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[阅读小分队] 【Native Speaker每日训练计划】No.2779 科技

发表于 2020-5-18 02:36:52 | 显示全部楼层 |阅读模式
内容:Alice Ge 编辑:Alvin Wei

Wechat ID: NativeStudy  / Weibo:

Part I: Speaker

Donut Sugar Could Help Stored Blood Last
By Susanne Bard on May 12, 2020
[Rephrase 1, 02:56]
Source: Scientific American Sugar Could Help Stored Blood Last/

Part II: Speed

Deadly temperatures expected to arrive later this century are already here
By Jonathan Lambert | MAY 8, 2020 AT 2:00 PM

[Time 2]
Human beings have a superpower — sweating.

When temperatures rise, beads of sweat exude from our pores and evaporate, releasing energy that cools the skin and keeps our bodies from overheating.

This self-cooling mechanism has helped humans spread to every hot and humid corner of the globe. But that sweating superpower has a theoretical upper limit: When it gets too hot and humid, the laws of physics inhibit sweat from cooling skin. That limit is hit when a bulb thermometer wrapped in a wet towel (a measure of heat and humidity known as “wet-bulb” temperature) reads 35° Celsius, or 95° Fahrenheit. Even the fittest human supplied with unlimited water would probably die after a few hours in these conditions.

Scientists have thought that this temperature extreme occurs rarely, if ever, on Earth. But as the globe warms, wet-bulb temperatures around 35° C could become more common toward the end of the century in certain regions, endangering hundreds of millions of people, recent climate simulations suggest (SN: 8/2/17).

It turns out we won’t have to wait that long.

An analysis of global weather station data shows that this human survivability limit has been briefly surpassed at least a dozen times in the last four decades at sites along the Persian Gulf and Indus River Valley in India and Pakistan, researchers report May 8 in Science Advances. Slightly lower, but still dangerous, wet-bulb temperatures are increasingly familiar features of summer across larger swaths of the Middle East, South Asia and the U.S. Gulf Coast, the study shows.
[254 words]

[Time 3]
“We expect these extreme wet-bulb values to be rare, but to become more common as the world warms,” says Matthew Huber, a climate scientist at Purdue University in West Lafayette, Ind., who wasn’t involved in the study. “It’s disturbing to see it happening in real time.”

Researchers have only relatively recently begun using statistical simulations to estimate where and when this extreme moist-heat threshold might be approached or crossed, which could have dire consequences for societies. (SN: 4/3/18). But these models work by simplifying and aggregating weather station data across a region. The fine details often get sacrificed in service of broader trends, potentially obscuring local spots where the temperature threshold is briefly reached.

Those fine details matter to Colin Raymond, a climate scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Whether temperatures already have reached this physiological limit somewhere on Earth “seems almost to be an essential piece of knowledge for us as a species,” says Raymond, who did the work while at Columbia University.

He and his team scoured data from 4,576 weather stations across the globe, looking for instances of extreme wet-bulb temperatures and tracking trends from 1979 to 2017. After removing measurements that didn’t jibe with nearby stations or seemed like obvious errors, a clear pattern emerged: Extreme wet-bulb temperatures have occurred, mostly along subtropical coasts, where warm, moist air from the ocean collides with hot air on land. In South Asia, such extremes are fueled by monsoon winds.
[245 words]

[Time 4]
Temperatures at or beyond that physiological limit were rare and confined to an hour or two at hot spots along the Persian Gulf, such as a weather station at the Abu Dhabi International Airport in the United Arab Emirates. Nearly 1.5 million people live in Abu Dhabi. (An interactive map created by the researchers plots the highest wet-bulb temperatures recorded at stations across the world.)

The team also documented wet-bulb temperatures of 33° C, which roughly translates to a heat index of 60° C or 139° F. (The heat index, or what a temperature feels like with humidity, isn’t designed to go this high, so comparisons are rough.) That temperature is just shy of the physiological limit but still “much hotter and more humid than many of us have experienced,” Raymond says. The analysis found that 40 years ago, these events happened once or twice a year on Earth. But now, such oppressive moist-heat events happen 25 to 30 times a year. “There is a doubling or more of these extreme events over four decades,” he says.

So are the simulations predicting that these temperatures wouldn’t arrive until midcentury wrong?

Not necessarily, says Joy Merwin Monteiro, a climate scientist at the Indian Institute of Science Education and Research in Pune, who wasn’t involved in the study. “Models are too coarse to give a clear picture of what’s happening at these finer spatial and temporal scales.” Monteiro says that complementing existing models with more detailed, on-the-ground data is long overdue.

If carbon emissions aren’t drastically curbed in the coming decades, these relatively rare extremes will become increasingly common, researchers say. Such conditions are unbearable without technology like air conditioning and make outdoor labor near impossible.

“We may have to rethink how to live in a place that’s experiencing conditions outside of what we’ve evolved to experience,” Raymond says. “Living in the Persian Gulf in the summer may come to resemble living at the South Pole in the winter.”
[328 words]

Source: Science News

A gene variant partly explains why Peruvians are among the world’s shortest people
By Tina Hesman Saey | 10 HOURS AGO

[Time 5]
Nearly 4,000 common variations in DNA are known to affect height, with each one nudging stature up or down a millimeter or so. But a gene variant found in almost 5 percent of Peruvians reduces height by 2.2 centimeters, on average.

That’s the biggest effect on stature recorded to date for a common version of a gene. Some rare variations in DNA have much larger effects on height, but they tend to be found in less than 1 percent of people.

People who carry two copies of the gene variant — one inherited from each parent — are, on average, about 4.4 centimeters shorter than the average height of people who don’t carry the variant, researchers report May 13 in Nature. The finding partially explains why the Peruvian people are among the shortest in the world. Men average 165.3 centimeters (about 5 feet, 4 inches) tall and women 152.9 cm (about 5 feet) tall.

The variant is located in the gene known as fibrillin 1, or FBN1, which produces a protein involved in forming bone, connective tissues, skin and other tissues. Some rare FBN1 variations lead to Marfan syndrome, a disorder that leads people to be tall, lanky and prone to heart and blood vessel ruptures and other health problems (SN: 6/25/08).

“But those 5 percent of Peruvians who carry [this common variant] are not sick by any pathological definition,” says statistical geneticist Samira Asgari of Brigham and Women’s Hospital and Harvard Medical School in Boston.

Asgari and colleagues found evidence that natural selection has favored the short-stature variant, although exactly what evolutionary advantage it gives the Peruvians who carry it is not clear.
[273 words]

Source: Science News

New hybrid embryos are the most thorough mixing of humans and mice yet
By Laura Sanders | 7 HOURS AGO

[Time 6]
Scientists have made embryos that are a lot mouse and a little bit human.

With a little help, human stem cells can knit themselves into growing mouse embryos, populating the developing liver, heart, retina and blood, researchers report May 13 in Science Advances.

Finicky human cells don’t tend to grow well in other animals. But in one of the new mouse embryos, 4 percent of its cells were human — the most thorough mixing between human and mouse yet.

That level of integration is “quite striking to me,” says Juan Carlos Izpisua Belmonte, a stem cell and developmental biologist at the Salk Institute for Biological Studies in La Jolla, Calif. If other scientists can replicate the findings, “it potentially represents a major advance,” says Izpisua Belmonte, who was not involved in the study.

Such chimeras could help reveal how a single cell can give rise to an entire organism. More humanized animals could also prove valuable in studying diseases such as malaria that affect people more than other animals. And with more advances, chimeras could ultimately turn out to be a source of human organs.

Many scientists have hit roadblocks in growing human stem cells in mice or other animals, including pigs and cows (SN: 1/26/17). “We have analyzed thousands of embryos but never saw robust chimeric contribution” of human stem cells to mouse embryos beyond day 12, says stem cell and developmental biologist Jun Wu of the University of Texas Southwestern Medical Center in Dallas, who wasn’t involved in the study.

The new method’s success comes down to timing, says neuroscientist and stem cell biologist Jian Feng. To grow and thrive in a mouse embryo, human stem cells’ developmental clocks must be turned back to an earlier phase called the naïve stage. “You need to basically push the human cells back” to that phase, says Feng, of the University at Buffalo in New York.

Feng and his colleagues reset the stem cells’ clocks by silencing a protein called mTOR for three hours. This brief treatment shocked the cells back to their naïve stage, presumably restoring their ability to turn into any cell in the body.
[355 words]

[The Rest]
Researchers injected batches of 10 to 12 of these more youthful human stem cells into mouse embryos containing about 60 to 80 mouse cells, and allowed the embryos to develop for 17 days.

To outward appearances, these embryos grew normally despite harboring human cells. By tallying DNA that was specific to either mouse or human, the researchers found that human cells accounted for between 0.1 and 4 percent of the total cells in the embryos.

Human cells knitted themselves into most developing tissues of the mouse, destined to become the liver, heart, bone marrow and blood. Human red blood cells were particularly abundant in these mouse embryos, the researchers found. A small number of human cells showed up in tissue that will form a brain; one embryo had a swarm of human photoreceptors, eye cells that help detect light.

As far as the researchers could tell, no human cells were among the cells that go on to form sperm and egg. The capacity of chimeras to reproduce is one of the worrisome ethical questions surrounding the organisms that scientists are still trying to figure out.

Once inside a mouse embryo, the normally sluggish developmental pace of the human cells sped up to match their hosts. Human stem cells typically are slow to turn into certain types of mature photoreceptors, liver cells or red blood cells, Feng says, but not when the human cells are inside a mouse embryo. “You put the same human cells in a mouse embryo, [and] they go fast,” Feng says. “In 17 days, you get all these mature cells that would otherwise take months to get in a normal human embryo.”

Other scientists emphasize that different laboratories need to repeat the results. But “if it works — a big if here — this has big implications,” Wu says.
[300 words]

Source: Science News

Part III: Obstacle

How does the brain link events to form a memory? Study reveals unexpected mental processes
May 8, 2020 | The Zuckerman Institute at Columbia University

[Paraphrase 7]
A woman walking down the street hears a bang. Several moments later she discovers her boyfriend, who had been walking ahead of her, has been shot. A month later, the woman checks into the emergency room. The noises made by garbage trucks, she says, are causing panic attacks. Her brain had formed a deep, lasting connection between loud sounds and the devastating sight she witnessed.

This story, relayed by clinical psychiatrist and co-author of a new study Mohsin Ahmed, MD, PhD, is a powerful example of the brain's powerful ability to remember and connect events separated in time. And now, in that new study in mice published today in Neuron, scientists at Columbia's Zuckerman Institute have shed light on how the brain can form such enduring links.

The scientists uncovered a surprising mechanism by which the hippocampus, a brain region critical for memory, builds bridges across time: by firing off bursts of activity that seem random, but in fact make up a complex pattern that, over time, help the brain learn associations. By revealing the underlying circuitry behind associative learning, the findings lay the foundation for a better understanding of anxiety and trauma- and stressor-related disorders, such as panic and post-traumatic stress disorders, in which a seemingly neutral event can elicit a negative response.

"We know that the hippocampus is important in forms of learning that involve linking two events that happen even up to 10 to 30 seconds apart," said Attila Losonczy, MD, PhD, a principal investigator at Columbia's Mortimer B. Zuckerman Mind Brain Behavior Institute and the paper's co-senior author. "This ability is a key to survival, but the mechanisms behind it have proven elusive. With today's study in mice, we have mapped the complex calculations the brain undertakes in order to link distinct events that are separated in time."

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 to the hippocampus leaves the animals with trouble learning to associate two events separated by tens of seconds.

"The prevailing view has been that cells in the hippocampus keep up a level of persistent activity to associate such events," said Dr. Ahmed, an assistant professor of clinical psychiatry at Columbia's Vagelos College of Physicians and Surgeons, and co-first author of today's study. "Turning these cells off would thus disrupt learning."

To test this traditional view, the researchers imaged parts of the hippocampus of mice as the animals were exposed to two different stimuli: a neutral 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 tone with the soon-to-follow puff of air. Using advanced two-photon microscopy and functional calcium imaging, they recorded the activity of thousands of neurons, a type of brain cell, in the animals' hippocampus simultaneously over the course of each trial for many days.

"With this approach, we could mimic, albeit in a simpler way, the process our own brains undergo when we learn to connect two events," said Dr. Losonczy, who is also a professor of neuroscience at Columbia's Vagelos College of Physicians and Surgeons.

To make sense of the information they collected, the researchers teamed up with computational neuroscientists who develop powerful mathematical tools to analyze vast amounts of experimental data.

"We expected to see repetitive, continuous neural activity that persisted during the fifteen-second gap, an indication of the hippocampus at work linking the auditory tone and the air puff," said computational neuroscientist Stefano Fusi, PhD, a principal investigator at Columbia's Zuckerman Institute and the paper's co-senior author. "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. Only a small number of neurons fired, and they did so seemingly at random. This sporadic activity looked distinctly different from the continuous activity that the brain displays during other learning and memory tasks, like memorizing a phone number.

"The activity appears to come in fits and bursts at intermittent and random time periods throughout the task," said James Priestley, a doctoral candidate co-mentored by Drs. Losonczy and Fusi at Columbia's Zuckerman Institute and the paper's co-first author. "To understand activity, we had to shift the way we analyzed data and use tools designed to make sense of random processes."

Ultimately, the researchers discovered a pattern in the randomness: a style of mental computing that seems to be a remarkably efficient way that neurons store information. Instead of communicating with each other constantly, the neurons save energy -- perhaps by encoding information in the connections between cells, called synapses, rather than through the electrical activity of the cells.

"We were happy to see that the brain doesn't maintain ongoing activity over all these seconds because, metabolically, that's not the most efficient way to store information," said Dr. Fusi, who is also a professor of neuroscience at Columbia's Vagelos College of Physicians and Surgeons. "The brain seems to have a more efficient way to build this bridge, which we suspect may involve changing the strength of the synapses."

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

"While our study does not explicitly model the clinical syndromes of either of these disorders, it can be immensely informative," said Dr. Ahmed, who is also a member of the Losonczy lab at Columbia's Zuckerman Institute. "For example, it can help us to model some aspects of what may be happening in the brain when patients experience a fearful association between two events that would, to someone else, not elicit fright or panic."
[977 words]

Source: Science Daily


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发表于 2020-5-18 20:49:11 | 显示全部楼层
发表于 2020-5-18 21:52:01 发自手机 Web 版 | 显示全部楼层
T2 1‘22
T3 1’15
T4 1’32
T5 2’00
T6 1’34
TR 2’01
OB 6’54
发表于 2020-5-18 22:49:28 | 显示全部楼层
T2 2‘22
T3 2’15
T4 2’32
T5 3’00
T6 2’34
TR 3’01
OB 7’54
发表于 2020-5-18 23:38:27 发自手机 Web 版 | 显示全部楼层
T2 2‘32
T3 2’20
T4 2’45
T5 3’15
T6 2’45
OB 8‘30
发表于 2020-5-19 08:43:16 | 显示全部楼层
T2 2'37
T3 1'19
T4 2'09
T5 4'03
T6 3'43
P7 9'59 The passage describes a recent study that suggested a brain mechanism by which associate memory happens, a mechanism different from that in the traditional view and explains its implications.
发表于 7 天前 | 显示全部楼层
Obstacle 4'06
The passage talks about the working pattern of the brain in connecting seperate information.
发表于 7 天前 发自手机 Web 版 | 显示全部楼层
T2 2'37
T3 1'19
T4 2'09
T5 4'03
T6 3'43
发表于 7 天前 | 显示全部楼层
Time2 1'12
Humans will be in danger when the temperature is too high (35 Celsius).

Time3 1'12
Study on extreme wet-bulb temperatures showed that the living environment on Earth is devastating.

Time4 1'34
The prediction is not necessarily wrong, but we have to take action.

Time5 1'16
The research on the DNA revealt the reason for the shortness of P.

Time6 1'46
A recent study successfully mixed human and mouse embryos.

The Rest 1'30
The human part grow quickly in mouse embryos.
发表于 6 天前 | 显示全部楼层
TREHALOSE in dunut can help prelong the preserving timeof donated blood.

T2  01'52  [254]
sweating superpower has a theoretical upper limit.

T3  01'48  [245]
Extreme wet-bulb temperatures have occurred.

T4  02'25  [328]
The frequence of extreme temperatures surges recently.Such conditions are unbearable without technology like air conditioning and make outdoor labor near impossible.
T5  02'04  [273]
The variant located in the gene known as  FBN1 makes people shorter and it is carried by some Peruvians.
Natural selection has favored the short-stature variant, although exactly what evolutionary advantage it gives the Peruvians who carry it is not clear.
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