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Molinari, Alessio. "Designing a Performant Ablation Study Framework for PyTorch." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-285560.
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PyTorch is becoming a really important library for any deep learning practitioner, as it provides many low-level functionalities that allow a fine-grained control of neural networks from training to inference, and for this reason it is also heavily used in deep learning research, where ablation studies are often conducted to validate neural architectures that researchers come up with. To the best of our knowledge, Maggy is the first open-source framework for asynchronous parallel ablation studies and hyperparameter optimization for TensorFlow, and in this work we added important functionalities such as the possibility to execute ablation studies on PyTorch models as well as the generalization of feature ablation on any data type. This work also shows the main challenges and interesting points of developing a framework on top of PyTorch and how these challenges have been addressed in the extension of Maggy.PyTorch blir ett oerhört viktigt bibliotek för alla utövare inom djupinlärning, detta eftersom PyTorch innehåller flertalet lågnivåfunktioner som möjliggör en finkorning kontroll av neurala nätverk - från träning till inferens. Av den anledningen används PyTorch också kraftigt i forskning om djupinlärning, där ablationsstudier ofta genomförs för att validera neurala arkitekturer som forskare framtagit. Så vitt vi vet är Maggy det första open-source ramverk för asynkrona parallella ablationsstudier och hyperparameteroptimering för TensorFlow. I detta arbete har vi lagt till viktiga funktioner såsom möjligheten att utföra ablationsstudier på PyTorch-modeller samt generalisering av funktionsablation för alla datatyper. Detta arbete upplyser också dem viktigaste utmaningarna och mest intressanta punkterna för att utveckla en ram ovanpå PyTorch och hur dessa utmaningar har hanterats i förlängningen av Maggy.
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Frassetto, Marco. "Study of nanostructured targets for plasma production via laser ablation." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/12058/.
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Metal nanowires (NWs) - nanostructures 20-100 nm in diameter and up to tens of micrometers long - behave as waveguides when irradiated with light with wavelength much greater than their diameter. This is due to collective excitations of free electrons (plasmons) in the metal which couple to light and travel on the surface of the nanowire. This effect can be used to efficiently absorb laser pulses to produce dense and hot plasma on special nanostructured targets with metal nanowires vertically aligned on the surface.
In this thesis work, nanostructured targets with different parameters (length, diameter, metal and fabrication process) have been irradiated with infrared laser light. X-ray flux emitted by the cooling plasma is measured during irradiation, and the depth of craters formed on the target is measured later. This data is used to choose which target parameters are best for plasma production.
Different targets are compared with each other and against a control, non-nanostructured (bulk) target. As will be shown, highly significant (> 5 sigma) differences are found between targets with different nanostructures, and between nanostructured and bulk target.
This differences are very difficult to explain whithout accounting for the nanostructures in the targets. Therefore, data collected and analized in this thesis work supports the hypotesys that nanostructured targets perform better than bulk targets for laser plasma production purposes, and provides useful indications for optimization of NWS' parameters.
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Labonté, Sylvain. "A theoretical study of radio frequency ablation of the myocardium." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7559.
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Theoretical modeling of the lesion formation process during radio-frequency ablation of the myocardium is presented. The model is axisymmetric and consists of a catheter electrode coming in contact at right angle with the heart tissue. The electric power dissipated in the tissue is calculated and from it the temperature distribution and the resulting lesion are evaluated as a function of time. The cooling effect of the blood flow and the temperature dependence of the electrical conductivity are included in the model, making it non-linear. The finite-element method is used to discretize the spatial domain and a finite-difference algorithm resolves the time dependence. The numerical simulator is validated with a series of experiments performed on a tissue-equivalent material. Both the measured temperature distribution in the tissue sample and the electrode resistance as a function of time agree well with the theoretical predictions. The model is used to study the effect of the electrode geometry and the electrical excitation on the resulting lesion. Theoretical predictions for the time evolution of the lesion size and the electrode resistance are presented for the first time. Recommendations for the improvement of the RF ablation procedure are formulated.
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Roper, Ryan Todd. "A Study of Radiofrequency Cardiac Ablation Using Analytical and Numerical Techniques." Diss., CLICK HERE for online access, 2003. http://contentdm.lib.byu.edu/ETD/image/etd262.pdf.
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Haboub, Abdelmoula. "Study of ablation and implosion phases in cylindrical and star wire arrays." abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3387809.
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Papanicolaou, Kyriakos. "Consequences of mitofusin ablation in cardiac myocytes. A genetic study in mice." Thesis, Boston University, 2013. https://hdl.handle.net/2144/12827.
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Thesis (Ph.D.)--Boston University
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.Mitofusin-1 (Mfn-1) and mitofusin-2 (Mfn-2) are membrane-embedded mechanoenzymes involved in the remodelling and merging of the mitochondrial biomembrane. In differentiated cardiac myocytes, mitochondria occupy a third of the cell's volume and express both Mfn-1 and Mfn-2. The present thesis was aimed at exploring the roles of Mfn-1 and Mfn-2 specifically in cardiac myocytes using loss-offunction approaches in mice. We individually ablated either Mfn-1 or Mfn-2 specifically in cardiac myocytes. Ultramicroscopic analysis conducted in hearts of Mfn-1 KO or Mfn-2 KO mice revealed significant alterations in mitochondrial structure. Nevertheless, these knockout mice had normal heart function and a normal lifespan. Furthermore, Mfn-1 and Mfn-2 deficient mitochondria exhibited normal respiratory function in vitro. We also tested the susceptibility of Mfu-1 and Mfu-2 mitochondria against stress and unexpectedly found that the absence of these proteins conferred resistance to mitochondrial permeability transition (MPT). MPT reflects the loss of membrane integrity in mitochondria and is strongly associated with cell death. Using isolated adult cardiac myocytes we were able to demonstrate that the cell death in either Mfu-1 KO or Mfn-2 KO cells was delayed, consistent with the idea that MPT is attenuated in the absence of these proteins. We also utilized Mfn-2 KO mice to demonstrate that loss of Mfn-2 was associated with protection against cardiac ischemia/reperfusion injury, a stress model strongly linked to MPT. This work suggested for the first time that both Mfu-1 and Mfu-2 have important roles in the process of MPT. To incorporate these novel findings in context with the well-known role of mitofusins in membrane merging, I propose a working model where mitochondrial membrane fusion proceeds through formation of transient lipidic pores that compromise mitochondrial membrane integrity and serve as hotspots for MPT in conditions of stress. Lastly, we generated and characterized mice double-knockout (DKO) for Mfu-1 and Mfu-2. These mice are born in the expected ratios but undergo aberrant cardiac remodelling during the first week of their life and eventually succumb. The DKO mitochondria present multiple morphological and molecular abnormalities. This latter work illustrates that Mfn-1 and Mfn-2 operate interchangeably to regulate the early postnatal development of cardiac myocytes.
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Müller, Halina [Verfasser]. "Fluid-modulated radiofrequency ablation : an ex-vivo study in porcine liver / Halina Müller." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2012. http://d-nb.info/1021953172/34.
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Sujono, Susan. "Analytical study of steady state plasma ablation from soft X-ray laser target." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10180.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (leaves 99-100).
by Susan Sujono.
M.Eng.
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Ong, Seok Ling. "Pilot study of hepatic microwave ablation using an extracorporeally perfused porcine liver model." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/36067.
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Introduction: Preclinical research into many aspects of microwave hepatic ablation has been traditionally conducted in in vivo studies. These are costly, can only be performed in laboratories with animal facilities and are associated with significant ethical issues. The main aim of this project was to study microwave ablation using an extracorporeally perfused porcine liver model to confirm that it accurately mimicked an in vivo model and could be used to investigate ablative techniques. Methods: Seventeen livers harvested from domestic pigs were subjected to extracorporeal normothermic autologous haemoperfusion followed by dissection of the hepatic artery and its branches to establish an effective procedure of liver procurement for subsequent experiments. A further seventeen livers in three experimental groups (control, microwave and Pringle groups) were perfused for six hours with tissue and blood samples collected at various time points for histological, biochemical and cytokine analyses. Seven livers in the control group did not undergo any ablation. Five livers in the microwave group underwent microwave ablations at three power settings after the first hour of perfusion for a fixed duration of two minutes per ablation. Five livers in the Pringle group underwent microwave ablation at the same power settings and for the same duration as the microwave group but the ablations were carried out with temporary cessation of blood flow to the liver. Results: Dissection of the hepatic artery and its bifurcation identified all the common variants and understanding these is crucial for successful liver perfusion. The livers were perfused at flows and pressures mimicking physiological levels with biochemical and blood gas analyses indicating normal function across all three experimental groups. The volume of the lesions increased with power of ablation in both the microwave and Pringle groups (p < 0.001 and p=0.003 respectively), with no significant differences in overall volume between the groups (p=0.275) but a greater transition zone volume in the microwave group (p=0.012). Apoptotic activities in the transition zone lessened towards the periphery of the ablation in both microwave and Pringle groups (p < 0.001 for both groups). There were significant elevations in the levels of circulating interleukin-6 and interleukin-8 over time with or without microwave ablation (p < 0.001 for both cytokines in both groups). Conclusion: An extracorporeally perfused porcine liver model has a role in the preclinical study of microwave ablation. The model can be reliably used to study the histological and physical profile of microwave lesions. It also permits the study of the heat sink effect of ablation. Overall, it has a considerable potential to reduce the number of in vivo preclinical studies required. However, the ability of this isolated organ (which has a relatively short perfusion lifespan) to study the systemic effect of a microwave ablation is limited. Further experiments involving other hepatic ablative techniques should be conducted using this model to fully establish its role as a preclinical liver ablation research tool.
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Ahmad, Muhammad Fateh. "A comparative study of the systemic inflammatory response to hepatic resection, microwave ablation, cryotherapy and radiofrequency ablation : which is safest and how much can we safely ablate?" Thesis, University of Leicester, 2010. http://hdl.handle.net/2381/9049.
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Liver cancer, whether primary or secondary, is a common clinical condition which carries a high mortality. Up until the last 50 years or so, patients with these conditions were thought to be untreatable, confined to alternative medicine and with extremely poor survival rates. Surgical resection was in theory a viable option for tumours limited to the liver such as hepatocellular carcinomas and colorectal liver metastases; however this was accompanied by unacceptable morbidity and mortality rates. Newer surgical techniques, combined with anaesthetic and technological advances then allowed a subset of these tumours to be removed more safely, either as a debulking procedure or in its entirety. Attempts to resect larger tumours or malpositioned tumours (i.e. approximating major hepatobiliary structures) continued to be associated with high complication rates. Advances in chemotherapy led to some improvement in survival, although with high morbidity. Over the last 3 decades, clinicians have sought alternative ways of treating these tumours, partly to increase efficacy of treatment, but also to increase resectability and operability. It was widely recognised that for larger tumours, or tumours involving several segments, there was a need to leave the maximum amount of normal hepatic parenchyma by selectively destroying or removing the tumour-affected portion of the liver only. The 3- dimensional anatomy of the liver segments as described by Couinaud (1952) greatly improved our understanding of what was possible to resect or ablate (Figure 1.1). Thus evolved the concept in in-situ ablation whether thermal, chemical or ultrasonic. More recently, neoadjuvant and adjuvant chemotherapy have been used in treating these patients to downstage tumours and make them amenable to resection and/or ablation. Percutaneous and minimal access ablation procedures have also made possible multiple visits to treat recurrence in the same areas of the liver, whilst leaving as much normal hepatic parenchyma as possible. These advances have been facilitated by technological breakthroughs in imaging techniques, particularly crosssectional computed tomography and MRI.
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Dilwith, Jason. "Feasibility Study of Laser Ablation using Long Pulsed 300W, CW Single Mode Fiber Laser." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-06132005-191622/.
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Many applications now require micro sized holes that are difficult to produce with conventional methods. The entrance of lasers in the industry has brought about a better method for producing these holes. However the ultra-short pulse lasers that are normally used are extremely expensive and require many pulses to remove the material due to the small amount of energy they deposit. The objective of this research is to examine the feasibility of laser ablation using a 300W, CW Single Mode fiber laser which has high continuous power output for each pulse and has excellent beam quality. The results show that laser ablation occurs when a 100mm lens is used with pulse durations at 40 microseconds or below. Using one 18 microsecond pulse, a blind hole of 43.6 microns in diameter and 23.6 microns in depth with an aspect ratio of 0.54 can be created with little heat affected zone. This performance is comparable to nanosecond lasers, but with much higher hole depth per pulse. It was also found that the pulse duration must be short enough so that the ablating effect of the initial spike of an enhanced pulse is not nullified due to melting. At longer pulse durations (50 microseconds or more), raised surfaces are created instead of holes.
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Wilson, Sarah. "A study of extreme ultraviolet capillary discharge lasers and the ablation of solid targets." Thesis, University of York, 2018. http://etheses.whiterose.ac.uk/22259/.
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This thesis discusses the use of capillary discharge laser output in the Extreme Ultraviolet (EUV) as a means of ablating solid targets. The EUV capillary discharge laser uses a neon like argon plasma as the lasing medium contained within a ceramic capillary. The laser produces a pulse of duration 1.2ns, at a wavelength of 46.9nm, with a repetition rate of up to 10Hz. A review of EUV production and the optical properties of EUV radiation at 46.9nm is given. From this a review of potential focusing methods for the laser is presented. An on-axis spherical mirror has been experimentally tested to give focal spot diameters of 3μm. The characterisation and optimisation of the capillary discharge laser is discussed. Optical spectra have been shown to enable a new method of measuring the average electron temperature of the plasma medium of the laser by modelling it as a black body. Plasma temperatures of approximately 3eV are measured. The capillary discharge laser has been used to ablate solid targets of aluminium, gold, copper and Poly-methyl methacrylate (PMMA). The ablation craters for each target material were measured using an atomic force microscope. Single shot depths of ablation of 1.3μm (Al), 0.9μm (Au), 0.6μm (Cu) and 0.3μm (PMMA) using fluences of approximately 200Jcm-2 were obtained. Ablation depths for aluminium are well modelled assuming ablation only occurs over the EUV attenuation length in the solid. For targets with short attenuation lengths another model based on a propagating ablation wave fits the experimental ablation depths. Both models allow an estimate of the ablated plasma temperature which is typically in the range of 3eV to 50eV, meaning the ablating plasma can be classed as a warm dense plasma.
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Hern, Sunita. "Cutaneous angiogenesis in psoriasis : a study using selective laser ablation and monitoring of microvessels in vivo." Thesis, St George's, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399347.
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See, Tian Long. "Laser surface texturing : fundamental study and applications." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/laser-surface-texturing--fundamental-study-and-applications(7668bd61-9ed9-43ad-9795-79a53f77b6a7).html.
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The increased demand in stringent requirements on engineered surfaces in the aerospace and manufacturing industries drove the need for developing advanced surface engineering techniques such as chemical etching, plasma etching, corona discharge and laser surface texturing in order to alter material surface physical and chemical properties. Among these techniques, laser surface texturing has been identified as one of the most efficient and effective surface treatment/ texturing techniques which utilizes laser ablation to meet the demand of practical engineering requirements. This thesis details three practical engineering challenges in the field of paint adhesion, dust adhesion and tribology performance of SPF sheet forming dies in which case the problems and motivation for development came from projects by industrial partner collaborations with BAe Systems, Rolls-Royce and Dyson Ltd. The proposed solutions to these challenges are formulated around laser surface texturing techniques using excimer and femtosecond lasers on three engineering materials which are CFRP, ABS polymer and HR4 nickel alloy. As ablation is the main mechanism used in laser surface texturing techniques in achieving surface property changes, the understanding of laser beam interaction with materials is crucial. The fundamental understanding of laser beam interaction with different materials has been researched since the use of lasers in practical engineering applications by which laser material interaction parameters such as ablation threshold, incubation coefficient and optical penetration depth are of primary interest in addition to the ablation rate. Currently the published literatures are either material specific or laser specific with minimal or zero comparison between different types of lasers and materials as such which limits the understanding of laser beam interaction with materials. In addition, laser beam interaction with polymers has always been done using ultraviolet wavelength lasers. In this thesis, the interaction between two types of lasers and three types of materials which includes metals and polymers are presented through comparison and discussion between different interactions. It has been discovered that the ablation threshold value is lower for ABSinteraction with excimer laser as compared to the interaction with femtosecond laser due to the difference in the ablation mechanism. The optical penetration depth value is higher for ABS interaction with the excimer laser as compared to the interaction with the femtosecond laser due to differences in the photon energy of the laser beam of different wavelength. Two ablation rate curves were identified on ABS interaction with infrared wavelength femtosecond laser beams which has not been reported before. Chemical composition of the laser treated layer changes through chain scission process, creating free radical carbons that reacted with oxygen, nitrogen and water vapour in air creating oxygen and nitrogen rich functional groups which increased with increasing laser fluence and number of pulses. Laser ablation is known for its capability of altering surface morphology and surface chemistry of materials through excitation of electrons causing bond scission or melt where materials are vaporised, ejected or undergo chemical compositional changes. In the case of polymers, addition of oxygen and nitrogen rich functional groups are identified whereas in the case of metals, changes in crystallographic, orientation and oxidation states are identified. Such changes are deemed ideal for applications such as adhesion where it is mainly used for bonding and joining of similar or dissimilar materials. In this research, excimer laser surface treatment showed improvement in CFRP paint adhesion where a better adhesion is achieved than sand-papered surfaces. Paint adhesion of CFRP surfaces is affected by surface contaminants, surface chemical composition and surface roughness where the degree of inuence is in the respective order. In addition, excimer and femtosecond laser surface treated ABS also improved dust adhesion. The main factors that affect the ABS surface dust adhesion performance are surface roughness and surface chemical composition. The increase in surface roughness increases the surface area available for dust to adhere to. In addition, it also increases the drag coefficient of the air flow results in a higher removal force exerted by the air flow onto the dust particles through changes in the localised aerodynamic flow. The increase in polar functional groups increases the adhesion of the dust particles onto the surface due to an induced dipole moment by the charged dust particles. Laser micro-dimpled surfaces have been reported to be effective in reducing friction coefficient and wear rate of surfaces under oil lubricated conformal contact conditions where the dimples act as reservoirs to store lubricant and wear particles. But such surfaces have not been extensively researched under non-conformal contact conditions for different lubricated environments. In addition, there are contradictory results found between published literatures which observe under similar wear environments and conditions but with different dimple geometry. Hence a detailed investigation on dimpled surfaces under non-conformal contact conditions is being carried out. Laser surface texturing of 100 μm size dimples shows a reduction in nickel alloy wear rate under dry and oil lubricated environments. A higher dimple area ratio reduces the wear rate under dry condition with abrasive wear as the main wear mechanism. Under oil lubricated environments, the friction coefficient is dependent on the surface contact pressure, sliding speed and the viscosity of the lubricant and the wear rate is dependent on the film thickness which correlates to the friction coefficient. The wear rate of a dimpled surface is dependent on three factors which are the dimple diameter to contact area diameter ratio, depth of the dimple produced and the density of the dimples. Positive results are obtained in all three engineering applications indicating the feasibility of laser surface texturing techniques in providing suitable material surface properties for these applications.
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Sánchez, Arciniegas Jorge Patricio. "A Multiscale in Silico Study to Characterize the Atrial Electrical Activity of Patients With Atrial Fibrillation. A Translational Study to Guide Ablation Therapy." Doctoral thesis, Universitat Politècnica de València, 2021. http://hdl.handle.net/10251/171456.
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[ES] La fibrilación auricular es la arritmia cardíaca más común. Durante la fibrilación auricular, el sustrato auricular sufre una serie de cambios o remodelados a nivel eléctrico y estructural. La remodelación eléctrica se caracteriza por la alteración de una serie de canales iónicos, lo que cambia la morfología del potential de transmembrana conocido como potencial de acción. La remodelación estructural es un proceso complejo que involucra la interacción de varios procesos de señalización, interacción celular y cambios en la matriz extracelular. Durante la remodelación estructural, los fibroblastos que abundan en el tejido cardíaco, comienzan a diferenciarse en miofibroblastos que son los encargados de mantener la estructura de la matriz extracelular depositando colágeno. Además, la señalización paracrina de los miofibroblastos afecta a los canales iónicos de los miocitos circundantes.
Se utilizaron modelos computacionales muy detallados a diferentes escalas para estudiar la remodelación estructural inducida a nivel celular y tisular. Se realizó una adaptación de un modelo de fibroblastos humanos a nivel celular para reproducir la electrofisiología de los miofibroblastos durante la fibrilación auricular. Además, se evaluó la exploración de la interacción del calcio en la electrofisiología de los miofibroblastos ajustando el canal de calcio a los datos experimentales. A nivel tisular, se estudió la infiltración de miofibroblastos para cuantificar el aumento de vulnerabilidad a una arritmia cardíaca. Los miofibroblastos cambian la dinámica de la reentrada. Una baja densidad de miofibroblastos permite la propagación a través del área fibrótica y crea puntos de salida de actividad focal y roturas de ondas dentro de esta área. Además, las composiciones de fibrosis juegan un papel clave en la alteración del patrón de propagación. La alteración del patrón de propagación afecta a los electrogramas recogidos en la superficie del tejido. La morfología del electrograma se alteró dependiendo de la disposición y composición del tejido fibrótico.
Se combinaron modelos detallados de tejido cardíaco con modelos realistas de los catéteres de mapeo disponibles comercialmente para comprender las señales registradas clínicamente. Se generó un modelo de ruido a partir de señales clínicas para reproducir los artefactos de señal en el modelo. Se utilizaron electrogramas de modelos de dos dominios altamente detallados para entrenar un algoritmo de aprendizaje automático para caracterizar el sustrato fibrótico auricular. Las características que cuantifican la complejidad de las señales fueron extraídas para identificar la densidad fibrótica y la transmuralidad fibrótica. Posteriormente, se generaron mapas de fibrosis utilizando el registro del paciente como prueba de concepto. El mapa de fibrosis proporciona información sobre el sustrato fibrótico sin utilizar un valor único de corte de 0,5 milivoltios. Además, utilizando la medición del flujo de información como la entropía de transferencia combinada con gráficos dirigidos, en este estudio, se siguió la dirección de propagación del frente de onda. La transferencia de entropía con gráficos dirigidos proporciona información crucial durante la electrofisiología para comprender la dinámica de propagación de ondas durante la fibrilación auricular.
En conclusión, esta tesis presenta un estudio in silico multiescala que proporciona información sobre los mediadores celulares responsables de la remodelación de la matriz extracelular y su electrofisiología. Además, proporciona una configuración realista para crear datos in silico que pueden ser usados para aplicaciones clínicas y servir de soporte al tratamiento de ablación.[CA] La fibril·lació auricular és l'arrítmia cardíaca més freqüent, en la qual el substrat auricular patix una sèrie de remodelacions elèctriques i estructurals. La remodelació de tipus elèctric es caracteritza per l'alteració d'un conjunt de canals iònics que modifica la morfologia del voltatge transmembrana, conegut com a potencial d'acció. La remodelació estructural és un fenomen complex que implica la relació entre diversos processos de senyalització, interaccions cel·lulars i canvis en la matriu extracel·lular. Durant la remodelació estructural, els abundants fibroblasts presents en el teixit cardíac comencen a diferenciar-se en miofibroblasts, els quals s'encarreguen de mantenir l'estructura de la matriu extracel·lular dipositant-hi col·lagen. A més, la senyalització paracrina dels miofibroblasts amb els miòcits circumdants també afectarà els canals iònics. Es van utilitzar models computacionals molt detallats a diferents escales per estudiar la remodelació estructural induïda a nivell tissular i cel·lular. Es va fer una adaptació a nivell cel·lular d'un model de fibroblasts humans per reproduir-hi l'electrofisiologia dels miofibroblasts durant la fibril·lació auricular. A més, l'exploració de la interacció del calci amb l'electrofisiologia dels miofibroblasts va ser avaluada mitjançant l'adequació del canal de calci a les dades experimentals. A nivell tissular es va estudiar la infiltració de miofibroblasts per tal de quantificar l'augment de vulnerabilitat que això conferia per patir una arrítmia cardíaca. Els miofibroblasts canvien la dinàmica de la reentrada, i presentar-ne una baixa densitat permet la propagació a través de la zona fibròtica, tot creant punts de sortida d'activitat focal i trencaments d'ones dins d'aquesta àrea. A més, les composicions de fibrosi tenen un paper clau en l'alteració del patró de propagació, afectant els electrogrames recollits en la superfície del teixit. La morfologia dels electrogrames es va veure alterada en funció de la disposició i la composició del teixit fibròtic. Per comprendre els senyals clínicament registrats es van combinar models detallats de teixits cardíacs amb models realistes dels catèters de cartografia disponibles comercialment. Es va generar un model de soroll a partir de senyals clínics per reproduir-hi els artefactes de senyal. Es van utilitzar electrogrames de models de bidominis molt detallats per entrenar un algoritme d'aprenentatge automàtic destinat a caracteritzar el substrat fibròtic auricular. Les característiques que quantifiquen la complexitat dels senyals van ser extretes per identificar la densitat i transmuralitat fibròtica. Posteriorment, es van generar mapes de fibrosi mitjançant la gravació del pacient com a prova de concepte. El mapa de fibrosi proporciona informació sobre el substrat fibròtic sense utilitzar un sol valor de tensió de tall de 0,5 mV. A més, utilitzant la mesura del flux d'informació com l'entropia de transferència combinada amb gràfics dirigits, en aquest estudi es va fer un seguiment de la direcció de propagació de l'ona. L'entropia de transferència amb gràfics dirigits proporciona informació crucial durant l'electrofisiologia per entendre la dinàmica de propagació d'ones durant la fibril·lació auricular. En conclusió, aquesta tesi presenta un estudi multi-escala in silico que proporciona informació sobre els mediadors cel·lulars responsables de la remodelació de la matriu extracel·lular i la seva electrofisiologia. A més, proporciona una configuració realista per crear dades in silico que es poden traduir a aplicacions clíniques que puguen donar suport al tractament de l'ablació.
[EN] Atrial fibrillation is the most common cardiac arrhythmia. During atrial fibrillation, the atrial substrate undergoes a series of electrical and structural remodeling. The electrical remodeling is characterized by the alteration of specific ionic channels, which changes the morphology of the transmembrane voltage known as action potential. Structural remodeling is a complex process involving the interaction of several signalling pathways, cellular interaction, and changes in the extracellular matrix. During structural remodeling, fibroblasts, abundant in the cardiac tissue, start to differentiate into myofibroblasts, which are responsible for maintaining the extracellular matrix structure by depositing collagen. Additionally, myofibroblasts paracrine signalling with surrounding myocytes will also affect ionic channels. Highly detailed computational models at different scales were used to study the effect of structural remodeling induced at the cellular and tissue levels.At the cellular level, a human fibroblast model was adapted to reproduce the myofibroblast electrophsyiology during atrial fibrillation. Additionally, the calcium handling in myofibroblast electrophysiology was assessed by fitting calcium ion channel to experimental data. At the tissue level, myofibroblasts infiltration was studied to quantify the increase of vulnerability to cardiac arrhythmia. Myofibroblasts alter the dynamics of reentry. A low density of myofibroblasts allows the propagation through the fibrotic area and creates focal activity exit points and wave breaks inside this area. Moreover, fibrosis composition plays a key role in the alteration of the propagation pattern. The alteration of the propagation pattern affects the electrograms computed at the surface of the tissue. Electrogram morphology was altered depending on the arrangement and composition of the fibrotic tissue. Detailed cardiac tissue models were combined with realistic models of the commercially available mapping catheters to understand the clinically recorded signals. A noise model from clinical signals was generated to reproduce the signal artifacts in the model. Electrograms from highly detailed bidomain models were used to train a machine learning algorithm to characterize the atrial fibrotic substrate. Features that quantify the complexity of the signals were extracted to identify fibrotic density and fibrotic transmurality. Subsequently, fibrosis maps were generated using patient recordings as a proof of concept. Fibrosis map provides information about the fibrotic substrate without using a single cut-off voltage value of 0.5 mV. Furthermore, in this study, using information theory measurements such as transfer entropy combined with directed graphs, the wave propagation direction was tracked. Transfer entropy with directed graphs provides crucial information during electrophysiology to understand wave propagation dynamics during atrial fibrillation. In conclusion, this thesis presents a multiscale in silico study atrial fibrillation mechanisms providing insight into the cellular mediators responsible for the extracellular matrix remodeling and its electrophysiology. Additionally, it provides a realistic setup to create in silico data that can be translated to clinical applications that could support ablation treatment.
Sánchez Arciniegas, JP. (2021). A Multiscale in Silico Study to Characterize the Atrial Electrical Activity of Patients With Atrial Fibrillation. A Translational Study to Guide Ablation Therapy [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/171456
TESIS
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Bysakh, Sandip. "Pulsed Laser Ablation Deposition of Intermetallic Thin Films: A Study of Evolution of Metastable Phases and Ultra-fine Microstructures." Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/135.
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This thesis is devoted to the deposition of intermetallic thin films by laser ablation deposition (LAD) and their characterization. Pulsed laser ablation and subsequent deposition of the ablated vapours produces films under conditions very far away from equilibrium. Besides the film, which forms directly by quenching the vapour or plasma on substrate, one also obtains under certain conditions micron and sub-micron sized spherical droplets of alloy melt on to the film. The latter travel at very high velocities and impinge on the substrate resulting in a very high rate of heat transfer during solidification from liquid state. Therefore, in this work it was possible to study the microstructure evolution depending on quenching rates of different sized droplets and compare with the extreme case of vapour/plasma quenching.
The compositions selected correspond to the intermetallic compounds in Al-Fe, Al-Ni and Ti-Si binary systems. Pre-alloyed targets of the appropriate intermetallic compositions were used for ablation by laser. The deposition system has been designed and built in-house. The
characterization is mainly done by transmission electron microscopy (TEM). The study focuses on microstructure and phase evolution within these intermetallic films at room temperature, at elevated temperature and during heating the room temperature deposited films in heating stage inside the TEM.
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Abraham, Meg. "Incorporation of laser ablation into a PIXE system in order to study metallurgy and corrosion products on archaeological objects." Thesis, University of Oxford, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.645189.
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This work demonstrates the set up and testing of a laser ablation system incorporated into a Particle Induced X-ray Emission Beam line in order to expose bare metal for analysis. The setup allows for X-ray analysis of the composition of the objects without large scale or visible damage to the patina on the object. In some instances the process also allows for some analysis of the corrosion products that make up the patina on the objects. The process is developed as a method for handling a specific class of archaeological objects which are not suited to sampling for various reasons. The aim is to minimize invasive testing of these objects while gaining information about their composition. Using this technique it is possible to infer something about the bulk makeup of the corrosion products on the surface of the objects. It also allows for a good quantitative understanding of the trace elements in the underlying metal substrate that remains below the corroded surface in most cases. This process is not intended to produce exact descriptions of the mineralogical makeup of the corrosion products that form the patina on the object, such as those which can be obtained through metallurgical cross-sectioning. Further it will not yield good quantitative analysis of the trace elements in corrosion products like those obtained using synchrotron radiation. Finally this technique cannot give detailed information regarding the metallurgical structure of the base metal composition of the object again like the data obtained using cross-sections.
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Fani-Pakdel, Farzad. "Microsecond pulsed Grimm glow discharge time-of-flight mass spectrometry study of aerosols generated by nebulization and laser ablation." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024978.
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Chen, Hui. "DEVELOPMENT AND APPLICATION STUDY OF NANOSCALE THIN FILM MATERIALS AND POLYMER NANOCOMPOSITES." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2124.
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This dissertation demonstrated that the manipulation of substances at the molecular or nanometer level can lead to the discovery and development of new materials with interesting properties and important applications. Chapter 1 describes the development of a nanoscale molecular thin film material for corrosion protection. By using a self-assembled monolayer film with a thickness of only about 1 nanometer as a linkage, a covalent bonding was achieved between a polyurethane top coating and an aluminum alloy substrate. This covalent bonding between polymer top coating and the aluminum alloy substrate significantly improved the corrosion resistance of the substrate. Chapter 2 and Chapter 3 describe the development of a gold nanoparticle-polymer composite material in different forms with a number of applications. Gold nanoparticles are among one of the most extensively studied nanomaterials. When the size of gold is shrunk to the nanometer scale, many interesting and new physical properties start to appear from gold nanoparticles. The optical properties of gold nanoparticles, particularly the surface plasmon resonance absorption, have been investigated in this dissertation for the development of multifunctional nanocomposite materials. Chapter 2 presents the preparation of a gold nanoparticle/poly(methyl methacrylate) (PMMA) nanocomposite film and the application of such films for microstructure fabrication using a direct laser writing technique. Gold nanoparticles are excellent photon-thermal energy converters due to their large absorption cross section at the surface plasmon resonance region. Upon laser irradiation of the nanocomposite film, the thermal energy converted from the absorbed photon energy by gold nanopaticles induced a complete decomposition of PMMA, leading to the formation of various microstructures on the nanocomposite films. Chapter 3 reports the further development of a nanoparticle/polymer composite nanofiber material fabricated through an electrospinning process. The matrix of the nanofiber is made of two polyelectrolytes, poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH). Three methods were developed to incorporate gold nanoparticles into the polymer matrix. The composite nanofiber materials developed in this study demonstrate multifunctional properties, including good electrical conductivity, photothermal response, and surface-enhanced IR absorption. This material may be used for many important applications including catalysis, chemical and biological sensors, and scaffold materials for tissue engineering. In Chapter 4, another most important nanomaterial, carbon naotubes (CNTs), were introduced as fillers to prepare polymer nanocomposites. A dispersion method for multi-walled carbon nanotubes (MWCNTs) using a conjugated conducting polymer, poly(3-hexylthiophene) (P3HT) as the third component and trifluoroacetic acid (TFA) as a co-solvent was developed. Due to the excellent dispersion of carbon nanotubes in PMMA and enhanced conductivity of the nanocomposites by the conjugated conducting polymers, the prepared composite materials has an extremely low percolation threshold of less than 0.006 wt% of MWCNT content. The potential use of MWCNT/conducting polymer composites for energy storage applications such as suppercapacitors was further investigated by Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and charging-discharging cycles. Compared to pure carbon nanotubes, the nanocomposite materials have significantly improved properties and are promising for supercapacitor applications.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Materials Science & Engr PhD
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Champ-Rigot, Laure. "Nouvelles perspectives diagnostiques et thérapeutiques dans la prise en charge rythmologique des patients en situation d'insuffisance cardiaque Rationale and Design for a Monocentric Prospective Study: Sleep Apnea Diagnosis Using a Novel Pacemaker Algorithm and Link With Aldosterone Plasma Level in Patients Presenting With Diastolic Dysfunction (SAPAAD Study) Usefulness of sleep apnea monitoring by pacemaker sensor in elderly patients with diastolic dysfunction : the SAPAAD Study Clinical outcomes after primary prevention defibrillator implantation are better predicted when the left ventricular ejection fraction is assessed by magnetic resonance imaging Predictors of clinical outcomes after cardiac resynchronization therapy in patients ≥75 years of age: a retrospective cohort study Comparison between novel and standard high-density 3D electro-anatomical mapping systems for ablation of atrial tachycardia Safety and acute results of ultra-high density mapping to guide catheter ablation of atrial arrhythmias in heart failure patients Long-term clinical outcomes after catheter ablation of atrial arrhythmias guided by ultra-high density mapping system in heart failure patients." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMC430.
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L’insuffisance cardiaque est un problème de santé publique dans les pays développés, touchant 1 à 2% de la population générale, mais dont la prévalence atteint 10% après 70 ans. Les progrès thérapeutiques ont permis d’améliorer le pronostic des patients, notamment ceux ayant une altération de la fonction systolique ventriculaire gauche. Les troubles du rythme sont fréquents et nécessitent une pris en charge particulière au cours des situations d’insuffisance cardiaque. Cependant, il reste des questions non résolues : comment améliorer l’efficacité du traitement de l’insuffisance cardiaque à fonction systolique préservée, comment mieux sélectionner les patients pouvant bénéficier de la prévention primaire de la mort subite par un défibrillateur implantable, les patients âgés peuvent-ils bénéficier de la même prise en charge que les patients plus jeunes, et pour finir comment améliorer les résultats de l’ablation de fibrillation auriculaire dans les situations d’insuffisance cardiaque. Nous avons mis en place une étude prospective chez des patients présentant une dysfonction diastolique pour évaluer l’intérêt de l’algorithme de surveillance de l’apnée du sommeil disponible dans des stimulateurs cardiaques. En parallèle, nous avons analysé l’impact de l’évaluation par résonance magnétique des patients candidats à un défibrillateur sur la prédiction des évènements rythmiques, mais aussi le devenir des patients de plus de 75 ans appareillés avec un système de resynchronisation cardiaque. Enfin, nous nous sommes intéressés aux résultats d’un nouveau système de cartographie électroanatomique ultra-haute densité pour guider les procédures d’ablation de troubles du rythme supraventriculaires complexes chez des patients insuffisants cardiaques comparés à des patients contrôlesHeart failure is a major public health issue in developed countries, with a prevalence of 1-2% of global population, rising to 10% after 70 years of age. Therapeutic progresses have succeeded in improving patients’ prognosis, particularly in case of reduced left ventricular ejection fraction. Rhythm abnormalities are frequent, and need special consideration in case of heart failure. Meanwhile, there are still some gaps in the evidence: heart failure with preserved systolic function is complex and difficult to treat, primary prevention of sudden cardiac death is effective but there is a need to better select candidates, whether elderly patients should be treated as younger individuals, and finally how to improve outcomes of atrial fibrillation catheter ablation. Firstly, we have conducted a prospective study to evaluate the Sleep Apnea Monitoring algorithm provided in a novel pacemaker in patients with diastolic dysfunction. Besides, we analyzed whether magnetic resonance imaging could predict cardiac outcomes in patients with an implantable cardioverter defibrillator better than echocardiography. We also reported the outcomes of the cardiac resynchronization therapy in patients ≥75 years old compared to younger patients. Finally, we studied the results of a novel ultra-high density mapping system to guide ablation procedures of complex atrial arrhythmias in heart failure patients compared to controls
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Johansson, Johannes. "Thermocoagulation in Deep Brain Structures : Modelling, simulation and experimental study of radio-frequency lesioning." Licentiate thesis, Linköping : Linköping University, Department of Biomedical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-7406.
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Eichhorn, Anna Vera [Verfasser], Marco [Akademischer Betreuer] Durante, and Thomas [Akademischer Betreuer] Aumann. "In-Vivo Feasibility Study and Developments for Cardiac Arrhythmia Ablation using Scanned Carbon Ions / Anna Vera Eichhorn ; Marco Durante, Thomas Aumann." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2017. http://d-nb.info/1127729322/34.
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Eichhorn, Anna [Verfasser], Marco [Akademischer Betreuer] Durante, and Thomas [Akademischer Betreuer] Aumann. "In-Vivo Feasibility Study and Developments for Cardiac Arrhythmia Ablation using Scanned Carbon Ions / Anna Vera Eichhorn ; Marco Durante, Thomas Aumann." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2017. http://nbn-resolving.de/urn:nbn:de:tuda-tuprints-60822.
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Vesperini, Doriane. "Biomechanical study of cells in microfluidic flow : application to sorting and platelet production." Thesis, Compiègne, 2018. http://www.theses.fr/2018COMP2437/document.
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Les mégacaryocytes sont des cellules de la moelle osseuse, à l’origine de la production des plaquettes sanguines. Quand elles arrivent à maturité, elles grossissent et émettent des prolongements de cytoplasme à travers la paroi des vaisseaux irriguant la moelle. Dans la circulation sanguine, ces prolongements, soumis aux forces de l’écoulement, s’allongent et se rompent pour former des plaquettes. Des techniques microfluidiques capables de produire des plaquettes in vitro existent et sont une alternative prometteuse au don. Mais le rendement reste à améliorer. Pour cela, il est nécessaire de mieux comprendre la fragmentation des mégacaryocytes en plaquettes. Ce travail de doctorat s’inscrit dans ce contexte et sera développé en deux axes principaux dans ce manuscrit. Dans une première partie nous développons une méthode pour trier des cellules en fonction de leur déformabilité, afin de savoir si les propriétés mécaniques d’un mégacaryocyte sont liées à leur stade de maturité. La méthode a d’abord été mise au point avec des microcapsules. Leurs propriétés mécaniques sont déterminées par analyse inverse à partir de la mesure de leur forme en écoulement dans des constrictions droites. Puis le dispositif utilisé a été miniaturisé pour s’adapter à la taille des cellules. Pour la caractérisation de leurs propriétés mécaniques, deux outils ont été utilisés: l’analyse inverse et la microscopie à force atomique sans pointe. Une deuxième partie porte sur l’étude de l’élongation et de la rupture de mégacaryocytes soumis écoulement. Nous avons quantifié les variations spatiotemporelles du taux d’élongation et développé un protocole d’ablation laser pour étudier les mécanismes de rupture de cellules en élongationWhen they mature in the bone marrow, the precursors of platelets, called megakaryocytes, grow and extend protrusions able to join blood circulation. There these protrusions elongate and break into platelets. Microfluidic techniques for in vitro platelet production represent a promising alternative to donation. In order to enhance platelet production and match the needs of clinical applications such as transfusion, we need to better understand the fragmentation of megakaryocytes into platelets. Our contribution will be described in this manuscript in two main axes. First, in order to know if mechanical properties of megakaryocytes can indicate their maturity stage, we develop a cell sorting method based on deformability. The method is first validated with microcapsules. Their mechanical properties are determined by inverse analysis from their shape under flow in straight microchannels. Then the device is downscaled. The characterization of cell mechanical properties are performed using inverse analysis and tipless atomic force microscopy. Second, we study megakaryocyte elongation and rupture in a microfluidic device. We quantify the spatial and temporal variations of the elongation rate and develop a laser ablation protocol to trigger and study the rupture of elongating cells
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Velasquez, Alejandro. "Trace element analysis of native gold by laser ablation ICP-MS : a case study in greenstone-hosted quartz-carbonate vein ore deposits, Timmins, Ontario." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46409.
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Native gold contains trace amounts of other elements and from the relative abundance of these a geochemical signature can be obtained. The trace element composition provides a “fingerprint” that is unique to the gold deposit it comes from. This fingerprint can be used to distinguish gold sources and potentially provide insight into the geochemical processes operating in the formation of Au deposits. Native gold grains were acquired from 3 gold ore deposits; Hollinger, McIntyre, and Aunor. These ore deposits are located near Timmins, Ontario, in the western end of the Porcupine gold camp, the south-western part of the Abitibi greenstone belt. Respectively, Scanning Electron Microscope analysis/Energy Dispersive Spectrometry (SEM/EDS) was used to determine major elements in gold grains. Ag concentrations from the SEM/EDS analyses were used as the internal standard for the laser ablation inductively coupled plasma mass spectrometry technique (LA-ICP-MS) that yielded trace element concentrations. A new reference material (AuRM2) served as the external standard for 22 elemental analytes for the LA-ICP-MS analyses. Trace elements in native Au associate according to Goldschmidt’s classification of elements demonstrating that element behavior in native Au is not random. Such element behavior suggests that samples from each deposit formed under similar geological conditions. Chalcophile and siderophile elements provide the most compelling fingerprints of the three ore deposits and they appear to be in solid solution in Au whereas lithophile elements are not very advantageous for distinguishing deposits and element concentrations appear to be controlled by micro inclusions such as tourmaline. The deposits show low Ag contents, which is consistent with mesothermal Au. Hollinger and McIntyre deposits have similar trace element abundances with high Ag, Pb, Bi, Sb and Pd and low Cu; however Cu concentrations in McIntyre are higher than in Hollinger. In contrast, Aunor has high Cu abundances and low Ag, Bi, Sb, Pb and Pd. Gold grain signatures reflect the chemical characteristics of the host rock superimposed on the chemical signature of the mineralizing fluid. The association of Pb-Bi-Cu bearing phases such as galena and chalcopyrite with gold supports hydrothermal fluids with high concentrations of these elements.
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Blanco, Sequeiros R. (Roberto). "Magnetic resonance imaging guided musculoskeletal interventions at 0.23T:optical instrument guidance, bone biopsy, periradicular nerve root therapy, discography, osteoid osteoma laser ablation; a feasibility study." Doctoral thesis, University of Oulu, 2003. http://urn.fi/urn:isbn:9514269039.
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Abstract
The purpose of this study was firstly to evaluate the optical instrument tracking system integrated to the MRI scanner as a guidance facility in performing bone biopsy and secondly to develop and evaluate clinical musculoskeletal applications of interventional MRI at 0,23T. The clinical results and feasibility of MR-guided bone biopsy (n=14), periradicular nerve root therapy (n=61), discography (n=12) and percutaneous laser therapy of osteiod osteomas (n=5) were studied.
Bone biopsies were performed with the optical instrument tracker and bone biopsy set modified for the tracker system. The biopsy system and optical tracker mounting proved to be safe and reliable tool for bone biopsies. 14 consecutive bone biopsies and 13 fine needle aspirations were performed under MR-guidance. The clinical accuracy of MR-guided bone biopsy was 95%.
The periradicular therapy was applied to the anatomical region of lumbosacral area of 61 consecutive patients with sciatic pain. Procedural success rate was 98,5%. Of patients, 51,5% had good or excellent effect with regard to radicular pain from procedure. The therapy effect achieved with MR-guided procedure was comparable to that achieved with conventional techniques.
MR-guided discography technique and imaging protocol was developed as part of diagnostic pain provocation for patients suspected for intervertebral pain source at lumbosacral area. 34 MR-guided discographies were performed on 12 patients. In all patients positive or negative pain provocation response was obtained.
Laser induced thermal therapy for osteiod osteoma was studied in MRI. The initial guidance of the instrument and monitoring of the thermal procedure were done under MRI control. All the 5 patients were successfully treated.
The MR-guidance in musculoskeletal applications seems safe and accurate.
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Nazaré, Ana Sofia Relvas. "Complications and surgical outcome in dogs with otitis media undergoing total ear canal ablation and lateral bulla osteotomy : a retrospective study of 37 cases." Master's thesis, Universidade de Lisboa, Faculdade de Medicina Veterinária, 2021. http://hdl.handle.net/10400.5/20970.
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Dissertação de Mestrado Integrado em Medicina VeterináriaNowadays total ear canal ablation combined with lateral bulla osteotomy (TECA-LBO) is the gold standard surgical technique for the treatment of dogs diagnosed with chronic otitis externa or otitis media nonresponsive to medical treatment. Regardless, of its efficiency in the resolution of otitis, several types of complications may occur. This study aimed to retrospectively revise postoperative complications and surgical outcome in a group of dogs submitted to this procedure in 2 referral institutions. Bacterial infection was found in 86.49% of the cases and postoperative complications were present in 54.05% of the cases. Neurological complications occurred in 35.14% of the cases, abscess or fistulation occurred in 18.92% of the cases, and suture dehiscence in 21.62% of the cases. No associations were found between the occurrence of complications and the dog’s age, sex, breed or presence of bacterial infection. There was also no association between the surgical outcome and the animal’s age, sex, breed or presence of bacterial infection. It was found an association between the postoperative complications and a poor surgical outcome, in particular with the presence of abscess or fistulation. On the contrary it was found an association between the suture dehiscence and a better surgical outcome. No association was found between the occurrence of neurological complications and the surgical outcome. In the great majority of the cases the outcome was good, corroborating the fact that TECA-LBO is an effective surgical technique in the resolution of otitis media.
RESUMO - Complicações e resultado cirúrgico em cães com otite média submetidos a ablação total do conduto auditivo e osteotomia lateral da bula timpânica: estudo retrospetivo de 37 casos - Atualmente, a ablação total do conduto auditivo associada à osteotomia lateral da bula timpânica (TECA-LBO) é a técnica cirúrgica recomendada para o tratamento de cães com diagnóstico de otite externa crónica ou otite média não responsiva ao tratamento médico. Apesar de ser uma técnica extremamente eficaz na resolução de otites, vários tipos de complicações podem ocorrer. O objetivo deste estudo foi rever retrospetivamente as complicações pós-operatórias e os resultados cirúrgicos de um grupo de cães submetidos a este procedimento em 2 instituições de referência. A presença de infeção bacteriana foi encontrada em 86.49% dos casos e as complicações pós-operatórias em 54.05% dos casos. Complicações neurológicas ocorreram em 35.14% dos casos, abscesso ou fístula em 18.92% dos casos e deiscência de sutura em 21.62% dos casos. Não foram encontradas associações entre a ocorrência de complicações e a idade, sexo, raça ou presença de infeção bacteriana. Também não houve associação entre o resultado cirúrgico e a idade, sexo, raça ou presença de infeção bacteriana. Foi encontrada associação entre as complicações pós-operatórias e um mau resultado cirúrgico, principalmente na presença de abscesso ou fístula. Pelo contrário, foi encontrada associação entre a deiscência de sutura e um melhor resultado cirúrgico. Não foi encontrada associação entre a ocorrência de complicações neurológicas e o resultado cirúrgico. Na grande maioria dos casos o resultado foi bom, corroborando o fato da TECA-LBO ser uma técnica cirúrgica eficaz na resolução da otite média.
N/A
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Ek, Adam. "Blending Words or: How I Learned to Stop Worrying and Love the Blendguage : A computational study of lexical blending in Swedish." Thesis, Stockholms universitet, Avdelningen för datorlingvistik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-160763.
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This thesis investigates Swedish lexical blends. A lexical blend is defined as the concatenation of two words, where at least one word has been reduced. Lexical blends are approached from two perspectives. First, the thesis investigates lexical blends as they appear in the Swedish language. It is found that there is a significant statistical relationship between the two source words in terms of orthographic, phonemic and syllabic length and frequency in a reference corpus. Furthermore, some uncommon lexical blends created from pronouns and interjections are described. A description of lexical blends through semantic construction and similarity to other word formation processes are also described. Secondly, the thesis develops a model which predicts source words of lexical blends. To predict the source words a logistic regression model is used. The evaluation shows that using a ranking approach, the correct source words are the highest ranking word pair in 32.2% of the cases. In the top 10 ranking word pairs, the correct word pair is found in 60.6% of the cases. The results are lower than in previous studies, but the number of blends used is also smaller. It is shown that lexical blends which overlap are easier to predict than lexical blends which do not overlap. Using feature ablation, it is shown that semantic and frequency related features have the most important for the prediction of source words.
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Sánchez, Arciniegas Jorge Patricio [Verfasser], O. [Akademischer Betreuer] Dössel, and Trenor B. A. [Akademischer Betreuer] Gomis. "A Multiscale In Silico Study to Characterize the Atrial Electrical Activity of Patients With Atrial Fibrillation : A Translational Study to Guide Ablation Therapy / Jorge Patricio Sánchez Arciniegas ; O. Dössel, B.A. Gomis Trenor." Karlsruhe : KIT-Bibliothek, 2021. http://d-nb.info/1238148085/34.
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Diaz, Javier. "Study of amorphous carbon thin films grown by pulsed laser deposition." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10015.
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Le but de cette these est l'etude des parametres physiques qui font varier les proprietes electroniques et mecaniques des couches minces de carbone amorphe (a-c) evaporees par la technique de deposition par laser pulse (pld). Tout d'abord, on a fait des experiences pour connaitre le systeme experimental: on a etudie la composition du materiau evapore et la cinetique de deposition des particules sur la surface de si (111) 7x7. Cette derniere a ete observe a l'echelle atomique avec un microscope a effet tunnel dans l'ultra vide. Dans une deuxieme partie, on a caracterise les depots de a-c. Ces films ont une densite entre 2. 45 g/cm#3 et 2. 8 g/cm#3 et une durete jusqu'a 50 gpa. Ils sont semiconducteurs avec un gap optique de 0. 3 ev et une resistivite electrique de 10#5 cm. Ces proprietes sont degradees si l'energie cinetique des particules evaporees est diminuee. L'analyse physico-chimique de ces couches minces a ete faite en utilisant les spectroscopies de photoemission (xps et ups), d'absorption des rayons x (nexafs) et raman. Cette analyse revele que ces couches sont constituees par des atomes de carbone hybrides sp#2 et sp#3. La proportion des liaisons sp#3 par rapport aux liaisons sp#2 est de 40% pour les couches dures (45 gpa) et 25% pour les moins dures (22 gpa). Les resultats nexafs obtenus en detection d'electron et en fluorescence semblent indiquer un gradient de densite du materiau, celle-ci augmentant de la surface vers le volume. Finalement, la similitude observee entre les spectres raman de films de a-c avec des duretes semblables mais des gap optiques radicalement differents indiquent que la spectroscopie raman est plus sensible a l'organisation structurale qu'aux proprietes electroniques des depots de a-c
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Finegold, Judith. "Distal ablation and directly observed medical therapy as potential protocol advancements for renal denervation for hypertension : a study evaluating invasive hemodynamic parameters to predict response to renal denervation." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/49206.
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Aims: (1) Explore the physiological effect of renal denervation (RDN) (2) Explore the efficacy of distal denervation on blood pressure (BP) reduction in patients undergoing directly observed anti-hypertensive therapy (DOT) to minimise measurement bias (3) Evaluate the 6-month safety of distal denervation Methods: Patients with resistant hypertension were recruited and underwent assessment of drug compliance by assaying urinary drug levels. All subsequent measurements were recorded under DOT. Pre-denervation, office and ambulatory BP were measured, and patients underwent bilateral renal angiography and invasive measurement of aortic and renal arterial pressure and blood flow velocity. RDN was performed using the Symplicity Spyral catheter, denervating in the main renal arteries and each distal branch >3mm diameter. Invasive and non-invasive measurements were repeated 6-months post denervation under DOT. Results: 16 patients underwent denervation (age 63±12 years) with referral office SBP 180±18 mmHg. In total each patient received 22.6±5.0 ablations, 9.3±2.9 ablations in the main trunk and 13.3±4.8 ablations distally. At 6-months follow-up, overall unblinded 24-hour SBP reduction was -5.1±7.5 mmHg (p=0.020), with DBP reduction -3.4±4.9 mmHg (p=0.018). At 6-months follow-up an overall increase in renal blood flow velocity occurred at rest (1.91±3.51cm/s, p=0.04) and under identical sedation states (1.81±3.44 cm/s, p=0.05). Patients with the largest reduction in ambulatory SBP at 6-months had the largest increase in renal blood flow acutely after RDN (R 2=0.60, p < 0.001) and the largest decrease in renal resistance (R2=0.56, p < 0.001). Quantitative vessel angiography showed no significant change in any main or distal renal artery dimensions at 6-months. Conclusion: This unblinded study of distal RDN showed a significant reduction in ambulatory systolic and diastolic BP with no safety concerns at 6-months. These exploratory results suggest that acute changes in renal hemodynamics may be predictive of blood pressure response at 6-months follow-up.
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Ha, Man Linh [Verfasser], Reginald [Akademischer Betreuer] Birngruber, and Tobias [Akademischer Betreuer] Fischer. "Fractional ablation of skin using a carbon dioxide laser, a carbon monoxide laser, and a thulium fiber laser : a comparison study / Man Linh Ha ; Akademische Betreuer: Reginald Birngruber, Tobias Fischer." Lübeck : Zentrale Hochschulbibliothek Lübeck, 2020. http://d-nb.info/1217025340/34.
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Saha, Sanjib. "Study Of Pulsed Laser Ablated Barium Strontium Titanate Thin Flims For Dynamic Random Access Memory Applications." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/208.
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The present study describes the growth and characterization of pulsed laser ablated Bao.sSro.sTiOs (BST) thin films. Emphasis has been laid on the study of a plausible correlation between structure and property in order to optimize the processing parameters suitably for required application. An attempt has been made to understand the basic properties such as, origin of dielectric response, charge transfer under low and high-applied electric fields across the BST capacitor and finally the dielectric breakdown process.
Chapter 1 gives a brief introduction on the application of ferroelectric thin films in microelectronic industry and its growth techniques. It also addresses the present issues involved in the introduction of BST as a capacitor material for high-density dynamic random access memories. Chapter 2 outlines the motivation for the present study and briefly outlines the research work involved.
Chapter 3 describes the experimental procedure involved in the growth and characterization of BST thin films using pulsed laser ablation technique. Details include the setup design for PLD growth, material synthesis for the ceramic targets, deposition conditions used for thin film growth and basic characterizations methods used for study of the grown films.
Chapter 4 describes the effect of systematic variation of deposition parameters on the physical and electrical properties of the grown BST films. The variation in processing conditions has been found to directly affect the film crystallinity, structure and morphology. The change observed in these physical properties may also be correlated to the observed electrical properties. This chapter summarizes the optimal deposition conditions required for growing BST thin films using a pulsed laser ablation technique.
Microstructure of BST films has been categorized into two types: (a) Type I structure, with multi-grains through the film thickness, for amorphous as-grown films after high temperature annealing (exsitu crystallized), and (b) columnar structure (Type II) films, which were as-grown well-crystallized films, deposited at high temperatures.
The ac electrical properties have been reviewed in detail in Chapter 5. Type I films showed a relatively lower value of dielectric constant (e ~ 426) than Type II films with dielectric constant around 567. The dissipation factors were around 0.02 and 0.01 for Type I and Type II films respectively. The dispersion in the frequency domain characteristics has been quantitatively explained using Jonscher's theory. Complex impedance spectroscopy employed showed significant grain boundary response in the case of multi-grained Type I films while negligible contribution from grain boundaries has been obtained in the case of columnar grained Type II BST films. The average relaxation time r obtained from the complex impedance plane plots show almost three orders higher values for Type I films. The obtained results suggest that in multi-grained samples, grain boundary play a major role in electrical properties. This has been explained in accordance to a model proposed on the basis of depleted grains in the case of Type I films where the grain sizes are smaller than the grain boundary depletion width.
Chapter 6 describes the dc leakage properties of the grown BST thin films and the influence of microstructure on the leakage properties. It was evident from the analysis of the graph of leakage current against measurement temperature, that, the observed leakage behavior in BST films, can not be attributed to a single charge transport mechanism. For Type I films, the Arrhenius plot of the leakage current density with 1000/T exhibits different regions with activation energy values in the range of 0.5 and 2.73 for low fields (2.5kV/cm). The activation energy changes over to 1.28 eV at high fields (170 kV/cm). The obtained values agree well with that obtained from the ac measurements, thus implying a similarity in the origin of the transport process. The activation energy value in the range of 0.5 eV is attributed to the electrode/film Schottky barrier, while the value in the range of 2.73 eV is due to deep trap levels originating from Ti+3 centers. The value in the range of 1.28 eV has been attributed to oxygen vacancy motion. Similar results have been obtained from the Arrhenius plot of the leakage current for Type II films. In this case, only two different activation energy values can be identified in the measured temperature and applied electric field range. At low fields the activation energy value was around 0.38 eV while at high fields the value was around 1.06 eV. These values have been identified to be originating from the electrode/film Schottky barrier and oxygen vacancy motion respectively. Thus a complete picture of the charge transport process in the case of BST thin film may be summarized as comprising of both electronic motion as well as contribution from oxygen vacancy motion.
The effect of electrical stress on the capacitance-voltage (C-V) and the leakage current has been analyzed in Chapter 7. From the change in the zero bias capacitance after repeated electron injection through the films the values of the electronic capture cross-section and the total trap density for Type I and II films have been estimated. The results showed higher values for Type I film in comparison to Type II films. The difference has been attributed to the presence of grain boundaries and a different interface in the case of Type I films when compared to Type II films where the absence of grain boundaries is reflected in the columnar microstructure. A study of the time-dependent-dielectric-breakdown (TDDB) characteristics under high fields for Type I and Type II films showed higher endurance for Type I film. On the other hand space-charge-transient characteristics have been observed in the case of Type II films at elevated temperature of measurement. Mobility and activation energy values extracted from the transient characteristics are found to be in the range of 1 x 10~12 cm2 /V-sec and 0.73 eV respectively, suggesting a very slow charge transport process, which has been attributed to the motion of oxygen vacancies. An overall effect of electrical stress suggested that oxygen vacancy motion can be related to the observed resistance degradation and TDDB, which has been further enhanced by the combination of high temperature and high electric fields.
Chapter 8 deals with the effect of intentional doping in the BST films. The doping includes Al at the Ti-site, Nb in the Ti-site and La at the Ba/Sr-site. The effect of doping was observed both on the structure and electrical properties of the BST films. Acceptor doping of 0.1 atomic 7c Al was found to decrease the dielectric constant as well as the leakage current. For higher concentration of acceptor-dopant, the leakage current was found to increase while showing space-charge-transient in the TDDB characteristics, again suggesting the effect of increased concentration of oxygen vacancies. Donor doping using 2 atomic % La and Xb significantly improved the leakage as well as the TDDB characteristics by reducing the concentration of oxygen vacancies. A further procedure using graded donor doping in the BST films exhibits even better leakage and TDDB properties. An unconventional, graded doping of donor cations has been carried out to observe the impact on leakage behavior, in particular. The leakage current measured for a graded La-doped BST film show almost six orders of lower leakage current in comparison to undoped BST films, while endurance towards breakdown has been observed to increase many-fold.
Chapter 9 highlights the main findings of the work reported in this thesis and lists suggestions for future work, to explore new vistas ahead.
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Jaren, Sophie. "Étude de TbFe2 épitaxié par dépot laser pulsé : des couches minces aux nanostructures magnétiques." Université Joseph Fourier (Grenoble ; 1971-2015), 1998. http://www.theses.fr/1998GRE10064.
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Le compose tbfe#2 presente des proprietes de magnetostriction geante a temperature ambiante. Nous avons mene une etude des conditions de croissance, des proprietes structurales et des proprietes magnetiques des couches minces epitaxiees de tbfe#2(111). Les couches elaborees par depot laser pulse (pld) ont des epaisseurs de 60-240 a. Nous avons determine les effets de la temperature de depot sur la morphologie des couche, observee par microscopie afm. Nous montrons qu'un depot en gradient de temperature (type b) permet d'obtenir des couches plus continues qu'un depot a temperature constante elevee (type a). L'effet de la couche tampon et de la terre rare sur la morphologie ont ete etudies. Les relations d'epitaxie ont ete determinees et nous montrons qu'elles dependent de l'etat de surface de la couche tampon. Une etude detaillee des cliches rheed est presentee. Nous avons mesure des deformations de maille dans les echantillons. Les couches a presentent une dilatation dans le plan de la couche et une contraction suivant l'axe de croissance 111 alors que les couches b sont dilatees dans le plan de meme que sur l'axe 111. Nous avons etudie les proprietes magnetiques des echantillons de type a et b par vsm, squid et effets magneto-optique (kerr et faraday). Les echantillons a ont une anisotropie planaire qui n'apparait pas sur les couches b. Nous proposons un modele de calcul d'anisotropie base sur le couplage magnetoelastique reliant les deformations mesurees a l'anisotropie. Ce modele permet d'obtenir un accord qualitatif avec les observations experimentales. Enfin nous proposons un processus d'elaboration de nanostructures auto-assemblees de fe. Dans ce travail preliminaire la structure des nanostructures obtenues a ete analysee par rheed, diffusion centrale des rx, diffraction x et afm. Nous presentons les premiers resultats de l'etude magnetique macroscopique (mesures vsm) et locale, mesures par microsquid et dichroisme magnetique circulaire des rx.
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Ciaralli, Simone. "A study of the lifetime of miniaturized ablative pulsed plasma thrusters." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/379251/.
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Miniaturized satellites are one of the fastest growing sectors in the space industry, allowing cheap access to space. These satellites are currently limited by their lack of orbit control and their lifetime is therefore determined by the natural, drag-induced, de-orbiting. These issues can be solved using a dedicated propulsion system. Cold-gas micro-thrusters, successfully flown on miniaturized satellites, are characterised by a very low specific impulse (typically less than 100 s), which considerably limits their capabilities. Moreover, they require pressurized tanks, pressure regulators and valves that may significantly increase the dry mass of the system. Pulsed Plasma Thrusters (PPTs) represent an excellent alternative to the chemical thrusters thanks to their high scalability in terms of geometry, power input and performance. Within this research programme, the factors that affect the lifetime of solid state propellant PPTs for miniaturized satellites (e.g. Cubesat and nanosatellites) applications have been studied and addressed. Moreover, efforts have been made to optimise a PPT as a sub-system to be integrated into a satellite spacecraft. This included the characterization of the electromagnetic noise that PPTs generate and that may cause failures on the other Cubesat subsystems and a study aimed at the optimization of the PPT ignition process to produce a lighter and more reliable conditioning electronics. To complete all these tasks, a miniaturized PPT (called PPTCUP, which stands for PPT for Cubesat Propulsion) has been developed and tested in collaboration with Mars Space Ltd and Clyde Space Ltd. Results from the PPTCUP test campaign have proved the reliability of the thruster, being able to perform a number of shots almost two times bigger than the nominal number required to demonstrate the discharge chamber lifetime. Moreover, it has been found that the unit can work correctly in the range of the Cubesat operating temperatures, withstands the mechanical vibrations during launch and has main natural frequencies compliant with the Cubesat requirements. The results of the EMC characterization test show that the electromagnetic noise generated during the main PPT discharge is mostly compliant with the requirements or small enough to be impossible to distinguish from the facility background noise. The dedicated study to identify the best spark plug system working with a relative low breakdown voltage has shown that the semiconductor- coated spark plug insulator are able to trigger the PPT main discharge at a lower voltage (i.e. about 1700 V against the 7500 V needed for the no-coated propellant rods) without affecting the overall thruster performances.
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Lefèvre, Gauthier. "Propriétés physico-chimiques de nouveaux matériaux en couches minces pour le stockage d'hydrogène." Thesis, Artois, 2018. http://www.theses.fr/2018ARTO0406.
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Le stockage d'hydrogène est sans doute le dernier verrou au développement à grande échelle des piles à combustible. Utiliser l'hydrogène comme vecteur énergétique, produire efficacement de l'électricité sans avoir recours aux énergies fossiles et rejeter uniquement de l'eau, il s'agit là peut-être de la prochaine révolution technologique, écologique et qui signera la fin des problèmes environnementaux en terme d'énergie.L'hydrogène gazeux est dangereux et son stockage à l'état solide représente une solution mais au détriment de la quantité stockée et des conditions d'utilisation.Dans ce contexte, la recherche de nouveaux matériaux avec des propriétés physico-chimiques nouvelles est souhaitable.Cette thèse s’inscrit dans cette démarche d'investigation : d'une part mettre en oeuvre et utiliser de nouvelles techniques de recherche structurale théorique pour explorer les possibilités qu'offrent les alliages métalliques ; ensuite entreprendre la synthèse de couches minces de métaux et d'alliages au moyen de l’ablation laser pulsé pour bénéficier des atouts de cette méthode.L'étude théorique menée au cours de cette thèse a permis de montrer l'impact des contraintes de pression sur la formation et la stabilité d'alliages dans de nombreux systèmes binaires. Des pistes sur l'hydrogénation possible de nouvelles structures ont également été présentées.D'autre part, l'adversité de l'ablation laser pulsé pour la synthèse de couches minces a été mise en lumière et de grandes disparités dans les conditions de dépôts sont à déplorer. Cette méthode permet de parvenir à des morphologies singulières, ouvrant ainsi à des perspectives dans la conception de ces nouveaux matériauxHydrogen storage is probably the last lock facing the development of fuel cells system.Hydrogen is a non-harmful, non-polluting that can be used as an energy vector, allowing to produce fossil fuel free electricity efficiently and releasing only water.It could trigger the next technological and green revolution, marking the end of environmental concerns related to energy.Hydrogen is the most energetic gas. These double-edged caracteristics makes it attractive and unsafe at the same time. Solid state storage can be seen as a solution in spite of a moderate hydrogen uptake and a poor desorption process.In this context, research of new materials with enhanced physico-chemical properties is desirable and represent the aim of this work.This thesis is an investigation study. On the one hand, with the help of efficient theoretical structural prediction systems, an exploration of the infinite possibilities offered by metal alloys has been performed. On the other hand, pulsed laser deposition of metal thin films has been implemented to make use of its benefits.The present theoretical study has highlighted the influence of external strains on stability and emergence of alloys in numerous binary systems. In addition, a search for potential hydrides was carried out. Informations obtained are encouraging the use of similar prediction schemes in order to identify new systems.From metallic thin films made by pulsed laser ablation, deposition difficulties and disparities in procedures have been put forward. Nonetheless, singular morphologies have been achieved by this process, opening new insights for designing novel materials
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Nicoletti, Sergio. "Elaboration et caractérisation de jonctions Josephson YBaCuO sur joints de grains artificiels." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10091.
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Cette these presente une etude de realisation et de caracterisation de jonctions josephson fabriquees a partir de joints de grains artificiels induits dans le film d'ybco. Deux procedes differents ont ete etudies: la fabrication du joint de grains par bi-epitaxie et le depot d'une couche supraconductrice sur substrat bi-cristallin. Le but du travail a ete de developper un procede de fabrication reproductible et d'etudier les proprietes des dispositifs obtenus. Les couches minces ont ete fabriquees par ablation laser pulse. Les dispositifs ont ete obtenus en gravant des lignes de differentes largeurs traversant le joint. Pour les echantillons realises par bi-epitaxie nous avons obtenus a travers un empilement de couches tampons adapte, le joint de grains dans l'ybco sur substrat de saphir ainsi que sur srtio3. Les mesures electriques ont mis en evidence que, pour ce type de joint, le courant josephson est trop faible et que la distribution de courant dans la jonction est inhomogene. Les limitations principales de cette technique sont liees aux contraintes imposes par l'angle de desorientation et par les defauts de fabrication. Pour les jonctions fabriquees sur bi-cristaux, les mesures en champ magnetique ont montre qu'un controle soigne de l'etat de la surface est necessaire pour avoir une barriere homogene. Ce resultat permet le controle de la jonction en regime flux flow. Les resultats preliminaires obtenus sur les transistors a flux de vortex josephson ont mis en evidence que ce type de dispositifs peut etre comme element amplificateur dans un circuit electronique supraconducteur
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Rothman, Johan. "Etude des propriétés structurales, électroniques et magnétiques des couches minces épitaxiées de cerium." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10019.
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Les proprietes structurales, electroniques et magnetiques de couches minces epitaxiees de cerium ont ete etudiees avec l'objectif de mieux connaitre l'element ce lui meme, ainsi que d'effectuer une premiere etude d'un systeme de basse dimensionnalite presentant des proprietes de type reseau kondo. Les couches ont ete preparees sous ultra-vide par depot laser pulse sur une couche tampon de w(110) ou de wnb(110), elle meme initialement epitaxiee sur un substrat d'al#2o#3(1120). Une nouvelle methode originale de croissance des couches tampon a ete developpee, qui permet une croissance parfaitement bidimensionnelle des les plus faibles epaisseurs. Les couches de ce croissent dans la phase gamma (cfc) selon les plans (111), avec une relation d'epitaxie de type nichiyama-wassermann. Aucune deformation n'a pu etre etablie dans toute la gamme d'epaisseur etudiee. Une etude de diffraction x en geometrie planaire a montre que la phase gamma est conservee a basse temperature. La conservation de la phase gamma a ouvert la voie a l'etude approfondie des proprietes physiques de cette phase dans des couches minces. Les proprietes magnetiques et de structure electronique ont ete estimees a partir de mesures de spectroscopie d'absorptions des rayons x (xas) en lumiere polarisee circulairement (xmcd) aux seuils m#4#,#5dece. Les dependances thermiques de l'ensemble des grandeurs physiques correspondantes revelent la presence d'un effet de type impurete kondo couple a des effets de champ cristallin, l'intensite de ce champ differant a l'interface et dans le massif. Les mesures de resistivite magnetique amenent aux memes conclusions mais elles revelent en plus des effets specifiques associes a la presence d'un reseau kondo-anderson. Aux bassees epaisseurs une augmentation importante de la resistivite magnetique est observee, induite par des phenomenes d'interference entre, d'une part, l'effet kondo et, d'autre part, les interactions entre les electrons et la localisation faible.
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Dewitt, Matthew Ryan. "Strategies for Overcoming Shortcomings of Thermal Ablations: A Comprehensive Study of Nanoparticle Transport During Photothermal Chemotherapy Treatments, and High Frequency Irreversible Electroporation." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/80302.
Full textAbstract:
Cancer continues to be a leading cause of death worldwide despite the increasing
research advances into novel treatments. Thermal ablation of tumors is a relatively
established method for the destruction of many tumor types, despite inherent
shortcomings including incomplete tumor treatment and non-specific treatment. Novel
therapies are currently studied including nanoparticle-based therapies to overcome these
limitations. One field of research is focused on utilizing non-lethal hyperthermia to
enhance carried chemotherapeutic drugs. Additionally a novel field of non-thermal
ablations termed Irreversible Electroporation has recently been developed to treat tumors
by irreversibly destroying cell membrane function through short electrical pulses.
The goal of the present study is to research two novel potential treatments for
cancer that do not require thermal destruction of tissue. Firstly, we developed and tested
novel ways to load the antineoplastic agent Cisplatin into SWNHs to test the ability to
thermally enhance carried drugs with non-lethal, mild hyperthermia. We attached the
imaging agent Quantum Dots (QDs) to the particles to understand how hyperthermia
affects cellular uptake, minimizing thermal enhancement. Results of this study highlight
the need for better biomimetic in vitro models of the tumors to study how hyperthermia
affects tissue level transport of nanoparticles.
In the second aim we utilized a perfusable 3D collagen in vitro model of the tumor microenvironment, previously developed by our group to study tumor angiogenesis, to study nanoparticle transport. We demonstrated the ability of this model to study key mass transport obstacles nanoparticles face in the tumor including extravasation from a leaky, pro-angiogenic vasculature, diffusion in the extracellular matrix, and cellular uptake in a 3D environment. This model was then utilized in the third aim to study how mild hyperthermia affects transport of SWNHs. Results from this aim were valuable in showing the utility of the 3D in vitro model to controllably test the effects of external stimuli on transport of particles and shows how mild hyperthermia can selectively allow increased permeability of SWNHs in the tumor, increasing selectivity of nanoparticle transport to the targeted tissue.
Lastly, we tested the non-thermal ablation, high-frequency irreversible
electroporation (H-FIRE) in a 3D tumor platform and in an in vivo swine model to better
understand the ability of H-FIRE to produce repeatable destruction of hepatocellular
carcinoma, a disease state growing in incidence rate. We then used H-FIRE in an
outpatient treatment for infiltrative skin tumors in equines, showcasing the ability to
deliver high voltage, short duration pulses in a clinical setting without muscle
contractions.
Ultimately, the results of this study the engineering studies that must occur to
optimize novel treatments utilizing non-lethal hyperthermia, or non-thermal death
mechanism to treat cancer. The studies show the usefulness of more complex 3D in vitro
models of tumors for early development of novel therapies and the utility of in vivo
models to validate studies.Ph. D.
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Audigier, Chloé. "Modélisation de l’ablation radiofréquence pour la planification de la résection de tumeurs abdominales." Thesis, Nice, 2015. http://www.theses.fr/2015NICE4071/document.
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L'ablation par radiofréquence (ARF) de tumeurs abdominales est rendue difficile par l’influence des vaisseaux sanguins et les variations de la conductivité thermique, compliquant la planification spécifique à un patient donné. En fournissant des outils prédictifs, les modèles biophysiques pourraient aider les cliniciens à planifier et guider efficacement la procédure. Nous introduisons un modèle mathématique détaillé des mécanismes impliqués dans l’ARF des tumeurs du foie comme la diffusion de la chaleur et la nécrose cellulaire. Il simule l’étendue de l’ablation à partir d’images médicales, d’après lesquelles des modèles personnalisés du foie, des vaisseaux visibles et des tumeurs sont segmentés. Dans cette thèse, une nouvelle approche pour résoudre ces équations basée sur la méthode de Lattice Boltzmann est introduite. Le modèle est d’abord évalué sur des données de patients qui ont subi une ARF de tumeurs du foie. Ensuite, un protocole expérimental combinant des images multi-modales, anatomiques et fonctionnelles pré- et post-opératoires, ainsi que le suivi de la température et de la puissance délivrée pendant l'intervention est présenté. Il permet une validation totale du modèle qui considère des données les plus complètes possibles. Enfin, nous estimons automatiquement des paramètres personnalisés pour mieux prédire l'étendu de l’ablation. Cette stratégie a été validée sur 7 ablations dans 3 cas cliniques. A partir de l'étude préclinique, la personnalisation est améliorée en comparant les simulations avec les mesures faites durant la procédure. Ces contributions ont abouti à des résultats prometteurs, et ouvrent de nouvelles perspectives pour planifier et guider l’ARFThe outcome of radiofrequency ablation (RFA) of abdominal tumors is challenged by the presence of blood vessels and time-varying thermal conductivity, which make patient-specific planning extremely difficult. By providing predictive tools, biophysical models may help clinicians to plan and guide the procedure for an effective treatment. We introduce a detailed computational model of the biophysical mechanisms involved in RFA of hepatic tumors such as heat diffusion and cellular necrosis. It simulates the extent of ablated tissue based on medical images, from which patient-specific models of the liver, visible vessels and tumors are segmented. In this thesis, a new approach for solving these partial differential equations based on the Lattice Boltzmann Method is introduced. The model is first evaluated against clinical data of patients who underwent RFA of liver tumors. Then, a comprehensive pre-clinical experiment that combines multi-modal, pre- and post-operative anatomical and functional images, as well as the interventional monitoring of the temperature and delivered power is presented. This enables an end-to-end validation framework that considers the most comprehensive data set for model validation. Then, we automatically estimate patient-specific parameters to better predict the ablated tissue. This personalization strategy has been validated on 7 ablations from 3 clinical cases. From the pre-clinical study, we can go further in the personalization by comparing the simulated temperature and delivered power with the actual measurements during the procedure. These contributions have led to promising results, and open new perspectives in RFA guidance and planning
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陳岱屏. "The study of plasma-assisted laser ablation method." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/58873337771975612562.
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Chen, Yin-hao, and 陳胤豪. "The Study of ITO Ablation with Ultrafast Laser." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/32911170185009692936.
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碩士義守大學
機械與自動化工程學系碩士班
97
Indium tin oxide (ITO) is a material with high transparency and electric conductivity. Thin film ITO coatings are commonly used in flat panel displays, touch panels and other electronic devices as electrodes. The traditional patterning technique has used photolithography followed by wet etching process to ablate ITO on substrates. However, this technique involves complex multi-step processes and may induce chemical pollution. In this research, the laser direct-write patterning method is applied to the micromachining of ITO thin films on plastic substrates. Owing to the adiabatic heating characteristics of ultrafast laser, it is possible to complete the patterning process without damaging the substrates. The purpose of this study is to ideutify the proper processing parameters, namely the focal length, laser repetition rate and laser power, of a ultrafast laser machine, for the purpose of clean selective removal of the ITO films. The outcomes sre assessed by measuring the line width after processing using OM, observing the surface guality of ITO films and trench bottom using VMC, and calculating the laser energy density. The range of laser energy density that allowing clean ITO removal and good surface guality is obtained. In the experiments, the minimum lin width of 3.6μm with good surface guality and clean removal of ITO films is achieved by using the following processing parameters: platform moving speed 30mm/s, focal length -1.9mm, repetition rate 70kHz, and power 0.07W. This research shows when the laser energy density is in the range of 0.141~0.247J/cm2, the 120nm thick ITO film is completely removed without damaging the substrate.
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Chiang, M. J., and 蔣銘瑞. "Study on Synthesize Carbon Nnanotubes by Laser Ablation." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/60279919827394353263.
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Mei-YingChen and 陳玫瑛. "The Study of Femtosecond Laser Ablation for Inhomogeneous Biotissues." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/13718930559424780350.
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碩士國立成功大學
工程科學系專班
101
In this thesis, a developed femtosecond (1 fs =10-15 s) laser system is utilized to process drosophila’s head. The inhomogeneous biological tissue is covered by a shell which is constructed by chitonsan, scientific name is chitin. The shell is secreted by the epidermis and interconnected with the internal soft tissue. To consider the cross-section of drosophila’s head, the organization structure is heterogeneity definitely. In order to further study the inner brain tissue, the shell must be partially removed first. Therefore, the study of the drosophila machining is to investigate and optimal machining processing conditions for chitin to keep the inner tissue good enough for biological study. The advantage of femtosecond laser is that can processing with very low average power and very short pulse duration closing to the femtosecond or even sub-femtosecond in the focal point and result in strong peak power. In this thesis, the femtosecond laser system with the pulse width under 50 fs and through a high numerical aperture objective interacted with materials in local focal point may induce the nonlinear effect and two-photon excitation. In conjunction with three-dimensional scanning stage controlled by LabVIEW program and adjust the parameters of femtosecond laser machining processing and imaging system to achieve a more detailed machining result eventually. Through two photon excitation images, the improvements of machining results including edge sharpness, low thermal effect, and less contaminant are demonstrated.
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Yu, Feng-Er, and 余鳳兒. "Study on the Ablation Materials of Modified Polyurethane/Polysiloxane." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/93721519934054854739.
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博士國立中山大學
材料科學研究所
92
Hydroxyl terminated polybutadiene (HTPB) based polyurethanes (PUs) are low modulus materials and degrade easily at low temperature. Polycarbodiimide (PCDI) and polysiloxane (PSi) are reactive-type fillers when formed by carbodimidzation and sol-gel process, respectively. During the combustion, PCDI and PSi give off non-toxic, non-corrosive volatile gases, and finally form carbonaceous and siliceous chars. In this study, modified PUs were prepared by incorporating PCDI or PSi into PUs to give high carbon, nitrogen and silicon materials. These modified PUs are kinds of organic-inorganic hybrids with higher modulus and higher thermal stability than HTPB-based PUs. In addition, new silicone based insulation materials were prepared by mixing two silicone rubber materials LSR-2670 and RTV-627 from GE Silicones, in order to improve the heat insulation and to reduce the ablation rate. These inhibitors can keep the rocket motor from the high temperature ablation for a long time, especially castable silicone based heat insulations for the case of the ramjet engines. The mechanical properties at room temperature and the thermal stability of these modified PUs and silicone rubbers were investigated using a tensile tester and a thermogravimetric analyzer (TGA). ATR/FTIR (Attenuated total reflectance / Fourier transform infrared) technique is applied to monitor the synthesis process of PCDI and to examine the change of surface chemistry of insulator before and after thermal degradation via TGA. TGA coupled with FTIR (TGA/FTIR) was used to analyze the kinetics and the mechanism of thermal degradation under nitrogen and/or air. The Friedman and Kissinger methods of analysis were used for calculating the activation energy of degradation from dynamic TGA. The modified PUs (HIPTD-40%Psi及HIPTD-30%PMPS-PSi) with average activation energy of 88 and 112 kcal/mole (0.5＜α＜0.9, under N2) and the modified silicone rubber (LR-5%HTB) with activation energy of 46.2~67.0 kcal/mole (0.1＜α＜0.9, under N2) and 34.0~59.1 kcal/mole (0.1＜α＜0.9, under air).The maximum degradation temperature (Tmax) and char yield (CY) of thermal degradation were estimated from a series of experiments with heating rates of 1, 3, 5, 10, 20, 30, 40 and 50 ℃/min, under nitrogen or air. It is apparent that the maximum degradation temperature is dependent on heating rate. By assuming the heating rate for the insulator used in a rocket operating environment is about 5000℃/min, Tmax calculated for the modified PUs (HIPTD-40%PSi and HIPTD-30%PMPS-PSi under N2) are found as 538 and 562℃ and for the modified silicone rubber (LR-5%HTB under N2 and air) are found as 576 and 562℃, respectively. CY calculated for the modified silicone rubber (LR-5%HTB under N2 and air) is found as 71.5% and 66.2%. The morphology of modified PUs and silicone rubbers before and after thermal degradation via TGA was observed by optical and scanning electron microscope (SEM).
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Chen, Wei Chuan, and 陳韋銓. "Study on Tumor Ablation with OCT-Guided Laser Surgery." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/33k553.
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碩士長庚大學
電機工程學系
105
Cancer has become the top cause of death for several years in Taiwan. Also it take a large part in the death toll across the world. But if we can find tumor early and remove it clearly, cancer is possibly to be cure. Malignant tumor growth needs more nutrient. So when the tumor turns to malignant tumor. We can find the messy angiogenesis happened and observe the tumor structure changes by medical imaging technique, to recognize if the tumor lesion. Combining with medical imaging technique and surgery treatment to decrease the tumor size and remove all the tumor. Furthermore to avoid the tumor recurrent again, medical imaging technique can be helpful to follow up after operative. Optical coherence tomography (OCT) is a noninvasive, high speed, high resolution scanning technology, based on principle of interference. OCT can provide 2D/3D structure image without damage the sample. Currently OCT has wildly used in many clinical use, such as ophthalmology, dermatology, and Dentistry. In this thesis, we used OCT system as a medical imaging technique assist for cancer treatment. After tumor implanted into the mouse, we scanned 2D/3D image at the same region. In order to observe structure image and angiogenesis image. Furthermore, analyzed the characteristics of angiogenesis which caused by tumor growth, and quantified of vascular density information. We used OCT system guiding laser to treat the tumor, observed the structure image of ablation, and analyzed the laser thermal effect of angiogenesis. After the treatment finished, we still followed up the tumor region for several days by OCT system. Using the OCT system proposed in this thesis, we can observe the preoperative image, operative image and track the image after treatment. Besides with the guidance function, we can treat the specific small area, and also decline the side effect with other therapy. Moreover it can reduce time of treatment and so on…. According to the result, our system can effectively observe the malignant tumor growth, angiogenesis phenomenon, and guide laser to remove the tumor entire cells clearly.
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陳信孚. "A Study of Superconducting YSr2Cu3O7- Thin Films by Laser Ablation." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/06802182128383232204.
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碩士國立清華大學
材料科學工程學系
85
Superconducting YSr2Cu3O7－δ thin films were successfully synthesized on LaAlO3(100) and SrTiO3(100) substrates by pulsed laser deposition technique. The film deposited on LaAlO3(100) exhibited the superconducting transition at 70K and with zero resistivity at 57K. The stabilization of YSr2Cu3O7－δ structure by sbustrate materials, rather than partial substitution of transition metal elements into Cu site or fabrication at relatively high oxygen pressure, is also evident. The crystallinites, surface morphologies, and transport properties of the films are significantly influenced by the crystallographic structures and the unit cell dimensions of the underlying substrates. Transport behavior measurement under varioius magnetic fields shows the 2-D nature of the vortex dynamics in the YSr2Cu3O7－δ thin film being intrinsically identical to other high-Tc cuprates.
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Sashikanth, Aparna. "Microwave ablation of liver tumors experimental study and mathematical modeling /." 2002. http://catalog.hathitrust.org/api/volumes/oclc/51571065.html.
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Jia-Jhih, Yang, and 楊家治. "The Study of Silver Nano Wire Ablation with Fiber Laser." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/51596767209642411214.
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碩士中華科技大學
機電光工程研究所碩士班
102
In this study, using a 1064nm wavelength fiber laser equipment , replacing the traditional wet chemical processes for laser processing experiments. The way that the laser focused beam processes on conductive silver nanowire thin film , and removing the silver nanowire conductive layer without chemical pollutions . The main goal of the experiment is done under dry machining process after the laser process without damaging the flexible plastic substrate and complete the production of removing the Silver Nano wire conductive thin film which can insulate separated zone. Experimental methods for the removal of conductive material with laser dry machining and meets industry standards, then can plan and design laser equipment . Laser process parameters include：laser power (W), laser trigger distance (μm), the position of the laser focal length (mm), and then explore the laser process parameters affect the quality of the silver nanowires thin film removed. The results of the study on the thickness of 100nm silver nanowires conductive film, when the laser power of 12.56W and 15.55W, laser trigger distance 3μm, 4μm and 10μm, and the position of the laser focus 0.28mm, laser process to obtain the best quality and conform to the ideal processing line width 30μm, while silver nanowires conductive layer can be completely removed without damaging the plastic substrate , and is completely insulated.
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YU-LIN, HUNG, and 洪余林. "Study on the Ablation Efficacy of Er:YAG Laser on Human Dentin." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/87792392140690066892.
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碩士國立臺灣大學
臨床牙醫學研究所
90
Er:YAG lasers are the most popular solid lasers for dental clinic now. They produce much less vibration, noise and pain. However, they would cause harmful effects on the dentin surface when used under improper energy. The purpose of this study was to investigate the ablation efficacy of Er:YAG laser on human dentin. Moreover, we also evaluated the morphological compositional and phase changes of dentin surface after irradiation by different laser energy. Twenty five dentin specimens were used in part (I) of the study. After being ground, dentin surface was divided into four areas and were randomly divided into nine groups for subsequent different parameters of laser irradiation. Groups one to nine were irradiated by Er:YAG laser from 10J to 50J. The laser handpiece was mounted to make the tip perpendicular and 1 mm away from the dentinal surface. The specimen was then subjected to laser treatment for 10 seconds. All specimens in part (I) of the study were examined by scanning electron microscope(SEM) with the depth of each specimen evaluated. The aims of the part (II) of the study focus on the morphological changes of dentin surface after exposure to Er:YAG laser. The aims of the part (III) of the study consist of the evaluation of the compositional and phase changes of dentin surface under different energy of laser irradiation. The results revealed the depth of group (1) to group (9) as followed : (1):61.37(±9.29) μm、(2):231.28(±57.7) μm、(3):419.94(±121.76) μm、(4):578.39(±63.64) μm、(5):752.31(±115.23) μm、(6):930.36(±105.57) μm、(7):988.7(±32.46) μm、(8):1199.7(±69.7) μm、(9):1275.64(±90.89) μm . On laser-treated dentin, flaky, scaly, and rough surfaces were seen. The surfaces were clean with several morphological reliefs, which indicated that ER:YAG laser could selectively ablate the dentin structures. Crack lines and charring were shown on the samples of pulse energy over 350mJ group. Denti showed four peaks on the X-ray diffractometer corresponding to α- tricalcium phosphate (TCP) and β-TCP at 2θ=30.78 degrees/34.21 degrees and 32.47 degrees/33.05 degrees, respectively. In Fourier transforming infrared analysis, two absorption bands at 2200 cm-1and 2015 could be found on dentin treated by Er:YAG laser without water spray cooling. The results revealed the harmful effect on the dentin surface under powerful energy. Hence (in conclusion), we suggest the irradiation energy parameter of Er:YAG laser with water spray cooling that is the most appropriate for ablating the dentin is 300mJ/pulse- 10 pps-10 s.