Structure formation and phase behaviour in ferrofluid monolayers: theory and computer simulations

In order to investigate the peculiarities brought by the quasi-2D geometry into the aggregation processes in ferrofluids, a combination of density functional theory (DFT), and molecular dynamics (MD) simulations is presented. The microstructure formation and the phase behaviour of monodisperse ferrofluid monolayers is studied. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Valorization of Fly Ashes and Sands Wastes from Biomass Boilers in One-Part Geopolymers

Fly ash (FA) and exhausted bed sands (sands wastes) that are generated in biomass burners for energy production are two of the wastes generated in the pulp and paper industry. The worldwide production of FA biomass is estimated at 10 million tons/year and is expected to increase. In this context, the present work aims to develop one-part alkali-activated materials with biomass FA (0–100 wt.% of the binder) and sands wastes (100 wt.% of the aggregate). FA from two different boilers, CA and CT, was characterized and the mortar’s properties, in the fresh and hardened conditions, were evaluated. Overall, the incorporation of FA decreases the compressive strength of the specimens. However, values higher than 30 MPa are reached with 50 wt.% of FA incorporation. For CA and CT, the compressive strength of mortars with 28 days of curing was 59.2 MPa (0 wt.%), 56.9 and 57.0 MPa (25 wt.%), 34.9 and 46.8 MPa (50 wt.%), 20.5 and 13.5 MPa (75 wt.%), and 9.2 and 0.2 MPa (100 wt.%), respectively. The other evaluated characteristics (density, water absorption, leached components and freeze–thaw resistance) showed no significant differences, except for the specimen with 100 wt.% of CA. Therefore, this work proved that one-part geopolymeric materials with up to 90 wt.% of pulp and paper industrial residues (FA and sand) can be produced, thus reducing the carbon footprint associated with the construction sector.     

Development of ferroelectric liquid crystals with low birefringence

We propose an approach for development of ferroelectric liquid crystals (FLC) with low birefringence Δn. Two basic principles have been used to get lowering of Δn: selection of molecules with short chains of conjugation as components for achiral matrix and averaging of local refractive indices by FLC helical structure. FLC mixtures with low birefringence (0.07 < Δn < 0.10 at wavelength 589.3 nm of sodium line) were elaborated and investigated. They consist of an achiral matrix including both nematic and smectic liquid crystal components and of phenylpyrimidine derivatives as chiral dopants. The materials developed can be used for all basic electro-optical FLC modes such as surface stabilised FLC (SSFLC), deformed helix ferroelectrics (DHF) and electrically suppressed helix (ESH). The mixtures developed allow to reduce the FLC cells chromatic retardance variation due to the weaker birefringence dispersion as compared with the known FLC materials to date.     

Fluorescence modulation of eosin Y in a PMMA film by diarylethene switching

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同位旋非对称核物质性质与扩展的BHF方法(III)HVH定理与费米能量

在扩展的同位旋相关的Brueckner—Hartree—Fock理论框架内,在整个同位旋自由度范围内研究了质量算子的空穴线展开中不同等级近似下非对称核物质中Hugenholtz—Van Hove定理的满足程度,并计算了中子和质子的费米能量.结果表明为了使Hugenholtz-Van Hove定理达到令人满意的满足程度,需要同时考虑质量算子中的重排贡献和重正修正,从而指出了基态关联对于非对称核物质中单粒子性质的重要性.     

A possible helical model for sodium glycocholate micellar aggregates

Sodium glycocholate crystallizes in the tetragonal space group14 witha =b = 27.793(4),c = 7.937(1) Å andZ = 8. Refinement based on 2290 observed reflections led to a conventionalR = 0.10. The bile salt molecules are arranged in a helix with 2₁ symmetry stabilized mainly by polar interactions. Four helices are held together by hydrogen bonds involving water molecules, giving rise to hydrophilic channels, with a small cross section, which can include water molecules. The packing of these tetramers form hydrophobic channels containing some disordered acetone and water molecules. The helices will be checked as a model for the micellar aggregates of this important conjugated bile salt, following the same strategy successfully applied to sodium deoxycholate. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82107 (20 pages).     

Oxidative Polymerization of the Pheomelanin Precursor 5-Hydroxy-1,4-benzothiazinylalanine: A New Hint to the Pigment Structure

Biosynthetic studies have shown that pheomelanins, the distinctive pigments of red human hair, arise from oxidative polymerization of cysteinyldopas via 1,4-benzothiazinylalanine intermediates. However, the mode of formation of the pigment polymer remains controversial. To address this point, we have investigated the conversion of the major biosynthetic precursor 5-S-cysteinyldopa (2a) to pheomelanin under biomimetic conditions. Peroxidase/H(2)O(2) oxidation of 2a was shown to lead in the early stages to the 1,4-benzothiazinylalanine 8a, which rapidly declines with concomitant formation of a distinct pattern of oligomeric products. Reduction of the reaction mixture at this stage allowed the isolation of dimer 17 in 10% yield, along with trimers 18 and 19 in smaller amounts. A restricted rotation about the ethereal C-O bond of 17 was apparent by the presence of two NMR-detectable conformational isomers, separated by an activation energy barrier of 17.83 +/- 0.03 kcal mol(-)(1). Under similar oxidation conditions, the model catechol 2b gave the related dimers 15 and 16. The structure of oligomers 17-19, all characterized by C-C and C-O bonds between the benzothiazine units, would suggest that the peroxidase-promoted polymerization proceeds by phenol-type coupling of an aryloxy radical generated by initial one-electron oxidation of 8a. Overall, these results point to a structural model for the pheomelanin polymer which is basically different from that proposed on the basis of degradative studies.