77 research outputs found
Reversibly compressible and freestanding monolithic carbon spherogels
We present a versatile strategy to tailor the nanostructure of monolithic carbon aerogels. By use of an aqueous colloidal solution of polystyrene in the sol-gel processing of resorcinol-formaldehyde gels, we can prepare, after supercritical drying and successive carbonization, freestanding monolithic carbon aerogels, solely composed of interconnected and uniformly sized hollow spheres, which we name carbon spherogels. Each sphere is enclosed by a microporous carbon wall whose thickness can be adjusted by the polystyrene concentration, which affects the pore texture as well as the mechanical properties of the aerogel monolith. In this study, we used monodisperse polystyrene spheres of approximately 250âŻnm diameter, which result in an inner diameter of the final hollow carbon spheres of approximately 200âŻÂ±âŻ5âŻnm due to shrinkage during the carbonization process. The excellent homogeneity of the samples, as well as uniform sphere geometries, are confirmed by small- and angle X-ray scattering. The presence of macropores between the hollow spheres creates a monolithic network with the benefit of being reversibly compressible up to 10% linear strain without destruction. Electrochemical tests demonstrate the applicability of ground and CO2 activated carbon spherogels as electrode materials
Structural transitions in amorphous H 2 O and D 2 O: the effect of temperature
Abstract We have recently observed amorphous-amorphous transitions incurred upon decompressing very high density amorphous ice (VHDA) at 140 K from 1.1 to <0.02 GPa in a piston-cylinder setup by monitoring the piston displacement as a function of pressure and by taking powder x-ray diffractograms of quench-recovered samples (Winkel et al 2008 J. Chem. Phys. 128 044510). Here we study the effect of changing the temperature from 77 to 160 K during decompression from 1.1 to <0.02 GPa, and the effect of substituting D 2 O for H 2 O at 140 and 143 K. At 77 K all structural transitions are arrested and six-coordinated VHDA is quench recovered. At 125-136 K the continuous transition to five-coordinated expanded high density amorphous ice (eHDA) takes place. At 139-140 K, both the continuous transition to eHDA and the quasi-discontinuous transition to four-coordinated LDA are observed, i.e. VHDA â eHDA â LDA. At 142-144 K, crystallization to mixtures of cubic ice Ic and ice IX is observed prior to the quasi-discontinuous transition, i.e. VHDA â eHDA â ice Ic/ice IX. At 160 K ice Ic is recovered, which most likely transforms from a high-pressure ice (HPI) such as ice V, i.e. VHDA â HPI â ice Ic. Exchanging D 2 O for H 2 O at 140 K does not significantly affect the amorphous-amorphous transitions: both the decompression curves and the powder x-ray diffractograms are unaffected within the experimental resolution. However, at 143 K D 2 O-VHDA can be decompressed according to the sequence VHDA â eHDA â LDA, i.e. crystallization can be suppressed at âŒ3 K higher temperatures
Search for muon-neutrino emission from GeV and TeV gamma-ray flaring blazars using five years of data of the ANTARES telescope
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
Search for muon-neutrino emission from GeV and TeV gamma-ray flaring blazars using five years of data of the ANTARES telescope
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.AdriĂĄn MartĂnez, S.; Albert, A.; AndrĂ©, M.; Anton, G.; Ardid RamĂrez, 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 ΜΌ with the ANTARES neutrino telescope. Physics Letters B, 696(1-2), 16-22. doi:10.1016/j.physletb.2010.11.070AdriĂĄn-MartĂnez, S., Al Samarai, I., Albert, A., AndrĂ©, 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/760/1/53AdriĂĄn-MartĂnez, S., Albert, A., AndrĂ©, 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.2014.06.002AdriĂĄn-MartĂnez, S., Albert, A., Al Samarai, I., AndrĂ©, 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 Îł-ray variability in blazars. Monthly Notices of the Royal Astronomical Society, 439(1), 690-702. doi:10.1093/mnras/stt2494AdriĂĄn-MartĂnez, S., Al Samarai, I., Albert, A., AndrĂ©, 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)02026-5AdriĂĄn-MartĂnez, S., Ageron, M., Aguilar, J. A., Samarai, I. A., Albert, A., AndrĂ©, M., ⊠Ardid, M. (2012). The positioning system of the ANTARES Neutrino Telescope. 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âYou ainât gonna get away witâ this, Djangoâ: Fantasy, fiction and subversion in Quentin Tarantinoâs, Django Unchained
From 2009 to 2015, U.S. director, Quentin Tarantino, released three films that were notable for their focus on particular historical events, periods and individuals (Inglorious Basterds 2009; Django Unchained 2012; The Hateful Eight 2015). Together, these films offered a specifically âTarantinianâ rendering of history: rewriting, manipulating and, for some, unethically deploying history for aesthetic effect. With regard to Django Unchained, this article examines how Tarantinoâs historical revisionism provides a valuable point of inquiry into the ways in which âhistoryâ is depicted on-screen and, more importantly, how depictions of âthe pastâ can prove useful for highlighting underlying contradictions, ambivalences and ambiguities in the âpresentâ. Drawing upon Slavoj ĆœiĆŸekâs Lacanian approach to film analysis, it is argued that through a combination of fantasy, subversion and counterfactual possibility â most notable in the filmâs final stand-off between its leading black characters â Tarantino is able to render the Real of U.S. slavery as an ahistorical antagonism. This antagonism highlights the ongoing trauma of these events in the present as well as the use of fantasy to explore their traumatic subject matter. Such historical fictions are not fixed to the past but, via an encounter with the Real, can be used to appraise the present
Deep sea tests of a prototype of the KM3NeT digital optical module
The first prototype of a photo-detection unit of the future KM3NeT neutrino telescope has been deployed in the deepwaters of the Mediterranean Sea. This digital optical module has a novel design with a very large photocathode area segmented by the use of 31 three inch photomultiplier tubes. It has been integrated in the ANTARES detector for in-situ testing and validation. This paper reports on the first months of data taking and rate measurements. The analysis results highlight the capabilities of the new module design in terms of background suppression and signal recognition. The directionality of the optical module enables the recognition of multiple Cherenkov photons from the same (40)Kdecay and the localisation of bioluminescent activity in the neighbourhood. The single unit can cleanly identify atmospheric muons and provide sensitivity to the muon arrival directions
Letter of intent for KM3NeT 2.0
The main objectives of the KM3NeT Collaboration are
(
i
)
the discovery and
subsequent observation of high-energy neutrino sources in the Universe and
(
ii
)
the determination of the mass hierarchy of neutrinos. These objectives are
strongly motivated by two recent important discoveries, namely:
(
1
)
the high-
energy astrophysical neutrino signal reported by IceCube and
(
2
)
the sizable
contribution of electron neutrinos to the third neutrino mass eigenstate as
reported by Daya Bay, Reno and others. To meet these objectives, the
KM3NeT Collaboration plans to build a new Research Infrastructure con-
sisting of a network of deep-sea neutrino telescopes in the Mediterranean Sea.
A phased and distributed implementation is pursued which maximises the
access to regional funds, the availability of human resources and the syner-
gistic opportunities for the Earth and sea sciences community. Three suitable
deep-sea sites are selected, namely off-shore Toulon
(
France
)
, Capo Passero
(
Sicily, Italy
)
and Pylos
(
Peloponnese, Greece
)
. The infrastructure will consist
of three so-called building blocks. A building block comprises 115 strings,
each string comprises 18 optical modules and each optical module comprises
31 photo-multiplier tubes. Each building block thus constitutes a three-
dimensional array of photo sensors that can be used to detect the Cherenkov
light produced by relativistic particles emerging from neutrino interactions.
Two building blocks will be sparsely con
fi
gured to fully explore the IceCube
signal with similar instrumented volume, different methodology, improved
resolution and complementary
fi
eld of view, including the galactic plane. One
building block will be densely con
fi
gured to precisely measure atmospheric
neutrino oscillations.
Original content from this work may be used under the ter
Multiwavelength study of quiescent states of MRK 421 with unprecedented hard x-ray coverage provided by<i> NuSTAR</i> in 2013
The Changing Landscape for Stroke\ua0Prevention in AF: Findings From the GLORIA-AF Registry Phase 2
Background GLORIA-AF (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients with Atrial Fibrillation) is a prospective, global registry program describing antithrombotic treatment patterns in patients with newly diagnosed nonvalvular atrial fibrillation at risk of stroke. Phase 2 began when dabigatran, the first non\u2013vitamin K antagonist oral anticoagulant (NOAC), became available. Objectives This study sought to describe phase 2 baseline data and compare these with the pre-NOAC era collected during phase 1. Methods During phase 2, 15,641 consenting patients were enrolled (November 2011 to December 2014); 15,092 were eligible. This pre-specified cross-sectional analysis describes eligible patients\u2019 baseline characteristics. Atrial fibrillation disease characteristics, medical outcomes, and concomitant diseases and medications were collected. Data were analyzed using descriptive statistics. Results Of the total patients, 45.5% were female; median age was 71 (interquartile range: 64, 78) years. Patients were from Europe (47.1%), North America (22.5%), Asia (20.3%), Latin America (6.0%), and the Middle East/Africa (4.0%). Most had high stroke risk (CHA2DS2-VASc [Congestive heart failure, Hypertension, Age 6575 years, Diabetes mellitus, previous Stroke, Vascular disease, Age 65 to 74 years, Sex category] score 652; 86.1%); 13.9% had moderate risk (CHA2DS2-VASc = 1). Overall, 79.9% received oral anticoagulants, of whom 47.6% received NOAC and 32.3% vitamin K antagonists (VKA); 12.1% received antiplatelet agents; 7.8% received no antithrombotic treatment. For comparison, the proportion of phase 1 patients (of N = 1,063 all eligible) prescribed VKA was 32.8%, acetylsalicylic acid 41.7%, and no therapy 20.2%. In Europe in phase 2, treatment with NOAC was more common than VKA (52.3% and 37.8%, respectively); 6.0% of patients received antiplatelet treatment; and 3.8% received no antithrombotic treatment. In North America, 52.1%, 26.2%, and 14.0% of patients received NOAC, VKA, and antiplatelet drugs, respectively; 7.5% received no antithrombotic treatment. NOAC use was less common in Asia (27.7%), where 27.5% of patients received VKA, 25.0% antiplatelet drugs, and 19.8% no antithrombotic treatment. Conclusions The baseline data from GLORIA-AF phase 2 demonstrate that in newly diagnosed nonvalvular atrial fibrillation patients, NOAC have been highly adopted into practice, becoming more frequently prescribed than VKA in Europe and North America. Worldwide, however, a large proportion of patients remain undertreated, particularly in Asia and North America. (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients With Atrial Fibrillation [GLORIA-AF]; NCT01468701
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