A new intermediate intercalate in superconducting sodium-doped hafnium nitride chloride

A new phase has been observed during the sodium intercalation of hafnium nitride chloride as intermediate between the host beta-HfNCl and the already reported Na(0.29)HfNCl with Tc of 24 K; the new intermediate shows interlayer spacings ranging from 9.48 to 9.67 A, corresponds to a second stage intercalate of HfNCl and is superconducting with a critical temperature of 20 K.     

Cimetidine complexes derived from cobalt(II), nickel(II) and copper(II) salts of polyatomic anions

Summary Cobalt(II), nickel(II) and copper(II) complexes [M(CM)₂]X₂ (X = BF₄ or NO₃) have been prepared with cimetidine (CM). Powder data, molar conductivities, magnetic moments, i.r. and electronic spectra support apseudo-octahedral stereochemistry with MN₂N ₂ S₂ chromophore and tentative structures are proposed for the complexes. Their properties are compared with these of previously prepared complexes.     

Order and disorder in mixed metal linear chains: The homo and heterobimetallic EDTA (M(H2O)4OIOII)[M′(EDTA)] · 6H2O complexes (M = Mg,Mn, Co,Zn and Ni; M′ = Co,Ni, Cu and Zn)

Summary Polymetallic solid solutions of the ethylenediaminetetracetic acid (EDTA) and six divalent metal ions exist in the range: MgMnCoZnNiCu(EDTA) · 6H₂O where + + + + + =2, 01, 0,,2, 0, 1.This type of structure is characterized by the presence of two different octahedral carboxylate-bridged coordination sites forming infinite zig-zag chains. Visible and i.r. spectra and t.g.a. analysis show that there is occupational preference for the two coordination sites in the crystalline structure.Due to this preference, and also to the structural features, the heterobimetallic MM(EDTA) · 6H₂O compounds constitute a structurally new class of materials which can be described as ordered alternating-heterobimetallic polymeric coordination complexes.     

Multi-commodity rationing problems with maxmin payoffs

We address a multi-dimensional extension of standard rationing problems in which several commodities have to be shared among a set of agents who exhibit maxmin preferences on the results they obtain. In this context we investigate efficiency and introduce a property of stability which is supported on a transferable utility game. We also propose a procedure to construct rules for obtaining stable allocations for the special case where all commodities have the same weight.     

Application of the voltammetry of microparticles for dating archaeological lead using polarization curves and electrochemical impedance spectroscopy

The application of the voltammetry of microparticles methodology to date archaeological lead artifacts, based on the time-dependent formation of different layers of lead oxides, whose relative amount can be estimated from polarization curves and electrochemical impedance spectroscopy (EIS), is presented. This approach is complemented by additional data using square wave voltammetry data. Calibration of the method was performed with the help of a series of well-documented, lead pieces from the funds of different Spanish museums, covering since the 7th century BC to nowadays.     

First direct fluorescence polarization assay for the detection and quantification of spirolides in mussel samples

In 2009, we achieve the first inhibition FP assay to detect imine cyclic toxins. In the present paper we propose a new FP assay for direct quantify spirolides. This new method has resulted in significant improvement of sensitivity, rapidity and accessibility. In the method design, nicotinic acetylcholine receptor from Torpedo marmorata membranes labelled with a derivative of fluorescein was used. Spirolides, 13-desmethyl spirolide C (13-desMeC) and 13,19-didesmethyl spirolide C (13,19-didesMeC) were extracted and purified from cultures of the Alexandrium ostenfeldii dinoflagellate. Data showed the decrease of FP when toxin concentration was increased. Thus, a relationship between the FP units and the spirolides amount present in a sample was obtained. This direct assay is a reproducible, simple and very sensitive method with a detection limit about 25 nM for 13-desMeC and 150 nM for 13,19-didesMeC. The procedure was used to measure spirolides in mussel samples using an extraction and clean up protocol suitable for the FP assay. Results obtained show that this method is able to quantify 13-desMeC in the range of 50–350 μg kg⁻¹ meat. Other liposoluble toxins did not interfere with the assay, proving a specific method. Moreover, the matrix do not affect in the range of toxin concentrations that involving risk of spirolides intoxication.     

Multi-detection method for five common microalgal toxins based on the use of microspheres coupled to a flow-cytometry system

Freshwater and brackish microalgal toxins, such as microcystins, cylindrospermopsins, paralytic toxins, anatoxins or other neurotoxins are produced during the overgrowth of certain phytoplankton and benthic cyanobacteria, which includes either prokaryotic or eukaryotic microalgae. Although, further studies are necessary to define the biological role of these toxins, at least some of them are known to be poisonous to humans and wildlife due to their occurrence in these aquatic systems. The World Health Organization (WHO) has established as provisional recommended limit 1 μg of microcystin-LR per liter of drinking water. In this work we present a microsphere-based multi-detection method for five classes of freshwater and brackish toxins: microcystin-LR (MC-LR), cylindrospermopsin (CYN), anatoxin-a (ANA-a), saxitoxin (STX) and domoic acid (DA). Five inhibition assays were developed using different binding proteins and microsphere classes coupled to a flow-cytometry Luminex system. Then, assays were combined in one method for the simultaneous detection of the toxins. The IC₅₀'s using this method were 1.9 ± 0.1 μg L⁻¹ MC-LR, 1.3 ± 0.1 μg L⁻¹ CYN, 61 ± 4 μg L⁻¹ ANA-a, 5.4 ± 0.4 μg L⁻¹ STX and 4.9 ± 0.9 μg L⁻¹ DA. Lyophilized cyanobacterial culture samples were extracted using a simple procedure and analyzed by the Luminex method and by UPLC–IT-TOF-MS. Similar quantification was obtained by both methods for all toxins except for ANA-a, whereby the estimated content was lower when using UPLC–IT-TOF-MS. Therefore, this newly developed multiplexed detection method provides a rapid, simple, semi-quantitative screening tool for the simultaneous detection of five environmentally important freshwater and brackish toxins, in buffer and cyanobacterial extracts.     

Highly Enantioselective Copper(I)‐Catalyzed Conjugate Addition of Terminal Alkynes to 1,1‐Difluoro‐1‐(phenylsulfonyl)‐3‐en‐2‐ones: New Ester/Amide Surrogates in Asymmetric Catalysis

A highly enantioselective copper‐catalyzed conjugate alkynylation of monoactivated enones, namely 1,1‐difluoro‐1‐(phenylsulfonyl)‐3‐en‐2‐ones, is described. The reaction products are obtained with good yields and excellent enantioselectivities (from 92 to 99% ee). The β‐alkynylated difluoro(phenylsulfonyl) ketones can be converted into the corresponding β‐alkynylated difluoro‐ and trifluoromethyl ketones, esters and amides. This is the first example on the use of 1,1‐difluoro‐1‐(phenylsulfonyl)‐3‐en‐2‐ones as substrates in an enantioselective reaction, which have been shown to be new ester/amide surrogates.     

Introspection and equilibrium selection in 2 × 2 matrix games

Game theory lacks an explanation of how players' beliefs are formed and why they are in equilibrium. This is the reason why it has failed to make significant advances with the problem of equilibrium selection even for quite simple games, as 2 × 2 games with two strict Nash equilibria. Our paper models the introspection process by which the selected equilibrium is achieved in this class of games. Players begin their analysis with imprecise priors, obtained under weak restrictions formulated as Axioms. For a large class of reasoning dynamics we obtain as the solution the risk dominant Nash equilibrium.     

Preparation and characterization of hexyl methacrylate monolithic columns for CEC

The preparation of hexyl methacrylate (HMA) monolithic columns for CEC separations has been investigated with two initiation systems: (i) ammonium peroxodisulphate and TEMED to activate the polymerization reaction, and (ii) by thermal initiation with AIBN. For both initiators, the influence of composition of porogenic solvent on morphological and chromatographic properties of monoliths was investigated. Two porogenic solvent systems, aqueous and non-aqueous media, were also studied for monolithic beds polymerized with AIBN. Under optimal conditions, low minimum plate heights (9.6 mum for peroxodisulphate, 8.4 and 10.0 mum for AIBN in aqueous and non-aqueous porogenic solvents, respectively) were obtained. A comparison in terms of chromatographic performance of HMA monoliths with butyl methacrylate columns polymerized with both initiators was also performed. The resulting HMA-based stationary phases also exhibited a good repeatability and column-to-column reproducibility, with RSD values below 5.6% in the studied electrochromatographic parameters. The potential of HMA-based columns was demonstrated by the analysis of complex mixtures of polyaromatic hydrocarbons and anabolic steroids.