Protonenspinrelaxation und Wasserbeweglichkeit in Muskelgewebe / Proton Spin Relaxation and Mobility of Water in Muscle Tissue

The frequency dependence of the proton spin relaxation in muscle tissue shows that the mobility of the muscle water must be described by a continuous distribution of jumping times instead of the usually assumed two-phase model. Measurements on frog muscles (rana esculenta and rana pipiens, gastrocnemius) in the Larmor frequency range 3 kHz to 75 MHz can be understood quantitatively by a log-gaussian distribution, which supports a close relation to protein solutions.

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Proton Spin Relaxation of a Liquid Crystal with a Glassy Cholesteric State

Zeitschrift für Naturforschung A ◽

10.1515/zna-1990-9-1004 ◽

1990 ◽

Vol 45 (9-10) ◽

pp. 1077-1084 ◽

Cited By ~ 1

Author(s):

D. Pusiol ◽

F. Noack ◽

C. Aguilera

Keyword(s):

Spin Relaxation ◽

Rotational Diffusion ◽

Glassy State ◽

Larmor Frequency ◽

Proton Spin ◽

Relaxation Dispersion ◽

Proton Relaxation ◽

Relaxation Processes ◽

Molecular Reorientation ◽

Cholesteric Phase

Abstract Field-cycling and standard pulsed NMR techniques have been used to study the frequency dependence of the longitudinal proton spin relaxation time T x in the crystalline estradiol compound (+)3,1,7-ß-bis-(4n-butoxybenzoyloxy)-estra-1,3,5-(10)-trien or BET, which is a mesogenic material with a chiral molecular structure. From the measured Larmor frequency and temperature depen-dences we conclude that, at low NMR frequencies in the cholesteric phase, T1 reflects in addition to the relaxation process familiar from nematic liquid crystals (director fluctuation modes) another slow mechanism theoretically predicted for cholesteric systems, namely diffusion induced rotational molecular reorientation. These relaxation processes are not or much less effective in the crystalline and glassy state, where they are frozen. Also the high NMR frequency relaxation dispersion strongly differs between the cholesteric mesophase and the not liquid crystalline samples. This is interpreted by a change from essentially translational self-diffusion to rotational diffusion controlled proton relaxation.

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Nitrogen Nuclear Quadrupole Resonance Dips in the Proton Spin Relaxation Dispersion of Nematic and Smectic Thermotropic Liquid Crystals

Zeitschrift für Naturforschung A ◽

10.1515/zna-1992-1102 ◽

1992 ◽

Vol 47 (11) ◽

pp. 1105-1114 ◽

Cited By ~ 25

Author(s):

D. J. Pusiol ◽

R. Humpfer ◽

F. Noack

Keyword(s):

Spin Relaxation ◽

Liquid Crystalline ◽

Larmor Frequency ◽

Quadrupole Coupling Constant ◽

Proton Spin ◽

Relaxation Dispersion ◽

Coupling Constants ◽

Smectic Phases ◽

Nematic State ◽

Quadrupole Coupling

Abstract The Larmor frequency dependence of the proton spin relaxation time, obtained by means of the fast field-cycling NMR technique, has been used to study the 14N quadrupole coupling constant K and its asymmetry parameter η in the nematic and smectic phases of some liquid crystalline azoxybenzenes (PAA, BAB, HAB, HpAB), cyanobiphenyls (8CB, 9CB, 11CB) and oxycyanobiphenyls (9 OCB). Due to fast molecular reorientations, the effective quadrupole coupling constants are relatively small, whereas surprisingly the asymmetry parameters are rather large. The temperature dependence of both K and η within the mesophases, as well as their discontinuities at the different mesophase transitions, can be interpreted by the anisotropy of molecular rotations. It is found that temperature effects are significantly more pronounced for the (biaxial) smectic-C phase of the heptyloxyazoxybenzene (HpAB) than for the (uniaxial) smectic-A phase of the various investigated cyano- and oxycyanobiphenyls. As a rule, η turned out smaller in the smectic than in the nematic state, whereas K has similar values in both phases

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Modeling of proton spin relaxation in muscle tissue using nuclear magnetic resonance spin grouping and exchange analysis

Biophysical Journal ◽

10.1016/s0006-3495(86)83450-6 ◽

1986 ◽

Vol 50 (1) ◽

pp. 181-191 ◽

Cited By ~ 26

Author(s):

W.T. Sobol ◽

I.G. Cameron ◽

W.R. Inch ◽

M.M. Pintar

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Spin Relaxation ◽

Muscle Tissue ◽

Proton Spin ◽

Resonance Spin ◽

Nuclear Magnetic

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Proton spin relaxation in dilute methane gas: A symmetrized theory and its experimental verification

Canadian Journal of Physics ◽

10.1139/p76-204 ◽

1976 ◽

Vol 54 (16) ◽

pp. 1712-1727 ◽

Cited By ~ 11

Author(s):

P. A. Beckmann ◽

M. Bloom ◽

I. Ozier

Keyword(s):

Relaxation Rate ◽

Time Evolution ◽

Spin Relaxation ◽

Collision Cross Section ◽

Larmor Frequency ◽

Proton Spin ◽

Centrifugal Distortion ◽

Methane Gas ◽

Exponential Relaxation ◽

Nuclear Larmor Frequency

Nuclear spin relaxation in low density methane gas is investigated theoretically and experimentally. A theory is developed in which full account is taken of the tetrahedral symmetry of the molecule. For a nuclear Larmor frequency of 30 MHz, the time evolution of the nonequilibrium magnetization is measured as a function of density between approximately 0.005 and 17 amagats at temperatures of 110, 150, and 295 K. In all cases, exponential relaxation is observed. By using the theory in conjunction with the known spin rotation constants and rotational energy levels of CH4, the measured values of the relaxation rate R1 have been fit very well at each temperature, both for the maximum value of R1 which contains no adjustable parameters and for the density dependence of R1 which contains a single parameter taken to be the collision cross section for molecular reorientation. The centrifugal distortion splittings of the rotational levels are shown to have an important influence on the observed values of R1 at 30 MHz and. more generally on the dependence of the time evolution of the nonequilibrium magnetization on density and frequency. On the basis of the theory, a new type of 'relaxation rate spectroscopy' is proposed. Non-exponential relaxation is predicted to occur at low densities when the nuclear Larmor frequency is tuned to a centrifugal distortion splitting.

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Frequency Dependence of Proton Spin Relaxation in Liquid Crystalline PAA

Zeitschrift für Naturforschung A ◽

10.1515/zna-1975-0408 ◽

1975 ◽

Vol 30 (4) ◽

pp. 437-441 ◽

Cited By ~ 47

Author(s):

W. Wölfel ◽

F. Noack ◽

M. Stohrer

Keyword(s):

Relaxation Time ◽

Transition Temperature ◽

Frequency Dependence ◽

Spin Relaxation ◽

Correlation Time ◽

Liquid Crystalline ◽

Larmor Frequency ◽

Proton Spin ◽

Isotropic Phase ◽

Frequency Range

Abstract We report on measurements of the Larmor frequency dependence of the proton spin relaxation time T1 in the nematic and isotropic phase of p-azoxyanisole (frequency range: 3.8 kHz ≦ ωL/2 π≦75 MHz) . In both cases our results clearly support the Pincus-Cahane mechanism of spin relaxation by order fluctuations ("ωL−½-law") and exclude the alternative translational diffusion model (“ωL+½-law”). For the isotropic phase it was possible to evaluate the correlation time τ of the liquid crystalline order fluctuations from the observed T1 dispersion. As a function of the deviation ⊿ν=ν-νc from the critical nematic-isotropic transition temperature, νc= (136± 0.5)°C, we found τ=2.71·10-7-⊿ν-0.25s .

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