Browsing by Subject "Microspheres"
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Item Effects of Simultaneous Delivery of Silver and Zinc Oxide on the Efficacy of Healing Acute Wounds.(2013-05) Halldorson, Michael; Rivero, Iris V.; Nutter, Brian; Hamood, Abdul N.This thesis is aimed to establish the efficiency of the simultaneous delivery of Silver (Ag), a proven antibacterial, and Zinc Oxide (ZnO), a compound shown to assist wound healing, in treating wounds, and how the extended release aspect of microspheres improves upon current available healing agent. A review of existing literature provided a foundation for the process of planning the healing agent design. Original research developed through this study is presented in the form of a journal article in Chapter II. This research looks at a new method of simultaneous delivery of Ag and ZnO. The research was planned to show how various ratios of these elements could avoid toxicity, maintain bacteriostatic properties, and decrease the amount of time it would take for a wound to heal. By using PLA as the encapsulating polymer and petrolatum gel as a base carrier, we were able to present a healing gel that provided results showing significant inhibition of bacteria, significant increase in wound closure, and a treatment that can last for an extended period of time. The discussion of future work provides a brief discussion of how alternative base carriers can be used to deliver the microspheres. The results presented in this work provide the foundation for a potential new form of healing gel that can be used on all forms of acute wounds.Item High-sensitivity tracking of optically trapped particles in gases and liquids : observation of Brownian motion in velocity space(2014-08) Kheifets, Simon; Raizen, Mark G.The thermal velocity fluctuations of microscopic particles mediate the transition from microscopic statistical mechanics to macroscopic long-time diffusion. Prior to this work, detection methods lacked the sensitivity necessary to resolve motion at the length and time scales at which thermal velocity fluctuations occur. This dissertation details two experiments which resulted in velocity measurement of the thermal motion of dielectric microspheres suspended by an optical trap in gases and liquids. First, optical tweezers were used to trap glass microspheres in air over a wide range of pressures and a detection system was developed to track the trapped microspheres' trajectories with MHz bandwidth and <100 fm/rt(Hz) position sensitivity. Low-noise trajectory measurements allowed for observation of fluctuations in the instantaneous velocity of a trapped particle with a signal to noise ratio (SNR) of 26 dB, and provided direct verification of the equipartition theorem and of the Maxwell-Boltzmann velocity distribution for a single Brownian particle. Next, the detection technology was further optimized and used to track optically trapped silica and barium titanate glass microspheres in water and acetone with >50 MHz bandwidth and <3 fm/rt(Hz) sensitivity. Brownian motion in a liquid is influenced by hydrodynamic, time-retarded coupling between the particle and the fluid flow its motion generates. Our measurements allowed for instantaneous velocity measurement with an SNR of up to 16 dB and confirmed the Maxwell Boltzmann distribution for Brownian motion in a liquid. The measurements also revealed several unusual features predicted for Brownian motion in the regime of hydrodynamic coupling, including faster-than-exponential decay of the velocity autocorrelation function, correlation of the thermal force and non-zero cross-correlation between the particle's velocity and the thermal force preceding it.Item Plasma-laser interactions with solid polystyrene microspheres(Texas Tech University, 1977-05) Smith, David LNot availableItem Production of cerium oxide microsheres by an internal gelation sol-gel process(2010-01-14) Wegener, Jeffrey J.The experiments performed for this research were completed to produce solid cerium oxide microspheres by an internal gelation sol-gel process. The motivation for this work was to develop a process that would enable the fabrication of a storage or transmutation form for the plutonium and transuranics (TRU) from the Uranium Extraction Plus (UREX ) used fuel reprocessing process. This process is being investigated by the Department of Energy (DOE) and the Advanced Fuel Cycles Initiative (AFCI) through the Nuclear Energy Research Initiative. The internal gelation production of cerium oxide involves the combination of hexamethylenetetramine (HMTA), urea, and cerium nitrate solutions at ~100oC. Microspheres were produced by injection of a broth solution into a flowing stream of hot silicone oil. The captured microspheres were aged, washed, and then underwent Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and XRay Diffraction (XRD) analysis. The process variables examined in this study include the concentrations of HMTA, urea and cerium nitrate, the process temperature, the postgelation aging time, and the product washing conditions. Over a series of 70 experiments, it was determined that a broth solution containing a mixture of 1.45 M cerium nitrate and 1.65 M HMTA and urea (1:1 ratio) solutions produced the best cerium oxide microspheres. The spheres were aged for 30 to 60 minutes and then washed in hexane to remove the silicone oil and a subsequent series of ammonium hydroxide washes to remove unreacted product and to fully gel the microspheres. Through DSC analysis it was determined that excess wash or unreacted product may be removed by an exothermic reaction at approximately 200oC. The XRD analysis of unheated spheres showed the presence of cerium oxide with additional cerium-bearing organics. Following heating, the microspheres were completely converted to cerium oxide.Item Whispering-Gallery Modes in Quantum Dot Embedded Microspheres for Sensing Applications(2011-02-22) Beier, Hope T.New methods of biological analyte sensing are needed for development of miniature biosensors that are highly sensitive and require minimal sample preparation. One novel technique employs optical resonances known as Whispering Gallery Modes (WGMs). These modes arise from total internal reflection of light at the internal surface of a high index microsphere within a low index medium and produce an evanescent field that extends into the surrounding medium. The WGMs produce multiple narrow spectral peaks that shift position with variations in the local index of refraction sampled by the evanescent tail of the WGMs. To excite these WGMs, we embed quantum dots (QDs) in the periphery of polystyrene microspheres to serve as local light sources. By coupling emission from the QDs to the WGMs, the sensors can be excited and interrogated remotely and, by monitoring the shift of multiple resonance modes, may provide higher sensitivity and accuracy compared with similar techniques. The high refractometric sensitivity of the WGMs offers potential for trace detection of molecules adsorbed onto or bound to the microsphere sensor elements. The sensitivity of these sensors is demonstrated by monitoring the wavelength shift of multiple resonant modes as bulk index of refraction is changed. The potential for targeted biosensing is explored through addition of a protein that adsorbs to the microsphere surface, thrombin. Microsensor response in all cases demonstrated increased sensitivity over theoretical predictions. Models based on Mie theory and continuity of the radial functions across the sphere-media interface were used to model the location, Q-factor, and sensitivity of the WGMs in microspheres by considering the embedded QDs as a high index outer layer. This model was used, along with estimates of the QD-layer index and penetration depth, to relate the locations and sensitivities of the modes to our experimental results with strong agreement between the two. In all, these microspheres demonstrate feasibility for use as remote microsensors with sensitivities rivaling current techniques.