Dislocation Dynamics Investigated by Means of Nuclear Magnetic Resonance a Complementarynew Technique

1986 ◽  
Vol 82 ◽  
Author(s):  
J. Th. M. De Hosson ◽  
O. Kanert
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Lattice Relaxation ◽  
Dislocation Dynamics ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Jump Distance ◽  
Relaxation Measurements ◽  
The Mean ◽  
Nuclear Magnetic

ABSTRACTPulsed nuclear magnetic resonance proved to be a new complementary technique for the study of moving dislocations in Al—base alloys. Spin—lattice relaxation measurements clearly indicate that fluctuations in the quadrupolar field caused by moving dislocations in Al—base alloys are different compared to those in ultra—pure Al. From the motion induced part of the spin—lattice relaxation rate the mean jump distance of mobile dislocations has been determined as a function of strain. Measurements have been performed on Al—Cu, Al—Li and Al—Zn binary alloys. Asa typical illustration of the strength of this technique, this paper reports the resultsobtained of Al—(1—2 at%) Zn solid solution.

scholarly journals Dislocation dynamics in Al–Mg–Zn alloys: A nuclear magnetic resonance and transmission electron microscopic study

1988 ◽  
Vol 3 (4) ◽  
pp. 645-650 ◽  
Author(s):  
J. Th. M. De Hosson ◽  
O. Kanert ◽  
U. Schlagowski ◽  
G. Boom
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Striking Difference ◽  
Spin Lattice ◽  
Transmission Electron ◽  
The Mean ◽  
Zn Alloys ◽  
Nuclear Magnetic

Pulsed nuclear magnetic resonance (NMR) proved to be a complementary new technique for the study of moving dislocations in Al–Mg–Zn alloys. The NMR technique, in combination with transmission electron microscopy (TEM), has been applied to study dislocation motion in Al–0.6 at. % Mg–1 at. % Zn and Al–2 at. % Mg–2.5 at. % Zn. Spin-lattice relaxation measurements clearly indicate that fluctuations in the nuclear quadrupolar interactions caused by moving dislocations in Al–Mg–Zn are different compared to those in ultra pure Al. From the motion induced part of the spin-lattice relaxation rate the mean jump distance of mobile dislocations has been determined as a function of strain. From the NMR data it is concluded that moving dislocations advance over a number of solute atoms in these alloys as described by Mott-Nabarro's model. At large strains there exists a striking difference between the mean jump distances in Al–0.6 at. % Mg–1 at. % Zn and in Al–1.2 at. % Mg–2.5 at. % Zn. The latter is about five times smaller than the former one. This is consistent with TEM observations that show dislocation cell formation only in Al–0.6 at. % Mg-1 at. % Zn and the macroscopic stress-strain dependences of these alloys.

Nuclear Magnetic Resonance Brain Imaging in Chronic Schizophrenia

1987 ◽  
Vol 150 (2) ◽  
pp. 161-163 ◽  
Author(s):  
J. A. O. Besson ◽  
F. M. Corrigan ◽  
G. R. Cherryman ◽  
F. W. Smith
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Lattice Relaxation ◽  
Chronic Schizophrenia ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Magnetic Resonance Brain Imaging ◽  
Normal Controls ◽  
Nuclear Magnetic

Patients with chronic schizophrenia were examined by nuclear magnetic resonance imaging of the brain. Subgroups of the syndrome with high positive or high negative symptom scores and ventricular dilatation were compared with each other and with normal controls in respect of regional spin lattice relaxation time (T1) changes. Significant differences were not observed between the schizophrenic subgroups and controls but there were significant differences between the subgroups themselves. The presence of tardive dyskinesia was associated with increased T1 of the basal ganglia. The significance of these results is discussed in relation to findings using other techniques.

Nuclear Magnetic Resonance Studies of Molecular Motion in Natural Rubber

1963 ◽  
Vol 36 (2) ◽  
pp. 318-324
Author(s):  
W. P. Slichter ◽  
D. D. Davis
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Natural Rubber ◽  
Molecular Motion ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Nmr Studies ◽  
Spin Lattice ◽  
Nuclear Magnetic

Abstract Nuclear magnetic resonance measurements have been made on natural rubber to examine how frequency, temperature, and crystallinity affect the nuclear relaxation. Moecular motions were studied by observing NMR linewidths and spin-lattice relaxation times at temperatures between −100° and 100° C, and at radio frequencies between 2 and 60 Mc. The effect of crystallinity was seen in measurements on stark rubber. The relation between frequency and temperature in the spin-lattice relaxation process is examined in terms of the Arrhenius equation and the WLF expression. The importance of using frequency as a variable in NMR studies of molecular motion is stressed.

Solute 13C Nuclear Magnetic Resonance Spectrometric Investigation of Acetonitrile-Tetraalkylammonium Salt Interactions

1983 ◽  
Vol 37 (1) ◽  
pp. 29-31
Author(s):  
Neal R. Dando ◽  
Harvey S. Gold ◽  
Cecil Dybowski
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Salt Concentration ◽  
Alkyl Chain ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

Carbon-13 nuclear magnetic resonance spectrometry is used to observe changes in the spin-lattice relaxation time ( T1) of the alkyl chain carbons of symmetric tetraalkylammonium salts ( R4N+) X− in acetonitrile as a function of salt concentration in the range from 0.25 to 1.4 M. The T1 values of the alkyl chain carbons are observed to be differentially sensitive to salt concentration, the sensitivity being greatest at the α carbon position. These observations suggest accessibility of the cation nitrogen to solvent molecules and changing microviscosity about the salt molecule.

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