6,871 research outputs found
Lidar detection of metallic species at the mesopause level
The measurement alkali species present in the atomic form at the mesopause level has been performed by lidar for more than ten years. Atomic and ionic calcium density profiles are obtained for 3 years by the same technique in the visible range, at 423 nm for atomic calcium, and 393 nm for ionic calcium Ca(+). The experimental set-up and the preliminary results have been presented elsewhere. The 423 nm wavelength is directly obtained by the emission of a dye laser pumped by the third harmonic of a Nd-YAG laser. For the generation of the 393 nm wavelength, frequency mixing was used: the emission at 624 nm of a dye laser pumped by the 2nd harmonic of a Nd-Yag laser is mixed with the fundamental infrared emission (remaining after frequency doubling), in a non-linear KDP crystal, which gives the 393 nm emission. The behavior of the two atomic species, calcium and sodium, which are in the same altitude range are compared. For 45% of the observations, no ionic calcium was detected: the ionic calcium abundance was thus below the detection threshold. Contrasting with the density profiles of the atomic species, sodium and calcium, the ionic calcium profile present important variations on small time scales. The main characteristics of theatomic and ionic calcium behaviors that can be deduced from the measurements made are given
Multiresistant Salmonella enterica serovar 4,[5],12:i:- in Europe: a new pandemic strain?
A marked increase in the prevalence of S. enterica serovar 4,[5],12:i:- with resistance to ampicillin, streptomycin, sulphonamides and tetracyclines (R-type ASSuT) has been noted in food-borne infections and in pigs/pig meat in several European countries in the last ten years. One hundred and sixteen strains of S. enterica serovar 4,[5],12:i:- from humans, pigs and pig meat isolated in England and Wales, France, Germany, Italy, Poland, Spain and the Netherlands were further subtyped by phage typing, pulsed-field gel electrophoresis and multilocus variable number tandem repeat analysis to investigate the genetic relationship among strains. PCR was performed to identify the fljB flagellar gene and the genes encoding resistance to ampicillin, streptomycin, sulphonamides and tetracyclines. Class 1 and 2 integrase genes were also sought. Results indicate that genetically related serovar 4,[5],12:i:- strains of definitive phage types DT193 and DT120 with ampicillin, streptomycin, sulphonamide and tetracycline resistance encoded by blaTEM, strA-strB, sul2 and tet(B) have emerged in several European countries, with pigs the likely reservoir of infection. Control measures are urgently needed to reduce spread of infection to humans via the food chain and thereby prevent the possible pandemic spread of serovar 4,[5],12:i:- of R-type ASSuT as occurred with S. Typhimurium DT104 during the 1990s
Gyrofluid analysis of electron ÎČ e effects on collisionless reconnection
The linear and nonlinear evolutions of the tearing instability in a collisionless plasma with a strong guide field are analysed on the basis of a two-field Hamiltonian gyrofluid model. The model is valid for a low ion temperature and a finite. The finite effect implies a magnetic perturbation along the guide field direction, and electron finite Larmor radius effects. A Hamiltonian derivation of the model is presented. A new dispersion relation of the tearing instability is derived for the case and tested against numerical simulations. For the equilibrium electron temperature is seen to enhance the linear growth rate, whereas we observe a stabilizing role when electron finite Larmor radius effects become more relevant. In the nonlinear phase, stall phases and faster than exponential phases are observed, similarly to what occurs in the presence of ion finite Larmor radius effects. Energy transfers are analysed and the conservation laws associated with the Casimir invariants of the model are also discussed. Numerical simulations seem to indicate that finite effects do not produce qualitative modifications in the structures of the Lagrangian invariants associated with Casimirs of the model
Noncollisional plasmoid instability based on a gyrofluid and gyrokinetic integrated approach
In this work, the development of two-dimensional current sheets with respect
to tearing-modes, in collisionless plasmas with a strong guide field, is
analysed. During their non-linear evolution, these thin current sheets can
become unstable to the formation of plasmoids, which allows the magnetic
reconnection process to reach high reconnection rates. We carry out a detailed
study of the impact of a finite , which also implies finite electron
Larmor radius effects, on the collisionless plasmoid instability. This study is
conducted through a comparison of gyrofluid and gyrokinetic simulations. The
comparison shows in general a good capability of the gyrofluid models in
predicting the plasmoid instability observed with gyrokinetic simulations. We
show that the effects of promotes the plasmoid growth. The impact of
the closure applied during the derivation of the gyrofluid model is also
studied through the comparison of the energy variation
Mitochondrial proteomics: analysis of a whole mitochondrial extract with two-dimensional electrophoresis
Mitochondria are complex organelles, and their proteomics analysis requires a
combination of techniques. The emphasis in this chapter is made first on
mitochondria preparation from cultured mammalian cells, then on the separation
of the mitochondrial proteins with two-dimensional electrophoresis (2DE),
showing some adjustment over the classical techniques to improve resolution of
the mitochondrial proteins. This covers both the protein solubilization, the
electrophoretic part per se, and the protein detection on the gels, which makes
the interface with the protein identification part relying on mass
spectrometry
Influence of ion-to-electron temperature ratio on tearing instability and resulting subion-scale turbulence in a low- collisionless plasma
A two-field gyrofluid model including ion finite Larmor radius (FLR)
corrections, magnetic fluctuations along the ambient field and electron inertia
is used to study two-dimensional reconnection in a low collisionless
plasma, in a plane perpendicular to the ambient field. Both moderate and large
values of the ion-to-electron temperature ratio are considered. The
linear growth rate of the tearing instability is computed for various values of
, confirming the convergence to reduced electron magnetodynamics (REMHD)
predictions in the large limit. Comparisons with analytical estimates in
several limit cases are also presented. The nonlinear dynamics leads to a
fully-developed turbulent regime that appears to be sensitive to the value of
the parameter . For , strong large-scale velocity shears
trigger Kelvin-Helmholtz instability, leading to the propagation of the
turbulence through the separatrices, together with the formation of eddies of
size of the order of the electron skin depth. In the regime, the
vortices are significantly smaller and their accurate description requires that
electron FLR effects be taken into account
Marked long-term decline in ambient CO mixing ratio in SE England, 1997â2014:Evidence of policy success in improving air quality
Atmospheric CO at Egham in SE England has shown a marked and progressive decline since 1997, following adoption of strict controls on emissions. The Egham site is uniquely positioned to allow both assessment and comparison of âclean Atlantic backgroundâ air and CO-enriched air downwind from the London conurbation. The decline is strongest (approximately 50ppb per year) in the 1997â2003 period but continues post 2003. A âlocal CO incrementâ can be identified as the residual after subtraction of contemporary background Atlantic CO mixing ratios from measured values at Egham. This increment, which is primarily from regional sources (during anticyclonic or northerly winds) or from the European continent (with easterly air mass origins), has significant seasonality, but overall has declined steadily since 1997. On many days of the year CO measured at Egham is now not far above Atlantic background levels measured at Mace Head (Ireland). The results are consistent with MOPITT satellite observations and âbottom-upâ inventory results. Comparison with urban and regional background CO mixing ratios in Hong Kong demonstrates the importance of regional, as opposed to local reduction of CO emission. The Egham record implies that controls on emissions subsequent to legislation have been extremely successful in the UK
2005 French Salmonella Network data on antimicrobial resistance in the swine channels
The Salmonella Network is gathering, on a voluntary participation scheme, from approximately 150 public and private laboratories dissemmated throughout France, Salmonella strains and/or epidemiological information. Those non-human Salmonella strains are isolated either from animal health and production or food, feed and the environment sectors. Thus, in 2005, a total of 527 isolations from the swine channels were reported. The top 5 prevalent serotypes were : Typhimurium, Derby, Manhattan, lnfantis and Kedougou. Two-hundred and ninety five strains were received at the laboratory and, after double clearance, 185 strains were tested for their antimicrobial resistance against 16 antibiotics by the disk diffusion method. Twenty-one strains were associated to the animal health and production sector and 164 to the food sector
PHENIX Highlights
Recent highlights of measurements by the PHENIX experiment at RHIC are
presented.Comment: 8 pages, 9 figures. Talk at Quark Matter 200
No boundaries for whales interacting with fishing activities targeting Patagonian toothfish (Dissostichus eleginoides)
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