Measurements of atmospheric electricity aloft

Measurements of the electrical characteristics of the atmosphere above the surface have been made for over 200 years, from a variety of different platforms, including kites, balloons, rockets and aircraft. From these measurements, a great deal of information about the electrical characteristics of the atmosphere has been gained, assisting our understanding of the global atmospheric electric circuit, thunderstorm electrification and lightning generation mechanisms, discovery of transient luminous events above thunderstorms, and many other electrical phenomena. This paper surveys the history of atmospheric electrical measurements aloft, from the earliest manned balloon ascents to current day observations with free balloons and aircraft. Measurements of atmospheric electrical parameters in a range of meteorological conditions are described, including clear air conditions, polluted conditions, non-thunderstorm clouds, and thunderstorm clouds, spanning a range of atmospheric conditions, from fair weather, to the most electrically active

Catalytic wet air oxidation of sewage sludge: Performances of soluble metallic salts

internationa

Performances of soluble metallic salts in the catalytic wet air oxidation of sewage sludge

SSCI-VIDE+CARE:CDFA+CDS:MBEInternational audienceNon

Catalytic wet air oxidation of sewage sludge: performances of soluble metallic salts

SSCI-VIDE+CARE:CDFA+CDS:MBEInternational audienceNon

Performances of soluble metallic salts in the catalytic wet air oxidation of sewage sludge

Bernardi, Marco Cretenot, Didier Deleris, Stephane Descorme, Claude Chauzy, Julien Besson, Michele 6th World Congress on Oxidation Catalysis (6WCOC) JUL 05-10, 2009 Lille, FRANCEInternational audienceVarious soluble transition metal salts were compared in the wet air oxidation of industrial and municipal sewage sludges (2 5-25 g L-1 total organic carbon) at 200-250 degrees C under 4-15 bar O-2 partial pressure The evolution of the TOC content in both the liquid and solid phases and the overall TOC conversion were monitored While copper sulphate prevented the dissolution of the suspended organic matter due to strong bounding of copper to a fraction of the organic matter in sludge and showed high activity in the mineralization of the solubilized organic compounds (liquid phase) the implementation of iron sulphate resulted in a higher transfer of the organic matter to the liquid phase but in a moderate activity in the oxidation of solubilized molecules When used in combination a synergetic effect between these two salts was evidenced (C) 2010 Elsevier BV All rights reserve

Pharmacodynamic modelling of β-lactam/β-lactamase inhibitor checkerboard data: illustration with aztreonam–avibactam

International audienceOBJECTIVES: Checkerboard experiments followed by fractional inhibitory concentration (FIC) index determinations are commonly used to assess in vitro pharmacodynamic interactions between combined antibiotics, but FIC index cannot be determined in case of antibiotic/non-active compound combinations. The aim of this study was to use a simple modelling approach to quantify the in vitro activity of aztreonam-avibactam, a new β-lactam-β-lactamase inhibitor combination.METHODS: MIC checkerboard experiments were performed with 12 Enterobacteriaceae with diverse β-lactamases profiles. Aztreonam MICs in the absence and presence of avibactam at different concentrations (ranging from 0.0625 to 4 mg/L) were determined. Aztreonam MIC versus avibactam concentrations were fitted by an inhibitory Emax model with a baseline effect parameter.RESULTS: A concentration-dependent relationship was observed with a steep initial reduction of aztreonam MIC at low avibactam concentrations and reaching a maximum at higher avibactam concentrations that was adequately fitted by the model. Maximum avibactam effect was characterized by the ratio of aztreonam MICs in the absence of avibactam (MIC0) and when avibactam concentration tends toward infinity (MIC∞), and this ratio ranged between 90 and 10 068 depending on the strain. Avibactam potency was characterized by avibactam concentrations corresponding to 50% of the maximum effect (IC50 values between 0.00022 and 0.053 mg/L).CONCLUSIONS: An inhibitory Emax model with a baseline effect could quantify maximum avibactam effect and potency among various strains. This simple modelling approach can be used to compare the activity of other combinations of antibiotics with non-antibiotic drugs when FIC index is inappropriate

Surface precipitation electric current produced by convective rains during the Mesoscale Alpine Program.

This paper presents data from measurements of electric field, precipitation current density, and rainfall parameters performed during the Mesoscale Alpine Program experiment in northern Italy during autumn 1999. Several days of the period provided substantially charged rainfall of both polarities. The average proportions of each polarity are close, but the negative one is slightly larger (54%). Three Doppler radars provided a description of the cells' development and dynamics. A case of a deeply convective cell occurred on 17 September 1999. In this case, the precipitation current density is first positive, reaches more than 100 nA m-2, and changes its polarity when the rainfall is maximum with a value close to 200 mm h-1. We also consider several shallow convective cells passing over the experimental site on 3 October. Two cells among a set of eight did not produce electrical parameter variations although they displayed development and radar reflectivity structure similar to that of the others. The dynamical study shows that the vertical velocity (averaged over 1 km × 1 km mesh) was weaker within these two cells with a value of only 0.5 m s-1 while it reached 1.5 m s-1 within the other cells. Both charge polarities were observed on the rain produced by electrified cells, first the negative one and then the positive one. A very tight correlation between surface electric field and precipitation current is observed out at the surface, displaying the mirror image effect. The ground electric field is due to the cloud charge, in contrast with that carried down to the ground by the rainfall. In order to reproduce the field evolution created by the cell passage, we test different models of charge distribution. A model including a horizontal distribution is found to provide a field evolution in best agreement with the observations. According to this model the net charge of the cloud above the site is chronologically positive and negative, which can be the result of the evacuation of an opposite charge by the rain