Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

1995

Discipline
Institution
Keyword
Publication
Publication Type
File Type

Articles 1501 - 1530 of 2193

Full-Text Articles in Physical Sciences and Mathematics

Sar Models For Futile Metabolism: One-Electron Reduction Of Quinones, Phenols And Nitrobenzenes, Steven P. Bradbury, Ovanes Mekenyan, G. D. Veith, N. Zaharieva Jan 1995

Sar Models For Futile Metabolism: One-Electron Reduction Of Quinones, Phenols And Nitrobenzenes, Steven P. Bradbury, Ovanes Mekenyan, G. D. Veith, N. Zaharieva

Steven P. Bradbury

Benzoquinones, naphthoquinones and aziridinylbenzoquinones, can be reduced by flavoproteins to semiquinones that react with molecular oxygen to form superoxide anion with the subsequent regeneration of the parent compounds. This redox cycling, a form of futile metabolism, produces reactive oxygen species and depletes the reducing equivalents of cells without concomitant energy production. The ability of a toxicant to redox cycle is related to its one-electron reduction potential, and this study attempted to estimate reduction potential from structure using semi-empirical quantum chemical models for a diverse set of chemicals. The results of this study suggest that one-electron reduction potentials, within structural classes …

Go to article

Quantitative Structure-Activity Relationships And Ecological Risk Assessment: An Overview Of Predictive Aquatic Toxicology Research, Steven P. Bradbury Jan 1995

Quantitative Structure-Activity Relationships And Ecological Risk Assessment: An Overview Of Predictive Aquatic Toxicology Research, Steven P. Bradbury

Steven P. Bradbury

In the field of aquatic toxicology, quantitative structure-activity relationships (QSARs) have developed as scientifically credible tools for predicting the toxicity of chemicals when little or no empirical data are available. A fundamental understanding of toxicological principles has been considered an important component to the acceptance and application of QSAR approaches as biologically relevant in ecological risk assessments. As a consequence, there has been an evolution of QSAR development and application from that of a chemical-class perspective to one that is more consistent with assumptions regarding modes of toxic action. In this review, techniques to assess modes of toxic action from …

Go to article

Use Of Knowledge Bases And Qsars To Estimate The Relative Ecological Risk Of Agrichemicals: A Problem Formulation Exercise, Steven P. Bradbury, C. L. Russom, A. R. Carlson Jan 1995

Use Of Knowledge Bases And Qsars To Estimate The Relative Ecological Risk Of Agrichemicals: A Problem Formulation Exercise, Steven P. Bradbury, C. L. Russom, A. R. Carlson

Steven P. Bradbury

Ecological risk assessments can be used to establish the likelihood that an adverse effect will result from exposure to one or more chemicals. When evaluating contaminated sites with many chemicals present, risk assessors must grapple with the problem of quickly identifying the chemicals that are most likely to be of concern, based on effect and exposure assessment information. Many times data gaps exist and the risk assessor is left with decisions on which models to use to estimate the parameter of concern. In the present paper, a procedure is presented for ranking agrichemicals, utilizing the ASTER (ASsessment Tools for the …

Go to article

Commensurate And Incommensurate Ordering Tendencies In The Ternary Fcc Cu-Ni-Zn System, J. D. Althoff, Duane D. Johnson, F. J. Pinski Jan 1995

Commensurate And Incommensurate Ordering Tendencies In The Ternary Fcc Cu-Ni-Zn System, J. D. Althoff, Duane D. Johnson, F. J. Pinski

Duane D. Johnson

We show that Fermi-surface (FS) nesting drives both the incommensurate and commensurate ordering tendencies of the fcc ternary Cu-Ni-Zn system. Surprisingly, commensurate order persists over a wide range of composition, despite its origins. For Cu2NiZn, we discuss how FS nesting and the other effects of alloying lead to ordering tendencies consistent with the experimentally observed order-disorder transformations. All calculations are based on a first-principles theory of the atomic short-range order in alloys with an arbitrary number of components.

Go to article

Global Equatorial Ionosphericvertical Plasma Drifts Measured By The Ae-E Satellite, Bela G. Fejer, E. R. De Paula, R. A. Heelis, W. B. Hanson Jan 1995

Global Equatorial Ionosphericvertical Plasma Drifts Measured By The Ae-E Satellite, Bela G. Fejer, E. R. De Paula, R. A. Heelis, W. B. Hanson

Bela G. Fejer

Ion drift meter observations from the Atmosphere Explorer E satellite during the period of January 1977 to December 1979 are used to study the dependence of equatorial (dip latitudes ≤ 7.5°) F region vertical plasma drifts (east-west electric fields) on solar activity, season, and longitude. The satellite-observed ion drifts show large day-to-day and seasonal variations. Solar cycle effects are most pronounced near the dusk sector with a large increase of the prereversal velocity enhancement from solar minimum to maximum. The diurnal, seasonal, and solar cycle dependence of the longitudinally averaged drifts are consistent with results from the Jicamarca radar except …

Go to article

Extended Molecular Gas In Fsc 10214+4724, N Z. Scoville, Min S. Yun, R L. Brown, P A. Vanden Bout Jan 1995

Extended Molecular Gas In Fsc 10214+4724, N Z. Scoville, Min S. Yun, R L. Brown, P A. Vanden Bout

Min S. Yun

e report high resolution imaging of the CO (3-2) emission in the luminous infrared source FSC 10214+4724 at z = 2.2853. Maps at resolutions of 2farcs3 × 3farcs0 and 45-90 km s-1 show the CO emission peak coinciding with those of Hα and radio continuum. Two components are identified in the CO emission: an unresolved core and an extended source (~1farcs9 × 4farcs4)—elongated southeast-northwest. The implied size is 9 × 24 kpc for H0 = 75 km s-1 Mpc-1 and q0 = 0.5. The extent of the CO emission is significantly greater than that of either the optical or the …

Go to article

63. Ivan Panayotov, Otto Vogl, Christo Tsvetanov Jan 1995

63. Ivan Panayotov, Otto Vogl, Christo Tsvetanov

Otto Vogl

No abstract provided.

Go to article

Absolute Integrated Cross Sections For Some O2 Herzberg I Transitions Near 248–249 Nm, Zhen-Chuan Bao, Edward Yu, John R. Baker Jan 1995

Absolute Integrated Cross Sections For Some O2 Herzberg I Transitions Near 248–249 Nm, Zhen-Chuan Bao, Edward Yu, John R. Baker

Edward Yu

A frequency doubled tunable dye laser system with ∼0.4 cm−1 resolution was used to measure the integrated absorption cross sections of more than 20 rotational transitions in the O2 Herzberg I (A  3Σ+ u ←X  3Σ− g ) 8‐0 and 9‐0 vibrational bands near 248 nm and 249 nm. Oxygen pressures from 200 to 800 Torr and path lengths from 5 to 25 m were employed. The measured absorbances were fitted using a nonlinear least squares analysis and Beer’s Law to obtain absolute values for the individual transition integrated cross sections in good agreement with a recent spectral simulation and …

Go to article

Comparison Of Variable Rate To Single Rate Nitrogen Fertilizer Application: Corn Production And Residual Soil No3-N, N. R. Kitchen, D. F. Hughes, K. A. Sudduth, Stuart J. Birrell Jan 1995

Comparison Of Variable Rate To Single Rate Nitrogen Fertilizer Application: Corn Production And Residual Soil No3-N, N. R. Kitchen, D. F. Hughes, K. A. Sudduth, Stuart J. Birrell

Stuart J. Birrell

The questions most often asked by farmers when discussing variable rate (VR) fertilizer inputs are "How much will it cost?" and "How will it affect my yields?" Many farmers and custom application services share a reluctance to invest in the time and technology required for variable fertilizer application since studies to answer these questions are few and results have been inconsistent.

Go to article

Precise Experimental Test Of Models For The Breakdown Of The Born-Oppenheimer Separation: The Rotational Spectra Of Isotopic Variants Of Lithium Hydride, Thomas D. Varberg, M. Bellini, P. De Natale, M. Inquscio, J. M. Brown Jan 1995

Precise Experimental Test Of Models For The Breakdown Of The Born-Oppenheimer Separation: The Rotational Spectra Of Isotopic Variants Of Lithium Hydride, Thomas D. Varberg, M. Bellini, P. De Natale, M. Inquscio, J. M. Brown

Thomas D. Varberg

No abstract provided.

Go to article

Quintuples With Square Triplets, Stan Wagon Jan 1995

Quintuples With Square Triplets, Stan Wagon

Stan Wagon, Retired

No abstract provided.

Go to article

Articles Pre-1996, Daniel Kaplan Jan 1995

Articles Pre-1996, Daniel Kaplan

Daniel T. Kaplan

No abstract provided.

Go to article

A Thermodynamic Model For Pressurized Solids, Miron Kaufman, Herbert Schlosser Jan 1995

A Thermodynamic Model For Pressurized Solids, Miron Kaufman, Herbert Schlosser

Miron Kaufman

A thermodynamic model for solids under pressure is developed by assuming the universal equation of state and that under zero pressure the free energy is equal to the harmonic crystal (Debye) free energy. The model is applied to gold. In the case of nanocrystals this model reproduces the observed enhancement of the isobaric heat capacity and of the thermal expansion. Our model calculations are free of the ambiguities and inconsistencies connected with the Gruneisen equation, which was used in previous theoretical work.

Go to article

Historical Development Of The Newton-Raphson Method, Tjalling Ypma Jan 1995

Historical Development Of The Newton-Raphson Method, Tjalling Ypma

Mathematics Faculty Publications

This expository paper traces the development of the Newton-Raphson method for solving nonlinear algebraic equations through the extant notes, letters, and publications of Isaac Newton, Joseph Raphson, and Thomas Simpson. It is shown how Newton's formulation differed from the iterative process of Raphson, and that Simpson was the first to give a general formulation, in terms of fluxional calculus, applicable to nonpolynomial equations. Simpson's extension of the method to systems of equations is exhibited.

Go to article

Refinement Of The Solution Structure Of A Branched Dna Three-Way Junction, Neocles B. Leontis, Igor V. Ouporov Jan 1995

Refinement Of The Solution Structure Of A Branched Dna Three-Way Junction, Neocles B. Leontis, Igor V. Ouporov

Chemistry Faculty Publications

We have refined the structure of the DNA Three-Way Junction complex, TWJ- TC, described in the companion paper by quantitative analysis of two 2D NOESY spectra (mixing times 60 and 200 ms) obtained in D2O solution. NOESY crosspeak intensities extracted from these spectra were used in two kinds of refinement procedure: 1) distance-restrained energy minimization (EM) and molecular dynamics (MD) and 2) full relaxation matrix back calculation refinement. The global geometry of the refined model is very similar to that of a published, preliminary model (Leontis, 1993). Two of the helical arms of the junction are stacked. These are Helix …

Go to article

A Single-Stroke Orientation-Orient Gesture System, Yike Hu Jan 1995

A Single-Stroke Orientation-Orient Gesture System, Yike Hu

All Computer Science and Engineering Research

No abstract provided.

Go to article

Deregulation Of The Energy Industry, Elisabeth Pendley, University Of Colorado Boulder. Natural Resources Law Center Jan 1995

Deregulation Of The Energy Industry, Elisabeth Pendley, University Of Colorado Boulder. Natural Resources Law Center

Books, Reports, and Studies

43 p. ; 28 cm

Go to article

Report To The Washington State Board Of Natural Resources From The Independent Review Committee, Independent Review Committee (Wash.), Washington (State). Board Of Natural Resources, University Of Colorado Boulder. Natural Resources Law Center Jan 1995

Report To The Washington State Board Of Natural Resources From The Independent Review Committee, Independent Review Committee (Wash.), Washington (State). Board Of Natural Resources, University Of Colorado Boulder. Natural Resources Law Center

Books, Reports, and Studies

1 volume (various pagings) : illustrations, maps ; 28 cm

Go to article

A Sturm Separation Theorem For A Linear 2nth Order Self-Adjoint Differential Equation, Charles T. Fulton, Wu Limin, Steven Pruess Jan 1995

A Sturm Separation Theorem For A Linear 2nth Order Self-Adjoint Differential Equation, Charles T. Fulton, Wu Limin, Steven Pruess

Mathematics and System Engineering Faculty Publications

For the 2nth order equation, (−1)nv(2n)+qv=0, with q continuous, we obtain a Sturm Separation theorem, involving n+1 solutions of the equation, which is somewhat analogous to the classical result that the zeros of two linearly independent solutions of the second order equation separate each other.

Go to article

Exp For Windows, Version 3.0 A Software Review, Donn E. Miller-Harnish Jan 1995

Exp For Windows, Version 3.0 A Software Review, Donn E. Miller-Harnish

Mathematics and System Engineering Faculty Publications

No abstract provided.

Go to article

Optimality Conditions For Systems Driven By Nonlinear Evolution Equations, Nikolaos S. Papageorgiou Jan 1995

Optimality Conditions For Systems Driven By Nonlinear Evolution Equations, Nikolaos S. Papageorgiou

Mathematics and System Engineering Faculty Publications

Using the Dubovitskii-Milyutin theory we derive necessary and sufficient conditions for optimality for a class of Lagrange optimal control problems monitored by a nonlinear evolution equation and involving initial and/or terminal constraints. An example of a parabolic control system is also included.

Go to article

Stability Of Conditionally Invariant Sets And Controlled Uncertain Dynamic Systems On Time Scales, V. Lakshmikantham Jan 1995

Stability Of Conditionally Invariant Sets And Controlled Uncertain Dynamic Systems On Time Scales, V. Lakshmikantham

Mathematics and System Engineering Faculty Publications

A basic feedback control problem is that of obtaining some desired stability property from a system which contains uncertainties due to unknown inputs into the system. Despite such imperfect knowledge in the selected mathematical model, we often seek to devise controllers that will steer the system in a certain required fashion. Various classes of controllers whose design is based on the method of Lyapunov are known for both discrete [4], [10], [15], and continuous [3–9], [11] models described by difference and differential equations, respectively. Recently, a theory for what is known as dynamic systems on time scales has been built …

Go to article

Partial Least-Squares: Theoretical Issues And Engineering Applications In Signal Processing, Fredric M. Ham, Ivica Kostanic Jan 1995

Partial Least-Squares: Theoretical Issues And Engineering Applications In Signal Processing, Fredric M. Ham, Ivica Kostanic

Mathematics and System Engineering Faculty Publications

In this paper we present partial least-squares (PLS), which is a statistical modeling method used extensively in analytical chemistry for quantitatively analyzing spectroscopic data. Comparisons are made between classical least-squares (CLS) and PLS to show how PLS can be used in certain engineering signal processing applications. Moreover, it is shown that in certain situations when there exists a linear relationship between the independent and dependent variables, PLS can yield better predictive performance than CLS when it is not desirable to use all of the empirical data to develop a calibration model used for prediction. Specifically, because PLS is a factor …

Go to article

Bulk Input Queues With Quorum And Multiple Vacations, Jay Yellen, Jewgeni H. Dshalalow Jan 1995

Bulk Input Queues With Quorum And Multiple Vacations, Jay Yellen, Jewgeni H. Dshalalow

Mathematics and System Engineering Faculty Publications

The authors study a single-server queueing system with bulk arrivals and batch service in accordance to the general quorum discipline: a batch taken for service is not less than r and not greater than R(≥r). The server takes vacations each time the queue level falls below r(≥1) in accordance with the multiple vacation discipline. The input to the system is assumed to be a compound Poisson process. The analysis of the system is based on the theory of first excess processes developed by the first author. A preliminary analysis of such processes enabled the authors to obtain all major characteristics …

Go to article

Comment On 'Simulation Of A Two-Dimensional Rayleigh-Bénard System Using The Direct Simulation Monte Carlo Method, Alejandro Garcia, F. Baras, M. Malek Mansour Jan 1995

Comment On 'Simulation Of A Two-Dimensional Rayleigh-Bénard System Using The Direct Simulation Monte Carlo Method, Alejandro Garcia, F. Baras, M. Malek Mansour

Faculty Publications

No abstract provided.

Go to article

Many-To-Many Personalized Communication With Bounded Traffic, Sanjay Ranka, Ravi V. Shankar, Khaled A. Alsabti Jan 1995

Many-To-Many Personalized Communication With Bounded Traffic, Sanjay Ranka, Ravi V. Shankar, Khaled A. Alsabti

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

This paper presents solutions for the problem of many-to-many personalized communication, with bounded incoming and outgoing traffic, on a distributed memory parallel machine. We present a two-stage algorithm that decomposes the many-to-many communication with possibly high variance in message size into two communications with low message size variance. The algorithm is deterministic and takes time 2tµ (+ lower order terms) when t >= O(p2; + p tau/µ). Here t is the maximum outgoing or incoming traffic at any processor, tau is the startup overhead and µ is the inverse of the data transfer rate. Optimality is achieved when the traffic …

Go to article

Kripke Logical Relations And Pcf, Peter W. O'Hearn, John G. Riecke Jan 1995

Kripke Logical Relations And Pcf, Peter W. O'Hearn, John G. Riecke

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

Sieber has described a model of PCF consisting of continuous functions that are invariant under certain (finitary) logical relations, and shown that it is fully abstract for closed terms of up to third-order types. We show that one may achieve full abstraction at all types using a form of "Kripke logical relations" introduced by Jung and Tiuryn to characterize λ definability.

Go to article

Objects, Interference, And The Yoneda Embedding, Peter W. O'Hearn, Uday S. Reddy Jan 1995

Objects, Interference, And The Yoneda Embedding, Peter W. O'Hearn, Uday S. Reddy

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

We present a new semantics for Algol-like languages that combines methods from two prior lines of development: [1] the object-based approach of [28,29], where the meaning of an imperative program is described in terms of sequences of observable actions, and [2] the functor-category approach initiated by Reynolds [31], where the varying nature of the run-time stack is explained using functors from a category of store shapes to a category of cpos. The semantics gives an account of both the phenomena of local state and irreversibility of state change. As an indication of the accuracy obtained, we present a full abstraction …

Go to article

Syntactic Control Of Interference Revisited, Peter W. O'Hearn, A. J. Power, M. Takeyama, R. D. Tennent Jan 1995

Syntactic Control Of Interference Revisited, Peter W. O'Hearn, A. J. Power, M. Takeyama, R. D. Tennent

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

In "Syntactic Control of Interference" (POPL, 1978), J. C. Reynolds proposes three design principles intended to constrain the scope of imperative state effects in Algol-like languages. The resulting linguistic framework seems to be a very satisfactory way of combining functional and imperative concepts, having the desirable attributes of both purely functional languages (such as pcf) and simple imperative languages (such as the language of while programs). However, Reynolds points out that the "obvious" syntax for interference control has the unfortunate property that fi-reductions do not always preserve typings. Reynolds has subsequently presented a solution to this problem (ICALP, 1989), but …

Go to article

Parametricity And Local Variables, Peter W. O'Hearn, R. D. Tennent Jan 1995

Parametricity And Local Variables, Peter W. O'Hearn, R. D. Tennent

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

We propose that the phenomenon of local state may be understood in terms of Strachey 's concept of parametric (i.e., uniform) polymorphism. The intuitive basis for our proposal is the following analogy: a non-local procedure is independent of locally-declared variables in the same way that a parametrically polymorphic function is independent of types to which it is instantiated. A connection between parametricity and representational abstraction was first suggested by J. C. Reynolds. Reynolds used logical relations to formalize this connection in languages with type variables and user-defined types. We use relational parametricity to construct a model for an Algol-like language …

Go to article

First Prev Next Last