Influence of coating thickness on rolling contact fatigue of alumina ceramics thermally sprayed on steel roller

The influence of the sprayed layer thickness on rolling contact fatigue of a thermally sprayed alumina ceramics with a nominal composition of Al₂O₃–2.3 mass% TiO₂ was investigated using a two-roller test machine under pure rolling contact condition with oil lubricant. The influence of undercoating of sprayed nickel-based alloy on rolling contact fatigue was also investigated. Thicknesses of the ceramics-sprayed layer of tested rollers were 0.2, 0.5 and 1.0 mm. The failure mode of sprayed rollers was spalling caused by subsurface cracking. In the case of sprayed rollers without undercoating, rolling contact fatigue strength of rollers with 0.2 mm thickness sprayed layer was the smallest. Rolling contact fatigue strength of sprayed roller with 0.2 mm thickness sprayed layer was improved by undercoating. In case the failure depth was small as compared with the thickness of sprayed layer, effect of undercoating on the rolling contact fatigue strength was little. The depths where the maximum values of subsurface shear stresses occurred, almost corresponded to the observed depth of spalling cracks.     

BUCKLING OF TRUNCATED CONICAL SHELLS UNDER COMBINED PRESSURE AND HEATING

This paper presents a theoretical analysis of the elastic instability of truncated conical shells under combined uniform pressure and thermal loading. The problem is solved by applying a finite difference method to the Donnell-type shell equations with the effect of large prebuckling deflections taken into consideration. It is found that the interaction curve of the buckling loads changes drastically with the loading order for the shallow cones clamped to rigid end plates and constrained in the axial direction. This phenomenon is caused by a remarkable difference in the prebuckling deformation and the buckling pattern of each case with single load.     

Saturation and Polarization Characteristics of 1.56 μm Optical Probe Pulses in a LTG-GaAs Photoconductive Antenna Terahertz Detector

The characteristics of low temperature-grown GaAs photoconductive antenna (PCA) terahertz detectors probed by 1.56 μm laser pulses are investigated. The influence of TM and TE polarized probe, as well as the saturation characteristics are studied for 2 μm- and 5 μm-gap PCA’s. Different polarization characteristics at low probe powers and at the saturation regimes were observed. Results are explained in terms of the polarization-dependent photocarrier distribution at the PCA gap arising from tight focusing. This work also demonstrates using a 1.56 μm probe for a GaAs PCA to achieve ~60 dB SNR; matching its performance characteristics for above-bandgap probes.     

Structure-function analysis of a conserved aromatic cluster in the N- terminal domain of human epidermal growth factor

The importance of a cluster of conserved aromatic residues of human epidermal growth factor (hEGF) to the receptor binding epitope is suggested by the interaction of His10 and Tyr13 of the A-loop with Tyr22 and Tyr29 of the N-terminal beta-sheet to form a hydrophobic surface on the hEGF protein. Indeed, Tyr13 has previously been shown to contribute a hydrophobic determinant to receptor binding. The roles of His10, Tyr22 and Tyr29 were investigated by structure-function analysis of hEGF mutant analogues containing individual replacements of each residue. Substitutions with aromatic residues or a leucine at position 10 retained receptor affinities and agonist activities similar to wild- type indicating that an aromatic residue is not essential. Variants with polar, charged or aliphatic substitutions altered in size and/or hydrophobicity exhibited reduced binding and agonist activities. 1- Dimensional 1H NMR spectra of high, moderate and low-affinity analogues at position 10 suggested only minor alterations in hEGF native structure. In contrast, a variety of replacements were tolerated at position 22 or 29 indicating that neither aromaticity nor hydrophobicity of Tyr22 and Tyr29 is required for receptor binding. CD spectra of mutant analogues at position 22 or 29 indicated a correlation between loss of receptor affinity and alterations in hEGF structure. The results indicate that similar to Tyr13, His10 of hEGF contributes hydrophobicity to the receptor binding epitope, whereas Tyr22 and Tyr29 do not appear to be directly involved in receptor interactions. The latter conclusion, together with previous studies, suggests that hydrophobic residues on only one face of the N-terminal beta-sheet of hEGF are important in receptor recognition.      

Measuring System for Dynamic Characteristics of Semiconductor Switching Elements and Switching Loss of Thyristors

Thyristors today are used in various electrical apparatus where high operational reliability is of prime importance. For better operational reliability, it is essential that thyristors be used most effectively. It especially is important to predict quantitatively the thyristor's internal impedance (dynamic impedance) which varies by time and by switching loss as transiential stress is applied to the thyristor when it is turned-on and -off, and to design a thyristor circuit basing on the predicted dynamic impedance. This article introduces an outline of a measuring system which can be used for quantitative determination of dynamic characteristics of thyristors and discusses switching loss determined with the measuring system. The measuring system consists primarily of two A/D converters. Dynamic characteristics of a thyristor, either of a normal type or high-speed type, can be quantitatively measured in one turn-on or turn-off operation. This article also discusses the effect of variation of the element area of the thyristor on the switching loss.     

Microstructure design of lead-free piezoelectric ceramics

Computational and experimental methodologies are integrated into a novel combined technique to define microstructure design criteria and maximize the properties of rhombohedral Bi_0.5Na_0.4K_0.1TiO₃, from untextured (1 MRD), d₃₃ = 155 pC/N, to textured (4.41 MRDs), d₃₃ = 227 pC/N. Two-dimensional orientation maps obtained using electron backscatter diffraction on sequential parallel layers are used to computationally reconstruct three-dimensional samples, simulate the local piezoelectric grain interactions, and thus demonstrate that superior lead-free piezoelectric microstructures can be fabricated by engineering its associated crystallographic and polarization texture. Computer-generated material representations, based on the experimentally determined microstructures, were used to simulate the crystallographic orientation of each grain, as function a macroscopic polarization and crystallographic texture. Computer-generated material representations, based on the experimentally determined microstructures, were used to simulate the crystallographic orientation of each grain, as function a macroscopic polarization and crystallographic texture. The method takes advantage of the anisotropy of the properties of the underlying single-crystal phases and delivers a guide to search for material anisotropy |microstructure parameters that are optimal in piezoelectric performance and reliability, and thus establish practical links between structure and macroscopic length scales.     

Memory effect on semi-clathrate hydrate formation: A case study of tetragonal tetra-n-butyl ammonium bromide hydrate

Recrystallization in a tetragonal tetra-n-butyl ammonium bromide (hereafter, TBAB) semi-clathrate hydrate system has been investigated in TBAB aqueous solutions of two different concentrations (stoichiometric mole fraction for tetragonal TBAB hydrate formation and lower mole fraction than stoichiometric one) by use of optical microscopy. The recrystallization of TBAB hydrate has been observed under milder condition than that of the initial crystallization in both concentrations. In particular, solution of the lower concentration is easily recrystallized. This is the first observation of memory effect in a semi-clathrate hydrate system. In addition, the recrystallization occurs in the vicinity of the place where the last piece of initial crystal was dissociated. This implies that a small amount of residual structures remain in the dissociated water, but unfortunately they cannot be confirmed with Raman micro-spectroscopy.     

Survey of Japanese layer farms for Salmonella enteritidis with vaccination- and infection-specific antigens for egg yolk antibodies

Japanese layer farms were surveyed for Salmonella Enteritidis vaccination and infection with specific antigens for egg yolk antibodies with the use of vaccination-specific antigen Salmonella Enteritidis FliC-specific 9-kDa polypeptide (SEP9) and infection-specific antigen deflagellated Salmonella Enteritidis whole cell (DEWC). The specific antibodies in eggs from 201 commercial layer farms throughout Japan were surveyed. The percentages of farm flocks with a mean enzyme-linked immunosorbent assay (ELISA) titer of over 0.1 were 56.2% (113 of 201) in DEWC-ELISA and 22.3% (45 of 201) in SEP9-ELISA. Flocks indicating high titers in SEP9-ELISA always showed high titers in DEWC-ELISA. Because both specific antibody titers of the vaccinated flocks monitored long term remained high throughout life, flocks with high titers of both ELISAs in this survey must be vaccinated. On the other hand, 34.3% (69 of 201) of flocks had high titers of DEWC-specific antibody alone. Because Salmonella Enteritidis infection induces the DEWC-specific antibody but not the SEP9-specific antibody, detecting only high ELISA titers of DEWC-specific antibody can be an effective monitoring tool for Salmonella Enteritidis exposure rather than vaccination. These results suggest that vaccination programs in Japanese layer farms would be insufficient to control Salmonella Enteritidis infection, and egg screening to detect specific antibodies would be valuable in obtaining the necessary information to control Salmonella Enteritidis infection.     

Thermoluminescence and induced absorption in X-ray-irradiated CdS-doped glasses

Thermoluminescence of X-ray-irradiated CdS-doped glasses has been measured, and relation between thermoluminescence and induced absorption in the X-ray-irradiated CdS-doped glasses has been investigated. The effect of thermal annealing and the X-ray energy dependence of thermoluminescence is different from that on the induced absorption. Therefore, defects, which are responsible for thermoluminescence, are considered to be different from those responsible for the induced absorption.     

Significant expression of G-CSF-induced gene-1 (GIG-1) protein in myeloid cells and NK cells

25-Hydroxycholesterol negatively regulates cholesterol synthesis and activates cholesterol esterification in a variety of cultured cells. Concurrent with these effects, 25-hydroxycholesterol also stimulates the synthesis of sphingomyelin in Chinese hamster ovary (CHO)-K1 cells. The role of oxysterol binding protein (OSBP), a high affinity receptor for 25-hydroxycholesterol, in activation of SM synthesis was assessed by overexpression in CHO-K1 cells. When compared to mock transfected controls, three CHO-K1 clones overexpressing OSBP by 10- to 15-fold displayed a 2- to 3-fold enhancement of [3H]serine incorporation into sphingomyelin when treated with 25-hydroxycholesterol. Closer examination of one of these clones (CHO-OSBP cells) revealed a >8.5-fold stimulation of sphingomyelin synthesis after a 6-h treatment with 25-hydroxycholesterol compared to 3.5-fold in controls, slightly higher basal levels of sphingomyelin synthesis, and a more rapid response to 25-hydroxycholesterol. [3H]serine incorporation into phosphatidylserine, phosphatidylethanolamine, ceramide, or glucosylceramide was affected by <15%. Synthesis of sphingomyelin from exogenous [3H]sphinganine-labeled ceramide was enhanced in overexpressing cells treated with 25-hydroxycholesterol. However, in vitro activities of sphinganine N-acyltransferase, sphingomyelin synthase, and serine palmitoyltransferase were not affected by OSBP overexpression or 25-hydroxycholesterol. Overexpression of OSBP or 25-hydroxycholesterol did not significantly affect the ceramide content of Golgi-enriched fractions from control or overexpressing cells. However, diglyceride mass was reduced in Golgi-enriched fractions from overexpressing cells and by treatment with 25-hydroxycholesterol. Results from overexpressing cells show that OSBP potentiates the stimulatory effects of 25-hydroxycholesterol on sphingomyelin synthesis. 25-Hydroxycholesterol promotes translocation of OSBP to the Golgi apparatus where it appears to stimulate conversion of ceramide to sphingomyelin.