Advances in positron and electron scattering*

The topical issue on Advances in Positron and Electron Scattering” combines contributionsfrom POSMOL 2015 together with others devoted to celebrate the unprecedented scientificcareers of our loyal colleagues and trusted friends Steve Buckman (Australian NationalUniversity, Australia) and Michael Allan (University of Fribourg, Switzerland) on theoccasion of their retirements. POSMOL 2015, the XVIII International Workshop on Low-EnergyPositron and Positronium Physics and the XIX International Symposium on Electron-MoleculeCollisions and Swarms, was held at Universidade NOVA de Lisboa, Lisboa, Portugal, from17–20 July 2015. The international workshop and symposium allowed to achieve a veryprivileged forum of sharing and developing our scientific expertise on current aspects ofpositron, positronium and antiproton interactions with electrons, atoms, molecules andsolid surfaces, and related topics, as well as electron interactions with molecules inboth gaseous and condensed phases. Particular topics include studies of electroninteractions with biomolecules, electron induced surface chemistry and the study of plasmaprocesses. Recent developments in the study of swarms are also fully addressed.     

Bayesian Analysis of Exafs Data

In this paper we demonstrate the use of Bayesian analysis methods for the analysis of EXAFS data. We will discuss the physical parameters that may be estimated by the method and demonstrate the applicability of the method to Molybdenum coordination compounds.     

Cost-Effective and Large-Scale Synthesis of 16:0 Lysophosphatidic Acid

Abstract

Lysophosphatidic acid (LPA) is a bioactive compound that has gained attention because of its role in neoplastic diseases. Popularity of the compound has necessitated the use of large quantities of the phospholipid for in vivo and in vitro testing, but methods for generating LPA require the use of costly procedures, namely phosphoramidite coupling reagents. Additionally there has been no reported large-scale synthesis of LPA. In the present study we report the cost-effective and large-scale synthesis of 16:0 LPA.     

On the closedness of the linear image of a set with applications to generalized spline functions †

In many problems of approximation theory, especially in the field of spline functions and their generalizations, one seeks a u minimizing ||Tu-f|| for u in some constraint set U; it is usually easy to prove existence of such a u if IT/is closed. We consider hypotheses that will guarantee the closedness of TU, and, more generally, the closedness of the sum of U and a closed linear subspace     

Regioselectivity in the Acid Cleavage of Bicyclo[4.1.0]Heptan-3-Ones

Acid-promoted cyclopropane cleavage reactions have been employed with great success for the generation of angular methyl groups.² Sims has shown that the regioselectivity of such reactions may be influenced by acid strength.^2d We now report a case in which steric factors appear to direct the cleavage pathway.     

Structural studies of metal ligand complexes by ion mobility-mass spectrometry

Collision cross sections (CCS) have been measured for three salen ligands, and their complexes with copper and zinc using travelling-wave ion mobility-mass spectrometry (TWIMS) and drift tube ion mobility-mass spectrometry (DTIMS), allowing a comparative size evaluation of the ligands and complexes. CCS measurements using TWIMS were determined using peptide and TAAH calibration standards. TWIMS measurements gave significantly larger CCS than DTIMS in helium, by 9 % for TAAH standards and 3 % for peptide standards, indicating that the choice of calibration standards is important in ensuring the accuracy of TWIMS-derived CCS measurements. Repeatability data for TWIMS was obtained for inter- and intra-day studies with mean RSDs of 1.1 % and 0.7 %, respectively. The CCS data obtained from IM-MS measurements are compared to CCS values obtained via the projection approximation, the exact hard spheres method and the trajectory method from X-ray coordinates and modelled structures using density functional theory (DFT) based methods.     

Stereoselective Synthesis of Diaminosuberic Acid Via a Chiral Alkynyl Oxazolidine

A novel, stereoselective synthesis of enantiomerically pure, N-protected diaminosuberic acid (6) is presented. The key step in the synthesis is the oxidative dimerization of the chiral alkynyl oxazolidine (2).     

Nitrile Rubber Reactor Operation Troubleshooting with Principal Component Analysis

Principal Component Analysis (PCA) is employed as a tool in order to demonstrate yet another application of the technique, and, most importantly, to show that results from the statistical multivariate technique do make physico-chemical sense. The operation of a typical emulsion copolymerization of acrylonitrile and butadiene (nitrile butadiene rubber, NBR) is used as an example of process troubleshooting. In more general terms, a statistical tool is used to aid process data analysis and process operation (recipe, product property) troubleshooting.

The goal is to produce consistent Mooney Viscosity (MV) among different batches. The observation is that varying induction times lead to Mooney Viscosity inconsistencies. Firstly, we show results from the application of PCA to process data. Secondly, we deal with an even more important (and often ignored) question by examining whether the trends indicated by PCA make process sense.