The Radiation Element Method Coupled with the Bioheat Transfer Equation Applied to the Analysis of the Photothermal Effect of Tissues

The purpose of this study is to develop the radiation element method by ray emission method (REM²) code appropriate for coupling with the bioheat transfer equation, and to clarify the photothermal effect of various parameters inside biological tissues. First, the REM², which involves the air-tissue interface effect, is validated with the existing literature. In order to clarify the effects of optical and thermophysical properties of biological tissues, a one-dimensional tissue model of CW light transport and bioheat transfer is employed. The present study provides nondimensional results, which are obtained by varying refractive index, extinction coefficient, scattering albedo, blood perfusion parameter, and conduction-radiation parameter, show valuable guidance for understanding the coupled light and bioheat transport in tissues.     

Attraction to Herbivore-induced Plant Volatiles by the Host-foraging Parasitoid Fly <Emphasis Type="Italic">Exorista japonica</Emphasis>

Responses of the tachinid fly Exorista japonica Townsend to odors from corn plants infested with the fly’s host, the larvae of the noctuid moth Mythimna separata (Walker), were examined in a wind tunnel. Naïve female flies showed a higher rate of landing on M. separata-infested corn plants from which the host larvae had been removed than on artificially damaged or intact corn plants. When paper impregnated with a solution of headspace volatiles collected from host-infested plants was attached to intact plants, females landed on the plants at a high rate. Females also responded to intact plants to which had been attached with paper impregnated with a synthetic blend of nine chemicals identified previously in host-infested plants. There was an optimum concentration of the synthetic blend for the females’ landing. Of the nine chemicals identified previously, four [(E)-4,8-dimethyl-1,3,7-nonatriene, indole, 3-hydroxy-2-butanone, and 2-methyl-1-propanol] released only by host-infested plants were classified as a host-induced blend. The other five [(Z)-3-hexen-1-yl acetate, (E)-2-hexenal, hexanal, (Z)-3-hexen-1-ol, and linalool] were classified as a non-specific blend released not only by infested plants but also by artificially damaged or intact plants. In the wind tunnel, E. japonica females did not respond to intact plants to which paper containing a solution of non-specific blend or host-induced blend was attached. However, they showed a high level of response to a mixture of the non-specific and host-induced blends. These results indicate that naïve E. japonica use a combination of non-specific and host-induced blends as an olfactory cue for locating host-infested plants.     

Practical Design for Improving the Sensitivity to Search for Dark Matter Axions with Rydberg Atoms

A microwave single-photon detector was developed with highly-excited alkaline Rydberg-atoms in a cooled resonant cavity to search for dark matter axions. This detector belongs to a microwave single-photon counter, thus being free from the standard quantum limit (SQL). High sensitivity of the present detector system was demonstrated by measuring the thermal blackbody radiations in the cavity at temperatures as low as 70 mK where the sensitivity is below the SQL. The detection sensitivity of the present system is mainly limited by stray electric fields present in the detection region. Practical design of a new experimental scheme with a guiding electric field through the atomic-beam trajectory is here presented and discussed to avoid the effect of stray electric field and thus to improve the detection sensitivity.      

Improvement of Electrical Contact Between TE Material and Ni Electrode Interfaces by Application of a Buffer Layer

A single ??-structure thermoelectric (TE) module based on p-type NaCo₂O₄, n-type Mg₂Si, and Ni electrode was fabricated by the spark plasma sintering (SPS) method. The NaCo₂O₄ powder was synthesized by using a metal?Ccitric acid complex decomposition method. Bulk Mg₂Si prepared by melt quenching was ground into a powder and sieved to particle size of 75???m or less. To obtain a sintered body of NaCo₂O₄ or Mg₂Si, the powder was sintered using SPS. Pressed Ni powder or mixed powder consisting of Ni and SrRuO₃ powder was inserted between these materials and the Ni electrode in order to connect them, and electrical power was passed through the electrodes from the SPS equipment. The open-circuit voltage (V _OC) values of a single module in which TE materials were connected to the Ni electrodes by using pressed Ni powder was 82.7?mV, and the maximum output current (I _max) and maximum output power (P _max) were 212.4?mA and 6.65?mW at ??T?=?470?K, respectively. On the other hand, V _OC of a single module in which TE materials and an Ni electrode were connected with a mixed powder (Ni:SrRuO₃?=?6:4 volume fraction) was 109?mV, and I _max and P _max were 4034?mA and 109?mW at ??T?=?500?K, respectively. These results indicate that the resistance at the interface between the TE materials and the Ni electrode can be decreased and the output power can be increased by application of a buffer layer consisting of Ni and SrRuO₃.     

Large-scale genome reorganization in Saccharomyces cerevisiae through combinatorial loss of mini-chromosomes

A highly efficient technique, termed PCR-mediated chromosome splitting (PCS), was used to create cells containing a variety of genomic constitutions in a haploid strain of Saccharomyces cerevisiae. Using PCS, we constructed two haploid strains, ZN92 and SH6484, that carry multiple mini-chromosomes. In strain ZN92, chromosomes IV and XI were split into 16 derivative chromosomes, seven of which had no known essential genes. Strain SH6484 was constructed to have 14 mini-chromosomes carrying only non-essential genes by splitting chromosomes I, II, III, VIII, XI, XIII, XIV, XV, and XVI. Both strains were cultured under defined nutrient conditions and analyzed for combinatorial loss of mini-chromosomes. During culture, cells with various combinations of mini-chromosomes arose, indicating that genomic reorganization could be achieved by splitting chromosomes to generate mini-chromosomes followed by their combinatorial loss. We found that although non-essential mini-chromosomes were lost in various combinations in ZN92, one mini-chromosome (18kb) that harbored 12 genes was not lost. This finding suggests that the loss of some combination of these 12 non-essential genes might result in synthetic lethality. We also found examples of genome-wide amplifications induced by mini-chromosome loss. In SH6484, the mitochondrial genome, as well as the copy number of genomic regions not contained in the mini-chromosomes, was specifically amplified. We conclude that PCS allows for genomic reorganization, in terms of both combinations of mini-chromosomes and gene dosage, and we suggest that PCS could be useful for the efficient production of desired compounds by generating yeast strains with optimized genomic constitutions.     

Vacuolar H(+)-ATPase and plasma membrane H(+)-ATPase contribute to the tolerance against high-pressure carbon dioxide treatment in Saccharomyces cerevisiae

As a non-thermal sterilization process, high-pressure carbon dioxide treatment (HPCT) is considered to be promising. The main sterilizing effect of HPCT is thought to be acidification in cytoplasm of microorganisms. We investigated the tolerance mechanism of Saccharomyces cerevisiae to HPCT with special reference to vacuolar and plasma membrane H(+)-ATPases. HPCT was imposed at 35 degrees C, 4 to 10 MPa, for 10 min. slp1 mutant defective in vacuole morphogenesis was more sensitive to HPCT than its isogenic parent. Concanamycin A, a specific inhibitor of vacuolar H(+)-ATPase (V-ATPase), at 10 microM rendered the parent more HPCT-sensitive to the level of slp1. To confirm further the contribution of V-ATPase to the tolerance against HPCT in S. cerevisiae, we compared vma1 mutant of V-ATPase with its isogenic parent for their HPCT sensitivity. vma1 mutant was more sensitive to HPCT than its parent. Addition of 10 microM vanadate, an inhibitor of plasma membrane H(+)-ATPase (P-ATPase), to the wild type strains also increased the inactivation ratio. These results clearly show that V- and P-ATPases contribute to the tolerance against HPCT in S. cerevisiae by accumulating excess H(+) from cytoplasm to vacuole and excluding H(+) outside of the cell, respectively.     

THz-wave absorption by field-induced carriers in pentacene thin-film transistors for THz imaging sensors

Innovative sensing systems based on THz electromagnetic waves have been attracting a great deal of attention. Although many THz detectors have been developed over the years, it is currently difficult to manufacture low-cost THz sensing/imaging devices. In the present study, we propose to use organic field-effect transistors (OFETs) and small potential fluctuation against the carriers within them (N. Ohashi, H. Tomii, R. Matsubara, M. Sakai, K. Kudo, M. Nakamura, Appl. Phys. Lett. 91 (2007) 162105). We use THz time-domain spectroscopy for OFETs in which the carrier density in the pentacene active layer is modulated by the gate bias. We found evidence that the accumulated free holes in pentacene films can be excited by THz photons to overcome the surrounding barriers in the fluctuating potential. The Drude–Lorentz model could not account for the shape of the absorption spectra, which suggests that the holes are weakly restricted by the potential fluctuation. The integrated absorption intensity was proportional to the transfer characteristics of the OFETs. The present findings represent an important step toward developing a new class of THz-wave sensors.     

Dramatic Enhancement of Photoluminescence Quantum Yields for Surface‐Engineered Si Nanocrystals within the Solar Spectrum

Substantial improvements of the absolute photoluminescence quantum yield (QY) for surfactant‐free silicon nanocrystals (Si‐ncs) by atmospheric pressure microplasma 3‐dimensional surface engineering are reported. The effect of surface characteristics on carrier multiplication mechanisms is explored using transient induced absorption and photoluminescence QY. Surface engineering of Si‐ncs is demonstrated to lead to more than 120 times increase in the absolute QY (from 0.1% up to 12%) within an important spectral range of the solar emission (2.3–3 eV). The Si‐ncs QY is shown to be stable when Si‐ncs are stored in ethanol at ambient conditions for three months.     

Influence of separated vortex on aerodynamic noise of an airfoil blade

In order to clarify the mechanism by which aerodynamic noise is generated from separated flow around an airfoil blade, the relation between the attack angle and the aerodynamic noise of the blade was analyzed using a wind tunnel experiment and a CFD code. In the case of rear surface separation, the separated vortex which has a large-scale structure in the direction of the blade chord is transformed into a structure that concentrates at the trailing edge with an increase in the attack angle. The aerodynamic noise level then becomes small according to the vortex scale in the blade chord. When the flow is separated at the leading edge, a separated vortex of low pressure is formed at the vicinity of the trailing edge. The pressure fluctuations on the blade surface at the vicinity of the trailing edge become large due to the vortex in the wake. It is considered that the aerodynamic noise level increases when the flow is separated at the leading edge because the separated vortex is causing the fluctuations due to wake vortex shedding.