Steady-state global optimization of metabolic non-linear dynamic models through recasting into power-law canonical models

<p>Abstract</p> <p>Background</p> <p>Design of newly engineered microbial strains for biotechnological purposes would greatly benefit from the development of realistic mathematical models for the processes to be optimized. Such models can then be analyzed and, with the development and application of appropriate optimization techniques, one could identify the modifications that need to be made to the organism in order to achieve the desired biotechnological goal. As appropriate models to perform such an analysis are necessarily non-linear and typically non-convex, finding their global optimum is a challenging task. Canonical modeling techniques, such as Generalized Mass Action (GMA) models based on the power-law formalism, offer a possible solution to this problem because they have a mathematical structure that enables the development of specific algorithms for global optimization.</p> <p>Results</p> <p>Based on the GMA canonical representation, we have developed in previous works a highly efficient optimization algorithm and a set of related strategies for understanding the evolution of adaptive responses in cellular metabolism. Here, we explore the possibility of recasting kinetic non-linear models into an equivalent GMA model, so that global optimization on the recast GMA model can be performed. With this technique, optimization is greatly facilitated and the results are transposable to the original non-linear problem. This procedure is straightforward for a particular class of non-linear models known as Saturable and Cooperative (SC) models that extend the power-law formalism to deal with saturation and cooperativity.</p> <p>Conclusions</p> <p>Our results show that recasting non-linear kinetic models into GMA models is indeed an appropriate strategy that helps overcoming some of the numerical difficulties that arise during the global optimization task.</p

Alteration of Gene Expression Profile in Niemann-Pick Type C Mice Correlates with Tissue Damage and Oxidative Stress

Background: Niemann-Pick type C disease (NPC) is a neurovisceral lipid storage disorder mainly characterized by unesterified cholesterol accumulation in lysosomal/late endosomal compartments, although there is also an important storage for several other kind of lipids. The main tissues affected by the disease are the liver and the cerebellum. Oxidative stress has been described in various NPC cells and tissues, such as liver and cerebellum. Although considerable alterations occur in the liver, the pathological mechanisms involved in hepatocyte damage and death have not been clearly defined. Here, we assessed hepatic tissue integrity, biochemical and oxidative stress parameters of wild-type control (Npc1 +/+; WT) and homozygous-mutant (Npc1 -/-; NPC) mice. In addition, the mRNA abundance of genes encoding proteins associated with oxidative stress, copper metabolism, fibrosis, inflammation and cholesterol metabolism were analyzed in livers and cerebella of WT and NPC mice. Methodology/P

Stabilisation of the superoxide anion in bis(fluorosulfonyl)imide (FSI) ionic liquid by small chain length phosphonium cations: Voltammetric, DFT modelling and spectroscopic perspectives

Ionic liquids (ILs) containing the bis(fluorosulfonyl)imide anion, FSI, have been investigated as electrolytes for metal-air batteries. Full chemical reversibility is found for the reduction of oxygen to superoxide at 60 degrees C under short time scale conditions of cyclic voltammetry at a glassy carbon electrode when the IL contains the small chain length triisobutyl(methyl)phosphonium rather than a pyrrolidinium cation. DFT calculations suggest that this is a consequence of the higher ion pair association energy and shorter intermolecular distance associated with the interaction of the superoxide anion with the phosphonium cation. Stabilization on longer timescales was also established by spectroscopic techniques when the phosphonium based ILs were exposed to KO2. Studies on superoxide stability in related ionic liquids containing the triisobutyl(methyl)phosphonium cation with the fluorosulfonyl(trifluoromethanesulfonyl)imide, FTFSI, or bis(trifluoromethanesulfonyl)imide, TFSI, anions are also reported.

MODELLING SOLAR CELL S-SHAPED I-V CHARACTERISTICS WITH DC LUMPED-PARAMETER EQUIVALENT CIRCUITS ­ A REVIEW

This article reviews and appraises the dc lumped-parameter equivalent circuit models that have been proposed so far for representing some types of solar cells that can exhibit under certain circumstances a detrimental S-shaped concave deformation within the energy-producing fourth quadrant of their illuminated I–V characteristics. We first present a very succinct recollection of lumped-parameter equivalent circuits that are commonly used to model conventional solar cells in general. We then chronologically present and discuss lumped-parameter equivalent sub-circuits that, combined with conventional solar cell equivalent circuits, are used to specifically represent the undesired S-shaped behaviour. The mathematically descriptive equations of each complete equivalent circuit are also examined, and closed form solutions for the terminal current and voltage as explicit functions of each other are presented and discussed whenever available. While comparing the most salient features and explaining the practical advantages and disadvantages of such equivalent circuit models, we offer some comments on possible directions for further improvement

Microcirculatory alterations are more severe in anemic than in ischemic hypoxia

The intestinal mucosal-arterial PCO2 (ΔPCO2) remains remarkably stable in anemic hypoxia suggesting that the villi perfusion is well-maintained. The microcirculation, however, has been insufficiently studied in extreme hemodilution.Facultad de Ciencias Médica

Insight into the evolution of the Solanaceae from the parental genomes of Petunia hybrida

Petunia hybrida is a popular bedding plant that has a long history as a genetic model system. We report the whole-genome sequencing and assembly of inbred derivatives of its two wild parents, P. axillaris N and P. inflata S6. The current assemblies include 91.3% and 90.2% coverage of their diploid genomes (1.4 Gb; 2n=14) containing 32,928 and 36,697 protein-coding genes, respectively. The Petunia lineage has experienced at least two rounds of paleohexaploidization, the older gamma hexaploidy event, which is shared with other Eudicots, and the more recent Solanaceae paleohexaploidy event that is shared with tomato and other Solanaceae species. Transcription factors that were targets of selection during the shift from bee- to moth pollination reside in particularly dynamic regions of the genome, which may have been key to the remarkable diversity of floral color patterns and pollination systems. The high quality genome sequences will enhance the value of Petunia as a model system for basic and applied research on a variety of unique biological phenomena

Energy applications of ionic liquids

Ionic liquids offer a unique suite of properties that make them important candidates for a number of energy related applications. Cation–anion combinations that exhibit low volatility coupled with high electrochemical and thermal stability, as well as ionic conductivity, create the possibility of designing ideal electrolytes for batteries, super-capacitors, actuators, dye sensitised solar cells and thermoelectrochemical cells. In the field of water splitting to produce hydrogen they have been used to synthesize some of the best performing water oxidation catalysts and some members of the protic ionic liquid family co-catalyse an unusual, very high energy efficiency water oxidation process. As fuel cell electrolytes, the high proton conductivity of some of the protic ionic liquid family offers the potential of fuel cells operating in the optimum temperature region above 100 °C. Beyond electrochemical applications, the low vapour pressure of these liquids, along with their ability to offer tuneable functionality, also makes them ideal as CO2 absorbents for post-combustion CO2 capture. Similarly, the tuneable phase properties of the many members of this large family of salts are also allowing the creation of phase-change thermal energy storage materials having melting points tuned to the application. This perspective article provides an overview of these developing energy related applications of ionic liquids and offers some thoughts on the emerging challenges and opportunities

EuroPineDB: a high-coverage web database for maritime pine transcriptome

Pinus pinaster is an economically and ecologically important species that is becoming a woody gymnosperm model. Its enormous genome size makes whole-genome sequencing approaches are hard to apply. Therefore, the expressed portion of the genome has to be characterised and the results and annotations have to be stored in dedicated databases

Salud de los trabajadores

Actividad f&iacute;sica y su relaci&oacute;n con los factores de riesgo cardiovascular de carteros chilenosAn&aacute;lisis de resultados: riesgos psicosociales en el trabajo Suceso-Istas 21 en Cesfam Quell&oacute;nAusentismo laboral por enfermedades oftalmol&oacute;gicas, Chile 2009Brote de diarreas por norovirus, posterremoto-tsunami, Constituci&oacute;n, Regi&oacute;n del MauleCalidad de vida en profesionales de la salud p&uacute;blica chilenaCaracterizaci&oacute;n del reposo laboral en personal del SSMN durante el primer semestre de 2010Concentraci&oacute;n de nicotina en pelo en trabajadores no fumadores expuestos a humo de tabaco ambientalCondiciones de trabajo y bienestar/malestar docente en profesores de ense&ntilde;anza media de SantiagoDisfunci&oacute;n auditiva inducida por exposici&oacute;n a xilenoErgonom&iacute;a aplicada al estudio del s&iacute;ndrome de dolor lumbar en el trabajoEstimaci&oacute;n de la frecuencia de factores de riesgo cardiovascular en trabajadores de una empresa mineraExposici&oacute;n a plaguicidas inhibidores de la acetilcolinesterasa en Colombia, 2006-2009Factores de riesgo y da&ntilde;os de salud en conductores de una empresa peruana de transporte terrestre, 2009Las consecuencias de la cultura en salud y seguridad ocupacional en una empresa mineraPercepci&oacute;n de cambios en la pr&aacute;ctica m&eacute;dica y estrategias de afrontamientoPercepci&oacute;n de la calidad de vida en la Universidad del Biob&iacute;oPesos m&aacute;ximos aceptables para tareas de levantamiento manual de carga en poblaci&oacute;n laboral femeninaRiesgo coronario en trabajadores mineros seg&uacute;n la funci&oacute;n de Framingham adaptada para la poblaci&oacute;n chilenaTrastornos emocionales y riesgo cardiovascular en trabajadores de la salu

A collaboratively derived environmental research agenda for Galapagos

Galápagos is one of the most pristine archipelagos in the world and its conservation relies upon research and sensible management. In recent decades both the interest in, and the needs of, the islands have increased, yet the funds and capacity for necessary research have remained limited. It has become, therefore, increasingly important to identify areas of priority research to assist decision-making in Galápagos conservation. This study identified 50 questions considered priorities for future research and management. The exercise involved the collaboration of policy makers, practitioners and researchers from more than 30 different organisations. Initially, 360 people were consulted to generate 781 questions. An established process of preworkshop voting and three rounds to reduce and reword the questions, followed by a two-day workshop, was used to produce the final 50 questions. The most common issues raised by this list of questions were human population growth, climate change and the impact of invasive alien species. These results have already been used by a range of organisations and politicians and are expected to provide the basis for future research on the islands so that its sustainability may be enhanced. </jats:p