On nonparametric maximum likelihood for a class of stochastic inverse problems

We establish the consistency of a nonparametric maximum likelihood estimator for a class of stochastic inverse problems. We proceed by embedding the framework into the general settings of early results of Pfanzagl related to mixtures

Development of CMOS monolithic pixel sensors with in-pixel correlated double sampling and fast readout for the ILC

This paper presents the design and results of detailed tests of a CMOS active pixel chip for charged particle detection with in-pixel charge storage for correlated double sampling and readout in rolling shutter mode at frequencies up to 25 MHz. This detector is developed in the framework of R&D for the Vertex Tracker for the International Linear Collider.Comment: 3 pages, 4 figures, to appear on the Conference Record of the 2007 IEEE Nuclear Science Symposium, Honolulu, HI, October 200

Searching for faint companions with VLTI/PIONIER. II. 92 main sequence stars from the Exozodi survey

The Exozodi survey aims to determine the occurrence rate of bright exozodiacal discs around nearby main sequence stars using infrared interferometry. Although the Exozodi survey targets have been carefully selected to avoid the presence of binary stars, the results of this survey can still be biased by the presence of unidentified stellar companions. Using the PIONIER data set collected within the Exozodi survey, we aim to search for the signature of point-like companions around the Exozodi target stars. We use both the closure phases and squared visibilities collected by PIONIER to search for companions within the ~100 mas interferometric field of view. The presence of a companion is assessed by computing the goodness of fit to the data for a series of binary models with various separations and contrasts. Five stellar companions are resolved for the first time around five A-type stars: HD 4150, HD 16555, HD 29388, HD 202730, and HD 224392 (although the companion to HD 16555 was independently resolved by speckle interferometry while we were carrying out the survey). In the most likely case of main sequence companions, their spectral types range from A5V to K4V. Three of these stars were already suspected to be binaries from Hipparcos astrometric measurements, although no information was available on the companions themselves so far. In addition to debiasing the statistics of the Exozodi survey, these results can also be used to revise the fraction of visual binaries among A-type stars, suggesting that an extra ~13% A-type stars are visual binaries in addition to the ones detected in previous direct imaging surveys. We estimate that about half the population of nearby A-type stars could be resolved as visual binaries using a combination of state-of-the-art interferometry and single-aperture imaging, and we suggest that a significant fraction of these binaries remains undetected to date.Comment: Accepted for publication in A&

A near-infrared interferometric survey of debris-disc stars. IV. An unbiased sample of 92 southern stars observed in H-band with VLTI/PIONIER

Context. Detecting and characterizing circumstellar dust is a way to study the architecture and evolution of planetary systems. Cold dust in debris disks only traces the outer regions. Warm and hot exozodiacal dust needs to be studied in order to trace regions close to the habitable zone. Aims. We aim to determine the prevalence and to constrain the properties of hot exozodiacal dust around nearby main-sequence stars. Methods. We search a magnitude limited (H < 5) sample of 92 stars for bright exozodiacal dust using our VLTI visitor instrument PIONIER in the H-band. We derive statistics of the detection rate with respect to parameters such as the stellar spectral type and age or the presence of a debris disk in the outer regions of the systems. We derive more robust statistics by combining our sample with the results from our CHARA/FLUOR survey in the K-band. In addition, our spectrally dispersed data allows us to put constraints on the emission mechanism and the dust properties in the detected systems. Results. We find an over-all detection rate of bright exozodiacal dust in the H-band of 11% (9 out of 85 targets) and three tentative detections. The detection rate decreases from early type to late type stars and increases with the age of the host star. We do not confirm the tentative correlation between the presence of cold and hot dust found in our earlier analysis of the FLUOR sample alone. Our spectrally dispersed data suggest that either the dust is extremely hot or the emission is dominated by the scattered light in most cases. The implications of our results for the target selection of future terrestrial planet finding missions using direct imaging are discussed.Comment: 20 pages, 16 figures, 4 tables, updated references and minor changes to the text, accepted for publication in A&

CAPA neuropeptides and their receptor form an anti-diuretic hormone signalling system in the human disease vector, Aedes aegypti

Insect CAPA neuropeptides are homologs of mammalian neuromedin U and are known to influence ion and water balance by regulating the activity of the Malpighian ‘renal’ tubules (MTs). Several diuretic hormones are known to increase primary fluid and ion secretion by insect MTs and, in adult female mosquitoes, a calcitonin-related peptide (DH31) called mosquito natriuretic peptide, increases sodium secretion to compensate for the excess salt load acquired during blood-feeding. An endogenous mosquito anti-diuretic hormone was recently described, having potent inhibitory activity against select diuretic hormones, including DH31. Herein, we functionally deorphanized, both in vitro and in vivo, a mosquito anti-diuretic hormone receptor (AedaeADHr) with expression analysis indicating highest enrichment in the MTs where it is localized within principal cells. Characterization using a heterologous in vitro system demonstrated the receptor was highly sensitive to mosquito CAPA neuropeptides while in vivo, AedaeADHr knockdown abolished CAPA-induced anti-diuretic control of DH31-stimulated MTs. CAPA neuropeptides are produced within a pair of neurosecretory cells in each of the abdominal ganglia, whose axonal projections innervate the abdominal neurohaemal organs, where these neurohormones are released into circulation. Lastly, pharmacological inhibition of nitric oxide synthase (NOS) and protein kinase G (PKG) signaling eliminated anti-diuretic activity of CAPA, highlighting the role of the second messenger cGMP and NOS/PKG in this anti-diuretic signaling pathway.York University Librarie

Troubling island: the imagining and imaging of Haiti by African-American artists, 1915-1940

Images of Haiti have circulated in the social imagination of the United States through painting, sculpture, illustration, performance and film since the late eighteenth century. Although much scholarship addresses the intertwined and often problematic relationship between the United States and Haiti, sparse art historical research addresses the complexities of U.S. visualizations of Haiti. The period of the U.S. occupation of Haiti (1915-1934) and its immediate aftermath resulted in the opening up of Haiti to unprecedented numbers of writers, ethnographers, and artists who focused both on Haiti as a contemporary nation, and retold and reinterpreted its revolutionary history to express new social and political needs. This dissertation contributes to a greater understanding of how representations of Haiti overwhelmingly articulate issues of race, while also touching on cultural anxieties of class, religion, patriotism and national identity. This dissertation specifically examines how African-American artists have worked against mainstream representations of Haiti to create alternate visions, combating and complicating many stereotypes, while also furthering an understanding of the transnational influences and outlook of several prominent twentieth-century African-American artists. Aaron Douglas, Jacob Lawrence, and William E. Scott are just a few of the African-American artists who drew on Haiti as a source of racial pride and heritage, personal transformation, or as a signifier for revolutionary change. iv While rooted in art historical analysis, privileging the visual over the text, this is an interdisciplinary dissertation that focuses on the broader context of cultural studies. I draw on both popular media and the performing and fine arts, and match art historical traditions with histories of anthropology and its evolving ethnographic practices, and the politics of U.S. international relations in the Caribbean. Through this lens, I expose how creative representations by African-American artists attempted to open new spaces in interpretations of Haiti, escaping the litany of tired and derogatory tropes so frequently applied to the "Black Republic.

A Long Term Geospatial Investigation of Air Quality in Windsor, Ontario, Canada - Comparison to Nearby Cities and Applications of Inter-Species Ratios

Ambient air sampling campaigns were carried out in Windsor, Ontario, Canada as well as in Detroit, Michigan, USA and Sarnia, Ontario over a five year period. Sampling campaigns were for two-week periods in each of the four seasons of 2004-2006 in Windsor, fall 2005 in Sarnia and fall (2008) and spring (2009) for Windsor - Detroit. In Windsor, analyses of the benzene, toluene, ethylbenzene, and xylene (BTEX) species for 2004, 2005, and 2006 is reported in this thesis along with BTEX for Sarnia in 2005. Across the international airshed encompassing Windsor and Detroit, simultaneous sampling of nitrogen dioxide (NO2), particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), and BTEX is reported for 2008 and 2009. Temporal and spatial patterns of concentrations, ratios and correlations among pollutants, as well as the effects of sampler placement, wind patterns and transboundary pollution were studied. Windsor experienced similar concentrations compared with Sarnia and lower concentrations than Detroit. Correlation and inter-specie BTEX ratio analysis identified traffic as the common source of VOCs, BTEX, and NO 2 in Windsor and Detroit. An innovative approach was applied in Sarnia using BTEX concentrations and ratios to characterize mixtures of industrial and mobile sources in different areas of the city. Temporal and spatial variability was observed. Seasonal comparisons to annual concentrations and spatial patterns indicate that if resources are limited, fall would be preferred to conduct air quality campaigns in Windsor. The locations of hot spots in Windsor were not qualitatively associated with wind patterns during the sampling periods. Additionally there was a lack of association between air mass pathways and measured NO 2 and PM 2.5 concentrations in Windsor. Comparisons between concentrations obtained from the sampling campaigns and those from central monitoring stations indicate that these stations are adequate for representing citywide averages. For residential exposure assessment however, these could result in misclassification up to a factor of six. Risk maps demonstrate BTEX exposure risk across Windsor. Study design recommendations were made for future air quality campaigns. These include sampling frequency, density, and placement, exposure misclassification associated with central site measurements, and for identifying sources for pollutant reduction initiatives

Myrin Library News, Vol. 23 No. 1, September 2010

This newsletter announces recent acquisitions of Myrin Library at Ursinus College and provides information and updates about recent projects, exhibits and events.https://digitalcommons.ursinus.edu/library_news/1105/thumbnail.jp