Physical Sciences and Mathematics Commons^™

Rock Magnetic Criteria For The Detection Of Biogenic Magnetite, Bruce M. Moskowitz, Richard B. Frankel, Dennis A. Bazylinski

Physics

We report results on the magnetic properties of magnetites produced by magnetotactic and dissimilatory iron-reducing bacteria. Magnetotactic bacterial (MTB) strains MS1, MV1 and MV2 and dissimilatory iron-reducing bacterium strain GS-15, grown in pure cultures, were used in this study. Our results suggest that a combination of room temperature coercivity analysis and low temperature remanence measurements provides a characteristic magnetic signature for intact chains of single domain (SD) particles of magnetite from MTBs. The most useful magnetic property measurements include: (1) acquisition and demagnetization of isothermal remanent magnetization (IRM) using static, pulse and alternating fields; (2) acquisition of anhysteretic remanent magnetization …

Quantile-Locating Functions And The Distance Between The Mean And Quantiles, D. Gilat, Theodore P. Hill

Research Scholars in Residence

Given a random variable X with finite mean, for each 0 < p < 1, a new sharp bound is found on the distance between a p-quantile of X and its mean in terms of the central absolute first moment of X. The new bounds strengthen the fact that the mean of X is within one standard deviation of any of its medians, as well as a recent quantile-generalization of this fact by O'Cinneide.

Fe304 And Fe3S4 In A Bacterium, Dennis A. Bazylinski, Brigid R. Heywood, Stephen Mann, Richard B. Frankel

Physics

No abstract provided.

Cation Distribution In Natural Ferrites, H. A. Maia, F. F. T. De Araújo, M. A. B. De Araújo, J. Danon, Richard B. Frankel

Physics

Mössbauer spectra of jacobsite have been recorded at temperatures of 4.2, 125, 180, 240 and 300 K and with an external magnetic field of 60 kOe applied parallel to the incident radiation at 4.2 K. The results show the presence of two different magnetic hyperfine interactions associated with the iron nuclei. Spectra of samples in external magnetic fields indicate the same sign for the magnetic hyperfine interactions, implying that both iron ions occupy only the octahedral sublattice. These results are compared with data from synthetic stoichiometry manganese ferrite, and a model of cation distribution, assuming the existence of vacancies, is …

Review Of Genius In The Shadows: A Biography Of Leo Szilard, The Man Behind The Bomb By William Lanouette And Bela Silard, David W. Hafemeister

Physics

No abstract provided.

Copper Association With Iron Sulfide Magnetosomes In A Magnetotactic Bacterium, Dennis A. Bazylinski, Anthony J. Garratt-Reed, Afshin Abedi, Richard B. Frankel

Physics

Greigite (Fe₃S₄) and pyrite (FeS₂) particles in the magnetosomes of a many-celled, magnetotactic prokaryote (MMP), common in brackish-to-marine, sulfidic, aquatic habitats, contained relatively high concentrations of copper which ranged from about 0.1 to 10 atomic per cent relative to iron. In contrast, the greigite particles in the magnetosomes of a curved magnetotactic bacterium collected from the same sampling site did not contain significant levels of copper. The ability of the MMP to biomineralize copper within its magnetosomes appeared to be limited to that organism and dependent upon the site from which it was collected. …

Electron Microscopy Study Of Magnetosomes In A Cultured Coccoid Magnetotactic Bacterium, Fiona C. Meldrum, Stephen Mann, Brigid R. Heywood, Richard B. Frankel, D. A. Bazyllinski

Physics

Intracellular magnetite (Fe₃O₄) crystals produced by the magnetotactic bacterium MC-1 were analyzed by transmission electron microscopy (TEM). Strain MC-1 represents the first-reported isolation of a coccoid magnetotactic bacterium in axenic culture. The magnetosomes of this bacterium displayed a pseudo-hexagonal prismatic habit, were elongated along the crystallographic direction, and were truncated by {111}, {100} and {110} faces. The presence of {111} truncations represents a modification of the magnetosome morphology previously determined for those in other coccoid bacteria. Study of immature crystals produced by strain MC-1 showed that the crystal morphology was controlled even at early stages of …

Electron Microscopy Study Of Magnetosomes In Two Cultured Vibrioid Magnetotactic Bacteria, Fiona C. Meldrum, Stephen Mann, Brigid R. Heywood, Richard B. Frankel, Dennis A. Bazylinski

Physics

Magnetite (Fe₃0₄) crystals produced by two strains of cultured vibrioid magnetotactic bacteria were studied by high-resolution transmission electron microscopy (HRTEM). Both magnetotactic strains were characterized by single chains of magnetite crystals aligned along the long axes of the cells. The strains, designated as MV-2 and MV-4, produced crystals that differed markedly in size and morphology. Crystals present in MV-4 cells were generally larger than those in MV-2 cells and displayed significantly smaller aspect ratios. Crystallographic analysis of the magnetosomes of MV-2 revealed an elongated hexagonal habit based on a prism of {110} faces capped by {111} …

Multiple Evolutionary Origins Of Magnetotaxis In Bacteria, Edward F. Delong, Richard B. Frankel, Dennis A. Bazylinski

Physics

Magnetosomes are intracellular, iron-rich, membrane-enclosed magnetic particles that allow magnetotactic bacteria to orient in the earth's geomagnetic field as they swim. The magnetosomes of most magnetotactic bacteria contain iron oxide particles, but some magnetotactic species contain iron sulfide particles instead. Phylogenetic analyses of small subunit ribosomal RNA sequences showed that all known magnetotactic bacteria of the iron oxide type are associated with the a subgroup of the Proteobacteria in the domain Bacteria. In contrast, uncultured magnetotactic bacteria of the iron sulfide type are specifically related to the dissimilatory sulfate-reducing bacteria within the δ subdivision of the Proteobacteria. These findings indicate …

Isosymmetric Linear Transformations On Complex Hilbert Space, Mark Stankus

Mathematics

We explore the elementary operator theory of the equation
(0.1) ∑ c_m,nT^*nT^m=0
for c_m,n E C, c_m,n nonzero for only finitely many m, n and Ta bounded linear transformation on a complex Hilbert space in Chapters 1 and 2. We explore the equation

(0.2) T^*2T - T^*T² + T - T^* = 0
in greater depth in Chapters 4 and 5.

Chapter 1 explores the algebraic and C^*-algebraic aspects of the equation (0.1) and both the spectral picture of and growth conditions on …

Orbifolds Of Maximal Diameter, Joseph Borzellino

Mathematics

In this paper the Maximal Diameter Theorem of Riemannian geometry is proven for Riemannian orbifolds. In particular, it is shown that a complete Riemannian orbifold with Ricci curvature bounded below by (n−1) and diameter = π, must have constant sectional curvature 1, and must be a quotient of the sphere (Sn, can) of constant sectional curvature 1 by a subgroup of the orthogonal group O(n+1) acting discontinuously and isometrically on Sn. It is also shown that the singular locus of the orbifold forms a geometric barrier to the length minimization property of geodesics. We also extend the Bishop relative volume …

Partitioning Inequalities In Probability And Statistics, Theodore P. Hill

Research Scholars in Residence

This article surveys fair-division or cake-cutting inequalities in probability statistics, including bisection inequalities, basic fairness inequalities, convexity tools, superfairness inequalities, and partitioning inequalities hypotheses testing and optimal stopping theory. The emphasis is measure theoretic, as opposed to game theoretic or economic, and a number of open problems in the area are mentioned.