Chemical Engineering Commons^™

Identification Of An Archaeal Presenilin-Like Intramembrane Protease, Celia Torres-Arancivia, Carolyn M. Ross, Jose Chavez, Zahra Assur, Georgia Dolios, Filippo Mancia, Iban Ubarretxena-Belandia

Publications and Research

Background: The GXGD-type diaspartyl intramembrane protease, presenilin, constitutes the catalytic core of the c-secretase multi-protein complex responsible for activating critical signaling cascades during development and for the production of b-amyloid peptides (Ab) implicated in Alzheimer’s disease. The only other known GXGD-type diaspartyl intramembrane proteases are the eukaryotic signal peptide peptidases (SPPs). The presence of presenilin-like enzymes outside eukaryots has not been demonstrated. Here we report the existence of presenilin-like GXGD-type diaspartyl intramembrane proteases in archaea.

Methodology and Principal Findings: We have employed in vitro activity assays to show that MCMJR1, a polytopic membrane protein from the archaeon Methanoculleus marisnigri JR1, …

Predicting Stability Of Alpha-Helical, Orthogonal-Bundle Proteins On Surfaces, Shuai Wei, Thomas A. Knotts

Faculty Publications

The interaction of proteins with surfaces is a key phenomenon in many applications, but current understanding of the biophysics involved is lacking. At present, rational design of such emerging technologies is difficult as no methods or theories exist that correctly predict how surfaces influence protein behavior. Using molecular simulation and a coarse-grain model, this study illustrates for the first time that stability of proteins on surfaces can be correlated with tertiary structural elements for alpha-helical, orthogonal-bundle proteins. Results show that several factors contribute to stability on surfaces including the nature of the loop region where the tether is placed and …

Sintering Of Metal Nanoparticles On Model Substrates, Levi R. Houk

Chemical and Biological Engineering ETDs

The sintering of precious metal catalysts is an important problem for the automotive and chemical process industry. As these precious metal catalysts sinter, the metal nanoparticles grow, which in return causes a loss in the overall surface area from loss of the number of available reaction sites. At high temperatures, sintering as a thermally activated process occurs more rapidly and the energetics of the sample changes. In automotive catalysis, for the catalytic converter, the exhaust gases from automobiles contain carbon monoxide, nitrogen oxide compounds, and other hydrogen compounds, which are detrimental to the atmosphere, and a catalyst is required to …

Field-Structured Chemiresistors : Tunable Sensors For Chemical-Switch Arrays, Douglas Read

Chemical and Biological Engineering ETDs

We have developed a significantly improved composite material for applications to chemiresistors, which are resistance-based sensors for volatile organic compounds. This material is a polymer composite containing Au-coated magnetic particles organized into electrically conducting pathways by magnetic fields. This improved material overcomes the various problems inherent to conventional carbon-black chemiresistors, while achieving an unprecedented magnitude of response. When exposed to chemical vapors, the polymer swells only slightly, yet this is amplified into large, reversible resistance changes—as much as 9 decades at a swelling of only 1.5 %. These conductor-insulator transitions occur over such a narrow range of analyte vapor concentration …

Model Electrode Structures For Studies Of Electrocatalyst Degradation, Ronald Goeke

Chemical and Biological Engineering ETDs

Proton exchange membrane fuel cells (PEMFCs) are being extensively studied as power sources because of their technological advantages such as high energy efficiency, high energy and power densities, environmental friendliness, low noise, rapid refueling, and fuel flexibility. The most effective catalyst in these systems consists of nanoparticles of Pt or Pt-based alloys on carbon supports. Understanding the role of the nanoparticle size and structure on the catalytic activity and degradation is needed to optimize the fuel cell performance and reduce the noble metal loading. Electrocatalyst degradation is believed to occur by four mechanisms; particle sintering (Ostwald ripening and migration and …

Dna Translocation Through An Array Of Kinked Nanopores, Zh Chen

Chemical and Biological Engineering ETDs

Synthetic solid-state nanopores are being intensively investigated as single-molecule sensors for detection and characterization of DNA, RNA, and proteins. This field has been inspired by the exquisite selectivity and flux demonstrated by natural biological channels and the dream of emulating these behaviors in more robust synthetic materials that are more readily integrated into practical devices. To date, the guided etching of polymer films, focused ion beam sculpting, and electron-beam lithography and tuning of silicon nitride membranes have emerged as three promising approaches to define synthetic solid-state pores with sub-nanometer resolution. These procedures have in common the formation of nominally cylindrical …

2,2′,5,5′-Tetra­Chloro­Benzidine, Onome Ugono, Marcel Douglas Jr, Nigam P. Rath, Alicia M. Beatty

Educator Preparation & Leadership Faculty Works

No abstract provided.

Design Of A Conditioner For Smoothing Wind Turbine Output Power, Murali Bottu, Mariesa Crow, A. Curt Elmore

Electrical and Computer Engineering Faculty Research & Creative Works

As a result of wind speed intermittency, highly variable wind power output can adversely impact local loads. We propose a conditioner to smooth the variable wind power by utilizing the energy of an ultracapacitor. The conditioner is based on a single phase voltage source inverter (VSI) connected between the grid interconnection point and the ultracapacitor. The shunt VSI injects or absorbs active power from the line to smooth the wind power by utilizing the short term storage capabilities of the ultracapacitor. The ultracapacitor is connected to the DC link through a DC-DC converter, which maintains the voltage of the DC …

Design Of Novel Drug Delivery System And Optimal Dosage Regimens, Kwang Seok Kim

Dissertations

Three representative drug delivery systems were analyzed to emphasize the roles of mathematical models and computer-aided simulations in pharmaceutical research. In the first project, a protocol was developed so that the optimal regimen, consisting of the intravenous boluses and subsequent infusion of theophylline, could be obtained once information on the pharmacokinetics became available. The method was based on a two-compartment model of the human body. A module was created and posted on a website for free access. The second project dealt with the transdermal heat-assisted delivery of corticosterone. Heat conduction and drug diffusion through the patch and the skin were …

An In Situ Fourier Transform Infrared Spectroelectrochemical Study On Alcohols Electrocatalytic Oxidation At Pd Electrode In Acidic Solution, Hai-Ping Huang, Lian-Qin Wang, Pei-Kang Shen

Journal of Electrochemistry

The methanol and ethylene glycol electrooxidation on palladium electrode in acidic solution has been investigated by cyclic voltammetry and in situ Fourier transform infrared spectroelectrochemistry. It shows that the oxidation of methanol and ethylene glycol at Pd electrode cannot proceed until over 1.5 V in acidic and neutral media. The overpotential decreases and the peak current density increases with the reduction in pH values. The formation of the oxygen-containing species significantly affects the alcohol oxidation on Pd electrode. The in situ FTIR spectroscopic measurements show that the oxidation products of ethylene glycol on Pd electrode are CO₂ and oxalic …

Electrooxidation Of Carbon Monoxide On Pd Thin Film-Coated Au Electrodes: Film Thickness Dependence, Yuqing Yang, Shouzhong Zou

Journal of Electrochemistry

The adsorption and electrooxidation of CO on Pd-coated Au electrodes were studied by cyclic voltammetry and surface-enhanced Raman spectroscopy (SERS) . It is found that CO oxidation activity is film thickness dependent. Cyclic voltammograms (CVs) showed that CO oxidation peak potential shifted positively with the increase of the Pd thickness. SERS showed a redshift of the C—O stretching frequency with increasing Pd film thickness. These observations were explained by the dband theory. The strain effect strengthens CO adsorption and stabilizes adsorbed CO,while the ligand effect weakens CO adsorption and eases its oxidation. The ligand effect overpowers the strain effect.

Comparative Study Of Nanoporous Pt, Ptru And Ptruir Catalysts Using Electrochemical Ftir Spectroscopy, M. Amussen Robert, Holt-Hindle Peter, Nigro Samantha, Aicheng Chen

Journal of Electrochemistry

In recent years much effort has been put towards developing efficient Pt-based electrocatalysts for applications in fuel cells. With the rising cost of precious metals such as Pt,the need to enhance the activity and to decrease the load of catalysts is prominent. Herein we report on the synthesis and comparative study of nanoporous Pt,PtRu and PtRuIr electrocatalysts. The nanoporous electrodes were fabricated using a hydrothermal method and characterized by scanning electron microscopy (SEM) ,energy dispersive spectroscopy (EDS) ,X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) . The electrocatalytic activity of the fabricated nanopo- rous materials was evaluated using both CO …

Studies Of Oxidation Processes Of Adsorbed And Solution Co On Pt(110) Electrode By Cyclic Voltammetry And In Situ Ftirs, Li Tian, Jun-Tao Li, Jin-Yu Ye, Chun-Hua Zhen, Shi-Gang Sun

Journal of Electrochemistry

The oxidation processes of adsorbed CO (COad) and solution phase CO (COsol) on Pt(110) electrode were investigated by cyclic voltammetry and in-situ FTIR spectroscopy. It has revealed that in comparison with COad on Pt(110) in a CO-free solution,the oxidation current peak of COsol in a CO-saturated solution is positively shifted ca. 168 mV,and the peak current density has been increased by 6. 70 times. Linear adsorbed CO (COL) is determined by in-situ FTIR spectroscopy as the main species,which is uniformly distributed on Pt (110) surface. In a CO-free solution,the onset potential of COL is measured by in-situ FTIRS ca. 0. …

Experimental Determination Of The Stable Boundary For A Cylindrical Ion Trap, Andrew Alexander, Victor Kwong, Brad Clarke, James Benavente

Undergraduate Research Opportunities Program (UROP)

The first radio frequency (rf) quadrupole ion traps were designed with hyperbolic trapping electrodes and had the advantage of a working theoretical model with an analytical solution for the equation of motion for an ion. This came at the cost of a difficult fabrication process by the nature of the hyperbolic design. Cylindrical designs were found to be an easily constructed and functional alternative for ion trapping, but a sound theoretical model for this geometry has yet to emerge. While the hyperbolic theory yields approximate parameters for stable ion trapping, experiments conducted near the stable/unstable boundary require an experimental determination …

Catalysis Of Ethanol Synthesis From Syngas, Jia Gao

All Dissertations

Catalytic synthesis of ethanol and other higher alcohols from CO hydrogenation has been a subject of significant research since the 1980s. The focus of this research is to establish a better fundamental insight into heterogeneous catalysis for CO hydrogenation reactions, in an attempt to design the best catalysts for ethanol synthesis.
It has been reported widely that promoted Rh-based catalysts can exhibit high selectivity to C2+ oxygenates during CO hydrogenation. The doubly promoted Rh-La-V/SiO2 catalysts exhibited higher activity and selectivity for ethanol and other C2+ oxygenates than singly promoted catalysts. The better performance appears to be due to a synergistic …

Process Development For The Fractionation And Isolation Of Corn Fiber Hemicellulose, Justin Montanti

All Theses

Corn fiber is a co-product of the corn wet-milling process that holds potential to become a value-added product. A process was developed to fractionate and isolate the hemicellulose B component of corn fiber generated by corn wet milling. The process consisted of pretreatment by soaking in aqueous ammonia (SAA) of starch-free corn fiber followed by enzymatic cellulose hydrolysis, during which the hemicellulose B was solubilized by cleavage into xylo-oligosaccharides. The hemicellulose A and B fractions were separated by adjustment of pH, and the hemicellulose B recovered by precipitation with ethanol.
The pretreatment step resulted in a high retention of major …

A New Methodology For Hydrodynamic Similarity In Bubble Columns, Ashfaq Shaikh, Muthanna H. Al-Dahhan

Chemical and Biochemical Engineering Faculty Research & Creative Works

Bubble Columns Are Widely Used in Chemical, Petrochemical, and Biochemical Industries for Various Processes Such as Alkylation, Oxidation, Chlorination, Wet Oxidation of Effluents, Etc. a New Hypothesis for Hydrodynamic Similarity that Can Be Subsequently Used for Scale-Up of Bubble Column Reactors Was Proposed. This Hypothesis Was Evaluated using Advanced Diagnostic Techniques. the Conditions of Similarity Where overall Gas Holdup and Radial Gas Holdup Profiles Were the Same, and Mismatch Where overall Gas Holdup Was the Same But Gas Holdup Radial Profiles Were Different, Were Identified. the Condition that Two Systems Must Operate in the Same Flow Regime to Be Hydrodynamically …

Local Gas Holdup In A Draft Tube Airlift Bioreactor, Hu Ping Luo, Muthanna H. Al-Dahhan

Chemical and Biochemical Engineering Faculty Research & Creative Works

Airlift Column Bioreactors Are Gas-Liquid Contact Devices Characterized by a Rising Channel and a Down Flow Channel Due to Gas Holdup Differences in These Two Channels. Local Gas Holdup Distribution Strongly Affects the overall Gas-Liquid Flow Dynamics in Airlift Columns. in This Work, Local Gas Holdup Distributions in a Draft Tube Airlift Column Covering Both Bubbly Flow and Churn-Turbulent Flow Regimes Have Been Studied using Computed Tomography (CT) Technique as Well as Conventional Techniques. the Radial and Axial Evolutions of the Gas Holdup Distribution Will Be Discussed, Together with the Effects of Superficial Gas Velocity and Geometry Parameters. the Obtained …

A Molecular Dynamics Study On The Transport Of A Charged Biomolecule In A Polymeric Adsorbent Medium And Its Adsorption Onto A Charged Ligand, Enrico Riccardi, Jee-Ching Wang, Athanasios I. Liapis

Chemical and Biochemical Engineering Faculty Research & Creative Works

The transport of a charged adsorbate biomolecule in a porous polymeric adsorbent medium and its adsorption onto the covalently immobilized ligands have been modeled and investigated using molecular dynamics modeling and simulations as the third part of a novel fundamental methodology developed for studying ion-exchange chromatography based bioseparations. To overcome computational challenges, a novel simulation approach is devised where appropriate atomistic and coarse grain models are employed simultaneously and the transport of the adsorbate is characterized through a number of locations representative of the progress of the transport process. The adsorbate biomolecule for the system studied in this work changes …

Prediction Of Liquid Crystalline Content And Molecular Structures Present In Carbonaceous Pitches, Ward Burgess

All Dissertations

ABSTRACT
Previous research at Clemson has shown that multistage, packed column, supercritical extraction (also called dense-gas extraction, or DGE) of petroleum pitches is a promising technique for the production of carbonaceous precursors that can be processed into a variety of carbon products, including activated carbons and high thermal conductivity carbon fibers. As the existence (or lack thereof) of a liquid crystalline phase, or mesophase, plays a key role in establishing the suitability of a potential precursor material for a given application, we developed the SAFT-LC (liquid crystal) equation of state by combining Maier-Saupe theory for multicomponent mixtures with the SAFT …