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Articles 2281 - 2310 of 2507

Full-Text Articles in Physical Sciences and Mathematics

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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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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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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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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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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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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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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Biomineralization Of Ferrimagnetic Greigite (Fe3s4) And Iron Pyrite (Fes2) In A Magnetotactic Bacterium, Stephen Mann, Nicholas C.H. Sparks, Richard B. Frankel, Dennis A. Bazylinski, Holger W. Jannasch Jan 1990

Biomineralization Of Ferrimagnetic Greigite (Fe3s4) And Iron Pyrite (Fes2) In A Magnetotactic Bacterium, Stephen Mann, Nicholas C.H. Sparks, Richard B. Frankel, Dennis A. Bazylinski, Holger W. Jannasch

Physics

The ability of magnetotactic bacteria to orientate and navigate along geomagnetic field lines is due to the controlled intracellular deposition of the iron oxide mineral, magnetite (Fe3O4)1,2. The function and crystal chemical specificity of this mineral has been considered to be unique amongst the prokaryotes3. Moreover, the bacterial production of magnetite may represent a significant contribution to the natural remanent magnetism of sediments4,5. Here we report, the intracellular biomineralization of single crystals of the ferrimagnetic iron sulphide, greigite (Fe3S4), in a multicellular magnetotactic bacterium common in …

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Multicolored Simon Newcomb Problems, Don Rawlings Jan 1990

Multicolored Simon Newcomb Problems, Don Rawlings

Mathematics

Recent progress made by Desarmenien and Foata in the area of permutation statistics indirectly points out a certain gap in the theory of sequence enumeration. The remedy of the situation lies in the consideration of some colorful extensions of the Simon Newcomb problem.

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Iron Compounds In Brazilian Pre-Columbian Pigments Identified By 57Fe Mossbauer Spectroscopy And X-Ray Powder Diffraction, F. F.T. De Araujo, M. A.B. De Araujo, R. B. Frankel, G. C. Papaefthymiou, V. W. Vieira Jan 1990

Iron Compounds In Brazilian Pre-Columbian Pigments Identified By 57Fe Mossbauer Spectroscopy And X-Ray Powder Diffraction, F. F.T. De Araujo, M. A.B. De Araujo, R. B. Frankel, G. C. Papaefthymiou, V. W. Vieira

Physics

Mossbauer spectroscopy and X-ray powder diffraction have been used to identify iron compounds in pre-Columbian pigments, probably used for art decorating, collected from the oldest archaeological site of Early Man presently known in American at Sao Raimundo Nonato, in Northeastern Brazil. The iron compounds were identified as being alpha-Fe203 (haematite) with full Morin transition supressed and small particles of alpha-FeOOH (goethite).

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Prophet Inequalities For Parallel Processes, Theodore P. Hill, D. P. Kennedy Nov 1989

Prophet Inequalities For Parallel Processes, Theodore P. Hill, D. P. Kennedy

Research Scholars in Residence

Generalizations of prophet inequalities for single sequences are obtained for optimal stopping of several parallel sequences of independent random variables. For example, if {Xi, j, 1 ≤ i ≤ n, 1 ≤ j < ∞} are independent non-negative random variables, then E(sup Xi,j) ≤ (n + 1) max sup {E(Xi,t): t is a stop rule for Xi,1, Xi,2, ...} and this bound is best possible. Applications are made to comparisons of the optimal expected returns of various alternative methods of stopping of parallel processes.

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Optimal-Partitioning Inequalities In Classification And Multi-Hypotheses Testing, Theodore P. Hill, Y. L. Tong Sep 1989

Optimal-Partitioning Inequalities In Classification And Multi-Hypotheses Testing, Theodore P. Hill, Y. L. Tong

Research Scholars in Residence

Optimal-partitioning and minimax risk inequalities are obtained for the classification and multi-hypotheses testing problems. Best possible bounds are derived for the minimax risk for location parameter families, based on the tail concentrations and Levy concentrations of the distributions. Special attention is given to continuous distributions with the maximum likelihood ratio property and to symmetric unimodal continuous distributions. Bounds for general (including discontinuous) distributions are also obtained.

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A Comparison Of Magnetite Particles Produced Anaerobically By Magnetotactic And Dissimilatory Iron‐Reducing Bacteria, Bruce M. Moskowitz, Richard B. Frankel, Dennis A. Bazylinski, Holger W. Jannasch, Derek R. Lovley Jul 1989

A Comparison Of Magnetite Particles Produced Anaerobically By Magnetotactic And Dissimilatory Iron‐Reducing Bacteria, Bruce M. Moskowitz, Richard B. Frankel, Dennis A. Bazylinski, Holger W. Jannasch, Derek R. Lovley

Physics

We compare the magnetic properties of fine‐grained magnetite produced by two newly isolated anaerobic bacteria, a magnetotactic bacterium (MV‐1) and a dissimilatory iron‐reducing bacterium (GS‐15). Although room‐temperature magnetic properties are generally different between the two microorganisms, MV‐1 and GS‐15 magnetites can be most easily distinguished by the temperature variation of saturation remanence obtained at liquid helium temperatures. Magnetite produced by MV‐1 displays a sharp discontinuity in intensity at 100 K related to the Verwey transition. Magnetite produced by GS‐15 displays a gradual decrease in intensity with temperature due to the progressive unblocking of magnetization. The differing behavior is due exclusively …

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Method For Automatic Level Matching In A Local Network, In Particular A Multicomputer Arrangement, Comprising A Bus System Having Lightwaves Guides, For The Purpose Of Collision Recognition, Hans Thinschmidt, Franz J. Kurfess Feb 1989

Method For Automatic Level Matching In A Local Network, In Particular A Multicomputer Arrangement, Comprising A Bus System Having Lightwaves Guides, For The Purpose Of Collision Recognition, Hans Thinschmidt, Franz J. Kurfess

Computer Science and Software Engineering

A method is disclosed for automatic level matching in a local network, particularly for a multicomputer arrangement, comprising an optical bus system, for the purpose of collision recognition. Given a required level matching, the process is executed such that a fundamental phase is provided in which level matching devices respectively individually assigned to the computers are synchronized with one another. A first matching phase is provided in which all level matching devices simultaneously execute a process for setting a reference voltage to the lowest received level, whereby the sum of all attenuation components of the signal path at the receiving …

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Alexander's Subbase Lemma, Todor D. Todorov, S. Salbany Jan 1989

Alexander's Subbase Lemma, Todor D. Todorov, S. Salbany

Mathematics

No abstract provided.

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