Browsing by Subject "mineral magnetism, biomagnetism"
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Item Biomineralization of magnetic minerals(Reviews of Geophysics (American Geophysical Union), 1995) Moskowitz, BruceNew developments and discoveries in biomineralization have occurred almost continuously in the intervening decade since the previous IUGG quadrennial report on biomineralization and biomagnetism was published [Kirschvink, 1983]. Biomineralization is widespread in the biosphere and over 60 different inorganic minerals are produced by a variety of organisms from bacteria to humans [Lowenstam and Weiner, 1989]. The literature on biomineralization is interdisplinary, combining research in microbiology, biotechnology, physics, geology, and paleomagnetism. For paleomagnetism and rock magnetism, iron biomineralization of magnetic minerals is of prime importance. From a paleomagnetism perspective, biogenic magnetic minerals can be deposited in sediments and acquire a natural remanent magnetization that preserves a record of the ancient geomagnetic field. From a rock magnetism perspective, biogenic magnetic minerals provide novel sources of magnetic material for experimental studies in fine particle magnetism. Both perspectives are interrelated through a common goal of developing magnetic techniques to detect biogenic magnetic minerals in sediments and soils. For example, the extent to which iron biominerals contribute to the fine-grained magnetic mineral assemblages in freshwater and marine sediments is important for identifying and interpreting the magnetic record of environmental change [Oldfield, 1992; Reynolds and King, this issue].Item Interactions between single domain particles(Journal of Applied Physics (American Institute of Physics), 1994) Proksch, Roger; Moskowitz, BruceWe present a variation of the Wohlfarth–Henkel technique for studying interactions in single domain particles (SDPs) in which samples are prepared in different remanent states before the remanent magnetization curves are measured. By analyzing the resulting series of switching field distributions (SFDs), it is possible to separate the effects of positive (magnetizing) and negative (demagnetizing) interactions, even when one type dominates the other. The method is applied to two types of samples consisting of uniform SPDs of magnetite produced by magnetotactic bacteria: (1) whole bacterial cells containing single, linear chains of SDPs; and (2) SDPs extracted from the cells and allowed to aggregate into clumps.