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101.
Andrási E Bélavári C Stibilj V Dermelj M Gawlik D 《Analytical and bioanalytical chemistry》2004,378(1):129-133
Iodine is one of the most important essential elements as demonstrated by the fact that its deficiency can cause goitre. Nevertheless, quantitative data on its concentration in biological materials, especially in the human brain, are scarce. There is therefore a demand for accurate and reliable information on iodine in these types of samples. The purpose of the present work was to determine the concentration of total iodine in some control human brain parts by rapid radiochemical neutron activation analysis. Our second goal was to determine I distribution between lipid fraction and in brain tissue without lipid by applying two types of solvent extraction methods. The results were checked by the analysis of biological standard reference materials with certified or literature values for iodine and good agreement was found. 相似文献
102.
This study presents the organogels of glyceryl monostearate emulsifiers and coconut oil as an alternative for developing the traditional organogels. We investigated how the emulsifier type affects the semisolid consistency and the drug release. In these aspects we compared glyceryl monostearate organogels (GMSO) to commercially available references, while studying the effect of the individual constituents on the structural and functional properties.Rheology provided indirect information on the structure, relevant from an application point of view. We observed that glyceryl monostearate as an organogelator results in a network with elastic nature and moderate crosslink energy. The products had low viscosity and low yield value which means practically an easily spreadable pharmaceutical dosage form with soft consistency.Modelling the percutaneous absorption in vitro, we observed that the diffusion of the piroxicam incorporated was significantly affected by the thermodynamical potency of piroxicam, which was favoured by the emulsifier. The glyceryl monostearate enhanced the partition of the suspended drug, resulting in higher drug release.This paper was presented at the first Annual European Rheology Conference (AERC) held in Guimarães, Portugal, September 11-13, 2003. 相似文献
103.
We describe and test a novel molecular dynamics method which combines quantum-mechanical embedding and classical force model optimization into a unified scheme free of the boundary region, and the transferability problems which these techniques, taken separately, involve. The scheme is based on the idea of augmenting a unique, simple parametrized force model by incorporating in it, at run time, the quantum-mechanical information necessary to ensure accurate trajectories. The scheme is tested on a number of silicon systems composed of up to approximately 200 000 atoms. 相似文献
104.
We have studied the influence of the substrate on superfluidity in thin 4He films. The inert coverage, the amount of nonsuperfluid 4He localized by the substrate, is found to scale with the well depth of the 4He-substrate interaction potential for six different substrates. Although the inert coverages for these substrates differ by more than a factor of 4, the phase boundary in the temperature-coverage plane is found to have a universal shape. 相似文献
105.
Lengyel J Kalász H Szarvas T Peltz C Szarkáné-Bolehovszky A 《Journal of chromatographic science》2003,41(4):177-181
Radiolabelled (-)-deprenyl is orally administered to rats, and urinary elimination of radiolabelled formaldehyde is detected. The separation is performed using high-performance liquid chromatography on octadecyl-silica stationary phase. Both the radioactivity and the UV absorbance of the dinitrophenylhydrazine formaldehyde peak are determined. Formaldehyde generation takes place by N-demethylation. Low levels of formaldehyde may have a beneficial role in counterbalancing the oxidative stress of the everyday person's life. 相似文献
106.
Creanga A. Pokol G. Hurduc N. Novák Cs. Alazaroaie S. Hurduc N. 《Journal of Thermal Analysis and Calorimetry》2001,66(3):859-868
The present paper describes a thermogravimetric study combined with mass spectrometry of some aromatic polyethers and copolyethers
in order to obtain information on the degradation mechanism. The investigated polymers were synthesized starting from 3,3-bis(chloromethyl)
oxetane and various bisphenols: 4,4'-dihydroxyazobenzene, 4,4'-dihydroxydiphenyl, bisphenol A and 4,4'-dihydroxydiphenylether.
The presence of an oxetanic spacer in the structure, permitting the opening of the cycle, induces more complications in the
characterization procedure. But, due to the possibilities relative to the modification of polymers or cross-linking reactions,
the presence of the oxetanic moiety may offer some advantages.
Out of all the investigated polymers, those containing azobenzenic moieties have the lower thermostability. If the chain flexibility
is augmented, the degradation mechanism is based on chain transfer reactions. All polymers present higher thermostability
in an argon atmosphere. Based on mass spectra, a degradation mechanism sustained with the assumption that the oxetanic unit
is the most labile was proposed. The opening of the oxetanic cycle begins with the most tensioned bond (-C-CH2-) and generates across-linking process, which is more evident if the polymer melts below 200°C.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
107.
Chen Cs Ran S Liu W Yang Ph Peng Dk Bouwmeester HJ 《Angewandte Chemie (International ed. in English)》2001,40(4):784-786
108.
It is well known that the recurrence relations
are periodic, in the sense that they define periodic sequences for all choices of the initial data, and lead to sequences
with periods 2, 5 and 8, respectively. In this paper we determine all periodic recursions of the form
where are complex numbers, are non-zero and . We find that, apart from the three recursions listed above, only
lead to periodic sequences (with periods 6 and 8). The non-periodicity of (R) when (or and ) depends on the connection between (R) and the recurrence relations
and
We investigate these recursions together with the related
Each of (A), (B), and (C) leads to periodic sequences if k = 1 (with periods 6, 5, and 9, respectively). Also, for k = 2, (B) leads to periodicity with period 8. However, no other cases give rise to periodicity. We also prove that every real
sequence satisfying any of (A), (B), and (C) must be bounded. As a consequence, we find that for an arbitrary k, every rational sequence satisfying any of (A), (B), and (C) must be periodic.
(Received 27 June 2000; in revised form 5 January 2001) 相似文献
109.
Á. Császár 《Acta Mathematica Hungarica》2000,89(3):199-203
Let (X,) be a topological space, X
i
X for i I, and <
i
be a topogenity on X
i
. We look for a topogenity < on X such that is the topology induced by < and <|X
i
=<
i
for i I. 相似文献
110.
The Mössbauer spectra of 57Fe in CoSi2 have been measured in 3.5 and 4.0 T external magnetic fields. The measured spectra showed only magnetic splitting thereby proving the cubic symmetry around 57Fe atoms in CoSi2 (fluorite‐type lattice). Two iron positions were found: in one the iron atoms substitute Co atoms, in the other one the iron populates the empty cubic site in the lattice. It is considered that the results may well contribute to clarifying the atomic positions and local symmetries in metastable Co‐ and Fe‐silicides forming after implantation of Co and Fe in Si at elevated temperatures. 相似文献