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Articles 2491 - 2520 of 2725

Full-Text Articles in Physical Sciences and Mathematics

A Binary Tree Decomposition Space Of Permutation Statistics, Don Rawlings Jan 1992

A Binary Tree Decomposition Space Of Permutation Statistics, Don Rawlings

Mathematics

Based on the binary tree decomposition of a permutation, a natural vector space of permutation statistics is defined. Besides containing many well known permutation statistics, this space provides the general context for an archetypal recurrence relationship that contains most of the classic combinatorial sequences and some of their known generalizations.

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A Survey Of Prophet Inequalities In Optimal Stopping Theory, Theodore P. Hill, Robert P. Kertz Jan 1992

A Survey Of Prophet Inequalities In Optimal Stopping Theory, Theodore P. Hill, Robert P. Kertz

Research Scholars in Residence

This paper surveys the origin and development of what has come to be known as "prophet inequalities" in optimal stopping theory. Included is a review of all published work to date on these problems, including extensions and variations, descriptions and examples of the main proof techniques, and a list of a number of basic open problems.

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One-Sided Refinements Of The Strong Law Of Large Numbers And The Glivenko-Cantelli Theorem, David Gilat, Theodore P. Hill Jan 1992

One-Sided Refinements Of The Strong Law Of Large Numbers And The Glivenko-Cantelli Theorem, David Gilat, Theodore P. Hill

Research Scholars in Residence

A one-sided refinement of the strong law of large numbers is found for which the partial weighted sums not only converge almost surely to the expected value, but also the convergence is such that eventually the partial sums all exceed the expected value. The new weights are distribution-free, depending only on the relative ranks of the observations. A similar refinement of the Glivenko-Cantelli theorem is obtained, in which a new empirical distribution function not only has the usual uniformly almost-sure convergence property of the classical empirical distribution function, but also has the property that all its quantiles converge almost surely. …

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Variation Of Superparamagnetic Properties With Iron Loading In Mammalian Ferritin, Richard B. Frankel, G. C. Papaefthymiou, G. D. Watt Nov 1991

Variation Of Superparamagnetic Properties With Iron Loading In Mammalian Ferritin, Richard B. Frankel, G. C. Papaefthymiou, G. D. Watt

Physics

The average blocking temperatures of ferritin molecules containing differing amounts of iron were determined by Mossbauer spectroscopy. The results imply that the magnetic anisotropy of the ferritin core particles is a function of particle volume. By addition of 57Fe to ferritin core particles it was determined that, at a given temperature within the superpara-magnetic temperature region, the “last-in” ferric ions have average relaxation times that are shorter than those of the bulk ferric ions.

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Visual Interaction: A Link Between Perception And Problem Solving, Erika Rogers, Ronald C. Arkin Oct 1991

Visual Interaction: A Link Between Perception And Problem Solving, Erika Rogers, Ronald C. Arkin

Computer Science and Software Engineering

The approach taken in this research is to develop a cognitive model of how a human observer extracts information from a visual display and then uses this perceptual information in a decision-making task. Knowledge about this relationship provides information about the occurrence of perceptual events in the course of problem-solving activities, and suggests that perceptual assistance in the form of image enhancements is a useful supplement to the user’s own abilities. This knowledge is then to be embedded in an intelligent computerized assistant which is designed to facilitate and stimulate the human problem-solving process.

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Inorganic Particles Produced By Microorganisms, Richard B. Frankel Oct 1991

Inorganic Particles Produced By Microorganisms, Richard B. Frankel

Physics

The processes by which microorganisms, particularly bacteria, produce inorganic mineral particles are reviewed.

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Structure, Morphology And Growth Of Biogenic Greigite (Fe3S4), Brigid R. Heywood, Stephen Mann, Richard B. Frankel Oct 1991

Structure, Morphology And Growth Of Biogenic Greigite (Fe3S4), Brigid R. Heywood, Stephen Mann, Richard B. Frankel

Physics

Several species of aquatic bacteria are known to exploit the earth's geomagnetic field as a means of directing their motion towards suitable habitats. A feature common to these bacteria is the presence of discrete intracellular magnetic inclusions, magnetosomes, aligned in chains along the long axis of the organism. The size and orientation of the individual magnetic particles imparts a permanent magnetic dipole moment to the cell which is, in turn, responsible for the magnetotactic response. In all species examined to date the magnetic particles have been found to be well-ordered, single domain, membrane-bounded crystals with reproducible, species-specific morphologies. Until recently, …

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Paper Or Plastic?, Matthew J. Moelter Sep 1991

Paper Or Plastic?, Matthew J. Moelter

Physics

Letter to the Editor.

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Visual Interaction In Diagnostic Radiology, Erika Rogers, Ronald C. Arkin, M. Baron May 1991

Visual Interaction In Diagnostic Radiology, Erika Rogers, Ronald C. Arkin, M. Baron

Computer Science and Software Engineering

The concept of Visual Interaction is introduced as the process which links perception and problem-solving such that problem-solving is affected by what is seen, and conversely, what is seen and perceived is affected by the current state of the problem-solving process. This paper describes the development of a cognitively-based model of the visual interaction process in diagnostic radiology, and shows how aspects of this model are being incorporated into the design and implementation of an intelligent computer-based radiological assistant. In order to achieve this, it is necessary to extract information about the nature and type of knowledge involved in this …

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Method For The Automatic Level Adjustment In A Local Area Network, In Particular For A Multiprocessor Arrangement With A Bus System Of Optical Fibres, For The Purpose Of Collision Detection, Hans Thinschmidt, Franz J. Kurfess May 1991

Method For The Automatic Level Adjustment In A Local Area Network, In Particular For A Multiprocessor Arrangement With A Bus System Of Optical Fibres, For The Purpose Of Collision Detection, Hans Thinschmidt, Franz J. Kurfess

Computer Science and Software Engineering

European Patent. Written in German.

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Redox Capacity Of Apo Mammalian Ferritin, Gerald D. Watt, Richard B. Frankel Mar 1991

Redox Capacity Of Apo Mammalian Ferritin, Gerald D. Watt, Richard B. Frankel

Physics

No abstract provided.

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Iron Biominerals: An Overview, Richard B. Frankel Mar 1991

Iron Biominerals: An Overview, Richard B. Frankel

Physics

No abstract provided.

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Biomineralization Of Iron Sulfides In Magnetotactic Bacteria From Sulfidic Environments, Dennis A. Bazylinski, Richard B. Frankel, Anthony J. Garratt-Reed, Stephen Mann Mar 1991

Biomineralization Of Iron Sulfides In Magnetotactic Bacteria From Sulfidic Environments, Dennis A. Bazylinski, Richard B. Frankel, Anthony J. Garratt-Reed, Stephen Mann

Physics

No abstract provided.

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Intercellular Junctions, Motility, And Magnetosome Structure In A Multicellular Magnetotactic Prokaryote, Frank G. Rodgers, Richard P. Blakemore, Nancy A. Blakemore, Richard B. Frankel, Dennis A. Bazylinski, Denise Maratea, Christine Rodgers Mar 1991

Intercellular Junctions, Motility, And Magnetosome Structure In A Multicellular Magnetotactic Prokaryote, Frank G. Rodgers, Richard P. Blakemore, Nancy A. Blakemore, Richard B. Frankel, Dennis A. Bazylinski, Denise Maratea, Christine Rodgers

Physics

A many-celled, magnetotactic, prokaryote obtained from brackish water possessed intercellular connections at points of contact between the outer membranes of constituent cells. These connections structurally resembled the "gap junctions" found in eukaryotes. Each aggregate organism consisted of 10 to 30 individual gram-negative cells containing material with the appearance of poly-𝛽-hydroxybutyrate and magnetosomes of unusual arrangement, structure and composition. The aggregate, which possessed prokaryotic-type flagella arranged at the outward surfaces of each cell, showed motility indicative of coordination between individual component cells. These results suggest that this organism is a multicellular prokaryote.

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Minimax-Optimal Stop Rules And Distributions In Secretary Problems, Theodore P. Hill, Ulrich Krengel Jan 1991

Minimax-Optimal Stop Rules And Distributions In Secretary Problems, Theodore P. Hill, Ulrich Krengel

Research Scholars in Residence

For the secretary (or best-choice) problem with an unknown number N of objects, minimax-optimal stop rules and (worst-case) distributions are derived, under the assumption that $N$ is a random variable with unknown distribution, but known upper bound n. Asymptotically, the probability of selecting the best object in this situation is of order of (log n)-1. For example, even if the only information available is that there are somewhere between 1 and 100 objects, there is still a strategy which will select the best item about one time in five.

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Electronic Properties Of Monocapped Prismane And Basket Iron-Sulphur Clusters, B. S. Snyder, M. S. Reynolds, R. H. Holm, G. C. Papaefthymiou, R. B. Frankel Jan 1991

Electronic Properties Of Monocapped Prismane And Basket Iron-Sulphur Clusters, B. S. Snyder, M. S. Reynolds, R. H. Holm, G. C. Papaefthymiou, R. B. Frankel

Physics

The ground state electronic properties of the mixed-valence clusters Fe7S6 (PEt3)4Cl3 (1), Fe6S6(PEt3)4L2 [L = Cl− (2), Br− (4), I− (5) and PhS− (6)], Fe6Se6 (PEt3)4Cl2 (3) and [Fe6S6(PEt)6]1− (9), have been investigated by magnetic susceptibility, magnetization and Mössbauer spectroscopic measurements. Cluster 1 has a (idealized C3v) monocapped prismane structure and clusters 2–6 and 9 adopt the C2v “basket” configuration based on the [Fe6 …

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Magnetic Fine Particles In Biological Systems, Dominic P.E. Dickson, Richard B. Frankel Jan 1991

Magnetic Fine Particles In Biological Systems, Dominic P.E. Dickson, Richard B. Frankel

Physics

Two examples of biological magnetic fine particles are considered: iron-storage proteins and magnetotactic bacteria. These cover many aspects of this field, including the use of well-defined biological systems for testing theoretical models, using magnetic properties to distinguish between different biological materials, producing magnetic materials by biological processes, and using optimised biological magnetic systems as a guide to the production of synthetic magnetic materials.

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A Nonstandard Delta Function, Todor D. Todorov Dec 1990

A Nonstandard Delta Function, Todor D. Todorov

Mathematics

We prove that the Dirac delta distribution has a kernel in the class of the pointwise nonstandard functions.

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Controlled Biosynthesis Of Greigite (Fe3S4) In Magnetotactic Bacteria, Brigid R. Heywood, Dennis A. Bazylinski, Anthony J. Garratt-Reed, Stephen Mann, Richard B. Frankel Nov 1990

Controlled Biosynthesis Of Greigite (Fe3S4) In Magnetotactic Bacteria, Brigid R. Heywood, Dennis A. Bazylinski, Anthony J. Garratt-Reed, Stephen Mann, Richard B. Frankel

Physics

No abstract provided.

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Mossbauer Spectroscopy Of Fe2+ Binding To Apo And Holo Mammalian Ferritin, Richard B. Frankel, Gerald D. Watt, Georgia C. Papaefthymiou Oct 1990

Mossbauer Spectroscopy Of Fe2+ Binding To Apo And Holo Mammalian Ferritin, Richard B. Frankel, Gerald D. Watt, Georgia C. Papaefthymiou

Physics

The anaerobic binding of Fe2+ to apo and holo Mammalian ferritin has been studied in the pH range from 6.0 to 10.0. Mossbauer spectroscopy of samples in which the added Fe 2+ is enriched in Fe-57 shows that the Fe2+ ions bind to the ferritin core and exchange electrons with Fe3+ ions in the core.

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Review Of Verification And Compliance: A Problem Solving Approach By Michael Krepon & Mary Umberger, Toward A Comprehensive Test Ban By Steve Fetter, And Making Space Defense Work: Must The Superpowers Cooperate? By A. Fenner Milton, M. Scott Davis, & John Parmentola, David W. Hafemeister Sep 1990

Review Of Verification And Compliance: A Problem Solving Approach By Michael Krepon & Mary Umberger, Toward A Comprehensive Test Ban By Steve Fetter, And Making Space Defense Work: Must The Superpowers Cooperate? By A. Fenner Milton, M. Scott Davis, & John Parmentola, David W. Hafemeister

Physics

No abstract provided.

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Magnetic Polarity Fractions In Magnetotactic Bacterial Populations Near The Geomagnetic Equator, F. F. Torres De Araujo, F. A. Germano, L. L. Goncalves, M. A. Pires, Richard B. Frankel Aug 1990

Magnetic Polarity Fractions In Magnetotactic Bacterial Populations Near The Geomagnetic Equator, F. F. Torres De Araujo, F. A. Germano, L. L. Goncalves, M. A. Pires, Richard B. Frankel

Physics

The relative numbers of North-seeking and South-seeking polarity types in natural populations of magnetotactic bacteria were determined at sites on the coast of Brazil. These sites were South of the geomagnetic equator and had upward geomagnetic inclinations of 1–12°. For upward inclinations >6°, South-seeking cells predominated over North-seeking cells by more than a factor of 10. For upward inclinations

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Intercellular Structure In A Many-Celled Magnetotactic Prokaryote, Frank G. Rodgers, Richard P. Blakemore, Nancy A. Blakemore, Richard B. Frankel, Dennis A. Bazylinski, Denise Maratea, Christine Rodgers Jun 1990

Intercellular Structure In A Many-Celled Magnetotactic Prokaryote, Frank G. Rodgers, Richard P. Blakemore, Nancy A. Blakemore, Richard B. Frankel, Dennis A. Bazylinski, Denise Maratea, Christine Rodgers

Physics

A many-called magnetotactic prokaryote obtained from brackish water was observed to possess intercellular connections at points of contact between the outer membranes of constituent cells. Each aggregate organism consisted of 10 to 30 individual Gram-negative cells containing material with the appearance of poly-β-hydroxybutyrate and magnetosomes of unusual arrangement, structure and composition. The aggregate, which possessed prokaryotic-type flagella arranged at the outwards surfaces of each cell, showed motility indicative of co-ordination between individual component cells. These results suggest that this organism could be a multicellular prokaryote.

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Lifted P-Adic Homology With Compact Supports Of The Weierstrass Family And Its Zeta Endomorphism, Goro Kato Jun 1990

Lifted P-Adic Homology With Compact Supports Of The Weierstrass Family And Its Zeta Endomorphism, Goro Kato

Mathematics

The relations among the generators for the lifted p-adic homology with compact supports of the various subfamilies of the Weierstrass family in characteristic p > 0 (p ≠ 2, 3) are explicitly given in Section 2. Then, the universal coefficient spectral sequence and the zeta endomorphism in Section 3 enable one to compute explicitly the lifted p-adic homology with compact supports of all fibres, including all the elliptic curves and all their singular degenerations in the family.

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Review Of Atoms For Peace And War, 1953-1961: Eisenhower And The Atomic Energy Commission By Richard G. Hewlett And Jack M. Holl, David W. Hafemeister Jun 1990

Review Of Atoms For Peace And War, 1953-1961: Eisenhower And The Atomic Energy Commission By Richard G. Hewlett And Jack M. Holl, David W. Hafemeister

Physics

No abstract provided.

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Visual Protocol Collection For The Enhancement Of The Radiological Diagnostic Process, Erika Rogers, Ronald C. Arkin, M. Baron, N. Ezquerra, E. Garcia May 1990

Visual Protocol Collection For The Enhancement Of The Radiological Diagnostic Process, Erika Rogers, Ronald C. Arkin, M. Baron, N. Ezquerra, E. Garcia

Computer Science and Software Engineering

This paper describes the Observation Phase of a research project that is designed to explore the nature of visual radiological diagnosis. It is concerned with the collection and analysis of visual protocol data in an effort to determine the salient image features that may impact on the different stages of the diagnostic process, both perceptual and cognitive. These features, once identified, will lead to the formulation of image enhancement hypotheses and the development of knowledge-based visualization techniques to assist the radiological diagnostic process.

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Changes To Simulated Fire Behaviour And Societal Benefits After Two Levels Of Thinning In A Mixed-Conifer Wildland-Urban Interface Community, Christopher Dicus Apr 1990

Changes To Simulated Fire Behaviour And Societal Benefits After Two Levels Of Thinning In A Mixed-Conifer Wildland-Urban Interface Community, Christopher Dicus

Natural Resources Management and Environmental Sciences

Potential fire behaviour and various societal benefits (air pollution removal, carbon sequestration, and stormwater runoff) were quantified in a California Sierra mixed-conifer forest in (a) untreated conditions, (b) after removing all understorey trees dbh, and (c) after thinning 50% of the stand's total basal area. Potential fire behaviour was modelled under constant conditions near a hypothetical development by the FARSITE fire behaviour and growth simulator and societal benefits were calculated by CITY green, both GIS-based software applications. Results showed that fire behaviour was considerably moderated by both thinning treatments. Modelled societal benefits, however, were largely unaffected by either treatment, which …

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Structure And Morphology Of Magnetite Anaerobically-Produced By A Marine Magnetotactic Bacterium And A Dissimilatory Iron-Reducing Bacterium, N. H. C. Sparks, Stephen Mann, D. A. Bazylinski, D. R. Lovley, H. W. Jannasch, Richard B. Frankel Apr 1990

Structure And Morphology Of Magnetite Anaerobically-Produced By A Marine Magnetotactic Bacterium And A Dissimilatory Iron-Reducing Bacterium, N. H. C. Sparks, Stephen Mann, D. A. Bazylinski, D. R. Lovley, H. W. Jannasch, Richard B. Frankel

Physics

Intracellular crystals of magnetite synthesized by cells of the magnetotactic vibroid organism, MV-1, and extracellular crystals of magnetite produced by the non-magnetotactic dissimilatory iron-reducing bacterium strain GS-15, were examined using high-resolution transmission electron microscopy, electron diffraction and 57Fe Mo¨ssbauer spectroscopy. The magnetotactic bacterium contained a single chain of approximately 10 crystals aligned along the long axis of the cell. The crystals were essentially pure stoichiometric magnetite. When viewed along the crystal long axis the particles had a hexagonal cross-section whereas side-on they appeared as rectangules or truncated rectangles of average dimension, 53 × 35 nm. These findings are explained …

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Cost-Effective Wilderness Fire Management: A Case Study In Southern California, Christian A. Childers, Douglas D. Piirto Mar 1990

Cost-Effective Wilderness Fire Management: A Case Study In Southern California, Christian A. Childers, Douglas D. Piirto

Natural Resources Management and Environmental Sciences

Federal wilderness fire management policies have been scrutinized since the catastrophic fires in the Greater Yellowstone Area in 1988. While wilderness tire management objectives are still aimed at recreating natural fire regimes, all USDA Forest Service fire management programs must be cost-effective. Since current Forest Service economic analyses do not fully represent the value of fire to wilderness, a cost-effectiveness analysis was developed to compare wilderness fire management options. The analytical procedure is briefly reviewed, illustrated through a southern California case study and case study results are discussed. These results suggest that containment of some tires may be more cost-effective …

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A Generalization Of Levy's Concentration-Variance Inequality, R. D. Foley, Theodore P. Hill, M. C. Spruill Mar 1990

A Generalization Of Levy's Concentration-Variance Inequality, R. D. Foley, Theodore P. Hill, M. C. Spruill

Research Scholars in Residence

Sharp lower bounds are found for the concentration of a probability distribution as a function of the expectation of any given convex symmetric function φ. In the case φ(x)=(x-c)2, where c is the expected value of the distribution, these bounds yield the classical concentration-variance inequality of Lévy. An analogous sharp inequality is obtained in a similar linear search setting, where a sharp lower bound for the concentration is found as a function of the maximum probability swept out from a fixed starting point by a path of given length.

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