Oxidation of the 1‐naphthyl radical C₁₀H₇• with oxygen: Thermochemistry, kinetics, and possible reaction pathways

The reaction of the 1-naphthyl radical C10H7• (A2•) with molecular (3O2) and atomic oxygen, as part of the oxidation reactions of naphthalene, is examined using ab-initio and DFT quantum chemistry calculations. The study focuses on pathways that produce the intermediate final products CO, phenyl and C2H2, which may constitute a repetitive reaction sequence for the successive diminution of six-membered rings also in larger polycyclic aromatic hydrocarbons. The primary attack of 3O2 on the 1-naphthyl radical leads to a peroxy radical C10H7OO• (A2OO•), which undergoes further propagation and/or chain branching reactions. The thermochemistry of intermediates and transition state structures is investigated as well as the identification of all plausible reaction pathways for the A2• + O2 / A2• + O systems. Structures and enthalpies of formation for the involved species are reported along with transition state barriers and reaction pathways. Standard enthalpies of formation are calculated using ab initio (CBS-QB3) and DFT calculations (B3LYP, M06, APFD). The reaction of A2• with 3O2 opens six main consecutive reaction channels with new ones not currently considered in oxidation mechanisms. The reaction paths comprise important exothermic chain branching reactions and the formation of unsaturated oxygenated hydrocarbon intermediates. The primary attack of 3O2 at the A2• radical has a well depth of some 50 kcal mol−1 while the six consecutive channels exhibit energy barriers below the energy of the A2• radical. The kinetic parameters of each path are determined using chemical activation analysis based on the canonical transition state theory calculations. The investigated reactions could serve as part of a comprehensive mechanism for the oxidation of naphthalene. The principal result from this study is that the consecutive reactions of the A2• radical, viz. the channels conducting to a phenyl radical C6H5•, CO2, CO (which oxidized to CO2) and C2H2 are by orders of magnitude faster than the activation of naphthalene by oxygen (A2 + O2 → A2• + HO2)

Risk-taking behaviours among fishermen in Morocco by the evaluation of “ordalique” functioning

Background: The aim was to investigate the potential fishermen’s psychological functioning which induces risk-taking behaviours by evaluating the ordalique functioning. Materials and methods: This cross-sectional epidemiological study was conducted in three ports of northern Morocco in 2016 and concerned 1413 traditional fishermen working in small embarkations and 1049 administrative staff working in the maritime sector on land. Both groups were male, comparable for age and educational level. The survey support was an individual questionnaire covering socio-demographic characteristics, toxic habits and ordalique functioning questionnaire (le questionnaire de fonctionnement ordalique, QFO). It is composed of 42 items and four dimensions which are evaluated: risk-taking, transgression, positive representation of risk-taking and believes. Results: The prevalence of the ordalique behaviour and its four dimensions was significantly higher among traditional fishermen than administrative staff on land; 66.4% vs. 33.6% (p < 0.0001) for risk-taking, 65.2% vs. 34.8% (p < 0.0001) for transgression, 60.4% vs. 39.6% (p < 0.0001) for positive representation, 59.8% vs. 51.2% (p < 0.0001) for believes. For all range ages, the prevalence of ordalique functioning was higher among fishermen than administrative staff on land. Among fishermen, the prevalence of the was significantly higher among the under 40 years old (69.1% vs. 54.7%, p < 0.0001). The prevalence of toxic habits among ordalique fishermen was significantly greater than no-ordalique ones: tobacco (54.5% vs. 48.6%, p < 0.035), alcohol (42.8% vs. 32.4%, p < 0.0001), cannabis (34.8% vs. 26.6%, p < 0.0001), psychotropic drugs (13.8% vs. 10.4%, p < 0.081) and a combination of toxic habits (27.7% vs. 19.6%, p < 0.0001). Conclusions: Ordalique behaviour among fishermen may explain the partial failure of preventive measures in this sector. Risk-taking behaviours into account in the safety system could reduce occupational hazards in the fishery

Thermochemistry and Kinetics for the Oxidative Degradation of Dibenzofuran and Precursors

The emission of dibenzofurans and dioxins from industrial processes is a major environmental concern. Focussing on dibenzofuran, this study tend to improve our understanding of the general oxidation chemistry and to provide a mechanism suitable for future modelling studies. Based on quantum chemical methods, energies, chemical structures and reactions are calculated numerically. Not only stable molecules and radicals, but also transition states are reported in this work

Thermochemistry and Kinetics for the Oxidative Degradation of Dibenzofuran and Precursors

The emission of dibenzofurans and dioxins from industrial processes is a major environmental concern. Focussing on dibenzofuran, this study tend to improve our understanding of the general oxidation chemistry and to provide a mechanism suitable for future modelling studies.Based on quantum chemical methods, energies, chemical structures and reactions are calculated numerically. Not only stable molecules and radicals, but also transition states are reported in this work

Perron's theorem for nondensely defined partial functional differential equations

The aim of this work is to establish a Perron type theorem for some nondensely defined partial functional differential equations with infinite delay. More specifically, we show that if the nonlinear delayed part is "small" (in a sense to be made precise below), then the asymptotic behavior of solutions can be described in terms of the dynamic of the unperturbed linear part of the equation

A thermochemical study on the primary oxidation of sulfur

Several chemical reactions related to the oxidation and combustion of sulfur are investigated using a number of computational chemistry methods with the objective of determining appropriate methods for use in developing an elementary reaction mechanism for oxidation of sulfur. Calculations are focused on thermochemical properties and reaction energetics for reactive species and transition state structures for reactions in the oxidation / combustion of sulfur. Reactions involving several intermediates resulting from the reactions of S2 with oxygen were investigated with the density functional theory B3LYP (with several basis sets) and BB1K/GTLarge. The composite ab-initio methods G2, G3, G3MP2, G3B3, G3MP2B3 and CBS-QB3 were also used. Enthalpies of a series of sulfur compounds and transition state structures are calculated using the ab initio and DFT calculations. The calculations were combined with isodesmic reaction analysis, whenever possible, in order to cancel error and improve the accuracy of the calculations. Results show that all B3LYP DFT calculations including the 6-311++G(3df,2p) basis set show poor outcome in estimating the enthalpy of reactions involving S2. The six composite methods have all shown consistency with each other and their calculated reaction energies / bond energies are in good agreement with the available literature. Kinetic parameters for calculation of the kinetic parameters on SO3 dissociation to SO2 and O using the canonical transition state theory are reported

Prevalence and molecular characterization of avian infectious bronchitis virus in poultry flocks in Morocco from 2010 to 2014 and first detection of Italy 02 in Africa

The aim of this study was to investigate the prevalence and diversity of infectious bronchitis virus (IBV) genotypes in poultry flocks in 16 areas of Morocco between 2010 and 2014. A total of 360 chicken flocks suspected of being infected by IBV were screened for the IBV N gene using real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Flocks were classified into four groups according to their IBV vaccination programme. Group 1 contained unvaccinated birds. Group 2 received a single application of live H120 vaccine. Groups 3 and 4 birds received one or two booster vaccination(s), respectively, mostly using the H120 vaccine. The real-time RT-PCR results showed that 51.7% of the flocks were positive for the IBV genome with geographical disparities. Molecular characterization of IBV was performed on 50 RT-PCR positive samples by partially sequencing the S1 gene, including the hypervariable regions (nucleotides 705-1097). Two predominant genotypes were detected, with the Massachusetts type dominating (66%), among which 25% of the samples were identical to the H120 vaccine. The second most common genotype (present in 32% of the flocks) was surprisingly Italy 02, revealing the first detection of this genotype in Morocco and also in Africa. 793B, the predominant genotype in the late 1990s in Morocco, was only detected on one occasion and was identical to the 4/91 vaccine strain. This study highlights the high prevalence of IBV in poultry farms in Morocco and confirms its continuous dynamic changes and evolution