University of Rennes

About: University of Rennes is a education organization based out in Rennes, France. It is known for research contribution in the topics: Population & Crystal structure. The organization has 18404 authors who have published 40374 publications receiving 995327 citations.

Singularities of Electromagnetic Fields¶in Polyhedral Domains

Abstract: In this paper, we investigate the singular solutions of time-harmonic Maxwell equations in a domain which has edges and polyhedral corners. It is now well known that in the presence of non-convex edges, the solution fields have no square integrable gradients in general and that the main singularities are the gradients of singular functions of the Laplace operator [4,–5]. We show how this type of result can be derived from the classical Mellin analysis, and how this analysis leads to sharper results concerning the singular parts which belong to H 1. For the singular functions, we exhibit simple and explicit formulas based on (generalized) Dirichlet and Neumann singularities for the Laplace operator. These formulas are more explicit than the results announced in our note [10].

Global sea-level budget 1993 - present

Abstract: Global mean sea level is an integral of changes occurring in the climate system in response to unforced climate variability as well as natural and anthropogenic forcing factors. Its temporal evolution allows detecting changes (e.g., acceleration) in one or more components. Study of the sea level budget provides constraints on missing or poorly known contributions, such as the unsurveyed deep ocean or the still uncertain land water component. In the context of the World Climate Research Programme Grand Challenge entitled “Regional Sea Level and Coastal Impacts”, an international effort involving the sea level community worldwide has been recently initiated with the objective of assessing the various data sets used to estimate components of the sea level budget during the altimetry era (1993 to present). These data sets are based on the combination of a broad range of space-based and in situ observations, model estimates and algorithms. Evaluating their quality, quantifying uncertainties and identifying sources of discrepancies between component estimates is extremely useful for various applications in climate research. This effort involves several tens of scientists from about fifty research teams/institutions worldwide (www.wcrp-climate.org/grand-challenges/gc-sea- level). The results presented in this paper are a synthesis of the first assessment performed during 2017-2018. We present estimates of the altimetry-based global mean sea level (average rate of 3.1 +/- 0.3 mm/yr and acceleration of 0.1 mm/yr2 over 1993-present), as well as of the different components of the sea level budget (http://doi.org/10.17882/54854). We further examine closure of the sea level budget, comparing the observed global mean sea level with the sum of components. Ocean thermal expansion, glaciers, Greenland and Antarctica contribute by 42%, 21%, 15% and 8% to the global mean sea level over the 1993-present. We also study the sea level budget over 2005-present, using GRACE-based ocean mass estimates instead of sum of individual mass components. Results show closure of the sea level budget within 0.3 mm/yr. Substantial uncertainty remains for the land water storage component, as shown in examining individual mass contributions to sea level.

Surface-Based 3D Modeling of Geological Structures

Abstract: Building a 3D geological model from field and subsurface data is a typical task in geological studies involving natural resource evaluation and hazard assessment. However, there is quite often a gap between research papers presenting case studies or specific innovations in 3D modeling and the objectives of a typical class in 3D structural modeling, as more and more is implemented at universities. In this paper, we present general procedures and guidelines to effectively build a structural model made of faults and horizons from typical sparse data. Then we describe a typical 3D structural modeling workflow based on triangulated surfaces. Our goal is not to replace software user guides, but to provide key concepts, principles, and procedures to be applied during geomodeling tasks, with a specific focus on quality control.

Palladium‐Catalyzed C3 or C4 Direct Arylation of Heteroaromatic Compounds with Aryl Halides by C ? H Bond Activation

Abstract: In recent years, palladium-catalyzed direct C2 or C5 arylation of heteroaromatic compounds with aryl halides by C-H bond activation has become a popular method for generating carbon-carbon bonds For this reaction, a wide variety of heteroaromatics, such as furans, thiophenes, pyrroles, thiazoles, oxazoles, imidazoles, pyrazoles, indoles, triazoles, or even pyridines, can be employed C3 and C4 arylations of heteroaromatics by C-H bond activation have also been described Such reactions initially attracted much less attention than the C2 or C5 arylations due to the lower reactivity of the C3 and C4 positions However, in more recent years, several results from using modified and improved catalysts and reaction conditions have been reported, which permit C3 and C4 arylations in synthetically useful yields Several intramolecular cyclizations of 2-substituted heterocycles have been described, with formation of a C—C bond on C3 resulting in the formation of five- to nine-membered rings incorporating pyrroles, indoles, thiophenes, furans, isoxazoles, or pyridines Intermolecular C3 or C4 direct arylations are still quite rare for some heteroaromatics and are in several cases not highly regioselective For such reactions, the best results have been obtained using pyrroles, thiophenes, or furans For selected substrates, regioselective arylation at C3 or C4 of the heteroaromatic compounds took place under appropriate reaction conditions Only a few examples of intermolecular couplings using oxazoles, thiazoles, imidazoles, isoxazoles, pyrazoles, triazoles, or pyridines have been reported For most of these reactions, aryl iodides or bromides have been used as coupling partners, although a few examples with aryl chlorides are also known This method allows the synthesis of complex molecules in only a few steps, and will provide access to a very wide variety of new heteroaryl derivatives in the next years