Linear and nonlinear behaviour of two-stream instabilities in collisionless plasmas

2015 ◽  
Vol 81 (6) ◽  
Author(s):  
Y. W. Hou ◽  
M. X. Chen ◽  
M. Y. Yu ◽  
B. Wu
Keyword(s):  
Normal Mode Analysis ◽  
System Size ◽  
Point Of View ◽  
Mode Analysis ◽  
Nonlinear Behaviour ◽  
Initial Growth ◽  
Small Magnitude ◽  
Plasma Oscillations ◽  
Numerical Noise ◽  
Growth Properties

The transient, growth and nonlinear saturation stages in the evolution of the electrostatic two-stream instabilities as described by the Vlasov–Poisson system are reconsidered by numerically following the evolution of the total wave energy of the plasma oscillations excited from (numerical) noise. Except for peculiarities related to the necessarily finite (even though very small) magnitude of the perturbations in the numerical simulation, the existence and initial growth properties of the instabilities from the numerical results are found to be consistent with those from linear normal mode analysis and the Penrose criteria. However, contradictory to the traditional point of view, the growth of instability before saturation is not always linear. The initial stage of the growth can exhibit fine structures that can be attributed to the harmonics of the excited plasma oscillations, whose wavelengths are determined by the system size and the numerical noise. As expected, saturation of the unstable oscillations is due to electron trapping when they reach sufficiently large amplitudes.

Electrostatic oscillations in cold inhomogeneous plasma I. Differential equation approach

1971 ◽  
Vol 5 (2) ◽  
pp. 239-263 ◽  
Author(s):  
Z. Sedláček
Keyword(s):  
Differential Equation ◽  
Green Function ◽  
Normal Mode Analysis ◽  
Inhomogeneous Plasma ◽  
Mode Analysis ◽  
Complex Frequency ◽  
Plasma Oscillations ◽  
The Laplace Transform ◽  
Collective Oscillations ◽  
The Green Function

Small amplitude electrostatic oscillations in a cold plasma with continuously varying density have been investigated. The problem is the same as that treated by Barston (1964) but instead of his normal-mode analysis we employ the Laplace transform approach to solve the corresponding initial-value problem. We construct the Green function of the differential equation of the problem to show that there are branch-point singularities on the real axis of the complex frequency-plane, which correspond to the singularities of the Barston eigenmodes and which, asymptotically, give rise to non-collective oscillations with position-dependent frequency and damping proportional to negative powers of time. In addition we find an infinity of new singularities (simple poles) of the analytic continuation of the Green function into the lower half of the complex frequency-plane whose position is independent of the spatial co-ordinate so that they represent collective, exponentially damped modes of plasma oscillations. Thus, although there may be no discrete spectrum, in a more general sense a dispersion relation does exist but must be interpreted in the same way as in the case of Landau damping of hot plasma oscillations.

The role of coupling in intramolecular proton transfer reactions. The hydrogen oxalate anion as an example

1992 ◽  
Vol 70 (1) ◽  
pp. 100-106 ◽  
Author(s):  
Enric Bosch ◽  
Miquel Moreno ◽  
José María Lluch
Keyword(s):  
Proton Transfer ◽  
Degrees Of Freedom ◽  
Normal Mode Analysis ◽  
Intramolecular Proton Transfer ◽  
Point Of View ◽  
Mode Analysis ◽  
Intrinsic Reaction Coordinate ◽  
Isotope Substitution ◽  
Oxalate Anion ◽  
Proton Transfer Reactions

Coupling between the proton motion and the internal degrees of freedom for intramolecular proton transfer in the hydrogen oxalate anion has been studied. A normal mode analysis at a sequence of points along the Intrinsic Reaction Coordinate (IRC) has been performed and the coupling functions Bk.F have been obtained. It is shown that, although for the reactant the IRC direction essentially consists of the motion of oxygen atoms, the coupling changes this IRC direction towards the motion corresponding to proton transfer itself. From a quantum point of view, the curvature that appears as a consequence allows comer-cutting tunneling. Finally, the effect of isotope substitution is considered. Keywords: intramolecular proton transfer, coupling functions, IRC curvature, tunneling splitting, isotope substitution.

scholarly journals ProMode-Oligomer: Database of Normal Mode Analysis in Dihedral Angle Space for a Full-Atom System of Oligomeric Proteins

2012 ◽  
Vol 6 (1) ◽  
pp. 9-19 ◽  
Author(s):  
Hiroshi Wako ◽  
Shigeru Endo
Keyword(s):  
Normal Mode ◽  
Protein Complexes ◽  
Normal Mode Analysis ◽  
Normal Modes ◽  
Point Of View ◽  
Mode Analysis ◽  
Dihedral Angles ◽  
Oligomeric Proteins ◽  
Displacement Vectors ◽  
Atom System

The database ProMode-Oligomer (http://promode.socs.waseda.ac.jp/promode_oligomer) was constructed by collecting normal-mode-analysis (NMA) results for oligomeric proteins including protein-protein complexes. As in the ProMode database developed earlier for monomers and individual subunits of oligomers (Bioinformatics vol. 20, pp. 2035–2043, 2004), NMA was performed for a full-atom system using dihedral angles as independent variables, and we released the results (fluctuations of atoms, fluctuations of dihedral angles, correlations between atomic fluctuations, etc.). The vibrating oligomer is visualized by animation in an interactive molecular viewer for each of the 20 lowest-frequency normal modes. In addition, displacement vectors of constituent atoms for each normal mode were decomposed into two characteristic motions in individual subunits, i.e., internal and external (deformation and rigid-body movements of the individual subunits, respectively), and then the mutual movements of the subunits and the movement of atoms around the interface regions were investigated. These results released in ProMode-Oligomer are useful for characterizing oligomeric proteins from a dynamic point of view. The analyses are illustrated with immunoglobulin light- and heavy-chain variable domains bound to lysozyme and to a 12-residue peptide.

Application of the ESMACS Binding Free Energy Protocol to a Highly Varied Ligand Dataset: Lactate Dehydogenase A

2019 ◽  
Author(s):  
David Wright ◽  
Fouad Husseini ◽  
Shunzhou Wan ◽  
Christophe Meyer ◽  
Herman Van Vlijmen ◽  
...  
Keyword(s):  
Free Energy ◽  
Surface Area ◽  
Binding Free Energy ◽  
Normal Mode Analysis ◽  
Binding Mode ◽  
Accessible Surface Area ◽  
Solvent Accessible Surface Area ◽  
Mode Analysis ◽  
Energy Calculation ◽  
Accessible Surface

<div>Here, we evaluate the performance of our range of ensemble simulation based binding free energy calculation protocols, called ESMACS (enhanced sampling of molecular dynamics with approximation of continuum solvent) for use in fragment based drug design scenarios. ESMACS is designed to generate reproducible binding affinity predictions from the widely used molecular mechanics Poisson-Boltzmann surface area (MMPBSA) approach. We study ligands designed to target two binding pockets in the lactate dehydogenase A target protein, which vary in size, charge and binding mode. When comparing to experimental results, we obtain excellent statistical rankings across this highly diverse set of ligands. In addition, we investigate three approaches to account for entropic contributions not captured by standard MMPBSA calculations: (1) normal mode analysis, (2) weighted solvent accessible surface area (WSAS) and (3) variational entropy. </div>

RAMAN SPECTRA OF TITANIUM DI-, TRI-, AND TETRA-CHLORIDES

2001 ◽  
Vol 15 (28n30) ◽  
pp. 3865-3868 ◽  
Author(s):  
H. MIYAOKA ◽  
T. KUZE ◽  
H. SANO ◽  
H. MORI ◽  
G. MIZUTANI ◽  
...  
Keyword(s):  
Force Constant ◽  
Raman Spectra ◽  
Normal Mode ◽  
Raman Band ◽  
Normal Mode Analysis ◽  
Force Constants ◽  
Mode Analysis ◽  
Oxidation Number

We have obtained the Raman spectra of TiCl n (n= 2, 3, and 4). Assignments of the observed Raman bands were made by a normal mode analysis. The force constants were determined from the observed Raman band frequencies. We have found that the Ti-Cl stretching force constant increases as the oxidation number of the Ti species increases.

scholarly journals Normal mode analysis of spectral density of FMO trimers: Intra- and intermonomer energy transfer

2020 ◽  
Vol 153 (21) ◽  
pp. 215103
Author(s):  
Alexander Klinger ◽  
Dominik Lindorfer ◽  
Frank Müh ◽  
Thomas Renger
Keyword(s):  
Energy Transfer ◽  
Spectral Density ◽  
Normal Mode ◽  
Normal Mode Analysis ◽  
Mode Analysis

scholarly journals Normal-mode analysis for scalar fields in BTZ black-hole background

2009 ◽  
Vol 60 (2) ◽  
pp. 169-173 ◽  
Author(s):  
Sayan K. Chakrabarti ◽  
Pulak Ranjan Giri ◽  
Kumar S. Gupta
Keyword(s):  
Black Hole ◽  
Normal Mode ◽  
Normal Mode Analysis ◽  
Scalar Fields ◽  
Mode Analysis ◽  
Btz Black Hole ◽  
Black Hole Background

scholarly journals Rapid Characterization of Allosteric Networks with Ensemble Normal Mode Analysis

2016 ◽  
Vol 120 (33) ◽  
pp. 8276-8288 ◽  
Author(s):  
Xin-Qiu Yao ◽  
Lars Skjærven ◽  
Barry J. Grant
Keyword(s):  
Normal Mode ◽  
Normal Mode Analysis ◽  
Mode Analysis ◽  
Rapid Characterization

THEORETICAL INVESTIGATIONS ON ELUCIDATING FUNDAMENTAL MECHANISMS OF CATALYSIS AND DYNAMICS INVOLVED IN TRANSCRIPTION BY RNA POLYMERASE

2013 ◽  
Vol 12 (08) ◽  
pp. 1341005 ◽  
Author(s):  
FÁTIMA PARDO-AVILA ◽  
LIN-TAI DA ◽  
YING WANG ◽  
XUHUI HUANG
Keyword(s):  
Rna Polymerase ◽  
Conformational Changes ◽  
Normal Mode Analysis ◽  
Md Simulations ◽  
Mode Analysis ◽  
Transcription Process ◽  
Nucleotide Addition ◽  
Theoretical Investigations ◽  
State Models ◽  
Elongation Process

RNA polymerase is the enzyme that synthesizes RNA during the transcription process. To understand its mechanism, structural studies have provided us pictures of the series of steps necessary to add a new nucleotide to the nascent RNA chain, the steps altogether known as the nucleotide addition cycle (NAC). However, these static snapshots do not provide dynamic information of these processes involved in NAC, such as the conformational changes of the protein and the atomistic details of the catalysis. Computational studies have made efforts to fill these knowledge gaps. In this review, we provide examples of different computational approaches that have improved our understanding of the transcription elongation process for RNA polymerase, such as normal mode analysis, molecular dynamic (MD) simulations, Markov state models (MSMs). We also point out some unsolved questions that could be addressed using computational tools in the future.

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