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Articles 1 - 24 of 24
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Computational Geometry Column 36, Joseph O'Rourke
Computational Geometry Column 36, Joseph O'Rourke
Computer Science: Faculty Publications
Two results in "computational origami" are illustrated.
Pushpush Is Np-Hard In 3d, Joseph O'Rourke, The Smith Problem Solving Group
Pushpush Is Np-Hard In 3d, Joseph O'Rourke, The Smith Problem Solving Group
Computer Science: Faculty Publications
We prove that a particular pushing-blocks puzzle is intractable in 3D. The puzzle, inspired by the game PushPush, consists of unit square blocks on an integer lattice. An agent may push blocks (but never pull them) in attempting to move between given start and goal positions. In the PushPush version, the agent can only push one block at a time, and moreover, each block, when pushed, slides the maximal extent of its free range. We prove this version is NP-hard in 3D by reduction from SAT. The corresponding problem in 2D remains open.
The Energetics Of A Bouncing Ball, Warren A. Turner, Glenn W. Ellis
The Energetics Of A Bouncing Ball, Warren A. Turner, Glenn W. Ellis
Engineering: Faculty Publications
Computer-based, real-time data collection is used to explore the energetics of a bouncing ball. Discussion centers around student comprehension and misconceptions surrounding interconversion of mechanical energy and the pedagogical use of this experiment.
Inflation And Preheating In Nonoscillatory Models, Gary Felder, Lev Kofman, Andrei Linde
Inflation And Preheating In Nonoscillatory Models, Gary Felder, Lev Kofman, Andrei Linde
Physics: Faculty Publications
We study inflationary models in which the effective potential of the inflaton field does not have a minimum, but rather gradually decreases at large φ. In such models the inflaton field does not oscillate after inflation, and its effective mass becomes vanishingly small, so the standard theory of reheating based on the decay of the oscillating inflaton field does not apply. For a long time the only mechanism of reheating in such non-oscillatory (NO) models was based on gravitational particle production in an expanding universe. This mechanism is very inefficient. We will show that it may lead to cosmological problems …
Pituitary Adenylate Cyclase Activating Peptide Phase Shifts Circadian Rhythms In A Manner Similar To Light, Mary E. Harrington, Sabina Hoque, Adam Hall, Diego Golombek, Stephany Biello
Pituitary Adenylate Cyclase Activating Peptide Phase Shifts Circadian Rhythms In A Manner Similar To Light, Mary E. Harrington, Sabina Hoque, Adam Hall, Diego Golombek, Stephany Biello
Psychology: Faculty Publications
The endogenous circadian pacemaker in mammals is located in the suprachiasmatic nuclei (SCN) of the hypothalamus. Various cues can reset circadian rhythm phase, thereby entraining the internal rhythm to the environmental cycle, and these effects can be investigated using an in vitro method to measure phase shifts of the SCN. Although pituitary adenylate cyclase activating peptide (PACAP) is localized in retinal inputs to the SCN, it has been reported to alter clock phase only during the subjective day (Hannibal et al., 1997), whereas light alters phase only in the subjective night. In this study we show that PACAP can reset …
Zero-Parity Stabbing Information, Joseph O'Rourke, Irena Pashchenko
Zero-Parity Stabbing Information, Joseph O'Rourke, Irena Pashchenko
Computer Science: Faculty Publications
Everett et al. [EHN96, EHN97] introduced several varieties of stabbing information for the lines determined by pairs of vertices of a simple polygon P, and established their relationships to vertex visibility and other combinatorial data. In the same spirit, we define the “zero-parity (ZP) stabbing information” to be a natural weakening of their “weak stabbing information,” retaining only the distinction among {zero, odd, even > 0} in the number of polygon edges stabbed. Whereas the weak stabbing information’s relation to visibility remains an open problem, we completely settle the analogous questions for zero parity information, with three results: (1) ZP information …
Instant Preheating, Gary Felder, Lev Kofman, Andrei Linde
Instant Preheating, Gary Felder, Lev Kofman, Andrei Linde
Physics: Faculty Publications
We describe a new efficient mechanism of reheating. Immediately after rolling down the rapidly moving inflaton field φ produces particles χ, which may be either bosons or fermions. This is a nonperturbative process which occurs almost instantly; no oscillations or parametric resonance is required. The effective masses of the χ particles may be very small at the moment when they are produced, but they “fatten” when the field φ increases. When the particles χ become sufficiently heavy, they rapidly decay to other, lighter particles. This leads to an almost instantaneous reheating accompanied by the production of particles with masses which …
Structural And Kinetic Studies Of A Cisplatin-Modified Dna Icosamer Binding To Hmg1 Domain B*, Elizabeth R. Jamieson, Matthew P. Jacobson, Carmen M. Barnes, Christine S. Chow, Stephen J. Lippard
Structural And Kinetic Studies Of A Cisplatin-Modified Dna Icosamer Binding To Hmg1 Domain B*, Elizabeth R. Jamieson, Matthew P. Jacobson, Carmen M. Barnes, Christine S. Chow, Stephen J. Lippard
Chemistry: Faculty Publications
The high mobility group (HMG) domain is a DNA-binding motif found in the non-histone chromosomal proteins, HMG1 and HMG2, and some transcription factors. Experimental evidence has demonstrated that HMG-domain proteins can play a role in sensitizing cells to the anticancer drug cisplatin. Fluorescence resonance energy transfer (FRET) experiments were performed in the present study to investigate structural changes that accompany complex formation between the HMG domain B of HMG1 and a cisplatin-modified, 20-base pair double-stranded DNA probe containing fluorescein and rhodamine tethered at its two ends. The binding affinity of HMG1 domain B for the cisplatin-modified DNA probe was investigated …
Search For Exchange-Antisymmetric Two-Photon States, D. De Mille, D. Budker, N. Derr, E. Deveney
Search For Exchange-Antisymmetric Two-Photon States, D. De Mille, D. Budker, N. Derr, E. Deveney
Biological Sciences: Faculty Publications
Atomic two-photon J = 0 ↔ J′ = 1 transitions are forbidden for photons of the same energy. This selection rule is related to the fact that photons obey Bose-Einstein statistics. We have searched for small violations of this selection rule by studying transitions in atomic Ba. We set a limit on the probability v that photons are in exchange-antisymmetric states: v < 1.2 × 10-7.
Vodou Imagery, African-American Tradition And Cultural Transformation In Zora Neale Hurston's "Their Eyes Were Watching God", Daphne Lamothe
Vodou Imagery, African-American Tradition And Cultural Transformation In Zora Neale Hurston's "Their Eyes Were Watching God", Daphne Lamothe
Africana Studies: Faculty Publications
No abstract provided.
Chemiluminescent Detection Of Sequential Dna Hybridizations To High- Density, Filter-Arrayed Cdna Libraries: A Subtraction Method For Novel Gene Discovery, D. Guiliano, M. Ganatra, J. Ware, J. Parrot, J. Daub, L. Moran, H. Brennecke, J. M. Foster, T. Supali, M. Blaxter, A. L. Scott, Steven A. Williams, B. E. Slatko
Chemiluminescent Detection Of Sequential Dna Hybridizations To High- Density, Filter-Arrayed Cdna Libraries: A Subtraction Method For Novel Gene Discovery, D. Guiliano, M. Ganatra, J. Ware, J. Parrot, J. Daub, L. Moran, H. Brennecke, J. M. Foster, T. Supali, M. Blaxter, A. L. Scott, Steven A. Williams, B. E. Slatko
Biological Sciences: Faculty Publications
A chemiluminescent approach for sequential DNA hybridizations to high- density filter arrays of cDNAs, using a biotin-based random priming method followed by a streptavidin/alkaline phosphatase/CDP-Star(TM) detection protocol, is presented. The method has been applied to the Brugia malayi genome project, wherein cDNA libraries, cosmid and bacterial artificial chromosome (BAC) libraries have been gridded at high density onto nylon filters for subsequent analysis by hybridization. Individual probes and pools of rRNA probes, ribosomal protein probes and expressed sequence tag probes show correct specificity and high signal-to-noise ratios even after ten rounds of hybridization, detection, stripping of the probes from the membranes …
Machiavelli's Philanthropy, John Patrick Coby
Machiavelli's Philanthropy, John Patrick Coby
Government: Faculty Publications
Machiavelli claims to be animated by a "natural desire" to "bring common benefit to everyone" (Discourses, I.Pr.). But what kind of benefit is it that subjects so many people to tyrannical rule and world empire? What has Machiavelli to offer those whose freedom and independence are sacrificed to the greater glory of imperial powers? After framing the indictment against Machiavelli–in effect, that the world is worse off for having been instructed by him–the paper turns to composing his apology. The defense speech comes in five parts. Most importantly, it makes no use of the association presumed to exist between Machiavelli …
Only God Decides': Young Children's Perceptions Of Divorce And The Legal System, Kyle D. Pruett, Marsha Kline Pruett
Only God Decides': Young Children's Perceptions Of Divorce And The Legal System, Kyle D. Pruett, Marsha Kline Pruett
School for Social Work: Faculty Publications
Objective: To describe research on perceptions of children aged 6 and younger from 21 families of their parents' divorce, of its impact on their families, and of legal officials. Method: Semistructured play interviews were conducted during home visits as parents were conjointly interviewed as part of a larger study on divorce in legal context. Results: Children had much misinformation about divorce as an event and process. What they did know was often inappropriate, frightening, and confusing. They resented how the process 'ruined their parents' being friends any more' and proposed reforms based on their wishes and observations. Conclusions: Greater awareness …
Parasitic Helminth Genomics, M. Blaxter, M. Aslett, D. Guiliano, J. Daub, Steven A. Williams, Kunthala Jayaraman, Reda Ramzy, Alan Scott, Tania Supali, Barton Slatko
Parasitic Helminth Genomics, M. Blaxter, M. Aslett, D. Guiliano, J. Daub, Steven A. Williams, Kunthala Jayaraman, Reda Ramzy, Alan Scott, Tania Supali, Barton Slatko
Biological Sciences: Faculty Publications
The initiation of genome projects on helminths of medical importance promises to yield new drug targets and vaccine candidates in unprecedented numbers. In order to exploit this emerging data it is essential that the user community is aware of the scope and quality of data available, and that the genome projects provide analyses of the raw data to highlight potential genes of interest. Core bioinformatics support for the parasite genome projects has promoted these approaches. In the Brugia genome project, a combination of expressed sequence tag sequencing from multiple cDNA libraries representing the complete filarial nematode lifecycle, and comparative analysis …
Lagrangian Systems On Hyperbolic Manifolds, Philip Boyland, Christophe Golé
Lagrangian Systems On Hyperbolic Manifolds, Philip Boyland, Christophe Golé
Mathematics Sciences: Faculty Publications
This paper gives two results that show that the dynamics of a time-periodic Lagrangian system on a hyperbolic manifold are at least as complicated as the geodesic flow of a hyperbolic metric. Given a hyperbolic geodesic in the Poincaré ball, Theorem A asserts that there are minimizers of the lift of the Lagrangian system that are a bounded distance away and have a variety of approximate speeds. Theorem B gives the existence of a collection of compact invariant sets of the Euler-Lagrange flow that are semiconjugate to the geodesic flow of a hyperbolic metric. These results can be viewed as …
The Influence Of Spatial Reference Frames On Imagined Object-And Vvewer Rotations, Maryjane Wraga, Sarah H. Creem, Dennis R. Proffitt
The Influence Of Spatial Reference Frames On Imagined Object-And Vvewer Rotations, Maryjane Wraga, Sarah H. Creem, Dennis R. Proffitt
Psychology: Faculty Publications
The human visual system can represent an object's spatial structure with respect to multiple frames of reference. It can also utilize multiple reference frames to mentally transform such representations. Recent studies have shown that performance on some mental transformations is not equivalent: Imagined object rotations tend to be more difficult than imagined viewer rotations. We reviewed several related research domains to understand this discrepancy in terms of the different reference frames associated with each imagined movement. An examination of the mental rotation literature revealed that observers' difficulties in predicting an object's rotational outcome may stem from a general deficit with …
Weighting Unusual Feature Types, Nicholas Howe, Claire Cardie
Weighting Unusual Feature Types, Nicholas Howe, Claire Cardie
Computer Science: Faculty Publications
Feature weighting is known empirically to improve classification accuracy for k-nearest neighbor classifiers in tasks with irrelevant features. Many feature weighting algorithms are designed to work with symbolic features, or numeric features, or both, but cannot be applied to problems with features that do not fit these categories. This paper presents a new k-nearest neighbor feature weighting algorithm that works with any kind of feature for which a distance function can be defined. Applied to an image classification task with unusual set-like features, the technique improves classification accuracy significantly. In tests on standard data sets from the UCI repository, the …
Embedded Training For Complex Information Systems, Brant A. Cheikes
Embedded Training For Complex Information Systems, Brant A. Cheikes
Computer Science: Faculty Publications
One approach to providing affordable operator training in the workplace is to augment applications with intelligent embedded training systems (ETS). Intelligent embedded training is highly interactive: trainees practice realistic problem-solving tasks on the prime application with guidance and feedback from the training system. This article makes three contributions to the theory and technology of ETS design. First, we describe a framework based on Norman’s “stages of user activity” model for defining the instructional objectives of an ETS. Second, we demonstrate a non-invasive approach to instrumenting software applications, thereby enabling them to collaborate with an ETS. Third, we describe a method …
Computational Geometry Column 35, Joseph O'Rourke
Computational Geometry Column 35, Joseph O'Rourke
Computer Science: Faculty Publications
The subquadratic algorithm of Kapoor for finding shortest paths on a polyhedron is described.
Locked And Unlocked Polygonal Chains In 3d, Therese Biedl, Erik D. Demaine, Martin L. Demaine, Sylvain Lazard, Anna Lubiw, Joseph O'Rourke, Mark Overmars, Steve Robbins, Ileana Streinu, Godfried Toussaint, Sue Whitesides
Locked And Unlocked Polygonal Chains In 3d, Therese Biedl, Erik D. Demaine, Martin L. Demaine, Sylvain Lazard, Anna Lubiw, Joseph O'Rourke, Mark Overmars, Steve Robbins, Ileana Streinu, Godfried Toussaint, Sue Whitesides
Computer Science: Faculty Publications
In this paper, we study movements of simple polygonal chains in 3D. We say that an open, simple polygonal chain can be straightened if it can be continuously reconfigured to a straight sequence of segments in such a manner that both the length of each link and the simplicity of the chain are maintained throughout the movement. The analogous concept for closed chains is convexification: reconfiguration to a planar convex polygon. Chains that cannot be straightened or convexified are called locked. While there are open chains in 3D that are locked, we show that if an open chain has a …
Stretchability Of Star-Like Pseudo-Visibility Graphs, Ileana Streinu
Stretchability Of Star-Like Pseudo-Visibility Graphs, Ileana Streinu
Computer Science: Faculty Publications
We present advances on the open problem of characterizing vertex-edge visibility graphs (ve-graphs), reduced by results of O'Rourke and Streinu to a stretchability question for pseudo-polygons. We introduce star-like pseudo-polygons as a special subclass containing all the known instances of non-stretchable pseudo-polygons. We give a complete combinatorial characterization and a linear-time decision procedure for star-like pseudo-polygon stretchability and star-like ve-graph recognition. To the best of our knowledge, this is the first problem in computational geometry for which a combinatorial characterization was found by first isolating the oriented matroid substructure and then separately solving the stretchability question. It is also the …
Stable Isotope And Crystal Chemistry Of Tourmaline Across Pegmatite - Country Rock Boundaries At Black Mountain And Mount Mica, Southwestern Maine, U.S.A, Darby Dyar, Charles V. Guidott, Daniel P. Core, Katherine M. Wearn, Michael A. Wise, Carl A. Francis, Kathleen Johnson, John B. Brady, J. David Robertson, Laura R. Cross
Stable Isotope And Crystal Chemistry Of Tourmaline Across Pegmatite - Country Rock Boundaries At Black Mountain And Mount Mica, Southwestern Maine, U.S.A, Darby Dyar, Charles V. Guidott, Daniel P. Core, Katherine M. Wearn, Michael A. Wise, Carl A. Francis, Kathleen Johnson, John B. Brady, J. David Robertson, Laura R. Cross
Geosciences: Faculty Publications
Major element and stable isotope chemistry of tourmaline from two complexly-zoned rare element pegmatites has been studied to gain insights into the processes by which the pegmatites were formed. Two locations in the Oxford Pegmatite Field of western Maine, U.S.A., were chosen for this study: Black Mountain, an isolated body located in sillimanite zone, highly sulfidic metapelites and quartzite; and Mount Mica, which is bounded by schists and pegmatite and aplitic granite bodies commonly having gradational contacts with each other. At each locality, tourmaline was sampled from the surrounding country rocks into the contact and wall zones through to the …
Change, Consolidation, And Competition In Health Care Markets, Martin Gaynor, Deborah Haas-Wilson
Change, Consolidation, And Competition In Health Care Markets, Martin Gaynor, Deborah Haas-Wilson
Economics: Faculty Publications
The health care industry is being transformed. Large firms are merging and acquiring other firms. Alliances and contractual relations between players in this market are shifting rapidly. Within the next few years, many markets are predicted to be dominated by a few large firms. Antitrust enforcement authorities like the Department of Justice and the Federal Trade Commission, as well as courts and legislators at both the federal and state levels, are struggling with the implications of these changes for the nature and consequences of competition in health care markets. In this paper we summarize the nature of the changes in …
Generative Concern, Political Commitment, And Charitable Actions, Bill E. Peterson, Lauren Duncan
Generative Concern, Political Commitment, And Charitable Actions, Bill E. Peterson, Lauren Duncan
Psychology: Faculty Publications
The implications of psychosocial generativity (Erikson, 1950) for understanding contemporary politics were explored. Study 1 replicated, in two samples, previous findings that generativity concerns are related to a variety of political activities, including the expenditure of time and money in support of political organizations. Using path analyses, Study 2 extended these findings and demonstrated how midlife generativity concerns interacted with political orientation and interest in politics to produce stronger relationships with giving. These findings suggest that people view the political arena as one important way to improve society and thereby manifest cultural generativity. Although focusing on the domain of politics, …