3,554 research outputs found

    A wireless sensor network system deployment for detecting stick slip motion in glaciers

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    The behaviour of glaciers is an area in which only limited research has been carried out due to the difficulties of monitoring sub-glacial movements. The authors believe that this can be addressed by the deployment of a wireless sensor network, consisting of heterogeneous sensors to instrument this activity. By deploying a sensor network measurements can be taken for a longer period than would otherwise be possible. The initial designs for this sensor network are presented along with details of some of the challenges posed by the project

    Elastic Form Factors of 3,4^{3,4}He up to Large Q2Q^2

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    Elastic electron scattering off 3^3He and 4^4He has recently been studied at forward and backward scattering angles in Hall A at JLab. The results will provide accurate data on the elastic form factors, charge and magnetic for 3^3He and charge only for 4^4He, up to squared momentum transfer Q2Q^2-values of 3.2 GeV2^2.Comment: 3 pages, Proceedings of EFB2

    On the universal X-ray luminosity function of binary X-ray sources in galaxies

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    The empirically determined universal power-law shape of X-ray luminosity function of high mass X-ray binaries in galaxies is explained by fundamental mass-luminosity and mass-radius relations for massive stars.Comment: 4 pages, plain LaTeX, no figures. Submitted to Astronomy Letter

    HESS J1507-622: an unique unidentified source off the Galactic Plane

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    Galactic very high energy (VHE, > 100 GeV) gamma ray sources in the inner Galaxy H.E.S.S. survey tend to cluster within 1 degree in latitude around the Galactic plane. HESS J1507-622 instead is unique, since it is located at latitude of ~3.5 degrees. HESS J1507-622 is slightly extended over the PSF of the instrument and hence its Galactic origin is clear. The search for counterparts in other wavelength regimes (radio, infrared and X-rays) failed to show any plausible counterparts; and given its position off the Galactic plane and hence the absorption almost one order of magnitude lower, it is very surprising to not see any counterparts especially at X-rays wavelengths (by ROSAT, XMM Newton and Chandra). Its latitude implies that it is either rather close, within about 1 kpc, or is located well off the Galactic plane. And also the models reflect the uniqueness of this object: a leptonic PWN scenario would place this source due to its quite small extension to multi-kpc distance whereas a hadronic scenario would preferentially locate this object at distances of < 1 kpc where the density of target material is higher

    New unidentified H.E.S.S. Galactic sources

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    H.E.S.S. is one of the most sensitive instruments in the very high energy (VHE; > 100 GeV) gamma-ray domain and has revealed many new sources along the Galactic Plane. After the successful first VHE Galactic Plane Survey of 2004, H.E.S.S. has continued and extended that survey in 2005-2008, discovering a number of new sources, many of which are unidentified. Some of the unidentified H.E.S.S. sources have several positional counterparts and hence several different possible scenarios for the origin of the VHE gamma-ray emission; their identification remains unclear. Others have so far no counterparts at any other wavelength. Particularly, the lack of an X-ray counterpart puts serious constraints on emission models. Several newly discovered and still unidentified VHE sources are reported here.Comment: ICRC 2009 proceeding

    Herkomstonderzoek Beuk in Nederland

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    In dit rapport worden de resultaten van toetsing van 20 herkomsten van beuk uit Nederland behandeld. Hiervan zijn reeds 8 herkomsten opgenomen in de Rassenlijst Bomen in de categorie 'geselecteerd uitgangsmateriaal'. Door gebruik te maken van herkomsten, die goed teeltmateriaal leveren is de kans het grootst dat een beplanting succes: vol aangeplant kan worden onder onze ecologische omstandigheden. Het onderzoek is onderdeel van het Cultuur: en Gebruikswaarde Onderzoek (CGO) ten behoeve van de Rassenlijst Bomen. De beuk wordt als een belangrijke loofboomsoort voor het Nederlandse bos beschouwd. Het grootste deel van het beukenbos bevindt zich op de zandgronden in het midden en het oosten van Nederland. Het beleid is momenteel gericht op verdere uitbreiding van het beukenareaal. Behalve bosbouwkundig belangrijke eigenschappen als groei en vorm zijn wellicht nog belangrijker de eigenschappen als tijdstip van uitlopen, het slagingspercentage en de overle: ving, die bepalen of een herkomst hier thuis hoort en met succes aangeplant kan worden onder onze ecologische omstandigheden. In 1987 werden vijf proefvelden aangelegd met acht Nederlandse herkomsten, die opgenomen zijn in de Rassenlijst Bomen in de categorie 'geselecteerd uitgangsmateriaal' en twaalf niet opgenomen Nederlandse herkomsten. Deze proeven liggen in het Harderbos, Oud:Sabbinge, Sanoer, Urkerbos en Wolphaartsdijk

    Weak Quasi-elastic Production of Hyperons

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    The quasielastic weak production of Λ\Lambda and Σ\Sigma hyperons from nucleons and nuclei induced by antineutrinos is studied in the energy region of some ongoing neutrino oscillation experiments in the intermediate energy region. The hyperon nucleon transition form factors determined from neutrino nucleon scattering and an analysis of high precision data on semileptonic decays of neutron and hyperons using SU(3) symmetry have been used. The nuclear effects due to Fermi motion and final state interaction effects due to hyperon nucleon scattering have also been studied. The numerical results for differential and total cross sections have been presented.Comment: 26 pages, 10 figure

    Knee extension with less hip flexion: biomechanical and evoked EMG analysis during selective surface stimulation of the quadriceps

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    During FES cycling when the Quadriceps muscles are activated both knee extension and hip flexion moments occur simultaneously, decreasing the total power output. Of the three superficial muscles, Rectus femoris is a biarticular muscle that produces both a knee extension and a hip flexion, while Vastus lateralis and Vastus medialis are only knee extensors. This thesis is an investigation whether, using surface stimulation, selective stimulation of the Vastii can produce knee extension moment with less hip flexion. A system was developed for measurement of the joint moments and evoked myoelectric response in these three muscles, while seated subjects were stimulated. The dynamometer measures the magnitude and position of two forces that restrain the leg, from which joint moments are calculated. The design and construction of the hardware, electronics and software is presented. Validation of the dynamometer against known moments produced with a spring-loaded dummy leg showed good correlation. The influence of random and systematic errors on the estimated joint moments indicate that the dynamometer should be used for comparing the responses for different electrode configurations within single sessions. The close proximity of the EMG recording electrodes to the stimulating electrodes causes artefact that obscures the M-wave. This was partly overcome by amplifying with a current conveyor circuit, and by a novel biphasic stimulator with pulse width ratio adjustment. The design and construction of both stimulator and amplifier are discussed, also the mechanisms causing the artefact (voltage gradient, skin-electrode interface and common mode voltage). A study with ten able-bodied subjects was performed. EMG analysis showed that it is possible to selectively stimulate the Vastii and this does reduce hip flexion moment, however beside the inevitable reduction of knee extension moment, the reduction of the hip flexion is less than expected, perhaps due to stimulation of other muscles of the anterior thigh
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