The Role of Oxidative Stress in Pancreatic β Cell Dysfunction in Diabetes

Diabetes is a chronic metabolic disorder characterized by inappropriately elevated glucose levels as a result of impaired pancreatic β cell function and insulin resistance. Extensive studies have been conducted to elucidate the mechanism involved in the development of β cell failure and death under diabetic conditions such as hyperglycemia, hyperlipidemia, and inflammation. Of the plethora of proposed mechanisms, endoplasmic reticulum (ER) stress, mitochondrial dysfunction, and oxidative stress have been shown to play a central role in promoting β cell dysfunction. It has become more evident in recent years that these 3 factors are closely interrelated and importantly aggravate each other. Oxidative stress in particular is of great interest to β cell health and survival as it has been shown that β cells exhibit lower antioxidative capacity. Therefore, this review will focus on discussing factors that contribute to the development of oxidative stress in pancreatic β cells and explore the downstream effects of oxidative stress on β cell function and health. Furthermore, antioxidative capacity of β cells to counteract these effects will be discussed along with new approaches focused on preserving β cells under oxidative conditions.     

Development of control technology for HTTR hydrogen production system with mock-up test facility: System controllability test for loss of chemical reaction

The Japan Atomic Energy Agency has been planning the demonstration test of hydrogen production with the High Temperature Engineering Test Reactor (HTTR). In a HTTR hydrogen production system (HTTR-H2), it is required to control a primary helium temperature within an allowable value at a reactor inlet to prevent a reactor scram. A cooling system for a secondary helium with a steam generator (SG) and a radiator is installed at the downstream of a chemical rector in a secondary helium loop in order to mitigate the thermal disturbance caused by the hydrogen production system. Prior to HTTR-H2, the simulation test with a mock-up test facility has been carried out to establish the controllability on the helium temperature using the cooling system against the loss of chemical reaction. It was confirmed that the fluctuations of the helium temperature at chemical reactor outlet, more than 200 K, at the loss of chemical reaction could be successfully mitigated within the target of ±10 K at SG outlet. A dynamic simulation code of the cooling system for HTTR-H2 was verified with the obtained test data.     

The effect of a single tensile overload on stress corrosion cracking growth of stainless steel in a light water reactor environment

It has been found that a single tensile overload applied during constant load amplitude might cause crack growth rate retardation in various crack propagating experiments which include fatigue test and stress corrosion cracking (SCC) test. To understand the affecting mechanism of a single tensile overload on SCC growth rate of stainless steel or nickel base alloy in light water reactor environment, based on elastic-plastic finite element method (EPFEM), the residual plastic strain in both tips of stationary and growing crack of contoured double cantilever beam (CDCB) specimen was simulated and analyzed in this study. The results of this investigation demonstrate that a residual plastic strain in the region immediately ahead of the crack tips will be produced when a single tensile overload is applied, and the residual plastic strain will decrease the plastic strain rate level in the growing crack tip, which will causes crack growth rate retardation in the tip of SCC.     

Glass Microspheres for Optics

Preparation and application of glass spheres as resonators are discussed. Surface-tension mold (StM) and localized-laser heating (LLH) techniques have been developed to fabricate glass super spheres and true spheres, respectively. These prepared glass spherical particles have been examined to evaluate their suitability for whispering gallery mode (WGM) oscillators or laser cavities. Super spherical glass acts as a WGM oscillator using its equatorial plane. An equatorial circle roundness > 0.99 provides a high Q-value to lead laser oscillation. LLH demonstrates its excellent capability to prepare “true spheres” on a transparent substrate under gravity. A tellurite glass sphere prepared by the LLH technique exhibits a few-mW-order threshold for lasing at the 1.06-μm region. An added-on terrace and an installed bubble in the sphere serve as an input/output gate and as a “non-WGM” coupling input gate for laser action, respectively. Glass is showed to have strong potential with respect to both preparation and utilization of spherical shapes for optics.     

Elastic-plastic analysis of the deformation mechanism of PP-EPDM thermoplastic elastomer: Origin of rubber elasticity

Polyolefinic thermoplastic elastomer (TPE) is a two-phase material in which cured EPDM (ethylene-propylene-diene rubber) particles are densely dispersed in a PP (polypropylene) matrix. It can be melt-processed at high temperatures and behaves like a vulcanized rubber at ambient temperature. The question is on its strain recovery, i.e., why the TPE can shrink back from the highly deformed states, even though the matrix consists of the ductile polymer. We constructed a two-dimensional model with four rubber inclusions in ductile matrix and carried out the elastic-plastic analysis on the deformation mechanism of the two-phase system by FEM (finite element method). FEM analysis revealed that, even at the highly deformed states at which almost the whole matrix has been yielded by the stress concentration, the ligament matrix between rubber inclusions in the stretching direction is locally preserved within an elastic limit and it acts as an “in-situ formed adhesive” for interconnecting rubber particles. It will provide a key mechanism of the strain recovery in the two-phase system.     

Raman Scattering from Metal-Deposited Porous Silicon

Raman scattering from porous silicon layer into which silver is immersion-plated was studied. Ag-deposited samples show extra Raman bands. Heat treatment of the Ag-deposited samples results in a great decrease in such Raman bands. Also dipping in hydrofluoric acid solution causes a spectral change. Some comments on the assignment of the Raman peaks of the Ag-deposited porous silicon are given, and the structure of porous silicon on which metal is immersion-plated is discussed.     

Leachate treatment by the reverse osmosis system

The DT-Module system for landfill leachate treatment installed at Yachiyo Town in the Kanto District of Japan was put into service in April 1999. The system, which is equipped with a disc-tube type reverse osmosis (RO) membrane module called the DT-Module, has been operating satisfactorily for more than two and a half years, producing very-high-quality product water, after treating very-high-salinity water with high-scaling ions. On the other hand, in Japan, the dioxin problem has become increasingly severe, and development work for dioxin removal incorporated in leachate treatment has also been requested. The DT-Module system showed excellent performance in removing dioxins from leachate. For dioxins in sludge from the settling basin and dried salt from the concentrate of the RO system, successful destruction data were obtained by furnace system heating in an oxygen-deficient atmosphere. The removal rate of dioxins by the DT-Module system and the destruction rate by the furnace were both higher than 99.9%. By applying the DT-Module system together with the furnace system, an excellent leachate treatment and a complete dioxin removal and destruction system have become available for leachate from landfills depositing incineration residue-containing dioxins.     

C nuclear magnetic resonance spectral analysis of stereosequences in ethylene-propylene copolymer

A number of split peaks dependent on both comonomer sequences and stereosequences were observed in the ¹³C nuclear magnetic resonance (n.m.r.) spectrum of ethylene-propylene (E-P) copolymer. The ¹³C chemical shifts of methylene carbon in stereoisomers of the respective hexad comonomer sequences were predicted by a chemical-shift calculation using the gamma effect on ¹³C chemical shifts and Mark's rotational isomeric state model for E-P copolymer. Assignments of the split peaks that arise from different hexad stereosequences were given by comparison between the observed and calculated chemical shifts. Reference was made to the hexad assignments of comonomer-sequence-dependent peak splittings determined in our previous calculation of ¹³C n.m.r. chemical shifts of stereoregular E-P copolymers. The tacticities were estimated for successive (not separated by ethylene units) propylene units in the hexad sequences.     

Effect of specimen thickness on the statistical properties of fatigue crack growth resistance in BS4360 steel

In this paper the effect of specimen thickness on fatigue crack growth with the spatial distribution of material properties is presented. Basically, the material resistance to fatigue crack growth is treated as a spatial stochastic process, which varies randomly on the crack surface. The theoretical autocorrelation functions of fatigue crack growth resistance with specimen thickness are discussed for several correlation lengths. Constant ΔK fatigue crack growth tests were also performed on CT type specimens with three different thicknesses of BS 4360 steel. Applying the proposed stochastic model and statistical analysis procedure, the experimental data were analyzed for different specimen thicknesses for determining the autocorrelation functions and probability distributions of the fatigue crack growth resistance.