Physics Commons^™

Call For Abstracts - Resrb 2019, July 8-9, Wrocław, Poland, Wojciech M. Budzianowski

Wojciech Budzianowski

No abstract provided.

Hyperpolarization Of Silicon Nanoparticles With Tempo Radicals, Jingzhe Hu, Nicholas Whiting, Pratip Bhattacharya

Nicholas Whiting

Removal Of Chlorine From Chlorine-Nitrogen Mixture In A Film Of Liquid Water, Sarwan S. Sandhu

Sarwan S. Sandhu

In industry there are many examples of absorption of a gas with or without chemical reaction in the liquid phase. In physical absorption, a particular gaseous component is removed from a gas mixture due to its larger solubility in the liquid phase solvent. The removal of butane and pentane from a refinery gas mixture by a heavy oil in the liquid phase is an example of physical absorption. In absorption with chemical reaction, the gaseous component to be removed transfers across the gas-liquid interface due to a difference in the bulk chemical potentials or concentrations in the two phases. The …

Simulation Model Of An Automatic Commercial Ice Machine, Haithem Murgham, David Myszka, Vijay Bahel, Rajan Rajendran, Kurt Knapke, Suresh Shivashankar, Kyaw Wynn

David Myszka

Automatic commercial ice-making machines that produce a batch of cube ice at regular intervals are known as “cubers." Such machines are commonly used in food service, food preservation, hotel, and health service industries. The machines are typically rated for the weight of ice produced over a 24-hour period at ambient air temperatures of 90°F and water inlet temperature of 70°F.

These cubers typically utilize an air-cooled, vapor-compression cycle to freeze circulating water flowing over an evaporator grid. Once a sufficient amount ice is formed, a valve switches to enable a harvest mode, where the compressor’s discharge gas is routed into …

Retardation Of Bulk Water Dynamics By Disaccharide Osmolytes.Pdf, Nimesh Shukla

Nimesh Shukla

No abstract provided.

Fine‐Structure Mixing Within The Zn(43pj) Multiplet By Collisions With The Noble Gases, Xianming Han, J. F. Kelly

Xianming Han

Measurements of rate coefficients for intramultiplet state transfer of Zn(4 ³ P ₁→4 ³ P _J’) by collisions with the rare gases are presented. The state‐to‐state binary rate coefficients are derived from least‐squares fittings of the time‐resolved triexponential behavior of the 4 ³ P ₁fluorescence. These rate coefficients were studied systematically over a temperature range of 690–1100 K in order to characterize the velocity dependence of the collisional coupling. The systematic behavior of the rate coefficients with varying temperature and noble gas species is qualitatively consistent with a nearly adiabatic coupling limit for noncrossing levels.

Lithium Bonding Interaction In H2Cy⋯Lif (Y=O,S) Complexes: A Theoretical Probe, Salai Cheettu Ammal, P. Venuvanalingam, S. Pal

Salai C. Ammal

Ab initio calculations at 6-31++G(d,p) level have been done on H2CY⋯LiF (Y=O,S) complexes choosing ten possible orientations in each complex. The effect of correlation on complex binding energies has been studied via single point MP2 (full) calculations done on 6-31++G(d,p) geometry. Binding energies have been corrected for basis set superposition error. Frequency calculations confirm that H2CO⋯LiF and H2CS⋯LiF complexes have three and two stable forms, respectively. The most stable form in each complex has been found to have a strong lithium bonding interaction and a secondary hydrogen bondinginteraction. NBO analysis has revealed that in this form oxygen donates nσ lone …

Sucralose Destabilization Of Protein Structure, Christina M. Othon

Christina M Othon

Sucralose is a commonly employed artificial sweetener that behaves very differently than its natural disaccharide counterpart, sucrose, in terms of its interaction with biomolecules. The presence of sucralose in solution is found to destabilize the native structure of two model protein systems: the globular protein bovine serum albumin and an enzyme staphylococcal nuclease. The melting temperature of these proteins decreases as a linear function of sucralose concentration. We correlate this destabilization to the increased polarity of the molecule. The strongly polar nature is manifested as a large dielectric friction exerted on the excited-state rotational diffusion of tryptophan using time-resolved fluorescence …

Sucralose Destabilization Of Protein Structure.Pdf, Nimesh Shukla

Nimesh Shukla

No abstract provided.

Sucralose Destabilization Of Protein Structure, Lee Chen, Nimesh Shukla, Inha Cho, Erin F. Cohn, Erika A. Taylor, Christina M. Othon

Erika A. Taylor, Ph.D.

Sucralose is a commonly employed artificial sweetener that behaves very differently than its natural disaccharide counterpart, sucrose, in terms of its interaction with biomolecules. The presence of sucralose in solution is found to destabilize the native structure of two model protein systems: the globular protein bovine serum albumin and an enzyme staphylococcal nuclease. The melting temperature of these proteins decreases as a linear function of sucralose concentration. We correlate this destabilization to the increased polarity of the molecule. The strongly polar nature is manifested as a large dielectric friction exerted on the excited-state rotational diffusion of tryptophan using time-resolved fluorescence …

Epr Studies On The Mono- And Dicobalt(Ii)-Substituted Forms Of The Aminopeptidase From Aeromonas Proteolytica. Insight Into The Catalytic Mechanism Of Dinuclear Hydrolases, Brian Bennett, Richard C. Holz

Richard C. Holz

The structure and function of the prototypical dinuclear hydrolase, namely, the aminopeptidase from Aeromonas proteolytica (AAP), was probed by EPR spectroscopy of the mono- and dicobalt(II)-substituted derivatives. A new systematic protocol for the interpretation of Co(II) EPR spectra is described and the S = 3/2 spin states of the Co(II)-substituted forms of the enzyme have been characterized. This protocol allows the simulation of line shape using theoretically allowed geff values corresponding to an isotropic greal value. In addition, the gross distortion of EPR spectra of high-spin S = 3/2 Co(II) ions has been investigated, and the effects of saturation on …

Importance And Reliability Of Small Basis Set Ccsd(T) Corrections To Mp2 Binding And Relative Energies Of Water Clusters, Berhane Temelso, Carla Renner, George Shields

Berhane Temelso

MP2 describes hydrogen-bonded systems well, yet a higher-order electron correlation correction in the form of a CCSD(T) calculation is usually necessary to achieve benchmark quality energies. We evaluated the importance and reliability of small basis set CCSD(T) corrections to MP2(δCCSD(T)) both on the binding (ΔE) and relative (ΔΔE) MP2 energies for a large number of systems including four water dimer stationary points and 57 other clusters up to undecamers, (H2O)11. By comparing the MP2 energies with CCSD(T) and the explicitly correlated MP2-F12 energies with variants of CCSD(T)-F12 using different basis sets, we were able to establish that the correction to …

Zespół Energii Odnawialnej I Zrównoważonego Rozwoju (Eozr), Wojciech M. Budzianowski

Wojciech Budzianowski

No abstract provided.

Heterogeneous Rotational Diffusion Of A Fluorescent Probe In Lipid Monolayers, Christina M. Othon

Christina M Othon

The rotational correlation time of the lipid probe 1-palmitoyl-2-{6-[(7-nitro-2-1,3-benzoxadiazol-4-yl)amino]hexanoyl}-sn-glycero-3-phosphocholine (NBD-PC) is measured using fluorescence anisotropy for two lipid species. We measure the rotational diffusion in a monolayer of 1,2-Didecanoyl-sn-glycero-3-phosphocholine (DPPC) which displays a phase transition at room temperature from the liquid expanded to the liquid-condensed phase. The constant rotational diffusion of the probe throughout the phase transition reflects the measurement of dynamics in only the liquid-expanded phase. We contrast the dynamic changes during this phase coexistence to the continuous density increase observed in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) at room temperature. We observe a non-exponential decay of the probe diffusion consistent with heterogeneity …

Structure And Dynamics Of Model Systems: From Ferrofluids To Brain Membranes, Matthew A. Barrett

Matthew J. Barrett

Soft condensed matter systems are a very diverse and challenging subject to study. To understand the complex macro-properties of such systems one approach is to characterize the microscopic structure and dynamics. A powerful technique for determining micro and nanoscale properties is scattering of radiation sources. Light, electron and neutron scattering techniques provide insight into the complicated molecular structures and the processes happening on these small scales. We have used neutron and x-ray scattering techniques to determine structural and dynamical information from two different types of soft condensed matter systems. The microscopic nature of a cobalt magnetic fluid was studied using …

Escherichia Coli Heptosyltransferase I: Investigation Of Protein Dynamics Of A Gt-B Structural Enzyme, Erika A. Taylor, Daniel J. Czyzyk, Shreya S. Sawant, Carlos A. Ramirez-Mondragon

Erika A. Taylor, Ph.D.

Heptosyltransferase I (HepI), the enzyme responsible for the transfer of l-glycero-d-manno-heptose to a 3-deoxy-α-d-manno-oct-2-ulopyranosonic acid (Kdo) of the growing core region of lipopolysaccharide, is a member of the GT-B structural class of enzymes. Crystal structures have revealed open and closed conformations of apo and ligand-bound GT-B enzymes, implying that large-scale protein conformational dynamics play a role in their reaction mechanism. Here we report transient kinetic analysis of conformational changes in HepI reported by intrinsic tryptophan fluorescence and present the first real-time evidence of a GT-B enzyme undergoing a substrate binding-induced transition from an open to closed state prior to catalysis.

Computational Design Optimization For Microfluidic Magnetophoresis, Brian Dennis Plouffe, Laura H. Lewis, Shashi Krishna Murthy

Laura H. Lewis

Current macro- and microfluidic approaches for the isolation of mammalian cells are limited in both efficiency and purity. In order to design a robust platform for the enumeration of a target cell population, high collection efficiencies are required. Additionally, the ability to isolate pure populations with minimal biological perturbation and efficient off-chip recovery will enable subcellular analyses of these cells for applications in personalized medicine. Here, a rational design approach for a simple and efficient device that isolates target cell populations via magnetic tagging is presented. In this work, two magnetophoretic microfluidic device designs are described, with optimized dimensions and …

An Ethnographic Study: Becoming A Physics Expert In A Biophysics Research Group, Idaykis Rodriguez

Idaykis Rodriguez

Expertise in physics has been traditionally studied in cognitive science, where physics expertise is understood through the difference between novice and expert problem solving skills. The cognitive perspective of physics experts only create a partial model of physics expertise and does not take into account the development of physics experts in the natural context of research. This dissertation takes a social and cultural perspective of learning through apprenticeship to model the development of physics expertise of physics graduate students in a research group. I use a qualitative methodological approach of an ethnographic case study to observe and video record the …

Determination Of Kinetic Parameters From The Thermogravimetric Data Set Of Biomass Samples, Karol Postawa, Wojciech M. Budzianowski

Wojciech Budzianowski

This article describes methods of the determination of kinetic parameters from the thermogravimetric data set of biomass samples. It presents the methodology of the research, description of the needed equipment, and the method of analysis of thermogravimetric data. It describes both methodology of obtaining quantitative data such as kinetic parameters as well as of obtaining qualitative data like the composition of biomass. The study is focused mainly on plant biomass because it is easy in harvesting and preparation. Methodology is shown on the sample containing corn stover which is subsequently pyrolysed. The investigated sample show the kinetic of first order …

Toward High-Performance Nanostructured Thermoelectric Materials: The Progress Of Bottom-Up Solution Chemistry Approaches, Yixin Zhao, Jeffrey S. Dyck, Clemens Burda

Jeffrey Dyck

Significant research effort has recently gone into the synthesis of thermoelectric nanomaterials through different chemical approaches since nanomaterials chemistry became a promising strategy for improving thermoelectric performance. Different thermoelectric nanocrystals, especially PbTe, Bi2Te3 and CoSb3, with various compositions and morphologies have been successfully prepared by solvo/hydrothermal, electrochemical, and ligand-based synthesis methods. Such nanoscale materials show not only substantial reduction in thermal conductivity due to increased phonon scattering at nanoscale grain boundaries and lower densities of phonon states but possibly also an enhancement in thermopower due to electronic quantum size effects. More recently, the notoriously low power factors of thermoelectric nanomaterials …

Structure Inhomogeneities, Shallow Defects, And Charge Transport In The Series Of Thermoelectric Materials K2bi8−Xsbxse13, Jeffrey S. Dyck, T. Kyratski, E. Hatzikraniotis, K. M. Paraskevopoulos, C. D. Malliakas, C. Uher, M. G. Kanatzidis

Jeffrey Dyck

The charge transport properties of the low-dimensional thermoelectric materials K2Bi8-xSbxSe13 (02Bi8-xSbxSe13 was analyzed on the basis of the classical semiconductor theory and discussed in the context of recent band calculations. The results suggest that the K2Bi8-xSbxSe13 materials possess coexisting domains with semimetallic and semiconducting characters whose ratio is influenced by the value of x and by local defects. The extent and relative distribution of these domains control the charge transport properties. Electron diffraction experiments performed on samples of K2Bi8-xSbxSe13 with x=1.6 show evidence for such domains by indicating regions with long range ordering of K+/Bi3+ atoms and regions with increased …

Double Layer In Ionic Liquids: Overscreening Versus Crowding, Martin Z. Bazant, Brian D. Storey, Alexei A. Kornyshev

Brian Storey

We develop a simple Landau-Ginzburg-type continuum theory of solvent-free ionic liquids and use it to predict the structure of the electrical double layer. The model captures overscreening from short-range correlations, dominant at small voltages, and steric constraints of finite ion sizes, which prevail at large voltages. Increasing the voltage gradually suppresses overscreening in favor of the crowding of counterions in a condensed inner layer near the electrode. This prediction, the ion profiles, and the capacitance-voltage dependence are consistent with recent computer simulations and experiments on room-temperature ionic liquids, using a correlation length of order the ion size.

Tension-Induced Straightening Transition Of Self-Assembled Helical Ribbons, Yevgeniya V. Zastavker, Brice Smith, George B. Benedek

Yevgeniya V. Zastavker

Helical ribbons with pitch angles of either 11° or 54° self-assemble in a wide variety of quaternary surfactant-phospholipid/fatty acid-sterol-water systems. By elastically deforming these helices, we examined their response to uniaxial forces. Under sufficient tension, a low pitch helix reversibly separates into a straight domain with a pitch angle of 90° and a helical domain with a pitch angle of 16.5°. Using a newly developed continuum elastic free energy model, we have shown that this phenomenon can be understood as a first order mechanical phase transition.

Hydrogen Production From Biogas By Oxy-Reforming: Reaction System Analysis, Aleksandra Terlecka, Wojciech M. Budzianowski

Wojciech Budzianowski

Oxy-reforming is emerging as an interesting alternative to conventional methods of hydrogen generation. The current article characterises this process through analysis of individual reactions: SMR (steam methane reforming), WGS (water gas shift) and CPO (catalytic partial oxidation). Analyses relate to optimisation of thermal conditions thus enabling cost-effectivenes of the process.

Photolithographic Surface Micromachining Of Polydimethylsiloxane (Pdms), Weiqiang Chen, Raymond H. W. Lam, Jianping Fu

Weiqiang Chen

A major technical hurdle in microfluidics is the difficulty in achieving high fidelity lithographic patterning on polydimethylsiloxane (PDMS). Here, we report a simple yet highly precise and repeatable PDMS surface micromachining method using direct photolithography followed by reactive ion etching (RIE). Our method to achieve surface patterning of PDMS applied an O2 plasma treatment to PDMS to activate its surface to overcome the challenge of poor photoresist adhesion on PDMS for photolithography. Our photolithographic PDMS surface micromachining technique is compatible with conventional soft lithography techniques and other silicon-based surface and bulk micromachining methods. To illustrate the general application of our …

Violence On The Brain: A Critique Of Neuroscience In Criminal Law, Amanda C. Pustilnik

Amanda C Pustilnik

Is there such a thing as a criminally "violent brain"? Does it make sense to speak of "the neurobiology of violence" or the "psychopathology of crime"? Is it possible to answer on a physiological level what makes one person engage in criminal violence and another not, under similar circumstances? This Article first demonstrates parallels between certain current claims about the neurobiology of criminal violence and past movements that were concerned with the law and neuroscience of violence: phrenology, Lombrosian biological criminology, and lobotomy. It then engages in a substantive review and critique of several current claims about the neurological bases …

Dna− Gold Nanoparticle Reversible Networks Grown On Cell Surface Marker Sites: Application In Diagnostics, Kyuwan Lee

Kyuwan Lee

Effective identification of breast cancer stem cells (CSC) benefits from a multiplexed approach to detect cell surface markers that can distinguish this subpopulation, which can invade and proliferate at sites of metastasis. We present a new approach for dual-mode sensing based on targeting using pointer and signal enhancement using enhancer particle networks for detection by surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS). We demonstrate our concept to detect cell surface markers, CD44 and CD24, in three breast cancer cell lines to identify a CD44+/CD24− subpopulation of CSCs. The designed network structure can be well-controlled and has improved sensitivity …

Hydration Dynamics At Fluorinated Protein Surfaces, Oh-Hoon Kwon, Tae Hyeon Yoo, Christina M. Othon, James A. Van Deventer, David A. Tirrell, Ahmed H. Zewail

Christina M Othon

Water-protein interactions dictate many processes crucial to protein function including folding, dynamics, interactions with other biomolecules, and enzymatic catalysis. Here we examine the effect of surface fluorination on water-protein interactions. Modification of designed coiled-coil proteins by incorporation of 5,5,5-trifluoroleucine or (4S)-2-amino-4-methylhexanoic acid enables systematic examination of the effects of side-chain volume and fluorination on solvation dynamics. Using ultrafast fluorescence spectroscopy, we find that fluorinated side chains exert electrostatic drag on neighboring water molecules, slowing water motion at the protein surface.

Valency Dependence Of Polymorphism And Polyamorphism In Dna-Functionalized Nanoparticles, Wei Dai, Chia Wei Hsu, Francesco Sciortino, Francis W. Starr

Francis Starr

Nanoparticles (NP) functionalized with single-stranded DNA (ssDNA) offer a route to custom-designed, self- assembled nanomaterials with potentially unusual properties. The bonding selectivity of DNA guarantees one-to-one binding to form double-stranded DNA (dsDNA), and an appropriate base sequence results in head-to-tail binding linking NP into networks. We explore the phase behavior and structure of a model for NP functionalized with between 3 and 6 short ssDNA through simulations of a coarse-grained molecular model, allowing us to examine both the role of the number of attached strands (valency) and their relative orientations. The NP assemble into networks where the number of NP …

Charge Transfer Assisted By Collective H-Bonding Network Dynamics, Omar F. Mohammed, Christina M. Othon, Oh-Hoon Kwon, Ahmed H. Zewail

Christina M Othon

Although there have been numerous studies of solvation, the role of solvent specific and collective interactions, especially for charge-transfer processes, remains difficult to unravel. Here, we report, using femtosecond fluorescence up-conversion and steady-state spectroscopic measurements, studies of well-designed single-sited formylperylene (FPe) in binary solvents. One of the solvents (methanol, MOH) can selectively hydrogen (H) bond to the carbonyl (C=O) site, while the other (acetonitrile, ACN) cannot, but both have similar polarity ( for MOH and for ACN). The results reveal that ultrafast charge transfer from the perylene unit to the carbonyl group of FPe is facilitated by site-specific H-bonding interactions …