113,603 research outputs found
Scientometric Portrait of Nobel Laureate S. Chandrasekhar
No full textScientometric analysis of the publications productivity of Nobel Laureate S. Chandrasekhar is documented
THE DISCOVERY OF THE CHANDRASEKHAR MASS AND THE CHANDRASEKHAR-EDDINGTON CONTROVERSY
No full textThe so called Chandrasekhar limiting mass is a a quantum mechanical relativistic effect. The discovery and establishment of the concept involved a major controversy between the young Chandrasekhar and the hilarious Eddington. We review the origin and evolution of the controversy
Escape of stars from gravitational clusters in the Chandrasekhar model
No full textInternational audienceWe study the evaporation of stars from globular clusters using the simplified Chandrasekhar model. This is an analytically tractable model giving reasonable agreement with more sophisticated models that require complicated numerical integrations. In the Chandrasekhar model: (i) the stellar system is assumed to be infinite and homogeneous (ii) the evolution of the velocity distribution of stars f(v,t) is governed by a Fokker-Planck equation, the so-called Kramers-Chandrasekhar equation (iii) the velocities |v| that are above a threshold value R>0 (escape velocity) are not counted in the statistical distribution of the system. In fact, high velocity stars leave the system, due to free evaporation or to the attraction of a neighboring galaxy (tidal effects). Accordingly, the total mass and energy of the system decrease in time. If the star dynamics is described by the Kramers-Chandrasekhar equation, the mass decreases to zero exponentially rapidly. Our goal is to obtain non-perturbative analytical results that complement the seminal studies of Chandrasekhar, Michie and King valid for large times and large escape velocities . In particular, we obtain an exact semi-explicit solution of the Kramers-Chandrasekhar equation with the absorbing boundary condition f(R,t)=0. We use it to obtain an explicit expression of the mass loss at any time t when . We also derive an exact integral equation giving the exponential evaporation rate , and the corresponding eigenfunction , when for any sufficiently large value of the escape velocity R. For , we obtain an explicit expression of the evaporation rate that refines the Chandrasekhar results
On the non radial oscillations of stars V. A fully relativistic treatment of a newtonian star
No full textIt is shown how the non-radial oscillations of a Newtonian star (i.e. a star built in the Newtonian framework) can be treated fully relativistically as the result of the scattering of gravitational radiation by its own, shallow, curved spacetime. It has the distinguishing characteristic that no gravitational radiation emerges
Reactions of n-Bu2SnO and (n-Bu3Sn)2O with 1,1,2,3,3-Pentamethyltrimethylene Phosphinic Acid: Synthesis and X-ray Crystal Structures of a Novel Spirocyclic Coordination Polymer and a 16-Membered Inorganic Macrocycle
No full textPolarimetry of the transient relativistic jet of GRB 110328/Swift J164449.3+573451
No full textWe present deep infrared (Ks-band) imaging polarimetry and radio (1.4- and 4.8-GHz) polarimetry of the enigmatic transient Swift J164449.3+573451. This source appears to be a short-lived jet phenomenon in a galaxy at redshift z= 0.354, activated by a sudden mass accretion on to the central massive black hole, possibly caused by the tidal disruption of a star. We aim to find evidence for this scenario through linear polarimetry, as linear polarization is a sensitive probe of jet physics, source geometry and the various mechanisms giving rise to the observed radiation. We find a formal Ks-band polarization measurement of Plin= 7.4 ± 3.5 per cent (including systematic errors). Our radio observations show continuing brightening of the source, which allows sensitive searches for linear polarization as a function of time. We find no evidence of linear polarization at radio wavelengths of 1.4 and 4.8 GHz at any epoch, with the most sensitive 3σ limits as deep as 2.1 per cent. These upper limits are in agreement with expectations from scenarios in which the radio emission is produced by the interaction of a relativistic jet with a dense circumsource medium. We further demonstrate how polarization properties can be used to derive properties of the jet in Swift J164449.3+573451, exploiting the similarities between this source and the afterglows of gamma-ray bursts
Synthesis of a tetranuclear organooxotin cage by debenzylation reactions: X-ray crystal structure of [(PhCH2)2Sn2O(O2P(OH)-t-Bu)4 ]2
No full textThe reactions of (PhCH2)2SnCl2, (PhCH2)2SnO·H2O, and (PhCH2)3SnCl with 2 equiv of t-BuP(O)(OH)2 afford the tetranuclear organooxotin cage [(PhCH2)2Sn2O(O2P(OH)-t-Bu)4 ]2 (4) in good yields. The formation of the half-cage intermediate [(PhCH2)2Sn2O(O2P(OH)-t-Bu)4 ] (4a) en route to 4 has been detected by 119Sn and 31P NMR. The molecular structure of compound 4 as determined by single-crystal X-ray analysis shows a tetranuclear cage structure containing two Sn-O-Sn motifs connected by bridging [t-BuP(OH)(O)2]- ligands. The solid-state structure of 4 is retained in solution
A paradigm change in assembling OH functionalities on metal centers
No full textThe synthesis of terminal hydroxide containing Group 13 and 14 metals [LAl(OH)2], LAlMeOH, [{LAl(OH)}2(μ -O)], LAl(OH)-O-AlLL', LGeOH, and [TsiSn(O)OH]3 [Tsi = (Me3Si)3C] has been accomplished using innovative synthetic methodologies. All of these compounds have been structurally characterized, both in solution as well as in the solid state. The utility of such metal hydroxides [{LAl(OH)}2(μ -O)] and LAlMeOH [L = HC{(CMe)(2,6-i-Pr2C6H3N)}2] in the preparation of homo- and heterometallic compounds has been demonstrated. It has also been possible to prepare unusual terminal SH- and SeH-containing compounds LAl(SH)2, LAl(SeH)2, and LAl(SeH)-Se-Al(SeH)L using dihydride LAlH2 as a starting material. The synthesis, structure, and potential utility of these compounds is discussed
Scientometric analysis of synchronous references in the Physics Nobel lectures, 1981-1985 : a pilot study
No full textScientometric analysis of synchronous references in the nine Physics Nobel lectures by Nicolaas Bloembergen (1981), Arthur L. Schawlow (1981), Kai M. Siegbahn (1981), Kenneth G. Wilson (1982), Subrahmanyan Chandrasekhar (1983), William A. Fowler (1983), Carlo Rubbia (1984), Simon van der Meer (1984), and Klaus von Klitzing (1985) indicated high variations: No. of Synchronous References ranged from 24 (Meer) to 283 (Siegbahn); Synchronous Self-References ranged from 5 (Rubbia) to 88 (Siegbahn); synchronous references to others ranged from 10 (Chandrasekhar) to 255 (Wilson); Synchronous Self-Reference Rates ranged from 6.66 % (Rubbia) to 65.51 % (Chandrasekhar); Single-Authored References ranged from 15 (Klitzing) to 160 (Wilson); Multi-Authored References ranged from 4 (Chandrasekhar) to 194 (Siegbahn); Collaboration Coefficient in the synchronous references ranged from 0.14 (Chandrasekhar) to 0.75 (Klitzing); and Recency (age of 50 % of the latest references) ranged from 2 (Klitzing) to 18 (Chandrasekhar) years. Seventy five per cent of the references belonged to journal articles. Highly referred journals were Astrophysical Journal, Physical Review B, Physical Review Letters, Arkiv Fuer Fysik, Surface Science, Physics Letters, and IEEE Transactions on Nuclear Science.
See: Scientometrics Vol. 61 No.1, pp.55-68
author-bios-SRD-19-0063.R1 – Supplemental material for The Network Structure of Police Misconduct
No full textSupplemental material, author-bios-SRD-19-0063.R1 for The Network Structure of Police Misconduct by George Wood, Daria Roithmayr and Andrew V. Papachristos in Socius</p
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