Separation and control of the elution order of N-t-butyloxycarbonyl amino acids D/L isomers by reversed-phase HPLC using cyclodextrins as chiral selectors for the mobile phase.

The enantiomeric resolution of N-t-butyloxycarbonyl (N-t-Boc) amino acids D/L isomers by reversed-phase HPLC was investigated using cyclodextrins (CD's) as chiral selectors for the mobile phase. The use of a low pH (pH<4) for the mobile phase enabled the enantioseparation of N-t-Boc amino acids. The opposite elution order of D/L isomers was observed when hydroxypropyl-derivatized beta-CD was used instead of native beta-CD. A computer simulation of the enantioseparation showed that the ratio of the retention factors of the chiral selector and the sample determined the elution order and the resolution. When the retention factor of the chiral selector is smaller than that of the sample, an isomer having larger complex formation constant eluted faster. However, when the chiral selector had a larger retention factor than the sample, an opposite elution order of the isomers was obtained. The large difference in the retention factors between the chiral selector and the sample led to good enantiomeric separation.     

A microsensor for adenosine-5′-triphosphate pH-sensitive field effect transistors

The sensor for adenosine-5′-triphosphate (ATP) is based on H⁺-ATPase immobilized via a polyvinylbutyral resin on a pH-sensitive field effect transistor. A linear relationship was obtained between the initial rate of change of the differential gate output voltage and the logarithm of the ATP concentration over the range 0.2–1.0 mM ATP. The optimum pH was 9.0 at 40°C but pH 7.0 was preferred for routine measurements. Only slight responses were obtained for 1 mM glucose, creatinine or urea. The ATP-sensing system exhibited a response to 1 mM ATP for at least 18 days.     

Study of quantitative evaluation of liver volume and accumulation rate of radioactive agent with single photon emission computed tomography

The quantitative evaluation on measurement of liver volume and the hepatic accumulation rate of the radioactive agent were studied with respect to body constitution, background activity and splenic consumption rate, using single photon emission computed tomography (SPECT). The optical cut-off level for liver volume determination was proved to be reasonable as 35%. The background less than 5% had no influence to their clinical estimation with the error of less than 1.6%. The estimation of liver volume was mostly influenced by the splenic activity. When the splenic activity was increased two times of the hepatic activity, the liver volume was determined as 4.2% larger. Calculated counts by SPECT was well correlated with the hepatic activity. This study proved that SPECT was useful for the quantitative evaluation of the liver volume and the hepatic accumulation rate.     

Direct electron transfer with glucose oxidase immobilized in an electropolymerized poly( N-methylpyrrole) film on a gold microelectrode

Direct electron transfer between active glucose oxidase (GOD) and a gold electrode was obtained when GOD was immobilized in poly(N-methylpyrrole) electrochemically prepared on the gold electrode. When electropolymerization was accomplished at 50 °C, after glucose addition, the cyclic voltammograms showed an increased oxidation peak at ca. ?0.45 V vs. Ag/AgCl. This potential corresponds to the oxidation potential for FADH₂. Although the GOD becomes much less selective, a glucose-dependent current response is obtained.     

Parallel algorithms for variational inequalities over the Cartesian product of the intersections of the fixed point sets of nonexpansive mappings

This paper presents a framework of iterative algorithms for the variational inequality problem over the Cartesian product of the intersections of the fixed point sets of nonexpansive mappings in real Hilbert spaces. Strong convergence theorems are established under a certain contraction assumption with respect to the weighted maximum norm. The proposed framework produces as a simplest example the hybrid steepest descent method, which has been developed for solving the monotone variational inequality problem over the intersection of the fixed point sets of nonexpansive mappings. An application to a generalized power control problem and numerical examples are demonstrated.     

Possibilistic linear regression analysis for fuzzy data

Fuzzy data given by expert knowledge can be regarded as a possibility distribution by which possibilistic linear systems are defined. Recently, it has become important to deal with fuzzy data in connection with expert knowledge. Three formulations of possibilistic linear regression analysis are proposed here to deal with fuzzy data. Since our formulations can be reduced to linear programming problems, the merit of our formulations is to be able to obtain easily fuzzy parameters in possibilistic linear models and to add other constraint conditions which might be obtained from expert knowledge of fuzzy parameters. This approach can be regarded as a fuzzy interval analysis in a fuzzy environment.     

Characterization and quantification of fluoxymesterone metabolite in horse urine by gas chromatography/mass spectrometry

Fluoxymesterone, an anabolic steroid with the 17alpha-methyl,17beta-hydroxy group, has been developed as an oral formulation for therapeutic purposes. However, it is also used illegally in racehorses to enhance racing performance. In this study, we detected 9alpha-fluoro-17,17-dimethyl-18-norandrostane-4,13-dien-11beta-ol-3-one by gas chromatography/mass spectrometry (GC/MS), which has not been reported as a fluoxymesterone metabolite so far in horse. It was synthesized for use as a reference standard, and characterized on the basis of (1)H NMR and (13)C NMR spectra, as well as GC/MS EI mass spectra of TMS derivatives. It was excreted as the main metabolite in horse urine, and its reference standard could be synthesized easily. Therefore, this metabolite could be a useful target for a doping test of fluoxymesterone in racehorses.     

Printed circuit rat-race-type directional couplers for larger power-split ratio

Two different types of 5/2-wavelength rat-race-type directional couplers with a remarkably increased power-split ratio for a realizable ring-impedance, in particular which are useful for millimeter-wave circuits suffering from the severe restriction on the usable impedance range, are described. Experimental corroboration is provided in the microwave region (at 8 GHz).     

采用X射线吸收光谱表征单原子催化剂:至关重要与持久挑战

X射线吸收光谱(XAS)可为负载型单中心(单原子或单核金属络合物)催化剂的结构和电子特性提供重要信息.虽然XAS技术可表征真实反应条件下、无需长程有序结构的催化剂,并且可提供对于负载型单中心催化剂非常重要的金属-载体界面信息;但是它给出的信息是包括与催化有关或无关的所有负载型金属物种的平均信息.负载型催化剂的准确表征具有长期挑战性,也限制了我们准确地理解催化剂的构效关系.为了更好地利用XAS表征技术,深入研究催化剂的构效关系,并最终用其指导设计开发出高效的催化剂,制备具有均一结构活性位的负载型单中心催化剂,并采用XAS及相关技术对其表征至关重要.本文列举了一些实例以说明XAS在表征具有均一结构活性位的负载型单中心催化剂方面的能力,以及XAS如何与其他技术(如扫描透射电子显微镜和红外光谱)互补,为以分子筛和金属-有机骨架材料为载体而制得的具有均一结构活性位的负载型单中心催化剂提供原子尺度的信息.