排序方式: 共有47条查询结果,搜索用时 15 毫秒
1.
Yvon Pointud Anne-Gaelle Valade Christelle Pointon Georges Jeminet Jose-Luis Beltran 《Supramolecular chemistry》2013,25(4):261-269
The binding abilities of a new class of 14-membered ring ligands bearing diketal dilactam functions were explored by UV-visible spectrophotometry. Their formation constants, determined in THF solution, showed appreciable complexation with divalent cations (stability order: Sr2+≥Ca2+>Zn2+≥Mg2+>Ba2+) whereas no association was observed with monovalent cations. The stoichiometry of the complexes formed was essentially 1:1 although sometimes a low percentage (<10%) of 1:2 (cation–ligand) species was detected. The corresponding formation constants determined by computation (STAR program) were in the range 1.5<log?β 11<4.8 and 4.4<log?β 12<7.1. They depend significantly on the nature of the substituents. In addition, solvent extractions carried out in a water–chloroform system showed the highest constants (log K ex) for the most substituted macrocycles 7b and 7c (norephedrine series) with a lipophilic skeleton. 相似文献
2.
Joaquin Barbera Mercedes Marcos Ana Omenat Jose-Luis Serrano Jesus I. Martinez Pablo J. Alonso 《Liquid crystals》2013,40(2):255-262
The synthesis and liquid crystalline behaviour of the first and second generations of a dendrimeric structure based on poly(propyleneimine)(DAB-dendr(NH2)x) are reported. 4-(4-n-Alkoxybenzoyloxy)salicylaldehydes are used as mesogenic moieties attached at the peripheral amino groups of the dendrimers giving rise to dendromesogens with four and eight mesogenic branches. From these dendromesogens, considered as organic ligands, were prepared six metal-containing dendrimers which incorporate two or four copper atoms in their structures. All the dendrimeric ligands and three of the metal-containing dendrimers exhibit liquid crystalline properties which were studied by optical microscopy, DSC, X-ray diffraction and EPR spectroscopy. 相似文献
3.
Abstract. In this paper we prove the existence and uniqueness of strong solutions for the stochastic Navier—Stokes equation in bounded
and unbounded domains. These solutions are stochastic analogs of the classical Lions—Prodi solutions to the deterministic
Navier—Stokes equation. Local monotonicity of the nonlinearity is exploited to obtain the solutions in a given probability
space and this significantly improves the earlier techniques for obtaining strong solutions, which depended on pathwise solutions
to the Navier—Stokes martingale problem where the probability space is also obtained as a part of the solution. 相似文献
4.
Santos Alexandre F. Aguado Roberto Corazza Marcos L. Tarrs Quim Sanchez-Salvador Jose-Luis Blanco Angeles Negro Carlos Delgado-Aguilar Marc 《Cellulose (London, England)》2022,29(10):5609-5622
Cellulose - In this work a wide sample analysis, under similar conditions, has been carried out and a calibration strategy based on a careful selection of input variables combined with sensitivity... 相似文献
5.
Solar ultraviolet (UV) light within 280–320 nm (UVB) is the primary cause for virus inactivation in the atmosphere. Only the effect of the direct component has been previously evaluated. We developed a simple regression model to estimate the inactivation of a virus due to direct (unscattered), diffuse (scattered) and total (direct + diffuse) components of solar UV (daily integrated irradiances). The model predicts the maximum number of radiation-days a virus will survive at a given altitude above the ground in rural and urban environments under clear skies. We explored the effect of several environmental variables: visibility, altitude and ground reflectivity. We found that the effect of diffuse radiation on virus inactivation was larger than the direct component. The diffuse irradiance increased with ground albedo (mainly due to reflection of the direct attenuated solar off the ground) and decreased with increased visibility (proportional to aerosol loading in the atmosphere). The diffuse component increased with altitude, but the ratio of diffuse to the total decreased with increased altitude, highlighting the importance of the diffuse component of UV near the ground. Our model may help public health studies in predicting and understanding the effect of environmental parameters on the survival of germs. 相似文献
6.
Efren Diez-Jimenez Jose-Luis Perez-Diaz 《Physica C: Superconductivity and its Applications》2011,471(1-2):8-11
The torque between a permanent magnet and a toroidal superconductor in the Meissner state is calculated using a model previously proposed based on London’s and Maxwell’s equations. A flip effect on the stable orientation of the magnet as a function of position is demonstrated. At large distances the magnet tends to be perpendicular to the axis of the torus, but when you approach it, at a certain point there is a flip and it tends to be parallel to that axis while being closer than a certain limit. This effect can be easily used as a binary detector for proximity. 相似文献
7.
Jose-Luis Menaldi 《Acta Appl Math》1987,8(2):165-198
Optimal stopping and impulse control problems for degenerate diffusion with jumps are studied in this paper. Lipschitzian coefficients for the diffusion process, data with polynomial growth, and evolution in the whole space are the main assumptions on the models. Several characterizations of the optimal cost functions are given. Existence of optimal policies is obtained.This research has been supported in part by Army Research Office Contract DAAG29-83-K-0014 and by National Science Foundation Grant DMS-8601998. 相似文献
8.
José-Luis Menaldi 《Applied Mathematics and Optimization》1982,8(1):131-158
Résumé On caractérise le coût optimal d'un problème de temps d'arrêt déterministe comme la solution maximum d'une inéquation variationnelle du premier ordre. On obtient quelques propriétés de régularité pour le coût optimal.
We give a characterization of the optimal cost of a deterministic stopping time problem as the maximum solution of a first order variational inequality. We obtain some properties of regularity for the optimal cost.相似文献
9.
Several classes of problems can be modelled as queueing systems with failures where preventative maintenance has to be optimized: relevant examples are computer systems, databases and production lines. This paper studies a simple case of such a situation based on the M/M/1 queue where the state of the server can take two values (on, off); the transition on–off happens either when there is a failure or when one decides to maintain. The characterization and an approximation of an optimal policy are given. Extensions to more general models, including general Markov processes, are examined. 相似文献
10.