7,437 research outputs found
The Helotiales of India-VII
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Possible use of self-calibration to reduce systematic uncertainties in determining distance-redshift relation via gravitational radiation from merging binaries
By observing mergers of compact objects, future gravity wave experiments
would measure the luminosity distance to a large number of sources to a high
precision but not their redshifts. Given the directional sensitivity of an
experiment, a fraction of such sources (gold plated -- GP) can be identified
optically as single objects in the direction of the source. We show that if an
approximate distance-redshift relation is known then it is possible to
statistically resolve those sources that have multiple galaxies in the beam. We
study the feasibility of using gold plated sources to iteratively resolve the
unresolved sources, obtain the self-calibrated best possible distance-redshift
relation and provide an analytical expression for the accuracy achievable. We
derive lower limit on the total number of sources that is needed to achieve
this accuracy through self-calibration. We show that this limit depends
exponentially on the beam width and give estimates for various experimental
parameters representative of future gravitational wave experiments DECIGO and
BBO.Comment: 6 pages, 2 figures, accepted for publication in PR
Constraints on the Growth and Spin of the Supermassive Black Hole in M32 From High Cadence Visible Light Observations
We present 1-second cadence observations of M32 (NGC221) with the CHIMERA
instrument at the Hale 200-inch telescope of the Palomar Observatory. Using
field stars as a baseline for relative photometry, we are able to construct a
light curve of the nucleus in the g-prime and r-prime band with 1sigma=36
milli-mag photometric stability. We derive a temporal power spectrum for the
nucleus and find no evidence for a time-variable signal above the noise as
would be expected if the nuclear black hole were accreting gas. Thus, we are
unable to constrain the spin of the black hole although future work will use
this powerful instrument to target more actively accreting black holes. Given
the black hole mass of (2.5+/-0.5)*10^6 Msun inferred from stellar kinematics,
the absence of a contribution from a nuclear time-variable signal places an
upper limit on the accretion rate which is 4.6*10^{-8} of the Eddington rate, a
factor of two more stringent than past upper limits from HST. The low mass of
the black hole despite the high stellar density suggests that the gas liberated
by stellar interactions was primarily at early cosmic times when the low-mass
black hole had a small Eddington luminosity. This is at least partly driven by
a top-heavy stellar initial mass function at early cosmic times which is an
efficient producer of stellar mass black holes. The implication is that
supermassive black holes likely arise from seeds formed through the coalescence
of 3-100 Msun mass black holes that then accrete gas produced through stellar
interaction processes.Comment: 8 pages, 3 figures, submitted to the Astrophysical Journal, comments
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Geomechanical Studies for a Himalayan Tunnel in Jointed Dolomites: A Case History
Reported case history of Himalayan tunnel reveals that Barton\u27s and Bieniawski\u27s classification systems provide better assessment of the rock mass behavior. The design and shear strength parameters derived from these classifications provided a preliminary design of the tunnel, which has been critically evaluated with the design, adopted at site. Based on the structural feature and ground water conditions, a number of tunnelling conditions have been predicted. The studies indicated the loosening rock pressures would be occuring at site with an estimated range of 0. 25 kg/cm2 to 3. 58 kg/cm2. Problems of roof collapse, flowing ground condition and cavity formation may occur during the excavation. Multiple drift excavation method is suggested for extremely poor conditions
Effects of Gamma Radiation on the concentration of 5 Hydroxy L Tryptophan and 5 Hydroxytryptamine in presence of Radioprotector in Sprague Dawley Rats
The result of variation of 5-hydroxy-L-tryptophan (HT) and S-hydroxytryptamine (S-HT) in different tissues of control and gamma-irradiated Sprague Dawley rats with and without a radioprotector Beeta-amino-ethylisothiuronium bromide hydrobromide (AET) combination e.g. (HT + AET) have been studied. The retention of HT, in the tissues studied, decreased after lethal dose (10.5 Gy) but for 5-HT, no such trend was observed after incorporation of HT + AET. A slight tendency of both metabolites to come back to control level was also observed for Sprague Dawley rats. In urine, concentration of HT was less compared to 5-HT with a lethal dose (10.5 Gy). After incorporation of HT + AET the turnover rate of HT and 5-HT were found to be maximum when it was injected through intraperitoneal route
Soft x-rays absorption and high-resolution powder x-ray diffraction study of superconducting CaxLa(1-x)Ba(1.75-x)La(0.25+x)Cu3Oy system
We have studied the electronic structure of unoccupied states measured by O
K-edge and Cu L-edge x-ray absorption spectroscopy (XAS), combined with crystal
structure studied by high resolution powder x-ray diffraction (HRPXRD), of
charge-compensated layered superconducting CaxLa(1-x)Ba(1.75-x)La(0.25+x)Cu3Oy
(0<x<0.4, 6.4<y<7.3) cuprate. A detailed analysis shows that, apart from hole
doping, chemical pressure on the electronically active CuO2 plane due to the
lattice mismatch with the spacer layers greatly influences the superconducting
properties of this system. The results suggest chemical pressure to be the most
plausible parameter to control the maximum critical temperatures (Tcmax) in
different cuprate families at optimum hole density.Comment: 14 pages, 11 figures, accepted for publication in Journal of Physics
and Chemistry of Solid
Induction of Mutation in Rough Lemon (Citrus jambhiri Lush.) Using Gamma Rays
The present investigation was carried out to study variability induced by gamma rays with respect to vegetative characters and LD50 dose in Rough lemon. Rough lemon seeds were gamma irradiated at doses of 0, 4, 6 and 8 kr along with control. Seed germination decreased with increasing dose of gamma radiation. Seedling height and leaf size also decreased with increasing dose of gamma radiation, whereas, apical branching, number of branches/seedling, number of variegated / albino seedlings and number of leaves increased with increasing dose of gamma radiation. Maximum variability for seedling height, number of leaves, leaf size, colour, internode length, and per cent apical branching was observed at two months from sowing in seeds treated with 8 kr dose of gamma radiation. Variability for all characters was, however, found to be minimum in the control
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