Orbital reflectometry

The occupation of d-orbitals controls the magnitude and anisotropy of the inter-atomic electron transfer in transition metal oxides and hence exerts a key influence on their chemical bonding and physical properties. Atomic-scale modulations of the orbital occupation at surfaces and interfaces are believed to be responsible for massive variations of the magnetic and transport properties, but could thus far not be probed in a quantitative manner. Here we show that it is possible to derive quantitative, spatially resolved orbital polarization profiles from soft x-ray reflectivity data, without resorting to model calculations. We demonstrate that the method is sensitive enough to resolve differences of 3 % in the occupation of Ni e_g orbitals in adjacent atomic layers of a LaNiO3-LaAlO3 superlattice, in good agreement with ab-initio electronic-structure calculations. The possibility to quantitatively correlate theory and experiment on the atomic scale opens up many new perspectives for orbital physics in d-electron materials

Interdependency of subsurface carbon distribution and graphene-catalyst interaction.

The dynamics of the graphene-catalyst interaction during chemical vapor deposition are investigated using in situ, time- and depth-resolved X-ray photoelectron spectroscopy, and complementary grand canonical Monte Carlo simulations coupled to a tight-binding model. We thereby reveal the interdependency of the distribution of carbon close to the catalyst surface and the strength of the graphene-catalyst interaction. The strong interaction of epitaxial graphene with Ni(111) causes a depletion of dissolved carbon close to the catalyst surface, which prevents additional layer formation leading to a self-limiting graphene growth behavior for low exposure pressures (10(-6)-10(-3) mbar). A further hydrocarbon pressure increase (to ∼10(-1) mbar) leads to weakening of the graphene-Ni(111) interaction accompanied by additional graphene layer formation, mediated by an increased concentration of near-surface dissolved carbon. We show that growth of more weakly adhered, rotated graphene on Ni(111) is linked to an initially higher level of near-surface carbon compared to the case of epitaxial graphene growth. The key implications of these results for graphene growth control and their relevance to carbon nanotube growth are highlighted in the context of existing literature.R.S.W. acknowledges a Research Fellowship from St. John’s College, Cambridge. S.H. acknowledges funding from ERC grant InsituNANO (No. 279342) and EPSRC under grant GRAPHTED (Ref. EP/K016636/1). We acknowledge the Helmholtz-Zentrum-Berlin Electron storage ring BESSY II for provision of synchrotron radiation at the ISISS beamline and we thank the BESSY staff for continuous support of our experiments. This research was partially supported by the EU FP7 Work Programme under grant Graphene Flagship (No. 604391). PRK acknowledges funding the Cambridge Commonwealth Trust. H.A. and C.B. acknowledge J.-Y. Raty and B. Legrand for fruitful discussions.This is the final published version. It's also available from ACS at http://pubs.acs.org/doi/abs/10.1021/ja505454v

L’usage par les juges allemands de la connaissance scientifique sur la dangerosité des pesticides et des ondes électromagnétiques

This article offers an analysis of how German courts deal with scientific knowledge concerning the risks of pesticides and of electromagnetic waves. Of course, the courts need to establish scientific knowledge in all relevant cases dealing with risk evaluation, the question is, however, how this knowledge can be established in the proceedings. Concerning administrative court proceedings, the courts have a tendency to follow the results and evaluations of the competent authority. In case there exist official threshold value established by specialized authorities, the courts will generally apply these values, in administrative as well as ordinary proceedings. Opinions of judicial experts, however, are generally used only to confirm the result of the competent authority or the result found by application of the threshold values established by specialized authorities. If the opinion of a judicial expert is not in conformity with these findings, the court will usually argue that the opinion is not convincing

L’usage par les juges allemands de la connaissance scientifique sur la dangerosité des pesticides et des ondes électromagnétiques

This article offers an analysis of how German courts deal with scientific knowledge concerning the risks of pesticides and of electromagnetic waves. Of course, the courts need to establish scientific knowledge in all relevant cases dealing with risk evaluation, the question is, however, how this knowledge can be established in the proceedings. Concerning administrative court proceedings, the courts have a tendency to follow the results and evaluations of the competent authority. In case there exist official threshold value established by specialized authorities, the courts will generally apply these values, in administrative as well as ordinary proceedings. Opinions of judicial experts, however, are generally used only to confirm the result of the competent authority or the result found by application of the threshold values established by specialized authorities. If the opinion of a judicial expert is not in conformity with these findings, the court will usually argue that the opinion is not convincing

L’usage par les juges allemands de la connaissance scientifique sur la dangerosité des pesticides et des ondes électromagnétiques

This article offers an analysis of how German courts deal with scientific knowledge concerning the risks of pesticides and of electromagnetic waves. Of course, the courts need to establish scientific knowledge in all relevant cases dealing with risk evaluation, the question is, however, how this knowledge can be established in the proceedings. Concerning administrative court proceedings, the courts have a tendency to follow the results and evaluations of the competent authority. In case there exist official threshold value established by specialized authorities, the courts will generally apply these values, in administrative as well as ordinary proceedings. Opinions of judicial experts, however, are generally used only to confirm the result of the competent authority or the result found by application of the threshold values established by specialized authorities. If the opinion of a judicial expert is not in conformity with these findings, the court will usually argue that the opinion is not convincing

L'usage de la connaissance scientifique des pesticides et ondes électromagnétiques en Europe

Les articles présentés dans ce hors-série de [VertigO] sont issus d’une recherche collective menée au sein du laboratoire SAGE de l’Université de Strasbourg avec le soutien du CIERA (Centre Interdisciplinaire d’études et de recherche sur l’Allemagne) de 2015 à 2016. L’objectif est d’éclairer, à travers une mise en perspective pluridisciplinaire, les façons dont les divers acteurs que sont principalement le pouvoir exécutif, le législateur, le juge, l’avocat et les autorités indépendantes utilisent la connaissance scientifique relative aux risques liés aux ondes électromagnétiques et pesticides. Comment définir la connaissance scientifique, quelles méthodes concourent à son émergence? Existe-il un (risque de) détournement de ladite connaissance scientifique ? Est-ce de la responsabilité de ces acteurs de solliciter d’autres expertises en cas d’incertitudes ou de controverses scientifiques ? Quand peut-on parler de controverses et quelles conséquences en déduire quant au degré de protection pour le citoyen ? Ce sont certaines des questions qui sont abordées. Afin de circonscrire les études, deux risques majeurs ont été retenus qui ont les particularités communes d’être nouveaux, de faire l’objet d’un contentieux en pleine explosion, d’être invisibles et de nous concerner tous, du consommateur, travailleur au producteur. Le champ d’investigation se limite aussi aux ordres juridiques français et allemands, tout en prenant le soin d’inclure la réglementation européenne. Ces études révèlent comment la réglementation de ces nouveaux risques est fortement tributaire de la manière dont la science est, ou non, sollicitée. Ce Hors-série a été publié avec le concours de l'UMR Société, Acteurs, gouvernement en Europe (SAGE) et du Centre Interdisciplinaire d’études et de recherche sur l’Allemagne (CIERA)

Emerging Diluted Ferromagnetism in High- T

Defects in ceramic materials are generally seen as detrimental to their functionality and applicability. Yet, in some complex oxides, defects present an opportunity to enhance some of their properties or even lead to the discovery of exciting physics, particularly in the presence of strong correlations. A paradigmatic case is the high‐temperature superconductor YBa(2)Cu(3)O(7‐δ) (Y123), in which nanoscale defects play an important role as they can immobilize quantized magnetic flux vortices. Here previously unforeseen point defects buried in Y123 thin films that lead to the formation of ferromagnetic clusters embedded within the superconductor are unveiled. Aberration‐corrected scanning transmission microscopy has been used for exploring, on a single unit‐cell level, the structure and chemistry resulting from these complex point defects, along with density functional theory calculations, for providing new insights about their nature including an unexpected defect‐driven ferromagnetism, and X‐ray magnetic circular dichroism for bearing evidence of Cu magnetic moments that align ferromagnetically even below the superconducting critical temperature to form a dilute system of magnetic clusters associated with the point defects