Hexagonal Si−Ge Class of Semiconducting Alloys Prepared by Using Pressure and Temperature

Multi-anvil and laser-heated diamond anvil methods have been used to subject Ge and Si mixtures to pressures and temperatures of between 12 and 17 GPa and 1500–1800 K, respectively. Synchrotron angle dispersive X-ray diffraction, precession electron diffraction and chemical analysis using electron microscopy, reveal recovery at ambient pressure of hexagonal Ge−Si solid solutions (P6₃/mmc). Taken together, the multi-anvil and diamond anvil results reveal that hexagonal solid solutions can be prepared for all Ge−Si compositions. This hexagonal class of solid solutions constitutes a significant expansion of the bulk Ge−Si solid solution family, and is of interest for optoelectronic applications.     

A simple,efficient, regioselective and one-pot preparation of N-hydroxy- and N–O-protected hydroxyindoles via cycloaddition of nitrosoarenes with alkynes. Synthetic scope,applications and novel by-products

The thermal reaction between nitrosoarenes and alkynes under alkylating conditions produces N-alkoxyindoles as the major products in moderate to good yields and excellent regioselectivity. Various electrophiles are used affording different N–O-protected hydroxyindoles in a multi-component fashion. Privileged acetylenic substrates used in reactions with substituted nitrosoarenes are arylalkynes or propiolates. Potentially bioactive compounds and other classes of highly functionalizable indole products were prepared. Reactions between o-carbomethoxy-nitrosoarenes and arylacetylenes provided tricyclic compounds containing an acylaziridine indoline skeleton.     

Tuning the mesogenic properties of 5-alkoxy-2-(4-alkoxyphenyl)pyrimidine liquid crystals: the effect of a phenoxy end-group in two sterically equivalent series

Two sterically equivalent series of phenoxy-terminated 5-alkoxy-2-(4-alkoxyphenyl)pyrimidine liquid crystals were synthesised, and their mesogenic properties were characterised by polarised optical microscopy and differential scanning calorimetry (DSC). The phenoxy end-group causes a significant increase in melting point and inhibits – at least partially – the mesomorphism of these materials relative to the parent isomers; in most cases, the broad enantiotropic SmC phase formed by the parent isomers is suppressed by the addition of the phenoxy end-group. However, detailed analyses by small-angle X-ray scattering and monodomain 2D X-ray scattering suggest that these compounds form a SmA phase with a partially intercalated bilayer structure in which the phenoxy end-groups are nanosegregated. Such an intercalated bilayer structure might enable the tuning of smectogenic properties by appropriate substitution of the phenoxy end-groups.     

Screening of Tea (Camellia sinensis) for Trait-Associated Molecular Markers

This study was done to identify random amplified polymorphic DNA (RAPD) markers that may associate with seven important traits in tea. Sixty RAPD primers were first screened using 18 cultivars under each of the 7 traits, followed by confirmatory screening of 20 promising primers with 32 tea cultivars. Six RAPD primers generated a total of nine specific bands that associated with six desired traits: black tea quality and tolerance to drought, high temperature, low temperature, Phomopsis theae, and high yield. These markers would allow early identification of plant material with the desired traits that can be advanced to the next stage of selection and enhance targeted choice of breeding stocks with the desirable traits. The nine RAPD markers identified in this study could improve precision and efficiency in tea breeding and selection and are an important contribution towards the establishment of marker-assisted selection in tea breeding programmes.     

Fluorescence and absorbance spectroscopy of the uranyl ion in nitric acid for process monitoring applications

Near real time process monitoring of the uranium content in an aqueous fuel recycling plant is a desired component of an advanced safeguards suite; Ultraviolet–Visible spectroscopy and Time Resolved Laser induced Fluorescence Spectroscopy can contribute to this technology gap. This work presents the observation of the spectroscopic parameters (molar absorptivities, fluorescent response) of the uranyl ion across the range of conditions expected in reprocessing chemistry. From this data, a monitor using the ratio of the absorbance of the uranyl ion at 403 and 426 nm has been developed. This technique can determine the nitrate solution concentration and can be coupled with a condition appropriate molar absorptivity to determine the uranyl concentration. This method provides a reliable technique for online, real time process monitoring of the uranyl and nitrate concentration under a wide range of solution compositions.     

Synthesis of N-Alkoxy Amidine Salts Via Addition of (N-Alkyl-N-Alkoxyammine)Dimethylaluminum Chlorides to Nitriles

Abstract: The addition of (N-alkyl-N-alkoxyammine)dimethylaluminum chlorides to nitriles provides a convenient route to little investigated N-alkoxy amidine hydrochlorides. A survey of the scope of this reaction is presented.     

Mechanochemical Formation,Solution Rearrangements,and Catalytic Behavior of a Polymorphic Ca/K Allyl Complex

Without solvents present, the often far-from-equilibrium environment in a mechanochemically driven synthesis can generate high-energy, non-stoichiometric products not observed from the same ratio of reagents used in solution. Ball milling 2 equiv. K[A’] (A’=[1,3-(SiMe₃)₂C₃H₃]⁻) with CaI₂ yields a non-stoichiometric calciate, K[CaA’₃], which initially forms a structure ( 1 ) likely containing a mixture of pi- and sigma-bound allyl ligands. Dissolved in arenes, the compound rearranges over the course of several days to a structure ( 2 ) with only η³-bound allyl ligands, and that can be crystallized as a coordination polymer. If dissolved in alkanes, however, the rearrangement of 1 to 2 occurs within minutes. The structures of 1 and 2 have been modeled with DFT calculations, and 2 initiates the anionic polymerization of methyl methacrylate and isoprene; for the latter, under the mildest conditions yet reported for a heavy Group 2 species (one-atm pressure and room temperature).