Introduction: Elevated levels of tissue factor positive (TF +) microparticles (MPs) are observed in plasma from a variety of patients with an increased risk of thrombosis. We and others have described the measurement of TF activity in MPs isolated from plasma. The aim of this study was to investigate the effects of pre-analytical and analytical variables on TF activity of MPs isolated from blood of healthy volunteers either untreated or treated ex vivo with bacterial lipopolysaccharide. Materials and methods: We evaluated the following parameters: use of different centrifugation speeds to isolate the MPs; comparison of TF activity of MPs isolated from platelet poor plasma versus platelet free plasma; effect of freeze/thaw on MP TF activity; and comparison of the MP TF activity assay with the measurement of TF protein by ELISA or flow cytometry. Results: MPs prepared from platelet poor plasma by centrifugation at 20,000 × g or 100,000 × g for 15 minutes had similar levels of TF activity. However, significantly less TF activity was found in MPs isolated from platelet free plasma compared with platelet poor plasma. Interestingly, freeze/thawing of the plasma showed donor to donor variation in MP TF activity, with a moderate increase in some individuals. Conclusion: TF + MPs can be quantitatively isolated from platelet poor or platelet free plasma by centrifugation at 20,000 × g for 15 minutes. Measurement of MP TF activity in plasma may be used to detect a prothrombotic state in patients with various diseases.

Erosion and deposition in gas turbine engines are functions of particle/wall interactions and the Coefficient of Restitution (COR) is a fundamental property of these interactions. COR depends on impact velocity, angle of impact, temperature, particle composition, and wall material. In the first study, a novel Particle Tracking Velocimetry (PTV) / Computational Fluid Dynamics (CFD) hybrid method for measuring COR has been developed which is simple, cost-effective, and robust. A Laser-Camera system is used in the Virginia Tech Aerothermal Rig to measure microparticles velocity. The method solves for particle impact velocity at the surface by numerical methods. The methodology presented here characterizes a difficult problem by a combination of established techniques, PTV and CFD, which have not been used in this capacity before. The current study characterizes the fundamental behavior of sand at different impact angles. Two sizes of Arizona Road Dust (ARD) and one size of Glass beads are impacted on to 304-Stainless Steel. The particles are entrained into a free jet of 27m/s at room temperature. Mean results compare favorably with trends established in literature. This technique to measure COR of microparticle sand will help develop a computational model and serve as a baseline for further measurements at elevated, engine representative air and wall temperatures. In the second study, ARD is injected into a hot flow field at temperatures of 533oK, 866oK, and 1073oK to measure the effects of high temperature on particle rebound. The results are compared with baseline measurements at ambient temperature made in the VT Aerothermal Rig, as well as previously published literature. The effects of increasing temperature and velocity led to a 12% average reduction in total COR at 533oK (47m/s), a 15% average reduction at 866oK (77m/s), and a 16% average reduction at 1073oK (102m/s) compared with ambient results. From these results it is shown that a power law relationship may not conclusively fit the COR vs temperature/velocity trend at oblique angles of impact. The decrease in COR appeared to be almost entirely a result of increased velocity that resulted from heating the flow. / Ph. D.

This dissertation develops technology for microfluidic point-of-care (POC) immunoassay devices, divided into three papers, and explores the use of a quartz crystal microbalance for real time monitoring of blood coagulation in a fourth paper. The concept of POC testing has been well established around the world. With testing conveniently brought to the vicinity of the patient or testing site, results can be obtained in a much shorter time. There has been a global push in recent years to develop POC molecular diagnostics devices for resource-limited regions where well equipped centralized laboratories are not readily accessible. POC testing has applications in medical/veterinary diagnostics, environmental monitoring, as well as defense related testing. In the first paper, we demonstrated the use of latex immunoagglutination assays within a microfluidic chip to be an effective and sensitive method for detecting the bovine viral diarrhea virus. In the second paper the feasibility and general ease of integrating liquid core optical components onto a microfluidic lab-on-a-chip type device, for point-of-care AI diagnosis is demonstrated. In the third paper particle agglutination assays, utilizing light scattering measurements at a fixed angle from incident light delivery, for pathogen detection are explored in both Rayleigh and Mie scatter regimes through scatter intensity simulations and compared to experimental results. In the fourth paper a quartz crystal microbalance was used for real-time monitoring of fibrinogen cross-linking on three model biomaterial surfaces.

<p>Osteoarthritis (OA) is a degenerative disease of articular joints characterized by progressive deterioration of the cartilage lining, subchondral bone destruction and thickening of the joint capsule. These tissue changes lead to symptomatic joint pain and joint dysfunction, leading to restrictions on daily life activities. Intra-articular injections of corticosteroids or anti-inflammatory compounds are commonly given to relieve symptoms associated with OA; however, rapid clearance of these compounds from the joint space and into draining synovial lymphatics necessitates the use of drug carriers to increase drug residence and efficacy. </p><p>Silk fibroin, a protein polymer from the mulberry silkworm (Bombyx mori) and of slow biodegradation in vivo, has a long history of clinical use. Silk fibroin can be fabricated into nano- and micro-particles capable of entrapping small-molecule drugs to provide for sustained release. For this work, silk microparticles were fabricated entrapping the near-infrared fluorescent dye, Cy7, as a model small-molecule drug. The release kinetics of the Cy7 from the silk microparticles were characterized in vitro and fluorescence in vivo imaging was used to study the clearance of silk microparticles following intra-articular injection in healthy rat knee joints.</p><p>Furthermore, a surgically-induced model of OA was used in rat knee joints to study the effect of OA pathology on intra-articular clearance. Fluorescently-labeled dextrans of varying size (10 and 500 kDa molecular weight) were intra-articularly injected in the knee joints of healthy and OA rats, and fluorescence in vivo imaging was employed to detect changes in the intra-articular clearance. Additionally, a new method to characterize the trans-synovial clearance of the fluorescent dextrans was developed using the confocal microscopy of joint tissue sections from healthy and OA joints.</p> / Dissertation

No description available.

When a gas turbine operates in a particle laden environment, such as a desert, small solid particles are ingested into the engine. The ingested sand particles can cause damage to engine components and reduce the service life of the engine. Particle ingestion causes the erosion of metal blades and vanes, and, if the firing temperature is hot enough, deposition of molten particles in the hot sections of the engine. Both deposition and erosion phenomena can severely reduce overall engine performance. The Coefficient of Restitution (COR) is a measure of the particle-wall interaction, and has been widely used to quantify particle rebound characteristics in past particle impact studies. This work investigates the effects of temperature on sand particle impact characteristics by measuring the COR and other deposition related impact parameters. The first study presented as part of the dissertation contains a description of a novel method used to measure COR using a Particle Tracking Velocimetry (PTV) method. This is combined with Computational Fluid Dynamics (CFD) flow field to allow for an accurate determination of the particle impact velocity. The methodology described in this paper allows for measurement of the COR in a wide range of test conditions in a relatively simple manner. The COR data for two different sizes of Arizona Road Dust (ARD) and one size of glass beads are presented in this paper. Target material was stainless steel 304 and the impact angle was varied from 25 to 85 degrees. The second study details the first quantification of the COR of san particles at elevated temperatures. Temperatures used in this study were 533 K, 866 K, and 1073 K. In this study the mass flow rate through the experimental setup was fixed. This meant that velocity and temperature were coupled. Target material for this study was stainless steel 304 and the impact angle was varied from 30° to 80°. The COR was found to decrease substantially at the temperatures and velocity increased. It was determined that the decrease in COR was almost certainly caused by the increase in velocity, and not the decrease in temperature. The third study contains COR results at elevated temperatures. Significant improvements from the method used to calculate COR in the first paper are described. The particle used for these tests was an ARD sand of 20-40 μm size. Target materials used were stainless steel 304 and Hastelloy X. The particles impinged on the target coupon at a velocity of 28m/s. Tests were performed at three different temperatures, 300 K (ambient), 873 K, and 1073 K to simulate temperatures seen in gas turbine cooling flows. The angle of impingement of the bulk flow sand on the coupon was varied between 30° and 80°. A substantial decrease in COR was discovered at the elevated temperatures of this experiment. Hastelloy X exhibited a much larger decrease in COR than does stainless steel 304. The results were compared to previously published literature. The final study also used the ARD size of 20-40 μm. The target material was a nickel alloy Hastelloy X. Experiments for this study were performed at a constant velocity of 70m/s. Various temperatures ranging from 1073 K up to and including 1323 K were studied. Particle angle of impact was varied between 30° and 80°. Significant deposition was observed and quantified at the highest two temperatures. The COR of the ARD sand at the highest temperatures was found not to change despite the occurrence of deposition. At elevated temperatures, many of the particles are not molten due to sand's non-homogenous and crystalline nature. These particles rebound from the target with little if any change in COR. / Ph. D.

In many arid regions, particle ingestion can occur within propulsive gas turbines. The ingested particles can severely impact performance and may damage many primary gas path components through erosion or deposition. Characterizing crystalline deposits on metallic substrates can allow for the prediction of deposition to improve component resilience and develop health monitoring algorithms. This work investigates the effect of temperature and angle on sand deposits and attempts to quantitatively characterize the deposition of Arizona Test Dust (ATD) onto Hastelloy X. The first study presented in this thesis describes a preliminary investigation of sand deposition at temperatures and velocities similar to those found in the turbine section of propulsive gas turbine engines and presents an equation for predicting deposition as a function of gas path temperature and impact angle. The sand and air mixture maintained a constant flow velocity of approximately 70 m/s, impact angle was varied from 30° to 90°, and the gas path temperature was varied from 1000 °C to 1100 °C. The number of deposits was found to linearly increase with temperature for all coupon angles tested. The model was able to explain approximately 67% of the deposition that occurs, with the remaining percentage due to other factors such as injection rates and surface temperature. The second study describes an improved investigation of sand deposition and presents an equation for predicting deposition as a function of surface temperature and impact angle. This study characterizes deposition using percent coverage in addition to deposits per square millimeter. Deposition is a quadratic function of both near surface coupon temperature and coupon angle. The model using deposits per mm2 was able to explain 96.3% of the deposition that occurred and the model using percent coverage was able to explain 98.9% of the deposition that occurred. / Master of Science / In desert regions, sand particles can be sucked into helicopter and airplane jet engines which can severely impact performance and may damage many engine components through erosion or hot deposits. By measuring the sticking properties of sand on materials used in jet engines, equations to predict sticking can be created and combined with previous erosion research to develop computational simulations of sand behavior in jet engines. This work investigates the effect of temperature and angle on sand deposits and numerically characterizes the deposition of sand particles onto jet engine materials. The first study presented in this thesis describes an initial investigation of sand deposition at temperatures and speeds similar to those found in the turbine section of jet engines and presents an equation for predicting deposition as a function of flow temperature and impact angle. The model was able to explain approximately 67% of the deposition that occurs, with the remaining percentage due to other factors such as injection rates and test coupon surface temperature. The second study describes an improved investigation of sand deposition and presents an equation for predicting deposition as a function of metal surface temperature and impact angle. The model is able to explain 98.9% of the deposition that occurred. The improved sand sticking model will allow designers to improve engine resilience and develop health monitoring algorithms. Improved resilience and health monitoring will increase airplane safety as well as reducing maintenance and operating costs when flying in sandy or arid regions.

Les microparticules (MPs) sont des vésicules dérivées de la membrane plasmique lors de la vésiculation par les cellules stimulées. Les MPs interviennent dans l'inflammation, les communications intercellulaires et la coagulation. Tout d'abord, nous avons standardisé une méthode pour caractériser et quantifier des MPs par cytométrie en flux dans le plasma.L'implication des MPE est suggérée dans le psoriasis notamment par le rôle central du TNF-a qui est un puissant inducteur de vésiculation. Nous avons comparé les valeurs de MPs chez des patients psoriasiques à celles de donneurs sains. Les MPE étaient plus élevées chez les patients notamment les MPs de petite taille. Les MPs diminuaient sous traitements anti-TNF-a.Les MPs agissent sur la progression tumorale des cancers. Les MPs tumorales ou des cellules de l'hôte peuvent modifier les propriétés invasives de la tumeur par des propriétés transférées. Les MPs peuvent aussi interagir avec les cellules du système immunitaire. Dans le mélanome, le risque de thrombose est accru. Or, la libération de MPs conduit à un état d'hypercoagulabilité. Les MPP et les MPE étaient augmentés dans chaque stade de la maladie par rapport à une population témoin. De plus, les MPs des patients atteints de mélanome possédaient des propriétés procoagulantes. L'étude des MPs en Dermatologie permet d'appréhender de nouveaux angles de la physiopathologie des maladies inflammatoires ou en carcinogenèse. Le dosage des MPs pourrait devenir un outil intéressant de monitoring des biothérapies dans le psoriasis. Dans le mélanome, des études complémentaires permettront de déterminer si les taux de MPs constituent un facteur pronostique intéressant / Microparticles (MPs) are vesicles derived from the plasma membrane during vesiculation by the stimulated cells. MPsare involved in inflammation, intercellular communications and coagulation. First, we standardised a method tocharacterise and quantify MPs in plasma by flow cytometry.The implication of endothelial microparticles (EMPs) is suggested in psoriasis, in particular by the central role of TNF-a which is a powerful inducer of vesiculation. We compared the values of MPs in psoriatic patients to the values inhealthy donors. EMPs were higher in the patients, especially MPs of small size. MPs were reduced under anti-TNF-atreatments.MPs have an action on the tumoral development of cancers. Tumoral MPs or the host's cells can modify the invasiveproperties of the tumour through transferred properties. MPs can also interact with the cells of the immune System. Inmelanoma, the risk of thrombosis is increased, but the release of MPs leads to a state of hypercoagulability. Plateletsmicroparticles (PMPs) and EMPs were increased at each stage of the disease compared to a control population. Inaddition, MPs of patients with melanoma had procoagulant properties.The study of MPs in Dermatology allows to apprehend new approaches of the physiopathology of inflammatorydiseases or in carcinogenesis. The dosage of MPs could become an interesting tool in the monitoring of biotherapies inpsoriasis. In melanoma, additional studies will show if MPs rates are an interesting prognostic factor.

This study proposes a novel microfluidic system based on a computer controlled digital image processing (DIP) technique and optical tweezers for automatic cell/microparticle recognition, counting and sorting in a continuous flow environment. In the proposed system, the cells/microparticles are focused electrokinetically into a narrow sample stream and are then driven through the region of interest (ROI), where they are recognized and traced in real time using a proprietary DIP system. Synchronized control signals generated by the DIP system are then used to actuate a focused IR laser beam to displace the target cells from the main sample stream into a neighboring sheath flow, which carries them to a downstream collection channel where they are automatically counted. The proposed approach makes possible the continuous sorting and counting of cell samples without the need for any moving parts or embedded transducers. The experimental results show that the proposed system is capable of sorting 5 £gm or 10 £gm PS bead from a mixture of 5 £gm and 10 £gm samples in the flow speed 300 £gm/sec. The proposed system provides a simple, low-cost, high-performance solution for cell manipulation in microfluidic devices.

In this thesis, the effectiveness of microparticle retention aid systems comprising of different cationic starches (tapioca and waxy maize), cationic flocculants (flocculant 1, linear with low charge density and flocculant 2, branched with medium charge density polyacrylamides) and anionic colloidal silica in improving retention and drainage of thermomechanical pulp (TMP) suspensions loaded with precipitated calcium carbonate (PCC) is studied. While starch is primarily added as dry strength agent in PCC-filled TMP suspensions, it also has a significant role in improving retention and drainage. Tapioca starch, which has both amylose and amylopectin, is found to be a better retention and drainage aid than waxy maize starch, which only contains amylopectin. In the absence of starch, both flocculants are ineffective in improving retention and drainage. With starch, both flocculant and silica are significant in enhancing retention and drainage further. Increasing the dosage of either flocculant or silica generally increases retention as well as drainage. Flocculant 2 is found to give slightly worse total and filler retention but better drainage compared to flocculant 1. The dosage of flocculant 2 is only half that of flocculant 1 though – for this reason overall flocculant 2 is deemed more effective in improving retention and drainage than flocculant 1. Split starch addition, where a portion of the starch is premixed with PCC and the rest added to the pulp, causes a slight decrease in both retention and drainage. Therefore, should the papermaker decide to use this approach, the starch should be split in a 25:75 ratio between PCC and the pulp to minimize the negative effects. Due to the cost benefits of using increased amounts of PCC, it is desirable to increase PCC content beyond the standard currently used (250 kg/t OD pulp for communications-grade paper). However, at very high dosages of PCC (500 kg/t OD pulp), the best combination identified in this work (tapioca starch, flocculant 2 and silica) is unable to maintain good retention and drainage. Increasing retention aid dosages may help retain more PCC, however this tactic can rapidly become uneconomical. A new approach is thus needed to achieve such highly-filled papers.