A nanocomposite material formed by benzofulvene polymer nanoparticles loaded with a potent 5-HT3 receptor antagonist (CR3124)

Poly-BF3a, a new hydrophobic polymer obtained by spontaneous polymerization of 1-methylene-3-phenyl-1H-indene, was found to give nanoparticles characterized by favorable shape and dimensions. Poly-BF3a nanoparticles were loaded with CR3124, a potent 5HT₃ antagonist, as a drug model by desolvation methods either in the absence or in the presence of polyethylene glycol (PEG1000) as a wetting agent. The SEM studies showed that the introduction of CR3124 into the preparation led to a variable degree of aggregation–cementation, which afforded a sort of nanocomposite material. In the absence of PEG1000, the drug molecule was found to stay in the amorphous state (DSC studies) when its percentage is not higher than 10% by weight. In vitro release experiments showed that the formation and stability of the dispersion as well as the drug release were remarkably affected by the presence of PEG1000, demonstrating its beneficial effect to the nanoparticle morphology and disaggregation.     

Accelerating cosmologies from non-local higher-derivative gravity

We study accelerating cosmological solutions of a general class of non-linear gravities which depend on Gauss–Bonnet and other higher derivative invariants. To achieve this goal a local formulation with auxiliary scalars for arbitrary higher-derivative non-local gravity is developed. It is demonstrated that non-local Gauss–Bonnet gravity can be reduced, in the local formulation, to a model of string-inspired scalar-Gauss–Bonnet gravity. A natural unification, in the theory here developed, of the early-time inflation epoch with a late-time acceleration stage can also be realized.     

Electro-optical response due to mixed conduction electrodes, compared to ferroelectric ones, in asymmetric nematic liquid crystal cells

The usual liquid crystal cells show an electro-optical response symmetric to the applied voltage. On the contrary, when mixed conduction films such as tungsten trioxide or vanadium pentoxide are inserted on one side of the cell, the electro-optical response is asymmetric with respect to the applied voltage. Depending on the structural phase of the inserted film the electro-optical response is in phase (transmission ON during the anodic polarization on metal oxide electrode, transmission OFF during the cathodic one) or in opposition of phase (reverse combination). The first case has been explained by the formation of a double charge layer at the interface metal oxide–liquid crystal, because of migration of protons contained in the oxide films. The other case has been found after high-temperature treatments of metal oxides deposited on glass–ITO substrates, and it appears quite similar to the response collected by using films of ferroelectric materials such as lead zirconium titanate (PZT). This fact suggests a possible interpretation in terms of dielectric response, when the mixed conduction films undergo high-temperature treatments. A comparative study of films of WO₃, V₂O₅, and PZT is carried out in this work as a function of the annealing temperature. Paper presented at the 11th EuroConference on the Science and Technology of Ionics, Batz-sur-Mer, Sept. 9–15, 2007.     

Solubility and acid-base properties and activity coefficients of chitosan in different ionic media and at different ionic strengths, at T = 25 °C

Studies on the acid-base properties and solubility of a polyammonium polyelectrolyte (chitosan) with different molecular weights (MW 310 and 50 kDa), were performed at T = 25 °C, in the pH range 2.5–7. The protonation of chitosan was investigated by potentiometry ([H⁺]-glass electrode) in NaCl, NaNO₃ and mixed NaNO₃ + Na₂SO₄ ionic media, at different ionic strengths. Protonation constants were calculated as a function of dissociation degree α by means of two different models, namely, a simple linear model and the modified Henderson–Hasselbalch equation. Experimental data were also fitted using a model independent of α (Diprotic-like model), according to which the acid-base properties can be simply described by two protonation constants in all the acidic pH range. The dependence on ionic strength of protonation constants in NaCl aqueous solution was modelled by Specific ion Interaction Theory (SIT). The ion pair formation between protonated chitosan and Cl⁻, NO₃⁻ and SO₄²⁻ was also considered, and the relative formation constants are reported.Solubility investigations were performed in NaCl aqueous solutions in a wide range of ionic strength (0.1 < I/mol L^− 1 < 3.0), with the aim to determine the activity coefficients of neutral species and the Setschenow coefficient of chitosan 310 kDa.     

Complex formation between Zn2+ ion and 1,3-bis[bis(pyridin-2-ylmethyl)amino]propan-2-ol

The dinucleating ligand 1,3-bis[bis(pyridin-2-ylmethyl)amino] propan-2-ol (I, LOH) is becoming of increasing interest due to the exceptional phosphate monoester binding and phosphate diester hydrolytic properties of its dizinc(II) complexes in water. Potentiometric pH titrations using a range of Zn:I ratios reveals the formation of mononuclear and dinuclear metal complexes. In fact, when the Zn:I ratio is 1:1 only mononuclear complexes are formed. Previous work reported the formation of only dinuclear species. Thus, the results presented here should be important to interpret correctly and more accurately phosphate ester binding and hydrolysis data. Moreover, based on these findings we suggest that the phosphate binding and hydrolytic properties of mixtures containing Zn(II) ions and I should depend not only on the pH but also on the Zn:I ratio used.     

A fast heuristic algorithm for the maximum concurrent <Emphasis Type="Italic">k</Emphasis>-splittable flow problem

In this paper, we propose a fast heuristic algorithm for the maximum concurrent k-splittable flow problem. In such an optimization problem, one is concerned with maximizing the routable demand fraction across a capacitated network, given a set of commodities and a constant k expressing the number of paths that can be used at most to route flows for each commodity. Starting from known results on the k-splittable flow problem, we design an algorithm based on a multistart randomized scheme which exploits an adapted extension of the augmenting path algorithm to produce starting solutions for our problem, which are then enhanced by means of an iterative improvement routine. The proposed algorithm has been tested on several sets of instances, and the results of an extensive experimental analysis are provided in association with a comparison to the results obtained by a different heuristic approach and an exact algorithm based on branch and bound rules.     

Multiple criteria sorting with a set of additive value functions

We present a new multiple criteria sorting method that aims at assigning actions evaluated on multiple criteria to p pre-defined and ordered classes. The preference information supplied by the decision maker (DM) is a set of assignment examples on a subset of actions relatively well known to the DM. These actions are called reference actions. Each assignment example specifies a desired assignment of a corresponding reference action to one or several contiguous classes. The set of assignment examples is used to build a preference model of the DM represented by a set of general additive value functions compatible with the assignment examples. For each action a, the method computes two kinds of assignments to classes, concordant with the DM’s preference model: the necessary assignment and the possible assignment. The necessary assignment specifies the range of classes to which the action can be assigned considering all compatible value functions simultaneously. The possible assignment specifies, in turn, the range of classes to which the action can be assigned considering any compatible value function individually. The compatible value functions and the necessary and possible assignments are computed through the resolution of linear programs.     

Design of Bimodal PCL and PCL‐HA Nanocomposite Scaffolds by Two Step Depressurization During Solid‐state Supercritical CO2 Foaming

This communication reports the design and fabrication of porous scaffolds of poly(ε‐caprolactone) (PCL) and PCL loaded with hydroxyapatite (HA) nanoparticles with bimodal pore size distributions by a two step depressurization solid‐state supercritical CO₂ (scCO₂) foaming process. Results show that the pore structure features of the scaffolds are strongly affected by the thermal history of the starting polymeric materials and by the depressurization profile. In particular, PCL and PCL‐HA nanocomposite scaffolds with bimodal and uniform pore size distributions are fabricated by quenching molten samples in liquid N₂, solubilizing the scCO₂ at 37 °C and 20 MPa, and further releasing the blowing agent in two steps: (1) from 20 to 10 MPa at a slow depressurization rate, and (2) from 10 MPa to the ambient pressure at a fast depressurization rate. The biocompatibility of the bimodal scaffolds is finally evaluated by the in vitro culture of human mesenchymal stem cells (MSCs), in order to assess their potential for tissue engineering applications.

     

Strelitzia reginae leaf as a natural template for anisotropic wetting and superhydrophobicity

Artificial surfaces that exhibit unidirectional water spreading and superhydrophobicity are obtained by Strelitzia reginae leaves. Both green and dried leaves are used, thus exploiting the plant senescence. We demonstrate that the natural drying process of the leaves strongly affects the surface morphology and wettability. Polymeric stamps from the green leaf show an arrangement of periodic microridges/microgrooves that favor anisotropic wetting, with a water contact angle (WCA) variation of about 21% along the two principal directions. Instead, the shrinkage of the leaf tissue, as a consequence of the natural dehydration process, induces an enhancement of the superficial corrugation. This results in the establishment of a superhydrophobic state, which shows a WCA of up to 160°, and water rolling off. S. reginae leaves are therefore easily accessible stamps suitable for controlling wettability and realizing surfaces that exhibit various wetting behaviors.     

Symmetric vs. asymmetric squaraines as photosensitisers in mesoscopic injection solar cells: a structure-property relationship study

A symmetric squaraine and its related non-symmetric structure are shown to have comparable efficiencies in DSCs, but with undoubtedly advantages in the low cost and easiness of synthesis for the symmetrical structure.