【推荐1】A study found wireless signals are able to pass through bags and suitcases to judge the sizes of dangerous metal objects and identify them. “These items could include weapons, chemicals, laptops and batteries for bombs,” the research team said on Tuesday.

Research suggested that Wi-Fi can now be used to estimate the volume of liquids such as water, acid, alcohol and other chemicals for explosive material. The study led by researchers at the Wireless Information Network Laboratory (WINLAB) in the School of Engineering showed a wireless device with two to three antennas (天线) that could be fitted in existing Wi-Fi networks.

The detection system analyzes what happens when wireless signals go through and bounce off objects or materials. The approach, which the paper states, works by separating the wireless interference (干扰) caused by two factors of objects — the material and shape. “Most dangerous objects such as weapons are usually metal or liquid, which have significant interference,” researchers said.

When it was tested on a backpack, the accuracy rate topped 95 percent. “But the accuracy dropped to about 90 percent when objects inside bags are wrapped. And the tech could save lives if used in museums, stadiums, theme parks or schools,” the team said, noting its design can inspect bags or luggage without being an exposure to privacy.

It uses channel state information (CS) that is readily available in low-cost Wi-Fi devices. “This could have a great impact on protecting the public from dangerous objects,” said Yingying Chen, a co-author of the study, “There’s a growing need for that now. In large public areas, it’s hard to set up expensive screening equipment like what’s in airports. Manpower is always needed to check bags and we want to develop a method to try to reduce manpower. “

The peer-reviewed study, which recently won a best paper award at the 2018 IEEE Conference on Communications and Network Security, is now published online. “Future work will continue to focus on improving the accuracy of identifying objects and imaging shapes and volumes,” researchers said.

【推荐1】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 bird 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 most 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 American’s need for wood, which scattered (驱散) the flocks and forced the birds to go farther north, where cold temperatures and 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 on September 1, 1914.

A．were the biggest bird in the world

B．lived mainly in the south of America

C．did great harm to the natural environment

D．were the largest bird population in the US

【推荐3】Why elephants rarely get cancer is a mystery that has confused scientists for decades. A study led by researchers at Huntsman Cancer Institute (HCI), at the University of Utah and Arizona State University may have found the answer.   

According to the results, elephants have 38 additional modified copies of a gene that encodes p53, a definite tumor suppressor, as compared to humans, who have only two. Further, elephants may have a more powerful mechanism for killing damaged cells that are at risk for becoming cancerous. In isolated elephant cells, this activity is doubled compared to healthy human cells, and five times that of cells from patients with Li-Fraumeni Syndrome, who have only one working copy of p53 and more than a 90 percent lifetime cancer risk in children and adults. The results suggest extra p53 could explain elephants’ increased resistance to cancer.

“Nature has already figured out how to prevent cancer. It’s up to us to learn how different animals overcome the problem so we can adapt those strategies to prevent cancer in people,” says co-senior author Joshua Schiffman, M.D., pediatric oncologist (儿科肿瘤医生) at Huntsman Cancer Institute, University of Utah School of Medicine.

But Prof Mel Greaves, from the Institute of Cancer Research in London, says we should focus on why humans have such high levels of cancer. He pointed to the rise of unhealthy, cancer-causing behaviors, such as obesity and sunbathing. “You’ve never seen an elephant smoke!” he added.

According to Schiffman, elephants have long been considered a walking problem. Because they have 100 times as many cells as people, they should be 100 times more likely to have a cell slip into a cancerous state and cause the disease over their long life span of 50 to 70 years. And yet analysis of a large database of elephant deaths estimates a cancer death rate of less than 5 percent compared to 11 to 25 percent in people.