Thermal behaviour and biochemical activity of potassium-silicate-phosphate glasses modified by addition of Ca, Mg, acting
as ecological fertilisers of controlled release rate of the nutrients for plants were studied. It has been found that the
biochemical activity of silicate-phosphate glasses depends on the nature and the number of components forming the glassy framework
and is related to the thermal stability of glass demonstrated by the formation of new compounds during the process of crystallisation.
It is proved that these seemingly different properties are determined by the same parameters which are the strengths bonds
of glass network-formers and modifiers as well as their chemical affinity.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
Triallate residues in barley seedlings and soil samples were determined by gas chromatography with ion-trap detection. Soil was extracted with methanol on a mechanical shaker, and plants were extracted with acetonitrile in a Sorvall homogenizer. After evaporation of the organic solvents, the residue was dissolved in hexane, and plants extracts were cleaned-up on an alumina column. Gas chromatographic analysis was carried out using a BP-1 fused-silica capillary column with helium as carrier gas. To quantitate residues the total-ion chromatogram was obtained and then the selected-ion monitoring chromatograms were displayed at m/z 86 for triallate and at m/z 154 for the internal standard, methyl-(4-amino-2-chloro)-benzoate. The average recovery through the method from barley and soil samples was always higher than 80%. The limit of detection in the selected-ion mode was 0.01 mg/kg. Barley and soil samples treated with triallate were also analysed. A good agreement was observed between results obtained by this method and by gas chromatography with nitrogen-phosphorus detection. 相似文献
The adsorption of atomic S on the Fe(1 1 0) surface is examined using density functional theory (DFT). Three different adsorption sites are considered, including the atop, hollow and bridge sites and the S is adsorbed at a quarter monolayer coverage in a p(2 × 2) arrangement. The hollow site is found to be the most stable, followed by the bridge and atop sites. At all three sites, S adsorption results in relatively minor surface reconstruction, with the most significant being that for the hollow site, with lateral displacements of 0.09 Å. Comparisons between S-adsorbed and pure Fe surfaces revealed reductions in the magnetic moments of surface-layer Fe atoms in the vicinity of the S. At the hollow site, the presence of S causes an increase in the surface Fe d-orbital density of states between 4 and 5 eV. However, S adsorption has no significant effect on the structure and magnetic properties of the lower substrate layers. 相似文献
Described are the syntheses of 15 macrocyclic peptides designed to trap Holliday junctions (HJs) in bacteria during site-specific and homologous recombination. This leads to inhibiting bacterial growth. These second generation macrocycles were based on the C-2 symmetrical HJ. They were synthesized using a strategy that permits elucidation of the amino acid role in binding HJs. The syntheses of these macrocycles are an important step in the development of a new class of antibiotics. 相似文献
The exponential X-ray transform arises in single photon emission computed tomography and is defined on functions on ?n by , where μ is a constant. Approximate inversion, and inversion formulae of filtered back-projection type are derived for this operator in all dimensions. In particular, explicit formulae are given for convolution kernels (filters) K corresponding to a general point spread function E that can be used to invert the exponential X-ray transform via a filtered back-projection algorithm. The results extend and refine work of Tretiak and Metz17. 相似文献
A molecularly imprinted polymer (MIP) tailored for the HPLC determination of the fungicide thiabendazole (TBZ) has been synthesised in one single preparative step by precipitation polymerisation in an acetonitrile/toluene co-solvent, using TBZ as template molecule, methacrylic acid as functional monomer and divinylbenzene-80 as crosslinker. The imprinted polymer particulates obtained were characterised by scanning electron microscopy and nitrogen sorption porosimetry. These analyses showed clearly that spherical polymer particulates (polymer microspheres) with narrow size distributions (average particle diameter approximately 3.5 microm) and well-developed pore structures had been produced. The imprinted microspheres were packed into a stainless steel HPLC column (50 x 4.6 mm id) and evaluated as an imprinted stationary phase. The imprinting effect was demonstrated clearly, i.e., the column was observed to bind TBZ selectively, and the effect of different chromatographic parameters (e.g., temperature, flow-rate and elution solvents) on TBZ retention/elution studied. Under optimised conditions, the TBZ-imprinted column was used for the HPLC-fluorescence (HPLC-F) determination of TBZ directly from orange (both whole fruit and juice), lemon, grape and strawberry extracts at low concentration levels in less than 15 min, without any need for a clean-up step in the analytical protocol. 相似文献
The diagonal elements of the first and second order spinless density matrices have been calculated for the lowest excited1P and3P terms of Be, B+ and C++ using wavefunctions at different levels of approximations published in the literature. The analysis of these functions has
resulted in a new interpretation of Hund's first rule in terms of an anisotropic screening effect. 相似文献
Khusimone (1), one of the main odor-donating compounds of vetiver oil is subject of the following study on structure/odor relationship. The omittance of the ethano bridge of the tricyclic khusimone leads to a bicyclic system. The stereoselective approach to this degraded structure is described, and the olfactory properties are studied. The key step of the synthesis of the hydrindane nucleus is based on a highly diastereoselective conjugate addition to a chiral oxo-cyclopentene-2-carboxylate. 相似文献
For a translation plane P with respect to f we consider the group of collineations generated by all elations fixing f and a point F of f. All subgroups or are determined which operate regularly on the points of the affine plane P. Group-theoretic and operating properties of the groups are stated especially for the finite and the Desarguesian cases. In the latter case the companion NL-near modules are constructed. Finally we characterize the groups within PGL(3, K) with commutative field K of finite characteristic. 相似文献