Passenger pigeons（旅鸽）once flew over much of the United States in unbelievable numbers. Written accounts from the 18th and 19th centuries described flocks（群）so large that they darkened the sky for hours.

It was calculated that when its population reached its highest point, there were more than 3 billion passenger pigeons – a number equal to 24 to 40 percent of the total bird population in the United States, making it perhaps the most abundant birds in the world. Even as late as 1870 when their numbers had already become smaller, a flock believed to be 1 mile wide and 320 miles (about 515 kilometers) long was seen near Cincinnati.

Sadly, the abundance of passenger pigeons may have been their undoing. Where the birds were abundant, people believed there was an ever-lasting supply and killed them by the thousands. Commercial hunters attracted them to small clearings with grain, waited until pigeons had settled to feed, then threw large nets over them, taking hundreds at a time. The birds were shipped to large cities and sold in restaurants.

By the closing decades of the 19th century, the hardwood forests where passenger pigeons nested had been damaged by Americans’ need for wood, which scattered（驱散）the flocks and forced the birds to go farther north, where cold temperatures and spring storms contributed to their decline. Soon the great flocks were gone, never to be seen again.

In 1897, the state of Michigan passed a law prohibiting the killing of passenger pigeons, but by then, no sizable flocks had been seen in the state for 10 years. The last confirmed wild pigeon in the United States was shot by a boy in Pike County, Ohio, in 1900. For a time, a few birds survived under human care. The last of them, known affectionately as Martha, died at the Cincinnati Zoological Garden in September 1, 1914.

Australia’s koalas could be wiped out within 30 years unless urgent action is taken to stop the losing in population, according to researchers. They say development, climate change and bush fires have all combined to reduce the number of wild koalas sharply.

       The Australian Koala Foundation said a recent survey showed the population could have dropped by more than half in the past six years. Previous estimates (估计) put the number of koalas at more than 100,000, but the latest calculations (计算) suggest there could now be as few as 43,000.

       The foundation collected field data from 1,800 sites and 80,000 trees to calculate the numbers. In one area in northern Queensland estimated to have 20,000 koalas a decade ago, a team of eight people could not find a single animal in four days of searching.

       The foundation said besides problems caused by cutting down forests, hotter and drier conditions because of global warming had reduced the nutritional (营养的) value of their staple food, eucalyptus leaves, leading to poor nutrition for them.

       Koalas, which live in the forests in Australia’s east and south, are very fussy (爱挑剔的) about what types of the leaves they eat.

       Foundation chief Deborah Tabart said: “The koalas are missing everywhere we look. It’s really no tree, no me. If you keep cutting down trees you don’t have any koalas.”

       She is hoping the new figures will persuade the government’s Threatened Species Steering Committee (TSSC) to list the koala as threatened. But committee chairman Bob Beeton said a decision was not likely recently and the koala’s status as one of the country’s favourite animals would not be a factor. “There’s a number of species which are attractive and people have special feelings towards them. We don’t consider that,” Mr Beeton was reported as saying by the AFP agency.

El Nino, a Spanish term for "the Christ child," was named by South American fishermen who noticed that the global weather pattern, which happens every two to seven years, reduced the amount of fishes caught around Chrisms．El Nino sees warm water, collected over several years in the western Pacific, flow back eastwards when winds that normally blow westwards weaken, or sometimes the other way round．

    The weather effects, both good and bad, are felt in many places．Rich countries gain more from powerful Ninos, on balance, than they lose．A study found that a strong Nino in 1997-98 helped America's economy grow by %15 billion, partly because of better agricultural harvests; farmers in the Midwest gained from extra rain．The total rise in agricultural incomes in rich countries is greater than the fall in poor ones．

    But in Indonesia extremely dry forests are in flames．A multi-year drought (干旱) in south-east Brazil is becoming worse．Though heavy rains brought about by El Nino may relieve the drought in California, they are likely to cause surface flooding and other disasters．

    The most recent powerful Nino, in 1997-98, killed around 21,000 people and caused damage worth $36 billion around the globe．But such Ninos come with months of warning, and so much is known about how they happen that governments can prepare．

    According to the Overseas Development Institute (ODI), however, just 12% of disaster-relief funding in the past two decades has gone on reducing risks in advance, rather than recovery and rebuilding afterwards．This is despite evidence that a dollar spent on risk-reduction saves at least two on reconstruction．

    Simple improvements to infrastructure (基础设施) can reduce the spread of disease．Better sewers (下水道) make it less likely that heavy rain is followed by an outbreak of the disease of bad stomach．Stronger bridges mean village are less likely to be left without food and medicine after floods．According to a paper in 2011 by Mr Hsiang and co-authors, civil conflict is related to El Nino's harmful effects—and the poorer the county, the stronger the link．Though the relationship may not be causal, helping divided communities to prepare for disasters would at least reduce the risk that those disasters are followed by killing and wounding people．Since the poorest are least likely to make up for their losses from disasters linked to El Nino, reducing their losses need to be the priority．

A new study shows students who write notes by hand during lectures perform better on exams than those who use laptops(笔记本电脑).

    Students are increasingly using laptops for note-taking because of speed and legibility(清晰度). But the research has found laptop users are less able to remember and apply the concepts they have been taught.

Researchers performed experiments that aimed to find out whether using a laptop increased the tendency to make notes "mindlessly" by taking down word for word what the professors said.

     In the first experiment, students were given either a laptop or pen and paper. They listened to the same lectures and were told to use their usual note-taking skills. Thirty minutes after the talk, they were examined on their ability to remember facts and on how well they understood concepts.

    The researchers found that laptop users took twice as many notes as those who wrote by hand. However, the typists performed worse at remembering and applying the concepts. Both groups scored similarly when it came to memorizing facts.

    The researchersˈ report said, "While more notes are beneficial, if the notes are taken mindlessly, as is more likely the case on a laptop, the benefit disappears."

In another experiment aimed at testing long-term memory, students took notes as before but were tested a week after the lecture. This time, the students who wrote notes by hand performed significantly better on the exam.

These two experiments suggest that handwritten notes are not only better for immediate learning and understanding, but that they also lead to superior revision in the future.

Smart phones and pocket-sized computers are available to everybody. Robots and self-driving cars are just around the corner. Now, two groups of inventors say very soon we will be able to try flying platforms and flying bikes.

Being able to fly around as simply as riding a bicycle has been a long-standing dream of many inventors. But the safety and stability of such vehicles was always a huge problem. As relevant technologies, such as high-capacity batteries, have developed within the past decade, the dream of personal flying vehicles has moved closer to reality.

Martin Aircraft Company from New Zealand is already testing its personal flying device(装置) called Jetpack that can fly for more than 30 minutes, up to 1,000 meters high, and reach speed of 74 kilometers per hour.

“It’s inexpensive, it can carry a satisfactory load, it can get in and out of very small spaces very quickly, and it can be moved across continents very quickly because it can be folded and packed,” said Malloy Aeronautics’ marketing sales director, Grant Stapleton. The company will do further testing with more models. Inventors say Jetpack will most likely be used first by the army.

Martin CEO, Peter Coker, said, “This is built around safety from the start. Reliability is the most important element of it. We have safety, the primary concern, built into the actual structure itself. It opens at very low altitude and actually saves both the aircraft and the pilot in an emergency.” Coker also said Jetpack will be ready for the market by the end of 2016, with a price of about $200,000.

A rhino lazily chews on some grass at her feet. A short distance away, her baby plays in a muddy pool of water. Suddenly, the mother twitches (颤动) her ears, picking up the sounds of possible danger coming near.

It's not a lion or other wild animal that's a rhino's biggest threat. It's people.

One hundred years ago, 500,000 rhinos wandered around parts of Africa and Asia. But today, rhinos are threatened with extinction. If nothing is done to save them, they could vanish forever.

Poachers (偷猎者) are killing rhinos for their horns (角). They do it to make money.

In some countries, people pay high prices for rhino horn. They believe that eating ground-up rhino horn will make them healthy. But that isn't true. Rhino horn is made of keratin (角质). That's the same thing your fingernails are made of. Eating it cannot make anyone healthy.

Humane Society International is working to help save rhinos. They wrote a children's book and produced a video to help spread the word. The book, I'm a Little Rhino, was given to 1.5 million children in Vietnam. That country buys and uses the most rhino horn.

“The goal is to educate children about rhinos in general, and introduce the threat that poaching causes to their survival,” says Adam Peyman, program manager for HSI's wildlife department. “It also explains that rhino horn is not effective as medicine and encourages them and their families to avoid buying or using rhino horn.”

Carter and Olivia Ries have been working to save rhinos for several years. “We made two trips to South Africa where we visited a dozen schools and met with government officials,” says Carter. “We gave the officials over 10,000 letters we collected from the youth around the world to show that the youth of the world care for rhinos. The next step was to bring that same message to the youth of Vietnam.”

Carter and Olivia visited schools in Vietnam. They want kids to bring the message back to their parents that using rhino horn “is causing the species to be pushed to the edge of extinction.”

You’re surrounded by robots and you probably don’t even know it. Most are not all that   (1)   and they won’t come up to you and speak like a friend.   (2)   you’re unaware of them, they know you’re there. Robots are monitoring   (3)   in hospitals, providing banking services,   (4)   people from burning buildings and assisting astronauts in   (5)   . Robots are everywhere.

Are robots   (6)   or deadly enemies? Robotic expert Hans Moravec says intelligent robots today are no smarter than the average insect. But, don’t feel too   (7)   about that. For example, army ants in South America   (8)  everything in their path when they go to war—forests, crops, buildings, people...

In case you   (9)    don’t care about our little mechanical friends,   (10)   this: Robot technology is currently   (11)    at a rate 10 million times faster than the evolution of   (12)   .

Considering the advances in robot technology during the upcoming years, Moravec says that robots must pass through four   (13)   of development before they rule the planet.

First robot technology must achieve the ability to   (14)    as general­ purpose tools with software running at one million instructions per second (MIPS). Those robots will have the   (15)   of reptiles (爬行动物). Next, this happening into 2020, robots will have acquired brains capable of   (16)   300 million MIPS, which will give them the intelligence of smart mice. A hundred billion MIPS will be   (17)    sometime after 2030. By then robots will be provided by their   (18)    (humankind) with monkey­like brains.  (19)   , at the dawn of 2040, robots will   (20)   human intelligence and they will quickly surpass humans and challenge people for supremacy (至高无上) of the planet.

You use her as a shoulder to cry on. She texts you back with casual jokes. But she, Xiaoice, is only a virtual chatbot(虚拟聊天机器人).

      Xiaoice, Microsoft’s latest artificial intelligence robot, was briefly released in 2014, and returned to WeChat in 2015, where she became a big hit. Millions of young Chinese now exchange messages with her daily, The New York Times reported. On WeChat, Xiaoice is an official account. After following it, users can start text-based conversations with Xiaoice.

      “Her incredible learning ability was why people loved to talk with Xiaoice,” Liu Jinchang, a researcher at High-tech Research and Development Center under the Ministry of Science and Technology, told China Daily. Apart from her ability to identify photos and send emojis(表情符号) in conversations, Xiaoice gains 45 percent of her knowledge from interacting with users, China Daily reported.

      Chatbot programs first appeared in the mid-1960s in the US. Driven by top tech companies, they are becoming smarter and more common. For instance, IBM’s latest artificial intelligence program served as an academic consultant at Australia’s Deakin University, answering students’ questions about course schedules and financial aid. Apple’s Siri and Amazon’s Alexa have been used as voice assistants who can read news, play music and even make jokes for their users.

      These programs are expected to move beyond smartphones, into televisions, cars and living rooms, The New York Times pointed out. However, it may take decades before scientists develop a＂Samantha＂, the advanced chatbot seen in the fiction film Her. In the film, Samantha has a romantic relationship with her user played by US actor Joaquin Phoenix. Many viewers were enthusiastic about this fantasy of virtual soul mates.

The first decade of the 21st century has been a remarkable period for inventions. Here are some of the most influential inventions in the first decade.

1 iPod and iTunes:

These two inventions from Apple Inc. presented a revolutionary new way for people to listen to music and fundamentally changed the recording industry. iTunes was introduced in January, 2001 and was marketed as a program that transferred (转录) CDs into digital audio files and helped organize digital recordings. Later that year, Apple introduced the iPod, a device (设备)that used a hard disk to store music files. The first model had a 5GB capacity and could hold over 1,000 songs.

2 iPhone:

The iPhone from Apple Inc. was released in June of 2007 and completely changed the way mobile phones are used personally and in business. Older phones typically included voice communications and sometimes a keyboard to send text messages. Phones that offered internet access were usually unreadable and difficult to handle. The iPhone introduced the multi-touch interface(界面) that allows for quick and easy access to data, music, and pictures while providing storage for other important information.

3 Electric Car:

Tesla Motors was formed in 2003. It was the first company to produce a vehicle that did not have significant difficulty in production or sales. Tesla vehicles claim an 88% efficiency rating compared to 20-25% for traditional gasoline-powered cars. According to data from the National Fire Protection Association, a driver is “5 times more likely to experience a fire in a traditional gasoline car than a Tesla.”

4 Facebook:

Facebook was not the first social networking website, but since its introduction in 2004 it has been the most influential medium. 150 million users worldwide appreciate its multitude of features and easy accessibility. The concept of building connections through internet has changed the manner in which businesses market their products and people interact with one another.

B

How long are you willing to wait for a webpage to open before you start to lose your patience? Half a minute? A few seconds?

Google engineers have discovered that even 400 milliseconds—as short as the blink of an eye—is too long for most Internet users.

A millisecond is one thousandth of a second. People hardly notice such a small time difference, but it does cause them to stop searching, reported The New York Times.

“Subconsciously, you don’t like to wait,” said Arvind Jain, a Google engineer. “Every millisecond matters.”

Nowadays, millions of smart-phones and computers are constantly gathering and sending out information. With so many people downloading maps, sports videos, news and restaurant recommendations, you can get digital “traffic jams”. Meanwhile, users are expecting faster and faster service.

Google found that if one website is 250 milliseconds slower than another website, then people will visit it less often. This is why technology companies are now competing to be the fastest.

Google said people do expect different things from different websites because they realize not all loading times are the same. For example, a person will be more patient waiting for a video clip to load than for a search result.

Even so, four out of five online users will click away if a video takes too long to load. This makes it difficult for video websites to choose between the quality of pictures and fast loading times.

Pursuing a higher speed has always been part of the history of the Internet.

In the 1990s, when the World Wide Web first started to become popular, it was very crowded and slow; people called it the “World Wide Wait”. But engineers managed to fight the problem with new inventions. They laid a lot of fiber optic cables for high-speed transmissions; they improved software so it would work more smoothly; they placed computer servers all around the world to be nearer to users; all this increased speed.

Nowadays we can enjoy much faster Internet. Major search engines such as Google and Microsoft’s Bing usually find search results in less than a second. But they will need to keep fighting to keep up with the developing demands of Internet users.