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91.
MD. Akhtaruzzaman Masaaki Tomura Kazuko Takahashi Jun-Ichi Nishida 《Supramolecular chemistry》2013,25(4):239-243
Hydrogen-bonding networks of π-extended 4,4′-bipyridines, 2,5-di(4-pyridyl)thiophene (1), 2,5-di(4-pyridyl)furan (2) and 1,4-di(4-pyridyl)benzene (3) with 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid, CA) have been investigated. The dipyridyl compounds afforded complexes 4 [(dication of 1)·(monoanion of CA)2], 5 [(dication of 2)·(dianion of CA)·(MeOH)] and 6 [(3)·(dication of 3)·(dianion of CA)·(H2O)6] with CA. X-ray structure analyses revealed the formation of unusual molecular tape and sheet structures involving N–H ?O, O–H ?O, C–H ?O and N–H ?N hydrogen bonds, where the aromatic spacer groups play an important role in constructing the unique crystal structures. 相似文献
92.
We use the formalism of Geometrothermodynamics to describe chemical reactions in the context of equilibrium thermodynamics. Any chemical reaction in a closed system is shown to be described by a geodesic in a 2-dimensional manifold that can be interpreted as the equilibrium space of the reaction. We first show this in the particular cases of a reaction with only two species corresponding to either two ideal gases or two van der Waals gases. We then consider the case of a reaction with an arbitrary number of species. The initial equilibrium state of the geodesic is determined by the initial conditions of the reaction. The final equilibrium state, which follows from a thermodynamic analysis of the reaction, is shown to correspond to a coordinate singularity of the thermodynamic metric which describes the equilibrium manifold. 相似文献
93.
Hernando A. Trujillo Wendy M. Simon Erin T. Pelkey Gordon W. Gribble Jerry P. Jasinski 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):386-388
In the isomeric compounds 2‐benzyl‐3‐methyl‐1‐phenylbenzo[b]furo[2,3‐c]pyrrole and 2‐benzyl‐1‐methyl‐3‐phenylbenzo[b]furo[2,3‐c]pyrrole, both C24H19NO, the pyrrole ring, although presumably somewhat strained, does not differ appreciably from N‐methylpyrrole except for a relatively short C—C single bond in the pyrrole ring. 相似文献
94.
Hernando A Mayol R Pi M Barranco M Ancilotto F Bünermann O Stienkemeier F 《The journal of physical chemistry. A》2007,111(31):7303-7308
We present systematic results, based on density functional calculations, for the structure and energetics of 3He and 4He nanodroplets doped with alkaline earth atoms. We predict that alkaline earth atoms from Mg to Ba go to the center of 3He drops, whereas Ca, Sr, and Ba reside in a deep dimple at the surface of 4He drops, and Mg is at their center. For Ca and Sr, the structure of the dimples is shown to be very sensitive to the He-alkaline earth pair potentials used in the calculations. The 5s5p <-- 5s2 transition of strontium atoms attached to helium nanodroplets of either isotope has been probed in absorption experiments. The spectra show that strontium is solvated inside 3He nanodroplets, supporting the calculations. In the light of our findings, we emphasize the relevance of the heavier alkaline earth atoms for analyzing mixed 3He-4He nanodroplets, and in particular, we suggest their use to experimentally probe the 3He-4He interface. 相似文献
95.
We address the problem of defining the concept of entropy for anisotropic cosmological models. In particular, we analyze for
the Bianchi I and V models the entropy which follows from postulating the validity of the laws of standard thermodynamics
in cosmology. Moreover, we analyze the Cardy–Verlinde construction of entropy and show that it cannot be associated with the
one following from relativistic thermodynamics. 相似文献
96.
B. Hernando P. AlvarezJ.D. Santos P. GorríaM.L. Sánchez J. OliveraM.J. Pérez V.M. Prida 《Journal of magnetism and magnetic materials》2006
The influence of isothermal annealing (1 h at 600 °C in Ar atmosphere) on the soft magnetic properties and magnetoimpedance (MI) effect has been studied in ribbons of the following Nanoperm alloys: Fe91Zr7B2, Fe88Zr8B4, Fe87Zr6B6Cu1 and Fe80Zr10B10. A maximum MI ratio of about 27% was measured for the nanocrystalline alloy Fe87Zr6B6Cu1 at a driving frequency of 0.2 MHz. The thermal annealing led to magnetic softening for this alloy, while a hardening is observed for the Fe80Zr10B10 alloy. 相似文献
97.
A. Hernando V. Madurga J.M. Barandiarán O.V. Nielsen 《Solid State Communications》1985,54(12):1059-1063
Some previously reported experimental results dealing with magnetostriction and induced magnetic anisotropy are analyzed with respect to the alloy composition. It is found that the properties which are affected by directional order vary with the composition as the probability for finding Bernal tetrahedral holes surround by 3Co1Fe or 3Fe1Co and not as the probability for finding metal—metal pairs as predicted by diatomic ordering theory for ideal solutions. 相似文献
98.
In this study, we provide methods for drawing a tree with n vertices on a convex polygon, without crossings and using the minimum number of edges of the polygon. We apply the results to obtain planar packings of two trees in some specific cases. © 2002 Wiley Periodicals, Inc. J Graph Theory 40: 172–181, 2002 相似文献
99.
Chaos and multiple periods are presented for the harmonically excited unsymmetrical spring and damping system with clearance. This paper demonstrates the non-linear behaviour of the motion through simulation and experiment. Intensive care and caution are taken in the experiments to observe the chaos and the multiple periods properly. The focus in this paper is mainly on the change of the bilinear spring stiffness ratio as a prime factor by which chaotic motions occur from quasi-periodic motion. Other investigations and effects on motion are also discussed for the changing of the extent of clearance. The investigations are based on frequency response curves. To understand the dynamics of the non-linearity of this model, all possible data processing and displaying techniques are taken into account. To observe the overall phenomena of this bilinear system, the resonance curves and the bifurcation diagrams are taken thoroughly for a wide frequency region. 相似文献
100.
Electron bubbles in superfluid (4)He have been recently observed in low-temperature cavitation measurements under experimental conditions where quantized vortices are also present in the liquid, and which might be attached to the bubbles. We have calculated, within density functional theory, the structure and energetics of electron bubbles pinned to linear vortices in liquid (4)He at low temperature, and the pressure at which such structures become mechanically unstable. Our results are in semiquantitative agreement with the experiments. We discuss dynamical effects not included in the theoretical model used in the present calculations, and which could explain some discrepancies between our results and the experimental data. 相似文献