Can people change their skin color without suffering like pop king Michael Jackson? Perhaps yes. Scientists have found the gene that determines skin color.

    The gene comes in two versions, one of which is found in 99 percent of Europeans. The other is found in 93 to 100 percent of Africans, researchers at Pennsylvania State University report in the latest issue of Science.

    Scientists have changed the color of a dark-striped zebra-fish（斑马鱼） to uniform gold by inserting a version of the pigment (色素) gene into a young fish. As with humans, zebra-fish skin color is determined by pigment cells, which contain melanin (黑色素). The number, size and darkness of melanin per pigment cell determine skin color.

    It appears that, like the golden zebra-fish, light-skinned Europeans also have a mutation (变异) in the gene for melanin production. This results in less pigmented skin.

    However, Keith Cheng, leader of the research team, points out that the mutation is different in human and zebra-fish genes.

    Humans acquired dark skin in Africa about 1.5 million years ago to protect bodies from ultra-violet rays of the sun (太阳光紫外线), which can cause skin cancer.

    But when modern humans leave Africa to live in northern latitudes, they need more sunlight on their skin to produce vitamin D. So the related gene changes, according to Cheng.

    Asians have the same version of the gene as Africans, so they probably acquired their light skin through the action of some other gene that affects skin color, said Cheng.

    The new discovery could lead to medical treatments for skin cancer. It also could lead to research into ways to change skin color without damaging it like chemical treatment did on Michael Jackson.

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    A Sydney Pass gives you unlimited and flexible travel on the Explorer Buses: the 'red' Sydney Explorer shows you around our exciting city sights while the 'blue' Bondi Explorer visits Sydney Harbor bays and famous beaches. Take to the water on one of three magnificent daily harbor cruises(游船). You can also travel free on regular Sydney Buses, Sydney Ferries or City Rail services (limited area), so you can go to every corner of this beautiful city.

    Imagine browsing at Darling Harbor, sampling the famous seafood at Watsons Bay or enjoying the city lights on an evening ferry cruise. The possibilities and plans are endless with a Sydney Pass. Wherever you decide to go, remember that bookings are not required on any of our services so tickets are treated on a first in, first seated basis.

    Sydney Passes are available for 3, 5 or 7 days for use over a 7 calendar day period. With a 3 or 5 day pass you choose on which days out of the 7 you want to use it. All Sydney Passes include a free Airport Express inward trip before starting your 3, 5 or 7 days, and the return trip is valid (有效的) for 2 months from the first day your ticket was used.

Sydney Pass Fares

*A child is defined as anyone from the ages of 4 years to under 16 years. Children under 4 years travel free.

**A family is defined as 2 adults and any number of children from 4 to under 16 years of age from the same family.

    Lost cities that have been found

    The White City

    In 2015, a team of explorers to Honduras in search of “the Lost City of the Monkey God” led to the discovery of the White City. They found the ruins in the Mosquitia region of the Central American country — which is known for poisonous snakes, vicious jaguars and deadly insects. It is believed that local people hid here when the Spanish conquerors(征服者)occupied their homeland in the 16th century.

    Canopus and Heracleion

    Modern researchers were teased by the ancient writings about the Egyptian cities Canopus and Heracleion — where Queen Cleopatra often visited. But the cities weren't found until 1992, when a search in Alexandria waters found that the two cities had been flooded for centuries. Artifacts(史前器物)showed that the cities once highly developed as a trade network, which helped researchers piece together more about the last queen of Egypt.

Machu Picchu

    A Yale professor discovered “the Lost City in the Clouds” in 1911. A combination palaces, plazas, temples and homes, Machu Picchu displays the Inca Empire at the height of its rule. The city, which was abandoned in the 16th century for unknown reasons, was hidden by the local people from the Spanish conquerors for centuries, keeping it so well preserved.

Troy

    The ancient city of Troy in Homer's The Iliad was considered a fictional setting for his characters to run wild. But in 1871, explorations in northwestern Turkey exposed nine ancient cities layered(层叠)on top of each other, the earliest dating back to about 5,000 years before. It was later determined that the sixth or seventh layer contained the lost city of Troy and that it was actually destroyed by an earthquake, not a wooden horse.

    China now has 52 sites included on the UNESCO World Heritage List, which was established to safeguard unique and irreplaceable cultural and natural sites around the world. Let's have a look at some of them, which may give you some clues on your next travel plan.

    Mausoleum of the First Qin Emperor

    The Mausoleum of the First Qin Emperor is located in Lintong county, near Xi'an city, capital of Shaanxi province. A total of 8,000 life-size terracotta warriors, chariots and horses, and hundreds of bronze weapons have been unearthed from it. Many state leaders and experts worldwide believe that the discovery of the mausoleum is a major archeological find and can be called the eighth wonder of the world, paralleling Egypt's pyramids.

    Kulangsu, a Historic International Settlement

    Gulangyu Island, known in the local dialect as Kulangsu, is located on the entry of the Jiulong River, facing the city of Xiamen. The island was occupied by at least a dozen countries, including Great Britain, France and Japan. As a result, Western culture grew rapidly there in the 19th century, especially music. With such a harmonious blend of Western music and Eastern culture, Gulangyu is naturally referred to as the "island of music". It is famous for its outstanding musicians and musical instruments.

    Qinghai Hoh Xil

    Hoh Xil, which means "beautiful girl" in Mongolian, is located in the north-eastern end of the Qinghai-Tibetan Plateau. Hoh Xil National Nature Reserve is China's largest and the world's third largest uninhabited area. Because of the high altitude and fierce weather, it is impossible for people to live there, and therefore, it is a paradise for wildlife and home to more than 230 species of wild animals including endangered species such as the Tibetan antelope, which is recognized as the National Class I Protected animal.

    Huangshan Mountain

    Huangshan, known as "the loveliest mountain of China", lies in the south of Anhui province in eastern China. The scenic area covers 154 sq km, and is famous for its peaks, rocks, pines, clouds and springs. It also has a rich cultural heritage. Xu Xiake, a famous traveler of the Ming Dynasty (1368-1644), visited Huangshan twice, and described it in a poem, calling it the best of all mountains in China. Today it holds the same fascination for visitors, poets, painters and photographers.

    On average, Americans spend about 10 hours a day in front of a computer or other electronic devices and less than 30 minutes a day outdoors. That is a claim made by David Strayer, a professor of psychology at the University of Utah. In his 2017 TED Talk, Strayer explained that all this time spent with technology is making our brains tired.

    Using an electronic device to answer emails, listen to the news and look at Facebook puts a lot of pressure on the front of the brain, which, Strayer explains , is important for critical (有判断力的)thinking , problem-solving and decision-making.

So, it is important to give the brain a rest. And being in naure, Strayer claims, helps get a tired brain away from too much technology. More than 15,000 campers from around the world attended an international camping festival in September. That is when friends and family take time off and escape to nature for several days. They take walks, climb, explore, swim, sleep, eat and play. Camping may be just what a tired brain needs.

    Take Carl for example .He lives in West Virginia and enjoys camping. He says that staying outdoors makes him feel at ease. It also prepares him for the work he must do. Kate Somers is another example who also lives in West Virginia. She says she enjoys camping with her husband and two children. She calls it a “regenerative” experience.

    At the University of Utah, David Strayer has studied both short-term and long-term exposure to nature. He found that spending short amounts of time in nature without technology does calm the brain and helps it to remember better. However, he found, it is the long-term contact with nature that does the most good. He and his research team found that spending three days in nature without any technology is enough time for the brain to fully relax and reset itself.

    As the weather gets colder, we start wearing jackets, and most of us stop thinking about the sun. But the sun's rays can be just as harmful when it's cold and cloudy outside. "Any exposed area of your body can still get sunburned," Dr. Apple Bodemer, an associate professor at the University of Wisconsin-Madison, told Live Science.

    Whether you spend a day on the slopes, skating on a pond or clearing snow out of your driveway, your face is still getting exposed to the sun's radiation in the form of ultraviolet (紫外线) (UV) light, which can go deep into your skin cells causing DNA damage, according to Bodemer.

    The sun's long ultraviolet A (UVA) waves can cause earlier aging, sunspots and wrinkles, while its short ultraviolet B (UVB) rays are known for causing skin reddening and burns.

    Skin damage caused by UV exposure increases over time. More exposure to radiation contributes to more severe damage, even skin cancer. In addition, snow and ice can also make sun damage worse. They reflect up to 80 percent of UV rays reaching the ground. That means you get hit from both the sky and the ground. And skiers and snowboarders increase their risk of getting sunburned even more because UV exposure increases at higher altitudes.

    "Generally, the biggest factor for sun-sensitivity is how pale your skin is," he said. "But, the reality is that even the darkest individual can get sun damage."

    Luckily, the solution for protecting your skin is simple: Wear sunscreen every day. Rigel recommended using sunscreen with a sun protection factor (SPF) of at least 30, and going higher at high altitudes. As a rule of thumb, SPF 30 will block 97 percent of UVB rays, SPF 50 blocking 98 percent, and SPF 100 blocking 99 percent. Whatever kind of sunscreen you use, it's important to apply SPF about once every 2 hours.

    Rigel also suggested sunscreens with "broad spectrum (光谱)"—to protect against both UVB and UVA rays—as well as sunscreens that are water resistant for up to 80 minutes. That way, you can go about your day without it wearing off too quickly.