As the environmental regulations and technical progress have forced the factories’ old “end of pipe” solutions to improve, the metal emissions from point sources have decreased. Instead, the diffuse consumption emissions from goods in use now are in focus. The increased awareness of traffic as a major diffuse metal emission source emphasizes the need for more detailed information on the various traffic related sources. The main scope of this thesis is to study specific parts of metal emissions from some road traffic related sub sources such as brake lining and tyres. The metals in focus are antimony (Sb), cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb), nickel(Ni) and zinc (Zn), and the research quantifies emissions from the different sub sources, trace changes over time as well as dispersal patterns and metal mobility in the roadside environment. The results show that even if the road traffic associated metal stocks are small compared to total in use stocks, their emissions are of major importance. The updated figures show that despite material developments during the last 10 years, tyres still are one of the main sources of Zn and Cd, while it can be excluded as a source of concern for the other metals studied. Brake linings are shown to be an especially pronounced source for Cu and Sb. The Pb and Cd emissions from brake linings and tyres have decreased as a result of decreasing material concentrations in these sources, most likely a result of EU regulations. Further the results reveals galvanized goods to be a major road traffic related source for Zn. The results show that the total metal concentrations in roadside soils have increased 3-16 times compared to regional background during the last decades. Each metal has a limited dispersal distance from the roads as well as down in the soil profile. Most metals are found within 10 m from the road in the uppermost 10 cm of the topsoil. However, the sequential extractions show that a large part of the metals found in the soil are rather easily mobilized and can be redistributed if the roadside soils become disturbed. Metals emitted due to decelerating activities are not correlated to elevated concentrations near road junctions. Instead the metals appear to be more evenly spread along the whole driven distance. The study points out Sb as an element that might be problematic to analyse. For Sb, which is sparsely studied as a roadside contaminant, there is a need of more general knowledge as it has a high accumulation rate in roadside soils. / I takt med ökade regleringar inom miljöområdet och en snabb teknikutveckling har fabrikerna allt mer spelat ut sin roll som emissionskällor till miljön. Istället har den diffusa emissionen som kommer från produktanvändning fått en större betydelse. En ökad medvetenhet om transporter och trafikens betydelse för samhällets konsumtionsemissioner understryker det ökade kunskapsbehovet för de trafikrelaterade emissionskällorna. Avhandlingens huvudsyfte är att studera specifika delar av metallemissionen från vissa trafikrelaterade källor så som bromsbelägg och däck. Metallerna som är i fokus är antimon (Sb), bly (Pb), kadmium (Cd), koppar (Cu), krom (Cr), nickel (Ni) och zink (Zn) och forskningen strävar efter att kvantifiera emissionerna från de olika källorna, spåra förändringar i emissioner över tid, kartlägga utsläppsmönster och metallrörlighet i vägnära jord. Resultaten pekar på att även om de trafikrelaterade källorna kvantitativt är små i jämförelse med de totala källorna så är deras emissioner av stor betydelse. De nya siffrorna visar att trots en materialutveckling inom området under det senaste årtiondet så är fortfarande däck en av de största källorna för Cd och Zn i stadsmiljö, medan de kan avfärdas som källa för de övriga studerade metallerna. Studien visar att bromsbelägg fortfarande är en viktig källa för Cu och Sb. Bly- och Cd-emissionerna från däck och bromsbelägg har däremot minskat drastiskt under samma period. Denna minskning beror troligen på en reglering på EU-nivå. Dessutom visar resultaten att galvaniserade ytor är den viktigaste källan till Zn i stadsmiljö. Metallkoncentrationerna i vägnära jord har ökat med 3 – 16 ggr jämfört med bakgrundshalterna i de undersökta områdena. Metallerna uppvisar endast en begränsad spridning från vägen och ner i jordprofilen. Den största metallpåverkan återfinns inom 10 m från vägen och i de översta 10 cm av jorden. Trots den begränsade spridningen så uppvisar de flesta metallerna en förhållandevis hög rörlighet, vilket innebär att de kan bli mobila vid störning av jorden. De bromsrelaterade metallerna uppvisar ingen korrelation till förhöjda halter nära korsningar utan är mer jämnt spridda över hela körsträckan. Studien pekar ut Sb som ett element som kan vara problematiskt att analysera på grund av dess flyktighet. Trots att Sb för närvarande har en snabb ackumulationstakt i trafikmiljö så är den endast sparsamt studerad. Mer generell kunskap om Sb är därför önskvärd.

Dans le cadre de cette recherche, la production de biocharbon par pyrolyse est étudiée à des conditions visant sa valorisation comme biochar (amendement pour le sol), tout en considérant son potentiel comme charbon vert (pour bioénergie ou transformations subséquentes). La production du charbon de biomasse s'est effectuée à l'aide de deux réacteurs à lits fixes de types batch, d'une capacité de 1 et 25 gb.hlbatch, respectivement. Le panic érigé (Panicum virgatum) est la biomasse lignocellulosique qui a été utilisée dans le cadre des tests. Les facteurs de production étudiés sont principalement la température (300, 400 et 500 °C) pour un court temps de résidence en réacteur (2,5 et 5 min) et l'effet de l'usage du CO2 plutôt qu'un environnement plus conventionnel d'azote. L'effet de ces facteurs est étudié par rapport aux caractéristiques physico-chimiques des biocharbons obtenus. Un suivi des produits pyrolytiques complémentaires (bio-huile et gaz) a aussi été effectué. Des extractions de biocharbon par Soxhlet (à l'aide de dichlorométhane) ont été analysées par GC-MS et ont permis l'identification d'une multitude de produits présents dans les biocharbons. Les conditions spécifiques utilisées pour la pyrolyse, entre autres la convection forcée avec taux de chauffe rapide à 300 °C — N2 à l'aide du réacteur 1 glbatch, ont présenté des rendements et propriétés de biocharbon avantageux pour l'amélioration de la productivité du procédé de torréfaction (en comparaison avec des travaux rapportés, notamment ceux de Gilbert et al. [2009]). Les analyses des extractions de charbons de biomasse ainsi que des bio-huiles (par GC-MS), produites à l'aide du réacteur 25g/batch, ont permis d'observer des différences significatives dans les composés obtenus lors de l'usage de CO2 vs N2. Plusieurs composés observés dans les extraits de biocharbons, produits en atmosphère de N2, se retrouvent en quantités moindres dans les extraits de biocharbons produits en atmosphère de CO2 pour des températures communes. À titre d'exemple, le furfural, un composé aromatique commun provenant de la dégradation des glucides, s'est retrouvé uniquement dans les extraits de biocharbons en présence de N2 vs CO2, à 400 °C. Parmi l'ensemble des conditions étudiées (pour les 2 réacteurs), uniquement le naphtalène et des dérivés du naphtalène sont observés comme hydrocarbures aromatiques polycycliques, et ce, uniquement suivant les traitements à 500 °C. L'étude de l'usage du CO2 comme gaz d'entrée en réacteur mena à des différences significatives pour l'ensemble des températures étudiées, et ce, tant pour les biocharbons que pour les produits liquides et gazeux. À 300 °C, en environnement de CO2 comparé à N2, il est possible d'observer une production de bio-huile significativement plus faible (18,0 vs 24,6 %; CO2 vs N2 pour P<0,002), ce qui représente un résultat cohérent avec l'obtention de biocharbon au contenu en composés volatils significativement plus élevé obtenu aux mêmes conditions (0,29 vs 0,35 g composés volatils - biocharbotig biomasse originale; CO2 vs N2 pour P=0, I ). De plus, à 500 °C, un contenu en cendres de biocharbon significativement plus faible a été observé en environnement de CO2 vs N2 (P<0,06). [symboles non conformes]

Thesis (m.S. Ch. E.)--University of Puerto Rico, Mayagüez Campus, 2004. / Tables. Printout. Includes bibliographical references (leaves 88-91.)

Ziel: Das Ziel dieser Studie war es den Zusammenhang zwischen Zahnextraktionen und Patientenfaktoren in 3 Deutschen Zahnarztpraxen zu untersuchen. Material & Methoden: In einer retrospektiven Auswertung aller Patientenkarten von 3 deutschen Zahnarztpraxen wurden Extraktionsfälle ab Januar 2007 (Praxis 1), Mai 2010 ( Praxis 2) und Januar 2010 ( Praxis 3 ) auf Extraktionen hin durchsucht, bis in jeder Praxis jeweils 100 Extraktionspatienten gefunden wurden, die die Einschlusskriterien erfüllten. Alle Patienten ohne Extraktionen die innerhalb dieses Zeitraumes behandelt wurden und die die Einschlusskriterien erfüllten, dienten als Kontrollgruppe. Es wurden nur Patienten eingeschlossen (Fall und Kontrollgruppe), von denen die spezifischen Patientendaten zur Verfügung standen. Alle Patientendaten wurden in einem „Case-Report-Form\"-Formular (CRF) erfasst. Die individuellen Parameter der Patienten der Fallgruppe und der Kontrollgruppe wurden verglichen. Mittels schrittweiser logistischer Regressionsanalyse konnten die Faktoren für ein Extraktionsrisiko bestimmt werden. Ergebnisse: Insgesamt wurden 2174 Patientenakten untersucht (Fallgruppe 300; Kontrollgruppe 1874). Die Gesamtsumme der Zähne vor der Extraktionstherapie betrug 54316. In der Fallgruppe wurden insgesamt 459 Zähne extrahiert. Die Patienten der Fallgruppe waren im Schnitt mehr als 6,7 Jahre älter als die Patienten der Kontrollgruppe(52,4/45,7 Jahre (P< 0,001)), sie waren zu einem größeren Anteil männlich. (58/ 52%) ,es gab eine höhere Zahl an Rauchern, es gab vermehrt Patienten mit einer Kalziumkanalblocker Medikation [15/8 % (p<0,001)] und der parodontale Befund festgestellt mittels PSI der Fallgruppe war schlechter als der der Kontrollgruppe [PSI 2,5/1,8 , (p<0,001)]. Das Risiko einer Zahnextraktion im Allgemeinen und in Folge von Parodontalerkrankungen waren assoziiert mit Kalziumkanalblockermedikation, (OR 1,49/1,65) aktivem Rauchen (OR 1,35/1,71), Alter (10Jahre) OR 1,13/1,37 , Praxis Nr.1 (1,48/1,99) und der Anzahl der Sextanten mit dem PSI Code 4 (1,33/1,76) (p<0,001). Schlussfolgerung: Kalziumkanalblockermedikation, aktives Rauchen, Alter, Zahnarzt und die Anzahl der Sextanten mit einem PSI Wert 4 sind Risikoindikatoren für Zahnextraktionen. Nutzen : Kalziumkanalblockermedikation kann das Extraktionsrisiko erhöhen. Zahnverlust zieht in den meisten Fällen Zahnersatz nach sich, welcher in aller Regel aufwändig ist, den Patienten zusätzliche Belastungen abverlangt und die Kosten einer Therapie erhöht. Die Information über die Einnahme von Kalziumkanalblockern ist ein leicht zu erfassender Parameter und könnte als Indikator genutzt werden, um Betreuungsintervalle zu verkürzen. Es muss jedoch noch geprüft werden, ob eine intensivere Betreuung dieser Patienten deren Zahnextraktionsrate tatsächlich verringern kann.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As más oclusões de Classe I com biprotrusão dentária são caracterizadas pela projeção dos incisivos superiores e inferiores e podem ser corrigidas com extrações de primeiros pré-molares, permitindo reposicionar os incisivos, usando como ancoragem os dentes posteriores. Esse trabalho teve como objetivo comparar, por meio de superposição de modelos tridimensionais, a movimentação de molares e de incisivos com duas técnicas para fechamento de espaços. Foram selecionados, tomografados (T0) e distribuídos, aleatoriamente em dois grupos, seis pacientes com indicação de exodontia de quatro primeiros pré-molares. No grupo 1 (n=3) foi feito o fechamento dos espaços das extrações em uma única etapa (fechamento em massa) e no grupo 2 (n=3), em duas etapas (distalização de caninos seguida da retração de incisivos). Após o completo fechamento dos espaços foi solicitada nova tomografia (T1). Os modelos tridimensionais em T0 e T1 para os dois grupos foram superpostos para descrever e quantificar a movimentação ocorrida nos primeiros molares. A retração de incisivos foi avaliada de maneira bidimensional. Os molares superiores e inferiores do grupo 1 sofreram movimentação mesial de translação, enquanto os do grupo 2, apresentaram deslocamento de coroa maior do que de ápice radicular, demonstrando movimento de inclinação mesial de coroa. Ao se comparar o movimento mesial dos molares entre os dois grupos, observou-se que no grupo 1 houve maior movimentação mesial da raiz mésio-vestibular dos molares superiores (p=0,009). No entanto, em ambos os grupos os molares superiores giraram sobre a raiz palatina. No arco inferior verificou-se maior movimento mesial de coroa para o grupo 2 (p=0,015). A análise da movimentação dos incisivos apresentou variações semelhantes para as medidas lineares e angulares dos incisivos superiores nos dois grupos. Já, para as medidas angulares dos incisivos inferiores, observou-se que o grupo 1 apresentou menor controle de torque. O tempo de tratamento de todos os pacientes da amostra foi superior a 30 meses, exceto um paciente que apresentou tempo de tratamento inferior a 24 meses. Pôde-se concluir que a perda de ancoragem ocorreu por movimento de translação no fechamento de espaços em massa, e por inclinação mesial no fechamento de espaços em duas etapas, para ambos os arcos. Parece haver maior movimentação mesial radicular nos molares superiores no fechamento em massa e maior movimento mesial de coroa dos molares inferiores para o fechamento em duas etapas. Sugere-se que não há diferença na retração dos incisivos superiores e maior retroinclinação dos incisivos inferiores no fechamento de espaços em duas etapas. / Class I malocclusions with dental biprotrusion are characterized by the projection of upper and lower incisors and can be corrected with extractions of four first premolars, allowing incisor retraction using the posterior teeth as anchorage. The purpose of this research was to compare the movement of molars and incisors, by superimpostions of three-dimensional models, with two space closure techniques. Six patients with indication for four first premolar extractions were selected, tomographed (T0) and randomly assigned to two groups. For Group 1 (n=3) premolar extraction space closure was performed in one-stage (en masse retraction) and for group 2 (n=3) in two stages (canine retraction followed by incisor retraction). After complete space closure, a new tomograph was taken (T1). The three-dimensional models, in T0 and T1, for both groups were superimposed to describe and quantify first molar movement. Incisor retraction was evaluated in two dimensions. The upper and lower molars in group 1 presented bodily mesial movement, while those in group 2, presented greater crown than root movement, demonstrating mesial crown tipping. When the amount of mesial molar movement was compared between the two groups, a greater mesial root movement was observed for upper molars in group 1 (p=0.009). However, in both groups the upper molars rotated aroung the palatal root. In the lower arch, a greater mesial crown movement was observed in group 2 (p=0.015). Incisor movement analysis presented similar variations for linear and angular measurements for upper incisors in both groups. In contrast, the angular measurements for the lower incisors demonstrated more torque control in group 2. The treatment time for all patients in the sample was greater than 30 months, with the exception of one patient, who presented treatment time smaller than 24 months. In conclusion, anchorage loss ocurred by bodily movement in en masse space closure and by mesial crown tipping in two-stage space closure, in both arches. In addition, there might be greater mesial root movement for upper molars in en masse space closure and greater mesial crown movement in two-stage space closure. It can also be suggested that there are no differences in upper incisor retraction and there is greater lower incisor uprighting in two-stage space closure.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As más oclusões de Classe I com biprotrusão dentária são caracterizadas pela projeção dos incisivos superiores e inferiores e podem ser corrigidas com extrações de primeiros pré-molares, permitindo reposicionar os incisivos, usando como ancoragem os dentes posteriores. Esse trabalho teve como objetivo comparar, por meio de superposição de modelos tridimensionais, a movimentação de molares e de incisivos com duas técnicas para fechamento de espaços. Foram selecionados, tomografados (T0) e distribuídos, aleatoriamente em dois grupos, seis pacientes com indicação de exodontia de quatro primeiros pré-molares. No grupo 1 (n=3) foi feito o fechamento dos espaços das extrações em uma única etapa (fechamento em massa) e no grupo 2 (n=3), em duas etapas (distalização de caninos seguida da retração de incisivos). Após o completo fechamento dos espaços foi solicitada nova tomografia (T1). Os modelos tridimensionais em T0 e T1 para os dois grupos foram superpostos para descrever e quantificar a movimentação ocorrida nos primeiros molares. A retração de incisivos foi avaliada de maneira bidimensional. Os molares superiores e inferiores do grupo 1 sofreram movimentação mesial de translação, enquanto os do grupo 2, apresentaram deslocamento de coroa maior do que de ápice radicular, demonstrando movimento de inclinação mesial de coroa. Ao se comparar o movimento mesial dos molares entre os dois grupos, observou-se que no grupo 1 houve maior movimentação mesial da raiz mésio-vestibular dos molares superiores (p=0,009). No entanto, em ambos os grupos os molares superiores giraram sobre a raiz palatina. No arco inferior verificou-se maior movimento mesial de coroa para o grupo 2 (p=0,015). A análise da movimentação dos incisivos apresentou variações semelhantes para as medidas lineares e angulares dos incisivos superiores nos dois grupos. Já, para as medidas angulares dos incisivos inferiores, observou-se que o grupo 1 apresentou menor controle de torque. O tempo de tratamento de todos os pacientes da amostra foi superior a 30 meses, exceto um paciente que apresentou tempo de tratamento inferior a 24 meses. Pôde-se concluir que a perda de ancoragem ocorreu por movimento de translação no fechamento de espaços em massa, e por inclinação mesial no fechamento de espaços em duas etapas, para ambos os arcos. Parece haver maior movimentação mesial radicular nos molares superiores no fechamento em massa e maior movimento mesial de coroa dos molares inferiores para o fechamento em duas etapas. Sugere-se que não há diferença na retração dos incisivos superiores e maior retroinclinação dos incisivos inferiores no fechamento de espaços em duas etapas. / Class I malocclusions with dental biprotrusion are characterized by the projection of upper and lower incisors and can be corrected with extractions of four first premolars, allowing incisor retraction using the posterior teeth as anchorage. The purpose of this research was to compare the movement of molars and incisors, by superimpostions of three-dimensional models, with two space closure techniques. Six patients with indication for four first premolar extractions were selected, tomographed (T0) and randomly assigned to two groups. For Group 1 (n=3) premolar extraction space closure was performed in one-stage (en masse retraction) and for group 2 (n=3) in two stages (canine retraction followed by incisor retraction). After complete space closure, a new tomograph was taken (T1). The three-dimensional models, in T0 and T1, for both groups were superimposed to describe and quantify first molar movement. Incisor retraction was evaluated in two dimensions. The upper and lower molars in group 1 presented bodily mesial movement, while those in group 2, presented greater crown than root movement, demonstrating mesial crown tipping. When the amount of mesial molar movement was compared between the two groups, a greater mesial root movement was observed for upper molars in group 1 (p=0.009). However, in both groups the upper molars rotated aroung the palatal root. In the lower arch, a greater mesial crown movement was observed in group 2 (p=0.015). Incisor movement analysis presented similar variations for linear and angular measurements for upper incisors in both groups. In contrast, the angular measurements for the lower incisors demonstrated more torque control in group 2. The treatment time for all patients in the sample was greater than 30 months, with the exception of one patient, who presented treatment time smaller than 24 months. In conclusion, anchorage loss ocurred by bodily movement in en masse space closure and by mesial crown tipping in two-stage space closure, in both arches. In addition, there might be greater mesial root movement for upper molars in en masse space closure and greater mesial crown movement in two-stage space closure. It can also be suggested that there are no differences in upper incisor retraction and there is greater lower incisor uprighting in two-stage space closure.

O objetivo deste estudo retrospectivo foi comparar os resultados oclusais e a eficiência do tratamento das más oclusões de Classe I e de Classe II completa, ambas tratadas com extrações de quatro pré-molares. A eficiência do tratamento foi definida como a porcentagem de alterações oclusais pelo tempo de tratamento. O Grupo 1, constituído por 75 pacientes que apresentavam inicialmente má oclusão de Classe I, apresentava idade inicial média de 13.98 anos (D.P.: 2.08, mín.: 10.54 e máx.: 23.13), e o Grupo 2, composto por 32 pacientes que apresentavam inicialmente má oclusão de Classe II completa, bilateral, apresentava idade inicial média de 13.19 anos (D.P.: 1.58, mín.: 10.48 anos e máx.: 18.58 anos). As avaliações oclusais foram realizadas em modelos de gesso dos pacientes nas fases inicial e final utilizando os índices PAR e IPT. Os índices oclusais, o tempo de tratamento e o grau de eficiência dos grupos foram comparados pelo teste t. Os resultados demonstraram que o Grupo 1 obteve melhores resultados oclusais e maior porcentagem de alterações oclusais do que o Grupo 2. Entretanto, não houve diferença significante no tempo de tratamento e na eficiência dos protocolos de tratamento entre os grupos avaliados. / The objective of this retrospective study was to compare the occlusal outcomes and the treatment efficiency in the treatment of the Class I and Class II complete malocclusions, both treated with extraction of four premolars. The treatment efficiency was defined as the percentage of occlusal changes by the treatment time. The Group 1, composed by 75 patients who presented initially Class I malocclusion, presented initial mean age of 13.98 years (S.D.: 2.08, min.: 10.54 years and max.: 23.13 years), and the Group 2, composed by 32 patients who presented initially complete Class II, bilateral, presented initial mean age of 13.19 years (S.D.: 1.58, min.: 10.48 years and max.: 18.58 years). The occlusal evaluations were accomplished in study models of the patients in the initial and final phases using the indexes PAR and TPI. The occlusal indexes, the treatment time and efficiency of the groups were compared with the t test. The results demonstrated that the Group 1 achieved better occlusal outcomes and greater percentage of occlusal changes than the Group 2. However, there was no significant difference in the treatment time and efficiency in the treatment protocols between the groups considered.

O objetivo deste trabalho foi comparar o tempo de tratamento em pacientes com e sem apinhamento apresentando inicialmente má oclusão de Classe II tratados com exodontia de quatro pré-molares. A amostra do estudo foi selecionada a partir do arquivo de modelos de gesso iniciais e pastas de pacientes já tratados na Faculdade de Odontologia de Bauru, no Departamento de Ortodontia. A amostra selecionada foi composta de 57 pacientes e dividida inicialmente em dois grupos. O grupo 1, que não apresentava apinhamento ou apresentava um leve apinhamento de 0 a 3 mm, foi constituído de 23 pacientes sendo 11 do gênero masculino e 12 do gênero feminino com idade inicial média de 13,13 anos (idade mínima de 10,67 e máxima de 18,25). O grupo 2, que apresentava apinhamento igual ou maior a 4 mm, foi constituído de 34 pacientes sendo 19 do gênero masculino e 15 do gênero feminino com idade inicial média de 13,07 anos (idade mínima de 11,08 e máxima de 18,33). Para comparar os tempos de tratamento dos grupos, a análise estatística feita foi o teste t, pois os dados obtidos apresentavam uma distribuição normal. Os resultados mostraram que não há diferença estatisticamente significante entre os tempos de tratamento do grupo 1 (2,51 anos) e do grupo 2 (2,49 anos). Sendo assim, os resultados sustentam a ideia de que o principal fator responsável pela semelhança entre os tempos de tratamento é a necessidade da correção anteroposterior do molar, que é igual para ambos os grupos. / The objective of this study was to compare the treatment time of bilateral complete Class II malocclusion with and without crowding treated with four premolar extractions, The sample was selected from arquive of beginning models and pastes of pacients treated at Bauru Dental School, department of Orthodontics. The selected sample was composed by 57 patients and divided into two groups. Group 1 presented no crowding or crowding 0-3 mm was composed by 23 patients being 11 male and 12 female with a mean age of 13,13 years (minimum age 10,67 and maximum age 18,25). Group 2 presented crowding 4 mm or more was composed by 34 patients being 19 male and 15 female with a mean age of 13,07 years (minimum age of 11,08 and maximum age of 18,33). To compare treatment times between groups, t test was performed. Results demonstrated that there was not significantly difference in treatment times of group 1 (2,51 years) and 2 (2,49 years). Thus, the results support the idea the principal factor responsible for similarity treatment times is the need of the molar relationship correction, which is similar in both groups.

Indiana University-Purdue University Indianapolis (IUPUI) / Subglacial chemical processes in Antarctica are potentially significant contributors to global geochemical cycles, but current understanding of their scale and nature is limited. A sequential chemical extraction procedure was developed and tested to investigate the utility of meteoric 10Be as a tracer for chemical weathering processes beneath the East Antarctic Ice Sheet. Subglacial meltwater is widely available under the Antarctic Ice Sheet and chemical constituents within it have the potential to drive geochemical weathering processes in the subglacial environment. Meteoric 10Be is a cosmogenic nuclide with a half-life of 1.39×106 years that is incorporated into glacier ice, therefore its abundance in the subglacial environment in Antarctica is meltwater dependent. It is known to adsorb to fine-grained particles in aqueous solution, precipitate with amorphous oxides, and/or be incorporated into authigenic clay structures during chemical weathering. The presence of 10Be in weathering products derived from beneath the ice therefore indicates chemical weathering processes in the subglacial environment. Freshly emerging subglacial sediments from the Mt. Achernar blue ice moraine were subject to chemical extractions where these weathering phases were isolated and 10Be concentrations therein quantified. Optimization of the phase isolation was developed by examining the effects of each extraction on the sample mineralogy and chemical composition. Experiments on 10Be desorption revealed that pH 3.2-3.5 was optimal for the extraction of adsorbed 10Be. Vigorous disaggregation of the samples before grain size separations and acid extractions is crucial due to the preferential fractionation of the nuclide with clay-sized particles. 10Be concentrations of 2-22×107 atoms g-1 measured in oxides and clay minerals in freshly emerging sediments strongly indicate subglacial chemical weathering in the catchment of the Mt. Achernar moraine. Sediment-meltwater contact in the system was calculated to be on the order of thousands of years, based on total 10Be sample concentrations, local basal melt rates, and 10Be ice concentrations. Strong correlation (R = 0.96) between 10Be and smectite abundance in the sediments indicate authigenic clay formation in the subglacial environment. This study shows that meteoric 10Be is a useful tool to characterize subglacial geochemical weathering processes under the Antarctic Ice Sheet.

Magister Chirurgiae Dentium - MChD / The stable position of the mandibular incisors, and the extent to which their spatial position may be changed in the sagittal plane, represents a key point in determining orthodontic treatment goals and objectives. According to the equilibrium theory, the mandibular incisors lie in a narrow zone of stability that is governed by pressure from the lips, cheek, tongue and periodontium. Proclining the mandibular incisors more than 2 mm leads to instability because of an increase in lip pressure. The magnitude of incisor proclination therefore determines aesthetics, stability and function.