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

Digital Commons Network™

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

PDF

University of Massachusetts Amherst

2002

Discipline
Keyword
Publication

Articles 1 - 30 of 92

Full-Text Articles in Entire DC Network

Regulation Of Rac1 Activation By The Low Density Lipoprotein Receptor–Related Protein, Zhong Ma, Keena S. Thomas, Donna J. Webb, Radim Moravec, Ana Maria Salicioni, Wendy M. Mars, Steven L. Gonias Dec 2002

Regulation Of Rac1 Activation By The Low Density Lipoprotein Receptor–Related Protein, Zhong Ma, Keena S. Thomas, Donna J. Webb, Radim Moravec, Ana Maria Salicioni, Wendy M. Mars, Steven L. Gonias

Ana Maria Salicioni

The low density lipoprotein receptor–related protein (LRP-1) binds and mediates the endocytosis of multiple ligands, transports the urokinase-type plasminogen activator receptor (uPAR) and other membrane proteins into endosomes, and binds intracellular adaptor proteins involved in cell signaling. In this paper, we show that in murine embryonic fibroblasts (MEFs) and L929 cells, LRP-1 functions as a major regulator of Rac1 activation, and that this activity depends on uPAR. LRP-1–deficient MEFs demonstrated increased Rac1 activation compared with LRP-1–expressing MEFs, and this property was reversed by expressing the VLDL receptor, a member of the same gene family as LRP-1, with overlapping ligand-binding specificity. …

Go to article

Electricity Production By Geobacter Sulfurreducens Attached To Electrodes, Daniel R. Bond, Derek Lovley Dec 2002

Electricity Production By Geobacter Sulfurreducens Attached To Electrodes, Daniel R. Bond, Derek Lovley

Derek Lovley

Previous studies have suggested that members of the Geobacteraceae can use electrodes as electron acceptors for anaerobic respiration. In order to better understand this electron transfer process for energy production, Geobacter sulfurreducens was inoculated into chambers in which a graphite electrode served as the sole electron acceptor and acetate or hydrogen was the electron donor. The electron-accepting electrodes were maintained at oxidizing potentials by connecting them to similar electrodes in oxygenated medium (fuel cells) or to potentiostats that poised electrodes at +0.2 V versus an Ag/AgCl reference electrode (poised potential). When a small inoculum of G. sulfurreducens was introduced into …

Go to article

Osaka University: A Focus Of Polymer Science: 70th Anniversary Celebration, Otto Vogl, Koichi Hatada Dec 2002

Osaka University: A Focus Of Polymer Science: 70th Anniversary Celebration, Otto Vogl, Koichi Hatada

Otto Vogl

No abstract provided.

Go to article

Personalities In Polymer Science: Cover Page, Title Page, Introduction, And List Of Articles, Otto Vogl Dec 2002

Personalities In Polymer Science: Cover Page, Title Page, Introduction, And List Of Articles, Otto Vogl

Otto Vogl

A compilation of articles with short biographies of the scientists who played leading roles in the field and provided the basis of Polymer Science and Technology throughout the 20th century.

Go to article

Self-Consistent Three Dimensional Models For Quantum Ballistic Transport In Open Systems, Eric Polizzi, N. Ben Abdallah Dec 2002

Self-Consistent Three Dimensional Models For Quantum Ballistic Transport In Open Systems, Eric Polizzi, N. Ben Abdallah

Eric Polizzi

A quasi-three-dimensional model for quantum ballistic transport in nanostructures is proposed. The model goes beyond the Thomas-Fermi approximation and is numerically more tractable than the full three-dimensional Schrödinger-Poisson model. Its derivation relies on the strong confinement of electrons at the heterojunction which allows us to split the three-dimensional Schrödinger equation into a one-dimensional Schrödinger equation for the confined direction and a two-dimensional Schrödinger equation in the transport direction. The space charge effects are taken into account in a three-dimensional framework. Numerical simulations of quantum waveguide devices such as T stubs and directional couplers are used to illustrate the accuracy of …

Go to article

Whole-Genome Analysis Of Dorsal-Ventral Patterning In The Drosophila Embryo, Angelike Stathopoulos, Madeleine Van Drenth, Albert Erives, Michele Markstein, Michael Levine Nov 2002

Whole-Genome Analysis Of Dorsal-Ventral Patterning In The Drosophila Embryo, Angelike Stathopoulos, Madeleine Van Drenth, Albert Erives, Michele Markstein, Michael Levine

Michele Markstein

The maternal Dorsal regulatory gradient initiates the differentiation of several tissues in the early Drosophila embryo. Whole-genome microarray assays identified as many as 40 new Dorsal target genes, which encode a broad spectrum of cell signaling proteins and transcription factors. Evidence is presented that a tissue-specific form of the NF-Y transcription complex is essential for the activation of gene expression in the mesoderm. Tissue-specific enhancers were identified for new Dorsal target genes, and bioinformatics methods identified conserved cis-regulatory elements for coordinately regulated genes that respond to similar thresholds of the Dorsal gradient. The new Dorsal target genes and enhancers represent …

Go to article

The Use Of 4-Substituted Pyridines To Afford Amphiphilic, Pegylated Cadmium Selenide Nanoparticles, Habib Skaff, Todd S. Emrick Nov 2002

The Use Of 4-Substituted Pyridines To Afford Amphiphilic, Pegylated Cadmium Selenide Nanoparticles, Habib Skaff, Todd S. Emrick

Todd S. Emrick

Amphiphilic cadmium selenide (CdSe) nanoparticles were prepared by surface functionalization with novel ligands 1 and 2, composed of pyridine moieties substituted in the 4-position with polyethylene glycol (PEG) chains.

Go to article

1. Yukio Imanishi, Otto Vogl Nov 2002

1. Yukio Imanishi, Otto Vogl

Otto Vogl

No abstract provided.

Go to article

Plant Rac-Like Gtpases Are Activated By Auxin And Mediate Auxin-Responsive Gene Expression, L. Z. Tao, Alice Cheung, H. M. Wu Nov 2002

Plant Rac-Like Gtpases Are Activated By Auxin And Mediate Auxin-Responsive Gene Expression, L. Z. Tao, Alice Cheung, H. M. Wu

Alice Cheung

The auxin indole-3-acetic acid is a key plant hormone essential for a broad range of growth and developmental processes. Here, we show that auxin activates Rac-like GTPases (referred to as Rac/Rop GTPases), and they in turn stimulate auxin-responsive gene expression. In particular, we show that overexpressing a wild-type tobacco Rac/Rop GTPase, NtRac1, and its constitutively active mutant form activates auxin-responsive gene expression. On the other hand, overexpressing dominant-negative NtRac1 and Rac-negative regulators, or reducing the endogenous NtRac1 level, suppresses auxin-induced gene expression. Furthermore, overexpression of NtRac1 activity or suppression of its expression in transgenic seedlings induces phenotypes that are similar …

Go to article

A Study Of Indoor Carbon Dioxide Levels And Sick Leave Among Office Workers, Theodore A. Myatt, John W. Staudenmayer, Kate Adams, Michael Walters, Stephen N. Rudnick, Donald K. Milton Oct 2002

A Study Of Indoor Carbon Dioxide Levels And Sick Leave Among Office Workers, Theodore A. Myatt, John W. Staudenmayer, Kate Adams, Michael Walters, Stephen N. Rudnick, Donald K. Milton

John W Staudenmayer

Background A previous observational study detected a strong positive relationship between sick leave absences and carbon dioxide (CO2) concentrations in office buildings in the Boston area. The authors speculated that the observed association was due to a causal effect associated with low dilution ventilation, perhaps increased airborne transmission of respiratory infections. This study was undertaken to explore this association. Methods We conducted an intervention study of indoor CO2 levels and sick leave among hourly office workers employed by a large corporation. Outdoor air supply rates were adjusted periodically to increase the range of CO2 concentrations. We recorded indoor CO2 concentrations …

Go to article

2. Toshinobu Higashimura, Otto Vogl Oct 2002

2. Toshinobu Higashimura, Otto Vogl

Otto Vogl

No abstract provided.

Go to article

Additionality Of Debt Relief And Debt Forgiveness, And Implications For Future Volumes Of Official Assistance, Léonce Ndikumana Oct 2002

Additionality Of Debt Relief And Debt Forgiveness, And Implications For Future Volumes Of Official Assistance, Léonce Ndikumana

Léonce Ndikumana

This paper examines the impact of debt forgiveness and debt relief on official development assistance. From the recipient side, the econometric analysis suggests that countries that received debt relief also received more aid compared to those that did not qualify for debt relief. From the donor side, while the data indicate a decline in aid disbursement since the early 1990s, there is no econometric evidence for any direct causal relationship between the decline in aid and debt relief/forgiveness. Nonetheless, the decline in aid raises serious concerns given that developing countries’ need in external resources cannot be met by debt relief …

Go to article

Decoding Cis-Regulatory Dnas In The Drosophila Genome, Michele Markstein, Michael Levine Oct 2002

Decoding Cis-Regulatory Dnas In The Drosophila Genome, Michele Markstein, Michael Levine

Michele Markstein

Cis-regulatory DNAs control the timing and sites of gene expression during metazoan development. Changes in gene expression are responsible for the morphological diversification of metazoan body plans. However, traditional methods for the identification and characterization of cis-regulatory DNAs are tedious. During the past year, computational methods have been used to identify novel cis-DNAs within the entire Drosophila genome. These methods change the way that cis-DNAs will be analyzed in future studies and offer the promise of unraveling complex gene networks.

Go to article

A Discrete Nonlinear Model With Substrate Feedback, Panos Kevrekidis, B. A. Malomed, A. R. Bishop Oct 2002

A Discrete Nonlinear Model With Substrate Feedback, Panos Kevrekidis, B. A. Malomed, A. R. Bishop

Panos Kevrekidis

We consider a prototypical model in which a nonlinear field (continuum or discrete) evolves on a flexible substrate which feeds back to the evolution of the main field. We identify the underlying physics and potential applications of such a model and examine its simplest one-dimensional Hamiltonian form, which turns out to be a modified Frenkel-Kontorova model coupled to an extra linear equation. We find static kink solutions and study their stability, and then examine moving kinks (the continuum limit of the model is studied too). We observe how the substrate effectively renormalizes properties of the kinks. In particular, a nontrivial …

Go to article

A Model System For Study Of Sex Chromosome Effects On Sexually Dimorphic Neural And Behavioral Traits, Geert De Vries, E. F. Rissman, R. B. Simerly, Y. L. Yang, E. M. Scordalakes, C. J. Auger, A. Swain, R. Lovell-Badge, P. S. Burgoyne, A. P. Arnold Oct 2002

A Model System For Study Of Sex Chromosome Effects On Sexually Dimorphic Neural And Behavioral Traits, Geert De Vries, E. F. Rissman, R. B. Simerly, Y. L. Yang, E. M. Scordalakes, C. J. Auger, A. Swain, R. Lovell-Badge, P. S. Burgoyne, A. P. Arnold

Geert De Vries

We tested the hypothesis that genes encoded on the sex chromosomes play a direct role in sexual differentiation of brain and behavior. We used mice in which the testis-determining gene (Sry) was moved from the Y chromosome to an autosome (by deletion ofSry from the Y and subsequent insertion of anSry transgene onto an autosome), so that the determination of testis development occurred independently of the complement of X or Y chromosomes. We compared XX and XY mice with ovaries (females) and XX and XY mice with testes (males). These comparisons allowed us to assess the effect of sex chromosome …

Go to article

The Regulation Of Actin Organization By Actin-Depolymerizing Factor In Elongating Pollen Tubes, C. Y. Chen, E. I. Wong, L. Vidali, A. Estavillo, P. K. Hepler, H. M. Wu, Alice Cheung Sep 2002

The Regulation Of Actin Organization By Actin-Depolymerizing Factor In Elongating Pollen Tubes, C. Y. Chen, E. I. Wong, L. Vidali, A. Estavillo, P. K. Hepler, H. M. Wu, Alice Cheung

Alice Cheung

Pollen tube elongation is a polarized cell growth process that transports the male gametes from the stigma to the ovary for fertilization inside the ovules. Actomyosin-driven intracellular trafficking and active actin remodeling in the apical and subapical regions of pollen tubes are both important aspects of this rapid tip growth process. Actin-depolymerizing factor (ADF) and cofilin are actin binding proteins that enhance the depolymerization of microfilaments at their minus, or slow-growing, ends. A pollen-specific ADF from tobacco, NtADF1, was used to dissect the role of ADF in pollen tube growth. Overexpression of NtADF1 resulted in the reduction of fine, axially …

Go to article

3. Otto Vogl, Gerald S. Kirshenbaum, Helga Roder Sep 2002

3. Otto Vogl, Gerald S. Kirshenbaum, Helga Roder

Otto Vogl

No abstract provided.

Go to article

Medusae Fossae Formation: New Perspectives From Mars Global Surveyor, Bethany Bradley, S. E.H Sakimoto, H. Frey, J. R. Zimbelman Aug 2002

Medusae Fossae Formation: New Perspectives From Mars Global Surveyor, Bethany Bradley, S. E.H Sakimoto, H. Frey, J. R. Zimbelman

Bethany Bradley

The nature and origin of the Medusae Fossae Formation (MFF) on Mars has been debated since the return of the first Viking images. The MFF's young age, distinctive surface texture, and lack of obvious source have prompted multiple hypotheses for its origin. This study uses data from the Mars Global Surveyor (MGS) mission to examine the MFF at all available scales. We discuss and quantify observations from Mars Orbiter Laser Altimeter (MOLA) topography and Mars Orbiter Camera (MOC) images to better constrain the origin of the MFF. Topographic grid estimates yield a present extent of 2.1 × 106 km2 and …

Go to article

Review Of Frank Ryan: Tuberculosis: The Greatest Story Never Told, Lynn Margulis Jul 2002

Review Of Frank Ryan: Tuberculosis: The Greatest Story Never Told, Lynn Margulis

Lynn Margulis (1938 - 2011)

No abstract provided.

Go to article

Defining The Pattern Of The Sustainable Urban Region - Development Of Regional Measurement Methods, Elizabeth Brabec, Geoffrey Mcd. Lewis Jun 2002

Defining The Pattern Of The Sustainable Urban Region - Development Of Regional Measurement Methods, Elizabeth Brabec, Geoffrey Mcd. Lewis

Elizabeth Brabec

To date, the debate on the sustainability of human settlements has focused on the urban portion of the land use pattern. Since urban areas rely on suburban, rural, and other less densely settled areas for their existence, these areas must be included in any sustainability assessment. This need for a regional view has resulted in a typology of regional form, which allows comparisons of relative sustainability between various regional land use patterns. Based on resource efficiency, this regional analysis includes measurements related to water, agricultural land, habitat, energy use, and transportation and identifies primary indicators for each category. Existing methods …

Go to article

On The Minimum Ropelength Of Knots And Links, Jason Cantarella, Robert B. Kusner, John M. Sullivan Jun 2002

On The Minimum Ropelength Of Knots And Links, Jason Cantarella, Robert B. Kusner, John M. Sullivan

Robert Kusner

The ropelength of a knot is the quotient of its length by its thickness, the radius of the largest embedded normal tube around the knot. We prove existence and regularity for ropelength minimizers in any knot or link type; these are C 1,1 curves, but need not be smoother. We improve the lower bound for the ropelength of a nontrivial knot, and establish new ropelength bounds for small knots and links, including some which are sharp.

Go to article

Selling Canada To Canadians: Collective Memory, National Identity, And Popular Culture, Emily West Jun 2002

Selling Canada To Canadians: Collective Memory, National Identity, And Popular Culture, Emily West

Emily E. West

Two media endeavours, the Heritage Minutes and the CBC documentary Canada: A People’s History, hope to serve as a corrective to Canadians’ lack of interest in their history and to bolster national identity. However, the producers do not want to appear propagandistic in a country where there is conflict about what the shape of the nation should be. They accomplish this by appealing to the “on the spot” authority of journalistic representation and the emotional immediacy of dramatic story-telling. They also emphasize the multi-cultural and multi-perspectival nature of Canada’s past. However, ultimately these efforts exist within a larger narrative about …

Go to article

Mechanisms For Accessing Insoluble Fe(Iii) Oxide During Dissimilatory Fe(Iii) Reduction By Geothrix Fermentans, Kelly P. Nevin, Derek Lovley May 2002

Mechanisms For Accessing Insoluble Fe(Iii) Oxide During Dissimilatory Fe(Iii) Reduction By Geothrix Fermentans, Kelly P. Nevin, Derek Lovley

Kelly Nevin

Mechanisms for Fe(III) oxide reduction were investigated in Geothrix fermentans, a dissimilatory Fe(III)-reducing microorganism found within the Fe(III) reduction zone of subsurface environments. Culture filtrates of G. fermentans stimulated the reduction of poorly crystalline Fe(III) oxide by washed cell suspensions, suggesting that G. fermentans released one or more extracellular compounds that promoted Fe(III) oxide reduction. In order to determine if G. fermentans released electron-shuttling compounds, poorly crystalline Fe(III) oxide was incorporated into microporous alginate beads, which prevented contact between G. fermentans and the Fe(III) oxide. G. fermentans reduced the Fe(III) within the beads, suggesting that one of the compounds that …

Go to article

Impervious Surfaces And Water Quality: A Review Of Current Literature And Its Implications For Watershed Planning, Elizabeth Brabec May 2002

Impervious Surfaces And Water Quality: A Review Of Current Literature And Its Implications For Watershed Planning, Elizabeth Brabec

Elizabeth Brabec

Impervious surfaces have for many years been recognized as an indicator of the intensity of the urban environment and, with the advent of urban sprawl, they have become a key issue in habitat health. Although a considerable amount of research has been done to define impervious thresholds for water quality degradation, there are a number of flaws in the assumptions and methodologies used. Given refinement of the methodology, accurate and usable parameters for preventative watershed planning can be developed, which include impervious surface thresholds and a balance between pervious and impervious surfaces within a watershed.

Go to article

Knockout And Transgenic Mice Of Trp53: What Have We Learned About P53 In Breast Cancer?, Anneke C. Blackburn, D. Joseph Jerry Apr 2002

Knockout And Transgenic Mice Of Trp53: What Have We Learned About P53 In Breast Cancer?, Anneke C. Blackburn, D. Joseph Jerry

D. Joseph Jerry

The human p53 tumor suppressor gene TP53 is mutated at a high frequency in sporadic breast cancer, and Li-Fraumeni syndrome patients who carry germline mutations in one TP53 allele have a high incidence of breast cancer. In the 10 years since the first knockout of the mouse p53 tumor suppressor gene (designated Trp53) was published, much has been learned about the contribution of p53 to biology and tumor suppression in the breast through the use of p53 transgenic and knockout mice. The original mice deficient in p53 showed no mammary gland phenotype. However, studies using BALB/c-Trp53-deficient mice have demonstrated a …

Go to article

Images Of Bosnia, Joel Halpern Mar 2002

Images Of Bosnia, Joel Halpern

Joel M. Halpern

The images which appear here are, unless otherwise indicated, are copyright Joel M. Halpern and taken from the catalog of an exhibition entitled The Thin Veneer; the Peoples of Bosnia and their Disappearing Cultural Heritage (Copyright 1997, University of Massachusetts Amherst and used by permission). Copies of the catalog are available for $ 6.00 including postage, from: Betsy Siersma, Director, University Art Gallery, University of Massachusetts, Amherst, MA 01002. Part of this presentation is also available online at http://www.h-net.org/~sae/halpern/photos.html.

Go to article

Hormonal Control Of P53 And Chemoprevention, D. Joseph Jerry, Lisa M. Minter, Klaus A. Becker, Anneke C. Blackburn Mar 2002

Hormonal Control Of P53 And Chemoprevention, D. Joseph Jerry, Lisa M. Minter, Klaus A. Becker, Anneke C. Blackburn

D. Joseph Jerry

Improvements in the detection and treatment of breast cancer have dramatically altered its clinical course and outcome. However, prevention of breast cancer remains an elusive goal. Parity, age of menarche, and age at menopause are major risk factors drawing attention to the important role of the endocrine system in determining the risk of breast cancer, while heritable breast cancer susceptibility syndromes have implicated tumor suppressor genes as important targets. Recent work demonstrating hormonal modulation of the p53 tumor suppressor pathway draws together these established determinants of risk to provide a model of developmental susceptibility to breast cancer. In this model, …

Go to article

Enrichment Of Members Of The Family Geobacteraceae Associated With Stimulation Of Dissimilatory Metal Reduction In Uranium-Contaminated Aquifer Sediments, Dawn E. Holmes, Kevin T. Finneran, Regina A. O'Neil, Derek Lovley Feb 2002

Enrichment Of Members Of The Family Geobacteraceae Associated With Stimulation Of Dissimilatory Metal Reduction In Uranium-Contaminated Aquifer Sediments, Dawn E. Holmes, Kevin T. Finneran, Regina A. O'Neil, Derek Lovley

Derek Lovley

Stimulating microbial reduction of soluble U(VI) to insoluble U(IV) shows promise as a strategy for immobilizing uranium in uranium-contaminated subsurface environments. In order to learn more about which microorganisms might be involved in U(VI) reduction in situ, the changes in the microbial community when U(VI) reduction was stimulated with the addition of acetate were monitored in sediments from three different uranium-contaminated sites in the floodplain of the San Juan River in Shiprock, N.Mex. In all three sediments U(VI) reduction was accompanied by concurrent Fe(III) reduction and a dramatic enrichment of microorganisms in the family Geobacteraceae, which are known U(VI)- and …

Go to article

Agricultural Land Fragmentation: The Spatial Effects Of Three Land Protection Strategies In The Eastern United States, Elizabeth Brabec, Chip Smith Feb 2002

Agricultural Land Fragmentation: The Spatial Effects Of Three Land Protection Strategies In The Eastern United States, Elizabeth Brabec, Chip Smith

Elizabeth Brabec

Fragmentation of agricultural land by urban sprawl affects both the agricultural production capacity of the land and its rural scenic quality. In order to assess the resulting fragmentation of the three most common types of agricultural land conservation tools in the United States, this study analyzes the spatial form of three land protection strategies: a purchase of development rights (PDR) program, a clustering program and a transfer of development rights program. By assessing a series of measures of success such as total acreage protected, size of parcels, contiguity and farming status, the study compares the effectiveness of programs that have …

Go to article

Mechanisms For Accessing Insoluble Fe(Iii) Oxide During Dissimilatory Fe(Iii) Reduction By Geothrix Fermentans, Kelly P. Nevin, Derek Lovley Feb 2002

Mechanisms For Accessing Insoluble Fe(Iii) Oxide During Dissimilatory Fe(Iii) Reduction By Geothrix Fermentans, Kelly P. Nevin, Derek Lovley

Derek Lovley

Mechanisms for Fe(III) oxide reduction were investigated in Geothrix fermentans, a dissimilatory Fe(III)-reducing microorganism found within the Fe(III) reduction zone of subsurface environments. Culture filtrates of G. fermentans stimulated the reduction of poorly crystalline Fe(III) oxide by washed cell suspensions, suggesting that G. fermentans released one or more extracellular compounds that promoted Fe(III) oxide reduction. In order to determine if G. fermentans released electron-shuttling compounds, poorly crystalline Fe(III) oxide was incorporated into microporous alginate beads, which prevented contact between G. fermentans and the Fe(III) oxide. G. fermentans reduced the Fe(III) within the beads, suggesting that one of the compounds that …

Go to article

Next Last