【每日阅读训练第四期——速度越障11系列】【11-7】科技

CHRISTINE2010

【计时一】

Planet Rings Could Be Behind the Formation of Solar System Satellites

Two French researchers have recently proposed the first ever model explaining how the great majority of regular satellites in our solar system were formed out of planet rings. The model, the only one of its kind, was first tested in 2010 on Saturn's moons. It seems to account for the present distribution of "giant" planets and also explains how the satellites of the "terrestrial" planets such as Earth or Pluto came into being. These results are a major step forward in understanding and explaining the formation of planet systems across the universe.
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There is a fundamental difference between giant planet systems, such as Jupiter and Saturn, and the terrestrial plants, such as Earth or Pluto. Whereas the giants are surrounded by rings and a myriad of small natural satellites, the terrestrial planets have few moons, or just one, and no rings. Until now, two models have been commonly used to explain the presence of regular satellites in our solar system. These indicate that the satellites of the terrestrial planets like Earth or Pluto were formed following a giant collision. They also indicate that the satellites of the giant planets were formed in a nebula surrounding the planet. They do not, however, account for the specific distribution and chemical composition of the satellites orbiting the giant planets. Another theory therefore seemed necessary.
In 2010 and 2011, a French research team developed a new model to describe how Saturn's moons came into being based on numerical simulations and Cassini probe data. The researchers discovered that Saturn's rings, which are very thin disks made up of small blocks of ice surrounding the planet, in turn gave birth to ice satellites. This is due to the fact that the rings spread over time and, when they reach a certain distance from the planet (known as the Roche limit or Roche radius), their ends agglomerate and form small bodies that break off and move away. This is how rings give birth to satellites orbiting the planet.
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【计时二】

In this new study, two research lecturers, Aurélien Crida from the Université Nice Sophia Antipolis and the Observatoire de la Côte d'Azur and Sébastien Charnoz from the Université Paris Diderot and the CEA, set out to test the new model and discover whether it could be extended to other planets. Their calculations have brought several important facts to light. This model for satellite formation from planet rings explains why the largest satellites are located farther away from the planet than the smaller satellites. It also points to the accumulation of satellites close to the Roche limit, their "place of birth," on the outer edge of the rings. This distribution is in perfect agreement with Saturn's planetary system. The same model can also apply to the satellites of the giant planets, Uranus and Neptune, which are organized according to a similar layout. This suggests that these planets once had massive rings similar to Saturn's, which they then lost in giving birth to their satellites. Lastly, the model could also be applied to the formation of terrestrial planet satellites. And, according to the researchers' calculations, special cases exist where a single satellite may be formed from the ring around the planet. This is the case for Earth and the Moon, and for Pluto and Charon.
Thus, this planetary ring spreading mechanism alone could explain how the great majority of regular satellites were formed in our solar system.
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【计时三】

Titan, Saturn's Largest Moon, Icier Than Thought

Scientists have long suspected that a vast ocean of liquid water lies under the crusty exterior of Titan, Saturn's largest moon. New analysis suggests that the internally generated heat that keeps that ocean from freezing relies on the moon's interactions with Saturn and its other moons.
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A new analysis of topographic and gravity data from Titan, the largest of Saturn's moons, indicates that Titan's icy outer crust is twice as thick as has generally been thought.
Scientists have long suspected that a vast ocean of liquid water lies under the crust. The new study suggests that the internally generated heat that keeps that ocean from freezing solid depends far more on Titan's interactions with Saturn and its other moons than had been suspected.
Howard Zebker, a professor of geophysics and of electrical engineering at Stanford University, will present the findings at the annual meeting of the American Geophysical Union (AGU) in San Francisco on Dec. 4.
Zebker is part of the team interpreting radar data of Titan acquired by NASA's Cassini spacecraft, which has been orbiting Saturn since 2004. He has been studying the topography of Titan, and has combined improved radar measurements of the moon's surface with newly released gravity measurements to make the new analysis.
Titan has long intrigued scientists because of its similarities to Earth. Like Earth, Titan appears to have a layered structure, crudely similar to the concentric layers of an onion, albeit far less edible.
"Titan probably has a core that is a mixture of ice and rock," said Zebker. The core is overlain by the ocean and icy crust.
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【计时四】

The rock in the core is thought to contain radioactive elements left over from the formation of the solar system. As in Earth's core, when those elements decay, they generate heat. On Titan, that heat is crucial to keeping its ocean from freezing solid.
As Titan orbits Saturn, Titan is slowly spinning on its axis, one spin for each trip around Saturn. Still, that spin is enough for the gravity instrument onboard Cassini to measure the resistance of Titan to any changes in its spin -- also called the moment of inertia.
"The moment of inertia depends essentially on the thickness of the layers of material within Titan," Zebker said. Thus, he and his graduate students were able to use that data to calculate the moon's internal structure.
"The picture of Titan that we get has an icy, rocky core with a radius of a little over 2,000 kilometers, an ocean somewhere in the range of 225 to 300 kilometers thick and an ice layer that is 200 kilometers thick," he said.
Previous models of Titan's structure estimated the icy crust to be approximately 100 kilometers thick. So if there is more ice, then there should be less heat from the core than had been estimated. One way to account for less heat being generated internally is for there to be less rock and more ice in the core than previous models had predicted.
That all seems simple enough, but there is a complication. Titan is not a true sphere. Its shape is distorted by the gravitational pull of Saturn, making the moon sort of oblong along its equator and a little flattened at the poles.
From measurements of the observed gravitational field of Titan, one can compute what the shape of Titan ought to be. But the new data show that Titan's shape is much more distorted than would be predicted by a simple gravitational model.
That discrepancy means the internal structure of Titan isn't quite so simple.
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【计时五】

For Titan to exert its observed gravitational pull, the average density from any given point on the moon down to the center of the core has to be the same, said Zebker.
But that's not the case, since Titan is somewhat squashed. For the data to line up, the density of material under the poles must be slightly greater than it is under the equator.
Since liquid water is denser than ice, Zebker's team reasoned that the ice layer must be slightly thinner at the poles than at the core, and the layer of water correspondingly thicker.
The team members calculated that the thickness of the icy crust is about 3,000 meters less than average at the poles and 3,000 meters greater than average at the equator. And the combination of gravity and topography further suggests that the average thickness of the icy layer is about 200 km.
For the icy crust to vary in thickness across Titan's surface, the heat distribution within the moon must vary as well. But that variation is not likely to come from the moon's core -- heat generated there would be fairly uniform in all directions.
Zebker said the variation in ice thickness could be a result of variation in the shape of Titan's orbit around Saturn, which is not perfectly circular.
"The variation in the shape of the orbit, along with Titan's slightly distorted shape, means that there is some flexure within the moon as it orbits Saturn," said Zebker. The planet's other moons also exert some tidal influence on Titan as they all follow their different orbits, but the primary tidal influence is Saturn.
"The tides move around a little as Titan orbits and if you move anything, you generate a little bit of heat."
For example, if you take a thin strip of metal and flex it, it will begin to weaken and eventually you can break it. That weakening is the result of heat being generated as you flex the metal.
The tidal interactions tend to be more concentrated at the poles than the equator, which means that there is slightly more heat generated at the poles, which in turn melts a little bit of ice at the bottom of the ice layer, thinning the ice in that region in comparison to other parts of the planet, Zebker said.
The Cassini mission was recently given funding to continue operating through 2017, which means about five more years of data will be acquired that can contribute to further refinements of Zebker's model of Titan.
【423】



【越障】

Multitasking Plasmonic Nanobubbles Kill Diseased Cells, Modify Others

ScienceDaily (Dec. 3, 2012) — Researchers at Rice University have found a way to kill some diseased cells and treat others in the same sample at the same time. The process activated by a pulse of laser light leaves neighboring healthy cells untouched.
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The unique use for tunable plasmonic nanobubbles developed in the Rice lab of Dmitri Lapotko shows promise to replace several difficult processes now used to treat cancer patients, among others, with a fast, simple, multifunctional procedure.
The research is the focus of a paper published online this week by the American Chemical Society journal ACS Nano and was carried out at Rice by biochemist Lapotko, research scientist and lead author Ekaterina Lukianova-Hleb and undergraduate student Martin Mutonga, with assistance from the Center for Cell and Gene Therapy at Baylor College of Medicine (BCM), Texas Children's Hospital and the University of Texas MD Anderson Cancer Center.
Plasmonic nanobubbles that are 10,000 times smaller than a human hair cause tiny explosions. The bubbles form around plasmonic gold nanoparticles that heat up when excited by an outside energy source -- in this case, a short laser pulse -- and vaporize a thin layer of liquid near the particle's surface. The vapor bubble quickly expands and collapses. Lapotko and his colleagues had already found that plasmonic nanobubbles kill cancer cells by literally exploding them without damage to healthy neighbors, a process that showed much higher precision and selectivity compared with those mediated by gold nanoparticles alone, he said.
The new project takes that remarkable ability a few steps further. A series of experiments proved a single laser pulse creates large plasmonic nanobubbles around hollow gold nanoshells, and these large nanobubbles selectively destroy unwanted cells. The same laser pulse creates smaller nanobubbles around solid gold nanospheres that punch a tiny, temporary pore in the wall of a cell and create an inbound nanojet that rapidly "injects" drugs or genes into the other cells.
In their experiments, Lapotko and his team placed 60-nanometer-wide hollow nanoshells in model cancer cells and stained them red. In a separate batch, they put 60-nanometer-wide nanospheres into the same type of cells and stained them blue.
After suspending the cells together in a green fluorescent dye, they fired a single wide laser pulse at the combined sample, washed the green stain out and checked the cells under a microscope. The red cells with the hollow shells were blasted apart by large plasmonic nanobubbles. The blue cells were intact, but green-stained liquid from outside had been pulled into the cells where smaller plasmonic nanobubbles around the solid spheres temporarily pried open the walls.
Because all of this happens in a fraction of a second, as many as 10 billion cells per minute could be selectively processed in a flow-through system like that under development at Rice, said Lapotko, a faculty fellow in biochemistry and cell biology and in physics and astronomy. That has potential to advance cell and gene therapy and bone marrow transplantation, he said.
Most disease-fightingand gene therapies require "ex vivo" -- outside the body -- processing of human cell grafts to eliminate unwanted (like cancerous) cells and to genetically modify other cells to increase their therapeutic efficiency, Lapotko said. "Current cell processing is often slow, expensive and labor intensive and suffers from high cell losses and poor selectivity. Ideally both elimination and transfection (the introduction of materials into cells) should be highly efficient, selective, fast and safe."
Plasmonic nanobubble technology promises "a method of doing multiple things to a cell population at the same time," said Malcolm Brenner, a professor of medicine and of pediatrics at BCM and director of BCM's Center for Cell and Gene Therapy, who collaborates with the Rice team. "For example, if I want to put something into a stem cell to make it turn into another type of cell, and at the same time kill surrounding cells that have the potential to do harm when they go back into a patient -- or into another patient -- these very tunable plasmonic nanobubbles have the potential to do that."
The long-term objective of a collaborative effort among Rice, BCM, Texas Children's Hospital and MD Anderson is to improve the outcome for patients with diseases whose treatment requires ex vivo cell processing, Lapotko said.
Lapotko plans to build a prototype of the technology with an eye toward testing with human cells in the near future. "We'd like for this to be a universal platform for cell and gene therapy and for stem cell transplantation," he said.
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spencerX

沙发~christine的文章还是一如既往的有趣，谢谢分享！
ps：这个应该是11-7了~

0:01:44
0:01:16
0:01:31
0:01:50
0:01:56

0:04:16

skipper2012

谢谢Christine.先占座. 边记笔记边读，第一篇奇慢，后面略好一些。还是没有自己的笔记体系，所以记笔记耽误一些时间。科技文其实中心很明确，读完以后觉得比较思路清楚，不用回读就能写出大意来。但是分支和细节部分还是记不清楚。

Speed: 4'14, 2'53, 2'37, 2'51, 2'38
        The planetary rings might explain the distribution and formation of the giant planet system (without rings) and the terrestrial planets (with rings).
       Titan, the moon of Saturn, has thicker and icier-than-expected crust layers, underneath which was heat rather than liquid.

Obstacle: 6'55
      Multifunctional plasmonic nanobubble will kill cancer cells without damaging neighboring healthy  cells. This technology is expected to be applied in cell and gene therapy as well as stem cell and bone transplantation.

teddybearj4

谢谢Christine~~~——————
速度：
1‘35     1’01      1‘20     1’03      1‘12


越障：3’20
（头看的晕晕的！~~）

starkeita

先来占一个~

191128

zhen xin du bu dong zen me ban? dan ci bing bu nan.

yangreat

叮，谢lz~
速度
2:34, 346
The rings of planet can help us realize how our solar system were formed.
Two models of different planet systems -giant and terrestrial.
The births of satellites of two models are different.
1:53, 235
The Roche limit is the satellites' "place of birth".
The model for satellite formation from palnet rings can apply to giant planetary system.
3:00, 276
Scientists are aiming at Titan.
The probe help us to analysis the topography of Titan.
3:00,329
The radiocactive elements in the core is crucial to keeping Titan's ocean from freezing solid.
The shape of Titan is distorted because the gravitational pull of Saturn.
3:57, 423
The icy crust in the poles is thinner for two reasons: the result of variation in the shape of Titan's orbit around Saturn, which is not perfectly circular and the tidal influence.
越障
4:50, 760
The unique use for tunable plasmonic nanobubbles now used to treat cancer patients.
The bubbles are heat by a laser pulse.
The nanobubbles exploded to kill cancer cells without damage to healthy neighbors.
An experiment in which the plasmonic nanobubbles are tested to be accuracy and efficiency.
Current cell processing is often slow, expensive and labor intensive and suffers from high cell losses and poor selectivity.
Ideally both elimination and transfection should be highly efficient, selective, fast and safe.

CCcarol

占一个先~

铁板神猴

Christine辛苦了~！

铁板神猴

沙发~christine的文章还是一如既往的有趣，谢谢分享！
ps：这个应该是11-7了~

-- by 会员 spencerX (2012/12/5 6:31:48)

谢谢spencer提醒~ 我来搞定~