- Denis G. Rancourt is a former tenured and full professor of physics at the University of Ottawa in Canada. He practic... moreDenis G. Rancourt is a former tenured and full professor of physics at the University of Ottawa in Canada. He practiced several areas of science (including physics and environmental science) which were funded by a national agency and ran an internationally recognized laboratory. He has published over 100 articles in leading scientific journals and several social commentary essays. He developed popular activism courses and was an outspoken critic of the university administration and a defender of student and Palestinian rights. He was fired for his dissidence in 2009. His dismissal case is in court hearings that are extended into 2017.
For contributions by Denis G. Rancourt here:
http://activistteacher.blogspot.ca/2017/02/links-to-denis-rancourts-web-pages.htmledit
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Research Interests: Geology and Geochemistry
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ABSTRACT The Lake Sediment Structure and Evolution (LSSE) group at the University of Ottawa (www.science.uottawa.ca/LSSE/) is interested in both experimental characterization and modeling of metal and nutrient cycling in lacustrine... more
ABSTRACT The Lake Sediment Structure and Evolution (LSSE) group at the University of Ottawa (www.science.uottawa.ca/LSSE/) is interested in both experimental characterization and modeling of metal and nutrient cycling in lacustrine sediments. One of the prime research directions is to understand phosphorus releases from sediments that lead to nuisance algal blooms and partly determine the microbial ecologies of lakes. Modeling results will be presented and the possibility of creating a generalized quantitative model that would describe phosphorus releases under both oxic and anoxic conditions will be discussed. Particular attention is given to understanding the molecular mechanisms of the microscopic biogeochemical processes that lead to phosphorus mobilization. These include microbially mediated and inorganic dissolutions of oxyhydroxide phases to which phosphorus is sorbed, desorption of phosphorus in response to changing porewater pH, and a host of microbial processes that lead to increased production of labile phosphorus fractions. Our model allows investigating the relative importance of classes of mechanisms that predominate in different types of environments, as well as exploring the conditions for phosphorus releases from sediments by varying key parameters such as lake eutrophication level, water depth, sediment temperature, oxygen concentration, and Fe:P ratio. For example, our model allows one to quantify the extent to which laboratory oxyhydroxide dissolution rates are compatible with observed phosphorus releases when sediments become anoxic.
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We compare ferric/ferrous determinations in mica granules and powders, as obtained by the Pratt and Wilson wet chemical (WC) methods and by Mössbauer spectroscopy (MS). The Pratt method is accurate whereas the Wilson method is not but... more
We compare ferric/ferrous determinations in mica granules and powders, as obtained by the Pratt and Wilson wet chemical (WC) methods and by Mössbauer spectroscopy (MS). The Pratt method is accurate whereas the Wilson method is not but both have the same precision (sigma = 1.2 wt.% FeO). Assuming that the Pratt WC method gave accurate ferric/ferrous ratios leads to a calculated ferric/ferrous ratio of MS recoilless fractions at room temperature for a given biotite sample of f 3+/ f 2+ = 1.009(5). Also, the Mica-Fe and Mica-Mg international standards are shown to be unsuitable, with significant size-fraction dependencies of their oxidation states. These results are discussed in the general context of evaluating accuracy and precision of WC methods by comparisons with MS and of the special problems related to accuracy and precision with MS itself.
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ABSTRACT Reaction of the dipotassium salt of the dipyrrolide dianion [1,1-(2-C4H3N)2C6H10]2- with FeCl2(THF)1.5 afforded the tetranuclear [μ,η5-{[1,1-(2-C4H3N)2C6H10]2Fe}Fe]2 (1) cluster containing two diamagnetic ferrous links π-bonded... more
ABSTRACT Reaction of the dipotassium salt of the dipyrrolide dianion [1,1-(2-C4H3N)2C6H10]2- with FeCl2(THF)1.5 afforded the tetranuclear [μ,η5-{[1,1-(2-C4H3N)2C6H10]2Fe}Fe]2 (1) cluster containing two diamagnetic ferrous links π-bonded to two pyrrolyl rings of two ligands and closely reminiscent of a ferrocenoid-type arrangement. Reaction of the dianionic metalate {[[1,1-(2-C4H3N)2C6H10]2Co][K(THF)]2}n with FeCl2(THF)1.5 also afforded the corresponding [μ,η5-{[1,1-(2-C4H3N)2C6H10]2Co}Fe]2 nearly isostructural with 1. This indicates that the two ferrous links provide the driving force for assembling the two clusters, although the two structures are labile and may be disrupted by simple treatment with pyridine.
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The Mössbauer spectra of very small alpha-Fe2O3 particles supported by zeolite-Y were taken at various temperatures above and below the blocking temperature. A new technique for calculating the average particle volume is described. The... more
The Mössbauer spectra of very small alpha-Fe2O3 particles supported by zeolite-Y were taken at various temperatures above and below the blocking temperature. A new technique for calculating the average particle volume is described. The procedure is independent of the anisotropy constant and yields a diameter of d = (25+/-5) Å (for our sample), which is in agreement with the low
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The presence of magnetic and chemical clustering, in Fe65Ni35 Invar, had previously been inferred from various measurements which we review. We independently confirm both types of clustering and measure the associated supermoment dynamics... more
The presence of magnetic and chemical clustering, in Fe65Ni35 Invar, had previously been inferred from various measurements which we review. We independently confirm both types of clustering and measure the associated supermoment dynamics for the first time. The temperature dependence of the fluctuation frequency is understood in terms of inter-cluster surface exchange energy and leads to a spherical cluster radius
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It is now well established that, as with amorphous alloys, the Mssbauer spectra of icosahedral alloys exhibit QSD's. This is evidence for intrinsic local disorder present in icosahedral structures. The shapes of the QSD's... more
It is now well established that, as with amorphous alloys, the Mssbauer spectra of icosahedral alloys exhibit QSD's. This is evidence for intrinsic local disorder present in icosahedral structures. The shapes of the QSD's have not been unambiguously established and, as a result, it has been difficult to link these shapes with other physical properties of these novel and complex
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We report Mössbauer spectra, magnetic hysteresis, acquisition and demagnetization of isothermal remanent magnetization (IRM), and low-temperature IRM warming curves of biotite crystals, as well as a summary of domain observations on... more
We report Mössbauer spectra, magnetic hysteresis, acquisition and demagnetization of isothermal remanent magnetization (IRM), and low-temperature IRM warming curves of biotite crystals, as well as a summary of domain observations on magnetic extracts. The biotites are from 1.0 to 1.2 Ga gneisses and 1.85 Ga plutons of the Grenville, Churchill and Bear Provinces (Canada). Most have paramagnetic susceptibilities in the
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Research Interests: Geology and Geochemistry
Page 1. Hyperfine Interactions 117 (1998) 117129 117 Determination of cis and trans Fe 2+ populations in 2M1 muscovite by Mössbauer spectroscopy Amir AT Shabani a, Denis G. Rancourt b and André E. Lalonde a a Department ...
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Research Interests: Geology, Thermodynamics, Raman Spectroscopy, Scanning Electron Microscopy, X-Ray Fluorescence (XRF) Spectroscopy, and 12 moreCrystal chemistry, Phase Field, Phase Stability, Gas Chromatography, Powder X-Ray Diffraction, Soil sciences, Lattice Parameter, Differential Thermal Analysis, Thermogravimetric Analysis, Diagnostic Test, X ray Fluorescence, and Weight Gain
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Research Interests: Geology, Geochemistry, Transmission Electron Microscopy, Hydrous Ferric Oxide, Powder X-Ray Diffraction, and 10 moreBond Strength, Heterogeneous Nucleation, Bacillus subtilis, Particle Size, Room Temperature, Functional Group, Charge transfer, Cell Wall, Condition dependence, and Bacillus licheniformis
Pyroaurite is a layered double hydroxide, a hydrotalcite-like lamellar mineral of formula MgsFe~(OH)lsC03*4Hz0. Organopyroaurite derivatives, of general formula [MgsFez(OH)lsl-[OZC-(CH~)~-CO~HIZ~HZO with 1 I p I 14, were prepared by... more
Pyroaurite is a layered double hydroxide, a hydrotalcite-like lamellar mineral of formula MgsFe~(OH)lsC03*4Hz0. Organopyroaurite derivatives, of general formula [MgsFez(OH)lsl-[OZC-(CH~)~-CO~HIZ~HZO with 1 I p I 14, were prepared by coprecipitation of the