Copper diffusion in ion-exchanged soda-lime glass

Cu-alkali ion exchange in silicate glasses gives rise to a peculiar copper distribution, with the presence of both the Cu²⁺ and Cu⁺ oxidation states. Grazing incidence X-ray absorption near-edge structure spectroscopy and secondary ion mass spectrometry were performed on different ion-exchanged samples. The results show that the Cu²⁺/Cu⁺ ratio is strongly depth-dependent. The relative presence of the two species throughout the exchanged region turns out to be governed by their different diffusion regimes, while the chemistry of the red-ox process is shown to play a minor role. A phenomenological model is proposed to describe the diffusion process. PACS 61.10.Ht; 61.43.Fs; 82.65.+r; 67.80.Mg     

Thermodynamic data for solid AgI and its phase transitions from ENF measurements

From EMF measurements in the cell Ag(s)/AgI(s)/I₂(g), graphite as a function of temperature, the enthalpy and entropy values for the formation of γ-, β- and α-AgI were obtained. From these data, the following thermodynamic quantities corresponding to the phase transitions were also calculated: Δ_tH_γ→β= -34.3 ±2 kJmol^-1, Δ_tS_γ→β= -107 ± 4 Jmol^-1K^-1, Δ_tH_β→α = 5.4 ± 2 kJmol^-1, Δ_tS_β→α = 23 ± 4 Jmol^-1K^-1.     

Identification of dyes in toned and tinted XX century cinematographic films by surface enhanced Raman spectroscopy

In this paper some colored frames coming from the very popular cinematographic film Sardinian Drummer Boy, dating back to the beginning of the XX century, were analyzed. The presence in the emulsion of silver nanoparticles (AgNPs), which are formed thanks to the impression–development mechanism, confers to the cinematographic film the characteristic of being an efficient Surface Enhancement Raman Spectroscopy (SERS) substrate. This peculiarity makes it possible to investigate, in a non‐invasive way, the nature of the film components, such as the dyes used for the coloring process. In particular, Raman analyses allowed the unambiguous identification of the dyes used in tinted frames, i.e. tartrazine and safranin, in which the colorant is absorbed by the gelatin, and in toned frames, i.e. Rhodamine B, where the dye is fixed thanks to the formation of an insoluble species with AgI obtained by conversion of metallic silver. This second case is of particular interest to evaluate the possibility to identify the dye even when it is present as a silver iodide derivative. For this purpose an AgI‐colorant derivative has been prepared and its SERS spectrum compared with that obtained on the film sheet. Copyright © 2015 John Wiley & Sons, Ltd.     

Chromium doping of silicate glasses by field-assisted solid-state ion exchange

Field-assisted solid-state ion exchange (FASSIE) is a suitable way to dope glasses with metallic ions. This approach is a promising technique for the production of glass waveguides containing either bivalent or trivalent ions, allowing the doping of glass surfaces with multivalent ions which could not diffuse into the glass matrix by means of the usual thermal ion-exchange process in molten salt baths. In this paper, results on the diffusion of chromium in silicate glasses are presented. A metallic chromium film deposited on the top of the glass substrates was used as the metal ions supplier. The doped layers were investigated by secondary ion mass and Rutherford backscattering spectrometries, as well as by micro-Raman spectroscopy. Chromium entered the glass matrices for some hundreds of nanometers, depending on the process temperature and the applied electric field. Strong compositional modification of the treated glasses was detected, related to alkali and alkali-earth elements distribution. For field-assisted solid-state diffusion, borosilicate glasses seem to be more stable matrices than the soda-lime silicate ones.     

The perspective of a bank in granting credits: an optimization model

In this work, a model for legal financiers’ strategies is presented, taking into account that the aim of a bank is to minimize the default probability of the funded company, constrained with reaching a certain profit level. To obtain our purpose, a stochastic dynamics optimization model is constructed and solved in closed form and a Monte Carlo simulation involving empirical data is also implemented. The financial strategies are thus obtained.     

Characterization of TiO<Subscript>2</Subscript> nanoparticle suspensions for electrophoretic deposition

The rheology of suspensions is critically important for the successful achievement of defect-free TiO₂ deposits by electrophoretic deposition (EPD). The rheological behaviour of TiO₂ nanoparticle suspensions in acetylacetone with and without iodine was investigated over a broad solid-concentration range (0.3–2.5 wt.%) and at different shear rates ( = 10–250 s⁻¹). The influence of these parameters on the quality of TiO₂ films obtained by EPD on stainless steel substrates was assessed. The pure solvent and the 1 wt.% TiO₂ nanoparticles suspension without iodine exhibited shear-thickening flow behaviour. For other concentrations, the suspensions showed shear-thinning behaviour followed by an apparent shear-thickening effect at a critical shear rate (100 s⁻¹). For the suspension with 1 wt.% TiO₂ containing iodine, a shear-thickening flow behaviour was observed over the whole shear rate range investigated. The maximum solids fraction (ϕ_m) was experimentally determined from a linear relationship between solid concentration and viscosity. The estimated value was ϕ_m = 7.94 wt.% for this system. Using a suspension with 1 wt.% concentration, good-quality TiO₂ deposits on stainless steel planar substrates were obtained by EPD at constant voltage condition. The influence of pH on suspension stability was determined in the range pH = 1–9, being pH ≈ 5 the optimal value for this system in terms of EPD results.     

Fuzzy-based robust structural optimization

Robust optimization is conventionally defined as the collection of the possible problem solutions that can ensure acceptable performances and sufficient immunity against the effects of uncertain parameter variability. Methods proposed until now use a probabilistic way to model uncertainty and to quantify the final sensitivity. In this work, a fuzzy uncertainty modellization is adopted for structural engineering. In particular, to define solution performance scattering, the fuzzy entropy is used as a global measure of variable dispersion. The final formulation of the problem deals with two antithetical objective functions, the fuzzy expected value of structural performance and its fuzzy entropy. This fuzzy-based approach in robust design is able to give a set of Pareto optimal solutions in terms of structural efficiency and sensitivities regarding uncertainty, and represents a suitable tool in supporting the decision maker. Finally, different applications have been developed to demonstrate the applicability of the proposed method.     

Studies on the synthesis of gymnodimine. Stereocontrolled construction of the tetrahydrofuran subunit

[reaction: see text]. A bis-(2,6-dichlorobenzyl) ether is shown to undergo efficient and highly stereoselective intramolecular iodoetherification to yield a cis-2,5-disubstituted tetrahydrofuran, thus providing a powerful illustration of a stereodirecting effect first noted by Rychnovsky and Bartlett. The tetrahydrofuran was transformed into a subunit suitable for incorporation into the shellfish toxin gymnodimine.