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Durand, Thibaut. "Stratégies analytiques pour la caractérisation physico-chimique des particules ultrafines métalliques. Application aux aérosols ultrafins générés lors de procédés thermiques (fonderie, projection thermique)." Thesis, Pau, 2014. http://www.theses.fr/2014PAUU3057/document.
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Dans l’industrie, les sources d’expositions aux particules ultrafines (PUF) sont nombreuses et connues depuis longtemps. Ces particules quelles soient manufacturées ou non intentionnelles (générées au cours de procédés industriels) présentent des propriétés singulières qui impliquent des effets sur la santé différents de ceux induits par des particules de plus grande taille (micrométrique). L’étude spécifique des PUF nécessite donc le développement de méthodes de prélèvement et d’analyse adaptées permettant d’obtenir des informations pertinentes complémentaires à la masse totale de poussières prélevées. Cette métrique semblerait insuffisante pour caractériser correctement les effets toxiques des PUF. La thèse a donc été menée dans l’optique de disposer de méthodes dédiées à l’analyse des nanoparticules et en particulier sur la caractérisation chimique des particules en fonction de leur taille (couplage entre dispositifs de prélèvement en fonction de la taille des particules et méthode d’analyse). Les méthodes développées ont ensuite été testées sur des échantillons provenant soit de sites et/ou procédés industriels (fonderie, projection thermique) soit d’essais en laboratoire par prélèvement sur banc de génération de PUFExpositions to nanoparticles (NPs) are known in industrial hygiene for a long time. Either from primary or secondary sources (industrial processes), these particles have specific properties which imply different toxicities compared to larger particles (micrometric) from the same material. Therefore NPs study requires adapted sampling and analytical technique development and more specifically methods allowing to access relevant information other than total dust mass. The latter seems not be sufficient for toxic effect assessment. Thus, this work has been conducted in order to dispose of analytical methods dedicated to NPs and especially on size-dependent particle chemical analysis. Then, the developed methods have been applied on samples collected either from industrial sites and/or processes (smelter, thermal projection), either from NP generation bench
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Pešina, Zbyněk. "APLIKACE NANOMATERIÁLŮ PRO VÝVOJ PÁJEK BEZ OLOVA." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-234001.
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The present dissertation is motivated by the search for alternatives of lead-free soldering by nanoparticles of metals and their alloys. The research focuses on the possibility of replacing lead-free solders by nanoparticles. This issue is currently being addressed by the use of lead-free solders but their properties are not entirely equivalent to properties of lead-tin based alloys. The theoretical part of the dissertation first summarizes up-to date knowledge on the development of lead-free alloys currently used for soldering in the electronics. The work compares these lead-free solder candidates with previously used Pb-Sn alloys. The second section of the theoretical part is devoted to nanotechnology that offers possible solutions of problems associated with the use of lead-free solders. The text contains a description of the properties of nanocrystalline materials in comparison with those of compact alloys having the same chemical composition. The possibility of preparation of nanoparticles and potential problems associated with small particle sizes are also presented. Introduction of the experimental part focuses on the preparation of nanoparticles of pure metals and alloys by chemical and physical ways as well as on an instrumentation for characterisation and analysis. Attention is focused on the silver in nanoparticle form that exhibits the low temperature sintering effect, which is thermally activated by decomposition of oxide envelope covering the Ag nanoparticles. This factor is critical for low-temperature sintering and thus also for possible future applications. The thermal effects of the low sintering process were studied by methods of thermal analysis. The preparation of the Cu / Ag nano / Cu joints was carried out in-situ in inert atmosphere and under the action of atmospheric oxygen. In both cases varying conditions of thermal treatment were used. The cross sections of the prepared joints were then used for the metallographic analysis of the local mechanical properties of the resulting silver layer, for the chemical composition evaluation of the resulting layers of the joint, and for the microstructure study. Strength characteristics are represented by testing shear strength of individual joints.
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Walter, Aaron Joseph. "Approximate Thermal Modeling of Radiofrequency Cardiac Ablation." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd1002.pdf.
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Subramanian, Swetha. "Thermal Ablation Monitoring Using Ultrasound Echo Decorrelation Imaging." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1428068754.
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Andres, Matthias [Verfasser]. "Improving thermal ablation of liver tumors / Matthias Andres." München : Verlag Dr. Hut, 2021. http://d-nb.info/1235279383/34.
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Phipps, Jeffrey Howard. "Radiofrequency induced thermal endometrial ablation : invention and primary assessment." Thesis, University of Leicester, 1991. http://hdl.handle.net/2381/33169.
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The invention and development of Radiofrequency Endometrial Ablation (RaFEA) has been, by turns, exciting, frustrating and anxiety - provoking. Although one of the major motives for developing an alternative means of effective endometrial ablation to the hysteroscopically directed modalities was to improve safety, it seems that in using RaFEA, one set of potential dangers may have been exchanged for another set. Whilst the potentially fatal risks of uterine penetration and fluid toxicity are not encountered with RaFEA, the charging of the patient with an electric field for the duration of therapy brings its own risks, requiring very special precautions of their own (see section 2 - safety). At the time of writing, the future role of the technique is still being decided. It may be that the technique requires such specialist monitoring that it is unsuitable for general use, and may be restricted to one or two specialist centres for the treatment of certain patients who cannot be treated easily any other way. What is certain is that safety is of paramount importance, and the adequate training of those concerned and a basic knowledge of RF physics are both essential to safe practice. Practiced safely, the technique is highly successful, and has proved of considerable benefit to hundreds of patients. However, there have been a number of serious complications in other centres, each of which has been analysed in very great detail. These are considered in section 2 - safety.
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Kolen, Alexander Franciscus. "Elasticity imaging for monitoring thermal ablation therapy in liver." Thesis, Institute of Cancer Research (University Of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404968.
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Breen, Michael Scott. "TISSUE RESPONSE TO INTERVENTIONAL MRI-GUIDED THERMAL ABLATION THERAPY." Case Western Reserve University School of Graduate Studies / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=case1080938405.
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TUCCI, Claudio. "Modelling heat transfer in tissues treated with thermal ablation." Doctoral thesis, Università degli studi del Molise, 2021. http://hdl.handle.net/11695/100845.
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Thermal ablation is more and more recognized as an important alternative in cancer treatments, for which the most common procedures followed are surgery, chemotherapy, and radiotherapy. Nevertheless, these common techniques pose critical issues such as: they are too invasive for human body, they can reveal serious side effects and are expensive in terms of financial costs for the national health service. Thermal ablation of tumors, instead, is a minimally invasive treatment option for cancer, with certain advantages such as minor side effects, shorter hospital stays and consequently lower costs. It consists in focusing an energy source (commonly radiofrequency or microwave) in the target zone (the tumoral tissue) by means of a probe, that causes the tumor destruction. Generally, the complete necrosis of tissue happens instantaneously at temperatures over about 60 °C, but lower temperatures with longer exposure times can be achieved. The most common approach is a percutaneous treatment performed with the aid of imaging techniques. On the other hand, the main shortcoming of performing a thermal ablation is to not achieve the complete tissue ablation, so the risk of a tumor recurrence becomes higher. In this context, an in-depth knowledge of thermal therapy physics has a key role in modelling heat transfer in thermal therapies, in order to develop more and more accurate bioheat models for clinical applications, predicting the final necrotic tissue diameters and volumes. Moreover, the lack of experimentation in this field, makes bioheat models even more significant. The first simple bioheat model was developed in 1948 by Harry H. Pennes and it is still widely used, but it has some shortcomings that make the equation not so accurate. For this reason, over the years it has been modified and more complex models have been developed.
In this thesis work, a general overview of the different employed techniques in hyperthermia treatments of biological tissues and in particular tumors is first of all introduced, together with techniques used to estimate thermal damage.
Next, in the second chapter, a wide state-of-the-art of how the distinct bioheat models have been modified over the years when applied in various hyperthermia treatments of cancer, is described.
In chapter three, transient bioheat equations based on different bioheat models, such as Pennes’ model, and three porous media-based model are compared, where the porosity is the volume fraction of blood in the entire tissue domain. The considered porous media-based models are the Local Thermal Non-Equilibrium equations (LTNE), the Local Thermal Equilibrium equation (LTE), and the three-energy equations model. The models are implemented to a biological tissue modelled as a sphere with liver tissue properties. The effects of thermal ablation on the living tissue are included with a spherical energy source at the sphere center. Governing equations with the appropriate boundary conditions are solved with the finite-element software COMSOL Multiphysics®. Results are presented in terms of temperature profiles in the biological tissue, to appreciate differences due to the various bioheat models, concluding that LTNE model is preferable because it is a good compromise between accuracy and complexity.
Thus, in the next chapter, the LTNE model is applied to the same spherical biological model with tumoral properties, to investigate the pulsating energy source effects modeled with references to a cosine function with different frequencies, and such different heating protocols are compared at equal delivered energy, namely, different heating times at equal maximum power. The results are shown in terms of tissue temperature and percentage of necrotic tissue obtained. The most powerful result achieved using a pulsating heat source instead of a constant one is the decreasing of maximum temperature in any considered case, even reaching about 30% lower maximum temperatures. Furthermore, the evaluation of tissue damage at the end of treatment shows that pulsating heat allows to necrotize the same tumoral tissue area of the non-pulsating heat source. In addition, a more complex model is developed to study a pulsating protocols application for radiofrequency ablation (RFA) of in vivo liver tissue using a cooled electrode and three different voltage levels. Three distinct heat transfer models coupled to the electrical problem are compared: the simplest but less realistic Pennes’ equation and two porous media-based models, i.e., the LTNE and LTE models, both modified to take into account two-phase water vaporization (tissue and blood). Moreover, different blood volume fractions in liver are considered and the blood velocity is modeled to simulate a vascular network. The results in terms of coagulation transverse diameters and temperature fields at the end of the application show significant differences, especially between Pennes and the modified LTNE and LTE models at high voltage level. The new modified porous media-based models cover the ranges found in the few in vivo experimental studies in the literature and are closer to the published results with similar in vivo protocol. The same model is applied considering tumoral tissue surrounded by healthy tissue and the outcomes show relevant differences when the tumor is included in the model. Thus, the different electrical conductivity and thermal properties between the two types of tissues play a fundamental role in the outcomes.
In the final chapter five, the previous LTNE modified model is applied to a spherical tumoral tissue, in order to investigate the effects of different antennas configurations in thermal ablation. Single, double, and triple antennas arrangements are modelled in order to simulate the hepatic cancer treatment, which often requires the destruction of large volume lesions. Furthermore, different blood volume fractions and blood vessels are considered. The results show that using multiple antennas instead of a single antenna offers a potential solution for creating ablation zones with larger dimensions and to allow at the same time to have lower maximum tissue temperatures in all the cases compared to the single antenna configuration.
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Adams, Jacob James. "A coupled electromagnetic-thermal model of heating during radiofrequency ablation." Connect to resource, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1191454972.
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McWilliams, Brogan. "Approaches for improved precision of microwave thermal therapy." Thesis, Kansas State University, 2015. http://hdl.handle.net/2097/19088.
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Master of ScienceDepartment of Electrical and Computer Engineering
Punit Prakash
Thermal therapies employing interstitial microwave applicators for hyperthermia or ablation are in clinical use for treatment of cancer and benign disease in various organs. However, treatment of targets in proximity to critical structures with currently available devices is risky due to unfocused deposition of energy into tissue. For successful treatment, complete thermal coverage of the tumor and margin of surrounding healthy tissue must be achieved, while precluding damage to critical structures. This thesis investigates two approaches to increase precision of microwave thermal therapy. Chapter 2 investigates a novel coaxial antenna design for microwave ablation (MWA) employing a hemi-cylinderical reflector to achieve a directional heating pattern. A proof of concept antenna with an S₁₁ of -29 dB at 2.45 GHz was used in ex vivo experiments to characterize the antennas’ heating pattern with varying input power and geometry of the reflector. Ablation zones up to 20 mm radially were observed in the forward direction, with minimal heating (less than 4 mm) behind the reflector. Chapter 3 investigates the use of magnetic nanoparticles (MNP) of varying size and geometry for enhancing microwave tissue heating. A conventional dipole, operating at 2.45 GHz and radiating 15 W, was inserted into a 20 mm radius sphere of distributed MNPs and heating measurements were taken 5 mm, 10 mm, and 15 mm radially away. A heating rate of 0.08°C/s was observed at 10 mm, an increase of 2-4 times that of the control measurement. These approaches provide strong potential for improving spatial control of tissue heating with interstitial and catheter-based microwave antennas.
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Chen, Xin. "MRI MONITORING AND MODEL PREDICTION OF THERMAL ABLATION DYNAMICS IN TISSUE." Case Western Reserve University School of Graduate Studies / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=case1166155662.
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Krupka, Tianyi M. "DESIGN OF CONTROLLED AND TARGETED THERMAL SENSITIZER FOR ENHANCING RADIOFREQUENCY ABLATION." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1275655694.
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Li, Yifan Li. "NANOSCALE THERMAL CHARACTERIZATION BY SCANNING THERMAL MICROSCOPY (STHM)." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron159057422807603.
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Fu, Rui. "Thermo-Mechanical Coupling for Ablation." UKnowledge, 2018. https://uknowledge.uky.edu/me_etds/111.
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In order to investigate the thermal stress and expansion as well as the associated strain effect on material properties caused by high temperature and large temperature gradient, a two-way thermo-mechanical coupling solver is developed. This solver integrates a new structural response module to the Kentucky Aerothermodynamics and Thermal response System (KATS) framework. The structural solver uses a finite volume approach to solve either hyperbolic equations for transient solid mechanics, or elliptic equations for static solid mechanics. Then, based on the same framework, a quasi-static approach is used to couple the structural response and thermal response to estimate the thermal expansion and stress within Thermal Protection System (TPS) materials.
To better capture the thermal expansion and study its impacts on material properties such as conductivity and porosity, a moving mesh scheme is also developed and incorporated into the solver. Grid deformation is transferred among different modules in the form of variations of geometric parameters and strain effects. By doing so, a bi-direction information loop is formed to accomplish the two-way strong thermo-mechanical coupling.
Results revealed that the thermal stress experienced during atmospheric re-entry concentrates in a banded area at the edge of the pyrolysis zone and its magnitude can be large enough to cause the failure of the TPS. In addition, thermal expansion causes the whole structure to deform and the changes in material properties. Results also indicated that the impacts coming from structural response should not be ignored in thermal response.
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Reynoso, Francisco J. "Modeling of near infrared laser-mediated plasmonic heating with optically tunable gold nanoparticles for thermal therapy." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45966.
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Clinical hyperthermia refers to treatment of tumors by heating the lesions between 40 and 45° C. Several clinical trials have demonstrated that hyperthermia provides significant improvements in clinical outcomes for a variety of tumors, especially when combined with radiotherapy. However, its routine clinical application is still not optimal and major improvements are needed. The temperature distributions achieved are far from satisfactory and improved temperature control and monitoring are still in need of further development.
The use of gold nanoparticles (GNPs) has emerged as a good method to achieve local heat delivery when combined with near-infrared (NIR) laser. GNPs have a plasmon resonance frequency that can be tuned to absorb strongly in the NIR region where tissue absorption of laser light is minimal, allowing for less tissue heating and better penetration. For further development of the technique and appropriate clinical translation, it is essential to have a computational method by which the temperature distribution within the tumor and surrounding tissue can be estimated. Previously, our group developed a technique to estimate the temperature increase in a GNP-filled medium, by taking into account the heat generated from individual GNPs. This method involved a two-step approach combining the temperature rise due to GNPs and the solution to the heat equation using the laser light as heat source. The goal of this project was to develop a one-step approach that calculates the temperature distribution using the solution to the heat equation with multiple heat source terms, the laser light, and each individual GNP. This new method can be of great use in
developing a treatment planning technique for GNP-mediated thermal therapy including hyperthermia.
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Chapman, Rudy T., Katherine C. Burgess, Russ W. Brown, and Diego J. Rodriguez-Gil. "Axonal regrowth of olfactory sensory neurons after chemical ablation with methimazole." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/asrf/2018/schedule/17.
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The olfactory system is of great interest in research due to the olfactory epithelium’s regenerative capability and as a potential as a source of neural stem cells. The olfactory sensory neurons are constantly being replaced by the stem cells that lie at the base of the olfactory epithelium. These stem cells also remain intact after an injury to the epithelium and lead to the regeneration of the olfactory epithelium. We have developed a fate mapping technique to trace axonal regrowth from newly born olfactory sensory neurons using an inducible Cre-ERT2 model after chemical ablation by the drug methimazole. Our data shows that newly generated olfactory sensory neurons labeled 1 day after chemical ablation by injection of 4-HO-tamoxifen extend an axon that reaches the olfactory bulb and extend to the glomeruli in a timeline that is consistent with control mice that received 4-HO-tamoxifen but were injected with saline 1 day prior. In addition, we assessed the functional recovery of the olfactory epithelium by testing the ability of mice to find a hidden cookie after methimazole injection. Mice were tested at 3 and 14 days post methimazole. There was a severe impairment in the ability to find a hidden cookie at 3 days post methimazole. The mice tested at 14 days post methimazole showed an improvement in the ability to find the cookie but the latency to find the cookie was still significantly higher than controls. In conclusion, while we demonstrate that axons extend to the olfactory bulb and the glomeruli earlier than 14 days, our behavioral data suggest that there must be a critical number of axons that must reach each specific glomerulus to regain function of the olfactory system.
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Abbass, Mohamed A. M. S. "Real-time Control of Ultrasound Thermal Ablation using Echo Decorrelation Imaging Feedback." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535468911083998.
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Shepherd, Amanda Claire. "The role of endovenous thermal ablation in the treatment of varicose veins." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/9035.
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Varicose veins are a common problem affecting approximately 30% of the Western population. The majority of patients present to secondary care complaining of a number of commonly experienced symptoms, however, some present with severe complications of venous disease including venous ulceration. For hundreds of years varicose veins have been treated with compression and surgery. In the last decade, technological advances have lead to the introduction of minimally invasive therapies for varicose veins, with the aim of providing rapid treatment with minimum discomfort to the patient at acceptable cost to the healthcare provider. This study examined the current use of endovenous ablation procedures in the United Kingdom amongst consultant vascular surgeons using an online questionnaire and also explored the patient’s views regarding treatment of varicose veins and potential therapeutic options. Prior to conducting a randomised clinical trial comparing early outcomes following laser and radiofrequency ablation in patients with primary varicose veins, an observational pilot study was carried out in the department. In parallel, the use of disease specific quality of life tools were compared to clinical, anatomical and haemodynamic outcome measures in this cohort of patients. The findings of the study have shown that although endovenous ablation procedures appear to be increasing in popularity, traditional surgery remains the most frequently performed procedure. Overall, patients overall have little knowledge of potential treatment options and the majority would be in favour of a single treatment under a local anaesthetic. However, most would be strongly influenced by the advice and opinion of the surgeon to whom they were referred. Results from the pilot study and a randomised clinical trial showed that radiofrequency ablation is significantly less painful than laser ablation for up to 10 days post procedure. Clinical improvements and gains in quality of life were significantly improved at 6 weeks and 6 months post intervention compared with baseline scores and were comparable between the groups. No significant difference was observed in anatomical outcomes between the two treatments. Although radiofrequency may be less painful than laser ablation, both endovenous thermal ablation treatments result in significant improvements in quality of life and are likely to become increasingly popular in the future.
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O'Neill, David Patrick. "Mathematical modelling of the effects of hepatic radiofrequency ablation." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:b9ff47fd-0e1a-4ca6-a937-a7e4d49841ba.
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Liver cancer is a major cause of death worldwide and the impact that it has is set to increase in the coming decades. More than half a million cases are diagnosed each year and it is likely many more sufferers are dying unidentified in parts of the world with poor healthcare. Survival rates for untreated cases after diagnosis are low with few patients living beyond one year. A key cause for low survival rates being that the standard treatment is surgical resection; fewer than one quarter of patients are suitable for invasive surgery and five year survival rates rarely exceeds 66 %. RadioFrequency Ablation (RFA) is a minimally invasive technique which utilises the electrically resistive property of tissue to deposit heat energy locally in the vicinity of the tips of an RFA needle. Heat is transferred away through the tissue by conduction, convection of large blood vessels, and bulk flow of blood in smaller vessels. Liver cells, both cancerous and benign, when exposed to the resultant abnormally high temperatures die considerably more rapidly than in cases of natural hyperthermia. It is thus the radiotherapist’s objective to place the RFA needle in a position that maximises destruction of tumour cells, but minimises the collateral damage of surrounding healthy cells. The learning curve of this nontrivial task is reflected unfavourably in the statistics that relate patient survival rate to clinician experience. In this thesis two mathematical models are presented that could be combined into a ‘global’ model of the effects of RFA. To predict cell death in these conditions under RFA, the O’NeillModel is presented in which cells are accounted for by one of three states: alive, vulnerable, and dead. A mechanistic interpretation of the O’Neill Model is attained through comparison to a model from the literature. A known, but little investigated occurrence of tissue swelling in the annular region peripheral to the ablation volume is modelled in a novel way through equations from the literature that track ion transport across the cell membrane; the O’Neill Model for cell death is also incorporated into this model of oedema.
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Fadigati, Luca. "Numerical investigation of charring thermal protection pyrolysis and ablation in solid rocket motors." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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The solid rocket propulsion is a simple and reliable system, it is less complex than liquid propulsion because it does not require tanks, pumps and the propellant is already stored into the combustion chamber. The main issues are the lower propulsive performance and the lack of controllability. The solid rocket motor thrust can be controlled only moving the nozzle direction of few degrees while its magnitude can not be controlled, therefore it is very important to well know the thrust profile because there is no possibility to control its magnitude during the flight. The thrust shape can be obtained experimentally or performing simulations. The first way is quite expensive therefore the second one is preferable. The tool ROBOOST (ROcket BOOst Simulation Tool), developed by the university of Bologna propulsion laboratory in collaboration with Avio S.p.A., already achieves the goal to predict the thrust profile during the ignition phase and the combustion one. But it fails to follow the experimental curve in the tail-off, underestimating the residual thrust. This discrepancy can be due to different phenomena that are not considered in the this simulation: heat coming from the nozzle, heat coming from slugs and the mass flow rate due to the thermal protection pyrolysis and ablation. This thesis focuses on simulate thermal protection pyrolysis and ablation obtaining their behavior when they are exposed to the hot gases of the combustion chamber.
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Bäck, Leif. "The use of radiofrequency thermal ablation for the treatment of upper airway disorders." Helsinki : University of Helsinki, 2003. http://ethesis.helsinki.fi/julkaisut/laa/kliin/vk/back/.
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Dec, John A. "Three dimensional finite element ablative thermal response analysis applied to heatshield penetration design." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/39588.
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Heatshield design and analysis has traditionally been a decoupled process, the designer creates the geometry generally without knowledge about how the design variables affect the thermostructural response or how the system will perform under off nominal conditions. Heatshield thermal and structural response analyses are generally performed as separate tasks where the analysts size their respective components and feedback their results to the designer who is left to interpret them. The analysts are generally unable to provide guidance in terms of how the design variables can be modified to meet geometric constraints and not exceed the thermal or structural design specifications. In general, the thermal response analysis of ablative thermal protection systems has traditionally been performed using a one-dimensional finite difference calculation. The structural analyses are generally one, two, or three-dimensional finite element calculations.
In this dissertation, the governing differential equations for ablative thermal response are solved in three-dimensions using the finite element method. Darcy' Law is used to model the flow of pyrolysis gas through the ablative material. The three-dimensional governing differential equations for Darcy flow are solved using the finite element method as well. Additionally, the equations for linear elasticity are solved by the finite element method for the thermal stress using temperatures directly from the thermal response calculations.
This dissertation also links the analysis of thermal protection systems to their design. The link to design comes from understanding the variation in the thermostructural response over the range of the design variables. Material property sensitivities are performed and an optimum design is determined based on a deterministic analysis minimizing the design specification of bondline temperature subject to appropriate constraints. A Monte Carlo simulation is performed on the optimum design to determine the probability of exceeding the design specifications. The design methodology is demonstrated on the Orion Crew Exploration Vehicle's compression pad design.
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Merchant, Tushar Praful. "Modelling of rapid thermal processes." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11784.
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Ruschman, Chad. "Chemical tuning of thermal expansion in oxides." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34778.
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This work focuses on the chemical substitution of cations and anions in the frameworks of materials that have been known to exhibit negative thermal expansion (NTE). Zr2(PO4)2(SO4) is a member of the A(2)M(3)O(12) family which has been known to exhibit NTE. We have shown that Zr2(PO4)2(SO4) exhibits anisotropic positive thermal expansion. We have also shown that this material has been characterized in the wrong space group. Hf2(PO4)2(SO4) behaves similarly to Zr2(PO4)2(SO4) and follows this trend. Under pressure, Hf2(PO4)2(SO4) appears to undergo a phase transition. We have still yet to determine what space group the materials transitions to. While many members of the AX(2)O(7) family of frameworks have been fully characterized, the thermal expansion of PbP2O7 has yet to be reported. We were unable to obtain a reproducible procedure for synthesis of PbP2O7 from its precursor. Finally, variable temperature and variable pressure studies were performed on ZrMo2O8 in an attempt to learn more about the local structure. We found that space groups P213 and Pa-3 gave poor fits of the local structure at low r. Behavior of the nearest neighbor Zr-Mo distance was very similar to the bulk CTE. On compression, pressure induced amorphization is observed in ZrMo2O8. All interatomic correlations above 4 angstroms are washed out. Zr-O-Mo linkages remain well defined and do not massively deform as the pressure is increased. Finally, we we observed that Zr-O-Mo linkages change geometry reversibly as the pressure is increased.
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Melissa, Agustin. "Thermal Stabilization of Nanocellulose by Chemical Modification." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225674.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第20449号
農博第2234号
新制||農||1050(附属図書館)
学位論文||H29||N5070(農学部図書室)
京都大学大学院農学研究科森林科学専攻
(主査)教授 矢野 浩之, 教授 木村 恒久, 教授 髙野 俊幸
学位規則第4条第1項該当
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Lee, Jeong Woo. "Physical enhancement of transdermal drug delivery: polysaccharide dissolving microneedles and micro thermal skin ablation." Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/33920.
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Transdermal drug delivery system has been limited to small and lipophilic drugs because skin has the intrinsic function to protect the body preventing entry of the external species into the body. In this thesis, two physical methods were studied to overcome the skin barrier in the controlled breakage of the skin barrier and to deliver macromolecules-based drugs through the skin; (1) polysaccharide dissolving microneedles and (2) micro thermal skin ablation.
Polysaccharide dissolving microneedles system was designed to break the skin barrier in a minimized size with the mechanically poor material, to release them into skin with the dissolution of microneedles, and to deliver human growth hormone into the living hairless rats. Micro thermal skin ablation was designed to fabricate the device generating the energy impact with the basis of arc discharge, to transfer the energy impact on the skin, to remove stratum corneum selectively with three-dimensionally controlled manner, and to deliver hydrophilic macromolecules through skin.
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Simsek, Bugra. "Ablation Modeling Of Thermal Protection Systems Of Blunt-nosed Bodies At Supersonic Flight Speeds." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615414/index.pdf.
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The objective of this thesis is to predict shape change due to ablation and to find temperature distribution of the thermal protection system of a supersonic vehicle under aerodynamic heating by using finite element method. A subliming ablative is used as thermal protection material. Required material properties for the ablation analyses are found by using DSC (Differential Scanning Calorimetry) and TGA (Thermogravimetric Analysis) thermal analysis techniques. DSC is a thermal analysis technique that looks at how a material's specific heat capacity is changed by temperature and TGA is a technique in which the mass of a substance is monitored as a function of temperature. Moreover, oxyacetylene ablation tests are conducted for the subliming ablative specimens and measured recession values are compared with the analytically calculated values. Maximum difference between experimental results and analytical results is observed as 3% as seen in Table 7. For the finite element analyses, ANSYS Software is used. A numerical algorithm is developed by using programming language APDL (ANSYS Parametric Design Language) and element kill feature of ANSYS is used for simulation of ablation process. To see the effect of mesh size and time step on the solution of analyses, oxyacetylene test results are used. Numerical algorithm is also applied to the blunt-nosed section of a supersonic rocket which is made from subliming ablative material. Ablation analyses are performed for the nose section because nose recession is very important for a rocket to follow the desired trajectory and nose temperature is very important for the avionics in the inner side of the nose. By using the developed algorithm, under aerodynamic heating, shape change and temperature distribution of the nose section at the end of the flight are obtained. Moreover, effects of ablation on the trajectory of the rocket and on the flow around the rocket are examined by Missile DATCOM and CFD (computational fluid dynamics) analysis tools.
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Devarakonda, Surendra B. "Enhanced Thermal Ablation of Biomaterials Using High-Intensity Focused Ultrasound (HIFU) Energized Nano-particles." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1544001995977567.
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Corbin, Nadège. "Interventional magnetic resonance elastography dedicated to the monitoring of percutaneous thermal ablations." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAD047/document.
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Les ablations thermiques percutanées guidées par IRM sont actuellement contrôlées en temps réel grâce à la thermométrie IRM. Cependant, aucune information directement associée aux changement de propriétés intrinsèques du tissu n’est disponible pendant la procédure. Ces travaux offrent la possibilité d’un monitorage plus complet des ablations thermiques grâce à l’Elastographie par Résonance Magnétique (ERM) combinée à la thermométrie IRM. Le système proposé est composé d’un excitateur à aiguille, d’une séquence d’encodage du mouvement synchronisée sur la respiration et d’une méthode de reconstruction en temps réel de carte d’élasticité et de température. Les changements d’élasticité et de température se produisant lors d’ablations thermiques par laser ont été mesurés in vivo en temps réel avec succès grâce à ce système. Une nouvelle méthode de traitement des données ERM sans reconstruction d’images de phase est aussi proposée afin de s'affranchir d'étapes conventionnelles fastidieusesMR-guided percutaneous thermal ablations are currently monitored by MR thermometry. However, no information related to intrinsic property changes of the tissue is available during the procedure. The feasibility of monitoring in vivo thermal ablations by simultaneous Magnetic Resonance Elastography (MRE) and MR-thermometry is demonstrated in this work. The interventional MRE system includes a needle MRE driver, a respiratory triggered gradient-echo sequence with motion encoding, and an online reconstruction method that provides elasticity and temperature measurements in real-time. Changes in elasticity and temperature occurring during laser thermal ablations were successfully measured in vivo thanks to this interventional MRE system. An innovative method for MRE data processing without phase image reconstruction is also proposed in order to avoid challenging steps of the conventional process
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Brodin, Ida. "Chemical Properties and Thermal Behaviour of Kraft Lignins." Licentiate thesis, KTH, Fibre and Polymer Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11010.
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Research concerning lignin has increased during the last years due to its renewability and ready availability in black liquor at pulp mills. Today, the kraft lignin found in black liquor is used as a fuel to gain energy in the recovery boiler at the mill. However, a new isolation concept, LignoBoost®, has enabled isolation of part of the lignin while allowing the use of black liquor as a fuel. This isolated lignin can be utilised as a fuel in, for example, thermal power stations or further upgraded to more value-added products. In this context, the most interesting value-added product is carbon fibre. The demand for carbon fibre has increased, but the biggest obstacle for a more extended use is the high production cost. About half of the production cost is related to the raw material.
In this work, the possibility of using kraft lignin as a precursor for carbon fibre production has been investigated through fundamental studies. Kraft lignins originating from birch, Eucalyptus globulus, softwoods and softwoods from liner production have been studied. By separating the lignin while still in solution in the black liquor, unwanted large particles such as carbohydrates can easily be removed. After isolation according to the LignoBoost process and purification with the use of an ion-exchanger, the lignins have been both chemically and thermally characterised. Identification of the released compounds at different temperatures has been performed because only 40% of carbon relative to original lignin remains, down from theoretical 60% after thermal treatment up to 1000°C. The main released compounds were phenols, as revealed by pyrolysis-GC/MS. Additionally, a pre-oxidation was done in order to try to stabilise the lignins. It was shown that an oxidation prior to the thermal treatment increases the yield by more than 10% and that the main release of compounds takes place between 400°C and 600°C. Fractionated lignin is better qualified as raw material for carbon fibre production because it is purer and its softening temperature can be detected. Fractionated kraft lignins from all investigated wood sources have high possibilities to act as precursors for the manufacture of carbon fibre.
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Free, M. Benton. "Thermal modulation of microcalorimetric sensors for chemical analysis /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/8628.
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Shafiei, Rami. "Thermal imaging of tetrahydrofuran hydrates heat spread." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=95244.
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The research of gas hydrates has always been of industrial and scientific interests as their formation pose problems to the oil/gas industry while they also present a future energy resource as methane hydrates naturally occur in the earth crust. In the present study, Infrared imaging technology is utilized to observe and study heat spread of the formation and decomposition of tetrahydrofuran (THF) hydrates. Also, using infrared imaging technology, hydrates crystals are observed in the presence of poly(N-vinylpyrrolidone) (PVP) to study the crystals growth in presence of a kinetic inhibitor. THF was utilized due to its easy attainability conditions which make them suitable for lab experiments.La recherche des hydrates de gaz a toujours été des intérêts industriels et scientifiques que leur formation poser des problèmes à l'industrie pétrolière / gaz alors ils présentent également une ressource énergétique future que les hydrates de méthane se produisent naturellement dans la croûte terrestre. Dans la présente étude, la technologie d'imagerie infrarouge est utilisée pour observer et étudier la propagation de la chaleur de la formation et la décomposition de tétrahydrofurane (THF) hydrates. En outre, en utilisant la technologie d'imagerie infrarouge, les hydrates de cristaux sont observés dans la présence du poly (N-vinylpyrrolidone) (PVP) pour étudier la croissance des cristaux en présence d'un inhibiteur de cinétique. THF a été utilisé en raison de ses conditions attainability facile qui les rendent aptes à des expériences de laboratoire.
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Hong, Yu. "Microwave-enhanced thermal processing of algae." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/46682/.
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Algae are promising substitutes to the widely-used fossil fuels. The thermochemical conversion of algae has been investigated extensively in the past two decades. In this study, systematic investigation of microwave-enhanced pyrolysis of algae together with catalytic reforming was conducted aiming at developing a new approach for the production of more syngas-enriched gas product from algae and other marine biomass. Firstly, the characterisation of algae was conducted to show the nature of the raw materials followed by the kinetic study of the decomposition of a suite of micro- and macro-algae, i.e., spirulina, chlorella and porphyra. The kinetic study was carried out using model algae, i.e. the use of ovalbumin as protein, oil droplets as lipid and cellulose as polysaccharides or carbohydrate to simulate a real alga. The thermogravimetric characteristics of algal samples were studied based on the analysis of TG and DTG curves. Kissinger-Akahira-Sunose method was used to derive the activation energy and pre-exponential factor. Moreover, the optimal reaction mechanism was determined by using Coats-Redfern method of the decomposition of different samples. The morphology and composition of char after TG analysis were characterised by using SEM/EDS. By comparing the characteristics of chars prepared in N2 and CO2 atmosphere, it was found that CO2 atmosphere favored the pyrolysis of algal protein with lower required activation energy (about 235 kJ mol-1) and shortened the pyrolysis time by 5.9-20.2%. But it was also found that the algal lipid increased the difficulty for the pyrolysis of algae with relatively higher activation energy around 200 kJ mol-1 (>180 kJ mol-1 under N2). However, the activation energy of cellulose decomposition remained almost the same around 310 kJ mol-1 in N2 and CO2. Therefore, CO2 atmosphere is more suitable for the pyrolysis of algae with high protein content and low lipid content. It was also found that protein in algae decomposes first, which is followed by the decomposition of carbohydrates and then lipids. Secondly, in order to obtain a high yield of syngas-enriched gas product from algae, microwave-enhanced pyrolysis of algae (spirulina, chlorella, dunaliella, laminaria and porphyra) and primary model algal compounds, i.e. cellulose and ovalbumin, at 400, 550 and 700°C in N2 atmosphere was conducted. The distribution and composition of gaseous, liquid and solid products were also studied in detail. Amongst the five algae, porphyra is the most promising raw material for high syngas-enriched gas production with more than 85 wt.%, while protein-rich spirulina and chlorella favored bio-oil production which yielded in about 10 wt.%. Meanwhile, with 94 wt.% carbohydrate, dunaliella converted most of its carbohydrates into C1-C3 gases. With a high portion of incombustible components (14.7-23.3 vol.% of CO2), laminaria has relatively lower gaseous production which was less than 80 wt.%. It also found that the optimal pyrolysis temperature was in the range of 400 to 550 °C for most of the samples except for spirulina which was at 700 °C. For the production of bio-oil, microalgae, with high protein content, were favored to be the raw materials (oil yield of 5.2-15.4 wt.%), compared to macroalgae (oil yield of 1.8-5.2 wt.%). Moreover, microalgae- spirulina and chlorella-favoured the formation of more phenols and nitrogenated compounds (10.8-17.8% and 20.9- 28.7% respectively) primarily from protein content, while less PAHs of 11.4-29.9% which mainly derived from algal carbohydrates. Finally, microwave-enhanced reforming of algae under CO2 atmosphere was conducted at 400, 550 and 700°C, together with the comparison of the results including the distribution and composition of gas, bio-oil and char in N2 and CO2 atmospheres. Compared with the product distribution derived under N2, the bio-oil yield from most algae in CO2 increased by 50- 170%, whilst the production of gas slightly decreased by 1-7%. Under CO2 atmosphere, the syngas in spirulina and chlorella gas product dramatically decreased by 60.8-69.7% and 7.1-17.6% respectively, while that from dunaliella increased by 23.4-30.4%. The percentage of syngas for the other samples remained similar. For the bio-oil derived from all the five algae samples, there were nearly no PAHs contained. In addition, the ash of algae was used as catalyst and introduced into the pyrolysis of five algae respectively under N2 atmosphere at 550°C. Compared with the non-catalytic pyrolysis, the weight percent of char from most algae increased by 20-90% using laminaria and porphyra ash, due to the decomposition of compounds in bio-oil. The syngas percentage from microalgae significantly increased by 6-45%, while that from macroalgae slightly decreased by 2-15% with the addition of spirulina, chlorella and porphyra ash. The content of PAHs in the bio-oil of spirulina, chlorella, laminaria and porphyra considerably reduced by 29-94%, while the amount of aromatics from spirulina and chlorella increased to around 1.3-7.1 times. In summary, the microwave-enhanced pyrolysis of algae favored the production of more CO/H2 rich gas at lower pyrolysis temperature under N2 atmosphere, while under CO2 atmosphere the yield of bio-oil increased. With the addition of algal ash as catalysts, the CO+H2 percentage in gas production from microalgae increased significantly. Therefore, it can be concluded that the microwave-enhanced pyrolysis of algae is an effective and efficient process for the conversion of algal biomass into value-added fuels.
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Tang, Chen. "Novel Performance Evaluation Method for Electrosurgical Ablation by Monopolar Hot Biopsy Forceps." Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1461217424.
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Oberste, Berghaus Jürg. "Substrate bias assisted RF thermal plasma diamond deposition." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37803.
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Polycrystalline diamond films are produced by chemical vapor deposition (CVD) in a r.f.-induction thermal plasma system. A dc bias voltage between -400 V and +500 V is applied to the deposition substrate. This is made possible by maintaining the reactor environment at ground potential and introducing a high-impedance, high-power filter network, eliminating the r.f. voltage drop across the plasma-probe junction. The Ar, H2, CH4 plasma (8.45% H2, 0.21% CH4) impinges on a molybdenum substrate probe (5 mm in diameter) in stagnation point flow. The resulting diamond films are analyzed by Scanning Electron Microscopy (SEM) and Raman Spectroscopy. The initial nucleation density is enhanced at negative bias voltage. However, this comes at the expense of degradation in crystalline quality. Positive voltage improves the quality and augments the film growth rate. A threefold increase in linear growth rate is attained at +500 V as compared to the unbiased case. The growing diamond film is used as an electrical and thermal probe. Electron emission currents from the developing diamond structures are exploited to monitor the film evolution during deposition. Diamond nucleation and growth stages are identified, and the bias voltage is varied in-situ to adjust to the changing growth requirements. A numerical simulation and optical emission spectroscopic measurements are used to characterize the plasma free stream as well as the boundary layer region between the plasma and the substrate. Current-voltage characteristics of the substrate are interpreted, and electrical probe theory is applied. It is shown that at negative bias the plasma-substrate interface is described by an expanding collision-dominated sheath imbedded inside the chemically reacting thermal boundary layer. Contrary to dc arcjet CVD, there is no secondary discharge created in the r.f. system at positive bias voltage. Also, the role of ion bombardment at negative bias is shown to be of little importance. It is infer
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Ortiz, Luis G. "Design of a chemical sampling and analysis system using excimer laser ablation and quartz microcolumns." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43422.
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Bugaje, Idris M. "Thermal energy storage in phase change materials." Thesis, University of Newcastle Upon Tyne, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335920.
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PANDEY, AJIT K. "RADIO-FREQUENCY ABLATION IN A RECONSTRUCTED REALISTIC HEPATIC TISSUE." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1061210342.
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Torrens, Serrahima Esther. "Enhanced excess sludge digestion using thermal and chemical petreatments." Doctoral thesis, Universitat Rovira i Virgili, 2013. http://hdl.handle.net/10803/125661.
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Aquesta tesi versa sobre la problemàtica de la gestió de llots de purga generats a les depuradores urbanes. La directiva 86/278/EEC referent als llots de depuradora, regula l’ús i les propietats dels llots estabilitzats i recomana la reutilització i valorització de fangs en front a la deposició en abocador.
El tractament actual de llots de depuradora es basa en la digestió anaeròbia en rang mesofílic (33ºC), però la majoria d’aquest fang no acompleix amb les condicions per a la seva reutilització com a fertilitzant, generalment en quantitat de microorganismes patògens. La proposta d’aquesta tesi està dirigida a desenvolupar estratègies per a la reutilització i revalorització de llots de depuradora, concretament en la migració a temperatures de tractament en rang termòfil (>50ºC) tan anaerobi com aerobi, i en la utilització de pretractaments tèrmics i químics (H2O2). Es pretén estudiar diferents processos per reduir tant la toxicitat com la quantitat de llots generats, i simultàniament estudiar la seva transformació en vectors d’energia verda, com ara el metàThis thesis deals with the problem of excess sludge management generated in urban wastewater treatment plants. The adoption of the European directive 86/278/EEC concerning sewage sludge regulates the use and properties of stabilized sludge. Specifically the directive recommends and promotes the reuse and recovery of sludge. Anaerobic digestion at mesophilic temperature (~33°C) is the most common sludge treatment process used in wastewater treatment plants (WWTP) to stabilize urban sludge, however generally this digested sludge not ensure sanitary conditions imposed for fertilize uses. The proposal of this thesis is to develop strategies for reuse and upgrading of sewage sludge, specifically the migration into thermophilic (>50ºC) in both anaerobic and aerobic digestion, and the use of thermal and chemical pretreatments (H2O2). The aim is to develop different processes for reducing both the toxicity and the amounts of sludge produced and simultaneously study their transformation into green energy vectors such as methane.
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Khanyile, Sfiso Zwelisha. "Deposition of silicon nanostructures by thermal chemical vapour deposition." University of the Western Cape, 2015. http://hdl.handle.net/11394/4445.
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>Magister Scientiae - MScIn this thesis we report on the deposition of silicon nanostructures using a 3-zone thermal chemical vapour deposition process at atmospheric pressure. Nickel and gold thin films, deposited by DC sputtering on crystalline silicon substrates, were used as the catalyst material required for vapour-solid-liquid growth mechanism of the Si nanostructures. The core of this work is centred around the effect of catalyst type, substrate temperature and the source-to-substrate distance on the structural and optical properties of the resultant Si nanostructures, using argon as the carrier gas and Si powder as the source. The morphology and internal structure of the Si nanostructures was probed by using high resolution scanning and transmission electron microscopy, respectively. The crystallinity was measured by x-ray diffraction and the high resolution transmission electron microscopy. For composition and elemental analysis, Fourier transform infrared spectroscopy was used to quantify the bonding configuration, while electron energy-loss spectroscopy in conjunction with electron dispersion spectroscopy reveals the composition. Photoluminescence and UV-visible spectroscopy was used to extract the emission and reflection properties of the synthesized nanostructures.
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Qiu, Bin. "Simulating Thermal and Chemical Spills in Coupled Cooling Reservoirs." Thesis, University of North Texas, 1997. https://digital.library.unt.edu/ark:/67531/metadc279271/.
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Hot water discharges and potential chemical spills are factors that threaten water
quality in cooling reservoirs of chemical and power plants. In this thesis, three models are used to analyze the impact of these factors in a particular case study.
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Aykan, Serap Fatma. "Numerical Analysis Of Ablation Process On A Two Dimensional External Surface." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/2/12606675/index.pdf.
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The thermal response analysis of an ablative material on a two dimensional external surface is performed. The method is applied to both rectangular and cylindrical coordinate systems, where rectangular coordinate system is used for comparison with results available in literature. The current study solves the decomposition of the material at high temperatures by using the nth order Arrhenius equation but excludes the removal of char from the surface due to mechanical erosion or phase change and considers that the ablation process takes place in a finite zone. The method considers the whole domain as one computational domain, eliminating the necessity to check the positions of the start and end of decomposition zone. The decomposition of pyrolysis gases and/or char that may occur at high temperatures and the chemical reaction between pyrolysis gases and char is neglected while pyrolysis gases are assumed to behave as ideal gas. The pressure is taken as a constant value on a whole physical domain.
The formulation for one-dimensional case is validated by experimental results obtained from literature. The two-dimensional case in a Cartesian geometry is formulated and an algebraic transformation is used to normalize the region in both directions and transformed at same time into a square computational domain in order to get a solution for the variable thickness domains. The formulation for two-dimensional case is revised for the cylindrical coordinates with finite length in the axial direction. To solve geometries where the outer surface deviates from cylindrical, the formulation is scaled and transformed into a non-dimensional square computational domain. The method is also applied to a two layer material problem in axisymmetric geometry.
In all problems, the radiation and constant heat flux boundary conditions exist on the outer surface while whole domain is initially at a constant temperature.
Case studies are performed to demonstrate the application of the solution method in optimizing the insulation material thickness.
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Fosnight, Tyler R. "Echo Decorrelation Imaging of In Vivo HIFU and Bulk Ultrasound Ablation." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1447691239.
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Williams, Gregory R. (Gregory Richard). "Catalyzed thermal oxidation to recover value from waste polyethylene." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60482.
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Polyethylene was thermally oxidized in the presence of air with cobalt(III) tris-(2,4-pentanedionate) as a catalyst and dicumyl peroxide as an initiator. The optimum temperature for oxygen addition was found to be 150$ sp circ$C. At this temperature, after reaction with 4 wt% catalyst and.4 wt% initiator for three hours, the solid residue was 11.5 mol% oxygen, with a number average molecular weight of 2,500, and there was no overall weight loss. Higher temperatures led to lower oxygen content, equal or higher molecular weight and significant weight loss. Infrared analysis indicated that the ratio of carbonyl to hydroxyl oxygen was a constant.It was concluded that volatilization became a dominant factor and oxygen containing molecules were lost from the solid. Some of the samples were used as the sole carbon source in fermentations with Yarrowia lipolytica and Arthrobacter paraffineus, but no growth was achieved.
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Johnson, Carter David. "Examination of lignocellulosic fibers for chemical, thermal, and separations properties addressing thermo-chemical stability issues /." [Ames, Iowa : Iowa State University], 2007.
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Chapman, Rudy. "Axonal Regrowth of Olfactory Sensory Neurons After Chemical Ablation and Removal of Axonal Debris by Microglia." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/etd/3807.
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Olfactory sensory neurons (OSNs) are contained within the olfactory epithelium (OE) and are responsible for detecting odorant molecules in the air. The exposure of OSNs to the external environment is necessary for their function, but it also leaves them exposed to potentially harmful elements and thus results in a high turnover rate. Despite the high turnover, the olfactory sense is maintained throughout life through the division of a population of stem cells that produce new OSNs both during normal turnover and after an injury occurs in the OE. When new OSNs are born, they must extend axons from the OE to the olfactory bulb (OB) where they make specific synaptic contacts. To determine the timeline of axon extension in normal turnover and after a methimazole-induced injury, we used fate-tracing utilizing an inducible Cre-LoxP model in which a fluorescent reporter was expressed by neuronal precursors and subsequently used to track axonal growth as the OSNs matured. Our results show that axon extension in both conditions follow the same timeline. However, markers of synaptic connectivity in the OB were delayed after injury. The delay in synaptic connectivity was also corroborated with delays in olfactory behavior after injury, which took 40 days to recover to control levels. Additionally, we investigated the process of removal of axonal debris created after an injury. Immunohistochemical analysis after injury indicated upregulation of IBA1+ cells within the 3 olfactory nerve layer of the OB, suggesting a role of microglia in this process. These microglia also showed an activated morphology and some had very large cell bodies with multiple nuclei. Furthermore, qPCR analysis of post-injury OB tissue shows upregulation of the CD11b receptor that is expressed on microglia. Our results have also shown upregulation of components of the complement pathway after injury, which is suggestive of a mechanism that underlies axonal debris removal after injury in the OB. Taken together, these results shed light on the process by which the olfactory system is able to recover after injury and could lead to discovery of mechanisms that could translate to treatments for injuries in other areas of the nervous system.
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Chapman, Rudy. "Axonal Regrowth of Olfactory Sensory Neurons After Chemical Ablation and Removal of Axonal Debris by Microglia." Digital Commons @ East Tennessee State University, 2008. https://dc.etsu.edu/etd/3807.
Full textAbstract:
Olfactory sensory neurons (OSNs) are contained within the olfactory epithelium (OE) and are responsible for detecting odorant molecules in the air. The exposure of OSNs to the external environment is necessary for their function, but it also leaves them exposed to potentially harmful elements and thus results in a high turnover rate. Despite the high turnover, the olfactory sense is maintained throughout life through the division of a population of stem cells that produce new OSNs both during normal turnover and after an injury occurs in the OE. When new OSNs are born, they must extend axons from the OE to the olfactory bulb (OB) where they make specific synaptic contacts. To determine the timeline of axon extension in normal turnover and after a methimazole-induced injury, we used fate-tracing utilizing an inducible Cre-LoxP model in which a fluorescent reporter was expressed by neuronal precursors and subsequently used to track axonal growth as the OSNs matured. Our results show that axon extension in both conditions follow the same timeline. However, markers of synaptic connectivity in the OB were delayed after injury. The delay in synaptic connectivity was also corroborated with delays in olfactory behavior after injury, which took 40 days to recover to control levels. Additionally, we investigated the process of removal of axonal debris created after an injury. Immunohistochemical analysis after injury indicated upregulation of IBA1+ cells within the 3 olfactory nerve layer of the OB, suggesting a role of microglia in this process. These microglia also showed an activated morphology and some had very large cell bodies with multiple nuclei. Furthermore, qPCR analysis of post-injury OB tissue shows upregulation of the CD11b receptor that is expressed on microglia. Our results have also shown upregulation of components of the complement pathway after injury, which is suggestive of a mechanism that underlies axonal debris removal after injury in the OB. Taken together, these results shed light on the process by which the olfactory system is able to recover after injury and could lead to discovery of mechanisms that could translate to treatments for injuries in other areas of the nervous system.
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Chang, Cliff Cheng-Shiou. "Thermal reactions of freshly generated coal tar over calcium oxide." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/15046.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Bibliography: leaves 351-363.
by Cliff Cheng-Shiou Chang.
Ph.D.
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Westerlund, Simon. "Design of Ablative Insulator for Solid Rocket Booster." Thesis, KTH, Energiteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-179031.
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The objective of this master thesis was to investigate an ablative liner for the T-Minus DART booster that will accelerate a dart to Mach 5.2 within five seconds. An oxyacetylene torch test was used to sort out the obviously bad materials. Glass fiber/epoxy, with and without alumina as fire retardant, and carbon fiber/epoxy were selected for further investigation. A sub-scale motor was built to expose the materials for conditions similar to the booster conditions in regard to temperature, chemistry, flow velocity and pressure. The target pressure could not be reached in the sub-scale motor but a polynomial function was fitted to the data in order to extrapolate the data and estimate the ablation rate at 7 MPa. The final design is always based on measurements on full scale motors. This could not be done within this report. Recommendation for future work is to use an insulator of 1.8 mm of carbon fiber/epoxy or 1.3 mm of glass fiber/epoxy/alumina for the sub-scale firings to come.