Study of the quiescent and shear‐induced crystallization kinetics of intercalated PTT/MMT nanocomposites

An intercalated nanocomposite made of montmorillonite nanoclay, MMT, and poly(trimethylene terephthalate), PTT, was produced by twin screw extrusion and characterized by wide angle X‐ray diffraction, WAXD, and transmission electron microscopy, TEM. The quiescent isothermal and non‐isothermal and the flow‐induced crystallization of the nanocomposite were studied by differential scanning calorimetry, DSC, polarized light optical microscopy, PLOM, and rheometry. The quiescent results showed that the nanoclay acted as an efficient nucleating agent for the PTT, which result in an anticipation of the transition temperature between regimes II and III of crystallization. The fold interfacial free energy, σ_e, of the PTT in the nanocomposite during regime III was lower than in the pure state; that is, the pure PTT developed spherulites, whereas in the nanocomposite it produced a paracrystalline morphology. Under shear rate, the total times for crystallization in the nanocomposite were higher than in the pure PTT. In flow‐induced crystallization, a fibrillar nucleus must be formed as a result of chain orientation. In the nanocomposite, chain orientation only occurred after the percolated structure was broken. Therefore, the formation of a fibrillar nucleus in the nanocomposite took more time, which increased the total crystallization time. Inc. J Polym Sci Part B: Polym Phys 48: 113–127, 2010     

Uniqueness of selfdual periodic Chern–Simons vortices of topological-type

In analogy with the abelian Maxwell–Higgs model (cf. Jaffe and Taubes in Vortices and monopoles, 1980) we prove that periodic topological-type selfdual vortex-solutions for the Chern–Simons model of Jackiw–Weinberg [Phys Rev Lett 64:2334–2337, 1990] and Hong et al. Phys Rev Lett 64:2230–2233, 1990 are uniquely determined by the location of their vortex points, when the Chern–Simons coupling parameter is sufficiently small. This result follows by a uniqueness and uniform invertibility property established for a related elliptic problem (see Theorem 3.6 and 3.7). Research supported by M.I.U.R. project: Variational Methods and Nonlinear Differential Equations.     

Model reactions for abiotic mercury(II) methylation: Kinetics of methylation of mercury(II) by mono-, di-, and tri-methyltin in seawater

The usual presence of mercury(II) with monodi-, and tri-methyltin in water, sediments, and plants in estuarine environments suggests possible abiotic formation of methylmercury via methyl transfer from methyltin compounds. Kinetics studies of reactions between mercury(II) and methyltin compounds under pseudo-first-order conditions in seawater show that relative rate of methylmercury formation under the same conditions are: monomethyltin <trimethyltin> dimethyltin. This order is explainable mainly by the speciation and charge of methyltin compounds in seawater and by the existence of mercury(II) as a tetrachloro anion. A factorial experiment with the variables pH and salinity (seawater diluted with deionized water) showed that pH, but not salinity, is significant at the 95% confidence level; and that reaction rates increase as pH increases. These results suggest the possibility of abiotic methylation of mercury(II) in seawater. Additional experiments in seawater demonstrated an absence of methylation of mercury(II) (14 days) and mercury(0) (35 days) by methyl iodide.     

Synthesis of 7-methyl-4,6,6a,7,10,10a-hexa-hydroindolo[4,3-fg]quinazoline derivatives

The synthesis of a series of compounds indolo[4,3-fg]quinazoline related to ergoline (indolo[4,3-fg]quinoline) is reported. The key step of the synthetic sequence is the ring cleavage of the ketone IV. The stereochemistry of the chiral centers is established by the chirality of dihydrolysergic acid I.     

Effects of mobile phone exposure on time frequency fine structure of transiently evoked otoacoustic emissions

Mobile phones have become very commonly used worldwide within a short period of time. To date there is only limited knowledge about interaction between electromagnetic fields (EMFs) emitted by mobile phones and the auditory function. Moreover, there is widespread concern that there may be potential for harm. The aim of this study was to assess potential subtle changes in cochlear function by measuring the temporal and spectral fine structure of transiently evoked otoacoustic emissions (TEOAE) in normal hearing subjects after exposure to EMFs emitted by Global System for Mobile Communication (GSM) mobile phones. TEOAEs were recorded in 27 healthy young adults before and after 10 min of real or sham exposure in a double-blind design. TEOAE data were analyzed both globally (broadband analysis) and using the Wavelet Transform (analysis of the time-frequency fine structure). The broadband analysis revealed no significant effect on TEOAEs related to exposure, confirming results of previous studies; in addition, no significant change was detected in the analysis of the elementary wavelet components, suggesting that the temporal and spectral fine structure of TEOAEs is not affected by 10 min exposure to low-intensity EMFs emitted by GSM mobile phones.     

Cyclodextrin complexation improves aqueous solubility of the antiepileptic drug,rufinamide: solution and solid state characterization of compound-cyclodextrin binary systems

Rufinamide (RUF) was characterized in terms of cyclodextrin (CD) complexation in order to improve its aqueous solubility. Binary systems of RUF with three CDs—β-cyclodextrin (β-CD), randomly methylated-β-cyclodextrin (RAMEB) and sulfobutylether-β-cyclodextrin (SBE-β-CD)—were characterized with a wide variety of analytical techniques. Liquid state characterization was carried out by complementary techniques such as nuclear magnetic resonance spectroscopy (NMR), capillary electrophoresis (CE), mass spectrometry (MS) and phase solubility studies. The latter revealed that the stability of the complexes decreased in the order of RAMEB?>?β-CD?>?SBE-β-CD. A_L-type diagrams were obtained in all cases, characteristic of 1:1 stoichiometry, with a maximum of over 15-fold increase in RUF solubility, when complexed with RAMEB. NMR Job plot and MS studies confirmed phase solubility results, regarding the binding stoichiometry. ¹H NMR and 2D ROESY investigations revealed the inclusion of the triazole moiety of RUF, confirmed by molecular modeling. Solid state complexation in 1:1 molar ratio was carried out by kneading method and investigated by differential scanning calorimetry (DSC) and infrared spectroscopy (IR). Comparative dissolution studies indicated an over two-fold improvement in dissolution efficacy of the kneaded products, when compared to the pure drug. Results of the present study might pave the way for a drug formulation with improved bioavailability.     

On the turbulent couette flow of an incompressible fluid with temperature-dependent viscosity

Summary Starting from energy and Navier-Stokes equations with temperature-dependent viscosity, we have obtained the Reynolds equations for the mean values of velocity, temperature and pressure. We have then applied these equations to the Couette flow; on the well-known hypothesis of mixing-length and Prandtl turbulent number, the above mentioned relations have been written in a more amenable form.Some general considerations concerning the reciprocal dependence between temperature and velocity gradients at wall have been deduced.Finally some solutions numerically obtained for several values of Reynolds number are given and discussed in some detail to point out the influence of the temperature-dependent viscosity.

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Sommario Introducendo nelle equazioni dell'energia e di Navier-Stokes le parti medie e fluttuanti della velocità, temperatura, pressione e viscosità, vengono ricavate le cosiddette equazioni di Reynolds, ossia le equazioni che descrivono i campi di velocità e temperatura medi. Dal confronto di quest'ultime, in cui la viscosità è considerata dipendente dalla temperatura, con quelle originarie di Reynolds si deduce la forma che nel caso in esame assumono gli sforzi apparenti.Successivamente le equazioni ottenute vengono applicate al moto a Couette e discusse, dopo aver introdotto in esse le ipotesi della lunghezza di miscelamento e del numero di Prandtl turbolento; da questa analisi vengono tratte alcune conclusioni di carattere generale riguardanti i legami tra il campo dinamico e quello termico. Infine vengono date alcune soluzioni ottenute per via numerica, le quali illustrano l'influenza che sulle distribuzioni di temperatura e velocità viene esercitata dalla dipendenza della viscosità dalla temperatura.

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Synthesis and aggregation behaviour of a new sultaine surfactant

The aggregation properties of a new sultaine surfactant have been studied in buffered aqueous solution at pH 7.4 under controlled condition of osmolarity. Spontaneously formed sultaine vesicles with a mean diameter of about 1 μm can be observed by optical microscopy. The phase behaviour of the surfactant has been investigated by differential scanning calorimetry (DSC) and Nile Red fluorescence. Two critical vesicular concentrations (CVC(1) and CVC(2)) have been fluorimetrically measured, by using pyrene and Nile Red as the fluorescent probes. The two populations of vesicles behave differently as a consequence of their size. The stability of extruded large unilamellar vesicles (LUV) formed slightly above the CVC(1) has been evaluated in the temperature range 25-75°C by following the rate of spontaneous release of entrapped 5(6)-carboxyfluorescein (CF). The stability of the same vesicles at 70°C has also been investigated under osmotic stress obtained by adding NaCl or sucrose to the bulk solution. At a sultaine concentration above the CVC(2) LUV tend to associate and form stable larger closely packed aggregates as suggested by Dynamic Laser Light Scattering and rheological measurements.