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Sharan M.,Indian Institute of Technology Delhi | Singh S.K.,Indian Institute of Technology Delhi | Issartel J.P.,Center dEtudes du Bouchet
Pure and Applied Geophysics | Year: 2012

The identification of single and multiple-point emission sources from limited number of atmospheric concentration measurements is addressed using least square data assimilation technique. During the process, a new two-step algorithm is proposed for optimization, free from initialization and filtering singular regions in a natural way. Source intensities are expressed in terms of their locations reducing the degree of freedom of unknowns to be estimated. In addition, a strategy is suggested for reducing the computational time associated with the multiple-point source identification. The methodology is evaluated with the synthetic, pseudo-real and noisy set of measurements for two and three simultaneous point emissions. With the synthetic data, algorithm estimates the source parameters exactly same as the prescribed in all the cases. With the pseudo-real data, two and three point release locations are retrieved with an average error of 17 m and intensities are estimated on an average within a factor of 2. Finally, the advantages and limitations of the proposed methodology are discussed. © 2011 Springer Basel AG. Source

van Agthoven M.A.,University Pierre and Marie Curie | van Agthoven M.A.,Lille University of Science and Technology | Colomby P.,University Pierre and Marie Curie | Surugue M.,University Pierre and Marie Curie | And 3 more authors.
International Journal of Mass Spectrometry | Year: 2010

The kinetic energy of ion beams upon ejection from a quadrupole ion trap was measured in view of coupling quadrupole ion traps with other mass analyzers. Measurements were performed using a retarding grid analyser for two modes of ion ejection from the quadrupole ion trap based on the decrease of the amplitude of the radiofrequency voltage on the ring electrode simultaneously combined with the application of: (i) a positive voltage on the ring electrode and (ii) a voltage between the end-cap electrodes. We show that ion kinetic energy at ejection depends on the DC ejection voltage and the amplitude of the RF voltage at the moment of ejection, which means that the kinetic energy of the ions that are ejected from the ion trap depends on the m/. z ratio. Ion focusing depends on the depth of the pseudo-potential well in the quadrupole ion trap. © 2010 Elsevier B.V. Source

Al Dahouk S.,German Federal Institute for Risk Assessment | Al Dahouk S.,RWTH Aachen | Hofer E.,Austrian Agency for Health and Food Safety | Tomaso H.,Friedrich Loeffler Institute | And 11 more authors.
Applied and Environmental Microbiology | Year: 2012

Brucellosis is one of the major bacterial zoonoses worldwide. In the past decade, an increasing number of atypical Brucella strains and species have been described. Brucella microti in particular has attracted attention, because this species not only infects mammalian hosts but also persists in soil. An environmental reservoir may pose a new public health risk, leading to the reemergence of brucellosis. In a polyphasic approach, comprising conventional microbiological techniques and extensive biochemical and molecular techniques, all currently available Brucella microti strains were characterized. While differing in their natural habitats and host preferences, B. microti isolates were found to possess identical 16S rRNA, recA, omp2a, and omp2b gene sequences and identical multilocus sequence analysis (MLSA) profiles at 21 different genomic loci. Only highly variable microsatellite markers of multiple-locus variable-number tandem repeat (VNTR) analysis comprising 16 loci (MLVA-16) showed intraspecies discriminatory power. In contrast, biotyping demonstrated striking differences within the genetically homologous species. The majority of the mammalian isolates agglutinated only with monospecific anti-M serum, whereas soil isolates agglutinated with anti-A, anti-M, and anti-R sera. Bacteria isolated from animal sources were lysed by phages F1, F25, Tb, BK2, Iz, and Wb, whereas soil isolates usually were not. Rough strains of environmental origin were lysed only by phage R/C. B. microti exhibited high metabolic activities similar to those of closely related soil organisms, such as Ochrobactrum spp. Each strain was tested with 93 different substrates and showed an individual metabolic profile. In summary, the adaptation of Brucella microti to a specific habitat or host seems to be a matter of gene regulation rather than a matter of gene configuration. © 2012, American Society for Microbiology. Source

Issartel J.-P.,Center dEtudes du Bouchet | Sharan M.,Indian Institute of Technology Delhi | Singh S.K.,Indian Institute of Technology Delhi
Pure and Applied Geophysics | Year: 2012

This paper addresses the parametric inverse problem of locating the point of release of atmospheric pollution. A finite set of observed mixing ratios is compared, by use of least squares, with the analogous mixing ratios computed by an adjoint dispersion model for all possible locations of the release. Classically, the least squares are weighted using the covariance matrix of the measurement errors. However, in practice, this matrix cannot be determined for the prevailing part of these errors arising from the limited representativity of the dispersion model. An alternative weighting proposed here is related to a unified approach of the parametric and assimilative inverse problems corresponding, respectively, to identification of the point of emission or estimation of the distributed emissions. The proposed weighting is shown to optimize the resolution and numerical stability of the inversion. The importance of the most common monitoring networks, with point detectors at various locations, is stressed as a misleading singular case. During the procedure it is also shown that a monitoring network, under given meteorological conditions, itself contains natural statistics about the emissions, irrespective of prior assumptions. © 2011 Springer Basel AG. Source

Sharan M.,Indian Institute of Technology Delhi | Issartel J.-P.,Center dEtudes du Bouchet | Singh S.K.,Indian Institute of Technology Delhi
Quarterly Journal of the Royal Meteorological Society | Year: 2012

An inversion technique is proposed to reconstruct an elevated point emission source of known height of atmospheric trace species from a finite number of concentration measurements in low-wind stable conditions. Observations from the SF 6 diffusion experiment at Idaho National Engineering Laboratory in low-wind stable conditions are used for the point source reconstruction. The source location and its strength are both retrieved exactly with the model-generated measurements in all the runs. With real data, the location is reconstructed with an average error of 20 m, mostly along the wind, and the intensity is retrieved within a factor of 2 in all the runs. The incurred errors in the retrieval are justified by estimating the angular departure between the vectors of measurement and adjoint function. A sensitivity study is carried out to analyse the sensitivity of the source estimation with respect to signal perturbation caused by the background concentration of the species in the ambient air. Source reconstruction is shown to be improved and more focused when the samplers having a measurement value corresponding to the background concentration are maintained in the inversion process. © 2012 Royal Meteorological Society. Source

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