Collège de France

About: Collège de France is a education organization based out in Paris, France. It is known for research contribution in the topics: Population & Receptor. The organization has 6541 authors who have published 11983 publications receiving 648742 citations. The organization is also known as: College de France.

The North Anatolian fault in the Sea of Marmara

Abstract: [1] Using the detailed geometry and tectonics of the Main Marmara fault that connects the Gulf of Izmit fault with the Ganos fault established by Le Pichon et al. [2001] and the new GPS data set recently analyzed by Meade et al. [2002], we confirm the existence of a Marmara block delimited to the north by the northern branch of the North Anatolian fault (the Marmara branch) and to the south by the southern branch. The kinematics of this block indicate that the Marmara branch that crosses the Sea of Marmara is close to pure dextral strike slip at a rate of 23 mm/yr on its whole length. The short Cinarcik section is the only one where a significant extensional component is predicted. A simple kinematic model accounts for slip partitioning there, with 8–10 mm/yr of extension to the south of the basin and 23 mm/yr of dextral strike slip along the northern Cinarcik margin. The new GPS data demonstrate the existence of important asymmetric elastic loading along the Main Marmara fault that may have significant implications for the seismotectonics of the area. The expected future large earthquake may rupture the whole main Marmara fault. The partitioning in the Cinarcik basin may produce magnitude 7 normal faulting earthquakes if their repetition time is about 250 years. The 1896 earthquake may have been one of these normal fault earthquakes. The Marmara block is less than 1 Ma. Prior to its formation, it was part of the Anatolian block. At this time the Ganos fault was already a dextral strike-slip fault, but the fault system in the Sea of Marmara would have been affected by an extensional component increasing toward the east that accounts for the increasing size of the sedimentary basins eastward.

A ferroelectric quantum phase transition inside the superconducting dome of Sr1-xCaxTiO3-[delta]

Abstract: Slight changes in SrTiO’s nominal composition make it superconducting or ferroelectric. A compositional window for which the two phases exist is now reported; varying the fraction of Ca replacing Sr changes the superconducting critical temperature. SrTiO3, a quantum paraelectric1, becomes a metal with a superconducting instability after removal of an extremely small number of oxygen atoms2. It turns into a ferroelectric upon substitution of a tiny fraction of strontium atoms with calcium3. The two orders may be accidental neighbours or intimately connected, as in the picture of quantum critical ferroelectricity4. Here, we show that in Sr1−xCaxTiO3−δ (0.002 < x < 0.009, δ < 0.001) the ferroelectric order coexists with dilute metallicity and its superconducting instability in a finite window of doping. At a critical carrier density, which scales with the Ca content, a quantum phase transition destroys the ferroelectric order. We detect an upturn in the normal-state scattering and a significant modification of the superconducting dome in the vicinity of this quantum phase transition. The enhancement of the superconducting transition temperature with calcium substitution documents the role played by ferroelectric vicinity in the precocious emergence of superconductivity in this system, restricting possible theoretical scenarios for pairing.

Wasserspaltung mit Cobalt

Abstract: Die Energieversorgung der Zukunft kann nur durch grundlegende Neuerungen auf dem Gebiet billiger, nachhaltiger und effizienter Systeme zur Gewinnung und Speicherung von Energie aus erneuerbaren Quellen oder aus Sonnenlicht gesichert werden. Die Erzeugung von Wasserstoff, einem Brennstoff mit bemerkenswerten Eigenschaften, durch die Wasserspaltung mithilfe von Sonnenlicht ist in diesem Zusammenhang ein vielversprechender Ansatz. Wahrend die aktiven Zentren von wasserspaltenden Enzymen – wie Hydrogenasen und Photosystem II – Eisen-, Nickel- und Manganionen enthalten, hat sich Cobalt in den vergangenen funf Jahren als vielseitigstes unedles Metall bei der Entwicklung synthetischer Katalysatoren zur H2- und O2-Erzeugung durch Reduktion bzw. Oxidation von Wasser bewahrt. Solche Katalysatoren lassen sich mit Photosensibilisatoren zu Systemen fur die photokatalytische Wasserstofferzeugung aus Wasser koppeln.