排序方式: 共有102条查询结果,搜索用时 375 毫秒
51.
M.T. Borowiec V.P. Dyakonov A. Szewczyk M.U. Gutowska T. Zayarnyuk E.E. Zubov 《Phase Transitions》2013,86(11-12):944-951
The results of measurements of thermal properties (specific heat) of potassium holmium double tungstate KHo(WO4)2 as a function of temperature (from 0.5 to 300?K) and magnetic field (up to 2?T) are presented. The total specific heat without the phonon and Schottky contributions is found to have the anomaly with maximum at T SPT?~?5?K. This anomaly is likely related with the structural phase transition (SPT) caused by the cooperative Jahn–Teller effect. The increase of specific heat at very low temperatures and its shift towards high temperatures with increasing magnetic field are observed. The origin of this behaviour can be connected with possible magnetic phase transition induced by magnetic field. 相似文献
52.
Oksana Gorban Susanna Synyakina Galina Volkova Yurii Kulik Tetyana Konstantinova 《高压研究》2013,33(1):72-80
The surface state of partially stabilized zirconia with nanoparticles of sizes 10–30 nm after temperature and pressure treatments was investigated by Fourier transform infrared spectroscopy, X-ray diffraction and small-angle X-ray scattering. It is shown that the synthesized nanoparticles are surface fractals and the fractal dimensions non-monotonically change with nanoparticles size change. The martensite tetragonal-to-monoclinic transition of the partially stabilized zirconia nanoparticles under hydrostatic pressure (100–1000 MPa) was investigated. It was shown that the character of the martensite transition in nanoparticles’ system depends on the pressure values. Three ranges of pressures were revealed. It was shown that the stability of martensite tetragonal–monoclinic transition decreases with the increase in size of the nanoparticles only for the pressures range of 300–500 MPa. Below 200 MPa, the character of the martensite transition is extreme and has a maximum for the particle size of 17 nm. In pressure range of 600–1000 MPa, the degree of martensite transition is dependent on the fractal dimension of the surface. 相似文献
53.
Tetyana Petrova Bakhtiyor F. Rasulev Andrey A. Toropov Danuta Leszczynska Jerzy Leszczynski 《Journal of nanoparticle research》2011,13(8):3235-3247
Fullerenes are sparingly soluble in many solvents. The dependence of fullerene’s solubility on molecular structure of the
solvent must be understood in order to manage efficiently this class of compounds. To find such dependency ab initio quantum-chemical
calculations in combination with quantitative structure–property relationship (QSPR) tool were used to model the solubility
of fullerene C60 in 122 organic solvents. A genetic algorithm and multiple regression analysis (GA-MLRA) were applied to generate correlation
models. The best performance is accomplished by the four-variable MLRA model with prediction coefficient r
test2 = 0.903. This study reveals a correlation of highest occupied molecular orbital energy (HOMO), certain heteroatom fragments,
and geometrical parameters with solubility. Several other important parameters of solvents that affect the C60 solubility have been also evaluated by the QSPR analysis. The employed GA-MLRA approach enhanced by application of quantum-chemical
calculations yields reliable results, allowing one to build simple, interpretable models that can be used for predictions
of C60 solubility in various organic solvents. 相似文献
54.
In the energy domain of 1?C2 GeV kinetic energy per nucleon, HADES has measured rare and penetrating probes in elementary and heavy ion collisions. Our results demonstrate that electron pair emission in C+C collisions can essentially be explained as a superposition of independent N+N collisions. HADES results on e+e? production in Ar+KCl collisions, however, show a strong enhancement of the dilepton yield relative to a reference spectrum obtained from elementary nucleon-nucleon reactions, signal the onset of medium effects beyond the superposition of individual N+N collisions. Intriguing results where also obtained from the reconstruction of hadrons with open and hidden strangeness. Analyses of the experimentally obtained hadronic yields measured in Ar+KCl allows to extract the chemical freeze-out conditions in the T -??B phase diagram of strongly interacting matter. While the measured abundance of all reconstructed particles are well described assuming thermalization, the also reconstructed double strange baryon ??? appears about ten times more abundant than expected. This result will be discussed in the context of the exploration of the nuclear matter phase diagram in the region of finite density. Further investigations to search for significant medium effects, will be followed over the coming years with an upgraded HADES detector. 相似文献
55.
Mieczys?aw T. Borowiec Eugene N. Khatsko Vladimir P. Dyakonov Anna I. Rykova Andrzej Majchrowski Tetyana Zayarnyuk Marek Barański Józef ?mija Henryk Szymczak 《Central European Journal of Physics》2011,9(1):260-262
The magnetic investigations of potassium holmium double tungstate KHo(WO4)2 have been performed. The results of measurements of magnetic susceptibility and magnetization as a function of both temperature
(T = 0.5–100 K) and magnetic field (up to 2 T) are presented. 相似文献
56.
57.
Volodymyr Semeniuchenko Yana Garazd Myroslav Garazd Tetyana Shokol Ulrich Groth Volodymyr Khilya 《Monatshefte für Chemie / Chemical Monthly》2009,25(3):1503-1512
Abstract
A highly efficient procedure for glucosylation of flavonoids by acetobromoglucose is described. Glucosylation is carried out in a two-phase system CHCl3/H2O over 96 h using tetrabutylammonium bromide as phase-transfer catalyst. A purification procedure can be performed without column chromatography, and the yields of the glucosylated flavonoids are mostly quantitative. Acetylated glucosides were deprotected with sodium methanolate to afford the desired glucosides of flavonoids. 相似文献58.
In present work, an effective method to research geometrically nonlinear free vibrations of elements of thin-walled constructions that can be modeled as laminated shallow shells with complex planform is applied. The proposed method is numerical–analytical. It is based on joint use of the R-functions theory, variational methods, Bubnov–Galerkin procedure and Runge–Kutta method. The mathematical formulation of the problem is performed in a framework of the refined first-order shallow shells theory. To implement the developed method, appropriate software was developed. New problems of linear and nonlinear vibrations of laminated shallow shells with clamped cutouts are solved. To confirm reliability of the obtained results, their comparison with the ones known in the literature is provided. Effect of boundary conditions is studied. 相似文献
59.
A. D. Prokhorov M. T. Borowiec M. C. Pujol I. M. Krygin A. A. Prokhorov V. P. Dyakonov P. Aleshkevych T. Zayarnyuk H. Szymczak 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(4):389-395
The electron paramagnetic resonance (EPR) of Yb3+
ions in a KY(WO4)2 single crystal was investigated at T=4.2 K and
fixed frequency of 9.38 GHz. The resonance absorption observed on the lowest
Kramers doublet represents the complex superposition of three spectra,
corresponding to the ytterbium isotopes with different nuclear moments. The
EPR spectrum is characterized by a strong anisotropy of the g-factors. The
temperature dependence of the g-factors is shown to be caused by the strong
spin-orbital and orbital-lattice coupling. The resonance lines broaden with
increasing temperature due to the short spin-lattice relaxation times. 相似文献
60.
Dmytro M. Khomenko Tetyana V. Shokol Roman O. Doroshchuk Viktoriia S. Starova Ilona V. Raspertova Sergiu Shova Rostyslav D. Lampeka Yulian M. Volovenko 《Journal of heterocyclic chemistry》2021,58(6):1278-1285
New representatives of [1,2,4]triazolo[1,5-a]pyridine-8-carbonitriles were synthesized via the condensation of β-diketones or β-dialdehydes and characterized using MS spectrometry, 1H, 13C and, 19F NMR and IR spectroscopy. Crystal structures of two compounds were established using X-ray analysis and showed that title compounds are prone to the formation of planar molecules. The absence of band responsible for CN stretching vibration in trifluoromethyl-containing compounds was explained using the DFT calculations method, which also showed a significant influence of fluorines introducing on the energy gap between HOMO and LUMO. 相似文献