Low energy electron attachment to condensed formic acid

Dissociative electron attachment to formic acid in the condensed phase is studied using improved mass spectrometric detection of the negative ion fragments. The desorbed yields are measured as a function of incident electron energy in the range between 3 to 20 eV. Unlike previous work, the formation of the dehydrogenated anion HCOO? is observed and the signal to noise ratio is much higher for all other ions detected, i.e. OH?, O? and H?. Resonant structure seen in all anion yield functions, is attributed to dissociative electron attachment (DEA), whereas above 14 eV nonresonant dipolar dissociation (DD) dominates the desorption yields

The association between perceived stress, coping styles and personality traits in a sample of Psychology Honours students

Magister Psychologiae - MPsychLiterature identified Psychology students to be vulnerable to the stress associated with professional postgraduate studies and the nature of multiple processes. Less research has been conducted on Honours students as a cohort. The present study attempted to examine the associations between personality traits, perceived stress and coping styles in a sample of Honours students and post-Honours interns enrolled at a historically disadvantaged university. The present study was a cross-sectional internet survey including four instruments: the Brief COPE questionnaire (coping styles), the Perceived Stress Scale (subjective stress), the Big 5 Personality Survey (BFI-10) (personality traits) and a demographic questionnaire. All participation was voluntary and general principles of ethics were adhered to. The data was analysed using frequencies, correlation matrices, coefficients of determination and and regression. Findings indicated medium levels of perceived stress in this sample including contextual factors like gender, age and race. The B.Psych students reported reduced ranges on perceived stress compared to Honours students. Personality profiles indicated the four highest ranked traits (agreeableness, conscientiousness, openness and extraversion) closely banded. Neuroticism was ranked substantially lower in this sample. More adaptive coping styles like (planning, religion, active coping, acceptance etc.) were used than maladaptive coping styles. Associative relationships were indicated between demographic variables and coping, personality traits and perceived stress respectively. Race, Gender, relationship status, registration status and Age was found to correlate significantly with the three core constructs (perceived stress, coping and personality traits). Findings indicated predictive relationships between combinations of coping styles which could significantly predict perceived stress. Maladaptive coping significantly predicted perceived stress controlling for adaptive coping (e.g. emotion-focused coping and problem-focused coping)

Interactions of Low-Energy Electrons with Atomic and Molecular Solids

Low energy electrons are involved in a large number of analytical techniques for material analysis either as secondary particles or as the primary excitation source. The interaction of these electrons near the surface of solids can be investigated with high-resolution low-energy electron-beam techniques. The results of experiments performed on atomic and molecular solids in the range 0-30 eV with such techniques are reviewed in the present article. The major types of experiments are briefly described and examples of the results obtained from them are given to illustrate the basic mechanisms which control the electron-solid interactions and to provide a description of the basic degradation processes involved during sample irradiation. It is shown that elastic and quasi-elastic scattering of slow electrons can be described in terms of band structure parameters whereas inelastic scattering is usually governed by the formation of transient anions. These anions can decay by stabilization, by producing vibrationally and electronically excited molecules, or by dissociating into a stable anion and a neutral radical. These latter species usually initiate other reactions with nearby molecules causing further chemical damage. It is shown that the damage caused by transient anions can be controlled by modifying its molecular environment

(Play)Building Sexuality Education: Using participatory drama as queer pedagogy to explore youth experiences of sexuality education

The recent sex education curriculum update in Ontario sparked controversy in the media, reflecting a moral panic around sex education in Canada. Since its introduction in 2010 and implementation in 2015, debates ensued over the content of the curriculum, however, little attention was on the form through which it is delivered. This study explores experiences of sexuality education to critically reflect on the ways adolescents navigate discourses of sexuality through formal and informal education. In this thesis, I review discourses of sexuality education and argue that queer pedagogies can be used to foster critical, and queer spaces to negotiate sexuality. I conceptually frame playbuilding (Belliveau, 2006; Norris, 2009; Weigler, 2001), a drama-based research methodology, as a queer pedagogy and mobilize it in this study to co-author a play with participants based on our collective experiences. This participatory drama-based research process involved an exploration of themes and constructs in sexuality education, translating these into dramatic forms, and performing the co-authored scenes to an audience. Through playbuilding, this research tells critical stories of six individuals negotiating their experiences of the discourses of sexuality education. I explore the ways queer pedagogies in sexuality education and playbuilding, in particular, can create spaces wherein youth can exercise agency as sexual subjects and critically reflect on adolescent sexuality

Electron Transmission Spectroscopy in Atomic Hydrogen

An electron transmission experiment is used to study the resonances in the total scattering cross section of atomic hydrogen below the threshold of the first excited state. The three lowest resonances, designated 1S, 3P, and 1D, are observed and their energies and decay widths are found to be in good agreement with the values predicted theoretically using close coupling with correlation

Electron Transmission Spectroscopy in Atomic Hydrogen

An electron transmission experiment is used to study the resonances in the total scattering cross section of atomic hydrogen below the threshold of the first excited state. The three lowest resonances, designated 1S, 3P, and 1D, are observed and their energies and decay widths are found to be in good agreement with the values predicted theoretically using close coupling with correlation

Transient Anions in Radiobiology and Radiotherapy: From Gaseous Biomolecules to Condensed Organic and Biomolecular Solids

This chapter focuses on the fundamental processes that govern interactions of low‐energy (1–30 eV) electrons with biological systems. These interactions have been investigated in the gas phase and within complex arrangements in the condensed phase. They often lead to the formation of transient molecular anions (TMAs), and their decay by autoionization or dissociation accompanied by bond dissociation. The damage caused to biomolecules via TMAs is emphasized in all sections. Such damage, which depends on a large number of factors, including electron energy, molecular environment, and type of biomolecule, and its physical and chemical interactions with radiosensitizing agents are extensively discussed. A majority of recent findings resulting from experimental and theoretical endeavors are presented. They encompass broad research areas to elucidate important roles of TMAs in irradiated biological systems, from the molecular level to nanoscale cellular dimensions. Fundamental aspects of TMA formation are stressed in this chapter, but many practical applications in a variety of radiation‐related fields such as radiobiology and radiotherapy are addressed

Diffraction in low-energy electron scattering from DNA: bridging gas phase and solid state theory

Using high-quality gas phase electron scattering calculations and multiple scattering theory, we attempt to gain insights on the radiation damage to DNA induced by secondary low-energy electrons in the condensed phase, and to bridge the existing gap with the gas phase theory and experiments. The origin of different resonant features (arising from single molecules or diffraction) is discussed and the calculations are compared to existing experiments in thin films.Comment: 40 pages preprint, 12 figures, submitted to J. Chem. Phy

Effet des antirétroviraux sur la pathogénèse du VIH : une étude par modélisation mathématique intégrant la cinétique du virus, de l’immunité, du médicament, et le comportement d’adhésion avec leurs variabilités interindividuelles

Les traitements antirétroviraux actuels permettent à beaucoup de patients du VIH de maintenir leurs charges virales à de très faibles niveaux sur plusieurs décennies. Or, malgré ce succès scientifique, de nombreux problèmes persistent, et à ce jour, aucun traitement ne permet de venir à bout du virus. Une prise à vie d’antirétroviraux est donc nécessaire, impliquant ainsi des contraintes posologiques pour le patient, une potentielle atteinte à sa qualité de vie et un fardeau financier pour la société. À ces inconvénients s’ajoute le risque de développer de la résistance aux médicaments. Même si les traitements demeurent efficaces, la persistance du virus peut également causer des dommages aux différents tissus et organes de l’hôte. En se basant sur des connaissances de pointe dans le domaine du VIH, cette thèse aborde ces problématiques par une approche de pharmacologie quantitative des systèmes, appuyée par des données cliniques. L’objectif principal fut d’informer les mécanismes sous-jacents au développement de la résistance et à la persistance du virus in vivo. Nous avons tiré profit d’un maximum d’information sur l’ensemble des composantes impliquées dans la réponse virologique aux médicaments. Les modèles que nous avons développés joignent différentes échelles d’information, allant de l’échelle moléculaire, à virale, puis cellulaire, jusqu’au niveau clinique. Nous avons ensuite évalué la cohérence d’hypothèses de causalité aux phénomènes étudiés en testant la capacité de ces modèles à expliquer et reproduire des données empiriques. En premier lieu, nous avons développé un modèle visant à mieux comprendre l’ampleur du développement de la résistance chez les patients sous plusieurs traitements. Le modèle combine plusieurs composantes, dont la cinétique virale, l’immunité, la pharmacocinétique et pharmacodynamique, l’adhésion au médicament ainsi que leurs variabilités interindividuelles. Les prédictions du modèle in silico concordent avec les observations cliniques d’échec virologique pour les trois traitements considérés et qui font intervenir l’efavirenz, l’emtricitabine, le ténofovir, le darunavir et le ritonavir. Par cette approche intégrative, nous avons remédié à la lacune des modèles précédents qui sous-estimaient grandement le risque de résistance. Nos résultats soulignent le rôle important que joue la faible pénétration des médicaments au niveau des ganglions lymphatiques dans le développement de la résistance. Ce modèle se veut prometteur de son utilité dans la prédiction de réponse virologique en clinique. Nous nous sommes ensuite intéressés au phénomène du déclin en différentes phases, de plus en plus lentes, des charges virales des patients sous traitement antirétroviral. Les causes sous-jacentes à ce phénomène restent encore obscures. Une divergence d’opinions sur le rôle de la faible pénétration tissulaire des médicaments quant à l’existence de ces phases, divise actuellement les efforts de recherche. Afin de mettre la lumière sur cette implication, nous avons ajouté à notre modèle intégratif des taux différents de pénétration tissulaire. Nos résultats indiquent que l’implication seule de la pénétration des médicaments dans l’explication des phases de déclin serait synonyme d’un grand risque de développement de résistance. Ces prédictions contredisent quantitativement la réalité observée (peu de résistance), nous faisant conclure que cette hypothèse ne peut vraisemblablement pas expliquer le phénomène en question. La dernière partie de la thèse se penche sur la capacité de certains patients à maintenir de faibles charges virales après l’interruption d’un traitement prolongé. Nous avons revisité une corrélation rapportée entre la charge virale résiduelle et la durée de maintien post-interruption de charges faibles. L’interprétation de cette corrélation s’avère difficile, puisque la durée en question n’inclut pas seulement le temps de contrôle de la virémie, mais également le temps nécessaire à la charge virale d’atteindre un seuil de tolérance à partir de la charge virale résiduelle. En utilisant un modèle mécanistique et des techniques statistiques avancées, nous avons réussi à estimer la durée attendue de contrôle réel de la charge virale ainsi que la variabilité interindividuelle associée. Contrairement à l’interprétation directe de la corrélation rapportée dans la littérature, notre analyse révèle que la variabilité interindividuelle du temps de contrôle de la virémie n’est pas associée à la charge virale résiduelle. L’approche in silico adoptée dans cette thèse s’inscrit dans l’effort global de ces dernières années visant à minimiser le fardeau humain et le coût financier dans le développement du médicament. L’ensemble de nos résultats de modélisation suggèrent qu’une meilleure pénétration dans les ganglions lymphatiques diminuerait le nombre de cas de résistance chez les patients non-adhérents. Cependant, ils indiquent qu’une telle amélioration aurait peu d’influence sur la vitesse de déclin des charges virales. Aussi, quelle que soit l’influence de la pénétration lymphatique sur la virémie résiduelle, son amélioration n’aurait pas d’impact sur la capacité des patients à contrôler leurs charges virales après avoir cessé les antirétroviraux.Tremendous progress was made in treating people living with HIV. Nowadays, antiretroviral therapy usually allows patients to suppress viral loads for several years, if not decades. Despite this scientific achievement, chronic drug intake is usually necessary as no treatment can completely eradicate the virus. Patients under these conditions may experience constant side effects. Further, patients’ tissues and organs may become damaged over time, as chronic immune activation is observed in most patients despite adequate drug intake and undetectable viremia. The number of treatment options can also become seriously limited over time if patients’ viruses develop and accumulate drug resistance. These issues motivate current scientific efforts. Hopefully, results from these efforts may lead to improvements in patient’s quality of life and lower the financial burden HIV imposes on society. Using the most up-to-date knowledge in the field of HIV, this thesis addresses some of the above-mentioned issues through a quantitative systems pharmacology approach supported by clinical data. Our main objective was to inform the mechanisms underlying the development of resistance and the persistence of the virus in vivo. We used available information on the components involved in the virologic response to drugs. This allowed developing models that bridge multiple scales, going from molecular, to viral, then cellular and finally to the clinical level. By assessing the ensuing models’ ability to explain and reproduce empirical data, we studied the consistency of hypotheses regarding the causality of studied phenomena. First, we developed a model allowing to better understand the extent of drug resistance development in patients undergoing antiretrovial therapy. The model combines several components, including viral kinetics, immunity, pharmacokinetics and pharmacodynamics, drug adherence as well as their interindividual variability. Predictions originating from our in silico model are consistent with clinical observations of virologic failure for the three treatments that were considered consisting of efavirenz, emtricitabine, tenofovir, darunavir and ritonavir. Through this integrative approach, we have remedied previous models that largely underestimated the risk of resistance. Our results highlight the important role played by low lymph node drug penetration in the development of resistance. The model we developed is an added forward step toward the use of in silico methods in the prediction of virologic responses in HIV patients. We then investigated the causes underlying the increasingly slow phases of viral decline observed in patients initiating antiretroviral therapy. Opinions differ as to the role played by low drug penetration in tissues in the existence of these phases, leading to a fragmentation in research efforts. To shed light on this issue, we additionally considered, in our integrative model, different rates of tissue penetration. Our results indicate that, if low drug penetration were the only cause of the decline in phases of the viral load, then the ensuing low drug exposure would put patients at a very high risk of developing drug resistance. Prediction of high risk quantitatively contradicts the observed reality (little to no resistance), leading us to conclude that low penetration is unlikely a fair explanation to the phases of viral decline. The last part of the thesis examines the ability of some patients to maintain low viral loads after interrupting prolonged antiretroviral therapy. We revisited a reported correlation between viral load values at interruption (also called residual viremia) and the duration of time patients maintained low viral loads afterwards. The interpretation of this correlation proved to be challenging since this duration includes both a time of complete control of viremia and a time during which viremia grows to a low-level threshold once control is lost. Using a mechanistic model and advanced statistical techniques, we were able to estimate the expected duration of complete viremia control along with its interindividual variability. Contrary to a direct interpretation of the correlation reported in the literature, our analysis reveals that the time of viremia control is unlikely associated with patients’ residual viremia. In summary, the in silico approach adopted in this thesis is part of an overall effort aiming to minimize patient recruitment and the financial costs involved in drug development. Our models suggest that better drug penetration in lymph nodes would likely lead to a decreased risk of drug resistance in non-adherent patients. However, our results also suggest that such an improvement would have little influence on the rate of decline of viral loads. Further, and regardless of the influence lymphatic tissue drug penetration may have on residual viremia, this improvement would not favour viremia control after antiretroviral discontinuation

Déchloration réductive de lixiviats contaminés aux produits de préservation du bois par filtre réactif

RÉSUMÉ Un site industriel servant à l’entreposage de bois traité produit un lixiviat contaminé en produits de préservation du bois, soit en arséniate de cuivre chromaté (ACC) et en pentachlorophénol (PCP) associé aux polychlorodibenzodioxines et polychlorodibenzofuranes (PCDD/F). Les PCDD/F sont des polluants persistants parmi les plus toxiques connus. L’objectif du projet était de développer un filtre réactif semi-passif pour traiter ce lixiviat. Pour cette raison un filtre réactif pilote contenant une poudre de fer zéro valent (FZV) pour la déchloration du PCP et des PCDD/F a été utilisé. La caractérisation du matériau réactif (FZV) et du filtre réactif pilote ont constitué les deux premières étapes pour l’atteinte de l’objectif du projet. Ensuite, l’efficacité du filtre réactif pilote à traiter le lixiviat contaminé à l’ACC, au PCP et aux PCDD/F a été vérifiée et comparée à 3 autres filtres réactifs pilotes installés en parallèle sur le même site. La caractérisation du FZV a été effectuée par l’analyse granulométrique au laser de la poudre, une analyse de sa composition par lixiviation et des essais en cuvée sous environnement anaérobie pour vérifier l’effet du FZV sur la déchloration des composés phénoliques chlorés et des PCDD/F hautement chlorés (4 à 8 chlores). Trois solvants ont été testés; eau, eau:éthanol (1:1, v/v) et eau:huile de silicone (1:1, v/v), et le pH initial de 7,7 a été modifié à 10 pour deux essais. Les meilleurs résultats d’enlèvement en PCDD/F ont été rendus par l’essai à l’eau au pH initial non modifié avec plus de 70% d’enlèvement de tous les congénères sauf la tétrachlorodibenzo-p-dioxine en 6,6 jours. Le FZV n’a pas semblé être en cause pour l’enlèvement du PCP selon les essais en cuvée. Enfin, la composition m/m de la poudre de FZV était de 60%(Fe), 30%(Ni) et 5,6%(Cu) et sa granulométrie était de 25 μm.----------ABSTRACT An industrial site used for preserved wood storage produces leachate contaminated with wood preservatives of chromated copper arsenate (CCA) and pentachlorophenol (PCP) which is associated to polychlorodibenzodioxins and polychlorodibenzofurans (PCDD/Fs). PCDD/Fs are persistent pollutants amongst the most toxics pollutants known. The project goal was to develop a semi-passive reactive filter to treat this leachate. For this purpose, a pilot reactive filter was used which contained zero valent iron (ZVI) for the dechlorination of PCP and PCDD/Fs. Characterization of reactive media (ZVI) and pilot reactive filter constituted the two first steps to reach the project objective. Then, the efficiency of the pilot reactive filter to treat CCA, PCP, and PCDD/Fs contaminated leachate was verified and compared with three other pilot reactive filter installed in parallel on the same site. Characterization of ZVI was carried out by a laser particle size measurement of the iron powder, a composition leaching analysis, and anaerobic batch tests to verify the effect of ZVI on dechlorination of chlorinated phenolic compounds and highly chlorinated PCDD/Fs (4 to 8 chlorine). Three solvents were tested; water, water:ethanol (1:1, v/v) and water :silicone oil (1:1, v/v), and the initial pH of 7.7 was modified to 10 for two tests. Water as the only solvent and unchanged initial pH gave the best results with more than 70% of removal of all PCDD/Fs congeners except tetrachlorodibenzo-p-dioxin (TCDD) in 6.6 days. ZVI did not seem involved in the PCP removal according to batch tests results. ZVI’s composition w/w was 60%(Fe), 30%(Ni), and 5.6%(Cu) and its mean particle size was 25 μm