4,244 research outputs found
Neutrinos from supernovae: experimental status and perspectives
I discuss the state of the art in the search for neutrinos from galactic
stellar collapses and the future perspectives of this field. The implications
for the neutrino physics of a high statistics supernova neutrino burst
detection by the network of detectors operating around the world are also
reviewed.Comment: 19 pages, 12 figures. Extended version of talk given at IInd
International Workshop on Matter, Anti-Matter and Dark Matter, Trento
(Italy), 29-30 October 2001. A reduced version will appear in Int. J. of Mod.
Phys.
Thermal hadron production in high energy collisions
It is shown that hadron abundances in high energy e+e-, pp and p{\bar p}
collisions, calculated by assuming that particles originate in hadron gas
fireballs at thermal and partial chemical equilibrium, are in very good
agreement with the data. The freeze-out temperature of the hadron gas fireballs
turns out to be nearly constant over a large center of mass energy range and
not dependent on the initial colliding system. The only deviation from chemical
equilibrium resides in the incomplete strangeness phase space saturation.
Preliminary results of an analysis of hadron abundances in S+S and S+Ag heavy
ion collisions are presented.Comment: 10 pages, 1 .eps figure, talk given at the Strangeness and Quark
Matter 97 conferenc
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MGS accelerometer data analysis with the LMD GCM
Mars Global Surveyor aerobreaking phases, required to
achieve its mapping orbit, have yielded vertical profiles
of thermospheric densities, scale heights and temperatures
covering a broad range of local times, seasons and
spatial coordinates [Keating et al. 1998, 2001]. Phase
I covered local times from 11 to 16 h (assuming 24
"martian hours” per martian day or sols), with a latitude
coverage of approximately 40deg to 60deg N. Seasons
observed during this phase were centered around winter
solstice and altitudes of periapsis range from 115 to
135 km. The altitudes for Phase II were lower, with a
minimum around 100 km and a maximum around 120.
Martian spring was the season covered during this phase
and the local time was between 15 and 16 h. The latitude
covered by Phase II, however, was more extense
than that seen during Phase I, with a coverage from 60deg N
to basically the South Pole
Mineral oil paraffins in jute bags and cocoa butter
Jute bags and cocoa butter (CB) were analysed by gas chromatography (GC-FID/MS) to detect and quantify mineral oil saturated hydrocarbons (MOSH). Extraction clean-up on silica gel SPE (10 g/60 ml) was developed, as a unique sample preparation step for the determination of linear and branched n-alkanes in the range C14 to C31. The size of CB sample (500 mg) was sufficient for the detection of batching oil at levels of 2 mg kg−1, with satisfactory recovery and repeatability. MOSH from batching oil form a hump of unresolved components and the shape reflect balanced molecular-mass distribution between even and odd carbon atoms (from C14 to C22n-alkanes), expressed with the Carbon Preference Index (CPI=∑odd homologs/∑even homologs). Contaminated raw CB extracted from cocoa beans, transported and stored in jute bags during 2000 and 2001, showed MOSH (average 42 mg kg−1). However, only the 7.5% of the samples analysed of deodorized CB from 2007 to 2009 contained MOSH −1. High CPI values (>1.26) were attributed to natural hydrocarbons with a strong predominance of odd-numbered paraffins, situated between C22 and C31n-alkanes (average 31.7±5.37 mg kg−1). The results confirmed that MOSH components below n-C20 were fully eliminated by the deodorization process
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Towards a global model of the martian atmosphere
In an effort to continuously improve the capabilities of the Martian atmospheric predictions at LMD, the GCM has been extended into thermospheric heights thus creating the first model to self-consistently couple the lower and upper
regions of the Martian atmosphere. The behaviour of
the Martian thermosphere is strongly influenced by
lower atmospheric processes and has complex dynamics.
Such a fully coupled model will certainly aid in the preparation of future missions and on the analysis of future high altitude data, as well as serve as a base for the simulation of ionospheric processes, escape, etc
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Modeling of the general circulation with the LMD-AOPP-IAA GCM: Update on model design and comparison with observations
The LMD-AOPP GCM is developed conjointly by LMD in Paris and AOPP in Oxford, with the collaboration of
IAA in Granada for the physical processes specific to the upper atmosphere. The collaboration between the
two teams is based on the use of two different dynamical core (gridpoint at LMD, spectral at AOPP), which
allow us to estimate the likely uncertainty arising from certain types of modeling errors. Similarly, we use
different schemes to compute tracer transport, etc. The work has benefited from support from ESA (since 1995)
and CNES (since 2000). Within that context, the GCMs are used to produce a Martian climate 'database' which
is used by more than 30 teams around the world for mission design and scientific studies (see Bingham et al.,
this issue and Lewis et al., 1999). The baseline version of the GCM is described in detail in Forget et al. (1999). Here we describe the recent improvement and design changes since this publication. Compared to this previous version, the new GCM covers a wider range of altitude, from 0 to 120km in the vertical, it uses improved topography and thermal inertia surface
maps from Mars Global Surveyor (MGS), and includes a new 'dust scenario' to describe the distribution of airborne dust in the atmosphere
Positioning systems in Minkowski space-time: from emission to inertial coordinates
The coordinate transformation between emission coordinates and inertial
coordinates in Minkowski space-time is obtained for arbitrary configurations of
the emitters. It appears that a positioning system always generates two
different coordinate domains, namely, the front and the back emission
coordinate domains. For both domains, the corresponding covariant expression of
the transformation is explicitly given in terms of the emitter world-lines.
This task requires the notion of orientation of an emitter configuration. The
orientation is shown to be computable from the emission coordinates for the
users of a `central' region of the front emission coordinate domain. Other
space-time regions associated with the emission coordinates are also outlined.Comment: 20 pages; 1 figur
On the degrees of freedom of a semi-Riemannian metric
A semi-Riemannian metric in a n-manifold has n(n-1)/2 degrees of freedom,
i.e. as many as the number of components of a differential 2-form. We prove
that any semi-Riemannian metric can be obtained as a deformation of a constant
curvature metric, this deformation being parametrized by a 2-for
Overlooked impacts and challenges of the new European discard ban
Discards are the portion of animal and plant material in the catch that is dumped back at sea. The Common Fisheries Policy plan proposed by the European Commission for 2014-2020 presents a controversial goal: to enforce the landing of fishing discards as a measure to encourage their reduction. This historical and political decision will shape the future of the fishing exploitation in European Seas. Discards generated by European fleets are not negligible, and its reduction is an ecological, socioeconomical and moral imperative. However, it must be achieved through the reduction in discards at source and the promotion of selective and non-destructive gears. We argue it is doubtful that this discard ban will result in an effective reduction of discards. The proposed measure may, in fact, negatively affect ecosystems at all levels of biological hierarchy by disregarding the Ecosystem-Based Approach to Fisheries and the Precautionary Principle. It could negatively impact several species by increasing fishing mortality, also commercial species if discards are not accounted in the total allowable catch. Communities preying on discards will likely be affected. The role discards currently play in the energy turnover of current ecosystems will be modified and should be fully evaluated. The landing of discards will likely generate new markets of fishmeal due to the growing demands for marine living resources. The ban will require substantial public investment to deal with technical problems on board and to control and enforce. Therefore, this measure should be only implemented after rigorous scientific and technical studies have been developed
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The Mars Climate Database
The Mars Climate Database (MCD) [1] is a database of statistics describing the climate and environment of the Martian atmosphere. It was constructed directly on the basis of output from mulitannual integrations of two general circulation models (GCMs)developed by Laboratoire de Météorologie Dynamique du CNRS, France, the University of Oxford, UK, and Instituto de Astrofisica de Andalucia, Spain, with support from the European Space Agency (ESA) and Centre National d–Etudes Spatiales (CNES). A description of the MCD is given along with a comparison between spacecraft observations of Mars and results predicted at similar locations and times in the MCD.
The MCD can be used as a tool for mission planning and has been applied to prepare for several missions in Europe and the USA. It also provides information for mission design specialists on the mean state and variability of the Martian environment from the surface to above 120km. The GCMs on which the database is founded, include a set of physical parameterizations (radiative transfer in the visible and thermal infrared ranges, turbulent mixing, condensation-sublimation of CO2, thermal conduction in
the soil and representation of gravity waves) and two
different codes for the representation of large scale
dynamics: a spectral code for the AOPP version and
a grid-point code for the LMD version. The GCMs correctly reproduce the main meteorological features of Mars, as observed by the Mariner 9 and Viking orbiters, the Viking landers, and Mars Global Surveyor (MGS). As well as the standard statistical measures for mission design studies, the MCD includes a novel representation of large-scale variability, using empirical eigenfunctions derived from an
analysis of the full simulations, and small-scale variability based on parameterizations of processes such
as gravity wave propagation. The database allows the user to choose from 5 dust storm scenarios including a best guess, default scenario, deduced from recent MGS observations, an upper boundary for an atmosphere without dust storms, as observed by Viking the landers, and a clear, cold, lower boundary scenario, as observed by Phobos 2 and from Earth. The full version of the MCD is available on CDROM (for UNIX systems and PCs) and is also
accessible through an interactive WWW interface at
http://www-mars.lmd.jussieu.fr/
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