Gravitational instability of partially ionized molecular clouds

2007 ◽  
Vol 73 (6) ◽  
pp. 831-838 ◽  
Author(s):  
A.C. BORAH ◽  
A.K. SEN
Keyword(s):  
Molecular Clouds ◽  
Radial Direction ◽  
Gravitational Instability ◽  
Normal Mode Analysis ◽  
Equations Of Motion ◽  
Local Approximation ◽  
Mode Analysis ◽  
Interstellar Clouds ◽  
Electrons And Ions ◽  
Partially Ionized

AbstractStars are formed as a result of the gravitational (Jeans) collapse of dense clumps in interstellar clouds. These clouds are partially ionized by nearby ionizing sources. We investigate the gravitational instability in such molecular clouds considering the non-Boltzmannian distribution for electrons and ions, which is more realistic than the Boltzmannian distribution. Assuming the perturbation (fluctuation) response in a radial direction as a mathematical analogue of the x-direction in the plane geometry approximation in the form f ∼ exp(ikx–iωt), the equations of motion for different species of the multi-fluid plasma are linearized. Jeans' swindle is used as a local approximation for the equilibrium and the dispersion relation is derived by usual normal mode analysis. Then, an analytical solution to the dispersion equation with an explanation of the effects on star formation is given.

Effect of spin-induced magnetization and Hall current on self-gravitational instability of magnetized viscous quantum plasma

2014 ◽  
Vol 81 (2) ◽  
Author(s):  
Prerana Sharma ◽  
R. K. Chhajlani
Keyword(s):  
Gravitational Instability ◽  
Quantum Effect ◽  
Normal Mode Analysis ◽  
Longitudinal Direction ◽  
Transverse Mode ◽  
Mode Analysis ◽  
Quantum Plasma ◽  
Longitudinal Modes ◽  
Jeans Criterion ◽  
Basic Equations

The Jeans self-gravitational instability is studied for dense quantum viscous plasma with Hall term and intrinsic magnetization generated by collective electron spin. The quantum magnetohydrodynamic model is employed to formulate the basic equations of the problem. The dispersion relation is obtained using the normal mode analysis, and further reduced for both transverse and longitudinal modes of propagation. The transverse mode of propagation is found to be unaffected by the Hall term but affected by quantum effect, viscosity, and magnetization parameters. The Jeans criterion of instability in the transverse direction is modified by Alfven velocity, magnetization parameter, and quantum effect. The non-gravitating magnetized mode is obtained in the longitudinal direction, which is modified by Hall parameter and is not affected by quantum term, whereas the gravitational mode is unaffected by the magnetization parameter but affected by viscosity and quantum parameters. It is observed that the Jeans condition of instability is affected by the quantum term. The growth rate of Jeans instability is plotted for various values of magnetization, quantum, and viscosity parameters of the quantum plasma medium.

scholarly journals On the Magnetogravitational Instability of a Ferromagnetic Dust Cloud in the Presence of Nonuniform Rotation

2012 ◽  
Vol 2012 ◽  
pp. 1-6
Author(s):  
Joginder S. Dhiman ◽  
Rekha Dadwal
Keyword(s):  
Magnetic Field ◽  
Uniform Magnetic Field ◽  
Gravitational Instability ◽  
Normal Mode Analysis ◽  
Dust Cloud ◽  
Mode Analysis ◽  
Analysis Method ◽  
General Dispersion ◽  
Nonuniform Rotation ◽  
Ferromagnetic Medium

The effect of a nonuniform magnetic field on the gravitational instability of a nonuniformly rotating infinitely extending axisymmetric cylinder in a homogenous ferromagnetic medium has been studied. The propagation of the wave is allowed along radial direction. A general dispersion relation, using the normal mode analysis method on the perturbation equations of the problem, is obtained. It is found that Bel and Schatzman criterion determines the gravitational instability of this general problem. Thus, it appears that the effect of non-uniform magnetic field on the gravitational instability as discussed by (Dhiman and Dadwal, 2010) is marginalized by the magnetic polarizability of ferrofluid.

Dispersion properties of electromagnetic waves in a degenerate electron–ion magnetoplasma

2012 ◽  
Vol 78 (6) ◽  
pp. 683-687 ◽  
Author(s):  
A. A. MAMUN ◽  
N. ROY ◽  
P.K. SHUKLA
Keyword(s):  
Electromagnetic Waves ◽  
Fluid Model ◽  
Normal Mode Analysis ◽  
Plasma Pressure ◽  
Mode Analysis ◽  
Degenerate Plasma ◽  
Spatial And Temporal Scales ◽  
Dispersion Properties ◽  
Electrons And Ions ◽  
Linear Propagation

AbstractA theoretical investigation has been made of the linear propagation of different electromagnetic modes in a dense electron–ion magnetoplasma containing degenerate electrons and ions. The fluid model and the normal mode analysis have been employed. It has been found that the dispersion properties of the electromagnetic waves propagating in such a degenerate plasma are different (in view of both spatial and temporal scales) from those propagating in the usual electron–ion plasma because of the effects of degenerate plasma pressure, enthalpy, etc. The importance of this work has been discussed also.

scholarly journals Effect of Rotation in an Orthotropic Elastic Slab

2017 ◽  
Vol 22 (1) ◽  
pp. 163-174
Author(s):  
S. Santra ◽  
A. Lahiri ◽  
N.C. Das
Keyword(s):  
Normal Mode Analysis ◽  
Equations Of Motion ◽  
Generalized Thermoelasticity ◽  
Mode Analysis ◽  
Rate Dependent ◽  
Temperature Rate ◽  
Elastic Slab ◽  
Basic Equations ◽  
Matrix Differential ◽  
Vector Matrix

Abstract The fundamental equations of the two dimensional generalized thermoelasticity (L-S model) with one relaxation time parameter in orthotropic elastic slab has been considered under effect of rotation. The normal mode analysis is used to the basic equations of motion and heat conduction equation. Finally, the resulting equations are written in the form of a vector-matrix differential equation which is then solved by the eigenvalue approach. The field variables in the space time domain are obtained numerically. The results corresponding to the cases of conventional thermoelasticity CTE), extended thermoelasticity (ETE) and temperature rate dependent thermoelasticity (TRDTE) are compared by means of graphs.

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

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.

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
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