Indentation contact behavior of copper-graphite particulate composites: Correlation between the contact parameters and the electrical resistivity

The elastoplastic contact surface deformations of copper-graphite particulate composites are examined in instrumented Vickers/spherical indentation tests. The composites include various contents of metallic Cu-particles with various sizes and shapes originated from the starting powders, that are mixed with flaky natural graphite having various sizes. The elastoplastic surface deformations of the composites are characterized in term of the elastic modulus E′, contact hardness H, and the relative residual depth ξ_r of hardness impression. The surface deformations of the composites are well correlated to their microstructures and electrical resistivities. It is concluded that the evolution of the percolation structures of Cu-phases is essential in controlling the electrical resistivity and the plastic ductility of the composite.     

Current Concepts of Stem Cell Therapy for Chronic Spinal Cord Injury

Chronic spinal cord injury (SCI) is a catastrophic condition associated with significant neurological deficit and social and financial burdens. It is currently being managed symptomatically with no real therapeutic strategies available. In recent years, a number of innovative regenerative strategies have emerged and have been continuously investigated in clinical trials. In addition, several more are coming down the translational pipeline. Among ongoing and completed trials are those reporting the use of mesenchymal stem cells, neural stem/progenitor cells, induced pluripotent stem cells, olfactory ensheathing cells, and Schwann cells. The advancements in stem cell technology, combined with the powerful neuroimaging modalities, can now accelerate the pathway of promising novel therapeutic strategies from bench to bedside. Various combinations of different molecular therapies have been combined with supportive scaffolds to facilitate favorable cell–material interactions. In this review, we summarized some of the most recent insights into the preclinical and clinical studies using stem cells and other supportive drugs to unlock the microenvironment in chronic SCI to treat patients with this condition. Successful future therapies will require these stem cells and other synergistic approaches to address the persistent barriers to regeneration, including glial scarring, loss of structural framework, and immunorejection.     

A concentrator module of spherical Si solar cell

Spherical Si solar cell, which is made up of Si spheres with a diameter of approximately 1.0 mm, is expected to be a promising candidate for low consumption of Si feedstock and simple process technology. This paper describes the formation process and the structure of a concentrator module in detail. The concentrator lens was formed by casting with ultraviolet light hardening resin. The concentration ratio was 4.4 times and the pitch between the spheres was 2.0 mm. By this module design, it was possible to realize a consumption of the Si feedstock of about 3.0 g/W. Conversion efficiencies of 11.3% from single-sphere cell, 8.5% from a 23-spheres module and 5.2% from a 105-spheres module under AM1.5, 100 mW/cm² illumination were achieved.     

Analysis of alcohol oxidase isozymes in gene-disrupted strains of methylotrophic yeast Pichia methanolica

A cell-free extract of methanol-grown Pichia methanolica cells was found to contain nine alcohol oxidase (AOD) isozymes by active staining of a native polyacrylamide electrophoresis gel. Our previous study revealed that AOD in P. methanolica was encoded by two genes, MOD1 and MOD2, and the results of an experiment involving Candida boidinii as an expression host suggested that the AOD isozymes observed in P. methanolica were due to random association of Mod1p and Mod2p into an active octamer [Nakagawa et al., Yeast, 15, 1223-1230 (1999)]. This study was conducted using P. methanolica MOD1- and/or MOD2-gene disrupted strains to confirm a previous hypothesis. While the cell-free extract of the wild-type strain gave nine ladder bands, the mod1delta and mod2delta strains gave a single active AOD band corresponding to the mobilities of Mod2p and Mod1p on a native electrophoresis gel, respectively. The cell-free extract of glyceorl-grown wild-type cells gave a single band corresponding to Mod1p, showing that only MOD1 is expressed in glycerol-grown cells. While the expression of both MOD1 and MOD2 was induced by methanol, this finding and our previous observations indicated that the expression of MOD1 and MOD2 was controlled by a distinct regulatory mechanism in P. methanolica.     

Improved electrochemical activity of LiMnPO4 by high-energy ball-milling

Olivine lithium manganese phosphate (LiMnPO₄) becomes research focus because of its high energy density and improved thermal stability. However, its application in lithium ion batteries suffers severely from poor electrochemical activity due to low conductivity and structural instability upon the charge and discharge process. By applying a high-energy ball-milling method we succeed in improving the capacity delivery and rate capability. LiMnPO₄ materials ball-milled without or with acetylene black are able to deliver a high capacity of 135 and 127 mAh g⁻¹, respectively, more than 50% greater than the pristine one. Particularly, the latter also shows an improved discharge plateau and stable cyclability. High-energy synchrotron radiation X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, laser particle analysis, and galvanostatic charge and discharge are employed to understand the effect of ball-milling on the LiMnPO₄ material.     

Widening of harvesting layer and area of P3HT/PCBM bulk-heterojunction photovoltaic cells

We have fabricated P3HT/PCBM based bulk-heterojunction photovoltaic cells with P3HT layer as the hole transport layer and PCBM layer as the electron transport layer between electrode and blended P3HT/PCBM layer in order to widen the photon harvesting layer. Current density has increased by about 1 mA/cm² by the insertion of P3HT layer and the resulting conversion efficiency has been improved by about 20%. We have also fabricated a centimeter-scale active area with an efficiency of ∼1%.     

Proposal of Design Criteria for Gas Entrainment from Vortex Dimples Based on a Computational Fluid Dynamics Method

Design criteria for gas entrainments (GE) from the liquid surface in a fast breeder reactor system were proposed in this paper for the two types of GE phenomena from a vortex dimple based on a computational fluid dynamics (CFD) method. The first gas entrainment phenomenon is a gas core extension directly to the outlet piping level, which induces large amount of GE to the flow system. The second is continuous bubble detachments from the tip of the vortex dimple. Based on CFD calculations for elemental experiments of the surface vortex, local CFD non-dimensional numbers were defined as the design criteria to prevent GE. In conclusion, it was found that the CFD non-dimensional numbers are useful for the design parameters of GE prevention.     

Open dumping site in Asian developing countries: a potential source of polychlorinated dibenz-p-dioxins and polychlorinated dibenzofurans

Open landfill dumping areas for municipal wastes in Asian developing countries have recently received particular attention with regard to environmental pollution problems. Because of the uncontrolled burning of solid wastes, elevated contamination by various toxic chemicals including dioxins and related compounds in these dumping sites has been anticipated. In this study, concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (PCBs) were determined in soils from dumping sites in the Philippines, Cambodia, India, and Vietnam. Residue concentrations of PCDD/Fs and coplanar PCBs in dumping site soils were apparently greater than those in soils collected in agricultural or urban areas far from dumping sites, suggesting that dumping sites are potential sources of PCDD/Fs and related compounds. Observed PCDD/F concentrations in soils from dumping sites in the Philippines and Cambodia were comparable or higher than those reported for dioxin-contaminated locations in the world (e.g., near the municipal waste incinerators and open landfill dumping sites). Homologue profiles of PCDD/Fs in dumping site soils from the Philippines and, to a lesser extent, from Cambodia and India reflected patterns of samples representing typical emissions, while profiles of agricultural or urban soils were similar to those of typical environmental sinks. This result suggests recent formation of PCDD/Fs in dumping site areas and that open dumping sites are a potential source of dioxins in Asian developing countries. Uncontrolled combustions of solid wastes by waste pickers, generation of methane gas, and low-temperature burning can be major factors for the formation of dioxins in dumping sites. Elevated fluxes of PCDD/Fs to soils in dumping sites were encountered in the Philippines, Cambodia, India, and Vietnam-Hanoi, and these levels were higher than those reported for other countries. Considerable loading rates of PCDD/Fs in the dumping sites of these countries were observed, ranging from 20 to 3900 mg/yr (0.12-35 mg TEQ/yr). PCDD/F concentrations in some soil samples from the Philippines, Cambodia, India, and Vietnam-Hanoi exceeded environmental guideline values, suggesting potential health effects on humans and wildlife living near these dumping sites. The estimated intakes of dioxins via soil ingestion and dermal exposure for children were higher than those for adults, suggesting greater risk of dioxin exposure for children in dumping sites. To our knowledge, this is the first comprehensive study on PCDD/Fs contamination in open dumping sites of Asian developing countries. On the basis of the result of this study, we have addressed a new environmental issue that open dumping sites are potential sources of PCDD/Fs and related compounds, and dioxin contamination in dumping sites may become a key environmental problem in developing countries.     

Lipid peroxidation-derived cytotoxic aldehyde, 4-hydroxy-2-nonenal in smoked pork

The contents of 4-Hydroxy-2-nonenal (HNE), cytotoxic aldehyde, in smoked meat products (ham, bacon and sausage) were analyzed. All the samples analyzed contained HNE, although large differences in the contents between the different samples were observed. In one lot of ham (H1) and wiener sausage (WS1) a high level in HNE was observed. The changes of HNE contents of pork meats containing 0, 0.1, 0.5 and 1% Sugi wood vinegar (SWV) stored at 0?°C were also analyzed for 7 days. As an index of lipid peroxidation level, malonaldehyde (MA) contents were also analyzed in these samples. After 7 days of storage, HNE was detected only in pork meats containing 1% SWV and the level was similar to those of H1 and WS1. Judging from MA contents, SWV may act as a pro-oxidant in pork meats and HNE may accumulate in pork in which lipid peroxidation is in progress.     

Micropatterned organoid culture of rat hepatocytes and HepG2 cells

The culture of liver cell organoids (multicellular aggregates) such as spheroids or cylindroids, which can strongly express liver functions, has been advocated as a useful technique that has advantages over monolayer culture. This paper describes a micropatterning technique for obtaining spheroids and cylindroids by using rat hepatocytes or HepG2 cells. We developed culture chips that comprised multiple, circular or rectangular microwells; the bottom surface of each microwell was modified with collagen to create a cell adhesion area, and the entire microwell, excluding the collagen-coated spots, was modified with polyethylene glycol (PEG) to create a nonadhesive area. Rat hepatocytes and HepG2 cells formed uniform spheroids and cylindroids on the circular and rectangular chips, respectively. Consequently, two-dimensional micropatterned chips containing homogeneous spheroids or cylindroids were generated. The expression of liver functions (protein secretion and ammonia removal) was greater in the spheroids and cylindroids than in the monolayer culture, and this expression was maintained for at least 2 weeks of culture. Thus, this chip technology has potential for use in various applications that involve organoid culture.