2,257 research outputs found

    Comparative behaviour and ecology of two sympatric mongoose species (Cynictis penicillata and Galerella pulverulenta)

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    The activity, movements, home range size, habitat selection, social structure, density, pattern of faeces deposition, anti-predator behaviour, diet, and availability and distribution of the main food sources of two mongoose species [the yellow mongoose Cynictis penicillata and the Cape grey mongoose Gaierelia pulverulenta (= Herpestes pulverulentos) in a coastal area of South Africa are compared, Both species were diurnal. Galerella did not use dens, whereas Cynictis never rested outside a den. Total distance moved, home range size and density did not differ between the two species. Galerella frequented bush, whereas Cynictisfrequented open fields. The yellow mongoose was more social than the grey mongoose, but the basic social structure was similar. Faeces of Cynictis were found in large clumps close to the dens, while those of Galerella were more scattered. This parallels the greater constancy of use of the sleeping sites by Cynictis.Rodents (> 90% of Cape grey mongoose diet) were much more abundant in the bush, while availability of insects (main food source for the yellow mongoose) was higher in the open fields. Habitat selection, Ihrough its effects on anti-predator and feeding strategies, might have been the leading factor in the evolution of sociality in herpestids

    Solar Atmospheric Oscillations and the Chromospheric Magnetic Topology

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    We investigate the oscillatory properties of the quiet solar chromosphere in relation to the underlying photosphere, with particular regard to the effects of the magnetic topology. We perform a Fourier analysis on a sequence of line-of-sight velocities measured simultaneously in a photospheric (Fe I 709.0 nm) and a chromospheric line (Ca II 854.2 nm). The velocities were obtained from full spectroscopic data acquired at high spatial resolution with the Interferometric BIdimensional Spectrometer (IBIS). The field of view encompasses a full supergranular cell, allowing us to discriminate between areas with different magnetic characteristics. We show that waves with frequencies above the acoustic cut-off propagate from the photosphere to upper layers only in restricted areas of the quiet Sun. A large fraction of the quiet chromosphere is in fact occupied by ``magnetic shadows'', surrounding network regions, that we identify as originating from fibril-like structures observed in the core intensity of the Ca II line. We show that a large fraction of the chromospheric acoustic power at frequencies below the acoustic cut-off, residing in the proximity of the magnetic network elements, directly propagates from the underlying photosphere. This supports recent results arguing that network magnetic elements can channel low-frequency photospheric oscillations into the chromosphere, thus providing a way to input mechanical energy in the upper layers.Comment: 4 pages, 3 figure, A&A Letters in pres

    Elastic moduli approximation of higher symmetry for the acoustical properties of an anisotropic material

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    The issue of how to define and determine an optimal acoustical fit to a set of anisotropic elastic constants is addressed. The optimal moduli are defined as those which minimize the mean squared difference in the acoustical tensors between the given moduli and all possible moduli of a chosen higher material symmetry. The solution is shown to be identical to minimizing a Euclidean distance function, or equivalently, projecting the tensor of elastic stiffness onto the appropriate symmetry. This has implications for how to best select anisotropic constants to acoustically model complex materials.Comment: 20 page

    Radiative transfer effects on Doppler measurements as sources of surface effects in sunspot seismology

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    We show that the use of Doppler shifts of Zeeman sensitive spectral lines to observe wavesn in sunspots is subject to measurement specific phase shifts arising from, (i) altered height range of spectral line formation and the propagating character of p mode waves in penumbrae, and (ii) Zeeman broadening and splitting. We also show that these phase shifts depend on wave frequencies, strengths and line of sight inclination of magnetic field, and the polarization state used for Doppler measurements. We discuss how these phase shifts could contribute to local helioseismic measurements of 'surface effects' in sunspot seismology.Comment: 12 pages, 4 figures, Accepted for publication in the Astrophysical Journal Letter

    Radiation detection properties of 4H-SiC Schottky diodes irradiated up to 10(16) n/cm(2) by 1 MeV neutrons

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    We report the results of an experimental study on the radiation hardness of 4H-SiC diodes used as alpha-particle detectors with 1 MeV neutrons up to a fluence of 8 x 10(15) n/cm(2). As the irradiation level approaches the range 10(15) n/cm(2), the material behaves as intrinsic due to a very high compensation effect and the diodes are still able to detect with a reasonable good Charge Collection Efficiency (CCE = 80%).For fluences > 10(15) n/cm(2) CCE decreases monotonically to approximate to 20 % at the highest fluence. Heavily irradiated SiC diodes have been studied, by means of Photo Induced Current Transien

    Variation in the diet of the red fox in a Mediterranean area

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    Le régime alimentaire du Renard Vulpes vulpes a été étudié dans la province de Pise, en Italie centrale, par l'analyse de fèces (N = 1261; recueillies chaque mois pendant un an dans neuf zones) et de contenus du tube digestif (N = 330; collectés de janvier à mai dans toute la province). Ce régime est très varié, dominé par les vertébrés (notamment les mammifères) et les végétaux (en particulier les fruits), les invertébrés n'étant que peu abondants. Les aliments d'origine anthropique comptent pour à peu près la moitié du régime. En fin d'hiver et au printemps, les femelles consomment plus de petits mammifères et d'invertébrés que les mâles, les jeunes ayant un régime semblable à celui des adultes. Aucune relation n'a été trouvée entre l'adiposité et la taille corporelle des individus et le volume d'un quelconque item alimentaire. La variation saisonnière est importante pour la plupart des catégories d'aliments, les vertébrés tendant à être principalement consommés en hiver et au printemps, les fruits en été et en automne et les invertébrés surtout en été. Plusieurs de ces tendances s'expliquent par les disponibilités alimentaires mais les petits mammifères apparaissent moins consommés quand ils sont apparemment le plus abondants. Globalement, le régime est homogène dans les zones rurales et s'avère fort différent de celui observé dans les zones soumises à faible emprise humaine. Sur l'ensemble de la province, les différences se limitent à trois items d'origine humaine. Les herbes et autres végétaux contenus dans les estomacs et les intestins sont de manière significative associés à la consommation d'invertébrés mais pas à la présence de vers parasites dans les intestins. La forte consommation de fruits et d'aliments d'origine anthropique est un trait caractéristique du régime du renard dans cette région, et dans d'autres, de l'Italie. Les fruits pourraient être des aliments de complément alors que les petits mammifères seraient des aliments-clés. Les renards mangent plus de fruits quand et où leur densité de population est la plus forte. Les raisons de ces tendances sont discutées

    Technical characteristics can make the difference in a surgical linear stapler. or not?

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    Background Anastomotic leak (AL) after gastrointestinal surgery is a severe complication associated with relevant short- and long-term sequelae. Most of the anastomosis are currently performed with a surgical stapler that is required to have appropriate characteristics to guarantee good performances. The aim of our study was to evaluate, in the laboratory, pressure resistance and tensile strength of anastomosis performed with different surgical linear staplers, available in the market. Materials and methods We have been studying three linear staplers, with diverse cartridges and staple heights, of three different companies, used for gastrointestinal anastomosis and gastric or intestinal closure. We performed 50 anastomosis for each device, with the pertinent different cartridges, on fresh pig intestine, for a total of 350 anastomosis, then injected saline solution and recorded the pressure that provokes a leak on the staple line. There were no statistically significant differences between the mean pressure necessary to induce an AL in the various instruments (P > 0.05). For studying the tensile strength, we performed a total of 350 anastomosis with the different linear staplers on a special strong paper (Tyvek), then recorded the maximal tensile force that could open the anastomosis. Results There were no statistically significant differences between the different staplers about the strength necessary to open the staple line (P > 0.05). Conclusions we demonstrated that different linear staplers of three companies available in the market give comparable anastomotic pressure resistance and tensile strength. This might suggest that small dissimilarities between different devices are not involved, at least as major parameters, in AL etiology

    Tracing the identity of Parmigiano Reggiano “Prodotto di Montagna - Progetto Territorio” cheese using NMR spectroscopy and multivariate data analysis

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    Background Nuclear magnetic resonance (NMR) spectroscopy is one of the well-established tools for food metabolomic analysis, as it proved to be very effective in authenticity and quality control of dairy products, as well as to follow product evolution during processing and storage. The analytical assessment of the EU mountain denomination label, specifically for Parmigiano Reggiano "Prodotto di Montagna - Progetto Territorio" (Mountain-CQ) cheese, has received limited attention. Although it was established in 2012 the EU mountain denomination label has not been much studied from an analytical point of view. Nonetheless, tracing a specific profile for the mountain products is essential to support the value chain of this specialty. Results The aim of the study was to produce an identity profile for Parmigiano Reggiano “Prodotto di Montagna - Progetto Territorio” (Mountain-CQ) cheese, and to differentiate it from Parmigiano Reggiano PDO samples (conventional-PDO) using 1H NMR spectroscopy coupled with multivariate data analysis. Three different approaches were applied and compared. First, the spectra-as-such were analysed after proper preprocessing. For the other two approaches, Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) was used for signals resolution and features extraction, either individually on manually-defined spectral intervals or by reapplying MCR-ALS on the whole spectra with selectivity constraints using the reconstructed “pure profiles” as initial estimates and targets. All approaches provided comparable information regarding the samples’ distribution, as in all three cases the separation between the two product categories conventional-PDO and Mountain-CQ could be highlighted. Moreover, a novel MATLAB toolbox for features extraction via MCR-ALS was developed and used in synergy with the Chenomx library, allowing for a putative identification of the selected features. Significance A first identity profile for Parmigiano Reggiano “Prodotto di Montagna - Progetto Territorio” obtained by interpreting the metabolites signals in NMR spectroscopy was obtained. Our workflow and toolbox for generating the features dataset allows a more straightforward interpretation of the results, to overcome the limitations due to dimensionality and to peaks overlapping, but also to include the signals assignment and matching since the early stages of the data processing and analysis
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