Mass selective axial ion ejection from a linear quadrupole ion trap

AbstractThe electric fields responsible for mass-selective axial ejection (MSAE) of ions trapped in a linear quadrupole ion trap have been studied using a combination of analytic theory and computer modeling. Axial ejection occurs as a consequence of the trapped ions' radial motion, which is characterized by extrema that are phase-synchronous with the local RF potential. As a result, the net axial electric field experienced by ions in the fringe region, over one RF cycle, is positive. This axial field depends strongly on both the axial and radial ion coordinates. The superposition of a repulsive potential applied to an exit lens with the diminishing quadrupole potential in the fringing region near the end of a quadrupole rod array can give rise to an approximately conical surface on which the net axial force experienced by an ion, averaged over one RF cycle, is zero. This conical surface has been named the cone of reflection because it divides the regions of ion reflection and ion ejection. Once an ion penetrates this surface, it feels a strong net positive axial force and is accelerated toward the exit lens. As a consequence of the strong dependence of the axial field on radial displacement, trapped thermalized ions can be ejected axially from a linear ion trap in a mass-selective way when their radial amplitude is increased through a resonant response to an auxiliary signal

The anaerobic biodegradation of petroleum-related compounds.

The toxicity and biodegradation of mixtures of thiols, thiophenes, thiophenic acids and aromatic sulfides were determined under anaerobic conditions. Toxicity effects were dependent on the structure of the organosulfur compounds, the amounts added to cultures, and the available electron acceptor. The anaerobic biodegradation of eight different organothiols was observed under nitrate-reducing conditions but not methanogenic or sulfate-reducing conditions. Degradation of hexanethiol was linked to nitrate reduction and nitrite production.For biodegradation studies, enrichment cultures were established with target compounds added singly or as mixtures, often in a hydrophobic carrier. The degradation of compounds such as n-alkanes, n-alkanols, and n-alkcanoic acids depended on chemical structure as well as redox potential. n-alkanoic acids were degraded faster than n-alkanols, whereas n-alkanes were not metabolized. The susceptibility of n-alkanols and n-alkanoic acids to degradation was chain-length dependent. Alkanols were transformed to the corresponding alkanoic acids, and the formation of esters as a minor fate process was also noted.The anaerobic degradation of a variety of aromatic compounds was investigated with the sulfate-reducing bacterium Desulfotomaculum strain Groll. Initial steps of metabolic pathways for the degradation of m- and p-cresol were proposed. Degradation of both isomers proceeded by hydroxylation of the methyl groups to yield hydroxybenzyl alcohols which were further oxidized to hydroxybenzoic acids then metabolized as benzoyl-coenzyme A thioesters. These proposed pathways were supported by substrate degradation profiles, detection of metabolites, and biochemical studies. Although strain Groll degraded these cresol isomers by similar reactions, the enzymes catalyzing the oxidation of the meta and para isomers were biochemically distinct.A variety of compounds associated with petroleum and petroleum-derived wastes were examined for their susceptibility to biodegradation under methanogenic, sulfate-reducing, and nitrate-reducing conditions. Inocula from chronically contaminated environments were used to explore the limits of anaerobic degradation potential. In addition, an ecological approach to the prevention of sulfide emissions was evaluated. Nitrate was added to oily sludge incubations to test its efficacy in preventing sulfidogenesis by sulfate-reducing bacteria. Nitrate inhibited sulfate reduction in a concentration-dependent manner, and reduced sulfide concentrations under a variety of salinity conditions

Identification of a Marine Green Alga Percursaria percursa from Hypersaline Springs in the Middle of the North American Continent

The chlorophycean alga Percursaria percursa (Ulvaceae, Ulvales, Chlorophyceae), typical of marine inter-tidal zones, is reported for the first time from hypersaline springs located along the north-western shore of Lake Winnipegosis in Manitoba. Although not usually found inland, P. percursa is the dominant member of microbial mat communities that thrive in shallow pools at the outlets of hypersaline springs

Paleomagnetism of Archean rock units and mineralization in the Noranda area, Quebec.

Dept. of Geology and Geological Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1975 .L87. Source: Masters Abstracts International, Volume: 40-07, page: . Thesis (M.Sc.)--University of Windsor (Canada), 1975

Metal-macrofauna interactions determine microbial community structure and function in copper contaminated sediments

Peer reviewedPublisher PD

Natural-abundance radiocarbon as a tracer of assimilation of petroleum carbon by bacteria in salt marsh sediments

Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 70 (2006): 1761-1771, doi:10.1016/j.gca.2005.12.020.The natural abundance of radiocarbon (14C) provides unique insight into the source and cycling of sedimentary organic matter. Radiocarbon analysis of bacterial phospholipid lipid fatty acids (PLFAs) in salt-marsh sediments of southeast Georgia (USA) – one heavily contaminated by petroleum residues – was used to assess the fate of petroleum-derived carbon in sediments and incorporation of fossil carbon into microbial biomass. PLFAs that are common components of eubacterial cell membranes (e.g., branched C15 and C17, 10-methyl-C16) were depleted in 14C in the contaminated sediment (mean Δ14C value of +25 ± 19 ‰ for bacterial PLFAs) relative to PLFAs in uncontaminated “control” sediment (Δ14C = +101 ± 12‰). We suggest that the 14C-depletion in bacterial PLFAs at the contaminated site results from microbial metabolism of petroleum and subsequent incorporation of petroleum-derived carbon into bacterial membrane lipids. A mass balance calculation indicates that 6-10% of the carbon in bacterial PLFAs at the oiled site could derive from petroleum residues. These results demonstrate that even weathered petroleum may contain components of sufficient lability to be a carbon source for biomass production by marsh sediment microorganisms. Furthermore, a small but significant fraction of fossil carbon is assimilated even in the presence of a much larger pool of presumably more-labile and faster-cycling carbon substrates.This study was supported by Georgia Sea Grant (RR100-221/926784), the National Science Foundation (OCE-9911678) and NOSAMS (thanks to J. M. Hayes)

Improvement of local budget filling

This chapter describes the biological removal of sulphur compounds from gas streams. First, an overview is given of the toxicity of sulphur compounds to animals and humans whereafter biological and industrial formation routes for (organic) sulphur compounds are given. Microbial degradation routes of volatile organic sulphur compounds under both aerobic and anaerobic conditions are presented. Finally, the most commonly applied processes for sulphur removal from gaseous streams are discussed and an overview is given of operating experiences for biological gas treatment systems. The chapter concludes with some remarks on future developments