Eating too much fatty food, exercising too little and smoking can raise your future risk of heart disease．But there is another factor that can cause your heart problems more immediately: the air you breathe.

    Previous studies have linked high exposure (暴露）to environmental pollution to an increased risk of heart problem, but two analyses(分析) now show that poor air quality can lead to heart attack or stroke (中风）within as little as a few hours after exposure．In one review of the research, scientists found that people exposed to high levels of pollutants (污染物）were up to 5% more likely（可能的） to suffer a heart attack within days of exposure than those with lower exposure．A separate study of stroke patients showed that even air that the U．S．Environmental Protection Agency (EPA) considers to be of “moderate” (良好）quality and relatively safe for our health can raise the risk of stroke as much as 34% within 12 to 14 hours of exposure.

    The authors of both studies stress（强调）that these risks are relatively（相对的）small for healthy people and certainly modest compared with other risk factors such as smoking and high blood pressure．However, it is important to be aware of these dangers because everyone is exposed to air pollution regardless of lifestyle choices．So stricter regulation（规章制度）by the EPA of pollutants may not only improve environmental air quality but could also become necessary to protect public health.

    If you make a list of the world's top ten most challenging jobs,chances are that being a teacher will not make the cut.But think about the discouraging task millions of educators face each day as they try to shape a group of often bad-tempered,wild kids into intelligent,well-rounder individuals.That surely has to be the toughest job in the world, especially given that there is no promotion or bonus awaiting them even if they are wildly successful!

    What if there all-important individuals that we often take for granted（想当然）disappear from our lives?That was what Project Ed and Participant Media's Teach campaign asked filmmakers of all ages to imagine in their recently-held competition.Entitled "A World Without Teachers",its purpose was to inspire more young people to become teachers.However,the 62 amazing video submissions also serve as a reminder of how horrible things would be if we didn't have these selfless individuals guiding us through life.What was interesting is that even the youngest participants did not appear to be happy at the idea of not having anybody telling them what to do.

    High-school student Savannah Wakefield reflected if art as we know it today would have been different without teachers.Would Monet have discovered his talent for impressionism?Los Angeles-based Miles Horst,who won the 1000 USD prize for the best adult submission imagines a world where teachers are replaced by a “brain box” in his fun lively entry.

    Youth category winner Marina Barham's video represents a fact we all know but often forget.Teachers don't just teach,they inspire something that no electronic device,no matter how smart,can do!So the next time you think your teacher is being "mean" for trying to channel you in the right direction,imagine a life without him/her.We have a feeling it will not appear as rosy!

    When Nancy Flexer opened the door to her classroom near the end of her final school year, all 41 years of her career as a beloved first-grade teacher came to life right in front of her.

    Cole Elementary School in Tennessee surprised Flexer with a memorable and emotional retirement party featuring former students of all ages, dating back to the first class she taught in the 1973-74 school year. A video of the event shows an overwhelmed Flexer being moved to tears as she hears former students who are now adults tell her how much she affected their lives.

    "I'm one of the luckiest people in this world," Flexer said. "I remember I opened the door to the classroom thinking no one was in there, and it was wall-to-wall people and banners and everything. It was the coolest thing that could've ever happened in my life. How many times do we really realize the lives we've touched, the manner in which we've touched them, and that these are memories that stay with them for life?"

    Despite being young when they were taught by Flexer, students easily recalled the heartwarming notes she wrote them on report cards, the ways she helped them overcome shyness and awkwardness, and how she inspired them to future academic success to earn scholarships and advanced degrees.

Even though Flexer hadn't seen some of the former students for decades, she instantly remembered the names of every single one there.

    A scrapbook(剪贴簿) of her career was presented to her as one student after another recalled the effect Flexer had on his or her life.

    “I've had many opportunities to move to a school closer to my home, but I said 'Cole gave me so much in my life that when I retire, I will retire from Cole school and give back what's been given to me.” Flexer said. “My career could've taken me nowhere that would have made me happier. I think of it as a blessing.”

    Last April, on a Sunday, we took one of our “nowhere” drives. My husband was quietly driving along a back road. I was occupied in the front passenger seat watching the scenery.

    I noticed out of the corner of my eye that my husband was struggling to look out of my window. This frightened me, since his eyes should be on the road in front of him. I asked him what he was looking at out of the windows, and he quietly replied, “Nothing.”

    After a few minutes, I looked over at my husband and noticed a tear running down his cheek. I asked him what was wrong. This time he told me, “I was just thinking about Pop and a story he had once told.” It had something to do with Pop, his friend from childhood, and I wanted to know the story, so I asked him to share it with me.

    He said, “When I was about 8 years old, Pop and I were out fishing and he told me that the pine trees know when it is Easter.”

    I had no idea what he meant by that, so I pressed him for more information.

    He continued on… “The pine trees start their new growth in the weeks before Easter because spring is drawing near. If you look at the tops of the pine trees, you will see the yellow shoots(嫩芽). As the days get closer to Easter Sunday, the tallest shoot will branch off and form a cross. By the time Easter Sunday comes around, you will see that most of the pine trees will have small yellow crosses on all of the tallest shoots.”

    I turned to look out of the window and I couldn't believe my eyes. It was a week before Easter, and you could see all of the trees with the tall yellow shoots stretching to the sky.

    The tallest ones shone in the sunlight like rows of tiny golden crosses. May you find your Easter season filled with beautiful golden crosses!

    In the early decades of the United States, the agrarian(土地的) movement promoted the farmer as society's hero. In the minds of agrarian thinkers and writers, the farmer was a person on whose well-being the health of the new country depended. The period between the Revolution, which ended in 1783, and the Civil War, which ended in 1865, was the age of the farmer in the United States. Agrarian philosophers, represented most eloquently by Thomas Jefferson, celebrated farmers extravagantly for their supposed centrality in a good society, their political virtue, and their Superior morality. And virtually all policy makers, whether they subscribed to the tenets of the philosophy held by Jefferson or not, recognized agriculture as the key component of the American economy. Consequently, government at all levels worked to encourage farmers as a social group and agriculture as economic enterprise.

    Both the national and state governments developed transportation infrastructure, building canals, roads, bridges, and railroads, deepening harbors, and removing obstructions from navigable streams. The national government imported plant and animal varieties and launched exploring expeditions into prospective farmlands in the West. In addition, government trade policies facilitated the exporting of agricultural products.

    For their part, farmers seemed to meet the social expectations agrarian philosophers had for them, as their broader horizons and greater self-respect, both products of the Revolution, were reflected to some degree in their behavior. Farmers seemed to become more scientific, joining agricultural societies and reading the farm newspapers that sprang up throughout the country. They began using improved implements, tried new crops and pure animal breeds, and became more receptive to modern theories of soil improvement.

    They also responded to inducements by national and state governments. Farmers streamed to the West, filling frontier lands with stunning rapidity. But farmers responded less to the expectations of agrarians and government inducements than to growing market opportunities. European demand for food from the United States seemed insatiable. War, industrialization, and urbanization all kept demand high in Europe. United States cities and industries grew as well; even industries not directly related to farming thrived because of the market, money, and labor that agriculture provided.

    Scientists at the University of Oxford have developed new artificial intelligence(AI) software to recognize and follow up the faces of chimpanzees(黑猩猩)in the wild. The new software will allow researchers and wildlife conservationists to significantly cut back on time spent analyzing videos, according to the new paper published in Science Advances.

    For species(物种)like chimpanzees which have complex social lives and live for many years, getting photos of their behavior taken from short-term field research can only tell us so much," says Dan Schofield, researcher and DPhil student at Oxford University's Private Models Lab, School of Anthropology. "By taking advantage of the power of machine learning to unlock large video files, it makes it possible to measure behavior over the long term."

    The computer model was trained using over 10 million images(影像):from Kyoto University s Primate Research Institute(PRI) video files of wild chimpanzees in Guinea, West Africa. The new software is the first to continuously track and recognize individual a wide range of poses, performing with high accuracy in difficult conditions such as low lighting and poor image quality.

    "Access to this large video file has allowed us to use deep neural networks to train models to a degree that was previously not possible," says Arsha Nagrad, co-auther of the study and DPhil student at the Department of Engineer Science, University of Oxford." Additionally, our new software differs from previous primate face recognition software in that it can be applied to videos with limited manual intervention(人工干预), saving hours of time."

    The technology can be potentially used to monitor species for conservation Although the present application focuses on chimpanzees, the AI software provided will be applied to other species, and help drive the adoption of AI systems to solve(解决)a range of problems in the wildlife sciences.