Al2O3/ZrO2/Y3Al5O12 composites. A high-temperature mechanical characterization

An Al2O3/5 vol%·ZrO2/5 vol%·Y3Al5O12 (YAG) tri-phase composite was manufactured by surface modification of an alumina powder with inorganic precursors of the second phases. The bulk materials were produced by die-pressing and pressureless sintering at 1500 °C, obtaining fully dense, homogenous samples, with ultra-fine ZrO2 and YAG grains dispersed in a sub-micronic alumina matrix. The high temperature mechanical properties were investigated by four-point bending tests up to 1500 °C, and the grain size stability was assessed by observing the microstructural evolution of the samples heat treated up to 1700 °C. Dynamic indentation measures were performed on as-sintered and heat-treated Al2O3/ZrO2/YAG samples in order to evaluate the micro-hardness and elastic modulus as a function of re-heating temperature. The high temperature bending tests highlighted a transition from brittle to plastic behavior comprised between 1350 and 1400 °C and a considerable flexural strength reduction at temperatures higher than 1400 °C; moreover, the microstructural investigations carried out on the re-heated samples showed a very limited grain growth up to 1650 °C

Advances in the field of Nanostructured Ceramic Composites

In recent years, the production of ceramic composites having nanosized features is receiving increasing attention, as they demonstrated enhanced mechanical and/or functional performances as respect to conventional micronic materials [...

On the determination of constitutive parametersin a hyperelastic model for a soft tissue

The aim of this paper is to study a model of hyperelastic materials and itsapplications into soft tissue mechanics. In particular, we first determine an unbounded domain of the constitutive parameters of the model making our smoothstrain energy function to be polyconvex and hence satisfying the Legendre–Hadamard condition. Thus, physically reasonable material behaviour are described by our model with these parameters and a plently of tissues can betreated. Furthermore, we localize bounded subsets of constitutive parameters in fixed physical and very general bounds and then introduce a family of descrete stress–strain curves. Whence, various classes of tissues are characterized. Ourgeneral approach is based on a detailed analytical study of the first Piola–Kirchhoff stress tensor through its dependence on the invariants and on the constitutive parameters. The uniqueness of parameters for one tissue is discussed by introducing the notion of manifold of constitutive parameters, whichis locally represented by possibly different physical quantities. The advantage of our study is that we show a possible way to improve of the usual approachesshown in the literature which are mainly based on the minimization of a costfunction as the difference between experimental and model results

Serratiopeptidase reduces the invasion of osteoblasts by Staphylococcus aureus

Finding new strategies to counteract periprosthetic infection and implant failure is a main target in orthopedics. Staphylococcus aureus, the leading etiologic agent of orthopedic implant infections, is able to enter and kill osteoblasts, to stimulate pro-inflammatory chemokine secretion, to recruit osteoclasts, and to cause inflammatory osteolysis. Moreover, by entering eukaryotic cells, staphylococci hide from the host immune defenses and shelter from the extracellular antibiotics. Thus, infection persists, inflammation thrives, and a highly destructive osteomyelitis occurs around the implant. The ability of serratiopeptidase (SPEP), a metalloprotease by Serratia marcescens, to control S. aureus invasion of osteoblastic MG-63 cells and pro-inflammatory chemokine MCP-1 secretion was evaluated. Human osteoblast cells were infected with staphylococcal strains in the presence and in the absence of SPEP. Cell proliferation and cell viability were also evaluated. The release of pro-inflammatory chemokine MCP-1 was evaluated after the exposure of the osteoblast cells to staphylococcal strains. The significance of the differences in the results of each test and the relative control values was determined with Student’s t-test. SPEP impairs their invasiveness into osteoblasts, without affecting the viability and proliferation of bone cells, and tones down their production of MCP-1. We recognize SPEP as a potential tool against S. aureus bone infection and destruction

Proof of principle of a fuel injector based on a magnetostrictive actuator

One of the goals of modern internal combustion engines is the NOx-soot trade-off, and this would be better achieved by a better control of the fuel injection. Moreover, this feature can be also useful for high-performance hydraulic systems. Actual fuel injection technology either allows only the control of the injection time or it is based on very complex mechanical-hydraulic systems, as in the case of piezo-actuators. This work describes the basic steps that brought the authors to the realization of a concept fuel injector based on a Terfenol-D magnetostrictive actuator that could overcome the previous issues, being both simple and controllable. The study provides the design, development, and a feasibility analysis of a magnetostrictive actuator for fuel injection, by providing a basic magneto-static analysis of the actuator, the adaptation of a suitable standard fuel injector, and its experimental testing in a lab environment, with different shapes and amplitude of the reference signal to follow

Ribosomal RNA Pseudouridylation: Will Newly Available Methods Finally Define the Contribution of This Modification to Human Ribosome Plasticity?

In human rRNA, at least 104 specific uridine residues are modified to pseudouridine. Many of these pseudouridylation sites are located within functionally important ribosomal domains and can influence ribosomal functional features. Until recently, available methods failed to reliably quantify the level of modification at each specific rRNA site. Therefore, information obtained so far only partially explained the degree of regulation of pseudouridylation in different physiological and pathological conditions. In this focused review, we provide a summary of the methods that are now available for the study of rRNA pseudouridylation, discussing the perspectives that newly developed approaches are offering

Alkali-activation of marble sludge: Influence of curing conditions and waste glass addition

The use of marble sludge as precursor for new alkali activated materials was assessed studying three different curing conditions (air, humid and water immersion, respectively), after an initial curing at 60 °C for 24 h, and two glass powder fractions additions (2.5 and 5.0 vol%). Microstructural, physical (drying shrinkage, Fourier transform-infrared (FT-IR) spectroscopy, X-ray spectroscopy (XPS)), thermal (differential thermal analysis – thermogravimetric analysis, DTA-TGA) and mechanical (flexural and compressive strength) properties were investigated. Air curing was the most favourable atmosphere for mechanical properties development because it promotes Si-O-Si polymerization and gel densification, as demonstrated by FT-IR and FE-SEM observations, respectively. Satisfactory mechanical properties were achieved (18 MPa and 45 MPa, for flexural and compressive strength, respectively) in particular for glass containing mixtures. Moreover, glass powder addition significantly reduced drying shrinkage of air-cured samples because it operated as a rigid aggregate in the matrix and strengthened the formed gel

Phenotyping Key Fruit Quality Traits in Olive Using RGB Images and Back Propagation Neural Networks

To predict oil and phenol concentrations in olive fruit, the combination of back propagation neural networks (BPNNs) and contact-less plant phenotyping techniques was employed to retrieve RGB image-based digital proxies of oil and phenol concentrations. Fruits of cultivars (×3) differing in ripening time were sampled (∼10-day interval, ×2 years), pictured and analyzed for phenol and oil concentrations. Prior to this, fruit samples were pictured and images were segmented to extract the red (R), green (G), and blue (B) mean pixel values that were rearranged in 35 RGB-based colorimetric indexes. Three BPNNs were designed using as input variables (a) the original 35 RGB indexes, (b) the scores of principal components after a principal component analysis (PCA) pre-processing of those indexes, and (c) a reduced number (28) of the RGB indexes achieved after a sparse PCA. The results show that the predictions reached the highest mean R2 values ranging from 0.87 to 0.95 (oil) and from 0.81 to 0.90 (phenols) across the BPNNs. In addition to the R2, other performance metrics were calculated (root mean squared error and mean absolute error) and combined into a general performance indicator (GPI). The resulting rank of the GPI suggests that a BPNN with a specific topology might be designed for cultivars grouped according to their ripening period. The present study documented that an RGB-based image phenotyping can effectively predict key quality traits in olive fruit supporting the developing olive sector within a digital agriculture domain