简述盐碱地改良原理？

Mark Twain once observed that giving up smoking is easy. He knew, because he’d done it hundreds of times himself. Giving up for ever is a trifle more difficult, apparently, and it is well known that it is much more difficult for some people than for others. Why is this so

Few doctors believe any longer that it is simply a question of will power. And for those people that continue to view addicts as merely "weak", recent genetic research may force a rethink. A study conducted by Jacqueline Vink, of the Free University of Amsterdam, used a database called the Netherlands Twin Register to analyze the smoking habits of twins. Her results, published in the Pharmacogenomics Journal, suggest that an individual’s degree of nicotine dependence, and even the number of cigarettes he smokes per day, are ply genetically influenced.

The Netherlands Twin Register is a voluntary database that contains details of some 7,000 pairs of adult twins (aged between 15 and 70 ) and 28,000 pairs of childhood twins. Such databases are prized by geneticists because they allow the comparison of identical twins (who share all their genes) with fraternal twins (who share half). In this case, however, Dr. Vink did not make use of that fact. For her, the database was merely a convenient repository of information. Instead of comparing identical and fraternal twins, she concentrated on the adult fraternal twins, most of whom had completed questionnaires about their habits, including smoking, and 536 of whom had given DNA samples to the register.

The human genome is huge. It consists of billions of DNA "letters", some of which can be strung together to make sense (the genes) but many of which have either no function, or an unknown function. To follow what is going on, geneticists rely on markers they have identified within the genome. These are places where the genetic letters may vary between individuals. If a particular variant is routinely associated with a particular physical feature or a behavior pattern, it suggests that a particular version of a nearby gene is influencing that feature or behavior.

Dr. Vink found four markers which seemed to be associated with smoking. They were on chromosomes 3, 6, 10 and 14, suggesting that at least four genes are involved. Dr. Vink hopes that finding genes responsible for nicotine dependence will make it possible to identify the causes of such dependence. That will help to classify smokers better (some are social smokers while others are physically addicted) and thus enable "quitting" programs to be customized.

Results such as Dr. Vink’ s must be interpreted with care. Association studies, as such projects are known, have a disturbing habit of disappearing, as it were, in a puff of smoke when someone tries to replicate them. But if Dr. Vink really has exposed a genetic link with addiction, then Mark Twain’s problem may eventually become a thing of the past.

The word "genome" (line 1, paragraph 4) most probably means（）

A. a particular human gene

B. a DNA letter

C. a bank of genes

D. functional DNA letters

中国2010年上海世界博览会于2010年5月1日到10月31日举行。据此回答2—6题。

小题1:上海世博会的门票分为平日普通标价格为160元人民币、指定日普通标价格为200元人民币、指定日优惠标价为120元人民币、平日优惠票价为100元人民币、夜间票价格为90元人民币等不同档次。货币在门票定价中       

①执行价值尺度职能                     ②是观念中的货币

③执行流通手段职能                     ④是现实的货币

A．①④

B．③④

C．①②

D．②③小题2:制定上述各档次门票价格主要考虑的因素是                        

A．世博会门票的价值

B．人民币购买力的变化

C．参观人数的变化

D．消费结构的变化小题3:小李同学将赴上海参观世博会，许多同学都建议小了携带一张信用卡。这是因为信用卡

A．是一般等价物，能够作为财富的代表

B．集存取款、消费、结算为一体，方便安全

C．可随时随地地取现或进行消费结算

D．是表明个人信状况的信用凭证小题4:央行特为世博会发行了上海世界博览会纪念币一套。该套纪念币共4枚，其中金币2枚，银币2枚，均为中华人民共和国法定货币。此套纪念币                             

①可以充当商品交换的媒介               ②只能收藏不能流通

③体积小、价值大、久藏不坏             ④其发行以流通中实际需要量为依据

A．①②

B．③④

C．①③

D．②④小题5:上海世界博览会金银纪念币是                                    

①一般等价物         ②商品           ③铸币           ④货币符号

A．①②③

B．①②④

C．①③④

D．②③④

男，20岁，在一次体检中发现HBsAg阳性，当时无自觉症状及体征，肝功能正常。次年5月，因突然乏力、恶心、厌食、尿黄而入院。化验：AⅡ500u，血清总胆红素85μmol/L，抗一HAVIgM(+)。该患者的诊断可能为

A．急性黄疸型肝炎，甲、乙型肝炎病毒混合感染

B．急性甲型黄疽型肝炎，乙型肝炎病毒携带，者

C．急性乙型肝炎，合并甲型肝炎

D．乙型肝炎．慢性活动型，既往感染过甲型肝炎

E．乙型肝炎，慢性迁延型，既往感染过甲型肝炎

腮腺解剖学分为深、浅两部，其分界为（）

A.以面神经所在水平

B.以面神经管所在水平

C.以腮腺导管开口所在水平

D.以腮腺动脉所在水平

E.以面静脉所在水平

下列选项中说法错误的是

A．杜威关于教育本质的观点，可以概括为“教育即生长”、“教育即生活”、“教育即经验的继续不断的改造”

B．“从做中学”是杜威的教学理论及其基本原则

C．“从做中学”是杜威教育理论乃至整个现代派教育理论中的一个核心要求

D．杜威认为课程中占中心位置的应是各种形式的活动作业