Influence of Microbial Growth on Hydraulic Properties of Pore Networks

From laboratory experiments it is known that bacterial biomass is able to influence the hydraulic properties of saturated porous media, an effect called bioclogging. To interpret the observations of these experiments and to predict possible bioclogging effects on the field scale it is necessary to use transport models, which are able to include bioclogging. For these models it is necessary to know the relation between the amount of biomass and the hydraulic conductivity of the porous medium. Usually these relations were determined using bundles of parallel pore channels and do not account for interconnections between the pores in more than one dimension. The present study uses two-dimensional pore network models to study the effects of bioclogging on the pore scale. Numerical simulations were done for two different scenarios of the growth of biomass in the pores. Scenario 1 assumes microbial growth in discrete colonies clogging particular pores completely. Scenario 2 assumes microbial growth as a biofilm growing on the wall of each pore. In both scenarios the hydraulic conductivity was reduced by at least two orders of magnitude, but for the colony scenario much less biomass was needed to get a maximal clogging effect and a better agreement with previously published experimental data could be found. For both scenarios it was shown that heterogeneous pore networks could be clogged with less biomass than more homogeneous one

Global-scale quantification of mineralization pathways in marine sediments: A reaction-transport modeling approach

[1] The global-scale quantification of organic carbon (Corg) degradation pathways in marine sediments is difficult to achieve experimentally due to the limited availability of field data. In the present study, a numerical modeling approach is used as an alternative to quantify the major metabolic pathways of Corg oxidation (Cox) and associated fluxes of redox-sensitive species fluxes along a global ocean hypsometry, using the seafloor depth (SFD) as the master variable. The SFD dependency of the model parameters and forcing functions is extracted from existing empirical relationships or from the NOAA World Ocean Atlas. Results are in general agreement with estimates from the literature showing that the relative contribution of aerobic respiration to Cox increases from 80% in deep-sea sediments. Sulfate reduction essentially follows an inversed SFD dependency, the other metabolic pathways (denitrification, Mn and Fe reduction) only adding minor contributions to the global-scale mineralization of Corg. The hypsometric analysis allows the establishment of relationships between the individual terminal electron acceptor (TEA) fluxes across the sediment-water interface and their respective contributions to the Corg decomposition process. On a global average, simulation results indicate that sulfate reduction is the dominant metabolic pathway and accounts for approximately 76% of the total Cox, which is higher than reported so far by other authors. The results also demonstrate the importance of bioirrigation for the assessment of global species fluxes. Especially at shallow SFD most of the TEAs enter the sediments via bioirrigation, which complicates the use of concentration profiles for the determination of total TEA fluxes by molecular diffusion. Furthermore, bioirrigation accounts for major losses of reduced species from the sediment to the water column prohibiting their reoxidation inside the sediment. As a result, the total carbon mineralization rate exceeds the total flux of oxygen into the sediment by a factor of 2 globally

P3D-BRNS v1.0.0: a three-dimensional, multiphase, multicomponent, pore-scale reactive transport modelling package for simulating biogeochemical processes in subsurface environments

The porous microenvironment of soil offers various environmental functions which are governed by physical and reactive processes. Understanding reactive transport processes in porous media is essential for many natural systems (soils, aquifers, aquatic sediments or subsurface reservoirs) or technological processes (water treatment or ceramic and fuel cell technologies). In particular, in the vadose zone of the terrestrial subsurface the spatially and temporally varying saturation of the aqueous and the gas phase leads to systems that involve complex flow and transport processes as well as reactive transformations of chemical compounds in the porous material. To describe these interacting processes and their dynamics at the pore scale requires a well-suited modelling framework accounting for the proper description of all relevant processes at a high spatial resolution. Here we present P3D-BRNS as a new open-source modelling toolbox harnessing the core libraries of OpenFOAM and coupled externally to the Biogeochemical Reaction Network Simulator (BRNS). The native OpenFOAM volume-of-fluid solver is extended to have an improved representation of the fluid–fluid interface. The solvers are further developed to couple the reaction module which can be tailored for a specific reactive transport simulation. P3D-RBNS is benchmarked against three different flow and reactive transport processes: (1) fluid–fluid configuration in a capillary corner, (2) mass transfer across the fluid–fluid interface and (3) microbial growth with a high degree of accuracy. Our model allows for simulation of the spatio-temporal distribution of all biochemical species in the porous structure (obtained from μ-CT images), for conditions that are commonly found in the laboratory and environmental systems. With our coupled computational model, we provide a reliable and efficient tool for simulating multiphase, reactive transport in porous media.</p

Performance testing in continuous integration environments

The purpose of this case study is to evaluate how and which performance testing tools which can be used in continuous integration (CI) environments. By doing so, developers can see the effects of changes immediately and react against performance problems of their applications. This will help companies to eliminate performance issues which the media is reporting about more often every day. CI provides the reference platform for executing the performance tests and the performance testing tools provide metrics like response time and percentage of errors. These metrics can be combined through CI plugins. The results of this combination can be visualized in form of graphs and tables. Through this case study, we give a short market overview of current CI servers and performance testing tools. In respect of the requirements by adesso AG, we will only evaluate performance testing tools, which can be integrated into the Atlassian Bamboo or Jenkins CI. We evaluated six performance testing tools of which four were integratable into the CI servers. Based on the results of our evaluation we will give a recommendation

Anthropogenic perturbation of the carbon fluxes from land to ocean

A substantial amount of the atmospheric carbon taken up on land through photosynthesis and chemical weathering is transported laterally along the aquatic continuum from upland terrestrial ecosystems to the ocean. So far, global carbon budget estimates have implicitly assumed that the transformation and lateral transport of carbon along this aquatic continuum has remained unchanged since pre-industrial times. A synthesis of published work reveals the magnitude of present-day lateral carbon fluxes from land to ocean, and the extent to which human activities have altered these fluxes. We show that anthropogenic perturbation may have increased the flux of carbon to inland waters by as much as 1.0 Pg C yr-1 since pre-industrial times, mainly owing to enhanced carbon export from soils. Most of this additional carbon input to upstream rivers is either emitted back to the atmosphere as carbon dioxide (~0.4 Pg C yr-1) or sequestered in sediments (~0.5 Pg C yr-1) along the continuum of freshwater bodies, estuaries and coastal waters, leaving only a perturbation carbon input of ~0.1 Pg C yr-1 to the open ocean. According to our analysis, terrestrial ecosystems store ~0.9 Pg C yr-1 at present, which is in agreement with results from forest inventories but significantly differs from the figure of 1.5 Pg C yr-1 previously estimated when ignoring changes in lateral carbon fluxes. We suggest that carbon fluxes along the land–ocean aquatic continuum need to be included in global carbon dioxide budgets.Peer reviewe

Predictive Task Monitoring for Business Processes

Information sources providing real-time status of physical objects have drastically increased in recent times. So far, research in business process monitoring has mainly focused on checking the completion of tasks. However, the availability of real-time information allows for a more detailed tracking of individual business tasks. This paper describes a framework for controlling the safe execution of tasks and signalling possible misbehaviours at runtime. It outlines a real use case on smart logistics and the preliminary results of its application.European Union FP7/2007-2013 / 318275 (GET Service

Investigaciones sobre la ocurrencia, epidemiología e importancia económica de los helmintos en terneros en el departamento de Córdoba, Colombia.

El objetivo del trabajo, fué investigar los aspectos epidemiológicos y económicos de las infestaciones con helmintos en terneros del departamento de Córdoba (Colombia). Las investigaciones se realizaron durante un año (mayo 1987-julio 1988) con grupos de terneros tratados y no tratados con antihelmínticos en 2 fincas. Se estudió el curso de la excreción de huevos y la dinámica estacional de la infestación del pasto con L3 en terneros centinelas (29 Holstein - Friesian comprados en la Sabana de Bogotá y aclimatados en Turipaná-Monteria). Las muestras de materia fecal y de sangre se examinaron a intervalos mensuales para determinar los estadios parasitarios, el hematocrito y las concentraciones de hemoglobina, albúmina y proteina total. en ambas haciendas se expusieron los terneros centinelas en forma continua. La reducción de la excreción de huevos debida al desarrollo de la inmunidad para strongyloides papillosus, ocurrió cuando los terneros tenian 5 meses de edad, la inmunidad a Trichostrongylidae apareció a los 8 meses. Los géneros que predominaron fueron: Cooperia (punctata, oncophora), Haemonchus (similis, placei, mecistocirrus), Oesophagostomum radiatum, Dictyocaulus viviparus, Strongyloides papillosus. Se encontró un bajo número de larvas hipobióticas en la membrana mucosa de abomaso de terneros centinelas durante el verano. Los animales tratados con antihelmínticos presentaron ganancias de peso, mas altas, respecto a los no tratados. Se observó correlación entre la ganancia de peso y los componentes sanguíneos independientes de si habian recibido o no tratamiento antihelmíntico. Las diferencias en los niveles de albúmina entre terneros tratados o no, se encontró en una sola finca. En el período siguiente al de máxima carga de vermes.;Se recomienda como medida de control para Trichostrongylidae: tratamientos antihelmínticos al comienzo, mediados y final del verano, descontaminación de los potreros para vacas con terneros lactantes, destinados a pastura durante el verano, haciendo relevos (8 a 12 semanas) anticipados y removiendo la materia fecal depositada en los mismos en el verano, no concentrar terneros recién destetados en grupos separados, se puede dejar pastar en potreros con animales mayores de 18 mese

Elucidating the impact of micro-scale heterogeneous bacterial distribution on biodegradation

Groundwater microorganisms hardly ever cover the solid matrix uniformly–instead they form micro-scale colonies. To which extent such colony formation limits the bioavailability and biodegradation of a substrate is poorly understood. We used a high-resolution numerical model of a single pore channel inhabited by bacterial colonies to simulate the transport and biodegradation of organic substrates. These high-resolution 2D simulation results were compared to 1D simulations that were based on effective rate laws for bioavailability-limited biodegradation. We (i) quantified the observed bioavailability limitations and (ii) evaluated the applicability of previously established effective rate concepts if microorganisms are heterogeneously distributed. Effective bioavailability reductions of up to more than one order of magnitude were observed, showing that the micro-scale aggregation of bacterial cells into colonies can severely restrict the bioavailability of a substrate and reduce in situ degradation rates. Effective rate laws proved applicable for upscaling when using the introduced effective colony sizes