Engineering Commons^™

A Multicellular Model For Differential Regulation Of Circadian Signals In The Core And Shell Regions Of The Suprachiasmatic Nucleus, Christina Vasalou, Michael A. Henson

Michael A Henson

We developed a multicellular model of the mammalian circadian clock characterized by a high degree of heterogeneity with respect to single cell periodicity and behavior (intrinsic and driven oscillators), neurotransmitter release (VIP, GABA and glutamate synthesis) and spatial organization (core and shell regions), mimicking structural patterns within the SCN associated with distinct circadian functions. We simulated the SCN core and shell separately utilizing experimentally derived connectivity schemes for the two subdivisions as observed within the rat SCN. The core was modeled via a small world network characterized by VIP and GABA colocalization, whereas the shell was simulated as a nearest …

Identification And Thermochemical Analysis Of High-Lignin Feedstocks For Biofuel And Biochemical Production, Venugopal Mendu, Anne E. Harman-Ware, Mark Crocker, Jungho Jae, Jozsef Stork, Samuel Morton, Andrew Placido, George W. Huber, Seth Debolt

George W. Huber

Background - Lignin is a highly abundant biopolymer synthesized by plants as a complex component of plant secondary cell walls. Efforts to utilize lignin-based bioproducts are needed. Results - Herein we identify and characterize the composition and pyrolytic deconstruction characteristics of high-lignin feedstocks. Feedstocks displaying the highest levels of lignin were identified as drupe endocarp biomass arising as agricultural waste from horticultural crops. By performing pyrolysis coupled to gas chromatography-mass spectrometry, we characterized lignin-derived deconstruction products from endocarp biomass and compared these with switchgrass. By comparing individual pyrolytic products, we document higher amounts of acetic acid, 1-hydroxy-2-propanone, acetone and furfural …

Role Of Strongly Interacting Additives In Tuning The Structure And Properties Of Polymer Systems, Vikram Kumar Daga

Open Access Dissertations

Block copolymer (BCP) nanocomposites are an important class of hybrid materials in which the BCP guides the spatial location and the periodic assembly of the additives. High loadings of well-dispersed nanofillers are generally important for many applications including mechanical reinforcing of polymers. In particular the composites shown in this work might find use as etch masks in nanolithography, or for enabling various phase selective reactions for new materials development. This work explores the use of hydrogen bonding interactions between various additives (such as homopolymers and non-polymeric additives) and small, disordered BCPs to cause the formation of well-ordered morphologies with small …

Modeling And Simulation Of Nanoparticle Formation In Microemulsion Droplets, Sreekumar R. Kuriyedath

Open Access Dissertations

Semiconductor nanocrystals, also known as quantum dots (QDs), are an important class of materials that are being extensively studied for a wide variety of potential applications, such as medical diagnostics, photovoltaics, and solid-state lighting. The optical and electronic properties of these nanocrystals are different from their bulk properties and depend on the size of the QDs. Therefore an important requirement in their synthesis is a proper control on the final nanoparticle size. Recently, a technique has been developed for synthesizing zinc selenide (ZnSe) QDs using microemulsion droplets as templates. In these systems, a fixed amount of a reactant is dissolved …

Separation Of Carboxylic Acids From Aqueous Fraction Of Fast Pyrolysis Bio-Oils Using Nanofiltration And Reverse Osmosis Membranes, Achyuta Vara Prasada Rao Teella

Open Access Dissertations

There has been a growing interest in renewable sources of energy due to an increase in demand and potential shortages and environmental problems associated with fossil fuels. Bio-oils, complex liquid fuels produced from fast pyrolysis of biomass, have been recognized as one potential source of renewable energy. However, they cannot be utilized directly due to their high viscosity, corrosiveness, and high char content. Bio-oils readily phase separate into aqueous phase and organic phase upon addition of water. The aqueous fraction of bio oil (AFBO) is convenient to process and contains sugars, organic acids, hydroxyacetone, hydroxyacetaldehyde, furfural, phenols and other organic …

Development Of Plant Cell Culture Processes To Produce Natural Product Pharmaceuticals: Characterization, Analysis, And Modeling Of Plant Cell Aggregation, Martin Kolewe

Open Access Dissertations

Plant derived natural products represent some of the most effective anti-cancer and anti-infectious disease pharmaceuticals available today. However, uncertainty regarding the feasibility of commercial supply due to the limited availability of many plants in nature has resulted in a dramatic reduction in the use of natural products as leads in modern drug discovery. Plant cell suspension culture, consisting of dedifferentiated plant cells grown in vitro and amenable to large scale industrial biotechnology processes, is a production alternative which promises renewable and economical supply of these important drugs. The widespread application of this technology is limited by low product yields, slow …

A Systematic Method To Evaluate And Develop Renewable Energy Technologies, George W. Huber, A. A. Upadhye, W. Qi

George W. Huber

No abstract provided.

Flow Cytometry Of Cultured Plant Cells For Characterization Of Culture Heterogeneity And Cell Sorting Applications, Vishal Gaurav

Open Access Dissertations

Plant cells culture provides a production source for plant-derived pharmaceuticals in which environmental conditions can be more easily controlled, manipulated, and optimized to yield high quantities of these valuable natural products. The Roberts Laboratory focuses on development and optimization of bio-processes for production of the anti-cancer agent paclitaxel (Taxol®) in Taxus cell suspension cultures with an emphasis on understanding cellular metabolism at both the molecular and cellular level. Most studies concerning metabolite production via cell culture technology rely on culture-average parameters, which are often insufficient to describe culture heterogeneity. There are several limitations associated with this non-model system; and adapting …

Computational Analysis Of Structural Transformations In Carbon Nanostructures Induced By Hydrogenation, Andre R. Muniz

Open Access Dissertations

Carbon nanomaterials, such as carbon nanotubes and graphene, have attracted significant interest over the past several years due to their outstanding and unusual combination of physical properties. These properties can be modified in a controllable way by chemical functionalization in order to enable specific technological applications. One example is hydrogenation, achieved by the exposure of these materials to a source of atomic hydrogen. This process has been considered for hydrogen storage purposes and for the control of the band gap of these materials for applications in carbon-based electronics. Hydrogen atoms are chemisorbed onto the surface of these materials, introducing sp3-hybridized …

Atomic-Scale Modeling Of Transition-Metal Doping Of Semiconductor Nanocrystals, Tejinder Singh

Open Access Dissertations

Doping in bulk semiconductors (e.g., n- or p- type doping in silicon) allows for precise control of their properties and forms the basis for the development of electronic and photovoltaic devices. Recently, there have been reports on the successful synthesis of doped semiconductor nanocrystals (or quantum dots) for potential applications in solar cells and spintronics. For example, nanocrystals of ZnSe (with zinc-blende lattice structure) and CdSe and ZnO (with wurtzite lattice structure) have been doped successfully with transition-metal (TM) elements (Mn, Co, or Ni). Despite the recent progress, however, the underlying mechanisms of doping in colloidal nanocrystals are not well …

Pyrolysis Oils: Characterization, Stability Analysis, And Catalytic Upgrading To Fuels And Chemicals, Tushar Vispute

Open Access Dissertations

There is a growing need to develop the processes to produce renewable fuels and chemicals due to the economical, political, and environmental concerns associated with the fossil fuels. One of the most promising methods for a small scale conversion of biomass into liquid fuels is fast pyrolysis. The liquid product obtained from the fast pyrolysis of biomass is called pyrolysis oil or bio-oil. It is a complex mixture of more than 300 compounds resulting from the depolymerization of biomass building blocks, cellulose; hemi-cellulose; and lignin. Bio-oils have low heating value, high moisture content, are acidic, contain solid char particles, are …

Mechanical Evaluation Methods For Polymer And Composite Systems, Donna Theresa Wrublewski

Open Access Dissertations

This dissertation describes the development and application of various mechanical characterization techniques to four types of polymer composite materials. The composite nature of these materials ranges from molecular to macro-scale, as do the size scales probed by the techniques chosen. The two main goals of this work are to evaluate the suitability of existing characterization methods to new composite materials (and augment the methods as needed), and to use these methods to determine optimal composite system parameters to maximize the desired mechanical response. Chapter 2 employs nondestructive ultrasonic spectroscopy for characterizing the stiffness response of both micron-scale woven composites and …

Self-Nucleated Crystallization Of A Branched Polypropylene, Dhwaihi Alotaibi

Masters Theses 1911 - February 2014

Long chain branched polypropylene (LCBPP) crystallizes rapidly and with high nucleation density. The origin of this fast crystallization process is not well understood. It has been attributed to its complicated molecular architecture. In this research, we explore isothermal crystallization of LCBPP, 5%LCBPP and linear polypropylene (LPP) through rheological, thermal, microscopy and optical measurements at different experimental temperatures. The time resolved mechanical spectroscopy technique was used to predict the liquid-to-solid transition (gel point) at different crystallization temperatures (supercooling rates) in order to understand the structure during the crystallization process.

The crystallization process of LCBPP was completed in time scale less …

Mechanical Behavior Of Ultra-Low-Dielectric-Constant Mesoporous Amorphous Silica, Dimitrios Maroudas, M. R. Gungor, J. J. Watkins

Dimitrios Maroudas

We report results for the dependence of the mechanical properties of ordered mesoporous silica structures on the pore diameter based on molecular-dynamics simulations. We examine structures with spherical pores arranged in a simple cubic lattice and cylindrical pores arranged in a square lattice subjected to uniaxial tension and compression; for the structures with cylindrical pores, both radial and axial loading is studied with respect to the pore orientation. Our analysis provides a unifying explanation to the observed mechanical response based on the mechanical loading effects on the pore wall thickness.

Chemistry Of Furan Conversion Into Aromatics And Olefins Over Hzsm-5: A Model Biomass Conversion Reaction, George W. Huber, Y. Cheng

George W. Huber

The conversion of furan (a model of cellulosic biomass) over HZSM-5 was investigated in a thermogravimetric analysis–mass spectrometry system, in situ Fourier transform infrared analysis, and in a continuous-flow fixed-bed reactor. Furan adsorbed as oligomers at room temperature with a 1.73 of adsorbed furan/Al ratio. These oligomers were polycyclic aromatic compounds that were converted to CO, CO2, aromatics, and olefins at temperatures from 400 to 600 °C. Aromatics (e.g., benzene, toluene, and naphthalene), oligomer isomers (e.g., benzofuran, 2,2-methylenebisfuran, and benzodioxane), and heavy oxygenates (C12+ oligomers) were identified as intermediates formed inside HZSM-5 at different reaction temperatures. During furan conversion, graphite-type …

Catalytic Conversion Of Biomass-Derived Feedstocks Into Olefins And Aromatics With Zsm-5: The Hydrogen To Carbon Effective Ratio, George W. Huber, H. Zhang, Y. Cheng, T. P. Vispute, R. Xiao

George W. Huber

Catalytic conversion of ten biomass-derived feedstocks, i.e. glucose, sorbitol, glycerol, tetrahydrofuran, methanol and different hydrogenated bio-oil fractions, with different hydrogen to carbon effective (H/Ceff) ratios was conducted in a gas-phase flow fixed-bed reactor with a ZSM-5 catalyst. The aromatic + olefin yield increases and the coke yield decreases with increasing H/Ceff ratio of the feed. There is an inflection point at a H/Ceff ratio = 1.2, where the aromatic + olefin yield does not increase as rapidly as it does prior to this point. The ratio of olefins to aromatics also increases with increasing H/Ceff ratio. CO and CO2 yields …

Analysis Of Aggregate Size As A Process Variable Affecting Paclitaxel Accumulation In Taxus Suspension Cultures, Martin E. Kolewe, Michael A. Henson, Susan C. Roberts

Michael A Henson

Plant cell aggregates have long been implicated in affecting cellular metabolism in suspension culture, yet the rigorous characterization of aggregate size as a process variable and its effect on bioprocess performance has not been demonstrated. Aggregate fractionation and analysis of biomass-associated product is commonly used to assess the effect of aggregation, but we establish that this method is flawed under certain conditions and does not necessarily agree with comprehensive studies of total culture performance. Leveraging recent advances to routinely measure aggregate size distributions, we developed a simple method to manipulate aggregate size and evaluate its effect on the culture as …

Modeling Silicic Acid Polymerization Using A Low Coordination Lattice Model, Peter A. Monson, Scott M. Auerbach, Lin Jin

Peter A. Monson

We present an atomic lattice model for studying the polymerization of silicic acid in sol-gel and related processes for synthesizing silica materials. Our model is based on Si and O atoms occupying the sites of a body-centered-cubic lattice, with all atoms arranged in SiO4 tetrahedra. This is the simplest model that allows for variation in the Si–O–Si angle, which is largely responsible for the versatility in silica polymorphs. The model describes the assembly of polymerized silica structures starting from a solution of silicic acid in water at a given concentration and pH. This model can simulate related materials—chalcogenides and clays—by …

Simulating Infrared Spectra And Hydrogen Bonding In Cellulose Iβ At Elevated Temperatures, George W. Huber, V. Agarwal, W. C. Conner Jr.

George W. Huber

We have modeled the transformation of cellulose Iβ to a high temperature (550 K) structure, which is considered to be the first step in cellulose pyrolysis. We have performed molecular dynamics simulations at constant pressure using the GROMOS 45a4 united atom forcefield. To test the forcefield, we computed the density, thermal expansion coefficient, total dipole moment, and dielectric constant of cellulose Iβ, finding broad agreement with experimental results. We computed infrared (IR) spectra of cellulose Iβ over the range 300–550 K as a probe of hydrogen bonding. Computed IR spectra were found to agree semi-quantitatively with experiment, especially in the …

Production Of Green Aromatics And Olefins By Catalytic Fast Pyrolysis Of Wood Sawdust, George W. Huber, T. R. Carlson, Y. -T Cheng, J Jae

George W. Huber

Catalytic fast pyrolysis of pine wood sawdust and furan (a model biomass compound) with ZSM-5 based catalysts was studied with three different reactors: a bench scale bubbling fluidized bed reactor, a fixed bed reactor and a semi-batch pyroprobe reactor. The highest aromatic yield from sawdust of 14% carbon in the fluidized bed reactor was obtained at low biomass weight hourly space velocities (less than 0.5 h−1) and high temperature (600 °C). Olefins (primarily ethylene and propylene) were also produced with a carbon yield of 5.4% carbon. The biomass weight hourly space velocity and the reactor temperature can be used to …

Production Of Furfural And Carboxylic Acids From Waste Aqueous Hemicellulose Solutions From The Pulp And Paper And Cellulosic Ethanol Industries, George W. Huber, R. Xing, W. Qi

George W. Huber

In this paper we present a new process to produce furfural and co-products of formic and acetic acids from waste aqueous hemicellulose solutions using a continuous two zone biphasic reactor. We estimate this approach uses 67% to 80% less energy than the current industrial processes to produce furfural. An economic analysis indicates that furfural can be produced with this process at 366 US$ per metric ton which is 25% of the selling price of furfural in the U.S. market today. This analysis assumes a plant capacity of 78 kiloton per year of furfural, 12 kiloton per year of formic acid …

Aerosol Generation By Reactive Boiling Ejection Of Molten Cellulose, Paul J. Dauenhauer, A. R. Teixeira, K. G. Mooney, J. S. Kruger, C. L. Williams, W. J. Suszynski, L. D. Schmidt, D. P. Schmidt

Paul J. Dauenhauer

The generation of primary aerosols from biomass hinders the production of biofuels by pyrolysis, intensifies the environmental impact of forest fires, and exacerbates the health implications associated with cigarette smoking. High speed photography is utilized to elucidate the ejection mechanism of aerosol particles from thermally decomposing cellulose at the timescale of milliseconds. Fluid modeling, based on first principles, and experimental measurement of the ejection phenomenon supports the proposed mechanism of interfacial gas bubble collapse forming a liquid jet which subsequently fragments to form ejected aerosol particles capable of transporting nonvolatile chemicals. Identification of the bubble-collapse/ejection mechanism of intermediate cellulose confirms …

Renewable Gasoline From Aqueous Phase Hydrodeoxygenation Of Aqueous Sugar Solutions Prepared By Hydrolysis Of Maple Wood, George W. Huber, N. Li, G. A. Tompsett, T. Zhang, J. Shi, C. E. Wyman

George W. Huber

In this paper we demonstrate an integrated process for the production of high octane gasoline from maple wood by hydrolysis of maple wood into aqueous carbohydrate solutions followed by aqueous phase hydrodeoxygenation of the sugar solutions. The aqueous carbohydrate solutions were prepared by both hydrolysis in hot water and hydrolysis with dilute acids (H2SO4, oxalic acid). The aqueous carbohydrate solutions were a mixture of xylose, water soluble hemicellulose oligomers, acetic acid, glucose, glucose oligomers, and probably some lignin polymers. Hydrolysis with hot water produced primarily hemicellulose oligomers whereas hydrolysis with acids produced mainly xylose and acetic acid. The hydrolysis co-product …

Room Temperature Magnetic Materials From Nanostructured Diblock Copolymers, Zoha M. Al-Badri, Raghavendra R. Maddikeri, Yongping Zha, Hitesh D. Thaker, Priyanka Dobriyal, Raja Shunmugam, Thomas P. Russell, Gregory N. Tew

Gregory N. Tew

Nanostructured magnetic materials are important for many advanced applications. Consequently, new methods for their fabrication are critical. However, coupling self-assembly to the generation of magnetic materials in a simple, straight-forward manner has remained elusive. Although several approaches have been considered, most have multiple processing steps, thus diminishing their use of self-assembly to influence magnetic properties. Here we develop novel block copolymers that are preprogrammed with the necessary chemical information to microphase separate and deliver room temperature ferromagnetic properties following a simple heat treatment. The importance of the nanostructured confinement is demonstrated by comparison with the parent homopolymer, which provides only …

Depletion Versus Deflection: How Membrane Bending Can Influence Adhesion, Jin Nam, Maria Santore

Maria Santore

During depletion-driven vesicle adhesion, a stiff membrane’s resistance to bending at fixed tension prevents contact angle equilibrium and vesicle spreading over an opposing vesicle, while more flexible vesicles partially engulf opposing vesicles. Estimates of the bending cost associated with the spreading contact line, relative to the adhesion energy, were consistent with the observed spreading or lack of spreading for the flexible and stiff membranes, respectively, and predicted a lag time sometimes preceding spreading.

Synthesis Of Hydrogels Via Ring-Opening Metathesis Polymerization: Factors Affecting Gelation, Gregory N. Tew, Ahmad E. Madkour, Joshua M. Grolman

Gregory N. Tew

Ring-opening metathesis polymerization (ROMP) was used to synthesize hydrogels via copolymerization of a diamine monomer 3 and a novel cross-linker 5 using Grubbs' third generation catalyst as initiator. Reactions were performed at two different monomer concentrations and at various initial molar ratios of cross-linker to initiator. At low monomer concentration, gelation occurred at initial cross-linker to initiator ratios of 1.5 and greater, which decreased to values of 1.05 and greater when increasing the monomer concentration. This result is in agreement with the Flory–Stockmayer theory. The gel yield and swelling properties were also found to be dependent on the cross-linker to …