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University of Massachusetts Amherst

2008

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Articles 1 - 30 of 332

Full-Text Articles in Physical Sciences and Mathematics

Book I, Otto Vogl: Papers And Patents, 1948-1970, Jane C. Vogl Dec 2008

Book I, Otto Vogl: Papers And Patents, 1948-1970, Jane C. Vogl

Emeritus Faculty Author Gallery

Books I-XII include citations to Otto Vogl's publications and patents. Printed versions of these twelve volumes are also available in the Integrated Sciences and Engineering Library of the University of Massachusetts in Amherst. MA, Lederle Graduate Research Center. The printed volumes include the full reprints of all cited publications.


Centers Of Polymer Science: Introduction, Otto Vogl Dec 2008

Centers Of Polymer Science: Introduction, Otto Vogl

Emeritus Faculty Author Gallery

Centers of Polymer Science describes polymer research activities taking place in Europe, Asia, and Australia primarily during the years between 1980 and 2000. This series of articles shows and records the activity in Polymer Science in this part of polymer history.


Centers Of Polymer Science: Introduction, Otto Vogl Dec 2008

Centers Of Polymer Science: Introduction, Otto Vogl

Otto Vogl

Centers of Polymer Science describes polymer research activities taking place in Europe, Asia, and Australia primarily during the years between 1980 and 2000. This series of articles shows and records the activity in Polymer Science in this part of polymer history.


Book I, Otto Vogl: Papers And Patents, 1948-1970, Jane C. Vogl Dec 2008

Book I, Otto Vogl: Papers And Patents, 1948-1970, Jane C. Vogl

Otto Vogl

Books I-XII include citations to Otto Vogl's publications and patents. Printed versions of these twelve volumes are also available in the Integrated Sciences and Engineering Library of the University of Massachusetts in Amherst. MA, Lederle Graduate Research Center. The printed volumes include the full reprints of all cited publications.


E-Government And Inter-Organizational Collaboration In Mexico: Survey Results, Luis F. Luna-Reyes, J. Ramon Gil-Garcia Nov 2008

E-Government And Inter-Organizational Collaboration In Mexico: Survey Results, Luis F. Luna-Reyes, J. Ramon Gil-Garcia

National Center for Digital Government

From executive summary: This document summarizes the responses to questionnaires completed by participants from inter-organizational information technology (IT) projects in the Mexican federal government. The questionnaire was undertaken as part of a research project on e-government and inter-organizational collaboration funded by the National Council of Science and Technology (CONACYT) and conducted jointly by researchers from the Business School of the Universidad de las Américas in Puebla, México, the Centro de Investigación y Docencia Económicas in Mexico City, and the National Center for Digital Government at the University of Massachusetts in Amherst. The responses reflect the opinions of 282 government officials …


Open Source Software Collaboration: Foundational Concepts And An Empirical Analysis, Charles M. Schweik, Robert English, Sandra Haire Nov 2008

Open Source Software Collaboration: Foundational Concepts And An Empirical Analysis, Charles M. Schweik, Robert English, Sandra Haire

National Center for Digital Government

This paper has three primary goals. First, we provide an overview on some foundational concepts – “peer-production,” “user-centric innovation,” “crowdsourcing,” “task granularity,” and yes, open source and open content – for they are key elements of Internet-based collaboration we see today. Second, through this discussion on foundational concepts, we hope to make it clear why people interested in collaborative public management and administration should care about open source and open source-like collaboration. After this argument is made, we provide a very condensed summary of where we are to date on open source collaboration research. The goal of that research is …


Book Ii, Otto Vogl: Papers And Patents, 1970-1977, Jane C. Vogl Nov 2008

Book Ii, Otto Vogl: Papers And Patents, 1970-1977, Jane C. Vogl

Emeritus Faculty Author Gallery

Books I-XII include citations to Otto Vogl's publications and patents. Printed versions of these twelve volumes are also available in the Integrated Sciences and Engineering Library of the University of Massachusetts in Amherst. MA, Lederle Graduate Research Center. The printed volumes include the full reprints of all cited publications.


Book Ii, Otto Vogl: Papers And Patents, 1970-1977, Jane C. Vogl Nov 2008

Book Ii, Otto Vogl: Papers And Patents, 1970-1977, Jane C. Vogl

Otto Vogl

Books I-XII include citations to Otto Vogl's publications and patents. Printed versions of these twelve volumes are also available in the Integrated Sciences and Engineering Library of the University of Massachusetts in Amherst. MA, Lederle Graduate Research Center. The printed volumes include the full reprints of all cited publications.


Efficient Gene Delivery Vectors By Tuning The Surface Charge Density Of Amino Acid-Functionalized Gold Nanoparticles, Ps Ghosh, Ck Kim, G Han, Ns Forbes, Vm Rotello Oct 2008

Efficient Gene Delivery Vectors By Tuning The Surface Charge Density Of Amino Acid-Functionalized Gold Nanoparticles, Ps Ghosh, Ck Kim, G Han, Ns Forbes, Vm Rotello

Vincent Rotello

Gold colloids functionalized with amino acids provide a scaffold for effective DNA binding with subsequent condensation. Particles with lysine and lysine dendron functionality formed particularly compact complexes and provided highly efficient gene delivery without any observed cytotoxicity. Nanoparticles functionalized with first generation lysine dendrons (NP-LysG1) were approximately 28-fold superior to polylysine in reporter gene expression. These amino acid-based nanoparticles were responsive to intracellular glutathione levels, providing a tool for controlled release and concomitant expression of DNA.


Comparative Genomics Of Geobacter Chemotaxis Genes Reveals Diverse Signaling Function, Hoa T. Tran, Julia Krushkal, Frances M. Antommattei, Derek R. Lovley, Robert Weis Oct 2008

Comparative Genomics Of Geobacter Chemotaxis Genes Reveals Diverse Signaling Function, Hoa T. Tran, Julia Krushkal, Frances M. Antommattei, Derek R. Lovley, Robert Weis

Robert Weis

Background Geobacter species are δ-Proteobacteria and are often the predominant species in a variety of sedimentary environments where Fe(III) reduction is important. Their ability to remediate contaminated environments and produce electricity makes them attractive for further study. Cell motility, biofilm formation, and type IV pili all appear important for the growth of Geobacter in changing environments and for electricity production. Recent studies in other bacteria have demonstrated that signaling pathways homologous to the paradigm established for Escherichia coli chemotaxis can regulate type IV pili-dependent motility, the synthesis of flagella and type IV pili, the production of extracellular matrix material, and …


Book Iii, Otto Vogl: Publications, 1977-1979, Jane C. Vogl Oct 2008

Book Iii, Otto Vogl: Publications, 1977-1979, Jane C. Vogl

Emeritus Faculty Author Gallery

Books I-XII include citations to Otto Vogl's publications and patents. Printed versions of these twelve volumes are also available in the Integrated Sciences and Engineering Library of the University of Massachusetts in Amherst. MA, Lederle Graduate Research Center. The printed volumes include the full reprints of all cited publications.


Multiplexed Screening Of Cellular Uptake Of Gold Nanoparticles Using Laser Desorption/Ionization Mass Spectrometry, Zj Zhu, Ps Ghosh, Or Miranda, Rw Vachet, Vm Rotello Oct 2008

Multiplexed Screening Of Cellular Uptake Of Gold Nanoparticles Using Laser Desorption/Ionization Mass Spectrometry, Zj Zhu, Ps Ghosh, Or Miranda, Rw Vachet, Vm Rotello

Vincent Rotello

Gold nanoparticles (AuNPs) are highly promising candidates as drug delivery agents into cells of interest. We describe for the first time the multiplexed analysis of nanoparticle uptake by cells using mass spectrometry. We demonstrate that the cellular uptake of functionalized gold nanoparticles with cationic or neutral surface ligands can be readily determined using laser desorption/ionization mass spectrometry of cell lysates. The surface ligands have “mass barcodes” that allow different nanoparticles to be simultaneously identified and quantified at levels as low as 30 pmol. Using this method, we find that subtle changes to AuNP surface functionalities can lead to measurable changes …


Book Iii, Otto Vogl: Publications, 1977-1979, Jane C. Vogl Oct 2008

Book Iii, Otto Vogl: Publications, 1977-1979, Jane C. Vogl

Otto Vogl

Books I-XII include citations to Otto Vogl's publications and patents. Printed versions of these twelve volumes are also available in the Integrated Sciences and Engineering Library of the University of Massachusetts in Amherst. MA, Lederle Graduate Research Center. The printed volumes include the full reprints of all cited publications.


Semiinfiniate Flags. Ii. Local And Global Intersection Cohomology Of Quasimaps' Spaces, Boris Feigin, Michael Finkelberg, Alexander Kuznetsov, Ivan Mirkoviæ Sep 2008

Semiinfiniate Flags. Ii. Local And Global Intersection Cohomology Of Quasimaps' Spaces, Boris Feigin, Michael Finkelberg, Alexander Kuznetsov, Ivan Mirkoviæ

Mathematics and Statistics Department Faculty Publication Series

No abstract provided.


Book Iv, Otto Vogl: Publications, 1979-1981, Jane C. Vogl Sep 2008

Book Iv, Otto Vogl: Publications, 1979-1981, Jane C. Vogl

Emeritus Faculty Author Gallery

Books I-XII include citations to Otto Vogl's publications and patents. Printed versions of these twelve volumes are also available in the Integrated Sciences and Engineering Library of the University of Massachusetts in Amherst. MA, Lederle Graduate Research Center. The printed volumes include the full reprints of all cited publications.


Book Iv, Otto Vogl: Publications, 1979-1981, Jane C. Vogl Sep 2008

Book Iv, Otto Vogl: Publications, 1979-1981, Jane C. Vogl

Otto Vogl

Books I-XII include citations to Otto Vogl's publications and patents. Printed versions of these twelve volumes are also available in the Integrated Sciences and Engineering Library of the University of Massachusetts in Amherst. MA, Lederle Graduate Research Center. The printed volumes include the full reprints of all cited publications.


Observations Of The Gas Reservoir Around A Star Forming Galaxy In The Early Universe, Brenda L. Frye, David V. Bowen, Mairead Hurley, Todd M. Tripp, Xiaohui Fan, Bradley Holden, Puragra Guhathakurta, Dan Coe, Tom Broadhurst, Eiichi Egami, G. Meylan Aug 2008

Observations Of The Gas Reservoir Around A Star Forming Galaxy In The Early Universe, Brenda L. Frye, David V. Bowen, Mairead Hurley, Todd M. Tripp, Xiaohui Fan, Bradley Holden, Puragra Guhathakurta, Dan Coe, Tom Broadhurst, Eiichi Egami, G. Meylan

Todd M. Tripp

We present a high signal-to-noise spectrum of a bright galaxy at z = 4.9 in 14 h of integration on VLT FORS2. This galaxy is extremely bright, i_850 = 23.10 +/- 0.01, and is strongly-lensed by the foreground massive galaxy cluster Abell 1689 (z=0.18). Stellar continuum is seen longward of the Ly-alpha emission line at ~7100 \AA, while intergalactic H I produces strong absorption shortward of Ly-alpha. Two transmission spikes at ~6800 Angstroms (A) and ~7040 A are also visible, along with other structures at shorter wavelengths. Although fainter than a QSO, the absence of a strong central ultraviolet flux …


Book V, Otto Vogl: Publications, 1981-1984, Jane C. Vogl Aug 2008

Book V, Otto Vogl: Publications, 1981-1984, Jane C. Vogl

Emeritus Faculty Author Gallery

Books I-XII include citations to Otto Vogl's publications and patents. Printed versions of these twelve volumes are also available in the Integrated Sciences and Engineering Library of the University of Massachusetts in Amherst. MA, Lederle Graduate Research Center. The printed volumes include the full reprints of all cited publications.


Stream Simulation: An Ecological Approach To Providing Passage For Aquatic Organisms At Road-Stream Crossings Aug 2008

Stream Simulation: An Ecological Approach To Providing Passage For Aquatic Organisms At Road-Stream Crossings

Scott D. Jackson

No abstract provided.


Book V, Otto Vogl: Publications, 1981-1984, Jane C. Vogl Aug 2008

Book V, Otto Vogl: Publications, 1981-1984, Jane C. Vogl

Otto Vogl

Books I-XII include citations to Otto Vogl's publications and patents. Printed versions of these twelve volumes are also available in the Integrated Sciences and Engineering Library of the University of Massachusetts in Amherst. MA, Lederle Graduate Research Center. The printed volumes include the full reprints of all cited publications.


Dendron-Based Model Systems For Flavoenzyme Activity: Towards A New Class Of Synthetic Flavoenzyme, Ss Agasti, St Caldwell, G Cooke, Bj Jordan, A Kennedy, N Kryvokhyzha, G Rabani, S Rana, A Sanyal, Vm Rotello Jul 2008

Dendron-Based Model Systems For Flavoenzyme Activity: Towards A New Class Of Synthetic Flavoenzyme, Ss Agasti, St Caldwell, G Cooke, Bj Jordan, A Kennedy, N Kryvokhyzha, G Rabani, S Rana, A Sanyal, Vm Rotello

Vincent Rotello

Three generations of water-soluble flavin dendrons have been synthesized and the role dendrimer generation has on the physical and catalytic properties of these assemblies has been investigated.


Constraints On The Variability Of Quark Masses From Nuclear Binding, Thibault Damour, John Donoghue Jul 2008

Constraints On The Variability Of Quark Masses From Nuclear Binding, Thibault Damour, John Donoghue

John Donoghue

Based on recent work on nuclear binding, we update and extend the anthropic constraints on the light quark masses, with results that are more tightly constrained than previously obtained. We find that heavy nuclei would fall apart (because the attractive nuclear central potential becomes too weak) if the sum of the light quark masses m_u+m_d would exceed their physical values by 64% (at 95% confidence level). We summarize the anthropic constraints that follow from requiring the existence both of heavy atoms and of hydrogen. With the additional assumption that the quark Yukawa couplings do not vary, these constraints provide a …


Self-Assembly And Cross-Linking Of Fept Nanoparticles At Planar And Colloidal Liquid-Liquid Interfaces, P Arumugam, D Patra, B Samanta, Ss Agasti, C Subramani, Vm Rotello Jul 2008

Self-Assembly And Cross-Linking Of Fept Nanoparticles At Planar And Colloidal Liquid-Liquid Interfaces, P Arumugam, D Patra, B Samanta, Ss Agasti, C Subramani, Vm Rotello

Vincent Rotello

Terpyridine thiol functionalized FePt and Au NPs were self-assembled and cross-linked at the liquid−liquid interfaces using Fe(II) metal ion. Complexation of terpyridine with Fe(II) metal ion leads to NP network and affords stable membranes and colloidal shells at the liquid−liquid interfaces.


Self-Trapping Of Optical Vortices In Waveguide Lattices With A Self-Defocusing Nonlinearity, Dh Song, Cb Lou, Lq Tang, Xs Wang, W Li, Xy Chen, Kjh Law, H Susanto, Pg Kevrekidis, Jj Xu, Zg Chen Jul 2008

Self-Trapping Of Optical Vortices In Waveguide Lattices With A Self-Defocusing Nonlinearity, Dh Song, Cb Lou, Lq Tang, Xs Wang, W Li, Xy Chen, Kjh Law, H Susanto, Pg Kevrekidis, Jj Xu, Zg Chen

Panos Kevrekidis

We demonstrate the self-trapping of single- and double-charged optical vortices in waveguide lattices induced with a self-defocusing nonlinearity. Under appropriate conditions, a donut-shaped single-charged vortex evolves into a stable discrete gap vortex soliton, but a double-charged vortex turns into a self-trapped quadrupole-like structure. Spectrum measurement and numerical analysis suggest that the gap vortex soliton does not bifurcate from the edge of the Bloch band, quite different from previously observed gap spatial solitons. Our numerical findings are in good agreement with experimental observations.


Autonomous Geometric Precision Error Estimation In Low-Level Computer Vision Tasks, Andrés Corrada-Emmanuel, Howard Schultz Jul 2008

Autonomous Geometric Precision Error Estimation In Low-Level Computer Vision Tasks, Andrés Corrada-Emmanuel, Howard Schultz

Computer Science Department Faculty Publication Series

Errors in map-making tasks using computer vision are sparse. We demonstrate this by considering the construction of digital elevation models that employ stereo matching algorithms to triangulate real-world points. This sparsity, coupled with a geometric theory of errors recently developed by the authors, allows for autonomous agents to calculate their own precision independently of ground truth. We connect these developments with recent advances in the mathematics of sparse signal reconstruction or compressed sensing. The theory presented here extends the autonomy of 3-D model reconstructions discovered in the 1990s to their errors.


Book Vi, Otto Vogl: Publications, 1984-1986, Jane C. Vogl Jul 2008

Book Vi, Otto Vogl: Publications, 1984-1986, Jane C. Vogl

Emeritus Faculty Author Gallery

Books I-XII include citations to Otto Vogl's publications and patents. Printed versions of these twelve volumes are also available in the Integrated Sciences and Engineering Library of the University of Massachusetts in Amherst. MA, Lederle Graduate Research Center. The printed volumes include the full reprints of all cited publications.


Book Vi, Otto Vogl: Publications, 1984-1986, Jane C. Vogl Jul 2008

Book Vi, Otto Vogl: Publications, 1984-1986, Jane C. Vogl

Otto Vogl

Books I-XII include citations to Otto Vogl's publications and patents. Printed versions of these twelve volumes are also available in the Integrated Sciences and Engineering Library of the University of Massachusetts in Amherst. MA, Lederle Graduate Research Center. The printed volumes include the full reprints of all cited publications.


Manipulating Microparticles With Single Surface-Immobilized Nanoparticles, J Zhang, S Srivastava, R Duffadar, Jm Davis, Vm Rotello, Mm Santore Jun 2008

Manipulating Microparticles With Single Surface-Immobilized Nanoparticles, J Zhang, S Srivastava, R Duffadar, Jm Davis, Vm Rotello, Mm Santore

Vincent Rotello

This experimental study explores the capture and manipulation of micrometer-scale particles by single surface-immobilized nanoparticles. The nanoparticles, approximately 10 nm in diameter, are cationic and therefore attract the micrometer-scale silica particles in an analyte suspension. The supporting surface on which the nanoparticles reside is negative (also silica) and repulsive toward approaching microparticles. In the limit where there are as few as 9 nanoparticles per square micrometer of collector, it becomes possible to capture and hold micrometer-scale silica particles with single nanoparticles. The strong nanoparticle−microparticle attractions, their nanometer-scale protrusion forward of the supporting surface, and their controlled density on the supporting …


Book Vii, Otto Vogl: Publications, 1987-1989, Jane C. Vogl Jun 2008

Book Vii, Otto Vogl: Publications, 1987-1989, Jane C. Vogl

Emeritus Faculty Author Gallery

Books I-XII include citations to Otto Vogl's publications and patents. Printed versions of these twelve volumes are also available in the Integrated Sciences and Engineering Library of the University of Massachusetts in Amherst. MA, Lederle Graduate Research Center. The printed volumes include the full reprints of all cited publications.


Disk-Shaped Bose-Einstein Condensates In The Presence Of An Harmonic Trap And An Optical Lattice, T Kapitula, Pg Kevrekidis, Dj Frantzeskakis Jun 2008

Disk-Shaped Bose-Einstein Condensates In The Presence Of An Harmonic Trap And An Optical Lattice, T Kapitula, Pg Kevrekidis, Dj Frantzeskakis

Panos Kevrekidis

We study the existence and stability of solutions of the two-dimensional nonlinear Schrödinger equation in the combined presence of a parabolic and a periodic potential. The motivating physical example consists of Bose–Einstein condensates confined in an harmonic (e.g., magnetic) trap and an optical lattice. By connecting the nonlinear problem with the underlying linear spectrum, we examine the bifurcation of nonlinear modes out of the linear ones for both focusing and defocusing nonlinearities. In particular, we find real-valued solutions (such as multipoles) and complex-valued ones (such as vortices). A primary motivation of the present work is to develop “rules of thumb” …