• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 129
  • 103
  • 18
  • 16
  • 14
  • 7
  • 5
  • 4
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 341
  • 76
  • 57
  • 55
  • 45
  • 43
  • 40
  • 39
  • 38
  • 34
  • 30
  • 27
  • 24
  • 22
  • 21
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
281

Integrated Multimodal Analysis: Evaluating the Impacts of Chemotherapy and Electroporation-Based Therapy on Lymphatic and Blood Microvasculature in Cancer

Esparza, Savieay Luis 05 June 2024 (has links)
The lymphatic and blood vascular systems are two important vessel networks that serve different roles in healthy states and in cancer. In breast cancer the most common cancer amongst women, mortality remains high despite increased treatment response due to metastatic spread, preferentially through the lymphatics. One aggressive subtype, triple negative breast cancer (TNBC) contributing to 15 to 30 percent of cases and is characterized by the absence of expression of three therapeutic biomarkers. As targeted therapy is limited, treatment relies on standard of care via surgery, radiotherapy, and chemotherapy with limited efficacy and increase in survival. Chemotherapies negatively alter the lymphatic vasculature benefiting the tumor, through lymphangiogenesis. This dissertation seeks to understand how the mechanisms of commonly used chemotherapeutics, like carboplatin, and a novel 2nd generation ablative therapy called High Frequency Irreversible Electroporation (H-FIRE), which utilizes electric pulses to ablate tumor cells, affect the lymphatic and blood microvasculature in the tumor, surrounding fat pad, tumor draining lymph node (TDLN) using multiple analysis methods. This occurred through three main methods 1) identification of oxidative stress effects of chemotherapeutic application of carboplatin on lymphatic endothelial cells in vitro, 2) characterization of lymphatic and blood microvascular dynamics in a 4T1 breast cancer mouse model treated with sub-ablative H-FIRE, 3) through the development of a novel habitat imaging method to identify treatment specific changes in the tumor draining lymph node, and the development of a hybrid agent-based model (ABM) to test cancer cell flow mediated invasion in brain cancer. Herin the work showed that carboplatin induced lymphatic phenotypic changes occurred through generation of reactive oxygen species dependent on VEGFR3 and was reversed through treatment with the antioxidant N-acetylcysteine. In the 4T1 model, sub ablation with H-FIRE induced temporal remodeling of the lymphatic and blood vasculature within the viable tumor, in the surrounding fat pad, and in the tumor draining lymph node over seven days, suggesting an optimal time of application of adjuvant therapy. The development of a habitat imaging analysis method to identify TDLN vascular habitats and the perturbation to treatment in a retrospective analysis of prior work. Lastly, the development of a hybrid ABM through the incorporation of experimentally measured fluid flow fields from dynamic contrast enhanced MRI imaging building upon existing work, and showing the usefulness in comparing mechanisms of cancer cell invasion mediated fluid flow. Altogether, this work presents novel insight into the lymphatic system in cancer within various treatments contexts and new methods of quantifying changes due to treatment. Hopefully, these findings can be used to further inform the field towards a more comprehensive understanding of treatment effects in breast cancer. / Doctor of Philosophy / The lymphatic and blood vascular systems are two important vessel networks that serve different purposes in healthy states and in the disease called cancer. In breast cancer , a common form of cancer in women , spread of this cancer tends towards the lymphatic vasculature and eventually to other parts of the body. Triple negative breast cancer (TNBC) a less common, but more aggressive form, relies on clinical standard treatments with anti-tumor drugs called chemotherapies. These chemotherapies negatively alter the lymphatic vasculature to the tumors benefit, leaving a lack new methods of treatment. This dissertation seeks to understand how the mechanisms of commonly used chemotherapeutics and a new promising pulsed electric field therapy , High frequency Irreversible Electroporation (H-FIRE), change the lymphatic and blood vessels over time and in different locations using different tools. This occurred through three main methods 1) the effects on lymphatic vascular cells treated with chemotherapy, 2) in a breast cancer mouse model treated with H-FIRE, 3) in math models of the draining lymphatic organ, called the lymph node and an agent-based math model (ABM) of cancer cell movement due to fluid flow. The work showed that in the lymphatic cells, carboplatin a type of chemotherapeutic used to treat breast cancer, changed lymphatic vasculature through generating stress through oxidation and was reversed through treatment with an anti-oxidant. In the breast cancer mouse model, incomplete ablation with H-FIRE caused time dependent changes to the lymphatic and blood vasculature in the tumor, in the surrounding tissue, and in the lymph node over seven days. This work shows the novel findings of pulsed electric field therapy causing changes to the lymphatic vasculature. The creation of a new method of identifying habitats of the lymph node was used to compare changes to the lymphatic and blood vasculature to treatment. Lastly, the creation of an ABM added measured fluid flow maps from medical imaging methods to build upon existing work, and showed the usefulness in comparing mechanisms of cancer cell invasion due to fluid flow. Altogether, this work presents novel insight into the lymphatic system in cancer within after various treatments are applied and new methods of measuring these changes because of treatment using multiple methods. It is our hope that these findings can be used to further inform the field towards a more comprehensive understanding of treatment effects in breast cancer.
282

Praktikable Sjögren-Diagnostik bei interstitieller Lungenerkrankung: ein Diskussionsbeitrag

Aringer, Martin, Koschel, Dirk, Dörner, Thomas, Sewerin, Philipp, Prasse, Antje, Witte, Torsten 21 August 2024 (has links)
Das Sjögren-Syndrom (SjS) stellt eine mögliche autoimmune Ursache einer interstitiellen Lungenerkrankung dar. Die Abklärung in Richtung SjS ist aber im Vergleich zu anderen systemischen Autoimmunerkrankungen bisher kaum standardisiert. Die subjektive Sicca-Symptomatik, die Anti-SS-A/Ro-Antikörper und selbst die ANA-Diagnostik als Suchtest haben alle relevante Einschränkungen in ihrer Sensitivität und/oder Spezifität. Vor diesem Hintergrund haben wir in einer interdisziplinären Diskussion einen Konsens für die SjS-Abklärung entwickelt, den wir hier für die breitere Diskussion vorstellen. Neben ANA sollten sowohl Anti-SS-A/Ro-Antikörper als auch Antikörper gegen α‑Fodrin bestimmt werden. Wichtig ist die Objektivierung der Trockenheit mittels Schirmer- und Saxon-Test und bei fehlenden typischen Autoantikörpern die Speicheldrüsenbiopsie. / Sjögren’s syndrome (SjS) is a possible autoimmune cause of interstitial lung disease. The diagnostic pathway for SjS, however, is largely undefined in comparison to other systemic autoimmune diseases. Subjective sicca symptoms, anti-SS-A/Ro antibodies and even ANA as screening tests all have relevant limitations in sensitivity and/or specificity. Against this background, in an interdisciplinary discussion we have developed a consensus for the clarification of SjS, which is presented here for broader discussion. In addition to ANA and anti-SS-A/Ro antibodies, antibodies against alpha-fodrin should be included. Objective measures of dryness, such a Schirmer and Saxon tests are important, as is a salivary gland biopsy in the absence of typical autoantibodies.
283

3D-electron microscopic characterization of interstitial cells in the human bladder upper lamina propria

Neuhaus, Jochen, Schröppel, Birgit, Dass, Martin, Zimmermann, Hans, Wolburg, Hartwig, Fallier-Becker, Petra, Gevaert, Thomas, Burkhardt, Claus J., Minh Do, Hoang, Stolzenburg, Jens-Uwe 19 February 2018 (has links)
1) Aims To explore the ultrastructure of interstitial cells in the upper lamina propria of the human bladder, to describe the spatial relationships and to investigate cell-cell contacts. 2) Methods Focused ion beam scanning electron microscopy (FIB-SEM), 3-View SEM and confocal laser scanning microscopy were used to analyze the 3D ultrastructure of the upper lamina propria in male and female human bladders. 3) Results 3View-SEM image stacks as large as 59µm x 59µm x 17µm (xyz) at a resolution of 16nm x 16nm x 50 nm and high resolution (5nm x 5nm x 10nm) FIB-SEM stacks could be analyzed. Interstitial cells with myoid differentiation (mIC) and fibroblast like interstitial cells (fIC) were the major cell types in the upper lamina propria. The flat, sheet-like ICs were oriented strictly parallel to the urothelium sheet-like morphology. No spindle shaped cells were present. We furthermore identified one branched cell (bIC) with several processes contacting urothelial cells by penetrating the basal membrane. This cell did not make any contacts to other ICs within the upper lamina propria. We found no evidence for the occurrence of telocytes in the upper lamina propria. 4) Conclusions Comprehensive 3D-ultrastructural analysis of the human bladder confirmed distinct subtypes of interstitial cells. We provide evidence for a foremost unknown direct connection between a branched interstitial cell and urothelial cells of which the functional role has still to be elucidated. 3D-ultrastructure analyses at high resolution are needed to further define the subpopulations of lamina propria cells and cell-cell interactions.
284

Effect of Pre-Bending and Hydroforming Parameters on the Formability of Advanced High Strength Steel Tube

Bardelcik, Alexander January 2006 (has links)
With increasing fuel costs and the current drive to reduce greenhouse gas emissions and fuel consumption, a need to reduce vehicle weight is apparent. Weight reduction can be achieved by replacing conventionally stamped structural members with hydroformed parts. The weight reduction can be further enhanced by reducing the thickness of the hydroformed members through the use of advanced high strength steel (AHSS). A primary limitation in hydroforming AHSS, is the limited ductility or formability of these materials. This limitation becomes acute in multi-stage forming operations in which strain path changes become large making it difficult to predict formability. Thus, the focus of the current work is to study the effects of pre-bending on the subsequent hydroformability of Dual-Phase DP600 steel tubes. As part of this effort, the effect of key bending and hydroforming process parameters, bending boost and hydroforming end-feed, have been studied in a parametric fashion. <br /><br /> Multi-step pre-bending and hydroforming experiments were performed on 76. 2 mm (3. 0") OD tubes with a wall-thickness of 1. 85mm (DP600). Experiments were also performed on 1. 74mm Interstitial Free (IF) steel tube, which provided a low strength, high formability baseline material for comparison purposes. A fully instrumented servo-hydraulic mandrel-rotary draw tube bender was used in the pre-bending experiments in which various levels of boost were applied. The results showed that increased boost reduced the major (tensile) strain and thinning at the outside of the bend. At the inside of the bend, the compressive minor strain became larger and thickening increased. <br /><br /> Hydroforming of the straight and pre-bent tubes was conducted using various levels of load-control end-feed (EF). For both straight and pre-bend tube hydroforming, an increase in hydroforming EF resulted in increased burst pressure and corner-fill expansion (CFE). The effect of bending boost on CFE was also measured. For a given hydroforming EF case, a tube bent with greater boost achieved a higher burst pressure and consequently a greater CFE which increased the hydroformability of the material. Pre-bending was shown to consume a considerable amount of the formability of the tube in the hydroforming experiments. For the same EF case, the pre-bent tubes could only achieve a fraction of the straight tube CFE at burst. <br /><br /> The pre-bending and hydroforming experiments were complimented by finite element simulation in the hope of providing additional insight into these processes. The finite element (FE) models were able to accurately predict the strain and thickness changes imposed during pre-bending. The models were able to accurately predict the CFE, EF displacement, and strain and thickness distributions after hydroforming. <br /><br /> The extended stress-based forming limit curve (XSFLC) failure criterion was applied to predict failure (onset of necking) during hydroforming, which was measured as the burst pressure in the experiments. For straight tube hydroforming, the XSFLC predicted the correct failure pressure versus hydroforming EF load trend, but over predicted the failure pressures. In pre-bend hydroforming, the models were able to capture the effect of bending boost and hydroforming EF on the hydroformability of the tubes. The XSFLC was able to capture the drop in formability for bending versus straight tube hydroforming, but was unable to capture the failure pressure versus hydroforming EF load trend or magnitude. Further work is required to make the XSFLC applicable to straight and pre-bend hydroforming.
285

Rôle du système rénine-angiotensine intrarénal dans l’hypertension et les dommages rénaux chez les souris transgéniques diabétiques

Liu, Fang 09 1900 (has links)
Plusieurs expériences et études cliniques ont démontré que l’activation du système rénine-angiotensine (RAS) peut induire l’hypertension, un facteur de risque majeur pour les maladies cardiovasculaires et rénales. L’angiotensinogène (Agt) est l’unique substrat du RAS. Cependant, il n’a pas encore été démontré si l’activation du RAS intrarénal peut à elle seule induire des dommages rénaux, indépendamment de l’hypertension systémique, et ainsi jouer un rôle prépondérant dans la progression de la néphropathie diabétique. Afin d’explorer le rôle du RAS intrarénal dans les dommages rénaux, un diabète a été induit par l’injection de streptozotocin chez des souris transgéniques (Tg) surexprimant l’Agt de rat dans les cellules des tubules proximaux du rein (RPTC). Les souris Tg diabétiques ont été traitées soit avec des inhibiteurs du RAS (perindopril et losartan), de l’insuline ou une combinaison des deux pour 4 semaines avant d’être euthanasiées. Pour une autre étude, des souris Tg non-diabétiques ont été traitées soit avec des inhibiteurs du RAS, l’hydralazine (vasodilatateur) ou l’apocynine (inhibiteur de la NADPH oxydase) pour une période de 8 semaines avant l’euthanasie. Des souris non-Tg ont été utilisées comme contrôles. Des cellules immortalisées de tubule proximal de rat (IRPTC) transfectées de manière stable avec un plasmide contenant l’Agt ou un plasmide contrôle ont été employées comme modèle in vitro. Nos résultats ont démontré que les souris Tg présentaient une augmentation significative de la pression systolique, l’albuminurie, l’apoptose des RPTC et l’expression de gènes pro-apoptotiques par rapport aux souris non-Tg. Les mêmes changements ont été observés chez les souris Tg diabétiques par rapport aux souris non-Tg diabétiques. L’insuline et/ou les inhibiteurs du RAS ont permis d’atténuer ces changements, sauf l’hypertension qui n’était réduite que par les inhibiteurs du RAS. Chez les IRPTC transfectées avec l’Agt in vitro, les hautes concentrations de glucose augmentent l’apoptose et l’activité de la caspase-3 par rapport aux cellules contrôles et l’insuline et/ou les inhibiteurs du RAS empêchent ces augmentations. En plus des changements physiologiques, les RPTC des souris Tg présentent aussi une augmentation significative de la production des espèces réactive de l’oxygène (ROS) et de l’activité de la NADPH oxydase, ainsi qu’une augmentation de l’expression du facteur de croissance transformant-beta 1 (TGF-β1), de l’inhibiteur activateur du plasminogène de type 1 (PAI-1), des protéines de la matrice extracellulaire, du collagène de type IV et de la sousunité p47 de la NADPH oxydase. Le traitement des souris Tg avec l’apocynine et le perindopril a permis d’améliorer tous ces changements, sauf l’hypertension qui n’était pas corrigée par l’apocynine. D’autre part, l’hydralazine a prévenu l’hypertension, sans modifier l’albuminurie, l’apoptose des RPTC ou l’expression des gènes pro-apoptotiques. Ces résultats montrent bien que l’activation du RAS intrarénal et l’hyperglycémie agissent de concert pour induire l’albuminurie et l’apoptose des RPTC, indépendamment de l’hypertension systémique. La génération des ROS via l’activation de la NADPH oxydase induit en partie l’action du RAS intrarénal sur l’apoptose des RPTC, la fibrose tubulo-interstitielle et l’albuminurie chez les souris Tg. D’autre part, une expérience en cours a tenté d’encore mieux délimiter les effets de l’activation du RAS intrarénal, tout en éliminant la néphrotoxicité du STZ. Pour cette étude, les souris Tg surexprimant l’Agt de rat dans leurs RPTC ont été croisées aux souris Ins2Akita, un modèle spontané de diabète de type I, afin de générer des souris Akita-rAgt-Tg. Les résultats préliminaires indiquent que le RAS intrarénal est activé dans les souris Akita et que la combinaison avec l’hyperglycémie induit du stress du réticulum endoplasmique (ER) dans les RPTC in vivo. Le stress du ER contribue à l’apoptose des RPTC observée dans le diabète, à tout le moins dans le modèle Akita. Le traitement avec des inhibiteurs du RAS permet d’atténuer certains des dommanges rénaux observés dans les souris Akita-rAgt-Tg. / Experimental and clinical studies have shown that renin-angiotensin system (RAS)activation may lead to hypertension, a major cardiovascular and renal risk factor. Angiotensinogen (Agt) is the sole substrate of the RAS. However, it is unclear whether intrarenal RAS activation alone could induce kidney injury independently of systemic hypertension and play an important role in the progression of diabetic nephropathy (DN). To explore the role of intrarenal RAS in kidney injury, transgenic (Tg) mice overexpressing rat Agt in their renal proximal tubular cells (RPTCs) were rendered diabetic by streptozotocin (STZ). Diabetic Tg mice were treated with RAS blockers (perindopril and losartan), insulin or a combination of both and then euthanized after 4 weeks of treatment. In a separate study, non-diabetic Tg mice were treated with RAS blockers or hydralazine (a vasodilator) or apocynin (an NADPH oxidase inhibitor) and then euthanized after 8 weeks of treatment. Non-Tg littermates served as controls in both studies. Immortalized rat proximal tubule cells (IRPTCs) stably transfected with Agt cDNA or control plasmid were used in the experiments as an in vitro model. Our results showed that non-diabetic Tg mice displayed a significant increase in systolic blood pressure (SBP), albuminuria, RPTC apoptosis, and proapoptotic gene expression. Diabetic Tg mice had a further increase of albuminuria, RPTC apoptosis, and proapoptotic gene expression, though the SBP of the diabetic Tg mice was similar to that of non-diabetic Tg mice. RAS blockers and/or insulin treatments markedly attenuated these changes, except that insulin had no impact on hypertension. In vitro, high-glucose melieu significantly increased apoptosis and caspase-3 activity in Agt stable transfectants compared to control cells, and these changes were attenuated by insulin and/or RAS blockers. Furthermore, non-diabetic Tg mice showed significantly elevated reactive oxygen species (ROS) production and NADPH oxidase activity, as well as enhanced expression of transforming growth factor-beta 1 (TGF-β1), plasminogen activator inhibitor-1 (PAI-1), extracellular matrix proteins, collagen type IV, and NADPH oxidase subunit p47 in their RPTC. Treatment with apocynin and perindopril ameliorated these changes, but apocynin had no effect on SBP. In contrast, hydralazine prevented hypertension but not albuminuria, RPTC apoptosis, or proapoptotic gene expression. These data indicate that intrarenal RAS activation and hyperglycemia act in concert to induce albuminuria and RPTC apoptosis independent of systemic hypertension. ROS generation via NADPH oxidase activation mediates, at least in part, intrarenal RAS action on RPTC apoptosis, tubulointerstitial fibrosis and albuminuria in Tg mice. On the other hand, in an on-going experiment, to avoid the nephro-toxic effects of STZ and further delineate the effects of intrarenal RAS activation, Tg mice overexpressing rat Agt in their RPTCs were crossbred with Ins2Akita mice, a spontaneous type I diabetes model, to generate Akita-rAgt-Tg mice. Preliminary data indicated that hyperglycaemia and intrarenal RAS activation induced endoplasmic reticulum (ER) stress in RPTC in vivo, and the ER stress pathway contributed to RPTC apoptosis in diabetes, at least in the Akita model. RAS blockade was effective in attenuating some parameters of renal injury in AkitarAgt-Tg mice.
286

Planification de traitements de curiethérapie du sein à l’aide de l’imagerie par résonance magnétique

Truchon, Dany 12 1900 (has links)
Ce mémoire présente l’étude de la faisabilité de la planification de traitements pour la curiethérapie interstitielle du sein en utilisant l’imagerie par résonance magnétique (IRM) seule au lieu de l’imagerie par tomodensitométrie (CT). L'imagerie CT étant la référence, la mesure des différences observables sur la distribution de doses provenant des deux types d’imagerie a été effectuée. Des fantômes de seins ont été fabriqués et utilisés, ainsi que l’imagerie de patients. La taille des fantômes en fonction du positionnement dans l’appareil d’IRM et la longueur reconstruite des cathéters ont été analysées. Les différences dans les distributions de doses de fantômes et de patients ont été calculées en s’assurant que la reconstruction des cathéters provenant des images CT et IRM est la seule variable. La différence dans les critères de doses à respecter est plus grande lorsque la taille du fantôme et/ou un déplacement latéral dans l’IRM sont plus grands. La longueur reconstruite des cathéters est comparable entre les deux techniques d’imagerie. Pour le petit fantôme des différences <2% ont été observées pour tous les critères de dose. Pour le grand fantôme et pour les patients, une valeur maximale de 5% est observée pour les critères sur la cible, mais peut atteindre 19% pour le critère Externe V150%/V100% pour le grand fantôme et 33% pour les patients. Par contre, le seuil clinique de ce critére est toujours respecté. Ceci nous indique que pour la plupart des patients, la zone à traiter serait bien couverte en utilisant les images IRM uniquement pour planifier. / This dissertation presents the study of the feasibility of planning for interstitial breast brachytherapy treatments using only magnetic resonance imaging (MRI) instead of computed tomography (CT) imaging. CT imaging being the reference, the measurement of observable differences on dose distributions from the two types of imaging has been done. Breast phantoms has been fabricated and used, as imaging of patients. Size of the phantoms according to the positioning inside the MRI device and catheters reconstructed length has been analysed. Differences in dose distributions of phantoms and patients have been calculated by ensuring that catheters reconstruction from CT and MRI images is the only variable. The difference in respecting the dose’s criteria is bigger when the size and/or the lateral shift into the MRI are bigger. The catheters’ reconstructed length is similar between the two imaging techniques. For the small phantom, differences <2% has been observed for all dose criteria. For the large phantom and for patients, a maximum value of 5% is observed for targets criteria, but can reach 19% for External V150/V100 criterion for the large phantom and 33% for patients. However, clinical threshold for this criterion is still respected. This tells us that for most patients, the treatment region would be covered by using MRI images only for planning.
287

Influence des amas lacunes-solutés sur le vieillissement des solutions solides de Fer-α / Impact of vacancy-solute clusters on the aging of α-Fe solid solutions

Schuler, Thomas 17 September 2015 (has links)
La compréhension et la maîtrise des mécanismes qui pilotent le vieillissement des aciers en présence d’une sursaturation de lacunes est un défi dans de nombreux domaines industriels, et particulièrement dans le cas des réacteurs nucléaires. Ces aciers contiennent invariablement des solutés interstitiels en tant qu’éléments d’alliage ou impuretés, et des lacunes (V) qui sont des défauts structuraux d’équilibre. Nous avons choisi le système Fe-V –X (X = C, N ou O) comme matériau modèle d’un acier ferritique. Au sein de ce système, des amas lacunes-solutés interstitiels sont susceptibles de se former car, malgré les concentrations très faibles de leurs constituants, ces amas présentent une énergie de liaison importante. Dans cette étude, nous avons tout d’abord cherché à calculer les propriétés intrinsèques d’équilibre de ces amas traités individuellement, à la fois leur propriétés thermodynamiques (énergie libre de liaison) et cinétiques (mobilité, taux de dissociation, ainsi que leur lien avec une description continue de la diffusion). Cette caractérisation effectuée à l’échelle atomique a ensuite permis de mettre en évidence différents effets de ces amas sur un système macroscopique contenant simultanément différents types d’amas : augmentation des limites de solubilité des solutés et de la concentration totale des lacunes en solution solide, couplage de flux entre lacunes et solutés, accélération des cinétiques de précipitation des solutés et dissolution des précipités par une stabilisation de la solution solide par les lacunes. Ces résultats ont été obtenus grâce au développement et/ou à l’extension de méthodes analytiques de physique statistique qui décrivent les constituants de ces amas et leurs interactions à l’échelle atomique. Enfin, nous nous sommes également intéressés aux cavités dans le fer-α, dont l’étude nécessite une approche différente de celle des petits amas. Entre autres, nous avons étudié les effets d’un réseau discret sur la forme d’équilibre d’une cavité, et décrit différents mécanismes d’évolution de ces objets à l’échelle atomique. / Understanding and monitoring the aging of steels under vacancy supersaturation is a challenge of great practical interest for many industrial groups, and most of all for those related to nuclear energy. These steels always contain interstitial solutes, either as alloying elements or as impurities, and vacancies (V) that are equilibrium structural defects of materials. We have chosen the Fe-V -X system (X = C, N or O) as a model system for ferritic steels. Vacancy-solute clusters are likely to form in such systems because, despite the very low concentrations of their components, these cluster show very high attractive bonding. First of all, we have been working on the computation of intrinsic equilibrium properties of individual clusters, both thermodynamic (free binding energies) and kinetic (mobilities, dissociation coefficients, and their relationship with continuum diffusion) properties. Thanks to this atomic-scale characterization procedure, we have been able to highlight various effects of these clusters on a macroscopic system containing different cluster types : increase of solute solubility limits and total vacancy concentrations, flux couplings between interstitial solutes and vacancies, acceleration of solute precipitation kinetics and precipitate dissolution by solid solution stabilization due to vacancies. These results would not have been obtained without the development and/or extension of analytical methods in statistical physics which are able to describe cluster’s components and their interactions at the atomic scale. Finally, we have also been working on cavities in α-iron, the study of which requires a different approach. Our study highlights the impact of the atomic discrete lattice on the equilibrium shape of cavities, and describes various kinetic mechanisms of these objects at the atomic scale.
288

Identificação de poluentes orgânicos na represa Billings - São Paulo / Identification of organic pollutants in the dam Billings - São Paulo

Almeida, Gleby Aparecida de 01 October 2003 (has links)
Compostos químicos provenientes de várias origens como tráfico, agricultura, industria e efluentes domésticos são transportados à longas distâncias e podem atingir os corpos hídricos. A proliferação de compostos orgânicos sintéticos desencadeou a preocupação sobre seus efeitos tóxicos. Esses compostos sintéticos podem estar afetando o meio ambiente. Mesmo em concentrações muito baixas, eles interferem no sistema endócrino, tanto nos seres humanos quanto nos animais e também nas outras formas de vida que compõem os ecossistemas. Este trabalho teve como objetivo realizar estudo analítico-ambiental na Represa Billings, afim de verificar a ocorrência de poluentes orgânicos em amostras de água e sedimento. Foram analisados pesticidas organoclorados (OCs), bifenilas policloradas (PCBs), hidrocarbonetos policíclicos aromáticos (PAHs) e fármacos. Foram realizadas quatro campanhas para coleta de água e sedimento, em julho e novembro de 1999, maio de 2000 e janeiro de 2001. O sedimento foi coletado em perfil vertical, sendo possível verificar o acúmulo da contaminação. Foram validadas metodologias analíticas para determinação de poluentes orgânicos persistentes, como pesticidas organoclorados, bifenilas policloradas (PCBs), hidrocarbonetos policíclicos aromáticos (PAHs) em amostras de água. O método incluiu a extração em fase sólida (SPE) e análise por CG/MS. Para a determinação de fármacos em água e sedimento foi empregada a extração em fase sólida (SPE) e análise por LC/MS-MS. Foram detectados nos sedimentos e nas águas do reservatório Billings hidrocarbonetos policíclicos aromáticos, bifenilas policloradas, pesticidas organoclorados, fármacos como ibuprofen, diclofenac e cafeína. A presença desses compostos no reservatório é devido a associação com as fontes potenciais como o material particulado atmosférico e os efluentes industriais e municipais. / Chemicals from a wide range of sources as traffic, industry, agriculture and domestic wastewater are transported over long distances and can reach the aquatic environment. There is great concern about the proliferation of synthetic organic chemicals and their toxic effects as these chemicals may be affecting the environment. Even at low levels, they interfere in the endocrine system both in humans and in animals and other living organism. The aim of this study was to carry out an analytical-environmental analysis in the Billings reservoir, near the city of São Paulo in order to assess the occurrence of organic pollutants in water and sediment. Chlorinated pesticides, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and pharmaceuticals were analyzed. Sediments and water were collected during July and November 1999, May 2000 and January 2001. Sediments were collected in core samples that provided vertical delineation of contamination. Validation of the analytical procedure in order to determine persistent organic pollutants such as chlorinated pesticides, polychlorinated biphenyls (PCBs), polycyclic aromatic (PAHs) in water samples was carried out. Solid phase extraction (SPE) was used for sample preparation and detection and confirmation by GC/MS. The determination of pharmaceuticals was performed by tandem LC-MS(LC/MS-MS) after a solid phase extraction. Chlorinated pesticides, polychlorinated biphenyls, polycyclic aromatic and pharmaceuticals such Ibuprofen, Diclofenac and caffeine were detected.in sediment and water. The conclusion of the study was the occurrence of these compounds in the reservoir is due to sources like atmospheric particles, municipal and industrial waste.
289

"Pneumonias intersticiais idiopáticas: da patogênese e do remodelamento aos determinantes anátomo-clínico-radiológicos de prognóstico e sobrevida com ênfase ao componente vascular" / Idiopathic interstitial pneumonias : of the pathogenesis and remodeling to anatomic-physician-radiological determinatives of prognostic and survival with emphasis to the vascular component

Cuentas, Edwin Roger Parra 04 May 2006 (has links)
Estudou-se por morfologia, morfometria e imuno-histoquímica o remodelamento vascular (moléculas de adesão), epitelial (moléculas de adesão) e intersticial (colágeno V e células imunes) nos três tipos maiores de pneumonias intersticiais idiopáticas: em 62 casos de IPF, 22 casos de NSIP e 25 casos de AIP. O impacto dessas alterações foi avaliado nas provas de função, sobrevida e prognóstico. Demonstrou-se que o remodelamento vascular ativo e fibroelastótico é diretamente proporcional ao grau de atividade parenquimatosa principalmente na UIP. O colágeno V, o mapeamento das células imunes, o aumento da atividade endotelial e epitelial tiveram impacto no espectro diferencial e possivelmente na patogênese das três pneumonias intersticiais estudadas. A resposta imune celular na UIP teve impacto na sobrevida dos pacientes / Studied for morphology, morphometry and immunohischemistry the vascular (adhesion molecules), epithelial (adhesion molecules) and interstitial (collagen V and immune cells) remodeling in the three major types of idiopathic interstitial pneumonias: in 62 cases of IPF, 22 cases of NSIP, and 25 cases of AIP. The impact of these alterations was evaluated in the function tests, survival and prognostic. We demonstrated that the active and fibroelastotic vascular remodeling is directly proportional to the degree of parenchymal activity, mainly in the UIP. Collagen V, mapping of the immune cells, increase of the endothelial and epithelial activity had possibly impact in the distinguishing specter and in pathogenesis of the three interstitial pneumonias studied. The cellular immune reply in the UIP it had impact in survival of the patients
290

Fibrose centrilobular (FCL): um padrão histológico pulmonar distinto em pacientes com esclerose sistêmica e doença intersticial pulmonar / Centrilobular fibrosis (CLF): a distinct histological pattern in systemic sclerosis with interstitial lung disease (ILD)

Souza, Romy Beatriz Christmann de 15 January 2007 (has links)
Objetivos: A FCL é um novo padrão de doença intersticial pulmonar idiopática associado ao refluxo gastro-esofágico. Nós investigamos sua presença na ES com envolvimento pulmonar. Métodos: 28 pacientes com ES foram submetidos à biópsia pulmonar a céu aberto. As amostras foram classificadas conforme o novo consenso de classificação das pneumonias intersticiais idiopáticas e de acordo com os critérios do padrão FCL. Tomografia computadorizada de alta resolução (TCAR) de tórax, prova de função pulmonar (PFP), esofagograma de contraste e/ou endoscopia digestiva alta também foram realizadas. Resultados: Na ES, o padrão NSIP (67,8%) e a FCL (75%) foram os padrões mais freqüentemente encontrados e na maioria dos casos, eles co-existiam. Todos, exceto um paciente com FCL tinha a característica distribuição broncocêntrica das lesões, sendo mais extensa nos casos com FCL isolada (p=0,001). Da mesma forma, o conteúdo basofílico foi mais freqüente nos pacientes com FCL e completamente ausente no grupo NSIP (p<0,001). Na TCAR, a distribuição central do envolvimento pulmonar foi o achado mais prevalente nos pacientes com FCL isolada (57,14%) contrastando com a 10 predominância do padrão periférico nos outros grupos (p=0,02). Além disso, uma tendência quanto à distribuição segmentar na TCAR foi observada no grupo com FCL isolada (85,71%) e FCL+NSIP (71,43%), enquanto que 80% dos pacientes com NSIP tinham uma distribuição difusa das lesões pulmonares (p=0,08). Anormalidades esofágicas foram um achado quase universal. Conclusão: Está é a primeira descrição de fibrose centrilobular em pacientes com ES e envolvimento pulmonar. Este padrão tem características histológicas e tomográficas distintas e a identificação deste subgrupo de pacientes irá certamente contribuir para uma melhor abordagem terapêutica. / Objectives: CLF is a new histological pattern of idiopathic ILD associated to esophageal reflux. We have investigated its presence in SSc with lung involvement. Methods: 28 SSc patients were submitted to open lung biopsy. The specimens were classified according to the new consensus classification of idiopathic interstitial pneumonia and to the diagnostic criteria for CLF. High Resolution Computer Tomography (HRCT), Pulmonary Function Tests (PFT), contrast esophagogram and/or upper digestive endoscopy were also performed. Main Results: In SSc, the NSIP (67.8%) and the centrilobular (75%) patterns were the most frequent and in the majority of the cases, they co-existed. All, except one patient with CLF had the characteristic bronchocentric distribution and this lesion was more extensive in those with isolated CLF (p=0.01). Likewise, the basophilic content was more frequent in patients with CLF and completely absent in NSIP group (p<0.001). The central distribution of lung involvement on HRCT was the most prevalent finding in patients with isolated CLF (57.14%) contrasting with the predominant peripheral pattern in the other groups (p=0.02). Moreover, a trend towards a patchy distribution on HRCT was observed for CLF group (85.71%) and CLF+NSIP group (71.43%) whereas 80% of the NSIP group had diffuse distribution (p=0.08). Esophageal abnormalities were almost a universal finding. Conclusions: This is the first report of centrilobular fibrosis in SSc patients with lung involvement. This new pattern has distinct histological and tomographic features. The identification of this subgroup of patients will certainly contribute for a more appropriate therapeutic approach.

Page generated in 0.0887 seconds