4,312 research outputs found
The Design of Private Reinsurance Contracts
This paper examines the role of reinsurance relationships in the trading of underwriting risk when this trade takes place in an environment that is characterized by asymmetric information and in which information is revealed only over time. It begins by explaining how information problems affect the efficiency of the allocation of risk between insurer and reinsurer, and how long-term implicit contracts between insurers and reinsurers allow the inclusion of new information in the pricing of both future and past reinsurance coverage. Because of these features, the ceding company purchases a more efficient quantity of reinsurance. Specifically, such arrangements lead to more reinsurance coverage, higher insurer profits, and lower expected distress in the industry. It is, in short, Pareto improving.
Refined masses and distance of the young binary Haro 1-14 C
We aim to refine the dynamical masses of the individual component of the
low-mass pre-main sequence binary Haro 1-14 C. We combine the data of the
preliminary orbit presented previously with new interferometric observations
obtained with the four 8m telescopes of the Very Large Telescope
Interferometer. The derived masses are M_a=0.905\pm0.043\,\Msun and
M_b=0.308\pm0.011\,\Msun for the primary and secondary components,
respectively. This is about five times better than the uncertainties of the
preliminary orbit. Moreover, the possibility of larger masses is now securely
discarded. The new dynamical distance, pc, is smaller than the
distance to the Ophiuchus core with a significance of . Fitting
the spectral energy distribution yields apparent diameters of
\phi_a=0.13\pm0.01\mas and \phi_b=0.10\pm0.01\mas (corresponding to
\Ra=1.50\,\Rsun and \Rb=1.13\,\Rsun) and a visual extinction of
. Although the revised orbit has a nearly edge-on geometry, the
system is unlikely to be a long-period eclipsing binary. The secondary in
Haro~1-14C is one of the few low-mass, pre-main sequence stars with an
accurately determined dynamical mass and distance
Learning to Localize and Align Fine-Grained Actions to Sparse Instructions
Automatic generation of textual video descriptions that are time-aligned with
video content is a long-standing goal in computer vision. The task is
challenging due to the difficulty of bridging the semantic gap between the
visual and natural language domains. This paper addresses the task of
automatically generating an alignment between a set of instructions and a first
person video demonstrating an activity. The sparse descriptions and ambiguity
of written instructions create significant alignment challenges. The key to our
approach is the use of egocentric cues to generate a concise set of action
proposals, which are then matched to recipe steps using object recognition and
computational linguistic techniques. We obtain promising results on both the
Extended GTEA Gaze+ dataset and the Bristol Egocentric Object Interactions
Dataset
A PIONIER View on Mass-Transferring Red Giants
Symbiotic stars display absorption lines of a cool red giant together with
emission lines of a nebula ionized by a hotter star, indicative of an active
binary star system in which mass transfer is occurring. PIONIER at the VLT has
been used to combine the light of four telescopes at a time to study in
unprecedented detail how mass is transferred in symbiotic stars. The results of
a mini-survey of symbiotic stars with PIONIER are summarised and some tentative
general results about the role of Roche lobe overflow are presented.Comment: Report for the ESO Messenger June issu
On the kinematic detection of accreted streams in the Gaia era: a cautionary tale
The CDM cosmological scenario predicts that our Galaxy should
contain hundreds of stellar streams at the solar vicinity, fossil relics of the
merging history of the Milky Way and more generally of the hierarchical growth
of galaxies. Because of the mixing time scales in the inner Galaxy, it has been
claimed that these streams should be difficult to detect in configuration space
but can still be identifiable in kinematic-related spaces like the
energy/angular momenta spaces, E-Lz and Lperp-Lz, or spaces of orbital/velocity
parameters. By means of high-resolution, dissipationless N-body simulations,
containing between 25 and 35 particles, we model the
accretion of a series of up to four 1:10 mass ratio satellites then up to eight
1:100 satellites and we search systematically for the signature of these
accretions in these spaces. In all spaces considered (1) each satellite gives
origin to several independent overdensities; (2) overdensities of multiple
satellites overlap; (3) satellites of different masses can produce similar
substructures; (4) the overlap between the in-situ and the accreted population
is considerable everywhere; (5) in-situ stars also form substructures in
response to the satellite(s) accretion. These points are valid even if the
search is restricted to kinematically-selected halo stars only. As we are now
entering the 'Gaia era', our results warn that an extreme caution must be
employed before interpreting overdensities in any of those spaces as evidence
of relics of accreted satellites. Reconstructing the accretion history of our
Galaxy will require a substantial amount of accurate spectroscopic data, that,
complemented by the kinematic information, will possibly allow us to
(chemically) identify accreted streams and measure their orbital properties.
(abridged)Comment: Accepted on A&A. A high-resolution version of the paper is available
at http://aramis.obspm.fr/~paola/ELZ/Elz.pd
Effects of NHC-Backbone Substitution on Efficiency in Ruthenium-Based Olefin Metathesis
series of ruthenium olefin metathesis catalysts bearing N-heterocyclic carbene (NHC) ligands with varying degrees of backbone and N-aryl substitution have been prepared. These complexes show greater resistance to decomposition through CâH activation of the N-aryl group, resulting in increased catalyst lifetimes. This work has utilized robotic technology to examine the activity and stability of each catalyst in metathesis, providing insights into the relationship between ligand architecture and enhanced efficiency. The development of this robotic methodology has also shown that, under optimized conditions, catalyst loadings as low as 25 ppm can lead to 100% conversion in the ring-closing metathesis of diethyl diallylmalonate
Fluctuations of the Casimir-like force between two membrane inclusions
Although Casimir forces are inseparable from their fluctuations, little is
known about these fluctuations in soft matter systems. We use the membrane
stress tensor to study the fluctuations of the membrane-mediated Casimir-like
force. This method enables us to recover the Casimir force between two
inclusions and to calculate its variance. We show that the Casimir force is
dominated by its fluctuations. Furthermore, when the distance d between the
inclusions is decreased from infinity, the variance of the Casimir force
decreases as -1/d^2. This distance dependence shares a common physical origin
with the Casimir force itself.Comment: 5 pages, 3 figure
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