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  • 1
    Electronic Resource
    Electronic Resource
    Application of Monitoring Data forGiardia andCryptosporidium to Boil Water Advisories (2001)
    Boston, USA and Oxford, UK : Blackwell Publishers Inc.
    Risk analysis 21 (2001), S. 0 
    Details
    ISSN: 1539-6924
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Despite the problems associated with analyzing water samples forGiardia cysts andCryptosporidium oocysts, the data can be very useful if their strengths and weaknesses are understood. Two municipalities in northern Ontario, Temagami and Thunder Bay, both issued boil water advisories forGiardia contamination. Data from these two cities are compared to show that only one municipality experienced a real outbreak, whereas the other did not. The concentration ofGiardia cysts was much higher than background during the outbreak at Temagami, and the postoutbreak concentrations of cysts were very similar to the long-term average cyst concentration at Thunder Bay. The waterborne outbreak of giardiasis at Temagami was characterized by consistent positive results from water samples, concentrations two to three orders of magnitude higher than normal, and an obvious increase in the number of cases of giardiasis in the population. No outbreak was experienced at Thunder Bay, but a boil water advisory (BWA) was set in place for more than a year on the basis of a single sample from Loch Lomond in which only two cysts were detected but the sample equivalent volume was low. This gave the impression of a sudden increase in concentration, but 39 of 41 subsequent samples were negative. Additional factors that led to a BWA at Thunder Bay are described, and recommendations are presented to help determine when a BWA is necessary and when it should be rescinded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/0272-4332.216176
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Bilateral Finger Temperature and The Law of Initial Values (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Psychophysiology 24 (1987), S. 0 
    Details
    ISSN: 1469-8986
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: Twenty-two male and 43 female right-handed subjects engaged in three different cognitive tasks while finger temperature was recorded bilaterally. The tasks, presented in randomized order, were: counting backwards by 17's, the Stroop task (Stroop, 1935). and a spatial task. All tasks produced significant (p 〈 .001) temperature decreases on both sides of the body. Relative changes in left-right temperature did not differ significantly among tasks, indicating no task related asymmetries. The right hand decreased in temperature significantly more than The left hand to two of the three tasks, but it is argued that this difference reflects the Law of Initial Values, not differential hemispheric involvement. The Law of Initial Values is shown to hold for finger temperature, contrary to an earlier report. Additionally, left-right temperature differences are shown to reflect the law of Initial Values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1469-8986.1987.tb00347.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The electronic structure of polymers by the FSGO (Floating Spherical Gaussian Orbital) method (1980)
    Springer
    Theoretical chemistry accounts 57 (1980), S. 43-51 
    Details
    ISSN: 1432-2234
    Keywords: Floating Spherical Gaussian Orbitals ; Band structure calculations ; Polyethylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Non-empirical band-structure calculations have been performed on polyethylene using two basis sets introduced by Christoffersen. Both basis sets had to be optimised with respect to the carbon-carbon framework bond in order to yield solutions within the nearest-neighbour approximations. The valence bands of polyethylene are well reproduced by both basis sets whilst the conduction bands are only in fair agreement with those produced by conventional gaussian calculations. The use of the “unsplit” basis set was considered unsatisfactory for the representation of the core bands. The effect of increasing the number of interacting unit cells on the energy terms is discussed. Some of the energy terms converge when five unit cells are used and almost all of the terms reach a constant value when nine unit cells are employed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00547995
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  • 4
    Electronic Resource
    Electronic Resource
    Systematicab initio calculations on one- and three-dimensional polyethylene (1978)
    Springer
    Theoretical chemistry accounts 50 (1978), S. 193-209 
    Details
    ISSN: 1432-2234
    Keywords: Polyethylene, energy band structures and electron distribution of ∼
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The electronic structure of polyethylene has been re-examined using Gaussian basis sets in anab initio solid-state method. Previous calculations were shown to possess a minor error in unit-cell coordinates and were corrected. Six basis sets were used and the results compared within the nearest-neighbour approximation. The effect on the calculation of increasing the number of interacting unit cells to five was studied. The latter produces no significant change in the C-H polarity; the overall conduction band width remains essentially the same but the Koopmans' ionization potential is displaced more towards the experimental value. An investigation was made into the effects of neighbouring strands on a central filament. We find that the Point Charge Perturbation model is a useful one in this context and yields a realistic interstrand distance. This is dominated by the hydrogen atoms. It is essentially unaffected by extension of the perturbing field to second neighbour strands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00632191
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  • 5
    Electronic Resource
    Electronic Resource
    The electronic structures of polymeric beryllium hydride and polymeric boron hydride (1979)
    Springer
    Theoretical chemistry accounts 51 (1979), S. 163-172 
    Details
    ISSN: 1432-2234
    Keywords: BeH2 and BH2 polymers ; Energy band structures in polymeric BeH2 and BH2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The band structure of linear polymeric beryllium hydride is here calculated by anab initio technique. The doubly-degenerate valence band has π symmetry and is composed of a berylliump orbital and an antisymmetric combination of the appropriate hydrogen 1s orbitals. The Koopmans' ionization potential is calculated to be 16.1 eV and the direct band gap, found atX, is 15.2 eV. The charge distribution shows an electron drift of approximately 0.15 electrons from beryllium to the hydrogen atoms. The total energy calculation indicates that polymeric beryllium hydride is more stable than the monomer while polymeric boron hydride is less stable than the monomeric species. From the polymeric boron hydride system, an alternating-bond model is more stable than a symmetric bond model. The energy band structures of both models reveal that electron delocalization along the polymer chain is weak.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00554099
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  • 6
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    The abundance of seafloor massive sulfide deposits (2011)
    Geological Society of America (GSA)
    Details
    Publication Date: 2011-12-01
    Description: The possibility of mining seafloor massive sulfide deposits has stirred debate about the sustainable use of this new resource and whether commercial development is worth the risk. Among the outstanding questions is how many deposits might be accessible to deep-sea mining. More than 300 sites of high-temperature hydrothermal venting have been identified since the discovery of black smokers, but significant massive sulfide accumulation has been found at only 165 of these sites. Estimates of the total number of vent fields and associated mineral deposits, based on plume studies and deposit occurrence models, range from 500 to 5000. We have used new deposit occurrence data from 10,000 km of ridge, arc, and backarc spreading centers to estimate the amount of massive sulfide in the easily accessible neovolcanic zones of the global oceans. The total accumulation in these areas is estimated to be on the order of 6 x 108 tonnes, containing [~]3 x 107 tonnes of copper and zinc. This is similar to the total discovered copper and zinc in Cenozoic massive sulfide deposits mined on land but is insufficient to satisfy a growing global demand for these metals.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 7
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    Sulfide geochronology along the Endeavour Segment of the Juan de Fuca Ridge (2013)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 14 (2013); 2084–2099, doi:10.1002/ggge.20133.
    Description: Forty-nine hydrothermal sulfide-sulfate rock samples from the Endeavour Segment of the Juan de Fuca Ridge, northeastern Pacific Ocean, were dated by measuring the decay of 226Ra (half-life of 1600 years) in hydrothermal barite to provide a history of hydrothermal venting at the site over the past 6000 years. This dating method is effective for samples ranging in age from ∼200 to 20,000 years old and effectively bridges an age gap between shorter- and longer-lived U-series dating techniques for hydrothermal deposits. Results show that hydrothermal venting at the active High Rise, Sasquatch, and Main Endeavour fields began at least 850, 1450, and 2300 years ago, respectively. Barite ages of other inactive deposits on the axial valley floor are between ∼1200 and ∼2200 years old, indicating past widespread hydrothermal venting outside of the currently active vent fields. Samples from the half-graben on the eastern slope of the axial valley range in age from ∼1700 to ∼2925 years, and a single sample from outside the axial valley, near the westernmost valley fault scarp is ∼5850 ± 205 years old. The spatial relationship between hydrothermal venting and normal faulting suggests a temporal relationship, with progressive younging of sulfide deposits from the edges of the axial valley toward the center of the rift. These relationships are consistent with the inward migration of normal faulting toward the center of the valley over time and a minimum age of onset of hydrothermal activity in this region of 5850 years.
    Description: This work was supported by a NSERC PGS scholarship and SEG Canada Foundation Student Research grant to J. W. Jamieson, NSERC Discovery grant to M. D. Hannington, NSF Ocean Sciences grant OCE-0732661 to J. F. Holden, and NSF grant OCE-1038135 to M. K. Tivey. D. A. Clague and the MBARI cruise were supported by a grant to MBARI from the David and Lucile Packard Foundation.
    Description: 2014-01-08
    Keywords: Hydrothermal ; Sulphide ; Geochronology ; Endeavour
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 8
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    Precipitation and growth of barite within hydrothermal vent deposits from the Endeavour Segment, Juan de Fuca Ridge (2015)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 173 (2016): 64-85, doi:10.1016/j.gca.2015.10.021.
    Description: Hydrothermal vent deposits form on the seafloor as a result of cooling and mixing of hot hydrothermal fluids with cold seawater. Amongst the major sulfide and sulfate minerals that are preserved at vent sites, barite (BaSO4) is unique because it requires the direct mixing of Ba-rich hydrothermal fluid with sulfate-rich seawater in order for precipitation to occur. Because of its extremely low solubility, barite crystals preserve geochemical fingerprints associated with conditions of formation. Here, we present data from petrographic and geochemical analyses of hydrothermal barite from the Endeavour Segment of the Juan de Fuca Ridge, northeast Pacific Ocean, in order to determine the physical and chemical conditions under which barite precipitates within seafloor hydrothermal vent systems. Petrographic analyses of 22 barite-rich samples show a range of barite crystal morphologies: dendritic and acicular barite forms near the exterior vent walls, whereas larger bladed and tabular crystals occur within the interior of chimneys. A two component mixing model based on Sr concentrations and 87Sr/86Sr of both seawater and hydrothermal fluid, combined with 87Sr/86Sr data from whole rock and laser-ablation ICP-MS analyses of barite crystals indicate that barite precipitates from mixtures containing as low as 17% and as high as 88% hydrothermal fluid component, relative to seawater. Geochemical modelling of the relationship between aqueous species concentrations and degree of fluid mixing indicates that Ba2+ availability is the dominant control on mineral saturation. Observations combined with model results support that dendritic barite forms from fluids of less than 40% hydrothermal component and with a saturation index greater than ~0.6, whereas more euhedral crystals form at lower levels of supersaturation associated with greater contributions of hydrothermal fluid. Fluid inclusions within barite indicate formation temperatures of between ~120 and 240°C during barite crystallization. The comparison of fluid inclusion formation temperatures to modelled mixing temperatures indicates that conductive cooling of the vent fluid accounts for 60 – 120°C reduction in fluid temperature. Strontium zonation within individual barite crystals records fluctuations in the amount of conductive cooling within chimney walls that may result from cyclical oscillations in hydrothermal fluid flux. Barite chemistry and morphology can be used as a reliable indicator for past conditions of mineralization within both extinct seafloor hydrothermal deposits and ancient land-based volcanogenic massive sulfide deposits.
    Description: This work was supported by an NSERC PGS scholarship to JWJ and NSERC Discovery Grant to MDH. MKT acknowledges funding from NSF OCE- 1130019. DAB acknowledges funding from NSF OCE-0731947 and the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) under NOAA Cooperative Agreement NA10OAR4320148.
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 9
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    Magnetic and gravity surface geometry inverse modeling of the TAG active mound (2021)
    American Geophysical Union
    Details
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 126(10),(2021): e2021JB022228, https://doi.org/10.1029/2021JB022228.
    Description: Seafloor massive sulfide deposits form in remote environments, and the assessment of deposit size and composition through drilling is technically challenging and expensive. To aid the evaluation of the resource potential of seafloor massive sulfide deposits, three-dimensional inverse modeling of geophysical potential field data (magnetic and gravity) collected near the seafloor can be carried out to further enhance geologic models interpolated from sparse drilling. Here, we present inverse modeling results of magnetic and gravity data collected from the active mound at the Trans-Atlantic Geotraverse hydrothermal vent field, located at 26°08′N on the Mid-Atlantic Ridge, using autonomous underwater vehicle and submersible surveying. Both minimum-structure and surface geometry inverse modeling methods were utilized. Through deposit-scale magnetic modeling, the outer extent of a chloritized alteration zone within the basalt host rock below the mound was resolved, providing an indication of the angle of the rising hydrothermal fluid and the depth and volume of seawater/hydrothermal mixing zone. The thickness of the massive sulfide mound was determined by modeling the gravity data, enabling the tonnage of the mound to be estimated at 2.17 ± 0.44 Mt through this geophysics-based, noninvasive approach.
    Description: The authors would like to thank the captain, crew, and scientific team from the 2016 R/V Meteor M127 and 1994 R/V Yokosuka MODE'94 cruises for all their work collecting the data modeled in this study. C. Galley is funded through an NSERC Discovery Grant and Memorial University's School of Graduate Studies Grant.
    Description: 2022-03-29
    Keywords: Seafloor massive sulfide deposit ; Potential field modeling ; Inverse modeling ; Gravity ; Magnetics
    Repository Name: Woods Hole Open Access Server
    Type: Article
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