2013年医学博士外语真题试卷

Video game players may get an unexpected benefit from blowing away bad guys — better vision. Playing “action” video games improves a visual ability【C1】______tasks like reading and driving at night, a new study says.

The ability, called contrast sensitivity function, allows people to discern even subtle changes【C2】______gray against a uniformly colored backdrop. It’s also one of the first visual aptitudes to fade with age.

That’s【C3】______a regular regimen of action video game training can provide long-lasting visual power, according to work led by Daphne Bavelier of the University of Rochester.

Previous research shows that gaming improves other visual skills, such as the ability to track several objects at the same time and【C4】______attention to a series of fast-moving events, Bavelier said.

“A lot of different aspects of the visual system are being enhanced,【C5】______one,” she said. The new work suggests that playing video games could someday become part of vision-correction treatments, which currently rely mainly on surgery or corrective lenses.

“【C6】___you’ve had eye surgery or get corrective lenses, exposing yourself to these games should help the optical system to recover faster and better, you need to retrain the brain to make use of the better, crisper information that’s coming in【C7】___a result of your improved eyesight,” Bavelier said.

Expert action gamers in the study played first-person shooters Unreal Tournament 2004 and Call of Duty 2. A group of experienced nonaction gamers played The Sims 2, a “life simulation” video game. The players of nonaction video games didn’t see the same vision【C8】______, the study says.

Bavelier and others are now trying to figure out exactly why action games【C9】______seem to sharpen visual skill. It may be that locating enemies and aiming accurately is a strenuous, strength-building workout for the eyes, she said.

Another possible【C10】______is that the unpredictable, fast-changing environment of the typical action game requires players to constantly monitor entire landscapes and analyze optical data quickly. Finally, Bavelier said, the games’ rich payoff may also play a role.

“It’s pleasing to be successful in your mission,” she said. “When you combine rewards with these other “factors”, then you get much more learning.”

There is plenty we don’t know about criminal behavior. Most crime goes unreported so it is hard to pick out trends from the data, and even reliable sets of statistics can be difficult to compare. But here is one thing we do know: those with a biological predisposition to violent behavior who are brought up in abusive homes are very likely to become lifelong criminals.

Antisocial and criminal behavior tends to run in families, but no one was sure whether this was due mostly to social-environmental factors or biological ones. It turns out both are important, but the effect is most dramatic when they act together. This has been illustrated in several studies over the past six years which found that male victims of child abuse are several times as likely to become criminals and abusers themselves if they were born with a less-active version of a gene for the enzyme monoamine oxidase A(MAO-A), which breaks down neurotransmitters crucial to the regulation of aggression.

Researchers recently made another key observation: kids with this “double whammy” of predisposition and an unfortunate upbringing are likely to show signs of what’s to come at a very early age. The risk factors for long-term criminality— attention deficit hyperactivity disorder, low IQ, language difficulties — can be spotted in kindergarten. So given what we now know, shouldn’t we be doing everything to protect the children most at risk?

No one is suggesting testing all boys to see which variant of the MAO-A gene they have, but what the science is telling us is that we should redouble efforts to tackle abusive upbringings, and even simple neglect. This will help any child, but especially those whose biology makes them vulnerable. Thankfully there is already considerable enthusiasm in both the US and the UK for converting the latest in behavioral science into parenting and social skills: both governments have schemes in place to improve parenting in families where children are at risk of receiving poor care.

Some people are uncomfortable with the idea of early intervention because it implies our behavior becomes “set” as we grow up, compromising the idea of free will. That view is understandable, but it would be negligent to ignore what the studies are telling us. Indeed, the cost to society of failing to intervene — in terms of criminal damage, dealing with offenders and helping victims of crime — is bound to be greater than the cost of improving parenting. The value to the children is immeasurable.

After 25 years battling the mother of all viruses, have we finally got the measure of HIV? Three developments featured in this issue collectively give grounds for optimism that would have been scarcely believable a year ago in the wake of another failed vaccine and continuing problems supplying drugs to all who need them.

Perhaps the most compelling hope lies in the apparent “cure” of a man with HIV who had also developed leukemia. Doctors treated his leukemia with a bone marrow transplant that also vanquished the virus. Now US Company Sangamo Biosciences is hoping to emulate the effect patients being cured with a single shot of gene therapy, instead of taking antiretroviral drugs for life.

Antiretroviral therapy(ART)is itself another reason for optimism. Researchers at the World Health Organization have calculated that HIV could be effectively eradicated in Africa and other hard-hit places using existing drugs. The trick is to test everyone often, and give those who test positive ART as soon as possible. Because the drugs rapidly reduce circulating levels of the virus to almost zero, it would stop people passing it on through sex. By blocking the cycle of infection in this way, the virus could be virtually eradicated by 2050.

Bankrolling such a long-term program would cost serious money — initially around $3.5 billion a year in South Africa alone, ring to $85 billion in total. Huge as it sounds, however, it is peanuts compared with the estimated $1.9 trillion cost of the Iraq war, or the $700 billion spent in one go propping up the US banking sector. It also look small beer compared with the costs of carrying on as usual, which the WHO says can only lead to spiraling cases and costs.

The final bit of good news is that the cost of ART could keep on falling. Last Friday, GlaxoSmithKline chairman Andrew Witty said that his company would offer all its medicines to the poorest countries for at least 25 per cent less than the typical price in rich countries. GSK has already been doing this for ART, but the hope is that the company may now offer it cheaper still and that other firms will follow their lead.

No one doubt the devastation caused by AIDS. In 2007, 2 million people died and 2.7 million more contracted the virus. Those dismal numbers are not going to turn around soon — and they won’t turn around at all without huge effort and investment. But at least there is renewed belief that, given the time and money, we can finally start riddling the world of this most fearsome of viruses.

Archaeology can tell us plenty about how humans looked and the way they lived tens of thousands of years ago. But what about the deeper questions? Could early humans speak, were they capable of self-conscious reflection, did they believe in anything?

Such questions might seem to be beyond the scope of science. Not so. Answering them is the focus pf a burgeoning field that brings together archaeology and neuroscience. It aims to chart the development of human cognitive powers. This is not easy to do. A skull gives no indication of whether its owner was capable of speech, for example. The task then is to find proxies(普代物)for key traits and behaviors that have stayed intact over millennia.

Perhaps the most intriguing aspect of this endeavor is teasing out the role of culture as a force in the evolution of our mental skills. For decades, development of the brain has been seen as exclusively biological. But increasingly, that is being challenged.

Take what the Cambridge archaeologist Colin Renfrew calls “the sapient(智人的)paradox(矛盾)”. Evidence suggests that the human genome, and hence the brain, has changed little in the past 60,000 years. Yet it wasn’t until about 10,000 years ago that profound changes took place in human behavior: people settled in villages and built shrines. Renfrew’s paradox is why, if the hardware was in place, did it take so long for humans to start changing the world?

His answer is that the software — the culture — took a long time to develop. In particular, the intervening time saw humans vest(赋予)meaning in objects and symbols.Those meanings were developed by social interaction over successive generations, passed on through teaching, and stored in the neuronal connections of children.

Culture also changes biology by modifying natural selection, sometimes in surprising ways. How is it, for example, that a human gene for making essential vitamin C became blocked by junk DNA? One answer is that our ancestors started eating fruit, so the pressure to make vitamin C “relaxed” and the gene became unnecessary. By this reasoning, early humans then became addicted to fruit, and any gene that helped them to find it was selected for.

Evidence suggests that the brain is so plastic that, like genes, it can be changed by relaxing selection pressure. Our understanding of human cognitive development is still fragmented and confused, however. We have lots of proposed causes and effects, and hypotheses to explain them. Yet the potential pay-off makes answers worth searching for. If we know where the human mind came from and what changed it, perhaps we can gauge where it is going. Finding those answers will take all the ingenuity the modern human mind can muster.

Despite the numerous warnings about extreme weather, rising sea levels and mass extinctions, one message seems to have got lost in the debate about the impact of climate change. A warmer world won’t just be inconvenient. Huge swathes(片)of it, including most of Europe, the US and Australia as well as all of Africa and China will actually be uninhabitable — too hot, dry or stormy to sustain a human population.

This is no mirage. It could materialize if the world warms by an average of just 4°C, which some models predict could happen as soon as 2050. This is the world our children and grandchildren are going to have to live in. So what are we going to do about it?

One option is to start planning to move the at-risk human population to parts of the world where it will still be cool and wet. It might seem like a drastic move, but this thought experiment is not about scaremongering(危言耸听). Every scenario is extrapolated from predictions of the latest climate models, and some say that 4°C may actually turn out to be a conservative estimate.

Clearly this glacier-free, desertified world—with its human population packed into high-rise cities closer to the poles —would be a last resort. Aside from anything else, it is far from being the most practical option: any attempt at mass migration is likely to fuel wars, political power struggles and infighting.

So what are the alternatives? The most obvious answer is to radically reduce carbon dioxide levels now, by fast-tracking green technologies and urgently implementing energy-efficient measures. But the changes aren’t coming nearly quickly enough and global emissions are still rising. As a result, many scientists are now turning to “Earth’s plan B”.

Plan B involves making sure we have large scale geoengineering technologies ready and waiting to either suck CO₂out of the atmosphere or deflect the sun’s heat. Most climate scientists were once firmly against fiddling with the Earth’s thermostat, fearing that it may make a bad situation even worse, or provide politicians with an excuse to sit on their hands and do nothing.

Now they reluctantly acknowledge the sad truth that we haven’t managed to reorder the world fast enough to reduce CO₂emissions and that perhaps, given enough funding research and political muscle, we can indeed design, test and regulate geoengineering projects in time to avert the more horrifying consequences of climate change.

Whatever we do, now is the time to act. The alternative is to plan for a hothouse world that none of us would recognize as home.

Brittany Donovan was born 13 years ago in Pennsylvania. Her biological father was sperm donor G738. Unbeknownst to Brittany’s mother, G738 carried a genetic defect known as fragile X-a mutation that all female children born from his sperm will inherit, and which causes mental impairment, behavioral problems and atypical social development.

Last week, Brittany was given the green light to sue the sperm bank, Idant Laboratories of New York, under the state’s product liability laws. These laws were designed to allow consumers to seek compensation from companies whose products are defective and cause harm. Nobody expected them to be applied to donor sperm.

Thousands of people in the US have purchased sperm from sperm banks on the promise that the donor’s history has been carefully scrutinized and his sample rigorously tested, only for some of them to discover that they have been sold a batch of bad seed. Some parents learn about genetic anomalies after their disabled child is born and they press the sperm bank for more information. Others realize it when they contact biological half-siblings who have the same disorder.

So will Donovan vs Idant laboratories open the floodgates? It seems unlikely. New York’s product liability laws are highly unusual in that they consider donor sperm to be a product just like any other. Most other US states grant special status to blood products and body parts, including sperm. In these states, donor sperm is not considered a “product” in the usual sense, despite the fact that it is tested, processed, packaged, catalogued, marketed and sold. Similarly, European Union product liability law could not be used in this way.

Even if this lawsuit is an isolated case, it still raises some difficult questions. First, to what lengths should sperm banks go to ensure they are supplying defect-free sperm?

As we learn more and more about human genetics, there is growing list of tests that could be performed. Nobody would deny that donor sperm carrying the fragile X mutation should be screened out — and there is a test that can do so — but what about more subtle defects, such as language impairment or susceptibility to early Alzheimer’s?

Donovan vs Idant Laboratories also serves as a reminder of the nature of the trade in human gametes. Sperm bank catalogues can give the impression that babies are as guaranteed as dishwashers. The Donovans are entitled to their day in court, but in allowing the product liability laws to be used in this way, the legal system is not doing much to dispel that notion.

Stephanie Smith, a children’s dance instructor, thought she had a stomach virus. The aches and cramping were tolerable that first day, and she finished her classes. Then her diarrhea turned bloody. Her kidneys shut down. Seizures knocked her unconscious. The convulsions grew so relentless that doctors had to put her in a coma for nineweeks. When she emerged, she could no longer walk. The affliction had ravaged her nervous system and left her paralyzed from the waist down.

Ms. Smith, 22, was found to have a severe form of food-borne illness caused by E. coli, which Minnesota officials traced to the hamburger that her mother had grilled for their Sunday family party. In the simplest terms, she ran out of luck in a food-safety game of chance whose rules and risks are not widely known.

Meat companies and grocers have been barred from selling ground beef tainted by the virulent strain of E. coli known as ol57:H7 since 1994. Yet tens of thousands of people are still sickened annually by this pathogen with hamburger being the biggest culprit. Ground beef has been blamed for 16 outbreaks in the last three years alone. This summer, contamination led to the recall of beef from nearly 3,000 grocers in 41 states.

Ms. Smith’s reaction to the virulent strain of E. coli was extreme, but tracing the story of her burger shows that neither the system meant to make the meat safe, nor the meat itself, is what consumer have been led to believe.

Ground beef is usually not simply a chunk of meat run through a grinder. Instead, a single portion of hamburger meat is often an amalgam of various grades of meat from different parts of cows and even from different slaughterhouses. This makes the costs 25% less than it would have for cuts of whole meat. These cuts of meat are particularly vulnerable to E. coli contamination, food experts and officials say. Despite this, there is no federal requirement for grinders to test their ingredients for the pathogen.

Those ingredients include cuts from areas of the cow that are more likely to have had contact with feces, which carries E. coli, industry research shows. Yet most meat companies rely on their suppliers to check for the bacteria and do their own testing only after the ingredients are ground together.

Unwritten agreements between some companies appear to stand in the way of ingredient testing. Many big slaughterhouses will sell only to grinders who agree not to test their shipments for E. coli for fear of a recall of ingredients they sold to others.

“Ground beef is not a completely safe product,” said Dr. Jeffrey Bender, a food safety expert at the University of Minnesota who helped develop systems for tracing E. coli contamination. He said that while outbreaks had been on the decline, “unfortunately it looks like we are going a bit in the opposite direction.”