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Effect of Annealing on High Frequency Viscoelastic Waves in Spincoated Polymer thin Films

MRS Online Proceedings Library 2011年第1期356卷 535-540页

作者： J. R. Dutcher Z. Wang B. J. Neal T. Copeland J. R. Stevens Department of Physics and Guelph-Waterloo Program for Graduate Work in Physics University of Guelph Guelph Canada

We present a study of the effect of elevated temperatures on the high frequency viscoelastic waves guided by thin films of poly(styrene) [PS] and poly(methyl methacrylate) [PMMA]. The films, which are spincoated onto Si(OOl) wafers, have thicknesses h ~ 1000 Å. The frequencies and linewidths of the film-guided waves were measured using Brillouin light scattering (BLS). In both PS and PMMA, we observed guided waves for temperatures above the glass transition temperature Tg of the polymers, however, the damping of the waves for temperatures above Tg was significantly higher for PS. We observed no significant (< 1 %) difference between room temperature guided-wave frequencies for films annealed at temperatures below and above Tg for PS, and a slight (4 %) increase in the wave frequency for PMMA following annealing at a temperature above Tg. The heating effects due to the focussing of the laser beam on the film surface are quite small (~ 16°C/100 mW laser power).

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Brillouin Light Scattering Determination of the Glass Transition in Thin, Freely-Standing Poly(styrene) Films

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MRS Online Proceedings Library 2011年第1期407卷 131-136页

作者： J.A. Forrest K. Dalnoki-Veress J.R. Dutcher A.C. Rowat J.R. Stevens Department of Physics and Guelph-Waterloo Program for Graduate Work in Physics University of Guelph Guelph Canada

We have used Brillouin light scattering (BLS) to measure the glass transition temperature of thin, freely-standing poly(styrene) (PS) films. The freely-standing films were prepared by spincoating solutions of PS in toluene onto glass substrates, annealing the supported films in vacuum, and then using a water surface transfer technique to place the films across a 3 mm diameter orifice. Ellipsometry measurements of similar floated films transferred to Si(001) wafers allow the determination of the film thicknesses. Atomic force microscopy measurements revealed that the films have an rms roughness of less than 10 Å. With the freely-standing films placed in an optical furnace, we performed BLS measurements of the films using a high-contrast, multipassed, tandem Fabry-Perot interferometer. We obtained a reliable, reproducible measure of the glass transition temperature, Tg, from the large changes in the frequencies of the thermally-excited, viscoelastic, film-guided waves within the PS films as the films were heated above Tg. BLS results for bulk PS and a 1800 Å thick, freely-standing PS film are presented. We find the same glass transition temperature for the 1800 Å thick film as the bulk PS sample. This Tg value is the same as that obtained using differential scanning calorimetry (DSC).

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Vacuum electromagnetic counterparts of binary black-hole mergers

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Physical Review D 2010年第6期81卷 064017-064017页

作者： Philipp Mösta Carlos Palenzuela Luciano Rezzolla Luis Lehner Shin’ichirou Yoshida Denis Pollney Max-Planck-Institut für Gravitationsphysik Albert-Einstein-Institut Potsdam-Golm Germany Canadian Institute of Theoretical Astrophysics Toronto Ontario Canada Perimeter Institute for Theoretical Physics Waterloo Ontario Canada Department of Physics University of Guelph Guelph Ontario Canada Canadian Institute for Advanced Research Cosmology & Gravity Program Department of Earth Science and Astronomy Graduate School of Arts and Sciences University of Tokyo

As one step towards a systematic modeling of the electromagnetic (EM) emission from an inspiralling black hole binary we consider a simple scenario in which the binary moves in a uniform magnetic field anchored to a distant circumbinary disc. We study this system by solving the Einstein-Maxwell equations in which the EM fields are chosen with strengths consistent with the values expected astrophysically and treated as test fields. Our initial data consists of a series of binaries with spins aligned or antialigned with the orbital angular momentum and we study the dependence of gravitational and EM signals with different spin configurations. Overall we find that the EM radiation in the lowest ℓ=2, m=2 multipole accurately reflects the gravitational one, with identical phase evolutions and amplitudes that differ only by a scaling factor. This is no longer true when considering higher ℓ modes, for which the amplitude evolution of the scaled EM emission is slightly larger, while the phase evolutions continue to agree. We also compute the efficiency of the energy emission in EM waves and find that it scales quadratically with the total spin and is given by EEMrad/M≃10−15(M/108M⊙)2(B/104G)2, hence 13 orders of magnitude smaller than the gravitational energy for realistic magnetic fields. Although large in absolute terms, the corresponding luminosity is much smaller than the accretion luminosity if the system is accreting at near the Eddington rate. Most importantly, this EM emission is at frequencies of ∼10−4(108M⊙/M) Hz, which are well outside those accessible to astronomical radio observations. As a result, it is unlikely that the EM emission discussed here can be detected directly and simultaneously with the gravitational-wave one. However, indirect processes, driven by changes in the EM fields behavior could yield observable events. In particular we argue that if the accretion rate of the circumbinary disc is small and sufficiently stable over the timescale of the fi

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Understanding possible electromagnetic counterparts to loud gravitational wave events: Binary black hole effects on electromagnetic fields

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Physical Review D 2010年第8期81卷 084007-084007页

作者： Carlos Palenzuela Luis Lehner Shin Yoshida Canadian Institute for Theoretical Astrophysics (CITA) Toronto Ontario M5S 3H8 Canada Max-Planck-Institut für Gravitationsphysik Albert-Einstein-Institut Berlin D-14476 Golm Germany Perimeter Institute for Theoretical Physics Waterloo Ontario N2L 2Y5 Canada Department of Physics University of Guelph Guelph Ontario N1G 2W1 Canada Canadian Institute For Advanced Research (CIFAR) Cosmology and Gravity Program Canada Department of Earth Science and Astronomy Graduate School of Arts and Sciences University of Tokyo Meguro Tokyo 153-8902 Japan

In addition to producing loud gravitational waves, the dynamics of a binary black hole system could induce emission of electromagnetic radiation by affecting the behavior of plasmas and electromagnetic fields in their vicinity. We study how the electromagnetic fields are affected by a pair of orbiting black holes through the merger. In particular, we show how the binary’s dynamics induce a variability in possible electromagnetically induced emissions as well as an enhancement of electromagnetic fields during the late-merge and merger epochs. These time dependent features will likely leave their imprint in processes generating detectable emissions and can be exploited in the detection of electromagnetic counterparts of gravitational waves.

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Unified modeling of conductance kinetics for low- and high-conductance potassium ion channels

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Physical Review E 2006年第1期74卷 011902-011902页

作者： Igor S. Tolokh Saul Goldman C. G. Gray Guelph-Waterloo Physics Institute University of Guelph Guelph Ontario N1G 2W1 Canada Guelph-Waterloo Center for Graduate Work in Chemistry University of Guelph Guelph Ontario N1G 2W1 Canada

A kinetics model is proposed for the description of ion conductance of low- and high-conductance potassium ion channels. The model describes ion permeation through the selectivity filter, which is assumed to be the only conductance determining part of the open channel. The filter occupancy can vary from zero to three ions, affecting the ion entry and exit rates. Ion motion between the binding sites inside the filter is assumed fast compared to the latter rates allowing averaging the equilibrium entry and exit rate constants over the possible ion configurations in the filter with a particular occupancy. Averaged rate constants related to a pair of adjacent occupancy states characterize a particular ion permeation mechanism. An expression for the channel conductance as a function of the symmetrical external ion concentration is derived. It comprises a sum of concentration independent conductance amplitudes for different ion permeation mechanisms weighted by the equilibrium filter occupancy probabilities. It is shown that each amplitude (i.e., maximum contribution to the channel conductance from each conductance mechanism) is proportional to an averaged exit rate constant and to quantities characterizing the effect of the applied electric field on the rate constants and the equilibrium ion distribution in the filter. The conductance expression derived provides a good description of the experimentally observed conductance-concentration curves for low-conductance (e.g., Kir2.1) and high-conductance (e.g., KcsA) potassium channels. It enables one to obtain equilibrium ion binding constants at different filter occupancies and to calculate the average number of ions in the selectivity filter for a given external ion concentration. For KcsA this number (2.0 at 200mM) is in a good agreement with the available experimental value (2.1 at 200mM). For the high-conductance potassium channels the net negative electrical charge around the selectivity filter increases the ion binding

关键词： K+ CHANNEL SELECTIVITY FILTER CRYSTAL-STRUCTURE MOLECULAR-BASIS SIMULATION RECTIFICATION PERMEATION OCCUPANCY TRANSPORT MEMBRANES

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Non-Michaelis-Menten kinetics model for conductance of low-conductance potassium ion channels

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Physical Review E 2005年第2期71卷 021912-021912页

作者： Igor S. Tolokh Illya I. Tolokh Hee Cheol Cho Nazzareno D’Avanzo Peter H. Backx Saul Goldman C. G. Gray Guelph-Waterloo Physics Institute University of Guelph Guelph Ontario Canada N1G 2W1 Department of Physiology and Medicine Heart and Stroke/Richard Lewar Center University of Toronto Toronto Ontario Canada M5S 3E2 Division of Cardiology University Health Network Toronto Ontario Canada M5G 2C4 Guelph-Waterloo Center for Graduate Work in Chemistry University of Guelph Guelph Ontario Canada N1G 2W1

A reduced kinetics model is proposed for ion permeation in low-conductance potassium ion channels with zero net electrical charge in the selectivity filter region. The selectivity filter is assumed to be the only conductance-determining part of the channel. Ion entry and exit rate constants depend on the occupancy of the filter due to ion-ion interactions. The corresponding rates are assumed slow relative to the rates of ion motion between binding sites inside the filter, allowing a reduction of the kinetics model of the filter by averaging the entry and exit rate constants over the states with a particular occupancy number. The reduced kinetics model for low-conductance channels is described by only three states and two sets of effective rate constants characterizing transitions between these states. An explicit expression for the channel conductance as a function of symmetrical external ion concentration is derived under the assumption that the average electrical mobility of ions in the selectivity filter region in a limited range of ion concentrations does not depend on these concentrations. The simplified conductance model is shown to provide a good description of the experimentally observed conductance-concentration curve for the low-conductance potassium channel Kir2.1, and also predicts the mean occupancy of the selectivity filter of this channel. We find that at physiological external ion concentrations this occupancy is much lower than the value of two ions observed for one of the high-conductance potassium channels, KcsA.

关键词： SINGLE-FILE PORES K+ CHANNEL SELECTIVITY FILTER CRYSTAL-STRUCTURE MOLECULAR-BASIS PERMEATION SIMULATION TRANSPORT STATE KCSA

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Erratum: “Molecular constants and Rydberg–Klein–Rees (RKR) potential curve for the Na2 1 3Σg− state” [J. Chem. Phys. 111, 3494 (1999)]

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The Journal of Chemical physics 2002年第13期117卷 6380-6380页

作者： Yaoming Liu Jian Li Dieyan Chen Li Li Kevin M. Jones Bing Ji Robert J. Le Roy Department of Modern Applied Physics and Center of Atomic Molecular Sciences Tsinghua University Beijing 100084 China Department of Physics Williams College Williamstown Massachusetts 01267 Department of Chemistry Massachusetts Institute of Technology Cambridge Massachusetts 02139 Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry University of Waterloo Waterloo Ontario N2L 3G1 Canada

Yaoming Liu, Jian Li, Dieyan Chen, Li Li, Kevin M. Jones, Bing Ji, Robert J. Le Roy; Erratum: “Molecular constants and Rydberg–Klein–Rees (RKR) potential curve

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Dual wavelength chirped pulse amplification system

Dual wavelength chirped pulse amplification system

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Advanced Solid State Lasers, ASSL 2000

作者： Zhang, Zhuhong Deslauriers, Adam M. Strickland, Donna Physics Department Guelph-Waterloo Program for Graduate Work in Physics G/W University of Waterloo WaterlooONN2L 3G1 Canada

We demonstrate a Chirped Pulse Amplification system that simultaneously amplifies dual wavelength pulses from a two-colour oscillator in a single regenerative amplifier. © 1999 Optical Society of America

ISBN: (纸本)1557526281

关键词： Chirp modulation

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Dual wavelength chirped pulse amplification system

Dual wavelength chirped pulse amplification system

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Conference on Lasers and Electro-Optics (CLEO)

作者： Zhuhong Zhang A.M. Deslauriers D. Strickland Physics Department Guelph waterloo program for Graduate work in physics University of waterloo Waterloo Canada

ISBN: (纸本)1557526346

Summary form only given.A rapidly expanding field of research is coherent control of molecules. Several of the proposed techniques require two synchronized, broadband, high-intensity pulses. The dual wavelength mode-locked Ti:sapphire oscillators that have recently been developed give the appropriate wavelength separations for these techniques, but the pulses must be amplified to carry out these experiments.

关键词： Chirp Pulse amplifiers

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Progress towards chirped pulse dissociation of molecules

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AIP Conference Proceedings 2000年第1期500卷 192-197页

作者： Donna Strickland Zhuhong Zhang Adam M. Deslauriers Department of Physics Guelph-Waterloo Program for Graduate Work in Physics 〈G/W〉 University of Waterloo Ontario Canada N2L 3G1

Experimental investigations of coherently controlling molecular dynamics are currently hampered by the lack of high intensity, mid-infrared laser sources. This paper describes our approach to generating short pulse, high energy mid-infrared laser pulses. The laser will be used to investigate chirped dissociation of molecules.

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