Formation of solvated ions in the atmospheric interface of an electrospray ionization triple-quadrupole mass spectrometer

A simple method capable of generating and investigating various solvent clusters and solvated ions was developed. The technique opens a door to studying these complexes on commercially available instruments. Formation of the desired solvated ion in the gas phase was achieved by introducing the appropriate volatile solvent vapour into the curtain gas stream. Capabilities of the technique are illustrated by generating alkali, alkaline earth and transition metal cations solvated by various volatile compounds such as water, methanol and acetonitrile. Depending on the ligands and on the experimental conditions, clusters of 2-100 molecules may be observed. Isotope labelling suggests that these are formed by a re-solvation process in the curtain gas region.     

Organically modified Pd-silica catalysts applied in Heck coupling

Pd-silica catalysts prepared by depositing Pd onto silica precursors modified by surface methyl or phenyl groups through the reduction of Pd2+ ions with surface Si-H functions exhibit high activity and selectivity in Heck coupling.     

Remarkable 1,6-acyclic diastereoselection in the coupling of a novel butadienyl di-indium compound with aldehydes

The reaction between a novel butadienyl di-indium reagent and aldehydes showed remarkable 1,6-diastereoselectivity to give acetylenic diol products as a single diastereomer. A bicyclic transition state formed through intramolecular chelation control was proposed that might account for the high 1,6-diastereoselection result.     

Positivity and Negativity of Solutions to a Schrödinger Equation in ℝ N

Weak L ² -solutions u of the Schrödinger equation, –u + q(x) u – u = f(x) in L ² , are represented by a Fourier series using spherical harmonics in order to prove the following strong maximum and anti-maximum principles in (N 2): Let ₁ denote the positive eigenfunction associated with the principal eigenvalue ₁ of the Schrödinger operator . Assume that the potential q(x) is radially symmetric and grows fast enough near infinity, and f is a `sufficiently smooth' perturbation of a radially symmetric function, f 0 and 0 f / C const a.e. in . Then u is ₁-positive for - < < ₁ (i.e., u c ₁ with c const > 0) and ₁-negative for ₁ < < ₁ + (i.e., u –c₁ with c const > 0), where > 0 is a number depending on f. The constant c > 0 depends on both and f.     

Properties of superfine superconducting filaments embedded in normal matrix

The size-, surface- and proximity-effects are combined for calculating the critical temperature and some unusual electromagnetic properties of superfine superconducting NbTi filaments (i.e. with a diameterd _s < 0·1 μm) in the neighbourhood of normal metal (Cu). It is shown that the existence of the one-dimensional flux line lattice is responsible for the extremely large values of the critical current densities in low magnetic fields (B < 0·2B _c2,B _c2 — the upper critical magnetic field), for the maximum of the volume pinning force at low magnetic fields (B _m ≈ 0·1B _c2, comparing withB _m≈ 0·5B _c2 in usual macroscopic multifilamentary NbTi superconductors), as well as for the peculiar minimum of the magnetization after reversing the magnetic field direction. The possible role of the frozen-in flux lines in creating flux lines of opposite direction is sketched. It is proposed that for practical purposes the superconducting filaments should be coated with electrically insulating material (e.g. cupro-nickel or dielectric) to destroy the electro-magnetic coupling between the filaments and to ensure low ac losses in the composite.     

Synthesis and chromatographic study of methyl-2,3-O-isopropylidene-5-dimethyl-arsinoyl-β-d-ribofuranoside and methyl-2,3-O-isopropylidene-5-deoxy-5-dimethyl-thioarsinoyl-β-d-ribofuranoside

The synthesis of two riboside-containing arsenic compounds, methyl-2,3-O-isopropylidene-5-dimethyl-arsinoyl-β-d-ribofuranoside and methyl-2,3-O-isopropylidene-5-deoxy-5-dimethyl-thioarsinoyl-β-d- ribofuranoside is presented in this paper. Intermediates and final products of the synthesis were examined by gas chromatography and thin layer chromatography. The purity of the products was assessed by NMR spectroscopy. Trimethylsilylation was used to volatilise sugar compounds and thus use of the costly HPLC–MS technique was avoided. The results affirmed the presence of tautomers in case of arsenosugars.