【推荐1】A group of American tigers in a swampy(沼泽的)area of Brazil eat more fish than land animals, and are happy to socialise and play together, according to a new study. They are the first wild American tigers known to feed on large amounts of fish.

Researchers from Oregon State University in the US, with Brazilian colleagues studied a population of wild American tigers in the Brazilian Pantanal, a low-lying region of Brazil where water runs off nearby mountains to create swamps. It’s the world’s largest freshwater wetland habitat, but wildlife there can be difficult to study with few roads. Therefore, researchers set up cameras to film anything walking by. They also put tracking devices on 13 random American tigers.

Over 1,500 videos were gathered showing 69 individual American tigers. They are strong swimmers and the videos showed them eating lots of fish. They also ate reptiles living in the water, such as lizards. The analysis of 138 American tiger scats(粪便)also found they mostly contained bones of fish and reptiles living in the water—only 11% had mammal remains. This is surprising because mammals such as deer and monkeys form the main part of American tigers’ diets in other places. Even tigers in India’s wetlands eat mostly land-based mammals.

The cameras also delivered other surprises. American tigers usually enjoy being alone, only coming together to fight over territory, but the video showed two adult males playing, fishing and traveling together—a kind of behaviour that had never been seen before. Charlotte Eriksson, who led the study, thinks it possible if the wetlands provide adequate fish.

【推荐1】Gardeners are often puzzled by the sudden appearance of an unusual orchid(兰花) or sometimes are disappointed that their annuals have vanished. Scientists have discovered that some British flowers can lie dormant (休眠的) under the ground for up to 20 years, coming out to bloom only when the conditions are just right. Orchids seem particularly good at being dormant for years at a time, the scientists discovered.

Michael Hutchings, Professor of Ecology at the University of Suss, said: “Being underground means they cannot receive sunshine, neither flower nor reproduce. And yet this study has shown that many plants in a large number of species frequently go through dormancy (休眠). Many of these species have found ways to overcome the loss of sunshine during dormancy, especially by gradually developing their ability to get what they need from soil. This allows them to survive and even grow well during dormant periods.”

The research found that dormancy occurs when the weather is poor, or there is a new threat from animals or competing plants. Sometimes winters are so mild that the plant does not realize that spring has begun. Dormancy in seeds has been widely known about and studied for years, but the dormancy in adult plants is far less well-known and understood.

The study, led by Professor Richard Shefferson in University of Tokyo, is the first detailed analysis of the causes. Dormancy appears to be more common near the equator (赤道), where threats from factors such as disease, competition, animals and fire are more severe. Co-author Dr. Eric Menges said:“ In those areas, it is most suitable for plants to remain dormant and then to grow when favourable conditions exist for growth and flowering. ”

【推荐2】Throughout history, countless people have made valuable contributions to astronomy. Here is a list of some of them.

Nicolaus Copernicus

Polish astronomer Nicolaus Copernicus did just one thing. Most scholars, however, think it was the greatest thing ever done in astronomy. Copernicus formulated what’s now called the heliocentric model-he moved Earth from the center of the universe and replaced it with the Sun. He didn’t publish his theory until he was on his deathbed in 1543.

Johannes Kepler

Indeed, German astronomer Johannes Kepler’s laws, especially the first, which states that planets move in ellipses(not circles)—set the stage for the law of universal gravitation. In addition to many years of hard orbital calculations, Kepler also observed a supernova(超新星), now called Kepler’s Nova, in 1604.

Tycho Brahe

Danish astronomer Tycho Ottesen Brahe was history’s greatest pre-telescopic observer. In fact, his careful observations of Mars enabled Kepler to develop his laws of planetary motion. Two of his famous observations were of the supernova that appeared in 1572(now called Tycho’s Nova)and the Great Comet of 1577.

Galileo Galilei

The first lens Galileo made is where optical(光学的)astronomy began. For that reason, Italian astronomer Galileo di Vincenzo Bonaiuti de Galilei ranks No.1 on this list. Although he didn’t invent the telescope, Galileo was the first to use it to study the sky: He observed sunspots, the phases of Venus, Saturn’s rings, and the four large moons of Jupiter.

【推荐1】Processed foods—cheap, convenient, and beloved by many Americans—have once again been proven harmful to our health. Higher consumption of ultra-processed foods was associated with an increased risk of heart disease and death, according to a study carried out this week in the Journal American College of Cardiology.

Past research has also linked these preservative-laden (含防腐剂的) foods to weight gain, cancer, and early death. Many studies, including the recent cardiology paper, have proven the health risks are higher for people who eat a greater quantity of processed foods.

Each daily serving of ultra-processed food—such as a single protein bar or a 12 oz can of soda—was associated with a 7% increase in the risk of dying of cardiovascular disease and a 9% increase in the risk of dying due to heart disease, based on data from more than 3,000 adults followed for nearly 20 years.

Still, processed foods are “ubiquitous” in our diets, lead author Filipa Juul said in a press release. Although we know they’re bad for our health, ultra-processed foods account for more than half of the daily calories in the average American diet. Even seemingly healthy options like protein bars, breakfast cereals, and most industrially produced breads are filled with preservatives and added sugar, salt, and fat.

“As a poor diet is a major risk factor for heart disease, it represents a critical target in prevention efforts,” Juul, a researcher at the New York University School of Public Health, said in the press release. The authors recommended taxing (征税) processed foods with added sugar as a possible incentive (刺激) to reduce consumption.

More importantly, they acknowledged the need to make more nutritious choices available and affordable, especially for populations that have historically lacked that access. “Ultimately, the goal should be to make the unhealthy choice the hard choice and the healthy choice the easy choice,” Robert J. Ostfeld, MD, MSc, and Kathleen E. Allen, MS, RD, wrote in an editorial accompanying the study.

【推荐2】Lighthouses are built on or near the shore to help guide ships away from danger. However, the threat of rising sea level has many people worried about the future of lighthouses worldwide.

The East Point Lighthouse in New Jersey has been lighting up the Delaware Bay for more than 200 years. But the waters that surround it may bring about its end. During storms, water hits a wall that is just nine meters from the front of the lighthouse. After each major storm, the wall around the lighthouse has to be rebuilt and 1, 300-kilogram sand bags and other methods are used to protect it. A simple fix would cost about 3 million dollars.

Rising sea levels have already forced the relocation of several lighthouses. In 1999, the National Park Service moved the Cape Hatteras Lighthouse in North Carolina, nearly 884 meters inland, which cost about 11. 8 million dollars. In 1993, the Southeast Lighthouse on Block Island, which is still guiding ships, was moved more than 91 meters inland.

Tim Harrison is the editor of Lighthouse Digest, a publication (出版) based in the northern state of Maine. It has a list of 53 lighthouses around the United States that may be lost because of the effects of climate change. “Lighthouses were built for one purpose: to save lives. Some of America’s lighthouses continue to be used to guide ships and other boats. But a good number have been replaced by modern technology. Instead, the lighthouses are valued more for historical reasons.” Tim said. “Now it’s our turn to step up and save these lighthouses.”

But some lighthouses have already been lost. Both the Galveston Jetty Lighthouse in Texas and the Sabine Bank Lighthouse in Louisiana were lost to storms or rising seas. And the Kauhola Point Lighthouse on Hawaii’s Big Island was taken down after erosion nearby was so severe that it could not be saved. Other lighthouses that are considered to be in danger from rising seas include the Sand Island Lighthouse in Alabama and the New Point Comfort Lighthouse in Virginia.