Resistivity–viscosity relationship in liquid–liquid critical mixtures with added ions

Precise resistivity ρ (Ω cm) and viscosity η (10⁻² P) measurements for isobutyric acid–water (IBAW) critical mixtures with added K⁺ and Cl⁻ ions have been performed in the Arrhenius temperature domain of the electrolyte. From the activation energy, the resistivity–viscosity relation reveals a fraction power character over the whole range of parameters investigated. To analyze our data we have used an exponential formula derived from the equivalent Arrhenius law: ρ/T is proportional to (η/T)^R, where R = E_ρ/E_η is the ratio between the resistivity and viscosity activation energies. In the case of the pure system (IBAW), the value of R is in vicinity of 1, but when the salt is added, the ratio R shows dependence on the (K⁺, Cl⁻) concentrations: 0.6 < R < 1. The domain of the validity of R is in conformity with the theoretical prediction. The Coulombic interaction is the origin of the deviation.     

Theoretical study of the Ni growth on Pt stepped surfaces

We have investigated the growth of Ni on Pt stepped surfaces with (1 1 1) terraces by means of potentials derived from the second moment approximation in a tight-binding model. The activation energies associated to these processes are determined. The Schwoebel barriers of Ni atoms descending steps of Pt stepped surfaces are calculated for different kinds of straight steps (A and B steps) differing by the orientation of the ledge. In addition, we study the diffusion of Ni adatoms at fcc or hcp sites in the presence of small adislands on the terraces, in the vicinity of the A and B steps. We show that a good estimate of the potential wells and diffusion barriers could be given by introducing a lateral effective pair interaction model, the interactions extending up to the next nearest neighbors. Finally, we have carried out Kinetic Monte-Carlo simulations to investigate the Ni wire formation at Pt step edges and the influence of the exchange processes in the alloy formation.     

Pressure-broadened atomic Li(2s-2p) line perturbed by ground neon atoms in the spectral wings and core

Full quantum calculations are performed to investigate the broadening profiles of the atomic lithium Li(2s-2p) resonance line induced by interactions with ground Ne(2s~22p~6) perturbers in the spectral wings and core. The X~2Σ~+, A~2Π,and B~2Σ~+ potential-energy curves of the two first low lying Li Ne molecular states, as well as the corresponding transition dipole moments, are determined with ab initio methods based on the SA-CASSCF-MRCI calculations. The emission and absorption coefficients in the wavelength range 550-800 nm and the line-core width and shift are investigated theoretically for temperatures ranging from 130 K to 3000 K. Their temperature dependence is analyzed, and the obtained results are compared with the previous experimental measurements and theoretical works.     

In situ 3D Synchrotron Laminography Assessment of Edge Fracture in Dual-Phase Steels: Quantitative and Numerical Analysis

The mechanical performance of automotive structures made of advanced high strength steels (AHSS) is often seen reduced by the presence of cut edges. An attempt is made to assess and quantify the initial damage state and the damage evolution during mechanical testing of a punched edge and a machined edge via a recently developed 3D imaging technique called synchrotron radiation computed laminography. This technique allows us to observe damage in regions of interest in thin sheet-like objects at micrometer resolution. In terms of new experimental mechanics, steel sheets having sizes and mechanical boundary conditions of engineering relevance can be tested for the first time with in situ 3D damage observation and quantification. It is found for the investigated DP600 steel that the fracture zone of the punched edge is rough and that needle-shape voids at the surface and in the bulk follow ferrite-martensite flow lines. During mechanical in situ testing the needle voids grow from the fracture zone surface and coalesce with the sheared zone. In contrast, during in situ mechanical testing of a machined edge the damage starts away from the edge (～800μm) where substantial necking has occurred. Three-dimensional image analysis was performed to quantify the initial damage and its evolution. These data can be used as input and validation data for micromechanical damage models. To interpret the experimental findings in terms of mechanical fields, combined surface digital image correlation and 3D finite element analysis were carried out using an elasto-plastic constitutive law of the investigated DP steel. The stress triaxiality and the accumulated plastic strain were calculated in order to understand the influence of the edge profile and the hardening of the cutting-affected zone on the mechanical fields.     

Highly sensitive modified glassy carbon sensor based on TDAN for nitrate detection in real water

Glassy carbon electrodes modified with a plasticized PVC membrane including tetradodecyl ammonium nitrate (TDAN) and two different plasticizers [bis(2-etheylhexyl) sebacate (DOS) and dibutyl phthalate (DBP)]. TDAN is a quaternary ammonium salt, used in nitrate-selective field-effect transistor membrane, and it is applied as an ionophore for sensor development. Membranes were prepared as sensing matrix for nitrate detection through the intensity of its reduction peak using cyclic voltammetry. Under optimum conditions, the detection limits of nitrate obtained with TDAN + DOS and TDAN + DBP, are 10–6 mol/dm3 and 10–9 mol/dm3, respectively. As a result, the developed sensors based on TDAN + DOS and TDAN + DBP matrices demonstrate satisfactory quantified amounts in determination of nitrate in water where the measured values were less than 0.57 × 10–7 mol/dm3 and 0.73 × 10–10 mol/dm3, respectively.     

Exponential stabilization of a class of nonlinear systems: A generalized Gronwall–Bellman lemma approach

In this paper, stabilizing control design for a class of nonlinear affine systems is presented by using a new generalized Gronwall–Bellman lemma approach. The nonlinear systems under consideration can be non Lipschitz. Two cases are treated for the exponential stabilization: the static state feedback and the static output feedback. The robustness of the proposed control laws with regards to parameter uncertainties is also studied. A numerical example is given to show the effectiveness of the proposed method.     

Synthesis,X-ray analysis and photophysical properties of a new N-containing pentacyclic helicene

A new helically chiral pentacyclic system containing one pyrrole ring was prepared in a good yield and purity via a three-step sequence involving Heck coupling and classical oxidative photocyclization. X-ray crystal structure analysis indicated that the conformation resembled that of unsubstituted pentahelicene, the idealized symmetry of which is C₂. The optical properties of the pentacyclic helicene were investigated and show interesting behaviour.