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Full-Text Articles in Physics

Validating The Water Vapor Variance Similarity Relationship In The Interfacial Layer Using Observations And Large-Eddy Simulations, M. K. Osman, D. D. Turner, Thijs Heus, V. Wulfmeyer Oct 2019

Validating The Water Vapor Variance Similarity Relationship In The Interfacial Layer Using Observations And Large-Eddy Simulations, M. K. Osman, D. D. Turner, Thijs Heus, V. Wulfmeyer

Physics Faculty Publications

In previous work, the similarity relationship for the water vapor variance in the interfacial layer (IL) at the top of the convective boundary layer (CBL) was proposed to be proportional to the convective velocity scale and the gradients of the water vapor mixing ratio and the Brunt‐Vaisala frequency in the entrainment zone. In the presence of wind shear in the IL, the similarity relationship was hypothesized to also include a dependence on the gradient Richardson number. Simultaneous measurements of the surface buoyancy flux, wind‐shear profiles from a radar wind profiler, water vapor mixing ratio and temperature measurements and ...


Power-Law Scaling In The Internal Variability Of Cumulus Cloud Size Distributions Due To Subsampling And Spatial Organization, R. A. J. Neggers, P. J. Griewank, Thijs Heus Jun 2019

Power-Law Scaling In The Internal Variability Of Cumulus Cloud Size Distributions Due To Subsampling And Spatial Organization, R. A. J. Neggers, P. J. Griewank, Thijs Heus

Physics Faculty Publications

In this study, the spatial structure of cumulus cloud populations is investigated using three-dimensional snapshots from large-domain LES experiments. The aim is to understand and quantify the internal variability in cloud size distributions due to subsampling effects and spatial organization. A set of idealized shallow cumulus cases is selected with varying degrees of spatial organization, including a slowly organizing marine precipitating case and five more quickly organizing diurnal cases over land. A subdomain analysis is applied, yielding cloud number distributions at sample sizes ranging from severely undersampled to nearly complete. A strong power-law scaling is found in the relation between ...


Entropy Driven Phase Transition In Polymer Gels: Mean Field Theory, Miron Kaufman Jul 2018

Entropy Driven Phase Transition In Polymer Gels: Mean Field Theory, Miron Kaufman

Physics Faculty Publications

We present a mean field model of a gel consisting of P polymers, each of length L and Nz polyfunctional monomers. Each polyfunctional monomer forms z covalent bonds with the 2P bifunctional monomers at the ends of the linear polymers. We find that the entropy dependence on the number of polyfunctional monomers exhibits an abrupt change at Nz = 2P/z due to the saturation of possible crosslinks. This non-analytical dependence of entropy on the number of polyfunctionals generates a first-order phase transition between two gel phases: one poor and the other rich in poly-functional molecules.


Mixing Enhancement In Serpentine Micromixers With A Non-Rectangular Cross-Section, Joshua Clark, Miron Kaufman, Petru S. Fodor Mar 2018

Mixing Enhancement In Serpentine Micromixers With A Non-Rectangular Cross-Section, Joshua Clark, Miron Kaufman, Petru S. Fodor

Physics Faculty Publications

In this numerical study, a new type of serpentine micromixer involving mixing units with a non-rectangular cross-section is investigated. Similar to other serpentine/spiral shaped micromixers, the design exploits the formation of transversal vortices (Dean flows) in pressure-driven systems, associated with the centrifugal forces experienced by the fluid as it is confined to move along curved geometries. In contrast with other previous designs, though, the use of non-rectangular cross-sections that change orientation between mixing units is exploited to control the center of rotation of the transversal flows formed. The associated extensional flows that thus develop between the mixing segments complement ...


Methodology Development For The Implementation Ofmicrofluidic Mixers, Tahir Butt, Gautam Mahajan Jan 2018

Methodology Development For The Implementation Ofmicrofluidic Mixers, Tahir Butt, Gautam Mahajan

Undergraduate Research Posters 2018

Microfluidic platforms have been widely regarded as defining technologies for the development of chemical and biological synthesis and analysis systems, due to benefits associated with reduced reactant consumption, increases by orders of magnitude of the surface-to-volume ratios, and greatly enhanced control over reactions variables such as temperature and pressure. However, one of the bottlenecks for their wide application is the difficulty in achieving mixing, given the typical laminar flows in these systems. In this work we implement experimentally, various strategies using geometrical features to control the fluid motion and induce stirring flows. The mixers are fabricated using soft-lithography in PDMS ...


Implementation Of A Reverse Staggered-Herringbone Microfluidic Mixer For High-Throughput Polymeric Nanoparticles Synthesis, Alexa Roberts Jan 2018

Implementation Of A Reverse Staggered-Herringbone Microfluidic Mixer For High-Throughput Polymeric Nanoparticles Synthesis, Alexa Roberts

Undergraduate Research Posters 2018

The goal of this research is to implement and optimize the operating conditions of a microfluidic mixer to synthesize polymeric nanoparticles (NPs) in a high-throughput fashion. Using a reverse staggered-herringbone microfluidic mixer that we recently designed, the effects of experimental conditions such as flowrate and reactant composition on NP characteristics were investigated and optimized. The device design allowed for physical contact between two streams of fluids – one containing poly(lactic-co-glycolic acid; PLGA) in acetonitrile and the other deionized water, to allow for efficient mixing and NP precipitation to occur. The resulting NPs were characterized using dynamic light scattering (DLS) and ...


Characterization Of Microgels In Ionic Liquid, Dan Terrano Jan 2018

Characterization Of Microgels In Ionic Liquid, Dan Terrano

Undergraduate Research Posters 2018

Microgels are thermoresponsive polymeric nanoparticles whose size in aqueous solution is dependent on temperature. The microgels were studied using both dynamic light scattering (DLS) and scanning electron microscopy (SEM) to better understand the nanoparticles dynamics. The first part of the study focused on developing a controlled preparation procedure which would generate reproducible SEM images on a wet sample. The ionic liquid was mixed with a dilute solution of microgels and water was dried using nitrogen gas. This technique allowed a large volume of microgels to easily transition from their natural water solvent to a low vapor pressure ionic solvent. The ...


Construction And Applications Of An Inexpensive Muon Detector, Nicholas Knyszek Jan 2018

Construction And Applications Of An Inexpensive Muon Detector, Nicholas Knyszek

Undergraduate Research Posters 2018

Muons are important due to the abundance of them on earth. Muons that are on earth originate from the Sun and enter Earth’s atmosphere as decaying cosmic rays. Muons are somewhat unstable, with a lifespan of roughly 2.2 microseconds. Muons decay into electrons and two types of neutrinos. Since Muons travel near the speed of light they can still go thousands of meters into the Earth’s crust before stopping. Muons account for most of the cosmic radiation at sea level. Muons are harmless to humans. In this study, we built detectors and measured muon counts at different ...


The Effects Of Chemical Crosslinker On Polymeric Microgels, Samantha Tietjen, Jacob Adamczyk Jan 2018

The Effects Of Chemical Crosslinker On Polymeric Microgels, Samantha Tietjen, Jacob Adamczyk

Undergraduate Research Posters 2018

Microgels are nanoparticles suspended in solution and comprised of crosslinked polymer chains. Due to the amphiphilic property of the parent polymer, microgels exhibit a reversible volume phase transition. The standard behavior of these microgels is to deswell from a large to small size with an increase in temperature. Microgels in this study were synthesized by crosslinking hydroxypropylcellulose (HPC) in a surfactant solution. The amount of crosslinker used for synthesis was varied by a factor of a hundred. Using dynamic light scattering, microgels were characterized at various temperatures and scattering angles to determine the particles’ hydrodynamic radius (Rh) and dynamics both ...


Investigating The Influence Of Cloud Size On Cumulus Cloud Entrainment, Theresa Lincheck Jan 2018

Investigating The Influence Of Cloud Size On Cumulus Cloud Entrainment, Theresa Lincheck

Undergraduate Research Posters 2018

Clouds play a crucial role in determining the weather on local and global scales, yet their complexity accounts for some of the largest uncertainties in weather forecasts and climate models. Environmental air mixing or being drawn into a current, called entrainment, is one source to blame for this complexity. When air entrains into a cloud evaporation of in-cloud condensates increase and temperatures in the cloud drop, reducing buoyancy. The overall effect of entrainment inhibits a cloud’s development, and usually results in the dissipation of a cloud. With the use of data generated from a high-resolution computer model known as ...


Towards Understanding Microgel Volume Phase Transitions, Jacob Adamczyk, Samantha Tietjen Jan 2018

Towards Understanding Microgel Volume Phase Transitions, Jacob Adamczyk, Samantha Tietjen

Undergraduate Research Posters 2018

Microgels are polymer-based particles which are able to change size and shape during volume phase transition in response to external stimuli. We have investigated microgels which respond to changes in temperature for eventual use in drug-delivery systems on the nano to micro scale. Light scattering data on Hydroxypropylcellulose (HPC) microgels has been analyzed to determine microgel parameters such as radii, molecular weight, and polydispersity at various temperatures. The classic Flory- Huggins (FH) approach to mixing polymer-solvent solution is used to model a temperature-size dependence for the microgels. Existing theory on the microgel size dependence on the amount of crosslinker is ...


An Alternative Means For Observation-Based Cloud Size Distributions, Adam Stead Jan 2018

An Alternative Means For Observation-Based Cloud Size Distributions, Adam Stead

Undergraduate Research Posters 2018

Clouds are a poorly understood phenomenon that have a significant impact on climate and day-to-day weather. This research aims to measure cloud size distributions for shallow cumulus clouds from observational data. Clouds are sampled via a ceilometer, which indicates both the presence of cloudy air and the base height of the respective cloud. When combining this data with the recorded horizontal wind velocity, we can infer a cloud transect size distribution. After sufficient sampling, we can use an algorithm to deduce an approximate cloud area distribution for the specified time range and cloud field. Once the cloud size distributions are ...


Toward The Crystallization Of An Archaeal Dihydrorotase, Haley Newman, Ryan Godin Jan 2018

Toward The Crystallization Of An Archaeal Dihydrorotase, Haley Newman, Ryan Godin

Undergraduate Research Posters 2018

Dihydroorotase catalyzes the conversion of N-carbamoyl-L-aspartate to Ldihydroorotate in the de novo biosynthesis of pyrimidines. M. jannaschii is an archaeon that thrives in extreme environments such as the hypothermal vents at the bottom of the oceans in which both temperature and pressure are extremely high. It can serve as a model organism for research purposes. This experiment is a first step toward elucidating the structure of this enzyme in M. jannaschii. Our summer research started using a partially purified enzyme preparation from previous experiments. We further purified the enzyme primarily using hydrophobic interaction and hydroxyapatite chromatographies. Twenty-four closely related conditions ...


Characterizing The Turbulent Structure Of The Cbl And The Entrainment, Wei Jia Jan 2018

Characterizing The Turbulent Structure Of The Cbl And The Entrainment, Wei Jia

Undergraduate Research Posters 2018

The convective boundary layer (CBL) is the lowest part of the atmosphere. The turbulent motions in the CBL are important for redistributing trace gases, particles, heat, and momentum between the surface and the free troposphere thus it is important that this process is properly represented in numerical models that attempts to simulate the atmosphere. This study is trying to characterize the water vapor structure in the quasi-stationary CBL, using statistical way to build the turbulent model and uses a high resolution model: Large Eddy Simulation (LES) to investigate the adequacy of the model. We found that the water vapor flux ...


Determining Cloud Cover With Machine Learning, Sarah Sesek Jan 2018

Determining Cloud Cover With Machine Learning, Sarah Sesek

Undergraduate Research Posters 2018

The cloud cover provided by boundary layer cumulus clouds is one of the greatest uncertainties in climate and weather prediction models. It is difficult with current technology to cheaply and accurately collect cloud cover data. The TSI (Total Sky Imager) provides a hemispheric field of view in order to maximize the area it can see. The farther away from the center of the image, the more angled the view of the the cloud is. Therefore, more of the side of the cloud is captured in addition to the cloud base. Machine learning is well suited to seeing through this bias ...


Peer Quizzing: Are Two Heads Really Better Than One?, Leah Bunnell Jan 2018

Peer Quizzing: Are Two Heads Really Better Than One?, Leah Bunnell

Undergraduate Research Posters 2018

Instructors are often plagued with a difficult opened ended question; what measures can be implemented during class that will maximize students’ academic benefit? During this research project, the impact of frequent peer quizzing in introductory college level physics courses on subsequent learning assessments, such as midterms and percent gain, are examined. A peer quiz is initially administered to a student individually and graded but not returned to the students until they are given the opportunity to revisit the same quiz question with a partner. Two physics instructors’ student data is included in the data set, which is comprised of Introductory ...


Electrostatics At The Molecular Level, Ulrich Zurcher Jan 2017

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.


P1: How High Does The Lower Atmosphere Go?, Vladimir Sworski, Justin Flaherty Jan 2017

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 Jan 2017

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 ...


P1: Synthesis Optimization And Characterization Of Polymeric Microgels, Samantha Tietjen, Samantha Hudson Jan 2017

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 ...


P2: Implementation Of Groove Based Designs For Engineering Fluid Flow In Micromixers, Tahir Butt Jan 2017

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 ...


P2: Reconciling Linear Measurements Of Fractal Cloud Structures, Nicholas Barron Jan 2017

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.


Purification And Crystallization Trials Of The Dihydroorotase From Methanococcus Jannaschii, Amy K. Dadisman Jan 2017

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 ...


P3: What Determines The Shape Of A Cloud?, William Calabrase Jan 2017

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 Jan 2017

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.


Fabricating Non-Close Packed Colloidal Monolayers For Ion Irradiation Templates, Nandini Padaraju Jan 2017

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 ...


Achieving Atomically Smooth Surfaces And Ultra Sharp Platinum-Iridium Tips For Deposition Of Organic Molecules, William Myers Jan 2017

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 ...


Factors Controlling Stratocumulus Cloud Lifetime Over Coastal Land, Mohamed S. Ghonima, Thijs Heus, Joel R. Norris, Jan Kleissl Aug 2016

Factors Controlling Stratocumulus Cloud Lifetime Over Coastal Land, Mohamed S. Ghonima, Thijs Heus, Joel R. Norris, Jan Kleissl

Physics Faculty Publications

The breakup of stratocumulus clouds over coastal land areas is studied using a combination of large-eddy simulations (LESs) and mixed-layer models (MLMs) with a focus on mechanisms regulating the timing of the breakup. In contrast with stratocumulus over ocean, strong sensible heat flux over land prevents the cloud layer from decoupling during day. As the cloud thins during day, turbulence generated by surface flux becomes larger than turbulence generated by longwave cooling across the cloud layer. To capture this shift in turbulence generation in the MLM, an existing entrainment parameterization is extended. The MLM is able to mimic cloud evolution ...


Consequences Of The Angular Spectrum Decomposition Of A Focused Beam, Including Slower Than C Beam Propagation, Gérard Gouesbet, James A. Lock Jul 2016

Consequences Of The Angular Spectrum Decomposition Of A Focused Beam, Including Slower Than C Beam Propagation, Gérard Gouesbet, James A. Lock

Physics Faculty Publications

When dealing with light scattering and propagation of an electromagnetic beam, there are essentially two kinds of expansions which have been used to describe the incident beam (i) a discrete expansion involving beam shape coefficients and (ii) a continuous expansion in terms of an angular spectrum of plane waves. In this paper, we demonstrate that the angular spectrum decomposition readily leads to two important consequences, (i) laser light beams travel in free space with an effective velocity that is smaller than the speed of light c, and (ii) the optical theorem does not hold for arbitrary shaped beams, both in ...


First-Principles Definition And Measurement Of Planetary Electromagnetic-Energy Budget, Michael I. Mishchenko, James A. Lock, Andrew A. Lacis, Larry D. Travis, Brian Cairns Jan 2016

First-Principles Definition And Measurement Of Planetary Electromagnetic-Energy Budget, Michael I. Mishchenko, James A. Lock, Andrew A. Lacis, Larry D. Travis, Brian Cairns

Physics Faculty Publications

The imperative to quantify the Earths electromagnetic-energy budget with an extremely high accuracy has been widely recognized but has never been formulated in the framework of fundamental physics. In this paper we give a first-principles definition of the planetary electromagnetic-energy budget using the Poynting- vector formalism and discuss how it can, in principle, be measured. Our derivation is based on an absolute minimum of theoretical assumptions, is free of outdated notions of phenomenological radiometry, and naturally leads to the conceptual formulation of an instrument called the double hemispherical cavity radiometer (DHCR). The practical measurement of the planetary energy budget would ...