Chelate-Controlled Asymmetric Synthesis of 2-Substituted 2,3-Dihydropyridin-4(1H)-ones: Synthesis of D- and L-aminodeoxyaltrose derivatives

Asymmetric methylation and phenylation of the chiral pyridinium salt 7 , as well as methylation of chiral pyridinium salt 18 , with Grignard reagents occurred in good yield and with good-to-excellent diastereoselectivities (Schemes 2 and 3, resp.). These results are best explained by assuming chelate control to govern the asymmetric alkylation/arylation process. The minimum-energy conformations of the out-of-plane twisted pyridinium salts 7 and 18 , as determined by the ‘Molecular Simulations Cerius-Dreiding II’ program, are in good agreement with the postulated asymmetric chelate-control mechanism.     

Measuring the time evolution of the gas pressure in closed cell polyolefin foams produced by compression moulding

The evolution with time of the gas pressure in the cells of low density closed cell polyolefin based foams has been measured using a method that combines mechanical testing and modelling of the compressive response. The results have proved that foam blocks produced by compression moulding present a sub-atmospheric, non-constant gas pressure after production, the increase of pressure with time being a very slow process. In fact, it has been shown that this process has not finished 200 days after production. In addition, it has been also shown that the cooling of the foam during production affects the pressure distribution within the foam.     

Effect of ethanol on the micellization and gelation of pluronic p123

In certain applications copolymer P123 (E21P67E21) is dissolved in water-ethanol mixtures, initially to form micellar solutions and eventually to gel. For P123 in 10, 20, and 30 wt % aqueous ethanol we used dynamic light scattering from dilute solutions to confirm micellization, oscillatory rheometry, and visual observation of mobility (tube inversion) to determine gel formation in concentrated solutions and small-angle X-ray scattering (SAXS) to determine gel structure. Except for solutions in 30 wt % aqueous ethanol, a clear-turbid transition was encountered on heating dilute and concentrated micellar solutions alike, and as for solutions in water alone (Chaibundit et al. Langmuir 2007, 23, 9229) this could be ascribed to formation of wormlike micelles. Dense clouding, typical of phase separation, was observed at higher temperatures. Regions of isotropic and birefringent gel were defined for concentrated solutions and shown (by SAXS) to have cubic (fcc and hcp) and hexagonal structures, consistent with packed spherical and elongated micelles, respectively. The cubic gels (0, 10, and 20 wt % ethanol) were clear, while the hex gels were either turbid (0 and 10 wt % ethanol), turbid enclosing a clear region (20 wt % ethanol), or entirely clear (30 wt % ethanol). The SAXS profile was unchanged between turbid and clear regions of the 20 wt % ethanol gel. Temperature scans of dynamic moduli showed (as expected) a clear distinction between high-modulus cubic gels (G'max approximately 20-30 kPa) and lower modulus hex gels (G'max<10 kPa).     

Thermomechanical characterization of PVDF and P(VDF-TrFE) blends containing corn starch and natural rubber

Films of poly(vinylidene fluoride), PVDF, and poly(vinylidene fluoride – trifluoroethylene), P(VDF-TrFE), containing corn starch and latex of natural rubber as additives were produced by compressing/annealing forming blends visioning applications as biomaterials. Therefore, considering the possible applications of these blends, a basic characterization has been carried out targeting to infer on their thermomechanical properties. The polymer films (PVDF and P(VDF-TrFE)) with different percentage of additives were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), differential scanning calorimetry (DSC), and dynamical-mechanical analysis (DMA). The compressing/annealing process allowed discarding the necessity of using the solvents to dissolve either PVDF or P(VDF-TrFE), which are usually toxic to human. The results showed that the polymers do not interact chemically with the additives with the blends showing high thermal stability and elasticity modulus at the same order of magnitude of the bone, for instance. The SEM imaged revealed that the blends present morphological structures of typical physical mixtures where each material can be identified within the blends.     

Tsallis entropy approach to radiotherapy treatments

The biological effect of one single radiation dose on a living tissue has been described by several radiobiological models. However, the fractionated radiotherapy requires to account for a new magnitude: time. In this paper we explore the biological consequences posed by the mathematical prolongation of a previous model to fractionated treatment. Nonextensive composition rules are introduced to obtain the survival fraction and equivalent physical dose in terms of a time dependent factor describing the tissue trend towards recovering its radioresistance (a kind of repair coefficient). Interesting (known and new) behaviors are described regarding the effectiveness of the treatment which is shown to be fundamentally bound to this factor. The continuous limit, applicable to brachytherapy, is also analyzed in the framework of nonextensive calculus. Here a coefficient that rules the time behavior also arises. All the results are discussed in terms of the clinical evidence and their major implications are highlighted.     

Sertaconazole-HPβCD-pluronic F127 solid inclusion complexes: characterization and effect on drug solubility

The influence of Pluronic^® F127 (PF127) on hydroxypropyl-β-cyclodextrin (HP-βCD) complexation in solid state with sertaconazole, a highly active but poorly soluble antifungal drug, and its repercussion on drug solubilization and release rate were evaluated. Solid ternary systems comprising sertaconazole: HP-βCD:PF127 were obtained by (i) kneading of blends wetted with methanol:phosphate buffer; (ii) freeze-drying of filtered suspensions; and (iii) cast of films of filtered suspensions in an oven at 37°C. Two levels of PF127 concentrations were evaluated, one below (0.1%) and other above (5%) the critical micellar concentration (CMC). Physical mixtures were used as references. Differential scanning calorimetry, Raman spectroscopy and X-ray difractometry showed that PF127 did not significantly interfere in the complexation process, as confirmed by the total amount of sertaconazole nitrate (SN) dissolved. Nevertheless, the presence of 5% PF127 significantly delayed the release owing to its ability to form a gel layer. These ternary systems are potentially useful to combine drug solubilization ability with control of drug release.