79 research outputs found
LRRK2 A419V is not associated with Parkinson's disease in different Chinese populations
10.1371/journal.pone.0036123PLoS ONE77
The Supernova Relic Neutrino Background
An upper bound to the supernova relic neutrino background from all past Type
II supernovae is obtained using observations of the Universal metal enrichment
history. We show that an unambiguous detection of these relic neutrinos by the
Super-Kamiokande detector is unlikely. We also analyze the event rate in the
Sudbury Neutrino Observatory (where coincident neutrons from anti-nu_e + D -->
n + n + e+ might enhance background rejection), and arrive at the same
conclusion. If the relic neutrino flux should be observed to exceed our upper
bound and if the observations of the metal enrichment history (for z<1) are not
in considerable error, then either the Type II supernova rate does not track
the metal enrichment history or some mechanism may be responsible for
transforming anti-nu_{mu,tau} --> anti-nu_e.Comment: Matches version accepted for publication in Phys. Rev.
SPECTRA OF YOUNG GALAXIES
Invited review, Ringberg conference on "Galaxies in the Young Universe"
(Sept94)Comment: 12 pages, uuencoded compressed Postscript fil
Low-mass pre--main-sequence stars in the Magellanic Clouds
[Abridged] The stellar Initial Mass Function (IMF) suggests that sub-solar
stars form in very large numbers. Most attractive places for catching low-mass
star formation in the act are young stellar clusters and associations, still
(half-)embedded in star-forming regions. The low-mass stars in such regions are
still in their pre--main-sequence (PMS) evolutionary phase. The peculiar nature
of these objects and the contamination of their samples by the evolved
populations of the Galactic disk impose demanding observational techniques for
the detection of complete numbers of PMS stars in the Milky Way. The Magellanic
Clouds, the companion galaxies to our own, demonstrate an exceptional star
formation activity. The low extinction and stellar field contamination in
star-forming regions of these galaxies imply a more efficient detection of
low-mass PMS stars than in the Milky Way, but their distance from us make the
application of special detection techniques unfeasible. Nonetheless, imaging
with the Hubble Space Telescope yield the discovery of solar and sub-solar PMS
stars in the Magellanic Clouds from photometry alone. Unprecedented numbers of
such objects are identified as the low-mass stellar content of their
star-forming regions, changing completely our picture of young stellar systems
outside the Milky Way, and extending the extragalactic stellar IMF below the
persisting threshold of a few solar masses. This review presents the recent
developments in the investigation of PMS stars in the Magellanic Clouds, with
special focus on the limitations by single-epoch photometry that can only be
circumvented by the detailed study of the observable behavior of these stars in
the color-magnitude diagram. The achieved characterization of the low-mass PMS
stars in the Magellanic Clouds allowed thus a more comprehensive understanding
of the star formation process in our neighboring galaxies.Comment: Review paper, 26 pages (in LaTeX style for Springer journals), 4
figures. Accepted for publication in Space Science Review
Dust in Supernovae and Supernova Remnants I : Formation Scenarios
Supernovae are considered as prime sources of dust in space. Observations of local supernovae over the past couple of decades have detected the presence of dust in supernova ejecta. The reddening of the high redshift quasars also indicate the presence of large masses of dust in early galaxies. Considering the top heavy IMF in the early galaxies, supernovae are assumed to be the major contributor to these large amounts of dust. However, the composition and morphology of dust grains formed in a supernova ejecta is yet to be understood with clarity. Moreover, the dust masses inferred from observations in mid-infrared and submillimeter wavelength regimes differ by two orders of magnitude or more. Therefore, the mechanism responsible for the synthesis of molecules and dust in such environments plays a crucial role in studying the evolution of cosmic dust in galaxies. This review summarises our current knowledge of dust formation in supernova ejecta and tries to quantify the role of supernovae as dust producers in a galaxy.Peer reviewe
Numerical Simulation on the Photovoltaic Behavior of an Amorphous-Silicon Nanowire-Array Solar Cell
In this letter, we propose an amorphous-silicon (a-Si) solar cell with a nanowire-array structure. The proposed structure has photon absorption and carrier transport that are perpendicular to each other, which could overcome the efficiency limit of an a-Si solar cell. This nanowire structure has an n-type a-Si nanowire array in which the i-layer and the p-layer a-Si are sequentially grown along the surface of the nanowire. Under illumination, light is absorbed along the axial direction of the nanowire, and carrier transport is along the radial direction. Numerical simulations show that the photocurrent of the a-Si solar cell with a 4000-nm-long nanowire is nearly 40% more than that of a planar a-Si solar cell. A conversion efficiency of 11.6% was obtained, which is around 32% enhancement
Stable polymer dielectric film for polythiophene thin film transistor on modified poly(vinyl-phenol) with polar functional group
In this work, a modified poly(vinyl phenol) (MPVP) polymer dielectric solution with high permittivity and resistant to moisture was used. The MPVP was synthesized by replacing the hydroxyl group in PVP with. a polar amino functional group. The material properties of polymer films were characterized by nuclear magnetic resonance (NMR) analysis, get permeation chromatography (GPC), and thermogravimetric analysis (TGA). Dielectric layers properties were analyzed by current-voltage and capacitance-voltage measurement of a metal-dielectric-metal capacitor and a polythiophene (P3HT) polymer transistor. The stable leakage current, permittivity and output characteristic indicate that MPVP is suitable for a large-area continues-printing process
DNA Damage during the Spindle-Assembly Checkpoint Degrades CDC25A, Inhibits Cyclin–CDC2 Complexes, and Reverses Cells to Interphase
Cell cycle checkpoints that monitor DNA damage and spindle assembly are essential for the maintenance of genetic integrity, and drugs that target these checkpoints are important chemotherapeutic agents. We have examined how cells respond to DNA damage while the spindle-assembly checkpoint is activated. Single cell electrophoresis and phosphorylation of histone H2AX indicated that several chemotherapeutic agents could induce DNA damage during mitotic block. DNA damage during mitotic block triggered CDC2 inactivation, histone H3 dephosphorylation, and chromosome decondensation. Cells did not progress into G(1) but seemed to retract to a G(2)-like state containing 4N DNA content, with stabilized cyclin A and cyclin B1 binding to Thr14/Tyr15-phosphorylated CDC2. The loss of mitotic cells was not due to cell death because there was no discernible effect on caspase-3 activation, DNA fragmentation, or viability. Extensive DNA damage during mitotic block inactivated cyclin B1-CDC2 and prevented G(1) entry when the block was removed. The mitotic DNA damage responses were independent of p53 and pRb, but they were dependent on ATM. CDC25A that accumulated during mitosis was rapidly destroyed after DNA damage in an ATM-dependent manner. Ectopic expression of CDC25A or nonphosphorylatable CDC2 effectively inhibited the dephosphorylation of histone H3 after DNA damage. Hence, although spindle disruption and DNA damage provide conflicting signals to regulate CDC2, the negative regulation by the DNA damage checkpoint could overcome the positive regulation by the spindle-assembly checkpoint
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