Physics Commons^™

Solvation In Protein (Un)Folding: Effect Of Local And Bulk Dynamics In The Melittin Tetramer-Monomer Transition, Christina M. Othon, Oh-Hoon Kwon, Milo M. Lin, Ahmed H. Zewail

Christina M Othon

Protein structural integrity and flexibility are intimately tied to solvation. Here we examine the effect that changes in bulk and local solvent properties have on protein structure and stability. We observe the change in solvation of an unfolding of the protein model, melittin, in the presence of a denaturant, trifluoroethanol. The peptide system displays a well defined transition in that the tetramer unfolds without disrupting the secondary or tertiary structure. In the absence of local structural perturbation, we are able to reveal exclusively the role of solvation dynamics in protein structure stabilization and the (un)folding pathway. A sudden retardation in …

Gauge Federation As An Alternative To Unification, John Donoghue, Preema Pais

John Donoghue

We motivate and explore the possibility that extra SU(N) gauge groups may exist independently of the Standard Model groups, yet not be subgroups of some grand unified group. We study the running of the coupling constants as a potential evidence for a common origin of all the gauge theories. Several different example are displayed. Some of the multiple options involve physics at the TeV scale.

Quiescent Isolation: The Extremely Extended H I Halo Of The Optically Compact Dwarf Galaxy Adbs 113845+2008, John Cannon, John J. Salzer, Jessica L. Rosenberg

John Cannon

No abstract provided.

The True Durations Of Starbursts: Hubble Space Telescope Observations Of Three Nearby Dwarf Starburst Galaxies, Kristen B.W. Mcquinn, Evan D. Skillman, John Cannon, Julianne J. Dalcanton, Andrew Dolphin, David Stark, Daniel Weisz

John Cannon

No abstract provided.

Opinion Dynamics On An Adaptive Random Network, I. J. Benczik, S. Z. Benczik, Beate Schmittmann, R. K. P. Zia

Beate Schmittmann

We revisit the classical model for voter dynamics in a two-party system with two basic modifications. In contrast to the original voter model studied in regular lattices, we implement the opinion formation process in a random network of agents in which interactions are no longer restricted by geographical distance. In addition, we incorporate the rapidly changing nature of the interpersonal relations in the model. At each time step, agents can update their relationships. This update is determined by their own opinion, and by their preference to make connections with individuals sharing the same opinion, or rather with opponents. In this …

Bcc-To-Hcp Transformation Pathways For Iron Versus Hydrostatic Pressure: Coupled Shuffle And Shear Modes, J. B. Liu, Duane D. Johnson

Duane D. Johnson

Using density-functional theory, we calculate the potential-energy surface (PES), minimum-energy pathway (MEP), and transition state (TS) versus hydrostatic pressure σhyd for the reconstructive transformation in Fe from body-centered cubic (bcc) to hexagonal closed-packed (hcp). At fixed σhyd, the PES is described by coupled shear (ϵ) and shuffle (η) modes and is determined from structurally minimized hcp-bcc energy differences at a set of (η,ϵ). We fit the PES using symmetry-adapted polynomials, permitting the MEP to be found analytically. The MEP is continuous and fully explains the transformation and its associated magnetization and volume discontinuity at TS. We show that σhyd (while …

Analytical Solution For Stokes Flow Inside An Evaporating Sessile Drop: Spherical And Cylindrical Cap Shapes, Hassan Masoud, James D. Felske

Hassan Masoud

Periodic And Dynamic 3-D Gold Nanoparticle− Dna Network Structures For Surface-Enhanced Raman Spectroscopy-Based Quantification, Kyuwan Lee

Kyuwan Lee

The enhancement factor of gold nanoparticles linked by DNA in a three-dimensional (3-D) network structure was evaluated as 1.12 × 107 and shown to be greater than a two-dimensional (2-D) array by a factor of 10, possibly due to the dimensional expansion of resonance and periodicity of the so formed structures. Uniform and higher level of enhancement was possible from these DNA linked gold nanoparticle networks because of the matching of the resonant condition and the excitation wavelength (785 nm) to enable dynamic quantification of analytes by surface-enhanced Raman spectroscopy (SERS). The structure was first validated by obtaining a SERS …

Organo-Soluble Photoresponsive Azo Thiol Monolayer-Protected Gold Nanorods, Jouliana M. El Khoury, Xiaoli Zhou, Liangti Qu, Liming Dai, Augustine Urbas, Quan Li

Quan Li

Organo-soluble photoresponsive azo thiol monolayer-protected gold nanorods were synthesized; the resulting gold nanorods encapsulated by thiols on their entire surface with strong covalent Au-S linkages were very stable in both organic solvents and in the solid state without aggregation or decomposition.

Transitional Probabilities For The Four-State Random Walk On A Lattice In The Presence Of Partially Reflecting Boundaries, Ramakrishna Janaswamy

Ramakrishna Janaswamy

The four-state random walk (4RW) model, wherein the particle is endowed with two states of spin and two states of directional motion in each space coordinate, permits a stochastic solution of the Schrödinger equation (or the equivalent parabolic equation) without resorting to the usual analytical continuation in complex space of the particle trajectories. Analytical expressions are derived here for the various transitional probabilities in a 4RW by employing generating functions and eigenfunction expansions when the particle moves on a 1+1 space-time lattice with two-point boundary conditions. The most general case of dissimilar boundaries with partially reflecting boundary conditions is treated …

Quiet Variability Of Equatorial E × B Drifts During A Sudden Stratospheric Warning Event, J. L. Chau, Bela G. Fejer, L. P. Goncharenko

Bela G. Fejer

[1] We present strong evidence that during the January 2008 minor sudden stratospheric warming (SSW) event, the equatorial vertical E × B drifts exhibit a unique and distinctive daytime pattern. We do not think one event causes the other, however both events might be related through the global effects of planetary waves. The drifts were measured by the Jicamarca Incoherent scatter radar located under the magnetic equator. We have observed an anomalous temporal variation of the vertical E × B drifts during the minor SSW event, showing a semidiurnal variation with very large amplitudes lasting for several days. Large differences …

Ir-Dielectric Functions Of Znbete Alloys Determined By Spectroscopic Ellipsometry, Frank Peiris, Et Al.

Frank Peiris

All-Optical Control Of Nonlinear Focusing Of Laser Beams In Plasma Beat Wave Accelerator, Serguei Y. Kalmykov, Sunghwan A. Yi, Gennady Shvets

Serge Youri Kalmykov

Nonlinear focusing of a bi-color laser in plasma can be controlled by varying the difference frequency \Omega. The driven electron density perturbation forms a co-moving periodic focusing (de-focusing) channel if \Omega is below (above) the electron Langmuir frequency \omega_p. Hence, the beam focusing is enhanced for \Omega < \omega_p and is suppressed otherwise. In particular, a catastrophic relativistic self-focusing of a high-power laser beam can be prevented all-optically by a second, much weaker, co-propagating beam shifted in frequency by \Omega > \omega_p. A bi-envelope equation describing the early stage of the mutual de-focusing is derived and analyzed. Later stages, characterized by a well-developed electromagnetic cascade, are investigated numerically. Stable propagation of the over-critical laser pulse over several Rayleigh lengths is predicted. The non-resonant plasma beat wave (\Omega \not= \omega_p) can accelerate pre-injected electrons above …

Triggered Star Formation And The Creation Of The Supergiant H I Shell In Ic 2574, Daniel R. Weisz, Evan D. Skillman, John Cannon, Fabian Walter, Elias Brinks, Jürgen Ott, Andrew E. Dolphin

John Cannon

No abstract provided.

First Measurement Of The Neutron Beta Asymmetry With Ultracold Neutrons, Robert W. Pattie, J. Anaya, Henning O. Back, J. G. Boissevain, Thomas J. Bowles, Leah J. Broussard, Richard Carr, D. J. Clark, Scott Currie, S. Du, Bradley W. Filippone, Peter Geltenbort, A. García, Ayman I. Hawari, Kevin P. Hickerson, R. Hill, M. Hino, S. A. Hoedl, Gary E. Hogan, Anthony T. Holley, Takeyasu M. Ito, T. Kawai, K. Kirch, S. Kitagaki, Steve K. Lamoreaux, Chenyu Liu, Jingyang Liu, Mark Makela, Russell R. Mammei, J. W. Martin, Daniel Melconian, N. Meier, Michael P. Mendenhall, Charles L. Morris, R. Mortensen, A. Pichlmaier, Margaret L. Pitt, Blakely Plaster, John C. Ramsey, Roger Rios, Konstantin Sabourov, A. L. Sallaska, Alexander Saunders, R. Schmid, Susan J. Seestrom, C. Servicky, Sky K. L. Sjue, D. Smith, Walter E. Sondheim, E. Tatar, W. Teasdale, Christopher R. Terai, B. Tipton, M. Utsuro, R. Bruce Vogelaar, Bernard Wehring, Y. P. Xu, Andrew R. Young, J. Yuan

Robert W. Pattie Jr.

Effect Of Salts On The Electrospinning Of Poly(Vinyl Alcohol), Jonathan J. Stanger, Nick Tucker, Mark P. Staiger, Kerry Kirwan, Stuart Coles, Daniel Jacobs, Nigel Larsen

Jonathan J Stanger

Fibres with a diameter in the nanometer range were electrospun from aqueous poly(vinyl alcohol) (PVOH). In order to improve the mass deposition rate and decrease the final fibre diameter salts (NaCl, LiCl, LiBr and LiF) were added to the solution. The aim was to increase the charge density and hence increase the electrostatic forces on the fluid. It was found that with increasing salt concentration the charge density did increase. However the mass deposition rate was found to decrease and the final fibre diameter was found to increase. The decrease in mass deposition rate is explained by considering the concept …

Effect Of Charge Density On The Taylor Cone In Electrospinning, Jonathan J. Stanger, Nick Tucker, Kerry Kirwan, Stuart Coles, Daniel Jacobs, Mark P. Staiger

Jonathan J Stanger

A detailed understanding of charge density and its origins during the electrospinning process is desirable for developing new electrospinnable polymer-solvent systems and ensuring mathematical models of the process are accurate. In this work, two different approaches were taken to alter the charge density in order to measure its effect on the Taylor cone, mass deposition rate and initial jet diameter. It was found that an increase in charge density results in a decrease in the mass deposition rate and initial jet diameter. A theory is proposed for this behaviour in that an increase in charge density leads to the tip …

The Effect Of Electrode Configuration And Substrate Material On The Mass Deposition Rate Of Electrospinning, Jonathan J. Stanger, Nick Tucker, Andrew Wallace, Nigel Larsen, Mark P. Staiger, Roger Reeves

Jonathan J Stanger

Poly(vinyl alcohol) (PVOH) was electrospun using different methods to charge the polymer solution. A positive high voltage relative to the collecting electrode significantly increased the fibre deposition rate. Electron microscopy showed that approximately half of the increase in fibre mass was due to thicker fibres being deposited. The current flowing from the grounded electrode was measured to determine the charge carried on the PVOH jet. This showed that for a positive voltage charging condition there is a much larger current and hence more charge carriers generated in the PVOH solution. As a result, more mass is ejected from the Taylor …

The Fundamentals Of Local Fractional Derivative Of The One-Variable Non-Differentiable Functions, Yang Xiaojun

Xiao-Jun Yang

Based on the theory of Jumarie’s fractional calculus, local fractional derivative is modified in detail and its fundamentals of local fractional derivative are proposed in this paper. The uniqueness of local fractional derivative is obtained and the Rolle’s theorem, the mean value theorem, the Cauchy’s generalized mean value theorem and the L’Hospital’s rules are proved.

Local Fractional Newton’S Method Derived From Modified Local Fractional Calculus, Yang Xiao-Jun

Xiao-Jun Yang

A local fractional Newton’s method, which is derived from the modified local fractional calculus , is proposed in the present paper. Its iterative function is obtained and the convergence of the iterative function is discussed. The comparison between the classical Newton iteration and the local fractional Newton iteration has been carried out. It is shown that the iterative value of the local fractional Newton method better approximates the real-value than that of the classical one.

A Neural Network: Family Competition Genetic Algorithm And Its Application In Electromagnetic Optimization, Chien Hsun Chen, P. Y. Chen, H. Weng

Chien Hsun Chen

This study proposes a neural network-family competition genetic algorithm (NN-FCGA) for solving the electromagnetic (EM) optimization and other general-purpose optimization problems. The NN-FCGA is a hybrid evolutionary-based algorithm, combining the good approximation performance of neural network (NN) and the robust and effective optimum search ability of the family competition genetic algorithms (FCGA) to accelerate the optimization process. In this study, the NN-FCGA is used to extract a set of optimal design parameters for two representative design examples: the multiple section low-pass filter and the polygonal electromagnetic absorber. Our results demonstrate that the optimal electromagnetic properties given by the NN-FCGA are …

Five-Dimensional 2-Branes And The Universal Hypermultiplet, Moataz Emam

Moataz Emam

No abstract provided.

Symplectic Covariance Of The N = 2 Hypermultiplets, Moataz Emam

Moataz Emam

No abstract provided.

Climatology Of Early Night Equatorial Spread F Over Jicamarca, N. P. Chapagain, Bela G. Fejer

Bela G. Fejer

[1] We use radar observations from 1996 to 2006 to study the climatology of postsunset equatorial 3-m spread F irregularities over Jicamarca during all seasons. We show that the spread F onset times do not change with solar flux and that their onset heights, which occur near the altitude of the evening F region velocity vortex, increase linearly from about 260 to 400 km from solar minimum to solar maximum. Higher onset heights generally lead to stronger radar echoes. During the equinox, spread F onset occurs near vertical drift evening reversal times, while during the December solstice, they occur near …

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Agegnehu Atena, Mikhail Khenner

Mikhail Khenner

In this paper the lubrication-type dynamical model is developed of a molten, pulsed laser-irradiated metallic film. The heat transfer problem that incorporates the absorbed heat from a single beam or interfering beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the peak laser beam intensity, the film optical thickness, the Biot and …

A Percolation-Theoretic Approach To Spin Glass Phase Transitions, Jonathan Machta, C. M. Newman, D. L. Stein

Jonathan Machta

The magnetically ordered, low temperature phase of Ising ferromagnets is manifested within the associated Fortuin—Kasteleyn (FK) random cluster representation by the occurrence of a single positive density percolating cluster. In this paper, we review our recent work on the percolation signature for Ising spin glass ordering — both in the short-range Edwards—Anderson (EA) and infinite-range Sherrington—Kirkpatrick (SK) models — within a tworeplica FK representation and also in the different Chayes—Machta—Redner two-replica graphical representation. Numerical studies of the ±J EA model in dimension three and rigorous results for the SK model are consistent in supporting the conclusion that the signature of …

Strengths And Weaknesses Of Parallel Tempering, Jonathan Machta

Jonathan Machta

Parallel tempering, also known as replica exchange Monte Carlo, is studied in the context of two simple free-energy landscapes. The first is a double-well potential defined by two macrostates separated by a barrier. The second is a “golf course” potential defined by microstates having two possible energies with exponentially more high-energy states than low-energy states. The equilibration time for replica exchange is analyzed for both systems. For the double-well system, parallel tempering with a number of replicas that scales as the square root of the barrier height yields exponential speedup of the equilibration time. On the other hand, replica exchange …

Comments On The Minimal Vectorial Standard Model, Mohamed M. Anber, Ufuk Aydemir, John Donoghue, Preema Pais

John Donoghue

We explore the available parameter space of the minimal vectorial Standard Model. In this theory, the gauge currents are initially vectorial but the Higgs sector produces chiral mass eigenstates, leading to a set of heavy right-handed mirror particles. We describe the phenomenology of the residual parameter space and suggest that the model will be readily tested at the LHC.

Performance Of A Single-Crystal Diamond-Pixel Telescope, R. Hall-Wilton, V. Ryjov, M. Pernicka, V. Halyo, B. Harrop, A. Hunt, D. Marlow, E. Bartz, J. Doroshenko, D. Hits, S. Schnetzer, R. Stone, W. Bugg, M. Hollingsworth, Stefan Spanier, W. Johns

stefan spanier

We describe the results from a beam test of a telescope consisting of three planes of single-crystal, diamond pixel detectors. This telescope is a prototype for a proposed small-angle luminosity monitor, the Pixel Luminosity Telescope (PLT), for CMS. We recorded the pixel addresses and pulse heights of all pixels over threshold as well as the fast-or signals from all three telescope planes. We present results on the telescope performance including occupancies, pulse heights, fast-or efficiencies and particle tracking. These results show that the PLT design concept is sound and indicate that the project is ready to proceed with the next …

Overviewand Summary Of The Spread F Experiment (Spreadfex), D. C. Fritts, M. A. Abdu, B. R. Batista, I. S. Batista, P. P. Batista, R. Buritii, B. R. Clemesha, J. Comberiate, T. Dautermann, E. De Paula, B. J. Fechine, Bela G. Fejer, D. Gobbi, J. Haase, F. Kalamabadi, B. Laughman, P. P. Lima, H. L. Liu, A. Medeiros, D. Pautet, F. Sao Sabbas, J. H.A. Sobral, P. Stamus, H. Takahashi, M. J. Taylor, S. L. Vadas, C. Wrasse

Bela G. Fejer

We provide here an overview of, and a summary of results arising from, an extensive experimental campaign (the Spread F Experiment, or SpreadFEx) performed from September to November 2005, with primary measurements in Brazil. The motivation was to define the potential role of neutral atmosphere dynamics, specifically gravity wave motions propagating upward from the lower atmosphere, in seeding Rayleigh-Taylor instability (RTI) and plasma bubbles extending to higher altitudes. Campaign measurements focused on the Brazilian sector and included ground-based optical, radar, digisonde, and GPS measurements at a number of fixed and temporary sites. Related data on convection and plasma bubble structures …