Magnetism in 3He: measurements in a very restricted geometry

1987 ◽  
Vol 65 (11) ◽  
pp. 1545-1546 ◽  
Author(s):  
B. N. Engel ◽  
G. G. Ihas ◽  
G. F. Spencer
Keyword(s):  
Magnetic Susceptibility ◽  
Relaxation Time ◽  
Transverse Relaxation Time ◽  
External Pressure ◽  
Longitudinal Relaxation Time ◽  
Restricted Geometry ◽  
Transverse Relaxation ◽  
Vycor Glass ◽  
Multiply Connected ◽  
Flow Through

The nuclear magnetic susceptibility, χ, of 3He is seen to nearly obey a pure Curie Law, χ = C/T, over the temperature range 0.5 mK < T < 2 K when contained in the 20 Å, multiply connected pores of Vycor glass at low external pressure. Raising the external pressure to 5 bar (1 bar = 100 kPa) causes the susceptibility to obey the Curie–Weiss law, χ = C′/T−θ whose θ = 0.3 mK. The longitudinal relaxation time, T1, varies monotonically with T between 17 and 90 ms at both pressures. At 5 bar, the transverse relaxation time, T2*, is nearly temperature independent (about 600 μs) above 2 mK. Below 2 mK, T2* drops precipitously. Preliminary measurements indicate that the magnetism is produced by atoms that can flow through the pores of the Vycor glass.

scholarly journals Estimation of the permeability of hydrocarbon reservoir samples using induced polarization and nuclear magnetic resonance methods

Geophysics ◽  
2019 ◽  
Vol 84 (2) ◽  
pp. MR73-MR84 ◽  
Author(s):  
Fatemeh Razavirad ◽  
Myriam Schmutz ◽  
Andrew Binley
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Relaxation Time ◽  
Magnetic Resonance ◽  
Mechanistic Model ◽  
Transverse Relaxation Time ◽  
Induced Polarization ◽  
Permeability Model ◽  
Transverse Relaxation ◽  
Hydrocarbon Reservoir ◽  
Nuclear Magnetic

We have evaluated several published models using induced polarization (IP) and nuclear magnetic resonance (NMR) measurements for the estimation of permeability of hydrocarbon reservoir samples. IP and NMR measurements were made on 30 samples (clean sands and sandstones) from a Persian Gulf hydrocarbon reservoir. We assessed the applicability of a mechanistic IP-permeability model and an empirical IP-permeability model recently proposed. The mechanistic model results in a broader range of permeability estimates than those measured for sand samples, whereas the empirical model tends to overestimate the permeability of the samples that we tested. We also evaluated an NMR permeability prediction model that is based on porosity [Formula: see text] and the mean of the log transverse relaxation time ([Formula: see text]). This model provides reasonable permeability estimations for the clean sandstones that we tested but relies on calibrated parameters. We also examined an IP-NMR permeability model, which is based on the peak of the transverse relaxation time distribution, [Formula: see text] and the formation factor. This model consistently underestimates the permeability of the samples tested. We also evaluated a new model. This model estimates the permeability using the arithmetic mean of log transverse NMR relaxation time ([Formula: see text]) and diffusion coefficient of the pore fluid. Using this model, we improved estimates of permeability for sandstones and sand samples. This permeability model may offer a practical solution for geophysically derived estimates of permeability in the field, although testing on a larger database of clean granular materials is needed.

Brain gray and white matter transverse relaxation time in schizophrenia

1999 ◽  
Vol 91 (2) ◽  
pp. 93-100 ◽  
Author(s):  
Adolf Pfefferbaum ◽  
Edith V Sullivan ◽  
Maj Hedehus ◽  
Michael Moseley ◽  
Kelvin O Lim
Keyword(s):  
Relaxation Time ◽  
White Matter ◽  
Transverse Relaxation Time ◽  
Transverse Relaxation
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