The rpoS deficiency suppresses acetate accumulation in glucose-enriched culture of Escherichia coli under an aerobic condition

The role of Escherichiacoli rpoS on the central carbon metabolism was investigated through analyzing the deficiency of this regulon gene under aerobic and glucose-enriched culture conditions. The experimental results showed that while the wild type cells exhibited an overflow metabolism effect, the rpoS-deleting mutation alleviated this effect with the significant suppression of acetate accumulation under a high glucose condition. This gene deletion also induced the twofold upregulation of gltA and one-tenth downregulation of poxB, respectively. The overflow metabolism effect was confirmed to be recovered by re-introducing rpoS gene into the mutant. These results demonstrated rpoS changed the central carbon metabolism toward acetate overflow through dehydrogenation of pyruvate and reduction of TCA cycle activity.     

Structured intelligence for self-organizing manufacturing systems

This paper deals with fuzzy scheduling and path planning problems by genetic algorithms. We have proposed a self-organizing manufacturing system (SOMS) that is composed of a number of autonomous modules. Each module decides output through interaction with other modules, but the module does not share complete information concerning other modules in the SOMS. Therefore, we require structured intelligence as a whole system. In this paper, we consider a manufacturing line composed of machining centres and conveyor units. The manufacturing procedure can be divided into a sequence of three modules: (a) tool locating module, (b) scheduling module, and (c) path planning module. The tool locating problems have been already solved. In this paper, we first solve the scheduling problem as global preplanning. Here we assume that the processing time is not constant, because some delay may occur in the machining centres. We therefore apply fuzzy theory to represent incomplete information abou t the machining time. We solve the fuzzy scheduling problem with a genetic algorithm. After global preplanning, the path planning module transports materials and products. Next, the scheduling module acquires the actual processing time of each machining centre. Based on the processing time, the schedule module generates a fuzzy number for the processing time. We discuss the effectiveness of the proposed method through the computer simulation results.     

Traveling void wave in horizontal two-phase flow

In the framework of pattern dynamics approach, the discrete bubble model was developed for simulating inherent fluctuation of void fraction in a horizontal two-phase flow. Then flow patterns were identified based on the statistical properties of void fraction fluctuation, and the flow pattern map agreed with the experimental observation of high-pressure two-phase flow of CO₂ in horizontal tubes. The time-averaged pressure drop and the void fraction obtained in the simulation agreed reasonably with the existing correlations. Thus the horizontal flow version of the discrete bubble model demonstrates its relevance in simulating inherent fluctuation of two-phase flow.     

Catechol siderophore excretion by magnetotactic bacterium Magnetospirillum magneticum AMB-1

Siderophore activity was detected in the culture supernatant of the magnetotactic bacterium Magnetospirillum magneticum AMB-1. Here we report the first structural elucidation of a siderophore produced by a magnetotactic bacterium. The structure of the purified compound was 3,4-dihydroxybenzoic acid as determined by nuclear magnetic resonance (NMR) and electro-spray ionization mass spectroscopy (ESI-MS).     

Development of a flexible direct photosynthetic/metabolic biofuel cell for mobile use

We have developed a direct photosynthetic/metabolic biofuel cell (DPBFC) without a mediator, based on the extraction of electrons directly from bacteria using a polyaniline electrode. Since previous developments of this nature are rigid, they are not suitable for use on curved or soft surfaces. Our DPBFC has a flexible structure due to its flexible components: a membrane electrode assembly made of Nafion 117, a carbon cloth electrode made of modified polyaniline, a copper foil current collector, an anode chamber made from molded polydimethylsiloxane (PDMS), and a cathode chamber and cover cut from a PDMS membrane. Silicone bonds were used for assembling the individual parts. Our 50×50×3-mm flexible DPBFC has a stable electrical power output up to a bending angle of 170°. The maximum power density using purple photosynthetic bacteria (Rhodopesudomonas palustris) as a fuel source was 5.26μW/cm2 with an open-circuit voltage of 0.089 V.     

Evaluation of a 2k CCD camera with an epitaxially grown CsI scintillator for recording energy-filtered electron cryo-micrographs

Zero-loss imaging of frozen-hydrated specimens requires a detector with high sensitivity, a low noise level and high spatial resolution, because more electrons are scattered inelastically than elastically by cryo-specimens and the number of electrons detected is approximately 1/4 of incident electrons after energy filtering. Cameras using charge-coupled devices (CCDs) are good candidates due to their high sensitivity. They have been used mainly to record electron diffraction patterns for electron crystallography due to their limited spatial resolution but recently used for acquiring direct images due to their convenience. The spatial resolution has been limited by the characteristics of a phosphor that is necessary to convert high-energy electrons to photons and the coupling. We adopted a CsI scintillator with good modulation transfer function (MTF), which was epitaxially grown from each of optical fibres. The stripes of carbon graphite with 3.4 A spacing and 1.4 A stripes of gold thin crystals could be recorded with a magnification of 240,000x and 560,000x at 200 kV, respectively. A computed Fourier transform of an image of a frozen-hydrated crystal of catalase containing about 1000 units showed diffraction spots at spatial frequencies of 1/9.6 A(-1) up to 1/8 A(-1) without background subtraction, when the image was recorded at 140,000x. These results show that the resolution of the developed camera was good enough to record images. Our used test method for MTF determination may be useful for others.     

Modeling Growth and Dissolution Kinetics of Grain-Boundary Cementite in Cyclic Carburizing

In vacuum carburizing of steels, short-time carburizing is usually followed by a diffusion period to eliminate the filmlike cementite (θ _GB ) grown on the austenite (γ) grain boundary surface. In order to obtain the θ _GB amount during the process, the conventional model estimates the amount of cementite (θ) with the equilibrium fractions for local C contents within a framework of the finite difference method (FDM), which overestimates the amount of θ _GB observed after several minutes of carburizing. In our newly developed model, a parabolic law is assumed for the growth of θ _GB and the rate controlling process is considered to be Si diffusion rejected from θ under the isoactivity condition. In contrast, the rate constant for the dissolution of θ _GB is considered to be controlled by Cr diffusion of θ. Both rate coefficients (α) were validated using multicomponent diffusion simulation for the moving velocity of the γ/θ interface. A one-dimensional (1-D) FDM program calculates an increment of θ _GB for all grid points by the updated diffusivities and local equilibrium using coupled CALPHAD software. Predictions of the carbon (C) profile and volume fraction of cementite represent the experimental analysis much better than the existing models, especially for both short-time carburization and the cyclic procedure of carburization and diffusion processes.     

Effects of Fluid Directions on Heat Exchange in Thermoelectric Generators

Thermal fluids can transport heat to the large surface of a thermoelectric (TE) panel from hot and/or cold sources. The TE power thus obtainable was precisely evaluated using numerical calculations based on fluid dynamics and heat transfer. The commercial software FLUENT was coupled with a TE model for this purpose. The fluid velocity distribution and the temperature profiles in the fluids and TE modules were calculated in two-dimensional space. The electromotive force was then evaluated for counter-flow and split-flow models to show the effect of a stagnation point. Friction along the fluid surface along a long, flat path was larger than that along a short path split into two parts. The power required to circulate the fluids along the flow path is not negligible and should be considered in TE generation system design.