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Full-Text Articles in Physics
Hydrodynamic Forces And Band Formation In Swimming Magnetotactic Bacteria, D. C. Guell, H. Brenners, Richard B. Frankel, H. Hartman
Hydrodynamic Forces And Band Formation In Swimming Magnetotactic Bacteria, D. C. Guell, H. Brenners, Richard B. Frankel, H. Hartman
Physics
Dense suspensions of magnetotactic bacteria form long, thin, stable bands perpendicular to the common, net direction of motion of the cells in a magnetic field. A mechanism for this phenomenon is proposed in which the hydrodynamic coupling between two swimming cells is described in terms of an approximate, far-field solution for the flow around one swimming cell. The calculated hydrodynamic interaction force and torque based upon this analysis are of the correct orders of magnitude and in the right directions to provide a reasonable explanation for band formation and stability.
Redox Reactivity Of Bacterial And Mammalian Ferritin: Is Reductant Entry Into The Ferritin Interior A Necessary Step For Iron Release?, G. D. Watt, D. Jacobs, Richard B. Frankel
Redox Reactivity Of Bacterial And Mammalian Ferritin: Is Reductant Entry Into The Ferritin Interior A Necessary Step For Iron Release?, G. D. Watt, D. Jacobs, Richard B. Frankel
Physics
Both mammalian and bacterial ferritin undergo rapid reaction with small-molecule reductants, in the absence of Fe2+ chelators, to form ferritins with reduced (Fe2+) mineral cores. Large, low-potential reductants (flavoproteins and ferredoxins) similarly react anaerobically with both ferritin types to quantitatively produce Fe2+ in the ferritin cores. The oxidation of Fe2+ ferritin by large protein oxidants [cytochrome c and Cu(II) proteins] also occurs readily, yielding reduced heme and Cu(I) proteins and ferritins with Fe3+ in their cores. These latter oxidants also convert enthetically added Fe2+, bound in mammalian or bacterial apo- or holo-ferritin, …
Testimony On The Verification And Compliance Of Nuclear Testing Treaties, David W. Hafemeister
Testimony On The Verification And Compliance Of Nuclear Testing Treaties, David W. Hafemeister
Physics
No abstract provided.
Anaerobic Magnetite Production By A Marine, Magnetotactic Bacterium, Dennis A. Bazylinski, Richard B. Frankel, Holger W. Jannasch
Anaerobic Magnetite Production By A Marine, Magnetotactic Bacterium, Dennis A. Bazylinski, Richard B. Frankel, Holger W. Jannasch
Physics
Bacterial production of magnetite represents a significant contribution to the natural remanent magnetism of deep-sea and other sediments1–5. Because cells of the freshwater magnetotactic bacterium Aquaspirillum magnetotacticum require molecular oxygen for growth and magnetite synthesis6, production of magnetite by magnetotactic bacteria has been considered to occur only in surficial aerobic sediments7. Moreover, it has been suggested that deposits of single-domain magnetite crystals are palaeooxygen indicators presumably having been formed under predominantly microaerobic conditions5–8. In contrast, some nonmagnetotactic, dissimilatory iron-reducing bacteria, such as the recently described strain GS-15 by Lovley et al. 7, synthesize extracellular magnetite from hydrous ferric oxide under …
Magnetic Properties Of Magnetotactic Bacteria, B. M. Moskowitz, Richard B. Frankel, P. J. Flanders, R. P. Blakemore, Brian B. Schwartz
Magnetic Properties Of Magnetotactic Bacteria, B. M. Moskowitz, Richard B. Frankel, P. J. Flanders, R. P. Blakemore, Brian B. Schwartz
Physics
This paper reports on the magnetic properties of magnetosomes in the freshwater magnetotactic bacterium Aquaspirillum magnetotacticum. The magnetosomes are well crystallized particles of magnetite with dimensions of 40 to 50 nm, which are arranged within the cells in a single linear chain and are within the single-magnetic-domain (SD) size range for magnetite. A variety of magnetic properties have been measured for two samples of dispersions of freeze-dried cells consisting of (1) whole cells (M-1) and (2) magnetosomes chains separated from cells (M-2). An important result is that the acquisition and demagnetization of various type of remanent magnetizations are markedly …
Magnetic Properties Of Tunicate Blood Cells. I. Ascidia Nigra, Seunghee Lee, Kenneth Kustin, William E. Robinson, Richard B. Frankel, K. Spartalian
Magnetic Properties Of Tunicate Blood Cells. I. Ascidia Nigra, Seunghee Lee, Kenneth Kustin, William E. Robinson, Richard B. Frankel, K. Spartalian
Physics
The magnetic properties of intact and freeze-dried blood cells of the tunicate Ascidia nigra and of model vanadium(III) and (IV) compounds as polycrystalline solids and in aqueous solution have been measured up to 50 kOe with a SQUID susceptometer. Corrections for the samples' diamagnetism were extracted from the temperature dependence of the data without any further assumptions. For vanadium(IV), measured values of the magnetic moment at different values of the applied magnetic field over the temperature range 2–100 K obey a Brillouin function with spin 1/2. For vanadium(III), the magnetic moment data did not obey a Brillouin function and were …
Static Magnetic Susceptibility Of Zn1-XMnXSe, J. K. Furdyna, N. Samarth, Richard B. Frankel, J. Spalek
Static Magnetic Susceptibility Of Zn1-XMnXSe, J. K. Furdyna, N. Samarth, Richard B. Frankel, J. Spalek
Physics
We present results of an investigation of the static magnetic susceptibility of Zn1-xMnxSe for x=0.05, 0.15, 0.30, and 0.45. From the Curie-Weiss behavior of the susceptibility at high temperatures, we determine the effective Mn-Mn exchange constant J1 to be -13.5±0.95 K. By using the results of our study in conjunction with direct measurements of the nearest-neighbor exchange integral JNN from inelastic neutron scattering by nearest-neighbor pairs, we obtain an estimate of the next-nearest-neighbor exchange constant J2=-2.4 K.
Review Of The Advancement Of Science, And Its Burdens By Gerald Holton, David W. Hafemeister
Review Of The Advancement Of Science, And Its Burdens By Gerald Holton, David W. Hafemeister
Physics
No abstract provided.
Preparation, Crystal Structure, And Physical Properties Of A Pyrogallol-Bridged Vanadium(Iii) Complex, Seunghee Lee, Koji Nakanishi, Michael Y. Chiang, Richard B. Frankel, K. Spartalian
Preparation, Crystal Structure, And Physical Properties Of A Pyrogallol-Bridged Vanadium(Iii) Complex, Seunghee Lee, Koji Nakanishi, Michael Y. Chiang, Richard B. Frankel, K. Spartalian
Physics
The structure, n.m.r. spectrum, and magnetic properties of the vanadium(III) dimer [(acac)4V2{µ-OC6H3(OH)2}2] formed from [VO(acac)2] and an excess of pyrogallol are described.
Bacterial Biomagnetism And Geomagnetic Field Detection By Organisms, Richard P. Blakemore, Nancy A. Blakemore, Richard B. Frankel
Bacterial Biomagnetism And Geomagnetic Field Detection By Organisms, Richard P. Blakemore, Nancy A. Blakemore, Richard B. Frankel
Physics
No abstract provided.
Magnetite And Magnetotaxis In Microorganisms, Richard B. Frankel, R. P. Blakemore
Magnetite And Magnetotaxis In Microorganisms, Richard B. Frankel, R. P. Blakemore
Physics
No abstract provided.
Anomalous Magnetic Properties Of Some High-Temperature Magnetic Superconductors, P. H. Hor, R. L. Meng, C. W. Chu, C. Y, Huang, R, B. Frankel
Anomalous Magnetic Properties Of Some High-Temperature Magnetic Superconductors, P. H. Hor, R. L. Meng, C. W. Chu, C. Y, Huang, R, B. Frankel
Physics
No abstract provided.