While sweet treats can be hard to resist, the World Health Organization(WHO) has set new guidelines for people around the world. The guidelines, released on Wednesday, advise that both adults and children cut back on their sugar intake(摄取量) to stay healthy.

    In a statement, Francesco Branca, director of the WHO's nutrition department, said there is evidence that reducing daily sugar intake reduces the risk of being overweight and tooth decay(腐烂).

    The guidelines do not apply to the sugars in fresh fruit and vegetables or those that are naturally present in milk. According to the WHO, there is no reported evidence of negative effects of consuming those sugars. Instead, the new guidelines focus on “added” or “free” sugars. These include sugars that are added to processed foods and drinks such as candy and soft drinks.

    Added sugars are sometimes described as “ hidden” sugars because they exist in foods we might not think of as sweets, such as honey and ketchup(番茄酱). Health experts advise that consumers look at ingredients on food packages to help make better-informed decisions.

    The WHO recommends that people in the United States, Europe and other Western societies should cut their average sugar intake by about two-thirds, or down to just 10% of their overall calories. For developing countries, where dental care is less advanced, the WHO recommends that sugar intake be reduced to 5%.

    Scientist Kieran Clarke, of the University of Oxford, notes that for those people who can't shake their love for sweets, getting more exercise is a good solution. “If you get enough exercise, you can eat almost anything,” she said “But it's very hard to avoid large amounts of sugar unless all you're eating is fruit and vegetables.”

    Social change is more likely to occur in societies where there is a mixture of different kinds of people than in societies where people are similar in many ways. The simple reason for this is that there are more different ways of looking at things present in the first kind of society. There are more ideas, more disagreements in interest, and more groups and organizations with different beliefs. In addition, there is usually a greater worldly interest and greater tolerance in mixed societies. All these factors tend to promote social change by opening more areas of life to decision. In a society where people are quite similar in many ways, there are fewer occasions for people to see the need or the opportunity for change because everything seems to be the same. And although conditions may not be satisfactory, they are at least conventional and generally agreed.

    Within a society, social change is also likely to occur more frequently and more readily in the material aspects of the culture than in the non-material, for example, in technology rather than in values; in what has been learned later in life rather than what was learned early; in the less basic and less emotional aspects of society-than in their opposites; in the simple elements rather than in the complex ones; in form rather than in substance; and in elements that are acceptable to the culture rather than in strange elements.

    Furthermore, social change is easier if it is gradual. This is one reason why change has not come more quickly to Black Americans as compared to other American minorities, because of the sharp difference in appearance between them and white people.

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    When friends come to visit us in the evening, they spend their time telling us that they are in a hurry and looking at their watches. It isn't that our friends are all very busy. It is just that we haven't got a TV set. People think that we are very strange. “But what do you do in the evenings?” they are always asking. The answer is simple. Both my wife and I have hobbies. We certainly don't spend our evenings staring at（盯着）the walls. My wife enjoys cooking and painting and often attends evening classes in foreign languages. This is particularly useful as we always go abroad for our holidays. I collect stamps and I am always busy with my collection. Both of us enjoy listening to music and playing chess together.

Sometimes there are power cuts and we have no electricity in the house. This does not worry us. We just light candles and carry on with what we were doing before. Our friends are lost —no televisions! So they don't know what to do. On such evenings our house is very full as they all come to us. They all have a good time. Instead of sitting in silence in front of the television, everybody talks and plays games. Yes, life is possible without television!

    There are two main things that make aircraft engineering difficult: the need to make every component as reliable as possible and the need to build everything as light as possible. The fact that an airplane is up in the air and can't stop if anything goes wrong, makes it perhaps a matter of life or death that its performance is completely dependable.

    Given a certain power of engine, and consequently a certain fuel consumption, there is a practical limit to the total weight of aircraft that can be made to fly. Out of that weight as much as possible is wanted for fuel, radio navigational instruments, passenger seats, or freight room, and of course, the passengers or freight themselves. So the structure of the aircraft has to be as small and light as safety and efficiency will allow. The designer must calculate the normal load that each part will bear. This specialist is called the "stress man." He takes notice of any unusual stress that may be put on the part as a precaution against errors in manufacture, accidental damage etc.

    The stress man's calculations go to the designer of the part, and he must make it as strong as the stress man says is necessary. One or two small parts are always tested to prove that they are as strong as the designer intended. Each separate part is tested, then a whole assembly—for example, a complete wing, and finally the whole aeroplane. When a new type of aeroplane is being made, normally only one of the first three made will be flown. Two will be destroyed on the ground in strict tests. The third one will be tested in the air.

    When a plane has passed all the tests it can get a government certificate of airworthiness, without which it is illegal to fly, except for test flying.

    Making the working parts reliable is as difficult as making the structure strong enough. The flying controls, the electronic equipment, the fire precautions, etc. must not only be light in weight, but must work both at high altitudes where the temperature may be below freezing point and in the hot air of an airfield in the tropics.

    To solve all these problems the aircraft industry has a large number of research workers, with elaborate laboratories and test houses, and new materials to give the best strength in relation to weight are constantly being tested.

    There is an old saying that America and Britain are "two nations divided by a common language." No one knows exactly who said this, but it reflects the way many Brits feel about American English. But are American and British English really so different?

    Vocabulary

    The most obvious difference between American and British English is vocabulary. There are hundreds of everyday words that are different. For example, Americans go on vacation while Brits go on holidays; New Yorkers live in apartments while Londoners live in flats. There are far more examples than we can talk about here. Fortunately, most Americans and Brits can usually guess the meaning through the context of a sentence.

    Past Tense Verbs

    You'll also find some differences with past forms of irregular verbs. The past tense of "learn" in American English is "learned". British English has the option of "learned" or "learnt". The same rule applies to "dreamed" and "dreamt", "burned" and "burnt", and "leaned" and "leant". Americans tend to use the -ed ending; Brits tend to use the-t ending.

    Spelling

    There are hundreds of slight spelling differences between British and American English. Noah Webster, an author, politician and teacher, made an effort to reform English spelling in the late 1700s.

    Webster wanted to spell words the way they sounded. You can see Webster's legacy(遗产) in the American spelling of words like color (from colour), honor (from honour), and labor(from labour).

    Not So Different After All

    British and American English have far more similarities than differences. With the exception of some regional dialects, most Brits and Americans can understand each other without too much difficulty. They watch each other's TV shows, sing each other's songs and read each other's books. They even make fun of each others' accents.

    Microsoft announced this week that its facial-recognition system is now more accurate in identifying people of color, touting (吹嘘)its progress at tackling one of the technology's biggest biases (偏见).

    But critics, citing Microsoft's work with Immigration and Customs Enforcement, quickly seized on how that improved technology might be used. The agency contracts with Microsoft for cloud-computing tools that the tech giant says is largely limited to office work but can also include face recognition.

    Columbia University professor Alondra Nelson tweeted, "We must stop confusing 'inclusion' in more 'diverse' surveillance (监管)systems with justice and equality."

    Facial-recognition systems more often misidentify people of color because of a long-running data problem: The massive sets of facial images they train on skew heavily toward white men. A Massachusetts Institute of Technology study this year of the face-recognition systems designed by Microsoft, IBM and the China-based Face++ found that facial-recognition systems consistently giving the wrong gender for famous women of color including Oprah Winfrey, Serena Williams, Michelle Obama and Shirley Chisholm, the first black female member of Congress.

    The companies have responded in recent months by pouring many more photos into the mix, hoping to train the systems to better tell the differences among more than just white faces. IBM said Wednesday it used 1 million facial images, taken from the photo-sharing site Flickr, to build the "world's largest facial data-set" which it will release publicly for other companies to use.

    IBM and Microsoft say that allowed its systems to recognize gender and skin tone with much more precision. Microsoft said its improved system reduced the error rates for darker-skinned men and women by "up to 20 times," and reduced error rates for all women by nine times.

    Those improvements were heralded(宣布)by some for taking aim at the prejudices in a rapidly spreading technology, including potentially reducing the kinds of false positives that could lead police officers misidentify a criminal suspect.

    But others suggested that the technology's increasing accuracy could also make it more marketable. The system should be accurate, "but that's just the beginning, not the end, of their ethical obligation," said David Robinson, managing director of the think tank Upturn.

    At the center of that debate is Microsoft, whose multimillion-dollar contracts with ICE came under fire amid the agency's separation of migrant parents and children at the Mexican border.

    In an open letter to Microsoft chief executive Satya Nadella urging the company to cancel that contract, Microsoft workers pointed to a company blog post in January that said Azure Government would help ICE "accelerate recognition and identification." "We believe that Microsoft must take an ethical stand, and put children and families above profits," the letter said.

    A Microsoft spokesman, pointing to a statement last week from Nadella, said the company's "current cloud engagement" with ICE supports relatively anodyne(温和的)office work such as "mail, calendar, massaging and document management workloads." The company said in a statement that its facial-recognition improvements are "part of our going work to address the industry-wide and societal issues on bias."

    Criticism of face recognition will probably expand as the technology finds its way into more arenas, including airports, stores and schools. The Orlando police department said this week that it would not renew its use of Amazon. com's Rekognition system.

    Companies "have to acknowledge their moral involvement in the downstream use of their technology,"

    Robinson said. "The impulse is that they're going to put a product out there and wash their hands of the consequences. That's unacceptable."