2,491 research outputs found

    Identifying invertebrate invasions using morphological and molecular analyses: North American Daphnia ‘pulex’ in New Zealand fresh waters

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    We used a DNA barcoding approach to identify specimens of the Daphnia pulex complex occurring in New Zealand lakes, documenting the establishment of non-indigenous North American Daphnia 'pulex'. Morphological delineation of species in this complex is problematic due to a lack of good morphological traits to distinguish the species, as there is a relatively high degree of morphological stasis within the group through evolutionary time. Accordingly, genetic analyses were used to determine the specific identity and likely geographic origin of this species. Morphologically, individuals most closely resembled Daphnia pulicaria or Daphnia pulex sensu lato, which cannot be separated morphologically. Furthermore, each of these taxa comprises separate species in North America and Europe, despite carrying the same names. We identified individuals using a 658 bp nucleotide portion of the mitochondrial cytochrome c oxidase subunit 1 gene (COI) as North American Daphnia 'pulex', being distinct from European Daphnia pulex sensu stricto and D. pulicaria from Europe or North America. Cellulose allozyme electrophoresis was used to confirm that individuals were not hybrids with D. pulicaria. North American Daphnia 'pulex' in New Zealand were first recorded in New Zealand from South Island lakes that are popular for overseas recreational fishers, indicating a possible source of introduction for this species (e.g. on/in fishing gear). Our study provides an additional example of how genetic techniques can be used for the accurate identification of non-indigenous taxa, particularly when morphological species determination is not possible. The growth of global databases such as GenBank and Barcode of Life Datasystems (BOLD) will further enhance this identification capacity

    Timing verification of dynamically reconfigurable logic for Xilinx Virtex FPGA series

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    This paper reports on a method for extending existing VHDL design and verification software available for the Xilinx Virtex series of FPGAs. It allows the designer to apply standard hardware design and verification tools to the design of dynamically reconfigurable logic (DRL). The technique involves the conversion of a dynamic design into multiple static designs, suitable for input to standard synthesis and APR tools. For timing and functional verification after APR, the sections of the design can then be recombined into a single dynamic system. The technique has been automated by extending an existing DRL design tool named DCSTech, which is part of the Dynamic Circuit Switching (DCS) CAD framework. The principles behind the tools are generic and should be readily extensible to other architectures and CAD toolsets. Implementation of the dynamic system involves the production of partial configuration bitstreams to load sections of circuitry. The process of creating such bitstreams, the final stage of our design flow, is summarized

    Two novel flight-interception trap designs for low-cost forest insect surveys

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    This paper introduces two passive trap designs for the survey of flying Coleoptera and other insects which can be constructed on very low budgets at < £1 per trap. A trunk window trap and an aerial flight-interception trap are presented, based on commonly used designs, but using much cheaper materials than standard. Construction diagrams are given, along with a description of trap installation, operation and beetle species found using these methods during a survey of Ayr Gorge Woodland, South-West Scotland. The traps were found to be robust and easy to operate. It is hoped that these trap designs will be of use to charitable organisations, students and amateurs who may previously have been unable to consider monitoring flying insects at large scales due to the prohibitive cost of equipment

    The potential of dissociated methanol as a fuel for spark ignition engines

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    Bibliography: pages 128-134.This thesis examines the potential of dissociated methanol to increase the thermal efficiency or reduce the exhaust emissions of an internal combustion engine. It is assumed that liquid methanol will be dissociated onboard a vehicle using engine waste heat to produce a gas consisting of hydrogen and carbon monoxide in a molar ratio of 2:1. Tests were conducted on a single cylinder engine using liquid, vaporised and dissociated methanol fuels. The dissociated methanol was derived from bottled hydrogen and carbon monoxide. Indicated thermal efficiency together with methane, methanol and formaldehyde exhaust emissions were measured. The effect of the carbon monoxide in the dissociated methanol on efficiency was investigated by operating the engine on both hydrogen and carbon monoxide separately. The results for thermal efficiency showed that the presence of carbon monoxide resulted in a lower efficiency than for pure hydrogen. However, if the waste heat recovered in the dissociation reaction is not included in the calorific value of the fuel, then dissociated methanol offers a significant improvement in thermal efficiency compared to liquid methanol. Vaporised methanol offers efficiencies comparable to dissociated methanol for mixtures leaner than stoichiometric, again benefitting from the recovered heat. The results for exhaust emissions showed that methanol and formaldehyde emissions were effectively eliminated and methane emissions significantly reduced with dissociated methanol fueling. Vaporised methanol fueling reduced emissions of these species to approximately ⅓ of the value with liquid methanol fueling. NOx emissions may be expected to increase for both vaporised and dissociated methanol. Preliminary design considerations indicated that there is probably insufficient high temperature energy in the exhaust gas to dissociate all the engine's fuel requirement. As a result, it was concluded that while vaporised methanol could not match the increase in efficiency or the reduction in exhaust emissions of dissociated methanol, its greater practicability for onboard implementation probably makes it a better candidate for future development

    Tectonic Geomorphology of the NE Clark Canyon Reservoir Area, Beaverhead County, Montana

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    The Clark Canyon Reservoir occupies the northern Red Rock Valley in Beaverhead County, southwestern Montana. The region is a part of the northern Basin and Range province of western North America. It is characterized by a series of north-south trending extensional basins that have served as sediment traps since their formation. The Red Rock Valley is drained by the Red Rock River, which flows from Lower Red Rock Lake north to the Clark Canyon Reservoir at its confluence with the Beaverhead River. This river system has been active in the Red Rock Valley since the Miocene epoch. This study characterizes gravels of the Miocene-Pliocene Sixmile Creek Formation, Quaternary alluvial fans, and Quaternary fluvial terraces in the area of the northern Clark Canyon Reservoir. Nearly all cobbles present within the Sixmile Creek Formation and Quaternary fluvial terraces are well rounded, indicating extensive fluvial transport. Cobbles in the Quaternary fan deposits were recycled from the Sixmile Creek Formation. The lithologies of randomly selected clasts in exposed Sixmile Creek Formation and reworked alluvial fan gravels were dominated by quartzites that were likely derived from the Proterozoic Belt Supergroup and Cambrian Flathead Formation and basalt and rhyolite likely derived from the underlying Eocene Dillon volcanics. Undisturbed Sixmile Creek Formation fluvial gravels form deposits at least 100 m thick. The Quaternary fluvial terrace gravels had smaller clast sizes and were polymictic, containing minor gneissic pebbles. A study of cobble orientations in undisturbed sedimentary deposits indicated paleoflow directions in the depositing fluvial systems based on the dynamics of bed armor formation in active stream channels. Cobbles in the Sixmile Creek Formation indicated fluvial flow to the SW in Miocene-Pliocene time. In situ outcrops were rare for the alluvial fan deposits, but a single site indicated down-slope flow to the west. The Quaternary fluvial terrace gravel was well imbricated and indicated paleo flow to the NE, as it is today. These results were consistent with the lithologic provenance data, and show that the ancient Beaverhead/Red Rock River system flowed SW during the Miocene-Pliocene but transitioned to NE during the Quaternary. The change may have been related to faulting associated with tectonic uplift of the Continental Divide, which presently forms the headwaters of the Red Rock River. Geologic mapping and slope analysis demonstrated that the Monument Hill Fault and a newly mapped Clark Canyon Reservoir Fault cut some Quaternary fans, but were buried by others and that the traces of the faults trend to within 500 m of Clark Canyon Dam
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