Infrared light charge injector as a tool for the study of silicon detectors

In order to study the local response of silicon strip detectors, we have developed a local charge generator using near-infrared ligh emitting diode. The edge properties of the strip detectors were studied precisely with this tool. In the case of our tested detector, the lateral extension of the depletion area was measured to be about 120 μm at a bias voltage of 40 V.     

Work in progress. Intraoperative neurosurgical ultrasound: localization of brain tumors in infants and children

Intraoperative real-time ultrasonic sector scanning was performed through the unincised dura mater or the intact brain surface of eight patients (aged six months to 13 years), each of whom had a previously documented mass lesion (four supratentorial, three infratentorial, one intraventricular). In each case, there was a clear definition of the location, configuration, and tissue consistency of the mass. With the exception of a choroid plexus papilloma, all lesions demonstrated both solid and fluid components. The location of a subcortical parietal lobe mass (ependymoma) was apparent only by prior sonography. All neoplastic tissue of one cerebellar astrocytoma that was identified at gross examination was removed, but additional intraoperative scanning following removal of the neoplasm suggested the presence of residual abnormal tissue. This was confirmed during further exploration, and additional gross tumor tissue was excised.     

Enhanced tumor metastases in rats following cryosurgery of primary tumor

The incidence of tumor metastases was studied in WKA/Hok rats after cryosurgery and surgical excision of primary tumors. When rats with syngeneic fibrosarcoma, KMT-17, were treated by cryosurgery 5 days after transplantation of the tumor, 15 out of 31 rats (48.4%) died with tumor metastases. In contrast only 4 out of 34 (11.8%) died with tumor metastasis after surgical excision. Because tumor cells either in the regional lymph nodes or in the peripheral blood were already detectable in about half of the rats treated by either cryosurgery or surgical excision, mechanical and physical control of enhanced metastasis by cryosurgery is ruled out. The development of anti-tumor immunity was delayed in the rats treated by cryosurgery as compared with that in rats treated by surgical excision. This was investigated by means of Winn's assay. A marked reduction of tumor metastasis was seen after the surgical removal of cryonecrotized tumor tissue, while implantations of cryonecrotized tumor tissue into the rats treated by surgical excision resulted in an increment of metastasis. The mechanism of the enhanced metastasis observed in this experimental investigation is discussed from an immunological point of view.     

Static recrystallization simulations starting from predicted deformation microstructure by coupling multi-phase-field method and finite element method based on crystal plasticity

We have developed a numerical model of recrystallization taking the inhomogeneities of the plastic deformation of a polycrystalline metal into account. Here, the plastic deformation of the polycrystalline metal is simulated by the finite element method based on crystal plasticity theory and the microstructure evolution during recrystallization is simulated by the multi-phase-field method. In primary recrystallization simulations, nucleation is the most difficult problem. In the present model, the deformation microstructure is predicted from the results of a crystal plasticity finite element simulation, and spontaneous nucleation is achieved through abnormal grain growth that is enabled by introducing the misorientation dependences of grain boundary energy and mobility. As a result of simulations under three different compression strains, it is confirmed that primary recrystallization simulations depending on the amount of deformation and taking the inhomogeneities of the plastic deformation of a polycrystalline metal into consideration can be successfully performed by employing the proposed model.     

Photoanodic response of iron oxide electrode in aqueous solution and its application to Pb removal under visible light irradiation

The iron oxide electrode was prepared from thermal oxidation of iron at 600 °C for 3 h in air atmosphere. This electrode with the structure of Fe₃O₄ and α-Fe₂O₃ showed the response of photoanodic current to the light with wavelength shorter than 600 nm. The band gap energy of this electrode was 1.99 eV. The onset potential of distinct steady photocurrent and also the flatband potential were 0.80 and 0.09 V vs. Ag/AgCl, respectively, in 0.1 M HNO₃ aqueous solution. The cell consisting of the iron oxide photoanode in HNO₃-Pb(NO₃)₂ and the graphite cathode in H₂SO₄-Ce(SO₄)₂ caused the PbO₂ deposit on the surface of the former electrode due to visible light irradiation without application of voltage. By holding the potential of this electrode at more positive value than 0.90 V, the photoanodic removal rate of Pb²⁺ in HNO₃-Pb(NO₃)₂ solution was higher than that observed when Ce⁴⁺ was used as electron acceptor.     

A motif detection and classification method for peptide sequences using genetic programming

An exploration of common rules (property motifs) in amino acid sequences has been required for the design of novel sequences and elucidation of the interactions between molecules controlled by the structural or physical environment. In the present study, we developed a new method to search property motifs that are common in peptide sequence data. Our method comprises the following two characteristics: (i) the automatic determination of the position and length of common property motifs by calculating the physicochemical similarity of amino acids, and (ii) the quick and effective exploration of motif candidates that discriminates the positives and negatives by the introduction of genetic programming (GP). Our method was evaluated by two types of model data sets. First, the intentionally buried property motifs were searched in the artificially derived peptide data containing intentionally buried property motifs. As a result, the expected property motifs were correctly extracted by our algorithm. Second, the peptide data that interact with MHC class II molecules were analyzed as one of the models of biologically active peptides with buried motifs in various lengths. Twofold MHC class II binding peptides were identified with the rule using our method, compared to the existing scoring matrix method. In conclusion, our GP based motif searching approach enabled to obtain knowledge of functional aspects of the peptides without any prior knowledge.     

Onset and growth of wrinkles in thin square plates subjected to diagonal tension

A corner type constitutive equation is developed using the general quadratic anisotropic yield function. The wrinkling point of square plates subjected to diagonal tension was obtained by the bifurcation and Mindlin type plate theories, in conjunction with the finite element approximation. The growth of wrinkles was traced by a three-dimensional analysis in terms of an isoparametric shell element.

The numerical investigation was performed for the thin plates characterized by Hill's anisotropic yield function. The effects of such material characteristics as yield stress, hardening rate, orthotropy and normal anisotropy on the wrinkling limit and wrinkle height have been clarified.     

Axisymmetric deformation of circular elastic-plastic tubes under axial tension and internal pressure

The axisymmetric bifurcation and post-bifurcation behaviour of circular tubes subjected to the combined action of axial tension and internal pressure are investigated numerically using the finite element method. It is assumed that the tubes are made of elastic-plastic strain hardening material with a smooth yield surface and that they deform without shear stress at both ends under the proportional stress path based on the stress values averaged over the cross-section.The bifurcation point and associated mode shape are obtained for each stress path. The initial to medium nonuniform deformation was studied for several specific stress paths and the growth of necking of the tube wall and swelling of the middle plane due to bifurcation are clarified.