以辉锑矿为原料放电等离子烧结快速制备黝铜矿Cu_(12)Sb_4S_(13)及反应机理

采用辉锑矿为原料成功制备出Cu_(12)Sb_4S_(13)块体。研究以Sb_2S_3矿物为原料时烧结工艺对Cu_(12)Sb_4S_(13)合成的影响。在400 ～ 440℃温度区间内均可快速合成Cu_(12)Sb_4S_(13)块体且二次烧结能够进一步减小中间相CuSbS_2和Cu_3SbS_3。第二相Cu_3SbS_4和残留相CuS随着烧结时间的延长而降低。二次烧结前进行机械化球磨处理,干磨比湿磨更容易减小残留相。初次烧结块体的断面SEM和EDS能谱分析表明内部存在Cu或Cu_2S颗粒团聚现象。适当降低Cu或CuS摩尔量(化学计量比0.1 mol)能促进烧结块表面反应进行。烧结过程中,硫磺蒸汽压的导致烧结块表面成分和内部粉末的成分不同。     

Hot carrier analysis in low-temperature poly-Si thin-film transistors using pico-second time-resolved emission microscope

We have analyzed degradation of N-channel thin-film-transistor (TFT) under dynamic stress using a pico-second time-resolved emission microscope. We have successfully detected emission at pulse fall edge for the first time. Emission intensity increased with the decrease of pulse fall time. As the degradation depended on the pulse fall time, this dependence clearly illustrates that hot electrons are the dominant cause of the degradation under dynamic stress. Based on these dependences, we proposed a model considering electron traps in the poly-Si.     

Molecular cloning of human Frizzled-6

The Frizzled genes encode receptors for WNTs, secreted glycoproteins implicated in development as well as in carcinogenesis. In this paper, we report molecular cloning of Hfz6, the human homologue of Mfz6. Nucleotide sequence analysis showed that the Hfz6 gene encodes the 706 amino-acid protein with seven transmembrane domains, a cystein-rich domain in the N-terminal extracellular region, two N-linked glycosylation sites, and two cystein residues in the second and third extracellular loops. Hfz6 mRNA 4.4-kb in size was detected in various normal adult and fetal tissues, and a larger amount of Hfz6 mRNA was detected in both fetal lung and fetal kidney. The Hfz6 gene has been mapped to human chromosome 8q22.3-q23.1. In conclusion, we have cloned Hfz6, which encodes a seven-transmembrane receptor with the cystein-rich domain in the N-terminal extracellular region, but without the Ser/Thr-X-Val motif in the C-terminus.     

Inhibitory effect of bifemelane on superoxide generation by activated neutrophils measured using a simple chemiluminescence method

We evaluated the effect of 4-(2-benzylphenoxy)-N-methylbutylamine hydrochloride (bifemelane hydrochloride) on superoxide production by human neutrophils using an MCLA-dependent chemiluminescence assay. Bifemelane hydrochloride dose-dependently inhibited superoxide production by neutrophils stimulated with phorbol myristate acetate, opsonized zymosan, or N-formyl-methionyl-leucyl-phenylalanine, while it had no effect on superoxide production by a hypoxanthine-xanthine oxidase system. These results indicate that bifemelane hydrochloride does not have a scavenging effect, but has an inhibitory effect on superoxide generation by neutrophils. Although this drug is commonly used for treating chronic cerebral infarction, it may also have a protective effect on acute ischemia/reperfusion injury.     

Thermal response in thermal energy storage material around heat transfer tubes: effect of additives on heat transfer rates

The effects of carbon-fiber chips and carbon brushes as additives on the thermal conductivity enhancement of phase change materials (PCMs) using in latent heat thermal energy storage are investigated experimentally and numerically by considering the wall effect of the additives. The carbon-fiber chips are effective for improving the heat transfer rate in PCMs. However, the thermal resistance near the heat transfer surface is higher than that for the carbon brushes. As a result, the overall heat transfer rate for the fiber chips is lower than that for the carbon brushes. Consequently, the carbon brushes are superior to the fiber chips for the thermal conductivity enhancement under the present experimental conditions. The carbon brushes are moreover applied to the packed beds of particles to overcome their low thermal conductivity in chemical heat pump/storage. The carbon brushes essentially improve the heat transfer characteristics in the packed beds, though the thermal resistance is observed because the particles obstruct contact between the fibers and the heat transfer surfaces.     

Non-linear current–voltage characteristics related to native defects in SrTiO3 and ZnO bicrystals

SrTiO₃ and ZnO bicrystals with various types of boundaries were fabricated in order to examine their current–voltage characteristics across single grain boundaries. Their grain boundary structures were also investigated by high-resolution transmission electron microscopy. In Nb-doped SrTiO₃, electron transport behaviors depend on the type of boundaries. Random type boundaries exhibit highly non-linear current–voltage characteristics, while low angle boundaries show a slight non-linearity. On the contrary, undoped ZnO does not exhibit non-linear current–voltage characteristics in any type of boundaries including random ones. It is suggested that the differences observed in current–voltage properties between the two systems are mainly due to the difference in the accumulation behavior of acceptor-like native defects at grain boundaries. A clear non-linearity is obtained by means of Co-doping even for the highly coherent Σ1 boundary in a ZnO bicrystal. This is considered to result from the production of acceptor-like native defects by Co-doping.     

Preparation of SiB4±x and SiB6 plates by chemical vapour deposition of SiCl4 + B2H6 system

SiB_4±x and SiB₆ plates were prepared by chemical vapour deposition (CVD) using SiCl₄, B₂H₆ and H₂ gases under the conditions of deposition temperatures (T _dep) from 1323–1773 K, total gas pressures (P _tot) from 4–40 kPa and B/Si source gas ratio (m _B/Si=2B₂H₆/SiCl₄) from 0.2–2.8. The effects of CVD conditions on the morphology, structure and composition of the deposits were examined. High-purity and high-density SiB_4±x and SiB₆ plates about 1 mm thick were obtained at the deposition rates of 71 and 47 nm s⁻¹, respectively. The lattice parameter, composition and density of CVD SiB_4±x plates were dependent on their non-stoichiometry. The lattice parameter,a, was 0.6325 nm, butc ranged from 1.262–1.271 nm.The B/Si atomic ratio ranged from 3.1–5.0, and the density ranged from 2.39–2.45×10³ kg m⁻³. The CVD SiB₆ plates showed constant values of lattice parameters (a=1.444 nm,b=1.828 nm,c=0.9915 nm), composition (B/Si=6.0) and density (2.42×10³ kg m⁻³), independent of CVD conditions.     

Clinical implications of chromosomal abnormalities in 401 patients with myelodysplastic syndromes: a multicentric study in Japan

It is well known that cytogenetic analysis in patients with myelodysplastic syndrome (MDS) provides information useful in determining their prognosis. Based on the chromosomal results obtained from 401 MDS patients by a multicentric study in Japan, we studied correlations between chromosomal findings and prognosis or leukemic transformation in MDS patients. Patients with complex aberrations (cytogenetic abnormalities at more than three chromosomes), of any subtype, had a poor prognosis; for example, > 60% of patients with refractory anemia (RA) showing complex aberrations died within one year, but only 11% of them developed leukemia. In patients with RA with ringed sideroblasts (RARS), > 70% of those with complex aberrations evolved into the leukemic phase and survived for less than one year, suggesting a biologic heterogeneity in RARS patients. By contrast, about 5% of patients with RA or RARS exhibiting chromosomal findings other than -7/7q-, +8, two aberrations, and complex aberrations, developed leukemia and had a favorable prognosis. Therefore, the presence of chromosome abnormalities alone in patients with RA or RARS is not a factor in predicting leukemic transformation or poor prognosis. In patients with refractory anemia with an excess of blasts (RAEB), the presence of chromosome aberrations at MDS diagnosis affected the occurrence of leukemic transformation (24% versus 43%), however, no particular difference was noted in patients with RAEB in transformation with regard to whether they had chromosome changes or not, and about 60% of them evolved into leukemia. The poor prognosis related to complex aberrations was consistently noted in all MDS subtypes or age-matched groups, indicating that this cytogenetic anomaly is an independent risk factor for a poor prognosis in MDS patients. The duration between MDS diagnosis and development of the leukemic phase and that between the latter and death were significantly shorter in patients with complex aberrations than those without this change. Although the clinical significance of certain chromosomal abnormalities differs among subtypes of MDS, a new scoring system for predicting prognosis by cytogenetic changes, in combination with hematologic parameters, was proposed.