Long-term Declines in the Size of Northern Fulmar (Fulmarus glacialis) Colonies on Eastern Baffin Island, Canada

We censused three colonies of Northern Fulmars (Fulmarus glacialis) along eastern Baffin Island, Canada, that were estimated to support 155 000 breeding pairs in 1973, but had not been adequately counted since then. The colonies were surveyed in July and August 2018 using photographs taken from a helicopter or a drone. The combined estimated colony sizes were 36 500 pairs, much smaller than historical estimates. Although the 1973 estimates were coarse, this difference represents an apparent 3+% annual decline in numbers at each colony over approximately four decades or more than 87% over three generations (66 years). Several factors may be contributing to these declines, including changes in winter food supplies and the susceptibility of fulmars to fisheries bycatch. We recommend efforts to survey the remaining major fulmar colonies in Arctic Canada to assess the overall population size and trends, and allow for further analyses of potential population drivers.Nous avons recensé trois colonies de fulmars boréaux (Fulmarus glacialis) sur la côte est de l’île de Baffin, au Canada. Selon des estimations réalisées en 1973, 155 000 couples reproducteurs y nichaient, mais aucun dénombrement adéquat n’avait été effectué depuis. Les colonies ont été recensées en juillet et en août 2018 au moyen de photographies prises à partir d’un hélicoptère ou d’un drone. La taille combinée des colonies a été estimée à 36500 couples, soit un nombre beaucoup moins élevé que les estimations précédentes. Bien que les estimations de 1973 étaient des estimations grossières, cette différence représente une baisse annuelle apparente de plus de 3 % à chacune des colonies sur environ quatre décennies, soit plus de 87 % sur trois générations (66 ans). Ces diminutions peuvent être attribuables à plusieurs facteurs, dont les changements caractérisant les approvisionnements en nourriture pendant l’hiver et la susceptibilité des fulmars à faire l’objet de captures accessoires. Nous recommandons que des efforts soient faits pour recenser les grandes colonies de fulmars qui restent dans l’Arctique canadien afin d’évaluer la taille globale de la population et les tendances la caractérisant, ainsi que pour pousser plus loin l’analyse des facteurs susceptibles d’avoir un effet sur leurs populations

Characterization of an Ionization Readout Tile for nEXO

A new design for the anode of a time projection chamber, consisting of a charge-detecting "tile", is investigated for use in large scale liquid xenon detectors. The tile is produced by depositing 60 orthogonal metal charge-collecting strips, 3~mm wide, on a 10~\si{\cm} $\times$ 10~\si{\cm} fused-silica wafer. These charge tiles may be employed by large detectors, such as the proposed tonne-scale nEXO experiment to search for neutrinoless double-beta decay. Modular by design, an array of tiles can cover a sizable area. The width of each strip is small compared to the size of the tile, so a Frisch grid is not required. A grid-less, tiled anode design is beneficial for an experiment such as nEXO, where a wire tensioning support structure and Frisch grid might contribute radioactive backgrounds and would have to be designed to accommodate cycling to cryogenic temperatures. The segmented anode also reduces some degeneracies in signal reconstruction that arise in large-area crossed-wire time projection chambers. A prototype tile was tested in a cell containing liquid xenon. Very good agreement is achieved between the measured ionization spectrum of a $^{207}$Bi source and simulations that include the microphysics of recombination in xenon and a detailed modeling of the electrostatic field of the detector. An energy resolution $\sigma/E$=5.5\% is observed at 570~\si{keV}, comparable to the best intrinsic ionization-only resolution reported in literature for liquid xenon at 936~V/\si{cm}.Comment: 18 pages, 13 figures, as publishe

Sensitivity and discovery potential of the proposed nEXO experiment to neutrinoless double beta decay

The next-generation Enriched Xenon Observatory (nEXO) is a proposed experiment to search for neutrinoless double beta ($0\nu\beta\beta$) decay in $^{136}$Xe with a target half-life sensitivity of approximately $10^{28}$ years using $5\times10^3$ kg of isotopically enriched liquid-xenon in a time projection chamber. This improvement of two orders of magnitude in sensitivity over current limits is obtained by a significant increase of the $^{136}$Xe mass, the monolithic and homogeneous configuration of the active medium, and the multi-parameter measurements of the interactions enabled by the time projection chamber. The detector concept and anticipated performance are presented based upon demonstrated realizable background rates.Comment: v2 as publishe

Simultaneous assessment of rodent behavior and neurochemistry using a miniature positron emission tomograph

Positron emission tomography (PET) neuroimaging and behavioral assays in rodents are widely used in neuroscience. PET gives insights into the molecular processes of neuronal communication, and behavioral methods analyze the actions that are associated with such processes. These methods have not been directly integrated, because PET studies in animals have until now required general anesthesia to immobilize the subject, which precludes behavioral studies. We present a method for imaging awake, behaving rats with PET that allows the simultaneous study of behavior. Key components include the 'rat conscious animal PET' or RatCAP, a miniature portable PET scanner that is mounted on the rat's head, a mobility system that allows considerable freedom of movement, radiotracer administration techniques and methods for quantifying behavior and correlating the two data sets. The simultaneity of the PET and behavioral data provides a multidimensional tool for studying the functions of different brain regions and their molecular constituents. © 2011 Nature America, Inc. All rights reserved