The best bikes for the beginners

    When it comes to purchasing your first bike, the choice is endless, making it tough to know what to go for. Here are the the best buys on the market right now.

⒈Boardman Cx Comp

    This is a cross country bike, and it's so multifunctional that you can handle any terrain(地势) on it , making it a great choice for those wanting to try various cycling subjects. If you leave on the thick tires it comes with, it can ride on various paths and can even handle some less demanding mountain bike routes. Alternatively, put on thin, smooth tires and treat it asa road bike. It has a basket and comes with Shimano Sora gears (变速器), which are outstanding for its price.

£650, Halfords

⒉Planet X RT-58 v2

    Planet X is based in Yorkshire, which means you'd probably have to buy this bike without seeing it. But it's worth it，because this is an excellent machine at a lower price, Planet X is a highly rated manufacturer and this model comes with Shimano Sora gearing.

£585, Planet X

⒊Specialized Allez E5

    Specialized is one of the biggest and most popular brands in cycling, and this is its hugely popular primary road bike. It comes with solid components from front to back and you'll look great out on the road.

£ 75, Evans Cycles

⒋Boardman Road Team Carbon

    If you can push your budget further still, this bike is worth the extra investment. The frame is made entirely from carbon, which is lighter, faster and more comfortable than the composition metal models above and gives you an all round and more enjoyable ride. It also means that if you get really serious about cycling, you don't have to upgrade as quickly as you would with a cheaper bike.

£800, Halfords

    LOS ANGELES — Kobe Bryant is a winner in retirement, too. The former Los Angeles Lakers star won an Oscar in the animated short category for "Dear Basketball," a poem he wrote after ending his 20-year career on the court in 2016.

    He'll add it to an already jammed trophy collection that includes five NBA championships with the Lakers, two Olympic gold medals, NBA Finals most valuable player awards, a league MVP award and four All-Star game MVP awards.

    As executive producer, Bryant accepted his golden Oscar statue from "Star Wars" star Mark Hamill on Sunday night. He shared the award with Disney animator Glen Keane.

    Among those offering their congratulations via Twitter were Hall of Famers Magic Johnson, Bill Russell and Shaquille O'Neal, Bryant's former Lakers teammate who admitted, "I'm jealous!"

Since hanging up his basketball shoes, Bryant has thrown himself into business (a new Nike shoe) and various forms of storytelling.

    "As basketball players, we're told to shut up and dribble," Bryant said on stage. "I'm glad we did a little bit more than that."

    He thanked his wife, Vanessa, and his three daughters, naming each of them. He spoke a few words of Italian — a language he learned as a child growing up in Italy — and closed by telling them, "You are my inspiration."

    Cities usually have a good reason for being where they are, like a nearby port or river. People settle in these places because they are easy to get to and naturally suited to communications and trade. New York City, for example, is near a large harbour at the mouth of the Hudson River. Over 300 years its population grew gradually from 800 people to 8 million. But not all cities develop slowly over a long period of time. Boom towns grow from nothing almost overnight. In 1896, Dawson, Canada, was unmapped wilderness(荒野). But gold was discovered there in 1897, and two years later, it was one of the largest cities in the West, with a population of 30,000.

    Dawson did not have any of the natural conveniences of cities like London or Paris. People went there for gold. They travelled over snow-covered mountains and sailed hundreds of miles up icy rivers. The path to Dawson was covered with thirty feet of wet snow that could fall without warming. An avalanche(雪崩) once closed the path, killing 63 people. For many who made it to Dawson, however, the rewards were worth the difficult trip. Of the first 20,000 people who dug for gold, 4,000 got rich. About 100 of these stayed rich men for the rest of their lives.

    But no matter how rich they were, Dawson was never comfortable. Necessities like food and wood were very expensive. But soon, the gold that Dawson depended on had all been found. The city was crowded with disappointed people with no interest in settling down, and when they heard there were new gold discoveries in Alaska, they left Dawson City as quickly as they had come. Today, people still come and go — to see where the Canadian gold rush happened. Tourism is now the chief industry of Dawson City — its present population is 762.

    People have different ways of dealing with a common cold. Some take over-the- counter(非处方的) medicines such as aspirin while others try popular home remedies(治疗)like herbal tea or chicken soup. Yet here is the tough truth about the common cold: nothing really cures it.

    So why do people sometimes believe that their remedies work? According to James Taylor, professor at the University of Washington, colds usually go away on their own in about a week, improving a little each day after symptoms peak, so it's easy to believe it's medicine rather than time that deserves the credit, USA Today reported.

    It still seems hard to believe that we can deal with more serious diseases yet are powerless against something so common as a cold. Recently, scientists came closer to figuring out why. To understand it, you first need to know how antiviral(抗病毒的) drugs work. They attack the virus by attaching to and changing the surface structures of the virus. To do that, the drug must fit and lock into the virus like the right piece of a jigsaw(拼图), which means scientists have to identify the virus and build a 3-D model to study its surface before they can design an antiviral drug that is effective enough.

    The two cold viruses that scientists had long known about were rhinovirus(鼻病毒) A and B. But they didn't find out about the existence of a third virus, rhinovirus C, until 2006. All three of them contribute to the common cold, but drugs that work well against rhinovirus A and B have little effect when used against C.

    "This explains most of the previous failures of drug trials against rhinovirus," study leader Professor Ann Palmenberg at University of Wisconsin-Madison, US, told Science Daily.

    Now, more than 10 years after the discovery of rhinovirus C, scientists have finally built a highly-detailed 3-D model of the virus, showing that the surface of the virus is, as expected, different from that of other cold viruses.

    With the model in hand, hopefully a real cure for a common cold is on its way. Soon, we may no longer have to waste our money on medicines that don't really work.

    Cooking programs and classes for children seem to positively influence children's food preferences and behaviors, according to a recent review. And, although the review didn't look at long-term effects of such programs, the findings suggest that such programs might help children develop long-lasting healthy habits.

    This research comes at a time when childhood obesity(肥胖) rates have been rising rapidly. More than one-third of adolescents in the United States were obese in 2012, according to the U. S.Centers for Disease Control and Prevention (CDC). This trend has been caused, at least in part, by a significant decrease in the amount of meals that people consume at home since the 1980s, according to background information in the study.

    Cooking education programs, such as Food Explorers, teach children about new healthy foods and how to prepare them. They also stress the importance of eating five fruits and vegetables every day. A volunteer parent explains a new food to the group, and the kids make something based on the lesson, such as fruit or vegetable salad. Depending on the program, kids may be sent home with information about healthy foods to bring to their parents, the review explained.

    The study team reviewed eight other studies that tested different types of cooking education programs. Children in these classes were between 5 and 12 years old, according to the review. The goal of the study team was to learn more about developing an efficient program to encourage healthy food choices that last a lifetime. The study found that it is particularly important to expose kids to healthy foods on a number of occasions. This makes them feel comfortable with the new foods, which helps them build healthy habits.

    The study stressed the importance of getting parents involved in(参与) their children's eating habits. Parents who are unable to enroll their kids in a cooking class can achieve similar benefits by having their kids help them while they prepare meals at home. Children are more comfortable at home, which makes them more receptive to new foods because they will make the connection to a positive experience.

    Scientists have created a scent(气味)-delivery system that releases a pleasant fragrance when you sweat. Apply it to your skin, and the more you sweat, the better you'll smell. That's because the perfume only gets released upon contact with moisture(湿气).

Chemists from Harvard University combined two compounds to create their new system. One chemical is alcohol-based. This is the nice-smelling perfume. The other chemical is an ionic liquid(离子性液体), which is a type of salt that is liquid at room temperature. Ionic liquids are made of ions—molecules(分子) that have lost or gained one or more electrons(电子). If the molecule loses electrons, it will have a positive charge(正电荷). If it gains electrons, it gets a negative charge. Ionic liquids contain the same number of positive and negative ions, which makes them neutral, with no overall electric charge. In general, ionic liquids have no smell.

    When the perfume and ionic liquid are mixed together, a chemical reaction occurs. This bonds the molecules to each other. The reaction also temporarily inactivates the perfume's molecules. So when applied to the skin, the new perfume has no scent in the beginning. But adding water or sweat breaks the bond between the molecules. That releases the scent into the air.

    "The rate of the release of the fragrance depends on how much you sweat, in other words, how much water is available," explains chemist Nimal Gunaratne from Harvard University, who led the research. "Sweat is like the command to let the fragrance go."

    Christian Quellet is a chemist who has worked in the perfume industry for a long time. He is now an independent consultant based in Switzerland. "Gunaratne's perfume opens the door to new developments and applications of fragrance controlled-release systems," he says. Controlled-release systems allow small quantities of some compounds that they hold to enter the environment slowly.

    The system also traps some chemicals in sweat that are responsible for the bad sweat smell. These compounds are called thiols (硫醇). Just as water does, thiols break apart the bond that ties the perfume to the ionic liquid. When this happens, the thiols attach to the ionic liquid and their bad scent is inactivated as the perfume had been. This means the water in sweat and its thiols are both able to release the fragrance from the newly developed perfume.