T1 rho in nuclear quadrupole resonance: a theoretical study

A new NQR method of measuring the spectral density of slow motions in solids is proposed. It is shown that also in NQR a 90 degrees phase shift of a resonant rf magnetic field following a 90 degrees pulse locks the nuclear magnetization in a 'rotating frame' similarly as in NMR. The spin-lattice relaxation time T1 rho of the locked magnetization is calculated in general for an arbitrary spin. It is assumed that the fluctuations of the EFG tensor dominate the spin-lattice relaxation. The calculations show that T1 rho depends on the spectral density J(omega) of the electric quadrupole fluctuations at the NQR frequencies, and also at a low frequency omega. Here omega approximately gamma B1 kHz depends on the orientation of the rf magnetic field in the principal-axis system of the EFG tensor. The term containing J(omega) in the expression for T1 rho-1 depends on the orientation of the rf magnetic field in the principal-axis system of the EFG tensor, only through the orientation dependence of omega. This term vanishes when the electric quadrupole fluctuations do not modulate the frequency of the NQR transition excited by the rf magnetic field. Two particular examples: I = 1 and I = 3/2 are worked out in details.     

Recent developments in solid-state nuclear magnetic resonance of quadrupolar nuclei and applications to biological systems

Recent advances in nuclear magnetic resonance (NMR) methodology and improvements in high-field NMR instrumentation have generated a new wave of research interests in the application of solid-state NMR to the study of quadrupolar nuclei. These developments now permit increasingly complex biological systems to be probed by quadrupolar NMR. In this review I describe a few recent developments in NMR studies of quadrupolar nuclei and demonstrate the potential of solid-state quadrupolar NMR in the study of biological systems. In particular, I discuss the application of solid-state NMR of (17)O, 67Zn, 59Co, 23Na, and 39K nuclei with a prognosis for future work.     

Surface alloying of thin-walled metallic tube fragments using pulsed gas plasma flows

A technique is developed and conditions are determined for the surface liquid-phase alloying with aluminum and chromium of thin-walled tubes made of 12% Cr type steels with the use of high-temperature pulsed gas plasma flows. The surface morphology of the samples subjected to alloying is shown to depend on the type and thickness of a deposited film and the plasma treatment conditions. The optimum plasma treatment conditions are determined; as a result, alloying elements are rather uniformly distributed in a 10-μmthick near-surface layer at a preliminarily deposited film thickness of ～0.5 μm. In this case, the average aluminum content in the surface layer changes in the range 6–18 wt % and the chromium content increases from ～12 to ～25–40 wt %.     

Detection of macrosegregation in a large metallic specimen using XRF

Abstract

The characterisation of macroscopic chemical segregation in engineering components over length scales of many metres can be an arduous task. This report investigates the implementation of a technique that is capable of mapping long range variations in the chemical composition of metal components, without the need for extensive sample preparation. The capability of the method is optimised for large production components in a setting where process parameters such as measurement time and minimal surface preparation are of importance. Hence, a readily available hand held X-ray fluorescence instrument and analysis software are used to map macrosegregation in a low alloy steel slab.     

Phospholipid profiling of sediments using phosphorus-31 nuclear magnetic resonance

A phosphorus-31 nuclear magnetic resonance method has been developed for the determination of aquatic sediment phospholipid profiles that may be generally applied to all soils and deposits containing viable cellular material. A method of scrubbing chloroform/methanol extracts with potassium acid phosphate overcomes adverse signal broadening from the mineral component, permitting eleven sediment phospholipids to be determined at the quantitative level.