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91.
Degenerate Riemannian metrics exist naturally in various contexts. Unfortunately, their study stops to the ‘admission of failure’ that they are too poor, for instance, to generate a coherent intrinsic or extrinsic differential geometry, e.g. a kind of Levi-Civita connection. In this first text, we start the investigation of rigidity aspects of these structures, from the point of view of isometric actions of ‘big’ (e.g. semi-simple) Lie groups. To cite this article: E. Bekkara et al., C. R. Acad. Sci. Paris, Ser. I 343 (2006). 相似文献
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Frances Chevarley Edmonds 《Discrete Mathematics》1977,19(3):213-227
In this paper we studied m×n arrays with row sums and column sums where (n,m) denotes the greatest common divisor of m and n. We were able to show that the function Hm,n(r), which enumerates m×n arrays with row sums and column sums and respectively, is a polynomial in r of degree (m?1)(n?1). We found simple formulas to evaluate these polynomials for negative values, ?r, and we show that certain small negative integers are roots of these polynomials. When we considered the generating function Gm,n(y) = Σr?0Hm,n(r)yr, it was found to be rational of degree less than zero. The denominator of Gm,n(y) is of the form (1?y)(m?1)(n?1)+3, and the coefficients of the numerator are non-negative integers which enjoy a certain symmetric relation. 相似文献
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96.
Frances L. Moser 《Nuclear Physics B》1977,129(1):28-38
We present results of a study of hyperon and multikaon production in K+p. The data were obtained from a 7.37±0.18 event/μb exposure of the 30″ MURA-ANL hydrogen bubble chamber to a 4.27 GeV/c separated K+ beam. Cross-section results for 3, 4, 5, and 6-body hyperon and multi-kaon final states are presented. We observe production of φ(1019), K1(892), and Y1(1385), but find no evidence for a Y = 2, B = 0 exotic resonance in the KK invariant mass distributions. A study of the inclusive reaction K+p→Λ+ anything is also reported. 相似文献
97.
Frances Pleasonton 《Nuclear Physics A》1973,213(2):413-425
The average number and average energy of γ-rays emitted within ≈ 5 nsec after fission have been determined as functions of fragment mass and as functions of total kinetic energy. They were obtained from a four-parameter experiment that recorded, event-by-event, correlated of γ-rays and of fission-fragment pairs and the time, relative to fission, at which a γ-ray was detected. For 233U(nth, f) the average total number and energy emitted per fission were found to be 6.31 ± 0.3 and 6.69 ± 0.3 MeV, respectively, giving an average photon energy of 1.06 ± 0.07 MeV. The results for 239Pu(nth, f) given in the same order, are 6.88 ± 0.35,6.73 ± 0.35 MeV, and 0.98 ± 0.07 MeV. 相似文献
98.
Frances I. Hurwitz Haiquan Guo Richard B. Rogers Erik J. Sheets Derek R. Miller Katy N. Newlin Molly K. Shave Anna R. Palczer Michael T. Cox 《Journal of Sol-Gel Science and Technology》2012,64(2):367-374
Aluminosilicate aerogels offer potential for extremely low thermal conductivities at temperatures greater than 900?°C, beyond where silica aerogels reach their upper temperature use limits. Aerogels have been synthesized at two Al:Si ratios, a 3Al:1Si mullite composition, and an 8Al:1Si alumina rich composition. Boehmite (AlOOH) is used as the Al source, and tetraethoxysilane as the Si precursor. The influence of Ti as a ternary constituent, introduced through the addition of titanium isopropoxide in the sol?Cgel synthesis, on aerogel morphology and thermal properties is evaluated. Four different boehmite precursor powders are evaluated. Morphology, surface area and pore size, and thermal transformation vary with the crystallite size of the starting boehmite powder, as does incorporation of titanium and evolution of Ti-containing crystalline phases. The addition of Ti influences sol viscosity, gelation time, surface area and pore size distribution, as well as phase formation on heat treatment. 相似文献
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Structure and electrochemical properties for complexes of nitrocompounds with inorganic ions: A theoretical approach
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Liudmyla K. Sviatenko Leonid Gorb Frances C. Hill Danuta Leszczynska Jerzy Leszczynski 《Journal of computational chemistry》2016,37(13):1206-1213
Reduction and oxidation (redox) reactions are widely used for removal of nitrocompounds from contaminated soil and water. Structures and redox properties for complexes of nitrocompounds, such as 2,4,6‐trinitrotoluene (TNT), 2,4‐dinitrotoluene (DNT), 2,4‐dinitroanisole (DNAN), and 5‐nitro‐2,4‐dihydro‐3H?1,2,4‐triazol‐3‐one (NTO), with common inorganic ions (Na+, Cl?, ) were investigated at the SMD(Pauling)/PCM(Pauling)/MPWB1K/TZVP level of theory. Atoms in molecules (AIM) theory was applied to analyze the topological properties of the bond critical points involved in the interactions between the nitrocompounds and the ions. Topological analyses show that intermolecular interactions of the types O(N)…Na+, C‐H…Cl?( ), and C…Cl?( ) may be discussed as noncovalent closed‐shell interactions, while N‐H···Cl?( ) hydrogen bonds are partially covalent in nature. Complexation causes significant decrease of redox activity of the nitrocompounds. Analysis of the reduction potentials of the complexes obtained through application of the Pourbaix diagram of an iron/water system revealed that sodium complexes of NTO might be reduced by metallic iron. © 2016 Wiley Periodicals, Inc. 相似文献