45,419 research outputs found
Charged analogue of Finch-Skea stars
We present solutions to the Einstein-Maxwell system of equations in
spherically symmetric gravitational fields for static interior spacetimes with
a specified form of the electric field intensity. The condition of pressure
isotropy yields three category of solutions. The first category is expressible
in terms of elementary functions and does not have an uncharged limit. The
second category is given in terms of Bessel functions of half-integer order.
These charged solutions satisfy a barotropic equation of state and contain
Finch-Skea uncharged stars. The third category is obtained in terms of modified
Bessel functions of half-integer order and does not have an uncharged limit.
The physical features of the charged analogue of the Finch-Skea stars are
studied in detail. In particular the condition of causality is satisfied and
the speed of sound does not exceed the speed of light. The physical analysis
indicates that this analogue is a realistic model for static charged
relativistic perfect fluid spheres.Comment: 17 pages, To appear in Int. J. Mod. Phys.
Changes in murine anorectum signaling across the life course
Background: Increasing age is associated with an increase in the incidence of chronic constipation and fecal impaction. The contribution of the natural aging process to these conditions is not fully understood. This study examined the effects of increasing age on the function of the murine anorectum.Methods: The effects of increasing age on cholinergic, nitrergic, and purinergic signaling pathways in the murine anorectum were examined using classical organ bath assays to examine tissue function and electrochemical sensing to determine age‐related changes in nitric oxide and acetylcholine release.Key Results: Nitrergic relaxation increased between 3 and 6 months, peaked at 12 months and declined in the 18 and 24 months groups. These changes were in part explained by an age‐related decrease in nitric oxide (NO) release. Cholinergic signaling was maintained with age by an increase in acetylcholine (ACh) release and a compensatory decrease in cholinesterase activity. Age‐related changes in purinergic relaxation were qualitatively similar to nitrergic relaxation although the relaxations were much smaller. Increasing age did not alter the response of the anorectum smooth muscle to exogenously applied ACh, ATP, sodium nitroprusside or KCl. Similarly, there was no change in basal tension developed by the anorectum.Conclusions and Inferences: The decrease in nitrergic signaling with increasing age may contribute to the age‐related fecal impaction and constipation previously described in this model by partially obstructing defecation
Broadband study of blazar 1ES 1959+650 during flaring state in 2016
Aim : The nearby TeV blazar 1ES 1959+650 (z=0.047) was reported to be in
flaring state during June - July 2016 by Fermi-LAT, FACT, MAGIC and VERITAS
collaborations. We studied the spectral energy distributions (SEDs) in
different states of the flare during MJD 57530 - 57589 using simultaneous
multiwaveband data to understand the possible broadband emission scenario
during the flare. Methods : The UV/optical and X-ray data from UVOT and XRT
respectively on board Swift and high energy -ray data from Fermi-LAT
are used to generate multiwaveband lightcurves as well as to obtain high flux
states and quiescent state SEDs. The correlation and lag between different
energy bands is quantified using discrete correlation function. The synchrotron
self Compton (SSC) model was used to reproduce the observed SEDs during flaring
and quiescent states of the source. Results : A decent correlation is seen
between X-ray and high energy -ray fluxes. The spectral hardening with
increase in the flux is seen in X-ray band. The powerlaw index vs flux plot in
-ray band indicates the different emission regions for 0.1 - 3 GeV and
3-300 GeV energy photons. Two zone SSC model satisfactorily fits the observed
broadband SEDs. The inner zone is mainly responsible for producing synchrotron
peak and high energy -ray part of the SED in all states. The second
zone is mainly required to produce less variable optical/UV and low energy
-ray emission. Conclusions : Conventional single zone SSC model does
not satisfactorily explain broadband emission during observation period
considered. There is an indication of two emission zones in the jet which are
responsible for producing broadband emission from optical to high energy
-rays.Comment: 11 pages, 12 figures, Accepted in A&
Leptonic decay of Heavy-light Mesons in a QCD Potential Model
We study the masses and decay constants of heavy-light flavour mesons D, Ds,
B and Bs in a QCD Potential model. The mesonic wavefunction is used to compute
the masses of D and B mesons in the ground state and the wavefunction is
transformed to momentum space to estimate the pseudoscalar decay constants of
these mesons. The leptonic decay widths and branching ratio of these mesons for
different leptonic channels are also computed to compare with the experimental
values. The results are found to be compatible with available data.Comment: 9 pages,3 table
Anisotropic Approach: Compact star as generalized Model
We studied a new class of interior solutions that are singular-free and
useful for describing anisotropic compact star objects with spherically
symmetric matter distribution. We have considered metric potential selecting
B_0^2 (r)=1/(1-r^2/R^2 )^n ,where n>2 . The various physical characteristics of
the model are specifically examined for the pulsar PSRJ1903+327 with its
current estimated data. According to analysis, every physical need for a
physically admissible star is satisfied and all features are acceptable.
Further, the stability of the model has been examined. Numerous physical
characteristics are also highlighted in a graphical form.Comment: 20 pages and 14 figure
A various equation of state for anisotropic models of compact star
We obtain models of compact stars having pressure anisotropy on Finch-Skea
spacetime by considering generalized equation of state (EoS), whose particular
cases are linear, quadratic, polytropic, chaplygin and colour - flavor
locked(CFL) equation of states. The physical viability of models are tested for
strange star candidate 4U 1820 - 30 having mass M = 1.58Mass of the sun and
radius R = 9.1 km. All the models are physically plausible.Comment: 28 pages and 15 figure
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