Preparation of Cu2ZnSnS4 single crystals from Sn solutions

We investigated the phase diagrams of the Cu₂ZnSnS₄ (CZTS)–Sn pseudobinary system in order to obtain knowledge useful for the growth of high-quality CZTS single crystals using a solution-based method. For Sn solutions saturated with less than ～60 mol% CZTS, the solutes are separated into two phases (CZTS phase+SnS_x phase+liquid phase). On the other hand, for solutions with more than 60 mol% CZTS, the solutes are single phase (CZTS phase+liquid phase). The CZTS single crystals were obtained from a 70 mol% CZTS solution (liquid temperature 850 °C) at 900 °C. The powder X-ray diffraction (XRD) pattern of the CZTS single crystal shows preferred orientations of (112), (220) and (312) planes, confirming the Kesterite structure of CZTS. The Raman spectrum shows three peaks at 287, 338, 371 cm^?1, which corresponded to CZTS peaks. The composition of the CZTS single crystal along the growth direction is found to be slightly Cu-poor, Zn-rich and S-rich. Therefore, it is assumed that the Cu vacancy is the dominant p-type conduction mechanism.     

Determination of the absolute stereochemistry and asymmetric total synthesis of madindolines A and B: a practical improvement to a second-generation approach from the first-generation

In this report, we describe an efficient, highly convergent, stereocontrolled first total synthesis and a second-generation synthesis of madindolines A 1 and B 2, potent selective inhibitors of interleukin 6. The key steps include (1) asymmetric oxidative ring-closure reaction of tryptophol 3 to construct a chiral 3a-hydroxyfuroindoline 4 using the modified Sharpless asymmetric epoxidation condition, (2) highly diastereoselective acylation to build up the quaternary carbon center, and (3) intramolecular acylation of ester 32 with allylsilanes to produce the full substituted cyclopentenedione units. Our first synthetic route defines for the first time both their relative and absolute configurations. Moreover, a more efficient second-generation synthesis was designed, which is suitable for gram-scale preparation of these compounds.     

Studies on absorption, distribution, excretion and metabolism of ginseng saponins. VII. Comparison of the decomposition modes of ginsenoside-Rb1 and -Rb2 in the digestive tract of rats.

In order to clarify some similarities and differences of decomposition modes between 20(S)-protopanaxadiol (20(S)-ppd) saponins, represented by ginsenoside Rb1 (Rb1) and ginsenoside Rb2 (Rb2), the decompositions of Rb1 and Rb2 in the rat gastrointestinal tract, 0.1 N HCl and crude hesperidinase were investigated in detail. As in the case of Rb2 reported previously, Rb1 was hydrolyzed to 20(R,S)-ginsenoside Rg3 in 0.1 N HCl. On the other hand, hydroperoxidation of Rb1 occurred in rat stomach; the major hydroperoxide was separated and identified as the 25-hydroperoxy-23-ene derivative of Rb1 (VIII) by 1H- and 13C-nuclear magnetic resonance and fast atom bombardment mass spectrometry. The decomposition modes of 20(S)-ppd saponins (Rb1 and Rb2) differed from that of 20(S)-protopanaxatriol saponin (Rg1) in rat stomach. In rat large intestine, five decomposition products of Rb1 were observed by thin-layer chromatography, and these were identified as gypenoside XVII (G-XVII), ginsenoside Rd (Rd), ginsenoside F2 (F2), compound K (C-K) and VIII. The decomposition modes of Rb1 and Rb2, both 20(S)-ppd saponins, are considered to be different because of the hydrolysis rate in the terminal sugar moiety at the C-20 hydroxyl group in the rat large intestine. Using crude hesperidinase, Rb1 was decomposed to G-XVII, F2 and C-K, and Rb2 was decomposed to 3-O-beta-D-glucopyranosyl-20-O-[alpha-L-arabinopyranosyl(1----6)-b eta-D- glucopyranosyl]-20-(S)-ppd, F2 and C-K. Consequently, it appears that hydrolysis by beta-glucosidase, which is present in the rat large intestine, is distinct from that by crude hesperidinase.(ABSTRACT TRUNCATED AT 250 WORDS)     

Low Curie temperature material for induction heating self-temperature controlling system

This paper presents low Curie temperature magnetic materials for induction heating. These materials are alloys based on SUS430. The magnetization decreases with increasing amount of additives. In order to increase the saturation magnetization, while keeping the Curie temperature constant, rare earth materials were added in this study. The compositions of alloys were investigated to realize a suitable Curie temperature. The temperature self-controlling function was also investigated in measurement of temperature distribution by using thermograph apparatus. Furthermore, thermoelectromagnetic field analysis was carried out as a numerical examination.     

Design, synthesis, and evaluation of carbamate-substituted analogues of (+)-discodermolide

[Structure: see text] The design, syntheses, and biological evaluation of 22 totally synthetic analogues of the potent microtubule-stabilizing agent (+)-discodermolide (1) have been achieved. Structure-activity relationships of the C(19) carbamate were defined, exploiting two synthetically simplified scaffolds, as well as the parent (+)-discodermolide framework.     

Mixed magnetic phases in (Ga,Mn)As epilayers

Two different ferromagnetic-paramagnetic transitions are detected in (Ga,Mn)As/GaAs(001) epilayers from ac susceptibility measurements: transition at a higher temperature results from (Ga,Mn)As cluster phases with [110] uniaxial anisotropy and that at a lower temperature is associated with a ferromagnetic (Ga,Mn)As matrix with 100 cubic anisotropy. A change in the magnetic easy axis from [100] to [110] with increasing temperature can be explained by the reduced contribution of 100 cubic anisotropy to the magnetic properties above the transition temperature of the (Ga,Mn)As matrix.