Digital Commons Network^™

Voting, The Symmetric Group, And Representation Theory, Zajj Daugherty '05, Alexander K. Eustis '06, Gregory Minton '08, Michael E. Orrison

All HMC Faculty Publications and Research

We show how voting may be viewed naturally from an algebraic perspective by viewing voting profiles as elements of certain well-studied QS_n-modules. By using only a handful of simple combinatorial objects (e.g., tabloids) and some basic ideas from representation theory (e.g., Schur's Lemma), this allows us to recast and extend some well-known results in the field of voting theory.

Self-Organized Criticality In Sheared Suspensions, L. Corté, Sharon J. Gerbode, W. Man, D. J. Pine

All HMC Faculty Publications and Research

Recent studies reveal that suspensions of neutrally buoyant non-Brownian particles driven by slow periodic shear can undergo a dynamical phase transition between a fluctuating irreversible steady state and an absorbing reversible state. Using a computer model, we show that such systems exhibit self-organized criticality when a finite particle sedimentation velocity v_s is introduced. Under periodic shear, these systems evolve, without external intervention, towards the shear-dependent critical concentration ϕ_c as v_s is reduced. This state is characterized by power-law distributions in the lifetime and size of fluctuating clusters. Experiments exhibit similar behavior and, as v_s is reduced, …

Beguiled By Bananas: A Retrospective Study Of The Usage And Breadth Of Patron Vs. Librarian Acquired Ebook Collections, Jason S. Price, John D. Mcdonald

Library Staff Publications and Research

Library acquisitions lore contains a cautionary tale of a patron in a demand-driven environment who spent a huge chunk of the library budget on ebooks about bananas. This story and others like it have been used to perpetuate the argument that demand-driven acquisition will result in collections that don't appeal to a broad audience or are otherwise unbalanced. We apply post-acquisition usage data from multiple libraries to test the hypothesis that patron-acquired versus librarian-acquired collections have different usage profiles. In addition, we analyze their subject profiles to evaluate collection breadth and balance. Our results will help libraries to anticipate the …

How Much Can Guided Modes Enhance Absorption In Thin Solar Cells?, Peter N. Saeta, Vivian E. Ferry, Domenico Pacifici, Jeremy N. Munday, Harry A. Atwater

All HMC Faculty Publications and Research

Absorption enhancement in thin metal-backed solar cells caused by dipole scatterers embedded in the absorbing layer is studied using a semi-analytical approach. The method accounts for changes in the radiation rate produced by layers above and below the dipole, and treats incoherently the subsequent scattering of light in guided modes from other dipoles. We find large absorption enhancements for strongly coupled dipoles, exceeding the ergodic limit in some configurations involving lossless dipoles. An antireflection-coated 100-nm layer of a-Si:H on Ag absorbs up to 87% of incident above-gap light. Thin layers of both strong and weak absorbers show similar strongly enhanced …

Tracking Electronic Resource Acquisitions: Using A Helpdesk System To Succeed Where Your Erms Failed, Xan Arch, Jason S. Price

Library Staff Publications and Research

From selection to license negotiation through activation, libraries need the ability to track the electronic resource acquisition process and support uninterrupted workflow through multiple people and/or departments. Existing systems store fragments of information about a resource, but they don’t support management of the progress of each resource through the electronic resource acquisition maze. Stanford and Claremont have configured the JIRA and Footprints ticketing systems to address this fundamental need. Our systems facilitate efficient and complete activation of e-resources, and allow greater transparency in the acquisitions process throughout the organization. We will demonstrate the key features & functionality of our independently …

On Similarity Classes Of Well-Rounded Sublattices Of Z², Lenny Fukshansky

CMC Faculty Publications and Research

A lattice is called well-rounded if its minimal vectors span the corresponding Euclidean space. In this paper we study the similarity classes of well-rounded sublattices of Z². We relate the set of all such similarity classes to a subset of primitive Pythagorean triples, and prove that it has the structure of a non-commutative infinitely generated monoid. We discuss the structure of a given similarity class, and define a zeta function corresponding to each similarity class. We relate it to Dedekind zeta of Z[i], and investigate the growth of some related Dirichlet series, which reflect on …

A Preliminary Mathematical Model Of Skin Dendritic Cell Trafficking And Induction Of T Cell Immunity, Amy H. Lin Erickson, Alison Wise, Stephen Fleming, Margaret Baird, Zabeen Lateef, Annette Molinaro, Miranda Teboh-Ewungkem, Lisette G. De Pillis

All HMC Faculty Publications and Research

Chronic inflammation is a process where dendritic cells (DCs) are constantly sampling antigen in the skin and migrating to lymph nodes where they induce the activation and proliferation of T cells. The T cells then travel back to the skin where they release cytokines that induce/maintain the inflammatory condition. This process is cyclic and ongoing. We created a differential equations model to reflect the initial stages of the inflammatory process. In particular, we modeled antigen stimulation of DCs in the skin, movement of DCs from the skin to a lymph node, and the subsequent activation of T cells in the …

Probing Predispositions: The Pragmatism Of A Process Perspective, David S. Moore

Pitzer Faculty Publications and Research

As J. P. Spencer et al. (2009) argue, the theories of some developmental psychologists continue to be nativistic, even though nativism is an inherently nondevelopmental school of thought. Psychologists interested in development study the emergence of human characteristics—including predispositions—and are not content to simply catalogue competences that characterize human newborns; instead, they recognize that all human characteristics, including those present at birth, reflect the circumstances of development. A truly developmental science of behavior requires rejecting the nativism–empiricism debate outright, abandoning ideas such as “core knowledge” and psychological “endowments,” and adopting a process perspective that focuses on how traits emerge from …

Compression Theorems For Periodic Tilings And Consequences, Arthur T. Benjamin, Alex K. Eustis '06, Mark A. Shattuck

All HMC Faculty Publications and Research

We consider a weighted square-and-domino tiling model obtained by assigning real number weights to the cells and boundaries of an n-board. An important special case apparently arises when these weights form periodic sequences. When the weights of an nm-tiling form sequences having period m, it is shown that such a tiling may be regarded as a meta-tiling of length n whose weights have period 1 except for the first cell (i.e., are constant). We term such a contraction of the period in going from the longer to the shorter tiling as "period compression". It turns out that …

Institutional Resilience Amid Political Change: The Case Of Biodiversity Conservation, Paul F. Steinberg

All HMC Faculty Publications and Research

There is a substantial literature documenting the spatial mismatch between the geographic location of biological resources and the spatial jurisdiction of the institutions responsible for their management. But little attention has been paid to the disjuncture in temporal scales between the long-term requirements of biodiversity conservation and the short time horizons governing public and private decisions affecting the survival of species and ecosystems. How can we create socially agreed-upon rules governing the long-term use and conservation of biodiversity when ongoing change is one of the defining characteristics of modern society? This article describes a new approach to biodiversity conservation—conservation systems—that …

Asymptotic Dynamics Of Attractive-Repulsive Swarms, Andrew J. Leverentz '08, Chad M. Topaz, Andrew J. Bernoff

All HMC Faculty Publications and Research

We classify and predict the asymptotic dynamics of a class of swarming models. The model consists of a conservation equation in one dimension describing the movement of a population density field. The velocity is found by convolving the density with a kernel describing attractive-repulsive social interactions. The kernel’s first moment and its limiting behavior at the origin determine whether the population asymptotically spreads, contracts, or reaches steady state. For the spreading case, the dynamics approach those of the porous medium equation. The widening, compactly supported population has edges that behave like traveling waves whose speed, density, and slope we calculate. …

A Semilinear Wave Equation With Smooth Data And No Resonance Having No Continuous Solution, Jose F. Caicedo, Alfonso Castro

All HMC Faculty Publications and Research

We prove that a boundary value problem for a semilinear wave equation with smooth nonlinearity, smooth forcing, and no resonance cannot have continuous solutions. Our proof shows that this is due to the non-monotonicity of the nonlinearity.

Defining Best Practices In Electronic Thesis And Dissertation Metadata, Rebecca L. Lubas

Library Staff Publications and Research

The University of New Mexico will mandate in 2009 that theses and dissertations be submitted in electronic form as the copy of record. These documents will reside in the university’s digital repository, operated on a DSpace platform. This article reviews practices for thesis and dissertation metadata creation with a focus on DSpace instances, best practice recommendations for authorsubmitted metadata, recommendations for subject analysis, and training for metadata practitioners. The article recommends processes for author submission, metadata quality control and enhancement, and crosswalking of the metadata to the library’s catalog to maximize discovery.

Sum Rules And Universality In Electron-Modulated Acoustic Phonon Interaction In A Free-Standing Semiconductor Plate, Shigeyasu Uno, Darryl H. Yong, Nobuya Mori

All HMC Faculty Publications and Research

Analysis of acoustic phonons modulated due to the surfaces of a free-standing semiconductor plate and their deformation-potential interaction with electrons are presented. The form factor for electron-modulated acoustic phonon interaction is formulated and analyzed in detail. The form factor at zero in-plane phonon wave vector satisfies sum rules regardless of electron wave function. The form factor is larger than that calculated using bulk phonons, leading to a higher scattering rate and lower electron mobility. When properly normalized, the form factors lie on a universal curve regardless of plate thickness and material.

The Initial And Final States Of Electron And Energy Transfer Processes: Diabatization As Motivated By System-Solvent Interactions, Joseph E. Subotnik, Robert J. Cave, Ryan P. Steele, Neil Shenvi

All HMC Faculty Publications and Research

For a system which undergoes electron or energy transfer in a polar solvent, we define the diabatic states to be the initial and final states of the system, before and after the nonequilibrium transfer process. We consider two models for the system-solvent interactions: A solvent which is linearly polarized in space and a solvent which responds linearly to the system. From these models, we derive two new schemes for obtaining diabatic states from ab initio calculations of the isolated system in the absence of solvent. These algorithms resemble standard approaches for orbital localization, namely, the Boys and Edmiston–Ruedenberg (ER) formalisms. …

Generation Of Mie Size Microdroplet Aerosols With Applications In Laser-Driven Fusion Experiments, Andrew P. Higginbotham '09, O. Semonin '06, S. Bruce '08, C. Chan '08, M. Maindi '07, Thomas D. Donnelly, M. Maurer, W. Bang, I. Churina, J. Osterholz, I. Kim, A. C. Bernstein, T. Ditmire

All HMC Faculty Publications and Research

We have developed a tunable source of Mie scale microdroplet aerosols that can be used for the generation of energetic ions. To demonstrate this potential, a terawatt Ti:Al₂O₃ laser focused to 2×10¹⁹ W/cm² was used to irradiate heavy water (D₂O) aerosols composed of micron-scale droplets. Energetic deuterium ions, which were generated in the laser-droplet interaction, produced deuterium-deuterium fusion with approximately 2×10³ fusion neutrons measured per joule of incident laser energy.

Estimating The Macroeconomic Consequence Of 9/11, S. Brock Blomberg, Gregory Hess

CMC Faculty Publications and Research

We perform an empirical investigation to estimate the macroeconomic cost of September 11 attacks on the United States economy. We estimate the impact of the attacks to be approximately a 0.50 percentage point decrease in GDP growth or $60 billion. Our upper bound estimate of the impact of September 11 is approximately twice that or $125 billion.

Topics In Compressed Sensing, Deanna Needell

CMC Faculty Publications and Research

Compressed sensing has a wide range of applications that include error correction, imaging, radar and many more. Given a sparse signal in a high dimensional space, one wishes to reconstruct that signal accurately and efficiently from a number of linear measurements much less than its actual dimension. Although in theory it is clear that this is possible, the difficulty lies in the construction of algorithms that perform the recovery efficiently, as well as determining which kind of linear measurements allow for the reconstruction. There have been two distinct major approaches to sparse recovery that each present different benefits and shortcomings. …

Noisy Signal Recovery Via Iterative Reweighted L1-Minimization, Deanna Needell

CMC Faculty Publications and Research

Compressed sensing has shown that it is possible to reconstruct sparse high dimensional signals from few linear measurements. In many cases, the solution can be obtained by solving an L1-minimization problem, and this method is accurate even in the presence of noise. Recent a modified version of this method, reweighted L1-minimization, has been suggested. Although no provable results have yet been attained, empirical studies have suggested the reweighted version outperforms the standard method. Here we analyze the reweighted L1-minimization method in the noisy case, and provide provable results showing an improvement in the error bound over the standard bounds.

Counting On Chebyshev Polynomials, Arthur T. Benjamin, Daniel Walton '07

All HMC Faculty Publications and Research

Chebyshev polynomials have several elegant combinatorial interpretations. Specificially, the Chebyshev polynomials of the first kind are defined by T₀(x) = 1, T₁(x) = x, and T_n(x) = 2x T_n-1(x) - T_n-2(x). Chebyshev polynomials of the second kind U_n(x) are defined the same way, except U₁(x) = 2x. T_n and U_n are shown to count tilings of length n strips with squares and dominoes, where the tiles are given weights and sometimes color. Using these interpretations, many identities satisfied by Chebyshev polynomials can be given …

Academic Library As Publishing Agent: Showcasing Student, Faculty, And Campus Scholarship And Publications, Allegra Swift

Library Staff Publications and Research

Academic libraries of all sizes can and must strategically position themselves to be a campus publisher. A means of doing this is to implement an IR, providing institutions an opportunity to showcase senior theses, and student and faculty peer-reviewed journals. Presentation includes representatives from a small college, a consortium of small colleges, and a university with a university press.

A Life Cycle Perspective On Online Community Success, Alicia Iriberri '06, Gondy Leroy

CGU Faculty Publications and Research

Using the information systems lifecycle as a unifying framework, we review online communities research and propose a sequence for incorporating success conditions during initiation and development to increase their chances of becoming a successful community, one in which members participate actively and develop lasting relationships. Online communities evolve following distinctive lifecycle stages and recommendations for success are more or less relevant depending on the developmental stage of the online community. In addition, the goal of the online community under study determines the components to include in the development of a successful online community. Online community builders and researchers will benefit …

Thermal Links For The Implementation Of An Optical Refrigerator, John Parker, David Mar, Steven Von Der Porten, John Hankinson, Kevin Byram, Chris Lee, Michael K. Mayeda, Richard C. Haskell, Qimin Yang, Scott R. Greenfield, Richard I. Epstein

All HMC Faculty Publications and Research

Optical refrigeration has been demonstrated by several groups of researchers, but the cooling elements have not been thermally linked to realistic heat loads in ways that achieve the desired temperatures. The ideal thermal link will have minimal surface area, provide complete optical isolation for the load, and possess high thermal conductivity. We have designed thermal links that minimize the absorption of fluoresced photons by the heat load using multiple mirrors and geometric shapes including a hemisphere, a kinked waveguide, and a tapered waveguide. While total link performance is dependent on additional factors, we have observed net transmission of photons with …

An Undescribed Gecko (Gekkonidae: Cyrtodactylus) From Deer Cave, Gunung Mulu National Park, Sarawak, With Comments On The Distribution Of Bornean Cave Geckos, Donald A. Mcfarlane, Joyce Lundberg, Keith Christenson

WM Keck Science Faculty Papers

Geckos of the genus Cyrtodactylus are a speciose group in Southeast Asia, with at least nine species known from the island of Borneo (Das & Ismail, 2001; Das, 2006). Of these species, Cyrtodactylus cavernicolus has the smallest known range and is therefore the most vulnerable, a status that is reflected in the species having been designated a Totally Protected Species in Sarawak. Confirmed records of C. cavernicolus are known only from Niah Cave, located in an isolated limestone block known as the Gunung Subis massif, approximately 13 km² in extent. The Niah Cave Gecko is presumed to be dependent on …

Bats And Bell Holes: The Microclimatic Impact Of Bat Roosting, Using A Case Study From Runaway Bay Caves, Jamaica, Joyce Lundberg, Donald A. Mcfarlane

WM Keck Science Faculty Papers

The microclimatic effect of bats roosting in bell holes (blind vertical cylindrical cavities in cave roofs) in Runaway Bay Caves, Jamaica, was measured and the potential impact of their metabolism on dissolution modelled. Rock temperature measurements showed that bell holes with bats get significantly hotter than those without bats during bat roosting periods (by an average of 1.1 °C). The relationship is clearest for bell holes with more than about 300 g aggregate bat body mass and for bell holes that are moderately wide and deep, of W:D ratio between 0.8 and 1.6. Measurement of temperature decay after abandonment showed …

A Note On The Thermal Ecology And Foraging Behaviour Of The Egyptian Fruit Bat, Rousettus Aegyptiacus, At Mt. Elgon, Kenya, Donald A. Mcfarlane, Joyce Lundberg

WM Keck Science Faculty Papers

The Egyptian fruit bat, Rousettus aegyptiacus, is an abundant and widely distributed African pteropid (Nowak, 1999). The species is unusual amongst pteropids in being an obligate cave-dweller (Kwiecinski & Griffiths, 1999), sometimes reaching colony sizes in the thousands (Kingdon, 1974). In the caves of Mt. Elgon National Park, western Kenya (1° 08′N, 34° 39′E), precision temperature loggers placed in major Rousettus roosts and intervening passages have allowed us to precisely monitor bat emergence and return times.

The major caves of Mt. Elgon National Park consist of geophagically modified tunnels and collapse chambers cut into Miocene-aged pyroclastic strata (Lundberg & …

The Once And Future Forest Service: Land-Management Policies And Politics In Contemporary America, Char Miller

Pomona Faculty Publications and Research

The news from the Far North is not good. In the spring of 2007, University of Alberta scientists reported that portions of the Canadian tundra were transforming into new forests of spruce and shrubs much more rapidly than once was imaginable. "The conventional thinking on treeline dynamics has been that advances are very slow because conditions are so harsh at these high latitudes and altitudes," reported Dr. Ryan Danby, a member of the UA research team. "But what our data indicate is that there was an upslope surge of trees in response to warmer temperatures. It's like [the forest] waited …

A Different Pencil Too Good To Be Ignored? A First Look At Wolfram|Alpha, Gizem Karaali, Bruce Yoshiwara

Pomona Faculty Publications and Research

So you came across several news pieces about Wolfram|Alpha and you’re wondering what all the fuss is about. Let’s start with the basics.

Predicting The Drug Release Kinetics Of Matrix Tablets, Boris Baeumer, Lipika Chatterjee, Peter Hinow, Thomas Rades, Ami E. Radunskaya, Ian Tucker

Pomona Faculty Publications and Research

In this paper we develop two mathematical models to predict the release kinetics of a water soluble drug from a polymer/excipient matrix tablet. The first of our models consists of a random walk on a weighted graph, where the vertices of the graph represent particles of a drug, excipient and polymer, respectively. The graph itself is the contact graph of a multidisperse random sphere packing. The second model describes the dissolution and the subsequent diffusion of the active drug out of a porous matrix using a system of a partial differential equations. The predictions of both models show good qualitative …

Review: Spectra Of Toeplitz Operators And Compositions Of Muckenhoupt Weights With Blaschke Products, Stephan Ramon Garcia

Pomona Faculty Publications and Research

No abstract provided.