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71.
A rapid procedure for synthesis of highly crystalline and pure samples of JDF-L1 without using organics are reactants or templates is described and indexation of the powder X-ray diffraction pattern of this phase is presented. 相似文献
72.
73.
Krayushkin MM Yarovenko VN Semenov SL Zavarzin IV Ignatenko V Martynkin AY Uzhinov BM 《Organic letters》2002,4(22):3879-3881
[formula: see text] The influence of catalysts, acid chlorides, and solvents in the acylation of methyl 2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylate was studied. Conditions for the regioselective acylation processes were found. Thienopyrrole-based photochrome was synthesized for the first time. 相似文献
74.
The interstellar medium provides a unique laboratory for highly supersonic, driven hydrodynamic turbulence. We propose a theory of such turbulence, test it by numerical simulations, and use the results to explain observational scaling properties of interstellar molecular clouds, the regions where stars are born. 相似文献
75.
We study the continuous time integer valued process , which jumps to each of its two nearest neighbors at the rate of one plus the total time the process has previously spent
at that neighbor. We show that the proportion of the time before t which this process spends at integers j converges to positive random variables V
j
, which sum to one, and whose joint distribution is explicitly described. We also show
Received: 19 December 2000 / Revised version: 1 November 2001 / Published online: 17 May 2002 相似文献
76.
We have proved that every 3-connected planar graph G either contains a path on k vertices each of which has degree at most 5k or does not contain any path on k vertices; the bound 5k is the best possible. Moreover, for every connected planar graph H other than a path and for every integer m ≥ 3 there is a 3-connected planar graph G such that each copy of H in G contains a vertex of degree at least m. 相似文献
77.
A convenient synthesis of arachno-6,9-C2B8H14, based on the reduction of nido-5,6-C2B8H12 with sodium tetrahydroborate, is reported. Electrophilic halogenation of the former carborane produced a series of 1-X-6,9-C2B8H13 (X = Cl, Br and I) derivatives whose constitution was established on the basis of their 1H and 11B NMR spectra. 相似文献
78.
Brillouin and Raman spectroscopy were performed on B2O3 glass compressed to 57 GPa at 273 K. Upon compression the sound velocities increase smoothly and the boroxol ring Raman mode vanishes by 11 GPa. Upon decompression the sound velocities follow a different path and at 3 GPa a discontinuity of 3 km/s in V(p) and 2 km/s in V(s) returns the velocities to the values seen on compression. After the transition, the boroxol ring Raman mode reappears. A second pressure cycle produces the same behavior, suggesting the 3 GPa transition occurs between vitreous polymorphs with different boron coordination. 相似文献
79.
Dubberley SR Ignatov SK Rees NH Razuvaev AG Mountford P Nikonov GI 《Journal of the American Chemical Society》2003,125(3):642-643
A series of hydridosilyl complexes of tantalum, Cp(ArN)Ta(PMe3)(H)(SiClnR3-n) (n = 0-3), was prepared and studied by 29Si NMR, X-ray diffraction, and DFT calculations. An unprecedented increase of the J(Si-H) coupling constant between the hydride and silyl ligands from 14 Hz for n = 0 to 50 Hz n = 3 was observed, which however, according to DFT calculations, does not correspond to stronger bonding interaction between silicon and hydride ligands, with the strongest interaction being for n = 1. 相似文献
80.
Stanislav Kupin 《Arkiv f?r Matematik》2001,39(1):95-119
It is proved in Benamara-Nikolski [1] that if the spectrum σ(T) of a contractionT with finite defects (rank(I−T
*
T)=rank (I−TT
*)<∞) does not coincide with
, then the contraction is similar to a normal operator if and only if
The examples of Kupin-Treil [9] show that the result is no longer true if we replace the condition rank (I−T
*
T)<∞ by its weakened versionG, whereG denotes the class of nuclear operators.
We prove in this paper that, however, the following theorem holds 相似文献