Matching Items (153)
Description
A new theoretical model was developed utilizing energy conservation methods in order to determine the fully-atomized cross-sectional Sauter mean diameters of pressure-swirl atomizers. A detailed boundary-layer assessment led to the development of a new viscous dissipation model for droplets in the spray. Integral momentum methods were also used to determine the complete velocity history of the droplets and entrained gas in the spray. The model was extensively validated through comparison with experiment and it was found that the model could predict the correct droplet size with high accuracy for a wide range of operating conditions. Based on detailed analysis, it was found that the energy model has a tendency to overestimate the droplet diameters for very low injection velocities, Weber numbers, and cone angles. A full parametric study was also performed in order to unveil some underlying behavior of pressure-swirl atomizers. It was found that at high injection velocities, the kinetic energy in the spray is significantly larger than the surface tension energy, therefore, efforts into improving atomization quality by changing the liquid's surface tension may not be the most productive. From the parametric studies it was also shown how the Sauter mean diameter and entrained velocities vary with increasing ambient gas density. Overall, the present energy model has the potential to provide quick and reasonably accurate solutions for a wide range of operating conditions enabling the user to determine how different injection parameters affect the spray quality.
ContributorsMoradi, Ali (Author) / Lee, Taewoo (Thesis advisor) / Herrmann, Marcus (Committee member) / Huang, Huei-Ping (Committee member) / Arizona State University (Publisher)
Created2013
Description
Solution conformations and dynamics of proteins and protein-DNA complexes are often difficult to predict from their crystal structures. The crystal structure only shows a snapshot of the different conformations these biological molecules can have in solution. Multiple different conformations can exist in solution and potentially have more importance in the biological activity. DNA sliding clamps are a family of proteins with known crystal structures. These clamps encircle the DNA and enable other proteins to interact more efficiently with the DNA. Eukaryotic PCNA and prokaryotic β clamp are two of these clamps, some of the most stable homo-oligomers known. However, their solution stability and conformational equilibrium have not been investigated in depth before. Presented here are the studies involving two sliding clamps: yeast PCNA and bacterial β clamp. These studies show that the β clamp has a very different solution stability than PCNA. These conclusions were reached through various different fluorescence-based experiments, including fluorescence correlation spectroscopy (FCS), Förster resonance energy transfer (FRET), single molecule fluorescence, and various time resolved fluorescence techniques. Interpretations of these, and all other, fluorescence-based experiments are often affected by the properties of the fluorophores employed. Often the fluorescence properties of these fluorophores are influenced by their microenvironments. Fluorophores are known to sometimes interact with biological molecules, and this can have pronounced effects on the rotational mobility and photophysical properties of the dye. Misunderstanding the effect of these photophysical and rotational properties can lead to a misinterpretation of the obtained data. In this thesis, photophysical behaviors of various organic dyes were studied in the presence of deoxymononucleotides to examine more closely how interactions between fluorophores and DNA bases can affect fluorescent properties. Furthermore, the properties of cyanine dyes when bound to DNA and the effect of restricted rotation on FRET are presented in this thesis. This thesis involves studying fluorophore photophysics in various microenvironments and then expanding into the solution stability and dynamics of the DNA sliding clamps.
ContributorsRanjit, Suman (Author) / Levitus, Marcia (Thesis advisor) / Lindsay, Stuart (Committee member) / Yan, Hao (Committee member) / Arizona State University (Publisher)
Created2013
Description
The atomization of a liquid jet by a high speed cross-flowing gas has many applications such as gas turbines and augmentors. The mechanisms by which the liquid jet initially breaks up, however, are not well understood. Experimental studies suggest the dependence of spray properties on operating conditions and nozzle geom- etry. Detailed numerical simulations can offer better understanding of the underlying physical mechanisms that lead to the breakup of the injected liquid jet. In this work, detailed numerical simulation results of turbulent liquid jets injected into turbulent gaseous cross flows for different density ratios is presented. A finite volume, balanced force fractional step flow solver to solve the Navier-Stokes equations is employed and coupled to a Refined Level Set Grid method to follow the phase interface. To enable the simulation of atomization of high density ratio fluids, we ensure discrete consistency between the solution of the conservative momentum equation and the level set based continuity equation by employing the Consistent Rescaled Momentum Transport (CRMT) method. The impact of different inflow jet boundary conditions on different jet properties including jet penetration is analyzed and results are compared to those obtained experimentally by Brown & McDonell(2006). In addition, instability analysis is performed to find the most dominant insta- bility mechanism that causes the liquid jet to breakup. Linear instability analysis is achieved using linear theories for Rayleigh-Taylor and Kelvin- Helmholtz instabilities and non-linear analysis is performed using our flow solver with different inflow jet boundary conditions.
ContributorsGhods, Sina (Author) / Herrmann, Marcus (Thesis advisor) / Squires, Kyle (Committee member) / Chen, Kangping (Committee member) / Huang, Huei-Ping (Committee member) / Tang, Wenbo (Committee member) / Arizona State University (Publisher)
Created2013
Description
Single molecule DNA Sequencing technology has been a hot research topic in the recent decades because it holds the promise to sequence a human genome in a fast and affordable way, which will eventually make personalized medicine possible. Single molecule differentiation and DNA translocation control are the two main challenges in all single molecule DNA sequencing methods. In this thesis, I will first introduce DNA sequencing technology development and its application, and then explain the performance and limitation of prior art in detail. Following that, I will show a single molecule DNA base differentiation result obtained in recognition tunneling experiments. Furthermore, I will explain the assembly of a nanofluidic platform for single strand DNA translocation, which holds the promised to be integrated into a single molecule DNA sequencing instrument for DNA translocation control. Taken together, my dissertation research demonstrated the potential of using recognition tunneling techniques to serve as a general readout system for single molecule DNA sequencing application.
ContributorsLiu, Hao (Author) / Lindsay, Stuart M (Committee member) / Yan, Hao (Committee member) / Levitus, Marcia (Committee member) / Arizona State University (Publisher)
Created2013
Description
The need for a renewable and sustainable light-driven energy source is the motivation for this work, which utilizes a challenging, yet practical and attainable bio-inspired approach to develop an artificial oxygen evolving complex, which builds upon the principles of the natural water splitting mechanism in oxygenic photosynthesis. In this work, a stable framework consisting of a three-dimensional DNA tetrahedron has been used for the design of a bio-mimic of the Oxygen-Evolving Complex (OEC) found in natural Photosystem II (PSII). PSII is a large protein complex that evolves all the oxygen in the atmosphere, but it cannot be used directly in artificial systems, as the light reactions lead to damage of one of Photosystem II's core proteins, D1, which has to be replaced every half hour in the presence of sunlight. The final goal of the project aims to build the catalytic center of the OEC, including the Mn4CaCl metal cluster and its protein environment in the stable DNA framework of a tetrahedron, which can subsequently be connected to a photo-stable artificial reaction center that performs light-induced charge separation. Regions of the peptide sequences containing Mn4CaCl ligation sites are implemented in the design of the aOEC (artificial oxygen-evolving complex) and are attached to sites within the tetrahedron to facilitate assembly. Crystals of the tetrahedron have been obtained, and X-ray crystallography has been used for characterization. As a proof of concept, metal-binding peptides have been coupled to the DNA tetrahedron which allowed metal-containing porphyrins, specifically Fe(III) meso-Tetra(4-sulfonatophenyl) porphyrin chloride, to be encapsulated inside the DNA-tetrahedron. The porphyrins were successfully assembled inside the tetrahedron through coordination of two terminal histidines from the orthogonally oriented peptides covalently attached to the DNA. The assembly has been characterized using Electron Paramagnetic Resonance (EPR), optical spectroscopy, Dynamic Light Scattering (DLS), and x-ray crystallography. The results reveal that the spin state of the metal, iron (III), switches during assembly from the high-spin state to low-spin state.
ContributorsRendek, Kimberly Nicole (Author) / Fromme, Petra (Thesis advisor) / Chen, Julian (Committee member) / Ros, Alexandra (Committee member) / Arizona State University (Publisher)
Created2012
Description
The heat transfer enhancements available from expanding the cross-section of a boiling microchannel are explored analytically and experimentally. Evaluation of the literature on critical heat flux in flow boiling and associated pressure drop behavior is presented with predictive critical heat flux (CHF) and pressure drop correlations. An optimum channel configuration allowing maximum CHF while reducing pressure drop is sought. A perturbation of the channel diameter is employed to examine CHF and pressure drop relationships from the literature with the aim of identifying those adequately general and suitable for use in a scenario with an expanding channel. Several CHF criteria are identified which predict an optimizable channel expansion, though many do not. Pressure drop relationships admit improvement with expansion, and no optimum presents itself. The relevant physical phenomena surrounding flow boiling pressure drop are considered, and a balance of dimensionless numbers is presented that may be of qualitative use. The design, fabrication, inspection, and experimental evaluation of four copper microchannel arrays of different channel expansion rates with R-134a refrigerant is presented. Optimum rates of expansion which maximize the critical heat flux are considered at multiple flow rates, and experimental results are presented demonstrating optima. The effect of expansion on the boiling number is considered, and experiments demonstrate that expansion produces a notable increase in the boiling number in the region explored, though no optima are observed. Significant decrease in the pressure drop across the evaporator is observed with the expanding channels, and no optima appear. Discussion of the significance of this finding is presented, along with possible avenues for future work.
ContributorsMiner, Mark (Author) / Phelan, Patrick E (Thesis advisor) / Baer, Steven (Committee member) / Chamberlin, Ralph (Committee member) / Chen, Kangping (Committee member) / Herrmann, Marcus (Committee member) / Arizona State University (Publisher)
Created2013
Description
The numerical climate models have provided scientists, policy makers and the general public, crucial information for climate projections since mid-20th century. An international effort to compare and validate the simulations of all major climate models is organized by the Coupled Model Intercomparison Project (CMIP), which has gone through several phases since 1995 with CMIP5 being the state of the art. In parallel, an organized effort to consolidate all observational data in the past century culminates in the creation of several "reanalysis" datasets that are considered the closest representation of the true observation. This study compared the climate variability and trend in the climate model simulations and observations on the timescales ranging from interannual to centennial. The analysis focused on the dynamic climate quantity of zonal-mean zonal wind and global atmospheric angular momentum (AAM), and incorporated multiple datasets from reanalysis and the most recent CMIP3 and CMIP5 archives. For the observation, the validation of AAM by the length-of-day (LOD) and the intercomparison of AAM revealed a good agreement among reanalyses on the interannual and the decadal-to-interdecadal timescales, respectively. But the most significant discrepancies among them are in the long-term mean and long-term trend. For the simulations, the CMIP5 models produced a significantly smaller bias and a narrower ensemble spread of the climatology and trend in the 20th century for AAM compared to CMIP3, while CMIP3 and CMIP5 simulations consistently produced a positive trend for the 20th and 21st century. Both CMIP3 and CMIP5 models produced a wide range of the magnitudes of decadal and interdecadal variability of wind component of AAM (MR) compared to observation. The ensemble means of CMIP3 and CMIP5 are not statistically distinguishable for either the 20th- or 21st-century runs. The in-house atmospheric general circulation model (AGCM) simulations forced by the sea surface temperature (SST) taken from the CMIP5 simulations as lower boundary conditions were carried out. The zonal wind and MR in the CMIP5 simulations are well simulated in the AGCM simulations. This confirmed SST as an important mediator in regulating the global atmospheric changes due to GHG effect.
ContributorsPaek, Houk (Author) / Huang, Huei-Ping (Thesis advisor) / Adrian, Ronald (Committee member) / Wang, Zhihua (Committee member) / Anderson, James (Committee member) / Herrmann, Marcus (Committee member) / Arizona State University (Publisher)
Created2013
Description
This work demonstrated a novel microfluidic device based on direct current (DC) insulator based dielectrophoresis (iDEP) for trapping individual mammalian cells in a microfluidic device. The novel device is also applicable for selective trapping of weakly metastatic mammalian breast cancer cells (MCF-7) from mixtures with mammalian Peripheral Blood Mononuclear Cells (PBMC) and highly metastatic mammalian breast cancer cells, MDA-MB-231. The advantage of this approach is the ease of integration of iDEP structures in microfliudic channels using soft lithography, the use of DC electric fields, the addressability of the single cell traps for downstream analysis and the straightforward multiplexing for single cell trapping. These microfluidic devices are targeted for capturing of single cells based on their DEP behavior. The numerical simulations point out the trapping regions in which single cell DEP trapping occurs. This work also demonstrates the cell conductivity values of different cell types, calculated using the single-shell model. Low conductivity buffers are used for trapping experiments. These low conductivity buffers help reduce the Joule heating. Viability of the cells in the buffer system was studied in detail with a population size of approximately 100 cells for each study. The work also demonstrates the development of the parallelized single cell trap device with optimized traps. This device is also capable of being coupled detection of target protein using MALDI-MS.
ContributorsBhattacharya, Sanchari (Author) / Ros, Alexandra (Committee member) / Ros, Robert (Committee member) / Buttry, Daniel (Committee member) / Arizona State University (Publisher)
Created2013
Description
Spider dragline silk is well known for its outstanding mechanical properties - a combination of strength and extensibility that makes it one of the toughest materials known. Two proteins, major ampullate spidroin 1 (MaSp1) and 2 (MaSp2), comprise dragline silk fibers. There has been considerable focus placed on understanding the source of spider silk's unique mechanical properties by investigating the protein composition, molecular structure and dynamics. Chemical compositional heterogeneity of spider silk fiber is critical to understand as it provides important information for the interactions between MaSp1 and MaSp2. Here, the amino acid composition of dragline silk protein was precisely determined using a solution-state nuclear magnetic resonance (NMR) approach on hydrolyzed silk fibers. In a similar fashion, solution-state NMR was applied to probe the "13"C/"15"N incorporation in silk, which is essential to understand for designing particular solid-state NMR methods for silk structural characterization. Solid-state NMR was used to elucidate silk protein molecular dynamics and the supercontraction mechanism. A "2"H-"13"C heteronuclear correlation (HETCOR) solid-state NMR technique was developed to extract site-specific "2"H quadrupole patterns and spin-lattice relaxation rates for understanding backbone and side-chain dynamics. Using this technique, molecular dynamics were determined for a number of repetitive motifs in silk proteins - Ala residing nanocrystalline &beta-sheet; domains, 3"1"-helical regions, and, Gly-Pro-Gly-XX &beta-turn; motifs. The protein backbone and side-chain dynamics of silk fibers in both dry and wet states reveal the impact of water on motifs with different secondary structures. Spider venom is comprised of a diverse range of molecules including salts, small organics, acylpolyamines, peptides and proteins. Neurotoxins are an important family of peptides in spider venom and have been shown to target and modulate various ion channels. The neurotoxins are Cys-rich and share an inhibitor Cys knot (ICK) fold. Here, the molecular structure of one G. rosea tarantula neurotoxin, GsAF2, was determined by solution-state NMR. In addition, the interaction between neurotoxins and model lipid bilayers was probed with solid-state NMR and negative-staining (NS) transmission electron microscopy (TEM). It is shown that the neurotoxins influence lipid bilayer assembly and morphology with the formation of nanodiscs, worm-like micelles and small vesicles.
ContributorsShi, Xiangyan (Author) / Yarger, Jeffery L (Thesis advisor) / Holland, Gregory P (Thesis advisor) / Levitus, Marcia (Committee member) / Marzke, Robert F (Committee member) / Arizona State University (Publisher)
Created2014
Description
Increasing computational demands in data centers require facilities to operate at higher ambient temperatures and at higher power densities. Conventionally, data centers are cooled with electrically-driven vapor-compressor equipment. This paper proposes an alternative data center cooling architecture that is heat-driven. The source is heat produced by the computer equipment. This dissertation details experiments investigating the quantity and quality of heat that can be captured from a liquid-cooled microprocessor on a computer server blade from a data center. The experiments involve four liquid-cooling setups and associated heat-extraction, including a radical approach using mineral oil. The trials examine the feasibility of using the thermal energy from a CPU to drive a cooling process. Uniquely, the investigation establishes an interesting and useful relationship simultaneously among CPU temperatures, power, and utilization levels. In response to the system data, this project explores the heat, temperature and power effects of adding insulation, varying water flow, CPU loading, and varying the cold plate-to-CPU clamping pressure. The idea is to provide an optimal and steady range of temperatures necessary for a chiller to operate. Results indicate an increasing relationship among CPU temperature, power and utilization. Since the dissipated heat can be captured and removed from the system for reuse elsewhere, the need for electricity-consuming computer fans is eliminated. Thermocouple readings of CPU temperatures as high as 93°C and a calculated CPU thermal energy up to 67Wth show a sufficiently high temperature and thermal energy to serve as the input temperature and heat medium input to an absorption chiller. This dissertation performs a detailed analysis of the exergy of a processor and determines the maximum amount of energy utilizable for work. Exergy as a source of realizable work is separated into its two contributing constituents: thermal exergy and informational exergy. The informational exergy is that usable form of work contained within the most fundamental unit of information output by a switching device within a CPU. Exergetic thermal, informational and efficiency values are calculated and plotted for our particular CPU, showing how the datasheet standards compare with experimental values. The dissertation concludes with a discussion of the work's significance.
ContributorsHaywood, Anna (Author) / Phelan, Patrick E (Thesis advisor) / Herrmann, Marcus (Committee member) / Gupta, Sandeep (Committee member) / Trimble, Steve (Committee member) / Myhajlenko, Stefan (Committee member) / Arizona State University (Publisher)
Created2014