New research has found that even if you give up smoking,the damage it has done to your genes（基因）will stay there for a much longer time.

    In the research,a team of US scientists studied the blood of 16,000 people.Among them,some were smokers,some used to smoke,and the rest were non-smokers.Scientists compared their genes and found that more than 7,000 genes of smokers had changed-a number that is one-third of known human genes.

    According to NBC News,both heart disease and cancer are caused by genetic changes.Some people may have had the changes when they were born,but most people get them in their day-to-day lives while doing things like  smoking.

When you stop smoking,a lot of these genes will return to normal within five years.This means your body is trying to heal（治愈）itself of the harmful effects of smoking.But the changes in some of the genes stay for longer.They can stay for as long as 30 years.It's almost like leaving a footprint on wet cement（水泥）一it will always be there, even when you've walked away and when the cement becomes dry.

    Although the study results may make people unhappy,there is a bright side: the findings could help scientists invent medicine to treat genetic damage caused by smoking or find ways to tell which people have heart disease or cancer ricks.

    Let children learn to judge their own. A child who learns to talk does not learn by being corrected all the time; if corrected too much, he will stop talking. He notices a thousand times a day the difference between the language he uses and the language those around him use. Little by little, he makes the necessary changes to make his language like other people's, in the same way, children learn to do all the other things without being taught—to walk, run, climb, ride a bicycle—compare their own performances with those of more skilled people, and slowly make the needed changes. But in school we never give a child a chance to find out his mistakes if we thought that he would never notice a mistake unless it was pointed out to him, or correct it unless he was made to. Let him work out, with the help of other children if he wants it, what this word says, what the answer is to that problem, whether this is a good way of saying or doing this or not. If it is a matter of right answers, as it may be in mathematics or science, give him the answer book. Let him correct his own papers. Why should our teachers waste time in doing such work? Our job should be to help the child when he tells us that he can't find the way to get their own understanding, how to know what they know or do not know.

    Everyone can try his best to achieve something. We don't need to be the best, but to challenge the limits of what we are capable of. I gained this belief from my third grade teacher, the most special, honored, trustworthy, and beloved person in my life.

    Mr. Myrus was always perfectly dressed and spoke with the belief that talking to an eight－year－old child didn't mean he had to sacrifice proper statements or grammar. And he was demanding, but he wasn't unreasonable or cruel. He simply felt that no matter what your best was, you should achieve it.

    Luckily enough, I met him again as my eighth grade math teacher. I was not, nor ever will be, gifted in math. I remember my struggles in class. “I don't know the answer,” I would say. "I can't do it!" “Perhaps you don't know the answer,” he would say quietly. “Do you think we might figure it out together? How do you know what you can do if you don't have a try？”

    Mr. Myrus lived around the corner, and I would often stop by to talk while he worked in his garden. I knew there was someone who let me know that if I had really tried, that was enough. “Don't be so hard on yourself,”he'd say.“ Stop blaming yourself. Did you try your best? Well, then you're not a failure,” he often told me these words.

    Mr. Myrus died in 1978. I had never thought about his death. He was too young. I felt sorry. But when I think about him now, I don't feel so sorry. He taught me to be kind, not only to others, but to myself. He taught me my own value. He taught me about honor, about truth, and about doing my best and he also taught me that all feelings and beliefs have dignity and deserve respect. And of all the things I know, I believe that we can't all be “the best”, but we can, each of us, be our best. And I know that's true because Mr. Myrus told me that.

    The first organized system for sending messages began in Egypt around 1500 B.C. This system developed because the pharaohs frequently needed to send messages up and down the Nile River in order to keep their empire running smoothly. Later, the Persians developed a more efficient system for sending messages using men and horses. Messages carriers rode along the road system stretching from one end of the Persian Empire to the other. Along these roads, fresh men and horses waited at special stations to take and pass along any messages that needed to be sent. The stations where riders passed messages back and forth were built 23 kilometers apart, so the men and horses were able to travel quickly between them. The Romans later took up his idea and improved it by using a more advanced and extensive road system.

    In China, however, Kublai Khan had built up his own system for delivering messages. This system worked in the same basic way as the Roman system. The difference was that Kublai Khan kept 300,000 horses along the roads of this delivery lines. There were over 10,000 stations where a message would be passed from one rider to another with a fresh horse. In this way, Kublai Khan could receive messages from anywhere in the country in only a few days.

    It was not until the 1500s that a well-organized postal system appeared again in Europe. One family, the von Taxis family, gained the right to deliver mail for the Holy Roman Empire and parts of Spain. This family continued to carry mail, both government and private, throughout Europe for almost 300 years.

    In 1653, a Frenchman, Renouard de Velayer, established a system for delivering post in Paris. Postal charges at that time were paid by the recipient, but de Velayer's system was unique by allowing the sender to pre-pay the charges, in a similar way to the modern stamp. Unfortunately, de Velayer's system came to an end when jealous competitors put live mice in his letter boxes, ruining his business. Eventually, government-controlled postal systems took over from private postal businesses, and by the 1700s government ownership of most postal systems in Europe was an accepted fact of life.

    The thing that all these early systems had in common was that they were quite expensive for public use, and were intended for use by the government and the wealthy. However, in 1840, a British schoolteacher named Roland Hill suggested introducing postage stamps, and a postal rate based on weight. This resulted in lowering postal rates, encouraging more people to use the system to stay in touch with each other, His idea helped the British postal system begin to earn profits as early as 1850. Soon after that many other countries took up Mr. Hill's idea. And letter writing became accessible to anyone who could write. Today, the Roland Hill awards are given each year to "encourage and reward fresh ideas which help promote philately"(stamp collecting).

    Donna Strickland is a professor in the Department of Physics and Astronomy. Professor Strickland is one of the recipients(受领者) of the Nobel Prize in Physics 2018 with Gérard Mourou, her PhD supervisor at the time. They published this Nobel-winning research in 1985 when Strickland was a PhD student at the University of Rochester in New York state. Together they paved the way toward the most intense laser pulses ever created.

    Professor Donna Strickland is only the third woman ever to have won a Nobel Prize in physics. She and her fellow winners were honored for what the Nobel Committee called ground-breaking inventions in laser physics. Professor Strickland devised a way to use lasers as very precise drilling or cutting tools. Millions of eye operations are performed every year with these sharpest of laser beams.

    "How surprising do you think it is that you're the third woman to win this prize?"

"Well, that is surprising, isn't it? I think that's the story of Maria that people want to talk about — that why should it take 60 years? There are so many women out there doing fantastic research, so why does it take so long to get recognized?"

    Physics still has one of the largest gender gaps in science. One recent study concluded that at the current rates it would be more than two centuries until there were equal numbers of senior male and female researchers in the field.

    The last woman to win a physics Nobel was German-born Maria Goeppert-Mayer for her discoveries about the nuclei of atoms. Before that it was Marie Curie, who shared the 1903 prize with her husband, Pierre. This year's winners hope that breaking this half century hiatus will mean the focus in future will be on the research, rather than the gender of the researcher.

    History is full of tales of great ideas taking shape in sleeping minds; Paul McCartney said that he awoke with the tune of Yesterday in his head, and Robert Louis Stevenson said that the idea for The Strange Case of Dr Jekyll and Mr Hyde came to him in a dream.

    Scientists believe that the mind at night puts together bits of information in creative ways. Throughout the day your brain rarely gets a chance to stop and think. It constantly responds to a stream of challenges, from writing a report for a work deadline to remembering where you left your car keys and figuring out what to buy for dinner.

    "Think of your brain like a web," says Russell Foster, Professor of Neuroscience at Oxford University. "During the day the web is very tight, so you can only put information in a certain number of places. During sleep the web expands, and with the luxury of time, those bits of information can be put into lots of different places and make new associations."

    He adds that this process may help to foster the formation of new ideas. "This bringing together of seemingly unrelated bits of information is vital to helping the brain think itself out of problems," says Russell Foster.

    "Sleep seems to allow your mind to make non-obvious connections. It puts all the information from the day into a big biological theatre and forces the mind to speak to people at the back of the theatre, who you may not think you have any connection with. This is the basis of creativity connecting ideas, events and memories that wouldn't normally fit together.

    By placing volunteers into brain scanners and sending them to sleep, scientists have seen that the areas associated with emotion go into overdrive, especially while dreaming, while the areas that are responsible for logic (逻辑)are switched off. This not only explains why dreams are unbelievably random-you can be talking to a colleague one minute and the next minute sitting in your old school classroom dressed in your nightclothes­but also explains how the brain can put together different information.