254 research outputs found
r-Java 2.0: the nuclear physics
[Aims:] We present r-Java 2.0, a nucleosynthesis code for open use that
performs r-process calculations as well as a suite of other analysis tools.
[Methods:] Equipped with a straightforward graphical user interface, r-Java 2.0
is capable of; simulating nuclear statistical equilibrium (NSE), calculating
r-process abundances for a wide range of input parameters and astrophysical
environments, computing the mass fragmentation from neutron-induced fission as
well as the study of individual nucleosynthesis processes. [Results:] In this
paper we discuss enhancements made to this version of r-Java, paramount of
which is the ability to solve the full reaction network. The sophisticated
fission methodology incorporated into r-Java 2.0 which includes three fission
channels (beta-delayed, neutron-induced and spontaneous fission) as well as
computation of the mass fragmentation is compared to the upper limit on mass
fission approximation. The effects of including beta-delayed neutron emission
on r-process yield is studied. The role of coulomb interactions in NSE
abundances is shown to be significant, supporting previous findings. A
comparative analysis was undertaken during the development of r-Java 2.0
whereby we reproduced the results found in literature from three other
r-process codes. This code is capable of simulating the physical environment
of; the high-entropy wind around a proto-neutron star, the ejecta from a
neutron star merger or the relativistic ejecta from a quark nova. As well the
users of r-Java 2.0 are given the freedom to define a custom environment. This
software provides an even platform for comparison of different proposed
r-process sites and is available for download from the website of the
Quark-Nova Project: http://quarknova.ucalgary.ca/Comment: 26 pages, 18 figures, 1 tabl
Surface structure of Quark stars with magnetic fields
We investigate the impact of magnetic fields on the electron distribution in
the electrosphere of quark stars. For moderately strong magnetic fields G, quantization effects are generally weak due to the large number
density of electrons at surface, but can nevertheless affect the spectral
features of quark stars. We outline the main observational characteristics of
quark stars as determined by their surface emission, and briefly discuss their
formation in explosive events termed Quark-Novae, which may be connected to the
-process.Comment: 9 pages, 3 figures. Contribution to the proceedings of the IXth
Workshop on High Energy Physics Phenomenology (WHEPP-9), Bhubaneswar, India,
3-14 Jan. 200
A Spallation Model for the Titanium-rich Supernova Remnant Cassiopeia A
Titanium-rich subluminous supernovae are rare and challenge current SN
nucleosynthesis models. We present a model in which ejecta from a standard
Supernova is impacted by a second explosion of the neutron star (a Quark-nova),
resulting in spallation reactions that lead to 56Ni destruction and 44Ti
creation under the right conditions. Basic calculations of the spallation
products shows that a delay between the two explosions of ~ 5 days reproduces
the observed abundance of 44Ti in Cas A and explains its low luminosity as a
result of the destruction of 56Ni. Our results could have important
implications for lightcurves of subluminous as well as superluminous
supernovae.Comment: Accepted/to be published in Physical Review Letters. [ for more info
on the Quark Nova, see: http://quarknova.ucalgary.ca/
An Efficient Approach Formulation of Social Groups of User Calls of GSM
We are living in a world of wireless technology. The most widely used wireless i.e. mobile computing device today is the Mobile phone, can be used not only for voice and data communications but also as a computing device running context aware applications. In this paper we present a model that based on GSM data base. The objective of this paper identifies social and suspicious groups based on Cell Id, IMSI, IMEI, date and time, Location Area, MCC and MNC. This information can be used by applications for the detection of users, user context, discovering of groups and relation between them using clustering technique of data mining. One of the vital means in dealing with these data is to classify or group them into a set of categories or clusters. We demonstrate that even without knowledge of observed cell tower locations, we can recognize mobility modes that are useful for several application domains. Our mobility detection system was evaluated with GSM traces from the everyday lives of three data collector
Quark deconfinement in neutron star cores: The effects of spin-down
We study the role of spin-down in driving quark deconfinement in the high
density core of isolated neutron stars. Assuming spin-down to be solely due to
magnetic braking, we obtain typical timescales to quark deconfinement for
neutron stars that are born with Keplerian frequencies. Employing different
equations of state (EOS), we determine the minimum and maximum neutron star
masses that will allow for deconfinement via spin-down only. We find that the
time to reach deconfinement is strongly dependent on the magnetic field and
that this time is least for EOS that support the largest minimum mass at zero
spin, unless rotational effects on stellar structure are large. For a fiducial
critical density of for the transition to the quark phase
(g/cm is the saturation density of nuclear
matter), we find that neutron stars lighter than cannot reach a
deconfined phase. Depending on the EOS, neutron stars of more than
can enter a quark phase only if they are spinning faster than
about 3 milliseconds as observed now, whereas larger spin periods imply that
they are either already quark stars or will never become one.Comment: 4 pages, 4 figures, submitted to ApJ
EFFECT OF FLAVONE AND ITS MONOHYDROXY DERIVATIVES ON ANIMAL MODELS OF DEPRESSION IN SWISS ALBINO MICE
Objectives: This research was designed to investigate the antidepressant activity of a few structurally related flavones (flavone, 3‑hydroxyflavone, and 7‑hydroxyflavone) and the possible mechanisms involved.
Methods: Antidepressant activity was evaluated in mice by subjecting them to forced swim test and tail suspension test. The involvement of adrenergic, serotonergic, nitric oxide (NO), and opioid mechanisms was investigated using suitable interacting chemicals.
Results: Flavone, 3‑hydroxyflavone, and 7‑hydroxyflavone exhibited a significant and dose‑dependent reduction in total time of immobility in the forced swim test and tail suspension test. Pre‑treatment with alpha‑methyl‑para‑tyrosine and parachlorophenyl alanine attenuated the reduction in immobility period produced by flavone and its derivatives in forced swim test. Naloxone pre‑treatment partially reversed the effect of flavone while L‑arginine pre‑treatment did not alter their effect.
Conclusion: The investigated flavones exhibited promising antidepressant activity in both the animal models of depression. However, the flavone compounds did not alter the motor coordination and ambulatory behavior in the Rotarod and locomotor activity test. The participation of serotonergic, adrenergic, and opioid mechanism in the antidepressant activity of these compounds was elucidated from the results, and the role of NO pathway was excluded
Caprellids (Crustacea: Amphipoda) from India
The caprellid fauna of India is investigated. A
total of 538 samples (including algae, seagrasses, sponges,
hydroids, ascidians, bryozoans, encrusted dead corals, coral
rubble, fine and coarse sediments) were collected from 39
stations along the coast of India, covering a wide diversity
of habitats from intertidal to 12 m water depth. A new
species (Jigurru longimanus n.sp.) is described, and figures
of the 11 valid species reported so far from India are given
together with a key for their identification. No caprellids
were found in sediments from the northeast (16–208N)
coast of India while they were abundant in the southeast
and west coast. Decreases in salinity due to river discharges
associated with lower values of oxygen, higher water
temperatures and lower nutrient inputs along the east coast
could explain these differences in caprellid composition
between the two coastlines. Significantly, lower abundance
of caprellids in India, as in other tropical ecosystems, is
probably related to the lack of species belonging to the
genus Caprella, which reach very high abundances in
temperate waters.Ministerio de Educación y Ciencia de España y fondos FEDER de la Unión Europea. CGL2007-60044/ BOSConsejería de Innovación, Ciencia y Empresa, Junta de Andalucía, España. P07-RNM-02524Ministry of Earth Sciences (MoES) de India. DOD/10-MLR/1/2002/DT 19.12.200
Scalar-isoscalar excitation in dense quark matter
We study the spectrum of scalar-isoscalar excitations in the color-flavor
locked phase of dense quark matter. The sigma meson in this phase appears as a
four-quark state (of diquark and anti-diquark) with a well-defined mass and
extremely small width, as a consequence of it's small coupling to two pions.
The quark particle/hole degrees of freedom also contribute significantly to the
correlator just above the threshold 2\Delta where \Delta is the superconducting
gap.Comment: RevTeX, 11 pages, 4 fig
Neutrino Emission from Goldstone Modes in Dense Quark Matter
We calculate neutrino emissivities from the decay and scattering of Goldstone
bosons in the color-flavor-locked (CFL) phase of quarks at high baryon density.
Interactions in the CFL phase are described by an effective low-energy theory.
For temperatures in the tens of keV range, relevant to the long-term cooling of
neutron stars, the emissivities involving Goldstone bosons dominate over those
involving quarks, because gaps in the CFL phase are MeV while the
masses of Goldstone modes are on the order of 10 MeV. For the same reason, the
specific heat of the CFL phase is also dominated by the Goldstone modes.
Notwithstanding this, both the emissivity and the specific heat from the
massive modes remain rather small, because of their extremely small number
densities. The values of the emissivity and the specific heat imply that the
timescale for the cooling of the CFL core in isolation is y,
which makes the CFL phase invisible as the exterior layers of normal matter
surrounding the core will continue to cool through significantly more rapid
processes. If the CFL phase appears during the evolution of a proto-neutron
star, neutrino interactions with Goldstone bosons are expected to be
significantly more important since temperatures are high enough (
MeV) to admit large number densities of Goldstone modes.Comment: 29 pages, no figures. slightly modified text, one new eqn. and new
refs. adde
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