Crack path instabilities in DCDC experiments in the low speed regime

We studied the low speed fracture regime (0.1mm/s - 1nm/s) in different glassy materials (soda-lime glass, glass-ceramics) with variable but controlled length scale of heterogeneity. The chosen mechanical system enabled us to work in pure mode I (tensile) and at a fixed load on DCDC (double cleavage drilled compression) specimen. The internal residual stresses of studied samples were carefully relaxed by appropriate thermal treatment. By means of optical and atomic force (AFM) microscopy techniques fracture surfaces have been examined. We have shown for the first time that the crack front line underwent an out-of-plane oscillating behavior as a result of a reproducible sequence of instabilities. The wavelength of such a phenomenon is in the micrometer range and its amplitude in the nanometer range. These features were observed for different glassy materials providing that a typical length scale characterizing internal heterogeneities was lower than a threshold limit estimated to few nanometers. This effect is the first clear experimental evidence of crack path instabilities in the low speed regime in a uniaxial loading experiment. This phenomenon has been interpreted by referring to the stability criterion for a straight crack propagation as presented by Adda-Bedia et al. (Phys. Rev. Letters (1996) 76} p1497).Comment: 16 pages, 10 figures, submitted to Journal of Non-Crystalline Solid

Fracture of glassy materials as detected by real-time Atomic Force Microscopy (AFM) experiments

We have studied the low speed fracture regime for different glassy materials with variable but controlled length scales of heterogeneity in a carefully mastered surrounding atmosphere. By using optical and atomic force (AFM) microscopy techniques we tracked in real-time the crack tip propagation at the nanometer scale on a wide velocity range (1 mm/s and 0.1 nm/s and below). The influence of the heterogeneities on this velocity is presented and discussed. Our experiments revealed also -for the first time- that the crack advance proceeds through nucleation, growth and coalescence of nanometric damage cavities inside the amorphous phase, which generate large velocity fluctuations. The implications of the existence of such a nano-ductile fracture mode in glass are discussed.Comment: 6 pages, 5 figures, submitted to Applied surface Scienc

Glass breaks like metals, but at the nanometer scale

We report in situ Atomic Force Microscopy experiments which reveal the presence of nanoscale damage cavities ahead of a stress-corrosion crack tip in glass. Their presence might explain the departure from linear elasticity observed in the vicinity of a crack tip in glass. Such a ductile fracture mechanism, widely observed in the case of metallic materials at the micrometer scale, might be also at the origin of the striking similarity of the morphologies of fracture surfaces of glass and metallic alloys at different length scales.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Lett, few minor corrections, Fig. 1b change

‘This town’s a different town today’:: Policing and regulating the night-time economy

This article considers recent policing and regulatory responses to the night-time economy in England and Wales. Drawing upon the findings of a broader two-year qualitative investigation of local and national developments in alcohol policy, it identifies a dramatic acceleration of statutory activity, with 12 new or revised powers, and several more in prospect, introduced by the Labour Government within its first decade in office. Interview data and documentary sources are used to explore the degree to which the introduction of such powers, often accompanied by forceful rhetoric and high profile police action, has translated into a sustained expansion of control. Many of the new powers are spatially directed, as well as being focused upon the actions of distinct individuals or businesses, yet the willingness and capacity to apply powers to offending individuals in comparison to businesses is often variable and asymmetrical. The practice of negotiating order in the night-time economy is riddled with tensions and ambiguities that reflect the ad hoc nature and rapid escalation of the regulatory architecture. Night-time urban security governance is understood as the outcome of subtle organizational and interpersonal power-plays. Social orders, normative schemas and apportionments of blame thus arise as a byproduct of patterned (structural) relations

Mesure des émissions de pesticides pendant les applications. Le cas des traitements viticoles.

During 2 years (2001 to 2002) lab and field experimentation was carried out on a vineyard in south of France to quantify pesticide deposit on soil and vegetation and pesticide emission in air in real conditions and on a field unit scale. Original sampling methodologies were developed in this project. The objectives of this work was to forecast the amount of pesticide in the three compartments (soil, vegetation and air), in relation with spraying profiles, density of foliage, weather (rain episodes included). In addition, laboratory experimentation was carried out to finely characterise some processes (i.e. spray, flow penetration, droplets deposition, rain washing of deposits). In parallel three different models were developed: a representation of the vine at a field unit scale, a model of spray penetration and deposit in the vegetation and a model on rain washing of the pesticides deposits. The selected unit to couple the models is a representative volume of foliage.Des expérimentations ont été conduites pendant 2 ans, (2001 et 2002) dans un vignoble du Sud de la France pour quantifier le depot de pesticide sur le sol et la végétation ainsi que les émissions de produit vers l'air, en conditions réelles à l'échelle d'une parcelle. Des méthodes originales d'échantillonnage ont été développées dans ce projet. L'object est de prévoir les quantités de pesticide dans les compartiments sol, air et végétation en fonction du profil de pulvérisation, de la densité de végétation et du temps (y compris les épisodes pluvieux). Des expérimentations en laboratoires ont complété cette démarche pour caractériser certains procédés (pulvérisation, pénétration du jet, dépôt des gouttelettes, entraînement par ruissellement). En parallèle, trois différents modèles ont été développés : une représentation de la vigne à l'échelle de la parcelle, un modèle pour la pénétration du jet et le dépôt dans la végétation et un modèle d'entraînement par ruissellement. Le couplage de ces trois modèles s'est fait à l'échelle d'une un volume représentatif de végétation

Structure cristallographique de multicouches métalliques et magnétiques étudiées par spectroscopie d'absorption X

The results of X-ray Absorption Spectroscopy (XAS) measurements on magnetic Co/Cu and Fe/Cu multilayers show the capability of this technique to point out the dependence of crystallographic phase on the layers thickness and the presence of structural anisotropies and strain in these multilayers

Long-term results of monoclonal anti-Il2-receptor antibody versus polyclonal antilymphocyte antibodies as induction therapy in renal transplantation.

International audienceWe compared the influence of induction therapy on 5-year patient and graft survival as well as on renal function in 100 kidney graft recipients at low immunological risk treated with antilymphocyte globulin (n = 50) versus anti-IL-2R monoclonal antibody (n = 50) in a prospective multicenter study. Long-term immunosuppressive treatment included cyclosporine, mycophenolate mofetil, and a short course of steroids in all patients. Five year graft (86% vs 86%) and patient (94% vs 94%) survivals were identical in both study arms. Moreover, neither serum creatinine or proteinuria were significantly different between the two groups. Our results showed that the choice of the induction therapy seemed to not have a major impact on long-term outcomes among renal recipients at low immunological risk

Comparisons of the structures of the CM variants.

<p>(A) Sequence alignment of natural and simplified mutases. EcCM refers to the CM domain of the bifunctional chorismate mutase-prephenate dehydratase enzyme from <i>E. coli</i>. Residue numbers given here correspond to MjCM positions for all CMs. (B) Ribbon representation of 9-CM with the locations of the residues that change identity in going from 9-CM to 11-CM shown as black sticks and the transition state analog (TSA) ligands shown as sticks colored according to atom type. (C) Homology model structures of the reduced amino-acid alphabet variants (9-CM: red, 10-CM: blue, 11-CM black) superimposed on the X-ray crystal structure of EcCM (green) <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003187#pgen.1003187-Lee1" target="_blank">[27]</a> using Pymol. All structures were first energy-minimized in the GROMOS 53A6 force field.</p

Overview of amino acid substitutions at mutation hot spots for cassette mutagenesis libraries.

<p>The fraction of mutations is plotted as a function of selection stringency (where a high tetracycline concentration [Tet] corresponds to low stringency; unselected library members are grown in the presence of L-Phe and L-Tyr) under which corresponding clones grew. Approximately 10% and 0.5% of all library members complemented the CM-deficiency at 1000 ng/mL and 100 ng/mL tetracycline, respectively. For the selected variants, the numbers of occurrences were normalized over the number of clones sequenced at the given selection stringency. Values in parentheses indicate the number of clones sequenced.</p