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131.
A number of poly(N-isopropylacrylamide) (polyNIPAM) microgels were prepared with dimethacrylate cross-linking agents of various lengths, ether and ester groups in the backbone, and pendant vinylidine functionality. These materials were characterized by examining their morphological patterns using optical and scanning electron microscopy. When ethylene glycol dimethacrylate (EGDMA) was used as a cross-linking agent, microspheres of approximately 1 μm in diameter were obtained. Diethylene glycol dimethacrylate (DEGDMA) cross-linking resulted in relatively large spherical structures (1–5 μm) as well as spherical nanostructures (200 nm). Using triethylene glycol dimethacrylate (TEGDMA) resulted in spheres with diameters between 1 μm and 3 μm. The hydrodynamic particle diameter decreased with the increasing chain length of the dimethacrylate cross-linking agents. The turbidity increased with the temperature of transition points occurring at approximately 31–32°C confirming the thermosensitivity of the obtained polymeric structures. 相似文献
132.
Radosaw Lisiecki Witold Ryba-Romanowski Enrico Cavalli Marco Bettinelli 《Journal of luminescence》2010,130(1):131-136
Transparent single crystals of erbium-doped LaVO4 in form of platelets having an average size 0.5×2×2 mm3 were obtained by the flux method using Pb2V2O7 as the solvent. Inductively coupled plasma (ICP) measurement revealed that the actual Er/La=0.3% molar ratio in the crystals is lower than Er/La=1% nominal molar ratio due to significant difference of ionic radii of La and Er. Luminescence spectra and luminescence decay curves for Er3+ transitions in the visible and near infrared region were recorded. Unpolarized Raman spectrum of undoped LaVO4 crystal was acquired, too. Up-converted green emission following excitation at 808 and 970 nm was observed and dependence of its intensity on incident excitation power was determined. Based on experimental data gathered the relaxation dynamics of excited states of Er3+ was analyzed and mechanisms involved in the up-conversion phenomena were discussed. 相似文献
133.
Florinel‐Gabriel Bănică Dariusz Guziejewski Slawomira Skrzypek Witold Ciesielski Dorota Kaźmierczak 《Electroanalysis》2009,21(15):1711-1718
In a 0.02 M borax solution (pH 8.5), basic amino acids (arginine, lysine, and ornithine) react with Ni2+ to form a mono‐ligand complex that is reduced at a mercury electrode at about ?0.85 V vs. Ag|AgCl|KCl (3 M). At a long time scale (staircase voltammetry; scan rate<50 mV s?1), the complex reduction is a catalytic (EC′) process, the rate‐determining step being the regeneration of the reducible species by the reaction of the amino acid with free Ni2+. At a short time scale (differential pulse voltammetry or higher scan rate staircase voltammetry), the reaction rate is controlled by the diffusion of the complex. Although the same kind of complexation occurs with either basic amino acids or glycine, the last one does not induce a similar process. The peculiar effect of basic amino acids is due to the side chain that causes the ligand molecule to adopt a favorable orientation at the electrode surface. The differential pulse voltammetry peak current is proportional to the total amino acid concentration over the concentration range from 2 to 100 μM. Hence a voltammetric method for arginine determination in nutritional supplements was developed and validated using HPLC as reference method. 相似文献
134.
Witold Wnuk 《Mathematische Nachrichten》2010,283(5):775-779
The paper is devoted to investigations of the order structure of ultrapowers. A characterization of discrete normed lattices, all of whose ultrapowers are discrete, is presented (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
135.
Witold Korytowski Jared C. Schmitt Albert W. Girotti 《Photochemistry and photobiology》2010,86(4):747-751
Singlet oxygen attack on cholesterol (Ch), a prominent monounsaturated lipid of mammalian cell plasma membranes, gives rise to three hydroperoxide (ChOOH) isomers, 5α-OOH, 6α-OOH and 6β-OOH, the latter two in lower yield than 5α-OOH, and 6α-OOH in lowest yield. A third possible positional isomer, 7α-OOH and 7β-OOH, is produced by free radical attack. In the presence of iron and ascorbate (Fe/AH), 5α-OOH or 6β-OOH in phosphatidylcholine/Ch/ChOOH (20:15:1 by mol) liposomes was reduced to its corresponding alcohol, the rate constant being approximately the same for both ChOOHs. Using [14C]Ch as an in situ probe, we found that liposomal 5α-OOH readily set off free radical-mediated (chain) peroxidation reactions when exposed to Fe/AH, whereas 6β-OOH under the same conditions did not. Moreover, liposomal 5α-OOH triggered robust chain peroxidation in [14C]Ch-labeled L1210 cells, leading to cell death, whereas 6β-OOH was essentially inert in this regard. Thus, 5α-OOH and 6β-OOH undergo iron-catalyzed reductive turnover, but only the former can provoke toxic membrane damage. These novel findings have important implications for UVA-induced photodamage in Ch-rich tissues like skin and eye, where 1O2 often plays a major role. 相似文献
136.
In this study, the release of lidocaine hydrochloride was assessed considering the use of both the ionic and the non-ionic
polymeric carrier at temperatures of 22°C, 32°C, and 42°C; temperature of 32°C was chosen as the reference surface body temperature.
The obtained release rates and respective amounts of lidocaine hydrochloride loaded both to methylcellulose beads and polyacrylic
acid beads were compared with respective viscosity, pH and conductivity of the studied systems. The release of lidocaine hydrochloride
from the methylcellulose system is influenced by temperature; with the increase of temperature the release rate decreases
whereas the viscosity increases. In the polyacrylic acid system, release rates are lower, however, in the first stage they
are slightly increasing with the increase of temperature. The final amount of released drug after 24 h increases with the
temperature of the release process environment, and it is higher in case of a methylcellulose system. The maximum differences
between the released amounts for methylcellulose were in the range of 15 %, whereas in case of polyacrylic acid, the difference
was approximately 12 %. Thus, this research is important for patients with differentiated skin surface temperature conditions
to whom a local analgesic is to be applied. 相似文献
137.
Gabriela Jajko Pawe Kozyra Maciej Strzempek Paulina Indyka Marcin Zajc Stefan Witkowski Witold Piskorz 《Molecules (Basel, Switzerland)》2021,26(12)
In this article, the results of computational structural studies on Al-containing zeolites, via periodic DFT + D modelling and FDM (Finite Difference Method) to solve the Schrödinger equation (FDMNES) for XAS simulations, corroborated by EXAFS (Extended X-ray Absorption Fine Structure) spectroscopy and PXRD (powder X-ray diffractometry), are presented. The applicability of Radial Distribution Function (RDF) to screen out the postulated zeolite structure is also discussed. The structural conclusions are further verified by HR-TEM imaging. 相似文献
138.
139.
The paper is devoted to investigations of properties of regular Riesz subspaces and connections between regularity and some topological properties. The problem if a topological closure preserves regularity is solved in the class of discrete Riesz spaces. We also characterize Dedekind complete Riesz spaces possessing the same classes of -regular and regular Riesz subspaces Moreover, various examples of regular and non regular Riesz spaces are presented. 相似文献
140.