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1.
The influence of -irradiation on the paramagnetic properties of non-doped polyacetylene at low and high radiation doses has been studied and summarized. The dependence of the EPR spectra on the radiation dose in irradiated polyacetylene has been measured. No essential changes of the spin mobility as a consequence of irradiation were observed. Our measurements of spin concentration confirm the high resistivity of non-doped polyacetylene to radiation. 相似文献
2.
The image of growth striations in Si formed by the double crystal X-ray topography in the Laue case (DCTL) is investigated. The results of the dynamical diffraction theory for crystals with small microdefects have been compared with the contrast behaviour determined experimentally. It has been found that the theory explains qualitatively the contrast on the striations and it has been demonstrated that the DCTL method is suitable for detection of the presence of small microdefects in growth striations. Since the paper completes a series of papers on X-ray topography of growth striations, some general conclusions are formulated concerning the applicability of the X-ray topographical methods to the investigation of the structure of the growth striations 相似文献
3.
4.
Tushar S. Basu Baul Keisham Surjit Singh Michal Hol?apek 《Journal of organometallic chemistry》2005,690(6):1581-1587
The complex, [(PhCH2)2{O2CC6H4{N(H)N(C6H3-4(O)-5-O)}-o}Sn]2 (1), is obtained as the exclusive reaction product from the reaction of sodium 2-[(E)-2-(3-formyl-4-hydroxyphenyl)-1-diazenyl]benzoate and (PhCH2)3SnCl. The reaction possibly proceeds via Dakin type rearrangements where arylazosalicylaldehyde is oxidized to arylazocatechol, followed by facile Sn-C bond cleavage. Complete assignments were achieved by 1H, 13C, 2D 1H-119Sn HMQC (119Sn chemical shift), 1D gs 1H-15N HMQC (1J(15N, 1H) coupling constant) NMR and ESI-MS. The crystal structure of compound 1 as determined by X-ray diffraction analyses shows a cyclic centrosymmetric dinuclear moiety linked into extended chains by pairs of long Sn?O contacts of approximately 3.2 Å. Two polymorphs were identified and their structures differ primarily in the packing arrangement afforded by the benzyl groups. In one polymorph, when viewed along the Sn?Sn vector, the benzyl groups at each Sn-atom are oriented to form an S-shape, while they form a U-shape in the second polymorph. 相似文献
5.
Loss of light stabilizers. related to 2-hydroxybenzophenone and 2-(2-hydroxyphenyl) benzotriazole. from isotactic polypropylene was measured over the range 60–120° and during storage at 25'. The light stabilizer content in polypropylene corresponded to that used in practice. The rate constants and the activation energy were calculated from the rate of loss. The influence of the structure of stabilizer on the rate of loss from polymer is discussed. The losses of stabilizers from polymer were compared with the vapour pressure of stabilizers and with the losses of stabilizers alone at 280. The rate of diffusion of stabilizers to the surface of polypropylene and the rate of even evaporation may cause a rapid diminution of stabilizer or undesirable accumulation on the polymer surface. 相似文献
6.
L’ubica Holá 《Quaestiones Mathematicae》2018,41(6):829-838
Some boundedness properties of function spaces (considered as topo- logical groups) are studied. 相似文献
7.
Robert Jirásko Tomáš Mikysek Vitaliy Chagovets Ivan Vokřál Michal Holčapek 《Analytical and bioanalytical chemistry》2013,405(23):7181-7193
Ultrahigh-performance liquid chromatography coupled with high-mass-accuracy tandem mass spectrometry (UHPLC–MS–MS) has been used for elucidation of the structures of oxidation products of atorvastatin (AT), one of the most popular commercially available drugs. The purpose of the study was identification of AT metabolites in rat hepatocytes and comparison with electrochemically generated oxidation products. AT was incubated with rat hepatocytes for 24 h. Electrochemical oxidation of AT was performed by use of a three-electrode off-line system with a glassy carbon working electrode. Three supporting electrolytes (0.1 mol L?1 H2SO4, 0.1 mol L?1 HCl, and 0.1 mol L?1 NaCl) were tested, and dependence on pH was also investigated. AT undergoes oxidation by a single irreversible process at approximately +1.0 V vs. Ag/AgCl electrode. The results obtained revealed a simple and relatively fast way of determining the type of oxidation and its position, on the basis of characteristic neutral losses (NLs) and fragment ions. Unfortunately, different products were obtained by electrochemical oxidation and biotransformation of AT. High-mass-accuracy measurement combined with different UHPLC–MS–MS scans, for example reconstructed ion-current chromatograms, constant neutral loss chromatograms, or exact mass filtering, enable rapid identification of drug-related compounds. β-Oxidation, aromatic hydroxylation of the phenylaminocarbonyl group, sulfation, AT lactone and glycol formation were observed in rat biotransformation samples. In contrast, a variety of oxidation reactions on the conjugated skeleton of isopropyl substituent of AT were identified as products of electrolysis. Figure
Chemical structure of atorvastatin (AT) composed of four main parts assigned as A, B, C and D including the list of identified oxidation reactions for both electrochemical and in vitro experiments 相似文献
8.
Sebastian?BreuerEmail author Katrin?Pech Armin?Buss Christoph?Spitzer Juris?Ozols Elly?M?Hol Nicole?Heussen Johannes?Noth Franz-Werner?Schwaiger Andreas?B?Schmitt 《BMC neuroscience》2004,5(1):15
Background
Interruption of mature axons activates a cascade of events in neuronal cell bodies which leads to various outcomes from functional regeneration in the PNS to the failure of any significant regeneration in the CNS. One factor which seems to play an important role in the molecular programs after axotomy is the stearoyl Coenzyme A-desaturase-1 (SCD-1). This enzyme is needed for the conversion of stearate into oleate. Beside its role in membrane synthesis, oleate could act as a neurotrophic factor, involved in signal transduction pathways via activation of protein kinases C. 相似文献9.
We consider the space D(X, Y) of densely continuous forms introduced by Hammer and McCoy [5] and investigated also by Holá [6]. We show some additional
properties of D(X, Y) and investigate the subspace D*(X) of locally bounded real-valued densely continuous forms equipped with the topology of pointwise convergence τ-
p
. The largest part of the paper is devoted to the study of various cardinal functions for (D*(X), τ
p
), in particular: character, pseudocharacter, weight, density, cellularity, diagonal degree, π-weight, π-character, netweight etc.
This work was supported by Science and Technology Assistance Agency under the contract No. APVT-51-006904. The authors would
like to thank Ľubica Holá for suggestions and comments. 相似文献
10.
Milan Nádvorník Vratislav Langer Robert Jirásko Michal Holčapek Tomáš Weidlich Antonín Lyčka Alexander Popkov 《Polyhedron》2008
A preparative procedure for the synthesis of an important chiral synthon of side-chain protected tyrosine was developed and optimised for the minimisation of nickel salts waste. While preparing a similar side-chain protected tryptophan synthon, an unexpected low stability was found of the Boc-protective group of the tryptophan aromatic nitrogen during purification on silica gel. X-ray crystal structure determination, tandem mass spectrometry (MS/MS) and NMR were applied for the elucidation of the structures of the prepared complexes and by-products. Stereochemistry of products of α-methylation of the complexes was assessed using a model tyrosine-derived compound. 相似文献