12,196 research outputs found

    Atlas and zoogeography of common fishes in the Bering Sea and northeastern Pacific

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    The geographic and depth frequency distribution of 124 common demersal fish species in the northeastern Pacific were plotted from data on me at the Northwest and Alaska Fisheries Center (NWAFC), National Marine Fisheries Service. The data included catch records of fishes and invertebrates from 24,881 samples taken from the Chukchi Sea, throughout the Bering Sea, Aleutian Basin, Aleutian Archipelago, and the Gulf of Alaska, and from southeastern Alaska south to southern California. Samples were collected by a number of agencies and institutions over a 30-year period (1953-83), but were primarily from NWAFC demersal trawls. The distributions of all species with 100 or more occurrences in the data set were plotted by computer. Distributions plotted from these data were then compared with geographic and depth-range limits given in the literature. These data provide new range extensions (geographic, depth, or both) for 114 species. Questionable extensions are noted, the depth ranges determined for 95% of occurrences, and depths of most frequent occurrence are recorded. Ranges of the species were classified zoogeographically, according to life zone, and with regard to the depth zone of greatest occurrence. Because most species examined have broad geographic ranges, they do not provide the best information for testing the validity of proposed zoogeographic province boundaries. Because of the location of greatest sampling effort and methods used in sampling, most fIShes examined were eastern boreal Pacific, sublittoral-bathyal (outer shelf) species. (PDF file contains 158 pages.

    On Identification of Bayesian DSGE Models*

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    In recent years there has been increasing concern about the identification of parameters in dynamic stochastic general equilibrium (DSGE) models. Given the structure of DSGE models it may be di¢ cult to deter- mine whether a parameter is identi?ed. For the researcher using Bayesian methods, a lack of identi?cation may not be evident since the posterior of a parameter of interest may di¤er from its prior even if the parameter is unidentified. We show that this can even be the case even if the priors assumed on the structural parameters are independent. We suggest two Bayesian identification indicators that do not su¤er from this difficulty and are relatively easy to compute. The first applies to DSGE models where the parameters can be partitioned into those that are known to be identified and the rest where it is not known whether they are identi?ed. In such cases the marginal posterior of an unidenti?ed parameter will equal the posterior expectation of the prior for that parameter conditional on the identified parameters. The second indicator is more generally applicable and considers the rate at which the posterior precision gets updated as the sample size (T) is increased. For identi?ed parameters the posterior precision rises with T, whilst for an unidentified parameter its posterior precision may be updated but its rate of update will be slower than T. This result assumes that the identified parameters are pT-consistent, but similar differential rates of updates for identified and unidentified parameters can be established in the case of super consistent estimators. These results are illustrated by means of simple DSGE models.Bayesian identification, DSGE models, posterior updating, New Keynesian Phillips Curve.

    On Identification of Bayesian DSGE Models

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    In recent years there has been increasing concern about the identification of parameters in dynamic stochastic general equilibrium (DSGE) models. Given the structure of DSGE models it may be difficult to determine whether a parameter is identified. For the researcher using Bayesian methods, a lack of identification may not be evident since the posterior of a parameter of interest may differ from its prior even if the parameter is unidentified. We show that this can be the case even if the priors assumed on the structural parameters are independent. We suggest two Bayesian identification indicators that do not suffer from this difficulty and are relatively easy to compute. The first applies to DSGE models where the parameters can be partitioned into those that are known to be identified and the rest where it is not known whether they are identified. In such cases the marginal posterior of an unidentified parameter will equal the posterior expectation of the prior for that parameter conditional on the identified parameters. The second indicator is more generally applicable and considers the rate at which the posterior precision gets updated as the sample size (T) is increased. For identified parameters the posterior precision rises with T, whilst for an unidentified parameter its posterior precision may be updated but its rate of update will be slower than T. This result assumes that the identified parameters are ãT-consistent, but similar differential rates of updates for identified and unidentified parameters can be established in the case of super consistent estimators. These results are illustrated by means of simple DSGE models.Bayesian identification, DSGE models, posterior updating, New Keynesian Phillips Curve

    The Impacts of North American BSE Discoveries on U.S. and Canadian Cattle Prices

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    Demand and Price Analysis, Research and Development/Tech Change/Emerging Technologies,

    Evidence of a Mira-like tail and bow shock about the semi-regular variable V CVn from four decades of polarization measurements

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    Polarization is a powerful tool for understanding stellar atmospheres and circumstellar environments. Mira and semi-regular variable stars have been observed for decades and some are known to be polarimetrically variable, however, the semi-regular variable V Canes Venatici displays an unusually large, unexplained amount of polarization. We present ten years of optical polarization observations obtained with the HPOL instrument, supplemented by published observations spanning a total interval of about forty years for V CVn. We find that V CVn shows large polarization variations ranging from 1 - 6%. We also find that for the past forty years the position angle measured for V CVn has been virtually constant suggesting a long-term, stable, asymmetric structure about the star. We suggest that this asymmetry is caused by the presence of a stellar wind bow shock and tail, consistent with the star's large space velocity.Comment: 8 pages, 5 figures, 1 table. Accepted for publication in A&

    A practical method of predicting wellbeing at work: the Wellbeing Process Tool

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    Research has shown that short measuring instruments (e.g. the Wellbeing Process Questionnaire – WPQ) can provide information about aspects of wellbeing. These measures have been shown to have good validity and reliability and can be used to assess multi-dimensional models (e.g. the Demands-Resources-Individual Effects model – DRIVE). The present article describes the practical application of the approach

    Zipline-Related Injuries Treated in US EDs, 1997-2012

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    Purpose To investigate the epidemiology of zipline-related injuries in the United States. Basic Procedures The National Electronic Injury Surveillance System database was used to examine non-fatal zipline-related injuries treated in US emergency departments (EDs) from 1997 through 2012. Sample weights were applied to calculate national estimates. Main Findings From 1997 through 2012, an estimated 16850 (95% CI, 13188-20512) zipline-related injuries were treated in US EDs. The annual injury rate per 1 million population increased by 52.3% from 7.64 (95% CI, 4.86-10.42) injuries in 2009 (the first year with a stable annual estimate) to 11.64 (95% CI, 7.83-15.45) injuries in 2012. Patients aged 0-9 years accounted for 45.0% of injuries, females made up 53.1% of injuries, and 11.7% of patients required hospitalization. Fractures accounted for the largest proportion of injuries (46.7%), and the upper extremities were the most commonly injured body region (44.1%). Falls were the most common mechanism of injury, accounting for 77.3% of injuries. Among cases where the location of the injury event was known, 30.8% of injuries occurred in a residential setting and 69.2% occurred in a public place. Principal Conclusions This study is the first to characterize the epidemiology of zipline-related injuries using a nationally representative database. The rapid increase in zipline-related injuries in recent years suggests the need for additional safety guidelines and regulations. Commercial ziplines and publicly accessible non-commercial ziplines should be subject to uniform safety standards in all states and jurisdictions across the US, and homemade ziplines should not be used

    Coaligned observations of solar magnetic fields at different heights: MSFC Center director's discretionary fund final report (Project No. 88-10)

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    The objective was to develop the capability for and coaligned observations of the structure and evolution of the Sun's magnetic field at two different heights in the solar atmosphere: the photosphere, which is the lowest region observable with optical telescopes; and the chromosphere, which lies just above the photosphere and is the region where the magnetic field dominates the gas motion so that a well-ordered structure governed by the field is observed. By obtaining this three-dimensional picture of the solar magnetic field, a better understanding can be developed of the magnetic forces that produce and control the dynamic, high-energy phenomena occurring in the solar atmosphere that can affect the entire heliosphere, including the terrestrial environment

    The cosmology dependence of weak lensing cluster counts

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    We present the main results of a numerical study of weak lensing cluster counting. We examine the scaling with cosmology of the projected-density-peak mass function. Our main conclusion is that the projected-peak and the three-dimensional mass functions scale with cosmology in an astonishingly close way. This means that, despite being derived from a two-dimensional field, the weak lensing cluster abundance can be used to constrain cosmology in the same way as the three-dimensional mass function probed by other types of surveys.Comment: 4 pages, 2 figures. Accepted for publication in ApJL. Figure 1 modified, unchanged conclusion
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