【每日阅读训练第四期——速度越障9系列】【9-3】科技

CHRISTINE2010

【计时一】

Planet Found in Nearest Star System to Earth: HARPS Instrument Finds Earth-Mass Exoplanet Orbiting Alpha Centauri B

ScienceDaily (Oct. 16, 2012) — European astronomers have discovered a planet with about the mass of Earth orbiting a star in the Alpha Centauri system -- the nearest to Earth. It is also the lightest exoplanet ever discovered around a star like the Sun. The planet was detected using the HARPS instrument on the 3.6-metre telescope at ESO's La Silla Observatory in Chile.
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Alpha Centauri is one of the brightest stars in the southern skies and is the nearest stellar system to our Solar System -- only 4.3 light-years away. It is actually a triple star -- a system consisting of two stars similar to the Sun orbiting close to each other, designated Alpha Centauri A and B, and a more distant and faint red component known as Proxima Centauri [1]. Since the nineteenth century astronomers have speculated about planets orbiting these bodies, the closest possible abodes for life beyond the Solar System, but searches of increasing precision had revealed nothing. Until now.
"Our observations extended over more than four years using the HARPS instrument and have revealed a tiny, but real, signal from a planet orbiting Alpha Centauri B every 3.2 days," says Xavier Dumusque (Geneva Observatory, Switzerland and Centro de Astrofisica da Universidade do Porto, Portugal), lead author of the paper. "It's an extraordinary discovery and it has pushed our technique to the limit!"
The European team detected the planet by picking up the tiny wobbles in the motion of the star Alpha Centauri B created by the gravitational pull of the orbiting planet [2]. The effect is minute -- it causes the star to move back and forth by no more than 51 centimetres per second (1.8 km/hour), about the speed of a baby crawling. This is the highest precision ever achieved using this method.
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【计时二】

Alpha Centauri B is very similar to the Sun but slightly smaller and less bright. The newly discovered planet, with a mass of a little more than that of Earth [3], is orbiting about six million kilometres away from the star, much closer than Mercury is to the Sun in the Solar System. The orbit of the other bright component of the double star, Alpha Centauri A, keeps it hundreds of times further away, but it would still be a very brilliant object in the planet's skies.
The first exoplanet around a Sun-like star was found by the same team back in 1995 and since then there have been more than 800 confirmed discoveries, but most are much bigger than Earth, and many are as big as Jupiter [4]. The challenge astronomers now face is to detect and characterise a planet of mass comparable to Earth that is orbiting in the habitable zone [5] around another star. The first step has now been taken [6].
"This is the first planet with a mass similar to Earth ever found around a star like the Sun. Its orbit is very close to its star and it must be much too hot for life as we know it," adds Stéphane Udry (Geneva Observatory), a co-author of the paper and member of the team, "but it may well be just one planet in a system of several. Our other HARPS results, and new findings from Kepler, both show clearly that the majority of low-mass planets are found in such systems."
"This result represents a major step towards the detection of a twin Earth in the immediate vicinity of the Sun. We live in exciting times!" concludes Xavier Dumusque.
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Notes
[1] The components of a multiple star are named by adding uppercase letters to the name of the star. Alpha Centauri A is the brightest component, Alpha Centauri B is the slightly fainter second star and Alpha Centauri C is the much fainter Proxima Centauri. Proxima Centauri is slightly closer to Earth than A or B and hence is formally the closest star.
[2] HARPS measures the radial velocity of a star -- its speed towards or away from Earth -- with extraordinary precision. A planet in orbit around a star causes the star to regularly move towards and away from a distant observer on Earth. Due to the Doppler effect, this radial velocity change induces a shift of the star's spectrum towards longer wavelengths as it moves away (called a redshift) and a blueshift (towards shorter wavelengths) as it approaches. This tiny shift of the star's spectrum can be measured with a high-precision spectrograph such as HARPS and used to infer the presence of a planet.
[3] Using the radial velocity method, astronomers can only estimate a minimum mass for a planet as the mass estimate also depends on the tilt of the orbital plane relative to the line of sight, which is unknown. But, from a statistical point of view, this minimum mass is often close to the real mass of the planet.
[4] NASA's Kepler mission has found 2300 candidate planets using an alternative method -- searching for the slight drop in the brightness of a star as a planet passes in front of it (transits) and blocks some of the light. The majority of planet candidates detected by this transit method are very distant from us. But, in contrast, the planets found by HARPS are around stars close to the Sun -- with the new discovery being the closest yet. This makes them better targets for many kinds of additional follow-up observations such as characterising the planet's atmosphere.
[5] The habitable zone is a narrow annular region around a star in which water may be present in liquid form if conditions are right.
[6] ESPRESSO, the Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations, is to be installed on the ESO Very Large Telescope. Currently undergoing final design, it is scheduled to start operating in late-2016 or early-2017. ESPRESSO will feature radial velocity precision of 0.35 km/hour or less. For comparison, Earth induces a 0.32 km/hour radial velocity on the Sun. This resolution should thus enable ESPRESSO to discover Earth-mass planets in the habitable zone. The ESPRESSO consortium is led by team members responsible for the current discovery.




【计时三】

Scientists Identify Likely Origins of Vertebrate Air Breathing

ScienceDaily (Oct. 16, 2012) — University of Alaska Fairbanks scientists have identified what they think is the ancestral trait that allowed for the evolution of air breathing in vertebrates.



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"To breathe air with a lung you need more than a lung, you need neural circuitry that is sensitive to carbon dioxide," said Michael Harris, a UAF neuroscientist and lead researcher on a project investigating the mechanisms that generate and control breathing.


"It's the neural circuitry that allows air-breathing organisms to take in oxygen, which cells need to convert food into energy, and expel the waste carbon dioxide resulting from that process," he said. "I'm interested in where that carbon-dioxide-sensitive neural circuit, called a rhythm generator, came from."


Harris and colleagues think that air breathing likely evolved in an ancestral vertebrate that did not have a lung, but did have a rhythm generator.


"We try to find living examples of primitive non-air-breathing ancestors, like lamprey, and then look for evidence of a rhythm generator that did something other than air breathing," Harris said.


Lampreys are ancient fish that have characteristics similar to the first vertebrates. They do not have lungs and do not breathe air. As larvae, they live in tubes dug into soft mud and breathe and feed by pumping water through their bodies. When mud or debris clogs a lamprey's tube, they use a cough-like behavior to expel water and clear the tube. A rhythm generator in their brain controls that behavior.


A video clip recorded in Harris' lab shows the difference between gill ventilation and a 'cough' in a larval lamprey. The 'cough' occurs at about the 9 second mark.


"We thought the lamprey 'cough' closely resembled air breathing in amphibians," said Harris. "When we removed the brains from lampreys and measured nerve activity that would normally be associated with breathing, we found patterns that resemble breathing and found that the rhythm generator was sensitive to carbon dioxide."


Air breathing evolved in fish and allowed the movement of vertebrates to land and the evolution of reptiles, birds and mammals. Without a carbon-dioxide-sensitive rhythm generator, the structure that would become the lung might not have worked as a lung.


"The evolution of lung breathing may be a repurposing of carbon dioxide sensitive cough that already existed in lungless vertebrates, like the lamprey," said Harris.
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【计时四】

Ice Age Polarity Reversal Was Global Event: Extremely Brief Reversal of Geomagnetic Field, Climate Variability, and Super Volcano

ScienceDaily (Oct. 16, 2012) — Some 41,000 years ago, a complete and rapid reversal of the geomagnetic field occured. Magnetic studies of the GFZ German Research Centre for Geosciences on sediment cores from the Black Sea show that during this period, during the last ice age, a compass at the Black Sea would have pointed to the south instead of north.

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Moreover, data obtained by the research team formed around GFZ researchers Dr. Norbert Nowaczyk and Prof. Helge Arz, together with additional data from other studies in the North Atlantic, the South Pacific and Hawaii, prove that this polarity reversal was a global event. Their results are published in the latest issue of the scientific journal Earth and Planetary Science Letters.
What is remarkable is the speed of the reversal: "The field geometry of reversed polarity, with field lines pointing into the opposite direction when compared to today's configuration, lasted for only about 440 years, and it was associated with a field strength that was only one quarter of today's field," explains Norbert Nowaczyk. "The actual polarity changes lasted only 250 years. In terms of geological time scales, that is very fast." During this period, the field was even weaker, with only 5% of today's field strength. As a consequence, Earth nearly completely lost its protection shield against hard cosmic rays, leading to a significantly increased radiation exposure.
This is documented by peaks of radioactive beryllium (¹⁰Be) in ice cores from this time, recovered from the Greenland ice sheet. ¹⁰Be as well as radioactive carbon (¹⁴C) is caused by the collision of high-energy protons from space with atoms of the atmosphere.
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【计时五】

The Laschamp event
The polarity reversal now found with the magnetisation of Black Sea sediments has already been known for 45 years. It was first discovered after the analysis of the magnetisation of several lava flows near the village Laschamp near Clermont-Ferrand in the Massif Central, which differed significantly from today's direction of the geomagnetic field. Since then, this geomagnetic feature is known as the 'Laschamp event'. However, the data of the Massif Central represent only some point readings of the geomagnetic field during the last ice age, whereas the new data from the Black Sea give a complete image of geomagnetic field variability at a high temporal resolution.
Abrupt climate changes and a super volcano
Besides giving evidence for a geomagnetic field reversal 41,000 years ago, the geoscientists from Potsdam discovered numerous abrupt climate changes during the last ice age in the analysed cores from the Black Sea, as it was already known from the Greenland ice cores. This ultimately allowed a high precision synchronisation of the two data records from the Black Sea and Greenland.
The largest volcanic eruption on the Northern hemisphere in the past 100,000 years, namely the eruption of the super volcano 39,400 years ago in the area of today's Phlegraean Fields near Naples, Italy, is also documented within the studied sediments from the Black Sea. The ashes of this eruption, during which about 350 cubic kilometers of rock and lava were ejected, were distributed over the entire eastern Mediterranean and up to central Russia.
These three extreme scenarios, a short and fast reversal of Earth's magnetic field, short-term climate variability of the last ice age and the volcanic eruption in Italy, have been investigated for the first time in a single geological archive and placed in precise chronological order.

【295】



【越障】

Cold Viruses Point the Way to New Cancer Therapies

ScienceDaily (Oct. 16, 2012) — Cold viruses generally get a bad rap -- which they've certainly earned -- but new findings by a team of scientists at the Salk Institute for Biological Studies suggest that these viruses might also be a valuable ally in the fight against cancer.
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Adenovirus, a type of cold virus, has developed molecular tools -- proteins -- that allow it to hijack a cell's molecular machinery, including large cellular machines involved in growth, replication and cancer suppression. The Salk scientists identified the construction of these molecular weapons and found that they bind together into long chains (polymers) to form a three-dimensional web inside cells that traps and overpowers cellular sentries involved in growth and cancer suppression. The findings, published Oct. 11 in Cell, suggest a new avenue for developing cancer therapies by mimicking the strategies employed by the viruses.


"Cancer was once a black box," says Clodagh O'Shea, an assistant professor in Salk's Molecular and Cell Biology Laboratory, who led the study. "The key that opened that box was revealing the interactions between small DNA tumor virus proteins and cellular tumor suppressor complexes. But without knowing the structure of the proteins they use to attack cells, we were at a loss for how these tiny weapons win out over much larger tumor suppressors."


O'Shea's team studied E4-ORF3, a cancer-causing protein encoded by adenovirus, which prevents the p53 tumor suppressor protein from binding to its target genes. Known as the "guardian of the genome," p53 normally suppresses tumors by causing cells with DNA damage -- a hallmark of cancer -- to self-destruct. The p53 tumor suppressor pathway is inactivated in almost every human cancer, allowing cancer cells to escape normal growth controls. Similarly, by inactivating p53, the E4-ORF3 protein enables adenovirus replication in infected human cells to go unchecked.


Two years ago, O'Shea discovered that E4-ORF3 clears the way for adenovirus to proliferate by deactivating genes that help the cell defend itself against the virus. "It literally creates zip files of p53 target genes by compressing them until they can no longer be read," she explains.


E4-ORF3 self-assembles inside cells into a disordered, web-like structure that captures and inactivates different tumor suppressor protein complexes. Horng Ou, a postdoctoral researcher in O'Shea's laboratory, says E4-ORF3 is unusual. "It doesn't resemble any known proteins that assemble polymers or that function in cellular tumor suppressor pathways," he says. "Most cellular polymers and filaments form uniform, rigid chains. But E4-ORF3 is the virus's Swiss army knife -- it assembles into something that is highly versatile. It has the ability to build itself into all sorts of different shapes and sizes that can capture and deactivate the many defenses of a host cell."


In collaboration with scientists from the National Center for Microscopy and Imaging Research at University of California, San Diego, led by Mark Ellisman, the center's director, O'Shea's team used new techniques to reveal the ultrastructure of the remarkable polymer that E4-ORF3 assembles in the nucleus -- something that previously had proven difficult since the polymer is effectively invisible using conventional electron microscopy. "What you see is the E4-ORF3 polymer bending and weaving and twisting its way through the nucleus," she says. "It does appear to have a single repeating pattern and creates a matrix that captures several different tumor suppressors and silences p53 target genes."


Initially, E4-ORF3 forms a dimer, made up of only two subunits. In this form, E4-ORF3 largely ignores its cellular targets. The researchers theorized that when E4-ORF3 assembles into a polymer, however, it binds to tumor suppressor targets far more aggressively. To test this theory, they genetically fused E4-ORF3 polymer mutants to lamin, a cellular protein that assembles intermediate filaments that provide stability and strength to cells. They showed that the lamin-E4-ORF3 fusion protein assembled into cylinder-like superstructures in the nucleus that bind and disrupt PML, a protein complex that suppresses tumors.


The Salk findings may help scientists develop small molecules -- the basis for the vast majority of current drugs -- capable of destroying tumors by binding and disrupting large and complex cellular components that allow cancer cells to grow and spread. Understanding how viruses overcome healthy cells may also help scientists engineer tumor-busting viruses, which offer a new and potentially self-perpetuating cancer therapy. Such modified viruses would destroy only cancer cells, because they could only replicate in cells in which the p53 tumor suppressor has been deactivated. When a cancer cell is destroyed it would release additional copies of the engineered viruses, which would seek out and kill remaining cancer cells that have spread throughout the body.


Engineering these viruses requires disabling the ability of the E4-ORF3 protein to inactivate p53 in healthy cells -- otherwise, the virus could destroy healthy cells as well as cancer cells. At the same time, E4-ORF3 has certain important functions in allowing the virus to replicate in the first place, so it can't be completely removed from the virus's arsenal. Thus, the Salk researcher's work on understanding the protein's precise structure, functions and interactions is crucial to engineering viruses in which E4-ORF3's abilities have been precisely modified.
【858】

miffyhui

1’11”
1’28”
2’04”
1’14”
1’25”
越障：6'29"

映雪瑶渊

...速度慢了。只有板凳

2012Michelle

终于等到了，谢谢LZ！

1'56"
1'20"
2'14"
1'47"
1'46"
科技文生词、专有名词比较多，看起来比较吃力一些。
6‘10“

mix0oo

准备开始~~~占位先~~~终于赶上进度了 呼呼呼~

mix0oo

字体是不是有点太小了…………

1.08
1.00
1.25
1.04
58.3s


3.46
这篇比较有趣~

sawayisa

1.36  
1.20
2.09
1.45
1.46
6.14
越障，用病毒杀死癌细胞，嘿嘿，一点也看不懂。
只知道E4-ORF3 是坏的  p53是好的。一个神通广大，一个法力无边。前者把后者给制服了，细胞就玩完了。

ElenW

1.(01:41.6)--186/m  而且就为了提高速度 这篇文章的内容还是没有记住........
2.(02:00.4)--142/m  这个速度啊....................文章内容也没有记啊.............
3(02:24.9)--168/m   无力吐槽.............................................

ENJ0Y

lz辛苦啦......
1.52
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2.24
1.12
1.36
5.17

xiaodiehoo

速度：
2:15
1:46
2:39
2:14
2:00
越障:
7:15
地理生物什么的最不擅长了，总是有不少词不认识，影响速度和理解…… 越障刚开始还看得挺明白后面就不知道在说什么了。
但是越不擅长的就越要练，所以现在重新去看越障，把它弄懂了