High-speed and large noise margin tolerance E/D logic gates withLDD structure DMTs fabricated using selective RIE technology

The authors describe a novel design concept for enhancement (E) and depletion (D) mode FET formation using i-AlGaAs/n-GaAs doped-channel hetero-MISFET (DMT) and a novel self-aligned gate process technology for submicrometer-gate DMT-LSIs based on E/D logic gates. 0.5-μm gate E-DMTs (D-DMTs) with a lightly doped drain (LDD) structure show an average V_t of 0.18 (-0.46) V, a V_t standard deviation of 22.6 (24.9) mV, and a maximum transconductance of 450 (300) mS/mm. The V_t shift is less than 50 mV with a decrease in gate length down to 0.5 μm. The gate forward turn-on voltage V_f is more than 0.9 V, i.e. about 1.6 times that for MESFETs. This superiority in V _f, preserved in the high-temperature range, leads to an improvement in noise margin tolerance by a factor of three. In addition, 31-stage ring oscillators operate with a power consumption of 20 (1.0) mW/gate and a propagation delay of 4.8 (14.5) ps/gate. Circuit simulation based on the experimental data predicts 140 ps/gate and 1 mW/gate for DMT direct-coupled FET logic circuits under standard loading conditions. DMTs and the technology developed here are very attractive for realizing low-power and/or high speed LSIs     

Organic–silicate hybrid catalysts based on various defined structures for Knoevenagel condensation

Two types of organic–inorganic hybrid base catalysts are prepared. Organic-functionalized molecular sieves (OFMSs), particularly “amine-immobilized porous silicates”, are designed based on common idea to immobilize catalytic active sites on silicate surface. Silicate–organic composite materials (SOCMs), such as “ordered porous silicate–quaternary ammonium composite materials”, are the precursors of ordered porous silicates obtained during the synthesis. Both the OFMS and the SOCM are used as the catalysts for Knoevenagel condensation. Among the OFMSs, there is clear tendency that the use of molecular sieve with larger pore volume and/or surface area gives the product in higher yield. Aminopropylsilyl (AP)-functionalized mesoporous silicates such as AP-MCM-41 gives the product in high yield under mild conditions. No loss of activity is observed after repeated use for three times. The SOCMs are also active for the same reaction. The precursors of the mesoporous silicates are more active than those of microporous silicates. This material can be repeatedly used without significant loss of activity. High activity is not due to the leached species. The active sites of the SOCM catalysts are considered to be SiO⁻ moieties located on the pore-mouth. Activity of the SOCM increases when the reaction is carried out without solvent, whereas decrease in activity of the OFMS is observed in the solvent-free system.     

A 63-year-old man with progressive cauda equina/conus medullaris syndrome

BACKGROUND: This article presents results of the acute treatment phase of a 2-site study comparing cognitive behavioral group therapy (CBGT) and treatment with the monoamine oxidase inhibitor phenelzine sulfate for social phobia. METHODS: One hundred thirty-three patients from 2 sites received 12 weeks of CBGT, phenelzine therapy, pill placebo administration, or educational-supportive group therapy (an attention-placebo treatment of equal credibility to CBGT). The "allegiance effect," ie, the tendency for treatments to seem most efficacious in settings of similar theoretical orientation and less efficacious in theoretically divergent settings, was also examined by comparing responses to the treatment conditions at both sites: 1 known for pharmacological treatment of anxiety disorders and the other for cognitive behavioral treatment. RESULTs: After 12 weeks, phenelzine therapy and CBGT led to superior response rates and greater change on dimensional measures than did either control condition. However, response to phenelzine therapy was more evident after 6 weeks, and phenelzine therapy was also superior to CBGT after 12 weeks on some measures. There were few differences between sites, suggesting that these treatments can be efficacious at facilities with differing theoretical allegiances. CONCLUSIONS: After 12 weeks, both phenelzine therapy and CBGT were associated with marked positive response. Although phenelzine therapy was superior to CBGT on some measures, both were more efficacious than the control conditions. More extended cognitive behavioral treatment and the combination of modalities may enhance treatment effect.     

Fabrication of piezoelectric multilayer thin-film actuators

In this study, we fabricated multilayer ceramics (MLCs) composed of multilayered Pb(Zr,Ti)O₃ (PZT) piezoelectric thin films with internal electrodes and evaluated their dielectric and piezoelectric properties. The stack of PZT ferroelectric layers (550 nm) and SrRuO₃ (SRO, 80 nm) electrodes were alternatively deposited on Pt/Ti-coated silicon-on-insulator substrates by radio-frequency magnetron sputtering. The MLCs composed of one, three, and five PZT layers were fabricated by the alternate sputtering deposition of PZT ferroelectric layers and SRO electrodes through the movable shadow mask. The capacitances of MLCs were proportionally increased with the number of PZT layers, while their relative dielectric constants were almost same among the each MLC. The MLCs exhibited symmetric and saturated P–E hysteresis loops similar to the conventional PZT thin films. We estimated that the piezoelectric properties of MLCs by FEM simulation, and confirmed that the effective transverse piezoelectric coefficients (d _31,eff ) increased with the number of PZT layers. The piezoelectric coefficients calculated to be d _31,eff  = ?2964 pC/N at 25 PZT layers, which is much higher than those of conventional single-layer piezoelectric thin films.     

Structural stability and mechanochemical activity of titanium nitride prepared by mechanical alloying

Pure titanium nitride (TiN) was synthesized by mechanical alloying (MA). In order to prevent the contamination from the MA vial and atmospheric gas, the MA steel vial was replaced with a titanium vial and atmospheric gas was deoxidized using sponge titanium heated to 623 K. The mechanochemical activity during MA was estimated from the gas purification temperature. The investigation of thermal and pressure stability by thermal treatment and hot isostatic pressing (HIP) revealed that titanium nitride, TiN, was stable on heating to 1173 K under a vacuum, but became unstable under a high pressure, 100 MPa.     

Analysis and Design of a Dynamic Predistorter for WCDMA Handset Power Amplifiers

This paper presents a dynamic predistorter (PD), which linearizes the dynamic AM-AM and AM-PM of a wideband code division multiple access handset power amplifier (PA). The dynamic PD allows an adjacent channel leakage power ratio (ACPR) improvement of 15.7 dB, which is superior to conventional PDs that linearize static AM-AM and AM-PM. The dynamic PD was designed using an HBT generating nonlinearity, a short circuit at the baseband (les4 MHz), and a load circuit for the HBT at the RF fundamental band (ap1.95 GHz). Volterra-series analysis was performed to understand the mechanism of the dynamic PD. The analysis revealed that the short circuit at the baseband enabled the dynamic PD generating third-order intermodulation distortion (IMD3) with opposite phase to the fundamental tone (i.e., antiphase IMD3). The antiphase IMD3 allows dynamic gain compression, which linearizes the dynamic gain expansion of a PA with low quiescent current. The analysis also revealed that the IMD3 amplitude of the dynamic PD can be adjusted by load impedance at the RF fundamental band, which enables the gradient of dynamic AM-AM and AM-PM to be optimized to linearize the PA. The fabricated two-stage InGaP/GaAs HBT PA module with the dynamic PD exhibited an ACPR of -40 dBc and a power-added efficiency of 50% at an average output power of 26.8 dBm with a quiescent current of 20 mA     

Fabrication of submicron alumina ceramics by pulse electric current sintering using M2+ (M = Mg,Ca, Ni)-doped alumina nanopowders

Dense submicron-grained alumina ceramics were fabricated by pulse electric current sintering (PECS) using M²⁺(M: Mg, Ca, Ni)-doped alumina nanopowders at 1250 °C under a uniaxial pressure of 80 MPa. The M²⁺-doped alumina nanopowders (0–0.10 mass%) were prepared through a new sol–gel route using high-purity polyhydroxoaluminum (PHA) and MCl₂ solutions as starting materials. The composite gels obtained were calcined at 900 °C and ground by planetary ball milling. The powders were re-calcined at 900 °C to increase the content of α-alumina particles, which act as seeding for low-temperature densification. Densification and microstructural development depend on the M²⁺ dopant species. Dense alumina ceramics (relative density ≥99.0%) thus obtained had a uniform microstructure composed of fine grains, where the average grain size developed for non-doped, Ni-doped, Mg-doped and Ca-doped samples was 0.67, 0.67, 0.47 and 0.30 μm, respectively, showing that Ca-doping is the most promising method for tailoring of nanocrystalline alumina ceramics.     

A Microcomputer System for Spatiotemporal Visual Receptive Field Analysis

A microcomputer system was developed to measure visual spatiotemporal receptive fields. The system performs three functions: 1) generation of a binary spatiotemporal white-noise stimulus, 2) acquisition of spike discharges from retinal ganglion cells, and 3) extraction of the linear part of the spatiotemporal receptive flelds by cross correlating the input against the output. We have applied this system to the measurement of the spatiotemporal receptive fields of cat and catfish retinal ganglion cells.     

High-speed DCFL circuits with very shallow junction GaAs JFETs

High-speed DCFL (direct-coupled FET logic) circuits implemented with advanced GaAs enhancement-mode J-FETs are discussed. A divide-by-four static frequency divider operates at up to 6 GHz with a power consumption of 20 mW/flip-flop. A high channel concentration of more than 1×10¹⁸ cm^-3 together with a very shallow junction depth of less than 30 nm for the p⁺-gate results in a transconductance as high as 340 mS/mm at a gate length of 0.8 μm. Open-tube diffusion of Zn using diethylzinc and arsine makes it possible to control a very shallow p⁺-layer less than 10 nm thick. The propagation delay time, as measured with a ring oscillator, was 22 ps/gate with a power consumption of 0.42 mW/gate