H_2 Line Emission Associated with the Formation of the First Stars

Molecular hydrogen line radiation emitted in formation events of first-generation stars are evaluated in a discussion of its detectability by future observational facilities. H_2 luminosity evolution from the onset of prestellar collapse until the formation of a \sim 100 M_{\odot} protostar is followed. Calculations are extended not only to the early phase of the runaway collapse but also to the later phase of accretion, whose observational features have not been studied before. Contrary to the runaway collapse phase, where the pure-rotational lines are always dominant, in the accretion phase rovibrational line emission becomes prominent. The maximum luminosity is also attained in the accretion phase for strong emission lines. The peak intensity of the strongest rovibrational line reaches \sim 10^{-29} (W/m^2), corresponding to the flux density of 10^{-5} (\mu Jy), for a source at the typical redshift of first-generation star formation, 1+z=20. Although the redshifted rovibrational H_2 emission from such an epoch falls in the wavelength range of the next-generation infrared satellite, Space Infrared Telescope for Cosmology and Astrophysics, for exceeding the detection threshold 10^7 such protostars are required to reach the maximum luminosity simultaneously in a pregalactic cloud. It is improbable that this condition is satisfied in a realistic scenario of early structure formation.Comment: 16 pages, 5 figures, accepted by PAS

Results of the search for inspiraling compact star binaries from TAMA300's observation in 2000-2004

We analyze the data of TAMA300 detector to search for gravitational waves from inspiraling compact star binaries with masses of the component stars in the range 1-3Msolar. In this analysis, 2705 hours of data, taken during the years 2000-2004, are used for the event search. We combine the results of different observation runs, and obtained a single upper limit on the rate of the coalescence of compact binaries in our Galaxy of 20 per year at a 90% confidence level. In this upper limit, the effect of various systematic errors such like the uncertainty of the background estimation and the calibration of the detector's sensitivity are included.Comment: 8 pages, 4 Postscript figures, uses revtex4.sty The author list was correcte

Observation results by the TAMA300 detector on gravitational wave bursts from stellar-core collapses

We present data-analysis schemes and results of observations with the TAMA300 gravitational-wave detector, targeting burst signals from stellar-core collapse events. In analyses for burst gravitational waves, the detection and fake-reduction schemes are different from well-investigated ones for a chirp-wave analysis, because precise waveform templates are not available. We used an excess-power filter for the extraction of gravitational-wave candidates, and developed two methods for the reduction of fake events caused by non-stationary noises of the detector. These analysis schemes were applied to real data from the TAMA300 interferometric gravitational wave detector. As a result, fake events were reduced by a factor of about 1000 in the best cases. The resultant event candidates were interpreted from an astronomical viewpoint. We set an upper limit of 2.2x10^3 events/sec on the burst gravitational-wave event rate in our Galaxy with a confidence level of 90%. This work sets a milestone and prospects on the search for burst gravitational waves, by establishing an analysis scheme for the observation data from an interferometric gravitational wave detector

Depletion of Vitamin E Increases Amyloid β Accumulation by Decreasing Its Clearances from Brain and Blood in a Mouse Model of Alzheimer Disease*

Increased oxidative damage is a prominent and early feature in Alzheimer disease. We previously crossed Alzheimer disease transgenic (APPsw) model mice with α-tocopherol transfer protein knock-out (Ttpa−/−) mice in which lipid peroxidation in the brain was significantly increased. The resulting double-mutant (Ttpa−/−APPsw) mice showed increased amyloid β (Aβ) deposits in the brain, which was ameliorated with α-tocopherol supplementation. To investigate the mechanism of the increased Aβ accumulation, we here studied generation, degradation, aggregation, and efflux of Aβ in the mice. The clearance of intracerebral-microinjected 125I-Aβ1–40 from brain was decreased in Ttpa−/− mice to be compared with wild-type mice, whereas the generation of Aβ was not increased in Ttpa−/−APPsw mice. The activity of an Aβ-degrading enzyme, neprilysin, did not decrease, but the expression level of insulin-degrading enzyme was markedly decreased in Ttpa−/− mouse brain. In contrast, Aβ aggregation was accelerated in Ttpa−/− mouse brains compared with wild-type brains, and well known molecules involved in Aβ transport from brain to blood, low density lipoprotein receptor-related protein-1 (LRP-1) and p-glycoprotein, were up-regulated in the small vascular fraction of Ttpa−/− mouse brains. Moreover, the disappearance of intravenously administered 125I-Aβ1–40 was decreased in Ttpa−/− mice with reduced translocation of LRP-1 in the hepatocytes. These results suggest that lipid peroxidation due to depletion of α-tocopherol impairs Aβ clearances from the brain and from the blood, possibly causing increased Aβ accumulation in Ttpa−/−APPsw mouse brain and plasma