Effects of Trace Elements in Copper Fillers on the Electrical Properties of Conductive Adhesives

The properties of electrically conductive adhesives (ECAs) filled with Cu and Cu alloy fillers (with alloy elements Ag, Ge, Mg, and Zn) were investigated in terms of electrical conductivity, thermal stability, and the effects of the trace alloy elements on the oxidation resistance of the metallic fillers. Oxidation of metallic fillers under high-temperature exposure at 125°C was considered as the main reason that led to degradation of electrical conductivity in the ECAs. Cu fillers alloyed with a trace amount of Ag and Mg, respectively, had significant effects on the electrical conductivity and thermal stability of the ECAs as the electrical resistivity was substantially suppressed and a consistently high electrical conductivity could be maintained even after aging for 1000 h at 125°C.     

Improvement of life time of minority carriers in GaAs epi-layer grown on Ge substrate

A buffer layer structure on Ge substrate was studied for MOCVD growth of a high-quality GaAs layer. The buffer layer structure was designed taking into consideration both lattice constants and thermal expansion coefficients of GaAs and Ge. It consisted of a preliminarily grown thin layer of Al_xGa_1−xAs and a GaAs layer. Photoluminescence (PL) decay of a GaAs layer in an Alo_0.2Ga_0.8As-GaAs-Al_0.2Ga_0.8As double-hetero (DH) structure, which was grown on the buffer layer structure, was observed by time-resolved PL method to estimate the quality of epilayers in the DH structure. The PL decay time strongly depended on Al content (x) of the Al_xGa_1−x As preliminary layer, and the highest value was obtained when the x was 0.25. A PL decay time above 20 ns was successfully obtained for the DH structure grown on the buffer layer structure, which consisted of a 0.05 μm thick Al_0.25Ga_0.75As layer and a 1 μm thick GaAs layer. Although this value was half of that for the DH structure grown on GaAs substrate, it was much longer than the value of 3 ns for the DH structure grown on Ge substrate with a conventional GaAs buffer layer 1 μm thick.     

Experimental and numerical evaluation of bearing capacity of steel plate girder affected by end panel corrosion

The present study deals with the effect of uniform and non-uniform local corrosion damages at the bearing stiffener and nearby web on the bearing capacity of plate girder. Five plate girder ends simulated with different uniform and non-uniform types of corrosion damage, at the base of the bearing stiffener are used in the experimental program. The experimental results are modeled and verified on a Finite Element (FE) software ABAQUS, considering shell-solid coupling elements formulation. The study is further extended to various damage cases i.e., stiffener damage, stiffer plus web damages etc. considering different damage heights and residual thicknesses. The study concludes that minimum thickness within any damage height may be used to simulate the corrosion damage in a FE analysis. At the end, some empirical relationships are also proposed to estimate the bearing strength of the plate girder affected by the local corrosion damage at plate girder end.     

High Pressure Effect on Superconductivity of Hole-Doped Pr0.75Sr0.25FeAsO Iron Pnictides

We report the pressure dependence of superconductivity for hole-doped polycrystalline Pr_0.75Sr_0.25FeAsO by the resistivity study using high pressure cubic and diamond anvil pressure cells. The superconducting transition temperature is initially increased from 17 K (P=0) to 34 K (P=6 GPa) with positive pressure coefficient, which is remarkable among other pnictide superconductors. At high pressure, there is no incredible enhancement of T _c; in other words, it has a negative pressure effect on superconductivity, like in an electron-doped compounds. A systematic investigation of superconductivity for this 1111 type hole-doped iron pnictides is further carefully analyzed and discussed in detail using superconducting phase diagram under high pressure chart.     

Seismic Wave Propagation in Elastic-Viscoplastic Shear Layers

A computational method is introduced for simulating seismic wave propagation in elastic-viscoplastic shear layers. The fundamental dynamics are expressed by two partial differential equations for shear stress and velocity, the balance of momentum, and the elastic-viscoplastic constitutive law. They are converted to those for the upward and downward components of horizontally-polarized motion and then a finite difference method is applied. Seismic wave propagation is computed, considering the reflection and refraction rule at the contact boundary of two layers, as well as the boundary conditions at the bottom and top. Simulation analyses for the observed records show that the proposed method is effective and practical, although it cannot simulate liquefaction phenomena.     

Abundance of cyclo (His-Pro)-like immunoreactivity in the brain of TRH-deficient mice

Cyclo(His-Pro) or CHP was initially discovered as a metabolite of thyrotropin-releasing hormone (TRH) resulting from the action of the enzyme Pyroglutamyl aminopeptidase. Physiologic and pharmacologic studies that followed this initial discovery provided indirect evidence that all CHP may not be derived from TRH. However, the recent availability of a TRH-deficient mouse has made it possible to reinvestigate whether CHP is derived from TRH. In the present study, we examined distribution of CHP and TRH in TRH-deficient mice. Northern blot analysis confirmed the absence of preproTRH mRNA in both the hypothalamus and the cortex of TRH-deficient mice. Brains from the wild-type and TRH-deficient mice were dissected into 7 regions, and TRH and CHP concentrations were determined by specific radioimmunoassay (RIA) in each region. Whereas TRH was identified in all regions of the wild-type brain, with the highest concentration in the hypothalamus, no detectable TRH was observed in any region in the TRH-deficient mice. While CHP-like immunoreactivity (CHP-LI) was present in all regions in the wild-type brain, its concentration was reduced by approximately 50% in the hypothalamus and cerebral cortex of TRH-deficient mice, with no change in other brain regions. Furthermore, the CHP-LI present in the brain of TRH-deficient mice was immunologically and chromatographically identical to synthetic CHP. These findings strongly suggest that a portion of the CHP in the brain is derived from sources other than TRH.     

Improved growth of bifidobacteria by cocultivation with Lactococcus lactis subspecies lactis

Cultivation of bifidobacteria in milk is a difficult and industrially valuable task. In this paper, we report the finding of a novel technique to improve the growth of bifidobacteria in dairy products and the results of mechanism studies. The growth of bifidobacteria in skim milk medium was found to be stimulated upon cocultivation with certain strains of Lactococcus lactis ssp. lactis. Bifidobacterium growth-stimulating (BGS) activity was observed on a wide range of bifidobacterial species. Bifidobacterium growth-stimulating activity was associated with the ability to grow in skim milk medium and the presence of a cell wall-anchored proteinase (PrtP) in Lc. lactis ssp. lactis. Studies on one strain, Lc. lactis ssp. lactis MCC857, showed that crude PrtP extracts and casein hydrolysates exhibited BGS activity. The casein hydrolysate BGS activity was found in the low molecular weight fraction by HPLC separation. A combination of 2 AA, Met and Leu, was found to account for a large portion of the casein hydrolysate BGS activity. In conclusion, this cocultivation system is highly efficient and industrially applicable for the production of fermented milk with high cell counts of bifidobacteria.     

Short circuit current of thermoionic energy converter by resonance light irradiation

A thermoionic energy conversion is one of the methods of direct electricity generation. The space charge effect, which limits the space emission, is relaxed by enclosing cesium in the converter. In general, the converter is operated at high emitter temperature because of the production of cesium ion by contact thermal ionization. The high operating temperature causes short emitter lifetime which becomes a problem in terms of practical use. The converter is irradiated with the resonance light so that cesium ion is produced by photoionization. It is seen that the output resulting from the resonance light irradiation is much higher than that resulting from the visible light. Many cesium ions can be produced in the space between the electrodes since most of the resonance light is absorbed by cesium atoms. The maximum value of the short circuit current density is about 1kA/m². It is found that resonance light irradiation is one of the effective methods suitable for practical application. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(1): 14–21, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10250     

Numerical analysis of transit conduction current in an insulating liquid with added ionic electrolyte

We simulated the phenomena of transit conduction in an insulating liquid with added ionic molecules such as surfactant, by using the charge‐injection model with dissociation‐recombination. When the parameters of C_i (density of injected charge) and C₀ (density of created charge in the liquid) are C_i>C₀ in this simulation, the waveform of current density showed an injection type with a peak, and when C_i<C₀, it showed a dissociation‐recombination type. A decreasing characteristic appeared in the low electric field, maximum one in the middle field, and saturating one in the high field. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(1): 10– 16, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20327