InGaAs quantum dots formed in tetrahedral-shaped recesses on GaAs (111)B grown by metalorganic chemical vapor deposition

Novel semiconductor quantum dots (QDs), grown in tetrahedral-shaped recesses (TSRs) formed on a (111)B GaAs substrate, are described from both material science and device application points of view. After explaining the fabrication procedure for TSRs, growth of InGaAs QDs and their optical properties are explained. It is revealed that an InGaAs QD of indium-rich chemical composition is formed spontaneously at the bottom of each TSR. The mechanism of the QD formation is discussed in detail. It is proved from magneto-photoluminescence that the QDs actually have optical properties peculiar to zero-dimensional confinement. Several experimental results indicating excellent growth controllability of the QDs are presented. Finally, recent challenges to apply the QDs to electronic memory devices are reported. Two kinds of devices, where the position of individual QD is artificially controlled, are proposed for the first time and the preliminary experimental results are explained.     

Production of a Novel Proanthocyanidin-free Barley Line With High Quality

A proanthocyanidin-free (ant-free) barley with improved quality, Mokkei 92–130, was bred from the cross between Ant 13–347, an ant-free mutant and Haruna Nijo, a Japanese malting barley variety. The malting and brewing quality of the line are described in this paper, while its agronomic performance will be summarised elsewhere. Mokkei 92–130 achieved high levels in some malting quality character including hot water extract, diastatic power and apparent attenuation limit, which were significantly low in most of the ant-free lines and varieties previously reported. Cell wall degradation was also improved. Overall malting quality was found to be satisfactory in Mokkei 92–130. Pilot-scale brewing trials showed that Mokkei 92–130 had superior colloidal stability (less haze formed) in its final beer compared with the normal counterparts. Beer brewed with ant-free barley at a pilot-scale performed as well as the standard production in sensory evaluations soon after bottling, although it was rated poorer than the control after one month storage at ambient temperature.     

Phase separation mechanism during membrane formation by dry‐cast process

Phase separation mechanisms during the membrane formation by dry‐cast process were investigated by light scattering in the cellulose acetate/dimethylformamide (DMF)/2‐methyl‐2,4‐pentanediol system. Phase separation occurred by spinodal decomposition (SD) when paths of the composition changes due to the evaporation of DMF were close to the critical point in the phase diagram. Characteristic properties of the early stage of SD such as an apparent diffusion coefficient and an interface periodic distance were obtained from the Cahn theory. Phase separation occurred by nucleation and growth (NG) when paths of the composition changes were far from the critical point. SEM observation confirmed that the membrane formed by the SD mechanism had interconnected structure, whereas that by the NG mechanism had the closed cell porous structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 776–782, 2000     

Three-Dimensional Culture of Cartilage Tissue on Nanogel-Cross-Linked Porous Freeze-Dried Gel Scaffold for Regenerative Cartilage Therapy: A Vibrational Spectroscopy Evaluation

This study presents a set of vibrational characterizations on a nanogel-cross-linked porous freeze-dried gel (NanoCliP-FD gel) scaffold for tissue engineering and regenerative therapy. This scaffold is designed for the in vitro culture of high-quality cartilage tissue to be then transplanted in vivo to enable recovery from congenital malformations in the maxillofacial area or crippling jaw disease. The three-dimensional scaffold for in-plate culture is designed with interface chemistry capable of stimulating cartilage formation and maintaining its structure through counteracting the dedifferentiation of mesenchymal stem cells (MSCs) during the formation of cartilage tissue. The developed interface chemistry enabled high efficiency in both growth rate and tissue quality, thus satisfying the requirements of large volumes, high matrix quality, and superior mechanical properties needed in cartilage transplants. We characterized the cartilage tissue in vitro grown on a NanoCliP-FD gel scaffold by human periodontal ligament-derived stem cells (a type of MSC) with cartilage grown by the same cells and under the same conditions on a conventional (porous) atelocollagen scaffold. The cartilage tissues produced by the MSCs on different scaffolds were comparatively evaluated by immunohistochemical and spectroscopic analyses. Cartilage differentiation occurred at a higher rate when MSCs were cultured on the NanoCliP-FD gel scaffold compared to the atelocollagen scaffold, and produced a tissue richer in cartilage matrix. In situ spectroscopic analyses revealed the cell/scaffold interactive mechanisms by which the NanoCliP-FD gel scaffold stimulated such increased efficiency in cartilage matrix formation. In addition to demonstrating the high potential of human periodontal ligament-derived stem cell cultures on NanoCliP-FD gel scaffolds in regenerative cartilage therapy, the present study also highlights the novelty of Raman spectroscopy as a non-destructive method for the concurrent evaluation of matrix quality and cell metabolic response. In situ Raman analyses on living cells unveiled for the first time the underlying physiological mechanisms behind such improved chondrocyte performance.     

Selenoprotein P Concentrations in the Cerebrospinal Fluid and Serum of Individuals Affected by Amyotrophic Lateral Sclerosis,Mild Cognitive Impairment and Alzheimer’s Dementia

Selenoprotein P, a selenium-transporter protein, has been hypothesized to play a role in the etiology of neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and Alzheimer’s dementia (AD). However, data in humans are scarce and largely confined to autoptic samples. In this case–control study, we determined selenoprotein P concentrations in both the cerebrospinal fluid (CSF) and the serum of 50 individuals diagnosed with ALS, 30 with AD, 54 with mild cognitive impairment (MCI) and of 30 controls, using sandwich enzyme-linked immunosorbent assay (ELISA) methods. We found a positive and generally linear association between CSF and serum selenoprotein P concentrations in all groups. CSF selenoprotein P and biomarkers of neurodegeneration were positively associated in AD, while for MCI, we found an inverted-U-shaped relation. CSF selenoprotein P concentrations were higher in AD and MCI than in ALS and controls, while in serum, the highest concentrations were found in MCI and ALS. Logistic and cubic spline regression analyses showed an inverse association between CSF selenoprotein P levels and ALS risk, and a positive association for AD risk, while an inverted-U-shaped relation with MCI risk emerged. Conversely, serum selenoprotein P concentrations were positively associated with risk of all conditions but only in their lower range. Overall, these findings indicate some abnormalities of selenoprotein P concentrations in both the central nervous system and blood associated with ALS and neurocognitive disorders, though in different directions. These alterations may reflect either phenomena of etiologic relevance or disease-induced alterations of nutritional and metabolic status.     

Numerical Prediction of Eutectic Temperature Using a Multi-phase-Field Model

To evaluate the reliability of metal-carbon eutectic systems as fixed points for the next generation of the international temperature scale, the effect of the eutectic microstructure on the temperature at the solid/liquid (s/l) interface during solidification and melting is preliminarily investigated using a multi-phase-field model. First, the effects of furnace temperature, lamellar spacing, and interface energy on the average temperature of the s/l interface are studied in the solidification process. With increased furnace undercooling, the s/l interface temperature was found to decrease. Calculated eutectic microstructures are then adopted as initial conditions for a melting simulation. The interface undercooling during melting is observed to be smaller than that observed during solidification. This difference in interface undercooling is attributed to the solute/solvent concentration profiles in the liquid phase near the s/l interface being different for melting and solidification.     

Impact-damage visualization in CFRP by resistive heating: Development of a new detection method for indentations caused by impact loads

Rapid and automatic inspection of composite aircraft after every flight would reduce the safety factor and allow for more flights. Although, an electrical resistance change method (ERCM) has been proposed, there are many problems with its practical application. In this study, a new diagnostic method, impact-damage visualization, was developed. Indentation damage increases fiber-fiber contact at the interlaminar interface and electrical conductivity. Consequently, electrical current applied to the material will concentrate around the damaged area, and lead to selective and intense resistive heating. This temperature increase can be observed by thermography or detected as a change in electrical resistance caused by the temperature difference. The proposed method had sufficient reliability and sensitivity for practical application as a damage inspection method.     

Nanogel bottom-up gel biomaterials for protein delivery: Photopolymerization of an acryloyl-modified polysaccharide nanogel macromonomer

Polysaccharide nanogels are one of the most attractive carriers for drug delivery systems. Nanogels encapsulate proteins in their hydrated polymer networks, and minimize the denaturation of proteins. In this study, we demonstrated the cross-linking of acryloyl group-modified polysaccharide nanogels via photopolymerization, which allowed the formation of novel hydrogel particles and macrogels. The mechanical properties of the resultant hydrogels depended on the concentrations of the nanogels and the cross-linkers. The most significant property of the nanogel-cross-linked hydrogel was the ability to encapsulate insulin via hydrophobic interactions. After incubation of the hydrogel containing insulin in water, the hydrogel was degraded by hydrolysis, and insulin was gradually released from the hydrogels over a period of 1 week. According to these results, this nanogel-cross-linked hydrogel prepared via photopolymerization has potential for innovative biomaterials.     

Possible role of dentin matrix in region-specific deposition of cellular and acellular extrinsic fibre cementum

The mechanism whereby a region-specific deposition of the two types of cementum (cellular cementum and acellular extrinsic fibre cementum) is regulated on the growing root surface was tested using bisphosphonate-affected teeth of young rats and guinea pigs. The animals were injected subcutaneously with 8 or 10 mg P x kg body weight(-1) x day(-1) of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) for 1 or 2 weeks. In rat molars, HEBP prevented mineralization of newly formed root dentin matrix and totally inhibited de novo deposition of acellular extrinsic fibre cementum. Instead, thick cellular cementum was induced on the non-mineralized root dentin surface, irrespective of the position of the root. In both animals, cellular cementum was also induced on the non-mineralized surface of root analogue dentin in HEBP-affected incisors, where only acellular extrinsic fibre cementum is deposited under normal conditions. In normal rat molars, dentin sialoprotein (DSP) was concentrated along the dentin-cellular cementum border, but not that of dentin and acellular extrinsic fibre cementum. In HEBP-affected rat incisors, DSP was shown to penetrate through the non-mineralized dentin into the surrounding tissues, but not through the mineralized portions. These data suggest that, at the site of cellular cementum formation, putative inducing factors for cellular cementum might diffuse into the periodontal space through the newly deposited mantle dentin matrix before it is mineralized. At earlier stages of root formation, mantle dentin might mineralize more promptly not to allow such diffusion. The timing of mineralization of mantle dentin matrix might be the key determinant of the types of the cementum deposited on the growing root surface.     

Effect of diluents on membrane formation via thermally induced phase separation

The effect of diluents on isotactic polypropylene (iPP) membrane formation via thermally induced phase separation was investigated. The diluents were methyl salicylate (MS), diphenyl ether (DPE), and diphenylmethane (DPM). The cloud-point curve was shifted to a lower temperature in the order iPP–MS, iPP–DPE, and iPP–DPM, whereas the crystallization temperature was not influenced so much by diluent type. Droplet-growth processes were investigated under two conditions: quenching the polymer solution at the desired temperature and cooling at a constant rate. Although droplet sizes were in the order iPP–MS, iPP–DPE, and iPP–DPM in both cases, the difference was more pronounced with the constant cooling rate condition. Scanning electron microscopy indicated that interconnected structures were obtained when the polymer solution was quenched in ice water. The effect of the diluents on these structures was observed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 169–177, 2001