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Faculty Publications

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Articles 3541 - 3570 of 3651

Full-Text Articles in Physical Sciences and Mathematics

Absence Of Minimum Metallic Conductivity In Gd(3-X)Vxs4 At Very Low Temperature And Evidence For A Coulomb Gap, S. Washburn, Richard A. Webb, S. Von Molnar, F. Holtzberg Nov 1984

Absence Of Minimum Metallic Conductivity In Gd(3-X)Vxs4 At Very Low Temperature And Evidence For A Coulomb Gap, S. Washburn, Richard A. Webb, S. Von Molnar, F. Holtzberg

Faculty Publications

Gd(3-x)vxS4 provides a convenient analog of a compensated semiconductor in which, for x≃0.3, the mobility edge can be tuned smoothly through the Fermi energy by the application of a magnetic field. The results of a search for a minimum metallic conductivity demonstrate that, down to T=6 mK, the metal-insulator transition is smooth. In the insulating regime, the temperature dependence of the conductivity was more consistent with the theory of mutual interactions than with the theory of pure localization.

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Six Copyright Theories For The Protection Of Computer Object Programs, I. Trotter Hardy Oct 1984

Six Copyright Theories For The Protection Of Computer Object Programs, I. Trotter Hardy

Faculty Publications

No abstract provided.

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Magnetoresistance Of Small, Quasi-One-Dimensional, Normal-Metal Rings And Lines, C. P. Umbach, S. Washburn, R. B. Laibowitz, Richard A. Webb Oct 1984

Magnetoresistance Of Small, Quasi-One-Dimensional, Normal-Metal Rings And Lines, C. P. Umbach, S. Washburn, R. B. Laibowitz, Richard A. Webb

Faculty Publications

The magnetoresistance of sub-0.4-μm-diam Au and Au60Pd40 rings was measured in a perpendicular magnetic field at temperatures as low as 5 mK in search of simple, periodic resistance oscillations that would be evidence of flux quantization in normal-metal rings. However, instead of simple oscillations, a very complex structure developed in the magnetoresistance at low temperatures. Fourier analysis of all the data did not reveal convincing evidence for flux quantization in the rings. Complex structure similar to that observed in the rings was also found in the magnetoresistance of short, narrow, Au and Au60Pd …

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Characterization Of Glycated Proteins By 13C Nmr Spectroscopy, Carolyn I. Neglia, Helga J. Cohen, Albert R. Garber, Suzanne R. Thorpe, John W. Baynes Sep 1984

Characterization Of Glycated Proteins By 13C Nmr Spectroscopy, Carolyn I. Neglia, Helga J. Cohen, Albert R. Garber, Suzanne R. Thorpe, John W. Baynes

Faculty Publications

13C NMR spectroscopy has been used to characterize Amadori (ketoamine) adducts formed by reaction of [2-13C]glucose with free amino groups of protein. The spectra of glycated proteins were acquired in phosphate buffer at pH 7.4 and were interpreted by reference to the spectra of model compounds, N alpha-formyl-N epsilon-fructose-lysine and glycated poly-L-lysine (GlcPLL). The anomeric carbon region of the spectrum (approximately 90-105 ppm) of glycated cytochrome c was superimposable on that of N alpha-formyl-N epsilon-fructose-lysine, and contained three peaks characteristic of the alpha- and beta-furanose and beta-pyranose anomers of Amadori adducts to peripheral lysine residues on protein (pK alpha approximately …

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Deformation And Linkage Of Gorenstein Algebras, Andrew R. Kustin, Matthew Miller Aug 1984

Deformation And Linkage Of Gorenstein Algebras, Andrew R. Kustin, Matthew Miller

Faculty Publications

General double linkage of Gorenstein algebras is defined. Rigidity, genericity, and regularity up to codimension six all pass across general double linkage. Rigid strongly unobstructed codimension four Gorenstein algebras which lie in different Herzog classes are produced.

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The Expectation Of Success Using A Monte Carlo Factoring Method – Some Statistics On Quadratic Class Numbers, Duncan A. Buell Jul 1984

The Expectation Of Success Using A Monte Carlo Factoring Method – Some Statistics On Quadratic Class Numbers, Duncan A. Buell

Faculty Publications

A method has been proposed for factoring an integer N by using the structure of the class groups of quadratic fields of radicand – kN for various small multipliers k. We discuss the method and an implementation of the method, and various theoretical questions which have an impact on the practical use of the method in factoring. Some of the theoretical questions relate to the nature of class numbers and class groups; we present extensive statistical results on the class numbers and class groups of imaginary quadratic fields.

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On The Differentiability Of Functions In Rn, Ronald A. Devore, Robert C. Sharpley Jun 1984

On The Differentiability Of Functions In Rn, Ronald A. Devore, Robert C. Sharpley

Faculty Publications

No abstract provided.

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Isotropy Group Description Of A Phase Transition In Nano3, W. Scott Stornetta, Dorian M. Hatch Jun 1984

Isotropy Group Description Of A Phase Transition In Nano3, W. Scott Stornetta, Dorian M. Hatch

Faculty Publications

Predictions of the possible post-transition symmetries of an R 3c zone center continuous phase transition are made using recent extensions of the Landau theory. The Landau theory is summarized and direct group theoretical methods are applied to the R 3c phase. General techniques for solving systems of nonlinear polynomial equations are reviewed and these techniques are applied to the minimization of the free energy F for the aforementioned possible symmetries. The results of the direct methods and the minimization procedures are shown to be compatible. It is shown that the transition to R 3c in NaNO3 is consistent with the …

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Error-Bounds For Gaussian Quadrature And Weighted-L1 Polynomial Approximation, Ronald A. Devore, L R. Scott Apr 1984

Error-Bounds For Gaussian Quadrature And Weighted-L1 Polynomial Approximation, Ronald A. Devore, L R. Scott

Faculty Publications

Error bounds for Gaussian quadrature are given in terms of the number of quadrature points and smoothness properties of the function whose integral is being approximated. An intermediate step involves a weighted-L' polynomial approximation problem which is treated in a more general context than that specifically required to bound the Gaussian quadrature error.

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Weak Localization Of Two-Dimensional Conduction Holes, S. Washburn, Richard A. Webb, E. E. Mendez, L. L. Chang, L. Esaki Mar 1984

Weak Localization Of Two-Dimensional Conduction Holes, S. Washburn, Richard A. Webb, E. E. Mendez, L. L. Chang, L. Esaki

Faculty Publications

We report transport measurements which we interpret as weak localization of two-dimensional conduction holes in a GaSb-InAs-GaSb quantum-well structure. This system is unique in that it has parallel conduction channels containing both holes and electrons. The longitudinal resistance of the sample was measured for temperatures between 0.006 and 25 K; the magnetoresistance was measured in a perpendicular magnetic field. Weak localization of the holes was indicated by negative magnetoresistance and by a large logarithmic correction to the conductivity.

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Velocity Measurements Of Humans By Computers, J. B. Rafert, R. C. Nicklin Jan 1984

Velocity Measurements Of Humans By Computers, J. B. Rafert, R. C. Nicklin

Faculty Publications

Distance and time, two fundamental quantities, are discussed early in most introductory physics courses. By dividing a change in distance by time to get velocity, and by dividing a change in velocity by time to get acceleration, two more important quantities result. With these the real world of automobiles and jet planes and applications of Newton's second law is available for interpretation from an analytical point of view. In order to get students thinking reliably about these important ideas it seems important to have direct measurements of distance and time over short enough intervals to talk sensibly about "instantaneous" velocities.

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The Synthesis And Characterization Of Some Fluoride Perovskites, An Undergraduate Experiment In Solid State Chemistry, Richard H. Langley, Colleen K. Schmitz, Maureen B. Langley Jan 1984

The Synthesis And Characterization Of Some Fluoride Perovskites, An Undergraduate Experiment In Solid State Chemistry, Richard H. Langley, Colleen K. Schmitz, Maureen B. Langley

Faculty Publications

In light of the increasing importance of solid state chemistry, an experiment dealing with at least some aspects of this rapidly expanding area should he included in advanced chemistry laboratories. Herein is described one of the experiments that we have developed to meet this need. This experiment was designed for a senior level integrated chemistry lab taken by all our chemistry majors. Normally six to eight hours are needed to complete this experiment. This experiment deals with the synthesis and characterization of a perovskite. Perovskites were chosen because compounds with this structure are important in solid state technology, and since …

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Cenozoic Tectonic History Of The Sierra De Perija, Venezuela- Colombia, And Adjacent Basins, James N. Kellogg Jan 1984

Cenozoic Tectonic History Of The Sierra De Perija, Venezuela- Colombia, And Adjacent Basins, James N. Kellogg

Faculty Publications

The four major Cenozoic tectonic phases in the Sierra de Perija and adjacent basins are the early Eocene tectonic phase, the middle Eocene Caribbean orogeny, the late Oligocene phase, and the late Miocene to present Andean orogeny. Ages of unconformities associated with particularly rapid regional uplift during these phases are early Eocene (53 m.y.), middle Eocene (45 m.y.), late Oligocene (25 m.y.), and Pliocene (3 m.y.). Northwest-southeast compression may have commenced in the Perija and the Maracaibo Basin as early as the early Eocene. By the early Eocene the Macoa-Totumo arch had begun to to form during intense alpine-type folding …

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13C Nmr Investigation Of Nonenzymatic Glucosylation Of Protein, Carolyn I. Neglia, Helga J. Cohen, Albert R. Garber, Paul D. Ellis, Suzanne R. Thorpe, John W. Baynes Dec 1983

13C Nmr Investigation Of Nonenzymatic Glucosylation Of Protein, Carolyn I. Neglia, Helga J. Cohen, Albert R. Garber, Paul D. Ellis, Suzanne R. Thorpe, John W. Baynes

Faculty Publications

Nonenzymatic glucosylation of protein is initiated by the reversible condensation of glucose in its open chain form with the amino groups on the protein. The initial product is an aldimine (Schiff base) which cyclizes to the glycosylamine derivative. The aldimine can undergo a slow Amadori rearrangement to yield the relatively stable ketoamine adduct which is structurally analogous to fructose. 13C NMR has been used to characterize these early products of nonenzymatic glucosylation, using RNase A as a model protein. C-1 of the beta-pyranose anomer of the glycosylamine was identified at 88.8 ppm in the spectrum of RNase glucosylated approximately 1:1 …

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On First Countable, Countably Compact Spaces. I: (Omega-1,Omega-1-Star)-Gaps, Peter J. Nyikos, Jerry E. Vaughan Oct 1983

On First Countable, Countably Compact Spaces. I: (Omega-1,Omega-1-Star)-Gaps, Peter J. Nyikos, Jerry E. Vaughan

Faculty Publications

No abstract provided.

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Magnetic Field Behavior Of A Josephson-Junction Array: Two-Dimensional Flux Transport On A Periodic Substrate, Richard A. Webb, Richard F. Voss, G. Grinstein, P. M. Horn Aug 1983

Magnetic Field Behavior Of A Josephson-Junction Array: Two-Dimensional Flux Transport On A Periodic Substrate, Richard A. Webb, Richard F. Voss, G. Grinstein, P. M. Horn

Faculty Publications

This Letter reports measurements down to 3 mK of the magnetic field dependence of the resistance and critical current of a weakly coupled periodic array of Josephson junctions. Below 700 mK the resistance is an oscillatory function of field. The temperature dependence of the resistance for integral numbers of flux quanta per cell suggests the existence of a Kosterlitz-Thouless transition involving the unbinding of defects in the flux lattice.

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Nonenzymatic Glucosylation And Glucose-Dependent Cross-Linking Of Protein, Albert S. Eble, Suzanne R. Thorpe, John W. Baynes Aug 1983

Nonenzymatic Glucosylation And Glucose-Dependent Cross-Linking Of Protein, Albert S. Eble, Suzanne R. Thorpe, John W. Baynes

Faculty Publications

A model system using RNase A has been established for studying the nonenzymatic glucosylation and glucose-dependent cross-linking of protein (Maillard reaction) under physiological conditions in vitro. The rate of glucosylation of RNase was first order in glucose. Glucosylation was accompanied by a comparable decrease in primary amino groups in the protein and lysine recoverable by amino acid analysis. Analysis of glucosylation reaction mixtures by sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the presence of mercaptoethanol revealed the time-dependent formation of RNase dimer and trimer. The polymerization reaction was mixed order with respect to glucose concentration, but was approximately first order with …

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Unification Of Ernst-Equation Backlund Transformations Using A Modified Wahlquist-Estabrook Technique; Wahlquist-Estabrook, B. Kent Harrison Aug 1983

Unification Of Ernst-Equation Backlund Transformations Using A Modified Wahlquist-Estabrook Technique; Wahlquist-Estabrook, B. Kent Harrison

Faculty Publications

The three known Backlund transformations for the Ernst equation are derived using a modification of the Wahlquist-Estabrook prolongation procedure. The modification requires that the equation to be studied be cast into a set of differential forms and their exterior derivatives, such that all coefficients are constant (a "CC ideal''). Analysis of the resulting equations produces 16 solutions composed of the three basic transformations combined with identity and other essentially trivial transformations. The group structure of the transformations is discussed. A Backlund transformation (already known) for the Ernst-Maxwell equations can be found by the same method. Promising generalizations are mentioned.

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Fluorine, Richard H. Langley, Larry Welch Jan 1983

Fluorine, Richard H. Langley, Larry Welch

Faculty Publications

Considering the long time in which fluorine compounds have been used it seems rather surprising that it was not isolated as an element until 1886. This long delay was not due to lack of effort, but to the reactivity of fluorine and the hazards of working with it and many of its compounds.

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Sources Of Nosocomial Infections In Immunocompromised Patients (Letter), B. Burt Gerstman Jan 1983

Sources Of Nosocomial Infections In Immunocompromised Patients (Letter), B. Burt Gerstman

Faculty Publications

No abstract provided.

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Computing As A Part Of A P.H.D Students Education: A Position Paper, Andrew D. Bailey, Rayman D. Meservy Jan 1983

Computing As A Part Of A P.H.D Students Education: A Position Paper, Andrew D. Bailey, Rayman D. Meservy

Faculty Publications

The skills and abilities associated with computer literacy are becoming required tools for accounting Ph.D. students. Not only are new doctoral students entering Ph.D. programs with better skills, they are also applying these skills more on a day to day basis. This paper presents a brief discussion of a number of issues associated with computer use and computer literacy in general. The paper also presents several aspects of the Ph.D. program at the University of Minnesota and how computers are affecting the program.

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High-Temperature Battery Calorimeter, L. D. Hansen, R. H. Hart, D. M. Chen, H. F. Gibbard Apr 1982

High-Temperature Battery Calorimeter, L. D. Hansen, R. H. Hart, D. M. Chen, H. F. Gibbard

Faculty Publications

A battery calorimeter was built for the measurement of thermal energy generation of high-temperature lithium–aluminum/iron sulfide battery cells, which are under development for electric vehicle propulsion and other energy storage applications. The calorimeter was designed with a temperature range of 400˚–500˚C, a detection limit of 1 mW, and an upper limit of heat flow of 50 W. The results of measurements on 200-Ah LiAl/FeS cells were in excellent agreement with the predictions of thermodynamic calculations based on precise measurements of the total cell polarization and the temperature coefficient of the emf. Details of the construction and operation principles of this …

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A Hidden-Line Algorithm For Hyperspace, Robert P. Burton, David R. Smith Feb 1982

A Hidden-Line Algorithm For Hyperspace, Robert P. Burton, David R. Smith

Faculty Publications

An object-space hidden-line algorithm for higher-dimensional scenes has been designed and implemented. Scenes consist of convex hulls of any dimension, each of which is compared against the edges of all convex hulls not eliminated by a hyperdimensional clipper, a depth test after sorting and a minimax text. Hidden and visible elements are determined in accordance with the dimensionality of the selected viewing hyperspace. When shape alone is the attribute of interest, hidden-line elimination need be performed only in that hyperspace. The algorithm is of value in the production of shadows of hyperdimensional models, including but not limited to four-dimensional space-time …

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Conductance In Restricted-Dimensionality Accumulation Layers, A. B. Fowler, A. Hartstein, Richard A. Webb Jan 1982

Conductance In Restricted-Dimensionality Accumulation Layers, A. B. Fowler, A. Hartstein, Richard A. Webb

Faculty Publications

Conductance has been studied in metal-oxide-silicon field-effect transistor accumulation-layer samples in which it is possible to constrict the channel to small dimensions both perpendicular to the surface and perpendicular to the channel. A temperature-dependent conductance σ=σ0exp[-(T0/T)n] is observed, where n=1/2 for small channel widths and n=1/3 for larger channel widths. It is believed that this behavior arises from a transition from one-dimensional to two-dimensional variable-range hopping in the sample.

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Classroom Demonstration Of Sunspots, Thomas O. Callaway, Harry D. Downing, Glen T. Clayton Jan 1982

Classroom Demonstration Of Sunspots, Thomas O. Callaway, Harry D. Downing, Glen T. Clayton

Faculty Publications

No abstract provided.

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Physical Science Workshop Course For Elementary Teachers, Glen T. Clayton, Harry D. Downing, Thomas O. Callaway Jan 1982

Physical Science Workshop Course For Elementary Teachers, Glen T. Clayton, Harry D. Downing, Thomas O. Callaway

Faculty Publications

Science for elementary school grades K-6 varies somewhat in content from one textbook series to another, but it is fairly common that 40-60% of the material covered is directly related to physics. These texts suggest that certain learning activities such as experiments, demonstrations, and observations be carried out by the teacher and the class. Often the apparatus for a learning activity is to be constructed from simple, readily available materials. The typical elementary school teacher has had little experience in performing experiments and is often frustrated in his/her attempts at carrying out the suggested learning activity. To meet this need …

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Bond Hybrids And The Structures Of The Lanthanide Metals [Abstract], Richard H. Langley Jan 1982

Bond Hybrids And The Structures Of The Lanthanide Metals [Abstract], Richard H. Langley

Faculty Publications

The ideas developed by Altmann, Coulson, and Hume-Rothery to relate bond hybrids to metal structures are extended to include treatment of the f orbitals. A discussion of the possible hybrids along with their application to the lanthanide metals will be considered.

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Some Comments On The Erdos-Renyl Law And A Theorem Of Shepp, James Lynch Jan 1982

Some Comments On The Erdos-Renyl Law And A Theorem Of Shepp, James Lynch

Faculty Publications

We show that the finiteness of the moment generating function is necessary for the finiteness of the lim sup of the moving averages considered by Shepp (1964). This also implies that the same must be true for the Erdos-Renyi law of large numbers.

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Metrizability And The Frechet-Urysohn Property In Topological Groups, Peter J. Nyikos Dec 1981

Metrizability And The Frechet-Urysohn Property In Topological Groups, Peter J. Nyikos

Faculty Publications

A question of Arhangel'skii, whether weakly first countable topological groups are metrizable, is answered in two ways: if the Hausdorff axiom is assumed, the answer is yes, but in general a weakly first countable topological group need not be pseudometrizable. The former result is obtained as a corollary of a more general sufficient condition for a sequential group to be Fr&chet-Urysohn. A general necessary and sufficient condition for a sequential group to be Frechet-Urysohn is given, and a number of questions are raised. Examples are given to show in what respect the theorems of the paper are the "best possible".

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Macroscopic Quantum Tunneling In 1-Μm Nb Josephson Junctions, Richard F. Voss, Richard A. Webb Jul 1981

Macroscopic Quantum Tunneling In 1-Μm Nb Josephson Junctions, Richard F. Voss, Richard A. Webb

Faculty Publications

The probability distributions for switching out of the superconducting state of low-cur-rent-density 1-μm Nb Josephson junctions with capacitance ≈ 0.1 pF have been measured as a function of temperature T down to 3 mK. Below 100 mK the distribution widths become independent of T. The results are in excellent agreement with predictions for the quantum tunneling of the (macroscopic) junction phase that include the reduction of tunneling rates due to dissipation.

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