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

Digital Commons Network™

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

Smith College

2004

Discipline
Keyword
Publication

Articles 1 - 30 of 47

Full-Text Articles in Entire DC Network

Partitioning Regular Polygons Into Circular Pieces Ii: Nonconvex Partitions, Mirela Damian, Joseph O'Rourke Dec 2004

Partitioning Regular Polygons Into Circular Pieces Ii: Nonconvex Partitions, Mirela Damian, Joseph O'Rourke

Computer Science: Faculty Publications

We explore optimal circular nonconvex partitions of regular k-gons. The circularity of a polygon is measured by its aspect ratio: the ratio of the radii of the smallest circumscribing circle to the largest inscribed disk. An optimal circular partition minimizes the maximum ratio over all pieces in the partition. We show that the equilateral triangle has an optimal 4-piece nonconvex partition, the square an optimal 13-piece nonconvex partition, and the pentagon has an optimal nonconvex partition with more than 20 thousand pieces. For hexagons and beyond, we provide a general algorithm that approaches optimality, but does not achieve it.

Go to article

The Welfare Implications Of Increasing Disability Insurance Benefit Generosity, John Bound, Julie Berry Cullen, Austin Nichols, Lucie Schmidt Dec 2004

The Welfare Implications Of Increasing Disability Insurance Benefit Generosity, John Bound, Julie Berry Cullen, Austin Nichols, Lucie Schmidt

Economics: Faculty Publications

In order to evaluate whether workers are over- or under-insured through the Disability Insurance (DI) program, we develop a framework that allows us to simulate the benefits as well as the costs associated with marginal changes in payment generosity from a representative cross-sectional sample of the population. Under the assumption that individuals are reasonably risk averse, we find that the typical worker would value increased benefits somewhat above the average costs of providing them. However, whether the benefit increases tend to lower or raise utility when we average across all individuals in our sample is sensitive to assumptions that affect …

Go to article

Uncovering The Inner Power Of Teachers' Lives: Towards A Learning Profession, Ora W.Y. Kwo, Sam M. Intrator Dec 2004

Uncovering The Inner Power Of Teachers' Lives: Towards A Learning Profession, Ora W.Y. Kwo, Sam M. Intrator

Education and Child Study: Faculty Publications

No abstract provided.

Go to article

Unconformities And Age Relationships, Tongue River And Older Members Of The Fort Union Formation (Paleocene), Western Williston Basin, U.S.A., Edward S. Belt, Joseph H. Hartman, John A. Diemer, Timothy J. Kroeger, Neil E. Tibert, H. Allen Curran Dec 2004

Unconformities And Age Relationships, Tongue River And Older Members Of The Fort Union Formation (Paleocene), Western Williston Basin, U.S.A., Edward S. Belt, Joseph H. Hartman, John A. Diemer, Timothy J. Kroeger, Neil E. Tibert, H. Allen Curran

Geosciences: Faculty Publications

An unconformable relationship is observed within the Paleocene Fort Union Formation in the western Williston Basin at the contact between the Tongue River Member and the underlying Lebo and Ludlow Members. Isotopic dates and pollen biozone data reported here are integrated with previously published data. A new correlation of these facies results in a revised history of localized depositional and tectonic events. One unconformity occurs at this lithological contact in the Pine Hills (PH), Terry Badlands (TB), and Ekalaka (E) areas west of the Cedar Creek anticline (CCA), and another unconformity occurs at the same lithological contact in the Little …

Go to article

Population Recovery And Differential Heat Shock Protein Expression For The Corals Agaricia Agaricites And A. Tenuifolia In Belize, Martha L. Robbart, Paulette M. Peckol, Stylianos P. Scordilis, H. Allen Curran, Jocelyn Brown-Saracino Nov 2004

Population Recovery And Differential Heat Shock Protein Expression For The Corals Agaricia Agaricites And A. Tenuifolia In Belize, Martha L. Robbart, Paulette M. Peckol, Stylianos P. Scordilis, H. Allen Curran, Jocelyn Brown-Saracino

Geosciences: Faculty Publications

Over recent decades, coral reefs worldwide have experienced severe sea-surface temperature (SST) anomalies. Associated with an El Niño-Southern Oscillation (ENSO) event of 1997-1998, nearly 100% mortality of the space-dominated coral Agaricia tenuifolia was reported at several shelf lagoonal sites of the Belize barrier reef system; a less abundant congener, A. agaricites, had lower mortality rates. We assessed A. agaricites and A. tenuifolia populations at coral reef ridges in the south-central sector of the Belize shelf lagoon and forereef sites to document recovery following the 1998 ENSO event and subsequent passage of Hurricane Mitch. To investigate the difference in heat …

Go to article

Tandem Intramolecular Nicholas And Pauson-Khand Reactions For The Synthesis Of Tricyclic Oxygen-Containing Heterocycles, Miriam M. Quintal, Kristina D. Closser, Kevin M. Shea Nov 2004

Tandem Intramolecular Nicholas And Pauson-Khand Reactions For The Synthesis Of Tricyclic Oxygen-Containing Heterocycles, Miriam M. Quintal, Kristina D. Closser, Kevin M. Shea

Chemistry: Faculty Publications

Simple acyclic enynes can be easily converted into tricyclic ethers upon treatment with Co2(CO)8followed by Nicholas and Pauson−Khand reactions. Tricyclic [5,8,5]- and [5,7,5]-systems can be prepared in high overall yields in only seven synthetic steps.

Go to article

Filarial Genomics, Steven A. Williams Nov 2004

Filarial Genomics, Steven A. Williams

Biological Sciences: Faculty Publications

No abstract provided.

Go to article

Unfolding Smooth Prismatoids, Nadia Benbernou, Patricia Cahn, Joseph O'Rourke Oct 2004

Unfolding Smooth Prismatoids, Nadia Benbernou, Patricia Cahn, Joseph O'Rourke

Computer Science: Faculty Publications

We define a notion for unfolding smooth, ruled surfaces, and prove that every smooth prismatoid (the convex hull of two smooth curves lying in parallel planes), has a nonoverlapping “volcano unfolding.” These unfoldings keep the base intact, unfold the sides outward, splayed around the base, and attach the top to the tip of some side rib. Our result answers a question for smooth prismatoids whose analog for polyhedral prismatoids remains unsolved.

Go to article

Distinguishing Numbers For Graphs And Groups, Julianna Tymoczko Sep 2004

Distinguishing Numbers For Graphs And Groups, Julianna Tymoczko

Mathematics Sciences: Faculty Publications

A graph G is distinguished if its vertices are labelled by a map φ: V(G) → {1,2,..., k} so that no non-trivial graph automorphism preserves φ. The distinguishing number of G is the minimum number k necessary for φ to distinguish the graph. It measures the symmetry of the graph. We extend these definitions to an arbitrary group action of Γ on a set X. A labelling φ: X → {1, 2,..., k} is distinguishing if no element of Γ preserves Γ except those which fix each element of X. The distinguishing number of the group action on X is …

Go to article

Improving The Boosted Correlogram, Nicholas Howe, Amanda Ricketson Sep 2004

Improving The Boosted Correlogram, Nicholas Howe, Amanda Ricketson

Computer Science: Faculty Publications

Introduced seven years ago, the correlogram is a simple statistical image descriptor that nevertheless performs strongly on image retrieval tasks. As a result it has found wide use as a component inside larger systems for content-based image and video retrieval. Yet few studies have examined potential variants of the correlogram or compared their performance to the original. This paper presents systematic experiments on the correlogram and several variants under different conditions, showing that the results may vary significantly depending on both the variant chosen and its mode of application. As expected, the experimental setup combining correlogram variants with boosting shows …

Go to article

Inhomogeneous Fragmentation Of The Rolling Tachyon, Gary Felder, Lev Kofman Aug 2004

Inhomogeneous Fragmentation Of The Rolling Tachyon, Gary Felder, Lev Kofman

Physics: Faculty Publications

Dirac-Born-Infeld type effective actions reproduce many aspects of string theory classical tachyon dynamics of unstable Dp-branes. The inhomogeneous tachyon field rolling from the top of its potential forms topological defects of lower codimensions. In between them, as we show, the tachyon energy density fragments into a p-dimensional web-like high density network evolving with time. We present an analytic asymptotic series solution of the non-linear equations for the inhomogeneous tachyon and its stress energy. The generic solution for a tachyon field with a runaway potential in arbitrary dimensions is described by the free streaming of noninteracting massive particles whose initial velocities …

Go to article

The Clustering Of Galaxies Around Three Z ∼ 3 Damped Lyα Absorbers, Nicolas Bouché, James D. Lowenthal Jul 2004

The Clustering Of Galaxies Around Three Z ∼ 3 Damped Lyα Absorbers, Nicolas Bouché, James D. Lowenthal

Astronomy: Faculty Publications

We present our results on the cross-correlation of Lyman break galaxies (LBGs) around three damped Lyα absorbers (DLAs) at z ≃ 3 from deep [μ (sky) ≃ 27.6 mag arcsec ] UBVI KPNO 4 m/MOSAIC images. The large area of the MOSAIC images, 0.31 deg or ∼65 × 65 h Mpc comoving at redshift z = 3, allows us to probe the clustering of LBGs on scales up to 20 Mpc comoving. Our survey covers a total of 1 deg and contains ∼3000 LBGs with photometric redshifts between 2.8 and 3.5. Using the redshift likelihood distributions with m as a …

Go to article

Going Slitless: Images Of Forbidden Line Emission Regions Of Classical T Tauri Stars Observed With The Hubble Space Telescope, Patrick Hartigan, Suzan Edwards, Rachel Pierson Jul 2004

Going Slitless: Images Of Forbidden Line Emission Regions Of Classical T Tauri Stars Observed With The Hubble Space Telescope, Patrick Hartigan, Suzan Edwards, Rachel Pierson

Astronomy: Faculty Publications

We have observed five classical T Tauri stars known to have strong forbidden-line emission with STIS in slitless mode on the Hubble Space Telescope. This technique makes it possible to image jets within a few tens of AU of their exciting sources, a region of great interest for models of accretion disks and jets. Slitless images generate emission-line images at all wavelengths, including those where no narrowband filters exist. Images of the forbidden-line regions around each object, constructed by subtracting the stellar continuum and combining observations taken at different orientations, show [O I] jets from CW Tau, HN Tau, …

Go to article

Scoring Error Of Social Avoidance And Distress Scale And Its Psychometric Implications, Stefan G. Hofmann, Patricia Marten Dibartolo, Robert M. Holaway, Richard G. Heimberg Jun 2004

Scoring Error Of Social Avoidance And Distress Scale And Its Psychometric Implications, Stefan G. Hofmann, Patricia Marten Dibartolo, Robert M. Holaway, Richard G. Heimberg

Psychology: Faculty Publications

An error in the scoring instructions of the Social Avoidance and Distress Scale (SAD), one of the most popular instruments to measure social anxiety, is discussed.

Go to article

Marine Anthropogenic Debris Surveys On Hanna Bay And East Beaches, San Salvador Island, Bahamas, 1998–2004, Virginia White, H. Allen Curran Jun 2004

Marine Anthropogenic Debris Surveys On Hanna Bay And East Beaches, San Salvador Island, Bahamas, 1998–2004, Virginia White, H. Allen Curran

Geosciences: Faculty Publications

Reprinted from: R.L. Davis & D. Gamble, eds., Proceedings of the 12th Symposium on the Geology of the Bahamas and Other Carbonate Regions, San Salvador, Gerace Research Center

Go to article

Silhouette Lookup For Automatic Pose Tracking, Nicholas Howe Jun 2004

Silhouette Lookup For Automatic Pose Tracking, Nicholas Howe

Computer Science: Faculty Publications

Computers should be able to detect and track the articulated 3-D pose of a human being moving through a video sequence. Current tracking methods often prove slow and unreliable, and many must be initialized by a human operator before they can track a sequence. This paper introduces a simple yet effective algorithm for tracking articulated pose, based upon looking up observed silhouettes in a collection of known poses. The new algorithm runs quickly, can initialize itself without human intervention, and can automatically recover from critical tracking errors made while tracking previous frames in a video sequence.

Go to article

The Structure Of Optimal Partitions Of Orthogonal Polygons Into Fat Rectangles, Joseph O'Rourke, Geetika Tewari May 2004

The Structure Of Optimal Partitions Of Orthogonal Polygons Into Fat Rectangles, Joseph O'Rourke, Geetika Tewari

Computer Science: Faculty Publications

Motivated by a VLSI masking problem, we explore partitions of an orthogonal polygon of n vertices into isothetic rectangles that maximize the shortest rectangle side over all rectangles. Thus no rectangle is "thin"; all rectangles are "fat". We show that such partitions have a rich structure, more complex than what one might at first expect. For example, for partitions all "cuts" of which are anchored on the boundary, sometimes cuts are needed 1/2 or 1/3 of the distance between two polygon edges, but they are never needed at fractions with a larger denominator. Partitions using cuts without any restrictions seem …

Go to article

Braneworld Dynamics With The Branecode, Martin Johannes, Gary Felder, Andrei V. Frolov, Marco Peloso, Lev Kofman Apr 2004

Braneworld Dynamics With The Branecode, Martin Johannes, Gary Felder, Andrei V. Frolov, Marco Peloso, Lev Kofman

Physics: Faculty Publications

We give a full nonlinear numerical treatment of time-dependent 5D braneworld geometry, which is determined self-consistently by potentials for the scalar field in the bulk and at two orbifold branes, supplemented by boundary conditions at the branes. We describe the BRANECODE, an algorithm which we designed to solve the dynamical equations numerically. We apply the BRANECODE to braneworld models and find several novel phenomena of the brane dynamics. Starting with static warped geometry with de Sitter branes, we find numerically that this configuration is often unstable due to a tachyonic mass of the radion during inflation. If the model admits …

Go to article

The Great Escape: Phosphorylation Of Ena/Vasp By Pka Promotes Filopodial Formation, Timothy M. Gomez, Estuardo Robles Apr 2004

The Great Escape: Phosphorylation Of Ena/Vasp By Pka Promotes Filopodial Formation, Timothy M. Gomez, Estuardo Robles

Neuroscience: Faculty Publications

The Ena/VASP family of proteins consists of adaptor molecules that localize to subcellular sites of actin polymerization. The role of Ena/VASP proteins in the regulation of cell motility and axon outgrowth has been controversial. Recently, these proteins have been proposed to function as "anticapping" factors, which may have differential effects on filopodial versus lammelipodial actin-based protrusions. A study by Lebrand et al. in this issue of Neuron supports this model and identifies PKA as a key regulator of Ena/VASP function downstream of the chemoattractant Netrin.

Go to article

Race, Class, And Sexual Harassment In The 1970s, Carrie N. Baker Apr 2004

Race, Class, And Sexual Harassment In The 1970s, Carrie N. Baker

Study of Women and Gender: Faculty Publications

No abstract provided.

Go to article

Critical Dynamics Of Superconductors In The Charged Regime, Courtney Lannert, Smitha Vishveshwara, Matthew P.A. Fisher Mar 2004

Critical Dynamics Of Superconductors In The Charged Regime, Courtney Lannert, Smitha Vishveshwara, Matthew P.A. Fisher

Physics: Faculty Publications

The charged regime of the superconductor-metal transition was analyzed by applying a finite temperature critical dynamics. A transverse gage field coupling was applied to the superconducting order parameter. A new dynamic universality class characeterized by a finite fixed point ratio between the transport coefficients associated with the order parameter and gage fields was found by assuming relaxational dynamics for both the order parameter and gage fields within a renormalization group scheme. It was found that various features of the dynamic universality class of the charged superconductor appeared in measurable quantities.

Go to article

A Demonstration Of Phonons That Implements The Linear Theory, Dietrich Lüerßen, Nalini Easwar, Ayesha Malhotra, Libby Hutchins, Kim Schulze, Brandi Wilcox Feb 2004

A Demonstration Of Phonons That Implements The Linear Theory, Dietrich Lüerßen, Nalini Easwar, Ayesha Malhotra, Libby Hutchins, Kim Schulze, Brandi Wilcox

Physics: Faculty Publications

Beads on a vibrating wire are used to simulate the discrete structure of a solid-state material. The novel idea of the experiment is to use very small oscillation amplitudes of the wire to avoid nonlinearities in the interaction. We achieve a good signal-to-noise ratio using a lock-in technique. We find quantitative agreement between theory and experiment for not only a mono- and a diatomic chain, but also for the bare wire. The latter agreement is the crucial aspect that distinguishes our experiment from previous ones. This agreement assures that the fundamental assumption of the theory ~Hooke’s law! is satisfied. We …

Go to article

On The Number Of Embeddings Of Minimally Rigid Graphs, Ciprian Borcea, Ileana Streinu Feb 2004

On The Number Of Embeddings Of Minimally Rigid Graphs, Ciprian Borcea, Ileana Streinu

Computer Science: Faculty Publications

Rigid frameworks in some Euclidean space are embedded graphs having a unique local realization (up to Euclidean motions) for the given edge lengths, although globally they may have several. We study the number of distinct planar embeddings of minimally rigid graphs with $n$ vertices. We show that, modulo planar rigid motions, this number is at most ${{2n-4}\choose {n-2}} \approx 4^n$. We also exhibit several families which realize lower bounds of the order of $2^n$, $2.21^n$ and $2.28^n$. For the upper bound we use techniques from complex algebraic geometry, based on the (projective) Cayley--Menger variety ${\it CM}^{2,n}(C)\subset P_{{{n}\choose {2}}-1}(C)$ over the …

Go to article

Parameterization And Validation Of A Lumped Parameter Diffusion Model For Fuel Cell Stack Membrane Humidity Estimation#, Denise Mckay, Anna Stefanopoulou Jan 2004

Parameterization And Validation Of A Lumped Parameter Diffusion Model For Fuel Cell Stack Membrane Humidity Estimation#, Denise Mckay, Anna Stefanopoulou

Engineering: Faculty Publications

We present here a model for estimating the electrode humidity of a proton exchange membrane fuel cell (PEMFC) stack. We use this model to develop a nonlinear open loop estimator of the membrane humidity based on monitoring the pressure and temperature entering and exiting the electrodes, as well as the upstream humidity of each electrode. This lumped parameter model, calibrated and experimentally validated, quantifies the average vapor mass transport across a 24 cell, PEMFC stack of 1.4 kW continuous power output. The experimental method devised here for the parameterization of the model is simple and reproducible. The estimator can be …

Go to article

Afdc, Ssi, And Welfare Reform Aggressiveness: Caseload Reductions Versus Caseload Shifting, Lucie Schmidt, Purvi Sevak Jan 2004

Afdc, Ssi, And Welfare Reform Aggressiveness: Caseload Reductions Versus Caseload Shifting, Lucie Schmidt, Purvi Sevak

Economics: Faculty Publications

Welfare reform has made receipt of cash benefits more difficult and less attractive for single mothers. We examine whether reforms of AFDC affected caseloads of another program-Supplemental Security Income (SSI). We exploit state variation in welfare reform over time, and find that female-headed households in states aggressively pursuing welfare reform were 21.6 percent more likely to receive SSI. This implies that a decrease in caseloads in one program cannot be interpreted as an equal-sized decrease in the number of families receiving public assistance. In addition, our results have policy implications for the well-being of families affected by welfare reform time …

Go to article

Getting Complements On Your Mental State (Verbs), Jill De Villiers Jan 2004

Getting Complements On Your Mental State (Verbs), Jill De Villiers

Philosophy: Faculty Publications

There is a considerable body of theoretical and experimental work on how children develop a Theory of Mind. A recent meta-analysis by Wellman, Cross and Watson (2001) has revealed a consensus that children develop an awareness that other people might have false beliefs around the age of four years, give or take six months. Wellman and some other theorists believe that children undergo a conceptual change at this point, from a psychological theory based primarily on desire as the motivator of human action, to one that accords beliefs a causal role. Other theorists such as Leslie (1991; 1994) contend that …

Go to article

Talking When Talking Is Tough: Taking On Conversations About Race, Sexual Orientation, Gender, Class, And Other Aspects Of Social Identity, Joshua Miller, Susan Donner, Edith Fraser Jan 2004

Talking When Talking Is Tough: Taking On Conversations About Race, Sexual Orientation, Gender, Class, And Other Aspects Of Social Identity, Joshua Miller, Susan Donner, Edith Fraser

School for Social Work: Faculty Publications

No abstract provided.

Go to article

Holocene Tufa-Coated Serpulid Mounds From The Dominican Republic: Depositional And Diagenetic History, With Comparison To Modern Serpulid Aggregates From Baffin Bay, Texas, Bosiljka Glumac, Lisa Berrios, Lisa Greer, H. Allen Curran Jan 2004

Holocene Tufa-Coated Serpulid Mounds From The Dominican Republic: Depositional And Diagenetic History, With Comparison To Modern Serpulid Aggregates From Baffin Bay, Texas, Bosiljka Glumac, Lisa Berrios, Lisa Greer, H. Allen Curran

Geosciences: Faculty Publications

Ronald D. Lewis and Bruce C. Panuska (eds.) Proceedings of the 11th Symposium on the Geology of the Bahamas and Other Carbonate Regions: San Salvador, Gerace Research Center

Go to article

Aragonite Pseudomorphs In High Pressure Marbles Of Syros, Greece, John B. Brady, Michelle J. Markley, John C. Schumacher, John T. Cheney, Grace A. Bianciardi Jan 2004

Aragonite Pseudomorphs In High Pressure Marbles Of Syros, Greece, John B. Brady, Michelle J. Markley, John C. Schumacher, John T. Cheney, Grace A. Bianciardi

Geosciences: Faculty Publications

Numerous rod-shaped calcite crystals occur in the blueschist to eclogite facies marbles of Syros, Greece. The rods show a shape-preferred orientation, and the long axes of the rods are oriented at a large angle to foliation. The crystals also have a crystallographic-preferred orientation: calcite c-axes are oriented parallel to the long axes of the rods. Based on their chemical composition, shape, and occurrence in high-pressure marbles, these calcite crystals are interpreted as topotactic pseudomorphs after aragonite that developed a crystallographic-preferred orientation during peak metamorphism. This interpretation is consistent with deformation of aragonite by dislocation creep, which has been observed …

Go to article

The Cape Ann Plutonic Suite: A Field Trip For Petrology Classes, John B. Brady, John T. Cheney Jan 2004

The Cape Ann Plutonic Suite: A Field Trip For Petrology Classes, John B. Brady, John T. Cheney

Geosciences: Faculty Publications

Cape Ann, because of its proximity to Boston and many universities, has long been a focus of geologic study. Nineteenth century papers that consider mineralogy or petrology of Cape Ann rocks include Prescott (1839), Nichols (1856), Kimball (1860), Gregory (1862), Mudge (1862), Balch (1864), Cooke (1866, 1867), Knowlton (1867), Hyatt (1869, 1871a,b), Hunt (1871), Wadsworth (1878, 1882a,b, 1885), McDaniel (1884), Sears (1888, 1889, 1890a, 1891a,b, 1893a,b, 1894a,b, 1895, 1898), Shaler (1889), Pearce (1893), Penfield and Forbes (1896), and Washington (1898a,b,c, 1899a,b,c,d). More recent studies of note include Wright (1900), Clapp (1921), Warren and McKinstry (1924), Bowen and Schairer (1935), Palache …

Go to article

Next Last