Characteristic Relaxation Rate Research Articles

Protein determination by nuclear magnetic resonance

AbstractProtein may be determined using a pulsed nuclear magnetic reso‐nance (NMR) spectrometer in conjunction with a relaxation reagent. These reagents exhibit characteristic nuclear relaxation rates, controlled by a paramagnetic ingredient such as copper, and these rates are altered if substances are added which can bind the copper. The method is fast and simple. Sample and reagent are mixed, brought to a standard temperature and transferred to the spectrom‐eter for measurement. Sample throughput can be high since the time for the spectrometer reading is on the order of 30 sec. Compositions and methods of use are given for 2 copper‐based reagents together with the results on a number of materials. The alkaline copper reagent gives a very similar response to different types of protein and it appears suitable for meat, fish and for other protein materials low in carbohydrates. It shows a response to carbohydrate which depends strongly on type. The acid copper reagent is intended for measurements of vegetable or seed protein and similar applications where carbohydrate is present. This reagent does not respond to carbohydrates tested; the response to protein depends on the type of protein.

Order-disorder and central peak behavior in SrTiO3

Abstract Recent detailed Electron Paramagnetic Resonance (EPR) studies will be presented which gave insight into the central peak phenomenon concerning its width and intensity. The studies were conducted with the Fe3+ - Vo center in a monodomain single crystal of SrTiO3, for Tc ≤ T < 295 K.1 From the angular dependence of the observed width, an upper limit of 6 MHz is placed upon the characteristic frequency of the local rotation fluctuations between Tc < T < Tc + 11K. The characteristic collective-mode relaxation rate, i.e., the “central-peak” width, should be about an order of magnitude narrower. A comparison of its narrow width with existing computer simulations2 above Tc indicates that the width of the c.p. has extrinsic origin, i.e., is impurity dominated.

Ultrasonic dispersion and attenuation near the liquid-gas critical point of4He

We report ultrasonic dispersion and attenuation measurements near the liquid-gas critical point of 3He at frequencies from 0.5 to 5.0 MHz and densities from 0.89ϱ c to 1.15ϱ c . The singular part of the sound attenuation and the dispersion on the critical isochore ϱ c = 0.0414 g/cm3 are analyzed in terms of the Kawasaki-Mistura theory. If the Ornstein-Zernike order parameter correlation function is assumed in the analysis, good agreement with our data is achieved, except close to the critical temperature T cin the high-frequency region, where ω* = ω/ωD ≫ 1. Here Ω D is the characteristic relaxation rate of the critical fluctuations. From a fit of the theory to our data, and assuming the inverse correlation length κ is expressed by κ = κ0ɛΝ, where ɛ = (T−Tc)/Tc with Ν = 0.63, we obtain κ0 = (3.9 ± 0.4) × 109 m−1. It is found that a more realistic form of the correlation function, as proposed by Fisher and Langer and calculated by Bray, yields even poorer agreement with out data than does the classical Ornstein-Zernike form for Ω* > 10. The same difficulties appear in the analysis of the available data for xenon. Thus, the present mode coupling theory is unable to satisfactorily describe the acoustic experiments on fluids near the liquid-vapor critical point over a large range of reduced frequencies Ω*. In the appendix, we reanalyze previously reported ultrasonic data in 4He, taking into account the nonsingular term of the thermal conductivity. Using Ν = 0.63, we obtain a good fit of the experiment to the theory in the hydrodynamic region with κ0 = (5.5 ± 1) × 109 m−1.

Electron spin-lattice and cross relaxation in irradiated malonic acid

Electron spin-lattice and cross relaxation processes in X-ray and electron irradiated single crystals of malonic acid have been investigated over the temperature range 1.1° to 300°K as a function of radiation dosage and as a function of thermal aging. The recovery of the longitudinal magnetization following pulsed saturation is due to cross relaxation among the radicals R2⋯X2, R⋯X2, and R⋯X2CO (where R = COOH or COOD and X = H or D) and to the characteristic spin-lattice relaxation rates of these radicals. The spin-lattice relaxation times in these radicals appear to be determined by phonon modulation of the spin-orbit coupling rather than of the hyperfine interaction.