(B)

    Food prices offer a good proxy for agriculture’s health, notes Gerald Nelson, an economist with the International Food Policy Research Institute in Washington, D.C. Rising prices signal increasing resource scarcity, he explains, which can be triggered by expanding populations, growing incomes and declining crop yields. Recent food-price shocks and yield shortfalls initially surprised analysts, note IFPRI’s Derek Headey and Shenggen Fan in a November 18 report. Government officials had been lulled into complacency by decades of falling food costs. But prices bottomed out around 2000 and have since begun climbing in response to commodities speculation and a string of poor harvests. Nelson and his colleagues have now used computer models to get some grasp on how crop yields and prices might respond, several decades out, to Earth’s continuing low-grade fever. The team considered three scenarios of income and population growth that might reasonably be expected to occur between 2020 and 2050. Then they applied four “plausible” climate scenarios with warmer temperatures and anywhere from slightly to substantially wetter weather. They also included an “implausible fifth scenario of perfect mitigation (a continuation of today’s climate into the future).” The resulting scenarios all indicated that in contrast to the 20th century, when food prices fell, the 21st century would see prices rise probably by a lot. Even with today’s climate, food prices would rise over the next 40 years in response to pressures from growing populations and incomes. Rice prices, for instance, would increase roughly 11 to 55 percent. Throwing in additional warming, prices can rise substantially more—a minimum of 31 percent for rice and perhaps a doubling for corn. The analyses clearly point to “climate change as a threat-multiplier,” concludes Nelson. Lighter wallets are hardly the most dire fallout of rising food costs. An analysis that Nelson’s group issued last year projected that food affordability by 2050 will likely trigger a decline in intake throughout the developing world. This could hike childhood malnutrition rates 20 percent above what would occur in the absence of climate change. Investments could be made to offset the negative impacts of climate on agriculture and childhood malnutrition. But they’d be high, IFPR I estimated: more than $7 billion annually. Last year’s greenhouse-gas releases have been fueling pessimism that nations will be able to brake their emission trajectories soon. Owing to the global recession, people had expected 2009 greenhouse-gas releases to drop precipitously, notes climate scientist Pierre Friedlingstein of the University of Exeter in England. “Global emissions did decrease 1.3 percent, but that was only equivalent to four days of emissions.” “The globe essentially faces a daunting task in terms of climate change,” notes Bruce Campbell, director of a climate and food program of the Consultative Group on International Agricultural Research. Despite climate’s impacts on food production, agriculture remains largely ignored in international negotiations of climate and emissions policies. “What we’re hoping,” Campbell says, “is that agriculture gets to put on the agenda.”

The word “proxy” in line 1 is closest in meaning to “______”.

School Education and Self-taught Learning

   What Could Possibly Go Wrong: Genetically-Modified MosquitoesAs carriers for diseases such as malaria, dengue fever and yellow fever, mosquitoes are the deadliest creatures on the planet, responsible for millions of human deaths every year. And as the planet warms, the insects are broadly expanding their turf and bringing their diseases with them; thousands of cases of dengue, a tropical disease, have appeared in the U.S. in the past five years. DDT was long used to control the mosquito population, but it is now widely banned, and in any case, many scientists believe that mosquitoes quickly build up a resistance to the insecticide. That, in part, is why the battle against mosquitoes has gone genetic.Generally speaking, the goal of gene-based mosquito-control projects is either to kill the insects or make them benign. Researchers at Johns Hopkins University, for example, are studying mosquitoes that were made malaria-resistant through the activation of a gene responsible for a protein that blocks the infection. And the British company Oxitec has engineered a strain of mosquito that cannot survive without regular doses of tetracycline; in the wild, these mosquitoes would survive just long enough to mate and pass on their tetracycline-junkie genes to their doomed offspring. In a trial in the Cayman Islands last year, Oxitec-modified mosquitoes were able to cut the overall population by 80 percent in just six months.

   But the problem is that we don’t fully understand how mosquitoes and the diseases they carry would adapt in response to such experiments. New strains of malaria and other diseases could emerge. Jo Lines, a malaria expert at the London School of Hygiene and Tropical Medicine has described the process as “a series of arms races that the [malaria] parasite has consistently won.”

  Three percent of the offspring from Oxitec’s tetracycline-dependent mosquitoes survive-what happens if those bugs breed with wild mosquitoes?

   It’s even possible that the changes we induce in mosquitoes could move into other animals. Horizontal gene transfer could result in midges, gnats and black flies developing the same mutations, including the unfortunate characteristic of dying shortly after hatching-and a mass die-off of insects that provide sustenance to birds, bats, frogs and fish would be a food-chain disaster.

A very common operation in industry is that of pick and place. This would be typified by a packing operation, such as that shown in the figure, where items are taken from a conveyor and placed into a pallet.

The position of the item on the conveyor and the pallet position provide constraints on the endpoints of the trajectory of the item, but it does not matter from a functional point of view what path is taken by the robot. In practice, the path which gives the shortest time to perform the task will be the best. Note, however, that it will be desirable to constrain the robot to avoid collisions. Thus, once it has gripped the object it should move upwards from the conveyor, then move across to a position over the pallet, and then move downwards before releasing the object.

suffice for

compatible with

in the works

allow for

be exposed to

41、他进大学时，接触到许多新思想。

42、午餐有两瓶葡萄酒就够了。

43、他的证词和第一个证人的不一致。

44、你应该考虑到飞机误点。

45、我们听说那位作家正在写一部新小说。

Children of whatever background have to ________ the tests as they arecompulsory.

contrast     to         scientific     absent        inform       with       even          between

    The purpose of scientific literature is to inform and persuade peers as to the validity of observations and conclusions and the forensic efficacy of methods. Popular science attempts to (33) and convince scientific outsiders (sometimes along with scientists in other fields) of the significance of data and conclusions and to celebrate the results through epideictic rhetoric. Statements in(34) literature are often qualified and tentative, emphasizing that new observations and results are consistent(35) and similar (36) established knowledge wherein qualified scientists are assumed to recognize the relevance. By(37), popular science emphasizes uniqueness and generality, taking a tone of factual authority(38) from the scientific literature. Comparisons (39) original scientific reports and derivative science journalism and popular science typically reveal at least some level of distortion and oversimplification which can often be quite dramatic, (40) with politically neutral scientific topics.

Recent pressure at work may ________ his behavior.

All the people ________ children’s education.

He is not very ________ country music.

The term “special needs” covers ________ problems.