Characterization of single quantum wells on GaAs/Si grown bymetalorganic chemical vapor deposition

The use of Al_0.5Ga_0.5As/Al_0.55Ga _0.45P intermediate layers and in-situ thermal cycle annealing are shown to be effective in obtaining smooth and sharp heterointerfaces for Al_0.3Ga_0.7As/GaAs single quantum wells (SQWs) grown on Si substrates, as a result of an initial two-dimensional growth and a reduction in threading dislocation density. The best lasing characteristics are obtained in Al_0.3Ga_0.7As/GaAs SQW laser diodes fabricated using the above structure in comparison to those fabricated using the more conventional two-step growth technique     

On‐chip neural cell cultivation using agarose‐microchamber array constructed by a photothermal etching method

We have developed a novel method for on‐chip cultivation of neural cells in a flexible agarose‐microchamber array on a glass slide. The agarose microchamber is a micrometer‐order cavity constructed on the surface of an agarose layer by molding a 50‐µm‐high square/circular micro‐cast of thick SU‐8 photoresist. In addition, the shape of the agarose microchamber was rearranged by using the photothermal etching method, in which we used an infrared (1064‐nm) focused laser beam as the heat source to melt and remove a portion of agarose gel at the heating spot. With the photothermal etching method, we can also manufacture narrow tunnel‐shaped channels between microchambers. When nerve cells were cultured on the agar‐microchamber array chip, the nerve cells in two adjacent microchambers connected through the photothermal‐etched channel after 48 hours of cultivation. Those results suggest the potential of an agarose‐microchamber array integrated with the photothermal etching method for the next stage of single cell cultivation and measurement of nerve cells, such as real‐time control of cell interactions during cultivation. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(2): 37–42, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10215     

Theoretical analysis of the tensile strength of a powder bed

The authors have proposed an experimental equation which correlates the tensile strength of a powder bed measured by split cell methods with the porosity of a powder bed. In this report, the authors discuss the relationships between the porosity and the pre-compressive stress and also between the tensile strength and the pre-compressive stress. As the results of this discussion, the physical base of the proposed experimental equation is proved theoretically.Furthermore, it has also been proved that the pre-compression of a powder bed brings not only the decrease of the porosity but also the increase of compressive force at the contact point of particles, and therefore the increase of tensile strength by increasing the-compression force cannot be explained simply by the change of the porosity, and then another factor, such as the compressive force at the contact point, must be considered.     

Characterization of texture and mechanical properties of heat-induced soy protein gels

Heat-set gels were prepared from acid-precipitated soybean proteins at various heating temperatures (80–100°C), protein concentrations (18–20%), and proportions of glycinin. The gels were evaluated for mechanical parameters by means of a compression-decompression test. Gels formed at higher heating temperature and protein concentration were firm, tough and unfracturable. The elasticities of the gels were similar at all protein concentrations and were lower when heated at higher temperature. Heating above 93°C was necessary for formation of rigid gels. The glycinin/β-conglycinin ratio affected the texture of the gels. Three-dimensional representation of the gels through factor analysis of instrumental data and calculation of factor scores was useful to evaluate the texture of the gels.     

200 Channel Semiconductor Detectors for X-Ray Computed Tomography

Prototype 200 channel semiconductor detectors for third generation X-ray computed tomography have been developed using surface-barrier diodes fabricated from high-purity n-type silicon. The image reconstruction test was successful, and the relationship between the image quality and the detector characteristics has been studied.     

Involvement of a tyrosyl residue in the interaction of peanut lectin with lactose

The role of a tyrosyl residue in the binding of Arachis hypogaea (peanut) agglutinin, AHA, to lactose has been studied using two techniques, titration of the phenolic hydroxyl group of the tyrosine residue and chemical modification of the tyrosine with iodine. More than three tyrosyl residues per mol of AHA were masked when AHA was titrated in the presence of lactose. Lactose also protected some tyrosyl residues of AHA from the modification with iodine. Upon interaction with lactose, AHA iodinated in the presence of lactose gave a UV-difference spectrum with similar peaks to those of native AHA, while AHA iodinated in the absence of lactose gave a spectrum without such peaks. Though not only native AHA but also iodinated AHA was completely adsorbed on a column of lactamyl-Sepharose 6B, equilibrium dialysis showed that the binding constant and the number of binding sites of native AHA and iodinated AHA with lactose were 4.3 x 10(3) and 3.0 x 10(3) M-1, and 3.2 and 1.8, respectively. These results suggest that about two of four sugar binding sites have tyrosyl residues which induce the UV-difference spectra upon binding with lactose, and that the iodination of these tyrosyl residues results in a decrease of the number of binding sites on AHA.     

Isolation, amino acid sequence and biological activities of novel long-chain polyamine-associated peptide toxins from the sponge Axinyssa aculeata

A novel family of functionalized peptide toxins, aculeines (ACUs), was isolated from the marine sponge Axinyssa aculeate. ACUs are polypeptides with N-terminal residues that are modified by the addition of long-chain polyamines (LCPA). Aculeines were present in the sponge extract as a complex mixture with differing polyamine chain lengths and peptide structures. ACU-A and B, which were purified in this study, share a common polypeptide chain but differ in their N-terminal residue modifications. The amino acid sequence of the polypeptide portion of ACU-A and B was deduced from 3' and 5' RACE, and supported by Edman degradation and mass spectral analysis of peptide fragments. ACU induced convulsions upon intracerebroventricular (i.c.v.) injection in mice, and disrupted neuronal membrane integrity in electrophysiological assays. ACU also lysed erythrocytes with a potency that differed between animal species. Here we describe the isolation, amino acid sequence, and biological activity of this new group of cytotoxic sponge peptides.