Digital Commons Network^™

Statement Of Dr. David Hafemeister Regarding The Need To Convert Domestic Research Reactors From Highly Enriched To Low-Enriched Uranium Fuels, David W. Hafemeister

Physics

No abstract provided.

Structure, Morphology And Crystal Growth Of Bacterial Magnetite, Stephen Mann, Richard B. Frankel, Richard P. Blakemore

Physics

Recent high-resolution transmission electron microscopy (HRTEM) studies of the structure and morphology of bacterial magnetite (Fe₃O₄) crystals isolated from a magnetotactic coccus¹ and from an unidentified bacterium extracted from sediment² have shown the crystals to be well ordered single-domain particles with a morphology based on a hexagonal prism of {011} faces truncated by specific low index planes. We report here a HRTEM study of intact magnetite crystals (magnetosomes) in the microaerophilic bacterium Aquaspirillum magnetotacticum, grown in pure culture^3,4. Our aim has been to investigate the structure, morphology and crystal growth of …

Magnetosome Dynamics In Magnetotactic Bacteria, S. Ofer, I. Nowik, E. R. Bauminger, G. C. Papaefthymiou, Richard B. Frankel, Richad P. Blakemore

Physics

Diffusive motions of the magnetosomes (enveloped Fe₃O₄ particles) in the magnetotactic bacterium Aquaspirillum magnetotacticum result in a very broad-line Mössbauer spectrum (T ~ 100 mm/s) above freezing temperatures. The line width increases with increasing temperature. The data are analyzed using a bounded diffusion model to yield the rotational and translational motions of the magnetosomes as well as the effective viscosity of the material surrounding the magnetosomes. The results are <θ²>^l/2 < 1.5° and <x²>^1/2 < 8.4 Å for the rotational and translational motions, respectively, implying that the particles are fixed in whole cells. The effective viscosity is 10 cP at 295 K and increases with decreasing temperature. Additional Fe³⁺ material in the cell is shown to be associated with the magnetosomes. Fe²⁺ material in the cell appears to be …

On Maximizing The Average Time At A Goal, S. Demko, Theodore P. Hill

Research Scholars in Residence

In a decision process (gambling or dynamic programming problem) with finite state space and arbitrary decision sets (gambles or actions), there is always available a Markov strategy which uniformly (nearly) maximizes the average time spent at a goal. If the decision sets are closed, there is even a stationary strategy with the same property.Examples are given to show that approximations by discounted or finite horizon payoffs are not useful for the general average reward problem.

Magnetic Guidance Of Organisms, Richard B. Frankel

Physics

No abstract provided.

Basidiomycete Fungi Reported On Living Or Dead Giant Sequoia Or Coast Redwood, Douglas D. Piirto, John R. Parmeter, Jr., W. Wayne Wilcox

Natural Resources Management and Environmental Sciences

No abstract provided.

Precipitation Of Fe3O4 In Magnetotactic Bacteria, Richard B. Frankel, Richard P. Blakemore

Physics

The magnetotactic bacterium A. magnetotacticum contains ferrous ions, a low density hydrous ferric oxide, a high density hydrous ferric oxide (ferrihydrite) and Fe₃O₄, which is precipitated by partial reduction of the ferrihydrite precursor.

Causes Of Uprooting And Breakage Of Specimen Giant Sequoia Trees, Douglas D. Piirto, W. Wayne Wilcox, John R. Parmeter, Jr., David L. Wood

Natural Resources Management and Environmental Sciences

A study of the causes of uprooting and stem failure in old-growth giant sequoia (Sequoia gigantea [Lindl.] Decne) indicated many factors, depending upon the type of failure (by root, stem, or earth). Advanced decay and fire scars were the most frequently associated with failure. In 21 of 33 study trees, one-third or more of the roots were judged too decayed to provide support. Twenty-seven study trees possessed basal fire scars, and 26 fell toward the scarred side. Nine Basidiomycetes, including Fomes annosus, Poria albipellucida, Poria incrassata, and Armillaria mellea, were associated with decayed wood. Carpenter ants were found …

Enumeration Of Permutations By Descents, Idescents, Imajor Index, And Basic Components, Don Rawlings

Mathematics

Multivariable extensions of classic permutation cycle structure results are obtained by counting permutations by descents, idescents, imajor index, and basic components.

Hydrogeochemical Aspects Of Surface Mine Reclamation In The Northern Great Plains, Gerald H. Groenewold, Robert D. Koob

Office of the Provost Scholarship

Studies of several coal-mining sites in western North Dakota have resulted in the development of a hydrogeochemical model which accounts for the observed chemical characteristics of subsurface water in undisturbed settings. Critical hydrogeochemical processes include sulfide oxidation, gypsum precipitation and dissolution, carbonate mineral dissolution and cation exchange.

In the semi-arid climate of western North Dakota, the near-surface several meters of the landscape is constantly subjected to alternate wetting/drying. This mechanism is the key to hydrogeochemical evolution of both pore water in the rooting zone and subsurface water that eventually reaches the water table.

Recent refinements in the hydrogeochemical model have …

The Feasibility Of The X-Ray Laser Pumped With A Nuclear Explosion, David W. Hafemeister

Physics

Recent reports have indicated that an x-ray laser pumped with a nuclear explosion at a wavelength of 1.4nm (0.9 keV) has made some initial progress. It has been proposed to extend the development of this device to establish it as part of a layered ballistic missile defensive system to protect the United States against a nuclear attack. This paper will discuss the following aspects on the feasibility of this system: (1) Conditions affecting the efficiency of the X-ray laser; (2) Angular resolution and size of.the laser rods; (3) Energy on targets; (4) Basing Modes; (5) Countermeasures; and (6) Legal constraints.

Biomineralizationof Fe3O4 In Bacteria, R. B. Frankel, G. C. Papaefthymiou

Physics

No abstract provided.