John and Alice got()last year in Las Vegas.
We find that some birds _____ twice a year between hot and cold countries.
It _____ only last year _____ I made her acquaintance.
Which of the following SQL statements will return the year and average salary for all employees hired within a given year that have a salary greater than $30,000?()
Today ,as in every other day of the year ,more than 3000 U.S. adlescents will smoke their first cigarette on their way to becoming regular smokers as adults. During their lifetime,it can be expected that of these 3000 about 23 will be murdered,30 will die in traffic accidents, and nearly 750 will be killed by a smoking-related disease. The number of deaths attributed to cigarette smoking outweithts all other factors, whether voluntary or involuntary, as a cause of death. Since the late 1970s, when daily smoking among high school seniors reached 30 precent , smoking rates among youth have declined . While the decline is impressive ,several important issues must be raised. First, in the past several years,smoking rates among youth have declined very little. Second,in the late 1970s ,smoking among male high school seniors exceeded that among female by nearly 10 percent . The statistic is reversing.Third ,several recent studies have indicate high school dropouts have excessively high smoking rates, as much as 75 percent . Finally, thouth significant declines in adolescent smoking have occurred in the past decade,no definite reasons for the decline exist. Within this context,the Naional Cancer Instiute (NCI) began its current effort to determine the most effecive measures to reduce smoking levesl among youth. According to the author, the deaths among youth are mainly caused by ().
Merry Christmas and A Happy New Year!()
We()the bathroom and plan()the bedroom this year.
[A] The work builds on a study published last year by Shinya Yamanaka of Kyoto University in Japan, which showed that mouse tail cells could be transformed into ES-like cells by inserting four genes (Science Now, 3 July 2006).Those genes are normally switched off after embryonic cells differentiate into the various cell types. In June this year, Yamanaka and another group reported that the cells were truly pluripotent, meaning that they had the potential to grow into any tissue in the body (Science Now, 6 June).
[B] In the new work, Yamanaka and his colleagues used a retrovirus to ferry into adult cells the same four genes they had previously used to reprogram mouse cells: OCT3/4, SOX2, KLF4, and c-MYC. They reprogrammed cells taken from the facial skin of a 36-year-old woman and from connective tissue from a 69-year-old man. Roughly one iPS cell line was produced for every 5,000 cells the researchers treated using the technique, an efficiency that enabled them to produce several cell lines from each experiment.
[C] Now the race to repeat the feat in human cells has ended in a tie: Two groups report today that they have reprogrammed human skin cells into so-called induced pluripotent cells (iPSs). In a paper published online in Cell, Yamanaka and his colleagues show that their mouse technique works with human cells as well. And in a paper published online in Science, James Thomson of the University of Wisconsin, Madison, and his colleagues report success in reprogramming human cells, again by inserting just four genes, two of which are different from those Yamanaka uses.
[D] Once the kinks are worked out, “the whole field is going to completely change,” says stem cell researcher Jose Cibelli of Michigan State University in East Lansing. “People working on ethics will have to find something new to worry about.”
[E] Thomson’s team started from scratch, identifying its own list of 14 candidate reprogramming genes. Like Yamanaka’s group, the team used a systematic process of elimination to identify four factors: OCT3 and SOX2, as Yamanaka used, and two different genes, NANOG and LIN28. The group reprogrammed cells from fetal skin and from the foreskin of a newborn boy. The researchers were able to transform about one in 10,000 cells, less than Yamanaka’s technique achieved, Thomson says, but still enough to create several cell lines from a single experiment.
[F] Scientists have managed to reprogram human skin cells directly into cells that look and act like embryonic stem (ES) cells. The technique makes it possible to generate patient-specific stem cells to study or treat disease without using embryos or oocytes—and therefore could bypass the ethical debates that have plagued the field. “This is like an earthquake for both the science and politics of stem cell research,” says Jesse Reynolds, policy analyst for the Center for Genetics and Society in Oakland, California.
[G] Although promising, both techniques share a downside. The retroviruses used to insert the genes could cause tumors in tissues grown from the cells. The crucial next step, everyone agrees, is to find a way to reprogram cells by switching on the genes rather than inserting new copies. The field is moving quickly toward that goal, says stem cell researcher Douglas Melton of Harvard University. “It is not hard to imagine a time when you could add small molecules that would tickle the same networks as these genes” and produce reprogrammed cells without genetic alterations, he says.
(此文选自Science2007年刊)
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I have so much work to do that a holiday form this year is ______.
The ()of this recipe (烹饪法) was made public one year after it was put into the market.