1,273 research outputs found
Constraints on the environment and energetics of the Broad-Line Ic SN2014ad from deep radio and X-ray observations
Broad-line type Ic Supernovae (BL-Ic SNe) are characterized by high ejecta
velocity ( km s) and are sometimes associated with the
relativistic jets typical of long duration ( s) Gamma-Ray Bursts
(L-GRBs). The reason why a small fraction of BL-Ic SNe harbor relativistic jets
is not known. Here we present deep X-ray and radio observations of the BL-Ic
SN2014ad extending from to days post explosion. SN2014ad was not
detected at either frequency and has no observational evidence of a GRB
counterpart. The proximity of SN2014ad ( Mpc) enables very deep
constraints on the progenitor mass-loss rate and on the total energy
of the fast ejecta . We consider two synchrotron emission scenarios for a
wind-like circumstellar medium (CSM): (i) uncollimated non-relativistic ejecta,
and (ii) off-axis relativistic jet. Within the first scenario our observations
are consistent with GRB-less BL-Ic SNe characterized by a modest energy budget
of their fast ejecta ( erg), like SNe 2002ap and 2010ay.
For jetted explosions, we cannot rule out a GRB with erg
(beam-corrected) with a narrow opening angle ()
observed moderately off-axis () and
expanding in a very low CSM density ( M
yr). Our study shows that off-axis low-energy jets expanding in a
low-density medium cannot be ruled out even in the most nearby BL-Ic SNe with
extensive deep observations, and might be a common feature of BL-Ic SNe.Comment: 9 pages, 5 figures, accepted in Ap
Twisted Quantum Fields on Moyal and Wick-Voros Planes are Inequivalent
The Moyal and Wick-Voros planes A^{M,V}_{\theta} are *-isomorphic. On each of
these planes the Poincar\'e group acts as a Hopf algebra symmetry if its
coproducts are deformed by twist factors. We show that the *-isomorphism T:
A^M_{\theta} to A^V_{\theta} does not also map the corresponding twists of the
Poincar\'e group algebra. The quantum field theories on these planes with
twisted Poincar\'e-Hopf symmetries are thus inequivalent. We explicitly verify
this result by showing that a non-trivial dependence on the non-commutative
parameter is present for the Wick-Voros plane in a self-energy diagram whereas
it is known to be absent on the Moyal plane (in the absence of gauge fields).
Our results differ from these of (arXiv:0810.2095 [hep-th]) because of
differences in the treatments of quantum field theories.Comment: 12 page
Issues in the Design of a Pilot Concept-Based Query Interface for the Neuroinformatics Information Framework
This paper describes a pilot query interface that has been constructed to help us explore a "concept-based" approach for searching the
Neuroscience Information Framework (NIF). The query interface is
concept-based in the sense that the search terms submitted through the
interface are selected from a standardized vocabulary of terms
(concepts) that are structured in the form of an ontology. The NIF
contains three primary resources: the NIF Resource Registry, the NIF
Document Archive, and the NIF Database Mediator. These NIF resources
are very different in their nature and therefore pose challenges when
designing a single interface from which searches can be automatically
launched against all three resources simultaneously. The paper first
discusses briefly several background issues involving the use of
standardized biomedical vocabularies in biomedical information
retrieval, and then presents a detailed example that illustrates how
the pilot concept-based query interface operates. The paper concludes
by discussing certain lessons learned in the development of the current
version of the interface
The NIF LinkOut Broker: A Web Resource to Facilitate Federated Data Integration using NCBI Identifiers
This paper describes the NIF LinkOut Broker (NLB) that has been built as part of the Neuroscience Information Framework (NIF) project. The NLB is designed to coordinate the assembly of links to neuroscience information items (e.g., experimental data, knowledge bases, and software tools) that are (1) accessible via the Web, and (2) related to entries in the National Center for Biotechnology Information’s (NCBI’s) Entrez system. The NLB collects these links from each resource and passes them to the NCBI which incorporates them into its Entrez LinkOut service. In this way, an Entrez user looking at a specific Entrez entry can LinkOut directly to related neuroscience information. The information stored in the NLB can also be utilized in other ways. A second approach, which is operational on a pilot basis, is for the NLB Web server to create dynamically its own Web page of LinkOut links for each NCBI identifier in the NLB database. This approach can allow other resources (in addition to the NCBI Entrez) to LinkOut to related neuroscience information. The paper describes the current NLB system and discusses certain design issues that arose during its implementation
Inequivalence of QFT's on Noncommutative Spacetimes: Moyal versus Wick-Voros
In this paper, we further develop the analysis started in an earlier paper on
the inequivalence of certain quantum field theories on noncommutative
spacetimes constructed using twisted fields. The issue is of physical
importance. Thus it is well known that the commutation relations among
spacetime coordinates, which define a noncommutative spacetime, do not
constrain the deformation induced on the algebra of functions uniquely. Such
deformations are all mathematically equivalent in a very precise sense. Here we
show how this freedom at the level of deformations of the algebra of functions
can fail on the quantum field theory side. In particular, quantum field theory
on the Wick-Voros and Moyal planes are shown to be inequivalent in a few
different ways. Thus quantum field theory calculations on these planes will
lead to different physics even though the classical theories are equivalent.
This result is reminiscent of chiral anomaly in gauge theories and has obvious
physical consequences. The construction of quantum field theories on the
Wick-Voros plane has new features not encountered for quantum field theories on
the Moyal plane. In fact it seems impossible to construct a quantum field
theory on the Wick-Voros plane which satisfies all the properties needed of
field theories on noncommutative spaces. The Moyal twist seems to have unique
features which make it a preferred choice for the construction of a quantum
field theory on a noncommutative spacetime.Comment: Revised version accepted for publication in Phys.Rev.D; 18 page
Effective degradation of ibuprofen through an electron-Fenton process in the presence of zerovalent iron
An ontological approach to describing neurons and their relationships
The advancement of neuroscience, perhaps one of the most information rich disciplines of all the life sciences, requires basic frameworks for organizing the vast amounts of data generated by the research community to promote novel insights and integrated understanding. Since Cajal, the neuron remains a fundamental unit of the nervous system, yet even with the explosion of information technology, we still have few comprehensive or systematic strategies for aggregating cell-level knowledge. Progress toward this goal is hampered by the multiplicity of names for cells and by lack of a consensus on the criteria for defining neuron types. However, through umbrella projects like the Neuroscience Information Framework (NIF) and the International Neuroinformatics Coordinating Facility (INCF), we have the opportunity to propose and implement an informatics infrastructure for establishing common tools and approaches to describe neurons through a standard terminology for nerve cells and a database (a Neuron Registry) where these descriptions can be deposited and compared. This article provides an overview of the problem and outlines a solution approach utilizing ontological characterizations. Based on illustrative implementation examples, we also discuss the need for consensus criteria to be adopted by the research community, and considerations on future developments. A scalable repository of neuron types will provide researchers with a resource that materially contributes to the advancement of neuroscience
Length functions on currents and applications to dynamics and counting
The aim of this (mostly expository) article is twofold. We first explore a
variety of length functions on the space of currents, and we survey recent work
regarding applications of length functions to counting problems. Secondly, we
use length functions to provide a proof of a folklore theorem which states that
pseudo-Anosov homeomorphisms of closed hyperbolic surfaces act on the space of
projective geodesic currents with uniform north-south dynamics.Comment: 35pp, 2 figures, comments welcome! Second version: minor corrections.
To appear as a chapter in the forthcoming book "In the tradition of Thurston"
edited by V. Alberge, K. Ohshika and A. Papadopoulo
- …