p42MAPK-mediated phosphorylation of xEIAP/XLX in <Emphasis Type="Italic">Xenopus</Emphasis> cytostatic factor-arrested egg extracts

Background  

BIR family proteins are evolutionarily conserved anti-apoptotic molecules. One member of Xenopus BIR family proteins, xEIAP/XLX, is a weak apoptosis inhibitor and rapidly degraded in a cell-free apoptotic execution system derived from interphase egg extracts. However, unfertilized eggs are naturally arrested at the metaphase of meiosis II by the concerted activities of Mos-MEK-p42MAPK-p90Rsk kinase cascade (cytostatic factor pathway) and many mitotic kinases. Previous studies suggest that cytostatic factor-arrested egg extracts are more resistant to spontaneous apoptosis than interphase egg extracts in a p42MAPK-dependent manner. We tested whether xEIAP/XLX might be phosphorylated in cytostatic factor-arrested egg extracts, and also examined whether xEIAP/XLX could be functionally regulated by phosphorylation.     

Thickness and hole-shape dependence of flux penetration into square superconducting networks

We have observed flux penetrations into square superconducting networks of Nb with various thicknesses and hole-shapes by using magneto-optical imaging method. The penetrated pattern does not depend on the thickness and extends along diagonal direction when the samples have smaller area in the intersection of networks. We have also observed similar superconducting networks with and without small holes at the intersection. The small holes at the intersection do not work as a promoter for the diagonal flux penetration though the parallel flux penetration becomes weak. We discuss possible origins of these anomalous anisotropic flux penetrations.     

Reduced crystallization time of YBCO in a fluorine-free MOD process using uv-lamp irradiation

We have studied the crystallization time dependence of the epitaxial YBCO films (t = 0.8 μm) grown on CeO₂-buffered SrTiO₃ substrates by fluorine-free metal–organic deposition using uv-lamp irradiation (uv-MOD). As increasing the time (T₀) for heat treatment at the reaction temperature (760 °C) from 0 to 90 min, J_c and the YBCO 0 0 l XRD intensity are steeply increased and reach their maximum values at T₀ = 10 min. This suggests that the heat treatment required for YBCO crystallization is significantly shortened in uv-MOD compared to conventional all-pyrolytic F-free MOD processes, which consume T₀ = 90–150 min for crystallizing 0.4–0.5-μm-thick films. Scanning electron microscope measurement revealed a drastic change in surface morphology between T₀ = 8 and 10 min, showing a good correspondence to the J_c and XRD data which suggest that the epitaxial growth reaches the film surface at the very early stage in the heat treatment.     

EPMA line analysis of chemical states of chromium

A novel technique for determining the chemical states of elements with a heterogeneous distribution in samples involving EPMA line analysis is proposed. LLS (linear least squares) calculation was applied to a set of reduced spectra measured in the line analysis. The reduced spectra which have several energy points (including two points for backgrounds) were measured in order to save measuring time. The LLS calculation gives the mole fraction of each chemical state. We applied this method to the analysis of corrosion products formed on Cr-containing steel after corrosion tests. EPMA mapping revealed that Cr is enriched only in the inner layer of the corrosion products. From the results of the LLS calculation, it was determined that Cr in the corrosion products exists in the trivalent Cr state whereas in the steel Cr is in the metallic state. This result corresponds to the spectra of characteristic x-rays from the corroded steel. Copyright © 2001 John Wiley & Sons, Ltd.     

High-speed 1.55 μm InGaAs/InGaAsP multi-quantum well λ/4-shifted DFB lasers

The high-speed modulation properties of 1.5 μm multiquantum-well λ/4-shifted DFB lasers are filly reviewed. In particular, the dependence of intrinsic dynamic properties, such as relaxation oscillation frequency, nonlinear damping phenomenon, and spectral chirping under 10 Gbit/s direct modulation, on the number of quantum wells is systematically investigated and compared with those of bulk lasers. The results indicate that the dependence of the above three factors on the number of wells is clearly explained by the linear gain saturation of the quantum-well lasers and that the optimum number of wells should be more than ten in order to increase the modulation bandwidth.     

Formycin A resistant mutants due to defect in adenosine transport system in Vibrio parahaemolyticus

An antibiotic formycin A inhibited growth of Vibrio parahaemolyticus under certain conditions, which suggested that formycin A was taken up by cells under these conditions. We found that formycin A was transported via the adenosine transport system which we previously reported as a Na(+)-coupled cotransport system. We isolated many formycin A resistant mutants, and about half of them grew very poorly on adenosine as a sole source of carbon. Judging from their reversion frequencies, these mutants seemed to have single mutations. Respiration driven uptake of 14C-adenosine was not observed in such mutants; also, Na+ uptake induced by the addition of adenosine or formycin A to a cell suspension was completely abolished in them. Thus we conclude that these mutants possess a defect in the Na+/adenosine cotransport system, and have become formycin A resistant.     

A GENERAL FREQUENCY DEPENDENT DIGITAL OPTIMAL PREVIEW SERVO SYSTEM

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Bifurcation and chaos of a simple walking model driven by a rhythmic signal

The walk of animals is achieved by the interaction between the dynamics of their mechanical system and the central pattern generator (CPG). In this paper, we analyze dynamic properties of a simple walking model of a biped robot driven by a rhythmic signal from an oscillator. In particular, we examine the long-term global behavior and the bifurcation of the motion that leads to chaotic motion, depending on the model parameter values. The simple model consists of a hip and two legs connected at the hip through a rotational joint. The joint is driven by a rhythmic signal from an oscillator, which is an open loop. In order to analyze the bifurcation, we first obtained approximate solutions of the walking motion and then constructed discrete dynamics using the Poincaré map. As a result, we found that consecutive period-doubling bifurcations occur as the model parameter values change, and that the walking motion leads to chaotic motion over the critical value of the model parameters. Moreover, we approximately obtained the period-doubling solutions and the critical value by employing a Newton-Raphson method. Our analytical results were verified by the numerical simulations.