Spatial crowdsourcing with mobile agents in vehicular networks

In the last years, the automotive industry has shown interest in the addition of computing and communication devices to cars, thanks to technological advances in these fields, in order to meet the increasing demand of “connected” applications and services. Although vehicular ad hoc networks (VANETs) have not been fully developed yet, they could be used in a near future as a means to provide a number of interesting applications and services that need the exchange of data among vehicles and other data sources. In this paper, we propose a spatial crowdsourcing schema for the opportunistic collection of information within an interest area in a city or region (e.g., measures about the environment, such as the concentration of certain gases in the atmosphere, or information such as the availability of parking spaces in an area), using vehicular ad hoc communications. We present a method that exploits mobile agent technology to accomplish the distributed collection and querying of data among vehicles in such a scenario. Our proposal is supported by an extensive set of realistic simulations that prove the feasibility of the approach

Current sheets at three-dimensional magnetic nulls:effect of compressibility

The nature of current sheet formation in the vicinity of three-dimensional (3D) magnetic null points is investigated. The particular focus is upon the effect of the compressibility of the plasma on the qualitative and quantitative properties of the current sheet. An initially potential 3D null is subjected to shearing perturbations, as in a previous paper [Pontin et al., Phys. Plasmas, in press (2007)]. It is found that as the incompressible limit is approached, the collapse of the null point is suppressed, and an approximately planar current sheet aligned to the fan plane is present instead. This is the case regardless of whether the spine or fan of the null is sheared. Both the peak current and peak reconnection rate are reduced. The results have a bearing on previous analytical solutions for steady-state reconnection in incompressible plasmas, implying that fan current sheet solutions are dynamically accessible, while spine current sheet solutions are not.Comment: to appear in Physics of Plasmas. This version contains updated figures and references, additional discussion, and typos are fixed. This is the second in a series of papers - the first of which (by the same authors) is located at astro-ph/0701462. A version with higher quality figures can be found at http://www.maths.dundee.ac.uk/~dpontin

Service level agreement framework for differentiated survivability in GMPLS-based IP-over-optical networks

In the next generation optical internet, GMPLS based IP-over-optical networks, ISPs will be required to support a wide variety of applications each having their own requirements. These requirements are contracted by means of the SLA. This paper describes a recovery framework that may be included in the SLA contract between ISP and customers in order to provide the required level of survivability. A key concern with such a recovery framework is how to present the different survivability alternatives including recovery techniques, failure scenario and layered integration into a transparent manner for customers. In this paper, two issues are investigated. First, the performance of the recovery framework when applying a proposed mapping procedure as an admission control mechanism in the edge router considering a smart-edge simple-core GMPLS-based IP/WDM network is considered. The second issue pertains to the performance of a pre-allocated restoration and its ability to provide protected connections under different failure scenarios

Continuous upflows and sporadic downflows observed in active regions

We present a study of the temporal evolution of coronal loops in active regions and its implications for the dynamics in coronal loops. We analyzed images of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) at multiple temperatures to detect apparent motions in the coronal loops. Quasi-periodic brightness fluctuations propagate upwards from the loop footpoint in hot emission at 1MK, while sporadic downflows are seen in cool emission below 1MK. The upward motion in hot emission increases just after the cool downflows. The apparent propagating pattern suggests a hot upflow from the loop footpoints, and is considered to supply hot plasma into the coronal loop, but a wavelike phenomenon cannot be ruled out. Coronal condensation occasionally happens in the coronal loop, and the cool material flows down to the footpoint. Emission from cool plasma could have a significant contribution to hot AIA channels in the event of coronal condensation.Comment: 5 pages, 6 figures, A&A in pres

The structure and dynamics of a bright point as seen with Hinode, SoHO and TRACE

Our aim is to determine the plasma properties of a coronal bright point and compare its magnetic topology extrapolated from magnetogram data with its appearance in X-ray images. We analyse spectroscopic data obtained with EIS/Hinode, Ca II H and G-band images from SOT/Hinode, UV images from TRACE, X-ray images from XRT/Hinode and high-resolution/high-cadence magnetogram data from MDI/SoHO. The BP comprises several coronal loops as seen in the X-ray images, while the chromospheric structure consists of tens of small bright points as seen in Ca II H. An excellent correlation exists between the Ca II BPs and increases in the magnetic field, implying that the Ca II H passband is a good indicator for the concentration of magnetic flux. Doppler velocities between 6 and 15 km/s are derived from the Fe XII and Fe XIII lines for the BP region, while for Fe XIV and Si VII they are in the range from -15 to +15 km/s. The coronal electron density is 3.7x10^9 cm^-3. An excellent correlation is found between the positive magnetic flux and the X-ray light-curves. The remarkable agreement between the extrapolated magnetic field configuration and some of the loops composing the BP as seen in the X-ray images suggests that a large fraction of the magnetic field in the bright point is close to potential. The close correlation between the positive magnetic flux and the X-ray emission suggests that energy released by magnetic reconnection is stimulated by flux emergence or cancellation.Comment: 10 pages with 11 figures. Accepted in Astronomy and Astrophysic

New records of recently described chemosymbiotic bivalves for mud volcanoes within the European waters (Gulf of Cádiz)

Chemosymbiotic bivalves are important members of cold seep communities and information on their distribution in theEuropean waters is still quite scarce. This study reports the presence of living populations and shell remains of some recently described bivalves such as Lucinoma asapheus, Solemya elarraichensis and Acharax gadirae as well as Bathymodiolus sp. in the mud volcanoes of the Spanish Atlantic waters. Living populations of these species were thus far only found in Anastasya, Aveiro and Almazán mud volcanoes, together with other chemosymbiotic metazoa (Siboglinum spp.), suggesting the presence of moderate seepage activity. In other mud volcanoes (Albolote, Gazul), the benthic communities are dominated by sessile filter feeders on authigenic carbonates (chimneys, slabs) and only the shell remains of some chemosymbiotic bivalves were found, indicating earlier or very low seepage conditions. The present study elaborates on the known distribution of L. asapheus and S. elarraichensis to the European waters of the Gulf of Cádiz

Molluscs from deep bioclastic gravel bottoms of the Alborán Island (LIFE+ INDEMARES Project)

Resumen de posterDurante el proyecto LIFE+ INDEMARES Alborán (2011-2013), se tomaron diez muestras mediante arte de arrastre (bou de vara) en los fondos de cascajo profundo que aparecen entre 80 y 200 m en la plataforma insular de la isla de Alborán. Estos fondos están formados por restos calcáreos biógenos (bioclastos). En las muestras se han encontrado un total de 2.713 ejemplares vivos de moluscos pertenecientes a 147 especies (2 solenogastros, 2 poliplacóforos, 97 gasterópodos, 45 bivalvos, 1 cefalópodo). Los muestreos realizados han puesto de manifiesto la presencia de una alta riqueza de especies de invertebrados. En el caso de los moluscos, la riqueza específica de las muestras fue alta (entre 24 y 55 especies), mientras que las abundancias fueron entre moderadas y altas (entre 154 y 846 individuos), oscilando la diversidad de Shannon-Wiener (H’) entre 2,20 y 3,30. En las muestras estudiadas destaca la presencia de pocas especies comunes y de un elevado número de especies raras. Estas últimas pueden ser accidentales en estos fondos y comunes en otros hábitats próximos, pero otras, como Rugulina monterosatoi Aartsen y Bogi, 1987, Epitonium linctum (de Boury y Monterosato, 1890), Epitonium pseudonanum Bouchet y Warén, 1986, Strobiligera flammulata Bouchet y Warén, 1993, Cerithiopsis atalaya Watson, 1885, Cerithiopsis nofronii Amati, 1987 y Pseudobabylonella minima (Reeve, 1856), se consideran raras ya que no son frecuentes en ningún otro hábitat. La mayoría de las especies de moluscos encontradas en los fondos de cascajo de la isla de Alborán tienen una distribución atlántico-mediterránea, y están presentes normalmente en el Mediterráneo y en el Atlántico ibero-marroquí o más allá de esta zona. Se han encontrado dos especies de afinidad biogeográfica subtropical (costa occidental africana), cuya presencia es uno de los rasgos característicos del mar de Alborán: Mitrella pallaryi (Dautzenberg, 1891) y Nassarius denticulatus (A. Adams, 1852). Además, se ha recolectado viva una especie de reciente descripción, Trophonopsis alboranensis (Smriglio, Mariottini y Bonfitto, 1997), probablemente endémica de esta zona al no haberse encontrado fuera de la isla de Alborán. Los gasterópodos Anatoma aspera (Philippi, 1844), Xenophora crispa (König, 1825), Schilderia achatidea (Gray en G. B. Sowerby I, 1837), Trophonopsis alboranensis y Fusiturris similis (Bivona Ant. en Bivona And., 1838), así como los bivalvos Bathyarca pectunculoides (Scacchi, 1834), Similipecten similis (Laskey, 1811) y Parvamussium fenestratum (Forbes, 1844), entre otras especies, caracterizan el cascajo profundo en la plataforma de Alborán, y lo diferencian de los fondos coralígenos o de “maërl” adyacentes. Por su elevada diversidad y por ser un hábitat esencial para varias especies vulnerables (no sólo de moluscos), consideramos que los fondos de cascajo profundo deben ser incluidos en el Anexo I (Hábitats naturales de interés comunitario cuya conservación requiere la designación de zonas de especial conservación) de la Directiva 92/43/CEE de Hábitats, para lo cual se ha elaborado la correspondiente propuesta en el marco del proyecto LIFE+ INDEMARES.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Emission heights of coronal bright points on Fe XII radiance map

We study the emission heights of the coronal bright points (BPs) above the photosphere in the bipolar magnetic loops that are apparently associated with them. As BPs are seen in projection against the disk their true emission heights are unknown. The correlation of the BP locations on the Fe XII radiance map from EIT with the magnetic field features (in particular neutral lines) was investigated in detail. The coronal magnetic field was determined by an extrapolation of the photospheric field to different altitudes above the disk. It was found that most BPs sit on or near a photospheric neutral line, but that the emission occurs at a height of about 5 Mm. Some BPs, while being seen in projection, still seem to coincide with neutral lines, although their emission takes place at heights of more than 10 Mm. Such coincidences almost disappear for emissions above 20 Mm. We also projected the upper segments of the 3-D magnetic field lines above different heights, respectively, on to the x-y plane. The shape of each BP was compared with the respective field-line segment nearby. This comparison suggests that most coronal BPs are actually located on the top of their associated magnetic loops. Finally, we calculated for each selected BP region the correlation coefficient between the Fe XII intensity enhancement and the horizontal component of the extrapolated magnetic field vector at the same x-y position in planes of different heights, respectively. We found that for almost all the BP regions we studied the correlation coefficient, with increasing height, increases to a maximal value and then decreases again. The height corresponding to this maximum was defined as the correlation height, which for most bright points was found to range below 20 Mm.Comment: 7 pages, 4 figures, 1 tabl

What is the true nature of blinkers?

Aims. The aim of this work is to identify the true nature of the transient EUV brightenings, called blinkers. Methods. Co-spatial and co-temporal multi-instrument data, including imaging (EUVI/STEREO, XRT and SOT/Hinode), spectroscopic (CDS/SoHO and EIS/Hinode) and magnetogram (SOT/Hinode) data, of an isolated equatorial coronal hole were used. An automatic program for identifying transient brightenings in CDS O v 629 Å, EUVI 171 Å and XRT was applied. Results. We identified 28 blinker groups in the CDS O v 629 Å raster images. All CDS O v 629 Å blinkers showed counterparts in EUVI 171 Å and 304 Å images. We classified these blinkers into two categories, one associated with coronal counterparts and other with no coronal counterparts as seen in XRT images and EIS Fe xii 195.12 Å raster images. Around two-thirds of the blinkers show coronal counterparts and correspond to various events like EUV/X-ray jets, brightenings in coronal bright points or foot-point brightenings of larger loops. These brightenings occur repetitively and have a lifetime of around 40 min at transition region temperatures. The remaining blinker groups with no coronal counterpart in XRT and EIS Fe xii 195.12 Å appear as point-like brightenings and have chromospheric/transition region origin. They take place only once and have a lifetime of around 20 min. In general, lifetimes of blinkers are different at different wavelengths, i.e. different temperatures, decreasing from the chromosphere to the corona. Conclusions. This work shows that the term blinker covers a range of phenomena. Blinkers are the EUV response of various transient events originating at coronal, transition region and chromospheric heights. Hence, events associated with blinkers contribute to the formation and maintenance of the temperature gradient in the transition region and the corona