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951.
NMR spectra of N-acyletrahydro quinaldines 12–19 and of pyridodibenzoxazepines 21–24 show the Me group to be axially oriented with the tetrahydropyridine ring in a half-boat conformation. The aroyl phenyl in both is twisted out of the CO plane. While the Me group again occupies the axial position in pyridophenanthridones 5 and 7 and pyridooxazinones 8 and 9, the tetrahydropyridine ring exists as a half-chair. 相似文献
952.
C. G. Ramachandran Nair A. R. Vasudeva Murthy 《Monatshefte für Chemie / Chemical Monthly》1963,94(1):134-140
Zusammenfassung Elementarer Schwefel S8, Heptaschwefelimid S7NH und Tetraschwefeltetraimid S4(NH)4 werden bei Zimmertemp. durch Chloramin T in homogener saurer Lösung quantitativ zu Schwefelsäure oxydiert. Die Hydrolyse von S8 und S7NH in homogener alkalischer Lösung verläuft rasch und ergibt ein Gemisch von Sulfid, Sulfit und Thiosulfat. In neutraler homogener Lösung reagiert Natriumsulfit mit S7NH zu Trithionat und Thiosulfat, mit S8 zu Thiosulfat. S4(NH)4 ist etwas resistenter gegenüber nucleophilen Angriffen, wird aber durch Säuren in homogenem Medium zu elementarem Schwefel, Schwefeldioxyd und geringen Mengen Schwefelwasserstoff zersetzt. Unter gleichen Bedingungen bildet sich aus S7NH bei Säureeinwirkung haupt-sächlich elementarer Schwefel; Schwefeldioxyd und Schwefelwasserstoff werden nur in geringen Mengen gebildet. 相似文献
953.
Suppose that there are n jobs and n machines and it costs cij to execute job i on machine j. The assignment problem concerns the determination of a one‐to‐one assignment of jobs onto machines so as to minimize the cost of executing all the jobs. When the cij are independent and identically distributed exponentials of mean 1, Parisi [Technical Report cond‐mat/9801176, xxx LANL Archive, 1998] made the beautiful conjecture that the expected cost of the minimum assignment equals . Coppersmith and Sorkin [Random Structures Algorithms 15 ( 6 ), 113–144] generalized Parisi's conjecture to the average value of the smallest k‐assignment when there are n jobs and m machines. Building on the previous work of Sharma and Prabhakar [Proc 40th Annu Allerton Conf Communication Control and Computing, 20 , 657–666] and Nair [Proc 40th Annu Allerton Conf Communication Control and Computing, 17 , 667–673], we resolve the Parisi and Coppersmith‐Sorkin conjectures. In the process we obtain a number of combinatorial results which may be of general interest.© 2005 Wiley Periodicals, Inc. Random Struct. Alg. 2005 相似文献
954.
We introduce and analyze a stable procedure for the approximation of where is the least residual norm solution of the minimal norm of the ill-posed equation , with compact operator between Hilbert spaces, and has some smoothness assumption. Our method is based on a finite number of singular values of and some finite rank operators. Our results are in a more general setting than the one considered by Rieder and Schuster (2000) and Nair and Lal (2003) with special reference to the mollifier method, and it is also applicable under fewer smoothness assumptions on .
955.
Gangopadhyay P Kesavamoorthy R Bera S Magudapathy P Nair KG Panigrahi BK Narasimhan SV 《Physical review letters》2005,94(4):047403
Results obtained from the optical absorption and photoluminescence (PL) spectroscopy experiments have shown the formation of excitons in the silver-exchanged glass samples. These findings are reported here for the first time. Further, we investigate the dramatic changes in the photoemission properties of the silver-exchanged glass samples as a function of postannealing temperature. Observed changes are thought to be due to the structural rearrangements of silver and oxygen bonding during the heat treatments of the glass matrix. In fact, photoelectron spectroscopy does reveal these chemical transformations of silver-exchanged soda glass samples caused by the thermal effects of annealing in a high vacuum atmosphere. An important correlation between temperature-induced changes of the PL intensity and thermal growth of the silver nanoparticles has been established in this Letter through precise spectroscopic studies. 相似文献
956.
In a new general indole synthesis, the anion derived from benzotriazolyl derivative 5b underwent regioselective 1,4-addition to various alpha,beta-unsaturated ketones; subsequent acid-catalyzed cyclization formed the corresponding indoles 1a-f. 相似文献
957.
A facile synthesis of highly functionalized 2-oxymaleate and furanone derivatives by the multicomponent reaction of 1,3-dimesityl imidazolin-2-ylidene/imidazol-2-ylidene, DMAD, and aldehydes is described. 相似文献
958.
[reaction: see text] The reported synthesis of 2-arylbenzothiazoles mediated by ceric ammonium nitrate (CAN) is irreproducible; the only products formed in this reaction are bis-(p-tolyl) disulfide and p-tolyl p-toluenethiosulfonate. 相似文献
959.
A simple procedure is suggested for generating the 2n - 1 Lanczos tridiagonal elements from the 2n - 1 moments of any hamiltonian with regard to a given starting vector. The numerical feasibility is studied in the quartic oscillator example. 相似文献
960.
The Thomas-Fermi screening of non-Abelian gauge fields by fermions or screening of gluon fields in quark matter is discussed. It is described by an effective mass term which is, as with hard thermal loops, related to the eikonal for a Chern-Simons theory and the Wess-Zumino-Witten action. 相似文献