1,596 research outputs found

    Living in an Irrational Society: Wealth Distribution with Correlations between Risk and Expected Profits

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    Different models to study the wealth distribution in an artificial society have considered a transactional dynamics as the driving force. Those models include a risk aversion factor, but also a finite probability of favoring the poorer agent in a transaction. Here we study the case where the partners in the transaction have a previous knowledge of the winning probability and adjust their risk aversion taking this information into consideration. The results indicate that a relatively equalitarian society is obtained when the agents risk in direct proportion to their winning probabilities. However, it is the opposite case that delivers wealth distribution curves and Gini indices closer to empirical data. This indicates that, at least for this very simple model, either agents have no knowledge of their winning probabilities, either they exhibit an ``irrational'' behavior risking more than reasonable.Comment: 7 pages, 8 figure

    On the non-slip boundary condition enforcement in SPH methods.

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    The implementation of boundary conditions is one of the points where the SPH methodology still has some work to do. The aim of the present work is to provide an in-depth analysis of the most representative mirroring techniques used in SPH to enforce boundary conditions (BC) along solid proïŹles. We speciïŹcally refer to dummy particles, ghost particles, and Takeda et al. [1] boundary integrals. A Pouseuille ïŹ‚ow has been used as a example to gradually evaluate the accuracy of the different implementations. Our goal is to test the behavior of the second-order differential operator with the proposed boundary extensions when the smoothing length h and other dicretization parameters as dx/h tend simultaneously to zero. First, using a smoothed continuous approximation of the unidirectional Pouseuille problem, the evolution of the velocity proïŹle has been studied focusing on the values of the velocity and the viscous shear at the boundaries, where the exact solution should be approximated as h decreases. Second, to evaluate the impact of the discretization of the problem, an Eulerian SPH discrete version of the former problem has been implemented and similar results have been monitored. Finally, for the sake of completeness, a 2D Lagrangian SPH implementation of the problem has been also studied to compare the consequences of the particle movemen

    The Lubrication Ability of Ionic Liquids as Additives for Wind Turbine Gearboxes Oils

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    The amount of energy that can be gained from the wind is unlimited, unlike current energy sources such as fossil and coal. While there is an important push in the use of wind energy, gears and bearing components of the turbines often fail due to contact fatigue, causing costly repairs and downtime. The objective of this work is to investigate the potential tribological benefits of two phosphonium-based ionic liquids (ILs) as additives to a synthetic lubricant without additives and to a fully formulated and commercially available wind turbine oil. In this work, AISI 52100 steel disks were tested in a ball-on-flat reciprocating tribometer against AISI 440C steel balls. Surface finish also affects the tribological properties of gear surfaces. In order to understand the combined effect of using the ILs with surface finish, two surface finishes were also used in this study. Adding ILs to the commercial available or synthetic lubricant reduced the wear scar diameter for both surface finishes. This decrease was particularly important for trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl) amide, where a wear reduction of the steel disk around 20% and 23% is reached when 5 wt % of this IL is added to the commercially available lubricant and to the synthetic lubricant without additives, respectively

    Stellarator Optimization Using a Distributed Swarm Intelligence-Based Algorithm

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    The design of enhanced fusion devices constitutes a key element for the development of fusion as a commercial source of energy. Stellarator optimization presents high computational requirements because of the complexity of the numerical methods needed as well as the size of the solution space regarding all the possible configurations satisfying the characteristics of a feasible reactor. The size of the solution space does not allow to explore every single feasible configuration. Hence, a metaheuristic approach is used to achieve optimized configurations without evaluating the whole solution space. In this paper we present a distributed algorithm that mimics the foraging behaviour of bees. This behaviour has manifested its efficiency in dealing with complex problems

    Exercise Interventions for Improving Flexibility in People with Multiple Sclerosis: A Systematic Review and Meta-Analysis

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    [ES] Background and objectives: People with multiple sclerosis (MS) often experience limitations in joint range of motion, which is linked to spasticity and continued inactivity. Low flexibility levels in this population have been linked to postural problems and muscular pain. Therefore, the purpose of this study was to conduct a systematic review and a meta-analysis aimed at identifying the characteristics and methodological quality of investigations studying the effects of exercise interventions on the flexibility levels of people with MS. Materials and Methods: Three electronic databases (MEDLINE/PubMed, SPORTDiscus and Scopus) were systematically searched up to May 2019 for intervention studies focused on the effects of exercise on the flexibility levels of people with MS. A meta-analysis, including randomized controlled trials (RCT), which reported information regarding the effects of exercise on flexibility, was also conducted. The methodological quality of included studies was assessed using the Physiotherapy Evidence Database, and the Quality Assessment Tool for Before–After Studies, with no control group. The quality of the information reported, regarding the programs conducted, was assessed by means of the Consensus on Exercise Reporting Template (CERT) scale. Results: Seven studies, four RCTs and three uncontrolled investigations were finally selected. The methodological quality of the RCTs was considered “poor” in one study, and “good” and “excellent” in two studies and one investigation, respectively. The three uncontrolled studies showed a methodological quality between “fair” and “poor”. Following the CERT scale, four studies were graded as “high” and three as “low”. Findings from the meta-analysis indicated no significant effects on hamstring flexibility, or the range of motion in the hips, knees or ankles. Conclusions: There is preliminary evidence from individual studies which indicates that people with MS can improve their lower limb flexibility following participation in physical exercise programs, but the meta-analysis did not confirm these findings

    SPH no-slip BC implementation analysis at the continous level

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    The aim of this paper is to discuss whether there are structural problems in three of the most representative velocity mirroring techniques used to force no-slip boundary conditions (BC) in SPH for Newtonian incompressible ïŹ‚ows. We refer speciïŹcally to ïŹxed ïŹ‚uid particles, ghost particles, and Takeda et al. [1] boundary integrals. In Newtonian incompressible ïŹ‚ows, the viscous related terms in the momentum conservation equation depend on the evaluation of the Laplacian of the velocity ïŹeld. In order to analyze such techniques, the continuous version of the Laplacian approximation by Morris et al. [2] and Monaghan Cleary-Gingold [3] viscous terms has been considered. It has been shown that there are intrinsic inaccuracies in the computation of the Laplacian close to the boundaries and the onset of singularities in such evaluation for some ïŹ‚ows and mirroring techniques combinations. The impact of these deviations in the SPH simulation of viscous ïŹ‚ows is not clear at this stage

    Exercise Interventions for Improving Flexibility in People with Multiple Sclerosis: A Systematic Review and Meta-Analysis.

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    Background and objectives: People with multiple sclerosis (MS) often experience limitations in joint range of motion, which is linked to spasticity and continued inactivity. Low flexibility levels in this population have been linked to postural problems and muscular pain. Therefore, the purpose of this study was to conduct a systematic review and a meta-analysis aimed at identifying the characteristics and methodological quality of investigations studying the effects of exercise interventions on the flexibility levels of people with MS. Materials and Methods: Three electronic databases (MEDLINE/PubMed, SPORTDiscus and Scopus) were systematically searched up to May 2019 for intervention studies focused on the effects of exercise on the flexibility levels of people with MS. A meta-analysis, including randomized controlled trials (RCT), which reported information regarding the effects of exercise on flexibility, was also conducted. The methodological quality of included studies was assessed using the Physiotherapy Evidence Database, and the Quality Assessment Tool for Before–After Studies, with no control group. The quality of the information reported, regarding the programs conducted, was assessed by means of the Consensus on Exercise Reporting Template (CERT) scale. Results: Seven studies, four RCTs and three uncontrolled investigations were finally selected. The methodological quality of the RCTs was considered “poor” in one study, and “good” and “excellent” in two studies and one investigation, respectively. The three uncontrolled studies showed a methodological quality between “fair” and “poor”. Following the CERT scale, four studies were graded as “high” and three as “low”. Findings from the meta-analysis indicated no significant effects on hamstring flexibility, or the range of motion in the hips, knees or ankles. Conclusions: There is preliminary evidence from individual studies which indicates that people with MS can improve their lower limb flexibility following participation in physical exercise programs, but the meta-analysis did not confirm these findings.post-print1388 K

    Carbohydrate Metabolism in Bacteria: Alternative Specificities in ADP-Glucose Pyrophosphorylases Open Novel Metabolic Scenarios and Biotechnological Tools

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    We explored the ability of ADP-glucose pyrophosphorylase (ADP-Glc PPase) from different bacteria to use glucosamine (GlcN) metabolites as a substrate or allosteric effectors. The enzyme from the actinobacteria Kocuria rhizophila exhibited marked and distinctive sensitivity to allosteric activation by GlcN-6P when producing ADP-Glc from glucose-1-phosphate (Glc-1P) and ATP. This behavior is also seen in the enzyme from Rhodococcus spp., the only one known so far to portray this activation. GlcN-6P had a more modest effect on the enzyme from other Actinobacteria (Streptomyces coelicolor), Firmicutes (Ruminococcus albus), and Proteobacteria (Agrobacterium tumefaciens) groups. In addition, we studied the catalytic capacity of ADP-Glc PPases from the different sources using GlcN-1P as a substrate when assayed in the presence of their respective allosteric activators. In all cases, the catalytic efficiency of Glc-1P was 1–2 orders of magnitude higher than GlcN-1P, except for the unregulated heterotetrameric protein (GlgC/GgD) from Geobacillus stearothermophilus. The Glc-1P substrate preference is explained using a model of ADP-Glc PPase from A. tumefaciens based on the crystallographic structure of the enzyme from potato tuber. The substrate-binding domain localizes near the N-terminal of an α-helix, which has a partial positive charge, thus favoring the interaction with a hydroxyl rather than a charged primary amine group. Results support the scenario where the ability of ADP-Glc PPases to use GlcN-1P as an alternative occurred during evolution despite the enzyme being selected to use Glc-1P and ATP for α-glucans synthesis. As an associated consequence in such a process, certain bacteria could have improved their ability to metabolize GlcN. The work also provides insights in designing molecular tools for producing oligo and polysaccharides with amino moieties

    Electrocatalysis on shape-controlled metal nanoparticles: Progress in surface cleaning methodologies

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    The use of shape-controlled metal nanoparticles has produced not only a clear enhancement in the electrocatalytic activity of different reactions of interest but also a better understanding of the effect of the surface structure on nanoscaled materials. However, it is well-accepted that a correct understanding of the correlations between shape/surface structure and electrochemical reactivity indispensably requires the use of clean surfaces. In this regard, and considering that most of the synthetic methodologies available in the literature for the preparation of these shaped metal nanoparticles employ capping agents, the development of effective surface cleaning methodologies able to remove such capping agents from the surface of the corresponding nanoparticles, becomes an extremely important prerequisite to subsequently evaluate their electrocatalytic properties for any reaction of interest. Consequently, in this contribution, we summarize the most relevant advances about surface cleaning procedures applied to different shaped metal nanoparticles for electrocatalytic purposes. It is worth mentioning that this work will only include contributions in which the surface cleanness of the samples is specifically evaluated using well-established electrochemical tools.This work has been financially supported by the MINECO of Spain through project CTQ2013-48280-C3-3-R. JSG acknowledges financial support from VITC (Vicerrectorado de InvestigaciĂłn y Transferencia de Conocimiento) of the University of Alicante

    Maternal Cigarette Smoke Exposure Contributes to Glucose Intolerance and Decreased Brain Insulin Action in Mice Offspring Independent of Maternal Diet

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    Maternal smoking leads to intrauterine undernutrition and is associated with low birthweight and higher risk of offspring obesity. Intrauterine smoke exposure (SE) may alter neuroendocrine mediators regulating energy homeostasis as chemicals in cigarette smoke can reach the fetus. Maternal high-fat diet (HFD) consumption causes fetal overnutrition; however, combined effects of HFD and SE are unknown. Thus we investigated the impact of combined maternal HFD and SE on adiposity and energy metabolism in offspring.Female Balb/c mice had SE (2 cigarettes/day, 5 days/week) or were sham exposed for 5 weeks before mating. Half of each group was fed HFD (33% fat) versus chow as control. The same treatment continued throughout gestation and lactation. Female offspring were fed chow after weaning and sacrificed at 12 weeks.Birthweights were similar across maternal groups. Faster growth was evident in pups from SE and/or HFD dams before weaning. At 12 weeks, offspring from HFD-fed dams were significantly heavier than those from chow-fed dams (chow-sham 17.6±0.3 g; chow-SE 17.8±0.2 g; HFD-sham 18.7±0.3 g; HFD-SE 18.8±0.4 g, P<0.05 maternal diet effect); fat mass was significantly greater in offspring from chow+SE, HFD+SE and HFD+sham dams. Both maternal HFD and SE affected brain lactate transport. Glucose intolerance and impaired brain response to insulin were observed in SE offspring, and this was aggravated by maternal HFD consumption.While maternal HFD led to increased body weight in offspring, maternal SE independently programmed adverse health outcomes in offspring. A smoke free environment and healthy diet during pregnancy is desirable to optimize offspring health
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