Does cation dehydration drive the binding of metal ions to polyelectrolytes in water? What we can learn from the behaviour of aluminium(III) and chromium(III)

Much stronger binding is seen in aqueous solutions between the anionic polyelectrolyte potassium poly(vinyl sulfate) and the substitution labile aluminium(III) than with the kinetically inert chromium(III). This strongly supports the idea that entropy driven water loss from the hydration sphere of the metal ion plays a major role in driving binding of the trivalent metal ion to the polyelectrolyte.     

Validated dispersive liquid-liquid microextraction for analysis of organophosphorous pesticides in water

Dispersive liquid-liquid microextraction (DLLME) combined with gas chromatography and mass spectrometry (GC-MS) was applied to the determination of six organophosphorous pesticides (OPPs) in water samples. The analytes included in this study were prophos, diazinon, chlorpyrifos methyl, methyl parathion, fenchlorphos and chlorpyrifos. Several extraction and dispersion solvents were tested for dispersive liquid-liquid microextraction of these analytes and the best results were obtained using chloroform as extraction solvent and 2-propanol as dispersion solvent. Calibration curves of the analytes in water samples were constructed in the concentration range from 100 to 1100 ng/L for prophos, diazinon and methyl parathion and in the range from 100 to 1000 ng/L for chlorpyrifos methyl, fenchlorphos and chlorpyrifos. Limits of detection (LODs) were in the range of 1.5-9.1 ng/L and limits of quantification (LOQs) were in the range of 5.1-30.3 ng/L, below the maximum admissible level for drinking water. Relative standard deviations (RSDs) were between 6.5 and 10.1% in the concentration range of 100-1000 ng/L. The relative recoveries (%RRs) of tap, well and irrigation water samples fortified at 800 ng/L were in the range of 46.1-129.4%, with a larger matrix effect being detected in tap water.     

Kinetic study of thermal processing of glycerol by thermogravimetry

Over the past years, the production of biodiesel has significantly increased in Brazil due to its obligatory use in the composition of diesel for vehicle use. As a result, in the most ordinary processes, a hundred thousand tons of glycerol is produced as by-product per 1 billion liters of biodiesel. Glycerol has already been widely studied. Nonetheless, the quantity produced today demands new proposals for uses, such as a fuel. In this aim, the authors studied the kinetics of the thermal processing of glycerol. In this research, thermogravimetry (TG), derivative thermogravimetry (DTG), and differential thermal analysis (DTA) were used to provide the experimental data. Kinetic parameters were calculated by Kissinger method for the global process observed during the heating of the samples from the room temperature up to 600 °C, both in open and in sealed crucibles (with a little hole). Kinetic data were also determined at different isoconversion conditions during heating, by applying Ozawa–Flynn–Wall and Blazejowski methods to TG data. Results show that glycerol heated from 30 to 600 °C, under normal pressure, does not experience simple volatilization. The activation energies calculated at different conversion degrees by these methods show that only volatilization occurs when the mass loss of glycerol is lower than 40% and that for higher conversion degrees, partial thermal decomposition and/or dissociation of glycerol are occurring as well. These facts are also confirmed by the volatilization enthalpies estimated using another method developed by Blazejowski based on Van’t Hoff equation.     

Signaling advertising by multiproduct firms

We consider the use of advertising expenses as quality signals in multiproduct firms, extending previous results on single product firms. In our model, a firm introduces sequentially two products whose qualities are positively correlated. We investigate whether there exist information spillovers from the first to the second market. We show that, when correlation is high, the equilibrium in market 2 depends on the quality reputation the firm has gained in market 1. Moreover, if a firm with a high-quality product 1 wants to separate from its low-quality counterpart, it needs to advertise more in this market than if the qualities of the two products are unrelated. This advertising level signals not only high quality in the first market, but also the likely quality of the second product. Thus, advertising in the first market has information spillovers in the second market.     

Standard molar enthalpy of formation of 1-benzosuberone: An experimental and computational study

The energetics of 1-benzosuberone was studied by a combination of calorimetric techniques and computational calculations.The standard (p° = 0.1 MPa) molar enthalpy of formation of 1-benzosuberone, in the liquid phase, was derived from the massic energy of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The standard molar enthalpy of vaporization, at T = 298.15 K, was measured by Calvet microcalorimetry. From these two parameters the standard (p° = 0.1 MPa) molar enthalpy of formation, in the gaseous phase, at T = 298.15 K, was derived: ?(96.1 ± 3.4) kJ · mol^?1. The G3(MP2)//B3LYP composite method and appropriate reactions were used to computationally calculate the standard molar enthalpy of formation of 1-benzosuberone, in the gaseous phase, at T = 298.15 K. The computational results are in very good agreement with the experimental value.     

Subject mix and productivity in Portuguese universities

Recent changes in higher education, especially associated with its massification, have led to calls for more accountability and to an increasing need to evaluate universities’ performance. However, comparing universities with different subject mixes poses some significant problems. In this article, a linear mixed-effect model methodology allowing for random effects at university level is used to measure the productivity of Portuguese public universities, taking into account their subject composition, for a period of five years (1997–2001). The results show that subject mix is an important factor in explaining the variability in productivity between universities. However, even taking account of subject mix, a lot of inefficiency is found in the system, and a significant variability in productivity among universities exists.     

On the tropical Torelli map

We construct the moduli spaces of tropical curves and tropical principally polarized abelian varieties, working in the category of (what we call) stacky fans. We define the tropical Torelli map between these two moduli spaces and we study the fibers (tropical Torelli theorem) and the image of this map (tropical Schottky problem). Finally we determine the image of the planar tropical curves via the tropical Torelli map and we use it to give a positive answer to a question raised by Namikawa on the compactified classical Torelli map.     

Compactified Picard stacks over the moduli stack of stable curves with marked points

In this paper we give a construction of algebraic (Artin) stacks endowed with a modular map onto the moduli stack of stable curves of genus g with n marked points. The stacks we construct are smooth, irreducible and have dimension 4g−3+n, yielding a geometrically meaningful compactification of the universal Picard stack parametrizing n-pointed smooth curves together with a line bundle.     

Pre-analytical method for NMR-based grape metabolic fingerprinting and chemometrics

Although metabolomics aims at profiling all the metabolites in organisms, data quality is quite dependent on the pre-analytical methods employed. In order to evaluate current methods, different pre-analytical methods were compared and used for the metabolic profiling of grapevine as a model plant. Five grape cultivars from Portugal in combination with chemometrics were analyzed in this study. A common extraction method with deuterated water and methanol was found effective in the case of amino acids, organic acids, and sugars. For secondary metabolites like phenolics, solid phase extraction with C-18 cartridges showed good results. Principal component analysis, in combination with NMR spectroscopy, was applied and showed clear distinction among the cultivars. Primary metabolites such as choline, sucrose, and leucine were found discriminating for ‘Alvarinho’, while elevated levels of alanine, valine, and acetate were found in ‘Arinto’ (white varieties). Among the red cultivars, higher signals for citrate and GABA in ‘Touriga Nacional’, succinate and fumarate in ‘Aragonês’, and malate, ascorbate, fructose and glucose in ‘Trincadeira’, were observed. Based on the phenolic profile, ‘Arinto’ was found with higher levels of phenolics as compared to ‘Alvarinho’. ‘Trincadeira’ showed lowest phenolics content while higher levels of flavonoids and phenylpropanoids were found in ‘Aragonês’ and ‘Touriga Nacional’, respectively. It is shown that the metabolite composition of the extract is highly affected by the extraction procedure and this consideration has to be taken in account for metabolomics studies.