818 resultados para Access studies to university
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This paper presents the shaking table studies to investigate the factors that influence the liquefaction resistance of sand. A uniaxial shaking table with a perspex model container was used for the model tests, and saturated sand beds were prepared using wet pluviation method. The models were subjected to horizontal base shaking, and the variation of pore water pressure was measured. Three series of tests varying the acceleration and frequency of base shaking and density of the soil were carried out on sand beds simulating free field condition. Liquefaction was visualized in some model tests, which was also established through pore water pressure ratios. Effective stress was calculated at the point of pore water pressure measurement, and the number of cycles required to liquefy the sand bed were estimated and matched with visual observations. It was observed that there was a gradual variation in pore water pressure with change in base acceleration at a given frequency of shaking. The variation in pore water pressure is not significant for the range of frequency used in the tests. The frequency of base shaking at which the sand starts to liquefy when the sand bed is subjected to any specific base acceleration depends on the density of sand, and it was observed that the sand does not liquefy at any other frequency less than this. A substantial improvement in liquefaction resistance of the sand was observed with the increase in soil density, inferring that soil densification is a simple technique that can be applied to increase the liquefaction resistance.
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In this study, we combine available high resolution structural information on eukaryotic ribosomes with low resolution cryo-EM data on the Hepatitis C Viral RNA (IRES) human ribosome complex. Aided further by the prediction of RNA-protein interactions and restrained docking studies, we gain insights on their interaction at the residue level. We identified the components involved at the major and minor contact regions, and propose that there are energetically favorable local interactions between 40S ribosomal proteins and IRES domains. Domain II of the IRES interacts with ribosomal proteins S5 and S25 while the pseudoknot and the downstream domain IV region bind to ribosomal proteins S26, S28 and S5. We also provide support using UV cross-linking studies to validate our proposition of interaction between the S5 and IRES domains II and IV. We found that domain IIIe makes contact with the ribosomal protein S3a (S1e). Our model also suggests that the ribosomal protein S27 interacts with domain IIIc while S7 has a weak contact with a single base RNA bulge between junction IIIabc and IIId. The interacting residues are highly conserved among mammalian homologs while IRES RNA bases involved in contact do not show strict conservation. IRES RNA binding sites for S25 and S3a show the best conservation among related viral IRESs. The new contacts identified between ribosomal proteins and RNA are consistent with previous independent studies on RNA-binding properties of ribosomal proteins reported in literature, though information at the residue level is not available in previous studies.
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A link level reliable multicast requires a channel access protocol to resolve the collision of feedback messages sent by multicast data receivers. Several deterministic media access control protocols have been proposed to attain high reliability, but with large delay. Besides, there are also protocols which can only give probabilistic guarantee about reliability, but have the least delay. In this paper, we propose a virtual token-based channel access and feedback protocol (VTCAF) for link level reliable multicasting. The VTCAF protocol introduces a virtual (implicit) token passing mechanism based on carrier sensing to avoid the collision between feedback messages. The delay performance is improved in VTCAF protocol by reducing the number of feedback messages. Besides, the VTCAF protocol is parametric in nature and can easily trade off reliability with the delay as per the requirement of the underlying application. Such a cross layer design approach would be useful for a variety of multicast applications which require reliable communication with different levels of reliability and delay performance. We have analyzed our protocol to evaluate various performance parameters at different packet loss rate and compared its performance with those of others. Our protocol has also been simulated using Castalia network simulator to evaluate the same performance parameters. Simulation and analytical results together show that the VTCAF protocol is able to considerably reduce average access delay while ensuring very high reliability at the same time.
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Small heat shock proteins (sHSPs) are a family of ATP-independent molecular chaperones which prevent cellular protein aggregation by binding to misfolded proteins. sHSPs form large oligomers that undergo drastic rearrangement/dissociation in order to execute their chaperone activity in protecting substrates from stress. Substrate-binding sites on sHSPs have been predominantly mapped on their intrinsically disordered N-terminal arms. This region is highly variable in sequence and length across species, and has been implicated in both oligomer formation and in mediating chaperone activity. Here, we present our results on the functional and structural characterization of five sHSPs in rice, each differing in their subcellular localisation, viz., cytoplasm, nucleus, chloroplast, mitochondria and peroxisome. We performed activity assays and dynamic light scattering studies to highlight differences in the chaperone activity and quaternary assembly of sHSPs targeted to various organelles. By cloning constructs that differ in the length and sequence of the tag in the N-terminal region, we have probed the sensitivity of sHSP oligomer assembly and chaperone activity to the length and amino acid composition of the N-terminus. In particular, we have shown that the incorporation of an N-terminal tag has significant consequences on sHSP quaternary structure.
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Resumen: El artículo trata sobre la formación de una fracción de la elite dirigente porteña en el paso del siglo xix al xx. La carrera de derecho siempre estuvo ligada al poder político y a la formación de la clase dirigente porteña. A través de los discursos de colación de grados de los doctores en jurisprudencia se busca indagar en los aspectos que los propios actores rescataban de su formación académica y su función social. Esta mirada tiene como objetivo destacar el rol de la Facultad de Derecho y Ciencias Sociales de la Universidad de Buenos Aires como canal de acceso privilegiado a la clase dirigente. Al tiempo se intenta observar como la preparación brindada en sus aulas no buscaba necesariamente la formación para el desempeño de la profesión de abogados sino que estaba orientada a la formación de dirigentes políticos.
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Summary: The offshore shelf and canyon habitats of the OCNMS (Fig. 1) are areas of high primary productivity and biodiversity that support extensive groundfish fisheries. Recent acoustic surveys conducted in these waters have indicated the presence of hard-bottom substrates believed to harbor unique deep-sea coral and sponge assemblages. Such fauna are often associated with shallow tropical waters, however an increasing number of studies around the world have recorded them in deeper, cold-water habitats in both northern and southern latitudes. These habitats are of tremendous value as sites of recruitment for commercially important fishes. Yet, ironically, studies have shown how the gear used in offshore demersal fishing, as well as other commercial operations on the seafloor, can cause severe physical disturbances to resident benthic fauna. Due to their exposed structure, slow growth and recruitment rates, and long life spans, deep-sea corals and sponges may be especially vulnerable to such disturbances, requiring very long periods to recover. Potential effects of fishing and other commercial operations in such critical habitats, and the need to define appropriate strategies for the protection of these resources, have been identified as a high-priority management issue for the sanctuary. To begin addressing this issue, an initial pilot survey was conducted June 1-12, 2004 at six sites in offshore waters of the OCNMS (Fig. 2, average depths of 147-265 m) to explore for the presence of deep-sea coral/sponge assemblages and to look for evidence of potential anthropogenic impacts in these critical habitats. The survey was conducted on the NOAA Ship McARTHUR-II using the Navy’s Phantom DHD2+2 remotely operated vehicle (ROV), which was equipped with a video camera, lasers, and a manipulator arm for the collection of voucher specimens. At each site, a 0.1-m2 grab sampler also was used to collect samples of sediments for the analysis of macroinfauna (> 1.0 mm), total organic carbon (TOC), grain size, and chemical contaminants. Vertical profiles of salinity, dissolved oxygen (DO), temperature, and pressure were recorded at each site with a small SeaCat conductivity-temperature-depth (CTD) profiler. Niskin bottles attached to the CTD also obtained near-bottom water samples in support of a companion study of microbial indicators of coral health and general ecological condition across these sites. All samples except the sediment-contaminant samples are being analyzed with present project funds. Original cruise plans included a total of 12 candidate stations to investigate (Fig. 3). However, inclement weather and equipment failures restricted the sampling to half of these sites. In spite of the limited sampling, the work completed was sufficient to address key project objectives and included several significant scientific observations. Foremost, the cruise was successful in demonstrating the presence of target deepwater coral species in these waters. Patches of the rare stony coral Lophelia pertusa, more characteristic of deepwater coral/sponge assemblages in the North Atlantic, were observed for the first time in OCNMS at a site in 271 meters of water. A large proportion of these corals consisted of dead and broken skeletal remains, and a broken gorgonian (soft coral) also was observed nearby. The source of these disturbances is not known. However, observations from several sites included evidence of bottom trawl marks in the sediment and derelict fishing gear (long lines). Preliminary results also support the view that these areas are important reservoirs of marine biodiversity and of value as habitat for demersal fishes. For example, onboard examination of 18 bottom-sediment grabs revealed benthic infaunal species representative of 14 different invertebrate phyla. Twenty-eight species of fishes from 11 families, including 11 (possibly 12) species of ommercially important rockfishes, also were identified from ROV video footage. These initial discoveries have sparked considerable interests in follow-up studies to learn more about the spatial extent of these assemblages and magnitude of potential impacts from commercial-fishing and other anthropogenic activities in the area. It is essential to expand our knowledge of these deep-sea communities and their vulnerability to potential environmental risks in order to determine the most appropriate management strategies. The survey was conducted under a partnership between NOAA’s National Centers for Coastal Ocean Science (NCCOS) and National Marine Sanctuary Program (NMSP) and included scientists from NCCOS, OCNMS, and several other west-coast State, academic, private, and tribal research institutions (see Section 4 for a complete listing of participating scientists). (PDF contains 20 pages)
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Forward: Looe Key National Marine Sanctuary (LKNMS) was designated in 1981 to protect and promote the study, teaching, and wise use of the resources of Looe Key Sanctuary (Plate A). In order to wisely manage this valuable resource, a quantitative resource inventory was funded by the Sanctuary Programs Division (SPD), Office of Ocean and Coastal Resource Management, National Oceanic and Atmospheric Administration (NOAA) in cooperation with the Southeast Fisheries Center, National Marine Fisheries Service, NOAA; the Cooperative Institute for Marine and Atmospheric Studies (CIMAS), University of Miami; the Fisher Island Laboratory, United States Geological Survey; and the St. Petersburg Laboratory, State of Florida Department of Natural Resources. This report is the result of this cooperative effort. The objective of this study was to quantitatively inventory selected resources of LKNMS in order to allow future monitoring of changes in the Sanctuary as a result of human or natural processes. This study, referred to as Phase I, gives a brief summary of past and present uses of the Sanctuary (Chapter 2); and describes general habitat types (Chapter 3), geology and sediment distribution (Chapter 4), coral abundance and distribution (Chapter 5), the growth history of the coral Montastraea annularis (Chapter 6), reef fish abundance and distribution (Chapter 7), and status of selected resources (Chapter 8). An interpretation of the results of the survey are provided for management consideration (Chapter 9). The results are expected to provide fundamental information for applied management, natural history interpretation, and scientific research. Numerous photographs and illustrations were used to supplement the report to make the material presented easier to comprehend (Plate B). We anticipate the information provided will be used by managers, naturalists, and the general public in addition to scientists. Unless otherwise indicated, all photographs were taken at Looe Key Reef by Dr. James A. Bohnsack. The top photograph in Plate 7.8 was taken by Michael C. Schmale. Illustrations were done by Jack Javech, NMFS. Field work was initiated in May 1983 and completed for the most part by October 1983 thanks to the cooperation of numerous people and organizations. In addition to the participating agencies and organizations we thank the Newfound Harbor Marine Institute and the Division of Parks and Recreation, State of Florida Department of Natural Resources for their logistical support. Special thanks goes to Billy Causey, the Sanctuary Manager, for his help, information, and comments. We thank in alphabetical order: Scott Bannerot, Margie Bastian, Bill Becker, Barbara Bohnsack, Grant Beardsley, John Halas, Raymond Hixon, Irene Hooper, Eric Lindblad, and Mike Schmale. We dedicate this effort to the memory of Ray Hixon who participated in the study and who loved Looe Key. (PDF contains 43 pages)
Knowledge Exchange study: How Research Tools are of Value to Research: Use Cases and Recommendations
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Research tools that are freely available and accessible via the Internet cover an emergent field in the worldwide research infrastructure. Clearly, research tools have increasing value for researchers in their research activities. Knowledge Exchange recently commissioned a project to explore use case studies to show research tools’ potential and relevance for the present research landscape. Makers of successful research tools have been asked questions such as: How are these research tools developed? What are their possibilities? How many researchers use them? What does this new phenomenon mean for the research infrastructure? Additional to the Use Cases, the authors offer observations and recommendations to contribute to effective development of a research infrastructure that can optimally benefit from research tools. the Use Cases are: •Averroes Goes Digital: Transformation, Translation, Transmission and Edition •BRIDGE: Tools for Media Studies Researchers •Multiple Researchers, Single Platform: A Virtual Tool for the 21st Century •The Fabric of Life •Games with A Purpose: How Games Are Turning Image Tagging into Child’s Play •Elmer: Modelling a Future •Molecular Modelling With SOMA2 •An Online Renaissance for Music: Making Early Modern Music Readable •Radio Recordings for Research: How A Million Hours of Danish Broadcasts Were Made Accessible •Salt Rot: A Central Space for Essential Research •Cosmos: Opening Up Social Media for Social Science A brief analysis by the authors can be found: •Some Observations Based on the Case Studies of Research Tools
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This briefing paper offers insight into various open access business models, from institutional to subject repositories, from open access journals to research data and monographs. This overview shows that there is a considerable variety in business models within a common framework of public funding. Open access through institutional repositories requires funding from particular institutions to set up and maintain a repository, while subject repositories often require contributions from a number of institutions or funding agencies to maintain a subject repository hosted at one institution. Open access through publication in open access journals generally requires a mix of funding sources to meet the cost of publishing. Public or charitable research funding bodies may contribute part of the cost of publishing in an open access journal but institutions also meet part of the cost, particularly when the author does not have a research grant from a research funding body
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Despite its wide acceptance in other fisheries, limited access remains a controversial topic among Pacific coast groundfish fishermen and fishery managers. It is controversial because it immediately opens a wide array of public policy issues. How should the public conserve fish stocks, and who should benefit from harvesting those fish? What are the costs and benefits to the public, the taxpayer, the fishing industry, and the coastal communities supporting the groundfish industry? Should the government push the industry to be economically efficient in harvesting; or should it discourage technical efficiency to conserve fish stocks? Should management preserve the economic status quo by protecting existing harvest shares? These are the broad issues occupying the discussions of policy makers and academic writers concerned with resource management. The goal of this introductory section is to define limited access, to dispel some basic misunderstandings about limited access, to clarify the optional forms oflimited access, and to review the various resource management objectives addressed. This should set the stage for the following more lengthy discussions. By reducing the scope of needless misunderstandings, it should also help to make future discussions of limited access more productive. (PDF file contains 52 pages.)
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In spite of over a century of research on cortical circuits, it is still unknown how many classes of cortical neurons exist. Neuronal classification has been a difficult problem because it is unclear what a neuronal cell class actually is and what are the best characteristics are to define them. Recently, unsupervised classifications using cluster analysis based on morphological, physiological or molecular characteristics, when applied to selected datasets, have provided quantitative and unbiased identification of distinct neuronal subtypes. However, better and more robust classification methods are needed for increasingly complex and larger datasets. We explored the use of affinity propagation, a recently developed unsupervised classification algorithm imported from machine learning, which gives a representative example or exemplar for each cluster. As a case study, we applied affinity propagation to a test dataset of 337 interneurons belonging to four subtypes, previously identified based on morphological and physiological characteristics. We found that affinity propagation correctly classified most of the neurons in a blind, non-supervised manner. In fact, using a combined anatomical/physiological dataset, our algorithm differentiated parvalbumin from somatostatin interneurons in 49 out of 50 cases. Affinity propagation could therefore be used in future studies to validly classify neurons, as a first step to help reverse engineer neural circuits.
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A hipertensão arterial (HA) desempenha papel determinante na ocorrência de eventos clínicos graves, havendo entretanto controvérsia quanto ao seu impacto no cotidiano do portador. A incapacidade temporária para a realização de atividades habituais, definida como uma restrição temporária na capacidade funcional habitual do indivíduo, é um indicador de saúde recomendado pela Organização Mundial da Saúde para uso em estudos populacionais. A partir do objetivo geral de investigar a associação entre hipertensão arterial e incapacidade temporária para atividades habituais, delineamos os seguintes objetivos específicos: A) Investigar se a elevação dos níveis pressóricos determina a freqüência e o período acumulado de incapacidade temporária para atividades habituais; B) Investigar se o uso de medicações anti-hipertensivas associa-se a alterações na freqüência e no período acumulado de incapacidade temporária para atividades habituais. O estudo seccional com dados de 2953 participantes obtidos através de questionário auto-administrado no Estudo Pró-Saúde, uma coorte de funcionários técnico-administrativos de universidade localizada no estado do Rio de Janeiro. A exposição foi avaliada a partir do valor aferido da PA e do uso de drogas anti-hipertensivas. Conduzimos a análise separando os participantes em 4 grupos, combinando as informações quanto à PA aferida (< ou 140/90 mmHg), e o relato de uso ou não de medicação anti-hipertensiva. O desfecho foi avaliado com a utilização de uma variável composta com informação referente à ocorrência e ao período de incapacidade. Realizamos análise multivariada através de regressão logística multinomial. Temos como resultado 690 (23,4 %) participantes foram classificados como hipertensos, e 704 (23,8 %) relataram incapacidade temporária. O relato do uso de medicação anti-hipertensiva mostrou, entre os indivíduos com PA < 140/90 mmHg, associação direta com a prevalência de incapacidade temporária de longa duração, com OR=2,25 (IC 95 %: 1,31 3,87). A presença de PA 140/90 mmHg mostrou relação inversa com a chance de incapacidade temporária de curta duração entre os indivíduos que não usavam medicação anti-hipertensiva, a qual porém não foi estatisticamente significativa (OR=0,64; IC 95 %: 0,40 1,03). Encontramos uma associação direta entre o uso de drogas anti-hipertensivas e incapacidade temporária de longa duração, a qual pode relacionar-se a efeitos adversos da medicação; os resultados sugerem também uma relação inversa entre os valores da PA e a prevalência de incapacidade de curta duração, a qual não alcançou significância estatística, e que pode estar relacionada a um fenômeno conhecido como hipoalgesia associada à HA.