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Mixing Times Of Organic Molecules Within Secondary Organic Aerosol Particles: A Global Planetary Boundary Layer Perspective, Adrian M. Maclean, Christopher L. Butenhoff, James W. Grayson, Kelley Barsanti, Jose L. Jimenez, Allan K. Bertram 2017 University of British Columbia

Mixing Times Of Organic Molecules Within Secondary Organic Aerosol Particles: A Global Planetary Boundary Layer Perspective, Adrian M. Maclean, Christopher L. Butenhoff, James W. Grayson, Kelley Barsanti, Jose L. Jimenez, Allan K. Bertram

Physics Faculty Publications and Presentations

When simulating the formation and life cycle of secondary organic aerosol (SOA) with chemical transport models, it is often assumed that organic molecules are well mixed within SOA particles on the timescale of 1 h. While this assumption has been debated vigorously in the literature, the issue remains unresolved in part due to a lack of information on the mixing times within SOA particles as a function of both temperature and relative humidity. Using laboratory data, meteorological fields, and a chemical transport model, we estimated how often mixing times are < 1 h within SOA in the planetary boundary layer (PBL), the region of the atmosphere where SOA concentrations are on average the highest. First, a parameterization for viscosity as a function of temperature and RH was developed for α-pinene SOA using room-temperature and low-temperature viscosity data for α-pinene SOA generated in the laboratory using mass concentrations of ∼ 1000 µg m−3. Based on this parameterization, the mixing times within α-pinene SOA are < 1 h for 98.5 % and 99.9 % of the occurrences in the PBL during January and July, respectively, when concentrations are significant (total organic aerosol concentrations are > 0.5 µg m−3 at the surface). Next, as ...


Investigation Of Iron Oxide Nanocolloidal Suspension Diffusion Using A Direct Imaging Method, Ashley E. Rice, Ana Oprisan 2017 College of Charleston

Investigation Of Iron Oxide Nanocolloidal Suspension Diffusion Using A Direct Imaging Method, Ashley E. Rice, Ana Oprisan

Journal of the South Carolina Academy of Science

We performed a set of experiments using a direct imaging method to investigate the diffusion process of iron oxide, Fe2O3, nanoparticles. We studied concentration fluctuations that move against the concentration gradient and induce disturbances in the interface between the iron oxide suspension and water in the sample cell. Using this imaging method in combination with the differential dynamic algorithm for image processing, we are able to extract information about the power, size, and lifetime of the fluctuations. We performed this experiment both in the presence and in the absence of a 4.2 mT magnetic field. We ...


Thermodynamics Of An Evolving Gene Sequence, Brian Clark 2017 Illinois State University

Thermodynamics Of An Evolving Gene Sequence, Brian Clark

Annual Symposium on Biomathematics and Ecology: Education and Research

No abstract provided.


The Behavior Response Of Antlion Larvae To Alternating Magnetic Fields, Lindsey Wagner, Caleb L. Adams 2017 Radford University

The Behavior Response Of Antlion Larvae To Alternating Magnetic Fields, Lindsey Wagner, Caleb L. Adams

Annual Symposium on Biomathematics and Ecology: Education and Research

No abstract provided.


A Critical Firing Rate In Synchronous Transitions Of Coupled Neurons, Annabelle Shaffer, Epaminondas Rosa, Rosangela Follmann 2017 Illinois State University

A Critical Firing Rate In Synchronous Transitions Of Coupled Neurons, Annabelle Shaffer, Epaminondas Rosa, Rosangela Follmann

Annual Symposium on Biomathematics and Ecology: Education and Research

No abstract provided.


Mathematical Modeling Of Inhibitory Effects On Chemically Coupled Neurons, Nathhaniel Harraman, Epaminondas Rosa 2017 Illinois State University

Mathematical Modeling Of Inhibitory Effects On Chemically Coupled Neurons, Nathhaniel Harraman, Epaminondas Rosa

Annual Symposium on Biomathematics and Ecology: Education and Research

No abstract provided.


Temperature Effects On Neuronal Tonic-To-Bursting Transitions, Manuela Burek, Epaminondas Rosa 2017 Illinois State University

Temperature Effects On Neuronal Tonic-To-Bursting Transitions, Manuela Burek, Epaminondas Rosa

Annual Symposium on Biomathematics and Ecology: Education and Research

No abstract provided.


A Brief History Of Neuroscience, Zachary Mobille, Epaminondas Rosa 2017 Illinois State University

A Brief History Of Neuroscience, Zachary Mobille, Epaminondas Rosa

Annual Symposium on Biomathematics and Ecology: Education and Research

No abstract provided.


Structural And Functional Analysis Of The Transcriptional Regulator Rv3066 Of Mycobacterium Tuberculosis, Jani Reddy Bolla, Sylvia V. Do, Feng Long, Lei Dai, Chih-Chia Su, Hsiang-Ting Lei, Xiao Chen, Jillian E. Gerkey, Daniel C. Murphy, Kanagalaghatta R. Rajashankar, Qijing Zhang, Edward W. Yu 2017 Iowa State University

Structural And Functional Analysis Of The Transcriptional Regulator Rv3066 Of Mycobacterium Tuberculosis, Jani Reddy Bolla, Sylvia V. Do, Feng Long, Lei Dai, Chih-Chia Su, Hsiang-Ting Lei, Xiao Chen, Jillian E. Gerkey, Daniel C. Murphy, Kanagalaghatta R. Rajashankar, Qijing Zhang, Edward W. Yu

Qijing Zhang

The Mmr multidrug efflux pump recognizes and actively extrudes a broad range of antimicrobial agents, and promotes the intrinsic resistance to these antimicrobials in Mycobacterium tuberculosis . The expression of Mmr is controlled by the TetR-like transcriptional regulator Rv3066, whose open reading frame is located downstream of the mmr operon. To understand the structural basis of Rv3066 regulation, we have determined the crystal structures of Rv3066, both in the absence and presence of bound ethidium, revealing an asymmetric homodimeric two-domain molecule with an entirely helical architecture. The structures underscore the flexibility and plasticity of the regulator essential for multidrug recognition. Comparison ...


Stochastic Resonance In A Proton Pumping Complex I Of Mitochondria Membranes, Davneet Kaur, Ilan Filonenko, Lev Mourokh, Cornelius Fendler, Robert H. Blick 2017 CUNY Queens College

Stochastic Resonance In A Proton Pumping Complex I Of Mitochondria Membranes, Davneet Kaur, Ilan Filonenko, Lev Mourokh, Cornelius Fendler, Robert H. Blick

Publications and Research

We make use of the physical mechanism of proton pumping in the so-called Complex I within mitochondria membranes. Our model is based on sequential charge transfer assisted by conformational changes which facilitate the indirect electron-proton coupling. The equations of motion for the proton operators are derived and solved numerically in combination with the phenomenological Langevin equation describing the periodic conformational changes. We show that with an appropriate set of parameters, protons can be transferred against an applied voltage. In addition, we demonstrate that only the joint action of the periodic energy modulation and thermal noise leads to efficient uphill proton ...


Competing Irreversible Cooperative Reactions On Polymer Chains, James W. Evans, D. K. Hoffman, D. R. Burgess 2017 Iowa State University

Competing Irreversible Cooperative Reactions On Polymer Chains, James W. Evans, D. K. Hoffman, D. R. Burgess

James W. Evans

We analyze model processes involving competition between several irreversible reactions at the sites of a 1D, infinite, uniform polymer chain. These reactionscan be cooperative, i.e., the corresponding rates depend on the state of the surrounding sites. An infinite hierarchy of rate equations is readily derived for the probabilities of various subconfigurations. By exploiting a shielding property of suitable blocks of unreacted sites, we show how exact hierarchy truncation and solution is sometimes possible. The behavior of solutions is illustrated in several cases by plotting families of ‘‘reaction trajectories’’ for varying ratios of reactant concentrations ...


Energy Sudden Dissociative Collisions: Structure And Applications Of Factorization Relations, D. K. Chan, David K. Hoffman, James W. Evans 2017 Iowa State University

Energy Sudden Dissociative Collisions: Structure And Applications Of Factorization Relations, D. K. Chan, David K. Hoffman, James W. Evans

James W. Evans

In the energy sudden (ES) approximation for nonreactive molecular collisions,there exist factorization relations by which an arbitrary T‐matrix element can be predicted as a spectroscopic linear combination of those out of some other, input state. These were first discovered for ground state input but this restriction was later removed. This general form of the spectroscopicfactorization relations is straightforwardly extended here to ES dissociativecollisions. One finds that in predicting dissociation amplitudes out of some state, it is necessary to use input data out of a higher (energy) bound state. Thus ground state factorization relations cannot be used. The structure ...


The Kinematic Apse And Jz‐Preserving Propensities For Nonreactive, Dissociative, And Reactive Polyatomic Collisions, D. K. Hoffman, James W. Evans, D. J. Kouri 2017 Iowa State University

The Kinematic Apse And Jz‐Preserving Propensities For Nonreactive, Dissociative, And Reactive Polyatomic Collisions, D. K. Hoffman, James W. Evans, D. J. Kouri

James W. Evans

We consider the generalization of the kinematic apse to nonreactive polyatom–polyatom impulsive collisions, dissociative atom–molecule impulsive collisions,and (partially) impulsive reactive atom–diatom collisions. Appropriate generalizations of the kinematic apse are obtained along which there is a classical propensity for preserving the projection of the total intrinsic spin. In the case of reactive scattering, we discuss several different situations for which such a propensity occurs. For reactive systems in which no such propensity exists, the analysis may still provide a basis for classifying reactions.


Zgb Surface Reaction Model With High Diffusion Rates, James W. Evans 2017 Iowa State University

Zgb Surface Reaction Model With High Diffusion Rates, James W. Evans

James W. Evans

The diffusionless ZGB (monomer–dimer) surface reaction model exhibits a discontinuous transition to a monomer‐poisoned state when the fraction of monomer adsorption attempts exceeds 0.525. It has been claimed that this transition shifts to 2/3 with introduction of rapid diffusion of the monomerspecies, or of both species. We show this is not the case, 2/3 representing the spinodal rather than the transition point. For equal diffusion rates of both species, we find that the transition only shifts to 0.5951±0.0002.


The Reactive Quantum Boltzmann Equations: A Derivation From An Arrangement Channel Space Representation And Bbgky Hierarchy, James W. Evans, D. K. Hoffman, D. J. Kouri 2017 Iowa State University

The Reactive Quantum Boltzmann Equations: A Derivation From An Arrangement Channel Space Representation And Bbgky Hierarchy, James W. Evans, D. K. Hoffman, D. J. Kouri

James W. Evans

A rigorous derivation of the reactive quantum Boltzmann equations is presented for systems where breakup and recombination are excluded. The use of an arrangement channel space representation allows an exact decomposition of the N particle density matrix into components for different chemical compositions and an exact definition of reduced species density matrices (as opposed, e.g., to standard projection operator techniques). This necessitates the use of the combinatorially complex arrangement channel BBGKY hierarchy which, however, avoids the need for the usual heuristic specification of collision terms. Another advantage is that scattering equations generated for the reactive and nonreactive many body ...


Temperature Dependence Of Metal Film Growth Via Low‐Energy Electron Diffraction Intensity Oscillations: Pt/Pd(100), D. K. Flynn, James W. Evans, P. A. Thiel 2017 Iowa State University

Temperature Dependence Of Metal Film Growth Via Low‐Energy Electron Diffraction Intensity Oscillations: Pt/Pd(100), D. K. Flynn, James W. Evans, P. A. Thiel

James W. Evans

A commercial, conventional low‐energy electron diffraction apparatus is used to monitor Bragg intensity oscillations during the growth of Pt on Pd(100). The effect of substrate temperature between 80 and 400 K is investigated. Between 80 and 300 K, two to three Bragg oscillations are observed. The oscillation amplitude damps out quickly as film coverage increases at fixed temperature, but damp out less quickly at the higher substrate temperatures. Above ∼350 K, reconstruction of the Pt overlayer interferes with the oscillations. These data indicate that a kinetic barrier, most probably the barrier to surface diffusion,inhibits the system from ...


Cluster Diffusivity: Structure, Correlation, And Scaling, H. C. Kang, P. A. Thiel, James W. Evans 2017 Iowa State University

Cluster Diffusivity: Structure, Correlation, And Scaling, H. C. Kang, P. A. Thiel, James W. Evans

James W. Evans

We have investigated the diffusion of clusters on a triangular lattice using Monte Carlo simulations. A cluster is defined as a two‐dimensional collection of particles which are connected to each other, either directly or indirectly through other particles in the cluster, by nearest‐neighbor bonds. Each particle is allowed to hop, with probability αδb/2/(α−δb/2+αδb/2), to a vacant nearest‐neighbor site with the constraint that the hop does not break the cluster. The change in the number of bonds is given by δb. The equilibrium clusters are correlated animals with structure controlled by the ...


Modeling Spatiotemporal Behavior Of The No+Co Reaction On Pt, James W. Evans, H. H. Madden, R. Imbihl 2017 Iowa State University

Modeling Spatiotemporal Behavior Of The No+Co Reaction On Pt, James W. Evans, H. H. Madden, R. Imbihl

James W. Evans

Various features of NO+CO reaction kinetics on Pt(100) surfaces, including temporal oscillations, are well described by a three‐variable model incorporating only the CO, NO, and O coverages. Here we analyze the corresponding reaction–diffusion equations demonstrating the existence of chemical waves where an ‘‘oscillating phase’’ displaces an unreactive NO/CO phase leaving a spatially periodic structure in its wake; pulses excited via inhomogeneities from an unreactive NO/CO background; and Turing structures for sufficiently unequal NO and CO diffusion rates.


Interface Propagation And Nucleation Phenomena For Discontinuous Poisoning Transitions In Surface-Reaction Models, James W. Evans, T. R. Ray 2017 Iowa State University

Interface Propagation And Nucleation Phenomena For Discontinuous Poisoning Transitions In Surface-Reaction Models, James W. Evans, T. R. Ray

James W. Evans

Here, we consider discontinuous nonequilibrium phase transitions to poisoned or ‘‘adsorbing’’ states in lattice-gas models of surface reactions. Specifically, we examine the monomer or CO-poisoning transition in the Ziff-Gulari-Barshad monomer-dimer reaction model for CO oxidation, modified to include adspecies diffusion. For CO pressures below the poisoning transition, we first characterize the propagation of and fluctuations at an interface between reactive and CO-poisoned states. Here, we utilize ideas from spatial contact models, reaction-diffusion theory, and kinetic roughening theory. Evolution is described by the Kardar-Parisi-Zhang equation, but with the nonlinearity and kinetic surface tension vanishing on approaching the transition. Next, again for ...


Lattice‐Gas Model Mimicking The No+Co Reaction On Pt(100), Baoqi Meng, W. Henry Weinberg, James W. Evans 2017 University of California, Santa Barbara

Lattice‐Gas Model Mimicking The No+Co Reaction On Pt(100), Baoqi Meng, W. Henry Weinberg, James W. Evans

James W. Evans

Various NO‐reduction reactions on Pt(100) exhibit similar dynamical behavior, presumably due to an empty site requirement for NO dissociation. This motivates analysis of a lattice‐gas model which incorporates this feature, and which here is chosen to mimic the NO+CO reaction on Pt(100): both reactants adsorb at single empty sites, NO instantaneously dissociates given an adjacent empty site (and nitrogen adatoms thus formed are immediately removed), and adjacent CO and O instantaneously react. We also include desorption of adsorbed NO and CO, but no adspecies diffusion. At lower temperatures where desorption is absent, we show that ...


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