Interactions of cells with their chemical microenvironments are critical to many polarized processes, including differentiation, migration, and pathfinding. To investigate such cellular events, tools are required that can rapidly reshape the microscopic chemical landscapes presented to cultured cells. Existing chemical dosing technologies rely on use of pre-fabricated chemical gradients, thus offering static cell-reagent interactions. Such interactions are particularly limiting for studying migration and chemotaxis, during which cells undergo rapid changes in position, morphology, and intracellular signaling. This dissertation describes the use of laminar streams, containing cellular effector molecules, for precise delivery of effectors to selected subcellular regions. In this approach, cells are grown on an ultra-thin polymer membrane that serves as a barrier to an underlying reagent reservoir. By using a tightly-focused pulsed laser beam, micron-diameter pores can be ablated in the membrane upstream of desired subcellular dosing sites. Emerging through these pores are well-defined reagent streams, which dose the targeted regions. Multiple pores can be ablated to allow parallel delivery of effector molecules to an arbitrary number of targets. Importantly, both the directionality and the composition of the reagent streams can be changed on-the-fly under a second to present dynamically changing chemical signals to cells undergoing migration. These methods are applied to study the chemotactic responses of neutrophil precursor cells. The subcellular localization of the chemical signals emerging through pores is found to influence the morphological evolution of these motile cells as they polarize and migrate in response to rapidly altered effector gradients. / text

Ultrasound Current Source Density Imaging (UCSDI) is a noninvasive modality for mapping electrical activities in the body (brain and heart) in 4-dimensions (space + time). Conventional cardiac mapping technologies for guiding the radiofrequency ablation procedure for treatment of cardiac arrhythmias have certain limitations. UCSDI can potentially overcome these limitations and enhance the electrophysiology mapping of the heart. UCSDI exploits the acoustoelectric (AE) effect, an interaction between ultrasound pressure and electrical resistivity. When an ultrasound beam intersects a current path in a material, the local resistivity of the material is modulated by the ultrasonic pressure, and a change in voltage signal can be detected based on Ohm's Law. The degree of modulation is determined by the AE interaction constant K. K is a fundamental property of any type of material, and directly affects the amplitude of the AE signal detected in UCSDI. UCSDI requires detecting a small AE signal associated with electrocardiogram. So sensitivity becomes a major challenge for transferring UCSDI to the clinic. This dissertation will determine the limits of sensitivity and resolution for UCSDI, balancing the tradeoff between them by finding the optimal parameters for electrical cardiac mapping, and finally test the optimized system in a realistic setting. This work begins by describing a technique for measuring K, the AE interaction constant, in ionic solution and biological tissue, and reporting the value of K in excised rabbit cardiac tissue for the first time. K was found to be strongly dependent on concentration for the divalent salt CuSO₄, but not for the monovalent salt NaCl, consistent with their different chemical properties. In the rabbit heart tissue, K was determined to be 0.041 ± 0.012 %/MPa, similar to the measurement of K in physiologic saline: 0.034 ± 0.003 %/MPa. Next, this dissertation investigates the sensitivity limit of UCSDI by quantifying the relation between the recording electrode distance and the measured AE signal amplitude in gel phantoms and excised porcine heart tissue using a clinical intracardiac catheter. Sensitivity of UCSDI with catheter was 4.7 μV/mA (R² = 0.999) in cylindrical gel (0.9% NaCl), and 3.2 μV/mA (R² = 0.92) in porcine heart tissue. The AE signal was detectable more than 25 mm away from the source in cylindrical gel (0.9% NaCl). Effect of transducer properties on UCSDI sensitivity is also investigated using simulation. The optimal ultrasound transducer parameters chosen for cardiac imaging are center frequency = 0.5 MHz and f/number = 1.4. Last but not least, this dissertation shows the result of implementing the optimized ultrasound parameters in live rabbit heart preparation, the comparison of different recording electrode configuration and multichannel UCSDI recording and reconstruction. The AE signal detected using the 0.5 MHz transducer was much stronger (2.99 μV/MPa) than the 1.0 MHz transducer (0.42 μV/MPa). The clinical lasso catheter placed on the epicardium exhibited excellent sensitivity without being too invasive. 3-dimensional cardiac activation maps of the live rabbit heart using only one pair of recording electrodes were also demonstrated for the first time. Cardiac conduction velocity for atrial (1.31 m/s) and apical (0.67 m/s) pacing were calculated based on the activation maps. The future outlook of this dissertation includes integrating UCSDI with 2-dimensional ultrasound transducer array for fast imaging, and developing a multi-modality catheter with 4-dimensional UCSDI, multi-electrode recording and echocardiography capacity.

No description available.

Radio frequency ablation (RFA) is a commonly used minimally invasive method of treating liver cancer tumours which utilises RF current for heating tumour tissue up to a lethal temperature. RF current is generated by a power generator and applied to the tumour by an electrode which is inserted into the tumour either during percutaneous or open surgery. RFA is a method that has great advantages compared to traditional surgical resection of tumours due to minimal invasiveness, it can be used for a greater number of patients and enables repeated treatments. Even though there are many advantages coupled to RFA there are still some problems and difficulties associated with the method. One of these problems is the cooling effect from large vessel blood flow within the liver, the so called heat sink effect. The aim of this master thesis work has been to develop a theoretical finite element model of RFA within Comsol Multiphysics software. This theoretical model has been used to simulate blood perfusion effects on resulting ablation volume. The effects from different large vessel blood flow parameters has been investigated, these parameters are: blood flow velocity, blood vessel diameter and distance between blood vessel and RF electrode. A factorial design has been utilised to setup parameter levels for the different simulations. A linear- and a second degree regression model has been calculated based on simulation results. The parameter with largest impact on simulative ablation volume and the interaction effects between the parameters were determined from the regression model coefficients. In addition to this has two simulations been performed, modelling perfused- and unperfused liver tissue, in order to investigate the effects resulting from microvascular perfusion. The result shows that the parameter with largest impact on simulative ablation volume are the distance, it was also shown that there are a small interactional effects between diameter and distance, where a small distance increases the effect from a varying diameter. Modelled microvascular perfusion was shown to give a decrease in simulative ablation volume. A shortage of this master thesis work is the lack of experimental verification of the developed model.

No description available.

Les déchets solides générés par notre société sont nombreux. Les cendres volantes sont des déchets solides produits lors de la combustion de déchets domestiques ou industriels dans des incinérateurs. Les cendres volantes sont également produites par la combustion du charbon dans les centrales à charbon. Les cendres volantes sont des résultats de ces combustions et représentent importante quantité de déchets produits chaque année par notre société. Les possibilités de recyclage de ces déchets sont nombreuses : dans la construction, l'industrie routière. Elles sont également stockées pour une utilisation ultérieure. Les origines différentes des charbons et déchets incinérés conduisent à une minéralogie et une composition élémentaire complexe. En tant que sous-produit le devenir des cendres volantes est important à déterminer, aussi la détermination de la composition élémentaire de ces cendres volantes est-elle indispensable.Les méthodes classiques de préparation des échantillons solides sont la minéralisation acide ou la fusion alcaline. Ces procédures prennent du temps et supposent l'utilisation de réactif, de plus la digestion complète n'est pas toujours assurée. Le risque de contamination par les réactifs employés est important au cours de ces méthodes classiques de préparation. Au cours de la dernière décennie, le développement d'analyse directe d'échantillons solides en utilisant des méthodes d'ablation laser a été important en raison de la nécessité de réduire le temps d'analyse et de réduire aussi la consommation de réactifs. Dans ce travail, deux méthodes basées sur l'ablation par laser seront étudiées pour l'analyse des cendres: Laser Induced Breakdown Spectroscopy (LIBS) et Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). La spectrométrie LIBS sera étudiée pour la détermination quantitative des éléments majeurs dans les échantillons de cendres alors que le couplage ablation laser ICP / MS sera employé pour détermination des éléments traces. L'optimisation de la sensibilité et les stratégies d'étalonnage sont les principaux problèmes traités dans ce travail. La préparation des échantillons et l'optimisation ont été effectuées pour déterminer les éléments tels que Al, As, Ba, Ca, Cr, Cu, Fe, Mg, Mn, Pb, Sr, V et Zn par les deux méthodes.Les performances analytiques telles que les limites de détection, justesse ont été obtenus à la suite d'optimisations appropriées des liants et de la sélection de l'étalon interne approprié. En conclusion, l'analyse directe de solides en utilisant les techniques basées sur l'ablation laser développées dans ce travail conduisent à une justesse acceptable pour la détermination des éléments majeurs et traces dans les cendres volantes

Tyrimo metu apibendrinti ir išanalizuoti 74 knarkiančiųjų bei lengvu ir vidutinio sunkumo obstrukcinės miego apnėjos hipopnėjos sindromu (OMAHS) sergančių pacientų klinikiniai duomenys, ir įvertinta 38 jų miego partnerių emocinė būklė prieš pacientų gydymą ir praėjus 2–4 mėn. po pacientams taikyto knarkimo ir OMAHS gydymo – radiodažnuminės termoabliacijos (RDTA). Šio darbo uždaviniai: 1. Ištirti ir palyginti knarkiančiųjų bei sergančių lengvu ir vidutinio sunkumo OMAHS pacientų viršutinių kvėpavimo takų anatomines ir funkcines savybes, apnėjų hipopnėjų indeksą, nusiskundimus sveikata ir emocinę būklę. 2. Įvertinti knarkiančiųjų bei sergančių lengvu ir vidutinio sunkumo OMAHS pacientų gyvenimo kokybę prieš pradedant gydymą ir po gydymo RDTA. 3. Įvertinti su RDTA operacijomis susijusių pacientų nusiskundimų intensyvumą ir pooperacinių komplikacijų dažnį. 4. Ištirti ir įvertinti knarkiančiųjų bei sergančių lengvu ir vidutinio sun¬kumo OMAHS pacientų nusiskundimus ir apnėjų hipopnėjų indeksą po gydymo RDTA. 5. Ištirti ir įvertinti knarkiančiųjų bei sergančių lengvu ir vidutinio sunkumo OMAHS pacientų emocinę būklę po gydymo RDTA. 6. Ištirti ir įvertinti knarkiančiųjų bei sergančių lengvu ir vidutinio sunkumo OMAHS miego partnerių emocinę būklę ir jos pokyčius po pacientų gydymo RDTA. Po pacientų gydymo RDTA nustatytas pacientų nusiskundimų intensyvumo ir apnėjų hipopnėjų indekso sumažėjimas bei emocinės būklės pagerėjimas, ir pacientų miego part¬ne¬rių depresiškumo sumažėjimas... [toliau žr. visą tekstą] / A total of 74 snoring and mild to moderate obstructive sleep apnea hypopnea syndrome (OSAHS) patients underwent complete full night polysomnography (PSG) and clinical examination and were treated with two sessions of radiofrequency tissue ablation (RFTA). The emotional state of 38 bed partners of snoring and mild to moderate OSAHS patients were evaluated at the baseline and 2–4 months after the patients completed the treatment. Objectives of the study: 1. To examine and evaluate the relationship between complaints, anatomical features, PSG results, and emotional state of snoring and mild to moderate OSAHS patients. 2. To assess the quality of life among snoring and mild to moderate OSAHS patients before and after the RFTA treatment. 3. To analyze the morbidity and the rate of postoperative compli¬ca¬tions of RFTA. 4. To evaluate the influence of RFTA on the objective (PSG results) and subjective (complaints) outcomes in snoring and mild to moderate OSAHS patients. 5. To evaluate the influence of RFTA on the outcomes of anxiety and depression in snoring and mild to moderate OSAHS patients. 6. To examine the emotional state and to evaluate the effect of RFTA on anxiety and depression in bed partners of snoring and mild to moderate OSAHS patients. A remarkable improvement in patients’ complaints, PSG results and emotional state after RFTA was observed. RFTA therapy resulted in improved depression scores for the bed partners of snoring and mild to moderate OSAHS patients.

Šio mokslinio darbo tikslas buvo įvertinti efektyvumą bei saugumą gydant prieširdžių virpėjimą, naudojant elektrofiziologinius RD abliacijos unipolinius elektrodinius kateterius pacientams, kuriems mitralinio vožtuvo ydą koreguojančios operacijos atliekamos per prieširdžių pertvaros(tarprieširdinės ir viršutinio pertvaros) pjūvius. Atlikus šią operaciją – po 1 metų >80% pacientų neturi prieširdžių virpėjimo/plazdėjimo, iš jų 76% nevartoja antiaritminių vaistų. galutinio sekimo metu fiksuota, kad išliko 71,5% pacientų be prieširdžių virpėjimo ir plazdėjimo. Labirinto procedūra prailgina tik 16 ± 3 min dirbtinės kraujotakos laiką. Išeities ir operacinių parametrų atžvilgiu tarprieširdinės ir viršutinio pertvaros pjūvių grupės nesiskyrė. Mitralinio vožtuvo ydos korekcijos pobūdis – protezavimas ar plastika - statistiškai patikimai neturėjo PV gydymo rezultams. Gydymo efektyvumui įtakos turi: didesnė širdies nepakankamumo funkcinė klasė ir kairiojo prieširdžio išilginis dydis nustatytas echoskopiškai M - režimu. Pooperacinių antrinių prieširdinių tachikardijų ir atipinių prieširdžių plazdėjimo kombinuota (taikant antiaritminius vaistus, perstemplinę stimuliaciją ir perkateterinę radiodažnuminę abliacija) terapija leidžia pagerinti labirinto procedūros rezultatus. Viršutinis pertvaros pjūvis naudotinas sudėtingose operacijose, taip galima lengviau apžiūrėti mitralinį vožtuvą ir koreguoti mitralinę ydą. / The purpose of this scientific work was to evaluate safety and efficacy of treatment of atrial fibrillation using monopolar radiofrequency ablation electrodes in patients who undergo mitral valve surgical correction using incisions of atrial septum (trans-septal and superior septal approaches). More than 80% of the patients are free of atrial fibrillation one year after the operation and 76% of these patients do not use anti-arrhythmic drugs. During the final visit of follow-up it was recorded that 71.5% of the patients remained free of atrial fibrillation and flutter. The maze procedure increases duration of cardiopulmonary by-pas for 16 ± 3 min, only. The baseline and surgical correction data in groups of patients of trans-septal and superior septal approaches did not differ. The method of mitral valve correction (implantation of mitral valve prosthesis or plasty of the valve) had no statistically significant influence on the results of atrial fibrillation treatment. The factors influencing the efficacy of the treatment include higher class of heart failure and larger longitudinal measurement of the left atrium found on echoscopy using M-mode. Combined therapy of secondary atrial tachycardia and atypical atrial flutter (by means of anti-arrhythmic drugs, trans-oesophageal stimulation and per-catheter ablation) enables to improve the results of maze procedure. The superior septal approach should be used in complicated operations as using this incision it is more... [to full text]

Laser nano-patterning with near-field optical microscope (NSOM) and the associated energy transport analysis are achieved in this study. Based on combined experimental/theoretical analyses, it is found that laser nano-patterning with a NSOM probes strongly depend on the laser conditions and material properties of the target: the energy transport from the NSOM probes to the targets changes from pure optical to a combination of thermal and optical transport when the pulse duration of laser is increased from femtosecond to nanosecond. As a result, the mechanisms of nano-pattern formation on targets changes from nano-ablation to nano-oxidation/ recrystallization when the laser pulse duration is increased from femtosecond to nanosecond. Also, with the laser nano-patterning experiments, thermal damage of NSOM probes is observed which can be attributed to the low transport efficiency (10-4 – 10-6) and associated heating of the metal cladding of NSOM probes. The heating of NSOM probes are studied with developed time harmonic and transient thermoreflectance (TR) imaging. From time harmonic TR when the NSOM probes are driven with continuous laser, it is found that the location of heating of NSOM probes is ~20-30µm away from the NSOM tip. The strength of the heating is determined by the laser power (linear dependence), wavelength of the laser (stronger with short A), and aperture size of NSOM probes (stronger when aperture size < A/2). From the transient TR imaging when the NSOM probes are driven with pulsed laser, it is found that the peak temperature of the NSOM probe shifts much closer to the tip. The possible reason for the change in the location of peak temperature when continuous laser is changed to pulsed laser can be attributed to the competition between the heat generation and dissipation rates at different location of the probe: the tip experiences highest temperature with pulsed heating as the entire heating processes is adiabatic. The tip also experiences highest heat dissipation rate due to its large surface-to-volume ratio which overcomes the heat generation at the tip under quasi-steady state resulting in shift of the hot spot. The knowledge obtained in this study can be important in the future design of more efficient NSOM probes and other nano-optic devices.

L'ablation laser dans l'air à la pression atmosphérique est souvent appliquée dans l'industrie, l'analyse chimique, la chirurgie, ... Pour un développement plus approfondi des technologies laser basées sur l'effet d'ablation, il est nécessaire de mieux comprendre les phénomènes à l'origine de l'interaction laser-matière. Lors d'un impact du faisceau laser sur la surface d'un matériau, une plume plasma se forme au dessus de la cible. Ce plasma contient des électrons, des atomes et des ions du matériau évaporé, ainsi que du gaz ambiant, s'il est présent. Lors de l'impulsion laser, cette plume absorbe une grande partie d'énergie du faisceau laser, réduisant ainsi la quantité du rayonnement laser qui arrive à la surface de la cible. Les dimensions, ainsi que les paramètres de cette plume plasma évoluent très rapidement avec le temps. L'étude de la dynamique et des paramètres de cette plume est très importante, parce qu'ils influent sur tous les processus physiques ayant lieu à la surface du matériau traité. Nous avons étudié l'expansion de la plume plasma formée lors de l'ablation des échantillons métalliques (Al, Ti, Fe) par faisceau laser Nd :YAG nanoseconde (durée d'impulsion : 5.1 ns, longueur d'onde : 1064 nm, irradiance de l'ordre de grandeur de GW/cm2) dans l'air à la pression atmosphérique en utilisant la technique d'imagerie rapide. Cette technique nous a permis d'observer l'évolution spatio-temporelle de la plume au début de son expansion. Les résultats obtenus indiquent que la plume d'ablation laser a une structure : deux régions ont été distinguées - le cœur et la périphérie de la plume. La dynamique de ces deux régions de la plume a été étudiée et les vitesses de leur expansion ont été déterminées. En plus, nous avons examiné l'influence de l'irradiance laser, ainsi que l'influence de la composition de la cible sur la dynamique de la plume. D'autre part, nous avons développé des modèles numériques sous COMSOL Multiphysics pour simuler le processus d'ablation laser. Un modèle thermique a été utilisé pour simuler l'interaction laser - cible. Les résultats de ce modèle ont été employés comme conditions à la limite du modèle hydrodynamique, utilisé pour simuler l'expansion de la plume du plasma dans l'air ambiant. Deux approches ont été proposées : approche microscopique et macroscopique. Les résultats de simulation basée sur l'approche macroscopique donnent l'évolution temporelle et distribution spatiale (1D) des paramètres de la plume : masse volumique, vitesse, pression.