335 research outputs found

    Measuring and Understanding Connectivity

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    This report examines the correlation of Internet travel time to real-world travel times, and also compares the growth of the Internet to the growth of other technologies that connect people. In compiling a series of comprehensive datasets, and utilizing scripts to gather specific Internet and physical data, this project examines the impact of trends in connectivity on a local and national scale. Also investigated are the effects of routing on both forms of connectivity, as well as other influencing factors

    Application of wireless technologies to forward predict crop yields in the poultry production chain

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    Average bird weight is the primary measure of crop yield and is the basis for calculating payment for the grower by the wholesaler. Furthermore the profit per bird is very small. Thus very tight control of growing process is essential to ensure average bird weight is maximised. The important factors (air temperature, air humidity, Carbon Dioxide concentration and Ammonia concentration) that affect the intake of feed and water must be kept at their optimum during the progress of the growing cycle. These factors can be influenced by activating burners and opening the vents on walls of the growing house. It then follows that the burning and venting strategy will be influential on the average bird weight of the crop. Currently the burning and venting strategy is based on notional ideal levels and data from wall mounted sensors. This suffers from two fundamental problems; firstly the strategy is determined by ideals that may not be suitable for all growing houses and secondly the data is not measured from the chickens own airspace. Thus the management strategy is based on a model that may not reflect reality and on data that may not reflect reality  The “BOSCA” project addresses these problems by placing wireless environmental sensors into the chickens own airspace. This provides for direct measurement of the air experienced by the chickens and reports the recorded data in near real-time to a cloud based data management system. The sensor data is merged with the data from the growing house weighing scales in the cloud repository so a predictive model of average bird weight from the measured environmental data can be calibrated and validated. Furthermore, a timeshift can be applied to the environmental data during model calibration and validation so the average bird weight can be forward predicted by 72 hours (r2 up to 0.89 with neural networks). This gives the grower advance notice of a deviation from ideal feeding and watering conditions and the likely consequences of failing to take remedial action such as turning on the burners or venting the house

    Wildlife overpass structure size, distribution, effectiveness, and adherence to expert design recommendations

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    It is now well evidenced that wildlife crossing structures paired with exclusion fencing reduce wildlife vehicles collisions while facilitating wildlife connectivity across roadways. Managing animal mortality and subpopulation connectivity is crucial to successful species and landscape stewardship. Highway mitigation projects are large economic investments that remain on the landscape for many decades. Governments and planning agents thus strive to balance cost and benefit to build cost-effective structures with the greatest positive impact on local wildlife and motorists. Ideal dimensions of overpasses and underpasses vary by species, but scientists generally suggest that overpasses for large mammals should be approximately 50 m wide. Optimal width also depends on structure length, with longer structures requiring additional width. Accordingly, experts have suggested a width to length ratio of 0.8. We sought to assess how these recommendations manifested in practice—where agencies use this information to design and build structures while also balancing cost and logistical challenges—and the degree to which built structures conform to current recommendations. We identified 120 wildlife overpasses across the world that were constructed to reduce the negative impacts of roads. Using a novel measurement technique, we analyzed the dimensions of these 120 overpasses located in North America, Europe, Asia, and Oceania. The average width of the wildlife overpasses was 34 m. Most wildlife overpasses located in North America and Europe did not meet their respective dimensional expert guidelines. We investigate reasons explaining the non-compliance and provide recommendations for future overpass designs. Building on previous evidence showing that wider overpasses have increased crossing rates, we examined crossing rates for multiple large mammal species across 12 overpasses located in western North America. We qualitatively observed that wider North American overpasses (40–60 m), in or near compliance with expert guidelines, were associated with a more diverse set of species use and had nearly twice the average crossing rates when compared to non-compliant, narrow North American overpasses. In reviewing various studies from around the world, we conclude that wide overpasses (~50 m) continue to present ecologically sound and cost-effective solutions for decreasing the barrier of roadways, especially when targeting width-sensitive species and large assemblages of mammals. Future studies, however, are encouraged to further explore the specific instances when underpasses and narrower overpasses present more cost-effective ecological solutions, or how these structures can complement wide overpasses in successful wildlife crossing systems

    The hydrogenation of mandelonitrile over a Pd/C catalyst: towards a mechanistic understanding

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    A carbon supported Pd catalyst is used in the liquid phase hydrogenation of the aromatic cyanohydrin mandelonitrile (C6H5CH(OH)CH2CN) to afford the primary amine phenethylamine (C6H5CH2CH2NH2). Employing a batch reactor, the desired primary amine is produced in 87% selectivity at reaction completion. Detection of the by-product 2-amino-1-phenylethanol (C6H5CH(OH)CH2NH2) accounts for the remaining 13% and closes the mass balance. The reaction mechanism is investigated, with a role for both hydrogenation and hydrogenolysis processes established

    Hydrogenation of benzonitrile over supported Pd catalysts: kinetic and mechanistic insight

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    The liquid phase hydrogenation of benzonitrile over a 5wt% Pd/C catalyst using a stirred autoclave is investigated. The reaction conforms to a consecutive reaction sequence: firstly benzonitrile is hydrogenated to produce benzylamine, which subsequently undergoes a hydrogenolysis step to form toluene. Benzonitrile hydrogenation obeys first order kinetics with an activation energy of 27.6 kJ mol−1. In contrast, the benzylamine hydrogenolysis stage obeys zero order kinetics and exhibits an activation energy of 80.1 kJ mol−1. A 1wt% Pd/Al2O3 catalyst is additionally examined, which is also seen to support hydrogenolysis activity alongside the hydrogenation pathway. Gas phase transmission infrared spectroscopic measurements of the hydrogenation of benzonitrile and benzylamine over the 1wt% Pd/Al2O3 catalyst utilising hydrogen and deuterium are undertaken, which enable reaction schemes incorporating adsorption geometries of intermediate adsorption complexes to be proposed

    The production of tyramine via the selective hydrogenation of 4-hydroxybenzyl cyanide over a carbon-supported palladium catalyst

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    The selective production of primary amines is a problem that plagues heterogeneously catalysed nitrile hydrogenation reactions. Whilst the target amine tyramine (HOC6H4CH2CH2NH2) is biochemically available through the action of enzymes, synthetic routes to this species are not widely reported. Here, a heterogeneously catalysed method is proposed that utilises a Pd/C catalyst to effect the selective hydrogenation of 4-hydroxybenzyl cyanide within a three-phase reactor. The aforementioned selectivity issues are overcome by adjustment of various experimental parameters (hydrogen supply, agitation rate, temperature, use of an auxiliary agent) that result in improved catalytic performance, such that the desired tyramine salt (tyramine hydrogen sulphate) can be produced in quantitative yield. Accordingly, through consideration of the interconnectivity of hydrogenation and hydrogenolysis processes, a selective synthetic strategy is achieved with the findings suitable for extension to other substrates of this nature