Effects of combining microbial transglutaminase and high pressure processing treatments on the mechanical properties of heat-induced gels prepared from arrowtooth flounder (Atheresthes stomias)

The objective of this study was to evaluate the effect of setting conditions (25 °C for 2 h or 40 °C for 30 min) and combining of microbial transglutaminase (MTGase) and high pressure processing (HPP) on the mechanical properties of heat induced gels obtained from paste from arrowtooth flounder (Atheresthes stomias). Treatments included fish paste control without added MTGase, fish paste incubated with MTGase but not pressurized (MTGase + cooking), fish paste incubated with MTGase and pressurized at 600 MPa for 5 min (MTGase + HPP + cooking) and fish paste pressurized at 600 MPa for 5 min and incubated with MTGase (HPP + MTGase + cooking). The controls and the treated samples were then subjected to one of two thermal treatments: 90 °C for 15 min or 60 °C for 30 min before cooking at 90 °C for 15 min. Samples of fish paste heated at 60 °C before cooking could not be used to prepare gels for texture profile analysis (TPA). TPA showed that pressurization improved the mechanical properties of gels made from paste treated with MTGase and set at 25 °C. The opposite was observed for samples set at 40 °C. Setting at 40 °C appeared to induce proteolytic degradation of myofibrillar proteins.     

Synthesis, Characterization and Cold Workability of Cast Copper-Magnesium-Tin Alloys

The use of Mg as an alloying element in copper alloys has largely been overlooked in scientific literature and technological applications. Its supposed tribological compatibility with iron makes it an interesting option to replace Pb in tribological alloys. This work describes the casting process of high-quality thin slabs of Cu-Mg-Sn alloys with different compositions by means of conventional methods. The resulting phases were analyzed using X-ray diffraction, scanning electron microscopy, optical microscopy, and energy dispersive X-ray spectroscopy techniques. Typical dendritic α-Cu, eutectic Cu₂Mg(Sn) and eutectoid non-equilibrium microstructures were found. Tensile tests and Vickers microhardness show the excellent hardening capability of Mg as compared to other copper alloys in the as-cast condition. For some of the slabs and compositions, cold rolling reductions of over 95 pct have been easily achieved. Other compositions and slabs have failed during the deformation process. Failure analysis after cold rolling reveals that one cause for brittleness is the presence of casting defects such as microshrinkage and inclusions, which can be eliminated. However, for high Mg contents, a high volume fraction of the intermetallic phase provides a contiguous path for crack propagation through the connected interdendritic regions.     

Pre-bottling use of dehydrated waste grape skins to improve colour,phenolic and aroma composition of red wines

Different dehydrated waste grape skins from the juice industry were added into aged and young red wines as an innovative way of compensating for colour loss before bottling. After addition of grape skins, colour intensity of wines increased a mean 11% and a maximum of 31% with predominance of the red component. Total polyphenols mean increase was 10% with a maximum value of 20%. Analysis of low molecular weight phenolic compounds by HPLC–DAD showed a significant (p < 0.05) content increase of the bioactive compounds gallic acid, (+)-catechin, (−)-epicatechin, and (E)-resveratrol. Anthocyanins content also increased at an average of 50 mg/l. The volatile profile of wines analysed by SBSE–GC–MS was only moderately influenced by the treatments. Mixtures of dehydrated waste grape skins were useful to improve the colour and polyphenol profile of red wines, considering them a useful tool for correcting colour loss before bottling.     

Enhanced Van der Waals calculations in genetic algorithms for protein structure prediction

Several ab initio computational methods for protein structure prediction have been designed using full‐atom models and force field potentials to describe interactions among atoms. Those methods involve the solution of a combinatorial problem with a huge search space. Genetic algorithms (GAs) have shown significant performance increases for such methods. However, even a small protein may require hundreds of thousands of energy function evaluations making GAs suitable only for the prediction of very small proteins. We propose an efficient technique to compute the van der Waals energy (the greatest contributor to protein stability) speeding up the whole GA. First, we developed a Cell‐List Reconstruction procedure that divides the tridimensional space into a cell grid for each new structure that the GA generates. The cells restrict the calculations of van der Waals potentials to ranges in which they are significant, reducing the complexity of such calculations from quadratic to linear. Moreover, the proposal also uses the structure of the cell grid to parallelize the computation of the van der Waals energy, achieving additional speedup. The results have shown a significant reduction in the run time required by a GA. For example, the run time for the prediction of a protein with 147,980 atoms can be reduced from 217 days to 7 h. Copyright © 2012 John Wiley & Sons, Ltd.     

Global optimization of large‐scale mixed‐integer linear fractional programming problems: A reformulation‐linearization method and process scheduling applications

Mixed‐integer linear fractional program (MILFP) is a class of mixed‐integer nonlinear programs (MINLP) where the objective function is the ratio of two linear functions and all constraints are linear. Global optimization of large‐scale MILFPs can be computationally intractable due to the presence of discrete variables and the pseudoconvex/pseudoconcave objective function. We propose a novel and efficient reformulation–linearization method, which integrates Charnes–Cooper transformation and Glover's linearization scheme, to transform general MILFPs into their equivalent mixed‐integer linear programs (MILP), allowing MILFPs to be globally optimized effectively with MILP methods. Extensive computational studies are performed to demonstrate the efficiency of this method. To illustrate its applications, we consider two batch scheduling problems, which are modeled as MILFPs based on the continuous‐time formulations. Computational results show that the proposed approach requires significantly shorter CPU times than various general‐purpose MINLP methods and shows similar performance than the tailored parametric algorithm for solving large‐scale MILFP problems. Specifically, it performs with respect to the CPU time roughly a half of the parametric algorithm for the scheduling applications. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4255–4272, 2013     

Propagation of a cohesive crack crossing a reinforcement layer

This paper analyzes the propagation of a cohesive crack through a reinforcement layer and gives a solution that can be used for any specimen and loading condition. Here it faces the case of a reinforced prismatic beam loaded at three points. Reinforcement is represented by means of a free-slip bar bridging the cracked section, anchored at both sides of the crack at a certain distance that is called the effective slip length. This length is obtained by making the free-slip bar mechanically equivalent to the actual adherent reinforcement. With this model, the crack development depends on three parameters (apart from those that represent the specimen geometry): the size of the specimen, the cover thickness of the layer and the reinforcement strength. The latter depends on the reinforcement ratio and its adherence to the matrix while the reinforcement is in the elastic regime; otherwise, on the reinforcement ratio and its yielding strength. The thickness of the reinforcement cover influences the first stages of the development of the cohesive crack, and thus it also affects the value of the load peak. The computed load-displacement curves display a noticeable size effect, as real cohesive materials do. Finally, the model is able to fit the available experimental results, and accurately reproduces the influence of size, amount of reinforcement and adherence variations in the tests.     

Functional stabilization of unstable fixed points: Human pole balancing using time-to-balance information.

Humans are often faced with tasks that require stabilizing inherently unstable situations. The authors explored the dynamics of human functional stabilization by having participants continually balance a pole until a minimum time criterion was reached. Conditions were manipulated with respect to geometry, mass, and characteristic "fall time" of the pole. Distributions of timing between pole and hand velocities showed strong action–perception coupling. When actions demonstrated a potential for catastrophic failure, the period of hand oscillation correlated well with the perceptual quantity "time to balance" (τbal = θ/θ?), but not other quantities such as θ and θ? alone. This suggests that participants were using available τbal information during critical conditions, although they may not have been attending to this type of perceptual information during typical, noncritical motions of successful performance. In a model analysis and simulation, the authors showed how discrete τbal information may be used to adjust the parameters of a controller to perform this task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modafinil Administration to Preadolescent Rat Impairs Non-Selective Attention,Frontal Cortex D2 Expression and Mesolimbic GABA Levels

The misuse of psychostimulants is an increasing behavior among young people, highlighting in some countries the abuse of modafinil (MOD) as a neuropotentiator. However, several clinical trials are investigating MOD as an alternative pharmacological treatment for attentional deficit and hyperactivity disorder (ADHD) in children and adolescents. On the other hand, the early use of psychostimulants and the misdiagnosis rates in ADHD make it crucial to investigate the brain effects of this type of drug in young healthy individuals. The aim of this work was to evaluate the effects of chronic MOD treatment on neurochemicals (γ-aminobutyric acid and glutamate), dopamine receptor 2 (D₂) expression and behavior (non-selective attention “NSA”) in the mesocorticolimbic system of young healthy Sprague–Dawley rats. Preadolescent male rats were injected with MOD (75 mg/kg, i.p.) or a vehicle for 14 days (from postnatal day 22 to 35). At postnatal day 36, we measured the GLU and GABA contents and their extracellular levels in the nucleus accumbens (NAc). In addition, the GLU and GABA contents were measured in the ventral tegmental area (VTA) and D₂ protein levels in the prefrontal cortex (PFC). Chronic use of MOD during adolescence induces behavioral and neurochemical changes associated with the mesocorticolimbic system, such as a reduction in PFC D₂ expression, VTA GABA levels and NSA. These results contribute to the understanding of the neurological effects of chronic MOD use on a young healthy brain.     

t-Spanners for metric space searching

The problem of Proximity Searching in Metric Spaces consists in finding the elements of a set which are close to a given query under some similarity criterion. In this paper we present a new methodology to solve this problem, which uses a t-spanner G′(V, E) as the representation of the metric database. A t-spanner is a subgraph G′(V, E) of a graph G(V, A), such that E  A and G′ approximates the shortest path costs over G within a precision factor t.

Our key idea is to regard the t-spanner as an approximation to the complete graph of distances among the objects, and to use it as a compact device to simulate the large matrix of distances required by successful search algorithms such as AESA. The t-spanner properties imply that we can use shortest paths over G′ to estimate any distance with bounded-error factor t.

For this sake, several t-spanner construction, updating, and search algorithms are proposed and experimentally evaluated. We show that our technique is competitive against current approaches. For example, in a metric space of documents our search time is only 9% over AESA, yet we need just 4% of its space requirement. Similar results are obtained in other metric spaces.

Finally, we conjecture that the essential metric space property to obtain good t-spanner performance is the existence of clusters of elements, and enough empirical evidence is given to support this claim. This property holds in most real-world metric spaces, so we expect that t-spanners will display good behavior in most practical applications. Furthermore, we show that t-spanners have a great potential for improvements.