An American company has built a new drone（无人机）that could improve the speed of deliveries（送交的货）.

The drone is very different from other unmanned aircraft. It is made almost completely out of cardboard and has no motor.It can be packed with materials and sealed up with tape.

Because the drones do not have a motor, they are designed to be dropped from airplanes. Hundreds of drones could be sent out at once. Then they could be automatically guided to where they are supposed to go. The company says these drones could then complete deliveries to different places over an area covering hundreds of kilometers. The drones look bigger than the paper airplanes we used to make as kids. But this light flyer is not a toy. It is aerodynamically designed and equipped with a small computer, a battery and sensors to guide it to the ground.

The drones are being developed by Otherlab—a technology research company in San Francisco,California.It calls the drone a "Sky Machine."

The company says it can travel about 150 kilometers at speeds up to 88 kilometers an hour.Now,it can carry materials weighing up to one kilogram,but future models are expected to carry larger loads.

One of the droneˈs main advantages is that it does not have a heavy motor or large battery.This allows more room for materials and makes the drone cost less to build and operate.

The Otherlab development team has called its invention the "Ikea of drones."This is because it is packaged similarly to products from the Swedish furniture maker Ikea. The drone arrives as flat pieces of pre-cut cardboard that can be quickly and easily put together.

The technology that guides the drone can make it land within 10 meters of its target, according to Otherlab. Unlike other drones,even a crash landing is acceptable.The company says the drones can also be reused.

Once the drone completes its delivery,it can be thrown away and the cardboard material will likely break down within a few months.

The company has received money from the U.S. Department of Defense to carry out research on the drones.The money came from the Defense Advanced Research Projects Agency.The agency is attempting to find the best delivery vehicles that can disappear after their missions are complete.The U.S. military has a need for delivery drones.But it wants to simplify and lower the cost of using them.Otherlabˈs Sky Machines are an attempt to fill that need.

Military drones can also be stolen and studied by others if found after use.Before they can truly disappear,the electronic materials inside must also somehow disappear.Researchers are still working on ways to get the technology itself to self-destruct.

Scientists in Britain have managed to teach bumblebees(大黄蜂)to pull strings to get to food and then pass on what they have learned to others in their colony(群体)- showing a high level of intelligence despite their tiny brains.

   Researchers at Queen Mary University of London said the experiments, often used to test the intelligence of apes(猿)and birds, showed for the first time that some insects are up to the task, and can also pass skills on through several generations.

   The findings add to the evidence suggesting the ability for “culture spread”-the ability to learn and pass on knowledge and skills-may not be exclusive to humans.

   In the research, published in the journal PLOS Biology on Tuesday, the scientists were able to train 23 out of a group of 40 bees to pull strings with their legs and feet.

   The strings were attached to discs-or artificial “flowers”-containing food at their center but placed under a transparent screen. The bees, spotting the food beneath the screen, learned to pull the "flowers" out by pulling the string with their legs and feet to be able to get to it.

   From another group of bees given the chance to solve the task without any training, only two of 110 were successful.

   Another group of bees was then allowed to observe the trained bees pulling the strings, and 60 percent of them successfully learned the skill. Finally, trained bees were put in colonies, and the scientists found the technique spread successfully to a majority of the colony's worker bees.

   Lars Chittka, a Queen Mary University professor who guided the project, said the team is interested in figuring out the brain processes behind the bees' learning and teaching skills.

Crossing your legs is an extremely common habit;most people donˈt even notice that theyˈre doing it when they sit down. While you may find it comfortable to sit with one knee crossed over the other, it might be causing health problems that you are not aware of.

   A study published in Blood Pressure Monitoring stated that sitting with your legs crossed can increase your blood pressure. The reason for this is that the blood in your legs has to work against gravity to be pumped back to your heart and that crossing one leg over the other increases resistance, making it even harder for the blood to circulate. This causes your body to increase your blood pressure to push the blood back to the heart. You wonˈt feel any immediate effects, but repeated, drawn-out increases in blood pressure can cause long-term health issues. So, planning to sit for a long period of time? Donˈt keep your legs crossed.

   Crossing your legs at the knee can also cause pressure on the major nerve in your leg that passes just below your knee and along the outside of your leg, explains Richard Graves, a medical expert. This pressure can cause numbness and temporary paralysis(麻痹)of some of the muscles in your foot and leg, preventing you from being able to raise your ankle-what we know as that "pins and needles" sensation. While the feeling of discomfort may only last a minute or two, repeatedly crossing your legs until they feel numb can cause permanent nerve damage.

   So next time you sit down, try to get yourself in the habit of sitting with both of your feet on the floor. Not only will it help your posture and stability, but it will also save your health in the long run.

A new research study combining marine physiology, neuroscience, pharmacology（药物学）, and behavioral psychology has revealed a surprising outcome from increases of carbon dioxide uptake in the oceans: anxious fish.

A growing base of scientific evidence has shown that the absorption of human-produced carbon dioxide into the worldˈs oceans is causing surface waters to decline in pH, causing a rise in acidity(酸度). This ocean acidification is known to disrupt the growth of shells and skeletons（骨骼） of certain marine animals but other consequences such as behavioral impacts have been lately unknown until recently.

In a study published in the journal Proceedings of the Royal Society B (Biological Sciences), scientists at Scripps Institution of Oceanography at UC San Diego and MacEwan University in Edmonton, Canada, have shown for the first time that rising acidity levels increase anxiety in juvenile rockfish（岩鱼）, an important commercial species in California. Using a camera-based tracking software system, the researchers compared a control group of rockfish kept in normal seawater to another group in waters with elevated acidity levels matching those projected for the end of the century. They measured each groupˈs preference to swim in light or dark areas of a testing tank, which is a known test for anxiety in fish. The researchers found out that normal juvenile rockfish continuously moved between the light and dark areas of the tank. However, experiments have shown that fish administered with an anxiety-inducing drug prefer the darker area and seldom venture into the light. Hence（Thus）, _____________.

Next, the researchers found that rockfish exposed to acidified ocean conditions for one week also preferred the dark area of the tank, indicating they were significantly more anxious than their normal seawater counterparts. Rockfish exposed to acidified ocean conditions remained anxious even one week after being placed in seawater with normal carbon dioxide levels. Only after the twelfth day in normal seawater did the anxious fish behave like the control group and resumed normal behavior.

The researchers say the anxiety is traced to the fishˈs sensory(感官的) systems, and specifically "GABAA" (neural gamma-aminobutyric acid type A) receptors, which are also involved in human anxiety levels. Exposure to acidified water leads to changes in the concentrations of ions(离子) in the blood (especially chloride and bicarbonate), which reverses the flux of ions through the GABAA receptors. The end result is a change in neuronal（神经元） activity that is reflected in the altered behavioral responses described in this study.

"These results are novel and thought-provoking," said Martín Tresguerres, a Scripps marine biologist and study coauthor, "because they reveal a potential negative effect of ocean acidification on fish behavior that can possibly affect normal population dynamics and maybe even affect fisheries."

Tresguerres says anxious behavior is a concern for young rockfish because they live in highly dynamic environments such as kelp(巨藻) forests and drifting kelp paddies that offer variable lighting and shading conditions.

“If the behavior that we observed in the lab applies to the wild during ocean acidification conditions, it could mean that young rockfish may spend more time in the shaded areas instead of exploring around, "said Tresguerres "This would have negative effects due to reduced time to search for food, or among others.”

Tresguerres noted that laboratory tests cannot fully model the steady progression of acidity levels that will be seen in the wild over years and decades." Nonetheless results suggest that ocean acidification may affect an important aspect of behavior”

  Every now and then，a product comes along that proves itself a complete game－changer; as is the case with new British brand and invention，Eyejusters － the reading glasses that you can focus yourself － for less than ￡70！

      With 6 in 10 people wearing glasses in the UK，those with perfect vision are increasingly in the minority. And of those who do require glasses，many find themselves requiring two or three pairs of glasses in order to complete different tasks throughout the day. As well as being an added expense on top of everything else，this also means carrying around （and trying not to lose） those extra pairs！

      Evejusters allow you to instantly change the lens（镜片） strength of your glasses with hidden dials，tucked just inside the frames themselves. Eyejusters work by the wearer simply turning the concealed eyeDials to change the focus to fit your needs. The lenses adjust from ＋0.00 to ＋3.00 D，they also have anti－scratch technology and are lightweight in design so you aren't paying the price of comfort for convenience.

      The creator of Eyejusters，Owen Reading － who came up with the idea for Eyejusters with friend David Crosby，who studied physics at Oxford with him，explained: "Lots of people need reading glasses but they need glasses with lots of different strengths. They might have a pair with ＋l prescription－strength lenses for the computer，＋2s for reading and ＋3s for really close－up stuff. Eyejusters replace the need for multiple pairs of reading glasses，by covering the whole range from zero to ＋3，which is the strongest you will find in over－the－counter products."

      He added: "If you wear reading glasses，these are a much more flexible alternative. You can put them on and just turn the dial until what you want to see comes into focus. They are much like using binoculars（望远镜）."

Gray wolves once were seen here and there in the Yellowstone area and much of the continental United States, but they were gradually displaced by human development. By the 1920s, wolves had practically disappeared from the Yellowstone area. They went farther north into the deep forests of Canada, where there were fewer humans around.

The disappearance of the wolves had many unexpected results. Deer and elk populations—major food sources(来源) for the wolf—grew rapidly. These animals consumed large amounts of vegetation(植被), which reduced plant diversity in the park. In the absence of wolves, coyote populations also grew quickly. The coyotes killed a large percentage of the park’s red foxes, and completely drove away the park’s beavers.

As early as 1966, biologists asked the government to consider reintroducing wolves to Yellowstone Park. They hoped that wolves would be able to control the elk and coyote problems. Many farmers opposed the plan because they feared that wolves would kill their farm animals or pets.

The government spent nearly 30 years coming up with a plan to reintroduce the wolves. The U．S. Fish and Wildlife Service carefully monitors and manages the wolf packs in Yellowstone. Today, the debate continues over how well the gray wolf is fitting in at Yellowstone. Elk, deer, and coyote populations are down, while beavers and red foxes have made a comeback. The Yellowstone wolf project has been a valuable experiment to help biologists decide whether to reintroduce wolves to other parts of the country as well.

Most people are aware that outdoor air pollution can damage their health, but many do not know that indoor air pollution can also have significant health effects. Environmental Protection Agency studies indicate that indoor levels of pollutants(污染物) may be 2～5 times, and occasionally more than 100 times, higher than outdoor levels. These levels of indoor air pollutants may be of particular concern because most people spend about 90％ of their time indoors.

There are many sources of indoor air pollution in any home. These include combustion（燃烧）sources such as oil, gas, coal, wood, and tobacco products; building materials and furnishings such as wet or damp carpet, furniture made of certain pressed wood products; products for household cleaning and maintenance, personal care or hobbies; central heating and cooling systems and humidification devices(加湿器); and outdoor sources such as pesticides（农药）, and outdoor air pollution.

Immediate effects may show up after a single exposure or repeated exposures. These include irritation of the eyes, nose, and throat, headaches, dizziness(晕眩), and fatigue(乏力). Such immediate effects are usually short-term and treatable. Sometimes the treatment is simply eliminating(清除) the person’s exposure to the source of the pollution, if it can be identified. Symptoms(症状) of some diseases, including asthma, hypersensitivity, pneumonitis, and fever, may also show up soon after exposure to some indoor air pollutants.

The likelihood of immediate reactions to indoor air pollutants depends on several factors. Age and pre-existing medical conditions are two important influences. In other cases, whether a person reacts to a pollutant depends on individual sensitivity, which varies tremendously from person to person. Some people can become sensitized to biological pollutants after repeated exposures, and it appears that some people can become sensitized to chemical pollutants as well.

Certain immediate effects are similar to those from colds or other viral diseases, so it is often difficult to determine if the symptoms are a result of exposure to indoor air pollution. For this reason, it is important to pay attention to the time and place the symptoms occur. If the symptoms fade or go away when a person is away from the home and return when the person returns, an effort should be made to identify indoor air sources that may be possible causes. Some effects may be made worse by an inadequate supply of outdoor air or from the heating, cooling, or humidity conditions prevalent in the home.

There are an extremely large number of ants worldwide.Each individual(个体的)ant hardly weighs anything,but put together they weigh roughly the same as all of mankind.They also live nearly everywhere,except on frozen mountain tops and around the poles.For animals their size,ants have been astonishingly successful,largely due to their wonderful social behavior.

In colonies(群体)that range in size from a few hundred to tens of millions,they organize their lives with a clear division of labor.Even more amazing is how they achieve this level of organization.Where we use sound and sight to communicate,ants depend primarily on pheromones(外激素),chemicals sent out by individuals and smelled or tasted by fellow members of their colony.When an ant finds food,it produces a pheromone that will lead others straight to where the food is.When an individual ant comes under attack or is dying,it sends out an alarm pheromone to warn the colony to prepare for a conflict as a defense unit.

In fact,when it comes to the art of war,ants have no equal.They are completely fearless and will readily take on a creature much larger than themselves,attacking in large groups and overcoming their target.Such is their devotion to the common good of the colony that not only soldier ants but also worker ants will sacrifice their lives to help defeat an enemy. 

Behaving in this selfless and devoted manner,these little creatures have survived on Earth for more than 140 million years,far longer than dinosaurs.Because they think as one,they have a collective(集体的)intelligence greater than you would expect from its individual parts.

Human activities are largely responsible for climate change, which is already having an observable effect on our planet. Particularly emissions from the burning of fossil fuels such as oil and gas have led to an increase in the concentration of greenhouse gases in the atmosphere. Key indicators of climate change – including rising average temperatures, melting glaciers, and rising sea levels – are expected to have devastating consequences for humans and environments. Tackling the challenge posed by climate change will require a coordinated and global effort.

Acknowledging that climate change is a common concern of humankind, delegations from 195 states successfully negotiated a new and binding international agreement to protect the global climate at the 21st Conference of the Parties to the United Nations Framework Convention on Climate Change ( UNFCCC) held in Paris in December 2015. The successful adoption of the Paris Agreement was also due to the hard work of a host of non-state actors, including NGOs and research institutions working to address the challenges of climate change.

With the first commitment period of the Kyoto Protocol due to expire in 2012, governments agreed to begin negotiations on an emissions reductions treaty for the post-Kyoto era at the 2007 Conference of Parties (COP) in Bali. In line with the agreement reached by the parties to the UNFCCC at the 2011 COP in Durban to negotiate a new climate protection treaty, this process was concluded successfully with the adoption of the Paris Agreement in late 2015.

One of the key innovations of the Paris Agreement is the adoption of a clearly defined target to limit global warming. The signatory states have agreed to limit the rise in global average temperature to well below 2 °C above pre-industrial levels. In order to achieve this, the agreement requires parties to prepare, communicate and maintain so-called “Nationally Determined Contributions” (NDCs) that they intend to achieve. These national commitments represent a further departure from the model of the Kyoto Protocol.

The Paris Agreement does not include any language on precisely what states should include in these commitments. While the emissions reduction targets specified for each country under the terms of the Kyoto Protocol were the outcome of multilateral negotiations, under the Paris Agreement states are invited to determine their national contributions as they see fit. The NDCs submitted so far under the Paris Agreement will not be sufficient to keep global warming below the two degree target. However, the agreement also requires that states review the implementation of their NDCs and update their pledges every five years. The first evaluation of the implementation of the Paris Agreement is scheduled for 2023.

Some time people call each other “scared-cat”, but have you ever thought about this expression? When a cat is frightened, its heart starts beating faster, its muscles get tense, and there are changes in the chemicals in its bloodstream. Although the cat doesn’t realize this, its body is getting ready for action. If the danger continues, the animal will do one of two things. It will defend itself, or it will run away as fast as it can.

      Something like this also happens to people. When we are excited, angry, scared, or aroused by other emotions, our bodies go through many physical changes. Our hearts beat faster, and our muscles get tense. All of these changes make us more alert and ready to react. We, too get ready to defend ourselves or run.

      Human beings, however, have a problem that animals never face. If we give way to our feelings and let them take over, we can get into trouble. Have you ever said something in anger—or hit somebody—and regretted it later? Have you ever shouted at a teacher, told somebody you were lonely, or said you were in love, and then wished later you had kept your mouth shut? It isn’t always wise to express your feelings freely.

      Does this mean that it’s smarter always to hide our feelings? No! If you keep feelings of anger, sadness, and bitterness away or bottled up inside, your body stays tense. Physical illness can develop, and you can feel churned up inside. It can actually be bad for your health. (It isn’t good to keep pleasant feelings inside either; all feelings need to be expressed.)

      Feelings that keep all bottled up inside don’t just go away. It’s as if you bought some bananas and stuck them in a cupboard. You might not be able to see them, but before long you’d smell them. And if you opened the cupboard, chances are that you’d see little fruit flies hovering all over them. They’d be rotten.

      You can try to treat emotions as if they were bananas in the cupboard. You can hide them and you can pretend they don’t exist, but they’ll still be around. And at last you’ll have to deal with them, just like those bananas.