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Articles 1 - 16 of 16
Full-Text Articles in Physics
Erosion In Extruder Flows: Analytical And Numerical Study, Miron Kaufman, Petru S. Fodor
Erosion In Extruder Flows: Analytical And Numerical Study, Miron Kaufman, Petru S. Fodor
Physics Faculty Publications
© 2017 Author(s). We consider the erosion of particles (e.g. carbonblack agglomerates) advected by the polymeric flow in a single screw extruder. We assume a particle to be made of primary fragments bound together. In the erosion process a primary fragment breaks out of a given particle. Particles disperse because of the shear stresses imparted by the fluid. The time evolution of the numbers of particles of different sizes is described by the Bateman coupled differential equations developed a century ago to model radioactivity. Using the particle size distribution we compute an entropic fragmentation index which varies from 0 for …
Endothelial Nitric Oxide Synthase Oxygenase On Lipid Nanodiscs: A Nano-Assembly Reflecting Native-Like Function Of Enos, Ghaith Altawallbeh, Mohammad M. Haque, Kiril A. Streletzky, Dennis J. Stuehr, Mekki Bayachou
Endothelial Nitric Oxide Synthase Oxygenase On Lipid Nanodiscs: A Nano-Assembly Reflecting Native-Like Function Of Enos, Ghaith Altawallbeh, Mohammad M. Haque, Kiril A. Streletzky, Dennis J. Stuehr, Mekki Bayachou
Physics Faculty Publications
© 2017 Elsevier Inc. Endothelial nitric oxide synthase (eNOS) is a membrane-anchored enzyme. To highlight the potential role and effect of membrane phospholipids on the structure and activity of eNOS, we have incorporated the recombinant oxygenase subunit of eNOS into lipid nanodiscs. Two different size distribution modes were detected by multi-angle dynamic light scattering both for empty nanodiscs, and nanodiscs-bound eNOSoxy. The calculated hydrodynamic diameter for mode 1 species was 9.0 nm for empty nanodiscs and 9.8 nm for nanodisc bound eNOSoxy. Spectroscopic Griess assay was used to measure the enzymatic activity. Remarkably, the specific activity of nanodisc-bound eNOSoxy is …
Stabilization Of Hypoxia Inducible Factor By Cobalt Chloride Can Alter Renal Epithelial Transport, Subhra Nag, Andrew Resnick
Stabilization Of Hypoxia Inducible Factor By Cobalt Chloride Can Alter Renal Epithelial Transport, Subhra Nag, Andrew Resnick
Physics Faculty Publications
© 2017 The Authors. Given the importance of the transcriptional regulator hypoxia-inducible factor-1 (HIF-1) for adaptive hypoxia responses, we examined the effect of stabilized HIF-1α on renal epithelial permeability and directed sodium transport. This study was motivated by histological analysis of cystic kidneys showing increased expression levels of HIF-1α and HIF-2α. We hypothesize that compression induced localized ischemia-hypoxia of normal epithelia near a cyst leads to local stabilization of HIF-1α, leading to altered transepithelial transport that encourages cyst expansion. We found that stabilized HIF-1α alters both transcellular and paracellular transport through renal epithelial monolayers in a manner consistent with secretory …
Evaluation Of Wrf Scm Simulations Of Stratocumulus-Topped Marine And Coastal Boundary Layers And Improvements To Turbulence And Entrainment Parameterizations, Mohamed S. Ghonima, Handa Yang, Chang Ki Kim, Thijs Heus, Jan Kleissl
Evaluation Of Wrf Scm Simulations Of Stratocumulus-Topped Marine And Coastal Boundary Layers And Improvements To Turbulence And Entrainment Parameterizations, Mohamed S. Ghonima, Handa Yang, Chang Ki Kim, Thijs Heus, Jan Kleissl
Physics Faculty Publications
© 2017. The Authors. Stratocumulus-topped boundary layers (STBLs) are notoriously difficult to parameterize in single-column models due to the strong inversion layer across which entrainment mixing plays an important role in modulating the boundary layer mass, energy, and moisture balances. We compare three different WRF planetary boundary layer (PBL) schemes (Yonsei University, YSU; Asymmetric Convective Model version 2, ACM2; Mellor-Yamada-Nakanishi-Niino, MYNN) against large eddy simulations (LES) to find out that they underestimate entrainment flux in stratocumulus over both ocean and coastal land. Hence, the PBL schemes produce a cooler, moister STBL with higher liquid water content. In order to improve …
Microhh 1.0: A Computational Fluid Dynamics Code For Direct Numerical Simulation And Large-Eddy Simulation Of Atmospheric Boundary Layer Flows, Chiel C. Van Heerwaarden, Bart J.H. Van Stratum, Thijs Heus, Jeremy A. Gibbs, Evgeni Fedorovich, Juan Pedro Mellado
Microhh 1.0: A Computational Fluid Dynamics Code For Direct Numerical Simulation And Large-Eddy Simulation Of Atmospheric Boundary Layer Flows, Chiel C. Van Heerwaarden, Bart J.H. Van Stratum, Thijs Heus, Jeremy A. Gibbs, Evgeni Fedorovich, Juan Pedro Mellado
Physics Faculty Publications
© 2017 Author(s). This paper describes MicroHH 1.0, a new and open-source (www.microhh.org) computational fluid dynamics code for the simulation of turbulent flows in the atmosphere. It is primarily made for direct numerical simulation but also supports large-eddy simulation (LES). The paper covers the description of the governing equations, their numerical implementation, and the parameterizations included in the code. Furthermore, the paper presents the validation of the dynamical core in the form of convergence and conservation tests, and comparison of simulations of channel flows and slope flows against well-established test cases. The full numerical model, including the associated parameterizations for …
P1: Synthesis Optimization And Characterization Of Polymeric Microgels, Samantha Tietjen, Samantha Hudson
P1: Synthesis Optimization And Characterization Of Polymeric Microgels, Samantha Tietjen, Samantha Hudson
Undergraduate Research Posters 2017
Microgels are spherical particles suspended in solution, comprised of crosslinked polymer chains. Due to the amphiphilic property of the parent polymer, microgels display a temperature dependent de-swelling property, and therefore have the potential to be used for drug delivery. In this case, microgels were synthesized using hydroxypropyl cellulose (HPC) polymer and divinyl sulfone (DVS) cross-linker, as well as dodecyltrimethylammonium bromide (DTAB) surfactant to decrease particle size and promote microgel monodispersity. Synthesized particles were then characterized using dynamic light scattering (DLS) for both temperature and angle dependence to determine hydrodynamic radius, Rh, at a range of temperatures showing a transition from …
Purification And Crystallization Trials Of The Dihydroorotase From Methanococcus Jannaschii, Amy K. Dadisman
Purification And Crystallization Trials Of The Dihydroorotase From Methanococcus Jannaschii, Amy K. Dadisman
Undergraduate Research Posters 2017
Dihydroorotase is the enzyme that catalyzes the third step of the de novo biosynthesis of pyrimidines. M. jannaschii is a hyperthermophillic archaeon that can serve as a model organism for research purposes. This experiment is a first step toward elucidating the structure of the dihydroorotase in M. jannaschii. The enzyme was purified by salting out and heating the solution and then putting the supernatant through cation exchange chromatography and hydrophobic interaction chromatography. Twenty-four conditions were tested to determine if a crystal of dihydroorotase could be formed. Two of these conditions led to preliminary crystal formation. These findings can be utilized …
Achieving Atomically Smooth Surfaces And Ultra Sharp Platinum-Iridium Tips For Deposition Of Organic Molecules, William Myers
Achieving Atomically Smooth Surfaces And Ultra Sharp Platinum-Iridium Tips For Deposition Of Organic Molecules, William Myers
Undergraduate Research Posters 2017
Organic materials are used in traditional solar cells and in flexible electronics. Unfortunately, the conductivities of organic semiconductors are significantly lower than their inorganic counterparts. This project examines the crucial first steps to enhancing the conductivities of these organic materials by crystallization via surface reconstructions. For this, the surface must be not only atomically smooth, but also atomically clean because there must be both enough room for the molecule to lie on and no possible adsorbates for the deposited material to react with. In this work, we looked at two substrates, gold and silicon. For the gold, we examined two …
P1: How High Does The Lower Atmosphere Go?, Vladimir Sworski, Justin Flaherty
P1: How High Does The Lower Atmosphere Go?, Vladimir Sworski, Justin Flaherty
Undergraduate Research Posters 2017
The Atmospheric Boundary Layer (ABL), consisting of the bottom few kilometers of the troposphere, is a region with strong mixing of moisture and winds. This region's activity has a large impact on weather and climate models. In this study, we use a high resolution computer model: Large Eddy Simulation (LES). Statistics produced require a strong understanding of the height of the ABL. The purpose of this study was to create a method for determining this height accurately and consistently, as previous models demonstrated significant error.
P2: Developing Methodologies For Wet-Sample Electron Microscopy Imaging, Daniel Terrano, Petru Fodor
P2: Developing Methodologies For Wet-Sample Electron Microscopy Imaging, Daniel Terrano, Petru Fodor
Undergraduate Research Posters 2017
Scanning Electron Microscopy (SEM) is widely used to analyze the size, shape, and composition of material systems. However, using this tool for analyzing systems such as particles suspended in solution requires drastic sample alterations, such as precipitation and fixation. Besides altering their environment, this exposes the particles to the harsh conditions within an electron microscope, such as high vacuum and electron beam exposure. To this end, the first goal of this study was to develop methodologies for imaging wet samples using electron microscopy. This is realized by creating a sandwich structure containing the solution of interest between a partially electron …
P2: Reconciling Linear Measurements Of Fractal Cloud Structures, Nicholas Barron
P2: Reconciling Linear Measurements Of Fractal Cloud Structures, Nicholas Barron
Undergraduate Research Posters 2017
Clouds are a large unknown in meteorological predictions. Most of the issue can be derived from the odd shape of clouds. So, in order to correct the measurements of clouds, a thorough investigation of fractal cloud structures must be performed. Using the results from this study, a reconciliation method can then be constructed and applied to linear measurements of clouds.
P3: What Determines The Shape Of A Cloud?, William Calabrase
P3: What Determines The Shape Of A Cloud?, William Calabrase
Undergraduate Research Posters 2017
Current climate models and weather forecasts suffer due to an uncertainty associated with the behavior of clouds, which directly impact the energy exchange between the earth and the Sun. This impact is determined in part by the shape of the clouds, thereby making the study of what affects cloud shape an area of interest. To characterize the shape of cumulus clouds we study the behavior of the cloud overlap ratio, or the ratio between the average cloud fraction and projected cloud cover. In this study, we used a high resolution computer model to 1) determine how the cloud overlap ratio …
P1: Using Modified Dean Flow Designs To Increase Mixing Performance, Joshua Clark
P1: Using Modified Dean Flow Designs To Increase Mixing Performance, Joshua Clark
Undergraduate Research Posters 2017
We are using numerical solutions for the Navier-Stokes equations and the concentration - diffusion equation to model fluid flow and reactant distribution in serpentine type channels for micromixers/microreactors development. These mixers exploit centripetal forces on the fluid to induce cross-sectional fluid mixing, aka Dean flows. Various modifications are used to increase the mixing character of these crosssectional flows. We found that the performance of these mixers exceeds that of unmodified channels and we currently assess their performance relative to other state of the art methodologies used to induce mixing on the microscale.
P2: Implementation Of Groove Based Designs For Engineering Fluid Flow In Micromixers, Tahir Butt
P2: Implementation Of Groove Based Designs For Engineering Fluid Flow In Micromixers, Tahir Butt
Undergraduate Research Posters 2017
Mixing on microscale is important for the development of miniaturized chemical reactors that use small quantities of reactants and allow better control over the reaction conditions and products. Nevertheless, achieving rapid mixing in this type of micro-reactors is challenging due to the lack of turbulence and slow diffusion on the microscale. In this work we implement micromixers designs based on surface groove/ridge patterns targeted at inducing cross-sectional flows that both extend the interface between the different reactants, as well as induce chaotic advection. We discuss the fabrication of these structures using soft-lithography in PDMS employing a mold and their optical …
Fabricating Non-Close Packed Colloidal Monolayers For Ion Irradiation Templates, Nandini Padaraju
Fabricating Non-Close Packed Colloidal Monolayers For Ion Irradiation Templates, Nandini Padaraju
Undergraduate Research Posters 2017
Due to their unique properties, anisotropic nanoparticles are desirable components for future applications yet there are few processes capable of fabricating nanoparticle impregnated coatings for the manufacturing environment. Our work seeks to develop new masking techniques for the production of the templated substrates that will induce ordered nanoparticle films. Specifically, we are fabricating non-close packed colloidal monolayers onto silicon substrates, which then serve as the template for ion irradiation. The first steps to creating this monolayer are obtaining a spin-coated poly(vinyl alcohol) (PVA) thin film of ~200 nm and a close-packed colloidal monolayer using a peltier heater. We achieved a …
Electrostatics At The Molecular Level, Ulrich Zurcher
Electrostatics At The Molecular Level, Ulrich Zurcher
Physics Faculty Publications
In molecular systems, positive and negative charges are separated, making them ideal systems to examine electrostatic interactions. The attractive force between positive and negative charges is balanced by repulsive ‘forces’ that are quantum-mechanical in origin. We introduce an ‘effective’ potential energy that captures the repulsion; it allows us to obtain fairly accurate estimates of the bonding properties of molecular systems. We use units (e.g., kcal mol–1 for energy) that emphasize the relevance of electrostatics to macroscopic behavior.