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Articles 1741 - 1770 of 2640

Full-Text Articles in Physical Sciences and Mathematics

Deep-Uv Light Emitting Diodes: An Experimental Investigation Of Characterization And Optimization Techniques, Eric M. Fraser May 2005

Deep-Uv Light Emitting Diodes: An Experimental Investigation Of Characterization And Optimization Techniques, Eric M. Fraser

Pomona Senior Theses

Light emitting diodes (LEDs) and laser diodes (LDs) have many advantages over conventional light sources. Current commercial LEDs span the spectrum from IR to near- UV. There are a variety of applications for devices that extend into the deep-UV, including biological agent detection and optical storage. The nitride material system is a set of semiconducting compounds that have wavelengths that span a broad range, from yellow to deep-UV. AlGaN has a direct bandgap that extends into the deep-UV range; we will try to grow device-quality material, deposited epitaxially using metalorganic chemical vapor deposition on sapphire substrates.

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X-Ray Generation From Metal Targets Coated With Wavelength-Scale Spheres, D. R. Symes, H. A. Sumeruk, I. V. Churina, Thomas D. Donnelly, J. Landry, T. Ditmire May 2005

X-Ray Generation From Metal Targets Coated With Wavelength-Scale Spheres, D. R. Symes, H. A. Sumeruk, I. V. Churina, Thomas D. Donnelly, J. Landry, T. Ditmire

All HMC Faculty Publications and Research

X-ray yield measurements from targets coated with wavelength-scale spheres are compared with measurements from polished targets. Evidence for a hotter resonant electron temperature due to field enhancements from Mie resonances in the spheres is investigated.

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Deep-Uv Light Emitting Diodes: An Experimental Investigation Of Characterization And Optimization Techniques, Eric M. Fraser May 2005

Deep-Uv Light Emitting Diodes: An Experimental Investigation Of Characterization And Optimization Techniques, Eric M. Fraser

Pomona Senior Theses

Light emitting diodes (LEDs) and laser diodes (LDs) have many advantages over conventional light sources. Current commercial LEDs span the spectrum from IR to near- UV. There are a variety of applications for devices that extend into the deep-UV, including biological agent detection and optical storage. The nitride material system is a set of semiconducting compounds that have wavelengths that span a broad range, from yellow to deep-UV. AlGaN has a direct bandgap that extends into the deep-UV range; we will try to grow device-quality material, deposited epitaxially using metalorganic chemical vapor deposition on sapphire substrates.

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Lower Bounds For Simplicial Covers And Triangulations Of Cubes, Adam Bliss '03, Francis E. Su Apr 2005

Lower Bounds For Simplicial Covers And Triangulations Of Cubes, Adam Bliss '03, Francis E. Su

All HMC Faculty Publications and Research

We show that the size of a minimal simplicial cover of a polytope P is a lower bound for the size of a minimal triangulation of P, including ones with extra vertices. We then use this fact to study minimal triangulations of cubes, and we improve lower bounds for covers and triangulations in dimensions 4 through at least 12 (and possibly more dimensions as well). Important ingredients are an analysis of the number of exterior faces that a simplex in the cube can have of a specified dimension and volume, and a characterization of corner simplices in terms of their …

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A Mathematical Model For Treatment-Resistant Mutations Of Hiv, Helen Moore, Weiqing Gu Apr 2005

A Mathematical Model For Treatment-Resistant Mutations Of Hiv, Helen Moore, Weiqing Gu

All HMC Faculty Publications and Research

In this paper, we propose and analyze a mathematical model, in the form of a system of ordinary differential equations, governing mutated strains of human immunodeficiency virus (HIV) and their interactions with the immune system and treatments. Our model incorporates two types of resistant mutations: strains that are not responsive to protease inhibitors, and strains that are not responsive to reverse transcriptase inhibitors. It also includes strains that do not have either of these two types of resistance (wild-type virus) and strains that have both types. We perform our analysis by changing the system of ordinary differential equations (ODEs) to …

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Combinatorial Proofs Of Fermat's, Lucas's, And Wilson's Theorems, Peter G. Anderson, Arthur T. Benjamin, Jeremy A. Rouse Mar 2005

Combinatorial Proofs Of Fermat's, Lucas's, And Wilson's Theorems, Peter G. Anderson, Arthur T. Benjamin, Jeremy A. Rouse

All HMC Faculty Publications and Research

No abstract provided in this article.

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Selectron Mass Reconstruction And The Resolution Of The Linear Collider Detector, Sharon J. Gerbode, Heath Holguin, Troy Lau, Paul Mooser, Adam Pearlstein, Joe Rose, Bruce Schumm Mar 2005

Selectron Mass Reconstruction And The Resolution Of The Linear Collider Detector, Sharon J. Gerbode, Heath Holguin, Troy Lau, Paul Mooser, Adam Pearlstein, Joe Rose, Bruce Schumm

All HMC Faculty Publications and Research

We have used ISAJET and the JAS LCD fast simulation to explore the precision of Snowmass Point SPS1a selectron mass reconstruction for the Silicon Detector concept. Simulating collisions at E_cm = 1 TeV, we have found that most of the information constraining the selectron mass is carried in the forward (|cos(theta)| > 0.8) region. We have also found that, for a beam energy spread of 1% (conventional RF design), detector resolution limitations compromise the selectron mass reconstruction only in the forward region. However, for a beam energy spread of less than 0.2% (superconducting RF design), the detector resolution compromises the selectron …

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Counting Lattice Points In Admissible Adelic Sets, Lenny Fukshansky Feb 2005

Counting Lattice Points In Admissible Adelic Sets, Lenny Fukshansky

CMC Faculty Publications and Research

Lecture given at the Midwest Number Theory Conference for Graduate Students and Recent PhDs II, February 2005.

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At The Creation: The National Forest Commission Of 1896-97, Gerald W. Williams, Char Miller Jan 2005

At The Creation: The National Forest Commission Of 1896-97, Gerald W. Williams, Char Miller

Pomona Faculty Publications and Research

Among the central forces in the creation of the legislation necessary to establish federal forestry was the National Forest Commission. Its members included some of the leading conservationists of the 1890s, including Charles Sprague Sargent and Gifford Pinchot; John Muir was an unofficial member. Its final report advocated the establishment of a national forest system and served as the basis for the so-called Organic Act, which cleared the way for active management on federal forests and grasslands. Unlike the other articles, this one contains several excerpted documents interspersed with exposition.

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The 19th Century Excavation Of Kent's Cavern, England, Donald A. Mcfarlane, Joyce Lundberg Jan 2005

The 19th Century Excavation Of Kent's Cavern, England, Donald A. Mcfarlane, Joyce Lundberg

WM Keck Science Faculty Papers

Between 1858 and 1880, William Pengelly developed revolutionary new techniques for the archeological and paleontological excavation of cave deposits. His work at Brixham Cave and Kent’s Cavern, England, yielded tens of thousands of specimens from the mid-Pleistocene to the Holocene, settled the intellectual debate over the co-existence of humans and extinct mammals, and accumulated an unparalleled resource for continued study. Although the Brixham Cave work was thoroughly summarized in print, Pengelly never published the plans of his much more thorough and extensive excavations at Kent’s Cavern. Here we present a reconstructed plan of the Pengelly excavations that we hope will …

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Srt Division Algorithms As Dynamical Systems, Mark Mccann, Nicholas Pippenger Jan 2005

Srt Division Algorithms As Dynamical Systems, Mark Mccann, Nicholas Pippenger

All HMC Faculty Publications and Research

Sweeney--Robertson--Tocher (SRT) division, as it was discovered in the late 1950s, represented an important improvement in the speed of division algorithms for computers at the time. A variant of SRT division is still commonly implemented in computers today. Although some bounds on the performance of the original SRT division method were obtained, a great many questions remained unanswered. In this paper, the original version of SRT division is described as a dynamical system. This enables us to bring modern dynamical systems theory, a relatively new development in mathematics, to bear on an older problem. In doing so, we are able …

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The Closed Topological Vertex Via The Cremona Transform, Jim Bryan, Dagan Karp Jan 2005

The Closed Topological Vertex Via The Cremona Transform, Jim Bryan, Dagan Karp

All HMC Faculty Publications and Research

We compute the local Gromov-Witten invariants of the "closed vertex", that is, a configuration of three rational curves meeting in a single triple point in a Calabi-Yau threefold. The method is to express the local invariants of the vertex in terms of ordinary Gromov-Witten invariants of a certain blowup of CP^3 and then to compute those invariants via the geometry of the Cremona transformation.

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Nature's Assembly Line Logic For Natural Products, Christopher T. Walsh, Ryan G. Kruger, David A. Vosburg Jan 2005

Nature's Assembly Line Logic For Natural Products, Christopher T. Walsh, Ryan G. Kruger, David A. Vosburg

All HMC Faculty Publications and Research

Nature fashions a very large number of diverse products (molecular weights ranging from ca. 200 to 2000 daltons) from simple monomeric metabolites used in primary metabolism. These include polyketide scaffolds generated from the simple C₃ malonyl CoA and C₄ methylmalonyl CoA monomers and nonribosomal peptides made from both the 20 proteinogenic amino acids and dozens of nonpoteinogenic amino acids.¹ A large family of terpenoid skeletons are built from the Δ²- and Δ³-alkene isomers of the biological isoprene monomer, isoprenyl-pyrophosphate.²

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A Theoretical Investigation Of Charge Transfer In Several Substituted Acridinium Ions, Jason Lappe '00, Robert J. Cave, Marshall D. Newton, I.V. Rostov Jan 2005

A Theoretical Investigation Of Charge Transfer In Several Substituted Acridinium Ions, Jason Lappe '00, Robert J. Cave, Marshall D. Newton, I.V. Rostov

All HMC Faculty Publications and Research

We present calculations for various properties of the ground and excited states of several arylamine-substituted acridinium ion systems that have been studied experimentally. Using ab initio and semiempirical quantum mechanical methods together with the generalized Mulliken−Hush (GMH) model, we examine the excitation energies, dipole moment shifts, and electronic coupling elements for the vertical charge shift (CSh) processes in these systems. We also examine solvent effects on these properties using a dielectric continuum reaction field model. The results are in generally good agreement with available experimental results and indicate that there is strong electronic coupling in these systems over a wide …

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Properties Of One-Point Completions Of A Noncompact Metrizable Space, Melvin Henriksen, Ludvík Janoš, R. G. Woods Jan 2005

Properties Of One-Point Completions Of A Noncompact Metrizable Space, Melvin Henriksen, Ludvík Janoš, R. G. Woods

All HMC Faculty Publications and Research

If a metrizable space X is dense in a metrizable space Y, then Y is called a metric extension of X. If T1 and T2 are metric extensions of X and there is a continuous map of T2 into T1 keeping X pointwise fixed, we write T1 ≤ T2. If X is noncompact and metrizable, then (M(X),≤) denotes the set of metric extensions of X, where T1 and T2 are identified if T1 ≤ T2 and T2 ≤ T1, i.e., if there is a homeomorphism of …

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C(X) Can Sometimes Determine X Without X Being Realcompact, Melvin Henriksen, Biswajit Mitra Jan 2005

C(X) Can Sometimes Determine X Without X Being Realcompact, Melvin Henriksen, Biswajit Mitra

All HMC Faculty Publications and Research

As usual C(X) will denote the ring of real-valued continuous functions on a Tychonoff space X. It is well-known that if X and Y are realcompact spaces such that C(X) and C(Y ) are isomorphic, then X and Y are homeomorphic; that is C(X) determines X. The restriction to realcompact spaces stems from the fact that C(X) and C(uX) are isomorphic, where uX is the (Hewitt) realcompactifcation of X. In this note, a class of locally compact spaces X that includes properly the class of locally compact realcompact spaces is exhibited such that C(X) determines X. The problem of getting …

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Problems From The Cottonwood Room, Matthias Beck, Beifang Chen, Lenny Fukshansky, Christian Haase, Allen Knutson, Bruce Reznick, Sinai Robins, Achill Schürmann Jan 2005

Problems From The Cottonwood Room, Matthias Beck, Beifang Chen, Lenny Fukshansky, Christian Haase, Allen Knutson, Bruce Reznick, Sinai Robins, Achill Schürmann

CMC Faculty Publications and Research

This collection was compiled by Christian Haase and Bruce Reznick from problems presented at the problem sessions, and submissions solicited from the participants of the AMS/IMS/SIAM summer Research Conference on Integer points in polyhedra. Lattice points in homogeneously expanding compact domains. Presented by Lenny Fukshansky (Texas A&M University).

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Non-Verbal Communication With Autistic Children Using Digital Libraries, Gondy A. Leroy, John Huang '05, Serena Chuang '05, Marjorie H. Charlop Jan 2005

Non-Verbal Communication With Autistic Children Using Digital Libraries, Gondy A. Leroy, John Huang '05, Serena Chuang '05, Marjorie H. Charlop

CGU Faculty Publications and Research

Autism spectrum disorder (ASD) has become one of the most prevalent mental disorders over the last few years and its prevalence is still growing. The disorder is characterized by a wide variety of symptoms such as lack of social behavior, extreme withdrawal, and problems communicating. Because of the diversity in symptoms and the wide variety in severity for those, each autistic child has different needs and requires individualized therapy. This leads to long waiting lists for therapy.

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Deep Roots: The Late Nineteenth Century Origins Of American Forestry, Char Miller Jan 2005

Deep Roots: The Late Nineteenth Century Origins Of American Forestry, Char Miller

Pomona Faculty Publications and Research

The U.S. Forest Service celebrated its centennial in 2005, an event that depended on a set of individuals who in the years immediately prior to the agency’s creation in 1905 labored quietly, and sometimes not so quietly, to defuse opposition to the idea of it within the executive and legislative branches. Surely the most crucial of these figures was Gifford Pinchot, then head of the Bureau of Forestry, and President Theodore Roosevelt: animating their activism was a shared conviction that conservation of the nation’s natural resources would save the United States from economic ruin and a collective faith that a …

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New Approaches To Understanding The Mechanics Of Burgess Shale-Type Deposits: From The Micron Scale To The Global Picture, Robert Gaines, Mary L. Droser Jan 2005

New Approaches To Understanding The Mechanics Of Burgess Shale-Type Deposits: From The Micron Scale To The Global Picture, Robert Gaines, Mary L. Droser

Pomona Faculty Publications and Research

Cambrian Burgess Shale-type (BST) deposits are among the most significant deposits for understanding the “Cambrian explosion” because they contain the fossilized tissues of nonmineralized organisms and provide a substantially different window on the radiation of the Metazoa than is afforded by the more “typical” fossil record of skeletal parts of biomineralized organisms. Despite nearly a century of research, BST deposits remain poorly investigated as sedimentologic entities largely because they comprise fine-grained mudrocks. Here,we describe a new, integrative approach to understanding a single BST deposit, the middle Cambrian Wheeler Formation of Utah, which reveals a dynamic interplay of paleoenvironmental, paleoecologic, and …

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The Ims New Researchers' Survival Guide, Naomi Altman, David Banks, Janis Hardwick, Kathryn Roeder, Peter Craigmile, Johanna S. Hardin, Mayetri Gupta Jan 2005

The Ims New Researchers' Survival Guide, Naomi Altman, David Banks, Janis Hardwick, Kathryn Roeder, Peter Craigmile, Johanna S. Hardin, Mayetri Gupta

Pomona Faculty Publications and Research

Statistics is a wonderfully diverse profession and graduate students making career choices have many options — especially in light of the dearth of students moving into the statistical sciences today. The three main career paths at the PhD level are in academics, industry/business and government. Each of these job types offers its own mix of intellectual challenges, financial reward, pressure and security. How a new researcher selects (or is selected by) a specific occupation in the statistical sciences sometimes seems more a function of luck than of conscious decision making. This consideration was one of the first concerns addressed by …

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French Lessons: F.P. Baker, American Forestry, And The 1878 Paris Universal Exposition, Char Miller Jan 2005

French Lessons: F.P. Baker, American Forestry, And The 1878 Paris Universal Exposition, Char Miller

Pomona Faculty Publications and Research

Although he never became a forester, F. P. Baker did much to advance the profession’s cause. Its potential became clear to him while serving as a U.S. Commissioner to the 1878 Paris Exposition, during which he reported on European forestry, its scientific methods and political meaning. Returning home, he was inspired to advance forestry in America.

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Amateur Hour: Nathaniel H. Egleston And Professional Forestry In Post-Civil War America, Char Miller Jan 2005

Amateur Hour: Nathaniel H. Egleston And Professional Forestry In Post-Civil War America, Char Miller

Pomona Faculty Publications and Research

Nathaniel Egleston, the second head of the U.S. Division of Forestry (1883–1886), is a forgotten figure in the history of early American forestry. The one-time minister became a tireless advocate for trees in the post-Civil War era, writing innumerable and well-received essays and pamphlets. But his enthusiasm did not translate into administrative success, and he was replaced by Bernard Fernow, who in turn was succeeded by Gifford Pinchot; the pair’s scientific training signaled the professionalization of American forestry.

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The Backward Shift On Dirichlet-Type Spaces, Stephan Ramon Garcia Jan 2005

The Backward Shift On Dirichlet-Type Spaces, Stephan Ramon Garcia

Pomona Faculty Publications and Research

We study the backward shift operator on Hilbert spaces H_α (for α ≥ 0) which are norm equivalent to the Dirichlet-type spaces D_α. Although these operators are unitarily equivalent to the adjoints of the forward shift operator on certain weighted Bergman spaces, our approach is direct and completely independent of the standard Cauchy duality. We employ only the classical Hardy space theory and an elementary formula expressing the inner product on H_α in terms of a weighted superposition of backward shifts.

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A *-Closed Subalgebra Of The Smirnov Class, Stephan Ramon Garcia Jan 2005

A *-Closed Subalgebra Of The Smirnov Class, Stephan Ramon Garcia

Pomona Faculty Publications and Research

We study real Smirnov functions and investigate a certain *-closed subalgebra of the Smirnov class N^+ containing them. Motivated by a result of Aleksandrov, we provide an explicit representation for the space H^p ∩ H^p [overscore over the second H^p]. This leads to a natural analog of the Riesz projection on a certain quotient space of L^p for p ϵ (0, 1). We also study a Herglotz-like integral transform for singular measures on the unit circle ∂D.

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Microarray Data From A Statistician’S Point Of View, Johanna S. Hardin Jan 2005

Microarray Data From A Statistician’S Point Of View, Johanna S. Hardin

Pomona Faculty Publications and Research

No abstract provided.

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Inner Matrices And Darlington Synthesis, Stephan Ramon Garcia Jan 2005

Inner Matrices And Darlington Synthesis, Stephan Ramon Garcia

Pomona Faculty Publications and Research

We describe and parameterize the solutions of the scalar valued Darlington synthesis problem. In the case of rational data we derive a simple procedure for producing all possible solutions.

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Newton, Maclaurin, And The Authority Of Mathematics, Judith V. Grabiner Dec 2004

Newton, Maclaurin, And The Authority Of Mathematics, Judith V. Grabiner

Pitzer Faculty Publications and Research

Sir Isaac Newton revolutionized physics and astronomy in his Principia. How did he do it? Would his method work on any area of inquiry, not only in science, but also about society and religion? We look at how some Newtonians, most notably Colin Maclaurin, combined sophisticated mathematical modeling and empirical data in what has come to be called the "Newtonian Style." We argue that this style was responsible not only for Maclaurin’s scientific success but for his ability to solve problems ranging from taxation to insurance to theology. We show how Maclaurin’s work strengthened the prestige of Newtonianism and …

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A (Not So) Complex Solution To A² + B² = Cⁿ, Arnold M. Adelberg, Arthur T. Benjamin, David I. Rudel '99 Oct 2004

A (Not So) Complex Solution To A² + B² = Cⁿ, Arnold M. Adelberg, Arthur T. Benjamin, David I. Rudel '99

All HMC Faculty Publications and Research

No abstract provided in this article.

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Random Walks On The Torus With Several Generators, Timothy Prescott '02, Francis E. Su Oct 2004

Random Walks On The Torus With Several Generators, Timothy Prescott '02, Francis E. Su

All HMC Faculty Publications and Research

Given n vectors {i} ∈ [0, 1)d, consider a random walk on the d-dimensional torus d = ℝd/ℤd generated by these vectors by successive addition and subtraction. For certain sets of vectors, this walk converges to Haar (uniform) measure on the torus. We show that the discrepancy distance D(Q*k) between the kth step distribution of the walk and Haar measure is bounded below by D(Q*k) ≥ C1k−n/2, where C1 = C(n, d) is …

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