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941.
We consider the M/M
ij
/1 queue as a model of queues with changeover times, i.e., the service is exponential with parameter
ij
depending on the previous job type (i) and the current job type (j). It is shown that the departure process is renewal and Poisson iff
ij
= (constant). In this case, types of departures are dependent renewal processes. Crosscovariance and crosscorrelations are given. 相似文献
942.
Gonzalo Ramos Francisco del Monte Marcos Zayat Maria L. Ferrer David Levy 《Journal of Sol-Gel Science and Technology》2003,26(1-3):869-872
SiO2-TiO2 binary oxides are typically used as solid supports for different applications, from catalysts to optics. Tailoring the pore diameter, pore size distribution, and surface area is of great importance for any of those applications. Tailoring the chemical properties of the porous surface, e.g. in terms of polarity or acidity, is of capital importance as well. Thus, in catalytic applications or in sensing devices, where diffusion of a solute through the matrix is required, the affinity/compatibility of the solute with the matrix porous surface will determine the proper work of the device. Moreover, when the sensor is based on the adsorption of an active organic molecule or biomolecule on the porous surface matrix, the proton concentration at the surface may also modify the behavior of the active molecule. In this work, the proton affinity of the porous surface is tailored by the preparation of number of SiO2-TiO2 binary oxides with different SiO2/TiO2 weight ratios. Proton affinity is studied through the incorporation of a pH indicator as bromocresol green. 相似文献
943.
Jackson RA Valerio ME Couto Dos Santos MA Amaral JB 《Dalton transactions (Cambridge, England : 2003)》2004,(19):3098-3100
This paper describes a new computational method for predicting the optical behaviour of doped inorganic materials. There is considerable interest in using inorganic materials in photonic devices, and in many cases, the optical properties of these materials depend on doping by ions such as those from the rare earth series. Among the inorganic materials of interest are the mixed metal fluorides (e.g. BaLiF(3), BaY(2)F(8), YLiF(4), LiCaAlF(6), LiSrAlF(6)), doped with trivalent rare earth ions. The paper describes the use of Mott-Littleton calculations to determine the optimum location for dopant ions, followed by crystal field calculations which make direct use of the output of the Mott-Littleton calculations to calculate the optical properties of the dopant ion taking into account its symmetry and the positions of the surrounding ions, including any vacancies or interstitial ions present by virtue of charge compensation. It is then possible to predict whether a given dopant ion at a particular site in a material will have favourable optical properties. 相似文献
944.
Benito Alcaide Carmen López Mardomingo Rafael Pŕez-Ossorio Joaquín Plumet Marcos M. Sánchez 《Tetrahedron letters》1985,26(36):4403-4406
α-Iminoketones react with simple lithium ester enolates to give substituted β-hydroxy-λ-imino esters. Some reactions of these esters are reported. 相似文献
945.
Cindy?Elena?Bustamante-VargasEmail author Débora?de?Oliveira Eunice?Valduga Luciana?Dornelles?Venquiaruto Natalia?Paroul Geciane?Toniazzo?Backes Rogério?Marcos?DallagoEmail author 《Applied biochemistry and biotechnology》2016,179(6):1060-1072
Pectinases catalyze the degradation of pectic substances and are used in several processes, mainly in food and textile industries. In this study, a biomimetic matrix of alginate/gelatin/calcium oxalate (AGOCa) was synthesized for the in situ immobilization via encapsulation of crude pectinase from Aspergillus niger ATCC 9642, obtaining an immobilization efficiency of about 61.7 %. To determine the performance of AGOCa matrix, this was compared to control matrices of alginate/calcium oxalate (AOxal) and alginate/water (ACa). By the evaluation of pH and temperature effects on the enzyme activity, it was observed an increase on pectinolytic activity for both three tested matrices with an increase on pH and temperature. The kinetic parameters for pectinase immobilized in the three matrices were determined using citric pectin as substrate. Values of K m of 0.003, 0.0013, and 0.0022 g mL?1 and V max of 3.85, 4.32, and 3.17 μmol min?1 g?1 for AGOCa, AOxal, and ACa matrices were obtained, respectively. After 33 days of storage, the pectinase immobilized in the three different matrices kept its initial activity, but that immobilized in AGOCa presented high stability to the storage with a relative activity of about 160 %. The enzyme immobilized in AGOCa, AOxal, and ACa could be used in 10, 8, and 7 cycles, respectively, keeping 40 % of its initial activity. 相似文献
946.
947.
Wendell Costa Bila Reysla Maria da Silveira Mariano Valmin Ramos Silva Maria Emília Soares Martins dos Santos Joel Alves Lamounier Eduardo Ferriolli 《Isotopes in environmental and health studies》2017,53(4):327-343
The main aim goal of this review was to gather information about recent publications related to deuterium oxide (D2O), and its use as a scientific tool related to human health. Searches were made in electronic databases Pubmed, Scielo, Lilacs, Medline and Cochrane. Moreover, the following patent databases were consulted: EPO (Espacenet patent search), USPTO (United States Patent and Trademark Office) and Google Patents, which cover researches worldwide related to innovations using D2O. 相似文献
948.
Sean E. Pidgeon Dr. Marcos M. Pires 《Angewandte Chemie (International ed. in English)》2017,56(30):8839-8843
The surge in drug-resistant bacterial infections threatens to overburden healthcare systems worldwide. Bacterial cell walls are essential to bacteria, thus making them unique targets for the development of antibiotics. We describe a cellular reporter to directly monitor the phenotypic switch in drug-resistant bacteria with temporal resolution. Vancomycin-resistant enterococci (VRE) escape the bactericidal action of vancomycin by chemically modifying their cell-wall precursors. A synthetic cell-wall analogue was developed to hijack the biosynthetic rewiring of drug-resistant cells in response to antibiotics. Our study provides the first in vivo VanX reporter agent that responds to cell-wall alteration in drug-resistant bacteria. Cellular reporters that reveal mechanisms related to antibiotic resistance can potentially have a significant impact on the fundamental understanding of cellular adaption to antibiotics. 相似文献
949.
950.
M. Zamburlini J. L. Campbell G. de Silveira R. Butler A. Pejovi‐Mili D. R. Chettle 《X射线光谱测定》2009,38(4):271-277
Strontium is naturally present in human bone, where it may exert beneficial or detrimental health effects depending on its concentration. The way strontium influences bone health and the concentrations at which the beneficial/detrimental health effects of strontium become important are still unknown, due partly to the difficulty of assessing the bone strontium concentration in vivo non‐invasively. An x‐ray fluorescence (XRF) system was developed, which is capable of measuring normal bone strontium levels in vivo non‐invasively and therefore has the potential of becoming an important tool to understand bone strontium health effects. This technique, however, has the limitation that it relies on assumptions about bone strontium distribution to obtain a quantitative strontium measurement. To understand, to which degree, if any, the bone strontium distribution in bone changes from person to person, the bone strontium depth distribution was explored using micro‐PIXE in five ex vivo cadaver fingers, taken from normal people exposed to strontium only through diet. We found that, in the measured samples, strontium was uniformly distributed across the cortical and trabecular bone, and therefore corrections do not need to be applied to in vivo strontium XRF data to correct for strontium depth distribution. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献