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Heusler-type Fe2VAl thermoelectric materials have been processed by high-pressure torsion (HPT) to improve their thermoelectric performance through a drastic reduction of the thermal conductivity. While the thermal conductivity for Fe2VTa0.05Al0.95 is about 10 W/m K at 300 K, it is reduced to about 5.0 W/m K due to HPT processing. Furthermore, even after annealing at 873 K for recurrence of the Heusler-type structure, Ta-doped Fe2VTa0.05Al0.95 possesses an ultra-fine grained structure with an average grain size of about 80 nm, in contrast to the presence of large grains of about 270 nm for non-doped Fe2V1.05Al0.95. Since scanning transmission electron microscopy combined with energy-dispersive X-ray analysis reveals the solute segregation of Ta along grain boundaries and recrystallization interfaces, the retardation of recrystallization could be caused by the solute drag effect, leading to a suppression of grain coarsening. Thus, it is possible to retain the low thermal conductivity of about 5.0 W/m K at 300 K for Fe2VTa0.05Al0.95, in parallel with the restoration of a large power factor, so that the dimensionless figure of merit reaches ZT = 0.30 at around 500 K. [ABSTRACT FROM AUTHOR]

A 1T cryocooler-cooled oxide superconducting pulsed coil, which is a 16 layer solenoidal coil wound with an interlayer-transposed 4-strand parallel conductor composed of Bi2223 multifilamentary flat wires is fabricated. The thermal properties of the cryocooler-cooled oxide superinducting pulsed coil is described, taking into account the heat generation of ac loss and flux-flow loss and the cooling capacity of a cryocooler Ac loss and the cooling capacity of the cryocooler have been studied.

Four-dimensional (4-D) computed tomography (CT) is a dynamic volume imaging system of moving organs with an image quality comparable to conventional CT and it is realized by continuous and high-speed cone-beam CT. We have developed a novel two-dimensional (2-D) detector for 4-D CT, which is based on the present CT technology, and mounted it on the gantry frame of the state-of-the-art CT-scanner. In the present paper, we describe the design and the performance evaluation results of the first model of the 4-D CT-scanner. The X-ray detector for the 4-D CT-scanner is a discrete pixel detector in which pixel data are measured from independent detector elements. The numbers of elements are 912 (channels) x 256 (segments) and the element size is approximately 1 mm x 1 mm. Data sampling rate is 900 views (frames)/s and the dynamic range of the A/D converter is 16 bits. The rotation speed of the gantry is 1.0 s/rotation. The data transfer system between rotating and stationary parts in the gantry consists of laser diode and photodiode pairs and it achieves a net transfer speed of 5 Gbps. Volume data of 512 x 512 x 256 voxels are reconstructed with an Feldkamp-Davis-Kress (FDK) algorithm by parallel use of microprocessors. The image characteristics such as noise, uniformity, and spatial resolution were evaluated with stationary phantoms in a single rotation. Exposure dose to an object was measured with an extension of the standard measurement method of CT dose index (CTDI). Several volunteers were scanned to explore clinical potentials. For the 4-D CT-scanner, the image characteristics of stationary objects were almost the same as that of conventional CT, while CTDI of the 4-D CT was slightly higher than that of conventional CT. Isotropic resolving power of less than 0.5 mm was achieved for the stationary object. Index Terms--Dynamic volume imaging, four-dimensional computed tomography (4-D CT), phantom study.

Development and testing of a cryocooler-cooled superconducting pulse coil is described and discussed.

Venous diseases like iliofemoral deep vein thrombosis and valvular dysfunction induce venous hypertension. To know the effects of the hypertension on venous mechanics, blood pressure in the left femoral vein in the rabbit was chronically elevated by the constriction of the left external iliac vein. Wall dimensions and biomechanical properties of the femoral vein were studied in vitro at 1, 2, or 4 wk after surgery. Blood pressure measured immediately before the animal was killed was significantly higher in the left femoral vein than in the sham-operated, contralateral vein. Wall thickness was increased by blood pressure elevation even at I wk, which restored circumferential wall stress to a control level. The stress was kept at normal up to 4 wk. Vascular tone and vascular contractility were increased by the elevation of blood pressure; however, wall elasticity and compliance were kept at a normal level. These results are very similar to those observed in hypertensive arteries, indicating that not only arteries but veins optimally operate against blood pressure elevation. hypertrophy; remodeling; wall stress