Validation interlaboratory trial for ISO 12010: Water quality—Determination of short-chain polychlorinated alkanes (SCCP) in water

A validation interlaboratory trial was carried out to prepare ISO 12010: Water quality??Determination of short-chain polychlorinated alkanes (SCCP) in water??Method using gas chromatography/mass spectrometry (GC-MS) and electron capture negative ionisation (ECNI). The task was to determine the sum of short-chain polychlorinated n-alkanes with carbon chain lengths of C₁₀?CC₁₃ and a chlorine content between 49% (g/100?g) and 67% (g/100?g) in water by GC-ECNI-MS. The quantification had to be performed by multiple linear regression as described in ISO/DIS 12010, the compulsory method. Samples distributed were real river samples, and waste water spiked with a target concentration of 0.4 and 0.6???g/L for the sum of SCCPs, i.e. a concentration around the environmental quality target level according to the European Water Framework Directive. The different types of water samples tested were surface water with <150?mg/L suspended matter, surface water with 0.5?g/L suspended matter, and filtered waste waster. The interlaboratory trial included the extraction of the water samples, a column chromatographic clean up, a concentration step, and integration of chromatographic unresolved complex mixtures as well as the calibration and quantification by multiple linear regression. The reproducibility standard deviation of the standard concentration was 11.9%. Reproducibility standard deviations of concentrations in the three different water samples between 27.8 and 34.2% were achieved by 10?C12 participating laboratories from six countries.     

Microwave assisted "click" chemistry for the synthesis of multiple labeled-carbohydrate oligonucleotides on solid support

A versatile approach has been developed for the multiple labeling of oligonucleotides. First, three linkers as a H-phosphonate monoester derivative were condensed on a solid-supported T12 to introduce H-phosphonate diester linkages which were oxidized in the presence of propargylamine. Second, three galactosyl azide derivatives were conjugated to the solid-supported three-alkyne-modified T12 by a 1,3-cycloaddition so-called "click chemistry" in the presence of Cu(I) assisted by microwaves.     

Unfolding of Surfaces

This paper deals with the approximation of the unfolding of a smooth globally developable surface (i.e. "isometric" to a domain of ) with a triangulation. We prove the following result: let T_n be a sequence of globally developable triangulations which tends to a globally developable smooth surface S in the Hausdorff sense. If the normals of T_n tend to the normals of S, then the shape of the unfolding of T_n tends to the shape of the unfolding of S. We also provide several examples: first, we show globally developable triangulations whose vertices are close to globally developable smooth surfaces; we also build sequences of globally developable triangulations inscribed on a sphere, with a number of vertices and edges tending to infinity. Finally, we also give an example of a triangulation with strictly negative Gauss curvature at any interior point, inscribed in a smooth surface with a strictly positive Gauss curvature. The Gauss curvature of these triangulations becomes positive (at each interior vertex) only by switching some of their edges.     

Height Preserving Minimal Interval Extensions

We consider minimal interval extensions of a partial order which preserve the height of each vertex. We show that minimal interval extensions having this property bijectively correspond to the maximal chains of a sublattice of the lattice of maximal antichains of the given order. We show that they also correspond to the set of minimal interval extensions of a certain extension of this order.     

A comprehensive study of the spontaneous formation of nanoassemblies in water by a "lock-and-key" interaction between two associative polymers

Nanoassemblies (NAs) with sizes ranging from 60 to 160nm were spontaneously formed in water after mixing a host polymer (polymerized cyclodextrin (pβ-CD)) and a guest polymer (dextran grafted with lauroyl side chains (MD)). The combination of microscopy, dynamic light scattering (DLS), nuclear magnetic resonance ((1)H NMR), isothermal titration calorimetry (ITC) and molecular modelling was used to investigate the parameters which govern the association between MD and pβ-CD. Remarkably, when pβ-CD was progressively added to a solution of MD, NAs with a well-defined diameter were spontaneously formed and their diameter was constant whatever the composition of the system. According to NMR data, almost all the alkyl chains of MD were included into CDs' cavities of the polymer when the molar ratio lauroyl chain (C(12))/CD was ?1. The hydrophobic interaction between C(12) and the hydrophobic cavities of CDs appears as the main driving force for NAs' formation, with a minor contribution arising from van der Waals' interactions. The inclusion of C(12) into β-CD cavities is almost a completely enthalpy-driven process, whereas the MD-C(12)/pβ-CD interaction was found to be an entropy-driven process. Major conclusions which can be drawn from these studies are that the interactions between the two polymers are restricted neither by the MD substitution yield, nor by the micellization of MD. The simultaneous effects of several CD linked together in pβ-CD and of many alkyl chains grafted on dextran were necessary to generate these stable NAs.     

An SPH multi‐fluid model based on quasi buoyancy for interface stabilization up to high density ratios and realistic wave speed ratios

We introduce a smoothed particle hydrodynamics (SPH) concept for the stabilization of the interface between 2 fluids. It is demonstrated that the change in the pressure gradient across the interface leads to a force imbalance. This force imbalance is attributed to the particle approximation implicit to SPH. To stabilize the interface, a pressure gradient correction is proposed. In this approach, the multi‐fluid pressure gradients are related to the (gravitational and fluid) accelerations. This leads to a quasi‐buoyancy correction for hydrostatic (stratified) flows, which is extended to nonhydrostatic flows. The result is a simple density correction that involves no parameters or coefficients. This correction is included as an extra term in the SPH momentum equation. The new concept for the stabilization of the interface is explored in 5 case studies and compared with other multi‐fluid models. The first case is the stagnant flow in a tank: The interface remains stable up to density ratios of 1:1000 (typical for water and air), in combination with artificial wave speed ratios up to 1:4. The second and third cases are the Rayleigh‐Taylor instability and the rising bubble, where a reasonable agreement between SPH and level‐set models is achieved. The fourth case is an air flow across a water surface up to density ratios of 1:100, artificial wave speed ratios of 1:4, and high air velocities. The fifth case is about the propagation of internal gravity waves up to density ratios of 1:100 and artificial wave speed ratios of 1:4. It is demonstrated that the quasi‐buoyancy model may be used to stabilize the interface between 2 fluids up to high density ratios, with real (low) viscosities and more realistic wave speed ratios than achieved by other weakly compressible SPH multi‐fluid models. Real wave speed ratios can be achieved as long as the fluid velocities are not very high. Although the wave speeds may be artificial in many cases, correct and realistic wave speed ratios are essential in the modelling of heat transfer between 2 fluids (eg, in engineering applications such as gas turbines).     

Modeling Phononic Crystals via the Weighted Relaxed Micromorphic Model with Free and Gradient Micro-Inertia

In this paper the relaxed micromorphic continuum model with weighted free and gradient micro-inertia is used to describe the dynamical behavior of a real two-dimensional phononic crystal for a wide range of wavelengths. In particular, a periodic structure with specific micro-structural topology and mechanical properties, capable of opening a phononic band-gap, is chosen with the criterion of showing a low degree of anisotropy (the band-gap is almost independent of the direction of propagation of the traveling wave). A Bloch wave analysis is performed to obtain the dispersion curves and the corresponding vibrational modes of the periodic structure. A linear-elastic, isotropic, relaxed micromorphic model including both a free micro-inertia (related to free vibrations of the microstructures) and a gradient micro-inertia (related to the motions of the microstructure which are coupled to the macro-deformation of the unit cell) is introduced and particularized to the case of plane wave propagation. The parameters of the relaxed model, which are independent of frequency, are then calibrated on the dispersion curves of the phononic crystal showing an excellent agreement in terms of both dispersion curves and vibrational modes. Almost all the homogenized elastic parameters of the relaxed micromorphic model result to be determined. This opens the way to the design of morphologically complex meta-structures which make use of the chosen phononic material as the basic building block and which preserve its ability of “stopping” elastic wave propagation at the scale of the structure.     

Preparation and structure of novel hexaazaisowurtzitane cages

Hexaazaisowurtzitane or cage molecules have attracted attention concerning their synthesis because hexanitrohexaazaisowurtzitane (HNIW or CL20) is presently the most powerful energetic compound. The synthesis of hexaazaisowurtzitanes was considered to be limited solely to the condensation of certain benzylamines with glyoxal. Here, we present the synthesis and characterization of seven novel non-benzylic hexaazaisowurtzitanes, such as hexapropargylhexaazaisowurtzitane. The substituents on the six nitrogen atoms are different to those of the benzyl or substituted benzyl groups to which previous syntheses were limited. X-ray structures are given for the hexapropargyl and hexa-2-thienylmethylene derivatives. Steric strains limit the synthesis with alpha-substituted benzyl and allyl derivatives. The reaction mechanism and the role of the intermediate diimines are discussed. Some of the novel hexaazaisowurtzitanes are potential precursors of hexanitrohexaazaisowurtzitane.     

A matrix modular neural network based on task decomposition with subspace division by adaptive affinity propagation clustering

In this paper, a matrix modular neural network (MMNN) based on task decomposition with subspace division by adaptive affinity propagation clustering is developed to solve classification tasks. First, we propose an adaptive version to affinity propagation clustering, which is adopted to divide each class subspace into several clusters. By these divisions of class spaces, a classification problem can be decomposed into many binary classification subtasks between cluster pairs, which are much easier than the classification task in the original multi-class space. Each of these binary classification subtasks is solved by a neural network designed by a dynamic process. Then all designed network modules form a network matrix structure, which produces a matrix of outputs that will be fed to an integration machine so that a classification decision can be made. Finally, the experimental results show that our proposed MMNN system has more powerful generalization capability than the classifiers of single 3-layered perceptron and modular neural networks adopting other task decomposition techniques, and has a less training time consumption.