【每日阅读训练第四期——速度越障3系列】【3-10】科技

CHRISTINE2010

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Mars Weather Report: Size of Particles in Martian Clouds of Carbon Dioxide Snow Calculated

ScienceDaily (June 19, 2012) — In the dead of a Martian winter, clouds of snow blanket the Red Planet's poles -- but unlike our water-based snow, the particles on Mars are frozen crystals of carbon dioxide. Most of the Martian atmosphere is composed of carbon dioxide, and in the winter, the poles get so cold -- cold enough to freeze alcohol -- that the gas condenses, forming tiny particles of snow.

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Now researchers at MIT have calculated the size of snow particles in clouds at both Martian poles from data gathered by orbiting spacecraft. From their calculations, the group found snow particles in the south are slightly smaller than snow in the north -- but particles at both poles are about the size of a red blood cell.
"These are very fine particles, not big flakes," says Kerri Cahoy, the Boeing Career Development Assistant Professor of Aeronautics and Astronautics at MIT. If the carbon dioxide particles were eventually to fall and settle on the Martian surface, "you would probably see it as a fog, because they're so small."
Cahoy and graduate student Renyu Hu worked with Maria Zuber, the E.A. Griswold Professor of Geophysics at MIT, to analyze vast libraries of data gathered from instruments onboard the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO). From the data, they determined the size of carbon dioxide snow particles in clouds, using measurements of the maximum buildup of surface snow at both poles. The buildup is about 50 percent larger at Mars' south pole than its north pole.
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Over the course of a Martian year (a protracted 687 days, versus Earth's 365), the researchers observed that as it gets colder and darker from fall to winter, snow clouds expand from the planet's poles toward its equator. The snow reaches halfway to the equator before shrinking back toward the poles as winter turns to spring, much like on Earth.
"For the first time, using only spacecraft data, we really revealed this phenomenon on Mars," says Hu, lead author of a paper published in the Journal of Geophysical Research, which details the group's results.
Diving through data
To get an accurate picture of carbon dioxide condensation on Mars, Hu analyzed an immense amount of data, including temperature and pressure profiles taken by the MRO every 30 seconds over the course of five Martian years (more than nine years on Earth). The researchers looked through the data to see where and when conditions would allow carbon dioxide cloud particles to form.
The team also sifted through measurements from the MGS' laser altimeter, which measured the topography of the planet by sending laser pulses to the surface, then timing how long it took for the beams to bounce back. Every once in a while, the instrument picked up a strange signal when the beam bounced back faster than anticipated, reflecting off an anomalously high point above the planet's surface. Scientists figured these laser beams had encountered clouds in the atmosphere.
Hu analyzed these cloud returns, looking for additional evidence to confirm carbon dioxide condensation. He looked at every case where a cloud was detected, then tried to match the laser altimeter data with concurrent data on local temperature and pressure. In 11 instances, the laser altimeter detected clouds when temperature and pressure conditions were ripe for carbon dioxide to condense. Hu then analyzed the opacity of each cloud -- the amount of light reflected -- and through calculations, determined the density of carbon dioxide in each cloud.
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To estimate the total mass of carbon dioxide snow deposited at both poles, Hu used earlier measurements of seasonal variations in the Martian gravitational field done by Zuber's group: As snow piles up at Mars' poles each winter, the planet's gravitational field changes by a tiny amount. By analyzing the gravitational difference through the seasons, the researchers determined the total mass of snow at the north and south poles. Using the total mass, Hu figured out the number of snow particles in a given volume of snow cover, and from that, determined the size of the particles. In the north, molecules of condensed carbon dioxide ranged from 8 to 22 microns, while particles in the south were a smaller 4 to 13 microns.
"It's neat to think that we've had spacecraft on or around Mars for over 10 years, and we have all these great datasets," Cahoy says. "If you put different pieces of them together, you can learn something new just from the data."
What can the size of snow tell us?
Hu says knowing the size of carbon dioxide snow cloud particles on Mars may help researchers understand the properties and behavior of dust in the planet's atmosphere. For snow to form, carbon dioxide requires something around which to condense -- for instance, a small silicate or dust particle. "What kinds of dust do you need to have this kind of condensation?" Hu asks. "Do you need tiny dust particles? Do you need a water coating around that dust to facilitate cloud formation?"
Just as snow on Earth affects the way heat is distributed around the planet, Hu says snow particles on Mars may have a similar effect, reflecting sunlight in various ways, depending on the size of each particle. "They could be completely different in their contribution to the energy budget of the planet," Hu says. "These datasets could be used to study many problems."
This research was funded by the Radio Science Gravity investigation of the NASA Mars Reconnaissance Orbiter mission.
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Antibacterials in Personal-Care Products Linked to Allergy Risk in Children

ScienceDaily (June 19, 2012) — Exposure to common antibacterial chemicals and preservatives found in soap, toothpaste, mouthwash and other personal-care products may make children more prone to a wide range of food and environmental allergies, according to new research from Johns Hopkins Children's Center.

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Results of the NIH-funded study are published online ahead of print June 18 in the Journal of Allergy and Clinical Immunology.
Using existing data from a national health survey of 860 children ages 6 to 18, Johns Hopkins researchers examined the relationship between a child's urinary levels of antibacterials and preservatives found in many personal-hygiene products and the presence of IgE antibodies in the child's blood. IgE antibodies are immune chemicals that rise in response to an allergen and are markedly elevated in people with allergies.
"We saw a link between level of exposure, measured by the amount of antimicrobial agents in the urine, and allergy risk, indicated by circulating antibodies to specific allergens," said lead investigator Jessica Savage, M.D., M.H.S., an allergy and immunology fellow at Hopkins.
The researchers caution that the findings do not demonstrate that antibacterials and preservatives themselves cause the allergies, but instead suggest that these agents play a role in immune system development.
The investigators say their findings are also consistent with the so-called hygiene hypothesis, which has recently gained traction as one possible explanation behind the growing rates of food and environmental allergies in the developed world. The hypothesis suggests that early childhood exposure to common pathogens is essential in building healthy immune responses. Lack of such exposure, according to the theory, can lead to an overactive immune system that misfires against harmless substances such as food proteins, pollen or pet dander.
"The link between allergy risk and antimicrobial exposure suggests that these agents may disrupt the delicate balance between beneficial and bad bacteria in the body and lead to immune system dysregulation, which in turn raises the risk of allergies," Savage added.
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In the study, those with the highest urine levels of triclosan -- an antibacterial agent used in soaps, mouthwash and toothpaste -- had the highest levels of food IgE antibodies, and therefore the highest allergy risk, compared with children with the lowest triclosan levels. Children with the highest urinary levels of parabens -- preservatives with antimicrobial properties used in cosmetics, food and medications -- were more likely to have detectable levels of IgE antibodies to environmental allergens like pollen and pet dander, compared with those with low paraben levels.
The team initially zeroed in on seven ingredients previously shown to disrupt endocrine function in lab and animal studies. These compounds were bisphenol A -- found in plastics -- and triclosan, benzophenone-3 and propyl, methyl, butyl and ethyl parabens, found in personal-hygiene products and some foods and medications. Interestingly, triclosan and propyl and butyl parabens, all of which have antimicrobial properties, were the only ones associated with increased allergy risk in the current study, the researchers noted.
"This finding highlights the antimicrobial properties of these agents as a probable driving force behind their effect on the immune system," said senior investigator Corinne Keet, M.D., M.S., an allergist at Johns Hopkins Children's Center.
Children with the highest urine levels of triclosan had nearly twice the risk of environmental allergies as children with the lowest urinary concentrations. Those with highest levels of propyl paraben in the urine had twice the risk of an environmental allergy. Food allergy risk was more than twice as pronounced in children with the highest levels of urinary triclosan as in children with the lowest triclosan levels. High paraben levels in the urine were not linked to food allergy risk.
To clarify the link between antimicrobial agents and allergy development, the researchers are planning a long-term study in babies exposed to antibacterial ingredients at birth, following them throughout childhood.
he research was funded by the National Institutes of Health training grant number T32AI007056-31.
Co-investigators on the research were Elizabeth Matsui, M.D., M.H.S., and Robert Wood, M.D., both of Hopkins.
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Brothers in Arms: Commensal Bacteria Help Fight Viruses

ScienceDaily (June 18, 2012) — Healthy humans harbor an enormous and diverse group of bacteria and other bugs that live within their intestines. These microbial partners provide beneficial aid in multiple ways -- from helping digest food to the development of a healthy immune system. In a new study published online in the journal Immunity, David Artis, PhD, associate professor of Microbiology, and Michael Abt, PhD, a postdoctoral researcher in the Artis lab, Perelman School of Medicine, University of Pennsylvania, show that commensal bacteria are also essential to fight off viral infections.

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"From our studies in mice, we found that signals derived from these beneficial microbes are essential for optimal immune responses to experimental viral infections," says Artis. "In one way we could consider these microbes as our 'brothers in arms' in the fight against infectious diseases." Artis is also an associate professor of Pathobiology in the Penn School of Veterinary Medicine.
Signals from commensal bacteria influence immune-cell development and susceptibility to infectious or inflammatory diseases. Commensal microbial communities colonize barrier surfaces of the skin, vaginal, upper respiratory, and gastrointestinal tracts of mammals and consist of bacteria, fungi, protozoa, and viruses. The largest and most diverse microbial communities live in the intestine.
Previous studies in patients have associated alterations in bacterial communities with susceptibility to diabetes, obesity, cancer, inflammatory bowel disease, allergy, and other disorders. Despite knowing all of this, exactly how commensal bacteria regulate immunity after being exposed to pathogens is not well understood.
To get a better picture of how these live-in bacteria are beneficial, the Artis lab used several lines of investigation. First, they demonstrated that mice -- treated with antibiotics to reduce numbers of commensal bacteria -- exhibit an impaired antiviral immune response and a substantially delayed clearance of a systemic virus or influenza virus that infects the airways. What's more, the treated mice had severely damaged airways and increased rate of death after the experimental influenza virus infection, demonstrating that alterations in commensal bacterial communities can have a negative impact on immunity against viruses.
Next, they profiled the genes that were expressed in immune cells called macrophages isolated from the antibiotic-treated mice. These data revealed a decreased expression of genes associated with antiviral immunity. In addition, macrophages from antibiotic-treated mice showed defective responses to interferons, proteins made and released in response to viruses, bacteria, parasites, or tumor cells. Under normal circumstances, interferons facilitate communication between cells to trigger the immune cells that attack pathogens or tumors. The antibiotic-treated mice also had an impaired capacity to limit viral replication. However, when mice were treated with a compound that restored interferon responsiveness, protective antiviral immunity was re-established.
"It is remarkable that signals derived from one type of microbe, in this case bacteria, can have such a profound effect on immune responses to viruses that are a very different type of microbe," says first author Abt. "Just like we would set a thermostat to regulate when a heater should come on, our studies indicate that signals derived from commensal bacteria are required to set the activation threshold of the immune system."
Taken together, these lines of evidence indicate that signals from commensal bacteria beneficially stimulate immune cells in a way that is optimal for antiviral immunity. "Although more work needs to be done, these findings could illuminate new ways to promote better immunity to potentially life-threatening viral infections," adds Artis.
This research is supported by the National Institutes of Health National Institute of Allergy and Infectious Disease(grants AI061570, AI087990, AI074878, AI095608, AI091759, AI095466, AI071309, AI078897, AI095608, AI083022, AI077098, HHSN266200500030C, T32-AI05528, T32-AI007532, T32-RR007063, K08-DK093784, T32-AI007324); the Irvington Institute Postdoctoral Fellowship of the Cancer Research Institute; the Burroughs Wellcome Fund, the National Institute of Diabetes and Digestive and Kidney Disease Center for the Molecular Studies in Digestive and Liver Disease and the Molecular Pathology and Imaging Core.
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teddybearj4

咩哈哈~sofa~~~
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速度：
1'30     2'21    2'07     2'32      2'19  
越障：6'12(就明白了实验的目的和结论，中间作用机制各种乱呀~)
Main idea:
A few of the institutes are funded to study how the commensal bacteria help fight viruses.
Experiment:
*When mice were exposed to virus, their amount of commensal bacteria is decrease. This implies that the commensal bacteria have a negative impact on the immuning virus(?)
*macrophages.reveals a decreased expression of genes associated with antiviral immunity.(T.T)
Conclusion:
Commensal bacteria beneficially stimulate immune cells in a way that is optimal for antiviral immunity.
(像这种包含机制性的科技类文章，读的时候感觉逻辑关系把握得还是不是很好，第一遍读过去experiment分析Commensal bacteria 在virus入侵的机理的时候，还是好糊涂，求大家的方法！)

jiline

1'30
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越障：
3‘55
Commensal bacteria are essential to fight off viral infections.
They made experiements on mice with two situations and found those beneficial bacteria stimulate immue cells in a way that is optimal for antiviral immunity.

猫咪团团

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commensal virus benefit immunal system
an experiment:
mice with anti-comensal cell-> bad immunal system
mice with anti-biotic -> more microphage-> better immunal system

conclusion: commensal virus could arouse the immunal cells to optionally produce anti-virus cells.

spencerX

期末考试到底让我落下多少...现在考完了，人又生病了...我怎么那么倒霉...呜呜，最迟明天一定要开始继续征途！！

铁板神猴

期末考试到底让我落下多少...现在考完了，人又生病了...我怎么那么倒霉...呜呜，最迟明天一定要开始继续征途！！

-- by 会员 spencerX (2012/6/20 11:55:33)

慢慢来~take it easy~

铁板神猴

Christine的图总那么炫！
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1'35''
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jolene91

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5.41有一些bacteria在人体内起着重要的作用，研究表明commensal bacteria可以抵抗病毒感染。在人体的各个部位都有commensal microbial communities，但最多的在肠里面。它可以调节免疫，通过小白鼠的实验，其中用了两种方法，一是用抗生素使cb减少，导致了更多小白鼠的死亡或者是严重受伤，二是调节基因，antiviral immunity又下降。。科学家总结，然后说这可以提供新的方法提高免疫。。

暮已央

第一张星球的图图好漂亮~(*^__^*) 嘻嘻……
速度：
1:20；
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1:50
和地球不一样，火星大气层主要由CO2组成，火星冬天很冷，可以冻结酒精；也有小雪粒，在火星南极的比北极的要小，不过怎么也大不过一个红细胞；
在研究了火星的宇宙飞船传回来的资料，研究人员Hu发现火星上的小雪粒在秋天到冬天的时候会从两极移向赤道，春天又会回去，这点和地球很像；
现在正在研究关于CO2的凝结问题；
通过很多年···的观察，发现火星的重力会随着季节改变，小雪粒的大小在南北极不同，这也可以提出一些关于CO2凝结的问题，比如说灰尘颗粒啊~
同时也发现了雪在火星上也可以像地球一样反射阳光；
关于抗菌剂和防腐剂的应用，它们可能在免疫系统中扮演了角色，影响着儿童的过敏症；
对此做的实验表明t,p,bp是三种与过敏的风险联系上的抗菌剂；
为了更好地发现过敏与抗菌的联系，科学家准备在婴儿身上实验，并观察他们的童年情况。
越障：
4:05；
我们已知的一些细菌可以帮助人们的健康，像是促进消化之类的，现在发现有些细菌还可以当人类的“左右手”（还是好兄弟？）o(╯□╰)o
帮助人们对抗病毒感染。MIT的一个研究人在老鼠身上进行试验：
first:好像是让老鼠免疫力下降，感染病毒？
next:提取genes，然后干啥了···
in addition:发现老鼠的免疫系统重建了。
得出结论，这个结果会产生深远的影响，并提升人们对抗病毒感染的认识。

小胖宝

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