MAGNETIC ORIENTATION OF AMPHIBOLE FIBRES
Amphibole fibres have been exposed to a unitbrm magnetic field while suspended in a dilute solution of celloidin in amyl acetate. The solvent was allowed to evaporate while the field was maintained so as to obtain a coherent film of magnetically oriented fibres bonded together by celloidin. X-ray-diffraction patterns were then recorded in transmission geometry, and the orientation of the fibrils around their fibre axis was determined. The fibres are oriented in azimuth as well as lengthwise, though those that align normal to the field show a much more restricted range of azimuthal orientations than those that align parallel to the field. Crystallographic control of the principal maguetic axes is discussed; the orientation properties are not fully explained, but their attribution to magretite present in bulk samples is rejected.
Influence of metal cation order on magnetic order in manganogrunerite, (Fe,Mg,Mn)7Si8O22(OH)2, a quasi-one-dimensional chain antiferromagnet
Abstract The magnetic susceptibility of ordered and partially disordered manganogrunerites (composition Ca0.1Mn1.9Mg1.25Fe3.562+Fe0.383+Si7.81O22(OH)2 and Ca0.24Mn1.57Mg2.27Fe2.762+Fe0.323+Si7.84O22(OH)2) has been measured between room temperature and 5 K. The influence of disordering of metal cations over the M(1,2,3) sites of the octahedral ribbon in these amphiboles is to dilute Fe2+ within the ribbon. We observe a reduction in both θp and TN as a function of both increased Mg/(Mg+Fe) and metal cation disorder, linked to a reduction in the strength of magnetic coupling between and within the one-dimensional chains of the structure.
Sex and age differences in human platelet aggregation
MALES stand at risk in many pathological states1, especially cardiovascular disease, in which there is a statistically significant higher mortality in men than women2. We have described3 a sex difference in platelet responsivity in rats and guinea pigs where platelets from males were significantly more sensitive to aggregating stimuli than those from females. Increased platelet responsiveness has been detected in humans,in thromboembolic disease4 and after acute myocardial infarction5. Indeed, the principal post mortem finding in subjects who died suddenly is occlusion in the pulmonary circulation due to platelet aggregation6. We have suggested3 that platelet sensitivity is mediated by the androgenic steroids and that androgens contribute to the incidence of thrombotic disease.