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121.
A technique for incorporating a groove into a LiNbO(3) substrate is described. Both V grooves for fiber alignment and vertical grooves for waveguide end-face formation can be fabricated with this technique. The proposed fabrication method is based on an excimer-laser ablation and a high-speed rotation saw cut for LiNbO(3) . The former process provides a variety of cross-sectional groove shapes by changing the ablation mask shape of LiNbO(3) , and the latter provides an optical-quality cutting face. The proposed fabrication method is simple and provides low-cost optical platforms not only for LiNbO(3) but also for glasses, polymers, and semiconductors. 相似文献
122.
In the presence of phenylsilane and a catalytic amount of indium(III) acetate, organic iodides added to electron-deficient alkenes in ethanol at room temperature. Both simple and functionalized organic iodides were applicable to this reaction. A plausible reaction mechanism involves the formation of indium hydride species by hydride transfer from silicon to indium and an indium hydride-mediated radical chain process. 相似文献
123.
Usuki H Nitoda T Ichikawa M Yamaji N Iwashita T Komura H Kanzaki H 《Journal of the American Chemical Society》2008,130(12):4146-4152
A novel beta-N-acetylglucosaminidase (GlcNAcase) inhibitor named TMG-chitotriomycin (1) was isolated from the culture filtrate of Streptomyces anulatus NBRC13369. The strain produced 1 only when colloidal chitin was used as the sole carbon source in the production medium. The structure of 1 was determined by spectral and constitutive sugar analyses of the corresponding alditol derivatives to be an equilibrated mixture of alpha-d-N,N,N-triMeGlcNH2-(1,4)-beta-d-GlcNAc-(1,4)-beta-d-GlcNAc-(1,4)-d-GlcNAc and its C-2 epimer of the reducing end residue. TMG-chitotriomycin (1) showed potent and selective inhibition of insect and fungal GlcNAcases with no inhibition of mammalian and plant GlcNAcases. In contrast, the known GlcNAcase inhibitor nagstatin potently inhibited all GlcNAcases. It should be emphasized that synthesized d-N,N,N-triMeGlcNH2, which is the component sugar of 1, showed no inhibition of the insect Spodoptera litura GlcNAcase. These results suggest that the (GlcNAc)3 unit positioned at the reducing end of 1 is essential for its enzyme inhibitory activity. The unique inhibitory spectrum of 1 will be useful to study chitinolytic systems and to develop selective fungicides or pesticides. 相似文献
124.
Development of undersized (12.5 mm diameter) low‐dilution glass beads for X‐ray fluorescence determination of 34 components in 200 mg of igneous rock for applications with geochemical and archeological silicic samples 下载免费PDF全文
A low‐dilution, undersized (12.5 mm diameter) glass–bead technique was developed for X‐ray fluorescence determination of 34 components (Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, MnO, Fe2O3, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Cs, Ba, La, Pr, Nd, Sm, Gd, Dy, Er, Yb, Hf, W, and Pb) in precious silicic samples for geochemistry and archeology. This preparation was consolidated based on the properties of the specimen, including disk formability and detachability from a small crucible, through variation of the amounts of the two samples (basaltic and granitic rocks) and releasing reagent. The specimen was prepared by fusing a mixture of 200 mg of powdered sample, 200 mg of lithium tetraborate as a flux, and 60 µl of 18.42 mass% lithium chloride solution as a releasing agent in a small platinum crucible. Calibration curves were drawn using synthetic calibration standards, which were prepared by compounding chemical reagents, such as oxides, carbonates, and diphosphates containing analytes. The calibration curves showed good linearity with correlation coefficient values greater than 0.990. Using the proposed method, we determined 34 components in five igneous rock reference samples. The results were in agreement with the recommended values, accounting for uncertainties. With this method, preparation requires only small amounts of the powdered sample and alkali flux; however, still allowing for determination of many analytes, which is advantageous when dealing with limited quantities of precious samples. The present method has potential applications in the chemical characterization of various geological and archeological samples. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
125.
o-Formyl-substituted beta,beta-difluorostyrenes readily react with NH(2)OH.HCl or NH(4)OAc to afford 3-fluoroisoquinoline derivatives in good yield via (i) the formation of the corresponding oximes or imines and (ii) subsequent intramolecular replacement of a vinylic fluorine by the sp(2) nitrogen of the iminomethyl group (HON=CH- or HN=CH-). Beta,beta-Difluorostyrenes bearing an o-diazenyl group (HN=N-), generated by reduction of the corresponding diazonium ions, undergo a similar substitution to afford 3-fluorinated cinnolines. 相似文献
126.
Nakao Y Chen J Imanaka H Hiyama T Ichikawa Y Duan WL Shintani R Hayashi T 《Journal of the American Chemical Society》2007,129(29):9137-9143
Stable and reusable tetraorganosilicon reagents, alkenyl-, aryl-, and silyl[2-(hydroxymethyl)phenyl]dimethylsilanes, undergo 1,4-addition reactions to alpha,beta-unsaturated carbonyl acceptors under mild rhodium-catalysis. The reaction tolerates a diverse range of functional groups and is applicable to gram-scale synthesis. Use of a chiral diene ligand allows the achievement of the corresponding enantioselective transformations using the tetraorganosilicon reagents, providing the silicon-based approach to optically active ketones and substituted piperidones that serve as synthetic intermediates of pharmaceuticals. A rhodium alkoxide species is suggested to be responsible for a transmetalation step on the basis of the observed kinetic resolution of a racemic chiral phenylsilane in the enantioselective 1,4-addition reaction under the rhodium-chiral diene catalysis. 相似文献
127.
Y. Nagame I. Nishinaka Y. L. Zhao K. Tsukada S. Ichikawa Z. Qin H. Ikezoe Y. Oura K. Sueki H. Nakahara M. Tanikawa T. Ohtsuki S. Goto H. Kudo Y. Hamajima K. Takamiya K. Nakanishi H. Baba 《Journal of Radioanalytical and Nuclear Chemistry》1999,239(1):97-101
The correlation among the fission threshold energy, the scission configuration and the mass yield distribution has been studied
in proton-induced fission of light actinides. It was found that there exist at least two fission paths from the threshold
region to the scission. The elongated scission configuration is related with the fission process that goes over a higher threshold
energy and results in a symmetric mass division mode, while the compact scission configuration with the process that experiences
a lower threshold and ends up with an asymmetric mass division mode. 相似文献
128.
129.
The diffusion reaction of TBA2Cu(II)Cl4 (TBA = tetrabutylammonium) and a N-containing organic donor, BP-TTF [=bis(pyrazino)tetrathiafulvalene], yielded a 3-D supramolecular Cu complex, [CuCl2(BP-TTF)] (1). The magnetic measurement of 1 exhibits an antiferromagnetic interaction by fitting a Bonner-Fisher model from 2 to 300 K with S = 1/2 and J = -3.5 K between Cu(IotaIota) mediated by self-assembling donor columns. 相似文献
130.
Manabu Ichikawa Yo-ichi Ishikawa Takashi Wakasugi Kohei Kadono 《Journal of luminescence》2012,132(3):784-788
Emission properties were investigated in the infrared region for Ga2S3-GeS2-Sb2S3 glasses doped with Ho3+. We performed Judd–Ofelt analysis and lifetime measurements of the 5I4, 5I5, and 5I6 levels, which are the initial levels of the mid-infrared emissions between 3 to 5 μm of Ho3+. The quantum efficiencies reached approximately 18%, 64%, and ~100% for the 5I4, 5I5, and 5I6, respectively. Population analyses were carried out from the relative intensities of the emissions in the near-infrared region. We investigated the dependences on the Ho3+ ion concentration of the population ratio of the initial levels to the final levels, [initial]/[final], of the mid-infrared emissions. The population ratio of [5I5]/[5I6] decreased with increase of the Ho3+ concentration while those of [5I4]/[5I5] and [5I6]/[5I7] increased. Particularly, the former, [5I4]/[5I5], rapidly increased because of the strong concentration quenching of the 5I5 level through cross relaxation. It was found that the population inversion for the 4.8 μm emission due to the transition, 5I4→5I5, was achieved at high Ho3+ concentration in the present experiments. 相似文献