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- Prof. Stephanie Tristram-Nagle Ph.D. (21)
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Articles 31 - 60 of 73
Full-Text Articles in Physics
Orientation Of Tie-Lines In The Phase Diagram Of Dopc/Dppc/Cholesterol Model Biomembranes., Pradeep Uppamoochikkal, Stephanie Tristram-Nagle, John Nagle
Orientation Of Tie-Lines In The Phase Diagram Of Dopc/Dppc/Cholesterol Model Biomembranes., Pradeep Uppamoochikkal, Stephanie Tristram-Nagle, John Nagle
Prof. Stephanie Tristram-Nagle Ph.D.
We report the direction of tie-lines of coexisting phases in a ternary diagram of DOPC/DPPC/cholesterol lipid bilayers, which has been a system of interest in the discussion of biological rafts. For coexisting Ld and Lo phases, we find that the orientation angle α of the tie-lines increases as the cholesterol concentration increases and it also increases as temperature increases from T = 15 °C to T = 30 °C. Results at lower cholesterol concentrations support the existence of a different two-phase coexistence region of Ld and So phases and the existence of a three-phase region separating the two two-phase regions. …
Alamethicin Aggregation In Lipid Membranes., Jianjun Pan, Stephanie Tristram-Nagle, John Nagle
Alamethicin Aggregation In Lipid Membranes., Jianjun Pan, Stephanie Tristram-Nagle, John Nagle
Prof. Stephanie Tristram-Nagle Ph.D.
X-ray scattering features induced by aggregates of alamethicin (Alm) were obtained in oriented stacks of model membranes of DOPC(diC18:1PC) and diC22:1PC. The first feature obtained near full hydration was Bragg rod in-plane scattering near 0.11 A(-1) in DOPC and near 0.08 A(-1) in diC22:1PC at a 1:10 Alm:lipid ratio. This feature is interpreted as bundles consisting of n Alm monomers in a barrel-stave configuration surrounding a water pore. Fitting the scattering data to previously published molecular dynamics simulations indicates that the number of peptides per bundle is n = 6 in DOPC and n >or= 9 in diC22:1PC. The larger …
Lipid Bilayers: Thermodynamics, Structure, Fluctuations, And Interactions., Stephanie Tristram-Nagle, John Nagle
Lipid Bilayers: Thermodynamics, Structure, Fluctuations, And Interactions., Stephanie Tristram-Nagle, John Nagle
Prof. Stephanie Tristram-Nagle Ph.D.
This article, adapted from our acceptance speech of the Avanti Award in Lipids at the 47th Biophysical Society meeting in San Antonio, 2003, summarizes over 30 years of research in the area of lipid bilayers. Beginning with a theoretical model of the phase transition (J.F.N.), we have proceeded experimentally using dilatometry and density centrifugation to study volume, differential scanning calorimetry to study heat capacity, and X-ray scattering techniques to study structure of lipid bilayers as a function of temperature. Electron density profiles of the gel and ripple phases have been obtained as well as profiles from several fluid phase lipids, …
Crac Motif Peptide Of The Hiv-1 Gp41 Protein Thins Sopc Membranes And Interacts With Cholesterol., Alexander Greenwood, Jianjun Pan, Thalia Mills, John Nagle, Richard Epand, Stephanie Tristram-Nagle
Crac Motif Peptide Of The Hiv-1 Gp41 Protein Thins Sopc Membranes And Interacts With Cholesterol., Alexander Greenwood, Jianjun Pan, Thalia Mills, John Nagle, Richard Epand, Stephanie Tristram-Nagle
Prof. Stephanie Tristram-Nagle Ph.D.
This study uses low-angle (LAXS) and wide-angle (WAXS) X-ray synchrotron scattering, volume measurements and thin layer chromatography to determine the structure and interactions of SOPC, SOPC/cholesterol mixtures, SOPC/peptide and SOPC/cholesterol/peptide mixtures. N-acetyl-LWYIK-amide (LWYIK) represents the naturally-occurring CRAC motif segment in the pretransmembrane region of the gp41 protein of HIV-1, and N-acetyl-IWYIK-amide (IWYIK), an unnatural isomer, is used as a control. Both peptides thin the SOPC bilayer by approximately 3 A, and cause the area/unit cell (peptide+SOPC) to increase by approximately 9 A2 from the area/lipid of SOPC at 30 degrees C (67.0+/-0.9 A2). Model fitting suggests that LWYIK's average position …
Volumetric Stability Of Lipid Bilayers., Kelsey Hallinen, Stephanie Tristram-Nagle, John Nagle
Volumetric Stability Of Lipid Bilayers., Kelsey Hallinen, Stephanie Tristram-Nagle, John Nagle
Prof. Stephanie Tristram-Nagle Ph.D.
In agreement with recent reports, a commercial densimeter has yielded a gradual decrease in lipid molecular volume of DPPC multilamellar vesicle dispersions in the gel phase upon repeated thermal cycling between 10 °C and 50 °C. The considerable size of this decrease would have significant implications for the physical chemistry of biomembranes. In contrast, neutral buoyancy measurements performed with similar thermal cycling indicate no gradual change in lipid volume in the gel phase at 20 °C. Remixing the lipid in the densimeter shows that the apparent volume decrease is an artifact. We conclude that gel phase DPPC bilayers exist in …
Α-Synuclein Induces Both Positive Mean Curvature And Negative Gaussian Curvature In Membranes., Anthony Braun, Eva Sevcsik, Pamela Chin, Elizabeth Rhoades, Stephanie Tristram-Nagle, Jonathan Sachs
Α-Synuclein Induces Both Positive Mean Curvature And Negative Gaussian Curvature In Membranes., Anthony Braun, Eva Sevcsik, Pamela Chin, Elizabeth Rhoades, Stephanie Tristram-Nagle, Jonathan Sachs
Prof. Stephanie Tristram-Nagle Ph.D.
Using a combination of X-ray scattering, fluorescence correlation spectroscopy, coarse-grained molecular dynamics (MD) simulations and potential of mean force calculations, we have explored the membrane remodeling effects of monomeric α-synuclein (αS). Our initial findings from multiple approaches are that αS (1) causes a significant thinning of the bilayer and (2) stabilizes positive mean curvature, such that the maximum principle curvature matches that of synaptic vesicles, αS-induced tubules, and the synthetic lipid vesicles to which the protein binds most tightly. This suggests that αS binding to synaptic vesicles likely stabilizes their intrinsic curvature. We then show that αS induces local negative …
Structure Of Fully Hydrated Fluid Phase Lipid Bilayers With Monounsaturated Chains., Norbert Kucerka, Stephanie Tristram-Nagle, John Nagle
Structure Of Fully Hydrated Fluid Phase Lipid Bilayers With Monounsaturated Chains., Norbert Kucerka, Stephanie Tristram-Nagle, John Nagle
Prof. Stephanie Tristram-Nagle Ph.D.
Quantitative structures are obtained at 30 degrees C for the fully hydrated fluid phases of palmitoyloleoylphosphatidylcholine (POPC), with a double bond on the sn-2 hydrocarbon chain, and for dierucoylphosphatidylcholine (di22:1PC), with a double bond on each hydrocarbon chain. The form factors F(qz) for both lipids are obtained using a combination of three methods. (1) Volumetric measurements provide F(0). (2) X-ray scattering from extruded unilamellar vesicles provides /F(qz)/ for low q(z). (3) Diffuse X-ray scattering from oriented stacks of bilayers provides /F(qz)/ for high q(z). Also, data using method (2) are added to our recent data for dioleoylphosphatidylcholine (DOPC) using methods …
Polymorphism In Myristoylpalmitoylphosphatidylcholine., Stephanie Tristram-Nagle, Yisrael Isaacson, Yulia Lyatskaya, Yufeng Liu, Kay Brummond, John Katsaras, John Nagle
Polymorphism In Myristoylpalmitoylphosphatidylcholine., Stephanie Tristram-Nagle, Yisrael Isaacson, Yulia Lyatskaya, Yufeng Liu, Kay Brummond, John Katsaras, John Nagle
Prof. Stephanie Tristram-Nagle Ph.D.
This study focuses on the mixed-chain lipid myristoylpalmitoylphosphatidylcholine (MPPC) near full hydration. The lipid, synthesized according to the procedure of (Mason et al., 1981a, has a low degree of acyl chain migration. When MPPC is temperature-jumped (T-jumped) from the L alpha phase (T = 38 degrees C) to T = 20 degrees C or below, a subgel phase forms; this formation takes less than 1 h at a temperature below T = 12 degrees C. The subgel remains stable up to T = 29 degrees C. When MPPC is T-jumped from the L alpha phase to T = 24 degrees …
Polyunsaturated Docosahexaenoic Vs Docosapentaenoic Acid-Differences In Lipid Matrix Properties From The Loss Of One Double Bond., Nadukkudy Eldho, Scott Feller, Stephanie Tristram-Nagle, Ivan Polozov, Klaus Gawrisch
Polyunsaturated Docosahexaenoic Vs Docosapentaenoic Acid-Differences In Lipid Matrix Properties From The Loss Of One Double Bond., Nadukkudy Eldho, Scott Feller, Stephanie Tristram-Nagle, Ivan Polozov, Klaus Gawrisch
Prof. Stephanie Tristram-Nagle Ph.D.
Insufficient supply to the developing brain of docosahexaenoic acid (22:6n3, DHA), or its omega-3 fatty acid precursors, results in replacement of DHA with docosapentaenoic acid (22:5n6, DPA), an omega-6 fatty acid that is lacking a double bond near the chain's methyl end. We investigated membranes of 1-stearoyl(d(35))-2-docosahexaenoyl-sn-glycero-3-phosphocholine and 1-stearoyl(d(35))-2-docosapentaenoyl-sn-glycero-3-phosphocholine by solid-state NMR, X-ray diffraction, and molecular dynamics simulations to determine if the loss of this double bond alters membrane physical properties. The low order parameters of polyunsaturated chains and the NMR relaxation data indicate that both DHA and DPA undergo rapid conformational transitions with correlation times of the order of …
Implementation Of Standard Testbeds For Numerical Relativity, Maria Babiuc-Hamilton, Sascha Husa, Daniela Alic, Ian Hinder, Christiane Lechner, Erik Schnetter, Yosef Zlochower, Nils Dorband, Jeffrey Winicour, D. Pollney, B´Ela Szilagyi
Implementation Of Standard Testbeds For Numerical Relativity, Maria Babiuc-Hamilton, Sascha Husa, Daniela Alic, Ian Hinder, Christiane Lechner, Erik Schnetter, Yosef Zlochower, Nils Dorband, Jeffrey Winicour, D. Pollney, B´Ela Szilagyi
Maria Babiuc-Hamilton
We discuss results that have been obtained from the implementation of the initial round of testbeds for numerical relativity which was proposed in the first paper of the Apples with Apples Alliance. We present benchmark results for various codes which provide templates for analyzing the testbeds and to draw conclusions about various features of the codes. This allows us to sharpen the initial test specifications, design a new test and add theoretical insight.
Some Mathematical Problems In Numerical Relativity, Maria Babiuc-Hamilton, B´Ela Szilagyi, Jeffrey Winicour
Some Mathematical Problems In Numerical Relativity, Maria Babiuc-Hamilton, B´Ela Szilagyi, Jeffrey Winicour
Maria Babiuc-Hamilton
The main goal of numerical relativity is the long time simulation of highly nonlinear spacetimes that cannot be treated by perturbation theory. This involves analytic, computational and physical issues. At present, the major impasses to achieving global simulations of physical usefulness are of an analytic/ computational nature. We present here some examples of how analytic insight can lend useful guidance for the improvement of numerical approaches.
Binary Black Hole Waveform Extraction At Null Infinity, Maria Babiuc-Hamilton, Jeffrey Winicour, Yosef Zlochower
Binary Black Hole Waveform Extraction At Null Infinity, Maria Babiuc-Hamilton, Jeffrey Winicour, Yosef Zlochower
Maria Babiuc-Hamilton
In this paper, we present a work in progress toward an efficient and economical computational module which interfaces between Cauchy and characteristic evolution codes. Our goal is to provide a standardized waveform extraction tool for the numerical relativity community which will allow CCE to be readily applied to a generic Cauchy code. The tool provides a means of unambiguous comparison between the waveforms generated by evolution codes based upon different formulations of the Einstein equations and different numerical approximation.
Gravitational Wave Extraction Based On Cauchy–Characteristic Extraction And Characteristic Evolution, Maria Babiuc-Hamilton, Yosef Zlochower, Béla Szilágyi, Ian Hawke
Gravitational Wave Extraction Based On Cauchy–Characteristic Extraction And Characteristic Evolution, Maria Babiuc-Hamilton, Yosef Zlochower, Béla Szilágyi, Ian Hawke
Maria Babiuc-Hamilton
We implement a code to find the gravitational news at future null infinity by using data from a Cauchy code as boundary data for a characteristic code. This technique of Cauchy–characteristic extraction (CCE) allows for the unambiguous extraction of gravitational waves from numerical simulations. We first test the technique on non-radiative spacetimes: Minkowski spacetime, perturbations of Minkowski spacetime and static black hole spacetimes in various gauges. We show the convergence and limitations of the algorithm and illustrate its success in cases where other wave extraction methods fail. We further apply our techniques to a standard radiative test case for wave …
Testing Numerical Evolution With The Shifted Gauge Wave, Maria Babiuc-Hamilton, Jeffrey Winicour, B´Ela Szilágyi
Testing Numerical Evolution With The Shifted Gauge Wave, Maria Babiuc-Hamilton, Jeffrey Winicour, B´Ela Szilágyi
Maria Babiuc-Hamilton
Computational methods are essential to provide waveforms from coalescing black holes, which are expected to produce strong signals for the gravitational wave observatories being developed. Although partial simulations of the coalescence have been reported, scientifically useful waveforms have so far not been delivered. The goal of the AppleswithApples (AwA) Alliance is to design, coordinate and document standardized code tests for comparing numerical relativity codes. The first round of AwA tests has now been completed and the results are being analyzed. These initial tests are based upon the periodic boundary conditions designed to isolate performance of the main evolution code. Here …
Finite Difference Schemes For Second Order Systems Describing Black Holes, Mohammad Motamed, Maria Babiuc-Hamilton, B. Szilágyi, H-O. Kreiss, J. Winicour
Finite Difference Schemes For Second Order Systems Describing Black Holes, Mohammad Motamed, Maria Babiuc-Hamilton, B. Szilágyi, H-O. Kreiss, J. Winicour
Maria Babiuc-Hamilton
In the harmonic description of general relativity, the principal part of Einstein’s equations reduces to 10 curved space wave equations for the components of the space-time metric. We present theorems regarding the stability of several evolution-boundary algorithms for such equations when treated in second order differential form. The theorems apply to a model black hole space-time consisting of a spacelike inner boundary excising the singularity, a timelike outer boundary and a horizon in between. These algorithms are implemented as stable, convergent numerical codes and their performance is compared in a 2-dimensional excision problem.
Transport Properties Of The La1−Xcaxmno3 (0.5 ≤ X < 1), H. Zhou, R. Zheng, G. Li, S. Feng, Xiaojuan Fan, X. Lia
Transport Properties Of The La1−Xcaxmno3 (0.5 ≤ X < 1), H. Zhou, R. Zheng, G. Li, S. Feng, Xiaojuan Fan, X. Lia
Xiaojuan Fan
The transport properties of the La1−xCaxMnO3 (0.5 ≤ x < 1) system in magnetic fields up to 14 T were studied. We found that the relationship between the charge ordering temperature TCO and Mn4+ content nMn4+ obeys the formula TCO/Tmax = 1−a(nMn4+ −n0)2, here n0 and a are constants and Tmax is the maximum of TCO. For x = 0.65, TCO arrives at the maximum value of 249.5 K in zero magnetic field, while the charge ordered (CO) state is most stable around x = 0.75. For x = 0.5 when H < 6 T the resistivity displays Mott’s variable-range hopping (VRH) behavior, when 6 < H < 12 T it is suggested that two kinds of conduction mechanism, i.e., VRH and magnetic polarons, coexist in the material, and when H > 12 T the resistivity shows metallic-like behavior and the transport mechanism is attributed to coexistence of magnetic polarons and free carriers. For x = 0.95, the conduction mechanism accords with the coexistence of VRH and magnetic polarons.
The Jahn–Teller Effect And Electron–Phonon Interaction In La0.25ca0.75mn1−Xcrxo3, H. Zhou, G. Li, H. Chen, R. Zheng, Xiaojuan Fan, X. Li
The Jahn–Teller Effect And Electron–Phonon Interaction In La0.25ca0.75mn1−Xcrxo3, H. Zhou, G. Li, H. Chen, R. Zheng, Xiaojuan Fan, X. Li
Xiaojuan Fan
The ultrasonic (longitudinal and transverse) velocities and the transport and magnetic properties of polycrystalline La0.25Ca0.75Mn1-xCrxO3 (x = 0, 0.03, 0.05, and 0.07) have been studied systematically. It was found that with increasing Cr content, the resistivity increases, the charge-ordering transition temperature TCO shifts to low temperature, and the magnetic moment of the system is strengthened. From the temperature dependence of the ultrasonic velocities, one can establish that the Jahn-Teller energy and phonon exchange constant decrease with increasing Cr content.
Spontaneous Oscillations In Simple Fluid Networks, Nathaniel Karst, Brian Storey, John Geddes
Spontaneous Oscillations In Simple Fluid Networks, Nathaniel Karst, Brian Storey, John Geddes
Brian Storey
Nonlinear phenomena including multiple equilibria and spontaneous oscillations are common in fluid networks containing either multiple phases or constituents. In many systems, such behavior might be attributed to the complicated geometry of the network, the complex rheology of the constituent fluids, or, in the case of microvascular blood flow, biological control. In this paper we investigate two examples of a simple three-node fluid network containing two miscible Newtonian fluids of differing viscosities, the first modeling microvascular blood flow and the second modeling stratified laminar flow. We use a combination of analytic and numerical techniques to identify and track saddle-node and …
Spontaneous Oscillations In Simple Fluid Networks, Nathaniel Karst, Brian Storey, John Geddes
Spontaneous Oscillations In Simple Fluid Networks, Nathaniel Karst, Brian Storey, John Geddes
John B. Geddes
Nonlinear phenomena including multiple equilibria and spontaneous oscillations are common in fluid networks containing either multiple phases or constituents. In many systems, such behavior might be attributed to the complicated geometry of the network, the complex rheology of the constituent fluids, or, in the case of microvascular blood flow, biological control. In this paper we investigate two examples of a simple three-node fluid network containing two miscible Newtonian fluids of differing viscosities, the first modeling microvascular blood flow and the second modeling stratified laminar flow. We use a combination of analytic and numerical techniques to identify and track saddle-node and …
The Hyperspherical Four-Fermion Problem, Seth Rittenhouse, J Stecher, J D'Incao, Nirav Mehta, Chris Greene
The Hyperspherical Four-Fermion Problem, Seth Rittenhouse, J Stecher, J D'Incao, Nirav Mehta, Chris Greene
Nirav P Mehta
The problem of a few interacting fermions in quantum physics has sparked intense interest, particularly in recent years owing to connections with the behaviour of superconductors, fermionic superfluids and finite nuclei. This review addresses recent developments in the theoretical description of four fermions having finite-range interactions, stressing insights that have emerged from a hyperspherical coordinate perspective. The subject is complicated, so we have included many detailed formulae that will hopefully make these methods accessible to others interested in using them. The universality regime, where the dominant length scale in the problem is the two-body scattering length, is particularly stressed, including …
Born-Oppenheimer Study Of Two-Component Few-Particle Systems Under One-Dimensional Confinement, Nirav Mehta
Born-Oppenheimer Study Of Two-Component Few-Particle Systems Under One-Dimensional Confinement, Nirav Mehta
Nirav P Mehta
The energy spectrum, atom-dimer scattering length, and atom-trimer scattering length for systems of three and four ultracold atoms with δ-function interactions in one dimension are presented as a function of the relative mass ratio of the interacting atoms. The Born-Oppenheimer approach is used to treat three-body (“HHL”) systems of one light and two heavy atoms, as well as four-body (“HHHL”) systems of one light and three heavy atoms. Zero-range interactions of arbitrary strength are assumed between different atoms, but the heavy atoms are assumed to be noninteracting among themselves. Fermionic and bosonic heavy atoms with both positive and negative parity …
General Theoretical Description Of N-Body Recombination, Nirav Mehta, Seth Rittenhouse, J D’Incao, J Stecher, Chris Greene
General Theoretical Description Of N-Body Recombination, Nirav Mehta, Seth Rittenhouse, J D’Incao, J Stecher, Chris Greene
Nirav P Mehta
Formulas for the cross section and event rate constant describing recombination of N particles are derived in terms of general S-matrix elements. Our result immediately yields the generalized Wigner threshold scaling for the recombination of N bosons. A semianalytical formula encapsulates the overall scaling with energy and scattering length, as well as resonant modifications by the presence of N-body states near the threshold collision energy in the entrance channel. We then apply our model to the case of four-boson recombination into an Efimov trimer and a free atom.
Low-Energy Operators In Effective Theories, C Felline, Nirav Mehta, J Piekarewicz, James Shepard
Low-Energy Operators In Effective Theories, C Felline, Nirav Mehta, J Piekarewicz, James Shepard
Nirav P Mehta
Modern effective-theory techniques are applied to the nuclear many-body problem. A novel approach is proposed for the renormalization of operators in a manner consistent with the construction of the effective potential. To test this approach, a one-dimensional, yet realistic, nucleon-nucleon potential is introduced. An effective potential is then constructed by tuning its parameters to reproduce the exact effective-range expansion and a variety of bare operators are renormalized in a fashion compatible with this construction. Predictions for the expectation values of these effective operators in the ground state reproduce the results of the exact theory with remarkable accuracy (at the 0.5% …
Green’S Functions And The Adiabatic Hyperspherical Method, Seth Rittenhouse, Nirav Mehta, Chris Greene
Green’S Functions And The Adiabatic Hyperspherical Method, Seth Rittenhouse, Nirav Mehta, Chris Greene
Nirav P Mehta
We address the few-body problem using the adiabatic hyperspherical representation. A general form for the hyperangular Green’s function in d dimensions is derived. The resulting Lippmann-Schwinger equation is solved for the case of three particles with s-wave zero-range interactions. Identical particle symmetry is incorporated in a general and intuitive way. Complete semianalytic expressions for the nonadiabatic channel couplings are derived. Finally, a model to describe the atom loss due to three-body recombination for a three-component Fermi gas of Li6 atoms is presented.
Efimov States Embedded In The Three-Body Continuum, Nirav Mehta, Seth Rittenhouse, J D’Incao, Chris Greene
Efimov States Embedded In The Three-Body Continuum, Nirav Mehta, Seth Rittenhouse, J D’Incao, Chris Greene
Nirav P Mehta
We present analytical solutions for the three-body problem with multichannel interactions and identify a class of quasibound Efimov states that can be viewed as three-body Fano-Feshbach resonances. Our method employs a multichannel generalization of the Fermi pseudopotential to model low-energy atom-atom interactions near a magnetically tunable Fano-Feshbach resonance. We discuss the conditions under which quasibound Efimov states may be supported and identify the interaction parameters that limit the lifetimes of these states. We speculate that it may be possible to observe these states using spectroscopic methods, perhaps allowing for the measurement of multiple Efimov resonances.
Three-Body Recombination In One Dimension, Nirav Mehta, B Esry, Chris Greene
Three-Body Recombination In One Dimension, Nirav Mehta, B Esry, Chris Greene
Nirav P Mehta
We study the three-body problem in one dimension for both zero- and finite-range interactions using the adiabatic hyperspherical approach. Particular emphasis is placed on the threshold laws for recombination, which are derived for all combinations of the parity and exchange symmetries. For bosons, we provide a numerical demonstration of several universal features that appear in the three-body system, and discuss how certain universal features in three dimensions are different in one dimension. We show that the probability for inelastic processes vanishes as the range of the pairwise interaction is taken to zero and demonstrate numerically that the recombination threshold law …
Effects Of Bandgap On Secondary Electron Emission For Graphitic Carbon Semiconductiors, Jodie Gillespie, Jr Dennison
Effects Of Bandgap On Secondary Electron Emission For Graphitic Carbon Semiconductiors, Jodie Gillespie, Jr Dennison
Jodie Corbridge Gillespie
Preliminary data indicates a relationship between bandgap width and magnitude of secondary electron (SE) yield. Our work extends this research to investigate the correlation of small bandgap width to SE yield. These trends are compared with current semiempirical models of two limiting cases, conductors and large bandgap semiconductors. Specifically, five graphitic amorphous carbon (g-C) samples of decreasing bandgap width were produced by vacuum annealing from 0C-1050C. Preliminary data shows a 30of g-C above nanocrystalline graphite. Measurements include SE yields, backscattered yields and electron emission spectra, as well as characterization with SEM, photoyields, AES, resistivity, and Raman spectroscopy. SE yields were …
Effect Of Trans-Cis Photoisomerization On Phase Equilibria And Phase Transition Of Liquid-Crystalline Azobenzene Chromophore And Its Blends With Reactive Mesogenic Diacrylate, Namil Kim, Quan Li, Thein Kyu
Effect Of Trans-Cis Photoisomerization On Phase Equilibria And Phase Transition Of Liquid-Crystalline Azobenzene Chromophore And Its Blends With Reactive Mesogenic Diacrylate, Namil Kim, Quan Li, Thein Kyu
Thein Kyu
Photoisomerization-induced phase transition of neat liquid-crystalline azobenzene chromophore (LCAC) and its effect on phase diagrams of its mixtures with reactive mesogenic diacrylate monomer (RM257) have been investigated experimentally and theoretically. Upon irradiation with ultraviolet light, the nematic phase of LCAC transformed to isotropic, while the crystal phase showed corrugated textures on the surface (i.e., ripples). The phase-transition temperatures and corresponding morphologies of the blends have been investigated by means of differential scanning calorimetry and optical microscopy. A theoretical phase diagram of a binary nematic and crystalline system was constructed by self-consistently solving the combined free energies of Flory-Huggins, Maier-Saupe, and …
Spatio-Temporal Growth Of Nematic Domains In Liquid Crystal Polymer Mixtures, Hao-Wen Chiu, Thein Kyu
Spatio-Temporal Growth Of Nematic Domains In Liquid Crystal Polymer Mixtures, Hao-Wen Chiu, Thein Kyu
Thein Kyu
Dynamics of phase separation and morphology development in mixtures of a low molar mass liquid crystal (LC) and a polymer have been investigated theoretically in comparison with experimental results. In the theoretical model, the combined free-energy densities of Flory-Huggins theory for isotropic mixing and Maier-Saupe theory for nematic ordering have been incorporated into the time-dependent Ginzburg-Landau equation (type C). The temporal evolution of the structure factor and the emergence of phase-separated liquid crystal domains have been simulated on the basis of an explicit central difference method based on a square lattice (128 x 128) with a periodic boundary condition. Of …
Observation Of Novel Liquid-Crystalline Phase Above The Bulk-Melting Temperature, Keshav Gautam, Satyendra Kumar, Didier Wermeille, Doug Robinson, Ali Dhinojwala
Observation Of Novel Liquid-Crystalline Phase Above The Bulk-Melting Temperature, Keshav Gautam, Satyendra Kumar, Didier Wermeille, Doug Robinson, Ali Dhinojwala
Ali Dhinojwala
In this paper, we show that a noncrystalline but ordered smectic-like phase exists above the bulk-melting temperature (T-m) at poly(n-alkyl acrylates)-air interface. The surface ordered phase is one monolayer thick and undergoes a sharp transition from order to disorder 10degreesC above T-m for n=22. The presence of a surface phase that does not exist in the bulk has important implications in the design of thermally responsive adhesives.