1,474 research outputs found
Langmuir Wave Generation Through A Neutrino Beam Instability
A standard version of a kinetic instability for the generation of Langmuir
waves by a beam of electrons is adapted to describe the analogous instability
due to a beam of neutrinos. The interaction between a Langmuir wave and a
neutrino is treated in the one-loop approximation to lowest order in an
expansion in in the standard electroweak model.
It is shown that this kinetic instability is far too weak to occur in a
suggested application to the reheating of the plasma behind a stalled shock in
a type II supernova (SN). This theory is also used to test the validity of a
previous analysis of a reactive neutrino beam instability and various
shortcomings of this theory are noted. In particular, it is noted that
relativistic plasma effects have a significant effect on the calculated growth
rates, and that any theoretical description of neutrino-plasma interactions
must be based directly on the electroweak theory. The basic scalings discussed
in this paper suggest that a more complete investigation of neutrino-plasma
processes should be undertaken to look for an efficient process capable of
driving the stalled shock of a type II SN.Comment: 23 pages, incl. 5 postscript figure
Providing safe and supported accommodation for young people who are in the care system and who are at risk of, or experiencing, sexual exploitation or trafficking for sexual exploitation
This report presents the findings of a scoping study into accommodation for young people at risk of/experiencing sexual exploitation. The scoping study took place January to March 2011 and included a literature search, consultation with young people, consultation with practitioners and development of a full research proposal. The research was funded by the NSPCC
Neutrino emission via the plasma process in a magnetized plasma
Neutrino emission via the plasma process using the vertex formalism for QED
in a strongly magnetized plasma is considered. A new vertex function is
introduced to include the axial vector part of the weak interaction. Our
results are compared with previous calculations, and the effect of the axial
vector coupling on neutrino emission is discussed. The contribution from the
axial vector coupling can be of the same order as or greater than the vector
vector coupling under certain plasma conditions.Comment: 20 pages, 3 figure
Canonical quantization of electromagnetic field in an anisotropic polarizable and magnetizable medium with spatial-temporal dispersion
Modeling an anisotropic spatially and temporarily dispersive
magnetodielectric medium by two independent collections of three dimensional
vector fields, we demonstrate a fully canonical quantization of electromagnetic
field in the presence of such a medium. Two tensor fields which couple the
electromagnetic field with the medium and have an important role in this
quantization method are introduced. The electric and magnetic polarization
fields of the medium naturally are concluded in terms of the coupling tensors
and the dynamical variables modeling the magnetodielectric medium. In
Heisenberg picture, the constitutive equations of the medium together with the
Maxwell laws are obtained as the equations of motion of the total system and
the susceptibility tensors of the medium are calculated in terms of the
coupling tensors. Following a perturbation method the Green function related to
the total system is found and the time dependence of electromagnetic field
operators is derived.Comment: 19 pages, No figur
Cracks of unequal length at the edge of an elliptic hole in out of plane shear
AbstractIntegral transforms are used to find mode III stress intensity factors for two unequal length cracks at the edge of an elliptic hole in an infinite elastic solid
When the Worst Imaginable Becomes Reality: The Experience of Child Custody Loss in Mothers Recovering from Addictions
This article describes findings from a qualitative study that investigated the lived experiences of four mothers recovering from crack cocaine addictions who lost custody of their children. The project was guided by feminist interpretive inquiry, van Manen’s approach to hermeneutic phenomenology, and involved thematic analysis of in depth interview data. By telling the stories of these women and using their own words as well as interpretive poetry written by one of the authors to describe their suffering, our research offers important insights to professionals involved in the field of addictions
Glycans and glycosaminoglycans in neurobiology: key regulators of neuronal cell function and fate
The aim of the present study was to examine the roles of l-fucose and the glycosaminoglycans (GAGs) keratan sulfate (KS) and chondroitin sulfate/dermatan sulfate (CS/DS) with selected functional molecules in neural tissues. Cell surface glycans and GAGs have evolved over millions of years to become cellular mediators which regulate fundamental aspects of cellular survival. The glycocalyx, which surrounds all cells, actuates responses to growth factors, cytokines and morphogens at the cellular boundary, silencing or activating downstream signaling pathways and gene expression. In this review, we have focused on interactions mediated by l-fucose, KS and CS/DS in the central and peripheral nervous systems. Fucose makes critical contributions in the area of molecular recognition and information transfer in the blood group substances, cytotoxic immunoglobulins, cell fate-mediated Notch-1 interactions, regulation of selectin-mediated neutrophil extravasation in innate immunity and CD-34-mediated new blood vessel development, and the targeting of neuroprogenitor cells to damaged neural tissue. Fucosylated glycoproteins regulate delivery of synaptic neurotransmitters and neural function. Neural KS proteoglycans (PGs) were examined in terms of cellular regulation and their interactive properties with neuroregulatory molecules. The paradoxical properties of CS/DS isomers decorating matrix and transmembrane PGs and the positive and negative regulatory cues they provide to neurons are also discussed
Immunolocalization of keratan sulfate in rat spinal tissues using the keratanase generated BKS-1(+) neoepitope: correlation of expression patterns with the slass II SLRPs, lumican and keratocan
This study has identified keratan sulfate in fetal and adult rat spinal cord and vertebral connective tissues using the antibody BKS-1(+) which recognizes a reducing terminal N-acetyl glucosamine-6-sulfate neo-epitope exposed by keratanase-I digestion. Labeling patterns were correlated with those of lumican and keratocan using core protein antibodies to these small leucine rich proteoglycan species. BKS-1(+) was not immunolocalized in fetal spinal cord but was apparent in adult cord and was also prominently immunolocalized to the nucleus pulposus and inner annulus fibrosus of the intervertebral disc. Interestingly, BKS-1(+) was also strongly associated with vertebral body ossification centers of the fetal spine. Immunolocalization of lumican and keratocan was faint within the vertebral body rudiments of the fetus and did not correlate with the BKS-1(+) localization indicating that this reactivity was due to another KS-proteoglycan, possibly osteoadherin (osteomodulin) which has known roles in endochondral ossification. Western blotting of adult rat spinal cord and intervertebral discs to identify proteoglycan core protein species decorated with the BKS-1(+) motif confirmed the identity of 37 and 51 kDa BKS-1(+) positive core protein species. Lumican and keratocan contain low sulfation KS-I glycoforms which have neuroregulatory and matrix organizational properties through their growth factor and morphogen interactive profiles and ability to influence neural cell migration. Furthermore, KS has interactive capability with a diverse range of neuroregulatory proteins that promote neural proliferation and direct neural pathway development, illustrating key roles for keratocan and lumican in spinal cord development
Relativistic quantum plasma dispersion functions
Relativistic quantum plasma dispersion functions are defined and the
longitudinal and transverse response functions for an electron (plus positron)
gas are written in terms of them. The dispersion is separated into
Landau-damping, pair-creation and dissipationless regimes. Explicit forms are
given for the RQPDFs in the cases of a completely degenerate distribution and a
nondegenerate thermal (J\"uttner) distribution. Particular emphasis is placed
on the relation between dissipation and dispersion, with the dissipation
treated in terms of the imaginary parts of RQPDFs. Comparing the dissipation
calculated in this way with the existing treatments leads to the identification
of errors in the literature, which we correct. We also comment on a controversy
as to whether the dispersion curves in a superdense plasma pass through the
region where pair creation is allowed.Comment: 16 pages, 1 figur
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