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951.
We describe the use of alpha tracks from the 17O(n, α)14C as a means of oxygen determination and distribution in biological material. A determination of oxygen in alumina and citric acid using enriched tracer was made. 相似文献
952.
Samuel Natelson 《应用光谱学评论》2013,48(1):143-152
Abstract This article reviews the developments in X-ray spectrometry and electron–probe microanalysis as applied to biological systems which have taken place in the last year. In order to understand the requirements of the biochemist for the application of instrumentation to element analysis, it is first necessary to present the problem. 相似文献
953.
We developed optical simulation models for TFT-LCD modules in LED projectors to study the effects of optical properties and light projection tilting angle on the transmission rate of liquid crystals. Optical properties for modules in each of the LCD panel layers were included in the study. The experiment for establishing crystal rotation was first constructed to measure changes in the transmission rate as light was projected on the LCD panel from different angles. The relationship between light attenuation and the allowable angles at which the LCD panel is able to allow light to shine through, was investigated. The results were used as parameters in the optical simulations. Through the use of LightTools, an optical software package, optical simulation was built for different modules in each of the LCD panel layers and optical simulation analysis was performed on the overall structure of the TFT-LCD panel. Results from the simulation analysis were compared with experimental results from scanning illumination measurement. The disparity between simulated and experimental values was less than 13%, ensuring the rationality and accuracy of the optical simulation. 相似文献
954.
S. Janarthanan R. Sugaraj Samuel Y. C. Rajan P. R. Umarani S. Pandi 《Journal of Thermal Analysis and Calorimetry》2012,109(1):69-72
The growth of semicarbazone of p-hydroxy benzaldehyde (SPHB) single crystal by slow evaporation solution growth technique is reported in this article. The grown crystal was subjected to powder XRD study to identify the crystalline nature. Single crystal XRD study was done to measure unit cell parameters and to confirm the crystal structure. In the presence of various functional groups of SPHB was identified by FTIR spectrum. Its optical behavior was examined by UV?CVis?CNIR spectrum and the crystal was found to have transparency in the region between 245 and 1100?nm. Thermal properties of the crystal were investigated using thermogravimetric and differential thermal analysis (TG-DTA), which indicated that the melting of the material occurred before decomposition. The nonlinear optical (NLO) property was tested by Kurtz?CPerry powder technique for second harmonic generations. 相似文献
955.
Controlled ring‐opening polymerization of trimethylene carbonate and access to PTMC‐PLA block copolymers mediated by well‐defined N‐heterocyclic carbene zinc alkoxides 下载免费PDF全文
Four novel Zinc–NHC alkyl/alkoxide/chloride complexes ( 4 , 5 , 9 and 9′ ) were readily prepared and fully characterized, including X‐ray diffraction crystallography for 5 and 9′ . The reaction of N‐methyl‐N′‐butyl imidazolium chloride ( 3.HCl ) with ZnEt2 (2 equiv.) afforded the corresponding [(CNHC)ZnCl(Et)] complex ( 4 ) via a protonolysis reaction, as deduced from NMR data. The alcoholysis of 4 with BnOH led to quantitative formation of the dinuclear Zn(II) alkoxide species [(CNHC)ZnCl(OBn)]2 ( 5 ), as confirmed by X‐ray diffraction analysis. The NMR data are in agreement with species 5 retaining its dimeric structure in solution at room temperature. The protonolysis reaction of N‐(2,6‐diisopropylphenyl)‐N′‐ethyl methyl ether imidazolium chloride ( 8.HCl ) with ZnEt2 (2 equiv.) yielded the [(CNHC)ZnCl(Et)] species 9 . The latter was found to be reactive with CH2Cl2 in solution and to cleanly convert to the corresponding Zn(II) dichloride [(CNHC)ZnCl2]2 ( 9′ ), whose molecular structure was also elucidated using X‐ray diffractometry. Unlike Zn(II)–NHC alkoxide species 1 and 2 , which contain a NHC flanked with an additional N‐functional group (i.e. thioether and ether, respectively), the Zn(II) alkoxide species 5 incorporates a monodentate NHC ligand. The Zn(II) complexes 1 , 2 and 5 were tested in the ring‐opening polymerization (ROP) of trimethylene carbonate (TMC). All three species are effective initiators for the controlled ROP of trimethylene carbonate, resulting in the production of narrow disperse PTMC material. Initiator 1 (incorporating a thioether moiety) was found to perform best in the ROP of TMC. Notably, the latter also readily undergoes the sequential ROP of TMC and rac‐LA in the presence of a chain‐transfer agent, leading to well‐defined and high‐molecular‐weight PTMC/PLA block copolymers. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
956.
957.
Prenucleation Self‐Assembly and Chiral Discrimination Mechanisms during Solution Crystallisation of Racemic Diprophylline 下载免费PDF全文
Dr. Clément Brandel Dr. Yohann Cartigny Prof. Gérard Coquerel Prof. Joop H. ter Horst Prof. Samuel Petit 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(45):16103-16112
The crystallisation behaviour of (RS)‐diprophylline (DPL) in two different solvents is investigated to assess the incidence of solvated pre‐associations on nucleation, crystal growth and chiral discrimination. In the solvated state, Raman spectroscopy shows that dimeric associations similar to those depicted in the crystalline solid solution (ssRII) predominate in isopropanol (IPA), which may account for the systematic spontaneous nucleation of this crystal form from this solvent. By contrast, spontaneous nucleation in DMF yields the stable racemic compound RI, consistently with the distinct features of the Raman spectrum collected in this solvent. A crystal growth study of ssRII in IPA reveals that the crystal habitus is impacted by the solution enantiomeric excess; this is explained by increased competition between homo‐ and heterochiral pre‐associations. This is supported by a molecular modelling study on the enantiomeric selectivity of the DPL crystal lattices. The combination of assessment methods on solution chemistry, nucleation and chiral discrimination provides methodological tools from which the occurrence of solid solutions can be rationalised. 相似文献
958.
Samuel Monnier 《Letters in Mathematical Physics》2015,105(9):1321-1331
959.
Samuel Geniaut Erwan Galenne 《International Journal of Solids and Structures》2012,49(15-16):2094-2106
In this paper, a new method for level set update is proposed, in the context of crack propagation modeling with the extended finite element method (X-FEM) and level sets. Compared with the existing methods, such as the resolution of the Hamilton–Jacobi equations, this new method is much simpler because it does not required complex manipulations of the level sets. This method, called the “projection” method, uses both a classical discretization of the surface of the crack (segments for 2d cracks and triangles for 3d cracks) and a level set representation of the crack. This discretization is updated with respect to the position of the new crack front. Then the level sets are re-computed using the true distance to the new crack, by an orthogonal projection of each node of the structure onto the new crack surface. Then, numerical illustrations are given on 2d and 3d academic examples. Finally, three illustrations are given on 3d industrial applications. 相似文献
960.