Rank-one completions of partial matrices and completely rank-nonincreasing linear functionals

We obtain necessary and sufficient conditions for the existence and the uniqueness of rank-one completions of a partial matrix, and we verify a conjecture of Hadwin and Larson concerning the nature of completely rank-nonincreasing linear functionals defined on pattern subspaces.

     

Investigation of the degradation of commercial polyoxymethylene copolymer in water service applications

An investigation has been carried out on the influence of degradation on various properties of commercial polyoxymethylene (POM) copolymer fittings in chlorinated cold water service lines. Scanning electron microscope (SEM) was used to document interior bulk morphological changes and typical defects. The various types of irregular cracks and pits were observed at the innerface of the samples. DSC and intrinsic viscosity determination were carried out for investigation of crystallinity and molecular weight changes. It was seen that the crystallinity of the POM increases at a much higher rate at the inner surface layers than the outer layer in the used samples. The FT-IR spectra of the new and used samples indicate the extent of degradation of the samples.     

Minimal regular polygons serving as universal covers in R 2

A universal cover is a set K with the property that each set of unit diameter is a subset of a congruent copy of K. It is shown that the smallest regular n-gon, for fixed n 4, which serves as an universal cover in R ² is the smallest regular n-gon covering a Reuleaux triangle of unit width.     

Depolymerization and chemical modification of lignite coal byPseudomonas cepacia strain DLC-07

Applied Biochemistry and Biotechnology - Coal metabolizingPseudomonas cepacia DLC-07 was isolated from soil and shown to use soluble lignite coal as a carbon/energy source.Pseudomonas modified coal...     

Synthesis, structure, and alpha-elimination chemistry of hafnocene triarylstannyl complexes

New hafnocene triarylstannyl complexes were prepared and were shown to undergo clean thermal decompositions via alpha-aryl-elimination to produce the corresponding stannylene and a hafnocene aryl complex. The rate of the decomposition is highly dependent on the nature of the ancillary ligand, with the stabilities of the CpCp*Hf(SnPh(3))X compounds following the order X = NMe(2) > Np (alpha-agostic) > OMe > Cl > Me. Mechanistic information suggests that alpha-aryl-elimination may be viewed as a concerted process involving nucleophilic attack of the migrating aryl group onto the electrophilic metal center.     

Synthesis and characterization of scandium silyl complexes of the type Cp*2ScSiHRR'. sigma-Bond metathesis reactions and catalytic dehydrogenative silation of hydrocarbons

The scandium dihydrosilyl complexes Cp*(2)ScSiH(2)R (R = Mes (4), Trip (5), SiPh(3) (6), Si(SiMe(3))(3) (7); Mes = 2,4,6-Me(3)C(6)H(2), Trip = 2,4,6-(i)()Pr(3)C(6)H(2)) and Cp*(2)ScSiH(SiMe(3))(2) (8) were synthesized by addition of the appropriate hydrosilane to Cp*(2)ScMe (1). Studies of these complexes in the context of hydrocarbon activation led to discovery of catalytic processes for the dehydrogenative silation of hydrocarbons (including methane, isobutene and cyclopropane) with Ph(2)SiH(2) via sigma-bond metathesis.     

Neopentylallylsodium

Neopentylallylsodium (NpANa) has been prepared by the reaction of neopentylallyllithium with an equivalent amount of sodium 2,2-dimethyl-1-butoxide in hydrocarbon solvent. NpANa is stable in diethyl ether and THF solvents for extended periods of time, and proton NMR and UV data are reported for NpANa in THF at various temperatures. A more substantial degree of ionic delocalization is indicated for NpANa as compared to NpALi and apparently is greater for the trans isomer of NpANa. UV absorption maxima for NpANa and NpALi are explained in terms of cis/trans ratios rather than in terms of ion pairing.