T波振幅低平是指（） A. B. C. D. E.

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 ultimate purpose of Dr. Vink’ s research is to（）

A.identify all the genes that are responsible for smoking

B.determine the real cause of nicotine dependence

C.make a difference between social smokers and other smokers

D. help different smokers give up smoking more effectively

一组邻边分别是4厘米和6厘米的平行四边形，它的周长是______．

If you've been joining in chat room conversations, or trading e-mail with Web pals, you have become one of the millions who write in a peculiarly short form of English.

And you've got a sense of humor about short forms like SOHF(="sense" of humor failure) to describe Internet newcomers who don't understand you.

Across the globe, every night teenagers and their elders are “talking” online—many of them are talking at the same time.

It's fast: try talking to six people at once. It's brief: three or four words per exchange. It takes wit, concentration, and quick fingers.

And it requires tremendous linguistic economy. There's neither time nor space for explanations. Why consume precious key-strokes telling six friends you have to leave for a moment to take care of your little brother when BRB(="be" right back) will do? Want to enter a conversation? Just type PMFJI(="pardon" me for jumping in).  Interested in whom you're talking to? Type A/S/L, the nearly universal request to know your pal's age, sex and location. You may get 15/M/NY as a response from your pal.

If something makes you laugh, say you're OTF(="on" the floor),or LOL(="laughing" out loud),or combine the two into ROTFL(="rolling" on the floor laughing).

And when it's time to get back to work or go to bed, you type GTG(="got" to go) or TTYL(talk to you later).

People want to write as fast as possible, and they want to get their ideas across as quickly as they can. Capital letters are left in the dust, except when expressing emotion, as it takes more time to hold down the “shift” key and capitals. Punctuation is going, too.

小题1:In order to talk to several people at the same time on the Internet_______.

A．you have to speak fast and fluently

B．you have to express your ideas in a brief way

C．you should speak with wit and humor

D．one should pay much attention to the accuracy of the words小题2:If you get 17/F/NY as an answer to your A/S/L, it means_______.

A．the person on the other end is 17 from New York and he is fine

B．you are talking to a girl who is 17 and lives in New York

C．you are talking to 17 girls who are from New York

D．the person who are talking to you is a 1.7-foot tall New York girl小题3:To save time on the Internet_______.

A．some people leave their letters in the dustbin

B．some people never use “shift” in their writing

C．many people leave the capital and punctuation

D．people seldom use capital letters or punctuation

牙髓组织的增龄性变化是

A．细胞成分逐渐增多
B．纤维成分逐渐减少
C．牙本质吸收多于新生
D．牙髓血管增生
E．继发性牙本质不断形成

关系数据库的规范化理论规定，在执行分离时，必须遵守 【10】 ，保持原有的依赖关系和无损连接。