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881.
3-Phenylpyrimido-[3,4-a]-s-triazines exhibit antiparasitic, antibacterial and antifungal activity. In order to study the metabolism of these heterocycles, 9,9-diethyl-3-phenyl-6,8-dioxo-2,3,4,5,6,7,8,9-octahydropyrimido[3 ,4-a]-s- triazine (TZ) was administered to dogs. Three potential metabolites were synthesized, and these models were identified and quantified with gas chromatography-mass spectrometry. The heterobicyclic compounds, TZ and its hydroxy derivative, underwent thermal degradation under chromatographic conditions. Dog urine spiked with the model metabolites was extracted, and the substances were quantified. The urine of dogs treated with TZ was studied, and two of the potential metabolites were recovered, identified and quantified. 相似文献
882.
Yves Balcou 《Mikrochimica acta》1988,94(1-6):57-60
An FT transfer into time-domain, followed by a double FT deconvolution, allows us to analyze dispersion or absorption curves similar to those obtained in low frequency dielectric or ultrasonic experiments. 相似文献
883.
Reaction of lithium homocuprates with α-hydroxy β-bromo ester derivated from aspartic acid affords α-hydroxy esters of high enantiomerical purity. 相似文献
884.
The group theory for nonrigid molecules is used for studying the internal dynamics of the two equivalent C3v rotor “bent” molecules. Special emphasis is given to the deduction of the symmetry basis vectors which represent in box form the Hamiltonian operator. It is shown that these basis vectors may be advantageously employed in order to simplify the resolution of the two-rotor equation. The procedure is applied to the acetone molecule. It is found that the lowest solutions are clustered into groups of four. The four lowest levels are related to vibrational states, the upper 64 to vibro–rotational states, in which the rotors are rotating in a restricted manner. Only few states show some cogwheel effect. Internal rotation contributions to the principal thermodynamic parameters of acetone are also computed. 相似文献
885.
We study in this paper contraction properties of a matrix semi-groupT ⊂GL(d,R) acting on the flag space ofR
d
; then we obtain properties of the Liapunoff exponents of theT-valued products of random matrices. The principal result is that, in this study, we can replaceT by its algebraic closureH inGL(d,R). This implies a “decomposition” of the action ofT in a proximal part and an isometric part; then we can write, modulo cohomology, the corresponding cocycle in a block-diagonal
form, the blocks being similarities. In fact, we can express the multiplicities of the exponents in terms of the diagonal
part of a conjugate of the groupH. So we obtain an extension of a recent result of Goldsheid and Margulis about the simplicity of Liapunoff’s spectrum [5];
this work uses their ideas as well as those of previous work [6].
相似文献
886.
Efficient Scheduling Rules in a Combined Make-to-Stock and Make-to-Order Manufacturing System 总被引:1,自引:0,他引:1
Khaled Hadj Youssef Christian Van Delft Yves Dallery 《Annals of Operations Research》2004,126(1-4):103-134
In this paper, we consider a mixed MTS/MTO policy to manage a single manufacturing facility producing two classes of end-products. A few end-products have high volume demands, whereas a fairly large number of end-products have low volume demands. In this situation, it is appealing to try to produce the high volume products according to an MTS policy and the low volume products according to an MTO policy. The purpose of this paper is to analyze and compare the impact of the choice of the scheduling policy on the overall performance of the system. We consider two policies: the classical FIFO policy and a priority policy (PR). The PR policy gives priority to production orders corresponding to low volume products over production orders corresponding to high volume products. Under some simple stochastic modeling assumptions, we develop analytical/numerical solutions to optimise each system. We then provide insights regarding this issue with the help of numerical examples. It appears that for some range of parameters, the PR rule can outperform the FIFO rule in the sense that, to achieve the same service level constraint, the corresponding cost under the PR rule is much lower. This situation is encountered when the low volume products can be managed with an MTO policy under the PR scheduling rule, while they have to be managed according to an MTS policy under the FIFO scheduling rule. We also derive some theoretical properties that support our empirical findings. 相似文献
887.
Yves Martinez-Maure 《Archiv der Mathematik》2002,79(6):489-498
LetC be a convex curve of constant width and of classC
4
+
. It is known thatC has at least 6 vertices and its interior contains either a point through which infinitely many normals pass or an open set
of points through each of which pass at least 6 normals. If all its vertices are nondegenerate, then: (i)C has exactly 6 vertices if, and only if, its evolute is the boundary of a topological disc through each interior point of
which pass at least 6 normals; (ii) ifC has more than 6 vertices, then there exists an open set of points through each of which pass at least 10 normals. The proof:
(i) expresses the number of normals passing through a point as a function of the index with respect to the evolute; (ii) relates
this index to the number of singularities of the evolute (i.e. of vertices). Furthermore, we give formulas for counting singularities
of generic hedgehogs in ℝ2 and ℝ3.
相似文献
888.
Claude Benzaken Yves Crama Pierre Duchet Peter L. Hammer Frdric Maffray 《Journal of Graph Theory》1990,14(4):413-422
New characterizations of triangulated and cotriangulated graphs are presented. Cotriangulated graphs form a natural subclass of the class of strongly perfect graphs, and they are also characterized in terms of the shellability of some associated collection of sets. Finally, the notion of stability function of a graph is introduced, and it is proved that a graph is triangulated if and only if the polynomial representing its stability function has all its coefficients equal to 0, +1 or ?1. 相似文献
889.
An efficient method to determine the optimal configuration of a flexible manufacturing system 总被引:3,自引:0,他引:3
A frequently encountered design issue for a flexible manufacturing system (FMS) is to find the lowest cost configuration, i.e. the number of resources of each type (machines, pallets, ...), which achieves a given production rate. In this paper, an efficient method to determine this optimal configuration is presented. The FMS is modelled as a closed queueing network. The proposed procedure first derives a heuristic solution and then the optimal solution. The computational complexity for finding the optimal solution is very reasonable even for large systems, except in some extreme cases. Moreover, the heuristic solution can always be determined and is very close (and often equal) to the optimal solution. A comparison with the previous method of Vinod and Solberg shows that our method performs very well. 相似文献
890.
Yves Brihaye Stefan Giller Piotr Kosinski Jan Nuyts 《Communications in Mathematical Physics》1997,187(1):201-226
The set of linear, differential operators preserving the vector space of couples of polynomials of degrees n and n-2 in one real variable leads to an abstract associative graded algebra . The irreducible, finite dimensional representations of this algebra are classified into five infinite discrete sets and
one exceptional case. Their matrix elements are given explicitly. The results are related to the theory of quasi exactly solvable
equations.
Received: 1 February 1996 / Accepted: 20
December
1996 相似文献