250 research outputs found

    The State as Mujahid: Jihadist Norms in International Narrative of Saudi Arabia

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    This study explored Saudi narrative for the expression of jihadist norms and tested the extent to which Critical Constructivism can account for the presence (or absence) of those norms. Rather than identifying jihadist norms, this study found that contra-norms are expressed in Saudi narrative. These are expressed in a complex way, preserving the legitimacy of Saudi Arabia in multiple theatres. Further, it found Critical Constructivism is sufficient to explain the presence of these norms given the various power dynamics

    Health hazards of ultrafine metal and metal oxide powders

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    Study reveals that suggested threshold limit values are from two to fifty times lower than current recommended threshold limit values. Proposed safe limits of exposure to the ultrafine dusts are based on known toxic potential of various materials as determined in particle size ranges

    Energy input is primary controller of methane bubbling in subarctic lakes

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    Emission of methane (CH4) from surface waters is often dominated by ebullition (bubbling), a transport mode with high‐spatiotemporal variability. Based on new and extensive CH4 ebullition data, we demonstrate striking correlations (r2 between 0.92 and 0.997) when comparing seasonal bubble CH4 flux from three shallow subarctic lakes to four readily measurable proxies of incoming energy flux and daily flux magnitudes to surface sediment temperature (r2 between 0.86 and 0.94). Our results after continuous multiyear sampling suggest that CH4 ebullition is a predictable process, and that heat flux into the lakes is the dominant driver of gas production and release. Future changes in the energy received by lakes and ponds due to shorter ice‐covered seasons will predictably alter the ebullitive CH4 flux from freshwater systems across northern landscapes. This finding is critical for our understanding of the dynamics of radiatively important trace gas sources and associated climate feedback

    Thermoclinic Assessment Of A Preliminary Circulation Model For Lake George In The Jefferson Project

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    The Jefferson Project is a collaboration between the Rensselaer Polytechnic Institute, IBM, and the FUND for Lake George aimed at understanding and managing complex factors (road salt, storm water runoff, invasive species) threatening Lake George, New York. Lake George is located about 80 km north of Albany in upstate New York and is known internationally for its water clarity. Understanding the hydrodynamics of the lake is fundamental for creation and maintenance of a research and monitoring program for the early detection of and response to adverse environmental and biological change. In this work a 3D circulation model of the lake is developed to better understand the hydro-environmental conditions of the lake; forcing is by a combination of local public survey data for the water budget and atmospheric data from the NWS (NOAA National Weather Service). The model is validated by a combination of water chemistry data collected by Darrin Fresh Water Institute (DFWI) over the last three decades, and known empirical relationships of the lake\u27s structural profile. Numerical simulations run over several years to capture the seasonal progression of thermocline depth throughout the lake, the south to north salt and surface thermal gradients and the timing of the spring and fall overturn events. Validation is by comparison with physical and chemical measurements collected over the last three decades. The study presents a novel combination of observational data, numerical modelling and empirical relationships to better understand and predict the lake circulation, and consequently the natural ecosystem

    Estimating relative risk of within-lake aquatic plant invasion using combined measures of recreational boater movement and habitat suitability

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    Effective monitoring, prevention and impact mitigation of nonindigenous aquatic species relies upon the ability to predict dispersal pathways and receiving habitats with the greatest risk of establishment. To examine mechanisms affecting species establishment within a large lake, we combined observations of recreational boater movements with empirical measurements of habitat suitability represented by nearshore wave energy to assess the relative risk of Eurasian watermilfoil (Myriophyllum spicatum) establishment. The model was evaluated using information from a 17 year (1995–2012) sequence of M. spicatum presence and absence monitoring. M. spicatum presence was not specifically correlated with recreational boater movements; however its establishment appears to be limited by wave action in Lake Tahoe. Of the sites in the “High” establishment risk category (n = 37), 54% had current or historical infestations, which included 8 of the 10 sites with the highest relative risk. Of the 11 sites in the “Medium” establishment risk category, 5 had current or historical M. spicatum populations. Most (76%) of the sites in the “Low” establishment risk category were observed in locations with higher wave action. Four sites that received zero boater visits from infested locations were occupied by M. spicatum. This suggests that the boater survey either represents incomplete coverage of boater movement, or other processes, such as the movement of propagules by surface currents or introductions from external sources are important to the establishment of this species. This study showed the combination of habitat specific and dispersal data in a relative risk framework can potentially reduce uncertainty in estimates of invasion risk

    A trehalose biosynthetic enzyme doubles as an osmotic stress sensor to regulate bacterial morphogenesis

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    The dissacharide trehalose is an important intracellular osmoprotectant and the OtsA/B pathway is the principal pathway for trehalose biosynthesis in a wide range of bacterial species. Scaffolding proteins and other cytoskeletal elements play an essential role in morphogenetic processes in bacteria. Here we describe how OtsA, in addition to its role in trehalose biosynthesis, functions as an osmotic stress sensor to regulate cell morphology in Arthrobacter strain A3. In response to osmotic stress, this and other Arthrobacter species undergo a transition from bacillary to myceloid growth. An otsA null mutant exhibits constitutive myceloid growth. Osmotic stress leads to a depletion of trehalose-6-phosphate, the product of the OtsA enzyme, and experimental depletion of this metabolite also leads to constitutive myceloid growth independent of OtsA function. In vitro analyses indicate that OtsA can self-assemble into protein networks, promoted by trehalose-6-phosphate, a property that is not shared by the equivalent enzyme from E. coli, despite the latter's enzymatic activity when expressed in Arthrobacter. This, and the localization of the protein in non-stressed cells at the mid-cell and poles, indicates that OtsA from Arthrobacter likely functions as a cytoskeletal element regulating cell morphology. Recruiting a biosynthetic enzyme for this morphogenetic function represents an intriguing adaptation in bacteria that can survive in extreme environments
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