【每日阅读训练第四期——速度越障11系列】【11-2】科技

CHRISTINE2010

【神猴插播】PS.周三经管暂停一次，做这份科技就好了~
小分队第四期10系列封神榜

出勤率前五名的是！
No.1 attractg ---20 days
No.1 2012Michelle ---20 days
No.3 Victoriasong ---18 days
No.4 spencerX ---17 days
No.5 fpd ---15 days

获封10系列大神的是！
“不可思议神奇无比全满贯大神”---attractg、大米 (两连冠！！)
“10系列大神” --- Victoriasong

恭喜他们！！
【插播over】详细出勤数据，请查看10系列出勤排行榜 #31http://forum.chasedream.com/GMAT_RC/thread-782296-4-1.html

【计时一】

New Device Hides, On Cue, from Infrared Cameras

Now you see it, now you don't. A new device invented at the Harvard School of Engineering and Applied Sciences (SEAS) can absorb 99.75% of infrared light that shines on it. When activated, it appears black to infrared cameras.
[attachimg=300,370]110641[/attachimg]

Composed of just a 180-nanometer-thick layer of vanadium dioxide (VO2) on top of a sheet of sapphire, the device reacts to temperature changes by reflecting dramatically more or less infrared light.
Announced November 26 in the journal Applied Physics Letters, and featured on its cover, this perfect absorber is ultrathin, tunable, and exceptionally well suited for use in a range of infrared optical devices.
Perfect absorbers have been created many times before, but not with such versatile properties. In a Fabry-Pérot cavity, for instance, two mirrors sandwich an absorbing material, and light simply reflects light back and forth until it's mostly all gone. Other devices incorporate surfaces with nanoscale metallic patterns that trap and eventually absorb the light.
"Our structure uses a highly unusual approach, with better results," says principal investigator Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS. "We exploit a kind of naturally disordered metamaterial, along with thin-film interference effects, to achieve one of the highest absorption rates we've ever seen. Yet our perfect absorber is structurally simpler than anything tried before, which is important for many device applications."


With collaborators at Harvard and at the University of California, San Diego, Capasso's research group took advantage of surprising properties in both of the materials they used.
Vanadium dioxide is normally an insulating material, meaning that it does not conduct electricity well. Take it from room temperature up to about 68 degrees Celsius, however, and it undergoes a dramatic transition. The crystal quickly rearranges itself as the temperature approaches a critical value. Metallic islands appear as specks, scattered throughout the material, with more and more appearing until it has become uniformly metallic.
【332】



【计时二】

"Right near this insulator-to-metal transition, you have a very interesting mixed medium, made up of both insulating and metallic phases," says coauthor Shriram Ramanathan, Associate Professor of Materials Science at SEAS, who synthesized the thin film. "It's a very complex and rich microstructure in terms of its electronic properties, and it has very unusual optical properties."
Those properties, when manipulated correctly, happen to be ideal for infrared absorption.
Meanwhile, the underlying sapphire substrate has a secret of its own. Usually transparent, its crystal structure actually makes it opaque and reflective, like a metal, to a narrow subset of infrared wavelengths.
The result is a combination of materials that internally reflects and devours incident infrared light.
"Both of these materials have lots of optical losses, and we've demonstrated that when light reflects between lossy materials, instead of transparent or highly reflective ones, you get strange interface reflections," explains lead author Mikhail Kats, a graduate student at SEAS. "When you combine all of those resulting waves, you can coax them to destructively interfere and completely cancel out. The net effect is that a film one hundred times thinner than the wavelength of the incident light can create perfect absorption."
The challenge for Capasso, Ramanathan, Kats, and their colleagues was not only to understand this behavior, but also to learn how to fabricate pure enough samples of the vanadium dioxide.
"Vanadium oxide can exist in many oxidation states, and only if you have VO2 does it go through a metal-insulator transition close to room temperature," Ramanathan explains. "We have developed several techniques in our lab to allow exquisite compositional and structural control, almost at the atomic scale, to grow such complex films. The resulting phase purity allows us to see these remarkable properties, which otherwise would be very difficult to observe."
Because the device can be easily switched between its absorbent and non-absorbent states, the possible applications are quite wide ranging and include bolometers (thermal imaging devices) with tunable absorption, spectroscopy devices, tunable filters, thermal emitters, radiation detectors, and equipment for energy harvesting.
"An ideal bolometer design needs to absorb all of the infrared light that falls on it, turning it to heat, and correspondingly its resistance should change a lot per degree change in temperature," notes Kats. "In principle, our new perfect absorber could be used to make incredibly sensitive thermal cameras."
【390】



【计时三】

Do Missing Jupiters Mean Massive Comet Belts?

Using ESA's Herschel space observatory, astronomers have discovered vast comet belts surrounding two nearby planetary systems known to host only Earth-to-Neptune-mass worlds. The comet reservoirs could have delivered life-giving oceans to the innermost planets.
[attachimg=521,509]110642[/attachimg]

In a previous Herschel study, scientists found that the dusty belt surrounding nearby star Fomalhaut must be maintained by collisions between comets.
In the new Herschel study, two more nearby planetary systems -- GJ 581 and 61 Vir -- have been found to host vast amounts of cometary debris.
Herschel detected the signatures of cold dust at 200ºC below freezing, in quantities that mean these systems must have at least 10 times more comets than in our own Solar System's Kuiper Belt.
GJ 581, or Gliese 581, is a low-mass M dwarf star, the most common type of star in the Galaxy. Earlier studies have shown that it hosts at least four planets, including one that resides in the 'Goldilocks Zone' -- the distance from the central sun where liquid surface water could exist.
Two planets are confirmed around G-type star 61 Vir, which is just a little less massive than our Sun.
The planets in both systems are known as 'super-Earths', covering a range of masses between 2 and 18 times that of Earth.
Interestingly, however, there is no evidence for giant Jupiter- or Saturn-mass planets in either system.
The gravitational interplay between Jupiter and Saturn in our own Solar System is thought to have been responsible for disrupting a once highly populated Kuiper Belt, sending a deluge of comets towards the inner planets in a cataclysmic event that lasted several million years.
【275】



【计时四】

"The new observations are giving us a clue: they're saying that in the Solar System we have giant planets and a relatively sparse Kuiper Belt, but systems with only low-mass planets often have much denser Kuiper belts," says Dr Mark Wyatt from the University of Cambridge, lead author of the paper focusing on the debris disc around 61 Vir.
"We think that may be because the absence of a Jupiter in the low-mass planet systems allows them to avoid a dramatic heavy bombardment event, and instead experience a gradual rain of comets over billions of years."
"For an older star like GJ 581, which is at least two billion years old, enough time has elapsed for such a gradual rain of comets to deliver a sizable amount of water to the innermost planets, which is of particular importance for the planet residing in the star's habitable zone," adds Dr Jean-Francois Lestrade of the Observatoire de Paris who led the work on GJ 581.
However, in order to produce the vast amount of dust seen by Herschel, collisions between the comets are needed, which could be triggered by a Neptune-sized planet residing close to the disc.
"Simulations show us that the known close-in planets in each of these systems cannot do the job, but a similarly-sized planet located much further from the star -- currently beyond the reach of current detection campaigns -- would be able to stir the disc to make it dusty and observable," says Dr Lestrade.
"Herschel is finding a correlation between the presence of massive debris discs and planetary systems with no Jupiter-class planets, which offers a clue to our understanding of how planetary systems form and evolve," says Göran Pilbratt, ESA's Herschel project scientist.
【288】



【计时五】

Use of Stem Cells in Personalized Medicine

Johns Hopkins researchers report concrete steps in the use of human stem cells to test how diseased cells respond to drugs. Their success highlights a pathway toward faster, cheaper drug development for some genetic illnesses, as well as the ability to pre-test a therapy's safety and effectiveness on cultured clones of a patient's own cells.

[attachimg=424,283]110643[/attachimg]

The project, described in an article published November 25 on the website of the journal Nature Biotechnology, began several years ago, when Gabsang Lee, D.V.M., Ph.D., an assistant professor at the Johns Hopkins University School of Medicine's Institute for Cell Engineering, was a postdoctoral fellow at Sloan-Kettering Institute in New York. To see if induced pluripotent stem cells (iPSCs) could be used to make specialized disease cells for quick and easy drug testing, Lee and his colleagues extracted cells from the skin of a person with a rare genetic disease called Riley-Day syndrome, chosen because it affects only one type of nerve cell that is difficult if not impossible to extract directly from a traditional biopsy. These traits made Riley-Day an ideal candidate for alternative ways of generating cells for study.
In a so-called "proof of concept" experiment, the researchers biochemically reprogrammed the skin cells from the patient to form iPSCs, which can grow into any cell type in the body. The team then induced the iPSCs to grow into nerve cells. "Because we could study the nerve cells directly, we could for the first time see exactly what was going wrong in this disease," says Lee. Some symptoms of Riley-Day syndrome are insensitivity to pain, episodes of vomiting, poor coordination and seizures; only about half of affected patients reach age 30.
【284】



【剩余部分】

In the recent research at Johns Hopkins and Memorial Sloan-Kettering, Lee and his co-workers used these same lab-grown Riley-Day nerve cells to screen about 7,000 drugs for their effects on the diseased cells. With the aid of a robot programmed to analyze the effects, the researchers quickly identified eight compounds for further testing, of which one -- SKF-86466 -- ultimately showed promise for stopping or reversing the disease process at the cellular level.
Lee says a clinical trial with SKF-86466 might not be feasible because of the small number of Riley-Day patients worldwide, but suggests that a closely related version of the compound, one that has already been approved by the U.S. Food and Drug Administration for another use, could be employed for the patients after a few tests.
The implications of the experiment reach beyond Riley-Day syndrome, however. "There are many rare, 'orphan' genetic diseases that will never be addressed through the costly current model of drug development," Lee explains. "We've shown that there may be another way forward to treat these illnesses."
Another application of the new stem cell process could be treatments tailored not only to an illness, but also to an individual patient, Lee says. That is, iPSCs could be made for a patient, then used to create a laboratory culture of, for example, pancreatic cells, in the case of a patient with type 1 diabetes. The efficacy and safety of various drugs could then be tested on the cultured cells, and doctors could use the results to help determine the best treatment. "This approach could move much of the trial-and-error process of beginning a new treatment from the patient to the petri dish, and help people to get better faster," says Lee.
【287】



【越障】

Using Biomarkers from Prehistoric Human Feces to Track Settlement and Agriculture

ScienceDaily (Nov. 26, 2012) — For researchers who study Earth's past environment, disentangling the effects of climate change from those related to human activities is a major challenge, but now University of Massachusetts Amherst geoscientists have used a biomarker from human feces in a completely new way to establish the first human presence, the arrival of grazing animals and human population dynamics in a landscape.
[attachimg=400,299]110644[/attachimg]

Doctoral student Robert D'Anjou and his advisor Raymond Bradley, director of the Climate System Research Center at UMass Amherst, with UMass colleagues Nick Balascio and David Finkelstein, describe their findings in the current online edition of Proceedings of the National Academy of Sciences.
"We are really excited about how well this method worked," D'Anjou says. "Without even knowing it, early settlers were recording their history for us, and in the most unlikely of ways, in their poop. The prehistoric settlers and their livestock pooped and their feces washed into the lake, which over time left a record of trace amounts of specific molecules that are only produced in the intestines of higher mammals. When you find these molecules at certain concentrations and in specific ratios, it provides an unmistakable indicator that people were living in the area."
Bradley adds, "This approach opens the door to other studies, where the presence of humans is uncertain; we believe it has great potential for much wider applications in archaeology."
D'Anjou carried out the work just north of the Arctic Circle, at Lake Liland in the Lofoten Islands in northern Norway, where humans were thought to have lived in prehistoric settlements from the early Iron Age through the Viking period. They extracted two sediment cores from the lake bottom and used radiocarbon measurements and the presence of volcanic ash from Iceland to establish their chronology. The sediments provided a continuous record extending back roughly 7,000 years.
Paleoclimatologists have long used markers in lakebed sediments, such as charcoal from humans' fires and pollen from cultivated plants, as a natural archive of environmental changes to estimate when humans first began having an impact. But these indirect indicators must be used with care when reconstructing the history of a place because it's not always clear that they indicate human activity in the same area.
By contrast, the presence of a molecular biomarker directly linked to humans, one transmitted through their bowel movements, offers "a strong human signal," as the authors put it, one that can be dated with "excellent chronological control." D'Anjou and colleagues extracted the compound coprostanol, a molecular marker formed from the digestion of cholesterol in the human gut, from the sediment, plus other sterols characteristic of other mammals to estimate the presence of sheep and cattle. From these, they were able to produce a long-term record of the presence and relative population size of humans extending back over thousands of years at the site.
In addition, the geoscientists used two other molecular markers to reconstruct the vegetation history: relative length of carbon molecules found in leaf waxes (different in forest and grassland), and pyrolytic polycyclic aromatic hydrocarbons (PAH) as evidence of fire in the Lake Liland area. They say that taken together, the sediment cores, vegetation changes and fire records clearly define a pre-settlement period with no detectable human activity in the lake's water catchment area from about 7,300 to 2,250 years ago.
At that point, however, changes in the background state appear in the record, marking an "abrupt shift" to significantly increased levels of pyrolytic PAH first, followed by increased human fecal material. This likely indicates that as people moved in, they first cleared the land by burning before establishing a permanent settlement, the researchers say. "This interpretation is bolstered," they add, by the leaf wax record that shows a "marked transition to a more grassland-dominated landscape beginning at this time."
【643】



【剩余部分】

After the initial influx of people to the region, D'Anjou and colleagues say the record shows a lull in human activity from about 2,040 to 1,900 years ago, reflected in all markers. After this, the human and livestock populations steadily increased to a local maximum around the year 500, based on the fecal record, then fell again to a second minimum around the year 850.
The climate scientists note a further decline in human activity and population to another minimum at about AD 1750 that coincided with the highest relative grassland cover for the entire 7,300-year history. Findings related to human activity over the past 7,300 years in northern Norway correlate well with other climate reconstructions, in particular summer temperature patterns indicating poor vs. fruitful growing seasons. This shows that the early settlers were vulnerable to small changes in summer temperature at this far northern location.
Overall, the authors say, the new fecal markers are likely to prove valuable in many other places, to distinguish natural from human factors that influenced the environment in the past.
【176】

miffyhui

1’55”
2’12”看不懂了
1’29”
1’26”
1’58”
4’00”

好久没来，读起来困难

artpresent

占楼，读完写完然后回家，谢谢辛苦找文章

starkeita

抢走地板~~~~今天更新的好快哦，辛苦啦

今天做的好奇怪啊……前四个速度基本都没看懂……尤其是前两个，大把大把单词不认识


速度一2‘24
速度二 2’42
速度三 1‘47
速度四 1’43
速度五 1‘56
越障 3’44


今天越障出奇的快……我只看了大致的框架，把类似FOR EXAMPLE的句子，还有介绍人物、机构的句子全部略过去了，不知道这样对不对啊……

喜欢吃橙子的猫

2:15
2:40
1:53
1:47
time ??
5:40  A new way to study past climate; molecules at certain concentrations ; an example of Lake Liland; old method--by contrast,new method has human signal ; example-vegetation(human activity in summer)

喜欢吃橙子的猫

新人驾到。
读文章很容易看了后面忘了前面，然后不知所云。。。
有什么好方法推荐？？

映雪瑶渊

11月29日    Speed 1    2    6    332    158     11-02                    Speed 2    1    47    390    219     
                    Speed 3    1    10    275    236     
                    Speed 4    1    40    288    173     
                    Speed 5    2    12    571    260     
                   obstacle    2    59    819    275

Jessiffer

第一次做阅读，真心累。阅读是硬伤,当前难以克服走神。不过还是相信坚持就会有收获~
1.3'00
2.3'20"
3.2'11”
4.1'59"
5.??!!10'30"
6.10'03"

CCcarol

占一个~
-------------------------------------------------------------------------------------------------------------------
物理什么的好头疼...
1‘42 2’30
这篇读下来顺多了~
1‘39 1’46 1‘55(JHU的医学果蓝好厉害！)

越障：全部 5‘45 越障整体感觉跟考试的风格很像~ 字数什么的也都正好~
Main Idea：Researchers is using Biomarkers to track settlement and argiculture

Structure:
*Doctoral student Robert D'Anjou and his advisor Raymond Bradley describe their findings in the current online edition of Proceedings of the National Academy of Sciences
*The prehistoric settlers and their livestock left evidences that provide an unmistakable indicator that people were living in the area where the presence of humans is uncertain before.
* The presence of a molecular biomarker offers "a strong human signal", which can be dated with "excellent chronological control."
*The record that reflected in all markers shows a lull in human activity from about 2,040 to 1,900 years ago.

yangreat

叮