scholarly journals Temperature Fluctuations and Evolution of Dust Grains in Dense Interstellar Clouds

1987 ◽  
Vol 115 ◽  
pp. 88-89
Author(s):  
S. Aiello ◽  
B. Barsella ◽  
C. Cecchi-Pestellini ◽  
F. Ferrini ◽  
F. Mencaraglia ◽  
...  
Keyword(s):  
Steady State ◽  
Interstellar Medium ◽  
State Energy ◽  
Temperature Fluctuations ◽  
Interstellar Extinction ◽  
Incident Radiation ◽  
Dust Grains ◽  
Interstellar Clouds ◽  
Large Fluctuations ◽  
Small Grains

Interstellar extinction studies (Chlewicki et al, 1984), as well as IR observations (Sellgren et al, 1983) require the presence in the interstellar medium of a substantial number of small (a≲0.01 μm) dust grains. The temperature of such small grains is subjected, because of their small steady-state energy, to large fluctuations as they absorb photons from the incident radiation, which could prevent the accretion on such grains (Greenberg and Hong, 1974).

scholarly journals DIBs, Interstellar Dust, and Extinction

2013 ◽  
Vol 9 (S297) ◽  
pp. 147-152 ◽  
Author(s):  
G. C. Clayton
Keyword(s):  
Interstellar Medium ◽  
Interstellar Dust ◽  
Dust Grains ◽  
Weak Correlation ◽  
Interstellar Clouds ◽  
The Galaxy ◽  
The Relationship

AbstractThe relationship between DIBs and dust is still unknown. The correlation between reddening and DIB strength means that the DIBs are mixed in with the dust and gas in interstellar clouds. The DIBs are relatively stronger in the diffuse interstellar medium than in dense clouds. There is only a weak correlation between the DIBs and the UV extinction parameters including the 2175 Å bump strength and the far-UV rise. In addition, the bump dust grains are sometimes polarized, while the DIBs are not. However, observations of DIBs in the SMC show that when the 2175 Å bump is weak or missing so are the DIBs. Two of the four sightlines that deviate strongly from the CCM UV extinction in the Galaxy show weak DIBs.

Temperature Fluctuations and Evolution of Dust Grains in Dense Interstellar Clouds

1987 ◽  
pp. 88-89
Author(s):  
S. Aiello ◽  
B. Barsella ◽  
C. Cecchi-Pestellini ◽  
F. Ferrini ◽  
F. Mencaraglia ◽  
...  
Keyword(s):  
Temperature Fluctuations ◽  
Dust Grains ◽  
Interstellar Clouds

scholarly journals Photodesorption from Interstellar Dust Grains

1973 ◽  
Vol 52 ◽  
pp. 413-419 ◽  
Author(s):  
Lawrence T. Greenberg
Keyword(s):  
Interstellar Medium ◽  
Interstellar Dust ◽  
Quartz Substrate ◽  
Dust Grains ◽  
Interstellar Clouds ◽  
Interstellar Dust Grains ◽  
Fused Quartz ◽  
Uv Photons ◽  
Molecular Abundances ◽  
Vacuum Uv

An experiment to measure the photodesorption of physisorbed gases from a cold fused quartz substrate by near UV photons is described. The observed yield (mol photon–1) is as large as 10–5, a higher yield is likely in the vacuum UV. Included is a discussion of the photodesorption process and some applications to the interstellar medium. The observed yield is enough to maintain molecular abundances in moderate density interstellar clouds in equilibrium.

scholarly journals Modeling of Interstellar Dust Grains

2008 ◽  
Vol 7 (2) ◽  
pp. 78-87
Author(s):  
Nagalakshmi A. Rao
Keyword(s):  
Interstellar Medium ◽  
Interstellar Dust ◽  
Interstellar Extinction ◽  
Dipole Approximation ◽  
Dust Grains ◽  
Scattering Parameters ◽  
Light Passing ◽  
Interstellar Dust Grains ◽  
Blue Wavelength ◽  
Dust Grain

Dust has two major effects on light passing through the Interstellar Medium - Interstellar Extinction and Reddening. Interstellar dust grains are typically a fraction of a micron, approximately the wavelength of blue light and hence light passing through dust is depleted in blue wavelength, causing Interstellar Reddening. Dust Grain Models are mainly based on the analysis of interstellar extinction and polarization curves. Discrete Dipole Approximation (DDA) is the best studied model to compute scattering parameters of the grain.

scholarly journals On the settling of small grains in dusty discs: analysis and formulae

2020 ◽  
Vol 494 (4) ◽  
pp. 5134-5147
Author(s):  
Guillaume Laibe ◽  
Charles-Edouard Bréhier ◽  
Maxime Lombart
Keyword(s):  
Steady State ◽  
Numerical Simulations ◽  
Asymptotic Expansions ◽  
Dust Grains ◽  
Correlation Times ◽  
Small Grains ◽  
Balance Of Forces ◽  
Finite Correlation

ABSTRACT Instruments achieve sharper and finer observations of micrometre-in-size dust grains in the top layers of young stellar discs. To provide accurate models, we revisit the theory of dust settling for small grains, when gas stratification, dust inertia, and finite correlation times for the turbulence should be handled simultaneously. We start from a balance of forces and derive distributions at steady state. Asymptotic expansions require caution since limits do not commute. In particular, non-physical bumpy distributions appear when turbulence is purely diffusive. This excludes very short correlation times for real discs, as predicted by numerical simulations.

scholarly journals Stratified dust grains in the interstellar medium - II. Time-dependent interstellar extinction

2010 ◽  
Vol 408 (1) ◽  
pp. 535-541 ◽  
Author(s):  
C. Cecchi-Pestellini ◽  
A. Cacciola ◽  
M. A. Iatì ◽  
R. Saija ◽  
F. Borghese ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Interstellar Extinction ◽  
Time Dependent ◽  
Dust Grains

scholarly journals On the Mechanism of H2 Formation in the Interstellar Medium

1987 ◽  
Vol 120 ◽  
pp. 167-169
Author(s):  
Valerio Pirronello
Keyword(s):  
Interstellar Medium ◽  
Molecular Hydrogen ◽  
Formation Rate ◽  
Cosmic Ray ◽  
Interstellar Clouds ◽  
H2 Formation ◽  
Reduced Mobility

The problem of the formation of molecular hydrogen in interstellar clouds is revisited. the role played by cosmic ray bombardment under certain circumstances is considered mainly in the light of the low formation rate of H2 on grains due to the reduced mobility of adsorbed H atoms on their amorphous surfaces at interstellar temperatures.

Temperature fluctuations in interstellar dust grains

1979 ◽  
Vol 65 (1) ◽  
pp. 155-166 ◽  
Author(s):  
Per A. Aannestad ◽  
Scott J. Kenyon
Keyword(s):  
Interstellar Dust ◽  
Temperature Fluctuations ◽  
Dust Grains ◽  
Interstellar Dust Grains

Experimental Investigation of Power Umbilical Damping

2017 ◽  
Author(s):  
Torfinn Ottesen
Keyword(s):  
Steady State ◽  
Energy Input ◽  
State Energy ◽  
Seawater Temperature ◽  
Structural Damping ◽  
Stick Slip ◽  
Slip Regime ◽  
Free Decay ◽  
Vortex Induced Vibrations ◽  
Slip Transition

Ocean currents may cause vortex induced vibrations (VIV) of deep-water umbilicals and cables. Since the VIV response may give significant contributions to the total fatigue damage it is important to know the structural damping for relevant curvature levels. A laboratory test has been performed on a 12.5 m long test specimen to determine the damping for a range of curvature levels that are in the vicinity of the stick-slip transition region. The energy input to maintain steady state oscillations with curvature amplitudes in the range 0.0002–0.001 m−1 was measured. The steady state energy input is consistent with damping ratios obtained using the free decay method. The structural damping depends on construction temperature and curvature and is less for typically low seawater temperature and low curvatures. The transition between the stick- and the slip regime is seen for typical seawater temperature.

scholarly journals Calculating the Energy Spectrum of Complex Low-Dimensional Heterostructures in the Electric Field

2013 ◽  
Vol 2013 ◽  
pp. 1-7
Author(s):  
Svetlana N. Khonina ◽  
Sergey G. Volotovsky ◽  
Sergey I. Kharitonov ◽  
Nikolay L. Kazanskiy
Keyword(s):  
Steady State ◽  
Electric Field ◽  
Ground State ◽  
State Energy ◽  
Airy Functions ◽  
Piecewise Constant ◽  
Matrix Rank ◽  
The Matrix ◽  
Constant Potential ◽  
Low Dimensional

An algorithm for solving the steady-state Schrödinger equation for a complex piecewise-constant potential in the presence of theE-field is developed and implemented. The algorithm is based on the consecutive matching of solutions given by the Airy functions at the band boundaries with the matrix rank increasing by no more than two orders, which enables the characteristic solution to be obtained in the convenient form for search of the roots. The algorithm developed allows valid solutions to be obtained for the electric field magnitudes larger than the ground-state energy level, that is, when the perturbation method is not suitable.

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