Functional rearrangement of 3-Cl or 3,3-diCl-γ-lactams bearing a secondary 1-chloroalkyl substituent at C-4

The study of the reaction with MeONa/MeOH of chlorinated γ-lactams, prepared from the atom transfer radical cyclization of N-allyl-α-perchloroamides, has been extended to the case of substrates carrying an exo halogen atom on a branched carbon. Only with secondary exo C-Cl groups, that are not located on a fused ring, does the functional rearrangement follow the typical transformation route, which with trichloro-lactams can proceed further to give 4-alkylidene derivatives. From a practical point of view, the outcome of the reaction with di- or trichloro N-cinnamylamides is synthetically valuable, affording the 5-methoxy-1H-pyrrol-2(5H)-one or 3-benzylidenepyrrolidine-2,5-dione, respectively, in good to excellent yield.     

Localization of Bose-Einstein condensates in optical lattices

The dynamics of repulsive bosons condensed in an optical lattice is effectively described by the Bose-Hubbard model. The classical limit of this model, reproduces the dynamics of Bose-Einstein condensates, in a periodic potential, and in the superfluid regime. Such dynamics is governed by a discrete nonlinear Schrödinger equation. Several papers, addressing the study of the discrete nonlinear Schrödinger dynamics, have predicted the spontaneous generation of (classical) breathers in coupled condensates. In the present contribute, we shall focus on localized solutions (quantum breathers) of the full Bose-Hubbard model. We will show that solutions exponentially localized in space and periodic in time exist also in absence of randomness. Thus, this kind of states, reproduce a novel quantum localization phenomenon due to the interplay between bounded energy spectrum and non-linearity.     

On the motion of a phase interface by surface diffusion

Mullins, in a series of papers, developed a surface dynamics for phase interfaces whose evolution is controlled by mass diffusion within the interface. It is our purpose here to embed Mullins's theory within a general framework based on balance laws for mass and capillary forces in conjunction with a version of the second law, appropriate to a purely mechanical theory, which asserts that the rate at which the free energy increases cannot be greater than the energy inflow plus the power supplied. We develop an appropriate constitutive theory, and deduce general and approximate equations for the evolution of the interface.

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Sommario Mullins, in una serie di articoli inerenti la morfologia delle superfici di interfaccia tra fasi, ha sviluppato una dinamica delle superfici la cui evoluzione è governata dal fenomeno di diffusione di massa all'interno dell'interfaccia. Scopo di questo articolo è inscrire la teoria di Mullins in uno schema più generale basato su leggi di bilancio della massa e delle azioni capillari nonchè su una formulazione puramente meccanica del secondo principio della termodinamica, asserente ehe l'incremento di energia libera non possa essere superiore al flusso di energia ed alla potenza fornite all'interfaccia. Viene successivamente sviluppata una appropriata teoria costitutiva, e vengono dedotte le equazioni di evoluzione sia in forma generale che approssimata.

     

A version of Stöber synthesis enabling the facile prediction of silica nanospheres size for the fabrication of opal photonic crystals

A sol-gel synthesis procedure based on the method proposed by Stöber et al. (J Colloid Interface Sci 26:302–315, 1968) has been adopted for the one-step preparation of mono-dispersed silica nanospheres. An excellent control of the particle diameter over a wide range is obtained by varying the amount of silicon alkoxide only, while the concentration of all other components is kept fixed: this allows the fabrication of artificial opals with a finely tuned and precisely predictable lattice parameter.     

Expeditious synthesis of β-cycloacetalic sulfoxides. Introducing 1-phenylsulfinyl-2-phenylsulfanylethylene (SOSE), a promising new alkenylsulfur reagent

In similarity with the strongly electrophilic BPSEs and despite its more electron-rich character, 1-phenylsulfinyl-2-phenylsulfanylethylene (SOSE) reacts with nucleophiles with displacement of the phenylthio moiety. Specifically it reacts with diols under basic conditions to produce β-cycloacetalic sulfoxides. The reaction has been amply developed in carbohydrate chemistry.     

Spectrophotometric determination of advanced products of non-enzymatic glycosylation of lysine by means of their reaction with diazonium salts

A typical product (glycosyl lysine) formed by reaction of lysine with glyceraldehyde is measured at 490 nm after coupling with diazotized sulfanilic acid. Reaction with 4-dimethylaminobenzaldehyde was less satisfactory.     

Periodic and Non-Periodic Oscillations of a Class of Hysteretic Two Degree of Freedom Systems

The equations governing the response of hysteretic systems to sinusoidal forces, which are memory dependent in the classical phase space, can be given as a vector field over a suitable phase space with increased dimension. Hence, the stationary response can be studied with the aids of classical tools of nonlinear dynamics, as for example the Poincaré map. The particular system studied in the paper, based on hysteretic Masing rules, allows the reduction of the dimension of the phase space and the implementation of efficient algorithms. The paper summarises results on one degree of freedom systems and concentrates on a two degree of freedom system as the prototype of many degree of freedom systems. This system has been chosen to be in 1:3 internal resonance situation. Depending on the energy dissipation of the elements restoring force, the response may be more or less complex. The periodic response, described by frequency response curves for various levels of excitation intensity, is highly complex. The coupling produces a strong modification of the response around the first mode resonance, whereas it is negligible around the second mode. Quasi-periodic motion starts bifurcating for sufficiently high values of the excitation intensity; windows of periodic motions are embedded in the dominion of the quasi-periodic motion, as consequence of a locking frequency phenomenon.