Precipitation of (Si2-xAlx)Hf in an Al-Si-Mg-Hf Alloy.

The morphology, composition, and structure of precipitates in an Al-Si-Mg-Hf alloy after heat treatment at 560°C for 20 h were studied by means of C s -corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), energy dispersive X-ray spectrometry (EDS), high-resolution transmission electron microscopy (HRTEM), and first-principle calculations. Precipitates with three kinds of morphologies were observed. The rectangular and square precipitates were predominantly (Si2-x Al x )Hf phases, while the nanobelt-like precipitate is the Si2Hf phase. First-principle calculations were used to show that the Si6 and Si8 sites were the most favorable sites for Al incorporation in the orthorhombic Si2Hf phase.

Growth Directions of Precipitates in the Al-Si-Mg-Hf Alloy Using Combined EBSD and FIB 3D-Reconstruction Techniques.

Nanobelt-like precipitates in an Al-Si-Mg-Hf alloy were studied using electron backscattered diffraction (EBSD) and focused ion beam (FIB) scanning electron microscopy techniques. One grain of the Al matrix with a near [111] normal direction was identified by EBSD and the three-dimensional (3D) microstructure of nanobelt-like precipitates in this grain was studied using 3D-FIB. Ten growth directions of the nanobelt-like precipitates in the grain were identified.

An efficient approach to 1,2,3-trisubstituted indole via rhodium catalyzed carbene C(sp(3))-H bond insertion.

A method for convenient synthesis of N-alkyl-2-aryl-indole-3-carbaldehyde has been described. A variety of highly valuable indolyl aldehydes have been prepared through this method. Electron donating groups on both aromatic rings (anilinyl and benzyl) facilitate the formation of the desired products. A benzylic C-H insertion by rhodium carbene is the key step for this transformation.

Study on tribological mechanism for multi-layer porous structure of diatom frustule.

Tribological mechanism of the diatom frustule with multi-layers of pores is studied with the liquid-solid interaction (FSI) method. Based on the reconstructed representative Coscinodiscus sp. frustule with two-layer porous structure, the tribological performances for the diatom frustule at its different pore diameter ratios, pore depth ratios, and velocities are solved through governing equations involved with FSI method. The numerical result shows that the existence of the two-layer porous structure of the diatom helps to reduce the friction between it and ambient water, and to increase its ability to resist the ambient water pressure. The two-layer porous structure effectively improve the tribological performances for the diatom frustule due to the change in the frustule velocity.

One-pot protocol to functionalized benzopyrrolizidine catalyzed successively by Rh2(OAc)4 and Cu(OTf)2: a transition metal-Lewis acid catalysis relay.

4-N-allylarylpropylamino-1-sulfonyl triazoles are converted to structurally unique benzopyrrolizidinyl sulfonamides in a one-pot operation. Intramolecular capture of rhodium carbene with arylamino nitrogen gives rise to the formation of an ammonium ylide immediate. A [2,3]- or [1,2]-rearrangement occurs to give a 2-allylpyrrolidinyl-2-carbimine intermediate which undergoes Cu(OTf)2 catalyzed aza-Friedel-Crafts cyclization to finish a highly functionalized tricyclic system decorated with a synthetically difficult quaternary carbon center, a sulfonamide group, and an allyl segment.

Copper-catalyzed cyclization/aza-Claisen rearrangement cascade initiated by ketenimine formation: an efficient stereocontrolled synthesis of α-allyl cyclic amidines.

An efficient and convenient synthesis of α-allyl cyclic amidines has been achieved by applying a novel cascade reaction. Copper(I)-mediated in situ N-sulfonyl ketenimine formation from the reaction of a terminal alkyne with sulfonyl azide is followed by an intramolecular nucleophilic attack on the central carbon atom by an allylic tertiary amine, and then an aza-Claisen rearrangement takes place through a chair transition state to furnish the titled amidines with complete stereocontrol.

Stereoselective halocyclization of alkenes with N-acyl hemiaminal nucleophiles.

Halocyclization of alkenes was realized using N-acylhemiaminal nucleophiles. High diastereoselectivity could be achieved for the formation of three stereogenic centers in this halogen-mediated cyclization reaction. We also demonstrated that enantioselective bromocyclization of alkenes using N-acylhemiaminal nucleophiles was possible.

Simultaneous removal of thiolated membrane proteins resulting in nanostructured lipid layers.

Self-organization of membrane-embedded peptides and proteins causes the formation of lipid mesostructures in the membranes. One example is purple membranes (PM), which consist of lipids and bacteriorhodopsin (BR) as the only protein component. The BRs form a hexagonal crystalline lattice. A complementary structure is formed by the lipids. Employing BR and PM as an example, we report a method where major parts of the mesoscopic self-assembled protein structures can be extracted from the lipid bilayer membrane. A complementary lipid nanostructure remains on the substrate. To remove such a large number of thiolated proteins simultaneously by applying a mechanical force, they are first reacted at physiological conditions with gold nanoparticles, and then a thin gold film is sputtered onto them that fuses with the gold nanoparticles forming a uniform layer, which finally can be lifted off. In this step, all of the previously gold-labeled proteins are pulled out of the membrane simultaneously. A stable lipid nanostructure is obtained on the mica substrate. Its stability is due to either binding of the lipids to the substrate through ionic bonds or to enough residual proteins to stabilize the lipid nanostructure against reorganization. This method may be applied easily and efficiently wherever thiolated proteins or peptides are employed as self-assembling and structure-inducing units in lipid membranes.

[Effects of different mulches on rhizosphere temperature, growth, and physiological properties of fluecured tobacco].

With greenhouse plastic film, rice straw plus greenhouse plastic film, soil-mulching plastic film, rice straw, rice straw plus sun-shading net, and sun-shading net as test mulches, this paper studied their effects on the rhizosphere temperature, growth, and physiological properties of flue-cured tobacco. The results showed that after mulching for 22 days, the accumulative rhizosphere temperature at the depth of 5 cm was the highest (424.75 degrees C) for greenhouse plastic film and the lowest (378.75 degrees C) for rice straw plus sun-shading net, while that at the depth of 15 cm was the highest (396.75 degrees C) for greenhouse plastic film and the lowest (368.31 degrees C) for sun-shading net. With the increase of accumulative rhizosphere temperature, the dry weight of above- and underground parts, photosynthesis, and root vigor of flue-cured tobacco tended to increase, and at the 10th day after mulches removal, root biomass had the largest increment in the treatment of soil-mulching plastic film and the smallest increment in the treatment of rice straw plus sun-shading net.

Analyses of neurobehavioral screening data: benchmark dose estimation.

Zhu et al. (Zhu, Y., Wessel, M., Liu, T., Moser, V.C., 2005. Analyses of neurobehavioral screening data: dose-time-response modeling of continuous outcomes. Regul. Toxicol. Pharmacol. 41, 240-255) have recently applied dose-time-response models to longitudinal or time-course neurotoxicity data, and have illustrated the modeling process using continuous data from a functional observational battery (FOB). Following the work of these authors, the purpose of this paper is to show that the benchmark dose (BMD) method for single time point dose-response data can be generalized and applied to longitudinal data such as those generated in neurotoxicity studies. We propose a statistical procedure called bootstrap method for computing the lower confidence limits for the BMD. We demonstrate the method using three previously published FOB datasets of triethyltin (Moser, V.C., Becking, G.C., Cuomo, V., Frantik, E., Kulig, B., MacPhail, R.C., Tilson, H.A., Winneke, G., Brightwell, W.S., DeSalvia, M.A., Gill, M.W., Haggerty, G.C., Hornychova, M., Lammers, J., Larsson, J., McDaniel, K.L., Nelson, B.K., Ostergaard, G., 1997a. The IPCS study on neurobehavioral screening methods: results of chemical testing. Neurotoxicology 18, 969-1056.) and the models of Zhu et al. (Zhu, Y., Wessel, M., Liu, T., Moser, V.C., 2005. Analyses of neurobehavioral screening data: dose-time-response modeling of continuous outcomes. Regul. Toxicol. Pharmacol. 41, 240-255).

Hydrolytic and enzymatic degradation of liquid-crystalline aromatic/aliphatic copolyesters.

Aromatic/aliphatic copolyesters containing hydrophilic moieties in the main chain or side chain were synthesized by bulk polycondensation of aromatic monomers without or with solubilizing substituents and aliphatic monomers. Hydrolytic and enzymatic degradation studies were carried out in vitro at 37 degrees C in pH 7.4 phosphate buffer and in Tris-HCl buffer containing proteinase K. The results indicate that liquid-crystalline aromatic/aliphatic copolyesters are degradable hydrolytically as well as enzymatically. The change in composition and morphology of the polyester films were monitored by nuclear magnetic resonance and scanning electron microscopy. The results suggested that aromatic species and aliphatic moieties could be released into aqueous solution during hydrolytic degradation of aromatic/aliphatic copolyesters with ethyleneoxy groups on the side chain. Modifying aromatic species with hydrophilic groups in aromatic/aliphatic copolyesters was an efficient method to improve degradability and biocompatibility due to improved solubility of degradation products in aqueous solution. Mechanical tests indicated that the copolyesters exhibited good mechanical properties prior to degradation, which can be of relevance for bone tissue engineering.

Growth and vibrational spectra of doped KMgF3 single crystal.

The different ions doped KMgF(3) single crystals are prepared by the vertical Bridgman method. The near-infrared absorption spectra for different parts of all as-growth crystals indicate that there is the best transparency in middle part. The correlation between the vibronic frequencies of Eu(2+) and the site displacement of Cu(+) co-doped ions is firstly studied, which indicates that Cu(+) ions replace the site of the Mg(2+) ions. The co-doped Eu(2+) counteracts the charge misfit causing by the replacement of Mg(2+) with Cu(+). The overlapping of the emission spectra of the Eu(2+) and the excitation spectra of the Cu(+) results in the energy transfer from Eu(2+) to Cu(+).