Polystyrene microcellular plastic generation by quick‐heating process at high temperature

Generation of microcellular plastic in the polystyrene‐nitrogen system was studied in a batch process. In this study, a quick‐heating method was applied to study the effects of saturation temperature, decompression rate and heating time on the microcellular structure for sheet samples with a thickness of 1.3 mm. The saturation pressure in each process was kept constant at 25 MPa. At saturation temperatures above 393 K, we found that, although the solubility of nitrogen increased with increasing saturation temperature, cell density decreased, and the average cell diameter and volume expansion ratio increased. The samples that were saturated at 433 K shattered after microcellular processing. The change in decompression rate affected the supersaturation degree of the dissolved gas in the polymer, and affected the cell structure. Variation of heating time for difference saturation/heating temperature could be used to obtain the optimum relation between cell density, average cell diameter, and volume expansion ratio.     

Stock assessment and fishery management of Henicorhynchus spp., Cyclocheilichthys enoplos and Channa micropeltes in Tonle Sap Great Lake,Cambodia

Tonle Sap Great Lake, in the lower Mekong River basin, contributes 60% of Cambodia's inland fisheries catch. There are four types of fisheries, including the middle-scale fishery. The major species comprising the middle-scale fishery are Henicorhynchus spp. (16%), a small-bodied fish caught mainly with small-mesh nets, and Cyclocheilichthys enoplos (13%), and Channa micropeltes (7%) which are caught with a variety of gear. Here we apply the Schaefer surplus production model to the middle-scale fisheries using monitoring data collected between 1995 and 1999. Model simulations determined that the maximum sustainable yield (F_MSY) for Henicorhynchus spp., was obtained with the use of 47,206 gillnets (mesh size < 50 mm) and 4269 and 1605 fishing boats for C. enoplos and C. microplestes, respectively. Over 1995–1999, there was a strong trend of increase in fishing effort and decrease of catch-per-unit-effort in the waters of Pursat, Siem Riep and Kampong Chnnang provinces. These provinces have large population centres located close to the fishing grounds; fishing in these areas should be more strictly regulated.     

Agglomeration kinetics of monodisperse systems — computer simulation of agglomeration by a two-dimensional random walk model

Computer simulation has been used to elucidate agglomeration processes of monodisperse systems. It is shown that for processes where agglomeration occurs as a function of (a) particle encounter and (b) adherence probability, a relation results which is akin to Smoluchowski kinetics.     

Independent self-assembly of cadmium-binding {alpha}-fragment of metallothionein in Escherichia coli without participation of {beta}-fragment

We examined the independent self-assembly of the - and ß-fragmentsof human metallothionein (MT) into cadmiumbinding conformationin an Escherichia coli expression system, in addition to wild-typeMT expression. The expressed -fragment formed independentlythe structure of a metal-binding cluster without the aid ofthe ß-fragment. The -fragment and wild-type MT expressedin E.coli were purified and analyzed for their biochemical andspectroscopic properties. The apparent cadmium binding of the-fragment was approximately 12-fold greater than that for thewild-type MT, whereas in other respects the studied biochemicalproperties were similar. In contrast, we were unable to obtainany independently expressed ß-fragment as the cadmium-bindingform in this study. Possible explanations for this phenomenonare discussed.     

Effect of surface charges on the polarization of BaTiO3 thin films investigated by UHV‐SPM

Nanostructured BaTiO₃ polar thin films are increasingly critical to the function of future multilayer ceramic capacitors and related oxide‐based electronic devices. The effect of surface charges on BaTiO₃ polarization behavior is therefore investigated by ultra‐high vacuum scanning probe microscopy (UHV‐SPM) for 3 distinct morphologies—epitaxial, polycrystalline, and nanocrystalline films. Regardless of the film morphology, Kelvin probe force microscopy reveals that BaTiO₃ thin film surfaces exhibit positive charging after contact scanning by various noble AFM probes due to the work function difference between tip and specimen. According to piezoresponse force microscopy, these positive charges uniformly stabilize downward polarized domains. However, the hysteresis and concomitant surface charging behavior are strongly sensitive to microstructure and defects. In particular, the stability and switching behavior are influenced by bulk and interfacial defect distributions and hence correlated to film deposition methods and grain size. Such morphology dependent properties for BaTiO₃ films are revealed only through UHV measurements where screening charges from the ambient can be minimized, demonstrating the importance of UHV‐SPM for understanding ferroelectric thin films and nanostructures.     

A review of studies on the electric field and the current induced in a human body exposed to electromagnetic fields

How high an electric field or current is induced inside a human body when exposed to an electromagnetic field has recently attracted much attention. The background for this is twofold; concern about the possible health effects of electromagnetic fields (usually called ‘EMF issues’), and their positive application to medical treatment or new research subjects. This paper reviews various aspects related to this topic in terms of the following items: basic formulas for field calculation, effect of electromagnetic fields, calculation methods, an Investigation Committee in the IEEJ, and future research subjects. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Temporal and spatial trends of organotin contamination in the livers of finless porpoises (Neophocaena phocaenoides) and their association with parasitic infection status

Organotins (OTs) are globally ubiquitous contaminants. Contamination of OTs, particularly butyltins (BTs), has been suspected to cause immunosuppressive effects leading to subsequent infectious diseases or opportunistic infection by pathogens in marine mammals. In the present study, we collected individuals from five different populations of finless porpoises (Neophocaena phocaenoides) from coastal areas of Japan (Seto Inland Sea, Ise Bay, Omura Bay, and Pacific coast) and Hong Kong, and measured OT concentrations in their livers. In addition, infection status of lung nematodes and liver trematodes was also observed to analyze the relationship between OT contamination and parasitic infection in finless porpoises. Hepatic OT concentrations were highest in the Hong Kong population, while levels in the Japanese populations were equivalent to those of other cetaceans from different locations. OT levels in Japan have been decreasing in the past few decades, while OT contamination has shown little improvement in Hong Kong. Observation of parasite infection in Seto Inland Sea porpoises revealed that 16 and 11 out of 22 individuals were infected by lung nematodes and liver trematodes, respectively. Additionally, a significant association between BT levels and parasitic infection status of lung nematodes was detected. Thus, the present study suggests that BTs could be a factor affecting parasitic infection, especially the presence or severity of lung nematodes in finless porpoises. Since chemical exposure may alter the susceptibility of organisms to infectious diseases, the interaction of chemical contamination with infectious diseases needs to be investigated in greater depth to understand the risk of population decline due to these factors in marine mammals.     

Identification of major dioxin-like compounds and androgen receptor antagonist in acid-treated tissue extracts of high trophic-level animals

We evaluated the applicability of combining in vitro bioassays with instrument analyses to identify potential endocrine disrupting pollutants in sulfuric acid-treated extracts of liver and/or blubber of high trophic-level animals. Dioxin-like and androgen receptor (AR) antagonistic activities were observed in Baikal seals, common cormorants, raccoon dogs, and finless porpoises by using a panel of rat and human cell-based chemical-activated luciferase gene expression (CALUX) reporter gene bioassays. On the other hand, no activity was detected in estrogen receptor α (ERα)-, glucocorticoid receptor (GR)-, progesterone receptor (PR)-, and peroxisome proliferator-activated receptor γ2 (PPARγ2)-CALUX assays with the sample amount applied. All individual samples (n = 66) showed dioxin-like activity, with values ranging from 21 to 5500 pg CALUX-2,3,7,8-tetrachlorodibenzo-p-dioxin equivalent (TEQ)/g-lipid. Because dioxins are expected to be strong contributors to CALUX-TEQs, the median theoretical contribution of dioxins calculated from the result of chemical analysis to the experimental CALUX-TEQs was estimated to explain up to 130% for all the tested samples (n = 54). Baikal seal extracts (n = 31), but not other extracts, induced AR antagonistic activities that were 8-150 μg CALUX-flutamide equivalent (FluEQ)/g-lipid. p,p'-DDE was identified as an important causative compound for the activity, and its median theoretical contribution to the experimental CALUX-FluEQs was 59% for the tested Baikal seal tissues (n = 25). Our results demonstrate that combining in vitro CALUX assays with instrument analysis is useful for identifying persistent organic pollutant-like compounds in the tissue of wild animals on the basis of in vitro endocrine disruption toxicity.     

Design of a self-testing and self-repairing structure for highlyhierarchical ultra-large capacity memory chips

A memory architecture with the capability of self-testing and self-repairing is presented. The contributions of this memory architecture are twofold. First, because it incorporates self-testing and self-repairing structures, the memory chip can perform tests, locate faults, and repair itself without any external assistance from either test engineers or test equipment. This will greatly improve the functional yield and reduce the production cost. Second, the hierarchical organization used to achieve optimal conditions for memory access time also helps increase the efficiency of the self-testing and self-repairing structures     

On the possibility of SSR in longitudinal power systems

This paper presents a theoretical consideration on the possibility of subsynchronous resonance (SSR) in longitudinal power systems. Shunt capacitors are used for reactive power compensation in our country, but series capacitors are not used in general. The possibility of SSR is therefore small. However, if power transmission increases, and accordingly, if shunt compensation increases in amount, there is no guarantee that SSR will never occur. First, we investigate network impedance viewed from a generator. Its resonance frequencies become lower with increasing transmission power. One of them gets subsynchronous if the power exceeds a certain value. In this area, there is some possibility of SSR, which is confirmed with the damping property of the generator. The admittance matrix of the load buses is singular at the resonance frequencies. Their number is equal to the dimension of the matrix. The frequencies are common to all generators but not limited to one particular generator. One of them becomes equal to 60 Hz as we increase transmission power. We regard this power as a limit for SSR. However, steady‐state stability limit is lower than this limit, and steady operation is not possible at the limit. Therefore, it is impossible to enter the area of SSR. Thus, we conclude that SSR does not occur in shunt compensated systems. However, this property is easily lost if some series compensation is introduced. © 1999 Scripta Technica, Electr Eng Jpn, 130(3): 30–38, 2000