题目内容
Cell Phone Lets Your Secret Out
Your cell phone holds secrets about you. Besides the names and【51】 that you've programmed into it, traces of your DNA linger on the device, according to a new study.
DNA is genetic material that【52】 in every cell. Like your fingerprint, your DNA is unique to you【53】 you have an identical twin. Scientists today routinely analyze DNA in blood, saliva, or hair left【54】 at the scene of a crime. The results often help detectives identify【55】 and their victims. Your cell phone can reveal more about you【56】 you might think.
Method J. McFadden, a scientist at McMaster University in Hamilton, Ontario, heard about a crime in which the suspect bled onto a cell phone and later dropped the【57】. This made her wonder whether traces of DNA lingered on cell phones—even when no blood was involved.【58】she and colleague Margaret Wallace of the City University of New York analyzed the flip-open phones of 10 volunteers. They used swabs to collect【59】 traces of the users from two parts of the phone: the outside, where the user holds it, and the【60】 , which is placed at the user's ear.
The scientists scrubbed the phones using a solution made mostly【61】alcohol. The aim of washing was to remove all detectable traces of DNA. The owners got their phones【62】for another week. Then the researchers collected the phones and repeated the swabbing of each phone once more.
The scientists discovered DNA that【63】to the phone's speaker on each of the phones. Better samples were collected from the outside of each phone, but those swabs also picked up DNA that belonged to other people who had apparently also handled the phone.【64】, DNA showed up even in swabs that were taken immediately after the phones were scrubbed. That suggests that washing won't remove all traces of evidence from a criminal's device. So cell phones can now be added to the【65】of clues that can clinch a crime-scene investigation.
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Dr. Smith hopes to make this device smaller so as to help the blind navigate unfamiliar places.
American Immigrants
The percentage of immigrants (including those unlawfully present ) in the United states has been creeping upward for years. At 12.6 percent, it is now higher than at any point since the mid 1920s.
We are not about to go back to the days when congress openly worried about inferior races polluting America's bloodstream. But once again we are wondering whether we have too many of the wrong sort newcomers. Their loudest critics argue that the new wave of immigrants cannot, and indeed do not want to, fit in as previous generations did.
We now know that these racist views were wrong. In time, Italians, Romanians-and members of other so-called inferior races became exemplary Americans and contributed greatly, in ways too numerous to detail, to the building of this magnificent nation. There is no reason why these new immigrants should not have the same success.
Although children of Mexican immigrants do better, in terms of educational and professional attainment, than their parents, UCLA sociologist Edward Telles has found that the gains don't continue. Indeed, the fourth generation is marginally worse off than the third. James Jackson, of the University of Michigan, has found a similar trend among black Caribbean immigrants. Telles fears that Mexican-Americans may be fated to follow in the footsteps of American blacks-that large parts of the community may become mired(陷入) in a seemingly permanent state of poverty and underachievement. Like African-Americans, Mexican-Americans are increasingly relegated to (降入)segregated substandard schools, and their dropout rate is the highest for any ethnic group in the country.
We have learned much about the foolish idea of excluding people on the presumption of the ethnic/racial inferiority. But what we have not yet learned is how to make the process of Americanization work for all. I am not talking about requiring people to learn English or to adopt American ways; those things happen pretty much on their own, but as arguments about immigration hear up the campaign trail, we also ought to ask some broader question about assimilation, about how to ensure that people, once outsiders, don't forever remain marginalized within these shores.
That is a much larger question than what should happen with undocumented workers, or how best to secure the border, and it is one that affects not only newcomers but groups that have been here for generations. It will have more impact on our future than where we decide to set the admissions bar for the latest ware of would-be Americans. And it would be nice if we finally got the answer right.
How were immigrants viewed by U.S. congress in early days？
According to Dr. Oberdor, this device can lead the blind people to the exact place he/she
Sensory psychophysics play a vital part in the invention of this device.
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