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1.
Debjani Ghosh Shruti S. Bandyopadhyay Udipta R. Chatterjee Peter Capek Bimalendu Ray 《Food science and biotechnology》2012,21(2):409-417
Chirata (Swertia chirata) is widely used in Indian folk medicine for the prevention of various disorders. Herein, we analyzed the water-extracted
carbohydrate polymer (WECP) of this herb using chemical, chromatographic, and spectroscopic methods. The anti-oxidant capacity
of this fraction was studied by ferric reducing anti-oxidant power (FRAP) and DPPH radical assays. Effect of WECP on bovine
serum albumin spectrum (BSA) was determined using excitation wavelength of 282 nm. Anion exchange chromatography of WECP yielded
5 fractions (F1–F5) with different chemical compositions. The major fraction (F5) was homogeneous, had an apparent molecular
mass of 4.5 kDa, and contains both carbohydrates (57%) and phenolics (34%). The anti-oxidant capacities of WECP and F5 were
comparable to standard anti-oxidants. Notably, activities of the carbohydrate polymers (F1–F5) correlate with their phenolics
content. Fluorescence quenching measurement suggests that F5 can form complex with BSA and the value of the binding constant
is K=6.28×105/M. 相似文献
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4.
Ignác Capek 《Polymer-Plastics Technology and Engineering》2015,54(14):1513-1523
The preparation and characterization of noble metal nanoparticles that are coated by organic shells for the covalent immobilization of biopolymers were described. Plasmonic nanoparticles demonstrate unique size-dependent optical and photothermal properties due to the collective oscillation of free electrons in their conduction bands. The intensity of absorption and scattering of noble metal nanoparticles is significantly higher than most absorbing and scattering organic molecular dyes, which makes them excellent candidates as contrast agents in imaging. Cylindrical gold nanorods also demonstrate a tunable photothermal response to near infrared light as a function of nanoparticle aspect ratio. Organic functional groups on the nanoparticles allow the coupling of organic molecules to their shells. Several synthetic approaches to couple biomolecules to metal nanoparticles and to use the hybrid assemblies for various bioanalytical applications have been reported. 相似文献
5.
Ufuk Yildiz Ignác Capek Dušan Berek Yanko Sarov Ivo W Rangelow 《Polymer International》2007,56(3):364-370
The inverse microemulsion copolymerization of acrylamide and butyl acrylate initiated by ammonium peroxodisulphate, a water‐soluble initiator, and stabilized by anionic emulsifiers sodium bis‐2‐ethylhexylsulfosuccinate and sodium dodecylsulphate (SDS) has been studied. An increase of SDS concentration was observed to increase both the rate of polymerization and the particle size. The average number of radicals per particle (n?) is much below 0.5, which indicates desorption of monomeric radicals from polymer particles. The exit (desorption) rate constants k′des (cm2 s?1) and kdes (s?1) were evaluated as a function of SDS concentration (or the particle size) according to the Ugelstad/O'Toole (I), Nomura (II) and Gilbert (III) models. The value of kdes (s?1) decreases with increasing particle size (or SDS concentration) for all three (I, II and III) models. A complex trend appears for k′des (cm2 s?1): the Ugelstad/O'Toole model estimates a decrease, the Nomura model finds no variation and the Gilbert model estimates even a slight increase in k′des with increasing SDS concentration. Copyright © 2006 Society of Chemical Industry 相似文献
6.
Syncope is a very common presentation to the primary care provider and the emergency room physician. The consequences of syncope while driving can be tragic. Likewise the consequences in the flight environment can be devastating. This case presents tussive syncope while driving in a 41-yr-old previously healthy male aviator. The diagnosis, management, and aeromedical disposition are presented. 相似文献
7.
H T?nies J Capek H Hecht G Rothe C Sellner F Kummer 《Canadian Metallurgical Quarterly》1994,144(4):82-87
In 5 Viennese general practice offices we investigated patients by spirometry with the following indications: differential diagnosis of dyspnea; every 3rd smoker of more than 10 cigarettes a day (including asymptomatic ones); cough and nasal disorders of more than 4 weeks duration; indicative physical findings (cyanosis or auscultation). The sample control group was matched for age and gender and did not have any symptoms characteristic of the indication group. Nevertheless a spirometric test was also carried out in these patients. A total of 212 patients were examined in 4673 consultations on 202 workdays in the 5 offices. In the group of 109 patients 62 (56.9%) had dyspnea and/or positive signs on auscultation. Of these 62 patients 39 (62.9%) had 1 or more positive findings either from PEF or FEV 1 or both. There were significantly more referrals for X-rays in case of abnormal lung function. The control group of 103 obviously healthy persons in particular showed a significantly higher number of abnormal PEF values than expected (31 persons, 30.1%). 相似文献
8.
Graft copolymers (polystyrene-graft-polyoxyethylene) (PS-graft-PEO) were prepared by the dispersion copolymerization of methacryloyl-terminated polyoxyethylene macromonomer and styrene initiated by an oil-soluble initiator (dibenzoyl peroxide, DBP). The apparent molecular weights of graft copolymers measured by size exclusion chromatography in tetrahydrofuran were found to be proportional to the -0·8th power of DBP concentration. This reaction order supports the termination of growing radicals by a first order radical loss process. The molecular weight distribution estimated from the size exclusion chromatography (SEC) data was found to decrease slightly with DBP concentration and to drop rapidly with macromonomer concentration. This was attributed to chain transfer events and to the increase of particle number: the higher the particle number the lower the monomer concentration in the particles. The bulkiness of the macromonomer molecules and the high segment density around the propagating reaction loci hinder the incorporation of macromonomer molecules into a copolymer growing chain. ©1997 SCI 相似文献
9.
Vegso K Siffalovic P Benkovicova M Jergel M Luby S Majkova E Capek I Kocsis T Perlich J Roth SV 《Nanotechnology》2012,23(4):045704
We report on grazing-incidence small-angle x-ray scattering (GISAXS) study of 3D nanoparticle arrays prepared by two different methods from colloidal solutions-layer-by-layer Langmuir-Schaefer deposition and spontaneous self-assembling during the solvent evaporation. GISAXS results are evaluated within the distorted wave Born approximation (DWBA) considering the multiple scattering effects and employing a simplified multilayer model to reduce the computing time. In the model, particular layers are represented by nanoparticle chains where the positions of individual nanoparticles are generated following a model of cumulative disorder. The nanoparticle size dispersion is considered as well. Three model cases are distinguished-no shift between the neighboring chains (AA stacking), a shift equal to half of the mean interparticle distance (AB stacking) and random shift between the chains. The first two cases correspond to vertically correlated nanoparticle positions across different chains. A comparison of the experimental GISAXS patterns with the model cases enabled us to distinguish important differences between the 3D arrays prepared by the two methods. In particular, laterally ordered layers without vertical correlation of the nanoparticle positions were found in the nanoparticle multilayers prepared by the Langmuir-Schaefer method. On the other hand, the solvent evaporation under particular conditions produced highly ordered 3D nanoparticle assemblies where both laterally and vertically correlated nanoparticle positions were found. 相似文献
10.
The long-time behaviour of CP titanium in 1 M H2SO4 has been investigated. The authors revealed electrochemical behaviour during the long-time chrono-amperometric experiments. The ex-situ observations (EIS, ellipsometry, SEM and optical microscopy) brought out information concerning morphological changes of the surface as well as the change in the oxide thickness during the anodic oxidation process. From the obtained data, the authors developed a hypothesis describing the potentiostatic anodisation of titanium at voltages (up to 15 V) in 1 M H2SO4 with respect to time of anodisation. 相似文献