大学六级-602及答案解析.doc
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1、大学六级-602 及答案解析(总分:710.00,做题时间:90 分钟)一、Part Writing(总题数:1,分数:103.00)1.Directions: For this part, you are allowed 30 minutes to write a short essay entitled On Television Advertisement. You should write at least 150 words following the outline given below:1. 电视节目总广告很多2. 广告的利与弊3. 我的观点On Television Adve
2、rtisement(分数:103.00)_二、Part Reading Compr(总题数:1,分数:70.00)HIV Vaccine Feat Leaves More Questions Than AnswersOnly hours after HIV vaccine researchers announced the achievement of a milestone that has eluded them for a quarter of a century, they began plotting their next stepsand coming back to realit
3、y. Their ultimate goal, halting the spread of AIDS, remains far in the future. A Thai and American team had announced early Thursday in Bangkok that they had found a combination of vaccines that provided modest protection against infection with HIV, offering the first proof of principle that the dea
4、dly disease could be tamed by teaching the immune system to recognize the virus and defeat it. Scientists around the world hailed the achievement.But by Thursday afternoon, the initial wave of joy had given way to the recognition that many questions will have to be answered before researchers can pr
5、oduce a vaccine that will reliably shield people from HIV. For starters, it could take years to figure out the biological mechanisms that produced the apparent 31% reduction in infections among those given the vaccine treatment.Researchers have never before observed antibodies(抗体) or other molecules
6、 in the blood that could block an infection of HIV, the virus that causes AIDS. Now they will try to figure out whether this combination of vaccines stimulated new molecules, or provoked an unusual blend of ones previously observed. Experts predicted that it would require 2 to 3 years of research to
7、 better understand how the vaccine worked, and an additional 5 to 10 years to produce a vaccine that was ready to test in people. Some researchers even wondered whether the apparent reduction in infections was simply a statistical mistake resulting from the small number of HIV cases observed in the
8、trial.The abundance of unanswered questions hasnt sapped the enthusiasm of many HIV researchers. After 26 years of seemingly futile research on vaccines, they have finally made some progress on demonstrating the feasibility of an HIV vaccine, said Dr. Anthony Fauci, director of the National Institut
9、e of Allergy and Infectious Diseases, which largely funded the $120-million study. “This is the first positive signalmodest though it may bethat we have ever got with any vaccine that we have ever tested in humans,“ Fauci said. But “is it a vaccine that is ready for prime time? No.“The Thai trial, w
10、hich began in 2003, had been laughed at by many critics as a waste of time and money because its two vaccines had produced no benefit in individual trials. But a few researchers speculated that using them togetherwith one vaccine priming (开始修复) the immune system and the second boosting that response
11、 would be more effective. The primer in this combination is Alvac, made by Sanofi Pasteur, which uses a harmless virus to carry three synthetic HIV genes into the body. The boost comes from Aidsvax, originally made by VaxGen Inc. and now owned by the nonprofit group Global Solutions for Infectious D
12、iseases. It contains a genetically engineered version of a protein from the HIV surface.The study, led by Dr. Supachai Rerks-Ngarm of the Thai Ministry of Public Healths Department of Disease Control, involved more than 16,000 volunteers in Thailand, all from the general population rather than from
13、a pool of high-risk homosexuals and drug users used in past studies. Half received four priming doses of Alvac and two boost doses of Aidsvax over a six-month period; the other half received placebo(无效对照药) shots. After three years of follow-up, new HIV infections were observed in 74 of the 8,198 peo
14、ple who received the placebo, but in only 51 of the 8,197 given the vaccine, a statistically significant 31% reduction.To the researchers disappointment, however, the vaccine did not reduce levels of HIV activity in those who became infected after being vaccinated. The trial was carried out in Thail
15、and because the initial research was conducted there and the vaccine was based on the version of HIV that circulates in that country. Full details of the study will be released next month at a conference in Paris, and researchers are eagerly awaiting them.Dr. Salim S. Abdool Karim, an epidemiologist
16、 at Columbia University in New York and director of the Centre for the AIDS Programme of Research in South Africa in Durban, said he was particularly eager to know whether people who got vaccinated and stayed healthy had a bigger response from the white blood ceils known as cellular T lyrnphocytes(淋
17、巴球). “A whole range of vaccines were developed on the hypothesis(假想) that they generated sufficient cellular T lymphocyte responses to prevent infection,“ he said. “Weve never been able to test that hypothesis because no vaccine has worked until now.“And if it is not the lymphocytes, then “what kind
18、 of compounds were the cells making when you inoculate them with the vaccine?“ asked Dr. Spyros Kalams an HIV immunology researcher at Vanderbilt University in Nashville and director of the HIV Vaccine Trials Program there. “Was it a compound that can kill infected cells? Does it make proteins that
19、stop the virus from replicating?“ Researchers now will begin the painstaking work of comparing the blood of those who were vaccinated and resisted infection and those who did not. Then they will look for molecules that are more abundant in the healthy people, Fauci said.Once researchers identify the
20、se so-called correlates of immunity, they can begin to look for ways to prompt the body to make themthe key to producing an effective vaccine. The Thai results are “an opening of a door to answer some very important questions,“ he said. But several scientists cautioned that there was no guarantee th
21、e Thai blood samples would reveal the biological secrets of HIV immunity. Surely some of the people who resisted HIV infection were protected by the vaccine, but not all, said Dr. Otto Yang, an immunologist at UCLAs David Geffen School of Medicine.Yang also expressed doubt that a combination of vacc
22、ines made the difference in those who benefited. He and others noted that this was the first large study to focus on a low-risk population. Perhaps transmitting the virus through heterosexual sex instead of directly into the bloodstream on an needle gives the immune system a better chance of fightin
23、g off infection. Although it is also unclear whether these particular vaccines could be used elsewhere in the world, scientists said that if they could figure out what made this combination work, they could localize the approach to other regions. The dominant HIV strains vary from region to region.A
24、t least 33 million people worldwide are infected with HIV and 25 million have died, the World Health Organization said. An estimated 7,500 are infected each day, emphasizing the need for a vaccine. There have been three previous vaccine trials in humans. Aidsvax had previously failed in two large tr
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