Zur Deutung der kernmagnetischen Relaxation in Proteinlösungen

1970 ◽  
Vol 25 (11) ◽  
pp. 1680-1684 ◽  
Author(s):  
R. Kimmich ◽  
F. Noack
Keyword(s):  
Relaxation Time ◽  
High Frequency ◽  
Relaxation Times ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Proton Relaxation ◽  
Protein Solutions ◽  
Longitudinal Relaxation Time ◽  
Two Phase ◽  
Protein Molecules

Abstract Measurements of longitudinal and transversal proton relaxation times in both H2O and mixed H2O/D2O protein solutions show a low-frequency as well as a high-frequency dispersion of the longitudinal relaxation time and a nonexponential two-phase transversal relaxation. These results are discussed qualitatively in terms of “rigid” and “mobile” relaxation centers within the protein molecules.

Magnetic Permeability and Relaxation Frequency in High Frequency Magnetic Materials.

2001 ◽  
Vol 674 ◽  
Author(s):  
M.I. Rosales ◽  
H. Montiel ◽  
R. Valenzuela
Keyword(s):  
High Frequency ◽  
Domain Walls ◽  
Magnetocrystalline Anisotropy ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Anisotropy Constant ◽  
Relaxation Frequency ◽  
Resonance Relaxation ◽  
Frequency Behavior

ABSTRACTAn investigation of the frequency behavior of polycrystalline ferrites is presented. It is shown that the low frequency dispersion (f < 10 MHz) of permeability is associated with the bulging of pinned domain walls, and has a mixed resonance-relaxation character, closer to the latter. It is also shown that there is a linear relationship between the magnetocrystalline anisotropy constant, K1, and the relaxation frequency. The slope of this correlation depends on the grain size. Such a relationship could allow the determination of this basic parameter from polycrystalline samples.

Solid State NMR Evaluation of Natural Resin/Clay Nanocomposites

2009 ◽  
Vol 4 ◽  
pp. 117-126 ◽  
Author(s):  
Emerson O. da Silva ◽  
Maria I.B. Tavares ◽  
José S. Nogueira
Keyword(s):  
Relaxation Time ◽  
Solid State ◽  
Polymer Matrix ◽  
Spin Diffusion ◽  
Environmental Changes ◽  
Relaxation Times ◽  
Spin Lattice Relaxation ◽  
Proton Relaxation ◽  
Spin Lattice ◽  
Natural Resin

NMR nuclear relaxation times have been used by Tavares et al as a methodology to characterize the nano materials, especially nanocomposites, because NMR offers a great variety of relaxation parameters. The spin-lattice relaxation time, with a time constant T1, have been explored to get as much information as possible from the measurements of the spin-lattice proton relaxation (T1H), which can measure the fraction of available polymer/clay interface as well as the dispersion homogeneity of those interfaces actually formed. The spin-lattice has been evaluated since this relaxation time confirms the T1 and can give additional information to nanocomposite clay dispersion. The NMR relaxation times are sensitive to the chemical environmental, changes in the polymer matrix; chemical structure and interaction process, because they depend on the domain distribution and sample homogeneity, since they are measured in the solid state via intermolecular chains interaction and/or spin diffusion. The T1 relaxation time of the nanocomposite decreased very much in relation to the natural resin, according to the increase in the exfoliation clay process, forming a nanocomposite with polymer matrix around the clay lamella.

DIELECTRIC PROPERTIES OF DRY, GEOLOGIC MATERIALS

Geophysics ◽  
1970 ◽  
Vol 35 (4) ◽  
pp. 624-645 ◽  
Author(s):  
M. Saint‐Amant ◽  
David W. Strangway
Keyword(s):  
Dielectric Properties ◽  
Loss Tangent ◽  
Relaxation Times ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Relaxation Peak ◽  
Debye Relaxation ◽  
Thermally Activated ◽  
Geologic Materials ◽  
Frequency Independent

A detailed investigation of the dielectric properties of powdered and solid dry rocks in the frequency range of 50 hz to 2 mhz has revealed the following general characteristics: 1) All dry rocks, powdered and solid, show an increase in both the dielectric constant and the loss tangent as frequency decreases and as temperature increases. This dispersion is believed to be due to polarization associated with charge buildup at grain boundaries or at grain imperfections. 2) Dry powdered rocks often show a thermally‐activated relaxation peak with a typical Debye‐relaxation character. This is due to the presence of pyroxene and biotite and may be associated with other minerals. The relaxation peak is not seen in solid rocks, where it is hidden by the low‐frequency dispersion. 3) At high frequencies, the loss tangent approaches a constant value which is frequency independent. This behavior is observed in many dielectrics and may be the result of a distribution of relaxation times.

Effects of changes in dietary fatty acids on isolated skeletal muscle functions in rats

1996 ◽  
Vol 80 (2) ◽  
pp. 464-471 ◽  
Author(s):  
K. J. Ayre ◽  
A. J. Hulbert
Keyword(s):  
Fatty Acids ◽  
High Frequency ◽  
Relaxation Times ◽  
Low Frequency ◽  
Dietary Fatty Acids ◽  
High Frequency Stimulation ◽  
Stock Diet ◽  
Deficient Diet ◽  
Low Frequency Stimulation ◽  
Frequency Stimulation

The effects of manipulating dietary levels of essential polyunsaturated fatty acids on the function of isolated skeletal muscles in male Wistar rats were examined. Three isoenergetic diets were used: an essential fatty acid-deficient diet (EFAD), a diet high in essential (n-6) fatty acids [High (n-6)], and a diet enriched with essential (n-3) fatty acids [High (n-3)]. After 9 wk, groups of rats on each test diet were fed a stock diet of laboratory chow for a further 6 wk. Muscle function was examined by using a battery of five tests for soleus (slow twitch) and extensor digitorum longus (EDL; fast twitch). Tests included single muscle twitches, sustained tetanic contractions, posttetanic potentiation, sustained high-frequency stimulation, and intermittent low-frequency stimulation. Results for muscles from the High (n-6) and High (n-3) groups were very similar. However, the EFAD diet resulted in significantly lower muscular tensions and reduced response times compared with the High (n-6) and High (n-3) diets. Peak twitch tension in soleus muscles was 16-21% less in the EFAD group than in the High (n-6) and High (n-3) groups, respectively [analysis of variance (ANOVA), P < 0.01). During high-frequency stimulation, EDL muscles from the EFAD rats fatigued 32% more quickly (ANOVA, P < 0.01)]. Also, twitch contraction and half-relaxation times were significantly 5-7% reduced in the EFAD group (ANOVA, P < 0.01). During intermittent low-frequency stimulation, soleus muscles from the EFAD group generated 25-28% less tension than did the other groups (ANOVA, P < 0.01), but in EDL muscles from the EFAD group, endurance was 20% greater than in the High (n-6) group (ANOVA, P < 0.05). After 6 wk on the stock diet, there were no longer any differences between the dietary groups. Manipulation of dietary fatty acids results in significant, but reversible, effects in muscles of rats fed an EFAD diet.

Proton NMR-Relaxation Dispersion in Meconium Solutions and Healthy Amniotic Fluid: Possible Applications to Medical Diagnosis

1982 ◽  
Vol 37 (5-6) ◽  
pp. 394-398 ◽  
Author(s):  
Georges J. Béné ◽  
Bernard Borcard ◽  
Volker Graf ◽  
Emile Hiltbrand ◽  
Patric Magnin ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Amniotic Fluid ◽  
Medical Diagnosis ◽  
High Field ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Field Measurements ◽  
Relaxation Dispersion ◽  
Longitudinal Relaxation Time ◽  
Relaxation Experiments

Abstract In order to show that for a possible application in medical diagnosis NMR-relaxation experiments at low Larmor frequencies (v0 ≤ 20 kHz) are more sensitive than the up to now done high field measurements in the MHz-range, we present dispersion curves (v0 = 50 Hz to 50 MHz) of the proton longitudinal relaxation time T1 and values of the transversal relaxation time T2 for the example of amniotic fluids. Only for Larmor frequencies below ≃ 100 kHz the relaxation times for healthy amniotic fluid and pathological meconium solutions are significantly different, whereas at high Larmor frequencies, i. e. in the conventional MHz-range, the observed changes are rather small.

High-Frequency Features in the Distribution of Relaxation Times Related to Frequency Dispersion Effects in SOFCs

2021 ◽  
Author(s):  
Katharina Fitzek ◽  
Ute de Haart ◽  
Qingping Fang ◽  
Werner Lehnert
Keyword(s):  
Fuel Cells ◽  
High Frequency ◽  
Electrochemical Impedance ◽  
Relaxation Times ◽  
Frequency Dispersion ◽  
High Frequency Range ◽  
Frequency Range ◽  
Root Cause ◽  
Complex Planes ◽  
User Friendly

Abstract Electrochemical impedance spectroscopy (EIS) is commonly used for the characterization of electrochemical systems, such as solid oxide fuel cells (SOFCs). In recent years, the distribution of relaxation times (DRT) analysis has attracted increasing interest as a tool for investigating electrochemical loss mechanisms in fuel cells due to its ability to resolve electrochemical features that overlap in complex planes. Among the methods used for the deconvolution of the distribution function of relaxation times, DRTtools is commonly used due to its user-friendly graphical user interface. In this study, we investigate the root cause of the expression of additional DRT features in the high-frequency range and link them to characteristic properties of the processes that contribute to the polarization loss of SOFCs. Identification of the root cause leading to the expression of the features is performed by conducting a simulation study with synthetic EIS spectra that are then analyzed using DRTtools. It has been shown that the constant phase element behavior of high-frequency processes in SOFCs is the root cause of the expression of additional peaks in the high-frequency range of the DRT.

Characterization of periventricular edema in normal-pressure hydrocephalus by measurement of water proton relaxation times

1990 ◽  
Vol 73 (6) ◽  
pp. 864-870 ◽  
Author(s):  
Norihiko Tamaki ◽  
Takayuki Shirakuni ◽  
Kazumasa Ehara ◽  
Satoshi Matsumoto
Keyword(s):  
Relaxation Time ◽  
White Matter ◽  
Gray Matter ◽  
Normal Pressure Hydrocephalus ◽  
Relaxation Times ◽  
Normal Pressure ◽  
Water Proton ◽  
Proton Relaxation ◽  
Csf Shunting ◽  
Significant Difference

✓ The magnetic resonance longitudinal relaxation time (T1) and transverse relaxation time (T2) of the water proton of the periventricular white and cortical gray matter were measured for 17 control patients and 21 patients with suspected normal-pressure hydrocephalus (NPH). Of the latter group, 14 showed good response to shunting (true-NPH group) and seven showed no response (false-NPH group). In the true-NPH group, both the T1 and the T2 of the periventricular white matter were significantly prolonged compared to the control values, and slowly shortened after cerebrospinal fluid (CSF) shunting. The true-NPH group showed significantly longer T1 and T2 of the white matter than did the false-NPH group. The T1 and T2 of the white matter were longer than those of the gray matter in this group, which was the reverse of the relationship observed in the control patients. In the white matter of the false-NPH group, there was a significant prolongation of T1 only; no difference was seen in the T2 compared to control values. There was no change in either T1 or T2 of this region after CSF shunting. The false-NPH group showed no significant difference in either T1 or T2 between the white and the gray matter. There was no difference in either T1 or T2 of the gray matter between the false-NPH and control groups or between preshunt and postshunt measurements in each patient group. It is suggested that a distinction between true- and false-NPH, which cannot be made from the radiographic appearance alone, may be possible from measurement of relaxation times. The mechanism of varied relaxation behavior between two entities may be explained by a difference in properties of the biological water and its environment.

Dielectric Studies of Smectogenic Members of the 4’-alkyl-4-cyanobiphenyl (nCB) Homologous Series

2004 ◽  
Vol 59 (6) ◽  
pp. 316-324 ◽  
Author(s):  
Joanna Czub ◽  
Urszula Gubernat ◽  
Bo Gestblom ◽  
Roman Da̡browski ◽  
Stanisław Urban
Keyword(s):  
Homologous Series ◽  
High Frequency ◽  
Relaxation Times ◽  
Low Frequency ◽  
Activation Entropy ◽  
Viscosity Data ◽  
Dielectric Studies ◽  
Smectic A ◽  
Relaxation Measurements ◽  
Molecular Rotations

Results of dielectric studies of smectogenic members of the nCB (4’-alkyl-4-cyanobiphenyl, n = 9÷12) homologous series are presented. The dielectric relaxation measurements were performed in the isotropic (Is) and smectic A (SA) phases. The relaxation times characterizing the molecular rotations around the short axes (the low frequency, l. f., process) were established for both phases. In the Is phase the high frequency process connected with the molecular rotations around the long axes was also determined. The l. f. relaxation times were analysed using the Arrhenius and Bauer activation equations, which yielded the activation enthalpy ΔH and activation entropy ΔS. All results were analysed together with the literature data on the shorter members of the homologous series as well as on 14CB recently published. The ΔH and ΔS values show typical odd-even alternation that is especially well seen for the shorter members. In the Is phase the l. f. relaxation times are related to the viscosity data measured recently by Jadzyn et al.

Muscle contractile properties during intermittent nontetanic stimulation in rat skeletal muscle

2001 ◽  
Vol 281 (6) ◽  
pp. R1952-R1965 ◽  
Author(s):  
Esther Verburg ◽  
Hanne-Mari Schiøtz Thorud ◽  
Morten Eriksen ◽  
Nina K. Vøllestad ◽  
Ole M. Sejersted
Keyword(s):  
Skeletal Muscle ◽  
Relaxation Time ◽  
Low Frequency ◽  
Creatine Phosphate ◽  
Contractile Properties ◽  
Second Phase ◽  
Phase Relaxation ◽  
Two Phase ◽  
Muscle Contractile

To examine changes in contractile properties and mechanisms of fatigue during submaximal nontetanic skeletal muscle activity, in situ perfused soleus (60-min protocol) and extensor digitorum longus (EDL; 10-min protocol) muscles of the rat were electrically stimulated intermittently at low frequency. The partly fused trains of contractions showed a two-phase change in appearance. During the first phase, relaxation slowed, one-half relaxation time increased, and maximal relaxation first derivative of force (dF/d t) decreased. Developed force during the trains was reduced and was closely related to the rate of relaxation in this first phase. During the second phase, relaxation became faster again, one-half relaxation time decreased, and force returned to resting levels between contractions in a train. In contrast, developed force remained reduced, so that peak force of the contractions was 51% (soleus) and 30% (EDL) of control. In the soleus muscle, the changes in contractile properties were not related to ATP, creatine phosphate, or lactate content. The changes in contractile properties fit best with a mechanism of fatigue involving changes in Ca2+ handling by the sarcoplasmic reticulum.

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