If a diver surfaces too quickly, he may suffer the bends. Nitrogen(氮) dissolved(溶解) in his blood is suddenly liberated by the reduction of pressure. The consequence, if the bubbles (气泡)accumulate in a joint, is sharp pain and a bent body—thus the name. If the bubbles form in his lungs or his brain, the consequence can be death.

    Other air-breathing animals also suffer this decompression(减压) sickness if they surface too fast: whales, for example. And so, long ago, did ichthyosaurs. That these ancient sea animals got the bends can be seen from their bones. If bubbles of nitrogen form inside the bone they can cut off its blood supply. This kills the cells in the bone, and consequently weakens it, sometimes to the point of collapse. Fossil (化石)bones that have caved in on themselves are thus a sign that the animal once had the bends.

    Bruce Rothschild of the University of Kansas knew all this when he began a study of ichthyosaur bones to find out how widespread the problem was in the past. What he particularly wanted to investigate was how ichthyosaurs adapted to the problem of decompression over the 150 million years. To this end, he and his colleagues traveled the world's natural-history museums, looking at hundreds of ichthyosaurs from the Triassic period and from the later Jurassic and Cretaceous periods.

    When he started, he assumed that signs of the bends would be rarer in younger fossils, reflecting their gradual evolution of measures to deal with decompression. Instead, he was astonished to discover the opposite. More than 15% of Jurassic and Cretaceous ichthyosaurs had suffered the bends before they died, but not a single Triassic specimen(标本) showed evidence of that sort of injury.

    If ichthyosaurs did evolve an anti-decompression means, they clearly did so quickly—and, most strangely, they lost it afterwards. But that is not what Dr Rothschild thinks happened. He suspects it was evolution in other animals that caused the change.

    Whales that suffer the bends often do so because they have surfaced to escape a predator (捕食动物) such as a large shark. One of the features of Jurassic oceans was an abundance of large sharks and crocodiles, both of which were fond of ichthyosaur lunches. Triassic oceans, by contrast, were mercifully shark- and crocodile-free. In the Triassic, then, ichthyosaurs were top of the food chain. In the Jurassic and Cretaceous, they were prey(猎物) as well as predator—and often had to make a speedy exit as a result.

A huge lake of salty water appears to be buried deep in Mars, scientists reported this week. The presence of water raises the chances of finding life on the red planet. The discovery is based on observations by a European spacecraft. It has excited experts. Water is necessary for life, and scientists have long hoped to prove that it is present on Mars.

Cassie Stuurman is a geophysicist at the University of Texas. In 2016, she found evidence of a huge ice deposit(沉积)on Mars. “If these researchers are right, this is the first time we've found evidence of a large water body on Mars. ”Stuurman said. Researchers are not yet sure how deep the area of water is. So, they cannot say whether it is an underground pool, or just an area of soft and wet soil.

In order to find the water, Italian researchers examined radar signals. The signals were collected over three years by the European Space Agency's Mars Express spacecraft. The results suggest that a 20-kilometer-wide water body lies below ice that is 1.5 kilometers thick. They believe the area is close to the planet's southern pole.

    Mars is very cold, but salt in the water may have kept it from freezing. It is the same as when you put salt on a road to prevent ice from forming. The water would be extremely cold, right at the point where it's about to freeze. And it would be salty. Such conditions are not ideal for life to form. But, she said there are bacteria on the earth that have been able to survive in similar conditions.

Mars has been a popular planet for exploration, with some groups placing instruments on its surface and others examining it from space. In May, NASA launched another spacecraft, the InSight Mars lander which will dig deep into the data under the surface after it reaches a flat area of the planet in November.

    I left university with a good degree in English Literature, but no sense of what I wanted to do. Over the next six years, __________ just trying to earn an income. I tried journalism, but I didn't think I was any good, then finance, which I hated. Finally, I got a job as a rights assistant at a famous publisher. I loved working with books, although the job that I did was dull.

    I had enough savings to take a year off work, and I decided to try to satisfy a deep-down wish to write a novel. Attending a Novel Writing MA course gave me the structure I needed to write my first 55,000 words.

    It takes confidence to make a new start — there's a dark period in-between where you're neither one thing nor the other. You're out for dinner and people ask what you do, and you're too ashamed to say, "Well, I'm writing a novel, but I'm not quite sure if I'm going to get there." My confidence dived. Believing my novel could not be published.

    I put it aside.

    Then I met an agent(代理商)who said I should send my novel out to agents. So, I did and, to my surprise, got some wonderful feedback. I felt a little hope that I might actually become a published writer and, after signing with an agent, I finished the second half of the novel.

The next problem was finding a publisher. After two-and-a-half years of no income, just waiting and wondering, a publisher offered me a book deal — that publisher turned out to be the one I once worked for.

    It feels like an unbelievable stroke of luck — of fate, really. When you set out to do something different, there's no end in sight, so to find myself in a position where I now have my own name on a contract of the publisher — to be a published writer — is unbelievably rewarding.

    Do you still use a power button(开机键)to open your smart phones or computers? You are out of fashion! Now most smart phones are using facial-recognition system(面部识别系统), and we already have machines that can know you from your fingers and your voice too. But some companies are still willing to invent other systems to "break" these systems, for example, the eye-recognition system. As is reported, you'll just have to look at the computers and machines, and this system will be able to tell you who you are by looking at your eyes, even when you are wearing glasses.

    Do you wonder if this system will work well? The answer is YES. All you need is just look at your machines. The eye scanner(扫描仪)is put in the cameras of your machines. The eye-recognition system is safer and easier than other systems. This is because everyone's eyes are different. Since the system works easily, you won't have to remember a group of code when you want to open your computer or take money out of a bank in the future. Eye-recognition system is better than other kinds of systems because your eyes don't change as you get older, and don't get dirty like hands or fingers. Even twins' eyes are not the same. So the eye-recognition system can be up to 94 percent correct, but it depends on how good the technology is. Some systems may only 51% right. In Britain, it was found that 91 percent of the people who had tried it said that they liked the idea of eye-recognition. So scientists think it will become more popular than other systems.

    The eye-recognition system has already been tested in shops in the USA, Britain, Spain, Italy and Turkey Soon it will become a popular way among public. In the future, your computer will be opened by looking at your eyes.

    Amsterdam, the capital and most populous city in the Netherlands, is one of the most popular travel destinations in the world, famous for its beautiful canals, top art museum, cycling culture, and Red Light District. Here are some of the key points to remember as you plan your trip to Amsterdam.

    Must-See Attractions

    Most visitors begin their Amsterdam adventure in the Old Centre, which is full of traditional architecture, shopping centers, and coffee shops. You'll also want to check out Amsterdam's Museum Quarter in the South District, which is great for shopping at the Albert Cuyp Market and having a picnic in the Vondelpark. The top museums to visit are the Rijksmusuem, the Ann Frank House, and the Van Gogh Museum. The Canal Ring is a UNESCO World Heritage Site that was originally built to attract wealthy home owners and is a popular place for celebrity spotting and nightlife today.

    Transportation

    Travelers should be aware that Amsterdam Airport Schiphol is one of the busiest airports in the world. This airport is located about 15 kilometers southwest of city center. You can catch a train from Schiphol to Amsterdam Central Station, which has many connecting routes. It's typically not a good idea to drive a car to the city center because traffic is heavy and parking is difficult to find. Cycling is incredibly popular here, and it's easy to find cheap bike rentals around town. Amsterdam has a flat terrain (地形) and is a great city to explore on foot.

    Money Saving Tips

    Unless you really want to see the tulips (郁金香) blooming, avoid booking between mid-March and mid-May. This is when hotel and flight prices rise.

    Look for accommodations in Amsterdam's South District, where rates are generally cheaper than in the city center.

    Buy train tickets at the machine instead of the counter to save a bit of money.

    Instead of hiring a tour guide, hop on a canal boat. They're inexpensive and will give you a unique point of view of the city.

    Check out our homepage to view price comparisons for flights, hotels, and rental cars before you book.

When it comes to lowering blood pressure,studies have typically shown that aerobic(有氧的)exercises are best. Recent research suggests another type of physical activity is worth including as an effective tool to prevent and treat high blood pressure.

Exercises that engage muscles without movement,such as wall squats and planks,may be best for lowering blood pressure,according to a large study published in July,2023 in the British Journal of Sports Medicine.

This type of training is known as isometric exercise,according to the Mayo Clinic.Isometric muscle action happens when muscles contract but do not visibly change length,and the joints involved don't move,facilitating stability of the body.Isometric exercises can be done with weights or without,just relying on the body's own weight.

"These findings provide a comprehensive data-driven framework to support the development of new exercise guideline recommendations for the prevention and treatment of high blood pressure,"said study coauthor Dr.Jamie O'Driscoll in a news release.  The researchers looked into randomized controlled trials that had reported the effects of exercise interventions, lasting two or more weeks,on blood pressure between 1990 and February 2023.From a review of 270 trials with 15,827 participants,the researchers  found that  among HIIT  (high  intensity interval training),isometric  exercise, aerobic exercise,dynamic resistance training and a combination of the latter two,isometric exercise led to the greatest reductions in blood pressure.

It's also important to note that there are other lifestyle changes as well as exercise that can benefit your blood pressure.These include keeping to a healthy weight,eating a balanced diet,cutting down on salt,not drinking too much alcohol and ensuring that you continue to take any prescribed medication.

More research is needed to determine exactly why isometric exercises might be better for lowering blood pressure than other types of training,the authors said.