The impact of high order refraction on optical microbubble sizing in multiphase flows

High order refractions have been found to have a great impact on optical particle sizing using phase-Doppler anemometry (PDA) especially when the relative refractive index of the media is less than one. The high order refractions cannot be neglected because of the differences in spatial frequencies and motion directions of each order. A model of phase-size correlation is proposed that considers these high order refractions. By using the conversion factors of the high order refractions, the particle diameter can be determined. The capability of the newly developed method was evaluated by using generalized Lorenz Mie theory (GLMT), which was validated by experiments. The results of the simulation and experiments are compared with those based on the conventional method. An optimization method for accurately sizing air bubbles in water has been suggested.     

Chiral mesoporous silica: chiral construction and imprinting via cooperative self-assembly of amphiphiles and silica precursors

Fabrication of chiral materials and revealing the mechanisms involved in their formation are crucial issues in scientific research. The combination of cooperative self-assembly routes and the chiral templating process favors the formation of inorganic chiral materials with highly ordered mesostructures. This tutorial review highlights the recent research on chiral mesoporous silica (CMS) of hierarchical helical constructions transcribed from organic templates. The rules and mechanisms involved in the synthesis of CMS and related materials, especially the novel expression of chirality and imprinting of helical micellar superstructure by the functional groups immobilized on the mesopore surface, provide us with a deeper insight into the chiral self-assembly process and new strategies for the design and application of chiral materials. This review is addressed to researchers and students interested in chiral chemistry, supramolecular chemistry and mesoporous materials (53 references).     

A multistage pathway for human prion protein aggregation in vitro: from multimeric seeds to β-oligomers and nonfibrillar structures

Aberrant protein aggregation causes numerous neurological diseases including Creutzfeldt-Jakob disease (CJD), but the aggregation mechanisms remain poorly understood. Here, we report AFM results on the formation pathways of β-oligomers and nonfibrillar aggregates from wild-type full-length recombinant human prion protein (WT) and an insertion mutant (10OR) with five additional octapeptide repeats linked to familial CJD. Upon partial denaturing, seeds consisting of 3-4 monomers quickly appeared. Oligomers of ~11-22 monomers then formed through direct interaction of seeds, rather than by subsequent monomer attachment. All larger aggregates formed through association of these β-oligomers. Although both WT and 10OR exhibited identical aggregation mechanisms, the latter oligomerized faster due to lower solubility and, hence, thermodynamic stability. This novel aggregation pathway has implications for prion diseases as well as others caused by protein aggregation.     

A powerful new construction of complex chiral polycycles by an indium(III)-catalyzed cationic cascade

InI(3) and InBr(3) have been found to be effective catalysts for the π activation of C≡C bonds to initiate the conversion of chiral propargylic alcohols or silyl ethers to polycyclic products in excellent yields and with high stereoselectivity. The method has been applied to the synthesis of chiral fused hexacyclic ring systems with the creation of multiple new stereocenters. The power and scope of the method are illustrated by a variety of examples.     

Specific immunoreaction-induced controlled release strategy for sensitive impedance immunoassay of a cancer marker

A simple and facile impedance immunoassay strategy for sensitive detection of alpha-fetoprotein (AFP), as a model cancer marker, was developed by using target-induced release of nanogold particle-labelled anti-AFP antibodies from polyvinylpyrrolidone-coated magnetic carbon nanotubes.     

A covalently-linked microporous organic-inorganic hybrid framework containing polyhedral oligomeric silsesquioxane moieties

By a Yamamoto-type of Ullmann cross-coupling reaction, a well-defined covalently-linked microporous organic-inorganic hybrid framework polyoctaphenylsilsesquioxane (JUC-Z1) was effectively prepared from the nano building block p-iodio-octaphenylsilsesquioxane (I8OPS) with a yield of ca. 100%. The structure of JUC-Z1 was characterized by (13)C CP/MAS NMR and (29)Si MAS NMR experiments. Fourier transform infrared spectroscopy (FTIR) was performed to confirm the presence of functions in the framework. The results showed that inorganic silsesquioxane cubes were linearly covalently-linked by biphenyls, offering a highly cross-coupling framework. The powder X-ray diffraction (PXRD) pattern and transmission electron microscope (TEM) image show that JUC-Z1 is spherical with uniform micropores. N(2) adsorption results suggest that the hybrid framework has a narrow pore size distribution from 11.8 to 20.0 ?, with a BET surface area of 283 m(2)g(-1) and a pore volume of 0.226 cm(3)g(-1). A thermogravimetric (TG) analysis indicates the thermal stability of JUC-Z1 up to 397 °C in air. Moreover, a liquid sorption experiment reveals the favorable sorption of benzene and water.     

Chemical composition and antioxidant activity of the essential oil of endemic Viola tianshanica

The composition and in vitro antioxidant activities of the essential oil and methanol extract of the aerial parts of Viola tianshanica were evaluated in this research. GC-MS analysis of the essential oil resulted in the identification of 15 constituents, representing 89.67% of the oil. The major compounds detected in the essential oil were dibutyl phthalate (15.19%), hexadecanoate methyl (8.65%), n-hexadecanoic acid (3.07%) and 2,3-pentanedione (2.62%). Essential oil and methanol extract were tested for their antioxidant activities using 1,1-diphenyl-2-picryl-hydrazyl free radical scavenging and β-carotene linoleic acid assay. In addition, the total phenol of essential oil, polar subfraction and non-polar subfraction were determined.     

Encapsulation of tetrathiafulvalene inside a dimeric molecular capsule

Tetrathiafulvalene (TTF) is trapped inside a dimeric capsule formed by two octaacid, deep-cavity cavitands in aqueous solution. While the first one-electron oxidation of TTF is strongly hindered by encapsulation, the capsular assembly is eventually destabilized upon oxidation of the guest.     

Direct C-N coupling of imidazoles and benzylic compounds via iron-catalyzed oxidative activation of C-H bonds

Iron-catalyzed direct C-N bond formation between imidazoles and benzylic hydrocarbons is described. The reaction utilizes an inexpensive iron catalyst-oxidant system that is suitable for the coupling of a range of benzylic C-H bonds with various imidazoles.