1,115 research outputs found
Impact of different Agents on the Efficacy of Codling Moth Granulovirus in Tank Mixtures
In the control of codling moth it is common to combine the granulovirus with other agents,
especially fungicides, in spray application. Therefore the knowledge about the influence of
these agents on the efficacy of the virus in tank mix is very important. Studies on this
subject were part of a project supported by BMELV (German Federal Ministry for Food,
Agriculture and Consumer protection) at the Institute for Biological Control of JKI in
Darmstadt.
The granulovirus of Cydia pomonella (L.) (CpGV) was mixed with 10 different agents at
concentrations as applied in the field. After the exposure the virus activity was calculated
from larval mortality determined in bioassays with neonates of a susceptible codling moth
strain.
Only two agents with a pH of 11 (sodium silicate (water glass) and calcium polysulfide
(lime sulphur)) reduced the virulence of CpGV significantly
Spectroscopy of a fractional Josephson vortex molecule
In long Josephson junctions with multiple discontinuities of the Josephson
phase, fractional vortex molecules are spontaneously formed. At each
discontinuity point a fractional Josephson vortex carrying a magnetic flux
, Wb being the magnetic flux
quantum, is pinned. Each vortex has an oscillatory eigenmode with a frequency
that depends on and lies inside the plasma gap.
We experimentally investigate the dependence of the eigenfrequencies of a
two-vortex molecule on the distance between the vortices, on their topological
charge and on the bias current applied to the
Josephson junction. We find that with decreasing distance between vortices, a
splitting of the eigenfrequencies occurs, that corresponds to the emergence of
collective oscillatory modes of both vortices. We use a resonant microwave
spectroscopy technique and find good agreement between experimental results and
theoretical predictions.Comment: submitted to Phys. Rev.
Fourier decomposition and frequency analysis of the pulsating stars with P<1 d in the OGLE database. I. Monoperiodic Delta Scuti, RRc and RRab variables. Separation criteria and particularities
The OGLE database is revisited to investigate in more detail the properties
of the Fourier parameters. Methodological improvements led us to identify a
clear separation among High-Amplitude Delta Scuti (HADS), RRc and RRab stars.
The bimodal distribution of the R21 parameter in HADS stars is explained as a
contamination effect from RRc stars: there is evidence that all stars with
0.20<P<0.25 d are RRc variables. The previously claimed existence of a subclass
of unusual HADS is demonstrated to be a spurious result. Candidate overtone
pulsators are found among HADS and RRc variables. The properties of the Fourier
parameters are discussed as a function of the physical conditions in the stars
involved. Among the field RRab stars we detected different light-curve groups
producing distinct "tails" in the Fourier plots for P>0.55 d; evolutionary
phases or the combination of different physical conditions (not only
metallicity) are suggested to explain this separation, observed also in the
cluster RRab stars. The stellar parameters of RRc stars in a given globular
cluster show different tendencies than those of RRc stars from different
clusters.Comment: 12 pages (in A&A style), 14 eps figures. Accepted for A&A Main
Journal. Table 3, 4 and 5 are also included as ascii files. The atlas of the
light curves and least-squares fits can be requested from the autho
Use of a proposed antimicrobial susceptibility testing method for Haemophilus parasuis
The aim of this study was to examine the antimicrobial susceptibility of 97 Haemophilus parasuis cultured from Australian pigs. As there is no existing standard antimicrobial susceptibility technique available for H. parasuis, methods utilising the supplemented media, BA/SN for disc diffusion and test medium broth (TMB) for a microdilution technique, were initially evaluated with the reference strains recommended by the Clinical and Laboratory Standards Institute. The results of the media evaluation suggested that BA/SN and TMB can be used as suitable media for susceptibility testing of H. parasuis. The proposed microdilution technique was then used with 97 H. parasuis isolates and nine antimicrobial agents. The study found that Australian isolates showed elevated minimum inhibitory concentrations (MICs) for ampicillin (1%), penicillin (2%), erythromycin (7%), tulathromycin (9%), tilmicosin (22%), tetracycline (31%) and trimethoprim-sulfamethoxazole (40%). This study has described potential antimicrobial susceptibility methods for H. parasuis and has detected a low percentage of Australian H. parasuis isolates with elevated antimicrobial MICs
Hydrodynamical Survey of First Overtone Cepheids
A hydrodynamical survey of the pulsational properties of first overtone
Galactic Cepheids is presented. The goal of this study is to reproduce their
observed light- and radial velocity curves. The comparison between the models
and the observations is made in a quantitative manner on the level of the
Fourier coefficients. Purely radiative models fail to reproduce the observed
features, but convective models give good agreement.
It is found that the sharp features in the Fourier coefficients are indeed
caused by the P1/P4 = 2 resonance, despite the very large damping of the 4th
overtone. For the adopted mass-luminosity relation the resonance center lies
near a period of 4.2d +/- 0.2 as indicated by the observed radial velocity
data, rather than near 3.2d as the light-curves suggest.Comment: ApJ, 12 pages, (slightly) revise
Thermal escape of fractional vortices in long Josephson junctions
We consider a fractional Josephson vortex in a long 0-kappa Josephson
junction. A uniformly applied bias current exerts a Lorentz force on the
vortex. If the bias current exceeds the critical current, an integer fluxon is
torn off the kappa-vortex and the junction switches to the voltage state.
In the presence of thermal fluctuations the escape process takes place with
finite probability already at subcritical values of the bias current.
We experimentally investigate the thermally induced escape of a fractional
vortex by high resolution measurements of the critical current as a function of
the topological charge kappa of the vortex and compare the results to numerical
simulations for finite junction lengths and to theoretical predictions for
infinite junction lengths. To study the effect caused by the junction geometry
we compare the vortex escape in annular and linear junctions.Comment: submitted to PR
High Mass Triple Systems: The Classical Cepheid Y Car
We have obtained an HST STIS ultraviolet high dispersion Echelle mode
spectrum the binary companion of the double mode classical Cepheid Y Car. The
velocity measured for the hot companion from this spectrum is very different
from reasonable predictions for binary motion, implying that the companion is
itself a short period binary. The measured velocity changed by 7 km/ s during
the 4 days between two segments of the observation confirming this
interpretation. We summarize "binary" Cepheids which are in fact members of
triple system and find at least 44% are triples. The summary of information on
Cepheids with orbits makes it likely that the fraction is under-estimated.Comment: accepted by A
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