Electron multiplication CCD detector technology advancement for the WFIRST-AFTA coronagraph

The WFIRST-AFTA (Wide Field InfraRed Survey Telescope-Astrophysics Focused Telescope Asset) is a NASA space observatory. It will host two major astronomical instruments: a wide-field imager (WFI) to search for dark energy and carry out wide field near infrared (NIR) surveys, and a coronagraph instrument (CGI) to image and spectrally characterize extrasolar planets. In this paper, we discuss the work that has been carried out at JPL in advancing Electron Multiplying CCD (EMCCD) technology to higher flight maturity, with the goal of reaching a NASA technology readiness level of 6 (TRL-6) by early-to-mid 2016. The EMCCD has been baselined for both the coronagraph's imager and integral field spectrograph (IFS) based on its sub-electron noise performance at extremely low flux levels - the regime where the AFTA CGI will operate. We present results from a study that fully characterizes the beginning of life performance of the EMCCD. We also discuss, and present initial results from, a recent radiation test campaign that was designed and carried out to mimic the conditions of the WFIRST-AFTA space environment in an L2 orbit, where we sought to assess the sensor's end of life performance, particularly degradation of its charge transfer efficiency, in addition to other parameters such as dark current, electron multiplication gain, clock induced charge and read noise

Extensive palaeo-surfaces beneath the Evans–Rutford region of the West Antarctic Ice Sheet control modern and past ice flow

The subglacial landscape of Antarctica records and influences the behaviour of its overlying ice sheet. However, in many places, the evolution of the landscape and its control on ice sheet behaviour have not been investigated in detail. Using recently released radio-echo sounding data, we investigate the subglacial landscape of the Evans–Rutford region of West Antarctica. Following quantitative analysis of the landscape morphology under ice-loaded and ice-unloaded conditions, we identify 10 flat surfaces distributed across the region. Across these 10 surfaces, we identify two distinct populations based on clustering of elevations, which potentially represent remnants of regionally coherent pre-glacial surfaces underlying the West Antarctic Ice Sheet (WAIS). The surfaces are bounded by deeply incised glacial troughs, some of which have potential tectonic controls. We assess two hypotheses for the evolution of the regional landscape: (1) passive-margin evolution associated with the break-up of the Gondwana supercontinent or (2) an extensive planation surface that may have been uplifted in association with either the West Antarctic Rift System or cessation of subduction at the base of the Antarctic Peninsula. We suggest that passive-margin evolution is the most likely of these two mechanisms, with the erosion of glacial troughs adjacent to, and incising, the flat surfaces likely having coincided with the growth of the WAIS. These flat surfaces also demonstrate similarities to other identified surfaces, indicating that a similar formational process may have been acting more widely around the Weddell Sea embayment. The subsequent fluctuations of ice flow, basal thermal regime, and erosion patterns of the WAIS are therefore controlled by the regional tectonic structures

Spatial and seasonal patterns of communal latrine use by spotted hyenas (Crocuta crocuta) reflect a seasonal resource defense strategy

© 2020, Springer-Verlag GmbH Germany, part of Springer Nature. Abstract: Communal marking sites, or latrines, appear to play an important role in intraspecific communication and social dynamics in a wide range of mammal species. The spatial distribution of latrines can provide clues to their function and has been well documented in a number of species. Latrine use may vary considerably through time, however, and a more comprehensive approach to their study that considers spatial and seasonal patterns of use is required to understand more fully the costs and benefits of latrine use, and hence their adaptive significance. This study investigated spatial and seasonal patterns of latrine use by spotted hyena (Crocuta crocuta) in northern Botswana, examining their potential role in resource defense. Latrine characteristics and hyena activity were monitored to test the influence of season and location (relative to clan territories and roads) on latrine use. We conducted monthly scat counts (at 78 latrines) and continuously recorded hyena visitation (to 50 latrines) in five clan home ranges, demonstrating clear seasonal patterns in latrine use. Latrines were smaller in the wet season (November-March), resulting from fewer visits by hyenas, reduced scat accumulation, and the seasonal activity of coprophagous beetles. We speculate that such a seasonal pattern may be driven by reduced competition for food during the wet season. Latrines located within core clan areas were no larger or more frequently used than those in home-range boundary areas, but hyenas did preferentially place latrines alongside roads and were more likely to reuse road-side latrines in subsequent years. This pattern was not due to observer detection bias and adds to the growing body of literature on the impact that roads and other anthropogenic features have on the communication and movement ecology of wild animals. Significance statement: Although most mammals use communal marking sites, very little is known about their function and detailed patterns of use in many species. We investigated latrine use in spotted hyena (Crocuta crocuta) and describe spatial and temporal marking patterns that are consistent with optimizing scent longevity and detection. Spatially, hyenas preferentially located latrines along the edge of man-made vehicle tracks, which may increase signal detection and transmission. Seasonal marking patterns suggest that hyenas optimize their communication by concentrating activity in the dry season, thereby avoiding the disruptive effects of coprophagous dung beetles and rain, and focusing activity during periods when food resources are expected to be scarcer. These results demonstrate seasonal and spatial optimization of communication, including in response to novel anthropogenic features in the environment such as roads, advancing our understanding of communication strategies in mammals more broadly

Scent marking in wild banded mongooses: 2. Intrasexual overmarking and competition between males

Sexual selection has resulted in the elaboration of secondary sexual characteristics in many animals. Although mammalian scent glands, secretions and marking behaviour are commonly sexually dimorphic, these traits have received little attention compared to avian plumage and mammalian weaponry. Overmarking, when one individual places a scent mark directly over that of another individual, is of particular interest. Owing to the costs of repeatedly monitoring and covering the scent marks of rivals, overmarking may provide an honest indication of a male's resource-holding potential, perhaps explaining why female rodents exposed to experimental overmarks subsequently prefer to associate with males whose scent mark was on top. This study on wild banded mongooses, Mungos mungo, suggests that overmarking may primarily affect behavioural mating success through male competition not by female mate choice. First, chemical analyses of anal gland secretions demonstrated that males had individually distinctive scents, and a field experiment confirmed that mongooses were able to discriminate between scents from different individuals. Observations of overmarking patterns showed a relationship between overmarking score and behavioural mating success, but we found no evidence that females actively chose to mate with males with high overmarking scores. Instead, we found that males with higher overmarking scores first mate-guarded females at a significantly younger age than males with lower overmarking scores. Since mate-guarding males obtain the vast majority of matings, this suggests that overmarking may be an important component of intrasexual competition for mating opportunities in this species.

Protective efficacy of co-trimoxazole prophylaxis against malaria in HIV exposed children in rural Uganda: a randomised clinical trial

Objective To evaluate the protective efficacy of co-trimoxazole prophylaxis against malaria in HIV exposed children (uninfected children born to HIV infected mothers) in Africa