Early anisotropic expansion of aluminium foam precursors

This work reports a detailed study on the early expansion (before the melting point) of powder metallurgical (PM) aluminium foam precursors and its influence on the intrinsic anisotropy existing in the final cellular structure of PM foams. Hot uniaxial compressed tablets, rectangular and cylindrical extruded profiles and thixocast PM precursors have been considered to evaluate the effect of the processing technique on the early expansion behaviour. An optical device has been used to register, in situ, the dissimilar expansion of the precursors in the three spatial directions. Cellular morphology has been examined by X-ray microtomography and correlated to expansion behaviour. Results demonstrated a high influence of the processing technique and its correlation with powder debonding in preferential directions which, in combination with the early TiH₂ decomposition, generates elongated cracks and causes an anisotropic expansion at early foaming stages. As a consequence, a remaining structural anisotropy is found in the final solid cellular material, even at high porosities. A discussion of the possible factors affecting this early expansion behaviour, complemented with possible solutions to minimize it, is provided in the paper.     

Stability of the antimicrobial activity of acetogenins from avocado seed,under common food processing conditions,against Clostridium sporogenes vegetative cell growth and endospore germination

Anticlostridial activity of acetogenins from avocado seed was further characterised, and their stability and effectiveness under food processing conditions, and in a model food system, studied for the first time. Isolated AcO‐avocadenyne (1) and AcO‐avocadene (2) showed anticlostridial potential, particularly the latter molecule. Enriched acetogenins extracts, obtained at laboratory scale (EAE) and semi‐commercially (Avosafe^®), presented similar MIC values (3.9–9.8 ppm) and a bacteriostatic effect. Extracts bioactivity showed resistance to heat (≤120 °C), high hydrostatic pressure (HHP; 300–600 MPa, 3–6 min, 25 °C) and salt (≤3% w/v). In addition, the extract was most stable at pH ≥ 7.0 and potency against endospores increased after HHP treatment and exposure to pH 9.5, suggesting a positive effect on solubility or structure of particular acetogenins. In a model food system processed by HHP, acetogenins were retained; however, initial quantities gradually declined by 63% and 32% at 25 and 4 °C, respectively, at the end of the storage period (42 days). Most stable molecules (persediene (4) > persenones > AcO‐avocadene (2)) possess a keto or trans‐enone group at C‐4 in the aliphatic chain, which could support hydrogen donation to surrounding carbon atoms and confer antioxidant activity. Active endospores were completely inhibited by 5000 ppm Avosafe^® in the model food system (37 °C, 72 h) and lower concentrations (500–1000 ppm) resulted in 1–2 log reduction of a 3 log inoculum target. Efficacy information generated in the present work is considered crucial to improve scientific knowledge on spore inhibition properties of avocado acetogenins.     

The effect of ultra-thin graphite on the morphology and physical properties of thermoplastic polyurethane elastomer composites

Composites of thermoplastic polyurethane (TPU) and ultra-thin graphite (UTG) with concentrations ranging from 0.5 wt.% to 3 wt.% were prepared using a solution compounding strategy. Substantial reinforcing effects with increased loadings are achieved. Compared to neat TPU, values for storage modulus and shear viscosity are enhanced by 300% and 150%, respectively, for UTG concentrations of 3 wt.%. Additionally, an enhancement of thermal properties is accomplished. The crystallization temperature and thermal stability increased by 30 °C and 10 °C, respectively, compared to neat TPU. Furthermore, the use of oxidized UTG (UTGO) with its added functional oxygen groups suggests the presence of chemical interactions between UTG and TPU, which additionally impact on the thermal properties of the corresponding composites. Controlling the oxidation degree, thus offers further possibilities to obtain composites with tailored properties. The presented approach is straightforward, leads to homogeneous TPU-UTG composites with improved materials properties and is especially suitable for commercial UTG materials and further up-scaled production.     

Inhibition of colon adenocarcinoma cell proliferation by flavonols is linked to a G2/M cell cycle block and reduction in cyclin D1 expression

The moderate consumption of red wine has been proposed to reduce the incidence of colorectal cancer. Its anti-cancer action my in part be mediated by the actions of polyphenols on colon cancer epithelial cells. We show that a red wine phenolic (50 μg/ml) extract devoid of anthocyanins (removed to reflect polyphenol bioavailability to the large intestine) and the major red wine flavonols quercetin, myricetin, laricitrin and syringetin (50 μM) are capable of inhibiting the proliferation of colorectal epithelial adenocarcinoma cells. This anti-proliferative activity was partly mediated by the direct cytotoxic actions of flavonols and also their ability to cause a significant cell cycle blockage in G2/M. The anti-proliferative effects induced by flavonols were preceded, in most cases, by a strong and significant reduction of cyclooxygenase-2 (COX-2) and cyclin D1 expression. These results indicate that the observed inverse correlation between colon cancer and a moderate red wine intake may be partly mediated by the actions of red wine flavonols on the growth of cancer cells.     

Comparison of Peleg and Azuara et al. models in the modeling mass transfer during pile salting of goat sheets

Application of the Peleg and Azuara et al. models for describing mass transfer during pile salting of goat sheets using different mixtures of NaCl, KCl, CaCl₂ and MgCl₂ was investigated The high coefficient of determination (R² > 0.97 and R² > 0.95 for Peleg and Azuara et al. models, respectively) and the modulus of mean relative errors (MRE < 10% for both models) indicated the acceptability of both Peleg and Azuara et al. models for predicting both moisture loss and salt uptake. The equilibrium moisture and salt contents were estimated using Peleg rate constants and Azuara et al. model parameters. Equilibrium moisture (x_w) and salt contents (x_s) varied from 0.522 to 0.860 g water/g db and from 0.311 to 0.352 g NaCl/g db respectively. Multiple comparison of means showed that x_w and x_s predicted by the Peleg model were lower than those estimated by the Azuara et al. model. The values differed by 1.86–13.6% for x_w and by 1.13–10.57% for x_s.     

Evaluation of the light line displacement location for object shape detection

Abstract

The ability for detecting the location of the displacement of a projected light line with subpixel resolution is examined. This evaluation is carried out for measuring a three-dimensional object shape. The technique for measuring the object shape is based on the light line projection. To determine the height data, displacement of the light line is measured on a reference point and on the object surface. This line displacement is measured by approximating the line intensity to a continuous function by the least-squares method, the Gaussian approximation and the Bezier curves method. The light line position is defined by calculating a maximum from this continuous function. To evaluate these three methods it is necessary to know the best accuracy of the experimental results. To achieve this, the results extracted by these methods are compared with a contact method. This contact method is made with a coordinate-measuring machine. The rms error is calculated using data from these three methods and the data from the contact method to carry out this evaluation. Height data are obtained with great accuracy from the method, which has a better rms value. The time necessary for processing a light line using each of these three methods is also presented. In addition to this information, a correlation coefficient is presented giving the deviation of each function generated by these methods. This line projection technique has a great potential because a very simple experimental set-up is used which is inexpensive. This evaluation is tested with complicated objects and its experimental results are presented.     

Enhanced Performance of Nanostructured Coatings for Drilling by Droplet Elimination

Cutting tool performance is mainly characterized by material substrate, cutting edge geometry, and coating, and also by a good choice of the cutting parameters, mainly cutting speed, depth of cut, and feed. In drilling a good choice of substrate/coating can reduce production costs per hole cut by 50%. Coatings evolution has gone from monolayer to nanostructured and/or nanometric-scale multilayer coatings. These are used because of their high hardness, good corrosion and oxidation resistance, and thermal stability. Cutting edge preparation on the one hand and droplet elimination after the coating process on the other are important issues for reaching a good tool/coating performance, being a key issue. In this article a series of coatings for drilling low and medium carbon alloyed steels are presented, along with their performance. Validation tests were carried out on steel 42CrMo4, very often used in the automotive sector. Seven coatings were tested, including AlCrSiN, µAlTiN, TiAlCrN, AlTiCrN, AlCrN, AlTiSiN, and TiAlSiN. Flank wear, evolution of drilling thrust force and torque, damage on cutting edge faces on primary cutting edge, and behavior of drill bit secondary edges were studied. A final elimination of droplets by drag grinding was performed in several cases. Process monitoring, scanning electron microscope (SEM) microscopy, and energy-dispersive X-ray (EDX) analysis were used, concluding that the best results were for µAlTiN, TiAlSiN, and AlTiSiN. Reasons for the good behavior are the good surface finishing after droplet elimination and the high thermal stability of these protective layers.     

Investigation of solar hybrid system with concentrating Fresnel lens,photovoltaic and thermoelectric generators

An experimental model of a solar hybrid system including photovoltaic (PV) module, concentrating Fresnel lens, thermoelectric generator (TEG), and running water heat extracting unit was created and studied. The PV module used was of c‐Si and TEG of Bi₂Te₃; the Fresnel lens (solar concentrator) and TEG share an optical train, whereas PV module was illuminated separately with non‐concentrated light. Heat extracting unit operated in thermo siphon mode. In climatic conditions of Mexico (Queretaro, 20^o of North latitude, summer time), the Fresnel lens accepted 120 W of solar radiation power, and the system generated 7.0 W of electric power and 30 W of thermal one. The discussion is made of the possible characteristics of a hypothetical hybrid system where all its elements share the same optical train. Copyright © 2016 John Wiley & Sons, Ltd.     

Numerical Study of the Transient Cooling Process of Water Storage Tanks under Heat Losses to the Environment

The unsteady laminar heat transfer and fluid flow phenomena inside a water storage tank during its static mode of operation and submitted to heat losses to the environment has been investigated by means of CFD and heat transfer numerical simulations. A parametric study has been carried out considering several situations and varying the aspect ratio, insulation thickness, initial temperature, and tank volume. In order to characterize the cooling process, a nondimensional analysis has been performed. From the analysis of the results of several detailed numerical simulations, correlations for the Nusselt number at the lateral, top, and bottom walls have been obtained. The verification of the mathematical model assumed, together with the verification and validation of the results, have also been pointed out.