Solving Multiobjective Optimization Problems Using an Artificial Immune System

In this paper, we propose an algorithm based on the clonal selection principle to solve multiobjective optimization problems (either constrained or unconstrained). The proposed approach uses Pareto dominance and feasibility to identify solutions that deserve to be cloned, and uses two types of mutation: uniform mutation is applied to the clones produced and non-uniform mutation is applied to the not so good antibodies (which are represented by binary strings that encode the decision variables of the problem to be solved). We also use a secondary (or external) population that stores the nondominated solutions found along the search process. Such secondary population constitutes the elitist mechanism of our approach and it allows it to move towards the true Pareto front of a problem over time. Our approach is compared with three other algorithms that are representative of the state-of-the-art in evolutionary multiobjective optimization. For our comparative study, three metrics are adopted and graphical comparisons with respect to the true Pareto front of each problem are also included. Results indicate that the proposed approach is a viable alternative to solve multiobjective optimization problems.     

Parallel Approach for Ensemble Learning with Locally Coupled Neural Networks

Ensemble learning has gained considerable attention in different tasks including regression, classification and clustering. Adaboost and Bagging are two popular approaches used to train these models. The former provides accurate estimations in regression settings but is computationally expensive because of its inherently sequential structure, while the latter is less accurate but highly efficient. One of the drawbacks of the ensemble algorithms is the high computational cost of the training stage. To address this issue, we propose a parallel implementation of the Resampling Local Negative Correlation (RLNC) algorithm for training a neural network ensemble in order to acquire a competitive accuracy like that of Adaboost and an efficiency comparable to that of Bagging. We test our approach on both synthetic and real datasets from the UCI and Statlib repositories for the regression task. In particular, our fine-grained parallel approach allows us to achieve a satisfactory balance between accuracy and parallel efficiency.     

Serine Protease Inhibitors as Good Predictors of Meat Tenderness: Which Are They and What Are Their Functions?

Since years, serine proteases and their inhibitors were an enigma to meat scientists. They were indeed considered to be extracellular and to play no role in postmortem muscle proteolysis. In the 1990's, we observed that protease inhibitors levels in muscles are a better predictor of meat tenderness than their target enzymes. From a practical point of view, we therefore choose to look for serine protease inhibitors rather than their target enzymes, i.e. serine proteases and the purpose of this report was to overview the findings obtained. Fractionation of a muscle crude extract by gel filtration revealed three major trypsin inhibitory fractions designed as F1 (Mr:50–70 kDa), F2 (Mr:40–60 kDa) and F3 (Mr:10–15kD) which were analyzed separately. Besides antithrombin III, an heparin dependent thrombin inhibitor, F1 and F2 comprised a large set of closely related trypsin inhibitors encoded by at least 8 genes bovSERPINA3-1 to A3-8 and able to inhibit also strongly initiator and effector caspases. They all belong to the serpin superfamily, known to form covalent complexes with their target enzymes, were located within muscle cells and found in all tissues and fluids examined irrespective of the animal species. Potential biological functions in living and postmortem muscle were proposed for all of them. In contrast to F1 and F2 which have been more extensively investigated only preliminary findings were provided for F3. Taken together, these results tend to ascertain the onset of apoptosis in postmortem muscle. However, the exact mechanisms driving the cell towards apoptosis and how apoptosis, an energy dependent process, can be completed postmortem remain still unclear.     

Physical and Antioxidant Characterization of Edible Films Added with Red Prickly Pear (<Emphasis Type="Italic">Opuntia ficus-indica</Emphasis> L.) cv. San Martín Peel and/or Its Aqueous Extracts

The aim of this research was to investigate the effect of the addition of peel powder and/or its aqueous extract on physical and antioxidant characteristics of carboxymethyl cellulose (CMC) edible films. Prickly pear peel powder and aqueous extract (2 and 4%) were characterized in color, bioactive compounds (betalains and total phenolic compounds), antioxidant capacity and reducing power. Edible films were prepared with CMC, glycerol, varying the dissolution medium (0, 2, or 4% aqueous extract from prickly pear peel) and peel powder (0, 1, or 2%) using a face-centered central composite design. Physical, mechanical, bioactive compounds, and antioxidant capacity properties were investigated in edible films. Prickly pear peel powder presented 58.8 ± 0.08 mg of betacyanins/100 g, 53.8 ± 0.2 mg of betaxanthins/100 g, 967.8 ± 20 mg Gallic acid equivalent (GAE)/100 g for total phenolic compounds, an antioxidant capacity equivalent to 420.9 ± 4.9 mg GAE/100 g and a reducing power of 879.1 ± 115.9 mg ascorbic acid equivalent (AAE)/100 g. High concentration of aqueous extract and peel powder in CMC films increased the bioactive compounds content, antioxidant capacity and reducing power. Films mechanical properties were not affected by the aqueous extract; nevertheless, were strongly affected by the peel powder. Response surface methodology was used to optimize edible films formulation with high antioxidant characteristics, being the optimal formulation 1.7% of peel powder plus 3.3% of aqueous extract. This study may be the base for exploitation of prickly pear peel as source of bioactive compounds with antioxidant capacity for their use in edible coatings.     

Current Scenario of Adsorbent Materials Used in Ethylene Scavenging Systems to Extend Fruit and Vegetable Postharvest Life

Fruit and vegetables are much appreciated by consumers due to their nutritional values and health-promoting compounds. However, different factors affect the postharvest life of such products, in where ethylene is a major one, even at low concentrations, besides temperature and relative humidity. Therefore, high attention has been focused on the development of effective tools to remove ethylene from the atmosphere surrounding these products during storage or in transit. Potassium permanganate scrubbers are one of the most used technologies to remove ethylene from horticultural products. To facilitate and improve the oxidation process, potassium permanganate has been supported onto inert solid materials of a small particle size. In this review, we aim to provide an outline of the most common materials used as potassium permanganate supports on postharvest treatment and their respective effects on quality aspects of various fresh produce during postharvest life. Vermiculite, activated alumina, zeolite, silica gel, activated carbon and clays are the most popular materials that have been used as a support of potassium permanganate-based ethylene scrubbers. The literature suggests that potassium permanganate supported onto silica gel or zeolite seems to be a promising tool to maintain fruit and vegetables quality attributes for long-term storage. Although vermiculite and activated alumina are the most commonly used materials to reach this goal, not promising results have been reported.