【每日阅读训练第四期——速度越障11系列】【11-20】科技

2012Michelle

各位队友好，周二的科技作业又来拜会大家啦。

今天的速度部分内容不难，稍微有点长。越障篇幅较长，我没有硬生生切分成两个部分，免得打扰大家总结文章结构的思路。

读得开心！^_^ 复习的时候也要劳逸结合哦~

First road map of human sex-cell development

Study marks a step towards stem-cell treatment of infertility.
By Becky Summers 16 December 2012
[attachimg=595,335]111675[/attachimg]
【Time1】
The causes of infertility, which affects around 10% of couples, are often unknown, but may in some cases result from the body's inability to produce viable gametes — also known as sperm and egg cells. A new study of the development of these 'germ cells' could help scientists to learn how to create them in the laboratory instead.

Even though the reproductive age for humans is around 15–45 years old, the precursor cells that go on to produce human eggs or sperm are formed much earlier, when the fertilized egg grows into a tiny ball of cells in the mother’s womb. This ball of cells contains ‘pluripotent stem cells’ — blank slates that can be programmed into any type of cell in the body — and researchers are hoping to use these stem cells to treat various conditions, including infertility.

But little is known about the early developmental stages of human gametes — owing to the sensitivity of working with human tissue — and most work in this area has been conducted using mice. In a Nature Cell Biology paper today1, researchers from the University of California, Los Angeles, trace the development of early germ cells in human fetuses of between 6 to 20 weeks and analysed when genes were turned on or off.

The DNA within these early germ cells carries 'epigenetic modifications' — structural changes that do not affect the DNA sequence itself but do affect the way that genes are expressed. These changes may have accumulated during the parents’ lives, and need to be erased during the fetal stage. The study found two major events that wipe out, or reprogram, epigenetic modifications. Most of this reprogramming happened before 6 weeks, but the authors found a second event that completes the reprogramming after 6 weeks.

“This is an important and fundamental paper for understanding human germ-line cells and finding the basic information about human germ-cell biology,” says reproductive biologist Evelyn Telfer of the University of Edinburgh, UK. “The researchers are clearly working in an uncharted area.”

The Los Angeles team worked with anonymized samples from aborted fetuses (after consent) from the University of Washington's Birth Defects Research Laboratory in Seattle.

The researchers also observed that 6-week-old germ cells created in the lab do not match a 6-week-old human germ cell, suggesting that there is a blockage in the development of lab cells that scientists are failing to understand.

“Next, we need to look at what is missing to coax immature germ cells to become eggs or sperm in the lab. If we have no road map to follow, then we are just guessing. Now we have a snapshot of what these cells should look like, we can start to try and mimic them,” says study co-author Amander Clark.
【455】

Galaxy found at record-breaking distance
Seven primitive and distant galaxies observed in Hubble image.
Ron Cowen 12 December 2012
[attachimg=312,393]111676[/attachimg]
【Time2】
Seven distant galaxies — so remote that the light now recorded from them left the bodies less than 600 million years after the Big Bang — have been revealed by the deepest infrared images of the Universe ever recorded. And one of the galaxies, previously thought to be remote, has now been tentatively pegged at 13.29 billion light years (4.1 billion parsecs) away from Earth, which would make it the most distant object yet discovered1.

This is the first reliable sample of such distant galaxies to be identified using images taken by the Hubble Space Telescope’s Wide Field Camera 3. The images, recorded by Richard Ellis, an astronomer at the California Institute of Technology in Pasadena, and his colleagues, also constitute the first sample large enough to confirm the standard theory that astronomers should see a smooth decline in the number of galaxies the further back in time they peer, to when the cosmos was just 450 million old, less than 4% of its current age.

The abundance of the galaxies also suggests that an early galaxy population contained enough stars to reionize hydrogen atoms (strip them of their single electrons) — a key benchmark in the Universe's evolution — after they had cooled down from the Big Bang.

Ellis and his colleagues presented the findings at a NASA phone briefing on 12 December. The study is also forthcoming in Astrophysical Journal Letters.

“This study represents the deepest archaeological dig of the Universe so far,” says Avi Loeb, a theoretical astrophysicist at Harvard University in Cambridge, Massachusetts. It is also the most comprehensive, he adds.

Ellis and his colleagues trained the Hubble camera on a tiny patch of sky known as the Hubble Ultra Deep Field. Because the remote galaxies appear so faint, researchers cannot directly gauge distances by measuring the objects’ redshift — the amount by which the expansion of the Universe has shifted the ultraviolet light they radiate to longer, infrared wavelengths. Instead, astronomers estimate the distance by viewing the galaxies through several infrared filters.
【332】

【Rest】
Hubble's limits

Combined with earlier studies of the Hubble Deep Field, the new observations, recorded in August and September, generated images that were twice as deep (exposed for twice as long) as any the camera had previously recorded. They also included images taken with an extra filter that allowed the team to rule out with more certainty the possibility that some of the galaxies are spurious foreground objects.

“There is no doubt that these new data will help us all get the best sample of galaxies yet at redshift 8–10, from about 450 million years to 600 million years after the Big Bang,” says Garth Illingworth, an astrophysicist at the University of California (UC), Santa Cruz, and a member of a rival team of researchers who have also used the Hubble infrared camera to find distant galaxies.
Illingworth and Rychard Bouwens, an astronomer at UC Santa Cruz, and their collaborators had previously identified one of the galaxies examined by Ellis’s team as having a redshift of 10, corresponding to a time when the Universe was about 482 million years old. But the latest data suggest that the galaxy may in fact have a redshift of 11.9, putting it at a record-breaking distance of 13.29 billion light years (4.1 billion parsecs) away — the very limit of what the Hubble camera can detect.

The researchers on both teams warn, however, that there is also a possibility that it lies much closer to Earth, as this find was completely unexpected. “It defies all expectations,” says Bouwens.
【252】

Ordinary Heart Cells Become 'Biological Pacemakers' With Injection of Single Gene
【Time3】
Dec. 16, 2012 — Cedars-Sinai Heart Institute researchers have reprogrammed ordinary heart cells to become exact replicas of highly specialized pacemaker cells by injecting a single gene (Tbx18)-a major step forward in the decade-long search for a biological therapy to correct erratic and failing heartbeats.

The advance will be published in the Jan 8 issue of Nature Biotechnology and also will be available on the journal's website.

"Although we and others have created primitive biological pacemakers before, this study is the first to show that a single gene can direct the conversion of heart muscle cells to genuine pacemaker cells. The new cells generated electrical impulses spontaneously and were indistinguishable from native pacemaker cells," said Hee Cheol Cho, PhD., a Heart Institute research scientist.

Pacemaker cells generate electrical activity that spreads to other heart cells in an orderly pattern to create rhythmic muscle contractions. If these cells go awry, the heart pumps erratically at best; patients healthy enough to undergo surgery often look to an electronic pacemaker as the only option for survival.

The heartbeat originates in the sinoatrial node (SAN) of the heart's right upper chamber, where pacemaker cells are clustered. Of the heart's 10 billion cells, fewer than 10,000 are pacemaker cells, often referred to as SAN cells. Once reprogrammed by the Tbx18 gene, the newly created pacemaker cells -- "induced SAN cells" or iSAN cells -- had all key features of native pacemakers and maintained their SAN-like characteristics even after the effects of the Tbx18 gene had faded.

But the Cedars-Sinai researchers, employing a virus engineered to carry a single gene (Tbx18) that plays a key role in embryonic pacemaker cell development, directly reprogrammed heart muscle cells (cardiomyocytes) to specialized pacemaker cells. The new cells took on the distinctive features and function of native pacemaker cells, both in lab cell reprogramming and in guinea pig studies.

Previous efforts to generate new pacemaker cells resulted in heart muscle cells that could beat on their own. Still, the modified cells were closer to ordinary muscle cells than to pacemaker cells. Other approaches employed embryonic stem cells to derive pacemaker cells. But, the risk of contaminating cancerous cells is a persistent hurdle to realizing a therapeutic potential with the embryonic stem cell-based approach. The new work, with astonishing simplicity, creates pacemaker cells that closely resemble the native ones free from the risk of cancer.

For his work on biological pacemaker technology, Cho, the article's last author, recently won the Louis N. and Arnold M. Katz Basic Research Prize, a young investigator award of the American Heart Association.

"This is the culmination of 10 years of work in our laboratory to build a biological pacemaker as an alternative to electronic pacing devices," said Eduardo Marbán, MD, PhD, director of the Cedars-Sinai Heart Institute and Mark S. Siegel Family Professor, a pioneer in cardiac stem cell research. A clinical trial of Marbán's stem cell therapy for heart attack patients recently found the experimental treatment helped damaged hearts regrow healthy muscle.

If subsequent research confirms and supports findings of the pacemaker cell studies, the researchers said they believe therapy might be administered by injecting Tbx18 into a patient's heart or by creating pacemaker cells in the laboratory and transplanting them into the heart. But additional studies of safety and effectiveness must be conducted before human clinical trials could begin.
【555】

Engineers Develop New Energy-Efficient Computer Memory Using Magnetic Materials
[attachimg=314,224]111677[/attachimg]
【Time4】
Dec. 14, 2012 — By using electric voltage instead of a flowing electric current, researchers from UCLA's Henry Samueli School of Engineering and Applied Science have made major improvements to an ultra-fast, high-capacity class of computer memory known as magnetoresistive random access memory, or MRAM.

The UCLA team's improved memory, which they call MeRAM for magnetoelectric random access memory, has great potential to be used in future memory chips for almost all electronic applications, including smart-phones, tablets, computers and microprocessors, as well as for data storage, like the solid-state disks used in computers and large data centers.

MeRAM's key advantage over existing technologies is that it combines extraordinary low energy with very high density, high-speed reading and writing times, and non-volatility -- the ability to retain data when no power is applied, similar to hard disk drives and flash memory sticks, but MeRAM is much faster.

Currently, magnetic memory is based on a technology called spin-transfer torque (STT), which uses the magnetic property of electrons -- referred to as spin -- in addition to their charge. STT utilizes an electric current to move electrons to write data into the memory.

Yet while STT is superior in many respects to competing memory technologies, its electric current-based write mechanism still requires a certain amount of power, which means that it generates heat when data is written into it. In addition, its memory capacity is limited by how close to each other bits of data can be physically placed, a process which itself is limited by the currents required to write information. The low bit capacity, in turn, translates into a relatively large cost per bit, limiting STT's range of applications.

With MeRAM, the UCLA team has replaced STT's electric current with voltage to write data into the memory. This eliminates the need to move large numbers of electrons through wires and instead uses voltage -- the difference in electrical potential -- to switch the magnetic bits and write information into the memory. This has resulted in computer memory that generates much less heat, making it 10 to 1,000 times more energy-efficient. And the memory can be more than five-times as dense, with more bits of information stored in the same physical area, which also brings down the cost per bit.
【377】

【Time5】
The research team was led by principal investigator Kang L. Wang, UCLA's Raytheon Professor of Electrical Engineering, and included lead author Juan G. Alzate, an electrical engineering graduate student, and Pedram Khalili, a research associate in electrical engineering and project manager for the UCLA-DARPA research programs in non-volatile logic.

"The ability to switch nanoscale magnets using voltages is an exciting and fast-growing area of research in magnetism," Khalili said. "This work presents new insights into questions such as how to control the switching direction using voltage pulses, how to ensure that devices will work without needing external magnetic fields, and how to integrate them into high-density memory arrays.

"Once developed into a product," he added, "MeRAM's advantage over competing technologies will not be limited to its lower power dissipation, but equally importantly, it may allow for extremely dense MRAM. This can open up new application areas where low cost and high capacity are the main constraints."

Said Alzate: "The recent announcement of the first commercial chips for STT-RAM also opens the door for MeRAM, since our devices share a very similar set of materials and fabrication processes, maintaining compatibility with the current logic circuit technology of STT-RAM while alleviating the constrains on power and density."

The research was presented Dec. 12 in a paper called "Voltage-Induced Switching of Nanoscale Magnetic Tunnel Junctions" at the 2012 IEEE International Electron Devices Meeting in San Francisco, the semiconductor industry's "pre-eminent forum for reporting technological breakthroughs in the areas of semiconductor and electronic device technology."

MeRAM uses nanoscale structures called voltage-controlled magnet-insulator junctions, which have several layers stacked on top of each other, including two composed of magnetic materials. However, while one layer's magnetic direction is fixed, the other can be manipulated via an electric field. The devices are specially designed to be sensitive to electric fields. When the electric field is applied, it results in voltage -- a difference in electric potential between the two magnetic layers. This voltage accumulates or depletes the electrons at the surface of these layers, writing bits of information into the memory.

"Ultra-low-power spintronic devices such as this one have potential implications beyond the memory industry," Wang said. They can enable new instant-on electronic systems, where memory is integrated with logic and computing, thereby completely eliminating standby power and greatly enhancing their functionality."

The work was supported by the Defense Advanced Research Projects Agency (DARPA) NV Logic Program. Other authors included researchers from the UCLA Department of Electrical Engineering; UC Irvine's Department of Physics and Astronomy; Hitachi Global Storage Technologies (a Western Digital Company); and Singulus Technologies, of Germany.
【431】

【Obstacle】

The big picture
The world is getting wider, says Charlotte Howard. What can be done about it?
Dec 15th 2012 | from the print edition

IT IS LUNCHTIME at Eastside Elementary School in Clinton, Mississippi, the fattest state in the fattest country in the Western world. Uniformed lunch ladies stand at the ready. Nine-year-olds line up dutifully, trays in hand. Yes to chocolate milk, yes to breaded chicken sandwiches, yes to baked beans, yes to orange jelly, no to salad. Bowls of iceberg lettuce and tomatoes sit rim to rim, rejected. Regina Ducksworth, in charge of Clinton’s lunch menu, sighs. “Broccoli is very popular,” she says, reassuringly.

Persuading children to eat vegetables is hardly a new struggle, nor would it seem to rank high on the list of global priorities. In an age of plenty, individuals have the luxury of eating what they like. Yet America, for all its libertarian ethos, is now worrying about how its citizens eat and how much exercise they take. It has become an issue of national concern.

Two-thirds of American adults are overweight. This is defined as having a body mass index (BMI, a common measure of obesity) of 25 or more, which for a man standing 175cm (5’9”) tall means a weight of 77kg (170 pounds) or more. Alarmingly, 36% of adults and 17% of children are not just overweight but obese, with a BMI of at least 30, meaning they weigh 92kg or more at the same height. If current trends continue, by 2030 nearly half of American adults could be obese.

Americans may be shocked by these numbers, but for the rest of the world they fit a stereotype. Hamburgers, sodas and sundaes are considered as American as the Stars and Stripes. Food at state fairs is American cuisine at its most exuberantly sickening. At the Mississippi fair, a deep-fried Oreo biscuit’s crispy exterior gives way to soft dough, sweet cream and chocolate goo. It is irresistible.

The rest of the world should not scoff at Americans, because belts in many other places are stretched too, as shown by new data from Majid Ezzati of Imperial College, London, and Gretchen Stevens of the World Health Organisation (WHO). Some continental Europeans remain relatively slender. Swiss women are the slimmest, and most French women don’t get fat, as they like to brag (though nearly 15% do). But in Britain 25% of all women are obese, with men following close behind at 24%. Czech men take the European biscuit: 30% are obese.

And it is not just the rich world that is too big for its own good. The world’s two main hubs for blub are the Pacific islands and the Gulf region. Mexican adults are as fat as their northern neighbours. In Brazil the tall and slender are being superseded by the pudgy, with 53% of adults overweight in 2008. Even in China, which has seen devastating famine within living memory, one adult in four is overweight or obese, with higher rates among city-dwellers. In all, according to Dr Ezzati, in 2008 about 1.5 billion adults, or roughly one-third of the world’s adult population, were overweight or obese. Obesity rates were nearly double those in 1980.

Fat of the land

Not long ago the world’s main worry was that people had too little to eat. Malnourishment remains a serious concern in some regions: some 16% of the world’s children, mainly in sub-Saharan Africa and South Asia, were underweight in 2010. But 20 years earlier the figure was 24%. In a study of 36 developing countries, based on data from 1992 to 2000, Barry Popkin of the University of North Carolina found that most of them had more overweight than underweight women.

The clearest explanation of this extraordinary modern phenomenon comes from a doctor who lived in the 5th century BC. “As a general rule,” Hippocrates wrote, “the constitutions and the habits of a people follow the nature of the land where they live.” Men and women of all ages and many cultures did not choose gluttony and sloth over abstemiousness and hard work in the space of just a few decades. Rather, their surroundings changed dramatically, and with them their behaviour.

Much of the shift is due to economic growth. BMI rises in line with GDP up to $5,000 per person per year, then the correlation ends. Greater wealth means that bicycles are abandoned for motorbikes and cars, and work in the fields is swapped for sitting at a desk. In rich countries the share of the population that gets insufficient exercise is more than twice as high as in poor ones.

Very importantly, argues Boyd Swinburn of Deakin University in Melbourne, diets change. Families can afford to eat more food of all kinds, and particularly those high in fat and sugar. Mothers spend more time at work and less time cooking. Food companies push their products harder. Richard Wrangham of Harvard University says that heavily processed food may have helped increase obesity rates. Softer foods take less energy to break down and finely milled grains can be digested more completely, so the body absorbs more calories.

These global changes react with local factors to create different problems in different regions. Counter-intuitively, in some countries malnutrition is leading to higher obesity rates. Undernourished mothers produce babies who are predisposed to gaining weight easily, which makes children in fast-developing countries particularly prone to getting fat.

In Mexico unreliable tap water and savvy marketing have helped make the country the world’s leading guzzler of Coca-Cola: the average adult consumed 728 servings last year. In America junk-food calories are often cheaper than healthy ones. Suburban sprawl and the universal availability of food have made the car the new dining room. In the Middle East, Bedouin traditions of hosting and feasting have combined with wealth to make overeating a nightly habit. Any inclination to exercise is discouraged by heat and cultural restrictions. In Beijing teenagers and office workers cram the fast-food restaurants along Wangfujing. Even home-cooked Chinese meals contain more meat and oil than they used to. Doting grandparents shower edible treats on scarce grandchildren.

Together, these disparate changes have caused more and more people to become fat. Many cultures used to view a large girth with approval, as a sign of prosperity. But obesity has costs. It lowers workers’ productivity and in the longer term raises the risk of myriad ailments, including diabetes, heart disease, strokes and some cancers; it also affects mental health. In America, obesity-related illness accounted for one-fifth of total health-care spending in 2005, according to one paper.

A huge new global health study, led by Christopher Murray of the University of Washington, shows that since 1990 obesity has grown faster than any other cause of disease. For women a high BMI is now the third-largest driver of illness. At the same time childhood mortality has dropped and the average age of the world’s population has risen rapidly. In combination these trends may mark a shift in public-health priorities. Increasingly, early death is less of a worry than decades spent alive and sick.

It is plain that obesity has become a huge problem, that the factors influencing it are fiendishly hard to untangle and that reversing it will involve difficult choices. Radical moves such as banning junk food would infringe individuals’ freedom to eat what they like. Instead, some governments are cautiuosly prodding their citizens to eat less and exercise more, and food companies are offering at least some healthier foods.

In a few places obesity rates seem to be levelling, but for now waistlines in most countries continue to widen unabated. Jiang He and his colleagues at Tulane University have estimated that by 2030 the global number of overweight and obese people may double to 3.3 billion. That would have huge implications for individuals, governments, employers, food companies and makers of pharmaceuticals.
【1285】

2012Michelle

沙发自己坐，可怜我最近忙得连小分队的时间都没有了。哭~

**********************作业分割线**********************

终于把11系最后一篇赶完了。欠作业真是叫人头疼。

PS，我把11系所有的回忆笔记统计了一下，居然写了6030词。可见，还是很有点量的。每天练练对写作多少有点帮助。呵呵，真开心。

【11-20】
Time1-2'40"
Scientists are studying on sperms and eggs (germ cells) in lab to observe how they work together. New finding shows that the interaction causes two kind of changes: before 6weeks and after 6weeks.
Time2-1'53"
The scientist find a closest galax to earth out of seven. They found the importance of studying on the 7 galaxies is very significant.
Rest-1'03" 今天逆天了，这速度看科技文252词。。。肯定是timer出问题了。
The new camera collects new data which take important role to help scientists understand the galaxies.
Time3-3'08"
By injecting Tbx18 (a kind of biological pacemaker) into heart, the doctor will help more patients for their heart diseases. The Tbx18 can not only assist heart get electronical signal for normal action and also regrow health cells. So far the tests have done in lab and pigs, and the program has not been under clinical trial stage.
Time4-2'28"
Scientists have invented new technology MeRAM to increase the computers' speed with lower cost. The technology will be widely used in future devices such as smart-phone, computuers... The old STT depends on the bit numbers on the physically placed and transferred informaiton, which limited its usage.
Time5-2'07"
The STT already opened a door to MeRAM, the application is not complicated.

Obstacle 7'55"
Main Idea: Obesity becomes a seriously global problem, which needs special attention.
Author's attitude: Neutral
Article Structure:
1) Emphasizing the importance of obesity: Almost the whole world has the same problem, people get more and more unhealthy life style to make themselves obete.
2) The reasons:
-- Food, conveniences: in most countries, including developed, developing, and even poor areas, people's life have been changed a lot from poverity.
-- Economies: BMI increases along with the development of GDPs.
-- Habit(a kind of life style): parents pay more and more time on job and make more money to increase the life quality of theirs, but less time on healthy food for their children. People prefer to eating fast food to adap to the new work style.
-- Obesity will cause a lot of diseases that hurt health.
3) Call for attention: the situation will continue growing worse. People need to pay more attention to their food, life style, and so on,to get healthier.

映雪瑶渊

哼！！！我才是沙发

yangreat

11系列收官了啊！感谢大米啊！

attractg

占位~！！！

teddybearj4

血拼过后就是无穷补不完的作业……sigh~占座……

livia2012

占座，一会儿来做作业

miffyhui

2'30"
1'50"
1'03"
2'47"
1'54"
2'09"
6'39"the obese has become an problem in the world
the reason: the development of economy and the cultural circumstance
the company produce more heavily food rather than soft food
women have more time at and less time cook
mothers who are fat are more likely to has fat children and then these children will become more fatter in this circumstance
the serious consequence: 1. lower the productivity 2.leading to several serious disease
measures: government can't prohibit people from eating these food and some government encourage their citizens eat less and company produce more healthier food

lyc50336

周末考了个雅思·· 都没来读了··

spencerX

谢谢大米~~越障顺便提醒了我最近的发福状况= =

0:02:09
0:01:32
0:00:56
0:02:49
0:01:52
0:02:19

0:07:28