282 research outputs found

    Thermoelectricity of EuCu{2}(Ge{1-x}Si{x}){2} intermetallics

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    The evolution of the thermopower EuCu{2}(Ge{1-x}Si{x}){2} intermetallics, which is induced by the Si-Ge substitution, is explained by the Kondo scattering of conduction electrons on the Eu ions which fluctuate between the magnetic 2+ and non-magnetic 3+ Hund's rule configurations. The Si-Ge substitution is equivalent to chemical pressure which modifies the coupling and the relative occupation of the {\it f} and conduction states.Comment: 2 pages, Proceedings of the SCES 2005 confernece. Physica B (2006), in pres

    Exploration of a Polarized Surface Bidirectional Reflectance Model Using the Ground-Based Multiangle Spectropolarimetric Imager

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    Accurate characterization of surface reflection is essential for retrieval of aerosols using downward-looking remote sensors. In this paper, observations from the Ground-based Multiangle SpectroPolarimetric Imager (GroundMSPI) are used to evaluate a surface polarized bidirectional reflectance distribution function (PBRDF) model. GroundMSPI is an eight-band spectropolarimetric camera mounted on a rotating gimbal to acquire pushbroom imagery of outdoor landscapes. The camera uses a very accurate photoelastic-modulator-based polarimetric imaging technique to acquire Stokes vector measurements in three of the instrument's bands (470, 660, and 865 nm). A description of the instrument is presented, and observations of selected targets within a scene acquired on 6 January 2010 are analyzed. Data collected during the course of the day as the Sun moved across the sky provided a range of illumination geometries that facilitated evaluation of the surface model, which is comprised of a volumetric reflection term represented by the modified Rahman-Pinty-Verstraete function plus a specular reflection term generated by a randomly oriented array of Fresnel-reflecting microfacets. While the model is fairly successful in predicting the polarized reflection from two grass targets in the scene, it does a poorer job for two manmade targets (a parking lot and a truck roof), possibly due to their greater degree of geometric organization. Several empirical adjustments to the model are explored and lead to improved fits to the data. For all targets, the data support the notion of spectral invariance in the angular shape of the unpolarized and polarized surface reflection. As noted by others, this behavior provides valuable constraints on the aerosol retrieval problem, and highlights the importance of multiangle observations.NASAJPLCenter for Space Researc

    Are we planning blue-green infrastructure opportunistically or strategically? Insights from Sydney, Australia

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    Strategic placement of water-sensitive urban design (WSUD) is essential in optimising its performance and maximising co-benefits. However, little is known about the current placement and interconnectedness between WSUD assets and the performance of current planning strategies. We evaluated the placement of existing WSUDs in a highly urbanised catchment in Sydney, Australia. We used a three-step process: (1) compiling a comprehensive spatial asset database, (2) performing spatial correlation analysis between asset locations and biophysical, urban form and socioeconomic variables and (3) using a novel approach to facilitate holistic understanding through analysing asset locations compared with the outcome of the spatial suitability analysis tool (SSANTO). WSUD coverage was generally low, with clustering in some municipalities. Placement was constrained by physical variables, such as slope, limited space and varying land uses. However, placement was not detectably influenced by most socioeconomic variables. SSANTO's suitability score at asset locations was only slightly higher than average, suggesting that the placement of existing WSUD was opportunistic, rather than strategically planned. Further development and implementation of tools able to account for spatial constraints will help guide future WSUD placement as a component of green urban stormwater management

    Gap ratio in anharmonic charge-density-wave systems

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    Many experimental systems exist that possess charge-density-wave order in their ground state. While this order should be able to be described with models similar to those used for superconductivity, nearly all systems have a ratio of the charge-density-wave order parameter to the transition temperature that is too high for conventional theories. Recent work explained how this can happen in harmonic systems, but when the lattice distortion gets large, anharmonic effects must play an increasingly important role. Here we study the gap ratio for anharmonic charge-density wave systems to see whether the low-temperature properties possess universality as was seen previously in the transition temperature and to see whether the explanation for the large gap ratios survives for anharmonic systems as well.Comment: (5 pages, 3 figures, ReVTeX

    Influence of gaseous laser in continuous-wave and pulse regimes on biomaterial characteristics

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    Aromatic plants and laser beam wavelength in the red range of visible spectra (623.8 nm), most commonly used for treating plant species, were selected. As there is not much information in the references, it is necessary to set a scale with qualitative and partially quantitative evaluations of the results. Specimens of thyme seed (Thymus vulgaris) were selected as aromatic plants for studying the effect of low-power lasers on plant development, and continuous He-Ne laser, with irradiation times in the range of minutes

    Rosetta mission: Electron scattering cross sections-data needs and coverage in BEAMDB database

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    The emission of [O I] lines in the coma of Comet 67P/Churyumov-Gerasimenko during the Rosetta mission have been explained by electron impact dissociation of water rather than the process of photodissociation. This is the direct evidence for the role of electron induced processing has been seen on such a body. Analysis of other emission features is handicapped by a lack of detailed knowledge of electron impact cross sections which highlights the need for a broad range of electron scattering data from the molecular systems detected on the comet. In this paper, we present an overview of the needs for electron scattering data relevant for the understanding of observations in coma, the tenuous atmosphere and on the surface of 67P/Churyumov-Gerasimenko during the Rosetta mission. The relevant observations for elucidating the role of electrons come from optical spectra, particle analysis using the ion and electron sensors and mass spectrometry measurements. To model these processes electron impact data should be collated and reviewed in an electron scattering database and an example is given in the BEAMD, which is a part of a larger consortium of Virtual Atomic and Molecular Data Centre-VAMDC

    Study of interstrip gap effects and efficiency for full energy detection of Double Sided Silicon Strip Detectors

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    In this work is reported a study on the response of double sided silicon strip detectors. In order to investigate the eļ¬€ect of the electrode segmentation on the detector response, two experiments were performed aimed to measure the eļ¬ƒciency for full energy detection. Results show that the eļ¬ƒciency for full energy detection, that is directly related to eļ¬€ective width of the inter-strip region, varies with both detected ion energy and bias voltage. The experimental results are qualitatively reproduced by a simplified model based on the Shockley-Ramo-Gunn framework
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