Browsing by Title

Now showing 1 - 20 of 32613

1/f noise and Luttinger liquid phenomena in carbon nanotubes
(2007-08-03) Tobias, David; Lobb, Christopher; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Carbon nanotubes (CNTs) provide an ideal medium for testing the behavior of one-dimensional electron systems and are promising candidates for electronic applications such as sensors or field-effect transistors. This thesis describes the use of low frequency resistance fluctuations to measure both the properties of the one-dimensional electron system in CNTs, and the sensitivity of CNT devices to their environment. Low frequency noise was measured in CNTs in field effect transistor (FET) geometry. CNTs have a large amount of surface area relative to their volume and are expected to be strongly affected by their environment, leading to speculation that CNTs should have large amounts of 1/f noise. My measurements indicate that the noise level is in the same range as that of traditional FETs, an encouraging result for possible electronic applications. The temperature dependence of 1/f noise from 1.2 K to 300 K can be used to extract the characteristic energies of the fluctuators responsible for the noise. The characteristic energies allows for the elimination of structural and electronic transitions within the CNT itself as possible sources of 1/f noise in CNTs, leaving the motion of defects in the gate dielectric, or possibly strongly physisorbed species, as the likely culprits. Another form of low frequency noise found in CNTs is random telegraph signal (RTS), which manifests as the alternation between two current states at a stable voltage bias. In CNTs, this phenomenon occurs due to the tunneling of electrons into and out of the CNT from a nearby defect, and thus provides a way to probe the tunneling density of states of the CNT itself. The tunneling density of states in turn provides information on the strength of the electron-electron interaction in CNTs. Due to the one-dimensional structure of CNTs their electronic state is expected to be a Luttinger liquid, which should manifest as a power-law suppression of the tunneling density of states at the Fermi energy. The power law exponent is measured in both the temperature dependence and energy dependence of the tunneling rates. In agreement with theory, the power-law exponent is significantly larger in semiconducting CNTs than found in previous experiments on metallic CNTs. The RTS can also be used as a "defect thermometer" to probe the electron temperature of the CNT. The effect of the bias voltage on the electron temperature provides a means to determine the energy relaxation length for the electrons in the CNT.
10 best resources for . . . health research capacity strengthening
(2007) Nuyens, Yvo
Health research capacity strengthening (RCS) is widely recognized as a major unmet need, particularly in low- and middle-income countries (Lansang and Dennis 2006). It has been high on both national and international agendas for the past 20 years, as evidenced by a steady stream of peer-reviewed and grey literature, training tools, programmes, grants, workshops, task forces and conferences. Defined as ‘. . . the ongoing process of empowering individuals, institutions, organizations and nations to define and prioritize problems systematically, to develop and scientifically evaluate appropriate solutions, and share and apply the knowledge generated’ (Lansang and Dennis 2004), RCS encompasses a broad and complex spectrum of activities, including training programmes, tools and grants. In addition, anyone embarking on an RCS programme needs to address broader issues of which and whose capacities to strengthen, to do what, in which context and with which purpose.
10 Ways Historic Preservation Policy Supports White Supremacy and 10 Ideas to End It
(2021-05) Wells, Jeremy C.
In the United States, policy-driven work in historic preservation comprises about three-quarters of the field’s work. Addressing issues of diversity, inclusion, and equity in federal and local preservation policies has usually been synonymous with the need to recognize the history of people with non-dominant racial or ethnic identities. While this omission is very much a policy problem, it is far from the only manifestation of how preservation policies support White supremacy, especially through the field’s pervasive regulatory climate. To more fully explore the policy problems in the field, this paper attempts to define ten ways in which preservation policy supports White supremacy followed by specific recommendations to solve some of these issues. A central theme is for the National Park Service and the Advisory Council on Historic Preservation to open up and support the rule-making process around the National Register of Historic Places and the Secretary of the Interior’s Standards. A secondary theme is to support people-centered changes to historic preservation policy, including more flexibility around what have often been dogmatic approaches to significance and integrity.
100 Years Later, a Painful Episode Is Observed at Last
(The New York Times, 2006) Dewan, Shaila
Two years ago, Saudia Muwwakkil, the director of communications for the Martin Luther King Jr. National Historic Site, invited community leaders to discuss how to mark the 100th anniversary of a 1906 race riot in which mobs of whites descended on the city's black residents. The racial strife shut down Atlanta for four days and ended with the bodies of black men hanging from trees and streetlights. But of those Ms. Muwwakkil called, almost none had heard of it.
13 Episodes for String Quartet
(2019) Dizon, Quinn Gareth; Wilson, Mark E; Music; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
13 Episodes for String Quartet is an original composition with an approximate duration of 38 minutes. A dramatic narrative unfolds over a 13-movement arch form as two intervals, a tritone and a perfect fifth, are presented and explored in different harmonic and melodic contexts. As these two opposing forces compete for the foreground, a gradual shift takes place from musical material that is audibly tritone based to material that is audibly perfect fifth based. To help realize the structure and content for this composition, I developed a computational method to generate and parse pitch-class sets based on user supplied interval content and filter criteria. I call this Binary Harmony. In this method, I generate sequences of pitches, where each dyadic adjacency in the sequence forms one of two provided pitch class-intervals. The principal musical material for each movement is generated using this computational method.
13C and 15N Metabolic Flux Analysis on the Marine Diatom Phaeodactylum tricornutum to Investigate Efficient Unicellular Carbon and Nitrogen Assimilation Mechanisms
(2013) Zheng, Yuting; Sriram, Ganesh; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Photosynthesis is indispensable in carbon cycling and obtaining renewable carbon. Operated by cyanobacteria, algae and plants, this process provides reduced carbon and molecular oxygen, consumes atmospheric CO₂ and harnesses solar energy. Photosynthesis is also central to the production of biofuels. Diatoms, a class of marine algae, contribute 20% to 40% of global photosynthetic productivity despite surviving in CO₂-depleted and nitrogen-limited environments. This makes diatoms ideal models to study efficient photosynthetic, specifically carbon concentrating mechanisms (CCM). It has been long debated that whether the unicellular marine diatom Phaeodactylum tricornutum operates a CCM, and whether the CCM is biophysical or biochemical (C4) in nature, with existing (circumstantial) experimental evidence divided amongst the two possibilities. Through isotope labeling experiments (ILE) and metabolic flux analysis (MFA), we provide for the first time significant, direct evidence for a biochemical CCM and the potential combined operation of a biochemical and a biophysical CCM. Additionally, we shed light on how genes regulating this complex process respond to critical environmental variables. Furthermore, we report the use of isotope-assisted metabolic flux analysis to study organic carbon (especially glucose) assimilation in P. tricornutum. Our steady state ILEs reveal glucose assimilation under light and potentially which genes may be responsible for glucose metabolism. We then studied nitrogen (mainly urea) assimilation through instationary 15N and 13C labeling experiments, to find indications of an unusual pathway of urea assimilation. Gene expression trends under various environmental conditions suggest the possible participation of the urea cycle in assimilating nitrogen in P. tricornutum, and how this metabolically differs from nitrate and ammonium assimilation. We anticipate that this work will not only improve understanding of unicellular C4 CCMs, but provide insights to explain the ecological success of diatoms in adapting to challenging environments.
13C Metabolic Flux Analysis Indicates Endothelial Cells Attenuate Metabolic Perturbations by Modulating TCA Activity
(MDPI, 2021-04-07) Moiz, Bilal; Garcia, Jonathan; Basehore, Sarah; Sun, Angela; Li, Andrew; Padmanabhan, Surya; Albus, Kaitlyn; Jang, Cholsoon; Sriram, Ganesh; Clyne, Alisa Morss
Disrupted endothelial metabolism is linked to endothelial dysfunction and cardiovascular disease. Targeted metabolic inhibitors are potential therapeutics; however, their systemic impact on endothelial metabolism remains unknown. In this study, we combined stable isotope labeling with 13C metabolic flux analysis (13C MFA) to determine how targeted inhibition of the polyol (fidarestat), pentose phosphate (DHEA), and hexosamine biosynthetic (azaserine) pathways alters endothelial metabolism. Glucose, glutamine, and a four-carbon input to the malate shuttle were important carbon sources in the baseline human umbilical vein endothelial cell (HUVEC) 13C MFA model. We observed two to three times higher glutamine uptake in fidarestat and azaserine-treated cells. Fidarestat and DHEA-treated HUVEC showed decreased 13C enrichment of glycolytic and TCA metabolites and amino acids. Azaserine-treated HUVEC primarily showed 13C enrichment differences in UDP-GlcNAc. 13C MFA estimated decreased pentose phosphate pathway flux and increased TCA activity with reversed malate shuttle direction in fidarestat and DHEA-treated HUVEC. In contrast, 13C MFA estimated increases in both pentose phosphate pathway and TCA activity in azaserine-treated cells. These data show the potential importance of endothelial malate shuttle activity and suggest that inhibiting glycolytic side branch pathways can change the metabolic network, highlighting the need to study systemic metabolic therapeutic effects.
15 Minute Neighborhoods in College Park, Maryland
(Partnership for Action Learning Sustainability (PALS), 2024-05) Anderson, Alanna; Arazi, David; Attipoe, Senam; Elson, Jona; Goode, Maeghen; Jones, Asia; Malhotra, Aarushi; Provolo, Emmanuelle; Ravert, Megan; Sanabia, Rafael; Sanford, Mimi; Santana, Ariana; Thorpe, Carey; Walker, Emma; Woods, Kayla; Elzoghbi, Riem
The Department of Planning and Community Development in the City of College Park, Maryland is exploring the concept of a 15 Minute City to facilitate the creation of amenity-rich, easily accessible neighborhoods throughout the community. A 15 Minute City is an urban planning concept used to describe a city in which amenities and services - such as retail, education, social services, recreation, employment, and other needs - may be easily accessed within a 15-minute walk, bike ride, or commute by public transport from any point in the city. The urban fabrics of such cities incorporate a wide range of mixed-use developments, bike and pedestrian-friendly streets and paths, easily accessible public spaces, public transportation, and other interventions to create relatively denser, walkable, livable neighborhoods. The goal is to create neighborhoods in which residents, particularly residents for whom mobility may be restricted due to cost, disability, time, and other constraints, may satisfy their everyday needs within their existing neighborhoods. 15 Minute Cities are posited to increase equity by making accessible amenities and services within neighborhoods, reduce car-dependency, promote sustainability, healthy lifestyles, and aging in place, improve social relations, and generally improve the quality of life within communities. In partnership with the Department of Planning and Community Development, student planners in the Urban Studies and Planning Program at the University of Maryland’s School of Architecture, Planning and Preservation investigated and provided recommendations on ways in which existing neighborhoods in College Park may be transformed into 15 Minute Cities. The project was conducted during Spring Semester 2024 as part of the graduate-level URSP673 Community Development course, under the guidance of Dr. Riem ElZoghbi.
1620 GEOGRAPHOS AND 433 EROS: SHAPED BY PLANETARY TIDES?
(University of Chicago Press, 1999) BOTTKE, W. F. JR.; RICHARDSON, D. C.; MICHEL, P.; LOVE, S. G.
Until recently, most asteroids were thought to be solid bodies whose shapes were determined largely by collisions with other asteroids. Recent work by Burns and others has shown that many asteroids may be little more than rubble piles, held together by self-gravity ; this means that their shapes may be strongly distorted by tides during close encounters with planets. Here we report on numerical simulations of encounters between an ellipsoid-shaped rubble-pile asteroid and Earth. After an encounter, many of the simulated asteroids develop the same rotation rate and distinctive shape as 1620 Geographos (i.e., highly elongated with a single convex side, tapered ends, and small protuberances swept back against the rotation direction). Since our numerical studies show that these events occur with some frequency, we suggest that Geographos may be a tidally distorted object. In addition, our work shows that 433 Eros, which will be visited by the NEAR spacecraft in 1999, is much like Geographos, suggesting that it too may have been molded by tides in the past.
182W and HSE constraints from 2.7 Ga komatiites on the heterogeneous nature of the Archean mantle
(Elsevier - Geochimica et Cosmochimica Acta, 2018) Puchtel, Igor S; Blichert-Toft, Janne; Touboul, Mathieu; Walker, Richard J.
While the isotopically heterogeneous nature of the terrestrial mantle has long been established, the origin, scale, and longevity of the heterogeneities for different elements and isotopic systems are still debated. Here, we report Nd, Hf, W, and Os isotopic and highly siderophile element (HSE) abundance data for the Boston Creek komatiitic basalt lava flow (BCF) in the 2.7 Ga Abitibi greenstone belt, Canada. This lava flow is characterized by strong depletions in Al and heavy rare earth elements (REE), enrichments in light REE, and initial epsilon143Nd = +2.5 ± 0.2 and initial epsilon176Hf = +4.2 ± 0.9 indicative of derivation from a deep mantle source with time-integrated suprachondritic Sm/Nd and Lu/Hf ratios. The data plot on the terrestrial Nd-Hf array suggesting minimal involvement of early magma ocean processes in the fractionation of lithophile trace elements in the mantle source. This conclusion is supported by a mean mu142Nd = -3.8 ± 2.8 that is unresolvable from terrestrial standards. By contrast, the BCF exhibits a positive 182W anomaly (mu182W = +11.7 ± 4.5), yet is characterized by chondritic initial gamma187Os = +0.1 ± 0.3 and low inferred source HSE abundances (35 ± 5% of those estimated for the present-day Bulk Silicate Earth, BSE). Collectively, these characteristics are unique among Archean komatiite systems studied so far. The deficit in the HSE, coupled with the chondritic Os isotopic composition, but a positive 182W anomaly, are best explained by derivation of the parental BCF magma from a mantle domain characterized by a predominance of HSE-deficient, differentiated late accreted material. According to the model presented here, the mantle domain that gave rise to the BCF received only ~35% of the present-day HSE complement in the BSE before becoming isolated from the rest of the convecting mantle until the time of komatiite emplacement at 2.72 Ga. These new data provide strong evidence for a highly heterogeneous Archean mantle in terms of absolute HSE abundances and W isotopic composition, and also indicate slow mixing, on a timescale of at least 1.8 billion years. Additionally, the data are consistent with a stagnant-lid plate tectonic regime in the Hadean and Archean, prior to the onset of modern-style plate tectonics.
182W and HSE constraints from 2.7 Ga komatiites on the heterogeneous nature of the Archen mantle
(Elsevier, 2018-03-02) Puchtel, I.S.; Blichert-Toft, J.; Touboul, M.; Walker, Richard J.
While the isotopically heterogeneous nature of the terrestrial mantle has long been established, the origin, scale, and longevity of the heterogeneities for different elements and isotopic systems are still debated. Here, we report Nd, Hf, W, and Os isotopic and highly siderophile element (HSE) abundance data for the Boston Creek komatiitic basalt lava flow (BCF) in the 2.7 Ga Abitibi greenstone belt, Canada. This lava flow is characterized by strong depletions in Al and heavy rare earth elements (REE), enrichments in light REE, and initial e143Nd = +2.5 ± 0.2 and initial e176Hf = +4.2 ± 0.9 indicative of derivation from a deep mantle source with time-integrated suprachondritic Sm/Nd and Lu/Hf ratios. The data plot on the terrestrial Nd-Hf array suggesting minimal involvement of early magma ocean processes in the fractionation of lithophile trace elements in the mantle source. This conclusion is supported by a mean mu142Nd = -3.8 ± 2.8 that is unresolvable from terrestrial standards. By contrast, the BCF exhibits a positive 182W anomaly (mu182W = +11.7 ± 4.5), yet is characterized by chondritic initial g187Os = +0.1 ± 0.3 and low inferred source HSE abundances (35 ± 5% of those estimated for the present-day Bulk Silicate Earth, BSE). Collectively, these characteristics are unique among Archean komatiite systems studied so far. The deficit in the HSE, coupled with the chondritic Os isotopic composition, but a positive 182W anomaly, are best explained by derivation of the parental BCF magma from a mantle domain characterized by a predominance of HSE-deficient, differentiated late accreted material. According to the model presented here, the mantle domain that gave rise to the BCF received only ~35% of the present-day HSE complement in the BSE before becoming isolated from the rest of the convecting mantle until the time of komatiite emplacement at 2.72 Ga. These new data provide strong evidence for a highly heterogeneous Archean mantle in terms of absolute HSE abundances and W isotopic composition, and also indicate slow mixing, on a timescale of at least 1.8 billion years. Additionally, the data are consistent with a stagnant-lid plate tectonic regime in the Hadean and Archean, prior to the onset of modern-style plate tectonics.
19 Nation Poll on Global Issues: World Public Opinion Says World Not Going in Right Direction; Linked to Widespread Negative Views of US Influence
(2004-06-04) Program on International Policy Attitudes (PIPA)
A majority of people in the world do not feel the world is going in the right direction, a view strongly linked to the view--held by a majority--that the United States is not having a positive influence in the world. A majority views globalization positively, but majorities--especially in rich countries--say that the rich are not playing fair in trade negotiations with poor countries. In most countries the UN is well trusted.
The 1974 Bilingual Education Amendments: Revolution, Reaction or Reform
(1976) Schneider, Susan Gilbert; Baird, Janet R.; Languages, Literatures, & Cultures; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
Purpose: The study examined in detail the legislative history of the 1974 Bilingual Education Act, Section 105 of the Education Amendments of 1974, Public Law 93-380. The study examined the roles of Representatives, Senators, lobbyists, judicial decisions, minority groups and Administration officials in developing the 1974 Bilingual Education Act.
1991 Archaeological Excavations at the Charles Carroll House in Annapolis, Maryland, 18AP45
(1992) Logan, George C.; Bodor, Thomas W.; Jones, Lynn D.; Creveling, Marian C.; Leone, Mark P.
This report provides a detailed summary of archaeological excavations that were conducted by Archaeology in Annapolis inside the ground story of the Charles Carroll House in Annapolis (18AP45) during the summer and fall of 1991. This project was initiated by Charles Carroll House of Annapolis, Inc. (CCHA), and was made possible through an agreement between CCHA and Historic Annapolis Foundation. It was designed as an initial phase of a larger project to restore the Carroll House to its late 18th-century appearance, while at the same time adding modern facilities to accomodate receptions, conferences, and other adaptive uses. These excavations were conducted between June and mid October of 1991, prior to interior house restoration, with monitoring of site restoration activities continuing well into 1992. Archaeologists, working with fieldschool students, and volunteers, tested all identified rooms in the house's ground story and then expanded excavations as deemed necessary and as time permitted. In designing the project and in preparing this final report, the staff followed the "Guidelines for Archaeological Investigations in Maryland" (McNarnara 1981). The report includes several levels of summaries (from descriptive summaries of soil levels excavated from the individual units (Appendix A), to interpretive room summaries) in an effort to make the data easily accessible and understandable to archaeologists and others interested in this site.
1991 Human-Computer Interaction Laboratory Video Reports
(2000-06-23) Plaisant, Catherine (Editor)
Introduction - Ben Shneiderman, Scheduling home control devices - Catherine Plaisant, Ben Shneiderman, Touchscreen toggles - Catherine Plaisant , A home automation system - Reuel Launey (Custom Command Systems), PlayPen II (now known as PenPlay II) : A novel fingerpainting program - Andrew Sears, Ben Shneiderman, Touchscreen keyboards - Andrew Sears, Ben Shneiderman, Pie menus - Don Hopkins, Three interfaces for browsing tables of contents - Rick Chimera (Also cross-referenced as CAR-TR-791)
1992 Archaeological Excavations at the Retallick-Brewer House site in Annapolis, Maryland, 18AP37
(1992) Bodor, Thomas W.; Leone, Mark P.
This report provides a detailed summary of the archaeological excavations that were conducted over a period of 2 weeks at the Retallick-Brewer House site located in Annapolis, Maryland. The project was initiated by the Griffis Foundation in order to gain some insight into the changes that have occurred at this property over its 200 year occupation. The project was completed by staff and volunteers of Archaeology In Annapolis, a joint venture of the University of Maryland, College Park, and Historic Annapolis Foundation. The design of this report follows the "Guidelines for Archaeological Investigations in Maryland" (McNamara 1981). This report contains descriptive summaries of individual levels along with an interpretation for each excavated unit in order to allow archaeologists and interested others access to the information contained within.
1992 Human-Computer Interaction Laboratory Video Reports
(1998-10-15) Plaisant, Catherine (Editor)
Introduction - Ben Shneiderman, [3:00], Dynamic Queries: database searching by direct manipulation - Ben Shneiderman, Chris Williamson, Christopher Ahlberg, [10:55], Treemaps for visualizing hierarchical information - Ben Shneiderman, Brian Johnson, Dave Turo, [11:25], Three strategies for directory browsing - Rick Chimera, [10:30], Filter-Flow metaphor for boolean queries - Degi Young, Ben Shneiderman, [6:35], The AT&T Teaching Theater: active learning through computer supported collaborative courseware - Kent Norman, [8:25], ACCESS: an online public access catalog at the Library of Congress - Gary Marchionini, [8:15] Remote Direct Manipulation: a telepathology workstation - Catherine Plaisant, Dave Carr, [7:30], Guiding automation with pixels: a technique for programming in the user interface - Richard Potter, [11:50] (Also cross-referenced as CAR-TR-792)
1993 Human-Computer Interaction Laboratory Video Reports
(1998-10-15) Plaisant, Catherine (Editor)
Introduction and table of contents - Ben Shneiderman, [4:00] Dynamaps: dynamic queries on a health statistics atlas - Catherine Plaisant and Vinit Jain, [6:34], Hierarchical visualization with Treemaps: making sense of pro basketball data - Dave Turo, [10:47], TreeViz: file directory browsing - Brian Johnson, [10:04], HyperCourseware: computer integrated tools in the AT&T Teaching Theater - Kent Norman, [7:08], Improving access to medical abstracts: Grateful Med Interface prototype - Gary Marchionini, [6:08], Layout appropriateness: guiding interface desi gn with simple task descriptions - Andrew Sears, [4:00] (Also cross-referenced as CAR-TR-793)
1994 Human-Computer Interaction Laboratory Video Reports
(1998-10-15) Plaisant, Catherine (Edited by); Reesch, John (Video by)
80 minute video demonstrations of the past year's research Topics are: Introduction and table of contents - Ben Shneiderman, [3:18] Visual information seeking using the FilmFinder - Christopher Ahlberg, Ben Shneiderman, [6:12] Organization overviews and role management-Inspiration for future desktop environments - Catherine Plaisant, Ben Shneiderman, [9:39] Visual decision-making: using treemaps for the analytic hierarchy process - Toshiyuki Asahi, Ben Shneiderman, David Turo, [8:34] Visual information management for satellite network configuration-Catherine Plaisant, Harsha Kumar, Marko Teittinen, Ben Shneiderman, [8:49] Graphical macros: a technique for customizing any application using pixel-pattern matching-Richard Potter, [9:49] Education by engagement and construction: can distance learning be better than face to face?- Ben Shneiderman, [15:00] Dynamic queries demos: revised HomeFinder and text version plus health statistics atlas-Ben Shneiderman, [9:40] Dynamic Queries are user controlled displays of visual or textual information. Ben Shneiderman presents the HomeFinder (developed by Chris Williamson), followed by the text version (Vinit Jain) and the Health Statistics Atlas (Catherine Plaisant and Vinit Jain). CHI '94 slide and video show- [9:12]Open House '94 Video (Also cross-referenced as CAR-TR-794)
1995 Human-Computer Interaction Laboratory Video Reports
(2000-07-21) Plaisant, Catherine (Edited by)
49 minute video of the labs work over the past year. Topics are: Introduction and table of contents - Ben Shneiderman Using Dynamic Queries for Youth Services Information - Anne Rose, Ajit Vanniamparampil Life-Lines: Visualizing Personal Histories - Brett Milash, Catherine Plaisant, Anne Rose Dynamic Queries and Pruning for Large Tree Structures - Harsha Kumar Browsing Anatomical Image Databases : the Visible Human - Flip Korn, Chris North Spinning Your Web: WWW Interface Design Issues - Vince Boisselle BizView : Managing Business and Network Alarms - Catherine Plaisant, Wei Zhao and Rina Levy Animated Specifications Using Interaction Object Graphs - David Carr WinSurfer: Treemaps for Replacing the Windows File Manager - Marko Teittinen (Also cross-referenced as CAR-TR-795)