High stable sandwich-type polyoxometallates based on . Synthesis, chemical properties and characterization of [(A-β-SiW9O34)2(MOH2)3CO3] (M = Y and Yb)

Highly hydrolytic and thermally stable sandwich-type polyoxometallates of [(A-β-SiW₉O₃₄)₂(MOH₂)₃CO₃]¹³⁻ (M = Y³⁺ and Yb³⁺) have been synthesized at room temperature by stoichiometric reactions of the trilacunary ligand with M³⁺ in 0.1 M carbonate solution. The new complexes were isolated as sodium and mixed sodium/potassium salts and were characterized by elemental analysis, IR, ¹³C and ²⁹Si NMR, UV–Vis spectroscopy, TGA, DSC and single crystal structure analysis. The crystal structure of the complexes consist of two lacunary Keggin moieties which are linked by a (H₂OMO)₃C belt into an assembly of virtual C₂ symmetry. Each M³⁺ ion adopts a mono-capped trigonal-prismatic coordination. The C₂ axis of the complexes and the local 3-fold axis of the MO₆ group lies in the (H₂OMO)₃C belt plane. The trigonal prismatic geometry is achieved by the two terminal oxygen atoms of an edge shared pair of WO₆ octahedra from each moiety and two oxygen from the belt, and the cap by one external water ligand. The hydrolytic and thermal stabilities of the complexes and the reasons that prove the retention of the isomeric form of the trilacunary ligand upon complexation are discussed.     

Mild and highly efficient method for the synthesis of 2-arylbenzimidazoles and 2-arylbenzothiazoles

A new, convenient method for the syntheses of 2-substituted benzimidazole and benzothizole is described. Short reaction times, large-scale synthesis, easy and quick isolation of the products, excellent chemoselectivity, and excellent yields are the main advantages of this procedure.     

The oak (Quercus brantii) acorn as a growth promotor for rainbow trout (Oncorhynchus mykiss): growth performance,body composition,liver enzymes activity and blood biochemical parameters

Abstract

Medicinal plants play an important role in aquaculture as feed additives. This study aimed to investigate effects of alcoholic extract of acorn on growth performance, body composition, digestive enzymes activity and blood biochemical parameters of rainbow trout (O. mykiss) as a commercially important fish. Five dietary treatments were supplemented: 100, 200, 400 and 600?mg.kg^?1 of the extract. Fishes were fed twice per day for 8?weeks, and results showed that acorn extract positively affected all investigated parameters in rainbow trout fishes. Digestive enzymes activity and growth performance were increased, while activity of liver enzymes and cortisol were lowed in comparison to control individuals. Body composition of treated animals was also enhanced. Comparison between treated groups together with integrative biomarker response (IBR) values indicated greatest effects in animals fed with 400 and 600?mg.kg^?1 of the extract. Positive effects of the acorn represent promising start point for further studies.     

Synthesis and Characterization of Novel Monoazo N‐Ester‐1,8‐Naphthalimide Disperse Dyestuffs

Five novel monoazo disperse dyestuffs based on N‐ester‐1,8‐naphthalimide were synthesized. Acenaphthene was nitrated, then oxidized to 4‐nitro‐1,8‐naphthalic anhydride. 4‐Nitro‐1,8‐naphthalic anhydride was reacted with methyl and ethyl glycinate in alcoholic media, followed with reduction. 4‐Amino‐N‐methyl and ethyl glycinate‐1,8‐naphthalimide were obtained. These products were diazotized and coupled with appropriate aromatic amines to give bluish‐red or violet dyestuffs. All intermediates and dyestuffs were purified and characterized by ¹H‐NMR, FTIR, DSC, UV‐VIS and Elemental Analysis. Dispersion of dyestuffs was prepared in water and applied to polyester fabrics. The dyed fabrics showed that four of the synthesized dyestuffs were suitable for coloring polyester fibers, producing deep bluish red with very good build up properties.     

Determination of fatty acids by high-performance liquid chromatography and fluorescence detection using precolumn derivatization with 9-fluorenylmethyl chloroformate

A new high-performance liquid chromatographic method is described for the determination of fatty acids in seed oils. The method was based on precolumn derivatization with 9-fluorenylmethyl chloroformate as a labeling agent and fluorescence detection. Fatty acids were extracted from the samples and subjected to derivatization with the reagent at 60°C for 10?min. The chromatographic separation of 14 fatty acids (C10–C22) was achieved on a combined loading compression octadecyl sulfate (CLC-ODS) column with a run time of 30?min. Three-step gradient elution of a mobile phase consisted of acetonitrile and water was used, and the signal was monitored at excitation and emission wavelengths of 265 and 315?nm, respectively. The method indicated favorable sensitivity and reproducibility for fatty acids’ derivatives. The detection limits, at a signal-to-noise ratio of 3, were 0.01–0.05?µg/ml and relative standard deviations (RSDs) were less than 0.27%. Excellent linear responses were observed with coefficients of 0.9995. This method was applied to quantify fatty acids in white, brown, and black sesame seeds’ oil.     

Interlaminar hygrothermal stresses in laminated plates

Within the elasticity formulation the most general displacement field for hygrothermal problems of long laminated composite plates is presented. The equivalent single-layer theories are then employed to determine the global deformation parameters appearing in the displacement fields of general cross-ply, symmetric, and antisymmetric angle-ply laminates under thermal and hygroscopic loadings. Reddy’s layerwise theory is subsequently used to determine the local deformation parameters of various displacement fields. An elasticity solution is also developed in order to validate the efficiency and accuracy of the layerwise theory in predicting the interlaminar normal and shear stress distributions. Finally, various numerical results are presented for edge-effect problems of several cross-ply, symmetric, and antisymmetric angle-ply laminates subjected to uniform hygrothermal loads. All results indicate high stress gradients of interlaminar normal and shear stresses near the edges of laminates.     

Nonlinear dynamics of tapping mode atomic force microscopy in the bistable phase

Nonlinear dynamics of amplitude modulation atomic force microscopy (AFM) is studied employing a reduced-order model based on a differential quadrature method (DQM). The AFM microcantilever is assumed to be operating in the dynamic contact or tapping mode while the microcantilever tip being initially located in the bistable region. We have found that the DQM is capable of precise prediction of the static bifurcation diagram and natural frequencies of the microcantilever. We have used the DQM to discretize the partial-differential equation governing the microcantilever motion and a finite difference method (FDM) to calculate limit-cycle responses of the AFM tip. It is shown that a combination of the DQM and FDM applied, respectively, to discretize the spatial and temporal derivatives provides an efficient, accurate procedure to address the complicated dynamic behavior exhibited by the AFM probe. The procedure was, therefore, utilized to study the response of the microcantilever to a base harmonic excitation through several numerical examples. We found that the dynamics of the AFM probe in the bistable region is totally different from those in the monostable region.     

The use of combined synchrotron radiation micro FT-IR and XRD for the characterization of Romanesque wall paintings

The high analytical sensitivity and high spatial resolution of synchrotron radiation-based techniques, in particular SR-XRD and SR-FT-IR, allows the identification of complex micrometric mixtures of compounds that constitute the different layers of ancient paintings. The reliability of the measurements even with an extremely small amount of sampled material is very high, and this is particularly important when analyzing art works. Furthermore, the micro size (10×10μm for FT-IR and 30 to 50 μm squared spot size for XRD) of the beam enables one to obtain detailed compositional profiles from the different chromatic and preparation layers. The sensitivity of the techniques is high enough for the determination of minor and trace compounds, such as reaction and weathering compounds. We report here the identification of pigments in the Romanesque wall paintings found in situ in the church of Saint Eulàlia of Unha place in the Aran valley (central Pyrenees). During the first centuries of the second millennium numerous religious buildings were built in Western Europe in the Romanesque style. In particular, a great number of churches were built in the Pyrenees, most of which were decorated with wall paintings. Although only a few of these paintings have survived, they represent one of the most important collections of Romanesque art, both for their quantity and quality. A full identification of the pigments, binder, supports, and reaction and weathering compounds has been obtained. The results obtained, in particular aerinite as a pigment, indicate a clear connection between the paintings found in this Occitanian church and the Catalan Romanesque paintings from the south bound of the Pyrenees. PACS 61.10.Nz; 07.85.Qe; 82.80.Gk     

Investigation of a novel serpentine micromixer based on Dean flow and separation vortices

Meccanica - Passive micromixers, due to their relatively high mixing efficiency and simple fabrication, have wide applications in biological, medical, and chemical processes. Serpentine and...