The nucleon and Δ-resonance masses in relativistic chiral effective-field theory

We study the chiral behavior of the nucleon and Δ-isobar masses within a manifestly covariant chiral effective-field theory, consistent with the analyticity principle. We compute the πN and πΔ one-loop contributions to the mass and field-normalization constant, and find that they can be described in terms of universal relativistic loop functions, multiplied by appropriate spin, isospin and coupling constants. We show that these manifestly relativistic one-loop corrections, when properly renormalized, obey the chiral power-counting and vanish in the chiral limit. The results including only the πN-loop corrections compare favorably with the lattice QCD data for the pion-mass dependence of the nucleon and Δ masses, while inclusion of the πΔ loops tends to spoil this agreement.     

Integrals of Vertex Operators and uantum Shuffles

Given a braided vector space , we show that iterated integrals of operator-valued functions satisfying a certain exchange relation give rise to representations of the quantum shuffle algebra built on . Using the quantum shuffle construction of the 'upper triangular part' of a quantum shuffle, this provides a simple proof of the result of Bouwknegt, MacCarthy and Pilch saying that integrals of vertex operators acting on certain Fock modules give rise to representations of .     

Ultrafast dynamics and temperature effects on the quantum efficiency of the ring-opening reaction of a photochromic indolylfulgide

The ultrafast ring-opening reaction of the molecular switch 1,2-Dimethyl-3-indolylfulgide dissolved in acetonitrile is investigated by temperature dependent quantum efficiency measurements and time-resolved transient absorption spectroscopy in the ultraviolet and visible spectral range. The photoreaction is found to be thermally activated with an activation energy of about 1640 cm^− 1. The transient absorption signal is bi-exponential with the time constants τ₁ = 0.7 ps and τ₂ = 12 ps. The fast time constant is due to solvation dynamics, while the main component τ₂ is attributed to the excited state lifetime and product formation. A long-lived intermediate state in the photoreaction can be excluded.     

The Michael Addition of Enamines to Propenamidines. A Convenient Synthesis of 2β-Amidinoethylcyclo-Alkanones by Amidinoethylation Reaction

A variety of propenamidines 3 have been reacted with enamines of cyclopentanone and cyclohexanone giving after hydrolysis of the Stork enamine 6, 2-β-amidinoethylcyclopentanones 8 and -hexanones 7. This reaction illustrates the electrophilic character of the C=C double bond due to the conjugated amidine function, thus providing with propenamidines 3 a new class of Michael acceptors for enamines.     

Isolation of bicarbonate from equine urine for isotope ratio mass spectrometry

Sodium bicarbonate administration to horses prior to competition in order to enhance the buffer capacity of the organism is considered as a doping offence. The analysis of the isotopic composition of urinary bicarbonate/CO(2) (TCO(2)) may help to identify an exogenous bicarbonate source, as technical sodium bicarbonate exhibits elevated delta(13)C values compared with urinary total carbon. The isolation of TCO(2) from 60 equine urine samples as BaCO(3) followed by an isotopic analysis shows a significant variability of delta(13)C for TCO(2) of more than 10 per thousand. The delta(13)C of total carbon and TCO(2) seem to reflect different proportions of C3 and C4 plant material in the diet. The isotopic analysis of different mixtures of technical NaHCO(3) and equine urine shows that TCO(2) can be easily isolated without major isotopic fractionation; however, attention has to be paid to the storage time of urine samples, as a shift of delta(13)C of TCO(2) to lower values may occur.     

Recent developments in the synthesis and functionalization of conducting poly(thiophenes)

The mechanism of the electropolymerization of thiophene derivatives has been investigated by varying the electrosynthesis conditions and the monomer structure. The results of these analyses led to the definition of optimized electrosynthesis conditions allowing the control of the electrical and electrochemical properties of poly(thiophenes). On the basis of these results, the properties of these polymers have been modified by means of a new one-step electrosynthesis of conducting composite materials and by the direct electropolymerization of tailor-made functionalized monomers. For this purpose, the steric conditions associated to the various possibilities of covalent derivatization have been analyzed, leading to the definition of a “functionalization space”, compatible with the preservation of high conductivity and electrochemical reversibility in the resulting polymers. This concept has been applied to the synthesis of highly conducting chiral poly(thiophenes) on which an effect of enantioselective molecular recognition has been demonstrated for the first time.     

Ring-opening metathesis copolymerization employing ruthenium-based metathesis catalysts

The copolymerization of both high- and low-strain cyclic olefins employing three ruthenium-based metathesis catalysts is desribed. The effect of the ligand environment as well as the nature of the carbene on the copolymerizations is discussed.