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21.
Transient absorption spectra of adenine, adenosine and 2'-deoxyadenosine 5'-monophosphate (dAMP) arising from 248 nm laser flash photolysis using acetone as a photosensitizer have been observed. The intermediates recorded are assigned to the excited triplet states and dehydrogenated radicals of adenine and its nucleoside and nucleotide. The excited triplet states of adenine and its derivatives are produced via triplet-triplet excitation transfer and observed for the first time, while the dehydrogenated radicals stemming from the interaction of triplet acetone with adenine and its derivatives via electron transfer through a five-member-ring electron donor-acceptor intermediate. The site of dehydrogenation is suggested to be the hydrogen atom on C(8) of the adenine moiety. Moreover, three sets of kinetic parameters of the triplet decay have been determined. The rate constants of the unimolecular decay (k0), the triplet quenching by the ground state (ksq) and by the triplet quencher Mn2+ (kq) are 1.1 x 10(5), 7.9 x 10(4), 3.7 x 10(4) s-1, 6.9 x 10(8), 8.3 x 10(8), 3.6 x 10(8) dm3 mol-1 s-1 and 4.2 x 10(8), 3.5 x 10(8), 6.0 x 10(8) dm3 mol-1 s-1 respectively for adenine, adenosine and dAMP. 相似文献
22.
José?Luis?Pe?alvoEmail author M.?Con?eic?o?Castilho M.?Irene?N.?Silveira M.?Cruz?Matallana M.?Esperanza?Torija 《European Food Research and Technology》2004,219(3):251-253
Soymilk is a water extract of soybeans, closely resembling dairy milk in physical appearance and composition. Most fatty acids in soybean and its derivates are unsaturated, and therefore susceptible to oxidation. The aim of this study was to evaluate the possible effect of the thermal conditions during the elaboration process of soymilk on its fatty acid profile. For this, the fatty acid composition of soymilk, okara (soymilk residue), and soybean were studied by gas chromatography with flame ionization detection (GC-FID). No major differences in the fatty acid patterns were found. 相似文献
23.
We present an optoelectronic implementation of an adaptive-array processor that is capable of performing beam forming and jammer nulling in signals of wide fractional bandwidth that are detected by an array of arbitrary topology. The optical system makes use of a two-dimensional scrolling spatial light modulator to represent an array of input signals in 256 tapped delay lines, two acousto-optic modulators for modulating the feedback error signal, and a photorefractive crystal for representing the adaptive weights as holographic gratings. Gradient-descent learning is used to dynamically adapt the holographic weights to optimally form multiple beams and to null out multiple interference sources, either in the near field or in the far field. Space-integration followed by differential heterodyne detection is used for generating the system's output. The processor is analyzed to show the effects of exponential weight decay on the optimum solution and on the convergence conditions. Several experimental results are presented that validate the system's capacity for broadband beam forming and jammer nulling for linear and circular arrays. 相似文献
24.
We present a spatio-temporal operator formalism and beam propagation simulations that describe the broadband efficient adaptive method for a true-time-delay array processing (BEAMTAP) algorithm for an optical beamformer by use of a photorefractive crystal. The optical system consists of a tapped-delay line implemented with an acoustooptic Bragg cell, an accumulating scrolling time-delay detector achieved with a traveling-fringes detector, and a photorefractive crystal to store the adaptive spatio-temporal weights as volume holographic gratings. In this analysis, linear shift-invariant integral operators are used to describe the propagation, interference, grating accumulation, and volume holographic diffraction of the spatio-temporally modulated optical fields in the system to compute the adaptive array processing operation. In addition, it is shown that the random fluctuation in time and phase delays of the optically modulated and transmitted array signals produced by fiber perturbations (temperature fluctuations, vibrations, or bending) are dynamically compensated for through the process of holographic wavefront reconstruction as a byproduct of the adaptive beam-forming and jammer-excision operation. The complexity of the cascaded spatial-temporal integrals describing the holographic formation, and subsequent readout processes, is shown to collapse to a simple imaging condition through standard operator manipulation. We also present spatio-temporal beam propagation simulation results as an illustrative demonstration of our analysis and the operation of a BEAMTAP beamformer. 相似文献
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This paper describes the metadata and metadata management algorithms necessary to handle the concurrent execution of multiple tasks from a single workflow, in a collaborative service oriented architecture environment. Metadata requirements are imposed by the distributed workflow that calculates thermoelastic properties of materials at high pressures and temperatures. The scientific relevance of this workflow is also discussed. We explain the basic metaphor, the receipt, underlying the metadata management. We show the actual java representation of the receipt, and explain how it is converted to XML in order to be transferred between servers, and stored in a database. We also discuss how the collaborative aspect of user activity on running workflows could potentially lead to race conditions, how this affects requirements on metadata, and how these race conditions are precluded. Finally we describe an additional metadata structure, complementary to the receipts, that contains general information about the workflow. 相似文献
28.
Rodrigo S. da Silveira Andréa M. de Oliveira Sibele B. C. Pergher Victor Teixeira da Silva Ione M. Baibich 《Catalysis Letters》2009,129(3-4):259-265
Palladium and/or molybdenum catalysts supported on mordenite were prepared and characterized by XRD, UV–vis, DRS, textural properties analysis, TPR, TPD and chemical analysis. The Mo-catalyst rapidly deactivated after the first minutes reaction. The Pd-catalysts were active in the NO decomposition reactions. The incorporation of Mo in the Pd-catalysts improved their catalytic properties. 相似文献
29.
Fernanda de Carvalho Panzeri Pires‐de‐Souza Renata Espíndola Silveira Gabriel Abuna Michelle Alexandra Chinelatti Carla Cecilia Alandia‐Román Mario Alexandre Coelho Sinhoreti 《Microscopy research and technique》2015,78(12):1062-1068
The purpose of this study was to analyze, by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM), the morphology of sealant/enamel interface after surface treatment with Biosilicate. Before pits and fissures sealing, the occlusal surfaces of 10 sound human molars were sectioned perpendicularly at the fissures in order to obtain three slices for each tooth. Slices were randomly assigned into three groups (n = 10) according to sealing protocol: Group 1‐ Acid etching + Biosilicate + glass ionomer‐based sealant (Clinpro XT Varnish, 3M ESPE); Group 2‐ Acid etching + glass ionomer‐based sealant (Clinpro XT Varnish, 3M ESPE); Group 3‐ No sealing. All slices were subjected to thermal cycling (5,000 cycles; 5–55°C; dwell time: 30s). Half of the slices from each group (n = 5) were analyzed by CLSM and the other half by SEM. Groups 1 and 2 were also submitted to EDS analysis and their data were evaluated by Two‐Way ANOVA e Tukey's test (α=5%). EDS data analysis showed higher amounts of silicon (Si) ions than calcium (Ca) ions in Group 1 (P < 0.05); Group 2 presented higher amounts (P < 0.05) of Ca ions than Si ions. It may be concluded that the use of Biosilicate for surface treatment did not affect the morphology of glass ionomer‐based sealant/enamel interfaces. Microsc. Res. Tech. 78:1062–1068, 2015. © 2015 Wiley Periodicals, Inc. 相似文献
30.
A molecular absorption method is proposed for the determination of phosphorus in biodiesel. The samples are mineralized using an ashing procedure at 550 °C followed by dissolution of the residue. The analytical procedure is based on the formation of a blue molybdenum complex. 1-amino-2-naphthol-4-sulfonic acid is used as reducing agent. The method was applied to biodiesel samples prepared from soy, canola and sunflower oils and from bovine fat. The limit of detection is 0.57 mg P kg−1 and the limit of quantification is 1.7 mg P kg−1. The observed mean relative standard deviation is about 5%. The simplicity of the procedure added to its precision, accuracy and low cost suggest that it is an excellent option for the determination of phosphorus in biodiesel. 相似文献