WorldWideScience

Sample records for modeling leachate migration

  1. Household hazardous waste disposal to landfill: using LandSim to model leachate migration.

    Science.gov (United States)

    Slack, Rebecca J; Gronow, Jan R; Hall, David H; Voulvoulis, Nikolaos

    2007-03-01

    Municipal solid waste (MSW) landfill leachate contains a number of aquatic pollutants. A specific MSW stream often referred to as household hazardous waste (HHW) can be considered to contribute a large proportion of these pollutants. This paper describes the use of the LandSim (Landfill Performance Simulation) modelling program to assess the environmental consequences of leachate release from a generic MSW landfill in receipt of co-disposed HHW. Heavy metals and organic pollutants were found to migrate into the zones beneath a model landfill site over a 20,000-year period. Arsenic and chromium were found to exceed European Union and US-EPA drinking water standards at the unsaturated zone/aquifer interface, with levels of mercury and cadmium exceeding minimum reporting values (MRVs). The findings demonstrate the pollution potential arising from HHW disposal with MSW.

  2. Household hazardous waste disposal to landfill: Using LandSim to model leachate migration

    International Nuclear Information System (INIS)

    Slack, Rebecca J.; Gronow, Jan R.; Hall, David H.; Voulvoulis, Nikolaos

    2007-01-01

    Municipal solid waste (MSW) landfill leachate contains a number of aquatic pollutants. A specific MSW stream often referred to as household hazardous waste (HHW) can be considered to contribute a large proportion of these pollutants. This paper describes the use of the LandSim (Landfill Performance Simulation) modelling program to assess the environmental consequences of leachate release from a generic MSW landfill in receipt of co-disposed HHW. Heavy metals and organic pollutants were found to migrate into the zones beneath a model landfill site over a 20,000-year period. Arsenic and chromium were found to exceed European Union and US-EPA drinking water standards at the unsaturated zone/aquifer interface, with levels of mercury and cadmium exceeding minimum reporting values (MRVs). The findings demonstrate the pollution potential arising from HHW disposal with MSW. - Aquatic pollutants linked to the disposal of household hazardous waste in municipal landfills have the potential to exist in soil and groundwater for many years

  3. Migration of leachate solution through clay soil

    Energy Technology Data Exchange (ETDEWEB)

    Abdel Warith, M M

    1987-01-01

    The problem of domestic solid wastes buried in landfill sites is viewed from the aspect of leachate contamination and migration in the substrate, and the efficiency of natural clay barriers as an expedient economic lining material is assessed. Various chemical constituents of the landfill leachate of an actual waste containment site at Lachenaie (35 km east of Montreal) were determined from samples collected from specially designed basins. Data for companion tests on laboratory columns are also presented. Chemical analysis on samples from the basins and leachates from the columns measured changes in the concentration of: (a) cations (Na, K, Ca, and Mg), (b) anions (Cl, HCO/sub 3/, and CO/sub 3/) (c) total organic carbon (TOC), and (d) heavy metals (Fe, Zn, Pb, and Cu). The physical parameters measured included: (a) pH, and (b) specific conductivity. Predictions, using a dispersion-convection model for concentration profile development for either adsorbed or retained contaminants, were compared with the experimentally determined profiles (both in leaching columns and landfill laboratory model). Another set of experiments was also conducted to evaluate the effect of some organic fluids on the geotechnical properties of different clay soils (natural clay and two reference clay soils: illite and kaolinite). The results from this study have demonstrated that the natural clay soil can be used to adequately contain the different contaminant species usually present in the leachate solutions. Furthermore, the data suggested that under favorable soil conditions, landfill leachates containing low levels of trace metals will not pose a substantial contamination threat to the subsurface environment, provided that a proper thickness of barrier is used.

  4. Leachate migration and its impacts on the environment

    International Nuclear Information System (INIS)

    Hwang, Y. S.

    1998-12-01

    In Korea there are hundreds of landfill sites all over the peninsular and the leachate problem is one of the national concern. Heavy precipitation especially during hot summers creates the fast degradation of waste products in the site which accelerates the migration of the leachate. In this report current status of the landfill site related issues were studied along with potential solutions on them. Also the fundamental mathematical derivations to describe the movement of the leachate in geologic medium was studied. These results shall be used to assess the leachate migration in the specific landfill site in the 2nd R and D year

  5. Leachate migration and its impacts on the environment

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Y. S

    1998-12-01

    In Korea there are hundreds of landfill sites all over the peninsular and the leachate problem is one of the national concern. Heavy precipitation especially during hot summers creates the fast degradation of waste products in the site which accelerates the migration of the leachate. In this report current status of the landfill site related issues were studied along with potential solutions on them. Also the fundamental mathematical derivations to describe the movement of the leachate in geologic medium was studied. These results shall be used to assess the leachate migration in the specific landfill site in the 2nd R and D year.

  6. Migration behavior of landfill leachate contaminants through alternative composite liners

    Energy Technology Data Exchange (ETDEWEB)

    Varank, Gamze, E-mail: gvarank@yildiz.edu.tr; Demir, Ahmet, E-mail: ahmetd@yildiz.edu.tr; Top, Selin, E-mail: stop@yildiz.edu.tr; Sekman, Elif, E-mail: esekman@yildiz.edu.tr; Akkaya, Ebru, E-mail: ekoca@yildiz.edu.tr; Yetilmezsoy, Kaan, E-mail: yetilmez@yildiz.edu.tr; Bilgili, M. Sinan, E-mail: mbilgili@yildiz.edu.tr

    2011-08-01

    Four identical pilot-scale landfill reactors with different alternative composite liners were simultaneously operated for a period of about 540 days to investigate and to simulate the migration behaviors of phenolic compounds (phenol, 2-CP, 2-MP, 3-MP, 4-MP, 2-NP, 4-NP, 2,4-DNP, 2,4-DCP, 2,6-DCP, 2,4,5-TCP, 2,4,6-TCP, 2,3,4,6-TeCP, PCP) and heavy metals (Pb, Cu, Zn, Cr, Cd, Ni) from landfill leachate to the groundwater. Alternative landfill liners of four reactors consist of R1: Compacted clay liner (10 cm + 10 cm, k = 10{sup -8} m/sn), R2: Geomembrane (2 mm HDPE) + compacted clay liner (10 cm + 10 cm, k = 10{sup -8} m/sn), R3: Geomembrane (2 mm HDPE) + compacted clay liner (10 cm, k = 10{sup -8} m/sn) + bentonite liner (2 cm) + compacted clay liner (10 cm, k = 10{sup -8} m/sn), and R4: Geomembrane (2 mm HDPE) + compacted clay liner (10 cm, k = 10{sup -8} m/sn) + zeolite liner (2 cm) + compacted clay liner (10 cm, k = 10{sup -8} m/sn). Wastes representing Istanbul municipal solid wastes were disposed in the reactors. To represent bioreactor landfills, reactors were operated by leachate recirculation. To monitor and control anaerobic degradation in the reactors, variations of conventional parameters (pH, alkalinity, chloride, conductivity, COD, TOC, TKN, ammonia and alcaly metals) were also investigated in landfill leachate samples. The results of this study showed that about 35-50% of migration of organic contaminants (phenolic compounds) and 55-100% of migration of inorganic contaminants (heavy metals) to the model groundwater could be effectively reduced with the use of bentonite and zeolite materials in landfill liner systems. Although leachate contaminants can reach to the groundwater in trace concentrations, findings of this study concluded that the release of these compounds from landfill leachate to the groundwater may potentially be of an important environmental concern based on the experimental findings. - Research highlights: {yields} Migration of

  7. A study for the environmental impact assessment of the leachate migration in landfills

    International Nuclear Information System (INIS)

    Hwang, Y. S.

    1999-12-01

    In Korea there are hundreds of landfill sites all over the peninsula and the leachate problem is one of the national concern. Heavy precipitation especially during hot summers creates the fast degradation of waste products in the site which accelerates the migration of the leachate. To assess the source term, in the second year study, the computational modeling to predict the potential infiltration rate of groundwater into the landfill were developed and tested for different geomembrane sets. These results shall be used to assess the total risk of the landfill site if combined with the results in the first year R and D and potential future R and D on the biosphere. In addition the generation, migration of LFG were studied and then approaches for the monitoring and controlling of LFG were discussed. (author)

  8. Review of existing landfill leachate production models

    International Nuclear Information System (INIS)

    Khan, T.A.

    2000-01-01

    The protection of water resources is a fundamental consideration in managing landfill operations. Landfill sites should be designed and operated so as to control leachate production and hence minimize the risk of surface and ground water pollution. A further important development is the use of computer models to estimate the production of leachate from landfill sites. It is revealed from the literature that a number of landfill leachate management model lave been development in recent years. These models allow different engineering schemes to be evaluated and are essential tools for design and operation managements of modern landfills. This paper describes a review of such models mainly focused on their theory, practicability, data requirements, suitability to real situation and usefulness. An evaluation of these models identifies. (author)

  9. Fresh Kills leachate treatment and minimization study: Volume 2, Modeling, monitoring and evaluation. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Fillos, J.; Khanbilvardi, R.

    1993-09-01

    The New York City Department of Sanitation is developing a comprehensive landfill leachate management plan for the Fresh Kills landfill, located on the western shore of Staten Island, New York. The 3000-acre facility, owned and operated by the City of New York, has been developed into four distinct mounds that correspond to areas designated as Sections 1/9, 2/8, 3/4 and 6/7. In developing a comprehensive leachate management plan, the estimating leachate flow rates is important in designing appropriate treatment alternatives to reduce the offsite migration that pollutes both surface water and groundwater resources.Estimating the leachate flow rates from Sections 1/9 and 6/7 was given priority using an available model, hydrologic evaluation of landfill performance (HELP), and a new model, flow investigation for landfill leachate (FILL). The field-scale analysis for leachate flow included data collection of the leachate mound-level from piezometers and monitoring wells installed on-site, for six months period. From the leachate mound-head contours and flow-gradients, Leachate flow rates were computed using Darcy`s Law.

  10. Leachate migration from a solid waste disposal facility near Biscayne National Park, South Florida

    International Nuclear Information System (INIS)

    Waller, B.G.; Labowski, J.L.

    1987-01-01

    Leachate from the Dade County Solid Waste Disposal Facility (SWDF) is migrating to the east (seaward) and to the south from the currently active disposal cell. Water levels and ground-water flow directions are strongly influenced by water-management practices, especially in the Black Creek Canal and structure S-21 to the north of the SWDF. Ground-water flow is initially to the south, from Black Creek Canal, and then to the east through the disposal area. The SWDF is constructed over the salt-intruded part of the highly transmissive Biscayne aquifer and because of this, chloride ion concentrations and specific conductance levels could not be used as indicators of leachate concentrations. Water-quality indicators used to identify leachate migration were primarily ammonium, organic nitrogen, phenols, and chemical oxygen demand with cadmium, chromium, and lead used as auxiliary indicator constituents. Leachate was detected in multi-depth wells located 75 meters to the south and 20 meters to the east of the active cell. Concentrations of water-quality indicators had mean concentrations generally 2 to 10 times higher than baseline conditions. Leachate was not detected in any of the other ground-water, canal water, or Biscayne Bay sampling sites. Primary controls over leachate movement in the SWDF are water-management practices in the Black Creek and Gould Canals, configuration and integrity of the liner beneath the active cell, and low hydraulic gradients in the landfill area

  11. Cesium residue leachate migration in the tailings management area of a mine site : predicted vs. actual

    Energy Technology Data Exchange (ETDEWEB)

    Solylo, P.; Ramsey, D. [Wardrop Engineering, Winnipeg, MB (Canada). Mining and Minerals Section

    2009-07-01

    This paper reported on a study at a cesium products facility (CPF) that manufactures a non-toxic cesium-formate drilling fluid. The facility operates adjacent to a pollucite/tantalum/spodumene mine. The CPF was developed as a closed system, with the residue tailings slurry from the CPF process discharged to doublelined containment cells. Groundwater monitoring has shown that leachate has affected near-surface porewater quality within the tailings management area (TMA). Elevated concentrations of calcium, sulphate, strontium, cesium, and rubidium were used to identify the leachate. Porewater at the base of the tailings and in the overburden beneath the tailings has not been affected. A geochemical investigation was initiated to determine how the leachate behaves in the groundwater/tailings porewater system. Over the past 7 years of residue placement in the TMA, the footprint of the residue placement area has changed, making the comparison of predicted versus actual rate of leachate migration very subjective and difficult to quantify. Based solely on the analytical data, the source of the leachate is unknown, either from the original residue pile or the 2007 residue placement area. For purposes of long term residue management, an investigation of the geochemical behaviour of residue leachate in the groundwater/tailings system of the TMA is currently underway. 5 refs., 1 tab., 2 figs.

  12. Spatial and temporal migration of a landfill leachate plume in alluvium

    Science.gov (United States)

    Masoner, Jason R.; Cozzarelli, Isabelle M.

    2015-01-01

    Leachate from unlined or leaky landfills can create groundwater contaminant plumes that last decades to centuries. Understanding the dynamics of leachate movement in space and time is essential for monitoring, planning and management, and assessment of risk to groundwater and surface-water resources. Over a 23.4-year period (1986–2010), the spatial extent of the Norman Landfill leachate plume increased at a rate of 7800 m2/year and expanded by 878 %, from an area of 20,800 m2 in 1986 to 203,400 m2 in 2010. A linear plume velocity of 40.2 m/year was calculated that compared favorably to a groundwater-seepage velocity of 55.2 m/year. Plume-scale hydraulic conductivity values representative of actual hydrogeological conditions in the alluvium ranged from 7.0 × 10−5 to 7.5 × 10−4 m/s, with a median of 2.0 × 10−4 m/s. Analyses of field-measured and calculated plume-scale hydraulic conductivity distributions indicate that the upper percentiles of field-measured values should be considered to assess rates of plume-scale migration, spreading, and biodegradation. A pattern of increasing Cl− concentrations during dry periods and decreasing Cl− concentrations during wet periods was observed in groundwater beneath the landfill. The opposite occurred in groundwater downgradient from the landfill; that is, Cl− concentrations in groundwater downgradient from the landfill decreased during dry periods and increased during wet periods. This pattern of changing Cl−concentrations in response to wet and dry periods indicates that the landfill retains or absorbs leachate during dry periods and produces lower concentrated leachate downgradient. During wet periods, the landfill receives more recharge which dilutes leachate in the landfill but increases leachate migration from the landfill and produces a more concentrated contaminant plume. This approach of quantifying plume expansion, migration, and concentration during variable hydrologic

  13. Modeling of reactive chemical transport of leachates from a utility fly-ash disposal site

    International Nuclear Information System (INIS)

    Apps, J.A.; Zhu, M.; Kitanidis, P.K.; Freyberg, D.L.; Ronan, A.D.; Itakagi, S.

    1991-04-01

    Fly ash from fossil-fuel power plants is commonly slurried and pumped to disposal sites. The utility industry is interested in finding out whether any hazardous constituents might leach from the accumulated fly ash and contaminate ground and surface waters. To evaluate the significance of this problem, a representative site was selected for modeling. FASTCHEM, a computer code developed for the Electric Power Research Institute, was utilized for the simulation of the transport and fate of the fly-ash leachate. The chemical evolution of the leachate was modeled as it migrated along streamtubes defined by the flow model. The modeling predicts that most of the leachate seeps through the dam confining the ash pond. With the exception of ferrous, manganous, sulfate and small amounts of nickel ions, all other dissolved constituents are predicted to discharge at environmentally acceptable concentrations

  14. Leachate impacts on groundwater: modeling generation and transport at the naameh landfill

    International Nuclear Information System (INIS)

    Bou-Zeid, E.; El FAdel, M.; Basha, H.

    2000-01-01

    Full text.Although municipal solid waste is now managed through integrated schemes that rank land filling as one of the least favorable options for disposal, this management alternative continues to be the most economic and attractive in the vast majority of cases. An inevitable consequence of the practice of solid waste disposal in landfills is the generation, refuse characteristics and land filling operations. Leachate migration away from the landfill boundaries and its subsequent release into the surrounding environment, present serious environmental concerns at both existing and new facilities particularly in relation to surface and ground water pollution. While numerous mathematical models have been developed to simulate processes governing leachate occurrence and behavior in landfills and their potential migration away from landfill boundaries, none have been applied at former quarries converted to waste disposal facilities. The objective of this research work is to calibrate and apply mathematical models to predict the generation, fate and transport of leachate at a former quarry landfill facility (the Naameh landfill site). The site offers unique characteristics in that it is the first quarry converted to a landfill in Lebanon and is planned to have refuse depth in excess of one hundred meters, making it one of the deepest in the world. The modeling estimates leachate quantity in order to control its associated environmental impacts, particularly on ground water wells down gradient of the site. The sensitivity of leachate generation to meteorological, operation and design parameters was assessed. Guidance for leachate control, recirculation and collection to minimize these impacts is also provided. The fate and transport of contaminants released from the landfill to the subsurface was modeled. A sensitivity analysis with respect to geological properties of the site was conducted. Worst case scenarios were investigated as well

  15. Use of electrical tomography methods to determinate the extension and main migration routes of uncontrolled landfill leachates in fractured areas

    Energy Technology Data Exchange (ETDEWEB)

    Casado, Ismael, E-mail: iscaferr@gmail.com [Department of Petrology, Geochemistry and Geological Prospectio, Universitat de Barcelona, Martí i Franquès s/n, 08030 Barcelona (Spain); Department of Geology and Environmental Earth Science, Miami University, 501 East High Street, 45056 Oxford, OH (United States); Mahjoub, Himi [Department of Petrology, Geochemistry and Geological Prospectio, Universitat de Barcelona, Martí i Franquès s/n, 08030 Barcelona (Spain); Ecole Nationale des Sciences Appliquées d' Al Hoceima (ENSAH), University Mohammed Premier, Ajdir, Al Hoceima (Morocco); Lovera, Raul [Department of Petrology, Geochemistry and Geological Prospectio, Universitat de Barcelona, Martí i Franquès s/n, 08030 Barcelona (Spain); Fernández, Jesús, E-mail: jfernandezc@aragon.es [Department of Agriculture, Ranching and Environment, Diputación General de Aragon (DGA), Plaza de San Pedro Nolasco, 7, 50071 Zaragoza (Spain); Casas, Albert [Department of Petrology, Geochemistry and Geological Prospectio, Universitat de Barcelona, Martí i Franquès s/n, 08030 Barcelona (Spain)

    2015-02-15

    This study focuses on the uses of the electrical tomography and its relationship with hydrochemical data in order to characterize contaminated groundwater flows in fractured aquifers. The studied area is contaminated with different hazardous substances like lyndanes, organochlorinated compounds and benzenes coming from the old non-controlled Sardas landfill. The enormous volumes of wastes filling the landfill have generated a convoluted mixture of leachates. Due to the lack of a landfill liner, the leachates have migrated through the fractured Eocene marls towards the Gallego River. The striking correlation between high concentrations of polluted groundwater and low electrical resistivity of the subsurface (< 8 Ω·m) allows defining the principal contaminant migration route thanks to the distribution of these conductive anomalies. This mapping verifies that there is intense tectonical–structural control of the leachate migration, because the deep migration presents the same direction as the geological axis fold. - Highlights: • The outcrop topographic reconstruction is done using cores and aerial photographs. • Hydrochemical and geophysical data allow defining two leachate migration paths. • Conductive anomalies in ERT are linked to high contaminant concentration. • The distribution of conductive anomalies defines the fractured basement migration. • The plume direction reflects important tectonic control in the migration process.

  16. Tracking senescence-induced patterns in leaf litter leachate using parallel factor analysis (PARAFAC) modeling and self-organizing maps

    Science.gov (United States)

    Wheeler, K. I.; Levia, D. F.; Hudson, J. E.

    2017-09-01

    In autumn, the dissolved organic matter (DOM) contribution of leaf litter leachate to streams in forested watersheds changes as trees undergo resorption, senescence, and leaf abscission. Despite its biogeochemical importance, little work has investigated how leaf litter leachate DOM changes throughout autumn and how any changes might differ interspecifically and intraspecifically. Since climate change is expected to cause vegetation migration, it is necessary to learn how changes in forest composition could affect DOM inputs via leaf litter leachate. We examined changes in leaf litter leachate fluorescent DOM (FDOM) from American beech (Fagus grandifolia Ehrh.) leaves in Maryland, Rhode Island, Vermont, and North Carolina and from yellow poplar (Liriodendron tulipifera L.) leaves from Maryland. FDOM in leachate samples was characterized by excitation-emission matrices (EEMs). A six-component parallel factor analysis (PARAFAC) model was created to identify components that accounted for the majority of the variation in the data set. Self-organizing maps (SOM) compared the PARAFAC component proportions of leachate samples. Phenophase and species exerted much stronger influence on the determination of a sample's SOM placement than geographic origin. As expected, FDOM from all trees transitioned from more protein-like components to more humic-like components with senescence. Percent greenness of sampled leaves and the proportion of tyrosine-like component 1 were found to be significantly different between the two genetic beech clusters, suggesting differences in photosynthesis and resorption. Our results highlight the need to account for interspecific and intraspecific variations in leaf litter leachate FDOM throughout autumn when examining the influence of allochthonous inputs to streams.

  17. Assessment of the Spatial Variability in Leachate Migration from an Old Landfill Site

    DEFF Research Database (Denmark)

    Kjeldsen, Peter; Bjerg, Poul Løgstrup; Winther, Pia

    1995-01-01

    Investigations of the pollution of groundwater from old landfills have in most cases focused on delineating the pollution plume and only in very few cases on the landfill as a source to groundwater pollution. Landfills often cover large areas. Spatial variations in leachate composition may have...... great impact on the location of the main pollution plume in the downstream aquifer. Grindsted landfill in Denmark was investigated by sampling leachate beneath the landfill and in groundwater at the borders of the landfill. A pronounced variability in leachate quality and leakage patterns from...... the landfill was observed. Also variations in local groundwater flow directions were found. These observations are very important for delineation of the groundwater pollution and for proper choice of remedial action activities, related both to the plume and to the landfill....

  18. Reactive transport modelling of biogeochemical processes and carbon isotope geochemistry inside a landfill leachate plume.

    NARCIS (Netherlands)

    van Breukelen, B.M.; Griffioen, J.; Roling, W.F.M.; van Verseveld, H.W.

    2004-01-01

    The biogeochemical processes governing leachate attenuation inside a landfill leachate plume (Banisveld, the Netherlands) were revealed and quantified using the 1D reactive transport model PHREEQC-2. Biodegradation of dissolved organic carbon (DOC) was simulated assuming first-order oxidation of two

  19. Combining an experimental study and ANFIS modeling to predict landfill leachate transport in underlying soil-a case study in north of Iran.

    Science.gov (United States)

    Yousefi Kebria, D; Ghavami, M; Javadi, S; Goharimanesh, M

    2017-12-16

    In the contemporary world, urbanization and progressive industrial activities increase the rate of waste material generated in many developed countries. Municipal solid waste landfills (MSWs) are designed to dispose the waste from urban areas. However, discharged landfill leachate, the soluble water mixture that filters through solid waste landfills, can potentially migrate into the soil and affect living organisms by making harmful biological changes in the ecosystem. Due to well-documented landfill problems involving contamination, it is necessary to investigate the long-term influence of discharged leachate on the consistency of the soil beds beneath MSW landfills. To do so, the current study collected vertical deep core samples from different locations in the same unlined landfill. The impacts of effluent leachate on physical and chemical properties of the soil and its propagation depth were studied, and the leachate-transport pattern between successive boreholes was predicted by a developed mathematical model using an adaptive neuro-fuzzy inference system (ANFIS). The decomposition of organic leachate admixtures in the landfill yield is to produce organic acids as well as carbon dioxide, which diminishes the pH level of the landfill soil. The chemical analysis of discharged leachate in the soil samples showed that the concentrations of heavy metals are much lower than those of chloride, COD, BOD 5 , and bicarbonate. Using linear regression and mean square errors between the measured and predicted data, the accuracy of the proposed ANFIS model has been validated. Results show a high correlation between observed and predicated data.

  20. Leachate flow around a well in MSW landfill: Analysis of field tests using Richards model.

    Science.gov (United States)

    Slimani, R; Oxarango, L; Sbartai, B; Tinet, A-J; Olivier, F; Dias, D

    2017-05-01

    During the lifespan of a Municipal Solid Waste landfill, its leachate drainage system may get clogged. Then, as a consequence of rainfall, leachate generation and possibly leachate injection, the moisture content in the landfill increases to the point that a leachate mound could be created. Therefore, pumping the leachate becomes a necessary solution. This paper presents an original analysis of leachate pumping and injection in an instrumented well. The water table level around the well is monitored by nine piezometers which allow the leachate flow behaviour to be captured. A numerical model based on Richards equation and an exponential relationship between saturated hydraulic conductivity and depth is used to analyze the landfill response to pumping and injection. Decreasing permeability with depth appears to have a major influence on the behaviour of the leachate flow. It could have a drastic negative impact on the pumping efficiency with a maximum quasi-stationary pumping rate limited to approximately 1m 3 /h for the tested well and the radius of influence is less than 20m. The numerical model provides a reasonable description of both pumping and injection tests. However, an anomalous behaviour observed at the transition between pumping and recovery phases is observed. This could be due to a limitation of the Richards model in that it neglects the gas phase behaviour and other double porosity heterogeneous effects. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Identification and assessment of water pollution as a consequence of a leachate plume migration from a municipal landfill site (Tucumán, Argentina).

    Science.gov (United States)

    Fernández, Diego S; Puchulu, María E; Georgieff, Sergio M

    2014-06-01

    Landfills constitute potential sources of different pollutants that could generate human health and environmental problems. While some landfills currently work under the protection of a bottom liner with leachate collection, it was demonstrated that migration could take place even yet with these cautions. The purpose of this paper is to assess the pollution caused by a leachate plume from a municipal landfill that is affecting both groundwater and surface waters. The research was carried out at Pacará Pintado landfill in northwestern Argentina. Analysis of water samples indicates that leachate is affecting groundwater under the landfill area and an abandoned river channel hydraulically connected. In the center of the landfill area, the plume is anoxic and sulfate, nitrate, iron and manganese reduction zones were identified. Leachate plume presented high concentration of organic matter, Fe, Mn, NH(4)(+), Cl(-) and Cr reaching an extension of 900 m. The presence of a leachate plume in a landfill site with a single liner system implies that the use of this groundwater pollution control method alone is not enough especially if permeable sediments are present below.

  2. BIOLEACH: Coupled modeling of leachate and biogas production on solid waste landfills

    Science.gov (United States)

    Rodrigo-Clavero, Maria-Elena; Rodrigo-Ilarri, Javier

    2015-04-01

    One of the most important factors to address when performing the environmental impact assessment of urban solid waste landfills is to evaluate the leachate production. Leachate management (collection and treatment) is also one of the most relevant economical aspects to take into account during the landfill life. Leachate is formed as a solution of biological and chemical components during operational and post-operational phases on urban solid waste landfills as a combination of different processes that involve water gains and looses inside the solid waste mass. Infiltration of external water coming from precipitation is the most important component on this water balance. However, anaerobic waste decomposition and biogas formation processes play also a role on the balance as water-consuming processes. The production of leachate one biogas is therefore a coupled process. Biogas production models usually consider optimal conditions of water content on the solid waste mass. However, real conditions during the operational phase of the landfill may greatly differ from these optimal conditions. In this work, the first results obtained to predict both the leachate and the biogas production as a single coupled phenomenon on real solid waste landfills are shown. The model is applied on a synthetic case considering typical climatological conditions of Mediterranean catchments.

  3. Quantification of leachate discharged to groundwater using the water balance method and the hydrologic evaluation of landfill performance (HELP) model.

    Science.gov (United States)

    Alslaibi, Tamer M; Abustan, Ismail; Mogheir, Yunes K; Afifi, Samir

    2013-01-01

    Landfills are a source of groundwater pollution in Gaza Strip. This study focused on Deir Al Balah landfill, which is a unique sanitary landfill site in Gaza Strip (i.e., it has a lining system and a leachate recirculation system). The objective of this article is to assess the generated leachate quantity and percolation to the groundwater aquifer at a specific site, using the approaches of (i) the hydrologic evaluation of landfill performance model (HELP) and (ii) the water balance method (WBM). The results show that when using the HELP model, the average volume of leachate discharged from Deir Al Balah landfill during the period 1997 to 2007 was around, 6800 m3/year. Meanwhile, the average volume of leachate percolated through the clay layer was 550 m3/year, which represents around 8% of the generated leachate. Meanwhile, the WBM indicated that the average volume of leachate discharged from Deir Al Balah landfill during the same period was around 7660 m3/year--about half of which comes from the moisture content of the waste, while the remainder comes from the infiltration of precipitation and re-circulated leachate. Therefore, the estimated quantity of leachate to groundwater by these two methods was very close. However, compared with the measured leachate quantity, these results were overestimated and indicated a dangerous threat to the groundwater aquifer, as there was no separation between municipal, hazardous and industrial wastes, in the area.

  4. CFD modeling of hydro-biochemical behavior of MSW subjected to leachate recirculation.

    Science.gov (United States)

    Feng, Shi-Jin; Cao, Ben-Yi; Li, An-Zheng; Chen, Hong-Xin; Zheng, Qi-Teng

    2018-02-01

    The most commonly used method of operating landfills more sustainably is to promote rapid biodegradation and stabilization of municipal solid waste (MSW) by leachate recirculation. The present study is an application of computational fluid dynamics (CFD) to the 3D modeling of leachate recirculation in bioreactor landfills using vertical wells. The objective is to model and investigate the hydrodynamic and biochemical behavior of MSW subject to leachate recirculation. The results indicate that the maximum recirculated leachate volume can be reached when vertical wells are set at the upper middle part of a landfill (H W /H T  = 0.4), and increasing the screen length can be more helpful in enlarging the influence radius than increasing the well length (an increase in H S /H W from 0.4 to 0.6 results in an increase in influence radius from 6.5 to 7.7 m). The time to reach steady state of leachate recirculation decreases with the increase in pressure head; however, the time for leachate to drain away increases with the increase in pressure head. It also showed that methanogenic biomass inoculum of 1.0 kg/m 3 can accelerate the volatile fatty acid depletion and increase the peak depletion rate to 2.7 × 10 -6  kg/m 3 /s. The degradation-induced void change parameter exerts an influence on the processes of MSW biodegradation because a smaller parameter value results in a greater increase in void space.

  5. Paper for Publication in IOP: Conference Series Leachate Treatment using three Years Aged Lysimetric Bioreactor Models

    Science.gov (United States)

    Hartono, Djoko M.; Andari Kristanto, Gabriel; Gusniani Sofian, Irma; Fauzan, Ahmad; Mahdiana, Ghanis

    2018-03-01

    This study was conducted as a response to address the problem of land availability for Cipayung landfill that no longer able to accommodate waste generation Depok City and to protect water pollution in receiving water body. Law No. 8/2008 explained that local governments and cities are required to create a sanitary landfill as a final waste processing system to replace open dumping that had been done by almost all the final processing of waste in cities in Indonesia. Sanitary landfill is the final waste processing system that works best and is environmentally friendly. The sanitary landfill will generate leachate. Leachate is the result of precipitation, evaporation, surface runoff, water infiltration into the waste, and also including the water contained in the waste. The purpose of this study was to determine the utilization of leachate generated by three years aged reactor.This study use a modeling tools as bioreactor landfill tank or so called lysimetric, that made of the polymer material that susceptible to high heat and pressure. This bioreactor landfill tank has a diameter of 0.83 m, with a surface area of 0.54 m2 and a height of 2.02 m, with the examination duration of 115 days. This tank consists of several layer, such as sand layer, solid waste layer, water layer and piping system. These layer has 3 year aged. The In this research, leachate recirculation in bioreactor landfills was conducted with waste layered loading systems with percolation system. This research has been conducted since the beginning of 2016, sampling, field measurement and analysis of leachate and waste quality carried out for approximately 115 days of field measurements.Several parameter were measured such as pH, BOD, COD, nitrate, nitrite and TSS. From the analysis of the leachate quality parameters of pH, BOD, COD, nitrite, TSS, showed a reduction in the concentration of the three reactors. The concentration of parameters measured at the initial stage until the final stage, showed a

  6. Systematic model development for partial nitrification of landfill leachate in a SBR

    DEFF Research Database (Denmark)

    Ganigue, R.; Volcke, E.I.P.; Puig, S.

    2010-01-01

    ), confirmed by statistical tests. Good model fits were also obtained for pH, despite a slight bias in pH prediction, probably caused by the high salinity of the leachate. Future work will be addressed to the model-based evaluation of the interaction of different factors (aeration, stripping, pH, inhibitions....... Following a systematic procedure, the model was successfully constructed, calibrated and validated using data from short-term (one cycle) operation of the PN-SBR. The evaluation of the model revealed a good fit to the main physical-chemical measurements (ammonium, nitrite, nitrate and inorganic carbon......, among others) and their impact on the process performance....

  7. Biogeochemistry of landfill leachate plumes

    DEFF Research Database (Denmark)

    Christensen, Thomas Højlund; Kjeldsen, Peter; Bjerg, Poul Løgstrup

    2001-01-01

    are relatively narrow and do not in terms of width exceed the width of the landfill. The concept of redox zones being present in the plume has been confirmed by the reported composition of the leachate contaminated groundwater at several landfills and constitutes an important framework for understanding...... the behavior of the contaminants in the plume as the leachate migrates away from the landfill. Diverse microbial communities have been identified in leachate plumes and are believed to be responsible for the redox processes. Dissolved organic C in the leachate, although it appears to be only slowly degradable...... to be subject to anaerobic oxidation, but the mechanisms are not yet understood. Heavy metals do not seem to constitute a significant pollution problem at landfills, partly because the heavy metal concentrations in the leachate often are low, and partly because of strong attenuation by sorption...

  8. 2D Electrical Imaging Surveys for Leachate Plume Migration at an Old Dump Site in Ibadan South Western Nigeria: A Case Study

    Directory of Open Access Journals (Sweden)

    Dare Omolayo

    2014-01-01

    Full Text Available The site surveyed is along a popular ring road in Ibadan. It is an old dump site which had been closed over a long period of time. Development into industrial and residential house schemes had crowded around the site. This development resulted in the exploitation of groundwater within the thick regolith that characterize the area. The investigation was carried out to ascertain leachate plume generation and migration and its impact on the surrounding soil and the groundwater. 2D electrical resistivity imaging using Wenner array was used to delineate the plume and probable trend of migration. The method involves the injection of low frequency DC current into the subsurface and measuring the potential difference set up by another pair of electrodes called potential electrodes. All the traverses show areas of very low resistivity values ranging between 4 ohm-m and 13.8 ohm-m; in addition to this, the water samples collected from hand dug wells that surround the dump site show high total dissolved solids (TDS with an average value of 2033 mg/L, high conductivity with an average value of 2868 mg/L, and high nitrate value (63 mg/L; these values are above the World Health Organization (WHO permissible values. This poses a health challenge to the residents living around this site.

  9. Modelling collective cell migration of neural crest.

    Science.gov (United States)

    Szabó, András; Mayor, Roberto

    2016-10-01

    Collective cell migration has emerged in the recent decade as an important phenomenon in cell and developmental biology and can be defined as the coordinated and cooperative movement of groups of cells. Most studies concentrate on tightly connected epithelial tissues, even though collective migration does not require a constant physical contact. Movement of mesenchymal cells is more independent, making their emergent collective behaviour less intuitive and therefore lending importance to computational modelling. Here we focus on such modelling efforts that aim to understand the collective migration of neural crest cells, a mesenchymal embryonic population that migrates large distances as a group during early vertebrate development. By comparing different models of neural crest migration, we emphasize the similarity and complementary nature of these approaches and suggest a future direction for the field. The principles derived from neural crest modelling could aid understanding the collective migration of other mesenchymal cell types. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Comparative modeling of biological nutrient removal from landfill leachate using a circulating fluidized bed bioreactor (CFBBR).

    Science.gov (United States)

    Eldyasti, Ahmed; Andalib, Mehran; Hafez, Hisham; Nakhla, George; Zhu, Jesse

    2011-03-15

    Steady state operational data from a pilot scale circulating fluidized bed bioreactor (CFBBR) during biological treatment of landfill leachate, at empty bed contact times (EBCTs) of 0.49, and 0.41 d and volumetric nutrients loading rates of 2.2-2.6 kg COD/(m(3)d), 0.7-0.8 kg N/(m(3)d), and 0.014-0.016 kg P/(m(3)d), was used to calibrate and compare developed process models in BioWin(®) and AQUIFAS(®). BioWin(®) and AQUIFAS(®) were both capable of predicting most of the performance parameters such as effluent TKN, NH(4)-N, NO(3)-N, TP, PO(4)-P, TSS, and VSS with an average percentage error (APE) of 0-20%. BioWin(®) underpredicted the effluent BOD and SBOD values for various runs by 80% while AQUIFAS(®) predicted effluent BOD and SBOD with an APE of 50%. Although both calibrated models, confirmed the advantages of the CFBBR technology in treating the leachate of high volumetric loading and low biomass yields due to the long solid retention time (SRT), both BioWin(®) and AQUIFAS(®) predicted the total biomass and SRT of CFBBR based on active biomass only, whereas in the CFBBR runs both active as well as inactive biomass accumulated. Copyright © 2011 Elsevier B.V. All rights reserved.

  11. Attenuation of landfill leachate by UK Triassic sandstone aquifer materials. 1. Fate of inorganic pollutants in laboratory columns

    Science.gov (United States)

    Thornton, Steven F.; Tellam, John H.; Lerner, David N.

    2000-05-01

    The attenuation of inorganic contaminants in acetogenic and methanogenic landfill leachate by calcareous and carbonate-deficient, oxide-rich Triassic sandstone aquifer materials from the English Midlands was examined in laboratory columns. Aqueous equilibrium speciation modelling, simple transport modelling and chemical mass balance approaches are used to evaluate the key processes and aquifer geochemical properties controlling contaminant fate. The results indicate that leachate-rock interactions are dominated by ion-exchange processes, acid-base and redox reactions and sorption/precipitation of metal species. Leachate NH 4 is attenuated by cation exchange with the aquifer sediments; however, NH 4 migration could be described with a simple model using retardation factors. Organic acids in the acetogenic leachate buffered the system pH at low levels during flushing of the calcareous aquifer material. In contrast, equilibrium with Al oxyhydroxide phases initially buffered pH (˜4.5) during flushing of the carbonate-deficient sandstone with methanogenic leachate. This led to the mobilisation of sorbed and oxide-bound heavy metals from the aquifer sediment which migrated as a concentrated pulse at the leachate front. Abiotic reductive dissolution of Mn oxyhydroxides on each aquifer material by leachate Fe 2+ maintains high concentrations of dissolved Mn and buffers the leachate inorganic redox system. This feature is analogous to the Mn-reducing zones found in leachate plumes and in the experiments provides a sink for the leachate Fe load and other heavy metals. The availability of reactive solid phase Mn oxyhydroxides limits the duration of redox buffering and Fe attenuation by these aquifer sediments. Aquifer pH and redox buffering capacity exert a fundamental influence on leachate inorganic contaminant fate in these systems. The implications for the assessment of aquifer vulnerability at landfills are discussed and simple measurements of aquifer properties which

  12. Aspects of general linear modelling of migration.

    Science.gov (United States)

    Congdon, P

    1992-01-01

    "This paper investigates the application of general linear modelling principles to analysing migration flows between areas. Particular attention is paid to specifying the form of the regression and error components, and the nature of departures from Poisson randomness. Extensions to take account of spatial and temporal correlation are discussed as well as constrained estimation. The issue of specification bears on the testing of migration theories, and assessing the role migration plays in job and housing markets: the direction and significance of the effects of economic variates on migration depends on the specification of the statistical model. The application is in the context of migration in London and South East England in the 1970s and 1980s." excerpt

  13. The gravity model of labor migration behavior

    Science.gov (United States)

    Alexandr, Tarasyev; Alexandr, Tarasyev

    2017-07-01

    In this article, we present a dynamic inter-regional model, that is based on the gravity approach to migration and describes in continuous time the labor force dynamics between a number of conjugate regions. Our modification of the gravity migration model allows to explain the migration processes and to display the impact of migration on the regional economic development both for regions of origin and attraction. The application of our model allows to trace the dependency between salaries levels, total workforce, the number of vacancies and the number unemployed people in simulated regions. Due to the gravity component in our model the accuracy of prediction for migration flows is limited by the distance range between analyzed regions, so this model is tested on a number of conjugate neighbor regions. Future studies will be aimed at development of a multi-level dynamic model, which allows to construct a forecast for unemployment and vacancies trends on the first modeling level and to use these identified parameters on the second level for describing dynamic trajectories of migration flows.

  14. Phytoremediation of landfill leachate

    International Nuclear Information System (INIS)

    Jones, D.L.; Williamson, K.L.; Owen, A.G.

    2006-01-01

    Leachate emissions from landfill sites are of concern, primarily due to their toxic impact when released unchecked into the environment, and the potential for landfill sites to generate leachate for many hundreds of years following closure. Consequently, economically and environmentally sustainable disposal options are a priority in waste management. One potential option is the use of soil-plant based remediation schemes. In many cases, using either trees (including short rotation coppice) or grassland, phytoremediation of leachate has been successful. However, there are a significant number of examples where phytoremediation has failed. Typically, this failure can be ascribed to excessive leachate application and poor management due to a fundamental lack of understanding of the plant-soil system. On balance, with careful management, phytoremediation can be viewed as a sustainable, cost effective and environmentally sound option which is capable of treating 250 m 3 ha -1 yr -1 . However, these schemes have a requirement for large land areas and must be capable of responding to changes in leachate quality and quantity, problems of scheme establishment and maintenance, continual environmental monitoring and seasonal patterns of plant growth. Although the fundamental underpinning science is well understood, further work is required to create long-term predictive remediation models, full environmental impact assessments, a complete life-cycle analysis and economic analyses for a wide range of landfill scenarios

  15. Phytoremediation of landfill leachate.

    Science.gov (United States)

    Jones, D L; Williamson, K L; Owen, A G

    2006-01-01

    Leachate emissions from landfill sites are of concern, primarily due to their toxic impact when released unchecked into the environment, and the potential for landfill sites to generate leachate for many hundreds of years following closure. Consequently, economically and environmentally sustainable disposal options are a priority in waste management. One potential option is the use of soil-plant based remediation schemes. In many cases, using either trees (including short rotation coppice) or grassland, phytoremediation of leachate has been successful. However, there are a significant number of examples where phytoremediation has failed. Typically, this failure can be ascribed to excessive leachate application and poor management due to a fundamental lack of understanding of the plant-soil system. On balance, with careful management, phytoremediation can be viewed as a sustainable, cost effective and environmentally sound option which is capable of treating 250m(3)ha(-1)yr(-1). However, these schemes have a requirement for large land areas and must be capable of responding to changes in leachate quality and quantity, problems of scheme establishment and maintenance, continual environmental monitoring and seasonal patterns of plant growth. Although the fundamental underpinning science is well understood, further work is required to create long-term predictive remediation models, full environmental impact assessments, a complete life-cycle analysis and economic analyses for a wide range of landfill scenarios.

  16. The radionuclide migration model in river system

    International Nuclear Information System (INIS)

    Zhukova, O.M.; Shiryaeva, N.M.; Myshkina, M.K.; Shagalova, Eh.D.; Denisova, V.V.; Skurat, V.V.

    2001-01-01

    It was propose the model of radionuclide migration in river system based on principle of the compartmental model at hydraulically stationary and chemically equilibrium conditions of interaction of radionuclides in system water-dredge, water-sediments. Different conditions of radioactive contamination entry in river system were considered. The model was verified on the data of radiation monitoring of Iput' river

  17. Understanding leachate flow in municipal solid waste landfills by combining time-lapse ERT and subsurface flow modelling - Part II: Constraint methodology of hydrodynamic models.

    Science.gov (United States)

    Audebert, M; Oxarango, L; Duquennoi, C; Touze-Foltz, N; Forquet, N; Clément, R

    2016-09-01

    Leachate recirculation is a key process in the operation of municipal solid waste landfills as bioreactors. To ensure optimal water content distribution, bioreactor operators need tools to design leachate injection systems. Prediction of leachate flow by subsurface flow modelling could provide useful information for the design of such systems. However, hydrodynamic models require additional data to constrain them and to assess hydrodynamic parameters. Electrical resistivity tomography (ERT) is a suitable method to study leachate infiltration at the landfill scale. It can provide spatially distributed information which is useful for constraining hydrodynamic models. However, this geophysical method does not allow ERT users to directly measure water content in waste. The MICS (multiple inversions and clustering strategy) methodology was proposed to delineate the infiltration area precisely during time-lapse ERT survey in order to avoid the use of empirical petrophysical relationships, which are not adapted to a heterogeneous medium such as waste. The infiltration shapes and hydrodynamic information extracted with MICS were used to constrain hydrodynamic models in assessing parameters. The constraint methodology developed in this paper was tested on two hydrodynamic models: an equilibrium model where, flow within the waste medium is estimated using a single continuum approach and a non-equilibrium model where flow is estimated using a dual continuum approach. The latter represents leachate flows into fractures. Finally, this methodology provides insight to identify the advantages and limitations of hydrodynamic models. Furthermore, we suggest an explanation for the large volume detected by MICS when a small volume of leachate is injected. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Towards an integrated model of international migration

    Directory of Open Access Journals (Sweden)

    Douglas S. MASSEY

    2012-12-01

    Full Text Available Demographers have yet to develop a suitable integrated model of international migration and consequently have been very poor at forecasting immigration. This paper outlines the basic elements of an integrated model and surveys recent history to suggest the key challenges to model construction. A comprehensive theory must explain the structural forces that create a supply of people prone to migrate internationally, the structural origins of labour demand in receiving countries, the motivations of those who respond to these forces by choosing to migrate internationally, the growth and structure of transnational networks that arise to support international movement, the behaviour states in response to immigrant flows, and the influence of state actions on the behaviour of migrants. Recent history suggests that a good model needs to respect the salience of markets, recognize the circularity of migrant flows, appreciate the power of feedback effects, and be alert unanticipated consequences of policy actions.

  19. Migration of inorganic ions from the leachate of the Rio das Ostras landfill: a comparison of three different configurations of protective barriers.

    Science.gov (United States)

    Lacerda, Cláudia Virgínia; Ritter, Elisabeth; Pires, João Antônio da Costa; de Castro, José Adilson

    2014-11-01

    Batch tests and diffusion tests were performed to analyze the efficiency of a protective barrier in a landfill consisting of compacted soil with 10% bentonite compared to the results obtained for only compacted soil and for compacted soil covered with a 1-mm-thick HDPE geomembrane; the soil and leachate were collected from the Rio das Ostras Landfill in Rio de Janeiro, Brazil. The diffusion tests were performed for periods of 3, 10 and 60 days. After the test period, the soil pore water was analyzed and the profiles for chloride, potassium and ammonium were determined along a 6-cm soil depth. The results of the batch tests performed to define sorption parameters were used to adjust the profiles obtained in the diffusion cell experiment by applying an ion transfer model between the interstitial solution and the soil particles. The MPHMTP model (Multi Phase Heat and Mass Transfer Program), which is based upon the solution of the transport equations of the ionic contaminants, was used to solve the inverse problem of simultaneously determining the effective diffusion coefficients. The results of the experimental tests and of the model simulation confirmed that the compacted soil with 10% bentonite was moderately efficient in the retention of chloride, potassium and ammonium ions compared to the configurations of compacted soil with a geomembrane and compacted soil alone, representing a solution that is technically feasible and requires potentially lower costs for implementation in landfills. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. Modeling of brine migration in halite

    International Nuclear Information System (INIS)

    Cheung, H.; Fuller, M.E.; Gaffney, E.S.

    1979-01-01

    When canisters containing radwastes are emplaced in a repository the heat produced by the decaying radwaste will cause moderate thermal gradients to develop which will cause the brine present in a halite medium (salt deposits) to accumulate around the canister. Four different models of the migration process have been reviewed to determine their suitability as a working model. One model predicts that inclusions smaller than 0.1 mm dimension probably will not migrate. The other models do not consider size as a factor. Thermal diffusion (Soret effect) is considered insignificant in three models, while in the fourth model it is added to the concentration diffusion term. The following conclusions can be made: Temperature is the most significant parameter in all models and must be known as a function of time, and distance from the canister. All four models predict about the same migration velocity for it is a given set of conditions; for 100 0 C and 1 0 C/cm thermal gradient, it is 3.0, 4.8, 5.6 and 6.4 mm/y. Diffusion of ions through the brine inclusions is the rate controlling mechanism. The difference between the thermal gradients in the liquid and in the solid should always be considered and is a function of droplet shape. The model based upon work by Nernst is easiest to use, but it predicts the lowest migration rate. The maximum volume of pure brine accumulated at the canister surface would be less than 20-40 liters in 50 years, for a canister initial thermal power of 3.5 kW.Bitterns would migrate proportionately less volume. A computer code, BRINE, was developed to make these calculations by means of any of the four models

  1. Modeling collective cell migration in geometric confinement

    Science.gov (United States)

    Tarle, Victoria; Gauquelin, Estelle; Vedula, S. R. K.; D'Alessandro, Joseph; Lim, C. T.; Ladoux, Benoit; Gov, Nir S.

    2017-06-01

    Monolayer expansion has generated great interest as a model system to study collective cell migration. During such an expansion the culture front often develops ‘fingers’, which we have recently modeled using a proposed feedback between the curvature of the monolayer’s leading edge and the outward motility of the edge cells. We show that this model is able to explain the puzzling observed increase of collective cellular migration speed of a monolayer expanding into thin stripes, as well as describe the behavior within different confining geometries that were recently observed in experiments. These comparisons give support to the model and emphasize the role played by the edge cells and the edge shape during collective cell motion.

  2. Modelling the morphology of migrating bacterial colonies

    Science.gov (United States)

    Nishiyama, A.; Tokihiro, T.; Badoual, M.; Grammaticos, B.

    2010-08-01

    We present a model which aims at describing the morphology of colonies of Proteus mirabilis and Bacillus subtilis. Our model is based on a cellular automaton which is obtained by the adequate discretisation of a diffusion-like equation, describing the migration of the bacteria, to which we have added rules simulating the consolidation process. Our basic assumption, following the findings of the group of Chuo University, is that the migration and consolidation processes are controlled by the local density of the bacteria. We show that it is possible within our model to reproduce the morphological diagrams of both bacteria species. Moreover, we model some detailed experiments done by the Chuo University group, obtaining a fine agreement.

  3. A simple model of bedform migration

    DEFF Research Database (Denmark)

    Bartholdy, Jesper; Ernstsen, Verner Brandbyge; Flemming, Burg W

    2010-01-01

    and width) of naturally-packed bed material on the bedform lee side, qb(crest). The model is simple, built on a rational description of simplified sediment mechanics, and its calibration constant can be explained in accordance with estimated values of the physical constants on which it is based. Predicted......A model linking subaqueous dune migration to the effective (grain related) shear stress is calibrated by means of flume data for bedform dimensions and migration rates. The effective shear stress is calculated on the basis of a new method assuming a near-bed layer above the mean bed level in which...... the current velocity accelerates towards the bedform crest. As a consequence, the effective bed shear stress corresponds to the shear stress acting directly on top of the bedform. The model operates with the critical Shields stress as a function of grain size, and predicts the deposition (volume per unit time...

  4. Prestack exploding reflector modeling and migration in TI media

    KAUST Repository

    Wang, H.

    2014-01-01

    Prestack depth migration in anisotropic media, especially those that exhibit tilt, can be costly using reverse time migration (RTM). We present two-way spectral extrapolation of prestack exploding reflector modeling and migration (PERM) in acoustic transversely isotropic (TI) media. We construct systematic ways to evaluate phase angles and phase velocities in dip oriented TI (DTI), vertical TI (VTI) and tilted TI (TTI) media. Migration results from the Marmousi VTI model and the BP2007 TTI model show the feasibility of our approach.

  5. Hydrogeological modelling for migration of radioactivity

    International Nuclear Information System (INIS)

    Sunny, Faby; Chopra, Manish; Oza, R.B.

    2016-01-01

    The hydrogeological modelling for migration of radionuclides basically involves modelling of groundwater flow and contaminant transport through the groundwater. The water that occurs below the land surface or within the lithosphere is called groundwater. The groundwater constitutes about 4 % of the total water on the earth and about 30 % of freshwater on the earth. Groundwater models describe groundwater flow and contaminant transport processes using mathematical equations that are based on certain simplifying assumptions. These assumptions typically involve the direction of flow, geometry of the aquifer, the heterogeneity or anisotropy of sediments or bedrock within the aquifer, the contaminant transport mechanisms and chemical reactions. Because of the simplifying assumptions and the many uncertainties in the values of data, a model must be viewed as an approximation and not an exact duplication of field conditions. However, these models are useful investigation tool for a number of applications such as prediction of the possible fate and migration of contaminants for risk evaluation; tracking the possible pathway of groundwater contamination; evaluation of design of hydraulic containment and pump-and-treat systems; design of groundwater monitoring networks; evaluation of regional groundwater resources and prediction of the effect of future groundwater withdrawals on groundwater levels

  6. Migration model for the near field

    International Nuclear Information System (INIS)

    Andersson, G.; Rasmusson, A.; Neretnieks, I.

    1982-11-01

    The near field model describes the transport of substances dissolved in the groundwater to and from a canister in which radioactive materials are stored. The migration of substances that can cause corrosion (oxidants) of the canister is described by means of a mathematical model. The model takes into account diffusion through the buffer material and water flow in the rock fractures. Two distinct transport resistances can be distinguished in this transport process. The first consists of the diffusion resistance in the buffer material and the second arises due to diffusion resistance in the flowing water in the thin fractures in the rock. The model can also be used to calculate the non-steady-state phase of the inward or outward transport of dissolved species. The model has also been used to calculate how a redox front caused by radiolytically produced oxidants moves out through the clay and into the rock. It has been shown that the migration rate of the redox front can be calculated with good accuracy by means of simple mass balance computations. The transport of radiolytically formed hydrogen away from the fuel has been calculated. When dissolved in the water, hydrogen can be transported through the clay barrier by means of diffusion without the partial pressure of the hydrogen exceeding the hydrostatic pressure. (author)

  7. Removal of Cu(II) from leachate using natural zeolite as a landfill liner material

    International Nuclear Information System (INIS)

    Turan, N. Gamze; Ergun, Osman Nuri

    2009-01-01

    All hazardous waste disposal facilities require composite liner systems to act as a barrier against migration of contaminated leachate into the subsurface environment. Removal of copper(II) from leachate was studied using natural zeolite. A serial of laboratory systems on bentonite added natural zeolite was conducted and copper flotation waste was used as hazardous waste. The adsorption capacities and sorption efficiencies were determined. The sorption efficiencies increased with increasing natural zeolite ratio. The pseudo-first-order, the pseudo-second-order, Elovich and the intra-particle diffusion kinetic models were used to describe the kinetic data to estimate the rate constants. The second-order model best described adsorption kinetic data. The results indicated that natural zeolite showed excellent adsorptive characteristics for the removal of copper(II) from leachate and could be used as very good liner materials due to its high uptake capacity and the abundance in availability.

  8. Removal of Cu(II) from leachate using natural zeolite as a landfill liner material.

    Science.gov (United States)

    Turan, N Gamze; Ergun, Osman Nuri

    2009-08-15

    All hazardous waste disposal facilities require composite liner systems to act as a barrier against migration of contaminated leachate into the subsurface environment. Removal of copper(II) from leachate was studied using natural zeolite. A serial of laboratory systems on bentonite added natural zeolite was conducted and copper flotation waste was used as hazardous waste. The adsorption capacities and sorption efficiencies were determined. The sorption efficiencies increased with increasing natural zeolite ratio. The pseudo-first-order, the pseudo-second-order, Elovich and the intra-particle diffusion kinetic models were used to describe the kinetic data to estimate the rate constants. The second-order model best described adsorption kinetic data. The results indicated that natural zeolite showed excellent adsorptive characteristics for the removal of copper(II) from leachate and could be used as very good liner materials due to its high uptake capacity and the abundance in availability.

  9. Migration modelling in the New Economic Geography

    OpenAIRE

    Camacho Pérez, Maria del Carmen

    2010-01-01

    The benchmark of this paper is the Fujita and Thisse (2002) core-periphery model, which adds a R&D sector with skilled labor to create new varieties for the modern sector. The number of R&D firms increases not only with the number of existing patents and knowledge spillovers but also with the number of skilled workers who can migrate and choose theregion offering the better lifetime salary.The main objective of the present work is to analyse the long-term consequences of the choice of the mig...

  10. Migration Flows: Measurement, Analysis and Modeling

    NARCIS (Netherlands)

    Willekens, F.J.; White, Michael J.

    2016-01-01

    This chapter is an introduction to the study of migration flows. It starts with a review of major definition and measurement issues. Comparative studies of migration are particularly difficult because different countries define migration differently and measurement methods are not harmonized.

  11. Globalization and migration: A "unified brain drain" model

    OpenAIRE

    Brezis, Elise S.; Soueri, Ariel

    2012-01-01

    Globalization has led to a vast flow of migration of workers but also of students. The purpose of this paper is to analyze the migration of individuals encompassing decisions already at the level of education. We develop a unified brain drain model that incorporates the decisions of an individual vis - à - vis both education and migration. In the empirical part, this paper addresses international flows of migration within the EU and presents strong evidence of concentration of students in cou...

  12. Modeling seasonal migration of fall armyworm moths

    Science.gov (United States)

    Westbrook, J. K.; Nagoshi, R. N.; Meagher, R. L.; Fleischer, S. J.; Jairam, S.

    2016-02-01

    Fall armyworm, Spodoptera frugiperda (J.E. Smith), is a highly mobile insect pest of a wide range of host crops. However, this pest of tropical origin cannot survive extended periods of freezing temperature but must migrate northward each spring if it is to re-infest cropping areas in temperate regions. The northward limit of the winter-breeding region for North America extends to southern regions of Texas and Florida, but infestations are regularly reported as far north as Québec and Ontario provinces in Canada by the end of summer. Recent genetic analyses have characterized migratory pathways from these winter-breeding regions, but knowledge is lacking on the atmosphere's role in influencing the timing, distance, and direction of migratory flights. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to simulate migratory flight of fall armyworm moths from distinct winter-breeding source areas. Model simulations identified regions of dominant immigration from the Florida and Texas source areas and overlapping immigrant populations in the Alabama-Georgia and Pennsylvania-Mid-Atlantic regions. This simulated migratory pattern corroborates a previous migratory map based on the distribution of fall armyworm haplotype profiles. We found a significant regression between the simulated first week of moth immigration and first week of moth capture (for locations which captured ≥10 moths), which on average indicated that the model simulated first immigration 2 weeks before first captures in pheromone traps. The results contribute to knowledge of fall armyworm population ecology on a continental scale and will aid in the prediction and interpretation of inter-annual variability of insect migration patterns including those in response to climatic change and adoption rates of transgenic cultivars.

  13. How neurons migrate: a dynamic in-silico model of neuronal migration in the developing cortex

    LENUS (Irish Health Repository)

    Setty, Yaki

    2011-09-30

    Abstract Background Neuronal migration, the process by which neurons migrate from their place of origin to their final position in the brain, is a central process for normal brain development and function. Advances in experimental techniques have revealed much about many of the molecular components involved in this process. Notwithstanding these advances, how the molecular machinery works together to govern the migration process has yet to be fully understood. Here we present a computational model of neuronal migration, in which four key molecular entities, Lis1, DCX, Reelin and GABA, form a molecular program that mediates the migration process. Results The model simulated the dynamic migration process, consistent with in-vivo observations of morphological, cellular and population-level phenomena. Specifically, the model reproduced migration phases, cellular dynamics and population distributions that concur with experimental observations in normal neuronal development. We tested the model under reduced activity of Lis1 and DCX and found an aberrant development similar to observations in Lis1 and DCX silencing expression experiments. Analysis of the model gave rise to unforeseen insights that could guide future experimental study. Specifically: (1) the model revealed the possibility that under conditions of Lis1 reduced expression, neurons experience an oscillatory neuron-glial association prior to the multipolar stage; and (2) we hypothesized that observed morphology variations in rats and mice may be explained by a single difference in the way that Lis1 and DCX stimulate bipolar motility. From this we make the following predictions: (1) under reduced Lis1 and enhanced DCX expression, we predict a reduced bipolar migration in rats, and (2) under enhanced DCX expression in mice we predict a normal or a higher bipolar migration. Conclusions We present here a system-wide computational model of neuronal migration that integrates theory and data within a precise

  14. How neurons migrate: a dynamic in-silico model of neuronal migration in the developing cortex

    Directory of Open Access Journals (Sweden)

    Skoblov Nikita

    2011-09-01

    Full Text Available Abstract Background Neuronal migration, the process by which neurons migrate from their place of origin to their final position in the brain, is a central process for normal brain development and function. Advances in experimental techniques have revealed much about many of the molecular components involved in this process. Notwithstanding these advances, how the molecular machinery works together to govern the migration process has yet to be fully understood. Here we present a computational model of neuronal migration, in which four key molecular entities, Lis1, DCX, Reelin and GABA, form a molecular program that mediates the migration process. Results The model simulated the dynamic migration process, consistent with in-vivo observations of morphological, cellular and population-level phenomena. Specifically, the model reproduced migration phases, cellular dynamics and population distributions that concur with experimental observations in normal neuronal development. We tested the model under reduced activity of Lis1 and DCX and found an aberrant development similar to observations in Lis1 and DCX silencing expression experiments. Analysis of the model gave rise to unforeseen insights that could guide future experimental study. Specifically: (1 the model revealed the possibility that under conditions of Lis1 reduced expression, neurons experience an oscillatory neuron-glial association prior to the multipolar stage; and (2 we hypothesized that observed morphology variations in rats and mice may be explained by a single difference in the way that Lis1 and DCX stimulate bipolar motility. From this we make the following predictions: (1 under reduced Lis1 and enhanced DCX expression, we predict a reduced bipolar migration in rats, and (2 under enhanced DCX expression in mice we predict a normal or a higher bipolar migration. Conclusions We present here a system-wide computational model of neuronal migration that integrates theory and data within a

  15. Climate Shocks and Migration: An Agent-Based Modeling Approach

    Science.gov (United States)

    Entwisle, Barbara; Williams, Nathalie E.; Verdery, Ashton M.; Rindfuss, Ronald R.; Walsh, Stephen J.; Malanson, George P.; Mucha, Peter J.; Frizzelle, Brian G.; McDaniel, Philip M.; Yao, Xiaozheng; Heumann, Benjamin W.; Prasartkul, Pramote; Sawangdee, Yothin; Jampaklay, Aree

    2016-01-01

    This is a study of migration responses to climate shocks. We construct an agent-based model that incorporates dynamic linkages between demographic behaviors, such as migration, marriage, and births, and agriculture and land use, which depend on rainfall patterns. The rules and parameterization of our model are empirically derived from qualitative and quantitative analyses of a well-studied demographic field site, Nang Rong district, Northeast Thailand. With this model, we simulate patterns of migration under four weather regimes in a rice economy: 1) a reference, ‘normal’ scenario; 2) seven years of unusually wet weather; 3) seven years of unusually dry weather; and 4) seven years of extremely variable weather. Results show relatively small impacts on migration. Experiments with the model show that existing high migration rates and strong selection factors, which are unaffected by climate change, are likely responsible for the weak migration response. PMID:27594725

  16. Bench scale model studies on sanitary landfill leachate treatment with M. oleifera seed extract and hollow fibre micro-filtration membrane

    Directory of Open Access Journals (Sweden)

    S. A. Muyibi

    2002-10-01

    Full Text Available A laboratory-based study using a Bench Scale model of four unit operations made up of coagulation (using Moringa oleifera seed extract as a coagulant, flocculation, sedimentation and micro-filtration, have been adopted to treat the leachate from Air Hitman Sanitary Landfill at Puchong in Malaysia. M. oleifera dosages of 150 and 175 mg/L had achieved 43.8% Cadmium removal, 21.2% Total Chromium removal, 66.8% Lead removal and 16% Iron removal. It also removed 55.4% of Total Suspended Solids, 10% of Total Dissolved Solids and 24.2% of Volatile Suspended Solids. Micro-filtration hollow fibre membrane decreased the turbidity, total suspended solids, total dissolved solids, volatile suspended solids, and organic matter in the leachate by 98.3%, 96.7%, 20.8%, 36.6% and 21.9% respectively. Overall heavy metals removal after micro-filtration using hollow fibre membrane was 94% for Cadmium, 29.8% for Total Chromium, 73.2% for Lead, and 18.3% for Iron. The results have shown that M. oleifera is a promising natural polymer for removing heavy metals from leachates and may be used as a pre-treatment to eliminate a portion of the toxic heavy metals, which limits the activity of micro organisms in the leachates.

  17. DISCERNING EXOPLANET MIGRATION MODELS USING SPIN-ORBIT MEASUREMENTS

    International Nuclear Information System (INIS)

    Morton, Timothy D.; Johnson, John Asher

    2011-01-01

    We investigate the current sample of exoplanet spin-orbit measurements to determine whether a dominant planet migration channel can be identified, and at what confidence. We use the predictions of Kozai migration plus tidal friction and planet-planet scattering as our misalignment models, and we allow for a fraction of intrinsically aligned systems, explainable by disk migration. Bayesian model comparison demonstrates that the current sample of 32 spin-orbit measurements strongly favors a two-mode migration scenario combining planet-planet scattering and disk migration over a single-mode Kozai migration scenario. Our analysis indicates that between 34% and 76% of close-in planets (95% confidence) migrated via planet-planet scattering. Separately analyzing the subsample of 12 stars with T eff >6250 K-which Winn et al. predict to be the only type of stars to maintain their primordial misalignments-we find that the data favor a single-mode scattering model over Kozai with 85% confidence. We also assess the number of additional hot star spin-orbit measurements that will likely be necessary to provide a more confident model selection, finding that an additional 20-30 measurement has a >50% chance of resulting in a 95% confident model selection, if the current model selection is correct. While we test only the predictions of particular Kozai and scattering migration models in this work, our methods may be used to test the predictions of any other spin-orbit misaligning mechanism.

  18. AMEM-ADL Polymer Migration Estimation Model User's Guide

    Science.gov (United States)

    The user's guide of the Arthur D. Little Polymer Migration Estimation Model (AMEM) provides the information on how the model estimates the fraction of a chemical additive that diffuses through polymeric matrices.

  19. Landfilling: Bottom Lining and Leachate Collection

    DEFF Research Database (Denmark)

    Christensen, Thomas Højlund; Manfredi, Simone; Kjeldsen, Peter

    2011-01-01

    from entering the groundwater or surface water. The bottom lining system should cover the full footprint area of the landfill, including both the relatively flat bottom and the sideslopes in the case of an excavated configuration. This prevents the lateral migration of leachate from within the landfill...... triple) liners, are extremely effective in preventing leachate from entering into the environment. In addition, the risk of polluting the groundwater at a landfill by any leakage of leachate depends on several factors related to siting of the landfill: distance to the water table, distance to surface...... water bodies, and the properties of the soil beneath the landfill. In addition to the lining and drainage systems described in this chapter, the siting and hydrogeology of the landfill site (Chapter 10.12) and the top cover (Chapter 10.9) are also part of the barrier system, contributing to reducing...

  20. Detailed landfill leachate plume mapping using 2D and 3D Electrical Resistivity Tomography - with correlation to ionic strength measured in screens

    DEFF Research Database (Denmark)

    Maurya, P.K.; Rønde, Vinni; Fiandaca, G.

    2017-01-01

    Leaching of organic and inorganic contamination from landfills is a serious environmental problem as surface water and aquifers are affected. In order to assess these risks and investigate the migration of leachate from the landfill, 2D and large scale 3D electrical resistivity tomography were used...... at a heavily contaminated landfill in Grindsted, Denmark. The inverted 2D profiles describe both the variations along the groundwater flow as well as the plume extension across the flow directions. The 3D inversion model shows the variability in the low resistivity anomaly pattern corresponding to differences...... in the ionic strength of the landfill leachate. Chemical data from boreholes agree well with the observations indicating a leachate plume which gradually sinks and increases in size while migrating from the landfill in the groundwater flow direction. Overall results show that the resistivity method has been...

  1. Computer modelling of contaminant migration in natural disperse media

    International Nuclear Information System (INIS)

    Kundas, S.P.; Gishkelyuk, I.A.; Khil'ko, O.S.

    2012-01-01

    The theoretical foundations for modeling of the contaminants migration in natural disperses media taking into account interconnected heat and moisture transport are developed. The calculation of mass transfer parameters based on adsorption isotherms of water and thermodynamic equations in the developed mathematical models. The artificial neural networks use to predict migration of contaminants in natural disperse media is proposed. The developed software package is presented and results of practical application of models and software are discussed. (authors)

  2. The Physical Clogging of the Landfill Leachate Collection System in China: Based on Filtration Test and Numerical Modelling

    Directory of Open Access Journals (Sweden)

    Yili Liu

    2018-02-01

    Full Text Available Clogging of the leachate collection system (LCS has been a common operation problem in municipal solid waste (MSW landfills in China, which can result in high water levels that threaten the safety of landfill operations. To determine the cause of failure in an LCS, raw leachate from a municipal solid waste transfer station was collected and the high content of particulate matter was characterized. Based on the parameters obtained in a filtration test, a numerical simulation was performed to estimate the influence of particle deposition on drainage system clogging. The results showed that LCSs were confronted with the risk of clogging due to the deposition of particulate matter resulting from the higher concentration of total suspended solids (TSS level > 2200 mg L−1 and larger particle size (>30% TSS particles > 15 μm in the leachate. On one hand, the non-woven geotextile, as the upper layer of the LCS, retained most particulate matter of large diameters, reducing its hydraulic conductivity to approximately 10−8 to 10−9 m s−1 after 1–2 years of operation and perching significant leachate above it (0.6–0.7 m. On the other hand, the geotextile prevented the gravel layer from physically clogging and minimized the leachate head above the bottom liner. Therefore, the role of geotextile should be balanced to optimize the LCS in MSW landfills in China.

  3. Reverse time migration by Krylov subspace reduced order modeling

    Science.gov (United States)

    Basir, Hadi Mahdavi; Javaherian, Abdolrahim; Shomali, Zaher Hossein; Firouz-Abadi, Roohollah Dehghani; Gholamy, Shaban Ali

    2018-04-01

    Imaging is a key step in seismic data processing. To date, a myriad of advanced pre-stack depth migration approaches have been developed; however, reverse time migration (RTM) is still considered as the high-end imaging algorithm. The main limitations associated with the performance cost of reverse time migration are the intensive computation of the forward and backward simulations, time consumption, and memory allocation related to imaging condition. Based on the reduced order modeling, we proposed an algorithm, which can be adapted to all the aforementioned factors. Our proposed method benefit from Krylov subspaces method to compute certain mode shapes of the velocity model computed by as an orthogonal base of reduced order modeling. Reverse time migration by reduced order modeling is helpful concerning the highly parallel computation and strongly reduces the memory requirement of reverse time migration. The synthetic model results showed that suggested method can decrease the computational costs of reverse time migration by several orders of magnitudes, compared with reverse time migration by finite element method.

  4. Modeling Quasi-Static and Fatigue-Driven Delamination Migration

    Science.gov (United States)

    De Carvalho, N. V.; Ratcliffe, J. G.; Chen, B. Y.; Pinho, S. T.; Baiz, P. M.; Tay, T. E.

    2014-01-01

    An approach was proposed and assessed for the high-fidelity modeling of progressive damage and failure in composite materials. It combines the Floating Node Method (FNM) and the Virtual Crack Closure Technique (VCCT) to represent multiple interacting failure mechanisms in a mesh-independent fashion. Delamination, matrix cracking, and migration were captured failure and migration criteria based on fracture mechanics. Quasi-static and fatigue loading were modeled within the same overall framework. The methodology proposed was illustrated by simulating the delamination migration test, showing good agreement with the available experimental data.

  5. Leachate pollution management to overcome global climate change impact in Piyungan Landfill, Indonesia

    Science.gov (United States)

    Harjito; Suntoro; Gunawan, T.; Maskuri, M.

    2018-03-01

    Environmental problems associated with the landfill system are generated by domestic waste landfills, especially those with open dumping systems. In these systems, waste degrades and produces some gases, namely methane gas (CH4) and carbon dioxide (CO2), which can cause global climate change. This research aimed at identifying the areas that experience groundwater pollution and the spread pattern of leachate movement to the vicinity as well as to develop a leachate management model. The Electricity Resistivity Tomography (ERT) survey is deployed to assess the distribution of electrical resistivity in the polluted areas. In this study, the groundwater contamination is at a very low in the aquifer zone, i.e., 3-9 Ωm. It is caused by the downward migration of leachate to water table that raises the ion concentration of groundwater. These ions will increase the electrical conductivity (EC), i.e., up to 1,284 μmhos/cm, and decrease the electrical resistivity. The leachate spreads westward and northward at a depth of 6-17 m (aquifer) with a thickness of pollution between 4 and11 m.The recommended landfill management model involves the installation of rainwater drainage, use of cover and baseliner made of waterproof materials, and massive waste treatment.

  6. Graph and model transformation tools for model migration : empirical results from the transformation tool contest

    NARCIS (Netherlands)

    Rose, L.M.; Herrmannsdoerfer, M.; Mazanek, S.; Van Gorp, P.M.E.; Buchwald, S.; Horn, T.; Kalnina, E.; Koch, A.; Lano, K.; Schätz, B.; Wimmer, M.

    2014-01-01

    We describe the results of the Transformation Tool Contest 2010 workshop, in which nine graph and model transformation tools were compared for specifying model migration. The model migration problem—migration of UML activity diagrams from version 1.4 to version 2.2—is non-trivial and practically

  7. Temperature-influenced energetics model for migrating waterfowl

    Science.gov (United States)

    Aagaard, Kevin; Thogmartin, Wayne E.; Lonsdorg, Eric V.

    2018-01-01

    Climate and weather affect avian migration by influencing when and where birds fly, the energy costs and risks of flight, and the ability to sense cues necessary for proper navigation. We review the literature of the physiology of avian migration and the influence of climate, specifically temperature, on avian migration dynamics. We use waterfowl as a model guild because of the ready availability of empirical physiological data and their enormous economic value, but our discussion and expectations are broadly generalizable to migratory birds in general. We detail potential consequences of an increasingly warm climate on avian migration, including the possibility of the cessation of migration by some populations and species. Our intent is to lay the groundwork for including temperature effects on energetic gains and losses of migratory birds with the expected consequences of increasing temperatures into a predictive modeling framework. To this end, we provide a simulation of migration progression exclusively focused on the influence of temperature on the physiological determinants of migration. This simulation produced comparable results to empirically derived and observed values for different migratory factors (e.g., body fat content, flight range, departure date). By merging knowledge from the arenas of avian physiology and migratory theory we have identified a clear need for research and have developed hypotheses for a path forward.

  8. Disposal leachates treatment

    Energy Technology Data Exchange (ETDEWEB)

    Coulomb, I.; Renaud, P. (SITA, 75 - Paris (France)); Courant, P. (FD Conseil, 78 - Gargenville (France)); Manem, J.; Mandra, V.; Trouve, E. (Lyonnaise des Eaux-Dumez, 78 - Le Pecq (France))

    1993-12-01

    Disposal leachates are complex and variable effluents. The use of a bioreactor with membranes, coupled with a reverse osmosis unit, gives a new solution to the technical burying centers. Two examples are explained here.

  9. Application of environmental isotopes to characterize landfill gases and leachate

    International Nuclear Information System (INIS)

    Liu, C.L.; Hackley, K.C.; Baker, J.

    1992-01-01

    Environmental isotopes have been used to help characterize landfill gases and leachate for the purpose of identifying leachate and/or gas contamination in surrounding monitoring wells. Carbon isotopes (C-13/C-12 and C-14), hydrogen isotopes (H-3 and H-2/H-1) and oxygen isotopes (O-18/O-16) were used to characterize methane, carbon dioxide and leachate produced from two municipal landfills in northeastern Illinois. The isotopic results from the landfill-derived gases and leachate are compared to isotopic compositions of groundwater and gases from nearby monitoring wells. C-14 activity of landfill CH 4 is high compared to CH 4 normally found in subsurface sediments. For this study C-14 activities of the landfill methane range from 129--140 PMC. The C-14 of the dissolved inorganic carbon (DIC) of the leachate samples also have relatively high activities, ranging from 126--141 PMC. The δC-13 and δD values for CH 4 from the landfills fall within a range of values representative of microbial methane produced by acetate-fermentation. The δC-13 of the CO 2 and the DIC are very positive, ranging from 8--14 per-thousand for CO 2 and 13--22 per-thousand for DIC. The δO-18 values of the leachates are similar to current meteoric water values, however, two of the leachate samples are significantly enriched in deuterium by approximately 65 per-thousand. Tritium values of the leachate water are generally higher than expected. For one landfill the tritium activity ranges from 227--338 TU, for the second landfill the tritium activity is approximately 1,300 TU. Compared to tritium levels in normal groundwater, these higher tritium values in the leachates indicate that this isotope has the potential to be an effective tracer for detecting leachate migration

  10. Improvement of electrical resistivity tomography for leachate injection monitoring

    International Nuclear Information System (INIS)

    Clement, R.; Descloitres, M.; Guenther, T.; Oxarango, L.; Morra, C.; Laurent, J.-P.; Gourc, J.-P.

    2010-01-01

    Leachate recirculation is a key process in the scope of operating municipal waste landfills as bioreactors, which aims to increase the moisture content to optimize the biodegradation in landfills. Given that liquid flows exhibit a complex behaviour in very heterogeneous porous media, in situ monitoring methods are required. Surface time-lapse electrical resistivity tomography (ERT) is usually proposed. Using numerical modelling with typical 2D and 3D injection plume patterns and 2D and 3D inversion codes, we show that wrong changes of resistivity can be calculated at depth if standard parameters are used for time-lapse ERT inversion. Major artefacts typically exhibit significant increases of resistivity (more than +30%) which can be misinterpreted as gas migration within the waste. In order to eliminate these artefacts, we tested an advanced time-lapse ERT procedure that includes (i) two advanced inversion tools and (ii) two alternative array geometries. The first advanced tool uses invariant regions in the model. The second advanced tool uses an inversion with a 'minimum length' constraint. The alternative arrays focus on (i) a pole-dipole array (2D case), and (ii) a star array (3D case). The results show that these two advanced inversion tools and the two alternative arrays remove almost completely the artefacts within +/-5% both for 2D and 3D situations. As a field application, time-lapse ERT is applied using the star array during a 3D leachate injection in a non-hazardous municipal waste landfill. To evaluate the robustness of the two advanced tools, a synthetic model including both true decrease and increase of resistivity is built. The advanced time-lapse ERT procedure eliminates unwanted artefacts, while keeping a satisfactory image of true resistivity variations. This study demonstrates that significant and robust improvements can be obtained for time-lapse ERT monitoring of leachate recirculation in waste landfills.

  11. Improvement of electrical resistivity tomography for leachate injection monitoring.

    Science.gov (United States)

    Clément, R; Descloitres, M; Günther, T; Oxarango, L; Morra, C; Laurent, J-P; Gourc, J-P

    2010-03-01

    Leachate recirculation is a key process in the scope of operating municipal waste landfills as bioreactors, which aims to increase the moisture content to optimize the biodegradation in landfills. Given that liquid flows exhibit a complex behaviour in very heterogeneous porous media, in situ monitoring methods are required. Surface time-lapse electrical resistivity tomography (ERT) is usually proposed. Using numerical modelling with typical 2D and 3D injection plume patterns and 2D and 3D inversion codes, we show that wrong changes of resistivity can be calculated at depth if standard parameters are used for time-lapse ERT inversion. Major artefacts typically exhibit significant increases of resistivity (more than +30%) which can be misinterpreted as gas migration within the waste. In order to eliminate these artefacts, we tested an advanced time-lapse ERT procedure that includes (i) two advanced inversion tools and (ii) two alternative array geometries. The first advanced tool uses invariant regions in the model. The second advanced tool uses an inversion with a "minimum length" constraint. The alternative arrays focus on (i) a pole-dipole array (2D case), and (ii) a star array (3D case). The results show that these two advanced inversion tools and the two alternative arrays remove almost completely the artefacts within +/-5% both for 2D and 3D situations. As a field application, time-lapse ERT is applied using the star array during a 3D leachate injection in a non-hazardous municipal waste landfill. To evaluate the robustness of the two advanced tools, a synthetic model including both true decrease and increase of resistivity is built. The advanced time-lapse ERT procedure eliminates unwanted artefacts, while keeping a satisfactory image of true resistivity variations. This study demonstrates that significant and robust improvements can be obtained for time-lapse ERT monitoring of leachate recirculation in waste landfills. Copyright 2009 Elsevier Ltd. All rights

  12. Mechanisms and models of 137Cs migration in soil

    International Nuclear Information System (INIS)

    Frid, A.S.

    1999-01-01

    The most wide-spread mechanisms and models of the 137 Cs isotope migration in soil are considered because of urgency of this problem conditioned by global fallout during nuclear weapon tests and contamination of territories due to accidents on nuclear objects (including the East Urals and ChNPP accident). It is shown that the 137 Cs migration models with an account of the sorption-desorption kinetics have from the practical adequacy certain advantage in comparison with other models, though they are mathematically more complex and require complex calculations [ru

  13. A computer model for DNAPL potential migration study

    International Nuclear Information System (INIS)

    Yan, S.; Landry, G.R.; Tate, T.

    1994-01-01

    A computer model, named DNAPMIG (DNAPL Potential Migration), was developed to calculate the dense nonaqueous phase liquid (DNAPL) critical length required to initiate movement and direction of potential migration at locations within an area of interest. The model takes into consideration the potentiometric gradient, bottom structure elevation, DNAPL density, interfacial tension, contact angle, soil grain size, partitioning coefficient, effective solubility, and water saturation. The model is interfaced with SURFER graphics software to use vectors to indicate the DNAPL critical length and the potential migration direction. The potential for DNAPL existence and migration at a specific site can be estimated by relating chemical concentration in the ground water to its solubility limit and the DNAPL critical length. The possibility of vertical migration can also be determined. This model can be used to determine and compare the effectiveness of existing or alternative recovery well systems to capture a DNAPL plume or arrest its movement; to help determine optimum locations and pumping rates of recovery wells; and to help determine the optimum location of environmental borings to locate DNAPL. This paper presents two hypothetical examples and two site applications in south Louisiana

  14. Melt migration modeling in partially molten upper mantle

    Science.gov (United States)

    Ghods, Abdolreza

    The objective of this thesis is to investigate the importance of melt migration in shaping major characteristics of geological features associated with the partial melting of the upper mantle, such as sea-floor spreading, continental flood basalts and rifting. The partial melting produces permeable partially molten rocks and a buoyant low viscosity melt. Melt migrates through the partially molten rocks, and transfers mass and heat. Due to its much faster velocity and appreciable buoyancy, melt migration has the potential to modify dynamics of the upwelling partially molten plumes. I develop a 2-D, two-phase flow model and apply it to investigate effects of melt migration on the dynamics and melt generation of upwelling mantle plumes and focusing of melt migration beneath mid-ocean ridges. Melt migration changes distribution of the melt-retention buoyancy force and therefore affects the dynamics of the upwelling plume. This is investigated by modeling a plume with a constant initial melt of 10% where no further melting is considered. Melt migration polarizes melt-retention buoyancy force into high and low melt fraction regions at the top and bottom portions of the plume and therefore results in formation of a more slender and faster upwelling plume. Allowing the plume to melt as it ascends through the upper mantle also produces a slender and faster plume. It is shown that melt produced by decompressional melting of the plume migrates to the upper horizons of the plume, increases the upwelling velocity and thus, the volume of melt generated by the plume. Melt migration produces a plume which lacks the mushroom shape observed for the plume models without melt migration. Melt migration forms a high melt fraction layer beneath the sloping base of the impermeable oceanic lithosphere. Using realistic conditions of melting, freezing and melt extraction, I examine whether the high melt fraction layer is able to focus melt from a wide partial melting zone to a narrow region

  15. Modeling of Hydrodynamic Chromatography for Colloid Migration in Fractured Rock

    International Nuclear Information System (INIS)

    Li Shihhai; Jen, C.-P.

    2001-01-01

    The role of colloids in the migration of radionuclides in the geosphere has been emphasized in the performance assessment of high-level radioactive waste disposal. The literature indicates that the colloid velocity may not be equal to the velocity of groundwater owing to hydrodynamic chromatography. A theoretical model for hydrodynamic chromatography of colloid migration in the fracture is proposed in the present work. In this model, the colloids are treated as nonreactive and the external forces acting on colloidal particles are considered including the inertial force, the van der Waals attractive force, and the electrical double-layer repulsive force, as well as the gravitational force. A fully developed concentration profile for colloids is obtained to elucidate migration behavior for colloids in the fracture. The effects of parameters governing these forces and the aperture of the fracture are determined using a theoretical model

  16. Cost Model for Digital Preservation: Cost of Digital Migration

    Directory of Open Access Journals (Sweden)

    Ulla Bøgvad Kejser

    2011-03-01

    Full Text Available The Danish Ministry of Culture has funded a project to set up a model for costing preservation of digital materials held by national cultural heritage institutions. The overall objective of the project was to increase cost effectiveness of digital preservation activities and to provide a basis for comparing and estimating future cost requirements for digital preservation. In this study we describe an activity-based costing methodology for digital preservation based on the Open Archice Information System (OAIS Reference Model. Within this framework, which we denote the Cost Model for Digital Preservation (CMDP, the focus is on costing the functional entity Preservation Planning from the OAIS and digital migration activities. In order to estimate these costs we have identified cost-critical activities by analysing the functions in the OAIS model and the flows between them. The analysis has been supplemented with findings from the literature, and our own knowledge and experience. The identified cost-critical activities have subsequently been deconstructed into measurable components, cost dependencies have been examined, and the resulting equations expressed in a spreadsheet. Currently the model can calculate the cost of different migration scenarios for a series of preservation formats for text, images, sound, video, geodata, and spreadsheets. In order to verify the model it has been tested on cost data from two different migration projects at the Danish National Archives (DNA. The study found that the OAIS model provides a sound overall framework for the cost breakdown, but that some functions need additional detailing in order to cost activities accurately. Running the two sets of empirical data showed among other things that the model underestimates the cost of manpower-intensive migration projects, while it reinstates an often underestimated cost, which is the cost of developing migration software. The model has proven useful for estimating the

  17. On the development of a bedform migration model

    DEFF Research Database (Denmark)

    Bartholdy, Jesper; Ernstsen, V.B.; Flemming, B.W.

    2008-01-01

    A model linking subaqueous dune migration to the effective (grain related) shear stress is calibrated by means of flume data for bedform dimensions and migration rates. The effective shear stress is calculated on the basis of a new method assuming a near-bed layer above the mean bed level in which...... the current velocity accelerates towards the bedform crest. As a consequence, the effective bed shear stress corresponds to the shear stress acting directly on top of the bedform. The model operates with the critical Shields stress as a function of grain size. It predicts the deposition (volume per unit time...

  18. Gas migration mechanism of saturated dense bentonite and its modeling

    International Nuclear Information System (INIS)

    Tanaka, Yukihisa; Hironaga, Michihiko; Kudo, Koji

    2007-01-01

    In the current concept of repository for nuclear waste disposal, compacted bentonite will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. Hydrogen gas can be generated inside the engineered barrier by anaerobic corrosion of metals used for containers, etc. If the gas generation rate exceeds the diffusion rate of gas molecules inside of the engineered barrier, gas will accumulate in the void space inside of the engineered barrier until its pressure becomes large enough for it to enter the bentonite as a discrete gaseous phase. It is expected to be not easy for gas to entering into the bentonite as a discrete gaseous phase because the pore of compacted bentonite is so minute. Therefore it is necessary to investigate the following subjects: a) Effect of the accumulated gas pressure on surrounding objects such as concrete lining, rock mass. b) Effect of gas breakthrough on the barrier function of bentonite. c) Revealing and modeling gas migration mechanism for overcoming the scale effects in laboratory specimen test. Therefore in this study, gas migration tests for compacted and saturated bentonite to investigate and to model the mechanism of gas migration phenomenon. Firstly, the following conclusions were obtained through by the results of the gas migration tests which are conducted in this study: 1) Bubbles appear in the semitransparent drainage tube at first when the total gas is equal to the initial total axial stress or somewhat smaller. By increasing the gas pressure more, breakthrough of gas migration, which is defined as a sudden increase of amount of emission gas, occurred. When the total gas pressure exceeds the initial total axial stress, the total axial stress is always equal to the total gas pressure because specimens shrink in the axial direction with causing the clearance between the end of the specimen and porous metal. 2) Effective gas conductivity after breakthrough of gas migration is times larger than that

  19. Organic halogens in landfill leachates

    DEFF Research Database (Denmark)

    Grøn, C.; Christensen, J. B.; Jensen, Dorthe Lærke

    2000-01-01

    Using a group parameter, total organic halogens (TOX), high TOX concentrations were found in leachates and leachate contaminated groundwaters at two Danish mixed sanitary and hazardous waste sites. With commonly used screening procedures for organic contaminants, the individual halogenated organi...

  20. A generic model of contaminant migration from uranium tailings impoundments

    International Nuclear Information System (INIS)

    Shepherd, T.A.; Brown, S.E.

    1982-01-01

    This paper presents an analytical hydrogeochemical model based upon acid consumption-neutralization front movement. The development of contaminant plumes is discussed and distinct zones within these plumes are identified and characterized. The most important process influencing the rate and extent of contaminant migration at acid-leach uranium tailings impoundments is the neutralization of seepage water by soils along ground water flow paths. The chemical characteristics of the ground water is determined in order to identify and characterize zones within migrating plumes of tailings-derived water. It is concluded that the characterization of specific zones is useful in the interpretation of existing conditions, in the evaluation of future migration, and in the determination of appropriate models for the specific situation

  1. Using parallel factor analysis modeling (PARAFAC) and self-organizing maps to track senescence-induced patterns in leaf litter leachate

    Science.gov (United States)

    Wheeler, K. I.; Levia, D. F., Jr.; Hudson, J. E.

    2017-12-01

    As trees undergo autumnal processes such as resorption, senescence, and leaf abscission, the dissolved organic matter (DOM) contribution of leaf litter leachate to streams changes. However, little research has investigated how the fluorescent DOM (FDOM) changes throughout the autumn and how this differs inter- and intraspecifically. Two of the major impacts of global climate change on forested ecosystems include altering phenology and causing forest community species and subspecies composition restructuring. We examined changes in FDOM in leachate from American beech (Fagus grandifolia Ehrh.) leaves in Maryland, Rhode Island, Vermont, and North Carolina and yellow poplar (Liriodendron tulipifera L.) leaves from Maryland throughout three different phenophases: green, senescing, and freshly abscissed. Beech leaves from Maryland and Rhode Island have previously been identified as belonging to the same distinct genetic cluster and beech trees from Vermont and the study site in North Carolina from the other. FDOM in samples was characterized using excitation-emission matrices (EEMs) and a six-component parallel factor analysis (PARAFAC) model was created to identify components. Self-organizing maps (SOMs) were used to visualize variation and patterns in the PARAFAC component proportions of the leachate samples. Phenophase and species had the greatest influence on determining where a sample mapped on the SOM when compared to genetic clusters and geographic origin. Throughout senescence, FDOM from all the trees transitioned from more protein-like components to more humic-like ones. Percent greenness of the sampled leaves and the proportion of the tyrosine-like component 1 were found to significantly differ between the two genetic beech clusters. This suggests possible differences in photosynthesis and resorption between the two genetic clusters of beech. The use of SOMs to visualize differences in patterns of senescence between the different species and genetic

  2. Accelerated physical modelling of radioactive waste migration in soil

    International Nuclear Information System (INIS)

    Zimmie, T.F.; De, A.; Mahmud, M.B.

    1994-01-01

    A 100 g-tonne geotechnical centrifuge was used to study the long-term migration of a contaminant and radioactive tracer through a saturated soil medium. The use of the centrifuge simulates the acceleration of travel time in the prototype, which is N times larger than the model, by N 2 , where N is the desired g level. For a 5 h run at 60 g, the test modelled a migration time of about 2 years for a prototype 60 times larger than the small-scale model tested. Iodine 131, used as the tracer, was injected onto the surface of the soil, and was allowed to migrate with a constant head of water through the saturated soil. End window Geiger-Mueller (G-M) tubes were used to measure the count rate of the radioactive tracer flowing through the soil. The time from the peak response of one G-M tube to the other denotes the travel time between the two points in the flow domain. The results obtained using the radioactive tracer are in good agreement with the test performed on the same model setup using potassium permanganate as tracer and with numerical flow net modelling. Radioactive tracers can be useful in the study of nonradioactive contaminants as well, offering a nonintrusive (nondestructive) method of measuring contaminant migration. (author). 18 refs., 1 tab., 7 figs

  3. Modelling of radionuclide migration in forest ecosystems. A literature review

    Energy Technology Data Exchange (ETDEWEB)

    Avila, R.; Moberg, L.; Hubbard, L.

    1998-03-01

    The Chernobyl accident has clearly shown the long-term effects of a radioactive contamination of forest ecosystems. This report is based on a literature review of models which describe the migration of radionuclides, radioactive caesium in particular, in forest ecosystems. The report describes the particularities of the forest ecosystem, the time dynamics of the contamination, the transfer processes and factors influencing caesium migration. This provides a basis for a discussion of different approaches for modelling caesium migration in the forest. It is concluded that the studied dynamic models include the most relevant transfer processes both for the acute and the long-term phase after a radioactive deposition. However, most models are site specific and do not consider some of the factors responsible for the differences in radionuclide behaviour and distribution in different types of forests. Although model improvements are constrained by the availability of experimental data and by the lack of knowledge of the migration mechanisms some possible improvements are discussed. This report is part of the LANDSCAPE project. -An integrated approach to radionuclide flow in the semi-natural ecosystems underlying exposure pathways to man. 42 refs, 3 tabs, 9 figs.

  4. Modelling of radionuclide migration in forest ecosystems. A literature review

    International Nuclear Information System (INIS)

    Avila, R.; Moberg, L.; Hubbard, L.

    1998-03-01

    The Chernobyl accident has clearly shown the long-term effects of a radioactive contamination of forest ecosystems. This report is based on a literature review of models which describe the migration of radionuclides, radioactive caesium in particular, in forest ecosystems. The report describes the particularities of the forest ecosystem, the time dynamics of the contamination, the transfer processes and factors influencing caesium migration. This provides a basis for a discussion of different approaches for modelling caesium migration in the forest. It is concluded that the studied dynamic models include the most relevant transfer processes both for the acute and the long-term phase after a radioactive deposition. However, most models are site specific and do not consider some of the factors responsible for the differences in radionuclide behaviour and distribution in different types of forests. Although model improvements are constrained by the availability of experimental data and by the lack of knowledge of the migration mechanisms some possible improvements are discussed. This report is part of the LANDSCAPE project. -An integrated approach to radionuclide flow in the semi-natural ecosystems underlying exposure pathways to man

  5. Probabilistic migration modelling focused on functional barrier efficiency and low migration concepts in support of risk assessment.

    Science.gov (United States)

    Brandsch, Rainer

    2017-10-01

    Migration modelling provides reliable migration estimates from food-contact materials (FCM) to food or food simulants based on mass-transfer parameters like diffusion and partition coefficients related to individual materials. In most cases, mass-transfer parameters are not readily available from the literature and for this reason are estimated with a given uncertainty. Historically, uncertainty was accounted for by introducing upper limit concepts first, turning out to be of limited applicability due to highly overestimated migration results. Probabilistic migration modelling gives the possibility to consider uncertainty of the mass-transfer parameters as well as other model inputs. With respect to a functional barrier, the most important parameters among others are the diffusion properties of the functional barrier and its thickness. A software tool that accepts distribution as inputs and is capable of applying Monte Carlo methods, i.e., random sampling from the input distributions of the relevant parameters (i.e., diffusion coefficient and layer thickness), predicts migration results with related uncertainty and confidence intervals. The capabilities of probabilistic migration modelling are presented in the view of three case studies (1) sensitivity analysis, (2) functional barrier efficiency and (3) validation by experimental testing. Based on the predicted migration by probabilistic migration modelling and related exposure estimates, safety evaluation of new materials in the context of existing or new packaging concepts is possible. Identifying associated migration risk and potential safety concerns in the early stage of packaging development is possible. Furthermore, dedicated material selection exhibiting required functional barrier efficiency under application conditions becomes feasible. Validation of the migration risk assessment by probabilistic migration modelling through a minimum of dedicated experimental testing is strongly recommended.

  6. Student Migration to Online Education: An Economic Model

    Science.gov (United States)

    Eisenhauer, Joseph G.

    2013-01-01

    The popularity of distance education has increasingly led universities to consider expanding their online offerings. Remarkably few financial models have been presented for online courses, however, and fewer still have investigated the economic consequences of the migration, or cross-over, of students from traditional classes within the…

  7. Centrifuge modelling - migration of radionuclides from engineered trenches

    International Nuclear Information System (INIS)

    Dean, E.T.R.; Schofield, A.N.

    1991-12-01

    This report provides an overview of some centrifuge small-scale physical model tests and 1g experimental and theoretical work relating to the sub-surface migration of a model pollutant (sodium chloride) from a notional prototype surface landfill of width 25 metres and depth 3 metres cut into a 20 metre deep layer of nominally uniform soil overlying a more permeable base layer. An introduction is given to the application of geotechnical centrifuge modelling techniques to pollutant migration studies. Experiments performed at 1/100th scale using the Cambridge 10 metre diameter Geotechnical Beam Centrifuge simulating transport through silt over prototype time periods of around 35 years, are summarised. Comparisons of data with calculations using early versions of the POLLUTE and MIGRATE computer codes are presented. An experiment at 1/400th scale using the new Cambridge Geotechnical Drum Centrifuge, involving transport through clay over a prototype time period of around 1000 years, is described. Potential future uses of centrifuge modelling techniques to simulate long-term migration through more complex hydrological environments are also discussed. (author)

  8. Nitrogen frost migration on Triton: A historical model

    International Nuclear Information System (INIS)

    Spencer, J.R.

    1990-01-01

    The author presents the results of numerical simulations of the seasonal migration of nitrogen frost on Triton, constrained by Voyager observations of atmospheric pressure, temperature, and albedo distribution. Most of the exposed nitrogen is probably seasonal frost, whose migration can produce major variations in atmospheric pressure. For instance, models explored here predict a tenfold pressure drop in the coming decade. The observed albedo patterns can be understood if fresh nitrogen frost is relatively dark butt brightens with increasing insolation in a manner analogous to the Martian southern CO 2 cap

  9. Model-driven software migration a methodology

    CERN Document Server

    Wagner, Christian

    2014-01-01

    Today, reliable software systems are the basis of any business or company. The continuous further development of those systems is the central component in software evolution. It requires a huge amount of time- man power- as well as financial resources. The challenges are size, seniority and heterogeneity of those software systems. Christian Wagner addresses software evolution: the inherent problems and uncertainties in the process. He presents a model-driven method which leads to a synchronization between source code and design. As a result the model layer will be the central part in further e

  10. Multistate modelling extended by behavioural rules: An application to migration.

    Science.gov (United States)

    Klabunde, Anna; Zinn, Sabine; Willekens, Frans; Leuchter, Matthias

    2017-10-01

    We propose to extend demographic multistate models by adding a behavioural element: behavioural rules explain intentions and thus transitions. Our framework is inspired by the Theory of Planned Behaviour. We exemplify our approach with a model of migration from Senegal to France. Model parameters are determined using empirical data where available. Parameters for which no empirical correspondence exists are determined by calibration. Age- and period-specific migration rates are used for model validation. Our approach adds to the toolkit of demographic projection by allowing for shocks and social influence, which alter behaviour in non-linear ways, while sticking to the general framework of multistate modelling. Our simulations yield that higher income growth in Senegal leads to higher emigration rates in the medium term, while a decrease in fertility yields lower emigration rates.

  11. Modeling Bird Migration under Climate Change: A Mechanistic Approach

    Science.gov (United States)

    Smith, James A.

    2009-01-01

    How will migrating birds respond to changes in the environment under climate change? What are the implications for migratory success under the various accelerated climate change scenarios as forecast by the Intergovernmental Panel on Climate Change? How will reductions or increased variability in the number or quality of wetland stop-over sites affect migratory bird species? The answers to these questions have important ramifications for conservation biology and wildlife management. Here, we describe the use of continental scale simulation modeling to explore how spatio-temporal changes along migratory flyways affect en-route migration success. We use an individually based, biophysical, mechanistic, bird migration model to simulate the movement of shorebirds in North America as a tool to study how such factors as drought and wetland loss may impact migratory success and modify migration patterns. Our model is driven by remote sensing and climate data and incorporates important landscape variables. The energy budget components of the model include resting, foraging, and flight, but presently predation is ignored. Results/Conclusions We illustrate our model by studying the spring migration of sandpipers through the Great Plains to their Arctic breeding grounds. Why many species of shorebirds have shown significant declines remains a puzzle. Shorebirds are sensitive to stop-over quality and spacing because of their need for frequent refueling stops and their opportunistic feeding patterns. We predict bird "hydrographs that is, stop-over frequency with latitude, that are in agreement with the literature. Mean stop-over durations predicted from our model for nominal cases also are consistent with the limited, but available data. For the shorebird species simulated, our model predicts that shorebirds exhibit significant plasticity and are able to shift their migration patterns in response to changing drought conditions. However, the question remains as to whether this

  12. Verification and improvement of a predictive model for radionuclide migration

    International Nuclear Information System (INIS)

    Miller, C.W.; Benson, L.V.; Carnahan, C.L.

    1982-01-01

    Prediction of the rates of migration of contaminant chemical species in groundwater flowing through toxic waste repositories is essential to the assessment of a repository's capability of meeting standards for release rates. A large number of chemical transport models, of varying degrees of complexity, have been devised for the purpose of providing this predictive capability. In general, the transport of dissolved chemical species through a water-saturated porous medium is influenced by convection, diffusion/dispersion, sorption, formation of complexes in the aqueous phase, and chemical precipitation. The reliability of predictions made with the models which omit certain of these processes is difficult to assess. A numerical model, CHEMTRN, has been developed to determine which chemical processes govern radionuclide migration. CHEMTRN builds on a model called MCCTM developed previously by Lichtner and Benson

  13. Models of sorption and migration of radionuclides in geologic media

    International Nuclear Information System (INIS)

    Fukui, Masami

    1987-01-01

    Full understanding of the transportation of nuclides by groundwater is essential in designing an underground radioactive waste disposal site. What is the most important is to clarify in detail the process of sorption of nuclides by rock and soil. This report outlines various theories and experimental data that are currently available. In addition, studies made in various countries are reviewed and some problems are pointed out. First, a review is made of studies that deal with adsorption and behaviors of contaminants in natural barriers (rock, soil). Next, migration models that have been developed in studying migration processes in the field of chemical engineering or behaviors of agricultural chemicals in the field of soil physics are examined to see if they can be applied to investigations of the migration of radioactive contaminants in a porous medium. Finally, a review is made of basic underground migration models that are used in various countries in studying deep underground disposal of long-life radionuclides. Some laboratory experiments on TRU nuclides in rock are also outlined. (Nogami, K.)

  14. Transmission Model of Hepatitis B Virus with the Migration Effect

    Directory of Open Access Journals (Sweden)

    Muhammad Altaf Khan

    2013-01-01

    Full Text Available Hepatitis B is a globally infectious disease. Mathematical modeling of HBV transmission is an interesting research area. In this paper, we present characteristics of HBV virus transmission in the form of a mathematical model. We analyzed the effect of immigrants in the model to study the effect of immigrants for the host population. We added the following flow parameters: “the transmission between migrated and exposed class” and “the transmission between migrated and acute class.” With these new features, we obtained a compartment model of six differential equations. First, we find the basic threshold quantity Ro and then find the local asymptotic stability of disease-free equilibrium and endemic equilibrium. Furthermore, we find the global stability of the disease-free and endemic equilibria. Previous similar publications have not added the kind of information about the numerical results of the model. In our case, from numerical simulation, a detailed discussion of the parameters and their numerical results is presented. We claim that with these assumptions and by adding the migrated class, the model informs policy for governments, to be aware of the immigrants and subject them to tests about the disease status. Immigrants for short visits and students should be subjected to tests to reduce the number of immigrants with disease.

  15. Modeling Radionuclide Decay Chain Migration Using HYDROGEOCHEM

    Science.gov (United States)

    Lin, T. C.; Tsai, C. H.; Lai, K. H.; Chen, J. S.

    2014-12-01

    Nuclear technology has been employed for energy production for several decades. Although people receive many benefits from nuclear energy, there are inevitably environmental pollutions as well as human health threats posed by the radioactive materials releases from nuclear waste disposed in geological repositories or accidental releases of radionuclides from nuclear facilities. Theoretical studies have been undertaken to understand the transport of radionuclides in subsurface environments because that the radionuclide transport in groundwater is one of the main pathway in exposure scenarios for the intake of radionuclides. The radionuclide transport in groundwater can be predicted using analytical solution as well as numerical models. In this study, we simulate the transport of the radionuclide decay chain using HYDROGEOCHEM. The simulated results are verified against the analytical solution available in the literature. Excellent agreements between the numerical simulation and the analytical are observed for a wide spectrum of concentration. HYDROGECHEM is a useful tool assessing the ecological and environmental impact of the accidental radionuclide releases such as the Fukushima nuclear disaster where multiple radionuclides leaked through the reactor, subsequently contaminating the local groundwater and ocean seawater in the vicinity of the nuclear plant.

  16. Effect of increasing salinity on biogas production in waste landfills with leachate recirculation: A lab-scale model study

    Directory of Open Access Journals (Sweden)

    Yuka Ogata

    2016-06-01

    Full Text Available The effects of salinity on anaerobic waste degradation and microbial communities were investigated, in order to propose an appropriate leachate recirculation process in a waste landfill in a tropical region. A salt concentration of 21 mS cm−1 of electrical conductivity (EC did not affect waste degradation, but a salt concentration of 35 mS cm−1 of EC inhibited CH4 generation. A higher salt concentration of 80 mS cm−1 of EC inhibited not only CH4 and CO2 generation, but also degradation of organic compounds. The bacterial and archaeal community compositions were affected by high salinity. High salinity can exert selective pressure on bacterial communities, resulting in a change in bacterial community structure. Ammonium caused strong, dominant inhibition of biogas production in the salt concentration range of this study. Quality control, especially of ammonium levels, will be essential for the promotion of waste biodegradation in landfills with leachate recirculation.

  17. Modelling the Grimsel migration field experiments at PSI

    International Nuclear Information System (INIS)

    Heer, W.

    1997-01-01

    For several years tracer migration experiments have been performed at Nagra's Grimsel Test Site as a joint undertaking of Nagra, PNC and PSI. The aims of modelling the migration experiments are (1) to better understand the nuclide transport through crystalline rock; (2) to gain information on validity of methods and correlating parameters; (3) to improve models for safety assessments. The PSI modelling results, presented here, show a consistent picture for the investigated tracers (the non-sorbing uranine, the weakly sorbing sodium, the moderately sorbing strontium and the more strongly sorbing cesium). They represent an important step in building up confidence in safety assessments for radioactive waste repositories. (author) 5 figs., 1 tab., 12 refs

  18. Modelling the secular evolution of migrating planet pairs

    Science.gov (United States)

    Michtchenko, T. A.; Rodríguez, A.

    2011-08-01

    The subject of this paper is the secular behaviour of a pair of planets evolving under dissipative forces. In particular, we investigate the case when dissipative forces affect the planetary semimajor axes and the planets move inwards/outwards the central star, in a process known as planet migration. To perform this investigation, we introduce fundamental concepts of conservative and dissipative dynamics of the three-body problem. Based on these concepts, we develop a qualitative model of the secular evolution of the migrating planetary pair. Our approach is based on the analysis of the energy and the orbital angular momentum exchange between the two-planet system and an external medium; thus no specific kind of dissipative forces is invoked. We show that, under the assumption that dissipation is weak and slow, the evolutionary routes of the migrating planets are traced by the Mode I and Mode II stationary solutions of the conservative secular problem. The ultimate convergence and the evolution of the system along one of these secular modes of motion are determined uniquely by the condition that the dissipation rate is sufficiently smaller than the proper secular frequency of the system. We show that it is possible to reassemble the starting configurations and the migration history of the systems on the basis of their final states and consequently to constrain the parameters of the physical processes involved.

  19. Modeling of long-range migration of boron interstitials

    International Nuclear Information System (INIS)

    Velichko, O.I.; Burunova, O.N.

    2009-01-01

    A model of the interstitial migration of ion-implanted dopant in silicon during low-temperature thermal treatment has been formulated. It is supposed that the boron interstitials are created during ion implantation or at the initial stage of annealing. During thermal treatment a migration of these impurity interstitials to the surface and in the bulk of a semiconductor occurs. On this basis, a simulation of boron redistribution during thermal annealing for 35 minutes at a temperature of 800 0 C has been carried out. The calculated boron profile agrees well with the experimental data. A number of the parameters describing the interstitial diffusion have been derived. In particular, the average migration length of nonequilibrium boron interstitials is equal to 0.092 μm at a temperature of 800 0 C. To carry out modeling of ion-implanted boron redistribution, the analytical solutions of nonstationary diffusion equation for impurity interstitials have been obtained. The case of Dirichlet boundary conditions and the case of reflecting boundary on the surface of a semiconductor have been considered. (authors)

  20. Using Virtual ATE Model to Migrate Test Programs

    Institute of Scientific and Technical Information of China (English)

    王晓明; 杨乔林

    1995-01-01

    Bacause of high development costs of IC (Integrated Circuit)test programs,recycling existing test programs from one kind of ATE (Automatic Test Equipment) to another or generating directly from CAD simulation modules to ATE is more and more valuable.In this paper,a new approach to migrating test programs is presented.A virtual ATE model based on object-oriented paradigm is developed;it runs Test C++ (an intermediate test control language) programs and TeIF(Test Inftermediate Format-an intermediate pattern),migrates test programs among three kinds of ATE (Ando DIC8032,Schlumberger S15 and GenRad 1732) and generates test patterns from two kinds of CAD 9Daisy and Panda) automatically.

  1. Cost Model for Digital Curation: Cost of Digital Migration

    DEFF Research Database (Denmark)

    Kejser, Ulla Bøgvad; Nielsen, Anders Bo; Thirifays, Alex

    2009-01-01

    The Danish Ministry of Culture is currently funding a project to set up a model for costing preservation of digital materials held by national cultural heritage institutions. The overall objective of the project is to provide a basis for comparing and estimating future financial requirements...... for digital preservation and to increase cost effectiveness of digital preservation activities. In this study we describe an activity based costing methodology for digital preservation based on the OAIS Reference Model. In order to estimate the cost of digital migrations we have identified cost critical...

  2. Modeling the secular evolution of migrating planet pairs

    Science.gov (United States)

    Michtchenko, T. A.; Rodríguez, A.

    2011-10-01

    The secular regime of motion of multi-planetary systems is universal; in contrast with the 'accidental' resonant motion, characteristic only for specific configurations of the planets, secular motion is present everywhere in phase space, even inside the resonant region. The secular behavior of a pair of planets evolving under dissipative forces is the principal subject of this study, particularly, the case when the dissipative forces affect the planetary semi-major axes and the planets move inward/outward the central star, the process known as planet migration. Based on the fundamental concepts of conservative and dissipative dynamics of the three-body problem, we develop a qualitative model of the secular evolution of the migrating planetary pair. Our approach is based on analysis of the energy and the orbital angular momentum exchange between the two-planet system and an external medium; thus no specific kind of dissipative forces is invoked. We show that, under assumption that dissipation is weak and slow, the evolutionary routes of the migrating planets are traced by the Mode I and Mode II stationary solutions of the conservative secular problem. The ultimate convergence and the evolution of the system along one of these secular modes of motion is determined uniquely by the condition that the dissipation rate is sufficiently smaller than the proper secular frequency of the system. We show that it is possible to reassemble the starting configurations and migration history of the systems on the basis of their final states and consequently to constrain the parameters of the physical processes involved.

  3. A model for cell type localization in the migrating slug of ...

    Indian Academy of Sciences (India)

    PRAKASH

    . Localization of the three major cell types within the migrating slug stage is a dynamic process (Sternfeld 1992;. A model for cell type localization in the migrating slug of Dictyostelium discoideum based on differential chemotactic sensitivity to ...

  4. LCA and economic evaluation of landfill leachate and gas technologies.

    Science.gov (United States)

    Damgaard, Anders; Manfredi, Simone; Merrild, Hanna; Stensøe, Steen; Christensen, Thomas H

    2011-07-01

    Landfills receiving a mix of waste, including organics, have developed dramatically over the last 3-4 decades; from open dumps to engineered facilities with extensive controls on leachate and gas. The conventional municipal landfill will in most climates produce a highly contaminated leachate and a significant amount of landfill gas. Leachate controls may include bottom liners and leachate collection systems as well as leachate treatment prior to discharge to surface water. Gas controls may include oxidizing top covers, gas collection systems with flares or gas utilization systems for production of electricity and heat. The importance of leachate and gas control measures in reducing the overall environmental impact from a conventional landfill was assessed by life-cycle-assessment (LCA). The direct cost for the measures were also estimated providing a basis for assessing which measures are the most cost-effective in reducing the impact from a conventional landfill. This was done by modeling landfills ranging from a simple open dump to highly engineered conventional landfills with energy recovery in form of heat or electricity. The modeling was done in the waste LCA model EASEWASTE. The results showed drastic improvements for most impact categories. Global warming went from an impact of 0.1 person equivalent (PE) for the dump to -0.05 PE for the best design. Similar improvements were found for photochemical ozone formation (0.02 PE to 0.002 PE) and stratospheric ozone formation (0.04 PE to 0.001 PE). For the toxic and spoiled groundwater impact categories the trend is not as clear. The reason for this was that the load to the environment shifted as more technologies were used. For the dump landfill the main impacts were impacts for spoiled groundwater due to lack of leachate collection, 2.3 PE down to 0.4 PE when leachate is collected. However, at the same time, leachate collection causes a slight increase in eco-toxicity and human toxicity via water (0.007 E to 0

  5. The computer model development for radionuclide migration analysis in geosphere

    International Nuclear Information System (INIS)

    Mulyanto

    1998-01-01

    1-D numerical model for safety assessment of spent fuel disposal have been developed. The numerical solution with planar geometric was developed in order to solve mass transport in heterogenous geological media. In this paper, Crank-Nicolson method was discussed for solving of radionuclide migration equation. Demonstration was done for calculation of concentration distribution of several radionuclides in the exclusion zone. It was concluded that the exclusion zone was an important concept should be adopted in determination of disposal site. Site should be selected as far as possible from fracture or as long as possible exclusion zone. (author)

  6. Modelling the effects of spatial variability on radionuclide migration

    International Nuclear Information System (INIS)

    1998-01-01

    The NEA workshop reflect the present status in national waste management program, specifically in spatial variability and performance assessment of geologic disposal sites for deed repository system the four sessions were: Spatial Variability: Its Definition and Significance to Performance Assessment and Site Characterisation; Experience with the Modelling of Radionuclide Migration in the Presence of Spatial Variability in Various Geological Environments; New Areas for Investigation: Two Personal Views; What is Wanted and What is Feasible: Views and Future Plans in Selected Waste Management Organisations. The 26 papers presented on the four oral sessions and on the poster session have been abstracted and indexed individually for the INIS database. (R.P.)

  7. Cost Model for Digital Preservation: Cost of Digital Migration

    DEFF Research Database (Denmark)

    Kejser, Ulla Bøgvad; Nielsen, Anders Bo; Thirifays, Alex

    2011-01-01

    The Danish Ministry of Culture has funded a project to set up a model for costing preservation of digital materials held by national cultural heritage institutions. The overall objective of the project was to increase cost effectiveness of digital preservation activities and to provide a basis...... for comparing and estimating future cost requirements for digital preservation. In this study we describe an activity-based costing methodology for digital preservation based on the Open Archice Information System (OAIS) Reference Model. Within this framework, which we denote the Cost Model for Digital...... Preservation (CMDP), the focus is on costing the functional entity Preservation Planning from the OAIS and digital migration activities. In order to estimate these costs we have identified cost-critical activities by analysing the functions in the OAIS model and the flows between them. The analysis has been...

  8. Geophysical mapping of contaminant leachate around a reclaimed open dumpsite

    Directory of Open Access Journals (Sweden)

    W.O. Raji

    2017-07-01

    Full Text Available Very low frequency electromagnetic (VLF-EM, 2D Electrical Resistivity Profiling (2D ERP and Vertical Electrical Sounding (VES methods of geophysics were deployed to map the extent of leachate contamination in near-surface rocks around a popular reclaimed dumpsite in north central Nigeria. Two years after abandon and waste excavation; the dumpsite was converted to a residential area with over 80 houses under construction. Prior to waste dumping operation, clay-seal was installed at 2 m depth around the dumpsite to prevent leachate from the waste material flowing to the adjoining area. Results from VLF, 2D ERP, and VES show presence of leachate contamination in rocks and soil of the reclaimed dumpsite. Leachate has spread laterally up to a distance of about 1 km on the northern and southern parts of the dumpsite centre, and up to a depth of about 20 m. Compared to the results of similar survey in an area outside the dumpsite, leachate infiltration raised the conductivity signature of the rocks around the dumpsite by about 200%: from 7% to 22%. Both VLF-EM and 2D ERP show the presence of approximate north – south oriented structures/fracture characterised by high conductivity. VES results show the presence of four – five geo-electric layers. Important conclusions from the study are that (i leachate is still present in the rocks and soil of the reclaimed dumpsite two years after the abandonment and excavation of the waste materials, and (ii the clay seal installed around the dumpsite could not prevent leachate migration to the adjoining areas.

  9. Structural-equation models of migration: an example from the Upper Midwest USA.

    Science.gov (United States)

    Cadwallader, M

    1985-01-01

    "To date, most migration models have been specified in terms of a single equation, whereby a set of regional characteristics are used to predict migration rates for various kinds of spatial units. These models are inadequate in at least two respects. First, they omit any causal links between the explanatory variables, thus ignoring indirect effects between these variables and migration. Second, they ignore the possibility of reciprocal causation, or feedback effects, between migration and the explanatory variables...." The author uses data for State Economic Areas to construct a path model and simultaneous-equation model to identify both indirect and feedback effects on migration in the Upper Midwestern United States. "On the basis of the path model, it is suggested that the direct effects of many variables on migration are at least partially offset by the indirect effects, whereas the simultaneous-equation model emphasizes the reciprocal relationship between income and migration." excerpt

  10. Modeling of CO2 migration injected in Weyburn oil reservoir

    International Nuclear Information System (INIS)

    Zhou Wei; Stenhouse, M.J.; Arthur, R.

    2008-01-01

    Injecting CO 2 into oil and gas field is a way to enhance oil recovery (EOR) as well as mitigate global warming effect by permanently storing the greenhouse gas into underground. This paper details the models and results of simulating the long-term migration of CO 2 injected into the Weyburn field for both Enhanced Oil Recovery operations and CO 2 sequestration. A System Model was established to define the spatial and temporal extents of the analysis. The Base Scenario was developed to identify key processes, features, and events (FEPs) for the expected evolution of the storage system. A compositional reservoir simulator with equations-of-states (EOS) was used as the modeling tool in order to simulate multiphase, multi-component flow and transport coupled with CO 2 mass partitioning into oil, gas, and water phases. We apply a deterministic treatment to CO 2 migration in the geosphere (natural pathways), whereas the variability of abandoned wells (man-made pathways) necessitates a stochastic treatment. The simulation result was then used to carry out consequence analysis to the local environment. (authors)

  11. Efficient Modeling and Migration in Anisotropic Media Based on Prestack Exploding Reflector Model and Effective Anisotropy

    KAUST Repository

    Wang, Hui

    2014-01-01

    This thesis addresses the efficiency improvement of seismic wave modeling and migration in anisotropic media. This improvement becomes crucial in practice as the process of imaging complex geological structures of the Earth's subsurface requires

  12. MODELS OF LIVE MIGRATION WITH ITERATIVE APPROACH AND MOVE OF VIRTUAL MACHINES

    Directory of Open Access Journals (Sweden)

    S. M. Aleksankov

    2015-11-01

    Full Text Available Subject of Research. The processes of live migration without shared storage with pre-copy approach and move migration are researched. Migration of virtual machines is an important opportunity of virtualization technology. It enables applications to move transparently with their runtime environments between physical machines. Live migration becomes noticeable technology for efficient load balancing and optimizing the deployment of virtual machines to physical hosts in data centres. Before the advent of live migration, only network migration (the so-called, «Move», has been used, that entails stopping the virtual machine execution while copying to another physical server, and, consequently, unavailability of the service. Method. Algorithms of live migration without shared storage with pre-copy approach and move migration of virtual machines are reviewed from the perspective of research of migration time and unavailability of services at migrating of virtual machines. Main Results. Analytical models are proposed predicting migration time of virtual machines and unavailability of services at migrating with such technologies as live migration with pre-copy approach without shared storage and move migration. In the latest works on the time assessment of unavailability of services and migration time using live migration without shared storage experimental results are described, that are applicable to draw general conclusions about the changes of time for unavailability of services and migration time, but not to predict their values. Practical Significance. The proposed models can be used for predicting the migration time and time of unavailability of services, for example, at implementation of preventive and emergency works on the physical nodes in data centres.

  13. Grimsel Test Site: modelling radionuclide migration field experiments

    International Nuclear Information System (INIS)

    Heer, W.; Hadermann, J.

    1994-09-01

    In the migration field experiments at Nagra's Grimsel Test Site, the processes of nuclide transport through a well defined fractured shear-zone in crystalline rock are being investigated. For these experiments, model calculations have been performed to obtain indications on validity and limitation of the model applied and the data deduced under field conditions. The model consists of a hydrological part, where the dipole flow fields of the experiments are determined, and a nuclide transport part, where the flow field driven nuclide propagation through the shear-zone is calculated. In addition to the description of the model, analytical expressions are given to guide the interpretation of experimental results. From the analysis of experimental breakthrough curves for conservative uranine, weakly sorbing sodium and more stronger sorbing strontium tracers, the following main results can be derived: i) The model is able to represent the breakthrough curves of the migration field experiments to a high degree of accuracy, ii) The process of matrix diffusion is manifest through the tails of the breakthrough curves decreasing with time as t -3/2 and through the special shape of the tail ends, both confirmed by the experiments, iii) For nuclide sorbing rapidly, not too strongly, linearly, and exhibiting a reversible cation exchange process on fault gouge, the laboratory sorption coefficient can reasonably well be extrapolated to field conditions. Adequate care in selecting and preparing the rock samples is, of course, a necessary requirement. Using the parameters determined in the previous analysis, predictions are made for experiments in a smaller an faster flow field. For conservative uranine and weakly sorbing sodium, the agreement of predicted and measured breakthrough curves is good, for the more stronger sorbing strontium reasonable, confirming that the model describes the main nuclide transport processes adequately. (author) figs., tabs., 29 refs

  14. Plasticity of cell migration: a multiscale tuning model.

    NARCIS (Netherlands)

    Friedl, P.H.A.; Wolf, K. van der

    2010-01-01

    Cell migration underlies tissue formation, maintenance, and regeneration as well as pathological conditions such as cancer invasion. Structural and molecular determinants of both tissue environment and cell behavior define whether cells migrate individually (through amoeboid or mesenchymal modes) or

  15. Modeling of radionuclide migration through porous material with meshless method

    International Nuclear Information System (INIS)

    Vrankar, L.; Turk, G.; Runovc, F.

    2005-01-01

    To assess the long term safety of a radioactive waste disposal system, mathematical models are used to describe groundwater flow, chemistry and potential radionuclide migration through geological formations. A number of processes need to be considered when predicting the movement of radionuclides through the geosphere. The most important input data are obtained from field measurements, which are not completely available for all regions of interest. For example, the hydraulic conductivity as an input parameter varies from place to place. In such cases geostatistical science offers a variety of spatial estimation procedures. Methods for solving the solute transport equation can also be classified as Eulerian, Lagrangian and mixed. The numerical solution of partial differential equations (PDE) is usually obtained by finite difference methods (FDM), finite element methods (FEM), or finite volume methods (FVM). Kansa introduced the concept of solving partial differential equations using radial basis functions (RBF) for hyperbolic, parabolic and elliptic PDEs. Our goal was to present a relatively new approach to the modelling of radionuclide migration through the geosphere using radial basis function methods in Eulerian and Lagrangian coordinates. Radionuclide concentrations will also be calculated in heterogeneous and partly heterogeneous 2D porous media. We compared the meshless method with the traditional finite difference scheme. (author)

  16. Prestack exploding reflector modelling and migration for anisotropic media

    KAUST Repository

    Alkhalifah, Tariq Ali

    2014-10-09

    The double-square-root equation is commonly used to image data by downward continuation using one-way depth extrapolation methods. A two-way time extrapolation of the double-square-root-derived phase operator allows for up and downgoing wavefields but suffers from an essential singularity for horizontally travelling waves. This singularity is also associated with an anisotropic version of the double-square-root extrapolator. Perturbation theory allows us to separate the isotropic contribution, as well as the singularity, from the anisotropic contribution to the operator. As a result, the anisotropic residual operator is free from such singularities and can be applied as a stand alone operator to correct for anisotropy. We can apply the residual anisotropy operator even if the original prestack wavefield was obtained using, for example, reverse-time migration. The residual correction is also useful for anisotropic parameter estimation. Applications to synthetic data demonstrate the accuracy of the new prestack modelling and migration approach. It also proves useful in approximately imaging the Vertical Transverse Isotropic Marmousi model.

  17. Equilibrium and nonequilibrium attractors for a discrete, selection-migration model

    Science.gov (United States)

    James F. Selgrade; James H. Roberds

    2003-01-01

    This study presents a discrete-time model for the effects of selection and immigration on the demographic and genetic compositions of a population. Under biologically reasonable conditions, it is shown that the model always has an equilibrium. Although equilibria for similar models without migration must have real eigenvalues, for this selection-migration model we...

  18. Experimental and modelling studies of radionuclide migration from contaminated groundwaters

    International Nuclear Information System (INIS)

    Tompkins, J. A.; Butler, A. P.; Wheater, H. S.; Shaw, G.; Wadey, P.; Bell, J. N. B.

    1994-01-01

    Lysimeter-based studies of radionuclide uptake by winter wheat are being undertaken to investigate soil-to-plant transfer processes. A five year multi-disciplinary research project has concentrated on the upward migration of contaminants from near surface water-tables and their subsequent uptake by a winter wheat crop. A weighted transfer factor approach and a physically based modelling methodology, for the simulation and prediction of radionuclide uptake, have been developed which offer alternatives to the traditional transfer factor approach. Integrated hydrological and solute transport models are used to simulate contaminant movement and subsequent root uptake. This approach enables prediction of radionuclide transport for a wide range of soil, plant and radionuclide types. This paper presents simulated results of 22 Na plant uptake and soil activity profiles, which are verified with respect to lysimeter data. The results demonstrate that a simple modelling approach can describe the variability in radioactivity in both the harvested crop and the soil profile, without recourse to a large number of empirical parameters. The proposed modelling technique should be readily applicable to a range of scales and conditions, since it embodies an understanding of the underlying physical processes of the system. This work constitutes part of an ongoing research programme being undertaken by UK Nirex Ltd., to assess the long term safety of a deep level repository for low and intermediate level nuclear waste. (author)

  19. Mathematical modelling of sand wave migration and the interaction with pipelines

    NARCIS (Netherlands)

    Morelissen, Robin; Hulscher, Suzanne J.M.H.; Knaapen, Michiel; Nemeth, Attila; Bijker, Romke

    2003-01-01

    A new method is presented for identifying potential pipeline problems, such as hazardous exposures. This method comprises a newly developed sand wave amplitude and migration model, and an existing pipeline–seabed interaction model. The sand wave migration model is based on physical principles and

  20. Polyfluoroalkyl compounds in landfill leachates

    International Nuclear Information System (INIS)

    Busch, Jan; Ahrens, Lutz; Sturm, Renate; Ebinghaus, Ralf

    2010-01-01

    Polyfluoroalkyl compounds (PFCs) are widely used in industry and consumer products. These products could end up finally in landfills where their leachates are a potential source for PFCs into the aqueous environment. In this study, samples of untreated and treated leachate from 22 landfill sites in Germany were analysed for 43 PFCs. ΣPFC concentrations ranged from 31 to 12,819 ng/L in untreated leachate and 4-8060 ng/L in treated leachate. The dominating compounds in untreated leachate were perfluorobutanoic acid (PFBA) (mean contribution 27%) and perfluorobutane sulfonate (PFBS) (24%). The discharge of PFCs into the aqueous environment depended on the cleaning treatment systems. Membrane treatments (reverse osmosis and nanofiltrations) and activated carbon released lower concentrations of PFCs into the environment than cleaning systems using wet air oxidation or only biological treatment. The mass flows of ΣPFCs into the aqueous environment ranged between 0.08 and 956 mg/day. - The first comprehensive survey of polyfluoroalkyl compounds (PFCs) in landfill leachates.

  1. Bayesian parameter estimation for stochastic models of biological cell migration

    Science.gov (United States)

    Dieterich, Peter; Preuss, Roland

    2013-08-01

    Cell migration plays an essential role under many physiological and patho-physiological conditions. It is of major importance during embryonic development and wound healing. In contrast, it also generates negative effects during inflammation processes, the transmigration of tumors or the formation of metastases. Thus, a reliable quantification and characterization of cell paths could give insight into the dynamics of these processes. Typically stochastic models are applied where parameters are extracted by fitting models to the so-called mean square displacement of the observed cell group. We show that this approach has several disadvantages and problems. Therefore, we propose a simple procedure directly relying on the positions of the cell's trajectory and the covariance matrix of the positions. It is shown that the covariance is identical with the spatial aging correlation function for the supposed linear Gaussian models of Brownian motion with drift and fractional Brownian motion. The technique is applied and illustrated with simulated data showing a reliable parameter estimation from single cell paths.

  2. Incorporating pushing in exclusion-process models of cell migration.

    Science.gov (United States)

    Yates, Christian A; Parker, Andrew; Baker, Ruth E

    2015-05-01

    The macroscale movement behavior of a wide range of isolated migrating cells has been well characterized experimentally. Recently, attention has turned to understanding the behavior of cells in crowded environments. In such scenarios it is possible for cells to interact, inducing neighboring cells to move in order to make room for their own movements or progeny. Although the behavior of interacting cells has been modeled extensively through volume-exclusion processes, few models, thus far, have explicitly accounted for the ability of cells to actively displace each other in order to create space for themselves. In this work we consider both on- and off-lattice volume-exclusion position-jump processes in which cells are explicitly allowed to induce movements in their near neighbors in order to create space for themselves to move or proliferate into. We refer to this behavior as pushing. From these simple individual-level representations we derive continuum partial differential equations for the average occupancy of the domain. We find that, for limited amounts of pushing, comparison between the averaged individual-level simulations and the population-level model is nearly as good as in the scenario without pushing. Interestingly, we find that, in the on-lattice case, the diffusion coefficient of the population-level model is increased by pushing, whereas, for the particular off-lattice model that we investigate, the diffusion coefficient is reduced. We conclude, therefore, that it is important to consider carefully the appropriate individual-level model to use when representing complex cell-cell interactions such as pushing.

  3. The Spatio-Temporal Characteristics and Modeling Research of Inter-Provincial Migration in China

    Directory of Open Access Journals (Sweden)

    Xiaomei Fan

    2018-02-01

    Full Text Available The national census data during 1995 and 2000 and during 2005 and 2010 are selected in this paper to make an analysis of the spatio-temporal characteristics of the inter-provincial population migration in China. In addition, the general regression model, the extension regression model considering the historical dependent variable and the spatial lag model are established based on the gravity model to make the regression model on China’s inter-provincial population migration over two periods of time. The results show that: (1 the inter-provincial population migration increases rapidly in size with strong geographical proximity; (2 China’s inter-provincial population migration is still in the primary stage of the general process of population migration. In other words, the inter-provincial population emigration and immigration levels have increased greatly with the economic development; (3 Statistically, the inter-provincial population migration is negatively correlated with the level of economic development in the emigrant place and the migration distance and positively correlated with the level of economic development in the immigrant place and the population scale in the emigrant and immigrant places; and (4 The spatio-temporal factor is an important explanatory variable of population migration. The introduction of the historical dependent variable and the spatial lag factor can improve the regression effect of the gravity model greatly, and the historical variable and the spatial factor have strong explanatory power for the inter-provincial population migration.

  4. Coal pile leachate treatment

    Energy Technology Data Exchange (ETDEWEB)

    Davis, E C; Kimmitt, R R

    1982-09-01

    The steam plant located at the Oak Ridge National Laboratory was converted from oil- to coal-fired boilers. In the process, a diked, 1.6-ha coal storage yard was constructed. The purpose of this report is to describe the treatment system designed to neutralize the estimated 18,000 m/sup 3/ of acidic runoff that will be produced each year. A literature review and laboratory treatability study were conducted which identified two treatment systems that will be employed to neutralize the acidic runoff. The first, a manually operated system, will be constructed at a cost of $200,000 and will operate for an interim period of four years. This system will provide for leachate neutralization until a more automated system can be brought on-line. The second, a fully automated system, is described and will be constructed at an estimated cost of $650,000. This automated runoff treatment system will ensure that drainage from the storage yard meets current National Pollutant Discharge Elimination System Standards for pH and total suspended solids, as well as future standards, which are likely to include several metals along with selected trace elements.

  5. Migration modelling of different plutonium chemical forms through porous media

    International Nuclear Information System (INIS)

    Saltelli, A.

    1979-01-01

    Two solutions of the migration equations are described. The first relates to the transport equations for the decay chain Am 243→Pu 239→U 235. Numerical integration was performed in this case by a simulation code written in CSMP III language and plutonium is considered to be all in the same chemical form. The second case relates to the problem of Pu speciation and migration. The decay chain Pu 240→U 236 is considered and numerical integration is performed by a modified version of Bo code COLUMN. Pseudo first order reactions are supposed to act between Pu states to maintain equilibrium during the migration

  6. Use of Invasion Percolation Models To Study the Secondary Migration of Oil and Related Problems

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, G.

    1997-12-31

    This thesis studies simulations of the slow displacement of a wetting fluid by a non-wetting fluid in porous media and in a single fracture. The simulations are based on the invasion percolation model. New modified versions of the model are presented that simulate migration, fragmentation and coalescence processes of the clusters of non-wetting fluid. The resulting displacement patterns are characterized by scaling laws. In particular, simulations of the secondary migration of oil through porous homogeneous rock are discussed. Fractured rocks are extreme cases of inhomogeneous porous media. Simulations of the slow displacement of a wetting fluid by a non-wetting fluid in a single fracture using the standard invasion model are presented. There is a discussion of a scenario in which a cluster of non-wetting fluid migrates through a porous medium that was saturated with a wetting fluid. The migration is driven by continuously driven buoyancy forces. Both experiments and simulations are described. The same scenario is also studied theoretically and by simulations using a simplified percolation model of fluid migration in one dimension. The migration model in two dimensions, with constant buoyancy forces, is also discussed. Simulations of fluid migration, such as the secondary migration of oil, in two- and three-dimensional media are examined, the media having multi-affine properties rather than being homogeneous. Slow immiscible displacement processes in single fractures are studied using fractal geometries to model single fractures. 167 refs., 123 figs.

  7. Modelling gas migration in compacted bentonite: GAMBIT Club Phase 2. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Swift, B.T.; Hoch, A.R.; Rodwell, W.R. [AEA Technology (United Kingdom)

    2001-01-01

    This report describes the second phase of a programme of work to develop a computational model of gas migration through highly compacted bentonite. Experimental data that have appeared since the earlier report are reviewed for the additional information they might provide on the mechanism of gas migration in bentonite. Experiments carried out by Horseman and Harrigton (British Geological Survey) continued to provide the main data sets used in model evaluation. The earlier work (POSIVA Report 98-08) had resulted in a preliminary model of gas migration whose main features are gas invasion by microcrack propagation, and dilation of the pathways formed with increasing gas pressure. New work was carried out to further explore the capabilities of this model. In addition, a feature was added to the model to simulate gas pathway creation by water displacement rather than crack propagation. The development of a new alternative gas migration model is described. This is based on a volume-averaged representation of gas migration rather than on a description of flow in discrete pathways. Evaluation of this alternative model showed that it can produce similar agreement with experimental results to the other models examined. The implications of flow geometry, confining conditions and flow boundary conditions on gas migration behaviour in bentonite are reviewed. Proposals are made for the development of the new model into a tool for simulating gas migration through a bentonite buffer around a waste canister, and for possible enhancements to the model that might remove some of its currently perceived deficiencies. (orig.)

  8. Fly ash leachate generation and qualitative trends at Ohio test sites

    Energy Technology Data Exchange (ETDEWEB)

    Solc, J.; Foster, H.J.; Butler, R.D. [Energy & Environmental Research Center, Grand Forks, ND (United States)

    1995-12-01

    Under the sponsorship of the U.S. Department of Energy, the environmental impact and potential contamination from landfilled fly ash (coal conversion solid residues - CCSRs) have been studied at field sites in Ohio. The progressive increase of moisture content within pilot cells over depth and time facilitated intensive chemical processes and generation of highly alkaline (pH of 10 to 12) leachate. Chemistry of pore water from lysimeters and ASTM leachate from fly ash and soil cores indicate the leachate potential to migrate out of deposit and impact the pore water quality of surrounding soils. Na, SO{sub 4} and, particularly, K, Cl, pH, and EC appeared to be valuable indicator parameters for tracking potential leachate transport both within the cells and below the ash/soil interface.

  9. Mathematical modelling of migration: A suitable tool for the enforcement authorities?

    DEFF Research Database (Denmark)

    Petersen, Jens Højslev; Trier, Xenia Thorsager; Fabech, B.

    2005-01-01

    possibilities of implementing migration-modelling software as a tool in official food control and possibly in improving the own-check programmes of Danish plastic-converting plants. Food inspectors from nine regional food control centres initially attended a training course in the use of a commercial modelling...... reason was a lack of information from those in the raw material supply chain who considered their products protected by commercial confidentiality. In general, the food inspectors were in favour of using migration modelling for future control visits.......A few years ago, it became accepted that the plastics industry could use migration modelling for compliance testing. When a calculation confirms that the migration of a compound from a plastic material or article is below the specific migration limit, this is considered sufficient documentation...

  10. The Impact of a Sparse Migration Topology on the Runtime of Island Models in Dynamic Optimization

    DEFF Research Database (Denmark)

    Lissovoi, Andrei; Witt, Carsten

    2017-01-01

    similar to (Formula presented.) islands optimizing the so-called Maze fitness function (Kötzing and Molter in Proceedings of parallel problem solving from nature (PPSN XII), Springer, Berlin, pp 113–122, 2012). Previous work has shown that when a complete migration topology is used, migration must...... of logarithmic diameter as the migration topology allows the model to track the oscillating optimum through nMaze-like phases with high probability, while using any graph of diameter less than (Formula presented.) for some sufficiently small constant (Formula presented.) results in the island model losing track......Island models denote a distributed system of evolutionary algorithms which operate independently, but occasionally share their solutions with each other along the so-called migration topology. We investigate the impact of the migration topology by introducing a simplified island model with behavior...

  11. Effect of solute concentration on grain boundary migration with segregation in stainless steel and model alloys

    Science.gov (United States)

    Kanda, H.; Hashimoto, N.; Takahashi, H.

    The phenomenon of grain boundary migration due to boundary diffusion via vacancies is a well-known process for recrystallization and grain growth during annealing. This phenomenon is known as diffusion-induced grain boundary migration (DIGM) and has been recognized in various binary systems. On the other hand, grain boundary migration often occurs under irradiation. Furthermore, such radiation-induced grain boundary migration (RIGM) gives rise to solute segregation. In order to investigate the RIGM mechanism and the interaction between solutes and point defects during the migration, stainless steel and Ni-Si model alloys were electron-irradiated using a HVEM. RIGM was often observed in stainless steels during irradiation. The migration rate of boundary varied, and three stages of the migration were recognized. At lower temperatures, incubation periods up to the occurrence of the boundary migration were observed prior to first stage. These behaviors were recognized particularly for lower solute containing alloys. From the relation between the migration rates at stage I and inverse temperatures, activation energies for the boundary migration were estimated. In comparison to the activation energy without irradiation, these values were very low. This suggests that the RIGM is caused by the flow of mixed-dumbbells toward the grain boundary. The interaction between solute and point defects and the effective defect concentration generating segregation will be discussed.

  12. LANDFILL LEACHATES PRETREATMENT BY OZONATION

    Directory of Open Access Journals (Sweden)

    Jacek Leszczyński

    2016-06-01

    Full Text Available In this paper, the application of ozonation processes for stabilized landfill leachate treatment was investigated. The leachate came from a municipal sanitary landfill located nearby Bielsk Podlaski. The average values of its main parameters were: pH 8.23; COD 870 mgO2/dm3; BOD 90 mgO2/dm3; NH4+ 136.2 mgN/dm3; UV254 absorbance 0.312 and turbidity 14 NTU. The ozone dosages used were in the range of 115.5 to 808.5 mgO3/dm3 of the leachate. The maximum COD, color and UV254 absorbance removal wa.5 mgO3/dm3. After oxidation, the ratio of BOD/COD was increased from 0.1 up to 0.23.

  13. Leachate characterization and assessment of surface and ...

    African Journals Online (AJOL)

    The environment can be impacted negatively by leachates from these dumpsites if not properly managed. This study aimed at assessing the characteristics of municipal solid waste leachate and its contamination potential on surface and groundwater. Leachate, groundwater and surface water samples were collected from ...

  14. Uranium chemistry in stack solutions and leachates of phosphogypsum disposed at a coastal area in Cyprus.

    Science.gov (United States)

    Lysandrou, M; Pashalidis, I

    2008-02-01

    The effect of the matrix composition (main constituents) on the concentration and chemical behavior of uranium in phosphogypsum stack solutions and leachates has been investigated. Solid and aqueous samples were taken from three different sub-areas of a phosphogypsum stack at a coastal area in Vasilikos (Cyprus). The sub-areas are characterized whether by their acidity (e.g. "aged" and "non-aged" phosphogypsum) or by their salt content, originating from pulping water during wet stacking or (after deposition) from the adjacent sea. Measurements in stack solutions and leachates showed that phosphogypsum characteristics affect both, the concentration and the chemical behavior of uranium in solution. Uranium concentration in solutions of increased salinity is up to three orders of magnitude higher than in solutions of low salinity and this is attributed to the effect of ionic strength on the solubility of phosphogypsum. Modelling showed that uranium in stack solutions is predominantly present in the form of uranium(VI) phosphate complexes (e.g. UO(2)(H(2)PO(4))(2), UO(2)HPO(4)), whereas in leachates uranium(VI) fluoro complexes (e.g. UO(2)F(2), UO(2)F(3)(-)) are predominant in solution. The latter indicates that elution of uranium from phosphogypsum takes places most probably in the form of fluoro complexes. Both, effective elution by saline water and direct migration of uranium to the sea, where it forms very stable uranium(VI) carbonato complexes, indicate that the adjacent sea will be the final receptor of uranium released from Vasilikos phosphogypsum.

  15. Rural-urban migration: policy simulations in a dual economy model of Bangladesh.

    Science.gov (United States)

    Ahmed, S

    1986-03-01

    The process of rural-urban migration in Bangladesh is analyzed using a dual economy model. The focus is on the period 1976-1985. The main purpose of the paper is to examine alternative policies designed to reduce the level of such migration without adversely affecting the country's economy.

  16. Predictive modelling of migration from packaging materials into food products for regulatory purposes

    NARCIS (Netherlands)

    Helmroth, E.; Rijk, R.; Dekker, M.; Jongen, W.

    2002-01-01

    Migration of low-molecular weight compounds is one of the most important problems of packaging plastics and other plastics intended to come into contact with food products. Since migration experiments are time consuming and expensive, predictive modelling has been introduced as a promising

  17. Predictive model to describe water migration in cellular solid foods during storage

    NARCIS (Netherlands)

    Voogt, J.A.; Hirte, A.; Meinders, M.B.J.

    2011-01-01

    BACKGROUND: Water migration in cellular solid foods during storage causes loss of crispness. To improve crispness retention, physical understanding of this process is needed. Mathematical models are suitable tools to gain this physical knowledge. RESULTS: Water migration in cellular solid foods

  18. Certified reference materials for food packaging specific migration tests: development, validation and modelling

    NARCIS (Netherlands)

    Stoffers, N.H.

    2005-01-01

    Keywords:certified reference materials; diffusion; food contact materials; food packaging; laurolactam; migration modelling; nylon; specific migration This thesis compiles several research topics

  19. Uniqueness of polymorphism for a discrete, selection-migration model with genetic dominance

    Science.gov (United States)

    James F. Selgrade; James H. Roberds

    2009-01-01

    The migration into a natural population of a controlled population, e.g., a transgenic population, is studied using a one island selection-migration model. A 2-dimensional system of nonlinear difference equations describes changes in allele frequency and population size between generations. Biologically reasonable conditions are obtained which guarantee the existence...

  20. Predictive model to describe water migration in cellular solid foods during storage

    NARCIS (Netherlands)

    Voogt, J.A.; Hirte, A.; Meinders, M.B.J.

    2011-01-01

    Background: Water migration in cellular solid foods during storage causes loss of crispness. To improve crispness retention, physical understanding of this process is needed. Mathematical models are suitable tools to gain this physical knowledge. Results: Water migration in cellular solid foods

  1. Modeling of the Migration of Glycerol Monoester Plasticizers in Highly Plasticized Poly(vinyl chloride)

    DEFF Research Database (Denmark)

    Lundsgaard, Rasmus; Kontogeorgis, Georgios; Kristiansen, Jørgen K.

    2009-01-01

    soybean oil (ESBO) with regard to their migration from three different types of poly(vinyl chloride) into isooctane at 20, 40, and 60 degrees C. Diffusion coefficients derived from the experimental migration data were evaluated against diffusion coefficients estimated from a model based solely...

  2. Modern Gravity Models of Internal Migration. The Case of Romania

    Directory of Open Access Journals (Sweden)

    Daniela BUNEA

    2012-04-01

    Full Text Available Internal migration, although less investigated than international migration, is a key mechanism for adjustment to regional economic shocks, especially when other tools prove useless. But this process has very complex factors of determination which can be economic, social, demographic, environmental, etc. Based on previous international studies, in the case of Romania the robust variables proved to be the population size, the per capita gross domestic product, the road density, an amenity index and the crime rate from a static perspective, and the previous migration, the population size and the amenity index from a dynamic perspective. The techniques I have employed in making this study are the Least Square Dummy Variables (LSDV, or the fixed effects method and the Generalized Method of Moments (GMM, or the dynamic method both applied to panel data.

  3. ORBITAL MIGRATION OF LOW-MASS PLANETS IN EVOLUTIONARY RADIATIVE MODELS: AVOIDING CATASTROPHIC INFALL

    International Nuclear Information System (INIS)

    Lyra, Wladimir; Mac Low, Mordecai-Mark; Paardekooper, Sijme-Jan

    2010-01-01

    Outward migration of low-mass planets has recently been shown to be a possibility in non-barotropic disks. We examine the consequences of this result in evolutionary models of protoplanetary disks. Planet migration occurs toward equilibrium radii with zero torque. These radii themselves migrate inwards because of viscous accretion and photoevaporation. We show that as the surface density and temperature fall the planet orbital migration and disk depletion timescales eventually become comparable, with the precise timing depending on the mass of the planet. When this occurs, the planet decouples from the equilibrium radius. At this time, however, the gas surface density is already too low to drive substantial further migration. A higher mass planet, of 10 M + , can open a gap during the late evolution of the disk, and stops migrating. Low-mass planets, with 1 or 0.1 M + , released beyond 1 AU in our models avoid migrating into the star. Our results provide support for the reduced migration rates adopted in recent planet population synthesis models.

  4. Floating Node Method and Virtual Crack Closure Technique for Modeling Matrix Cracking-Delamination Migration

    Science.gov (United States)

    DeCarvalho, Nelson V.; Chen, B. Y.; Pinho, Silvestre T.; Baiz, P. M.; Ratcliffe, James G.; Tay, T. E.

    2013-01-01

    A novel approach is proposed for high-fidelity modeling of progressive damage and failure in composite materials that combines the Floating Node Method (FNM) and the Virtual Crack Closure Technique (VCCT) to represent multiple interacting failure mechanisms in a mesh-independent fashion. In this study, the approach is applied to the modeling of delamination migration in cross-ply tape laminates. Delamination, matrix cracking, and migration are all modeled using fracture mechanics based failure and migration criteria. The methodology proposed shows very good qualitative and quantitative agreement with experiments.

  5. Modelling migration in multilayer systems by a finite difference method: the spherical symmetry case

    International Nuclear Information System (INIS)

    Hojbota, C I; Toşa, V; Mercea, P V

    2013-01-01

    We present a numerical model based on finite differences to solve the problem of chemical impurity migration within a multilayer spherical system. Migration here means diffusion of chemical species in conditions of concentration partitioning at layer interfaces due to different solubilities of the migrant in different layers. We detail here the numerical model and discuss the results of its implementation. To validate the method we compare it with cases where an analytic solution exists. We also present an application of our model to a practical problem in which we compute the migration of caprolactam from the packaging multilayer foil into the food

  6. Comparing habitat suitability and connectivity modeling methods for conserving pronghorn migrations.

    Directory of Open Access Journals (Sweden)

    Erin E Poor

    Full Text Available Terrestrial long-distance migrations are declining globally: in North America, nearly 75% have been lost. Yet there has been limited research comparing habitat suitability and connectivity models to identify migration corridors across increasingly fragmented landscapes. Here we use pronghorn (Antilocapra americana migrations in prairie habitat to compare two types of models that identify habitat suitability: maximum entropy (Maxent and expert-based (Analytic Hierarchy Process. We used distance to wells, distance to water, NDVI, land cover, distance to roads, terrain shape and fence presence to parameterize the models. We then used the output of these models as cost surfaces to compare two common connectivity models, least-cost modeling (LCM and circuit theory. Using pronghorn movement data from spring and fall migrations, we identified potential migration corridors by combining each habitat suitability model with each connectivity model. The best performing model combination was Maxent with LCM corridors across both seasons. Maxent out-performed expert-based habitat suitability models for both spring and fall migrations. However, expert-based corridors can perform relatively well and are a cost-effective alternative if species location data are unavailable. Corridors created using LCM out-performed circuit theory, as measured by the number of pronghorn GPS locations present within the corridors. We suggest the use of a tiered approach using different corridor widths for prioritizing conservation and mitigation actions, such as fence removal or conservation easements.

  7. Comparing habitat suitability and connectivity modeling methods for conserving pronghorn migrations.

    Science.gov (United States)

    Poor, Erin E; Loucks, Colby; Jakes, Andrew; Urban, Dean L

    2012-01-01

    Terrestrial long-distance migrations are declining globally: in North America, nearly 75% have been lost. Yet there has been limited research comparing habitat suitability and connectivity models to identify migration corridors across increasingly fragmented landscapes. Here we use pronghorn (Antilocapra americana) migrations in prairie habitat to compare two types of models that identify habitat suitability: maximum entropy (Maxent) and expert-based (Analytic Hierarchy Process). We used distance to wells, distance to water, NDVI, land cover, distance to roads, terrain shape and fence presence to parameterize the models. We then used the output of these models as cost surfaces to compare two common connectivity models, least-cost modeling (LCM) and circuit theory. Using pronghorn movement data from spring and fall migrations, we identified potential migration corridors by combining each habitat suitability model with each connectivity model. The best performing model combination was Maxent with LCM corridors across both seasons. Maxent out-performed expert-based habitat suitability models for both spring and fall migrations. However, expert-based corridors can perform relatively well and are a cost-effective alternative if species location data are unavailable. Corridors created using LCM out-performed circuit theory, as measured by the number of pronghorn GPS locations present within the corridors. We suggest the use of a tiered approach using different corridor widths for prioritizing conservation and mitigation actions, such as fence removal or conservation easements.

  8. Modeling the migration of radioactive contaminants in groundwater of in situ leaching uranium mine

    International Nuclear Information System (INIS)

    Li Chunguang; Tai Kaixuan

    2011-01-01

    The radioactive contamination of groundwater from in situ leaching (ISL) of uranium mining is a widespread environmental problem. This paper analyzed the monitor results of groundwater contaminations for a in situ leaching uranium mine. A dynamic model of contaminants transport in groundwater in ISL well field was established. The processes and mechanisms of contaminant transport in groundwater were simulated numerically for a ISL well field. A small quantity of U and SO 4 2- migrate to outside of well field during ISL production stage. But the migration velocity and distance of contaminations is small, and the concentration is low. Contaminants migrate as anomalistic tooth-shape. The migration trend of U and SO 4 2- is consistent. Numerical modeling can provide an effective approach to analyse the transport mechanism, and forecast and control the migration of contaminants in groundwater in ISL well field. (authors)

  9. Modelling the adaptive behaviour of migrating white storks

    NARCIS (Netherlands)

    Shamoun-Baranes, J.; van Loon, E.E.; Bouten, W.

    2006-01-01

    White storks (Ciconia ciconia) are soaring migrants whose western Palearctic populations use several migration routes, concentrating mainly over Gibraltar and Israel to cross between their Palearctic breeding grounds and wintering grounds in Africa. A wealth of data has been collected during the

  10. Treating leachate by Fenton oxidation

    Directory of Open Access Journals (Sweden)

    Roger Iván Méndez Novelo

    2010-01-01

    Full Text Available Leachates are formed from liquids, mainly rainwater, percolating through solid wastes during stabilisation. Their composition is variable and highly toxic; leachate treatment is therefore a complex task. Leachates represent a high risk to health due to the Yucatan Peninsula’s highly permeable soil. The results are presented from applying the Fenton process to treating leachate from the sanitary Merida landfill, Yucatan, Mexico. The Fenton process consists of treating the contaminant load with an H2O2 and FeSO4 combination in acidic conditions. Optimal reaction time, pH value, Fenton reagent dose, post treatment coagulation – flocculation doses and increased biodegradability index were all determined. Optimal oxidation conditions and doses were 202+ minute contact time, 4 pH, 600 mg/L H2O2 concentration and 1,000 mg/L Fe. Average organic matter removal rate, measured as CODS and TOC, were 78% and 87% respectively. The biodegradability index increased from 0.07 to 0.11 during the Fenton process and up to 0.13 when the Fenton process was followed by coagulation-flocculation.

  11. Modelling gas migration in compacted bentonite: gambit club phase 3. Final report

    International Nuclear Information System (INIS)

    Hoch, A.R.; Cliffe, K.A.; Swift, B.T.; Rodwell, W.R.

    2004-04-01

    This report describes the third phase of a programme of work to develop a computational model of gas migration through highly compacted water-saturated bentonite. One difficulty with this endeavour is the definitive determination of the mechanism of the gas migration from the available experimental data. The report contains a brief review of the experimental data and their interpretation. The model development work reported involves the investigation of two ways of enhancing a model proposed in the previous phase of the programme. This model was based on the concept that gas migration pathways were created by consolidating the clay fabric by application of gas pressure to create porosity through which the gas could flow. The two developments of this model that are separately explored in this work are: (a) The incorporation of a proper treatment of the stress-strain behaviour of the clay in (b) response to gas migration. The previous model had only considered stress effects through simple volume changes to the clay fabric. The inclusion of a dual-porosity feature into the model in an attempt to address the role that the clay fabric might play in gas migration through the clay, in particular the role that pre-existing interstack voids might have in gas migration. The consideration of hysteresis effects was also included in this study. As in previous GAMBIT Club work, the models are tested against the results of laboratory experiments. (orig.)

  12. COD fractions of leachate from aerobic and anaerobic pilot scale landfill reactors

    International Nuclear Information System (INIS)

    Bilgili, M. Sinan; Demir, Ahmet; Akkaya, Ebru; Ozkaya, Bestamin

    2008-01-01

    One of the most important problems with designing and maintaining a landfill is managing leachate that generated when water passes through the waste. In this study, leachate samples taken from aerobic and anaerobic landfill reactors operated with and without leachate recirculation are investigated in terms of biodegradable and non-biodegradable fractions of COD. The operation time is 600 days for anaerobic reactors and 250 days for aerobic reactors. Results of this study show that while the values of soluble inert COD to total COD in the leachate of aerobic landfill with leachate recirculation and aerobic dry reactors are determined around 40%, this rate was found around 30% in the leachate of anaerobic landfill with leachate recirculation and traditional landfill reactors. The reason for this difference is that the aerobic reactors generated much more microbial products. Because of this condition, it can be concluded that total inert COD/total COD ratios of the aerobic reactors were 60%, whereas those of anaerobic reactors were 50%. This study is important for modeling, design, and operation of landfill leachate treatment systems and determination of discharge limits

  13. Evaluation of the 152Eu migration experiments using a combined reaction model

    International Nuclear Information System (INIS)

    Maloszewski, P.; Klotz, D.

    2001-01-01

    A transport and interaction model is applied to 152 Eu migration experiments which takes account simultaneously of fast (so-called local equilibrium) and slow (kinetic) exchange processes of the migrant between the aqueous and the solid phase [de

  14. A mathematical model, and code HADES, for migration of radionuclides from a shallow repository

    International Nuclear Information System (INIS)

    Fraser, J.L.; Jarvis, R.G.

    1985-06-01

    The mathematical model is one-dimensional, to describe migration of radionuclides, by diffusion and advection, through several consecutive layers that can represent vault materials and surrounding ground. The solutions are evaluated by a computer code HADES

  15. Emergence of long distance bird migrations: a new model integrating global climate changes

    Science.gov (United States)

    Louchart, Antoine

    2008-12-01

    During modern birds history, climatic and environmental conditions have evolved on wide scales. In a continuously changing world, landbirds annual migrations emerged and developed. However, models accounting for the origins of these avian migrations were formulated with static ecogeographic perspectives. Here I reviewed Cenozoic paleoclimatic and paleontological data relative to the palearctic paleotropical long distance (LD) migration system. This led to propose a new model for the origin of LD migrations, the ‘shifting home’ model (SHM). It is based on a dynamic perspective of climate evolution and may apply to the origins of most modern migrations. Non-migrant tropical African bird taxa were present at European latitudes during most of the Cenozoic. Their distribution limits shifted progressively toward modern tropical latitudes during periods of global cooling and increasing seasonality. In parallel, decreasing winter temperatures in the western Palearctic drove shifts of population winter ranges toward the equator. I propose that this induced the emergence of most short distance migrations, and in turn LD migrations. This model reconciliates ecologically tropical ancestry of most LD migrants with predominant winter range shifts, in accordance with requirements for heritable homing. In addition, it is more parsimonious than other non-exclusive models. Greater intrinsic plasticity of winter ranges implied by the SHM is supported by recently observed impacts of the present global warming on migrating birds. This may induce particular threats to some LD migrants. The ancestral, breeding homes of LD migrants were not ‘northern’ or ‘southern’ but shifted across high and middle latitudes while migrations emerged through winter range shifts themselves.

  16. Evaluating the impacts of migration in the biofilm anode using the model PCBIOFILM

    International Nuclear Information System (INIS)

    Marcus, Andrew K.; Torres, Cesar I.; Rittmann, Bruce E.

    2010-01-01

    Microbial electrochemical cells depend on the reaction by anode-respiring bacteria (ARB). The ARB reaction generates multiple e - and H + , which take diverging paths, creating a charge imbalance. An electric field must migrate ions to restore electrical neutrality. Here, the model proton condition in bioflim (PCBIOFILM) expands for evaluating the impact of migration on the biofilm anode: the expansion makes the proton condition (PC) work in tandem with the electrical-neutrality condition, which is a novel methodological advancement. The analysis with PCBIOFILM examines relevant scenarios of phosphate- and carbonate-buffered biofilm anodes using established parameters. The analysis demonstrates how: (1) the proton condition (PC) maintains electrical neutrality by achieving charge balance; (2) migration influences the biofilm anode more than non-ARB biofilms; (3) migration increases the overall current density, but by less than 15 percent; and (4) PCBIOFILM without migration accurately captures large-scale trends in biofilm anodes.

  17. Artificial neural network models' application for radioactive substances' migration forecasting in soil

    International Nuclear Information System (INIS)

    Kovalenko, V.I.; Khil'ko, O.S.; Kundas, S.P.

    2009-01-01

    The work is indicated to the use of artificial neural network (ANN) models in program complex SPS for radioactive substances' migration forecasting in soil. For the problem solution two ANN models are used. One of them forecasts radioactive substances' migration, another carries out forecasting of physical and chemical soil properties. Program complex SPS allows to achieve a low error of forecasting (no more than 5 %) and high training speed. (authors)

  18. Study on experimental models to analyze radionuclide migration behaviors through porous geologic media

    International Nuclear Information System (INIS)

    Tanaka, Tadao; Mukai, Masayuki

    2012-08-01

    The migration phenomenon of radionuclide through geological media such as soils and porous rocks, which is important in underground disposal of radioactive wastes, can be described by the advection-dispersion of groundwater and the interactions of radionuclide with geological media. On the other hand, to understand the migration phenomenon, actual migration data are experimentally acquired by a batch test, a column test and field trial. In the present study, experimental models about the interactions of radionuclide between the solid phase and the liquid phase were discussed systematically to interpret the migration data acquired by the various techniques and conditions. Equilibrium, reversibility, linearity, mechanism and chemistry in the interactions were considered in discussion of the experimental models. A calculation program, which can analyze migration data obtained under various conditions by applying the selected 9 types of experimental models, was maintained. The calculation program makes it be able to predict the migration behavior of radionuclide under various conditions and to decide the important parameter by a fitting analysis of the migration data. (author)

  19. Can lagrangian models reproduce the migration time of European eel obtained from otolith analysis?

    Science.gov (United States)

    Rodríguez-Díaz, L.; Gómez-Gesteira, M.

    2017-12-01

    European eel can be found at the Bay of Biscay after a long migration across the Atlantic. The duration of migration, which takes place at larval stage, is of primary importance to understand eel ecology and, hence, its survival. This duration is still a controversial matter since it can range from 7 months to > 4 years depending on the method to estimate duration. The minimum migration duration estimated from our lagrangian model is similar to the duration obtained from the microstructure of eel otoliths, which is typically on the order of 7-9 months. The lagrangian model showed to be sensitive to different conditions like spatial and time resolution, release depth, release area and initial distribution. In general, migration showed to be faster when decreasing the depth and increasing the resolution of the model. In average, the fastest migration was obtained when only advective horizontal movement was considered. However, faster migration was even obtained in some cases when locally oriented random migration was taken into account.

  20. Application of Deuterium and Oxygen-18 to Trace Leachate Movement in Bantar Gebang Sanitary Landfill

    International Nuclear Information System (INIS)

    Pujiindiyati, E.R.

    2011-01-01

    Bantar Gebang landfill was constructed in 1986 with total area of 108 ha and approximately 6000 ton/day solid waste is disposed to this landfill. Mostly, the people living surrounding landfill get afraid of impact of the hazardous chemicals produced by waste disposal to their health. The purpose of this investigation was to study the migration of leachate to Cibitung River water and shallow groundwaters near to the river. It is possible to be done because chemical contents and isotopic characteristics of municipal landfill leachate are unique, relative to aqueous media in the most natural environments. Laser absorption method developed by the LGR (Los Gatos Research) was used to measure absolute abundances of 2 HHO, HH 18 O and HHO in a number of water samples. In-situ measurements were also conducted as an additional parameter besides their isotopes. The δ 2 H of the H 2 O in landfill leachate was significantly enriched, with values of - 22.6 0/00 to + 4.3 0/00. This deuterium enrichment was undoubtedly due to the extensive production of microbial methane within the limited reservoir of the landfill. However, the enriched deuterium value in leachate was not detected in the river which still had depleted values. It was probably caused by the amount of natural water in the river was comparatively large, with respect to limited leachate discarded to the river. The electrical conductivity of the leachate was higher (3200 to 7600 μS) and the decreasing values were still monitored in the river to approximately 12 km after streaming the landfills. The effect of the high electrical conductivity and enriched deuterium of leachate was not clearly indicated in the groundwater samples which still represented the local precipitation recharge, except a monitoring well located in Bantar Gebang landfill area which has an indication of leachate contamination. (author)

  1. Application of Deuterium and Oxygen-18 to Trace Leachate Movement in Bantar Gebang Sanitary Landfill

    Directory of Open Access Journals (Sweden)

    E.R. Pujiindiyati

    2011-08-01

    Full Text Available Bantar Gebang landfill was constructed in 1986 with total area of 108 ha and approximately 6000 ton/day solid waste is disposed to this landfill. Mostly, the people living surrounding landfill get afraid of impact of the hazardous chemicals produced by waste disposal to their health. The purpose of this investigation was to study the migration of leachate to Cibitung River water and shallow groundwaters near to the river. It is possible to be done because chemical contents and isotopic characteristics of municipal landfill leachate are unique, relative to aqueous media in the most natural environments. Laser absorption method developed by the LGR (Los Gatos Research was used to measure absolute abundances of 2HHO, HH18O and HHO in a number of water samples. In-situ measurements were also conducted as an additional parameter besides their isotopes. The δ2H of the H2O in landfill leachate was significantly enriched, with values of - 22.6 ‰ to + 4.3 ‰. This deuterium enrichment was undoubtedly due to the extensive production of microbial methane within the limited reservoir of the landfill. However, the enriched deuterium value in leachate was not detected in the river which still had depleted values. It was probably caused by the amount of natural water in the river was comparatively large, with respect to limited leachate discarded to the river.The electrical conductivity of the leachate was higher (3200 to 7600 S and the decreasing values were still monitored in the river to approximately 12 km after streaming the landfills. The effect of the high electrical conductivity and enriched deuterium of leachate was not clearly indicated in the groundwater samples which still represented the local precipitation recharge, except a monitoring well located in Bantar Gebang landfill area which has an indication of leachate contamination.

  2. A Virtual Machine Migration Strategy Based on Time Series Workload Prediction Using Cloud Model

    Directory of Open Access Journals (Sweden)

    Yanbing Liu

    2014-01-01

    Full Text Available Aimed at resolving the issues of the imbalance of resources and workloads at data centers and the overhead together with the high cost of virtual machine (VM migrations, this paper proposes a new VM migration strategy which is based on the cloud model time series workload prediction algorithm. By setting the upper and lower workload bounds for host machines, forecasting the tendency of their subsequent workloads by creating a workload time series using the cloud model, and stipulating a general VM migration criterion workload-aware migration (WAM, the proposed strategy selects a source host machine, a destination host machine, and a VM on the source host machine carrying out the task of the VM migration. Experimental results and analyses show, through comparison with other peer research works, that the proposed method can effectively avoid VM migrations caused by momentary peak workload values, significantly lower the number of VM migrations, and dynamically reach and maintain a resource and workload balance for virtual machines promoting an improved utilization of resources in the entire data center.

  3. Understanding Migration as an Adaptation in Deltas Using a Bayesian Network Model

    Science.gov (United States)

    Lázár, A. N.; Adams, H.; de Campos, R. S.; Mortreux, C. C.; Clarke, D.; Nicholls, R. J.; Amisigo, B. A.

    2016-12-01

    Deltas are hotspots of high population density, fertile lands and dramatic environmental and anthropogenic pressures and changes. Amongst other environmental factors, sea level rise, soil salinization, water shortages and erosion threaten people's livelihoods and wellbeing. As a result, there is a growing concern that significant environmental change induced migration might occur from these areas. Migration, however, is already happening for economic, education and other reasons (e.g. livelihood change, marriage, planned relocation, etc.). Migration hence has multiple, interlinked drivers and depending on the perspective, can be considered as a positive or negative phenomenon. The DECCMA project (Deltas, Vulnerability & Climate Change: Migration & Adaptation) studies migration as part of a suite of adaptation options available to the coastal populations in the Ganges delta in Bangladesh, the Mahanadi delta in India and the Volta delta in Ghana. It aims to develop a holistic framework of analysis that assesses the impact of climate and environmental change on the migration patterns of these areas. This assessment framework will couple environmental, socio-economics and governance dimensions in an attempt to synthesise drivers and barriers and allow testing of plausible future scenarios. One of the integrative methods of DECCMA is a Bayesian Belief Network (BBN) model describing the decision-making of a coastal household. BBN models are built on qualitative and quantitative observations/expert knowledge and describe the probability of different events/responses etc. BBN models are especially useful to capture uncertainties of large systems and engaging with stakeholders. The DECCMA BBN model is based on household survey results from delta migrant sending areas. This presentation will describe model elements (livelihood sensitivity to climate change, local and national adaptation options, household characteristics/attitude, social networks, household decision) and

  4. On a Corporate Bond Pricing Model with Credit Rating Migration Risksand Stochastic Interest Rate

    Directory of Open Access Journals (Sweden)

    Jin Liang

    2017-10-01

    Full Text Available In this paper we study a corporate bond-pricing model with credit rating migration and astochastic interest rate. The volatility of bond price in the model strongly depends on potential creditrating migration and stochastic change of the interest rate. This new model improves the previousexisting models in which the interest rate is considered to be a constant. The existence, uniquenessand regularity of the solution for the model are established. Moreover, some properties includingthe smoothness of the free boundary are obtained. Furthermore, some numerical computations arepresented to illustrate the theoretical results.

  5. Testing the effects of the numerical implementation of water migration on models of subduction dynamics

    Science.gov (United States)

    Quinquis, M. E. T.; Buiter, S. J. H.

    2013-10-01

    Subduction of oceanic lithosphere brings water into Earth's upper mantle. Previous numerical studies have shown how slab dehydration and mantle hydration can impact the dynamics of a subduction system by allowing a more vigorous mantle flow and promoting localisation of deformation in lithosphere and mantle. The depths at which dehydration reactions occur in the hydrated portions of the slab are well constrained in these models by thermodynamic calculations. However, the mechanism by which free water migrates in the mantle is incompletely known. Therefore, models use different numerical schemes to model the migration of free water. We aim to show the influence of the numerical scheme of free water migration on the dynamics of the upper mantle and more specifically the mantle wedge. We investigate the following three migration schemes with a finite-element model: (1) element-wise vertical migration of free water, occurring independent of the material flow; (2) an imposed vertical free water velocity; and (3) a Darcy velocity, where the free water velocity is calculated as a function of the pressure gradient between water and the surrounding rocks. In addition, the material flow field also moves the free water in the imposed vertical velocity and Darcy schemes. We first test the influence of the water migration scheme using a simple Stokes flow model that simulates the sinking of a cold hydrated cylinder into a hot dry mantle. We find that the free water migration scheme has only a limited impact on the water distribution after 1 Myr in these models. We next investigate slab dehydration and mantle hydration with a thermomechanical subduction model that includes brittle behaviour and viscous water-dependent creep flow laws. Our models show how the bound water distribution is not greatly influenced by the water migration scheme whereas the free water distribution is. We find that a water-dependent creep flow law results in a broader area of hydration in the mantle

  6. Lime treatment of stabilized leachates

    International Nuclear Information System (INIS)

    Renou, S.; Poulain, S.; Givaudan, J. G.; Sahut, C.; Moulin, P.

    2009-01-01

    Reverse Osmosis is the most widely used method for treating municipal solid waste landfill leachates, since it produces a permeate in compliance with reject requirements. However, the efficiency of this process at the industrial scale is limited mainly because of membrane fouling and the high osmotic pressures involved. Although lime precipitation is traditionally used to eliminate the temporary hardness of water by de-carbonation, it has also been shown to be highly efficient in removing humic substances which are known to have strong fouling potential towards membranes. Our objective is to study the lime/leachate physico-chemistry, in order to determine the potential of the lime precipitation as pre-treatment for reverse osmosis. The results show that the lime treatment makes it possible (i) to act efficiently on the inorganic fraction of leachates through a de-carbonation mechanism which entails massive precipitation of the carbonates under the form of CaCO 3 , (ii) to eliminate by co-precipitation the high Molecular Weight (MW) organic macromolecules (≥ 50, 000 g.mol -1 ) such as humic acids, and (iii) to generate a stable residue that can be easily stored at a landfill. The reverse osmosis step will be facilitated through significant reduction of the osmotic pressures and prevention of membrane fouling. (authors)

  7. Efficient Modeling and Migration in Anisotropic Media Based on Prestack Exploding Reflector Model and Effective Anisotropy

    KAUST Repository

    Wang, Hui

    2014-05-01

    This thesis addresses the efficiency improvement of seismic wave modeling and migration in anisotropic media. This improvement becomes crucial in practice as the process of imaging complex geological structures of the Earth\\'s subsurface requires modeling and migration as building blocks. The challenge comes from two aspects. First, the underlying governing equations for seismic wave propagation in anisotropic media are far more complicated than that in isotropic media which demand higher computational costs to solve. Second, the usage of whole prestack seismic data still remains a burden considering its storage volume and the existing wave equation solvers. In this thesis, I develop two approaches to tackle the challenges. In the first part, I adopt the concept of prestack exploding reflector model to handle the whole prestack data and bridge the data space directly to image space in a single kernel. I formulate the extrapolation operator in a two-way fashion to remove he restriction on directions that waves propagate. I also develop a generic method for phase velocity evaluation within anisotropic media used in this extrapolation kernel. The proposed method provides a tool for generating prestack images without wavefield cross correlations. In the second part of this thesis, I approximate the anisotropic models using effective isotropic models. The wave phenomena in these effective models match that in anisotropic models both kinematically and dynamically. I obtain the effective models through equating eikonal equations and transport equations of anisotropic and isotropic models, thereby in the high frequency asymptotic approximation sense. The wavefields extrapolation costs are thus reduced using isotropic wave equation solvers while the anisotropic effects are maintained through this approach. I benchmark the two proposed methods using synthetic datasets. Tests on anisotropic Marmousi model and anisotropic BP2007 model demonstrate the applicability of my

  8. Ultrasound assisted biogas production from landfill leachate

    International Nuclear Information System (INIS)

    Oz, Nilgün Ayman; Yarimtepe, Canan Can

    2014-01-01

    Highlights: • Effect of low frequency ultrasound pretreatment on leachate was investigated. • Three different ultrasound energy inputs (200, 400 and 600 W/l) was applied. • Low-frequency ultrasound treatment increased soluble COD in landfill leachate. • Application of ultrasound to leachate increased biogas production about 40%. • Application of ultrasound to leachate increased total methane production rate about 20%. - Abstract: The aim of this study is to increase biogas production and methane yield from landfill leachate in anaerobic batch reactors by using low frequency ultrasound as a pretreatment step. In the first part of the study, optimum conditions for solubilization of organic matter in leachate samples were investigated using various sonication durations at an ultrasound frequency of 20 kHz. The level of organic matter solubilization during ultrasonic pretreatment experiments was determined by calculating the ratio of soluble chemical oxygen demand (sCOD) to total chemical oxygen demand (tCOD). The sCOD/tCOD ratio was increased from 47% in raw leachate to 63% after 45 min sonication at 600 W/l. Non-parametric Friedman’s test indicated that ultrasonic pretreatment has a significant effect on sCOD parameter for leachate (p < 0.05). In the second part of the study, anaerobic batch reactors were operated for both ultrasonically pretreated and untreated landfill leachate samples in order to assess the effect of sonication on biogas and methane production rate. In anaerobic batch reactor feed with ultrasonically pretreated leachate, 40% more biogas was obtained compared to the control reactor. For statistical analysis, Mann–Whitney U test was performed to compare biogas and methane production rates for raw and pretreated leachate samples and it has been found that ultrasonic pretreatment significantly enhanced biogas and methane production rates from leachate (p < 0.05) in anaerobic batch reactors. The overall results showed that low frequency

  9. Ultrasound assisted biogas production from landfill leachate

    Energy Technology Data Exchange (ETDEWEB)

    Oz, Nilgün Ayman, E-mail: nilgunayman@comu.edu.tr; Yarimtepe, Canan Can

    2014-07-15

    Highlights: • Effect of low frequency ultrasound pretreatment on leachate was investigated. • Three different ultrasound energy inputs (200, 400 and 600 W/l) was applied. • Low-frequency ultrasound treatment increased soluble COD in landfill leachate. • Application of ultrasound to leachate increased biogas production about 40%. • Application of ultrasound to leachate increased total methane production rate about 20%. - Abstract: The aim of this study is to increase biogas production and methane yield from landfill leachate in anaerobic batch reactors by using low frequency ultrasound as a pretreatment step. In the first part of the study, optimum conditions for solubilization of organic matter in leachate samples were investigated using various sonication durations at an ultrasound frequency of 20 kHz. The level of organic matter solubilization during ultrasonic pretreatment experiments was determined by calculating the ratio of soluble chemical oxygen demand (sCOD) to total chemical oxygen demand (tCOD). The sCOD/tCOD ratio was increased from 47% in raw leachate to 63% after 45 min sonication at 600 W/l. Non-parametric Friedman’s test indicated that ultrasonic pretreatment has a significant effect on sCOD parameter for leachate (p < 0.05). In the second part of the study, anaerobic batch reactors were operated for both ultrasonically pretreated and untreated landfill leachate samples in order to assess the effect of sonication on biogas and methane production rate. In anaerobic batch reactor feed with ultrasonically pretreated leachate, 40% more biogas was obtained compared to the control reactor. For statistical analysis, Mann–Whitney U test was performed to compare biogas and methane production rates for raw and pretreated leachate samples and it has been found that ultrasonic pretreatment significantly enhanced biogas and methane production rates from leachate (p < 0.05) in anaerobic batch reactors. The overall results showed that low frequency

  10. Cadmium complexation by solid waste leachates

    DEFF Research Database (Denmark)

    Xu Ze Lun; Christensen, Thomas H.

    1989-01-01

    A previously reported method for determination of Cd species in solid waste leachates has been applied to ten leachate samples representing five different types of solid waste: refuse compost, flyash from coal combustion, sewage sludge, refuse incineration residues and landfilled municipal waste......, slowly labile complexes and stable complexes. Leachates originating from the same type of solid waste showed different fractions of Cd, in particular with respect to free divalent Cd and stable Cd complexes. Only coal flyash showed almost identical fractions of Cd in the two leachates. The latter is due...

  11. Phthalate release in leachate from municipal landfills of central Poland.

    Science.gov (United States)

    Wowkonowicz, Paweł; Kijeńska, Marta

    2017-01-01

    Phthalate diesters (PAEs) are used as plasticizer additives to polymer chains to make the material more flexible and malleable. PAEs are bonded physically, not chemically, to the polymeric matrix and can migrate to and leach from the product surface, posing a serious danger to the environment and human health. There have been a number of studies on PAE concentrations in landfill leachate conducted in the EU and around the world, though few in Poland. In the present study, the leachate of five municipal landfills was analyzed for the presence of PAEs. Raw leachate was sampled four times over the period of one year in 2015/16. It was the first large study on this subject in Poland. PAEs were detected in the leachate samples on all of the landfills, thereby indicating that PAEs are ubiquitous environmental contaminants. The following PAEs were detected in at least one sample: Di(2-ethylhexyl) phthalate (DEHP), Diethyl phthalate (DEP), Dimethyl phthalate (DMP), Di-n-butyl phthalate (DBP), Di-isobutylphthalate (DIBP). Out of all ten PAEs, DEHP was the most predominant, with concentrations up to 73.9 μg/L. DEHP was present in 65% of analyzed samples (in 100% of samples in spring, 80% in winter, and 40% in summer and autumn). In only 25% of all samples DEHP was below the acceptable UE limit for surface water (1.3 μg/L), while 75% was from 1.7 to 56 times higher than that value. On the two largest landfills DEHP concentrations were observed during samples from all four seasons, including on a landfill which has been remediated and closed for the last 5 years.

  12. EVEGAS Project (European validation exercise of GAS migration model)

    Energy Technology Data Exchange (ETDEWEB)

    Manai, T. [Geostock S.A., Rueil-Malmaison (France)

    1995-03-01

    The EVEGAS project aims at the verification and validation of numerical codes suitable for simulating gas flow phenomenon in low permeability porous media. Physical phenomena involved in gas generation and gas flow are numerous, often complex, and may not be very well described. The existing numerical codes cannot represent all the occurring possible phenomena, but allow a good trade-off betwen simplicity and representativity of such phenomena. Two phase flow (Gas and Water) appear to be the most consequential phenomena in gas migration and pressure sizing. The project is organised in three major steps: (1) a simple problem with analytical solutions. (2) A few problems based on laboratory or in-situ experiments. (3) A 3-D repository scenarios involving the following aspects: a repository design; a source of gas; rock characteristics; and fluid characteristics.

  13. A behavior-oriented dynamic model for sandbar migration and 2DH evolution

    Science.gov (United States)

    Splinter, K.D.; Holman, R.A.; Plant, N.G.

    2011-01-01

    A nonlinear model is developed to study the time-dependent relationship between the alongshore variability of a sandbar, a(t), and alongshore-averaged sandbar position, xc(t). Sediment transport equations are derived from energetics-based formulations. A link between this continuous physical representation and a parametric form describing the migration of sandbars of constant shape is established through a simple transformation of variables. The model is driven by offshore wave conditions. The parametric equations are dynamically coupled such that changes in one term (i.e., xc) drive changes in the other (i.e., a(t)). The model is tested on 566 days of data from Palm Beach, New South Wales, Australia. Using weighted nonlinear least squares to estimate best fit model coefficients, the model explained 49% and 41% of the variance in measured xc and a(t), respectively. Comparisons against a 1-D horizontal (1DH) version of the model showed significant improvements when the 2DH terms were included (1DH and 2DH Brier skill scores were -0.12 and 0.42, respectively). Onshore bar migration was not predicted in the 1DH model, while the 2DH model correctly predicted onshore migration in the presence of 2DH morphology and allowed the bar to remain closer to shore for a given amount of breaking, providing an important hysteresis to the system. The model is consistent with observations that active bar migration occurs under breaking waves with onshore migration occurring at timescales of days to weeks and increasing 2DH morphology, while offshore migration occurs rapidly under high waves and coincides with a reduction in 2DH morphology. Copyright ?? 2011 by the American Geophysical Union.

  14. The peculiarity of the models of the contamination's migration in water in the Chernobyl region

    International Nuclear Information System (INIS)

    Kononovich, A.L.; Krishev, I.I.; Oskolkov, B.Ja.; Kulebakina, L.G.; Arhipov, N.P.

    1997-01-01

    The new factors become significant for Chernobyl's contamination's evolution after 8-10 years. Those factors were hidden in the early 3-5 years. Our paper describes the mathematical model of the migration's process of the radionuclides in Chernobyl cooling pond and some results about the migration of the 137 Cs by groundwater. Our model for radionuclide's migration in the Chernobyl cooling pond differ from other mathematical models, that it takes into account the destruction of the fuel's particles during the time. It shows increased concentration of the 90 Sr in water and the monotonous decrease 137 Cs concentration in water. The results of the model's calculation of the annual concentration of the 137 Cs and 90 Sr in water coincide with measurements results in less than 20%. It is the only model of the Chernobyl cooling pond, which has so good coincidence during 10 years. Result of this work shows that the main process, which determines the time's dependence of the annual concentration of the radionuclides in Chernobyl cooling pond, is the destruction of the fuel's particles. In the second part of the paper there is result of the investigation 137 Cs migration by groundwater. The investigation was made with combination of the physical's modelling and mathematical's modelling methods. Truer is discussion about similarity of the physical-chemical simulation and real process. We had investigated the real Chernobyl's ground's contamination in the physical-chemical's similar model's system. It has observed the fraction of the 137 Cs in groundwater's contamination with very low sorption's coefficient, and thus the big migration's velocity (like 90 Sr). The part of the speed component is about 10 -4 . But the components of 137 Cs contamination, which has the big sorption's coefficient, converts slowly into the 'speed form' during the time. We had no see any publication about 'speed component' of 137 Cs contamination in Chernobyl's groundwater. All contemporary models of

  15. Experimental Models for Investigating Intra-Stromal Migration of Corneal Keratocytes, Fibroblasts and Myofibroblasts

    Directory of Open Access Journals (Sweden)

    Lisha Ma

    2012-03-01

    Full Text Available Following laser vision correction, corneal keratocytes must repopulate areas of cell loss by migrating through the intact corneal stroma, and this can impact corneal shape and transparency. In this study, we evaluate 3D culture models for simulating this process in vitro. Buttons (8 mm diameter were first punched out of keratocyte populated compressed collagen matrices, exposed to a 3 mm diameter freeze injury, and cultured in serum-free media (basal media or media supplemented with 10% FBS, TGFb1 or PDGF BB. Following freeze injury, a region of cell death was observed in the center of the constructs. Although cells readily migrated on top of the matrices to cover the wound area, a limited amount of cell migration was observed within the constructs. We next developed a novel “sandwich” model, which better mimics the native lamellar architecture of the cornea. Using this model, significant migration was observed under all conditions studied. In both models, cells in TGFb and 10% FBS developed stress fibers; whereas cells in PDGF were more dendritic. PDGF stimulated the most inter-lamellar migration in the sandwich construct. Overall, these models provide insights into the complex interplay between growth factors, cell mechanical phenotypes and the structural properties of the ECM.

  16. An initial research on solute migration model coupled with adsorption of surface complexation in groundwater

    International Nuclear Information System (INIS)

    Qian Tianwei; Chen Fanrong

    2003-01-01

    The influence of solution chemical action in groundwater on solute migration has attracted increasing public attention, especially adsorption action occurring on surface of solid phase and liquid phase, which has play a great role in solute migration. There are various interpretations on adsorption mechanism, in which surface complexion is one of successful hypothesis. This paper first establishes a geochemical model based on surface complexion and then coupled it with traditional advection-dispersion model to constitute a solute migration model, which can deal with surface complexion action. The simulated results fit very well with those obtained by the precursors, as compared with a published famous example, which indicates that the model set up by this paper is successful. (authors)

  17. Computational modelling of multi-cell migration in a multi-signalling substrate

    International Nuclear Information System (INIS)

    Mousavi, Seyed Jamaleddin; Doblaré, Manuel; Doweidar, Mohamed Hamdy

    2014-01-01

    Cell migration is a vital process in many biological phenomena ranging from wound healing to tissue regeneration. Over the past few years, it has been proven that in addition to cell–cell and cell-substrate mechanical interactions (mechanotaxis), cells can be driven by thermal, chemical and/or electrical stimuli. A numerical model was recently presented by the authors to analyse single cell migration in a multi-signalling substrate. That work is here extended to include multi-cell migration due to cell–cell interaction in a multi-signalling substrate under different conditions. This model is based on balancing the forces that act on the cell population in the presence of different guiding cues. Several numerical experiments are presented to illustrate the effect of different stimuli on the trajectory and final location of the cell population within a 3D heterogeneous multi-signalling substrate. Our findings indicate that although multi-cell migration is relatively similar to single cell migration in some aspects, the associated behaviour is very different. For instance, cell–cell interaction may delay single cell migration towards effective cues while increasing the magnitude of the average net cell traction force as well as the local velocity. Besides, the random movement of a cell within a cell population is slightly greater than that of single cell migration. Moreover, higher electrical field strength causes the cell slug to flatten near the cathode. On the other hand, as with single cell migration, the existence of electrotaxis dominates mechanotaxis, moving the cells to the cathode or anode pole located at the free surface. The numerical results here obtained are qualitatively consistent with related experimental works. (paper)

  18. Testing the effects of basic numerical implementations of water migration on models of subduction dynamics

    Science.gov (United States)

    Quinquis, M. E. T.; Buiter, S. J. H.

    2014-06-01

    Subduction of oceanic lithosphere brings water into the Earth's upper mantle. Previous numerical studies have shown how slab dehydration and mantle hydration can impact the dynamics of a subduction system by allowing a more vigorous mantle flow and promoting localisation of deformation in the lithosphere and mantle. The depths at which dehydration reactions occur in the hydrated portions of the slab are well constrained in these models by thermodynamic calculations. However, computational models use different numerical schemes to simulate the migration of free water. We aim to show the influence of the numerical scheme of free water migration on the dynamics of the upper mantle and more specifically the mantle wedge. We investigate the following three simple migration schemes with a finite-element model: (1) element-wise vertical migration of free water, occurring independent of the flow of the solid phase; (2) an imposed vertical free water velocity; and (3) a Darcy velocity, where the free water velocity is a function of the pressure gradient caused by the difference in density between water and the surrounding rocks. In addition, the flow of the solid material field also moves the free water in the imposed vertical velocity and Darcy schemes. We first test the influence of the water migration scheme using a simple model that simulates the sinking of a cold, hydrated cylinder into a dry, warm mantle. We find that the free water migration scheme has only a limited impact on the water distribution after 1 Myr in these models. We next investigate slab dehydration and mantle hydration with a thermomechanical subduction model that includes brittle behaviour and viscous water-dependent creep flow laws. Our models demonstrate that the bound water distribution is not greatly influenced by the water migration scheme whereas the free water distribution is. We find that a bound water-dependent creep flow law results in a broader area of hydration in the mantle wedge, which

  19. A Computational Model of Water Migration Flux in Freezing Soil in a Closed System

    Institute of Scientific and Technical Information of China (English)

    裘春晗

    2005-01-01

    A computational model of water migration flux of fine porous soil in frost heave was investigated in a closed system. The model was established with the heat-mass conservation law and from some previous experimental results. Through defining an auxiliary function an empirical function in the water migration flux, which is difficult to get, was replaced. The data needed are about the water content along the soft colunm after test with enough long time. We adopt the test data of sample soil colunms in [1] to verify the model. The result shows it can reflect the real situation on the whole.

  20. Longitudinal data analysis in support of functional stability concepts for leachate management at closed municipal landfills

    International Nuclear Information System (INIS)

    Gibbons, Robert D.; Morris, Jeremy W.F.; Prucha, Christopher P.; Caldwell, Michael D.; Staley, Bryan F.

    2014-01-01

    Highlights: • Longitudinal data analysis using a mixed-effects regression model. • Dataset consisted of a total of 1402 samples from 101 closed municipal landfills. • Target analytes and classes generally showed predictable degradation trends. • Validates historical studies focused on macro organic indicators such as BOD. • BOD can serve as “gateway” indicator for planning leachate management. - Abstract: Landfill functional stability provides a target that supports no environmental threat at the relevant point of exposure in the absence of active control systems. With respect to leachate management, this study investigates “gateway” indicators for functional stability in terms of the predictability of leachate characteristics, and thus potential threat to water quality posed by leachate emissions. Historical studies conducted on changes in municipal solid waste (MSW) leachate concentrations over time (longitudinal analysis) have concentrated on indicator compounds, primarily chemical oxygen demand (COD) and biochemical oxygen demand (BOD). However, validation of these studies using an expanded database and larger constituent sets has not been performed. This study evaluated leachate data using a mixed-effects regression model to determine the extent to which leachate constituent degradation can be predicted based on waste age or operational practices. The final dataset analyzed consisted of a total of 1402 samples from 101 MSW landfills. Results from the study indicated that all leachate constituents exhibit a decreasing trend with time in the post-closure period, with 16 of the 25 target analytes and aggregate classes exhibiting a statistically significant trend consistent with well-studied indicators such as BOD. Decreasing trends in BOD concentration after landfill closure can thus be considered representative of trends for many leachate constituents of concern

  1. Longitudinal data analysis in support of functional stability concepts for leachate management at closed municipal landfills

    Energy Technology Data Exchange (ETDEWEB)

    Gibbons, Robert D., E-mail: rdg@uchicago.edu [Center for Health Statistics, University of Chicago, 5841 S. Maryland Avenue, Chicago, IL 60637 (United States); Morris, Jeremy W.F., E-mail: jmorris@geosyntec.com [Geosyntec Consultants, 10220 Old Columbia Road, Suite A, Columbia, MD 21046 (United States); Prucha, Christopher P., E-mail: cprucha@wm.com [Groundwater Protection Program, Waste Management, 1550 Balmer Road, Box 200, Model City, NY 14107 (United States); Caldwell, Michael D., E-mail: mcaldwell@wm.com [Groundwater Protection Program, Waste Management, 3623 Wilson Road, Humble, TX 77396 (United States); Staley, Bryan F., E-mail: BStaley@erefdn.org [Environmental Research and Education Foundation, 3301 Benson Drive, Suite 301, Raleigh, NC 27609 (United States)

    2014-09-15

    Highlights: • Longitudinal data analysis using a mixed-effects regression model. • Dataset consisted of a total of 1402 samples from 101 closed municipal landfills. • Target analytes and classes generally showed predictable degradation trends. • Validates historical studies focused on macro organic indicators such as BOD. • BOD can serve as “gateway” indicator for planning leachate management. - Abstract: Landfill functional stability provides a target that supports no environmental threat at the relevant point of exposure in the absence of active control systems. With respect to leachate management, this study investigates “gateway” indicators for functional stability in terms of the predictability of leachate characteristics, and thus potential threat to water quality posed by leachate emissions. Historical studies conducted on changes in municipal solid waste (MSW) leachate concentrations over time (longitudinal analysis) have concentrated on indicator compounds, primarily chemical oxygen demand (COD) and biochemical oxygen demand (BOD). However, validation of these studies using an expanded database and larger constituent sets has not been performed. This study evaluated leachate data using a mixed-effects regression model to determine the extent to which leachate constituent degradation can be predicted based on waste age or operational practices. The final dataset analyzed consisted of a total of 1402 samples from 101 MSW landfills. Results from the study indicated that all leachate constituents exhibit a decreasing trend with time in the post-closure period, with 16 of the 25 target analytes and aggregate classes exhibiting a statistically significant trend consistent with well-studied indicators such as BOD. Decreasing trends in BOD concentration after landfill closure can thus be considered representative of trends for many leachate constituents of concern.

  2. Petroleum migration pathways and charge concentration: A three-dimensional model

    Energy Technology Data Exchange (ETDEWEB)

    Hindle, A.D. [Anadarko Algeria Corp., Middlesex (United Kingdom)

    1997-09-01

    Petroleum migration pathways through a basin are determined by the three-dimensional distribution of discontinuous sealing surfaces, which are usually parallel to bedding. The petroleum migrates below the sealing surface, taking the structurally most advantageous route. The three-dimensional distribution of migration pathways within the petroleum system can be modeled on a personal computer using a program based on the parameters discussed in this paper. Application of the model to the Paris and Williston basins demonstrates that a good correlation between predicted pathways and discovered accumulations can be made using simple models. Pathways form a dense network overlying generating areas in the central parts of basins. Toward the basin margins these routes commonly become increasingly focused into discrete pathways by the sealing-surface morphologies. Eventually, these pathways may reach the surface as seepages. It is important to integrate surface outcrops of migration routes (surface seepages) into migration modeling. Deflection of the pathways from the structurally most advantageous route below the sealing surface may be caused by lateral sealing barriers due to faces variation in the carrier rock below the seal, fault juxtaposition, or cross-formational seals such as salt intrusions. Deflection of pathways also occurs where there are hydrodynamic conditions in response to topography-driven groundwater flow. Zones of vertical migration are associated with facies changes along the horizon of the sealing surface into a nonsealing facies, or juxtaposition to nonsealing strata by faults. Vertical migration from either normally or abnormally pressured strata is most likely to occur into normally or lesser pressured strata at intrabasinal highs where hydrocarbons can be stored and transferred at times of temporary seal rupture.

  3. Impact of pine needle leachates from a mountain pine beetle infested watershed on groundwater geochemistry

    Science.gov (United States)

    Pryhoda, M.; Sitchler, A.; Dickenson, E.

    2013-12-01

    The mountain pine beetle (MPB) epidemic in the northwestern United States is a recent indicator of climate change; having an impact on the lodgepole pine forest ecosystem productivity. Pine needle color can be used to predict the stage of a MPB infestation, as they change color from a healthy green, to red, to gray as the tree dies. Physical processes including precipitation and snowfall can cause leaching of pine needles in all infestation stages. Understanding the evolution of leachate chemistry through the stages of MPB infestation will allow for better prediction of the impact of MPBs on groundwater geochemistry, including a potential increase in soil metal mobilization and potential increases in disinfection byproduct precursor compounds. This study uses batch experiments to determine the leachate chemistry of pine needles from trees in four stages of MPB infestation from Summit County, CO, a watershed currently experiencing the MPB epidemic. Each stage of pine needles undergoes four subsequent leach periods in temperature-controlled DI water. The subsequent leaching method adds to the experiment by determining how leachate chemistry of each stage changes in relation to contact time with water. The leachate is analyzed for total organic carbon. Individual organic compounds present in the leachate are analyzed by UV absorption spectra, fluorescence spectrometry, high-pressure liquid chromatography for organic acid analysis, and size exclusion chromatography. Leachate chemistry results will be used to create a numerical model simulating reactions of the leachate with soil as it flows through to groundwater during precipitation and snowfall events.

  4. Examining speed versus selection in connectivity models using elk migration as an example

    Science.gov (United States)

    Brennan, Angela; Hanks, Ephraim M.; Merkle, Jerod A.; Cole, Eric K.; Dewey, Sarah R.; Courtemanch, Alyson B.; Cross, Paul C.

    2018-01-01

    ContextLandscape resistance is vital to connectivity modeling and frequently derived from resource selection functions (RSFs). RSFs estimate relative probability of use and tend to focus on understanding habitat preferences during slow, routine animal movements (e.g., foraging). Dispersal and migration, however, can produce rarer, faster movements, in which case models of movement speed rather than resource selection may be more realistic for identifying habitats that facilitate connectivity.ObjectiveTo compare two connectivity modeling approaches applied to resistance estimated from models of movement rate and resource selection.MethodsUsing movement data from migrating elk, we evaluated continuous time Markov chain (CTMC) and movement-based RSF models (i.e., step selection functions [SSFs]). We applied circuit theory and shortest random path (SRP) algorithms to CTMC, SSF and null (i.e., flat) resistance surfaces to predict corridors between elk seasonal ranges. We evaluated prediction accuracy by comparing model predictions to empirical elk movements.ResultsAll connectivity models predicted elk movements well, but models applied to CTMC resistance were more accurate than models applied to SSF and null resistance. Circuit theory models were more accurate on average than SRP models.ConclusionsCTMC can be more realistic than SSFs for estimating resistance for fast movements, though SSFs may demonstrate some predictive ability when animals also move slowly through corridors (e.g., stopover use during migration). High null model accuracy suggests seasonal range data may also be critical for predicting direct migration routes. For animals that migrate or disperse across large landscapes, we recommend incorporating CTMC into the connectivity modeling toolkit.

  5. Modeling dissolution and volatilization of LNAPL sources migrating on the groundwater table.

    Science.gov (United States)

    Kim, Jeongkon; Corapcioglu, M Yavuz

    2003-08-01

    A vertically averaged two-dimensional model was developed to describe areal spreading and migration of light nonaqueous-phase liquids (LNAPLs) introduced into the subsurface by spills or leaks from underground storage tanks. The NAPL transport model was coupled with two-dimensional contaminant transport models to predict contamination of soil gas and groundwater resulting from a LNAPL migrating on the water table. Numerical solutions were obtained by using the finite-difference method. Simulations and sensitivity analyses were conducted with a LNAPL of pure benzene to study LNAPL migration and groundwater contamination. The model was applied to subsurface contamination by jet fuel. Results indicated that LNAPL migration were affected mostly by volatilization. The generation and movement of the dissolved plume was affected by the geology of the site and the free-product plume. Most of the spilled mass remained as a free LNAPL phase 20 years after the spill. The migration of LNAPL for such a long period resulted in the contamination of both groundwater and a large volume of soil.

  6. Leachate characterization and identification of dominant pollutants using leachate pollution index for an uncontrolled landfill site

    International Nuclear Information System (INIS)

    De, S.; Maiti, S. K.; Hazra, T.; Debsarkar, A.; Dutta, A.

    2016-01-01

    Landfill leachates are potential threats for environmental degradation. This study was conducted to determine the leachate quality, to identify the dominant pollutants and to evaluate the leachate pollution potential of an active and closed dumping ground of an uncontrolled municipal solid waste (MSW) landfill site in Kolkata, India using leachate pollution index. The results of the physico-chemical and biological analyses of leachate indicated that landfill site was in its methanogenic phase. Among the analysed leachate pollutants, TDS, BOD5, COD, TKN, NH3-N, Cl¯ , TCB, Pb, and Hg surpassed the leachate discharge standards for inland surface water as specified by the municipal solid waste (management and handling) rules, 2013 for both the dumping grounds. Moreover the concentrations of total Cr and Zn also exceeded the leachate disposal standards for the active dumping ground. The leachate pollution potentialities of both the active and closed dumping grounds were comparable as the overall LPI obtained 34.02 and 31.80 respectively. The overall LPI, LPI organic (LPIor), LPI inorganic (LPIin) and LPI heavy metals (LPIhm) of both the dumping grounds largely exceeded the LPI and sub-LPI values for treated leachate before disposal to the inland surface water. In terms of the individual pollution rating, total coliform bacteria, TKN, NH3-N and Hg were identified as the dominant pollutants and major contributing factors for the leachate pollution potential.

  7. Leachate characterization and identification of dominant pollutants using leachate pollution index for an uncontrolled landfill site

    Directory of Open Access Journals (Sweden)

    S. De

    2016-03-01

    Full Text Available Landfill leachates are potential threats for environmental degradation. This study was conducted to determine the leachate quality, to identify the dominant pollutants and to evaluate the leachate pollution potential of an active and closed dumping ground of an uncontrolled municipal solid waste landfill site in Kolkata, India using leachate pollution index. The results of the physico-chemical and biological analyses of leachate indicated that landfill site was in its methanogenic phase. Among the analysed leachate pollutants, TDS, BOD5, COD, TKN, NH3-N, Cl¯, TCB, Pb, and Hg surpassed the leachate discharge standards for inland surface water as specified by the municipal solid waste (Management and Handling Rules, 2013 for both the dumping grounds. Moreover the concentrations of total Cr and Zn also exceeded the leachate disposal standards for the active dumping ground. The leachate pollution potentialities of both the active and closed dumping grounds were comparable as the overall LPI obtained 34.02 and 31.80 respectively. The overall LPI, LPI organic (LPIor, LPI inorganic (LPIin and LPI heavy metals (LPIhm of both the dumping grounds largely exceeded the LPI and sub-LPI values for treated leachate before disposal to the inland surface water. In terms of the individual pollution rating, total coliform bacteria, TKN, NH3-N and Hg were identified as the dominant pollutants and major contributing factors for the leachate pollution potential.

  8. A model describing water and salt migration in concrete during wetting/drying cycles

    NARCIS (Netherlands)

    Arends, T.; Taher, A.; van der Zanden, A.J.J.; Brouwers, H.J.H.; Bilek, V.; Kersner, Z.

    2014-01-01

    In order to predict the life span of concrete structures, models describing the migration of chloride are needed. In this paper, a start is made with a simple, theoretical model describing water and chloride transport in a concrete sample. First, transport of water in concrete is considered with

  9. Modeling gas and brine migration for assessing compliance of the Waste Isolation Pilot Plant

    International Nuclear Information System (INIS)

    Vaughn, P.; Butcher, B.; Helton, J.; Swift, P.

    1993-10-01

    At the request of the WIPP Project Integration Office (WPIO) of the DOE, the WIPP Performance Assessment (PA) Department of Sandia National Laboratories (SNL) has completed preliminary uncertainty and sensitivity analyses of gas and brine migration away from the undisturbed repository. This paper contains descriptions of the numerical model and simulations, including model geometries and parameter values, and a summary of major conclusions from sensitivity analyses. Because significant transport of contaminants can only occur in a fluid (gas or brine) medium, two-phase flow modeling can provide an estimate of the distance to which contaminants can migrate. Migration of gas or brine beyond the RCRA ''disposal-unit boundary'' or the Standard's accessible environment constitutes a potential, but not certain, violation and may require additional evaluations of contaminant concentrations

  10. Mechanisms and modelling of gas migration from deep radioactive waste repositories

    International Nuclear Information System (INIS)

    Rodwell, W.R.; Nash, P.J.

    1992-06-01

    This report discusses the mechanisms by which gas is able to migrate through the far-field. The mechanisms available are diffusion or advection of gas dissolved in groundwater or free gas phase flow as either bubbles or a continuous stream of gas. Modelling approaches adopted to assess the migration are (a) simple use of Darcy's law with an effective permeability to gas, (b) the development of a model based on the representation of the far-field rock as a bundle of capillaries with a suitable distribution of radii, and (c) the use of a numerical model of two-phase flow in porous media. Finally, surveys have been carried out of published work on gas escape from underground storage caverns and of literature relating to gas movement from underground hydrocarbon accumulations to determine whether these may be potential sources of data or understanding of underground gas migration relevant to that from deep waste repositories. (author)

  11. Cellular automaton for migration in ecosystem: Application of traffic model to a predator-prey system

    Science.gov (United States)

    Nagatani, Takashi; Tainaka, Kei-ichi

    2018-01-01

    In most cases, physicists have studied the migration of biospecies by the use of random walk. In the present article, we apply cellular automaton of traffic model. For simplicity, we deal with an ecosystem contains a prey and predator, and use one-dimensional lattice with two layers. Preys stay on the first layer, but predators uni-directionally move on the second layer. The spatial and temporal evolution is numerically explored. It is shown that the migration has the important effect on populations of both prey and predator. Without migration, the phase transition between a prey-phase and coexisting-phase occurs. In contrast, the phase transition disappears by migration. This is because predator can survive due to migration. We find another phase transition for spatial distribution: in one phase, prey and predator form a stripe pattern of condensation and rarefaction, while in the other phase, they uniformly distribute. The self-organized stripe may be similar to the migration patterns in real ecosystems.

  12. Hydrologic modelling of the migration site in the Grimsel rock laboratory -the steady state

    International Nuclear Information System (INIS)

    Herzog, F.

    1989-07-01

    Tracer migration experiments are in progress at the Grimsel Test Site (GTS) in order to test radionuclide transport models and to develop appropriate experimental techniques. In order to assist design and to interpret field tracer tests the knowledge of the hydrology of the site is essential. This report describes the hydraulic modelling efforts with the following objectives: 1) to interpret experimental findings. 2) to provide input, such as flowpaths and flow velocities, for transport modelling. 3) to assist in the design of the tracer experiments. The model concept is based upon the observations, that the fracture, where the migration experiments will take place, is relatively planar, has an average aperture of a few millimeters and is filled with a clayish mateial: The migration fracture is modelled as a two-dimensional, isotropic, heterogeneous equivalent porous medium. To allow for a sufficiently detailed model a hierarchical approach was followed where the boundaries for the 'local' model, i.e. the model in the vicinity of the migration site, were taken by first solving a larger 'regional' model with coarser discretization. Transmissivity values as extracted from single borehole tests were used for definition of the heterogeneous transmissivity field in the model calculations. Model results for hydrostatic pressures and discharge rates compare favourably with experimental data, even though some problems remain to be resolved. Calculations for dipole arrangements have been performed; they turned out to be useful tools for deciding on injection- and withdrawal rates to be applied in the migration experiments as well as for qualitatively estimating tracer recovery rates. (author) 20 figs., 10 tabs., 11 refs

  13. A mathematical model of collective cell migration in a three-dimensional, heterogeneous environment.

    Directory of Open Access Journals (Sweden)

    David P Stonko

    Full Text Available Cell migration is essential in animal development, homeostasis, and disease progression, but many questions remain unanswered about how this process is controlled. While many kinds of individual cell movements have been characterized, less effort has been directed towards understanding how clusters of cells migrate collectively through heterogeneous, cellular environments. To explore this, we have focused on the migration of the border cells during Drosophila egg development. In this case, a cluster of different cell types coalesce and traverse as a group between large cells, called nurse cells, in the center of the egg chamber. We have developed a new model for this collective cell migration based on the forces of adhesion, repulsion, migration and stochastic fluctuation to generate the movement of discrete cells. We implement the model using Identical Math Cells, or IMCs. IMCs can each represent one biological cell of the system, or can be aggregated using increased adhesion forces to model the dynamics of larger biological cells. The domain of interest is filled with IMCs, each assigned specific biophysical properties to mimic a diversity of cell types. Using this system, we have successfully simulated the migration of the border cell cluster through an environment filled with larger cells, which represent nurse cells. Interestingly, our simulations suggest that the forces utilized in this model are sufficient to produce behaviors of the cluster that are observed in vivo, such as rotation. Our framework was developed to capture a heterogeneous cell population, and our implementation strategy allows for diverse, but precise, initial position specification over a three- dimensional domain. Therefore, we believe that this model will be useful for not only examining aspects of Drosophila oogenesis, but also for modeling other two or three-dimensional systems that have multiple cell types and where investigating the forces between cells is of

  14. A mathematical model of collective cell migration in a three-dimensional, heterogeneous environment.

    Science.gov (United States)

    Stonko, David P; Manning, Lathiena; Starz-Gaiano, Michelle; Peercy, Bradford E

    2015-01-01

    Cell migration is essential in animal development, homeostasis, and disease progression, but many questions remain unanswered about how this process is controlled. While many kinds of individual cell movements have been characterized, less effort has been directed towards understanding how clusters of cells migrate collectively through heterogeneous, cellular environments. To explore this, we have focused on the migration of the border cells during Drosophila egg development. In this case, a cluster of different cell types coalesce and traverse as a group between large cells, called nurse cells, in the center of the egg chamber. We have developed a new model for this collective cell migration based on the forces of adhesion, repulsion, migration and stochastic fluctuation to generate the movement of discrete cells. We implement the model using Identical Math Cells, or IMCs. IMCs can each represent one biological cell of the system, or can be aggregated using increased adhesion forces to model the dynamics of larger biological cells. The domain of interest is filled with IMCs, each assigned specific biophysical properties to mimic a diversity of cell types. Using this system, we have successfully simulated the migration of the border cell cluster through an environment filled with larger cells, which represent nurse cells. Interestingly, our simulations suggest that the forces utilized in this model are sufficient to produce behaviors of the cluster that are observed in vivo, such as rotation. Our framework was developed to capture a heterogeneous cell population, and our implementation strategy allows for diverse, but precise, initial position specification over a three- dimensional domain. Therefore, we believe that this model will be useful for not only examining aspects of Drosophila oogenesis, but also for modeling other two or three-dimensional systems that have multiple cell types and where investigating the forces between cells is of interest.

  15. Simulation of construction and demolition waste leachate

    Energy Technology Data Exchange (ETDEWEB)

    Townsend, T.G.; Jang, Y.; Thurn, L.G.

    1999-11-01

    Solid waste produced from construction and demolition (C and D) activities is typically disposed of in unlined landfills. Knowledge of C{ampersand}D debris landfill leachate is limited in comparison to other types of wastes. A laboratory study was performed to examine leachate resulting from simulated rainfall infiltrating a mixed C and D waste stream consisting of common construction materials (e.g., concrete, wood, drywall). Lysimeters (leaching columns) filled with the mixed C and D waste were operated under flooded and unsaturated conditions. Leachate constituent concentrations in the leachate from specific waste components were also examined. Leachate samples were collected and analyzed for a number of conventional water quality parameters including pH, alkalinity, total organic carbon, total dissolved solids, and sulfate. In experiments with the mixed C and D waste, high concentrations of total dissolved solids (TDS) and sulfate were detected in the leachate. C and D leachates produced as a result of unsaturated conditions exhibited TDS concentrations in the range of 570--2,200 mg/L. The major contributor to the TDS was sulfate, which ranged in concentration between 280 and 930 mg/L. The concentrations of sulfate in the leachate exceeded the sulfate secondary drinking water standard of 250 mg/L.

  16. Modelling internal migration in Kenya: an econometric analysis with limited data.

    Science.gov (United States)

    Barber, G M; Milne, W J

    1988-09-01

    "In this paper the determinants of internal migration in Kenya are analyzed on the basis of a human capital model. Explanatory variables included in the specification are both economic (wage rates and employment rates) and noneconomic (for example, population density and educational attainment). Also incorporated are variables which reflect intervening opportunities.... The econometric results show that destination variables are important determinants of internal migration, as is distance between the districts. Further, the variables for the intervening opportunities add significantly to the explanatory power of the model." excerpt

  17. A theoretical and empirical evaluation and extension of the Todaro migration model.

    Science.gov (United States)

    Salvatore, D

    1981-11-01

    "This paper postulates that it is theoretically and empirically preferable to base internal labor migration on the relative difference in rural-urban real income streams and rates of unemployment, taken as separate and independent variables, rather than on the difference in the expected real income streams as postulated by the very influential and often quoted Todaro model. The paper goes on to specify several important ways of extending the resulting migration model and improving its empirical performance." The analysis is based on Italian data. excerpt

  18. Modeling Coupled THM Processes and Brine Migration in Salt at High Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rutqvist, Jonny [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Blanco-Martin, Laura [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Molins, Sergi [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Trebotich, David [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Birkholzer, Jens [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2015-09-01

    In this report, we present FY2015 progress by Lawrence Berkeley National Laboratory (LBNL) related to modeling of coupled thermal-hydrological-mechanical-chemical (THMC) processes in salt and their effect on brine migration at high temperatures. This is a combined milestone report related to milestone Salt R&D Milestone “Modeling Coupled THM Processes and Brine Migration in Salt at High Temperatures” (M3FT-15LB0818012) and the Salt Field Testing Milestone (M3FT-15LB0819022) to support the overall objectives of the salt field test planning.

  19. Modeling Coupled THM Processes and Brine Migration in Salt at High Temperatures

    International Nuclear Information System (INIS)

    Rutqvist, Jonny; Blanco-Martin, Laura; Molins, Sergi; Trebotich, David; Birkholzer, Jens

    2015-01-01

    In this report, we present FY2015 progress by Lawrence Berkeley National Laboratory (LBNL) related to modeling of coupled thermal-hydrological-mechanical-chemical (THMC) processes in salt and their effect on brine migration at high temperatures. This is a combined milestone report related to milestone Salt R&D Milestone ''Modeling Coupled THM Processes and Brine Migration in Salt at High Temperatures'' (M3FT-15LB0818012) and the Salt Field Testing Milestone (M3FT-15LB0819022) to support the overall objectives of the salt field test planning.

  20. Software for modelling groundwater transport and contaminant migration

    International Nuclear Information System (INIS)

    Gishkelyuk, I.A.

    2008-01-01

    Facilities of modern software for modeling of groundwater transport and process of contaminant distribution are considered. Advantages of their application are discussed. The comparative analysis of mathematical modeling software of 'Groundwater modeling system' and 'Earth Science Module' from 'COMSOL Multiphysics' is carried out. (authors)

  1. Modeling Studies to Constrain Fluid and Gas Migration Associated with Hydraulic Fracturing Operations

    Science.gov (United States)

    Rajaram, H.; Birdsell, D.; Lackey, G.; Karra, S.; Viswanathan, H. S.; Dempsey, D.

    2015-12-01

    The dramatic increase in the extraction of unconventional oil and gas resources using horizontal wells and hydraulic fracturing (fracking) technologies has raised concerns about potential environmental impacts. Large volumes of hydraulic fracturing fluids are injected during fracking. Incidents of stray gas occurrence in shallow aquifers overlying shale gas reservoirs have been reported; whether these are in any way related to fracking continues to be debated. Computational models serve as useful tools for evaluating potential environmental impacts. We present modeling studies of hydraulic fracturing fluid and gas migration during the various stages of well operation, production, and subsequent plugging. The fluid migration models account for overpressure in the gas reservoir, density contrast between injected fluids and brine, imbibition into partially saturated shale, and well operations. Our results highlight the importance of representing the different stages of well operation consistently. Most importantly, well suction and imbibition both play a significant role in limiting upward migration of injected fluids, even in the presence of permeable connecting pathways. In an overall assessment, our fluid migration simulations suggest very low risk to groundwater aquifers when the vertical separation from a shale gas reservoir is of the order of 1000' or more. Multi-phase models of gas migration were developed to couple flow and transport in compromised wellbores and subsurface formations. These models are useful for evaluating both short-term and long-term scenarios of stray methane release. We present simulation results to evaluate mechanisms controlling stray gas migration, and explore relationships between bradenhead pressures and the likelihood of methane release and transport.

  2. Use of Invasion Percolation Models To Study the Secondary Migration of Oil and Related Problems

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, G.

    1997-09-01

    In oil reservoir engineering, multi-phase displacement processes are important. This doctoral thesis describes simulations of the slow displacement of a wetting fluid by a non-wetting fluid in a complex, random porous medium and in a single fracture. The study is restricted to two-phase flow in the quasi-static limit in which viscous forces can be neglected. The secondary migration of oil takes place in this regime, however, the discussion is broader in scope. The thesis connects the problem of slow two-phase flow to percolation theory and discusses the mechanisms that control immiscible displacements. A new, modified version of the invasion percolation model is used to simulate an imbibition process in a porous medium and the migration of a cluster of non-wetting fluid through a porous medium saturated with a wetting fluid. The simulations include the secondary migration of oil through porous homogeneous rock. Fluid migration through heterogeneous porous media is simulated qualitatively. Slow displacement of a wetting fluid by a non-wetting fluid in a single rock fracture is simulated by using the standard invasion percolation model. Experiments and simulations are performed to study the fragmentation of invasion percolation-like structures of non-wetting fluid in a porous medium saturated with a wetting fluid. A scenario is studied in which a cluster of non-wettable fluid migrates through a porous medium that is saturated with a wetting fluid, the migration being driven by continuously increasing buoyancy forces. There is a simulation of the secondary migration of oil in both two- and three-dimensional media. 361 refs., 115 figs.

  3. Present and long-term composition of MSW landfill leachate: A review

    DEFF Research Database (Denmark)

    Kjeldsen, Peter; Barlaz, M.A.; Rooker, A.P.

    2002-01-01

    The major potential environmental impacts related to landfill leachate are pollution of groundwater and surface waters. Landfill leachate contains pollutants that can be categorized into four groups (dissolved organic matter, inorganic macrocomponents, heavy metals, and xenobiotic organic compounds...... are observed. In contrast, the concentration of ammonia does not decrease, and often constitutes a major long-term pollutant in leachate. A broad range of xenobiotic organic compounds is observed in landfill leachate. The long-term behavior of landfills with respect to changes in oxidation-reduction status...... is discussed based on theory and model simulations. It seems that the somewhere postulated enhanced release of accumulated heavy metals would not take place within the time frames of thousands of years. This is supported by a few laboratory investigations. The existing data and model evaluations indicate...

  4. The modelling of 2-D migration patterns of soluble waste in soils

    International Nuclear Information System (INIS)

    Villar, H.P.

    1998-01-01

    A novel approach to the modelling of two-dimensional migration patterns of soluble waste in soils is presented. This approach, albeit very simple and straightforward, was found to be powerful enough to simulate several aspects of the migration of conservative tracers in non-sorptive soils. In brief, the finite-difference technique is adopted for the solution of the two-dimensional advection-dispersion equation. Since the simulated data were to be verified against experimental data obtained through the use of radioactive tracers, the numerical model was modified to take into account the corresponding experimental aspects, with special regard to the attenuation of radiation through the soil mass. The introduction of this correcting factor rendered the simulation quite faithful to the experimental data, thus suggesting the feasibility of the proposed approach for the two-dimensional analysis of waste migration. (author)

  5. Sea level driven marsh expansion in a coupled model of marsh erosion and migration

    Science.gov (United States)

    Kirwan, Matthew L.; Walters, David C.; Reay, William G.; Carr, Joel

    2016-01-01

    Coastal wetlands are among the most valuable ecosystems on Earth, where ecosystem services such as flood protection depend nonlinearly on wetland size and are threatened by sea level rise and coastal development. Here we propose a simple model of marsh migration into adjacent uplands and couple it with existing models of seaward edge erosion and vertical soil accretion to explore how ecosystem connectivity influences marsh size and response to sea level rise. We find that marsh loss is nearly inevitable where topographic and anthropogenic barriers limit migration. Where unconstrained by barriers, however, rates of marsh migration are much more sensitive to accelerated sea level rise than rates of edge erosion. This behavior suggests a counterintuitive, natural tendency for marsh expansion with sea level rise and emphasizes the disparity between coastal response to climate change with and without human intervention.

  6. Modelling of artificial radioactivity migration in environment: a survey

    International Nuclear Information System (INIS)

    Bignoli, G.; Bertozzi, G.

    1979-01-01

    The aim of this report is to present a compilation and description of models to assess the environmental behaviour and effects of accidental and routine releases of artificial radioactivity from nuclear power facilities. About 60 models are described and a card is given for each one, to indicate in summarized form its features and data content. This collection is intended to help in developing specific personal models by assembling different parts chosen among the most suitable ones of different models of various degrees of sophistication

  7. Examining the physical meaning of the bank erosion coefficient used in meander migration modeling

    Science.gov (United States)

    Constantine, Candice R.; Dunne, Thomas; Hanson, Gregory J.

    2009-05-01

    Widely used models of meander evolution relate migration rate to vertically averaged near-bank velocity through the use of a coefficient of bank erosion ( E). In applications to floodplain management problems, E is typically determined through calibration to historical planform changes, and thus its physical meaning remains unclear. This study attempts to clarify the extent to which E depends on measurable physical characteristics of the channel boundary materials using data from the Sacramento River, California, USA. Bend-average values of E were calculated from measured long-term migration rates and computed near-bank velocities. In the field, unvegetated bank material resistance to fluvial shear ( k) was measured for four cohesive and noncohesive bank types using a jet-test device. At a small set of bends for which both E and k were obtained, we discovered that variability in k explains much of the variability in E. The form of this relationship suggests that when modeling long-term meander migration of large rivers, E depends largely on bank material properties. This finding opens up the possibility that E may be estimated directly from field data, enabling prediction of meander migration rates for systems where historical data are unavailable or controlling conditions have changed. Another implication is that vegetation plays a limited role in affecting long-term meander migration rates of large rivers like the Sacramento River. These hypotheses require further testing with data sets from other large rivers.

  8. Computational models reveal a passive mechanism for cell migration in the crypt.

    Directory of Open Access Journals (Sweden)

    Sara-Jane Dunn

    Full Text Available Cell migration in the intestinal crypt is essential for the regular renewal of the epithelium, and the continued upward movement of cells is a key characteristic of healthy crypt dynamics. However, the driving force behind this migration is unknown. Possibilities include mitotic pressure, active movement driven by motility cues, or negative pressure arising from cell loss at the crypt collar. It is possible that a combination of factors together coordinate migration. Here, three different computational models are used to provide insight into the mechanisms that underpin cell movement in the crypt, by examining the consequence of eliminating cell division on cell movement. Computational simulations agree with existing experimental results, confirming that migration can continue in the absence of mitosis. Importantly, however, simulations allow us to infer mechanisms that are sufficient to generate cell movement, which is not possible through experimental observation alone. The results produced by the three models agree and suggest that cell loss due to apoptosis and extrusion at the crypt collar relieves cell compression below, allowing cells to expand and move upwards. This finding suggests that future experiments should focus on the role of apoptosis and cell extrusion in controlling cell migration in the crypt.

  9. Comparison of models of radionuclide migration in food chains

    International Nuclear Information System (INIS)

    Hanusik, V.; Mitro, A.; Chorvat, D.

    1985-01-01

    Two models are compared used for describing the transfer of radioactive substances to man through food chains: the model used in US NRC Regulatory Guide 1.109 and that used in Interatomehnergo NTD No. 38.220.56-81. The models are compared with regard to the approach to model construction, with regard to mathematical expressions and recommended values of parameters. The comparative calculations show that with the use of the recommended values the contribution of direct contamination is prevalent in both models. The concentration of radioactive substances in selected products calculated for indirect contamination using the NRC method is more conservative. For direct and total contamination the NRC method provides higher values of concentrations in the leaf and non-leaf vegetables (cabbage, potatoes, cucumbers) than the NTD method. Concentrations in non-leaf vegetables are higher than in wheat for 4 nuclides only and in meat and milk for 13 radionuclides of the considered set of 22 radionuclides. Substitution of the recommended values of the parameters of the NRC model with recommended values of the corresponding parameters of the NTD model will reduce total concentrations in products as against initial results of the two studied models. (author)

  10. Predicting migratory flight altitudes by physiological migration models

    NARCIS (Netherlands)

    Liechti, F.; Klaassen, M.R.J.; Bruderer, B.

    2000-01-01

    Using the altitudinal profiles of wind, temperature, pressure, and humidity in three flight models, we tried to explain the altitudinal distributions of nocturnal migrants recorded by radar above a desert in southern Israel. In the simplest model, only the tailwind component was used as a predictor

  11. Leachate generation from landfill in a semi-arid climate: A qualitative and quantitative study from Sousse, Tunisia.

    Science.gov (United States)

    Frikha, Youssef; Fellner, Johann; Zairi, Moncef

    2017-09-01

    Despite initiatives for enhanced recycling and waste utilization, landfill still represents the dominant disposal path for municipal solid waste (MSW). The environmental impacts of landfills depend on several factors, including waste composition, technical barriers, landfill operation and climatic conditions. A profound evaluation of all factors and their impact is necessary in order to evaluate the environmental hazards emanating from landfills. The present paper investigates a sanitary landfill located in a semi-arid climate (Tunisia) and highlights major differences in quantitative and qualitative leachate characteristics compared to landfills situated in moderate climates. Besides the qualitative analysis of leachate samples, a quantitative analysis including the simulation of leachate generation (using the HELP model) has been conducted. The results of the analysis indicate a high load of salts (Cl, Na, inorganic nitrogen) in the leachate compared to other landfills. Furthermore the simulations with HELP model highlight that a major part of the leachate generated originates form the water content of waste.

  12. Radionuclide-migration model for buried waste at the Savannah River Plant

    International Nuclear Information System (INIS)

    King, C.M.; Root, R.W. Jr.

    1982-01-01

    Solid waste has been buried at the Savannah River Plant burial ground since 1953. The solid waste is contaminated with alpha-emitting transuranium (TRU) nuclides, with beta-gamma-emitting activation and fission products, and with tritium. To provide guidance for the current use and eventual permanent retirement of the burial site from active service, a radionuclide environmental transport model has been used to project the potential influence on man if the burial site were occupied after decommissioning. The model used to simulate nuclide migration includes the various hydrological, animal, vegetative, atmospheric, and terrestrial pathways in estimating dose to man as a function of time. Specific scenarios include a four-person home farm on the 195-acre burial ground. Key input to the model includes site-specific nuclide migration rates through soil, nuclide distribution coefficients, and site topography. Coupled with literature data on plant and animal concentration factors, transfer coefficients reflecting migration routes are input to a set of linear differential equations for subsequent matrix solution. Output from the model is the nuclide-specific decayed curie intake by man. To discern principal migration routes, model-compartment inventories with time can also be displayed. Dose projections subsequently account for organ concentrations in man for the nuclide of interest. Radionuclide migration has been examined in depth with the dose-to-man model. Movement by vegetative pathways is the primary route for potential dose to man for short-lived isotopes. Hydrological routes provide a secondary scheme for long-lived nuclides. Details of model methodology are reviewed

  13. Identification of genes regulating migration and invasion using a new model of metastatic prostate cancer

    International Nuclear Information System (INIS)

    Banyard, Jacqueline; Chung, Ivy; Migliozzi, Matthew; Phan, Derek T; Wilson, Arianne M; Zetter, Bruce R; Bielenberg, Diane R

    2014-01-01

    Understanding the complex, multistep process of metastasis remains a major challenge in cancer research. Metastasis models can reveal insights in tumor development and progression and provide tools to test new intervention strategies. To develop a new cancer metastasis model, we used DU145 human prostate cancer cells and performed repeated rounds of orthotopic prostate injection and selection of subsequent lymph node metastases. Tumor growth, metastasis, cell migration and invasion were analyzed. Microarray analysis was used to identify cell migration- and cancer-related genes correlating with metastasis. Selected genes were silenced using siRNA, and their roles in cell migration and invasion were determined in transwell migration and Matrigel invasion assays. Our in vivo cycling strategy created cell lines with dramatically increased tumorigenesis and increased ability to colonize lymph nodes (DU145LN1-LN4). Prostate tumor xenografts displayed increased vascularization, enlarged podoplanin-positive lymphatic vessels and invasive margins. Microarray analysis revealed gene expression profiles that correlated with metastatic potential. Using gene network analysis we selected 3 significantly upregulated cell movement and cancer related genes for further analysis: EPCAM (epithelial cell adhesion molecule), ITGB4 (integrin β4) and PLAU (urokinase-type plasminogen activator (uPA)). These genes all showed increased protein expression in the more metastatic DU145-LN4 cells compared to the parental DU145. SiRNA knockdown of EpCAM, integrin-β4 or uPA all significantly reduced cell migration in DU145-LN4 cells. In contrast, only uPA siRNA inhibited cell invasion into Matrigel. This role of uPA in cell invasion was confirmed using the uPA inhibitors, amiloride and UK122. Our approach has identified genes required for the migration and invasion of metastatic tumor cells, and we propose that our new in vivo model system will be a powerful tool to interrogate the metastatic

  14. Dispersive processes in models of regional radionuclide migration. Technical memorandum

    International Nuclear Information System (INIS)

    Evenson, D.E.; Dettinger, M.D.

    1980-05-01

    Three broad areas of concern in the development of aquifer scale transport models will be local scale diffusion and dispersion processes, regional scale dispersion processes, and numerical problems associated with the advection-dispersion equation. Local scale dispersion processes are fairly well understood and accessible to observation. These processes will generally be dominated in large scale systems by regional processes, or macro-dispersion. Macro-dispersion is primarily the result of large scale heterogeneities in aquifer properties. In addition, the effects of many modeling approximations are often included in the process. Because difficulties arise in parameterization of this large scale phenomenon, parameterization should be based on field measurements made at the same scale as the transport process of interest or else partially circumvented through the application of a probabilistic advection model. Other problems associated with numerical transport models include difficulties with conservation of mass, stability, numerical dissipation, overshoot, flexibility, and efficiency. We recommend the random-walk model formulation for Lawrence Livermore Laboratory's purposes as the most flexible, accurate and relatively efficient modeling approach that overcomes these difficulties

  15. Dynamical behaviour of a discrete selection-migration model with arbitrary dominance

    Science.gov (United States)

    James F. Selgrade; Jordan West Bostic; James H. Roberds

    2009-01-01

    To study the effects of immigration of genes (possibly transgenic) into a natural population, a one-island selection-migration model with density-dependent regulation is used to track allele frequency and population size. The existence and uniqueness of a polymorphic genetic equilibrium is proved under a general assumption about dominance in fitnesses. Also, conditions...

  16. Continental rift architecture and patterns of magma migration: a dynamic analysis based on centrifuge models.

    NARCIS (Netherlands)

    Corti, G.; Bonini, M.; Sokoutis, D.; Innocenti, F.; Manetti, P.; Cloetingh, S.A.P.L.; Mulugeta, G.

    2004-01-01

    Small-scale centrifuge models were used to investigate the role of continental rift structure in controlling patterns of magma migration and emplacement. Experiments considered the reactivation of weakness zones in the lower crust and the presence of magma at Moho depths. Results suggest that

  17. Stop early to travel fast: modelling risk-averse scheduling among nocturnally migrating birds

    NARCIS (Netherlands)

    McLaren, J.D.; Shamoun-Baranes, J.; Bouten, W.

    2013-01-01

    Many migrating birds divide their journeys into nocturnal flights interspersed by stopovers where they build up energy reserves (fuel) for subsequent flights. Given the difficulty in monitoring fuel loads of individual migrants over long distances, theoretical models are often used to interpret

  18. Dynamical Analysis of Density-dependent Selection in a Discrete one-island Migration Model

    Science.gov (United States)

    James H. Roberds; James F. Selgrade

    2000-01-01

    A system of non-linear difference equations is used to model the effects of density-dependent selection and migration in a population characterized by two alleles at a single gene locus. Results for the existence and stability of polymorphic equilibria are established. Properties for a genetically important class of equilibria associated with complete dominance in...

  19. A generalizable energetics-based model of avian migration to facilitate continental-scale waterbird conservation

    Science.gov (United States)

    Lonsdorf, Eric V.; Thogmartin, Wayne E.; Jacobi, Sarah; Coppen, Jorge; Davis, Amélie Y.; Fox, Timothy J.; Heglund, Patricia J.; Johnson, Rex; Jones, Tim; Kenow, Kevin P.; Lyons, James E.; Luke, Kirsten E.; Still, Shannon; Tavernia, Brian G.

    2016-01-01

    Conserving migratory birds is made especially difficult because of movement among spatially disparate locations across the annual cycle. In light of challenges presented by the scale and ecology of migratory birds, successful conservation requires integrating objectives, management, and monitoring across scales, from local management units to ecoregional and flyway administrative boundaries. We present an integrated approach using a spatially explicit energetic-based mechanistic bird migration model useful to conservation decision-making across disparate scales and locations. This model moves a mallard-like bird (Anas platyrhynchos), through spring and fall migration as a function of caloric gains and losses across a continental scale energy landscape. We predicted with this model that fall migration, where birds moved from breeding to wintering habitat, took a mean of 27.5 days of flight with a mean seasonal survivorship of 90.5% (95% CI = 89.2%, 91.9%) whereas spring migration took a mean of 23.5 days of flight with mean seasonal survivorship of 93.6% (95% CI = 92.5%, 94.7%). Sensitivity analyses suggested that survival during migration was sensitive to flight speed, flight cost, the amount of energy the animal could carry and the spatial pattern of energy availability, but generally insensitive to total energy availability per se. Nevertheless, continental patterns in the bird-use days occurred principally in relation to wetland cover and agricultural habitat in the fall. Bird-use days were highest in both spring and fall in the Mississippi Alluvial Valley and along the coast and near-shore environments of South Carolina. Spatial sensitivity analyses suggested that locations nearer to migratory endpoints were less important to survivorship; for instance, removing energy from a 1,036 km2 stopover site at a time from the Atlantic Flyway suggested coastal areas between New Jersey and North Carolina, including Chesapeake Bay and the North Carolina piedmont, are

  20. Dendritic cell migration assay: a potential prediction model for identification of contact allergens.

    Science.gov (United States)

    Gibbs, Susan; Spiekstra, Sander; Corsini, Emanuela; McLeod, Julie; Reinders, Judith

    2013-04-01

    This manuscript describes methodology and a prediction model for the MUTZ-LC migration assay. The assay represents the physiological change in Langerhans cell (LC) behavior after exposure to a sensitizing chemical, resulting in LC migration from the epidermis to the dermis. MUTZ-LC are derived from the commercially available MUTZ-3 cell line. Upon exposure to a sensitizer MUTZ-LC migrate preferentially towards CXCL12 whereas upon exposure to a non-sensitizer MUTZ-LC migrate towards CCL5. A CXCL12/CCL5 ratio >1.10 in 2/3 independent experiments is indicative of a sensitizer, whereas a CXCL12/CCL5 ratio ≤1.10 is indicative of a non-sensitizer. At non cytotoxic chemical concentrations 9 sensitizers (2,4-dinitrochlorobenzene, paraphenylendiamine, cinnamaldehyde, isoeugenol, nickel-sulfate, tetramethylthiuram disulfide, eugenol, cinnamic-alcohol, ammonium-hexachloroplatinate) were distinguished from 4 non sensitizers (sodium lauryl sulfate, salicylic acid, phenol, octanoic acid). Critical points in assay performance are (i) MUTZ-3 passage number after thawing (p6-p40); (ii) cell viability (>80%); (iii) standard curve to optimize correlation of fluorescence with cell number; and (iv) optimization of the concentration of rhCXCL12 and rhCCL5 in transwell. The protocol has been tested in three European laboratories and results suggest that it may provide working conditions for performing the DC migration assay which is aimed at distinguishing sensitizers from non sensitizers. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Running and rotating: modelling the dynamics of migrating cell clusters

    Science.gov (United States)

    Copenhagen, Katherine; Gov, Nir; Gopinathan, Ajay

    Collective motion of cells is a common occurrence in many biological systems, including tissue development and repair, and tumor formation. Recent experiments have shown cells form clusters in a chemical gradient, which display three different phases of motion: translational, rotational, and random. We present a model for cell clusters based loosely on other models seen in the literature that involves a Vicsek-like alignment as well as physical collisions and adhesions between cells. With this model we show that a mechanism for driving rotational motion in this kind of system is an increased motility of rim cells. Further, we examine the details of the relationship between rim and core cells, and find that the phases of the cluster as a whole are correlated with the creation and annihilation of topological defects in the tangential component of the velocity field.

  2. Modeling a secular trend by Monte Carlo simulation of height biased migration in a spatial network.

    Science.gov (United States)

    Groth, Detlef

    2017-04-01

    Background: In a recent Monte Carlo simulation, the clustering of body height of Swiss military conscripts within a spatial network with characteristic features of the natural Swiss geography was investigated. In this study I examined the effect of migration of tall individuals into network hubs on the dynamics of body height within the whole spatial network. The aim of this study was to simulate height trends. Material and methods: Three networks were used for modeling, a regular rectangular fishing net like network, a real world example based on the geographic map of Switzerland, and a random network. All networks contained between 144 and 148 districts and between 265-307 road connections. Around 100,000 agents were initially released with average height of 170 cm, and height standard deviation of 6.5 cm. The simulation was started with the a priori assumption that height variation within a district is limited and also depends on height of neighboring districts (community effect on height). In addition to a neighborhood influence factor, which simulates a community effect, body height dependent migration of conscripts between adjacent districts in each Monte Carlo simulation was used to re-calculate next generation body heights. In order to determine the direction of migration for taller individuals, various centrality measures for the evaluation of district importance within the spatial network were applied. Taller individuals were favored to migrate more into network hubs, backward migration using the same number of individuals was random, not biased towards body height. Network hubs were defined by the importance of a district within the spatial network. The importance of a district was evaluated by various centrality measures. In the null model there were no road connections, height information could not be delivered between the districts. Results: Due to the favored migration of tall individuals into network hubs, average body height of the hubs, and later

  3. Mechano-sensing and cell migration: a 3D model approach

    International Nuclear Information System (INIS)

    Borau, C; García-Aznar, J M; Kamm, R D

    2011-01-01

    Cell migration is essential for tissue development in different physiological and pathological conditions. It is a complex process orchestrated by chemistry, biological factors, microstructure and surrounding mechanical properties. Focusing on the mechanical interactions, cells do not only exert forces on the matrix that surrounds them, but they also sense and react to mechanical cues in a process called mechano-sensing. Here, we hypothesize the involvement of mechano-sensing in the regulation of directional cell migration through a three-dimensional (3D) matrix. For this purpose, we develop a 3D numerical model of individual cell migration, which incorporates the mechano-sensing process of the cell as the main mechanism regulating its movement. Consistent with this hypothesis, we found that factors, such as substrate stiffness, boundary conditions and external forces, regulate specific and distinct cell movements

  4. A 3D Microfluidic Model to Recapitulate Cancer Cell Migration and Invasion

    Directory of Open Access Journals (Sweden)

    Yi-Chin Toh

    2018-04-01

    Full Text Available We have developed a microfluidic-based culture chip to simulate cancer cell migration and invasion across the basement membrane. In this microfluidic chip, a 3D microenvironment is engineered to culture metastatic breast cancer cells (MX1 in a 3D tumor model. A chemo-attractant was incorporated to stimulate motility across the membrane. We validated the usefulness of the chip by tracking the motilities of the cancer cells in the system, showing them to be migrating or invading (akin to metastasis. It is shown that our system can monitor cell migration in real time, as compare to Boyden chambers, for example. Thus, the chip will be of interest to the drug-screening community as it can potentially be used to monitor the behavior of cancer cell motility, and, therefore, metastasis, in the presence of anti-cancer drugs.

  5. Numerical Modeling Tools for the Prediction of Solution Migration Applicable to Mining Site

    International Nuclear Information System (INIS)

    Martell, M.; Vaughn, P.

    1999-01-01

    Mining has always had an important influence on cultures and traditions of communities around the globe and throughout history. Today, because mining legislation places heavy emphasis on environmental protection, there is great interest in having a comprehensive understanding of ancient mining and mining sites. Multi-disciplinary approaches (i.e., Pb isotopes as tracers) are being used to explore the distribution of metals in natural environments. Another successful approach is to model solution migration numerically. A proven method to simulate solution migration in natural rock salt has been applied to project through time for 10,000 years the system performance and solution concentrations surrounding a proposed nuclear waste repository. This capability is readily adaptable to simulate solution migration around mining

  6. Assessment of the Eu migration experiments and their modelling

    International Nuclear Information System (INIS)

    Klotz, D.

    2001-01-01

    The humic acid transport of heavy metals in underground water was investigated in laboratory experiments using the lanthanide Eu in the form of 152 Eu 3+ , which is both a model heavy metal and an indicator for assessing the potential hazards of ultimate storage sites for radioactive waste [de

  7. International Family Migration and the Dual-Earner Model

    DEFF Research Database (Denmark)

    Munk, Martin D.; Nikolka, Till; Poutvaara, Panu

    2018-01-01

    Gender differences in labor force participation are exceptionally small in Nordic countries. We investigate how couples emigrating from Denmark self-select and sort into different destinations and whether couples pursue the dual-earner model, in which both partners work, when abroad. Female labor...

  8. Modelling gas migration in compacted bentonite. A report produced for the GAMBIT club

    International Nuclear Information System (INIS)

    Nash, P.J.; Swift, B.T.; Goodfield, M.; Rodwell, W.R.

    1998-08-01

    This report describes the first phase of a programme of work that has as its overall objective the development of a computational model that can simulate the results of experiments on gas migration through highly compacted bentonite, and will provide the basis of a model suitable to assess the effects of bentonite barriers on the build-up of pressure and the escape of hydrogen gas from disposal canisters in a radioactive waste repository. In this first phase of the project, the possible mechanisms and controlling features of gas migration through compacted bentonite have been reviewed, and a preliminary computational model of the process has been implemented and evaluated. In the model it is assumed that gas invasion of the clay occurs by induced microfissuring, and that the permeability of the pathways thus created depends on the gas pressure (or the effective stress). Experimental data on gas migration in compacted bentonite that was collected under well controlled conditions by Horseman and Harrington was used in a preliminary evaluation of the new model. The model was able to reproduce qualitatively all the features seen in the subset of the experimental data used in the evaluation, and to provide quantitative agreement to substantial sections of the results of test sequences, but quantitative agreement between simulation and experimental results over a whole test sequence was not obtained. As part of the model evaluation, the dependence of the results obtained on key model parameters is reported. Outline plans for a further phase of work are suggested. (orig.)

  9. Modelling gas migration in compacted bentonite. A report produced for the GAMBIT club

    Energy Technology Data Exchange (ETDEWEB)

    Nash, P.J.; Swift, B.T.; Goodfield, M.; Rodwell, W.R. [AEA Technology plc, Dorchester (United Kingdom)

    1998-08-01

    This report describes the first phase of a programme of work that has as its overall objective the development of a computational model that can simulate the results of experiments on gas migration through highly compacted bentonite, and will provide the basis of a model suitable to assess the effects of bentonite barriers on the build-up of pressure and the escape of hydrogen gas from disposal canisters in a radioactive waste repository. In this first phase of the project, the possible mechanisms and controlling features of gas migration through compacted bentonite have been reviewed, and a preliminary computational model of the process has been implemented and evaluated. In the model it is assumed that gas invasion of the clay occurs by induced microfissuring, and that the permeability of the pathways thus created depends on the gas pressure (or the effective stress). Experimental data on gas migration in compacted bentonite that was collected under well controlled conditions by Horseman and Harrington was used in a preliminary evaluation of the new model. The model was able to reproduce qualitatively all the features seen in the subset of the experimental data used in the evaluation, and to provide quantitative agreement to substantial sections of the results of test sequences, but quantitative agreement between simulation and experimental results over a whole test sequence was not obtained. As part of the model evaluation, the dependence of the results obtained on key model parameters is reported. Outline plans for a further phase of work are suggested. (orig.) 32 refs.

  10. Modelling of 90Sr in-situ migration: models comparison and coupled soil characterisation

    International Nuclear Information System (INIS)

    Piault, E.; van Dorpe, F.; Cartalade, A.; Beaucaire, C.; Fernandez, J.M.

    2005-01-01

    Full text of publication follows: In 1960, the Institute of Nuclear Protection and Safety of the French Atomic Energy Commission (CEA/IPSN) had launched a research program to quantify the soil-plant transfer of 90 Sr (transfer between soils, grapes and wine). The studies were conducted in-situ with the help of the National Institute for Agronomic Research (INRA) on an experimental site of Mediterranean type. The experiments consisted in contaminating with soluble strontium salt solutions (SrCl 2 ) a 400 m 2 (10 m x 40 m) piece of land bordered by two uncontaminated strip used as blanks. Prior to planting, the superficial layer of the contaminated plot had then been ploughed in order to homogenize the contamination on a depth of about 10 cm. Over time, the radionuclide was transported from the surface layer to the underground layers of the plot due to climatic factors. The 90 Sr migration over the last 40 years was studied owing eight 70 cm deep cores to perform a radiological and physico-chemical characterization of the soil. The vertical migration modelling of 90 Sr required the definition of a triple layers model whose the only external factor of influence considered is the rainwater infiltration at constant flux. Simulations were made using the code PORFLOW and also the code CAST3M, developed by CEA. These codes solve calculations of flows in unsaturated porous media taking into account the sorption/desorption phenomena of chemical species and radioactive decay. To complete the study an estimation of 90 Sr K d sorption coefficient (used by transfer models) using ion-exchange model was carried out for each layers. The dependence of 90 Sr K d on competitor cations present in fluids is analysed. The study shows that the agreement between the experimental and simulated results is acceptable if the characterization steps, including sampling are properly undertaken. The necessity to characterize the site according to needs of numerical modelling, in an iterative cycle

  11. Decision-Making in Agent-Based Models of Migration: State of the Art and Challenges.

    Science.gov (United States)

    Klabunde, Anna; Willekens, Frans

    We review agent-based models (ABM) of human migration with respect to their decision-making rules. The most prominent behavioural theories used as decision rules are the random utility theory, as implemented in the discrete choice model, and the theory of planned behaviour. We identify the critical choices that must be made in developing an ABM, namely the modelling of decision processes and social networks. We also discuss two challenges that hamper the widespread use of ABM in the study of migration and, more broadly, demography and the social sciences: (a) the choice and the operationalisation of a behavioural theory (decision-making and social interaction) and (b) the selection of empirical evidence to validate the model. We offer advice on how these challenges might be overcome.

  12. Modelling of far-field gas migration from a deep radioactive waste repository

    International Nuclear Information System (INIS)

    Rodwell, W.R.; Nash, P.J.

    1992-01-01

    In assessing the post-closure safety of a deep radioactive waste repository, it is necessary to show that gas generated within the repository can migrate away, through the far-field geology, without affecting repository safety. This paper discusses the contribution of various mechanisms to gas migration through the far field; for example, diffusion of dissolved gas versus gas-phase movement, and bubble flow versus formation of a connected gas stream. It outlines different approaches to modelling gas movement from a repository, with simple semi-analytical models furnishing physical insights into the factors controlling gas migration in the absence of directly applicable experimental data, and more comprehensive numerical computations allowing the exploration of more detailed behaviour when appropriate data is obtained. If gas can induce groundwater movement, this could accelerate the transport of water-borne contaminants. Processes by which this could occur are noted, and the current status of work on possible effects of gas migration on groundwater movement in fractured hard rocks is indicated. 14 refs., 4 figs

  13. Application of Geographic Information System (GIS) to Model the Hydrocarbon Migration: Case Study from North-East Malay Basin, Malaysia

    Science.gov (United States)

    Rudini; Nasir Matori, Abd; Talib, Jasmi Ab; Balogun, Abdul-Lateef

    2018-03-01

    The purpose of this study is to model the migration of hydrocarbon using Geographic Information System (GIS). Understanding hydrocarbon migration is important since it can mean the difference between success and failure in oil and gas exploration project. The hydrocarbon migration modeling using geophysical method is still not accurate due to the limitations of available data. In recent years, GIS has emerged as a powerful tool for subsurface mapping and analysis. Recent studies have been carried out about the abilities of GIS to model hydrocarbon migration. Recent advances in GIS support the establishment and monitoring of prediction hydrocarbon migration. The concept, model, and calculation are based on the current geological situation. The spatial data of hydrocarbon reservoirs is determined by its geometry of lithology and geophysical attributes. Top of Group E horizon of north-east Malay basin was selected as the study area due to the occurrence of hydrocarbon migration. Spatial data and attributes data such as seismic data, wells log data and lithology were acquired and processed. Digital Elevation Model (DEM) was constructed from the selected horizon as a result of seismic interpretation using the Petrel software. Furthermore, DEM was processed in ArcGIS as a base map to shown hydrocarbon migration in north-east Malay Basin. Finally, all the data layers were overlaid to produce a map of hydrocarbon migration. A good data was imported to verify the model is correct.

  14. Application of Geographic Information System (GIS to Model the Hydrocarbon Migration: Case Study from North-East Malay Basin, Malaysia

    Directory of Open Access Journals (Sweden)

    Rudini

    2018-01-01

    Full Text Available The purpose of this study is to model the migration of hydrocarbon using Geographic Information System (GIS. Understanding hydrocarbon migration is important since it can mean the difference between success and failure in oil and gas exploration project. The hydrocarbon migration modeling using geophysical method is still not accurate due to the limitations of available data. In recent years, GIS has emerged as a powerful tool for subsurface mapping and analysis. Recent studies have been carried out about the abilities of GIS to model hydrocarbon migration. Recent advances in GIS support the establishment and monitoring of prediction hydrocarbon migration. The concept, model, and calculation are based on the current geological situation. The spatial data of hydrocarbon reservoirs is determined by its geometry of lithology and geophysical attributes. Top of Group E horizon of north-east Malay basin was selected as the study area due to the occurrence of hydrocarbon migration. Spatial data and attributes data such as seismic data, wells log data and lithology were acquired and processed. Digital Elevation Model (DEM was constructed from the selected horizon as a result of seismic interpretation using the Petrel software. Furthermore, DEM was processed in ArcGIS as a base map to shown hydrocarbon migration in north-east Malay Basin. Finally, all the data layers were overlaid to produce a map of hydrocarbon migration. A good data was imported to verify the model is correct.

  15. Application of simplified models to CO2 migration and immobilization in large-scale geological systems

    KAUST Repository

    Gasda, Sarah E.

    2012-07-01

    Long-term stabilization of injected carbon dioxide (CO 2) is an essential component of risk management for geological carbon sequestration operations. However, migration and trapping phenomena are inherently complex, involving processes that act over multiple spatial and temporal scales. One example involves centimeter-scale density instabilities in the dissolved CO 2 region leading to large-scale convective mixing that can be a significant driver for CO 2 dissolution. Another example is the potentially important effect of capillary forces, in addition to buoyancy and viscous forces, on the evolution of mobile CO 2. Local capillary effects lead to a capillary transition zone, or capillary fringe, where both fluids are present in the mobile state. This small-scale effect may have a significant impact on large-scale plume migration as well as long-term residual and dissolution trapping. Computational models that can capture both large and small-scale effects are essential to predict the role of these processes on the long-term storage security of CO 2 sequestration operations. Conventional modeling tools are unable to resolve sufficiently all of these relevant processes when modeling CO 2 migration in large-scale geological systems. Herein, we present a vertically-integrated approach to CO 2 modeling that employs upscaled representations of these subgrid processes. We apply the model to the Johansen formation, a prospective site for sequestration of Norwegian CO 2 emissions, and explore the sensitivity of CO 2 migration and trapping to subscale physics. Model results show the relative importance of different physical processes in large-scale simulations. The ability of models such as this to capture the relevant physical processes at large spatial and temporal scales is important for prediction and analysis of CO 2 storage sites. © 2012 Elsevier Ltd.

  16. Environmental risk index: A tool to assess the safety of dams for leachate

    International Nuclear Information System (INIS)

    Colomer Mendoza, Francisco J.; Gallardo Izquierdo, Antonio

    2009-01-01

    Dams for leachate store very toxic substances that contain a large amount of organic material and, probably, heavy metals; they therefore constitute an important threat to the environment. Existing models of environmental risk assessment for landfills do not take into consideration the specific risk that leachate dams may represent for the environment. In this paper a methodology to improve the environmental safety is presented according to the parameters used in their construction and management. In order to do that, the following characteristics of the dam must be known: (1) geotechnical stability, (2) erosion of downstream slope, (3) type of sealing of the dam, (4) overtopping probability, (5) volume of leachate stored inside the dam and (6) pollution load of leachate. Once these parameters have been calculated, they are transformed by means of rating curves into homogeneous units, so as to make it possible to operate between them. From the study and analysis of these parameters an environmental risk index for a dam for leachate can be calculated. If the environmental risk index exceeds an established value then it involves a dam for leachate with high environmental risk, therefore preventive measures in its design, construction and management would be necessary

  17. Modelling the effect of diffusion into the rock matrix on radionuclide migration

    International Nuclear Information System (INIS)

    Lever, D.A.; Bradbury, M.H.; Hemingway, S.J.

    1983-01-01

    Diffusion into the rock matrix is potentially an important retardation mechanism for nuclides leached from an underground radioactive waste repository in a fractured hard rock. Models of this diffusion process are discussed and incorporated into three-dimensional radionuclide migration models. Simple solutions to these models are derived for two regions: the region near to the repository where the nuclide is diffusing into effectively infinite rock, and that much further downstream where the concentrations in the rock and fractures are almost in equilibrium. These solutions are used to evaluate the possible impact on migration. It is shown that retardation factors in excess of 100 and reductions in the peak concentration at a given point on the flow path by three or four orders of magnitude are possibe for non-sorbed ions, which would otherwise be carried by the flow and not retarded at all. (author)

  18. Biosorption of gold from computer microprocessor leachate solutions using chitin.

    Science.gov (United States)

    Côrtes, Letícia N; Tanabe, Eduardo H; Bertuol, Daniel A; Dotto, Guilherme L

    2015-11-01

    The biosorption of gold from discarded computer microprocessor (DCM) leachate solutions was studied using chitin as a biosorbent. The DCM components were leached with thiourea solutions, and two procedures were tested for recovery of gold from the leachates: (1) biosorption and (2) precipitation followed by biosorption. For each procedure, the biosorption was evaluated considering kinetic, equilibrium, and thermodynamic aspects. The general order model was able to represent the kinetic behavior, and the equilibrium was well represented by the BET model. The maximum biosorption capacities were around 35 mg g(-1) for both procedures. The biosorption of gold on chitin was a spontaneous, favorable, and exothermic process. It was found that precipitation followed by biosorption resulted in the best gold recovery, because other species were removed from the leachate solution in the precipitation step. This method enabled about 80% of the gold to be recovered, using 20 g L(-1) of chitin at 298 K for 4 h. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Domestic wells have high probability of pumping septic tank leachate

    Science.gov (United States)

    Bremer, J. E.; Harter, T.

    2012-08-01

    Onsite wastewater treatment systems are common in rural and semi-rural areas around the world; in the US, about 25-30% of households are served by a septic (onsite) wastewater treatment system, and many property owners also operate their own domestic well nearby. Site-specific conditions and local groundwater flow are often ignored when installing septic systems and wells. In areas with small lots (thus high spatial septic system densities), shallow domestic wells are prone to contamination by septic system leachate. Mass balance approaches have been used to determine a maximum septic system density that would prevent contamination of groundwater resources. In this study, a source area model based on detailed groundwater flow and transport modeling is applied for a stochastic analysis of domestic well contamination by septic leachate. Specifically, we determine the probability that a source area overlaps with a septic system drainfield as a function of aquifer properties, septic system density and drainfield size. We show that high spatial septic system density poses a high probability of pumping septic system leachate. The hydraulic conductivity of the aquifer has a strong influence on the intersection probability. We find that mass balance calculations applied on a regional scale underestimate the contamination risk of individual drinking water wells by septic systems. This is particularly relevant for contaminants released at high concentrations, for substances that experience limited attenuation, and those that are harmful even at low concentrations (e.g., pathogens).

  20. Domestic wells have high probability of pumping septic tank leachate

    Directory of Open Access Journals (Sweden)

    J. E. Bremer

    2012-08-01

    Full Text Available Onsite wastewater treatment systems are common in rural and semi-rural areas around the world; in the US, about 25–30% of households are served by a septic (onsite wastewater treatment system, and many property owners also operate their own domestic well nearby. Site-specific conditions and local groundwater flow are often ignored when installing septic systems and wells. In areas with small lots (thus high spatial septic system densities, shallow domestic wells are prone to contamination by septic system leachate. Mass balance approaches have been used to determine a maximum septic system density that would prevent contamination of groundwater resources. In this study, a source area model based on detailed groundwater flow and transport modeling is applied for a stochastic analysis of domestic well contamination by septic leachate. Specifically, we determine the probability that a source area overlaps with a septic system drainfield as a function of aquifer properties, septic system density and drainfield size. We show that high spatial septic system density poses a high probability of pumping septic system leachate. The hydraulic conductivity of the aquifer has a strong influence on the intersection probability. We find that mass balance calculations applied on a regional scale underestimate the contamination risk of individual drinking water wells by septic systems. This is particularly relevant for contaminants released at high concentrations, for substances that experience limited attenuation, and those that are harmful even at low concentrations (e.g., pathogens.

  1. Characterization and treatment of municipal landfill leachates

    Energy Technology Data Exchange (ETDEWEB)

    Welander, Ulrika

    1998-03-01

    The efficiency of different leachate treatment methods for the removal of refractory organic compounds and ammonium-nitrogen was investigated. The methods evaluated were nitrification, denitrification, adsorption onto activated carbon, precipitation by ferric chloride or aluminum sulphate and oxidation by ozone or Fenton`s reagent. Furthermore, analyses were performed on leachates from municipal landfills of different kinds (a biocell deposit, a conventional mixed landfill containing household and industrial waste, and an ash deposit) in order to study the leachate composition in regard to various hydrophobic organic compounds as a function of the type of waste deposited. The results suggested that, in order to achieve a satisfactory removal of both ammonium-nitrogen and organic substances, the treatment of methanogenic leachates should be performed through a process combining biological and physical or chemical stages. When the biological treatment was not combined with a physical or a chemical process a COD removal of only 20-30% was achieved, whereas the toxicity of the leachate was significantly reduced. In contrast, a combination of nitrification and either adsorption onto activated carbon or oxidation using Fenton`s reagent resulted in a COD removal of about 80%, although certain specific organic compounds, such as phthalates, were unaffected by the treatment. A combination of nitrification, precipitation by ferric chloride and adsorption onto activated carbon removed 96% of the TOC. The analyses of leachates from municipal landfills of different types showed the leachate from the ash deposit to contain more C4-substituted phenols than the other leachates and to likewise contain alkanes, which the others did not 154 refs, 12 figs, 4 tabs

  2. Forty years of 9Sr in situ migration: importance of soil characterization in modeling transport phenomena

    International Nuclear Information System (INIS)

    Fernandez, J.M.; Piault, E.; Macouillard, D.; Juncos, C.

    2006-01-01

    In 1960 experiments were carried out on the transfer of 9 Sr between soil, grapes and wine. The experiments were conducted in situ on a piece of land limited by two control strips. The 9 Sr migration over the last 40 years was studied by performing radiological and physico-chemical characterizations of the soil on eight 70 cm deep cores. The vertical migration modeling of 9 Sr required the definition of a triple layer conceptual model integrating the rainwater infiltration at constant flux as the only external factor of influence. Afterwards the importance of a detailed soil characterization for modeling was discussed and satisfactory simulation of the 9 Sr vertical transport was obtained and showed a calculated migration rate of about 1.0 cm year -1 in full agreement with the in situ measured values. The discussion was regarding some of the key parameters such as granulometry, organic matter content (in the Van Genuchten parameter determination), Kd and the efficient rainwater infiltration. Besides the experimental data, simplifying assumptions in modeling such as water-soil redistribution calculation and factual discontinuities in conceptual model were examined

  3. Fully coupled modeling of radionuclide migration in a clayey rock disturbed by alkaline plume

    International Nuclear Information System (INIS)

    Pellegrni, D.; Windt, L. de; Lee, J.V.D.

    2002-03-01

    The disposal of radioactive wastes in clayey formations may require the use of large amounts of concrete and cement as a barrier to minimize corrosion of steel containers and radionuclide migration and for supporting drifts and disposal vaults. In this context, reactive transport modeling of the interactions between cement or concrete and the argillaceous host rock aims at estimating the evolution in time of the containment properties of the multi-barriers system. The objectives of the paper are to demonstrate that integrating radionuclides migration in the modeling of strongly coupled geochemical processes of cement-clay stone interactions is feasible and that it represents an efficient way to assess the sensitivity and modification of the classical Kd and solubility parameters with respect to the chemical evolutions. Two types of modeling are considered in the paper: i): calculation of intrinsic solubility limits and Kd values backing up on the results of modeling of cement/clay stone interactions (radionuclides are assumed to be present over the whole domain at any time whatever the scenario), ii) full mechanistic modeling which explicitly introduces radionuclides in the calculation with ad hoc assumptions on radionuclide inventory, canister failure, migration pathway, etc. The reactive transport code HYTEC, based on the geochemical code CHESS, is used to simulate both the cement-clay stone interaction processes and the radionuclide migration in 1-D and 2-D configurations. Convective/dispersive and diffuse transport can be simulated for solutes and colloids. A wide range of processes such as aqueous chemistry, redox, dissolution/precipitation, surface complexation and ion exchange can be modeled at equilibrium or with kinetic control. In addition, HYTEC is strongly coupled, i.e. the hydrology (flow and diffusion) may change when mineral precipitation or dissolution changes the local porosity. (authors)

  4. Agent-Based Approach for Modelling the Labour Migration from China to Russia

    Directory of Open Access Journals (Sweden)

    Valeriy Leonidovich Makarov

    2017-06-01

    Full Text Available The article describes the process of labour migration from China to Russia and shows its modelling using the agent-based approach. This approach allows us to simulate an artificial society in a computer program taking into account the diversity of individuals under consideration, as well as to model a set of laws and rules of conduct that make up the institutional environment in which the members of this society live. A brief review and analysis of agent-based migration models presented in the foreign literature are given. The agent-based model of labour migration from China to Russia developed by the Central Economic Mathematical Institute of the Russian Academy of Sciences simulates human behaviour close to reality, which is based on their internal purposes, determining the agents choice of territory as a place of residence. Therefore, at the development of the agents of the model and their behaviour algorithms, as well as the organization of the environment in which they exist and interact, the main characteristics of the population of two neighbouring countries and their demographic processes have been considered. Using the model, two experiments have been conducted. The purpose of the first of them was to assess the effect of depreciation of the rubble against the yuan on the overall indexes of labour migration, as well as its structure. In the second experiment, the procedure of the search of the information by agents for the migratory decision-making was changing. Namely, all generalizing information on the average salary by types of activity and skill level of employees, both in China and Russia, became available to all agents irrespective of their qualification level.

  5. Magnetic and Electrical Properties of Leachate

    Directory of Open Access Journals (Sweden)

    Kartika Kirana

    2011-11-01

    Full Text Available Heavy metals content as well as magnetic and electrical properties of leachate from Sarimukti, West Java were studied in an attempt to seek correlation between heavy metals content and magnetic/electrical properties. Such correlation is expected to open the way for the use of magnetic/electrical properties as proxy indicators for the concentration of heavy metals in the leachate. The number of leachate samples studied is 21; 15 were taken spatially at depth of 1 m while the remaining 6 samples were taken vertically at a particular point. Measurement results showed that the heavy metals content in the leachate has a smaller concentration, except for Fe. The correlation between magnetic susceptibility and heavy metals content was found to be not so significant. The best correlation coefficient between magnetic susceptibility with heavy metals in leachate was found in Zn. Correlation between electrical conductivity and heavy metal is also not so significant, except for Zn and Cd. The use of magnetic properties as proxy indicator for heavy metals content in leachate is plausible provided that the magnetic susceptibility exceeds certain threshold value. Correlation between magnetic susceptibility, electrical conductivity and heavy metal content would be good if each quantity has a large value.

  6. Agent-Based Modeling of China's Rural-Urban Migration and Social Network Structure.

    Science.gov (United States)

    Fu, Zhaohao; Hao, Lingxin

    2018-01-15

    We analyze China's rural-urban migration and endogenous social network structures using agent-based modeling. The agents from census micro data are located in their rural origin with an empirical-estimated prior propensity to move. The population-scale social network is a hybrid one, combining observed family ties and locations of the origin with a parameter space calibrated from census, survey and aggregate data and sampled using a stepwise Latin Hypercube Sampling method. At monthly intervals, some agents migrate and these migratory acts change the social network by turning within-nonmigrant connections to between-migrant-nonmigrant connections, turning local connections to nonlocal connections, and adding among-migrant connections. In turn, the changing social network structure updates migratory propensities of those well-connected nonmigrants who become more likely to move. These two processes iterate over time. Using a core-periphery method developed from the k -core decomposition method, we identify and quantify the network structural changes and map these changes with the migration acceleration patterns. We conclude that network structural changes are essential for explaining migration acceleration observed in China during the 1995-2000 period.

  7. Basics elements for modelling the dynamics of cell migration in cell culture

    International Nuclear Information System (INIS)

    FarIas, Ro; Vidal, Cs; Rapacioli, M; Flores, V

    2007-01-01

    This paper introduces some basic elements for modelling the dynamics of cell migration activity over a bi-dimensional substratum. A square matrix, representing the substratum, is implemented in order to generate virtual cells with an initial random uniform distribution, with the ability to freely move within the matrix and to interact with each others by mean of adhesive forces. Two different conditions were examined: A) cells can freely move and after contacting with another cell they both completely inhibit their migration; B) cells that come into contact have the ability to rotate respect to each other without losing their contacts and retaining the ability to move together but at a slower rate, being the decrease in the rate of movement proportional to the number of contacting cells. The dynamics of the migration process in these two conditions was evaluated by recording the evolution of several parameters as a function of time. Minor modifications in some parameters (mobility, intensity of cell-cell and cell-substratum adhesiveness) significantly change the dynamics and the final result of the virtual migrating cells

  8. A pilot study to assess adductor canal catheter tip migration in a cadaver model.

    Science.gov (United States)

    Leng, Jody C; Harrison, T Kyle; Miller, Brett; Howard, Steven K; Conroy, Myles; Udani, Ankeet; Shum, Cynthia; Mariano, Edward R

    2015-04-01

    An adductor canal catheter may facilitate early ambulation after total knee arthroplasty, but there is concern over preoperative placement since intraoperative migration of catheters may occur from surgical manipulation and result in ineffective analgesia. We hypothesized that catheter type and subcutaneous tunneling may influence tip migration for preoperatively inserted adductor canal catheters. In a male unembalmed human cadaver, 20 catheter insertion trials were divided randomly into one of four groups: flexible epidural catheter either tunneled or not tunneled; or rigid stimulating catheter either tunneled or not tunneled. Intraoperative patient manipulation was simulated by five range-of-motion exercises of the knee. Distance and length measurements were performed by a blinded regional anesthesiologist. Changes in catheter tip to nerve distance (p = 0.225) and length of catheter within the adductor canal (p = 0.467) were not different between the four groups. Two of five non-tunneled stimulating catheters (40 %) were dislodged compared to 0/5 in all other groups (p = 0.187). A cadaver model may be useful for assessing migration of regional anesthesia catheters; catheter type and subcutaneous tunneling may not affect migration of adductor canal catheters based on this preliminary study. However, future studies involving a larger sample size, actual patients, and other catheter types are warranted.

  9. Agent-based modeling of China's rural-urban migration and social network structure

    Science.gov (United States)

    Fu, Zhaohao; Hao, Lingxin

    2018-01-01

    We analyze China's rural-urban migration and endogenous social network structures using agent-based modeling. The agents from census micro data are located in their rural origin with an empirical-estimated prior propensity to move. The population-scale social network is a hybrid one, combining observed family ties and locations of the origin with a parameter space calibrated from census, survey and aggregate data and sampled using a stepwise Latin Hypercube Sampling method. At monthly intervals, some agents migrate and these migratory acts change the social network by turning within-nonmigrant connections to between-migrant-nonmigrant connections, turning local connections to nonlocal connections, and adding among-migrant connections. In turn, the changing social network structure updates migratory propensities of those well-connected nonmigrants who become more likely to move. These two processes iterate over time. Using a core-periphery method developed from the k-core decomposition method, we identify and quantify the network structural changes and map these changes with the migration acceleration patterns. We conclude that network structural changes are essential for explaining migration acceleration observed in China during the 1995-2000 period.

  10. Modeled microgravity suppressed invasion and migration of human glioblastoma U87 cells through downregulating store-operated calcium entry

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Zi-xuan [Department of Traditional Chinese Medicine, Xijing Hospital, Fourth Military Medical University, Xi' an, 710032 (China); Rao, Wei [Department of Neurosurgery, Xijing Hospital, Fourth Military Medical University, Xi' an, 710032 (China); Wang, Huan [Department of Dermatology, Tangdu Hospital, Fourth Military Medical University, Xi' an, 710032 (China); Wang, Nan-ding [Department of Cardiology, Xi' an Traditional Chinese Medicine Hospital, Xi' an, 710032 (China); Si, Jing-Wen; Zhao, Jiao; Li, Jun-chang [Department of Traditional Chinese Medicine, Xijing Hospital, Fourth Military Medical University, Xi' an, 710032 (China); Wang, Zong-ren, E-mail: zongren@fmmu.edu.cn [Department of Traditional Chinese Medicine, Xijing Hospital, Fourth Military Medical University, Xi' an, 710032 (China)

    2015-02-13

    Glioblastoma is the most common brain tumor and is characterized with robust invasion and migration potential resulting in poor prognosis. Previous investigations have demonstrated that modeled microgravity (MMG) could decline the cell proliferation and attenuate the metastasis potential in several cell lines. In this study, we studied the effects of MMG on the invasion and migration potentials of glioblastoma in human glioblastoma U87 cells. We found that MMG stimulation significantly attenuated the invasion and migration potentials, decreased thapsigargin (TG) induced store-operated calcium entry (SOCE) and downregulated the expression of Orai1 in U87 cells. Inhibition of SOCE by 2-APB or stromal interaction molecule 1 (STIM1) downregulation both mimicked the effects of MMG on the invasion and migration potentials in U87 cells. Furthermore, upregulation of Orai1 significantly weakened the effects of MMG on the invasion and migration potentials in U87 cells. Therefore, these findings indicated that MMG stimulation inhibited the invasion and migration potentials of U87 cells by downregulating the expression of Orai1 and sequentially decreasing the SOCE, suggesting that MMG might be a new potential therapeutic strategy in glioblastoma treatment in the future. - Highlights: • Modeled microgravity (MMG) suppressed migration and invasion in U87 cells. • MMG downregulated the SOCE and the expression of Orai1. • SOCE inhibition mimicked the effects of MMG on migration and invasion potentials. • Restoration of SOCE diminished the effects of MMG on migration and invasion.

  11. Modeled microgravity suppressed invasion and migration of human glioblastoma U87 cells through downregulating store-operated calcium entry

    International Nuclear Information System (INIS)

    Shi, Zi-xuan; Rao, Wei; Wang, Huan; Wang, Nan-ding; Si, Jing-Wen; Zhao, Jiao; Li, Jun-chang; Wang, Zong-ren

    2015-01-01

    Glioblastoma is the most common brain tumor and is characterized with robust invasion and migration potential resulting in poor prognosis. Previous investigations have demonstrated that modeled microgravity (MMG) could decline the cell proliferation and attenuate the metastasis potential in several cell lines. In this study, we studied the effects of MMG on the invasion and migration potentials of glioblastoma in human glioblastoma U87 cells. We found that MMG stimulation significantly attenuated the invasion and migration potentials, decreased thapsigargin (TG) induced store-operated calcium entry (SOCE) and downregulated the expression of Orai1 in U87 cells. Inhibition of SOCE by 2-APB or stromal interaction molecule 1 (STIM1) downregulation both mimicked the effects of MMG on the invasion and migration potentials in U87 cells. Furthermore, upregulation of Orai1 significantly weakened the effects of MMG on the invasion and migration potentials in U87 cells. Therefore, these findings indicated that MMG stimulation inhibited the invasion and migration potentials of U87 cells by downregulating the expression of Orai1 and sequentially decreasing the SOCE, suggesting that MMG might be a new potential therapeutic strategy in glioblastoma treatment in the future. - Highlights: • Modeled microgravity (MMG) suppressed migration and invasion in U87 cells. • MMG downregulated the SOCE and the expression of Orai1. • SOCE inhibition mimicked the effects of MMG on migration and invasion potentials. • Restoration of SOCE diminished the effects of MMG on migration and invasion

  12. MODELLING OF RADIONUCLIDE MIGRATION IN THE SYSTEM OF NUCLEAR POWER PLANT BIOLOGICAL PONDS

    Directory of Open Access Journals (Sweden)

    Ю. Кутлахмедов

    2011-04-01

    Full Text Available Migration of radionuclide coming from nuclear power plant into the system of biological pondsand then into the water reservoir-cooler is considered in the article. The theme of the work ismodeling of radionuclide migration process in the system of biological ponds on the example of thePivdennoukrainska nuclear power plant using chamber models method. Typical water ecosystemconsisting of three chambers (chamber-water, chamber-biota and chamber-bed silt was the basistaken by the authors. Application of chamber models method allowed authors to develop thedynamic chamber model of radionuclide migration in nuclear power plant biological ponds. Thismodel allows to forecast values and dynamics of radioactive water pollution based on limitedecosystem monitoring data. Thus, parameters of radioactive capacity of nuclear power plantbiological ponds system and water reservoir-cooler were modeled by authors, the estimation andprognosis of radionuclide distribution and accumulation in the system of nuclear power plantbiological ponds were done. Authors also explain the roles of basin water, biomass and bed silt inradionuclide deposition

  13. Programme of research into the management and storage of radioactive waste, nuclide migration studies, and mathematical modelling

    International Nuclear Information System (INIS)

    1982-01-01

    The progress of the work is reported under the headings: nuclide migration studies (nuclide-rock interactions; physico-chemical effects; field experiments; groundwater dating); mathematical modelling (calculation of steady groundwater flow using NAMMU; comparison of thermally and naturally driven flows near a radioactive waste repository; diffusion of radionuclides into a rock matrix; radionuclide migration). (U.K.)

  14. Radionuclide migration experiments related to an underground nuclear test: II. modeling studies

    International Nuclear Information System (INIS)

    Tompson, A.; Carle, S.F.; Smith, D.K.; Hudson, G.B.; Bruton, C.J.

    2001-01-01

    Full text: The goal of this project is to improve our understanding of water and radionuclide migration in both saturated and unsaturated geologic media by coupling advanced simulation techniques, available characterization data, and radioanalytical measurements in the context of a remarkable field experiment. Between 1975 and 1991, groundwater was steadily pumped from a well adjacent to a 1965 underground test conducted in alluvium at the Nevada Test Site. The experiment was primarily conducted in order to elicit information on radionuclide migration through the saturated zone between the test and the well. The effluent was monitored. discharged to an unlined ditch, and allowed to infiltrate into the ground during flow towards a dry lake, about a kilometer away. The 16 years of pumping and infiltration created an unexpected second experiment in which the migration of the ditch effluent through the 200 meters of unsaturated media, back to the water table, could be studied. Pumping and effluent data are being utilized in conjunction with chemical measurements made in groundwater and a series of numerical models to better understand the movement of radionuclides in the system, both between the test and the well, and between the ditch and the water table. The release of radionuclides away from a testing area will be controlled by local groundwater flow rates, by their dissolution from solidified melt glass produced by the test, and by chemical sorption processes that retard their migration rates in chemically reactive geologic media. Only the more mobile and less reactive radionuclides (e.g.. tritium, 14 C, 36 Cl, 85 Kr, and 129 I) were measured in the well effluent. The movement of these radionuclides through the unsaturated media beneath the ditch will be affected additionally by the capillary nature of moisture movement under unsaturated conditions and by their interaction with and potential mass exchange with the gas (air) phase. Results of numerical simulations

  15. First Principles Modeling and Interpretation of Ionization-Triggered Charge Migration in Molecules

    Science.gov (United States)

    Bruner, Adam; Hernandez, Sam; Mauger, Francois; Abanador, Paul; Gaarde, Mette; Schafer, Ken; Lopata, Ken

    Modeling attosecond coherent charge migration in molecules is important for understanding initial steps of photochemistry and light harvesting processes. Ionization triggered hole migration can be difficult to characterize and interpret as the dynamics can be convoluted with excited states. Here, we introduce a real-time time-dependent density functional theory (RT-TDDFT) approach for modeling such dynamics from first principles. To isolate the specific hole dynamics from excited states, Fourier transform analysis and orbital occupations are used to provide a spatial hole representation in the frequency domain. These techniques are applied to hole transfer across a thiophene dimer as well as core-hole triggered valence motion in nitrosobenzene. This work was supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award No. DE-SC0012462.

  16. Application of in silico modelling to estimate toxicity of migrating substances from food packaging.

    Science.gov (United States)

    Price, Nicholas; Chaudhry, Qasim

    2014-09-01

    This study derived toxicity estimates for a set of 136 chemical migrants from food packaging materials using in silico (computational) modelling and read across approaches. Where available, the predicted results for mutagenicity and carcinogenicity were compared with published experimental data. As the packaging compounds are subject to safety assessment, the migrating substances were more likely to be negative for both the endpoints. A set of structural analogues with positive experimental data for carcinogenicity and/or mutagenicity was therefore used as a positive comparator. The results showed that a weight of evidence assembled from different in silico models and read-across from already-tested structurally similar compounds can provide a rapid and reliable means for rapid screening of new yet-untested intentional or unintentional chemical compounds that may migrate to packaged foodstuffs. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

  17. Application of centrifuge modelling and radiotracers to migration studies of buried toxic waste

    International Nuclear Information System (INIS)

    Villar, H.P.

    1995-01-01

    A new technique to study the migration of souble waste components in soils, based on the application of centrifugue modelling and of selected short-lived radiotracers, is presented. The technique is based on the acceleration of the migration proceses of a specific tracer in a soil model, with simple and well-established scaling laws being used to interpret the results. The use of radiotracers allows geat flexibility and the adoption of a wide range of concentrations. Demosntrations of the technique have been carried out with two elements of radically distinct behaviour: iodine noted for its mobility in soils, and thallium, which tends to be strongly sorbed. Two different soil types have been used. The results semed to confirm what is known about the behaviour of both elements, so that the feasibility of the technique for such studies has been concluded. (author). 7 refs, 4 figs, 1 tab

  18. Regional Intergration and Migration: An Economic Geography Model with Hetergenous Labour Force

    OpenAIRE

    Nicola D. Coniglio

    2002-01-01

    This paper aims to analyse the effect of deepening regional integration on the incentive for factors of production, in particular labour, to spatially relocate. We adopt a general equilibrium, economic-geography model built on Krugman (1991) allowing for skill heterogeneity in the manufacturing sector. At a given level of trade costs, due to the productivity premium associated with the concentration of high-skilled workers in one region, this type of worker will be more willing to migrate tha...

  19. 3D Modelling, Animation and Simulation of Mammal’s Migration Across Roads

    Directory of Open Access Journals (Sweden)

    Talapka Jozef

    2016-05-01

    Full Text Available The presented article is dealing with the new methods which are designated for data collection of mammals migrating across traffic networks. Nowadays, road construction and securing of older roads is usually accompanied by finding new solutions. Because of lack of collected data we have new opportunities how we can collect this input. The article below describes the most efficient method which is suitable for the model creation, process of creation and issues which are connected with the creation of simulations.

  20. Modeling the nuclide migration and dose estimating using GoldSim

    International Nuclear Information System (INIS)

    Xiong Xiaowei

    2010-01-01

    Nuclide migration of the high-level waste (HLW) repository in the near-and far-field as well as a transport through a biosphere under reference scenario has been modeled by utilizing GoldSim. The concept design of engineered barrier system (EBS), geosphere and biosphere characteristics are derived from H12 in Japan. The calculated results are consistent with H12 report, which can be considered as technical basis for the safety assessment of China HLW disposal. (authors)

  1. Fine element (F.E.) modelling of hydrogen migration and blister formation in PHWR coolant channels

    International Nuclear Information System (INIS)

    Prasad, P.S.; Dutta, B.K.; Sinha, R.K.; Kushwaha, H.S.; Mahajan, S.C.; Kakodkar, A.

    1995-01-01

    The formation of a cold spot in pressure tube due to its contact with calandria tube of PHWR coolant results in the migration of Hydrogen in pressure tube towards contact zone from its surrounding material. A 3-D finite element code SPARSH is developed to model the hydrogen redistribution and consequent hydride blister formation due to thermal and Hydrogen concentration gradients. In the present paper, the details and performance of this code are presented. (author). 6 refs., 2 figs

  2. Leaching of chromium from chromium contaminated soil: Speciation study and geochemical modeling

    Directory of Open Access Journals (Sweden)

    Anđelković Darko H.

    2012-01-01

    Full Text Available Distribution of chromium between soil and leachate was monitored. A natural process of percolating rainwater through the soil was simulated in the laboratory conditions and studied with column leaching extraction. Migration of chromium in the soil is conditioned by the level of chromium soil contamination, the soil organic matter content, and rainwater acidity. Chromium (III and chromium(VI were determined by spectrophotometric method with diphenilcarbazide in acidic media. Comparing the results of chromium speciation in leachate obtained by experimental model systems and geochemical modelling calculations using Visual MINTEQ model, a correlation was observed regarding the influence of the tested parameters. Leachate solutions showed that the concentration of Cr depended on the organic matter content. The influence of pH and soil organic matter content is in compliance after its definition through experimental and theoretical way. The computer model - Stockholm Humic Model used to evaluate the leaching results corresponded rather well with the measured values.

  3. Emissions and leachate recycling at Seutula landfill

    International Nuclear Information System (INIS)

    Nykaenen, V.

    1999-01-01

    The aim of this study was to examine the degradation process and the leachate and gas emissions at Seutula landfill Vantaa The influences on leachate recycling to gas production and on the power production and also the influences on landfill water and the quality of leachate was found out. The situation at the landfill before leachate recirculation was studied. In the literature part of this study the landfill gas generation, different phases of the landfill and factors effecting them were examined. The quality of leachate, leachate recirculation and advantages of recirculation were studied. Different kind of gas collection methods, gas utilization, advantages and disadvantages of gas collection and the future of utilization were studied. Methods for measuring methane emissions through the landfill surface was a central part of the literature section. Also the future of measuring techniques were studied. In the experimental part of this study the quantity and quality of collected gas were measured. Also emitted methane was measured. Water samples were taken from landfill water and leachate during 1998. Samples were analysed in situ and in laboratory. The changes of landfill water height were measured. The degradation phase of the landfill varied, a part of waste filling was in an acidogenic phase and most part of it was in a stable methanogenic phase because the landfill is not homogenous. The concentration of landfill water and leachate are about the same than in Finland average. The most remarkable correlation from analysed results was between BOD/COD-ratio and temperature. When the temperature increased, the BOD/COD-ratio decreased. Emitted gas in the gas collection area was rather low, about 10 kW. The power production of the collected gas was in average 2 800 kW. In areas 1 and 3 where leachate was recirculated, the recovered gas efficiencies increased 55% and 70%, respectively, but in a reference area without recirculation the increase was 12%. Recommendation

  4. Modeling Contamination Migration on the Chandra X-ray Observatory - II

    Science.gov (United States)

    O'Dell, Stephen L.; Swartz, Douglas A.; Tice, Neil W.; Plucinsky, Paul P.; Grant, Catherine E.; Marshall, Herman L.; Vikhlinin, Alexey A.; Tennant, Allyn F.

    2013-01-01

    During its first 14 years of operation, the cold (about -60C) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X-ray Observatory, has accumulated a growing layer of molecular contamination that attenuates low-energy x rays. Over the past few years, the accumulation rate, spatial distribution, and composition have changed. This evolution has motivated further analysis of contamination migration within and near the ACIS cavity. To this end, the current study employs a higher-fidelity geometric model of the ACIS cavity, detailed thermal modeling based upon temperature data, and a refined model of the molecular transport.

  5. Analysis gives sensibility two models gives migration and transport gives radionuclides in the geosphere

    International Nuclear Information System (INIS)

    Torres Berdeguez, M. B.; Gil Castillo, R.; Peralta Vidal, J.L.

    1998-01-01

    An sensibility analysis it was applied two models, the first one, a model compressible for the near field (I finish source) The second, a simple model gives migration and transport radionuclides in the geosphere. The study was developed varying the securities ed simultaneously at the same time each parameter and observing the results in changes in the output and input. The intention in analysis it is to determine the parameter that but it influences in the variation the concentration. The statistical technique Regression it was employee in the study. This statistical method is used to analyze the dependence between a dependent variable and an or but independent variables

  6. Modelling gas migration in fractured rock. A contribution to the EU's PROGRESS project

    International Nuclear Information System (INIS)

    Humm, J.; Robinson, P.; Clark, K.

    2001-01-01

    To assess the performance of a waste repository, it is necessary to be able to predict the rates of gas generation and to understand and evaluate both the way the gas may disperse from the repository and any effects that might be associated with this dispersal. This document describes the modelling work carried out by QuantiSci on behalf of the UK Environment Agency, in conjunction with the CEC PROGRESS Project (Research into Gas Generation and Migration in Radioactive Waste Repository Systems) which has been carried out as part of the European Commission's IV th framework R and D programme. The project was under the PEGASUS (Projects on the Effects of GAS in Underground Storage facilities) umbrella. A review is provided of alternative conceptual models for the migration of gas through an initially water saturated fracture. A range of front or interface tracking methods for computing gas migration through a fracture is described: direct discretisation, marker particle, volume of fluids and level set methods. Volume of fluids methods are identified as the most appropriate approach for models of this sort. Subsequently, a description is given of the development of a model of gas injection into a single fracture in a portion of Borrowdale Volcanic Granite. The theoretical approach for the model is described in detail and the model compared to experimental results obtained for the real fracture. The experimental results of the CEC PROGRESS Project (obtained using Positron Emission Tomography) do not show particularly good agreement with the model results. However, there are strong indications that this is largely the result of uncertainties in the interpretation of the PET results. The experimental results are acknowledged to be extremely hard to interpret and the apparent negative gas thicknesses observed experimentally confirm this fact. Given the clearly critical dependence of the gas migration pathways on the aperture distribution, any discrepancies of this sort

  7. A model for cell migration in non-isotropic fibrin networks with an application to pancreatic tumor islets.

    Science.gov (United States)

    Chen, Jiao; Weihs, Daphne; Vermolen, Fred J

    2018-04-01

    Cell migration, known as an orchestrated movement of cells, is crucially important for wound healing, tumor growth, immune response as well as other biomedical processes. This paper presents a cell-based model to describe cell migration in non-isotropic fibrin networks around pancreatic tumor islets. This migration is determined by the mechanical strain energy density as well as cytokines-driven chemotaxis. Cell displacement is modeled by solving a large system of ordinary stochastic differential equations where the stochastic parts result from random walk. The stochastic differential equations are solved by the use of the classical Euler-Maruyama method. In this paper, the influence of anisotropic stromal extracellular matrix in pancreatic tumor islets on T-lymphocytes migration in different immune systems is investigated. As a result, tumor peripheral stromal extracellular matrix impedes the immune response of T-lymphocytes through changing direction of their migration.

  8. Modeling Coupled THMC Processes and Brine Migration in Salt at High Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rutqvist, Jonny; Blanco Martin, Laura; Mukhopadhyay, Sumit; Houseworth, Jim; Birkholzer, Jens

    2014-08-14

    In this report, we present FY2014 progress by Lawrence Berkeley National Laboratory (LBNL) related to modeling of coupled thermal-hydrological-mechanical-chemical (THMC) processes in salt and their effect on brine migration at high temperatures. LBNL’s work on the modeling of coupled THMC processes in salt was initiated in FY2012, focusing on exploring and demonstrating the capabilities of an existing LBNL modeling tool (TOUGH-FLAC) for simulating temperature-driven coupled flow and geomechanical processes in salt. This work includes development related to, and implementation of, essential capabilities, as well as testing the model against relevant information and published experimental data related to the fate and transport of water. we provide more details on the FY2014 work, first presenting updated tools and improvements made to the TOUGH-FLAC simulator, and the use of this updated tool in a new model simulation of long-term THM behavior within a generic repository in a salt formation. This is followed by the description of current benchmarking and validations efforts, including the TSDE experiment. We then present the current status in the development of constitutive relationships and the dual-continuum model for brine migration. We conclude with an outlook for FY2015, which will be much focused on model validation against field experiments and on the use of the model for the design studies related to a proposed heater experiment.

  9. Leachate from market refuse and biomethanation study.

    Science.gov (United States)

    Mukherjee, S N; Kumar, Sunil

    2007-12-01

    The market place is considered to be an important centre of daily life of campus community. In India, as in Europe and the USA, other forms of shopping have emerged significantly and now predominate, for instance department stores and supermarkets. Though, it is suffered from poor waste management, but the place could be a potential source for obtaining non-conventional energy. The present study examined the quality of market waste management of the Indian Institute of Technology Campus along with the feasibility of biogas production from leachate generated in the waste. Solid wastes from different storage locations of the market place were collected and analyzed. The characteristics of solid wastes were found to be degradable in nature. The wastes, composed of 85% of vegetable origin, were placed in a container and water was added to to generate leachate. The self-purification efficiency of leachate was also studied in the Indian environment and compared with research findings in the USA under an identical moisture application rate. Leachate characterization was investigated both under saturated and submerged conditions. The treatability of leachate was studied in a laboratory-scale up-flow anaerobic filter with hollow burnt clay rings as packing media. It was observed that 4,000-6,000 mg/l would be the optimum range of inlet chemical oxygen demand (COD) concentration for leachate treatment because of the inhibitory effect of ammonia, sulphide, volatile fatty acids and toxic metals in high concentrations at higher strengths of leachate. The gas production rate was found to be at a maximum at 38 degrees C and containing 70-75% methane. From experimental data, it was revealed that 83% COD was removed with input COD concentration of 5,475 mg/l at 2 days hydraulic retention time with biogas yield coefficients of 0.61. The present study also investigated the removal efficiency of chloride, ammonia, sulphide and nitrate.

  10. Multicomponent mass transport model: a model for simulating migration of radionuclides in ground water

    International Nuclear Information System (INIS)

    Washburn, J.F.; Kaszeta, F.E.; Simmons, C.S.; Cole, C.R.

    1980-07-01

    This report presents the results of the development of a one-dimensional radionuclide transport code, MMT2D (Multicomponent Mass Transport), for the AEGIS Program. Multicomponent Mass Transport is a numerical solution technique that uses the discrete-parcel-random-wald (DPRW) method to directly simulate the migration of radionuclides. MMT1D accounts for: convection;dispersion; sorption-desorption; first-order radioactive decay; and n-membered radioactive decay chains. Comparisons between MMT1D and an analytical solution for a similar problem show that: MMT1D agrees very closely with the analytical solution; MMT1D has no cumulative numerical dispersion like that associated with solution techniques such as finite differences and finite elements; for current AEGIS applications, relatively few parcels are required to produce adequate results; and the power of MMT1D is the flexibility of the code in being able to handle complex problems for which analytical solution cannot be obtained. Multicomponent Mass Transport (MMT1D) codes were developed at Pacific Northwest Laboratory to predict the movement of radiocontaminants in the saturated and unsaturated sediments of the Hanford Site. All MMT models require ground-water flow patterns that have been previously generated by a hydrologic model. This report documents the computer code and operating procedures of a third generation of the MMT series: the MMT differs from previous versions by simulating the mass transport processes in systems with radionuclide decay chains. Although MMT is a one-dimensional code, the user is referred to the documentation of the theoretical and numerical procedures of the three-dimensional MMT-DPRW code for discussion of expediency, verification, and error-sensitivity analysis

  11. Modeling gas migration experiments in repository host rocks for the MEGAS project

    International Nuclear Information System (INIS)

    Worgan, K.; Impey, M.; Volckaert, G.; DePreter, P.

    1993-01-01

    In response to concerns over the possibility of hydrogen gas generation within an underground repository for high-level radioactive waste, and its implications for repository safety, a joint European research study (MEGAS) is underway. Its aims are to understand and characterize the behavior of gas migration within an argillacious, host-rock. Laboratory experiments are being carried out by SCK/CEN, BGS and ISMES. SCK/CEN are also conducting in situ experiments at the underground laboratory at Mol, Belgium. Modeling of gas migration is being done in parallel with the experiments, by Intera Information Technologies. A two-phase flow code, TOPAZ, has been developed specifically for this work. In this paper the authors report on the results of some preliminary calculations performed with TOPAZ, in advance of the in situ experiments

  12. Modelling and prediction of radionuclide migration from shallow, subgrade nuclear waste facilities in arid environments

    International Nuclear Information System (INIS)

    Smith, A.; Ward, A.; Geldenhuis, S.

    1986-01-01

    Over the past fifteen years, prodigious efforts and significant advances have been made in methods of prediction of the migration rate of dissolved species in aqueous systems. Despite such work, there remain formidable obstacles in prediction of solute transport in the unsaturated zone over the long time periods necessarily related to the radionuclide bearing wastes. The objective of this paper is to consider the methods, issues and problems with the use of predictive solute transport models for radionuclide migration from nuclear waste disposal in arid environments, if and when engineering containment of the waste fails. Having considered the ability for long term solute prediction for a number of geological environments, the advantages of a disposal environment in which the solute transport process is diffusion controlled will be described

  13. Review and assessment of models for predicting the migration of radionuclides through rivers

    International Nuclear Information System (INIS)

    Monte, Luigi; Boyer, Patrick; Brittain, John E.; Haakanson, Lars; Lepicard, Samuel; Smith, Jim T.

    2005-01-01

    The present paper summarises the results of the review and assessment of state-of-the-art models developed for predicting the migration of radionuclides through rivers. The different approaches of the models to predict the behaviour of radionuclides in lotic ecosystems are presented and compared. The models were classified and evaluated according to their main methodological approaches. The results of an exercise of model application to specific contamination scenarios aimed at assessing and comparing the model performances were described. A critical evaluation and analysis of the uncertainty of the models was carried out. The main factors influencing the inherent uncertainty of the models, such as the incompleteness of the actual knowledge and the intrinsic environmental and biological variability of the processes controlling the behaviour of radionuclides in rivers, are analysed

  14. Consideration for modelling studies of migration of accidentally released radionuclides in a river watershed

    International Nuclear Information System (INIS)

    Matsunaga, Takeshi; Tsuduki, Katsunori; Yanase, Nobuyuki; Hanzawa, Yukiko; Ueno, Takashi

    2004-01-01

    Concerning radionuclides that might be released in an event of an accident from a nuclear facility, much attention has been paid to the migration pathways including the atmospheric deposition and subsequent inflow to surface water bodies since the Chernobyl nuclear accident in 1986. In European countries, computer-coded systems for predicting the migration including those pathways and providing scientific supports for decision makers to manage the contamination have been developed. This report is a summary of presentations and discussion made at the occasion of the visit of Dr. Monte in order to have directions related to the current subject of research, development of a mathematical model of the behavior of radionuclides in a river watershed. Those presentations and discussions were made at JAERI and also at prominent universities and institutes of Japan involved in this study field. As a result of these discussions, distinct advantages and key issues in use of a mathematical model for prediction of the migration of radionuclides in a river watershed have been identified and analyzed. It was confirmed that the use of mathematical modeling has distinct advantages. Re-arrangement of the existing experimental knowledge on the environment in an ordered way according to a theory (a mathematical model) will lead to a new angle to consider a problem in that environment, despite several gaps in the data array. A model to assess the radionuclide behaviour in contaminated aquatic ecosystems is a basis of decision analysis tools for helping decision-makers to select the most appropriate intervention strategies for the ecosystems. Practical use of a mathematical model and continuous effort in its validation were recognized as crucial. (author)

  15. Nitrogen Removal from Landfill Leachate by Microalgae

    Science.gov (United States)

    Pereira, Sérgio F. L.; Gonçalves, Ana L.; Moreira, Francisca C.; Silva, Tânia F. C. V.; Vilar, Vítor J. P.; Pires, José C. M.

    2016-01-01

    Landfill leachates result from the degradation of solid residues in sanitary landfills, thus presenting a high variability in terms of composition. Normally, these effluents are characterized by high ammoniacal-nitrogen (N–NH4+) concentrations, high chemical oxygen demands and low phosphorus concentrations. The development of effective treatment strategies becomes difficult, posing a serious problem to the environment. Phycoremediation appears to be a suitable alternative for the treatment of landfill leachates. In this study, the potential of Chlorella vulgaris for biomass production and nutrients (mainly nitrogen and phosphorus) removal from different compositions of a landfill leachate was evaluated. Since microalgae also require phosphorus for their growth, different loads of this nutrient were evaluated, giving the following N:P ratios: 12:1, 23:1 and 35:1. The results have shown that C. vulgaris was able to grow in the different leachate compositions assessed. However, microalgal growth was higher in the cultures presenting the lowest N–NH4+ concentration. In terms of nutrients uptake, an effective removal of N–NH4+ and phosphorus was observed in all the experiments, especially in those supplied with phosphorus. Nevertheless, N–NO3− removal was considered almost negligible. These promising results constitute important findings in the development of a bioremediation technology for the treatment of landfill leachates. PMID:27869676

  16. Modeling of radionuclide migration and a temperature dynamics in underground disposal of liquid radioactive waste

    International Nuclear Information System (INIS)

    Larin, V.K.; Zubkov, A.A.; Balakhonov, V.G.; Sukhorukov, V.A.; Zhiganov, A.N.; Noskov, M.D.; Istomin, A.D.; Kesler, A.G.

    2002-01-01

    Mathematical model of radionuclide migration and temperature field dynamics during underground disposal of liquid radioactive wastes is presented. The model involves the description of filtration, convective-dispersion mass transfer, sorption and desorption of radionuclides, radioactive decay, convective heat transport and hear transfer. Software making possible to conduct prognosis calculations of changing state of stratum-collector of radioactive wastes was made. Results of the simulation of temperature field dynamics and behaviour of radionuclides on underground disposal of liquid radioactive wastes of the Siberian chemical plant are performed [ru

  17. Trace Elements in Basalts From the Siqueiros Fracture Zone: Implications for Melt Migration Models

    Science.gov (United States)

    Pickle, R. C.; Forsyth, D. W.; Saal, A. E.; Nagle, A. N.; Perfit, M. R.

    2008-12-01

    Incompatible trace element (ITE) ratios in MORB from a variety of locations may provide insights into the melt migration process by constraining aggregated melt compositions predicted by mantle melting and flow models. By using actual plate geometries to create a 3-D thermodynamic mantle model, melt volumes and compositions at all depths and locations may be calculated and binned into cubes using the pHMELTS algorithm [Asimow et al., 2004]. These melts can be traced from each cube to the surface assuming several migration models, including a simplified pressure gradient model and one in which melt is guided upwards by a low permeability compacted layer. The ITE ratios of all melts arriving at the surface are summed, averaged, and compared to those of the actual sample compositions from the various MOR locales. The Siqueiros fracture zone at 8° 20' N on the East Pacific Rise (EPR) comprises 4 intra-transform spreading centers (ITSCs) across 140 km of offset between two longer spreading ridges, and is an excellent study region for several reasons. First, an abundance of MORB data is readily available, and the samples retrieved from ITSCs are unlikely to be aggregated in a long-lived magma chamber or affected by along-axis transport, so they represent melts extracted locally from the mantle. Additionally, samples at Siqueiros span a compositional range from depleted to normal MORB within the fracture zone yet have similar isotopic compositions to samples collected from the 9-10° EPR. This minimizes the effect of assuming a uniform source composition in our melting model despite a heterogeneous mantle, allowing us to consistently compare the actual lava composition with that predicted by our model. Finally, it has been demonstrated with preliminary migration models that incipient melts generated directly below an ITSC may not necessarily erupt at that ITSC but migrate laterally towards a nearby ridge due to enhanced pressure gradients. The close proximity of the

  18. Integrated modelling of material migration and target plate power handling at JET

    International Nuclear Information System (INIS)

    Coster, D.P.; Bonnin, X.; Chankin, A.

    2005-01-01

    The complexity of the tokamak edge and scrape-off layer (SOL) region is such that extrapolation to ITER requires modelling to be pursued through the integration of a number of edge codes, each of which must be thoroughly tested against results from present day machines. This contribution demonstrates how the edge modelling effort at JET is focused on such an approach by considering two examples, target power loading and material erosion and migration, the understanding of which are crucial issues for ITER. (author)

  19. The Changing Nature of Adult Education in the Age of Transnational Migration: Toward a Model of Recognitive Adult Education

    Science.gov (United States)

    Guo, Shibao

    2015-01-01

    This chapter examines the changing nature of adult education in the age of transnational migration and proposes recognitive adult education as an inclusive model that acknowledges and affirms cultural difference and diversity as positive and desirable assets.

  20. Interregional migration in Indonesia. Macro, micro, and agent-based modelling approaches

    NARCIS (Netherlands)

    Wajdi, N.

    2017-01-01

    This thesis aims to explain the dynamics of interregional migration in Indonesia in the 2000-2010 period and to project migration dynamics up to 2035. Four empirical studies presented in this thesis are interregional migration flows in Indonesia, migration and its relation to macro factors,

  1. Leachate characterization and performance evaluation of leachate treatment plant in Cipayung landfill, Indonesia

    Science.gov (United States)

    Noerfitriyani, E.; Hartono, D. M.; Moersidik, S. S.; Gusniani, I.

    2018-01-01

    The operation of landfill can cause environmental problems due to waste decomposition in the form of leachate production. Cipayung Landfill has a leachate treatment plant using stabilization ponds. The objective of this research is to evaluate the performance of stabilization ponds at Cipayung Landfill. The data were analyzed based on leachate samples from treatment unit’s influent and effluent under rainy season condition from April to May 2017. The results show the average leachate quality based on parameters of temperature by 34.81°C, Total Suspended Solid (TSS) of 72.33 mg/L, pH of 7.83, Biochemical Oxygen Demand (BOD) of 3,959.63 mg/L, Chemical Oxygen Demand (COD) of 6,860 mg/L, Total Nitrogen of 373.33 mg/L, and heavy metal Mercury of 0.0016 mg/L. The treatment plant’s effluent quality exceeds the leachate standard limit based on Indonesia’s Ministry of Environment and Forestry Law No. 59 of 2016. The results of design evaluation show that the anaerobic pond, facultative pond, and maturation pond system do not meet the design criteria. Therefore, a design improvement is needed to increase the performance of the leachate treatment plant and to ensure that the leachate discharged to water bodies does not exceed the standard limit to prevent contamination of the environment.

  2. Numerical modeling of fracking fluid migration through fault zones and fractures in the North German Basin

    Science.gov (United States)

    Pfunt, Helena; Houben, Georg; Himmelsbach, Thomas

    2016-09-01

    Gas production from shale formations by hydraulic fracturing has raised concerns about the effects on the quality of fresh groundwater. The migration of injected fracking fluids towards the surface was investigated in the North German Basin, based on the known standard lithology. This included cases with natural preferential pathways such as permeable fault zones and fracture networks. Conservative assumptions were applied in the simulation of flow and mass transport triggered by a high pressure boundary of up to 50 MPa excess pressure. The results show no significant fluid migration for a case with undisturbed cap rocks and a maximum of 41 m vertical transport within a permeable fault zone during the pressurization. Open fractures, if present, strongly control the flow field and migration; here vertical transport of fracking fluids reaches up to 200 m during hydraulic fracturing simulation. Long-term transport of the injected water was simulated for 300 years. The fracking fluid rises vertically within the fault zone up to 485 m due to buoyancy. Progressively, it is transported horizontally into sandstone layers, following the natural groundwater flow direction. In the long-term, the injected fluids are diluted to minor concentrations. Despite the presence of permeable pathways, the injected fracking fluids in the reported model did not reach near-surface aquifers, either during the hydraulic fracturing or in the long term. Therefore, the probability of impacts on shallow groundwater by the rise of fracking fluids from a deep shale-gas formation through the geological underground to the surface is small.

  3. TREATMENT OF LANDFILL LEACHATE BY COUPLING COAGULATION-FLOCCULATION OR OZONATION TO GRANULAR ACTIVATED CARBON ADSORPTION.

    Science.gov (United States)

    Oloibiri, Violet; Ufomba, Innocent; Chys, Michael; Audenaert, Wim; Demeestere, Kristof; Van Hulle, Stijn W H

    2015-01-01

    A major concern for landfilling facilities is the treatment of their leachate. To optimize organic matter removal from this leachate, the combination of two or more techniques is preferred in order to meet stringent effluent standards. In our study, coagulation-flocculation and ozonation are compared as pre- treatment steps for stabilized landfill leachate prior to granular activated carbon (GAC) adsorption. The efficiency of the pre treatment techniques is evaluated using COD and UVA254 measurements. For coagulation- flocculation, different chemicals are compared and optimal dosages are determined. After this, iron (III) chloride is selected for subsequent adsorption studies due to its high percentage of COD and UVA254 removal and good sludge settle-ability. Our finding show that ozonation as a single treatment is effective in reducing COD in landfill leachate by 66% compared to coagulation flocculation (33%). Meanwhile, coagulation performs better in UVA254 reduction than ozonation. Subsequent GAC adsorption of ozonated effluent, coagulated effluent and untreated leachate resulted in 77%, 53% and 8% total COD removal respectively (after 6 bed volumes). The effect of the pre-treatment techniques on GAC adsorption properties is evaluated experimentally and mathematically using Thomas and Yoon-Nelson models. Mathematical modelling of the experimental GAC adsorption data shows that ozonation increases the adsorption capacity and break through time with a factor of 2.5 compared to coagulation-flocculation.

  4. A validation study for the gas migration modelling of the compacted bentonite using existing experiment data

    International Nuclear Information System (INIS)

    Tawara, Y.; Mori, K.; Tada, K.; Shimura, T.; Sato, S.; Yamamoto, S.; Hayashi, H.

    2010-01-01

    Document available in extended abstract form only. After the field-scaled Gas Migration Test (GMT) was carried out at Grimsel Test Site (GTS) in Switzerland from 1997 through 2005, a study on advanced gas migration modelling has been conducted as a part of R and D programs of the RWMC (Radioactive Waste Management funding and Research Center) to evaluate long-term behaviour of the Engineered Barrier System (EBS) for the TRU waste disposal system in Japan. One of main objectives of this modelling study is to provide the qualified models and parameters in order to predict long-term gas migration behaviour in compacted bentonite. In addition, from a perspective of coupled THMC (Thermal, Hydrological, Mechanical and Chemical) processes, the specific processes which may have considerable impact to the gas migration behaviour are discussed by means of scoping calculations. Literature survey was conducted to collect experimental data related to gas migration in compacted bentonite in order to discuss an applicability of the existing gas migration models in the bentonite. The well-known flow rate controlled-gas injection experiment by Horseman, et al. and the pressure-controlled-gas injection test using several data with wide range of clay density and water content by Graham, et al, were selected. These literatures show the following characteristic behaviour of gas migration in high compacted and water-saturated bentonite. The observed gas flow rate from the outlet in the experiment by Horseman et al. was numerically reproduced by using the different conceptual models and computer codes, and then an applicability of the models and the identified key parameters such as relative permeability and capillary pressure were discussed. Helium gas was repeatedly injected into fully water-saturated and isotropically consolidated MX-80 bentonite (dry density: 1.6 Mg/m 3 ) in the experiment. One of the most important conclusions from this experiment is that it's impossible for

  5. Environmental impact assessment of leachate recirculation in landfill of municipal solid waste by comparing with evaporation and discharge (EASEWASTE).

    Science.gov (United States)

    Xing, Wei; Lu, Wenjing; Zhao, Yan; Zhang, Xu; Deng, Wenjing; Christensen, Thomas H

    2013-02-01

    In some arid regions where landfill produces minimal amount of leachate, leachate recirculation is suggested as a cost-effective option. However, its long-term impacts to environment remain disputed. For the purpose of revealing the environmental impacts of leachate recirculation in landfill, four scenarios were modeled using EASEWASTE, comparing the strategies of leachate recirculation (with or without gas management), evaporation and discharge. In the current situation (Scenario A), a total of 280 t of waste was generated and then transported to a conventional landfill for disposal. A number of contaminants derived from waste can be stored in the landfill for long periods, with 11.69 person equivalent (PE) for stored ecotoxicity in water and 29.62 PE for stored ecotoxicity in soil, considered as potential risks of releasing to the environment someday. Meanwhile, impacts to ecotoxicity and human toxicity in surface water, and those to groundwater, present relatively low levels. In Scenario B, leachate evaporation in a collecting pool has minimal impacts on surface water. However, this strategy significantly impacts groundwater (1055.16 PE) because of the potential infiltration of leachate, with major contaminants of As, ammonia, and Cd. A number of ions, such as Cl(-), Mg(2+), and Ca(2+), may also contaminate groundwater. In Scenario C, the direct discharge of leachate to surface water may result in acidification (2.71 PE) and nutrient enrichment (2.88 PE), primarily attributed to soluble ammonia in leachate and the depositional ammonia from biogas. Moreover, the direct discharge of leachate may also result in ecotoxicity and human toxicity via water contaminated by heavy metals in leachate, with 3.96 PE and 11.64 PE respectively. The results also show that landfill gas is the main contributor to global warming and photochemical ozone formation due to methane emission. In Scenario D, landfill gas flaring was thus be modeled and proven to be efficient for reducing

  6. Growth and biomass of Populus irrigated with landfill leachate

    Science.gov (United States)

    Jill A. Zalesny; Ronald S., Jr. Zalesny; David R. Coyle; Richard B. Hall

    2007-01-01

    Resource managers are challenged with waste disposal and leachate produced from its degradation. Poplar (Populus spp.) trees offer an opportunity for ecological leachate disposal as an irrigation source for managed tree systems. Our objective was to irrigate Populus trees with municipal solid waste landfill leachate or fertilized well water (control...

  7. Effects of leachate on geotechnical characteristics of sandy clay soil

    Science.gov (United States)

    Harun, N. S.; Ali, Z. Rahman; Rahim, A. S.; Lihan, T.; Idris, R. M. W.

    2013-11-01

    Leachate is a hazardous liquid that poses negative impacts if leaks out into environments such as soil and ground water systems. The impact of leachate on the downgraded quality in terms of chemical characteristic is more concern rather than the physical or mechanical aspect. The effect of leachate on mechanical behaviour of contaminated soil is not well established and should be investigated. This paper presents the preliminary results of the effects of leachate on the Atterberg limit, compaction and shear strength of leachate-contaminated soil. The contaminated soil samples were prepared by mixing the leachate at ratiosbetween 0% and 20% leachate contents with soil samples. Base soil used was residual soil originated from granitic rock and classified as sandy clay soil (CS). Its specific gravity ranged between 2.5 and 2.64 with clay minerals of kaolinite, muscovite and quartz. The field strength of the studied soil ranged between 156 and 207 kN/m2. The effects of leachate on the Atterberg limit clearly indicated by the decrease in liquid and plastic limit values with the increase in the leachate content. Compaction tests on leachate-contaminated soil caused the dropped in maximum dry density, ρdry and increased in optimum moisture content, wopt when the amount of leachate was increased between 0% and 20%. The results suggested that leachate contamination capable to modify some geotechnical properties of the studied residual soils.

  8. Semi-continuous anaerobic treatment of fresh leachate from ...

    African Journals Online (AJOL)

    A semi-continuous leachate treatment process was developed in the present study. The fresh leachate was obtained from a municipal solid waste transfer station and palm oil mill effluent (POME) sludge was used as sources of anaerobic microbial complex. The semi-continuous treatment of leachate was operated in two ...

  9. [Manpower migrations and Arab unity: the challenges of the Iraqi model].

    Science.gov (United States)

    Roussillon, A

    1985-01-01

    the presence of large numbers of foreign workers not only to the countries employing them but to the Arab nation as a whole allows Iraq to criticize the migration policies of the Gulf oil exporters, which are increasingly favoring more productive labor from Asian countries and which cede much of the authority to select and admit workers to private concerns. The evolution of Iraq's policy demonstrates the concern of its governing party with reconciling its Arab identity and its analysis of international power relations with consolidation of its own position internally and in the Arab world as a whole. The labor policy of the oil exporters exposes their countries and thus the Arab world to the possibility of sabotage and to demographic overpowering of ethnic and cultural identity. Interpretations differ as to whether the Iraqi model has led to a better deployment of labor and as to its theoretical contribution to pan-Arab unity, given the diverging interests of the individual states concerned.

  10. A general mixture model and its application to coastal sandbar migration simulation

    Science.gov (United States)

    Liang, Lixin; Yu, Xiping

    2017-04-01

    A mixture model for general description of sediment laden flows is developed and then applied to coastal sandbar migration simulation. Firstly the mixture model is derived based on the Eulerian-Eulerian approach of the complete two-phase flow theory. The basic equations of the model include the mass and momentum conservation equations for the water-sediment mixture and the continuity equation for sediment concentration. The turbulent motion of the mixture is formulated for the fluid and the particles respectively. A modified k-ɛ model is used to describe the fluid turbulence while an algebraic model is adopted for the particles. A general formulation for the relative velocity between the two phases in sediment laden flows, which is derived by manipulating the momentum equations of the enhanced two-phase flow model, is incorporated into the mixture model. A finite difference method based on SMAC scheme is utilized for numerical solutions. The model is validated by suspended sediment motion in steady open channel flows, both in equilibrium and non-equilibrium state, and in oscillatory flows as well. The computed sediment concentrations, horizontal velocity and turbulence kinetic energy of the mixture are all shown to be in good agreement with experimental data. The mixture model is then applied to the study of sediment suspension and sandbar migration in surf zones under a vertical 2D framework. The VOF method for the description of water-air free surface and topography reaction model is coupled. The bed load transport rate and suspended load entrainment rate are all decided by the sea bed shear stress, which is obtained from the boundary layer resolved mixture model. The simulation results indicated that, under small amplitude regular waves, erosion occurred on the sandbar slope against the wave propagation direction, while deposition dominated on the slope towards wave propagation, indicating an onshore migration tendency. The computation results also shows that

  11. Variability in connectivity patterns of fish with ontogenetic migrations: Modelling effects of abiotic and biotic factors

    Directory of Open Access Journals (Sweden)

    Susanne Eva Tanner

    2015-10-01

    Full Text Available Connectivity is a critical property of marine fish populations as it drives population replenishment, determines colonization patterns and the resilience of populations to harvest. Understanding connectivity patterns is particularly important in species that present ontogenetic migrations and segregated habitat use during their life history, such as marine species with estuarine nursery areas. Albeit challenging, fish movement can be estimated and quantified using different methodologies depending on the life history stages of interest (e.g. biophysical modelling, otolith chemistry, genetic markers. Relative contributions from estuarine nursery areas to the adult coastal populations were determined using otolith elemental composition and maximum likelihood estimation for four commercially important species (Dicentrarchus labrax, Plathichtys flesus, Solea senegalensis and Solea solea and showed high interannual variability. Here, the effects of abiotic and biotic factors on the observed variability in connectivity rates and extent between estuarine juvenile and coastal adult subpopulations are investigated using generalized linear models (GLM and generalized mixed models (GMM. Abiotic factors impacting both larval and juvenile life history stages are included in the models (e.g. wind force and direction, NAO, water temperature while biotic factors relative to the estuarine residency of juvenile fish are evaluated (e.g. juvenile density, food availability. Factors contributing most to the observed variability in connectivity rates are singled out and compared among species. General trends are identified and results area discussed in the general context of identifying potential management frameworks applicable to different life stages and which may prove useful for ontogenetically migrating species.

  12. Electrocoagulation and decolorization of landfill leachate

    Science.gov (United States)

    Mussa, Zainab Haider; Othman, Mohamed Rozali; Abdullah, Md Pauzi

    2013-11-01

    In this study, several operating conditions such as electrode material, treatment time, applied voltage, Cl□ concentration and PH of solution were tested on treatability of landfill leachate by using electrocoagulation (EC) method. According to the results, EC method can be used efficiently for the treatment of landfill leachate by using proper operating conditions. The best removal rats were obtained when C (rod) electrode as anode, operating time is 120 min, voltage applied is 10 V, NaCl concentration is 5.85 g/L and the raw PH, for these conditions, 70% color removal was obtained.

  13. Prediction of radionuclide migration in the geosphere: is the porous-flow model adequate

    International Nuclear Information System (INIS)

    Neretnieks, I.

    1982-01-01

    Practically all models used today to describe radionuclide migration in geologic media are based on the concept of flow in porous media. Recently it has been questioned if Fickian dispersion is the most important dispersion mechanism. Field observations of dispersion indicate that the dispersion coefficient increases with observation distance. This should not be the case in a homogeneous porous medium. For a medium with essentially independent channels, on the other hand, such an effect can be predicted. In some calculated examples it is shown that the use of the Fickian dispersion mechanism will very seriously underestimate the radionuclide concentration at a point downstream if the spreading mechanism in reality is channelling. The consequences of the often-used assumption that the interaction between the radionuclides and the rock is instantaneous is also discussed. It has been shown that in sparsely fissured crystalline rock the whole rock mass will not be able to participate in the sorption reactions, because the radionuclides will not have time to penetrate all through the large blocks. On the other hand, the assumption that only the surface of the fissures interacts with the radionuclides is likely to be an extremely conservative assumption in view of some recent diffusion experiments in crystalline rocks performed in our laboratories and at the Canadian Geologic Survey. Some experimental results on radionuclide migration in a single natural fissure under well-controlled conditions in the laboratory are also presented and interpreted using a model which includes channelling, surface sorption, diffusion in the rock matrix and sorption in the rock matrix. Some implications of these mechanisms in predicting radionuclide migration in the geosphere are discussed and compared with what a porous-flow model would predict

  14. Credit risk migration rates modeling as open systems: A micro-simulation approach

    Science.gov (United States)

    Landini, S.; Uberti, M.; Casellina, S.

    2018-05-01

    The last financial crisis of 2008 stimulated the development of new Regulatory Criteria (commonly known as Basel III) that pushed the banking activity to become more prudential, either in the short and the long run. As well known, in 2014 the International Accounting Standards Board (IASB) promulgated the new International Financial Reporting Standard 9 (IFRS 9) for financial instruments that will become effective in January 2018. Since the delayed recognition of credit losses on loans was identified as a weakness in existing accounting standards, the IASB has introduced an Expected Loss model that requires more timely recognition of credit losses. Specifically, new standards require entities to account both for expected losses from when the impairments are recognized for the first time and for full loan lifetime; moreover, a clear preference toward forward looking models is expressed. In this new framework, it is necessary a re-thinking of the widespread standard theoretical approach on which the well known prudential model is founded. The aim of this paper is then to define an original methodological approach to migration rates modeling for credit risk which is innovative respect to the standard method from the point of view of a bank as well as in a regulatory perspective. Accordingly, the proposed not-standard approach considers a portfolio as an open sample allowing for entries, migrations of stayers and exits as well. While being consistent with the empirical observations, this open-sample approach contrasts with the standard closed-sample method. In particular, this paper offers a methodology to integrate the outcomes of the standard closed-sample method within the open-sample perspective while removing some of the assumptions of the standard method. Three main conclusions can be drawn in terms of economic capital provision: (a) based on the Markovian hypothesis with a-priori absorbing state at default, the standard closed-sample method is to be abandoned

  15. Modeling Contamination Migration on the Chandra X-Ray Observatory - III

    Science.gov (United States)

    O'Dell, Stephen L.; Swartz, Douglas A.; Tice, Neil W.; Plucinsky, Paul P.; Grant, Catherine E.; Marshall, Herman L.; Vikhlinin, Alexy A.; Tennant, Allyn F.; Dahmer, Matthew T.

    2015-01-01

    During its first 16 years of operation, the cold (about -60 C) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X-ray Observatory, has accumulated a growing layer of molecular contamination that attenuates low-energy x rays. Over the past few years, the accumulation rate, spatial distribution, and composition have changed. This evolution has motivated further analysis of contamination migration within and near the ACIS cavity, in part to evaluate potential bake-out scenarios intended to reduce the level of contamination. Keywords: X-ray astronomy, CCDs, contamination, modeling and simulation, spacecraft operations

  16. A model for radionuclide Migration in Urban Environment and Drainage Systems

    International Nuclear Information System (INIS)

    Garcia, E.; Gallego, E.; Jimenez, F.

    1998-01-01

    The Model for Radionuclide Migration in Urban Environment and Drainage Systems aims to estimate the discharge of radioactivity removed by natural or forced decontamination into the receiving waters from the drainage system, as well as the radioactivity joined with the sludge produced in treatments plants, whose various applications can mean a potential hazard. This model, built in Powersim, is included in the MOIRA system, a project whose main aim is the evaluation of the situation after a radioactive contamination of the aquatic ecosystems and the estimation of optimal remedial strategies to restore the contaminated waters. Powersim is an easy-to-use software package which simulates dynamic processes. Two sub-models compose the global model: one, simulating the evolution of Cs-137 in urban areas, and the other, the behaviour of this radionuclide, once it ha entered the drainage systems, with the various existing alternatives of waste water treatment in Europe. (Author) 8 refs

  17. A report on intercomparison studies of computer programs which respectively model: i) radionuclide migration ii) equilibrium chemistry of groundwater

    International Nuclear Information System (INIS)

    Broyd, T.W.; McD Grant, M.; Cross, J.E.

    1985-01-01

    This report describes two intercomparison studies of computer programs which respectively model: i) radionuclide migration ii) equilibrium chemistry of groundwaters. These studies have been performed by running a series of test cases with each program and comparing the various results obtained. The work forms a part of the CEC MIRAGE project (MIgration of RAdionuclides in the GEosphere) and has been jointly funded by the CEC and the United Kingdom Department of the Environment. Presentations of the material contained herein were given at plenary meetings of the MIRAGE project in Brussels in March, 1984 (migration) and March, 1985 (equilibrium chemistry) respectively

  18. Heterogeneous adsorption behavior of landfill leachate on granular activated carbon revealed by fluorescence excitation emission matrix (EEM)-parallel factor analysis (PARAFAC).

    Science.gov (United States)

    Lee, Sonmin; Hur, Jin

    2016-04-01

    Heterogeneous adsorption behavior of landfill leachate on granular activated carbon (GAC) was investigated by fluorescence excitation-emission matrix (EEM) combined with parallel factor analysis (PARAFAC). The equilibrium adsorption of two leachates on GAC was well described by simple Langmuir and Freundlich isotherm models. More nonlinear isotherm and a slower adsorption rate were found for the leachate with the higher values of specific UV absorbance and humification index, suggesting that the leachate containing more aromatic content and condensed structures might have less accessible sites of GAC surface and a lower degree of diffusive adsorption. Such differences in the adsorption behavior were found even within the bulk leachate as revealed by the dissimilarity in the isotherm and kinetic model parameters between two identified PARAFAC components. For both leachates, terrestrial humic-like fluorescence (C1) component, which is likely associated with relatively large sized and condensed aromatic structures, exhibited a higher isotherm nonlinearity and a slower kinetic rate for GAC adsorption than microbial humic-like (C2) component. Our results were consistent with size exclusion effects, a well-known GAC adsorption mechanism. This study demonstrated the promising benefit of using EEM-PARAFAC for GAC adsorption processes of landfill leachate through fast monitoring of the influent and treated leachate, which can provide valuable information on optimizing treatment processes and predicting further environmental impacts of the treated effluent. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. THE EVOLUTION OF ASTEROIDS IN THE JUMPING-JUPITER MIGRATION MODEL

    Energy Technology Data Exchange (ETDEWEB)

    Roig, Fernando [Observatòrio Nacional, Rua Gal. Jose Cristino 77, Rio de Janeiro, RJ 20921-400 (Brazil); Nesvorný, David, E-mail: froig@on.br, E-mail: davidn@boulder.swri.edu [Southwest Research Institute, 1050 Walnut St., Suite 300, Boulder, CO 80302 (United States)

    2015-12-15

    In this work, we investigate the evolution of a primordial belt of asteroids, represented by a large number of massless test particles, under the gravitational effect of migrating Jovian planets in the framework of the jumping-Jupiter model. We perform several simulations considering test particles distributed in the Main Belt, as well as in the Hilda and Trojan groups. The simulations start with Jupiter and Saturn locked in the mutual 3:2 mean motion resonance plus three Neptune-mass planets in a compact orbital configuration. Mutual planetary interactions during migration led one of the Neptunes to be ejected in less than 10 Myr of evolution, causing Jupiter to jump by about 0.3 AU in semimajor axis. This introduces a large-scale instability in the studied populations of small bodies. After the migration phase, the simulations are extended over 4 Gyr, and we compare the final orbital structure of the simulated test particles to the current Main Belt of asteroids with absolute magnitude H < 9.7. The results indicate that, in order to reproduce the present Main Belt, the primordial belt should have had a distribution peaked at ∼10° in inclination and at ∼0.1 in eccentricity. We discuss the implications of this for the Grand Tack model. The results also indicate that neither primordial Hildas, nor Trojans, survive the instability, confirming the idea that such populations must have been implanted from other sources. In particular, we address the possibility of implantation of Hildas and Trojans from the Main Belt population, but find that this contribution should be minor.

  20. Migration of the Three-dimensional Wind Field (3DWF) Model from Linux to Windows and Mobile Platforms

    Science.gov (United States)

    2017-11-01

    Results in netCDF 11 4.3 Morphological Data Generation 16 5. 3DWF on Mobile Platforms 17 5.1 3DWF on Windows Mobile Devices 18 5.2 3DWF Migration to...Windows and Mobile Platforms by Giap Huynh and Yansen Wang Approved for public release; distribution is unlimited. NOTICES...Migration of the Three-dimensional Wind Field (3DWF) Model from Linux to Windows and Mobile Platforms by Giap Huynh and Yansen Wang

  1. Modeling Contamination Migration on the Chandra X-ray Observatory II

    Science.gov (United States)

    O'Dell, Steve; Swartz, Doug; Tice, Neil; Plucinsky, Paul; Grant, Catherine; Marshall, Herman; Vikhlinin, Alexey

    2013-01-01

    During its first 14 years of operation, the cold (about -60degC) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X-ray Observatory, has accumulated a growing layer of molecular contamination that attenuates low-energy x rays. Over the past few years, the accumulation rate, spatial distribution, and composition may have changed, perhaps partially related to changes in the operating temperature of the ACIS housing. This evolution of the accumulation of the molecular contamination has motivated further analysis of contamination migration on the Chandra X-ray Observatory, particularly within and near the ACIS cavity. To this end, the current study employs a higher-fidelity geometric model of the ACIS cavity, detailed thermal modeling based upon monitored temperature data, and an accordingly refined model of the molecular transport.

  2. Random blebbing motion: A simple model linking cell structural properties to migration characteristics

    Science.gov (United States)

    Woolley, Thomas E.; Gaffney, Eamonn A.; Goriely, Alain

    2017-07-01

    If the plasma membrane of a cell is able to delaminate locally from its actin cortex, a cellular bleb can be produced. Blebs are pressure-driven protrusions, which are noteworthy for their ability to produce cellular motion. Starting from a general continuum mechanics description, we restrict ourselves to considering cell and bleb shapes that maintain approximately spherical forms. From this assumption, we obtain a tractable algebraic system for bleb formation. By including cell-substrate adhesions, we can model blebbing cell motility. Further, by considering mechanically isolated blebbing events, which are randomly distributed over the cell, we can derive equations linking the macroscopic migration characteristics to the microscopic structural parameters of the cell. This multiscale modeling framework is then used to provide parameter estimates, which are in agreement with current experimental data. In summary, the construction of the mathematical model provides testable relationships between the bleb size and cell motility.

  3. Random blebbing motion: A simple model linking cell structural properties to migration characteristics.

    Science.gov (United States)

    Woolley, Thomas E; Gaffney, Eamonn A; Goriely, Alain

    2017-07-01

    If the plasma membrane of a cell is able to delaminate locally from its actin cortex, a cellular bleb can be produced. Blebs are pressure-driven protrusions, which are noteworthy for their ability to produce cellular motion. Starting from a general continuum mechanics description, we restrict ourselves to considering cell and bleb shapes that maintain approximately spherical forms. From this assumption, we obtain a tractable algebraic system for bleb formation. By including cell-substrate adhesions, we can model blebbing cell motility. Further, by considering mechanically isolated blebbing events, which are randomly distributed over the cell, we can derive equations linking the macroscopic migration characteristics to the microscopic structural parameters of the cell. This multiscale modeling framework is then used to provide parameter estimates, which are in agreement with current experimental data. In summary, the construction of the mathematical model provides testable relationships between the bleb size and cell motility.

  4. Geochemical behavior of uranium mill tailings leachate in the subsurface

    International Nuclear Information System (INIS)

    Brookins, D.G.

    1993-01-01

    Leachate generated from surface disposal of acidic uranium mill tailings at Maybell, CO has impacted groundwater quality within the underlying mineralized Browns Park Formation. The extent of groundwater contamination, however, is located directly beneath the tailings impoundment. The milling process consisted of sulfuric acid extraction of uranium from the feed ore by a complex chemical leaching and precipitation process. Tailings leachate at the site contains elevated concentrations of Al, As, Cd, Mo, Ni, NO 3 , Se, U, and other solutes. From column leach tests, the concentrations of contaminants within tailings pore fluid are SO 4 >NH 4 >NO 3 >U>Se>Ni>As>Cd at pH 4.0. The carbonate buffering capacity of the tailings subsoil has decreased because of calcite dissolution in the presence of acidic leachate. Groundwater quality data, mineralogical and microbiological studies, and geochemical modeling suggest that As, NO 3 , Se, U and other solutes are being removed from solution through precipitation, adsorption, and denitrification processes under reducing conditions. Presence of hydrogen sulfide, liquid and gaseous hydrocarbons, dissolved organic, and abundant pyrite within the Browns Park Formations have maintained reducing conditions subjacent to the tailings impoundment. Groundwater is in close equilibrium with coffinite and uraninite, the primary U(IV) minerals extracted from the Browns Parks Formation. Denitrifying bacteria identified in this study catalyze redox reactions involving NO 3 . Subsequently, contaminant distributions of NO 3 decrease 1000 times beneath the tailings impoundment. Applying geochemical and biochemical processes occurring at Maybell provides an excellent model for in situ aquifer restoration programs considered at other uranium tailings and heavy-metal-mixed waste contaminated sites. (author) 4 figs., 4 tabs., 27 refs

  5. ON THE MIGRATION OF JUPITER AND SATURN: CONSTRAINTS FROM LINEAR MODELS OF SECULAR RESONANT COUPLING WITH THE TERRESTRIAL PLANETS

    International Nuclear Information System (INIS)

    Agnor, Craig B.; Lin, D. N. C.

    2012-01-01

    We examine how the late divergent migration of Jupiter and Saturn may have perturbed the terrestrial planets. Using a modified secular model we have identified six secular resonances between the ν 5 frequency of Jupiter and Saturn and the four apsidal eigenfrequencies of the terrestrial planets (g 1-4 ). We derive analytic upper limits on the eccentricity and orbital migration timescale of Jupiter and Saturn when these resonances were encountered to avoid perturbing the eccentricities of the terrestrial planets to values larger than the observed ones. Because of the small amplitudes of the j = 2, 3 terrestrial eigenmodes the g 2 – ν 5 and g 3 – ν 5 resonances provide the strongest constraints on giant planet migration. If Jupiter and Saturn migrated with eccentricities comparable to their present-day values, smooth migration with exponential timescales characteristic of planetesimal-driven migration (τ ∼ 5-10 Myr) would have perturbed the eccentricities of the terrestrial planets to values greatly exceeding the observed ones. This excitation may be mitigated if the eccentricity of Jupiter was small during the migration epoch, migration was very rapid (e.g., τ ∼< 0.5 Myr perhaps via planet-planet scattering or instability-driven migration) or the observed small eccentricity amplitudes of the j = 2, 3 terrestrial modes result from low probability cancellation of several large amplitude contributions. Results of orbital integrations show that very short migration timescales (τ < 0.5 Myr), characteristic of instability-driven migration, may also perturb the terrestrial planets' eccentricities by amounts comparable to their observed values. We discuss the implications of these constraints for the relative timing of terrestrial planet formation, giant planet migration, and the origin of the so-called Late Heavy Bombardment of the Moon 3.9 ± 0.1 Ga ago. We suggest that the simplest way to satisfy these dynamical constraints may be for the bulk of any giant

  6. Leachate storage transport tanker loadout piping

    International Nuclear Information System (INIS)

    Whitlock, R.W.

    1994-01-01

    This report shows the modifications to the W-025 Trench No. 31 leachate loadout discharge piping, and also the steps involved in installing the discharge piping, including dimensions and welding information. The installation of the discharge pipe should be done in accordance to current pipe installation standards. Trench No. 31 is a radioactive mixed waste land disposal facility

  7. Nonequilibrium free diffusion in seed leachate

    Science.gov (United States)

    Ortiz G., Luis; Riquelme P., Pablo; Guzmán, R.

    2013-11-01

    In this work, we use a Schlieren-like Near Field Scattering (SNFS) setup to study nonequilibrium free diffusion behavior of a colloidal solution obtained from seeds leachate. The main objective is to compare the temporal behavior of the diffusion coefficient of seed leachate with an electric conductivity based vigor test. SNFS sizing measurements, based on Mie theory, were carried out to ensure its reliability and sensitivity. Then, we performed a typical nonequilibrium free diffusion experiment of a glycerol-water mixture. In this way, we confirmed that SNFS setup is sensitive to giant concentration fluctuations of nanocolloidal solutions. The results obtained in this stage reproduce properly the data reported elsewhere in literature. Moreover, seed leachate diffuse, in water, in a similar way that glycerol does. In both cases we used the same method (dynamic structure factor) to determine thermo-physical properties. We show that time evolution of diffusion coefficient of Lupinus Albus leachate exhibits three defined regimes as electric conductivity measurements. The results also exhibit a correspondence between the behavior of the diffusion coefficient and electric conductivity values of the two regions in the temporal range studied. Finally, we discuss biological processes involved in germination that could modulate this dependence, and the role played by the electrolytic nature of solutes.

  8. Leachate storage transport tanker loadout piping

    International Nuclear Information System (INIS)

    Whitlock, R.W.

    1994-01-01

    This report contains schematic drawings for the pipe fittings for the Hanford waste tanks. Included are the modifications to the W-025 trench number-sign 31 leachate loadout piping, and also the modifications to the tanker trailers. The piping was modified to prevent spillage to the environment. The tankers were modified for loading and unloading purposes

  9. Quantification of regional leachate variance from municipal solid waste landfills in China

    DEFF Research Database (Denmark)

    Yang, Na; Damgaard, Anders; Kjeldsen, Peter

    2015-01-01

    The quantity of leachate is crucial when assessing pollution emanating from municipal landfills. In most cases, existing leachate quantification measures only take into account one source - precipitation, which resulted in serious underestimation in China due to its waste properties: high moisture...... contents. To overcome this problem, a new estimation method was established considering two sources: (1) precipitation infiltrated throughout waste layers, which was simulated with the HELP model, (2) water squeezed out of the waste itself, which was theoretically calculated using actual data of Chinese...... waste. The two sources depended on climate conditions and waste characteristics, respectively, which both varied in different regions. In this study, 31 Chinese cities were investigated and classified into three geographic regions according to landfill leachate generation performance: northwestern China...

  10. Alternative to dead reckoning for model state quantisation when migrating to a quantised discrete

    CSIR Research Space (South Africa)

    Duvenhage, A

    2008-06-01

    Full Text Available Some progress has recently been made on migrating an existing distributed parallel discrete time simulator to a quantised discrete event architecture. The migration is done to increase the scale of the real-time simulations supported...

  11. High-throughput migration modelling for estimating exposure to chemicals in food packaging in screening and prioritization tools

    DEFF Research Database (Denmark)

    Ernstoff, Alexi S; Fantke, Peter; Huang, Lei

    2017-01-01

    Specialty software and simplified models are often used to estimate migration of potentially toxic chemicals from packaging into food. Current models, however, are not suitable for emerging applications in decision-support tools, e.g. in Life Cycle Assessment and risk-based screening and prioriti...... to uncertainty and dramatically decreased model performance (R2 = 0.4, Se = 1). In all, this study provides a rapid migration modelling approach to estimate exposure to chemicals in food packaging for emerging screening and prioritization approaches....

  12. Characterizing and modelling river channel migration rates at a regional scale: Case study of south-east France.

    Science.gov (United States)

    Alber, Adrien; Piégay, Hervé

    2017-11-01

    An increased awareness by river managers of the importance of river channel migration to sediment dynamics, habitat complexity and other ecosystem functions has led to an advance in the science and practice of identifying, protecting or restoring specific erodible corridors across which rivers are free to migrate. One current challenge is the application of these watershed-specific goals at the regional planning scales (e.g., the European Water Framework Directive). This study provides a GIS-based spatial analysis of the channel migration rates at the regional-scale. As a case study, 99 reaches were sampled in the French part of the Rhône Basin and nearby tributaries of the Mediterranean Sea (111,300 km 2 ). We explored the spatial correlation between the channel migration rate and a set of simple variables (e.g., watershed area, channel slope, stream power, active channel width). We found that the spatial variability of the channel migration rates was primary explained by the gross stream power (R 2  = 0.48) and more surprisingly by the active channel width scaled by the watershed area. The relationship between the absolute migration rate and the gross stream power is generally consistent with the published empirical models for freely meandering rivers, whereas it is less significant for the multi-thread reaches. The discussion focused on methodological constraints for a regional-scale modelling of the migration rates, and the interpretation of the empirical models. We hypothesize that the active channel width scaled by the watershed area is a surrogate for the sediment supply which may be a more critical factor than the bank resistance for explaining the regional-scale variability of the migration rates. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Shorebird Migration Patterns in Response to Climate Change: A Modeling Approach

    Science.gov (United States)

    Smith, James A.

    2010-01-01

    The availability of satellite remote sensing observations at multiple spatial and temporal scales, coupled with advances in climate modeling and information technologies offer new opportunities for the application of mechanistic models to predict how continental scale bird migration patterns may change in response to environmental change. In earlier studies, we explored the phenotypic plasticity of a migratory population of Pectoral sandpipers by simulating the movement patterns of an ensemble of 10,000 individual birds in response to changes in stopover locations as an indicator of the impacts of wetland loss and inter-annual variability on the fitness of migratory shorebirds. We used an individual based, biophysical migration model, driven by remotely sensed land surface data, climate data, and biological field data. Mean stop-over durations and stop-over frequency with latitude predicted from our model for nominal cases were consistent with results reported in the literature and available field data. In this study, we take advantage of new computing capabilities enabled by recent GP-GPU computing paradigms and commodity hardware (general purchase computing on graphics processing units). Several aspects of our individual based (agent modeling) approach lend themselves well to GP-GPU computing. We have been able to allocate compute-intensive tasks to the graphics processing units, and now simulate ensembles of 400,000 birds at varying spatial resolutions along the central North American flyway. We are incorporating additional, species specific, mechanistic processes to better reflect the processes underlying bird phenotypic plasticity responses to different climate change scenarios in the central U.S.

  14. Slope stability of bioreactor landfills during leachate injection: effects of heterogeneous and anisotropic municipal solid waste conditions.

    Science.gov (United States)

    Giri, Rajiv K; Reddy, Krishna R

    2014-03-01

    In bioreactor landfills, leachate recirculation can significantly affect the stability of landfill slope due to generation and distribution of excessive pore fluid pressures near side slope. The current design and operation of leachate recirculation systems do not consider the effects of heterogeneous and anisotropic nature of municipal solid waste (MSW) and the increased pore gas pressures in landfilled waste caused due to leachate recirculation on the physical stability of landfill slope. In this study, a numerical two-phase flow model (landfill leachate and gas as immiscible phases) was used to investigate the effects of heterogeneous and anisotropic nature of MSW on moisture distribution and pore-water and capillary pressures and their resulting impacts on the stability of a simplified bioreactor landfill during leachate recirculation using horizontal trench system. The unsaturated hydraulic properties of MSW were considered based on the van Genuchten model. The strength reduction technique was used for slope stability analyses as it takes into account of the transient and spatially varying pore-water and gas pressures. It was concluded that heterogeneous and anisotropic MSW with varied unit weight and saturated hydraulic conductivity significantly influenced the moisture distribution and generation and distribution of pore fluid pressures in landfill and considerably reduced the stability of bioreactor landfill slope. It is recommended that heterogeneous and anisotropic MSW must be considered as it provides a more reliable approach for the design and leachate operations in bioreactor landfills.

  15. Transformation of metals speciation in a combined landfill leachate treatment

    International Nuclear Information System (INIS)

    Wu Yanyu; Zhou Shaoqi; Chen Dongyu; Zhao Rong; Li Huosheng; Lin Yiming

    2011-01-01

    Landfill leachate was treated by a combined sequential batch reactor (SBR), coagulation, Fenton oxidation and biological aerated filter (BAF) technology. The metals in treatment process were fractionated into three fractions: particulate and colloidal (size charge filtration), free ion/labile (cation exchange) and non-labile fractions. Fifty percent to 66% Cu, Ni, Zn, Mn, Pb and Cd were present as particulate/colloidal matter in raw leachate, whereas Cr was present 94.9% as non-labile complexes. The free ion/labile fractions of Ni, Zn, Mg, Mn, Pb and Cd increased significantly after treatment except Cr. Fifty-nine percent to 100% of Al was present mainly as particulate/colloidal matter > 0.45 μm and the remaining portions were predicted as non-labile complexes except in coagulation effluent. The speciation of Fe varied significantly in various individual processes. Visual MINTEQ simulation showed that 95-100% colloidal species for Cu, Cd and Pb were present as metal-humic complexes even with the lower dissolved organic carbon. Optimum agreements for the free ion/labile species were within acidic solution, whereas under-estimated in alkaline effluents. Overestimated particulate/colloidal fraction consisted with the hypothesis that a portion of colloids in fraction < 0.45 μm were considered as dissolved. - Research Highlights: → Metals in various landfill leachate treatments were size charge fractionated and the speciation transformations were compared. → Species predictions of metals were simulated by Visual MINTEQ model. → Optimum agreements for the free ion/labile species were within acidic solution. → Predictions of colloidal species agree with experimental data well in alkaline solution.

  16. High-throughput migration modelling for estimating exposure to chemicals in food packaging in screening and prioritization tools.

    Science.gov (United States)

    Ernstoff, Alexi S; Fantke, Peter; Huang, Lei; Jolliet, Olivier

    2017-11-01

    Specialty software and simplified models are often used to estimate migration of potentially toxic chemicals from packaging into food. Current models, however, are not suitable for emerging applications in decision-support tools, e.g. in Life Cycle Assessment and risk-based screening and prioritization, which require rapid computation of accurate estimates for diverse scenarios. To fulfil this need, we develop an accurate and rapid (high-throughput) model that estimates the fraction of organic chemicals migrating from polymeric packaging materials into foods. Several hundred step-wise simulations optimised the model coefficients to cover a range of user-defined scenarios (e.g. temperature). The developed model, operationalised in a spreadsheet for future dissemination, nearly instantaneously estimates chemical migration, and has improved performance over commonly used model simplifications. When using measured diffusion coefficients the model accurately predicted (R 2  = 0.9, standard error (S e ) = 0.5) hundreds of empirical data points for various scenarios. Diffusion coefficient modelling, which determines the speed of chemical transfer from package to food, was a major contributor to uncertainty and dramatically decreased model performance (R 2  = 0.4, S e  = 1). In all, this study provides a rapid migration modelling approach to estimate exposure to chemicals in food packaging for emerging screening and prioritization approaches. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Consequences of the genetic threshold model for observing partial migration under climate change scenarios.

    Science.gov (United States)

    Cobben, Marleen M P; van Noordwijk, Arie J

    2017-10-01

    Migration is a widespread phenomenon across the animal kingdom as a response to seasonality in environmental conditions. Partially migratory populations are populations that consist of both migratory and residential individuals. Such populations are very common, yet their stability has long been debated. The inheritance of migratory activity is currently best described by the threshold model of quantitative genetics. The inclusion of such a genetic threshold model for migratory behavior leads to a stable zone in time and space of partially migratory populations under a wide range of demographic parameter values, when assuming stable environmental conditions and unlimited genetic diversity. Migratory species are expected to be particularly sensitive to global warming, as arrival at the breeding grounds might be increasingly mistimed as a result of the uncoupling of long-used cues and actual environmental conditions, with decreasing reproduction as a consequence. Here, we investigate the consequences for migratory behavior and the stability of partially migratory populations under five climate change scenarios and the assumption of a genetic threshold value for migratory behavior in an individual-based model. The results show a spatially and temporally stable zone of partially migratory populations after different lengths of time in all scenarios. In the scenarios in which the species expands its range from a particular set of starting populations, the genetic diversity and location at initialization determine the species' colonization speed across the zone of partial migration and therefore across the entire landscape. Abruptly changing environmental conditions after model initialization never caused a qualitative change in phenotype distributions, or complete extinction. This suggests that climate change-induced shifts in species' ranges as well as changes in survival probabilities and reproductive success can be met with flexibility in migratory behavior at the

  18. An agent-based model of leukocyte transendothelial migration during atherogenesis.

    Directory of Open Access Journals (Sweden)

    Rita Bhui

    2017-05-01

    Full Text Available A vast amount of work has been dedicated to the effects of hemodynamics and cytokines on leukocyte adhesion and trans-endothelial migration (TEM and subsequent accumulation of leukocyte-derived foam cells in the artery wall. However, a comprehensive mechanobiological model to capture these spatiotemporal events and predict the growth and remodeling of an atherosclerotic artery is still lacking. Here, we present a multiscale model of leukocyte TEM and plaque evolution in the left anterior descending (LAD coronary artery. The approach integrates cellular behaviors via agent-based modeling (ABM and hemodynamic effects via computational fluid dynamics (CFD. In this computational framework, the ABM implements the diffusion kinetics of key biological proteins, namely Low Density Lipoprotein (LDL, Tissue Necrosis Factor alpha (TNF-α, Interlukin-10 (IL-10 and Interlukin-1 beta (IL-1β, to predict chemotactic driven leukocyte migration into and within the artery wall. The ABM also considers wall shear stress (WSS dependent leukocyte TEM and compensatory arterial remodeling obeying Glagov's phenomenon. Interestingly, using fully developed steady blood flow does not result in a representative number of leukocyte TEM as compared to pulsatile flow, whereas passing WSS at peak systole of the pulsatile flow waveform does. Moreover, using the model, we have found leukocyte TEM increases monotonically with decreases in luminal volume. At critical plaque shapes the WSS changes rapidly resulting in sudden increases in leukocyte TEM suggesting lumen volumes that will give rise to rapid plaque growth rates if left untreated. Overall this multi-scale and multi-physics approach appropriately captures and integrates the spatiotemporal events occurring at the cellular level in order to predict leukocyte transmigration and plaque evolution.

  19. Demographic Models for Projecting Population and Migration: Methods for African Historical Analysis

    Directory of Open Access Journals (Sweden)

    Patrick Manning

    2015-08-01

    Full Text Available This study presents methods for projecting population and migration over time in cases were empirical data are missing or undependable. The methods are useful for cases in which the researcher has details of population size and structure for a limited period of time (most obviously, the end point, with scattered evidence on other times. It enables estimation of population size, including its structure in age, sex, and status, either forward or backward in time. The program keeps track of all the details. The calculated data can be reported or sampled and compared to empirical findings at various times and places to expected values based on other procedures of estimation. The application of these general methods that is developed here is the projection of African populations backwards in time from 1950, since 1950 is the first date for which consistently strong demographic estimates are available for national-level populations all over the African continent. The models give particular attention to migration through enslavement, which was highly important in Africa from 1650 to 1900. Details include a sensitivity analysis showing relative significance of input variables and techniques for calibrating various dimensions of the projection with each other. These same methods may be applicable to quite different historical situations, as long as the data conform in structure to those considered here.

  20. Earthquake Clusters and Spatio-temporal Migration of earthquakes in Northeastern Tibetan Plateau: a Finite Element Modeling

    Science.gov (United States)

    Sun, Y.; Luo, G.

    2017-12-01

    Seismicity in a region is usually characterized by earthquake clusters and earthquake migration along its major fault zones. However, we do not fully understand why and how earthquake clusters and spatio-temporal migration of earthquakes occur. The northeastern Tibetan Plateau is a good example for us to investigate these problems. In this study, we construct and use a three-dimensional viscoelastoplastic finite-element model to simulate earthquake cycles and spatio-temporal migration of earthquakes along major fault zones in northeastern Tibetan Plateau. We calculate stress evolution and fault interactions, and explore effects of topographic loading and viscosity of middle-lower crust and upper mantle on model results. Model results show that earthquakes and fault interactions increase Coulomb stress on the neighboring faults or segments, accelerating the future earthquakes in this region. Thus, earthquakes occur sequentially in a short time, leading to regional earthquake clusters. Through long-term evolution, stresses on some seismogenic faults, which are far apart, may almost simultaneously reach the critical state of fault failure, probably also leading to regional earthquake clusters and earthquake migration. Based on our model synthetic seismic catalog and paleoseismic data, we analyze probability of earthquake migration between major faults in northeastern Tibetan Plateau. We find that following the 1920 M 8.5 Haiyuan earthquake and the 1927 M 8.0 Gulang earthquake, the next big event (M≥7) in northeastern Tibetan Plateau would be most likely to occur on the Haiyuan fault.

  1. Green sturgeon distribution in the Pacific Ocean estimated from modeled oceanographic features and migration behavior.

    Science.gov (United States)

    Huff, David D; Lindley, Steven T; Wells, Brian K; Chai, Fei

    2012-01-01

    The green sturgeon (Acipenser medirostris), which is found in the eastern Pacific Ocean from Baja California to the Bering Sea, tends to be highly migratory, moving long distances among estuaries, spawning rivers, and distant coastal regions. Factors that determine the oceanic distribution of green sturgeon are unclear, but broad-scale physical conditions interacting with migration behavior may play an important role. We estimated the distribution of green sturgeon by modeling species-environment relationships using oceanographic and migration behavior covariates with maximum entropy modeling (MaxEnt) of species geographic distributions. The primary concentration of green sturgeon was estimated from approximately 41-51.5° N latitude in the coastal waters of Washington, Oregon, and Vancouver Island and in the vicinity of San Francisco and Monterey Bays from 36-37° N latitude. Unsuitably cold water temperatures in the far north and energetic efficiencies associated with prevailing water currents may provide the best explanation for the range-wide marine distribution of green sturgeon. Independent trawl records, fisheries observer records, and tagging studies corroborated our findings. However, our model also delineated patchily distributed habitat south of Monterey Bay, though there are few records of green sturgeon from this region. Green sturgeon are likely influenced by countervailing pressures governing their dispersal. They are behaviorally directed to revisit natal freshwater spawning rivers and persistent overwintering grounds in coastal marine habitats, yet they are likely physiologically bounded by abiotic and biotic environmental features. Impacts of human activities on green sturgeon or their habitat in coastal waters, such as bottom-disturbing trawl fisheries, may be minimized through marine spatial planning that makes use of high-quality species distribution information.

  2. Testing and intercomparison of model predictions of radionuclide migration from a hypothetical area source

    International Nuclear Information System (INIS)

    O'Brien, R.S.; Yu, C.; Zeevaert, T.; Olyslaegers, G.; Amado, V.; Setlow, L.W.; Waggitt, P.W.

    2008-01-01

    This work was carried out as part of the International Atomic Energy Agency's EMRAS program. One aim of the work was to develop scenarios for testing computer models designed for simulating radionuclide migration in the environment, and to use these scenarios for testing the models and comparing predictions from different models. This paper presents the results of the development and testing of a hypothetical area source of NORM waste/residue using two complex computer models and one screening model. There are significant differences in the methods used to model groundwater flow between the complex models. The hypothetical source was used because of its relative simplicity and because of difficulties encountered in finding comprehensive, well-validated data sets for real sites. The source consisted of a simple repository of uniform thickness, with 1 Bq g -1 of uranium-238 ( 238 U) (in secular equilibrium with its decay products) distributed uniformly throughout the waste. These approximate real situations, such as engineered repositories, waste rock piles, tailings piles and landfills. Specification of the site also included the physical layout, vertical stratigraphic details, soil type for each layer of material, precipitation and runoff details, groundwater flow parameters, and meteorological data. Calculations were carried out with and without a cover layer of clean soil above the waste, for people working and living at different locations relative to the waste. The predictions of the two complex models showed several differences which need more detailed examination. The scenario is available for testing by other modelers. It can also be used as a planning tool for remediation work or for repository design, by changing the scenario parameters and running the models for a range of different inputs. Further development will include applying models to real scenarios and integrating environmental impact assessment methods with the safety assessment tools currently

  3. Signaling through three chemokine receptors triggers the migration of transplanted neural precursor cells in a model of multiple sclerosis.

    Science.gov (United States)

    Cohen, Mikhal E; Fainstein, Nina; Lavon, Iris; Ben-Hur, Tamir

    2014-09-01

    Multiple sclerosis (MS) is a multifocal disease, and precursor cells need to migrate into the multiple lesions in order to exert their therapeutic effects. Therefore, cell migration is a crucial element in regenerative processes in MS, dictating the route of delivery, when cell transplantation is considered. We have previously shown that inflammation triggers migration of multi-potential neural precursor cells (NPCs) into the white matter of experimental autoimmune encephalomyelitis (EAE) rodents, a widely used model of MS. Here we investigated the molecular basis of this attraction. NPCs were grown from E13 embryonic mouse brains and transplanted into the lateral cerebral ventricles of EAE mice. Transplanted NPC migration was directed by three tissue-derived chemokines. Stromal cell-derived factor-1α, monocyte chemo-attractant protein-1 and hepatocyte growth factor were expressed in the EAE brain and specifically in microglia and astrocytes. Their cognate receptors, CXCR4, CCR2 or c-Met were constitutively expressed on NPCs. Selective blockage of CXCR4, CCR2 or c-Met partially inhibited NPC migration in EAE brains. Blocking all three receptors had an additive effect and resulted in profound inhibition of NPC migration, as compared to extensive migration of control NPCs. The inflammation-triggered NPC migration into white matter tracts was dependent on a motile NPC phenotype. Specifically, depriving NPCs from epidermal growth factor (EGF) prevented the induction of glial commitment and a motile phenotype (as indicated by an in vitro motility assay), hampering their response to neuroinflammation. In conclusion, signaling via three chemokine systems accounts for most of the inflammation-induced, tissue-derived attraction of transplanted NPCs into white matter tracts during EAE. Copyright © 2014. Published by Elsevier B.V.

  4. Modeling and predictions of biphasic mechanosensitive cell migration altered by cell-intrinsic properties and matrix confinement.

    Science.gov (United States)

    Pathak, Amit

    2018-04-12

    Motile cells sense the stiffness of their extracellular matrix (ECM) through adhesions and respond by modulating the generated forces, which in turn lead to varying mechanosensitive migration phenotypes. Through modeling and experiments, cell migration speed is known to vary with matrix stiffness in a biphasic manner, with optimal motility at an intermediate stiffness. Here, we present a two-dimensional cell model defined by nodes and elements, integrated with subcellular modeling components corresponding to mechanotransductive adhesion formation, force generation, protrusions and node displacement. On 2D matrices, our calculations reproduce the classic biphasic dependence of migration speed on matrix stiffness and predict that cell types with higher force-generating ability do not slow down on very stiff matrices, thus disabling the biphasic response. We also predict that cell types defined by lower number of total receptors require stiffer matrices for optimal motility, which also limits the biphasic response. For a cell type with robust biphasic migration on 2D surface, simulations in channel-like confined environments of varying width and height predict faster migration in more confined matrices. Simulations performed in shallower channels predict that the biphasic mechanosensitive cell migration response is more robust on 2D micro-patterns as compared to the channel-like 3D confinement. Thus, variations in the dimensionality of matrix confinement alters the way migratory cells sense and respond to the matrix stiffness. Our calculations reveal new phenotypes of stiffness- and topography-sensitive cell migration that critically depend on both cell-intrinsic and matrix properties. These predictions may inform our understanding of various mechanosensitive modes of cell motility that could enable tumor invasion through topographically heterogeneous microenvironments. © 2018 IOP Publishing Ltd.

  5. Asymmetric migration of human keratinocytes under mechanical stretch and cocultured fibroblasts in a wound repair model.

    Directory of Open Access Journals (Sweden)

    Dongyuan Lü

    Full Text Available Keratinocyte migration during re-epithelization is crucial in wound healing under biochemical and biomechanical microenvironment. However, little is known about the underlying mechanisms whereby mechanical tension and cocultured fibroblasts or keratinocytes modulate the migration of keratinocytes or fibroblasts. Here we applied a tensile device together with a modified transwell assay to determine the lateral and transmembrane migration dynamics of human HaCaT keratinocytes or HF fibroblasts. A novel pattern of asymmetric migration was observed for keratinocytes when they were cocultured with non-contact fibroblasts, i.e., the accumulative distance of HaCaT cells was significantly higher when moving away from HF cells or migrating from down to up cross the membrane than that when moving close to HF cells or when migrating from up to down, whereas HF migration was symmetric. This asymmetric migration was mainly regulated by EGF derived from fibroblasts, but not transforming growth factor α or β1 production. Mechanical stretch subjected to fibroblasts fostered keratinocyte asymmetric migration by increasing EGF secretion, while no role of mechanical stretch was found for EGF secretion by keratinocytes. These results provided a new insight into understanding the regulating mechanisms of two- or three-dimensional migration of keratinocytes or fibroblasts along or across dermis and epidermis under biomechanical microenvironment.

  6. Worst case prediction of additives migration from polystyrene for food safety purposes: a model update.

    Science.gov (United States)

    Martínez-López, Brais; Gontard, Nathalie; Peyron, Stéphane

    2018-03-01

    A reliable prediction of migration levels of plastic additives into food requires a robust estimation of diffusivity. Predictive modelling of diffusivity as recommended by the EU commission is carried out using a semi-empirical equation that relies on two polymer-dependent parameters. These parameters were determined for the polymers most used by packaging industry (LLDPE, HDPE, PP, PET, PS, HIPS) from the diffusivity data available at that time. In the specific case of general purpose polystyrene, the diffusivity data published since then shows that the use of the equation with the original parameters results in systematic underestimation of diffusivity. The goal of this study was therefore, to propose an update of the aforementioned parameters for PS on the basis of up to date diffusivity data, so the equation can be used for a reasoned overestimation of diffusivity.

  7. A stable implementation of the prestack exploding reflector modeling and migration

    KAUST Repository

    Alkhalifah, Tariq Ali

    2011-01-01

    The double square-root DSR equation is known to image data by downward continuation using one-way depth extrapolation methods. A two-way time extrapolation of the DSR-derived phase operator suffers from an essential singularity for horizontally traveling waves. This singularity can be avoided by limiting the range of wavenumbers treated in a spectral-based extrapolation referred to as the low-rank method. However, the region around the singularity will still induce instability. We derive an approximation to the DSR formulation based on a high frequency approximation. The resulting equation is both highly accurate and free of singularities. Applications to synthetic data including imaging of the Marmousi dataset demonstrate the accuracy of the new prestack modeling and migration approach. © 2011 Society of Exploration Geophysicists.

  8. Numerical modelling of moisture migration in non-uniformly heated concrete

    International Nuclear Information System (INIS)

    Khoylou, N.; England, G.L.

    1995-01-01

    This paper describes a numerical modelling procedure, capable of predicting temperature-dependent moisture flow in concrete. The flow direction is not defined by the sign of the temperature gradient. Irreversible thermodynamic process based on the production of entropy are used to check the course of the numerical calculations which take place in a stepwise manner in time. Numerical results indicate that thick walls will take many years to dry significantly. They also show that if venting to atmosphere is introduced at locations within the wall, the pore-water pressure, the water migration behaviour and the drying rate will be changed. This behaviour has also been experimentally observed. (author). 7 refs., 10 figs

  9. A coupled reaction and transport model for assessing the injection, migration and fate of waste fluids

    International Nuclear Information System (INIS)

    Liu, X.; Ortoleva, P.

    1996-01-01

    The use of reaction-transport modeling for reservoir assessment and management in the context of deep well waste injection is evaluated. The study is based on CIRF.A (Chemical Interaction of Rock and Fluid), a fully coupled multiphase flow, contaminant transport, and fluid and mineral reaction model. Although SWIFT (Sandia Waste-Isolation Flow and Transport Model) is often the numerical model of choice, it can not account for chemical reactions involving rock, wastes, and formation fluids and their effects on contaminant transport, rock permeability and porosity, and the integrity of the reservoir and confining units. CIRF.A can simulate all these processes. Two field cases of waste injection were simulated by CIRF.A. Both observation data and simulation results show mineral precipitation in one case and rock dissolution in another case. Precipitation and dissolution change rock porosity and permeability, and hence the pattern of fluid migration. The model is shown to be invaluable in analyzing near borehole and reservoir-scale effects during waste injection and predicting the 10,000 year fate of the waste plume. The benefits of using underpressured compartments as waste repositories were also demonstrated by CIRF.A simulations

  10. Migration of Gas in Water Saturated Clays by Coupled Hydraulic-Mechanical Model

    Directory of Open Access Journals (Sweden)

    Aliaksei Pazdniakou

    2018-01-01

    Full Text Available Understanding the gas migration in highly water saturated sedimentary rock formations is of great importance for safety of radioactive waste repositories which may use these host rocks as barrier. Recent experiments on drainage in argillite samples have demonstrated that they cannot be represented in terms of standard two-phase flow Darcy model. It has been suggested that gas flows along highly localized dilatant pathways. Due to very small pore size and the opacity of the material, it is not possible to observe this two-phase flow directly. In order to better understand the gas transport, a numerical coupled hydraulic-mechanical model at the pore scale is proposed. The model is formulated in terms of Smoothed Particle Hydrodynamics (SPH and is applied to simulate drainage within a sample reconstructed from the Focused Ion Beam (FIB images of Callovo-Oxfordian claystone. A damage model is incorporated to take into account the degradation of elastic solid properties due to local conditions, which may lead to formation of new pathways and thus to modifications of fluid transport. The influence of the damage model as well as the possible importance of rigid inclusions is demonstrated and discussed.

  11. Regional-scale brine migration along vertical pathways due to CO2 injection - Part 1: The participatory modeling approach

    Science.gov (United States)

    Scheer, Dirk; Konrad, Wilfried; Class, Holger; Kissinger, Alexander; Knopf, Stefan; Noack, Vera

    2017-06-01

    Saltwater intrusion into potential drinking water aquifers due to the injection of CO2 into deep saline aquifers is one of the potential hazards associated with the geological storage of CO2. Thus, in a site selection process, models for predicting the fate of the displaced brine are required, for example, for a risk assessment or the optimization of pressure management concepts. From the very beginning, this research on brine migration aimed at involving expert and stakeholder knowledge and assessment in simulating the impacts of injecting CO2 into deep saline aquifers by means of a participatory modeling process. The involvement exercise made use of two approaches. First, guideline-based interviews were carried out, aiming at eliciting expert and stakeholder knowledge and assessments of geological structures and mechanisms affecting CO2-induced brine migration. Second, a stakeholder workshop including the World Café format yielded evaluations and judgments of the numerical modeling approach, scenario selection, and preliminary simulation results. The participatory modeling approach gained several results covering brine migration in general, the geological model sketch, scenario development, and the review of the preliminary simulation results. These results were included in revised versions of both the geological model and the numerical model, helping to improve the analysis of regional-scale brine migration along vertical pathways due to CO2 injection.

  12. Modeling approach to various time and spatial scale environmental issues in Fukushima. Related to radioactive cesium migration in aquatic systems

    International Nuclear Information System (INIS)

    Kurikami, Hiroshi; Kitamura, Akihiro; Yamada, Susumu; Machida, Masahiko

    2015-01-01

    Several numerical models have been prepared to deal with various time- and spatial-scale issues related to radioactive cesium migration in environment in Fukushima area. The SACT (Soil and Cesium Transport) model developed by the Japan Atomic Energy Agency (JAEA) predicts middle- to long-term evolution of radioactive cesium distribution due to soil erosion, subsequent sediment transport and deposition, and radioactive cesium migration based on the Universal Soil Loss Equation (USLE). The TODAM (Time-dependent One-dimensional Degradation and Migration) model, iRIC/Nays2D and the FLESCOT (Flow, Energy, Salinity, Sediment, Contaminant Transport) model are one-, two- and three-dimensional river/reservoir/coastal models, respectively. Based on conservation equations of sediment and radioactive cesium, they treat advection and diffusion of suspended sediment and cesium, deposition of sediment to bed, re-suspension from bed and adsorption/desorption of radioactive cesium. These models are suitable for small and short time scale issues such as high discharges of sediment and radioactive cesium from rivers due to heavy rainfall events. This paper describes fragments of the JAEA’s approaches of modeling to deal with the issues corresponding to radioactive cesium migration in environment with some case studies. (author)

  13. Modeling Systematic Change in Stopover Duration Does Not Improve Bias in Trends Estimated from Migration Counts.

    Directory of Open Access Journals (Sweden)

    Tara L Crewe

    Full Text Available The use of counts of unmarked migrating animals to monitor long term population trends assumes independence of daily counts and a constant rate of detection. However, migratory stopovers often last days or weeks, violating the assumption of count independence. Further, a systematic change in stopover duration will result in a change in the probability of detecting individuals once, but also in the probability of detecting individuals on more than one sampling occasion. We tested how variation in stopover duration influenced accuracy and precision of population trends by simulating migration count data with known constant rate of population change and by allowing daily probability of survival (an index of stopover duration to remain constant, or to vary randomly, cyclically, or increase linearly over time by various levels. Using simulated datasets with a systematic increase in stopover duration, we also tested whether any resulting bias in population trend could be reduced by modeling the underlying source of variation in detection, or by subsampling data to every three or five days to reduce the incidence of recounting. Mean bias in population trend did not differ significantly from zero when stopover duration remained constant or varied randomly over time, but bias and the detection of false trends increased significantly with a systematic increase in stopover duration. Importantly, an increase in stopover duration over time resulted in a compounding effect on counts due to the increased probability of detection and of recounting on subsequent sampling occasions. Under this scenario, bias in population trend could not be modeled using a covariate for stopover duration alone. Rather, to improve inference drawn about long term population change using counts of unmarked migrants, analyses must include a covariate for stopover duration, as well as incorporate sampling modifications (e.g., subsampling to reduce the probability that individuals will

  14. Leachate pretreatment for enhancing organic matter conversion in landfill bioreactor

    International Nuclear Information System (INIS)

    He Pinjing; Qu Xian; Shao Liming; Li Guojian; Lee Duujong

    2007-01-01

    Direct recycling of leachate from refuse of high food waste content was shown to ineffectively stabilize the refuse. This work aims at evaluating the effects of three pretreatments of leachate on the refuse stabilization efficiency were investigated. Pretreatment of leachate using an anaerobic upflow filtration bioreactor (UFB) or a well-decomposed waste layer could reduce the COD and provide methanogens, both were beneficial to establish early methanogenesis status. Using an aerobic sequential batch reactor (SBR) to pretreat the leachate could reduce its COD to 1000 mg l -1 , but the fully developed methanogenesis phase would be built up in a later stage. The organic matters in the effluent leachate inhibited both the hydrolysis/acidogenesis and the methanogenesis steps in the refuse. With the dilution and acid neutralization effects by the recycled leachate, a favorable methanogenetic environment could be produced from the column's top, which moved downward along, and finally made the breakthrough of the column

  15. Biodegradability of leachates from Chinese and German municipal solid waste

    Institute of Scientific and Technical Information of China (English)

    SELIC E.; WANG Chi; BOES N., HERBELL J.D.

    2007-01-01

    The quantitative and qualitative composition of Chinese municipal solid waste (MSW) differs significantly from German waste. The focus of this paper is on whether these differences also lead to dissimilar qualities of leachates during storage or landfilling. Leachates ingredients determine the appropriate treatment technique. MSW compositions of the two cities Guilin (China) and Essen (Germany), each with approx. 600000 inhabitants, are used to simulate Chinese and German MSW types. A sequencing batch reactor (SBR) is used, combining aerobic and anaerobic reaction principles, to test the biodegradability of leachates. Leachates are tested for temperature, pH-value, redox potentials, and oxygen concentration. Chemical oxygen demand (COD) values are determined. Within 8 h, the biodegradation rates for both kinds of leachates are more than 90%. Due to the high organic content of Chinese waste, the degradation rate for Guilin MSW leachate is even higher, up to 97%. The effluent from SBR technique is suitable for direct discharge into bodies of water.

  16. Effect of amendments addition on adsorption of landfill leachate

    Science.gov (United States)

    Bai, X. J.; Zhang, H. Y.; Wang, G. Q.; Gu, J.; Wang, J. H.; Duan, G. P.

    2018-03-01

    The disposal of leachate has become one of the most pressing problems for landfills. This study taking three kinds of amendments, corn straw, mushroom residue and garden waste as adsorbent materials, evaluates the different amendments on the leachate adsorption effect through analyzing indicators as the saturation adsorption ratio, sulfur containing odor emission, heat value. The results showed that all three kinds of amendments can effectively adsorb leachate, with saturation adsorption ratio between 1: 2 and 1: 4. Adding amendment could significantly reduce the sulfur containing odor emission of leachate. Compared the three kinds of amendments, mushroom residue could adsorb leachate at a maximize degree with a low concentration of sulfur containing odor emission. The industrial analysis showed that the heat values of the amendments after absorbing leachate are more than 14MJ/kg, and it can be utilized as a biomass fuel.

  17. LCA and economic evaluation of landfill leachate and gas technologies

    DEFF Research Database (Denmark)

    Damgaard, Anders; Manfredi, Simone; Merrild, Hanna Kristina

    2011-01-01

    Landfills receiving a mix of waste, including organics, have developed dramatically over the last 3–4 decades; from open dumps to engineered facilities with extensive controls on leachate and gas. The conventional municipal landfill will in most climates produce a highly contaminated leachate...... and a significant amount of landfill gas. Leachate controls may include bottom liners and leachate collection systems as well as leachate treatment prior to discharge to surface water. Gas controls may include oxidizing top covers, gas collection systems with flares or gas utilization systems for production...... of electricity and heat.The importance of leachate and gas control measures in reducing the overall environmental impact from a conventional landfill was assessed by life-cycle-assessment (LCA). The direct cost for the measures were also estimated providing a basis for assessing which measures are the most cost...

  18. Cellular automata model for human articular chondrocytes migration, proliferation and cell death: An in vitro validation.

    Science.gov (United States)

    Vaca-González, J J; Gutiérrez, M L; Guevara, J M; Garzón-Alvarado, D A

    2017-01-01

    Articular cartilage is characterized by low cell density of only one cell type, chondrocytes, and has limited self-healing properties. When articular cartilage is affected by traumatic injuries, a therapeutic strategy such as autologous chondrocyte implantation is usually proposed for its treatment. This approach requires in vitro chondrocyte expansion to yield high cell number for cell transplantation. To improve the efficiency of this procedure, it is necessary to assess cell dynamics such as migration, proliferation and cell death during culture. Computational models such as cellular automata can be used to simulate cell dynamics in order to enhance the result of cell culture procedures. This methodology has been implemented for several cell types; however, an experimental validation is required for each one. For this reason, in this research a cellular automata model, based on random-walk theory, was devised in order to predict articular chondrocyte behavior in monolayer culture during cell expansion. Results demonstrated that the cellular automata model corresponded to cell dynamics and computed-accurate quantitative results. Moreover, it was possible to observe that cell dynamics depend on weighted probabilities derived from experimental data and cell behavior varies according to the cell culture period. Thus, depending on whether cells were just seeded or proliferated exponentially, culture time probabilities differed in percentages in the CA model. Furthermore, in the experimental assessment a decreased chondrocyte proliferation was observed along with increased passage number. This approach is expected to having other uses as in enhancing articular cartilage therapies based on tissue engineering and regenerative medicine.

  19. Generation of leachate and the flow regime in landfills

    Energy Technology Data Exchange (ETDEWEB)

    Bendz, D.

    1998-06-01

    In this thesis the generation of leachate and the presence and movement of water in landfilled municipal solid waste (MSW) is investigated. The precipitation-leachate discharge relationship for landfills was found to be dominated by evaporation, accumulation in the soil cover, accumulation in the solid waste and fast gravitational flow in a network of channels. The flow regime is governed by the heterogeneity of the internal geometry of the landfill, which is characterized by a discrete structure, significant horizontal stratification, structural voids, impermeable surfaces, and low capillarity. Also the boundary conditions, that is the water input pattern, has shown to be important for the flow process. Based on this, landfilled waste can be conceptualized as a dual domain medium, consisting of a channel domain and a matrix domain. The matrix flow is slow and diffusive, whereas the channel flow is assumed to be driven solely by gravity and to take place as a thin viscous film on solid surfaces. A kinematic wave model for unsaturated infiltration and internal drainage in the channel domain is presented. The model employs a two-parameter power expression as macroscopic flux law. Solutions were derived for the cases when water enters the channel domain laterally and when water enters from the upper end. The model parameters were determined and interpreted in terms of the internal geometry of the waste medium by fitting the model to one set of infiltration and drainage data derived from a large scale laboratory experiment under transient conditions. The model was validated using another set of data from a sequence of water input events and was shown to perform accurately. A solute transport model was developed by coupling a simple piston flux expression and a mobile-immobile conceptualization of the transport domains with the water flow model. Breakthrough curves derived from steady and transient tracer experiments where interpreted with the model. The transport

  20. Rubber tire leachates in the aquatic environment.

    Science.gov (United States)

    Evans, J J

    1997-01-01

    Tires have a deleterious effect on the environment. This review discusses the background of scrap tires discarded in the environment, including tire composition, adverse environmental effects, threats to public health and safety, and solid waste management. Despite the widespread use of scrap tires in environmental applications, both land-based and aquatic, data on the indicators of environmental degradation are extremely scarce. Indicators of environmental degradation include analysis of chemicals within the water and sediment, analysis of contaminants within organisms, and analysis of the biological effects of these compounds on plants, animals, microbes, and organelles. Although these indicators are most useful when used in parallel, a review of the available information on chemical characterization of tire leachate from tire storage facilities, manufacturing, usage in recycling applications, and toxicity exposure studies, of vegetation surveys from waste tire areas and reviews of mammalian tire product toxicity, and of toxicity, mutagenicity, and carcinogenicity of tire exposure in experimental aquatic animals, microbes, and organelles is presented. The major characteristics of these studies are discussed in specific sections. The "Discussion and Conclusions" section discusses and summarizes the biological effects and chemical characterization of tire leachates. A global environmental perspective is included to improve our understanding of the deficiency of the current knowledge of tire leachate toxicity from various sources and to encourage interdisciplinary studies to establish the pattern of pollution associated with waste tire management.

  1. Tritium distribution in leachates from domestic solid waste landfills

    International Nuclear Information System (INIS)

    Park, Soon Dal; Kim, Jung Suk; Joe, Kih Soo; Kim, Jong Gu; Kim, Won Ho

    2004-01-01

    It is for the purpose of investigating the tritium distribution in the leachates, the raw and treated leachates and the condensates of the methane gas, which have occurred from domestic solid waste landfills. Also it aims to measure the tritium distribution level on the colloid size of the leachates, the raw and treated leachates. It was found that the major inorganic contaminants of the leachates were Na, K, Ca, Mg, NH 4 + -N and Cl - . The mean tritium level of the raw leachates of the investigated 13 landfill sites for 6 months was 17∼1196 TU. It corresponded to a several scores or hundreds of magnitude higher value than that of the normal environmental sample level except for two landfill sites. Also such a high concentration of the tritium was found in the treated leachates and methane gas condensates as well. Nevertheless it is important to emphasize that the tritium level which was found in this research is about 100 times lower than the tritium limit for the drinking water quality. And most of the tritium existed in the dissolved colloid of the leachate of which the colloid size is below 0.45 μm. Also, according to the tritium analysis results of the leachates after filtration with 0.45μm membrane filter for some landfills, it is likely that some tritium of the leachate would be distributed in a colloid size over 0.45μm. In general the relationship between the tritium and other contaminants in the raw leachate was low, but it was relatively high between the tritium and TOC. However, the tritium content in the leachate had no meaningful relationship with the scale, hydrological characteristics and age of the landfill

  2. Assessment of leachates from uncontrolled landfill: Tangier case study

    Directory of Open Access Journals (Sweden)

    Elmaghnougi I.

    2018-01-01

    Full Text Available Landfill site of Tangier City is non-engineered low lying open dump. It has neither bottom liner nor leachate collection and treatment system. Therefore, all the leachate generated finds its paths into the surrounding environment Leachate samples of landfill site were collected and analyzed to estimate its pollution potential. The analyzed samples contained a high concentration of organic and inorganic compounds, beyond the permissible limits.

  3. Assessment of leachates from uncontrolled landfill: Tangier case study

    Science.gov (United States)

    Elmaghnougi, I.; Afilal Tribak, A.; Maatouk, M.

    2018-05-01

    Landfill site of Tangier City is non-engineered low lying open dump. It has neither bottom liner nor leachate collection and treatment system. Therefore, all the leachate generated finds its paths into the surrounding environment Leachate samples of landfill site were collected and analyzed to estimate its pollution potential. The analyzed samples contained a high concentration of organic and inorganic compounds, beyond the permissible limits.

  4. Approach to stochastic modelling of consumer exposure for any substance from canned foods using simulant migration data.

    Science.gov (United States)

    Castle, L; Hart, A; Holmes, M J; Oldring, P K T

    2006-05-01

    A two-dimensional probabilistic model was constructed to estimate the short-term dietary exposure of UK consumers to any generalized migrant from coated light metal food packaging. Using three UK National Dietary and Nutrition Surveys (NDNS) comprising 4-7-day dietary surveys for different age and gender groups, actual body weights and survey years, a sample representative of the dietary consumption of the UK population was obtained comprising around 4,200 food items. Interrogation of the raw data showed that the per capita consumption of food and beverage for an adult was 2.9 kg per person day(-1), which is comparable with the US FDA value of 3.0 kg. The packaging type of each food item was assigned from the survey descriptions or by sampling from distributions based upon market share information and expert judgement. Each food item was assigned to the relevant food simulant: A (aqueous), B (acidic) or D (fatty), so that simulant migration data could be used. The exposure model was used to evaluate exposure for a given level of migration and, conversely, the level of migration that could be tolerated whilst keeping within a target threshold exposure level. As examples, migration at 10 microg dm(-2) into fatty foods only resulted in an exposure ranging from 0.06 to 0.22 microg kg(-1) body (actual) weight day(-1) depending on the scenario. The model revealed that if migration from metal coatings was only into fatty foods, migration in the range 1.83-4.95 microg dm(2) (97.5th percentile, depending on the scenario) would give an exposure of less than 1.5 microg per person day(-1). This is a toxicological threshold limit used in the USA. If migration into simulants A and B is also considered to be at the same level as that for simulant D, then the level of migration for the threshold to be reached is, not surprisingly, lower (0.64-0.87 microg dm(-2)) than that if migration were only into fatty foods. In this case, clearly the main contributors to the exposure were

  5. A combined approach to investigate the toxicity of an industrial landfill's leachate: Chemical analyses, risk assessment and in vitro assays

    International Nuclear Information System (INIS)

    Baderna, D.; Maggioni, S.; Boriani, E.; Gemma, S.; Molteni, M.; Lombardo, A.; Colombo, A.; Bordonali, S.; Rotella, G.; Lodi, M.; Benfenati, E.

    2011-01-01

    Solid wastes constitute an important and emerging problem. Landfills are still one of the most common ways to manage waste disposal. The risk assessment of pollutants from landfills is becoming a major environmental issue in Europe, due to the large number of sites and to the importance of groundwater protection. Furthermore, there is lack of knowledge for the environmental, ecotoxicological and toxicological characteristics of most contaminants contained into landfill leacheates. Understanding leachate composition and creating an integrated strategy for risk assessment are currently needed to correctly face the landfill issues and to make projections on the long-term impacts of a landfill, with particular attention to the estimation of possible adverse effects on human health and ecosystem. In the present study, we propose an integrated strategy to evaluate the toxicity of the leachate using chemical analyses, risk assessment guidelines and in vitro assays using the hepatoma HepG2 cells as a model. The approach was applied on a real case study: an industrial waste landfill in northern Italy for which data on the presence of leachate contaminants are available from the last 11 years. Results from our ecological risk models suggest important toxic effects on freshwater fish and small rodents, mainly due to ammonia and inorganic constituents. Our results from in vitro data show an inhibition of cell proliferation by leachate at low doses and cytotoxic effect at high doses after 48 h of exposure. - Research highlights: → We study the toxicity of leachate from a non-hazardous industrial waste landfill. → We perform chemical analyses, risk assessments and in vitro assays on HepG2 cells. → Risk models suggest toxic effects due to ammonia and inorganic constituents. → In vitro assays show that leachate inhibits cell proliferation at low doses. → Leachate can induce cytotoxic effects on HepG2 cells at high doses.

  6. Oil migration through unsaturated soils and its effect on the Vadose Zone Interactive Processes (VIP) model output

    International Nuclear Information System (INIS)

    Joseph, A.T.; Grenney, W.J.; Stevens, D.K.

    1994-01-01

    The VIP model, which simulates the concentration profiles of the hazardous compounds in the soil, water, and the air phases, assumes a fixed oily phase. The purpose of this study was to measure oil migration in soil systems and to determine its effect on the VIP model output. Experiments were conducted to demonstrate the mobility of an oil through the unsaturated zone of the soil. The studies were conducted in laboratory scale glass columns. A light petroleum oil and two types of soil were used. The experiments demonstrated that oil migrates down significantly through the soil columns. The extent of migration depended on the volume of oil applied and the type of soil. However, the applied oil was completely immobilized in the columns. The model was modified to incorporate oil migration. The modified model can be expected to produce more realistic contaminant concentration profiles during land treatment of oily wastes when compared to that produced by the present version of the VIP model. (Author)

  7. Dynamic pore network simulator for modelling buoyancy-driven migration during depressurisation of heavy-oil systems

    Energy Technology Data Exchange (ETDEWEB)

    Ezeuko, C.C.; McDougall, S.R. [Heriot-Watt Univ., Edinburgh (United Kingdom); Bondino, I. [Total E and P UK Ltd., London (United Kingdom); Hamon, G. [Total S.A., Paris (France)

    2008-10-15

    In an attempt to investigate the impact of gravitational forces on gas evolution during solution gas drive, a number of vertically-oriented heavy oil depletion experiments have been conducted. Some of the results of these studies suggest the occurrence of gas migration during these tests. However, a major limitation of these experiments is the difficulty in visualizing the process in reservoir rock samples. Experimental observations using transparent glass models have been useful in this context and provide a sound physical basis for modelling gravitational gas migration in gas-oil systems. This paper presented a new pore network simulator that was capable of modelling the time-dependent migration of growing gas structures. Multiple pore filling events were dynamically modelled with interface tracking allowing the full range of migratory behaviours to be reproduced, including braided migration and discontinuous dispersed flow. Simulation results were compared with experiments and were found to be in excellent agreement. The paper presented the model and discussed the implication of evolution regime on recovery from heavy oil systems undergoing depressurization. The simulation results demonstrated the complex interaction of a number of network and fluid parameters. It was concluded that the concomitant effect on the competition between capillarity and buoyancy produced different gas evolution patterns during pressure depletion. 28 refs., 2 tabs., 19 figs.

  8. Monitoring of Leachate Recirculation in a Bioreactor Using Electrical Resistivity

    Science.gov (United States)

    Grellier, S.; Bureau, N.; Robain, H.; Tabbagh, A.; Camerlynck, C.; Guerin, R.

    2004-05-01

    The bioreactor is a concept of waste landfill management consisting in speeding up the biodegradation by optimizing the moisture content through leachate recirculation. Electrical resistivity tomography (ERT) is carried out with fast resistivity-meter (Syscal Pro, IRIS Instruments, developed in the framework of the research project CERBERE 01V0665-69, funded by the French Research Ministry) to monitor leachate recirculation. During a recirculation period waste moisture increases, so that electrical resistivity may decrease, but at the same time temperature and mineralization of both waste and leachate become intermixed. If waste temperature is much higher than leachate temperature electrical resistivity will not decrease as much as if the temperature difference was smaller. If leachate mineralization (i.e. leachate conductivity) is higher than that of wet waste in the landfill, electrical resistivity will tend to decrease. Otherwise for example after an addition of rain water into the leachate storage or in case of very wet waste, the resistivities of each medium (leachate and wet waste) can be almost the same, so that leachate mineralization will not have a great influence on waste resistivity. Resistivity measurements were performed during 85 minutes injection trials (with a discharge of 20 m3 h-1) where leachate was injected through a vertical borehole perforated between 1.85 and 4.15 m. Three first measurements are made during the injection (3, 30 and 60 minutes from the beginning of the injection) and the two other after the injection period (8 and 72 minutes after the end of the injection). Apparent and interpreted resistivity variations that occurred during injection trials, expressed as the relative differences (in %) between apparent, respectively interpreted, resistivity during injection and apparent, respectively interpreted, resistivity before injection (reference measurement) show the formation of a plume (a negative anomaly: resistivity decreases with

  9. BATCH ANAEROBIC TREATMENT OF FRESH LEACHATE FROM TRANSFER STATION

    Directory of Open Access Journals (Sweden)

    SEYED MOHAMMAD DARA GHASIMI

    2008-12-01

    Full Text Available Leachate from transfer station requires treatment before being discharged into the environment to avoid surface and underground water contamination. Various factors such as waste composition, availability of oxygen and moisture, designing and controlling of transfer station operations have been shown to affect the composition of the leachate. The high COD, BOD, ammonia nitrogen (NH3-N and heavy metals contents of fresh leachate are the main problems faced by leachate treatment operators. The result of the present study indicated that this process reduced the COD content by 43%.The average removal efficiencies of BOD5, TS, TSS, and VSS were 80, 49, 37 and 39 %, respectively.

  10. Numerical modeling of fracking fluid and methane migration through fault zones in shale gas reservoirs

    Science.gov (United States)

    Taherdangkoo, Reza; Tatomir, Alexandru; Sauter, Martin

    2017-04-01

    Hydraulic fracturing operation in shale gas reservoir has gained growing interest over the last few years. Groundwater contamination is one of the most important environmental concerns that have emerged surrounding shale gas development (Reagan et al., 2015). The potential impacts of hydraulic fracturing could be studied through the possible pathways for subsurface migration of contaminants towards overlying aquifers (Kissinger et al., 2013; Myers, 2012). The intent of this study is to investigate, by means of numerical simulation, two failure scenarios which are based on the presence of a fault zone that penetrates the full thickness of overburden and connect shale gas reservoir to aquifer. Scenario 1 addresses the potential transport of fracturing fluid from the shale into the subsurface. This scenario was modeled with COMSOL Multiphysics software. Scenario 2 deals with the leakage of methane from the reservoir into the overburden. The numerical modeling of this scenario was implemented in DuMux (free and open-source software), discrete fracture model (DFM) simulator (Tatomir, 2012). The modeling results are used to evaluate the influence of several important parameters (reservoir pressure, aquifer-reservoir separation thickness, fault zone inclination, porosity, permeability, etc.) that could affect the fluid transport through the fault zone. Furthermore, we determined the main transport mechanisms and circumstances in which would allow frack fluid or methane migrate through the fault zone into geological layers. The results show that presence of a conductive fault could reduce the contaminant travel time and a significant contaminant leakage, under certain hydraulic conditions, is most likely to occur. Bibliography Kissinger, A., Helmig, R., Ebigbo, A., Class, H., Lange, T., Sauter, M., Heitfeld, M., Klünker, J., Jahnke, W., 2013. Hydraulic fracturing in unconventional gas reservoirs: risks in the geological system, part 2. Environ Earth Sci 70, 3855

  11. A stage-structured, spatially explicit migration model for Myotis bats: mortality location affects system dynamics

    Science.gov (United States)

    Erickson, Richard A.; Thogmartin, Wayne E.; Russell, Robin E.; Diffendorfer, James E.; Szymanski, Jennifer A.

    2014-01-01

    Bats are ecologically and economically important species because they consume insects, transport nutrients, and pollinate flowers.  Many species of bats, including those in the Myotis genus, are facing population decline and increased extinction risk.  Despite these conservation concerns, few models exist for providing insight into the population dynamics of bats in a spatially explicit context.  We developed a model for bats by considering the stage-structured colonial life history of Myotis bats with their annual migration behavior.  This model provided insight into network dynamics.  We specifically focused on two Myotis species living in the eastern United States: the Indiana bat (M. sodalis), which is a Federally listed endangered species, and the little brown bat (M. lucifugus), which is under consideration for listing as an endangered species.  We found that multiple equilibria exist for the local, migratory subpopulations even though the total population was constant.  These equilibria suggest the location and magnitude of stressors such as White-nose Syndrome, meteorological phenomena, or impacts of wind turbines on survival influence system dynamics and risk of population extirpation in difficult to predict ways.

  12. Significance analysis of the leachate level in a solid waste landfill in a coastal zone using total water balance and slope stability alternatives

    Energy Technology Data Exchange (ETDEWEB)

    Koo, Ja-Kong; Do, Nam-Young [Korea Advanced Institute of Science & Technology, Taejon (Korea, Republic of)

    1996-12-31

    The K site near Seoul began landfilling in 1992. The landfilled wastes include municipal solid waste (66.4%), construction residues (20.4%), water and wastewater sludges (trace levels), and hazardous waste (trace levels). The water content of the municipal solid waste is very high (47.3%); as a result, the leachate level (average E.L.) of the landfill, the design value of which is 7.0 m, was measured at 10.3 m in January 1995 and is increasing. The increase of leachate level in the landfill site causes a problem with slope stability. The leachate level at each disposal stage divided by the intermediate cover layer was calculated with the HELP (Hydrologic Evaluation of Landfill Performance) model and calibrated with the data measured from February 1993 to June 1995. Also, the hydraulic conductivities of the waste layer and the intermediate cover layer in each stage were calibrated continuously with HELP model analysis. To verify these results, the total water balance in the landfill site was calculated using the infiltration rate calculated from HELP modeling. The leachate level was E.L. 10.0 m, which was close to the measured leachate level. To estimate the change of the leachate level in the future, the total water balances with different leachate discharge rates of 3,000, 3,500, and 5,000 m{sup 3}/day were analyzed. When the leachate discharge rate was 5,000 ton/day and the initial water content was decreased below 25%, the average leachate level was 10.8 m. This result satisfies the safety factor requirements (=1.3) for landfill slope stability. 4 refs., 8 figs., 1 tab.

  13. Modelling of migration of radionuclides and trace elements between the components of the Black Sea ecosystems

    International Nuclear Information System (INIS)

    Egorov, V.N.

    1999-01-01

    This report considers peculiarities of the mathematical description of radionuclides migration between water environment and biotic and abiotic components of the Black Sea ecosystems at different periods of averaging, from the time scale of metabolic processes, taking place in hydrobionts, to the large-scale description of radionuclides migration in the Black Sea

  14. Radon migration from soil to a house. Computer modelling and its verification on the base of measurements in living houses

    International Nuclear Information System (INIS)

    Janik, M.

    2005-09-01

    In this thesis the Loureiro model of radon migration from soil to a house has been verified. For this purpose the computer code TRIAD has been used. The input data for this code are the ground penetrability and porosity. Methods for determination of these parameters have bee developed and equipment for its measurements has been manufactured and tested

  15. A brain slice culture model for studies of endogenous and exogenous precursor cell migration in the rostral migratory stream

    DEFF Research Database (Denmark)

    Tanvig, Mette; Blaabjerg, Morten; Andersen, Rikke K

    2009-01-01

    The rostral migratory stream (RMS) is the main pathway by which newly born subventricular zone (SVZ) cells reach the olfactory bulb (OB) in rodents. This migration has been well studied in vivo, but an organotypic in vitro model would facilitate more experimental investigations. Here we introduce...

  16. Current status of gas migration and swelling experiments using engineering scale model for immediate depth disposal in Japan

    International Nuclear Information System (INIS)

    Higashihara, Tomohiro; Ono, Makoto; Kawaragi, Chie; Saito, Shigeyuki

    2010-01-01

    In intermediate depth disposal facility of radioactive waste in Japan, waste is surrounded with bentonite layer to retard interaction of the waste and groundwater, because the bentonite layer saturated with the groundwater has very low hydraulic conductivity. On the other hand, it is important to confirm stability of barrier system for stress generated together with swelling of the bentonite and to understand effect of increase of gas pressure because of generation of hydrogen gas by corrosion of metallic waste. To understand and evaluate the swelling behavior of the bentonite layer, JNES carries out the experiment. In the experiments, we carry out the swelling experiment to examine the swelling behavior of the bentonite layer and the gas migration experiment to understand the gas migration behavior in the bentonite layer, using engineering scale model of the disposal facility. The swelling experiment has been in operation since June 2010. After this experiment, the gas migration experiment will start in July 2011. (orig.)

  17. Radon depth migration

    International Nuclear Information System (INIS)

    Hildebrand, S.T.; Carroll, R.J.

    1993-01-01

    A depth migration method is presented that used Radon-transformed common-source seismograms as input. It is shown that the Radon depth migration method can be extended to spatially varying velocity depth models by using asymptotic ray theory (ART) to construct wavefield continuation operators. These operators downward continue an incident receiver-array plane wave and an assumed point-source wavefield into the subsurface. The migration velocity model is constrain to have longer characteristic wavelengths than the dominant source wavelength such that the ART approximations for the continuation operators are valid. This method is used successfully to migrate two synthetic data examples: (1) a point diffractor, and (2) a dipping layer and syncline interface model. It is shown that the Radon migration method has a computational advantage over the standard Kirchhoff migration method in that fewer rays are computed in a main memory implementation

  18. Prediction of COD and NH4+-N Concentrations in Leachate from Lab-scale Landfill Bioreactors Using Artificial Neural Networks

    Directory of Open Access Journals (Sweden)

    Mohamad Javad Zoqi

    2010-06-01

    Full Text Available In this study, we present an Artificial Neural Network (ANN model for predicting COD and NH4+-N concentrations in landfill leachate from lab-scale landfill bioreactors. For this purpose, two different lab-scale systems were modeled. for neural network’s data obtained. In the first system, the leachate from a fresh-waste reactor was drained to a recirculation tank and recycled every two days. In the second, the leachate from a fresh waste landfill reactor was fed through a well-decomposed refuse landfill reactor, while the leachate from a well-decomposed refuse landfill reactor was simultaneously recycled to a fresh waste landfill reactor. The results indicate that leachate NH4+-N and COD concentrations accumulated to a high level in the first system, while. NH4+-N and COD removals were successfully carried out in the second. Also, average removal efficiencies in the second system reached 85% and 34% for COD and NH4+-N, respectively. Finally, the ANN’s results exhibited the success of the model as witnessed by the excellent agreement obtained between measured and predicted values.

  19. Long-term gas migration modelling in compacted bentonite using swelling/shrinkage-dependent two phase flow parameters

    International Nuclear Information System (INIS)

    Tawara, Y.; Mori, K.; Tada, K.; Shimura, T.; Sato, S.; Yamamoto, S.; Asano, H.; Namiki, K.

    2012-01-01

    Document available in extended abstract form only. After the completion of field-scaled Gas Migration Test (GMT) at the Grimsel Test Site (GTS Phase V Project, 1996-2004), an advanced gas migration modelling study has been implemented to increase the accuracy and reliability as a part of the R and D programs by the Radioactive Waste Management funding and research Center (RWMC) in Japan. The multiple gas migration modes which consist of diffusive transport of dissolved gas, conventional two phase flow, pore failure induced microscopic fissuring and macroscopic fracturing flow, were identified in GMT bentonite. However the required parameters and constitutive models governing those modes are still uncertain. To tackle this issue, an extended validation and scoping study aiming to generalize such gas migration behavior has been performed in the advanced gas migration modelling study. One of the main objectives of the validation study is to identify gas migration modes using laboratory test data and to qualify the alternative models and parameters. In the scoping study, we have extracted the specific THMC (Thermal, Hydrological, Mechanical and Chemical) coupled processes which have impacts on the performance measures such as the pressure built-up in EBS (Engineered Barrier System) and expelled water to the geosphere by gas generation and transport. The measured data of hydration tests and gas injection tests using bentonite specimens with different water contents were reproduced. Two phase flow parameters were estimated using the observed data of both types of tests, independently. The simulated results of the conventional two phase flow model were well-matched with the hydration test data. In the gas injection test, the extended two phase flow model which simulates the pressure-induced pore failure (pathway dilation), was able to reproduce observed data reasonably. However, we found that the identified parameters obtained from the hydration test data were

  20. Stochastic cellular automata model of cell migration, proliferation and differentiation: validation with in vitro cultures of muscle satellite cells.

    Science.gov (United States)

    Garijo, N; Manzano, R; Osta, R; Perez, M A

    2012-12-07

    Cell migration and proliferation has been modelled in the literature as a process similar to diffusion. However, using diffusion models to simulate the proliferation and migration of cells tends to create a homogeneous distribution in the cell density that does not correlate to empirical observations. In fact, the mechanism of cell dispersal is not diffusion. Cells disperse by crawling or proliferation, or are transported in a moving fluid. The use of cellular automata, particle models or cell-based models can overcome this limitation. This paper presents a stochastic cellular automata model to simulate the proliferation, migration and differentiation of cells. These processes are considered as completely stochastic as well as discrete. The model developed was applied to predict the behaviour of in vitro cell cultures performed with adult muscle satellite cells. Moreover, non homogeneous distribution of cells has been observed inside the culture well and, using the above mentioned stochastic cellular automata model, we have been able to predict this heterogeneous cell distribution and compute accurate quantitative results. Differentiation was also incorporated into the computational simulation. The results predicted the myotube formation that typically occurs with adult muscle satellite cells. In conclusion, we have shown how a stochastic cellular automata model can be implemented and is capable of reproducing the in vitro behaviour of adult muscle satellite cells. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Comparison of slow and fast neocortical neuron migration using a new in vitro model

    Directory of Open Access Journals (Sweden)

    Carney Laurel H

    2008-06-01

    Full Text Available Abstract Background Mutations, toxic insults and radiation exposure are known to slow or arrest the migration of cortical neurons, in most cases by unknown mechanisms. The movement of migrating neurons is saltatory, reflecting the intermittent movement of the nucleus (nucleokinesis within the confines of the plasma membrane. Each nucleokinetic movement is analogous to a step. Thus, average migration speed could be reduced by lowering step frequency and/or step distance. Results To assess the kinetic features of cortical neuron migration we developed a cell culture system that supports fiber-guided migration. In this system, the majority of fiber-apposed cells were neurons, expressed age-appropriate cortical-layer specific markers and migrated during a 30 min imaging period. Comparison of the slowest and fastest quartiles of cells revealed a 5-fold difference in average speed. The major determinant of average speed in slower cells (6–26 μm/hr was step frequency, while step distance was the critical determinant of average speed in faster cells (>26 μm/hr. Surprisingly, step distance was largely determined by the average duration of the step, rather than the speed of nucleokinesis during the step, which differed by only 1.3-fold between the slowest and fastest quartiles. Conclusion Saltatory event frequency and duration, not nucleokinetic speed, are the major determinants of average migration speed in healthy neurons. Alteration of either saltatory event frequency or duration should be considered along with nucleokinetic abnormalities as possible contributors to pathological conditions.

  2. Vanadium removal and recovery from bauxite residue leachates by ion exchange.

    Science.gov (United States)

    Gomes, Helena I; Jones, Ashley; Rogerson, Mike; Burke, Ian T; Mayes, William M

    2016-11-01

    Bauxite residue is an important by-product of the alumina industry, and current management practices do not allow their full valorisation, especially with regard to the recovery of critical metals. This work aims to test the efficiency of ion exchange resins for vanadium (V) removal and recovery from bauxite residue leachates at alkaline pH (11.5 and 13). As an environmental pollutant, removal of V from leachates may be an obligation of bauxite residue disposal areas (BRDA) long-term management requirements. Vanadium removal from the leachate can be coupled with the recovery, and potentially can be used to offset long-term legacy treatment costs in legacy sites. Kinetics studies were performed to understand the adsorption process. The rate kinetics for the V adsorption was consistent with the pseudo-first-order kinetic model, with a higher adsorption rate for pH 11.5 (1.2 min -1 ). Adsorption isotherm data fitted better to Freundlich equations than to the Langmuir model. The maximum adsorption capacity (Langmuir value q max ) was greatest for pH 13 (9.8 mg V g -1 resin). In column tests, breakthrough was reached at 70 bed volumes with the red mud leachate at pH 13, while no breakthrough was achieved with the effluent at pH 11.5. In regeneration, 42 and 76 % of V were eluted from the resin with 2 M NaOH from the red mud leachate at pH 13 and 11.5, respectively. Further optimization will be needed to upscale the treatment.

  3. Migration of the model HCR to the SAIC/TRC in the analysis of human reliability of the APS de CN Vandellos II

    International Nuclear Information System (INIS)

    Nos, V.; Rosa, J. C. de la; Hernandez, H.

    2011-01-01

    This paper describes the systematics of adaptation and conversion of models, to migrate the detailed analysis of human actions from the APS (in operation at power) of NPP Vandellos, which uses the HCR to SAIC-CRT model. Are offered the results achieved after the migration and the main conclusions.

  4. Larval migration in PERL chambers as an in vitro model for percutaneous infection stimulates feeding in the canine hookworm Ancylostoma caninum

    Directory of Open Access Journals (Sweden)

    Welz Claudia

    2011-01-01

    Full Text Available Abstract Background Ancylostoma caninum third-stage larvae are the non-feeding infective stage of this parasite and are able to infect potential hosts via different infection routes. Since percutaneous infection is one of the most important routes and skin penetration is the first step into parasitic life, an existing in vitro model for percutaneous migration was modified and evaluated. The main parameter used to evaluate migration was the migration ratio (migrated larvae as a percentage of total number of larvae recovered. Additionally, the skin lag was calculated, expressing the percentage of larvae remaining in the skin and therefore not being recovered. Since initiation of feeding is proposed to be an important step in the transition from free-living to parasitic A. caninum larvae, feeding assays were performed with in vitro percutaneously migrated larvae. Additionally, infective larvae of A. caninum were activated via serum-stimulation and feeding behaviour was analysed and compared between percutaneously migrated and serum-stimulated larvae. Results Maximum skin migration levels of infective larvae were observed at temperatures above 32°C when larvae were placed on the epidermal side of skin for more than 12 hours. The medium beneath the skin had no effect on migration ratio, and no significant difference between the migration ratios through fresh and frozen/thawed skin was observed. Maximum feeding levels of 93.2% were observed for percutaneously migrated larvae after 48 h incubation, whereas serum-stimulated larvae reached the maximum of 91.0% feeding larvae after 24 h. Conclusions The PERL chamber system was optimised and standardised as an in vitro model for percutaneous migration. The larvae recovered after percutaneous migration showed characteristic signs of activation similar to that of serum-stimulated larvae. The observed difference in time course of resumption of feeding indicates that percutaneously migrated larvae are not

  5. A general equilibrium model of guest-worker migration: the source-country perspective.

    Science.gov (United States)

    Djajic, S; Milbourne, R

    1988-11-01

    "This paper examines the problem of guest-worker migration from an economy populated by identical, utility-maximizing individuals with finite working lives. The decision to migrate, the rate of saving while abroad, as well as the length of a migrant's stay in the foreign country, are all viewed as part of a solution to an intertemporal optimization problem. In addition to studying the microeconomic aspects of temporary migration, the paper analyses the determinants of the equilibrium flow of migrants, the corresponding domestic wage, and the level of welfare enjoyed by a typical worker. Effects of an emigration tax are also investigated." excerpt

  6. THE IMPACT OF THE “BEATEN PATH” MODEL ON ROMANIAN MIGRATION

    Directory of Open Access Journals (Sweden)

    Elena Raluca CRISTIAN

    2015-08-01

    Full Text Available The migrations process is influenced by a series of factors such as: degree of employment, migrant’s salary level in the origin and destination countries, age, gender, education and professional training, economic development, unemployment, prices and purchase power. The migrations flows originate especially from the poor or very poor countries, believed to be underprivileged, the migrant choosing, obviously, developed countries. International migration involves a series of effects and consequences (positive and negative for both countries involved - the origin and the destination - for undetermined periods of time.

  7. GPU-accelerated Modeling and Element-free Reverse-time Migration with Gauss Points Partition

    Science.gov (United States)

    Zhen, Z.; Jia, X.

    2014-12-01

    Element-free method (EFM) has been applied to seismic modeling and migration. Compared with finite element method (FEM) and finite difference method (FDM), it is much cheaper and more flexible because only the information of the nodes and the boundary of the study area are required in computation. In the EFM, the number of Gauss points should be consistent with the number of model nodes; otherwise the accuracy of the intermediate coefficient matrices would be harmed. Thus when we increase the nodes of velocity model in order to obtain higher resolution, we find that the size of the computer's memory will be a bottleneck. The original EFM can deal with at most 81×81 nodes in the case of 2G memory, as tested by Jia and Hu (2006). In order to solve the problem of storage and computation efficiency, we propose a concept of Gauss points partition (GPP), and utilize the GPUs to improve the computation efficiency. Considering the characteristics of the Gaussian points, the GPP method doesn't influence the propagation of seismic wave in the velocity model. To overcome the time-consuming computation of the stiffness matrix (K) and the mass matrix (M), we also use the GPUs in our computation program. We employ the compressed sparse row (CSR) format to compress the intermediate sparse matrices and try to simplify the operations by solving the linear equations with the CULA Sparse's Conjugate Gradient (CG) solver instead of the linear sparse solver 'PARDISO'. It is observed that our strategy can significantly reduce the computational time of K and Mcompared with the algorithm based on CPU. The model tested is Marmousi model. The length of the model is 7425m and the depth is 2990m. We discretize the model with 595x298 nodes, 300x300 Gauss cells and 3x3 Gauss points in each cell. In contrast to the computational time of the conventional EFM, the GPUs-GPP approach can substantially improve the efficiency. The speedup ratio of time consumption of computing K, M is 120 and the

  8. Ecotoxicological assessment of solar cell leachates: Copper indium gallium selenide (CIGS) cells show higher activity than organic photovoltaic (OPV) cells.

    Science.gov (United States)

    Brun, Nadja Rebecca; Wehrli, Bernhard; Fent, Karl

    2016-02-01

    Despite the increasing use of photovoltaics their potential environmental risks are poorly understood. Here, we compared ecotoxicological effects of two thin-film photovoltaics: established copper indium gallium selenide (CIGS) and organic photovoltaic (OPV) cells. Leachates were produced by exposing photovoltaics to UV light, physical damage, and exposure to environmentally relevant model waters, representing mesotrophic lake water, acidic rain, and seawater. CIGS cell leachates contained 583 μg L(-1) molybdenum at lake water, whereas at acidic rain and seawater conditions, iron, copper, zinc, molybdenum, cadmium, silver, and tin were present up to 7219 μg L(-1). From OPV, copper (14 μg L(-1)), zinc (87 μg L(-1)) and silver (78 μg L(-1)) leached. Zebrafish embryos were exposed until 120 h post-fertilization to these extracts. CIGS leachates produced under acidic rain, as well as CIGS and OPV leachates produced under seawater conditions resulted in a marked hatching delay and increase in heart edema. Depending on model water and solar cell, transcriptional alterations occurred in genes involved in oxidative stress (cat), hormonal activity (vtg1, ar), metallothionein (mt2), ER stress (bip, chop), and apoptosis (casp9). The effects were dependent on the concentrations of cationic metals in leachates. Addition of ethylenediaminetetraacetic acid protected zebrafish embryos from morphological and molecular effects. Our study suggests that metals leaching from damaged CIGS cells, may pose a potential environmental risk. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. levels of some physiochemical parameters in leachates from open

    African Journals Online (AJOL)

    based building materials and gypsum based materials changing the ... dumpsite leachates may be characterized as a water- ... The physical appearance of leachates from a typical ... “placing” waste in line pit or a mound with ... the quality of the urban environment. ... rinsed with distilled water before drying in the oven.

  10. Assessment of groundwater contamination by leachate near a ...

    African Journals Online (AJOL)

    The results show that the leachate from the landfill has a minimal impact on the groundwater resource and this can be attributed to the existing soil stratigraphy at the site consisting of clay which is deduced to have a significant influence on the natural attenuation of leachate into groundwater. Keywords: Groundwater ...

  11. Leachate characterization of active and closed dump sites in Port ...

    African Journals Online (AJOL)

    This study characterizes the leachate quality of both active and closed dump sites in Port Harcourt City. Leachates were sampled from the base of the dum psites and analysed, pH, dissolved oxygen (DO), electrical conductivity and total dissolved solids were determined on the samples in-situ. While chloride, sulphate ...

  12. Adsorption of heavy metal from landfill leachate by wasted biosolids ...

    African Journals Online (AJOL)

    However, the concentration of Cd, Cu and Zn was not detected in the leachate but Fe was found to be in high concentration (184 mg/L) in raw leachate collected from a municipal landfill site. Therefore, the effects of biomass dosage, contact time, pH and agitation speed were observed for optimal adsorption of iron from ...

  13. The Effects of Leachate on Groundwater in Ota Industrial Area ...

    African Journals Online (AJOL)

    Compositions of landfill leachate and groundwater pollution were studied at industrial sites landfill, which are located at Ota, Nigeria. The leachate was sampled at 5 different locations at the landfill, and at 15 and 20 m downstream of the landfill. Groundwater samples were collected from 10 different sources to study the ...

  14. How do salt withdrawal minibasins form? Insights from forward modelling, and implications for hydrocarbon migration

    Science.gov (United States)

    Peel, Frank J.

    2014-09-01

    Existing models for the initiation of salt withdrawal minibasins focus on the role of triggers that exist within the minibasin, either stratigraphic (e.g. differential deposition) or tectonic (extension, translation or contraction). Existing studies tend to focus on complex settings, such as continental margins, which contain many different potential triggering mechanisms. It can be difficult in these settings to identify which process is responsible for minibasin initiation, or the influence of individual factors on their subsequent development. Salt withdrawal minibasins also exist in simpler settings, without any obvious intrinsic trigger; the region of the North German Basin used by Trusheim (1960) in the classic definition of salt withdrawal geometries was of this nature. There is no overall basal or surface slope, no major lateral movement, and there is no depositional heterogeneity. Previously recognized trigger processes for minibasin initiation do not apply in this benign setting, suggesting that other, potentially more fundamental, influences may be at work. A simple forward-modelling approach shows how, in the absence of any other mechanism, a new minibasin can develop as the consequence of salt movement driven by its neighbour, and families of withdrawal minibasins can propagate across a region from a single seed point. This new mechanism may explain how some minibasins appear to initiate before the sediment density has exceeded that of the underlying salt. The forward modelling also indicates that some minibasins begin to invert to form turtle anticlines before the underlying salt has been evacuated, so that the timing of turtle formation may not be diagnostic of weld formation. This mechanism may also give rise to salt-cored turtles that have a lens of salt trapped beneath their cores. These new findings have implications for hydrocarbon migration and trapping.

  15. Psychosocial factors of migration: adaptation and application of the health belief model

    NARCIS (Netherlands)

    Groenewold, W.G.F.; de Bruijn, B.J.; Bilsborrow, R.

    2012-01-01

    Psychosocial factors influencing behaviour play a central role in health research but seem under-explored in migration research. This is unfortunate because these factors, which include knowledge, attitudes, beliefs, intentions and personality traits, provide essential and potentially effective

  16. INDIVIDUAL BASED MODELLING APPROACH TO THERMAL REFUGE USE BY MIGRATING ADULT SALMON AND STEELHEAD

    Science.gov (United States)

    Diadromous fish populations in the Pacific Northwest face challenges along their migratory routes from declining habitat quality, harvest, and barriers to longitudinal connectivity. Changes in river temperature regimes are producing an additional challenge for upstream migrating ...

  17. Application of simplified models to CO2 migration and immobilization in large-scale geological systems

    KAUST Repository

    Gasda, Sarah E.; Nordbotten, Jan M.; Celia, Michael A.

    2012-01-01

    Long-term stabilization of injected carbon dioxide (CO 2) is an essential component of risk management for geological carbon sequestration operations. However, migration and trapping phenomena are inherently complex, involving processes that act

  18. Source-receiver two-way wave extrapolation for prestack exploding-reflector modelling and migration

    KAUST Repository

    Alkhalifah, Tariq Ali

    2014-10-08

    Most modern seismic imaging methods separate input data into parts (shot gathers). We develop a formulation that is able to incorporate all available data at once while numerically propagating the recorded multidimensional wavefield forward or backward in time. This approach has the potential for generating accurate images free of artiefacts associated with conventional approaches. We derive novel high-order partial differential equations in the source-receiver time domain. The fourth-order nature of the extrapolation in time leads to four solutions, two of which correspond to the incoming and outgoing P-waves and reduce to the zero-offset exploding-reflector solutions when the source coincides with the receiver. A challenge for implementing two-way time extrapolation is an essential singularity for horizontally travelling waves. This singularity can be avoided by limiting the range of wavenumbers treated in a spectral-based extrapolation. Using spectral methods based on the low-rank approximation of the propagation symbol, we extrapolate only the desired solutions in an accurate and efficient manner with reduced dispersion artiefacts. Applications to synthetic data demonstrate the accuracy of the new prestack modelling and migration approach.

  19. Management of landfill leachate: The legacy of European Union Directives.

    Science.gov (United States)

    Brennan, R B; Healy, M G; Morrison, L; Hynes, S; Norton, D; Clifford, E

    2016-09-01

    Landfill leachate is the product of water that has percolated through waste deposits and contains various pollutants, which necessitate effective treatment before it can be released into the environment. In the last 30years, there have been significant changes in landfill management practices in response to European Union (EU) Directives, which have led to changes in leachate composition, volumes produced and treatability. In this study, historic landfill data, combined with leachate characterisation data, were used to determine the impacts of EU Directives on landfill leachate management, composition and treatability. Inhibitory compounds including ammonium (NH4-N), cyanide, chromium, nickel and zinc, were present in young leachate at levels that may inhibit ammonium oxidising bacteria, while arsenic, copper and silver were present in young and intermediate age leachate at concentrations above inhibitory thresholds. In addition, the results of this study show that while young landfills produce less than 50% of total leachate by volume in the Republic of Ireland, they account for 70% of total annual leachate chemical oxygen demand (COD) load and approximately 80% of total 5-day biochemical oxygen demand (BOD5) and NH4-N loads. These results show that there has been a decrease in the volume of leachate produced per tonne of waste landfilled since enactment of the Landfill Directive, with a trend towards increased leachate strength (particularly COD and BOD5) during the initial five years of landfill operation. These changes may be attributed to changes in landfill management practices following the implementation of the Landfill Directive. However, this study did not demonstrate the impact of decreasing inputs of biodegradable municipal waste on leachate composition. Increasingly stringent wastewater treatment plant (WWTP) emission limit values represent a significant threat to the sustainability of co-treatment of leachate with municipal wastewater. In addition

  20. Characteristics of Leachate at Sukawinatan Landfill, Palembang, Indonesia

    International Nuclear Information System (INIS)

    Yusmartini, Eka Sri; Setiabudidaya, Dedi; Ridwan; Marsi; Faizal

    2013-01-01

    Landfill (TPA) Sukawinatan Palembang is an open dumping system which covers an area of 25 hectares. This system may bring an environmental damage to the surrounding area because it does not provide leachate treatment. Leachate is the landfill waste that dissolves many compounds that contain pollutants from both organic substances and heavy metal origin. This paper presents the results of laboratory analysis on samples of leachate as well as shallow groundwater from the surrounding area. The results were compared to established quality standards to evaluate whether the leachate has influenced the quality of the shallow groundwater in the surrounding area. The results show that there are some indications that the quality of groundwater has been polluted by the leachate of both organic substances and heavy metals produced by the Sukawinatan landfill.

  1. Simulated evapotranspiration from a landfill irrigated with landfill leachate

    International Nuclear Information System (INIS)

    Aronsson, P.

    1996-01-01

    Evapotranspiration from a landfill area, irrigated with leachate water, was simulated with the SOIL model. Three different types of vegetation (bare soil, grass ley, and willow) were used both with and without irrigation. The highest simulated evapotranspiration (604 mm) during the growing season was found from an irrigated willow stand with a high interception capacity. The lowest evapotranspiration (164 mm) was found from the bare soil. The relatively high evapotranspiration from the willow was probably caused by the high LAI (Leaf Area Index) and the low aerodynamic resistance within the willow stand. The results indicate that it is possible to reduce most of the leakage water from a landfill by irrigation of willow stands. 9 refs, 4 figs, 1 tab

  2. Dynamic evaluation of municipal solid waste ash leachate

    International Nuclear Information System (INIS)

    Theis, T.L.; Gardner, K.H.

    1992-01-01

    The incineration of municipal solid waste (MSW) produces ashes which are concentrated in many inorganic species. The release of toxic elements from the ash to the aqueous environment is of concern as present methods of ash disposal consist primarily of landfilling. It was the goal of this paper to achieve an understanding of the mechanisms by which elements are transported from the solid ash phase to the aqueous phase. Twelve ash samples were collected from six different incinerators with varying designs and capacities. The leaching experiments were conducted using small (mini) dynamic columns to investigate the variation of leachate chemical characteristics with time. In analyzing the data, a multicomponent chemical equilibrium model was used to determine chemical speciation and component activities. Auxiliary experiments included an array of physical measurements, and aqueous batch leach tests

  3. Model complexity and choice of model approaches for practical simulations of CO2 injection, migration, leakage and long-term fate

    Energy Technology Data Exchange (ETDEWEB)

    Celia, Michael A. [Princeton Univ., NJ (United States)

    2016-12-30

    This report documents the accomplishments achieved during the project titled “Model complexity and choice of model approaches for practical simulations of CO2 injection,migration, leakage and long-term fate” funded by the US Department of Energy, Office of Fossil Energy. The objective of the project was to investigate modeling approaches of various levels of complexity relevant to geologic carbon storage (GCS) modeling with the goal to establish guidelines on choice of modeling approach.

  4. Verification and validation of models: far-field modelling of radionuclide migration

    International Nuclear Information System (INIS)

    Porter, J.D.; Herbert, A.W.; Clarke, D.S.; Roe, P.; Vassilic Melling, D.; Einfeldt, B.; Mackay, R.; Glendinning, R.

    1992-01-01

    The aim of this project was to improve the capability, efficiency and realism of the NAMMU and NAPSAC codes, which simulate groundwater flow and solute transport. Using NAMMU, various solution methods for non linear problems were investigated. The Broyden method gave a useful reduction in computing time and appeared robust. The relative saving obtained with this method increased with the problem size. This was also the case when parameter stepping was used. The existing empirical sorption models in NAMMU were generalized and a ternary heterogeneous ion exchange model was added. These modifications were tested and gave excellent results. The desirability of coupling NAMMU to an existing geochemical speciation code was assessed

  5. Bone marrow cell migration to the heart in a chimeric mouse model of acute chagasic disease.

    Science.gov (United States)

    Irion, Camila Iansen; Paredes, Bruno Diaz; Brasil, Guilherme Visconde; Cunha, Sandro Torrentes da; Paula, Luis Felipe; Carvalho, Alysson Roncally; Carvalho, Antonio Carlos Campos de; Carvalho, Adriana Bastos; Goldenberg, Regina Coeli Dos Santos

    2017-08-01

    Chagas disease is a public health problem caused by infection with the protozoan Trypanosoma cruzi. There is currently no effective therapy for Chagas disease. Although there is some evidence for the beneficial effect of bone marrow-derived cells in chagasic disease, the mechanisms underlying their effects in the heart are unknown. Reports have suggested that bone marrow cells are recruited to the chagasic heart; however, studies using chimeric mouse models of chagasic cardiomyopathy are rare. The aim of this study was to investigate the migration of bone marrow cells to the heart after T. cruzi infection in a model of chagasic disease in chimeric mice. To obtain chimerical mice, wild-type (WT) C57BL6 mice were exposed to full body irradiation (7 Gy), causing bone marrow ablation. Then, bone marrow cells from green fluorescent protein (GFP)-transgenic mice were infused into the mice. Graft effectiveness was confirmed by flow cytometry. Experimental mice were divided into four groups: (i) infected chimeric (iChim) mice; (ii) infected WT (iWT) mice, both of which received 3 × 104 trypomastigotes of the Brazil strain; (iii) non-infected chimeric (Chim) mice; and (iv) non-infected WT mice. At one-month post-infection, iChim and iWT mice showed first degree atrioventricular block with decreased heart rate and treadmill exercise parameters compared to those in the non-infected groups. iChim mice showed an increase in parasitaemia, myocarditis, and the presence of amastigote nests in the heart tissue compared to iWT mice. Flow cytometry analysis did not detect haematopoietic progenitor cells in the hearts of infected mice. Furthermore, GFP+ cardiomyocytes were not detected in the tissues of chimeric mice.

  6. Impact of policies regulating foreign physician migration to Switzerland: a modelling case study in anaesthesia.

    Science.gov (United States)

    Haller, Guy; Combescure, Christophe; Mamie, Chantal; Zoccatelli, Davide; Clergue, François

    2015-05-22

    Several countries have developed policies that restrict or limit duration of stay, clinical privileges or the number of residency permits allocated to migrating physicians. Switzerland is currently preparing a new law limiting overall foreign immigration. The impact of such restrictive policies is currently unknown. In a case study of anaesthesia care in Switzerland we modelled, trends in the size of physicians' workforce until 2024, following the implementation of a strict quota policy for foreign medical trainees. We developed a computer-based Markov model with Monte-Carlo simulations to project, in the context of a strict quota policy for foreign trainees, supply and demand for anaesthesia positions until 2024. We used data from a cross-sectional study performed in the French- and Italian-speaking cantons of Switzerland and the Health dataset from the OECD. With 8 to 12 (95% CI 4-20) anaesthetists retiring per year, the implementation of strict quotas of foreign graduates would result in a 38% decrease in the number of anaesthetists in intermediary (senior registrars) positions by 2024. This decrease would be particularly important in district hospitals where nearly half (49%) of the non-Swiss anaesthetists are practising. Swiss graduates are unlikely to balance the shortage. Despite efforts by Swiss universities to increase the number of medical graduates, their number has dropped from 10.5 to 9.7/100 000 inhabitants between 2000 and 2012, due to the growth of the population. This case study in Latin Switzerland shows that a restrictive policy limiting foreign immigration of trainees would result in a major deficit in the number of anaesthetists available to meet population needs. These aspects should be carefully considered when countries develop restrictions and limitations of foreign immigration.

  7. The effects of single-walled carbon nanotubes on cancer cell migration using a pancreatic tumor model

    Science.gov (United States)

    Layton, Elivia; McNamar, Rachel; Hasanjee, Aamr M.; McNair, Cayman; Stevens, Brianna; Vaughan, Melville; Zhou, Feifan; Chen, Wei R.

    2017-02-01

    Non-invasive laser immunotherapy (NLIT) is a viable alternative to traditional cancer treatment because it combines the photothermal and immunological effects of non-invasive laser irradiation and single-walled carbon nanotubes (SWNT) with an immunoadjuvant, glycated chitosan (GC). This combination forms SWNT-GC, a photosensitive immunoadjuvant, which creates a tumor-specific immunity that targets both the primary tumor and any metastasis. It is known that NLIT induces anti-tumor as well as anti-metastatic immune responses, but its immunological mechanism is not clear. The objective of this study is to clarify the role of SWNT-GC in cancer cell migration. Panc02 (non-metastatic) and Panc02-H7 (metastatic) pancreatic cancer cells were used in two-dimensional elastomer plug assays to observe the restriction of cell migration induced by SWNT, GC, and SWNT-GC individually. To replicate a three-dimensional in vivo study, a similar assay was repeated using embedded collagen lattices. Both the 2D and the 3D studies confirmed previous results indicating that GC inhibits cancer cell motility. The 2D and 3D studies also showed that SWNT-GC inhibited the migration of cancer cells, but a discrepancy was observed regarding the effect of SWNT alone. The 2D model concluded that SWNT inhibited migration while the 3D model determined that SWNT promoted migration. The results of this study will guide future work to determine the mechanism behind NLIT, including how metastases are eradicated and how the tumor specific immunity is created.

  8. The Stent Patency and Migration Rate of Different Shaped Plastic Stents in Bile Flow Phantom Model and In Vivo Animal Bile Duct Dilation Model.

    Science.gov (United States)

    Kwon, Chang-Il; Kim, Gwangil; Jeong, Seok; Lee, Don Haeng; Kim, Kyoung Ah; Ko, Kwang Hyun; Cho, Joo Young; Hong, Sung Pyo

    2017-05-01

    In research and development of biliary plastic stents (PS), continuous efforts have been made to overcome short patency time and high rate of migration. The aim of this study was to evaluate the patency and migration rate of different PS shapes for a given period of time. Using an in vitro bile phantom model, we compared the patency among different shapes of PS (three straight PS, four double-pigtail PS, and a new screw-shaped PS). We performed an analysis of the degree of luminal narrowing by light microscopic examination. Using an in vivo swine model, we compared the patency and migration rate among the three different types of PS. Eight weeks after the bile exposure in the bile flow phantom model, 80 PS were retrieved and analyzed. The straight PS showed less biofilm formation and luminal narrowing than other types of PS (p stent migration occurred less frequently in the double-pigtail PS and the screw-shaped PS than it did in the straight PS (11.1, 10, and 27.3%, respectively). However, there was no statistical difference in stent patency among the different shapes. Stent patency may not be significantly different depending on the shape of PS for 8 weeks. The screw-shaped PS showed similar patency and migration rate to the double-pigtail PS. These results may help guiding future PS development and clinical decisions.

  9. Effects of wood preservative leachates from docks

    Energy Technology Data Exchange (ETDEWEB)

    Wendt, P.H.; Van Dolah, R.F.; Bobo, M.Y.; Mathews, T.D. [South Carolina Marine Resources Research Inst., Charleston, SC (United States)

    1994-12-31

    Recent evidence indicates that the wood preservative commonly used in dock pilings (chromated copper arsenate or CCA) is highly toxic to several estuarine organisms in laboratory experiments. Increasing demand for residential docks prompted a field study intended to complement these earlier laboratory investigations. Objectives of the study were to: (1) examine concentrations of Cu, Cr, and As in sediments and oysters from intertidal locations in several creeks with and without high densities of docks; (2) examine the bioaccumulation of wood preservative leachates by laboratory-reared oysters transferred to field sites near and distant from newly constructed docks; and (3) investigate the acute toxicity of wood preservative leachates for several species of estuarine fishes and invertebrates exposed to these compounds in the field. Preliminary results indicate that sediment concentrations of all three metals were well below ER-L levels reported by Long and Morgan at all but one dock site. In an ancillary study, 24h LC{sub 50} bioassays were performed using rotifers (Brachionus plicatilis) which were exposed to pore water from sediments in creeks with and without docks. Toxicities of bulk sediments from the same sites were examined using Microtox which measures decreases in bioluminescence of marine bacteria (Photobacterium phosphoreum) as a function of sediment concentration. Neither the rotifer nor the Microtox bioassays showed any significant differences in toxicity between creeks with and without docks.

  10. Migration of antioxidants from polylactic acid films, a parameter estimation approach: Part I - A model including convective mass transfer coefficient.

    Science.gov (United States)

    Samsudin, Hayati; Auras, Rafael; Burgess, Gary; Dolan, Kirk; Soto-Valdez, Herlinda

    2018-03-01

    A two-step solution based on the boundary conditions of Crank's equations for mass transfer in a film was developed. Three driving factors, the diffusion (D), partition (K p,f ) and convective mass transfer coefficients (h), govern the sorption and/or desorption kinetics of migrants from polymer films. These three parameters were simultaneously estimated. They provide in-depth insight into the physics of a migration process. The first step was used to find the combination of D, K p,f and h that minimized the sums of squared errors (SSE) between the predicted and actual results. In step 2, an ordinary least square (OLS) estimation was performed by using the proposed analytical solution containing D, K p,f and h. Three selected migration studies of PLA/antioxidant-based films were used to demonstrate the use of this two-step solution. Additional parameter estimation approaches such as sequential and bootstrap were also performed to acquire a better knowledge about the kinetics of migration. The proposed model successfully provided the initial guesses for D, K p,f and h. The h value was determined without performing a specific experiment for it. By determining h together with D, under or overestimation issues pertaining to a migration process can be avoided since these two parameters are correlated. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Migration behavior of Cu and Zn in landfill with different operation modes

    International Nuclear Information System (INIS)

    Long Yuyang; Shen Dongsheng; Wang Hongtao; Lu Wenjing

    2010-01-01

    Cu and Zn were chosen to study the heavy metal migration behavior and mechanism in three simulated landfills with different operation modes, namely conventional landfill (CL), leachate directly recirculated landfill (RL) and leachate pre-treated bioreactor landfill (BL). It showed that Cu and Zn in refuse experienced periodic migration and retention gradually during decomposition, and the variation of Cu(II) and Zn(II) in leachate correspondingly reflected the releasing behavior of Cu and Zn in landfill refuse at different stabilization stages. Except for their accumulated leaching amounts, Cu(II) and Zn(II) concentrations in leachate from landfills with different operation modes had no significant difference. The accumulated leaching amounts of Cu and Zn from CL showed exponential increase, while those of RL and BL showed exponential decay. The operation of bioreactor landfill with leachate recirculation can obviously attenuate the heavy metal leaching than conventional operation. The introduction of methanogenic reactor (MR) in bioreactor landfill can further promote the immobilization of heavy metal in refuse than leachate recirculation directly.

  12. A random walk model for the migration of Strongylus vulgaris in the intestinal arteries of the horse.

    Science.gov (United States)

    Aref, S

    1982-01-01

    A study of the migration of fourth stage larvae of the parasite Strongylus vulgaris in the intestinal arteries of the horse is presented. It is established, that the larvae migrate along the arteries in almost straight lines. It is suggested that this is primarily due to their ability to sense the curvature of the vessel wall, and not, as might have been expected, because of an ability to sense the direction of blood flow. A larva will sometimes alter its direction of motion when encountering a small off-branching artery. This behaviour suggests, that the migration of S. vulgaris larvae can be modeled as a one-dimensional discrete random walk on a long time scale. This model is simpler than any deterministic model and, in particular, does not require the existence of a predilection site. The available data is not, however, sufficient for a convincing, quantitative test of the model. The proposed reluctance of the larvae to bend into off-branching arteries is used to explain the crowding of larvae in the cranial mesenteric artery.

  13. Regional Redistribution and Migration

    DEFF Research Database (Denmark)

    Manasse, Paolo; Schultz, Christian

    We study a model with free migration between a rich and a poor region. Since there is congestion, the rich region has an incentive to give the poor region a transfer in order to reduce immigration. Faced with free migration, the rich region voluntarily chooses a transfer, which turns out...... to be equal to that a social planner would choose. Provided migration occurs in equilibrium, this conclusion holds even in the presence of moderate mobility costs. However, large migration costs will lead to suboptimal transfers in the market solution...

  14. Effect of migration in a diffusion model for template coexistence in protocells.

    Science.gov (United States)

    Fontanari, José F; Serva, Maurizio

    2014-03-01

    The compartmentalization of distinct templates in protocells and the exchange of templates between them (migration) are key elements of a modern scenario for prebiotic evolution. Here we use the diffusion approximation of population genetics to study analytically the steady-state properties of such a prebiotic scenario. The coexistence of distinct template types inside a protocell is achieved by a selective pressure at the protocell level (group selection) favoring protocells with a mixed template composition. In the degenerate case, where the templates have the same replication rate, we find that a vanishingly small migration rate suffices to eliminate the segregation effect of random drift and so to promote coexistence. In the nondegenerate case, a small migration rate greatly boosts coexistence as compared with the situation where there is no migration. However, increase of the migration rate beyond a critical value leads to the complete dominance of the more efficient template type (homogeneous regime). In this case, we find a continuous phase transition separating the homogeneous and the coexistence regimes, with the order parameter vanishing linearly with the distance to the transition point.

  15. To the predicted calculations of Cs-137 and Sr-90 migration in soil in the frame of the compartment model

    International Nuclear Information System (INIS)

    Knat'ko, B.A.; Skomorokhov, A.G.

    1994-01-01

    The method of calculation of migration of radionuclides in soil according to compartment model and based on analitical solution of the system of differential equations of the model is proposed. Calculations of the content of radionuclides in the soil layer for Cs-137 and Sr-90 for four types of soil for the periods of 0, 21, 34,46 and 73 months are carried out. Calculations were done for three upper soil layers 0-2.5, 2.5-5, 5.0-15.0 cm, which give the main contribution into transport of radionuclides into plants on meadows and pastures. Such method increases precision of calculations of cesium-137 and strontium-90 migration in comparison with the prosedure, which uses the system of finite difference equations. 6 refs., 1 fig

  16. Mechanism of formation of humus coatings on mineral surfaces 3. Composition of adsorbed organic acids from compost leachate on alumina by solid-state 13C NMR

    Science.gov (United States)

    Wershaw, R. L.; Llaguno, E.C.; Leenheer, J.A.

    1996-01-01

    The adsorption of compost leachate DOC on alumina is used as a model for elucidation of the mechanism of formation of natural organic coatings on hydrous metal oxide surfaces in soils and sediments. Compost leachate DOC is composed mainly of organic acid molecules. The solid-state 13C NMR spectra of these organic acids indicate that they are very similar in composition to aquatic humic substances. Changes in the solid-state 13C NMR spectra of compost leachate DOC fractions adsorbed on alumina indicate that the DOC molecules are most likely adsorbed on metal oxide surfaces through a combination of polar and hydrophobic interaction mechanisms. This combination of polar and hydrophobic mechanism leads to the formation of bilayer coatings of the leachate molecules on the oxide surfaces.

  17. Model for the interaction between interface migration and carbon diffusion during annealing of martensite-austenite microstructures in steels

    International Nuclear Information System (INIS)

    Santofimia, M.J.; Zhao, L.; Sietsma, J.

    2008-01-01

    The interaction between carbon partitioning from martensite to austenite and interface migration during annealing of martensite-austenite microstructures is modeled, assuming the same chemical potential of carbon in martensite and austenite at the interface and allowing the motion of the phase interface when a free-energy difference occurs. The simulations show that the motion of the martensite-austenite interface can be significant and can takes place in either direction

  18. Natural attenuation, biostimulation and bioaugmentation of landfill leachate management

    Science.gov (United States)

    Er, X. Y.; Seow, T. W.; Lim, C. K.; Ibrahim, Z.

    2018-04-01

    Landfills used for solid waste management will lead to leachate production. Proper leachate management is highly essential to be paid attention to protect the environment and living organisms’ health and safety. In this study, the remedial strategies used for leachate management were natural attenuation, biostimulation and bioaugmentation. All treatment samples were treated via 42-days combined anaerobic-aerobic treatment and the treatment efficiency was studied by measuring the removal rate of COD and ammonia nitrogen. In this study, all remedial strategies showed different degrees of contaminants removal. Lowest contaminants removal rate was achieved via bioaugmentation of B. panacihumi strain ZB1, which were 39.4% of COD and 37.6% of ammonia nitrogen removed from the leachate sample. Higher contaminants removal rate was achieved via natural attenuation and biostimulation. Native microbial population was able to remove 41% of COD and 59% of ammonia nitrogen from the leachate sample. The removal efficiency could be further improved via biostimulation to trigger microbial growth and decontamination rate. Through biostimulation, 58% of COD and 51.8% of ammonia nitrogen were removed from the leachate sample. In conclusion, natural attenuation and biostimulation should be the main choice for leachate management to avoid any unexpected impacts due to introduction of exogenous species.

  19. Large-scale effects of migration and conflict in pre-agricultural groups: Insights from a dynamic model.

    Directory of Open Access Journals (Sweden)

    Francesco Gargano

    Full Text Available The debate on the causes of conflict in human societies has deep roots. In particular, the extent of conflict in hunter-gatherer groups remains unclear. Some authors suggest that large-scale violence only arose with the spreading of agriculture and the building of complex societies. To shed light on this issue, we developed a model based on operatorial techniques simulating population-resource dynamics within a two-dimensional lattice, with humans and natural resources interacting in each cell of the lattice. The model outcomes under different conditions were compared with recently available demographic data for prehistoric South America. Only under conditions that include migration among cells and conflict was the model able to consistently reproduce the empirical data at a continental scale. We argue that the interplay between resource competition, migration, and conflict drove the population dynamics of South America after the colonization phase and before the introduction of agriculture. The relation between population and resources indeed emerged as a key factor leading to migration and conflict once the carrying capacity of the environment has been reached.

  20. Numerical modeling of compositional variation in petroleum secondary migration; Modelagem numerica da variacao composicional na migracao secundaria de petroleo

    Energy Technology Data Exchange (ETDEWEB)

    Magalhaes, Marcia Santos de Almeida

    1999-07-01

    The secondary migration of petroleum is analyzed in this study from a compositional perspective, with phase separation, using a numerical simulator. The modeling is focused on two different geologic scenarios, where migration occurs along the formation rocks or through a fault. Each scenario is initialized with a single-phase hydrocarbon bank, with mixtures defined in the oil and gas zones and in the proximity of the critical point in their respective phase envelopes. These fluids are obtained using a PVT simulator based on four samples (Black-oil, volatile oil and two retrograde gases) which generate various hydrocarbon mixtures from which some are selected to meet the pressure and temperature conditions established for the models. The results obtained indicate that the phase separation process, the migration and the oil and gas differences are adequately represented, and that this type of modeling may be used to explain complex fluid distribution in a single accumulation or petroleum province. However, the analysis of post-filling processes indicate the need for the inclusion of a diffusive term in the flow equations used in the simulator and for a higher precision in the fluid properties outputs. (author)

  1. Migrating Toward Fully 4-D Geodynamical Models of Asthenospheric Circulation and Melt Production at Mid-Ocean Ridges

    Science.gov (United States)

    van Dam, L.; Kincaid, C. R.; Pockalny, R. A.; Sylvia, R. T.; Hall, P. S.

    2017-12-01

    Lateral migration of mid-ocean ridge spreading centers is a well-documented phenomenon leading to asymmetric melt production and the surficial expressions thereof. This form of plate motion has been difficult to incorporate into both numerical and analogue geodynamical models, and consequently, current estimates of time-dependent flow, material transport, and melting in the mantle beneath ridges are lacking. To address this, we have designed and built an innovative research apparatus that allows for precise and repeatable simulations of mid-ocean ridge spreading and migration. Three pairs of counter-rotating belts with adjustable lateral orientations are scaled to simulate spreading at, and flow beneath, three 600km wide ridge segments with up to 300km transform offsets. This apparatus is attached to a drive system that allows us to test a full range of axis-parallel to axis-normal migration directions, and is suspended above a reservoir of viscous glucose syrup, a scaled analogue for the upper mantle, and neutrally buoyant tracers. We image plate-driven flow in the syrup with high-resolution digital cameras and use particle image velocimetry methods to obtain information about transport pathlines and flow-induced anisotropy. Suites of experiments are run with and without ridge migration to determine the overall significance of migration on spatial and temporal characteristics of shallow mantle flow. Our experiments cover an expansive parameter space by including various spreading rates, migration speeds and directions, degrees of spreading asymmetry, transform-offset lengths, and upper mantle viscosity conditions. Preliminary results highlight the importance of modeling migratory plate forces. Mantle material exhibits a significant degree of lateral transport, particularly between ridge segments and towards the melt triangle. Magma supply to the melting region is highly complex; parcels of material do not necessarily move along fixed streamlines, rather, they can

  2. Simulated Leaching (Migration) Study for a Model Container-Closure System Applicable to Parenteral and Ophthalmic Drug Products.

    Science.gov (United States)

    Jenke, Dennis; Egert, Thomas; Hendricker, Alan; Castner, James; Feinberg, Tom; Houston, Christopher; Hunt, Desmond G; Lynch, Michael; Nicholas, Kumudini; Norwood, Daniel L; Paskiet, Diane; Ruberto, Michael; Smith, Edward J; Holcomb, Frank; Markovic, Ingrid

    2017-01-01

    A simulating leaching (migration) study was performed on a model container-closure system relevant to parenteral and ophthalmic drug products. This container-closure system consisted of a linear low-density polyethylene bottle (primary container), a polypropylene cap and an elastomeric cap liner (closure), an adhesive label (labeling), and a foil overpouch (secondary container). The bottles were filled with simulating solvents (aqueous salt/acid mixture at pH 2.5, aqueous buffer at pH 9.5, and 1/1 v/v isopropanol/water), a label was affixed to the filled and capped bottles, the filled bottles were placed into the foil overpouch, and the filled and pouched units were stored either upright or inverted for up to 6 months at 40 °C. After storage, the leaching solutions were tested for leached substances using multiple complementary analytical techniques to address volatile, semi-volatile, and non-volatile organic and inorganic extractables as potential leachables.The leaching data generated supported several conclusions, including that (1) the extractables (leachables) profile revealed by a simulating leaching study can qualitatively be correlated with compositional information for materials of construction, (2) the chemical nature of both the extracting medium and the individual extractables (leachables) can markedly affect the resulting profile, and (3) while direct contact between a drug product and a system's material of construction may exacerbate the leaching of substances from that material by the drug product, direct contact is not a prerequisite for migration and leaching to occur. LAY ABSTRACT: The migration of container-related extractables from a model pharmaceutical container-closure system and into simulated drug product solutions was studied, focusing on circumstances relevant to parenteral and ophthalmic drug products. The model system was constructed specifically to address the migration of extractables from labels applied to the outside of the

  3. 生物反应器填埋场中水平沟回灌渗滤液非饱和-饱和渗流分析%Unsaturated-saturated seepage analysis for leachate recirculation using horizontal trenches in bioreactor landfills

    Institute of Scientific and Technical Information of China (English)

    冯世进; 张旭

    2013-01-01

    The horizontal trench is one of the main methods which are available to recirculate leachates.To study the unsaturated-saturated seepage laws during leachate recirculation process,different flow control equations are used for the saturated/unsaturated zones in bioreactor landfills.The saturated Richards' equation is adopted as the flow governing equation in the saturated area of the waste mass.For the unsaturated area of the waste mass,based on the law of conservation of mass,the modified Darcy's law and the Elagroudy's settlement model,a new flow governing equation considering solid waste settlement is developed.Based on the two-dimensional saturated/unsaturated model which has been developed considering solid waste settlement,the migration laws of recirculated leachates are studied.The simulated results indicate that the various parameters (i.e.,settlement of MSW,pressure head,initial void ratio,etc.) have effects on the zone of impact,pressure head,water content of MSW and recirculation leachate volume per m of trench length.The design method of horizontal trenches is proposed for the bioreactor landfills.%水平沟回灌是生物反应器填埋场中渗滤液回灌的主要模式之一,为研究水平沟回灌时生物反应器填埋场中渗滤液的非饱和-饱和运移规律,垃圾体的饱和与非饱和区域采用不同水流控制方程,饱和区域的水流控制方程采用饱和Richards方程,对垃圾体非饱和区域,由质量守恒原理,以修正的Darcy定理为基础,结合Elagroudy等提出的垃圾体沉降模型,建立了考虑垃圾体沉降的非饱和渗滤液运移控制方程.基于建立的考虑沉降特性的二维非饱和-饱和水平沟回灌计算模型,研究了水平沟回灌时渗滤液在生物反应器填埋场中的运移规律,提出水平沟回灌系统的设计方法.

  4. Consequences of the genetic treshold model for observing partial migration under climate change scenarios

    NARCIS (Netherlands)

    Cobben, M.M.P.; Van Noordwijk, A.J.

    2017-01-01

    Migration is a widespread phenomenon across the animal kingdom as a response to seasonality in environmental conditions. Partially migratory populations are populations that consist of both migratory and residential individuals. Such populations are very common, yet their stability has long been

  5. Mechanistic models of animal migration behaviour - their diversity, structure and use

    NARCIS (Netherlands)

    Bauer, S.; Klaassen, M.R.J.

    2013-01-01

    Summary Migration is a widespread phenomenon in the animal kingdom, including many taxonomic groups and modes of locomotion. Developing an understanding of the proximate and ultimate causes for this behaviour not only addresses fundamental ecological questions but has relevance to many other fields,

  6. An insight on acyl migration in solvent-free ethanolysis of model triglycerides using Novozym 435.

    Science.gov (United States)

    Sánchez, Daniel Alberto; Tonetto, Gabriela Marta; Ferreira, María Luján

    2016-02-20

    In this work, the ethanolysis of triglycerides catalyzed by immobilized lipase was studied, focusing on the secondary reaction of acyl migration. The catalytic tests were performed in a solvent-free reaction medium using Novozym 435 as biocatalyst. The selected experimental variables were biocatalyst loading (5-20mg), reaction time (30-90min), and chain length of the fatty acids in triglycerides with and without unsaturation (short (triacetin), medium (tricaprylin) and long (tripalmitin/triolein)). The formation of 2-monoglyceride by ethanolysis of triglycerides was favored by long reaction times and large biocatalyst loading with saturated short- to medium-chain triglycerides. In the case of long-chain triglycerides, the formation of this monoglyceride was widely limited by acyl migration. In turn, acyl migration increased the yield of ethyl esters and minimized the content of monoglycerides and diglycerides. Thus, the enzymatic synthesis of biodiesel was favored by long-chain triglycerides (which favor the acyl migration), long reaction times and large biocatalyst loading. The conversion of acylglycerides made from long-chain fatty acids with unsaturation was relatively low due to limitations in their access to the active site of the lipase. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Competition, predation, and migration : Individual choice patterns of Serengeti migrants captured by hierarchical models

    NARCIS (Netherlands)

    Hopcraft, J. Grant C.; Morales, J. M.; Beyer, H. L.; Borner, Markus; Mwangomo, Ephraim; Sinclair, A. R. E.; Olff, Han; Haydon, Daniel T.

    Large-herbivore migrations occur across gradients of food quality or food abundance that are generally determined by underlying geographic patterns in rainfall, elevation, or latitude, in turn causing variation in the degree of interspecific competition and the exposure to predators. However, the

  8. Analysis of the theoretical model of the rapid chloride migration test

    NARCIS (Netherlands)

    Spiesz, P.; Brouwers, H.J.H.; Fisher, Gregor; Geiker, Metta Rica; Hededal, Ole; Ottosen, Lisbeth M.; Stang, Henrik

    2010-01-01

    Chloride ion diffusion coefficient in concrete is estimated very often by using electromigration tests, among which the Rapid Chloride Migration (RCM) test is becoming more and more popular. Nevertheless, this test receives much criticism due to lacks in its scientific background. In this paper the

  9. Modelling the impact of rural migration on tropical deforestation in South-West Ethiopia

    NARCIS (Netherlands)

    Van Rompaey, Anton; Debonne, N.; Vanmaercke, Matthias

    2016-01-01

    A major driver of tropical deforestation is rural frontier migration. In this paper an attempt is made to formally describe the human-environment interactions that are manifested in a forested system experiencing a large influx of rural migrants. The Guraferda district in South-West Ethiopia was

  10. Modelling of migration from multi-layers and functional barriers: Estimation of parameters

    NARCIS (Netherlands)

    Dole, P.; Voulzatis, Y.; Vitrac, O.; Reynier, A.; Hankemeier, T.; Aucejo, S.; Feigenbaum, A.

    2006-01-01

    Functional barriers form parts of multi-layer packaging materials, which are deemed to protect the food from migration of a broad range of contaminants, e.g. those associated with reused packaging. Often, neither the presence nor the identity of the contaminants is known, so that safety assessment

  11. Modelling of radionuclide migration and heat transport from an High-Level-Radioactive-Waste-repository (HLW) in Boom clay

    International Nuclear Information System (INIS)

    Put, M.; Henrion, P.

    1992-01-01

    For the modelling of the migration of radionuclides in the Boom clay formation, the analytical code MICOF has been updated with a 3-dimensional analytical solution for discrete sources. the MICOF program is used for the calculation of the release of α and β emitters from the HIGH LEVEL RADIOACTIVE WASTES (HLW). A coherent conceptual model is developed which describes all the major physico-chemical phenomena influencing the migration of radionuclides in the Boom clay. The concept of the diffusion accessible porosity is introduced and included in the MICOF code. Different types of migration experiments are described with their advantages and disadvantages. The thermal impact of the HLW disposal in the stratified Boom clay formation has been evaluated by a finite element simulation of the coupled heat and mass transport equation. The results of the simulations show that under certain conditions thermal convection cells may form, but the convective heat transfer in the clay formation is negligible. 6 refs., 19 figs., 2 tabs., 5 appendices

  12. New technique for landfill leachate well installation

    International Nuclear Information System (INIS)

    Hornsby, R.G.; Miller, M.S.

    1991-01-01

    The installation method fulfilled our expectations. The entire well installation took eight writing days to complete, for an average of two wells per day. It met our Health and Safety, waste volume, environmental risk and uniform sandpack expectations. Health and Safety concerns were minimal. We found that virtually all work could be completed using Level D protection. The volume of waste produced by the well installation was extremely low. The core samples and casing scrapings were the only well installation wastes directly produced. The waste containers which required sampling prior to disposal were: Decontaminated water (330 gallons), Personnel protective equipment and water (715 gallons), Soil cores (25 gallons), Land leachate (440 gallons). Each waste type was sampled and submitted to a laboratory for analyses of full Appendix 3 plus U.S. EPA toxicity parameters. The results verified that all of the wastes could be disposed of on-site. Since the only drilling wastes were the clay core samples and the very small amount of material adhering to the casing, contamination of the new clay cap did not occur. A uniform sandpack was guaranteed through the use of a presanded well screen. The loose sand added when the casing was removed served to fill any voids. All the leachate wells have water in them, and it appears that they will function adequately. We are in the process of constructing a treatment and storage facility to manage the liquids to be extracted for off-site disposal. The long-term effectiveness of the wells will be quantified. This well installation method should be considered in situations requiring the following: expedited installation; reduced Health and Safety concerns; reduced disposal costs; reduced potential for adverse environmental impact; and comparable installation costs. The choice of this method must include considerations of the subsurface geology and the nature of any manmade materials

  13. Global developmental gene expression and pathway analysis of normal brain development and mouse models of human neuronal migration defects.

    Directory of Open Access Journals (Sweden)

    Tiziano Pramparo

    2011-03-01

    Full Text Available Heterozygous LIS1 mutations are the most common cause of human lissencephaly, a human neuronal migration defect, and DCX mutations are the most common cause of X-linked lissencephaly. LIS1 is part of a protein complex including NDEL1 and 14-3-3ε that regulates dynein motor function and microtubule dynamics, while DCX stabilizes microtubules and cooperates with LIS1 during neuronal migration and neurogenesis. Targeted gene mutations of Lis1, Dcx, Ywhae (coding for 14-3-3ε, and Ndel1 lead to neuronal migration defects in mouse and provide models of human lissencephaly, as well as aid the study of related neuro-developmental diseases. Here we investigated the developing brain of these four mutants and wild-type mice using expression microarrays, bioinformatic analyses, and in vivo/in vitro experiments to address whether mutations in different members of the LIS1 neuronal migration complex lead to similar and/or distinct global gene expression alterations. Consistent with the overall successful development of the mutant brains, unsupervised clustering and co-expression analysis suggested that cell cycle and synaptogenesis genes are similarly expressed and co-regulated in WT and mutant brains in a time-dependent fashion. By contrast, focused co-expression analysis in the Lis1 and Ndel1 mutants uncovered substantial differences in the correlation among pathways. Differential expression analysis revealed that cell cycle, cell adhesion, and cytoskeleton organization pathways are commonly altered in all mutants, while synaptogenesis, cell morphology, and inflammation/immune response are specifically altered in one or more mutants. We found several commonly dysregulated genes located within pathogenic deletion/duplication regions, which represent novel candidates of human mental retardation and neurocognitive disabilities. Our analysis suggests that gene expression and pathway analysis in mouse models of a similar disorder or within a common pathway can

  14. Optimization of composite coagulant made from polyferric chloride and tapioca starch in landfill leachate treatment

    Science.gov (United States)

    Shaylinda, M. Z. N.; Hamidi, A. A.; Mohd, N. A.; Ariffin, A.; Irvan, D.; Hazreek, Z. A. M.; Nizam, Z. M.

    2018-04-01

    In this research, the performance of polyferric chloride and tapioca flour as composite coagulants for partially stabilized leachate was investigated. Response surface methodology (RSM) was used to optimize the coagulation and flocculation process of partially stabilized leachate. Central composite design a standard design tool in RSM was applied to evaluate the interactions and effects of dose and pH. Dose 0.2 g/L Fe and pH 4.71 were the optimum value suggested by RSM. Experimental test based on the optimum condition, resulted in 95.9%, 94.6% and 50.4% of SS, color and COD removals, respectively. The percentage difference recorded between experimental and model responses was <5%. Therefore, it can be concluded that RSM was an appropriate optimization tool for coagulation and flocculation process.

  15. Geo-electrical investigation of Leachate Impact on Groundwater: A ...

    African Journals Online (AJOL)

    Michael Horsfall

    ABSTRACT: In the past few decades, disposal sites have been filled with household ... kinds of potentially dangerous industrial waste in an uncontrolled manner ... m from the studied area suggests that the leachate has not spread to this area,.

  16. Biological Treatment of Leachate using Sequencing Batch Reactor

    Directory of Open Access Journals (Sweden)

    WDMC Perera

    2014-12-01

    Full Text Available Normal 0 false false false EN-US X-NONE TA Abstract   In Sri Lanka municipal solid waste is generally disposed in poorly managed open dumps which lack liner systems and leachate collection systems. Rain water percolates through the waste layers to produce leachate which drains in to ground water and finally to nearby water bodies, degrading the quality of water. Leachate thus has become a major environmental concern in municipal waste management and treatment of leachate is a major challenge for the existing and proposed landfill sites.   The study was conducted to assess the feasibility of the usage of the Sequencing Batch Reactor in the treatment of the landfill leachate up to the proposed levels in the draft report of “Proposed Sri Lankan standard for landfill leachate to be disposed to the inland waters". Leachate collected from the open dumpsite at Meethotamulla, Western Province, Sri Lanka was used for leachate characterization.   SBR was constructed with a 10-liter working volume operated in an 18 hour cycle mode and each cycle consists of 15hours of aerobic, 2h settle and 0.5 h of fill/decant stages. The Dissolved Oxygen level within the SBR was maintained at 2 mg/l through the aerobic stage. Infeed was diluted with water during the acclimatization period and a leachate to water ratio of 55:45 was maintained. The removal efficiencies for different parameters were; COD (90.5%, BOD (92.6%, TS (92.1%, Conductivity (83.9%, Alkalinity (97.4%, Hardness (82.2%, Mg (80.5%, Fe (94.2%, Zn (63.4%, Cr (31.69%, Pb (99.6%, Sulphate (98.9%, and Phosphorus (71.4% respectively. In addition Ni and Cd were removed completely during a single SBR cycle. Thus the dilution of leachate in the dumpsites using municipal wastewater, groundwater or rainwater was identified as the most cost effective dilution methods. The effluent from the Sequencing batch reactor is proposed to be further treated using a constructed wetland before releasing to surface water.

  17. Giant planet migration during FU Orionis outbursts: 1D disc models

    Science.gov (United States)

    Dunhill, A. C.

    2018-05-01

    I present the results of semi-analytic calculations of migrating planets in young, outbursting circumstellar discs. Formed far out in the disc via gravitational fragmentation early on in its lifetime, these planets typically migrate at very slow rates and are therefore mostly expected to remain at large radii (such as is the case in HR 8799). I show that changes in the disc structure during FUor outbursts affect the planet's ability to maintain a gap and can allow a massive giant planet's semimajor axis to reduce by almost 5 per cent in a single outburst under the most optimistic conditions. Given that a single disc will likely undergo ˜10 such outbursts this process can significantly alter the expected radial distribution for GI-formed planets.

  18. Natural attenuation processes in landfill leachate plumes at three Danish sites

    DEFF Research Database (Denmark)

    Bjerg, Poul Løgstrup; Tuxen, Nina; Reitzel, Lotte

    2011-01-01

    This article provides an overview of comprehensive core and fringe field studies at three Danish landfill sites. The goal of the research activities is to provide a holistic description of core and fringe attenuation processes for xenobiotic organic compounds in landfill leachate plumes. The appr......This article provides an overview of comprehensive core and fringe field studies at three Danish landfill sites. The goal of the research activities is to provide a holistic description of core and fringe attenuation processes for xenobiotic organic compounds in landfill leachate plumes....... The approach used is cross-disciplinary, encompassing integration of field-scale observations at different scales, field injection experiments, laboratory experiments, and reactive solute transport modeling. This is illustrated in examples from the most recently investigated site-the Sjoelund Landfill...... approaches and tools used in the application of MNA. In particular, the use of in situ indicators to document mass removal in landfill leachate plumes is emphasized. In this article, we advocate the application of conceptual and numerical models as tools for the integration of data and testing of hypotheses....

  19. Modelling of contaminant migration in acidic groundwater plumes at uranium tailings impoundments: ADNEUT3

    International Nuclear Information System (INIS)

    Cherry, J.A.; Morin, K.A.; Dubrovsky, N.M.

    1984-06-01

    This report describes the creation and application of ADNEUT3, the latest addition to the ADNEUT (Acid-Drainage NEUTralization) family of computer programs for simulating acid-drainage transport and neutralization. The creation of ADNEUT3 involved the expansion of ADNEUT1 to allow variable input conditions such as changing input solution with time, variable initial amounts of minerals through the simulated streamtube, variable velocities through the streamtube, and variable solubilities for relevant minerals dependent on aqueous chemical composition. Concepts for simulating acid-drainage neutralization are reviewed and ADNEUT3 is then applied to a field-study site of acidic contaminant migration from the Nordic Main uranium-tailings impoundment near Elliot Lake, Ontario. A sensitivity study is first implemented to calibrate ADNEUT3 to the results of the 1979 to 1983 field studies. Then ADNEUT3 is used to define probable past conditions at the site which are not reliably known. In particular, ADNEUT3 is used to help identify: 1) the approximate year when acidic seepage began leaving the tailings impoundment (1966-1967), 2) the past chemical composition of the seepage (somewhat more acidic for a short period of time), and 3) the location of the source area within the tailings for the acidic seepage (near the impoundment dam, close to the field site). Finally, ADNEUT3 is used to predict future contaminant migration. Results indicate that hundreds of years are required under present conditions for the most acidic water with associated high levels of contaminants to migrate about 100 m from the tailings impoundment. The cause of this slow movement is the significant neutralization capacity of the aquifer. If acid production within the tailings decreases in the future, migration rates of contaminants will also decrease

  20. Modelling of Eu migration in groundwater with high humic acid concentrations using a kinetic approach (KICAM)

    International Nuclear Information System (INIS)

    Klotz, D.

    2001-01-01

    The influence of humic acids on the migration of lanthanides and actinides in nonbinding loose sediments was investigated in flow column experiments. Experiments with Am were described by a reaction scheme based on kinetically controlled processes, and reaction rate constants were derived and used successfully for describing independent Am experiments. It was investigated inhowfar these data can be used for describing the Eu experiments of GSF Munich [de

  1. Modeling potential migration of petroleum hydrocarbons from a mixed-waste disposal site in the vadose zone

    International Nuclear Information System (INIS)

    Rawson, S.A.; Walton, J.C.; Baca, R.G.

    1989-01-01

    Environmental monitoring of a mixed-waste disposal site at the Idaho National Engineering Laboratory has confirmed release and migration into the vadose zone of: (1) chlorinated hydrocarbons in the vapor phase and (2) trace levels of certain transuranic elements. The finding has prompted an evaluation of the potential role of waste petroleum hydrocarbons in mediating or influencing contaminant migration from the disposal site. Disposal records indicate that a large volume of machine oil contaminated with transuranic isotopes was disposed at the site along with the chlorinated solvents and other radioactive wastes. A multiphase flow model was used to assess the possible extent of oil and vapor movement through the 177 m thick vadose zone. One dimensional simulations were performed to estimate the vertical distribution of the vapor phase, the aqueous phase, and immiscible free liquid as a function of time. The simulations indicate that the oil may migrate slowly through the vadose zone, to potentially significant depths. Calculated transport rates support the following ranking with regard to relative mobility: vapor phase > aqueous phase > free liquid. 21 refs., 7 figs., 2 tabs

  2. Effects of atelocollagen on neural stem cell function and its migrating capacity into brain in psychiatric disease model.

    Science.gov (United States)

    Yoshinaga, Toshihiro; Hashimoto, Eri; Ukai, Wataru; Ishii, Takao; Shirasaka, Tomohiro; Kigawa, Yoshiyasu; Tateno, Masaru; Kaneta, Hiroo; Watanabe, Kimihiko; Igarashi, Takeshi; Kobayashi, Seiju; Sohma, Hitoshi; Kato, Tadafumi; Saito, Toshikazu

    2013-10-01

    Stem cell therapy is well proposed as a potential method for the improvement of neurodegenerative damage in the brain. Among several different procedures to reach the cells into the injured lesion, the intravenous (IV) injection has benefit as a minimally invasive approach. However, for the brain disease, prompt development of the effective treatment way of cellular biodistribution of stem cells into the brain after IV injection is needed. Atelocollagen has been used as an adjunctive material in a gene, drug and cell delivery system because of its extremely low antigenicity and bioabsorbability to protect these transplants from intrabody environment. However, there is little work about the direct effect of atelocollagen on stem cells, we examined the functional change of survival, proliferation, migration and differentiation of cultured neural stem cells (NSCs) induced by atelocollagen in vitro. By 72-h treatment 0.01-0.05% atelocollagen showed no significant effects on survival, proliferation and migration of NSCs, while 0.03-0.05% atelocollagen induced significant reduction of neuronal differentiation and increase of astrocytic differentiation. Furthermore, IV treated NSCs complexed with atelocollagen (0.02%) could effectively migrate into the brain rather than NSC treated alone using chronic alcohol binge model rat. These experiments suggested that high dose of atelocollagen exerts direct influence on NSC function but under 0.03% of atelocollagen induces beneficial effect on regenerative approach of IV administration of NSCs for CNS disease.

  3. Migration of radionuclides with ground water: a discussion of the relevance of the input parameters used in model calculations

    International Nuclear Information System (INIS)

    Jensen, B.S.

    1982-01-01

    It is probably obvious to all, that establishing the scientific basis of geological waste disposal by going deeper and deeper in detail, may fill out the working hours of hundreds of scientists for hundreds of years. Such an endeavor is, however, impossible to attain, and we are forced to define some criteria telling us and others when knowledge and insight is sufficient. In thepresent case of geological disposal one need to be able to predict migration behavior of a series of radionuclides under diverse conditions to ascertain that unacceptable transfer to the biosphere never occurs. We have already collected a huge amount of data concerning migration phenomena, some very useful, oter less so, but we still need investigatoins departing from the simple ideal concepts, which most often have provided modellers with input data to their calculations. I therefore advocate that basic research is pursued to the point where it is possible to put limits on the effect of the lesser known factors on the migration behavior of radionuclides. When such limits have been established, it will be possible to make calculations on the worst cases, which may also occur. Although I personally believe, that these extra investigations will prove additional safety in geological disposal, this fact will convince nobody, only experimental facts will do

  4. A new isolation with migration model along complete genomes infers very different divergence processes among closely related great ape species.

    Directory of Open Access Journals (Sweden)

    Thomas Mailund

    Full Text Available We present a hidden Markov model (HMM for inferring gradual isolation between two populations during speciation, modelled as a time interval with restricted gene flow. The HMM describes the history of adjacent nucleotides in two genomic sequences, such that the nucleotides can be separated by recombination, can migrate between populations, or can coalesce at variable time points, all dependent on the parameters of the model, which are the effective population sizes, splitting times, recombination rate, and migration rate. We show by extensive simulations that the HMM can accurately infer all parameters except the recombination rate, which is biased downwards. Inference is robust to variation in the mutation rate and the recombination rate over the sequence and also robust to unknown phase of genomes unless they are very closely related. We provide a test for whether divergence is gradual or instantaneous, and we apply the model to three key divergence processes in great apes: (a the bonobo and common chimpanzee, (b the eastern and western gorilla, and (c the Sumatran and Bornean orang-utan. We find that the bonobo and chimpanzee appear to have undergone a clear split, whereas the divergence processes of the gorilla and orang-utan species occurred over several hundred thousands years with gene flow stopping quite recently. We also apply the model to the Homo/Pan speciation event and find that the most likely scenario involves an extended period of gene flow during speciation.

  5. Comparison of two different Radiostereometric analysis (RSA) systems with markerless elementary geometrical shape modeling for the measurement of stem migration.

    Science.gov (United States)

    Li, Ye; Röhrl, Stephan M; Bøe, B; Nordsletten, Lars

    2014-09-01

    Radiostereometric analysis (RSA) is the gold standard of measurement for in vivo 3D implants migration. The aim of this study was to evaluate the in vivo precision of 2 RSA marker-based systems compared with that of marker-free, elementary geometrical shape modeling RSA. Stem migration was measured in 50 patients recruited from an on-going Randomized Controlled Trial. We performed marker-based analysis with the Um RSA and RSAcore systems and compared these results with those of the elementary geometrical shape RSA. The precision for subsidence was 0.118 mm for Um RSA, 0.141 mm for RSAcore, and 0.136 mm for elementary geometrical shape RSA. The precision for retroversion was 1.3° for elementary geometrical shape RSA, approximately 2-fold greater than that for the other methods. The intraclass correlation coefficient between the marker-based systems and elementary geometrical shape RSA was approximately 0.5 for retroversion. All 3 methods yielded ICCs for subsidence and varus-valgus rotation above 0.9. We found an excellent correlation between marker-based RSA and elementary geometrical shape RSA for subsidence and varus-valgus rotation, independent of the system used. The precisions for out-of-plane migration were inferior for elementary geometrical shape RSA. Therefore, as a mechanism of failure, retroversion may be more difficult to detect early. This is to our knowledge the first study to compare different RSA systems with or without markers on the implant. Marker-based RSA has high precision in all planes, independent of the system used. Elementary geometrical shape RSA is inferior in out-of-plane migration. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Model studies of migration from paper and board into fruit and vegetables and into Tenax as a food simulant.

    Science.gov (United States)

    Bradley, E L; Castle, L; Speck, D R

    2014-01-01

    Four samples of paper and board (P/B) of a type used for packaging dry foods were subjected to migration tests using mushrooms, apples, potatoes and bananas, and using the polymeric powder Tenax as a food simulant. The P/B samples contained only low levels of diisopropylnaphthalene (DiPN) and diisobutyl phthalate (DiBP) and so the experiments were conducted after impregnating the P/B with added model substances. These were o-xylene, acetophenone, dodecane, benzophenone, DiPN and DiBP. Migration levels depended strongly on the nature of the substance and on the nature of the food and much less on the characteristics of the P/B, except insofar as they affected the contact area - flexible papers giving more extensive contact with the food than thick rigid board. Migration into Tenax was at least a factor of 10 higher than migration into the fresh fruit and vegetables. The food samples were placed in contact with the P/B and then overwrapped loosely with aluminium foil and so this correction factor will tend to be conservative compared with a more open storage of the packed foods. Washing, peeling or cooking the fruits and vegetables after contact with the P/B had a surprisingly small effect on contaminant levels in general, and no one processing step was effective in giving a significant reduction of all the types of chemicals studied. This was because either they had penetrated into the food (so resisting peeling), or were not freely water-soluble (so resisting washing) or were not particularly volatile (so resisting loss by evaporation during cooking).

  7. Modelling migration in the marine environment of radioactive substances from Fukushima Daiichi with the use of computer code POMRad

    Energy Technology Data Exchange (ETDEWEB)

    Krylov, A.L.; Nossov, A.V.; Kisselev, V.P. [Nuclear Safety Institute of Russian Academy of Sciences, 52, B. Tulskaya, Moscow (Russian Federation)

    2014-07-01

    Fukushima accident proved once more the necessity of computer codes for modelling of radioactive substances migration in the marine environment. Radionuclides were discharged (and leaked) into the sea with contaminated waters and fell-out from the atmosphere. Unfortunately assessments of the radioactivity sources differ significantly. The uncertainty is significant as for contamination that took place in months following the disaster as for leakages that took place in 2013. According to most researches, in the spring of 2011 the most important sources of radioactive pollution of the sea were direct inflows of contaminated water. In the long-term, due to contamination of river basins, the inflow of radioactivity with river waters may become the most significant source. Strontium, iodine and cesium tend to migrate in seas in dissolved state due to small values of K{sub d} (distribution factor water - suspended sediments). However distribution factor of Cs in fresh water is high. Thus it can be assumed that most of cesium entering the sea with a river flow will be sorbed on suspended particles. Sedimentation of the particles can lead to development of contaminated areas of bottom sediments. Thus modelling migration and transformation of radionuclides in water bodies is an important radioecological problem. The three-dimensional dynamic computer code POMRad is a tool for solution of the problem. It can be used to implement full cycle of modelling: - hydrological modelling - computation of fields of currents (and other important hydrological characteristics); - sediment transport modelling (cohesive, non-cohesive and 'hot particles' if necessary); - radioactivity transport modelling (taking into account decay, sorption, desorption, etc). The article is aimed to give a brief description of the computer code and examples of its use for modelling of migration in the sea of radionuclides from Fukushima Daiichi nuclear power plant (NPP). The base of POMRad is the

  8. Nitrous oxide flux from landfill leachate-sawdust nitrogenous compost

    International Nuclear Information System (INIS)

    Hui, C.H.; So, M.K.; Lee, C.M.; Chan, G.Y.S.

    2003-01-01

    Composted nitrogenous waste has the potential to produce excessive amounts of nitrous oxide (N 2 O), a potent greenhouse gas that also contributes to stratospheric ozone depletion. In this laboratory study, sawdust was irrigated with varying amounts of landfill leachate with high NH 4 + -N content (3950 mg l -1 ). Physicochemical properties, including the amount of N 2 O produced, were monitored during the composting process over 28 days. A rapid decline in NH 4 + -N in the first 4 days and increasing NO 3 - -N for 11 days was followed by lower but stabilized levels of available-N, even with repeated leachate irrigation. Less than 0.03% of the leachate-applied N was lost as N 2 O. Higher leachate applications as much as tripled N 2 O production, but this represented a lesser proportion overall of the total nitrogen. Addition of glucose to the composting process had no significant effect on N 2 O production. The derived sawdust-leachate compost supported healthy growth of Sesbania rostrata. It is concluded that compost can be produced from sawdust irrigated with landfill leachate without substantial emission of N 2 O, although excessive flux of N 2 O remains about high application rates over longer time periods. (Author)

  9. Characterization of Leachate at Simpang Renggam Landfill Site, Johor, Malaysia

    Science.gov (United States)

    Zailani, L. W. M.; Amdan, N. S. M.; Zin, N. S. M.

    2018-04-01

    Nowadays, the world facing a major problem in managed solid waste due to the increasing of solid waste. Malaysia, one of the country also involves in this matter which is 296 landfills are open to overcome this problem. Currently, the best alternative option to manage solid waste is by using landfilling method because it has low costing advantages. The disadvantage of landfill method, it might cause a pollution by producing leachate that will give an effect to the ground and surface water resources. This study focuses on analysing the leachate composition at Simpang Renggam Landfill(SRL) site for seven parameters such as COD, BOD, SS, turbidity, pH, BOD5/COD, and ammonia (NH3-N). All the data obtained were compared with previous researcher and Malaysia Environmental Quality Act 1974. From the result, SRL site was categorized as partially stabilized leachate with the parameter of BOD5/COD > 0.1. The SRL site is recommended to use a physical-chemical method for a better treatment because the leachate composition is classified as old leachate and aerated lagoon method are not satisfied to be used in treating the aging leachate at SRL site.

  10. Studying uranium migration in natural environment: experimental approach and geochemical modeling

    International Nuclear Information System (INIS)

    Phrommavanh, V.

    2008-10-01

    The present study deals with characterizing uranium migration in a limited zone of Le Bouchet site, a former uranium ore treatment facility, which is dismantled and the rehabilitation of which is under process. Some wastes are packed in a rehabilitated disposal nearby, called the Itteville site. In the framework of the monitoring of the deposit environment (air, water, sediment) set by prefectorial decrees, a piezometer (PZPK) located downstream to the latter, has shown total dissolved uranium peaks each winter since the 1990's. PZPK collects both the interstitial water of a calcareous peat formation, between the surface and 3 m, and an alluvial aquifer near 6 m of depth. Firstly, a hydrogeochemical characterization of the site has evidenced the uranium source term, which is present in the peat soil near 0.8 m, hence excluding any leaching from the waste disposal. Actually, a few microparticles of uranium oxide and mixed uranium-thorium oxide have been detected, but they do not represent the major part of the source term. Secondly, water chemistry of the peat soil water and PZPK has been monitored every two months from 2004 to 2007 in order to understand the reasons of the seasonal fluctuations of [U]tot.diss.. Completed with geochemical modeling and a bacterial identification by 16S rDNA sequence analysis, water chemistry data showed an important sulfate-reducing bacterial activity in summertime, leading to reducing conditions and therefore, a total dissolved uranium content limited by the low solubility of uraninite U IV O 2 (s). In wintertime, the latter bacterial activity being minimal and the effective pluviometry more important, conditions are more oxidant, which favors U(VI), more soluble, notably as the Ca 2 UO 2 (CO 3 ) 3 (aq) complex, evidenced by TRLFS. Finally, bacterial activity has been reproduced in laboratory in order to better characterize its impact on uranium solubility in the peat soil. Various parameters were tested (C sources, temperature

  11. Effects of ferric ions on the catalytic ozonation process on sanitary landfill leachates

    Directory of Open Access Journals (Sweden)

    Messias Borges Silva

    2013-04-01

    Full Text Available Leachates exhibiting an unstable ratio of biochemical oxygen demand (BOD and chemical oxygen demand (COD of approximately 0.45 are typical of new landfills in the City of Cachoeira Paulista, Brazil. Although the organic matter portion is bio-treatable, the presence of refractory leached organic material requires unconventional effluent-treatment processes. Leachate treatment with ozone oxidation, in the presence of ferric ions, acts as catalyst in the formation of hydroxyl radicals. Ozone was obtained by corona-discharge from high-purity O2 gas. The treatment was performed in natura in a jacketed borosilicate glass reactor containing 900 ml of leachate. The analyzed response variable was expressed as the concentration of dissolved organic carbon (DOC. In order to determine the optimal proportions to produce the greatest degradation rate for organic materials, variations in experimental O2 flow-fed to the generator, the Fe(iii concentration, and the output of the ozonator were conducted over two experimental runs. Experimental models showed a DOC degradation on the order of 81.25%.

  12. Geochemical analysis of leachates from cement/low-level radioactive waste/soil systems

    International Nuclear Information System (INIS)

    Criscenti, L.J.; Serne, R.J.

    1988-09-01

    Laboratory experiments were conducted as part of the Special Waste Form Lysimeters/endash/Arid Program. These experiments were conducted to investigate the performance of solidified low-level nuclear waste in a typical arid, near-surface disposal site, and to evaluate the ability of laboratory tests to predict leaching in actual field conditions. Batch leaching, soil adsorption column, and soil/waste form column experiments were conducted using Portland III cement waste forms containing boiling-water reactor evaporator concentrate and ion-exchange resin waste. In order to understand the reaction chemistry of the cement waste form/soil/ground-water system, the compositions of the leachates from the laboratory experiments were studied with the aid of the MINTEQ ion speciation/solubility and mass transfer computer code. The purpose of this report is to describe the changes in leachate composition that occur during the course of the experiments, to discuss the geochemical modeling results, and to explore the factors controlling the major element chemistry of these leachates. 18 refs., 84 figs., 14 tabs

  13. Sensitivity analysis and uncertainties simulation of the migration of radionuclide in the system of geological disposal-CRP-GEORC model

    International Nuclear Information System (INIS)

    Su Rui; Wang Ju; Chen Weiming; Zong Zihua; Zhao Honggang

    2008-01-01

    CRP-GEORC concept model is an artificial system of geological disposal for High-Level radioactive waste. Sensitivity analysis and uncertainties simulation of the migration of radionuclide Se-79 and I-129 in the far field of this system by using GoldSim Code have been conducted. It can be seen from the simulation results that variables used to describe the geological features and characterization of groundwater flow are sensitive variables of whole geological disposal system. The uncertainties of parameters have remarkable influence on the simulation results. (authors)

  14. Thermal gradient brine inclusion migration in salt study: gas-liquid inclusions, preliminary model

    International Nuclear Information System (INIS)

    Olander, D.R.; Machiels, A.J.

    1979-10-01

    Natural salt deposits contain small cubical inclusions of brine distributed through the salt. Temperature gradients, resulting from storing heat-generating wastes in the salt, can cause the inclusions to move through the salt. Prediction of the rate and amount of brine-inclusion migration is necessary for the evaluation of bedded or domed salts as possible media for waste repositories. Inclusions filled exclusively with liquid migrate up the temperature gradient towards the heat source. The solubility of salt in the brine inclusion increases with temperature. Consequently, salt dissolves into the inclusion across the hot surface and crystallizes out at the cold surface. Diffusion of salt within the liquid phase from the hot to the cold faces causes the inclusions to move in the opposite direction. In so doing, they change shape and eventually become rectangular parallelipipeds with a width (dimension perpendicular to the thermal gradient) much larger than the thickness (dimension in the direction of the thermal gradient). The inclusions may also contain a gas phase predominantly consisting of water vapor. These entities are termed two-phase or gas-liquid inclusions. The two-phase inclusions usually migrate down the temperature gradient away from the heat source remaining more-or-less cubical. A two-phase inclusion also forms when an all-liquid inclusion reaches the waste package; upon opening up at the salt-package interface, the brine partially evaporates and the inclusion reseals with some insoluble gas trapped inside. These gas-liquid inclusions proceed to move down the temperature gradient, in the opposite sense of the all-liquid inclusions. The gas-liquid inclusions phenomenon provides a pathway by which radionuclides leached from the wasteform by the brine can be transported away from the waste package and thus might have greater access to the biosphere

  15. Fate of organic contaminants in the redox zones of a landfill leachate pollution plume (Vejen, Denmark)

    DEFF Research Database (Denmark)

    Lyngkilde, John; Christensen, Thomas Højlund

    1992-01-01

    Samples from 75 sample locations in a landfill leachate pollution plume reveal a significant disappearance of specific organic compounds (SOC's) within the first 100 m of the plume. Only the herbicide Mecoprop® (MCPP) migrates further. Since sorption and dilution cannot account for the decreasing...... concentrations, degradation is considered to be the governing process. Non-volatile organic carbon shows a corresponding fate probably acting as a substrate for the microbial processes. The first 20 m of the plume are methanogenic/sulfidogenic, judged on the chemistry of the groundwater, followed...... by a significant ferrogenic zone exhibiting a substantial capacity to degrade the SOC's. The presence of intermediary products (here an oxidized camphor compound) supports the concept of degradation within the ferrogenic zone. This investigation draws the attention to the significant natural attenuation of organic...

  16. The Globalisation of migration

    Directory of Open Access Journals (Sweden)

    Milan Mesić

    2002-04-01

    Full Text Available The paper demonstrates that contemporary international migration is a constitutive part of the globalisation process. After defining the concepts of globalisation and the globalisation of migration, the author discusses six key themes, linking globalisation and international migration (“global cities”, the scale of migration; diversification of migration flows; globalisation of science and education; international migration and citizenship; emigrant communities and new identities. First, in accordance with Saskia Sassen’s analysis, the author rejects the wide-spread notion that unqualified migrants have lost an (important role in »global cities«, i.e. in the centres of the new (global economy. Namely, the post-modern service sector cannot function without the support of a wide range of auxiliary unqualified workers. Second, a critical comparison with traditional overseas mass migration to the USA at the turn of the 19th and 20th centuries indicates that present international migration is, perhaps, less extensive – however it is important to take into consideration various limitations that previously did not exist, and thus the present migration potential is in really greater. Third, globalisation is more evident in a diversification of the forms of migration: the source area of migrants to the New World and Europe has expanded to include new regions in the world; new immigration areas have arisen (the Middle East, new industrial countries of the Far East, South Europe; intra-regional migration has intensified. Forth, globalisation is linked to an increased migration of experts and the pessimistic notion of a brain drain has been replaced by the optimistic idea of a brain gain. Fifth, contemporary international migration has been associated with a crisis of the national model of citizenship. Sixth, the interlinking of (migrant cultural communities regardless of distance and the physical proximity of cultural centres (the

  17. The Alligator rivers natural analogue - Modelling of uranium and thorium migration in the weathered zone at Koongarra

    International Nuclear Information System (INIS)

    Skagius, K.; Lindgren, M.; Boghammar, A.; Brandberg, F.; Pers, K.; Widen, H.

    1993-08-01

    The Koongarra Uranium Deposit in the Alligator Rivers Region in the Northern Territory of Australia is a natural analogue being investigated with the aim to contribute to the understanding of the scientific basis for the long term prediction of radionuclide migration within geological environments relevant to radioactive waste repositories. The dispersion of uranium and decay products in the weathered zone has been modelled with a simple advection-dispersion-reversible sorption model and with a model extended to also consider α-recoil and transfer of radionuclides between different mineral phases of the rock. The modelling work was carried out in several iterations, each including a review of available laboratory and field data, selection of the system to be modelled and suitable model, and a comparison of modelling results with field observations. Uranium concentrations in bulk rock calculated with the simple advection-dispersion- reversible sorption model were in fair agreement with observed data using parameter values within ranges recommended based on independent interpretations. The advection-dispersion-reversible sorption model is a large simplification of the system among other things because the partitioning of radionuclides between water and solid phase is described with a sorption equilibrium term only. Although the results from this study not are enough to validate simple performance assessment models in a strict sense, it has been shown that even simple models are able to describe the present day distribution of uranium in the weathered zone at Koongarra. 23 refs, 61 figs

  18. The Alligator rivers natural analogue - Modelling of uranium and thorium migration in the weathered zone at Koongarra

    Energy Technology Data Exchange (ETDEWEB)

    Skagius, K; Lindgren, M; Boghammar, A; Brandberg, F; Pers, K; Widen, H [Kemakta, Stockholm (Sweden)

    1993-08-01

    The Koongarra Uranium Deposit in the Alligator Rivers Region in the Northern Territory of Australia is a natural analogue being investigated with the aim to contribute to the understanding of the scientific basis for the long term prediction of radionuclide migration within geological environments relevant to radioactive waste repositories. The dispersion of uranium and decay products in the weathered zone has been modelled with a simple advection-dispersion-reversible sorption model and with a model extended to also consider {alpha}-recoil and transfer of radionuclides between different mineral phases of the rock. The modelling work was carried out in several iterations, each including a review of available laboratory and field data, selection of the system to be modelled and suitable model, and a comparison of modelling results with field observations. Uranium concentrations in bulk rock calculated with the simple advection-dispersion- reversible sorption model were in fair agreement with observed data using parameter values within ranges recommended based on independent interpretations. The advection-dispersion-reversible sorption model is a large simplification of the system among other things because the partitioning of radionuclides between water and solid phase is described with a sorption equilibrium term only. Although the results from this study not are enough to validate simple performance assessment models in a strict sense, it has been shown that even simple models are able to describe the present day distribution of uranium in the weathered zone at Koongarra. 23 refs, 61 figs.

  19. The Development and Application of Reactive Transport Modeling Techniques to Study Radionuclide Migration at Yucca Mountain, NV

    International Nuclear Information System (INIS)

    Hari Selvi Viswanathan

    1999-01-01

    Yucca Mountain, Nevada has been chosen as a possible site for the first high level radioactive waste repository in the United States. As part of the site investigation studies, we need to make scientifically rigorous estimations of radionuclide migration in the event of a repository breach. Performance assessment models used to make these estimations are computationally intensive. We have developed two reactive transport modeling techniques to simulate radionuclide transport at Yucca Mountain: (1) the selective coupling approach applied to the convection-dispersion-reaction (CDR) model and (2) a reactive stream tube approach (RST). These models were designed to capture the important processes that influence radionuclide migration while being computationally efficient. The conventional method of modeling reactive transport models is to solve a coupled set of multi-dimensional partial differential equations for the relevant chemical components in the system. We have developed an iterative solution technique, denoted the selective coupling method, that represents a versatile alternative to traditional uncoupled iterative techniques and the filly coupled global implicit method. We show that selective coupling results in computational and memory savings relative to these approaches. We develop RST as an alternative to the CDR method for solving large two- or three-dimensional reactive transport simulations for cases in which one is interested in predicting the flux across a specific control plane. In the RST method, the multidimensional problem is reduced to a series of one-dimensional transport simulations along streamlines. The key assumption with RST is that mixing at the control plane approximates the transverse dispersion between streamlines. We compare the CDR and RST approaches for several scenarios that are relevant to the Yucca Mountain Project. For example, we apply the CDR and RST approaches to model an ongoing field experiment called the Unsaturated Zone

  20. Particle migration using local variation of the viscosity (LVOV) model in flow of a non-Newtonian fluid for ceramic tape casting

    DEFF Research Database (Denmark)

    Jabbaribehnam, Mirmasoud; Spangenberg, Jon; Hattel, Jesper Henri

    2016-01-01

    In this paper, the migration of secondary particles in a non-Newtonian ceramic slurry inthe tape casting process is investigated with the purpose of understanding the particle distribution patterns along the casting direction. The Ostwald-de Waele power law model for the non-Newtonian flow...... the substratevelocity (casting speed) leads to a more uniform distribution of the particles inside the ceramic slurry, in which case the shear induced particle migration is dominating over the gravity induced one....

  1. Study of the influence of hydrogeological conditions in the upper aquifer on radionuclide migration from a geological repository using a 2D groundwater flow model

    Energy Technology Data Exchange (ETDEWEB)

    Shestopalov, Vyacheslav; Bohuslavskyy, Alexander; Shybetskyi, Iurii [National Academy of Science of Ukaraine, Kyiv (Ukraine). Radioenvironmental Centre

    2015-07-01

    Results are presented of a case groundwater flow-transport modeling to predict the radionuclide migration from a deep geological repository (DGR) of radioactive waste. The influence of hydrogeological conditions in the upper aquifers of a storey water exchange system on the rate of contaminant migration from the DGR to its natural far-field groundwater discharges (a shallow well and a river) as a general DGR safety condition is considered.

  2. Transplanted Dental Pulp Stem Cells Migrate to Injured Area and Express Neural Markers in a Rat Model of Cerebral Ischemia.

    Science.gov (United States)

    Zhang, Xuemei; Zhou, Yinglian; Li, Hulun; Wang, Rui; Yang, Dan; Li, Bing; Cao, Xiaofang; Fu, Jin

    2018-01-01

    Ischemic stroke is a major cause of disability and mortality worldwide, while effective restorative treatments are limited at present. Stem cell transplantation holds therapeutic potential for ischemic vascular diseases and may provide an opportunity for neural regeneration. Dental pulp stem cells (DPSCs) origin from neural crest and have neuro-ectodermal features including proliferation and multilineage differentiation potentials. The rat model of middle cerebral artery occlusion (MCAO) was used to evaluate whether intravenous administration of DPSCs can reduce infarct size and to estimate the migration and trans-differentiation into neuron-like cells in focal cerebral ischemia models. Brain tissues were collected at 4 weeks following cell transplantation and analyzed with immunofluorescence, immunohistochemistry and real-time polymerase chain reaction (RT-PCR) methods. Intravenously administration of rat-derived DPSCs were found to migrate into the boundary of ischemic areas and expressed neural specific markers, reducing infarct volume and cerebral edema. These results suggest that DPSCs treatment may serve as a potential therapy for clinical stroke patients in the future. © 2018 The Author(s). Published by S. Karger AG, Basel.

  3. Atomic scale modeling of twinning in hexagonal metals: germination and migration of disconnections in zirconium, titanium and magnesium

    International Nuclear Information System (INIS)

    Mackain, Olivier

    2017-01-01

    We perform an atomic scale study of twinning in three hexagonal close packed metals: zirconium, titanium and magnesium. For that, we use two energetic models, an empirical potential suited for the study of zirconium and ab initio calculations in order to compare the three metals. The study of perfect twin boundaries shows that their surface energies are not relevant to predict which twin system is going to activate experimentally. We study nucleation and then migration of disconnections, that is to say interfacial dislocations whose glide along twin plane leads to twin thickening. We show that disconnections nucleation, rather than their migration, is the rate limiting step of twin thickening. In particular, by developing a coupling with elastic theory, we extract the core energies of each disconnection. With this method we prove that for a given twin system, the disconnection with the lowest formation energy is always the one compatible with twin mode observed experimentally, even if its elastic energy is higher. Finally, we construct the preliminary elements of a model considering the effect of stress on nucleation of disconnection. (author) [fr

  4. Species distribution models may misdirect assisted migration: insights from the introduction of Douglas-fir to Europe.

    Science.gov (United States)

    Boiffin, Juliette; Badeau, Vincent; Bréda, Nathalie

    2017-03-01

    Species distribution models (SDMs), which statistically relate species occurrence to climatic variables, are widely used to identify areas suitable for species growth under future climates and to plan for assisted migration. When SDMs are projected across times or spaces, it is assumed that species climatic requirements remain constant. However, empirical evidence supporting this assumption is rare, and SDM predictions could be biased. Historical human-aided movements of tree species can shed light on the reliability of SDM predictions in planning for assisted migration. We used Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), a North American conifer introduced into Europe during the mid-19th century, as a case-study to test niche conservatism. We combined transcontinental data sets of Douglas-fir occurrence and climatic predictors to compare the realized niches between native and introduced ranges. We calibrated a SDM in the native range and compared areas predicted to be climatically suitable with observed presences. The realized niches in the native and introduced ranges showed very limited overlap. The SDM calibrated in North America had very high predictive power in the native range, but failed to predict climatic suitability in Europe where Douglas-fir grows in climates that have no analogue in the native range. We review the ecological mechanisms and silvicultural practices that can trigger such shifts in realized niches. Retrospective analysis of tree species introduction revealed that the assumption of niche conservatism is erroneous. As a result, distributions predicted by SDM are importantly biased. There is a high risk that assisted migration programs may be misdirected and target inadequate species or introduction zones. © 2016 by the Ecological Society of America.

  5. Model for predicting the restoration of and ammonium migration from in situ mine sites

    International Nuclear Information System (INIS)

    Anon.

    1979-01-01

    There are many uranium deposits which are too deep, too poor in quality or too small in extent to be economically strip mined. It now appears that this uranium can be mined using in situ leaching processes. One component of the lixiviant is necessarily a cation and, during the course of mining, the ion exchange sites of the minerals in the mine zone become saturated with this cation. Ammonium is the cation now commonly used. Clearly, any restoration procedure or question involving the rate of cation migration with the groundwater all necessarily involve the process of ion exchange coupled with flow in porous media. The equations describing this process are presented in this paper and numerical solutions obtained. 16 refs

  6. Geochemical modelling. Column 2: a computer program for simulation of migration

    International Nuclear Information System (INIS)

    Nielsen, O.J.; Carlsen, L.; Bo, P.

    1985-01-01

    COLUMN2 is a 1D FORTRAN77 computer program designed for studies of the effects of various physicochemical processes on migration. It solves the solute transport equation and can take into account dispersion, sorption, ion exchange, first and second order homogeneous chemical reactions. Spatial variations of input pulses and retention factors are possible. The method of solution is based on a finite difference discretion followed by the application of the method of characteristics and two separate grid systems. This report explains the mathematical and numerical methods used, describes the necessary input, contains a number of test examples, provides a listing of the program and explains how to acquire the program, adapt it to other computers and run it. This report serves as a manual for the program

  7. Migration chemistry

    International Nuclear Information System (INIS)

    Carlsen, L.

    1992-05-01

    Migration chemistry, the influence of chemical -, biochemical - and physico-chemical reactions on the migration behaviour of pollutants in the environment, is an interplay between the actual natur of the pollutant and the characteristics of the environment, such as pH, redox conditions and organic matter content. The wide selection of possible pollutants in combination with varying geological media, as well as the operation of different chemical -, biochemical - and physico-chemical reactions compleactes the prediction of the influence of these processes on the mobility of pollutants. The report summarizes a wide range of potential pollutants in the terrestrial environment as well as a variety of chemical -, biochemical - and physico-chemical reactions, which can be expected to influence the migration behaviour, comprising diffusion, dispersion, convection, sorption/desorption, precipitation/dissolution, transformations/degradations, biochemical reactions and complex formation. The latter comprises the complexation of metal ions as well as non-polar organics to naturally occurring organic macromolecules. The influence of the single types of processes on the migration process is elucidated based on theoretical studies. The influence of chemical -, biochemical - and physico-chemical reactions on the migration behaviour is unambiguous, as the processes apparently control the transport of pollutants in the terrestrial environment. As the simple, conventional K D concept breaks down, it is suggested that the migration process should be described in terms of the alternative concepts chemical dispersion, average-elution-time and effective retention. (AB) (134 refs.)

  8. Application of photochemical technologies for treatment of landfill leachate.

    Science.gov (United States)

    Meeroff, Daniel E; Bloetscher, Frederick; Reddy, D V; Gasnier, François; Jain, Swapnil; McBarnette, André; Hamaguchi, Hatsuko

    2012-03-30

    Because of widely varying practices in solid waste management, an all-inclusive solution to long-term management of landfill leachate is currently not available. There is a major technological need for sustainable, economical options for safe discharge of leachate to the environment. Two potential on-site pretreatment technologies, photochemical iron-mediated aeration (PIMA) and TiO(2) photocatalysis were compared for treatment of landfill leachate at laboratory scale. Results of bench scale testing of real landfill leachate with PIMA and TiO(2) photocatalysis showed up to 86% conversion of refractory COD to complete mineralization, up to 91% removal of lead, up to 71% removal of ammonia without pH adjustment, and up to 90% effective color removal with detention times between 4 and 6h, in field samples. The estimated contact times for 90% removal of COD, ammonia, lead, and color were found to be on the order of 10-200 h for PIMA and 3-37 h for TiO(2) photocatalysis. Testing with actual leachate samples showed 85% TiO(2) photocatalyst recovery efficiency with no loss in performance after multiple (n>4 uses). Pre-filtration was not found to be necessary for effective treatment using either process. Copyright © 2012 Elsevier B.V. All rights reserved.

  9. Environmental Isotope Characteristics of Landfill Leachates and Gases

    Science.gov (United States)

    Hackley, Keith C.; Liu, Chao-Li; Coleman, D.D.

    1996-01-01

    The isotopic characteristics of municipal landfill leachate and gases (carbon dioxide and methane) are unique relative to the aqueous and gaseous media in most other natural geologic environments. The ??13 C of the CO2 in landfills is significantly enriched in 13C, with values as high as +20??? reported. The ?? 13C and ??D values of the methane fall within a range of values representative of microbial methane produced primarily by the acetate-fermentation process. The ??D of landfill leachate is strongly enriched in deuterium, by approximately 30??? to nearly 60??? relative to local average precipitation values. This deuterium enrichment is undoubtedly due to the extensive production of microbial methane within the limited reservoir of a landfill. The concentration of the radiogenic isotopes, 14C and 3H, are significantly elevated in both landfill leachate and methane. The 14C values range between approximately 120 and 170 pMC and can be explained by the input of organic material that was affected by the increased 14C content of atmospheric CO2 caused by atmospheric testing of nuclear devices. The tritium measured in leachate, however, is often too high to be explained by previous atmospheric levels and must come from material buried within the landfill. The unique isotopic characteristics observed in landfill leachates and gases provide a very useful technique for confirming whether contamination is from a municipal landfill or some other local source.

  10. Mutagenicity and genotoxicity of coal fly ash water leachate.

    Science.gov (United States)

    Chakraborty, Rajarshi; Mukherjee, Anita

    2009-03-01

    Fly ash is a by-product of coal-fired electricity generation plants. The prevalent practice of disposal is as slurry of ash and water to storage or ash ponds located near power stations. This has lain to waste thousands of hectares of land all over the world. Since leaching is often the cause of off-site contamination and pathway of introduction into the human environment, a study on the genotoxic effects of fly ash leachate is essential. Leachate prepared from the fly ash sample was analyzed for metal content, and tested for mutagenicity and genotoxicity. Analyses of metals show predominance of the metals-sodium, silicon, potassium, calcium, magnesium, iron, manganese, zinc, and sulphate. The Ames Salmonella mutagenicity assay, a short-term bacterial reverse mutation assay, was conducted on two-tester strains of Salmonella typhimurium strains TA97a and TA102. For genotoxicity, the alkaline version of comet assay on fly ash leachate was carried in vitro on human blood cells and in vivo on Nicotiana plants. The leachate was directly mutagenic and induced significant (Ppercentage (%), tail length (mum), and olive tail moment (arbitrary units). Our results indicate that leachate from fly ash dumpsites has the genotoxic potential and may lead to adverse effects on vegetation and on the health of exposed human populations.

  11. The effect of landfill age on municipal leachate composition.

    Science.gov (United States)

    Kulikowska, Dorota; Klimiuk, Ewa

    2008-09-01

    The influence of municipal landfill age on temporal changes in municipal leachate quality on the basis of elaboration of 4 years monitoring of leachate from landfill in Wysieka near Bartoszyce (Poland) is presented in this study. In leachate, concentrations of organic compounds (COD, BOD(5)), nutrients (nitrogen, phosphorus), mineral compounds, heavy metals and BTEX were investigated. It was shown that the principal pollutants in leachate were organics and ammonia - as landfill age increased, organics concentration (COD) in leachate decreased from 1,800 mg COD/l in the second year of landfill exploitation to 610 mg COD/l in the sixth year of exploitation and increase of ammonia nitrogen concentration from 98 mg N(NH)/l to 364 mg N(NH4) /l was observed. Fluctuation of other indexes (phosphorus, chlorides, calcium, magnesium, sulfate, dissolved solids, heavy metals, BTEX) depended rather on season of the year (seasonal variations) than landfill age. Moreover, the obtained data indicate that despite of short landfill's lifetime some parameters e.g. high pH (on average 7.84), low COD concentration (metal concentration, indicated that the landfill was characterized by methanogenic conditions already at the beginning of the monitoring period.

  12. Studying uranium migration in natural environment: experimental approach and geochemical modeling; Etude de la migration de l'uranium en milieu naturel: approche experimentale et modelisation geochimique

    Energy Technology Data Exchange (ETDEWEB)

    Phrommavanh, V.

    2008-10-15

    The present study deals with characterizing uranium migration in a limited zone of Le Bouchet site, a former uranium ore treatment facility, which is dismantled and the rehabilitation of which is under process. Some wastes are packed in a rehabilitated disposal nearby, called the Itteville site. In the framework of the monitoring of the deposit environment (air, water, sediment) set by prefectorial decrees, a piezometer (PZPK) located downstream to the latter, has shown total dissolved uranium peaks each winter since the 1990's. PZPK collects both the interstitial water of a calcareous peat formation, between the surface and 3 m, and an alluvial aquifer near 6 m of depth. Firstly, a hydrogeochemical characterization of the site has evidenced the uranium source term, which is present in the peat soil near 0.8 m, hence excluding any leaching from the waste disposal. Actually, a few microparticles of uranium oxide and mixed uranium-thorium oxide have been detected, but they do not represent the major part of the source term. Secondly, water chemistry of the peat soil water and PZPK has been monitored every two months from 2004 to 2007 in order to understand the reasons of the seasonal fluctuations of [U]tot.diss.. Completed with geochemical modeling and a bacterial identification by 16S rDNA sequence analysis, water chemistry data showed an important sulfate-reducing bacterial activity in summertime, leading to reducing conditions and therefore, a total dissolved uranium content limited by the low solubility of uraninite U{sup IV}O{sub 2}(s). In wintertime, the latter bacterial activity being minimal and the effective pluviometry more important, conditions are more oxidant, which favors U(VI), more soluble, notably as the Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3}(aq) complex, evidenced by TRLFS. Finally, bacterial activity has been reproduced in laboratory in order to better characterize its impact on uranium solubility in the peat soil. Various parameters were tested

  13. Optimized evaporation technique for leachate treatment: Small scale implementation.

    Science.gov (United States)

    Benyoucef, Fatima; Makan, Abdelhadi; El Ghmari, Abderrahman; Ouatmane, Aziz

    2016-04-01

    This paper introduces an optimized evaporation technique for leachate treatment. For this purpose and in order to study the feasibility and measure the effectiveness of the forced evaporation, three cuboidal steel tubs were designed and implemented. The first control-tub was installed at the ground level to monitor natural evaporation. Similarly, the second and the third tub, models under investigation, were installed respectively at the ground level (equipped-tub 1) and out of the ground level (equipped-tub 2), and provided with special equipment to accelerate the evaporation process. The obtained results showed that the evaporation rate at the equipped-tubs was much accelerated with respect to the control-tub. It was accelerated five times in the winter period, where the evaporation rate was increased from a value of 0.37 mm/day to reach a value of 1.50 mm/day. In the summer period, the evaporation rate was accelerated more than three times and it increased from a value of 3.06 mm/day to reach a value of 10.25 mm/day. Overall, the optimized evaporation technique can be applied effectively either under electric or solar energy supply, and will accelerate the evaporation rate from three to five times whatever the season temperature. Copyright © 2016. Published by Elsevier Ltd.

  14. Ecotoxicological assessment of solar cell leachates: Copper indium gallium selenide (CIGS) cells show higher activity than organic photovoltaic (OPV) cells

    Energy Technology Data Exchange (ETDEWEB)

    Brun, Nadja Rebecca [University of Applied Sciences and Arts Northwestern Switzerland, School of Life Sciences, Gründenstrasse 40, CH-4132 Muttenz (Switzerland); Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Universitätsstrasse 16, CH-8092 Zürich (Switzerland); Wehrli, Bernhard [Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Universitätsstrasse 16, CH-8092 Zürich (Switzerland); Fent, Karl, E-mail: karl.fent@fhnw.ch [University of Applied Sciences and Arts Northwestern Switzerland, School of Life Sciences, Gründenstrasse 40, CH-4132 Muttenz (Switzerland); Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Universitätsstrasse 16, CH-8092 Zürich (Switzerland)

    2016-02-01

    Despite the increasing use of photovoltaics their potential environmental risks are poorly understood. Here, we compared ecotoxicological effects of two thin-film photovoltaics: established copper indium gallium selenide (CIGS) and organic photovoltaic (OPV) cells. Leachates were produced by exposing photovoltaics to UV light, physical damage, and exposure to environmentally relevant model waters, representing mesotrophic lake water, acidic rain, and seawater. CIGS cell leachates contained 583 μg L{sup −1} molybdenum at lake water, whereas at acidic rain and seawater conditions, iron, copper, zinc, molybdenum, cadmium, silver, and tin were present up to 7219 μg L{sup −1}. From OPV, copper (14 μg L{sup −1}), zinc (87 μg L{sup −1}) and silver (78 μg L{sup −1}) leached. Zebrafish embryos were exposed until 120 h post-fertilization to these extracts. CIGS leachates produced under acidic rain, as well as CIGS and OPV leachates produced under seawater conditions resulted in a marked hatching delay and increase in heart edema. Depending on model water and solar cell, transcriptional alterations occurred in genes involved in oxidative stress (cat), hormonal activity (vtg1, ar), metallothionein (mt2), ER stress (bip, chop), and apoptosis (casp9). The effects were dependent on the concentrations of cationic metals in leachates. Addition of ethylenediaminetetraacetic acid protected zebrafish embryos from morphological and molecular effects. Our study suggests that metals leaching from damaged CIGS cells, may pose a potential environmental risk. - Highlights: • Photovoltaics may be disposed in the environment after usage. • Copper indium gallium selenide (CIGS) and organic (OPV) cells were compared. • Morphological and molecular effects were assessed in zebrafish embryos. • Environmental condition affected metal leaching and ecotoxicological activity. • Damaged CIGS cells pose higher risk to the environment than OPV cells.

  15. Influence of leachate recirculation on aerobic and anaerobic decomposition of solid wastes

    International Nuclear Information System (INIS)

    Bilgili, M. Sinan; Demir, Ahmet; Ozkaya, Bestamin

    2007-01-01

    In this study, the effect of leachate recirculation on aerobic and anaerobic degradation of municipal solid wastes is determined by four laboratory-scale landfill reactors. The options studied and compared with the traditional anaerobic landfill are: leachate recirculation, landfill aeration, and aeration with leachate recirculation. Leachate quality is regularly monitored by the means of pH, alkalinity, total dissolved solids, conductivity, oxidation-reduction potential, chloride, chemical oxygen demand, ammonia, and total Kjeldahl nitrogen, in addition to generated leachate quantity. Aerobic leachate recirculated landfill appears to be the most effective option in the removal of organic matter and ammonia. The main difference between aerobic recirculated and non-recirculated landfill options is determined at leachate quantity. Recirculation is more effective on anaerobic degradation of solid waste than aerobic degradation. Further studies are going on to determine the optimum operational conditions for aeration and leachate recirculation rates, also with the operational costs of aeration and recirculation

  16. Characteristic of leachate at Alor Pongsu Landfill Site, Perak, Malaysia: A comparative study

    Science.gov (United States)

    Nor Farhana Zakaria, Siti; Aziz, Hamidi Abdul

    2018-04-01

    Leachate is a harmful by product generated from the landfill site. Leachate contains a high concentration of pollutant which can cause serious pollution to environmental. In this study, characteristics of leachate in Alor Pongsu Landfill Site (APLS) were monitored and analyzed according to the Standard Methods for the Examination of Water and Wastewater (2005). Composition in leachate at APLS was monitored for one year starting from January 2015 until January 2016. Nine parameters were monitored including color, chemical oxygen demand (COD), biological oxygen demand (BOD5), ammoniacal nitrogen (NH3-N), biodegradability ratio (BOD5/COD), temperature, dissolved oxygen (DO), total dissolved solid (TDS) and pH. Based on the analysis, Alor Pongsu Landfill leachate was categorized as stabilized landfill leachate by referring to the BOD5/COD < 0.1. Comparison with allowable discharge limits for leachate shows that most of parameters exceeded the standard discharge limitation. Thus, proper treatment is needed before leachate can be discharged to the environment.

  17. 3D seismic modeling and reverse‐time migration with the parallel Fourier method using non‐blocking collective communications

    KAUST Repository

    Chu, Chunlei

    2009-01-01

    The major performance bottleneck of the parallel Fourier method on distributed memory systems is the network communication cost. In this study, we investigate the potential of using non‐blocking all‐to‐all communications to solve this problem by overlapping computation and communication. We present the runtime comparison of a 3D seismic modeling problem with the Fourier method using non‐blocking and blocking calls, respectively, on a Linux cluster. The data demonstrate that a performance improvement of up to 40% can be achieved by simply changing blocking all‐to‐all communication calls to non‐blocking ones to introduce the overlapping capability. A 3D reverse‐time migration result is also presented as an extension to the modeling work based on non‐blocking collective communications.

  18. Japanese migration in contemporary Japan: economic segmentation and interprefectural migration.

    Science.gov (United States)

    Fukurai, H

    1991-01-01

    This paper examines the economic segmentation model in explaining 1985-86 Japanese interregional migration. The analysis takes advantage of statistical graphic techniques to illustrate the following substantive issues of interregional migration: (1) to examine whether economic segmentation significantly influences Japanese regional migration and (2) to explain socioeconomic characteristics of prefectures for both in- and out-migration. Analytic techniques include a latent structural equation (LISREL) methodology and statistical residual mapping. The residual dispersion patterns, for instance, suggest the extent to which socioeconomic and geopolitical variables explain migration differences by showing unique clusters of unexplained residuals. The analysis further points out that extraneous factors such as high residential land values, significant commuting populations, and regional-specific cultures and traditions need to be incorporated in the economic segmentation model in order to assess the extent of the model's reliability in explaining the pattern of interprefectural migration.

  19. Use of sepiolite as an adsorbent for the removal of copper (II) from industrial waste leachate

    Science.gov (United States)

    Gamze Turan, N.; Ardali, Yüksel

    2013-04-01

    as talc, but it has discontinuities and inversion of the silica sheets, which give rise to structural tunnels and blocks. In the inner blocks, all corners of the silica tetrahedral are connected to adjacent blocks, but in the outer blocks, some of the corners are Si atoms bound to hydroxyls (Si-OH). This unique structure allows the penetration of organic and inorganic species into the structure and assigns sepiolite an industrial importance in adsorption. The objective of the present study is to investigate the feasibility of using sepiolite for the adsorptive removal of Cu (II) from the industrial waste leachate. The adsorption capacities and sorption efficiencies are determined. The pseudo first order, the pseudo-second order, Elovich and the intra particle diffusion kinetic models are used to describe the kinetic data to estimate the rate constants. The adsorption of Cu (II) from the aqueous leachate of industrial wastes onto sepiolite was performed using a batch equilibrium technique. At first stage, one-factor-at-a-time experiments were performed to see the individual effects of initial pH, adsorbent dosage and contact time. The adsorption of Cu (II) was favorably influenced by an increase in the adsorbent dosage. The maximum percent removal of Cu (II) were observed at pH>6, and significantly decreased at lower pH value. The optimum contact time is found as 10 min. for the removal of Cu (II). The increment in contact time from 10 min. to 120 min. did not show a significant effect on efficiency. The maximum Cu (II) adsorption efficiencies were obtained at 94.45%. The pseudo second order kinetic model agrees very well with the dynamical behavior for the adsorption of Cu (II) from aqueous leachate of industrial waste onto sepiolite. The results indicate that the use of sepiolite that is locally available and almost free of cost as an adsorbent could be a viable alternative to activated carbon for the removal of Cu (II) ions from aqueous solutions.

  20. Soya-cerebroside, an extract of Cordyceps militaris, suppresses monocyte migration and prevents cartilage degradation in inflammatory animal models

    Science.gov (United States)

    Liu, Shan-Chi; Chiu, Ching-Peng; Tsai, Chun-Hao; Hung, Chun-Yin; Li, Te-Mao; Wu, Yang-Chang; Tang, Chih-Hsin

    2017-01-01

    Pathophysiological events that modulate the progression of structural changes in osteoarthritis (OA) include the secretion of inflammatory molecules, such as proinflammatory cytokines. Interleukin-1beta (IL-1β) is the prototypical inflammatory cytokine that activates OA synovial cells to release cytokines and chemokines in support of the inflammatory response. The monocyte chemoattractant protein-1 (MCP-1/CCL2) is one of the key chemokines that regulate migration and infiltration of monocytes in response to inflammation. We show in this study that IL-1β-induced MCP-1 expression and monocyte migration in OA synovial fibroblasts (OASFs) is effectively inhibited by soya-cerebroside, an extract of Cordyceps militaris. We found that soya-cerebroside up-regulated of microRNA (miR)-432 expression via inhibiting AMPK and AKT signaling pathways in OASFs. Soya-cerebroside also effectively decreased monocyte infiltration and prevented cartilage degradation in a rat inflammatory model. Our findings are the first to demonstrate that soya-cerebroside inhibits monocyte/macrophage infiltration into synoviocytes, attenuating synovial inflammation and preventing cartilage damage by reducing MCP-1 expression in vitro and in vivo. Taken together, we suggest a novel therapeutic strategy based on the use of soya-cerebroside for the management of OA. PMID:28225075

  1. Evaluation of DNA bending models in their capacity to predict electrophoretic migration anomalies of satellite DNA sequences.

    Science.gov (United States)

    Matyášek, Roman; Fulneček, Jaroslav; Kovařík, Aleš

    2013-09-01

    DNA containing a sequence that generates a local curvature exhibits a pronounced retardation in electrophoretic mobility. Various theoretical models have been proposed to explain relationship between DNA structural features and migration anomaly. Here, we studied the capacity of 15 static wedge-bending models to predict electrophoretic behavior of 69 satellite monomers derived from four divergent families. All monomers exhibited retarded mobility in PAGE corresponding to retardation factors ranging 1.02-1.54. The curvature varied both within and across the groups and correlated with the number, position, and lengths of A-tracts. Two dinucleotide models provided strong correlation between gel mobility and curvature prediction; two trinucleotide models were satisfactory while remaining dinucleotide models provided intermediate results with reliable prediction for subsets of sequences only. In some cases, similarly shaped molecules exhibited relatively large differences in mobility and vice versa. Generally less accurate predictions were obtained in groups containing less homogeneous sequences possessing distinct structural features. In conclusion, relatively universal theoretical models were identified suitable for the analysis of natural sequences known to harbor relatively moderate curvature. These models could be potentially applied to genome wide studies. However, in silico predictions should be viewed in context of experimental measurement of intrinsic DNA curvature. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Landfill Leachate Treatment by Electrocoagulation and Fiber Filtration.

    Science.gov (United States)

    Li, Runwei; Wang, Boya; Owete, Owete; Dertien, Joe; Lin, Chen; Ahmad, Hafiz; Chen, Gang

    2017-11-01

      Landfilling is widely adopted as one of the most economical processes for solid waste disposal. At the same time, landfill leachate is also a great environmental concern owing to its complex composition and high concentrations of contaminants. This research investigated electrocoagulation and fiber filtration for the treatment of landfill leachate. Besides electrical current (i.e., current density) and reaction time, pH played a very important role in arsenic and phosphorus removal by electrocoagulation. The combination of electrocoagulation with fiber filtration achieved a 94% chemical oxygen demand (COD), 87% arsenic, 96% iron, and 86% phosphorus removal. During electrocoagulation, the micro-particles that could not be settled by gravity were removed by the first stage of fiber filtration. Organic contaminants in the leachate were further removed by biodegradation in the second stage of fiber biofiltration.

  3. A porous flow approach to model thermal non-equilibrium applicable to melt migration

    Science.gov (United States)

    Schmeling, Harro; Marquart, Gabriele; Grebe, Michael

    2018-01-01

    We develop an approach for heat exchange between a fluid and a solid phase of a porous medium where the temperatures of the fluid and matrix are not in thermal equilibrium. The formulation considers moving of the fluid within a resting or deforming porous matrix in an Eulerian coordinate system. The approach can be applied, for example, to partially molten systems or to brine transport in porous rocks. We start from an existing theory for heat exchange where the energy conservation equations for the fluid and the solid phases are separated and coupled by a heat exchange term. This term is extended to account for the full history of heat exchange. It depends on the microscopic geometry of the fluid phase. For the case of solid containing hot, fluid-filled channels, we derive an expression based on a time-dependent Fourier approach for periodic half-waves. On the macroscopic scale, the temporal evolution of the heat exchange leads to a convolution integral along the flow path of the solid, which simplifies considerably in case of a resting matrix. The evolution of the temperature in both phases with time is derived by inserting the heat exchange term into the energy equations. We explore the effects of thermal non-equilibrium between fluid and solid by considering simple cases with sudden temperature differences between fluid and solid as initial or boundary conditions, and by varying the fluid velocity with respect to the resting porous solid. Our results agree well with an analytical solution for non-moving fluid and solid. The temperature difference between solid and fluid depends on the Peclet number based on the Darcy velocity. For Peclet numbers larger than 1, the temperature difference after one diffusion time reaches 5 per cent of \\tilde{T} or more (\\tilde{T} is a scaling temperature, e.g. the initial temperature difference). Thus, our results imply that thermal non-equilibrium can play an important role for melt migration through partially molten systems

  4. Effect of Irradiation on Tumor Microenvironment and Bone Marrow Cell Migration in a Preclinical Tumor Model

    Energy Technology Data Exchange (ETDEWEB)

    Kane, Jonathan L. [Department of Biological Sciences, Oakland University, Rochester, Michigan (United States); Department of Radiation Oncology, William Beaumont Health System, Royal Oak, Michigan (United States); Krueger, Sarah A.; Hanna, Alaa [Department of Radiation Oncology, William Beaumont Health System, Royal Oak, Michigan (United States); Raffel, Thomas R. [Department of Biological Sciences, Oakland University, Rochester, Michigan (United States); Wilson, George D. [Department of Radiation Oncology, William Beaumont Health System, Royal Oak, Michigan (United States); Madlambayan, Gerard J. [Department of Biological Sciences, Oakland University, Rochester, Michigan (United States); Marples, Brian, E-mail: Brian.Marples@beaumont.edu [Department of Radiation Oncology, William Beaumont Health System, Royal Oak, Michigan (United States)

    2016-09-01

    Purpose: To characterize the tumor microenvironment after standard radiation therapy (SRT) and pulsed radiation therapy (PRT) in Lewis lung carcinoma (LLC) allografts. Methods and Materials: Subcutaneous LLC tumors were established in C57BL/6 mice. Standard RT or PRT was given at 2 Gy/d for a total dose of 20 Gy using a 5 days on, 2 days off schedule to mimic clinical delivery. Radiation-induced tumor microenvironment changes were examined after treatment using flow cytometry and antibody-specific histopathology. Normal tissue effects were measured using noninvasive {sup 18}F-fluorodeoxyglucose positron emission tomography/computed tomography after naïve animals were given whole-lung irradiation to 40 Gy in 4 weeks using the same 2-Gy/d regimens. Results: Over the 2 weeks of therapy, PRT was more effective than SRT at reducing tumor growth rate (0.31 ± 0.02 mm{sup 3}/d and 0.55 ± 0.04 mm{sup 3}/d, respectively; P<.007). Histopathology showed a significant comparative reduction in the levels of Ki-67 (14.5% ± 3%), hypoxia (10% ± 3.5%), vascular endothelial growth factor (2.3% ± 1%), and stromal-derived factor-1α (2.5% ± 1.4%), as well as a concomitant decrease in CD45{sup +} bone marrow–derived cell (BMDC) migration (7.8% ± 2.2%) after PRT. The addition of AMD3100 also decreased CD45{sup +} BMDC migration in treated tumors (0.6% ± 0.1%). Higher vessel density was observed in treated tumors. No differences were observed in normal lung tissue after PRT or SRT. Conclusions: Pulsed RT–treated tumors exhibited slower growth and reduced hypoxia. Pulsed RT eliminated initiation of supportive mechanisms utilized by tumors in low oxygen microenvironments, including angiogenesis and recruitment of BMDCs.

  5. Choosing tree genotypes for phytoremediation of landfill leachate using phyto-recurrent selection

    Science.gov (United States)

    Jill A. Zalesny; Ronald S., Jr. Zalesny; Adam H. Wiese; Richard B. Hall

    2007-01-01

    Information about the response of poplar (Populus spp.) genotypes to landfill leachate irrigation is needed, along with efficient methods for choosing genotypes based on leachate composition. Poplar clones were irrigated during three cycles of phyto-recurrent selection to test whether genotypes responded differently to leachate and water, and to test...

  6. Establishment and early growth of Populus hybrids irrigated with landfill leachate

    Science.gov (United States)

    Ronald S., Jr. Zalesny; Adam H. Wiese; Edmund O. Bauer; Jill A. Zalesny

    2007-01-01

    Hybrid poplar genotypes exhibit great potential for tree establishment and growth when irrigated with municipal solid waste landfill leachate. We evaluated the potential for establishment on leachate-irrigated soils by testing: 1) aboveground growth of hybrid poplar during repeated irrigation with landfill leachate and 2) aboveground and belowground biomass after 70 d...

  7. Impact of Leachate Discharge from Cipayung Landfill on Water Quality of Pesanggrahan River, Indonesia

    Science.gov (United States)

    Noerfitriyani, Eki; Hartono, Djoko M.; Moersidik, Setyo S.; Gusniani, Irma

    2018-03-01

    The landfill operation can cause environmental problems due to solid waste decomposition in the form of leachate. The evaluation of environmental impacts related with solid waste landfilling is needed to ensure that leachate discharge to water bodies does not exceed the standard limit to prevent contamination of the environment. This study aims to analyze the impact of leachate discharge from Cipayung Landfill on water quality of Pesanggrahan River. The data were analyzed based on leachate samples taken from influent and effluent treatment unit, and river water samples taken from upstream, stream at leachate discharge, and downstream. All samples were taken three times under rainy season condition from April to May 2017. The results show the average leachate quality temperature is 34,81 °C, TSS 72.33 mg/L, pH 7.83, BOD 3,959.63 mg/L, COD 6,860 mg/L, TN 373.33 mg/L, Hg 0.0016 mg/L. The BOD5/COD ratio 0.58 indicated that leachate characteristics was biodegradable and resemble intermediate landfill due to the mixing of young leachate and old leachate. The effluent of leachate treatment plant exceeds the leachate standard limit for BOD, COD, and TN parameters. Statistical results from independent T-test showed significant differences (p<0,05) between upstream and downstream influenced with leachate discharge for DO parameter.

  8. Application of photochemical technologies for treatment of landfill leachate

    International Nuclear Information System (INIS)

    Meeroff, Daniel E.; Bloetscher, Frederick; Reddy, D.V.; Gasnier, François; Jain, Swapnil; McBarnette, André; Hamaguchi, Hatsuko

    2012-01-01

    Highlights: ► Photochemical iron-mediated aeration and TiO 2 photocatalysis for leachate treatment. ► Removal efficiency tested on COD, BOD 5 , color, ammonia, and lead. ► Contact times for 90% removal were 10–200 h for PIMA ► Contact times for 90% removal were 3–37 h for TiO 2 photocatalysis. ► Pre-filtration is not necessary. - Abstract: Because of widely varying practices in solid waste management, an all-inclusive solution to long-term management of landfill leachate is currently not available. There is a major technological need for sustainable, economical options for safe discharge of leachate to the environment. Two potential on-site pretreatment technologies, photochemical iron-mediated aeration (PIMA) and TiO 2 photocatalysis were compared for treatment of landfill leachate at laboratory scale. Results of bench scale testing of real landfill leachate with PIMA and TiO 2 photocatalysis showed up to 86% conversion of refractory COD to complete mineralization, up to 91% removal of lead, up to 71% removal of ammonia without pH adjustment, and up to 90% effective color removal with detention times between 4 and 6 h, in field samples. The estimated contact times for 90% removal of COD, ammonia, lead, and color were found to be on the order of 10–200 h for PIMA and 3–37 h for TiO 2 photocatalysis. Testing with actual leachate samples showed 85% TiO 2 photocatalyst recovery efficiency with no loss in performance after multiple (n > 4 uses). Pre-filtration was not found to be necessary for effective treatment using either process.

  9. Application of photochemical technologies for treatment of landfill leachate

    Energy Technology Data Exchange (ETDEWEB)

    Meeroff, Daniel E., E-mail: dmeeroff@fau.edu [Department of Civil, Environmental and Geomatics Engineering, Florida Atlantic University, Boca Raton, FL (United States); Bloetscher, Frederick; Reddy, D.V.; Gasnier, Francois; Jain, Swapnil; McBarnette, Andre; Hamaguchi, Hatsuko [Department of Civil, Environmental and Geomatics Engineering, Florida Atlantic University, Boca Raton, FL (United States)

    2012-03-30

    Highlights: Black-Right-Pointing-Pointer Photochemical iron-mediated aeration and TiO{sub 2} photocatalysis for leachate treatment. Black-Right-Pointing-Pointer Removal efficiency tested on COD, BOD{sub 5}, color, ammonia, and lead. Black-Right-Pointing-Pointer Contact times for 90% removal were 10-200 h for PIMA Black-Right-Pointing-Pointer Contact times for 90% removal were 3-37 h for TiO{sub 2} photocatalysis. Black-Right-Pointing-Pointer Pre-filtration is not necessary. - Abstract: Because of widely varying practices in solid waste management, an all-inclusive solution to long-term management of landfill leachate is currently not available. There is a major technological need for sustainable, economical options for safe discharge of leachate to the environment. Two potential on-site pretreatment technologies, photochemical iron-mediated aeration (PIMA) and TiO{sub 2} photocatalysis were compared for treatment of landfill leachate at laboratory scale. Results of bench scale testing of real landfill leachate with PIMA and TiO{sub 2} photocatalysis showed up to 86% conversion of refractory COD to complete mineralization, up to 91% removal of lead, up to 71% removal of ammonia without pH adjustment, and up to 90% effective color removal with detention times between 4 and 6 h, in field samples. The estimated contact times for 90% removal of COD, ammonia, lead, and color were found to be on the order of 10-200 h for PIMA and 3-37 h for TiO{sub 2} photocatalysis. Testing with actual leachate samples showed 85% TiO{sub 2} photocatalyst recovery efficiency with no loss in performance after multiple (n > 4 uses). Pre-filtration was not found to be necessary for effective treatment using either process.

  10. 2D compositional modeling of petroleum generation, expulsion and migration in the Southern compartment of the Reconcavo Basin, Brazil; Modelisation compositionnelle 2D de la genese, expulsion et migration du petrole dans le compartiment sud du Bassin de Reconcavo, Bresil

    Energy Technology Data Exchange (ETDEWEB)

    Barroz Penteado, H.L. de

    1999-01-07

    The Reconcavo Basin is part of a rift formed between the Late Jurassic and the Early Cretaceous in northeastern Brazil. The objective of this thesis was the compositional modeling of petroleum generation, expulsion and migration along a cross-section in the Southern Compartment of the basin with the Temispack basin simulation software. A geochemical study of the lacustrine shales of the Gomo Member (Candelas Fm.) has been performed to determine their petroleum potential, the evolution of maturation with depth and changes in petroleum composition. Hydrogen indices of immature kerogens (400-850 mg/g TOC) were shown to be higher than those of whole rocks, thus indicating a retention of Rock-Eval pyrolysis products in the mineral matrix of these type I source rocks. Saturates (30-50% of organic extracts in the immature zone) increase both in absolute and in relative (60-80%) terms in the oil window (2000-2600 m) because of a partial secondary cracking of NSOs and aromatics. After having tested several scenarios of geodynamic evolution between the Aptian and the Oligocene, a variable thickness of post-rift sediments (maximum of 1200 m) has been shown to be necessary to calibrate maturity parameters. Petroleum migration has been modeled to understand migration pathways as well as the role of faults as drains. Thus, two petroleum migration systems have been identified for the Dom Joao and Cexis accumulations. Petroleum compositional variations have been modeled by coupling the processes of retention and secondary cracking. A good calibration of compositions was obtained with secondary cracking parameters for NSOs and aromatics which are close to those of the main primary cracking reaction of a type I kerogen, coupled with a retention of 50% of NSOs within the source rocks. (author)

  11. Validation of the global model for 90SR migration from the waste burial in the Chernobyl exclusion zone

    International Nuclear Information System (INIS)

    Dewiere, L.; Bugai, D.; Kashparov, V.; Barthes, V.

    2004-01-01

    The Institute for Radiation Protection and Nuclear Safety (IRSN) has managed (1999-2003) the Chernobyl Pilot Site Project (CPS project) in collaboration with the Ukrainian Institute of Agricultural Radiology (UIAR), the Institute of Geological Sciences (IGS) and the Tracer Application Section (CEA/SAT). The special focus of the CPS project was environmental behavior and radionuclide release mechanisms from dispersed nuclear fuel particles, forming radionuclide migration source-term. So, the contaminated environment was used as an open-sky laboratory to develop site characterization techniques, better understand and model processes of radionuclides migration in soils and geological environment. The CPS project resulted in detailed characterization of site geology structure, hydrogeology regime, hydro-dispersion regime in the aquifer and unsaturated zone, radionuclide inventory and distribution in trench no.22, focused at 137 Cs and 90 Sr. The special research program using scanning electron microscopy and sequential extraction analytical techniques was devoted to characterization of fuel particles and quantification of their dissolution behavior. It was established that Chernobyl radionuclides are associated with uranium oxide matrix particles of different degree of oxidation, characterized by different dissolution rates, as well as with non-dissolvable zirconium containing matrix particles. The multi-component fuel particles dissolution model with empirical dissolution rate constants was developed to describe the source-term. The methodology for radionuclide transport was based on application of the classical advection-diffusion equation and utilization of effective transport parameters. The developed so far modeling methodology is mostly suited for producing spatially averaged parameter values (such as radionuclide concentrations in trench porous solution, and/or integral radionuclide release to aquifer), and for long-term predictions on a scale of years and

  12. Modelling of nuclide migration for support of the site selection for near surface repository in Lithuania

    International Nuclear Information System (INIS)

    Kilda, R.; Poskas, P.; Ragaisis, V.

    2006-01-01

    Construction of the near surface repository (NSR) for disposal of short-lived low-and intermediate-level waste (LILW) is planned in Lithuania. Reference design of the repository was prepared. Site selection process is going on. Environmental Impact Assessment (EIA) Program and Report were prepared and are under review by regulators. Releases of radionuclides to water pathway and potential human exposure after closure of the NSR have been assessed for support of the site selection for NSR installation. Two candidate sites were taken under consideration. The assessments have been performed following ISAM methodology recommended by IAEA for safety assessments of near surface disposal facilities. The conceptual design of NSR as well as peculiarities of geological and hydro-geological environment relevant to each candidate site is taken into account. The results of the analysis as part of EIA Report are presented in the paper. It is demonstrated that estimated impact of potential radionuclide migration for both candidate sites is below dose constrain established by regulations of Lithuania. (author)

  13. Mathematical modeling of methane migration into the mine workings during the face downtime

    Science.gov (United States)

    Govorukhin, Yu M.; Domrachev, A. N.; Krivopalov, V. G.; Paleev, D. Yu

    2017-09-01

    For the estimation of safe distances during explosions of mixtures of coal dust, methane, and air in the process of emergency rescue operations in coal mines, it is necessary to determine the gas volumes in the mine workings. Errors in determining such volumes often lead to tragic consequences. The calculation schemes are suggested that allow the methane generation rate into the mine air to be determined on the basis of physical regularities (mine and gas pressures, gas permeability dynamics, depth of the gas drainage zone, etc.), underlying the processes of gas migration from coal and rocks into the mine workings. The following methane emission sources are considered at the site: the surface of the stopped face; walls of development opening; the gob (potential volume of the gas reservoir in the caving area). Test calculations of methane generation have been performed based on the mining, geological and technological data of one of the mines in Baydaevsky geological and economic region. In general, the results obtained are consistent with the data of long-term empirical observations. The directions of further research aimed at improving the synthesized methodology are presented.

  14. Report on Evaluation, Verification, and Assessment of Porosity Migration Model in Fast Reactor MOX Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Novascone, Stephen Rhead [Idaho National Lab. (INL), Idaho Falls, ID (United States); Peterson, John William [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-09-01

    Abstract This report documents the progress of simulating pore migration in ceramic (UO2 and mixed oxide or MOX) fuel using BISON. The porosity field is treated as a function of space and time whose evolution is governed by a custom convection-diffusion-reaction equation (described here) which is coupled to the heat transfer equation via the temperature field. The porosity is initialized to a constant value at every point in the domain, and as the temperature (and its gradient) are increased by application of a heat source, the pores move up the thermal gradient and accumulate at the center of the fuel in a time-frame that is consistent with observations from experiments. There is an inverse dependence of the fuel’s thermal conductivity on porosity (increasing porosity decreases thermal conductivity, and vice-versa) which is also accounted for, allowing the porosity equation to couple back into the heat transfer equation. Results from an example simulation are shown to demonstrate the new capability.

  15. ISO-66, a novel inhibitor of macrophage migration, shows efficacy in melanoma and colon cancer models.

    Science.gov (United States)

    Ioannou, Kyriaki; Cheng, Kai Fan; Crichlow, Gregg V; Birmpilis, Anastasios I; Lolis, Elias J; Tsitsilonis, Ourania E; Al-Abed, Yousef

    2014-10-01

    Macrophage migration inhibitory factor (MIF) is a pleiotropic pro-inflammatory cytokine, which possesses a contributing role in cancer progression and metastasis and, thus, is now considered a promising anticancer drug target. Many MIF-inactivating strategies have proven successful in delaying cancer growth. Here, we report on the synthesis of ISO-66, a novel, highly stable, small-molecule MIF inhibitor, an analog of ISO-1 with improved characteristics. The MIF:ISO-66 co-crystal structure demonstrated that ISO-66 ligates the tautomerase active site of MIF, which has previously been shown to play an important role in its biological functions. In vitro, ISO-66 enhanced specific and non-specific anticancer immune responses, whereas prolonged administration of ISO-66 in mice with established syngeneic melanoma or colon cancer was non-toxic and resulted in a significant decrease in tumor burden. Subsequent ex vivo analysis of mouse splenocytes revealed that the observed decrease in tumor growth rates was likely mediated by the selective in vivo expansion of antitumor-reactive effector cells induced by ISO-66. Compared to other MIF-inactivating strategies employed in vivo, the anticancer activity of ISO-66 is demonstrated to be of equal or better efficacy. Our findings suggest that targeting MIF, via highly specific and stable compounds, such as ISO-66, may be effective for cancer treatment and stimulation of anticancer immune responses.

  16. Hydrocarbon migration and accumulation in the Upper Cretaceous Qingshankou Formation, Changling Sag, southern Songliao Basin: Insights from integrated analyses of fluid inclusion, oil source correlation and basin modelling

    Science.gov (United States)

    Dong, Tian; He, Sheng; Wang, Dexi; Hou, Yuguang

    2014-08-01

    The Upper Cretaceous Qingshankou Formation acts as both the source and reservoir sequence in the Changling Sag, situated in the southern end of the Songliao Basin, northeast China. An integrated approach involving determination of hydrocarbon charging history, oil source correlation and hydrocarbon generation dynamic modeling was used to investigate hydrocarbon migration processes and further predict the favorable targets of hydrocarbon accumulations in the Qingshankou Formation. The hydrocarbon generation and charge history was investigated using fluid inclusion analysis, in combination with stratigraphic burial and thermal modeling. The source rocks began to generate hydrocarbons at around 82 Ma and the hydrocarbon charge event occurred from approximately 78 Ma to the end of Cretaceous (65.5 Ma) when a large tectonic uplift took place. Correlation of stable carbon isotopes of oils and extracts of source rocks indicates that oil was generated mainly from the first member of Qingshankou Formation (K2qn1), suggesting that hydrocarbon may have migrated vertically. Three dimensional (3D) petroleum system modeling was used to evaluate the processes of secondary hydrocarbon migration in the Qingshankou Formation since the latest Cretaceous. During the Late Cretaceous, hydrocarbon, mainly originated from the Qianan depression, migrated laterally to adjacent structural highs. Subsequent tectonic inversion, defined as the late Yanshan Orogeny, significantly changed hydrocarbon migration patterns, probably causing redistribution of primary hydrocarbon reservoirs. In the Tertiary, the Heidimiao depression was buried much deeper than the Qianan depression and became the main source kitchen. Hydrocarbon migration was primarily controlled by fluid potential and generally migrated from relatively high potential areas to low potential areas. Structural highs and lithologic transitions are potential traps for current oil and gas exploration. Finally, several preferred hydrocarbon

  17. International Migration of Couples

    DEFF Research Database (Denmark)

    Junge, Martin; Munk, Martin D.; Nikolka, Till

    2018-01-01

    Migrant self-selection is important to labor markets and public finances in both origin and destination countries. We develop a theoretical model regarding the migration of dual-earner couples and test it using population-wide administrative data from Denmark. Our model predicts that the probabil...

  18. Predictive geochemical modeling of contaminant concentrations in laboratory columns and in plumes migrating from uranium mill tailings waste impoundments

    International Nuclear Information System (INIS)

    Peterson, S.R.; Martin, W.J.; Serne, R.J.

    1986-04-01

    A computer-based conceptual chemical model was applied to predict contaminant concentrations in plumes migrating from a uranium mill tailings waste impoundment. The solids chosen for inclusion in the conceptual model were selected based on reviews of the literature, on ion speciation/solubility calculations performed on the column effluent solutions and on mineralogical characterization of the contacted and uncontacted sediments. The mechanism of adsorption included in the conceptual chemical model was chosen based on results from semiselective extraction experiments and from mineralogical characterization procedures performed on the sediments. This conceptual chemical model was further developed and partially validated in laboratory experiments where assorted acidic uranium mill tailings solutions percolated through various sediments. This document contains the results of a partial field and laboratory validation (i.e., test of coherence) of this chemical model. Macro constituents (e.g., Ca, SO 4 , Al, Fe, and Mn) of the tailings solution were predicted closely by considering their concentrations to be controlled by the precipitation/dissolution of solid phases. Trace elements, however, were generally predicted to be undersaturated with respect to plausible solid phase controls. The concentration of several of the trace elements were closely predicted by considering their concentrations to be controlled by adsorption onto the amorphous iron oxyhydroxides that precipitated

  19. A strategy for validation a concept model for radionuclide migration in the saturated zone beneath Yucca Mountain

    International Nuclear Information System (INIS)

    Robinson, B.A.

    1994-01-01

    A conceptual model for radionuclide migration in the saturated zone beneath Yucca Mountain is presented. The available hydrologic data from the site is compiled to present a qualitative picture of transport of radionuclides horizontally within the first 100-200 m of the saturated zone. The transport model consists of flow within fractures and interchange of dissolved species between the fractures and surrounding matrix blocks via molecular diffusion. A parametric study illustrates that at the groundwater conditions expected to exist in the saturated zone, radionuclide will have ample time to diffuse fully within the matrix blocks. The result is a predicted solute transport time several orders of magnitude greater than the groundwater travel time (GWTT). To validate this model, a suite of interwell tracer tests are proposed at various flow rates and with conservative and sorbing species. Numerical simulations show that these tests will allow us to discriminate between a matrix diffusion model and a more conventional continuum transport model. (author) 8 figs., tabs., 35 refs

  20. Proceedings of the meeting on computational and experimental studies for modeling of radionuclide migration in complex aquatic ecosystems

    International Nuclear Information System (INIS)

    Matsunaga, Takeshi; Hakanson, Lars

    2010-09-01

    The Research Group for Environmental Science of JAEA held a meeting on computational and experimental studies for modeling of radionuclide migration in complex aquatic ecosystems during November 16-20 of 2009. The aim was to discuss the relevance of various computational and experimental approaches to that modeling. The meeting was attended by a Swedish researcher, Prof. Dr. Lars Hakanson of Uppsala University. It included a joint talk at the Institute for Environmental Sciences, in addition to a field and facility survey of the JNFL commercial reprocessing plant located in Rokkasho, Aomori. The meeting demonstrated that it is crucial 1) to make a model structure be strictly relevant to the target objectives of a study and 2) to account for inherent fluctuations in target values in nature in a manner of qualitative parameterization. Moreover, it was confirmed that there can be multiple different approaches of modeling (e.g. detailed or simplified) with relevance for the objectives of a study. These discussions should be considered in model integration for complex aquatic ecosystems consisting catchments, rivers, lakes and coastal oceans which can interact with the atmosphere. This report compiles research subjects and lectures presented at the meeting with associated discussions. The 10 of the presented papers indexed individually. (J.P.N.)

  1. Virtual-source diffusion approximation for enhanced near-field modeling of photon-migration in low-albedo medium.

    Science.gov (United States)

    Jia, Mengyu; Chen, Xueying; Zhao, Huijuan; Cui, Shanshan; Liu, Ming; Liu, Lingling; Gao, Feng

    2015-01-26

    Most analytical methods for describing light propagation in turbid medium exhibit low effectiveness in the near-field of a collimated source. Motivated by the Charge Simulation Method in electromagnetic theory as well as the established discrete source based modeling, we herein report on an improved explicit model for a semi-infinite geometry, referred to as "Virtual Source" (VS) diffuse approximation (DA), to fit for low-albedo medium and short source-detector separation. In this model, the collimated light in the standard DA is analogously approximated as multiple isotropic point sources (VS) distributed along the incident direction. For performance enhancement, a fitting procedure between the calculated and realistic reflectances is adopted in the near-field to optimize the VS parameters (intensities and locations). To be practically applicable, an explicit 2VS-DA model is established based on close-form derivations of the VS parameters for the typical ranges of the optical parameters. This parameterized scheme is proved to inherit the mathematical simplicity of the DA approximation while considerably extending its validity in modeling the near-field photon migration in low-albedo medium. The superiority of the proposed VS-DA method to the established ones is demonstrated in comparison with Monte-Carlo simulations over wide ranges of the source-detector separation and the medium optical properties.

  2. Assessment on the leakage hazard of landfill leachate using three-dimensional excitation-emission fluorescence and parallel factor analysis method.

    Science.gov (United States)

    Pan, Hongwei; Lei, Hongjun; Liu, Xin; Wei, Huaibin; Liu, Shufang

    2017-09-01

    A large number of simple and informal landfills exist in developing countries, which pose as tremendous soil and groundwater pollution threats. Early warning and monitoring of landfill leachate pollution status is of great importance. However, there is a shortage of affordable and effective tools and methods. In this study, a soil column experiment was performed to simulate the pollution status of leachate using three-dimensional excitation-emission fluorescence (3D-EEMF) and parallel factor analysis (PARAFAC) models. Sum of squared residuals (SSR) and principal component analysis (PCA) were used to determine the optimal components for PARAFAC. A one-way analysis of variance showed that the component scores of the soil column leachate were significant influenced by landfill leachate (plandfill to that of natural soil could be used to evaluate the leakage status of landfill leachate. Furthermore, a hazard index (HI) and a hazard evaluation standard were established. A case study of Kaifeng landfill indicated a low hazard (level 5) by the use of HI. In summation, HI is presented as a tool to evaluate landfill pollution status and for the guidance of municipal solid waste management. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. A cellular Potts model for the MMP-dependent and -independent cancer cell migration in matrix microtracks of different dimensions

    Science.gov (United States)

    Scianna, Marco; Preziosi, Luigi

    2014-03-01

    Cell migration is fundamental in a wide variety of physiological and pathological phenomena, among other in cancer invasion and development. In particular, the migratory/invasive capability of single metastatic cells is fundamental in determining the malignancy of a solid tumor. Specific cell migration phenotypes result for instance from the reciprocal interplay between the biophysical and biochemical properties of both the malignant cells themselves and of the surrounding environment. In particular, the extracellular matrices (ECMs) forming connective tissues can provide both loosely organized zones and densely packed barriers, which may impact cell invasion mode and efficiency. The critical processes involved in cell movement within confined spaces are (i) the proteolytic activity of matrix metalloproteinases (MMPs) and (ii) the deformation of the entire cell body, and in particular of the nucleus. We here present an extended cellular Potts model (CPM) to simulate a bio-engineered matrix system, which tests the active motile behavior of a single cancer cell into narrow channels of different widths. As distinct features of our approach, the cell is modeled as a compartmentalized discrete element, differentiated in the nucleus and in the cytosolic region, while a directional shape-dependent movement is explicitly driven by the evolution of its polarity vector. As outcomes, we find that, in a large track, the tumor cell is not able to maintain a directional movement. On the contrary, a structure of subcellular width behaves as a contact guidance sustaining cell persistent locomotion. In particular, a MMP-deprived cell is able to repolarize and follow the micropattern geometry, while a full MMP activity leads to a secondary track expansion by degrading the matrix structure. Finally, we confirm that cell movement within a subnuclear structure can be achieved either by pericellular proteolysis or by a significant deformation of cell nucleus.

  4. The shadow continuum : testing the records continuum model through the Djogdja Documenten and the migrated archives

    NARCIS (Netherlands)

    Karabinos, Michael Joseph

    2015-01-01

    This dissertation tests the universal suitability of the records continuum model by using two cases from the decolonization of Southeast Asia. The continuum model is a new model of records visualization invented in the 1990s that sees records as free to move throughout four ‘dimensions’ rather than

  5. Development of solute transport models in YMPYRÄ framework to simulate solute migration in military shooting and training areas

    Science.gov (United States)

    Warsta, L.; Karvonen, T.

    2017-12-01