41,801 research outputs found
First Disk-Resolved Millimeter Observations Of Io's Surface And SO2 Atmosphere
Aims. In spite of considerable progress in the last two decades, Io's atmosphere remains poorly understood. The goal of this work is to improve our understanding of its spatial distribution, temperature and dynamics. Methods. We present millimeter observations of Io's surface and SO2 atmosphere at 1.4 mm obtained with the IRAM Plateau de Bure Interferometer in January-February 2005. With a synthesized beam of 0.5 x 1.5 '', these observations resolve Io's similar to 1.0 '' disk in the longitudinal/local time direction, and sample the leading and trailing hemispheres of Io. Results. The measured continuum total flux and visibilities show that continuum radiation originates from a depth of at least 1 cm in Io's subsurface. On both the leading and trailing sides, emission in the SO2 216.643 GHz line appears spatially narrower than the continuum, and suggests that the atmosphere covers similar to 80% of the surface on the leading side and similar to 60% on the trailing. On the leading side, disk-resolved spectra yield Doppler shift measurements, indicating a beam-integrated limb-to-limb velocity difference of 330 +/-3 100 m/s in the prograde direction. Such a flow allows an improved fit of disk-averaged SO2 spectra, but its origin remains to be understood. Mean gas temperatures are in the range 130-180 K, in agreement with estimates from IR measurements, and with a tendency for higher trailing vs leading side gas temperatures. On the basis of realistic plume models, we find that the contribution of isolated volcanic plumes to the SO2 emission is small.Astronom
Searching for Very High Energy Emission from Pulsars Using the High Altitude Water Cherenkov (HAWC) Observatory
There are currently over 160 known gamma-ray pulsars. While most of them are
detected only from space, at least two are now seen also from the ground. MAGIC
and VERITAS have measured the gamma ray pulsed emission of the Crab pulsar up
to hundreds of GeV and more recently MAGIC has reported emission at
TeV. Furthermore, in the Southern Hemisphere, H.E.S.S. has detected the Vela
pulsar above 30 GeV. In addition, non-pulsed TeV emission coincident with
pulsars has been detected by many groups, including the Milagro Collaboration.
These GeV-TeV observations open the possibility of searching for
very-high-energy (VHE, > 100GeV) pulsations from gamma-rays pulsars in the HAWC
field of view.Comment: Presented at the 34th International Cosmic Ray Conference (ICRC2015),
The Hague, The Netherlands. See arXiv:1508.03327 for all HAWC contribution
Errors on the inverse problem solution for a noisy spherical gravitational wave antenna
A single spherical antenna is capable of measuring the direction and
polarization of a gravitational wave. It is possible to solve the inverse
problem using only linear algebra even in the presence of noise. The simplicity
of this solution enables one to explore the error on the solution using
standard techniques. In this paper we derive the error on the direction and
polarization measurements of a gravitational wave. We show that the solid angle
error and the uncertainty on the wave amplitude are direction independent. We
also discuss the possibility of determining the polarization amplitudes with
isotropic sensitivity for any given gravitational wave source.Comment: 13 pages, 4 figures, LaTeX2e, IOP style, submitted to CQ
Elysia timida (Risso, 1818) three decades of research
Elysia timida (Risso, 1818) three decades of research.— During the last 30 years, studies on Elysia timida (Risso,
1818) have addressed various aspects related to food sources, photosynthetic efficiency of kleptoplasts, population
genetics, chemical ecology and reproductive biology, both in the Mediterranean Sea and in the Mar Menor
coastal lagoon. E. timida shows a strong specific interaction with Acetabularia acetabulum, retaining functional
chloroplasts for at least 45 days and obtaining extra energy in periods when food resources are scarce. It shows
control of parapodia, avoiding pigment photodestruction under oversaturated light conditions. The chemical ecological
relationships established between E. timida and its potential predator fish, Thalassoma pavo, have also
been evaluated, and it has been found that that the extracts of the mollusc contain repellent and unpalatable
polypropionate compounds. Population genetics has demonstrated the genetic divergence between populations
showing high and significant values of FST and genetic distances, and at least six privative alleles that are not
shared with Mediterranean populations have been detected in lagoon populations. This sacoglossan is a poecilogonic
species, and its lagoon populations show a greater reproductive output than Mediterranean populations; they
produce a greater number of egg masses and embyros per individual, and the capsules have a wider diameter
Entanglement of two qubits mediated by one-dimensional plasmonic waveguides
We investigate qubit-qubit entanglement mediated by plasmons supported by
one-dimensional waveguides. We explore both the situation of spontaneous
formation of entanglement from an unentangled state and the emergence of driven
steady-state entanglement under continuous pumping. In both cases, we show that
large values for the concurrence are attainable for qubit-qubit distances
larger than the operating wavelength by using plasmonic waveguides that are
currently available.Comment: 4 pages, 4 figures. Minor Changes. Journal Reference added.
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