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Articles 31 - 60 of 377
Full-Text Articles in Chemical Engineering
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
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
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
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 …
Operating Parameters And Selectivity In Batch Reactive Distillation, W. Qi, M. F. Malone
Operating Parameters And Selectivity In Batch Reactive Distillation, W. Qi, M. F. Malone
Michael F. Malone
This Article provides new predictions for selectivity in batch reactive distillation, identifying the reflux or reboil ratio and a Damkhler number (Da) as the key operating parameters. The dimensionless Da incorporates the influence of liquid holdup, vapor rate, and rate of reaction. Example results for a system of serial isomerization reactions and for the synthesis of ethylene glycol are provided. The results show that selectivity improvements in BRD are limited for high values of Da or for high values of the reflux or reboil ratio and that selectivity is enhanced as Da or reflux or reboil ratio is decreased. However, …
Dynamic Flux Balance Modeling Of Microbial Co-Cultures For Efficient Batch Fermentation Of Glucose And Xylose Mixtures, Timothy J. Hanly, Michael A. Henson
Dynamic Flux Balance Modeling Of Microbial Co-Cultures For Efficient Batch Fermentation Of Glucose And Xylose Mixtures, Timothy J. Hanly, Michael A. Henson
Michael A Henson
Sequential uptake of pentose and hexose sugars that compose lignocellulosic biomass limits the ability of pure microbial cultures to efficiently produce value-added bioproducts. In this work, we used dynamic flux balance modeling to examine the capability of mixed cultures of substrate-selective microbes to improve the utilization of glucose/xylose mixtures and to convert these mixed substrates into products. Co-culture simulations of Escherichia coli strains ALS1008 and ZSC113, engineered for glucose and xylose only uptake respectively, indicated that improvements in batch substrate consumption observed in previous experimental studies resulted primarily from an increase in ZSC113 xylose uptake relative to wild-type E. coli. …
Mechanistic Modelling Of Dynamic Mri Data Predicts That Tumour Heterogeneity Decreases Therapeutic Response, R Venkatasubramanian, Rb Arenas, Michael A. Henson, Ns Forbes
Mechanistic Modelling Of Dynamic Mri Data Predicts That Tumour Heterogeneity Decreases Therapeutic Response, R Venkatasubramanian, Rb Arenas, Michael A. Henson, Ns Forbes
Michael A Henson
BACKGROUND: Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) contains crucial information about tumour heterogeneity and the transport limitations that reduce drug efficacy. Mathematical modelling of drug delivery and cellular responsiveness based on underutilised DCE-MRI data has the unique potential to predict therapeutic responsiveness for individual patients. METHODS: To interpret DCE-MRI data, we created a modelling framework that operates over multiple time and length scales and incorporates intracellular metabolism, nutrient and drug diffusion, trans-vascular permeability, and angiogenesis. The computational methodology was used to analyse DCE-MR images collected from eight breast cancer patients at Baystate Medical Center in Springfield, MA. RESULTS: Computer simulations …
Contact Angle Hysteresis: A Different View And A Trivial Recipe For Low Hysteresis Hydrophobic Surfaces, Joseph W. Krumpfer, Thomas J. Mccarthy
Contact Angle Hysteresis: A Different View And A Trivial Recipe For Low Hysteresis Hydrophobic Surfaces, Joseph W. Krumpfer, Thomas J. Mccarthy
Thomas J. McCarthy
Contact angle hysteresis is addressed from two perspectives. The first is an analysis of the events that occur during motion of droplets on superhydrophobic surfaces. Hysteresis is discussed in terms of receding contact line pinning and the tensile failure of capillary bridges. The sign of the curvature of the solid surface is implicated as playing a key role. The second is the report of a new method to prepare smooth low hysteresis surfaces. The thermal treatment of oxygen plasma-cleaned silicon wafers with trimethylsilyl-terminated linear poly(dimethylsiloxane) (PDMS - commercial silicone oils) in disposable glass vessels is described. This treatment renders silicon/silica …
Characterization Of Aggregate Size In Taxus Suspension Cell Culture, Martin E. Kolewe, Michael A. Henson, Susan C. Roberts
Characterization Of Aggregate Size In Taxus Suspension Cell Culture, Martin E. Kolewe, Michael A. Henson, Susan C. Roberts
Michael A Henson
Plant cells grow as aggregates in suspension culture, but little is known about the dynamics of aggregation, and no routine methodology exists to measure aggregate size. In this study, we evaluate several different methods to characterize aggregate size in Taxus suspension cultures, in which aggregate diameters range from 50 μm to 2000 μm, including filtration and image analysis, and develop a novel method using a specially equipped Coulter counter system. We demonstrate the suitability of this technology to measure plant cell culture aggregates, and show that it can be reliably used to measure total biomass accumulation compared to standard methods …
A Multiscale Model To Investigate Circadian Rhythmicity Of Pacemaker Neurons In The Suprachiasmatic Nucleus, Christina Vasalou, Michael A. Henson
A Multiscale Model To Investigate Circadian Rhythmicity Of Pacemaker Neurons In The Suprachiasmatic Nucleus, Christina Vasalou, Michael A. Henson
Michael A Henson
The suprachiasmatic nucleus (SCN) of the hypothalamus is a multicellular system that drives daily rhythms in mammalian behavior and physiology. Although the gene regulatory network that produces daily oscillations within individual neurons is well characterized, less is known about the electrophysiology of the SCN cells and how firing rate correlates with circadian gene expression. We developed a firing rate code model to incorporate known electrophysiological properties of SCN pacemaker cells, including circadian dependent changes in membrane voltage and ion conductances. Calcium dynamics were included in the model as the putative link between electrical firing and gene expression. Individual ion currents …
Electromechanically Driven Chaotic Dynamics Of Voids In Metallic Thin Films, Dimitrios Maroudas, M. R. Gungor, V. Tomar
Electromechanically Driven Chaotic Dynamics Of Voids In Metallic Thin Films, Dimitrios Maroudas, M. R. Gungor, V. Tomar
Dimitrios Maroudas
We report a systematic investigation of complex asymptotic states reached in the electromigration-driven morphological evolution of void surfaces in thin films of face-centered cubic metals with ⟨110⟩- and ⟨100⟩-oriented film planes under the simultaneous action of biaxial tension. The analysis is based on self-consistent dynamical simulations according to a realistic, well-validated, and fully nonlinear model. For ⟨110⟩-oriented film planes, we show that upon increasing the applied mechanical stress level, morphologically stable steady states transition to time-periodic states through a subcritical Hopf bifurcation. Further increase in the stress level triggers a sequence of period-doubling bifurcations that sets the driven nonlinear system …
Improved Utilization Of Biomass-Derived Carbon By Millisecond Co-Processing With Hydrogen Rich Feedstocks, Paul J. Dauenhauer, J. L. Colby, A. Bhan, L. D. Schmitt
Improved Utilization Of Biomass-Derived Carbon By Millisecond Co-Processing With Hydrogen Rich Feedstocks, Paul J. Dauenhauer, J. L. Colby, A. Bhan, L. D. Schmitt
Paul J. Dauenhauer
A reactor capable of improving the utilization of biomass-derived carbon during thermochemical conversion to synthesis gas is demonstrated experimentally. By co-processing hydrogen-deficient biomass (H/C[similar]2) with hydrogen-rich feedstocks (H/C≥4) through catalytic partial oxidation, 100% of the fuel carbon atoms fed to the reactor can be converted to CO.
Predicting Bite Force In Mammals: Two-Dimensional Versus Three-Dimensional Lever Models, Jl Davis, Se Santana, Er Dumont, Ir Grosse
Predicting Bite Force In Mammals: Two-Dimensional Versus Three-Dimensional Lever Models, Jl Davis, Se Santana, Er Dumont, Ir Grosse
Jeffrey M. Davis
Bite force is a measure of whole-organism performance that is often used to investigate the relationships between performance, morphology and fitness. When in vivo measurements of bite force are unavailable, researchers often turn to lever models to predict bite forces. This study demonstrates that bite force predictions based on two-dimensional (2-D) lever models can be improved by including three-dimensional (3-D) geometry and realistic physiological cross-sectional areas derived from dissections. Widely used, the 2-D method does a reasonable job of predicting bite force. However, it does so by over predicting physiological cross-sectional areas for the masseter and pterygoid muscles and under …
Kinetics Of Furfural Production By Dehydration Of Xylose In A Biphasic Reactor With Microwave Heating, George W. Huber, R. Weingarten, J. Cho, W. C. Conner Jr.
Kinetics Of Furfural Production By Dehydration Of Xylose In A Biphasic Reactor With Microwave Heating, George W. Huber, R. Weingarten, J. Cho, W. C. Conner Jr.
George W. Huber
In this paper we report a kinetic model for the dehydration of xylose to furfural in a biphasic batch reactor with microwave heating. There are four key steps in our kinetic model: (1) xylose dehydration to form furfural; (2) furfural reaction to form degradation products; (3) furfural reaction with xylose to form degradation products, and (4) mass transfer of furfural from the aqueous phase into the organic phase (methyl isobutyl ketone - MIBK). This kinetic model was used to fit experimental data collected in this study. The apparent activation energy for xylose dehydration is higher than the apparent activation energy …
Probing The Mechanism Of Silica Polymerization At Ambient Temperatures Using Monte Carlo Simulations, Peter A. Monson, Ateeque Malani, Scott M. Auerbach
Probing The Mechanism Of Silica Polymerization At Ambient Temperatures Using Monte Carlo Simulations, Peter A. Monson, Ateeque Malani, Scott M. Auerbach
Peter A. Monson
We have developed a model for silica polymerization at ambient temperatures and low densities and have studied this using reactive Monte Carlo simulations. The model focuses on SiO4 coordination with the energetics of hydrolysis and condensation reactions treated via the reaction ensemble. The simplicity of the model makes large system sizes accessible on a modest computation budget, although it is necessary to make additional assumptions in order to use the reactive Monte Carlo method as a simulation of the system dynamics. Excellent agreement for the evolution of the Qn distribution is obtained upon comparing the simulation results to experimental observations. …
Modeling Nanoparticle Formation During Early Stages Of Zeolite Growth: A Low-Coordination Lattice Model Of Template Penetration, Peter A. Monson, L. Jin, Scott M. Auerbach
Modeling Nanoparticle Formation During Early Stages Of Zeolite Growth: A Low-Coordination Lattice Model Of Template Penetration, Peter A. Monson, L. Jin, Scott M. Auerbach
Peter A. Monson
We present an extension of the simple-cubic lattice model developed by Jorge et al. [ J. Am. Chem. Soc. 2005, 127, 14388] of nanoparticle growth in the clear solution synthesis of silicalite-1 (MFI). We have implemented the model on a body-center cubic (bcc) lattice with second-neighbor repulsions, to generate a four-coordinate network that mimics the tetrahedral structure of silica. With this low-coordination lattice model we observe that the nanoparticles are metastable, possessing a core−shell structure with mostly silica in the core and templates forming a shell. Nanoparticle size is found to increase with temperature and decrease with solution pH, in …
Stabilization Of Thin Liquid Films Flowing Over Locally Heated Surfaces Via Substrate Topography, N Tiwari, Jm Davis
Stabilization Of Thin Liquid Films Flowing Over Locally Heated Surfaces Via Substrate Topography, N Tiwari, Jm Davis
Jeffrey M. Davis
A long-wave lubrication analysis is used to study the influence of topographical features on the linear stability of noninertial coating flows over a locally heated surface. Thin liquid films flowing over surfaces with localized heating develop a pronounced ridge at the upstream edge of the heater. This ridge becomes unstable to transverse perturbations above a critical Marangoni number and evolves into an array of rivulets even in the limit of noninertial flow. Similar fluid ridges form near topographical variations on isothermal surfaces, but these ridges are stable to perturbations. The influence of basic topographical features on the stability of the …
Apolar Ortho-Phenylene Ethynylene Oligomers: Conformational Ordering Without Intermolecular Aggregation, Jing Jiang, Morris M. Slutsky, Ticora V. Jones, Gregory N. Tew
Apolar Ortho-Phenylene Ethynylene Oligomers: Conformational Ordering Without Intermolecular Aggregation, Jing Jiang, Morris M. Slutsky, Ticora V. Jones, Gregory N. Tew
Gregory N. Tew
This paper describes the characterization of solvent induced folding behavior for non-polar (NP) alkoxy substituted ortho-phenylene ethynylene (o-PE) oligomers. Oligomers of lengths up to nine units have been shown to adopt helical conformations in heptane by NMR and CD spectroscopy, while chloroform promotes extended conformations. Surprisingly, the molar ellipticity values found in heptane for these oligomers are very small compared to other literature values of meta-phenylene ethynylene (m-PE) folded systems; however, comparable molar ellipticity values were found for a closed macrocyclic o-PE suggesting the weak ellipticity is a molecular-feature rather than a quality of folding indicator.
Understanding Adsorption And Desorption Processes In Mesoporous Materials With Independent Disordered Channels, Peter A. Monson, Sergej Naumov, Rustem Valiullin, Jörg Kärger
Understanding Adsorption And Desorption Processes In Mesoporous Materials With Independent Disordered Channels, Peter A. Monson, Sergej Naumov, Rustem Valiullin, Jörg Kärger
Peter A. Monson
Using a lattice-gas model in mean-field theory, we discuss the problem of how adsorption and desorption of fluids in independent cylinderlike pores is influenced by variations in the pore diameter along the length of the pore, surface roughness of the pore walls, and chemical heterogeneity. We also consider the impact of contact with the bulk phase via the pore opening and the possibility of interactions between neighboring pores via a liquid film on the external surface of the material. We find that a combination of pore size variation along the length of the pore and surface roughness yields sorption hysteresis …
Small-World Network Models Of Intercellular Coupling Predict Enhanced Synchronization In The Suprachiasmatic Nucleus, Christina Vasalou, Erik D. Herzog, Michael A. Henson
Small-World Network Models Of Intercellular Coupling Predict Enhanced Synchronization In The Suprachiasmatic Nucleus, Christina Vasalou, Erik D. Herzog, Michael A. Henson
Michael A Henson
The suprachiasmatic nucleus (SCN) of the hypothalamus is a multioscillator system that drives daily rhythms in mammalian behavior and physiology. Based on recent data implicating vasoactive intestinal polypeptide (VIP) as the key intercellular synchronizing agent, we developed a multicellular SCN model to investigate the effects of cellular heterogeneity and intercellular connectivity on circadian behavior. A 2-dimensional grid was populated with 400 model cells that were heterogeneous with respect to their uncoupled rhythmic behavior (intrinsic and damped pacemakers with a range of oscillation periods) and VIP release characteristics (VIP producers and nonproducers). We constructed small-world network architectures in which local connections …
A Multipurpose Microfluidic Device Designed To Mimic Microenvironment Gradients And Develop Targeted Cancer Therapeutics, Neil S. Forbes, Colin L. Walsh, Brett M. Babin, Rachel W. Kasinskas, Jean A. Foster, Marissa J. Mcgarry
A Multipurpose Microfluidic Device Designed To Mimic Microenvironment Gradients And Develop Targeted Cancer Therapeutics, Neil S. Forbes, Colin L. Walsh, Brett M. Babin, Rachel W. Kasinskas, Jean A. Foster, Marissa J. Mcgarry
Neil S. Forbes
The heterogeneity of cellular microenvironments in tumors severely limits the efficacy of most cancer therapies. We have designed a microfluidic device that mimics the microenvironment gradients present in tumors that will enable the development of more effective cancer therapies. Tumor cell masses were formed within micron-scale chambers exposed to medium perfusion on one side to create linear nutrient gradients. The optical accessibility of the PDMS and glass device enables quantitative transmitted and fluorescence microscopy of all regions of the cell masses. Time-lapse microscopy was used to measure the growth rate and show that the device can be used for long-term …
Kinetics And Mechanism Of Cellulose Pyrolysis, George W. Huber, Y. C. Lin, J Cho, P. R. Westmoreland
Kinetics And Mechanism Of Cellulose Pyrolysis, George W. Huber, Y. C. Lin, J Cho, P. R. Westmoreland
George W. Huber
In this paper we report the kinetics and chemistry of cellulose pyrolysis using both a Pyroprobe reactor and a thermogravimetric analyzer mass spectrometer (TGA-MS). We have identified more than 90% of the products from cellulose pyrolysis in a Pyroprobe reactor with a liquid nitrogen trap. The first step in the cellulose pyrolysis is the depolymerization of solid cellulose to form levoglucosan (LGA; 6,8-dioxabicyclo[3.2.1]octane-2,3,4-triol). LGA can undergo dehydration and isomerization reactions to form other anhydrosugars including levoglucosenone (LGO; 6,8-dioxabicyclo[3.2.1]oct-2-en-4-one), 1,4:3,6-dianhydro-β-d-glucopyranose (DGP) and 1,6-anhydro-β-d-glucofuranose (AGF; 2,8-dioxabicyclo[3.2.1]octane-4,6,7-triol). The anhydrosugars can react further to form furans, such as furfural (furan-2-carbaldehyde) and hydroxymethylfurfural (HMF; 5-(hydroxymethyl)furan-2-carbaldehyde) …
Rippling Instability On Surfaces Of Stressed Crystalline Conductors, Dimitrios Maroudas, M. R. Gungor, V. Tomar
Rippling Instability On Surfaces Of Stressed Crystalline Conductors, Dimitrios Maroudas, M. R. Gungor, V. Tomar
Dimitrios Maroudas
We report a surface morphological stability analysis for stressed, conducting crystalline solids without and with the simultaneous application of an electric field based on self-consistent dynamical simulations according to a fully nonlinear model. The analysis reveals that in addition to a cracklike surface instability, a very-long-wavelength instability may be triggered that leads to the formation of secondary ripples on the surface morphology. We demonstrate that the number of ripples formed scales linearly with the wavelength of the initial perturbation from the planar surface morphology and that a sufficiently strong electric field inhibits both the cracklike and the rippling instability.
Aromatic Production From Catalytic Fast Pyrolysis Of Biomass-Derived Feedstocks, George W. Huber, T. R. Carlson, G. A. Tompsett
Aromatic Production From Catalytic Fast Pyrolysis Of Biomass-Derived Feedstocks, George W. Huber, T. R. Carlson, G. A. Tompsett
George W. Huber
The conversion of biomass compounds to aromatics by thermal decomposition in the presence of catalysts was investigated using a pyroprobe analytical pyrolyzer. The first step in this process is the thermal decomposition of the biomass to smaller oxygenates that then enter the catalysts pores where they are converted to CO, CO2, water, coke and volatile aromatics. The desired reaction is the conversion of biomass into aromatics, CO2 and water with the undesired products being coke and water. Both the reaction conditions and catalyst properties are critical in maximizing the desired product selectivity. High heating rates and high catalyst to feed …
Analysis Of Diamond Nanocrystal Formation From Multiwalled Carbon Nanotubes, Dimitrios Maroudas, E. S. Aydil, T. Singh, A. R. Muniz
Analysis Of Diamond Nanocrystal Formation From Multiwalled Carbon Nanotubes, Dimitrios Maroudas, E. S. Aydil, T. Singh, A. R. Muniz
Dimitrios Maroudas
A systematic analysis is presented of the nanocrystalline structures generated due to the intershell C-C bonding between adjacent concentric graphene walls of multiwalled carbon nanotubes (MWCNTs). The analysis combines a comprehensive exploration of the entire parameter space determined by the geometrical characteristics of the individual graphene walls comprising the MWCNT with first-principles density-functional theory calculations of intershell C-C bonding and structural relaxation by molecular-dynamics simulation of the resulting nanocrystalline structures. We find that these structures can provide seeds for the nucleation of the cubic-diamond and hexagonal-diamond phase in the form of nanocrystals embedded in the MWCNTs. The resulting lattice structure …
Linear Stability Of A Volatile Liquid Film Flowing Over A Locally Heated Surface, N Tiwari, Jm Davis
Linear Stability Of A Volatile Liquid Film Flowing Over A Locally Heated Surface, N Tiwari, Jm Davis
Jeffrey M. Davis
The dynamics and linear stability of a volatile liquid film flowing over a locally heated surface are investigated. The temperature gradient at the leading edge of the heater induces a gradient in surface tension that leads to the formation of a pronounced capillary ridge. Lubrication theory is used to develop a model for the film evolution that contains three key dimensionless groups: a Marangoni parameter (M), an evaporation number (E), and a measure of the vapor pressure driving force for evaporation (K), which behaves as an inverse Biot number. The two-dimensional, steady solutions for the local film thickness are computed …
Reactive Boiling Of Cellulose For Integrated Catalysis Through A Liquid Intermediate, Paul J. Dauenhauer, J. L. Colby, C. M. Balonek, W. J. Wieslaw, L. D. Schmidt
Reactive Boiling Of Cellulose For Integrated Catalysis Through A Liquid Intermediate, Paul J. Dauenhauer, J. L. Colby, C. M. Balonek, W. J. Wieslaw, L. D. Schmidt
Paul J. Dauenhauer
Advanced biomass processing technology integrating fast pyrolysis and inorganic catalysis requires an improved understanding of the thermal decomposition of biopolymers in contact with porous catalytic surfaces. High speed photography (1000 frames per second) reveals that direct impingement of microcrystalline cellulose particles (300 μm) with rhodium-based reforming catalysts at high temperature (700 °C) produces an intermediate liquid phase that reactively boils to vapors. The intermediate liquid maintains contact with the porous surface permitting high heat transfer (MW m−2) generating an internal thermal gradient visible within the particle as a propagating wave of solid to liquid conversion. Complete conversion to liquid yields …
The Critical Role Of Heterogeneous Catalysis In Lignocellulosic Biomass Conversion, George W. Huber, Y. -C Lin
The Critical Role Of Heterogeneous Catalysis In Lignocellulosic Biomass Conversion, George W. Huber, Y. -C Lin
George W. Huber
Lignocellulosic biofuels have a tremendous potential to reduce problems caused by our dependence on fossil fuels. The current roadblock with biofuels is the lack of economical conversion technologies. Heterogeneous catalysis offers immense potential in helping to make lignocellulosic biofuels a commercial reality. In this article we discuss the central role of heterogeneous catalysis in biomass conversion. We review the science of catalysis and the different routes to make biofuels. During the last several decades multiple new spectroscopic, theoretical, and synthesis tools are available that allow us to study catalysis at a molecular level. These new tools will allow us to …
Comparative Study Of The Mechanical Behavior Under Biaxial Strain Of Prestrained Face-Centered Cubic Metallic Ultrathin Films, Dimitrios Maroudas, M. R. Gungor, K. Kolluri
Comparative Study Of The Mechanical Behavior Under Biaxial Strain Of Prestrained Face-Centered Cubic Metallic Ultrathin Films, Dimitrios Maroudas, M. R. Gungor, K. Kolluri
Dimitrios Maroudas
We report a molecular-dynamics study of the mechanical response to dynamic biaxial tensile straining of nanometer-scale-thick Al, Cu, and Ni films. We find that the mechanical behavior of such films of face-centered cubic metals with moderate-to-high propensity for stacking-fault formation (Cu and Ni) is significantly different from those where such propensity is low (Al). The plastic strain rate in Cu and Ni films is greater than that in Al ones, leading to an extended easy-glide stage in Cu and Ni but not in Al films. These differences arise due to the different dislocation annihilation mechanisms in the two film categories.
Molecular-Dynamics Simulations Of Stacking-Fault-Induced Dislocation Annihilation In Prestrained Ultrathin Single-Crystalline Copper Films, Dimitrios Maroudas, K. Kolluri, M. R. Gungor
Molecular-Dynamics Simulations Of Stacking-Fault-Induced Dislocation Annihilation In Prestrained Ultrathin Single-Crystalline Copper Films, Dimitrios Maroudas, K. Kolluri, M. R. Gungor
Dimitrios Maroudas
We report results of large-scale molecular-dynamics simulations of dynamic deformation under biaxial tensile strain of prestrained single-crystalline nanometer-scale-thick face-centered cubic (fcc) copper films. Our results show that stacking faults, which are abundantly present in fcc metals, may play a significant role in the dissociation, cross slip, and eventual annihilation of dislocations in small-volume structures of fcc metals. The underlying mechanisms are mediated by interactions within and between extended dislocations that lead to annihilation of Shockley partial dislocations or formation of perfect dislocations. Our findings demonstrate dislocation starvation in small-volume structures with ultrathin film geometry, governed by a mechanism other than …
Modeling Relaxation Processes For Fluids In Porous Materials Using Dynamic Mean Field Theory: An Application To Partial Wetting, Peter A. Monson, John R. Edison
Modeling Relaxation Processes For Fluids In Porous Materials Using Dynamic Mean Field Theory: An Application To Partial Wetting, Peter A. Monson, John R. Edison
Peter A. Monson
We review a recently developed dynamic mean field theory for fluids confined in porous materials and apply it to a case where the solid-fluid interactions lead to partial wetting on a planar surface. The theory describes the evolution of the density distribution for a fluid in a pore that has contact with the bulk during a quench in the bulk chemical potential. In this way the dynamics of adsorption and desorption can be studied. By focusing on partial wetting situation we can investigate influence of a weaker surface field on the mechanisms of capillary condensation and desorption. We have studied …