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排序方式: 共有78条查询结果,搜索用时 218 毫秒
51.
Koon S. Nak-Heon Choi Hyoung-Bin Park Duk-In Choi 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1995,23(4):609-616
A one-dimensional fluid model of the microwave electron cyclotron resonance (ECR) discharge, which includes the inhomogeneity effects of the external magnetic field, is developed. We use fluid equations which are obtained from the one-dimensional Bolzmann equation expressed in terms of magnetic moment and parallel velocity. We model the plasma and sheath separately, and appropriate plasma-sheath boundary conditions are utilized. Microwave is represented by an energy flow, and treated by a ray tracing technique. For the argon discharge, we obtain various quantities such as the axial profiles of plasma density, electron temperature, electrostatic potential, fluid velocity, and microwave power deposition. The results of simulation compare well with the experimental observation of the mirror field effects on the plasma parameters 相似文献
52.
C.M. Williams N.C. Koon J.B. Milstein 《Journal of Physics and Chemistry of Solids》1978,39(8):823-827
Room temperature magnetic anisotropy measurements have been made on a series of low anisotropy HoxTb1?xFe2 compounds, with 0.826 < x < 0.908, using torque magnetometry techniques. An analysis of the data using the conventional expansion of anisotropy energy in terms of the direction cosines proved inadequate because of the presence of higher order contributions to the anisotropy. When these contributions were included in the expansion, non unique anisotropy constants were obtained which were not consistent with the predictions of the single ion model. An analysis of the data using an expansion of the anisotropy in terms of an orthonormal set of functions, namely the cubic harmonics developed by Mueller and Priestly, proved more successful. The results showed that the two lowest order anisotropy constants, κ4 and κ6, both varied linearly with holmium concentrations as predicted by the single ion model; however, κ8, the next higher order term, was not consistent with the predicted behavior. The origin of this contribution is believed to be related to the magnetostriction. 相似文献
53.
Cumulative evidence shows that eicosanoids such as prostaglandins, leukotrienes, thromboxanes and hydroxy eicosatetraenoic acids play an important role in associating inflammation with human colorectal cancer (CRC). In this study an ultra‐pressure liquid chromatography/tandem mass spectrometry (UPLC/MS/MS) method was developed and validated for the targeted profiling of eight relevant eicosanoids and the major metabolic precursor, arachidonic acid (AA), in human colon. Multiple reaction monitoring (MRM) experiments were performed in negative electrospray ionization mode. The metabolites were separated using a C18 column consisting of 1.7 µm ethylene‐bridged hybrid particles (100 × 2.1 mm i.d.) and gradient elution (50 to 95% of solvent B) with a mobile phase comprising water (0.1% formic acid) [solvent A] and acetonitrile (0.1% formic acid) [solvent B] at a flow rate of 0.4 mL/min. The analysis time for each sample was 5.5 min. Our UPLC/MS/MS method demonstrated satisfactory validation results in terms of selectivity, sensitivity, matrix effect, linearity, extraction efficiency, intra‐ and inter‐day precision, accuracy and autosampler stability. The method was applied for the clinical profiling of matched pairs of cancerous and normal colon mucosae obtained from eight colorectal cancer patients. Endogenous levels of AA and selected eicosanoids such as prostaglandin E2 (PGE2), prostacyclin (PGI2) [assayed as its stable hydrolytic product 6‐keto‐prostaglandin1α (6‐k PGF1α)] and 12‐hydroxy‐5Z,8Z,10E,14Z‐eicosatetraenoic acid (12‐HETE) were found to be significantly different (p <0.05; paired t‐test) between cancerous and normal mucosae. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
54.
Zeolite micropattern for biological applications 总被引:2,自引:0,他引:2
A facile method was established using composition-gradient pattern on zeolite surface to guide the deposition and formation of chemical and biomolecular patterns with features as small as five microns. 相似文献
55.
Ultrasonic interferometry is an indispensable tool in molecular chemistry and imaging, inclusive of liquid state studies where the standard theory is used to determine many physico-chemical parameters, such as the isentropic compressibility and adiabatic bulk modulus. The first principle analysis conducted here augments the standard model with potentially significant consequences in the interpretation of these parameters and the output spectrum. The effect of attenuation of a wave on the observed separation between peaks in acoustic interferometry is a focus of the investigation. Important aspects of the theory of Hubbard and others were collated to derive two mathematical models that were used to fit experimental spectra. The first model does not assume fictitious quantities found in Hubbard’s theory and fits the experimental data well. The second model includes the effects of the electronics of the measuring system and is in excellent agreement with the experimental data. Theoretical and numerical analyses were performed to validate the two models. Numerically, the attenuation of a wave is shown to cause the peaks to deviate either positively or negatively from the otherwise ideal half-wavelength of \(\lambda /2\) and exact equations governing such deviations are derived that could have significant implications in theory and applications. 相似文献
56.
57.
Protoplast fusion, induced by polyethylene glycol and Ca2+, was carried out between two auxotrophic strains ofAspergillus niger. The fusion frequency ranged from 6.2 × 10-2-9.1 × 10-2. After induced haploidization of a diploid, various segregants showing combinations of the parental genetic markers were
isolated. Unlike diploids, haploid segregants exhibited greater variations in their morphology and β-glucosidase activities.
One segregant showed a 2.5-fold increase in β-glucosidase activity over those of the parents. Thus, this method appears promising
for creating new recombinant strains ofA. niger with improved β-glucosidase activities. 相似文献
58.
High‐quality DFT calculations are employed to estimate the arene exchange energies for reactions of general formula: For C60 and C70 complexes of Cr(CO)3, full geometry optimizations at the DFT level using moderately large basis sets were performed, while for the other systems a hybrid approach was developed in which the geometries were obtained at the PM3(tm) level and the energetics were evaluated at the DFT level. C70 is shown to be a slightly better arene ligand than C60; however, no enhancements of arene‐like bonding capabilities are seen for C78 and C84 relative to C70. Explicit calculation of a series of exchange energies at the DFT level using both DFT and PM3(tm) geometries demonstrates that PM3(tm) geometries are sufficiently accurate for the calculation of energetics at a higher theoretical level, but PM3(tm) calculations are inadequate for a quantitative assessment of exchange energies. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1881–1886, 2001 相似文献
59.
Plasma protein adsorption and thrombus formation on surface functionalized polypyrrole with and without electrical stimulation 总被引:4,自引:0,他引:4
A surface modification technique was developed in which heparin was covalently immobilized onto electrically conductive polypyrrole (PPY) film through poly(ethylene glycol) methacrylate (PEGMA) graft copolymerization and subsequent cyanuric chloride activation. In vitro plasma protein adsorption and thrombus formation experiments were carried out on the various films. The PEGMA-graft-copolymerized PPY surfaces with immobilized heparin have good bioactivity indicated by low level of protein adsorption, high ratio of albumin to fibrinogen adsorption, and low thrombus formation, making them potentially good candidates for biomedical applications. Since the PPY film retained significant electrical conductivity after surface modification, the effect of electrical stimulation on protein adsorption and thrombus formation was also evaluated. The covalently immobilized heparin on the PPY film was able to retain its bioactivity after 4 days of immersion in PBS. The film after long-term immersion in PBS also retained sufficient electrical conductivity for electrical stimulation still to be effective for reducing protein adsorption. 相似文献
60.