Development of calibration models for quality control in the production of ethylene/propylene copolymers by FTIR spectroscopy,multivariate statistical tools,and artificial neural networks

Principal component regression (PCR), partial least squares (PLS), StepWise ordinary least squares regression (OLS), and back‐propagation artificial neural network (BP‐ANN) are applied here for the determination of the propylene concentration of a set of 83 production samples of ethylene–propylene copolymers from their infrared spectra. The set of available samples was split into (a) a training set, for models calculation; (b) a test set, for selecting the correct number of latent variables in PCR and PLS and the end point of the training phase of BP‐ANN; (c) a production set, for evaluating the predictive ability of the models. The predictive ability of the models is thus evaluated by genuine predictions. The model obtained by StepWise OLS turned out to be the best one, both in fitting and prediction. The study of the breakdown number of samples to be included in the training set showed that at least 52 experiments are necessary to build a reliable and predictive calibration model. It can be concluded that FTIR spectroscopy and OLS can be properly employed for monitoring the synthesis or the final product of ethylene–propylene copolymers, by predicting the concentration of propylene directly along the process line. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mode I Fracture Resistance of a Laminated Fiber-Reinforced Ceramic

The mode I fracture resistance of a ceramic matrix composite has been measured. Simultaneous observations have revealed that the resistance is dominated by frictional dissipation upon the pullout of fibers that fracture in the crack wake off the crack plane. Numerical and analytical crack growth simulations have been compared with the experimental results. One important feature in this comparison concerns the occurrence of large-scale bridging. With these effects taken into account, the simulations and the experiments are found to be in good correspondence for acceptable magnitudes of the interface sliding stress.     

The morphological properties of PP coextruded tape fabrics

In the field of self‐reinforced composites many researchers have focused their attention on the coextruded tapes composed of polypropylene core and PP/PE copolymer skin. Two similar commercial fabrics (P and T) have been compared in respect of their peel resistance. For both materials, peel resistance has a periodic trend that regularly follows fabric weave style. T has demonstrated an average peel resistance and a well‐bonded area slightly greater than P. Skin/core interfacial properties have been investigated and a crosscheck between differential scanning calorimetry (DSC) and Raman spectroscopy has been adopted to understand the influence of skin structure on consolidated laminate. DSC curves exhibit three melting peaks during first heating for both fabrics, corresponding to copolymer, skin/core interface, and core melting. After consolidation at 140°C stretching‐induced superstructure and PP crystallinity degree are preserved. The presence of PP/PE copolymer + PE blend only in fabric P has been pointed out and PE content has been calculated. POLYM. ENG. SCI., 56:727–734, 2016. © 2016 Society of Plastics Engineers     

The Role of Cytoskeleton Revealed by Quartz Crystal Microbalance and Digital Holographic Microscopy

The connection between cytoskeleton alterations and diseases is well known and has stimulated research on cell mechanics, aiming to develop reliable biomarkers. In this study, we present results on rheological, adhesion, and morphological properties of primary rat cardiac fibroblasts, the cytoskeleton of which was altered by treatment with cytochalasin D (Cyt-D) and nocodazole (Noc), respectively. We used two complementary techniques: quartz crystal microbalance (QCM) and digital holographic microscopy (DHM). Qualitative data on cell viscoelasticity and adhesion changes at the cell–substrate near-interface layer were obtained with QCM, while DHM allowed the measurement of morphological changes due to the cytoskeletal alterations. A rapid effect of Cyt-D was observed, leading to a reduction in cell viscosity, loss of adhesion, and cell rounding, often followed by detachment from the surface. Noc treatment, instead, induced slower but continuous variations in the rheological behavior for four hours of treatment. The higher vibrational energy dissipation reflected the cell’s ability to maintain a stable attachment to the substrate, while a cytoskeletal rearrangement occurs. In fact, along with the complete disaggregation of microtubules at prolonged drug exposure, a compensatory effect of actin polymerization emerged, with increased stress fiber formation.     

Solid Yttria-Stabilized Zirconia Films by Pulsed Chemical Vapor Deposition from Metal-organic Precursors

A pulsed chemical vapor deposition from metal-organic precursors (MOCVD) system was used to produce solid zirconia, and yttria-stabilized zirconia (YSZ) films. A total of six candidate metal-organic precursors for zirconia and three for yttria were investigated. Three precursor solutions for YSZ proved suitable for pulsed-MOCVD processing. Layers were deposited on metal, alumina, and porous nickel cermet substrates. Under optimal deposition conditions, precursor conversion efficiency of 90% was achieved using a solution of 3.74 vol% zirconium 2-methyl-2-butoxide + 0.42% yttium methoxyethoxide in toluene. The film growth rate was 7.5 μm·h⁻¹ at 525°C deposition temperature. Two alkoxide precursors produced YSZ layers with material costs under $0.50/(μm·cm²).     

The influence of consolidation and artificial weathering on all‐PP composite behavior

The purpose of this work was to evaluate the effect of consolidation parameters on the mechanical properties of all‐polypropylene composites. Consolidation time does not induce any significant influence, whereas processing temperature and in particular coextruded tape characteristics deeply affect laminate performance. The DSC analysis demonstrated that the proximity of copolymer and homopolymer melting points results in a reduction in the operating window. This suggests the implementation of a more effective temperature control during thermoforming to avoid reinforcement relaxation and localized melting. Artificial weathering was conducted under noon summer light condition to assess the effect of ultraviolet exposure on laminates. After 100 and 250 h, sample performance drops significantly, with overall strength and elongation reduction up to 70 and 88%, respectively. Low molecular weight by‐products were identified using Raman spectroscopy on specimens surface, confirming the mechanical property decrement due to photo‐oxidation process. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41283.     

Technique based on LED multispectral imaging and multivariate analysis for monitoring the conservation state of the Dead Sea Scrolls

The aim of this project is the development of a noninvasive technique based on LED multispectral imaging (MSI) for monitoring the conservation state of the Dead Sea Scrolls (DSS) collection. It is well-known that changes in the parchment reflectance drive the transition of the scrolls from legible to illegible. Capitalizing on this fact, we will use spectral imaging to detect changes in the reflectance before they become visible to the human eye. The technique uses multivariate analysis and statistical process control theory. The present study was carried out on a "sample" parchment of calfskin. The monitoring of the surface of a commercial modern parchment aged consecutively for 2 h and 6 h at 80 °C and 50% relative humidity (ASTM) was performed at the Imaging Lab of the Library of Congress (Washington, DC, U.S.A.). MSI is here carried out in the vis-NIR range limited to 1 μm, with a number of bands of 13 and bandwidths that range from about 10 nm in UV to 40 nm in IR. Results showed that we could detect and locate changing pixels, on the basis of reflectance changes, after only a few "hours" of aging.     

Compromised Biomechanical Properties,Cell–Cell Adhesion and Nanotubes Communication in Cardiac Fibroblasts Carrying the Lamin A/C D192G Mutation

Clinical effects induced by arrhythmogenic cardiomyopathy (ACM) originate from a large spectrum of genetic variations, including the missense mutation of the lamin A/C gene (LMNA), LMNA D192G. The aim of our study was to investigate the biophysical and biomechanical impact of the LMNA D192G mutation on neonatal rat ventricular fibroblasts (NRVF). The main findings in mutated NRVFs were: (i) cytoskeleton disorganization (actin and intermediate filaments); (ii) decreased elasticity of NRVFs; (iii) altered cell–cell adhesion properties, that highlighted a strong effect on cellular communication, in particular on tunneling nanotubes (TNTs). In mutant-expressing fibroblasts, these nanotubes were weakened with altered mechanical properties as shown by atomic force microscopy (AFM) and optical tweezers. These outcomes complement prior investigations on LMNA mutant cardiomyocytes and suggest that the LMNA D192G mutation impacts the biomechanical properties of both cardiomyocytes and cardiac fibroblasts. These observations could explain how this mutation influences cardiac biomechanical pathology and the severity of ACM in LMNA-cardiomyopathy.     

Delamination Cracking in a Laminated Ceramic-Matrix Composite

Delamination crack propagation has been investigated in a laminated fiber-reinforced ceramic-matrix composite. The crack growth initiation resistance has been shown to be dominated by the critical strain energy release rate for the matrix. However, the resistance increases with crack extension because of bridging effects associated with intact fibers and, in some cases, intact segments of matrix. The delamination cracks also assume a steady-state trajectory within a 0° layer close to the 0°/90° interface.     

Microstructural Studies of the Interfacial Zone of a SiC-Fiber-Reinforced Lithium Aluminum Silicate Glass-Ceramic

Transmission electron microscopy studies have been conducted on interfaces in a lithium aluminum silicate/SiC-fiberreinforced composite. In the as-processed state, interphases of amorphous C and carbides of Nb have been confirmed, with circumferential thermal debonds evident in the C layer. After heat treatment in air at 800°C, the C is found to be replaced by amorphous SiO₂, and the carbides of Nb replaced by oxides. The SiO₂ thickens with exposure time and typically contains circumferential separations. Some Mg and Al diffusion also accompanies the heat-treatment process and eventually leads to the formation of MgO and Mg silicates in the interfacial zone.