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991.
Alexey Bobrovsky Valery Shibaev Vera Hamplova Miroslav Kaspar Milada Glogarova 《Colloid and polymer science》2010,288(14-15):1375-1384
For the first time, a photochromic azobenzene-containing liquid crystalline (LC) acrylic polymer was used for gelation of low-molar-mass nematic mixture (LMNM). Dissolution of LC polymer in amount of only 2.5 wt.% in LMNM at 120°C (isotropic state) followed by cooling down results in formation of the solid-like photochromic LC gel. Gelation is associated with a phase separation and formation of microsized LC polymer domains, which form a physical “network” containing encapsulated nematic host. Textural changes of mixture during gel formation were analyzed, and absorbance spectra were measured. A special attention was paid to the kinetic study of photoinduced E-Z and Z-E isomerization of azobenzene side groups of polymer in gel. It was shown that ultraviolet (UV)-irradiation and E-Z isomerization processes are accompanied by disruption of H-aggregates of azobenzene moieties and partial dissolution of polymer. 相似文献
992.
Continuity of the dynamics in a localized large diffusion problem with nonlinear boundary conditions
Vera Lúcia Carbone Karina Schiabel-Silva 《Journal of Mathematical Analysis and Applications》2009,356(1):69-85
This paper is concerned with singular perturbations in parabolic problems subjected to nonlinear Neumann boundary conditions. We consider the case for which the diffusion coefficient blows up in a subregion Ω0 which is interior to the physical domain Ω⊂Rn. We prove, under natural assumptions, that the associated attractors behave continuously as the diffusion coefficient blows up locally uniformly in Ω0 and converges uniformly to a continuous and positive function in . 相似文献
993.
Vera Koponen 《Archive for Mathematical Logic》2009,48(6):515-522
A probability distribution can be given to the set of isomorphism classes of models with universe {1, ..., n} of a sentence in first-order logic. We study the entropy of this distribution and derive a result from the 0–1 law for first-order
sentences.
相似文献
994.
995.
Slaveykova VI Guignard C Eybe T Migeon HN Hoffmann L 《Analytical and bioanalytical chemistry》2009,393(2):583-589
This work demonstrates the capabilities of nanoscale secondary-ion mass spectrometry, using the Cameca NanoSIMS50 ion microprobe,
to detect and image the copper-ion distribution in microalgal cells exposed to nanomolar and micromolar copper concentrations.
In parallel to 63Cu− secondary-ion maps, images of 12C−, 12C14N−, and 31P− secondary ions were collected and analysed. A correlation of 63Cu− secondary-ion maps with those found for 12C14N− and 31P− demonstrated the possible association of Cu with cell components rich in proteins and phosphorus. The results highlighted
the potential of NanoSIMS for intracellular tracking of essential trace elements such as Cu in single cells of the microalga
Chlorella kesslerii.
Figure
12C14N-, 63Cu- secondary-ion distributions in algal cell 相似文献
996.
The oxygen radical absorbance capacity (ORAC) method has been adapted to the instrumental laboratory and optimized for the
determination of the antioxidant capacity of a novel active packaging. As the ORAC assay requires the monitorization of a
reaction at controlled temperature by means of the fluorescence signal decrease over time, specific instrumental is usually
necessary. In this work, a common liquid chromatographic device has been adapted to perform the ORAC assay, leaving it accessible
to any laboratory. Using this adaptation, five different essential oils have been determined resulting in the following antioxidant
order: clove (2.66 g Trolox per gram of essential oil), oregano (2.25), cinnamon (1.93), rosemary (1.66), and ginger (1.47).
After incorporating the essential oils to the film, its antioxidant capacity has also been checked and related to the concentration
of essential oil as well as the thickness of the active film. The results point out that for the same amount of essential
oil incorporated measured as grams per square meter, thicker films have more antioxidant capacity than the thinner and more
concentrated ones. Furthermore, the antioxidant capacity found in the films was always higher than expected taking into account
the amount of essential oil incorporated. Some likely explanations have been proposed, leading to the improvement of the antioxidant
film under development. 相似文献
997.
Stabilization for a Fourth Order Nonlinear Schrödinger Equation in Domains with Moving Boundaries 下载免费PDF全文
Octavio Paulo Vera Villagran 《偏微分方程(英文版)》2021,34(3):268-283
In the present paper we study the well-posedness using the Galerkin method and the stabilization considering multiplier techniques for a fourth-order nonlinear Schrödinger equation in domains with moving boundaries. We consider two situations for the stabilization: the conservative case and the dissipative case. 相似文献
998.
Mattiza JT Meyer V Ozüduru G Heine T Fohrer J Duddeck H 《Natural product communications》2012,7(3):359-362
Thirty-eight derivatives of 3-hydroxy-2-methylpropanoic acid, each with two different oxygen functionalities, were synthesized and subjected to the standard dirhodium experiment (1H NMR in the presence of an equimolar amount of the chiral dirhodium tetracarboxylate complex Rh*). Their structures represent ester, amide, carbonate, ether, alcohol and/or epoxy groups. Significant selectivity in the binding of those oxygen groups to the complex were determined. From these results, a priority list in binding to a rhodium atom of Rh* was established: epoxides > primary alcohols > ethers > or = esters > or = amides > carbonates > tertiary alcohols. This sequence allows the prediction of the preferred binding site of oxygen-containing groups in polyfunctional compounds, which frequently occur among natural products, and, particularly, in asymmetric synthesis of such compounds. Differentiation of the enantiomers by the dirhodium experiment is easily accomplished due to numerous signal dispersions in nearly all cases. 相似文献
999.
Virgínia C. Fernandes Jose L. Vera Valentina F. Domingues Luís M. S. Silva Nuno Mateus Cristina Delerue-Matos 《Journal of the American Society for Mass Spectrometry》2012,23(12):2187-2197
Multiclass analysis method was optimized in order to analyze pesticides traces by gas chromatography with ion-trap and tandem mass spectrometry (GC-MS/MS). The influence of some analytical parameters on pesticide signal response was explored. Five ion trap mass spectrometry (IT-MS) operating parameters, including isolation time (IT), excitation voltage (EV), excitation time (ET), maximum excitation energy or ??q?? value (q), and isolation mass window (IMW) were numerically tested in order to maximize the instrument analytical signal response. For this, multiple linear regression was used in data analysis to evaluate the influence of the five parameters on the analytical response in the ion trap mass spectrometer and to predict its response. The assessment of the five parameters based on the regression equations substantially increased the sensitivity of IT-MS/MS in the MS/MS mode. The results obtained show that for most of the pesticides, these parameters have a strong influence on both signal response and detection limit. Using the optimized method, a multiclass pesticide analysis was performed for 46 pesticides in a strawberry matrix. Levels higher than the limit established for strawberries by the European Union were found in some samples. 相似文献
1000.
Fernando José Malagueño de Santana Valquíria Aparecida Polisel Jabor Evandro José Cesarino Vera Lúcia Lanchote Pierina Sueli Bonato 《Journal of separation science》2010,33(2):268-276
A selective and reproducible off‐line solid‐phase microextraction procedure was developed for the simultaneous enantioselective determination of mirtazapine (MRT), demethylmirtazapine and 8‐hydroxymirtazapine in human urine. CE was used for optimization of the extraction procedure whereas LC‐MS was used for method validation and application. The influence of important factors in the solid‐phase microextraction efficiency is discussed, such as the fiber coatings, extraction time, pH, ionic strength, temperature and desorption time. Before extraction, human urine samples were submitted to enzymatic hydrolysis at 37°C for 16 h. Then, the enzyme was precipitated with trichloroacetic acid and the pH was adjusted to 8 with 1 mol/L pH 11 phosphate buffer solution. In the extraction, the analytes were transferred from the aqueous solution to the polydimethylsiloxane‐divinylbenzene fiber coating and then desorbed in methanol. The mean recoveries were 5.4, 1.7 and 1.0% for MRT, demethylmirtazapine and 8‐hydroxymirtazapine enantiomers, respectively. The method was linear over the concentration range of 62–1250 ng/mL. The within‐day and between‐day assay precision and accuracy were lower than 15%. The method was successfully employed in a preliminary cumulative urinary excretion study after administration of racemic MRT to a healthy volunteer. 相似文献