Low-Voltage and High-Speed Operations of 30-nm-Gate Pseudomorphic $hbox{In}_{0.52}hbox{Al}_{0.48}hbox{As}/hbox{In}_{0.7}hbox{Ga}_{0.3} hbox{As}$ HEMTs Under Cryogenic Conditions

In this letter, we fabricated 30-nm-gate pseudomorphic In_0.52 Al_0.48As/In_0.7Ga_0.3As HEMTs with multilayer cap structures to reduce source and drain parasitic resistances; we measured their dc and radio-frequency characteristics at 300, 77, and 16 K under various bias conditions. The maximum cutoff frequency fT was 498 GHz at 300 K and 577 GHz at 77 K. The maximum fT exceeded 600 GHz at 16 K. Even at a drain-source voltage V _ds of 0.4 V, we obtained an fT of 500 GHz at 16 K. This indicates that cryogenic HEMTs are favorable for low-voltage and high-speed operations. Furthermore, the present 30-nm-gate HEMTs at 300 K show almost the same fT values at the same dc-power dissipation as compared to 85-nm-gate InSb-channel HEMTs. The improvement of the maximum-oscillation-frequency f _max values was also observed at 77 and 16 K.     

Effects of shear flow on a semidilute polymer solution under phase-separating condition

We studied the effects of a step-up shear flow from zero shear rate to the given shear rate, , on formation of shear-induced structures for a semidilute polystyrene (PS)/diethyl malonate (DEM) solution below its cloud point temperature where the solution undergoes phase separation via spinodal decomposition (SD) in quiescent state. We elucidated that the effects of step-up shear can be divided into two regions: below and above a critical shear rate, . At , growing phase-separated domains via SD are found to be deformed under the flow, so that FFT spectra of the shear-microscopy images become elliptical with the wave number q_mx at the maximum intensity parallel to the flow being smaller than the corresponding wave number q_mz parallel to the neutral axis. However, strikingly enough, the aspect ratio q_mz/q_mx of the elliptic spinodal ring observed for this system was much smaller than that observed for binary fluids. The unique feature was proposed to be the elastic effect inherent in this system. When is larger than , however, initially phase-separating structures via SD are strongly deformed and distorted. Interestingly enough, the light scattering pattern was transformed from the isotropic ring pattern into the butterfly pattern. This is interpreted as follows: when , there may not be enough time for the domains composed of elastically deformed swollen-network chains to relax, and consequently the domains are cooperatively disrupted. The disrupted domains tend to squeeze solvent in order to release the elastic free energy stored in the deformed swollen-network chains, resulting in anisotropic domain more extended to neutral axis than flow direction and hence giving rise to the butterfly pattern.     

Efficient dispersing and shortening of super-growth carbon nanotubes by ultrasonic treatment with ceramic balls and surfactants

A low-power ultrasonic treatment together with ceramic balls was applied to disperse and shorten super-growth carbon nanotubes (SG-CNTs) in aqueous solutions containing an anionic surfactant, sodium deoxycholate (SDC) or a polymeric nonionic surfactant, tocopheryl PEG 1000 succinate (TPGS). With this mild treatment, the long tubes of as-received SG-CNTs (>200 μm) were efficiently and significantly shortened to below about 1 μm after the treatment. In the same time, the shortened SG-CNTs were well-dispersed in aqueous medium to form stable SG-CNTs solutions containing relatively high SG-CNTs concentration (>0.1% w/v).     

Control method for a combined active filter system employing acurrent source converter and a high pass filter

This paper describes a control method with a combined filter system which senses load current, source current, and line voltage to create reference signals for an active filter. The transfer function of the active filter is identified and is used for the control system design. It is shown that the source current feedback is most effective in suppressing the harmonic-enlarging effects due to parallel resonance and the harmonic current generated by source harmonic voltages. A small setup controlled by a DSP was built, and the validity of the proposed method was demonstrated by experimental results     

Local structural instability of high-Tc oxide superconductors studied by inelastic neutron scattering

The scattering function,S(Q, E), of superconducting La_1.85Sr_0.15CuO₄ and YBa₂Cu₃O₇ was measured over a wide range ofQ-E space by inelastic neutron scattering. Fine structures in their phonon density of states as well as theQ-dependences ofS(Q, E) were observed. TheQ-dependence ofS(Q, E) is very susceptive atT _c , with an anomalous behavior similar to a critical phenomenon. We have found that the anomalous behavior is related to the local structural instability, i.e., the 110 buckling motion of the Cu-O plane and the shortening of the distance between the apical oxygen and the copper atom in the plane.This work was done under the UK-Japan collaboration on neutron scattering at the Rutherford Appleton Laboratory in the United Kingdom.     

Induction of nitric oxide synthase by lipopolysaccharide inhalation enhances substance P-induced microvascular leakage in guinea-pigs

Inducible nitric oxide (NO) synthase (iNOS)-mediated hyperproduction of NO in airways has been reported in asthmatic patients. However, the role of NO in the pathogenesis of asthma has not yet been fully elucidated. The aim of this study was to examine whether the iNOS-derived NO affects airway microvascular leakage, one of the characteristic features of asthmatic airway inflammation. Guinea-pigs were exposed to lipopolysaccharide (LPS) (1 mg x mL(-1)) by inhalation in order to induce iNOS in the airways, and the histochemical staining of reduced nicotinamide-adenine dinucleotide phosphate (NADPH)-diaphorase activity was determined 5 h after the inhalation to confirm the iNOS induction. Airway microvascular leakage to subthreshold doses of substance P (0.3 microg x kg(-1), i.v.) was also examined in the absence and presence of an iNOS inhibitor (aminoguanidine) in LPS- or saline-exposed (control) animals using Evans blue dye and Monastral blue dye. In the LPS-exposed animals, increased NADPH-diaphorase activity was observed in the airway microvasculature compared with the control animals. Substance P caused significant airway microvascular leakage assessed by Evans blue dye in all airway levels in the LPS-exposed animals but not in the control group. This was also confirmed by Monastral blue dye extravasation. Aminoguanidine abolished this LPS-induced enhancement of plasma leakage to substance P without changing the systemic blood pressure. These results may suggest that inducible nitric oxide synthase-derived nitric oxide is capable of potentiating neurogenic plasma leakage in airways.     

Pseudomorphic In/sub 0.52/Al/sub 0.48/As/In/sub 0.7/Ga/sub 0.3/As HEMTs with an ultrahigh f/sub T/ of 562 GHz

We fabricated decananometer-gate pseudomorphic In/sub 0.52/Al/sub 0.48/As/In/sub 0.7/Ga/sub 0.3/As high-electron mobility transistors (HEMTs) with a very short gate-channel distance. We obtained a cutoff frequency f/sub T/ of 562 GHz for a 25-nm-gate HEMT. This f/sub T/ is the highest value ever reported for any transistor. The ultrahigh f/sub T/ of our HEMT can be explained by an enhanced electron velocity under the gate, which was a result of reducing the gate-channel distance.     

Left ventricular mass regression after implantation of St. Jude Medical cardiac valves in small aortic roots

In this study, we analyzed the extent of regression of left ventricular hypertrophy in patients who received small St. Jude Medical (SJM) aortic valves and compared the results with those of another group receiving larger valves. Eighty-eight patients received either 19 or 21 mm valves (Group 1, 25 patients) or either 23 or 25 mm valves (Group 2, 53 patients). Echocardiographic studies were done before the operation and 5 years postoperatively. At follow-up a significant reduction in the left ventricular mass was found for both patient groups (p < 0.0001). Doppler echocardiography derived pressure gradients for both groups were obtained during the follow-up period. As expected, the patients in Group 1 had higher peak pressure gradients than did those in Group 2. However, there was no significant difference between the 2 groups or any significant correlations between peak pressure gradients and body surface area (BSA). Actuarial survival was 84.7% at 15 years for Group 1 and 85.9% at 17 years for Group 2. Actuarial freedom from valve related events was 91.4% at 15 years for Group 1 and 82.7% at 17 years for Group 2. There was no significant difference in survival or valve related event free curves between the 2 groups. After implantations of SJM valves in small aortic roots, significant left ventricular mass regression was obtained, and the results were comparable to those for valves of other sizes. The long-term performance of aortic valve replacement with small valves was satisfactory as judged by improvement in the functional class of patients and survival statistics, the durability of the prosthesis, and valve related morbidity comparable to that of valves of other sizes.     

0.18-μm CMOS 10-Gb/s multiplexer/demultiplexer ICs using currentmode logic with tolerance to threshold voltage fluctuation

A feedback MOS current mode logic (MCML) is proposed for the high-speed operation of CMOS transistors. This logic is more tolerant to the threshold voltage fluctuation than the conventional MCML and is suitable for gigahertz operation of deep-submicron CMOS transistors. Using this logic, 8:1 multiplexer (MUX) and 1:8 demultiplexer (DEMUX) ICs for optical-fiber-link systems have been fabricated with 0.18-μm CMOS transistors. The ICs are faster than conventional CMOS MUX and DEMUX ICs and their power consumption is less than 1/4 of that of the conventional 10-Gb/s MUX and DEMUX ICs made using Si bipolar or GaAs transistors