532 research outputs found

    Description of Anteon seramense (Hymenoptera. Dryinidae), a new species from Indonesia

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    Anteon seramense sp. nov. is described from Seram Island (Indonesia). Seram is an island situated in a transition area between the Oriental and the Australian regions. Anteon seramense can be distinguished from the related Australian species A. giluwense Olmi and A. chelogynoides (Perkins) by the different sculpture of the scutum (granulated in A. seramense, punctate and unsculptured among punctures in A. giluwense and A. chelogynoides) and the different distal apex of the protarsal segment 5 (deeply hollow in A. seramense, not hollow in A. giluwense and A. chelogynoides). Anteon seramense sp. nov. can be distinguished from the related Oriental species A. heppneri Olmi and A. thai Olmi by the different shape of the protarsal segment 5 (basal part slightly longer than distal part in A. seramense, much longer in A. heppneri and A. thai)

    Description of Bocchus irwini sp. nov. from Madagascar (Hymenoptera Dryinidae)

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    Bocchus irwini sp. nov. is described from a male collected in Analagnambe forest, Mahajanga Province, Madagascar. The new species is similar to Bocchus watshami Olmi 1987. Keys to the Afrotropical species of Bocchus are modified to include the new species

    Definition of the linearity loss of the surface temperature in static tensile tests

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    Static traction tests on material samples for mechanical constructions have pointed out the loss of linearity of the specimen surface temperature with the applied load. This phenomenon is due to the heat generation caused by the local microplasticizations which carry the material to deviate from its behavior, perfectly thermoelastic. The identification of the static load which determines the loss of linearity under the temperature stress becomes extremely important to define an initial dynamic characterization of the material. The temperature variations that can be read during the static loads applications are often very limited (a few tenths of degree for every 100 MPa in steels) and they require the use of special temperature sensors able to measure the temperature variations. The experience acquired in such analysis highlighted that, dealing with highly accurate sensors or with particular materials, the identification of the first loss of linearity can be influenced by the investigator himself mainly for the above mentioned limited temperature variations which can lead to incorrect estimations, sometimes really significant. Checking the validity and the above mentioned observations on the different steels, this work proposes the application of the autocorrelation function to the data collected during the application of a static load in order to make the results of the thermal analysis free from the sensitivity of the operator and also to make the result as objective as possible in order to detect the time of the loss of linearity of the temperature-time function

    The Lockman Hole Project: new constraints on the sub-mJy source counts from a wide-area 1.4 GHz mosaic

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    This paper is part of a series discussing the results obtained in the framework of a wide international collaboration - the Lockman Hole Project - aimed at improving the extensive multiband coverage available in the Lockman Hole region, through novel deep, wide-area, multifrequency (60, 150, 350 MHz, and 1.4 GHz) radio surveys. This multifrequency, multi-band information will be exploited to get a comprehensive view of star formation and active galactic nucleus activities in the high-redshift Universe from a radio perspective. In this paper, we present novel 1.4 GHz mosaic observations obtained with the Westerbork Synthesis Radio Telescope. With an area coverage of 6.6 deg2, this is the largest survey reaching an rms noise of 11 uJy/beam. In this paper, we present the source catalogue (~6000 sources with flux densities S>55 uJy (5sigma), and we discuss the 1.4 GHz source counts derived from it. Our source counts provide very robust statistics in the flux range 0.1<S<1 mJy, and are in excellent agreement with other robust determinations obtained at lower and higher flux densities. A clear excess is found with respect to the counts predicted by the semi-empirical radio sky simulations developed in the framework of the Square Kilometre Array Simulated Skies project. A preliminary analysis of the identified (and classified) sources suggests this excess is to be ascribed to star-forming galaxies, which seem to show a steeper evolution than predicted.Comment: accepted for publication on MNRAS. New version that corrects latex errors and contain the correct version of figure 1

    The 2013 February 17 sunquake in the context of the active region's magnetic field configuration

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    © 2017. The American Astronomical Society. All rights reserved. Sunquakes are created by the hydrodynamic response of the lower atmosphere to a sudden deposition of energy and momentum. In this study, we investigate a sunquake that occurred in NOAA active region 11675 on 2013 February 17. Observations of the corona, chromosphere, and photosphere are brought together for the first time with a nonlinear force-free model of the active region's magnetic field in order to probe the magnetic environment in which the sunquake was initiated. We find that the sunquake was associated with the destabilization of a flux rope and an associated M-class GOES flare. Active region 11675 was in its emergence phase at the time of the sunquake and photospheric motions caused by the emergence heavily modified the flux rope and its associated quasi-separatrix layers, eventually triggering the flux rope's instability. The flux rope was surrounded by an extended envelope of field lines rooted in a small area at the approximate position of the sunquake. We argue that the configuration of the envelope, by interacting with the expanding flux rope, created a “magnetic lens” that may have focussed energy on one particular location of the photosphere, creating the necessary conditions for the initiation of the sunquake

    Historical solar Ca II K observations at the Rome and Catania observatories

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    Here we present the little explored Ca II K archives from the Rome and the Catania observatories and analyse the digitised images from these archives to derive plage areas.Comment: 5 pages, 3 figures, to be published in "Nuovo Cimento C" as proceeding of the Third Meeting of the Italian Solar and Heliospheric Communit

    Theoretical Approach for Developing the Thermographic Method in Ultrasonic Fatigue

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    AbstractIn the last years, several approaches were developed in literature for predicting the fatigue strength of different kinds of materials. One approach is the Thermographic Method, based on the thermographic technique. This study is devoted to the development of a theoretical approach for modeling of surface and undersurface fatigue crack initiation and temperature evolution during ultrasonic fatigue test. The proposed model is based on the statistical description of mesodefect ensemble and describes an energy balance in materials (including power of energy dissipation) under cyclic loading. The model allows us to simulate the damage to fracture transition and corresponding temperature evolution in critical cross section of a sample tested in very high cyclic fatigue regime

    Ground deformation modeling of flank dynamics prior to the 2002 eruption of Mt. Etna

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    On 22 September 2002, 1 month before the beginning of the flank eruption on the NE Rift, an M-3.7 earthquake struck the northeastern part of Mt. Etna, on the westernmost part of the Pernicana fault. In order to investigate the ground deformation pattern associated with this event, a multi-disciplinary approach is presented here. Just after the earthquake, specific GPS surveys were carried out on two small sub-networks, aimed at monitoring the eastern part of the Pernicana fault, and some baselines belonging to the northeastern EDM monitoring network of Mt. Etna were measured. The leveling route on the northeastern flank of the volcano was also surveyed. Furthermore, an investigation using SAR interferometry was performed and also the continuous tilt data recorded at a high precision sensor close to the epicenter were analyzed to constrain the coseismic deformation. The results of the geodetic surveys show a ground deformation pattern that affects the entire northeastern flank of the volcano, clearly shaped by the Pernicana fault, but too strong and wide to be related only to an M-3.7 earthquake. Leveling and DInSAR data highlight a local strong subsidence, up to 7 cm, close to the Pernicana fault. Significant displacements, up to 2 cm, were also detected on the upper part of the NE Rift and in the summit craters area, while the displacements decrease at lower altitude, suggesting that the dislocation did not continue further eastward. Three-dimensional GPS data inversions have been attempted in order to model the ground deformation source and its relationship with the volcano plumbing system. The model has also been constrained by vertical displacements measured by the leveling survey and by the deformation map obtained by SAR interferometry

    Kinematics and Magnetic Properties of a Light Bridge in a Decaying Sunspot

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    We present the results obtained by analyzing high spatial and spectral resolution data of the solar photosphere acquired by the CRisp Imaging SpectroPolarimeter at the Swedish Solar Telescope on 6 August 2011, relevant to a large sunspot with a light bridge (LB) observed in NOAA AR 11263. These data are complemented by simultaneous Hinode Spectropolarimeter (SP) observation in the Fe I 630.15 nm and 630.25 nm lines. The continuum intensity map shows a discontinuity of the radial distribution of the penumbral filaments in correspondence with the LB, which shows a dark lane (about 0.3" wide and about 8.0" long) along its main axis. The available data were inverted with the Stokes Inversion based on Response functions (SIR) code and physical parameters maps were obtained. The line-of-sight (LOS) velocity of the plasma along the LB derived from the Doppler effect shows motions towards and away from the observer up to 0.6 km/s, which are lower in value than the LOS velocities observed in the neighbouring penumbral filaments. The noteworthy result is that we find motions toward the observer up to 0.6 km/s in the dark lane where the LB is located between two umbral cores, while the LOS velocity motion toward the observer is strongly reduced where the LB is located between an umbral core at one side and penumbral filaments on the other side. Statistically, the LOS velocities correspond to upflows/downflows andcomparing these results with Hinode/SP data, we conclude that the surrounding magnetic field configuration (whether more or less inclined) could have a role in maintaining the conditions for the process of plasma piling up along the dark lane. The results obtained from our study support and confirm outcomes of recent magnetohydro-dynamic simulations showing upflows along the main axis of a LBs
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