Ellagic acid derivatives from the leaves of Eugenia jambos Linn

1316-131

Gremlin Enhances the Determined Path to Cardiomyogenesis

BACKGROUND: The critical event in heart formation is commitment of mesodermal cells to a cardiomyogenic fate, and cardiac fate determination is regulated by a series of cytokines. Bone morphogenetic proteins (BMPs) and fibroblast growth factors have been shown to be involved in this process, however additional factors needs to be identified for the fate determination, especially at the early stage of cardiomyogenic development. METHODOLOGY/PRINCIPAL FINDINGS: Global gene expression analysis using a series of human cells with a cardiomyogenic potential suggested Gremlin (Grem1) is a candidate gene responsible for in vitro cardiomyogenic differentiation. Grem1, a known BMP antagonist, enhanced DMSO-induced cardiomyogenesis of P19CL6 embryonal carcinoma cells (CL6 cells) 10-35 fold in an area of beating differentiated cardiomyocytes. The Grem1 action was most effective at the early differentiation stage when CL6 cells were destined to cardiomyogenesis, and was mediated through inhibition of BMP2. Furthermore, BMP2 inhibited Wnt/beta-catenin signaling that promoted CL6 cardiomyogenesis. CONCLUSIONS/SIGNIFICANCE: Grem1 enhances the determined path to cardiomyogenesis in a stage-specific manner, and inhibition of the BMP signaling pathway is involved in initial determination of Grem1-promoted cardiomyogenesis. Our results shed new light on renewal of the cardiovascular system using Grem1 in human

Effects of Crystal Defects in GaN on Electron Devices

GaN 系半導体材料は結晶成長，プロセス技術に大きな進展を成し遂げ，光デバイスだけでなく，電子デバイス応用としても高出力パワーアンプ，パワースイッチングの分野で実用化を迎える段階に研究開発が進展した．本稿では著者がデバイス開発の過程で観測した結晶欠陥起因の現象として，転位と電気的特性の相関，p-GaN 電極のショットキー障壁高さ及びメモリー効果，熱処理による2 次元電子ガス濃度の変動，及び結晶の平坦性が電子速度に与える影響の4 つの例を取り上げ，そのメカニズムを解明した結果について解説を行う．AlGaN/GaN high-electron-mobility transistors have been intensively studied as high-temperature high-power high-frequency electron devices. In this article， four topics， which related to the effects of crystal quality on device characteristics are reported. （i） Correlation between current－voltage （I－V） characteristics and dislocations was evaluated by using sub-micron diameter n-GaN Schottky contacts. The diodes showed that neither mixed nor edge dislocation affected I－V characteristics. （ii） Evaluation of Schottky barrier height was conducted for low-Mg-doped p-GaN. Large Schottky barrier height of 2.4 eV was obtained and memory effects were observed. （iii） Thermal stability of 2 dimensional electron gas was evaluated. The carrier concentration was sensitive to AlGaN crystal quality. （iv） The electron velocity in short-gate HEMTs with different crystal quality was evaluated. The measured velocities were virtually the same for all devices

Evaluation of the Initial Stage of Formation of Ti/Al Ohmic Contacts Using Photoresponse Method

Ti/Al contacts formed on n-GaN and AlGaN/GaN layers upon annealing at temperatures below the melting point of Al were evaluated by photoresponse (PR), current-voltage (I-V), and secondary ion mass spectroscopy (SIMS) measurements. In the PR spectra, the photocurrent based on the internal photoemission was detected, and the Schottky barrier height (qφB) was determined for all the samples, even though the I-V characteristics were very leaky. The AlGaN/GaN samples had constant qφB values of 0.85-1.0 eV independent of the annealing temperature. In contrast, the n-GaN samples had very low qφB values of 0.2 eV under the as-deposited condition. Upon annealing, qφB significantly increases and finally reaches almost the same values as those of the AlGaN/GaN samples. This can be explained by the change from Ti- to Al-rich interfaces in conjunction with the SIMS results.本著作物の著作権は公益社団法人応用物理学会に帰属します。/公益社団法人応用物理学会 2013/ 2013 The Japan Society of Applied Physic

Effect of Inductively Coupled Plasma Etching in p-Type GaN Schottky Contacts

The effects of inductively coupled plasma (ICP) etching damage on the electrical characteristics of low-Mg-doped p-GaN Schottky contacts were evaluated. The ICP etching greatly reduced the memory effect in the current-voltage characteristics and the difference between the depletion layer capacitances before and after forward current injection. These reductions indicate that acceptor-type interfacial defects were passivated by H atoms during ICP etching. Additionally, photoresponse (PR) measurements revealed that Schottky barrier height was increased from 2.08 to 2.63 eV by the etching. Because of the surface state change, the Fermi level position would be moved toward the conduction band edge slightly by the etching. After annealing, the memory effect and the capacitance change were partially restored, and the PR spectra showed less variation. Absorbed H atoms on the p-GaN surface might be released by annealing.本著作物の著作権は公益社団法人応用物理学会に帰属します。/公益社団法人応用物理学会 2013/ 2013 The Japan Society of Applied Physic

A new chiratane triterpenoid from <i>Swertia chirata</i>

228-231Reinvestigation of Swertia chirata resulted in the isolation of a new chiratane triterpenoid, chirat- 16-en-3β, 24-diol, besides known 24-ethylcholest-4-en-3-one and 1, 5, 8-trihydroxy-3-methoxy-xanthone-8-O-β--glucopyranoside. The structure of the new triterpenoid has been elucidated on the basis of 2D NMR spectral analyses