Oxygen permeance: a method applied to modified atmosphere packages containing fresh plant foods

A method to determine the oxygen content and oxygen permeance of composite packages is described. It can be used for packages comprising materials of different permeability, or ones that have pinhole or sealing defects. The method requires little specialized apparatus and is well‐suited to the determination of the temperature coefficient of permeance for a package. The results are relevant to the design and quality control of modified atmosphere packaging for respiring fresh vegetables. Copyright © 1999 John Wiley & Sons, Ltd.     

Physiochemical Changes of Starch During Maize Tortilla Production

The physiochemical changes of starch in maize tortillas and their intermediate products commercially processed by the traditional way have been determined. Samples of maize, nixtamal, dough or masa, tortilla and nejayote (steep liquor) were analyzed. The samples were assayed for water absorption index (WAI), resistant starch (RS), X-ray diffraction patterns, viscosity and with Differential Scanning Calorimetry (DSC). Enthalpy of fusion (ΔH), initial temperature (T_o) and transition temperature (T_p) of gelatinization were obtained from DSC curves. Resistant starch contents increased as the products advanced in the process. Significant differences (p > 0.05) in the fusion enthalpy values of maize, nixtamal and masa could not be found. X-ray diffraction patterns of maize, nixtamal and masa did not show significant changes; however, when masa was transformed into tortillas there was a large loss in crystallinity. The viscoamylograph peak viscosities increased from maize to masa and decreased drastically in tortillas. The data showed that the tortilla baking stage caused the most pronounced changes in starch.     

Potential Anti-Metastatic Role of the Novel miR-CT3 in Tumor Angiogenesis and Osteosarcoma Invasion

Osteosarcoma (OS) is the most common primary bone tumor mainly occurring in young adults and derived from primitive bone-forming mesenchyme. OS develops in an intricate tumor microenvironment (TME) where cellular function regulated by microRNAs (miRNAs) may affect communication between OS cells and the surrounding TME. Therefore, miRNAs are considered potential therapeutic targets in cancer and one of the goals of research is to accurately define a specific signature of a miRNAs, which could reflect the phenotype of a particular tumor, such as OS. Through NGS approach, we previously found a specific molecular profile of miRNAs in OS and discovered 8 novel miRNAs. Among these, we deepen our knowledge on the fifth candidate renamed now miR-CT3. MiR-CT3 expression was low in OS cells when compared with human primary osteoblasts and healthy bone. Through TargetScan, VEGF-A was predicted as a potential biological target of miR-CT3 and luciferase assay confirmed it. We showed that enforced expression of miR-CT3 in two OS cell lines, SAOS-2 and MG-63, reduced expression of VEGF-A mRNA and protein, inhibiting tumor angiogenesis. Enforced expression of miR-CT3 also reduced OS cell migration and invasion as confirmed by soft agar colony formation assay. Interestingly, we found that miR-CT3 behaves inducing the activation of p38 MAP kinase pathway and modulating the epithelial-mesenchymal transition (EMT) proteins, in particular reducing Vimentin expression. Overall, our study highlights the novel role of miR-CT3 in regulating tumor angiogenesis and progression in OS cells, linking also to the modulation of EMT proteins.     

Effect of processing additives on (bio)degradability of film-blown poly(ε-caprolactone)

Poly(ε-caprolactone)s (PCL) with slip masterbatch, Erucamide, SiO₂ and Erucamide + CaCO₃ as low-molecular-weight processing additives, were film-blown in a single screw extruder. The films and recycled PCL without additives were exposed to composting, anaerobic sewage sludge (37 and 55°C), pure fungal culture, and chemical hydrolysis at two pH (7 and 10.5) and at two temperatures (room temperature and 50°C). Recycling and addition of processing additives resulted in a slightly slower degradation rate compared with the degradation of pure PCL. The degradations in biotic environment were generally faster than in abiotic environment. Higher degradation rates are observed in more complex environments (composts and anerobic sewage sludge) due to synergism between high temperature and a richer fauna of microorganisms. In the biotic environments, faster reductions in number-average molecular weight (M _n) than in weight-average molecular weight (M _w) were observed. A decrease of M _n with up to 75–80% was estimated for composted pure PCL, while similar samples in anaerobic sludge at 55°C were completely degraded in 50 days. The mechanical properties of the samples subjected to composting exhibited a more rapid enbrittlement compared to the samples subjected to abiotic hydrolysis. The observed increase in crystallinity with increasing degree of degradation is explained by crystallization made possible by chain cleavage in the amorphous phase. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 61–74, 1998     

Effect of water and oxygen traces on the cathodic stability of N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide

Although research in the field of ionic liquids for electrochemical applications has led to a deeper knowledge in their electrochemical properties, doubts in the interpretation of the experimental results are still encountered in the literature due to the poor control of the experimental conditions and/or to the limited number of experiments conducted. In this work, the effect of water and oxygen traces on the cathodic stability window of hydrophobic, air-stable ionic liquids composed of N-alkyl-N-methylpyrrolidinium (PYR_1A⁺) cations and bis(trifluoromethanesulfonyl)imide (TFSI⁻) anion, is reported. The extensive investigation performed by linear sweep voltammetry (LSV) and cyclic voltammetry (CV) indicates that the TFSI⁻ anion is cathodically stable if the ionic liquid is pure and dry. The N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquids investigated showed featureless cathodic linear sweep voltammetry curves before the massive cation decomposition took place at very low potentials.     

Cathodic reduction of benzil in acetone and in dichloromethane

The cathodic reduction of benzil has been carried out at a controlled potential on a mercury cathode in two different SSE (solvent-supporting-electrolyte) conditions: (a) acetone/lithium perchlorate in absence of electrophile where 2,3-diphenyl-5-methyl-furan and 1,2-diphenyl-2-hydroxy-1,4-pentanedione were obtained as main products and (b) dichloromethane/tetrabuthylammonium chloride with the addition of oxalyl chloride as electrophile, where a fast electron transfer took place.     

Failure Mechanisms in Sand over a Deep Active Trapdoor

An experimental testing program was undertaken to investigate failure mechanisms induced by the active movement of a deep rectangular trapdoor underlying a granular soil. Reduced-scale models were tested under normal gravity as well as under an increased gravitational field using a centrifuge facility. Some models were used to evaluate the performance of both flexible and rigid pipes undergoing a localized loss of support. Failure mechanisms in the longitudinal direction of the models were characterized by a single, well-defined failure surface that developed within the limits of the trapdoor. However, failure mechanisms in the transverse direction of the models were characterized by multiple failure surfaces extending outside the limits of the trapdoor. Significant dilation of the soil located immediately above the trapdoor was identified in the failure of the models. The pattern of the failure mechanisms was found to be affected by the stress level and backfill density. Higher stress levels were found to lead to well-developed failure zones. The influence of backfill density was found to be more relevant in models involving flexible pipes. Pipes embedded within loose backfill were severely damaged after loss of support, while pipes embedded in dense backfill experienced negligible deformations. These results indicate that damage to pipelines caused by ground loss of support can be significantly minimized by controlling the compaction of the fill.     

Applying a constructivist and collaborative methodological approach in engineering education

In this paper, a methodological educational proposal based on constructivism and collaborative learning theories is described. The suggested approach has been successfully applied to a subject entitled “Computer Architecture and Engineering” in a Computer Science degree in the University of La Laguna in Spain.     

On the numerical solution of fault trees

In this paper an account will be given of the numerical solution of the logic trees directly extracted from the Recursive Operability Analysis. Particular attention will be devoted to the use of the NOT and INH logic gates for correct logical representation of Fault Trees prior to their quantitative resolution.The NOT gate is needed for correct logical representation of events when both non-intervention and correct intervention of a protective system may lead to a Top Event.The INH gate must be used to correctly represent the time link between two events that are both necessary, but must occur in sequence. Some numerical examples will be employed to show both the correct identification of the events entering the INH gates and how use of the AND gate instead of the INH gate leads to overestimation of the probability of occurrence of a Top Event.