Electrospray thrusters are low thrust, high specific impulse electric propulsion devices with applications in precision attitude control of space vehicles and efficient propulsion of small spacecraft platforms. These devices operate by electrostatically extracting particles from the surface of ionic liquid propellants and accelerating them away from the vehicle at high speed. Unlike more conventional propulsion technologies which only require electronics for control and regulation, electrospray thruster systems require extensive electronics to operate. The power processing unit (PPU) is a device used to produce the high voltage levels required to operate an electrospray thruster and to measure its operating parameters. The digital control interface unit (DCIU) functions to communicate with the parent system, issue low-level commands to the PPU, and to track propulsion parameters. In this work, a DCIU/PPU system is developed to support parallel developments of electrospray thruster platforms at California Polytechnic State University, San Luis Obispo. The system designed includes commercial off-the-shelf XP Power A-Series high voltage power supplies to support bias levels up to 2kV for two separate electrospray thruster heads, allowing for potential operation in the bipolar emission mode. A Microchip Technologies PIC24F microcontroller is selected to control the system and communicate with a parent system. Instrumentation is designed to support high voltage and sub-microampere current measurement. A down-scaled prototype of the designed system is fabricated for testing of core functionality.

none

A new fabrication process of organic and inorganic nanoparticles and cups by electrospraying blended polymer-sol-gel solutions followed by calcination has been investigated. Because of low viscosity and high surface tension of blended polymersol- gel solutions, an electrostatically extruded continuous liquid jet from the spray source became tiny droplets with diameter of less than 1µm in transit. They were collected as dried formats at the counter electrode. These are then calcinated to eliminate polymers as well as cross-link sol-gel material. Silica nanocups have been fabricated using the above technique and the probable methods to control their morphology by varying the ionic concentration have been investigated. Experiments with biodegradable polymers, like Poly Lactic Acid (PLA) and polyvinylpyrrolidine (PVP) to fabricate nanoparticles using the above technique, have also been carried out. The potential use of such biodegradable particles in drug delivery has been demonstrated. This method can encapsulate drug in the particles without the need of any stabilizer which can cause unwanted effect on the drug. The effect of solvents, polymer concentration and deposition distance on morphology and diameter of particles was also investigated on PLA particles. This process is a simple and efficient approach for producing nanocomposite cups that cannot be made by an aggregation method and also nano/micro particles which may find their use in drug delivery and filtration media. Finally, a new technique to sort the particles based on their dimensions is demonstrated. Because of interactions between charged droplets and a non-linear electrostatic field, nanoparticles with different dimensions are deposited at different locations. By using this principle, silica nanocups have been sorted into three groups with mean diameters of 0.31 µm, 0.7 µm and 1.1µm and a standard deviation of 20%.

No description available.

No description available.

The covalent and non-covalent interactions between DNA and external ligands and between DNA and itself are critical for cellular function. An increased knowledge of these interactions can be used for the development of disease-fighting agents, specifically anti-cancer drugs with improved sensitivity and specificity for tumor cells. Electrospray ionization mass spectrometry (ESI-MS) is useful in the screening and characterization of the interactions involving nucleic acids given the speed and small sample sizes that can be analyzed. In this dissertation, ESI-MS is used to characterize covalent and non-covalent interactions involving DNA to assist in determining how these interactions can lead to better therapeutics. The non-covalent binding of ligands to quadruplex oligonucleotides is discussed first. Pyrrole inosine ligands, which bind to guanine bases, were found to interact with both quadruplexes and with guanine rich oligonucleotides without a quadruplex structure. While those interactions were specific with guanine, novel platinum complexes were found to form specific interactions with quadruplex structures themselves as the size of the ligands matched the size of a guanine quartet. This allowed the ligands to end-stack with quadruplexes with large thymine-rich loops between guanine-rich regions. The non-covalent and covalent interactions between ligands and other DNA structures were also studied. The non-covalent binding of anthracycline ligands to mismatched DNA hairpins was probed. The analysis of solutions of approximately equimolar ligand and oligonucleotide indicated preferential binding to the mismatched sequences. Diazirdinyl benzoquinone crosslinkers, including the clinically studied RH1 and an analogue of RH1, were reacted with a variety of duplex oligonucleotides. The complexes were observed by LC-MS and dissociated using both CID and IRMPD to determine the sites of crosslinking. It was determined that both ligands could form interstrand crosslinks in DNA with 5’-GNC or 5’-GNNC sequences. The RH1 analogue, with a bulky phenyl group, formed fewer crosslinks than RH1. In addition to studying DNA/ligand interactions, the interactions between oligonucleotides were also probed. Oligonucleotides containing non-standard isoguanine repeats were annealed in the presence of various cations to determine how those cations would affect the resulting secondary structures. In most cases, isoguanine containing strands formed pentaplexes rather than quadruplexes, which were observed for strands containing guanine bases. / text

No description available.

No description available.

This dissertation reports the fabrication and characterization of thin films from the water soluble polymer sodium poly[2-(3-thienyl)-ethyloxy-4-butylsulfonate] (PTEBS) by electrospray deposition (ESD). Contiguous thin films were created by adjusting the parameters of the electrospray apparatus and solution properties to maintain a steady Taylor cone for uniform nanoparticle aerosolization and controlling the particle water content to enable coalescence with previously deposited particles. The majority of deposited particles had diameters less than 52 nm. A thin film of 64.7 nm with a root mean square surface roughness of 20.2 nm was achieved after 40 minutes of ESD. Hybrid Solar Cells (HSCs) with PTEBS thin films from spin coating and electrospray deposition (ESD) were fabricated, tested, and modeled. A single device structure of FTO/TiO2/PTEBS/Au was used to study the effects of ESD of the PTEBS layer on device performance. ESD was found to double the short circuit current density (Jsc) by a factor of 2 while decreasing the open circuit voltage (Voc) by half compared to spin coated PTEBS films. Comparable efficiencies of 0.009% were achieved from both device construction types. Current-Voltage curves were modeled using the characteristic solar cell equation showed a similar increase in generated photocurrent with a decrease of two orders of magnitude in the saturation current in devices from ESD films. Increases in Jsc are attributed to increased interfacial contact area between the TiO2 and PTEBS layers, while decreases in Voc are from poor film quality from ESD. Polymer solar cells (PSCs) with water-soluble active layers deposited by ESD were fabricated and tested. The water soluble, bulk heterojunction active layers consisted of PTEBS and the fullerene C60 pyrrolidine tris-acid. A single device structure of ITO/PEDOT:PSS/bulk(PTEBS+C60)/Al was used to study the effect of PTEBS to C60 tris-acid ratio on photovoltaic performance. An active layer ratio of PTEBS:C60 tris-acid (1:2) achieved the highest power conversion efficiency (0.0022%), fill factor (0.25), and open circuit voltage (0.56 V). The percolation threshold of C60 was achieved between 1 part PTEBS and 2 to 3 parts C60. Increasing the C60 tris-acid ratio (1:3) improved short circuit current, but reduced the open circuit voltage enough to lower efficiency.

Yeung, Hoi Sze. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 120-134). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese.