3,889 research outputs found
Neutrinos from type Ia supernovae: the deflagration-to-detonation transition scenario
It has long been recognized that the neutrinos detected from the next
core-collapse supernova in the Galaxy have the potential to reveal important
information about the dynamics of the explosion and the nucleosynthesis
conditions as well as allowing us to probe the properties of the neutrino
itself. The neutrinos emitted from thermonuclear - type Ia - supernovae also
possess the same potential, although these supernovae are dimmer neutrino
sources. For the first time, we calculate the time, energy, line of sight, and
neutrino-flavor-dependent features of the neutrino signal expected from a
three-dimensional delayed-detonation explosion simulation, where a
deflagration-to-detonation transition triggers the complete disruption of a
near-Chandrasekhar mass carbon-oxygen white dwarf. We also calculate the
neutrino flavor evolution along eight lines of sight through the simulation as
a function of time and energy using an exact three-flavor transformation code.
We identify a characteristic spectral peak at MeV as a signature of
electron captures on copper. This peak is a potentially distinguishing feature
of explosion models since it reflects the nucleosynthesis conditions early in
the explosion. We simulate the event rates in the Super-K, Hyper-K, JUNO, and
DUNE neutrino detectors with the SNOwGLoBES event rate calculation software and
also compute the IceCube signal. Hyper-K will be able to detect neutrinos from
our model out to a distance of kpc. At 1 kpc, JUNO, Super-K, and DUNE
would register a few events while IceCube and Hyper-K would register several
tens of events.Comment: 44 pages, 29 figures & 2 tables. Updated to match Phys. Rev. D
version, including a new event channel discussion and improved IceCube
result
Annihilation of vortex dipoles in an Oblate Bose-Einstein Condensate
We theoretically explore the annihilation of vortex dipoles, generated when
an obstacle moves through an oblate Bose-Einstein condensate, and examine the
energetics of the annihilation event. We show that the gray soliton, which
results from the vortex dipole annihilation, is lower in energy than the vortex
dipole. We also investigate the annihilation events numerically and observe
that the annihilation occurs only when the vortex dipole overtakes the obstacle
and comes closer than the coherence length. Furthermore, we find that the noise
reduces the probability of annihilation events. This may explain the lack of
annihilation events in experimental realizations.Comment: 8 pages and 9 figure
A C-Function For Non-Supersymmetric Attractors
We present a c-function for spherically symmetric, static and asymptotically
flat solutions in theories of four-dimensional gravity coupled to gauge fields
and moduli. The c-function is valid for both extremal and non-extremal black
holes. It monotonically decreases from infinity and in the static region
acquires its minimum value at the horizon, where it equals the entropy of the
black hole. Higher dimensional cases, involving -form gauge fields, and
other generalisations are also discussed.Comment: References adde
Bulk Entanglement Entropy and Matrices
Motivated by the Bekenstein Hawking formula and the area law behaviour of
entanglement entropy, we propose that in any UV finite theory of quantum
gravity with a smooth spacetime, the total entropy for a pure state in a
co-dimension one spatial region, to leading order, is given by , where is the area of the co-dimension two boundary. In the context
of brane holography we show that for some specially chosen regions bulk
entanglement can be mapped to ``target space" entanglement in the boundary
theory. Our conjecture then leads to a precise proposal for target space
entanglement in the boundary theory at strong coupling and large . In
particular it leads to the conclusion that the target space entanglement would
scale like which is quite plausible in a system with degrees
of freedom. Recent numerical advances in studying the D0 brane system hold out
the hope that this proposal can be tested in a precise way in the future.Comment: Submitted 11 March 2020 to the Peter Freund Memorial Volume. J Phys
Coercivity and stability results for an extended Navier-Stokes system
In this article we study a system of equations that is known to {\em extend}
Navier-Stokes dynamics in a well-posed manner to velocity fields that are not
necessarily divergence-free. Our aim is to contribute to an understanding of
the role of divergence and pressure in developing energy estimates capable of
controlling the nonlinear terms. We address questions of global existence and
stability in bounded domains with no-slip boundary conditions. Even in two
space dimensions, global existence is open in general, and remains so,
primarily due to the lack of a self-contained energy estimate. However,
through use of new coercivity estimates for the linear equations, we
establish a number of global existence and stability results, including results
for small divergence and a time-discrete scheme. We also prove global existence
in 2D for any initial data, provided sufficient divergence damping is included.Comment: 29 pages, no figure
Synthesis, x-ray crystal structures and biological evaluation of some mono- and bi-cyclic 1,3-diazetidin-2-ones: non-natural β -lactam analogues
Mono- and bi-cyclic 1,3-diazetidin-2-ones (aza-β -lactams) are synthesised and evaluated as non-natural analogues of β -lactams. The aza-β -lactams are designed on the principle that their reaction with active site serine hydroxy will form a carbamoyl-enzyme intermediate that is sluggish to hydrolysis. The synthesis of racemic mono- and bi-cyclic aza-β -lactams is carried out starting from pyrimidinone 18 which is transformed to the densely functionalised substrate 20. The chemical reactivity of tricarbonyl 20 for selective functional group manipulation was first assessed and then it was transformed to amino alcohol 24. Cyclisation of 24 affords aza-carbapenams and its homologation followed by aldol cyclisation provides access to aza-carbacephams. The X-ray structures of aza-carbapenam 35 and aza-carbacepham 42 suggest that the structural requirements for biological activity in β -lactams are fulfilled. An unexpected ozonolysis product, phenol 52 resolves spontaneously during crystallisation and its crystal structure was also determined. The biological activity of the novel mono- and bi-cyclic aza-β -lactams was evaluated with potent gram-positive bacterial strain, Bacillus subtilis and compared with β -lactam antibiotics, ampicillin and penicillin G. Of the 19 aza-β -lactams tested, eight compounds show inhibition better than the standards while another eight are of comparable activity. This study shows that aza-β -lactams represent a novel and non-natural lead towards serine peptidase inhibitors
Assessment of clinical profile, antibiotic sensitivity and prescription pattern in blood culture positive enteric fever among pediatric and adult patients admitted in a tertiary care hospital: a prospective study
Background: Asterion Introduction: Enteric fever is a major concern in developing country. It is predominantly caused by serovars typhi and paratyphi of Salmonella enterica. Recently, an upsurge in antimicrobial resistant strains has worsened the management of enteric fever. So, aim of present study is to evaluate the clinical profile, antibiotic sensitivity and prescription pattern in blood culture proven cases of enteric fever in pediatric and adult patients.Methods: Single centre, prospective study was conducted at a tertiary care hospital. Demographic and clinical details of blood culture proven enteric fever admitted in hospital were collected over the period from August 2016 to November 2018.Results: Total 58 blood cultures grew Salmonella spp. , amongst them 84.48 % had growth of Salmonella typhi. Blood culture was sent after a mean period of 9 days and 10 days of fever in pediatric and adult patients respectively. All isolates of S. paratyphi A were pansusceptible, whereas 36.73 % isolates of S. typhi were multidrug resistant and nalidixic acid resistant. 68.97% patients received antibiotics before admission. The difference between mean time to defervescence in patients who received ceftriaxone and those who received more than one antibiotic was not statistically significant. (P value 0.87)Conclusion: Blood cultures are the important diagnostic tool to identify multidrug resistant Salmonellae. Study showed that combination therapy was not statistically superior and awareness of local antimicrobial susceptibility pattern significantly helps for better management of the patients
- …