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Articles 2401 - 2430 of 2865

Full-Text Articles in Physical Sciences and Mathematics

Calculation Of Electronic Coupling Matrix Elements For Ground And Excited State Electron Transfer Reactions: Comparison Of The Generalized Mulliken–Hush And Block Diagonalization Methods, Robert J. Cave, Marshall D. Newton Jun 1997

Calculation Of Electronic Coupling Matrix Elements For Ground And Excited State Electron Transfer Reactions: Comparison Of The Generalized Mulliken–Hush And Block Diagonalization Methods, Robert J. Cave, Marshall D. Newton

All HMC Faculty Publications and Research

Two independent methods are presented for the nonperturbative calculation of the electronic coupling matrix element (Hab) for electron transfer reactions using ab initio electronic structure theory. The first is based on the generalized Mulliken–Hush (GMH) model, a multistate generalization of the Mulliken Hush formalism for the electronic coupling. The second is based on the block diagonalization (BD) approach of Cederbaum, Domcke, and co-workers. Detailed quantitative comparisons of the two methods are carried out based on results for (a) several states of the system Zn2OH2+ and (b) the low-lying states of the benzene–Cl atom complex and its contact ion pair. Generally …

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Was Newton's Calculus A Dead End? The Continental Influence Of Maclaurin's Treatise Of Fluxions, Judith V. Grabiner May 1997

Was Newton's Calculus A Dead End? The Continental Influence Of Maclaurin's Treatise Of Fluxions, Judith V. Grabiner

Pitzer Faculty Publications and Research

We will show that Maclaurin's Treatise of Fluxions did develop important ideas and techniques and that it did influence the mainstream of mathematics. The Newtonian tradition in calculus did not come to an end in Maclaurin's Britain. Instead, Maclaurin's Treatise served to transmit Newtonian ideas in calculus, improved and expanded, to the Continent. We will look at what these ideas were, what Maclaurin did with them, and what happened to this work afterwards. Then, we will ask what by then should be an interesting question: why has Maclaurin's role been so consistently underrated? Thse questions will involve general matters of …

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Optimization Of Plasmas For Recombination-Pumped Short-Wavelength Lasers, M. Murphy, C. Glasheen, F. A. Moscatelli, Thomas D. Donnelly Apr 1997

Optimization Of Plasmas For Recombination-Pumped Short-Wavelength Lasers, M. Murphy, C. Glasheen, F. A. Moscatelli, Thomas D. Donnelly

All HMC Faculty Publications and Research

We report on experiments investigating the optimization of laser-ablated plasmas which are used to produce recombination-pumped, short-wavelength lasers. We evaluate the density of electrons and neutral atoms in laser ablated lithium and carbon plasmas as a function of time and distance away from the ablated target surface. We use an interferometric technique which can reveal information about the temperature of the plasma electrons. We find that the cold electrons which result in gain in recombination-pumped lithium lasers on the Lyman-α transition are produced by the high-intensity pump pulse rather than the lower intensity ablating pulse.

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Photoluminescence Properties Of Silicon Quantum-Well Layers, Peter N. Saeta, A. C. Gallagher Feb 1997

Photoluminescence Properties Of Silicon Quantum-Well Layers, Peter N. Saeta, A. C. Gallagher

All HMC Faculty Publications and Research

Nanometer-scale crystal silicon films surrounded by SiO2 were prepared by oxidizing silicon-on-insulator substrates prepared from SIMOX (separation by implantation of oxygen) and crystallized hydrogenated amorphous silicon films. Average silicon layer thickness was determined from reflection spectra. When sufficiently thin (<2 >nm), all layers emitted red photoluminescence under blue and UV cw excitation, with a spectrum that did not depend on the mean layer thickness. The spectrum was roughly Gaussian with a peak energy of 1.65 eV, which is lower than for most porous silicon spectra. The time scale for the luminescence decay was ~35 μs at room temperature and …

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Jamaican Cave Vertebrates, Donald A. Mcfarlane Jan 1997

Jamaican Cave Vertebrates, Donald A. Mcfarlane

WM Keck Science Faculty Papers

Limestone caves in the tropics are typically associated with a more diverse assemblage of vertebrates than are caves in temperate regions. Chapman [87] for example, has reported 37 species from the caves of Gunung Mulu National Park, Sarawak, whereas Bailey [43] lists only 13 for the equally cavernicolous Guadeloupe Mountains National Park, New Mexico, USA. Twenty-eight vertebrate species have been recorded from Jamaican caves. The relative importance of the five Classes differ in these three areas as shown in Table 1 (overleaf).

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Diagonal Operators, S-Numbers, And Bernstein Pairs, Asuman Güven Aksoy, Grzegorz Lewicki Jan 1997

Diagonal Operators, S-Numbers, And Bernstein Pairs, Asuman Güven Aksoy, Grzegorz Lewicki

CMC Faculty Publications and Research

Replacing the nested sequence of ''finite" dimensional subspaces by the nested sequence of "closed" subspaces in the classical Bernstein lethargy theorem, we obtain a version of this theorem for the space B(X , Y) of all bounded linear maps. Using this result and some properties of diagonal operators, we investigate conditions under which a suitable pair of Banach spaces form an exact Bernstein pair.We also show that many "classical" Banach spaces, including the couple (Lp [O, 1] , Lq[O, 1]) form a Bernstein pair with respect to any sequence of s-numbers (sn) ,for 1 < p < ∞ and 1 ≤ q < ∞ …

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Optical Polarimetry, High–Resolution Spectroscopy And Ir Analysis Of The Chamaeleon I Dark Cloud, E. Covino, E. Palazzi, Bryan E. Penprase, H. E. Schwarz, L. Terranegra Jan 1997

Optical Polarimetry, High–Resolution Spectroscopy And Ir Analysis Of The Chamaeleon I Dark Cloud, E. Covino, E. Palazzi, Bryan E. Penprase, H. E. Schwarz, L. Terranegra

Pomona Faculty Publications and Research

We present optical polarimetry and high resolution spectroscopy of a sample of stars toward the Chamaeleon I dark cloud. We use our polarimetry which includes 33 stars to study the wavelength dependence of the degree and position angle of polarization.

From our data we found, by interpretation of the various correlations between the polarimetry, photometry and IRAS fluxes, the following:
the probable presence of shocked molecular gas; a warm molecular CH component; small dust grains at the edges of the cloud, and larger grains in the central parts, which are causing the polarization.

Our results provide a consistent picture of …

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Positive Solution Curves Of Semipositone Problems With Concave Nonlinearities, Alfonso Castro, Sudhasree Gadam, Ratnasingham Shivaji Jan 1997

Positive Solution Curves Of Semipositone Problems With Concave Nonlinearities, Alfonso Castro, Sudhasree Gadam, Ratnasingham Shivaji

All HMC Faculty Publications and Research

We consider the positive solutions to the semilinear equation:

-Δu(x) = λf(u(x)) for x ∈ Ω

u(x) = 0 for x ∈ ∂Ω

where Ω denotes a smooth bounded region in RN (N > 1) and λ > 0. Here f :[0, ∞)→R is assumed to be monotonically increasing, concave and such that f(0) < 0 (semipositone). Assuming that f'(∞) ≡ lim t→∞ f'(t) > 0, we establish the stability and uniqueness of large positive solutions in terms of (f(t)/t)'. When Ω is a ball, we determine the exact number of positive solutions for each λ > 0. We also obtain the geometry of the branches of positive solutions completely and establish how …

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The Interaction Of A Point Vortex With A Wall-Bounded Vortex Layer, Oliver V. Atassi, Andrew J. Bernoff, Seth Lichter Jan 1997

The Interaction Of A Point Vortex With A Wall-Bounded Vortex Layer, Oliver V. Atassi, Andrew J. Bernoff, Seth Lichter

All HMC Faculty Publications and Research

The interaction of a point vortex with a layer of constant vorticity, bounded below by a wall and above by an irrotational flow, is investigated as a model of vortex–boundary layer interaction. This model calculates both the evolution of the interface which separates the vortex layer from the irrotational flow and the trajectory of the vortex. In order to determine the conditions which lead to sustained unsteady interaction, three cases are investigated where the mutual interaction between the vortex and interface is initially assumed to be weak. (i) When a weak point vortex lies outside the layer, the vortex moves …

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Adaptive Multicast Routing In Wormhole Networks, Ran Libeskind-Hadas, Tom Hehre '96, Andrew Hutchings '98, Mark Reyes '98, Kevin Watkins '97 Jan 1997

Adaptive Multicast Routing In Wormhole Networks, Ran Libeskind-Hadas, Tom Hehre '96, Andrew Hutchings '98, Mark Reyes '98, Kevin Watkins '97

All HMC Faculty Publications and Research

Multicast communication has applications in a number of fundamental operations in parallel computing. An effective multicast routing algorithm must be free from both livelock and deadlock while minimizing communication latency. We describe two classes of multicast wormhole routing algorithms that employ the multi-destination wormhole hardware mechanism proposed by Lin et al. [12] and Panda et al. [17]. Specific examples of these classes of algorithms are described and experimental results suggests that such algorithms enjoy low communication latencies across a range of network loads.

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Magnetic Levitation And Noncoalescence Of Liquid Helium, M. A. Weilert, Dwight L. Whitaker, H. J. Maris, G. M. Seidel Dec 1996

Magnetic Levitation And Noncoalescence Of Liquid Helium, M. A. Weilert, Dwight L. Whitaker, H. J. Maris, G. M. Seidel

Pomona Faculty Publications and Research

We describe experiments in which drops of liquid helium-4, as large as 2 cm in diameter, are magnetically levitated. We have found that, when two or more drops are levitated in the same magnetic trap, the drops often remain in a state of apparent contact without coalescing. It appears that this effect is caused by the slow evaporation of liquid from the drops.

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Puzzles, Patterns Drums: The Dawn Of Mathematics In Rwanda And Burundi., D. Huylebrouck Nov 1996

Puzzles, Patterns Drums: The Dawn Of Mathematics In Rwanda And Burundi., D. Huylebrouck

Humanistic Mathematics Network Journal

No abstract provided.

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Book Review: Emblems Of Mind, The Inner Life Of Music And Mathematics, By Edward Rothstein, Dan Fitzgerald, Joel Haack Nov 1996

Book Review: Emblems Of Mind, The Inner Life Of Music And Mathematics, By Edward Rothstein, Dan Fitzgerald, Joel Haack

Humanistic Mathematics Network Journal

No abstract provided.

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Book Review: Ethnomathematics: A Multicultural View Of Mathematical Ideas, By Marcia Ascher, Bernadette Anne Berken Nov 1996

Book Review: Ethnomathematics: A Multicultural View Of Mathematical Ideas, By Marcia Ascher, Bernadette Anne Berken

Humanistic Mathematics Network Journal

No abstract provided.

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The Folktale: Linking Story To Mathematical Principles, Audrey Kopp Nov 1996

The Folktale: Linking Story To Mathematical Principles, Audrey Kopp

Humanistic Mathematics Network Journal

No abstract provided.

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Psychosis, Lee Goldstein Nov 1996

Psychosis, Lee Goldstein

Humanistic Mathematics Network Journal

No abstract provided.

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From The Editor, Issue 14, 1996, Alvin White Nov 1996

From The Editor, Issue 14, 1996, Alvin White

Humanistic Mathematics Network Journal

No abstract provided.

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What's All The Fuss About?, Sherman K. Stein Nov 1996

What's All The Fuss About?, Sherman K. Stein

Humanistic Mathematics Network Journal

No abstract provided.

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The Triex: Explore, Extract, Explain, Sherman K. Stein Nov 1996

The Triex: Explore, Extract, Explain, Sherman K. Stein

Humanistic Mathematics Network Journal

No abstract provided.

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Noesis, Lee Goldstein Nov 1996

Noesis, Lee Goldstein

Humanistic Mathematics Network Journal

No abstract provided.

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Music And Mathematics, Roxanne Kitts Nov 1996

Music And Mathematics, Roxanne Kitts

Humanistic Mathematics Network Journal

No abstract provided.

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Book Review: Emblems Of Mind, The Inner Life Of Music And Mathematics, By Edward Rothstein, Sandra Z. Keith Nov 1996

Book Review: Emblems Of Mind, The Inner Life Of Music And Mathematics, By Edward Rothstein, Sandra Z. Keith

Humanistic Mathematics Network Journal

No abstract provided.

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Mathematical Rebuses, Florentin Smarandache Nov 1996

Mathematical Rebuses, Florentin Smarandache

Humanistic Mathematics Network Journal

No abstract provided.

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Fibonacci Melodies, Robert Lewand Nov 1996

Fibonacci Melodies, Robert Lewand

Humanistic Mathematics Network Journal

No abstract provided.

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On The Use Of Intelligent Tutoring Systems For Teaching And Learning Mathematics, M.D. C. Mendes, M.G. V. Nunes, C. A. Andreucci Nov 1996

On The Use Of Intelligent Tutoring Systems For Teaching And Learning Mathematics, M.D. C. Mendes, M.G. V. Nunes, C. A. Andreucci

Humanistic Mathematics Network Journal

No abstract provided.

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Dynamical Effects Of Partial Orderings In Physical Systems, Adam S. Landsberg, Eric J. Friedman Oct 1996

Dynamical Effects Of Partial Orderings In Physical Systems, Adam S. Landsberg, Eric J. Friedman

WM Keck Science Faculty Papers

We demonstrate that many physical systems possess an often overlooked property known as a partial-ordering structure. The detection and analysis of this special geometric property can be crucial for understanding a system's dynamical behavior. We review here the fundamental dynamical features common to all such systems, and describe how the partial ordering imposes interesting restrictions on their possible behavior. We show, for instance, that though such systems are capable of displaying highly complex and even chaotic behaviors, most of their experimentally observable behaviors will be simple. Partial orderings are illustrated with examples drawn from many branches of physics, including solid …

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Positive Solutions For A Semilinear Elliptic Problem With Critical Exponent, Ismail Ali, Alfonso Castro Aug 1996

Positive Solutions For A Semilinear Elliptic Problem With Critical Exponent, Ismail Ali, Alfonso Castro

All HMC Faculty Publications and Research

No abstract provided in article.

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A Mathematician Among The Molasses Barrels: Maclaurin's Unpublished Memoir On Volumes, Judith V. Grabiner Jun 1996

A Mathematician Among The Molasses Barrels: Maclaurin's Unpublished Memoir On Volumes, Judith V. Grabiner

Pitzer Faculty Publications and Research

Suppose we are given a solid of revolution generated by a conic section. Slice out a frustum of the solid [14, diagrams pp. 77, 80]. Then, construct a cylinder, with the same height as the frustum, whose diameter coincides with the diameter of the frustum at the midpoint of its height. What is the difference between the volume of the frustum and the volume of this cylinder? Does this difference depend on where in the solid the frustum is taken?

The beautiful theorems which answer these questions first appear in a 1735 manuscript by Colin Maclaurin (1698–1746). This …

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Methodological And Substantive Issues In Substance Abuse Prevention Research, C. Anderson Johnson, John W. Farquhar, Steve Sussman Jun 1996

Methodological And Substantive Issues In Substance Abuse Prevention Research, C. Anderson Johnson, John W. Farquhar, Steve Sussman

CGU Faculty Publications and Research

This article summarizes current issues in drug abuse prevention research through integration of other articles in this journal and by heeding historical trends in prevention science. Recommendations are made for future research directions. For prevention to advance, iterative processes are needed involving both quasi-experimental and experimental designs and involving both small, simple units and large, complex, interactive units. Accuracy of measurement and replication are of paramount importance.

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The Structure Of Alkali Halide Dimers: A Critical Test Of Ionic Models And New Ab Initio Results, T. Törring, S. Biermann, J. Hoeft, Richard J. Mawhorter, Robert J. Cave, C. Szemenyei May 1996

The Structure Of Alkali Halide Dimers: A Critical Test Of Ionic Models And New Ab Initio Results, T. Törring, S. Biermann, J. Hoeft, Richard J. Mawhorter, Robert J. Cave, C. Szemenyei

All HMC Faculty Publications and Research

In semiempirical ionic models a number of adjustable parameters have to be fitted to experimental data of either monomer molecules or crystals. This leads to strong correlations between these constants and prevents a unique test and a clear physical interpretation of the fit parameters. Moreover, it is not clear whether these constants remain unchanged when the model is applied to dimers or larger clusters. It is shown that these correlations can be substantially reduced when reliable information about dimers is available from experiments or ab initio calculations. Starting with Dunham coefficients of the monomer potential determined from microwave measurements, we …

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