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  • 1
    Language: English
    In: Ecological Modelling, 2011, Vol.222(12), pp.1998-2010
    Description: ► The individual-based INDISIM-SOM model is far more sensitive to some parameters than to others. ► Key parameters for the evolution of C and N are microbial maintenance, energy, and death probability. ► The nitrification rate, in particular, appears highly affected by the death probability. ► The sensitivity analysis indicates what simplification of the model is possible. ► It also shows which parameters need to be evaluated with more accuracy than is currently achievable. The fate of soil carbon and nitrogen compounds in soils in response to climate change is currently the object of significant research. In particular, there is much interest in the development of a new generation of micro-scale models of soil ecosystems processes. Crucial to the elaboration of such models is the ability to describe the growth and metabolism of small numbers of individual microorganisms, distributed in a highly heterogeneous environment. In this context, the key objective of the research described in this article was to further develop an individual-based soil organic matter model, INDISIM-SOM, first proposed a few years ago, and to assess its performance with a broader experimental data set than previously considered. INDISIM-SOM models the dynamics and evolution of carbon and nitrogen associated with organic matter in soils. The model involves a number of state variables and parameters related to soil organic matter and microbial activity, including growth and decay of microbial biomass, temporal evolutions of easily hydrolysable N, mineral N in ammonium and nitrate, CO and O . The present article concentrates on the biotic components of the model. Simulation results demonstrate that the model can be calibrated to provide good fit to experimental data from laboratory incubation experiments performed on three different types of Mediterranean soils. In addition, analysis of the sensitivity toward its biotic parameters shows that the model is far more sensitive to some parameters, i.e., the microbial maintenance energy and the probability of random microbial death, than to others. These results suggest that, in the future, research should focus on securing better measurements of these parameters, on environmental determinants of the switch from active to dormant states, and on the causes of random cell death in soil ecosystems.
    Keywords: Individual-Based Model ; Soil Microbial Activity ; Soil Organic Matter ; C and N Mineralization ; Microbial Parameters ; Environmental Sciences ; Ecology
    ISSN: 0304-3800
    E-ISSN: 1872-7026
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  • 2
    Language: English
    In: PLoS ONE, 01 January 2014, Vol.9(6), p.e100830
    Description: The temporo-spatial relationship between the three organs (lung, spleen and lymph node) involved during the initial stages of Mycobacterium tuberculosis infection has been poorly studied. As such, we performed an experimental study to evaluate the bacillary load in each organ after aerosol...
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 3
    Language: English
    In: PLoS ONE, June 24, 2014, Vol.9(6)
    Description: The temporo-spatial relationship between the three organs (lung, spleen and lymph node) involved during the initial stages of Mycobacterium tuberculosis infection has been poorly studied. As such, we performed an experimental study to evaluate the bacillary load in each organ after aerosol or intravenous infection and developed a mathematical approach using the data obtained in order to extract conclusions. The results showed that higher bacillary doses result in an earlier IFN-[gamma] response, that a certain bacillary load (BL) needs to be reached to trigger the IFN-[gamma] response, and that control of the BL is not immediate after onset of the IFN-[gamma] response, which might be a consequence of the spatial dimension. This study may have an important impact when it comes to designing new vaccine candidates as it suggests that triggering an earlier IFN-[gamma] response might not guarantee good infection control, and therefore that additional properties should be considered for these candidates.
    Keywords: Interferon – Health Aspects ; Tuberculosis – Health Aspects
    ISSN: 1932-6203
    Source: Cengage Learning, Inc.
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  • 4
    Language: English
    In: IEEE Transactions on Applied Superconductivity, December 2015, Vol.25(6), pp.1-9
    Description: Wind energy is the world's fastest growing energy source. Specifically in the recent decade, offshore wind energy is the technology that has developed the fastest due to the stronger and stable winds produced at sea and the huge areas where it can be employed. Electricity production from wind sources has seen high growth along with wind turbine capacity, foreseeing a linear evolution in the next decade. Additionally, it has been well demonstrated recently that the larger the power per wind turbine unit installed, the lower the levelized cost of energy. Second-generation high-temperature superconductor synchronous generators with direct-drive technology (2GHTSDDSG) for offshore wind energy applications have recently emerged as an alternative to consider instead of permanent-magnet direct-drive synchronous generators (PMDDSG), due to their lower dimensions and low weight per megawatt. This paper contains a detailed "cradle-to-gate" life-cycle assessment of the 15-MW 2GHTSDDSG and PMDDSG, using GaBi 6 commercial software and PE International Professional and Ecoinvent 2.2 databases, as a result of quantifying each component required for the production. After a detailed inspection of each component fabrication, conclusions and recommendations are obtained and presented.
    Keywords: Wind Turbines ; Synchronous Generators ; Permanent Magnet Generators ; High-Temperature Superconductors ; Wind Energy Generation ; Second Generation High Temperature Superconductor Direct Drive Synchronous Generators (2ghtsddsg) ; Permanent Magnet Direct Drive Synchronous Generators (Pmddsg) ; Life Cycle Assessment Analysis (Lca) ; Environmental Impacts ; Global Warming Potential (Gwp) ; Engineering ; Physics
    ISSN: 1051-8223
    E-ISSN: 1558-2515
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  • 5
    In: Malaria Journal, 2010, Vol.9(Suppl 2), p.P9-P9
    Description: Global strategies to fight malaria consist of three components: medical coverage scale-up in the affected regions, sustained control of the disease and increasing local elimination. These strategies normally consider long-term temporal scales of the order of the decade and are typically formulated either in technical terms or through mathematical models that are not easily communicated to non-experts (e.g. local people that act as malaria control technicians and local governments). Yet, global strategies finally lie on local specific interventions, carried out by agents with a limited scope of action and covering short spans. Field actions against malaria typically have to struggle against logistic limitations and must be very well coordinated in order to succeed. There is a need for models that can connect field actors with strategy designers in order to tackle the specific constraints of each particular intervention, and to redefine objectives on the fly, in accordance with the field results.
    Keywords: Poster Presentations
    E-ISSN: 1475-2875
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  • 6
    Language: English
    In: Tuberculosis, November 2013, Vol.93(6), pp.690-698
    Description: The aim of this study was to evaluate the evolution and role of corded cell aggregation in cultures according to growth time and conditions. Thus, in standard culture using aerated 7H9 Middlebrook broth supplemented with 0.05% Tween 80, a dramatic CFU decrease was observed at the end of the exponential phase. This phase was followed by a stable stationary phase that led to dissociation between the optical density (O.D.) and CFU values, together with the formation of opaque colonies in solid culture. Further analysis revealed that this was due to cording. Scanning electron microscopy showed that cording led to the formation of very stable coiled structures and corded cell aggregations which proved impossible to disrupt by any of the physical means tested. Modulation of cording with a high but non-toxic concentration of Tween 80 led to a slower growth rate, avoidance of a sudden drop-off to the stationary phase, the formation of weaker cording structures and the absence of opaque colonies, together with a lower survival at later time-points. An innovative automated image analysis technique has been devised to characterize the cording process. This analysis has led to important practical consequences for the elaboration of inocula and suggests the importance of biofilm formation in survival of the bacilli in the extracellular milieu.
    Keywords: Mycobacterium Tuberculosis ; Cording ; Corded Cell Aggregation ; Culture Growth Characteristics ; Medicine
    ISSN: 1472-9792
    E-ISSN: 1873-281X
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  • 7
    Language: English
    In: Journal of Theoretical Biology, 2006, Vol.241(4), pp.939-953
    Description: The lag phase has been widely studied for years in an effort to contribute to the improvement of food safety. Many analytical models have been built and tested by several authors. The use of Individual-based Modelling (IbM) allows us to probe deeper into the behaviour of individual cells; it is a bridge between theories and experiments when needed. INDividual DIScrete SIMulation (INDISIM) has been developed and coded by our group as an IbM simulator and used to study bacterial growth, including the microscopic causes of the lag phase. First of all, the evolution of cellular masses, specifically the mean mass and biomass distribution, is shown to be a determining factor in the beginning of the exponential phase. Secondly, whenever there is a need for an enzyme synthesis, its rate has a direct effect on the lag duration. The variability of the lag phase with different factors is also studied. The known decrease of the lag phase with an increase in the temperature is also observed in the simulations. An initial study of the relationship between individual and collective lag phases is presented, as a complement to the studies already published. One important result is the variability of the individual lag times and generation times. It has also been found that the mean of the individual lags is greater than the population lag. This is the first in a series of studies of the lag phase that we are carrying out. Therefore, the present work addresses a generic system by making a simple set of assumptions.
    Keywords: Lag Phase ; Bacterial Growth ; Individual-Based Modelling ; Growth Rate ; Mathematical Modelling ; Biology
    ISSN: 0022-5193
    E-ISSN: 1095-8541
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  • 8
    Language: English
    In: BMC Plant Biology, 01 November 2010, Vol.10(1), p.255
    Description: Abstract Background The genus Arachis comprises 80 species and it is subdivided into nine taxonomic sections (Arachis, Caulorrhizae, Erectoides, Extranervosae, Heteranthae, Procumbentes, Rhizomatosae, Trierectoides, and Triseminatae). This genus is naturally confined to South America and most...
    Keywords: Botany
    ISSN: 1471-2229
    E-ISSN: 1471-2229
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  • 9
    Language: English
    In: IEEE Transactions on Applied Superconductivity, June 2013, Vol.23(3), pp.5401204-5401204
    Description: HTS power cable systems are an emerging technology aimed at competing with XLPE cable systems. Knowledge on the thermal operating conditions of HTS power devices is needed to estimate their availability when connected to a power system, because the HTS material must remain below its critical temperature to transport current. In this work, a simple finite difference method is used to assess the temperature distribution at certain cross-section of a second-generation coaxial HTS cable. This method has been implemented in MATLAB and its proper functioning has been verified with the software package FLUX. This method is a tool to establish temperature distributions among HTS cable layers under normal operating conditions. Additionally, the aim of this work is to serve as basis for future simulations including heat generation changes within the cable layers typically caused by grid fault events.
    Keywords: High Temperature Superconductors ; Superconducting Cables ; Copper ; Power Cables ; Cable Shielding ; Heating ; Dielectrics ; Finite Difference Methods ; High Temperature Superconductors ; Power Engineering Computing ; Superconducting Devices ; Engineering ; Physics
    ISSN: 1051-8223
    E-ISSN: 1558-2515
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  • 10
    Language: English
    In: Frontiers in microbiology, 2016, Vol.7, pp.33
    Description: The evolution of a tuberculosis (TB) infection toward active disease is driven by a combination of factors mostly related to the host response. The equilibrium between control of the bacillary load and the pathology generated is crucial as regards preventing the growth and proliferation of TB lesions. In addition, some experimental evidence suggests an important role of both local endogenous reinfection and the coalescence of neighboring lesions. Herein we propose a mathematical model that captures the essence of these factors by defining three hypotheses: (i) lesions grow logistically due to the inflammatory reaction; (ii) new lesions can appear as a result of extracellular bacilli or infected macrophages that escape from older lesions; and (iii) lesions can merge when they are close enough. This model was implemented in Matlab to simulate the dynamics of several lesions in a 3D space. It was also fitted to available microscopy data from infected C3HeB/FeJ mice, an animal model of active TB that reacts against Mycobacterium tuberculosis with an exaggerated inflammatory response. The results of the simulations show the dynamics observed experimentally, namely an initial increase in the number of lesions followed by fluctuations, and an exponential increase in the mean area of the lesions. In addition, further analysis of experimental and simulation results show a strong coincidence of the area distributions of lesions at day 21, thereby highlighting the consistency of the model. Three simulation series removing each one of the hypothesis corroborate their essential role in the dynamics observed. These results demonstrate that three local factors, namely an exaggerated inflammatory response, an endogenous reinfection, and a coalescence of lesions, are needed in order to progress toward active TB. The failure of one of these factors stops induction of the disease. This mathematical model may be used as a basis for developing strategies to stop the progression of infection toward disease in human lungs.
    Keywords: Mycobacterium Tuberculosis ; Active Tuberculosis ; Computational Model ; Dynamic Hypothesis ; Tuberculosis Lesions in Lungs
    ISSN: 1664-302X
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