In recent days, Americans have lost two civil rights leaders of the twentieth century, Dorothy Height and Benjamin Hooks.

Dorothy Height died this Tuesday at the age of ninety-eight. She witnessed more civil rights history than any other African-American leader of her time. She said the greatest change she witnessed was the ending of racial segregation(隔离) laws in the United States.

She was the longtime chairwoman of the National Council of Negro Women. She was an activist, humanitarian and advisor to presidents including Barack Obama. He remembered her as “The godmother of the Civil Rights Movement.”

Dorothy Height grew up in Pennsylvania. She won a four-year college scholarship, the top prize nationally in a public speaking contest on the Constitution.

She arrived at school in New York City-only to learn that an unwritten limit of “two Negro students per year”had already been met. Dorothy Height: “I was accepted at Barnard College and I was denied admission when I arrived because they had a quota(指标) of two. And they did not know that I was not white. And so when I got there I was turned away.”

Dorothy Height went on to earn bachelor and master's degrees in four years at New York University. She worked with Marin Luther King Junior in the push for civil rights for blacks in the nineteen fifties and sixties.

Yet she had to push to make herself heard as a woman among mostly male civil rights leaders. She was the only woman standing nearby as Martin Luther King gave his “I Have a Dream” speech in Washington

Dorothy Height received the Presidential Medal of Freedom and the Congressional Gold Medal for her work for racial and gender equality.

Some students get so nervous before a test, they do poorly even if they know the material. Sian Beilock, a psychology professor at the University of Chicago in IIIionois, has studied these highly anxious test-takers.

Sian Beilock:"They start worrying about the consequences. They might even start worrying about whether this exam is going to prevent them from getting into the college they want. And when we worry , it actually uses up attention and memory resources. I talk about it as your cognitive (认知) horsepower that you could otherwise be using to focus on the exam.

Professor Beilock and another researcher, Gerardo Ramirez, have developed a possible solution. Just before an exam, highly anxious test-takers spend ten minutes writing about their worries about the test.

Sian Beilock:" What we think happens is when students put it down on paper, they think about the worst that could happen and they reassess the situation. They might realize it's not as had as they might think it was before and, in essence, it prevents these thoughts from popping up when they're actually taking a test."

The researchers tested the idea on a group of twenty anxious college students. They gave them two short math tests. After the first one, they asked the students to either sit quietly or write about their feelings about the upcoming second test.

The researchers added to the pressure. They told the students that those who did well on the second test would get money. They also told them that their performance would affect other students as part of a team effort.

Professor Beilock says those who sat quietly scored an average of twelve percent worse on the second test. But the students who had written about their fears improved their performance by an average of five percent.

Next, the researchers used younger students in a biology class. They told them before final exams either to write about their feelings or to think about things unrelated to the test.

Professor Beilock says highly anxious students who did the writing got an average grade of B+,compared to a B- for those who did not.

Sian Beilock :" What we showed is that for students who are highly test-anxious, who'd done our writing intervention(干预), all of a sudden there was no relationship between test anxiety and performance. Those students most likely to worry were performing just as well as their classmates who don't normally get nervous in these testing situations."

But what if students do not have a chance to write about their fears immediately before and exam or presentation? Professor Beilock says students can try it themselves at home or in the library and still improve their performance.

Regardless of their preferred mode, bats, elephant, honeybee, humans and more all sleep. In fact, scientists have yet to find a truly sleepless creature. But is sleep really necessary for survival?

Most humans will acknowledge that sleep is absolutely necessary. People often struggle to function after even just one sleepless night. Poor sleep over the long term has been linked to many negative health effects, from heart disease and stroke to weight gain and diabetes(糖尿病) . These connections, and the fact that all animals seem to sleep, suggest that sleep must play an essential function for animals. But what is that function? Does sleep allow the brain to repair damage and process information? Scientists and thinkers have offered explanations for why we sleep, and yet, the exact purpose of sleep remains an open question.

In the 1890s, Marie de Manaceine, a female physician in Russia, was troubled by the mystery of sleep. In her quest to figure out what exactly sleep is, she conducted the firstsleep-deprivationexperiment in animals.

Using an approach that now seems quite cruel, the physician kept puppies continuously awake, finding that they died after a few days of the experiment. Over following decades, further such experiments using other animals found similarly fatal results. However, the underlying cause of death in these cases, and how it relates to sleep are still unknown.

While total sleeplessness seems dangerous, some creatures can get by with a remarkably short sleep. They could be the key to understanding sleep's function, scientists have said.

A study published in Science Advances monitored the sleeping habits of fruit flies. "We found that some flies hardly ever slept," study co-author Giorgio Gilestro told Live Science."But these flies didn't die prematurely(过早)，like the Russian puppies did. These virtually sleepless flies instead lived just as long as a control group that was left to sleep normally"."

In a 2016 study, Rattenborg and his colleagues provided great frigatebirds in the Galapagos Islands with a small device to measure electrical activity in the brain. The study found that the frigatebirds, while flying, slept on average just 42 minutes per day, even though they typically got more than 12 hours of shut-eye on land.

Does Rattenborg think we'll ever find an animal that doesn't sleep at all?

"Anything is possible," he said, "however, an emerging pattern among the studies of short-sleeping animals is that none are completely sleepless. This preservation of a little sleep suggests that there is a minimum amount of sleep that is essential, even in these remarkable short sleepers."

Ways we can fed the world in 2050

Some estimates suggest our global population could reach a total of 10 billion people by 2050. It’s clear that traditional agriculture has to change to fed that many people.    11    

Creating robot farmers

Such exploration has been done. The Small Robot Company in Britain has created three small robots: Tom, Dick and Harry. Tom takes geography pictures of plants in the field, and sends them back for analysis. Then Dick spray(喷洒) crops with precision, avoiding unnecessary polluting and saving resources. Harry plants, completing with a robotic drill(机械钻).     12    These tasks are traditionally done by a human.

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Ordinary heavy tractors(拖拉机) roll across the field, compacting(压实) the soil and squeezing the gaps inside. This compaction greatly affects the soil's ability to hold onto water and nutrients. Using smaller, lighter robots to do the jobs currently performed by tractors could hugely help reduce these issues, hence promoting to keep precious soil in good condition.

Giving waste a second chance

According to the United Nations, “An estimated third of all food produced ends up rotting in the dustbins of consumers and sellers." There are countless brilliant ideas and measures to help, but I advocate one brilliant approach—using app like“Too Good To Go".    14    These foods may be abandoned but still perfectly eatable.

Making smarter choices

We spend time with farmers, producers, sellers and consumers.    15    Building a world fed by sustainable(可持续的) agriculture is a tough task, which requires changes to the whole model of growing, processing, transporting, storing and selling.

On the Whole, in order to ensure we have enough food in the future, farmers, scientists, engineers, sellers, business leaders, governments and individuals should come together to join the effort, taking action to value our food and its producer.