Homogeneous almost disjoint families

An almost disjoint family is constructed which is isomorphic to any almost disjoint family which can be constructed from it by taking subsets and finite unions. This is applied to the construction of a Boolean algebra with related properties.Presented by R. McKenzie.Partially supported by Israel-US Binational Research Fund.Partially supported by NSERC.     

The number of translates of a closed nowhere dense set required to cover a Polish group

For a Polish group let be the minimal number of translates of a fixed closed nowhere dense subset of required to cover . For many locally compact this cardinal is known to be consistently larger than which is the smallest cardinality of a covering of the real line by meagre sets. It is shown that for several non-locally compact groups . For example the equality holds for the group of permutations of the integers, the additive group of a separable Banach space with an unconditional basis and the group of homeomorphisms of various compact spaces.     

Trees and continuous mappings into the real line

Trees of height ω₁ are characterized in terms of continuous mappings to the real line. In particular Souslin trees are characterized as those uncountable trees with no uncountable continuous image in the real line. Trees which can not be continuously embeded in the real line are also characterized.     

Selenium and sulfur trichalcogenides from the chalcogenide exchange reaction

Various selenium- and sulfur-containing volatiles have been detected and characterized as products of chalcogen exchange reactions. The formation of all possible selenium- and sulfur-containing trichalcogenide isomers (-SeSS-, -SSeS-, -SeSeS-, -SeSSe- and -SeSeSe-) was observed at room temperature in the solutions containing diselenide and trisulfide. Because of the low activation barrier of the selenium exchange reaction, these species are expected also to form in biological systems in the presence of diselenides and higher sulfides. Methyl and ethyl derivatives of these species were characterized using gas chromatography coupled to time-of-flight mass spectrometry with electron impact, chemical, and field ionization. Rearrangements of triselenides lead also to the formation of isomeric branched-structure triselenides, selanadiselenides. Because of the very similar structural properties, the behavior of these novel species was studied under various ionization modes (EI+, CI+, EI-, and CI-).     

Assessing MS-based quantitation strategies for low-level impurities in peptide reference materials: application to angiotensin II

Analytical and Bioanalytical Chemistry - Identification and quantitation of related impurities is vital in obtaining corrected purity values for peptide certified reference materials. The...     

Comment on the uncertainties in isotope patterns of molecules

Here we outline several misconceptions and caveats in the uncertainty evaluation of isotope patterns of molecules, most notably the failure of the traditional first-order error propagation models in certain situations. We also demonstrate that many of the questions regarding the uncertainty evaluation of molecular isotope patterns have direct analytical solutions that do not require elaborate computational approaches.     

Alkylation of Aryl and Hetaryl Ketoximes with Alkyl Iodides Prepared In Situ from Alkyl Chlorides Under Phase Transfer Catalysis Conditions

Two simple one-pot phase transfer catalytic methods for the preparation of ketoxime O-ethers from the corresponding ketoximes and alkyl iodides prepared in situ from alkyl chlorides were developed. The corresponding aryl and hetaryl ketoxime O-ethers were obtained in 15–83% yields.