Dynamical <i>in situ</i> nuclear-magnetic-resonance tensile apparatus

A combination of a servohydraulic tensile machine and NMR pulse spectrometer is described enabling nuclear-spin relaxation rates to be recorded simultaneously with stress-strain data incorporating tension as well as compression of nonmetallic as well as of metallic samples. The data of the mechanical system are as follows: Maximum load: 5000 N; minimum deformation speed: 10 µm s–1, maximum deformation speed: 3×10^5 µm s–1; deformation stroke: digitally controlled between 1 and 8×10^3 µm; bandwidth: dc to 1 kHz; resolution: 2–4 µm; temperature conditions of the sample: from 80 to 570 K. The operation and performance of the system is described by means of experiments observing nuclear-spin relaxation rates which are induced by the movement of dislocations due to the finite deformation rate of the sample

What the radiologist needs to know about the diabetic patient

Diabetes mellitus (DM) is recognised as a major health problem. Ninety-nine percent of diabetics suffer from type 2 DM and 10% from type 1 and other types of DM. The number of diabetic patients worldwide is expected to reach 380 millions over the next 15 years. The duration of diabetes is an important factor in the pathogenesis of complications, but other factors frequently coexisting with type 2 DM, such as hypertension, obesity and dyslipidaemia, also contribute to the development of diabetic angiopathy. Microvascular complications include retinopathy, nephropathy and neuropathy. Macroangiopathy mainly affects coronary arteries, carotid arteries and arteries of the lower extremities. Eighty percent of deaths in the diabetic population result from cardiovascular incidents. DM is considered an equivalent of coronary heart disease (CHD). Stroke and peripheral artery disease (PAD) are other main manifestations of diabetic macroangiopathy. Diabetic cardiomyopathy (DC) represents another chronic complication that occurs independently of CHD and hypertension. The greater susceptibility of diabetic patients to infections completes the spectrum of the main consequences of DM. The serious complications of DM make it essential for physicians to be aware of the screening guidelines, allowing for earlier patient diagnosis and treatment

Sketches from Life

Pulsed nuclear magnetic resonance techniques as well as transmission electron microscopy have been applied to study dislocation motion in ultrapure aluminium and aluminium-copper alloys (Al:xCu with xmax = 1 at.%). The spin-lattice relaxation rate in the rotating frame, T1ρ^-1 of 27Al has been measured as a function of the plastic strain rate ε· at 77 K. For finite strain rates ε·, the movement of dislocations induces an additional relaxation rate arising from time fluctuations in the nuclear quadrupole interaction. From this motion-induced part of the relaxation rate the mean free path L of mobile dislocations can be calculated which is determined by the distribution of lattice defects acting as obstacles for moving dislocations. The NMR experiments are combined with transmission electron microscopic investigations to reveal the static structure of defects in the samples. Correlations between the in situ observed mean free path L of mobile dislocations and between the microscopic defect structure arising from the ageing process (θ’ phase, solid solution) and the degree of plastic deformation ε are shown. It turns out that in the θ’ phase at small strains L is determined by the microstructure and is equal to the mean separation between the precipitates. For large strains L is determined by the statistical distribution of the dislocation loops lying between the precipitates. On the other hand, in ultrapure aluminium L is determined by the dislocation cell structure