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| Registros recuperados: 83 | |
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| Sierra Rayne; Kaya Forest. |
| Enthalpies of formation (Δ~f~H~(g)~) at 298.15 K and 0 K were calculated for various potential high energy materials (HEMs) using the high-level Gaussian-4 (G4) and W1BD methods with the atomization approach. Where prior high level estimates are available in the literature, the G4 and W1BD Δ~f~H~(g)~ are in good agreement. The results presented herein represent the highest level calculations performed to date on this suite of HEMs. These G4/W1BD enthalpies of formation should provide utility among the research community as a benchmark set of values against which to assess future experimental and/or theoretical data. |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2011 |
URL: http://precedings.nature.com/documents/6461/version/1 |
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| Sierra Rayne; Kaya Forest. |
| Perfluoroalkyl aldehydes (PFAlds) and n:2 fluorotelomer aldehydes (FTAlds) are degradation products of precursor compounds that include fluorotelomer alcohols, iodides, acrylates, phosphate esters, and other derivatives, as well as hydrofluorocarbons and hydrochlorofluorocarbons. The SPARC software program and comparative density functional theory (DFT) calculations were used to investigate the aqueous phase hydration equilibrium constants (K~hyd~) of PFAlds and FTAlds. DFT studies suggest that all PFAlds will be dominantly present as the hydrated form in aqueous solution. While SPARC correctly estimates the K~hyd~ for the C~1~ PFAld, it appears to incorrectly predict a large decline in K~hyd~ (particularly between C~1~ and C~2~) with increasing... |
| Tipo: Manuscript |
Palavras-chave: Chemistry; Earth & Environment. |
| Ano: 2010 |
URL: http://precedings.nature.com/documents/4520/version/1 |
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| Sierra Rayne; Kaya Forest. |
| Groundwater resources play a key role in supplying water for domestic, industrial, agricultural, and ecological functions on the Canadian prairies. The current study investigates potential temporal trends in groundwater levels for the Canadian province of Saskatchewan over the past several decades. Overall, the large majority of areally distributed stations throughout Saskatchewan with increasing groundwater level time trends suggests that this hydrogeological resource is growing in quantity and is not under current threat from depletion. |
| Tipo: Manuscript |
Palavras-chave: Earth & Environment. |
| Ano: 2011 |
URL: http://precedings.nature.com/documents/6696/version/1 |
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| Sierra Rayne. |
| Sumac is the common name for a genus (Rhus) with >250 individual species of flowering plants in the family Anacardiaceae. These plants are globally distributed in temperate and tropical regions and can grow on marginal lands, making them strong candidates for renewable bioproduct sources. Despite the extensive historical use of some members of Rhus spp. for tannins and other commercial phenolics, little is known about the non-phenolic components of extracts and essentials oils. The current review highlights opportunities available to extend these limited prior studies to other sumac species, and for obtaining value-added compounds to complement already established phenolic extractions in these commercial plant species. To date, a number of... |
| Tipo: Manuscript |
Palavras-chave: Chemistry; Plant Biology. |
| Ano: 2011 |
URL: http://precedings.nature.com/documents/5926/version/1 |
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| Sierra Rayne; Kaya Forest. |
| Theoretical studies were conducted on the predicted gas and solution phase thermodynamic properties for isomerization of various [1.1]paracyclophane derivatives to their corresponding transannular[4+4] adducts at representative levels of density functional and composite method theory. Calculations suggest the [1.1]paracyclophane to transannular[4+4] adduct isomerizations are not likely amenable to thermodynamic solvent tuning for the methylene, ether, and thioether bridged derivatives using a broad range of nonpolar and polar aprotic and polar protic implicit solvation models, but may be receptive towards solvent tuning for the amine bridged analogs. Varying the nature of the cyclophanic bridging atoms and the electron withdrawing/releasing character of... |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2010 |
URL: http://precedings.nature.com/documents/5332/version/1 |
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| Sierra Rayne; Kaya Forest. |
| A number of mining sites worldwide, particularly gold mines, have tailings management facilities (TMFs) that contain high levels of arsenic. Current closed mine site regulatory agencies tend to prefer revegetation of TMFs as part of the mandated reclamation activities. At many sites, often in polar regions, vegetation is difficult to establish either directly on the tailings or on the coarse-rock covers due to nutrient poor soils, phytotoxicity problems, and/or a less than optimum climate. Addition of phosphorus-based fertilizers to the tailings and/or cover material is commonly considered in order to promote the revegetation process and – ideally – allow the site owners to discharge their closure duties as rapidly as possible.... |
| Tipo: Manuscript |
Palavras-chave: Chemistry; Earth & Environment. |
| Ano: 2008 |
URL: http://precedings.nature.com/documents/1740/version/1 |
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| Michael G. Ikonomou; Sierra Rayne; Norman F. Crewe. |
| Concentrations of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and polybrominated diphenyl ethers (PBDEs) were examined as a function of depth in killer whale (Orcinus orca) blubber samples. Lipid-normalized concentrations of PCBs, PCDD/Fs, and PBDEs did not display significant variation with depth in three distinct blubber layers (outer, central, and inner). Significantly more variation in contaminant concentrations were observed with depth on a wet weight basis for the killer whale sample. The current study indicates that non-invasive microdart biopsy sampling methods commonly used for monitoring contaminants in marine mammals yield representative details on contaminant burdens for chlorinated and... |
| Tipo: Manuscript |
Palavras-chave: Chemistry; Ecology; Earth & Environment. |
| Ano: 2007 |
URL: http://precedings.nature.com/documents/638/version/1 |
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| Sierra Rayne; Kaya Forest. |
| A long-term analysis of temporal trends and frequency analyses for temperatures (1913-2010), precipitation (1909-2010), and wind speed (1954-1996) was conducted on the Moose Jaw climate station in south-central Saskatchewan, Canada. Average annual and springtime temperatures are increasing over time, as are daily mean temperatures during March. Mean daily maximum temperatures are increasing on an annual basis and during the spring period, whereas mean daily minimum temperatures are increasing during February, March, August, and September, as well as on an annual basis and during spring and summer. There are significant positive time trends for growing degree days base 8C (GDD~8~) and 10C (GDD~10~). Rainfall has been increasing during March as well as... |
| Tipo: Poster |
Palavras-chave: Earth & Environment. |
| Ano: 2011 |
URL: http://precedings.nature.com/documents/6703/version/1 |
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| Sierra Rayne; Kaya Forest. |
| Gas phase calculations at 1 atmosphere pressure between 300 and 1500 K at 200 K intervals were conducted using the Gaussian-4 (G4) composite method level of theory on a representative set of reactions having broad relevance in hydrocarbon combustion chemistry. Reasonable agreement between the experimental and theoretical data was obtained across the temperature range under consideration for all bond dissociation enthalpies, isomerization enthalpies, and enthalpies of reaction. For some reaction schemes, chemical accuracy for the theoretical method was maintained over the complete temperature range, whereas other systems displayed up to several kcal mol^-1^ deviations from experimental data. The direction of signed errors generally increased as the... |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2010 |
URL: http://precedings.nature.com/documents/5021/version/1 |
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| Sierra Rayne; Kaya Forest. |
| Historical trends in monthly, seasonal, and annual mean streamflows, as well as minimum and maximum monthly streamflows, were investigated at nine hydrometric stations in the Okanagan River watershed from south-central British Columbia, Canada. Overall, mean annual streamflows in the Okanagan River watershed are not exhibiting any significant time trends. No consistent declines in monthly minimum streamflows are evident at any point during the hydrologic year. Mean monthly and monthly maximum streamflows in tributary streams to the mainstem system appear to be significantly increasing over time during the spring snowmelt period of March and April. Any temporal changes in flow patterns at the mainstem Okanagan River stations likely reflect alterations in... |
| Tipo: Manuscript |
Palavras-chave: Earth & Environment. |
| Ano: 2011 |
URL: http://precedings.nature.com/documents/6662/version/1 |
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| Sierra Rayne; Kaya Forest. |
| The Okanagan Basin in south-central British Columbia, Canada, includes the Okanagan River watershed upstream from the outlet of Osoyoos Lake, with a total area of 8,046 km^2^. Over the past century, the population of the Basin has grown rapidly, and this trend is expected to continue. Water management issues attract significant attention in the region, given projected declines in supply and increases in demand. Historical streamflow data was obtained for three hydrometric stations on the Okanagan River between the outlet of Okanagan Lake at Penticton and near the U.S. border at Oliver. Collectively, the historical data series indicate no temporal changes in regional annual water yields for the Okanagan Basin over the past century, despite large increases... |
| Tipo: Manuscript |
Palavras-chave: Earth & Environment. |
| Ano: 2010 |
URL: http://precedings.nature.com/documents/4946/version/1 |
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| Sierra Rayne; Kaya Forest. |
| Organic carbon normalized soil and sediment-water partitioning coefficients (K~oc~) were estimated for all C~1~ through C~8~ perfluoroalkyl carboxylic (PFCA) and sulfonic (PFSA) acid congeners. The limited experimental K~oc~ dataset for the straight chain C~7~ through C~10~ PFCAs and C~8~ and C~10~ PFSAs was correlated to SPARC and ALOGPS computationally estimated octanol-water partitioning / distribution constants and used to predict K~oc~ values for both branched and linear C~1~ through C~8~ isomers. Branched and linear congeners in this homologue range are generally expected to have K~oc~ values >1, leading to their accumulation in organic matter on sediments and soils, retardation during ground and pore water flow, and the preferential... |
| Tipo: Manuscript |
Palavras-chave: Chemistry; Earth & Environment. |
| Ano: 2009 |
URL: http://precedings.nature.com/documents/3011/version/2 |
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| Sierra Rayne; Kaya Forest. |
| Gas phase (298.15 K, 1 atm) enthalpies of formation ([DELTA]~f~H~(g)~) were calculated at the G4MP2 and G4 levels of theory using the atomization energy approach for various nitro-substituted borazines proposed as high energy materials (HEMs). Modest general agreement was obtained between the G4MP2/G4 atomization energy [DELTA]~f~H~(g)~ estimates and those previously reported using density functional theory methods and homodesmic reaction approaches, with deviations ranging between +9.7 to -56.5 kJ/mol. The results should help constrain the actual enthalpies of formation for these potential HEMs, and suggest the nitroborazines are a particularly challenging case for [DELTA]~f~H~(g)~ calculations using theoretical approaches, requiring high-level composite... |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2011 |
URL: http://precedings.nature.com/documents/5580/version/1 |
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| Sierra Rayne; Kaya Forest. |
| New experimental data is available in the literature regarding the octanol-water distribution behavior of representative straight chain perfluoroalkyl carboxylate (PFCA) and sulfonate (PFSA) congeners. The current study provides the first investigation into the predictive ability of various software programs for estimating the corresponding octanol-water partitioning (log P) and distribution (log D) constants of PFCAs and PFSAs. Wide predictive variation was found within and between the various methods. Several programs were able to accurately estimate the log P/D fragmental contributions of a -CF~2~- group for PFCAs, as well as the associated Gibbs free energies for partitioning into octanol from water due to the hydrophobic character of the... |
| Tipo: Manuscript |
Palavras-chave: Chemistry; Earth & Environment. |
| Ano: 2009 |
URL: http://precedings.nature.com/documents/3282/version/1 |
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| Sierra Rayne; Kaya Forest. |
| The KOWWIN and ALOGPS octanol-water partition coefficient (K~ow~) estimation software programs were compared for their capacity to accurately predict log K~ow~ values of 1596 organic compounds on the publicly available Domestic Substances List (DSL) from Environment Canada for which experimental data is available. KOWWIN contained a significantly lower number and magnitude of prediction errors compared to ALOGPS, particularly at experimental log K~ow~ values <2. Substantial predictive differences were observed between the two programs for 9093 compounds not having experimental K~ow~ data on the Canadian DSL. Predictive differences of up to 40 log K~ow~ units were found between KOWWIN and ALOGPS, and in some cases, the discrepancies were... |
| Tipo: Manuscript |
Palavras-chave: Chemistry; Pharmacology; Earth & Environment. |
| Ano: 2009 |
URL: http://precedings.nature.com/documents/3882/version/1 |
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| Sierra Rayne; Kaya Forest. |
| Historical temporal trends in annual water yields were examined at 109 hydrometric monitoring stations in the Mackenzie, Saskatchewan-Nelson, Churchill, and Missouri-Mississippi River watersheds from the western Canadian provinces of Alberta, Saskatchewan, and northeastern British Columbia, as well as the Northwest Territories and the eastern portion of the Yukon territory. Effective drainage areas range in size from 325 to 1,680,000 (mean=65,600; median=9,300) km^2^, with associated hydrometric record lengths ranging between 18 and 97 (mean=41; median=38) years. Approximately three-quarters of the stations have no significant trend in average annual flow, with about equal numbers of stations exhibiting significant temporal increases or decreases in annual... |
| Tipo: Manuscript |
Palavras-chave: Earth & Environment. |
| Ano: 2010 |
URL: http://precedings.nature.com/documents/5342/version/1 |
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| Sierra Rayne; Kaya Forest. |
| Gas phase (298.15 K, 1 atm) enthalpies of formation were calculated at the Gaussian-4 (G4) level of theory using the atomization energy approach for the proposed high energy materials aminonitroacetylene (284.0 to 285.7 kJ/mol), aminonitromethane (-66.4 to -65.0 kJ/mol), and diaminodinitromethane (-84.0 to -81.6 kJ/mol). The results are in good agreement with prior G2 and G3 level estimates, and should help constrain the actual enthalpies of formation for these potential HEMs. |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2010 |
URL: http://precedings.nature.com/documents/5467/version/1 |
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| Sierra Rayne. |
| Melatonin and serotonin are important phytochemicals with hormonal, antioxidant, immunoactive, and neuroactive biological properties, and have been identified and quantitated in a broad range of fruits, vegetables, and derivative products. Relatively little is known about the temporal profiles of these compounds during fruit and vegetable development. Improved knowledge in this area would help guide our understanding of fundamental plant physiology, as well as potentially facilitate better control of melatonin and serotonin concentrations and relative abundances in functional foods. The current work synthesizes the current state-of-the-art regarding the presence and trends of these compounds during fruit and vegetable development. The literature reflects... |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2010 |
URL: http://precedings.nature.com/documents/4722/version/1 |
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| Sierra Rayne; Kaya Forest. |
| The gas and solution phase relative thermodynamic stabilities of the 89 perfluorooctane sulfonic acid (PFOS) congeners play an important role in assessing whether synthetic conditions for commercial mixtures are under thermodynamic or kinetic control, and in calculating various physico-chemical properties for these important industrial compounds and environmental contaminants. In the present study, 4,272 gas and solvent phase (water and n-octanol) calculations were conducted at various levels of semiempirical (PM6), density functional (B3LYP, B97D, PBE1PBE [PBE0], and M062X functionals with the 6-311++G(d,p) basis set), and second order Moller-Plesset perturbation (MP2/6-311++G(d,p)//B3LYP/6-311++G(d,p)) theory and the SMD, IEFPCM-UFF, and CPCM implicit... |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2010 |
URL: http://precedings.nature.com/documents/5353/version/1 |
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| Sierra Rayne; Kaya Forest. |
| Gas phase enthalpies of formation at 298.15 and 1 atm (Δ~f~H~(g),298K~) were calculated using the atomization approach at the G4MP2 composite method level of theory for 86 polyaromatic hydrocarbons (PAHs) and other C~10~ through C~20~ unsaturated hydrocarbons. Where available, good agreement with prior experimental data and/or high level theoretical estimates was obtained. Linear regressions between semiempirical MNDO, MNDO-d, AM1, PM3, RM1, and PM6 estimated Δ~f~H~(g),298K~ and the corresponding G4MP2 values were employed to obtain G4MP2 corrected semiempirical Δ~f~H~(g),298K~ for a suite of 156 C~11~ through C~42~ unsaturated hydrocarbons and PAHs. |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2011 |
URL: http://precedings.nature.com/documents/6450/version/1 |
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| Registros recuperados: 83 | |
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