Fracture Toughness Analysis of Advanced Ceramic Composite for Hip Prosthesis

The fracture behavior of a zirconia-toughened alumina-matrix composite (added with small amounts of mixed oxides) for ceramic hip joint prostheses has been evaluated with emphasis placed on the effect of environmental surface degradation in moist environment. Accelerated aging tests were performed up to 300 h in an autoclave operating at 121°C (under 0.1 MPa pressure) in vapor environment, which represents a quite severe environmental testing condition. Besides conventional fracture mechanics characterizations, including different types of fracture toughness test, microscopic insight into the effect of environmental surface degradation on toughness could be obtained according to Raman and fluorescence microprobe spectroscopy. The main outcomes of this study were as follows: (i) after 10-h autoclaving (according to ISO standard recommendation) no significant change of monoclinic volume fraction and fracture toughness could be detected; (ii) after very long exposure time (300 h) the monoclinic phase content increased and the surface fracture toughness decreased by approximately 30%, although it was still above the toughness level of pure alumina; and (iii) the bulk toughness was unaffected by autoclave exposure, independent of exposure time elongation.     

Sintering,high temperature strength and oxidation resistance of liquid-phase-pressureless-sintered SiC–AlN ceramics with addition of rare-earth oxides

SiC–AlN composites can be pressureless sintered with the addition of rare-earth oxides (RE = Y, Yb, Er, Lu, Ho, Sm, Ce) and without protective powder bed. Sintered bodies showed high density (≥97% T.D.) and were mainly composed by 2H SiC–AlN solid solution with additive containing grain boundary phases. The high temperature strength and oxidation resistance of the composites were also investigated and correlated with the cationic radii of the oxide additives. The flexural strength at 1500 °C increased from 269 MPa to 587 MPa as direct consequence of the rare-earth cationic radius decrease. The specific weight gain during oxidation at 1500 °C for 200 h showed the same behaviour, decreasing from 12.60 mg/cm² to 3.13 mg/cm².     

Fast three-dimensional nanoscale metrology in dual-beam FIB–SEM instrumentation

A quantitative surface reconstruction technique has been developed for the geometric characterization of three-dimensional structures by using a combined focused ion beam—scanning electron microscopy (FIB–SEM) instrument. A regular pattern of lines is milled at normal incidence on the sample to be characterized and an image is acquired at a large tilt angle. By analyzing the pattern under the tilted view, a quantitative estimation of surface heights is obtained. The technique has been applied to a test sample and nanoscale resolution has been achieved. The reported results are validated by a comparison with atomic force microscopy measurements.     

Synthesis,characterisation and properties of α,β-poly(N-2-hydroxyethyl)-dl-aspartamide-graft-maleic anhydride precursors and their stimuli-responsive hydrogels

A family of poly(amino acid)-maleic anhydride hydrogels were designed and synthesized. Water soluble polymeric precursors were prepared by partially substituting the hydroxyl groups of the α,β-poly(N-2-hydroxyethyl)-dl-aspartamide backbone with maleic anhydride, so as to provide double bonds for crosslinking and carboxylic acid groups for pH and electric field responsiveness. Reaction conditions (reactive mixture composition and catalysis) were systematically varied in order to obtain PHEA–MA precursors with different and reliable graft-maleic anhydride levels. PHEA–MA precursors were characterised by titration, Nuclear Magnetic Resonance (¹H NMR), Fourier-Transformed Infrared Spectroscopy (FTIR) and Size Exclusion Chromatography (SEC) for structural and molecular determination. Aqueous solutions of selected PHEA–MA precursors were subjected to gamma-irradiation at different irradiation doses and polymer to water concentrations in order to induce chemical crosslinking without the addition of crosslinking agents. The yield of crosslinking reactions was evaluated by solubility tests as well as the effect of ammonium persulphate, as assistant radical initiator for gamma crosslinking. Selected hydrogels were tested through swelling measurements to prove their pH and electric field responsiveness. Structural features of the different variants produced were related to the swelling behaviour.     

Controlling Cellular Uptake by Surface Chemistry,Size, and Surface Topology at the Nanoscale

Cell cytosol and the different subcellular organelles house the most important biochemical processes that control cell functions. Effective delivery of bioactive agents within cells is expected to have an enormous impact on both gene therapy and the future development of new therapeutic and/or diagnostic strategies based on single‐cell–bioactive‐agent interactions. Herein a biomimetic nanovector is reported that is able to enter cells, escape from the complex endocytic pathway, and efficiently deliver actives within clinically relevant cells without perturbing their metabolic activity. This nanovector is based on the pH‐controlled self‐assembly of amphiphilic copolymers into nanometer‐sized vesicles (or polymersomes). The cellular‐uptake kinetics can be regulated by controlling the surface chemistry, the polymersome size, and the polymersome surface topology. The latter is controlled by the extent of polymer–polymer phase separation within the external envelope of the polymersome.     

Simplified procedures for vibration serviceability analysis of footbridges subjected to realistic walking loads

This paper deals with the vibration serviceability analysis of footbridges subjected to realistic pedestrian traffic conditions, based on a probabilistic characterization of pedestrian-induced forces. The dynamic response to three different loading conditions is analysed through a non-dimensional approach, which permits the identification of the essential non-dimensional parameters governing the dynamic behaviour. Two simplified procedures are then proposed, founded on the sound definition of two coefficients, the Equivalent Amplification Factor and the Equivalent Synchronization Factor, which allow the evaluation of the vibration serviceability without requiring numerical analyses. Final applications confirm the efficiency of the proposed methods.     

Internal pressure and counterpunch action design in Y-shaped tube hydroforming processes: A multi-objective optimisation approach

In sheet metal forming most of the problems are multi-objective problems, generally characterised by conflicting objectives. A classical approach to investigate such kind of problems is focused on a combination of multiple objectives into a unique objective function to be optimised. Actually, in metal forming processes optimisation two main phases have to be developed in order to reach an optimal solution: the former is the modelling phase (definition of the design variables and objective function) and the latter concerns the computational aspect (numerical simulations or experiment to be developed). In this paper, an integration between numerical simulations, response surface methodology and Pareto optimal solution search techniques was applied in order to design a complex Y shaped tube hydroforming. In particular, the calibration of internal fluid pressure and counterpunch action was investigated with the aim to achieve three different quality objectives: minimization of thinning, reduction of underfilling and accuracy of the final fillet radius at the bulge zone corner.     

Discussion on the objective evaluation of virgin olive oil bitterness

The study aims at investigating the suitability of absorbance at 225 nm as an objective means to evaluate virgin olive oil (VOO) bitterness. Calculation of oleuropein score (OLS) using a standard curve instead of the so far employed K₂₂₅ value is proposed and a “taste index” based on the total phenol content determined by fluorimetry is examined as a complementary tool. Data from sensory evaluation of a series of VOO samples and RP-HPLC determination of phenolic compounds using diode array, fluorimetric or MS detection supported the applicability and merits of the introduced criteria. Phenol profiling using fluorescence detection (280 nm_excitation/320 nm_emission) became useful regarding oil bitterness. The presence of the non-fluorescent elenolic acid at 225 nm, indicated that the K₂₂₅ value is influenced by the presence of this non-bitter compound found at significant levels even in fresh oils. Our finding offers further ground to our proposal for the calculation of the “taste index”.     

Surface functionalization of cotton cellulose with glycidyl methacrylate and its application for the adsorption of aromatic pollutants from wastewaters

Cellulose material C1 was prepared by grafting of glycidyl methacrylate (GMA) in the presence of Fenton-type reagent. This one-pot procedure provided C1 with glycidyl isobutyrate branches. Glycidyl epoxide ring opening with water turned C1–C2 material branched with glycerol isobutyrate. So, C1 surface bears hydrophobic branches ending with the glycidyl group, while C2 surface presents hydrophilic branches ending with the glycerol group. The adsorption of aromatic polluting substances like phenol (Ph), 4-nitrophenol (pNPh), 2,4-dinitrophenol (dNPh), 2,4,6-trinitrophenol (picric acid, tNPh) and 2-naphtol (BN) from their water solutions was tested with C1, C2 and with the untreated cellulose material C0. Phenol adsorption did not occur. All the other aromatic molecules were removed in different amount both by C1 and C2. C1 and C2 showed different affinities towards nitrophenols and 2-naphtol. While C1 was much more effective for removing the hydrophobic 2-naphtol, C2 had higher adsorption capacity towards the hydrophilic nitrophenols, in agreement with their branches polarity, respectively.