Chaotic transport in antidot lattices

A review is given of quantum effects and roles of chaos in transport in antidot lattices mainly from a theoretical point of view. The topics include diffusive orbits combined with a magnetic focusing effect as the origin of the commensurability peaks, semiclassical quantization of periodic orbits as the origin of the Aharonov-Bohm type oscillation superimposed, and the importance of inherent disorder in the antidot potential itself.     

A 2.5-GFLOPS, 6.5 million polygons per second, four-way VLIWgeometry processor with SIMD instructions and a software bypassmechanism

A four-way very long instruction word (VLIW), 312-MHz geometry processor with peripheral component interconnect/accelerated graphic port bus bridge was implemented in a 0.21-μm, 2.5-V, three-layer-metal CMOS process. We adopted (1) a software bypass mechanism, (2) single-instruction multiple-data stream instructions, (3) four sets of floating-point multiply add and accumulate execution units, (4) special condition code registers and a branch condition generator for a clipping operation, and (5) automatic clock delay tuning methodology. As a result of these features, we achieved a performance of 2.5 GFLOPS and 6.5 million polygons per second for a three-dimensional geometry processor, which is the highest published performance as a single geometry processor. The processor is applicable to computer-aided-design systems that require very high graphics performance     

Effects of species and moisture content on penetration of liquid in laser incised lumber by the passive impregnation method

Penetration of liquid by passive impregnation method for Douglas-fir (Pseudotsuga menziesii Franco), sugi (Cryptomeria japonica D. Don) and Japanese larch (Larix leptolepis Gordon) was studied. Effects of initial moisture content of sugi (16, 43 and 70% moisture content) on liquid penetration were also studied. Dried Douglas-fir (mc=14%) and sugi (mc=16%), and green Japanese larch (mc=45%) and sugi (mc=70%) were treated by passive impregnation method for penetration analysis. It was observed that dried sugi had the highest level of liquid penetration both in length (170 mm) and width (8 mm) for all measured sections followed by green sugi, green Japanese larch and dried Douglas-fir. In case of different initial moisture content, the highest absorption (624 kg/m³) and penetration (maximum 87 and 96% at cross and longitudinal surfaces, respectively) was observed for sugi having the lowest initial moisture content under the same passive impregnation conditions. Absorption and penetration decreased with the increase of initial moisture content for sugi. These results could help in designing incising pattern and density, as well as solving the problems related to high initial moisture content of wood for passive impregnation.     

Post-Mortem Softening of Fish Muscle During Chilled Storage as Affected by Bleeding

Bleeding caused the delay of muscle softening in yellowtail, horse mackerel, and striped jack, which are pelagic fish. Conversely, bleeding had no influence on the muscle firmness of red sea bream, flatfish, and rudder-fish, which are demersal fish. Transmission electron microscopy showed delay of degradation of pericellular collagen fibrils in bled yellowtail and horse mackerel. Striped jack showed slower weakening of the pericellular connective tissue in a compression test. However, the demersal fish had no structural difference due to bleeding. These results indicate that removal of blood could delay collagen fibril degradation and muscle softening of pelagic fish.     

Micro 3D measurement method using SEM

Three diamensional (3D) measurement method by Scanning Electron Microscope (SEM) has already been proposed by using the principle of shadow moiré. In the method, the image of original grid in shadow moiré image must be clearly removed in fringe analysis process in order to perform high resolution analysis. A new method based on the principle of projection moiré is proposed to solve the trouble concerning the grid. In this paper, the mechanism of producing some shadows of grid on the surface of the object by back scattering electron beam in the new method is discussed. Fringe image as shadow of grid is analyzed by Wavelet transform. The precise 3D measurement is realized by using the phenomenon of shadows of grid. Furthermore, a 3D micro structure on the head of a hard disk is measured. From the comparison of results obtained by Atomic Force Microscope (AFM), it is confirmed that the proposed method has high-resolution power(about 20nm).     

Fabrication of high‐strength steel fibre reinforced metal matrix composites by explosive bonding and their tensile properties

Summary

Steel fibre reinforced metal matrix composites (FRM) consisting of high‐strength ductile steel wire and aluminium or titanium foil were fabricated by explosive bonding. The strength properties were evaluated by tensile tests. The optimum explosive loading (explosive mass/driver plate mass) increases with the volume fraction of fibre. For the aluminium matrix composites, the micrographs obtained show sound bonding between the adjoining foils and non‐bonding between the foil and steel wire. The tensile strength of the aluminium matrix composites is 80% of the value predicted by the rule of mixtures. For the titanium matrix composites, the micrographs obtained show both bonded and unbonded regions between the adjoining foils or between the foil and steel wire. The tensile strength of the titanium matrix composites agrees with the value predicted by the rule of mixtures.     

Quantification of singlet oxygen from hematoporphyrin derivative by electron spin resonance

The mechanism of the generation and the quantitative analysis of singlet oxygen (1O2) formed by the exposure of a hematoporphyrin derivative (HpD) to light was re-evaluated by electron spin resonance (ESR) combined with 2,2,6,6,-tetramethyl-4-piperidine (TMPD). The change from TMPD to 2,2,6,6,-tetramethyl-4-piperidine-N-oxide (TAN) has been reported to depend on singlet oxygen. However, we confirmed that this reagent also react with superoxide anion (O2-) and hydroxyl radicals (OH). Therefore, the reactions between TMPD and 1O2, O2- and OH were re-examined using a kinetic approach. We found that the generation of TAN was proportional to the concentration of TMPD and HpD, as well as to the duration and strength of the illumination. The generation of TAN was not inhibited by dimethyl-sulfoxide (DMSO) or superoxide dismutase (SOD). The reaction rate between TMPD and 1O2 was determined to be 5.0 x 10(-7) M min-1. The generation of 1O2 from HpD was 2.7 x 10(-7) M min-1 under our conditions. The competitive reaction observed between 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and TMPD for O2- or OH shows that TMPD reacts with both forms of active oxygen, but gave no ESR signal. The second-order reaction rate constant of TMPD between O2- and OH was calculated as 73 M-1 s-1 and 1.5 x 10(9) M-1 s-1, respectively. The photochemical generation of 1O2 from methylene blue, another sensitizer, was also demonstrated by this method. These results show that ESR signal of TAN can be used for the highly selective monitoring of 1O2.     

The effect of cyber-friends on loneliness and social anxiety: Differences between high and low self-evaluated physical attractiveness groups

This study examined the causal relationships between the number of cyber-friends participants had and their social anxiety or loneliness. We predicted that participants who gave low self-evaluations of physical attractiveness would be able to lower their social anxiety or reduce their loneliness through Internet-based interpersonal relationships. Also, such effects would be more prominent if the cyber-friends were of the opposite sex. A two-wave panel study was conducted with 178 Japanese undergraduate students (63 men and 115 women; mean age was 20.29). Results showed that for those who gave a low evaluation of their physical attractiveness, having a large number of cyber-friends lowered their social anxiety and reduced the loneliness felt in friendships. These effects differed by gender of the cyber-friends. In particular, for those who gave a low evaluation of their physical attractiveness, having a large number of cyber-friends of the same sex had a positive effect on social anxiety. In contrast, cyber-friends of the opposite sex had no effect on social anxiety, but had a complex effect upon loneliness. Namely, while a large number of cyber-friends of the opposite sex reduced the loneliness felt in friendships, it also heightened the loneliness felt in family relationships. Implications of these results for further research and practice are provided.     

10-W/mm AlGaN-GaN HFET with a field modulating plate

AlGaN-GaN heterojunction field-effect transistors (HFETs) with a field modulating plate (FP) were fabricated on an SiC substrate. The gate-drain breakdown voltage (BV/sub gd/) was significantly improved by employing an FP electrode, and the highest BV/sub gd/ of 160 V was obtained with an FP length (L/sub FP/) of 1 /spl mu/m. The maximum drain current achieved was 750 mA/mm, together with negligibly small current collapse. A 1-mm-wide FP-FET (L/sub FP/=1 /spl mu/m) biased at a drain voltage of 65 V demonstrated a continuous wave saturated output power of 10.3 W with a linear gain of 18.0 dB and a power-added efficiency of 47.3% at 2 GHz. To our knowledge, the power density of 10.3 W/mm is the highest ever achieved for any FET of the same gate size.     

Exaggerated urinary excretion of aquaporin-2 in the pathological state of impaired water excretion dependent upon arginine vasopressin

The present study was undertaken to determine whether urinary excretion of aquaporin-2 (UAQP-2) is of value to diagnose the pathological state of water retention and hyponatremia. UAQP-2 under ad libitum water drinking was 429 fmol/mg creatinine in the patients with water retention, a value significantly greater than that of 153 fmol/mg creatinine in the normal subjects. An acute oral water load test (20 mL/kg BW) was performed in 7 normal subjects (22-25 yr old) and 10 patients with water retention and hyponatremia (55-75 yr old). The percent excretion of the water load was only 30% in the patient group compared with 70% in the control group (P < 0.01). In the control group, minimal urinary osmolality was as low as 131 mosmol/kg H2O, which was responsible for the decrease in plasma arginine vasopressin (AVP) levels after the reduction in plasma osmolality. In the patient group, minimal urinary osmolality was 320 mosmol/kg H2O, and free water clearance remained below 0.6 mL/min after the water load. This impaired water excretion was consistent with the nonsuppressible levels of plasma AVP despite hypoosmolality. The nadir of UAQP-2 was obtained at 60-90 min. The minimal UAQP-2 was reduced to 284 fmol/mg creatinine, a value significantly greater than that of 76 fmol/mg creatinine in the control group. Similar results were obtained in the 6 patients with hypopituitarism, who had impaired water excretion and marked hyponatremia. Water excretion was totally normalized after the replacement of hydrocortisone (excretion of water load, 31% vs. 102%; P < 0.01). Hydrocortisone replacement also significantly reduced the minimal UAQP-2 from 225 to 49 fmol/mg creatinine after the acute oral water load, a value comparable to that in the control subjects. These results indicate that UAQP-2 is a potent marker to diagnose the pathological state of impaired water excretion and hyponatremia, dependent upon AVP, in patients with water retention and hypopituitarism.