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61.
We propose and experimentally demonstrate a novel subwavelength grating coupler on silicon-on-insulator, for coupling to optical fibers with a wide optical bandwidth. Theoretical analysis and design optimization of the coupler are described. About 73?nm 1?dB bandwidth was experimentally demonstrated with -5.6 dB coupling efficiency. Better than -3.4 dB efficiency with 86?nm 1?dB bandwidth is predicted for these structures with optimized buried oxide thickness. 相似文献
62.
The structure of the lithium manganese tartrate precursor and the synthesis mechanism of LiMn2O4 were investigated by FT-IR, NMR, TG/DSC, and XRD in this study. The results of FT-IR and 7Li and 13C NMR measurements revealed that lithium ions bond with carboxylic acid ligands and the O–H stretching modes of tartaric acid. Manganese ion bonds only with carboxylic acid. Lithium and manganese ions were trapped homogeneously on an atomic scale throughout the precursor. Such a structure eliminates the need for long-range diffusion during the formation of lithium manganese oxides. Therefore, spinel LiMn2O4 was synthesized at temperatures as low as 300°C. In this work, the electrochemical properties of Li/LixMn2O4 were studied. It is clear that the discharge curves exhibit two pseudo plateaus as the LiMn2O4 is fired to higher temperatures. The discharge capacity of LiMn2O4 increases from 84 to 117 mAh/g as the calcination temperature increases from 300 to 500°C. The LiMn2O4 powders calcined at low temperatures with a high specific surface area and an average valence of manganese exhibit a better cycle life. 相似文献
63.
Ozonolysis of mono-substituted alkenes A-1 followed by reacting with a preheated mixture of CH2Br2-Et2NH affords α-substituted acroleins A-2 in good yields. Under very mild reaction conditions, these α-substituted acroleins A-2 can be easily converted to α-methylene esters A-4, which could be further converted to the corresponding α-keto esters A-5. This methodology can be also applied to the preparation of α-methylene lactones B-4, α-methylene lactams, and α-keto lactones B-5 with various ring sizes. 相似文献
64.
Shyh‐Ying Chiou Gin‐Win Lai Yi‐Hon Tsai Yu‐Ru Lee Long‐Yau Lin Gia‐Lih Lin 《中国化学会会志》2005,52(4):843-848
The goal of this work is to determine enzyme kinetics and mechanisms of acetylcholinesterase and butyrylcholinesterase inhibition by five cardiovascular drugs, lovastatin, simvastatin, amlodipine besylate, nifedipine, and hydralazine hydrochloride, and two benzodiazepines, diazepam and chlordiazepoxide hydrochloride. All drugs in this study are reversible mixed‐type inhibitors of acetylcholinesterase and butyrylcholinesterase. The pKi values for acetylcholinesterase and butyrylcholinesterase inhibition by the cardiovascular drugs are linearly correlated with the molecular weights of the drugs with the slopes of 0.005 and 0.0021, respectively. Therefore, van der Waals' interactions between acetylcholinesterase and the cardiovascular drugs are stronger than those between butyrylcholinesterase and the drugs. This is probably due to a smaller active site gorge and a more significant peripheral anionic substrate binding site of acetylcholinesterase than those of butyrylcholinesterase. The fact that the pKi values for both butyrylcholinesterase and acetylcholinesterase inhibition by the cardiovascular drugs are linearly correlated with each other suggests that both enzyme inhibition reactions proceed via a common mechanism. Furthermore, amlodipine besylate may be useful in Alzheimer's disease treatment similar to donepezil. 相似文献
65.
Calorimetric measurements of the enthalpy of reaction of WO3(c) with excess OH?(aq) have been made at 85°C. Similar measurements have been made with MoO3(c) at both 85 and 25°C, to permit estimation of ΔH°=?13.4 kcal mol?1 for the reaction WO3(c)+2OH?(aq)=WO2?4(aq)+H2O(liq) at 25°C. Combination of this ΔH° with ΔH°f for WO3(c) leads to ΔH°f=?256.5 kcal mol?1 for WO2?4(aq). We also obtain ΔH°f=?269.5 kcal mol?1 for H2WO4(c). Both of these values are discussed in relation to several earlier investigations. 相似文献
66.
A method of coupling capillary zone electrophoresis (CZE) with electrospray ionization-mass spectrometry (ESI-MS) detection has been developed for monitoring an antiepileptic drug, lamotrigine (LTG) in human plasma. The CZE-MS was developed in three stages: (i) CZE separation and ESI-MS detection of LTG and tyramine (TRM, internal standard) were simultaneously optimized by studying the influence of CZE background electrolyte (BGE) pH, BGE ionic strength, and nebulizer pressure of the MS sprayer; (ii) sheath liquid parameters, such as pH, ionic strength, organic modifier content, and flow rate of the sheath liquid, were systematically varied under optimum CZE-MS conditions developed in the first stage; (iii) MS sprayer chamber parameters (drying gas temperature and drying gas flow rate) were varied for the best MS detection of LTG. The developed assay was finally applied for the determination of LTG in plasma samples. The linear range of LTG in plasma sample assay was between 0.1-5.0 microg/mL with a limit of detection as low as 0.05 microg/mL and run time less than 6 min. Finally, the concentration-time profile of LTG in human plasma sample was found to correlate well when CZE-ESI-MS was compared to a more established method of high-performance liquid chromatography with ultraviolet detection. 相似文献
67.
A new synthetic method is described for the mild and selective reduction of 3-methyl-5-aryl-1,2,4-oxadiazoles to amidines employing iron powder in aqueous medium. Its application is demonstrated in the synthesis of 1, a potent and selective urokinase-type plasminogen activator (uPA) inhibitor. 相似文献
68.
Chlorided 0.57 wt. % Pt/γ-Al2O3 is a moderately active and highly selective catalyst for the isomerization of n-hexane at 300 °C when an excess of H2 is present. Chlorine, which is continuously lost from the catalyst, may be replaced by adding a small amount of chloroform to the reactant stream. The catalyst exhibits activity and high isomerization selectivity even at 150 °C. Under the conditions of these lower temperature experiments, the equilibrium concentration of C6 alkenes would be only 8 × 10?7 Torr. This suggests that the classical mechanism, which involves the formation of n-hexene on the Pt, is not applicable. Rather, it is proposed that isomerization of the alkane occurs at acid sites on the catalyst, and the role of Pt is to catalyze the hydrogenation of any alkenes that might be formed as a result of cracking reactions. At temperatures ≤ 300 °C Brönsted acid sites are present in the catalyst, and presumably are responsible for the isomerization and cracking activity, but at higher temperatures Lewis acid sites play a dominant role. 相似文献
69.
David N.-S. Hon Josefina M. San Luis 《Journal of polymer science. Part A, Polymer chemistry》1989,27(12):4143-4160
Cyanoethylation was attempted to convert wood into thermoplastic material as a means to utilize low quality wood species as well as wood waste materials. Cyanoethylation reaction was conducted with control of the alkalinity of the reaction media, reaction temperature and time, and wood-to-acrylonitrile ratio. Cyanoethylated wood was purified and its nitrogen content and weight gain were determined. Fourier transform infrared (FTIR) spectroscopy was used to monitor the absorption peak of cyano group. Thermoproperties of cyanoethylated wood were analyzed by means of a differential scanning calorimeter (DSC) and a dynamic mechanical thermal analyzer (DMTA). Reaction mechanisms and chemistry influencing the thermoproperties of cyanoethylated wood were discussed. 相似文献
70.
Souza J Molfetta FA Honório KM Santos RH da Silva AB 《Journal of chemical information and computer sciences》2004,44(3):1153-1161
The AM1 semiempirical method is employed to calculate a set of molecular properties (variables) of 45 flavone compounds with antipicornavirus activity, and 9 new flavone molecules are used for an activity prediction study. Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA), Stepwise Discriminant Analysis (SDA), and K-Nearest Neighbor (KNN) are employed in order to reduce dimensionality and investigate which subset of variables should be more effective for classifying the flavone compounds according to their degree of antipicornavirus activity. The PCA, HCA, SDA, and KNN methods showed that the variables MR (molar refractivity), B(9) (bond order between C(9) and C(10) atoms), and B(25) (bond order between C(11) and R(7) atoms) are important properties for the separation between active and inactive flavone compounds, and this fact reveals that electronic and steric effects are relevant when one is trying to understand the interaction between flavone compounds with antipicornavirus activity and the biological receptor. In the activity prediction study, using the PCA, HCA, SDA, and KNN methodologies, three of the 9 new flavone compounds studied were classified as potentially active against picornaviruses. 相似文献