57 research outputs found
Performance of a Time-Projection-Chamber with a Large-Area Micro-Pixel-Chamber Readout
A micro time-projection-chamber (micro-TPC) with a detection volume of
23*28*31 cm^3 was developed, and its fundamental performance was examined. The
micro-TPC consists of a micro pixel chamber with a detection area of 31*31 cm^2
as a two-dimensional imaging device and a gas electron multiplier with an
effective area of 23*28 cm^2 as a pre-gas-multiplier. The micro-TPC was
operated at a gas gain of 50,000, and energy resolutions and spatial
resolutions were measured.Comment: 4 pages, 7 figures, proceedings of IWORID
Direction-sensitive dark matter search results in a surface laboratory
We developed a three-dimensional gaseous tracking device and performed a
direction-sensitive dark matter search in a surface laboratory. By using 150
Torr carbon-tetrafluoride (CF_4 gas), we obtained a sky map drawn with the
recoil directions of the carbon and fluorine nuclei, and set the first limit on
the spin-dependent WIMP (Weakly Interacting Massive Particles)-proton cross
section by a direction-sensitive method. Thus, we showed that a WIMP-search
experiment with a gaseous tracking device can actually set limits. Furthermore,
we demonstrated that this method will potentially play a certain role in
revealing the nature of dark matter when a low-background large-volume detector
is developed.Comment: 9 figures, accepted for publication in Phys. Lett.
Mao-to Prolongs the Survival of and Reduces TNF-α Expression in Mice with Viral Myocarditis
Goal of this study was to evaluate effects of Mao-to on development of myocarditis induced by encephalomyocarditis (EMC) virus in mice. Mice were randomly divided into five groups. Group N included uninfected controls (n = 18), while group A, B and C underwent intraperitoneal injection of EMC virus. Group A was administered oral saline from day 0 to day 4. Group B was administered oral Mao-to (500 mg−1 kg−1 day−1) from day 0 to day 4. Group C was administered Mao-to from day 2 to day 6. Group D was administered Mao-to from day 5 to day 10. Treated mice were followed for survival rates during 2 weeks after infection. Body weight (BW) and organ weights including heart (HW), lungs, thymus and spleen were examined on days 4, 6 and 14. Survival rate of group C (36.4%) was significantly improved compared with group A, B or D (0% of each, P < 0.05). HW and HW/BW ratio in group C was significantly (P < 0.05) lower than those in group A, B or D. Viral titers of hearts were significantly different among groups A, B and C. Cardiac expression in tumor necrosis factor-α (TNF-α) was significantly reduced in group C in comparison with group A, B or D on day 6 by immunohistochemical study. Administration of Mao-to starting on day 2 improves mortality resulting from viral myocarditis in mice with reduced expression of cardiac TNF-α. These findings suggest that timing of Mao-to is crucial for preventing cardiac damage in mice with viral myocarditis
First underground results with NEWAGE-0.3a direction-sensitive dark matter detector
A direction-sensitive dark matter search experiment at Kamioka underground
laboratory with the NEWAGE-0.3a detector was performed. The NEWAGE- 0.3a
detector is a gaseous micro-time-projection chamber filled with CF4 gas at 152
Torr. The fiducial volume and target mass are 20*25*31 cm3 and 0.0115 kg,
respectively. With an exposure of 0.524 kgdays, improved spin-dependent weakly
interacting massive particle (WIMP)-proton cross section limits by a
direction-sensitive method were achieved including a new record of 5400 pb for
150 GeV/c2 WIMPs. We studied the remaining background and found that ambient
gamma-rays contributed about one-fifth of the remaining background and
radioactive contaminants inside the gas chamber contributed the rest.Comment: 21 pages, 8 figures, to appear in Physics Letters
Development of an atmospheric Cherenkov imaging camera for the CANGAROO-III experiment
A Cherenkov imaging camera for the CANGAROO-III experiment has been developed
for observations of gamma-ray induced air-showers at energies from 10 to
10 eV. The camera consists of 427 pixels, arranged in a hexagonal shape
at 0.17 intervals, each of which is a 3/4-inch diameter photomultiplier
module with a Winston-cone--shaped light guide. The camera was designed to have
a large dynamic range of signal linearity, a wider field of view, and an
improvement in photon collection efficiency compared with the CANGAROO-II
camera. The camera, and a number of the calibration experiments made to test
its performance, are described in detail in this paper.Comment: 25 pages, 29 figures, elsart.cls, to appear in NIM-
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