Analytica Chimica Acta565(2006)
97–102
Food safety evaluation:Detection and con?rmation of chloramphenicol in milk by high performance liquid chromatography-tandem mass spectrometry Rebecca S.Nicolich a,?,Eduardo Werneck-Barroso b,Marlice A.S′?poli Marques a
a Dep?Qu′?mica Anal′?tica-IQ/UFRJ,C.Tecnologia,BL A,Ilha do Fund?a o,Rio de Janeiro,RJ CEP219749-970,Brazil
b FIOCRUZ-SEFAR/IPEC,Av.Brasil,4365,Manguinhos,Rio de Janeiro,RJ CEP21040-900,Brazil
Received18October2005;received in revised form29January2006;accepted31January2006
Available online9March2006
Abstract
A simple and rapid procedure for extraction of chloramphenicol(CAP)in milk and analysis by high-performance liquid chromatography coupled with quadrupole mass spectrometry in tandem was developed.The method consisted of one step of liquid–liquid extraction using ethyl acetate and acidi?ed water(10mmol L?1formic acid)and HPLC-MS/MS detection.CAP-D5was used as internal standard.The method was validated according to Commission Decision2002/657/EC.The calibration curves were linear,with typical r2values higher than0.98.Absolute recovery of CAP from milk proved to be more than95%,however CAP-D5absolute recovery was75%.The method was accurate and reproducible,being successfully applied to the monitoring of CAP in milk samples obtained from the Brazilian market.Decision limit(CC?)was0.05ng mL?1and detection capability(CC?)was0.09ng mL?1.
?2006Elsevier B.V.All rights reserved.
Keywords:Chloramphenicol;Antibiotic;Food control;High performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS)
1.Introduction
Chloramphenicol(CAP,Fig.1)is a broad-spectrum antibi-otic,which is capable of causing fatal blood diseases in humans. It is reserved to the treatment of serious infections,when no other alternative is available.However,the use of CAP in animals can be very appealing,since it is well tolerated by them and it is largely distributed among tissues and?uids.Other properties of CAP can also be very interesting to producers.In?shery, for example,this drug is preferable because of its long half-life in solution;other antibiotics,like tetracyclines,are less stable,requiring larger doses and more frequent applications [1].
In Brazil,only recently the production,importation and com-mercialization of CAP for food-producing animals were banned [2].Therefore,other drugs must be used for the treatment of infections of those animals.In the speci?c case of milking cat-
?Corresponding author.Present address:R.Fabio da Luz325BL1/205Rio de Janeiro,RJ CEP20720-350Brazil.Tel.:+552139790768;
fax:+552125957131.
E-mail address:rebecca@ufrj.br(R.S.Nicolich).tle,some diseases can cause a decrease in feed consumption and milk production,being mastitis the most worrisome[3].
The use of CAP in food-producing animals is prohibited, because it is not possible to establish a safe intake level for its residues or its metabolites’residues in food.The Joint FAO/WHO Expert Committee on Food Additives,considering the existence of fatal dose-independent effects of this substance, was not able to determine an acceptable daily intake(ADI)for CAP,neither a maximum residue limit(MRL).Therefore,in compliance with JECFA’s recommendation,not only Brazil but also the USA and the European Union established a zero toler-ance for CAP residues in food.
The possibility of disseminating resistant bacteria is also very important when discussing the impact of antibiotic residues in food.In general,these drugs cause a favorable selective pressure for the propagation of resistant bacteria.In veterinary medicine, the use of such agents can also cause this effect[4].Conse-quently,resistant phenotypes have already been found in food products commercially available[5–7].Nonetheless,it is dif-?cult to determine unequivocally the source of these bacteria, since food handlers can present them in their?ora[8].
To analyze veterinary drugs residues in food,at least two methods need to be used:one for screening and another for
0003-2670/$–see front matter?2006Elsevier B.V.All rights reserved. doi:10.1016/j.aca.2006.01.105
98R.S.Nicolich et al./Analytica Chimica Acta 565(2006)
97–102
Fig.1.Structures of (A)CAP and (B)CAP-D5.
con?rmation.Screening methods must be optimized to avoid false-negative results,allow high sample throughput and present low cost.On the other hand,con?rmation methods must be opti-mized to avoid false-positive results (that is,it must have superior speci?city),provide structure elucidation and quantify the ana-lyte [9].
It is possible to ?nd in the literature several review articles on chromatographic methods to analyze antibiotics in different food matrixes [10–14].There are also many speci?c articles on the analysis of CAP in milk [15–19,26,27].However,of?cial anal-yses require the use of methods which comply with qualitative and quantitative criteria established by local sanitary agencies.In Brazil,it is common to adopt the European regulation for this type of analysis.
In the European Communities,performance criteria for analytical methods are laid down by Commission Decision 2002/657/EC [20].In the case of prohibited substances (Group IV ,by Council Regulation 90/2377/CEE [21],which includes CAP),another requirement is the compliance of the minimum required performance limit (MRPL).Nowadays,the MRPL for the analysis of CAP in milk is 0.3?g kg ?1[22].
The main goal of this study was to establish and dissemi-nate a rapid and innovative method for the detection of CAP in milk,based on liquid–liquid extraction and quadrupole HPLC-MS/MS detection.The method was validated according to Com-mission Decision 2002/657/EC and applied in the analysis of milk samples collected by a Brazilian health surveillance pro-gram.
2.Experimental
The following reagents were used:acetonitrile,methanol,ethyl acetate and formic acid.All reagents were HPLC-grade,being acquired from Tedia (Fair?eld,USA).Water was puri?ed by reverse osmosis (Milli-Q,Millipore).2.1.Standard preparation
Standards were obtained from the following suppliers:chloramphenicol from United States Pharmacopoeia (USP,Rockville,MD,USA),chloramphenicol-D5(CAP-D5)from Cambridge Isotope Laboratories (CIL,Andover,MA,USA).CAP-D5was used as internal standard (IS).
Stock solutions of CAP were prepared in methanol/water (50:50,v:v)at a concentration of 1mg mL ?1.These solutions were further diluted to yield appropriate working solutions
for the preparation of the calibration standards.Working solu-tions of the IS were prepared in methanol/water (50:50,v:v)at 48ng mL ?1.All standard solutions were sealed and kept at ?20?C,protected from light,for no longer than 3months.2.2.Instrumental conditions
The HPLC-MS/MS system consisted of Varian 1200L MS/MS detector with an ESI source,Varian ProStar 430AutoSampler and Varian ProStar 210Solvent Delivery Modules (Varian,Walnut Creek,CA,USA).The detector was tuned by infusing a polypropileneglycol solution at a rate of 20mL min ?1,using a syringe pump,and optimized with a standard solution of CAP (0.1mg mL ?1in methanol/water 50:50,v:v,containing 10mmol L ?1of formic acid),using the same procedure.
Chromatographic separation was achieved using a Varian Pursuit column (100?m ×20?m ×5?m)in combination with a Varian MetaGuard pre-column.The mobile phase consisted of 0.1%formic acid in water (mobile phase A)and 0.1%formic acid in acetonitrile (mobile phase B).Gradient elution was per-formed (0–3min,5%B;3.5–6min,70%B;6.5–15min,5%B)at a ?ow rate of 0.3mL min ?1.The temperature of the autosam-pler and the column was 23±2?C.
The mass spectrometer was used in the positive ion MS/MS mode (ESI).The following instrument conditions were used for CAP and CAP-D5:needle,3600V;shield,600V;capillary,76V;nebulizing gas,50psi;drying gas,30psi,300?C;collision gas,argon,1.80mTorr;multiplier,2000V;scan time,1s;SIM width,0.7amu.
The instrument was operated in multiple reaction-monitoring (MRM)mode,using the following transitions m /z 323→275(quanti?cation ion)and m /z 323→165(con?rmation ion)for CAP and m /z 328→280(quanti?cation ion)for CAP-D5;with collision energies of ?13.5,?23.0and ?11.0V ,respectively.Relative abundance of the two MRM transitions monitored for CAP was superior to 50%(Fig.2).2.3.Sample preparation
Two milliliters of milk samples were spiked with 50?L of IS working solution (48ng mL ?1)and vortexed for 10s.After 10min of equilibration,0.8mL of water acidi?ed with 10mmol L ?1of formic acid and 4mL of ethyl acetate were added.The samples were extracted for 10min on a rotary mixer (Fanem,model 255B,S?a o Paulo,SP),at 400rpm.After that,they were centrifuged for 5min at 3200rpm.The supernatant
R.S.Nicolich et al./Analytica Chimica Acta565(2006)97–102
99
Fig.2.Typical chromatogram of a blank milk sample forti?ed with CAP at 0.3ng mL?1(A and B)and CAP-D5at1.2ng mL?1(C).
was transferred to another tube,and the sediment was once again extracted with4mL of ethyl acetate(no water added this time).The second supernatant obtained was added to the one from the?rst extraction and they were evaporated to dryness at40?C,under nitrogen?ow.The residues were dissolved in 200?L of mixture solution(water/methanol,50:50,v:v,con-taining10mmol mL?1of formic acid)and vortexed for20s. The volume of extract injected into the LC was50?L.
In case of powdered milk samples,the reconstitution was made following label instructions.The aliquot of2mL was pipetted from reconstituted milk.
All samples had been kept at?20?C,protected from light, until they were processed.
2.4.Method validation
The experimental design used in the method validation was based on the one proposed by ResVal Versie2.1?,from CRL-Bilthoven(RIVM,Netherlands),which was kindly provided by Dr.Saskia Sterk and Dr.Henk Herkbold.
A homogenous pool of blank UHT milk previously screened with ELISA RidaScreen(R-Biopharm,Darmstadt,Germany) was divided in93sub-samples and divided again in three groups of31samples.In different days,each group of31samples was used to construct two calibration lines,one for the calcu-lations of CAP concentrations for the accuracy and precision tests(which shall be referred to as“calibration curve”)and the other for the estimation of CC?and CC?(“control curve”); therefore,three experiments were conducted in3different days.
Calibration lines consisted of six concentration levels:0.00, 0.30,0.45,0.60,1.20and3.00ng mL?1of CAP in milk.For the “calibration curves”,all levels were prepared in duplicate.For the“control curves”,levels0.30,0.45and0.60ng mL?1were prepared in six replicates and levels0.00,1.20and3.00ng mL?1 were not prepared in replicate(only one sample prepared).The concentration of the IS was1.20ng mL?1of CAP-D5in milk in all samples.The ratios of the peak area of varying concentration of analytes to that of IS were calculated and plotted against the level of forti?cation.Linearity was determined by linear regression.No special calculation correction for losses during extraction(such as a recovery factor)was applied,since an IS was used.
Precision and accuracy of the method were evaluated intra-and inter-assay at levels0.30,0.45and0.60ng mL?1(which corresponded to1×MRPL,1.5×MRPL and2×MRPL).This evaluation was made by calculating CAP concentration of these three levels from the“control curve”using the model from the “calibration curve”.
Speci?city of the method was evaluated by the analysis of10 different blank samples(including UHT and powdered milk)in order to investigate possible interferents eluting on CAP reten-tion time.In addition,these samples were forti?ed at one time the validation level(0.30ng mL?1)in order to investigate whether there is any matrix effect on the quanti?cation of CAP.For this quanti?cation a new calibration curve was prepared(six levels in duplicate).
Absolute recovery of analytes was determined by comparison of peak areas from blank UHT milk samples spiked with known amounts of CAP(0.30,0.45and0.60ng mL?1)and IS before the preparation procedure to peak areas from matrix extracts spiked after it.Six replicates were conducted at each level.
2.5.Application to real samples
The present method was applied to con?rm the presence of CAP in41suspect milk samples previously screened with ELISA RidaScreen(R-Biopharm,Darmstadt,Germany).These samples were obtained along with others from the Brazilian market by local health surveillance authorities in2004.The HPLC-MS/MS analyses were performed in two separate batches on the same day.
The presence of the CAP in a given sample would be char-acterized by comparison of the relative retention time of the suspect peak and the ratio of the relative abundance of its main diagnostic ions with those obtained by analysis of a positive con-trol(QC).While the relative abundance of diagnostic ions must not differ by more than20%from those observed in the QC, the relative retention time of the peak observed in the suspect sample must not differ by more than1%from the one obtained in the QC.
3.Results and discussion
3.1.Fragmentation pattern and chromatography
The fragmentation proposals for CAP diagnostic ions are shown on Fig.3.Typical chromatograms of blank milk sam-ples and milk forti?ed with CAP at0.30ng mL?1and IS are illustrated on Figs.2and4.Both substances presented reten-tion time of7.9min and there were no chromatographic peaks interfering with their signal.
3.2.Validation study
3.2.1.Speci?city
Mass spectrometry is the most reliable technique for the identi?cation of substances.Its application observing the iden-ti?cation point system introduced by Commission Decision 2002/657/EC allows a high probability of correct identi?cation
100R.S.Nicolich et al./Analytica Chimica Acta 565(2006)
97–102
Fig.3.Proposal for the fragmentation of CAP.
of the analyte.There are even proposals for mathematic models expressing the con?ability of this technique [23].
Commercially available milk is a mixture of ?uids from several cows from different farms,that is,a pool.Therefore,endogenous compounds unique to one individual would be diluted.Since the developed method was going to be applied to the analysis of UHT and powdered milk commercially avail-able,not milk originated from just one animal,the speci?city test was performed with samples from different brands and in different states of alteration.Chromatographic peaks from inter-ferents eluted at different retention times from CAP,with signals below 20%from the one obtained with CAP at 0.30ng mL ?1(Fig.4).
The accuracy of CAP quanti?cation in these 10different blank samples forti?ed at 0.30ng mL ?1in the speci?city test was 100%,which is the same value obtained in the inter-assay inves-tigation at the same forti?cation level (Section 3.2.3).However,comparing the variance obtained for this quanti?cation in
the
Fig.4.Chromatograms of normal UHT milk—blank (A)and forti?ed with CAP at 0.3ng mL ?1(B);alterated UHT milk—blank (C)and forti?ed (D);reconstituted powder milk—blank (E)and forti?ed (F).
speci?city test with the variance obtained in the inter-assay pre-cision test,a signi?cant difference between them can be found when a bi-lateral F -test is used at 0.05con?dence level.This result may indicate the existence of some matrix effect on the quanti?cation of CAP at that concentration level.
3.2.2.Linearity
The calibrations lines were prepared over the concentration range of 0–3.00ng mL ?1of CAP in milk.Regression analysis of the correlation between the chromatographic peak areas ratio of CAP/IS versus known concentrations of analyte yielded linear correlation over the concentration range analyzed.The corre-sponding correlation coef?cients (r 2)for the curves prepared were higher than 0.98.
3.2.3.Precision and accuracy
Intra-assay and inter-assay precision and accuracy of the method,assessed by analysing control samples (0.30,0.45and 0.60ng mL ?1),are given in Table 1.
According to Commission Decision 2002/657/EC,coef?-cient of variation (CV)from a method should not exceed the value calculated by the Horwitz equation:CV =2(1?0.5log),where C is the mass fraction expressed in power of 10.How-ever,for mass fractions below 1?g kg ?1,this equation gives unacceptably high CV values.Therefore,2002/657/EC recom-mends that the CV should be as low as possible in these cases.
Table 1
Intra-and inter-assay precision and accuracy results Performance criteria
Forti?cation level (ng mL ?1)0.30
0.450.60Precision CV (%)Assay 18.3916.769.61Assay 216.268.0016.49Assay 314.94 5.8315.54Inter-assay 13.62 3.09 2.76Accuracy (%)Assay 1105.5780.5794.93Assay 2107.7283.4091.98Assay 383.3383.4489.90Inter-assay
100.00
82.22
91.67
R.S.Nicolich et al./Analytica Chimica Acta565(2006)97–102101 Meanwhile,Codex Alimentarius guidelines recommend that the
CV should be below35%[9].
For the mass fraction tested,both European regulations and
Codex guidelines establishes that accuracy should be within
50–120%.
As shown in Table1,the intra-assay and inter-assay preci-
sions were below17%,and intra-day and inter-day accuracies
ranged from82to108%.These results indicate that the method
has adequate precision and accuracy.
3.2.
4.Recovery
The mean absolute recoveries of CAP in milk samples
after extraction procedure were97.02%(0.30ng mL?1,n=6),
98.76%(0.45ng mL?1,n=6),95.04%(0.60ng mL?1,n=6).
Mean absolute recovery of CAP-D5was75.07%(1.20ng mL?1,
n=18).
One possible explanation for the difference in recovery of
CAP and CAP-D5would be the effect of the substitution of?ve
hydrogen atoms for deuterium atoms in CAP-D5(especially the
ones at the aromatic ring).Such substitution could be responsi-
ble for affecting the pattern of intermolecular interactions CAP
would be able to make with matrix/solvent molecules.These
differences may include variations in polarity,dipole–dipole
interactions and proton-donor/proton-acceptor qualities.In GC,
for example,deuterated compounds seldom present lower reten-
tion times than their original molecules.This phenomenon can
also be accounted to differences in nature and intensity of inter-
molecular interactions between analogs.
3.2.5.Decision limit(CCα)and detection capability(CCβ)
The CC?and CC?were calculated using calibration lines
which gave more weight to the lower concentration levels(the
control curves,as described in Section2.4).This strategy allows
an estimation of the standard deviation of the intercept which
can be more representative of the uncertainty associated to those
levels.
The equations used in CC?and CC?calculations were:
CC?=y intercept+2.33×s intercept
slope
,
CC?=y intercept+2.33×s intercept+1.64×s intercept
slope
For each control curve constructed,CC?and CC?were cal-culated(Table2).The average of these values was considered the decision limit and the detection capability of the method: 0.05and0.09ng mL?1,respectively.
3.2.6.Robustness
During the development of the present method for the analysis of CAP in milk,it was veri?ed that the following experimental conditions could have impact on the analytical results:
1.Mobile phase acid concentration.An acid content inferior to
0.1%in both phases can make CAP’s signal unstable.On
the other hand,values superior to0.1%(0.15and0.2%)do Table2
Calculation of CC?and CC?of the method
Assay Slope(a)y-Intercept(b)s intercept CC?a
(ng mL?1)
CC?b
(ng mL?1) 10.65460.06540.01490.050.09
20.7164?0.00780.01700.060.09
30.54550.03800.00990.040.07 Mean0.050.09
a CC?,limit of decision,is the limit at which it can be decided that a sample is truly violative with an error probability ofα[20]
b CC?,detection capability,is the smallest content at which a method is able, with an error probability ofβ,to detect,identify and quantify the analyte[20].
not seem to affect CAP’s signal,even thought they could be harmful to the analytical column.
2.Water acidi?cation on the liquid–liquid extraction.Water
acidi?cation on this step(formic acid at10mM,pH5.5) seems to promote CAP extraction by ethyl acetate,prevent-ing variation on its recuperation,which was veri?ed when pure water was used instead.
3.3.Application to real samples
CAP was not detected in any of the suspect samples.Besides the possibility of these samples include some false-positive results,the hypotheses of alterated matrix affecting the anal-ysis and CAP degradation occurring during storage cannot be rejected(these samples had been stored for one year at?20?C, protected from light,before they were kindly donated to us and were analyzed).An explanation for such result is still being investigated by our group.
Nonetheless,it is known that CAP is susceptible to degra-dation by enzymes found in animal and microorganisms.Some examples of reactions that could take place include reduction of the nitro group,hydrolysis of the amide or conjugation of the hydroxyls[24].Moreover,it has been recommended that CAP extraction is performed immediately after tissue homog-enization in order to prevent analyte loss due to reaction with endogenous enzymes[25].
4.Conclusions
The developed method proved to be useful and reliable for the determination of CAP in milk by HPLC-MS/MS.It was validated for CAP quanti?cation at the concentration range from0.30to3.00ng mL?1,being able to con?rm results at 0.05ng mL?1with an error probability of1%.Therefore,the present method is suitable for the control of CAP in milk.
In comparison to other methods based on HPLC-MS/MS recently published in the literature,ours appears to be simpler and less expensive than[26],which uses af?nity chromatogra-phy for sample puri?cation.And although[27]has a lower limit of decision,it is exclusive to powdered milk;ours,on the other hand,can be applied to both?uid and powdered milk.
Regarding real sample analysis,stability studies of the ana-lyte in matrix are necessary before any conclusions are made.
102R.S.Nicolich et al./Analytica Chimica Acta565(2006)97–102
Acknowledgements
To CAPES,FAPERJ and FIOTEC for?nancial support.To INCQS for providing the CAP standard and real samples. References
[1]Y.Bishop,The Veterinary Formulary,Pharmaceutical Press,USA,1998
(Apud H.M.Ashwin,S.L.Stead,J.C.Taylor,J.R.Startin,S.F.Rich-mond,V.Homer,T.Bigwood,M.Sharman,Anal.Chim.Acta529 (2005)103).
[2]Brazil’s Ministry of Agriculture,Normative Instruction No.38of8of
May of2002.
[3]N.Bareille,F.Beaudeau,S.Billon,A.Robert,P.Faverdin,Livest.Prod.
Sci.83(2003)53.
[4]W.Witte,Science279(1998)996.
[5]J.Peters,K.Mac,H.Wichmann-Schauer,G.Klein,L.Ellerbroek,Int.
J.Food Microb.88(2003)311.
[6]C.M.Schroeder,D.G.White,B.Gea,Y.Zang,P.F.McDermott,S.Ayers,
S.Zhao,J.Meng,Int.J.Food Microbiol.85(2003)197.
[7]S.Zhao,A.D.Datta,S.Ayers,S.Friedman,R.D.Walker,D.G.White,
Int.J.Food Microbiol.84(2003)87.
[8]M.Acco,F.S.Ferreira,J.A.P.Henriques,E.C.Tondo,Food Microbiol.
20(2003)489.
[9]Codex Alimentarius Commission,CAC/GL16,1993.
[10]G.Balizs,A.Hewitt,Anal.Chim.Acta492(2003)105.[11]D.G.Kennedy,R.J.McCracken,A.Cannavan,S.A.Hewitt,J.Chro-
matogr.A812(1998)77.
[12]W.M.A.Niessen,J.Chromatogr.A812(1998)53.
[13]F.J.Schenck,P.S.Callery,J.Chromatogr.A812(1998)99.
[14]B.Shaikh,W.A.Moats,J.Chromatogr.643(1993)369.
[15]C.Van de Water,N.Haagsma,J.Chromatogr.566(1991)173.
[16]P.J.Kijak,J.AOAC77(1994)34.
[17]A.P.Pfenning,M.R.Madsons,J.E.Roybal,J.AOAC81(1998)
714.
[18]N.Perez,R.Gutierrez,M.Noa,G.Diaz,H.Luna,I.Escobar,Z.Munive,
J.AOAC85(2002)20.
[19]L.K.Sorensen,T.H.Elbaek,H.Hansen,J.AOAC86(2003)703.
[20]Commission Decision2002/657/CE of12de August2002,Off.J.Eur.
Commun.L221(2002)8.
[21]Council Regulation(EEC)2377/90of26June1990,https://www.doczj.com/doc/b98246518.html,-
mun.L224(1990)1.
[22]Commission Decision2003/181/CE of13de March2003,Off.J.Eur.
Commun.L71(2003)17.
[23]G.Stoev,A.Michailova,J.Chromatogr.A1031(2004)11.
[24]T.E.Woodward, C.L.Wisseman,Antibiotics Monographs No.9
Chloromycetin,Medical Encyclopedia Inc.,USA,1958.
[25]A.Gantverg,I.Shishani,M.Hoffman,Anal.Chim.Acta483(2003)
125.
[26]P.Gallo,A.Nasi,F.Vinci1,G.Guadagnuolo,G.Brambilla,M.Fiori,
L.Serpe,Rapid Commun.Mass Spectrom.19(2005)574.
[27]P.A.Guy,D.Royer,P.Mottier,E.Gremaud,A.Perisset,R.H.Stadler,
J.Chromatogr.A1054(2004)365.
高级财务会计习题答案 Prepared on 22 November 2020
《高级财务会计》习题答案 第一章非货币资产交换 1、2007年5月，A公司以其一直用于出租的一幢房屋换入B公司生产的办公家具准备作为办公设备使用，B公司则换入的房屋继续出租。交换前A公司对该房屋采用成本模式进行后续计量，该房屋的原始成本为500 000元，累计已提折旧180 000元，公允价值为400 000元，没有计提减值准备；B公司换入房屋后继续采用成本模式进行计量。B公司办公家具账面价值为280 000元，公允价值与计税价格均为300 000元，适用的增值税税率为17%，B公司另外支付A公司49 000元的补价。假设交换不涉及其他的相关税费。 要求：分别编制A公司和B公司与该资产交换相关的会计分录。 A公司的会计处理： 49 000/400 000=%，所以交换属于非货币资产交换。 换入设备的入账价值=400 000-（300 000×17%）-49 000=300 000元 换出资产应确认的损益=400 000-320 000=80 000元 借：固定资产清理 320 000 累计折旧 180 000 贷：投资性房地产 500 000 借：固定资产——办公设备 300 000 银行存款 49 000 应交税金—增值税（进项） 51 000 贷：固定资产清理 320 000
其他业务收入（投资性房地产收益） 80 000 B公司的会计处理 换入设备的入账价值=300 000+300 000×17%+49 000=400 000元 换出资产应确认的损益=300 000-280 000=20 000元 借：投资性房地产 400 000 贷：主营业务收入 300 000 应交税金——增值税（销项） 51 000 银行存款 49 000 借：主营业务成本 280 000 贷：库存商品 280 000 2、2007年9月，X公司生产经营出现现金短缺，为扭转财务困境，遂决定将其正在建造的一幢办公楼及购买的办公设备与Y公司的一项专利技术及其对Z公司的一项长期股权投资进行交换。截止交换日，X公司办公楼的建设成本为900 000元。办公设备的账面价值为600 000元，公允价值为620 000元；Y公司的专利技术的账面价值为400 000元，长期股前投资的账面价值为600 000元。由于正在建造的办公楼的完工程度难以合理确定，Y公司的专利技术为新开发的前沿技术，Z公司是非上市公司，因而X公司在建的办公楼、Y公司的专利技术和对Z公司的长期股权投资这三项资产的公允价值均不能可靠计量。Y公司另支付X公司300 000元补价。假设该资产交换不涉及相关税费。 要求：分别编制X公司和Y公司与该资产交换相关的会计分录。 X公司的会计处理： 因为公允价值均不能可靠计量，所以采用账面价值计量换入资产。
化工热力学答案_课后总习题答案详解 第二章习题解答 一、问答题： 2-1为什么要研究流体的pVT 关系？ 【参考答案】：流体p-V-T 关系是化工热力学的基石，是化工过程开发和设计、安全操作和科学研究必不可少的基础数据。（1）流体的PVT 关系可以直接用于设计。（2）利用可测的热力学性质（T ，P ，V 等）计算不可测的热力学性质（H ，S ，G ，等）。只要有了p-V-T 关系加上理想气体的id p C ，可以解决化工热力学的大多数问题。 2-2在p -V 图上指出超临界萃取技术所处的区域，以及该区域的特征；同时指出其它重要的点、线、面以及它们的特征。 【参考答案】：1）超临界流体区的特征是：T >T c 、p >p c 。 2）临界点C 的数学特征： 3）饱和液相线是不同压力下产生第一个气泡的那个点的连线； 4）饱和汽相线是不同压力下产生第一个液滴点（或露点）那个点的连线。 5）过冷液体区的特征：给定压力下液体的温度低于该压力下的泡点温度。 6）过热蒸气区的特征：给定压力下蒸气的温度高于该压力下的露点温度。 7）汽液共存区：在此区域温度压力保持不变，只有体积在变化。 2-3 要满足什么条件，气体才能液化？ 【参考答案】：气体只有在低于T c 条件下才能被液化。 2-4 不同气体在相同温度压力下，偏离理想气体的程度是否相同？你认为哪些是决定偏离理想气体程度的最本质因素？ 【参考答案】：不同。真实气体偏离理想气体程度不仅与T 、p 有关，而且与每个气体的临界特性有 ()() () () 点在点在C V P C V P T T 00 2 2 ==?? ?
关，即最本质的因素是对比温度、对比压力以及偏心因子r T ，r P 和ω。 2-5 偏心因子的概念是什么？为什么要提出这个概念？它可以直接测量吗？ 【参考答案】：偏心因子ω为两个分子间的相互作用力偏离分子中心之间的作用力的程度。其物理意义为：一般流体与球形非极性简单流体（氩，氪、氙）在形状和极性方面的偏心度。为了提高计算复杂分子压缩因子的准确度。 偏心因子不可以直接测量。偏心因子ω的定义为：000.1)p lg(7.0T s r r --==ω ， ω由测定的对比温度为0.7时的对比饱和压力的数据计算而得，并不能直接测量。 2-6 什么是状态方程的普遍化方法？普遍化方法有哪些类型？ 【参考答案】：所谓状态方程的普遍化方法是指方程中不含有物性常数a ，b ，而是以对比参数作为独立变量；普遍化状态方程可用于任何流体、任意条件下的PVT 性质的计算。普遍化方法有两种类型：（1）以压缩因子的多项式表示的普遍化关系式 (普遍化压缩因子图法)；（2）以两项virial 方程表示的普遍化第二virial 系数关系式(普遍化virial 系数法) 2-7简述三参数对应状态原理与两参数对应状态原理的区别。 【参考答案】：三参数对应状态原理与两参数对应状态原理的区别在于为了提高对比态原理的精度，引入了第三参数如偏心因子ω。三参数对应态原理为：在相同的 r T 和r p 下，具有相同ω值的所有 流体具有相同的压缩因子Z ，因此它们偏离理想气体的程度相同，即),P ,T (f Z r r ω=。而两参数对应状态原理为：在相同对比温度r T 、对比压力 r p 下，不同气体的对比摩尔体积r V （或压缩因子z ） 是近似相等的，即(,) r r Z T P =。三参数对应状态原理比两参数对应状态原理精度高得多。 2-8总结纯气体和纯液体pVT 计算的异同。 【参考答案】： 由于范德华方程（vdW 方程）最 大突破在于能同时计算汽、液两相性质，因此，理论上讲，采用基于vdW 方程的立方型状态方程能同时将纯气体和纯液体的性质计算出来（最小值是饱和液体摩尔体积、最大值是饱和气体摩尔体积），但事实上计算的纯气体性质误差较小，而纯液体的误差较大。因此，液体的p-V-T 关系往往采用专门计算液体体积的公式计算，如修正Rackett 方程，它与立方型状态方程相比，既简单精度又高。 2-9如何理解混合规则？为什么要提出这个概念？有哪些类型的混合规则？ 【参考答案】：对于混合气体，只要把混合物看成一个虚拟的纯物质，算出虚拟的特征参数，如Tr ，
(一) 假定你是红星中学初三学生李华。你的美国朋友Jim在给你的邮件中提到他对中国新近出现的一种共享单车“mobike”很感兴趣，并请你做个简要介绍。请你给Jim回信，内容包括： 1. 这种单车的使用方法(如：APP查看车辆、扫码开锁等); 2. 这种单车的优势; 3. 你对这种单车的看法。 注意：1. 词数不少于80; 2. 开头和结尾已给出，不计入总词数。 提示词：智能手机smartphone, 二维码the QR code 参考范文 Dear Jim, I’m writing to tell you more about the new form of sharing bike mobike mentioned in your latest letter. It’s very convenient to use if you have a smartphone. What you do is find a nearest mobikethrough the APP, scan the QR code on the bike, and enjoy your trip. Compared to other forms of sharing bike, the greatest advantage of mobike is that you can easily find one and never worry about where to park it. It is becoming a new trend as a means of transportation, which relieves the traffic pressure and does good to the environment as well. Hope to ride a mobike with you in China. Yours, Li Hua (二) 最近很多大城市都投放了共享单车(shared bikes)，比如摩拜单车(Mobike)、Ofo共享单车等。由于它们方便停放，骑车也能起到锻炼身体的作用，作为代步工具很受大家欢迎。但是，各地也出现了很多毁车现象，比如刮掉车上的二维码(QR code)、上私锁等。 你对这种现象怎么看?你对共享单车公司有什么建议吗?写一篇符合逻辑的英语短文，80词左右。 参考词汇：bike-sharing companies 共享单车公司，Mobike 和Ofo 是两家共享单车公司，convenience 方便，register登记 参考范文 The shared bikes like Mobike and Ofo bring great convenience to people. You needn’t lock them by simply using your smart phone. They can take you where the subway and bus don’t go. And they can be left anywhere in public for the next user. However, bad things happen. Some people damage the QR code on the bike, or use their own lock, which causes trouble to other users. In my opinion, it’s difficult to turn these people’s ideas in a short time. Therefore, bike-sharing companies like Mobike and Ofo need to do something. For example, those who damage the bike should pay for their actions. Also, because people use their real name toregister as a user, it’s a good way to connect to one’s personal credit. In the end, what I want to say is to take good care of public services. (三) 共享单车(bicycle sharing)已成为时下最热的话题之一，请你就这一话题写一篇短文。内容须包括三方面：1. 共享单车蓬勃发展，成为社会热潮;2. 共享单车带来便利，但也存在问题;3. 我对解决问题的建议。 参考范文 Bicycle Sharing With the development of technology, bicycle sharing comes into people's lives. It becomes more and more popular and much news reported it. At the same time, we should see that there are some problems caused by bicycle sharing. On one side, bicycle sharing makes it very convenient of people traveling. You can find a bicycle anywhere at any time when you want to go out for a cycling, and the price of one trip is very low. It can save time for people. On the other side, its management is not perfect. Even kids can open the lock and ride the bicycle, there is no doubt that such behavior is very dangerous.
三分钟励志拼搏演讲稿 亲爱的老师，同学们： 大家好！ 人生是一场戏，是一场不需别人演唱和吹奏的戏。你就是演唱者，你就是吹奏员。等待你的或是兴奋的喝彩，或是无奈的叹息；人生是一场梦，是一场丰富多彩而又曲折宛转的梦。它不须别人的编织与装点，你就是编织者，编出来的或是绚丽多彩，或是枯萎变形；人生是一碗药，是一碗苦在嘴里，甜在心中的药。不要怕刚开始有多苦，有多么地难喝，因为良药苦口。无须计较眼前的苦，重在以后的甜。当你品完这碗药时，你将会获得人生无穷尽的甜！人生是一条崎岖的山路，它不可能让你毫无阻碍地走下去，但只要你脚踏实地，你必将冲破种种险阻，到达胜利的那头；人生是一条波涛汹涌的长河，你随时都有被惊涛骇浪覆灭的可能。但只要你有信心、有毅力，把握航向，你必将到达胜利的彼岸。 人生到底是何物？ 人生是考验？是前世的冤孽？还是说不清、道不完的故事？不，人生是一次表现，一次拼搏。人生不会是平坦的大道，它不会主动给你指明方向，完全靠你自己！
美国大萧条时代的詹姆士屡屡失业。一家人苦苦挣扎，靠着政府的救济金，才勉强没有死于饥饿。对于詹姆士来说。他的出路就是打拳。以养活老婆和3个孩子。最后。这个多年没打过拳、对拳击台已非常陌生的男人，决定重操旧业，为家人、为自己的尊严而战斗。 一直以来。詹姆士只不过是个平庸的拳手。但是这一次，他却一路走到最后。还出乎所有人的意料，拿到了丰厚的奖金并夺得了拳王的称号！在记者招待会上。有人问詹姆士。是什么让他变得如此之强？詹姆士轻声说：“因为。我的心里清楚地知道。自己要什么！”当记者询问是什么时。他简单地说了两个字：“牛奶！”平静语气中道出的两个字。包含了詹姆士对妻子儿女深厚的爱。 如果不是因为穷困到连牛奶也买不起。我想詹姆士永远也得不到拳王的称号，会一生都是个毫无建树的拳击手。虽然现在大多数人都不必因饥饿而挣扎。也不必踏上危险的拳击场。但是生活中的挑战却随处可见。我们的对手没有电影里主人公的对手那么显而易见。不是一个戴拳套的壮汉。但是它却极不容易对付。我们要与之战斗的。是我们甘于安稳生活的心理！
1、请解释为什么在非理想环境下,当计算期望现值时,无须进行估计?请解释为什么在非理 想环境下，必须在相关和可靠之间进行权衡？在你的答案中，请定义这两个术语。 P25—8 在非理想环境下，确定一整套的自然事件及其相关的现金流是非常困难的，因为有那么多的事件会发生，他们将影响未来事件的实现并导致相应的现金流。即使能够确定一整套合理的事件组合，仍然会存在困难，因为可观察的事件发生的概率我们也无法获得。这些概率必须要进行客观的估计，但是这些就会产生偏差的可靠性问题和准确度缺失问题。此外，并不一定能给出一个固定的利率。虽然期望现值仍然可以计算，但是它是一个估计值，因为现金流，概率和利率都是估计的。 P25—10 相关信息是给投资者提供关于一家企业未来经济预期的信息。更具体的讲，相关信息是帮助投资者来估计一项资产的未来现金收入或者是一项债务的未来现金支出，可靠信息是精确和无偏的信息。 当条件为不理想环境时，相关信息就要求估计可能的自然事件及其概率，这些估计在以后回顾起来可能就是不正确的，因此就会成为前期准备中的偏差，因此相关信息就好像是不可靠的。 反过来，可靠信息，例如资本资产的历史成本或者是债务的票面价值，就会失去了相关性，因为它没有包含对未来收入或者支出的预测。在资产的获得或者带息债务产生的时候，历史成本可能是具有一些相关性的，但是资产的价格和利率是时刻变化的，因此，通常情况下可靠的信息蕴含了较少的企业未来经济预期的信息，因为没有预测未来的收入和支出。 因此，一个想保留更多相关性的会计就需要处理更多更大量的自然事件组合以及与之相关的概率。然而，这意味着将会较少的可靠性。因此，关于会计信息的这两个属性必须进行权衡，因为他们是此消彼长的关系。 2、解释财务报表的信息观，它依赖于会计的历史成本基础吗？ P95—1 信息观认为财务报告是向投资者传达有用信息一种途径，然后，投资就需要决定是否使用这一信息来形成他们自己对未来盈利能力和股票收益的后验概率。 信息观与会计的历史成本基础是一致的，但是不依赖于它。基于理论和经验的证据表明历史成本基础的财务报告向投资者提供了有用的信息。但是，没有特别的理由来解释为什么这些信息必须由历史成本基础来提供。RRA（储备确认会计）信息不是历史成本基础的，也不是说明事项和管理层讨论分析（MD&A）的大多数信息。这个信息的本质，就像上面提到的一样，是指投资者在形成他们自己对未来业绩的估计的时候，是被假设成不仅仅使用会计信息，还会使用其它的相关信息，而会计是不会为他们做这些的。披露的特别形式并不重要，重要的仅仅是信息被公开。因此，在有附加信息来补充财务报告的时候，信息观可以用于证明以历史成本作为财务报告的基础是合适的。进而根据有效市场理论就可以保证，通常，投资者是能够合适地理解这一信息。 3、为什么决策有用性建议，在恰当的财务报表中包含更多的价值相关信息，而有效资本市 场理论暗示，报表附注以及其他披露方式同样有效？当会计人员采用计量观时会对相关性、可靠性以及财务报表信息的决策有用性产生什么影响？
2 习题 第1章 绪言 一、是否题 1. 孤立体系的热力学能和熵都是一定值。( 错。 和 ，如一 体积等于2V 的绝热刚性容器，被一理想的隔板一分为二，左侧状态是T ，P 的理想气体，右侧是T 温度 的真空。当隔板抽去后，由于Q ＝W ＝0， ， ，，故体系将在T ，2V ，0.5P 状态下 达到平衡， ， ， ） 2. 封闭体系的体积为一常数。（错） 3. 封闭体系中有两个相 。在尚未达到平衡时，两个相都是均相敞开体系；达到平衡时，则 两个相都等价于均相封闭体系。（对） 4. 理想气体的焓和热容仅是温度的函数。（对） 5. 理想气体的熵和吉氏函数仅是温度的函数。（错。还与压力或摩尔体积有关。） 6. 要确定物质在单相区的状态需要指定两个强度性质，但是状态方程 P=P (T ，V )的自变量中只有一个强度 性质，所以，这与相律有矛盾。（错。V 也是强度性质） 7. 封闭体系的1mol 气体进行了某一过程，其体积总是变化着的，但是初态和终态的体积相等，初态和终 态的温度分别为T 1和T 2，则该过程的 ；同样，对于初、终态压力相等的过程有 。（对。状态函数的变化仅决定于初、终态与途径无关。） 8. 描述封闭体系中理想气体绝热可逆途径的方程是（其中 ），而一位学生认 为这是状态函数间的关系，与途径无关，所以不需要可逆的条件。(错。) 9. 自变量与独立变量是一致的，从属变量与函数是一致的。（错。有时可能不一致） 10. 自变量与独立变量是不可能相同的。（错。有时可以一致） 三、填空题 1. 状态函数的特点是：状态函数的变化与途径无关，仅决定于初、终态 。 2. 单相区的纯物质和定组成混合物的自由度数目分别是 2 和 2 。 3. 封闭体系中，温度是T 的1mol 理想气体从(P ，V )等温可逆地膨胀到(P ，V )，则所做的功为 i i f f (以V 表示)或 (以P 表示)。 4. 封闭体系中的1mol 理想气体(已知 )，按下列途径由T 1、P 1和V 1可逆地变化至P ，则
[标签:标题] 篇一：关于汽车的英语作文 好的 Nowadays, with the rapid improvement of people’s living standards, cars have become an indispensable part of people's lives,so that more and more people have a car of their own, especially in cities. It brings some benefits for us but also causes many problems at the same time. For one thing,there’s no doubt that cars provide much convenience for people to go where they want to quickly and easily. Especially on weekday,driving a car can save a lot of time for us to go to work.When some places are too far away from our home, driving our own car is also convenient, we can go wherever we want. However,for another, too many cars will lead to the pressure of public transport, a series of problems will appear.First of all,it will bring about more air pollution,a large amount of polluted air given off by cars do great harm to our health.What’s more, as the existing roads are not so wide for the increasing number of cars,undoubtedly,traffic jams will become more and more serious. Last but not least, cars also place burden on the public facilities in providing more parking lots. As far as I am concerned,everything has its advantages and disadvantages. It’s high time that effective action must be token to limit the ever growing number of cars, the government should take measures to control the air pollution from the cars. Some roads should be widened and more new roads should be constructed. Only in this way，will people benefit from the popularity of cars. 坏的 Nowadays, with the rapid improvement of people's living standards, cars have become an indispensable part of people's lives,so that more and more people have a car of their own, especially in cities.It brings some benefit for us but also causes many problems at the same time. For one thing,it's no doubt that that cars provide much convenience for people to go where they want to quickly and easily. Especially on weekday,driving a car can save a lot of time for us to go to work.When some places are too far away from our home, driving our own car is also convenient, we can go wherever we want. However,for another, too many cars will lead to the pressure of public transport, a series of problems will appear.First of all,it will bring about more air pollution,a large amount of polluted air given off by cars do great harm to our health .What's more, as the existing roads are not so wide for the increasing number of cars,undoubtedly,traffic jams will become more and more serious. Last but not least, cars also place burden on the public facilities in providing more parking lots. As far as I am concerned,everything has its advantages and disadvantages. It's high time that effective action must be token to limit the ever growing number of cars, the government should take measures to control the air pollution from the cars. Some roads should be widened and more new roads should be constructed. Only in this way,will people benefit from the popularity of cars. 篇二：雅思作文高分范文：私家车的利与弊 智课网IELTS备考资料 雅思作文高分范文：私家车的利与弊
关于人生拼搏的励志演讲稿 【拼搏与成功】 亲爱的老师，同学们： 大家好! 只有拼搏才会成功。铅笔不经历刀削般的疼痛，怎会写出美丽的 文字?种子不经历破壳的疼痛，怎能绽放出甜美的笑容?蛹儿不经历破 茧的挣扎，怎能化蝶，凌飞于天空?我们人类不经过拼搏，怎能成功? 拼搏的奏出了成功的高潮。 林肯的人生路上，到处布满了荆棘和阻石，可谁会想到，在那一 个个挫折后竟是无上的光辉。人生能经历多少次失败?林肯却总能在失 败处顽强地站起来。人生有多少个日子去拼搏?林肯却坚持着永不言弃。他相信花儿败了，有再开的时候，于是他承受住了经常失败的痛苦。 他相信再幸运的水手也会遇到风浪，于是他一次又一次竞选议员，渴 望迎风破浪就能看见雨后灿烂的阳光。于是他坚信了自己的信念，正 视一次次失败，收获一个个经验，换来经久不息的掌声。他的拼搏换 来的是万人崇尊的总理，他对于人生的价值观和对于现代经济的独特 看法更使他成为了一代伟人。如果林肯在其中的任何一次失败中沉沦 下去，他必定不能获得后来的成功与喜悦。 大家都知道“邰丽华”吗?2000年，在富丽堂皇的纽约卡内基音 乐厅，邰丽华领衔主演的《千手观音》，受到全国观众的一致好评。 邰丽华以其“孔雀般的美丽，高洁与轻灵”征服了不同肤色的观众。即使，她是个残疾人。可“台上一分钟，台下十年功。”她将自 己变成一只旋转的陀螺，24小时中除了吃饭和睡觉，其他时间都在舞蹈。每一次跌倒，她都勇敢的站起来，舞蹈就是她的生命，她的一切，哪怕在那雪白的舞裙上染上她的鲜红的血。她也想过放弃，她也有过
退缩，但是她离不开舞蹈。于是，她用心去伴奏，用生命来舞蹈，为 理想而奋斗，让圣洁的灵魂和美妙的舞姿感动了每一位观众。 梅树经过与霜雪的拼搏，开出动人的美丽，她在刻骨的寒风中含 苞怒放。 亲爱的朋友们，努力吧，只有拼搏才会成功! 我的演讲完毕。 谢谢大家! 【拼搏的青春路】 亲爱的老师，同学们： 大家好! 青春年华，似水而逝。钟表上的时针与分针争分夺秒地你追我赶，时间就在这个分一秒中流逝，青春路虽不如所想象的那般美好，但只 要奋力拼搏过，再回首时就不会后悔。 青春就像是挂在门口的风铃，微风吹过，叮当作响，唤醒了我的 心扉。 桌子上堆着高高的习题，我一页一页地做着，题目似乎越来越难，我越想加快进度，却感觉到这些习题偏要和我对着干，它们古怪刁钻 的面孔，越来越陌生，我心里一时有些无助。那些难题们似乎在嘲笑我，看不起我，我冷冷地盯着它们，心里顿时燃起了熊熊的火焰，不 服输的青春斗志蓦然迸发，脑子飞速转动，手下的笔毫不懒怠。一番 较量之后，心中满意的答案终于表现于笔下，我微笑着把这页习题拿 过一边，微风拂过，烦躁无影无踪。盛夏的午后，太阳的金色光辉洒 满了大地，倾听树上的蝉鸣声，细嗅小草的淡雅清香，花儿的浓郁芬 芳在空气中弥漫，心中阴霾一挥而散。 青春就像是悦耳动听的音符，陪我一路奔跑，冲向希望的方向。
化工热力学复习题 一、选择题 1. T 温度下的纯物质，当压力低于该温度下的饱和蒸汽压时，则气体的状态为（ C ） A. 饱和蒸汽 超临界流体 过热蒸汽 2. 纯物质的第二virial 系数B （ A ） A 仅是T 的函数 B 是T 和P 的函数 C 是T 和V 的函数 D 是任何两强度性质的函数 3. 设Z 为x ，y 的连续函数，，根据欧拉连锁式，有（ B ） A. 1x y z Z Z x x y y ?????????=- ? ? ?????????? B. 1y x Z Z x y x y Z ?????????=- ? ? ?????????? C. 1y x Z Z x y x y Z ?????????= ? ? ?????????? D. 1y Z x Z y y x x Z ?????????=- ? ? ?????????? 4. 关于偏离函数M R ，理想性质M *，下列公式正确的是（ C ） " A. *R M M M =+ B. *2R M M M =- C. *R M M M =- D. *R M M M =+ 5. 下面的说法中不正确的是 ( B ) （A ）纯物质无偏摩尔量 。 （B ）任何偏摩尔性质都是T ，P 的函数。 （C ）偏摩尔性质是强度性质。 （D ）强度性质无偏摩尔量 。 6. 关于逸度的下列说法中不正确的是 ( D ) （A ）逸度可称为“校正压力” 。 （B ）逸度可称为“有效压力” 。 （C ）逸度表达了真实气体对理想气体的偏差 。 （D ）逸度可代替压力，使真实气体的状态方程变为fv=nRT 。 （E ）逸度就是物质从系统中逃逸趋势的量度。 7. 二元溶液，T, P 一定时,Gibbs —Duhem 方程的正确形式是 ( C ). a. X 1dlnγ1/dX 1+ X 2dlnγ2/dX 2 = 0 b. X 1dlnγ1/dX 2+ X 2 dlnγ2/dX 1 = 0 ` c. X 1dlnγ1/dX 1+ X 2dlnγ2/dX 1 = 0 d. X 1dlnγ1/dX 1– X 2 dlnγ2/dX 1 = 0 8. 关于化学势的下列说法中不正确的是( A ) A. 系统的偏摩尔量就是化学势 B. 化学势是系统的强度性质 C. 系统中的任一物质都有化学势 D. 化学势大小决定物质迁移的方向 9．关于活度和活度系数的下列说法中不正确的是 ( E ) （A ）活度是相对逸度，校正浓度,有效浓度；(B) 理想溶液活度等于其浓度。 （C ）活度系数表示实际溶液与理想溶液的偏差。（D ）任何纯物质的活度均为1。 （E ）r i 是G E /RT 的偏摩尔量。 10．等温等压下，在A 和B 组成的均相体系中，若A 的偏摩尔体积随浓度的改变而增加，则B 的偏摩尔体积将（B ） A. 增加 B. 减小 C. 不变 D. 不一定 " 11．下列各式中，化学位的定义式是 ( A ) 12．混合物中组分i 的逸度的完整定义式是（ A ）。 A. d G ___i =RTdln f ^i , 0lim →p [f ^i /(Y i P)]=1 B. d G ___i =RTdln f ^i , 0lim →p [f ^ i /P]=1 C. dG i =RTdln f ^i , 0lim →p f i =1 ； D. d G ___i =RTdln f ^i , 0lim →p f ^ i =1 j j j j n nS T i i n T P i i n nS nV i i n nS P i i n nU d n nA c n nG b n nH a ,,,,,,,,])([.])([.])([.])([.??≡??≡??≡??≡μμμμ
奋斗主题励志演讲稿三篇 奋斗主题励志演讲稿三篇 青春一个如彩虹般的阶段，一个值得拥有的阶段，她充满了酸，甜，苦，辣。激扬青春，真我风采;激扬青春，放飞理想;激扬青春，畅想未来。下面wtt和大家分享奋斗主题励志演讲稿。仅供参考，欢迎大家喜欢阅读。 篇一 各位领导、各位评委、各位青年朋友们:大家好! 我叫xx，很高兴能够和大家一起探讨追求卓越，奉献青春，这个话题，今天我要演讲的题目是《甘于奉献，点燃烈火青春》。 让青春烈火燃烧永恒，让生命闪电划过天边，用所有热情换回时间，让年轻的梦没有终点!我非常欣赏《烈火青春》里面的这段话，并一直用它激励自己的学习、工作和生活。我认为，青春就应该燃烧，发出亮光才有价值!人的一生可能燃烧也可能腐朽，既然这样，我不愿腐朽，也不能腐朽，我愿意燃烧起来!在座的朋友们!你们愿意吗? 青春，是我们一生中最美丽的季节，她孕育着早春的生机，展现着盛夏的热烈，暗藏着金秋的硕实，昭示着寒冬的希望，充满诗意而不缺乏拼搏的激-情，时尚浪漫而又饱含着奋斗的艰辛。当一个人的青春融汇到一个时代、一份事业中，这样的青春就不会远去，而这份
事业也必将在岁月的历练中折射出耀眼的光芒。 说到这里，我想起了这样一句话:“有的人活着，他已经死了;有的人死了，他还活着。”生命的意义在于活着，那么活着的意义又是什么呢?当然不是为了活着而活着，答案只有两个字，奉献!我们可以设想一下，不付出、不创造、不追求，这样的青春必然在似水年华中渐渐老去，回首过往，没有痕迹，没有追忆，人生四处弥漫着叹息。我想，这绝对不是我们存在的意义。古往今来，有无数能人志士在自己的青春年华就已经成就了不朽的人生，在这里我来不及一一列举。可是，有一个人的名字我却不能不提，他是我们永远的学习榜样，一个最平凡最无私也是最伟大的人。大家知道他是谁吗?这个传奇人物就是雷锋，他告诫我们说:“青春啊，永远是美好的，可是真正的青春，只属于那些永远力争上游的人，永远忘我劳动的人，永远谦虚的人!”我想在座的每一位包括我自己都可以成为这样的人。 实话，三年前，我刚来工作的时候也有过失落和茫然，感觉现实不尽如人意，感觉离曾经的梦想总是有一些距离，一度陷入困惑之中。可是，青春的我是一把刚铸好的刀，不容得你有片刻的等待和迟疑。我决不能眼睁睁看着这把刀慢慢氧化，失去光泽，随即斑驳、锈蚀、风化，最后成为一块废铁。我告诉自己，“只要你是金子，就能放光，只要你斗志昂扬的面对生活、面对工作，你就会有所获得。”路漫漫其修远兮，吾将上下而求索。青春是学习的季节，青春是奋斗的岁月，不要停止我们前进的步伐，因为青春的路正长。有空的时候静下心来好好看看书，回头想想自己走过的路，为自己的人生做好一个规划，
《高级财务会计》习题答案 第一章非货币资产交换 1、2007年5月，A公司以其一直用于出租的一幢房屋换入B公司生产的办公家具准备作为办公设备使用，B公司则换入的房屋继续出租。交换前A公司对该房屋采用成本模式进行后续计量，该房屋的原始成本为500 000元，累计已提折旧180 000元，公允价值为400 000元，没有计提减值准备；B公司换入房屋后继续采用成本模式进行计量。B公司办公家具账面价值为280 000元，公允价值与计税价格均为300 000元，适用的增值税税率为17%，B公司另外支付A公司49 000元的补价。假设交换不涉及其他的相关税费。 要求：分别编制A公司和B公司与该资产交换相关的会计分录。 A公司的会计处理： 49 000/400 000=12.25%，所以交换属于非货币资产交换。 换入设备的入账价值=400 000-（300 000×17%）-49 000=300 000元 换出资产应确认的损益=400 000-320 000=80 000元 借：固定资产清理320 000 累计折旧180 000 贷：投资性房地产500 000 借：固定资产——办公设备300 000 银行存款49 000 应交税金—增值税（进项）51 000 贷：固定资产清理320 000 其他业务收入（投资性房地产收益）80 000 B公司的会计处理 换入设备的入账价值=300 000+300 000×17%+49 000=400 000元 换出资产应确认的损益=300 000-280 000=20 000元 借：投资性房地产400 000 贷：主营业务收入300 000 应交税金——增值税（销项）51 000 银行存款49 000 借：主营业务成本280 000 贷：库存商品280 000 2、2007年9月，X公司生产经营出现现金短缺，为扭转财务困境，遂决定将其正在建造的一幢办公楼及购买的办公设备与Y公司的一项专利技术及其对Z公司的一项长期股权投资进行交换。截止交换日，X公司办公楼的建设成本为900 000元。办公设备的账面价值为600 000元，公允价值为620 000元；Y公司的专利技术的账面价值为400 000元，长期股前投资的账面价值为600 000元。由于正在建造的办公楼的完工程度难以合理确定，Y公
化工热力学习题集(附标准答案)
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模拟题一 一．单项选择题（每题1分，共20分） 本大题解答（用A 或B 或C 或D ）请填入下表： 1. T 温度下的纯物质，当压力低于该温度下的饱和蒸汽压时，则气体的状态为（C ） A. 饱和蒸汽 B. 超临界流体 C. 过热蒸汽 2. T 温度下的过冷纯液体的压力P （ A ） A. >()T P s B. <()T P s C. =()T P s 3. T 温度下的过热纯蒸汽的压力P （ B ） A. >()T P s B. <()T P s C. =()T P s 4. 纯物质的第二virial 系数B （ A ） A 仅是T 的函数 B 是T 和P 的函数 C 是T 和V 的函数 D 是任何两强度性质的函数 5. 能表达流体在临界点的P-V 等温线的正确趋势的virial 方程，必须至少用到（ ） A. 第三virial 系数 B. 第二virial 系数 C. 无穷项 D. 只需要理想气体方程 6. 液化石油气的主要成分是（ A ） A. 丙烷、丁烷和少量的戊烷 B. 甲烷、乙烷 C. 正己烷 7. 立方型状态方程计算V 时如果出现三个根，则最大的根表示（ B ） A. 饱和液摩尔体积 B. 饱和汽摩尔体积 C. 无物理意义 8. 偏心因子的定义式（ A ） A. 0.7lg()1 s r Tr P ω==-- B. 0.8lg()1 s r Tr P ω==-- C. 1.0lg()s r Tr P ω==- 9. 设Z 为x ，y 的连续函数，，根据欧拉连锁式，有（ B ） A. 1x y z Z Z x x y y ???? ?????=- ? ? ?????????? B. 1y x Z Z x y x y Z ????????? =- ? ? ?????????? C. 1y x Z Z x y x y Z ????????? = ? ? ?????????? D. 1y Z x Z y y x x Z ????????? =- ? ? ?????????? 10. 关于偏离函数M R ，理想性质M *，下列公式正确的是（ C ） A. *R M M M =+ B. *2R M M M =- C. *R M M M =- D. *R M M M =+ 11. 下面的说法中不正确的是 ( B ) （A ）纯物质无偏摩尔量 。 （B ）任何偏摩尔性质都是T ，P 的函数。 （C ）偏摩尔性质是强度性质。（D ）强度性质无偏摩尔量 。 12. 关于逸度的下列说法中不正确的是 ( D ) （A ）逸度可称为“校正压力” 。 （B ）逸度可称为“有效压力” 。 （C ）逸度表达了真实气体对理想气体的偏差 。 （D ）逸度可代替压力，使真实气体 的状态方程变为fv=nRT 。 （E ）逸度就是物质从系统中逃逸趋势的量度。 题号 1 2 3 4 5 6 7 8 9 10 答案 题号 11 12 13 14 15 16 17 18 19 20 答案
汽车的重要性《英语作文》 The automobile has become one of the most important means/ways of transportation in the world since it was invented. The automobile has completely changed the lifestyles of almost all the people in the world. In the past, animals like horses and camels were used for traveling and transporting goods. Automobiles are more comfortable and faster. Automobiles have also made it possible for us to transport large quantities of goods and people at the same time. Besides, the invention of the automobile has provided jobs for millions of people all over the world. 翻译： 汽车已经成为世界上最重要的交通工具之一，因为它是发明的。汽车已经完全改变了世界上几乎所有的人的生活方式。 在过去，像马和骆驼的动物被用来运送货物。汽车更舒适，更快速。汽车也使我们能够在同一时间运送大量货物和人。 此外，汽车的发明为全世界上百万的人提供了工作。