2,340 research outputs found
The RRAT Trap: Interferometric Localization of Radio Pulses from J0628+0909
We present the first blind interferometric detection and imaging of a
millisecond radio transient with an observation of transient pulsar J0628+0909.
We developed a special observing mode of the Karl G. Jansky Very Large Array
(VLA) to produce correlated data products (i.e., visibilities and images) on a
time scale of 10 ms. Correlated data effectively produce thousands of beams on
the sky that can localize sources anywhere over a wide field of view. We used
this new observing mode to find and image pulses from the rotating radio
transient (RRAT) J0628+0909, improving its localization by two orders of
magnitude. Since the location of the RRAT was only approximately known when
first observed, we searched for transients using a wide-field detection
algorithm based on the bispectrum, an interferometric closure quantity. Over 16
minutes of observing, this algorithm detected one transient offset roughly 1'
from its nominal location; this allowed us to image the RRAT to localize it
with an accuracy of 1.6". With a priori knowledge of the RRAT location, a
traditional beamforming search of the same data found two, lower significance
pulses. The refined RRAT position excludes all potential multiwavelength
counterparts, limiting its optical luminosity to L_i'<1.1x10^31 erg/s and
excluding its association with a young, luminous neutron star.Comment: Submitted to ApJ, 7 pages, 5 figure
Creativity and the computer nerd: an exploration of attitudes
This study arises from our concern that many of our best art and design students are failing to make the most of the opportunities provided by IT because of their fear or dislike of computers. This not only deprives them of useful skills, but, even more importantly, deprives many IT based developments of their input. In this paper we investigate the relationship between attitudes to creativity and to computers among students. We quickly discard an approach based on theories of personality types as philosophically and educationally problematic. An approach based on the self-concept of artists and designers, in relation to their own creativity and to their feelings about computers, offers more hope of progress. This means that we do not try to define the attributes of "creative people". Rather, we ask what creativity means to students of art and design and relate these responses to their attitudes to computers. Self-concept depends on how the subjects see themselves within society and culture, and is liable to change as culture changes. One major instrument of cultural change at the present time is the growth of IT itself. We then describe a first attempt at using a psychological method - Kelly's Repertory Grids - to investigate the self-concept of artists and designers. It is hoped to continue with this approach in further studies over the next few years
Molecular basis for clinical diversity between autoantibody subsets in diffuse cutaneous systemic sclerosis.
OBJECTIVES: Clinical heterogeneity is a cardinal feature of systemic sclerosis (SSc). Hallmark SSc autoantibodies are central to diagnosis and associate with distinct patterns of skin-based and organ-based complications. Understanding molecular differences between patients will benefit clinical practice and research and give insight into pathogenesis of the disease. We aimed to improve understanding of the molecular differences between key diffuse cutaneous SSc subgroups as defined by their SSc-specific autoantibodies METHODS: We have used high-dimensional transcriptional and proteomic analysis of blood and the skin in a well-characterised cohort of SSc (n=52) and healthy controls (n=16) to understand the molecular basis of clinical diversity in SSc and explore differences between the hallmark antinuclear autoantibody (ANA) reactivities. RESULTS: Our data define a molecular spectrum of SSc based on skin gene expression and serum protein analysis, reflecting recognised clinical subgroups. Moreover, we show that antitopoisomerase-1 antibodies and anti-RNA polymerase III antibodies specificities associate with remarkably different longitudinal change in serum protein markers of fibrosis and divergent gene expression profiles. Overlapping and distinct disease processes are defined using individual patient pathway analysis. CONCLUSIONS: Our findings provide insight into clinical diversity and imply pathogenetic differences between ANA-based subgroups. This supports stratification of SSc cases by ANA antibody subtype in clinical trials and may explain different outcomes across ANA subgroups in trials targeting specific pathogenic mechanisms
Caribbean Corals in Crisis: Record Thermal Stress, Bleaching, and Mortality in 2005
BACKGROUND The rising temperature of the world's oceans has become a major threat to coral reefs globally as the severity and frequency of mass coral bleaching and mortality events increase. In 2005, high ocean temperatures in the tropical Atlantic and Caribbean resulted in the most severe bleaching event ever recorded in the basin. METHODOLOGY/PRINCIPAL FINDINGS Satellite-based tools provided warnings for coral reef managers and scientists, guiding both the timing and location of researchers' field observations as anomalously warm conditions developed and spread across the greater Caribbean region from June to October 2005. Field surveys of bleaching and mortality exceeded prior efforts in detail and extent, and provided a new standard for documenting the effects of bleaching and for testing nowcast and forecast products. Collaborators from 22 countries undertook the most comprehensive documentation of basin-scale bleaching to date and found that over 80% of corals bleached and over 40% died at many sites. The most severe bleaching coincided with waters nearest a western Atlantic warm pool that was centered off the northern end of the Lesser Antilles. CONCLUSIONS/SIGNIFICANCE Thermal stress during the 2005 event exceeded any observed from the Caribbean in the prior 20 years, and regionally-averaged temperatures were the warmest in over 150 years. Comparison of satellite data against field surveys demonstrated a significant predictive relationship between accumulated heat stress (measured using NOAA Coral Reef Watch's Degree Heating Weeks) and bleaching intensity. This severe, widespread bleaching and mortality will undoubtedly have long-term consequences for reef ecosystems and suggests a troubled future for tropical marine ecosystems under a warming climate.This work was partially supported by salaries from the NOAA Coral Reef Conservation Program to the NOAA Coral Reef Conservation Program authors. NOAA provided funding to Caribbean ReefCheck investigators to undertake surveys of bleaching and mortality. Otherwise, no funding from outside authors' institutions was necessary for the undertaking of this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Recommended from our members
Phenological tracking of a seasonal climate window in a recovering tropical island bird species
Constraints on evolutionary adaptation and range shifts mean that phenotypic plasticity, which includes physiological, developmental or behavioural responses to environmental conditions, could be an important mode of adaptation to a changing climate for many species with small insular populations. While there is evidence to suggest adaptive plasticity to climate in some island populations, little is known about this capacity in species that have experienced a severe population bottleneck. In a changing climate, plasticity in the timing of life-history events, such as in breeding phenology, is adaptive if timing is optimised in seasonal environments, although these processes are poorly understood for tropical species. Here, we quantify the effects of climate on the breeding phenology and success of the Mauritius kestrel (Falco punctatus), a tropical raptor whose extinction has been averted by conservation management. We show that the timing of egg-laying is advancing in response to warming, at rates similar to temperate bird populations. Individual females show plasticity to temperature, although there is limited variation among individual responses. We show that advances in breeding phenology are likely to be adaptive, as they track changes in a seasonal climate window of favourable conditions, defined by late winter-early spring temperatures and the onset of the summer rainy season. Our results provide a rare example of a small and bottlenecked insular population that has adjusted to recent climate change through phenotypic plasticity. Furthermore, seasonal climate windows and their dynamics may be widespread mechanisms through which tropical species are impacted by and respond to climate change
Coincidence analysis to search for inspiraling compact binaries using TAMA300 and LISM data
Japanese laser interferometric gravitational wave detectors, TAMA300 and
LISM, performed a coincident observation during 2001. We perform a coincidence
analysis to search for inspiraling compact binaries. The length of data used
for the coincidence analysis is 275 hours when both TAMA300 and LISM detectors
are operated simultaneously. TAMA300 and LISM data are analyzed by matched
filtering, and candidates for gravitational wave events are obtained. If there
is a true gravitational wave signal, it should appear in both data of detectors
with consistent waveforms characterized by masses of stars, amplitude of the
signal, the coalescence time and so on. We introduce a set of coincidence
conditions of the parameters, and search for coincident events. This procedure
reduces the number of fake events considerably, by a factor
compared with the number of fake events in single detector analysis. We find
that the number of events after imposing the coincidence conditions is
consistent with the number of accidental coincidences produced purely by noise.
We thus find no evidence of gravitational wave signals. We obtain an upper
limit of 0.046 /hours (CL ) to the Galactic event rate within 1kpc from
the Earth. The method used in this paper can be applied straightforwardly to
the case of coincidence observations with more than two detectors with
arbitrary arm directions.Comment: 28 pages, 17 figures, Replaced with the version to be published in
Physical Review
Results of the search for inspiraling compact star binaries from TAMA300's observation in 2000-2004
We analyze the data of TAMA300 detector to search for gravitational waves
from inspiraling compact star binaries with masses of the component stars in
the range 1-3Msolar. In this analysis, 2705 hours of data, taken during the
years 2000-2004, are used for the event search. We combine the results of
different observation runs, and obtained a single upper limit on the rate of
the coalescence of compact binaries in our Galaxy of 20 per year at a 90%
confidence level. In this upper limit, the effect of various systematic errors
such like the uncertainty of the background estimation and the calibration of
the detector's sensitivity are included.Comment: 8 pages, 4 Postscript figures, uses revtex4.sty The author list was
correcte
Agricultural intensification and the evolution of host specialism in the enteric pathogen Campylobacter jejuni.
Modern agriculture has dramatically changed the distribution of animal species on Earth. Changes to host ecology have a major impact on the microbiota, potentially increasing the risk of zoonotic pathogens being transmitted to humans, but the impact of intensive livestock production on host-associated bacteria has rarely been studied. Here, we use large isolate collections and comparative genomics techniques, linked to phenotype studies, to understand the timescale and genomic adaptations associated with the proliferation of the most common food-born bacterial pathogen (Campylobacter jejuni) in the most prolific agricultural mammal (cattle). Our findings reveal the emergence of cattle specialist C. jejuni lineages from a background of host generalist strains that coincided with the dramatic rise in cattle numbers in the 20th century. Cattle adaptation was associated with horizontal gene transfer and significant gene gain and loss. This may be related to differences in host diet, anatomy, and physiology, leading to the proliferation of globally disseminated cattle specialists of major public health importance. This work highlights how genomic plasticity can allow important zoonotic pathogens to exploit altered niches in the face of anthropogenic change and provides information for mitigating some of the risks posed by modern agricultural systems
GLACE: the global landâatmosphere coupling experiment. Part I: overview
Permission to place copies of these works on this server has been provided by the American Meteorological Society (AMS). The AMS does not guarantee that the copies provided here are accurate copies of the published work. © Copyright 2006 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be âfair useâ under Section 107 of the U.S. Copyright Act or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108, as revised by P.L. 94-553) does not require the AMSâs permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. Additional details are provided in the AMS Copyright Policy, available on the AMS Web site located at (http://www.ametsoc.org/AMS) or from the AMS at 617-227-2425 or [email protected] Global LandâAtmosphere Coupling Experiment (GLACE) is a model intercomparison study focusing on a typically neglected yet critical element of numerical weather and climate modeling: landâatmosphere coupling strength, or the degree to which anomalies in land surface state (e.g., soil moisture) can affect rainfall generation and other atmospheric processes. The 12 AGCM groups participating in GLACE performed a series of simple numerical experiments that allow the objective quantification of this element for boreal summer. The derived coupling strengths vary widely. Some similarity, however, is found in the spatial patterns generated by the models, with enough similarity to pinpoint multimodel âhot spotsâ of landâatmosphere coupling. For boreal summer, such hot spots for precipitation and temperature are found over large regions of Africa, central North America, and India; a hot spot for temperature is also found over eastern China. The design of the GLACE simulations are described in full detail so that any interested modeling group can repeat them easily and thereby place their modelâs coupling strength within the broad range of those documented here
- âŠ