| 1. |
- Armstrong, Chelsey, et al.
(författare)
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Anthropological contributions to historical ecology : 50 questions, infinite prospects
- 2017
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the results of a consensus-driven process identifying 50 priority research questions for historical ecology obtained through crowdsourcing, literature reviews, and in-person workshopping. A deliberative approach was designed to maximize discussion and debate with defined outcomes. Two in-person workshops (in Sweden and Canada) over the course of two years and online discussions were peer facilitated to define specific key questions for historical ecology from anthropological and archaeological perspectives. The aim of this research is to showcase the variety of questions that reflect the broad scope for historical-ecological research trajectories across scientific disciplines. Historical ecology encompasses research concerned with decadal, centennial, and millennial human-environmental interactions, and the consequences that those relationships have in the formation of contemporary landscapes. Six interrelated themes arose from our consensus-building workshop model: (1) climate and environmental change and variability; (2) multi-scalar, multi-disciplinary; (3) biodiversity and community ecology; (4) resource and environmental management and governance; (5) methods and applications; and (6) communication and policy. The 50 questions represented by these themes highlight meaningful trends in historical ecology that distill the field down to three explicit findings. First, historical ecology is fundamentally an applied research program. Second, this program seeks to understand long-term human-environment interactions with a focus on avoiding, mitigating, and reversing adverse ecological effects. Third, historical ecology is part of convergent trends toward transdisciplinary research science, which erodes scientific boundaries between the cultural and natural.
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| 2. |
- Fakhardji, Wissam, et al.
(författare)
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Collision-induced absorption in Ar–Kr gas mixtures : A molecular dynamics study with new potential and dipole data
- 2019
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 151:14
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Tidskriftsartikel (refereegranskat)abstract
- We have implemented a scheme for classical molecular dynamics simulations of collision-induced absorption. The program has been applied to a gas mixture of argon (Ar) and krypton (Kr). The simulations are compared with accurate quantum dynamical calculations. The comparisons of the absorption coefficients show that classical molecular dynamics is correct within 10% for photon wave numbers up to 220 cm−1 at a temperature of 200 K for this system. At higher temperatures, the agreement is even better. Molecular dynamics accounts for many-body interactions, which, for example, give rise to continuous dimer formation and destruction in the gas. In this way, the method has an advantage compared with bimolecular classical (trajectory) treatments. The calculations are carried out with a new empirical Ar–Kr pair potential. This has been obtained through extensive analysis of experimental thermophysical and transport properties. We also present a new high level ab initio Ar–Kr potential curve for comparison, as well as ab initio interaction-induced dipole curves computed with different methods. In addition, the Ar–Kr polarizability and hyperpolarizability are reported. A comparison of the computed absorption spectra with an experiment taken at 300 K shows satisfactory agreement although a difference in absolute magnitude of 10%–15% persists. This discrepancy we attribute mainly to experimental uncertainty.
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| 3. |
- Fakhardji, Wissam, 1990-, et al.
(författare)
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Direct method for MD simulations of collision-induced absorption : application to an Ar–Xe gas mixture
- 2021
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier. - 0022-4073 .- 1879-1352. ; 276
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Tidskriftsartikel (refereegranskat)abstract
- With the reformulation of the classical equations of collision-induced absorption, we present a method to perform the direct computation of the spectral density function. This way the absorption coefficient can be computed from classical molecular dynamics (MD) without the computationally demanding evaluation of the dipole autocorrelation function. In addition, we have developed an algorithm to extract the bound-to-bound dimer contribution to the MD simulated absorption. The method has been tested on the Ar–Xe rare gas system. Comparisons with quantum mechanical (QM) and conventional MD methods validate the approach. The obtained MD bound-to-bound spectra generally agree in shape and magnitude with QM results, including features stemming from rotations and vibrations of the Ar–Xe dimer.
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| 4. |
- Fakhardji, Wissam, et al.
(författare)
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Molecular dynamics calculations of collision-induced absorption in a gas mixture of neon and krypton
- 2020
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 152:23
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Tidskriftsartikel (refereegranskat)abstract
- We continue the development of the in-house molecular dynamics software package SpaCIAL and test it for the computation of the collision-induced absorption coefficients for a neon (Ne) and krypton (Kr) gas mixture. An apodization procedure for the dipole autocorrelation function is implemented and tested. We also carry out a statistical study of the convergence rate with respect to ensemble size. The resulting absorption coefficients show a good accordance with quantum mechanical results. Comparison with laboratory measurements shows agreement within 10%–20% at T = 295 K. At T = 480 K, a larger difference of 40%–80% is observed, which can presumably be explained by experimental uncertainties. For the study, an empirical (Barker, Fisher, and Watts) interaction-potential [Mol. Phys. 21, 657 (1971)] for Ne–Kr has been developed. Ab initio {coupled cluster with singles and doubles (triples) [CCSD(T)]} potentials for Ne–Ne, Kr–Kr, and Ne–Kr have been computed, as well as the CCSD(T) interaction-induced Ne–Kr dipole moment curve.
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| 5. |
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| 6. |
- Gergely, Andras, et al.
(författare)
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Hydrogen Sulfide Corrosion of Carbon and Stainless Steel Alloys in Mixtures of Renewable Fuel Sources under Co-Processing Conditions
- 2018
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Ingår i: Modern Applied Science. - : Canadian Center of Science and Education. - 1913-1844 .- 1913-1852. ; 12:4, s. 227-255
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion rates of steel alloys were investigated in gas oil and its mixture with waste cooking oil and animal waste lard over 1, 3, 7 and 21 days under desulfurizing condition. Co-processing conditions were attempted to simulate by batch-reactor experiment at temperatures between 200 and 300oC and pressures between 20 and 90 bar in the presence of 2 volume% hydrogen sulfide. Integral and differential corrosion rates were defined by weight losses. Intense sulfide corrosion of carbon steels was less impacted by the biomass sources. Thinner scales in gas oil was probably due to frequent cohesive failure, whereas thicker layers in biomass mixtures were allowed to form to afford limited physical protection. The high corrosion rate of low alloy steel with temperature over time is related to inefficient protection by the metal sulfide scales. Greater activation energy and enthalpy balance in the formation of activated complex is expected to reflect in thick cohesive scales. Loose layers and the less unfavorable entropy balance in the transition state did not lead to valuable barrier protection. High sulfide corrosion resistance of stainless steels is in chemical in nature markedly impacted by the biomass fuel sources and contributed especially by the acidic species. Corrosion rates increased with temperature by magnitude similar to those of carbon steels, which probably owes to the less unfavorable entropy and free energy balance between the initial and transition states of the reactants.
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| 7. |
- Góger, Szabolcs, et al.
(författare)
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Flame Inhibition Chemistry : Rate Coefficients of the Reactions of HBr with CH3 and OH Radicals at High Temperatures Determined by Quasiclassical Trajectory Calculations
- 2018
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 32:10, s. 10100-10105
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Tidskriftsartikel (refereegranskat)abstract
- Reactions of HBr with radicals are involved in atmospheric chemistry and in the mechanism of operation of bromine-containing flame retardants. The rate coefficients for two such reactions, HBr + OH and HBr + CH3, are available from earlier experiments at near or below room temperature, relevant for atmospheric chemistry, and in this domain, the activation energy for both has been found to be negative. However, no experimental data are available at combustion temperatures. In this work, to provide reliable data needed for modeling the action of brominated flame suppressants, we used the quasiclassical trajectory (QCT) method in combination with high-level ab initio potential energy surfaces to evaluate the rate coefficients of the two title reactions at combustion temperatures. The QCT calculations have been validated by reproducing the experimental rate coefficients at room temperature. At temperatures between 600 and 3200 K, the QCT rate coefficients display positive activation energies. We recommend the following extended Arrhenius expressions to describe the temperature dependence of the thermal rate coefficients: k6 = (9.86 ± 2.38) × 10–16T(1.23±0.03) exp[(5.93 ± 0.33) kJ mol–1/RT] cm3 molecule–1 s–1 for the HBr + OH → H2O + Br reaction, and k–2 = (4.06 ± 2.72) × 10–18T(1.83±0.08) exp[(7.53 ± 0.18) kJ mol–1/RT] cm3 molecule–1 s–1 for the HBr + CH3 → CH4 + Br reaction. The latter is in very good agreement with the formula proposed by Burgess et al. [Burgess, D. R., Jr.; Babushok, V. I.; Linteris, G. T.; Manion, J. A. A Chemical Kinetic Mechanism for 2-Bromo-3,3,3-trifluoropropene (2-BTP) Flame Inhibition. Int. J. Chem. Kinet. 2015, 47, 533−619, DOI: 10.1002/kin.20923]. The conventional transition state theory has been tested against the rate data obtained by the QCT method and was found to overestimate not only the rate coefficients but also the activation energies
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| 8. |
- Papp, Máte, et al.
(författare)
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Mono- and double carbonylation of aryl iodides with amine nucleophiles in the presence of recyclable palladium catalysts immobilised on a supported dicationic ionic liquid phase
- 2017
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 7:70, s. 44587-44597
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Tidskriftsartikel (refereegranskat)abstract
- Silica modified with organic dicationic moieties proved to be an excellent support for palladium catalysts used in the aminocarbonylation of aryl iodides. By an appropriate choice of the reaction conditions, the same catalyst could be used for selective mono- or double carbonylations leading to amide and α-ketoamide products, respectively. The best catalyst could be recycled for at least 10 consecutive runs with a loss of palladium below the detection limit. By the application of the new support, efficient catalyst recycling could be achieved under mild reaction conditions (under low pressure and in a short reaction time). Palladium-leaching data support a mechanism with dissolution—re-precipitation of the active palladium species.
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| 9. |
- Reda, Souheil, 1988-, et al.
(författare)
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Pre-operative beta-blocker therapy does not affect short-term mortality after esophageal resection for cancer
- 2020
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Ingår i: BMC Surgery. - : BioMed Central. - 1471-2482. ; 20:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: It has been postulated that the hyperadrenergic state caused by surgical trauma is associated with worse outcomes and that β-blockade may improve overall outcome by downregulation of adrenergic activity. Esophageal resection is a surgical procedure with substantial risk for postoperative mortality. There is insufficient data to extrapolate the existing association between preoperative β-blockade and postoperative mortality to esophageal cancer surgery. This study assessed whether preoperative β-blocker therapy affects short-term postoperative mortality for patients undergoing esophageal cancer surgery.METHODS: All patients with an esophageal cancer diagnosis that underwent surgical resection with curative intent from 2007 to 2017 were retrospectively identified from the Swedish National Register for Esophagus and Gastric Cancers (NREV). Patients were subdivided into β-blocker exposed and unexposed groups. Propensity score matching was carried out in a 1:1 ratio. The outcome of interest was 90-day postoperative mortality.RESULTS: A total of 1466 patients met inclusion criteria, of whom 35% (n = 513) were on regular preoperative β-blocker therapy. Patients on β-blockers were significantly older, more comorbid and less fit for surgery based on their ASA score. After propensity score matching, 513 matched pairs were available for analysis. No difference in 90-day mortality was detected between β-blocker exposed and unexposed patients (6.0% vs. 6.6%, p = 0.798).CONCLUSION: Preoperative β-blocker therapy is not associated with better short-term survival in patients subjected to curative esophageal tumor resection.
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| 10. |
- Szabo, Peter, 1988-, et al.
(författare)
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Formation of the BeH+ and BeD+ Molecules in Be+ + H/D Collisions Through Radiative Association
- 2021
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Ingår i: Frontiers in Astronomy and Space Sciences. - : Frontiers Media S.A.. - 2296-987X. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Cross sections and rate coefficients for the formation of BeH+ and BeD+ molecules in Be+ + H/D collisions through radiative association are calculated using quantum mechanical perturbation theory and Breit-Wigner theory. The local thermodynamic equilibrium limit of the molecule formation is also studied, since the process is also relevant in environments with high-density and/or strong radiation fields. The obtained rate coefficients may facilitate the kinetic modelling of BeH+/BeD+ production in astrochemical environments as well as the corrosion chemistry of thermonuclear fusion reactors.
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