Quantitative measurement of solids distribution in gas–solid riser flows using electrical impedance tomography and gamma densitometry tomography

An electrical impedance tomography (EIT) system has been developed to non-invasively measure particle distributions in the riser of a pilot-scale circulating fluidized bed (CFB). Although EIT systems have often been applied to yield qualitative information about gas–solid flows, the present EIT system yields quantitative information that is validated by comparison to a gamma densitometry tomography (GDT) system. EIT and GDT were applied to the CFB riser (14-cm inner diameter, 5.77-m height) containing fluid catalytic cracking particles in air. The flows examined were annular with a dilute core and had average and near-wall solids volume fractions up to 0.25 and 0.66, respectively. For all cases, the average and near-wall solids volume fractions from EIT and GDT agreed to within 0.03 and 0.07, respectively. This good agreement suggests that, where feasible, EIT can be used in place of GDT, which is advantageous since EIT systems are often safer, less expensive, and faster than GDT systems.     

Electrochemical investigation of the interaction between lysozyme-shelled microbubbles and vitamin C

We report loading of vitamin C (ascorbic acid) on to lysozyme-shelled microbubbles. The interaction between lysozyme-shelled microbubbles and vitamin C was studied by use of cyclic and differential pulse voltammetry, zeta potential measurements, and scanning electron microscopy. The effect of microbubbles on electrochemical measurement of ascorbic acid was evaluated. The linear range for ascorbic acid obtained for differential pulse measurement in the presence of 1 mg mL^?1 microbubbles was 1–50 μmol L^?1 (y?=?0.067x?+?0.130, r ²?=?0.995), with a detection limit of 0.5 μmol L^?1. The experimental conditions, i.e., pH and ionic strength, were optimized to improve the interaction between ascorbic acid and lysozyme-shelled microbubbles. The results were satisfactory when the interaction was performed for 1 h in aqueous solution at pH 6. The amount of vitamin C loaded on the microbubbles (90 % of the analyte added, RSD _inter-expt. = 3 %, n?=?6) and the stability of microbubbles–ascorbic acid complex (until 72 h at 25 °C) were also evaluated by use of differential pulse voltammetry and zeta potential measurements.

Existence and continuous dependence for solutions to the equations of a one-dimensional model in gas-dynamics

Summary We prove existence and continuous dependence of solutions to one-dimensional motions of a politropic viscous gas in arbitrary regions. In particular, in case of unbounded regions we do not assume the initial density distribution to have a strict positive lower bound.

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Sommario Proviamo l'esistenza e la dipendenza continua di soluzioni per i moti unidimensionali di un gas viscoso politropico in regioni arbitrarie. In particolare, nel caso in cui la regione del moto è non limitata, non assumiamo che la distribuzione di densità all'istante iniziale abbia estremo inferiore strettamente positivo.

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This work has been realized within the activities of the Italian Council for the Research (C.N.R.), gruppo nazionale della fisica matematica (G.N.F.M.).     

Methods of preparation of novel composites of poly(ϵ‐caprolactone) and a modified Mg/Al hydrotalcite

12‐Hydroxydodecanoate (HD) anions were intercalated, via an ion‐exchange procedure, onto a Mg/Al hydrotalcite‐like compound with the formula [Mg_0.65Al_0.35(OH)₂](NO₃)_0.35·0.56H₂O. The obtained intercalate, characterized by chemical and thermal analyses, X‐ray powder diffraction, and Fourier transform infrared spectroscopy, had the formula [Mg_0.65Al_0.35(OH)₂](NO₃)_0.08(HD)_0.28·0.56H₂O and an interlayer distance of 2.27 nm. Structural considerations indicated that the charge‐balancing HO? (CH₂)₁₁? COO^? anions were accommodated in the interlayer region as a monofilm of partially interdigitated alkyl chains in a trans planar conformation and bearing the alcoholic group. The organically modified hydrotalcite was used to prepare novel composites based on poly(?‐caprolactone) (PCL) with different procedures: (1) solvent casting, (2) ring‐opening polymerization of ?‐caprolactone, and (3) blending of precursors consisting of a PCL intercalated oligomer with a high‐molecular‐weight PCL. Microcomposites were obtained by the solvent casting of a mixture of a high‐molecular‐weight PCL and the modified hydrotalcite. The ring‐opening polymerization of ?‐caprolactone initiated by the ? OH groups of the alkyl chains intercalated in the hydrotalcite led to hybrid materials in which a low‐molecular‐weight PCL was in part intercalated into the modified hydrotalcite. Nanocomposites containing exfoliated hydrotalcite were obtained through the mixing, in different weight ratios, of hybrids consisting of PCL oligomers and modified hydrotalcite with a commercial high‐molecular‐weight PCL. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2281–2290, 2005     

Mutual coherence of supercontinuum pulses collinearly generated in bulk media

We report the collinear generation of white light pulses in bulk media by phase-locked and time-delayed intense laser pulses. The mutual phase coherence of the pump pulses is fully transferred to the two supercontinua, which thus show a highly-modulated two-pulse spectrum extending from all of the visible down to the near-infrared. We have investigated the effects of changing the relative delay between the pulses as well as the role of imbalances in the pump energy, and we have found that, at least in a limited energy interval, the mutual phase coherence of the two white-light pulses is surprisingly robust.     

A mixture of generalized hyperbolic factor analyzers

The mixture of factor analyzers model, which has been used successfully for the model-based clustering of high-dimensional data, is extended to generalized hyperbolic mixtures. The development of a mixture of generalized hyperbolic factor analyzers is outlined, drawing upon the relationship with the generalized inverse Gaussian distribution. An alternating expectation-conditional maximization algorithm is used for parameter estimation, and the Bayesian information criterion is used to select the number of factors as well as the number of components. The performance of our generalized hyperbolic factor analyzers model is illustrated on real and simulated data, where it performs favourably compared to its Gaussian analogue and other approaches.     

Poly(epsilon-caprolactone)-poly(oxyethylene) multiblock copolymers bearing along the chain regularly spaced pendant amino groups

Poly(epsilon-caprolactone) (PCL) macromers (M(n) = 1.7-3.8 kDa) which contain one Z-protected -NH2 group per chain were synthesized by ring-opening polymerization of epsilon-caprolactone in the presence of Sn(oct)2 using as initiator a diamine prepared by condensation of N-Boc-1,6-hexanediamine and N(alpha)-Boc-N(epsilon)-Z-L-Lysine. The coupling of these macromers with -COCl end-capped poly(oxyethylene) (PEO), M(n) = 1.0 kDa, afforded amphiphilic multiblock poly(ether ester)s (PEEs) which have, along the chain, regularly spaced pendant protected amino groups. Deprotection, accomplished without chain degradation, yielded -NH2 groups available for further reactions. The molecular structure of macromers and PEEs was investigated by 1H NMR and SEC. DSC and WAXS analyses showed that macromers and copolymers were semicrystalline and their T(m) increased with increase in the molecular weight of PCL segments. The inherent viscosity values (0.25-0.30 dL x g(-1)), together with SEC analysis results, indicated moderate polymerization degrees.     

Magnetic–Fluorescent Colloidal Nanobeads: Preparation and Exploitation in Cell Separation Experiments

Nanostructures displaying fluorescence and magnetic properties at the same time are potentially useful for achieving simultaneous bio‐separation and bio‐sensing (e.g., magnetic separation coupled with multiplexing optical detection of different tumour cell populations). Spherical nanobeads that display both fluorescent and magnetic features are reported; they are fabricated by grafting fluorescent oligothiophene molecules to an amphiphilic polymer that is then used to enwrap iron oxide nanoparticles, which acts as the magnetic domain. By tuning experimental conditions, control over the number of magnetic nanoparticles per bead and over the bead diameter (30–400 nm) was achieved. A cell separation efficiency of the level required for cell sorting applications is also reported.

     

β-Nitro-5,10,15-tritolylcorroles

Functionalization of the β-pyrrolic positions of the corrole macrocycle with -NO(2) groups is limited at present to metallocorrolates due to the instability exhibited by corrole free bases under oxidizing conditions. A careful choice of the oxidant can limit the transformation of corroles into decomposition products or isocorrole species, preserving the corrole aromaticity, and thus allowing the insertion of nitro groups onto the corrole framework. Here we report results obtained by reacting 5,10,15-tritolylcorrole (TTCorrH(3)) with the AgNO(2)/NaNO(2) system, to give mono- and dinitrocorrole derivatives when stoichiometry is carefully controlled. Reactions were found to be regioselective, affording the 3-NO(2)TTCorrH(3) and 3,17-(NO(2))(2)TTCorrH(3) isomers as the main products in the case of mono- and disubstitution, in 53 and 20% yields, respectively. In both cases, traces of other mono- and disubstituted isomers were detected, which were structurally characterized by X-ray crystallography. The influence of the β-nitro substituents on the corrole properties is studied in detail by UV-visible, electrochemical, and spectroelectrochemical characterization of these functionalized corroles. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations of the ground and excited state properties of these β-nitrocorrole derivatives also afforded significant information, closely matching the experimental observations. It is found that the β-NO(2) substituents conjugate with the π-aromatic system of the macrocycle, which initiates significant changes in both the spectroscopic and redox properties of the so functionalized corroles. This effect is more pronounced when the nitro group is introduced at the 2-position, because in this case the conjugation is, for steric reasons, more efficient than in the 3-nitro isomer.