Magma-crust interaction in magma reservoirs and conduits is a crucial process during magma evolution and ascent. This interaction is recorded by crustal xenoliths that frequently show partial melting, inflation and disintegration textures. Frothy xenoliths are widespread in volcanic deposits from all types of geological settings and indicate crustal gas liberation. To unravel the observed phenomena of frothy xenolith formation we experimentally simulated the behaviour of crustal lithologies in volcanic conduits. We subjected various sedimentary lithologies to elevated temperature (maximum 916 °C) and pressure (maximum 160 MPa) in closed-system autoclaves. Experimental conditions were held constant between 24h and 5 days. Controlled decompression to atmospheric pressure then simulated xenolith ascent. Pressure release was a function of temperature decline in our setup. Temperature lapse rate proceeded exponentially; the mean rate during the first 30 minutes was 17.8 ˚C/min and the mean decompression rate during the same interval was 3.0 MPa/min, eventually reaching room temperature after approximately 5.5 hours of slow cooling. The experimental products have been analysed for internal textures by synchrotron X-ray μ-CT at a resolution of 3.4 – 9 microns/pixel. This method permits visualisation and quantification of vesicle volumes, -networks and-connectivity in 3D without destroying the sample. Experimental products closely reproduced textures of natural frothy xenoliths in 3D and define anevolutionary sequence from partial melting to gas exsolution and bubble nucleation that eventually leads to the development of three-dimensional bubble networks. Experimental P-T-t conditions and especially rock lithology proved decisive for degassing behaviour and ensuing bubble nucleation during decompression. Progressive bubble nucleation leads to subsequent bubble coalescence to form interconnected bubble networks. This, in turn, enables efficient gas liberation and release. Our results attest to significant potential of even very common crustal rock types to release volatiles and develop interconnected bubble networks upon heating and decompression in magmatic systems. Crustal volatile input from xenoliths affects magma rheology and may drive magmas to sudden explosive eruptions. Our experiments offer insight into the mechanism of how such crustal volatile liberation is accomplished.

Ruapehu is an active volcano located on the North Island of New Zealand, with the most recent major eruptions occurring in 1945, 1969, 1975, and 1995/96. Ruapehu is also home to the three major North Island ski areas, Whakapapa, Turoa, and Tukino. Because of the high frequency of eruptions, there is a significant volcanic hazard at the ski areas particularly from lahars which can form even after minor eruptions. Most recently, lahars have affected Whakapapa ski area in 1969, 1975, and 1995/96. The most significant risk at Turoa is from ballistic bombs due to the proximity of the top two T-Bars to the crater. Ash fall has also caused disruption at the ski areas, covering the snow and causing damage to structures. There is yet to be a death at the ski areas from a volcanic event; however the risk at the ski areas is too high to be completely ignored. The ski areas at Whakapapa and Turoa are currently operated by Ruapehu Alpine Lifts (RAL), who have been significantly improving their commitment to providing volcanic hazard training for their staff and preparing for handling a volcanic eruption. RAL is joined by the Institute of Geological Sciences (GNS) and the Department of Conservation (DoC) in trying to mitigate this risk through a range of initiatives, including an automated Eruption Detection System (EDS), linked to sirens and loudspeakers on Whakapapa ski areas, as well as by providing staff training and public education. The aim of this study was to provide RAL with recommendations to improve their staff training and warning system response. Staff induction week at both Turoa and Whakapapa ski areas was observed. Surveys were distributed and collected from staff at both ski areas, and interviews were conducted with staff at Whakapapa ski area. Data obtained from staff interviews and surveys provided the author with insight into staff's mental models regarding a volcanic event response. A simulation of the warning system was observed, as well as a blind test, to collect data on the effectiveness of training on staff response. Results indicated permanent and seasonal staff were knowledgeable of the volcanic hazards that may affect the ski areas, but had differing perspectives on the risk associated with those hazards. They were found to be confident in the initial response to a volcanic event (i.e. move to higher ground), but were unsure of what would happen after this initial response. RAL was also found to have greatly improved their volcanic hazard training in the past year, however further recommendations were suggested to increase training effectiveness. A training needs analysis was done for different departments at the ski areas by taking a new approach of anticipating demands staff may encounter during a volcanic event and complementing these demands with existing staff competencies. Additional recommendations were made to assist RAL in developing an effective plan to use when responding to volcanic events, as well as other changes that could be made to improve the likelihood of customer safety at the ski areas during an eruption.

L'éruption de 2010 du Merapi est la première grande éruption explosive du volcan qui a été observée instrumentalement. Dans ce travail, nous étudions les précurseurs de l'éruption et le comportement du volcan avant l'éruption en reliant les caractéristiques sismiques avec d'autres observations disponibles. Nous présentons les principaux aspects de l'activité sismique au cours de la crise de 2010, tels que la chronologie de la sismicité, l'évolution spatio-temporelle des positions de source de séisme et les changements de vitesse sismique. En effectuant des localisations absolues et relatives, nous obtenons des preuves de l'existence de zones asismiques, concordant avec des études antérieures, que nous interprétons comme des zones plus ductiles. La migration du magma de la partie profonde à la partie superficielle du conduit à travers la zone asismique supérieure est mise en évidence par un déplacement vers le haut des hypocentres. Nous analysons l'énergie sismique quantifiée par le RSAM calculé pour plusieurs bandes de fréquences. Ces fonctions affichent des accélérations claires dans les dernières semaines avant l'éruption. Ce comportement est utilisé pour effectuer des prévisions d'éruption volcanique rétrospective avec la méthode « Material Failure Forecast » ou FFM. Le début de la première éruption est estimé avec une bonne précision. Nous proposons une méthode originale de détection d'événement basée sur un rapport d'énergie. En utilisant cette méthode et la corrélation de la forme d'onde, nous identifions 10 familles de séismes similaires. Ces multiplets sismiques sont situés en dessous ou au -dessus de la zone asismique supérieure et sont composés soit d'événements volcano-tectoniques soit d'événements basse fréquence. Certains de ces groupes ont été actifs pendant plusieurs mois avant la crise éruptive alors qu'une famille qui comprend 119 événements répétitifs est apparue 20 heures avant le début de l'éruption. Nous estimons des variations de vitesse sismique, liées principalement à l'activité magmatique, en utilisant la coda des multiplets et les fonctions d'intercorrélation du bruit sismique. Ces variations montrent une forte variabilité spatiale et temporelle de leur amplitude et de leur signe. Bien qu'elles ne puissent pas être décrites par une simple tendance unique, ces variations de vitesse peuvent être considérées comme un précurseur de l'éruption. En utilisant les résultats précédents ainsi que d'autres observations, nous déterminons les particularités associées à la grande éruption explosive de 2010. En outre, nous proposons un scénario chronologique de l'activité pré- éruptive du Merapi. / The 2010 eruption of Merapi is the first large explosive eruption of the volcano that has been instrumentally observed. In this work, we study the eruption precursors and the pre-eruptive volcano behaviour by linking seismic features with other available observations. The main characteristics of the seismic activity during the 2010 crisis, including the chronology of seismicity, the spatio-temporal evolution of earthquake source positions and the seismic velocity changes, are presented. By performing absolute and relative locations, we obtain evidences of aseismic zones which are consistent with earlier studies and are interpreted as more ductile zones. Magma migration from the deep to the shallow part of the conduit through the upper aseismic zone is revealed by an upward shift of the hypocenters. We analyse the seismic energy quantified by RSAM calculated for several frequency bands. These functions display clear accelerations in the last few weeks before the eruption. This behaviour is used to perform hindsight eruption forecasting with the Material Failure Forecast method (FFM). The onset of the first eruption is estimated with a good precision. We propose an original method of event detection based on energy ratio. Using this method and waveform correlation, we identify 10 families of similar earthquakes. The seismic multiplets are located either below or above the upper aseismic zone and are composed of either volcano-tectonic or low-frequency events. Some of the clusters were active during several months before the eruptive crisis while a family that includes 119 repeating events appeared 20 hours before the eruption onset. Seismic velocity variations associated mainly with magmatic activity are estimated using the coda of both multiplets and noise cross correlation functions. These variations display strong temporal and spatial variability of their amplitude and sign. Although they cannot be described by a unique simple trend, these velocity variations can be considered as an eruption precursor. Using the preceding results together with other observations, we determine the specific features associated with the large explosive eruption of 2010. Furthermore, we propose a chronological scenario of the pre-eruptive activity of Merapi 2010 unrest.

O objetivo geral desta pesquisa foi avaliar fatores associados à atividade de lesões de cárie não cavitadas, bem como, critérios para a sua avaliação em superfícies oclusais de molares permanentes. Para isso, dois estudos foram conduzidos. O primeiro estudo teve como objetivos: (1) avaliar a efetividade de um tratamento para pacientes com lesões de cárie em molares em diferentes estágios de erupção e (2) avaliar se o estágio de erupção e o acúmulo de biofilme estão associados à atividade de lesões de cárie em pacientes submetidos a um tratamento não invasivo. Já o segundo estudo teve como objetivo avaliar a associação entre dois critérios visuais para a determinação da atividade de lesões de cárie não cavitadas em molares permanentes. Para o primeiro estudo, foram selecionados 48 pacientes, com idades entre 5 e 13 anos, que apresentavam pelo menos um molar permanente com lesão não cavitada ativa na superfície oclusal. Os molares foram classificados quanto ao tipo, estágio de erupção, presença de biofilme e presença de lesão, bem como, sua condição de atividade. Os pacientes foram submetidos a um protocolo de tratamento não invasivo de 4 sessões com intervalos semanais baseado na educação para saúde bucal e fluorterapia. Após 3 semanas do término do tratamento, 39 pacientes foram re-examinados. Observou-se que os molares parcialmente erupcionados apresentaram maiores chances de permanecerem com lesão ativa após o protocolo de tratamento não invasivo quando comparados aos dentes totalmente em oclusão. Além disso, maior acúmulo de biofilme na superfície oclusal mostrou estar associado com maiores chances de uma lesão permanecer ativa após o tratamento quando comparada a ausência de biofilme visível. Para o segundo estudo, foram selecionados 39 pacientes, com pelo menos um molar permanente com lesão de cárie não cavitada em superfície oclusal, os quais foram classificados com relação à presença de lesões não cavitadas, bem como, sua condição de atividade segundo dois critérios: ICDAS-LAA e um critério padrão (características clínicas consenso na literatura). Os resultados mostraram fraca associação entre os dois critérios na determinação da atividade das lesões de cárie e baixa especificidade para o ICDAS-LAA. Com base nos resultados obtidos no primeiro estudo, pode-se concluir que: (1) o protocolo de tratamento não foi efetivo em inativar as lesões de cárie não cavitadas ativas de pacientes com molares parcialmente erupcionados e (2) foi encontrada uma forte associação entre molares permanentes parcialmente erupcionados, maior acúmulo de biofilme e a presença de lesões ativas mesmo após o tratamento instituído. A partir 7 dos resultados do segundo estudo, concluiu-se que o critério ICDAS-LAA não foi apropriado para a determinação da atividade de lesões de cárie não cavitadas em superfícies oclusais de molares permanentes, visto que parece superestimar a atividade das lesões. / The aim of this study was to evaluate associated factors to non-cavitated caries lesions activity as well as different criteria for its assessment on occlusal surfaces of permanent molars. Therefore, two studies were carried out. The aims of the first study were: (1) to evaluate the effectiveness of a treatment for patients with non-cavitated caries lesions on permanent molars in different eruption stages and (2) to evaluate if the eruption stage and biofilm accumulation are associated to caries lesions activity in patients that received a non-operative treatment. The second study aimed at evaluating the association between two visual criteria in assessing non-cavitated caries lesions activity on permanent molars. For the first study, 48 patients aged from 5 to 13 years old were selected. Those patients should have presented at least one permanent molar with an active non-cavitated caries lesion on its occlusal surface. Molars were classified according to type, eruption stage, biofilm accumulation and presence of lesion as well as their activity status. All patients received a weekly non-operative treatment during 4 weeks based on oral health instructions and fluoride application. After 3 weeks, 39 patients were re-assessed. After the treatment, partially erupted molars were more prone to show active caries lesions than molars in full occlusion. Likewise, high biofilm accumulation was more associated to the presence of active caries lesions when compared to the absence of visible biofilm. For the second study, 39 patients with at least on permanent molar with non-cavitated caries lesion on occlusal surface were selected. Molars were classified according to the presence of caries lesions as well as to their activity status following two criteria: ICDAS-LAA and a standard criterion (based on clinical characteristics which are consensus in the literature). The results showed a weak association between both criteria in assessing caries lesions activity and low specificity for ICDAS-LAA. Based on the results from the first study, it can be concluded that: (1) treatment was not effective in arrest active non-cavitated caries lesion in patients with partially erupted molars and (2) a strong association between partially erupted molars, high biofilm accumulation and presence of active lesions was observed even after the treatment. From the results of the second study, it can be concluded that ICDAS-LAA criterion was not appropriate for activity assessment of non-cavitated caries lesions on occlusal surfaces of permanent molars, since this criterion seems to overestimate caries lesions activity.

L'augmentation artificielle de la couche stratosphérique d'aérosol de sulfate a été proposée comme méthode pour réduire le réchauffement climatique causé par les émissions anthropiques de gaz à effet de serre. Dans cette thèse, nous présentons un modèle global atmosphère-aérosol nouvellement développé, évaluons sa performance par rapport aux observations et l'appliquons pour étudier l'efficacité et les impacts de cette forme possible d'ingénierie climatique. Nous trouvons que l'effet de refroidissement réalisable par unité de masse de soufre injectée peut diminuer de façon plus drastique qu'estimé précédemment pour des taux d'injection élevés et que des injections à plus haute altitude ou dans des régions plus grandes n'entraînent pas un refroidissement plus fort. L'efficacité de la méthode pourrait donc être plutôt limitée, tout au moins dans les cas d'injections tropicales de dioxyde de soufre que nous avons modélisées. Par ailleurs, il existe plusieurs effets secondaires potentiellement nocifs, tels que le chauffage stratosphérique dû à l'absorption de rayonnement par l'aérosol provoquant de fortes perturbations dans la dynamique atmosphérique, la composition chimique de la stratosphère et les nuages hauts. Enfin, nous trouvons que les effets radiatifs de l'injection d'aérosol stratosphérique et de l'éclaircissement des nuages marins, une autre technique de géo-ingénierie proposée, seraient largement additifs et complémentaires lors de leur application parallèle. Cela pourrait permettre de concevoir un port-folio d'approches pour atteindre des objectifs climatiques spécifiques et réduire les effets secondaires indésirables de l'ingénierie climatique. / The enhancement of the stratospheric sulphate aerosol layer has been proposed as a method to abate the global warming caused by anthropogenic greenhouse gas emissions. In this thesis we present a newly developed global atmosphere-aerosol model, evaluate its performance against observations, and apply it to study the effectiveness and impacts of this possible form of climate engineering. We find that the achievable cooling effect per injected sulphur mass unit may decrease more drastically for larger injections than previously estimated and that injections at higher altitude or over larger areas do not result in a stronger cooling. The effectiveness of the method may therefore be rather limited, at least when using tropical injections of sulphur dioxide as in our model experiments. In addition, there are several potentially harmful side effects, such as stratospheric heating due to absorption of radiation by the aerosol causing strong perturbations in atmospheric dynamics, composition, and high-level clouds. Furthermore, we find that the radiative effects of stratospheric aerosol injection and marine cloud brightening, another proposed geoengineering technique, would be largely additive and complementary when applying them together. This might allow the design of portfolio approaches to achieve specific climate goals and reduce unintended side effects of climate engineering.

O objetivo geral desta pesquisa foi avaliar fatores associados à atividade de lesões de cárie não cavitadas, bem como, critérios para a sua avaliação em superfícies oclusais de molares permanentes. Para isso, dois estudos foram conduzidos. O primeiro estudo teve como objetivos: (1) avaliar a efetividade de um tratamento para pacientes com lesões de cárie em molares em diferentes estágios de erupção e (2) avaliar se o estágio de erupção e o acúmulo de biofilme estão associados à atividade de lesões de cárie em pacientes submetidos a um tratamento não invasivo. Já o segundo estudo teve como objetivo avaliar a associação entre dois critérios visuais para a determinação da atividade de lesões de cárie não cavitadas em molares permanentes. Para o primeiro estudo, foram selecionados 48 pacientes, com idades entre 5 e 13 anos, que apresentavam pelo menos um molar permanente com lesão não cavitada ativa na superfície oclusal. Os molares foram classificados quanto ao tipo, estágio de erupção, presença de biofilme e presença de lesão, bem como, sua condição de atividade. Os pacientes foram submetidos a um protocolo de tratamento não invasivo de 4 sessões com intervalos semanais baseado na educação para saúde bucal e fluorterapia. Após 3 semanas do término do tratamento, 39 pacientes foram re-examinados. Observou-se que os molares parcialmente erupcionados apresentaram maiores chances de permanecerem com lesão ativa após o protocolo de tratamento não invasivo quando comparados aos dentes totalmente em oclusão. Além disso, maior acúmulo de biofilme na superfície oclusal mostrou estar associado com maiores chances de uma lesão permanecer ativa após o tratamento quando comparada a ausência de biofilme visível. Para o segundo estudo, foram selecionados 39 pacientes, com pelo menos um molar permanente com lesão de cárie não cavitada em superfície oclusal, os quais foram classificados com relação à presença de lesões não cavitadas, bem como, sua condição de atividade segundo dois critérios: ICDAS-LAA e um critério padrão (características clínicas consenso na literatura). Os resultados mostraram fraca associação entre os dois critérios na determinação da atividade das lesões de cárie e baixa especificidade para o ICDAS-LAA. Com base nos resultados obtidos no primeiro estudo, pode-se concluir que: (1) o protocolo de tratamento não foi efetivo em inativar as lesões de cárie não cavitadas ativas de pacientes com molares parcialmente erupcionados e (2) foi encontrada uma forte associação entre molares permanentes parcialmente erupcionados, maior acúmulo de biofilme e a presença de lesões ativas mesmo após o tratamento instituído. A partir 7 dos resultados do segundo estudo, concluiu-se que o critério ICDAS-LAA não foi apropriado para a determinação da atividade de lesões de cárie não cavitadas em superfícies oclusais de molares permanentes, visto que parece superestimar a atividade das lesões. / The aim of this study was to evaluate associated factors to non-cavitated caries lesions activity as well as different criteria for its assessment on occlusal surfaces of permanent molars. Therefore, two studies were carried out. The aims of the first study were: (1) to evaluate the effectiveness of a treatment for patients with non-cavitated caries lesions on permanent molars in different eruption stages and (2) to evaluate if the eruption stage and biofilm accumulation are associated to caries lesions activity in patients that received a non-operative treatment. The second study aimed at evaluating the association between two visual criteria in assessing non-cavitated caries lesions activity on permanent molars. For the first study, 48 patients aged from 5 to 13 years old were selected. Those patients should have presented at least one permanent molar with an active non-cavitated caries lesion on its occlusal surface. Molars were classified according to type, eruption stage, biofilm accumulation and presence of lesion as well as their activity status. All patients received a weekly non-operative treatment during 4 weeks based on oral health instructions and fluoride application. After 3 weeks, 39 patients were re-assessed. After the treatment, partially erupted molars were more prone to show active caries lesions than molars in full occlusion. Likewise, high biofilm accumulation was more associated to the presence of active caries lesions when compared to the absence of visible biofilm. For the second study, 39 patients with at least on permanent molar with non-cavitated caries lesion on occlusal surface were selected. Molars were classified according to the presence of caries lesions as well as to their activity status following two criteria: ICDAS-LAA and a standard criterion (based on clinical characteristics which are consensus in the literature). The results showed a weak association between both criteria in assessing caries lesions activity and low specificity for ICDAS-LAA. Based on the results from the first study, it can be concluded that: (1) treatment was not effective in arrest active non-cavitated caries lesion in patients with partially erupted molars and (2) a strong association between partially erupted molars, high biofilm accumulation and presence of active lesions was observed even after the treatment. From the results of the second study, it can be concluded that ICDAS-LAA criterion was not appropriate for activity assessment of non-cavitated caries lesions on occlusal surfaces of permanent molars, since this criterion seems to overestimate caries lesions activity.

A erupção dentária depende de uma coordenada interação entre o germe dentário e o tecido ósseo da cripta que o envolve. Para que seja formada a via eruptiva, a reabsorção da porção oclusal da cripta óssea por osteoclastos é indispensável. Os bisfosfonatos são drogas com reconhecida capacidade de inibir a atividade clástica e foram empregados no presente estudo a fim de interferir no tecido ósseo da cripta alveolar durante a formação e erupção de molares de ratos. Doses diárias dos bisfosfonatos alendronato ou etidronato de 2,5 e 8 mg/kg, respectivamente, foram administradas a ratos recém nascidos. Os controles foram injetados com solução salina. Nos períodos de 4, 8, 14, 21 e 28 dias, as maxilas foram fixadas em 2,5% de formaldeído + 2% de glutaraldeído, 4% de formaldeído + 0,1% de glutaraldeído ou fixador Zamboni, descalcificadas em EDTA a 4,13% e processadas para análise em microscopias de luz, eletrônica de transmissão e confocal, histoquímica TRAP, imunocitoquímica para OPN, BSP, RANK, RANKL e OPG. Alguns espécimes não foram descalcificados para análise em microscopia eletrônica de varredura, ou congelados em nitrogênio líquido para extração e análise e da expressão de proteínas por Western Blotting. O etidronato ocasionou alterações no metabolismo ósseo da cripta que resultaram no atraso da erupção e da formação radicular em relação ao controle. O alendronato aumentou o número de osteoclastos no osso alveolar, porém a maioria apresentou estado latente, o que diminuiu a reabsorção óssea da cripta ao redor do germe dentário e impediu a erupção dos molares e a formação radicular. A expressão de RANKL, molécula ativadora dos osteoclastos, durante o início do processo eruptivo, diminuiu em comparação ao controle. Com a diminuição da remodelação óssea, o tecido apresentou distribuição de OPN e BSP típica de osso primário. Os resultados demonstram que a reabsorção óssea é importante em todos os pontos da cripta e não apenas em sua porção oclusal durante a formação da via eruptiva, para que a formação e erupção dentária ocorram adequadamente. / Tooth eruption depends on coordinated interactions between the tooth germ and the surrounding bony crypt. The formation of the eruptive pathway requires the resorption of the occlusal portion of the bony crypt by osteoclasts. The bisphosphonates are drugs with known capability to inhibit clastic activity, and were employed in the present study with the aim of interfering in the alveolar bony crypt during the formation and eruption of rat molars. Daily alendronate or etidronate 2.5 and 8 mg/kg doses, respectively, were administered to newborn rats. The controls were injected with saline solution. At 4, 8, 14, 21 and 28 days, the maxillae were fixed in 2.5% formaldehyde + 2% glutaraldehyde, 4% formaldehyde + 0,1% glutaraldehyde or Zambonis fixative, decalcified in 4.13% EDTA and processed for light, confocal and transmission electron microscopy analyzes, TRAP histochemistry, and immunocytochemistry for OPN, BSP, RANK, RANKL and OPG. Some specimens were left undecalcified for scanning electron microscopy analyzes, or frozen in liquid nitrogen for protein extraction and Western Blotting protein expression analyzes. Etidronate occasioned alterations in the alveolar bony crypt metabolism that resulted in the delay of tooth eruption. Alendronate increased osteoclast number in the alveolar bone; however, most of them were latent, which decreased the resorption of the bony crypt surrounding the tooth germ and impeded the eruption and root formation of the molars. The expression of RANKL, an osteoclast-activating molecule, was decreased. The inhibition of the bone remodeling resulted in typical primary bone OPN and BSP labeling pattern. These results demonstrate that bone resorption at the entire surface of the crypt, and not only during the eruptive pathway formation, is crucial for adequate tooth eruption and formation.

Osteopetrosis is a metabolic bone disease in mammals characterized by a generalized skeletal sclerosis caused by reduced bone resorption. This reduced bone resorption is manifested in afflicted animals by abnormal bone shape, reduced or absent marrow cavities, extramedullary hemopoiesis, abnormal mineral homeostasis and absent or delayed tooth eruption. The available osteopetrotic animal mutations have been a constant source of fruitful investigations concerning the systemic regulation of osteoclastogenesis and bone metabolism. Tooth eruption, on the other hand, is a localized manifestation of the timely activation of bone resorption and bone formation on opposite sides of an erupting tooth. Its rate-limiting step is the speed of bone resorption to form the eruption pathway. In this dissertation, we used two osteopetrotic rat mutations, toothless (tl) and microphthalmia blanc (mib), to investigate the abnormal development of osteoclasts and tooth eruption in mutant rats with an emphasis on the role of systemic and local factors. The significant contributions to this work are listed below. 1. In the toothless rat, a mutation lacking erupted dentition due to severely reduced bone resorption, colony-stimulating factor-1 (CSF-1) promoted tooth eruption but this was delayed compared to normal rats. Eruption was accompanied by changes in the populations of tartrate-resistant acid phosphatase-positive (TRAP+) mononuclear cells in the dental follicle and TRAP+ osteoclasts on adjacent alveolar bone surfaces. These cell populations were dramatically increased in treated mutants compared to untreated tl rats, but the timing of their appearance was delayed compared to normal littermates. This lag in the appearance of osteoclasts and their precursors corresponded to the delay in eruption of first molars in treated tl rats. 2. CSF-1 also accelerated the eruption of molars in normal rats. CSF-1 increased the number of TRAP+ mononuclear cells in the dental follicle and TRAP+ osteoclasts on adjacent alveolar bone surfaces, but had no effect on the timing of their appearance in normal rats. 3. Our data revealed a differential effect on tooth eruption of the growth factors CSF-1 and epidermal growth factor (EGF). CSF-1 accelerated eruption of molars in normal rats, but had no effect on incisor eruption. On the other hand, EGF accelerated incisor eruption; but did not affect molar eruption in normal rats. 4. We have described the mechanism for the transient, mild form of osteopetrosis inherited by mib rats. Mutant animals possess a typical sclerosis at birth, which diminished--but was not resolved--during the first postnatal month. These characteristics are caused by early reductions in osteoclast number and function which improve to normal levels by 4 weeks. Osteoclast numbers were severely reduced in mib rats between birth and 2 weeks, but improved to near normal levels by 4 weeks. Neonatal abnormalities in osteoclast function included reduced staining for the functional enzymes TRAP and TrATPase, decreased levels of mRNA for both TrATPase and CAll, and inability to form a well-developed ruffled border. None of these defects were apparent after the first postnatal month. 5. Finally, we have shown that the dental abnormalities caused by the mild, transient form of osteopetrosis in mib rats are limited to incisor defects and delayed eruption of all teeth. Histologic and radiographic examination of mutant incisors revealed that, contrary to the situation in normal rats, the apex of the incisors of mib rats failed to extend past the first molar region to the third molar. The incisor apex of newborn mib rats was misshaped due to ankylosis of incisor matrices with alveolar bone. This ankylosis was temporary, being resolved by the third postnatal day. The delayed eruption of incisors in mib rats and abnormal shape and occlusion of these teeth in older animals is a consequence of the temporary ankylosis in newborn rats.

Le dioxyde de soufre (SO2) est un des principaux gaz émis lors des éruptions volcaniques. Au Piton de la Fournaise (La Réunion) environ 230 kT de SO2 ont été libérés pour la seule éruption d'avril 2007. Ces émissions ont provoqué d'importants problèmes sanitaires associés à des dégradations des infrastructures et des écosystèmes. Les mesures de SO2 réalisées par l'ORA ont relevé des concentrations supérieures aux seuils critiques pour la santé mais pas aux périodes où l'éruption était la plus intense. SO2 étude consiste à utiliser le modèle meso-échelle atmosphérique Meso-NH pour simuler le transport de SO2 entre le 2 et le 7 avril, avec une attention portée sur l'influence des flux de chaleur provenant des coulées de lave. Trois domaines sont imbriqués de 2 km à 100m de résolution horizontale. Cette étude de modélisation couple simultanément (i) la dynamique atmosphérique de méso-échelle Meso-NH, (ii) un module de chimie en phase gazeuse et phase aqueuse, et (iii) un modèle de surface simulant une propagation de coulée de lave. Tous les flux (chaleur, vapeur, SO2, CO2 et HCl) sont déclenchés en ligne et sont fonction de la dynamique du front de propagation. Nos simulations reproduisent les observations des concentrations en surface de SO2 pour cette période et diverses analyses de sensibilité montrent que la distribution de soufre a été principalement contrôlée par le flux de chaleur de lave. Les dernières simulations incluent la modélisation du panache de vapeur d'eau lors de l'entrée de la lave en mer. Enfin, deux tests de sensibilités ont été réalisés sur la journée du 5 avril afin d'analyser les interactions dynamiques entre les différentes convections : au cratère et au-dessus de la lave (flux de chaleur sensible) et lors de l'entrée de la lave en mer (flux de chaleur latente). / Sulphur dioxide (SO2) is one of the main gases emitted during volcanic eruptions. The Reunion Island experienced its biggest eruption of Piton de la Fournaise Volcano during April 2007 and this event degassed more than 230 kt of SO2. Theses emissions led to important health issues, accompanied by environmental and infrastructure degradations. SO2 measurements made by the ORA noted higher concentrations than the critical threshold for health but not to periods when the eruption was the most intense. Our study is to use the atmospheric mesoscale model Meso-NH to simulate the transport of SO2 between 2 and 7April, with a focus on the influence of heat flow from lava flows. Three domains are nested from 2km to 100m of horizontal resolution. This modeling study torque simultaneously (i) atmospheric dynamics of mesoscale Meso-NH, (ii) a chemistry module in the gas phase and aqueous phase, and (iii) a surface model simulating a lava flow spread. All flow (heat,vapor, SO2, CO2 and HCl) are triggered online and are function of the dynamics of thepropagation front. Our simulations reproduce the observations of surface concentrations of SO2 for that period and various sensitivity analyzes show that the sulfur distribution was mainly controlled by the lava heat flow. The latest simulations include the modeling of the Laze plume when the lava meet the sea. Finally, two sensitivity tests were performed on the day of April 5 to analyze the dynamic interactions between convections: the crater andover the lava (sensible heat flux) and at the entry of lava into the sea (latent heat flux).

El estudio tuvo como objetivo determinar la prevalencia del fallo primario de la erupción dental en radiografías panorámicas de un centro imagenológico, Chiclayo, 2023. Este estudio fue descriptivo, retrospectivo, observacional y transversal. Se analizaron las radiografías panorámicas de 220 pacientes de 11 a 15 años de edad, de ambos sexos, que presentaban al menos una primera molar permanente, que corresponden al año 2022. Según sexo 125 radiografías fueron de sexo masculino y 95 de sexo femenino. Se obtuvo, una prevalencia total de fallo primario de erupción de 0.91%, de los cuales 0,45% corresponde a cada sexo. Respecto a edad se encontró mayor predominancia en la edad de 14 años con un porcentaje del 1%, finalmente en la prevalencia según pieza dentaria se observó mayor incidencia de la pieza dentaria 85 en el 50% del total. Se concluyó que la prevalencia del fallo primario de la erupción dental alcanzó un nivel muy bajo, similar a otros estudios previos. / The study aimed to determine the prevalence of primary failure of dental eruption in panoramic radiographs of an imaging center, Chiclayo, 2023. This study was descriptive, retrospective, observational and cross-sectional. Panoramic radiographs were analyzed in 220 patients aged 11 to 15 years, of both sexes, who had at least one permanent first molar, corresponding to the year 2022. According to sex 125 x-rays were male and 95 female. A total prevalence of primary eruption failure of 0.91% was obtained, of which 0.45% corresponds to each sex. Regarding age, we found greater predominance in the age of 14 years with a percentage of 1%, finally in the prevalence according to tooth was observed greater incidence of the 85th tooth in 50% of the total. It was concluded that the prevalence of primary failure of dental eruption reached a very low level, similar to other previous studies.