【推荐1】Scientists have transfused (输血) lab-made red blood cells into a human volunteer in a world-first trial that experts say has major potential for people with hard-to-match blood types or conditions such as sickle cell disease. The research could someday mean an end to long searches for compatible donors (匹配的捐赠者) or dangerous transfusion reactions.

The experimental transfusion was done at Addenbrooke’s Hospital in Cambridge, England, as part of a joint effort among UK scientists to understand how lab-made blood transfusions could work.

The scientists took whole blood from donors in a UK database and separated out the stem cells. These are the body’s raw materials — the cells from which all specialized cells,like a red blood cell, can generate.Researchers grew red blood cells from those stem cells and transfused them into two healthy volunteers.

The transfusions involved only a tiny amount of blood: about one or two teaspoons. A standard blood transfusion would involve many hundred times that amount. This stage of the trial involves two mini transfusions at least four months apart, one with a standard donation of red cells and the other with lab-made cells from the same donor.

The researchers are closely monitoring the volunteers to determine whether the process was safe. They say there have been with“no unexpected side effects” so far. They’re also watching how long the lab-grown cells last compared with an infusion of standard red blood cells. Red blood cells typically last about 120 days, but a transfusion from a standard donation contains cells that are a variety of ages because the bone marrow (骨髓) continuously makes these cells.

Previous tests have shown that manufactured cells function like normal cells and that these lab-made cells are likely to survive longer overall while in circulation. This study will determine for the first time whether that’s true.

Further trials will be necessary to determine whether there could be a clinical use of this lab-grown product.

The research could eventually make a difference for people with sickle cell disease, those who. develop antibodies against most donor blood types, or those with genetic disorders in which their bod can’t make red blood cells or the blood cells they make don’t work well.

【推荐1】The scholars at Yale University have been carrying out a study of more than 10,000 cadets(学员) at the U.S. Military Academy at West Point to determine the relative success of those who were motivated by internal rewards versus(与…相对) those driven by “instrumental”, or external rewards.

They assumed that some combination of internal and external motives would lead to the most success, as measured by the officers’ willingness to stay beyond the five-year commitment to the Army and to graduate and become commissioned officers. In fact, they found that cadets who expressed the most internal motivation were more successful than those who showed mixed motives to serve.

The same subtle(微妙的) interplay between motivation and rewards is also at work when it comes to education and learning. Rewarding students for getting their schoolwork done with prizes, snacks and even grades, as most schools do, can have the unintended effect of dismantling a child’s drive to learn for its own good.

“When you hold a burger in front of kids’ noses, you are telling them what kind of consequence matters, and what motive to pay attention to, “says psychology professor Barry Schwartz.” And education will suffer.”

Randy Wallock, a seventh-grade language arts teacher in New Jersey, encourages learning for its own good among his students: They’re given choice and autonomy and the freedom to work at their own pace. He also tries to build what he calls “little cultures within the classroom to encourage learning”; teenagers are responsive to social expectations, and creating environments where curiosity is cool invites more self-directed learning.

“As a teacher, you have a choice of what you respond to,” says Amy Wrzesniewski, an associate professor at Yale University. “Do you pay attention to students who have their laptops out, or do you pay attention to students who are asking intelligent questions?” she asks. Making those kids who ask intelligent questions feel “valued, responded to and celebrated,” she says, brings more of that out in others.

Schwartz agrees, but warns that sending out these kinds of signals must be done slowly and subtly. He adds, “You have to be careful you’re not making this another instrumental reward.”

【推荐1】The skies are raining big blocks of ice, and experts are trying to learn what's going on.

For the second time in six days, California was attacked by ice balls. The latest happened early Thursday. A large block of ice dropped into Loma Linda, California. The ice crashed through the metal roof(房顶) of a fitness center, leaving a hole up to 2% feet wide. No one was hurt.

Two tennis players were playing outside the Drayson Center on Thursday morning. Suddenly they heard a strange sound, said Crawford, an official of the Loma Linda Fire Department.

A similar event happened last Saturday in Oakland, California. Early in the morning an ice dropped into a field at Bushrod Park and made a hole up to 2 feet wide. Luckily, no one in the park was injured.

One theory (理论) is the ice was dropped from planes. But there's little direct support for that. A few experts have suggested there may be other causes of similar ice falls, perhaps even global (全球的) warming.

Stories about dropping ice go back for centuries. They didn't begin to receive serious scientific attention until a few years ago, however, when Spain was attacked by a dozen large ice balls in 2000.

Scientist Jesus Martinez—Frias in Madrid and his team have collected reports of forty cases around the world since 1999 of puzzling falling ice. He thinks the ice forms in the air by a process similar to the formation of hail (冰雹) inside storms but without a storm.

Martinez—Frias believes global warming is causing the troposphere (对流层) to rise. This means the roof of the troposphere is forced to a greater height, where it cools more than normal. Thus, the temperature difference between warm and cold air in the troposphere produces strong up—and—down winds that repeat the hail—formation process, without a storm.

【推荐3】Chemicals taken from sawdust (锯屑) and water can knock out more than 99 percent of some disease-causing microbes (微生物). That makes the sawdust mix a potential alternative to current microbe-killing chemicals.

Many disinfectants (消毒剂) used today can harm the environment. They form poisonous by-products when they get washed. Some potentially greener disinfectants exist. They rely on a chemical called “phenol (苯酚)”. But these cleaners can be costly and take a lot of energy to make.

Shicheng Zhang went searching for a better option. He’s an environmental engineer at Fudan University in Shanghai, China. Wood contains many molecules (分子) that look like phenol. So Zhang wondered if microbe-killing chemicals could be obtained from sawdust through a low-cost and low-energy process.

He and his fellow researchers cooked mixtures of water and sawdust for one hour. They heated this sawdust soup under pressure, and then filtered it. Later, they tested how well the liquid killed off microbes. This liquid wiped out E.coli bacteria—microbes that can cause food poisoning. The liquid also killed anthrax bacteria. These microbes cause dangerous infections. What’s more, the disinfectant stopped flu viruses from being infectious.

The researchers also added different amounts of water to the sawdust soup. That let them test how concentrated it had to be to knock out microbes. Depending on its concentration, the mix could kill more than 99 percent of the microbes.

Looking at killed microbes under a microscope revealed some of the ways the sawdust mix kills. The disinfectant damaged the microbes’ cell walls. It also may have messed with the microbes’ proteins and DNA.

Zhang and his fellow researchers didn’t stop at a sawdust disinfectant. They made disinfectants from other plant materials, too. Some of these started as bamboo powder. Others were made using rice plant. Plant materials that are richer in molecules that release phenol-like compounds are best at killing microbes. One example is corn straw.