Experimental and modeling study of C5H10O2 ethyl and methyl esters

Due to the world's over-reliance on fossil fuels there has been a developing interest in the production of renewable biofuels such as methyl and ethyl esters derived from vegetable oils and animal fats. To increase our understanding of the combustion chemistry of esters, the oxidation of methyl butanoate and ethyl propanoate, both with a molecular formula of C5H10O2, have been studied in a series of high-temperature shock tube experiments. Ignition delay times for a series of mixtures, of varying fuel/oxygen equivalence ratios (phi = 0.25-1.5), were measured behind reflected shock waves over the temperature range 1100-1670 K, and at pressures of 1.0, and 4.0 atm. It was found that ethyl propanoate was consistently faster to ignite than methyl butanoate, particularly at lower temperatures. Detailed chemical kinetic mechanisms have been assembled and used to simulate these experiments with good agreement observed. Rate of production analyses using the detailed mechanisms shows that the faster reactivity of ethyl propanoate can be explained by a six-centered unimolecular decomposition reaction with a relatively low activation energy barrier producing propanoic acid and ethylene. The elimination reaction itself is not responsible for the increased reactivity; it is the faster reactivity of the two products, propanoic acid and ethylene that leads to this behavior.     

DNA-protein interaction analysis using polyacrylamide gel electrophoresis and a simple and sensitive UV crosslinking procedure.

A simple and reproducible technique for DNA-protein interaction analysis is described using UV crosslinking and polyacrylamide gel electrophoresis, leading to visualization of the complexes as distinct and strong signals. It avoids incorporation of bromodeoxyuridine (BrdU) into DNA and requires no special equipment. It was successfully applied to an oligonucleotide sequence from within the first intron of the mouse myb proto-oncogene and nuclear extracts from a myb-expressing cell line.     

Stability and microtox response of butenyltin compounds

Tributenyltin bromides containing double bonds at carbon atoms C-1, C-2 or C-3 were synthesized from symmetrical tetrabutenyltins. Although all three tetrabutenyltin compounds were stable, only the tributenyltin bromides with double bonds at C-1 and C-3 were sufficiently stable for further studies. In aqueous sodium bromide (NaBr) solution containing 1% acetone, tri-1-butenyltin bromide was more stable in sunlight than tri-3-butenyltin bromide, yet neither compound was as stable as tributyltin bromide. Stability in seawater, in the absence of ultraviolet (UV) light, was less for both tri-1-butenyltin bromide and tri-3-butenyltin bromide than for tributyltin bromide. The relative toxicities of the tributenyltin bromides were determined using a bioluminescent bacteria assay. The concentrations of tributenyltin bromides necessary to produce a toxic response were three to six times greater than for tributyltin bromide.     

Families of type III0 ergodic transformations in distinct orbit equivalent classes

A new isomorphism invariant of certain measure preserving flows, using sequences of integers, is introduced. Using this invariant, we are able to construct large families of type III₀ systems which are not orbit equivalent. In particular we construct an uncountable family of nonsingular ergodic transformations, each having an associated flow that is approximately transitive (and therefore of zero entropy), with the property that the transformations are pairwise not orbit equivalent.     

The Rokhlin lemma for homeomorphisms of a Cantor set

For a Cantor set , let denote the group of all homeomorphisms of . The main result of this note is the following theorem. Let be an aperiodic homeomorphism, let be Borel probability measures on , and let 0$"> and . Then there exists a clopen set such that the sets are disjoint and 1 - \varepsilon, i= 1,\ldots,k$">. Several corollaries of this result are given. In particular, it is proved that for any aperiodic the set of all homeomorphisms conjugate to is dense in the set of aperiodic homeomorphisms.

     

Ethyltetramethylcyclopentadienyl complexes of cobalt,rhodium, iridium and ruthenium

Summary The syntheses of the ethyltetramethylcyclopentadienyl complexes Ru(⁵-C₅Me₄Et)(CO)₂Cl, CO( ⁵-C₅Me₄Et)(CO)₂, and [M( ⁵-C₅Me₄Et)Cl₂]₂ (M = Rh or Ir) are described; the ruthenium complex reacts with triphenylarsine to give Ru( ⁵-C₅Me₄Et)(AsPh₃)(CO)Cl.¹H and¹³C n.m.r. spectra, i.r. spectra and the physical properties of the compounds are discussed and contrasted with the known C₅H₅ and C₅Me₅ analogues.     

Gold electrodes wired for coupling with the deeply buried active site of Arthrobacter globiformis amine oxidase

Diethylaniline-terminated oligo(phenyl-ethynyl)-thiol (DEA-OPE-SH) wires on Au-bead electrodes facilitate electron tunneling to and from the deeply buried topaquinone (TPQ) cofactor in Arthrobacter globiformis amine oxidase (AGAO). Reversible cyclic voltammograms were observed when AGAO was adsorbed onto this DEA-OPE-SAu surface: the 2e-/2H+ reduction potential is -140 mV versus SCE.