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101.
Edward Witten 《Communications in Mathematical Physics》1985,100(2):197-229
A general formula for global gauge and gravitational anomalies is derived. It is used to show that the anomaly free supergravity and superstring theories in ten dimensions are all free of global anomalies that might have ruined their consistency. However, it is shown that global anomalies lead to some restrictions on allowed compactifications of these theories. For example, in the case of O(32) superstring theory, it is shown that a global anomaly related to 7(O(32)) leads to a Dirac-like quantization condition for the field strength of the antisymmetric tensor field.Related to global anomalies is the question of the number of fermion zero modes in an instanton field. It is argued that the relevant gravitational instantons are exotic spheres. It is shown that the number of fermion zero modes in an instanton field is always even in ten dimensional supergravity.Supported in part by NSF Grant No. PHY80-19754 相似文献
102.
Rosenberg Edward Freeman William Carlos Zinnia Hardcastle Kenneth Yong Jin Yoo Milone Luciano Gobetto Roberto 《Journal of Cluster Science》1992,3(4):439-457
The general relationships between trinuclear cluster reactivity and the ligand dynamical processes in these systems are explored. Three specific mechanistic studies are presented: (1) the rate and stereochemistry of ligand addition to 3-imidoyl complexes, (2) the factors influencing the rate of carbon-hydrogen bond activation in 3-alkyne complexes, and (3) the origin of anomalously large kinetic deuterium isotope effect in metal to ligand and ligand to metal hydrogen transfer in trinuclear and binuclear complexes. In all three cases, the current state of the mechanistic studies are summarized and the possible rate of specific ligand dynamical processes in controlling the mechanism are put forth. 相似文献
103.
Edward E. Flagg Donald L. Schmidt 《Journal of polymer science. Part A, Polymer chemistry》1970,8(1):1-14
Poly[tris(diorganophosphinato)alanes], [Al(OPRR′O)3]n, were synthesized in which the organic moieties (R,R′) contained from one to eighteen carbon atoms. Polymeric properties depended upon the organic moieties; polymers were fusible, tractable, and flexible when the organic moieties contained six or more carbon atoms. Soluble polymers were prepared by using mixtures of symmetrical and unsymmetrical phosphinates. One polymer, poly{bis[n-butyl(benzyl)phosphinato]di-n-octylphosphinatoalane}, exhibited a degree of polymerization greater than 1000 and an exceptionally high intrinsic viscosity of 37 dl/g. The properties of the different polymers are discussed, and feasible structures are proposed. 相似文献
104.
Jaan A. Pesti Jill A. Downard Mark D. Lauritsen Goss S. Kauffman Walter M. Bryant George F. Huhn John F. Arnett Robert E. Yule James Segretario Kimberly A. Nelson Edward F. Gorko Gary O. Page Lisa M. Lloyd Richard E. Olson Christopher S. Bamum Joseph J. Mrowca 《Journal of heterocyclic chemistry》1998,35(1):249-255
The methanesulfonates of (α-(4-chlorophenyl)-α-[1-(2-chlorophenyl)ethenyl]-1H-1,2,4-triazole-1-ethanol and α-[1-(2-chlorophenyl)ethenyl]-α-(2,4-difluorophenyl)-1H-1,2,4-triazole-1-ethanol ( 1a, b ) are orally effective α-styryl carbinol derivatives developed for the treatment and prevention of systemic fungal infections. Practical new processes amenable for the large-scale production of these compounds are described. Of note is the selection of dichlorostyrene as a convenient precursor of the styryl portion, modification of a sensitive Grignard addition into a realistic preparative reaction and the use of 1,2,4-triazole simultaneously as a base transfer agent and nucleophile. 相似文献
105.
A procedure for the evaluation of heats of transition in scanning calorimetry has been developed. A formula for evaluation of the energy of fusion of a compound at its melting point is derived that takes into account the baseline shift that is attributable to the heat capacity change on melting. Several other calorimeter parameters of importance are discussed. These include heat exchange between calorimeter vessel and jacket, the time constant of the instrument, the scanning rate, and the heater placement. 相似文献
106.
107.
The hydrolysis of ethyl formate catalysed by hydrochloric acid was studied at three temperatures in water-acetone media and in water media containing different concentrations of sodium nitrate. The effect of various ionic strengths and dielectric constants upon the rate of acid hydrolysis of ethyl formate is presented from the point of electrostatics and the results were compared to like effects upon the acid hydrolysis of ethyl acetate and methyl propionate. Neither the dielectric constant effect nor the salt effect lends itself readily to theoretical interpretation. It was assumed that a partial explanation of these anomalous results might be in the extrapolation of the acid radical to the simplest carboxylic acid. This suggestion was supported somewhat by the trends towards less adherance to the electrostatic theory at certain temperatures in the series methyl propionate, ethyl acetate and ethyl formate. 相似文献
108.
Acetonitrile and [D3]acetonitrile in the vicinal region of a planar AgX fiber contain linear dipole–dipole linked oligomers as shown by 1) comparison of infrared band intensity ratios in the gaseous and condensed phases and 2) remarkable plots of absorbance (C? N stretch) versus time during evaporation from an AgX planar fiber element. The plots (CH3CN 2252 cm?1, CD3CN 2262 cm?1) reveal the presence of octamers, hexamers, tetramers, and dimers along with some heptamer, trimer, and monomer structures. A novel isotope effect arises from the somewhat smaller size of the CD3CN resulting in an increase in the CN band intensity. The organized oligomers may be termed pseudocrystals and are the main components responsible for absorption intensity in the infrared spectrum of acetonitrile, on the AgX planar fiber or in an IR cell. 相似文献
109.
[reaction: see text] The synthesis of four bioactive analogues of the somatostatin (SRIF-14) mimetic, beta-d-glucoside (+)-2, in which the C1 indole side chain is replaced with indole surrogates, has been achieved. These congeners, possessing the naphthyl, benzothiophene, benzyl, and benzofuran substituents, were predicted to satisfy the electrostatic requirements of the tryptophan binding pocket of SRIF. Unlike the previously described C4 picolyl and pyrazinyl congeners, these ligands bind the hSST4 receptor. 相似文献
110.
Treatment of α-hydroxy-α-phenyl-o-toluidide with phosphorus tribromide afforded a series of 4H-3,1-benzoxazines. These last, when reacted with potassium amide in liquid ammonia, ring contracted to 2,3-disubstituted 3H-indol-3-ols. The scope of this rearrangement was examined. The indolols on treatment with hot base were found to rearrange to indoxyls. Several of these as well as their N-alkylation products are described. 相似文献