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271.
A new method for the fabrication of high uniformity monolithic 1 × 4 singlemode fused coupler is described together with details of its performance in terms of coupling ratio, spectral response and uniformity. The fabricated device exhibits ultra-broadband performance with a port-to-port uniformity of 0.4 dB. The reliability of such couplers is also evaluated and found to have good stability. Moreover, by controlling the process parameters it is possible to control the power remaining in the through put port of the device, which can be used for dedicated non-intrusive network health monitoring. 相似文献
272.
The electron donating properties, surface acidity/basicity and catalytic activity of lanthana for various dopant concentrations of strontium are reported at two activation temperatures. The catalytic activity has been correlated with electron donating properties and surface acidity/basicity of the oxide. 相似文献
273.
274.
Synthesis of a tetrakis(1-pyrenylethynyl)-substituted rigid hinge-like molecule (1) is described. The intramolecular pi-stacking interaction of the pyrene units is studied by 1H NMR and fluorescence spectroscopy. Due to intramolecular pi-stacking interactions, chemical shifts of the pyrene protons in 1 are highly shielded in the NMR spectrum. Fluorescence from the static excimer state is observed due to pi-stacking interactions among the pyrene units in the ground state of 1. Based on the spectroscopic evidence, conformations and dynamics of 1, arising from the hindered rotation of the major axis, are proposed. 相似文献
275.
A Convenient Approach to Stereoisomeric Iminocyclitols: Generation of Potent Brain‐Permeable OGA Inhibitors
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Milan Bergeron‐Brlek Dr. Jake Goodwin‐Tindall Nevena Cekic Dr. Christian Roth Dr. Wesley F. Zandberg Dr. Xiaoyang Shan Dr. Vimal Varghese Sherry Chan Prof. Gideon J. Davies Prof. David J. Vocadlo Prof. Robert Britton 《Angewandte Chemie (International ed. in English)》2015,54(51):15429-15433
Pyrrolidine‐based iminocyclitols are a promising class of glycosidase inhibitors. Reported herein is a convenient epimerization strategy that provides direct access to a range of stereoisomeric iminocyclitol inhibitors of O‐GlcNAcase (OGA), the enzyme responsible for catalyzing removal of O‐GlcNAc from nucleocytoplasmic proteins. Structural details regarding the binding of these inhibitors to a bacterial homologue of OGA reveal the basis for potency. These compounds are orally available and permeate into rodent brain to increase O‐GlcNAc, and should prove useful tools for studying the role of OGA in health and disease. 相似文献
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277.
We analyze the ignition delay in hydrogen–oxygen combustion and the important chain ‐branching reaction H + O2→ OH + O that occurs behind the shock waves in shock tube experiments. We apply a stochastic Bayesian approach to quantify uncertainties in the theoretical model and experimental data. The approach involves a statistical inverse problem, which has four “components” as input information: (a) model, (b) prior joint probability density function (PDF) of the uncertain parameters, (c) experimental data, and (d) uncertainties in the scenario parameters. The solution of this statistical inverse problem is a posterior joint PDF of the uncertain parameters from which we can easily extract statistical information. We first perform a parametric study to investigate how the level of the total uncertainty (which we define as the sum of model uncertainty and experimental uncertainty) affects the uncertainty in the rate coefficient k1 of the reaction H + O2→ OH + O, which is “most likely” expressed by k1=1.73×1023T?2.5exp(?11550/T) cm3 mol?1 s?1 over the experimental temperature range 1100–1472 K. We also introduce the idea of “irreducible” uncertainty when considering other parameters in the system. After statistically calibrating the parameters modeling the rate coefficient k1, we predict its 95% confidence interval (CI) for different temperature regimes and compare the CI against the values of k1 obtained deterministically. Our results show that a small uncertainty in gas temperature (±5 K) introduces appreciable uncertainty in k1. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 586–597, 2012 相似文献
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279.
Management and measurement of risk is an important issue in almost all areas that require decisions to be made under uncertain information. Chance Constrained Programming (CCP) have been used for modelling and analysis of risks in a number of application domains. However, the resulting mathematical problems are non-trivial to represent using algebraic modelling languages and pose significant computational challenges due to their non-linear, non-convex, and the stochastic nature. We develop and implement C++ classes to represent such CCP problems. We propose a framework consisting of Genetic Algorithm and Monte Carlo Simulation in order to process the problems. The non-linear and non-convex nature of the CCP problems are processed using Genetic Algorithm, whereas the stochastic nature is addressed through Simulation. The computational investigations have shown that the framework can efficiently represent and obtain good solutions for seven test problems. 相似文献
280.
Balasubramanian Sridhar Krishnan Ravikumar Babu Varghese 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(5):o202-o206
In 9H‐adenine‐1,7‐diium hemioxalate chloride, C5H7N52+·0.5C2O42−·Cl−, (I), adenine is doubly protonated, while in 7H‐adenin‐1‐ium semioxalate hemi(oxalic acid) monohydrate, C5H6N5+·C2HO4−·0.5C2H2O4·H2O, (II), adenine and one oxalate anion are both monoprotonated. In (I), the adeninium cation forms R22(8) and R12(5) hydrogen‐bonding motifs with the centrosymmetric oxalate anion, while in (II), the cation forms R21(6) and R12(5) motifs with the centrosymmetric oxalic acid molecule and R12(5)and R22(9) motifs with the monoprotonated oxalate anion. Linear hydrogen‐bonded trimers are observed in (I) and (II). In both structures, the hydrogen bonds lead to the formation of two‐dimensional supramolecular hydrogen‐bonded sheets in the crystal packing. The significance of this study lies in the analysis of the interactions occurring via hydrogen bonds and the diversity seen in the supramolecular hydrogen‐bonded networks as a result of such interactions. 相似文献