Coherent and incoherent bands in La and Rh doped Sr3Ir2O7

In Sr2IrO4 and Sr3Ir2O7, correlations, magnetism and spin-orbit coupling compete on similar energy scales, creating a new context to study metal-insulator transitions (MIT). We use here Angle-Resolved photoemission to investigate the MIT as a function of hole and electron doping in Sr3Ir2O7, obtained respectively by Ir/Rh and Sr/La substitutions. We show that there is a clear reduction as a function of doping of the gap between a lower and upper band on both sides of the Fermi level, from 0.2eV to 0.05eV. Although these two bands have a counterpart in band structure calculations, they are characterized by a very different degree of coherence. The upper band exhibits clear quasiparticle peaks, while the lower band is very broad and loses weight as a function of doping. Moreover, their ARPES spectral weights obey different periodicities, reinforcing the idea of their different nature. We argue that a very similar situation occurs in Sr2IrO4 and conclude that the physics of the two families is essentially the same

Nonequilibrium thermodynamics versus model grain growth: derivation and some physical implications

Nonequilibrium thermodynamics formalism is proposed to derive the flux of grainy (bubbles-containing) matter, emerging in a nucleation growth process. Some power and non-power limits, due to the applied potential as well as owing to basic correlations in such systems, have been discussed. Some encouragement for such a discussion comes from the fact that the nucleation and growth processes studied, and their kinetics, are frequently reported in literature as self-similar (characteristic of algebraic correlations and laws) both in basic entity (grain; bubble) size as well as time scales.Comment: 8 pages, 1 figur

Overexpression of Protein Kinase C Confers Protection Against Antileukemic Drugs by Inhibiting the Redox-Dependent Sphingomyelinase Activation

ABSTRACT Induction of apoptosis by chemotherapeutic drugs involves the sphingomyelin-ceramide (SM-CER) pathway. This signaling is critically dependent on reactive oxygen species (ROS) generation and p53/p56 Lyn activation. In this study, we have investigated the influence of protein kinase C (PKC) overexpression on the SM-CER pathway in U937 human leukemia cell line. We show that PKC overexpression resulted in delayed apoptosis and significant resistance to both 1-␤-D-arabinofuranosylcytosine (ara-C) and daunorubicin (DNR), but there was no significant protection against cell-permeant C 6 -CER. Moreover, PKC overexpression abrogated drug-induced neutral sphingomyelinase stimulation and CER generation by inhibiting ROS production. We further investigated p53/p56 Lyn activation in PKC-overexpressing U937 cells treated with ara-C or DNR. We demonstrate that PKC inhibited p53/p56 Lyn phosphorylation and stimulation in drug-or H 2 O 2 -treated cells, suggesting that p53/p56 Lyn redox regulation is altered in PKC-overexpressing cells. Finally, we show that PKC-overexpressing U937 cells displayed accelerated H 2 O 2 detoxification. Altogether, our study provides evidence for the role of PKC in the negative regulation of drug-induced SM-CER pathway

A Re-examination of the Portevin-Le Chatelier Effect in Alloy 718 in Connection with Oxidation-Assisted Intergranular Cracking

In Alloy 718, a sharp transition exists in the fracture path changing from an intergranular brittle mode to a transgranular ductile mode which is associated with a transition of flow behavior from smooth in the dynamic strain aging regime to a serrated one in the Portevin-Le Chatelier (PLC) regime. In order to better understand both deformation and rupture behavior, PLC phenomenon in a precipitation-hardened nickel-base superalloy was carefully investigated in a wide range of temperatures [573 K to 973 K (300°C to 700°C)] and strain rates (109^-5 to 3.2910^-2 s^-1 ). Distinction was made between two PLC domains characterized by different evolutions of the critical strain to the onset of the first serration namely normal and inverse behavior. The apparent activation energies associated with both domains were determined using different methods. Results showed that normal and inverse behavior domains are related to dynamic interaction of dislocations with, respectively, interstitial and substitutional solutes atoms. This analysis confirms that normal PLC regime may be associated to the diffusion of carbon atoms, whereas the substitutional species involves in the inverse regime is discussed with an emphasis on the role of Nb and Mo

Numerical simulation of a coarsening two-dimensional network

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Etude du rayonnement solaire global et direct à Carpentras

In this paper, we establish relations giving power of global radiation falling on a horizontal surface and of direct radiation on a normal surface, versus time, for typical clear days, in Carpentras (France), for the year 1979.Dans cette étude, nous établissons des relations permettant le calcul, en fonction du temps, de l'éclairement énergétique global sur une surface horizontale et de l'éclairement énergétique direct sur une surface normale au rayonnement solaire, pour des journées types de temps clair à Carpentras en 1979

Etude du rayonnement solaire global et direct à Carpentras

Dans cette étude, nous établissons des relations permettant le calcul, en fonction du temps, de l'éclairement énergétique global sur une surface horizontale et de l'éclairement énergétique direct sur une surface normale au rayonnement solaire, pour des journées types de temps clair à Carpentras en 1979