Scanning electron microscopy of food-poisoning bacterium Bacillus cereus using a variable-pressure SEM

A variable-pressure scanning electron microscopy (VP-SEM) with a cooling stage permits long hours of observation of water-containing specimens in their natural or close to natural state, without the conventional specimen preparations of fixation, dehydration, drying and metal coating. It reduces water vaporization and beam damage by keeping the specimens at a low temperature. We observed Bacillus cereus colonies on nutrient agar, which would shrink significantly if any conventional specimen preparation technique were used. We also studied the growing process of the bacteria on raw and steamed rice using the VP-SEM without conventional preparation techniques. Original specimens were directly mounted onto specimen holders and their backscattered electron images observed under the following conditions: specimen stage temperature, -10 degrees C; specimen chamber vacuum level, 30-70 Pa; and accelerating voltage, 15-20 kV. We recognized that the VP-SEM minimized deformation of the colonies due to shrinkage of the nutrient agar, and successfully imaged the morphology of the colonies and bacteria without a decline in bacteria number, which is apt to occur during fixation and dehydration. Also, the growth process of the bacteria on raw or steamed rice could be observed promptly, since there is no specimen preparation step.     

Fault-tolerant decentralized H-infinity control for multi-channel systems using homotopy method

This paper considers a fault-tolerant decentralized H-infinity control problem for multi-channel linear time-invariant systems. The purpose is to design a decentralized H-infinity output feedback controller to.stabilize the given system and achieve a certain H-infinity performance requirement both in the normal situation and in the situation where any one of the local controllers fails. The designed problem is reduced to a feasibility problem of a set of bilinear matrix inequalities （BMIs）. An algorithm is proposed to solve the BMIs. First, the normal situation is considered where all the local controllers are functioning. The local controllers are obtained from a standard centralized H-infinity controller by using a homotopy method imposing a structural constraint progressively. Secondly, the above case is extended to the one where any one of the local controllers fails. We again use a homotopy method where the coefficient matrices of the failed controller are decreased progressively to zero. The efficiency of the proposed algorithm is demonstrated by an example.     

Characterisation of optically driven microstructures for manipulating single DNA molecules under a fluorescence microscope

Optical tweezers are powerful tools for manipulating single DNA molecules using fluorescence microscopy, particularly in nanotechnology‐based DNA analysis. We previously proposed a manipulation technique using microstructures driven by optical tweezers that allows the handling of single giant DNA molecules of millimetre length that cannot be manipulated by conventional techniques. To further develop this technique, the authors characterised the microstructures quantitatively from the view point of fabrication and efficiency of DNA manipulation under a fluorescence microscope. The success rate and precision of the fabrications were evaluated. The results indicate that the microstructures are obtained in an aqueous solution with a precision ∼50 nm at concentrations in the order of 10⁶ particles/ml. The visibility of these microstructures under a fluorescence microscope was also characterised, along with the elucidation of the fabrication parameters needed to fine tune visibility. Manipulating yeast chromosomal DNA molecules with the microstructures illustrated the relationship between the efficiency of manipulation and the geometrical shape of the microstructure. This report provides the guidelines for designing microstructures used in single DNA molecule analysis based on on‐site DNA manipulation, and is expected to broaden the applications of this technique in the future.Inspec keywords: DNA, molecular biophysics, fluorescence, optical microscopy, radiation pressure, biological techniquesOther keywords: optically driven microstructures, single DNA molecule analysis, fluorescence microscopy, optical tweezers, nanotechnology‐based DNA analysis, manipulation technique, aqueous solution, fine tune visibility, yeast chromosomal DNA molecules, geometrical shape, on‐site DNA manipulation     

Development of new‐type outdoor termination using composite insulator with SF6 gas: Commercial use for 77‐kV transmission lines and development for 154‐kV XLPE cable

Recently, composite insulators have been increasingly employed mainly for economic reasons. We have developed a new type of outdoor termination using a composite insulator, which can be installed horizontally on a steel tower in order to reduce the construction cost. In this outdoor termination, SF₆ gas is filled in the composite insulator and a cold shrinkable premolded rubber unit is applied instead of the combined use of a rubber‐molded stress relief cone, epoxy resin insulator and spring unit. The application of the composite insulator, SF₆ gas and cold shrinkable premolded rubber unit reduces the total weight and makes it possible to install the termination horizontally on the tower. The new‐type outdoor termination for 77‐kV XLPE cable has already been applied in commercial use and enabled a reduction of the construction costs for power transmission lines. A 154‐kV new‐type outdoor termination has been developed and its initial electrical tests were successfully completed. This paper describes the design and performance of both 77‐kV and 154‐kV new‐type outdoor termination, and a follow‐up survey of the 77‐kV new termination in a commercial use. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(4): 18– 26, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20511     

Natural language understanding based on mental image description language <Emphasis Type="Italic">L</Emphasis><Subscript><Emphasis Type="Italic">md</Emphasis></Subscript> and its application to language-centered robot manipulation

The authors have been working on natural language understanding based on the knowledge representation language L _md and its application to robot manipulation by verbal suggestion. The most remarkable feature of L _md is its capability of formalizing spatiotemporal events in good correspondence with human/robotic sensations and actions, which can lead to integrated computation of sensory, motory and conceptual information. This paper describes briefly the process from text to robot action via semantic representation in L _md and the experimental results of robot manipulation driven by verbal suggestion. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Biomimetic ion-channel sensors based on host-guest molecular recognition in Langmuir-Blodgett membrane assemblies

Biomimetic “ion-channel sensors” based on host-guest molecular recognition were constructed by incorporating several kinds of receptor molecules in Langmuir-Blodgett (LB) molecular assemblies deposited directly on glassy carbon electrodes. The receptors used were valinomycin, bis(crown ether)s, macrocyclic polyamine and cyclodextrin polyamine. The binding of charged stimulants (metal ions, inorganic and organic anions) to these receptors induced a marked increase (or decrease) in the ion permeability of the membranes, as detected by cyclic voltammetry using [Fe(CN)₆]^4- or [Ru(bpy)₃]²⁺ as marker ion. Such a mode of response, corresponding to model “channel opening (or closing)”, can be explained on the basis of the charge-charge interaction involving the stimulant, marker ion and lipid.     

Photoelectrochemical decomposition of bio-related compounds at a nanoporous semiconductor film photoanode and their photocurrent-photovoltage characteristics

Photoelectrochemical decomposition of bio-related compounds such as amino acids was investigated with a biophotochemical cell comprising a mesoporous TiO₂ thin film photoanode and an O₂-reducing cathode. It was concluded that a kind of Schottky junction formed at the surface of the TiO₂ (called as liquid junction) induced the photodecomposition followed by generation of photocurrent/photovoltage. Complete photodecomposition was investigated by the CO₂ formation yield. The photocurrent-photovoltage (J-V) characteristics of amino acids and other typical bio-related compounds were investigated, and the short circuit photocurrent (J_sc), open circuit photovoltage (V_oc), and Fill factor (ff) were exhibited. Effect of pH on the photodecomposition of phenylalanine and cysteine were studied; for cysteine alkaline conditions gave a high efficiency, which was interpreted by the high electron-donating ability of the dissociated -S⁻ group. The incident light-to-current conversion efficiency (IPCE) of cysteine was 25% at 350 nm. It was for the first time shown that organic acids gave high internal quantum efficiency (η′) over 8 (=800%) in the photodecomposition; for oxalic acid it was 9.3 (=930%) and for butyric acid 8.2. The alternating current impedance spectroscopy of glycine showed that the cell performance is determined by the chemical reactions at TiO₂ or Pt electrodes.     

Anaerobic Biodegradation Tests of Poly(lactic acid) under Mesophilic and Thermophilic Conditions Using a New Evaluation System for Methane Fermentation in Anaerobic Sludge

Anaerobic biodegradation tests of poly(lactic acid) (PLA) powder were done at the thermophilic (55 °C) and mesophilic temperature (35 °C) under aquatic conditions [total solid concentrations of the used sludge were 2.07% (at 55 °C) and 2.24% (at 35 °C)] using a newly developed evaluation system. With this system, the evolved biogas is collected in a gas sampling bag at atmospheric pressure. This method is more convenient than using a pressure transducer or inverted graduated cylinder submerged in water. PLA was degraded about 60% in 30 days, about 80% in 40 days and about 90% in 60 days at 55 °C. On the other hand, the PLA degradation started in 55 days at 35 °C and degradation rate was much slower than at 55 °C.     

Fabrication of Three-Dimensional Micro Photonic Crystals of Resin-Incorporating TiO2 Particles and their Terahertz Wave Properties

Three-dimensional (3D) photonic crystals with a diamond structure made from 40 vol% TiO₂–acrylate dielectric composites were formed by means of a CAD/CAM micro-stereolithography system. The lattice constant of the diamond unit cell was 500 μm and the forming accuracy was 10 μm. The photonic band gap in the Γ–X 〈100〉 direction measured by terahertz-time-domain spectroscopy appeared at 280–360 GHz, which agreed fairly well with the band gap calculated by the plane wave expansion method.