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911.
The interaction of halofantrine with phosphatidylcholine and phosphatidylethanolamine bilayers has been investigated by differential scanning calorimetry. Halofantrine caused a broadening of the gel to liquid crystalline phase transition endotherm of the phosphatidylcholines. A decrease in the transition temperature Tm and enthalpy (delta H) of transition was also observed. This varied with the chain length of the phospholipid and was more pronounced with short chain members. Halofantrine-induced changes to the thermotropic characteristics of dipalmitoylphosphatidylcholine (DPPC)/cholesterol bilayers suggested that the penetration of halofantrine into the bilayer was diminished in the presence of cholesterol. A more complex calorimetric profile was observed in the interaction of halofantrine with phosphatidylethanolamines and the results suggested that halofantrine did not disrupt the cooperativity of the phosphatidylethanolamine bilayers to the same extent as that observed with the phosphatidylcholines. Halofantrine caused significant perturbation of phospholipids and this property might have an important bearing on its pharmacodynamic effects. 相似文献
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916.
K.Y. Lim Y.S. Lee Y.D. Chung I.W. Lyo C.N. Whang J.Y. Won H.J. Kang 《Applied Physics A: Materials Science & Processing》2000,70(4):431-434
In this study, the grain boundary diffusion of Cu through a TiN layer with columnar structure was investigated by X-ray photoelectron
spectroscopy (XPS). It was observed that Cu atoms diffuse from the Cu layer to the surface along the grain boundaries in the
TiN layer at elevated temperature. In order to estimate the grain boundary diffusion constants, we used the surface accumulation
method. The diffusivity of Cu through TiN layer with columnar structure from 400 °C to 650 °C is Db≈6×10−11exp(−0.29/(kBT )) cm2/s.
Received: 18 May 1999 / Accepted: 8 September 1999 / Published online: 23 February 2000 相似文献
917.
We demonstrate that all the known single- and double-logarithm summations for a parton distribution function can be unified
in the Collins–Soper resummation technique by applying soft approximations appropriate in different kinematic regions to real
gluon emissions. Neglecting the gluon longitudinal momentum, we obtain the (double-logarithm) resummation for two-scale QCD processes, and the Balitsky–Fadin–Kuraev–Lipatov (single-logarithm) equation
for one-scale processes. Neglecting the transverse momentum, we obtain the threshold (double-logarithm) resummation for two-scale
processes, and the Dokshitzer–Gribov–Lipatov–Altarelli–Parisi (single-logarithm) equation for one-scale processes. If we keep
the longitudinal and transverse momenta simultaneously, we derive a unified resummation for a large Bjorken variable x, and a unified evolution equation appropriate for both intermediate and small x.
Received: 9 March 1999 / Revised version: 12 April 1999 / Published online: 3 August 1999 相似文献
918.
A series of miniemulsion systems based on styrene/azobisisobutyronitrile in the presence of poly(methyl methacrylate‐b‐2‐(dimethylamino)ethyl methacrylate) as a surfactant and hexadecane (HD) as a cosurfactant were developed. For comparison, a series of pseudoconventional emulsions also were carried out with the same procedure used for the aforementioned series but without the cosurfactant (HD). Both the droplet size and shelf life were also measured. Experimental results indicate that it is possible to slow the effect of Ostwald ripening and thereby produce a stable miniemulsion with the block copolymer as the surfactant and HD as the cosurfactant. In addition, the extent to which varying the surfactant concentration and copolymer composition could affect both the polymer particle size during the polymerization and the polymerization rate was examined. Variation in the polymer particle sizes during polymerization indicates that droplet and aqueous (micellar or both homogeneous) nucleation occurs in the miniemulsion polymerization. With the same concentration of the surfactant used in the miniemulsion polymerization, the polymerization rates of systems with M12B36 are faster than those of systems with M12B12. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1818–1827, 2000 相似文献
919.
Soon Young Cha Jong Keun Lee Bum Soon Lim Taek Seung Lee Won Ho Park 《Journal of polymer science. Part A, Polymer chemistry》2001,39(6):880-887
The introduction of a conjugated vinyl group to chitooligosaccharide (COS) has been easily accomplished by the coupling of glycidyl methacrylate (GMA) to COS in aqueous solution without an additional catalyst. Depolymerization of chitosan was carried out by deaminative cleavage using sodium nitrite. The average degree of polymerization of COS could be controlled by varying the molar ratio of sodium nitrite and the amino group of chitosan. The degree of substitution (percentage), as determined by 1H NMR, of GMA to COS increased up to 60% at a reaction time of 48 h. The structure of products (COS‐GMAs) were identified by Fourier transform infrared spectroscopy, 1H NMR, and 13C NMR. The resulting COS‐GMAs were readily soluble in neutral water, like the original COS, and exhibited an excellent antimicrobial activity. The reactivity of COS‐GMA was investigated by the reaction with poly(vinyl alcohol) (PVA). The reaction products were found to have a lower crystallinity than PVA because of the introduction of the COS‐GMA units. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 880–887, 2001 相似文献
920.
Yirang Lim Seung-Heon Lee Yan Li Seung-Hyun Kim Tae Hui Kang Yung Doug Suh Soojin Lee Yongjin Kim Gi-Ra Yi 《Particle & Particle Systems Characterization》2020,37(4):1900405
For an optically transparent, UV-reflective film, hollow silica nanospheres smaller than the visible wavelength (<λvis) are prepared and assembled into colloidal glasses, of which interstices are then backfilled with a polymer. The polymer refractive index is matched with the silica shell to minimize backscattering in the visible range, and the average distance between the hollow silica particles is adjusted by tuning the shell thickness to satisfy the interference resonance condition for a UV selective reflection. The resulting composite film shows a strong UV reflection as expected, but it is translucent in visible light due to non-negligible backscattering, which may be caused by large defects or fluctuation of the particle concentration. In order to avoid such backscattering, another polymer is introduced of which the refractive index is matched with the average refractive index of the hollow nanospheres. This allows an optically transparent film that selectively reflects the UV light. Furthermore, spherical aggregates of hollow silica nanospheres called “supraballs” are prepared and their average refractive index is matched with a solvent by adjusting the mixture ratio of water and ethylene glycol, which yields an optically transparent solution, selectively reflecting UV. 相似文献