488 research outputs found
Invariance principle, multifractional Gaussian processes and long-range dependence
This paper is devoted to establish an invariance principle where the limit
process is a multifractional Gaussian process with a multifractional function
which takes its values in . Some properties, such as regularity and
local self-similarity of this process are studied. Moreover the limit process
is compared to the multifractional Brownian motion.Comment: Published in at http://dx.doi.org/10.1214/07-AIHP127 the Annales de
l'Institut Henri Poincar\'e - Probabilit\'es et Statistiques
(http://www.imstat.org/aihp/) by the Institute of Mathematical Statistics
(http://www.imstat.org
A Primer for Black Hole Quantum Physics
The mechanisms which give rise to Hawking radiation are revealed by analyzing
in detail pair production in the presence of horizons. In preparation for the
black hole problem, three preparatory problems are dwelt with at length: pair
production in an external electric field, thermalization of a uniformly
accelerated detector and accelerated mirrors. In the light of these examples,
the black hole evaporation problem is then presented.
The leitmotif is the singular behavior of modes on the horizon which gives
rise to a steady rate of production. Special emphasis is put on how each
produced particle contributes to the mean albeit arising from a particular
vacuum fluctuation. It is the mean which drives the semiclassical back
reaction. This aspect is analyzed in more detail than heretofore and in
particular its drawbacks are emphasized. It is the semiclassical theory which
gives rise to Hawking's famous equation for the loss of mass of the black hole
due to evaporation . Black hole thermodynamics is derived
from the evaporation process whereupon the reservoir character of the black
hole is manifest. The relation to the thermodynamics of the eternal black hole
through the Hartle--Hawking vacuum and the Killing identity are displayed.
It is through the analysis of the fluctuations of the field configurations
which give rise to a particular Hawking photon that the dubious character of
the semiclassical theory is manifest. The present frontier of research revolves
around this problem and is principally concerned with the fact that one calls
upon energy scales that are greater than Planckian and the possibility of a non
unitary evolution as well. These last subjects are presented in qualitative
fashion only, so that this review stops at the threshold of quantum gravity.Comment: An old review article on black hole evaporation and black hole
thermodynamics, put on the archive following popular demand, 178 pages, 21
figures (This text differs in slightly from the published version
Bulk Photodriven CO 2 Conversion through TiO 2 @Si(HIPE) Monolithic Macrocellular Foams
International audienceOperating photoâinduced reactions exclusively on catalyst surfaces while not exploiting the full catalyst volume generates a major footprint penalty for the photocatalytic reactor and leads to an inefficient use of the catalytic material. Photonic investigations clearly show that the solid foams have a strongly multidiffusive character, with photons being significantly trapped within the sample cores while addressing a photon mean free path lt = 20.1 ± 1.3 ”m. This 3D process both greatly limits backâreactions and promotes outstanding selectivity toward methane (around 80%) generation, and even ethane (around 18%) through CâC coupling reaction, with residual carbon monoxide and dihydrogen contents (around 2%). Silicaâtitania TiO2@Si(HIPE) selfâstanding macrocellular catalysts lead to optimal efficient thicknesses up to 20 times those of powders, thereby enhancing the way for real 3Dâphotodriven catalytic processes above the millimeter scale and up to a 6 mm thickness. A rather simple LangmuirâHinshelwood based kinetic model is proposed which highlights the strong dependence of photocatalytic reaction rates on light scattering and the crucial role on oxidation backâreactions. In addition, a strong correlation between light attenuation coefficient and photon mean free path and median pore aperture diameter is demonstrated, offering thus a tool for photocatalytic behavior prediction
The flavour of grape colour: anthocyanin content tunes aroma precursor composition by altering the berry microenvironment
Anthocyaninless (white) instead of black/red (coloured) fruits develop in grapevine cultivars without functional VviMYBA1 and VviMYBA2 genes, and this conditions the colour of wines that can be produced. To evaluate whether this genetic variation has additional consequences on fruit ripening and composition, we performed comparisons of microenvironment, transcriptomics, and metabolomics of developing grapes between near-isogenic white- and black-berried somatic variants of Garnacha and Tempranillo cultivars. Berry temperature was as much as 3.5 ÂșC lower in white- compared to black-berried Tempranillo. An RNA-seq study combined with targeted and untargeted metabolomics revealed that ripening fruits of white-berried variants were characterized by the up-regulation of photosynthesis-related and other light-responsive genes and by their higher accumulation of specific terpene aroma precursors, fatty acid-derived aldehyde volatiles, and phenylpropanoid precursor amino acids. MYBA1-MYBA2 function proved essential for flavonol trihydroxylation in black-berried somatic variants, which were also characterized by enhanced expression of pathogen defence genes in the berry skin and increased accumulation of C6-derived alcohol and ester volatiles and Îł-aminobutyric acid. Collectively, our results indicate that anthocyanin depletion has side-effects on grape composition by altering the internal microenvironment of the berry and the partitioning of the phenylpropanoid pathway. Our findings show how fruit colour can condition other fruit features, such as flavour potential and stress homeostasis
Excursion ArdĂšche (13-15 mai 1977)
International audienceLes massifs hercyniens ont été longuement érodés pendant le Permien. Des sédiments gréseux et dolomitiques du Trias se sont ensuite déposés sur une plate-forme uniformisée et peu profonde. Toutefois la monotonie de l'ensemble n'excluait pas l'influence de reliefs sous-marins d'origine hercynienne. Les termes liasiques montrent à la fois une épaisseur réduite et des variations de faciÚs dues à une plate-forme sous-marine instable. Les influences obéissent d'une part à la direction cévenole (NE-SW) et d'autre part à une direction qui lui est orthogonale. A partir du Callovien les conditions deviennent homogÚnes dans l'ensemble de la région et paraissent le rester jusque dans le Jurassique terminal
Urban Climate, Human behavior & Energy consumption: from LCZ mapping to simulation and urban planning (the MapUCE project)
International audienceThe MApUCE project aims to integrate in urban policies and most relevant legal documents quantitative data from urban microclimate, climate and energy.The primary objective of this project is to obtain climate and energy quantitative data from numerical simulations, focusing on urban microclimate and building energy consumption in the residential and service sectors, which represents in France 41% of the final energy consumption. Both aspects are coupled as building energy consumption is highly meteorologically dependent (e.g. domestic heating, air-conditioning) and heat waste impact the Urban Heat Island. We propose to develop, using national databases, a generic and automated method for generating Local Climate Zones (LCZ) for all cities in France, including the urban architectural, geographical and sociological parameters necessary for energy and microclimate simulations.As will be presented, previous projects on adaptation of cities to climate change have shown that human behavior is a very potent level to address energy consumption reduction, as much as urban forms or architectural technologies. Therefore, in order to further refine the coupled urban climate and energy consumption calculations, we will develop within TEB (and its Building Energy Module) a model of energy consumer behavior.The second objective of the project is to propose a methodology to integrate quantitative data in urban policies. Lawyers analyze the potential levers in legal and planning documents. A few âbest casesâ are also studied, in order to evaluate their performances. Finally, based on urban planning agencies requirements, we will define vectors to include quantified energy-climate data to legal urban planning documents. These vectors have to be understandable by urban planners and contain the relevant information.To meet these challenges, the project is organized around strongly interdisciplinary partners in the following fields: law, urban climate, building energetics, architecture, sociology, geography and meteorology, as well as the national federation of urban planning agencies.In terms of results, the cross-analysis of input urban parameters and urban micro-climate-energy simulated data will be available on-line as standardized maps for each of the studied cities. The urban parameter production tool as well as the models will be available as open-source. LCZ and associated urban (and social!) indicators may be integrated within the WUDAPT database
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