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Badie, Laetitia. "Adhésion sur les tissus biologiques." Thesis, Pau, 2016. http://www.theses.fr/2016PAUU3017/document.
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L’utilisation des adhésifs dans le domaine médical prend de plus en plus de place jusqu’à leur utilisation par le grand public pour refermer certaines plaies superficielles. Les adhésifs les plus courants pour applications médicales sont formulés à partir d’hydrogel voire de silicone, prêts à l’emploi, très peu étant associés à une préparation particulière avant application comme c’est le cas dans le domaine dentaire avec l’utilisation de la photo-polymérisation. Notre travail de recherche a consisté à formuler des adhésifs photo-polymérisables permettant un collage résistant sur les tissus biologiques internes et à comprendre les mécanismes permettant d’aboutir à un collage de bonne qualité en tenant compte des contraintes fortes liées à l’application visée : (i) milieu humide dans lequel sera disposé l’adhésif, (ii) nature viscoélastique des tissus biologiques et (iii) facilité de mise en œuvre. L’ensemble des expériences a été mené sur un substrat considéré comme « modèle », le péricarde bovin, dont il a été montré que les propriétés mécaniques sont similaires à celles du péricarde humain. Ce travail a démontré que l’adhésion sur un tissu interne est dépendante de plusieurs paramètres. Pour assurer un bon collage, il est nécessaire que l’adhésif mouille le tissu biologique et pénètre suffisamment pour assurer un bon ancrage mécanique. De ce fait, des formulations adhésives à base d’acrylates de faible viscosité ont été réalisées. Nous avons montré que l’énergie d’adhésion développée diminue linéairement avec la viscosité de l’adhésif avant photo-polymérisation. Ce résultat a mené à l’hypothèse de la pénétration de l’adhésif dans le péricarde, validée par plusieurs techniques. Nous avons ainsi démontré le lien entre une adhésion forte sur un tissu biologique, la viscosité initiale de la solution adhésive et sa capacité à pénétrer le substrat. L’ensemble de ce travail a mené à la compréhension des mécanismes induits par le dépôt d’un monomère sur un substrat vivant et à des hypothèses sur la polymérisation de la couche adhésive et son interaction avec le substrat. Des expériences in-vivo sur différents organes de souris et de lapins ont permis de montrer des résultats prometteurs qui ne demandent qu’à être confirmés par une étude systématique à plus grande échelle. Enfin, une description phénoménologique est proposée au travers d’une équation simplifiée tenant compte de différents paramètres essentiels pour décrire les mécanismes en jeuAdhesives are more and more used by the public to seal superficial wounds. The current adhesives for medical use are formulated on the basis of hydrogels, silicon and are ready to use. Only a few of them are associated to a particular preparation before application as the dental adhesives. The main goals of this research were to formulate some photo-polymerizable adhesives which induce a permanent strong anchorage into the internal biological tissues and to understand the mechanisms leading to a good quality adhesion and respecting the high constraints of the application: (i) the wetness of the media in which the adhesive is deposited, (ii) the viscoelasticity of the biological tissues and (iii) the easiness of the set up. The whole experiments were done onto a substrate considered as a “model”, the bovine pericardium, which was demonstrated to have the same mechanical properties as the human pericardium. This study showed that the adhesion onto internal tissue depends on several parameters. To create the adhesion, the adhesive has to wet and penetrate deep enough the tissue to get a strong mechanical anchorage. Thus, some low viscous acrylate-based adhesive formulations were realized. A linear correlation was found between the viscosity of the formulation before photo-polymerization and the adhesion energy: as the viscosity increases, the adhesion energy decreases. This result led to the hypothesis of the penetration of the adhesive into the tissue, which was proven by different techniques. Finally, it was proven that a strong adhesion onto a biological tissue depends on the viscosity and its capability to penetrate the substrate. This whole work led to the understanding of the mechanisms induced by the deposit of a monomer onto a living substrate and to some hypotheses about the polymerization of the adhesive layer and its interaction with the substrate. Some in-vivo experiments onto internal organs of mice or rabbits have shown promising results which are to be confirmed by multiple other experiments. Finally, a phenomenological description is proposed through a simplified equation takin into account different essential parameters to describe the mechanisms taking part into this phenomenon
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Chen, Guoyan. "Dielectric characterizations, ex vivo experiments and multiphysics simulations of microwave hyperthermia of biological tissues." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066289/document.
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La recherche et développement de dispositifs médicaux avec diverses applications en diagnostiques et en thérapie ont été réalisés. Actuellement, tous les systèmes micro-ondes disponibles d'hyperthermie proposent uniquement des traitements avec une puissance élevée de micro-ondes. Dans cette thèse, un nouveau système d'hyperthermie micro-ondes est étudié pour le bénéfice des fonctions de diagnostic et de thérapie. L'utilisation d'un applicateur avec un niveau très faible et inoffensif de puissance micro-ondes permet de faire le premier diagnostic. Le traitement thérapeutique thermique sera effectué en utilisant le même applicateur avec une puissance micro-ondes élevée et adaptée sur la partie pathologique. Des caractérisations micro-ondes large bande de cinq tissus biologiques différents ont été effectuées à différentes températures avec une méthode de sonde coaxiale ouverte et le modèle de ligne virtuelle. Les expérimentations ex vivo d'hyperthermie micro-ondes avec des puissances de quelques watts à 2,45GHz ont été réalisées sur ces tissus d'épaisseurs variées. L'évolution de la température des tissus a été mesurée en utilisant un capteur infrarouge. Les simulations électromagnétiques et thermiques pour les expérimentations ex vivo d'hyperthermie micro-ondes ont été effectuées en utilisant COMSOL Multiphysics avec la méthode des éléments finis et la symétrie axiale 2D en considérant les tissus variés de différentes épaisseurs et puissances micro-onde incidente. Les simulations du modèle correspondent bien aux mesures. Cette recherche illustre la possibilité d'avoir un câble coaxial souple et adapté à la fois au diagnostic et au traitement pour une thérapie mini invasiveResearch and development of medical devices with various diagnostic and therapeutic applications have been carried out in different countries because of the great advances in electronic and electromagnetic devices during recent decades. However, at present, all of available existing microwave hyperthermia system can just offer treatment, by using high microwave power. In this thesis, a new microwave hyperemia system is researched which could have both diagnostic and therapeutic functions. One single applicator is used to measure dielectric properties of tissue with a very low harmless microwave power for diagnosis first. Then thermal therapeutic treatment will be carried out by using the same applicator with higher and adapted microwave power. Microwave broad band characterization of five different biological tissues at different temperatures with an open–ended coaxial probe method and the virtual line model has been carried out. Ex vivo microwave hyperthermia experiments using microwave power of a few Watts at 2.45GHz have been carried out on five tissues of various thicknesses. Temperature evolution of the biological tissues has been measured by using an infra-red senor. Electromagnetic and thermal simulations for ex vivo microwave hyperthermia experiment have also been achieved by using COMSOL Multiphysics software with 2D axisymmetrical finite–element method and considering different tissues of various thicknesses and incident microwave powers. Simulation results correlate well with the experimental ones. This research, illustrates the possibility to have a flexible and feasible coaxial cable for both diagnosis and treatment for a minimally invasive therapy
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Ta, Anh Tuan. "Modélisation de lois de comportement anisotropes par la théorie mathématique des invariants : application aux matériaux biologiques fibreux." Thesis, Belfort-Montbéliard, 2014. http://www.theses.fr/2014BELF0236/document.
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Les travaux de cette thèse s’inscrivent dans le cadre de la formalisation mathématique des lois de comportement de matériaux anisotropes permettant de modéliser les tissus organiques (ligaments, muscles, tendons, parois artérielles …), les caoutchoucs renforcés par des fibres ou encore les composites textiles utilisés en aéronautique ou en génie civil. A partir des années 1950, l’utilisation de la théorie des invariants a été intensivement étudiée dans le cadre de la mécanique des milieux continus et plusieurs familles d’invariants ont alors été proposées. Cependant, l’utilisation de ces invariants soulève plusieurs difficultés :• Il en existe une grande diversité, ce qui ne facilite pas leur choix dans le cadre d’une modélisation éléments finis,• Certains sont difficiles à interpréter physiquement,• Ils nécessitent souvent la superposition deux densités d’énergie : l’une pour la description du comportement isotrope et l’autre pour la description du comportement purement anisotrope.Pour surmonter ces difficultés, une méthode constructive a été récemment proposée par Thionnet et al. Elle permet de s'assurer de l'unicité (à une relation près) de l'écriture polynômiale des invariants. Nous avons adapté cette méthode au cas des matériaux hyperélastiques anisotropes dans les cas d’un matériau constitué de deux familles puis d’une seule famille de fibre de collagène. Dans le premier cas, le théorème de Noether et l’opérateur de Reynolds ont été employés. Le second cas est techniquement plus complexe à aborder car le groupe de symétrie matérielle n’est plus de cardinal fini. L’opérateur de Reynolds n’a alors plus de sens et le théorème de Noether n’est plus applicable. Pour pallier cette situation, nous avons introduit un opérateur de Reynolds généralisé et avons montré que les propriétés associées à ce nouvel opérateur constituaient une extension de l’opérateur classique. Dans les deux cas, nous avons réussi à exhiber une base d’intégrité constituée d’invariants qui, pour certains, se démarquent de ceux classiquement trouvés dans la littérature.En particulier, dans le cas d’une famille de fibre, nous avons pu établir, grâce au théorème de Kantorovich, que l’un de ces invariants était relié au maximum de l’angle de cisaillement entre la fibre et la matriceThis thesis concerns a mathematical formulation of anisotropic behavior laws for the modeling of biological soft tissues (such as ligaments, muscle, tendons or arterial walls), fibers reinforced rubbers and textile composites used in aeronautical industry or for civil engineering applications. From the fifties, the theory of invariants was extensively developped in the framework of continuum mechanics and several families of invariants were proposed. However the use of these invariants meets some problems:• Because of a wide diversity, it is uneasy to well choose them in order to perform a finite element analysis.• It is difficult to give a physical meaning to some of them.• They often require the superposition of two strain energy densities: one for the description of the isotropic behavior of the material and one for the purely anisotropic behavior.To overcome these problems, a constructive method was recently proposed by Thionnet et al. It ensures the uniqueness (up to an algebraic relation) of the polynomial expression of the invariants. We have adapted this method to the case of anisotropic hyperelastic materials with two and with one single family of collagen fibers. In the first case, the Noether theorem and the Reynolds operator were used. The second case is more complex because the symmetry group is not of finite cardinal. Therefore, the Reynolds operator does not make sense anymore and the Noether theorem cannot be used. To overcome these technical difficulties, we have introduced a generalized Reynolds operator and we have shown that this operator is nothing but the extension of the classical one. In both cases of materials treated, we have succeeded to calculate an integrity basis made of invariants which are different (for some of them) from the classical ones found in the literature. In the case of the single family of fibers, we have demonstrated, thanks to the Kantorovich theorem, that one of those invariant was linked to the maximum value of the shear angle between the fiber and the matrix
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Wang, Mengze. "Système radio-fréquences sans contact pour la caractérisation diélectrique de tissus biologiques." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS015.
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La connaissance des propriétés diélectriques des tissus biologiques constitue un enjeu majeur pour la santé. Ces propriétés traduisent la manière dont un tissu stocke ou dissipe l’énergie électromagnétique transmise par un champ extérieur ; étant liées à la composition et à la structure du milieu organique, elles traduisent également la nature et l’état physiologique d’un tissu. Leur estimation fine permet donc, le cas échéant, de détecter et/ou de suivre l’évolution d’une pathologie. Parmi les méthodes de caractérisation diélectrique des tissus possibles, nous nous sommes concentrés sur une technique de caractérisation électromagnétique par antenne inductive exploitée en émission/réception, qui permet une mise en œuvre sans contact entre le système de mesure et le tissu. Celle-ci opère dans la gamme des radiofréquences (RF) ce qui présente l’avantage de rendre le dispositif sensible à la fois à la conductivité électrique et à la permittivité diélectrique du tissu. Cette technique travaillant en champ proche nécessite l’utilisation d’un modèle électromagnétique 3D des interactions sonde / tissu pour être mise en œuvre de manière pertinente. Dans ces travaux, nous nous sommes donc intéressés au problème de la modélisation des interactions, ainsi qu’à la résolution du problème inverse qui consiste à estimer les paramètres diélectriques recherchés à partir des données de mesure fournies par l’antenne et du modèle élaboré. Pour cela, nous nous sommes concentrés sur une configuration canonique, constituée d’une antenne RF filiforme circulaire, interagissant avec un milieu diélectrique homogène « sain » dont les paramètres diélectriques macroscopiques sont représentatifs d’un tissu organique (conductivité de 0.6 S/m et permittivité relative de 80), et d’une inclusion sphérique représentative d’une lésion présentant un contraste de 10% à 50% avec les paramètres du milieu « sain ». Nous avons établi un modèle d’interactions électromagnétiques 3D reposant sur une formulation semi – analytique à sources distribuées (DPSM) adaptée à cette configuration. Une étude paramétrique de la mise en œuvre du modèle, validée dans des configurations simples par rapport à des modèles analytiques et des expérimentations, a permis de construire un modèle qui montre des écarts inférieurs à 5 % par rapport à l’expérimentation, et qui établit un compromis acceptable entre exactitude et ressources informatiques nécessaires pour calculer la solution. Enfin, nous nous sommes intéressés à la résolution du problème inverse, consistant à retrouver les paramètres géométriques et diélectriques d’une lésion enfouie dans un milieu diélectrique « sain », à partir des variations d’impédances de l’antenne RF. Pour cela, nous avons construit un modèle inverse à réseaux de neurones artificiels (RNA) à partir de banque de données produites par le modèle DPSM. Une étude paramétrique a permis d’identifier les configurations de mise œuvre (fréquences, positions des antennes) les plus pertinentes permettant d’estimer les propriétés diélectrique, la taille et la position de l’inclusion dans le tissu, avec des erreurs d’estimation de l’ordre de 7% avec une antenne unique monofréquence, pour la caractérisation d’une inclusion de 3 cm de rayon enfouie jusqu’à 6 cm de profondeur. Ces travaux ouvrent la voix à des techniques de diagnostics de dans des milieux plus complexes (tissus stratifiés…) avec des techniques d’investigation multi-antennes et/ou multifréquences particulièrement prometteusesThe characterization of the dielectric properties of organic tissues is a major issue in health diagnosis. These properties reflect the way organic material stores or dissipates the electromagnetic energy transmitted by an external field. They are related to the composition and the structure of the organic medium. Furthermore, they are also related to the nature and the physiological state of a tissue. For that reason the estimation of these properties is very valuable for detecting and/or monitoring the evolution of tissue pathology.Among the existing dielectric characterization methods, we focused on a characterization technique using an inductive antenna, which acts as a transmitter/receiver sensor and allows a contactless implementation between the measuring system and investigated tissue to be carried out. This system is operated in the radio-frequency (RF) band. Indeed, in the RF the device is equally sensitive to both the electrical conductivity and the dielectric permittivity of the tissue. This technique operates in a near-field and therefore a 3D electromagnetic modeling technique is required to accurately model the interactions between the sensor and the investigated tissue.This work deals with the 3D modeling and with the resolution of the inverse problem required to estimate the dielectric parameters of tissues starting from the data provided by the antenna and the outputs of the model. For this purpose, a canonical configuration featuring a filiform circular antenna is considered. This antenna interacts with a “healthy” homogeneous dielectric medium, which possess the macroscopic dielectric parameters of a typical organic tissue (i.e. conductivity 0.6S/m and relative permittivity of 80 at 100 MHz). Meanwhile, a spherical inclusion buried within the tissue is considered to simulate a tissue lesion. This inclusion features a dielectric contrast of 10% up to 50% by reference to the parameters of the “healthy” medium. A 3D modeling of the sensor/tissue interactions is established, which is based on the distributed point source method (DPSM), a versatile semi-analytical modeling technique. The model is adjusted using a parametric study and validated against analytical models (in simplified configurations) and experiments. The implemented DPSM modeling was found to feature a 5% accuracy error, compared to the experimentations, together with offering an acceptable trade-off between accuracy and the computation cost. Finally, we focused on the solving of the inverse problem which consists in estimating the geometric and dielectric parameters of a buried lesion in the “healthy” dielectric medium, starting from the variations of the impedance of the RF antenna. To do so, a behavioral model build up using an artificial neural network (ANN) was established. The model is build using a data base elaborated using the DPSM model. The parameters of the ANN is discussed in order to identify the relevant configuration (frequency, position of the antenna) to estimate the dielectric properties, the size and the position of the inclusion in the tissue. For a single antenna operated at a single frequency, an inclusion of 3cm radius buried as deep at 6 cm within the tissue was located and characterized with estimation errors of the order of 7%.The methodologies developed in these works open the way to the diagnosis of more complex material (such as layered tissues), using promising techniques such as multi-frequency non contact RF antenna arrays
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Harb, Nizar. "Identification inverse de paramètres biomécaniques en hyperélasticité anisotrope." Phd thesis, Université de Technologie de Belfort-Montbeliard, 2013. http://tel.archives-ouvertes.fr/tel-00879257.
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Les travaux de cette thèse s'inscrivent dans le cadre du développement de méthodes d'identification inverse de paramètres matériau. On porte un intérêt particulier à la biomécanique des tissus souples renforcés par des fibres de collagène (artère, disque intervertébral, peau, tendon, ligament, etc.), dans le cadre de leurs réponses viscoélastiques et en grandes déformations et en grands déplacements (hyperélasticité). Fortement non-linéaires et anisotropes, les lois constitutives en biomécanique contiennent un nombre important de paramètres matériau. Le problème inverse qui permet de les identifier est de grande dimension et fortement non linéaire. En raison de difficultés numériques liées à sa résolution avec des méthodes à base de gradient, nous avons développé deux nouvelles méthodes d'identification inverse de paramètres nommées GAO (Genetic algorithms & Analytical Optimization) et MMIM (Maximum-Minimum Identification Method).La méthode GAO combine de manière avantageuse les méthodes déterministes de type gradient avec les algorithmes génétiques. Son originalité consiste à introduire des calculs analytiques pour la partie déterministe, ce qui permet d'accélérer et d'améliorer la convergence des algorithmes génétiques. Cette stratégie est appliquée dans le cadre de l'hyperélasticité anisotrope.En ce qui concerne la méthode MMIM, elle opère selon un critère d'identification basé sur la norme infinie et elle utilise les algorithmes génétiques. Elle permet d'identifier les paramètres de lois viscoélastiques quasi-linéaires. Elle garantit une réponse visqueuse constante qui est caractéristique des tissus souples qui sont insensibles à la vitesse de chargement.Les méthodes GAO et MMIM ont identifié avec succès des paramètres de tissus artériels et de tissus du disque intervertébral. Les propriétés de ces tissus sont décrits par ailleurs dans le mémoire dans un contexte plus général où on expose l'anatomie, l'histologie et le mécanisme de déformation aux différents niveaux hiérarchiques (nano-échelle à milli-échelle) d'un tissu souple renforcé par des fibres de collagène. Ceci permet de comprendre le rôle des efforts dans la relation liant la structure à la fonction en biologie.
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Boulvert, Frédéric. "ANALYSE DE MILIEUX FORTEMENT DIFFUSANTS PAR POLARIMETRIE DE MUELLER ET METHODES OPTIQUES COHERENTES. APPLICATION A L'ETUDE DU SYNDROME CUTANE D'IRRADIATION AIGUE." Phd thesis, Université de Bretagne occidentale - Brest, 2006. http://tel.archives-ouvertes.fr/tel-00079822.
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CE TRAVAIL AVAIT POUR OBJECTIF DE MONTRER LA POSSIBILITE D'UTILISER DES METHODES OPTIQUES DANS L'INVESTIGATION BIOPHYSIQUE NON INVASIVE DU SYNDROME CUTANE D'IRRADIATION AIGUË, POUR DES DOSES D'IRRADIATION RELATIVEMENT FAIBLES. LA PREMIERE PARTIE REVIENT SUR LES MOTIVATIONS QUI ONT ABOUTI AU CHOIX DE LA POLARISATION COMME AGENT DE CONTRASTE DANS LE CADRE DE CETTE ETUDE. NOUS AVONS ALORS OPTE POUR LA POLARIMETRIE DE MUELLER, TECHNIQUE ADAPTEE A L'ETUDE D'UN MILIEU DEPOLARISANT TEL QUE LA PEAU.
LA DEUXIEME PARTIE POSE LES BASES THEORIQUES DANS L'INTERPRETATION DES RESULTATS OBTENUS A PARTIR DE LA MESURE DE LA MATRICE DE MUELLER D'UN MILIEU. LA LECTURE DE CETTE DERNIERE N'ETANT PAS IMMEDIATE, UN ALGORITHME DE DECOMPOSITION ET DE CLASSIFICATION DES MATRICES DE MUELLER DEPOLARISANTES ET NON DEPOLARISANTES A ETE DEVELOPPE. CELUI-CI EST VALIDE SUR UNE SERIE D'ECHANTILLONS DE NATURES TRES DIVERSES.
LA TROISIEME PARTIE PRESENTE LE POLARIMETRE ET LES RESULTATS, ANGULAIRES ET SPECTRAUX, OBTENUS SUR DES ECHANTILLONS DE PEAU IRRADIES OU IL N'Y A AUCUN SIGNE CLINIQUE VISIBLE. EN UTILISANT L'ALGORITHME PRECEDENT NOUS AVONS MIS EN EVIDENCE DEUX AGENTS DE CONTRASTE POLARIMETRIQUE QUI SEULS OU COMBINES APPORTENT UNE INFORMATION SUR LE TAUX D'IRRADIATION. CES RESULTATS SONT CONFORTES PAR UNE ETUDE HISTOLOGIQUE MENEE EN PARALLELE PAR L'IRSN. NOUS AVONS AINSI MONTRE QUE LA POLARISATION PEUT ETRE UN AGENT DE CONTRASTE POUR DE FAIBLES DOSES D'IRRADIATION.
LA DERNIERE PARTIE MONTRE L'INTERET D'UTILISER EN COMPLEMENT A LA POLARIMETRIE UNE METHODOLOGIE D'OPTIQUE COHERENTE (SPECKLE, TOMOGRAPHIE PAR COHERENCE OPTIQUE) POUR LOCALISER LES ALTERATIONS CUTANEES.
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Daft, C. M. W. "Acoustic microscopy of biological tissue." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379997.
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Zerrari, Naoual. "Caractérisation des tissus biologiques mous par diffusion multiple de la lumière." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10052/document.
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La diffusion multiple de la lumière(DWS) est une technique qui permet de sonder la dynamique interne de milieux opaques et concentrés à des fréquences élevées. Elle a été utilisée pour déterminer les propriétés viscoélastiques de ces milieux. Elle a l'avantage d'être non destructive, rapide et sensible. Ce travail a pour objectif l'étude des tissus biologiques mous par DWS. La première étape est la mise en place du dispositif expérimental. Afin d'évaluer les limites de la technique, des études successives ont été réalisées sur des matériaux de complexité croissante (une suspension, le lait et une mousse) tendant vers la complexité structurale des tissus biologiques. Pour la suspension et le lait, la théorie de DWS peut s'appliquer et permet de mesurer avec une bonne précision leur viscosité. Les limites de DWS pour évaluer la viscosité sont atteintes avec la mousse dont la structure complexe est proche de celle des tissus biologiques. Enfin, le cortex rénal, le parenchyme hépatique et le cerveau de porc ont été étudiés. La théorie appliquée pour les milieux précédents ne permet pas de remonter à leur viscosité. Mais la DWS a permis de suivre leur microstructure au cours de la déshydratation et de la dégénérescence. Pour tous ces milieux la répétabilité, la reproductibilité, la variabilité et l'effet des conditions expérimentales ont été évalués. La DWS pourrait être utilisée pour étudier l'effet de la température et de la congélation sur le spectre de DWS des tissus biologiques ou combinée à la rhéologie pour suivre l'évolution des spectres de DWS au cours d'un cisaillementDiffusing Wave Spectroscopy (DWS) is a technique that allows to probe the internal dynamics of opaque media and concentrated at high frequencies. It has been used to determine the viscoelastic properties of these media. It has the advantage of being nondestructive, rapid and sensitive. This work aims to study soft biological materials by DWS. The first step is setting up of the experimental device. To evaluate the limits of the art, successive studies were conducted on materials of increasing complexity (a suspension, milk and a foam) tending to the structural complexity of biological tissues. Concerning the suspension and milk, two concentrated media, and mono-dispersed in which the particles are in Brownian motion, DWS allowed to measure with good precision their viscosity. The limits of DWS to evaluate the viscosity of the medium are achieved with the foam which the complex structure is similar to that of soft biological tissues. Finally, the renal cortex, the hepatic parenchyma and porcine brain were studied. The theory applied to previous media does not allow to calculate viscosity. But the DWS allowed us to follow their microstructure during dehydration and degeneration. For all these media, repeatability, reproducibility, variability and effect of experimental conditions were evaluated. The DWS could be used to study the effect of temperature and freezing on the DWS spectrum of biological tissues, or combined with rheology to monitor the evolution spectra DWS during shear
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Yvanoff, Marie. "LC sensor for biological tissue characterization /." Online version of thesis, 2008. http://hdl.handle.net/1850/8044.
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Brookner, Carrie Kazinoff. "Biological basis of cervical tissue autofluorescence /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Guntupalli, Jyothi Swaroop. "Physical sectioning in 3D biological microscopy." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2037.
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Waterworth, Alan Richard. "Data analysis techniques of measured biological impedance." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340146.
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Forsyth, Donald Scott. "Determination of organolead salts in biological tissue." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=73971.
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El, Babli Inas. "Interaction of electromagnetic waves with biological tissue." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq62633.pdf.
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Poland, Simon. "Techniques in deep imaging within biological tissue." Thesis, University of Strathclyde, 2006. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21651.
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This thesis is concerned with the development of low-cost and practical biological optical imaging and diagnosis systems that will allow the user to image and resolve structure deep into biological tissue without the need for physical dissection. Research within this thesis can be divided into two main sections, namely (a) the development of optically sectioning microscopy systems incorporating adaptive optics to compensate for system and specimen induced aberrations, and (b) as an example of biological tissue and disease, the development of dental imaging devices to detect and diagnose dental disease (caries). Section (a) The ability of confocal and multiphoton microscopy techniques to image optical sections deep within biological samples is a major advantage in biology. Unfortunately, as one images deeper within a sample, image degradation increases due to aberrations and scattering. In this investigation, operating a confocal microscope in reflection, a deformable membrane mirror (DMM) was used to counteract for sample aberrations within a closed feedback loop. By selecting various image properties (e. g. brightness, contrast or resolution), various optimisation algorithms were used to improve this property by altering the shape of the DMM and compensate for aberrations. Taking axial and lateral point spread functions (PSFs), the improvement of the system was monitored. The ability of the adaptive optic system to optimise to a particular axial PSF (PSF engineering) was also examined. The use of various algorithms with an adaptive element in a confocal system has been demonstrated to show significant improvement in the axial resolution and signal intensity. While global optimisation algorithms such as the genetic algorithm are more likely to find the global maximum in solution space in comparison to hillclimbing, it usually takes longer to achieve an optimum solution. Particular fitness parameters have shown promise in increasing the effectiveness of the algorithmic search routines. Optimising certain axial PSF components appears to have a detrimental effect on the lateral PSF and resolution. In the situation where the best axial and lateral resolution is required, optimising for intensity appears to show the best all round result. By adapting the axial fitness parameter program, it has been shown that particular desired axial PSF shapes can be reproduced within an aberrated sample. This does appear to have some limitations due to the relative power of the mirror (stroke). Section (b) Using optical techniques, physiological changes associated with the onset of disease in biological tissue can be detected. Taking dental tissue as an example of a highly scattering biological media, a computer model based upon commercially available software was used to theoretically reproduce experimental results taken using a fibre optical confocal system on dental tissue. From simulations, it has been shown that such a system could microscopically measure the optical properties of a caries lesion within dental enamel non-invasively. A system based on the use of structured light to penetrate and quantify early stage dental caries was presented as a possible aid to dentistry. Although the system was able to optically section the carious surface as well as detect inhomogeneities greater than 60μm deep into the tooth sample, more studies must be carried out to assess the limitations of the system. On a macroscopic scale, a cost effective system known as near-infrared Lateral Illumination (L. I.) (which is based on transillumination techniques) was presented. In a preliminary study involving 15 ex-in vivo adult pre-molars and molars at various stages of dental decay, L. I. was shown to be the most effective occlusal caries diagnosis system when compared to some techniques currently available and in development.
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Tobin, Jill M. "Laser induced plasma ablation of biological tissue." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15155.
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Blomgren, Bo. "Morphometrical Methodology in Quantification of Biological Tissue Components." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4628.
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Li, Teng. "Advanced Photoacoustic Measurement and Imaging in Biological Tissue." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506584.
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Roy, Ranadhir. "Image reconstruction from light measurements on biological tissue." Thesis, University of Hertfordshire, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338567.
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Phillips, Christopher George. "Transport in biological tissue and in shear flow." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257212.
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Chan, Wilson (Wilson Sian Chew) 1976. "Instrumentation to characterize needle insertion into biological tissue." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/17541.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes bibliographical references (leaves 52-53).
The Transdermal Drug Delivery Project in the BioInstrumentation Laboratory involves the design of a device to deliver drugs through the human skin using micro needles. It is crucial to characterize the insertion of micro needles into biological tissues. Hence, instrumentation will be designed and fabricated for the characterization of micro needle insertion. This thesis focuses on the design and fabrication of such instrumentation. The instrument is multi-modal, multi-axis, mobile and compact. It is capable of precise insertion positioning and acquiring accurate insertion force data. Characterization of micro needle insertion into biological tissues is done successfully using the data acquired by this instrument and an existing physical force model.
by Wilson Chan.
S.M.
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Cai, Renye. "Original strain energy density functions for modeling of anisotropic soft biological tissue." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCA003/document.
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Cette thèse a porté sur la construction de densités d'énergie de déformation permettant de décrire le comportement non linéaire de matériaux anisotropes tels que les tissus biologiques souples (ligaments, tendons, parois artérielles etc.) ou les caoutchoucs renforcés par des fibres. Les densités que nous avons proposées ont été élaborées en se basant sur la théorie mathématique des polynômes invariants et notamment sur le théorème de Noether et l'opérateur de Reynolds. Notre travail a concerné deux types de matériaux anisotropes, le premier avec une seule famille de fibre et le second avec quatre familles. Le concept de polyconvexité a également été étudié car il est notoire qu'il joue un rôle important pour s'assurer de l'existence de solutions. Dans le cas d'un matériau comportant une seule famille de fibre, nous avons démontré qu'il était impossible qu'une densité polynomiale de degré quelconque puisse prédire des essais de cisaillement avec un chargement parallèle puis perpendiculaire à la direction des fibres. Une densité polynomiale linéaire combinée avec une fonction puissance a permis de contourner cet obstacle. Dans le cas d'un matériau comportant quatre familles de fibre, une densité polynomiale a permis de prédire correctement des résultats d'essai en traction bi-axiale extraits de la littérature. Les deux densités proposées ont été implémentées avec la méthode des éléments finis et en langage C++ dans le code de calcul universitaire FER. Pour se faire, une formulation lagrangienne totale a été adoptée. L'implémentation a été validée par des comparaisons avec des solutions analytiques de référence que nous avons exhibée dans le cas de chargements simples conduisant à des déformations homogènes. Des exemples tridimensionnels plus complexes, impliquant des déformations non-homogènes, ont également été étudiésThis thesis has focused on the construction of strain energy densities for describing the non-linear behavior of anisotropic materials such as biological soft tissues (ligaments, tendons, arterial walls, etc.) or fiber-reinforced rubbers. The densities we have proposed have been developed with the mathematical theory of invariant polynomials, particularly the Noether theorem and the Reynolds operator. Our work involved two types of anisotropic materials, the first with a single fiber family and the second with a four-fiber family. The concept of polyconvexity has also been studied because it is well known that it plays an important role for ensuring the existence of solutions. In the case of a single fiber family, we have demonstrated that it is impossible for a polynomial density of any degree to predict shear tests with a loading parallel and then perpendicular to the direction of the fibers. A linear polynomial density combined with a power-law function allowed to overcome this problem. In the case of a material made of a four-fiber family, a polynomial density allowed to correctly predict bi-axial tensile test data extracted from the literature. The two proposed densities were implemented in C++ language in the university finite element software FER by adopting a total Lagrangian formulation. This implementation has been validated by comparisons with reference analytical solutions exhibited in the case of simple loads leading to homogeneous deformations. More complex three-dimensional examples, involving non-homogeneous deformations, have also been studied
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Bettinger, Christopher John 1981. "Biodegradable microfluidic scaffolds for vascular tissue engineering." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/18047.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Biological Engineering Division, 2004.Includes bibliographical references (leaves 91-93).
This work describes the integration of novel microfabrication techniques for vascular tissue engineering applications in the context of a novel biodegradable elastomer. The field of tissue engineering and organ regeneration has been born out of the high demand for organ transplants. However, one of the critical limitations in regeneration of vital organs is the lack of an intrinsic blood supply. This work expands on the development of microfluidic scaffolds for vascular tissue engineering applications by employing microfabrication techniques. Unlike previous efforts, this work focuses on fabricating this scaffolds from poly(glycerol-sebacate) (PGS), a novel biodegradable elastomer with superior mechanical properties. The transport properties of oxygen and carbon dioxide in PGS were measured through a series of time-lag diffusion experiments. The results of these measurements were used to calculate a characteristic length scale for oxygen diffusion limits in PGS scaffolds. Microfluidic scaffolds were then produced using fabrication techniques specific for PGS. Initial efforts have resulted in solid PGS-based scaffolds with biomimetic fluid flow and capillary channels on the order of 10 microns in width. These scaffolds have also been seeded with endothelial cells and perfused continuously in culture for up to 14 days resulting in partially confluent channels. More complex fabrication techniques were also demonstrated. A novel electrodeposition technique was used in the fabrication of biomimetic microfluidic masters. Thin-walled devices were also synthesized to accommodate the relatively low gas permeability of PGS.
by Christopher John Bettinger.
M.Eng.
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Cheang, Maggie Chon U. "Biological classification of clinical breast cancer using tissue microarrays." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2430.
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Gene expression profiles have identified five major molecular breast cancer subtypes (Luminal A, Luminal B, Basal-like, HER2+/estrogen receptor− , and Normal Breast-like) that show significant differences in survival. The cost and complexity of gene expression technology has impeded its clinical implementation. By comparison, immunohistochemistry is an economical technique applicable to the standard formalin-fixed, paraffin-embedded material commonly used in hospital labs, and has the advantage of simultaneously interpretation with histomorphology.
In this thesis, I hypothesize that a surrogate panel of immunohistochemical biomarkers can be developed to discriminate the breast cancer biological subtypes. The main study cohort consists of over 4000 primary invasive breast tumors, assembled into tissue microarrays. These patients were referred to the British Columbia Cancer Agency between 1986-1992 and have staging, pathology, treatment and follow-up information. In summary, our results demonstrate that (1) the rabbit monoclonal antibody, SP1, is an improved standard for immunohistochemiscal estrogen receptor assessment in breast cancer; (2) the transcription factor, GATA-3, is almost exclusively expressed among estrogen receptor positive tumors but does not seem to predict for tamoxifen response among estrogen receptor positive patients; (3) the proliferation marker, Ki-67, together with HER2 can segregate Luminal A from Luminal B subtypes, which carry distinct risks for breast cancer relapse and death; and (4) the inclusion of the basal markers EGFR and ck5/6 to “triple negative” breast cancers provides a more specific definition of basal-like breast cancer that better predicts patient survival.
These results consistently demonstrate that an immunopanel of six biomarkers (estrogen receptor, progesterone receptor, HER2, Ki-67, epidermal growth factor receptor and cytokeratin 5/6) can be readily applied to standard pathology specimens to subtype breast cancer samples based on their underlying molecular biology. These findings have been considered sufficient to justify application of this panel onto NCIC (MA5, MA12) and CALGB (9341 and 9741) clinical trials specimens. This followup work which is underway and will determine if the six marker immunopanel can guide decisions about which patients need aggressive systemic drug treatment, and thereby ensure patients get the most effective, individualized adjuvant systemic therapy for their breast tumor.
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Walker, Gillian Claire. "Modelling the propagation of terahertz radiation in biological tissue." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406881.
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Holden, Elizabeth. "New effective descriptions of deformable, adaptively remodelling biological tissue." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/53213/.
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Biological tissue is distinguished from materials described historically by continuum mechanical theory by its ability to grow and remodel adaptively, driven by a wide range of processes across multiple spatial and temporal scales. In this thesis we derive new mathematical descriptions that capture details from across various scales and their effect on the resulting overall behaviour. Motivated by tissue engineering, we consider tissue growth on a porous scaffold. Using the multiscale homogenisation method of O'Dea \emph{et al.}, [Mathematical Medicine and Biology, 32(3):345--366, 2014] and Penta \emph{et al.}, [The Quarterly Journal of Mechanics and Applied Mathematics, 67(1):69--91, 2014] we derive a macroscale description from one posed on the microscale. Through use of a multiphase mixture model for the tissue we extend the ideas in the above to incorporate interstitial growth and cell motility. Macroscale models are obtained via two simplifications which facilitate the homogenisation: first, by taking the limit of large interphase drag and second, by linearisation about a uniform steady state. These models consist of Darcy flow and differential equations for the cell volume fraction within the scaffold and concentration of nutrient, required for growth. Effective parameters are obtained via solution of a cell problems, hence providing explicit dependence on the microscale geometry and dynamics. Closure of the model is provided by an expression for the tissue-interstitium boundary velocity, obtained from numerical investigation of the underlying multiphase description, and solutions for a sample geometry are given. The same multiscale homogenisation technique is then employed in a different context: drug uptake by cancer cells and spheroids. Beginning with a description of drug uptake and binding for a single spheroid, two different macroscale models are derived based on different scaling assumptions. These are fitted to experimental data to provide insight into uptake behaviour, with a view to revealing underlying dynamics.
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Sweeney, Paul William. "Realistic numerical image-based modelling of biological tissue substrates." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10049410/.
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The development of preclinical tools to study fluid transport within biological tissue is critical to understanding not only the progression of disease, but the role of the microenvironment in healthy tissue. The limited availability of experimental data across all length scales provides scope for the development of mathematical models to simulate fluid transport throughout the microvasculature and surrounding tissue. Here, the novel REANIMATE (REAlistic Numerical Image-based Modelling of biologicAl Tissue substratEs) platform is developed which, guided by both ex vivo and in vivo imaging data, simulates fluid and solute transport in silico, based on real-world tissue substrates. In this thesis, the intravascular flow model of Fry et al. (2012) and and oxygen transport model of Secomb et al. (2004) are applied to an in vivo cortical microvascular network containing the locations of fluorescently-labelled vascular smooth muscle cells. The simulated results provide insights into the mechanisms underpinning local regulation of cerebral blood flow which would be inaccessible in a conventional experimental setting. Secondly, a transvascular model is developed to simulate the effective transport of fluid through the vasculature and into the interstitium. parameterised against in vivo perfusion data, the model is applied to two ex vivo colorectal tumour datasets to investigate the role of vascular heterogeneity in elevated interstitial fluid pressure within tumours. Next, this platform is used to simulate the steady-state fluid dynamics in a further two murine xenograft models of human colorectal carcinoma, allowing for the prediction of heterogeneous delivery of specific therapeutic agents to be compared with that observed in vivo. Finally, developing upon work by Shipley and Chapman (2010), a discrete-continuum model is developed which allows for the approximation of fluid transport through tissue in the absence of experimental data on tissue-specific vascular micro-structures, thereby providing additional information unavailable in the traditional experimental setting.
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Albagli, D. (Douglas). "Fundamental mechanisms of pulsed laser ablation of biological tissue." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/33521.
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Yablon, Andrew D. 1970. "Photothermal effects of pulsed laser irradiation of biological tissue." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10244.
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Ali, S. (Syed). "Employing VLC technology for transmitting data in biological tissue." Master's thesis, University of Oulu, 2019. http://jultika.oulu.fi/Record/nbnfioulu-201905141758.
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Abstract. With the development in wireless communication methods, visible light communication (VLC), a subset of Optical Wireless Communication (OWC) has garnered much attention to employ the technology for a secure short-range wireless communication. We present a feasibility study to determine the performance of VLC in short range wireless transmission of data through biological tissue. VLC is a cost efficient and secure means of transmitting high volume of data wirelessly which can considerably reduce the interference issues caused by electromagnetic pulses and external electric fields.
We present a simple measurement approach based on Monte Carlo simulation of photon propagation in tissue to estimate the strength of wireless communication with body implant devices. Using light for communication brings inherent security against unauthorized access of digital data which could be acquired from the low energy body implant devices used for medical diagnosis and other studies.
This thesis discusses the typical components required to establish VLC such as, transmitter, receiver and the channel mediums. Furthermore, two cases of Monte Carlo simulation of photon-tissue interaction are studied to determine a possibility if VLC is a suitable substitute to radio frequency (RF) for a more wireless communication with the body implants. The process of theoretical measurement begins with conversion of light intensity into an electrical signal and an estimation of achievable data rate through a complex heterogeneous biological tissue model.
The theoretically achieved data rates of the communication were found to be in the order of megabits per second (Mbps), ensuring a possibility to utilize this technology for short range reliable wireless communication with a wider range and application of implant medical devices. Biophotonics.fi presents a computational simulation of light propagation in different types of computational tissue models comprehensively validated by comparison with the team’s practical implementation of the same setup. This simulation is also used in this thesis (5.2.2) to approximate more accurate data rates of communication in case of a practical implementation.
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Zorgani, Ali. "Passive Elastography : Tomography and Mechanical Characterization of Biological Tissue." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1191/document.
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Les travaux menés lors de cette thèse portent sur le développement d'une approche passive d'Elastographie, l'imagerie de l'élasticité des tissus mous. Inspirée des techniques de corrélation de bruit sismique développée en séismologie, et du retournement temporel en acoustique. L'Elastographie passive utilise des ondes de cisaillement naturellement présentent dans le corps humain pour extraire les propriétés mécaniques des tissues biologiques. La faisabilité de cette approche passive est démontrée pour divers applications. En ultrason, un échographe à cadence lente ont été utilisés pour le guidage du traitement par ultrason à haut intensité dans une étude préclinique. Puis l'utilisation d'un échographe ultra-rapide pour la reconstruction des cartes de vitesses dans des gels calibrés ainsi que in-vivo. L'Elastographie passive par résonnance magnétique a été également mise en place pour imager les mouvements naturels dans le cerveau d'un volontaire sain et la réalisation d'une tomographie de longueurs d'ondes. En optique pour des applications en ophtalmologie ou en dermatologie, la faisabilité de l'Elastographie passive par cohérence optique a été démontrée dans un gel puis in-vivo dans l'œil d'une souris pour des. Puis une preuve du concept d'un dispositif d'imagerie d'ondes de surfaces complètement optique été testé dans des gels plan, courbé, isotrope ou anisotrope. Finalement, la limite de la résolution de l'Elastographie passive par ultrason est évaluéeThe aim of this thesis was the development of a new approach called passive elastography. This approach is inspired from noise correlation methods well developed in seismology and time reversal technics in acoustics. Passive elastography uses shear waves naturally induced in the human body to extract its mechanical properties of soft tissue. The feasibility of this method was tested in several applications. First in ultrasound, slow frame rate ultrasound scanner was used to monitor high intensity focused ultrasound treatment on porcine pancreas. Then, an ultrafast ultrasound scanner was used to retrieve shear wave speed map in a calibrated phantom and in-vivo. Second, Magnetic resonance elastography was implemented to image natural motion in the brain of healthy volunteers and conduct shear wavelength tomography. Third, of ophthalmological and dermatological applications, optical coherence passive elastography was tested in a phantom and a cornea of healthy mouse. Also, a fully optical setup was established to image surface wave for elastography applications. Finally, the resolution limit of elastography was measured using and ultrasound ultrafast scanner
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Eriksson, Emil. "Simulation of Biological Tissue using Mass-Spring-Damper Models." Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-27663.
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The goal of this project was to evaluate the viability of a mass-spring-damper based model for modeling of biological tissue. A method for automatically generating such a model from data taken from 3D medical imaging equipment including both the generation of point masses and an algorithm for generating the spring-damper links between these points is presented. Furthermore, an implementation of a simulation of this model running in real-time by utilizing the parallel computational power of modern GPU hardware through OpenCL is described. This implementation uses the fourth order Runge-Kutta method to improve stability over similar implementations. The difficulty of maintaining stability while still providing rigidness to the simulated tissue is thoroughly discussed. Several observations on the influence of the structure of the model on the consistency of the simulated tissue are also presented. This implementation also includes two manipulation tools, a move tool and a cut tool for interaction with the simulation. From the results, it is clear that the mass-springdamper model is a viable model that is possible to simulate in real-time on modern but commoditized hardware. With further development, this can be of great benefit to areas such as medical visualization and surgical simulation.Målet med detta projekt var att utvärdera huruvida en modell baserad på massa-fjäderdämpare är meningsfull för att modellera biologisk vävnad. En metod för att automatiskt generera en sådan modell utifrån data tagen från medicinsk 3D-skanningsutrustning presenteras. Denna metod inkluderar både generering av punktmassor samt en algoritm för generering av länkar mellan dessa. Vidare beskrivs en implementation av en simulering av denna modell som körs i realtid genom att utnyttja den parallella beräkningskraften hos modern GPU-hårdvara via OpenCL. Denna implementation använder sig av fjärde ordningens Runge-Kutta-metod för förbättrad stabilitet jämfört med liknande implementationer. Svårigheten att bibehålla stabiliteten samtidigt som den simulerade vävnaden ges tillräcklig styvhet diskuteras genomgående. Flera observationer om modellstrukturens inverkan på den simulerade vävnadens konsistens presenteras också. Denna implementation inkluderar två manipuleringsverktyg, ett flytta-verktyg och ett skärverktyg för att interagera med simuleringen. Resultaten visar tydligt att en modell baserad på massa-fjäder-dämpare är en rimlig modell som är möjlig att simulera i realtid på modern men lättillgänglig hårdvara. Med vidareutveckling kan detta bli betydelsefullt för områden så som medicinsk bildvetenskap och kirurgisk simulering.
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Ng, Shengyong. "Engineering human hepatic tissue for modeling liver-stage malaria." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90150.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biological Engineering, 2014.Cataloged from PDF version of thesis. Vita.
Includes bibliographical references (pages 132-153).
The Plcsmodium liver stage is an attractive target for the development of antimalarial drugs and vaccines, as it provides an opportunity to interrupt the life cycle of the parasite at a critical early stage. However, targeting the liver stage has been difficult due to a lack of human liver models that robustly recapitulate host-pathogen interactions in a physiologically relevant cell type. Through the application of hepatic tissue engineering concepts and techniques, this thesis sought to develop advanced models of liver-stage malaria that will allow the facile interrogation of potential antimalarial drugs in primary human hepatocytes. In the first part of this work, we established liver-stage Plasmodium infection in an engineered microscale human liver platform based on micropatterned cocultures of primary human hepatocytes and supportive stromal cells, enabling medium-throughput phenotypic screens for potential antimalarial drugs in a more authentic host cell, and demonstrated the utility of this model for malaria vaccine testing. We further hypothesized and showed that recapitulation of a more physiologically relevant oxygen tension that is experienced by hepatocytes in vivo improved infection rates and parasite growth in vitro. Next, we demonstrated the feasibility of establishing liver-stage malaria infections in human induced pluripotent stem cell-derived hepatocyte-like cells (iHLCs), thus enabling the study of host genetic variation on liver-stage malaria infection and antimalarial drug responses. We also applied recently discovered small molecules to induce further hepatic maturation, thus increasing the utility of using iHLCs for antimalarial drug development. Finally, we designed and provided a proof-of-concept for a humanized mouse model of liver-stage malaria that involves the fabrication and ectopic implantation of PEG-cryogel-based engineered human artificial livers, and can be generated in a facile, rapid and scalable fashion for future preclinical antimalarial drug testing in vivo. The results of this research represent a three-pronged approach towards engineering scalable human liver models that recapitulate liver-stage malaria infection which may ultimately facilitate antimalarial drug discovery at various stages of the drug development pipeline.
by Shengyong Ng.
Ph. D.
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Rothman, Craig Jeremy. "Tissue-specific classification of alternatively spliced human exons." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39920.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Biological Engineering Division, 2007.Includes bibliographical references (p. 53-57).
Alternative splicing is involved in numerous cellular functions and is often disrupted and involved in disease. Previous research has identified methods to distinguish alternative conserved exons (ACEs) in human and mouse. However, the cellular machinery, the spliceosome, does not use comparative genomics to decide when to include and when to exclude an exon. Human RefSeq exons obtained from the University of California Santa Cruz (UCSC) genome browser were analyzed for tissue-specific skipping. Expressed sequence tags (ESTs) were aligned to exons and their tissue of origin and histology were identified. ACEs were also identified as a subset of the skipped exons. About 18% of the exons were identified as tissue-specifically skipped in one of sixteen different tissues at four stringency levels. The different datasets were analyzed for both general features such as exon and intron length, splice site strength, base composition, conservation, modularity, and susceptibility to nonsense-mediated mRNA decay caused by skipping. Cis-element motifs that might bind protein factors that affect splicing were identified using overrepresentation analysis and conserved occurrence rate between human and mouse.
(cont.) Tissue-specific skipped exons were then classified with both a decision-tree based classifier (Random ForestsTM) and a support vector machine. Classification results were better for tissue-specific skipped exons vs. constitutive exons than for tissue-specific skipped exons vs. exons skipped in other tissues.
by Craig Jeremy Rothman.
M.Eng.
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Casasnovas, Ortega Nicole. "Developing osteoarthritis treatments through cartilage tissue engineering and molecular imaging." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76172.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Biological Engineering, 2012.Cataloged from PDF version of thesis. Page 104 blank.
Includes bibliographical references.
Tissue engineering can be applied to develop therapeutic techniques for osteoarthritis, a degenerative disease caused by the progressive deterioration of cartilage in joints. An inherent goal in developing cartilage-replacement treatments is ensuring that tissue-engineered constructs possess the same properties as native cartilage tissue. Biochemical assays and imaging techniques can be used to study some of the main components of cartilage and assess the value of potential therapies. Agarose and self-assembling peptides have been used to make hydrogels for in vitro culture of bovine bone marrow stromal cells (BMSCs) which can differentiate into chondrocytes, undergo chondrogenesis, and produce cartilage tissue. So far, differences in cell morphology that characterize chondrogenesis had been observed in peptide hydrogels like KLD and RAD but not in the 2.0% agarose hydrogels typically used for culture. A tissue engineering study was conducted to determine if a suitable environment for cell proliferation and differentiation could be obtained using different agarose compositions. BMSCs were cultured in 0.5%, 1.0%, and 2.0% agarose hydrogels for 21 days following TGF-p1 supplementation. Results indicate that the 0.5% agarose hydrogels are clearly inferior scaffolds when compared to the 1.0% and 2.0% agarose hydrogels, which are generally comparable. Since agarose gels appear to be suboptimal in promoting chondrogenesis, self-assembling peptides should be used in future studies. In addition to the biochemical assays traditionally used in cartilage tissue engineering studies, atomic force microscopy (AFM) can be used to image aggrecan, one of the main components of cartilage. Imaging studies were carried out using fetal bovine epiphyseal aggrecan to optimize previous extraction and sample preparation procedures, as well as an AFM imaging protocol, for samples containing aggrecan. Experiments were conducted with 10, 25, and 50 ptg/mL aggrecan solutions to find the minimum concentration needed to create aggrecan monolayers on APTES-mica that would yield acceptable AFM images (25 [mu]g/mL). AFM instrument and software parameters were optimized to find the working range of the integral and proportional gains (0.2 - 0.4 and 0.6 - 0.8, respectively) and to increase the resolution, showing fields at the 800 nm level. Finally, an image processing protocol relevant to these molecules was established.
by Nicole Casasnovas Ortega.
S.M.
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Qing, Bo Ph D. Massachusetts Institute of Technology. "Mechanical characterization of mammalian brain tissue and energy dissipative polymers." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119974.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biological Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references.
The high incidence of traumatic brain injury due to adverse impact events ranging from head collisions to ballistic attacks has prompted significant interest in synthetic polymer gels capable of mimicking key mechanical properties of brain tissue. These so-called brain tissue simulants are valuable tools for developing protective strategies because they can serve as test media to evaluate new helmets or optimize robotic surgery techniques. However, the so-called "soft matter" employed to date for ballistic applications, such as ballistic gelatin and clay, are crude mechanical representations of brain tissue. Therefore, there remains a need for a class of tissue simulant materials that more accurately replicates the mechanical behavior of brain tissue under impact loading, specifically in terms of deformation resistance and impact energy dissipation. This thesis focuses on design and synthesis of hierarchically structured gels, and mechanical characterization of these compliant gels for comparison with mammalian brain tissue. In particular, we use impact indentation to explore how the impact energy dissipation response varies as a function of species for brain tissue, or as a function of molecular composition and structure for synthetic gels. We find that a bilayered polydimethylsiloxane (PDMS) composite system enables the decoupling of the material's deformation resistance and energy dissipation characteristics, and can be tuned to fully match porcine brain tissue. However, given that the top PDMS layer is highly adhesive, we investigate whether adhesion plays a significant role in modulating the energy dissipation response, which has important implications in the utility of the tissue simulant material for ballistic applications. With a separate bilayered PDMS composite system, we decouple surface adhesion from bulk viscoelasticity, and quantify their individual contributions to impact energy dissipation. Through these experimental studies, in addition to a finite element computational analysis, we establish fundamental design principles and provide new insights regarding mechanisms that govern the extent of deformation and energy dissipation in compliant polymeric materials. Finally, we extend the capabilities of our impact indentation technique by demonstrating a novel analytical approach to extract viscoelastic moduli and relaxation time constants directly from the measured impact deformation response, thus significantly broadening the utility of impact indentation. With conventional characterization techniques such as shear rheology, several challenges arise when the material of interest has stiffness on the order of 1 kPa or lower, as is the case with brain tissue, largely due to difficulties detecting initial contact with the compliant sample surface. In contrast, impact indentation does not require contact detection a priori, and thus can potentially be utilized as a more accurate tool to characterize the viscoelastic properties of a wider range of soft matter for diverse biomedical or engineering applications, not limited to brain tissue simulants. This semi-analytical approach enables future studies to extract viscoelastic properties of brain tissue and tissue simulant polymers with increased accuracy and spatial resolution, in the context of traumatic brain injury, protection, and recovery.
by Bo Qing.
Ph. D.
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Kelly, Michael. "Characterisation of the biological potential of fracture non-union tissue." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/24765.
Full textAbstract:
Over 1.1 million fractures are estimated to occur annually in England and Wales. Up to 10% of these are likely be complicated by a delay or failure to heal with significant health and financial implications. Definitions of fracture non-union are not clear and although the Weber and Cech classification is still the definitive, misinterpretations remain common. Current treatment is surgical but the morbidity, particularly where autologous bone grafting is used, can be as high as 30%. Novel approaches are being tried but few of the strategies have made the translational impact that the laboratory and animal model data suggested. The work presented here investigates the feasibility of quantifying the biological potential of non-unions in patients and in a validated, in vivo model. Hypothesis: there is quantifiable biological potential in fracture non-union tissue that can be stimulated leading to osseous union by closed percutaneous injection of induction factors. Tissue from patients with non-infected fracture non-union undergoing treatment was examined to determine the feasibility of quantifying gene activity in small samples of non-union gap tissue. Non-union tissue from the animal model of an established non-union was examined to assess its osteoblastic potential by culture of extracted cells. Ortho bio logical agents that have shown great potential in gap models of non-union (BMP2 delivered in a viral construct (AdBMP2) and the thrombin peptide, TP508) were assessed to determine their efficacy in a clinically analogous model of fracture non-union. Quantifiable metabolic activity was found in the small samples of human non-union tissue. There was potential to correlate this to the histomorphometric architecture of the tissue. Cells extracted from the gap tissue of a non-union site in the rat model demonstrated osteoblastic potential in vitro. However, percutaneous injection of the orthobio logical agents into the non-union site in vivo failed to stimulate healing. The tissue at the site of a fracture non-union has a quantifiable metabolic activity that may have great clinical application and research benefits. Tissue from the non-union site of the animal model did demonstrate osteoblastic capacity but attempts to effect healing using percutaneously injected orthobiological agents that have previously shown potential, failed. This may be due to the chronic timepoint chosen to replicate the clinical situation. Further work is necessary to determine the prognostic potential of the gene assays and to continue to characterise the biological potential of the non-union tissue so that interventions can be more accurately directed.
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Hollmann, Joseph. "Multi-layer diffusion approximation for photon transport in biological tissue." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1901.
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Guermazi, Mahdi. "In-Vitro Biological Tissue State Monitoring based on Impedance Spectroscopy." Doctoral thesis, Universitätsverlag der Technischen Universität Chemnitz, 2016. https://monarch.qucosa.de/id/qucosa%3A20484.
Full textAbstract:
The relationship between post-mortem state and changes of biological tissue impedance has been investigated to serve as a basis for developing an in-vitro measurement method for monitoring the freshness of meat. The main challenges thereby are the reproducible measurement of the impedance of biological tissues and the classification method of their type and state.
In order to realize reproducible tissue bio-impedance measurements, a suitable sensor taking into account the anisotropy of the biological tissue has been developed. It consists of cylindrical penetrating multi electrodes realizing good contacts between electrodes and the tissue. Experimental measurements have been carried out with different tissues and for a long period of time in order to monitor the state degradation with time. Measured results have been evaluated by means of the modified Fricke-Cole-Cole model. Results are reproducible and correspond to the expected behavior due to aging. An appropriate method for feature extraction and classification has been proposed using model parameters as features as input for classification using neural networks and fuzzy logic.
A Multilayer Perceptron neural network (MLP) has been proposed for muscle type computing and the age computing and respectively freshness state of the meat. The designed neural network is able to generalize and to correctly classify new testing data with a high performance index of recognition.
It reaches successful results of test equal to 100% for 972 created inputs for each muscle. An investigation of the influence of noise on the classification algorithm shows, that the MLP neural network has the ability to correctly classify the noisy testing inputs especially when the parameter noise is less than 0.6%. The success of classification is 100% for the muscles Longissimus Dorsi (LD) of beef, Semi-Membraneous (SM) of beef and Longissimus Dorsi (LD) of veal and 92.3% for the muscle Rectus Abdominis (RA) of veal.
Fuzzy logic provides a successful alternative for easy classification. Using the Gaussian membership functions for the muscle type detection and trapezoidal member function for the classifiers related to the freshness detection, fuzzy logic realized an easy method of classification and generalizes correctly the inputs to the corresponding classes with a high level of recognition equal to 100% for meat type detection and with high accuracy for freshness computing equal to 84.62% for the muscle LD beef, 92.31 % for the muscle RA beef, 100 % for the muscle SM veal and 61.54% for the muscle LD veal.Auf der Basis von Impedanzspektroskopie wurde ein neuartiges in-vitro-Messverfahren zur Überwachung der Frische von biologischem Gewebe entwickelt. Die wichtigsten Herausforderungen stellen dabei die Reproduzierbarkeit der Impedanzmessung und die Klassifizierung der Gewebeart sowie dessen Zustands dar. Für die Reproduzierbarkeit von Impedanzmessungen an biologischen Geweben, wurde ein zylindrischer Multielektrodensensor realisiert, der die 2D-Anisotropie des Gewebes berücksichtigt und einen guten Kontakt zum Gewebe realisiert. Experimentelle Untersuchungen wurden an verschiedenen Geweben über einen längeren Zeitraum durchgeführt und mittels eines modifizierten Fricke-Cole-Cole-Modells analysiert. Die Ergebnisse sind reproduzierbar und entsprechen dem physikalisch-basierten erwarteten Verhalten. Als Merkmale für die Klassifikation wurden die Modellparameter genutzt.
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Woods, Stephan M. "VIBRATIONAL SPECTROSCOPY AND SPECTROSCOPIC IMAGING OF BIOLOGICAL CELLS AND TISSUE." Kent State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=kent1322540287.
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Guermazi, Mahdi. "In-Vitro Biological Tissue State Monitoring based on Impedance Spectroscopy." Doctoral thesis, Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-206710.
Full textAbstract:
The relationship between post-mortem state and changes of biological tissue impedance has been investigated to serve as a basis for developing an in-vitro measurement method for monitoring the freshness of meat. The main challenges thereby are the reproducible measurement of the impedance of biological tissues and the classification method of their type and state. In order to realize reproducible tissue bio-impedance measurements, a suitable sensor taking into account the anisotropy of the biological tissue has been developed. It consists of cylindrical penetrating multi electrodes realizing good contacts between electrodes and the tissue. Experimental measurements have been carried out with different tissues and for a long period of time in order to monitor the state degradation with time. Measured results have been evaluated by means of the modified Fricke-Cole-Cole model. Results are reproducible and correspond to the expected behavior due to aging. An appropriate method for feature extraction and classification has been proposed using model parameters as features as input for classification using neural networks and fuzzy logic. A Multilayer Perceptron neural network (MLP) has been proposed for muscle type computing and the age computing and respectively freshness state of the meat. The designed neural network is able to generalize and to correctly classify new testing data with a high performance index of recognition. It reaches successful results of test equal to 100% for 972 created inputs for each muscle. An investigation of the influence of noise on the classification algorithm shows, that the MLP neural network has the ability to correctly classify the noisy testing inputs especially when the parameter noise is less than 0.6%. The success of classification is 100% for the muscles Longissimus Dorsi (LD) of beef, Semi-Membraneous (SM) of beef and Longissimus Dorsi (LD) of veal and 92.3% for the muscle Rectus Abdominis (RA) of veal. Fuzzy logic provides a successful alternative for easy classification. Using the Gaussian membership functions for the muscle type detection and trapezoidal member function for the classifiers related to the freshness detection, fuzzy logic realized an easy method of classification and generalizes correctly the inputs to the corresponding classes with a high level of recognition equal to 100% for meat type detection and with high accuracy for freshness computing equal to 84.62% for the muscle LD beef, 92.31 % for the muscle RA beef, 100 % for the muscle SM veal and 61.54% for the muscle LD vealAuf der Basis von Impedanzspektroskopie wurde ein neuartiges in-vitro-Messverfahren zur Überwachung der Frische von biologischem Gewebe entwickelt. Die wichtigsten Herausforderungen stellen dabei die Reproduzierbarkeit der Impedanzmessung und die Klassifizierung der Gewebeart sowie dessen Zustands dar. Für die Reproduzierbarkeit von Impedanzmessungen an biologischen Geweben, wurde ein zylindrischer Multielektrodensensor realisiert, der die 2D-Anisotropie des Gewebes berücksichtigt und einen guten Kontakt zum Gewebe realisiert. Experimentelle Untersuchungen wurden an verschiedenen Geweben über einen längeren Zeitraum durchgeführt und mittels eines modifizierten Fricke-Cole-Cole-Modells analysiert. Die Ergebnisse sind reproduzierbar und entsprechen dem physikalisch-basierten erwarteten Verhalten. Als Merkmale für die Klassifikation wurden die Modellparameter genutzt
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Assar, Cuevas Rodrigo. "Modeling and simulation of hybrid systems and cell factory applications." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14335/document.
Full textAbstract:
Les fonctions biologiques sont le résultat de l'interaction de beaucoup de processus, avec différents objectifs, complexités, niveaux de hiérarchie, et changements de conditions que modifient le comportement de systèmes. Nous utilisons des équations différentielles ou dynamiques plus générales, et systèmes stochastiques de transition pour décrire la dynamique de changements des modèles. La composition, réconciliation et réutilisation des modèles nous permettent d'obtenir des descriptions de systèmes biologiques complètes et compatibles et leur combiner. Notre spécification de systèmes hybrides avec BioRica assure l'intégrité de modèles, et implémente notre approche. Nous appliquons notre approche pour décrire in-silico deux systèmes: la dynamique de la fermentation du vin, et des décisions cellulaires associées à la formation de tissu d'osThe main aim of this thesis is to develop an approach that allows us to describe biological systems with theoretical sustenance and good results in practice. Biological functions are the result of the interaction of many processes, that connect different hierarchy levels going from macroscopic to microscopic level. Each process works in different way, with its own goal, complexity and hierarchy level. In addition, it is common to observe that changes in the conditions, such as nutrients or environment, modify the behavior of the systems. So, to describe the behavior of a biological system over time, it is convenient to combine different types of models: continuous models for gradual changes, discrete models for instantaneous changes, deterministic models for completely predictable behaviors, and stochastic or non- deterministic models to describe behaviors with imprecise or incomplete information. In this thesis we use the theory of Composition and Hybrid Systems as basis, and the BioRica framework as tool to model biological systems and analyze their emergent properties in silico.With respect to Hybrid Systems, we considered continuous models given by sets of differential equations or more general dynamics. We used Stochastic Transition Systems to describe the dynamics of model changes, allowing cofficient switches that control the parameters of the continuous model, and strong switches that choose different models. Composition, reconciliation and reusing of models allow us to build complete and consistent descriptions of complex biological systems by combining them. Compositions of hybrid systems are hybrid systems, and the refinement of a model forming part of a composed system results in a refinement of the composed system. To implement our approach ideas we complemented the theory of our approach with the improving of the BioRica framework. We contributed to do that giving a BioRica specification of Hybrid Systems that assures integrity of models, allowing composition, reconciliation, and reuse of models with SBML specification.We applied our approach to describe two systems: wine fermentation kinetics, and cell fate decisions leading to bone and fat formation. In the case of wine fermentation, we reused known models that describe the responses of yeasts cells to different temperatures, quantities of resources and toxins, and we reconciled these models choosing the model with best adjustment to experimental data depending on the initial conditions and fermentation variable. The resulting model can be applied to avoid process problems as stuck and sluggish fermentations. With respect to cell fate decisions the idea is very ambitious. By using accurate models to predict the bone and fat formation in response to activation of pathways such as the Wnt pathway, and changes of conditions affecting these functions such as increments in Homocysteine, one can analyze the responses to treatments for osteoporosis and other bone mass disorders. We think that here we are giving a first step to obtain in silico evaluations of medical treatments before testing them in vitro or in vivo
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Appelt, Jessika. "Advanced scaffold for adipose tissue reconstruction." Thesis, University of Brighton, 2016. https://research.brighton.ac.uk/en/studentTheses/9be07efe-bd1f-46be-b1b4-e43e801d6696.
Full textAbstract:
Adipose tissue is a large loose connective tissue with functions comprising thermogenesis, homeostasis, metabolic activity and cushioning of bordering tissue layers. The tissue is predominantly composed of adipocytes and importantly contributes to the individual body shape. Loss of the fatty tissue due to trauma or disease often results in disfigurement, which affects patients physically as well as emotionally. Different surgical and scientific approaches have been studied to address this problem; in this regard tissue engineered scaffolds have received increased attention. Although there has been significant development in the efforts to address tissue loss, the reconstruction and maintaining of tissue with large dimensions remains a challenge. Hence, the overall aim of this project was to engineer a bulk scaffold suitable for adipose tissue reconstruction. The scaffold, cell source and extracellular signalling aspects of a tissue engineering strategy were approached to design a scaffold suitable for restoring adipose tissue defects of large dimensions. A particulate leaching method was developed and combined with the application of different freezing temperatures to produce a range of microporous macroporous gelatin scaffolds. Constructs were physically characterised for suitability in cell based studies. Scaffold design was investigated through biological characterisation using adipose derived stem cells (ADSCs) and an artificial ADSC stem cell niche was created through the utilisation of extracellular matrix components. The artificial environment was combined with the scaffolds and evaluated to support adipogenesis. A range of novel microporous macroporous scaffolds were produced, differing in micropore size range. Selection of scaffolds with defined features resulted in two constructs with a physical and biological profile suitable for adipose tissue construction. The scaffolds displayed high porosity and the materials supported ADSC viability and proliferation. Furthermore, cells were easily absorbed throughout the whole construct. The final resulting composite scaffold consisting of scaffold and artificial ADSC stem cell niche displayed in vitro support of adipogenesis. Concluding, a platform of novel composite adipogenic regeneration scaffolds were constructed that support adipogenesis as well as the preservation of ADSC stemness. Further, the gelatin sponges display a physical and biological profile suitable for adipose tissue reconstruction.
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Ongaro, Federica. "Theoretical and numerical modelling of biologically inspired composite materials." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/30826.
Full textAbstract:
The cellular nature of many biological materials, providing them with low density, high strength and high toughness, have fascinated many researchers in the field of botany and structural biology since at least one century. Bamboo, sponges, trabecular bone, tooth and honeybee combs are only few examples of natural materials with cellular architecture. It has been widely recognised that the geometric and mechanical characteristics of the microscopic building blocks play a fundamental role on the behavior observed at the macroscale. Up to date, many efforts have been devoted to the analysis of cellular materials with empty cells to predict the structure-property relations that link the macroscopic properties to the mechanics of their underlying microstructure. Surprisingly, notwithstanding the great advantages of the composite solutions in nature, in the literature a limited number of investigations concern cellular structures having the internal volumes of the cells filled with fluids, fibers or other bulk materials as commonly happens in biology. In particular, a continuum model has not been derived and explicit formulas for the effective elastic constants and constitutive relations are currently not available. To provide a contribution in this limitedly explored research area, this thesis describes the mathematical formulation and modelling technique leading to explicit expressions for the macroscopic elastic constants and stress-strain relations of biologically inspired composite cellular materials. Two examples are included. The first deals with a regular hexagonal architecture inspired by the biological parenchyma tissue. The second concerns a mutable cellular structure, composed by mutable elongated hexagonal cells, inspired by the hygroscopic keel tissue of the ice plant Delosperma nakurense. In both cases, the predicted results are found to be in very good agreement with the available data in the literature. Then, by taking into account the benefits offered by the complex hierarchical organisation of many natural systems, the attention is focused on the potential value of adding structural hierarchy into two-dimensional composite cellular materials having a self-similar hierarchical architecture, in the first case, and different levels with different cell topologies, in the second. In contrast to the traditional cellular materials with empty cells, the analysis reveals that, in the cell-filled configuration, introducing levels of hierarchy leads to an improvement in the specific stiffness. Finally, to offer concrete and relevant tools to engineers for developing future generations of materials with enhanced performance and unusual functionalities, a novel strategy to obtain a honeycomb with mutable cells is proposed. The technique, based on the ancient Japanese art of kirigami, consists in creating a pattern of cuts into a flat sheet of starting material, which is then stretched to give a honeycomb architecture. It emerges a vast range of effective constants that the so-called kirigami honeycomb structures can be designed with, just by changing the value of the applied stretch.
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Camp, James (James Patrick) 1977. "Development of simple 3D-printed scaffolds for liver tissue engineering." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/16864.
Full textAbstract:
Thesis (S.M. in Bioengineering)--Massachusetts Institute of Technology, Biological Engineering Division, 2002.Includes bibliographical references (leaves 51-52).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
One solution to the increasing need for liver transplants is to grow implantable liver tissue in the lab. A tissue-engineered liver for transplantation will require complex structures to support cell differentiation and integration with surrounding vasculature. Recent developments in 3D-printing (3DP™) technology allow the construction of such geometrically complex scaffolds out of biodegradable polymers. These artificial tissues should maintain healthy, functional hepatocytes in proper contact with supporting cell types in the context of proper flow cues. This project comprises three major efforts. First, the design and development of a 3D-printed scaffold, constructed of a porous biodegradable polymer matrix, for flow bioreactor culture. Second, the development of protocols for the production, preparation, and flow support of these scaffolds. And third, the employment of standard cell culture methodologies to test the ability of these scaffolds to support liver tissue cultures. Initial cell culture experiments showed similar rates of albumin production in the polymer disk scaffolds compared to cells in silicon-chip scaffolds under appropriately scaled flow conditions, indicating that the polymer scaffolds maintain functioning liver tissue. Further, histology sections of liver tissue grown on these polymer scaffolds show organization of cells into structures reminiscent of in vivo liver. The results of this study show that 3D-printed porous polymer scaffolds have great potential for use as biodegradable tissue culture support devices. It is believed that, combined with printing technologies now under development, the technologies developed in this thesis will help facilitate the construction of an implantable tissue engineered liver.
by James Camp.
S.M.in Bioengineering
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Olurinde, Mobolaji O. "Antigen-specific memory T cell distribution in non-lymphoid tissue." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40951.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Biological Engineering Division, 2007.Includes bibliographical references (leaves 28-34).
CD8+ T cells are the main adaptive immune system cell type responding to intracellular pathogens, particularly viruses, and tumor antigens. In the case of influenza, activated T cells migrate from the mediastinal (draining) lymph nodes to the lung where they perform their cytolytic function. After pathogen clearance, memory CD8+ T cells are generated, giving rise to long-term protection from reinfection. However, these cells are no longer detectable in the lung parenchyma six months post-infection, and cell-mediated immunity, and protection is lost. Knock-out studies in mice show that interleukin 15 (IL-15) is essential for memory CD8+ T cell proliferation. Fibroblasts, macrophages, dendritic cells and epithelial cells express IL-15 and its receptor isoform [alpha] (IL-15R[alpha]). Histological studies suggest that memory CD8+ T cells preferentially reside in peribronchiolar and perivascular areas, the stroma, of the lung. We hypothesize that memory CD8+ T cells preferentially reside in regions where molecules necessary for their maintenance, for example, IL-15/R secreting cells, are located. In this study, we have shown that antigen-specific 2C GFP effector memory CD8+ T cells are generated in B6 recipient mice 30-32 days after influenza virus infection, preferentially reside in peribronchiolar areas. Both 2C and 2C GFP recipient mice have severe vasculitis and widely distributed inflammatory infiltrates 7 days post-infection. Lower lung lobes appear to be more affected than upper lobes at this time point. On day 30, most of the airways have been cleared and restored. Although lymphoid-appearing nodules were detected in the lungs 31 dpi, no clusters of B cells and T cells suggesting induced BALT were identified by immunofluorescence.
(cont.) Interestingly, antigen-specific GFP cells preferentially remained in the lung tissue and were almost undetectable in spleens, lymph nodes, and livers. This preference was not observed in 2C (non-GFP) recipient mice. Immunofluorescence studies showed no colocalization between 2C GFP T cells and dendritic cells that might suggest stable dendritic cell interactions contribute to antigen-specific cells preferentially residing in the lung stroma. Further studies are necessary to determine what other cell types might contribute to this phenomenon. These results provide some insight into how structural elements in non-lymphoid tissue influence cell-mediated immunity.
by Mobolaji O. Olurinde.
S.M.
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Kilaru, Aruna. "Insights into Oil Biosynthesis in Nonseed Tissues." Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/etsu-works/4765.
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Kilaru, Aruna. "Oil Biosynthesis in Nonseed Tissues." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etsu-works/4768.
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Goyal, Poorva. "Development of dendritic and polymeric scaffolds for biological and catalysis applications." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24826.
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Thesis (Ph.D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2008.Committee Chair: Weck, Marcus; Committee Member: Bunz, Uwe H. F.; Committee Member: Dickson, Robert M; Committee Member: Fahrni, Christoph J; Committee Member: Jones, Christopher W; Committee Member: Murthy, Niren.
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Kocová, Lucie. "Návrh a realizace měření elektrických vlastností biologických tkání." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220027.
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This master’s thesis is focused on the electrical properties of biological tissues and flesh in particular. Their electrical characteristics depend on the physical and chemical parameters that determine the concentration and mobility of ions in metabolic fluids. From the electrical point of view, flesh can be simply substituted by a field of elongated conductive cells which are separated by the insulating membrane from each other. In the next part, the Fricke model is introduced. The model describes the measurement of impedance of the tissue at low and high frequencies. The aim of the work is to assess how the impedance of the dielectric sample is dependent on the frequency of the electrical signal during the optimal aging or ripening of flesh.