Systematic evaluation of the conformational properties of aliphatic omega-hydroxy acids

A systematic conformational study of omega-hydroxy acids, HO-(CH(2))(n)()-COOH with n ranging from 2 to 5, has been performed using quantum mechanical calculations at the MP2 level. To distinguish between intrinsic and environmentally induced conformational preferences, calculations have been carried out in both gas phase and chloroform solution, a polarizable continuum solvation model being used to represent the latter. Results indicate a consistent conformational behavior, as reflects the feature that the lowest energy minimum for n = 2, 3, 4, and 5 corresponds to the g+g-t, g+g+g-t, g-g+g+g-t, and g+g-g+g+g-t conformations, respectively. Furthermore, the stability of the extended and semi-extended conformations increases systematically with the size of the central aliphatic segment. The relationship between the size of the aliphatic segment and the stability of folded conformations is analyzed and discussed.     

Magnetization process in twisted uniaxial polycrystals

A single model has been developed to obtain the general features of the Matteucci, ME, and the inverse Wiedemann, IWE, effects. The model will be confined to polycrystalline tubes and thin wires whose uniaxial crystals are arbitrarily oriented. The domain arrangement is expressed as a function of applied twist in order to determine the remanent magnetization of the M_z-M_ø and M_ø-H_z hysteresis loops. Theory shows that, for certain values of the applied magnetic field, the ME and IWE decrease and vanish with torsion. The relation between the symmetry properties of the ME and IWE and the symmetry of the initial domain structure of the sample is discussed.     

Studies on the hydrogenation of 6-(hydroxymethyl)pyridine-2-carboxylates and its application to the synthesis of 6-(hydroxymethyl)piperidine-2-carboxylic acid derivatives

The synthesis of the novel amino acid 6-(hydroxymethyl)-2-piperidinecarboxylic acid ( 1a ) and its ethyl ester 1b is reported. In the hydrogenation of 6-(hydroxymethyl)pyridine-2-carboxylates, hydrogenolysis of the alcohol group appeared as an unusual side reaction. Optimization of the reaction conditions allowed us to minimize hydrogenolysis and afforded pure 1 .     

Backbone conformational preferences and pseudorotational ring puckering of 1-aminocyclopentane-1-carboxylic acid

We have used quantum mechanical calculations at the B3LYP/6-311G(d,p) level to determine the conformational preferences of the N-acetyl-N'-methylamide derivative of 1-aminocyclopentane-1-carboxylic acid in the gas phase, chloroform solution, and water solution. The backbone conformation of this dipeptide has been described through the dihedral angles varphi and psi, while the pseudorotational phase angle was used to define the conformation of the cyclopentane ring. Results indicate that the backbone flexibility of this amino acid is restricted by the cyclic nature of the side chain, the relative stability of the different conformations depending on the polarity of the environment. The potential energy of the pseudorotation was also studied as a function of the backbone conformation. Interestingly, the conformation of the cyclic side chain depends on the backbone arrangement. Furthermore, the number of pseudorotational states accessible at room temperature is high in all the investigated environments, especially in aqueous solution. Finally, a set of force-field parameters for classical molecular mechanics calculations was developed for the investigated amino acid. Molecular dynamics simulations in both chloroform and aqueous solutions were performed to demonstrate the reliability of such parameters.     

Ordered patterning of nanometric rings of single molecule magnets on polymers by lithographic control of demixing

We report a new patterning process which takes place as a result of demixing of a binary polymer/solute mixture. An efficient, sustainable approach for ordering nanosized rings of so-called single molecule magnets (SMMs) is thus provided. It exploits the self-organization process in which SMM patterned film evolves to a spatially correlated pattern of nanosized rings. At long time, the anisotropic patterning of the film drives the ring to coalesce, into parallel lines of nanometric width.     

On the 2-adic valuation of the cardinality of elliptic curves over finite extensions of $$\mathbb {F}_{\varvec{q}} $$

In this paper we study the difference between the 2-adic valuations of the cardinalities \( \# E( \mathbb {F}_{q^k} ) \) and \( \# E( \mathbb {F}_q ) \) of an elliptic curve E over \( \mathbb {F}_q \). We also deduce information about the structure of the 2-Sylow subgroup \( E[ 2^\infty ]( \mathbb {F}_{q^k} ) \) from the exponents of \( E[ 2^\infty ]( \mathbb {F}_q ) \).     

Iterates and Hypoellipticity of Partial Differential Operators on Non-Quasianalytic Classes

Let P be a linear partial differential operator with constant coefficients. For a weight function ω and an open subset Ω of \mathbbR^N{\mathbb{R}^N} , the class E_P,{w}(W){\mathcal{E}_{P,\{\omega\}}(\Omega)} of Roumieu type involving the successive iterates of the operator P is considered. The completeness of this space is characterized in terms of the hypoellipticity of P. Results of Komatsu and Newberger-Zielezny are extended. Moreover, for weights ω satisfying a certain growth condition, this class coincides with a class of ultradifferentiable functions if and only if P is elliptic. These results remain true in the Beurling case E_P,(w)(W){\mathcal{E}_{P,(\omega)}(\Omega)}.