【推荐2】Of the more than 3,000 species of mosquitoes in the world, just a small number specialize in sucking human blood. How mosquitoes track us down so effectively isn’t currently known, but it matters, since they carry dangerous diseases which may cause death.

“In fact, stopping these annoying insects in their tracks could save up to half a million lives lost to those diseases each year,” said Carolyn Gauff, a professor of ecology and evolutionary biology at the Princeton Neuroscience Institute. That’s why Gauff’s team wants to understand how they find and target humans.

Mosquitoes mostly choose what to bite based on odor (气味). Knowing how a potentially disease-carrying mosquito finds a person, while ignoring other warm-blooded animals, is a key question. But it’s not easy to answer, since any animal smell is made up of hundreds of chemicals mixed together in specific percentage. “The actual chemicals that are found in human odor are basically the same as the chemicals found in animal odor—it’s the percentages and the relative large amount of those substances in human mixtures that’s unique,” said Gauff.

To investigate, researchers decided to record neural activity in the brain of mosquitoes while exposing them to natural human and animal odor samples. They collected odor samples from about 40 different animals. When they compared some of those with the 16 human samples, something jumped out. Decanal is particularly rich in human skin. Common in the natural world, in humans, decanal comes from another, more complex substance. When one component of our skin’s natural oils, sapienic acid, breaks down, decanal is left over. This acid is only found in human beings. It’s what likely leads to the high levels of decanal that help the mosquitoes smell their way to us.

Understanding what the mosquitoes are targeting is only part of the story; knowing how they do it is also important. To see exactly how mosquitoes use this sense, scientists used genetically modified (转基因的) mosquitoes so that they could cut open mosquitoes’ heads and watch neurons firing when they’re exposed to human and animal odors. The research team already knew that mosquitoes have about 60 different types of neurons that sense odors, so when they looked in the insects’ brains, they thought they might see a lot of activity. But it was surprisingly quiet, meaning that the signal was perhaps quite simple, down to just a couple types of neurons. “One type of neuron responded really strongly to both humans and animals. Another type of neuron responded to both—but it responded much more strongly to humans than animals,” Gauff said.

How to keep mosquitoes’ decanal signal from being transmitted will be the research team’s next focus. Gauff hoped their current work could be used to make mosquito killers and attractants to prevent disease.

【推荐3】You know those lovely little ears of corn that show up in some of your favorite Chinese take-out dishes? Ever wondered how they grow so small? Are there tiny little farmers out somewhere taking care of tiny cornfields? Are they specially grown to be tiny or are they just little baby regular corn? Well the answer is that they truly are just baby ears of regular corn. The corn is harvested in an early stage from nearly any variety of regular-sized corn plant.

There’s evidence showing that humans’ love for miniature(微型的)things can date back 3000 years. By the 1400s,miniature things had become more popular, with painters like Jean Fouquet creating images only7.5 centimeters wide. Somewhere along the way, our fascination with things in miniature from goats and owls to tiny houses came to include vegetables, too.

Baby carrots, little ears of corn, and micro greens are common today from fresh produce and frozen meals to take-out and fancy restaurant foods. But where do those tiny vegetables come from? It turns out, a vegetable packaged, sold or served as a baby may actually be a young vegetable-or it may not.It’s also entirely possible that a baby vegetable is a dwarf(侏儒)or hybrid version of a full-sized vegetable.

Baby bok choy for example, is a young vegetable that is harvested early for its tender and mild qualities. However there also are dwarf varieties of baby bok choy that have a similar look and taste to their early-harvested cousins.

There are about 50 different types of vegetables that are grown or imported as miniatures in the United States. And while the United States produces the most com in the world, it imports almost all of its baby com from other countries. Thailand produces the most baby corn, followed by Sir Lanka.

【推荐1】Better grades might be found on the playground. A new study of elementary-age children shows that those who were not part of an after-school exercise program tended to pack on a particular type of body fat that can have deleterious impacts on brain health and thinking. But prevention and treatment could be as simple as playing more games of tag (捉迷藏，捉人游戏).

Most children do not meet the federal health guidelines for exercise, which call for at least an hour of it a day for anyone under the age of 18. Physical inactivity can result in weight gain especially around the midsection-including visceral (内脏的) fat, a type of tissue deep inside the abdomen (腹部) that is known to increase inflammation (炎症) throughout the body. It is also linked to heightened risks for diabetes and cardiovascular complications (并发症) even in children, and may contribute to declining brain function. Obese adults often perform worse than people of normal weight on tests of thinking skills.

But little has been known about visceral fat and brain health in children. For a soon-to-be-published study, researchers from Northeastern University in Boston and the University of Illinois at Urbana-Champaion tracked hundreds of 8-to-10-year-old children in a nine-month after-school exercise program in Urbana. Every day, one group of children played tag and other active games for about 70 minutes. The subjects in a control group continued with their normal lives, with the promise that they could join the program the following year. All the children completed tests of fitness, body composition and cognitive skills at the start and end of the program. The researchers did not ask the children to change their diets.

After the trial the exercising children who were obese at the study’s onset had less visceral fat relative to their starting weight, even if they remained overweight. They also showed significant improvements in their scores on a computerized test that measures how well children pay attention, process information and avoid being impulsive. Notably a similar effect was observed in children whose weight was normal at the start. Across the board the more visceral fat a child shed during the nine months of play, the better he or she performed on the test.

The children in the control group, in contrast had generally added to their visceral fat; this was particularly true among those who were already obese. They gained on average, four times as much visceral fat as the normal-weight children in the control group, and also did not perform as well on the subsequent test. Lauren Raine, a postdoctoral researcher at Northeastern University who conducted the study with Charles Hillman and others, says that the trial was designed to study aerobic fitness and children’s ability to think not the relation of abdominal flab to inflammation. But a reduction in overall inflammation very likely plays a role because it is thought to be unhealthy for the brain. More broadly, Raine says the study suggests that getting children to run around won’t just enhance their bodies-it might also improve their report cards.

【推荐3】Cimabue, the greatest painter in medieval(中世纪的)Italy, was surprised one day when he came back from his lunch break and discovered a fly was under the nose of a character he had been working on. So he reached out to touch the insect. To his surprise, he found only wet paint. Turning around, he saw that his apprentice(学徒), Giotto di Bondone, was doing everything he could to keep from laughing. Giotto had painted the fly when Cimabue was away, and it looked so real that Cimabue had been completely fooled.

Giotto was born into a poor farming family. Legend has it that one day when Cimabue was walking around the countryside, he spotted a young shepherd(牧羊人)boy. The boy was not tending his sheep. Instead, he was drawing pictures of them, and the sheep he drew were so lifelike that Cimabue stopped to ask the boy his name. The boy replied that it was Giotto, and Cimabue immediately asked him to come to Florence so that the young shepherd could learn how to paint.

In the Middle Ages, an artist not only had to concern himself with things like design and technique, but he also had to learn how to make paints. Almost all artists were men, and they began their apprenticeships at an early age. An apprentice’s job was to copy his master as exactly as he could. The unfortunate result of this imitation(模仿)was a lack of new ideas.

In fact, art in the Middle Ages remained the same for hundreds of years. The people in paintings didn’t look like real people, and the symbolism of art was often so remote that it must have been difficult for viewers to connect with it on a personal level. Giotto used many techniques that were uncommon at the time to bring the paintings to life for viewers. He painted people the way he saw them, instead of the overly tall people that other artists painted. He created three-dimensional space by using perspective, something that had not been done since Roman times. Finally, he threw out parts of the symbolism associated with medieval painting.