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61.
62.
Glycerol is widely used as an additive to stabilize proteins in aqueous solution. We have studied the effect of up to 40 wt % glycerol on the crystallization of lysozyme from brine. As the glycerol concentration increased, progressively larger amounts of salt were needed to crystallize the protein. Like previous authors, we interpret this as evidence for glycerol changing the interaction between lysozyme molecules. We quantitatively model the interprotein interaction using a Derjaguin-Landau-Verwey-Overbeek potential. We find that the effect of glycerol can be entirely accounted for by the way it modifies the dielectric constant and refractive index of the solvent. Quantifying the interprotein interaction by the second virial coefficient, B(2), we find a universal crystallization boundary for all glycerol concentrations. 相似文献
63.
The gas-surface reaction dynamics of NO impinging on an iron(II) phthalocyanine (FePc) monolayer were investigated using King and Wells sticking measurements. The initial sticking probability was measured as a function of both incident molecular beam energy (0.09-0.4 eV) and surface temperature (100-300 K). NO adsorption onto FePc saturates at 3% of a monolayer for all incident beam energies and surface temperatures, suggesting that the final chemisorption site is confined to the Fe metal centers. At low surface temperature and low incident beam energy, the initial sticking probability is 40% and decreases linearly with increasing beam energy and surface temperature. The results are consistent with the NO molecule sticking onto the FePc molecules via physisorption to the aromatics followed by diffusion to the Fe metal center, or precursor-mediated chemisorption. The adsorption mechanism of NO onto FePc was confirmed by control studies of NO sticking onto metal-free H2Pc, inert Au111, and reactive Al111. 相似文献
64.
ZHANG Yong HONG Hua-Sheng Michael H W Lam Ka-Fai Poon Bruce J Richardson Rudolf S S Wu Gene J S Zheng 《高等学校化学学报》1999,20(Z1):554
A new mimic biological sampling devices, which consisted of lipid-containing semipermeable-membrane (SPMD) for sampling organic pollutants has been introduced. 相似文献
65.
66.
Tai-Chia Lin Chi-Cheung Poon Dong-Ho Tsai 《Calculus of Variations and Partial Differential Equations》2009,34(2):153-178
We study the evolution driven by curvature of a given convex immersed closed plane curve. We show that it will converge to
a self-similar solution eventually. This self-similar solution may or may not contain singularities. In case it does, we also
have estimate on the curvature blow-up rate. 相似文献
67.
A HPLC method was developed and applied to analyze aristolochic acids (AA-I and AA-II) in Chinese medicinal herbs. The herb samples were extracted by using ultrasonication with the extraction efficiency of better than 82%. Extracts were then filtered and injected onto a C18 column eluting under a gradient program using methanol and water-containing 0.5% acetic acid. The method with the detection limits of 1.33 ng for AA-I and 7.29 ng for AA-II per injection was successfully applied for the analysis of traditional Chinese medicine (TCM) and related products and differentiation of Chinese medicinal herbs that have previously been misused and caused toxicological effects. The developed protocol provided an example that analysis of selected component markers could serve for health security and quality control of TCM consumption. 相似文献
68.
We study optical trapping of microparticles on an optofluidic chip using silicon nitride waveguide junctions and tapered-waveguide junctions. We demonstrate the trapping of single 1 μm-sized polystyrene particles using the evanescent field of waveguide junctions connecting a submicrometer-sized input-waveguide and a micrometer-sized output-waveguide. Particle trapping is localized in the vicinity of the junction. We also demonstrate trapping of one and two 1μm-sized polystyrene particles using tapered-waveguide junctions connecting a submicrometer-sized singlemode input-waveguide and a micrometer-sized multimode output-waveguide. Particle trapping occurs near the taper output end, the taper center and the taper input end, depending on the taper aspect ratio. 相似文献
69.
Purpose
The purpose was to study the effect of estrogen deficiency on contrast agent diffusion into intervertebral disc in a rat model.Materials and Methods
Seven-month-old female Sprague–Dawley rats were used. Fourteen rats had ovariectomy, and nine rats had sham surgery. Magnetic resonance imaging (MRI) of sagittal midsection of lumbar spine was performed with a 1.5-T magnet. Dynamic MRI was performed after a bolus injection of Gd-DOTA (0.3 mmol/kg) through tail vein. Eight hundred images were acquired at 0.6 s per acquisition. Regions of interests were drawn over three discs per rat. Maximum enhancement (Emax) and enhancement slope (Eslope) were evaluated. MRI was carried out at baseline and 8 weeks postsurgery.Result
All disc enhancements demonstrated an initial fast wash-in phase followed by a second slower wash-in phase. For initial wash-in phase, E1max and E1slope of all rats remained unchanged at the two time points. For second wash-in phase, E2max and E2slope of control rats remained unchanged, while with ovariectomized rats, E2max showed reduction at 8 weeks (4.5%±5.6%) compared to baseline (10.3%±6.3%, P=.037), and E2slope was lower at 8 weeks (0.015±0.017) than the baseline (0.029±0.022), although it was not statistically significant (P=.101).Conclusion
Ovariectomy induced detectable decrease in second wash-in phase of contrast agent into lumbar disc. 相似文献70.
We use hydrofluoric acid microdroplets to directly etch highly birefringent biconical fiber tapers from standard single-mode fibers. The fiber tapers have micrometer-sized cross sections, which are controlled by the etching condition. The characteristic teardrop cross section leads to a high group birefringence of B(G)≈0.017 and insertion losses <0.7 dB over waist lengths of about 2.1 mm. 相似文献