A study on the mechanism of reaction between refractory materials and aluminium deoxidised molten steel

The conditions of formation of inclusions in steel during ladle refining in MgO-C lined ladles have been investigated in laboratory experiments at 1873 K in MgO-C crucibles with 50 g iron. From both the experimental results as well those of a thermodynamic study conducted in parallel, the following conclusions can be made about the reaction mechanism between the MgO-C refractory and aluminium deoxidised molten steel: At steelmaking temperature an internal oxidation-reduction occurs in the MgO-C refractory. The formation of a thin oxide layer at the interface is due to the reaction between magnesium vapour and aluminium dissolved into the molten steel and the CO(g) generated by the reaction between MgO and C in the crucible walls. The oxide inclusions formed in the steel have been shown mainly to consist of MgO, Al₂O₃ or mixture of them. Some of the finest inclusions are considered to be formed as secondary inclusions during cooling and solidification of the steel and they are connected only with the diffusion of magnesium from the crucible to the molten steel. The thermodynamic calculations indicate that during vacuum refining, as the pressure decreases, the chemical compatibility of carbon-bonded magnesia for ladle lining decreases.     

Propagation of material and surface profile uncertainties on MEMS micro‐resonators using a stochastic second‐order computational multi‐scale approach

This paper aims at accounting for the uncertainties because of material structure and surface topology of micro‐beams in a stochastic multi‐scale model. For micro‐resonators made of anisotropic polycrystalline materials, micro‐scale uncertainties exist because of the grain size, grain orientation, and the surface profile. First, micro‐scale realizations of stochastic volume elements are obtained based on experimental measurements. To account for the surface roughness, the stochastic volume elements are defined as a volume element having the same thickness as the microelectromechanical system (MEMS), with a view to the use of a plate model at the structural scale. The uncertainties are then propagated up to an intermediate scale, the meso‐scale, through a second‐order homogenization procedure. From the meso‐scale plate‐resultant material property realizations, a spatially correlated random field of the in‐plane, out‐of‐plane, and cross‐resultant material tensors can be characterized. Owing to this characterized random field, realizations of MEMS‐scale problems can be defined on a plate finite element model. Samples of the macro‐scale quantity of interest can then be computed by relying on a Monte Carlo simulation procedure. As a case study, the resonance frequency of MEMS micro‐beams is investigated for different uncertainty cases, such as grain‐preferred orientations and surface roughness effects. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermoanalytical and infrared spectroscopy investigations of some mineral pastes containing organic polymers

The interaction in the presence of water between organic polymers [two polyvinyl alcohol acetate (PVA1 and PVA2)-, one polyvinyl acetate (PVAc)-, and one acryloethyl-metacrylomethyl (R)-type copolymers] and inorganic materials (3CaO·Al₂O₃+CaSO₄·2H₂O, 12CaO·7Al₂O₃, and CaO·Al₂O₃) was investigated using complex thermal analyses and infrared (IR) spectroscopy. The DTA curves of the 1-to 28-day-hydrated organo-mineral composite samples showed some significant differences in comparison with those of the hydrated inorganic materials. The most important differences consist in the presence of some exothermic peaks that are not attributable to the pure organic polymers. More than that, none of the specific effects of the pure organic polymers are evidenced on the DTA curves of the hydrated organo-mineral composite materials. This, in connection with their IR spectra, which clearly evidence the disappearance of some investigated polymers specific IR bands, can be considered as an indirect evidence of the cross-linking of polymer chains via metal ions.     

On the Electrical Interaction as an Elastic Coupling Through the Flux Lines

By using the elastic coupling through the field lines, we present a new theoretical treatment of the electrical interaction. We consider both static and oscillatory fields. The obtained results show that the static interaction energy is in reverse proportion with respect to the distance between the centers of the two bodies whereas the oscillatory interaction energy contains two terms: one which is in reverse proportion with respect to the third power of this distance and the other which is in reverse proportion with this distance. The latter term appears because of retardation. An attraction between the two charged particles of the same sign may appear if the oscillatory energy of interaction is larger than the static energy of interaction. This is the case of the electron pairs in superconductors.     

The influence of collagen support and ionic species on the morphology of collagen/hydroxyapatite composite materials

The purpose of this investigation is to study the influence of collagenous supports and ionic species on the precipitation of hydroxyapatite (HA) from aqueous solutions. To this end, we obtained hydroxyapatite by co-precipitation from a solution of calcium hydroxide and sodium dihydrogenophosphate. The formation of HA was studied by energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results of this study indicate that the morphology of hydroxyapatite is highly influenced by the support material and the ionic species present. The obtained materials were studied by scanning electron microscopy (SEM).     

On the Electron–Electron Interaction in Superconductors

By using an attractive potential that varies in reverse proportion with respect to the third power of the distance between the two particles, we resolved the Schrodinger equation for an electron pair. We applied these statements to superconductors and obtained a good agreement with experimental data and BCS theory.     

New Investigations with Lupane Type A-Ring Azepane Triterpenoids for Antimycobacterial Drug Candidate Design

Twenty lupane type A-ring azepano-triterpenoids were synthesized from betulin and its related derivatives and their antitubercular activity against Mycobacterium tuberculosis, mono-resistant MTB strains, and nontuberculous strains Mycobacterium abscessus and Mycobacterium avium were investigated in the framework of AToMIc (Anti-mycobacterial Target or Mechanism Identification Contract) realized by the Division of Microbiology and Infectious Diseases, NIAID, National Institute of Health. Of all the tested triterpenoids, 17 compounds showed antitubercular activity and 6 compounds were highly active on the H37Rv wild strain (with MIC 0.5 µM for compound 7), out of which 4 derivatives also emerged as highly active compounds on the three mono-resistant MTB strains. Molecular docking corroborated with a machine learning drug-drug similarity algorithm revealed that azepano-triterpenoids have a rifampicin-like antitubercular activity, with compound 7 scoring the highest as a potential M. tuberculosis RNAP potential inhibitor. FIC testing demonstrated an additive effect of compound 7 when combined with rifampin, isoniazid and ethambutol. Most compounds were highly active against M. avium with compound 14 recording the same MIC value as the control rifampicin (0.0625 µM). The antitubercular ex vivo effectiveness of the tested compounds on THP-1 infected macrophages is correlated with their increased cell permeability. The tested triterpenoids also exhibit low cytotoxicity and do not induce antibacterial resistance in MTB strains.     

New polymeric structures designed for the removal of Cu(II) ions from aqueous solutions

New polymeric structures obtained by chemical transformations of maleic anhydride/dicyclopentadiene copolymer with triethylenetetraamine, p‐aminobenzoic acid, and p‐aminophenylacetic acid were used for the removal Cu(II) ions from aqueous solutions. The experimental values prove the importance of the chelator nature and of the macromolecular chain geometry for the retention efficiency. The retention efficiency (η_r), the retention capacity (Q _e ), and the distribution coefficient of the metal ion into the polymer matrix (K _d ) are realized by evaluation of residual Cu(II) ions in the effluent waters, by atomic adsorption. Also are discussed the influence of pH, the thermal stability of the polymer, and their polymer–metal complex, as well as the particular aspects regarding the contact procedure and the batch time. Based on the polymers and polymer–metal complexes characterization a potential retention mechanism is proposed. All polymer supports as well theirs metal–complexes are characterized by ATD and FTIR measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1397–1405, 2007     

Language-Based Program Verification via Expressive Types

Recent developments in the area of expressive types have the prospect to supply the ordinary programmer with a programming language rich enough to verify complex program properties. Program verification is made possible via tractable type checking. We explore this possibility by considering two specific examples; verifying sortedness and resource usage verification. We show that advanced type error diagnosis methods become essential to assist the user in case of type checking failure. Our results point out new research directions for the development of programming environments in which users can write and verify their programs.