Crown shyness (树冠羞避) is a mysterious natural phenomenon in which the crowns of some tree species do not touch each other, but get separated by a gap clearly seen from ground level. The effect usually occurs between trees of the same species, but has also been observed between trees of different species.

    There are many theories going around, most of which make sense, but no one has been able to prove without the shadow of a doubt why some trees avoid touching each other.

    In his 1955 book Growth Habits of the Eucalypts, Australian forester M. R. Jacobs writes that the growing tips of the trees are sensitive to abrasion (擦伤), which results in crown shyness phenomenon. This theory was also supported by Dr. Miguel Franco. Some experiments have shown that if trees displaying crown shyness are artificially prevented from swaying (摇摆)in the wind and touching each other, they gradually fill up the gaps between them.

    But while the above theory is arguably the most widespread, it's certainly not the only one. Some scientists have suggested that crown shyness is a mechanism to stop the spreading of leaf-eating insects. The gaps mean pests wouldn't be able to reach other trees, so they are the tree's natural defense method.

    One Malaysian scholar studied many trees, but found no traces of abrasions, despite their clear crown shyness. Instead, he suggests that the growing tips of the trees were sensitive to light levels and stopped growing when they got too close to other trees. Plants are able to sense how close they are to other plants and in order to get more light, they give off some chemical to stop other trees from growing too close.

    Whatever the reason, one thing is for sure, plants are more intelligent than people.

    I am sorry that I haven't written this letter before now. It has taken me three years to gather the courage. I have started it so many times in my head, but was afraid that you would think it disrespectful of me to write to you. It does seem strange writing to someone I have never met, but part of me feels that I know you very, very well.

    We read your file one morning in September. We knew the contents would be difficult. Later that afternoon, we received the call from our social worker to tell us that you had passed away. Suddenly, we knew what we had to do.

    There was never any doubt. All I remember was a desire to protect this little boy, to give him the love and care he deserved. And really that was that; as far as we were concerned, David was now our son. There were further meetings, questions, paperwork, decisions, arrangements and preparations. Then, two months later, we met him for the first time. I hope the fact that I call him “our son” does not offend you. Sarah, you will always be his birth mother. But I make no apology in referring to him as our son.

    For the past three years, we have loved and cared for David. We have dealt with his anger, his confusion and his anxieties. David was taken away from you soon after his second birthday. I cannot imagine the pain that must have caused you. We know that you really wanted to be a good mother to David, but you could not cope when his father left.

    It is tragic that your life ended so early. I don't know how I will explain all these things to David as he grows up, or how he will explain his story and what happened to him during his early years. I hope that it does not cast a shadow over his life as his understanding deepens. I hope you can find comfort in the fact that, from all this pain, Sarah, you have given us the most wonderful gift – an amazing little boy who is completely fearless.

    It is so unfair that you did not receive the love and the warmth in your childhood that David now takes for granted. And although you never chose to hand your beautiful baby over, I can only feel gratitude towards you for this wonderful little boy who has made our lives complete.

    A month before my first marathon, one of my ankles was injured and this meant not running for two weeks, leaving me only two weeks to train. Yet, I was determined to go ahead.

    I remember back to my 7th year in school. In my first P.E. class, the teacher required us to run laps and then hit a softball. I didn't do either well. He later informed me that I was "not athletic".

    The idea that I was "not athletic" stuck with me for years. When I started running in my 30s, I realized running was a battle against myself, not about competition or whether or not I was athletic. It was all about the battle against my own body and mind. A test of wills!

    The night before my marathon, I dreamt that I couldn't even find the finish line. I woke up sweating and nervous, but ready to prove something to myself.

    Shortly after crossing the start line, my shoe laces(鞋带) became untied. So I stopped to readjust. Not the start I wanted!

    At mile 3, I passed a sign: "GO FOR IT, RUNNERS!"

    By mile 17, I became out of breath and the once injured ankle hurt badly. Despite the pain, I stayed the course walking a bit and then running again.

    By mile 21, I was starving!

    As I approached mile 23, I could see my wife waving a sign. She is my biggest fan. She never minded the alarm clock sounding at 4 a.m. or questioned my expenses on running.

    I was one of the final runners to finish. But I finished! And I got a medal. In fact, I got the same medal as the one that the guy who came in first place had.

    Determined to be myself, move forward, free of shame and worldly labels(世俗标签), I can now call myself a "marathon winner".

    Teenagers around the world can be happy with the news that the brain will ignore parents' order when they use their smart phones. A new scientific study from the University College London has shown that humans may temporarily go deaf when they're focusing on something visual (视觉的) at the same time.

    The researchers played the normal-volume sounds in the background. And 13 volunteers experienced inattentional deafness as their visual tasks became increasingly difficult. "We found that when volunteers were performing the difficult visual task, they were unable to hear sounds that they would normally hear," Maria Chait said in a statement. "The brain scans showed that people didn't filter out the sounds on purpose. They were not actually hearing them in the first place."

    The findings, published in the Journal of Neuroscience, suggest that the centre of sights and the center of sounds share limited resources. Inattentional deafness is a common everyday experience and the study explains why, according to UCL Institute of Cognitive Neuroscience Professor Nili Lavie.

    If you try to talk to someone focusing on a book, game, or television program and don't receive a response, they aren't necessarily ignoring you. They simply might not hear you at all. This could also explain why you might not hear your bus or train stop being announced if you're lost in your phone, book or newspaper. However, some loud sounds will still be able to break through.

    Some situations could become possibly dangerous when the quieter ones go unheard. As you can imagine, in the operating room, when a doctor concentrates on his work, he might not hear the equipment beeping. It also applies to drivers who center on complex directions. Fortunately, experts have given us some useful tips on preventing such situations.

    Have you ever complained, "I remember reading it, but I can't remember what it said? " then you should try the SQ4R reading method.

    S = Survey. The first step is to take a few minutes skimming the chapter. Don't read it yet, just look at topic headings, key words, and read the summary.

    Q = Question. As you prepare to read the chapter, turn the first topic into a question or two. As you read, seach for the answer. This will help you organize your reading-find the parts that answer your question, give an example, consist of related information or that may answer a later question. Most importantly, this gives you a reason to read the next paragraph.

    R = Read. Read in short "bites" (部分), then determine how that answers question(s) you originally posed (提出). Often as you read other questions will arise.

    R = Recite. Now can you answer your question(s) in your own words? If you can't, reread the material to find the answers or determine if you need to change the question. You are rehearsing (重复，默诵) for the time when you will need o know the answer. A good technique for rehearsing answers is to briefly jot down (草草记下) the key words that remind you of the essence of the answer without writing down every detail.

    R = Relate. Most of us try to relate what we are reading to what we already know. It is always easier and more satisfying to remember information that is personally meaningful. Everything has a context. Some information may take more reflection before you are able to grasp its relationship with what you already know while other information may simply require more research, to understand how it fits with other data.

    R = Review. One way to minimize memory decay (衰退) and to store the material you have studied firmly in your mind is by reviewing it. After you finish reading the entire chapter, skim back over it and any note you made.

    Effective studying requires effective reading. Rather than getting "intellectual indigestion" while reading straight through a chapter, instead you should stop to survey, question, read, recite, relate, and review so as to improve your reading comprehension.

    Like any new ninth-grader on the first day of school, Joemar Class had ninth-grader- emotion (情绪). He's not used to school in Hartford. He's used to going to school in his home town of Florida, used to seeing his friends, used to having class in Spanish.

    "Nervioso," he said in Spanish.

    We first met Joemar in mid-October in the San Juan Airport. His father, Guillermo Class, had sold his car to buy plane tickets to get his kids and fly them up from Puerto Rico. The island was almost destroyed (毁坏) by the deadly storm—Hurricane Maria.

    Now, they are settling into their new home in Hartford's South End. A week later, and, using his wife's car, Class drove 16-year-old Joemar to his first day at Bulkeley High School. After a short ride, he got out in front of his new school. Inside, he met Gretchen Levitz—the school's program director.

    "I see you have new uniform (校服)," Levitz said. "You look great. Are you ready for a good first day?"

    Then he met couple of teachers.

     "Hello," they each said in Spanish. They asked where he's from, and told him they were happy to see him. Then Levitz took him on a quick tour of the school before classes began—to her office the school store, the library, and the dining hall.

    A total of 19 languages are spoken in Bulkeley High School. "We have so many new students coming here from other countries every single day," Levitz said. "So it's not like he's the only one who has that feeling."

    "You could tell he's little worried," Guillermo said as we left." But, at the same time, he's looking forward to it."