Low-frequency low-field magnetic susceptibility measurements were made on four samples of mammalian tissue iron oxide deposits. The samples comprised: (1) horse spleen ferritin; (2) dugong liver hemosiderin; (3) thalassemic human spleen ferritin; and (4) crude thalassemic human spleen hemosiderin. These samples were chosen because Mössbauer spectroscopic measurements on the samples indicated that they exemplified the variation in magnetic and mineral structure found in mammalian tissue iron oxide deposits. The AC-magnetic susceptometry yielded information on the magnetization kinetics of the four samples indicating samples 1, 2, and 3 to be superparamagnetic with values of around 10(11) s(-1) for the pre-exponential frequency factor in the Néel-Arrhenius equation and values for characteristic magnetic anisotropy energy barriers in the range 250-400 K. Sample 4 was indicated to be paramagnetic at all temperatures above 1.3 K. The AC-magnetic susceptometry data also indicated a larger magnetic anisotropy energy distribution in the dugong liver sample compared with samples 1 and 3 in agreement with previous Mössbauer spectroscopic data on these samples. At temperatures below 200 K, samples 1-3 exhibited Curie-Weiss law behavior, indicating weak particle-particle interactions tending to favor antiparallel alignment of the particle magnetic moments. These interactions were strongest for the dugong liver hemosiderin, possibly reflecting the smaller separation between mineral particles in this sample. This is the first magnetic susceptometry study of hemosiderin iron deposits and demonstrates that the AC-magnetic susceptometry technique is a fast and informative method of studying such tissue iron oxide deposits.

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Metal-catalysed exchange has been used extensively in the laboratories of AstraZeneca plc at R&D Charnwood to label a variety of molecules of pharmaceutical interest with the isotopes of deuterium and tritium. Despite early prejudices against the use of tritiated compounds, particularly in ADME studies, the development of directed isotopic exchange techniques has enabled timely and economic support for many pharmaceutical projects.

Recent years have seen an explosion of popular complaint about the British 'political class'. Within this narrative, the political class is feckless, unrepresentative, immoral and elitist. It rules over 'ordinary people' from Westminster with no conception of what 'real people' think. How can one respond to such complaints? It is argued in this article that a coherent solution will only be possible when the problem can be defined clearly. 'Political class' should not be a catch-all description for elected politicians. Instead, the 'political class' narrative should be divided into three distinct but related concepts -the political elite, political professionalisation and political careerism -in order to highlight the ways in which the term needlessly conflates distinct ideas and adds more confusion to an already vague debate.