Subregular Representations of {\mathfrak{s}}{\mathfrak{l}}_n and Simple Singularities of Type A n−1

Alexander Premet has stated the following problem: what is a relation between subregular nilpotent representations of a classical semisimple restricted Lie algebra and non-commutative deformations of the corresponding singularities? We solve this problem for type A.     

Enolization of acetone in superheated water detected via radical formation

Muoniated free radicals have been detected in muon-irradiated aqueous solutions of acetone at high temperatures and pressures. At temperatures below 250 degrees C, the radical product is consistent with muonium addition to the keto form of acetone. However, at higher temperatures, a different radical was detected, which is attributed to muonium addition to the enol form. Muon hyperfine coupling constants have been determined for both radicals over a wide range of temperatures, significantly extending the range of conditions under which these radicals and the keto-enol equilibrium have been studied.     

Enhanced chromatographic resolution of amine enantiomers as carbobenzyloxy derivatives in high-performance liquid chromatography and supercritical fluid chromatography

The carbobenzyloxy (cbz) protecting group is evaluated for it's potential to enhance the resolution of chiral amine enantiomers using high-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC). A series of cbz derivatives of commercially available racemates was prepared and analyzed by enantioselective chromatography using a variety of mobile phases and polysaccharide and Pirkle-type chiral stationary phases (CSPs). The cbz-derivatized product consistently demonstrated enhanced chiral resolution under HPLC and SFC conditions. Improved selectivity and resolution combined with an automated preparative HPLC or SFC system can lead to the rapid generation of highly purified enantiomers of desirable starting materials, intermediates or final products.     

Reactions of N-heterocyclic carbenes (NHCs) with one-electron oxidants: possible formation of a carbene cation radical

One-electron oxidation of N-heterocyclic carbenes (NHCs) has been carried out using oxidising agents such as tetracyanoethylene (TCNE) and ferrocenium [Cp(2)Fe](+); the formation of carbene radical cations is postulated.     

Synthesis of the ABC ring system of manzamine A

A synthesis of the core ABC ring system of the manzamine alkaloids is described, starting from arecoline. The key steps involve a Claisen rearrangement to set up a 4-substituted-3-methylenepiperidine and a stereoselective azomethine ylide dipolar cycloaddition reaction. Condensation of the aldehyde 6 and sarcosine ethyl ester hydrochloride salt gives an intermediate azomethine ylide, which undergoes an intramolecular cycloaddition reaction to set up two new rings and three new chiral centers stereoselectively. The aldehyde 6 was not a suitable substrate for related azomethine ylide cycloaddition reactions with other amines. However, the related dimethyl acetal 26 could be condensed with a variety of amines to give the desired tricyclic products. The cycloaddition reaction with N-methyl or N-allyl glycine ethyl ester gave almost exclusively the exo adduct, whereas cycloaddition with glycine ethyl ester gave the endo adduct.     

Digests or extracts?—Some interesting but conflicting results for three widely differing polluted sediment samples

Three sets of samples have been investigated in some detail. One set is from a river polluted by mine workings, containing substantial levels of Fe, Mn,Cu, Zn and Ni with traces of many other metals. The second set consists of typical estuarine sediments contaminated from a wide range of industrial sources, and the third set consists of oily drilling cuttings from the sea bottom in the vicinity of a North Sea oil production platform.These samples have been subjected to treatment 1) with EDTA at two different pH's (extracts) 2) with HNO₃/H₂O₂ 3) with HNO₃/HCl and 4) with HNO₃/HCl/HF (digests). EDTA recoveries, compared toaqua regia digests, are often very reproducible, not dependent on pH, and usually significantly low. Nitric/peroxide andaqua regia digests often give very close results suggesting that these are meaningful values indicating the maximum levels of polluting metals in the sediments. However, the triple acid digest with HF does sometimes give higher values (and reasonable agreement for CRM's such as MESS-1) but with poorer reproducibility.     

Synthesis of pyranosyl amidoximes by addition of amines to pyranosyl nitrile oxides

Addition of amines to pyranosyl nitrile oxides, generated by base-induced dehydrochlorination of the corresponding hydroximoyl chloride, affords pyranosyl N-alkyl/aryl-formamide oximes (41-90%). Reaction with amino acid esters yields the corresponding amidoximes and/or 3-pyranosyl-1,2,4-oxadiazin-6-ones. The structure of N-phenyl-C-(2,3,4-tri-O-acetyl-β-D-xylopyranosyl)formamide oxime was established by X-ray crystallography.     

A computational study of the reactions of a beta-diketiminatoaluminium(I) complex with the hydrogen atom and the electron

A computational study has been performed to examine the reactions of a model beta-diketiminatoaluminium (I) complex with the hydrogen atom and with the electron. It was found that the hydrogen atom adds to the metal centre exothermically (DeltaH(rxn)=-202 kJ mol(-1)), and the spin density in the resulting radical resides entirely on the beta-diketiminato ligand. The spin density of the corresponding radical anion is very similar to the H-adduct.     

Lamination method for the study of interfaces in polymeric thin film transistors

A method for the fabrication of polymeric thin-film transistors (TFTs) by lamination is described. Poly(dimethylsiloxane) stamps were used to delaminate thin films of semiconducting polymers from silicon wafers coated with a self-assembled monolayer (SAM) formed from octyltrichlorosilane. These supported films were laminated onto electrode structures to form coplanar TFTs. The fabrication process was used to make TFTs with poly(3-hexylthiophene), P3HT, and poly[5,5'-bis(3-dodecyl-2-thienyl)-2,2'-bithiophene], PQT-12. TFTs, where these polymers were laminated onto gate dielectrics coated with SAMs from octyltrichlorosilane, had effective field-effect mobilities of 0.03 and 0.005 cm2/(V s), respectively. TFTs where PQT-12 was laminated onto gate dielectrics that were not coated with a SAM also had mobility of 0.03 cm2/(V s). In contrast, TFTs fabricated by spin-coating PQT-12 onto the same structure had mobilities ranging from 10-3 to 10-4 cm2/(V s). These results suggest that the lower mobilities of polymer TFTs made with hydrophilic gate dielectrics are caused by molecular ordering in the semiconducting film rather than electronic effects of dipolar groups at the interface.