382 research outputs found
DBD PLASMA CATALYSIS PROCESS FOR CARBON RECOVERY
Since many years carbon dioxide reduction by hydrogen through catalyst processes is a usual way from the Paul Sabatier reaction to produce CH4. this process is able to be done from thermal process by using an heterogeneous catalyst such as zirconia cerium support with nickel sites for the hydrogen reduction of CO2 .However this reaction is well working ( 85%-90%) at 350?c and its selectivity depends of the secondary reactions such us carbon monoxide or carbon deposit which appears above 350?C.199-19
Interactions Between a Condensed Target and a Non-Equilibrium Plasma: Acid-Base Reactions at the Interface
A new approach of plasma processes of industrial use is presented, with emphasis on the chemical properties of the plasma gas. Reactions occurring at the gas/target interface are for the first time interpreted in terms of acid-base reactions and pertinent examples are given of laboratory experiments and of industrial treatments (e. g., etching, plasma polymerization or surface modification processes). Proton exchanges between the plasma phase and an aqueous target gives evidence of Bronsted acid-base phenomena. Illustrations of Lewis acid-base characters are provided by the role of biradicals (e.g., halogenocarbenes, nitrenc) which are the main reacting species in etching or in surface treatment processes
Structure and diversity of shallow soft-bottom benthic macrofauna in the Gulf of Lions (NW Mediterranean).
14 páginas, 10 figuras, 4 tablas.Samples of soft-sediment macrobenthos from
92 sites between 10 and 50 m depth were used to assess (1)
the main soft-bottom macrofauna communities in the Gulf
of Lions, (2) the different components of the diversity of
benthic macrofauna in this area, and (3) the relevance of
the use of major taxonomic groups as surrogates for the
analysis of the structure and diversity of total macrofauna.
Three main communities were identified by cluster analysis
and associated procedures. These communities corresponded well to the assemblages recently identified on the
basis of polychaete composition. The a-diversity indices
were in accordance with those reported for similar communities in the Mediterranean. Conversely, the b-diversity
value was higher than the few other data available in the
literature for marine soft-bottom macrofauna. The total
number of species in the studied area estimated by the
‘‘total species accumulation curve’’ (TS) method was
2,319, which was only 10% higher than the number
obtained by extrapolation of the species–area curve. The
similarity matrix based on polychaetes correlated best with
the one based on total macrofauna. Polychaetes and crustaceans were also the best surrogates of total macrofauna
when assessing a-diversity (except in the case of D*).
Conversely, molluscs were the best surrogates of total
macrofauna b-diversity. Our results show that the choice of
an optimal surrogate for total benthic macrofauna depends
on the characteristic of the benthic macrofauna to be
studied. Moreover, this choice is also dependent on the
environment to be studiedThis work is part of the PhD thesis of Ce´line
Labrune. It was carried out within the EC Network of Excellence
MARBEF. Ce´line Labrune was supported by the SYSCOLAG project
run by the Re´gion Languedoc-Roussillon.Peer reviewe
Spring molybdenum enrichment in scallop shells: a potential tracer of diatom productivity in temperate coastal environments (Brittany, NW France)
Skeletal molybdenum/calcium ([Mo]/[Ca])<sub>shell</sub> ratios were examined in
shells of the Great Scallop <i>Pecten maximus</i> collected in temperate coastal environments of
Western Europe (42 to 49° N). These ratios were determined by
quantitative LA-ICP-MS analyses of daily striae taken every third day (i.e.
a temporal resolution of 3 days) in 36 flat valves (2-years old; 3
shells/year). Variations of ([Mo]/[Ca])<sub>shell</sub> ratios were significant
and reproducible for scallops from the same population, from different years
(1998–2004) and temperate coastal locations (NW France). The
[Mo]/[Ca])<sub>shell</sub> ratios exhibit typical profiles characterized by a
background content, below the detection limit for this method
(<0.003 μmol/mol) for most of the shell growth period, which is punctuated by a
significant transient enrichment (0.031–2.1 μmol/mol) mainly occurring
from May to June. The Bay of Brest (France) was investigated in particular
because of its long term observations on scallop communities, environmental
variables, and high resolution analyses of dissolved Mo in bottom seawater
in 2000. In 2000, dissolved Mo exhibited a significant increase in
concentration just preceding the maximum ([Mo]/[Ca])<sub>shell</sub> ratio. Both
the intense monitoring survey in 2000 and over the 7-year period indicates
that the ([Mo]/[Ca])<sub>shell</sub> maximum is directly influenced by spring
changes of environmental conditions at the sediment water interface (SWI),
occurring subsequent to the intense and periodic spring bloom. Spring maxima
of ([Mo]/[Ca])<sub>shell</sub> ratios are closely correlated to the extent of
silicic acid and nitrate depletion in seawater between winter and late
spring (<i>r</i><sup>2</sup>=0.878 and 0.780, <i>p</i><0.05, <i>n</i>=6) that reflects diatom
uptake and productivity in the Bay of Brest. The Mo inputs in bottom waters
and subsequent shell enrichment are thus suggested to be directly or
indirectly influenced by such biogenic material input at the SWI. The
[Mo]/[Ca])<sub>shell</sub> records thus reveal unexpected biogeochemical cycles of
Mo influenced by coastal spring productivity, faithfully recorded in scallop
shells
A survey on parallel and distributed Multi-Agent Systems
International audienceSimulation has become an indispensable tool for researchers to explore systems without having recourse to real experiments. Depending on the characteristics of the modeled system, methods used to represent the system may vary. Multi-agent systems are, thus, often used to model and simulate complex systems. Whatever modeling type used, increasing the size and the precision of the model increases the amount of computation, requiring the use of parallel systems when it becomes too large. In this paper, we focus on parallel platforms that support multi-agent simulations. Our contribution is a survey on existing platforms and their evaluation in the context of high performance computing. We present a qualitative analysis, mainly based on platform properties, then a performance comparison using the same agent model implemented on each platform
Abundance of Delta Resonances in 58Ni+58Ni Collisions between 1 and 2 AGeV
Charged pion spectra measured in 58Ni-58Ni collisions at 1.06, 1.45 and 1.93
AGeV are interpreted in terms of a thermal model including the decay of Delta
resonances. The transverse momentum spectra of pions are well reproduced by
adding the pions originating from the Delta-resonance decay to the component of
thermal pions, deduced from the high transverse momentum part of the pion
spectra. About 10 and 18% of the nucleons are excited to Delta states at
freeze-out for beam energies of 1 and 2 AGeV, respectively.Comment: 14 pages, LaTeX with 3 included figures; submitted to Physics Letters
Stopping and Radial Flow in Central 58Ni + 58Ni Collisions between 1 and 2 AGeV
The production of charged pions, protons and deuterons has been studied in
central collisions of 58Ni on 58Ni at incident beam energies of 1.06, 1.45 and
1.93 AGeV. The dependence of transverse-momentum and rapidity spectra on the
beam energy and on the centrality of the collison is presented. It is shown
that the scaling of the mean rapidity shift of protons established for AGS and
SPS energies is valid down to 1 AGeV. The degree of nuclear stopping is
discussed; the IQMD transport model reproduces the measured proton rapidity
spectra for the most central events reasonably well, but does not show any
sensitivity between the soft and the hard equation of state (EoS). A radial
flow analysis, using the midrapidity transverse-momentum spectra, delivers
freeze-out temperatures T and radial flow velocities beta_r which increase with
beam energy up to 2 AGeV; in comparison to existing data of Au on Au over a
large range of energies only beta_r shows a system size dependence
Distinct spatiotemporal patterns and PARP dependence of XRCC1 recruitment to single-strand break and base excision repair
Single-strand break repair (SSBR) and base excision
repair (BER) of modified bases and abasic sites
share several players. Among them is XRCC1, an
essential scaffold protein with no enzymatic
activity, required for the coordination of both
pathways. XRCC1 is recruited to SSBR by PARP-1,
responsible for the initial recognition of the break.
The recruitment of XRCC1 to BER is still poorly
understood. Here we show by using both local and
global induction of oxidative DNA base damage that
XRCC1 participation in BER complexes can be distinguished
from that in SSBR by several criteria. We
show first that XRCC1 recruitment to BER is independent
of PARP. Second, unlike SSBR complexes
that are assembled within minutes after global
damage induction, XRCC1 is detected later in BER
patches, with kinetics consistent with the repair of
oxidized bases. Third, while XRCC1-containing foci
associated with SSBR are formed both in eu- and
heterochromatin domains, BER complexes are
assembled in patches that are essentially excluded
from heterochromatin and where the oxidized bases
are detected
K^+ production in the reaction at incident energies from 1 to 2 AGeV
Semi-inclusive triple differential multiplicity distributions of positively
charged kaons have been measured over a wide range in rapidity and transverse
mass for central collisions of Ni with Ni nuclei. The transverse
mass () spectra have been studied as a function of rapidity at a beam
energy 1.93 AGeV. The distributions of K^+ mesons are well described by a
single Boltzmann-type function. The spectral slopes are similar to that of the
protons indicating that rescattering plays a significant role in the
propagation of the kaon. Multiplicity densities have been obtained as a
function of rapidity by extrapolating the Boltzmann-type fits to the measured
distributions over the remaining phase space. The total K^+ meson yield has
been determined at beam energies of 1.06, 1.45, and 1.93 AGeV, and is presented
in comparison to existing data. The low total yield indicates that the K^+
meson can not be explained within a hadro-chemical equilibrium scenario,
therefore indicating that the yield does remain sensitive to effects related to
its production processes such as the equation of state of nuclear matter and/or
modifications to the K^+ dispersion relation.Comment: 24 pages Latex (elsart) 7 PS figures to be submitted to Nucl. Phys
- …