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Pore-scale modelling is appealing for investigating and obtaining macroscale constitutive equations for multiphase porous medium systems, because this approach bridges the macroscopic and microscopic scales. In this study, we develop a method to simulate and study the dissolution of non-aqueous phase liquid (NAPL) blobs; accurately quantifying NAPL mass transfer is crucial for modelling decontamination studies faithfully. We simulate a random packing of spheres and a residual NAPL distribution by matching macroscopic morphological descriptors of an experimental NAPL distribution; then we simulate single-phase flow by using a lattice-Boltzmann approach. Finally we numerically solve the advection-diffusion equation in the pore space to simulate mass transfer and transport of the dissolved components. Based upon different simulation results, we evaluate the sensitivity of the mass transfer coefficient with respect to two non-dimensional parameters and compare the simulation results to existing empirical relationships.

The conformational behavior of four [Ln(DOTA)(H(2)O)](-) systems (Ln = La, Gd, Ho, and Lu) has been characterized by means of ab initio calculations performed in vacuo and in aqueous solution, the latter by using the polarizable continuum model (PCM). Calculated molecular geometries and conformational energies of the [Ln(DOTA)(H(2)O)](-) systems, and interconversion mechanisms, barriers, and (13)C NMR spectra of the [Lu(DOTA)](-) complex are compared with experimental values. For each system, geometry optimizations, performed in vacuo and in solution at the HF/3-21G level and using a 46+4f(n) core electron effective core potential (ECP) for lanthanides, provide two minima corresponding to a square antiprismatic (A) and an inverted antiprismatic (IA) coordination geometry. All the systems are nonacoordinated, with the exception of the IA isomer of the Lu complex that, from in solution calculations, is octacoordinated, in agreement with experimental data. On comparing the in vacuo relative free energies calculated at different theory levels it can be seen that the nonacoordinated species dominates at the beginning of the lanthanide series while the octacoordinated one does so at the end. Furthermore, on passing along the series the IA isomer becomes less and less favored with respect to A and for the Lu complex a stabilization of the IAisomer is observed in solution (but not in vacuo), in agreement with the experimental data. Investigation of the A<-->IA isomerization process in the [Lu(DOTA)](-) system provides two different interconversion mechanisms: a single-step process, involving the simultaneous rotation of the acetate arms, and a multistep path, involving the inversion of the cyclen cycle configuration. While in vacuo the energy barrier for the acetate arm rotation is higher than that involved in the ring inversion (23.1 and 13.1 kcal mol(-)(1) at the B3LYP/6-311G level, respectively), in solution the two mechanisms present comparable barriers (14.7 and 13.5 kcal mol(-)(1)), in fairly good agreement with the experimental values. The NMR shielding constants for the two isomers of the [Lu(DOTA)](-) complex have been calculated by means of the ab initio GIAO and CSGT methods, and using a 46-core-electron ECP for Lu. The calculated (13)C NMR chemical shifts are in close agreement with the experimental values (rms 3.3 ppm, at the HF/6-311G level) and confirm the structural assignment of the two isomers based on experimental NMR spectra in solution. The results demonstrate that our computational approach is able to predict several physicochemical properties of lanthanide complexes, allowing a better characterization of this class of compounds for their application as contrast agents in medical magnetic resonance imaging (MRI).

The performance of the supercritical fluid extraction (SFE) technique to obtain a new and more appropriate model support for PCDD/F formation studies was investigated. To characterize fly ash and model supports and relate their chemical-physical properties, surface area and pore size were determined. To evaluate the influence on reactivity of the different model supports with respect to raw fly ash, a kinetic study of the thermal behavior of dibenzofuran (DF) was performed. Rate constants as well as the activation and thermodynamic parameters for the different systems were also compared. The model support obtained from SFE was very similar to raw fly ash from the structural, physical-chemical, and kinetic points of view.

Ligand binding by the aryl hydrocarbon receptor (AhR), a member of the bHLH-PAS family of transcriptional regulatory proteins, has been mapped to a region within the second 'PAS' domain, a conserved sequence motif first discovered in the Per-ARNT-Sim family of proteins. In addition to the bacterial photoactive yellow protein (PYP), which had been proposed as a structural prototype for the three dimensional fold of PAS domains, two crystal structures of the PAS domain have recently been determined: the human potassium channel HERG and the heme binding domain of the bacterial O(2) sensing FixL protein. The three structures reveal a highly conserved structural framework in evolutionary rather distant PAS domains, provide a more general view of how these domains can recognize their ligands and suggest a structure-function relationship that we exploited to build a three-dimensional model of the ligand binding domain (LBD) of the mouse aryl hydrocarbon receptor (mAhR). The model allowed us to putatively identify the residues responsible for the recognition of polychlorinated dibenzo-p-dioxins (PCDDs) by AhR receptors and to formulate an hypothesis on the signal transduction mechanism.

The organic fraction of a sludge from a wastewater biological treatment plant is characterized by the total organic carbon, TOC, content, cyclohexane and toluene extractions, and thermal desorptions in nitrogen and air flow at different temperatures. The inorganic fraction is characterized by water extraction, FT-IR spectroscopy, thermogravimetric analysis, and scanning electron microscopy/energy dispersion X-ray analysis. The thermal degradation rate of organic carbon is studied in batch experiments in air, in the 250-500 degrees C temperature range. The sample TOC is used to measure the decrease of reagent concentration with time. The TOC vs time data are well fitted by a generalized kinetic model, previously proposed for the MSWIs fly ash thermal degradation. The rate constants of the immediate carbon gasification, k2, and of the dissociative oxygen chemisorption, k1, followed by C(O) intermediate gasification, k3, together with activation and thermodynamic parameters are calculated. The rate determining step is the C(O) oxidation. The influence of desorbed or extracted organic compounds on kinetics and the role of the C(O) formation in explaining the reaction mechanism as well as the comparison with fly ash kinetics are discussed.

The synergy of the micro FT-IR (Fourier Transform-Infrared) and SEM-EDX (Scanning Electron Microscopy-Energy Dispersive X-ray) techniques has been shown to be particularly helpful and effective for the characterization of inorganic compounds in fly ashes. The experimental data obtained by these techniques have been interpreted in comparison with those of other techniques. The presence of calcium carbonate, some sulfates, ammonium nitrate, calcium hydrogen phosphate, some chlorides, some oxides and aluminium silicates have been verified.