Spin vortices in the Abelian–Higgs model with cholesteric vacuum structure

We continue the study of U(1)$U\left(1\right)$ vortices with cholesteric vacuum structure. A new class of solutions is found which represent global vortices of the internal spin field. These spin vortices are characterized by a non-vanishing angular dependence at spatial infinity, or winding. We show that despite the topological Z₂${\mathbb{Z}}_2$ behavior of SO(3)$SO\left(3\right)$ windings, the topological charge of the spin vortices is of the Z$\mathbb{Z}$ type in the cholesteric. We find these solutions numerically and discuss the properties derived from their low energy effective field theory in 1+1$1+1$ dimensions.     

Calorimetric Study of the Aggregation of Lithium Perfluorohexanoate on Poly(ethyleneglycol) Oligomers in Water

The interaction of lithium perfluorohexanoate (LiPFHex) with poly(ethylene glycol) (PEG) of different molecular weights (600 Da≤ MW≤20000 Da) was investigated in aqueous solution at 25.00 °C by isothermal titration calorimetry (ITC). The interaction with one of the PEG polymers (MW=8000 Da) was also followed at the same temperature by viscosity and conductivity measurements. The aggregation pattern of this surfactant on the PEG polymeric chain was very similar to that exhibited by the homologous salts of perfluoroheptanoate, perfluorooctanoate and perfluorononanoate ions. The interaction enthalpies with PEG of this class of surfactants are always endothermic and decrease steeply with the decreasing length of the fluorocarbon chain. Experimental data from calorimetry, viscosity and conductivity consistently indicate a very small tendency of PEG polymers to wrap around the small LiPFHex micellar aggregates. The PFHex ion appears to be the shortest member of the series able to interact with a polyoxyethylenic chain. The same CF₂ contribution to the Gibbs energy of micellization or aggregation on the polymers was found within the series, indicating a common hydrophobic driving force for the two processes.     

Stereocontrolled Synthesis of Unnatural Tetrapeptides Containing L‐Valine Units. Part 3

The stereoselective synthesis of the new nonproteinogenic branched tetrapeptides 9a – 9d and 15a , b , containing two L ‐valine units and unnatural α‐amino acids, was accomplished starting from the chiral synthon 1a , a monolactim ether easily obtained from L ‐valine.     

Stereoselective synthesis of new vicinal diaminoalkyl naphthols by three component Mannich type reaction of α,β-unsaturated aldehydes

The application of the aromatic Mannich reaction to α,β-unsaturated aldehydes, affords a series of new diaminoalkyl naphthols, by a convenient solventless reaction, starting from inexpensive and easily available starting materials. The absolute configurations of the products obtained are attributed on the basis of the coupling constant values of ¹H NMR spectra, joined with the conformational analysis of the molecules by molecular modelling. A mechanistic hypothesis is proposed, which involves an imino–amino intermediate.     

The source of differences in population distributions

This note shows that when the distribution of a variable in different populations is affected by two or more factors, differences in population distributions may be due exclusively to differences in the distribution of one factor only.     

Determination of the conformation of diethylmethyl-2-[p-(o-propoxybenzamido)benzoyloxy]ethylammonium bromide in solution by measurement of selective proton spin–lattice relaxation rates

The relative conformation of the aromatic rings and the amide bridge of diethylmethyl-2-[p-(o-propoxybenzamido)benzoyloxy]ethylammonium bromide has been established by a combined analysis of non-selective, single-selective and double-selective pulse experiments using, as a basis of comparison, the Dreiding molecular model of the compound.     

Studies on the synthesis of heterocyclic compounds. Synthesis of 1,3,2-benzoxathia- and 1,3,2-benzodioxastibole derivatives

The preparation of 1,3,2-benzoxathia- and 1,3,2-benzodioxachlorostiboles (IIa-b) by reaction of antimony trichloride with 2-hydroxythiophenol (Ia) or 1,2-benzodiol (Ib) is described. The halogen was easily removed. Thus a Wurtz-like reaction gave the distibole compounds (IVa-b), which were also produced by organolithium compounds or pyridine. The compounds Va-b were obtained with sodium hydroxide, ethoxide and phenoxide, but spiran derivatives VIIa-b, of antimony, were obtained by treating IIa-b with 2-hydroxythiophenol or 1,2-benzodiol in the presence of triethylamine. The structure of the prepared compounds was determined by spectro-scopic methods.     

Studio di una disequazione quasi-variazionale relativa ad un problema di filtrazione in tre dimensioni

Summary A 3-dimensional problem related to the theory of fluid flow through porous media is translated into a quasi-variational inequality: an existence theorem is proved.

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Entrata in Redazione il 17 marzo 1976.

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Lavoro svolto nell'ambito del ? Gruppo Nazionale per l'Analisi Funzionale e le sue applicazioni ? e del ? Laboratorio di Analisi Numerica ? di Pavia del C.N.R.