33,529 research outputs found

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    Walking the Talk: The Impact of High Commitment Values and Practices on Technology Start-ups

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    We examine the impact of high commitment work systems (HCWS) on high-technology start-ups. We differentiate two components of a HCWS: the human resource practices and the espoused values of the firm\u27s leadership and demonstrate that both are associated with an increased likelihood of IPO and a decreased likelihood of firm failure. Importantly, there are interactions between practices and values such that the benefit of one tends to amplify the other. Implications of these interactions for future research on high commitment work systems are discussed

    Quasi-static granular flow of ice mélange

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    We use Landsat 8 imagery to generate ice mélange velocity fields at Greenland’s three most productive outlet glaciers: Jakobshavn Isbræ, Helheim Glacier, and Kangerdlugssuaq Glacier. Winter velocity fields are generally steady and highly uniform. Summer velocity fields, on the other hand, tend to be much more variable and can be uniform, compressional, or extensional. We rarely observe compressional flow at Jakobshavn Isbræ or extensional flow at Helheim Glacier, while both are observed at Kangerdlugssuaq Glacier. Transverse velocity profiles from all three locations are suggestive of viscoplastic flow, in which deformation occurs primarily in shear zones along the fjord walls. We analyze the transverse profiles in the context of quasi-static flow using continuum rheologies for granular materials and find that the force per unit width that ice mélange exerts on glacier termini increases exponentially with the ice mélange length-to-width ratio and the effective coefficient of friction. Our estimates of ice mélange resistance are consistent with other independent estimates and suggest that ice mélange may be capable of inhibiting iceberg calving events, especially during winter. Moreover, our results provide geophysical-scale support for constitutive relationships for granular materials and suggest a potential avenue for modeling ice mélange dynamics with continuum models.From acknowledgments: Funding for this project was provided by the U.S. National Science Foundation (DMR-1506446 and DMR-1506307). Digital elevation models were provided by the Polar Geospatial Center under the U.S. National Science Foundation (OPP-1043681, OPP-1559691, and OPP-1542736)Ye

    Ks-band (2.14 micron) imaging of southern massive star formation regions traced by methanol masers

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    We present deep, wide-field, Ks-band (2.14 micron) images towards 87 southern massive star formation regions traced by methanol maser emission. Using point-spread function fitting, we generate 2.14 micron point source catalogues towards each of the regions. For the regions between 10 degrees and 350 degrees galactic longitude and galactic latitude +/- 1 degree, we match the 2.14 micron sources with the GLIMPSE point source catalogue to generate a combined 2.14 to 8.0 micron point source catalogue. We provide this data for the astronomical community to utilise in studies of the stellar content of embedded clusters.Comment: Accepted PASA. Full version including figures available from http://www.cfa.harvard.edu/~slongmor/snl_iris2_withfigs.pd

    An infrared proper motion study of the Orion bullets

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    We report the first IR proper motion measurements of the Herbig-Haro objects in the Orion Molecular Cloud--One using a four-year time baseline. The [Fe II] emitting bullets are moving of order 0.08 arcsec per year, or at about 170 \kms. The direction of motion is similar to that inferred from their morphology. The proper motions of \h2 emitting wakes behind the [Fe II] bullets, and of newly found \h2 bullets, are also measured. \h2 bullets have smaller proper motion than [Fe II] bullets, while \h2 wakes with leading [Fe II] bullets appear to move at similar speeds to their associated bullets. A few instances of variability in the emission can be attributed to dense, stationary clumps in the ambient cloud being overrun, setting up a reverse--oriented bullet. Differential motion between [Fe II] bullets and their trailing \h2 wakes is not observed, suggesting that these are not separating, and also that they have reached a steady--state configuration over at least 100 years. The most distant bullets have, on average, larger proper motions, but are not consistent with free expansion. Nevertheless an impulsive, or short--lived (≪\ll 1,000 years) duration for their origin seems likely.Comment: 9 pages, 8 figure

    Quasi-static granular flow of ice mélange

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    We use Landsat 8 imagery to generate ice mélange velocity fields at Greenland’s three most productive outlet glaciers: Jakobshavn Isbræ, Helheim Glacier, and Kangerdlugssuaq Glacier. Winter velocity fields are generally steady and highly uniform. Summer velocity fields, on the other hand, tend to be much more variable and can be uniform, compressional, or extensional. We rarely observe compressional flow at Jakobshavn Isbræ or extensional flow at Helheim Glacier, while both are observed at Kangerdlugssuaq Glacier. Transverse velocity profiles from all three locations are suggestive of viscoplastic flow, in which deformation occurs primarily in shear zones along the fjord walls. We analyze the transverse profiles in the context of quasi-static flow using continuum rheologies for granular materials and find that the force per unit width that ice mélange exerts on glacier termini increases exponentially with the ice mélange length-to-width ratio and the effective coefficient of friction. Our estimates of ice mélange resistance are consistent with other independent estimates and suggest that ice mélange may be capable of inhibiting iceberg calving events, especially during winter. Moreover, our results provide geophysical-scale support for constitutive relationships for granular materials and suggest a potential avenue for modeling ice mélange dynamics with continuum models.From acknowledgments: Funding for this project was provided by the U.S. National Science Foundation (DMR-1506446 and DMR-1506307). Digital elevation models were provided by the Polar Geospatial Center under the U.S. National Science Foundation (OPP-1043681, OPP-1559691, and OPP-1542736)Ye

    Statistical complexity of reasons for encounter in high users of out of hours primary care:analysis of a national service

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    Background: Managing demand for urgent and unscheduled care is a major problem for health services globally. A particular issue is that some patients appear to make heavy use of services, including primary care out of hours. We hypothesised that greater variation (statistical complexity) in reasons for attending primary care out of hours services may be a useful marker of patients at high risk of ongoing heavy service use. Methods: We analysed an anonymised dataset of contacts with the primary care out of hours care for Scotland in 2011. This contained 120,395 contacts from 13,981 high-using patients who made 5 or more contacts during a calendar year. We allocated the stated reason for each encounter into one of 14 categories. For each patient we calculated measures of statistical complexity of reasons for encounter including the count of different categories, Herfindahl index and statistical entropy of either the categories themselves, or the category transitions. We examined the association of these measures of statistical complexity with patient and healthcare use characteristics. Results: The high users comprised 2.4% of adults using the service and accounted for 15% of all contacts. Statistical complexity (as entropy of categories) increased with number of contacts but was not substantially influenced by either patient age or sex. This lack of association with age was unexpected as with increasing multi-morbidity one would expect greater variability in reason for encounter. Between 5 and 10 consultations, higher entropy was associated with a reduced likelihood of further consultations. In contrast, the occurrence of one or more contacts for a mental health problem was associated with increased likelihood of further consultations. Conclusion: Complexity of reason for encounter can be estimated in an out of hours primary care setting. Similar levels of statistical complexity are seen in younger and older adults (suggesting that it is more to do with consultation behaviour than morbidity) but it is not a predictor of ongoing high use of urgent care.</p

    Coming From Good Stock: Career Histories and New Venture Formation

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    We examine how the social structure of existing organizations influences entrepreneurship and suggest that resources accrue to entrepreneurs based on the structural position of their prior employers. We argue that information advantages allow individuals from entrepreneurially prominent prior firms to identify new opportunities. Entrepreneurial prominence also reduces the perceived uncertainty of a new venture. Using a sample of Silicon Valley start-ups, we demonstrate that entrepreneurial prominence is associated with initial strategy and the probability of attracting external financing. New ventures with high prominence are more likely to be innovators; furthermore, innovators with high prominence are more likely to obtain financing
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