When it comes to medical care, many patients and doctors believe “more is better.” But what they do not realize is that overtreatment—too many scans, too many blood tests, too many procedures—may bring harm. Sometimes a test leads you down a path to more and more testing, some of which may be invasive, or to treatment for things that should be left alone.

       Terrence Power, for example, complained that after his wife learned she had Wegener's disease, an uncommon disorder of the immune system, they found it difficult to refuse testing recommended by her doctor. The doctor insisted on office visits every three weeks, even when she was feeling well. He frequently ordered blood tests and X－rays, and repeatedly referred her to specialists for even minor complaints. Even when tests came back negative, more were ordered, and she was hospitalized as prevention when she developed a cold.   She had as many as 25 doctor visits during one six－month period. The couple was spending about $30,000 a year for her care.

       After several years of physical suffering and near financial ruin from the medical costs, the couple began questioning the treatment after discussing with other patients in online support groups. “It's a really hard thing to determine when they've crossed the line，” Mr. Power said. “You think she's getting the best care in the world, but after a while you start to wonder: What is the purpose？” Mr. Power then spoke with his own primary care doctor, who advised him to find a new specialist to oversee Mrs. Power's care. Under the new doctor's care, the regular testing stopped and Mrs. Power's condition stabilized. Now she sees the doctor only four or five times a year.

       A team of engineers at Harvard University has been inspired by Nature to create the first robotic fly. The mechanical fly has become a platform for a series of new high－tech systems. Designed to do what a fly does naturally, the tiny machine is the size of a fat housefly. Its mini wings allow it to stay in the air and perform controlled flight tasks.

    “It's extremely important for us to think about this as a whole system and not just the sum of a bunch of individual components (元件), ” said Robert Wood, the Harvard engineering professor who has been working on the robotic fly project for over a decade. A few years ago, his team got the go－ahead to start piecing together the components. “The added difficulty with a project like this is that actually none of those components are off the shelf and so we have to develop them all on our own，” he said.

       They engineered a series of systems to start and drive the robotic fly. “The seemingly simple system which just moves the wings has a number of interdependencies on the individual components, each of which individually has to perform well, but then has to be matched well to everything it' s connected to，” said Wood. The flight device was built into a set of power, computation, sensing and control systems. Wood says the success of the project proves that the flying robot with these tiny components can be built and manufactured.

        While this first robotic flyer is linked to a small, off－board power source, the goal is eventually to equip it with a built－in power source, so that it might someday perform data－gathering work at rescue sites, in farmers' fields or on the battlefield. “Basically it should be able to take off, land and fly around，” he said.

        Wood says the design offers a new way to study flight mechanics and control at insect－scale. Yet, the power, sensing and computation technologies on board could have much broader applications. “You can start thinking about using them to answer open scientific questions, you know, to study biology in ways that would be difficult with the animals, but using these robots instead，” he said. “So there are a lot of technologies and open interesting scientific questions that are really what drives us on a day－to－day basis.”

        Carrots are easy to raise and easy to harvest. They taste good. {#blank#}1{#/blank#}.

        When people think of carrots, they usually picture in their mind a vegetable that islong, thin and orange.{#blank#}2{#/blank#} And not all carrots are orange. For example, Paris Market carrots are about five centimeters around. Rome carrots are thin andabout twenty－five centimeters long. And Belgian White carrots are, as their name suggests, white.

        For the best results, carrots should be grown in sandy soil that does not hold water for a long time. The soil also should have no rocks. To prepare your garden for carrots, dig up the soil, loosen it and turn it over. Then, mix insome plant material or animal fertilizer (肥料)．

{#blank#}3{#/blank#}Experts say warm days, cool nights and a medium soil temperature are the best conditions for growing carrots that taste great.

Carrots need time to develop their full sugar content. This gives them their sweetness if you wait too long to pull them from the ground.{#blank#}4{#/blank#} Usually, the brighter the color, the better the taste.

{#blank#}5{#/blank#}If the winter is not cold enough to freeze the ground, you can grow and harvest carrots the same way as during the summer months. If the ground does freeze,simply cover your carrot garden with a thick layer of leaves or straw. Thiswill prevent the ground from freezing.

a．But carrots come in many differentsizes and shapes.

b．They are economic crops.

c．The best time for planting carrots isduring the winter months.

d．Weather, soil conditions and age willaffect the way carrots taste.

e．The best way to judge if a carrot isready to be harvested is by its color.

f．And they contain a lot of carotene (胡萝卜素), which the body make into vitamin A.

g．Many people do not know that carrotscan be grown during the winter months.