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31.
Masoud Behzad Karel Samec Sang-In Bak Yacine Kadi Claudio Tenreiro Seung-Woo Hong Jong-Seo Chai 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(2):1001-1006
A worldwide challenge in the near future will be to find a way of producing radioisotopes in sufficient quantity without relying on research reactors. The motivation for this innovative work on targets lies in the accelerator-based production of radioisotopes using a neutron converter target as in the transmutation by adiabatic resonance crossing concept. Thermal analysis of a multi-channel helium cooled device is performed with the computational fluid dynamics code CFX. Different boundary conditions are taken into account in the simulation process and many important parameters such as maximum allowable solid target temperature as well as uniform inlet velocity and outlet pressure changes in the channels are investigated. The results confirm that the cooling configuration works well; hence such a solid target could be operated safely and may be considered for a prototype target. 相似文献
32.
We explore two- and three-state Markov models driven out of thermal equilibrium by non-potential forces, to demonstrate basic properties of the steady heat capacity based on the concept of quasistatic excess heat. It is shown that large enough driving forces can make the steady heat capacity negative. For both the low- and high-temperature regimes we propose an approximative thermodynamic scheme in terms of “dynamically renormalized” effective energy levels. 相似文献
33.
Karel Kolomazník Ji?í Pecha Veronika Friebrová Dagmar Janá?ová Vladimír Va?ek 《Heat and Mass Transfer》2012,48(9):1505-1512
Biostimulators are substances able to enhance the immune system of cultivated crops and support plant metabolism. Their utilization helps to reduce the amount of chemicals used in agriculture. To perform the desired effect, a biostimulator must be able to penetrate into the plant tissue. The time of penetration however, is limited, since the biostimulator must remain in a liquid state. This is of great importance—especially in field conditions, where the treated plants are exposed to different weather condition and other extrinsic factors. A mathematical model based on diffusion mechanisms has been elaborated to describe the biostimulator transport process from penetration of the leaves into the plant’s inner tissues. By means of the effective diffusion coefficient of the prepared specific protein hydrolyzate, this model can be used to estimate the time necessary for the uptake of the minimal active amount of the biostimulator. 相似文献
34.
Oxidative stress plays a key role in the pathophysiology of many diseases. Hydroxyl radical is the oxidative species most commonly causing damage to cells. The aim of this work was to optimize the method for antioxidant activity determination on a model lipophilic geranylated flavanone, diplacone. This method uses protection of plasmid DNA from oxidation by a hydroxyl radical generated by the Fenton reaction involving oxidation of metal ions using H2O2 and ascorbate. The method was optimized for lipophilic compounds using several solvents and co-solvents. It was found that (2-hydroxypropyl)-β-cyclodextrin (0.1 mass % aq. sol.) is the best co-solvent for our model lipophilic compound to measure the antioxidant activity by the method presented. Other solvents, namely dimethyl sulfoxide, Cremophor EL® (0.1 mass % aq. sol.), ethanol, and methanol, were not suitable for the determination of the antioxidant activity by the method described. Tween 80 (0.1 mass % aq. sol.) and a mixture of 10 vol. % ethanol and 9 mass % bovine serum albumin (aq. sol.) significantly decreased the antioxidant activity of the model lipophilic compound and thus were not suitable for this method. 相似文献
35.
Karel Lacina Martin Konhefr Jan Novotný David Potěšil Zbyněk Zdráhal Petr Skládal 《Tetrahedron letters》2014
A redox-active affinity ligand suitable for reagentless sensing of cis-diols was synthesised and characterised. 4-[(Ferrocenylamino)methyl]thiophene-3-boronic acid (FcTBA) was allowed to interact with the model cis-diol, sorbitol. A discrete, cathodic shift of the redox potential was observed upon interaction of FcTBA with sorbitol thus providing simultaneous differentiation between the free and bound forms of this sensor molecule. Similar behaviour was observed also for FcTBA co-immobilised with thiophene in a mixed self-assembled monolayer on a gold electrode. 相似文献
36.
The power supply for IEF based on features of the Cockcroft‐Walton voltage multiplier (CW VM) is described in this work. The article describes a design of the IEF power supply, its electric characteristics, and testing by IEF analysis. A circuit diagram of the power supply included two opposite charged branches (each consisting of four voltage doublers). The designed CW VM was powered by 230 V/50 Hz alternate current and it generated up to 5 kV and 90 mW at the output. Voltage and current characteristics of the power supply were measured by known load resistances in the range from 10 kΩ to 1 GΩ, which is a common resistance range for IEF strip geometry. Further, the power supply was tested by a separation of a model mixture of colored pI markers using a 175 × 3 × 0.5 mm focusing bed. Automatically limited power load enabled analysis of samples without previous optimization of the focusing voltage or electric current time courses according to sample composition. Moreover, the developed power supply did not produce any intrinsic heat and was easy to set up with cheap and commonly available parts. 相似文献
37.
A new approach for the evaluation of chiral purity of serine esterification products bearing long-chain alkyl substituents was developed. The compounds were simply converted to aryl-substituted oxazolines which: (i) facilitates effective chromatographic enantioseparation and (ii) enables direct detection using ultraviolet absorption. The method employs a polysaccharide-based chiral stationary phase and allows enantioseparation of highly stable oxazoline products in less than 6 min using a simple binary mobile phase. As opposed to the previously used normal phase method the developed method was performed in the reversed-phase mode. Aside from the benefits of switching to less hazardous solvents with regard to the principles of Green Chemistry, this has also led to a reduction in the analysis time. In comparison with known serine chromophores, the best enantioseparation of aryloxazoline rigid structure may be achieved only based on non-polar interactions with the chiral stationary phase. In contrast, the substitution of the chromophore moiety with hydroxyl substituent affected intra and intermolecular interactions that caused enantioseparation differences. Concurrently, we found high chirality retention of (R)- and (S)-configuration oxazoline standards (≥99% enantiomeric excess) during the introduction of the ultraviolet label. The method is suitable for rapid injection of the mixture containing the ultraviolet absorption marker without prior purification. 相似文献
38.
Proteoliposomes carrying reconstituted yeast plasma membrane H+-ATPase in their lipid membrane or plasma membrane vesicles are model systems convenient for studying basic electrochemical
processes involved in formation of the proton electrochemical gradient (ΔμH
+) across the microbial or plant cell membrane. Δψ- and pH-sensitive fluorescent probes were used to monitor the gradients
formed between inner and outer volume of the reconstituted vesicles. The Δψ-sensitive fluorescent ratiometric probe oxonol
VI is suitable for quantitative measurements of inside-positive Δψ generated by the reconstituted H+-ATPase. Its Δψ response can be calibrated by the K+/valinomycin method and ratiometric mode of fluorescence measurements reduces undesirable artefacts. In situ pH-sensitive fluorescent probe pyranine was used for quantitative measurements of pH inside the proteoliposomes. Calibration
of pH-sensitive fluorescence response of pyranine entrapped inside proteoliposomes was performed with several ionophores combined
in order to deplete the gradients passively formed across the membrane. Presented model system offers a suitable tool for
simultaneous monitoring of both components of the proton electrochemical gradient, Δψ and ΔpH. This approach should help in
further understanding how their formation is interconnected on biomembranes and even how transport of other ions is combined
to it. 相似文献
39.
A macroscopic model for an intermediate state between type‐I and type‐II superconductivity 下载免费PDF全文
Karel Van Bockstal Marián Slodička 《Numerical Methods for Partial Differential Equations》2015,31(5):1551-1567
A vectorial nonlocal and nonlinear parabolic problem on a bounded domain for an intermediate state between type‐I and type‐II superconductivity is proposed. The domain is for instance a multiband superconductor that combines the characteristics of both types. The nonlocal term is represented by a (space) convolution with a singular kernel arising in Eringen's model. The nonlinearity is coming from the power law relation by Rhyner. The well‐posedness of the problem is discussed under low regularity assumptions and the error estimate for a semi‐implicit time‐discrete scheme based on backward Euler approximation is established. In the proofs, the monotonicity methods and the Minty–Browder argument are used. © 2015 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 31: 1551–1567, 2015 相似文献
40.
Katarína Kráľová František Šeršeň Matúš Peško Karel Waisser Lenka Kubicová 《Chemical Papers》2014,68(1):46-52
5-Bromo-(Br-PBA) and 3,5-dibromo-2-hydroxy-N-phenylbenzamides (Br2-PBA) inhibited photosynthetic electron transport (PET) and their inhibitory efficiency depended on the compound lipophilicity as well as on the electronic properties of the R substituent in the N-phenyl moiety. Br-PBA showed higher PET inhibiting activity than Br2-PBA with the same R substituent. The most effective inhibitors in the tested series were the derivatives with R = 3-F (Br-PBA; IC50 = 4.3 μmol dm?3) and R = 3-Cl (Br2-PBA; IC50 = 8.6 μmol dm?3). Bilinear dependence of the PET inhibiting activity on the lipophilicity of the compounds as well as on the Hammett constant, σ, of the R substituent was observed for both investigated series. Using EPR spectroscopy it was found that the site of action of the tested compounds in the photosynthetic apparatus is situated on the donor side of PS 2, in D· or in the Z·/D· intermediates. Interaction of the studied compounds with chlorophyll a and aromatic amino acids present in the pigment-protein complexes mainly in photosystem 2 was documented by fluorescence spectroscopy. 相似文献