Surface degradation of polyamide nanocomposites caused by partial discharges using IEC (b) electrodes

Partial discharge (PD) degradation of polyamide both without nanoscale fillers (nanofillers) and with 2,4 and 5 wt% additions of nanofillers was investigated. Such materials were subjected to PDs using the IEC (b) electrodes for evaluation. Comparisons were made as to the surface roughness observed by scanning electron microscopy and atomic force microscopy. It was found that the change in the surface roughness is far smaller in specimens with nanofillers than those without nanofillers, and that the 2 wt% addition is sufficient for improvement of the surface roughness. Furthermore, it was elucidated that the difference of surface roughness of the degraded area due to PDs among the specimens originates from the difference in their crystalline structures. These results indicate that polyamide nanocomposite is more resistance to PDs than polyamide without nanofillers.     

Meshless analysis of potential problems in three dimensions with the hybrid boundary node method

Combining a modified functional with the moving least‐squares (MLS) approximation, the hybrid boundary node method (Hybrid BNM) is a truly meshless, boundary‐only method. The method may have advantages from the meshless local boundary integral equation (MLBIE) method and also the boundary node method (BNM). In fact, the Hybrid BNN requires only the discrete nodes located on the surface of the domain. The Hybrid BNM has been applied to solve 2D potential problems. In this paper, the Hybrid BNM is extended to solve potential problems in three dimensions. Formulations of the Hybrid BNM for 3D potential problems and the MLS approximation on a generic surface are developed. A general computer code of the Hybrid BNM is implemented in C++. The main drawback of the ‘boundary layer effect’ in the Hybrid BNM in the 2D case is circumvented by an adaptive face integration scheme. The parameters that influence the performance of this method are studied through three different geometries and known analytical fields. Numerical results for the solution of the 3D Laplace's equation show that high convergence rates with mesh refinement and high accuracy are achievable. Copyright © 2004 John Wiley & Sons, Ltd.     

A single solution method for converting 2D assembly drawings to 3D part drawings

Although solid models play a central role in modern CAD systems, 2D CAD systems are still commonly used for designing products without complex curved faces. Therefore, an important task is to convert 2D drawings to solid models, and this is usually carried out manually even in present CAD systems. Many methods have been proposed to automatically convert orthographic part drawings of solid objects to solid models. Unfortunately, products are usually drawn as 2D assembly drawings, and therefore, these methods cannot be applied. A further problem is the difficult and time-consuming task of decomposing 2D assembly drawings into 2D part drawings. In previous work, the authors proposed a method to automatically decompose 2D assembly drawings into 3D part drawings, from which 2D part drawings can be easily generated. However, one problem with the proposed method was that the number of solutions could easily explode if the 2D assembly drawings became complex. Building on this work, here we describe a new method to automatically convert 2D assembly drawings to 3D part drawings, generating a unique solution for designers regardless of the complexity of the original 2D assembly drawings. The only requirement for the approach is that the assembly drawings consist of standard parts such as bars and plates. In 2D assembly drawings, the dimensions, part numbers and parts lists are usually drawn, and the proposed method utilizes these to obtain a unique solution.     

Transfer of semicrystalline polymers sliding against a smooth steel surface

The interrelationships between transfer and wear in polymers were studied using a pin-disk-type wear testing apparatus. The wear rates of polymers except polytetrafluoroethylene (PTFE) were high for up to about the first 100 revolutions of the disk and decreased gradually until the steady low wear rates which generally occurred after about 2000 revolutions. However, PTFE exhibited an almost constant high wear rate throughout the wear process. The thickness of transferred polymer increased rapidly with increasing number of revolutions in the initial wear stage but after about several hundred revolutions remained constant. A coherent transfer film was formed in most parts of the friction track after about 100 revolutions. It was found that polymer wear could occur in polymers sliding on a transferred polymer layer. All polymers except PTFE exhibited smaller wear rates when sliding on the transferred layer. The load dependence of the thickness was very small compared with that of the wear rate. PTFE produced a very dense and coherent transferred layer compared with that of other polymers. However, there was no clear relationship between friction and the thickness of the transferred polymer layer.     

A preparation method for observing intracellular structures by scanning electron microscopy

In order to observe intracellular structures by scanning electron microscopy, excess cytoplasmic matrix must be removed from the fractured surface of cells. Previously we reported an Osmium-DMSO-Osmium method devised for this purpose. This method is very effective in revealing intracellular structures, but requires osmium tetroxide for initial fixation with some consequent disadvantages. In the present study, a revised Osmium-DMSO-Osmium method is reported, in which an aldehyde mixture is used as the initial fixative instead of osmium tetroxide. As fixation is carried out by perfusion in this revised method, better preservation of fine structures is achieved than by the original method, especially in the central nervous tissue which tends to suffer from post-mortem degeneration. Moreover this method can be applied to cytochemical studies of intracellular structures with a scanning electron microscope (SEM). In this study, acid phosphatase of lysosomes is demonstrated in a coloured SEM micrograph.     

Detection of a tryptophan radical as an intermediate species in the reaction of horseradish peroxidase mutant (Phe-221 --> Trp) and hydrogen peroxide

The crucial reaction intermediate in the reaction of peroxidase with hydrogen peroxide (H2O2), compound I, contains a porphyrin pi-cation radical in horseradish peroxidase (HRP), which catalyzes oxidation of small organic and inorganic compounds, whereas cytochrome c peroxidase (CcP) has a radical center on the tryptophan residue (Trp-191) and oxidizes the redox partner, cytochrome c. To investigate the roles of the amino acid residue near the heme active center in discriminating the function of the peroxidases in these two enzymes, we prepared a CcP-like HRP mutant, F221W (Phe-221 --> Trp). Although the rapid spectral scanning and stopped-flow experiments confirmed that the F221W mutant reacts with H2O2 to form the porphyrin pi-cation radical at the same rate as for the wild-type enzyme, the characteristic spectral features of the porphyrin pi-cation radical disappeared rapidly, and were converted to the compound II-type spectrum. The EPR spectrum of the resultant species produced by reduction of the porphyrin pi-cation radical, however, was quite different from that of compound II in HRP, showing typical signals from a Trp radical as found for CcP. The sequential radical formation from the porphyrin ring to the Trp residue implies that the proximal Trp is a key residue in the process of the radical transfer from the porphyrin ring, which differentiates the function of peroxidases.     

A Technique to Eliminate Redundant Inter-Processor Communication on Parallelizing Compiler TINPAR

Optimizing inter-processor (PE) communication is crucial for parallelizing compilers for message-passing parallel machines to achieve high performance. In this paper, we propose a technique to eliminate redundant inter-PE messages. This technique utilizes data-flow analysis to find a definition point that corresponds to a use point where the definition and the use occur in different PEs. If several read accesses occurred in the same PE use the data defined at the same definition point in another PE, redundant inter-PE messages are eliminated as follows: only one inter-PE communication is performed for the earliest read access and the previously received data are used for the following read. In order to guarantee the consistency of the data, a valid flag and a sent flag are provided for each chunk of received data. The control of these flags is equivalent to the coherence control by the self invalidation on a compiler aided cache coherence scheme.     

Psychological Stress Exacerbates Inflammation of the Ileum via the Corticotropin-Releasing Hormone-Mast Cell Axis in a Mouse Model of Eosinophilic Enteritis

The effects of psychological stress on eosinophilic gastrointestinal disorders have not been elucidated. This study investigated the effects of psychological stress in a mouse model of eosinophilic enteritis (EoN). BALB/c mice were treated with ovalbumin (OVA) to create an EoN model and subjected to either water avoidance stress (WAS) or sham stress (SS). Microscopic inflammation, eosinophil and mast cell counts, mRNA expression, and protein levels of type 2 helper T cell (Th2) cytokines in the ileum were compared between groups. We evaluated ex vivo intestinal permeability using an Ussing chamber. A corticotropin-releasing hormone type 1 receptor (CRH-R1) antagonist was administered before WAS, and its effects were analyzed. WAS significantly increased diarrhea occurrence and, eosinophil and mast cell counts, and decreased the villus/crypt ratio compared to those in the SS group. The mRNA expression of CRH, interleukin IL-4, IL-5, IL-13, eotaxin-1, and mast cell tryptase β2 significantly increased, and the protein levels of IL-5, IL-13, and OVA-specific immunoglobulin E (IgE) also significantly increased in the WAS group. Moreover, WAS significantly increased the intestinal permeability. The CRH-R1 antagonist significantly inhibited all changes induced by WAS. Psychological stress exacerbated ileal inflammation via the CRH-mast cell axis in an EoN mouse model.