Development of an Mg2Si Unileg Thermoelectric Module Using Durable Sb-Doped Mg2Si Legs

Mg₂Si unileg structure thermoelectric (TE) modules, which are composed only of n-type Mg₂Si legs, were fabricated using Sb-doped Mg₂Si. The Mg₂Si TE legs used in our module were fabricated by a plasma-activated sintering method using material produced from molten commercial doped polycrystalline Mg₂Si, and, at the same time, nickel electrodes were formed on the Mg₂Si using a monobloc plasma-activated sintering technique. The source material used for our legs has a ZT value of 0.77 at 862 K. The TE modules, which have dimensions of 21 mm × 30 mm × 16 mm, were composed of ten legs that were connected in series electrically using nickel terminals, and the dimensions of a single leg were 4.0 mm  × 4.0 mm × 10 mm. From evaluations of the measured output characteristics of the modules, it appeared that the electrical resistance of the wiring that is used to connect each leg considerably affects the power output of the unileg module. Thus, we attempted to reduce the wiring resistance of the module and fabricated a module using copper terminals. The observed values of the open-circuit voltage and output power of the Sb-doped Mg₂Si unileg module were 496 mV and 1211 mW at ΔT = 531 K (hot side: 873 K; cool side: 342 K).     

THE DESIGNS OF HIGH EFFICIENCY LAUNCHER OF QUASI-OPTICAL MODE CONVERTER FOR HIGH POWER GYROTRONS

A high efficiency launcher of quasi-optical (QO) mode converters for high power gyrotrons have been designed and tested. A helical cut launcher radiates the RF power via its straight cut onto the first phase correcting mirror. The launchers have been optimized for the TE_31.8 mode at 170 GHz and TE_22.6 mode at 110 GHz by numerically optimizing a launcher surface. The helical cut of the launcher has been optimized by taking the taper angle into account. Further more, the amplitude of the surface perturbation have been optimized for improved focusing in order to reduce the diffraction losses at the helical cut. Low power measurement shows a good agreement with the design. High efficiency characteristics of the design have also been calculated on the assumption of frequency downshift due to the thermal expansion of the cavity and stepwise frequency tuning by changing the operating mode. Besides, the possibility of high efficiency launcher for higher mode is discussed, and these results give the prospect to high efficiency long pulse gyrotrons.     

Low-Temperature Thermoelectric Properties of Co<Subscript>0.9</Subscript>Fe<Subscript>0.1</Subscript>Sb<Subscript>3</Subscript>-Based Skutterudite Nanocomposites with FeSb<Subscript>2</Subscript> Nanoinclusions

Bulk thermoelectric nanocomposite materials have great potential to exhibit higher ZT due to effects arising from their nanostructure. Herein, we report low-temperature thermoelectric properties of Co_0.9Fe_0.1Sb₃-based skutterudite nanocomposites containing FeSb₂ nanoinclusions. These nanocomposites can be easily synthesized by melting and rapid water quenching. The nanoscale FeSb₂ precipitates are well dispersed in the skutterudite matrix and reduce the lattice thermal conductivity due to additional phonon scattering from nanoscopic interfaces. Moreover, the nanocomposite samples also exhibit enhanced Seebeck coefficients relative to regular iron-substituted skutterudite samples. As a result, our best nanocomposite sample boasts a ZT = 0.041 at 300 K, which is nearly three times as large as that for Co_0.9Fe_0.1Sb₃ previously reported.     

Calculation method for computer-generated holograms with cylindrical basic object light by using a graphics processing unit

It takes an enormous amount of time to calculate a computer-generated hologram (CGH). A fast calculation method for a CGH using precalculated object light has been proposed in which the light waves of an arbitrary object are calculated using transform calculations of the precalculated object light. However, this method requires a huge amount of memory. This paper proposes the use of a method that uses a cylindrical basic object light to reduce the memory requirement. Furthermore, it is accelerated by using a graphics processing unit (GPU). Experimental results show that the calculation speed on a GPU is about 65 times faster than that on a CPU.     

Characterization of D-galacturonate reductase purified from the psychrophilic yeast species Cryptococcus diffluens

An efficient method for the direct extraction of yeast genomic DNA from agave must was developed. The optimized protocol, which was based on silica-adsorption of DNA on microcolumns, included an enzymatic cell wall degradation step followed by prolonged lysis with hot detergent. The resulting extracts were suitable templates for subsequent qPCR assays that quantified mixed yeast populations in artisan Mexican mezcal fermentations.     

PIXE analysis of trace elements in northern fur seal teeth

Trace elements in teeth of northern fur seal Collorhinus ursinus were analyzed by PIXE and micro-PIXE (μ-PIXE). Trace elements such as Mn, Fe, Zn, Cu, As, Br, Sr, and Pb were detected in the teeth, which were composed of hydroxyapatite crystals. Among these elements, the concentrations of Fe and Zn were relatively higher in winter and lower in summer and also Zn varied along with growth of individuals. These elemental fluctuation seems to correspond to the life history of the northern fur seal. It suggests that the PIXE analysis will make a powerful tool to reconstruct the life history.     

Antibody fragments as inhibitors of Japanese radish acid phosphatase

VH (heavy-chain variable region) and VL (light-chain variable region) genes were amplified by PCR from hybridomas producing MAb-11 and MAb-18 which inhibited Japanese radish acid phosphatase. Nucleotide sequencing of the V genes demonstrates that the MAbs contained similar VH and identical VL domains. Initially, the VH and VL genes were expressed in Escherichia coli as single-chain Fv (ScFv) fragments. Fragments ScFv-11 and ScFv-18, named for MAb-11 and MAb-18, respectively, inhibited the enzyme activity to the same extent as the intact MAbs. Both of the antibody fragments widely cross-reacted with other phosphatases, including some phosphomonoesterases and phosphodiesterases from different sources. ScFv-18 also inhibited acid phosphatase from a different origin, but stimulated the activity of alkaline phosphatase from calf intestine. The PCR-amplified VH and VL genes were subsequently expressed separately in Escherichia coli as fusion products with glutathione S-transferase. The fusion proteins had little effect on Japanese radish acid phosphatase. Furthermore, a large number of recombinant ScFv fragments specific to the acid phosphatase were generated by using a bacteriophage expression system and a mouse ScFv gene library. These ScFv fragments had a range of effects on the enzyme activity, including inhibition, stimulation, and none. Among them, an ScFv fragment, designated ScFv-G7, inhibited more strongly than ScFv-11 and ScFv-18.