This thesis describes the theoretical results of mercury-sensitized photochemical reactions of isopropyl benzene and methylcyclohexane. The reactions are carried out and the results are analyzed.

Les diatomées constituent le principal groupe du phytoplancton dans les océans, contribuant à près de 20% de la production primaire globale. Dans leur environnement très variable, les diatomées sont particulièrement efficaces dans leur capacité à ajuster leur activité photosynthétique en dissipant sous forme de chaleur l’énergie lumineuse absorbée en excès, par un processus appelé le « Non-Photochemical Quenching of chlorophyll fluorescence », (NPQ). Chez la diatomée modèle, Phaeodactylum tricornutum, il a été montré que LHCX1, une protéine proche des antennes photosynthétiques, est impliquée dans le NPQ. Par des approches intrégrées de génétique, biologie moléculaire, biochimie, imagerie des cinétiques de fluorescence et spectroscopie ultrarapide, j’ai étudié le rôle de la famille des LHCX chez P. tricornutum. J’ai tout d’abord pu corréler une expression différentielle des 4 gènes LHCX de P. tricornutum avec différentes dynamiques de NPQ et activités photosynthétiques, dans différentes conditions de lumiére et nutriments. En localisant les LHCX dans les differents complexes photosynthétiques et les différents sites de dissipation d’énergie, j’ai pu proposer un modèle de régulation dynamique du NPQ impliquant à court terme principalement LHCX1 au niveau des centres réactionnels, et une autre isoforme, possiblement LHCX3, au niveau des antennes lors d’un stress lumineux prolongé. Enfin, par le criblage d’une série de mutants potentiellement dérégulés dans leur contenu en LHCXs, j’ai pu identifier des lignées avec un NPQ altéré qui pourront constituer des nouveaux outils de recherche. Dans l’ensemble ce travail de thèse a permis de mettre en évidence la diversification fonctionnelle et l’importance de la famille des LHCX dans la fine modulation des capacités de collecte de lumière et de photoprotection, expliquant sans doute en partie le succès des diatomées dans leur environnement très fluctuant. / Diatoms dominate phytoplanktonic communities in contemporary oceans, contributing to 20% of global primary productivity. In their extremely variable environment, diatoms are especially efficient in adjusting their photosynthetic activity by dissipating as heat the light energy absorbed in excess, through a process called “Non-Photochemical Quenching of chlorophyll fluorescence”, (NPQ). In the model diatom Phaeodactylum tricornutum, it has been shown that LHCX1, a photosynthetic antenna-related gene, is involved in the NPQ process. Through integrated approaches of genetics, molecular biology, biochemistry, study of the kinetics of chlorophyll fluorescence yields and ultrafast spectroscopy, I studied the role of the LHCX family in the photoprotection activity of P. tricornutum. I first correlated a differential regulation of the 4 P. tricornutum LHCX genes with different dynamics of NPQ and photosynthetic activity, in different light and nutrient conditions. By localizing the LHCXs in fractioned photosynthetic complexes and the different sites of energy dissipation, I was able to propose a model of dynamic regulation of NPQ capacity involving mainly the LHCX1 in the reaction centers, during short-term high light responses. During prolonged high light stress, the quenching occurs mainly in the antennas, potentially mediated by the LHCX3 isoform. Finally, using photosynthetic parameters, I screened a series of transgenic lines putatively deregulated in their LHCX amount, and I identified lines with altered NPQ, which could represent novel investigation tools. Altogether, this work highlighted the functional diversification and the importance of the LHCX protein family in the fine-tuning of light harvesting and photoprotection capacity, possibly contributing to explain diatoms success in their highly fluctuating environment.

Anticiper les impacts des changements climatiques sur les écosystèmes terrestres, notamment sur le cycle du carbone, nécessite la compréhension et la quantification du fonctionnement photosynthétique des végétaux et leurs réponses aux contraintes abiotiques. Suivre l’évolution des propriétés spectrales des couverts végétaux par la télédétection permet d’avoir accès à leur fonctionnement à des échelles spatiales et temporelles variées. Plusieurs indicateurs optiques ont été développés afin d’accéder à la structure, la biochimie et le fonctionnement écophysiologique des végétaux. Le PRI (photochemical reflectance index), déterminé à partir de la réflectance mesurée dans des bandes étroites à 531 nm et 570 nm, est un proxy de l’efficacité de la plante à utiliser la lumière (LUE, light use efficiency) et plus particulièrement du cycle des xanthophylles, utilisé par la plante pour dissiper l’énergie lumineuse excédentaire sous forme de chaleur. Cependant son usage à l’échelle du couvert végétal, ou à plus larges échelles temporelles et spatiales, entraine l’implication de nombreuses sources de variabilités qui masquent la sensibilité du PRI au fonctionnement photosynthétique, particulièrement les variations biochimiques et phénologiques. L’objectif de ce travail est de mieux comprendre les facteurs qui jouent sur la variabilité du PRI à l’échelle de la feuille et du couvert, afin de caractériser ses réponses aux variations abiotiques de l’environnement et de démêler la composante phénologique de la composante physiologique du PRI. Des études ont été menées en conditions contrôlées, semi-naturelles et naturelles, sur des jeunes arbres et en forêt adulte, soumis à différentes contraintes abiotiques. L’analyse des courbes de réponse du PRI aux variations de lumière incidente utilisée pour la photosynthèse (PAR, photosynthetically active radiation) permet d’isoler 3 paramètres. Le PARsat, la valeur de PAR pour laquelle le PRI sature, le PRI₀, la valeur du PRI à une intensité lumineuse faible (mesurée) ou nulle (estimée) et le ∆PRI, l’amplitude de variation entre le PRI₀ et la valeur de PRI maximum. En période de végétation, la variabilité du PARsat est principalement contrôlée par la disponibilité en eau pour la plante. La variabilité du PARsat est aussi impactée par la concentration d’ozone atmosphérique. En période de débourrement et de sénescence, la variabilité du contenu en chlorophylle régit la valeur du PARsat. Ce paramètre explique la variabilité physiologique du PRI et varie en fonction du facteur limitant la photosynthèse. La variabilité du PRI₀ a été expliquée par la variabilité du contenu biochimique des feuilles en réponse au cycle saisonnier de la chlorophylle et à sa variabilité en conditions de stress. A l’échelle de la canopée, la variabilité de la structure du couvert s’ajoute à la variabilité biochimique du PRI₀. Le PRI₀, en temps que composante phénologique de la variabilité du PRI, peut être utilisé pour corriger le PRI afin de lui soustraire la variabilité structurale et obtenir un PRIc fortement corrélé à la LUE. A l’échelle de la canopée, il a été montré que le PRI est principalement représentatif de la strate supérieure du couvert. Le ∆PRI n’a montré aucune variation intra et inter-journalière, suggérant que le PRI répond non pas au contenu en xanthophylle des plantes, mais à un ratio maintenu constant. Ces résultats mettent en évidence l’importance d’isoler les différentes sources de variabilité du PRI avant de l’utiliser comme proxy du fonctionnement photosynthétique des écosystèmes terrestres. / Anticipating impacts of climate change on terrestrial ecosystems, particularly on the carbon cycle, requires the understanding and the quantification of the plant photosynthetic functioning and of their responses to abiotic factors. Tracking variations of spectral properties of plants using remote sensing allows the access of plant functioning at various spatial and temporal scales. Several optical indices have been developed to assess plant canopy structure, biochemistry and ecophysiological functioning. The PRI (photochemical reflectance index), determined from reflectances measured in narrow bands at 531 nm and 570 nm, may be used as a proxy of light use efficiency (LUE) at leaf and canopy scales, and more particularly of the xanthophyll cycle used by plants to dissipate the excess light energy as heat. However the use of PRI at the canopy scale and at large temporal and spatial scales faces several difficulties related to the involvement of different sources of variability that blur PRI sensitivity to photosynthetic functioning. These sources of PRI variability are particularly linked to spatial and temporal variations of biochemical and phenological canopy properties. The aim of these studies is to better understand the factors affecting PRI variability at leaf and canopy scales, to assess the strength of the relationships between PRI and vegetation responses to environmental abiotic constraints and disentangling the phenological component from the physiological component of PRI. Studies were conducted under controlled, semi-natural and natural conditions, on young trees and a mature deciduous forest subjected to various abiotic constraints. The analysis of PRI responses to the variations of photosynthetically active radiation (PAR) allowed isolating three parameters. The PARsat, the PAR value at the PRI saturation; the PRI₀, the value of PRI at dim light (measured) or in darkness (estimated) and the ΔPRI, the range of PRI variations between the PRI₀ and the maximum value of PRI. During the leaf growing season, PARsat variability is mainly controlled by the availability of water content for the plant. The PARsat variability is also impacted by the atmospheric ozone concentration. During the phenological phases of budburst and the senescence, the variability of the leaf chlorophyll content governs PARsat values. This parameter describes the physiological variability of PRI and varies depending on the limiting factor for photosynthesis. The PRI₀ variability has been explained by the dynamic of the biochemical content of the leaves linked to the seasonal variations of chlorophyll content and to abiotic stress conditions. At canopy scale, the structural variability is added to the biochemical variability of PRI₀. The PRI₀, as the phenological component of PRI variability, can be used to correct PRI, removing its structural variability to obtain a PRIc strongly correlated to LUE. At canopy scale, it was shown that the PRI is mostly representative of the upper layer of the canopy. The ΔPRI showed no variation within and between days, suggesting that the PRI does not respond to the plant xanthophyll content but rather to a ratio maintained constant. These results highlight the importance of isolating the different sources of PRI variability before its use as a proxy of the photosynthetic functioning of terrestrial ecosystems.

Photochemical grid models are used to evaluate air pollution control strategies by simulating the physical and chemical processes that influence pollutant concentrations. Their accuracy depends on the accuracy of input data used for anthropogenic and biogenic emissions, land surface characteristics, initial and boundary conditions and meteorological conditions. Evaluation of model performance requires sufficient ambient data. This work develops approaches for applying satellite data to allow more frequent and timely estimates of parameters required to estimate emissions and pollutant removal processes for regional air quality modeling. Land use and land cover (LULC) data prepared from remote sensing satellite data were evaluated for use as inputs to photochemical grid models for estimating dry deposition velocities and biogenic emissions. The results indicated that satellite-based data derived from the Moderate Resolution Imaging Spectroradiometer instrument can be used to provide periodic updates to LULC information used in photochemical models. The sensitivity of predicted ozone concentrations to LULC data used for biogenic emission estimates was examined by comparing the database currently used for modeling in southeastern Texas with a new database prepared from Landsat satellite imagery and field data. The satellite data and image classification techniques provide useful tools for mapping and monitoring changes in LULC. However, field validation is necessary to link species and biomass densities to the classification system needed for accurate biogenic emissions estimates, especially in areas that have dense concentrations of species that emit high levels of biogenic hydrocarbons. The application of NO2 measurements from the Ozone Monitoring Instrument (OMI) to validation of NOx emission estimates and identification of emission sources for regional air quality modeling for Texas was examined. OMI observations can be used to identify regions with changes in emissions over time or where estimates have large uncertainties and to evaluate the effectiveness of emission reduction strategies. For example, in the Dallas-Fort Worth area, observed NO2 column densities from OMI indicate that emission controls are less effective than anticipated due to increased area source emissions. The techniques developed in this work have broad applicability in the advancement of methods for including satellite remote sensing data in regional air quality modeling. / text

No description available.

No description available.

No description available.

Purpose: 1) To estimate the threshold dose and the time evolution for cataract induction by near infrared radiation (IRR) in seconds exposure time domain; 2) to determine the ocular temperature development during the threshold exposure; 3) to investigate if near IRR induces cumulative lens damage considering irradiance exposure time reciprocity; 4) to experimentally estimate the temperature in the lens indirectly from the measurement of temperature-induced light scattering increase. Methods: Before exposure, 6-weeks-old albino rats were anesthetized and the pupils of both eyes were dilated. Then the animals were unilaterally exposed to 1090 nm IRR within the pupil area. Temperature was recorded with thermocouples placed in the selected positions of the eye. At the planned post-exposure time, the animal was sacrificed and the lenses were extracted for measurements of forward light scattering and macroscopic imaging (Paper I-III). In Paper IV, the lens was extracted from six-weeks-old albino Sprague-Dawley female rats and put into a temperature-controlled cuvette filled with balanced salt solution. Altogether, 80 lenses were equally divided on four temperature groups, 37, 40, 43 and 46 ºC. Each lens was exposed for 5 minutes to temperature depending on group belonging while the intensity of forward light scattering was recorded. Results: The in vivo exposure to 197 W/cm2 1090 nm IRR required a minimum 8 s for cataract induction. There was approximately 16 h delay between exposure and light scattering development in the lens. The same radiant exposure was found to cause a temperature increase of 10 °C at the limbus and 26 °C close to the retina. The in vivo exposure to 96 W/cm2 1090 nm IRR with exposure time up to 1 h resulted in an average temperature elevation of 7 °C at the limbus with the cornea humidified and no significant light scattering was induced one week after exposure. Arrhenius equation implies that the natural logarithm of the inclination coefficient for light scattering increase is linearly dependent on the inverse of the temperature. The proportionality constant and the intercept, estimated as CI(0.95)s, were 9.6±2.4 x103 K and 22.8±7.7. Further, it implies that if averaging 20 measurements of inclination coefficients in a new experiment at constant heat load, the confidence limits for prediction of temperature correspond to ±1.9 °C. Conclusions: It is indicated that IRR at 1090 nm produces thermal but not cumulatively photochemical cataract, probably by indirect heat conduction from absorption in tissues surrounding the lens. Applying the Arrhenius equation the in vivo temperature in the lens can be determined retrospectively with sufficient resolution.

Ce travail de thèse s‟articule autour de l‟apport des techniques de l‟analyse thermique à l‟étude et au suivi des phénomènes de vieillissement thermique et photochimique des matériaux polymères. Après une étude bibliographique sur l‟état de l‟art dans ce domaine, la thèse a présenté les résultats obtenus lors de l‟application de l‟Analyse Thermique Différentielle (DSC) à l‟étude du vieillissement de ces matériaux. Le travail de cette partie a porté sur la cristallinité du Poly (Acide Lactique) (PLA) et du Poly (Ethylène Téréphtalate) (PET). Une corrélation a été établie entre les résultats issus de la DSC et ceux obtenus par Spectroscopie Infrarouge à Transformée de Fourier (FTIR) en ce qui concerne l‟évolution de la cristallinité au cours du vieillissement du polymère. Une seconde partie du travail a porté sur le suivi des propriétés thermo-optiques par photo-DSC. Ce travail a été illustré par l‟étude du Poly (Chlorure de Vinyle) (PVC). Une dernière section de ce travail s‟est attachée au suivi, par DSC et par Analyse Thermogravimétrique (ATG), de la diffusion de l‟eau dans la matrice polymère en cours de vieillissement. Ici, c‟est la technique dite thermoporosimétrie qui a été choisie. Les résultats ont été comparés à ceux obtenus par le couplage ATG-DSC-Humidité. Le travail, dans cette partie, a porté sur le PolyIsoprène (PI) et sur le PolyDiMéthylSiloxane) (PDMS). / This work focuses on the contribution of thermal analysis techniques to the multi-scale study and monitoring of the phenomena of thermal and photochemical aging of polymer materials.After a bibliographic study on the state of the art in this field, the thesis presented the results obtained during the application of the Differential Scanning Calorimetry (DSC) to the study of the aging of these materials. First of all, this part focused on the crystallinity of Poly (Lactic Acid) (PLA) and Poly (Ethylene Terephthalate) (PET). A correlation was established between the results obtained from the DSC and those obtained by Fourier Transform Infrared Spectroscopy (FTIR) with respect to the evolution of the crystallinity during aging of the polymer.Furthermore, our work focused on the follow-up of the thermo-optical properties by photo-DSC. This work was illustrated by the study of Poly (Vinyl Chloride) (PVC).A final section of this work focuses on the DSC and ThermoGravimetric Analysis (TGA) monitoring of the diffusion of water in the polymer matrix during aging. Here, the technique known as Thermoporosimetry was chosen. The results were compared with those obtained by coupling ATG-DSC-Moisture. The type of products which are chosen in this part of study, were Polyisoprene (PI) and on PolyDiMethylSiloxane (PDMS).

A Região Metropolitana de São Paulo (RMSP) enfrenta sérios problemas relacionados à degradação da qualidade do ar devido às emissões de sua intensa frota veicular, apresentando constantes ultrapassagens dos Padrões de Qualidade do Ar de poluentes como o ozônio (PQAr ~80ppbv). O Ozônio é formado na atmosfera em condições complexas em presença de intensa radiação solar, altas temperaturas, baixa umidade relativa, ventos fracos e altas concentrações dos precursores, óxidos de nitrogênio (NOx = NO + NO2) e compostos orgânicos voláteis (COVs). Assim, o problema da poluição do ar em centros urbanos precisa ser tratado com metodologias mais modernas para que possam ser estabelecidos novos critérios para redução de seus precursores e o conhecimento das condições mais adequadas (relação entre os COVs e os NOx, além da especiação destes COVs) para a redução do ozônio troposférico. Neste contexto, modelos fotoquímicos de qualidade do ar têm sido usados para auxiliar na tomada de decisões ambientais estratégicas. O módulo químico SAPRC Statewide Air Pollution Research Center é um mecanismo detalhado para simular reações entre COVs e NOX, desenvolvido para ser aplicado para atmosferas urbanas e regionais dos Estados Unidos. Porém, devido características específicas do combustível (aproximadamente 30% da frota usa etanol), no Brasil a poluição urbana apresenta características próprias. Dessa forma, baseado em campanhas anteriores de amostragem de COVs, no presente estudo foram modificados o inventário de emissões e o módulo químico (SAPRC99) do modelo fotoquímico CIT a fim de melhorar a representação do ozônio quanto a sua formação e consumo na atmosfera da RMSP. Para isso, alguns COVs como xilenos, 1-buteno e trimetilbenzenos foram explicitados. As simulações para os dias 30 e 31 de outubro de 2006 mostraram aumentos de espécies como peroxiacetilnitrato e ozônio de aproximadamente 10% para o centro de formação de pluma sobre a RMSP. / The Metropolitan Area of São Paulo (MASP) suffers severe problems related to air quality degradation presenting constant air quality standard overpasses for pollutants like ozone (QSAir ~80ppbv), due to its intense vehicular fleet. Ozone is formed in the atmosphere under complex conditions in the presence of strong solar radiation, high temperatures, low relative humidity, weak winds and also high precursor concentrations, such as nitrogen oxides (NOx = NO + NO2) and volatile organic compounds (VOCs). Therefore, the problem of air pollution in urban centers has to be treated using modern methodologies in order to establish new criteria for reduction of precursors and to know more adequate conditions (relation between VOCs and NOx, as well as speciation of these VOCs) in order to reduce tropospheric ozone. In this context, air quality photochemical models have been used to support strategic environmental decisions. SAPRC chemical mechanism Statewide Air Pollution Research Center developed to be applied in the United States urban atmospheres, consists of a detailed mechanism to simulate reactions between VOCs and NOx. However, due to specific fuel properties (about 30% of vehicular fleet uses ethanol), urban air pollution in Brazil presents its own characteristics, such as higher level of the oxygenated compounds. Hence, based on previous campaigns where VOCs had been sampled, the emission inventory and the chemical module (SAPRC99) were modified in order to improve ozone consumption and formation representation in the MASP atmosphere. As a result, some VOCs like xylenes, 1-butene and trimethilbenzens were explicated. Simulations for 30 and 31 of October 2006 presented increases in species formation like peroxyacetylnitrate and ozone about 10% in the centre of the MASP plume.