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171.
Petr Řepa Ladislav Peksa Tomáš Gronych Radek Ulman Jan Wild Oldřich Schneeweiss 《Czechoslovak Journal of Physics》2006,56(12):1389-1399
This article describes a measuring system that was proposed so as to enable measurement of the content of dissolved gas in
samples, whose shape is determined by the specific requirements of the simultaneous measurements and cannot be modified to
satisfy the requirements on solubility measurements. The apparatus — a dynamic UHV vacuum system — consists of a measuring
chamber fitted with a heater based on electron bombardment, which permits a change in the sample temperature according to
the selected schedule. The design of the heater permits reduction of additional heating in the actual measuring chamber, so
that the increase in pressure caused by the action of the heater can be neglected. The measuring part of the system permits
recording of changes in the overall pressure and partial pressures of selected gases in the measuring chamber. The lowest
detectable amount of dissolved gas is less than 10−5 Pa m3.
The results of measurement of the solubility of hydrogen in Ti and Fe aluminides in samples that are simultaneously used to
measure the electrical conductivity are given as an example of the suitability of the apparatus for such measurements.
This work is a part of research plan MSM 0021620834 financed by the Ministry of Education, Youth and Sports of the Czech Republic. 相似文献
172.
Ladislav Novotny 《Fresenius' Journal of Analytical Chemistry》1998,362(2):184-188
Information is given about the development of renewed miniaturized mercury multi-purpose (multi-mode) electrodes as an inseparable
part of the development of modern polarography and voltammetry; casette-type, pen-type and PC-controlled systems, incl. the
polarographic/voltammetric set. According to the experimental behavior and ranges of their radii the regimes of renewed stationary
mercury electrodes are divided into three categories – mini-, semimicro- and microelectrodes (mE, sμE and μE). Their spontaneously
growing, stepwisely growing, stationary and contracting (compression) modes are schematically outlined. Information on basic
functional properties of the discussed renewed mercury semimicro- or microelectrodes using meniscus and microdrop-electrodes,
by means of the d. c., anodic stripping and adsorptive stripping voltammetry is given.
Received: 25 March 1998 / Accepted: 20 May 1998 相似文献
173.
František Žáček Karel Jakubka Jan Badalec Jan Stöckel Pavel Kletečka Ladislav Kryška Vítězslav Kříha 《Czechoslovak Journal of Physics》1994,44(2):121-129
A diagnostic impulse arc source of a beam of lithium atoms was used for the measurement of electron density profile in front of the lower hybrid grill on the CASTOR tokamak. It was shown that this profile is modified significantly during lower hybrid wave application if the regime with improved particle confinement is achieved.The work was performed under Grants of the Czechoslovak Academy of Sciences No. 14308 and 14310. 相似文献
174.
175.
Sychrovský V Benda L Prokop A Blechta V Schraml J Spirko V 《The journal of physical chemistry. A》2008,112(23):5167-5174
The rotation of a trimethylsiloxy (TMSO) group in three silylated phenols (with three different ortho substituents -H, -CH3, and -C(CH3)3) was studied with the NMR (n)J(Si,C), n = 2, 3, 4, 5, scalar spin-spin coupling between the (29)Si nucleus of the TMSO group and the (13)C nuclei of the phenyl ring. The internal rotation potential calculated with the B3LYP and MP2 calculation methods including the effect of a solvent environment (gas phase, chloroform, and water) was used for the calculation of the dynamical averages of the scalar coupling constants in the framework of the rigid-bender formalism. Solvent effects, the quality of the rotational potential, and the applicability of the classical molecular dynamic to the problem is discussed. Quantum effects have a sizable impact on scalar couplings, particularly for the internal rotational states well localized within the wells of the potential surfaces for the TMSO group. The overall difference between the experimental and theoretical scalar couplings calculated for the global energy-minima structures (static model) decreases substantially for both model potentials (B3LYP, MP2) when the molecular motion of the TMSO group is taken into account. The calculated data indicate that the inclusion of molecular motion is necessary for the accurate calculation of the scalar coupling constants and their reliable structural interpretation for any system which possesses a large-amplitude motion. 相似文献
176.
Ladislav Kosa Iveta Macková Ivo Proks Ondrej Pritula Ľubomír Smrčok Miroslav Boča Håkan Rundlőf 《Central European Journal of Chemistry》2008,6(1):27-32
Three thermal effects on heating/cooling of K2TaF7 in the temperature interval of 680–800°C were investigated by the DSC method. The values determined for the enthalpy change
of the individual processes are: ΔtransIIHm(K2TaF7; 703°C) = 1.7(2) kJ mol−1, ΔtransIHm(K2TaF7; 746°C) = 19(1) kJ mol−1 and ΔtransIIIHm(K2TaF7; 771°C) = 13(1) kJ mol−1. The first thermal effect was attributed to a solid-solid phase transition; the second to the incongruent melting of K2TaF7 and the third to mixing of two liquids. These findings are supported by in situ neutron powder diffraction experiments performed in the temperature interval of 654–794°C.
相似文献
177.
Majer F Trnka L Vítek L Jirkovská M Marecek Z Smíd F 《Biomedical chromatography : BMC》2007,21(5):446-450
Hepatic ganglioside composition was investigated in normal and cholestatic Wistar rats. Cholestasis was induced by 17alpha-ethinylestradiol (EE; 5 mg/kg body weight s.c. for 18 days). As compared with controls, the EE administration resulted in severe cholestasis, as indicated by biochemical as well as morphological signs. Gangliosides isolated from the liver tissue were separated by TLC, with resorcinol-HCl detection and densitometric evaluation. As compared with controls, the total hepatic lipid sialic acid content in cholestatic rats was increased almost 2-fold (44.3 +/- 15.2 vs 79.1 +/- 9.0 nmol/g wet weight of liver tissue, p < 0.01). This increase was primarily due to the increase of ganglioside GD1a (3.6 +/- 1.0 vs 11.8 +/- 3.0 nmol/g wet weight of liver tissue, p = 0.001), as well as to the enormous up-regulation of b-series gangliosides GD3 (0.08 +/- 0.03 vs 2.0 +/- 1.2 nmol/g wet weight of liver tissue, p = 0.002), GD1b (0.1 +/- 0.06 vs 5.4 +/- 1.6 nmol/g wet weight of liver tissue, p = 0.002) and GT1b (0.06 +/- 0.03 vs 6.4 +/- 2.6 nmol/g wet weight of liver tissue, p = 0.002). As the majority of gangliosides are concentrated in cell membranes, our findings suggest that dramatic increase of b-series gangliosides might contribute to the protection of hepatocytes against the deleterious effects of cholestasis. 相似文献
178.
We propose a new Broyden method for solving systems of nonlinear equations, which uses the first derivatives, but is more efficient than the Newton method (measured by the computational time) for larger dense systems. The new method updates QR or LU decompositions of nonsymmetric approximations of the Jacobian matrix, so it requires O(n 2) arithmetic operations per iteration in contrast with the Newton method, which requires O(n 3) operations per iteration. Computational experiments confirm the high efficiency of the new method. 相似文献
179.
Petra Becker Eugen Libowitzky Reiner Kleinschrodt Ladislav Bohatý 《Crystal Research and Technology》2016,51(4):282-289
Precision refractive indices and their dispersion in the visible and near IR range (430 – 2400 nm) and thermal expansion (including its anisotropy and temperature dependence between 144 K and 673 K) were determined for gem‐quality crystals of fluorapatite from Durango, Mexico. In addition, results of a polarized Raman spectroscopy study on these crystals are given. Fluorapatite crystals show moderate values of thermal expansion with small anisotropy. The linear optical properties of the crystals allow no phase matching for third harmonic generation, but signalize, together with the Raman characteristics, a potential suitability of fluorapatite as nonlinear optical material for χ(3)‐based stimulated Raman scattering. 相似文献
180.
Alexander A. Kaminskii Ladislav Bohatý Hanjo Rhee Andr Kaltenbach Oliver Lux Hans J. Eichler Reinhard Rückamp Petra Becker 《Laser \u0026amp; Photonics Reviews》2013,7(3):425-431
Orthorhombic PbCO3, known as natural crystal cerussite, is presented as a new Stimulated Raman Scattering (SRS)‐active crystal. With picosecond laser pumping high‐order Raman‐induced χ(3) generation is observed. All registered Stokes and anti‐Stokes sidebands in the visible and near‐IR are identified and attributed to the SRS‐promoting phonon mode A1g of the carbonate group, with ωSRS ≈ 1054 cm−1. The first Stokes steady‐state Raman gain coefficient in the visible spectral range is estimated as well to a value not less than 4.6 cm·GW−1. 相似文献