1,640 research outputs found
A Circumstellar Disc in a High-Mass Star Forming Region
We present an edge-on Keplerian disc model to explain the main component of
the 12.2 and 6.7 GHz methanol maser emission detected toward NGC7538-IRS1 N.
The brightness distribution and spectrum of the line of bright masers are
successfully modeled with high amplification of background radio continuum
emission along velocity coherent paths through a maser disc. The bend seen in
the position-velocity diagram is a characteristic signature of differentially
rotating discs. For a central mass of 30 solar masses, suggested by other
observations, our model fixes the masing disc to have inner and outer radii of
about 350 AU and 1000 AU.Comment: 11 pages, accepted for publication in ApJ Letter
Methods for monitoring for the population consequences of disturbance in marine mammals : a review
This work was sponsored by the Office of Naval Research: Marine Mammal Biology Program, under award N000141612858.Assessing the non-lethal effects of disturbance and their population-level consequences is a significant ecological and conservation challenge, because it requires extensive baseline knowledge of behavioral patterns, life-history and demography. However, for many marine mammal populations, this knowledge is currently lacking and it may take decades to fill the gaps. During this time, undetected population declines may occur. In this study we identify methods that can be used to monitor populations subject to disturbance and provide insights into the processes through which disturbance may affect them. To identify and address the knowledge gaps highlighted above, we reviewed the literature to identify suitable response variables and methods for monitoring these variables. We also used existing models of the population consequences of disturbance (PCoD) to identify demographic characteristics (e.g., the proportion of immature animals in the population, or the ratio of calves/pups to mature females) that may be strongly correlated with population status and therefore provide early warnings of future changes in abundance. These demographic characteristics can be monitored using established methods such as visual surveys combined with photogrammetry, and capture-recapture analysis. Individual health and physiological variables can also inform PCoD assessment and can be monitored using photogrammetry, remote tissue sampling, hands-on assessment and individual tracking. We then conducted a workshop to establish the relative utility and feasibility of all these approaches for different groups of marine mammal species. We describe how future marine mammal monitoring programs can be designed to inform population-level analysis.Publisher PDFPeer reviewe
Down-Regulation of Porcine Heart Diaphorase Reactivity by Trimanganese Hexakis(3,5-Diisopropylsalicylate), Mn3(3,5-DIPS)6, and Down-Regulation of Nitric Oxide Synthase Reactivity by Mn3(3,5-DIPS)6 and Cu(II)2(3,5-DIPS)4
Purposes of this work were to examine the plausible down-regulation of porcine heart diaphorase
(PHD) enzyme reactivity and nitric oxide synthase (NOS) enzyme
reactivity by trimanganese hexakis(3,5-diisopropylsalicylate), [Mn3(3,5-DIPS)6]
as well as dicopper tetrakis(3,5- diisopropylsalicylate, [Cu(II)2(3,5-DIPS)4]
as a mechanistic accounting for their pharmacological activities
Advances in Measuring the Apparent Optical Properties (AOPs) of Optically Complex Waters
This report documents new technology used to measure the apparent optical properties (AOPs) of optically complex waters. The principal objective is to be prepared for the launch of next-generation ocean color satellites with the most capable commercial off-the-shelf (COTS) instrumentation. An enhanced COTS radiometer was the starting point for designing and testing the new sensors. The follow-on steps were to apply the lessons learned towards a new in-water profiler based on a kite-shaped backplane for mounting the light sensors. The next level of sophistication involved evaluating new radiometers emerging from a development activity based on so-called microradiometers. The exploitation of microradiometers resulted in an in-water profiling system, which includes a sensor networking capability to control ancillary sensors like a shadowband or global positioning system (GPS) device. A principal advantage of microradiometers is their flexibility in producing, interconnecting, and maintaining instruments. The full problem set for collecting sea-truth data--whether in coastal waters or the open ocean-- involves other aspects of data collection that were improved for instruments measuring both AOPs and inherent optical properties (IOPs), if the uncertainty budget is to be minimized. New capabilities associated with deploying solar references were developed as well as a compact solution for recovering in-water instrument systems from small boats
Central contracts in Test cricket: a model of best practice?
Across the last two decades, management of international cricket players has changed substantially, with the main Test playing nations using central contracts to guide their team selection. Increased management control over player workload has been a key focus of this. This paper aims to analyse selection in relation to performance for eight Test playing nations in 1,135 matches over thirty years (1985-2015), particularly in relation to the introduction of central contracts. The results demonstrated a relationship between selection stability (i.e. changes made) and performance (overall results and win ratio). The improvement was more pronounced immediately following the introduction of a contract system, as the competitive advantage appears to be at its highest in the two years following their introduction. The data presented argues that the implementation of central contracts as a best practice model has been a beneficial addition to nations' performance in Test matches. Despite this, team managers, coaches and selectors should focus their work on developing an organisational culture where the elite environment has long term stability as its focus. This is particularly pertinent as selection uncertainty can be a de-stabilising factor, as suggested in this paper and in previous research
Optical Sensors for Planetary Radiant Energy (OSPREy): Calibration and Validation of Current and Next-Generation NASA Missions
A principal objective of the Optical Sensors for Planetary Radiance Energy (OSPREy) activity is to establish an above-water radiometer system as a lower-cost alternative to existing in-water systems for the collection of ground-truth observations. The goal is to be able to make high-quality measurements satisfying the accuracy requirements for the vicarious calibration and algorithm validation of next-generation satellites that make ocean color and atmospheric measurements. This means the measurements will have a documented uncertainty satisfying the established performance metrics for producing climate-quality data records. The OSPREy approach is based on enhancing commercial-off-the-shelf fixed-wavelength and hyperspectral sensors to create hybridspectral instruments with an improved accuracy and spectral resolution, as well as a dynamic range permitting sea, Sun, sky, and Moon observations. Greater spectral diversity in the ultraviolet (UV) will be exploited to separate the living and nonliving components of marine ecosystems; UV bands will also be used to flag and improve atmospheric correction algorithms in the presence of absorbing aerosols. The short-wave infrared (SWIR) is expected to improve atmospheric correction, because the ocean is radiometrically blacker at these wavelengths. This report describes the development of the sensors, including unique capabilities like three-axis polarimetry; the documented uncertainty will be presented in a subsequent report
Sedentary behavior and subclinical atherosclerosis in African Americans: cross-sectional analysis of the Jackson heart study
BACKGROUND: Previous studies have reported conflicting results as to whether an association exists between sedentary time and cardiovascular disease (CVD) risk among African Americans. These studies, however, were limited by lack of consideration of sedentary behavior in leisure versus non-leisure settings. To elucidate this relation, we investigated the associations of television (TV) viewing time and occupational sitting with carotid intima-media thickness (CIMT), a subclinical atherosclerosis measure, in a community-based sample of African Americans. METHODS: We studied 3410 participants from the Jackson Heart Study, a single-site, community-based study of African Americans residing in Jackson, MS. CIMT was assessed by ultrasonography and represented mean far-wall thickness across right and left sides of the common carotid artery. TV viewing time, a measure of leisure sedentary behavior, and occupational sitting, a measure of non-leisure sedentary behavior, were assessed by questionnaire. RESULTS: In a multivariable regression model that included physical activity and CVD risk factors, longer TV viewing time (2-4 h/day and >4 h/day) was associated with greater CIMT (adjusted mean ± SE difference from referent [4 h/day; P-trend =0.001). In contrast, more frequent occupational sitting ('sometimes' and 'often/always') was associated with lower CIMT (adjusted mean ± SE difference from referent ['never/seldom']:-0.021 ± 0.009 mm for 'sometimes', and-0.018 ± 0.008 mm for 'often/always'; P-trend = 0.042). CONCLUSIONS: Longer TV viewing time was associated with greater CIMT, while occupational sitting was associated with lower CIMT. These findings suggest the role of sedentary behaviors in the pathogenesis of CVD among African Americans may vary by whether individuals engage in leisure versus non-leisure sedentary behaviors
The effect of vertical ductions on the near lateral phoria
The effect of vertical ductions on the near lateral phori
Spatial description of hake-directed fishing activity off the west coast of South Africa
Historically, the two species of Cape hakes Merluccius capensis and M. paradoxus off South Africa were commercially exploited exclusively by demersal trawling. In 1994, hake-directed demersal longline was introduced on an experimental basis, and in 1998 was initiated as a commercial fishing sector. The effect of a combined fleet composed of both trawlers and longliners on the Cape hake resource is not fully understood. Analysis of fishing intensity and catch-rate data revealed that the highest catch rates were found around the 400m and 500m isobaths for the trawl and longline fisheries respectively. Catch rates from both fishing sectors were also noted to be higher over sediments with a sand component. Differences between areas of the highest fishing intensity and highest catch rates were noted. In addition to other factors, it is suggested that a ‘friction of distance’ effect applies — vessels will trade-off higher catch rates with the increased costs associated with fishing in deeper waters
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