13,487 research outputs found
VLA Polarimetry of Two Extended Radio Galaxies
Multi-wavelength VLA observations of two extended radio galaxies, 0235-197
and 1203+043 are presented. There is some evidence from earlier studies that
these two sources exhibit low frequency (<1 GHz) variability. This work shows
that both sources have linear polarizations, if any, below the detection limits
at 320 MHz, so we cannot explain the variability as being due to instrumental
polarization effects as has been suggested for 3C159. Refractive scintillation
may be the cause of the variability in 0235-197. This would require the
existence of a bright, compact component in one of the hot spots seen in these
observations. This is not implausible but the resolution of this observational
program is insufficent to address that question. The radio source 1203+043
lacks any bright compact component thereby ruling out a refractive
scintillation mechanism for its variability. Consequently, it is possible that
claims of variability in this source are spurious. However, the 320 MHz VLA
observations show that 1203+043 has an `X'-shaped radio structure. This is a
rare morphology for the brightness distribution of a radio galaxy; the
implications of this are examined.Comment: 8 pages, plain tex, accepted by Astronomy and Astrophysics,
Supplement Serie
Credit availability in the crisis: which role for the European Investment Bank Group?
In this paper we consider a moral hazard problem between a creditworthy firm which needs funding and a bank. We first study under which conditions the firm does not obtain the loan. We then determine whether and how the intervention of an external financial institution can facilitate the access to credit. In particular, we focus on the European Investment Bank Group (EIBG), which provides (i) specific credit lines to help banks that finance small and medium-sized enterprises (SMEs)and (ii) guarantees for portfolios of SMEs'loans. We show that only during crises the EIBG intervention allows to totally overcome the credit crunch.
Geo-neutrinos
We review a new interdisciplinary field between Geology and Physics: the
study of the Earth's geo-neutrino flux. We describe competing models for the
composition of the Earth, present geological insights into the make up of the
continental and oceanic crust, those parts of the Earth that concentrate Th and
U, the heat producing elements, and provide details of the regional settings in
the continents and oceans where operating and planned detectors are sited.
Details are presented for the only two operating detectors that are capable of
measuring the Earth's geo-neutrinos flux: Borexino and KamLAND; results
achieved to date are presented, along with their impacts on geophysical and
geochemical models of the Earth. Finally, future planned experiments are
highlighted
Two-sided radio emission in ON231 (W Comae)
Recent radio images of the BL Lac object ON231 (W Com, 1219+285) show
remarkable new features in the source structure compared to those previously
published. The images were obtained from observations made with the European
VLBI Network plus MERLIN at 1.6 GHz and 5 GHz after the exceptional optical
outburst occurred in Spring 1998. The up-to-date B band historic light curve of
ON231 is also presented together with the R band luminosity evolution in the
period 1994--1999. We identify the source core in the radio images with the
brightest component having the flattest spectrum. A consequence of this
assumption is the existence of a two--sided emission in ON231 not detected in
previous VLBI images. A further new feature is a large bend in the jet at about
10 mas from the core. The emission extends for about 20 mas after the bend,
which might be due to strong interaction with the environment surrounding the
nucleus. We suggest some possible interpretations to relate the changes in the
source structure with the optical and radio flux density variation in the frame
of the unification model.Comment: 8 pages, 8 figure
Reactor Antineutrinos Signal all over the world
We present an updated estimate of reactor antineutrino signal all over the
world, with particular attention to the sites proposed for existing and future
geo-neutrino experiment. In our calculation we take into account the most
updated data on Thermal Power for each nuclear plant, on reactor antineutrino
spectra and on three neutrino oscillation mechanism.Comment: 4 pages including 1 figur
Mantle geoneutrinos in KamLAND and Borexino
The KamLAND and Borexino experiments have observed, each at ~4 sigma level,
signals of electron antineutrinos produced in the decay chains of thorium and
uranium in the Earth's crust and mantle (Th and U geoneutrinos). Various pieces
of geochemical and geophysical information allow an estimation of the crustal
geoneutrino flux components with relatively small uncertainties. The mantle
component may then be inferred by subtracting the estimated crustal flux from
the measured total flux. To this purpose, we analyze in detail the experimental
Th and U geoneutrino event rates in KamLAND and Borexino, including neutrino
oscillation effects. We estimate the crustal flux at the two detector sites,
using state-of-the-art information about the Th and U distribution on global
and local scales. We find that crust-subtracted signals show hints of a
residual mantle component, emerging at ~2.4 sigma level by combining the
KamLAND and Borexino data. The inferred mantle flux slightly favors scenarios
with relatively high Th and U abundances, within +-1 sigma uncertainties
comparable to the spread of predictions from recent mantle models.Comment: Slight changes and improvements in the text & figures. Results
unchanged. To appear in Phys. Rev.
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