第2周高三年级英语听力(导学案)

No Proof Lifestyle Changes Can Prevent Mental Decline

A new study has failed to find any that lifestyle changes can prevent cognitive decline in older adults.

But researchers say there are still good reasons to make positive changes in how we live and what we eat as we age.

Cognitive decline is the loss of ability to learn new skills, or words, names, and faces that is most common as we age. To reduce or avoid it, researchers have examined the effect of smoking, diet,games, exercise and other .

Researchers at Duke University sifted through more than 160 published studies and found an of strong evidence that any of these can make a big difference.

"In the studies we found that some of the B vitamins, like folic acid, were beneficial." said co-author James Burke, who helped design the study. "Exercise, diet, cognitive stimulation showed some positive effects, although the evidence was not so strong that we could actually consider these firmly established."

Some previous studies have suggested that challenging your brain with mentally stimulating activities might help. Burke said that actually does seem to help, based on studies - the researcher's gold standard.

"Cognitive stimulation is one of the areas where we did find some benefit. The exact type of that an individual uses is not as important as being ," Burke said.

The expert review also found insufficient evidence to recommend any drugs or dietary that could prevent or slow cognitive decline.

However, given that there is at least some evidence for positive effects from some of these lifestyle changes, plus other benefits to cognitive decline, Burke offered some.

"I think that by having people adopt a healthy lifestyle, both from a medical

as well as nutritional and cognitive stimulation standpoint, that we can reduce the incidence of cognitive decline, which will be proof that these factors are, in fact, important."

James Burke of Duke University is one of the authors of a study

on cognitive decline. The paper is published online by the Annals of Internal Medicine.

Ever Seen a Mountain Goat on Wheels?

The charming city of San Francisco, California, is world famous for its . As one song puts it, they climb halfway to the stars up the city's steep hills and down again. Each open-air car seats 30, but ,, love to grab a strap, hang on for the ride, and hop off when they feel like it.

The job was once handled by , pulled by horses. But they struggled to get a foothold, especially in wet weather. Electrifying them did not help. They simply could not get enough on San Francisco's 42 steep hills, some of which have a 30-degree or more.

Then, in 1873, a fellow named Andrew Halladie suggested streetcars to a moving cable buried in a trench below ground. When the operator chosen for the test run took one look down the hill ahead, he jumped out and ran away. So Halladie made the run, and an was born.

Powered by motors and wheels in a , three heavy wire cables the size of your arm run up, down, and around San Francisco in . Even when there's no cable car in sight, you can hear the moving cables whirring beneath the street.

The cars themselves have no power other than a little generator that runs their headlights and overhead bulbs.

When it's time to move forward, the operator - or gripman, as he's called - pulls a lever, and a pincer-like device the car grabs the moving cable like a pair of pliers. The car moves ahead at a modest 15 kilometers per hour. To stop, the gripman lets go of the cable, the car coasts for awhile, and brakes are applied.

There are never runaways, because cable cars have three types of braking. Most accidents happen when automobiles run into them.

Los Angeles; Chicago; Washington, D.C.; and cities in Europe and Australia once had cable-car systems as well. But they're all gone. San Francisco's is the last?

In 1947, the shutting down the system as too slow, but San Franciscans howled in protest. Now it's written into law that the hilly city by the San Francisco Bay MUST keep its moving treasures.