79 research outputs found
Diversity of thiosulfate-oxidizing bacteria from marine sediments and hydrothermal vents
Species diversity, phylogenetic affiliations, and environmental occurrence patterns of thiosulfate-oxidizing marine bacteria were investigated by using new isolates from serially diluted continental slope and deep-sea abyssal plain sediments collected off the coast of New England and strains cultured previously from Galapagos hydrothermal vent samples. The most frequently obtained new isolates, mostly from 103- and 104-fold dilutions of the continental slope sediment, oxidized thiosulfate to sulfate and fell into a distinct phylogenetic cluster of marine alpha-Proteobacteria. Phylogenetically and physiologically, these sediment strains resembled the sulfate-producing thiosulfate oxidizers from the Galapagos hydrothermal vents while showing habitat-related differences in growth temperature, rate and extent of thiosulfate utilization, and carbon substrate patterns. The abyssal deep-sea sediments yielded predominantly base-producing thiosulfate-oxidizing isolates related to Antarctic marine Psychroflexus species and other cold-water marine strains of the Cytophaga-Flavobacterium-Bacteroides phylum, in addition to gamma-proteobacterial isolates of the genera Pseudoalteromonas and Halomonas-Deleya. Bacterial thiosulfate oxidation is found in a wide phylogenetic spectrum of Flavobacteria and Proteobacteria
In-situ characterization of the Hamamatsu R5912-HQE photomultiplier tubes used in the DEAP-3600 experiment
The Hamamatsu R5912-HQE photomultiplier-tube (PMT) is a novel high-quantum
efficiency PMT. It is currently used in the DEAP-3600 dark matter detector and
is of significant interest for future dark matter and neutrino experiments
where high signal yields are needed.
We report on the methods developed for in-situ characterization and
monitoring of DEAP's 255 R5912-HQE PMTs. This includes a detailed discussion of
typical measured single-photoelectron charge distributions, correlated noise
(afterpulsing), dark noise, double, and late pulsing characteristics. The
characterization is performed during the detector commissioning phase using
laser light injected through a light diffusing sphere and during normal
detector operation using LED light injected through optical fibres
A new and sensitive reaction rate method for spectrophotometric determination of trace amounts of thiourea in different water samples based on an induction period
BACKGROUNDAgrilus bigutattus (Fabricius) is a forest pest of increasing importance in the United Kingdom. The larvae damage weakened native oaks and are thought to contribute to premature tree death. Suspected links with acute oak decline (AOD) are not yet confirmed, but AOD-predisposed trees appear to become more susceptible to A. biguttatus attack. Thus, management may be necessary for control of this insect. To explore the possibility of monitoring beetle populations by baited traps, the host tree volatiles regulating A. biguttatus-oak interactions were studied. RESULTSBiologically active volatile organic compounds in dynamic headspace extracts of oak foliage and bark were identified initially by coupled gas chromatography-electroantennography (GC-EAG) and GC-mass spectrometry (GC-MS), and the structures were confirmed by GC coinjection with authentic compounds. Of two synthetic blends of these compounds comprising the active leaf volatiles, the simpler one containing three components evoked strongly positive behavioural responses in four-arm olfactometer tests with virgin females and males, although fresh leaf material was more efficient than the blend. The other blend, comprising a five-component mixture made up of bark volatiles, proved to be as behaviourally active for gravid females as bark tissue. CONCLUSIONSThese initial results on A. biguttatus chemical ecology reveal aspects of the role of attractive tree volatiles in the host-finding of beetles and underpin the development of semiochemically based surveillance strategies for this forest insect. (c) 2015 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry
Diversity of thiosulfate-oxidizing bacteria from marine sediments and hydrothermal vents
Author Posting. © American Society for Microbiology, 2000. This article is posted here by permission of American Society for Microbiology for personal use, not for redistribution. The definitive version was published in Applied and Environmental Microbiology 66 (2000): 3125-3133, doi:10.1128/AEM.66.8.3125-3133.2000.Species diversity, phylogenetic affiliations, and environmental occurrence patterns of thiosulfate-oxidizing marine bacteria were investigated by using new isolates from serially diluted continental slope and deep-sea abyssal plain sediments collected off the coast of New England and strains cultured previously from Galapagos hydrothermal vent samples. The most frequently obtained new isolates, mostly from 103- and 104-fold dilutions of the continental slope sediment, oxidized thiosulfate to sulfate and fell into a distinct phylogenetic cluster of marine alpha-Proteobacteria. Phylogenetically and physiologically, these sediment strains resembled the sulfate-producing thiosulfate oxidizers from the Galapagos hydrothermal vents while showing habitat-related differences in growth temperature, rate and extent of thiosulfate utilization, and carbon substrate patterns. The abyssal deep-sea sediments yielded predominantly base-producing thiosulfate-oxidizing isolates related to Antarctic marine Psychroflexus species and other cold-water marine strains of the Cytophaga-Flavobacterium-Bacteroides phylum, in addition to gamma-proteobacterial isolates of the genera Pseudoalteromonas and Halomonas-Deleya. Bacterial thiosulfate oxidation is found in a wide phylogenetic spectrum of Flavobacteria and Proteobacteria.Andreas Teske was supported by DFG postdoctoral fellowship 262-1/1 and a subsequent WHOI postdoctoral fellowship
Search for inelastic dark matter-nucleus scattering with the PICO-60 CFI and CF bubble chambers
PICO bubble chambers have exceptional sensitivity to inelastic dark
matter-nucleus interactions due to a combination of their extended nuclear
recoil energy detection window from a few keV to (100 keV) or more and the
use of iodine as a heavy target. Inelastic dark matter-nucleus scattering is
interesting for studying the properties of dark matter, where many theoretical
scenarios have been developed. This study reports the results of a search for
dark matter inelastic scattering with the PICO-60 bubble chambers. The analysis
reported here comprises physics runs from PICO-60 bubble chambers using
CFI and CF. The CFI run consisted of 36.8 kg of
CFI reaching an exposure of 3415 kg-day operating at thermodynamic
thresholds between 7 and 20 keV. The CF runs consisted of 52 kg of
CF reaching exposures of 1404 kg-day and 1167 kg-day running at
thermodynamic thresholds of 2.45 keV and 3.29 keV, respectively. The analysis
disfavors various scenarios, in a wide region of parameter space, that provide
a feasible explanation of the signal observed by DAMA, assuming an inelastic
interaction, considering that the PICO CFI bubble chamber used iodine as
the target material.Comment: 7 pages, 3 figure
Determining the bubble nucleation efficiency of low-energy nuclear recoils in superheated CF dark matter detectors
The bubble nucleation efficiency of low-energy nuclear recoils in superheated
liquids plays a crucial role in interpreting results from direct searches for
weakly interacting massive particle (WIMP) dark matter. The PICO Collaboration
presents the results of the efficiencies for bubble nucleation from carbon and
fluorine recoils in superheated CF from calibration data taken with 5
distinct neutron spectra at various thermodynamic thresholds ranging from 2.1
keV to 3.9 keV. Instead of assuming any particular functional forms for the
nuclear recoil efficiency, a generalized piecewise linear model is proposed
with systematic errors included as nuisance parameters to minimize
model-introduced uncertainties. A Markov-Chain Monte-Carlo (MCMC) routine is
applied to sample the nuclear recoil efficiency for fluorine and carbon at 2.45
keV and 3.29 keV thermodynamic thresholds simultaneously. The nucleation
efficiency for fluorine was found to be for nuclear recoils of
3.3 keV (3.7 keV) at a thermodynamic Seitz threshold of 2.45 keV (3.29 keV),
and for carbon the efficiency was found to be for recoils of
10.6 keV (11.1 keV) at a threshold of 2.45 keV (3.29 keV). Simulated data sets
are used to calculate a p-value for the fit, confirming that the model used is
compatible with the data. The fit paradigm is also assessed for potential
systematic biases, which although small, are corrected for. Additional steps
are performed to calculate the expected interaction rates of WIMPs in the
PICO-60 detector, a requirement for calculating WIMP exclusion limits.Comment: 17 pages, 22 figures, 5 table
Design and construction of the DEAP-3600 dark matter detector
The Dark matter Experiment using Argon Pulse-shape discrimination (DEAP) has been designed for a direct detection search for particle dark matter using a single-phase liquid argon target. The projected cross section sensitivity for DEAP-3600 to the spin-independent scattering of Weakly Interacting Massive Particles (WIMPs) on nucleons is 10−46cm2 for a 100 GeV/c2 WIMP mass with a fiducial exposure of 3 tonne-years. This paper describes the physical properties and construction of the DEAP-3600 detector
Electromagnetic backgrounds and potassium-42 activity in the DEAP-3600 dark matter detector
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