield Glider.” These birds had longer wings, sharper beaks, and an enhanced abilityto navigate complex environments. The Gliders were soon becoming a symbol of hope and innovation in the town.Questions:1.What was the main focus of Dr.Evelyn Carter’s research?A) The impact of the new mineral on the local wildlife.B) The evolution of the town’s human population.C) The economic benefits of the new mineral.D) The history of the town of Greenfield.2.What effect did the Evolium mineral have on the animals in Greenfield?A) It caused them to become extinct.B) It made them more aggressive.C) It stimulated their DNA, leading to genetic mutations.D) It had no effect on their evolution.3.What is the significance of the Greenfield Glider?A) It is a rare bird species that is on the brink of extinction.B) It is the town’s mascot, representing its hope for innovation.C) It is the first bird to be discovered in the town’s history.D) It has no special features and is no different from other birds.Answers:1.A) The impact of the new mineral on the local wildlife.2.C) It stimulated their DNA, leading to genetic mutations.3.B) It is the town’s mascot, representing its hope for innovation.三、完型填空（15分）Complete the following passage with the most appropriate options.In the small town of Greenfield, the local library was facing a dilemma. For years, it had been a cherished community hub, but now, its aging building was in dire need of repairs. The mayor, Mr. Thompson, convened a meeting with the library board and community leaders to discuss the best course of action.The first option presented was to [] the existing building, which would cost a considerable amount of money. However, this solution was met with skepticism from some board members who feared that [] would result in the loss of the library’s unique charm.The second option was to [] a new, modern library on the outskirts of town, which would offer more space and amenities. This idea was more popular with the younger generation, but it raised concerns about the [] of the older residents who preferred to stay close to their homes.A third suggestion was made by Mrs. Jenkins, a long-time library volunteer. She proposed [] a partnership with a local university to create a [] library that would combine the resources of the library and the university, thereby providing a unique educational experience for students and the community.The mayor listened to all the proposals a nd then asked the group, “What do you think will be the most beneficial for Greenfield in the long run?”1.A. rebuild2.A. preserving3.A. construction4.A. establish5.A. hybridAnswer Key:1.A. rebuild2.A. preserving3.A. construction4.A. establish5.A. hybrid四、语法填空题（本大题有10小题，每小题1分，共10分）1、In the_______(1) place, I prefer staying at home rather than going out on weekends.答案：first解析：此处需要填入一个表示顺序的形容词，根据句意“首先”，应该使用“first”。

Similarities of the Images Used in the Two Poems1 The reasons of the depressed mood in the imageAlthough they were in different history period and had different backgrounds, Wordsworth and Li Bai had the same misfortunes and frustrations.If reading lots of the reference about I Wandered Lonely As A Cloud and Drinking Alone Under The Moon, we are not difficult to find that, they were in the same turbulent social backgrounds which influenced them deeply. “wandered lonely(Line 1)”, “drinking alone(Line 2)” are he vivid portrayals of Wordsworth and Li Bai in their times respectively. The special social background that will be discussed in detail in chapter 4 and special personal experience molded their special characteristics and tempers. The same misfortunes and frustrations affected their emotion. So the moods of the two poems resulted from the same reason.2 The indications of the depressed mood in the imageThe titles of the two poems both have the same words, i.e. “lonely”and “alone”,expressing the painful and lonely feelings.About I Wandered Lonely As A Cloud the first person in the single form of “I(Line 1)”instead of plural form of “we”, vividly showed the dire figure ofWilliam Wordsworth himself. The poet compared him to a “cloud (Line 1)” and his wandering to the cloud’s floating, which sharpened his lonely sense. Secondly, “a crowd (line 4)”, “a host (line 4)” of daffodils came in our visual scope, “fluttering(line 6)”and “dancing(line 6)”. Such happy and gleeful visual sense broke the beginning “lonely”mood. Thirdly, “continuous (line 7)”, set a fundamental visual sense of the visual image of “crowd”, and “twinkle(line 8)”suggested a bright golden color of the visual image because of the word’s implication of “sharp and bright”vision.The same as true of Li Bai’s Drinking Alone Under The Moon,“Amid the flowers, from a pot of wineI drink alone beneath the bright moonshine”(Lines 1-2)the two lines suggested an obvious fundamental mood of the poem, i.e. the depressed poet, the speaker was drinking lonely under the cool moonshine, sad and cold.Very often we drink wine for 2 reasons: pleasant and painful. From the title, we get to know Li Bai, as a poem speaker, must be in a desperate mood in which he could not and would not disturb his friends by pouring out his sufferings. He found no other way to release his lonely emption, but to “drink alone”; secondly, “the bright moonshine” provided him with a quiet and peaceful environment where he could enjoy himself; thirdly, “the flowers” symbolizing the happy surrounded him and sharply shapedhis depressed mood as a foil.The auditory images of the two poems indicated the depressed mood. The auditory image of I Wandered Lonely As A Cloud twists and turns in the changing process of the visual image. The developing tendency is from the placid melody to the surprising pleasure, and when the poet found comfort from the great nature, his mood returned to placid situation, so the auditory melody was mild and gentle as well. Although the auditory image of Drinking Alone Under The Moon is not the end of placid and quiet mood, but the first mood was very placid and depressed.3 The Aims at Voicing EmotionThe image in poetry is a kind of symbol to express poet s’some strong emotion. Romantic poets are the firm supporters for the perfect ideals. When they were frustrated by the unreasonable reality, they always voiced the depressed and discontent emotion. Coincidently, in the two poems, both of poets found the objects which can be entrusted their depressed and painful feelings. The “crowd”, “golden”daffodils, the “bright” moon and the “mess” shadow are all the ways to unbosom the emotion for the two poets when they were very depressed and lonely. They created the images in order to voice the strong emotion and reflect the developing tendency of the poets’ emotion.In I Wandered Lonely As A Cloud, the melody developing tendency began from a placid melody (“I wandered lonely as a cloud / That floats on high o'er vales and hills” Lines 1-2) to climax melody gradually when he saw the crowd of daffodils and got surprising pleasure. He“could not be but gay, / In such a jocund company!”(Lines 15-16). The climax melody just voiced his strong emotion.It is same to Drinking Alone Under The Moon.“Amid the flowers, from a pot of wine.I drink alone beneath the bright moonshine”(lines 1-2)A sad and depressed melody sounds in brain when a lonely and sad scene appeared. When Li Bai, “I raised my cup to invite the moon who blends”(Line 3) and danced with his own shadow, the melody was led up to the climax. However, “I”“my shadow” and “the moon” became friends, “cheerful and guy”, the more exciting his posture and movements were performed, the more pent-up loneliness was given vent to. As we all known that, the music is usually in the fast pace in order to express the strong emotion, especially the music accompanied the dancer who was drunk and the pace of dance was mess, the music always became much faster and happier. This is like the artistic effect of the color contrast in I Wandered Lonely As a Cloud.The faster and happier music were, the lonelier feeling was.“I raised my cup to invite the moon who blendsHer light with my shadow and we’re three friends.My shadow’s a mess while I dance along.Sober, we three remain cheerful and gay,Drunk, we part and each may go his way.”(Lines 3-7) The auditory image became brighter and happier gradually because the poet invited the moon to drink together and danced with his own shadow happily. So the melody developing tendency of Drinking Alone Under The Moon is similar to that of I Wandered Lonely As A Cloud.。