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101.
ubomír Smr
ok Radovan erný Miroslav Bo
a Iveta Mackov Blanka Kubíkov 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(2):i16-i18
The crystal structure of tripotassium octafluoridotantalate, K3TaF8, determined from laboratory powder diffraction data by the simulated annealing method and refined by total energy minimization in the solid state, is built from discrete potassium cations, fluoride anions and monocapped trigonal–prismatic [TaF7]2− ions. All six atoms in the asymmetric unit are in special positions of the P63mc space group: the Ta and one F atom in the 2b (3m) sites, the K and two F atoms in the 6c (m) sites, and one F atom in the 2a (3m) site. The structure consists of face‐sharing K6 octahedra with a fluoride anion at the center of each octahedron, forming chains of composition [FK3]2+ running along [001] with isolated [TaF7]2− trigonal prisms in between. The structure of the title compound is different from the reported structure of Na3TaF8 and represents a new structure type. 相似文献
102.
Holčapek M Dvořáková H Lísa M Girón AJ Sandra P Cvačka J 《Journal of chromatography. A》2010,1217(52):8186-8194
Silver-ion high-performance liquid chromatography (HPLC) coupled to atmospheric pressure chemical ionization mass spectrometry (APCI-MS) is used for the regioisomeric analysis of triacylglycerols (TGs). Standard mixtures of TG regioisomers are prepared by the randomization reaction from 8 mono-acid TG standards (tripalmitin, tristearin, triarachidin, triolein, trielaidin, trilinolein, trilinolenin and tri-gamma-linolenin). In total, 32 different regioisomeric doublets and 11 triplets are synthesized, separated by silver-ion HPLC using three serial coupled chromatographic columns giving a total length of 75cm. The retention of TGs increases strongly with the double bond (DB) number and slightly for regioisomers having more DBs in sn-1/3 positions. DB positional isomers (linolenic vs. γ-linolenic acids) are also separated and their reverse retention order in two different mobile phases is demonstrated. APCI mass spectra of all separated regioisomers are measured on five different mass spectrometers: single quadrupole LC/MSD (Agilent Technologies), triple quadrupole API 3000 (AB SCIEX), ion trap Esquire 3000 (Bruker Daltonics), quadrupole time-of-flight micrOTOF-Q (Bruker Daltonics) and LTQ Orbitrap XL (Thermo Fisher Scientific). The effect of different types of mass analyzer on the ratio of [M+H-R(i)COOH](+) fragment ions in APCI mass spectra is lower compared to the effect of the number of DBs, their position on the acyl chain and the regiospecific distribution of acyl chains on the glycerol skeleton. Presented data on [M+H-R(i)COOH](+) ratios measured on five different mass analyzers can be used for the direct regioisomeric determination in natural and biological samples. 相似文献
103.
Juraj Racko Miroslav Mikolá?ek Ralf Granzner Juraj Breza Daniel Donoval Alena Grmanová Ladislav Harmatha Frank Schwierz Karol Fr?hlich 《Central European Journal of Physics》2011,9(1):230-241
A new model is presented of current transport in Metal Insulator Metal (MIM) structures by quantum mechanical tunnelling.
In addition to direct tunnelling through an insulating layer, tunnelling via defects present in the insulating layer plays
an important role. Examples of the influence of the material and thickness of the insulating layer, energy distribution of
traps, and metal work functions are also provided. 相似文献
104.
Melinda VargováGustav Plesch Ulrich F. Vogt Miroslav ZahoranMichal Gorbár Karol Jesenák 《Applied Surface Science》2011,257(10):4678-4684
TiO2 thick films deposited on macroporous reticulated Al2O3 foams with pore size of 10 ppi and 15 ppi were prepared using dip coating from slurries of Aeroxide® P25 nanopowder and precipitated titania. All prepared films have sufficiently good adhesion to the surface of the substrate also in case of strongly cracked films. No measurable release of deposited TiO2 after repeated photocatalytic cycles was observed. The photocatalytic activity was characterized as the rate of mineralization of aqueous phenol solution under irradiation of UVA light by TOC technique. The best activity was obtained with Aeroxide® P25 coated Al2O3 foam with the pore size of 10 ppi, annealed at 600 °C. The optimal annealing temperature for preparation of films from precipitated titania could be determined at 700 °C. Films prepared by sol-gel deposition technique were considerably thinner compared to coatings made of suspensions and their photocatalytic activity was significantly smaller. 相似文献
105.
Bohumír Bastl Bert Jüttler Miroslav Lávička Tino Schulz Zbyněk Šír 《Mathematics in Computer Science》2014,8(2):299-319
Ringed surfaces and canal surfaces are surfaces that contain a one-parameter family of circles. Ringed surfaces can be described by a radius function, a directrix curve and vector field along the directrix curve, which specifies the normals of the planes that contain the circles. In particular, the class of ringed surfaces includes canal surfaces, which can be obtained as the envelopes of a one-parameter family of spheres. Consequently, canal surfaces can be described by a spine curve and a radius function. We present parameterization algorithms for rational ringed surfaces and rational canal surfaces. It is shown that these algorithms may generate any rational parameterization of a ringed (or canal) surface with the property that one family of parameter lines consists of circles. These algorithms are used to obtain rational parameterizations for Darboux cyclides and to construct blends between pairs of canal surfaces and pairs of ringed surfaces. 相似文献
106.
Miroslav Vetrík Martin P?ádnýMartin Hrubý Ji?í Michálek 《Polymer Degradation and Stability》2011,96(5):756-759
We describe the synthesis of new crosslinker N′-{3-[2-(4-{2-[3-(methacryloylamino)propanoyl]hydrazono}cyclohexyliden)hydrazino]-3-oxopropyl}-2-methylacrylamide, which is stable at physiological pH, but is hydrolytically cleaved in acidic pH. Study of acid hydrolysis showed that the crosslinker is hydrolyzed into two N′-(3-hydrazino-3-oxopropyl)-2-methylacrylamide molecules and one 1,4-cyclohexanedione molecule. Hydrogels based on poly[N-(2-hydroxypropyl)methacrylamide] crosslinked with this crosslinker were prepared and their degradation rate was studied as a function of pH (in the range of pH 1.5-7.4). The hydrogel is cleaved within 8-27 days at pH between 1.5 and 6 and is stable at pH 7.4 making it promising for the construction of oesophageal stents. 相似文献
107.
Jian Feng Gu Miroslav Grmela Mosto Bousmina 《ournal of non Newtonian Fluid Mechanics》2010,165(3-4):75-83
Doi–Ohta rheological model of immiscible blends is extended by replacing the fluid interface with an elastic membrane. A symmetric tensor characterizing the in-membrane deformations joins the surface area and the orientation tensor (used in the Doi–Ohta theory) to provide morphological state variables. The governing equations of the model are solved numerically and the morphological and rheological predictions are presented. As an illustration, we regard the model as a first step in mesoscopic rheological modeling of suspensions of red blood cells. The material properties of the membrane enclosing the red blood cells, that are inferred from rheology, are indeed found to be close to the ones seen in direct experimental measurements. A more realistic model of human blood has to include additional morphological state variables describing larger structures (in particular whole red blood cells). 相似文献
108.
Miroslav Petrović 《Graphs and Combinatorics》1999,15(2):221-232
In this paper, by means of computer checking, all simple graphs with at most two nonnegative eigenvalues, and all minimal
simple graphs with exactly two (respectively, three) nonnegative eigenvalues are determined.
Received: April 5, 1996 / Revised: May 2, 1997 相似文献
109.
110.
Černý Miroslav Šandera Pavel Pokluda Jaroslav 《Czechoslovak Journal of Physics》1999,49(10):1495-1501
Ab initio calculation of ideal strength of cubic crystals under three-axial tension was performed using the LMTO-ASA method. Computed values are in a good agreement with those obtained previously by means of semi-empirical polynomial approach. The values of equilibrium lattice parameter obtained in the framework of ab initio method are well comparable with the experimental data whereas a less satisfactory agreement was achieved in the case of bulk moduli. 相似文献