213 research outputs found
Gravitational Lens Systems to probe Extragalactic Magnetic Fields
The Faraday rotation measurements of multiply-imaged gravitational lens
systems can be effectively used to probe the existence of large-scale ordered
magnetic fields in lensing galaxies and galaxy clusters. The available sample
of lens systems appears to suggest the presence of a coherent large-scale
magnetic field in giant elliptical galaxies somewhat similar to the spiral
galaxies.Comment: 11 pages, 1 figur
Does Viscosity turn inflation into the CMB and
Consideration of the entropy production in the creation of the CMB leads to a
simple model of the evolution of the universe during this period which suggests
a connection between the small observed acceleration term and the early
inflation of a closed universe. From this we find an unexpected relationship
between the Omega's of cosmology and calculate the total volume of the
universe.Comment: 8 pages , 2 figure
On the magnetic field required for driving the observed angular-velocity variations in the solar convection zone
A putative temporally varying circulation-free magnetic-field configuration
is inferred in an equatorial segment of the solar convection zone from the
helioseismologically inferred angular-velocity variation, assuming that the
predominant dynamics is angular acceleration produced by the azimuthal Maxwell
stress exerted by a field whose surface values are consistent with photospheric
line-of-sight measurements.Comment: to appear in MNRA
Role of the scalar field in gravitational lensing
A static and circularly symmetric lens characterized by mass and scalar
charge parameters is constructed. For the small values of the scalar charge to
the mass ratio, the gravitational lensing is qualitatively similar to the case
of the Schwarzschild lens; however, for large values of this ratio the lensing
characteristics are significantly different. The main features are the
existence of two or nil Einstein ring(s) and a radial critical curve, formation
of two or four images and possibility of detecting three images near the lens
for sources located at relatively large angular positions. Such a novel lens
may also be treated as a naked singularity lens.Comment: 11 pages using A&A LaTex, 3 figures included, misprints corrected,
changes in section five, two references added Journal- ref : Astronomy &
Astrophysics, 337(1) 1 (1998
Temporal Variations in the Sun's Rotational Kinetic Energy
AIM: To study the variation of the angular momentum and the rotational
kinetic energy of the Sun, and associated variations in the gravitational
multipole moments, on a timescale of the solar cycle. METHOD: Inverting
helioseismic rotational splitting data obtained by the Global Oscillation
Network Group and by the Michelson Doppler Imager on the Solar and Heliospheric
Observatory. RESULTS: The temporal variation in angular momentum and kinetic
energy at high latitudes (>\pi/4) through the convection zone is positively
correlated with solar activity, whereas at low latitudes it is anticorrelated,
except for the top 10% by radius where both are correlated positively.
CONCLUSION: The helioseismic data imply significant temporal variation in the
angular momentum and the rotational kinetic energy, and in the gravitational
multipole moments. The properties of that variation will help constrain
dynamical theories of the solar cycle.Comment: To appear in Astronomy & Astrophysic
Convective instability in the solar envelope
The characteristics of the most unstable fundamental mode and the first harmonic excited in the convection zone of a variety of solar envelope models are shown to be in reasonable agreement with the observed features of granulation and supergranulation
Applications of satellite technology to broadband ISDN networks
Two satellite architectures for delivering broadband integrated services digital network (B-ISDN) service are evaluated. The first is assumed integral to an existing terrestrial network, and provides complementary services such as interconnects to remote nodes as well as high-rate multicast and broadcast service. The interconnects are at a 155 Mbs rate and are shown as being met with a nonregenerative multibeam satellite having 10-1.5 degree spots. The second satellite architecture focuses on providing private B-ISDN networks as well as acting as a gateway to the public network. This is conceived as being provided by a regenerative multibeam satellite with on-board ATM (asynchronous transfer mode) processing payload. With up to 800 Mbs offered, higher satellite EIRP is required. This is accomplished with 12-0.4 degree hopping beams, covering a total of 110 dwell positions. It is estimated the space segment capital cost for architecture one would be about 250M. The net user cost is given for a variety of scenarios, but the cost for 155 Mbs services is shown to be about $15-22/minute for 25 percent system utilization
Cost-effectiveness Study of Antihypertensive Drugs in Mumbai, India
Hypertension is a serious global public health problem. It accounts for 10% of all deaths in India and is the leading noncommunicable disease.1 Recent studies have shown that the prevalence of hypertension is 25% in urban and 10% in rural people in India.2 It exerts a substantial public health burden on cardiovascular health status and health care systems in India.3 Antihypertensive treatment effectively reduces hypertension-related morbidity and mortality.1 The cost of medications has always been a barrier to effective treatment
The gravitational lens system 2016+112 revisited
In the light of recently reported observations of the triple radio source 2016+112 by Schneider et al. (1985, 1986), gravitational lens models of this system are constructed based on two lens galaxies and a cluster. Various observations of this multiply imaged quasar system, including some of the features accompanying object C, are reasonably well reproduced. The admissible lens models involve a five-image configuration with two merging images rather than just three images. In this respect this lens system is analogous to the triple quasar 1115+080. In the models the emission line regions accompanying images A and B arise from two distinct sources. A measurement of time delays, a relation between conceivable VLBI structures associated with images, and further radio observations of the object C as possible tests of the lens models are suggested
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