Synthesis of nickel-iron spinel by non-conventional methods

Nickel-iron black ceramic pigments of (Fe_0.8Mg_0.2)(Fe_0.2Ni_0.8Cr)O₄ and (Fe_0.8Mg_0.1Zn_0.1)(Fe_0.2Ni_0.8Cr)O₄ compositions have been prepared by non conventional methods such as coprecipitation, microemulsion and polymeric gel routes (alkoxides hydrolysis-condensation), and compared with ceramic samples prepared by the solid state reaction from oxide precursors. The mineralising effect of a 2NaCl:NaF flux agent has been also analysed. Both non conventional methods and mineraliser presence increase the reactivity of the samples. The highest reactivity and the best black colour are obtained in the polymeric gel sample prepared from alkoxides; coprecipitated and microemulsion fired pigments are partially solubilised by glazes due to the small particle size exhibited, leading to brown colours.     

Remote dipole effects as a means to accelerate [Ru(amino alcohol)]-catalyzed transfer hydrogenation of ketones

A new generation of 2-aza-norbornyl amino alcohol ligands for the catalytic transfer hydrogenation reaction of aromatic ketones was synthesized. Extremely active catalysts were formed by introducing a ketal functionality at the rear end of the ligand. Acetophenone was reduced in 96% ee at low catalyst loading, substrate to catalyst ratio, S/C 5000, within 90 minutes with isopropyl alcohol as the hydrogen donor. It was found that the dioxolane substituent in the ligand increased the turnover frequency, TOF50, from 1050 h(-1) to 3000 h(-1) at an S/C ratio of 1000. Introduction of a methyl group at the carbinol carbon resulted in TOF50 as high as 8500 h(-1). Transfer hydrogenation of a range of aromatic ketones was evaluated and found to reach completion within 30 minutes at room temperature, and excellent enantioselectivity, up to 99 % ee, was obtained. A possible explanation for the enhanced activity was provided by density functional calculations, which showed that the presence of a remote dipole in the ligand lowered the transition state energy.     

Hyphenated flow injection systems and high discrimination instruments

An overview of the state-of-the-art in flow injection analysis (FIA) coupled to instruments capable of providing either multidetection and/or multi-information is reported. The versatility of FIA endows the hyphenated instruments with analytical capabilities which increase from simple sample introduction to more complex sample handling such as automatic dilution and calibration, solvent exchange, derivatization reactions and on-line separation processes, among others. Unexplored aspects of these powerful problem solvers are also discussed.     

Within-season dismissal of football coaches: Statistical analysis of causes and consequences

The paper examines the triggers for, and, consequences of, within-season dismissals of managers (head coaches) in the top division of the Spanish Football League during seasons 2002–2003 to 2004–2005. A major reason for directors deciding on dismissal is shown to have been concern that the club in question was in danger of demotion out of the division. This suggests that the clubs hoped to bring about short-term improvement in performance by changing manager. Employing an ordered probit model of match results, we demonstrate that an improvement in results tended to be achieved but only in home matches. The finding vindicates the decisions taken by club directors who dismissed their managers and implies that appeasing fans can have on-the-field benefits. It is consistent with the importance attributed to crowd support in the literature on home advantage in sports.     

Determination of the aggregation constants of bile salts by capillary electrophoresis

Summary Capillary electrophoresis has been investigated as a novel experimental method for determination of the aggregation constants of surfactants. The tendency of sodium cholate and sodium taurodeoxycholate to associate was studied in phosphate buffers of pH 8.0 and pH 7.0, respectively. Stepwise aggregation equilibria of bile salt monomers has been described in terms of massbalance equations. The Offord equation was used to model the electrophoretic mobility of the bile salt associates, and the experimental mobility values could be fitted to the model. Interestingly, only even-membered aggregates-dimers and tetramers-besides the monomers were proposed from the results of the curve-fitting for both bile salts. The aggregation constants calculated were (in molar units): cholate logK _A2=1.37, logK _A4=4.98 taurodeoxycholate logK _A2=1.68, logK _A4=6.46. From these values, more pronounced aggregation of taurodeoxycholate starting at lower concentrations has been deduced, supporting the back-to-back association model of bile salts.     

Polymorphism in Multisymmetric Close Packings of Equal Spheres on a Spherical Surface

Locally optimum, high-symmetry solutions are sought to the Tammes problem: to determine the maximum angular diameter of n equal circles, which can be packed on a sphere without overlapping. By using triangular surface lattices, in the range 1 n 500, those values of n are determined, for which the circles can be close packed in arrangements different from each other with tetrahedral, octahedral, and icosahedral symmetry. Tables are given of the results.     

Pressurized liquid extraction with in-cell clean-up followed by gas chromatography-tandem mass spectrometry for the selective determination of parabens and triclosan in indoor dust

This work studied the possibility of using polyethyleimine (PEI) as an affinity ligand for the purification of plasmid DNA (pDNA) from alkaline lysates using aqueous two-phase systems (ATPSs). The goal was to find conditions under which this cationic polymer could steer the partition of pDNA to the phase where less impurities accumulate. In poly(ethylene glycol) (PEG)/ammonium sulphate systems, neither free nor PEGylated PEI (pPEI) were able to change the partition of pDNA. This is probably due to the high salt concentration present in these systems that impair the interaction between pDNA and PEI. In PEG 3350/dextran 110 systems, the desired effect could be observed but 0.2-0.5M ammonium sulphate had to be added to prevent the co-partition of RNA to the same phase. These results were used to develop a methodology to obtain polyplexes from alkaline lysates in a two-step ATPSs extraction process. In the first step, a PEG 600/ammonium sulphate system is used to remove most impurities to the top phase. The pDNA-containing bottom phase is then isolated and contacted with a second PEG 3350/dextran 110 system supplemented with a small amount of pPEI (0.2%). Plasmid yield was 100% and the final preparation had no RNA and only small amounts of contaminant protein. Additionally, pDNA was obtained in the form of 53nm-sized polyplexes which are likely to suit specific gene delivery applications.     

Economic value of weather forecasting: the role of risk aversion

Extreme meteorological events have increased over the last decades and it is widely accepted that it is due to climate change (IPCC, Climate Change 2007, Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, 2007; Beniston et al., Clim. Change 81:71–95, 2007). Some of these extremes, like drought or frost episodes, largely affect agricultural outputs, and risk management becomes crucial. The goal of this paper it is to analyze farmers’ decisions about risk management, taking into account climatological and meteorological information. We consider a situation in which the farmer, as part of crop management, has available technology to protect the harvest from weather effects. This approach has been used by Murphy et al. (Mon. Weather Rev. 113:801–813, 1985), Katz and Murphy (J. Forecast. 9:75–86, 1990 and Economic Value of Weather and Climate Forecasts, pp. 183–217, Cambridge University Press, Cambridge, 1997) and others in the case when the farmer maximizes the expected returns. In our model, we introduce the attitude towards risk. Thus we can evaluate how the optimal decision is affected by the absolute risk aversion coefficient of Arrow and Pratt, and compute the economic value of the information in this context, while proposing a measure to estimate the amount of money that the farmer is willing to pay for this information in terms of the certainty equivalent.     

Equilibrium binding model of bile salt-mediated chiral micellar electrokinetic capillary chromatography.

Optimum concentration of bile salts in chiral separations depends on both the aggregation properties of the surfactant and the stability of the analyte-micelle complexes. An equilibrium model is proposed in which these two effects are treated separately. First the aggregation constants should be determined under the experimental conditions of the chiral MEKC analysis. With these data, the equilibrium concentrations of bile salt aggregates can be calculated at any total surfactant concentration. Using the Offord equation to approximate the mobilities of the enantiomer-bile salt complexes, a model function has been derived to fit the experimental mobilities. The method yields the binding constants of the enantiomers to each aggregate present. Those species are assumed to be important in the chiral recognition process, which have significantly different stability constants for the enantiomers. The method is demonstrated by the chiral separation of R- and S-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate with sodium taurodeoxycholate. Based on the calculated binding constants, tetrameric aggregates are assumed to be the discriminating species, while no significant difference in enantiomer binding to dimers was found.     

A rietveld study of the cation substitution between uvarovite and yttrium-aluminum synthetic garnets,obtained by sol-gel method

A series of synthetic garnets solid solutions is compositions between Y₃Al₂Al₃O₁₂ (Y-Al garnet) (YAG) and Ca₃Cr₂Si₃O₁₂ (uvarovite) was synthesized using the sol-gel method. The expected general formula is (Ca_xY_1-x)₃ (Cr_xAl_1-x)₂ (Si_xAl_1-x)₃O₁₂ where x = 0 to x = 1. The cation distribution in dodecahedral, octahedral and tetrahedral sites and bond distances in these synthetic garnets were determined using the Rietveld method. It shows the incomplete substitution in small sites. The smaller site the smaller substitution there is.