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Eigenmode frequencies calculations in the charge-density-wave states of 2H-TaSe2

Ribeiro Filho,A.; Nascimento,E. M. do; Vasconcelos,D. S. de
Fonte: Sociedade Brasileira de Física Publicador: Sociedade Brasileira de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/1998 EN
Relevância na Pesquisa
26.94%
We have performed some calculations involving two eigenmode frequencies of 2H - TaSe2. We have obtained a good comparison with some well established Raman scattering data for the commensurate and incommensurate charge-density-wave phases in this compound. We outline an approximated method to compute the determinantal equation.

On the difference between negative damping and eigenmode synchronization as two phonation onset mechanisms

Zhang, Zhaoyan
Fonte: Acoustical Society of America Publicador: Acoustical Society of America
Tipo: Artigo de Revista Científica
Publicado em /04/2011 EN
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27.39%
Negative damping and eigenmode synchronization as two different mechanisms of phonation onset are distinguished. Although both mechanisms lead to a favorable phase relationship between the flow pressure and the vocal fold motion as required for a net energy transfer into the vocal folds, the underlying mechanisms for this favorable phase relationship are different. The negative damping mechanism relies on glottal aerodynamics or acoustics to establish before onset and maintain after onset the favorable phase relationship, and therefore has minimum requirements on vocal fold geometry and biomechanics. A single degree-of-freedom vocal fold model is all that is needed for self-oscillation in the presence of a negative damping mechanism. In contrast, the mechanism of eigenmode synchronization critically depends on the geometrical and biomechanical properties of the vocal folds (at least 2-degrees-of-freedom are required), and has little requirement on the glottal aerodynamics other than flow separation. The favorable phase relation is established once synchronization occurs, regardless of the phase relationship imposed by glottal aerodynamics before onset. Unlike that of the negative damping mechanism, initiation of eigenmode synchronization requires neither a velocity-dependent flow pressure nor an alternating convergent-divergent glottis. The clinical implications of the distinctions between these two mechanisms are discussed.

Spatially-Resolved Eigenmode Decomposition of Red Blood Cells Membrane Fluctuations Questions the Role of ATP in Flickering

Boss, Daniel; Hoffmann, Annick; Rappaz, Benjamin; Depeursinge, Christian; Magistretti, Pierre J.; Van de Ville, Dimitri; Marquet, Pierre
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 10/08/2012 EN
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26.94%
Red blood cells (RBCs) present unique reversible shape deformability, essential for both function and survival, resulting notably in cell membrane fluctuations (CMF). These CMF have been subject of many studies in order to obtain a better understanding of these remarkable biomechanical membrane properties altered in some pathological states including blood diseases. In particular the discussion over the thermal or metabolic origin of the CMF has led in the past to a large number of investigations and modeling. However, the origin of the CMF is still debated. In this article, we present an analysis of the CMF of RBCs by combining digital holographic microscopy (DHM) with an orthogonal subspace decomposition of the imaging data. These subspace components can be reliably identified and quantified as the eigenmode basis of CMF that minimizes the deformation energy of the RBC structure. By fitting the observed fluctuation modes with a theoretical dynamic model, we find that the CMF are mainly governed by the bending elasticity of the membrane and that shear and tension elasticities have only a marginal influence on the membrane fluctations of the discocyte RBC. Further, our experiments show that the role of ATP as a driving force of CMF is questionable. ATP...

Bimodal atomic force microscopy driving the higher eigenmode in frequency-modulation mode: Implementation, advantages, disadvantages and comparison to the open-loop case

Ebeling, Daniel; Solares, Santiago D
Fonte: Beilstein-Institut Publicador: Beilstein-Institut
Tipo: Artigo de Revista Científica
Publicado em 18/03/2013 EN
Relevância na Pesquisa
27.39%
We present an overview of the bimodal amplitude–frequency-modulation (AM-FM) imaging mode of atomic force microscopy (AFM), whereby the fundamental eigenmode is driven by using the amplitude-modulation technique (AM-AFM) while a higher eigenmode is driven by using either the constant-excitation or the constant-amplitude variant of the frequency-modulation (FM-AFM) technique. We also offer a comparison to the original bimodal AFM method, in which the higher eigenmode is driven with constant frequency and constant excitation amplitude. General as well as particular characteristics of the different driving schemes are highlighted from theoretical and experimental points of view, revealing the advantages and disadvantages of each. This study provides information and guidelines that can be useful in selecting the most appropriate operation mode to characterize different samples in the most efficient and reliable way.

Optical Characteristic Research on Fiber Bragg Gratings Utilizing Finite Element and Eigenmode Expansion Methods

He, Yuejing; Chen, Xuanyang
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 19/06/2014 EN
Relevância na Pesquisa
26.94%
Compared with coupled-mode theory (CMT), which is widely used for studies involving optical fiber Bragg gratings (FBGs), the proposed investigation scheme is visualized, diagrammatic, and simple. This method combines the finite element method (FEM) and eigenmode expansion method (EEM). The function of the FEM is to calculate all guided modes that match the boundary conditions of optical fiber waveguides. Moreover, the FEM is used for implementing power propagation for HE11 in optical fiber devices. How the periodic characteristic of FBG causes this novel scheme to be substantially superior to CMT is explained in detail. Regarding current numerical calculation techniques, the scheme proposed in this paper is the only method capable of the 3D design and analysis of large periodic components. Additionally, unlike CMT, in which deviations exist between the designed wavelength λD and the maximal reflection wavelength λmax, the proposed method performs rapid scans of the periods of optical FBG. Therefore, once the operating wavelength is set for the component design, the maximal reflection wavelength of the final products can be accurately limited to that of the original design, such as λ = 1550 nm. Furthermore, a comparison between the period scan plot and the optical spectra plot for FBG indicated an inverse relationship between the periods and wavelengths. Consequently...

Dynamic calibration of higher eigenmode parameters of a cantilever in atomic force microscopy by using tip–surface interactions

Borysov, Stanislav S; Forchheimer, Daniel; Haviland, David B
Fonte: Beilstein-Institut Publicador: Beilstein-Institut
Tipo: Artigo de Revista Científica
Publicado em 29/10/2014 EN
Relevância na Pesquisa
27.39%
We present a theoretical framework for the dynamic calibration of the higher eigenmode parameters (stiffness and optical lever inverse responsivity) of a cantilever. The method is based on the tip–surface force reconstruction technique and does not require any prior knowledge of the eigenmode shape or the particular form of the tip–surface interaction. The calibration method proposed requires a single-point force measurement by using a multimodal drive and its accuracy is independent of the unknown physical amplitude of a higher eigenmode.

The impact of magnetic geometry on wave modes in cylindrical plasmas

Chang, Lei
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
EN_AU
Relevância na Pesquisa
27.59%
Both space and laboratory plasmas can be associated with static magnetic field, and the field geometry varies from uniform to non-uniform. This thesis investigates the impact of magnetic geometry on wave modes in cylindrical plasmas. The cylindrical configuration is chosen so as to explore this impact in a tractable but experimentally realisable configuration. Three magnetic geometries are considered: uniform, focused and rippled. For a uniform magnetic field, wave oscillations in a plasma cylinder with axial flow and azimuthal rotation are modelled through a two-fluid flowing plasma model. The model provides a qualitatively consistent description of the plasma configuration on a Radio Frequency (RF) generated linear magnetised plasma (WOMBAT, Waves On Magnetised Beams And Turbulence [Boswell and Porteous, Appl. Phys. Lett. 50, 1130 (1987)]), and yields agreement between measured and predicted dependences of the wave oscillation frequency with axial field strength. The radial profile of the density perturbation predicted by this model is consistent with the data. Parameter scans show that the dispersion curve is sensitive to the axial field strength and the electron temperature, and the dependence of the oscillation frequency with electron temperature matches the experiment. These results consolidate earlier claims that the density and floating potential oscillations are a resistive drift mode...

Pressure Effects on the Ensemble Dynamics of Ubiquitin Inspected with Molecular Dynamics Simulations and Isotropic Reorientational Eigenmode Dynamics

Sgourakis, Nikolaos G.; Day, Ryan; McCallum, Scott A.; Garcia, Angel E.
Fonte: The Biophysical Society Publicador: The Biophysical Society
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.94%
According to NMR chemical shift data, the ensemble of ubiquitin is a mixture of “open” and “closed” conformations at rapid equilibrium. Pressure perturbations provide the means to study the transition between the two conformers by imposing an additional constraint on the system's partial molar volume. Here we use nanosecond-timescale molecular dynamics simulations to characterize the network of correlated motions accessible to the conformers at low- and high-pressure conditions. Using the isotropic reorientational eigenmode dynamics formalism to analyze our simulation trajectories, we reproduce NMR relaxation data without fitting any parameters of our model. Comparative analysis of our results suggests that the two conformations behave very differently. The dynamics of the “closed” conformation are almost unaffected by pressure and are dominated by large-amplitude correlated motions of residues 23–34 in the extended α-helix. The “open” conformation under conditions of normal pressure displays increased mobility, focused on the loop residues 17–20, 46–55, and 58–59 at the bottom of the core of the structure, as well as the C-terminal residues 69–76, that directly participate in key protein-protein interactions. For the same conformation...

Gap eigenmode of radially localized helicon waves in a periodic structure

Chang, Lei; Breizman, Boris; Hole, Matthew
Fonte: Institute of Physics Publishing Publicador: Institute of Physics Publishing
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
26.94%
An ElectroMagnetic Solver (Chen et al 2006 Phys. Plasmas 13 123507) is employed to model a spectral gap and a gap eigenmode in a periodic structure in the whistler frequency range. A radially localized helicon mode (Breizman and Arefiev 2000 Phys. Rev. Le

Quantum Chaos Analysis of the Ideal Interchange Spectrum in a Stellarator

Dewar, Robert; Nuehrenberg, C.; Tatsuno, Tomoya
Fonte: Cambridge University Press Publicador: Cambridge University Press
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
26.94%
The eigenmode spectrum is a fundamental starting point for the analysis of plasma stability and the onset of turbulence. Quantum chaos theory provides tools for characterizing the spectrum statistically, from the regular spectrum of the separable case (in

Eigenmode Analysis of Radial Velocities

Hoffman, Yehuda
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/09/1999
Relevância na Pesquisa
27.22%
Radial velocity surveys are examined in terms of eigenmode analysis within the framework of CDM-like family of models. Rich surveys such as MARK III and SFI, which consist of more than $10^{3}$ radial velocities, are found to have a few tens of modes that are not noise dominated. Poor surveys, which have only a few tens of radial velocities, are noise dominated across the eigenmode spectrum. In particular, the bulk velocity of such surveys has been found to be dominated by the more noisy modes. The MARK III and SFI are well fitted by a tilted flat CDM model found by a maximum likelihood analysis and a $\chi^{2}$ statistics . However, a mode-by-mode inspection shows that a substantial fraction of the modes lie outside the $90% $ confidence level. This implies that although globally the CDM-like family of models seems to be consistent with radial velocity surveys, in detail it does not. This might indicate a need for a revised power spectrum or for some non-trivial biasing scheme.; Comment: Contribution to ``Cosmic Flows. Towards an Understanding of Large-Scale Structure'', Workshop Victoria B.C., July 1999, eds. S. Courteau, M. Strauss, and J. Willick (ASP). 8 pages of LaTeX including 9 postscript figures

Eigenmode in a misaligned triangular optical cavity

Kawazoe, Fumiko; Schilling, Roland; Lueck, Harald
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 27/10/2010
Relevância na Pesquisa
27.22%
We derive relationships between various types of small misalignments on a triangular Fabry-Perot cavity and associated geometrical eigenmode changes. We focus on the changes of beam spot positions on cavity mirrors, the beam waist position, and its angle. A comparison of analytical and numerical results shows excellent agreement. The results are applicable to any triangular cavity close to an isosceles triangle, with the lengths of two sides much bigger than the other, consisting of a curved mirror and two flat mirrors yielding a waist equally separated from the two flat mirrors. This cavity shape is most commonly used in laser interferometry. The analysis presented here can easily be extended to more generic cavity shapes. The geometrical analysis not only serves as a method of checking a simulation result, but also gives an intuitive and handy tool to visualize the eigenmode of a misaligned triangular cavity.; Comment: 17 pages, 21 figures

Optical eigenmode imaging

De Luca, Anna Chiara; Kosmeier, Sebastian; Dholakia, Kishan; Mazilu, Michael
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/05/2011
Relevância na Pesquisa
27.22%
We present an indirect imaging method that measures both amplitude and phase information from a transmissive target. Our method is based on an optical eigenmode decomposition of the light intensity and the first-order cross correlation between a target field and these eigenmodes. We demonstrate that such optical eigenmode imaging does not need any a priori knowledge of the imaging system and corresponds to a compressive full-field sampling leading to high image extraction efficiencies. Finally, we discuss the implications with respect to second-order correlation imaging.

Dynamic Calibration of Higher Eigenmode Parameters of a Cantilever in Atomic Force Microscopy Using Tip-Surface Interactions

Borysov, Stanislav S.; Forchheimer, Daniel; Haviland, David B.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.39%
We present a theoretical framework for the dynamic calibration of the higher eigenmode parameters (stiffness and optical lever responsivity) of a cantilever. The method is based on the tip-surface force reconstruction technique and does not require any prior knowledge of the eigenmode shape or the particular form of the tip-surface interaction. The calibration method proposed requires a single-point force measurement using a multimodal drive and its accuracy is independent of the unknown physical amplitude of a higher eigenmode.; Comment: 4 pages, 4 figures

Statistical Eigenmode Transmission over Jointly-Correlated MIMO Channels

Gao, Xiqi; Jiang, Bin; Li, Xiao; Gershman, Alex B.; McKay, Matthew R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 11/03/2009
Relevância na Pesquisa
27.22%
We investigate MIMO eigenmode transmission using statistical channel state information at the transmitter. We consider a general jointly-correlated MIMO channel model, which does not require separable spatial correlations at the transmitter and receiver. For this model, we first derive a closed-form tight upper bound for the ergodic capacity, which reveals a simple and interesting relationship in terms of the matrix permanent of the eigenmode channel coupling matrix and embraces many existing results in the literature as special cases. Based on this closed-form and tractable upper bound expression, we then employ convex optimization techniques to develop low-complexity power allocation solutions involving only the channel statistics. Necessary and sufficient optimality conditions are derived, from which we develop an iterative water-filling algorithm with guaranteed convergence. Simulations demonstrate the tightness of the capacity upper bound and the near-optimal performance of the proposed low-complexity transmitter optimization approach.; Comment: 32 pages, 6 figures, to appear in IEEE Transactions on Information Theory

Gap eigenmode of radially localised helicon waves in a periodic structure

Chang, Lei; Breizman, Boris N.; Hole, Matthew J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/10/2012
Relevância na Pesquisa
27.5%
An ElectroMagnetic Solver (EMS) [Chen et al., Phys. Plasmas, 13, 123507 (2006)] is employed to model a spectral gap and a gap eigenmode in a periodic structure in the whistler frequency range. A Radially Localised Helicon (RLH) mode [Breizman and Arefiev, Phys. Rev. Lett, 84, 3863 (2000)] is considered. We demonstrate that the computed gap frequency and gap width agree well with a theoretical analysis, and find a discrete eigenmode inside the gap by introducing a defect to the system's periodicity. The axial wavelength of the gap eigenmode is close to twice the system's periodicity, which is consistent with Bragg's law. Such an eigenmode could be excited by energetic electrons, similar to the excitation of Toroidal Alfv\'{e}n Eigenmodes (TAE) by energetic ions in tokamaks.; Comment: Submitted to Plasma Physics and Controlled Fusion on 18 Oct 2012

Eigenmode decomposition of the near-field enhancement in localized surface plasmon resonances of metallic nanoparticles

Sandu, Titus
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 29/05/2013
Relevância na Pesquisa
27.22%
I present a direct and intuitive eigenmode method that evaluates the near-field enhancement around the surface of metallic nanoparticles of arbitrary shape. The method is based on the boundary integral equation in the electrostatic limit. Besides the nanoparticle polarizability and the far-field response, the near-field enhancement around nanoparticles can be also conveniently expressed as an eigenmode sum of resonant terms. Moreover, the spatial configuration of the near-field enhancement depends explicitly on the eigenfunctions of both the BIE integral operator and of its adjoint. It is also established a direct physical meaning of the two types of eigenfunctions. While it is well known that the eigenfunctions of the BIE operator are electric charge modes, it is less known and used that the eigenfunctions of the adjoint represent the electric potential generated by the charge modes. For the enhanced spectroscopies the present method allows an easy identification of hot spots which are located in the regions with maximum charge densities and/or regions with fast variations of the electric potential generated by the charge modes on the surface. This study also clarifies the similarities and the differences between the far-field and the near-field behavior of plasmonic systems. Finally...

The Strange Eigenmode in Lagrangian Coordinates

Thiffeault, Jean-Luc
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.39%
For a distribution advected by a simple chaotic map with diffusion, the "strange eigenmode" is investigated from the Lagrangian (material) viewpoint and compared to its Eulerian (spatial) counterpart. The eigenmode embodies the balance between diffusion and exponential stretching by a chaotic flow. It is not strictly an eigenmode in Lagrangian coordinates, because its spectrum is rescaled exponentially rapidly.; Comment: 15 pages, 6 figures. RevTeX4 format with psfrag

Eigenmode analysis of the susceptibility matrix of the four-dimensional Edwards-Anderson spin-glass model

Hukushima, Koji; Iba, Yukito
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 04/07/2002
Relevância na Pesquisa
27.22%
The nature of spin-glass phase of the four-dimensional Edwards-Anderson Ising model is numerically studied by eigenmode analysis of the susceptibility matrix up to the lattice size 10^4. Unlike the preceding results on smaller lattices, our result suggests that there exist multiple extensive eigenvalues of the matrix, which does not contradict replica-symmetry-breaking scenarios. The sensitivity of the eigenmodes with respect to a temperature change is examined using finite-size-scaling analysis and an evidence of anomalous sensitivity is found. A computational advantage of dual formulation of the eigenmode analysis in the study of large lattices is also discussed.; Comment: 4 pages, 2 figures

MIMO Identical Eigenmode Transmission System (IETS) - A Channel Decomposition Perspective

Shakir, M. Zeeshan; Durrani, Tariq S.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 19/09/2010
Relevância na Pesquisa
27.39%
In the past few years considerable attention has been given to the design of Multiple-Input Multiple-Output (MIMO) Eigenmode Transmission Systems (EMTS). This paper presents an in-depth analysis of a new MIMO eigenmode transmission strategy. The non-linear decomposition technique called Geometric Mean Decomposition (GMD) is employed for the formation of eigenmodes over MIMO flatfading channel. Exploiting GMD technique, identical, parallel and independent transmission pipes are created for data transmission at higher rate. The system based on such decomposition technique is referred to as MIMO Identical Eigenmode Transmission System (IETS). The comparative analysis of the MIMO transceiver design exploiting nonlinear and linear decomposition techniques for variable constellation is presented in this paper. The new transmission strategy is tested in combination with the Vertical Bell Labs Layered Space Time (V-BLAST) decoding scheme using different number of antennas on both sides of the communication link. The analysis is supported by various simulation results.