Sea water desalination by dynamic layer melt crystallization: Parametric study of the freezing and sweating steps

This work aims at developing a dynamic layer crystallizer operated batchwise, for freezing desalination of sea water. The experiments were performed with water/NaCl solutions and with samples of sea water from Nice, Rabat and Marseille. The pilot crystallizer consists of a cooled tube immersed in a cylindrical double jacketed tank. The solution is poured into the tank and the crystallization takes place on the external surface of the tube, by applying a cooling ramp in the tube. The solution is agitated by air bubbling. The whole process involves the freezing step, leading to the crystallization of the ice layer and the sweating step, which consists of purifying in depth the ice layer by melting the impure zones. A parametric study on the effect of the operating parameters has allowed quantifying the role of the different key parameters of the freezing and sweating steps. Three experiments allowed reaching salinities lower than 0.5 g/kg, satisfying the standards of drinking water. The duration of the whole process dropped to only 8 h (5 h for freezing and 3 h for sweating), with a yield of sweating equal to about 50%, provided severe conditions were applied for sweating. Higher yields required longer times. Overall, the results show the feasibility of the technique.     

Synthesis of microsphere-loaded porous polymers by combining emulsion and dispersion polymerisations in supercritical carbon dioxide

Highly porous materials were produced by acrylamide polymerisation templated by supercritical CO(2)-in-water emulsions using new fluorinated glycosurfactants. Properties of the resulting polymer scaffolds were tuned by performing dispersion polymerisations within their cavities filled with supercritical CO(2).     

Analytical and Preparative Chiral Separation of β-Carboline Derivatives, LDL Oxidation Inhibitors, Using HPLC and CE Methodologies: Determination of Enantiomeric Purity

In the present study, baseline separation of the enantiomers of 16 β-carboline derivatives was successfully achieved using both capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) techniques in short run times (<15?min) and thus permit the determination of enantiomeric excess. In HPLC methodology, cellulose chiral stationary phase (Chiralcel OD-H) was used with a binary mobile phase constituted of n-hexane/ethanol 85/15 leading to a resolution factor of 12.6 in 15?min. Preparative HPLC allowed to obtain pure enantiomers of two compounds. In CE, chiral selectivity was developed with an in-capillary stacking strategy using anionic (highly sulfated-γ) cyclodextrins 5% (w/v) as chiral selectors and a 60?mM phosphate buffer (pH 2.5) resulting in a resolution of 10.26 in 14?min of analysis. The analytical characteristics of the two developed methods were studied in terms of repeatability, limits of detection and limits of quantification showing their suitability to be extended to all the other molecules.     

Electronic, spectroscopic, and ion-sensing properties of a dehydro[m]pyrido[14]- and [15]annulene isomer library

An isomeric series of dehydro[m]pyrido[n]annulenes incorporating strained 1,4-buta-1,3-diyne units have been synthesized, where m = 2, n = 14 (1a-d); m = 2, n = 15 (2a,b); and m = 3, n = 15 (3). The number of pyridine rings and annulene ring π-electrons are denoted by m and n, respectively. The X-ray crystal structures of 1b and 1c confirmed their cyclic formulation. All macrocycles were found to be luminescent chromophores with differing isomer-dependent proton and metal ion-sensory emission responses, which appear collectively as analyte-specific color patterns. Within the series studied, 1a was singular in displaying the highest luminescence quantum yield and sharing the strongest emission energy and molar absorption changes upon protonation and Hg(II) binding. Spectroscopic and electrochemical results were supported by density functional theory calculations in showing 1a, 2a, and 3 to be low bandgap materials with lowest unoccupied molecular orbitals delocalized over the 1,4-di(pyridin-4-yl)buta-1,3-diyne bridges that provide a pathway for electronic communication between the nitrogens. Overall, the investigations suggest that 1a, 2a, and 3 would be excellent ligands for the construction of novel conjugated hybrid metallosupramolecular nanostructures, polymers, and ion-sensory systems.     

Implementation of renormalized excitonic method at ab initio level

The renormalized excitonic method [Hajj et al., Phys Rev B 2005, 72, 224412], in which the excited state of the whole system may be described as a linear combination of local excitations, has been implemented at ab initio level. Its performance is tested on the ionization potential and the energy gap between singlet ground state and lowest triplet for linear molecular hydrogen chains and more realistic systems, such as polyenes and polysilenes, using full configuration interaction (FCI) wave functions with a minimal basis set. The influence of different block sizes and the extent of interblock interactions are investigated. It has been demonstrated that satisfactory results can be obtained if the near degeneracies between the model space and the outer space are avoided and if interactions between the next-nearest neighbor blocks are considered. The method can be used with larger basis sets and other accurate enough ab initio evaluations (instead of FCI) of local excited states, from blocks, or from dimers or trimers of blocks. It provides a new possibility to accurately and economically describe the low-lying delocalized excited states of large systems, even inhomogeneous ones.     

The low‐temperature barium fluoridozirconate variety α‐BaZr2F10

The low‐temperature triclinic variety α‐BaZr₂F₁₀ constitutes a new structure type, less symmetrical than the higher‐temperature β‐variety. It is based on the stacking of double sheets of Zr polyhedra, connecting three different kinds of ZrF₇ polyhedra and one ZrF₈ polyhedron via vertices and edges, separated by corrugated Ba²⁺ layers. It is compared to the high‐temperature β‐variety, directly recrystallizing from barium fluoridozirconate glass, and also to BaTe₂F₁₀ and KTe₂F₉.     

Accelerating the development of phase-change random access memory with in-fab plasma profiling time-of-flight mass spectrometry

We demonstrate the potential of using plasma profiling time-of-flight mass spectrometry (PP-TOFMS) to accelerate process developments for phase-change random access memory (PCRAM) applications, which require advanced materials with composition-driven properties. We assess the performances of PP-TOFMS for the chemical depth-profiling of GeSbTe phase change materials, first after deposition steps to investigate the top surface layer and the incorporation of silicon into the amorphous matrix, then after the thermal annealing step to refine in situ capping strategies, and finally in close loop with etching process steps. Comparison of reference-free semiquantitative PP-TOFMS analysis based on ion beam ratio with Rutherford backscattering spectrometry shows remarkable agreement (~10% relative). PP-TOFMS proves to be a fast screening tool, which allows process monitoring and selection of samples that indeed need more complex analysis.     

Geometrical inverse matrix approximation for least-squares problems and acceleration strategies

Numerical Algorithms - We extend the geometrical inverse approximation approach to the linear least-squares scenario. For that, we focus on the minimization of $1-\cos \limits (X(A^{T}A),I)$ ,...