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31.
32.
Quinone was reacted in vitro with free haem under ultraviolet light. Two principal products were detected by liquid chromatography and purified by column chromatography. Mass spectral and Fourier transform infrared analyses showed that both products contained pyrroles and that the first product was probably an ether formed after reaction with the haem vinyl moieties. This product was entirely different from the known N-alkyl intermediates in the haem-catalysed epoxidation reactions of porphyrin dimerization by quinone. 相似文献
33.
The Effect of Temperature on Sorbitan Surfactant Monolayers 总被引:1,自引:0,他引:1
The effect of temperature on four sorbitan ester (Span 20, sorbitan monolaurate; Span 40, sorbitan monopalmitate; Span 60, sorbitan monostearate; and Span 80, sorbitan monooleate) monolayers was analyzed. The covered temperature range was from 22 to 42 degrees C. Surface pressure-molecular area isotherms were measured with a Langmuir-type instrument. As the temperature was increased, the monolayers expanded more. This change can also be seen from the surface compressional modulus that was lowered as the temperature was increased. Also, the collapse pressure was lowered as the temperature was increased. Copyright 2001 Academic Press. 相似文献
34.
Low molecular weight (M(w)) poly(L-lactic acid) (PLA) nanoparticles were coated with polyelectrolytes (PEs) by layer-by-layer (LbL) technique using a filtration approach. Poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate) were applied as PEs in coating. LbL coating is aimed to use in producing (nano)particulate drug delivery systems with improved biocompatibility and sustained or targeted release of drug substances. Nanoparticles of rapidly biodegradable polymers, like the low M(w) PLA, open up a possibility to control the release of the encapsulated substance by the coating, but set challenges to the coating process due to increased aggregation tendency and degradation rate of the polymer. When the core PLA nanoparticles were prepared by nanoprecipitation, surface properties of the nanoparticles were affected by solvent selection. Successful LbL coating of the PLA nanoparticles was obtained only with chloroform, but not with dichloromethane as the solvent during nanoprecipitation. Reason for this was found to be the more charged surface of the nanoparticles prepared with chloroform compared to the nanoparticles prepared with dichloromethane. 相似文献
35.
Teemu Lukkari 《Journal of Evolution Equations》2010,10(3):711-729
We study the existence of solutions to the porous medium equation with a nonnegative, finite Radon measure on the right-hand
side. We show that such problems have solutions in a wide class of supersolutions. These supersolutions are defined as lower
semicontinuous functions obeying a parabolic comparison principle with respect to continuous solutions. We also consider the
question of how the integrability of the gradient of solutions is affected if the measure is given by a function in L
s
, for a small exponent s > 1. 相似文献
36.
Murtola T Falck E Patra M Karttunen M Vattulainen I 《The Journal of chemical physics》2004,121(18):9156-9165
We construct a coarse-grained (CG) model for dipalmitoylphosphatidylcholine (DPPC)/cholesterol bilayers and apply it to large-scale simulation studies of lipid membranes. Our CG model is a two-dimensional representation of the membrane, where the individual lipid and sterol molecules are described by pointlike particles. The effective intermolecular interactions used in the model are systematically derived from detailed atomic-scale molecular dynamics simulations using the Inverse Monte Carlo technique, which guarantees that the radial distribution properties of the CG model are consistent with those given by the corresponding atomistic system. We find that the coarse-grained model for the DPPC/cholesterol bilayer is substantially more efficient than atomistic models, providing a speedup of approximately eight orders of magnitude. The results are in favor of formation of cholesterol-rich and cholesterol-poor domains at intermediate cholesterol concentrations, in agreement with the experimental phase diagram of the system. We also explore the limits of the coarse-grained model, and discuss the general validity and applicability of the present approach. 相似文献
37.
Timo Viero Kim Rounioja Teemu Sipilä Raimo Verkasalo Jarmo Takala Jorma Lilleberg 《Wireless Personal Communications》2007,43(2):281-293
In this paper, dual antenna receiver architectures are studied including RAKE, chip-level linear equalizer, and their combination.
The arithmetic complexity of single and dual antenna receiver methods is analyzed. Cost of such receivers when implemented
with customized hardware or software on application-specific instruction set processors (ASIP) is estimated. The study shows
that feasible dual antenna detection can be obtained with less than 70% additional costs. More flexible implementation supporting
several standards can be obtained with software but it requires higher power consumption due to additional memory. 相似文献
38.
Petri Ihalainen Joakim Järnström Anni Määttänen Jouko Peltonen 《Colloids and surfaces. A, Physicochemical and engineering aspects》2011,373(1-3):138-144
In this study, torsional harmonic atomic force microscopy (TH-AFM, HarmoniX mode) was applied for surface mapping of the mechanical properties of pigment-latex coated paper samples. In addition, topographic images and force maps of adhesive tip-sample interactions were captured concurrently. The spatial distribution of latex binder on the composite surface was distinguished with high resolution. The latex was found to dominate the surface chemistry of the composite coating, despite the fact that latex is a minor component in the coating color formulation. The latex resided as a thick layer between the pigments and as a thin layer on the individual pigments. In addition, the tip-sample thermodynamic work of adhesion of the composite materials on the coated surface was compared to the surface energy values obtained by contact angle measurements. A high tip-sample work of adhesion correlated to high surface energy. 相似文献
39.
40.
Roy Pöllänen Teemu Siiskonen Sakari Ihantola Harri Toivonen Andreas Pelikan Kenneth Inn Jerome La Rosa Balazs Bene 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(3):551-555
High-resolution alpha spectrometry was applied for the activity determination of 10 reference sources containing different
amounts of 238Pu, 239Pu, 240Pu and 242Pu. They were analyzed as blind sources using a novel spectrum analysis tool ADAM. The information needed in the spectrum
unfolding was taken only from the spectrum under investigation, and no tracers were applied. Therefore, a Monte Carlo program
AASI was used to compute geometrical detection efficiency of the measurement setup. All reported activities corresponded to
those of the reference sources within expanded uncertainty. The developed tools can be used for the activity determination
in nondestructive alpha spectrometry or when the radionuclide composition does not change during the sample processing. 相似文献