1,240 research outputs found
Even perturbations of self-similar Vaidya space-time
We study even parity metric and matter perturbations of all angular modes in
self-similar Vaidya space-time. We focus on the case where the background
contains a naked singularity. Initial conditions are imposed describing a
finite perturbation emerging from the portion of flat space-time preceding the
matter-filled region of space-time. The most general perturbation satisfying
the initial conditions is allowed impinge upon the Cauchy horizon (CH), whereat
the perturbation remains finite: there is no ``blue-sheet'' instability.
However when the perturbation evolves through the CH and onto the second future
similarity horizon of the naked singularity, divergence necessarily occurs:
this surface is found to be unstable. The analysis is based on the study of
individual modes following a Mellin transform of the perturbation. We present
an argument that the full perturbation remains finite after resummation of the
(possibly infinite number of) modes.Comment: Accepted for publication in Physical Review D, 27 page
On the existence of dyons and dyonic black holes in Einstein-Yang-Mills theory
We study dyonic soliton and black hole solutions of the
Einstein-Yang-Mills equations in asymptotically anti-de Sitter space. We prove
the existence of non-trivial dyonic soliton and black hole solutions in a
neighbourhood of the trivial solution. For these solutions the magnetic gauge
field function has no zeros and we conjecture that at least some of these
non-trivial solutions will be stable. The global existence proof uses local
existence results and a non-linear perturbation argument based on the (Banach
space) implicit function theorem.Comment: 23 pages, 2 figures. Minor revisions; references adde
Dynamical extensions for shell-crossing singularities
We derive global weak solutions of Einstein's equations for spherically
symmetric dust-filled space-times which admit shell-crossing singularities. In
the marginally bound case, the solutions are weak solutions of a conservation
law. In the non-marginally bound case, the equations are solved in a
generalized sense involving metric functions of bounded variation. The
solutions are not unique to the future of the shell-crossing singularity, which
is replaced by a shock wave in the present treatment; the metric is bounded but
not continuous.Comment: 14 pages, 1 figur
Age and geochemistry of granitoids in the Precambrian basement of Öland, SE Sweden – implications for the extension of the Transscandinavian Igneous Belt in the Baltic Sea region
The Precambrian crust in the Baltic
Sea region is mostly covered by Phanerozoic sedimentary rocks but can be
studied in drill cores. Two granitoids from the crystalline basement below
Öland were collected from the archives of the Geological Survey of Sweden and
analyzed for geochemistry and dated with the U-Pb method on zircons. The Böda
Hamn granitoid (northern Öland) has a monzodioritic composition and an age of
1799.8±3 Ma while the Valsnäs granitoid (central Öland) has a quartz monzonitic
composition and an age of 1784.9±5.7 Ma. These geochemical-isotopic
characteristics are compatible with those of generation 1 of the
Transscandinavian Igneous Belt (TIB) in the Fennoscandian Shield, ≥30 km west
of Öland.A more detailed review of the TIB-1
generation shows that two
sub-generations (1a and 1b) can
be distinguished on each respective side of the Oskarshamn-Jönköping Belt
(OJB). Sub-generation 1a (north of OJB) has an age span of 1794-1808 Ma while sub-generation
1b (south of OJB) has an age span of 1769-1793 Ma. According to this subdivision, the Böda Hamn monzodiorite belongs to sub-generation 1a, which also can be followed to southernmost Gotland
(Sundblad et al. 2003) and the Valsnäs quartz monzonite belongs to sub-generation 1b, which can be followed to
the Latvian/Lithuanian border, where a marginally younger granitoid was
reported from off shore drill core E-7 (Salin et al. 2016). Taken
together, these data suggest that the Transscandinavian Igneous Belt can
be traced across the Baltic Sea from the exposed parts within the Fennoscandian
Shield to the Latvian/Lithuanian border.Salin, E.,
Sundblad, K., Woodard, J. and Lahaye, Y. 2016: The Precambrian crust in the
Baltic Sea region. Bulletin of the Geological Society of Finland, 32nd Nordic
Geological Winter Meeting, Helsinki. Abstract volume, p. 162.Sundblad, K., Claesson, S.
& Gyllencreutz, R. 2003: The Precambrian of
Gotland – a key to the understanding of the geologic environment for granitoids
in the Baltic Sea region. Granitic systems – State of the art and future
avenues. An international symposium in honor of professor Ilmari Haapala.
Abstract volume, Helsinki, 102–106.
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Development and calibration of an on-line aerosol monitor for PHEBUS test FPT1
An on-line aerosol monitor (OLAM2) has been developed and tested for PHEBUS test FPT1. OLAM2 utilizes new detachable fiber optic cables and sapphire light pipes for light transmission between the OLAM and the electronics. This light transmission system was tested and found to provide better signal-to-noise performance than was achieved with the continuous fibers used for test FPT0. An additional advantage of the detachable fiber/light pipe system is ease of installation. Aerosol testing (OLAM calibration) was performed in order to verify adequate signal-to-noise performance of the new fiber optic system over the specified operating conditions and to check the quantitative light attenuation measurements against theoretical predictions. Results of the testing indicated that light extinction measurements obtained during Phebus tests could be used to estimate aerosol volume concentrations, if diamond window fouling can be avoided. OLAM2 was also subjected to a proof pressure test and a long-term thermal stability test. These tests verified the mechanical and thermal integrity of the OLAM within design specifications. Long-term output signal stability was also verified with the system maintained at design temperature and half-design pressure
Wool and meat genetics - the joint possibilities
Wool and meat contribute to profit in sheep enterprises and both need to be considered in breeding programs. The relative responses expected from selection for a range of traits are presented and the realised responses that have been achieved in Merinos and variation in maternal breeds are illustrated. Knowledge of genetic parameters is required for the development of complex breeding objectives and selection indexes, comprehensive genetic evaluation of animals and the design of effective breeding programs. A review of world literature has highlighted the lack of accurate estimates of genetic parameters, especially for genetic correlations between trait groups. Analyses of a combined dataset from seven Australian Merino resource flocks comprising over 2000 sires and up to 100,000 records for each of various traits have provided accurate estimates of parameters to fill these gaps in current knowledge. The results show that there are no major genetic antagonisms between wool and meat traits and that improvement of both can be achieved by using appropriate selection indexes. Sheep Genetics Australia now provides a common system for genetic evaluation of Australian sheep, including across-flock estimated breeding values for a comprehensive range of traits and several standard indexes for various wool and meat breeding objectives
Yang's gravitational theory
Yang's pure space equations (C.N. Yang, Phys. Rev. Lett. v.33, p.445 (1974))
generalize Einstein's gravitational equations, while coming from gauge theory.
We study these equations from a number of vantage points: summarizing the work
done previously, comparing them with the Einstein equations and investigating
their properties. In particular, the initial value problem is discussed and a
number of results are presented for these equations with common energy-momentum
tensors.Comment: 28 pages, to appear in Gen. Rel. Gra
Functional analysis of antibodies against dengue virus type 4 reveals strain-dependent epitope exposure that impacts neutralization and protection
Although prior studies have characterized the neutralizing activities of monoclonal antibodies (MAbs) against dengue virus (DENV) serotypes 1, 2, and 3 (DENV-1, DENV-2, and DENV-3), few reports have assessed the activity of MAbs against DENV-4. Here, we evaluated the inhibitory activity of 81 new mouse anti-DENV-4 MAbs. We observed strain- and genotype-dependent differences in neutralization of DENV-4 by MAbs mapping to epitopes on domain II (DII) and DIII of the envelope (E) protein. Several anti-DENV-4 MAbs inefficiently inhibited at least one strain and/or genotype, suggesting that the exposure or sequence of neutralizing epitopes varies within isolates of this serotype. Remarkably, flavivirus cross-reactive MAbs, which bound to the highly conserved fusion loop in DII and inhibited infection of DENV-1, DENV-2, and DENV-3, more weakly neutralized five different DENV-4 strains encompassing the genetic diversity of the serotype after preincubation at 37°C. However, increasing the time of preincubation at 37°C or raising the temperature to 40°C enhanced the potency of DII fusion loop-specific MAbs and some DIII-specific MAbs against DENV-4 strains. Prophylaxis studies in two new DENV-4 mouse models showed that neutralization titers of MAbs after preincubation at 37°C correlated with activity in vivo. Our studies establish the complexity of MAb recognition against DENV-4 and suggest that differences in epitope exposure relative to other DENV serotypes affect antibody neutralization and protective activity
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