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We review the process of star formation, detailing the theories underlying the stability of molecular clouds and their collapse to protostars, and discussing the empirical evidence and models which inform them. We give emphasis to the role that the magnetic field plays in influencing the stability of molecular clouds and hence the star formation rate. The end result of star formation is a mass function which appears constant within our Galaxy. A relative abundance of low mass stars is observed over high mass stars and most of the stars that do form are found to exist as members of a binary system. The origin of binarity is reviewed as is the discovery, formation and observations of some of the lowest mass stars known, the brown dwarfs. 相似文献
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高温SHPB实验技术及其应用 总被引:4,自引:0,他引:4
介绍了高温分离式Hopkinson压杆(SHPB)实验方法,建立了一套高温SHPB实验系统,利用该系统研究了温度对某种抗氢钢动态压缩力学性能的影响,实验温度最高达到1000 ℃,应变率为500~1000 s-1。仅对试件进行加温,并利用一套气动装置在加载前快速完成系统的组装,以尽量减小试件中温度分布的不均匀性。研究结果表明:该气动装置可以将加载前杆端与试件的完全接触时间控制在500 ms内;该抗氢钢的温度软化效应很明显,且温度敏感性随温度升高而下降。 相似文献
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本文简述了人类寻找反物质的历程;目前产生反氢原子的方法及利用反物质的美好前景. 相似文献
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In view of current interest in the trapping of antihydrogen (
) atoms at low temperatures [1–3], we have carried out a full four-body variational calculation to determine s-wave elastic phase shifts for hydrogen antihydrogen scattering, using the Kohn Variational Principle. Terms outside the Born–Oppenheimer
approximation have been taken into account using the formalism of Kołos and Wolniewicz [4]. As far as we are aware, this is
the first time that these terms have been included in an H
scattering calculation. This is a continuation of earlier work on H–
interactions [5–7]. Preliminary results differ substantially from those calculated using the Born–Oppenheimer approximation
[8–10]. A method is outlined for reducing this discrepancy and taking the rearrangement channel into account.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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We present a combined Paul-Penning trap to study CO2 laser stimulated recombination of protons and electrons. The trap is located in the center of an optical resonator for 11
μm radiation. In this manner the available laser intensity is enhanced for stimulated recombination to the n=1 state of hydrogen.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Thomas J. Phillips 《Hyperfine Interactions》1997,109(1-4):357-365
There has never been a direct measurement of the gravitational force on antimatter. This paper describes a possible measurement
of this force by measuring the phase shift of neutral antimatter in a transmission-grating interferometer caused by the Earth’s
gravitational field. This experiment avoids the severe problem of shielding stray electromagnetic fields necessary for making
a gravity measurement with charged particles, and also avoids the need to trap neutral particles. The neutral antimatter for
this experiment could be either antihydrogen, positronium, or antineutrons.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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M. C. Fujiwara M. Amoretti C. Amsler G. Bendiscioli G. Bonomi A. Bouchta P. Bowe C. Carraro M. Charlton M. Collier M. Doser V. Filippini K. Fine A. Fontana R. Funakoshi P. Genova D. Grögler J. S. Hangst R. S. Hayano H. Higaki M. H. Holzscheiter W. Joffrain L. Jorgensen V. Lagomarsino R. Landua C. Lenz Cesar D. Lindelöf E. Lodi-Rizzini M. Macri N. Madsen G. Manuzio M. Marchesotti P. Montagna H. Pruys C. Regenfus P. Riedler A. Rotondi G. Rouleau P. Salvini G. Testera D. P. van der Werf A. Variola L. Venturelli T. Watson T. Yamazaki Y. Yamazaki 《Hyperfine Interactions》2001,138(1-4):153-158
The ATHENA experiment at the Antiproton Decelerator facility at CERN aims at testing CPT symmetry with antihydrogen. An overview
of the experiment, together with preliminary results of development towards the production of slow antihydrogen are reported.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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ATHENA, one of the three approved experiments at the new facility for low energy antiprotons (AD) at CERN, has the primary
goal to test CPT invariance by comparing the atomic energy levels of antihydrogen to those of hydrogen. The extended experimental
program also contains studies on differences in gravitational acceleration of antimatter and matter. The production of antihydrogen
atoms and their spectral response to laser light will be monitored by a sophisticated detector for the end products of antiproton
and positron annihilations.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Yasunori YAMAZAKI 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2020,96(10):471
The field of cold antimatter physics has rapidly developed in the last 20 years, overlapping with the period of the Antiproton Decelerator (AD) at CERN. The central subjects are CPT symmetry tests and Weak Equivalence Principle (WEP) tests. Various groundbreaking techniques have been developed and are still in progress such as to cool antiprotons and positrons down to extremely low temperature, to manipulate antihydrogen atoms, to construct extremely high-precision Penning traps, etc. The precisions of the antiproton and proton magnetic moments have improved by six orders of magnitude, and also laser spectroscopy of antihydrogen has been realized and reached a relative precision of 2 × 10−12 during the AD time. Antiprotonic helium laser spectroscopy, which started during the Low Energy Antiproton Ring (LEAR) time, has reached a relative precision of 8 × 10−10. Three collaborations joined the WEP tests inventing various unique approaches. An additional new post-decelerator, Extra Low ENergy Antiproton ring (ELENA), has been constructed and will be ready in 2021, which will provide 10–100 times more cold antiprotons to each experiment. A new era of the cold antimatter physics will emerge soon including the transport of antiprotons to other facilities. 相似文献
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