4,024 research outputs found
Remote Sensing and the Earth
A text book on remote sensing, as part of the earth resources Skylab programs, is presented. The fundamentals of remote sensing and its application to agriculture, land use, geology, water and marine resources, and environmental monitoring are summarized
Eccentricity evolution during planet–disc interaction
During the process of planet formation, the planet\u2013disc interactions might excite (or damp) the orbital eccentricity of the planet. In this paper, we present two long (t 3c 3
7 105 orbits) numerical simulations: (a) one (with a relatively light disc, Md/Mp = 0.2), where the eccentricity initially stalls before growing at later times and (b) one (with a more massive disc, Md/Mp = 0.65) with fast growth and a late decrease of the eccentricity. We recover the well-known result that a more massive disc promotes a faster initial growth of the planet eccentricity. However, at late times the planet eccentricity decreases in the massive disc case, but increases in the light disc case. Both simulations show periodic eccentricity oscillations superimposed on a growing/decreasing trend and a rapid transition between fast and slow pericentre precession. The peculiar and contrasting evolution of the eccentricity of both planet and disc in the two simulations can be understood by invoking a simple toy model where the disc is treated as a second point-like gravitating body, subject to secular planet\u2013planet interaction and eccentricity pumping/damping provided by the disc. We show how the counterintuitive result that the more massive simulation produces a lower planet eccentricity at late times can be understood in terms of the different ratios of the disc-to-planet angular momentum in the two simulations. In our interpretation, at late times the planet eccentricity can increase more in low-mass discs rather than in high-mass discs, contrary to previous claims in the literature
One-loop calculations of hyperon polarizabilities under the large N_c consistency condition
The spin-averaged electromagnetic polarizabilities of the hyperons
and are calculated within the one-loop approximation by use of the
dispersion theory. The photon and meson couplings to hyperons are determined so
as to satisfy the large N_c consistency condition. It is shown that in order
for the large N_c consistency condition to hold exotic hyperon states such as
with I=2 and J=3/2 are required in the calculation of the
magnetic polarizability of the state.Comment: 17 pages, REVTeX, no figure
Complete one-loop analysis of the nucleon's spin polarizabilities
We present a complete one-loop analysis of the four nucleon spin
polarizabilities in the framework of heavy baryon chiral perturbation theory.
The first non-vanishing contributions to the isovector and first corrections to
the isoscalar spin polarizabilities are calculated. No unknown parameters enter
these predictions. We compare our results to various dispersive analyses. We
also discuss the convergence of the chiral expansion and the role of the delta
isobar.Comment: 4 pp, REVTE
Fixed-t subtracted dispersion relations for Compton scattering off the nucleon
We present fixed- subtracted dispersion relations for Compton scattering
off the nucleon at energies 500 MeV, as a formalism to extract
the nucleon polarizabilities with a minimum of model dependence. The subtracted
dispersion integrals are mainly saturated by intermediate states in the
-channel and intermediate states
in the -channel . For the subprocess
, we construct a unitarized amplitude and find a
good description of the available data. We show results for Compton scattering
using the subtracted dispersion relations and display the sensitivity on the
scalar polarizability difference and the backward spin
polarizability , which enter directly as fit parameters in the
present formalism
Generalized Polarizabilities of the Nucleon in Chiral Effective Theories
Using the techniques of chiral effective field theories we evaluate the so
called generalized polarizabilities of the nucleon, which characterize the
structure dependent components in virtual Compton scattering (VCS) as probed in
the electron scattering reaction e N \to e' N gamma. Results are given for both
spin-dependent and spin-independent structure effects to O(p^3) in SU(2) Heavy
Baryon Chiral Perturbation Theory and to O(epsilon^3) in the SU(2) Small Scale
Expansion. Finally we compare our calculations with results from the pioneering
VCS experiment on the proton from Mainz.Comment: 39 pages, 12 figures, revte
Harnack inequality and regularity for degenerate quasilinear elliptic equations
We prove Harnack inequality and local regularity results for weak solutions
of a quasilinear degenerate equation in divergence form under natural growth
conditions. The degeneracy is given by a suitable power of a strong
weight. Regularity results are achieved under minimal assumptions on the
coefficients and, as an application, we prove local estimates
for solutions of a degenerate equation in non divergence form
A recipe for postfledging survival in great tits Parus major: be large and be early (but not too much)
Survival of juveniles during the postfledging period can be markedly low, which may have major consequences on avian population dynamics. Knowing which factors operating during the nesting phase affect postfledging survival is crucial to understand avian breeding strategies. We aimed to obtain a robust set of predictors of postfledging local survival using the great tit (Parus major) as a model species. We used markârecapture models to analyze the effect of hatching date, temperatures experienced during the nestling period, fledging size and body mass on first-year postfledging survival probability of great tit juveniles. We used data from 5192 nestlings of first clutches ringed between 1993 and 2010. Mean first-year postfledging survival probability was 15.2%, and it was lower for smaller individuals, as well as for those born in either very early or late broods. Our results stress the importance of choosing an optimum hatching period, and raising large chicks to increase first-year local survival probability in the studied population.SecretarĂa de Estado de InvestigaciĂłn, Desarrollo e InnovaciĂłn (Grant/Award Number: âCGL2013-48001-C2-1-Pâ)Peer reviewe
Beam Test Results of the BTeV Silicon Pixel Detector
The results of the BTeV silicon pixel detector beam test carried out at
Fermilab in 1999-2000 are reported. The pixel detector spatial resolution has
been studied as a function of track inclination, sensor bias, and readout
threshold.Comment: 8 pages of text, 8 figures, Proceedings paper of Pixel 2000:
International Workshop on Semiconductor Pixel Detectors for Particles and
X-Rays, Genova, June 5-8, 200
Beam Test of BTeV Pixel Detectors
The silicon pixel vertex detector is one of the key elements of the BTeV
spectrometer. Detector prototypes were tested in a beam at Fermilab. We report
here on the measured spatial resolution as a function of the incident angles
for different sensor-readout electronics combinations. We compare the results
with predictions from our Monte Carlo simulation.Comment: 7 pages, 5 figures, Invited talk given by J.C. Wang at "Vertex 2000,
9th International Workshop on Vertex Detectors", Michigan, Sept 10-15, 2000.
To be published in NIM
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