题目内容
Electric Backpack
Backpacks are convenient．They can hold your books，your lunch，and a change of clothes，leaving your hands free to do other things．Someday，if you don’t mind carrying a heavy load，your backpacks might also power your MP3 player，keep your cell phone running，and maybe even light your way home． Lawrence C．Rome and his colleagues from the University of Pennsylvania in Philadelphia and the Marine Biological Laboratory in Woods Hole3，Mass. ，have invented a backpack that makes electricity from energy produced while its wearer walks．In military actions，search-and-rescue operations，and scientific field studies，people rely increasingly on cell phones，global positioning system（GPS） receivers，night-vision goggles，and other battery-powered devices to get around and do their work．The backpack’s electricity-generating feature could dramatically reduce the amount of a wearer’s load now devoted to spare batteries，report Rome and his colleagues in the Sept．9 Science．
The backpack ’s electricity-creating powers depend on springs used to hang a cloth pack from its metal flame．The frame. sits against the wearer’s back，and the whole pack moves up and down as the person walks． A gear mechanism converts vertical movements of the pack to rotary motions of an electrical generator，producing up to 7.4 watts．
Unexpectedly．tests showed that wearers of the new backpack alter their gaits in response to the pack ’s oscillations．so that they carry loads more comfortably and with less effort than they do ordinary backpacks．Because of that surprising advantage，Rome plans to commercialize both electric and non—electric versions of the backpack．
The backpack could be especially useful for soldiers，scientists，mountaineers，and emergency workers who typically carry heavy backpacks．For the rest of us．power—generating backpacks could make it possible to walk，play video games，watch TV，and listen to music，a11 at the same time．Electricity-generating packs aren’t on the market yet，but if you do get one eventually，just make sure to look both ways before crossing the street!
第 1 题 Backpacks are convenient because
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A．speak B．have C．1ink D．put
The Operation Of InternationaI Airlines
International airlines have rediseovered the business traveler，the man or woman who regularly jets from country to country as part of the job．This does not neeessarily mean that airlines ever abandoned their business travelers． Instead，eompanies like Lufthansa and Swissair would right argue that they have always catered best for the executive class passengers．But many airlines could be accused of concentrating too heavily in the recent past on attracting passengers by volume，often at the expense of the regular traveler．Too often，they have seemed geared for quantity rather than quality．
Operating a major airline is essentially a matter of finding the right mix of passengers．The airlines need to fill up the back of their wide—bodied jets with low fare passengers，without forgetting that the front end should he filled with people who pay suhstalltially more for their tickets．
It is no coincidence that the two major airline bankruptcies were among the companies specializing in cheap flights．But low fares require consistently full aircraft to make flights economically viable，and in the recent recession the volume of traffic has not grown．Equally the large number of airlines jostling for the available passengers has created a huge excess of capacity．The net result of excess capacity and cut—throat competition driving down fares had been to push some airlines into collapse and leave many others hovering on the brink．
Against this grim background，it is no surprise that airlines are turning increasingly towards the business travelers to improve their rates of return．They have invested much time and effort to establish exactly what the executive demands for sitting apart from the tourists．
High on the list of priorities is punctuality；an executive’s time is money．In—flight service is another area where the airlines are jostling for the executive’s attention．The free drinks and headsets and better food are all part of the lure．
Another development has been the accent of seating arrangements．Regular travelers have become well versed in the debate about seat pitch-the amount of room between each passenger．And first-class passengers are now offered sleeperettes， which，for long journeys，make it possible to snatch a proper night’s sleep．Sleeperettes have proved so popular that they will soon become universal
in the front end of most aircraft．
The airlines are also trying to improve things on the ground．Executive lounges are commonplace and intended to make the inevitable waiting between flights a little more bearable．Luggage handling is being improved．Regrettably，there is little the airlines can do to speed up the boring immigration and customs process，which manages to upset and frustrate passengers of all classes in every continent．
Although it is the airlines’intention to attract executive passengers from their rivals，the airlines themselves would nonetheless like to change one bad habit of this kind of traveler—the expensive habit of booking a flight and then failing to turn up．The practice is particularly widesptead in Europe，where businessmen frequently book return journeys home one on severnl flights．
第 46 题 According to the passage，in operating airlines it is essential to________．
More about Alzheimer’s Disease
Scientists have developed skin tests that may be used in the future to identify people with Alzheimer’s disease and may ultimately allow physicians to predict who is at risk of getting this neurological disorder.
The only current means of diagnosing the disease in a living patient is a 1ong and expensive series of tests that eliminate every other cause of dementia.
“Since A1ois Alzheimer described the disease nearly a century ago，people have been trying to find a way to accurately diagnose it in its early stages，”said Patricia Grady，acting director of the National Institute of Neurological Disorders and Stroke in Bethesda，Maryland.“This discovery，if confirmed，could prove a big step forward in our efforts to deal with and understand the disease.”
A1zheimer，s is the single greatest cause of mental deterioration in older people，affecting between 2.5 million and 4 million people in the United States alone．The devastating disorder gradually destroys memory and the ability t0 function，and eventually causes death．There is currently no known treatment for the disease．
Researches discovered that the kin cells of Alzheimer’s patients have defects that interfere with their ability to regulate the now of potassium in and out of the cells．The fact that the cell defects are present in the skin suggests that Alzheimer’s results from physiological changes throughout the body，and that dementia may be the first noticeable effect of these changes as the deflects affect the cells in the brain．scientists said．
The flow of potassium is especially critical in cells responsible for memory formation． The scientists also found two other defects that affect the cells’ supply of calcium，another critical element．
0ne test developed by researchers calls for growing skin cells in a laboratory calture and then testing them with an electrical detector to determine if the microscopic tunnels that govern the now 0f potassium are open． 0pen potassium channels create a unique electrical signature．
A spokesman for the Alzheimer’s association said that if the validity of the diagnostic test can be proven it would he important rlevelopment，but tautioned that 0ther promising tests for Alzheimer’s have been disappointing．
第 46 题 The newly developed skin tests may be used in the future to allow doctors to
‘Hidden’ Species May Be Surprisingly Common
Cryptic species—animals that appear identical but are genetically quite distant—may be much more widespread than previously thought． The findings could have major implications in areas ranging from biodiversity estimates and wildlife management，to our understanding of infectious diseases and evolution．
Reports of cryptic species have increased dramatically over the past two decades with the advent of relatively inexpensive DNA sequencing technology．Markus Pfenninger and Klaus Schwenk，of the Goethe—Universitat in Frailkfurt，Germany，analyzed all known data on cryptic animal species and discovered that they are found in equal pmponions throughout all major branches 0f the animal kingdom and occur in equal numbers in all biogeographical regions．
Scientists had previously speculated that cryptic species were predominantly found in insects and reptiles．and were more likely to occur in tropical rather than temperate regions．“Species that are seemingly widespread and abundant could in reality be many different cryptic species that have low populations and are highly endangered，”says Pfenninger．Until the genetic information of all species in at least one taxon is thoroughly studied，no one will know just how many cryptic species exist．“It could be as high as 30％．”Pfenninger says．
“I’m extremely surprised by their results，”says Alex Smith of the University of Guelph in Ontario．Canada．“It’s a call to arms to keep doing the broad kind of genetic studies that we are doing．"
Sampling as many individuals as possible．scientists hope to complete work on aU fish and birds in another 5 to 10 years． Once either of these taxonomic groups is completed，Pfenninger says researchers will able t0 decide how many cryptic species exist throughout the animal kingdom．
Examples of cryptic species include the African elephant．A 2001 study found the elephants were actually two genetically distinct，non—interbreeding species，the African bush elephant and the African elephant．The species are currently listed as vulnerable and threatened，respectively，by the World Conservation Union（WCU）．
The reclassifications are more than an academic exercise．They define populations that have evolved independently of each other and whose genetic differences can have significant consequences．
In the early 1900s misidentification of mosquito species based on morphology confused attempts to control malaria in Europe． Ultimately，what was thought to be a single species was actually made up of six sibling species，only three of which transmitted the disease．“The basic unit in biology is always the species．and you have to know what you are dealing with，”Pfenninger says．Much previous research is now no longer used．he says，because it is not clear what species was being studied．
第 36 题 Which of the following about the significance of the research on cryptic species is NOT true？
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