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排序方式: 共有288条查询结果,搜索用时 15 毫秒
121.
The existence and stability closed timelike curves in a Bonnor–Ward spacetime without torsion line singularities is shown
by exhibiting particular examples. 相似文献
122.
Fredy R. Prez Julio Belmar Claudio Jimnez Yanko Moreno Patricio Hermosilla Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(6):m318-m320
The title compound, [Cu(C19H26N3O)2], is the first reported complex of the alkylpyrazolone‐derived ligand 1‐n‐hexyl‐3‐methyl‐4‐[1‐(phenylimino)propyl]‐1H‐pyrazol‐5(4H)‐one. The most notable feature is the imine–enol character presented by the ligand due to coordination, in spite of its enamine–ketone structure in the free state. The ligand chelates through N and O atoms, resulting in a square‐planar coordination around the CuII atom, which lies on an inversion centre. 相似文献
123.
Generalizing the $$\mathfrak {bms}_{3}$$ and 2D-conformal algebras by expanding the Virasoro algebra
Ricardo Caroca Patrick Concha Evelyn Rodríguez Patricio Salgado-Rebolledo 《The European Physical Journal C - Particles and Fields》2018,78(3):262
By means of the Lie algebra expansion method, the centrally extended conformal algebra in two dimensions and the \(\mathfrak {bms}_{3}\) algebra are obtained from the Virasoro algebra. We extend this result to construct new families of expanded Virasoro algebras that turn out to be infinite-dimensional lifts of the so-called \(\mathfrak {B}_{k}\), \(\mathfrak {C}_{k}\) and \(\mathfrak {D}_{k}\) algebras recently introduced in the literature in the context of (super)gravity. We also show how some of these new infinite-dimensional symmetries can be obtained from expanded Ka?–Moody algebras using modified Sugawara constructions. Applications in the context of three-dimensional gravity are briefly discussed. 相似文献
124.
Olalla Barreiro-Costa Gabriela Morales-Noboa Patricio Rojas-Silva Eliana Lara-Barba Javier Santamaría-Aguirre Natalia Bailn-Moscoso Juan Carlos Romero-Benavides Ana Herrera Cristina Cueva Lenin Ron-Garrido Ana Poveda Jorge Heredia-Moya 《Molecules (Basel, Switzerland)》2021,26(16)
This work focuses on the search and development of drugs that may become new alternatives to the commercial drugs currently available for treatment of leishmaniasis. We have designed and synthesized 12 derivatives of bis(spiropyrazolone)cyclopropanes. We then characterized their potential application in therapeutic use. For this, the in vitro biological activities against three eukaryotic models—S. cerevisiae, five cancer cell lines, and the parasite L. mexicana—were evaluated. In addition, cytotoxicity against non-cancerous mammalian cells has been evaluated and other properties of interest have been characterized, such as genotoxicity, antioxidant properties and, in silico predictive adsorption, distribution, metabolism, and excretion (ADME). The results that we present here represent a first screening, indicating two derivatives of bis(spiropyrazolone)cyclopropanes as good candidates for the treatment of leishmaniasis. They have good specificity against parasites with respect to mammalian cells. 相似文献
125.
Oscar A. Negrete Patricio Vargas Francisco J. Pea Gonzalo Saravia Eugenio E. Vogel 《Entropy (Basel, Switzerland)》2021,23(8)
Beyond the usual ferromagnetic and paramagnetic phases present in spin systems, the usual q-state clock model presents an intermediate vortex state when the number of possible orientations q for the system is greater than or equal to 5. Such vortex states give rise to the Berezinskii-Kosterlitz-Thouless (BKT) phase present up to the XY model in the limit . Based on information theory, we present here an analysis of the classical order parameters plus new short-range parameters defined here. Thus, we show that even using the first nearest neighbors spin-spin correlations only, it is possible to distinguish the two transitions presented by this system for q greater than or equal to 5. Moreover, the appearance at relatively low temperature and disappearance of the BKT phase at a rather fix higher temperature is univocally determined by the short-range interactions recognized by the information content of classical and new parameters. 相似文献
126.
The ion/molecule reactions of molybdenum and tungsten monoxide cations MO+ (M═Mo, W) with ethanol have been studied by Fourier transform ion-cyclotron resonance mass spectrometry (FT-ICR MS) and density functional theory (DFT) calculations. As observed in the previously reported reactions of MO2 + (M═Mo, W) towards ethanol, the dehydration of ethanol to give rise to the elimination of neutral C2H4 constitutes also the dominating reaction channel for the monoxides. Likewise, both systems result in a combined dehydrogenation/dehydration process, thus forming the ionic product MOC2H2 +; moreover, the tungsten system presents two additional reaction channels: double dehydrogenation of ethanol with concomitant formation of the ionic product WO2C2H2 + and the generation of C2H5 + which takes place by OH? transfer from ethanol to the tungsten atom. This combined experimental/computational study of gas-phase ion molecule reactions may shed some new light on the mechanisms that occur in complex catalytic systems. 相似文献
127.
Skip lists, introduced by Pugh, provide an alternative to search trees, although a precise analysis of their behaviour had been elusive. The exact value of the expected cost for the search of themth element in a skip list ofn elements is derived first in terms of previously studied functions, and secondly as an asymptotic expression. The latter suggests that Pugh's upper bound of the expected search cost is fairly tight for the interesting cases. Assuming a uniform query distribution, the exact and an asymptotic value of the average (over allm) expected search cost in a skip list ofn elements is also derived. Finally, all insert and delete costs are obtained.This research was supported in part by the Natural Science and Engineering Research Council of Canada under grant No. A-8237, the Information Technology Research Centre of Ontario, and FON-DECYT (Chile) under grant 91-1252. 相似文献
128.
The title problem is solved using very simple polynomial co-ordinate functions and a variational approach.Rather general boundary conditions are assumed at the edge support. It is shown that the approach is valid for axi- and antisymmetric modal configurations. 相似文献
129.
Eduardo A. Soto-Bustamante Rafael Vergara-Toloza Danilo Salda o-Hurtado Patricio Navarrete-Encina 《Liquid crystals》2003,30(5):585-589
The synthesis and measurement of thermodynamic properties of six methacrylate-based polymers were undertaken to observe the relationship between structural aliphatic features and mesophase properties. X-ray measurements on some of the polymers investigated show, as expected, the existence of bilayered smectic phases SmC 2 and SmA d . Taking into account our previous results, an interesting trend in the tilt angle was found that might be related to the difference in alkyl chain substitution. 相似文献
130.