A Calculation of the Culler-shalen Seminorms Associated to Small Seifert Dehn Fillings

We determine the relationship between the multiplicities ofthe zeros of certain rational functions defined on the SL₂(C)and PSL₂C character varieties of knot exteriors. This leadsto a formula for the Culler–Shalen seminorms associatedto small Seifert Dehn fillings of such manifolds. 2000 MathematicsSubject Classification: 57M05, 57M27, 57R65.     

Novel long chain unsaturated diisocyanate from fatty acid: Synthesis,characterization, and application in bio‐based polyurethane

A novel long chain linear unsaturated terminal diisocyanate, 1,16‐diisocyanatohexadec‐8‐ene (HDEDI) was synthesized from oleic acid via Curtius rearrangement. Its chemical structure was identified by FTIR, ¹H NMR, ¹³C NMR, and HRMS. This diisocyanate was used as a starting material for the preparation of entirely bio‐based polyurethanes (PUs) by reacting it with canola diol and canola polyol, respectively. The physical properties and crystalline structure of the PUs prepared from this diisocyanate were compared to their counterparts prepared from similar fatty acid‐derived diisocyanate, 1,7‐heptamethylene diisocyanate (HPMDI). The HDEDI based PUs demonstrated various different properties compared to those of HPMDI based PUs. For example, HDEDI based PUs exhibited a triclinic crystal form; whereas HPMDI based PUs exhibited a hexagonal crystal lattice. In addition, canola polyol‐HDEDI PU demonstrated a higher tensile strength at break than that of canola polyol‐HPMDI, attributed to the higher degree of hydrogen bonding associated with the former sample. Nevertheless, lower Young's modulus and higher elongation in canola polyol‐HDEDI PU were obtained because of the flexibility of the long chain introduced by the HDEDI diisocyanate. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3302–3310, 2010     

Gas chromatographic technique for determination of Irgafos 168 in polyolefin samples after conversion to the related phenolic compound by saponification

A gas chromatographic technique is reported for the determination of a secondary antioxidant, Irgafos 168, in polymeric samples. Irgafos 168 [tris(2,4-di-tert-butyl phenyl)phosphite] is extracted by dissolution/precipitation, saponified to 2,4-di-tert-butyl phenol by refluxing in the presence of methanolic potassium hydroxide, and determined by gas chromatography-flame ionization detection. The method’s repeatability is good, and the relative standard deviation is 7.5% (between runs) and 15.5% (between days). This method was applied to the determination of Irgafos 168 in commercial polymers, and the obtained results were in relatively good agreement with those obtained by the previously reported spectrophotometric method. Correspondence: Mir Ali Farajzadeh, Department of Chemistry, Faculty of Science, Urmia University, Urmia, Iran     

Extended UNIQUAC model for thermodynamic modeling of CO2 absorption in aqueous alkanolamine solutions

The extended UNIQUAC model [K. Thomsen, P. Rasmussen, Chem. Eng. Sci. 54 (1999) 1787–1802] was applied to the thermodynamic representation of carbon dioxide absorption in aqueous monoethanolamine (MEA), methyldiethanolamine (MDEA) and varied strength mixtures of the two alkanolamines (MEA–MDEA). For these systems, altogether 13 interaction model parameters are adjusted. Out of these parameters, 11 are temperature dependent.     

Compatibility of electron ionization and soft ionization methods in gas chromatography/orthogonal time‐of‐flight mass spectrometry

Orthogonal acceleration time‐of‐flight (oa‐TOF) mass spectrometry (MS) was coupled to gas chromatography (GC) to measure ion yields (ratio of ion counts to number of neutrals entering the ion source) and signal‐to‐noise (S/N) in the electron ionization (EI) mode (hard ionization) as well as in the soft ionization modes of chemical ionization (CI), electron capture negative ion chemical ionization (NICI) and field ionization (FI). Mass accuracies of the EI and FI modes were also investigated. Sixteen structurally diverse volatile organic compounds were chosen for this study. The oa‐TOF mass analyzer is highly suited for FI MS and provided an opportunity to compare the sensitivity of this ionization method to the more conventional ionization methods. Compared to the widely used quadrupole mass filter, the oa‐TOF platform offers significantly greater mass accuracy and therefore the possibility of determining the empirical formula of analytes. The findings of this study showed that, for the instrument used, EI generated the most ions with the exception of compounds able to form negative ions readily. Lower ion yields in the FI mode were generally observed but the chromatograms displayed greater S/N and in many cases gave spectra dominated by a molecular ion. Ion counts in CI are limited by the very small apertures required to maintain sufficiently high pressures in the ionization chamber. Mass accuracy for molecular and fragment ions was attainable at close to manufacturer's specifications, thus providing useful information on molecular ions and neutral losses. The data presented also suggests a potentially useful instrumental combination would result if EI and FI spectra could be collected simultaneously or in alternate scans during GC/MS. Copyright © 2009 John Wiley & Sons, Ltd.