Showing papers by "University of Seville published in 2014"

Lipid peroxidation: production, metabolism, and signaling mechanisms of malondialdehyde and 4-hydroxy-2-nonenal.

Abstract: Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970–1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010–2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Highly active copper-ceria and copper-ceria-titania catalysts for methanol synthesis from co2

Abstract: The transformation of CO2 into alcohols or other hydrocarbon compounds is challenging because of the difficulties associated with the chemical activation of CO2 by heterogeneous catalysts. Pure metals and bimetallic systems used for this task usually have low catalytic activity. Here we present experimental and theoretical evidence for a completely different type of site for CO2 activation: a copper-ceria interface that is highly efficient for the synthesis of methanol. The combination of metal and oxide sites in the copper-ceria interface affords complementary chemical properties that lead to special reaction pathways for the CO2→CH3OH conversion.

Model Predictive Control: A Review of Its Applications in Power Electronics

Abstract: Model-based predictive control (MPC) for power converters and drives is a control technique that has gained attention in the research community. The main reason for this is that although MPC presents high computational burden, it can easily handle multivariable case and system constraints and nonlinearities in a very intuitive way. Taking advantage of that, MPC has been successfully used for different applications such as an active front end (AFE), power converters connected to resistor inductor RL loads, uninterruptible power supplies, and high-performance drives for induction machines, among others. This article provides a review of the application of MPC in the power electronics area.

Cytoplasmic 5 -3 exonuclease Xrn1p is also a genome-wide transcription factor in yeast

Abstract: The 5’ to 3’ exoribonuclease Xrn1 is a large protein involved in cytoplasmatic mRNA degradation as a critical component of the major decaysome. Its deletion in the yeast Saccharomyces cerevisiae is not lethal, but it has multiple physiological effects. In a previous study, our group showed that deletion of all tested components of the yeast major decaysome, including XRN1, results in a decrease in the synthetic rate and an increase in half-life of most mRNAs in a compensatory manner. Furthermore, the same study showed that the all tested decaysome components are also nuclear proteins that bind to the 5’ region of a number of genes. In the present work, we show that disruption of Xrn1 activity preferentially affects both the synthesis and decay of a distinct subpopulation of mRNAs. The most affected mRNAs are the transcripts of the highly transcribed genes, mainly those encoding ribosome biogenesis and translation factors. Previously, we proposed that synthegradases play a key role in regulating both mRNA synthesis and degradation. Evidently, Xrn1 functions as a synthegradase, whose selectivity might help coordinating the expression of the protein synthetic machinery. We propose to name the most affected genes “Xrn1 synthegradon”.

Global dissemination of a multidrug resistant Escherichia coli clone

Abstract: Escherichia coli sequence type 131 (ST131) is a globally disseminated, multidrug resistant (MDR) clone responsible for a high proportion of urinary tract and bloodstream infections. The rapid emergence and successful spread of E. coli ST131 is strongly associated with several factors, including resistance to fluoroquinolones, high virulence gene content, the possession of the type 1 fimbriae FimH30 allele, and the production of the CTX-M-15 extended spectrum β-lactamase (ESBL). Here, we used genome sequencing to examine the molecular epidemiology of a collection of E. coli ST131 strains isolated from six distinct geographical locations across the world spanning 2000-2011. The global phylogeny of E. coli ST131, determined from whole-genome sequence data, revealed a single lineage of E. coli ST131 distinct from other extraintestinal E. coli strains within the B2 phylogroup. Three closely related E. coli ST131 sublineages were identified, with little association to geographic origin. The majority of single-nucleotide variants associated with each of the sublineages were due to recombination in regions adjacent to mobile genetic elements (MGEs). The most prevalent sublineage of ST131 strains was characterized by fluoroquinolone resistance, and a distinct virulence factor and MGE profile. Four different variants of the CTX-M ESBL-resistance gene were identified in our ST131 strains, with acquisition of CTX-M-15 representing a defining feature of a discrete but geographically dispersed ST131 sublineage. This study confirms the global dispersal of a single E. coli ST131 clone and demonstrates the role of MGEs and recombination in the evolution of this important MDR pathogen.

Impaired autophagic flux is associated with increased endoplasmic reticulum stress during the development of NAFLD

Abstract: The pathogenic mechanisms underlying the progression of non-alcoholic fatty liver disease (NAFLD) are not fully understood. In this study, we aimed to assess the relationship between endoplasmic reticulum (ER) stress and autophagy in human and mouse hepatocytes during NAFLD. ER stress and autophagy markers were analyzed in livers from patients with biopsy-proven non-alcoholic steatosis (NAS) or non-alcoholic steatohepatitis (NASH) compared with livers from subjects with histologically normal liver, in livers from mice fed with chow diet (CHD) compared with mice fed with high fat diet (HFD) or methionine-choline-deficient (MCD) diet and in primary and Huh7 human hepatocytes loaded with palmitic acid (PA). In NASH patients, significant increases in hepatic messenger RNA levels of markers of ER stress (activating transcription factor 4 (ATF4), glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP)) and autophagy (BCN1) were found compared with NAS patients. Likewise, protein levels of GRP78, CHOP and p62/SQSTM1 (p62) autophagic substrate were significantly elevated in NASH compared with NAS patients. In livers from mice fed with HFD or MCD, ER stress-mediated signaling was parallel to the blockade of the autophagic flux assessed by increases in p62, microtubule-associated protein 2 light chain 3 (LC3-II)/LC3-I ratio and accumulation of autophagosomes compared with CHD fed mice. In Huh7 hepatic cells, treatment with PA for 8 h triggered activation of both unfolding protein response and the autophagic flux. Conversely, prolonged treatment with PA (24 h) induced ER stress and cell death together with a blockade of the autophagic flux. Under these conditions, cotreatment with rapamycin or CHOP silencing ameliorated these effects and decreased apoptosis. Our results demonstrated that the autophagic flux is impaired in the liver from both NAFLD patients and murine models of NAFLD, as well as in lipid-overloaded human hepatocytes, and it could be due to elevated ER stress leading to apoptosis. Consequently, therapies aimed to restore the autophagic flux might attenuate or prevent the progression of NAFLD.

Functional group directed C-H borylation.

Abstract: The direct borylation of hydrocarbons via C–H activation has reached an impressive level of sophistication and efficiency, emerging as a fundamental tool in synthesis because of the versatility offered by organoboron compounds. As a remarkable particularity, the catalytic systems originally developed for these reactions are relatively insensitive to directing effects, and the regioselectivity of the borylations is typically governed by steric factors. Likely stimulated by the great synthetic potential of the expected functionalised organoboranes, however, many groups have recently focused on the development of complementary strategies for directed, site-selective borylation reactions where a directing group controls the course of the reaction. In this tutorial review, the different strategies and findings related to the development of these directed borylation reactions via C(sp2)–H or C(sp3)–H activation will be summarized and discussed.

Magnetic interactions in molecules and highly correlated materials: physical content, analytical derivation, and rigorous extraction of magnetic Hamiltonians.

Abstract: Physical Content, Analytical Derivation, and Rigorous Extraction of Magnetic Hamiltonians Jean Paul Malrieu,† Rosa Caballol,‡ Carmen J. Calzado, Coen de Graaf,‡,∥ and Nathalie Guiheŕy*,† †Laboratoire de Chimie et Physique Quantiques, Universite ́ de Toulouse 3, 118 route de Narbonne, 31062 Toulouse, France ‡Departament de Química Física i Inorgaǹica, Universitat Rovira i Virgili, Marcel·lí Domingo s/n, 43007 Tarragona, Spain Departamento de Química Física, Universidad de Sevilla, Profesor Garcia Gonzalez s/n, 41012 Sevilla, Spain Institucio ́ Catalana de Recerca i Estudis Avanca̧ts (ICREA), Passeig Lluis Companys 23, 08010 Barcelona, Spain

NLRP3 inflammasome is activated in mononuclear blood cells from patients with major depressive disorder.

Abstract: Introduction Major depressive disorder (MDD) is a very prevalent disease which pathogenic mechanism remains elusive. There are some hypotheses and pilot studies suggesting that cytokines may play an important role in MDD. In this respect, we have investigated the role of NLRP3 inflammasome complex in the maturation of caspase-1 and the processing of its substrates, IL-1β and IL-18, in blood cells from MDD patients. Methods Forty MDD patients were selected for this study, twenty without treatments and twenty treated with amitriptyline, a common tricyclic antidepressant. Blood samples from twenty healthy volunteers were included in the study. The inflammasome activation was studied by Western blot and real-time PCR of NLRP3 and caspase 1 and serum levels of IL-1β and 18. Results We observed increased gene expression of NLRP3 and caspase-1 in blood cells, and increased serum levels of IL-1β and IL-18 in non-treated patients. IL-1β and IL-18 correlated with Beck Depression Inventory (BDI) scores of MDD patients. Interestingly, amitriptyline treatment reduced NLRP3 and caspase-1 gene expression, and IL-1β and IL-18 serum levels. As it is well established that oxidative stress is associated with NLRP3 inflammasome activation, we next studied mitochondrial ROS and lipid peroxidation (LPO) levels in MDD patients. Increased levels of mitochondrial ROS and LPO were observed in MDD patients, however oxidative damage was higher in MDD patients treated with amitriptyline. Conclusions These findings provide new insight into the pathogenesis of MDD and the effects of amitriptyline treatment on NLRP3 inflammasome activation and IL-1β and IL-18 serum levels.

Graph-theoretic approach to quantum correlations.

Abstract: Correlations in Bell and noncontextuality inequalities can be expressed as a positive linear combination of probabilities of events. Exclusive events can be represented as adjacent vertices of a graph, so correlations can be associated to a subgraph. We show that the maximum value of the correlations for classical, quantum, and more general theories is the independence number, the Lovasz number, and the fractional packing number of this subgraph, respectively. We also show that, for any graph, there is always a correlation experiment such that the set of quantum probabilities is exactly the Grotschel-Lovasz-Schrijver theta body. This identifies these combinatorial notions as fundamental physical objects and provides a method for singling out experiments with quantum correlations on demand.

Insight into the informational-structure behavior of the Diels-Alder reaction of cyclopentadiene and maleic anhydride.

Abstract: The course of the Diels-Alder reactions of cyclopentadiene and maleic anhydride were studied. Two reaction paths were modelled: endo- and exo-selective paths. All structures within the transient region were characterized and analyzed by means of geometrical descriptors, physicochemical parameters and information-theoretical measures in order to observe the linkage between chemical behavior and the carriage of information. We have shown that the information-theoretical characterization of the chemical course of the reaction is in complete agreement with its phenomenological behavior in passing from reactants to products. In addition, we were able to detect the main differences between the two reaction mechanisms. This type of informational analysis serves to provide tools to help understand the chemical reactivity of the two simplest Diels-Alder reactions, which permits the establishment of a connection between the quantum changes that molecular systems exert along reaction coordinates and standard physicochemical phenomenology. In the present study, we have shown that every reaction stage has a family of subsequent structures that are characterized not solely by their phenomenological behavior but also by informational properties of their electronic density distribution (localizability, order, uniformity). Moreover, we were able to describe the main differences between endo-adduct and exo-adduct pathways. With the advent of new experimental techniques, it is in principle possible to observe the structural changes in the transient regions of chemical reactions. Indeed, through this work we have provided the theoretical concepts needed to unveil the concurrent processes associated with chemical reactions.

Distributed Model Predictive Control: An Overview and Roadmap of Future Research Opportunities

Abstract: Model-predictive control (MPC) is an optimization-based control technique that uses 1) a mathematical model of a system to predict the system's behavior over a given horizon, 2) an objective function that represents what system behavior is desirable, 3) a mathematical formalization of operational constraints that have to be satisfied, 4) measurements of the state of the system at each time step, and 5) any information regarding upcoming disturbances that may be available. This article surveyed and categorized 35 distributed MPC approaches. Subsequently, several of the insights gained from the survey were presented. This study provides a picture of what features have received more or less attention over the last years, bringing about potential research niches for new approaches.

From Entrepreneurial Orientation and Learning Orientation to Business Performance: Analysing the Mediating Role of Organizational Learning and the Moderating Effects of Organizational Size

Abstract: Following the organizational learning theory and the knowledge-based view approach, this contribution aims to study the influence of entrepreneurial orientation and learning orientation on organizational learning, considering the latter as a mediating variable in the relationships between both antecedent cultural values and business performance. We also analyse the moderating role of organizational size on these previous relationships. The hypotheses proposed in our research model are tested on a sample of 140 Spanish industrial companies, applying variance-based structural equation modelling: partial least squares. In order to assess the moderating effects of organizational size, we adopt a multi-group approach using two subsamples with large firms and small and medium-sized enterprises (SMEs). Our findings indicate that organizational learning partially mediates the relationship between entrepreneurial orientation and performance and fully mediates the link between learning orientation and performance. Likewise, the results reveal that the relationship established between entrepreneurial orientation and organizational learning is more intense for the group of large firms than for the group of SMEs. Moreover, the influence of learning orientation on organizational learning is greater in SMEs than in large firms.

An optimization spiking neural p system for approximately solving combinatorial optimization problems.

Abstract: Membrane systems (also called P systems) refer to the computing models abstracted from the structure and the functioning of the living cell as well as from the cooperation of cells in tissues, organs, and other populations of cells. Spiking neural P systems (SNPS) are a class of distributed and parallel computing models that incorporate the idea of spiking neurons into P systems. To attain the solution of optimization problems, P systems are used to properly organize evolutionary operators of heuristic approaches, which are named as membrane-inspired evolutionary algorithms (MIEAs). This paper proposes a novel way to design a P system for directly obtaining the approximate solutions of combinatorial optimization problems without the aid of evolutionary operators like in the case of MIEAs. To this aim, an extended spiking neural P system (ESNPS) has been proposed by introducing the probabilistic selection of evolution rules and multi-neurons output and a family of ESNPS, called optimization spiking neural P system (OSNPS), are further designed through introducing a guider to adaptively adjust rule probabilities to approximately solve combinatorial optimization problems. Extensive experiments on knapsack problems have been reported to experimentally prove the viability and effectiveness of the proposed neural system.

One-month strawberry-rich anthocyanin supplementation ameliorates cardiovascular risk, oxidative stress markers and platelet activation in humans.

Abstract: Strawberries are an important fruit in the Mediterranean diet because of their high content of essential nutrients and beneficial phytochemicals, which seem to exert beneficial effects in human health. Healthy volunteers were supplemented daily with 500 g of strawberries for 1 month. Plasma lipid profile, circulating and cellular markers of antioxidant status, oxidative stress and platelet function were evaluated at baseline, after 30 days of strawberry consumption and 15 days after the end of the study. A high concentration of vitamin C and anthocyanins was found in the fruits. Strawberry consumption beneficially influenced the lipid profile by significantly reducing total cholesterol, low-density lipoprotein cholesterol and triglycerides levels (−8.78%, −13.72% and −20.80%, respectively; P P P P P

Beyond entrepreneurial intentions: values and motivations in entrepreneurship

Abstract: The role of values and motivations in understanding the entrepreneurial cognitive process deserves closer attention. So far, the predominant approach has been studying the entrepreneurial intention. This has been a very fruitful avenue of research. However, there is still much to be known to fully understand how the decision to start a venture is formed, and how the individual acts to implement that decision. Values and motivations are closely related, since both of them are linked to the notion of goals. The higher the importance attached to a goal, the more likely the person will form action plans to achieve it. In this paper, we present some ideas on how values and motivations could be integrated into the predominant entrepreneurial intention model. Firstly, we propose that values may help to explain the formation of intention antecedents (e.g., attitudes), and also moderate their effect on the entrepreneurial intention. Secondly, we point to the possibility that values and motivations may also play a role in the intention–action link. In particular, they may be instrumental in overcoming the barriers and obstacles toward effective start-up. In addition, this paper is also an introduction to the special issue, and we present the four papers selected to be included and highlight some of the most interesting aspects of their contributions.

Experiments of drops impacting a smooth solid surface: a model of the critical impact speed for drop splashing

Abstract: Making use of experimental and theoretical considerations, in this Letter we deduce a criterion to determine the critical velocity for which a drop impacting a smooth dry surface either spreads over the substrate or disintegrates into smaller droplets. The derived equation, which expresses the splash threshold velocity as a function of the material properties of the two fluids involved, the drop radius, and the mean free path of the molecules composing the surrounding gaseous atmosphere, has been thoroughly validated experimentally at normal atmospheric conditions using eight different liquids with viscosities ranging from μ=3×10(-4) to μ=10(-2) Pa s, and interfacial tension coefficients varying between σ=17 and σ=72 mN m(-1). Our predictions are also in fair agreement with the measured critical speed of drops impacting in different gases at reduced pressures given by Xu et al. [Phys. Rev. Lett. 94, 184505 (2005).

Speed of the internationalization process: The role of diversity and depth in experiential learning

Abstract: By analyzing internationalization as a dynamic process, we attempt to explain the speed of international operations in terms of learning acquired in the course of past international activities. We consider that the speed of the internationalization process depends on the type of experiential learning that results from decisions implicit in the internationalization process: choice of location and modes of operation. Firms develop two types of learning activities with respect to the selection of foreign markets and modes of operation: diversity and depth of accumulated international activities. We propose that depth of international activities has an inverted U-shaped impact on the speed of the internationalization process, while diversity of international activities has a U-shaped influence on the speed of internationalization process. The results of our longitudinal study of 889 firms over 23 years (1986–2008) suggest that diversity of international activities promotes long-term learning by exposing the firm to richer experiences, although such learning only takes place over time. Depth of international activities may accelerate the internationalization process in the short term, but it eventually restrains its potential for development in the long term. Our research highlights the short-term vs long-term consequences of different types of decisions related to the internationalization process.

Seidman, I. (2013). Interviewing as qualitative research: A guide for researchers in education & the social sciences. New York: Teachers College.

Abstract: El profesor emerito en investigacion cualitativa Irving Seidman, nos proporciona en esta obra un compendio de aspectos que se deben considerar, a la hora de realizar un optimo proceso de investigacion.

Speed Control of Five-Phase Induction Motors With Integrated Open-Phase Fault Operation Using Model-Based Predictive Current Control Techniques

Abstract: Fault tolerance is one of the most interesting features in stand-alone electric propulsion systems. Multiphase induction motor drives are presented like a better alternative to their three-phase counterparts because of their capability to withstand faulty situations, ensuring the postfault operation of the drive. Finite-control set model-based predictive control (FCS-MPC) has been introduced in the last decade like an interesting alternative to conventional controllers for the electrical torque and current regulation of multiphase drives. However, FCS-MPC strategies for multiphase drives with the ability to manage pre- and postfault operations have not been addressed at all. This paper proposes a fault-tolerant speed control for five-phase induction motor drives with the ability to run the system before and after an open-phase fault condition using an FCS-MPC strategy. Experimental results are provided in order to validate the functionality of the proposed control method, maintaining rated currents and ensuring fast and ripple-free torque response.

Oxidative Stress in Traumatic Brain Injury

Abstract: Traumatic brain injury (TBI) is a major healthcare concern, constituting a major cause of death and disability throughout the world. Among the factors leading to TBI outcome are biochemical cascades which occur in response to primary and secondary injury. These mechanisms generate oxidative stress, an imbalance between oxidant and antioxidant agents that can result in neural dysfunction and death. After TBI, an assembly of oxidative stress markers (carbonylated proteins, lipid peroxides, reactive oxygen and reactive nitrogen species) are produced in the brain, while antioxidant defense enzymes decrease (GSH, ratio GSH/GSSG, GPx, GR, GST, G-6PD, SOD, CAT). This imbalance is directly related to the pathogenesis of TBI. Therefore, the development of antioxidant strategies is of primary interest in ongoing efforts to optimize brain injury treatment. The success of any drug intervention strategy relies, in part, on knowledge of the optimal dosage and therapeutic window for its administration. But while the enzymes involved in oxidative stress have been identified, the temporal course of this imbalance following TBI has yet to be determined. This would explain why most antioxidant strategies developed to treat patients with TBI have failed.

Single-line rail rapid transit timetabling under dynamic passenger demand

Abstract: Railway planning is a complex activity which is usually decomposed into several stages, traditionally network design, line design, timetabling, rolling stock, and staffing. In this paper, we study the design and optimization of train timetables for a rail rapid transit (RRT) line adapted to a dynamic demand environment, which focuses on creating convenient timetables for passengers. The objective is to minimize the average passenger waiting time at the stations, thus focusing on passenger welfare. We first propose two mathematical programming formulations which generalize the non-periodic train timetabling problem on a single line under a dynamic demand pattern. We then analyze the properties of the problem before introducing a fast adaptive large neighborhood search (ALNS) metaheuristic in order to solve large instances of the problem within short computation times. The algorithm yields timetables that may not be regular or periodic, but are adjusted to a dynamic demand behavior. Through extensive computational experiments on artificial and real-world based instances, we demonstrate the computational superiority of our ALNS compared with a truncated branch-and-cut algorithm. The average reduction in passenger waiting times is 26%, while the computational time of our metaheuristic is less than 1% of that required by the alternative CPLEX-based algorithm. Out of 120 open instances, we obtain 84 new best known solutions and we reach the optimum on 10 out of 14 instances with known optimal solutions.

Formation Control of Autonomous Underwater Vehicles Subject to Communication Delays

Abstract: This paper addresses the formation control problem for fleets of autonomous underwater vehicles (AUVs). The solution is based on the virtual leader approach, with the main goal of designing a control system to cope with the inter-vehicle communication problems, especially significant in underwater environments. The use of kinematic relations allows the linearization of the AUV dynamics maintaining its turning capacities. The control strategy consists of a feedback H2/H∞ controller in combination with a feedforward controller, which makes it possible to deal with delays and packets dropouts while ensuring a good formation control performance.

National culture, entrepreneurship and economic development: different patterns across the European Union

Abstract: The aim of this paper is double. Firstly, it contributes to identifying the specific role of national culture as a variable that helps explain the level of economic development and reinforces the effect of entrepreneurship on the income level. Secondly, a deeper understanding of these relations in the case of the European Union is sought. In this study, data from two different sources have been used. The Schwartz Value Survey measures seven cultural orientations that are then grouped into three bipolar dimensions (embeddedness vs. autonomy, hierarchy vs. egalitarianism and mastery vs. harmony). The Global Entrepreneurship Monitor provides information regarding entrepreneurial activity. Using linear regression analysis, cultural and entrepreneurial variables are able to classify countries according to their development level, explaining over 60 % of the variance in Gross Domestic Product per capita. The role of culture is complex, with geographical elements being significantly relevant. In the case of Europe, some common elements conform what could be called “a European culture”: autonomy and egalitarianism clearly predominate over embeddedness and hierarchy, while harmony tends to prevail over mastery. Nevertheless, four well-defined groups of countries within the European Union emerge. Central and Northern Europe is closer to this European stereotypical culture, while English-speaking countries, Eastern Europe and the Mediterranean area exhibit their own differentiating elements each. These differences also exist with regard to entrepreneurial activity (overall Total Entrepreneurial Activity, necessity and opportunity-driven activity). Each of the four regional entrepreneurial cultures is characterized by a different entrepreneurial dynamics that may be plausibly explained by culture and income.