Stress concentration in steel bridge orthotropic decks

The structural behaviour of orthotropic steel decks is characterized by the complex interaction between its components (deck plate, ribs and floorbeams) and also by the interaction between the structure, the pavement and the vehicle’s wheels tyres. Stress concentration resulting from out-of-plane bending of deck components at typical welded joints can make these structures quite susceptible to traffic-induced fatigue cracks. This paper addresses some of these issues through numerical modeling of orthotropic decks with trapezoidal closed ribs, via finite element method and elastic analysis of the structure under heavy vehicle wheel loading. The numerical model was calibrated with experimental results obtained from laboratory tests on a deck model. The obtained numerical results lead to a better understanding of the complex structural behaviour of slender orthotropic decks, with emphasis on the stress distribution and concentration at the rib to deck plate welded connection. A parametric analysis was performed to determine possible and rational combinations of the geometric parameters leading to the lowest values of stress peaks and the best consequent fatigue performance of the focused welded connection. Hence, the overall output can be addressed towards a safe and rational design as far as fatigue life is concerned.     

DSC study of the cure kinetics during nanocomposite formation: Epoxy/poly(oxypropylene) diamine/organically modified montmorillonite system

The effect of an organically modified montmorillonite (OMMT) on the curing kinetics of a thermoset system based on a bisphenol A epoxy resin and a poly(oxypropylene)diamine curing agent were studied by means of differential scanning calorimetry (DSC) in isothermal and dynamic (constant heating rate) conditions. Montmorillonite and prepared composites were characterized by X‐ray diffraction analysis (XRD) and simultaneous differential scanning calorimetry–thermogravimetric analysis (DSC–TGA). Analysis of DSC data indicated that the presence of the filler has a very small effect on the kinetics of cure. A kinetic model, arising from an autocatalyzed reaction mechanism, was applied to the DSC data. Fairly good agreement between experimental and modeling data was obtained. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 550–557, 2006     

Isothermal and nonisothermal cure kinetics of an epoxy/poly(oxypropylene)diamine/octadecylammonium modified montmorillonite system

The effect of an octadecylammonium‐exchanged montmorillonite on the curing kinetics of a thermoset system based on a bisphenol A epoxy resin and a poly(oxypropylene)diamine curing agent were studied with differential scanning calorimetry (DSC) in isothermal and dynamic (constant‐heating‐rate) conditions. Montmorillonite and the prepared composites were characterized by X‐ray diffraction analysis and simultaneous DSC and thermogravimetric analysis. The analysis of the DSC data indicated that the intercalated octadecylammonium cations catalyzed the epoxy–amine polymerization. A kinetic model, arising from an autocatalyzed reaction mechanism, was applied to the DSC data. Fairly good agreement between the experimental data and the modeling data was obtained. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1765–1771, 2006     

Intracellular production of a major cytomegalovirus antigenic protein in the methylotrophic yeast Pichia pastoris

We have previously shown that single or multiple epitopes of the major human cytomegalovirus (HCMV) antigens, produced as fusion proteins in prokaryotes can be valuable diagnostic material in the serology of HCMV infection. In this work we moved to a eukaryotic system, to produce one of the most immunogenic HCMV antigens, ppUL44 (also called pp52 due to its apparent molecular size on acrylamide gels), as a non-fusion protein, in an attempt to eliminate some non-specific reactivity of human sera with bacterial carrier proteins. We expressed the DNA encoding ppUL44 in a highly efficient expression system based on the methylotrophic yeast, Pichia pastoris. Good levels of intracellular, soluble pp52 were produced. We observed an indistinguishable pattern of the yeast pp52 from the viral native protein in immunoblotting and a good reactivity with human sera.     

Food wastes and sewage sludge as feedstock for an urban biorefinery producing biofuels and added-value bioproducts

The updated Bioeconomy Strategy document “A sustainable bioeconomy for Europe: strengthening the connection between economy, society and the environment”, which was issued by the European Commission in October 2018, encourages the exploitation of organic wastes according to a pyramidal hierarchy in which the extraction of valuable biomolecules, which will be used as they are or as precursors of high-added-value compounds, is a priority in biofuel production. This review considers a biorefinery platform in which food waste and sewage sludge are adopted to produce volatile fatty acids (VFAs) through a dark fermentation process. VFA fermentation is optimized by slightly acid pH (6–7), short hydraulic retention time (1–7 days) and high organic load rate (more than 10 gTS L⁻¹ d⁻¹). Attention has been focused on VFA exploitation for polyhydroxyalkanoate (PHA) production via a ‘feast and famine’ strategy performed in sequencing batch reactors. The obtained PHA yields are around 0.4–0.5 gPHA gCOD⁻¹. Moreover, VFAs allow for the production of biofuels, such as hydrogen and methane, through single- or double-staged anaerobic digestion. Innovative bioelectrochemical upgrade strategies for biogas helps producers to obtain biomethane for the automotive sector. Moreover, biogas has recently been tested for the production of polyhydroxybutyrate, a biodegradable and biocompatible thermoplastic made by microorganisms from C1 carbon sources (CO₂ and CH₄). Digestates from anaerobic bioreactors are still rich in nitrogen and phosphorus compounds. These latter compounds have been identified as critical raw materials due to their low availability in the European Union and to increasing demand from the growing global population. Thus, nutrient recovery from digestate allows users to close the loop of the ‘circular economy’ approach. © 2019 Society of Chemical Industry     

Core − shell microgels with controlled structural properties

Microgels have gained great attention in the biomedical field for their wide application in diagnostic and drug delivery systems. The bulk properties as well as the surface features of these particular microparticles define their final performance. In particular, multifunctional microgels with complex architectures have been widely used in multiplex assays for their favourable capability to accommodate encoding systems and anchoring groups for probes to capture circulating targets by simply changing synthesis parameters. In this work a limited set of fluorescent encoded poly(ethyleneglycol) based microgels, of size ranging between 0.5 and 1.3 µm, with a core ? shell architecture were obtained by combining precipitation and seeded polymerizations. Here we demonstrate the possibility of tailoring and controlling the bulk and surface properties according to the synthesis by fluorescence imaging and pH titrations. Concerning the structural characterization, we adopted a method to calculate polymer fraction volumes from AFM images and combined these with equilibrium swelling theory (Peppas–Merrill equation) to determine the mesh size of the microgels. Surface composition was probed by X‐ray photoelectron spectroscopy directly on freeze‐dried microgels. In such a way we were able to describe the organizations of the different adlayers also in response to pH, highlighting the possibility of some overlap of the adlayers representing physical barriers at the boundaries of each shell. © 2016 Society of Chemical Industry