2,971 research outputs found
A Characterisation of the Weylian Structure of Space-Time by Means of Low Velocity Tests
The compatibility axiom in Ehlers, Pirani and Schild's (EPS) constructive
axiomatics of the space-time geometry that uses light rays and freely falling
particles with high velocity, is replaced by several constructions with low
velocity particles only. For that purpose we describe in a space-time with a
conformal structure and an arbitrary path structure the radial acceleration, a
Coriolis acceleration and the zig-zag construction. Each of these quantities
give effects whose requirement to vanish can be taken as alternative version of
the compatibility axiom of EPS. The procedural advantage lies in the fact, that
one can make null-experiments and that one only needs low velocity particles to
test the compatibility axiom. We show in addition that Perlick's standard clock
can exist in a Weyl space only.Comment: to appear in Gen.Rel.Gra
Screening of entomopathogenic nematodes for virulence against the invasive western corn rootworm, Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae) in Europe
Entomopathogenic nematode species available in Europe were screened for their efficacy against both the root-feeding larvae and silk-feeding adults of the western corn rootworm, Diabrotica virgifera virgifera LeConte. Laboratory screening tests were aimed at the selection of candidate biological control agents for the management of this invasive alien pest in Europe. Steinernema glaseri, S. arenarium, S. abassi, S. bicornutum, S. feltiae, S. kraussei, S. carpocapsae and Heterorhabditis bacteriophora were studied to determine their virulence against third instar larvae and adults of D. v. virgifera in small-volume arenas (using nematode concentrations of 0.5, 0.8, 7.9 and 15.9 infective juveniles cm-2). All nematode species were able to invade and propagate in D. v. virgifera larvae, but adults were rarely infected. At concentrations of 7.9 and 15.9 cm-2, S. glaseri, S. arenarium, S. abassi and H. bacteriophora caused the highest larval mortality of up to 77%. Steinernema bicornutum, S. abassi, S. carpocapsae and H. bacteriophora appeared to have a high propagation level, producing 5970±779, 5595±811, 5341±1177 and 4039±1025 infective juveniles per larva, respectively. Steinernema glaseri, S. arenarium, S. feltiae, S. kraussei and H. bacteriophora were further screened at a concentration of 16.7 nematodes cm-2 against third instar larvae in medium-volume arenas (sand-filled trays with maize plants). Heterorhabditis bacteriophora, S. arenarium and S. feltiae caused the highest larval mortality with 77±16.6%, 67±3.5%, and 57±17.1%, respectively. In a next step, criteria for rating the entomopathogenic nematode species were applied based on results obtained for virulence and propagation, and for current production costs and availability in Europe. These criteria were then rated to determine the potential of the nematodes for further field testing. Results showed the highest potential in H. bacteriophora, followed by S. arenarium and S. feltiae, for further testing as candidate biological control agent
The influence of phase variants of Xenorhabdus spp. and Escherichia coli (Enterobacteriaceae) on the propagation of entomopathogenic nematodes of the genera Steinernema and Heterorhabditis
Symmetries of the Energy-Momentum Tensor: Some Basic Facts
It has been pointed by Hall et al. [1] that matter collinations can be
defined by using three different methods. But there arises the question of
whether one studies matter collineations by using the ,
or or . These alternative
conditions are, of course, not generally equivalent. This problem has been
explored by applying these three definitions to general static spherically
symmetric spacetimes. We compare the results with each definition.Comment: 17 pages, accepted for publication in "Communications in Theoretical
Physics
Proficiency Test of Four Salmonella Antibody ELISA-Tests for their Harmonization
The paper describes the necessity to only use tests for national salmonella monitoring and reduction programmes that are âharmonizedâ, i.e. that produce at least at herd level the same results. Four in Germany licensed tests were audited in a proficiency test by four independent and neutral laboratories. The test was designed rather to harmonize the tests, if necessary, than to evaluate the single tests. The methods used to provide a high credibility for the proficiency testâs outcome are explained. The conclusion of the ring test is that three of the four tests can be used for the salmonella monitoring programme in Germany as long as not single results are compared to each other, but the results of sets of sera are used for the herd categorization for their risk level of introducing Salmonella spec. into the food chain
High serum levels of sCD23 and sCD25 in early stage B-CLL correlate with clinical characteristics predictive for progressive disease
Existence of families of spacetimes with a Newtonian limit
J\"urgen Ehlers developed \emph{frame theory} to better understand the
relationship between general relativity and Newtonian gravity. Frame theory
contains a parameter , which can be thought of as , where
is the speed of light. By construction, frame theory is equivalent to general
relativity for , and reduces to Newtonian gravity for .
Moreover, by setting \ep=\sqrt{\lambda}, frame theory provides a framework to
study the Newtonian limit \ep \searrow 0 (i.e. ). A number of
ideas relating to frame theory that were introduced by J\"urgen have
subsequently found important applications to the rigorous study of both the
Newtonian limit and post-Newtonian expansions. In this article, we review frame
theory and discuss, in a non-technical fashion, some of the rigorous results on
the Newtonian limit and post-Newtonian expansions that have followed from
J\"urgen's work
A comparative health economic evaluation of two treatments for grass pollen induced allergic rhinoconjunctivitis
Orbits in the Field of a Gravitating Magnetic Monopole
Orbits of test particles and light rays are an important tool to study the
properties of space-time metrics. Here we systematically study the properties
of the gravitational field of a globally regular magnetic monopole in terms of
the geodesics of test particles and light. The gravitational field depends on
two dimensionless parameters, defined as ratios of the characteristic mass
scales present. For critical values of these parameters the resulting metric
coefficients develop a singular behavior, which has profound influence on the
properties of the resulting space-time and which is clearly reflected in the
orbits of the test particles and light rays.Comment: 24 pages, 15 figures. Accepted for publication in GR
Dynamics of spatially homogeneous solutions of the Einstein-Vlasov equations which are locally rotationally symmetric
The dynamics of a class of cosmological models with collisionless matter and
four Killing vectors is studied in detail and compared with that of
corresponding perfect fluid models. In many cases it is possible to identify
asymptotic states of the spacetimes near the singularity or in a phase of
unlimited expansion. Bianchi type II models show oscillatory behaviour near the
initial singularity which is, however, simpler than that of the mixmaster
model.Comment: 27 pages, 3 figures, LaTe
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