Microstructure and deformation mechanisms in nanocrystalline Ni–Fe. Part I. Microstructure

We investigate various microstructural features of nanocrystalline electrodeposited Ni–Fe with a nominal iron content of 50% and compare them with the well-known nanocrystalline Ni system. In-depth electron microscopy analysis reveals the existence of large strain variations in the grain interior. Three-dimensional atom probe studies demonstrate no significant segregation to grain boundaries. However, significant deviations from a perfect chemically disordered system are found, which can be related to compositional variations of 5% over length scales of only a few nanometres. Finally, X-ray diffraction measurements suggest higher dislocation and twin density in Ni–Fe compared to Ni.     

Thermal behaviour of the consumable electrode in the vacuum arc remelting process

The thermal behaviour of the consumable electrode is studied using both experimental measurements and mathematical modelling. Infrared thermography measurements performed on an industrial furnace highlight qualitatively that the electrode height thermally affected by the electric arc is very small and depends on the melting rate. The vertical temperature gradient recorded at the base of the electrode varies between 350 K/cm and 650 K/cm, while the average measured superheat lies between 150 K and 200 K. A 2D mathematical model of the thermal behaviour of the consumable electrode during melting has been developed. Using the operating parameters as model inputs, it makes it possible to predict the melt rate and the evolution of the shape of the electrode base. The results of the model are successfully compared to melt rate experimental data obtained in a real VAR furnace. The thermal effect of cracks in the electrode is investigated and reveals a significant influence on the variation in melt rate.     

Nonlinear predictive control based on artificial neural network model for industrial crystallization

This paper illustrates the benefits of a nonlinear model based predictive control (NMPC) strategy for setpoint tracking control of an industrial crystallization process. A neural networks model is used as internal model to predict process outputs. An optimization problem is solved to compute future control actions taking into account real-time control objectives. Furthermore, a more suitable output variable is used for process control: the mass of crystals in the solution is used instead of the traditional electrical conductivity. The performance of the NMPC implementation is assessed via simulation results based on industrial data.     

Symmetric and Asymmetric Convective Oscillations in a Multilayer System

The nonlinear development of oscillatory instability under the joint action of buoyant and thermocapillary effects in a multilayer system, is investigated. The nonlinear convective regimes are studied by the finite difference method. The rigid heat-insulated lateral walls, are considered. Transitions between the motions with different spatial structures are investigated. Specific types of flows, symmetric and asymmetric oscillations, have been found. It is shown that the oscillatory motion takes place in an interval of the Grashof number values bounded both from below—by the mechanical equilibrium, and from above—by the steady state.     

Paclitaxel-Loaded Lipid Nanoparticles Prepared by Solvent Injection or Ultrasound Emulsification

ABSTRACT

Lipid nanoparticles were fabricated as an injectable carrier system for paclitaxel. The components for the lipid matrix were based on phospholipids, and sucrose fatty acid ester was used as an emulsifier. Formulation prepared with solvent injection has a slightly larger particle size (187.6 nm) than the formulation (147.7 nm) prepared with ultrasound emulsification. Differential scanning calorimetry results indicated that paclitaxel entrapped in the lipid nanoparticles existed in an amorphous state in the lipid matrix. In vitro drug release was rather slow; only 12.5–16.5% of the drug released from the formulations within 14 days. Lipid nanoparticles demonstrated their potential as a promising pharmaceutical formulation of paclitaxel.     

Traduction et validation d'une nouvelle mesure d'épuisement professionnel: Le shirom-melamed burnout measure.

This research aims to empirically validate into the French language and for the first time the Shirom Melamed Burnout Measure (Shirom & Melamed, 2006). First proposed by its designers as an alternative to the Maslach Burnout Inventory (Maslach & Jackson, 1981, 1986; Maslach, Jackson, & Leiter, 1996), this new measure of professional burnout is presented as an extension of the conservation of resources theory (Hobfoll, 1989). Based on 2 samples of 203 and 214 individuals, respectively, the present study not only validates the French wording of English items but also confirms satisfactory psychometric properties of the original scale. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Use of Atomic Force Microscopy to Study Crack Tips in Glass

This article presents a review of the application of atomic force microscopy (AFM) to crack-tip corrosion during subcritical crack growth in glass. The two principal experimental techniques used in this type of study are (1) the direct observation of crack motion by scanning the tip of a crack during crack growth and (2) the examination of fracture surfaces once the specimen has been fractured in two. The first technique has been used to demonstrate and quantify water condensation at crack tips during subcritical crack growth and is particularly useful at low crack velocities. The second technique has been used to quantify the crack-tip corrosion process and the shape of the crack tip during crack growth. In this article, we discuss experimental results showing that the environment that develops at the tips of freshly fractured glass surfaces in soda lime glass can corrode the glass surfaces near the crack tip. Soda lime silicate glass contains mobile alkali ions that will exchange with hydronium ions in solution at the crack tip, forming a highly basic solution that is corrosive to glass. Experimental evidence for such corrosion has been obtained by the atomic force microscope, which demonstrates a displacement of the two fracture surfaces near the crack tip that can be as much as 20 nm, depending on how long the crack is held open at the fatigue limit. Despite the corrosion and displacement of the crack surfaces, the crack tip itself appears to remain sharp, suggesting that the fatigue limit in soda lime silicate glass is not due to crack-tip blunting. Most likely, the fatigue limit is a consequence of ion exchange at the crack tip, in which hydronium ions in the crack-tip solution exchange with sodium ions in the glass. As hydronium ions are larger than sodium ions, this exchange process leaves a compressive stress within the fresh fracture surface of the glass that resists crack motion and results in a stress-corrosion fatigue limit, as first proposed by Bunker and Michalske. In agreement with this mechanism, no fatigue limit is observed for silica glass, which also exhibits no ion exchange. As the crack-tip solution in silica glass is only mildly acidic, pH ≈ 5, corrosion does not occur at crack tips of this glass as supported by the observation that no crack-tip displacements are observed in silica glass by AFM. As the proposed ion exchange mechanism used to explain the stress corrosion limit in glass is at variance with the belief that the fatigue limit in glass is the result of crack-tip blunting, we discuss the possibility of plastic deformation at crack tips in glass and conclude that the available experimental data does not support such a model. At the present time, chemical reaction based crack growth theories are most consistent with the body of crack growth data that is available on glass and are probably the best explanation for the phenomenon.     

Assessment of phylogenetic diversity of bacterial microflora in drinking water using serial analysis of ribosomal sequence tags

We examined chlorinated drinking water samples from three different surface water treatment plants for bacterial 16S rDNA diversity using the serial analysis of V6 ribosomal sequence tag (SARST-V6) method. A considerable degree of diversity was observed in each sample, with an estimated richness ranging from 173 to 333 phylotypes. The community structure shows that there are differences in bacterial evenness between sampled sites. The taxonomic composition of the microbial communities was found to be dominated by members of the Proteobacteria (57.2-77.4%), broadly distributed among the classes Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria. Additionally, a large proportion of sequences (6.3-36.5%) were found to be distantly related to database sequences of unknown phylogenetic affiliation. Given the apparent significance of this bacterial group in drinking water, a 16S rDNA analysis was performed and confirmed their presence and phylogeny. Notwithstanding the potential under-representation of certain bacterial phyla using the SARST-V6 primer pairs, as revealed by a refined computer algorithm, our results suggest that 16S rDNA corresponding to a variety of eubacterial groups can be detected in finished drinking water, suggesting that this water may contain a higher level of bacterial diversity than previously observed.     

Assessment of actions in a multi-actor and multicriteria framework: application to the refunding of microfinance institutions

This article formulates a methodology that describes the decision making process in which a group of actors (in this case, microfinance experts) become involved in actions. The actions, Microfinance Institutions (MFIs) being selected for refinancing, are described using several conflictual, ordinal criteria. This methodology is constructed in three consecutive steps: the first involves obtaining decision strategies from interactive input received from experts, the second compiles and merges individual decision strategies so as to create a common decision base and the third involves using this common decision base to construct a decision-making aid destined to help experts with the decision-making process. This methodology was tested with five microfinance experts in Cameroon.     

Incorporating institutions, norms and territories in a generic model to simulate the management of renewable resources

Management of the renewable natural resources in Madagascar is gradually being transferred to the local communities, particularly that of forest resources. However, these local communities are struggling to assess the consequences of management plans that they themselves must develop and implement on ecologically, economically and socially sustainable grounds. In order to highlight key aspects of different management options beforehand, we have developed MIRANA, a computer model to simulate various scenarios of management plan implementation. MIRANA differs from other simulation models by not only taking into account individual practices and economic exchanges, but also by accounting for the applicable regulations. These regulations are taken into consideration by means of a multiplicity of normative structures within a spatial context. The objective of this paper is to describe the representations of institutions, norms and territories proposed by MIRANA and to discuss these representations in relation to the state of the art in the field of normative multi-agent systems.