Experimental and computational evidence for an inversion in guest capacity in high-generation triazine dendrimer hosts

The synthesis, characterization, and host-guest chemistry of high-generation triazine dendrimers are described. With pyrene and camptothecin as guests, experiments revealed that the guest capacity of odd-generation triazine dendrimers increased until generation 7 but decreased at generation 9. Molecular dynamics simulations conducted in explicit solvent showed a useful fingerprint for this behavior in radial distribution functions of water molecules penetrating the interior of the dendrimers. A linear relationship between the guest capacity of dendrimers measured experimentally and the number of water molecules within the interior determined computationally was observed.     

Bi-Sobolev homeomorphism with zero Jacobian almost everywhere

Let \(N\ge 3\) . We construct a homeomorphism \(f\) in the Sobolev space \(W^{1,1}((0,1)^N,(0,1)^N)\) such that \(f^{-1}\in W^{1,1}((0,1)^N,(0,1)^N)\) , \(J_f=0\) a.e. and \(J_{f^{-1}}=0\) a.e. It follows that \(f\) maps a set of full measure to a null set and a remaining null set to a set of full measure.We also show that such a pathological homeomorphism cannot exist in dimension \(N=2\) or with higher regularity \(f\in W^{1,N-1}\) .     

Chemo-enzymatic preparation from renewable resources of enantiopure 1,3-oxazolidine-2-thiones

Chiral 1,3-oxazolidine-2-thiones were prepared in enantiopure form from renewable resources through an enzymatic process involving immobilized myrosinase (thioglucoside glucohydrolase E.C. 3.2.3.1).     

Preequilibrium GDR excitation and entrance channel angular momentum effects

The energy spectra of the γ-rays emitted in the ³⁵Cl + ⁹²Mo reaction at incident energy E = 260 MeV were measured in coincidence with the ejectiles produced in dissipative reaction events. The cumulative energy spectrum of the γ-rays coming from the decay of the ejectiles was calculated within the statistical model and its comparison to the experimental spectrum evidences an excess in the data for E _γ = 8 to 12 MeV. Such an excess, fitted with a Lorentz curve, is attributed to the preequilibrium GDR γ-decay of the intermediate dinuclear system. The centroid energy of the Lorentz curve corresponds to a dipole oscillation along the symmetry axis of the system and its width is found to be comparable to that of the ground state GDR low energy component of the deformed dinucleus. The small quantal dispersion Δ? = (10.3 ± 0.1)? of the entrance channel angular momentum, determined by analysing the dissipative fragment angular distribution in the framework of the Strutinsky model, is suggested to limit the broadening of the preequilibrium GDR width.     

Composition of Coexisting Liquid Phases Determined by Rayleigh Interferometry

Rayleigh interferometry is a precise macroscopic gradient technique that has been utilized for the determination of multicomponent diffusion coefficients. Because concentration gradients in multicomponent systems drive a diffusion-based partial separation of different solutes, this interferometric technique may be potentially used for the determination of solute concentrations. We have therefore theoretically examined how Rayleigh interferometry can be applied for the determination of composition of ternary aqueous mixtures. The effect of cross-term diffusion coefficients on the accuracy of this method is also discussed. Furthermore, since the poly(vinyl)alcohol+poly(ethylene)glycol+water system undergoes liquid–liquid phase separation (LLPS), we have experimentally characterized its LLPS boundary at 25 °C. The corresponding tie-lines were characterized by determining the composition of the two coexisting liquid phases using Rayleigh interferometry.     

Dispersion polymerization of vinyl monomers in supercritical carbon dioxide in the presence of drug molecules: A one‐pot route for the preparation of controlled delivery systems

The polymerization of 1‐vinyl‐2‐pyrrolidone in supercritical carbon dioxide in the presence of ibuprofen as a model drug was investigated as a new one‐pot process for the preparation of polymer‐based drug delivery systems (DDSs). The composites were prepared at 65 °C and P = 31–42 MPa by changing the initial concentration of the drug and the concentration of a crosslinking agent and that of a hydrophobic comonomer. The effects of these parameters on the performances of the polymerization and on the in vitro release kinetics of ibuprofen were studied. In all the experiments, part of the drug was entrapped inside the polymer particles and dissolved more slowly with respect to the pure compound. Copolymerization with methyl methacrylate was the most effective route to obtain a DDS with sustained temporal release of the drug molecule. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7429–7446, 2008     

Polymerization of vinylidene fluoride with perfluoropolyether surfactants in supercritical carbon dioxide as a dispersing medium

The heterogeneous polymerization of vinylidene fluoride (VDF) was investigated at 50 °C with supercritical carbon dioxide (scCO₂) as a dispersing medium and diethylperoxidicarbonate as an initiator in the presence of different perfluoropolyether surfactants. When FLK 7004A ammonium carboxylate salts were used at a 5% (w/w) concentration with respect to VDF, with an initial pressure of 31–45 MPa and with an olefin concentration of about 5.5 mol/L, monomer conversions up to 63% were obtained, corresponding to a final solid content higher than 200 g/L, and the polymer was collected at the end of the process in the form of a white powder completely composed of microspheres. The effects of the density of the polymerization mixture, the monomer loading, and the surfactant concentration were studied. Collected experimental results suggest that Fluorolink ammonium perfluoropolyether carboxylic salts are the most effective surfactants yet tested in the dispersion polymerization of VDF in scCO₂. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2406–2418, 2006     

Globally stable vaccine-induced eradication of horizontally and vertically transmitted infectious diseases with periodic contact rates and disease-dependent demographic factors in the population

Within the framework of SEIR-like epidemic models, we studied the conditions for the stable eradication of some families of vertically and horizontally transmitted infectious diseases in the case of periodically varying contact rate. By means of Floquet’s theory, we found a condition for the eradication solution to be locally asymptotically stable. We then demonstrated that the same condition guarantees also that this vaccine-induced disease-free solution is globally asymptotically stable. A model with interacting populations is also considered. In the final part of this work, we extended the model by taking into account the variation of population size, the impact of disease-related deaths and reduction of fertility.     

A characterization of *-minimal algebras with involution

Let (A, *) be a *-PI algebra with involution over a field of characteristic zero and let c _m (A, *) denote its m-th *-codimension. Giambruno and Zaicev, in [10], proved that, if A is finite dimensional, there exists the \({\lim _{m \to + \infty }}\root m \of {{c_m}(A,*)} \), and it is an integer, which is called the *-exponent of A. As a consequence of the presence of this invariant, in a natural manner in [2] the definition of *-minimal algebra was introduced. Our goal in this paper is to characterize, up to *-PI equivalence, *-minimal algebras.