Introduction to the effect of the screening phenomenon of slip bands within grain microstructure

AbstractThe aim of the current contribution is to compute grain boundary (GB) stress fields and fracture using respectively finite elements (FE) methods and analytical model in the case of several slip bands (SB) impinging the GB. Indeed, local plasticity in thin bands is largely observed during straining of polycrystals. For instance, channels (or clear bands) within grains are observed after post-irradiation tensile loading [Cui et al, 2013]. Slip bands thickness is about 50 nm which is about hundred times higher than the classical pile-up thickness. The intersection of such slip bands (SBs) with grain boundaries (GBs) can trigger microcracks initiation. Then, it is important to propose a fracture criterion for predicting GB microcracks nucleation as SBs impinge GB. Despite of many issuesdevelop pile-up based models of GB stress fields, observations showthat morethan single slip band are observed in real situation.Then, the main carried out tool is the analysis of the screening effects of SB on parameters of early validated single SB model

Le rôle de l'information en droit des entreprises en difficulté

L’information est un moyen de gestion fiable et une garantie indispensable pour la protection des intérêts des acteurs de l’activité économique. Elle joue un rôle important dans la prévention et le traitement des difficultés des entreprises. En effet, à la lumière des informations comptables, financières et sociales, les dirigeants peuvent prévenir les difficultés et prendre les décisions adaptées à la situation de l’entreprise. Toutefois, en cas de procédures collectives, le besoin de protection se substitue à celui de prévention. Le rôle de l’information est dès lors de garantir le bon déroulement de la procédure collective et d’assurer la protection des intérêts des parties.Information is a reliable means of management and essential for the protection of the interests of actors in economic activity. It plays an important role in the prevention and treatment of business difficulties. Indeed, in light of the accounting, financial and social information, managers can prevent problems and make decisions appropriate to the situation of the company. However, in case of insolvency, the need for protection is substituted for that of prevention. The role of information is therefore to ensure the smooth running of insolvency and to protect the interests of the parties

Thirty Femtograms Detection of Iron in Mammalian Cells

Inorganic nanomaterials and particles with enhanced optical, mechanical or magnetic attributes are currently being developed for a wide range of applications. Safety issues have been formulated however concerning their potential cyto- and genotoxicity. For in vivo and in vitro experimentations, recent developments have heightened the need of simple and facile methods to measure the amount of nanoparticles taken up by cells or tissues. In this work, we present a rapid and highly sensitive method for quantifying the uptake of iron oxide nanoparticles in mammalian cells. Our approach exploits the digestion of incubated cells with concentrated hydrochloric acid reactant and a colorimetric based UV-Visible absorption technique. The technique allows the detection of iron in cells over 4 decades in masses, from 0.03 to 300 picograms per cell. Applied on particles of different surface chemistry and sizes, the protocol demonstrates that the coating is the key parameter in the nanoparticle/cell interactions. The data are corroborated by scanning and transmission electron microscopy and stress the importance of resiliently adsorbed nanoparticles at the plasma membrane.Comment: 18 pages, 6 figure

Faillite de l'État et montée de l'islamisme : une interprétation de la crise algérienne

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

In vitro toxicity of nanoceria: effect of coating and stability in biofluids

Due to the increasing use of nanometric cerium oxide in applications, concerns about the toxicity of these particles have been raised and have resulted in a large number of investigations. We report here on the interactions between 7 nm anionically charged cerium oxide particles and living mammalian cells. By a modification of the particle coating including low-molecular weight ligands and polymers, two generic behaviors are compared: particles coated with citrate ions that precipitate in biofluids and particles coated with poly(acrylic acid) that are stable and remain nanometric. We find that nanoceria covered with both coating agents are taken up by mouse fibroblasts and localized into membrane-bound compartments. However, flow cytometry and electron microscopy reveal that as a result of their precipitation, citrate-coated particles interact more strongly with cells. At cerium concentration above 1 mM, only citrate-coated nanoceria (and not particles coated with poly(acrylic acid)) display toxicity and moderate genotoxicity. The results demonstrate that the control of the surface chemistry of the particles and its ability to prevent aggregation can affect the toxicity of nanomaterials.Comment: 33 pages 10 figures, accepted at Nanotoxicolog

Dynamique non linéaire d'un oscillateur à mémoire de forme

Nous étudions les réponses forcées d'un oscillateur reproduisant le comportement pseudo-élastique d'un alliage à mémoire de forme. Le modèle est dérivé d'une loi de comportement tridimensionnelle prenant en compte les couplages entre la thermique, la mécanique et les changments de phase solide-solide du matériau. Les réponses forcées montrent un comportement assouplissant dès que la transformation martensitique est activée, ainsi que l'existence de zones chaotiques. Nous présenterons aussi des comparaisons calcul/essai réalisées sur des fils en torsion

A hospital based case control study of female breast cancer risk factors in a Sub-Saharan African country

Background: Breast cancer is the most common cancer diagnosed in women worldwide with over 1.3 million new cases per year. There is a wide variation in the geographical burden of the disease with the highest incidences seen in the developed regions of the world and the lowest incidences observed in the least developed regions. The objective of this study was to understand further the risks for breast cancer in Senegalese population which can then inform public health strategies to try and reduce the burden of breast cancer.Methods: This matched case control study was conducted in 2015 in Aristide Le Dantec Teaching Hospital in Dakar. All women with pathologically confirmed primary breast cancer were considered as cases. For each case, 2 age-matched women were recruited. We collected and compared demographic factors, family history of breast cancer, socioeconomic variables, reproductive variables (age at menarche, age at first pregnancy and first live birth, parity, menopausal status, duration of breastfeeding), and exogenous hormone use up to 6 months. Odds ratios from univariate logistic regression were used to estimate the relative risk of breast cancer associated with the various factors, and their predictive effects.Results: In all, 212 women with breast cancer who were diagnosed as having breast cancer and 424 control women were involved in the study. The mean±SD age of cases and controls was 43.37±11.94 years (range 18-83 years) and 42.04±11.08 years (range 18-84 years), respectively. There were no significant differences between cases and controls with regards to marital status, parity, age at menarche, past oral contraceptive use, age at first last full-term pregnancy and history of breastfeeding. Breast cancer risk was significantly greater in women with a family history of the disease (OR 2.12, 95% confidence interval [CI] 1.35-3.31). A significant increase in breast cancer was observed among illiterate women compared to educated women (OR 1.27, CI 1.02-1.58), in premenopausal women and those without occupation.Conclusions: In this study, reproductive factors as early menarche or menopausal status were not associative to the risk of breast cancer and the early age at diagnosis and the positive history of breast cancer suggest a genetic pattern of this disease in Senegalese woman. But this fact is difficult to confirm for financial reasons

Wavelength selective light-induced magnetic effects in the binuclear spin crossover compound {[Fe(bt)(NCS)2]2(bpym)}

International audienceUsing Fourier transform infrared spectroscopy, x-ray diffraction, and magnetic susceptibility measurements under light irradiation, the selective light-induced excited spin state trapping (LIESST) and the reversible-LIESST effect have been evidenced and studied in depth in the binuclear spin crossover compound {[Fe(bt)(NCS)2]2bpym}. In this system, each magnetic site can switch from low spin (LS) to high spin (HS), so that three states exist, namely, the LS-LS, HS-LS, and HS-HS. All these techniques shine a new light on the high phototunability of this system. In addition to the direct photoswitching from the LS-LS to the HS-LS or to the HS-HS state, here we show that photoinduced switching between the excited photoinduced states can be triggered in a reversible way: from HS-LS to HS-HS (irradiation around 800 nm), or reverse from HS-HS to HS-LS (irradiation around 1300 nm). The nature of the intermediate HS-LS state during the thermal and light-induced spin state changes is also discussed by comparing the spectroscopic measurements and the structural analysis. The loss of inversion symmetry in the HS-LS molecular state, where the two magnetic Fe sites are no more equivalent, is not accompanied by any long-range ordering of the noncentrosymmetric molecules in the crystal. Therefore the continuous double-step spin conversion corresponds to a double crossover

Photoinduced HS state in the first spin-crossover chain containing a cyanocarbanion as bridging ligand

A new polymeric approach, based on cyanocarbanion ligands, for the design of spin crossover (SCO) compounds led us to the compound [Fe(abpt)2(tcpd)] (1) (tcpd^2 = (C[C(CN)2|3)^2 , abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) which has been characterised as the first SCO molecular chain involving a cyanocarbanion as bridging ligand.Gomez Garcia, Carlos Jose, [email protected]

Pressure and Temperature Spin Crossover Sensors with Optical Detection

Iron(II) spin crossover molecular materials are made of coordination centres switchable between two states by temperature, pressure or a visible light irradiation. The relevant macroscopic parameter which monitors the magnetic state of a given solid is the high-spin (HS) fraction denoted nHS, i.e., the relative population of HS molecules. Each spin crossover material is distinguished by a transition temperature T1/2 where 50% of active molecules have switched to the low-spin (LS) state. In strongly interacting systems, the thermal spin switching occurs abruptly at T1/2. Applying pressure induces a shift from HS to LS states, which is the direct consequence of the lower volume for the LS molecule. Each material has thus a well defined pressure value P1/2. In both cases the spin state change is easily detectable by optical means thanks to a thermo/piezochromic effect that is often encountered in these materials. In this contribution, we discuss potential use of spin crossover molecular materials as temperature and pressure sensors with optical detection. The ones presenting smooth transitions behaviour, which have not been seriously considered for any application, are spotlighted as potential sensors which should stimulate a large interest on this well investigated class of materials