4,544 research outputs found
Bulk Viscous Cosmological Models in Barber's Second Self Creation Theory
Barber's second self creation theory with bulk viscous fluid source for an
LRS Bianchi type-I metric is considered by using deceleration parameter to be
constant where the metric potentials are taken as function of and . The
coefficient of bulk viscosity is assumed to be a power function of the mass
density. Some physical and geometrical features of the models are discussedComment: latex, 10 pages, submitted in Int. J. Mod. Phys.
Studying the Variation of the Fine Structure Constant Using Emission Line Multiplets
As an extension of the method by Bahcall et al. (2004) to investigate the
time dependence of the fine structure constant, we describe an approach based
on new observations of forbidden line multiplets from different ionic species.
We obtain optical spectra of fine structure transitions in [Ne III], [Ne V], [O
III], [OI], and [SII] multiplets from a sample of 14 Seyfert 1.5 galaxies in
the low-z range 0.035 < z < 0.281. Each source and each multiplet is
independently analyzed to ascertain possible errors. Averaging over our sample,
we obtain a conservative value alpha^2(t)/\alpha^2(0) = 1.0030+-0.0014.
However, our sample is limited in size and our fitting technique simplistic as
we primarily intend to illustrate the scope and strengths of emission line
studies of the time variation of the fine structure constant. The approach can
be further extended and generalized to a "many-multiplet emission line method"
analogous in principle to the corresponding method using absorption lines. With
that aim, we note that the theoretical limits on emission line ratios of
selected ions are precisely known, and provide well constrained selection
criteria. We also discuss several other forbidden and allowed lines that may
constitute the basis for a more rigorous study using high-resolution
instruments on the next generation of 8 m class telescopes.Comment: 20 pages, 4 figures, sumbitted to A
One qubit almost completely reveals the dynamics of two
From the time dependence of states of one of them, the dynamics of two
interacting qubits is determined to be one of two possibilities that differ
only by a change of signs of parameters in the Hamiltonian. The only exception
is a simple particular case where several parameters in the Hamiltonian are
zero and one of the remaining nonzero parameters has no effect on the time
dependence of states of the one qubit. The mean values that describe the
initial state of the other qubit and of the correlations between the two qubits
also are generally determined to within a change of signs by the time
dependence of states of the one qubit, but with many more exceptions. An
example demonstrates all the results. Feedback in the equations of motion that
allows time dependence in a subsystem to determine the dynamics of the larger
system can occur in both classical and quantum mechanics. The role of quantum
mechanics here is just to identify qubits as the simplest objects to consider
and specify the form that equations of motion for two interacting qubits can
take.Comment: 6 pages with new and updated materia
The Influence of High-Energy Lithium Ion Irradiation on Electrical Characteristics of Silicon and GaAs Solar Cells
Space-grade Si and GaAs solar cells were irradiated with 15 & 40 MeV Li ions.
Illuminated (AM0 condition) and unilluminated I-V curves reveal that the effect
of high-energy Li ion irradiation has produced similar effects to that of
proton irradiation. However, an additional, and different, defect mechanism is
suggested to dominate in the heavier-ion results. Comparison is made with
proton-irradiated solar-cell work and with non-ionizing energy-loss (NIEL)
radiation-damage models.Comment: 8 pages, 12 figures, Data presented at 2006 NSREC, Final Version to
be published in IEEE Transactions on Nuclear Science, 53, NO. 6, December
2006. Index Terms: GaAs, Ion-irradiation, Lithium, NIEL, Photovoltaic cells,
Radiation effects, Silico
Synthetic perspective optical flow: Influence on pilot control tasks
One approach used to better understand the impact of visual flow on control tasks has been to use synthetic perspective flow patterns. Such patterns are the result of apparent motion across a grid or random dot display. Unfortunately, the optical flow so generated is based on a subset of the flow information that exists in the real world. The danger is that the resulting optical motions may not generate the visual flow patterns useful for actual flight control. Researchers conducted a series of studies directed at understanding the characteristics of synthetic perspective flow that support various pilot tasks. In the first of these, they examined the control of altitude over various perspective grid textures (Johnson et al., 1987). Another set of studies was directed at studying the head tracking of targets moving in a 3-D coordinate system. These studies, parametric in nature, utilized both impoverished and complex virtual worlds represented by simple perspective grids at one extreme, and computer-generated terrain at the other. These studies are part of an applied visual research program directed at understanding the design principles required for the development of instruments displaying spatial orientation information. The experiments also highlight the need for modeling the impact of spatial displays on pilot control tasks
Hydrodynamic changes due to large seabed installations in coastal waters off west coast of India
Offshore marine environment can very well be utilized for mass storage of liquids which are not harmful to that environment. Improper placement of large tanks on the seabed, to store large quantities of liquids, would adversely affect the hydrodynamics of adjoining environment. Thorough understanding on the hydrodynamics of the adjoining environment is thus required before and after placing such tanks so as to properly plan the placement of these large tanks. A two dimensional numerical hydrodynamic model is used to study influence of placing large number of tanks in a dynamic marine environment. Cylindrical tanks (5 m dia.) are arranged in three rows with 50 tanks placed in each row with their length (100 m) aligned perpendicular to the coast. These tanks cover an area of about 36000 m2 and are placed on seabed in water depths about 15 m. Hydrodynamic simulations carried out with tidal forcing for cases of (a) before and (b) after placement of tanks showed that current speeds increase up to 65% in the region where the tanks are placed compared to currents without placement of tanks. However, up to 85% increase in current speeds is observed in regions beyond the tanks. In this manuscript results of the effects on the hydrodynamics of a region due to placing large number of tanks in shallow waters are presented
Final Report of the Commission to Address the Unfunded Liability of the MSRS and the Equity of Retirement Benefits for State Employees and Teachers
The possibility of cryopreservingBalanus amphitrite(Cirripedia; thoracica) nauplii is explored. The effects on the postthaw survival of a range of cryobiological variables are reported; three different cryoprotectants (ethylene glycol, EG; dimethyl sulfoxide, Me<SUB>2</SUB>SO; and glycerol, GL), the influence of the final temperature (−20, −30, −40, and −50°C), and the effect of transferring to liquid nitrogen (−196°C) were studied. The larvae showed increasing susceptibility to cryoprotectant concentration. Equilibration of larvae for 15 min at 5°C with each of the cryoprotectants revealed that GL was the least toxic. EG at 3 to 4Mdid not cause marked damage as the equilibration period was extended up to 2 h. This was not true with Me<SUB>2</SUB>SO and GL. The postthaw survival rate decreased as the final temperature was reduced, and none of the larvae revived after thawing from −50°C. The postthaw survival with 2 mol/liter EG as the cryoprotectant ranged from 86% after cooling to −20°C to 56% after cooling to −40°C. The larvae that were transferred to liquid nitrogen from different temperatures revealed that the greatest survival (36%) was achieved when the larvae were transferred from −40 to −196°C. When the larvae were reared after cooling to −40°C and then transferring to liquid nitrogen, the rate of subsequent metamorphosis was 30% in the case of EG at 3M. Me<SUB>2</SUB>SO and GL gave results that were inferior in comparison to those obtained with EG
Bio-Prospecting of a Few Brown Seaweeds for Their Cytotoxic and Antioxidant Activities
Methanolic extracts (MEs) of seven brown seaweeds occurring in the Indian coastal waters were screened for their cytotoxic and antioxidant properties following various assays. The methanolic extracts of seaweeds in the order of Dictyopteris australis > Spatoglossum variabile > Stoechospermum marginatum > Spatoglossum aspermum showed significant cytotoxic activity. A very high DPPH radical scavenging activity was exhibited by the methanolic extracts prepared from St. marginatum, Padina tetrastromatica, Dictyopteris delicatula and S. aspermum. The total phenolic content of the MEs varied from 13.19 ± 0.32 to 25.29 ± 0.445 gallic acid equivalents (mg g−1 of methanolic extract). The reducing power assay indicated a dose dependency, at concentrations of 0.1, 0.5 and 1.0 and 2.0 mg mL−1 of MEs and decreased in the following order: Butylated hydroxy toluene > P. tetrastromatica > D. delicatula > S. aspermum > S. variabile > S. marginatum > D. australis > S. marginatum. Furthermore, D. australis, S. aspermum, S. variabile and S. marginatum demonstrated good metal ion chelating properties. All the above evidences suggest that, the antioxidant compounds found in brown seaweeds scavenge free radicals through effective intervention. This decisively promotes them as a potential source of natural antioxidants
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