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801.
Vincent Calvez Nicolas Meunier Raphael Voituriez 《Comptes Rendus Mathematique》2010,348(11-12):629-634
We investigate in this Note the dynamics of a one-dimensional Keller–Segel type model on the half-line. On the contrary to the classical configuration, the chemical production term is located on the boundary. We prove, under suitable assumptions, the following dichotomy which is reminiscent of the two-dimensional Keller–Segel system. Solutions are global if the mass is below the critical mass, they blow-up in finite time above the critical mass, and they converge to some equilibrium at the critical mass. Entropy techniques are presented which aim at providing quantitative convergence results for the subcritical case. This Note is completed with a brief introduction to a more realistic model (still one-dimensional). 相似文献
802.
Raphael Loewy 《Linear and Multilinear Algebra》2013,61(3):213-229
An (n m) hypergraph is a coupleH=(N E), where the vertex set N is {1,…n} and the edge set E is an m-element multiset of nonempty subsets of N. In this paper, we count nonisomorphic hypergraphs where isomorphism of hypergraphs is the natural extension of that of graphs. A main result is an explicit formula for the cycle index of the permutation representation of any permutation group P with object set N acting on the k-element subsets of N. By making a simple substitution in these cycle indices for P the symmetric group SN and k=1,…,n, we obtain generating functions which enumerate various types of hypergraphs. Using the technique developed, we extend Snapper's results on characteristic polynomials of permutation representations and group characters from the case where the group has odd order to the general case. 相似文献
803.
Victoria Mae Tsuruzaki Shinkai Izana Marize Oliveira Sampaio Eline Gomes dos Santos Adan Jesús Galu-Parra Dionisia Pelaes Ferreira Drielly Dayanne Monteiro Santos Baliza Neidiane Farias Ramos Raphael Sanzio Pimenta Rommel Mario Rodriguez Burbano Chubert Bernardo Castro Sena Barbarella Matos Macchi Irlon Maciel Ferreira Edilene Oliveira Silva Jos Luiz Martins do Nascimento 《Molecules (Basel, Switzerland)》2022,27(24)
804.
Let D be a simple digraph without loops or digons. For any v ? V(D) v\in V(D) , the first out-neighborhood N+(v) is the set of all vertices with out-distance 1 from v and the second neighborhood N++(v) of v is the set of all vertices with out-distance 2 from v. We show that every simple digraph without loops or digons contains a vertex v such that |N++(v)| 3 g|N+(v)| |N^{++}(v)|\geq\gamma|N^+(v)| , where % = 0.657298... is the unique real root of the equation 2x3 + x2 -1 = 0. 相似文献
805.
Gagik Ghazaryan Raphael Schaller Kirill Feldman Theo A. Tervoort 《Journal of Polymer Science.Polymer Physics》2016,54(21):2233-2244
Poly(l ‐lactic acid) (PLLA) is a bio‐degradable polyester which exhibits brittle behaviour due to relatively fast physical ageing of the amorphous phase. This work describes the effects of thermal rejuvenation and molecular orientation of the amorphous phase on this physical ageing process. Uniaxial compression testing showed that physical ageing of the amorphous phase increases the yield stress and the associated strain softening response, both contributing to the observed embrittlement of PLLA in tension. Molecular orientation at constant crystallinity was applied by uniaxial and biaxial plastic deformation just above the glass transition temperature, up to plastic strains of 200% to avoid strain‐induced crystallisation. Using stress‐relaxation experiments combined with tensile testing, both as a function of ageing time, it is shown that both uniaxial and biaxial plastic deformation in excess of 150% plastic strain, decelerates and possibly prohibits the physical ageing process. The oriented monofilaments and films have improved mechanical properties such as stiffness, strength and strain‐to‐break, which were not affected by physical ageing during the whole testing period (40 days). In addition, plastic deformation to higher draw ratios and/or higher temperatures strongly enhanced crystallinity and resulted in PLLA monofilaments and films that also exhibited tough behaviour, not affected by physical ageing. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2233–2244 相似文献
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Raphael J. F. Berger Michael Hartmann Pekka Pyykkoe Dage Sundholm Hubert Schmidbaur 《ChemInform》2001,32(32):no-no
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献