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With so much focus on the Ohio energy firm whose lapses may have triggered the blackout of 2003, it’s been hard to remember that the real question is not how it started, but why it spread so far and so fast. Rather than tackle that question head-on, most commentators have reached for the usual metaphors: it was a chain reaction, a cascading failures domino effect. All of these are borrowed from the physical sciences. Maybe a better way to look at it is in biological terms.We already use the language of epidemiology when we speak of “viruses” propagating across the Internet, “infecting” our computer. Likewise, it’s tempting to view the blackout, spreading from link to link along the power grid, as a pernicious kind of electrical contagion. But that’s not quite the right metaphor, either. The blackout was not caused by an infectious electrical disease; it was caused by the grid’s immune response to the threat of such a disease. In other words, the grid suffered a violent allergic reaction, a sort of anaphylactic shock.Just as the symptoms of a severe allergic reaction are caused not by the offending bee who stings itself but by the overzealous response of the body’s immune system to it, so the blackout was aggravated by the grid’s attempt to defend itself, one power station at a time. Threatened by a torrent of electrical energy gone berserker overwhelmed by the sudden loads placed on it, each power plant in turn tripped its circuit breakers, detaching itself from the grid. Though this strategy achieved its desired aim-saving each plant’s generator from being damaged—it was too myopic to serve the best interests of the grid as a whole.What is needed is a more subtle, coordinated mode of response. When our own immune systems are performing at their best, they orchestrate their defenses through countless chemical conversations among T-cells and antibodies, enabling these defenders to calibrate their response to pathogens. In the same way, the thousands of power plants substations in the grid need to be able to communicate with one another when any part of the system is breached, so they can collectively decide which circuit breakers should be tripped and which can safely remain intact.The technology necessary to achieve this has existed for about a decade. It relies on computer, sensors and protective devices tied together by optical fiber so that all parts of the grid would be able to talk to one another at the speed of light-fast enough to get ahead of an onrushing blackout and confine it.The sensors would continuously monitor the voltage, frequency and other important characteristics of the electricity coursing through the transmission lines. When a line appeared at risk of being overloaded, a computer would decide whether to switch on a protective device. At present, such decisions are made purely parochially. Power plants defend themselves first, and don’t worry about the consequences for neighboring plants on the grid. Nor do they consider any potentially helpful or harmful actions that those neighbors might be taking at the same time.In the new approach, each plant would have nearly instantaneous information about all the other plants and power lines in its extended neighborhood. Everyone would know what everyone else was doing and thinking. As threats arose (either from random failures or malicious attacks), the sensors would fire a flurry of warning signals down the optical fibers, and the networked computers would decide which protective devices to activate to contain the threat most effectively. The grid would then be responding as an integrated entity, not as a ragtag collection of selfish units. It would look a lot like an organism defending itself.Granted, such a distributed control system would cost billions of dollars and, in this era of deregulation, there would be little incentive for energy companies to join forces and build it, especially when the big money is in power generation. But the construction of a system wide immune network would be well worth the cost. Without it, our overburdened grid is likely to fail more and more often, and might even collapse, with costs that would be incalculable, both economically and in terms of national security. State and federal governments need to step in and provide incentives for utilities to do the right thing.Of course, even if this new kind of smart defense system were to be built someday, one can already imagine an insidious disorder that might eventually outsmart it and afflict it, a catastrophic disruption of the immune system itself, rather than the grid it’s supposed to protect. Such a thing would be the technological analog of AIDS.A grim prospect, perhaps, but a realistic one. We need to stop pretending that the grid is ever going to be a perfectible machine. Just as bacteria eventually develop resistance to the antibiotics used to kill them, the defense of the grid will require ever-more inventive strategies on our part. We should recognize that the power grid needs to evolve and adapt, just like any other successful living creature.1. In the author’s opinion, which of the following is an appropriate description for why the blackout of 2003 spread so far and so fast?（）2. The author’s attitude towards the views made by most commentators on the blackout of 2003 is（）.3. The article says the best way to prevent such a blackout from happening in the future is to（）.4. Setting up a distributed control system for the grid would be（）.5. The article points out that the proposed preventive measures against blackouts（）.

Judging from recent surveys and clinical experiments, most experts in sleep behavior agree that there is virtually a(n)（1）of sleepiness in the nation. Even people who think they are sleeping enough would probably be better off with more rest.The beginning of our sleep-deficit crisis can be traced to the invention of the light Bulb a century ago. By the 1950s and 1960s, that sleep schedule had been（2）dramatically, to between 7 and 8 hours.Perhaps the most（3）robber of sleep, researchers say, is the complexity of the day. Whenever pressures from work, family, friends and community mount, many people consider sleep most expendable item on the agenda. Often, though our efforts to squeeze ever more tasks into our days and nights（4）. The person who invests in a full night’s sleep, experts say, will be more than（5）in heightened productivity, creativity, and focus. Another thief of sleep is shift work, in which people work regularly in the evening, at night or on rotating schedules. Researchers say the brain has difficulty varying sleep times, which means that these employees usually suffer a（6）loss of sleep. The availability of round-the-clock entertainment, especially all-night television, also takes its（72）.To assess the consequences of sleep-deficit, researchers have put subjects through a（8）of psychological and performance tests requiring them to add columns of numbers or recall a passage read to them only minutes earlier. Researchers found that if the subjects were sleep-（9）. Their performance suffered, short-term memory was impaired, as were abilities to make decisions and to concentrate. Because their reaction time and attention span are affected, sleepy people may be more prone to making mistakes.Sleeping（10）on weekends does not help the body recoup. But in chronic cases, people may need weeks of catching up to reverse the effects of sleep loss.

After the Democratic shellacking in the midterm election, everyone wondered how President Obama would respond.

Square-jawed, with a pasty complexion and an athletic but not overly bulked-up build, he looks like a man meant to have a whistle around his neck.

No longer are these considered arcane questions that draw scrutiny only from the few Washingtonians who read the “notices of proposed rule-making” in the Federal Reserve.

China’s response to North Korea’s shelling of Yeonpyeong Island two weeks ago has been remarkably flaccid.

The argument was simultaneously a policy debate and an extended exegesis of a crucial phrase in a 1986 federal law that regulates the hiring procedures.

The proposed change in the federal estate tax, in the deal worked out with President Obama and Congressional Republicans, has ramifications for the California estate tax.

A 21-year-old recent convert to Islam tried to blow up a military recruiting station in a Baltimore suburb on Wednesday, ensnaring himself in a sting operation orchestrated by the Federal Bureau of Investigation.

Such a sanguine conclusion may seem odd at a time when furious arguments are no doubt raging behind the scenes.

The wizened old man in the home for the aged was still active and energetic.

Attempts to reconcile these two decisions have expanded, human ingenuity and expended unconscionable amount of time, effort and paper.

America’s Congress passed a housing bill that includes measures to shore up Fannie Mae and Freddie Mac, two troubled mortgage giants.

Such alarms reflected the Alsop’s tendency to cloak their analyses in portentous terms of dread and dismay.

There is likely to be tension between landlord and tenant, between large landowners and impecunious peasants.

Mike Devine, chief financial officer of New York-headquartered Coach, which makes luxury hand bags, said at a conference recently a move was in the pipeline.

Nakheel, a property developer owned by Dubai World, met creditors as part of its attempts to renegotiate $10.5 billion in bank debt. Dubai World spooked markets in November after announcing a standstill on debt repayments.

I tried in vain to（）the man the slip.

If she marries him, he will certainly（）her for a dance.

She didn’t（）matters; she just told him he was useless.

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