A new buried-gate GTO structure having a large safe operating area

A novel structure of a buried-gate GTO (gate turn-off thyristor) was proposed for expanding the safe operating area (SOA) of unit-GTOs. The SOA of unit-GTOs in a test sample GTO and the spike voltage at the limit of turn-off of the test sample were investigated experimentally. The SOA was calculated by means of a simple model in order to study the mechanism of the expansion of SOA in the structure. The SOA was expanded due to the reduction of the sheet resistance of the p-base layer by the fine mesh pattern of the buried layer. Corresponding to the increased size of the SOA, the spike voltage increased to 1000 V     

A 385–500 GHz SIDEBAND-SEPARATING (2SB) SIS MIXER BASED ON A WAVEGUIDE SPLIT-BLOCK COUPLER

We have developed a 385–500 GHz sideband-separating (2SB) mixer, which is based on a waveguide split-block coupler at the edge of the H-plane of the 508 μm × 254 μm (WR 2.0) waveguide, for the Atacama Large Millimeter/submillimeter Array (ALMA). An RF/LO coupler, which contains an RF quadrature hybrid, two LO couplers, and an in-phase power divider, was designed with the issue of mechanical tolerance taken into account. The RF/LO coupler was measured optically with a microscope and electrically with a submillimeter vector network analyzer. The image rejection ratio (IRR) and the single-sideband (SSB) noise temperature of the receiver using the RF/LO coupler have also been measured. The IRR was found to be larger than 8 dB and typically ～ 12 dB in the 385–500 GHz band. The SSB noise temperature of this receiver is 80 K at the band center, which corresponds to 4 times the quantum noise limit (hf/k) in SSB, and 250 K at the band edges.     

Development of a cryogenic stage for an ion-milling instrument

A specimen-cooling device has been designed, manufactured and integrated into a commercial ion-milling instrument for transmission electron microscopy. The instrument enables us to prepare section specimens of tin-plated Cu without forming intermetallic compound particles and/or voids. The results show that cooling of specimen during ion-milling process is necessary for fine structure investigations of low melting temperature materials.     

A 600-MHz single-chip multiprocessor with 4.8-GB/s internal shared pipelined bus and 512-kB internal memory

A 600-MHz single-chip multiprocessor, which includes two M32R 32-bit CPU cores , a 512-kB shared SRAM and an internal shared pipelined bus, was fabricated using a 0.15-/spl mu/m CMOS process for embedded systems. This multiprocessor is based on symmetric multiprocessing (SMP), and supports modified-exclusive-shared-invalid (MESI) cache coherency protocol. The multiprocessor inherits the advantages of previously reported single-chip multiprocessors, while its multiprocessor architecture is optimized for use as an embedded processor. The internal shared pipelined bus has a low latency and large bandwidth (4.8 GB/s). These features enhance the performance of the multiprocessor. In addition, the multiprocessor employs various low-power techniques. The multiprocessor dissipates 800 mW in a 1.5-V 600-MHz multiprocessor mode. Standby power dissipation is less than 1.5 mW at 1.5 V. Hence, the multiprocessor achieves higher performance and lower power consumption. This paper presents a single-chip multiprocessor architecture optimized for use as an embedded processor and its various low-power techniques.     

An adult case of extra-hepatic portal obstruction with bleeding from esophageal varices

PURPOSE: This study examined the use of a locking reconstruction bone plate/screw system for use in mandibular surgery. PATIENTS AND METHODS: All patients treated with a locking reconstruction bone plate/screw system for fractures of the mandible or continuity defects in an 18-month period were prospectively studied. Ease of use of the locking plate/screw system, characteristics of the fractures/defects, and complications were tabulated. RESULTS: One hundred two locking bone plates were placed in 84 patients. Most patients (n=75) were treated for fractures of the mandible; there were eight continuity defects and one case of mandibular narrowing. There were no cases of malocclusion or difficulties encountered in using the plate/screw system. Loss of fixation was encountered in only one patient. CONCLUSIONS: The use of a locking plate/screw system was found to be simple, and it offers advantages over conventional bone plates by not requiring the plate to be compressed to the bone to provide stability.     

Spectroscopic Study on Ultrafast Carrier Dynamics and Terahertz Amplified Stimulated Emission in Optically Pumped Graphene

This paper reviews recent advances in spectroscopic study on ultrafast carrier dynamics and terahertz (THz) stimulated emission in optically pumped graphene. The gapless and linear energy spectra of electrons and holes in graphene can lead to nontrivial features such as negative dynamic conductivity in the THz spectral range, which may lead to the development of new types of THz lasers. First, the non-equilibrium carrier relaxation/recombination dynamics is formulated to show how photoexcited carriers equilibrate their energy and temperature via carrier-carrier and carrier-phonon scatterings and in what photon energies and in what time duration the dynamic conductivity can take negative values as functions of temperature, pumping photon energy/intensity, and carrier relaxation rates. Second, we conduct time-domain spectroscopic studies using an optical pump and a terahertz probe with an optical probe technique at room temperature and show that graphene sheets amplify an incoming terahertz field. Two different types of samples are prepared for the measurement; one is an exfoliated monolayer graphene on SiO₂/Si substrate and the other is a heteroepitaxially grown non-Bernal stacked multilayer graphene on a 3C-SiC/Si epi-wafer.     

New steroidal constituents from the bulbs of Lilium candidum

Eight spirostanol saponins, including four new compounds, and two known furostanol saponins were isolated from the fresh bulbs of Lilium candidum. The structures of new compounds were determined to be (25R,26R)-26-methoxyspirost-5-ene-3 beta,17 alpha-diol 3-O-?O-alpha-L-rhamnopyranosyl-(1-->2)-O-[beta-D-glucopyranosyl-(1-->4)] -beta-D-glucopyranoside?, (25R,26R)-26-methoxyspirost-5-ene-3 beta,17 alpha-diol 3-O-?O-alpha-L-rhamnopyranosyl-(1-->2)-O-[6-O-acetyl-beta-D-glucopyranos yl- (1-->4)]-beta-D-glucopyranoside?, (25R,26R)-26-methoxyspirost-5-ene-3 beta,17 alpha-diol 3-O-?O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranoside? and (25S)-spirost-5-ene-3 beta,27-diol 3-O-?O-beta-D-glucopyranosyl-(1-->3)-O-alpha-L-rhamnopyranosyl-(1-->2)-O - [beta-D-glucopyranosyl-(1-->4)]-beta-D-glucopyranoside?, respectively, on the basis of spectroscopic analysis, including two-dimensional NMR techniques, and the result of hydrolysis. The inhibitory activity of the isolated saponins on Na+/K+ ATPase was evaluated.     

A new subculture and nematocidal assay using a species of diplogastridae

A new subculture method and a novel microplate assay for nematocidal activity using a species of Diplogastridae have been developed. The assay gives results rapidly, with high sensitivity in 4 h, and indicated good correlation between action mechanism and the nematode shape when examining 15 known compounds, including the antiparasitic avermectin, antimalarial quinine, and the gamma-amino-n-butyric acidA (GABAA) activated Cl- channel antagonist picrotoxinin. Thus new assay could be used as a primary screening method for new nematocidal compounds.