2,693 research outputs found
Shell Crossing Singularities in Quasi-Spherical Szekeres Models
We investigate the occurrence of shell crossing singularities in
quasi-spherical Szekeres dust models with or without a cosmological constant.
We study the conditions for shell crossing singularity both from physical and
geometrical point of view and they are in agreement.Comment: 10 latex pages, RevTex style, no figure
A study of higher dimensional inhomogeneous cosmological model
In this paper we present a class of exact inhomogeneous solutions to
Einstein's equations for higher dimensional Szekeres metric with perfect fluid
and a cosmological constant. We also show particular solutions depending on the
choices of various parameters involved and for dust case. Finally, we examine
the asymptotic behaviour of some of these solutions.Comment: 9 Latex pages, No figure, Revtex styl
The study of gravitational collapse model in higher dimensional space-time
We investigate the end state of the gravitational collapse of an
inhomogeneous dust cloud in higher dimensional space-time. The naked
singularities are shown to be developing as the final outcome of non-marginally
bound collapse. The naked singularities are found to be gravitationally strong
in the sense of Tipler .Comment: 6 Latex pages, No figure, Revtex styl
Origin of the anomalous magnetic circular dichroism spectral shape in ferromagnetic (Ga,Mn)As: Impurity bands inside the band gap
The electronic structure of a prototype dilute magnetic semiconductor (DMS),
Ga1-xMnxAs, is studied by magnetic circular dichroism (MCD) spectroscopy. We
prove that the optical transitions originated from impurity bands cause the
strong positive MCD background. The MCD signal due to the E0 transition from
the valence band to the conduction band is negative indicating that the p-d
exchange interactions between the p-carriers and d-spin is antiferromagnetic.
The negative E0 MCD signal also indicates that the hole-doping of the valence
band is not so large as previously assumed. The impurity bands seem to play
important roles for the ferromagnetism of Ga1-xMnxAs.Comment: 13 pages, 3 figure
Emergent Universe with Exotic Matter in Brane World Scenario
In this work, we have examined the emergent scenario in brane world model for
phantom and tachyonic matter. For tachyonic matter field we have obtained
emergent scenario is possible for closed, open and at model of the universe
with some restriction of potential. For normal scalar field the emergent
scenario is possible only for closed model and the result is identical with the
work of Ellis et al [2], but for phantom field the emergent scenario is
possible for closed, open and at model of the universe with some restriction of
potential
Spin - Phonon Coupling in Nickel Oxide Determined from Ultraviolet Raman Spectroscopy
Nickel oxide (NiO) has been studied extensively for various applications
ranging from electrochemistry to solar cells [1,2]. In recent years, NiO
attracted much attention as an antiferromagnetic (AF) insulator material for
spintronic devices [3-10]. Understanding the spin - phonon coupling in NiO is a
key to its functionalization, and enabling AF spintronics' promise of
ultra-high-speed and low-power dissipation [11,12]. However, despite its status
as an exemplary AF insulator and a benchmark material for the study of
correlated electron systems, little is known about the spin - phonon
interaction, and the associated energy dissipation channel, in NiO. In
addition, there is a long-standing controversy over the large discrepancies
between the experimental and theoretical values for the electron, phonon, and
magnon energies in NiO [13-23]. This gap in knowledge is explained by NiO
optical selection rules, high Neel temperature and dominance of the magnon band
in the visible Raman spectrum, which precludes a conventional approach for
investigating such interaction. Here we show that by using ultraviolet (UV)
Raman spectroscopy one can extract the spin - phonon coupling coefficients in
NiO. We established that unlike in other materials, the spins of Ni atoms
interact more strongly with the longitudinal optical (LO) phonons than with the
transverse optical (TO) phonons, and produce opposite effects on the phonon
energies. The peculiarities of the spin - phonon coupling are consistent with
the trends given by density functional theory calculations. The obtained
results shed light on the nature of the spin - phonon coupling in AF insulators
and may help in developing innovative spintronic devices.Comment: 16 pages; 2 figure
Rolling Element Bearing Condition Monitoring using Filtered Acoustic Emission
The defect present in the bearing of a rolling element may affect the performance of the rotating machinery and may reduce its efficiency. For this reason the condition monitoring of a rolling element bearing is very essential. So many measuring parameters are there to diagnose the fault in a rolling element bearing. Acoustic signature monitoring is one of them. Every rolling element bearing has its own acoustic signature when it is in healthy condition and when the bearing get defected then there is a change in its original acoustic signature. This change in acoustic signature can be monitored and analyzed to detect the fault present in the bearing. But the noise present in the acquired acoustic signal may affect the analysis. So the noisy acoustic signal must be filtered before the analysis. In this work the experiment is performed in two stages. In first stage the filtration of the acquired acoustic signal is done by employing the active noise cancellation (ANC) filtering techniques. In second stage the filtered signal is used for the further analysis. For the analysis initially the static analysis is done and then the frequency and the time-frequency analysis is done to diagnose the defect in the bearing. From all the three analysis the information about the defect present in the bearing is well detected
Density Evolution in the New Modified Chaplygin Gas Model
In this paper, we have considered new modified Chaplygin gas (NMCG) model
which interpolates between radiation at early stage and CDM at late
stage. This model is regarded as a unification of dark energy and dark matter
(with general form of matter). We have derived the density parameters from the
equation of motion for the interaction between dark energy and dark matter.
Also we have studied the evolution of the various components of density
parameters.Comment: 6 Latex pages, 4 figures, RevTex styl
Correspondence between Electro-Magnetic Field and other Dark Energies in Non-linear Electrodynamics
In this work, we have considered the flat FRW model of the universe filled
with electro-magnetic field. First, the Maxwell's electro-magnetic field in
linear form has been discussed and after that the modified Lagrangian in
non-linear form for accelerated universe has been considered. The corresponding
energy density and pressure for non-linear electro-magnetic field have been
calculated. We have found the condition such that the electro-magnetic field
generates dark energy. The correspondence between the electro-magnetic field
and the other dark energy candidates namely tachyonic field, DBI-essence,
Chaplygin gas, hessence dark energy, k-essenece and dilaton dark energy have
been investigated. We have also reconstructed the potential functions and the
scalar fields in this scenario.Comment: 11 pages, 7 figure
CLINICAL EVALUATION OF APAMARGA PRATI-SHARANIYA (TEEKSHNA) KSHARA (LOCAL APPLICATION) HARITAKI CHURNA IN THE MANAGEMENT OF ARSHA (HEMORRHOIDS)
Arsha (Hemorrhoids) is one of the most common conditions affecting peoples since time immemorial. The prevalence is equal in both sexes, peaks between the ages of 45 and 65 and declining thereafter. The main cause of hemorrhoids is constipation over a prolonged period of time and has to strain to pass stools, it can damage the lining of anal canal. Sushruta the Father of Surgery advocated four method of treatment of Arsha, which are Bheshaja, Kshara, Agni and Shastra. Under Sushrutas operative procedure local application of Pratisharaniya Kshara in the prolapse piles mass helps to reduce pile mass effectively (Ref.Su.Chi.6). It is safe, cheap, effective, simple, easily approachable procedure and ambulatory treatment and the patients acceptability is good to overcome such problem. Aims & Objective is to evaluate the clinical efficacy of Apamarga Pratisharaniya teekshna kshara in the management of Arsha. & to evaluate the safety of Apamarga Pratisharaniya teekshna kshara in the management of Arsha. Material and Methods: 30 patients were enrolled for the study within a period of one year and Teekshna pratisharaniya kshara was applied on piles mass intra anally under operative procedure with the help of a instrument proctoscope. Observation and result: Reduction in the piles mass evident by Inspection/ proctoscopy /Visual perception was observed remarkably.Bleeding and pain were also reduced remarkably in all the piles patient. 100% relief in bleeding, reduction of pile mass and total reduction in size of pile mass was recorded. Conclusion: Recently these Oldest technique advocated by Sushruta have been proven to be most effective and free from post-operative complications
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