Thomsen, M. C., Fuentes, A., Demarco, R., Volkwein, C., Consalvi, J. L., & Reszka, P. (2017). Soot measurements in candle flames. Exp. Therm. Fluid Sci., 82, 116–123.
Abstract: Soot volume fractions and soot temperatures have been measured for the first time on candle flames. Measurements on laminar steady flames were carried out using candles with wick diameters of 2, 3 and 4 mm. Wick length was varied between 4 and 10 mm. The shape of the candle flame was obtained from CH* spontaneous emissions. Measured flame heights show an increase with wick dimensions, approaching an asymptotic value for increasing wick lengths. Soot volume fractions were obtained from laser extinction measurements with the Modulated Absorption/Emission (MAE) technique. A deconvolution technique and a regularization procedure were applied to the data. Radial profiles of soot volume fractions increase when varying the wick dimensions; this effect is produced by the greater amount of fuel released by the wick. Radially integrated soot volume fractions were also calculated, presenting a similar behavior to the soot volume fraction radial profiles. The peak integrated soot volume fraction was found at approximately half the flame height, independent of the wick dimensions and burning rates. Soot temperature was obtained from emission measurements at two different wavelengths considering the attenuation of the soot particles in the optical path length. A deconvolution and regularization procedure was carried out in order to obtain temperature profiles for different heights in the flame. The observed increase in soot production and soot temperature profiles was directly related to the higher burning rate experienced by the candle. The results show that peak integrated soot volume fractions are proportional to both the mass loss rates and the flame heights. (C) 2016 Elsevier Inc. All rights reserved.
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Timmermann, T., Armijo, G., Donoso, R., Seguel, A., Holuigue, L., & Gonzalez, B. (2017). Paraburkholderia phytofirmans PsJN Protects Arabidopsis thaliana Against a Virulent Strain of Pseudomonas syringae Through the Activation of Induced Resistance. Mol. Plant-Microbe Interact., 30(3), 215–230.
Abstract: Paraburkholderia phytofirmans PsJN is a plant growth promoting rhizobacterium (PGPR) that stimulates plant growth and improves tolerance to abiotic stresses. This study analyzed whether strain PsJN can reduce plant disease severity and proliferation of the virulent strain Pseudomonas syringae pv. tomato DC3000, in Arabidopsis plants, through the activation of induced resistance. Arabidopsis plants previously exposed to strain PsJN showed a reduction in disease severity and pathogen proliferation in leaves compared with noninoculated, infected plants. The plant defense related genes WRKY54, PR1, ERFI, and PDF1.2 demonstrated increased and more rapid expression in strain PsJN-treated plants compared with noninoculated, infected plants. Transcriptional analyses and functional analysis using signaling mutant plants suggested that resistance to infection by DC3000 in plants treated with strain PsJN involves salicylic acid, jasmonate-, and ethylene-signaling pathways to activate defense genes. Additionally, activation occurs through a specific PGPR-host recognition, being a necessary metabolically active state of the bacterium to trigger the resistance in Arabidopsis, with a strain PsJN associated molecular pattern only partially involved in the resistance response. This study provides the first report on the mechanism used by the PGPR P. phytofirmans PsJN to protect A. thaliana against a widespread virulent pathogenic bacterium.
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Uranga, R. M., Millan, C., Barahona, M. J., Recabal, A., Salgado, M., Martinez, F., et al. (2017). Adenovirus-mediated suppression of hypothalamic glucokinase affects feeding behavior. Sci Rep, 7, 13 pp.
Abstract: Glucokinase (GK), the hexokinase involved in glucosensing in pancreatic beta-cells, is also expressed in arcuate nucleus (AN) neurons and hypothalamic tanycytes, the cells that surround the basal third ventricle (3V). Several lines of evidence suggest that tanycytes may be involved in the regulation of energy homeostasis. Tanycytes have extended cell processes that contact the feeding-regulating neurons in the AN, particularly, agouti-related protein (AgRP), neuropeptide Y (NPY), cocaine-and amphetamine-regulated transcript (CART) and proopiomelanocortin (POMC) neurons. In this study, we developed an adenovirus expressing GK shRNA to inhibit GK expression in vivo. When injected into the 3V of rats, this adenovirus preferentially transduced tanycytes. qRT-PCR and Western blot assays confirmed GK mRNA and protein levels were lower in GK knockdown animals compared to the controls. In response to an intracerebroventricular glucose injection, the mRNA levels of anorexigenic POMC and CART and orexigenic AgRP and NPY neuropeptides were altered in GK knockdown animals. Similarly, food intake, meal duration, frequency of eating events and the cumulative eating time were increased, whereas the intervals between meals were decreased in GK knockdown rats, suggesting a decrease in satiety. Thus, GK expression in the ventricular cells appears to play an important role in feeding behavior.
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Valle, M. A., Ruz, G. A., & Masias, V. H. (2017). Using self-organizing maps to model turnover of sales agents in a call center. Appl. Soft. Comput., 60, 763–774.
Abstract: This paper proposes an approach for modeling employee turnover in a call center using the versatility of supervised self-organizing maps. Two main distinct problems exist for the modeling employee turnover: first, to predict the employee turnover at a given point in the sales agent's trial period, and second to analyze the turnover behavior under different performance scenarios by using psychometric information about the sales agents. Identifying subjects susceptible to not performing well early on, or identifying personality traits in an individual that does not fit with the work style is essential to the call center industry, particularly when this industry suffers from high employee turnover rates. Self-organizing maps can model non-linear relations between different attributes and ultimately find conditions between an individual's performance and personality attributes that make him more predisposed to not remain long in an organization. Unlike other models that only consider performance attributes, this work successfully uses psychometric information that describes a sales agent's personality, which enables a better performance in predicting turnover and analyzing potential personality profiles that can identify agents with better prospects of a successful career in a call center. The application of our model is illustrated and real data are analyzed from an outbound call center. (C) 2017 Elsevier B.V. All rights reserved.
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Vargas, C. A., Lagos, N. A., Lardies, M. A., Duarte, C., Manriquez, P. H., Aguilera, V. M., et al. (2017). Species-specific responses to ocean acidification should account for local adaptation and adaptive plasticity. Nat. Ecol. Evol., 1(4), 7 pp.
Abstract: Global stressors, such as ocean acidification, constitute a rapidly emerging and significant problem for marine organisms, ecosystem functioning and services. The coastal ecosystems of the Humboldt Current System (HCS) off Chile harbour a broad physical-chemical latitudinal and temporal gradient with considerable patchiness in local oceanographic conditions. This heterogeneity may, in turn, modulate the specific tolerances of organisms to climate stress in species with populations distributed along this environmental gradient. Negative response ratios are observed in species models (mussels, gastropods and planktonic copepods) exposed to changes in the partial pressure of CO2 (p(CO2)) far from the average and extreme P-CO2 levels experienced in their native habitats. This variability in response between populations reveals the potential role of local adaptation and/or adaptive phenotypic plasticity in increasing resilience of species to environmental change. The growing use of standard ocean acidification scenarios and treatment levels in experimental protocols brings with it a danger that inter-population differences are confounded by the varying environmental conditions naturally experienced by different populations. Here, we propose the use of a simple index taking into account the natural p(CO2) variability, for a better interpretation of the potential consequences of ocean acidification on species inhabiting variable coastal ecosystems. Using scenarios that take into account the natural variability will allow understanding of the limits to plasticity across organismal traits, populations and species.
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Vargas, I. T., Fischer, D. A., Alsina, M. A., Pavissich, J. P., Pasten, P. A., & Pizarro, G. E. (2017). Copper Corrosion and Biocorrosion Events in Premise Plumbing. Materials, 10(9), 30 pp.
Abstract: Corrosion of copper pipes may release high amounts of copper into the water, exceeding the maximum concentration of copper for drinking water standards. Typically, the events with the highest release of copper into drinking water are related to the presence of biofilms. This article reviews this phenomenon, focusing on copper ingestion and its health impacts, the physicochemical mechanisms and the microbial involvement on copper release, the techniques used to describe and understand this phenomenon, and the hydrodynamic effects. A conceptual model is proposed and the mathematical models are reviewed.
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Vasco, D. A., Munoz-Mejias, M., Pino-Sepulveda, R., Ortega-Aguilera, R., & Garcia-Herrera, C. (2017). Thermal simulation of a social dwelling in Chile: Effect of the thermal zone and the temperature-dependant thermophysical properties of light envelope materials. Appl. Therm. Eng., 112, 771–783.
Abstract: As in most countries, Chile exhibits a continuous growth of energy demand, although nowadays the country does not have enough conventional energy sources to supply it. For this reason, energy saving approaches in the residential sector have been encouraged. One of the solutions to improve the energy performance of the buildings is to decrease wasting energy through the building's envelope, therefore the thermal properties of materials used in building envelopes must be analyzed to evaluate the thermal response of houses. Normally, the thermal envelope of a social house in Chile is made of brick or wood along with light materials such as fiber cement, plasterboard, and thermal insulating materials as polystyrene foam. The experimental part of this work deals with the measurement of the thermal conductivity and thermal diffusivity of the aforementioned light materials in a temperature range from -5 degrees C to 40 degrees C through the transient line heat source method. The experimental results allowed the identification of 10-20% variation of those thermophysical properties. The response of the thermal envelope and the inner temperature of a social dwelling under seven different climatological conditions was evaluated through transient simulations with EnergyPlus. The results allowed to identify that the dwellings located in hotter zones are prone to having higher temperatures than the comfort temperature, and the recommendations of the thermal regulations in Chile are more effective in the colder thermal zones 6 and 7. (C) 2016 Elsevier Ltd. All rights reserved.
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Vera, J. (2017). Self-Organization of Vocabularies under Different Interaction Orders. Artif. Life, 23(2), 287–294.
Abstract: Traditionally, the formation of vocabularies has been studied by agent-based models (primarily, the naming game) in which random pairs of agents negotiate word-meaning associations at each discrete time step. This article proposes a first approximation to a novel question: To what extent is the negotiation of word-meaning associations influenced by the order in which agents interact? Automata networks provide the adequate mathematical framework to explore this question. Computer simulations suggest that on two-dimensional lattices the typical features of the formation of word-meaning associations are recovered under random schemes that update small fractions of the population at the same time; by contrast, if larger subsets of the population are updated, a periodic behavior may appear.
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Villena, M. J., & Araneda, A. A. (2017). Dynamics and stability in retail competition. Math. Comput. Simul., 134, 37–53.
Abstract: Retail competition today can be described by three main features: (i) oligopolistic competition, (ii) multi-store settings, and (iii) the presence of large economies of scale. In these markets, firms usually apply a centralized decisions making process in order to take full advantage of economies of scales, e.g. retail distribution centers. In this paper, we model and analyze the stability and chaos of retail competition considering all these issues. In particular, a dynamic multi-market Cournot Nash equilibrium with global economies and diseconomies of scale model is developed. We confirm the non-intuitive hypothesis that retail multi-store competition is more unstable than traditional small business that cover the same demand. The main sources of stability are the scale parameter, the number of markets, and the number of firms. (C) 2016 International Association for Mathematics and Computers in Simulation (IMACS). Published by Elsevier B.V. All rights reserved.
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Zuniga, A., Donoso, R. A., Ruiz, D., Ruz, G. A., & Gonzalez, B. (2017). Quorum-Sensing Systems in the Plant Growth-Promoting Bacterium Paraburkholderia phytofirmans PsJN Exhibit Cross-Regulation and Are Involved in Biofilm Formation. Mol. Plant-Microbe Interact., 30(7), 557–565.
Abstract: Quorum-sensing systems play important roles in host colonization and host establishment of Burkholderiales species. Beneficial Paraburkholderia species share a conserved quorum-sensing (QS) system, designated BraI/R, that controls different phenotypes. In this context, the plant growth-promoting bacterium Paraburkholderia phytofirmans PsJN possesses two different homoserine lactone QS systems BpI. 1/R.1 and BpI. 2/R.2 (BraI/R-like QS system). The BpI. 1/R.1 QS system was previously reported to be important to colonize and produce beneficial effects in Arabidopsis thaliana plants. Here, we analyzed the temporal variations of the QS gene transcript levels in the wild-type strain colonizing plant roots. The gene expression patterns showed relevant differences in both QS systems compared with the wild-type strain in the unplanted control treatment. The gene expression data were used to reconstruct a regulatory network model of QS systems in P.phytofirmans PsJN, using a Boolean network model. Also, we examined the phenotypic traits and transcript levels of genes involved in QS systems, using P. phytofirmans mutants in homoserine lactone synthases genes. We observed that the BpI. 1/R.1 QS system regulates biofilm formation production in strain PsJN and this phenotype was associated with the lower expression of a specific extracytoplasmic function sigma factor ecf26.1 gene (implicated in biofilm formation) in the bpI.1 mutant strain.
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