Global ETD Search

1	Conductivity studies of beta-alumina Hunter, Catherine C. January 1981 (has links) The a.c. conductivity of the solid electrolyte beta-alumina with blocking Au electrodes has been examined by complex plane analysis using the complex impedance (Z), admittance (A), modulus (M) and permittivity (epsilon) formalisms. The electrode response which gives rise to the characteristic "spikes" in the Z* plots is attributed to a highly resistive layer on the surface of beta-alumina. This is found on single crystal and polycrystalline materials, and is sensitive both to the effects of polishing and the uptake of water vapour. Water vapour does not affect the bulk properties. For the first time, both the conductivity and the modulus spectra of single crystal beta"-alumina have been reported. It is confirmed that beta"-alumina has a much higher activation energy (~27kJ/mole) than beta-alumina (16.0kj/mole) and thus has a lower conductivity at lower temperatures (100°C). On this basis, an attempt has been made to explain the behaviour of the (commercial) polycrystalline sinters which are mixtures of beta and beta" phases. While the grain boundary activation energy remains constant at ~ 26kJ/mole, the bulk activation energy varies with beta/beta" content. The mixtures of approx 50-70% beta" content have the lowest bulk activation energy. These effects may be related in some way to the method of charge compensation, and in particular to the interstitial oxygen content (Oi2-). A "mixed-alkali" effect has been discovered in Na/Ag beta-aluminas which is remarkably similar to the effects found in glass. Both conductance minima and modulus (M") peak "narrowing" are observed. The results add some support to the weak electrolyte theory of beta-alumina, and also offer an interesting new exception to Jonscher's "universal" dielectric behaviour. 530.41 Solid state battery research
2	Biodiversity in human-modified landscapes : case studies, the state of research, and implications for conservation Trimble, Morgan Jayne January 2014 (has links) Protected areas (PAs) cover 12.9% of Earth’s land, while just 5.8% has strict protection for biodiversity (Earth’s variety of ecosystems, species, and genetic variation). Constraints of size and configuration, mismanagement, anthropogenic pressure, and climate change hamstring the capacity of PAs to conserve biodiversity. Increasingly, studies of biodiversity in human-modified landscapes provide an evidence base to support policies to make land outside of PAs as amenable as possible for biodiversity persistence. I reviewed research on biodiversity in sub-Saharan Africa’s human-modified landscapes within four ecosystem categorizations: rangelands, tropical forest, Cape Floristic Region, and urban and rural built environment. I found potential for humanmodified landscapes to contribute to conservation across ecosystems. Available research could guide policy-making; nonetheless, several issues require further investment, e.g. research deficiencies, implementation strategies, and conflict with biodiversity. I also conducted case studies that could support land-use planning in South Africa’s coastal forest, part of a biodiversity hotspot. By comparing herpetofaunal communities over a land-use gradient, I found old-growth forest harbored the highest richness and abundance. Richness was low in sugar cane cultivation and degraded forest but substantial in acacia woodland and eucalyptus plantation. Composition differed between natural and anthropogenic vegetation types. Functional group richness decreased monotonically along the gradient, driven by sensitivity of fossorial herpetofauna and vegetation-dwelling frogs. Environmental variables were good predictors of frog abundance, but less so for reptiles. Maintaining forest and preventing degradation is important for herpetofaunal conservation while restoration and plantations have more value than cultivation. Old-growth remnants and post-disturbance regenerating vegetation also provide habitat for birds. However, occurrence does not ensure persistence. I calculated population trends for 37 bird species and general trends in overall bird density in different vegetation types. Seventy-six percent of species assessed have declined, 57% significantly so at an average rate of 13.9% per year. Overall, bird density fell at 12.2% per year across vegetation types. Changes in rainfall, habitat area, and survey coverage may partly explain trends. However, species with larger range extents declined more sharply than others and may be responding to environmental changes on a broad scale. These results cast doubt on the future persistence of birds in this human-modified landscape and justify further study. Such studies can support sensible land-use management; however, biases in study topics should not lead to gaps in the evidence base. By reviewing the global literature, I demonstrated clear geographical bias among biomes and geopolitical regions and taxonomic bias among species groups. Furthermore, distribution of published papers did not generally reflect threats of low PA coverage, high land conversion, and high human population density. Forests were the subject of 87% of papers, and 75% focused on the Americas and Europe, while Africa and Asia were critically understudied. This thesis highlights that managing human-modified landscapes for biodiversity could contribute to conservation. However, responses to land uses are complex, locationand species-specific, and often poorly understood, hindering integration of information into policy recommendations. Further research is needed to elucidate what, where, and how biodiversity persists alongside humans to enhance conservation efficacy, especially in understudied regions. / Thesis (PhD)--University of Pretoria, 2014. / gm2014 / Zoology and Entomology / unrestricted Biodiversity Human-modified landscapes State of research Conservation UCTD
3	The state of network research / Tillståndet för nätverksforskning Zhu, Haoyu January 2020 (has links) In the past decades, networking researchers experienced great changes. Being familiar with the development of networking researches is the first step for most scholars to start their work. The targeted areas, useful documents, and active institutions are helpful to set up the new research. This project is focused on developing an assistant tool based on public accessed papers and information on the Internet that allows researchers to view most cited papers in networking conferences and journals. NLP tools are implemented over crawled full-text in order to classify the papers and extract the keywords. Papers are located based on authors to show the most active countries around the world that are working in this area. References are analyzed to view the most cited topics and detailed paper information. We draw some interesting conclusions from our system, showing that some topics attract more attention in the past decades. / Under de senaste decennierna upplevde nätverksundersökningar stora förändringar. Att känna till utvecklingen av nätverksundersökningar är det första steget för de flesta forskare att starta sitt arbete. De riktade områdena, användbara dokument och aktiva institutioner är användbara för att skapa den nya forskningen. Projektet fokuserade på att utveckla ett assistentverktyg baserat på offentliga åtkomstpapper och information via internet. Som gör det möjligt för forskare att se de mest citerade artiklarna i nätverkskonferenser och tidskrifter. NLP- verktyg implementeras över genomsökt fulltext för att klassificera papperet och extrahera nyckelorden. Artiklar är baserade på författare för att visa de mest aktiva länderna runt om i världen som arbetar inom detta område. Hänvisningar analyseras för att se det mest citerade ämnet och detaljerad pappersinformation. Vi drar några intressanta slutsatser från vårt system och visar att något ämne inte lockar till sig mer under de senaste decennierna. Natural Language Processing Network Spider Network Topic Modelling State of Research. Naturlig Språkbearbetning Nätverksspindel Nätverk Ämnesmodellering Forskningstillstånd. Computer and Information Sciences Data- och informationsvetenskap
4	Biophysical studies of cholesterol in unsaturated phospholipid model membranes Williams, Justin A. January 2013 (has links) Indiana University-Purdue University Indianapolis (IUPUI) / Cellular membranes contain a staggering diversity of lipids. The lipids are heterogeneously distr ibuted to create regions, or domains, whose physical properties differ from the bulk membrane and play an essential role in modulating the function of resident proteins. Many basic questions pertaining to the formation of these lateral assemblies remain. T his research employs model membranes of well - defined composition to focus on the potential role of polyunsaturated fatty acids (PUFAs) and their interaction with cholesterol (chol) in restructuring the membrane environment. Omega - 3 (n - 3) PUFAs are the main bioactive components of fish oil, whose consumption alleviates a variety of health problems by a molecular mechanism that is unclear. We hypothesize that the incorporation of PUFAs into membrane lipids and the effect they have on molecular organization may be, in part, responsible. Chol is a major constituent in the plasma membrane of mammals. It determines the arrangement and collective properties of neighboring lipids, driving the formation of domains via differential affinity for different lipids . T he m olecular organization of 1 -[ 2 H 31 ]palmitoyl -2- eicosapentaenoylphosphatidylcholine (PEPC - d 31 ) and 1 -[ 2 H 31 ]palmitoyl -2- docosahexaenoylphosphatidylcholine (PDPC -d 31 ) in membran es with sphingomyelin (SM) and chol (1:1:1 mol) was compared by solid - state 2 H NMR spectroscopy. Eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids are the two major n - 3 PUFAs found in fish oil, while PEPC -d 31 and PDPC -d 31 are phospholipids containing the respective PUFAs at the sn - 2 position and a perdeuterated palmitic acid a t the sn - 1 position . Analysis of s pectra recorded as a function of temperature indicate s that in both cases, formation of PUFA - rich (less ordered) and SM - rich (more ordered) domains occurred. A surprisingly substantial proportion of PUFA was found to infil trate the more ordered domain. There was almost twice as much DHA (65%) as EPA (30%) . The implication is that n - 3 PUFA s can incorporate into lipid rafts, which are domains enriched in SM and chol in the plasma membrane, and potentially disrupt the activity of signaling proteins that reside therein. DHA, furthermore, may be the more potent component of fish oil. PUFA - chol interactions were also examined through affinity measurements. A novel method utilizing electron paramagnetic resonance (EPR) was develope d, to monitor the partitioning of a spin - labeled analog of chol , 3β - doxyl - 5α - cholestane (chlstn), between large unilamellar vesicles (LUVs) and met hyl - β - cyclodextrin (mβCD). The EPR spectra for chlstn in the two environments are distinguishable due to the substantial differences in tumbling rates , allowing the population distribution ratio to be determined by spectral simulation. Advantages of this approach include speed of implementation and a vo idance of potential artifact s associated with physical separation of LUV and mβCD . Additionally, in a check of the method, t he relative partition coefficients between lipids measured for the spin label analog agree with values obtained for chol by isothermal titration calorimetry (ITC). Results from LUV with different composition confirmed a hierarchy of decreased sterol affinity for phospholipids with increasing acyl chain unsaturation , PDPC possessing half the affinity of the corresponding monounsaturated phospholipid. Taken together, the results of these studies on model membranes demonstrate the potential for PUFA - driven alteration of the architecture of biomembranes, a mechanism through which human health may be impacted. Polyunsaturated Lipids Cholesterol EPA DHA Solid State Deuterium NMR Membrane Domains Cholestane Unsaturated fatty acids -- Metabolism Phospholipids -- Research Cell membranes Docosahexaenoic acid Membranes (Biology) Thermometric titration Palmitic acid Solid state physics -- Research Deuterium Unsaturated fatty acids -- Research
5	Factors Influencing Indiana Residents' Level of Interest in Engaging with Purdue University Ashley E Rice (6615803) 15 May 2019 (has links) The land-grant university system was founded in the 19th century as a public means to help improve people’s everyday lives. A century and a half later, the challenges that the public faces to live a quality life are constantly changing, creating a need for the land-grant system to respond and adapt to continue to fulfill its mission. While the literature contains a wealth of conceptual papers addressing the role and mission of land-grant universities, relatively few papers could be found that reported empirical data or proposed and tested metrics for public engagement constructs. The current study sought to address this void in the literature through the investigation of factors influencing Indiana residents’ level of interest in engaging with Purdue University. Mail survey methods were used in which up to three contacts were made with adult members of 4,500 Indiana households identified through address-based sampling. Stratified random sampling was employed to ensure adequate rural household participation for other project purposes. Usable responses were received from 1,003 households representing 87 Indiana counties for a total response rate of 26%. <br><div><br> </div><div> A theoretical perspective was developed from Public Sphere Theory and the social science writings of Jurgen Habermas and Alexis de Tocqueville. Descriptive findings revealed some to moderate concerns about community and social issues such as affordable health care, violent crime, pollution and prescription drug abuse. Moderate levels of anomie, or perceived social disconnectedness, were also reported by respondents. Several items tapped respondents’ past levels of interaction with and current perceptions of Purdue University. Nearly a fifth of respondents reported interacting with Purdue University by having visited a website for news or information, followed by interacting with a Purdue University Extension professional. Regarding perceptions of Purdue University, the results of this study revealed relative consensus among respondents that Purdue University makes a positive contribution to the state of Indiana through its educational, research and outreach programs. For a majority of the perceptual items regarding Purdue University, more than one-third of the respondents neither agreed nor disagreed with the statement, suggesting some areas in which the university might improve its reputational standing with Indiana residents in the future. Nearly one-quarter to about half of the respondents indicated interest in topical areas addressed by Purdue Extension programs as well as an interest in engaging with the university. Respondents reported the highest levels of interest in free Extension programs in their local area, followed by the topics of science and technology, health and well-being, and gardening.</div><div><br> </div><div> A predictive model of respondent interest in engaging with Purdue University was developed and tested using binary logistic regression procedures. The model was shown to be of modest utility in accounting for variance in respondent interest in engaging with Purdue University, explaining 12% to 16% of total variance. Past interaction with Purdue University, perceived level of concern for social and community issues, and highest level of education were the strongest predictors in the model.</div><div><br> </div><div> The current research was completed in 2019 as Purdue University celebrated its 150th anniversary. Results and implications of this study provide important insight into current engagement levels, concerns and perceptions of residents within the state of Indiana, whom the university is mandated to serve. One of the study’s primary contributions is the establishment of baseline engagement data on current levels of Indiana residents’ interest in engaging with Purdue University on selected topics. Findings from this study could be of benefit to university administrators, faculty, staff and Extension professionals in assessing and improving future programming and setting strategic priorities. This study also adds to the conceptual and empirical body of literature, which may help inform future public engagement efforts at other land-grant universities. Periodic social science and public opinion research is needed to keep pace with the changing needs and perceptions of Indiana residents. Different data collection modes should be utilized to reach more audience segments and add to the growing knowledge base of public engagement.</div> Education Health Care Family Care Social and Community Psychology Decision Making Continuing and Community Education Higher Education Environment and Resource Economics Organisational Behaviour Marketing Communications Family and Household Studies Population Trends and Policies Education Policy Public Administration Social Policy Citizenship Farming Systems Research Consumption and Everyday Life Rural Sociology Sociology of Education Urban Sociology and Community Studies Education not elsewhere classified Communication Studies Social Change land grant colleges land grant institutions Morrill Land-Grant Acts public engagement with science Public Engagement with Research Public Perceptions public perceptions of science public perceptions of risk Past Interaction Past Behavior Higher Educational Institutions Colleges Universities Social Issues Community Issues Anomie hopelessness future behavior Rural Community Urban Cities Purdue University Indiana state-wide research Agricultural Sciences Health Sciences Sociology Psychology Public Sphere Tocqueville Habermas Classical Theories Democracy Citizenship United States Public Policy Issues Life-long learning Continuing Education Extension Cooperative Extension Purdue University Extension America Level of Concern

1

Page generated in 0.0635 seconds