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Conversion Of Biorenewable Feedstocks: New Challenges In Heterogeneous Catalysis, Brent H. Shanks 2010 Iowa State University

Conversion Of Biorenewable Feedstocks: New Challenges In Heterogeneous Catalysis, Brent H. Shanks

Chemical and Biological Engineering Publications

For biorenewable feedstocks to serve as a significant source of chemicals and/or fuels, the development of new chemical processes as well as biological processes will be required. However, the conversion of biorenewable feedstocks with heterogeneous catalyst-based processes provides new challenges in inorganic catalyst research and development relative to historical work with petrochemical feedstocks. These catalyst and process challenges include the need to convert highly functionalized molecules with high selectivity, to develop stable catalytic liquid-solid interfaces in which the liquid phase is commonly aqueous, to control solvent phase effects and to develop novel reaction systems. While some of these challenges ...


Metabolic Analysis Of Wild-Type Escherichia Coli And A Pyruvate Dehydrogenase Complex (Pdhc)-Deficient Derivative Reveals The Role Of Pdhc In The Fermentative Metabolism Of Glucose, Abhishek Murarka, James M. Clomburg, Sean Moran, Jacqueline V. Shanks, Ramon Gonzalez 2010 Rice University

Metabolic Analysis Of Wild-Type Escherichia Coli And A Pyruvate Dehydrogenase Complex (Pdhc)-Deficient Derivative Reveals The Role Of Pdhc In The Fermentative Metabolism Of Glucose, Abhishek Murarka, James M. Clomburg, Sean Moran, Jacqueline V. Shanks, Ramon Gonzalez

Chemical and Biological Engineering Publications

Pyruvate is located at a metabolic junction of assimilatory and dissimilatory pathways and represents a switch point between respiratory and fermentative metabolism. In Escherichia coli, the pyruvate dehydrogenase complex (PDHC) and pyruvate formate-lyase are considered the primary routes of pyruvate conversion to acetyl-CoA for aerobic respiration and anaerobic fermentation, respectively. During glucose fermentation, the in vivo activity of PDHC has been reported as either very low or undetectable, and the role of this enzyme remains unknown. In this study, a comprehensive characterization of wild-type E. coli MG1655 and a PDHC-deficient derivative (Pdh) led to the identification of the role of ...


Catalytic Strategies Of Glycoside Hydrolases, Luis Petersen 2010 Iowa State University

Catalytic Strategies Of Glycoside Hydrolases, Luis Petersen

Graduate Theses and Dissertations

Glycoside hydrolases (GHs) are enzymes that catalyze the hydrolysis of the glycosidic bond between two carbohydrate residues or a carbohydrate unit linked to a non-carbohydrate aglycon unit. Despite years of research dedicated to GHs, there are still several mechanistic details, relevant for individual GH enzymes, that remain to be investigated. In this work, a computational analysis of the detailed mechanism of several GHs is presented. QM/MM metadynamics simulations of two glycoside hydrolases, GH8 endoglucanase and GH43 β-xylosidase, give insight into the enzymatic deconstruction of the plant cell wall, and the detailed reaction mechanism of both enzymes. In addition, an ...


Tertiary Structure And Characterization Of A Glycoside Hydrolase Family 44 Endoglucanase From Clostridium Acetobutylicum, Christopher D. Warner, Julie A. Hoy, Taran C. Shilling, Michael J. Linnen, Nathaniel D. Ginder, Clark Ford, Richard B. Honzatko, Peter J. Reilly 2010 Iowa State University

Tertiary Structure And Characterization Of A Glycoside Hydrolase Family 44 Endoglucanase From Clostridium Acetobutylicum, Christopher D. Warner, Julie A. Hoy, Taran C. Shilling, Michael J. Linnen, Nathaniel D. Ginder, Clark Ford, Richard B. Honzatko, Peter J. Reilly

Chemical and Biological Engineering Publications

A gene encoding a glycoside hydrolase family 44 (GH44) protein from Clostridium acetobutylicum ATCC 824 was synthesized and transformed into Escherichia coli.The previously uncharacterized protein was expressed with a C-terminal His tag and purified by nickel-nitrilotriacetic acid affinity chromatography. Crystallization and X-ray diffraction to a 2.2-Å resolution revealed a triose phosphate isomerase (TIM) barrel-like structure with additional Greek key and β-sandwich folds, similar to other GH44 crystal structures. The enzyme hydrolyzes cellotetraose and larger cellooligosaccharides, yielding an unbalanced product distribution, including some glucose. It attacks carboxymethylcellulose and xylan at approximately the same rates. Its activity on carboxymethylcellulose is ...


Theoretical Study Of The Pyrolysis Of Methyltrichlorosilane In The Gas Phase. 3. Reaction Rate Constant Calculations, Yingbin Ge, Mark S. Gordon, Francine Battaglia, Rodney O. Fox 2010 Central Washington University

Theoretical Study Of The Pyrolysis Of Methyltrichlorosilane In The Gas Phase. 3. Reaction Rate Constant Calculations, Yingbin Ge, Mark S. Gordon, Francine Battaglia, Rodney O. Fox

Chemical and Biological Engineering Publications

The rate constants for the gas-phase reactions in the silicon carbide chemical vapor deposition of methyltrichlorosilane (Ge, Y. B.; Gordon, M. S.; Battaglia, F.; Fox, R. O. J. Phys. Chem. A 2007, 111, 1462.) were calculated. Transition state theory was applied to the reactions with a well-defined transition state; canonical variational transition state theory was applied to the barrierless reactions by finding the generalized transition state with the maximum Gibbs free energy along the reaction path. Geometry optimizations were carried out with second-order perturbation theory (MP2) and the cc-pVDZ basis set. The partition functions were calculated within the harmonic oscillator ...


Kinetic Modeling Of Nanoprecipitation Using Cfd Coupled With A Population Balance, Janine C. Cheng, Rodney O. Fox 2010 Iowa State University

Kinetic Modeling Of Nanoprecipitation Using Cfd Coupled With A Population Balance, Janine C. Cheng, Rodney O. Fox

Chemical and Biological Engineering Publications

A model study has been conducted for Flash Nanoprecipitation (FNP)sa novel approach to produce functional nanoparticles. A population balance equation with the FNP kinetics has been integrated into a computational fluid dynamics (CFD) simulation of a custom-designed microscale multi-inlet vortex reactor (MIVR) to yield conditions comparable to the real experimental settings. In coping with the complicated aggregation model in the CFD code, a new numerical approach, the conditional quadrature method of moments (CQMOM), has been proposed, which is capable of solving the multivariate system efficiently and accurately. It is shown that the FNP process is highly influenced by mixing ...


Micro-Recanalization In A Biodegradable Graft For Reconstruction Of The Vas Deferens Is Enhanced By Sildenafil Citrate, Peter A. Holoch, Surya K. Mallapragada, Carlos Atico Ariza, Thomas S. Griffith, Barry R. DeYoung, Moshe Wald 2010 University of Iowa

Micro-Recanalization In A Biodegradable Graft For Reconstruction Of The Vas Deferens Is Enhanced By Sildenafil Citrate, Peter A. Holoch, Surya K. Mallapragada, Carlos Atico Ariza, Thomas S. Griffith, Barry R. Deyoung, Moshe Wald

Chemical and Biological Engineering Publications

This study investigated the effect of sildenafil citrate on micro-recanalization and neovascularization, which were previously demonstrated in a rat model using biodegradable grafts (BGs) for vas deferens reconstruction. A total of 24 male rats underwent bilateral vasectomy with removal of a 0.5-cm vasal segment and were randomly assigned to four groups. Groups 1 and 2 underwent immediate vasovasostomy. Groups 3 and 4 underwent interposition of a 0.5-cm BG in the vasal gap. Groups 1 and 3 were given 5 mg kg -1 day -1 oral sildenafil. Other groups were given placebo. Rats were housed with females 12 weeks ...


Solar-Thermochemical Hydrogen Production Using Thin Film Ald Ferrites And Other Metal Oxides, Jonathan Richard Scheffe 2010 University of Colorado, Boulder

Solar-Thermochemical Hydrogen Production Using Thin Film Ald Ferrites And Other Metal Oxides, Jonathan Richard Scheffe

Chemical & Biological Engineering Graduate Theses & Dissertations

Production of renewable hydrogen is achievable via two-step redox cycles using metal oxide-based intermediates. Concentrated solar energy is capable of decomposing the metal oxide in the first high temperature step, and in the second step water is reacted with the reduced metal oxide to produce H2 and regenerate the starting material.

The thermodynamics of relevant ferrite-based water splitting cycles has been investigated using the thermodynamics software package FactSage. The effect of different metal substitutions in MxFe3-xO4, has been explored, and indicates that Co and Ni based ferrites are both superior to Fe3O ...


Development And Characterization Of Porous And Patterned Hydrogel Scaffolds For Cardiac Muscle Tissue Engineering, Stephanie Marie LaNasa 2010 University of Colorado at Boulder

Development And Characterization Of Porous And Patterned Hydrogel Scaffolds For Cardiac Muscle Tissue Engineering, Stephanie Marie Lanasa

Chemical & Biological Engineering Graduate Theses & Dissertations

Coronary heart disease has become increasingly prevalent in the U.S. and worldwide, and now affects over one million Americans annually. The damaged tissue that results from cardiac injury lacks the ability to regenerate, but no therapies exist to regenerate heart tissue. Tissue engineering is one promising method through which cardiac tissue could be regenerated. This research focuses on developing a tissue engineered hydrogel scaffold using a design regimen that facilitates nutrient transport, tensile properties, and cardiomyocyte adhesion and alignment. A porous structure incorporated into the bulk of the scaffold was selected as a means to enhance nutrient transport. Variations ...


Experimental And Modeling Studies On Catalysis For Photocatalytic Reactions And Detection Of Trace Gases, Kristi Leigh Pelz 2010 University of Colorado, Boulder

Experimental And Modeling Studies On Catalysis For Photocatalytic Reactions And Detection Of Trace Gases, Kristi Leigh Pelz

Chemical & Biological Engineering Graduate Theses & Dissertations

The first part of this thesis focuses on the accelerating effects of water on formic acid photocatalytic oxidation (PCO) and decomposition (PCD) rates on TiO2 and Pt/TiO2.Density functional theory (DFT) calculations indicated that formic acid adsorbed molecularly on a dry anatase (101) surface, but dissociated to monodentate formate when water adsorbed, depending on formic acid and water coverages. For monolayer (ML)formic acid coverage, O-H dissociation required a 1:1 ratio of water to formic acid, and for 1 ML formic acid coverage, 2 monolayers of water were required to stabilize the adsorbed formate species. The 2nd ...


Processing And Conversion Of Algae To Bioethanol, Sara Katherine Kampfe 2010 College of William & Mary - Arts & Sciences

Processing And Conversion Of Algae To Bioethanol, Sara Katherine Kampfe

Dissertations, Theses, and Masters Projects

No abstract provided.


An Ambient Pressure Absorption Heat Pump Using Microporous Membranes: Design, Modeling, And Experimental Investigation, Jason David Woods 2010 National Renewable Energy Laboraratory

An Ambient Pressure Absorption Heat Pump Using Microporous Membranes: Design, Modeling, And Experimental Investigation, Jason David Woods

Mechanical Engineering Graduate Theses & Dissertations

A membrane absorption heat pump uses absorbent (a salt solution) and refrigerant (water) flows separated by a membrane to create a temperature difference, or temperature lift, used for heating or cooling. Compared to conventional absorption heat pumps, an ambient-pressure membrane heat pump is built from simpler, more compact, and potentially less expensive components. Storing the absorbent in an unpressurized tank offers unique options for thermal energy storage for solar heating and cooling of buildings and potential applications in long-distance thermal energy transport.

The contributions of this thesis can be summarized as: (1) design characterization of this novel process, focusing on ...


Multimetallic Electrocatalysts Of Pt, Ru, And Ir Supported On Anatase And Rutile Tio2 For Oxygen Evolution In An Acid Environment, Roderick E. Fuentes, Jake Farell, John W. Weidner 2010 University of South Carolina - Columbia

Multimetallic Electrocatalysts Of Pt, Ru, And Ir Supported On Anatase And Rutile Tio2 For Oxygen Evolution In An Acid Environment, Roderick E. Fuentes, Jake Farell, John W. Weidner

Faculty Publications

Anatase and rutile TiO2 were investigated as stable supports for different multimetallic nanoparticles (i.e., Pt:Ru, Pt:Ir, Pt:Ru:Ir, and Ir:Ru) and tested for activity toward the oxygen evolution reaction (OER). Overall, Ir:Ru had the highest activity toward OER (i.e., current per gram of metal) compared to the other multimetallic combinations studied. This bimetallic supported on anatase TiO2 had a 53% higher current per gram of metal than an unsupported electrocatalyst of the same composition. The higher catalyst utilization of the supported electrocatalysts for OER is consistent with small, well-dispersed nanoparticles, which were observed ...


Quantifying Individual Potential Contributions Of The Hybrid Sulfur Electrolyzer, John A. Staser, Maximilian B. Gorensek, John W. Weidner 2010 University of South Carolina - Columbia

Quantifying Individual Potential Contributions Of The Hybrid Sulfur Electrolyzer, John A. Staser, Maximilian B. Gorensek, John W. Weidner

Faculty Publications

The hybrid sulfur cycle has been investigated as a means to produce clean hydrogen efficiently on a large scale by first decomposing H2SO4 to SO2, O2, and H2O and then electrochemically oxidizing SO2 back to H2SO4 with the cogeneration of H2. Thus far, it has been determined that the total cell potential for the hybrid sulfur electrolyzer is controlled mainly by water transport in the cell. Water is required at the anode to participate in the oxidation of SO2 to H2SO4 and to hydrate ...


Mesoporous Tin Oxide As An Oxidation-Resistant Catalyst Support For Proton Exchange Membrane Fuel Cells, Peng Zhang, Sheng-Yang Huang, Branko N. Popov 2010 University of South Carolina - Columbia

Mesoporous Tin Oxide As An Oxidation-Resistant Catalyst Support For Proton Exchange Membrane Fuel Cells, Peng Zhang, Sheng-Yang Huang, Branko N. Popov

Faculty Publications

Mesoporous catalyst support based on tin oxide (SnO2) is synthesized with high surface area of 205 m2 g−1 and with narrow pore size distribution. Modified polyol method is used to deposit platinum on SnO2. The physical properties of the support and the SnO2-supported Pt catalyst (Pt/SnO2) are characterized by using the Brunauer, Emmett, and Teller method, X-ray diffraction, and transmission electron microscopy. The electrochemical stability and durability of the Pt/SnO2 catalyst are investigated by the accelerated stress tests proposed by the U.S. Department of Energy. Pt/SnO2 catalyst ...


An Efficient Electrochemical–Thermal Model For A Lithium-Ion Cell By Using The Proper Orthogonal Decomposition Method, Long Cai, Ralph E. White 2010 University of South Carolina - Columbia

An Efficient Electrochemical–Thermal Model For A Lithium-Ion Cell By Using The Proper Orthogonal Decomposition Method, Long Cai, Ralph E. White

Faculty Publications

The proper orthogonal decomposition method was applied to develop an efficient, reduced order electrochemical–thermal model for a lithium-ion cell. This model was validated for discharge simulations over a wide range of C rates and various cooling conditions of the cell. The reduced order model agrees well with the COMSOL model, a commercial finite element method solver, and requires times less computation time than the COMSOL model. The model predictions indicate that the discharge time or percent of capacity removed from the cell at an end of discharge voltage of 3.0 V depends on the rate of the discharge ...


Maximizing The Life Of A Lithium-Ion Cell By Optimization Of Charging Rates, Saeed Khaleghi Rahimian, Sean Rayman, Ralph E. White 2010 University of South Carolina

Maximizing The Life Of A Lithium-Ion Cell By Optimization Of Charging Rates, Saeed Khaleghi Rahimian, Sean Rayman, Ralph E. White

Faculty Publications

Using a dynamic optimization method, the optimum charge currents as a function of cycle number during cycling for the lithium-ion cell are obtained. A single particle physics-based model, which includes capacity fade, was applied to simulate the cell performance under low earth-orbit (LEO) cycling conditions. Useful cell life is defined as the number of cycles before the end of discharge voltage drops below 3.0 V or the cell discharge capacity becomes less than 20% of the original discharge capacity. The simulated useful cell life can be increased by ∼29.28% by varying the charge current.


Theoretical Analysis Of Stresses In A Lithium Ion Cell, Sindhuja Renganathan, Godfrey Sikha, Shriram Santhanagopalan, Ralph E. White 2010 University of South Carolina

Theoretical Analysis Of Stresses In A Lithium Ion Cell, Sindhuja Renganathan, Godfrey Sikha, Shriram Santhanagopalan, Ralph E. White

Faculty Publications

A mathematical model to simulate the generation of mechanical stress during the discharge process in a dual porous insertion electrode cell sandwich comprised of lithium cobalt oxide and carbon is presented. The model attributes stress buildup within intercalation electrodes to two different aspects: changes in the lattice volume due to intercalation and phase transformation during the charge/discharge process. The model is used to predict the influence of cell design parameters such as thickness, porosity, and particle size of the electrodes on the magnitude of stress generation. The model developed in this study can be used to understand the mechanical ...


Fabrication Of A Memory Device Using Polyaniline Nanofibers And Gold Nanoparticles, Krunal R. Waghela 2010 Missouri University of Science and Technology

Fabrication Of A Memory Device Using Polyaniline Nanofibers And Gold Nanoparticles, Krunal R. Waghela

Masters Theses

"Fabrication of a memory device using one-step/one-pot synthesis for making a PANI (polyaniline)/Au nanocomposite is reported. Although various devices with horizontal and vertical electrode structures were made, the basic structure used consisted of a PANI/Au thin film sandwiched between two electrodes. The ratio of the current in the OFF state to the current in the ON state was seen to be as high as 5000. These devices showed a bistable behavior, which is typical of memory devices. The PANI/Au nanocomposite thin film was constructed right on the electrode using microfabrication techniques with ultraviolet irradiation. The fabrication ...


Electronic And Magnetic Structure Of (Crcl 3 ) 3, M. Grodzicki, B. Mallick, Anja V. Mudring 2010 Iowa State University

Electronic And Magnetic Structure Of (Crcl 3 ) 3, M. Grodzicki, B. Mallick, Anja V. Mudring

Anja V. Mudring

Electronic structure calculations in the local spin-density approximation have been carried out on the recently synthesized trimer (CrCl 3 ) 3 exhibiting antiferromagnetic ordering below T N =55 K. The calculated magnetic coupling constant, the paramagnetic Curie temperature, and the decrease of the magnetic moment below T N are well reproduced by the calculations. An interpretation of the spin structure is given that is consistent with all experimental data currently available.


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