The aim of this study is to investigate the effects of coformers and polymers on the phase transformation and release profiles of cocrystals. Pharmaceutical cocrystals of Carbamazepine (CBZ) (namely 1:1 carbamazepine-nicotinamide (CBZ-NIC), 1:1 carbamazepine-saccharin (CBZ-SAC) and 1:1 carbamazepine-cinnamic acid (CBZ-CIN) cocrystals, were synthesized. A Quality by Design (QbD) approach was used to construct the formulation. Dissolution and solubility were studied using UV imaging and High Performance Liquid Chromatography (HPLC). The polymorphic transitions of cocrystals and crystalline properties were examined using Differential Scanning Calorimetry (DSC), X-Ray Powder Diffraction (XRPD), Raman spectroscopy (Raman) and Scanning Electron Microscopy (SEM). JMP 11 software was used to design the formulation. It has been found that Hydroxupropyl methylcellulose (HPMC) cannot inhibit the transformation of CBZ-NIC cocrystals to Carbamazepine Dihydrate (CBZ DH) in solution or in the gel layer of the matrix, as opposed to its ability to inhibit CBZ Form III (CBZ III) phase transition to CBZ DH. The selection of different coformers of SAC and CIN can affect the stability of CBZ in solution, resulting in significant differences in the apparent solubility of CBZ. The dissolution advantage of the CBZ-SAC cocrystal can only be shown for 20 minutes during dissolution because of the conversion to its dihydrate form (CBZ DH). In contrast, the improved CBZ dissolution rate of the CBZ-CIN cocrystal can be realised in both solution and formulation because of its stability. The polymer of Hypromellose Acetate Succinate (HPMCAS) seemed to best augment the extent of CBZ-SAC and CBZ-CIN cocrystal supersaturation in solution. At 2 mg/ml of HPMCAS concentration, the apparent CBZ solubility of CBZ-SAC and CBZ-CIN cocrystals can increase the solubility of CBZ III in pH 6.8 phosphate buffer solutions (PBS) by 3.0 and 2.7 times respectively. All pre-dissolved polymers in pH 6.8 PBS can increase the dissolution rates of CBZ cocrystals. In the presence of a 2 mg/ml HPMCAS in pH 6.8 PBS, the cocrystals of CBZ-NIC and CBZ-CIN can dissolve by about 80% within five minutes in comparison with 10% of CBZ III in the same dissolution period. Finally, CBZ-NIC cocrystal formulation was designed using the QbD principle. The potential risk factors were determined by fish-bone risk assessment in the initial design, after which Box-Behnken design was used to optimize and evaluate the main interaction effects on formulation quality. The results indicate that in the Design Space (DS), CBZ sustained release tablets meeting the required Quality Target Product Profile (QTPP) were produced. The tablets’ dissolution performance could also be predicted using the established mathematical model.

Extreme conditions allow us to reveal unusual material properties. At the same time an experimental approach is di-cult under such conditions. Capabilities of a theoretical approach based on simplied models are limited. This explainsa wide application of computer simulations at extreme conditions. My thesis is concerned with computer simulations undersuch a conditions. I address such problems as melting, solidsolid phase transitions, shockwave impact on material properties and chemical reactions under extreme conditions. We addressed these problems to facilitate simulations of phase transitions to provide some interpretation of experimental data andexplain enigmatic phenomena in interior of the Earth. / <p>QC 20160615</p>

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / An agile RF routing system has been developed which utilizes phasing techniques to direct signal power to any one of four orthogonally mounted antennae, or either set of two antennae mounted 180° apart on a launch vehicle. The system has been integrated into a telemetry transmitter and has shown superior performance to traditional methods of antennae switching. The unit is self-correcting to maintain maximum RF power at the desired antenna port(s) across a dynamic mission environment. Due to its low loss and high reliability, this method of antennae switching provides a robust RF link.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / The Advanced Range Telemetry (ARTM) program is a tri-service telemetry modernization project whose goal is to assure that all Department of Defense (DoD) test and training ranges are able to use telemetry as necessary to carry out their respective missions. Multi-h Continuous Phase Modulation (CPM) has been selected by the ARTM JPO as the Tier II ARTM waveform, because it offers significant improvements over both legacy telemetry waveforms (PCM/FM) and the newly-introduced Tier I waveform (Feher-patented FQPSK) in terms of spectral containment and detection efficiency, while retaining a constant envelope characteristic. The paper describes the theoretical and measured performance of the ARTM Tier II multi-h CPM waveform, and the implementation of the trellis demodulator being developed for it.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Neutron radiography is well suited to non-invasive imaging of water within metal containers. The goal of this work is to determine if neutron radiography can be used to image water freezing within a 1.6mm diameter capillary tube with the ultimate goal of observing this phenomena within fuel cells. In this work, radiography was completed at the Thermal Neutron Imaging Facility in the Nuclear Engineering Teaching Lab at The University of Texas at Austin. The source of neutrons was a TRIGA Mark II nuclear research reactor capable of 1.1 MW steady state power, which creates a neutron flux at the neutron imaging plane in beam port 5 of 5×10^6 neutrons/cm^2s. A scintillation screen and CCD camera are utilized to obtain digital radiographs, in which differences in pixel intensity are related to differences in neutron attenuation. An image processing algorithm was developed in Matlab to extract necessary data from each image, analyze water column images, and compare one to another. Also, a neutron flux model was implemented in Matlab in order to understand how a non-unidirectional neutron flux will affect final results. Raw image intensities of the water column in liquid and solid form were found to differ from expectations by at most 12.0% and 13.3%, respectively from the predictions of the Matlab flux model. A difference in pixel intensity comparing liquid water to solid water data is apparent and quantified. A ratio of pixel intensity for the ice image to the water image at full thickness of the water column is expected to be 1.038. Experimental results find a maximum ratio of 1.027, 1.1% off from expectations. / text

Peptides are short, sequence and length specific oligomers composed of small amino acid residues. Nature has refined these peptide sequences and their endogenous function through evolution. In addition, peptides have played an important role in medicine, which has lead to further research into developing peptides as lead pharmaceuticals (therapeutic peptides). Unfortunately, therapeutic peptides are inferior as drug candidates due to their low oral bioavailability; immunogenicity and potential to be attacked by peptidases. Fortunately, peptides can be modified by steric constraints, cyclization, and/or replacement of the peptide backbone itself creating a mimic (peptidomimetic) of the original peptide. Peptidomimetics are deliberately designed to have increased protease resistance, reduced immunogenicity and improved bioavailability when compared to the original endogenous peptide. One such peptide, Magainin is a O One such peptide, Magainin is a well-studied, a-helical peptide found in African clawed frogs. This peptide has antibiotic properties (against pathogenic bacteria), which partly arises from the hydrophilic portion of the peptide having basic amino acid side chains periodically disposed on one side of the a-helix. This property of magainin causes its attraction to negatively charged bacteria cell membranes. Unfortunately, as in the case of other antibiotics, pathogenic bacteria have developed effective countermeasures against magainin. We designed a peptidomimetic based on magainin and implemented a plan to determine what type of molecules could be assembled for a magainin mimic. We successfully utilized molecular modeling (Monte Carlo conformational search), as well as results from previous experiments to elucidate what type of molecules, as well as how many molecules would be necessary to create a novel helical-like magainin peptidomimetic. It was discovered that C2 symmetric diamines would be best at generating the helical-like motif and the amino acid lysine to generate the basic side chain. The next step was the successful connection of two C2 symmetric molecules via a urea linkage and then one more connection to a lysine (a-amino group) residue, creating a short sequence of oligoureas (trimers). Finally, attempts to connect the oligoureas trimers were attempted using a solid-phase synthesis approach to generate a functional magainin mimic.

<p>This thesis focuses on femtosecond studies of relaxation and photo-induced dissociation processes in the liquid environment. Measurements are performed using both polarization sensitive and magic angle transient absorption spectroscopy with excitation wavelengths of 387 nm and 258 nm and a white light continuum probe.</p><p>In the first three papers the photodissociation of the trihalides I₃^- in acetonitrile and methanol as well as I₂Br^- in acetonitrile solution is investigated. These studies address such issues as the time scale for the production of the main photoproduct I₂^-, rotational dynamics of the formed diatomic anions, the subsequent wavepacket dynamics of the coherently excited diiodide anion and vibrational relaxation in, and the geminate recombination of, the I₂^-fragment. A nearly equal, bent geometry for the parent anion at the moment of bond breakage is proposed in all three solutions. However, the rotational temperature of the diiodide anion produced in the various solutions, reveals that motion along the bending coordinate of the dissociating triatomic anions plays an important role. The first signs of I₂^- fragments can already be observed at delays of approximately 130 – 190 fs which indicates a faster dissociation than suggested in earlier publications. The production of I₂^- seems fastest for I₃^- in methanol, followed by I₂Br^- in acetonitrile and is slowest for I₃^- in acetonitrile. It appears that vibrational relaxation of newly formed I₂^- fragments happens on a short time scale of a few hundred femtoseconds from initially excited vibrational states centered around v = 60 to v = 20. This fast relaxation was never directly observed before in solution. After that it relaxes with a slower time constant of approximately 2 ps which is shorter than most former reported values. This biexponential behavior agrees well with earlier molecular dynamics simulations. The dependence of the dissociation product formation on excitation energy, parent anion and solvent is found to be relatively strong. These findings lead us to believe that the photo-induced dissociation of the triatomic anions I₃^- and I₂Br^- in solution may very well resemble the gas phase process more than previously thought.</p><p>In paper IV electronic and vibrational relaxation rates of the cyanine dye Methyl-DOTCI are determined after excitation to high lying electronic states. The measurements are performed with two different excitation wavelengths and in various solvents. They reveal a fast electronic relaxation to the second excited electronic state which subsequently relaxes to the first excited electronic state with a time constant of about 10 ps. This relatively long relaxation time may partly be explained by the badly overlapping electronic wavefunctions obtained from theoretical calculations. Vibrational relaxation proceeds with a similar time constant of 10 ps but shows a marked solvent dependence with faster relaxation rates in alcohol solutions.</p>

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