Roton–phonon relaxation times in helium II

2002 ◽  
pp. 349-350
Keyword(s):  
Relaxation Times ◽  
Helium Ii

Roton-phonon relaxation times in helium II

1969 ◽  
Vol 30 (8) ◽  
pp. 468-469 ◽  
Author(s):  
R.J. Donnelly ◽  
P.H. Roberts
Keyword(s):  
Relaxation Times ◽  
Helium Ii

The absorption of sound in dilute solutions of 3 He in liquid helium II

1962 ◽  
Vol 268 (1334) ◽  
pp. 424-436 ◽  
Keyword(s):  
Liquid Helium ◽  
Sound Wave ◽  
Relaxation Times ◽  
Temperature Curve ◽  
Dilute Solutions ◽  
Helium Ii ◽  
Temperature Range ◽  
Pure Helium

The coefficient of the absorption of sound in dilute solutions of 3 He in liquid helium II has been measured in the temperature range down to 0.4 °K at a frequency of 14 Mc/s. Results are given for molar concentrations of 3 He of 0.32, 1.6 and 5.2%. In all cases the absorption is less than in pure helium II, and the peak in the absorption-temperature curve is shifted to somewhat lower temperatures. It appears that the 3 He speeds up the interactions between the thermal excitations in the liquid, and thus reduces the second viscosity which is responsible for most of the absorption in pure helium II at the higher temperatures (Khalatnikov 1950; Dransfeld, Newell & Wilks 1958). Our results are compared with a calculation of this effect due to Andreev (1961). At lower temperatures the absorption arises through a different mechanism, and a treatment taking into account the fact that all the relaxation times are long compared to the period of the sound wave has been given by Dransfeld (1958, 1962). Our results are consistent with, and give support to, Dransfeld’s treatment which involves the ‘bunching’ of the thermal phonons by the sound wave.

An emerging technology: Nuclear magnetic resonance microscopy

1988 ◽  
Vol 46 ◽  
pp. 1000-1001
Author(s):  
M.J. Hennessy ◽  
E. Kwok
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Basic Research ◽  
Local Environment ◽  
Magnetic Resonance Images ◽  
Nmr Microscopy ◽  
Mri Scans ◽  
Temperature Relaxation ◽  
Nuclear Magnetic

Much progress in nuclear magnetic resonance microscope has been made in the last few years as a result of improved instrumentation and techniques being made available through basic research in magnetic resonance imaging (MRI) technologies for medicine. Nuclear magnetic resonance (NMR) was first observed in the hydrogen nucleus in water by Bloch, Purcell and Pound over 40 years ago. Today, in medicine, virtually all commercial MRI scans are made of water bound in tissue. This is also true for NMR microscopy, which has focussed mainly on biological applications. The reason water is the favored molecule for NMR is because water is,the most abundant molecule in biology. It is also the most NMR sensitive having the largest nuclear magnetic moment and having reasonable room temperature relaxation times (from 10 ms to 3 sec). The contrast seen in magnetic resonance images is due mostly to distribution of water relaxation times in sample which are extremely sensitive to the local environment.

On relaxation times

1999 ◽  
Vol 169 (10) ◽  
pp. 1163
Author(s):  
V.L. Vaks ◽  
V.V. Mityugov
Keyword(s):  
Relaxation Times

Dielectric Relaxation Studies of Silver Nanoparticles dispersed Liquid Crystal

2015 ◽  
Vol 8 (3) ◽  
pp. 2176-2188 ◽  
Author(s):  
Keisham Nanao Singh
Keyword(s):  
Activation Energy ◽  
Silver Nanoparticles ◽  
Liquid Crystal ◽  
Dielectric Relaxation ◽  
Relaxation Process ◽  
Relaxation Times ◽  
Low Frequency ◽  
Bulk Liquid ◽  
Molecular Rearrangement ◽  
Relaxation Studies

This article reports on the Dielectric Relaxation Studies of two Liquid Crystalline compounds - 7O.4 and 7O.6 - doped with dodecanethiol capped Silver Nanoparticles. The liquid crystal molecules are aligned homeotropically using CTAB. The low frequency relaxation process occurring above 1 MHz is fitted to Cole-Cole formula using the software Dielectric Spectra fit. The effect of the Silver Nanoparticles on the molecular dipole dynamics are discussed in terms of the fitted relaxation times, Cole-Cole distribution parameter and activation energy. The study indicate a local molecular rearrangement of the liquid crystal molecules without affecting the order of the bulk liquid crystal molecules but these local molecules surrounding the Silver Nanoparticles do not contribute to the relaxation process in the studied frequency range. The observed effect on activation energy suggests a change in interaction between the nanoparticles/liquid crystal molecules.

Relaxation times of normal breast tissues

1994 ◽  
Vol 35 (3) ◽  
pp. 258-261 ◽  
Author(s):  
Kirsti Dean ◽  
M. -L. Majurin ◽  
M. Komu
Keyword(s):  
Relaxation Times ◽  
Normal Breast ◽  
Breast Tissues
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