Inorganic mercury and methylmercury determination in polluted waters by HPLC coupled to cold vapour atomic fluorescence spectroscopy

A systematic study of Hg²⁺ and CH₃Hg⁺ (MeHg⁺) speciation using hyphenated techniques, was performed for high-performance liquid chromatography coupled to on-line UV irradiation and cold-vapour atomic fluorescence spectroscopy (HPLC-UV-CV-AFS). First, a comparative study of the behaviour of three mobile phase compositions (using tetrabutylammonium bromide (TBAB), L-cysteine and ammonium pyrrolidinedithiocarbamate (APDC)) is presented. The separation and detection system was optimised by considering factors that modify fluorescence signal and the separation such as, the addition of different percentages of an organic modifier (methanol (MeOH) and acetonitrile (ACN)) to the mobile phase, the type of reducing agent used (SnCl₂ and NaBH₄) and the potential memory effects of the material of which the injection system is made (stainless steel, PEEK). The mobile phase selected for its sensitivity was a mixture 80?:?20 MeOH?:?0.0015?mol?l^–1 APDC and 0.01?mol?l^–1 NH₄CH₃COO (pH 5.5). The detection and quantification limits were close to 1.5 and 5?µg?l^?1 for both species (as Hg), respectively. Recoveries obtained using fortified water samples of distinct origin (soft mineral, tap, river, seawater, and wastewater), ranged from 90 to 115% for concentrations about 2 and 20 times over quantification limits. Good repeatability was obtained (about 5%) independently of the concentrations, with reproducibility values about 20% at low concentrations and 5–10% at higher concentrations. Our proposed method proved to be straightforward for use by environmental laboratories for routine Hg²⁺ and MeHg⁺ determinations in polluted water samples.     

TETRATHIAFULVALENE S-OXIDE: A FATAL “DONOR IMPURITY” IN THE ORGANIC METAL TTF-TCNQ

Abstract

Tetrathiafulvalene S-oxide (TTF-ox) was first detected by mass spectrometry in samples of Tetrathiafulvalene (TTF) which had been exposed to oxygen. Pure TTF-ox was prepared by peracid oxidation of TTF and isolated as a relativly stable solid. Physical data will be presented.     

Shape-Adaptability and Redox-Switching Properties of a Di-Gold Metallotweezer

The use of a carbazolyl-connected di-gold(I) metallotweezer for the encapsulation of several electron-poor organic substrates, and a planar Au(III) complex containing a CNC pincer ligand, is described. The binding affinity of the receptor depends on the electron-deficient character of the planar guest, with larger association constants found for the more electron-poor guests. The X-ray diffraction molecular structures of two host:guest adducts show that the host approaches its arms in order to facilitate the optimum interaction with the surface of the planar guests, in a clear example of an guest-induced fit conformational arrangement. The electrochemical studies of the encapsulation of N,N’-dimethyl-naphthalenetetracarboxy diimide (NTCDI) show that the redox active guest is released from the receptor upon one electron reduction, thus constituting an example of redox-switchable binding.     

Interpolating minimal energy C1‐Surfaces on Powell–Sabin Triangulations: Application to the resolution of elliptic problems

In this article, we present a method to obtain a C¹‐surface, defined on a bounded polygonal domain Ω, which interpolates a specific dataset and minimizes a certain “energy functional.” The minimization space chosen is the one associated to the Powell–Sabin finite element, whose elements are C¹‐quadratic splines. We develop a general theoretical framework for that, and we consider two main applications of the theory. For both of them, we give convergence results, and we present some numerical and graphical examples. © 2014 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 31: 798–821, 2015     

Code2vect: An efficient heterogenous data classifier and nonlinear regression technique

The aim of this paper is to present a new classification and regression algorithm based on Artificial Intelligence. The main feature of this algorithm, which will be called Code2Vect, is the nature of the data to treat: qualitative or quantitative and continuous or discrete. Contrary to other artificial intelligence techniques based on the “Big-Data,” this new approach will enable working with a reduced amount of data, within the so-called “Smart Data” paradigm. Moreover, the main purpose of this algorithm is to enable the representation of high-dimensional data and more specifically grouping and visualizing this data according to a given target. For that purpose, the data will be projected into a vectorial space equipped with an appropriate metric, able to group data according to their affinity (with respect to a given output of interest). Furthermore, another application of this algorithm lies on its prediction capability. As it occurs with most common data-mining techniques such as regression trees, by giving an input the output will be inferred, in this case considering the nature of the data formerly described. In order to illustrate its potentialities, two different applications will be addressed, one concerning the representation of high-dimensional and categorical data and another featuring the prediction capabilities of the algorithm.     

On fundamental groups of symplectically aspherical manifolds

A smooth manifold M is called symplectically aspherical if it admits a symplectic form with |₂(M) = 0. It is easy to see that, unlike in the case of closed symplectic manifolds, not every finitely presented group can be realized as the fundamental group of a closed symplectically aspherical manifold. The goal of the paper is to study the fundamental groups of closed symplectically aspherical manifolds. Motivated by some results of Gompf, we introduce two classes of fundamental groups ₁(M) of symplectically aspherical manifolds M. The first one consists of fundamental groups of such M with ₂(M)=0, while the second with ₂(M)0. Relations between these classes are discussed. We show that several important (classes of) groups can be realized in both classes, while some groups can be realized in the first class but not in the second one. Also, we notice that there are some interesting dimensional phenomena in the realization problem. The above results are framed by a general study of symplectically aspherical manifolds. For example, we find some conditions which imply that the Gompf sum of symplectically aspherical manifolds is symplectically aspherical, or that a total space of a bundle is symplectically aspherical.Mathematics Subject Classification (1991): 57R15, 53D05, 14F35