2 . Language as a System of Symbols (符号)

Of all systems of symbols, language is the most highly developed. It has been pointed out that human beings, by agreement, can make anything stand for anything. Human beings have agreed, in the course of centuries of mutual dependency, to let the various noises that they can produce with their lungs, throats, tongues, teeth, and lips systematically stand for certain happenings in their nervous systems. We call that system of agreements language.

There is no necessary connection between the symbol and that which it stands for. Just as social positions can be symbolized by feathers worn on the head, by gold on the watch chain, or by a thousand other things according to the culture we live in, so the fact of being hungry can be symbolized by a thousand different noises according to the culture we live in.

However obvious these facts may appear at first glance, they are actually not so obvious as they seem except when we take special pains to think about the subject. Symbols and the things they stand for are independent of each other, yet we all have a way of feeling as if, and sometimes acting as if, there were necessary connections. For example, there are people who feel that foreign languages are unreasonable by nature; foreigners have such funny names for things, and why can’t they call things by their right names? This feeling exhibits itself most strongly in those English and American tourists who seem to believe that they can make the natives of any country understand English if they shout loud enough. Like the little boy who is reported to have said, “Pigs are called pigs because they are such dirty animals, ” they feel that the symbol is inherently connected in some way with the things symbolized.

4 . Albert Einstein’s 1915 masterpiece “The Foundation of the General Theory of Relativity” is the first and still the best introduction to the subject, and I recommend it as such to students. But it probably wouldn’t be publishable in a scientific journal today.

Why not? After all, it would pass with flying colours the tests of correctness and significance. And while popular belief holds that the paper was incomprehensible to its first readers, in fact many papers in theoretical physics are much more difficult.

As the physicist Richard Feynman wrote, “There was a time when the newspapers said that only 12 men understood the theory of relativity. I do believe there might have been a time when only one man did, because he was the only guy who caught on, before he wrote his paper. But after people read the paper a lot understood the theory of relativity in some way or other, certainly more than 12.”

No, the problem is its style. It starts with a leisurely philosophical discussion of space and time and then continues with an exposition of known mathematics. Those two sections, which would be considered extraneous today, take up half the paper. Worse, there are zero citations of previous scientists’ work, nor are there any graphics. Those features might make a paper not even get past the first editors.

A similar process of professionalization has transformed other parts of the scientific landscape. Requests for research time at major observatories or national laboratories are more rigidly structured. And anything involving work with human subjects, or putting instruments in space, involves piles of paperwork.

We see it also in the Regeneron Science Talent Search, the Nobel Prize of high school science competitions. In the early decades of its 78-year history, the winning projects were usually the sort of clever but naive, amateurish efforts one might expect of talented beginners working on their own. Today, polished work coming out of internships(实习) at established laboratories is the norm.

These professionalizing tendencies are a natural consequence of the explosive growth of modern science. Standardization and system make it easier to manage the rapid flow of papers, applications and people. But there are serious downsides. A lot of unproductive effort goes into jumping through bureaucratic hoops(繁文缛节), and outsiders face entry barriers at every turn.

Of course, Einstein would have found his way to meeting modern standards and publishing his results. Its scientific core wouldn’t have changed, but the paper might not be the same taste to read.

5 . It is an honor for me to deliver this speech and on behalf of the graduating students, welcome you to this special ceremony 2020.

This is a unique moment. We are stepping up to another phase of our lives at a time of great hardship and global difficulties. Hope this ceremony will help erase sad memories, refresh beautiful ones and add more splendid memories into our lives.

I was born in the middle of war, which caused my family to move to Serbia for three years. When the war ended, we returned to Bosnia. My mother, who is and will ever be my heroine, was the only figure who guided me, provided for me and kept me on the right track, in the hope for a better life. I owed her so much as she is responsible for huge part of my success. I will always remember her teachings “to complain less and always find solutions at the price of whatever it takes” ， which brought me to China, an ancient land of new hopes.

During the COVID-19 outbreak, I got the best opportunity to understand China. I saw millions of people united with one goal-to win the battle against this epidemic. I have never seen such a collective dedication from a nation, turning things for the better by sacrificing personal convenience on a grand scale. China's governance and health care system proves to be one of the most efficient in the world. With a population of 1.4 billion, China not only has successfully controlled the transmission of the corona-virus but also assisted many other countries across the globe.

Everyone has a role to play in the battle against the virus. In Tsinghua, I played a tiny but necessary role: Staying on campus, studying online, cooperating during temperature checks and respecting social distancing measures. The rules set by the university and Chinese government had everyone's health and safety as first priority. This made me feel safe and confident that China was on the right track towards victory. Throughout this time, despite the immense challenges, Tsinghua has facilitated many online conferences, which helped me nurture more skills in my field of study.

Friends, we are now graduating from one of the world’s most prestigious universities. Tsinghua has been like a mother to us over the past months and years, guiding and nurturing us along the way, providing us with great vision and placing on us high expectations. So what comes next? Actions speak louder than words. Let us accept new challenges, think beyond our limits and keep in mind the ethics of life.

Let's undertake everything we can for the sake of unity, humanity and the international community. Let's work together for a more promising future and prosperous world.

6 . We all do it. We put off that dreaded task for five more minutes, then for thirty minutes, then for another hour, until it doesn’t get done at all. And the worst part is we still weren’t able to enjoy our day. We spend so much time stressing over that looming task that it deprives us from actually being able to focus on other tasks.

Why do we do it? We know it never ends well. The problem is that the cycle can feel nearly impossible to break. We get so caught up in the cycle of procrastination that we almost forget how to effectively tackle hard tasks.

Here are five tips for nipping procrastination in the bud and taking back control over your daily life.

Tackle the most difficult task first.

You’re probably thinking “Duh, I already knew that.” But you may not have realized that there’s scientific backing for this suggestion. We only have a limited supply of willpower. Once it’s been used up for the day, chances of us tackling hard tasks are pretty slim. Dive into your hardest task when your energy level is at its highest. This will ensure the best results.

When we push the hard tasks to the end of the day, it takes a toll on our energy all day long. In the end, stressing for hours over the task we’re procrastinating negatively affects all the other tasks on our list.

So next time you’re scheduling the items on your list, make sure to start out with worst one. It may not necessarily be the largest, but it should be the one you’re dreading the most. By accomplishing it so early in the day, you will feel energized and productive. You’ll know the rest of the day is all downhill and cruise through the list with remarkable speed.

Divide the task into smaller tasks.

We tend to get overwhelmed when a giant project looms ahead of us. We don’t know where to start or what to do first. Keep in mind that forests are made up of individual trees. Though you may not be able to take down a whole forest at once, you could certainly start with one tree (or even a branch).

If you need to organize your entire kitchen, start by working on just one cupboard. Organizing one cupboard is much more feasible than trying to get everything done in one swoop. Make a commitment to complete a small step each day, and you’ll find the task becoming less and less daunting with each new task that you accomplish.

Set a mid-day alarm.

There’s nothing more guilt-inducing than ending a day and realizing you haven’t accomplished a single task. We can avoid this rut by setting an alarm on our phone to ring every day around 1 p.m. When the ringer goes off, assess how many things on your list have been attended to.

Re-plan your schedule for the remainder of the afternoon and shift it around to take care of the most important item first. If necessary, you can indulge in a second cup of coffee to jumpstart your “second morning.” By doing this, you will avoid going to bed at night mulling over all the things you didn’t get done.

Dedicate yourself for a small period of time.

To stimulate productivity, there’s an old trick of setting a timer for ten minutes. By frantically racing the clock for that short period, you’ll likely find you become engrossed in your tasks and continue working.

The feeling of dread that has been on your mind will quickly be replaced with a sense of pride and satisfaction. Seeing what you can accomplish in ten minutes when you put your mind to it is quite motivating.

Schedule your tasks on the calendar.

Creating a game plan will help you move past the initial paralysis you feel. Instead of just writing the tasks down in a to-do list, take it a step further and identify when and how you’ll accomplish it.

For example, plan to go to the grocery store at 4:00 p.m. and start cooking dinner promptly at 4:30. By clearing up the anticipatory stress, you’ll avoid a large part of the dread that holds you back. Creating the plan is half the battle!

Though it feels impossible, you have it in you to accomplish everything that you need to every single day. With a fresh perspective, a little prodding (敦促), and a detailed plan, you’ll be well on your way to ending the procrastination cycle once and for all.

7 . I was given a voice. That’s what people said about me I trained my voice, because it would be a shame to waste such a gift. I pictured this voice as a greenhouse plant and made sure it was provided with the right temperature, the right amount of water. I relieved its fears. I told it not to tremble. I nursed it, I trained it, and I watched it climb up inside my neck

My voice bloomed. People said I had grown into my voice. Invitations to perform flooded over us. All the best places wanted us. I was sought after, or rather my voice was. We went everywhere together and gave performances. Bouquets （花束）were thrown to it. Money was presented to it. Men fell on their knees before it. Applause flew around it.

Then my voice began to shrivel. People said my voice would bloom only for a certain term: finally it would drop off and gone with it would be all the fame and wealth. I have noticed it so far. Fear has entered me since my voice has used up most of my life. I’ve given it all my love. But my voice is still as greedy as ever. It wants more: more and more, more of everything it has had so far.

Now it’s evening: the bright lights come on, and excitement quickens in the streets. We sit in this hotel room. Soon it will be time for us to go out. We have to attend a grand occasion. The two of us chained together as always. I have to put on its favourite dress, its favourite necklace and wind a fur around it. Then I have to go out: shining like ice: my voice attached to my throat like an invisible vampire （吸血鬼）.

8 . The brain has a powerful ability to remember and connect events separated in time. And now, in that new study in mice published in Neuron, scientists at Columbia’s Zuckerman Institute have cast light on how the brain can form lasting links.

The hippocampus-a small, seahorse-shaped region buried deep in the brain-is an important headquarters for learning and memory. Previous experiments in mice showed that disruption (中断) to the hippocampus leaves the animals with trouble learning to associate two events separated by tens of seconds.

“The traditional view has been that cells in the hippocampus keep up a level of continuous activity to associate such events,” said Dr. Ahmed, co-first author of the study. “Turning these cells off would thus disrupt learning.”

To test this view, the researchers imaged parts of the hippocampus of mice as the animals were exposed to two different stimuli (刺激物): a neutral (神经的) sound followed by a small but unpleasant puff of air. A fifteen-second delay separated the two events. The scientists repeated this experiment across several trials. Over time, the mice learned to associate the sound with the soon-to-follow puff of air. Using advanced microscopy, they recorded the activity of thousands of neurons (神经元) , a type of brain cell, in the animals’ hippocampus over the course of each trial for many days.

“We expected to see continuous neural activity that lasted during the fifteen-second gap, an indication of the hippocampus at work linking the auditory sound and the air puff,” said computational neuroscientist Stefano Fusi, PhD. “But when we began to analyze the data, we saw no such activity.” Instead, the neural activity recorded during the fifteen-second time gap was sparse (稀少的). Only a small number of neurons worked, and they did so seemingly at random.

To understand activity, they had to shift the way they analyzed data and use tools designed to make sense of random processes. Finally, the researchers discovered a complex pattern in the randomness: a style of mental computing that seems to be a remarkably efficient way that neurons store information.

“We were happy to see that the brain doesn’t maintain ongoing activity over all these seconds because that’s not the most efficient way to store information,” said Dr. Ahmed. “The brain seems to have a more efficient way to build this bridge.”

In addition to helping to map the circuitry involved in associative learning, these findings also provide a starting point to more deeply explore disorders, such as panic and post-traumatic stress disorder.

9 . Mathew White, an environmental psychologist, is on a mission to give Mother Nature the respect he thinks she deserves when it comes to human health. For decades, scientists and health-care professionals have recognized that exposure to green spaces, such as public parks or forests, is linked with lower risks of all sorts of illnesses common in the world. Experimental work has demonstrated various physiological responses that occur when people spend time in natural environments: blood pressure drops, heart rate decreases, immune function improves, and the nervous system directs the body to rest and digest.

As humans increasingly populate urbanized areas, they are spending less and less time in natural environments. But before doctors can start advising their patients to head to the nearest park, there is an important outstanding question, says White: How much time in nature do you need to generate these apparent benefits? Most of the research that has linked health outcomes with exposure to the natural world didn’t use frequency or duration of park visits, but rather the amount of green space within a certain distance of a person’s home, White says. But “it’s not so much where you live; it’s whether you use it or not.”

So he collected data to estimate what dose（剂量） of nature was needed to show benefits to a person’s health. White’s group found the answer he was after: Spending at least two hours in nature per week was strongly correlated with self-reports of being in good health or having high wellbeing. “I was very surprised, to be honest,” says White, who had been expecting a much longer time. “We had no idea that such a clear threshold of time per week would emerge from the data.”

He was further surprised to learn that it didn’t seem to matter how many trips to a park people took, so long as they got in their two hours per week. It could be a long visit one day, a couple of hour-long trips, three visits of 40 minutes, or four half-hour excursions. He and his colleagues speculate that, if nature’s apparent health benefits are a result of being able to de-stress, then whatever pattern of green space exposure fits one’s schedule is probably the best way to achieve that goal.

Health-care recommendations for people to spend time in nature are probably years away, but the movement has begun. Several organizations around the world are working to promote awareness of nature’s contribution to health. Some researchers have used the term “a dose of nature” to evaluate the amount of exposure needed to gain benefits. “That was kind of the deliberate medicalization of the language around nature and health,” says White.

10 . Though people have discussed the relationship between science and nature for many years, there is no consensual(统一的) explanation. While some view science as a powerful tool in ______ nature’s source of power, others view it as a danger. One example is Barry Commoner’s article, Unraveling(解开) the DNA Myth, which explains the recent developments in DNA technology and expresses ______. Another example is Nathaniel Hawthorne’s short story, The Birthmark. It is a tale about a famous scientist, Aylmer, who seems to be unraveling nature’s deepest secrets one by one. Despite all of his ______ and vast understanding of science, Aylmer is unable to direct that knowledge into ______ free from nature’s grasp. He was unable to rid his wife of her birthmark and, in the end, killed her.

Despite the different presentations of the concepts, though time separated the two men, both pieces express a similar view on the relationship between science and nature. Both pieces suggest that nature is ______ and holds wonders, secrets, and powers that many scientists constantly dream about discovering. Although there is a gap of one hundred and sixty years, Commoner still shares and gives evidence to Hawthorne’s beliefs that there is a unique ______ in nature that cannot be discovered or understood through science and that the ______ to uncover nature’s secrets are ______ and can lead to disaster. According to Commoner, nature’s universal power continues to prevent and control their discoveries. Commoner criticizes and ______ doubt on the true power of science.

As Commoner’s article suggests, nature only allows science to have limited power and success. Both men believe that complete trust in science is ______, however wonderful and groundbreaking some scientific discoveries are. Commoner believes that people only seem to focus on the few achievements, while avoiding and ignoring all of the laws. For example, “most clones exhibit developmental failure before or soon after birth”. By stressing all of the ______ and shortcomings of science, he conveys the notion that nature’s secrets are well kept and far from being understood and ______ by man. The government and private companies have invested billions of dollars in mapping the human genome, but we still have no ______ for it. Such a discovery is useless, however interesting it might be.

Commoner’s article clearly represents science as weak and useless, but more importantly, dangerous. It gives evidence to support the suggested dangers ______ with science’s attempts to discover nature’s power. If the result is not ______ dangerous, it can still have harmful side effects.