SILC and NBTI in pMOSFETs With Ultrathin SiON Gate Dielectrics

Degradation of pMOSFETs under negative gate bias stress has been intensively studied, bearing in mind the macroscopic and phenomenological similarity between stress-induced leakage current (SILC) and negative bias temperature instability (NBTI). By investigating the electrical characteristics of small-size pMOSFETs, the microscopic mechanisms of the degradation have been vividly revealed. In particular 1) NBTI-induced positive charge generation leading to a decrease in gate hole current and 2) some kind of leak path formation giving rise to SILC are found to occur in parallel, but not simultaneously. This finding enables us to conclude that SILC and NBTI in pMOS are not linked directly at least from the microscopic perspective despite their macroscopic similarity. These results have brought about new insights into the degradation of pMOS under negative gate bias, which is now quite important to CMOS reliability     

Chorioretinal damage caused by the excision of choroidal neovascularization

BACKGROUND: In recent years many longitudinal studies have examined the predictors of smoking acquisition. However, only a few studies have focused on the precursors of smoking cessation. The current study is one of the first concentrating on longitudinal predictors of young people's smoking cessation. METHODS: Subjects were 215 smokers ages 14-15 years who were reinterviewed 3 years later. These smokers were allocated to four groups based on their motivation to quit and actual quitting behavior at the last wave. Independent variables were smoking-specific cognitions, social influences, and aspects of smoking habits. RESULTS: Univariate comparisons between the four groups showed that those with a positive attitude toward smoking and lower self-efficacy were less likely to be motivated to quit 3 years later. No long-term effects of environmental influences were found. Aspects of smoking habits, such as intensity and frequency of smoking, and the context of cigarette use affected the motivation to quit. Logistic regression analyses were conducted to examine differences in predictors between the groups in more detail. These analyses revealed that differences mainly in attitudes and self-efficacy affected whether subjects were absolutely not motivated to quit or had actually quit 3 years later. Differences in smoking behavior affected the allocation to the more closely related groups (e.g., preparing versus quitting). CONCLUSIONS: Adolescents' motivation to quit is affected by smoking-related cognitions and habitual factors. More research is needed to decide whether the relation between intensity and frequency of smoking and the likelihood to quit later on should be interpreted in terms of differences in smoking initiation or in terms of preparation to quit.     

Forecasting based on time series with correlated errors by information preserving filter Demand forecasting from information theory

An optimal forecasting technique has been developed by us from the viewpoint of mutual information. Generalization of this process is considered for the time series with correlated errors. The recommended technique is also compared with the prevailing method based on the Kalman filter in the optimality. The results indicate that the former may improve the latter in the effectiveness of forecasting.     

Penalty-free dispersion-managed soliton transmission over a 100-km low-loss PCF

A long photonic-crystal fiber (PCF) with a low loss was successfully fabricated by first preparing a large pure silica glass preform. The fiber is 100 km long and has a low loss of 0.3 dB/km at 1550 nm. The fiber has a Rayleigh scattering coefficient of 0.85 dB/(km/spl middot//spl mu/m/sup 4/), which is the lowest value ever reported in a PCF. Using this fiber, the first penalty-free dispersion-managed soliton transmission at 10 Gb/s was achieved in a PCF.     

Evidence for bulk trap generation during NBTI phenomenon in pMOSFETs with ultrathin SiON gate dielectrics

Negative bias temperature instability (NBTI) of pMOSFETs with direct-tunneling SiON gate dielectrics was studied in detail. By investigating the effects of applying positive gate bias on pMOSFETs after exposure to NBT stress, the generation of bulk charge traps in the gate dielectrics during NBTI was clearly demonstrated. In particular, it was found that a positive charge generated by negative bias temperature stress (NBT stress) can be neutralized and that the neutralized site can return to the positive state. We consider that the bulk trap is due to hydrogen atoms released from the interface between the SiON gate dielectric and the Si substrate (and this is what has conventionally been considered a positive fixed charge). Moreover, the bulk trap generation was shown to give rise to stress-induced leakage current.     

Serum hepatocyte growth factor activity and hepatocyte proliferation in Long-Evans with a cinnamon-like coat color rats with hepatic lesions

We classified hepatic lesions spontaneously developed by Long-Evans with a cinnamon-like coat color (LEC) rats into the following four stages: Normal liver, acute hepatitis, chronic hepatitis, and hepatoma, by biochemical tests of the sera, and anatomical and histopathological examination of the livers. Hepatocyte growth factor (HGF) activity in the sera of LEC rats which developed acute hepatitis, chronic hepatitis, and hepatoma was higher than that of normal LEC rats. In particular, HGF activity in the sera of the LEC rats with acute hepatitis was about 70-fold that of normal LEC rats. However, primary cultured hepatocytes of LEC rats with hepatic lesions were hardly proliferated by stimulation with EGF and insulin in vitro or with increased HGF in vivo. These results suggest that the hepatocytes of LEC rats with hepatic lesions disorder the signal transduction of growth factors.     

Secretion of a variant of human single-chain urokinase-type plasminogen activator without an N-glycosylation site in the methylotrophic yeast,Pichia pastoris and characterization of the secreted product

Human single-chain urokinase-type plasminogen activator without an N-glycosylation site (scu-PA-Q³⁰²) was produced in the methylotrophic yeast, Pichia pastoris using the shortened prepeptide sequence of a fungal aspartic proteinase, Mucor pusillus rennin (MPR). The level of urokinase-type plasminogen activator (u-PA) immunoreactive material in YPM medium was 0·47 mg/l; however, most of the secreted product had been processed to smaller polypeptides. The N-terminal amino acid sequence of major species was identical to that of the low molecular weight two-chain u-PA. Some approaches to minimizing the proteolysis of scu-PA-Q³⁰² were attempted. Addition of Triton X-100, l-arginine and ammonium phosphate to the YPM medium minimized the proteolysis of scu-PA-Q³⁰² and increased the yield of immunoreactive material to approximately 5 mg/l. Use of proteinase A- or proteinase B-deficient strains of yeast did not reduce the degradation. Co-expression of scu-PA-Q³⁰² and urinary trypsin inhibitor resulted in partial reduction of the major species of proteolysis. Scu-PA-Q³⁰² was purified from the culture supernatant of the improved medium by two successive chromatographies on Phenyl-Sepharose and S-Sepharose. The purified protein had a molecular weight of 47 kDa. It did not contain detectable N-linked oligosaccharides, but contained O-linked oligosaccharides attached to the light chain. N-terminal amino acid sequencing of the purified preparation showed that the shortened prepeptide sequence of MPR was correctly processed by the Pichia yeast. Scu-PA-Q³⁰² closely resembles natural scu-PA with respect to its enzymatic activity against the chromogenic substrate S-2444 and its in vitro fibrinolytic properties.     

Hole-assisted dual concentric core fiber with ultralarge negative dispersion coefficient of -13,200 ps/nm/km

We propose a dual concentric core fiber (DCCF) with six homogeneous air holes, designed to realize a large negative dispersion coefficient. We clarify numerically that the dispersion property of the proposed DCCF can be controlled flexibly by adjusting the air-hole structure, and we realize the largest reported negative dispersion of -13,200 ps/nm/km experimentally.