28,977 research outputs found

    Atlas and checklist of the bark and ambrosia beetles of Texas and Oklahoma (Curculionidae: Scolytinae and Platypodinae)

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    180 species of bark and ambrosia beetles (Curculionidae: Scolytinae and Platypodinae) are known to occur in Texas and Oklahoma. 175 species are known from Texas, 35 of which are reported here for the first time. 78 species are known from Oklahoma, 47 of which are new records for the state. Based on overall distribution patterns the largest group of species found in Texas and virtually all known from Oklahoma are widely distributed in eastern and southeastern North America, reaching their southwestern limits here. In the case of Texas other large elements include Neotropical elements shared with Mexico and a large number found in southwestern North America. New distribution and significant new host records are discussed. Distribution maps are included for most species and a checklist is provided as an appendix

    Calibration, navigation, and registration of MAMS data for FIFE

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    The International Satellite Land Surface Climatology Project (ISLSCP) was conducted to study the interaction of the atmosphere with the land surface and the research problems associated with the interpretation of satellite data over the Earth's land surface. The experimental objectives of the First ISLSCP Field Experiment (FIFE) were the simultaneous acquisition of satellite, atmospheric, and surface data and to use these data to understand the processes controlling energy/mass exchange at the surface. The experiment site is a 15 x 15 km area southeast of Manhattan, Kansas, intersected by Interstate 70 and Kansas highway 177. The Konza Prairie portion is 5 x 5 km and is a controlled experiment site consisting primarily of native tall grass prairie vegetation. The remainder of the site is grazing and farm land with trees along creek beds that are scattered over the area. Airborne multispectral imagery from the Multispectral Atmospheric Mapping Sensor (MAMS) was collected over this region on two days during Intensive Field Campaign-1 (1FC-1) to study the time and space variability of remotely-sensed geophysical parameters. These datasets consist of multiple overflights covering about a 60-min period during late morning on June 4, 1987 and shortly after dark on the following day. Image data from each overpass were calibrated and Earth located with respect to each other using aircraft inertial navigation system parameters and ground control points. These were the first MAMS flights made with 10-bit thermal data

    Transport of Vegetables in Papua New Guinea

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    Crop Production/Industries, Marketing,

    Charge and spin state readout of a double quantum dot coupled to a resonator

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    State readout is a key requirement for a quantum computer. For semiconductor-based qubit devices it is usually accomplished using a separate mesoscopic electrometer. Here we demonstrate a simple detection scheme in which a radio-frequency resonant circuit coupled to a semiconductor double quantum dot is used to probe its charge and spin states. These results demonstrate a new non-invasive technique for measuring charge and spin states in quantum dot systems without requiring a separate mesoscopic detector

    Empirical modelling and simulation of transmission loss between wireless sensor nodes in gas turbine engines

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    Transmission loss measurements between a grid of hypothetical WSN node locations on the surface of a gas turbine engine are reported for eight frequencies at 1 GHz intervals in the frequency range 3.0 to 11.0 GHz. An empirical transmission loss model is derived from the measurements. The model is incorporated into an existing system channel model implemented using Simulink as part of a wider project concerning the development of WSNs for the testing and condition monitoring of gas turbine engines

    Multiple transport disadvantages: A cluster analysis of the socio-spatial distribution of levels of accessibility and pedestrian mobility in a metropolitan area.

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    The concept of social justice is increasingly called upon in the assessment of the social and environmental sustainability of urban transport. This paper brings together two strands of the literature on this topic: the role of accessibility in social inclusion and the distribution of the environmental impacts of transport. Using the Lisbon Metropolitan Area as case study, we test if there are cumulative social inequalities in terms of accessibility and pedestrian mobility, considering that the latter depends on local environmental quality. We use GIS methods to estimate a series of neighbourhood-level indicators, such as private and public transport accessibility to jobs and urban facilities, community severance and pedestrian exposure to traffic noise. Neighbourhoods are then classified based on the scores of those indicators at two moments in time. We found six clusters. Accessibility increases and pedestrian mobility decreases as we move from the ‘main centre’ towards the ‘suburban’, ‘small centres’, ‘semi-rural’ and ‘rural’ clusters. A sixth cluster is labelled ‘multiple disadvantages’ and groups dispersed neighbourhoods that fare poorly in all indicators. The clusters are then characterized in terms of their socio-economic composition. We find that central areas usually have elderly populations, while rural areas and the “multiple disadvantaged” cluster tend to have low-qualified populations. We also test if disadvantages based on a neighbourhood’s location persist after accounting for the daily destinations and travel modes used by its population. We find that ‘multiple disadvantaged’ areas have the poorest scores in time to work, effects of congestion, and pedestrian noise exposures for commuters on the way to work. The main conclusion is that ‘hotspots’ of multiple transport-related disadvantages tend to have populations traditionally at risk of social exclusion. More emphasis should be put on locally-based interventions on and public participation methods in the definition of strategies for urban transport planning

    Van der Waals interactions in the ground state of Mg(BH4)2 from density functional theory

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    In order to resolve an outstanding discrepancy between experiment and theory regarding the ground-state structure of Mg(BH4)2, we examine the importance of long-range dispersive interactions on the compound's thermodynamic stability. Careful treatment of the correlation effects within a recently developed nonlocal van der Waals density functional (vdW-DF) leads to a good agreement with experiment, favoring the {\alpha}-Mg(BH4)2 phase (P6122) and a closely related Mn(BH4)2-prototype phase (P3112) over a large set of polymorphs at low temperatures. Our study demonstrates the need to go beyond (semi)local density functional approximations for a reliable description of crystalline high-valent metal borohydrides.Comment: Phys. Rev. B, accepted, 7 pages, 4 figure

    Reactions of C2_2({\it a}3Piu^3Pi_u) with selected saturated alkanes: A temperature dependence study

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    We present a temperature dependence study on the gas phase reactions of the C2_2({\it a}3Piu^3Pi_u) radical with a selected series of saturated alkanes (C2_2H6_6, C3_3H8_8, n-C4_4H10_10, i-C4_4H10_10, and n-C6_6H14_14) by means of pulsed laser photolysis/laser-induced fluorescence technique. The bimolecular rate constants for these reactions were obtained between 298 and 673 K. A pronounced negative temperature effect was observed for n-C4_4H10_10, i-C4_4H10_10, and n-C6_6H14_14 and interpreted in terms of steric hindrance of the more reactive secondary or tertiary C-H bonds by less reactive CH3_3 groups. Detailed analysis of our experimental results reveals quantitatively the temperature dependence of reactivities for the primary, secondary, and tertiary C-H bonds in these saturated alkanes and further lends support to a mechanism of hydrogen abstraction.Comment: 26 pages, 8 figures, 1 table, 30 references; accepted to JC
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