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Rayne S.,Chemologica Research | Forest K.,Saskatchewan Institute of Applied Science and Technology
Computational and Theoretical Chemistry | Year: 2014

The thermodynamic properties of chemical reactions proposed to occur during the ozonation of bromide containing waters were examined via high-level G4MP2 and G4 composite theoretical methods with the SMD, PCM, and CPCM solvation models. Enthalpies and free energies of reaction for the sequential oxidation of bromide to bromate and related reactions were determined under standard state conditions. For a select subset of reactions where entropic changes were significant, the effects of varying temperature in the range of 0-100°C were also considered. Based on the current work, previously proposed BrOO-, BrOOO-, and BrO4- intermediates thought to exist during the bromide ozonation process are called into question. Similarly, bromide oxidation reactions involving Br2O4, BrOH-, and HO2Br appear to be speculative. Analogous to the chloramines, the aqueous phase production of bromamines from hypobromous acid and ammonia is predicted to be highly energetically favorable. © 2014 Elsevier B.V. Source


Rayne S.,Chemologica Research | Forest K.,Saskatchewan Institute of Applied Science and Technology
Journal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering | Year: 2014

A high-level gas and aqueous phase theoretical thermodynamic study was conducted on the primary and related chemical reactions which occur during chloramination for water treatment using the G4MP2, G4, and W1BD composite methods with the SMD, PCM, and CPCM solvation models. The standard state (298.15 K, 1 atm or 1M) formation of mono-, di-, and tri-chloramines from their precursors via hypochlorous acid chlorination is substantially exothermic and exergonic in both the gas and aqueous phases. The excellent agreement between experimental and theoretical values for a range of structural and thermodynamic calculations on a suite of calibration compounds suggests that the G4MP2, G4, and W1BD calculations meet or exceed criteria for thermochemical accuracy. The temperature influence on the thermodynamics of chloramine formation is projected to be negligible regardless of phase between 0 and 100°C. Additional thermodynamic calculations were undertaken on associated chloramination reactions involving the disproportionation of monochloramine, the decomposition of di- and tri-chloramine, and the reactions of trichloramine with ammonia and dichloramine. The results from these investigations not only provide a better understanding of the reaction thermodynamics, they also allow for a more rigorous interpretation of proposed chloramination mechanisms. © 2014 Copyright Taylor & Francis Group, LLC. Source


Rayne S.,Chemologica Research | Forest K.,Saskatchewan Institute of Applied Science and Technology
Computational and Theoretical Chemistry | Year: 2011

Singlet-triplet (S0→T1) well-to-well (WWES-T) and vertical (VES-T) excitation energies of the [4×n] rectangular graphene nanoribbon series (n=2-6) were estimated using various semiempirical, Hartree-Fock (HF), density functional (DFT), and second order Moller-Plesset perturbation theory methods with the assumption of a closed-shell singlet state. Significant model chemistry dependent variability in theoretically obtained WWES-T/VES-T is evident for the rectangular graphene nanoribbons. With the exception of the B2PLYP density functional (which, along with the mPW2PLYP functional, combines exact HF exchange with an MP2-like correlation to the DFT calculation), all DFT, semiempirical, and HF methods investigated predict the onset of a negative WWES-T/VES-T (ground state triplet) starting somewhere between the [4×3] through [4×6] derivatives, with most functionals predicting a transition from a singlet to triplet ground state between the [4×4] and [4×5] rectangular graphene nanoribbons. Consistent with previous work on the n-acene series, MP2 WWES-T/VES-T estimates have a significant positive systematic bias and HF estimates have substantial negative systematic biases. Extrapolation of the B2PLYP results, which are in excellent agreement with prior FPA-QZ VES-T estimates, for any [m×n] rectangular graphene nanoribbon derivatives predicts a vanishingly small singlet-triplet gap at the polymeric limit (m→∞ and/or n→∞). © 2011 Elsevier B.V. Source


Rayne S.,Ecologica Research | Forest K.,Okanagan College | Forest K.,Saskatchewan Institute of Applied Science and Technology
Computational and Theoretical Chemistry | Year: 2011

Singlet-triplet (S0-T1) well-to-well (WWES-T) and adiabatic (AES-T) excitation energies of benzene and the linear polyacenes naphthalene through decacene were estimated using a range of density functional theory (DFT) methods and basis sets along with the assumption of a closed-shell singlet state. Via single exponential decay regression based extrapolations to the polymeric limit, significant variability in theoretically obtained WWES-T/AES-T predicted for longer polyacenes is evident that is primarily dependent on the model chemistry employed, with minor variations due to basis set incompleteness and zero-point energy (ZPE) corrections. With the exception of the B2PLYPD density functional (which, along with the mPW2PLYPD functional, combines exact HF exchange with an MP2-like correlation to the DFT calculation), all DFT methods investigated predict a negative WWES-T/AES-T (ground state triplet) at the polymer limit, with most functionals predicting a transition from a singlet to triplet ground state between octacene and decacene. Extrapolation of the B2PLYPD results predicts a vanishingly small singlet-triplet gap at the polymeric limit for an infinitely long homolog. Hartree-Fock calculations significantly underestimate the polyacene WWES-T/AES-T, whereas MPn methods overestimate the singlet-triplet gap but display a convergence toward experimental values with increasing truncation order and substitutions. The B2PLYPD and mPW2PLYPD functionals appear to balance the WWES-T/AES-T underestimating tendency of HF/DFT methods for longer polyacenes against the propensity for MPn methods to overestimate the WWES-T/AES-T for these compounds, and predict all acenes from benzene through decacene will be ground state singlets with positive singlet-triplet gaps. © 2011 Elsevier B.V. Source


Grant L.G.,Saskatchewan Institute of Applied Science and Technology | Oliffe J.L.,University of British Columbia | Johnson J.L.,University of British Columbia | Bottorff J.L.,University of British Columbia
Qualitative Health Research | Year: 2014

Smoke-free grounds policies (SFGPs) were introduced to inpatient psychiatric hospital settings to improve health among patients, staff, and visitors. We conducted an ethnographic study in Northern British Columbia, Canada, to describe how the implementation of SFGPs is affected by institutional cultures. Data reported here included participant observation, document review, informal discussions (n = 11), and interviews with health care professionals (HCPs; n = 19) and staff (n = 2) at two hospitals. We used iterative and inductive processes to derive thematic findings. Findings related to HCPs illustrate how local contexts and cultural factors affect SFGP implementation. These factors included individual beliefs and attitudes, the influence of group norms, leadership and consensus building, and locale-specific norms. Strong, consultative leadership, in which leaders solicited input from and long-term support of people most directly responsible for policy implementation, was key to success. © The Author(s) 2014. Source

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