There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of $1.0 \times 10^{-21}$. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1 {\sigma}. The source lies at a luminosity distance of $410^{+160}_{-180}$ Mpc corresponding to a redshift $z = 0.09^{+0.03}_{-0.04}$. In the source frame, the initial black hole masses are $36^{+5}_{-4} M_\odot$ and $29^{+4}_{-4} M_\odot$, and the final black hole mass is $62^{+4}_{-4} M_\odot$, with $3.0^{+0.5}_{-0.5} M_\odot c^2$ radiated in gravitational waves. All uncertainties define 90% credible intervals.These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

https://physics.aps.org/featured-article-pdf/10.1103/PhysRevLett.116.061102

Observation of Gravitational Waves from a Binary Black Hole Merger

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

On August 17, 2017 at 12∶41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave detectors made their first observation of a binary neutron star inspiral. The signal, GW170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per 8.0×10^{4}  years. We infer the component masses of the binary to be between 0.86 and 2.26  M_{⊙}, in agreement with masses of known neutron stars. Restricting the component spins to the range inferred in binary neutron stars, we find the component masses to be in the range 1.17-1.60  M_{⊙}, with the total mass of the system 2.74_{-0.01}^{+0.04}M_{⊙}. The source was localized within a sky region of 28  deg^{2} (90% probability) and had a luminosity distance of 40_{-14}^{+8}  Mpc, the closest and most precisely localized gravitational-wave signal yet. The association with the γ-ray burst GRB 170817A, detected by Fermi-GBM 1.7 s after the coalescence, corroborates the hypothesis of a neutron star merger and provides the first direct evidence of a link between these mergers and short γ-ray bursts. Subsequent identification of transient counterparts across the electromagnetic spectrum in the same location further supports the interpretation of this event as a neutron star merger. This unprecedented joint gravitational and electromagnetic observation provides insight into astrophysics, dense matter, gravitation, and cosmology.

/pdf/gw170817-observation-of-gravitational-waves-from-a-binary-q2x9byg981.pdf

GW170817: observation of gravitational waves from a binary neutron star inspiral

Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

/pdf/climate-change-2007-the-physical-science-basis-1x93ttz9jt.pdf

Climate Change 2007: The Physical Science Basis.

Les reseaux intranet s'affirment comme l'un des nouveaux dispositifs techniques majeurs dans les organisations et ce, quel que soit le contexte de celles-ci, pedagogique ou entrepreneurial. Toutefois, au-dela des potentialites affichees, l'image structurelle du systeme d'information, de communication et de travail supporte par l'intranet s'affirme de facon ambivalente, entre reduction a une dimension instrumentale connue et exploitation multidimensionnelle des ressources proposees. Nous etudions cette dialectique fondamentale au niveau des usages developpes dans un environnement de ce type. L'interaction de la dimension technique avec les composantes humaine et organisationnelle tend simultanement a consolider des niveaux d'usages elabores sur la base des dispositifs anterieurs et a stimuler de nouvelles logiques d'echanges. La realite de l'utilisation du reseau se situe dans une negociation permanente et iterative entre ces deux poles et se traduit par differentes strategies d'appropriation du systeme intranet. Pour mettre en evidence ces phenomenes d'usages, nous proposons de recueillir des indices mesurables et presentons une ebauche de protocole quantitatif illustre sur certains points avec un exemple concret (l'intranet du departement informatique de l'universite Michel de Montaigne). La methode proposee est quantitative et s'appuie sur des techniques relevant du Web Usage Mining.

https://archivesic.ccsd.cnrs.fr/sic_00000329/document

Les réseaux Intranet : stratégies d'usages et d'usagers dans l'appropriation des outils de communication. Etude expérimentale d'un contexte pédagogique

[orientation] La construction de la valeur hedonique d’une bibliotheque s’appuie sur les emotions et le plaisir ressentis lors des visites. Les methodes centrees utilisateurs peuvent etre utilisees dans un contexte academique pour construire ce type de valeur.

L’expérience utilisateur au cœur de la stratégie

Ice algae are critical components to the lipid-driven Arctic marine food web, particularly early in the spring. As little is known about these communities in multiyear ice (MYI), we aimed to provide a baseline of fatty acid (FA) and stable isotope signatures of sea-ice communities in MYI from the Lincoln Sea and compare these biomarkers to first-year ice (FYI). Significant differences in the relative proportions of approximately 25% of the identified FAs and significantly higher nitrogen stable isotope values (δ15N) in bottom-ice samples of FYI (δ15N = 6.4 ± 0.7%) compared to MYI (δ15N = 5.0 ± 0.4%) reflect different community compositions in the two ice types. Yet, the relative proportion of diatom- and dinoflagellate-associated FAs, as well as their bulk and most of the FA-specific carbon stable isotope compositions (δ13C) were not significantly different between bottom FYI (bulk δ13C: –28.4% to –26.7%, FA average δ13C: –34.4% to –31.7%) and MYI (bulk δ13C: –27.6% to –27.2%, FA average δ13C: –33.6% to –31.9%), suggesting at least partly overlapping community structures and similar biochemical processes within the ice. Diatom-associated FAs contributed, on average, 28% and 25% to the total FA content of bottom FYI and MYI, respectively, indicating that diatoms play a central role in structuring sea-ice communities in the Lincoln Sea. The differences in FA signatures of FYI and MYI support the view that different ice types harbor different inhabitants and that the loss of Arctic MYI will impact complex food web interactions with ice-associated ecosystems. Comparable nutritional quality of FAs, however, as indicated by similar average levels of polyunsaturated FAs in bottom FYI (33%) and MYI (28%), could help to ensure growth and reproduction of ice-associated grazers despite the shift from a MYI to FYI-dominated sea-ice cover with ongoing climate warming.

/pdf/fatty-acids-and-stable-isotope-signatures-of-first-year-and-4som3jgdta.pdf

Fatty acids and stable isotope signatures of first-year and multiyear sea ice in the Canadian High Arctic

The main purpose of our study is to design a new multimedia learning platform to help the staff acquire new skills for their professional progression In particular, this new platform is aimed at learners who do not appreciate conventional training methods, and who prefer training with new media supports personalized to their own background From a learner's point of view, the platform provides semantic searches for media supports and proposes automatically the most appropriate video according to the user's personalized pathway That video can be rendered according to the user's profile for enhancing specific information In addition, the platform allows users to add new video resources, which will be automatically annotated, and to update learning domains The present paper proposes a general design of the platform and the main ideas for addressing the arised research problems

Learning Café: a semantic multimedia collaborative platform for e-learning.

Low loss DIBS mirrors 1064 nm for the VIRGO interferometer

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