Isolation of antimicrobial agent from the marine algae Cystoseira hakodatensis

Cystoseira hakodatensis is an unutilised brown algae belonging to family Sargassaceae. A crude methanol extract from the algae showed inhibitory effects on the growths of Bacillus cereus and Bacillus licheniformis. To isolate the major antimicrobial agent, a sequential active‐guided isolation procedure was applied: liquid–liquid extraction, column chromatography and bio‐autography. A marked antimicrobial agent (active α) was isolated in hydrophobic fraction and was determined to phenolics without carbohydrates and proteins by phytochemical test. Regarding the antimicrobial potential, the isolated active α showed better inhibitory effects against B. cereus and B. licheniformis at 2 and 4 times of lower concentrations (62.5 and 31.3 μg mL^?1) in comparison with epigallocatechin gallate. These results showed that C. hakodatensis is a potential source of antimicrobial agent capable of preventing the growth of the two bacteria.     

Microstructure and mechanical behaviour of 3Y-TZP/Mo nanocomposites possessing a novel interpenetrated intragranular microstructure

Yttria stabilized tetragonal zirconia polycrystal (Y-TZP)/0-100 vol % molybdenum (Mo) composites were fabricated by hot-pressing a mixture of Y-TZP powder containing 3 mol % yttria (Y₂O₃) and a fine Mo powder in vacuum. This composite system possessed a novel microstructural feature composed of an interpenetrated intragranular nanostructure, in which either nanometer sized Mo particles or equivalent sized zirconia (ZrO₂) particles located within the ZrO₂ grains or Mo grains, respectively. The strength and toughness were both greatly enhanced with increasing Mo content for the 3Y-TZP/Mo composites thus breaking through the strength-toughness tradeoff relation in transformation toughened ZrO₂ and its composite materials. They exhibited a maximum strength of 2100 MPa and a toughness of 11.4 MPa·m^1/2 for the composite containing 70 vol % Mo. These simultaneous improvements in strength and toughness were determined to be the result of a decrease in flaw size associated with the interpenetrated intragranular nanostructure, and a stress shielding effect created in the crack tip by the elongated Mo polycrystals bridging the crack tip in addition to the stress induced phase transformation.     

Flashover voltage characteristics of contaminated station insulators under temporary ac overvoltages in the ac system connected with a frequency converter station

According to the recent analysis results of temporary ac overvoltage in the ac system connected with a frequency converter station, large-magnitude over-voltages were confirmed to occur under some special system conditions. Most of the station insulators currently used cannot withstand such overvoltages according to an evaluation based on the data obtained earlier. The necessity of tests to be done to evaluate such performance more accurately was recognized. Both power frequency and switching impulse overvoltage flashover tests were made on contaminated insulators by the method well simulating the natural wetting condition. Switching impulse flashover voltage with the waveshape having a long wavefront time of 2 ms can be well correlated with the flashover voltage characteristics of temporary ac overvoltage. Higher flashover voltage characteristics were obtained by a clean fog test method compared with those obtained by equivalent fog test method.     

IBM's Linux watch, the challenge of miniaturization

Nearly four years in development, the IBM Linux watch contains a complete computer system that runs Linux, displays X11 graphics, and has wireless connectivity. The system fits in a case that could pass as a slightly unusual analog timepiece with a somewhat odd shape and an extraordinarily brilliant face. The developers have created two versions of the watch, one with an organic light-emitting diode display and the other with a liquid crystal display. Still considered a research prototype, the watch already runs some personal information management applications, and it can communicate with PCs, PDAs, and other wireless-enabled devices, viewing condensed e-mail and directly receiving pager-like messages. Eventually, users will be able to access various Internet-based services, such as up-to-the-minute information about weather, traffic conditions, the stock market, and sports     

Radiative ignition mechanism of solid fuels

Transmittance of external radiation from a CO₂ laser through a boundary layer of decomposition products over a vertical sample surface is measured during the ignition period. The results indicate that there is significant absorption of the external radiation for PMMA, and a lesser but still not negligible amount, for red oak. An increase in gas phase temperature over surface temperature is observed over much of the ignition interval. Using the experimentally measured incident flux at the sample surface, surface temperature history was calculated from a model that included re-radiation and convection losses from the surface, endothermic decomposition and conduction into the material. The results confirm the significant effect of gas phase absorption on surface temperature. Steady-state-derived surface regression rate expression was used for PMMA in this model. The results raise questions about the validity of such data for the dynamic heating conditions during the ignition period. Further studies needed to understand the radiative ignition mechanism are identified.     

Ru-catalyzed anode materials for direct hydrocarbon SOFCs

A solid oxide fuel cell using a thin ceria-based electrolyte film with a Ru-catalyzed anode was directly operated on hydrocarbons, including methane, ethane, and propane, at 600 °C. The role of the Ru catalyst in the anode reaction was to promote the reforming reaction of the unreacted hydrocarbons by the produced steam and CO₂, which avoided interference from steam and CO₂ in the gas-phase diffusion of the fuels. The resulting peak power density reached 750 mW cm⁻² with dry methane, which was comparable to the peak power density of 769 mW cm⁻² with wet (2.9 vol.% H₂O) hydrogen. More important was the fact that the cell performance was maintained at a high level regardless of the change in the methane utilization from 12 to 46% but was significantly reduced by increasing the hydrogen utilization from 13 to 42%. While the anodic reaction of hydrogen was controlled by the slow gas diffusion, the anodic reaction of methane was not subject to the onset of such a gas-diffusion process.     

A 6-ns ECL 100 K I/O and 8-ns 3.3-V TTL I/O 4-Mb BiCMOS SRAM

The authors report a 4 M word×1 b/1 M word×4 b BiCMOS SRAM that can be metal mask programmed as either a 6-ns access time for an ECL 100 K I/O interface to an 8-ns access time for a 3.3-V TTL I/O interface. Die size is 18.87 mm×8.77 mm. Memory cell size is 5.8 μm×3.2 μm. In order to achieve such high-speed address access times the following technologies were developed: (1) a BiCMOS level converter that directly connects the ECL signal level to the CMOS level; (2) a high-speed BiCMOS circuit with low threshold voltage nMOSFETs; (3) a design method for determining the optimum number of decoder gate stages and the optimum size of gate transistors; (4) high-speed bipolar sensing circuits used at 3.3-V supply voltage; and (5) 0.55-μm BiCMOS process technology with a triple-well structure     

Deposition of carbon films by electrolysis of a water-ethylene glycol solution

An attempt was made to deposit carbon films by electrolysis of a water-ethylene glycol solution. Carbon plate and an n-type silicon substrate were dipped in the solution and a high d.c. potential was negatively applied on the silicon substrate. Some deposits were observed in the region between the boiling point curve and the line approximately 50 °C below and parallel to the boiling point, when electrolysis was carried out at 1 kV for 6 h. For higher potentials of 1.4–2.0 kV and longer electrolysis of 12 h, some samples showed a broad X-ray diffraction peak and Raman peaks, corresponding to graphitic carbon.