【每日阅读训练第四期——速度越障4系列】【4-17】科技

CHRISTINE2010

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Why Is Earth So Dry? Planet Formed from Rocky Debris in Hotter Region, Inside of Solar System's 'Snow Line'

ScienceDaily (July 17, 2012) — With large swaths of oceans, rivers that snake for hundreds of miles, and behemoth glaciers near the north and south poles, Earth doesn't seem to have a water shortage. And yet, less than one percent of our planet's mass is locked up in water, and even that may have been delivered by comets and asteroids after Earth's initial formation.

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Astronomers have been puzzled by Earth's water deficiency. The standard model explaining how the solar system formed from a protoplanetary disk, a swirling disk of gas and dust surrounding our Sun, billions of years ago suggests that our planet should be a water world. Earth should have formed from icy material in a zone around the Sun where temperatures were cold enough for ices to condense out of the disk. Therefore, Earth should have formed from material rich in water. So why is our planet comparatively dry?


A new analysis of the common accretion-disk model explaining how planets form in a debris disk around our Sun uncovered a possible reason for Earth's comparative dryness. Led by Rebecca Martin and Mario Livio of the Space Telescope Science Institute in Baltimore, Md., the study found that our planet formed from rocky debris in a dry, hotter region, inside of the so-called "snow line." The snow line in our solar system currently lies in the middle of the asteroid belt, a reservoir of rubble between Mars and Jupiter; beyond this point, the Sun's light is too weak to melt the icy debris left over from the protoplanetary disk. Previous accretion-disk models suggested that the snow line was much closer to the Sun 4.5 billion years ago, when Earth formed.
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"Unlike the standard accretion-disk model, the snow line in our analysis never migrates inside Earth's orbit," Livio said. "Instead, it remains farther from the Sun than the orbit of Earth, which explains why our Earth is a dry planet. In fact, our model predicts that the other innermost planets, Mercury, Venus, and Mars, are also relatively dry. "


The results have been accepted for publication in the journal Monthly Notices of the Royal Astronomical Society.


In the conventional model, the protoplanetary disk around our Sun is fully ionized (a process where electrons are stripped off of atoms) and is funneling material onto our star, which heats up the disk. The snow line is initially far away from the star, perhaps at least one billion miles. Over time, the disk runs out of material, cools, and draws the snow line inward, past Earth's orbit, before there is sufficient time for Earth to form.


"If the snow line was inside Earth's orbit when our planet formed, then it should have been an icy body," Martin explained. "lanets such as Uranus and Neptune that formed beyond the snow line are composed of tens of percents of water. But Earth doesn't have much water, and that has always been a puzzle."


Martin and Livio's study found a problem with the standard accretion-disk model for the evolution of the snow line. "We said, wait a second, disks around young stars are not fully ionized," Livio said. "They're not standard disks because there just isn't enough heat and radiation to ionize the disk."


"Very hot objects such as white dwarfs and X-ray sources release enough energy to ionize their accretion disks," Martin added. "But young stars don't have enough radiation or enough infalling material to provide the necessary energetic punch to ionize the disks."
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So, if the disks aren't ionized, mechanisms that would allow material to flow through the region and fall onto the star are absent. Instead, gas and dust orbit around the star without moving inward, creating a so-called "dead zone" in the disk. The dead zone typically extends from about 0.1 astronomical unit to a few astronomical units beyond the star. (An astronomical unit is the distance between Earth and the Sun, which is roughly 93 million miles.) This zone acts like a plug, preventing matter from migrating towards the star. Material, however, piles up in the dead zone and increases its density, much like people crowding around the entrance to a concert, waiting for the gates to open.


The dense matter begins to heat up by gravitational compression. This process, in turn, heats the area outside the plug, vaporizing the icy material and turning it into dry matter. Earth forms in this hotter region, which extends to around a few astronomical units beyond the Sun, from the dry material. Martin and Livio's altered version of the standard model explains why Earth didn't wind up with an abundance of water.


Martin cautioned that the revised model is not a blueprint for how all disks around young stars behave. "Conditions within the disk will vary from star to star," Livio said, "and chance, as much as anything else, determined the precise end results for our Earth."
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【附加：图片说明】
A Tale of Two Disk Models: This illustration of two different disk models shows overhead views of the structure of the protoplanetary disk that encircled the newborn Sun 4.6 billion years ago. The Sun's family of planets agglomerated from dust and ices within the disk. The major difference between the two models is the location of the so-called snow line, which divides a warm, dry area of the disk from an icy, turbulent region. In the standard disk model, shown at left, Earth formed beyond the snow line, in an icy region. Our planet should, therefore, contain lots of water because it formed from ices that would have been a major fraction of its composition. However, it's estimated that less than 1 percent of Earth's mass is locked up in water, which has puzzled scientists. In the new disk model, shown at right, Earth formed in a warmer, dry region, outside the snow line, which is much farther away from the Sun. This model explains why Earth is comparatively dry. It provides new insights into estimates of the abundance of Earth-like planets in the galaxy. (Credit: NASA, ESA, and A. Feild (STScI); Science: NASA, ESA, and R. Martin and M. Livio (STScI))
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Infants' Recognition of Speech More Sophisticated Than Previously Known

ScienceDaily (July 17, 2012) — The ability of infants to recognize speech is more sophisticated than previously known, researchers in New York University's Department of Psychology have found. Their study, which appears in the journal Developmental Psychology, showed that infants, as early as nine months old, could make distinctions between speech and non-speech sounds in both humans and animals.

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"Our results show that infant speech perception is resilient and flexible," explained Athena Vouloumanos, an assistant professor at NYU and the study's lead author. "This means that our recognition of speech is more refined at an earlier age than we'd thought."


It is well-known that adults' speech perception is fine-tuned -- they can detect speech among a range of ambiguous sounds. But much less is known about the capability of infants to make similar assessments. Understanding when these abilities become instilled would shed new light on how early in life we develop the ability to recognize speech.


In order to gauge the aptitude to perceive speech at any early age, the researchers examined the responses of infants, approximately nine months in age, to recorded human and parrot speech and non-speech sounds. Human (an adult female voice) and parrot speech sounds included the words "truck," "treat," "dinner," and "two." The adult non-speech sounds were whistles and a clearing of the throat while the parrot non-speech sounds were squawks and chirps. The recorded parrot speech sounds were those of Alex, an African Gray parrot that had the ability to talk and reason and whose behaviors were studied by psychology researcher Irene Pepperberg.
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Since infants cannot verbally communicate their recognition of speech, the researchers employed a commonly used method to measure this process: looking longer at what they find either interesting or unusual. Under this method, looking longer at a visual paired with a sound may be interpreted as a reflection of recognition. In this study, sounds were paired with a series of visuals: a checkerboard-like image, adult female faces, and a cup.


The results showed that infants listened longer to human speech compared to human non-speech sounds regardless of the visual stimulus, revealing the ability recognize human speech independent of the context.
Their findings on non-human speech were more nuanced. When paired with human-face visuals or human artifacts like cups, the infants listened to parrot speech longer than they did non-speech, such that their preference for parrot speech was similar to their preference for human speech sounds. However, this did not occur in the presence of other visual stimuli. In other words, infants were able to distinguish animal speech from non-speech, but only in some contexts.


"arrot speech is unlike human speech, so the results show infants have the ability to detect different types of speech, even if they need visual cues to assist in this process," explained Vouloumanos.


The study's other co-author was Hanna Gelfand, an undergraduate at NYU's College of Arts and Science at the time of the study and currently a graduate student in the San Diego State University/University of California, San Diego Joint Doctoral Program in Language and Communicative Disorders.
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New Evidence Links Immune Irregularities to Autism, Mouse Study Suggests

ScienceDaily (July 17, 2012) — Scientists at the California Institute of Technology (Caltech) pioneered the study of the link between irregularities in the immune system and neurodevelopmental disorders such as autism a decade ago. Since then, studies of postmortem brains and of individuals with autism, as well as epidemiological studies, have supported the correlation between alterations in the immune system and autism spectrum disorder.

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What has remained unanswered, however, is whether the immune changes play a causative role in the development of the disease or are merely a side effect. Now a new Caltech study suggests that specific changes in an overactive immune system can indeed contribute to autism-like behaviors in mice, and that in some cases, this activation can be related to what a developing fetus experiences in the womb.


The results appear in a paper this week in the Proceedings of the National Academy of Sciences (PNAS).


"We have long suspected that the immune system plays a role in the development of autism spectrum disorder," says Paul Patterson, the Anne P. and Benjamin F. Biaggini Professor of Biological Sciences at Caltech, who led the work. "In our studies of a mouse model based on an environmental risk factor for autism, we find that the immune system of the mother is a key factor in the eventual abnormal behaviors in the offspring."


The first step in the work was establishing a mouse model that tied the autism-related behaviors together with immune changes. Several large epidemiological studies -- including one that involved tracking the medical history of every person born in Denmark between 1980 and 2005 -- have found a correlation between viral infection during the first trimester of a mother's pregnancy and a higher risk for autism spectrum disorder in her child. To model this in mice, the researchers injected pregnant mothers with a viral mimic that triggered the same type of immune response a viral infection would.


"In mice, this single insult to the mother translates into autism-related behavioral abnormalities and neuropathologies in the offspring," says Elaine Hsiao, a graduate student in Patterson's lab and lead author of the PNAS paper.


The team found that the offspring exhibit the core behavioral symptoms associated with autism spectrum disorder -- repetitive or stereotyped behaviors, decreased social interactions, and impaired communication. In mice, this translates to such behaviors as compulsively burying marbles placed in their cage, excessively self grooming, choosing to spend time alone or with a toy rather than interacting with a new mouse, or vocalizing ultrasonically less often or in an altered way compared to typical mice.


Next, the researchers characterized the immune system of the offspring of mothers that had been infected and found that the offspring display a number of immune changes. Some of those changes parallel those seen in people with autism, including decreased levels of regulatory T cells, which play a key role in suppressing the immune response. Taken together, the observed immune alterations add up to an immune system in overdrive -- one that promotes inflammation.


"Remarkably, we saw these immune abnormalities in both young and adult offspring of immune-activated mothers," Hsiao says. "This tells us that a prenatal challenge can result in long-term consequences for health and development."


With the mouse model established, the group was then able to test whether the offspring's immune problems contribute to their autism-related behaviors. In the most revealing test of this hypothesis, the researchers were able to correct many of the autism-like behaviors in the offspring of immune-activated mothers by giving the offspring a bone-marrow transplant from typical mice. The normal stem cells in the transplanted bone marrow not only replenished the immune system of the host animals but altered their autism-like behavioral impairments.


The researchers emphasize that because the work was conducted in mice, the results cannot be readily extrapolated to humans, and they certainly do not suggest that bone-marrow transplants should be considered as a treatment for autism. They also have yet to establish whether it was the infusion of stem cells or the bone-marrow transplant procedure itself -- complete with irradiation -- that corrected the behaviors.


However, Patterson says, the results do suggest that immune irregularities in children could be an important target for innovative immune manipulations in addressing the behaviors associated with autism spectrum disorder. By correcting these immune problems, he says, it might be possible to ameliorate some of the classic developmental delays seen in autism.


In future studies, the researchers plan to examine the effects of highly targeted anti-inflammatory treatments on mice that display autism-related behaviors and immune changes. They are also interested in considering the gastrointestinal (GI) bacteria, or microbiota, of such mice. Coauthor Sarkis Mazmanian, a professor of biology at Caltech, has shown that gut bacteria are intimately tied to the function of the immune system. He and Patterson are investigating whether changes to the microbiota of these mice might also influence their autism-related behaviors.


Along with Patterson, Hsiao, and Mazmanian, additional Caltech coauthors on the PNAS paper, "Modeling an autism risk factor in mice leads to permanent immune dysregulation," are Mazmanian lab manager Sara McBride and former graduate student Janet Chow. The work was supported by an Autism Speaks Weatherstone Fellowship, National Institutes of Health Graduate Training Grants, a Weston Havens Foundation grant, a Gregory O. and Jennifer W. Johnson Caltech Innovation Fellowship, a Caltech Innovation grant, and a Congressionally Directed Medical Research Program Idea Development Award.
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草莓葡萄

抢到了沙发~~

2:13： 地球水资源丰富，产生的可能原因--在地球产生初期有冰带融入到地球
2:00： 地球上的水比预想中的少， 提出了新的model解释， 可能是新生的star没有足够的energy使冰带融化
1:32： 没读懂o(╯□╰)o
1:45： human & animal distinguish speech and non-speech earlier than humen have thought
1:53： recent researches for the method of measureing infants and parrot 's  ability of distinguishing  sheeches
6:53: 免疫系统对自闭是有相关性的， 对老鼠的实验得出这种结论； 已经实行的实验分三步骤解释了这种结果， 但是老鼠实验并不一定对人类也有相同的结果， future study 需要做的事情。。。。

暮已央

来了来了~
计时：
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1:15；
附加：1:05；
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越障：
6:25；
先查了一下词典，那个ASD是自闭症谱系障碍···
一个新研究表明，免疫系统的不规则很可能与ASD有关
科学家认为免疫系统在一系列精神疾病中扮演关键角色，
现在的问题是还不知道免疫系统在ASD疾病中扮演什么角色，又是起了哪方面的作用（正向反向）
研究人员建立了一个老鼠实验模型，通过丹麦的几十年出生人口中ASD患者与母亲的免疫系统changes，
表明很可能ASD是由母亲怀孕时就有潜在风险的，于是给母鼠注射XX，使她们的免疫系统改变来模拟
研究发现出生的后代的确有不少ASD症状，研究人员又通过骨髓移植到他们细胞中改变免疫系统，发现ASD减缓
但由于是在老鼠身上试验，所以能否在人类身上奏效还不肯定
但是值得说的是免疫系统一定是ASD等一系列精神疾病的key point
研究人员下一步要研究G和M，认为这两者也很可能与ASD相关
最后是参与实验的一堆人~~~

风静静

2:16
1:53
1:58
1:53
1:45
6:36

科学家们怀疑，免疫系统障碍和神经错乱有关系。
然后他们在老鼠身上做了实验
给老鼠注入了一种什么物质，是的鼠妈妈免疫系统障碍，鼠宝宝出生有神经错乱的表现（记不清楚了）
然后得出，妈妈对后代有很大影响。
额，然后后面的，不记得了（稍微走了下神，就回不来了，T.T）

ladyMcc

来鸟~

haibaraaifly

遭了，2个月没练完全lost了啊...啥都记不起来了...
Scientists built a mouse model to test whether immune changes can lead to autism.
Firstly, they inject something like virus, bringing the immune system of mice disorder. Then they found that the offspring of the injected mother actually showed some behavior of autism.
Secondly, they tried to find out whether it was the immune irregularities that caused the autism and it turned out it is.

cleotina

第一页  第一页

7-18
2'03
why earth so much dry?  as the model show, the earth should be dry. so this article is explain the reason. thers is a snow line around the earth, and it is changing. thus the earth becoma dry.

1'50
the stars that nearer the sun more than earth do are even more drier. so the rasearchers give more illustration about the modling, and they also interpretate that the stars new born are not heat to punch to ionize the disks
1'20''
原理不甚明白

1'16
the lauguage recognization skill of infant is more sophiscated than the scientist thought before.  
the rasearcher made a experients about this, they found that a nine moths infant can recognize the voice of the language from other noies.
1'18
infant can also distinguish the voice of parrot and the human.
5'30''
好困好困 偷个懒~~

esther小冰

科技文真的是硬伤啊，硬伤

jiline

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越障：
5‘24
Specific changes in an overactive immune system can indeed contribute to autism-like behaviors in mice.
The immune system of mother is a key factor in the abnormal behaviors in the offspring.
Do the experiment:
Viral infection and found the offspring exhibit the autism spectrum disorder and immune changes.
Giving the offspring a bone-marrow transplant can corret many of the autism-like behaviors, but the effecitve method can not be readily extrapolated to humans. Because the work was conducted in mice.
Future studies: examine the effects of hightly targeted anti-inflammatory treatments on mice that display antism-related behaviors and immune changes.

bet

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5’54“
文章介绍了免疫反应与自闭症的相关性研究。通过老鼠的实验证明，母亲的免疫反应会使胎儿产生自闭行为。而且已经产生的自闭行为，可以靠骨髓移植治愈。但是这个实验结果还不能马上迁移到人类身上，治愈的实验也有可能是巧合。但是实验的结果还是会对解决儿童迟缓发育的问题产生积极影响。此外科学家还研究了多种和免疫相关的细菌。