270 research outputs found

    Bayesian Inference for the White Dwarf Initial-Final Mass Relation

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    Stars lose mass as they age, and understanding mass loss is important for understanding stellar evolution. The initial-final mass relation (IFMR) is the relationship between a white dwarf’s initial mass on the main sequence and its final mass. We have developed a new method for fitting the IFMR based on a Bayesian analysis of photometric observations, combining deterministic models of stellar evolution in an internally coherent way. No mass data are used. Our method yields precise inferences (with uncertainties) for a parameterized linear IFMR. Our method can also return posterior distributions of white dwarf initial and final masses

    Enhancing an Inclusive Environment: Employee Resource Groups - Best Practices

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    Best practices research suggests that Employee Resource Groups (ERGs) are an effective vehicle for enhancing inclusion within organizations. MIT has just completed its pilot year with four newly formed ERGs. Come hear about our journey and, at the same time, assess your own organizations’ readiness for ERGs or other inclusive practices

    Alexandrium cyst distribution and germination in Puget Sound

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    The Puget Sound Alexandrium Harmful Algal Bloom (PS-AHAB: www.tiny.cc/psahab) program, funded by NOAA/ECOHAB, seeks to understand environmental controls on the benthic (cyst) and planktonic life stages of the toxic dinoflagellate Alexandrium catenella, and disentangle the effects of climate pathways on the timing and location of blooms. Spatially detailed mapping of winter surface sediment cyst distributions in 2011, 2012, and 2013 found the highest cyst concentrations in Bellingham Bay in the north and Quartermaster Harbor in central Puget Sound. However, the viability of cysts at these seed bed areas is low – with fewer than 54% of cysts germinating when incubated at favorable temperatures. The time of year that cysts can germinate does not appear to be controlled by an endogenous clock, but the rate of germination is strongly determined by temperature. These results may complicate potential relationships between cyst abundances and bloom magnitude the following season. A monthly time series of cyst abundances was also collected at two locations in Quartermaster Harbor from 2012-2013 as part of a related Sea Grant project investigating the seasonal variability in cyst abundances. Cyst abundances varied by a factor of ~6 with the lowest cyst abundances occurring in the spring (Apr) and the highest cyst abundances occurring in late fall (Oct/Nov). This seasonal pattern is consistent with observed A. catenella bloom dynamics in Quartermaster Harbor. The improved understanding of the processes that govern cyst germination and bloom initiation provided by this study contribute towards the development of a predictive capacity for A. catenella blooms in Puget Sound. Details on A. catenella growth rates and toxicity and an analysis of potential bloom transport using a high-resolution hydrodynamic simulation of Puget Sound and adjacent coastal waters (MoSSea: http://faculty.washington.edu/pmacc/MoSSea/), as well as simulations of potential future climate impacts on blooms, will be discussed in separate presentations by B.D. Bill and S.K. Moore respectively, at this conference

    Tracking of Energy Performance Indicators in Residential Building Stocks – Different Approaches and Common Results - EPISCOPE Synthesis Report No. 4

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    A central task of IEE EPISCOPE project was to carry out energy balance calculations and scenario analysis for national, regional or local residential building stocks against the background of energy saving and climate protection targets. The EPISCOPE Synthesis Report No. 4 documents the individual approaches of collecting information for the investigated residential building stocks as a foundation for building stock models and scenario calculations. Issues related to the availability of data and data quality are discussed, and concepts for a continuous monitoring (a regular data collection) are presented as a basis for a future tracking of energy performance in the observed building stocks

    Modelling creativity: identifying key components through a corpus-based approach

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    Creativity is a complex, multi-faceted concept encompassing a variety of related aspects, abilities, properties and behaviours. If we wish to study creativity scientifically, then a tractable and well-articulated model of creativity is required. Such a model would be of great value to researchers investigating the nature of creativity and in particular, those concerned with the evaluation of creative practice. This paper describes a unique approach to developing a suitable model of how creative behaviour emerges that is based on the words people use to describe the concept. Using techniques from the field of statistical natural language processing, we identify a collection of fourteen key components of creativity through an analysis of a corpus of academic papers on the topic. Words are identified which appear significantly often in connection with discussions of the concept. Using a measure of lexical similarity to help cluster these words, a number of distinct themes emerge, which collectively contribute to a comprehensive and multi-perspective model of creativity. The components provide an ontology of creativity: a set of building blocks which can be used to model creative practice in a variety of domains. The components have been employed in two case studies to evaluate the creativity of computational systems and have proven useful in articulating achievements of this work and directions for further research

    HEART UK statement on the management of homozygous familial hypercholesterolaemia in the United Kingdom

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    This consensus statement addresses the current three main modalities of treatment of homozygous familial hypercholesterolaemia (HoFH): pharmacotherapy, lipoprotein (Lp) apheresis and liver transplantation. HoFH may cause very premature atheromatous arterial disease and death, despite treatment with Lp apheresis combined with statin, ezetimibe and bile acid sequestrants. Two new classes of drug, effective in lowering cholesterol in HoFH, are now licensed in the United Kingdom. Lomitapide is restricted to use in HoFH but, may cause fatty liver and is very expensive. PCSK9 inhibitors are quite effective in receptor defective HoFH, are safe and are less expensive. Lower treatment targets for lipid lowering in HoFH, in line with those for the general FH population, have been proposed to improve cardiovascular outcomes. HEART UK presents a strategy combining Lp apheresis with pharmacological treatment to achieve these targets in the United Kingdom (UK). Improved provision of Lp apheresis by use of existing infrastructure for extracorporeal treatments such as renal dialysis is promoted. The clinical management of adults and children with HoFH including advice on pregnancy and contraception are addressed. A premise of the HEART UK strategy is that the risk of early use of drug treatments beyond their licensed age restriction may be balanced against risks of liver transplantation or ineffective treatment in severely affected patients. This may be of interest beyond the UK

    Recurrent Die-Offs of Adult Coho Salmon Returning to Spawn in Puget Sound Lowland Urban Streams

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    Several Seattle-area streams in Puget Sound were the focus of habitat restoration projects in the 1990s. Post-project effectiveness monitoring surveys revealed anomalous behaviors among adult coho salmon returning to spawn in restored reaches. These included erratic surface swimming, gaping, fin splaying, and loss of orientation and equilibrium. Affected fish died within hours, and female carcasses generally showed high rates (>90%) of egg retention. Beginning in the fall of 2002, systematic spawner surveys were conducted to 1) assess the severity of the adult die-offs, 2) compare spawner mortality in urban vs. non-urban streams, and 3) identify water quality and spawner condition factors that might be associated with the recurrent fish kills. The forensic investigation focused on conventional water quality parameters (e.g., dissolved oxygen, temperature, ammonia), fish condition, pathogen exposure and disease status, and exposures to metals, polycyclic aromatic hydrocarbons, and current use pesticides. Daily surveys of a representative urban stream (Longfellow Creek) from 2002–2009 revealed premature spawner mortality rates that ranged from 60–100% of each fall run. The comparable rate in a non-urban stream was <1% (Fortson Creek, surveyed in 2002). Conventional water quality, pesticide exposure, disease, and spawner condition showed no relationship to the syndrome. Coho salmon did show evidence of exposure to metals and petroleum hydrocarbons, both of which commonly originate from motor vehicles in urban landscapes. The weight of evidence suggests that freshwater-transitional coho are particularly vulnerable to an as-yet unidentified toxic contaminant (or contaminant mixture) in urban runoff. Stormwater may therefore place important constraints on efforts to conserve and recover coho populations in urban and urbanizing watersheds throughout the western United States
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