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Syftet med denna undersökning är att utvärdera en XRFmätuppställning som använder högre spänning påröntgenröret än konventionella XRF-instrument. Iutvärderingen uppskattas Limit Of Detection (LOD) påtungmetaller genom att använda XRF-metoden, där dettestades olika filter, vinklar och rörspänning och derasinverkan på provet.Metaller med hög densitet kallas för tungmetaller. Vissatungmetaller är livsnödiga men vissa är skadliga för bådemänniskor och naturen. Några exempel på dessa tungmetallerär kvicksilver, kadmium och bly, vilka är farliga grundämnensom människor kan få i sig via föda.Vid utförande av denna undersökning användes enröntgenkälla (30-120keV) som var kopplad till mjukvaransom skickade fotonenergi och ström. En spektrometer med CdTe-detektor användes för att mäta energin på fotonerna från provet. Detektorn var kopplad till mjukvara där det uppmätt spektra kunde observeras och energitopparnas intensitet kunde avläsas. Topparnas intensitet kan härledas tillprovets samansättning. Sedan uppskattades LOD förproverna. Den teknik som jag har studerat ger möjlighet till bättre mätresultat än konventionella XRFutrustningar. Detta eftersom högre rörspänning gör att K-linjerna, inte bara L-linjerna, för tungmetaller kan avläsas

De nombreuses études de biométrologie sont menées à l’INRS, pour évaluer l’exposition professionnelle à des substances chimiques, en France, et pour compléter les connaissances en proposant des valeurs de références destinées à protéger des salariés exposés à ces substances. Ces études consistent à mesurer simultanément l’imprégnation biologique et l’exposition atmosphérique à une substance, chez des salariés exposés à celle-ci. La relation entre ces mesures biologiques et atmosphériques est ensuite estimée à travers un modèle de régression linéaire. Lorsque que cette relation existe et que la voie d’absorption du toxique est essentiellement inhalatoire, il est ensuite possible de dériver une Valeur Limite Biologique (VLB) à partir de la Valeur Limite d’Exposition Professionnelle (VLEP-8h) du toxique. Deux aspects de ces données ont été identifiés, qui ne sont pas ou seulement partiellement prises en compte dans les modélisations statistiques courantes : la censure due aux limites de détection (LD)/quantification (LQ) des mesures biologiques et atmosphériques et la variabilité inter-individuelle. Ignorer ces deux particularités lors de la modélisation mène à une perte de puissance statistique et à de potentielles conclusions biaisées. Les travaux menés dans le cadre de cette thèse ont permis d’adapter le modèle de régression à ces deux caractéristiques, dans un cadre bayésien. L’approche proposée repose sur la modélisation des mesures atmosphériques à l’aide de modèles à effets aléatoires prenant en compte les valeurs inférieures à la LD/LQ, et sur la modélisation simultanée des mesures biologiques, supposée être linéairement dépendantes sur une échelle logarithmique, de l'exposition atmosphérique, tout en tenant compte de la variabilité inter-individuelle. Ce travail a donné lieu à une publication scientifique dans une revue à comité de lecture. L’application de cette méthodologie a été réalisée sur des jeux d’exposition professionnelle au béryllium et au chrome, après avoir été cependant adaptée aux caractéristiques toxicocinétiques de ces deux substances. Il a ainsi été possible de proposer une VLB pour le béryllium (0,06 µg/g créatinine). L’exploitation de mesures de chrome dans deux secteurs d’activités différents (exposition professionnelle aux peintures de chromates, et exposition professionnelle dans le secteur du chromage électrolytique) a permis de mettre en évidence que le chrome urinaire dépend essentiellement de l’exposition au chrome VI, le chrome non VI ayant moins d’impact. Nous n’avons pas pu montrer de relation entre la solubilité du CrVI et le chrome urinaire. Une VLB de 0,41 µg/g créatinine, de l’ordre de la Valeur Biologique de Référence (VBR) proposée par l’ANSES (0,54 µg/g créatinine), a été estimée pour l’exposition professionnelle aux peintures de chromates, et une VLB de 1,85 µg/g créatinine a été estimée pour l’exposition professionnelle dans le secteur du chromage électrolytique, qui est en cohérence avec la VLB proposée par l’ANSES dans ce secteur, à savoir 1,8 µg/g créatinine / Many biomonitoring studies are conducted at INRS, in order to assess occupational exposure to chemicals in France, and to propose reference values to protect workers exposed to these substances. These studies consist in measuring simultaneously biological and airborne exposure of workers exposed to a toxic substance. The relationship between these biological and airborne measurements is then estimated through a linear regression model. When this relationship exists and the route of absorption of the toxic is essentially inhalatory, it is possible to derive a Biological Limit Value (BLV) from the Occupational Exposure Limit Value (OEL) of the toxic substance. However, two characteristics of these data have been identified, which are not or only partially taken into account in the current statistical modelling: the left-censoring due to limits of detection (LoD)/quantification (LoQ) of biological and airborne measurements, and the between-individual variability. Ignoring both of these features in modelling leads to a loss of statistical power and potentially biased conclusions. The work carried out in this thesis allowed us to adapt the regression model to these two characteristics, in a Bayesian framework. The proposed approach is based on the modelling of airborne measurements using random effects models adapted for values below the LoD / LoQ, and on the simultaneous modelling of biological measurements, assumed to depend linearly on a logarithmic scale, on the airborne exposure, while taking into account between-subject variability. This work resulted in a scientific publication in a peer-reviewed journal. This methodology has been applied on beryllium and chromium occupational exposure datasets, after adaptation to the toxicokinetic characteristics of these two substances. It has thus been possible to propose a BLV for beryllium (0.06 μg / g creatinine). The analysis of chromium measurements in two different sectors of activity (occupational exposure to chromate paints, and occupational exposure in the electroplating sector) made it possible to show that urinary chromium depends mainly on airborne exposure to VI chromium, non-VI chromium having less impact. We were not able to show a relationship between the solubility of airborne VI chromium and urinary chromium. A BLV of 0.41 μg / g creatinine, close to the Biological Guidance Value (BGV) proposed by ANSES (0.54 μg / g creatinine), was estimated for occupational exposure to chromate paints, and a BLV of 1.85 μg/g creatinine was obtained for occupational exposure in the electrolytic chromium plating sector, which is consistent with the ANSES proposed BLV in this sector, i-e 1.8 μg / g creatinine

Made available in DSpace on 2014-07-29T15:07:41Z (GMT). No. of bitstreams: 1 Eveline_Xavier.pdf: 537505 bytes, checksum: f46fc6f4fae888045c26180cb3ce26b0 (MD5) Previous issue date: 2008-08-05 / Mastitis is the most frequent disease in dairy cows, it causes great economic losses in herds and dairy industries and represents a hazard for public health. Among the etiologic agents identified, there is a predominance of bacteria species. However, several other groups of microorganisms may be present, one of those is a unicellular alga of the Prototheca genus, the Prototheca zopfii, an environmental agent of bovine mastitis. The infected cows usually have granulomatous changes in mammary tissue. Moreover microorganisms do not respond to routine therapy, resulting in the elimination of the infected animals. The main purposes of this study was to determine the occurrence of Prototheca zopfii on bulk tank milk in the state of Goiás and identify the limit of detection for Prototheca zopfii by two different approaches. We also wanted to know the samples pre-incubated with small concentration of Protoheca zopfii permits us to obtain positive growth in microbiological culture. We analyzed 473 samples from farms with high somatic cell count patterns but we did not detect Protoheca zopfii in any of those samples. The limit of sensitivity of the Prototheca zopfii was analyzed, in the approach of isolation the limit of detection was between 130 to 3,400 UFC/mL. In the approach of tally the limit was between 25 to 300 UFC/mL. It wasn t observed significant difference (p>0,05) between the approaches analyzed. However, significant statistical difference (p<0,05) occurred between the five types analyzed. After the pre-incubation at 37ºC/24h, the limit of sensibility was analyzed by the approach isolation, the limit was 30 UFC/mL, what means that the pre-incubation is so important to decrease the possibility of occurrence of false negative / Entre as enfermidades de grande preocupação para os bovinos leiteiros encontram-se as mastites, incluindo aquelas causadas por Prototheca spp., um agente ambiental, relacionado à mastite bovina que destaca-se pela gravidade das lesões que causam no tecido mamário e pela resistência a ações terapêuticas. Objetivou-se com o presente estudo determinar a ocorrência de Prototheca zopfii no leite cru refrigerado no estado de Goiás, identificar o limite de detecção deste patógeno pelos métodos de semeadura para isolamento, e semeadura para contagem e também verificar se a incubação de amostras de leite com baixo número de células da Prototheca zopfii permite a obtenção de resultados positivos na cultura microbiológica. Foram analisadas 473 amostras originárias de propriedades com histórico de elevada contagem de células somáticas e procedeu-se a avaliação do limite de sensibilidade para o agente por meio do método de semeadura para isolamento, cujo limite de detecção correspondeu à faixa de 130 a 3.400 UFC/mL. Quanto ao método de semeadura para contagem o limite estabelecido foi 25 a 300 UFC/mL. Portanto houve diferença estatística (p<0,05) entre os métodos analisados, porém, não houve diferença estatística (p>0,05) entre as cinco cepas analisadas. Após a incubação das amostras por 24 horas a 37ºC verificou-se que o limite de sensibilidade pelo método semeadura para isolamento diminui para 30 UFC/mL, diminuindo-se assim a possibilidade de ocorrência de falso negativo. Em nenhuma das amostras analisadas foi detectada a presença da Prototheca zopfi

Philosophiae Doctor - PhD / Breast cancer is regarded as the most common cancer in South Africa and its rate of occurrence is increasing. About one in every 31 South African women are at the risk of developing breast cancer and early diagnosis and treatment guarantee 90% survival rate. Tamoxifen is the drugs of choice for the treatment of all stages of breast cancer. The drug binds with estrogen receptor (ER) to minimize the transcription of estrogen dependent genes. However, nearly 50% of ER-positive breast cancer patients either become resistant or fail to respond to tamoxifen resulting in a serious clinical challenge in breast cancer management. The Grand Health Challenges of South Africa includes the development of cost effective diagnostic systems suitable for early detection of diseases and drug resistivity for timely invention and better patient management. / 2020-08-31

Philosophiae Doctor - PhD / Tuberculosis (TB) is an infectious disease that, despite all efforts devoted towards its eradication, remains a threat to many countries including South Africa. Current diagnostic assays do offer better performance than the conventional sputum smear microscopy and tuberculin skin tests. However, these assays have been proven to be affected by various factors including the condition of an individual's immune system and vaccination history. By far, electrochemical biosensors are amongst the currently investigated techniques to address the shortcomings associated with these diagnostics. / 2020-08-31

Cette thèse porte sur le développement d’un capteur plasmonique intégrant une fonction d’actuation des objets visés. L’objectif est de passer outre la limite de diffusion rencontrée à basse concentration en piégeant les particules sur la surface de détection. La stratégie adoptée est de structurer le film d’or servant à la détection de manière à pouvoir l’utiliser pour mettre en mouvement le fluide et les molécules par le biais de champs électriques. Le transfert de masse est réalisé par diélectrophorèse et électroosmose, deux effets électrocinétiques mis en oeuvre par des électrodes servant à la fois d’actuateur et de capteur plasmonique. Un état de l’art exhaustif et des simulations multiphysiques ont permis de concevoir un prototype de capteur intégré constitué d’électrodes interdigitées en or permettant la détection plasmonique. Le dispositif proposé a été obtenu par microfabrication en salle blanche puis caractérisé avant l’étude de ses performances. Une première phase de tests sur un système modèle, des billes de polystyrène dans de l’eau, a permis d’apporter la preuve de concept du fonctionnement du capteur, qui est effectivement capable de piéger rapidement les objets visés à sa surface afin de les détecter. Les mécanismes de transfert de masse ont été expliqués et la preuve de l’amélioration de la limite de détection par un facteur supérieur à 100 a été apportée. Dans un second temps, les performances du capteur appliqué à des objets biologiques ont été évaluées. Celui-ci piège efficacement des levures et des protéines, mais aucune amélioration n’a été observée dans le cas de la détection spécifique de l’hybridation entre deux brins d’acide désoxyribonucléique (ADN). Les causes de ce résultat ont été discutées et comprises et deux solutions différentes ont été explorées : l’adaptation de la fréquence d’opération et l’optimisation de la géométrie des électrodes. Ainsi, cette étude a permis de souligner la problématique de la mise en oeuvre d’effets électrocinétiques dans des milieux biologiques et de réfléchir aux pistes pertinentes pour sa résolution. / This thesis focuses on the development of an integrated plasmonic sensor capable to perform mass transport on targeted objects. The goal is to overcome the diffusion limit by trapping particules directly on the sensing surface. The adopted strategy was to structure the gold layer used for plasmonic detection in order to use the sofabricated structures to set the fluid and the molecules in motion by applying electric fields in the fluid. The mass transfer is realized through dielectrophoresis and electroosmosis, those two electrokinetic effects being operated by electrodes acting as sensor and actuator at the same time. An exhaustive state of the art as well as multiphysical simulations allowed us for designing a prototype for an integrated sensor consisting in gold interdigitated electrodes enabling plasmoninc sensing. The proposed device was obtained through microfabrication in clean room facilities and was characterized before the study of its performances. A first sequence of tests on a model system – polystyrene microbeads in water – brought the proof of concept we needed to validate the correct operation of the sensor, which is indeed capable of quickly trapping targeted objects on its surface and detecting them. The mass transfer mechanisms were explained and we showed the enhancement of the limit of detection by a factor greater than 100. In a second phase, performances of the sensor applied to biological objects were evaluated. It can effectively trap yeasts and proteins but no enhancement has been observed while detecting DNA hybridization events. Causes for this result were discussed and understood and two different solutions were explored: the adaptation of the operating frequency and the optimization of the electrodes geometry. Thus, this study highlighted the problematic of operating electrokinetic effects in biological media and suggested relevant leads towards its resolution.

Magister Scientiae - MSc (Chemistry) / Pollutants such as polycyclic aromatic hydrocarbons (PAHs) are known for their toxic effects which may lead to the cause of degenerative diseases in both humans and animals. PAHs are widespread in the environment, and may be found in water, food, automotive industry and petrochemical industries to name but a few sources. Literature reports have highlighted industrial workplace exposure to PAHs as a leading cause for development of cancer in workers. Particularly, workers in the petrochemical industry are adversely affected and the incidence of skin and lung cancer in this population group is high. The United States of America in its guidelines developed by environmental protection agency (EPA) has identified 18 PAHs as priority pollutants. Among these are anthracene, benzo[a]pyrene and pyrene which have been selected as the focal point of this study due to their significance in the petrochemical industry. Due to the carcinogenic and mutagenic properties reported in literature for certain PAHs, there have been monitoring procedures taken in most countries around the world. The commonly used analytical methods for the detection of PAHs from industrial samples are high performance liquid chromatography (HPLC) coupled to fluorescence detection, membrane filtration, ozonation and reverse osmosis. Analysis of PAHs from the petrochemical industry is typically performed by HPLC method as well as sono-degredation in the presence of oxygen and hydrogen peroxide.