n*****e
发帖数: 19 | 1 Postdoctoral Openings at Center for Nanophase Materials Sciences, Oak Ridge
National Laboratory
Two postdoctoral positions are available immediately in the Macromolecular
Nanomaterials Group at the Center for Nanophase Materials Sciences at the
Oak Ridge National Laboratory (ORNL), focusing on theory and simulation of
dynamics and rheology of dynamically-bonded polymers [e.g. Nature Materials
10, 14-27 (2011)], in collaboration with the synthetic chemists and
experimental polymer physicists in t... 阅读全帖 |
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y***o
发帖数: 9 | 2 At a special seminar on 10 February, spokespersons from the experiments on CERN* 's Heavy Ion programme
presented compelling evidence for the existence of a new state of matter in which quarks, instead of being bound
up into more complex particles such as protons and neutrons, are liberated to roam freely.
Theory predicts that this state must have existed at about 10 microseconds after the Big Bang, before the
formation of matter as we |
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c**********g
发帖数: 222 | 3 >>>> this is wrong. what offset the gravity of the sun is the gas pressure
( acturally, it is the gradient of the gas pressure). The pressure is positive.
when we mean that the pressure is positive, we mean that P1,P2 and P3 the trace
of the energy-monentum tensor (\rho+P1+P2+P3) is positive. Here, \rho is the energy
density
>>> Also, in NS, gravity is balanced by the gradient of the neutron denenerate
pressure. Again, this pressure itself is positive. |
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S******y
发帖数: 39 | 4
I met Witten once at a seminar (Jocelyn Belle's talk, the woman who
discovered
first neutron star).
Andrew Wales is also at Princeton, he's more typically a
mathematician.. proved
Ferma theorem. |
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f*******d
发帖数: 339 | 5 I think you have some misconception of spin. Spin HAS
NOTHING TO
DO WITH magnetic field. The only connection between spin and
magnetic
field is that for some particles (such as electron, proton,
neutron)
it is easier to measure spin using Stern-Gerlach experiment
because they
have magnetic moment. However, there are also particles
which have
spin but no (or very small) magnetic moment, for example
photon,
neutrino, etc. The spin of these particles could be
measured, but not
using SG type experim |
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a***n
发帖数: 578 | 6 Hugh David Politzer has won the 2004 Nobel Prize in physics for work
he began as a graduate student on how the elementary particles known
as quarks are bound together to form the protons and neutrons of
atomic nuclei. The announcement was made today by the Royal Swedish
Academy of Sciences.
Politzer, a professor of theoretical physics at Caltech, shares the
prize with David Gross and Frank Wilczek. The key discovery
celebrated by today's prize was made in 1973, when Politzer, a
Harvard Univers |
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g******w
发帖数: 852 | 7 【 以下文字转载自 Biology 讨论区 】
发信人: geneshow (AirBus-380), 信区: Biology
标 题: paper help
发信站: BBS 未名空间站 (Sat Dec 16 10:01:34 2006)
Electrophoresis
Volume 8, Issue 12 , Pages 545 - 551
Published Online: 13 Apr 2005
Differences in protein staining by Coomassie Brilliant Blue and neutron
activated Coomassie Brilliant Blue dyes
Dr. Douglas M. Gersten 1 *, Pamela H. Wolf 2, Edward J. Zapolski 1 2
1Department of Pathology, Georgetown University Medical Center, Washington,
DC
2Center for Population Research, N |
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o********e
发帖数: 34 | 8 【 以下文字转载自 ChemEng 讨论区 】
发信人: olivertree (Life is good), 信区: ChemEng
标 题: Postdoctoral Positions in UNIVERSITY OF DELAWARE
发信站: BBS 未名空间站 (Tue Jun 8 21:36:42 2010, 美东)
Link: http://www.che.udel.edu/postdoc.html
POSTDOCTORAL RESEARCHER position is available immediately with Dr. Yun Liu
and Professor Norman J. Wagner in the Center for Molecular and Engineering
Thermodynamics and the Center for Neutron Science of the Department of
Chemical Engineering at the University of Delaware. Initial appoint |
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E**********e
发帖数: 1736 | 9 不干啥。 就是想比较两种算法，了解一下。 免得面试时，说不上来。
我看了一下。 Neuton-Raphason需要找到目标函数的一次和二次direvatives， 然后根
据taylor 近似，用迭代的方法求出解。
gauss-newton不许要，可以避免求二次direvative。所说我还没试这个gauss-neutron
， 不过我估计两者获得的解在logistic regression应该会好很接近。
stochastic gd 的解就差别很大。或者way crazy。 系数有时根本就不一致，nr里正的
系数， sgd里是负的，完全不一致。 当然可能就是你说的， 不是找梯度为0的解。 而
是近似解。 在neutral network里，大家也不知道黑盒子了到底干啥， 知道得到的预
测力好久行了。
我应该比较预测的准确力，来比较两种方法的优劣。 |
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E**********e
发帖数: 1736 | 10 不干啥。 就是想比较两种算法，了解一下。 免得面试时，说不上来。
我看了一下。 Neuton-Raphason需要找到目标函数的一次和二次direvatives， 然后根
据taylor 近似，用迭代的方法求出解。
gauss-newton不许要，可以避免求二次direvative。所说我还没试这个gauss-neutron
， 不过我估计两者获得的解在logistic regression应该会好很接近。
stochastic gd 的解就差别很大。或者way crazy。 系数有时根本就不一致，nr里正的
系数， sgd里是负的，完全不一致。 当然可能就是你说的， 不是找梯度为0的解。 而
是近似解。 在neutral network里，大家也不知道黑盒子了到底干啥， 知道得到的预
测力好久行了。
我应该比较预测的准确力，来比较两种方法的优劣。 |
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i******s
发帖数: 566 | 11 （二）经部的观点
经部关于微观世界的观点，基本上与一切有部相似。二者之间的差别，在于经部进一步
将时间、空间、速度、方向等判定为非实有。
何谓空间？所谓空间，就是在一个范围内没有被任何物体所占据的位置，这种没有被占
的位置，就是空间，除此以外，并没有空间的存在。如果有东西占据了某个位置，这个
位置就没有空间了；当物体被移走后，腾出来的位置就是空间。由此可见，所谓的空间
，实际上是假立的、不实在的。
再说时间，不论是一分钟或一小时，一个月或一年，都只不过是物质变化的过程而已，
除此之外，并不存在所谓的时间。我们只能通过世上万物的变化来判定时间，譬如根据
气候的变化过程，而建立起春夏秋冬的时间概念等等。这种物质变化的过程，我们称之
为时间。
我们可以设想，如果太空中没有任何星球的话，我们能算定时间吗？不能。由此可知，
时间只不过是以物质变化为基础，由人的意识而增上安立的法。
虽然现代物理学对时间也有不同说法，到底时间存不存在，它的本体究竟为何，都是学
术界激烈讨论的课题之一，但经部的论师们却认为，时间只是人的一种概念而已，除了
物质的变化以外，实际上并不存在独立的时间本质。
那么速度又是什... 阅读全帖 |
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y*****l
发帖数: 5997 | 12 ☆─────────────────────────────────────☆
tanmaomao (坛猫猫) 于 (Tue Nov 16 18:13:00 2010, 美东) 提到:
RT
☆─────────────────────────────────────☆
tanmaomao (坛猫猫) 于 (Tue Nov 16 18:24:25 2010, 美东) 提到:
发信人: tanmaomao (坛猫猫), 信区: Stock
标 题: Re: 铀价格走势图 (转载)
发信站: BBS 未名空间站 (Tue Nov 16 18:23:29 2010, 美东)
Ux U3O8 Price indicator is the longest-running weekly uranium price series,
used by the industry in sales contracts
☆─────────────────────────────────────☆
tanmaomao (坛猫猫) 于 (Wed Nov 17 09:34:37 20... 阅读全帖 |
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m****y
发帖数: 3437 | 13 昨晚的读聊会映象还鲜明，罗唆出来作为例子吧:
读的是关于space的书，读了10分钟，几页而已。聊的很杂，乱跑题:
Spiral galaxy and elliptical galaxy, the milky way, 牛郎织女的故事，yes,
bird made a bridge, according to the ecologist the bird population could be
related to the wild wolf population sometimes,
light year, luminosity, categories of stars--supergiant, dwarf, neutron,
middle aged sun, middle age for people, snow white and the 7 dwarfs, dwarf
中文叫“矮”，stepmom, divorce, no I’m never ever gonna divorce your dad,
temperature of stars, Fahrenheit and Ce... 阅读全帖 |
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E*********e
发帖数: 10297 | 14 你这个是超级推英语阿
这个是老大还是老二？
could be
neutron,
dwarfs, dwarf
never
the |
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s******o
发帖数: 298 | 15 Another pulsar turns up with an age that defies conventional wisdom.
by Richard Talcott
A thousand years ago, most astronomers thought Earth lay at the center of the
cosmos. One hundred years ago, most thought the universe consisted of a
single galaxy. And just two years ago, most would have said they understood
how neutron stars and pulsars evolve. Conventional wisdom, it seems has taken
another beating.
For the second time in the past two years, astronomers have found a pulsar
that doesn’t con |
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s******o
发帖数: 298 | 16 By Govert Schilling
April 24, 2002 | Using NASA's Rossi X-ray Timing Explorer satellite,
astronomers have found definitive proof that low-mass X-ray binary stars are
the precursors of millisecond pulsars. New observations of two X-ray binaries
provide convincing evidence that neutron stars are, indeed, whipped up to high
spin rates by mass transfer from a lower-mass companion star.
About 150 low-mass X-ray binaries (LMXBs) are known. In all cases, the X-rays
are due to gas from the companion sta |
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s*****t
发帖数: 1994 | 17 M51: X-Rays from the Whirlpool
Explanation: Fresh from yesterday's episode, a popular pair of interacting galaxies known
as the Whirlpool debut here beyond the realm of visible light -- imaged at high energies by
the orbiting Chandra X-ray Observatory. Still turning in a remarkable performance, over 80
glitering x-ray stars are present in the Chandra image data from the region. The number of
luminous x-ray sources, likely neutron star and black hole binary systems within the
confines of M51, is |
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s*****t
发帖数: 1994 | 18 The Crab Nebula Pulsar Shrugs
Credit: J. Hester (ASU), CXC, HST, NRAO, NSF, NASA
Explanation: How does a city-sized neutron star power the vast Crab Nebula? The
expulsion of wisps of hot gas at high speeds appears to be at least part of the answer.
Yesterday time-lapse movies taken from both the Chandra X-ray Observatory and the
Hubble Space Telescope were released showing a wisp of gas moving out at about half the
speed of light. Wisps like this likely result from tremendous electri |
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s*****t
发帖数: 1994 | 19 Accretion Disk Simulation
Credit: Michael Owen, John Blondin (North Carolina State Univ.)
Explanation: Don't be fooled by the familiar symmetry. The graceful spiral structure seen
in this computer visualization does not portray winding spiral arms in a distant galaxy of
stars. Instead, the graphic shows spiral shock waves in a three dimensional simulation of an
accretion disk -- material swirling onto a compact central object that could represent a white
dwarf star, neutron star, or bla |
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s*****t
发帖数: 1994 | 20 （五）中子星、超新星和黑洞(Neutron Star, Supernova and Black Hole)
离开主序时质量超过八倍太阳的恒星能制造重原子核。在温度升到六亿开氏度时，
碳保不住了，相互猛撞并聚合成氖和镁。一条“生产线”就此建立，因为每个新的热核
反应都能释放更多的能量，使温度升得更高，从而导致新的转变。然而核转变并不能就
无限制地继续，反应的洪流最后都朝着一个元素汇集：铁。铁是大质量恒星核心的最后
灰烬。与此同时恒星还不断地膨胀其外壳以调节平衡，它会膨胀到一个异常巨大的尺度
，成为红超巨星。红超巨星是宇宙中最大的恒星。如果把这样一个星放在太阳系中心，
它将吞没包括远在五十亿公里外的冥王星在内的所有行星。
虽然铁核的温度在十亿度以上，却没有能量从中流出。它不足以使超巨星维持引力
平衡，铁核就会被压得更紧密，使其中的电子处于简并态。当简并电子的巨大压力能暂
时地支持外层的重量时，恒星活动会出现一个间歇。但是当核心里铁和简并电子的质量
超过一点四个太阳质量时，电子已简并的核突然塌陷，剧烈收缩，在十分之一秒内温度
猛升到五十亿度。涌出的光子带有的巨大能量将铁原子核炸开，蜕变成氦原 |
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r******y
发帖数: 21907 | 21 Scientists watch black hole born in split-second light flash
After 30 years, they finally caught one. Scientists on Monday have for the f
irst time detected and pinned down the location of a so-called "short" gamma
-ray burst, lasting only 50 milliseconds.
The burst marks the birth of a black hole. The astronomy community is buzzin
g with speculation on what could have caused the burst, perhaps a collision
of two older black holes or two neutron stars. A multitude of follow-up obse
rvations are |
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