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Helene Jonassen Anna-Lena Kj?niksen Marianne Hiorth 《Colloid and polymer science》2012,290(10):919-929
In this work, chitosan nanoparticles were prepared by ionotropic gelation of chitosan with tripolyphosphate (TPP). The effects of the ionic strength of the solvent employed in the particle preparation on the average size and compactness of the particles were investigated. In addition, the effects of the chitosan concentration and the crosslinker to polymer ratio on the particle characteristics were studied. The chitosan–TPP nanoparticles were characterized by dynamic light scattering, zeta potential, and turbidity measurements. The compactness of the nanoparticles was estimated with a method based on the size of the nanoparticles and the turbidity of the nanoparticle suspension. All the investigated preparation parameters, i.e., the ionic strength of the solvent, the chitosan concentration, and the TPP to chitosan ratio, affected the particle characteristics. For instance, smaller and more compact particles were formed in saline solvents, compared to particles formed in pure water. Further, the addition of monovalent salt rendered it possible to prepare particles in the nanometer size range at a higher polymer concentration. Solvent salinity is thus an important parameter to address in the preparation of chitosan nanoparticles crosslinked with TPP. 相似文献
107.
Hlne Airault Paul Malliavin Jiagang Ren 《Journal de Mathématiques Pures et Appliquées》1999,78(10):1069
For an elliptic diffusion process, we prove that the exit time from an open set is in the fractional Sobolev spaces Epα (or Dpα) provided that pα<1. The result is almost optimal. 相似文献
108.
Joél Smet Sara Seneca Boel De Paepe Ann Meulemans Helene Verhelst Jules Leroy Linda De Meirleir Willy Lissens Rudy Van Coster 《Electrophoresis》2009,30(20):3565-3572
Complex V, site of the final step in oxidative phosphorylation, uses the proton gradient across the inner mitochondrial membrane for the production of ATP. It is a multi‐subunit complex composed of a catalytic domain (F1) and a membrane domain (F0) linked by two stalks. Subcomplexes of complex V containing the F1 domain have previously been reported in small series of patients. We report the results in tissue samples and/or cultured skin fibroblasts studied by blue native PAGE followed by activity staining in the gel. Catalytically active subcomplexes of complex V were detected in 66 tissues originating from 53 patients. In 29 of the latter (55%), a mitochondrial DNA (mtDNA) defect was identified. Twelve patients had a pathogenic point mutation in a mitochondrial tRNA, one a large mtDNA deletion, 12 showed mtDNA depletion and four had a mutation in the MT‐ATP6 gene. We conclude that the presence of subcomplexes of complex V is a valuable indicator in the detection of mtDNA defects. 相似文献
109.
Podszun S Vulto P Heinz H Hakenberg S Hermann C Hankemeier T Urban GA 《Lab on a chip》2012,12(3):451-457
Macro- to micro-volume concentration of viable bacteria is performed in a microfluidic chip. The enrichment principle is based on free flow electrophoresis and is demonstrated for Gram positive bacteria. Bacteria from a suspension flow are trapped on a gel interface that separates the trapping location from integrated actuation electrodes in order to enable non-destructive trapping. The microfluidic chip contains integrated electrolytic gas expulsion structures and phaseguides for gel and liquid handling. Trapping efficiency is systematically optimized to reach 25 times the initial concentration from a theoretical maximum of 30. Finally, enrichment from analytically relevant concentrations down to 3 × 10(2) colony forming units per millilitre is demonstrated with a trapping efficiency of 80% which represents the most important parameter in enrichment. 相似文献
110.
Hopfer H Haar N Stockreiter W Sauer C Leitner E 《Analytical and bioanalytical chemistry》2012,402(2):903-919
In a previous study, we identified carbonyls as highly odor-active compounds in both unprocessed and processed polypropylene
(PP) with higher intensities after processing, indicating a temperature-driven forming mechanism. In the presented work, we
studied whether (a) these carbonyls are the major odor drivers to the overall odor of polyolefins, (b) their formation is
taking place already at moderate temperatures well below the typical processing temperatures, (c) conventional antioxidants
in polyolefins can prevent or reduce their formation, and (d) whether reducing the amount of oxygen present can decrease the
overall odor. One polyethylene (PE) and one PP were selected, and both stabilized and unstabilized polymer powder samples
were exposed to conditions differing in oxygen concentration and aging time. The changes in the volatile fraction as well
as the formation of odor-active compounds were monitored using a multidisciplinary approach by combining analytical methods
based on gas chromatography (GC), multivariate data analysis, and sensory methods (GC–olfactometry and a sensory panel). Both
investigated materials (PE and PP) showed similar degradation products (aldehydes, ketones, carboxylic acids, alcohols, and
lactones) which increased dramatically with increasing aging time and the lack of stabilization. Oxidation products, mainly
carbonyl compounds, were responsible for the odor of the investigated materials. The main odor drivers were unsaturated ketones
and aldehydes with a chain length between six and nine C-atoms. Interestingly, similar odor patterns were found for both stabilized
and unstabilized samples, indicating that similar formation processes take place independent of the stabilization. 相似文献