Effects of different composition ratio on the dielectric relaxation and dynamic mechanical properties of poly(ω‐dodecalactam‐co‐ε‐caprolactam‐co‐propylene oxide) copolymers

The molecular dynamics of new poly (ω‐dodecalactam‐co‐ε‐caprolactam‐co‐propylene oxide) copolymers (DL/CL/PAC) has been investigated by using dynamic mechanical thermal analysis (DMTA) and dielectric relaxation spectroscopy (DRS) measurements. The copolymers were synthesized via anionic polymerization of relevant lactams activated with carbamoyl derivatives of telechelic hydroxyl terminated polypropylene oxide with isophorone diisocyanate (PAC). The calorimetric, X‐ray diffraction, and DMTA measurements were performed to recognize the influence of the composition ratio and the type of PAC on the physical, thermal, and mechanical properties of the synthesized copolymers. The DRS was used to study the frequency dependence of the dielectric permittivity of some isotherms from ?110 to 145 °C. Copolymerization of ε‐caprolactam with about 10 wt % ω‐dodecalactam results in a copolymer that has lower water absorption, a melting point close to that of polyamide 6 and has a high enough degree of crystallinity in respect to high storage modulus. Five dielectric relaxations have been observed in the dielectric spectra, three at lower temperature and two at higher temperature. The copolymers have two glass transition temperatures for polyamide segments and polyether blocks, indicating microphase separation in the copolymers. Other studies directed toward molecular dynamics of polyamide DL/CL/PAC copolymers have not been reported. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Phenylalanine Ammonia Lyase Catalyzed Synthesis of Amino Acids by an MIO‐Cofactor Independent Pathway

Phenylalanine ammonia lyases (PALs) belong to a family of 4‐methylideneimidazole‐5‐one (MIO) cofactor dependent enzymes which are responsible for the conversion of L ‐phenylalanine into trans‐cinnamic acid in eukaryotic and prokaryotic organisms. Under conditions of high ammonia concentration, this deamination reaction is reversible and hence there is considerable interest in the development of PALs as biocatalysts for the enantioselective synthesis of non‐natural amino acids. Herein the discovery of a previously unobserved competing MIO‐independent reaction pathway, which proceeds in a non‐stereoselective manner and results in the generation of both L ‐ and D ‐phenylalanine derivatives, is described. The mechanism of the MIO‐independent pathway is explored through isotopic‐labeling studies and mutagenesis of key active‐site residues. The results obtained are consistent with amino acid deamination occurring by a stepwise E₁cB elimination mechanism.     

From gas chromatography to gaia

Summary This paper is an account of the development of the gaia hypothesis as seen through the eyes of a gas chromatographer. Gaia is a radical notion about the Earth which postulates the climate and chemical composition to be regulated at an optimum by and for life. Gas chromatography played an important role in the gathering of evidence for the hypothesis but most significantly the art of inventing detectors lead to the developement of a planetary life detector through which gaia was revealed.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Complex spaces with locally product metrics: special spaces

Summary Certain special spaces are considered within the framework of the general theory of complex Riemannian spaces with locally product metrics. Spaces of constant curvature are discussed and a counterpart of Schur's Theorem is established. It is also shown that there exist what may be regarded as complex Schwarzschild metrics. No physical interpretation is suggested. Entrata in Redazione il 30 ottobre 1968. On leave of absence from the Department of Mathematics, The University, Bristol.     

Weakened field equations in General Relativity admitting an ‘unphysical’ metric

Certain weakened vacuum field equations which have been suggested as alternatives to the vacuum field equations of General Relativity are investigated. It is shown that they each possess a solution which corresponds to an isolated mass at the origin which repels test particles. In view of the contradiction with experiment this solution is an embarrassment to these proposed vacuum field equations.On leave of absence from the Department of Mathematics, The University, Bristol.     

Divergence-free tensorial concomitants

Aequationes mathematicae -     

Pyrrolidinium-based ionic liquids. 1-Butyl-1-methyl pyrrolidinium dicyanoamide: thermochemical measurement, mass spectrometry, and ab initio calculations

The standard molar enthalpy of formation of the ionic liquid 1-butyl-1-methylpyrrolidinium dicyanamide has been determined at 298 K by means of combustion calorimetry, while the enthalpy of vaporization and the mass spectrum of the vapor (ion pairs) have been determined by temperature-programmed desorption and line of sight mass spectrometry. Ab initio calculations for 1-butyl-1-methylpyrrolidinium dicyanamide have been performed using the G3MP2 and CBS-QB3 theory, and the results from homodesmic reactions are in excellent agreement with the experiments.