Optimal Operations Management and Network Planning of a District Heating System with a Combined Heat and Power Plant

District heating plants are becoming more common in European cities. These systems make it possible to furnish users with warm water while locating the production plants in the outskirts having the double benefit of lowering the impact of pollution on the center of the city and achieving better conversion performances. In order to amortize the costs throughout the year, the system often includes a combined heat and power (CHP) plant, to exploit the energy during the summer as well, when the demand for warm water decreases. A linear programming model for the optimal resource management of such a plant is presented and some results for a real case are reported. A distribution network design problem is also addressed and solved by means of mixed integer linear programming.     

Identification of genotoxic compounds in the airborne particulate matter endowed by small aerodynamic diameter in the city of Catania (Italy)

Airborne particulate matter (PM) is one of the most important polluting factors in the atmosphere containing solid particles generated during the combustion processes. PM, due to the particle size, is easily inhaled and constitutes a potential hazard for the human health. We previously documented, using in vitro cell culture systems, cytogenetic damages caused by exposure to a non-fractionated PM in two different areas from the city of Catania (Sicily, Italy). In the present work, the PM was fractionated in six different sub-fractions, and the relative extractable organic matters (EOM) were analyzed in order to quantify the presence of Polycyclic Aromatic Hydrocarbons (PHAs), a well known class of genotoxic agents. More than 70% of the total EOM was found in the PM with aerodynamic diameters less than 3.5 microm (PM35), and about 60% of the total EOM was detected between PM0.14 and PM1.2. Also the large amount of all the analyzed PAHs were found between the PM0.14 and PM1.2. The obtained data indicates that the genotoxic effect previously shown on mammalian cells (Chinese hamster epithelial liver cells) should be due, in the large part, to the PM with smaller particle size, namely less than PM1.2.     

Thermal lens spectrometric determination of hexavalent chromium

The applicability of thermal lens spectrometry (TLS) for quantification and routine determination of hexavalent chromium was investigated by using a collinear dual beam thermal lens spectrometer. In aqueous solutions the LOD of 0.1 μg l⁻¹ was obtained for Cr(VI) by using 160 mW laser power. The performance of the technique was verified by the determination of hexavalent chromium in standard reference water samples (NIST SRM 1643a and NIST SRM 1643c) and comparing the results for Cr(VI) in CCA (Cr, Cu, As)-treated timber extracts to concentrations obtained by atomic absorption spectrometry (AAS). Good agreement between the TLS results and reported values for Cr(VI) in SRMs as well as AAS results for Cr(VI) in CCA-treated timbers confirmed that TLS is a reliable and accurate analytical technique applicable for the determination of Cr(VI) in aqueous solutions at concentration levels 0.5–100 μg l⁻¹.     

The effect of the anion on the physical properties of trihalide-based N,N-dialkylimidazolium ionic liquids

Low viscosity, high density trihalide-based 1-n-butyl-3-methylimidazolium ionic liquids have been prepared and characterised. Key physical properties (density, conductivity, melting point, refractive index, surface tension and diffusion coefficient) of the ionic liquids have been determined and are compared with those of other 1,3-dialkylimidazolium molten salts. The relationship between anion identity and the physical properties of the ionic liquids under investigation is discussed.     

Structure, bonding, and reactivity of Ti and Zr amidate complexes: DFT and X-ray crystallographic studies

Easily prepared and highly modular organic amide proligands have been used to synthesize a series of new bis(amidate)-bis(amido) Ti and Zr complexes via protonolysis. These complexes have been structurally characterized by NMR spectroscopy and X-ray crystallography. The solid-state molecular structures of these complexes indicate that the amidate ligands bind to the metal centers in an exclusively bidentate fashion, resulting in discrete monomeric species. Geometric isomerism in these species is highly dependent upon the steric characteristics of the proligands utilized in the synthesis. In solution, these complexes are observed to isomerize on the NMR time scale, with one isomer being predominant. Bonding in the bis(amidate)-bis(amido) complexes was investigated by DFT calculations. The geometric isomers predicted by theory matched the experimentally observed results, within experimental error. The orbitals associated with amidate-metal bonding are energetically well below the frontier orbitals. The HOMO in these complexes is a pi orbital associated with amido ligand-to-metal bonding character, while the LUMO in all cases is a vacant d orbital on the metal center.     

Critical percolation exploration path and SLE 6: a proof of convergence

It was argued by Schramm and Smirnov that the critical site percolation exploration path on the triangular lattice converges in distribution to the trace of chordal SLE ₆. We provide here a detailed proof, which relies on Smirnov’s theorem that crossing probabilities have a conformally invariant scaling limit (given by Cardy’s formula). The version of convergence to SLE ₆ that we prove suffices for the Smirnov–Werner derivation of certain critical percolation crossing exponents and for our analysis of the critical percolation full scaling limit as a process of continuum nonsimple loops. Research of Charles M.Newman was partially supported by the US NSF under grants DMS-01-04278 and DMS-06-06696.     

Synthesis of butyrolactones by nickel-catalyzed reductive cyanation of alkynols in water

One-pot catalytic synthesis of butyrolactones from alkynols under mild conditions is described here. The methodology involves the use of the K₂[Ni(CN)₄]/NaBH₄ system in presence of KCN and water. According to the experimental evidences, a possible mechanism pathway is suggested, which involves the nickel-catalyzed reductive cyanation of alkynol, followed by nitrile hydration, reduction of double bond and lactonization.     

Subharmonic generation in physical systems: An interaction-box approach

A so-called “interaction-box” formalism, which has recently been introduced to describe hysteresis in dynamical systems in the case of higher harmonic generation, is further discussed and generalized to describe the phenomenon of subharmonic generation. In this case, the increase in the periodicity of the response is reflected in the formation of multiple loops in the Effect (output) vs. Cause (input) diagrams. Conversely, we show how this type of response represents a sort of “signature” of the system, and can thus be employed to draw general conclusions about the features of the latter. A specific example of a nonlinear system is chosen to illustrate the approach, namely a vibrating cantilever beam with a breathing crack. Effect vs. Cause curves are calculated for this system in the presence of higher harmonics and subharmonics.     

Fast atom bombardment mass spectrometry of carbobenzyloxy-protected amino acids and peptides

The positive fast atom bombardment (FAB) mass spectra of 15 N-carbobenzyloxy derivatives of α-amino acids are presented together with those of some synthetic peptides containing other widely employed protecting groups. The data obtained allow a fragmentation pattern to be established for the N-carbobenzyloxy moiety and to obtain detailed structural information on the main fragment ions. A study of the ion current ratio vs. time pattern shows that important fragments derive from the parent protonated molecule through FAB-induced condensed-phase reactions.