6,161 research outputs found
On the robust determination of eigenmodes in 2D stratified wave guiding systems with Berenger-type PML's.
A contour integration method is presented to determine the eigenmodes in a layered structure closed with PML layers at the boundaries of the computational window. Improvements are provided to ensure the accuracy of contour integration and to assure that all the encircled eigenvalues are determined. Numerical examples are presented to test the accuracy of the method
Vibration-Induced Conductivity Fluctuation (VICOF) Testing of Soils
In this Letter, we propose and experimentally demonstrate a simple method to
provide additional in-formation by conductivity measurements of soils. The AC
electrical conductance of the soil is measured while it is exposed to a
periodic vibration. The vibration-induced density fluctuation implies a
corresponding conductivity fluctuation that can be seen as combination
frequency components, the sum and the difference of the mean AC frequency and
the double of vibration frequency, in the current response. The method is
demonstrated by measurements on clayey and sandy soils
The Anticorrelated Nature of the Primary and Secondary Eclipse Timing Variations for the Kepler Contact Binaries
We report on a study of eclipse timing variations in contact binary systems,
using long-cadence lightcurves in the Kepler archive. As a first step,
'observed minus calculated' (O-C) curves were produced for both the primary and
secondary eclipses of some 2000 Kepler binaries. We find ~390 short-period
binaries with O-C curves that exhibit (i) random-walk like variations or
quasi-periodicities, with typical amplitudes of +/- 200-300 seconds, and (ii)
anticorrelations between the primary and secondary eclipse timing variations.
We present a detailed analysis and results for 32 of these binaries with
orbital periods in the range of 0.35 +/- 0.05 days. The anticorrelations
observed in their O-C curves cannot be explained by a model involving mass
transfer, which among other things requires implausibly high rates of ~0.01
M_sun per year. We show that the anticorrelated behavior, the amplitude of the
O-C delays, and the overall random-walk like behavior can be explained by the
presence of a starspot that is continuously visible around the orbit and slowly
changes its longitude on timescales of weeks to months. The quasi-periods of
~50-200 days observed in the O-C curves suggest values for k, the coefficient
of the latitude dependence of the stellar differential rotation, of
~0.003-0.013.Comment: Published in The Astrophysical Journal, 2013, Vol. 774, p.81; 14
pages, 12 figures, and 2 table
Extended Weak Coupling Limit for Friedrichs Hamiltonians
We study a class of self-adjoint operators defined on the direct sum of two
Hilbert spaces: a finite dimensional one called sometimes a ``small subsystem''
and an infinite dimensional one -- a ``reservoir''. The operator, which we call
a ``Friedrichs Hamiltonian'', has a small coupling constant in front of its
off-diagonal term. It is well known that under some conditions in the weak
coupling limit the appropriately rescaled evolution in the interaction picture
converges to a contractive semigroup when restricted to the subsystem. We show
that in this model, the properly renormalized and rescaled evolution converges
on the whole space to a new unitary evolution, which is a dilation of the above
mentioned semigroup. Similar results have been studied before \cite{AFL} in
more complicated models and they are usually referred to as "stochastic Limit".Comment: changes in notation and title, minor correction
Photometry of SN 2002bo with template image subtraction
VRI photometry of the type Ia supernova 2002bo is presented. This SN exploded
in a dusty region of the host galaxy NGC 3190, thus, subtraction of a template
frame was necessary to obtain reliable photometry. We used a template frame of
NGC 3190 taken during the course of our galaxy imaging project, fortunately,
just a few days before SN 2002bo was discovered. The aim of this project is to
collect template frames of nearby galaxies that are potential hosts of bright
SNe. Subtraction of pre-SN images helped us to exclude the background light
contamination of the host galaxy. The maximum occurred at JD 2452346, with
maximal V brightness of 13.58. MLCS analysis led to T0(B)=JD 2452346.1 pm 0.8
(fiducial B-maximum), E(B-V)=0.24 pm 0.02, mu0=32.46 pm 0.06, Delta=-0.14 pm
0.04. E(B-V)=0.24(2) indicates a significant extinction in the host galaxy as
the galactic reddening is negligible toward NGC 3190. The accepted value of
Delta indicates that SN 2002bo was a slightly overluminous SN by about 0.14
relative to fiducial SN Type Ia. The distance turned out to be 31.0 pm 3 Mpc.
In addition, the heavily obscured SN 2002cv was also detected on the I frame
taken on JD 2452434 (June 8, 2002), and a variable star is found in the field,
very close to the host galaxy.Comment: accepted by Astronomy and Astrophysic
Ising-like dynamical signatures and the end-point of the QCD transition line
An increase in the size of coherent domains in the one component
field theory under the influence of a uniformly changing external magnetic
field near the critical end-point was proposed
recently as an estimate also for the variation of the chiral correlation length
of QCD near its respective hypothetical end point in the
plane. The present detailed numerical investigation of the effective model
suggests that passing by the critical QCD end point with realistic rate of
temperature change will trigger large amplitude oscillations in the temporal
variation of the chiral correlation length. A simple mechanism for producing
this phenomenon is suggested.Comment: 10 pages, RevTeX, 5 figures. Version accepted for publication in PR
Exoplanet Research with the Stratospheric Observatory for Infrared Astronomy (SOFIA)
When the Stratospheric Observatory for Infrared Astronomy (SOFIA) was
conceived and its first science cases defined, exoplanets had not been
detected. Later studies, however, showed that optical and near-infrared
photometric and spectrophotometric follow-up observations during planetary
transits and eclipses are feasible with SOFIA's instrumentation, in particular
with the HIPO-FLITECAM and FPI+ optical and near infrared (NIR) instruments.
Additionally, the airborne-based platform SOFIA has a number of unique
advantages when compared to other ground- and space-based observatories in this
field of research. Here we will outline these theoretical advantages, present
some sample science cases and the results of two observations from SOFIA's
first five observation cycles -- an observation of the Hot Jupiter HD 189733b
with HIPO and an observation of the Super-Earth GJ 1214b with FLIPO and FPI+.
Based on these early products available to this science case, we evaluate
SOFIA's potential and future perspectives in the field of optical and infrared
exoplanet spectrophotometry in the stratosphere.Comment: Invited review chapter, accepted for publication in "Handbook of
Exoplanets" edited by H.J. Deeg and J.A. Belmonte, Springer Reference Work
Evaluating the effect of some botanical insecticides on the citrus mealybug Planococcus citri (Risso) (Hemiptera: Pseudococcidae)
Planococcus citri (Risso) (Homoptera: Pseudococcidae), is one of the key pests of citrus. The use of chemical pesticides for a long time can cause many problems such as pesticide resistance, as well as having an adverse effect on the environment. The use of chemical pesticides needs to be replaced with non-chemical control methods. The effects of tondexir (pepper extract) and palizin (eucalyptus extract) using five doses (500, 1000, 1500, 2000 and 3000 ppm) and sirinol (garlic extract) with five doses (1000, 1500, 2000, 2500 and 3500 ppm) on citrus mealybug was investigated. The effect of barter (a botanical synergist) using a single dose (1000 ppm) being added to tondexir and palizin at three doses (500, 1000 and 1500 ppm) and barter (1000 ppm) added to sirinol at four doses (1000, 1500, 2000 and 2500) on citrus mealybug was examined. Mortality was recorded after 24, 48, 72 and 96 h post-treatments. Analysis of variance showed that the highest mortality with 3000 ppm doses of tondexir and palizin was 90/60 ± 2/93 and 89/16 ± 1/92% with sirinol (3500 ppm) with 87.11 ± 1.11% mortality, respectively. However, the highest mortality by using barter plus tondexir and palizin (1500 ppm) was 94.44 ± 2.59 and 86.66 ± 3.6% and barter plus sirinol (2500 ppm) was 83.33 ± 3.6% mortality, respectively. There were significant differences between the two experiments (p < 1%).Keywords: Palizin, sirinol, tondexir, bartar synergist, Planococcus citr
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