Precise metabolic flux analysis of coryneform bacteria by gas chromatography-mass spectrometry and verification by nuclear magnetic resonance

Precise metabolic flux analysis (MFA) by gas chromatography-mass spectrometry (GC-MS) and computer calculation was performed, and the consistency of the estimated results was verified by independently performed nuclear magnetic resonance (NMR) analysis. The precise estimation of flux by the integration method of the mass isotopomer signal, defined as the coefficient of variance (CV) of multiple determination, was investigated, and the results estimated using different data sets with the same magnitude of error were confirmed. The CV of multiple determinations was sufficiently small to discuss and compare the fluxes of a metabolic pathway. The estimated fluxes using the GC-MS data were cross-validated with the NMR data that were independently measured and not used for MFA. The developed method was successfully applied to the MFA of the growth phase of two different glutamate-producing coryneform bacteria, Corynebacterium glutamicum and C. efficiens. The difference in the growth rate between these two bacterial species was discussed while considering the results of MFA, including forward and backward (exchange) fluxes.     

Thermodynamics of oxygen behaviour in cobalt-nickel alloys

In this study the concentration and chemical potential of oxygen in liquid Co-Ni alloys equilibrated with cobalt-nickel aluminate spinel solid solutions and alumina have been determined at 1773, 1823 and 1873K as a function of nickel concentration. The oxygen content of the melt has been measured by suction sampling and inert gas fusion analysis. The corresponding oxygen potential has been determined with the following solid state cell: Mo, Mo+MoO₂ | (MgO)ZrO₂ | (Co, Ni) melt + AI₂O₃ + (Co, Ni)O·(1+x)Al₂O₃, Mo. The effect of nickel on the activity coefficient of oxygen in Co-Ni alloys has been determined. The results for the activity coefficient have been modelled with Wagner's interaction parameters and also the more recent exponential method of St. Pierre et al. at the three temperatures.     

Development of InxGa1−xAs-based ohmic contacts for p-type GaAs by radio-frequency sputtering

In_xGa_1−xAs-based ohmic contacts which showed excellent contact properties for n-GaAs were demonstrated to be applicable to p-GaAs ohmic contacts. These contacts, prepared by radio-frequency sputtering, provided low contact resistance (0.2 Ω-mm), excellent thermal stability, smooth surface, and good reproducibility. The contact resistances had a weak dependence on the annealing temperatures, which was desirable in a manufacturing view point. This weak temperature dependence was explained to be due to a unique Schottky barrier height at the metal/p-In_xGa_1−xAs interface which does not depend on the In concentration in the In_xGa_1−xAs layer. The present experiment showed the possibility of simultaneous preparation of ohmic contacts for both n and p-GaAs using the same contact materials.     

Reliability consideration on a compound redundant system with repair

This paper considers a standby-redundant system consisting of 2 systems, in which one is main and the other is its standby-redundant system. These systems also consist of 2 subsystems connected in series.A feature of this system is that the system has 2 switching devices connecting subsystems, in addition to one connecting main and standby systems, in order to utilize surviving subsystem. In this consideration it is assumed that all the units are repairable.We shall obtain the system reliability, the mean time to system failure, the steady state availability, and examine numerically the effects of this model to the usual one without particular switching devices.     

Simulated annealing and its application to cobb-douglas economic model

Recently, the simulated annealing has been applied to several combinatorial optimization problems. In this paper, the simulated annealing method for continuous functions is reviewed, and it is applied to an economic model having multiple optimal solutions, in which all optimal solutions cannot be simultaneously obtained by Scarf's algorithm.     

Microdetermination of bromide in water by gas chromatography

For the determination of micro order bromide in waters, a rapid, selective and sensitive method was studied. Bromide reacted with citric acid and potassium permanganate to form pentabromoacetone, which then turned into bromoform. The bromoform was measured by a head space gas chromatograph. The ion-exchange chromatograph (Amberlite CG-400, 10 mm i.d. × 70 mm; elutant, 0.1 M sodium nitrate, 70 ml and 0.5 M sodium nitrate, 25 ml) was applied to bromide without interfering substances such as chloride and phenols. Bromide of ppb levels in water can be accurately determined by ion-exchange chromatograph, potassium permanganate oxidation and head space gas chromatograph (ECD).     

The production of ultrahigh-purity copper for advanced applications

Ultrahigh-purity copper (UHPC) of five to seven nines has been developed, and commercial production has been started by Nippon Mining and Metals Company. This value-added copper has such characteristics as high electrical and thermal conductivity at very low temperatures, low softening temperatures, and high workability due to fewer nonmetallic inclusions and voids as compared with conventional high-purity copper (i.e., four nines). Taking advantages of these characteristics, UHPC is being applied to bonding wire of integrated circuits and cables for audio devices.