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Search Results: 1 - 10 of 297714 matches for " J. Turk "
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How to Scale a Code in the Human Dimension
Matthew J. Turk
Physics , 2013,
Abstract: As scientists' needs for computational techniques and tools grow, they cease to be supportable by software developed in isolation. In many cases, these needs are being met by communities of practice, where software is developed by domain scientists to reach pragmatic goals and satisfy distinct and enumerable scientific goals. We present techniques that have been successful in growing and engaging communities of practice, specifically in the yt and Enzo communities.
Nein danke, heute nicht": Für ethische und professionelle Beziehungen in gro en qualitativen Studien No thank you, not today": Supporting Ethical and Professional Relationships in Large Qualitative Studies No gracias, hoy no": Apoyando relaciones éticas y profesionales en estudios cualitativos grandes
Lisa J. Blodgett,Wanda Boyer,Emily Turk
Forum : Qualitative Social Research , 2005,
Abstract: Ausgehend von einer laufenden Untersuchung zur Entwicklung von Selbstregulation in der frühen Kindheit (BOYER 2005a, 2005b; BOYER, BLODGETT & TURK 2004) besch ftigt sich dieser Beitrag mit ethischen und professionellen überlegungen zum Sampling in einer gro angelegten qualitativen Studie. An der Untersuchung nahmen 146 Familien mit Kindern im Vorschulalter und 15 Erzieher und Erzieherinnen aus sieben Vorschulen teil. Das Datenmaterial setzte sich zusammen aus 30- bis 45-minütigen Tonbandaufnahmen von Einzelinterviews und aus (insgesamt 28) 90- bis 120-minütigen fokussierten Gruppendiskussionen sowie aus 30-minütigen Videoaufnahmen, die jedes Kind beim natürlichen Spiel zeigen. über die Herausforderungen in Bezug auf informiertes Einverst ndnis und l ngerfristige Teilnahme bei gro en Untersuchungen berichtet die Literatur (GALL, GALL & BORG, 2005). Teilnehmer und Teilnehmerinnen qualitativer Studien werden gezielt ausgew hlt, um m glichst Informatives zum Thema beizusteuern (CRESWELL, 2002). Dies stellt eine Herausforderung für die qualitative Sozialforschung dar, die um maximale Teilnahme und gro e Stichproben bemüht ist, weil freiwillige Teilnehmende "in der Regel besser gebildet sind, einen h heren sozio konomischen Status haben, intelligenter sind, bedürftiger nach sozialer Anerkennung, geselliger, unkonventioneller, unautorit rer und weniger konform als Nichtfreiwillige" (MCMILLAN, 2004, S.116). Dieser Beitrag zeigt eine Umgehensweise mit diesen Sampling-Schwierigkeiten und pl diert für den Aufbau von Beziehungen zum Forschungsfeld auf ethischen, interpersonalen und professionellen Grundlagen. URN: urn:nbn:de:0114-fqs0503353 Based on an ongoing research study of the development of self-regulation in early childhood (BOYER, 2005a, 2005b; BOYER, BLODGETT, & TURK, 2004), this work explores both the ethical and professional considerations of participant sampling in a large qualitative study. The study involved 146 families of preschool children and 15 educators across 7 preschools. Data collection included 30-45 minute audiotaped individual interviews, twenty-eight 90-120 minute audiotaped focus group sessions, and 30 minute videotaped footage of each child's natural play. The challenge of gaining informed consent and ongoing participation within a large study has been considered in the literature (GALL, GALL, & BORG, 2005). In qualitative studies the participants are selected purposefully because they will be par-ticularly informative about the topic (CRESWELL, 2002). This is a challenge for qualitative re-searchers seeking maximal participation and la
An empirical Bayesian analysis applied to the globular cluster pulsar population
P. J. Turk,D. R. Lorimer
Physics , 2013, DOI: 10.1093/mnras/stt1850
Abstract: We describe an empirical Bayesian approach to determine the most likely size of an astronomical population of sources of which only a small subset are observed above some limiting flux density threshold. The method is most naturally applied to astronomical source populations at a common distance (e.g.,stellar populations in globular clusters), and can be applied even to populations where a survey detects no objects. The model allows for the inclusion of physical parameters of the stellar population and the detection process. As an example, we apply this method to the current sample of radio pulsars in Galactic globular clusters. Using the sample of flux density limits on pulsar surveys in 94 globular clusters published by Boyles et al., we examine a large number of population models with different dependencies. We find that models which include the globular cluster two-body encounter rate, $\Gamma$, are strongly favoured over models in which this is not a factor. The optimal model is one in which the mean number of pulsars is proportional to $\exp(1.5 \log \Gamma)$. This model agrees well with earlier work by Hui et al. and provides strong support to the idea that the two-body encounter rate directly impacts the number of neutron stars in a cluster. Our model predicts that the total number of potentially observable globular cluster pulsars in the Boyles et al. sample is 1070$^{+1280}_{-700}$, where the uncertainties signify the 95% confidence interval. Scaling this result to all Galactic globular clusters, and to account for radio pulsar beaming, we estimate the total population to be 2280$^{+2720}_{-1490}$.
High-Performance Astrophysical Simulations and Analysis with Python
Matthew J. Turk,Britton D. Smith
Physics , 2011,
Abstract: The usage of the high-level scripting language Python has enabled new mechanisms for data interrogation, discovery and visualization of scientific data. We present yt, an open source, community-developed astrophysical analysis and visualization toolkit for data generated by high-performance computing (HPC) simulations of astrophysical phenomena. Through a separation of responsibilities in the underlying Python code, yt allows data generated by incompatible, and sometimes even directly competing, astrophysical simulation platforms to be analyzed in a consistent manner, focusing on physically relevant quantities rather than quantities native to astrophysical simulation codes. We present on its mechanisms for data access, capabilities for MPI-parallel analysis, and its implementation as an in situ analysis and visualization tool.
Platelet Activating Factor Synthesis and Metabolism in Intestinal Ischaemia-Reperfusion Injury
M. J. Mangino,M. Murphy,A. Bohrer,J. Turk
Mediators of Inflammation , 1994, DOI: 10.1155/s0962935194000554
Abstract:
Machine Learning and Cosmological Simulations I: Semi-Analytical Models
Harshil M. Kamdar,Matthew J. Turk,Robert J. Brunner
Physics , 2015, DOI: 10.1093/mnras/stv2310
Abstract: We present a new exploratory framework to model galaxy formation and evolution in a hierarchical universe by using machine learning (ML). Our motivations are two-fold: (1) presenting a new, promising technique to study galaxy formation, and (2) quantitatively analyzing the extent of the influence of dark matter halo properties on galaxies in the backdrop of semi-analytical models (SAMs). We use the influential Millennium Simulation and the corresponding Munich SAM to train and test various sophisticated machine learning algorithms (k-Nearest Neighbors, decision trees, random forests and extremely randomized trees). By using only essential dark matter halo physical properties for haloes of $M>10^{12} M_{\odot}$ and a partial merger tree, our model predicts the hot gas mass, cold gas mass, bulge mass, total stellar mass, black hole mass and cooling radius at z = 0 for each central galaxy in a dark matter halo for the Millennium run. Our results provide a unique and powerful phenomenological framework to explore the galaxy-halo connection that is built upon SAMs and demonstrably place ML as a promising and a computationally efficient tool to study small-scale structure formation.
Machine Learning and Cosmological Simulations II: Hydrodynamical Simulations
Harshil M. Kamdar,Matthew J. Turk,Robert J. Brunner
Physics , 2015,
Abstract: We extend a machine learning (ML) framework presented previously to model galaxy formation and evolution in a hierarchical universe using N-body + hydrodynamical simulations. In this work, we show that ML is a promising technique to study galaxy formation in the backdrop of a hydrodynamical simulation. We use the Illustris Simulation to train and test various sophisticated machine learning algorithms. By using only essential dark matter halo physical properties and no merger history, our model predicts the gas mass, stellar mass, black hole mass, star formation rate, $g-r$ color, and stellar metallicity fairly robustly. Our results provide a unique and powerful phenomenological framework to explore the galaxy-halo connection that is built upon a solid hydrodynamical simulation. The promising reproduction of the listed galaxy properties demonstrably place ML as a promising and a significantly more computationally efficient tool to study small-scale structure formation. We find that ML mimics a full-blown hydrodynamical simulation surprisingly well in a computation time of mere minutes. The population of galaxies simulated by ML, while not numerically identical to Illustris, is statistically and physically robust and follows the same fundamental observational constraints. Machine learning offers an intriguing and promising technique to create quick mock galaxy catalogs in the future.
Updates on the use of ureteral stents: focus on the Resonance stent
Manoj V Rao, Anthony J Polcari, Thomas MT Turk
Medical Devices: Evidence and Research , 2011, DOI: http://dx.doi.org/10.2147/MDER.S11744
Abstract: ates on the use of ureteral stents: focus on the Resonance stent Review (3874) Total Article Views Authors: Manoj V Rao, Anthony J Polcari, Thomas MT Turk Published Date December 2010 Volume 2011:4 Pages 11 - 15 DOI: http://dx.doi.org/10.2147/MDER.S11744 Manoj V Rao, Anthony J Polcari, Thomas MT Turk Department of Urology, Loyola University Medical Center, Maywood, IL, USA Abstract: The Resonance metallic ureteral stent is one of the latest additions to the urologist’s armamentarium in managing ureteral obstruction. One advantage of this stent over traditional polymer-based stents is resistance to encrustation with stone material, which allows longer dwell times and less frequent exchange procedures. Although exchanging a metallic stent is slightly more complicated than exchanging a polymer stent, the fluoroscopic techniques required are familiar to most urologists. The Resonance stent is also more resistant to compression by external forces, potentially allowing greater applicability in patients with metastatic cancer. Furthermore, the use of this stent in patients with benign ureteral obstruction is shown to be associated with significant cost reduction. Clinical studies on the use of this stent are accumulating and the results are mixed, although Level 1 evidence is lacking. In this article we present a comprehensive review of the available literature on the Resonance metallic ureteral stent.
Updates on the use of ureteral stents: focus on the Resonance® stent
Manoj V Rao,Anthony J Polcari,Thomas MT Turk
Medical Devices: Evidence and Research , 2010,
Abstract: Manoj V Rao, Anthony J Polcari, Thomas MT TurkDepartment of Urology, Loyola University Medical Center, Maywood, IL, USAAbstract: The Resonance metallic ureteral stent is one of the latest additions to the urologist’s armamentarium in managing ureteral obstruction. One advantage of this stent over traditional polymer-based stents is resistance to encrustation with stone material, which allows longer dwell times and less frequent exchange procedures. Although exchanging a metallic stent is slightly more complicated than exchanging a polymer stent, the fluoroscopic techniques required are familiar to most urologists. The Resonance stent is also more resistant to compression by external forces, potentially allowing greater applicability in patients with metastatic cancer. Furthermore, the use of this stent in patients with benign ureteral obstruction is shown to be associated with significant cost reduction. Clinical studies on the use of this stent are accumulating and the results are mixed, although Level 1 evidence is lacking. In this article we present a comprehensive review of the available literature on the Resonance metallic ureteral stent.Keywords: resonance, metallic, ureteral, stent, obstruction
Portal Hypertension, Nodular Regenerative Hyperplasia of the Liver, and Obstructive Portal Venopathy due to Metastatic Breast Cancer
Andrew T. Turk,Matthias J. Szabolcs,Jay H. Lefkowitch
Case Reports in Pathology , 2013, DOI: 10.1155/2013/826284
Abstract: Nodular regenerative hyperplasia (NRH) of the liver is associated with noncirrhotic portal hypertension, rheumatologic and hematologic disorders, administration of certain drugs, and other underlying conditions. This report describes a 64-year-old man with clinically presumed cirrhosis who presented to our institution with coffee-ground emesis, esophageal varices, ascites, and encephalopathy. Eleven years earlier he had been treated for breast cancer with mastectomy and chemo-radiotherapy. He died suddenly, and the autopsy showed no evidence of cirrhosis but instead demonstrated NRH with extensive emboli of recurrent breast carcinoma within the portal vein and its intrahepatic branches. Neoplastic occlusion of the portal vein as a cause of presinusoidal noncirrhotic portal hypertension has not previously been reported for metastatic breast carcinoma. This case highlights the importance of obstructive portal venopathy in the pathogenesis of NRH as well as the diagnostic difficulties that may be encountered in determining the cause of portal hypertension. 1. Report of a Case The patient was a 64-year-old man with a history of invasive carcinoma of the left breast 11 years earlier which had been treated by mastectomy (4 of 15?lymph nodes involved), radiotherapy, and chemotherapy. There was a maternal history of breast cancer. There was no known tumor recurrence during the subsequent 10 years. Nine months before his terminal admission, during evaluation for constipation, he underwent an abdominal/pelvic CT scan that showed “mild nodularity of the liver parenchyma,” raising the possibility of cirrhosis (which was also considered likely because of a history of alcohol use and risk factors for nonalcoholic fatty liver disease including hyperlipidemia and diabetes). Seven months later the patient had developed ascites and encephalopathy that resolved with rifaximin/lactulose treatment. He was hospitalized elsewhere for several days of coffee-ground emesis and then was transferred to our medical center for further care and evaluation for liver transplantation. Esophagogastroduodenoscopy demonstrated grade II esophageal varices, and banding was performed. Serum liver function tests showed a disproportionately elevated alkaline phosphatase of 405?U/L (normal < 140) and gamma glutamyl transferase (GGT) of 215?U/L (normal < 65). Total bilirubin and aspartate aminotransferase (AST) were minimally elevated at 1.5?mg/dL (normal < 1.0) and 57?U/L (normal < 40), respectively. Alanine aminotransferase (ALT), albumin, and total protein levels were normal. MRI showed portal
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