11,445 research outputs found
Correlated Spectral and Temporal Variability in the High-Energy Emission from Blazars
Blazar flare data show energy-dependent lags and correlated variability
between optical/X-ray and GeV-TeV energies, and follow characteristic
trajectories when plotted in the spectral-index/flux plane. This behavior is
qualitatively explained if nonthermal electrons are injected over a finite time
interval in the comoving plasma frame and cool by radiative processes.
Numerical results are presented which show the importance of the effects of
synchrotron self-Compton cooling and plasmoid deceleration. The use of INTEGRAL
to advance our understanding of these systems is discussed.Comment: 8 pages, 5 figures, uses epsf.sty, rotate.sty Invited paper in "The
Extreme Universe," 3rd INTEGRAL Workshop, 14-18 September 1998, Taorimina,
Ital
Testing Gaussian random hypothesis with the cosmic microwave background temperature anisotropies in the three-year WMAP data
We test the hypothesis that the temperature of the cosmic microwave
background is consistent with a Gaussian random field defined on the celestial
sphere, using de-biased internal linear combination (DILC) map produced from
the 3-year WMAP data. We test the phases for spherical harmonic modes with l <=
10 (which should be the cleanest) for their uniformity, randomness, and
correlation with those of the foreground templates. The phases themselves are
consistent with a uniform distribution, but not for l <= 5, and the differences
between phases are not consistent with uniformity. For l=3 and l=6, the phases
of the CMB maps cross-correlate with the foregrounds, suggestion the presence
of residual contamination in the DLC map even on these large scales. We also
use a one-dimensional Fourier representation to assemble a_lm into the \Delta
T_l(\phi) for each l mode, and test the positions of the resulting maxima and
minima for consistency with uniformity randomness on the unit circle. The
results show significant departures at the 0.5% level, with the one-dimensional
peaks being concentrated around \phi=180 degs. This strongly significant
alignment with the Galactic meridian, together with the cross-correlation of
DILC phases with the foreground maps, strongly suggests that even the lowest
spherical harmonic modes in the map are significantly contaminated with
foreground radiation.Comment: submitted to ApJL, one paragraph is added in Section 3 and some more
in the Referenc
Attempts to Enrich the Parasite Fauna of the European Corn Borer in Minnesota
Four parasitic insect species were tested in laboratory experimentation for adaptability to the European corn borer (ECB). Apanreles sesamiae, Apanteles flavipes and Chelonus knabi did not adapt to the ECB, Lixophaga diatraeae was able to survive on ECB. Three other species. Macrocentrus grandii, Eriborus terebrans and Lydella rhompsoni, all known parasites of ECB, were obtained and reared in the laboratory on ECB for propagation, release and ecological studies. Methodology for experimentation and propagation of parasites was described
Auto and cross correlation of phases of the whole-sky CMB and foreground maps from the 1-year WMAP data
The issue of non-Gaussianity is not only related to distinguishing the
theories of the origin of primordial fluctuations, but also crucial for the
determination of cosmological parameters in the framework of inflation
paradigm. We present an advenced method for testing non-Gaussianity on the
whole-sky CMB anisotropies. This method is based on the Kuiper's statistic to
probe the two-dimensional uniformity on a periodic mapping square associating
phases: return mapping of phases of the derived CMB (similar to auto
correlation) and cross correlations between phases of the derived CMB and
foregrounds. Since phases reflect morphology, detection of cross correlation of
phases signifies the contamination of foreground signals in the derived CMB
map. The advantage of this method is that one can cross check the auto and
cross correlation of phases of the derived CMB and foregrounds, and mark off
those multipoles in which the non-Gaussianity results from the foreground
contaminations. We apply this statistic on the derived signals from the 1-year
WMAP data. The auto-correlations of phases from the ILC map shows the
significance above 95% CL against the random phase hypothesis on 17 spherical
harmonic multipoles, among which some have pronounced cross correlations with
the foreground maps. We conclude that most of the non-Gaussianity found in the
derived CMB maps are from foreground contaminations, except, among others, l=6.
With this method we are better equipped to approach the issue of
non-Gaussianity of primordial origin for the upcoming PLANCK mission.Comment: 2 figures added: new representation of reconstructed (from 1D Fourier
composition) DT distribution for each multipole number el
European Corn Borer Parasitoids; Distribution in Southern Minnesota
During the 1940\u27s and 1950\u27s seven exotic parasitoids of the European corn borer (ECB) Ostrinia nubilalis (Hubner), were released in Minnesota. This study was done to determine which introduced parasitoids became established and their distribution in Minnesota. The experiment was conducted during the summer of 1977 and fall of 1977, 78, 79- and 80 in conjunction with the annual ECB population surveys in southern Minnesota by the State Department of Agriculture, Division of Plant Industry. Three introduced parasitoids, Macrocentrus grandii Goidanich, Eriborus Terebrans (Gravenhorst), and Sympiesis viridula (Thomson) and two native parasitoids, lshnus inquisitorius artricollaris (Walsh) and Aplomya caesar (Aldrich) were recovered. M. grandii was confined to the eastern portion, while E. terebrans was recovered from throughout southern Minnesota. S. viridula was found in only three counties, perhaps because of its biology it may have eluded recovery, resulting in underestimated distribution. The two native species, I. inquisitorius atricollaris and A. caesar, occur only occasionally in Minnesota
Dynamical coupled-channel model of kaon-hyperon interactions
The pi N --> KY and KY --> KY reactions are studied using a dynamical
coupled-channel model of meson-baryon interactions at energies where the baryon
resonances are strongly excited. The channels included are: pi N, K \Lambda,
and K\Sigma. The resonances considered are: N^* [S_{11}(1650), P_{11}(1710),
P_{13}(1720),D_{13}(1700)]; \Delta^* [S_{31}(1900), P_{31}(1910),
P_{33}(1920)]; \Lambda ^* [S_{01}(1670), P_{01}(1810)] \Sigma^* [P_{11}(1660),
D_{13}(1670)]; and K^*(892). The basic non-resonant \pi N --> KY and KY --> KY
transition potentials are derived from effective Lagrangians using a unitary
transformation method. The dynamical coupled-channel equations are simplified
by parametrizing the pi N -->pi N amplitudes in terms of empirical pi N
partial-wave amplitudes and a phenomenological off-shell function. Two models
have been constructed. Model A is built by fixing all coupling constants and
resonance parameters using SU(3) symmetry, the Particle Data Group values, and
results from a constituent quark model. Model B is obtained by allowing most of
the parameters to vary around the values of model A in fitting the data. Good
fits to the available data for pi^- p to K^0 \Lambda, K^0 \Sigma^0 have been
achieved. The investigated kinematics region in the center-of-mass frame goes
from threshold to 2.5 GeV. The constructed models can be imbedded into
associated dynamical coupled-channel studies of kaon photo- and
electro-production reactions.Comment: 35 pages, 11 Figure
Spin injection from perpendicular magnetized ferromagnetic -MnGa into (Al,Ga)As heterostructures
Electrical spin injection from ferromagnetic -MnGa into an (Al,Ga)As
p-i-n light emitting diode (LED) is demonstrated. The -MnGa layers show
strong perpendicular magnetocrystalline anisotropy, enabling detection of spin
injection at remanence without an applied magnetic field. The bias and
temperature dependence of the spin injection are found to be qualitatively
similar to Fe-based spin LED devices. A Hanle effect is observed and
demonstrates complete depolarization of spins in the semiconductor in a
transverse magnetic field.Comment: 4 pages, 3 figure
On the Antenna Beam Shape Reconstruction Using Planet Transit
The calibration of the in-flight antenna beam shape and possible
beamdegradation is one of the most crucial tasks for the upcoming Planck
mission. We examine several effects which could significantly influence the
in-flight main beam calibration using planet transit: the problems of the
variability of the Jupiter's flux, the antenna temperature and passing of the
planets through the main beam. We estimate these effects on the antenna beam
shape calibration and calculate the limits on the main beam and far sidelobe
measurements, using observations of Jupiter and Saturn. We also discuss
possible effects of degradation of the mirror surfaces and specify
corresponding parameters which can help us to determine these effects.Comment: 10 pages, 8 figure
Shifts of the nuclear resonance in the vortex lattice in YBaCuO
The NMR and NQR spectra of Cu in the CuO plane of
YBaCuO in the superconducting state are discussed in terms of the
phenomenological theory of Ginzburg-Landau type extended to lower temperatures.
We show that the observed spectra, Kumagai {\em et al.}, PRB {\bf 63}, 144502
(2001), can be explained by a standard theory of the Bernoulli potential with
the charge transfer between CuO planes and CuO chains assumed.Comment: 11 pages 7 figure
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