Plastic﹣Eating Worms

    Humans produce more than 300 million tons of plastic every year． Almost half of that winds up in landfills（垃圾填埋场）， and up to 12 million tons pollute the oceans． So far there is no effective way to get rid of it， but a new study suggests an answer may lie in the stomachs of some hungry worms．

    Researchers in Spain and England recently found that the worms of the greater wax moth can break down polyethylene， which accounts for 40% of plastics． The team left 100 wax worms on a commercial polyethylene shopping bag for 12 hours， and the worms consumed and broke down about 92 milligrams， or almost 3% of it． To confirm that the worms' chewing alone was not responsible for the polyethylene breakdown， the researchers made some worms into paste（糊状物） and applied it to plastic films． 14 hours later the films had lost 13% of their mass﹣﹣apparently broken down by enzymes（酶）from the worms' stomachs． Their findings were published in Current Biology in 2017．

    Federica Bertocchini， co﹣author of the study， says the worms' ability to break down their everyday food﹣beeswax﹣also allows them to break down plastic． "Wax is a complex mixture， but the basic bond in polyethylene， the carbon﹣carbon bond， is there as well， "she explains． "The wax worm evolved a method or system to break this bond． "

    Jennifer DeBruyn， a microbiologist at the University of Tennessee， who was not involved in the study， says it is not surprising that such worms can break down polyethylene． But compared with previous studies， she finds the speed of breaking down in this one exciting． The next step， DeBruyn says， will be to identify the cause of the breakdown． Is it an enzyme produced by the worm itself or by its gut microbes（肠道微生物）？

    Bertocchini agrees and hopes her team's findings might one day help employ the enzyme to break down plastics in landfills． But she expects using the chemical in some kind of industrial process﹣not simply "millions of worms thrown on top of the plastic．"

    A buld-it-yourself solar still(蒸流器) is one of the best ways to obtain drinking water in areas where the liquid is not readily available. Developed by two doctors in the U. S. Department of Agriculture, it's an excellent water collector. Unfortunately, you must carry the necessary equipment with you, since it's all but impossible to find natural substitutes. The only components required, though, are a 5' x 5' sheet of clear or slightly milky plastic, six feet of plastic tube, and a container-perhaps just a drinking cup-to catch the water. These pieces can be folded into a neat little pack and fastened on your belt.

    To construct a working still, use a sharp stick or rock to dig a hole four feet across and three feet deep. Try to make the hole in a damp area to increase the water catcher's productivity. Place your cup in the deepest part of the hole. Then lay the tube in place so that one end rests all the way in the cup and the rest of the line runs up-and out the side of the hole.

    Next, cover the hole with the plastic sheet, securing the edges of the plastic with dirt and weighting the sheet's center down with a rock. The plastic should now form a cone(圆锥体) with 45-degree-angled sides. The low point of the sheet must be centered directly over, and no more than three inches above, the cup.

    The solar still works by creating a greenhouse under the plastic. Ground water evaporates (蒸发) and collects on the sheet until small drops of water form, run down the material, and fall off into the cup. When the container is full, you can suck the refreshment out through the tube, and won't have to break down the still every time you need a drink.

In the 1960s，Douglas McGregor，one of the key thinkers in the art of management，developed the mow famous Theory X and Theory Y．Theory X is the idea that people instinctively (1)work and will do anything to avoid it．Theory Y is the view that everyone has the potential to find satisfaction in work．

In any case，despite so much evidence to the (2)，many managers still agree to Theory X．They believe，(3)，that their employees need constant supervision if they are to work effectively，or that decisions must be imposed from (4)without consultation．This，of course，makes for authoritarian（专制的）managers．

Different cultures have different ways of (5)people．Unlike authoritarian management，some cultures，particularly in Asia，are well known for the consultative nature of decision﹣making﹣all members of the department or work group are asked to (6) to this process．This is management by the collective opinion．Many western companies have tried to imitate such Asian ways of doing things，which are based on general (7)．Some experts say that women will become more effective managers than men because they have the power to reach common goals in a way that traditional(8) managers cannot．

A recent trend has been to encourage employees to use their own initiative，to make decisions on their own without(9) managers first．This empowerment（授权）has been part of the trend towards downsizing：(10)the number of management layers in companies．After de﹣layering in this way，a company may be (11) with just a top level of senior managers，front﹣line managers and employees with direct contact with the public．Empowerment takes the idea of delegation（委托）much further than has (12) been the case．Empowerment and delegation mean new forms of management control to (13) that the overall business plan is being followed，and that operations become more profitable under the new organization，rather than less．

Another trend is off﹣site or (14) management，where teams of people linked by e﹣mail and the Internet work on projects from their own houses．Project managers evaluate the (15) of the team members in terms of what they produce for projects，rather than the amount of time they spend on them．

California Condor’s Shocking Recovery

California condors are North America’s largest birds，with wind﹣length of up to 3 meters．In the 1980s，electrical lines and lead poisoning（铅中毒） nearly drove them to dying out．Now，electric shock training and medical treatment are helping to rescue these big birds．

In the late 1980s，the last few condors were taken from the wild，and there are now more than 150flying over California and nearby Arizona，Utah and Baja in Mexico．

Electrical lines have been killing them off．“As they go in to rest for the night，they just don’t see the power lines，”says Bruce Ride out of San Diego Zoo．Their wings can bridge the gap between lines，resulting in electrocution（电死） if they touch two lines at once．

So scientists have come up with a shocking idea．Tall poles，placed in large training areas，teach the birds to stay clear of electrical lines by giving them a painful but undeadly electric shock．Before the training was introduced，66% of set﹣freed condors died of electrocution．This has now dropped to 18%．

Lead poisonous has proved more difficult to deal with．When condors eat dead bodies of other animals containing lead，they absorb large quantities of lead．This affects their nervous systems and ability to produce baby birds，and can lead to kidney（肾） failures and death．So condors with high levels of lead are sent to Los Angeles Zoo，where they are treated with calcium EDTA，a chemical that removes lead from the blood over several days．This work is starting to pay off．The annual death rate for adult condors has dropped from 38% in 2000 to 5.4% in 2011．

Ride out’s team thinks that the California condors’ average survival time in the wild is now just under eight years．“Although these measures are not effective forever，they are vital for now，”he says．“They are truly good birds that are worth every effort we put into recovering them．”

California condors attract researchers’ interest because they 　　．

Researchers have found electrical lines are 　　．

According to Paragraph 5，lead poisoning 　　．

The passage shows that 　　．

Many Native Americans value silence and feel it is a basic part of communicating among people，just as some traditional Chinese and Thai persons do．Therefore，when a person from one of these cultures is speaking and suddenly stops，what may be implied（暗示） is that the person wants the listener to consider what has been said before continuing．In these cultures，silence is a call for reflection．

Other cultures may use silence in other ways，particularly when dealing with conflicts among people or in relationships of people with different amounts of power．For example，Russian，French，and Spanish persons may use silence to show agreement between parties about the topic under discussion．However，Mexicans may use silence when instructions are given by a person in authority rather than be rude to that person by arguing with him or her．In still another use，persons in Asian cultures may view silence as a sign of respect，particularly to an elder or a person in authority．

Nurses and other care﹣givers need to be aware of the possible meanings of silence when they come across the personal anxiety their patients may be experiencing．Nurses should recognize their own personal and cultural construction of silence so that a patient’s silence is not interrupted too early or allowed to go on unnecessarily．A nurse who understands the healing（治愈） value of silence can use this understanding to assist in the care of patients from their own and from other cultures．