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2003

University of Massachusetts Amherst

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Articles 1 - 30 of 132

Full-Text Articles in Physical Sciences and Mathematics

The Second Hull Of A Knotted Curve, Jason Cantarella, Greg Kuperberg, Robert B. Kusner, John M. Sullivan Dec 2003

The Second Hull Of A Knotted Curve, Jason Cantarella, Greg Kuperberg, Robert B. Kusner, John M. Sullivan

Robert Kusner

The convex hull of a set K in space consists of points which are, in a certain sense, "surrounded" by K. When K is a closed curve, we define its higher hulls, consisting of points which are "multiply surrounded" by the curve. Our main theorem shows that if a curve is knotted then it has a nonempty second hull. This provides a new proof of the Fary/Milnor theorem that every knotted curve has total curvature at least 4pi.

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Race, Place, And Information Technology, Karen Mossberger, Caroline J. Tolbert Nov 2003

Race, Place, And Information Technology, Karen Mossberger, Caroline J. Tolbert

National Center for Digital Government

What role does environment play in influencing information technology access and skills – over and above individual characteristics such as income, education, race, and ethnicity? One of the puzzles that emerged from our recent research on the “digital divide” was that African-Americans, and to a lesser extent, Latinos, had more positive attitudes toward information technology than similarly-situated whites. And yet, African-Americans and Latinos are less likely to have information technology access and skills, even when controlling for other factors such as income and education (Mossberger, Tolbert and Stansbury 2003). The research presented in this paper takes a first step toward …

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Guía De Mentoría: Guía Para Mentores, Center For Health Leadership & Practice Nov 2003

Guía De Mentoría: Guía Para Mentores, Center For Health Leadership & Practice

Ethics in Science and Engineering National Clearinghouse

No abstract provided.

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Mentoring Guide A Guide For Protégés, The Center For Health Leadership & Practice Nov 2003

Mentoring Guide A Guide For Protégés, The Center For Health Leadership & Practice

Ethics in Science and Engineering National Clearinghouse

No abstract provided.

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Guía De Mentoría: Guía De Los Protegidos, Center For Health Leadership & Practice Nov 2003

Guía De Mentoría: Guía De Los Protegidos, Center For Health Leadership & Practice

Ethics in Science and Engineering National Clearinghouse

No abstract provided.

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Mentoring Guide: A Guide For Mentors, Center For Health Leadership & Practice Nov 2003

Mentoring Guide: A Guide For Mentors, Center For Health Leadership & Practice

Ethics in Science and Engineering National Clearinghouse

No abstract provided.

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E-Government Cross-Agency And Intergovernmental Initiatives Research Project: Web Survey Results, Jane E. Fountain, Robin Mckinnon, Eunyun Park Oct 2003

E-Government Cross-Agency And Intergovernmental Initiatives Research Project: Web Survey Results, Jane E. Fountain, Robin Mckinnon, Eunyun Park

National Center for Digital Government

One of the central challenges of E-Government is organizational and institutional change. Professor Jane E. Fountain, the founder and Director of the National Center for Digital Government at the Kennedy School of Government, Harvard University, and her research team are currently continuing a practical research program on the development of crossagency collaboration and integration using information technologies. The project is designed to describe and explain critical success factors in successful E-Government cross-agency collaborative projects. The study should contribute significant management, economic and policy benefits as a result of better understanding how to structure conditions for success in cross-agency initiatives that …

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The 19th Annual International Conference On Soils, Sediments And Water Oct 2003

The 19th Annual International Conference On Soils, Sediments And Water

Annual Conference on Soils, Sediments and Water: Abstracts

Conference at a Glance Monday, October 20, 2003 Workshops Workshops #1-2: 10:00am – 5:00pm Workshops # 3-4: 1:00 – 5:00pm Workshop # 5: 1:00 – 3:00pm Workshop # 6: 3:00 – 5:00pm Workshop # 1: Theory and Use of Field Portable X-ray Fluorescence for Soil Analysis Workshop # 2: In-Situ Chemical Oxidation Workshop Workshop # 3: TBA/MTBE Remediation Seminar Workshops # 4: A Practical Approach for Assessing Upward Vapor Instrusion Risk Workshop # 5: The Arsenic Nobody Wanted: Now What? A Panel Discussion on Arsenic in Communities Workshop # 6: Implementing the Massachusetts DEP's New Data Enhancement Policy - PRACTICAL …

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Quantum Corrections To The Schwarzschild And Kerr Metrics, N. E. J. Bjerrum-Bohr, John Donoghue, Barry R. Holstein Oct 2003

Quantum Corrections To The Schwarzschild And Kerr Metrics, N. E. J. Bjerrum-Bohr, John Donoghue, Barry R. Holstein

John Donoghue

We examine the corrections to the lowest order gravitational interactions of massive particles arising from gravitational radiative corrections. We show how the masslessness of the graviton and the gravitational selfinteractions imply the presence of nonanalytic pieces ;A2q2,;q2ln2q2, etc., in the form factors of the energy-momentum tensor and that these correspond to long range modifications of the metric tensor gmn of the form G2m2/r2,G2m\/r3, etc. The former coincide with well known solutions from classical general relativity, while the latter represent new quantum mechanical effects, whose strength and form is necessitated by the low energy quantum nature of the general relativity. We …

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Bureaucratic Networks Or Networked Bureaucracies? Knowledge Sharing In Ict-Enabled Innovation Projects, Maria C. Binz-Scharf Oct 2003

Bureaucratic Networks Or Networked Bureaucracies? Knowledge Sharing In Ict-Enabled Innovation Projects, Maria C. Binz-Scharf

National Center for Digital Government

This paper examines knowledge sharing processes in digital government projects (DGPs). Although knowledge sharing processes are a central feature of the functioning of government, they have received little attention in the literature. The importance of knowledge sharing has become even more evident with the rise of digital government initiatives, as these have a networking effect on bureaucracies. With multiple agencies and multidisciplinary knowledge coming together, it is necessary to combine and reconnect the required knowledge. Based on empirical data from four DGPs in Switzerland and the United States, a theoretical model for knowledge sharing in DGPs is proposed. The model …

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Deciding The Nature Of The Coarse Equation Through Microscopic Simulations: The Baby-Bathwater Scheme, J Li, Pg Kevrekidis, Cw Gear, Pg Kevrekidis Jul 2003

Deciding The Nature Of The Coarse Equation Through Microscopic Simulations: The Baby-Bathwater Scheme, J Li, Pg Kevrekidis, Cw Gear, Pg Kevrekidis

Panos Kevrekidis

Recent developments in multiscale computation allow the solution of coarse equations for the expected macroscopic behavior of microscopically evolving particles without ever obtaining these coarse equations in closed form. The closure is obtained on demand through appropriately initialized bursts ofmicroscopic simulation. The effective coupling of microscopic simulators with macrosocopic behavior requires certain decisions about the nature of the unavailable coarse equation. Such decisions include (a) the highest spatial derivative active in the coarse equation, (b) whether the equation satisfies certain conservation laws, and (c) whether the coarse dynamics is Hamiltonian. These decisions affect the number and type of boundary conditions …

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Qcd Condensates For The Light Quark V-A Correlator, Vincenzo Cirigliano, Eugene Golowich, Kim Maltman Jul 2003

Qcd Condensates For The Light Quark V-A Correlator, Vincenzo Cirigliano, Eugene Golowich, Kim Maltman

Physics Department Faculty Publication Series

No abstract provided.

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Maximally Inflected Real Rational Curves, Viatcheslav Kharlamov, Frank Sottile Jul 2003

Maximally Inflected Real Rational Curves, Viatcheslav Kharlamov, Frank Sottile

Mathematics and Statistics Department Faculty Publication Series

We introduce and begin the topological study of real rational plane curves, all of whose inflection points are real. The existence of such curves is a corollary of results in the real Schubert calculus, and their study has consequences for the important Shapiro and Shapiro conjecture in the real Schubert calculus. We establish restrictions on the number of real nodes of such curves and construct curves realizing the extreme numbers of real nodes. These constructions imply the existence of real solutions to some problems in the Schubert calculus. We conclude with a discussion of maximally inflected curves of low degree.

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Threshold Electrodisintegration Of 3he, R S. Hicks, A Hotta, S Churchwell, X Jiang, Gerald Alvin Peterson, J Shaw, B Asavapibhop, M C. Berisso, P E. Bosted, K Burchesky, R A. Miskimen, S E. Rock Jun 2003

Threshold Electrodisintegration Of 3he, R S. Hicks, A Hotta, S Churchwell, X Jiang, Gerald Alvin Peterson, J Shaw, B Asavapibhop, M C. Berisso, P E. Bosted, K Burchesky, R A. Miskimen, S E. Rock

Gerald Alvin Peterson

Cross sections were measured for the near-threshold electrodisintegration of 3He at momentum transfer values of q=2.4, 4.4, and 4.7fm-1. From these and prior measurements the transverse and longitudinal response functions RT and RL were deduced. Comparisons are made against previously published and new nonrelativistic A=3 calculations using the best available nucleon-nucleon NN potentials. In general, for q<2fm-1 these calculations accurately predict the threshold electrodisintegration of 3He. Agreement at increasing q demands consideration of two-body terms, but discrepancies still appear at the highest momentum transfers probed, perhaps due to the neglect of relativistic dynamics, or to the underestimation of high-momentum wave-function components.

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Review Of Irwin M. Brodo, Sylvia Duran Sharnoff, Stephen Sharnoff: Lichens Of North America, Lynn Margulis Jun 2003

Review Of Irwin M. Brodo, Sylvia Duran Sharnoff, Stephen Sharnoff: Lichens Of North America, Lynn Margulis

Lynn Margulis (1938 - 2011)

No abstract provided.

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Mobility Of Taxol In Microtubule Bundles, Jennifer Ross, D. Kuchnir Fygenson Jun 2003

Mobility Of Taxol In Microtubule Bundles, Jennifer Ross, D. Kuchnir Fygenson

Jennifer Ross

Mobility of taxol inside microtubules was investigated using fluorescence recovery after photobleaching on flowaligned bundles. Bundles were made of microtubules with either GMPCPP or GTP at the exchangeable site on the tubulin dimer. Recovery times were sensitive to bundle thickness and packing, indicating that taxol molecules are able to move laterally through the bundle. The density of open binding sites along a microtubule was varied by controlling the concentration of taxol in solution for GMPCPP samples. With [63% sites occupied, recovery times were independent of taxol concentration and, therefore, inversely proportional to the microscopic dissociation rate, koff. It was found …

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Quantum Gravitational Corrections To The Nonrelativistic Scattering Potential Of Two Masses, N. E. J. Bjerrum-Bohr, John Donoghue, Barry R. Holstein Apr 2003

Quantum Gravitational Corrections To The Nonrelativistic Scattering Potential Of Two Masses, N. E. J. Bjerrum-Bohr, John Donoghue, Barry R. Holstein

John Donoghue

We treat general relativity as an effective field theory, obtaining the full nonanalytic component of the scattering matrix potential to one-loop order. The lowest order vertex rules for the resulting effective field theory are presented and the one-loop diagrams which yield the leading nonrelativistic post-Newtonian and quantum corrections to the gravitational scattering amplitude to second order in G are calculated in detail. The Fourier transformed amplitudes yield a nonrelativistic potential and our result is discussed in relation to previous calculations. The definition of a potential is discussed as well and we show how the ambiguity of the potential under coordinate …

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Optimal Surface Temperature Reconstructions Using Terrestrial Borehole Data, M. E. Mann, S. Rutherford, Raymond S. Bradley, M. K. Hughes, F. T. Keimig Apr 2003

Optimal Surface Temperature Reconstructions Using Terrestrial Borehole Data, M. E. Mann, S. Rutherford, Raymond S. Bradley, M. K. Hughes, F. T. Keimig

Raymond S Bradley

We derive an optimal Northern Hemisphere mean surface temperature reconstruction from terrestrial borehole temperature profiles spanning the past five centuries. The pattern of borehole ground surface temperature (GST) reconstructions displays prominent discrepancies with instrumental surface air temperature (SAT) estimates during the 20th century, suggesting the presence of a considerable amount of noise and/or bias in any underlying spatial SAT signal. The vast majority of variance in the borehole dataset is efficiently retained by its two leading eigenvectors. A sizable share of the variance in the first eigenvector appears to be associated with non-SAT related bias in the borehole data. A …

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Adventures In Collaborative Research: A Case Study For Performance And Discussion, Kenneth D. Pimple Apr 2003

Adventures In Collaborative Research: A Case Study For Performance And Discussion, Kenneth D. Pimple

Ethics in Science and Engineering National Clearinghouse

No abstract provided.

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Dynamics Of Conformal Maps For A Class Of Non-Laplacian Growth Phenomena, Martin Z. Bazant, Jaehyuk Choi, Benny Davidovitch Mar 2003

Dynamics Of Conformal Maps For A Class Of Non-Laplacian Growth Phenomena, Martin Z. Bazant, Jaehyuk Choi, Benny Davidovitch

Benny Davidovitch

Time-dependent conformal maps are used to model a class of growth phenomena limited by coupled non-Laplacian transport processes, such as nonlinear diffusion, advection, and electro- migration. Both continuous and stochastic dynamics are described by generalizing conformal- mapping techniques for viscous fingering and diffusion-limited aggregation, respectively. A gen- eral notion of time in stochastic growth is also introduced. The theory is applied to simulations of advection-diffusion-limited aggregation in a background potential flow. A universal crossover in mor- phology is observed from diffusion-limited to advection-limited fractal patterns with an associated crossover in the growth rate, controlled by a time-dependent effective Peclet number. …

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Balanced Configurations Of Lattice Vectors And Gkz-Rational Toric Fourfolds In P^6, Eduardo Cattani, Alicia Dickenstein Mar 2003

Balanced Configurations Of Lattice Vectors And Gkz-Rational Toric Fourfolds In P^6, Eduardo Cattani, Alicia Dickenstein

Eduardo Cattani

We introduce a notion of balanced configurations of vectors. This is motivated by the study of rational A-hypergeometric functions in the sense of Gelfand, Kapranov and Zelevinsky. We classify balanced configurations of seven plane vectors up to GL(2,R)-equivalence and deduce that the only gkz-rational toric four-folds in P6 are those varieties associated with an essential Cayley configuration. We show that in this case, all rational A-hypergeometric functions may be described in terms of toric residues. This follows from studying a suitable hyperplane arrangement.

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Complex C: A Low-Metallicity High-Velocity Cloud Plunging Into The Milky Way, Todd M. Tripp, Bart P. Wakker, Edward B. Jenkins, C. W. Bowers, A. C. Danks, R. F. Green, S. R. Heap, C. L. Joseph, M. E. Kaiser, J. L. Linsky, B. E. Woodgate Feb 2003

Complex C: A Low-Metallicity High-Velocity Cloud Plunging Into The Milky Way, Todd M. Tripp, Bart P. Wakker, Edward B. Jenkins, C. W. Bowers, A. C. Danks, R. F. Green, S. R. Heap, C. L. Joseph, M. E. Kaiser, J. L. Linsky, B. E. Woodgate

Todd M. Tripp

We present evidence that high-velocity cloud (HVC) complex C is a low-metallicity gas cloud that is plunging toward the disk and beginning to interact with the ambient gas that surrounds the Milky Way. This evidence begins with a new high-resolution (7 km s-1 FWHM) echelle spectrum of 3C 351 obtained with the Space Telescope Imaging Spectrograph (STIS). 3C 351 lies behind the low-latitude edge of complex C, and the new spectrum provides accurate measurements of O I, Si II, Al II, Fe II, and Si III absorption lines at the velocity of complex C; N I, S II, Si IV, …

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Search For Neutral Baryon Resonances Below Pion Threshold, X Jiang, R Gilman, R Ransome, P Markowitz, T H. Chang, C C. Chang, Gerald Alvin Peterson Feb 2003

Search For Neutral Baryon Resonances Below Pion Threshold, X Jiang, R Gilman, R Ransome, P Markowitz, T H. Chang, C C. Chang, Gerald Alvin Peterson

Gerald Alvin Peterson

The reaction p(e,e′π+)X0 was studied with two high-resolution magnetic spectrometers to search for narrow baryon resonances. A missing mass resolution of 2.0 MeV was achieved. A search for structures in the mass region of 0.97

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Photoproduction Of The Ω Meson On The Proton At Large Momentum Transfer, M Battaglieri, M Brunoldi, R De Vita, B Asavapibhop, R S. Hicks, D Lawrence, R Miskimen, Gerald Alvin Peterson Jan 2003

Photoproduction Of The Ω Meson On The Proton At Large Momentum Transfer, M Battaglieri, M Brunoldi, R De Vita, B Asavapibhop, R S. Hicks, D Lawrence, R Miskimen, Gerald Alvin Peterson

Gerald Alvin Peterson

The differential cross section, dσ/dt, for ω meson exclusive photoproduction on the proton above the resonance region (2.6

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Macromolecules In The 21st Century: An International Symposium On Polymer Science And Technology On The Occasion Otto Vogl's 75th Birthday, Gerald S. Kirshenbaum, Helga Roder Jan 2003

Macromolecules In The 21st Century: An International Symposium On Polymer Science And Technology On The Occasion Otto Vogl's 75th Birthday, Gerald S. Kirshenbaum, Helga Roder

Emeritus Faculty Author Gallery

No abstract provided.

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Electronic Government And Electronic Civics, Jane Fountain Jan 2003

Electronic Government And Electronic Civics, Jane Fountain

National Center for Digital Government

Electronic government and electronic civics embrace a wide range of topics. Electronic government and electronic civics include in their purview the development, use, and implications of new practices, processes, forms and interests in government and civic life occasioned by the Internet, World Wide Web and related information and communication technologies. They are concerned with individuals and the groups they form and sustain in order to bring coherence and stability to community life. At a slightly higher level of analysis, electronic government and electronic civics take account of the use and implications of the Internet for all forms of civic engagement …

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Local Government Stimulation Of Broadband: Effectiveness, E-Government, And Economic Development, David Clark, Sharon Gillett, William Lehr, Marvin Sirbu, Jane E. Fountain Jan 2003

Local Government Stimulation Of Broadband: Effectiveness, E-Government, And Economic Development, David Clark, Sharon Gillett, William Lehr, Marvin Sirbu, Jane E. Fountain

National Center for Digital Government

Access to broadband is widely recognized as a prerequisite for a community’s economic welfare and the delivery of government services. In communities where the private sector is perceived as having failed to deliver adequate and affordable broadband services, municipal and county governments face pressures to stimulate broadband deployment. However, no systematic data documents the nature and status of municipal broadband initiatives, the comparative effectiveness of alternative policies for promoting broadband access, or their implications for local economic development, private provisioning of infrastructure, and the operation of local government. As a result, hundreds of communities are proceeding independently to develop their …

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Department Of Physics Newsletter: Spring 2003, Bob Krotkov, Tony Papirio, Gerry Peterson, Monroe Rabin, Hajime Sakai Jan 2003

Department Of Physics Newsletter: Spring 2003, Bob Krotkov, Tony Papirio, Gerry Peterson, Monroe Rabin, Hajime Sakai

Physics Newsletters

No abstract provided.

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Spatial And Temporal Gradients In The Cosmological Constant, Jf Donoghue Jan 2003

Spatial And Temporal Gradients In The Cosmological Constant, Jf Donoghue

Physics Department Faculty Publication Series

It is possible that there may be differences in the fundamental physical parameters from one side of the observed universe to the other. I show that the cosmological constant is likely to be the most sensitive of the physical parameters to possible spatial (or temporal) variation, because a small variation in any of the other parameters produces a huge variation of the cosmological constant. It therefore provides a very powerful indirect evidence against spatial gradients or temporal variation in the other fundamental physical parameters, at least 40 orders of magnitude more powerful than direct experimental constraints. Moreover, a gradient may …

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Quantum Gravitational Corrections To The Nonrelativistic Scattering Potential Of Two Masses, Nej Bjerrum-Bohr, Jf Donoghue, Br Holstein Jan 2003

Quantum Gravitational Corrections To The Nonrelativistic Scattering Potential Of Two Masses, Nej Bjerrum-Bohr, Jf Donoghue, Br Holstein

Physics Department Faculty Publication Series

We treat general relativity as an effective field theory, obtaining the full nonanalytic component of the scattering matrix potential to one-loop order. The lowest order vertex rules for the resulting effective field theory are presented and the one-loop diagrams which yield the leading nonrelativistic post-Newtonian and quantum corrections to the gravitational scattering amplitude to second order in G are calculated in detail. The Fourier transformed amplitudes yield a nonrelativistic potential and our result is discussed in relation to previous calculations. The definition of a potential is discussed as well, and we show that the ambiguity of the potential under coordinate …

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