Purpose: To compare hemodynamic of malignant and benign SRMs on CT and CEUS. Method: Seventy biopsy proven SRM underwent CEUS. Sixty-three had CT. After injection of 0.2 ml of Definity, 3min and after 0.9 ml infusion, 30 sec of data were acquires. Lesion hemodynamics relative to the cortex was evaluated both qualitatively and quantitatively. Results: Considering 15 and 20 HU as enhancement threshold, 10% to 13% of patients did not enhance on CT, while all lesions enhanced on CEUS. Papillary RCCs showed hypovascularity with 100% specificity. In other RCCs, PI, WI slope 5 to45%, 50 to100%, 10 to 90%, WO slope 100 to 50%, 100 to 10%, WO intensity at peak+30 seconds were statistically higher than benign SRMs. Conclusion: All solid SRMs enhance on CEUS, while CT does not show vascularity in 10-13% of solid SRMs. CEUS can differentiate malignant from benign SRMs by evaluating their hemodynamics.

The effects of microbubbles injection in the boundary layer of a turbulent channel flow are investigated. Electrolysis demonstrated to be an effective method to produce microbubbles with an average diameter of 30 ??m and allowed the placement of microbubbles at desired locations within the boundary layer. Measurement of velocity fluctuations and the instantaneous wall shear stress were carried out in a channel flow facility. The wall shear stress is an important parameter that can help with the characterization of the boundary layer. This parameter can be obtained indirectly by the measurement of the flow pressure at the wall. The wall shear stress in the channel was measured by means of three different independent methods: measurement of the pressure gradient by a differential pressure transducer, Particle Image Velocimetry (PIV), and an optical wall shear stress sensor. The three methods showed reasonable agreement of the wall shear stress values for single-phase flow. However, differences as skin friction reductions were observed when the microbubbles were injected. Several measurements of wall-pressure were taken at various Reynolds numbers that ranged from 300 up to 6154. No significant drag reduction was observed for flows in the laminar range; however, a drag reduction of about 16% was detected for turbulent Reynolds numbers. The wall-pressure measurements were shown to be a powerful tool for the measurement of drag reduction, which could help with the design of systems capable of controlling the skin friction based on feedback given by the wall-pressure signal. The proposed measurement system designed in this work has capabilities for application in such diverse fields as multiphase flows, drag reduction, stratified flows, heat transfer among others. The synchronization between independent systems and apparatus has the potential to bring insight about the complicated phenomena involved in the nature of fluid flows.

This dissertation introduces a new approach to measure the mechanical properties of soft tissues. A laser-induced microbubble, created by focusing a single nanosecond laser pulse with a custom-made objective lens, was created at desired locations inside a tissue sample. An acoustic radiation force was generated by a low frequency transducer to displace the microbubble. A custom-built high pulse repetition frequency (PRF) ultrasound system, consisting of two 25 MHz single element transducers, was used to track the dynamics of the microbubble. Reconstruction of the mechanical properties at the specific location in a tissue sample was performed using a theoretical model, which calculated the dynamics of a microbubble under an externally applied force in a viscoelastic medium. The theoretical model and the high PRF ultrasound system were successfully validated in both gelatin phantoms and ex vivo bovine crystalline lenses. Age-related sclerosis of the crystalline lenses from bovine was clearly detected, which might be linked to changes in the crystalline. Location-dependent variation explained that the outer cortex and the inner nucleus had different mechanical properties. In the old and young porcine vitreous humors, age-related changes were not found. However, local variations of the mechanical properties were discovered, which may coincide with the different distributions of the molecular compositions. The laser-induced microbubble approach shows potential for future research into the origin of physiological phenomena and the development of inherent disorders in the eye. I hope that further studies – in the development of a more suitable theoretical model for the microbubble dynamics, in extension to in vivo applications, and in defining the relationship of the mechanical properties to molecular components in the eye – may provide a plan for the therapeutic treatment of eye-related diseases. / text

Purpose: To compare hemodynamic of malignant and benign SRMs on CT and CEUS. Method: Seventy biopsy proven SRM underwent CEUS. Sixty-three had CT. After injection of 0.2 ml of Definity, 3min and after 0.9 ml infusion, 30 sec of data were acquires. Lesion hemodynamics relative to the cortex was evaluated both qualitatively and quantitatively. Results: Considering 15 and 20 HU as enhancement threshold, 10% to 13% of patients did not enhance on CT, while all lesions enhanced on CEUS. Papillary RCCs showed hypovascularity with 100% specificity. In other RCCs, PI, WI slope 5 to45%, 50 to100%, 10 to 90%, WO slope 100 to 50%, 100 to 10%, WO intensity at peak+30 seconds were statistically higher than benign SRMs. Conclusion: All solid SRMs enhance on CEUS, while CT does not show vascularity in 10-13% of solid SRMs. CEUS can differentiate malignant from benign SRMs by evaluating their hemodynamics.

We demonstrate a versatile phase-change sub-micron contrast agent providing three modes of contrast enhancement: 1) photoacoustic imaging contrast, 2) ultrasound contrast with optical activation, and 3) ultrasound contrast with acoustic activation. This agent, which we name 'Cy-droplet', has the following novel features. It comprises a highly volatile perfluorocarbon for easy versatile activation, and a near-infrared optically absorbing dye chosen to absorb light at a wavelength with good tissue penetration. It is manufactured via a 'microbubble condensation' method. The phase-transition of Cy-droplets can be optically triggered by pulsed-laser illumination, inducing photoacoustic signal and forming stable gas bubbles that are visible with echo-ultrasound in situ. Alternatively, Cy-droplets can be converted to microbubble contrast agents upon acoustic activation with clinical ultrasound. Potentially all modes offer extravascular contrast enhancement because of the sub-micron initial size. Such versatility of acoustic and optical 'triggerability' can potentially improve multi-modality imaging, molecularly targeted imaging and controlled drug release. (C) 2017 The Authors. Published by Elsevier GmbH.

<p> Fouling is one of the main problems in the food processing industry. The formation of fouling generates complications that could significantly impact the cost of production due to a reduction in heat transfer capacity or sanitation problems. Fouling formation inside enclosed systems can also lead to the growth of biofilms, causing food safety hazards. The fouling layers are firmly attached to the food contact surface of the equipment in ultra-high temperature (UHT) systems where a food product gets sterilized. Clean in place (CIP) is the most common process for cleaning and removal of fouling as it reduces cleaning time, chemicals, and water consumption compared to a regular cleaning out of place process. While cleaning and solids removal, microbubbles (MB) have shown improvement by enhancing the interaction of the components in the cleaning process with the source of contamination. Therefore, a novel pilot-scale microbubble-based CIP (MBCIP) technology was used for cleaning of fouled surfaces and compared to the traditional CIP process in terms of efficiency and reduction in water usage. The fouling layers attached to the food contact surface of the equipment in UHT was the main area examined. The research evaluated the fouling created at 110ºC in sections of stainless-steel pipes heated in a convection oven and at 121 ºC during regular processing in a UHT with coil heat exchangers system. Reconstituted Non-fat Dry Milk Powder (NFDM) was used as the primary source of protein to evaluate the cleaning efficiency. CIP factors were combined with temperatures at 21.11 ºC, 43.33 ºC, and 76.66 ºC, together with water, alkali, and acid, respectively. The optimal conditions for MBCIP were established and applied to a pilot-scale UHT system representative of a commercial-scale UHT system. The sequence of the CIP was water, alkali, water, acid, and water. The results showed that the acid solution at 76.66 ºC with microbubbles had a significantly higher protein removal compared to the rest of the evaluated conditions, removing 72% of the initial protein content compared to alkali and water which were 10 and <2.55%, respectively during 60 minute of CIP. During the full CIP with the combination of water, alkali, and acid, the effect of alkali was significantly higher than in the rest of the steps performed individually. With the addition of MB overall, CIP removed a considerable amount of protein (>21.5%) in a UHT system compared to the traditional CIP method within the 60 minutes period. CIP chemicals were the main factor contributing to the protein removal, and the gas content was the second most crucial factor in determining the removal. The addition of MB will have a meaningful impact when interacting with cleaning chemicals for industrial CIP. MB also occupies a very small amount of space inside the pipelines representing <0.05% of the volume fraction of the fluid inside the pipes, nevertheless, it can potentially reduce water consumption and provides a sustainable cleaning method for the food industry </p>

Drop impacts are present in our everyday lives, from showering and washing the dishes to inkjet printing and many industrial processes, such as spray coatings and spray cooling. In many of these applications it may be undesirable to have air entrained within the drop when it impacts a surface. As a drop approaches a surface, the gas beneath the drop is unable to fully escape resulting in a rising pressure which becomes sufficient to form a dimple in the bottom center of the drop. Therefore, when the drop makes contact with the surface, it is around the perimeter of this dimple, thus entrapping a disc of air which contracts into a minute bubble. In this dissertation, we study the very early time dynamics of the formation of the central air disc under a variety of circumstances using ultra-high-speed interferometry at rates up to 5 million frames per second. We show the effects of the liquid viscosity for viscosities spanning 7 orders of magnitude, for impacts of drops onto solid surfaces or a film of the same liquid. We find that the size of the air disc is weakly dependent on the drop viscosity to the -1/9 power. We also explore the extended gliding of the drop on a less than 160 nm thick film of air. For impacts onto a solid surface, this gliding layer is rupture in multiple random locations and each localized contact wets the surface at extreme rates compared with the expected viscous-capillary velocity. For impacts onto liquid films, the localized contacts are rarely observed and the gliding layer ruptures at a uniform location. The central bubble contracts much faster than expected in this case as well. Furthermore, we study the effects of reducing the ambient air pressure discovering a compressible and rarified-gas regime wherein the drop makes a double contact with the surface. Lastly, we study the effects of nano-scale surface roughness on the central bubble and the formation of thick bands of microbubbles around the periphery of the air disc.

The induced rupturing of Poly Vinyl Alcohol (PVA) microbubbles with high mechanical index (MI)ultrasound beam is used in multiple medical application such as drug delivery, image contrastenhancement and perfusion imaging.In this work, Triggered imaging technique with subtraction algorithm is used to enhance themicrobubble’s (MB) contrast over tissue (CTR). The technique is performed by rupturing MBwith one destruction wave sequence followed by 100 B-mode imaging pulse sequences. Theimages obtained are then subtracted by a base image that is selected after the destruction pulse[1].The result of this technique depends mainly on the effectiveness of destruction pulse inrupturing highest number of MB. This has been tested through tissue mimicking phantomwithout replenishing the MB. The evaluation of the methods is done through the CTR and CNRcalculation for each of the 100 frames.The contrast enhancement technique used has also been tested with similar setup but withcontinuous replenishment of MB. The evaluation is done by comparing CNR and CTR results forthe 100 frames obtained by B-mode imaging with the ones resulted from the subtractionalgorithm.The contrast values obtained from both experiments are used in driving the characterization ofPVA response to high MI.The result for the destruction pulse effectiveness shows that the pulse indeed managed toreduce number of MB, but not to the lowest. This is because of leaked gas from cracked shell,the shell acoustic enhancement effect, and large bubbles which managed to survive.The Triggered imaging has shown large improvement in CTR value with use of the subtractionalgorithm when compared to B-mode results. In addition, it has provided an experimental wayfor perfusion imaging and quantification by monitoring CTR value after the destructive pulse[2]. This sets the bases for experimental research relevant to tissue perfusion at ultrasound labof KTH.

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A microbubble dispersion (MBD) was used to supply oxygen for an aerobic fermentation of Baker's yeast. The 1-liter microbubble dispersion generator supplied bubbles for 20-liter and 50-liter working volume fermentations in a 72-liter pilot scale fermenter. The microbubbles were stabilized by the surfactants naturally present in the culturing broth medium. The growth patterns of yeast Saccharomyces cerevisiae, cultured at agitation speeds of 150 rpm and 500 rpm, were compared for oxygen supplied by ordinary air sparging and by MBD sparging. Both air sparged and MBD systems were supplied air at equivalent volumetric flow rates. The volumetric oxygen transfer coefficients (KLa) were estimated by the yield coefficient method. The KLa values increased from 142.5 to 458.3 h-1 and from 136.1 to 473.3 h-1 for 20- and 50- liter runs, respectively, as the agitation speed was increased from 150 to 500 rpm in the ordinary air sparged fermentations. The oxygen transfer coefficients in the MBD sparged fermentations were found to be independent of the fermenter agitation speed at approximately 480 h-1 for 20-liter runs and 340 h-1 for 50-liter runs. The growth rates for MBD at 150 rpm were essentially equivalent with air sparged fermentations at 500 rpm. The total power consumption per unit volume of broth for the 150 rpm, MBD fermentation was 68% lower than the 500 rpm, air sparged run for the 20-liter fermentations and was 55% lower for the 50-liter fermentations. / Master of Science