Uranium enrichment determination by high-energy photon interrogation

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朝鲜半岛重新开战？ - FT中文网视频听写稿

There is been an escalation of tensions today on the Korean peninsula with the North Korean military and the South Korean military triggering artillery blushes. Last count, we have 2 dead and some 20 injured. We just heard from the Reuters that the UN security Council is likely to gather for an emergency meeting in the next couple of days. With me here is James Bleeds, the FT’s diplomatic editor. James, very simple question, are we seeing a resumption of war on the Korean peninsula?Well, this is certainly the most serious incident that happened for a while because for the first time we are seeing brushes being traded from land. You’ve see skirmishes at sea. Of course, of course earlier this year, the North Korea sank a South Korean ship with a lost of more than 40 lives. But this is a more serious one because it’s at land it also come of course, a day after North Korea effectively revealed that it has an uranium enrichment facility which is significantly speeding up its process to create nuclear weapon. So enormous round of tension is now developing clearly between North and South.What do you think is the reactions that we gonna see from the South Koreans here? Well, the () of things in the past, the North Korea does a major kind of incursion and the South shows restraint. One of the main reasons I think why the South does show restraint is that it knows all out the war fair between the two sides being absolutely catastrophe. From the North Korean point of view, they know, if they know anything, they can’t possibly win a kind conventional war against the South. They have about a million under arms but it’s not a strong army, doesn’t have strong access to things like fuel and supplies. It doesn’t have conventional forces. The South would win easily. The South has 30 thousand US troops. The problem for the South is that any victory against the North would be a completely () victory. So the South Korean capital is only 25 kilometers from the demilitarized zone that separates North and South. So the North would the very least be able to do a massive artilary against the Seoul population. The estimates are that about half a million people would die in all-out war against North and South. So the idea is that there could actually being a all-out war would be pretty much unthinkable..What is the North Korea up to here? What is it caused this?I think there are two things that people think are happening, the first is obviously a succession taking place, from Kim Jiongri to Kim joingwoo, in the North, his son. And what is being done is a kind of show of a strength that happening both on the nuclear side and the on conventional military side to sort of underpin that succession with others people possibly in North Korea not want that to happen. The other thing that the North Korea probably wanting to do is to show the US and China that it is still a big play and still do lots of things that they don’t like. They want to lead towards the resumption of the 6-party talks which were abandoned April last year. What they effectively want is to end sanctions, more economic support but ability to retain parts of their nuclear programs. This is to try to underpin that position.You mentioned China. How does China’s react is to appeal calm today so far. But whether they go from here?China is clearly a big play on this. On the one hand, China is by far and way the North Korea’s closest support that have its historical linked back to the regional Korean war in the 1950s when China supported the North. It also has a big trade relationship. China is very concerned in particular about the North regime is not stabilized. It has a 800 miles ofborers. It doesn’t want to see a huge refugee crisis developing if the North would collapse. So it has been very supportive to the Kim Jiongri regime. Nevertheless, China does not want to see unplanned and difficult escalations of that kind the North is doing. And so it may reaction very badly and toughly what the North is doing.James, just briefly, the US potion, how is US gonna react?The US’s fundamental concern is nuclear proliferation. Up till now, it has been very firm, not wanting to deal with North Korea, not wanting the resumption of the 6-party talks. It wants the fullest possible verification of what the North Korea is doing. But ultimately, the ball is on the China’s court. What China does,the UN as you mentioned at the start, UN Security Council. () response is will be absolutely critical in determining whether this escalates or not.Just quickly on Iran, another so called rogue nuclear state. We get the regular report of the IAEA nuclear inspectors today. What’s that gonna show us?The advance brief report suggests that Iran has had quite a number of difficulties with its nuclear program. And suggestion, this is speculation is that the stuxnet virus which people have been talking about earlier this year a kind of cyber war fair worm may have done some damage. If you like, the contrast you got today is that the North Korea crisis is really developing and lots of concerns about their uranium enrichment plans. Conversely, Iran seems to be having more and more problems developing its nuclear facilities. The question is whether we actually see a () towards even more serious problems for Iran.。

宁波理工学院外语平台第四学期阅读答案

was the one field of awareness about which humans had anything more than the vaguest of insights. It is impossible to know today just what our Stone Age ancestors knew about plants, but from what we can observe of preindustrial societies that still exist, a detailed learning of plants and their properties must be extremely ancient. This is logical. Plants are the basis of the food pyramid for all living things, even for other plants. They have always been enormously important to the welfare of people, not only for food, but also for clothing, weapons, tools, dyes, medicines, shelter, and a great many other purposes. Tribes living today in the jungles of the Amazon recognize literally hundreds of plants and know many properties of each. To them botany, as such, has no name and is probably not even recognized as a special branch of "knowledge" at all. Unfortunately, the more industrialized we become the farther away we move from direct contact with plants, and the less distinct our knowledge of botany grows. Yet everyone comes unconsciously on an amazing amount of botanical knowledge, and few people will fail to recognize a rose, an apple, or an orchid. When our Neolithic（新石器时代）ancestors, living in the middle East about 10,000 yearsago, discovered that certain grasses could be harvested and their seeds planted for richer yields the next season, the first great step in a new association of plants and humans was taken. Grains were discovered and from them flowed the marvel of agriculture: cultivated crops. From then on, humans would increasingly take their living from the controlled production of a few plants, rather than getting a little here and a little there from many varieties that grew wild---and the accumulated knowledge of tens of thousands of years of experience and intimacy with plants in the wild would begin to fade away.-------------------------------------------------------------------------------- 1. Which of the following assumptions about early humans is expressed in the passage? A . They probably had a detailed learning of plants. B . They enjoyed the study of welfare. C . They attached much importance to their property. D . They thought that cultivating crops were not important. 正确答案:They probably had a detailed learning of plants. 题目详解:根据问题中…assu mptions about early humans is expressed‟的提示，从第1 段的第3 句中…a detailed learning of plants and their properties must be extremely ancient‟提供的信息判断，选项中的"Theyprobably had a detailed learning of plants" 符合题意。

土壤污染及防治(英语)

3
Soil pollution hazards and the status quo
4
Of soil pollution prevention and control measures
First, the concept of the characteristics of the soil pollution
2 air pollution
Atmospheric pollution can be divided into two categories: gas pollution, such as sulfur dioxide, fluoride, ozone, nitrogen oxides, hydrocarbons, etc.; aerosol pollution, such as dust, soot and other solid particles and liquid smoke, fog and other particles, they are by sedimentationor precipitation into the soil and cause pollution.
What is soil pollution？
Soil pollution harmful toxic substances into the soil beyond the self-purification capacity of the soil, resulting in soil physical, chemical and biological properties change, reducing crop yields and quality, the phenomenon of harm to human health. From the perspective of environmental science to define soil pollution is the waste and toxic and hazardous substances into the soil over the soil selfpurification capacity, destruction of the state of the natural balance of the soil system completely soil quality deterioration or recession phenomenon.

分光光度法测定维生素C的含量外文翻译原文

1 IntroductionVitamin C occurs in different concentrations in a vari-ety of natural samples. It is added to several pharma-ceutical products as an essential ingredient, a stabilizer for vitamin B complex, and as an antioxidant.Consequent upon its desirable effects, it is widely used in the treatment of certain diseases such as scurvy,common cold, anemia, haemorrhagic disorders, wound healing, and even infertility, to mention some stark cases. It is considered essential for the development and regeneration of muscles, bones, teeth and skin.The increasing use of pharmaceuticals and other natural samples containing vitamin C has meant that the practi-cising chemists should develop analytical procedures for its determination which are simple to operate, rapid,accurate, sensitive and selective. The desire to develop methods with ideal characteristics has resulted a large number of procedures with varying applicability. Many instrument-based analyses including fluorometry 1–4,HPLC 5–10, polarography 11–13and enzymatic 14,15methods are reported in the literature. But due to their inherent limitations, these techniques are not commonly used for routine analyses. However, photometric methods are particularly attractive because of their speed and sim-plicity. Consequently, a large number of such proce-dures have been developed for the determination of ascorbic acid (AA). Though some short reviews 16–18have been reported, a critical assessment of these meth-ods is desirable to examine their salient features and utility. This review is an attempt to assess exclusively the existing spectrophotometric methods for the deter-mination of vitamin C as regards their simplicity, rapid-ity, Beer’s law range, sensitivity, selectivity and applic-ability. It is primarily based on the information collect-ed through the Chemical Abstracts for the period 1970to mid-1997.2 Results and DiscussionSeveral dyes such as 2,6-dichlorophenolindophenol (DCIP), dimethoxydiquinone (DMDQ), ninhydrin, fast red AL salt and 2′,7′-dichlorofluorescein etc . have been used for the determination of vitamin C. Among these dyes, DCIP has been most extensively studied. It is included in the official titrimetric methods as reported in different pharmacopoeias 19–21and it also forms the basis of many colorimetric methods. The blue dye DCIP is reduced to the colorless form on addition of ascorbic acid as shown in Fig.1, but it gives a pink color to the acidic solutions. Using the dye, ascorbic acid present in human urine 22and processed potatoes 23has been determined. The excess dye can be extracted with xylene or butanol.24Many substances which are capable of reducing the dye resulting from the prepara-tion and processing of food samples interfere. Flow dialysis proposed by Gary et al .25and continuous flow systems have been used to monitor the decrease in absorbance of DCIP. Such automated systems appear to be justified only when routine analysis of a largeANALYTICAL SCIENCES OCTOBER 1998, VOL. 14Photometric Methods for the Determination of Vitamin CSatya P. A RYA †, Meenakshi M AHAJAN and Preeti J AINDepartment of Chemistry, Kurukshetra University, Kurukshetra –136119, Haryana State, IndiaThe importance of vitamin C to the human body is widely acknowledged throughout the globe. The deficiency of this vitamin leads to various diseases. In view of its importance, numerous methods including spectrophotometric ones have been developed for its determination in pharmaceuticals, foods and biological samples. A comprehensive review of the available spectophotometric methods for the determination of ascorbic acid is presented.Keywords Vitamin C determination, spectrophotometric method†To whom correspondence should be addressed.Fig.1The reduction of DCIP with ascorbic acid.Ascorbic acidDCIP(Oxidized, Blue-Pink)Dehydroascorbic acid DCIP (Reduced, Colorless)number of samples is needed; otherwise it is tedious to use for a single estimation.Dimethoxydiquinone 26gives a violet-colored product with ascorbic acid in a phosphate buffer (pH 6.6). The reduced “indigoid” quinhydrone form is perhaps responsible for the formation of violet-colored product as shown in Fig. 2. After diluting with dioxane,absorbance of the colored solution which is stable over 24 h only under dark conditions is measured at 510 nm.Heating leads to a decrease in color intensity. Beer’s law holds good up to 80 µg ml –1with a detection limit of 10 µg ml –1. Riboflavin and copper interfere. The interference of iron(II) sulfate responsible for precipita-tion can be removed by centrifugation. Though the method is not sufficiently sensitive (ε=1.62×103), it can still be applied to the analysis of citrus fruits 27after extracting the colored product into chloroform (λmax =530 nm). Lin et al .28and Pandey 29reported pro-cedures based on the reaction of ascorbic acid with fast Red AL salt (1)(zinc chloride salt of diazotized 1-aminoanthraquinone) and tetrachlorobenzoquinone (2).The reaction of (1)proceeds in acid medium but the blue color develops only after the addition of alkali,which exhibits three absorption bands between 500–630 nm. If one uses the latter reagent (2), ascorbic acid is determined at 336 nm (ε=535 cm 2mol –1) via a decrease in absorbance of 7×10–4M tetrachlorobenzo-quinone (chloranil) in 80% acetone –water (v/v) medi-um. With these methods, mixtures of ascorbic acid with thiols like o -mercaptobenzoic acid, mercaptosuc-cinic acid, 3-mercaptopropionic acid can not be resolved.Methylene Blue 30, (3)and ninhydrin 31,32(4)find applications with the determination of ascorbic acid in food products. The colorless form of the dye (3)is extracted into chloroform after its reduction with ascor-bic acid; back oxidation of the dihydro derivative to Methylene Blue has been used for the assay of ascorbic acid (λmax =653 nm). The method is reported to be highly sensitive. The reaction of ascorbic acid with ninhydrin carried out on a boiling water bath using 80% aqueous solution as a medium in 0.01 M NH 4OH is used for its determination in pharmaceuticals (λmax =415 nm), but without added advantages.In the sixties, many methods based on the coupling of ascorbic acid with aniline diazonium salts were report-ed. A purplish or blue colored species is produced by these salts with ascorbic acid in alkaline medium.Diazotized-4-methoxy-2-nitroaniline couples withascorbic acid in oxalic acid medium in the presence of ethanol or isopropanol, giving a purplish color in alka-line solutions. Though Fe(II), Sn(II) and dehydroascor-bic acid (DHAA) do not interfere, the presence of reductones and reductic acid requires formaldehyde condensation. Low contents of vitamin C in the pres-ence of flavanoids and pectic substances are also detected. The reaction of ascorbic acid with 4-nitrobenzene diazonium fluoroborate in acetic acid medium was used for its determination at λmax 415 nm.But the mixture has to be kept for 25 min in the dark,followed by the addition of sodium hydroxide. The sensitivity of a large number of stabilized diazonium salts was evaluated; diazotized 4-nitroaniline-2:5-dimethoxy-aniline was found to give the most intense color reaction.Enzymic 33–35colorimetric determinations of ascorbic acid in commercial vitamin C tablets and in fruits and vegetables were made by measuring the absorbance at 358 nm or 320 nm of the resulting products obtained by oxidation of o -phenylenediamine/1,4-diaminobenzene using ascorbate oxidase or peroxidase in presence of H 2O 2at pH 5.3. Ascorbic acid is determined after oxi-dation with mercuric chloride and condensing the DHAA with 4,5-disubstituted phenylenediamine 36,which gives the quinoxaline derivative used for absorbance measurement. The method involving 4-nitro-1,2-phenylenediamine 37(λmax =375 nm) is very complex and laborious, since it involves many time-consuming steps including purification of the sample with anionic Sephadex column.In the recent past, the determination of oxidized and reduced vitamin C in pharmaceuticals, foods and bio-logical samples has gained importance since AA and DHAA redox couple is an important component of many biological systems. Simultaneous measurement of both AA and DHAA using HPLC has been carried out by various workers 38–45in different laboratories.Rose and Nahrwold 38determined AA and DHAA by monitoring UV absorbance at 254 nm and 210 nm respectively for the analysis of foods, biological sam-ples and pharmaceutical preparations. Graham and Donald 39have carried out the analysis at 254 nm after extracting the food samples with 62.5 mM metaphos-phoric acid using an ion exchange column (Aminex-HPX 87H). Both these forms have also been deter-mined in vegetable samples 40using a UV detector (254nm). Yasui and Hayashi 41made such determinations by converting to compounds having λmax at 300 nm under alkaline conditions. Derivatization of DHAA is accel-erated in the presence of sodium borohydride.Validation of the micromethod for the determination of the oxidized and reduced vitamin C in plasma by HPLC fluorescence method has been reported by Tessier et al .45These methods are useful and a single step HPLC assay of such detections has been helpful in overcoming the burden of derivatization.Ascorbic acid gives colored species with substituted benzene such as m -dinitrobenzene 46in formaldehydeFig.2Reduction reaction of dimethoxydiquinone (DMDQ).‘Indigoid’quinhydroneDMDQand trinitrobenzene47in tartrate buffer when studied for its determination over the concentration ranges 2–50 and 0–125 µg ml–1of ascorbic acid respectively. Methanolic solution of resorcinol48gives a pale yellow color (λmax=425 nm) with ascorbic acid in hydrochloric acid medium, obeying Beer’s law for 80–400 µg ml–1. 4-Chloro-7-nitrobenzofurazane49forms a bluish green colored species with ascorbic acid in presence of 0.2 M sodium hydroxide. The absorbance is measured at 582 nm after diluting the reaction contents with 50% (v/v) aqueous acetone solution. Beer’s law is obeyed in the concentration range 5–20 µg ml–1. The colored prod-uct is stable for 30 min only when kept away from direct sunlight or artificial day light. The method is reported free from the interference of all other vitamins and minerals present in multivitamin preparations and can be applied to the analysis of pharmaceuticals, fresh fruit juices and vegetables.Hashmi et al.50proposed a method based on the reac-tion of 2,3,5-triphenyltetrazolium chloride with ascor-bic acid in alkaline medium. The pink solution is allowed to stand in the dark for 30 min at 25˚C; it obeys Beer’s law over the range 5–25 µg ml–1. Sugars (>15 µg ml–1) except sucrose interfere by forming a similar color to that of the reagent. Riboflavin, cyanocobalamin and folic acid interfere due to their own color. Beutler et al.51,52investigated the use of methylthiazolyltetrazolium salt in presence of ascorbate oxidase enzyme and 3-(4,5-dimethylthiazolyl-2-yl)-2,5-diphenyltetrazolium chloride or bromide in the pres-ence of 5-methylphenazinium methyl sulfate (electron carrier) at pH 3.5 for the determination of ascorbic acid in foods, fruit juices and vegetables juices. These reac-tions involve the formation of formazon (λmax=578 nm). The interference of sulfur dioxide requires treat-ment with formaldehyde, and color interference from dark juices is removed by decolorization with 1% polyvinylpolypyrrolidone before filtration. Sorbitol, alcohol and oxalate interfere with the ascorbic acid oxi-dase. However, the effect of oxalate can be checked by adding a slight excess of Ca(II) ions. Other derivatives such as 2,5-diphenyl-3-thiazolyl tetrazolium chloride53 at pH 12.2, 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium chloride at pH 10.5 (λmax=540 nm) and 2,2′,5,5′-tetra-(4-nitrophenyl)-3,3′-(3,3′-dimethoxy-4,4′-biphenyl)ditetrazolium chloride54have also been employed for the assay of ascorbic acid.The coupling of 2,4-dinitrophenylhydrazine (DNPH) with ketonic groups of DHAA and diketogulonic acid (DKGA) has been the basis of many methods for the determination of total vitamin C contents. Proteins present in the samples are precipitated by adding trichloroacetic acid (TCA) and aliquots of filtrate are shaken with acid–washed charcoal (norit) or activated charcoal55to clarify the solutions and to oxidize AA to DHAA. A reducing medium is produced by adding thiourea prior to DNPH addition, otherwise unspecific coloration is given by oxidants. The osazones (λmax=545 nm) thus formed during the 3 h incubation at 37˚C by the reaction of DNPH and DHAA are dis-solved by adding 85% H2SO4. Vitamin C can be extracted with metaphosphoric acid–stannous chloride solution without charcoal treatment for differential determination of DKGA, DHAA and AA in the same tissue extracts. The interference of sugars can be mini-mized by carrying out incubation at 15˚C and measur-ing the absorbance only after adding sulfuric acid for 75 min.56The use of several acid mixtures has been proposed for replacing the tedious dropwise addition of sulfuric acid. Lack of specificity is found with many of these methods; interfering osazones can be separated by chromatographic methods such as TLC57and HPLC58, but at the cost of making these procedures tedious and cumbersome. The nature of DNPH meth-ods for total vitamin C also makes it amenable to auto-matic flow through analyses.59–61 Phenylhydrazinium chloride62produces a yellow color (λmax=395 nm) when treated with ascorbic acid in0.1 M HCl medium. The reaction contents are kept for1 h in an incubator or water bath at 50±2˚C, thus mak-ing the method time-consuming. Beer’s law is obeyed in the range 25–100 µg of ascorbic acid. No interfer-ence is observed from other vitamins, minerals, glucose, sucrose, excipients and reducing agents. However, the presence of excessive amounts of riboflavin requires the addition of 0.5 g talc, which imparts a yellow color to the solution. 3-Methyl-2-benzothiazolone hydrazone63reacts in the presence of sodium metaperiodate to form a blue colored solution (λmax=630 nm) which helps in the determination of ascorbic acid over the range 6–14 meq ml–1.Wang64suggested the use of potassium iodate for the determination of vitamin C in pharmaceuticals. The absorbance is measured either in the UV region (288 nm) or in the visible region (445 nm). Besides aqueous phase measurements, the yellow precipitate can be extracted into chloroform65(λmax=514 nm). The ICl2–generated in the oxidation of AA by iodate66in acid medium in the presence of Cl–ions has been used to iodinate 2′,7′-dichlorofluorescein dye. The iodinated dye (λmax=525 nm) obeys Beer’s law up to 300 µg (ε=8.81×103). Soft drinks67have been analyzed using the reaction of iodine in an acetic acid medium (λmax= 350 nm). Sirividya and Balasubramanian68reported an indirect procedure based on the oxidation of ascorbic acid by a known excess of iodate in the presence of acid for the analysis of pharmaceuticals and fresh fruit juices. The unreacted iodate is used for hydroxylamine oxidation to generate nitrite, which is then diazotized with sulfanilic acid. The resulting diazonium salt is coupled with N-(1-naphthyl)ethylenediamine dihy-drochloride to form an azo dye (λmax=540 nm). The procedure is a complicated one as it involves many steps.The reaction of hexacyanoferrate(III)69(5)was used for the determination of micro quantities of vitamin C by measuring the decrease in color intensity of the reagent (5)(λmax=420 nm) in McIlvaine buffer (pH 5.2)solutions. Beer’s law is restricted within the range 180–270 µg of AA. A 200-fold amount of glucose, urea,citric acid and tartaric acid; 50-fold excess of creatineand 2-fold excess of creatinine do not interfere, but apositive error is observed even with very small quanti-ties of uric acid. In general, all such reagents thatreduce hexacyanoferrate(III) or oxidize hexacyanofer-rate(II) under experimental conditions interfere.Further the utility of the method is limited to colorlesssolutions. Yet another method involving the oxidationof phthalophenone to phenolphthalein by the reagent(5)in alkaline solution was proposed by Al-Tamrah.70This obeys Beer’s law up to 7 µg ml–1(λmax=553 nm). Sugars are tolerated only in microgram amounts. Therelative standard deviation and detection limit are0.65% and 0.1 µg ml–1respectively.Direct UV spectrophotometry71–73with backgroundcorrection methods such as thermal decomposition, UVlight irradiation, catalytic destruction and alkaline treat-ment has been used for the determination of AA in softdrinks, fruit juices and pharmaceuticals. However, therate of thermal decomposition is found to be very low72and fruit juice samples that are unstable to alkalinetreatment, have fine particles, have a deep coloration orcontain high concentrations of caffeine, saccharin,caramel and tannic acid can not be analyzed. Somemethods based on the Cu(II)-catalyzed oxidation arereported for the assay of pharmaceuticals, fruits andbeverages74–77allowing the determination of AA up to120 µg ml–1at λmax=267 nm. Fe(II) interferes seriously. Only minute amounts of folic acid are tolerated. Thepresence of Al(III), Mg(II) or Zn(II) gives a negativeerror due to their catalytic effect.Some methods involving the coinage metal (Cu, Ag,Au) complexes have been worked out. The reductionof Cu(II) in a biphasic system of isopentyl alcohol andan aqueous solution of pH 4.6 to Cu(I), followed by itscomplexation with cuproine to give a colored complex(λmax=454 nm), was reported by Contreras et al.78for the analysis of foods and vegetables. Fresh fruits andvegetables and dehydrated samples were analyzed afterextracting with 5% HPO3and with a 1:1 mixture of0.5% HPO3and 0.05 M H2SO4respectively. Also thecolored complexes of Cu(I) with 2,2-biquinoline79(λmax=540 nm), rhodanine80(λmax=473 nm) and 2,9-dimethyl-1,10-phenanthroline81–83(λmax=450 nm) have been used to determine ascorbic acid in different sam-ples. However, the method using 2,9-dimethyl-1,10-phenanthroline obeys Beer’s law over the range 2–20µg ml–1, though it requires 1 h waiting time for full color intensity. These methods based on the complex-ation of reduced Cu(I) are rather unselective, since sub-stances such as Fe(II), cysteine, or sodium thiosulfatewhich lead to the reduction of Cu(II) to Cu(I) interfereseriously. The gelatin complexes84,85of Ag(I)(λmax=415 nm; ε=2.2×103) and Au(III) (λmax=540 nm;ε=2.3×103) give colored products on adding AA to their alkaline solutions. The procedure as suggested by Pal et al.84is not interfered with by glycine, alanine, fruc-tose, sucrose, citric acid, tartaric acid or other reducingagents.Analytical applications of Molybdenum Blue formedon reduction of phosphomolybdate complex86, ammoni-um molybdate87–89or molybdic acid90have been report-ed by many workers for the determination of ascorbicacid in pharmaceuticals, fruits and vegetables, pastriesand beverages. Ammonium molybdate–sulfuric acidsystem requires 1 h for complete development of colorwith ascorbic acid.87However, such waiting time canbe decreased to 15 min by the addition of metaphos-phoric acid–acetic acid solution.88The colored speciesobeys Beer’s law over the range 2–32 µg ml–1at 760nm (ε=4.3×104). Serious interferences are observed due to phenolic compounds such as catechins, gallicacid, pyrogallol and gallotannins; thiosulfate ions andthiourea. Recently, P-Sb-Mo heteropoly acid91hasbeen used to produce heteropoly blue (λmax=710 nm) for the assay of ascorbic acid over the range 1–50 µgml–1(ε=3.68×103). The use of folin reagent92and folin phenol93(λmax=760 nm) has also been described for the assay of biological samples after deproteinizing withTCA. Beer’s law is obeyed up to 45 µg ml–1. Thecolor development is not obstructed by bovine serumalbumin, adenine, guanine, thymol and oxyhaemoglo-bin. Folin-ciocalteu94reagent reacts with ascorbic acidto give a blue colored complex (λmax=730 nm) as well. However, the method is time-consuming, as the fullcolor intensity requires 40–50 min. Ammonium meta-vanadate95gives a green color (λmax=680 nm) on heat-ing for 10 min in the presence of ascorbic acid.Though the method has been put to use for the analysisof some samples, it is not sufficiently sensitive.Many spectrophotometric methods based on thereduction of Fe(III) to Fe(II) with ascorbic acid, fol-lowed by the complexation of reduced Fe(II) with dif-ferent reagents, have been reported. Amongst them,α,α′-bipyridyl96–101and 1,10-phenanthroline102–109(o-phen) find extensive use in the development of analyti-cal procedures. Most of these methods are time-con-suming, as full color development is achieved onlyafter waiting for 30–60 min. Micromodification97ofthe procedure applicable to human plasma and animaltissue has been reported without the interference of glu-cose, fructose, sucrose, glutathione and cysteine.Recently, the procedure has been simplified by Aryaand Mahajan99so as to require only 5 min waiting time,instead of 30 or 60 min, with Beer’s law range up to 12µg ml–1(λmax=522 nm). Total ascorbic acid has been determined in blood plasma100after reducing DHAA with dithiothreitol at pH 6.5–8.0, removing the excess of dithiothreitol with N-ethylmaleimide and in urine101 by acidifying with TCA and shaking with activated chorcoal. The reduced Fe(II) forms a water-soluble colored complex with o-phenanthroline (λmax=510–515 nm) at pH 1.5–6.5, with obedience of Beer’s law up to 8 µg ml–1(ε=2.2×104). Background correction104 as achieved by Cu(II)-catalyzed oxidation is necessary for most samples, while the addition of NH4F106as theinhibitor of light reduction of Fe(III)-phen complex is needed in some cases. Selectivity for some of these methods is poor. However, an improvement using orange-red ferroin chelate in aqueous micellar medium formed in the presence of the cationic surfactant cetylpyridinium bromide109has been reported (ε=2.6×104at 510 nm). Ascorbic acid in fruits was determined after extracting the ternary complex of Fe(II) with α,α′-bipyridyl/o-phen and sulfophthalein110 dyes into chloroform (λmax=602 nm).Many other compounds including oximes111–113(6), 2-oximinocyclohexanone thiosemicarbazone114(2-OCHT) (7), 2-(5-bromo-2-pyridylazo)-5-dimethyl-aminophenol115(8)and 2-nitroso-5-(N-propyl-N-sulfo-propylamino)phenol116(9)have been investigated for their use in the analysis of pharmaceuticals and biologi-cal samples for ascorbic acid contents. The earlier reported extraction111of Fe(II)-dimethylglyoxime com-plex into chloroform, which allows the determination of 0.04–0.5 mM ascorbic acid, was modified by Arya et al.112They determined its concentration up to 14 µg ml–1at 514 nm. A proportionate decrease in color intensity of Fe(III)-resacetophenone oxime113complex in sodium acetate–acetic acid buffer (pH 5) with the increasing amounts of ascorbic acid was used for its assay in the range 3.5–17.5 µg (ε=4×103). The method using 2-OCHT determines ascorbic acid up to 12 µg ml–1(ε=1.49×104), but is interfered with by metal ions such as Cu(II), Co(II), Ni(II) and Pd(II), in addition to the interference caused by the oxalic acid, riboflavin, oxidants and reductants. Color-forming reactions of Fe(II) with ferrozine117–119(λmax=562 nm) in acidic solu-tions (pH 3–6), TPTZ120–122(λmax=593, 595 nm), quinaldic acid in presence of pyridine123(λmax=380 nm), picolinic acid in presence of pyridine124(λmax=400 nm) and nitroso-R salt125(λmax=705 nm) have been used for the determination of vitamin C in a variety of samples. The reagents picolinic acid and quinaldic acid, when complexed with iron(II) in the presence of pyridine, resulted in methods used successfully in the analysis of pharmaceuticals, food products and biologi-cal samples. The respective colored complexes getting extracted into chloroform obey Beer’s law in the range 0.4–5.6 µg ml–1and 2.5–25 µg ml–1ascorbic acid without the interference of common ingredients of the samples studied. Though the method using ferrozine117 is not interfered with by sucrose, glucose, mannose, fructose and formaldehyde, yet it suffers interferences from tartaric acid, citric acid, Co(II), Ni(II) and Fe(II). However, reactions of citric acid and tartaric acid can be masked by adding Al(III) or La(III) ions and that of iron(II) by passing the solution through a cation exchanger.Most of the reported methods based on the reducing action of ascorbic acid on metal ions invariably make use of an iron(III)–iron(II) redox system. A few use copper(II)–copper(I), vanadium(V)–vanadium(IV) or molybdenum/tungsten blue formation reactions, as mentioned earlier in the text. Arya et al. have reported a new redox system involving Cr(VI)-diphenyl-carbazide complex126(λmax=540 nm), which obeys Beer’s law up to 3.2 µg ml–1. Common additives of pharmaceutical preparations have no adverse effect on the absorbance of the complex. Another fast and facile method based on the proportionate decrease in absorbance of iron(III)-ferronate complex127(λmax=465 nm) by the addition of ascorbic acid was proposed by the same authors after extracting the complex into TBA/CHCl3solution. Beer’s law is valid up to 10 µg ml–1.3 ConclusionEven after the introduction of other instrument-based procedures, photometric methods continue to be of interest because of the ease in accessibility and their quick applicability to the routine analyses. The molar absorptivity for most of the colored species used in col-orimetric analysis of vitamin C lies over the range 103 to 1041 mol–1cm–1at the wavelength of maximum absorbance. This enables the precise determination of vitamin C in a variety of samples. The presence of cer-tain substances, especially the matrix constituents, may cause serious interferences. However, attempts to over-come such interferences either by using masking agents or making preliminary separations are invariably tried, but sometimes without much success, thus resulting in methods of varying selectivity. It has not been possible to categorize the methods based on the selectivity since the relevant data is found to be missing in the summary part of most methods reported in Chemical Abstracts. But none of the methods is found entirely specific for vitamin C. Despite the reporting of several new photo-metric methods, old procedures still continue to be cited in different pharmacopoeias, indicating either the lack of reliability or of general applicability of these methods of vitamin C determination. Research workers try to justify their work in terms of specific applica-tions, but seldom give an comparative account with other methods regarding analysis of particular type of matrix. Therefore, to incorporate the comparative use of such methods under specific analytical environment requires some patience.The authors wish to thank the Chairman, Department of Chemistry, Kurukshetra University, Kurukshetra, for necessary library facilities and Dr. Meenakshi Mahajan is grateful to CSIR for financial assistance.4 References1.H. Nie and S. Peng, Yingyang Xuebao, 6, 293 (1984).2.X. Shao and Y. Zhang, Guangpuxue Yu Guangpu Fenxi,14, 125 (1994).3.K. Vamos, Elmelz Ip., 43, 16 (1989).4.H. P. Huang, R. X. Cai, Y. M. Du and Y. E. Zeng, Chin.Chem.Lett., 6, 235 (1995).5. D. B. Dennison, G. B. Troy and L. D. Hunter, J.Agric.Food Chem., 29, 927 (1981).6.M. Yoshida, T. Nishimune and K. Sureki, Korean J.Pharmacol., 28, 53 (1992).7. E. Racz, K. Parlagh-Huszar and T. Kecskes, Period.Polytech.,Chem.Eng., 35, 23 (1991).8.H. Iwase, J.Chromatogr., 606, 277 (1992).9.R. Leubolt and H. Klein, J.Chromatogr., 640, 271 (1993).10.X. Chen and M. Sato, Anal.Sci., 11, 749 (1995).11. F. Sahbaz and G. Somer, Food Chem., 44, 141 (1992).12.R. Barbera, R. Farre, M. J. Legarda and R. Pintor,Alimentaria, 247, 89 (1993).13.G. Lu, Y. Wang, L. Yao and S. Hu, Food Chem., 51, 237(1994).14. A. Lechien, P. Valenta, H. W. Naurnberg and G. J.Partriarche, Fresenius’Z.Anal.Chem., 311, 105 (1982).15.I. D. H. C. Marques, E. T. A. Jr. Marques, A. C. Silva, W.M. Ledingham, E. H. M. Melo, V. L. da Silva and J. L.Lima Filho, Appl.Biochem.Biotechnol., 44, 81 (1994). 16.W. Zang, J. Wang and L. Jianyan, Huaxue Fence, 32, 239(1996).17.Y. Liu, Huaxue Shiji, 16, 282 (1994).18. F. Kober, Prax.Naturwiss.Chem., 37, 27 (1988).19.Indian Pharmacopoeia, Photolitho Press, Faridabad, p. 49,1985.20.Pharmacopoeia of the United States XVIII, pp. 51, 52,Mack Printing Co., Easton PA, 1970.21.British Pharmacopeia, p. 901, H. M. Stationary Office,London, 1988.22.T. Koba, M. Motomura, A. Tsuboi, T. Abekawa and K.Ito,Eisei Kensa, 35, 1565 (1986).23.M. J. Egoville, J. F. Sullivan, M. F. Kozempel and W. J.Jones, Am.Potato J., 65, 91 (1988).24.R. Hernandez and F. Bosch, Ars.Pharm., 15, 39 (1974).25.P. J. Gary, G. M. Owen and D. W. Lashley and P. C. Ford,Clin.Biochem., 7, 131 (1974).26.M. A. Eldawy, A. S. Tawfik and S. R. Elshabouri, Anal.Chem., 47, 461 (1975).27.T. Kamangar, A. B. Fawzi and R. H. Maghssoudi, J.Assoc.Off.Anal.Chem., 60, 528 (1977).28.S. Y. Lin, K. J. Duan and C. L. Tsung, Pharm.Acta.Helv., 69, 39 (1994).29.N. K. Pandey, Anal.Chem., 54, 793 (1982).30. A. M. Frigola Canovas and F. Bosch Serrat, An.Bromatol,40, 79 (1988).31.I. A. Biryuk, B. P. Zorya, V. V. Petrenko and S. B. But,Izobreteniya, 19, 194 (1993).32.I. A. Biryuk and V. V. Petrenko, Farm.Zh., 6, 52 (1991).33.M. R. Esteban and C. N. Ho, Microchem.J., 56, 122(1997).34.L. Casella, M. Gulloti, A. Marchesini and A. Petrarulo, J.Food Sci., 54, 374 (1989).35.W. Lee, S. M. Roberts and R. F. Labbe, Clin.Chem., 43,154 (1997).36.G. Szepesi, Fresenius’ Z.Anal.Chem., 265, 334 (1973).37. C. F. Bourgeosis and P. R. Mainguy, Intern.J.Vit.Nutr.Res., 45, 70 (1975).38.R. C. Rose and D. L. Nahrwold, Anal.Biochem., 114, 140(1981).39.W. D. Graham and A. Donald, J.Chromatogr., 594, 187(1992).40.T. Tsutui and T. Adachi, Kyoto-fu Eisei Kogai KenkyushoNenpo, 35, 42 (1990).41.Y. Yasui and M. Hayashi, Anal.Sci., 7, 125 (1991).42.M. O. Nisperos-Carriedo, B. S. Busling and P. E. Shaw, J.Agric.Food Chem., 40, 1127 (1992).43.J. Commack, A. Oke and R. N. Adama, J.Chromatogr.,565, 529 (1991).44.M. J. Esteve, R. Fare, A. Frigola and J. M. Garcia-Cantabella, J.Chromatogr.B.Biomed.Appl., 688, 345 (1997).45. F. Tessier, I. Birlouez-Aragon, G. Jani-Chantal and C.Jean, Vitam.Nutr.Res., 66, 166 (1996).46.S. Z. Qureshi, A. Saeed and T. Hasan, Anal.Lett., 22,1927 (1989).47.V. Nirmalchandar and N. Balasubramanian, Z.GesamteHyg.Ihre.Grenzgeb, 33, 497 (1987).48.R. G. Bhatkar and M. H. Saldonha, East Pharm., 25, 117(1982).49.O. H. Abdelmageed, P. Y. Khashaba, H. F. Askal, G. A.Saleh and I. H. Reffat, Talanta, 42, 573 (1995).50.M. H. Hashmi, A. S. Adil, A. Viegas and A. I. Ajmol,Mikrochim.Acta, 3, 457 (1970).51.H. O. Beutler and G. Beinstingl, Dtsch.Lebensm.Rundsch., 76, 69 (1980).52.H. O. Beutler, G. Beinstingl and G. Michal, Ber.—Int.Fruchtsaft Union Wiss—Tech.Komm, 16, 325 (1980). 53.P. W. Alxandrova and A. Nejtscheva, Mikrochim.Acta,1982 I, 387.54.P. V. Aleksandrova and A. Neicheva, Mikrochim.Acta,1979 II, 337.55.G. Xiao and G. Zhao, Shipin Yu Fajiao Gongye, 5, 35(1987).56.O. Pelletier and R. Brassard, J.Food Sci., 42, 1471(1977).57.Z. Zloch, Mikrochim.Acta, 1975, 213.58.S. Garcia-Castineiras, V. D. Bonnet, R. Figueroa and M.Miranda, J.Liq.Chromatogr., 4, 1619 (1981).59.O. Pelletier and R. Brassard, Adv.Automat.Anal.Technicon Int.Congr., 9, 73 (1973).60.O. Pelletier and R. Brassard, J.Assoc.Off.Anal.Chem.,58, 104 (1975).61.W. A. Behrens and R. Madere, Anal.Biochem., 92, 510(1979).62.N. Wahba, D. A. Yassa and R. S. Labib, Analyst[London], 99, 397 (1974).63.M. N. Reddy, G. K. Mohan, N. R. P. Singh and D. G.Sankar, Indian Drugs, 25, 204 (1988).64.Z. Wang, Yingyand Xuebao, 9, 174 (1987).65.W. Zhang, Zhongguo Yiyuan Yaoxue Zazhi, 12, 409(1992).66.N. Balasubramanian, S. Usha and K. Sirividya, IndianDrugs, 32, 73 (1995).67.Y. Yonemura, Y. Miura and T. Koh, Bunseki Kagaku, 39,567 (1990).68.K. Sirividya and N. Balasubramaninan, Analyst[London],121, 1653 (1996).69.N. Burger and V. Karas-Gasparec, Talanta, 20, 782(1973).70.S. A. Al-Tamrah, Anal.Chim.Acta, 209, 309 (1988).71.S. Baczyk and K. Swizinska, Farm.Pol., 31, 399 (1975).72.Y. S. Fung and S. F. Luk, Analyst[London], 110, 201(1985).73.Y. S. Fung and S. F. Luk, Analyst[London], 110, 1439(1985).74.O. W. Lau, S. F. Luk and K. S. Wong, Analyst[London],112, 1023 (1987).75.J. Yan, Zhongguo Yaoxue Zazhi, 25, 478 (1990).。

2-24 Selective Uranium Extraction from Salt Lake Brine by Amidoximated Saccharomyces cerevisiae

·82·IMP&HIRFL Annual Report20152-24Selective Uranium Extraction from Salt Lake Brine byAmidoximated Saccharomyces cerevisiaeBai Jing,Yin Xiaojie and Qin ZhiUranium concentration in salt lake brines is tens even thousands times higher than seawater,which makes salt lake brine being another ideal resource for uranium.However,the content of salt lake brine is very complicate,a large amount of K,Na,Ca,Mg elements coexisting with uranium.Hence,only sorbent with high uranium selectivity can be well used in uranium extraction from salt lake brine.Fig.1(color online)Uranium sorption from salt lake brine by raw biomass and amidoximated S.cerevisiae.To enhance the selectivity of Saccharomyces cere-visiae for uranium,amidoximation of the biomass was performed.–CN groups wasﬁrstly grafted on the biomass surface by radical induced grafting reaction (PAN-B),followed by converting nitrile(–CN)groups to amidoxime(–C(NH2)NOH)groups through reaction with free hydroxylamine(amidoximation).Amidoxi-mated S.cerevisiae(PAO-B)can be obtained through these two steps.The eﬀect of solution pH,extraction time,initial uranium concentration and ion strength on uranium sorption by amdoximated S.cerevisiae was studied in detail and optimum uranium sorption condi-tion was conﬁrmed.Desorption experiment was alsoperformed and the corresponding results showed that amidoximation did not decrease the uranium sorption capacity of the biomass and the amidoximated S.cerevisiae couldbe used at least three times with little loss of uranium uptake capacity.Trace uranium extraction from real salt lake brine samples were conducted,and75%of uranium in the salt lake brine samples was successful absorbed by amidoximated biomass while hardly any uranium was absorbed by raw biomass(Fig.1).Hence,amidoximation can obviously enhance the uranium selectivity of the biomass and amidoximated S.cerevisiae has the potential to selectively extract traceuranium ions from salt lake brine.2-25Gas-phase Chemistry of Short-lived Re Carbonyl Complexes Part1:Adsorption Enthalpy on Teﬂon SurfaceWang Yang1,Qin Zhi1,Fan Fangli1,Hiromitsu.Haba2,Yukiko.Komori2and Shinya.Yanou2 (1Institute of Modern Physics,Chinese Academy of Sciences,Lanzhou730070,China;2Nishina Center for Accelerator-Based Science,RIKEN,Wako,Saitama351-0198,Japan) In the collaboration of RI Applications Team from RIKEN(Japan)and the Nuclear Chemistry Group from IMP(China),the short-lived Re carbonyl complexes were synthesized and investigated.As the lighter homologs of superheavy element Bh,Re belongs to period6,group7of the periodic table.Short-lived Re isotopes with half-lives of several minutes were produced in the reactions of nat Gd(23Na7+,xn)172−177Re at Nishina center of RIKEN.The nat Gd2O3target with a thickness of340µg·cm−2was prepared by electro deposition onto a2µm Ti foil. The23Na7+ion beam was extracted from RILAC(RIKEN Linear Accelerator).The beam energy was130.6MeV cot. The Gas-ﬁlled Recoil Ion Separator(GARIS)was employed to separate the evaporation residues.A gasﬁlled recoil chamber was installed at the focal plane of GARIS[1].Then,volatile carbonyls were synthesized with short-lived Re isotopes and CO contained gas mixture.Gas-phase chemistry technique was used to measure the adsorption enthalpies of these carbonyls on Teﬂon(FEP)surface[2].Fig.1shows the experimental setups.Fig.2shows typicalγ-spectra measured with three diﬀerent kinds of transport.As a result,Re isotopes and their daughters W isotopes were observed in the charcoal trap when CO gas was added into Ar gas,which could prove that volatile Re carbonyls were synthesized with Re atoms and CO gas.After changing the isothermal temperature from25to–70◦C with10◦a step,breakthrough curves of these carbonyls were measured.Monte Carlo simulation program was used to get their adsorption enthalpies on Teﬂon surface.172,174176Re carbonyls were listed as representative,see Fig.3.。

伊朗核协议

Geneva, 24 November 2013Joint Plan of ActionPreambleThe goal for these negotiations is to reach a mutually-agreed long-term comprehensive solution that would ensure Iran's nuclear programme will be exclusively peaceful. Iran reaffirms that under no circumstances will Iran ever seek or develop any nuclear weapons.This comprehensive solution would build on these initial measures and result in a final step for a period to be agreed upon and the resolution of concerns. This comprehensive solution would enable Iran to fully enjoy its right to nuclear energy for peaceful purposes under the relevant articles of the NPT in conformity with its obligations therein. This comprehensive solution would involve a mutually defined enrichment programme with practical limits and transparency measures to ensure the peaceful nature of the programme. This comprehensive solution would constitute an integrated whole where nothing is agreed until everything is agreed. This comprehensive solution would involve a reciprocal, step-by- step process, and would produce the comprehensive lifting of all UN Security Council sanctions, as well as multilateral and national sanctions related to Iran's nuclear programme.There would be additional steps in between the initial measures and the final step, including,among other things, addressing the UN Security Council resolutions, with a view towardbringing to a satisfactory conclusion the UN Security Council's consideration of this matter. TheE3+3 and Iran will be responsible for conclusion and implementation of mutual near-termmeasures and the comprehensive solution in good faith. A Joint Commission of E3/EU+3 and Iranwill be established to monitor the implementation of the near-term measures and address issuesthat may arise, with the IAEA responsible for verification of nuclear-related measures. The Joint Commission will work with the IAEA to facilitate resolution of past and present issues ofconcern.Elements of a first stepThe first step would be time-bound, with a duration of 6 months, and renewable by mutual consent, during which all parties will work to maintain a constructive atmosphere for negotiations in good faith. Iran would undertake the following voluntary measures:•From the existing uranium enriched to 20%, retain half as working stock of 20% oxide for fabrication of fuel for the TRR. Dilute the remaining 20% UF6 to no more than 5%.No reconversion line.•Iran announces that it will not enrich uranium over 5% for the duration of the 6 months.1•Iran announces that it will not make any further advances of its activities at the Natanz Fuel Enrichment Plant1, Fordow2,or the Arak reactor3, designated by the IAEA as IR-40.•Beginning when the line for conversion of UF6 enriched up to 5% to UO2 is ready, Iran has decided to convert to oxide UF6 newly enriched up to 5% during the 6 month period, as provided in the operational schedule of the conversion plant declared to the IAEA.•No new locations for the enrichment.•Iran will continue its safeguarded R&D practices, including its current enrichment R&D practices, which are not designed for accumulation of the enriched uranium.•No reprocessing or construction of a facility capable of reprocessing.•Enhanced monitoring:o Provision of specified information to the IAEA, including information on Iran's plans for nuclear facilities, a description of each building on each nuclear site, adescription of the scale of operations for each location engaged in specifiednuclear activities, information on uranium mines and mills, and information onsource material. This information would be provided within three months of theadoption of these measures.o Submission of an updated DIQ for the reactor at Arak, designated by the IAEA as the IR-40, to the IAEA.o Steps to agree with the IAEA on conclusion of the Safeguards Approach for the reactor at Arak, designated by the IAEA as the IR-40.o Daily IAEA inspector access when inspectors are not present for the purpose of Design Information Verification, Interim Inventory Verification, PhysicalInventory Verification, and unannounced inspections, for the purpose of access tooffline surveillance records, at Fordow and Natanz.o IAEA inspector managed access to:centrifuge assembly workshops4;centrifuge rotor production workshops and storage facilities; and,uranium mines and mills.1 Namely, during the 6 months, Iran will not feed UF6 into the centrifuges installed but not enriching uranium. Not install additional centrifuges. Iran announces that during the first 6 months, it will replace existing centrifuges with centrifuges ofthe same type.2At Fordow, no further enrichment over 5% at 4 cascades now enriching uranium, and not increase enrichment capacity. Not feed UF6 into the other 12 cascades, which would remain in a non-operative state. No interconnections between cascades.Iran announces that during the first 6 months, it will replace existing centrifuges with centrifuges of the same type.3 Iran announces on concerns related to the construction of the reactor at Arak that for 6 months it will not commission the reactor or transfer fuel or heavy water to the reactor site and will not test additional fuel or produce more fuel for the reactoror install remaining components.4 Consistent with its plans, Iran's centrifuge production during the 6 months will be dedicated to replace damaged machines.2In return, the E3/EU+3 would undertake the following voluntary measures:•Pause efforts to further reduce Iran's crude oil sales, enabling Iran's current customers to purchase their current average amounts of crude oil. Enable the repatriation of an agreedamount of revenue held abroad. For such oil sales, suspend the EU and U.S. sanctions onassociated insurance and transportation services.•Suspend U.S. and EU sanctions on:o Iran's petrochemical exports, as well as sanctions on associated services.5o Gold and precious metals, as well as sanctions on associated services.•Suspend U.S. sanctions on Iran's auto industry, as well as sanctions on associated services.•License the supply and installation in Iran of spare parts for safety of flight for Iranian civil aviation and associated services. License safety related inspections and repairs in Iran as well as associated services.6•No new nuclear-related UN Security Council sanctions.•No new EU nuclear-related sanctions.•The U.S. Administration, acting consistent with the respective roles of the President and the Congress, will refrain from imposing new nuclear-related sanctions.•Establish a financial channel to facilitate humanitarian trade for Iran's domestic needs using Iranian oil revenues held abroad. Humanitarian trade would be defined as transactionsinvolving food and agricultural products, medicine, medical devices, and medical expensesincurred abroad. This channel would involve specified foreign banks and non-designatedIranian banks to be defined when establishing the channel.o This channel could also enable:transactions required to pay Iran's UN obligations; and,direct tuition payments to universities and colleges for Iranian studentsstudying abroad, up to an agreed amount for the six month period.•Increase the EU authorisation thresholds for transactions for non-sanctioned trade to an agreed amount.5 "Sanctions on associated services" means any service, such as insurance, transportation, or financial, subject to the underlying U.S. or EU sanctions applicable, insofar as each service is related to the underlying sanction andrequired to facilitate the desired transactions. These services could involve any non-designated Iranian entities.6 Sanctions relief could involve any non-designated Iranian airlines as well as Iran Air.3Elements of the final step of a comprehensive solution*The final step of a comprehensive solution, which the parties aim to conclude negotiating and commence implementing no more than one year after the adoption of this document, would: •Have a specified long-term duration to be agreed upon.•Reflect the rights and obligations of parties to the NPT and IAEA SafeguardsAgreements.•Comprehensively lift UN Security Council, multilateral and national nuclear-related sanctions, including steps on access in areas of trade, technology, finance, and energy, ona schedule to be agreed upon.•Involve a mutually defined enrichment programme with mutually agreed parameters consistent with practical needs, with agreed limits on scope and level of enrichmentactivities, capacity, where it is carried out, and stocks of enriched uranium, for a period tobe agreed upon.•Fully resolve concerns related to the reactor at Arak, designated by the IAEA as the IR-40.No reprocessing or construction of a facility capable of reprocessing.•Fully implement the agreed transparency measures and enhanced monitoring. Ratify and implement the Additional Protocol, consistent with the respective roles of the Presidentand the Majlis (Iranian parliament).•Include international civil nuclear cooperation, including among others, on acquiring modern light water power and research reactors and associated equipment, and the supplyof modern nuclear fuel as well as agreed R&D practices.Following successful implementation of the final step of the comprehensive solution for its full duration, the Iranian nuclear programme will be treated in the same manner as that of any non-nuclear weapon state party to the NPT.* With respect to the final step and any steps in between, the standard principle that "nothing is agreed until everything is agreed" applies.4。

英语辩论赛___核能发展弊端

开发核能源弊大于利第一：核能是绿色能源吗？也许你会认为核能不会像煤炭和石油等化石燃料那样产生大气污染，也不会排放温室气体二氧化碳，但是你错了！其实事实完全相反。

用于核电的原料之一是铀，铀浓缩设施需要依靠煤炭提供电力的工厂。

这些工厂向大气排放了大量的的二氧化碳。

此外铀浓缩过程还会排放大量氯氟烃，氯氟烃除了导致臭氧层变得稀薄以外，还是比二氧化碳强度高一万到两万倍的温室气体。

此外由于核能发电热效率较低，比一般化石燃料电厂排放更多废热到环境中，故核能电厂的热污染较严重。

而且，在核发电过程中，每年又要向空气和水中持续排放超过上千万居里的放射性同位素。

尽管核工业坚持说，某些放射性物质从生物角度不会引起严重后果。

但事实远非如此。

First: Nuclear energy is green energy sources?You might think that nuclear energy is not like coal and oil and other fossil fuels that produce air pollution, greenhouse gas emissions of carbon dioxide will not, but you are wrong! Quite the opposite in fact. One of the raw materials for nuclear power is uranium, uranium enrichment facilities need to rely on coal to power plants. These factories are a lot of the atmosphere of carbon dioxide emissions. Besides uranium enrichment process also emit large quantities of chlorofluorocarbons, CFCs cause the ozone layer becomes thinner than in addition to, or higher than the carbon dioxide intensity 10000-2 times of greenhouse gases. Furthermore, since the thermal efficiency of nuclear power generation lower than the average fossil fuel power plants emit more heat to the environment, so the nuclear power plant thermal pollution is more serious. Moreover, in the process of nuclear power, but also to the annual emissions of air and water continue to exceed tens of millions of curies of radioisotopes. Although the nuclear industry insists that some of the radioactive material from a biological point of view does not cause serious consequences. However, far from it.第二：核能是高效能源吗？核工业的真正经济价值从来就没有被认真地分析过，这其中包括铀浓缩的成本，发生核事故后的巨大经济索赔，拆卸到期反应堆成本，现有核反应堆的维护，核原料和废料的运输和将放射性核废料储存25万年的所需费用。

郑州大学研究生期末英语测试题

AGENERAL ENGLISH QUALIFYING TESTFOR NON-ENGLISH MAJOR GRADUATE STUDENTS(GETJUN2109)考试注意事项一、本考试由两份试卷组成：试卷一（Paper One）包括听力理解、词汇、完形填空与阅读理解四部分，共80题，按顺序统一编号；试卷二 (Paper Two) 包括翻译与写作两部分，共3题。

二、试卷一（题号1-80）为客观评分题（听力Section C 部分除外），答案一律用2B铅笔做在机读答题纸上，在对应题号下所选的字母中间划黑道，如[A][B][C][D]。

三、试卷二为主观评分题，答案做在ANSWER SHEET II上。

答题前，请仔细阅读试卷二的注意事项。

四、试卷一、试卷二上均不得作任何记号（听力Section C部分除外），答案一律写在答题纸上，否则无效。

五、本考试全部时间为150分钟，采用试卷一与试卷二分卷计时的办法。

试卷一考试时间为90分钟，听力理解部分以放完录音带为准，大约25分钟；其余部分共计时65分钟，每部分所占时间均标在试卷上，考生可自行掌握。

试卷二共计时60分钟，每部分所占时间均标在试卷上，考生可自行掌握。

六、试卷一与试卷二采取分别收卷的办法。

每次终了时间一到，考生一律停笔，等候监考教师收点试卷及答题纸。

全部考试结束后，须待监考教师将全部试卷及答题纸收点无误并宣布本考试结束，方可离开考场。

PAPER ONEPART I LISTENING COMPREHENSION (25 MINUTES, 20 POINTS)Section A (1 point each)Directions: In this section, you will hear nine short conversations between two speakers. At the end of each conversation a question will be askedabout what was said. The conversations and the questions will beread only once. Choose the best answer from the four choices givenby marking the corresponding letter with a single bar across thesquare brackets on your machine-scoring Answer Sheet.1. A. Visit her parents.B. Go to the dentist.C. Meet her professor.D. Have a job interview.2. A. Bob is majoring in history.B. Bob is a little boring.C. He likes Bob very much.D. They should invite Bob to the party.3. A. The flight was delayed.B. She didn’t like the movies.C. She had seen both movies before.D. No movies were shown on her flight.4. A. It’s drier.B. It’s wetter.C. It’s abnormal.D. It’s an average year.5. A. Western.B. Horror.C. Science fiction.D. Action.6. A. Wait for Mike.B. Ask Mike to come.C. Pick Mike up in the morning.D. Stop working for the day.7. A. She doesn’t like playing tennis.B. She was thinking the same as the man.C. She had something else in mind.D. She had suggested the same thing earlier.8. A. Matt wants to be cheered up.B. Matt has lost himself.C. Matt worries little about the game.D. Matt feels a little depressed.9. A. The man is a coward.B. The man is too careful.C. Martha likes chicken very much.D. Martha is not the right person for him.Section B (1 point each)Directions: In this section you will hear two mini-talks. At the end of each talk, there will be some questions. Both the talks and the questions will beread to you only once. After each question, there will be a pause.During the pause, you must choose the best answer from the fourchoices given by marking the corresponding letter with a single baracross the square brackets on your machine-scoring Answer Sheet. Mini-talk One10. A. Mr. Lee always wastes time in class.B. Mr. Lee likes talking about history.C. Mr. Lee always feels bored in class.D. Mr. Lee is a little funny.11. A. Boring.B. Satisfactory.C. Inconsistent.D. Inspiring.12. A. Jim has taken a low end job.B. Jim has got a well-paid job.C. Jim is not hopeless in finding a job.D. Jim is desperate in finding a job.Mini-talk Two13. A. The control of drug trafficking in the United States.B. The anti-drug war about the border between Mexico and U.S.C. The investigation of the death of a retired U.S. general.D. The fight of corruption inside Mexican police.14. A. The criminal groups are growing very rapidly.B. The criminal groups can get more profits now.C. Mexican government has not been serious about the drug trade.D. Mexican government is effective in fighting the drug trade.15. A. 6,000B. 10,000C. 45,000D. 54,000Section C (1 point each)Directions: In this section, you will hear a short lecture. Listen to the recording and complete the notes about the lecture. You will hear the recordingtwice. After the recording, you are asked to write down your answerson the Answer Sheet. You now have 25 seconds to read the notesbelow.(请在录音结束后把16-20题的答案抄写在答题纸上)16. For best results with the least risk, tomatoes should be planted when ________.17. Some larger tomatoes may need at least a meter and a half ________.18. The average air temperature should be about _________ Celsius.19. There was a time when people thought tomatoes ________, which is not true.20. Some fruits may be called "vegetables" because they are used in deliciousfoods instead of ________.PART II VOCABULARY (10 minutes, 10 points)Section A (0.5 point each)Directions: There are ten questions in this section. Each question is a sentence with one word or phrase underlined. Below the sentence are fourwords or phrases marked A, B, C and D. Choose the word or phrasethat is closest in meaning to the underlined one. Mark thecorresponding letter with a single bar across the square brackets onyour machine-scoring Answer Sheet.21. People who work overtime at any job are more likely to sustain awork-related injury than those who work their regular hours.support D.sufferendureA.maintainB.C.22. These instruments are so powerful as to enable them to ascertain many factsof the deepest interest.out D.turnoutout C.wearfindputA.outB.23. Kunz looked set to become a star in his field, but he gave it all up after thesefailures.C.D.builtdeterminedA.fixed B.stereotyped24. In the disciplines underlying our high-tech economy, America is steadily losingits global edge.D.territoryappealC.A. borderB. superiority25. The Chinese economy is less affected, so there is no reason to take a dimview of economic growth.A. pessimisticB. blackC. vagueD. positive26. The spacecraft touched down on schedule and the astronauts were helped outof it.crashedD.A. launchedB. operatedC.landed27. In the tropic rainforest there is a wide range of species peculiar to this area.distinct D.odd C.familiarB.A.specific28. The officer distributed among the youngster all the blankets and provisions,withholding himself only a canteen.A. keeping offB. keeping backC. keeping atD. keeping up29. These graduates are more than obliged to the college for the happy four yearsof college life.A. obligatoryB. reluctantC. indifferentD. grateful30. Regular exercise can keep you energetic and contribute to a productive life inthe long run.A. athleticallyB. successivelyC. ultimatelyD. persistentlySection B (0.5 point each)Directions: There are ten questions in this section. Each question is a sentence with something missing. Below each sentence are four words orphrases marked A, B, C and D. Choose the word or phrase that bestcompletes the sentence. Mark the corresponding letter with a singlebar across the square brackets on your machine-scoring AnswerSheet.31. Observers commented that loss of independence was too high a(n) _______ topay for peace.D.expenditurepriceA.costB.expense C.32.The journalist who had set out to obtain these important facts _______ along time to send them.D.consumedpassedA.spentB.took C.33.Telling your doctor about all the medicines you take may help avoid seriousdrug _______.A.interactionsB. interruptionsC. interventionsD. institutions34.Two dozen New Yorkers stood on the platform at the subway station,_______ briefcases and newspapers.clashing D.clarifyingA.clippingB.clutching C.35.Each _______ effort a baby makes at speech is a sign of intellectualdevelopment.clumsy D.chroniccompact C.A.cordialB.36.Iran has expanded its uranium enrichment activities _______ UN demandsto scrap its nuclear-related programs.A. in defiance ofB. in line withC. in return forD. in relation to37.China moved to _______ its grain production when its grain output had keptdeclining for five consecutive years.A.turn upB. take upC. step upD. make up38.The most interesting thing _______ Americans is that they are brought up tobelieve they are the best at everything.A.withB. inC. fromD. about39.The dean asked the secretary if there were enough people _______ to hold afaculty meeting.onhand D.averageC.onendonpurposeA.onB.40.Visitors to this war museum are _______ to see photos of mass massacre byJapanese soldiers.A. amazedB. startledC. wonderedD. startedPART III CLOZE TEST (10 minutes, 10 points, 1 point each)Directions: There are 10 questions in this part of the test. Read the passage through. Then go back and choose one suitable word or phrasemarked A, B, C, or D for each blank in the passage. Mark thecorresponding letter of the word or phrase you have chosen with asingle bar across the square brackets on your machine-scoringAnswer Sheet.It’s a new world, and we barely seem to have noticed. Places we 41 with inexpensive low-end manufacturing are going high-tech in a big 42 .The spotlight is mainly in China and India, for good 43 . The Chinese economy is surging, 44 by increasingly sophisticated engineering, with products 45 from automobiles to semiconductors. India has nearly as46 an economy, powered by a cheap English-speaking labor force who47 in software and services.Along with these 48 giants, countries like Japan, South Korea and Singapore are also challenging America’s 49 . If present trends continue, 90% of all the world’s scientists and engineers will be living in Asia 50 2010, according to Nobel Prize winner Richard E. Smalley, professor of chemistry and physics at Rice University.communicate D.concernassociate C.A.B.41.dealC.way D.routedimension scale B.42.A.effect D.healthpurpose C.reason B.A.43.fueledextinguishedD.burned C.B.A.44.checkeddiffering C.changing D.B.ranging varying45.A.C.staticdynamic D.drastictragic B.46.A.C.bypassovertake D.excelB.A.47.surpassD.mergingsubmergingA.48.emerging B.diverging C.49. A. manipulation B. presidency C. constitution D. dominanceby D.50.in C.before until B.A.PART IV READING COMPREHENSION (45 minutes, 30 points, 1 point each)Directions: In this part of the test, there are five short passages. Read each passage carefully, and then do the questions that follow. Choose thebest answer from the four choices given and mark the correspondingletter with a single bar across the square brackets on yourmachine-scoring Answer Sheet.Passage OneHeadphones used with MP3 digital music players like the iPod may interfere with heart pacemakers（起搏器）and implantable defibrillators（除颤器）, U.S. researchers said.The MP3 players themselves posed no threat to pacemakers and defibrillators, used to normalize heart rhythm. But strong little magnets inside the headphones can foul up the devices if placed within 1.2 inches of them, the researchers told an American Heart Association meeting in New Orleans.Dr. William Maisel of the Medical Device Safety Institute in Boston led a team that tested eight models of MP3 player headphones, including clip-on and ear-plug types, in 60 defibrillator and pacemaker patients.They placed the headphones on the patients' chests, directly over the devices. The headphones interfered with the heart devices in about a quarter of the patients -- 14 of the 60 -- and interference was twice as likely in those with a defibrillator than with a pacemaker.Another study presented at the meeting showed that cellular phones equipped with wireless technology known as Bluetooth are unlikely to interfere with pacemakers.A pacemaker sends electrical impulses to the heart to speed up or slow heart rhythm. The magnet, however, could make it deliver a signal no matter what the heart rate is, the researchers said.An implantable defibrillator signals the heart to normalize its rhythm if it gets too fast or slow. A magnet could de-activate it, making it ignore an abnormal heart rhythm instead of delivering an electrical shock to normalize it.The devices usually go back to working the right way after the headphones are removed, the researchers said."The main message here is: it's fine for patients to use their headphones normally, meaning they can listen to music and keep the headphones in their ears. But what they should not do is put the headphones near their device," Maisel said in a telephone interview.So that means people with pacemakers or defibrillators should not place the headphones in a shirt pocket or coat pocket near the chest when they are not being used, and should not place them over their chest or have others who are wearing headphones rest their head on the patient's chest, Maisel said.51. How can MP3 digital music players hinder pacemakers and defibrillators?A. MP3 players can interfere with heart pacemakers and defibrillators.B. The magnets inside the headphones can interfere with pacemakers anddefibrillators.C. The loud music beats pose a threat to pacemakers and defibrillators.D. MP3 players are placed too close to pacemakers and defibrillators.52. Dr. William Maisel’s tests showed that ________.A. headphones had interference with the heart devices in every patientB. half of the models of MP3 player headphones had interference with heartdevicesC. headphones had much stronger interference with a defibrillator than witha pacemakerD. headphones had much stronger interference with a pacemaker than witha defibrillator53. Bluetooth is mentioned as an example of cell phones that________.A. have little interference with the heart devicesB. are used in the tests in Dr. William Maisel’s studyC. are equipped with wireless technologyD. will replace the MP3 player headphones54. The magnets inside the headphones can cause problems by ________.A. sending out electrical shock to damage heartsB. sending out signals to make hearts beat too slowC. sending out signals to make hearts beat too fastD. making the heart devices malfunction55. People with pacemakers or defibrillators should ________.A. never use MP3 digital music playersB. not use MP3 headphonesC. not use the headphones near their heartsD. put the headphones in a pocket when they are not being used56. The writer’s purpose in writing this article is to ________.A. report the effects of cell phones on heartsB. warn people not to use modern gadgetsC. compare different headphone productsD. inform people of the safe use of MP3 playersPassage TwoCyber crime is likely to bring about as much destruction as the credit crisis in the coming years if international regulation is not improved, some of the world's top crime experts said. Damage caused by cyber crime is estimated at $100 billion annually, said Kilian Strauss, of the Organization for Security and Cooperation in Europe (OSCE)."These criminals outsmart us ten, or a hundred to one," Strauss told Reuters, adding more Internet experts were needed to investigate and tackle cyber crime.Criminal organizations are exploiting a regulatory vacuum to commit Internet crimes such as computer spying, money-laundering and theft of personal information, and the scope for damage is vast, experts told a European Economic Crime conference in Frankfurt. "We need multilateral understanding, account and oversight to avoid, in the years to come, a cyber crisis equivalent to the current financial crisis," Antonio Maria Costa, Executive Director of the United Nations Office on Drugs and Crime, said.Internet crime is also a threat to national security, they said. Several countries, including the United States, have voiced concern over some hackers’ abilities to electronically spy on them and disrupt computer networks.Calls for greater regulation of the Internet come at a time of regulatory renaissance, with policymakers looking to support the powers of financial sector watchdogs in the wake of the global financial crisis. "Because of the transnational nature of identity-related crime, and especially of cyber-crime, if we do not tackle the crime everywhere we will not solve it anywhere," Costa said.The President of Interpol, Khoo Boon Hui, said increasingly highly technological gangs from Asia, Eastern Europe and Africa were coming up with ever more sophisticated ways of swindling money from vulnerable people. He also said there was a trend of company bosses being bribed by fraudsters claiming to have guilty evidence about their firms.Strauss, who works as Senior Program Officer at the Office of the Coordinator of OSCE Economic and Environmental activities, said Internet crime watchdogs could learn a lot from criminals willing to switch sides.57. The main idea of the passage is that ________.A. cyber crime is as destructive as the credit crisis in the coming yearsB. damage caused by cyber-crime is very serious and will get worseC. to fight cyber crime requires enhanced international regulationD. international organizations should be established to crush cyber-crime58. According to Kilian Strauss, ________.A. cyber criminals are 10 or 100 times smarter than Internet expertsB. Internet experts are 10 or 100 times smarter than cyber criminalsC. as cyber criminals are very smart, more experts are needed to fightagainst themD. the investigation of the cyber crime takes time and money59. Criminal organizations can commit internet crimes because ________.A. there is no effective regulationB. they can exploit the present regulationsC. no country has paid enough attention to themD. the current financial crisis has put the authorities at a loss60. To win the war against cyber crime, ________.A. policymakers should support their governments financiallyB. each country should solve its own problems effectivelyC. United States should play a very important roleD. international cooperation is crucial61. The underlined word swindling (in the 5th paragraph) is closest in meaning to“________”.A. bribingB. cheatingC. corruptingD. robbing62. Straus believes that ________.A. Internet security experts can learn a lot from cyber criminalsB. if cyber criminals will cooperate with the police, they can be helpfulC. Internet crime watchdogs will make cyber criminals shift groundsD. international organizations can solve the problems of cyber crimePassage ThreeIt’s hard to know who to trust these days. When we see people staging protests we think, Wow! These folks are passionate about their cause – otherwise, why would they stand in the rain for hours? But sometimes it’s a show: You and even your Congressman may have been raised to power by manipulative marketers who pay serious money to hire protesters.It’s a mean trick. Let’s say you want to stage a political rally, but you just can’t find enough people for a good turnout. What you need are folks with lots of time on their hands, who can be persuaded to make a fuss over almost anything.Solution: Head down to a homeless shelter and take out cash.No joke – hiring the homeless is catching on. Last October, a Georgia activist pushing a state law to crack down on illegal immigrants paid 14 homeless men $10 each to hold signs and march around. It worked. People thought the rally was genuine – a local radio station even broadcast it live. But listeners had no idea this was just a crowd for hire.Pay for rage works – the homeless get a little income and the lobbying group gets a crowd. The only losers are citizens and the media, who think the whole show is legitimate. After a Phoenix TV station recently noticed rallies featuring the homeless, they asked some of the protesters, who were holding signs about a local labor dispute, what they were upset about. Many had no idea. “All we do is stand out here and hold the signs,” said one.Some bold organizers have been known to “borrow” people’s names. In one case a few years ago, members of Congress were swamped with telegrams about a telecom bill. But some constituents were confused when they got phone calls from their concerned Congressmen – because they’d never written in to begin with. It turned out that thousands of the telegrams were faked by a telecom-industry PR firm. And guess what? No aspect of this campaign appears to have violated Postal Service regulations. That means your name could be used next in support of a corporate cause you’ve never heard of.All of this amounts to a corruption of our democratic system: You can’t trust someone who’s calling you about a political issue, and if you write to your Congressman, he might not trust that you haven’t been manipulated.Maybe the solution starts with unmasking all those protest rallies that are just outrage-for-hire purchased down at the local shelter.63. From the first paragraph it can be learned that ________.A. those protesting in the cold rain are respectableB. most Congressmen were elected by fake votesC. in some cases protesters are hiredD. people staging protests are passionate64. Which of the following statements is true?A. The homeless tend to organize protests and rallies.B. Political rallies are sometimes manipulated by power and money.C. The homeless are to blame for deceiving the public and media.D. Political rallies attended by the homeless are on the decline.65. The passage implies that sometimes ________.A. people were deceived into believing that this was a real and legal rallyB. the hired protesters knew clearly what they were pushing forC. such protests have never attracted any attentionD. organizers paid generously for these protesters66. The underlined sentence in Paragraph 4 “pay for rage works” means that________.A. organizers of such rallies have to pay the participantsB. expressing anger can lead to good solutionsC. the homeless have to be paid moreD. hiring people to show your outrage is effective67. To shape the Congressmen’s opinion, a telecom-industry PR firm ________.A. asked the constituents to send telegrams to the CongressmenB. wrote to local residents for supportC. tried to violate Postal Service regulationsD. sent telegrams to the Congressmen in the names of local constituents68. Protest rallies of this kind might result in ________.A. business deceptionsB. disappearance of political trustC. the increase of the homelessD. the collapse of a political partyPassage FourIt had been a long, brutal day on the sales floor for young Brent. He’d had his share of “ups”—what retail salespeople say when it’s their turn with the next customer—and more than his share of downs. And now he was in danger of being shut out for the day.He hadn’t been shut out in a long time. Even in his early days with the company, he could always sell something to someone. He was a natural.But not on this day. This, of course, exposed him to some good-natured ridicule from his associates, who took not-so-secret delight in seeing the sales genius get his stroke of misfortune.Brent had more at stake here than just professional pride and reputation, however. Brent was a new father. He and his wife, Kay, had decided that she would be a full-time mom, which meant he would financially support the family. When he did well on the sales floor, finances weren’t a problem. But when he struggled to make sales, the whole family struggled.Toward the end of the day, a man came in to buy a suit. This was potentially a good sale, the kind that can turn a bad day into a good one—just like that. Brent worked hard to make the sale. But the man hesitated. Brent knew all too well the look he saw in his eyes—the look of a customer about to walk out the door empty-handed. When it became clear that the man was going to leave to do a little comparison shopping, Brent handed him his business card and invited him to return after he’d had a chance to look around.The man looked at Brent’s card, then took a long look at Brent.“So you’re Brent’s boy,” the man said, referring to the card that identified him as Brent Jr.“Do you know my dad?” Brent asked.“Sure do,” the man said. They chatted for a moment, establishing the link between father and son. Then the man said, “Your dad’s a good man. If you’re anything like him . . . well, tell me again about that suit.”Brent called his father that night, but not to recount the story. “I just wanted to thank you,” he said, “for giving me a name I can be proud of.”69. We can learn from Paragraph 2 that as a salesman Brent was ________.A. creativeB. hard-workingC.D.warm-heartedexperienced70. The underlined words “stroke of misfortune” in Paragraph 3 are closest inmeaning to ________.A. change of fateB. bad luckC. a rare opportunityD. an unexpected reward71. It is known from the passage that ________.A. Brent’s family had to struggle to make ends meetB. Brent’s family had to experience a temporary hard timeC. the family’s future depended on Brent and his wife keeping their jobsD. the family’s well-being was closely related to Brent’s sales performance72. As soon as the man entered the store to buy a suit, ________.A. Brent felt that his chance finally cameB. Brent decided to chat with him for a whileC. Brent gave him his greeting and business cardD. Brent was sure that he couldn’t make the sale73. Brent made a call to his father because he________.A. had had a good day on the sales floorB. had met an old friend of his father’s earlier in the dayC. was proud of his father’s achievementD. was grateful for having a respectable name74. We can learn from the story that ________.A. we should cherish what we haveB. the key to success is to never give upC. it is important to have a good reputationD. our family is the most valuable treasurePassage FiveIf the universality of immersion-style language programs, emergency test prep classes, tired college kids is any indication, cramming (临时抱佛脚) is a wildly popular study strategy. Professors frown upon it yet conspire by squeezing vast topics like “Evolution” or “World history 1914 to present” into the last week of a course. So is cramming effective or not? A new study by UC–San Diego psychologists confirms what you may suspect deep down: The answer is no. Hurried memorization is a hopeless approach for retaining information. But it’s not all bad news. The team offers a precise formula for better study habits, and it doesn’t necessarily need dogged discipline and routine.To arrive at their prescription, the scientists tested the “spacing effect” on long-term memory. In other words, they wanted to know how the time gap between study sessions influences the ability to remember material on test day. They asked 1,354 volunteers to memorize 32 trivial facts, such as “Who invented snow golf?” (Rudyard Kipling) and “What European nation consumes the most spicy Mexican food?” (Norway). Participants reviewed the answers anywhere from several minutes to several months after first learning them, and then were tested up to a year later.The findings? Students perform better when they space their study sessions rather than when they try to cram everything into their heads during one sitting. But for those who must cram, timing is everything. According to the researchers, if you have only one date on which to study, choose a day that’s closer to when you first learned the material than when you take the test—but not too close. For instance, if you have a French lesson on Monday and a quiz the following Monday, you should study on Wednesday for maximum retention. Tuesday is too early and Sunday is too late. If you want to remember something for a year, wait。

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SCIENCE CHINAPhysics, Mechanics & Astronomy© Science China Press and Springer-Verlag Berlin Heidelberg 2011 *Corresponding author (email: zhujyu@)• Research Paper •October 2011 Vol.54 No.10: 1–5doi: 10.1007/s11433-011-4468-9Uranium enrichment determination by high-energyphoton interrogationZHU JianYu *, ZHANG SongBai & WU JunCenter for Strategic Studies, China Academy of Engineering Physics, Beijing 100088, ChinaReceived December 30, 2010; accepted February 24, 2011Uranium enrichment determination by non-destructive assay is an important method in authenticating the nuclear warhead or uranium component in deep nuclear reduction verifications. In this paper, the feasibility of applying the high-energy photon interrogation to determine the uranium enrichment is studied. Simplified models are presented which were simulated by par-ticle Monte Carlo transport code. The results indicate that the relation curves of the released neutrons and the enrichment of uranium objects are almost linear. For a uranium object of a given shape, the uranium enrichment can be obtained with the re-lation curves, which could be got in advance by calibration experiments or simulations. uranium enrichment, photonuclear reaction, particle Monte Carlo transport PACS: 25.85.Jg, 25.85.Ec, 24.10.Lx, 27.90.+b1 IntroductionThe verification technology to confirm the authenticity of anuclear warhead or a nuclear component is very importantfor the future nuclear reductions. In order to confirm that anuclear warhead or component being inspected is the de-clared one, it is essential to detect and verify its attributes,such as the presence of nuclear material, nuclear materialisotopic enrichment, mass, absence of nuclear material oxide, symmetry, and the age of the nuclear material [1].The isotopic enrichment is a decisive factor to determinewhether the material is weapon-grade or not. In arms con-trol verification, some information on the inspected object isclassified and it is impossible to get any samples from theobject to analyze, so only non-destructive assay could beused [2,3].Non-destructive assay has two approaches, passive mea-surement and active interrogation. In passive measure-ments, the radiation emitted from the object spontaneously and the results are derived directly from analyzing the radi-ation of the object [4,5]. While in active interrogation, the object is stimulated by a neutron or high-energy photon source and the results are derived by analyzing the induced emissions [6]. The radioactivity of uranium is relatively weak, and the energy of characteristic γ emission is low, and it is hard to detect the released radiation for shielded uranium objects. So the active interrogations are needed fordetermining uranium enrichment [7,8]. This paper describes our recent work on exploring the feasibility of applying high-energy photon interrogation to determine the uranium enrichment for verification purpose. The method was examined by simulations with MCNP code. The simulation system with mono-energy high-energy in-terrogation photon and specified geometry are presented to simplify the calculations. In the simulations, the intensities of released neutrons from different shapes of uranium ob-jects are calculated and analyzed.2Zhu J Y , et al . Sci China Phys Mech Astron October (2011) Vol. 54 No. 102 Physics and simulation2.1 Nuclear reactions by high-energy photonHigh-energy photons lead to photoneutron reactions and photofission reactions in some fission materials with neu-tron released [9]. The photonuclear reaction thresholds for 235U and 238U are about 6 MeV. In uranium objects, the high-energy photons can induce both photoneutron reac-tions and photofission reactions with neutron produced.Neutrons from a photoneutron reaction are emitted prom-ptly (~10−12s) after the reaction occurs, while photofissionreactions emit both prompt and delayed neutrons. Theseneutrons moderate in the material, and induce more fissionreactions, with more prompt and delayed neutrons released.Those neutrons can penetrate the material and its shields,with information on the uranium object [10,11].The released neutron intensity is related to the total amount of neutron produced in nuclear reaction, the detec-tive solid angle, the location of the detector and the detec-tion efficiency of the detector. Thus the neutron intensitycan be expressed by the following integral equation,ected d d d det 20()()(,,,)(,,),4V I S C E g E n E E r ∞Ω′=⎧⎫⎪⎪ΩΩ′Ω⎨⎬π⎪⎪⎩⎭∫∫∫∫r r r (1) where, the integral equation is carried out for the total vo-lume (V ) and the energy of produced neutron (E ),(,,,)g E ΩΩ′r and (,,)n E Ωr are the self-absorption fac-tor and the total neutron yield of energy element E and vo-lume element r , Ω is the direction of the neutrons, Ω′is the direction of the detector, S is the detective area, d r is the distance between the detector and the inspected uranium object, ()C E is the detection efficiency for neutron with energy E . The total neutron yield of energy element E and volume element is composed of two parts neutron produced by photon source ((,,))n E γΩr and the neutron produced by secondary neutron n ((,,)).n E Ωr These can be expressed byn n n n n n d d 00(,,)(,)(,)(,),(,,)(,)(,)(,),i i ij j j n E e I e N E e e n E e I e N E e e ∞γγγγγγ∞⎧Ω=ΣΩ⎪⎪⎨⎪Ω=ΣΩ⎪⎩∑∫∑∫r r r r (2) where, ()i j is the neutron producing reaction for photon(neutron), (,)I v E γ (n (,)I v E ) is the flux for photon (sec-ondary neutron), (,)i N E e γ n ((,))j N E e is the photon (neutron) induced neutron spectrum with energy e γ(n e ) ofneutron producing reaction (),i j (,)i e γΣΩ (n (,)j e ΣΩ) is the macroscopic cross-section for photon (neutron) of ener-gy e γ(n e ).Because 235U and 238U have different photonuclear andneutron induced fission cross sections, they will respond differently to the interrogation [9]. The method to determine uranium enrichment by high-energy photon interrogation is based on the difference between the reaction cross sections of 235U and 238U.2.2 MCNP code and simulation processes MCNP is a general-purpose, continuous-energy, genera-lized-geometry, time-dependent, coupled neutron/photon/electron Monte Carlo transport code. In MCNP calculation,the particle intensity is obtained by tracking and summingevery transportation history from the source until the result is constant within an accepted variance.In the simulation, three processes are calculated. The first process is the transportation and reaction of photon. In the process, photons transport in the inspected uranium objects, and the photonuclear reactions as well as photoelectric reac-tions are considered. The second process is the transporta-tion and reaction of neutron. In the process, neutrons trans-port and moderate in the objects, inducing fission reactions in the uranium with neutrons being generated. The calcula-tions are carried out for all the neutrons, including thoseinduced by neutrons, until they leave the system consideredin the simulation. The third process is neutron detection. Inthe process, the neutron is recorded, if the released neutronsget into the detecting area.2.3 Simulation system configuration To study the feasibility of this method, Simplified models are set up. The simulation system contains three parts, pho-ton source, inspected object and neutron detector. To simpl-ify the calculation, a mono-energy and mono-direction photon source is used. The neutron intensity is obtained by recording the average neutron flux of a cylinder locatedaround the object with a height of 100 cm, inner diameter of 100 cm, and outer diameter of 102 cm, which represents agroup of 3He neutron detector tubes located in a cylinder. Three different structures of inspected objects are analyzed, respectively. Model A is a naked spherical uranium shell with no shields outside; model B is a shielded spherical uranium shell with 0.5 cm depleted uranium (DU) ortungsten (W) shields outside; model C is a shielded spheri-cal uranium shell with 3 cm depleted uranium or tungstenshields outside. These three models are used to obtain therelation curves of neutron intensity and 235U enrichment indifferent objects, In the calculation, different uraniumenrichments are used from 0.1% to 99.9%. The parametersin each uranium object model are shown in Table 1.Zhu J Y , et al . Sci China Phys Mech Astron October (2011) Vol. 54 No. 103Table 1 Parameters in the models of uranium object Model Uranium object Shield235U enrichment Radius (cm) Material Radius (cm)A0.1%–99.9% 5.77–7 None− B 0.1%–99.9% 5.77–7 DU or W 7–7.5 C0.1%–99.9% 5.77–7 DU or W 7–103 Results and discussions3.1 Relation curve of neutron intensity and 235UenrichmentIn order to get the relation curve of neutron intensity and the 235U enrichment, the neutron intensities for model A with 12 MeV interrogation photons are calculated for 235U enrich-ment from 0.1% to 99.9%. In our calculation, the neutrons detected before 10−3 s from the interrogating photon emit-ting, are considered as prompt neutrons. The delayed neu-trons are calculated for the neutrons detected after 0.5 s. Figure 1 shows the relation curves of neutron intensity and the 235U enrichment. The left panel of the figure is ob-tained with prompt neutrons; while the right panel obtained with delayed neutrons. The components of the prompt and delayed neutrons are different: the prompt neutrons are con-tributed by (γ,n), (γ,2n), (n,n ′), (n,n ′) reactions and the prompt parts in γ and neutron induced fission reactions, while the delayed neutrons are contributed only by the de-layed parts in fission reactions [12]. Higher 235U enrichment, which means higher multiplication factor, results in moreprompt and delayed neutrons produced from chain reaction.Figure 1 The relation curve of neutron flux and the 235U enrichment for buck uranium shell. The left and right panels are presented for the result of prompt and delayed neutron, respectively.For the uranium martial with 0.1% 235U, the non-zero cross sections of photoneutron and photofission reactions for 238U lead to non-zero neutron intensity of prompt neu-tron. The intensity of delayed neutron is low, because the delayed neutron is only related to the fission reactions and the fission cross sections for 238U are small [9].For both the prompt and delayed neutrons, the relation curves between neutron intensity and 235U enrichment are monotonic. The 235U enrichment can be determined by the neutron intensity. Therefore, if the shape of the inspected uranium object is given, the relation curve for that object can be obtained. After detecting the data of neutron intensi-ty for the inspected uranium object by high-energy photon interrogation, it is possible to retrieve the uranium enrich-ment with the relation curve.3.2 235U enrichment for shielded objectsTo test the capability of detection of the shielded objects, calculations are carried out for shielded uranium shells. The relation curves of neutron intensity and 235U enrichment for models D and E are shown in Figure 2.Due to the photon absorption in the shielding martial, the slope of the relation curves are flatter than that of the un-shielded model. But all the curves are monotonic. The 235U enrichment can be obtained with the relation curves. Al-though the intensity of prompt neutrons is about one hun-dred times higher than that of the delayed neutron, the si-mulations indicate that the intensity of delayed neutron is more sensitive to the 235U enrichment. The capability forFigure 2 The relation curves of neutron flux and the 235U enrichment for shielded uranium shell. The left and right panels are presented for the result of prompt and delayed neutron, respectively. The square symbols and circle symbols are presented for uranium and tungsten shielding, the line and dashed line are presented for 0.5 cm and 3 cm shields, respectively.4Zhu J Y , et al . Sci China Phys Mech Astron October (2011) Vol. 54 No. 10prompt neutron to distinguish 235U and 238U is weakened bythe prompt neutron from photoneutron and photofission reactions. The total cross sections of 235U and 238U for pho-toneutron and photofission reactions are not significantly different, the intensities of prompt neutrons generated from 235U and 238U by photonuclear reaction are almost the same. They cannot provide information on distinguishing the 235U and 238U in efficient precision. Only the neutrons generated from chain reaction provide useful information to distin-guish the two uranium isotopes.While for delayed neutrons, the contribution of photofis-sion reactions is much lower than that of chain reactions, due to the low cross section of photofission reaction for 238U. Neutron induced neutrons play a more important role in the result, thus the relation curve for delayed neutron is more sensitive to the 235U enrichment.Therefore, for a shielded object, the curve is not only re-lated to the uranium enrichment but also to the shielding material. The enrichment of a uranium object of a given shape can be obtained by high-energy photon interrogation. If the configuration of the inspected uranium object is un-known, some other methods should be used additionally to determine the attributes of the inspected object. 3.3 Optimal interrogation energyThe photonuclear cross sections of 235U and 238U are related to the energy of the interrogation photon [9]. Different in-terrogation energies will result in different capability of the determination of the 235U enrichment. In order to determine the optimal interrogation energies, calculations are carried out for models B and C with 235U enrichment of 30% and 90% with different interrogation energies. The neutron in-tensities ratios between the results for the 235U enrichment of 30% and 90% are obtained and shown in Figure 3. Larger difference means higher capability in distinguishing the two isotopes. The figure shows that the intensity ratio reaches its maximum at 12 MeV. Photon of higher energy can pene-trate the shields easily. In the nuclear material detectionsystem, photon of higher energy can increase the nuclearFigure 3 Ratios of neutron intensities for the 235U enrichment of 30% and 90% objects, the symbols are the same as in Figure 2.material detection capabilities [13]. However, our calcula-tions indicate that the optimal interrogation energy to de-termine the 235U enrichment is around 12 MeV. 3.4 Direction detectingThe released neutron intensity is anisotropic. To decide the optimal direction of the detector, by which the highest neu-tron intensities can be got, we design a system with seven detectors in different directions. The neutron intensities in different directions are calculated for model A. The results in Figure 3 show that the neutron intensity around 180° is higher than in other directions.In unite martial the intensity of the fission neutrons is in proportion to the induced particles. As photons being ab-sorbed in the martial, less neutrons are produced in the other side of the inspected uranium object, thus less fission neu-trons are generated. So we suggest that, in high-energy photon interrogation experiment, the detectors should be located at the same side of the photon source. This configu-ration is also more convenient than locating the source and the detectors in the different side of the inspected object.4 ConclusionsThe feasibility of applying the high-energy photon interro-gation method to determine the uranium enrichment in deep nuclear reduction verifications is investigated. Transporta-tion and reaction processes of photon and neutron are simu-lated with MCNP code by building simplified models of naked and shielded uranium shells. Simulations are carried out for these models with different 235U enrichment to ob-tain the relation curves of neutron intensities and uranium enrichment. For both prompt and delayed neutron, results indicate that neutron intensities are monotonically increased with 235U enrichment. Therefore, with the monotonic rela-tion curve, which can be obtained by calibration experi-ments or simulations in advance, the 235U enrichment couldFigure 4 The neutron flux ratio in different directions around the in-spected object normalized by the result obtained in 0°, which is the direc-tion of the interrogating photon.Zhu J Y, et al. Sci China Phys Mech Astron October (2011) Vol. 54 No. 105be retrieved.In summary, for a uranium object of a given shape, the uranium enrichment can be determined by high-energy photon interrogation method. 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