70 research outputs found
Antifouling activity of crude extracts from some Red Sea soft corals
EnThe antifouling activity of crude extracts of 5 common Red Sea soft corals was examined. The extracts were mixed with a marine paint, applied to PVC panels immersed in the seawater of Suez Bay (Red Sea). The barnacle Balanus amphitrite (Crustacea) and tube worms Hydroides elegans (Polychaeta) are the dominant fouling organisms in this area. The results demonstrated that all the tested soft coral extracts exhibited significant antifouling activities with varying degrees. Extracts of Sinularia heterospiculata and Sinularia variabilis showed the highest and potent wide spectrum antifouling activity, particularly in the first 17 days of fouling formation. Extracts of Sinularia polydactyla exhibited significant selective inhibition against settlement of barnacle, while the extracts of Lithophyton arboreum showed significant antifouling activity against the latter successional stages of tube worms. The results of the current study propose that these soft corals may contain bioactive compounds with antifouling activity. These bioactive molecules can be isolated, purified, identified and chemically synthesized for commercial uses in the development of nontoxic and environmentally acceptable antifouling coatings
L.R.S. Bianchi type II Stiff Fluid cosmological model with Decaying Vacuum Energy Density in general relativity
Locally rotationally symmetric (L.R.S.) Bianchi type II stiff fluid
cosmological model is investigated. To get the deterministic model of the
universe, we have assumed a condition between metric potentials
where is the constant. It is shown that the vacuum energy density
is positive and proportional to . The values of
deceleration parameter , matter-energy density and dark-energy
density are found to be in good agreement with the values
obtain from 5-years WMAP observations. the predicted value of the jerk
parameter agrees with the SNLS SNIa and X-ray galaxy cluster distance data but
does not with the SNIa gold sample data. In general, the model represent
accelerating, shearing and non-rotating universe.The physical and geometrical
behavior of these models are also discussed
Scientometrics Profile of the Banasthali Vidyapith: A Deemed University of Rajasthan, India
The current investigation work utilized bibliometric and visualization techniques. Scopus bibliographic database sources used to retrieve data. Two thousand seven hundred sixty-four (2764) papers retrieved by applying the \u27Affiliation\u27 in Scopus\u27 simple search section. Biblioshiny (3.0), MS-Access, Excel, and VOS Viewer software used to analyze data and bibliometric indicator extraction employ to evaluate the research productivity of Banasthali University for a period of twenty-one years from 2000 to 2020. This data analysis leads to monitor the university\u27s past and present status to maps its future perspectives. This study ventured to examine the overall performance of the faculties and researchers of the Banasthali University in research productivity and publications. The study concerned on finding the year-wise distribution of the publications, author\u27s keywords ID, period, average citations per documents, top-ranked subjects, authors, most distinguished and productive author, author appearances, single-authored documents, multi-authored documents, top-ranked publications, co-authors per documents, co-authorship index, degree of collaboration based on the collected data and information gathered
A study of the angular size-redshift relation for models in which decays as the energy density
By modifying the Chen and Wu ansatz, we have investigated some Friedmann
models in which varies as . In order to test the consistency of
the models with observations, we study the angular size - redshift relation for
256 ultracompact radio sources selected by Jackson and Dodgson. The angular
sizes of these sources were determined by using very long-baseline
interferometry in order to avoid any evolutionary effects. The models fit the
data very well and require an accelerating universe with a positive
cosmological constant. Open, flat and closed models are almost equally
probable, though the open model provides a comparatively better fit to the
data. The models are found to have intermediate density and imply the existence
of dark matter, though not as much as in the canonical Einstein-de Sitter
model.Comment: LaTex, 15 pages including 2 figures (Revised version appeared in CQG
Higher Dimensional Dust Cosmological Implications of a Decay Law for Term : Expressions for Some Observable Quantities
In this paper we have considered the multidimensional cosmological
implications of a decay law for term that is proportional to , where is a constant and is the scale factor
of RW-space time. We discuss the cosmological consequences of a model for the
vanishing pressure for the case . It has been observed that such models
are compatible with the result of recent observations and cosmological term
gradually reduces as the universe expands. In this model
varies as the inverse square of time, which matches its natural units. The
proper distance, the luminosity distance-redshift, the angular diameter
distance-redshift, and look back time-redshift for the model are presented in
the frame work of higher dimensional space time. The model of the Freese {\it
et al.} ({\it Nucl. Phys. B} {\bf 287}, 797 (1987)) for is retrieved for
the particular choice of and also Einstein-de Sitter model is obtained
for . This work has thus generalized to higher dimensions the
well-know result in four dimensional space time. It is found that there may be
significant difference in principle at least, from the analogous situation in
four dimensional space time.Comment: 10 pages, no figure, to be appear in IJMP
Kaluza-Klein Type Robertson Walker Cosmological Model With Dynamical Cosmological Term
In this paper we have analyzed the Kaluza-Klein type Robertson Walker (RW)
cosmological models by considering three different forms of variable :
, and
. It is found that, the connecting free parameters of the
models with cosmic matter and vacuum energy density parameters are equivalent,
in the context of higher dimensional space time. The expression for the look
back time, luminosity distance and angular diameter distance are also derived.
This work has thus generalized to higher dimensions the well-known results in
four dimensional space time. It is found that there may be significant
difference in principle at least, from the analogous situation in four
dimensional space time.Comment: 16 pages, no figur
Statefinder Parameter for Varying G in Three Fluid System
In this work, we have considered variable G in flat FRW universe filled with
the mixture of dark energy, dark matter and radiation. If there is no
interaction between the three fluids, the deceleration parameter and
statefinder parameters have been calculated in terms of dimensionless density
parameters which can be fixed by observational data. Also the interaction
between three fluids has been analyzed due to constant . The statefinder
parameters also calculated in two cases: pressure is constant and pressure is
variable.Comment: 5 pages, Accepted for publication in "Astrophysics and Space Science
Generation of Bianchi type V cosmological models with varying -term
Bianchi type V perfect fluid cosmological models are investigated with
cosmological term varying with time. Using a generation technique
(Camci {\it et al.}, 2001), it is shown that the Einstein's field equations are
solvable for any arbitrary cosmic scale function. Solutions for particular
forms of cosmic scale functions are also obtained. The cosmological constant is
found to be decreasing function of time, which is supported by results from
recent type Ia supernovae observations. Some physical aspects of the models are
also discussed.Comment: 16 pages, 3 figures, submitted to CJ
Plane-symmetric inhomogeneous magnetized viscous fluid universe with a variable
The behavior of magnetic field in plane symmetric inhomogeneous cosmological
models for bulk viscous distribution is investigated. The coefficient of bulk
viscosity is assumed to be a power function of mass density . The values of cosmological constant for these models are
found to be small and positive which are supported by the results from recent
supernovae Ia observations. Some physical and geometric aspects of the models
are also discussed.Comment: 18 pages, LaTex, no figur
FRW Cosmology with Variable G and Lambda
We have considered a cosmological model of the FRW universe with variable
and . The solutions have been obtained for flat model with particular
form of cosmological constant. The cosmological parameters have also been
obtained for dust, radiation and stiff matter. The statefinder parameters are
analyzed and have shown that these depends only on and . Further
the lookback time, proper distance, luminosity distance and angular diameter
distance have also been calculated for our model.Comment: 14 pages, 4 figure
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