Scandium fluorophosphate glasses: a structural approach

A systematic investigation on glass formation in the ternary system InF₃–BaF₂–Sc(PO₃)_3n has been carried out. Scandium polyphosphate Sc(PO₃)_3n has been used as a third component in order to investigate the possibilities of obtaining new stable glasses. The above long-chain polyphosphate has been prepared using a specially elaborated cryo-technique, which allowed the preparation of high-purity product. Stable ternary compositions have been obtained within the compositions range (in mol%): 5–75 InF₃, 0–80% BaF₂, 0–50% Sc(PO₃)_3n. Glasses were characterized by Differential Scanning Calorimetry, vibrational spectroscopy (Raman) and ³¹P NMR. Structural features for the glass were put forward. Isolated P(O,F)4 groups or fluoroindated metaphosphate units could be identified depending on glass compositions.     

Calculating thermal conductivity in a transient conduction regime: theory and implementation

We present a molecular dynamics method addressed to the calculation of the latticethermal conductivity during the transient regime of approach to equilibrium from aninitial condition of nonuniform temperature profile. We thoroughly assess the basics, therobustness, and the accuracy of the method, in particular by showing that its results arebasically independent of most of the arbitrary simulation parameters. In addition, themethod here presented is computationally light, thus paving the way for the investigationof large systems. This feature is fully exploited to investigate the thermal transportproperties of disordered and nanostructured silicon samples, providing a clear atomisticpicture on the ability of grain boundaries and lattice disorder to affect thermalconductivity by improved scattering of vibrational modes with long mean free path.     

Critical point equation on four‐dimensional compact manifolds

The aim of this article is to study the space of metrics with constant scalar curvature of volume 1 that satisfies the critical point equation for simplicity CPE metrics. It has been conjectured that every CPE metric must be Einstein. Here, we shall focus our attention for 4‐dimensional half conformally flat manifolds M⁴. In fact, we shall show that for a nontrivial must be isometric to a sphere and f is some height function on      

A Clustering Search metaheuristic for the Point-Feature Cartographic Label Placement Problem

The Point-Feature Cartographic Label Placement (PFCLP) problem consists of placing text labels to point features on a map avoiding overlaps to improve map visualization. This paper presents a Clustering Search (CS) metaheuristic as a new alternative to solve the PFCLP problem. Computational experiments were performed over sets of instances with up to 13,206 points. These instances are the same used in several recent and important researches about the PFCLP problem. The results enhance the potential of CS by finding optimal solutions (proven in previous works) and improving the best-known solutions for instances whose optimal solutions are unknown so far.     

Merocyanine solvatochromic dyes in the study of synergistic effects in mixtures of chloroform with hydrogen-bond accepting solvents

The molar transition energy (E(T)) polarity values for the solvatochromic probes 2,6-diphenyl-4-(2,4,6-triphenylpyridinium)phenolate (1), 4[(1-methyl-4-(1H)-pyridinylidene)-ethylidene]-2,5-cyclohexadien-1-one (2), and 4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide (3) were collected in binary mixtures comprising chloroform and a hydrogen-bond accepting (HBA) solvent [dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), acetone or acetonitrile], aiming to investigate the ability of the chlorinated component to act as hydrogen-bond donating (HBD) solvent. Plots of E(T) as a function of X(2), the mole fraction of chloroform, were obtained and the data were analysed to investigate the preferential solvation (PS) of each probe in terms of both solute-solvent and solvent-solvent interactions. For dyes 1 and 2 a strong synergistic behavior was observed for all mixtures studied, indicating that the dyes are preferentially solvated by complexes formed through hydrogen bonding between chloroform and the HBA component in the mixtures. A study of 1 in deuterated chloroform with an HBA component (DMF and DMA) demonstrated that while almost no differences occur with the DMF mixtures, the presence of deuterated chloroform in its mixtures with DMA increases the synergistic effect, suggesting that it interacts more strongly with DMA, making its mixtures more polar. These data were successfully fitted to a model based on solvent-exchange equilibria. The features of the mixtures with dye 3 revealed a very different profile in comparison with the other two dyes, which suggests that in mixtures containing chloroform, the microenvironment of the dye seems to be important in determining the contribution of the structure resonances responsible for the stability of the dye.