2012年12月英語(yǔ)四級(jí)閱讀選詞填空真題來源于《時(shí)代周刊》

選詞填空材料來源于《時(shí)代周刊》，原文地址：https://www.time.com/time/magazine/article/0,9171,2055191,00.html#ixzz2FlBbHsNg

For a device so many people use so frequently in the course of a day, surprisingly little is certain about the health effects of cell-phone use. Manufacturers maintain that mobile phones meet government standards for safe radio-frequency radiation emission, but enough studies are beginning to document a possible increase in rare brain tumors, migraines and behavioral disorders in children to cause concern. So far, the bulk of the evidence isn't conclusive on whether cell-phone use contributes to any increased risk of cancer. But a new trial analyzing how handsets directly affect brain activity reignites the health worry.

Led by Dr. Nora Volkow, director of the National Institute on Drug Abuse, researchers asked 47 volunteers to undergo two positron-emission tomography scans, which measure glucose consumption in the brain, an indication of how cells use energy. For both 50-minute scans, the volunteers had a cell phone fixed to each ear. During the first scan, the devices were turned off, but for the second scan, the phone on the right ear was switched on and received a recorded-message call, although the volume was muted so the noise wouldn't bias the results. The results of the second scan showed that the regions of the brain nearest to the device's antenna had higher rates of glucose consumption than the rest of the brain.

What does that mean? Increases in glucose metabolism are normal; it's what happens as various parts of the brain are activated during speaking, thinking or moving. But what isn't known is whether repeated spikes in activity due to exposure to electromagnetic radiation from cell phones can permanently alter brain function or result in harm. This study doesn't answer that question, nor does it say anything about whether cell-phone radiation can cause cancer. But it is one of the first to show that cell phones can change brain activity, and it reveals a whole new avenue for scientific inquiry.

OSTEOPOROSIS

Bone Drugs Don't Stop All Fractures

Bisphosphonate drugs like Boniva and Fosamax are widely used to slow the bone loss associated with osteoporosis. But a new study finds that the popular medications may actually increase the risk of certain fractures in the femur, the thick bone of the thigh.

A Canadian study of nearly 4,300 women ages 68 or older found that long-term bisphosphonate use does indeed prevent the typical osteoporosis-related breaks in the hip, wrist and spine. But it also found that women who take bone drugs for more than five years have a slightly higher risk of atypical fractures in the femur than those using the drugs for a shorter period.

Such breaks, however, are relatively rare. For most women, the risk of developing osteoporosis outweighs the chance they may suffer such an unusual fracture. But women who don't have strong risk factors for osteoporosis--including family history of the disease, being of Caucasian or Asian descent or smoking--should balance the pros and cons of treatment before taking bone-boosting drugs.

HEART DISEASE

Black Air, Blue Hearts