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Search Results: 1 - 10 of 318521 matches for " R. O. Gray "
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Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Northern Sample I
R. O. Gray,C. J. Corbally,R. F. Garrison,M. T. McFadden,P. E. Robinson
Physics , 2003, DOI: 10.1086/378365
Abstract: We have embarked on a project, under the aegis of the Nearby Stars (NStars)/ Space Interferometry Mission Preparatory Science Program to obtain spectra, spectral types, and, where feasible, basic physical parameters for the 3600 dwarf and giant stars earlier than M0 within 40 parsecs of the sun. In this paper we report on the results of this project for the first 664 stars in the northern hemisphere. These results include precise, homogeneous spectral types, basic physical parameters (including the effective temperature, surface gravity and the overall metallicity, [M/H]) and measures of the chromospheric activity of our program stars. Observed and derived data presented in this paper are also available on the project's website at http://stellar.phys.appstate.edu/ .
Extending the SDSS Batch Query System to the National Virtual Observatory Grid
Maria A. Nieto-Santisteban,William O'Mullane,Jim Gray,Nolan Li,Tamas Budavari,Alexander S. Szalay,Aniruddha R. Thakar
Computer Science , 2004,
Abstract: The Sloan Digital Sky Survey science database is approaching 2TB. While the vast majority of queries normally execute in seconds or minutes, this interactive execution time can be disproportionately increased by a small fraction of queries that take hours or days to run; either because they require non-index scans of the largest tables or because they request very large result sets. In response to this, we added a multi-queue job submission and tracking system. The transfer of very large result sets from queries over the network is another serious problem. Statistics suggested that much of this data transfer is unnecessary; users would prefer to store results locally in order to allow further cross matching and filtering. To allow local analysis, we implemented a system that gives users their own personal database (MyDB) at the portal site. Users may transfer data to their MyDB, and then perform further analysis before extracting it to their own machine. We intend to extend the MyDB and asynchronous query ideas to multiple NVO nodes. This implies development, in a distributed manner, of several features, which have been demonstrated for a single node in the SDSS Batch Query System (CasJobs). The generalization of asynchronous queries necessitates some form of MyDB storage as well as workflow tracking services on each node and coordination strategies among nodes.
When Database Systems Meet the Grid
Maria A. Nieto-Santisteban,Alexander S. Szalay,Aniruddha R. Thakar,William J. O'Mullane,Jim Gray,James Annis
Computer Science , 2005,
Abstract: We illustrate the benefits of combining database systems and Grid technologies for data-intensive applications. Using a cluster of SQL servers, we reimplemented an existing Grid application that finds galaxy clusters in a large astronomical database. The SQL implementation runs an order of magnitude faster than the earlier Tcl-C-file-based implementation. We discuss why and how Grid applications can take advantage of database systems.
Notes on Hybridization in Leaf frogs of the Genus Agalychnis (Anura, Hylidae, Phyllomedusinae)
Andrew R. Gray
Quantitative Biology , 2011,
Abstract: Two species of Endangered Leaf frogs, Agalychnis moreletii and Agalychnis annae, belonging to the tree frog Subfamily Phyllomedusinae, Genus Agalychnis, were hybridized for the first time whilst being maintained in captivity. Previous to this, these allopatric Central American species were considered as being distinctly separate. Crossbreeding following genetic analysis reveals that the two species are extremely closely related, and the hybrid of A. moreletii and A. annae is presented for the first time. The importance of identifying degrees of genetic variation between species and different populations of the same species, for conservation purposes, is highlighted and discussed.
The Young Solar Analogs Project: I. Spectroscopic and Photometric Methods and Multi-year Timescale Spectroscopic Results
R. O. Gray,J. M. Saken,C. J. Corbally,M. M. Briley,R. A. Lambert,V. A. Fuller,I. M. Newsome,M. F. Seeds,Y. Kahvaz
Physics , 2015,
Abstract: This is the first in a series of papers presenting methods and results from the Young Solar Analogs Project, which began in 2007. This project monitors both spectroscopically and photometrically a set of 31 young (300 - 1500 Myr) solar-type stars with the goal of gaining insight into the space environment of the Earth during the period when life first appeared. From our spectroscopic observations we derive the Mount Wilson $S$ chromospheric activity index ($S_{\rm MW}$), and describe the method we use to transform our instrumental indices to $S_{\rm MW}$ without the need for a color term. We introduce three photospheric indices based on strong absorption features in the blue-violet spectrum -- the G-band, the Ca I resonance line, and the Hydrogen-$\gamma$ line -- with the expectation that these indices might prove to be useful in detecting variations in the surface temperatures of active solar-type stars. We also describe our photometric program, and in particular our "Superstar technique" for differential photometry which, instead of relying on a handful of comparison stars, uses the photon flux in the entire star field in the CCD image to derive the program star magnitude. We present time series plots of our spectroscopic data for all four indices, and carry out extensive statistical tests on those time series demonstrating the reality of variations on timescales of years in all four indices. We also statistically test for and discover correlations and anti-correlations between the four indices. We discuss the physical basis of those correlations. As it turns out, the "photospheric" indices appear to be most strongly affected by continuum emission. We thus anticipate that these indices may prove to be useful proxies for monitoring continuum emission in the near ultraviolet.
The role of volatile organic compounds in the polluted urban atmosphere of Bristol, England
A. C. Rivett, D. Martin, D. J. Gray, C. S. Price, G. Nickless, P. G. Simmonds, S. J. O’Doherty, B. R. Greally, A. Knights,D. E. Shallcross
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2003,
Abstract: The results of a field campaign carried out from early spring through to the late summer of 2000, in Bristol, England, are presented. Continuous measurements of over 40 hydrocarbons have been made at an urban background site, located at Bristol University, for approximately nine months using a Gas Chromatography - Flame Ionisation Detection (GC-FID) system and for a selection of halocarbons for approximately one month using a Gas Chromatography - Electron Capture Detection (GC-ECD) system. In this paper we present the time-series of the nine halocarbons and selected hydrocarbons. Daytime and night-time hydroxyl radical concentrations have been estimated based on the diurnal variations of a selection of the measured hydrocarbons. The average summer daytime concentration of OH was found to be 2.5x106 molecules cm-3 and the night-time concentration to be in the range 104 to 105 molecules cm-3. In addition, the role played by certain VOCs in the formation of ozone is assessed using the POCP (Photochemical Ozone Creation Potential) concept.
There Goes the Neighborhood: Relational Algebra for Spatial Data Search
Jim Gray,Alexander S. Szalay,Aniruddha R. Thakar,Gyorgy Fekete,William O'Mullane,Maria A. Nieto-Santisteban,Gerd Heber,Arnold H. Rots
Computer Science , 2004,
Abstract: We explored ways of doing spatial search within a relational database: (1) hierarchical triangular mesh (a tessellation of the sphere), (2) a zoned bucketing system, and (3) representing areas as disjunctive-normal form constraints. Each of these approaches has merits. They all allow efficient point-in-region queries. A relational representation for regions allows Boolean operations among them and allows quick tests for point-in-region, regions-containing-point, and region-overlap. The speed of these algorithms is much improved by a zone and multi-scale zone-pyramid scheme. The approach has the virtue that the zone mechanism works well on B-Trees native to all SQL systems and integrates naturally with current query optimizers - rather than requiring a new spatial access method and concomitant query optimizer extensions. Over the last 5 years, we have used these techniques extensively in our work on SkyServer.sdss.org, and SkyQuery.net.
The pervasive nature of unconscious social information processing in executive control
Ranjani Prabhakaran,Jeremy R. Gray
Frontiers in Human Neuroscience , 2012, DOI: 10.3389/fnhum.2012.00105
Abstract: Humans not only have impressive executive abilities, but we are also fundamentally social creatures. In the cognitive neuroscience literature, it has long been assumed that executive control mechanisms, which play a critical role in guiding goal-directed behavior, operate on consciously processed information. Although more recent evidence suggests that unconsciously processed information can also influence executive control, most of this literature has focused on visual masked priming paradigms. However, the social psychological literature has demonstrated that unconscious influences are pervasive, and social information can unintentionally influence a wide variety of behaviors, including some that are likely to require executive abilities. For example, social information can unconsciously influence attention processes, such that simply instructing participants to describe a previous situation in which they had power over someone or someone else had power over them has been shown to unconsciously influence their attentional focus abilities, a key aspect of executive control. In the current review, we consider behavioral and neural findings from a variety of paradigms, including priming of goals and social hierarchical roles, as well as interpersonal interactions, in order to highlight the pervasive nature of social influences on executive control. These findings suggest that social information can play a critical role in executive control, and that this influence often occurs in an unconscious fashion. We conclude by suggesting further avenues of research for investigation of the interplay between social factors and executive control.
Selective Chemical Inhibition of agr Quorum Sensing in Staphylococcus aureus Promotes Host Defense with Minimal Impact on Resistance
Erin K. Sully,Natalia Malachowa,Bradley O. Elmore,Susan M. Alexander,Jon K. Femling,Brian M. Gray,Frank R. DeLeo,Michael Otto,Ambrose L. Cheung,Bruce S. Edwards,Larry A. Sklar,Alexander R. Horswill,Pamela R. Hall ,Hattie D. Gresham
PLOS Pathogens , 2014, DOI: doi/10.1371/journal.ppat.1004174
Abstract: Bacterial signaling systems are prime drug targets for combating the global health threat of antibiotic resistant bacterial infections including those caused by Staphylococcus aureus. S. aureus is the primary cause of acute bacterial skin and soft tissue infections (SSTIs) and the quorum sensing operon agr is causally associated with these. Whether efficacious chemical inhibitors of agr signaling can be developed that promote host defense against SSTIs while sparing the normal microbiota of the skin is unknown. In a high throughput screen, we identified a small molecule inhibitor (SMI), savirin (S. aureus virulence inhibitor) that disrupted agr-mediated quorum sensing in this pathogen but not in the important skin commensal Staphylococcus epidermidis. Mechanistic studies employing electrophoretic mobility shift assays and a novel AgrA activation reporter strain revealed the transcriptional regulator AgrA as the target of inhibition within the pathogen, preventing virulence gene upregulation. Consistent with its minimal impact on exponential phase growth, including skin microbiota members, savirin did not provoke stress responses or membrane dysfunction induced by conventional antibiotics as determined by transcriptional profiling and membrane potential and integrity studies. Importantly, savirin was efficacious in two murine skin infection models, abating tissue injury and selectively promoting clearance of agr+ but not Δagr bacteria when administered at the time of infection or delayed until maximal abscess development. The mechanism of enhanced host defense involved in part enhanced intracellular killing of agr+ but not Δagr in macrophages and by low pH. Notably, resistance or tolerance to savirin inhibition of agr was not observed after multiple passages either in vivo or in vitro where under the same conditions resistance to growth inhibition was induced after passage with conventional antibiotics. Therefore, chemical inhibitors can selectively target AgrA in S. aureus to promote host defense while sparing agr signaling in S. epidermidis and limiting resistance development.
Is Being “Smart and Well Behaved” a Recipe for Happiness in Western Australian Primary Schools?
John O'Rourke,Martin Cooper,Christina Gray
International Journal of Psychological Studies , 2012, DOI: 10.5539/ijps.v4n3p139
Abstract: Little is known about the relationship between students’ perceptions of their behaviour and intellectual status within the classroom and their happiness. Educational practitioners consistently confront misbehaviour and academic failure; whether this is an indicator of student happiness is unclear. In this exploratory research two hundred and fifty six students were asked to self-rate their happiness via a faces scale. These students also completed a self-concept scale focussed on behavioural adjustment and intellectual and school status to determine whether these were factors that impacted on their happiness. Additionally, parents and teachers rated the participant’s happiness. The findings of this research indicate that the students’ perceptions of their behaviour and academic capability accounted for variance in their self-rated happiness. Both sub-scales accounted for more variance in the students’ self-reported happiness than the teachers’ and parents’ ratings. The findings of this research are consistent with the few previous studies that attribute social factors such as belonging to childhood happiness.
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