Dry Ice is a unique substance which has many uses. Essentially, dry ice is frozen CO2. The first report of what we now call dry ice came from the French chemist Charles Thilorier in 1834. In 1924, the Drylee Corporation of America named the solid form of CO2 as "Dry Ice", which is what it is popularly called today.

    At normal atmospheric pressure, CO2changes directly from solid to gas. It skips the liquid phase（阶段）which makes regular ice wet. Frozen CO2is also much colder than regular ice. But regular ice freezes at 32 degrees Fahrenheit, CO2 changes from gas to solid at -109.3 degrees Fahrenheit. This extremely cold temperature makes it very dangerous to handle with bare hands. It can cause frostbite in a very short period of time.

    Dry ice has been used for a variety of purposes throughout the past century. Its primary use is to refrigerate food when electrical refrigeration isn't available. Through the process of sublimation (when CO2 changes from solid to gas), it can maintain cold food for a long time.

    If you've ever been to a play and seen heavy fog on the ground, it is likely that you have seen dry ice in action. This effect can be achieved because CO2 is heavier than air, so evaporated （挥发的）CO2 will sink and accumulate on the ground.

    Another interesting use for this substance is to bait（诱杀）insects like mosquitoes. These insects have sensors which guide them to CO2. They find the high concentration of CO2 in dry ice quite attractive.

    Mars has long been a mystery for human beings. We have been looking for evidence of life on Mars. In the 1960s scientists guessed that the polar ice cap of Mars was made of frozen CO2. More recent observations have shown that while the topmost layer consists of frozen CO2, the most of it is probably regular frozen water.

    LOS ANGELES, Nov. 12 (Xinhua)—Legendary comic book writer Stan Lee has died at the age of 95, according to media reports on Monday.

    Lee, born in Stanley Lieber on Dec. 28, 1922, began his career in 1939 and joined the Marvel Comics in 1961.

    He is considered as one of the most legendary names in the history of comic books and the leading creative force behind the rise of Marvel Comics. He co-created iconic fictional characters such as Spider-Man, X-Men, the Avengers, and many more.

    Lee's characters often have super powers, but they also have weaknesses. They were humans, not gods. They not only struggled to save the world, but also to pay their bills, make friends, and hold jobs. This made Marvel comic book heroes stand apart from its competitor DC, which produced the seemingly perfect heroes like Superman and Wonder Woman. Those superheroes have been adapted into blockbuster films, most of which were made after Disney acquired Marvel in a 4-billion-dollar deal in 2009.

    In a statement, Bob Iger, chairman and CEO of the Walt Disney Company said Stan Lee was as extraordinary as the characters he created.

Marvel also praised Lee on its website by putting on one of Lee's famous quotes, which goes, "I used to be embarrassed because I was just a comic-book writer while other people were building bridges or going on to medical careers. And then I began to realize: entertainment is one of the most important things in people's lives. Without it, they might go off the deep end. I feel that if you're able to entertain, you're doing a good thing. "

Praise from his Hollywood peers and colleagues was generous. President of Marvel Studios Kevin Feige appreciated Lee's unparalleled impact on the industry. "No one has had more of an impact on my career than Stan Lee, " Feige said. "Our thoughts are with his family and the millions of fans who have been forever touched by Stan's genius, charisma and heart. "

    Planning a visit to the UK? Here we help with ways to cut your costs.

    AVOID BIG EVENTS Big sporting events, concerts and exhibitions can increase the cost of accommodation and make it harder to find a room. A standard double room at the Thistle Brighton on the final Friday of the Brighton Comedy Festival (19 Oct.) cost £169.15 at Booking.com. A week later, the same room cost £l18.15.

    If you can be flexible and want to know dates to avoid-or you're looking for a big event to pass your time—check out sites such as Whatsonwhen.com, which allow you to search for events in the UK by city, date and category.

    STAY AWAY FROM THE STATION If traveling to your destination by train, you may want to find a good base close to the station, but you could end up paying more for the sake of convenience at the start of your holiday.

    Don't be too choosy about the part of town you stay in. Booking two months in advance, the cheapest room at Travelodge's Central Euston hotel in London for Saturday 22 September was £95.95. A room just a tube journey away at its Covent Garden hotel was £75.75. And at Farringdon, a double room cost just £62.95.

    GET ON A BIKE London's 'Boris bikes' have attracted the most attention but other cities also have similar programmes that let you rent a bicycle and explore at your own pace, saving you on public transport or car parking costs.

    Among the smaller cities with their own programmes are Newcastle (casual members pay around £1.50 for two hours) and Cardiff (free for up to 30 minutes, or £5 per day).

    Today, the Chinese traditions of Qixi have combined with Western celebrations of love and romance. Lovers often use flowers, chocolates, sweet gifts or grand declarations to express feelings deep in their hearts.

    But this year, you could let your love take off by traveling with that special someone on a romantic adventure. Where should you travel? Find inspiration (灵感) from these four romantic movies, which all took place in breathtakingly beautiful places. Choose one as the ideal setting for your own real-life love story.

    Trevi Fountain in Rome

    Trevi Fountain is the largest Baroque fountain in the city and one of the most famous fountains in the world. It has appeared in several notable films, including Roman Holiday. In the film, Ann (played by Audrey Hepburn) has her hair cut a barbershop near the fountain, which becomes the style-setting “gamine” haircut in fashion history.

    Empire State Building, New York

    The Empire Sate Building is an American cultural icon and has been featured in more than 250 TV shows and movies. In the comedy-drama Sleepless in Seattle, Annie (played by Meg Ryan) writes a letter to Sam (Tom Hanks) suggesting meeting on top of the Empire State building on Valentine's Day. After twists and turns, they finally see each other on the observation deck on top of the building.

    Somerset House in London

    Located in central London, Somerset House is a popular filming location with its exterior featuring in several big budget Hollywood films. In the winter, its central courtyard is turned into an open-air ice rink, as seen during the well-received film Love Actually.

    Daocheng, Sichuan Province

    Daocheng is a county in Southwest China's Sichuan Province, located at the eastern Hengduan Mountains. This magical place combines the beauty of snow mountain, glacier, lake, grassland and waterfall. After the film I Belonged to You, Daocheng grows to be a major tourist attraction, a remote sacred place for unchanging love.

    A study based on data gathered by a NASA sensor has revealed China and India, the world's two most populous countries, are primarily responsible for making the Earth greener over the past two decades.

    The study, published on Feb 11 in the journal Natural Sustainability, has found that since 2000 the Earth's green leaf area has increased by over 5 million square kilometers. That's an area equivalent to the total of the Amazon rainforests. "China and India account for one-third of the greening, considering the general idea of land degradation (退化) in populous countries from overexploitation," said Chen Chi from Boston University, lead author of the study.

    The effect mainly comes from ambitious tree-planting programs in China and intensive agriculture in both countries, NASA said in a statement. China is the source of a quarter of the planet's increase in forest area, despite having only 6.6 percent of the world's vegetated (固定植被的)area, according to the study. Forest conservation and expansion programs account for 42 percent of the increase, and another 32 percent come from intensive agriculture of food crops, NASA said. While raising their green leaf areas, China and India have also greatly increased their food production through" multiple cropping" practices, where a field is replanted and crops are harvested several time each year. "Production of grains, vegetable, fruits and more have increased by about 35 to 40 percent since 2000 to feed their large population," NASA said.

    Over the past decades, China has made great efforts to green the land. In 1978, the central government launched a national-level forestation project-the Three North Shelterbelt Forest Program. By the end of 2017, the forest coverage rate among the regions in the project reached 13.57 percent, compared to 5.05 percent 40 years ago. In a greening project, Kubuqi Desert, seventh largest in the country, has seen one-third of its area covered by vegetation during the past three decades thanks to forestation efforts.

    Mark Twain left school when he was twelve. He had little school education. In spite of this, he became the most famous writer of his time. He made millions of dollars by writing. His real name was Samuel Langhorne Clemens, but he is better known all over the world as Mark Twain, his penname.

    Mark Twain was born in 1835 and he was not a healthy baby. In fact, he was not expected to live through the first winter. But with his mother's care, he managed to survive. As a boy, he caused much trouble for his parents. He used to play jokes on all his friends and neighbors. He didn't like to go to school, and he often ran away from home. He always went in the direction of the nearby Mississippi(密西西比河). He was nearly drowned nine times.

    After his father's death, Mark Twain began to work for a printer, who only provided him with food and clothing. Then, he worked as a printer, a river-boat pilot and later joined the army. But shortly after that he became a miner. During this period, he started to write short stories. Afterwards he became a full time writer.

    In 1870, Mark Twain got married. In the years that followed he wrote many books including Tom Sawyer in 1876, and Huckleberry Finn in 1884, which made him famous, and brought him great fortune.

    Unfortunately, Mark Twain got into debts in bad investments(投资) and he had to write large numbers of stories to pay these debts. In 1904, his wife died, and then three of his children passed away.

    At the age of 70, his hair was completely white. He bought many white suits and neckties. He wore nothing but white from head to foot until his death on April 21, 1910.