Relaxivity concentration dependency

Here p is the solution density, v the sound velocity, ctp the coefficient of thermal expansion, Cp the specific heat, and F the concentration dependence of the equilibrium, r = [LS] -f- [HS] . The measurement of ultrasonic relaxation thus enables the determination of both the relaxation time x and the... 

The dipole interaction depends on the distance between the ions (6.4). Therefore, the transition probability increases with increasing concentration of magnetic ions. Studies of the concentration dependence of the relaxation can be conveniently performed on samples of amorphous frozen solutions with a uniform distribution... 

When (DEB), is much smaller than unity, the polymer relaxation is relatively rapid compared to diffusion. In this case, conformational changes take place instantaneously and equilibrium is attained after each diffusional jump. This is the type of diffusion encountered ordinarily and is called viscous diffusion. Therefore, the transport will obey classical theories of diffusion. When (DEB), is much larger than unity, the molecular relaxation is very slow compared to diffusion and there are no conformational changes of the medium within the diffusion time scale. In this case, Fick s law is generally valid, but no concentration dependence of the diffusion coefficient is expected. This is termed elastic diffusion. When (DEB), is in the neighborhood of unity, molecular rearrangment... 

Most commonly absorption or fluorescence spectroscopy is used for detection of the changes in the concentration of G or HG. The monitoring wavelength is chosen so that the difference between the molar absorptivities, in case of absorption, or emission quantum yields, in the case of fluorescence detection, between G and HG is maximized. The amplitude of the relaxation process depends on the difference in the molar absorptivities or fluorescence quantum yields, but the observed rate constants are the same at all observation wavelengths when the kinetics are first- or pseudo-first order (Fig. 3). 

The non-linear dependence of the relaxation process on the DNA concentration was also observed in stopped-flow experiments and the same mechanism, i.e. fast pre-equilibrium followed by a slow intercalation step, was proposed." This latter study did not report values for the individual rate constants. The mechanism proposed in Scheme 4 was employed in subsequent studies despite the criticism on the accuracy for the data related to the fast kinetic component (see below). The original temperature jump study also showed that the relaxation kinetics depend on the structure of the DNA.117 The slower intercalation rate for 5 with T2 Bacteriophage DNA when compared to ct-DNA was ascribed to the glucosylation of the former DNA (Table 3). 

When counterion binding reaction II is extremely rapid, the concentration dependence of the relaxation time is given by (11)... 

For reactions VII and VIII, the concentration dependences of the relaxation times are given by... 

Vascular and hematologic effects Ginkgo exerts vascular effects through at least two mechanisms inhibition of platelet-activating factor (PAF) and nitric oxide mechanisms. Ginkgo extract relaxes the porcine basilar artery in a concentration-dependent and partly endothelium-dependent manner (Chen et al. 1997). It also enhances vasorelaxation created by transmural nerve stimulation in arteries with and without the endothelium intact, and is prevented by nitro-L-arginine, indicating that the effect is mediated by nitric oxide. 

Mechanisms for the formation of [W60i9(0H)3] (paratungstate A) have been discussed. The relaxation spectra of aqueous molybdate have been determined by the temperature-jump technique at 25 °C(/i = 1.0 M, pH = 5.5— 6.8, and monomer concentration = 0.01—0.25 M). The results indicate two concentration-dependent relaxation effects, which are sensitive to heptamer, [Mo7 0 24] , and octamer, [Mog026]", formation. ... 

The concentration dependence of polymer or solvent motion has been studied only rarely over a wide range in concentration. Typically, polymer carbon-13 relaxation is not concentration dependent up to 20-30 percent polymer. Little is known concerning the concentration dependence of the solvent motion. 

Figure 5. Temperature and concentration dependence of the ester methylene C-13 relaxation (9), 10% 20%> (O), 30%.

Figure 9. Temperature and concentration dependence of the solvent proton-polymer proton relaxation rate (0), 10% polymer (X), 20% polymer.

Antispasmodic activity. Gum extract, administered to isolated guinea pig ileum at a dose of 3 mg/mL, produced a decrease of spontaneous contraction to 54 7% of control. Exposure of precontracted ileum by acetylcholine, histamine, and KCl to Ferula gum extract produced a concentration-dependent relaxation. Preincubation with in-domethacin, propanolol, atropine, and chlorpheniramine before exposure to the gum, did not produce any relaxation " . Antitumor activity. Water extract of the dried oleoresin, administered by gastric intubation to mice at a dose of 50 mg/ani-mal daily for 5 days, was active on CA-Ehrlich ascites, 53% increase in life span Water extract administered intra-peritoneally was inactive on Dalton s lymphoma, 4.8% ILS, and CA-Ehrlich ascites, 5.5%... 

A linear concentration dependence of the reciprocal relaxation time upon total ion-pair concentration would therefore point to a main recombination process between a simple ion and a triple ion. 

Considering these different limiting forms of the recombination term an Important tentative conclusion emerges the concentration dependence of the reciprocal relaxation time is a direct measure of the main ionic recombination process and yields therefore information on the ionic species present in solution. A linear dependence on total ion-pair concentration would therefore indicate unilateral triple ion formation or, if both kinds of triple ions are present as indicated by conductance, a sufficient difference in their stability. At this point it should be noted that the usual method of Fuoss and Draus... 

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