482 research outputs found

    Assessing the performance of a renewable district heating system to achieve nearly zero-energy status in renovated university campuses : a case study for Spain

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    This paper presents the implementation of a biomass-fuelled District Heating System (DHS), as a part of a deep energy renovation exercise to achieve a climate-resilient campus with minimum carbon dioxide emissions. The case study is carried out for the University of Valladolid, an average-sized university in Spain, with a continental weather climate. Prior to renovation, the different building blocks had a wide-ranging level of fossil fuel consumption for space heating and domestic hot water ranging between 60 and 430 kWh/m2 ⋅year. The application of this centralised heating system allows to achieve the minimum threshold for near zero-energy buildings (nZEB) of 100–120 kWh/m2 , in accordance with the Spanish Standards. These values correspond to the maximum European indicators for offices in continental weather conditions. Results of this comprehensive study show that 15 out of the 19 buildings reached the nZEB target, due to the proposed strategy. The overall carbon dioxide emissions have dropped by 92.69% as compared to the original fossil-fuel powered boiler, thus bringing carbon dioxide emissions down to 1.57 kgCO2/m2 ⋅y. Therefore, it is shown that deep energy renovation strategies through renewable energy DHS have the potential of achieving nZEB for universities in continental weather conditions.peer-reviewe

    Axial Vector JPC=1++J^{PC}=1^{++} Charmonium and Bottomonium Hybrid Mass Predictions with QCD Sum-Rules

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    Axial vector (JPC=1++)(J^{PC}=1^{++}) charmonium and bottomonium hybrid masses are determined via QCD Laplace sum-rules. Previous sum-rule studies in this channel did not incorporate the dimension-six gluon condensate, which has been shown to be important for 11^{--} and 0+0^{-+} heavy quark hybrids. An updated analysis of axial vector charmonium and bottomonium hybrids is presented, including the effects of the dimension-six gluon condensate. The axial vector charmonium and bottomonium hybrid masses are predicted to be 5.13 GeV and 11.32 GeV, respectively. We discuss the implications of this result for the charmonium-like XYZ states and the charmonium hybrid multiplet structure observed in recent lattice calculations.Comment: 10 pages, 7 figures. Updated to match published versio

    Search for muon-neutrino emission from GeV and TeV gamma-ray flaring blazars using five years of data of the ANTARES telescope

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    The ANTARES telescope is well-suited for detecting astrophysical transient neutrino sources as it can observe a full hemisphere of the sky at all times with a high duty cycle. The background due to atmospheric particles can be drastically reduced, and the point-source sensitivity improved, by selecting a narrow time window around possible neutrino production periods. Blazars, being radio-loud active galactic nuclei with their jets pointing almost directly towards the observer, are particularly attractive potential neutrino point sources, since they are among the most likely sources of the very high-energy cosmic rays. Neutrinos and gamma rays may be produced in hadronic interactions with the surrounding medium. Moreover, blazars generally show high time variability in their light curves at different wavelengths and on various time scales. This paper presents a time-dependent analysis applied to a selection of flaring gamma-ray blazars observed by the FERMI/LAT experiment and by TeV Cherenkov telescopes using five years of ANTARES data taken from 2008 to 2012. The results are compatible with fluctuations of the background. Upper limits on the neutrino fluence have been produced and compared to the measured gamma-ray spectral energy distribution.Comment: 27 pages, 16 figure

    Liquid crystal relaxation in three dimensions: the effect of hydrodynamic interactions

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    We investigate the relaxation of two line defects of opposite strength in a confined nematic liquidcrystal by solving the coupled tensor order parameter evolution and momentum balance equations in three dimensions. The inclusion of hydrodynamic interactions causes the defects to move at different velocities and slows the overall relaxation process, but this effect is suppressed by increasing the degree of confinement. The most notable flow features that develop in the system are large vortices that surround and follow the defects as they approach each other

    Performance of the First ANTARES Detector Line

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    In this paper we report on the data recorded with the first Antares detector line. The line was deployed on the 14th of February 2006 and was connected to the readout two weeks later. Environmental data for one and a half years of running are shown. Measurements of atmospheric muons from data taken from selected runs during the first six months of operation are presented. Performance figures in terms of time residuals and angular resolution are given. Finally the angular distribution of atmospheric muons is presented and from this the depth profile of the muon intensity is derived.Comment: 14 pages, 9 figure

    Strong interface-induced spin-orbit coupling in graphene on WS2

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    Interfacial interactions allow the electronic properties of graphene to be modified, as recently demonstrated by the appearance of satellite Dirac cones in the band structure of graphene on hexagonal boron nitride (hBN) substrates. Ongoing research strives to explore interfacial interactions in a broader class of materials in order to engineer targeted electronic properties. Here we show that at an interface with a tungsten disulfide (WS2) substrate, the strength of the spin-orbit interaction (SOI) in graphene is very strongly enhanced. The induced SOI leads to a pronounced low-temperature weak anti-localization (WAL) effect, from which we determine the spin-relaxation time. We find that spin-relaxation time in graphene is two-to-three orders of magnitude smaller on WS2 than on SiO2 or hBN, and that it is comparable to the intervalley scattering time. To interpret our findings we have performed first-principle electronic structure calculations, which both confirm that carriers in graphene-on-WS2 experience a strong SOI and allow us to extract a spin-dependent low-energy effective Hamiltonian. Our analysis further shows that the use of WS2 substrates opens a possible new route to access topological states of matter in graphene-based systems.Comment: Originally submitted version in compliance with editorial guidelines. Final version with expanded discussion of the relation between theory and experiments to be published in Nature Communication

    Peri-conception and first trimester diet modifies reproductive development in bulls

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    Nutritional perturbation during gestation alters male reproductive development in rodents and sheep. In cattle both the developmental trajectory of the feto–placental unit and its response to dietary perturbations is dissimilar to that of these species. This study examined the effects of dietary protein perturbation during the peri-conception and first trimester periods upon reproductive development in bulls. Nulliparous heifers (n = 360) were individually fed a high- or low-protein diet (HPeri and LPeri) from 60 days before conception. From 24 until 98 days post conception, half of each treatment group changed to the alternative post-conception high- or low-protein diet (HPost and LPost) yielding four treatment groups in a 2 × 2 factorial design. A subset of male fetuses (n = 25) was excised at 98 days post conception and fetal testis development was assessed. Reproductive development of singleton male progeny (n = 40) was assessed until slaughter at 598 days of age, when adult testicular cytology was evaluated. Low peri-conception diet delayed reproductive development: sperm quality was lowered during pubertal development with a concomitant delay in reaching puberty. These effects were subsequent to lower FSH concentrations at 330 and 438 days of age. In the fetus, the low peri-conception diet increased the proportion of seminiferous tubules and decreased blood vessel area in the testis, whereas low first trimester diet increased blood vessel number in the adult testis. We conclude that maternal dietary protein perturbation during conception and early gestation may alter male testis development and delay puberty in bulls

    Search for muon-neutrino emission from GeV and TeV gamma-ray flaring blazars using five years of data of the ANTARES telescope

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    The ANTARES telescope is well-suited for detecting astrophysical transient neutrino sources as it can observe a full hemisphere of the sky at all times with a high duty cycle. The background due to atmospheric particles can be drastically reduced, and the point-source sensitivity improved, by selecting a narrow time window around possible neutrino production periods. Blazars, being radio-loud active galactic nuclei with their jets pointing almost directly towards the observer, are particularly attractive potential neutrino point sources, since they are among the most likely sources of the very high-energy cosmic rays. Neutrinos and gamma rays may be produced in hadronic interactions with the surrounding medium. Moreover, blazars generally show high time variability in their light curves at different wavelengths and on various time scales. This paper presents a time-dependent analysis applied to a selection of flaring gamma-ray blazars observed by the FERMI/LAT experiment and by TeV Cherenkov telescopes using five years of ANTARES data taken from 2008 to 2012. The results are compatible with fluctuations of the background. Upper limits on the neutrino fluence have been produced and compared to the measured gamma-ray spectral energy distributionThe authors acknowledge the financial support of the funding agencies: Centre National de la Recherche Scientifique (CNRS), Commissariat a l'energie atomique et aux energies alternatives (CEA), Commission Europeenne (FEDER fund and Marie Curie Program), Region Ile-de-France (DIM-ACAV) Region Alsace (contrat CPER), Region Provence-Alpes-Cote d'Azur, Departement du Var and Ville de La Seyne-sur-Mer, France; Bundesministerium fur Bildung und Forschung (BMBF), Germany; Istituto Nazionale di Fisica Nucleare (INFN), Italy; Stichting voor Fundamenteel Onderzoek der Materie (FOM), Nederlandse organisatie voor Wetenschappelijk Onderzoek (NWO), the Netherlands; Council of the President of the Russian Federation for young scientists and leading scientific schools supporting grants, Russia; National Authority for Scientific Research (ANCS), Romania; Ministerio de Economia y Competitividad (MINECO), Prometeo and Grisolia programs of Generalitat Valenciana and MultiDark, Spain; Agence de l'Oriental and CNRST, Morocco. We also acknowledge the technical support of Ifremer, AIM and Foselev Marine for the sea operation and the CC-IN2P3 for the computing facilities.Adrián Martínez, S.; Albert, A.; André, M.; Anton, G.; Ardid Ramírez, M.; Aubert, J.; Baret, B.... (2015). Search for muon-neutrino emission from GeV and TeV gamma-ray flaring blazars using five years of data of the ANTARES telescope. Journal of Cosmology and Astroparticle Physics. 12(14):1-26. https://doi.org/10.1088/1475-7516/2015/12/014S1261214Becker, J. K. (2008). High-energy neutrinos in the context of multimessenger astrophysics. Physics Reports, 458(4-5), 173-246. doi:10.1016/j.physrep.2007.10.006Bloom, S. D., & Marscher, A. P. (1996). An Analysis of the Synchrotron Self-Compton Model for the Multi--Wave Band Spectra of Blazars. The Astrophysical Journal, 461, 657. doi:10.1086/177092Maraschi, L., Ghisellini, G., & Celotti, A. (1992). A jet model for the gamma-ray emitting blazar 3C 279. 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Search for a diffuse flux of high-energy νμ with the ANTARES neutrino telescope. Physics Letters B, 696(1-2), 16-22. doi:10.1016/j.physletb.2010.11.070Adrián-Martínez, S., Al Samarai, I., Albert, A., André, M., Anghinolfi, M., Anton, G., … Aubert, J.-J. (2012). SEARCH FOR COSMIC NEUTRINO POINT SOURCES WITH FOUR YEARS OF DATA FROM THE ANTARES TELESCOPE. The Astrophysical Journal, 760(1), 53. doi:10.1088/0004-637x/760/1/53Adrián-Martínez, S., Albert, A., André, M., Anghinolfi, M., Anton, G., Ardid, M., … Barrios, J. (2014). A search for time dependent neutrino emission from microquasars with the ANTARES telescope. Journal of High Energy Astrophysics, 3-4, 9-17. doi:10.1016/j.jheap.2014.06.002Adrián-Martínez, S., Albert, A., Al Samarai, I., André, M., Anghinolfi, M., Anton, G., … Aubert, J.-J. (2013). Search for muon neutrinos from gamma-ray bursts with the ANTARES neutrino telescope using 2008 to 2011 data. Astronomy & Astrophysics, 559, A9. doi:10.1051/0004-6361/201322169Abdo, A. A., Ackermann, M., Ajello, M., Antolini, E., Baldini, L., Ballet, J., … Bellazzini, R. (2010). GAMMA-RAY LIGHT CURVES AND VARIABILITY OF BRIGHTFERMI-DETECTED BLAZARS. The Astrophysical Journal, 722(1), 520-542. doi:10.1088/0004-637x/722/1/520Ackermann, M., Ajello, M., Allafort, A., Antolini, E., Atwood, W. B., Axelsson, M., … Bastieri, D. (2011). THE SECOND CATALOG OF ACTIVE GALACTIC NUCLEI DETECTED BY THEFERMILARGE AREA TELESCOPE. The Astrophysical Journal, 743(2), 171. doi:10.1088/0004-637x/743/2/171Hovatta, T., Pavlidou, V., King, O. G., Mahabal, A., Sesar, B., Dancikova, R., … Surace, J. (2014). Connection between optical and γ-ray variability in blazars. Monthly Notices of the Royal Astronomical Society, 439(1), 690-702. doi:10.1093/mnras/stt2494Adrián-Martínez, S., Al Samarai, I., Albert, A., André, M., Anghinolfi, M., Anton, G., … Aubert, J.-J. (2012). Search for neutrino emission from gamma-ray flaring blazars with the ANTARES telescope. Astroparticle Physics, 36(1), 204-210. doi:10.1016/j.astropartphys.2012.06.001Aguilar, J. A., Albert, A., Ameli, F., Amram, P., Anghinolfi, M., Anton, G., … Aubert, J.-J. (2005). Study of large hemispherical photomultiplier tubes for the ANTARES neutrino telescope. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 555(1-2), 132-141. doi:10.1016/j.nima.2005.09.035Amram, P., Anghinolfi, M., Anvar, S., Ardellier-Desages, F. ., Aslanides, E., Aubert, J.-J., … Battaglieri, M. (2002). The ANTARES optical module. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 484(1-3), 369-383. doi:10.1016/s0168-9002(01)02026-5Adrián-Martínez, S., Ageron, M., Aguilar, J. A., Samarai, I. A., Albert, A., André, M., … Ardid, M. (2012). The positioning system of the ANTARES Neutrino Telescope. 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    Murchison Widefield Array limits on radio emission from Antares neutrino events

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    We present a search, using the Murchison Widefield Array (MWA), for electromagnetic (EM) counterparts to two candidate high-energy neutrino events detected by the ANTARES neutrino telescope in 2013 November and 2014 March. These events were selected by ANTARES because they are consistent, within 0°.4, with the locations of galaxies within 20 Mpc of Earth. Using MWA archival data at frequencies between 118 and 182 MHz, taken ~20 days prior to, at the same time as, and up to a year after the neutrino triggers, we look for transient or strongly variable radio sources that are consistent with the neutrino positions. No such counterparts are detected, and we set a 5s upper limit for low-frequency radio emission of ~1037 erg s-1 for progenitors at 20 Mpc. If the neutrino sources are instead not in nearby galaxies, but originate in binary neutron star coalescences, our limits place the progenitors at z 0.2. While it is possible, due to the high background from atmospheric neutrinos, that neither event is astrophysical, the MWA observations are nevertheless among the first to follow up neutrino candidates in the radio, and illustrate the promise of wide-field instruments like MWA for detecting EM counterparts to such events
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