Multimodal characteristics of a piezoelectric lead zirconate titanate element impacted with iron particles having velocities above 20 km/s

The responses of a piezoelectric lead zirconate titanate (PZT) element to hypervelocity collisions were experimentally studied. In this study, the particles of masses ranging from 0.3 to 10 fg were made to collide with PZT at velocities between 20 and 96 km/s. The amplitude and the corresponding rise time of the single-pulse output signals that were produced in the piezoelectric PZT element were measured to determine the possible collision states. The results revealed an apparently multimodal output; three classes were assumed to be involved in the pulse formation mechanism. The amplitude and rise time were sensitive to the collision velocity. The multimodal behavior implied that the PZT-based cosmic dust detectors should be calibrated according to the class they belong to.     

Ground-based millimeter-wave observations of water vapor emission (183 GHz) at Atacama,Chile

We report the first results of ground-based millimeter-wave measurements of 183 GHz atmospheric water vapor spectra from Atacama highland (4800 m alt.), Chile. The measurements were carried out in December 2005 by using a spectroscopic radiometer equipped with a superconductive heterodyne receiver. A conspicuous H₂O spectrum at 183 GHz was detected with an integration time of only 1.5 min, and this is the first high frequency-resolution H₂O spectrum at 183 GHz obtained in the southern subtropical region. The vertical profile of H₂O volume mixing ratio between 40 and 64 km were retrieved from the spectrum by using the modified optimal estimation method.     

Characteristics of piezoelectric lead zirconate titanate multilayered detector bombarded with hypervelocity iron particles

A cosmic dust detector is currently being developed using a piezoelectric lead zirconate titanate (PZT) element. The characteristics of the multilayered detector (MD), which was composed of one hundred PZT disks, were investigated by bombarding it with hypervelocity iron particles supplied by a Van de Graaff accelerator. It was confirmed that there was a linear relationship between the signal amplitude observed from MD and the momentum of the particles. As compared with the single-layered detector (SD) that was composed of one PZT disk, it was found that the sensitivity of MD was ∼3 times higher than that of SD within the limits of the experimental conditions.     

Bone metabolism and formation of mice bred in a 2 G environment.

The purpose of this study is to reveal the effect of chronic hypergravity exposure on the bone formation and the bone metabolism when mammals produce offspring in a 2 G environment. We measured the length and width of the thighbone, the length of the pelvis, the width of the pelvic cavity and the width of the fourth cervical vertebra on the second (F2) and the third (F3) generation mice bred in a 2 G environment every ten days from 20 days old to 60 days old in an experiment on bone formation. In an experiment on bone metabolism, we measured calcium and phosphorus in the bones of the F3 in the 2 G group. Ratios of the thighbone length, pelvis length, pelvic cavity width, and fourth cervical vertebra width versus the body length were calculated. These ratios were higher in the 2 G group than the control group during all measuring periods. Calcium and phosphorus concentrations in the thighbone and the lumbar vertebra were lower in the 2 G group than in the control group. However, the calcium and phosphorus concentrations in the cervical vertebrae of the 2G group were higher. These results suggest that the influence of gravity load may vary in the bones.     

Response of a pentagonal PZT element as a component of a 4π-real-time detector

The detector characteristics of a pentagonal element were studied by colliding it with hypervelocity micro-particles. A charge-sensitive amplifier was developed for the element of its capacitance ∼10 nF. The output amplitudes were expressed as a linear function of the momentum at collision. Empirical formulas obtained from on-ground experiments could be used for the calibration of the detector. The pentagonal element was potential to measure the momentum during collision from the output amplitude. A set of electrodes on the surface was used to confirm the measurement of the coordinates at collision. A possible application of this pentagonal element on a real-time dust detector was discussed.