Termination dependence of surface stacking at 4H-SiC (0001) -1×1: Density functional theory calculations

We study the effect of adsorbates on the relative stability of hexagonal and cubic stacking sequences at the topmost SiC bilayers of 4H-SiC (0001) -1×1 surfaces using first-principles calculations. We investigate F-terminated, OH-terminated, H-terminated, and clean surfaces, and in all cases, the cubic structure is more stable than the hexagonal structure. The energy difference between the two structures, however, significantly depends on adsorbates and is largest on the clean surface while it is smallest on the H-terminated surface. Stabilization of the cubic structure at F-terminated and OH-terminated surfaces is in contradiction to a simple argument based on the electrostatic interaction and we attribute it to orbital hybridization between occupied states of adsorbates and unoccupied states of the substrate surface. The present results suggest a possible means of controlling step bunching and the SiC stacking sequence by surface adsorbates. © 2009 The American Physical Society.Hideyuki Hara, Yoshitada Morikawa, Yasuhisa Sano, and Kazuto Yamauchi Phys. Rev. B 79, 153306 (2009)

Development of Heated Narrow Channels with Enhanced Liquid Supply in Forced Convective Boiling

Abstract Heat generation density from semiconductor devices increases with the rapid development of electronic technology. The cooling system using boiling two-phase phenomena attracts much attention because of its high heat removal potential. Most of heat transfer researches concerning the development of electronic devices are conducted for the cooling of small semiconductor chips, while there are limited numbers of innovative investigations for the cooling of a large area at extremely high heat flux larger than 2×10 6 W/m 2 . The technology can be applied to the cooling systems in space, e.g., cooling of laser medium in solar power satellites when solar energy is converted to laser power. To develop compact and high-performance cooling systems, a structure of narrow heated channel between parallel plates with auxiliary unheated channel was devised and tested by using water in three different kinds of experimental conditions. One of liquid supply method, where liquid is supplied to both of the main heated and the auxiliary unheated channel keeping the exit of the auxiliary channel closed, gives the highest CHF value at total volumetric flow rates more than 3.0×10 -5 m 3 /s and 2mm gap size of main heated channel

Atomic-scale flattening of SiC surfaces by electroless chemical etching in HF solution with Pt catalyst

The authors present a method for flattening SiC surfaces with Pt as a catalyst in HF solution. The mechanism for flattening SiC surfaces is discussed. The flattened 4H-SiC (0001) surface is composed of alternating wide and narrow terraces with single-bilayer-height steps, which are induced by the rate difference of the catalytic reactions between adjacent terraces. Scanning tunneling microscopy images reveal a 1×1 phase on the terraces. The 1×1 phase is composed of coexisting of F- and OH-terminated Si atoms, which originate from the polarization of the underlying Si-C bonds. © 2007 American Institute of Physics.Kenta Arima, Hideyuki Hara, et al. "Atomic-scale flattening of SiC surfaces by electroless chemical etching in HF solution with Pt catalyst", Appl. Phys. Lett. 90(20), 202106 (2007) https://doi.org/10.1063/1.2739084

脳虚血後神経細胞障害における小胞体ストレスの役割

近年、細胞死の原因として、従来知られていたミトコンドリア障害やDNA障害によるものとは異なる、小胞体機能の破綻（小胞体ストレス）が関与することが明らかになってきた。小胞体ストレスは、アルツハイマー病などの神経変性疾患の神経細胞死メカニズムに関与していることが示唆され、アポトーシスシグナルの新たな発信地として注目を集めている。そこで、脳虚血後神経細胞障害の病態・機序を解明するための一環として、動物脳虚血モデルにおける小胞体ストレスの役割について検討した。砂ネズミ前脳虚血モデルにおける一過性脳虚血誘発海馬CA1野選択的神経細胞死およびマウス中大脳動脈閉塞モデルにおける永久閉塞誘発神経細胞死において小胞体ストレスの関与が認められた。そこで、新規脳卒中治療薬探索のため、小胞体ストレスにより誘導される分子シャペロンBiPの選択的誘導薬（BiP inducer X: BIX）の脳保護作用について検討した。BIXは、砂ネズミ前脳虚血誘発海馬CA1野選択的神経細胞死およびマウス中大脳動脈永久閉塞誘発神経細胞死を抑制した。以上より、脳虚血後神経細胞障害の機序に小胞体ストレス誘導性アポトーシスの関与が示唆され、BiP選択的誘導薬は神経細胞保護作用を有する新規な脳卒中治療薬の候補となる可能性が示唆された。Recent studies have revealed that perturbation of endoplasmic reticulum (ER) functions, which is called ER stress, induces apoptosis. ER stress, which is caused by an accumulation of unfolded proteins in the ER lumen, is associated with neurodegenerative diseases such as Alzheimer disease. The purpose of this study was to provide new insights into the pathogenesis of brain ischemia for development of new therapeutic approaches to ischemic brain diseases. We suggest that ER stress is involved in the CA1-selective neuronal cell death and permanent middle cerebral artery occlusion (MCAO) induced cell death. Furthermore, to investigate a possible role of a selective inducer of BiP (BIX), we evaluated the neuroprotective effects of BIX against acute ischemic neuronal damage. BIX provided significant protection against CA1-selective neuronal cell death and permanent MCAO-induced cell death. In conclusion, ER stress plays an important causal role both in transient and permanent ischemic damage, and drugs which selectively induce BiP may exert a neuroprotective effect and may be a candidate of new therapeutic treatments of stroke

Fabrication of elliptically figured mirror for focusing hard x rays to size less than 50 nm

In this study, we designed, fabricated, and evaluated a hard x-ray focusing mirror having an ideally focused beam with a full width at half maximum in the intensity profile of 36 nm at an x-ray energy of 15 keV. The designed elliptically curved shape was fabricated by a computer-controlled fabrication system using plasma chemical vaporization machining and elastic emission machining, on the basis of surface profiles accurately measured by combining microstitching interferometry with relative angle determinable stitching interferometry. A platinum-coated surface was employed for hard x-ray focusing with a large numerical aperture. Line-focusing tests on the fabricated elliptical mirror are carried out at the 1-km -long beamline of SPring-8. A full width at half maximum of 40 nm was achieved in the focused beam intensity profile under the best focus conditions. © 2005 American Institute of Physics.Hirokatsu Yumoto, Hidekazu Mimura, Satoshi Matsuyama, Hideyuki Hara, Kazuya Yamamura, Yasuhisa Sano Kazumasa Ueno, Katsuyoshi Endo Yuzo Mori, Makina Yabashi, Yoshinori Nishino, Kenji Tamasaku, Tetsuya Ishikawa and Kazuto Yamauchi, "Fabrication of elliptically figured mirror for focusing hard x rays to size less than 50nm", Review of Scientific Instruments 76(6), 063708 (2005) https://doi.org/10.1063/1.1922827

Heterogeneous circulating miRNA profiles of PBMAH

ObjectivePrimary bilateral macronodular adrenal hyperplasia (PBMAH), a rare cause of Cushing syndrome, is often diagnosed as a bilateral adrenal incidentaloma with subclinical cortisol production. Circulating microRNAs (miRNAs) are a characteristic of adrenocortical adenomas, but miRNA expression in PBMAH has not been investigated. We aimed to evaluate the circulating miRNA expression in patients with PBMAH and compare them with those in patients with non-functioning adrenocortical adenoma (NFA) and cortisol-producing adrenocortical adenoma (CPA).MethodsmiRNA profiling of plasma samples from four, five, and five patients with NFA, CPA, and PBMAH, respectively, was performed. Selected miRNA expressions were validated using quantitative RT-PCR.ResultsPBMAH samples showed distinct miRNA expression signatures on hierarchical clustering while NFA and CPA samples were separately clustered. PBMAH was distinguished from the adenoma group of NFA and CPA by 135 differentially expressed miRNAs. Hsa-miR-1180-3p, hsa-miR-4732-5p, and hsa-let-7b-5p were differentially expressed between PBMAH and adenoma (P = 0.019, 0.006, and 0.003, respectively). Furthermore, PBMAH could be classified into two subtypes based on miRNA profiling: subtype 1 with a similar profile to those of adenoma and subtype 2 with a distinct profile. Hsa-miR-631, hsa-miR-513b-5p, hsa-miR-6805-5p, and hsa-miR-548av-5p/548k were differentially expressed between PBMAH subtype 2 and adenoma (P = 0.027, 0.027, 0.027, and 1.53E-04, respectively), but not between PBMAH, as a whole, and adenoma.ConclusionCirculating miRNA signature was identified specific for PBMAH. The existence of subtype-based miRNA profiles may be associated with the pathophysiological heterogeneity of PBMAH

Generation and Characterization of Conditional Heparin-Binding EGF-Like Growth Factor Knockout Mice

Recently, neurotrophic factors and cytokines have been shown to be associated in psychiatric disorders, such as schizophrenia, bipolar disorder, and depression. Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a member of the EGF family, serves as a neurotrophic molecular and plays a significant role in the brain. We generated mice in which HB-EGF activity is disrupted specifically in the ventral forebrain. These knockout mice showed (a) behavioral abnormalities similar to those described in psychiatric disorders, which were ameliorated by typical or atypical antipsychotics, (b) altered dopamine and serotonin levels in the brain, (c) decreases in spine density in neurons of the prefrontal cortex, (d) reductions in the protein levels of the NR1 subunit of the N-methyl-D-aspartate (NMDA) receptor and post-synaptic protein-95 (PSD-95), (e) decreases in the EGF receptor, and in the calcium/calmodulin-dependent protein kinase II (CaMK II) signal cascade. These results suggest the alterations affecting HB-EGF signaling could comprise a contributing factor in psychiatric disorder