WorldWideScience

Sample records for net freshwater flux

  1. Net Ecosystem Carbon Flux

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Net Ecosystem Carbon Flux is defined as the year-over-year change in Total Ecosystem Carbon Stock, or the net rate of carbon exchange between an ecosystem and the...

  2. Freshwater flux to Sermilik Fjord, SE Greenland

    Directory of Open Access Journals (Sweden)

    S. H. Mernild

    2010-10-01

    Full Text Available Terrestrial inputs of freshwater flux to Sermilik Fjord, SE Greenland, were estimated, indicating ice discharge to be the dominant source of freshwater. A freshwater flux of 40.4 ± 4.9×109 m3 y−1 was found (1999–2008, with an 85% contribution originated from ice discharge (65% alone from Helheim Glacier, 11% from terrestrial surface runoff (from melt water and rain, 3% from precipitation at the fjord surface area, and 1% from subglacial geothermal and frictional melting due to basal ice motion. The results demonstrate the dominance of ice discharge as a primary mechanism for delivering freshwater to Sermilik Fjord. Time series of ice discharge for Helheim Glacier, Midgård Glacier, and Fenris Glacier were calculated from satellite-derived average surface velocity, glacier width, and estimated ice thickness, and fluctuations in terrestrial surface freshwater runoff were simulated based on observed meteorological data. These simulations were compared and bias corrected against independent glacier catchment runoff observations. Modeled runoff to Sermilik Fjord was variable, ranging from 2.9 ± 0.4×109 m3 y−1 in 1999 to 5.9 ± 0.9×109 m3 y−1 in 2005. The sub-catchment runoff of the Helheim Glacier region accounted for 25% of the total runoff to Sermilik Fjord. The runoff distribution from the different sub-catchments suggested a strong influence from the spatial variation in glacier coverage, indicating high runoff volumes, where glacier cover was present at low elevations.

  3. GALILEO PROBE NET FLUX RADIOMETER DATA V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — The Galileo Probe Net Flux Radiometer (NFR) measured net and upward radiation fluxes in Jupiter's atmosphere between about 0.44 bars and 14 bars, using five spectral...

  4. Short-term impacts of enhanced Greenland freshwater fluxes in an eddy-permitting ocean model

    Directory of Open Access Journals (Sweden)

    R. Marsh

    2010-07-01

    Full Text Available In a sensitivity experiment, an eddy-permitting ocean general circulation model is forced with realistic freshwater fluxes from the Greenland Ice Sheet, averaged for the period 1991–2000. The fluxes are obtained with a mass balance model for the ice sheet, forced with the ERA-40 reanalysis dataset. The freshwater flux is distributed around Greenland as an additional term in prescribed runoff, representing seasonal melting of the ice sheet and a fixed year-round iceberg calving flux, for 8.5 model years. By adding Greenland freshwater fluxes with realistic geographical distribution and seasonality, the experiment is designed to investigate the oceanic response to a sudden and spatially/temporally uniform amplification of ice sheet melting and discharge, rather than localized or gradual changes in freshwater flux. The impacts on regional hydrography and circulation are investigated by comparing the sensitivity experiment to a control experiment, without additional fluxes. By the end of the sensitivity experiment, the majority of additional fresh water has accumulated in Baffin Bay, and only a small fraction has reached the interior of the Labrador Sea, where winter mixed layer depth is sensitive to small changes in salinity. As a consequence, the impact on large-scale circulation is very slight. An indirect impact of strong freshening off the west coast of Greenland is a small anti-cyclonic component to the circulation around Greenland, which opposes the wind-driven cyclonic circulation and reduces net southward flow through the Canadian Archipelago by ~10%. Implications for the post-2000 acceleration of Greenland mass loss are discussed.

  5. Thermal net flux measurements on the Pioneer Venus entry probes

    Science.gov (United States)

    Revercomb, H. E.; Sromovsky, L. A.; Suomi, V. E.; Boese, R. W.

    1985-01-01

    Corrected thermal net (upward minus downward flux) radiation data from four Pioneer Venus probes at latitudes of 4 deg and 60 deg N, and 27 deg and 31 deg S, are presented. Comparisons of these fluxes with radiative transfer calculations were interpreted in terms of cloud properties and the global distribution of water vapor in the lower atmosphere of Venus. The presence of an as yet undetected source of IR opacity is implied by the fluxes in the upper cloud range. It was also shown that beneath the clouds the fluxes at a given altitude increase with latitude, suggesting greater IR cooling below the clouds at high latitudes and a decrease of the water vapor mixing ratios toward the equator.

  6. Quantifying Greenland freshwater flux underestimates in climate models

    Science.gov (United States)

    Little, Christopher M.; Piecuch, Christopher G.; Chaudhuri, Ayan H.

    2016-05-01

    Key processes regulating the mass balance of the Greenland Ice Sheet (GIS) are not represented in current-generation climate models. Here using output from 19 different climate models forced with a high-end business-as-usual emissions pathway, we compare modeled freshwater fluxes (FWF) to a parameterization based on midtropospheric temperature. By the mid 21st century, parameterized GIS FWF is 478 ± 215 km3 yr-1 larger than modeled—over 3 times the 1992-2011 rate of GIS mass loss. By the late 21st century, ensemble mean parameterized GIS FWF anomalies are comparable to FWF anomalies over the northern North Atlantic Ocean, equivalent to approximately 11 cm of global mean sea level rise. The magnitude and spread of these underestimates underscores the need for assessments of the coupled response of the ocean to increased FWF that recognize: (1) the widely varying freshwater budgets of each model and (2) uncertainty in the relationship between GIS FWF and atmospheric temperature.

  7. Net carbon flux in organic and conventional olive production systems

    Science.gov (United States)

    Saeid Mohamad, Ramez; Verrastro, Vincenzo; Bitar, Lina Al; Roma, Rocco; Moretti, Michele; Chami, Ziad Al

    2014-05-01

    Agricultural systems are considered as one of the most relevant sources of atmospheric carbon. However, agriculture has the potentiality to mitigate carbon dioxide mainly through soil carbon sequestration. Some agricultural practices, particularly fertilization and soil management, can play a dual role in the agricultural systems regarding the carbon cycle contributing to the emissions and to the sequestration process in the soil. Good soil and input managements affect positively Soil Organic Carbon (SOC) changes and consequently the carbon cycle. The present study aimed at comparing the carbon footprint of organic and conventional olive systems and to link it to the efficiency of both systems on carbon sequestration by calculating the net carbon flux. Data were collected at farm level through a specific and detailed questionnaire based on one hectare as a functional unit and a system boundary limited to olive production. Using LCA databases particularly ecoinvent one, IPCC GWP 100a impact assessment method was used to calculate carbon emissions from agricultural practices of both systems. Soil organic carbon has been measured, at 0-30 cm depth, based on soil analyses done at the IAMB laboratory and based on reference value of SOC, the annual change of SOC has been calculated. Substracting sequestrated carbon in the soil from the emitted on resulted in net carbon flux calculation. Results showed higher environmental impact of the organic system on Global Warming Potential (1.07 t CO2 eq. yr-1) comparing to 0.76 t CO2 eq. yr-1 in the conventional system due to the higher GHG emissions caused by manure fertilizers compared to the use of synthetic foliar fertilizers in the conventional system. However, manure was the main reason behind the higher SOC content and sequestration in the organic system. As a resultant, the organic system showed higher net carbon flux (-1.7 t C ha-1 yr-1 than -0.52 t C ha-1 yr-1 in the conventional system reflecting higher efficiency as a

  8. MetaFluxNet: the management of metabolic reaction information and quantitative metabolic flux analysis.

    Science.gov (United States)

    Lee, Dong-Yup; Yun, Hongsoek; Park, Sunwon; Lee, Sang Yup

    2003-11-01

    MetaFluxNet is a program package for managing information on the metabolic reaction network and for quantitatively analyzing metabolic fluxes in an interactive and customized way. It allows users to interpret and examine metabolic behavior in response to genetic and/or environmental modifications. As a result, quantitative in silico simulations of metabolic pathways can be carried out to understand the metabolic status and to design the metabolic engineering strategies. The main features of the program include a well-developed model construction environment, user-friendly interface for metabolic flux analysis (MFA), comparative MFA of strains having different genotypes under various environmental conditions, and automated pathway layout creation. http://mbel.kaist.ac.kr/ A manual for MetaFluxNet is available as PDF file.

  9. Recent increases in Arctic freshwater flux affects Labrador Sea convection and Atlantic overturning circulation.

    Science.gov (United States)

    Yang, Qian; Dixon, Timothy H; Myers, Paul G; Bonin, Jennifer; Chambers, Don; van den Broeke, M R

    2016-01-22

    The Atlantic Meridional Overturning Circulation (AMOC) is an important component of ocean thermohaline circulation. Melting of Greenland's ice sheet is freshening the North Atlantic; however, whether the augmented freshwater flux is disrupting the AMOC is unclear. Dense Labrador Sea Water (LSW), formed by winter cooling of saline North Atlantic water and subsequent convection, is a key component of the deep southward return flow of the AMOC. Although LSW formation recently decreased, it also reached historically high values in the mid-1990s, making the connection to the freshwater flux unclear. Here we derive a new estimate of the recent freshwater flux from Greenland using updated GRACE satellite data, present new flux estimates for heat and salt from the North Atlantic into the Labrador Sea and explain recent variations in LSW formation. We suggest that changes in LSW can be directly linked to recent freshening, and suggest a possible link to AMOC weakening.

  10. Zero-Net Mass-Flux Actuator Cavity Vortex

    Science.gov (United States)

    Krieg, Michael; Mohseni, Kamran

    2013-11-01

    Zero-Net Mass-Flux (ZNMT) devices are used commonly as synthetic jet actuators for flow control in various applications. The authors have recently proposed using larger ZNMF jet actuators for underwater propulsion; similar to squid and jellyfish. Generally the external flow generated by these devices is characterized according to momentum and energy transfer rates, and little attention is paid to the dynamics of flow inside the cavity. In fact the flow inside the cavity, especially during the refilling phase is not only highly dynamic but greatly influences the pressure distribution at the opening as well as the external flow during the following jetting phase. A completely transparent axisymmetric ZNMF cavity was constructed in order to investigate the internal vortex dynamics. The flow is seeded with reflective particles and illumined with a laser sheet bisecting the axis of symmetry. Standard 2D DPIV techniques are used to recover the velocity field in this cross section. During filling it is observed that a starting jet extending from the opening to the inside of the cavity rolls into a vortex ring much like the jetting phase. However, the effect of the cavity walls becomes apparent almost immediately. In this talk we characterize how the circulation within the cavity decays as a function of both cavity/orifice geometry and the mass flux program. In addition a load cell measures the total thrust acting on the device which is used to validate pressure calculations performed on the moving surface inside the cavity, showing excellent agreement. This work is supported by a grant from the Office of Naval Research.

  11. Mapping Daily Net CO2 Flux From Grasslands Using Remote Sensing

    Science.gov (United States)

    Holifield, C.; Emmerich, W.; Moran, M. S.; Bryant, R.; Verdugo, C.

    2003-12-01

    The daily net carbon dioxide (CO2) flux from extensive grassland ecosystems is an important component of the global carbon cycle. In previous studies, instantaneous net CO2 flux was estimated using a Water Deficit Index (WDI) determined from the relation between surface reflectance and temperature. The mean absolute difference between measured and WDI-derived CO2 flux was 0.23 over a range of CO2 flux values from -0.10 to 1.10 (mg m-2 s-1). The objective of this study was to determine daily net CO2 flux from instantaneous estimates for a semiarid grassland site in Southeast Arizona. This objective was reached through two main steps. First, a linear relationship (R2 = 0.95) was found between instantaneous net CO2 flux and net daytime (6 a.m. to 6 p.m.) flux and used to generate maps of daytime CO2 flux. Second, a field study was conducted to relate night time flux measurements to daytime measurements. These relations made it possible to map daily (24-hour) net CO2 flux from a single satellite image and basic meteorological information. A limitation of this approach is the dependence upon empirical relations for deriving daytime and night time estimates from instantaneous measurements. On the other hand, the empirical relations derived at this location were strong and consistent for the six-year study period.

  12. Spatial-temporal variability in GHG fluxes and their functional interpretation in RusFluxNet

    Science.gov (United States)

    Vasenev, Ivan; Meshalkina, Julia; Sarzhanov, Dmitriy; Mazirov, Ilia; Yaroslavtsev, Alex; Komarova, Tatiana; Tikhonova, Maria

    2016-04-01

    High spatial and temporal variability is mutual feature for most modern boreal landscapes in the European Territory of Russia. This variability is result of their relatively young natural and land-use age with very complicated development stories. RusFluxNet includes a functionally-zonal set of representative natural, agricultural and urban ecosystems from the Central Forest Reserve in the north till the Central Chernozemic Reserve in the south (more than 1000 km distance). Especial attention has been traditionally given to their soil cover and land-use detailed variability, morphogenetic and functional dynamics. Central Forest Biosphere Reserve (360 km to North-West from Moscow) is the principal southern-taiga one in the European territory of Russia with long history of mature spruce ecosystem structure and dynamics investigation. Our studies (in frame of RF Governmental projects #11.G34.31.0079 and #14.120.14.4266) have been concentrated on the soil carbon stocks and GHG fluxes spatial variability and dynamics due to dominated there windthrow and fallow-forest successions. In Moscow RTSAU campus gives a good possibility to develop the ecosystem and soil monitoring of GHG fluxes in the comparable sites of urban forest, field crops and lawn ecosystems taking especial attention on their meso- and micro-relief, soil cover patterns and subsoil, vegetation and land-use technologies, temperature and moisture spatial and temporal variability. In the Central Chernozemic Biosphere Reserve and adjacent areas we do the comparative analysis of GHG fluxes and balances in the virgin and mowed meadow-steppe, forest, pasture, cropland and three types of urban ecosystems with similar subsoil and relief conditions. The carried out researches have shown not only sharp (in 2-5 times) changes in GHG ecosystem and soil fluxes and balances due to seasonal and daily microclimate variation, vegetation and crop development but their essential (in 2-4 times) spatial variability due to

  13. Freshwater fluxes from Greenland into the ocean: A Case Study of Sermilik Fjord

    Science.gov (United States)

    Straneo, Fiamma; Beaird, Nicholas; Catania, Ginny; Felikson, Denis; Heimbach, Patrick; Moon, Twila; Sutherland, Dave; Masina, Simona; Colleoni, Florence

    2017-04-01

    Mass loss from the Greenland Ice Sheet quadrupled from 1992 to 2011, discharging an additional 2700 cubic kilometers of freshwater into the Arctic and North Atlantic Oceans. Future projections are for continued and enhanced mass loss, implying an even larger freshwater discharge into the ocean. Given the potential impact of this additional freshwater on the regional circulation, dense water formation and the marine ecosystems, it is important to include it in past model reconstructions and future model projections. At present, studies investigating the impact of Greenland freshwater on the ocean largely assume that it enters the ocean as a distributed, surface freshwater flux. Observation and model studies, however, show that much of Greenland's freshwater discharge into the ocean occurs subsurface via the melting of deep icebergs and glaciers and through the injection of seasonal surface melt from the base of glaciers hundreds of meters below the surface. Spatially, the discharge is concentrated around the major glacier/fjord systems. Here, we develop a framework to account for the different components of Greenland's freshwater discharge (ice sheet and glacier runoff, non-glaciated margin runoff, and ice discharge from marine terminating glaciers) for the period 1958-2015 and apply it to Sermilik Fjord, southeast Greenland, where present day discharge estimates can be compared to extensive observations. This effort is led by the GRISO Research Coordination Network.

  14. High net calcium uptake explains the hypersensitivity of the freshwater pulmonate snail, Lymnaea stagnalis, to chronic lead exposure.

    Science.gov (United States)

    Grosell, Martin; Brix, Kevin V

    2009-03-09

    Previous studies have shown that freshwater pulmonate snails of the genus Lymnaea are exceedingly sensitive to chronic Pb exposure. An EC20 of influx was significantly inhibited (39%) and corresponding net Ca(2+) flux was significantly reduced from 224 to -23nmolg(-1)h(-1). An 85% increase in Cl(-) influx was also observed, while Na(+) ion transport appeared unaffected. Finally, a marked alkalosis of extracellular fluid was observed with pH increasing from 8.35 in the control to 8.65 in the 18.9microgl(-1) Pb-exposed group. Results based on direct measurement of Ca(2+) influx in 1g snails gave an influx nearly an order of magnitude higher (750nmolg(-1)h(-1)) than in comparably sized fish in similar water chemistry. Under control conditions, specific growth rate in newly hatched snails was estimated at 16.7% per day over the first 38-day post-hatch and whole body Ca(2+) concentrations were relatively constant at approximately 1100nmolg(-1) over this period. Based on these data, it is estimated that newly hatched snails have net Ca(2+) uptake rates on the order of 7600nmolg(-1)h(-1). A model was developed integrating these data and measured inhibition of Ca(2+) influx rates of 13.4% and 38.7% in snails exposed to 2.7 and 18.9microgl(-1)Pb, respectively. The model estimates 45% and 83% reductions in newly hatched snail growth after 30-day exposure in these two Pb-exposed groups. These results compare well with previous direct measurements of 47% and 90% reductions in growth at similar Pb concentrations, indicating the high net Ca(2+) uptake is the controlling factor in observed Pb hypersensitivity.

  15. Reconciled freshwater flux into the Godthåbsfjord system from satellite and airborne remote sensing

    DEFF Research Database (Denmark)

    Simonsen, Sebastian Bjerregaard; Barletta, Valentina Roberta; Forsberg, René

    2015-01-01

    As the rapid reduction in ice volume of the Greenland ice sheet (GrIS) continues, increased melt water flux from the GrIS enters the deep Greenlandic fjords. This increased freshwater flux may change the salinity and eventually the ecology of the fjords. Here, we present a case study in which we......, from various remote-sensing data sets, estimate the freshwater flux from the GrIS into a specific fjord system, the Godthåbsfjord, in southwest Greenland. The area of the GrIS draining into Godthåbsfjord covers approximately 36,700 km2. The large areal extent and the multiple outlets from the Gr...

  16. Impact of macrozoobenthic bioturbation and wind fluctuation interactions on net methylmercury in freshwater lakes.

    Science.gov (United States)

    Wang, Peifang; Yao, Yu; Wang, Chao; Hou, Jun; Qian, Jin; Miao, Lingzhan

    2017-11-01

    The methylmercury (MeHg) as the toxic fractions has presented significant threats to biota in freshwater ecosystems. Hg methylation process is demonstrated to be manipulated by biota process (benthic disturbance and algae bloom existence) as well as the abiotic influence (wind fluctuation and illumination intensity) in freshwater ecosystems. However, the mechanisms influencing Hg methylation are still unclear, and the coupled influences of the biotic and abiotic process with the shifts in variation on methylmercury remain unexplored. Accordingly, an annular flume experiment which simulated the freshwater ecosystem, was conducted for 108 days to examine the influences of typical disturbance by chironomid larvae and wind fluctuations on MeHg variation in sediment profiles. The in-situ, passive sampler technique of revealing diffusive gradients in thin films (DGT) encompassed the special resin, based on referenced extraction and coloration-computer imaging densitometry, were employed to obtain labile MeHg, Fe, and S concentrations at high resolution. The results indicate that larval bioturbation during the initial period of the experiment could diminish bioavailable MeHg concentrations and change the diffusion direction of MeHg fluxes. However, this inhibitive effect on MeHg concentrations ceased with larvae eclosion. Compared to bioturbation, wind fluctuation exerted slow but sustained inhibition on MeHg release. Furthermore, the eight parameters (dissolved organic carbon (DOC), DO, labile Fe and S concentrations, pH, sulfate-reducing bacteria (SRB) abundance in sediment, oxidation-reduction potential (ORP) and EC) could explain more of variation in MeHg concentrations which indicated by the canonical correspondence analysis. And these eight parameters manifest higher explanatory power for MeHg distributed in newly formed sediment. More notably, the comparison results of the multiple and simple regression directly demonstrated the DOC was the fundamental and robust

  17. Climatic variability, hydrologic anomaly, and methane emission can turn productive freshwater marshes into net carbon sources.

    Science.gov (United States)

    Chu, Housen; Gottgens, Johan F; Chen, Jiquan; Sun, Ge; Desai, Ankur R; Ouyang, Zutao; Shao, Changliang; Czajkowski, Kevin

    2015-03-01

    Freshwater marshes are well-known for their ecological functions in carbon sequestration, but complete carbon budgets that include both methane (CH4 ) and lateral carbon fluxes for these ecosystems are rarely available. To the best of our knowledge, this is the first full carbon balance for a freshwater marsh where vertical gaseous [carbon dioxide (CO2 ) and CH4 ] and lateral hydrologic fluxes (dissolved and particulate organic carbon) have been simultaneously measured for multiple years (2011-2013). Carbon accumulation in the sediments suggested that the marsh was a long-term carbon sink and accumulated ~96.9 ± 10.3 (±95% CI) g C m(-2)  yr(-1) during the last ~50 years. However, abnormal climate conditions in the last 3 years turned the marsh to a source of carbon (42.7 ± 23.4 g C m(-2)  yr(-1) ). Gross ecosystem production and ecosystem respiration were the two largest fluxes in the annual carbon budget. Yet, these two fluxes compensated each other to a large extent and led to the marsh being a CO2 sink in 2011 (-78.8 ± 33.6 g C m(-2)  yr(-1) ), near CO2 -neutral in 2012 (29.7 ± 37.2 g C m(-2)  yr(-1) ), and a CO2 source in 2013 (92.9 ± 28.0 g C m(-2)  yr(-1) ). The CH4 emission was consistently high with a three-year average of 50.8 ± 1.0 g C m(-2)  yr(-1) . Considerable hydrologic carbon flowed laterally both into and out of the marsh (108.3 ± 5.4 and 86.2 ± 10.5 g C m(-2)  yr(-1) , respectively). In total, hydrologic carbon fluxes contributed ~23 ± 13 g C m(-2)  yr(-1) to the three-year carbon budget. Our findings highlight the importance of lateral hydrologic inflows/outflows in wetland carbon budgets, especially in those characterized by a flow-through hydrologic regime. In addition, different carbon fluxes responded unequally to climate variability/anomalies and, thus, the total carbon budgets may vary drastically among years. © 2014 John Wiley & Sons Ltd.

  18. Sol-Rad Net Flux (L 1.0, 1.5, 2.0)

    Data.gov (United States)

    National Aeronautics and Space Administration — SolRad-Net (Solar Radiation Network) is an established network of ground-based sensors providing high-frequency solar flux measurements in quasi-realtime to the...

  19. NACP North American 8-km Net Ecosystem Exchange and Component Fluxes, 2004

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides modeled carbon flux estimates at 8-km spatial resolution over North America for the year 2004 of (1) net ecosystem exchange (NEE) of carbon...

  20. Hotspots in ground and surface water carbon fluxes through a freshwater to marine (mangrove) transition zone

    Science.gov (United States)

    Larsen, J.; Welti, N.; Hayes, M.; Lockington, D. A.

    2014-12-01

    The transfer of carbon and water from coastal freshwater wetlands to intertidal and marine zones is significant for sustaining ecosystem processes, particularly within mangroves environments. Large increases in carbon and nutrient fluxes within spatially confined zones (hotspots) are significant as drivers for broader cycling. How these processes relate to the transfers between surface and groundwater systems, as well as the transition from freshwater to marine environments, remains poorly understood. We investigated the flux of carbon and water from a freshwater wetland, to a saltmarsh and then mangroves, both within the main surface channel and within a comprehensive shallow groundwater bore network. We were able to characterise the main spatial trends in water gradients and mixing (using salinity, hydraulic gradients, stable water isotopes, and temperature) over seasonal cycles. In addition, at the same time we investigated the changes in dissolved organic carbon concentration and quality (fluorescence, UV), as well as nutrients (NO3, NH4). This revealed the river and tidal channel to be a significant export pathway for organic carbon, which was generally highly aromatic and recalcitrant. However, we also found that isolated sections of the brackish groundwater mixing zone between freshwater and marine provided a consistently high DOC 'hotspot' of very high quality carbon. This hotspot has high lateral groundwater gradients and therefore likely transports this carbon to the rest of the mangrove subsurface, where it is rapidly assimilated. These results imply large spatial heterogeneity in the carbon cycling between freshwater and marine environments, and have significant implications for the processing of the organic matter, and therefore also the respiration of greenhouse gases such as CO2 and CH4.

  1. Freshwater fluxes from the Northern Hemisphere ice sheets during the Last Deglaciation

    Science.gov (United States)

    Nemec, J.; Janssens, I.; Goelzer, H.; Huybrechts, P.

    2009-04-01

    The disintegration of the Northern Hemisphere Ice Sheets during the Last Deglaciation is thought to have significantly influenced the global climate through oceanic and atmospheric feedbacks. Besides changes in topography and albedo over the large continental ice sheets, freshwater fluxes probably had large effects on the ocean circulation and on the global temperature evolution. To study possible changes in the ocean circulation, it is crucial to track both the intensity and location of meltwater runoff and iceberg calving into the ocean. We have simulated the northern hemisphere ice sheets with a 3D thermomechanical ice sheet model forced with output from a coupled atmosphere-ocean model (ECBilt-Clio) with prescribed ice sheets (extent, elevation, and albedo) for the Last Deglacation. The ice sheet model calculates changes in topography as well as the evolution of the freshwater fluxes, resulting from iceberg calving, basal melt and surface ablation. The ice sheet melt fluxes are routed through a continental runoff scheme that provides the runoff paths over the continents and gives for each continental grid point a corresponding drainage location in the ocean. The results are very dependent on the climate forcing that serves as input for the ice sheet model. Taking GRIP (Greenland Ice Core Project) scaled temperature and precipitation input, we find three major freshwater pulses during the Last Deglaciation. The first meltwater peak occurred at approximately 17 kyr BP, with an amplitude of 0.45 Sverdrup. The second, with the highest intensity of 0.8 Sverdrup, occurred around 14 kyr BP. Large parts of this meltwater is channeled to the North Atlantic, where it might have triggered the Younger Dryas cold period. The third and last meltwater peak happened about 10 kyr BP, corresponding to a switch in the freshwater routing from the North Atlantic to the Artic Ocean.

  2. Net carbon flux from agricultural ecosystems: methodology for full carbon cycle analyses.

    Science.gov (United States)

    West, T O; Marland, G

    2002-01-01

    Agricultural ecosystems have the potential to sequester carbon in soils by altering agricultural management practices (i.e. tillage practice, cover crops, and crop rotation) and using agricultural inputs (i.e. fertilizers and irrigation) more efficiently. Changes in agricultural practices can also cause changes in CO2 emissions associated with these practices. In order to account for changes in net CO2 emissions, and thereby estimate the overall impact of carbon sequestration initiatives on the atmospheric CO2 pool, we use a methodology for full carbon cycle analysis of agricultural ecosystems. The analysis accounts for changes in carbon sequestration and emission rates with time, and results in values representing a change in net carbon flux. Comparison among values of net carbon flux for two or more systems, using the initial system as a baseline value, results in a value for relative net carbon flux. Some results from using the full carbon cycle methodology, along with US national average values for agricultural inputs, indicate that the net carbon flux averaged over all crops following conversion from conventional tillage to no-till is -189 kg C ha(-1) year(-1) (a negative value indicates net transfer of carbon from the atmosphere). The relative net carbon flux, using conventional tillage as the baseline, is -371 kg C ha(-1) year(-1), which represents the total atmospheric CO2 reduction caused by changing tillage practices. The methodology used here illustrates the importance of (1) delineating system boundaries, (2) including CO2 emissions associated with sequestration initiatives in the accounting process, and (3) comparing the new management practices associated with sequestration initiatives with the original management practices to obtain the true impact of sequestration projects on the atmospheric CO2 pool.

  3. Evaluation of satellite and reanalysis-based global net surface energy flux and uncertainty estimates

    Science.gov (United States)

    Allan, Richard; Liu, Chunlei

    2017-04-01

    The net surface energy flux is central to the climate system yet observational limitations lead to substantial uncertainty (Trenberth and Fasullo, 2013; Roberts et al., 2016). A combination of satellite-derived radiative fluxes at the top of atmosphere (TOA) adjusted using the latest estimation of the net heat uptake of the Earth system, and the atmospheric energy tendencies and transports from the ERA-Interim reanalysis are used to estimate surface energy flux globally (Liu et al., 2015). Land surface fluxes are adjusted through a simple energy balance approach using relations at each grid point with the consideration of snowmelt to improve regional realism. The energy adjustment is redistributed over the oceans using a weighting function to avoid meridional discontinuities. Uncertainties in surface fluxes are investigated using a variety of approaches including comparison with a range of atmospheric reanalysis input data and products. Zonal multiannual mean surface flux uncertainty is estimated to be less than 5 Wm-2 but much larger uncertainty is likely for regional monthly values. The meridional energy transport is calculated using the net surface heat fluxes estimated in this study and the result shows better agreement with observations in Atlantic than before. The derived turbulent fluxes (difference between the net heat flux and the CERES EBAF radiative flux at surface) also have good agreement with those from OAFLUX dataset and buoy observations. Decadal changes in the global energy budget and the hemisphere energy imbalances are quantified and present day cross-equator heat transports is re-evaluated as 0.22±0.15 PW southward by the atmosphere and 0.32±0.16 PW northward by the ocean considering the observed ocean heat sinks (Roemmich et al., 2006) . Liu et al. (2015) Combining satellite observations and reanalysis energy transports to estimate global net surface energy fluxes 1985-2012. J. Geophys. Res., Atmospheres. ISSN 2169-8996 doi: 10.1002/2015JD

  4. Tidal day organic and inorganic material flux of ponds in the Liberty Island freshwater tidal wetland.

    Science.gov (United States)

    Lehman, Peggy W; Mayr, Shawn; Liu, Leji; Tang, Alison

    2015-01-01

    The loss of inorganic and organic material export and habitat produced by freshwater tidal wetlands is hypothesized to be an important contributing factor to the long-term decline in fishery production in San Francisco Estuary. However, due to the absence of freshwater tidal wetlands in the estuary, there is little information on the export of inorganic and organic carbon, nutrient or phytoplankton community biomass and the associated mechanisms. A single-day study was conducted to assess the potential contribution of two small vegetated ponds and one large open-water pond to the inorganic and organic material flux within the freshwater tidal wetland Liberty Island in San Francisco Estuary. The study consisted of an intensive tidal day (25.5 h) sampling program that measured the flux of inorganic and organic material at three ponds using continuous monitoring of flow, chlorophyll a, turbidity and salt combined with discrete measurements of phytoplankton community carbon, total and dissolved organic carbon and nutrient concentration at 1.5 h intervals. Vegetated ponds had greater material concentrations than the open water pond and, despite their small area, contributed up to 81% of the organic and 61% of the inorganic material flux of the wetland. Exchange between ponds was important to wetland flux. The small vegetated pond in the interior of the wetland contributed as much as 72-87% of the total organic carbon and chlorophyll a and 10% of the diatom flux of the wetland. Export of inorganic and organic material from the small vegetated ponds was facilitated by small-scale topography and tidal asymmetry that produced a 40% greater material export on ebb tide. The small vegetated ponds contrasted with the large open water pond, which imported 29-96% of the inorganic and 4-81% of the organic material into the wetland from the adjacent river. This study identified small vegetated ponds as an important source of inorganic and organic material to the wetland and the

  5. Net Ecosystem Fluxes of Hydrocarbons from a Ponderosa Pine Forest in Colorado

    Science.gov (United States)

    Rhew, R. C.; Turnipseed, A. A.; Ortega, J. V.; Smith, J. N.; Guenther, A. B.; Shen, S.; Martinez, L.; Koss, A.; Warneke, C.; De Gouw, J. A.; Deventer, M. J.

    2015-12-01

    Light (C2-C4) alkenes, light alkanes and isoprene (C5H8) are non-methane hydrocarbons that play important roles in the photochemical production of tropospheric ozone and in the formation of secondary organic aerosols. Natural terrestrial fluxes of the light hydrocarbons are poorly characterized, with global emission estimates based on limited field measurements. In 2014, net fluxes of these compounds were measured at the Manitou Experimental Forest Observatory, a semi-arid ponderosa pine forest in the Colorado Rocky Mountains and site of the prior BEACHON campaigns. Three field intensives were conducted between June 17 and August 10, 2014. Net ecosystem flux measurements utilized a relaxed eddy accumulation system coupled to an automated gas chromatograph. Summertime average emissions of ethene and propene were up to 90% larger than those observed from a temperate deciduous forest. Ethene and propene fluxes were also correlated to each other, similar to the deciduous forest study. Emissions of isoprene were small, as expected for a coniferous forest, and these fluxes were not correlated with either ethene or propene. Unexpected emissions of light alkanes were also observed, and these showed a distinct diurnal cycle. Understory flux measurements allowed for the partitioning of fluxes between the surface and the canopy. Full results from the three field intensives will be compared with environmental variables in order to parameterize the fluxes for use in modeling emissions.

  6. Modeling the Tidewater Glacier Kangiata Nunaata Sermia and the Freshwater Flux into Godthaabsfjorden

    DEFF Research Database (Denmark)

    Fitzner, Antje

    The Greenland ice sheet loses mass due to changing surface mass balance, direct melting on the surface, ice flow through the numerous outlet glaciers, and basal melt. This Ph.D. thesis focuses on the outlet glaciers terminating in Godthåbsfjord near Nuuk in West Greenland, with Kangiata Nunaata...... Sermia (KNS) being the main contributing glacier. The mass loss of this glacier forms a small contribution to the total mass loss of the Greenland ice sheet, but it will have a large impact on the local ecosystem when there is a large freshwater flux into the fjord. Here, two independent methods are used...

  7. Channelling can affect concentrations of metabolic intermediates at constant net flux: artefact or reality?

    Science.gov (United States)

    Cornish-Bowden, A; Cárdenas, M L

    1993-04-01

    We show that if a metabolic intermediate is directly transferred ('channelled') from an enzyme that catalyses its production to another that uses it as substrate, there is no change in its free concentration compared with a system with the same net flux in which there is no direct transfer. Thus the widespread idea that channelling provides a mechanism for decreasing metabolite concentrations at constant flux is false. Results from computer simulation that suggest otherwise [Mendes, P., Kell, D. B. & Westerhoff, H. V. (1992) Eur. J. Biochem. 204, 257-266] are artefacts either of variations in flux or of alterations in opposite directions of the activities of the relevant enzymes.

  8. Validation of a minimum microclimate disturbance chamber for net ecosystem flux measurements

    NARCIS (Netherlands)

    Graf, A.; Werner, J.; Langensiepen, M.; Boer, van de A.; Schmidt, M.; Kupisch, M.; Vereecken, H.

    2013-01-01

    A minimum-disturbance chamber for canopy net CO2 and H2O flux measurements is described. The system is a passively (optionally actively) ventilated tunnel with large (similar to 0.14 m2) in- and outlet cross sections covering a surface area of approximately 1.6 m2. A differential, non-drying

  9. Net Ecosystem Fluxes of Methyl Halides from a Coastal Salt Marsh with Invasive Pepperweed

    Science.gov (United States)

    Deventer, M. J.; Jiao, Y.; Lewis, J. A.; Weiss, R. F.; Rhew, R. C.; Turnipseed, A. A.

    2016-12-01

    Terrestrial emissions of methyl bromide (CH3Br) and methyl chloride (CH3Cl) are believed to constitute the `missing' source of these compounds to the atmosphere, but the variability of emission rates from natural ecosystems has led to large uncertainties in scaling up. Since April 2016, surface-atmosphere fluxes for methyl halides have been measured at Suisun Marsh, a coastal salt marsh in northern California, USA. Flux measurements are performed in two ways: tower based relaxed eddy accumulation (REA) for net ecosystem fluxes and static flux chamber measurements for plant-scale fluxes. The study site is invaded by perennial pepperweed (Lepidium latifolium), a methyl halide emitting species, covering a significant part of the flux source area. Both, REA and chamber samples are analyzed for methyl chloride (CH3Cl) and methyl bromide (CH3Br) using gas chromatography with electron capture detector (GC-ECD). The analytical precision [ppt] and REA flux detection limits [μmol m-2 d-1] are on the order of 3.9/0.6 for CH3Cl and 0.01/0.2 for CH3Br. Chamber measurements confirmed that methyl halide emissions of pepperweed are large, but that the native alkali heath (Frankenia salina) is a much stronger emitter, when normalized by biomass. REA measurements show that during the summer, the studied marsh is a substantial methyl halide source with net fluxes of 20 μmol m-2 d-1 (CH3Cl) and 1 μmol m-2 d-1 (CH3Br). Notably, these fluxes are comparable with reported chamber based emissions from southern California salt marshes. Furthermore, a positive response to light and temperature was found. The presentation will also expand on the diurnal variability and seasonality of the measured fluxes.

  10. Temporal and spatial changes in mixed layer properties and atmospheric net heat flux in the Nordic Seas

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, A; Alekseev, G [SI ' Arctic and Antarctic Research Institute' , St. Petersburg (Russian Federation); Korablev, A; Esau, I, E-mail: avsmir@aari.nw.r [Nansen Environmental and Remote Sensing Centre, Bergen (Norway)

    2010-08-15

    The Nordic Seas are an important area of the World Ocean where warm Atlantic waters penetrate far north forming the mild climate of Northern Europe. These waters represent the northern rim of the global thermohaline circulation. Estimates of the relationships between the net heat flux and mixed layer properties in the Nordic Seas are examined. Oceanographic data are derived from the Oceanographic Data Base (ODB) compiled in the Arctic and Antarctic Research Institute. Ocean weather ship 'Mike' (OWS) data are used to calculate radiative and turbulent components of the net heat flux. The net shortwave flux was calculated using a satellite albedo dataset and the EPA model. The net longwave flux was estimated by Southampton Oceanography Centre (SOC) method. Turbulent fluxes at the air-sea interface were calculated using the COARE 3.0 algorithm. The net heat flux was calculated by using oceanographic and meteorological data of the OWS 'Mike'. The mixed layer depth was estimated for the period since 2002 until 2009 by the 'Mike' data as well. A good correlation between these two parameters has been found. Sensible and latent heat fluxes controlled by surface air temperature/sea surface temperature gradient are the main contributors into net heat flux. Significant correlation was found between heat fluxes variations at the OWS 'Mike' location and sea ice export from the Arctic Ocean.

  11. Characterization of methyl bromide and methyl chloride fluxes at temperate freshwater wetlands

    Science.gov (United States)

    Hardacre, Catherine J.; Heal, Mathew R.

    2013-01-01

    Methyl bromide (CH3Br) and methyl chloride (CH3Cl) are important natural sources of halogens to the atmosphere. A total of 568 CH3Br and 418 CH3Cl net flux measurements were made for up to 2 years at the same locations within four different wetlands in Scotland. Mean (± 1 standard deviation (SD)) CH3Br and CH3Cl net fluxes across all measurements at each wetland were: Auchencorth Moss, 8 (± 7) and 3560 (± 1260) ng m-2 h-1; Old Castle Farm, 420 (± 70) and 500 (± 260) ng m-2 h-1; Red Moss of Balerno, 500 (± 90) and 140,000 (± 36,000) ng m-2 h-1; and St Margaret's Marsh, 3600 (± 600) and -270 (± 450) ng m-2 h-1. None of the wetlands was a large net sink. Where substantial emissions were observed, these followed seasonal trends, increasing early in the growing season and declining in early autumn. Some diurnal cycles were observed, with emissions greatest during the day, although lower emissions were present at night. None of the measured environmental parameters was a strong "universal" driver for fluxes, which were heterogeneous within and between the wetlands, and larger on average than reported to date; plant species appeared to be the dominant factor, the latter confirmed by vegetation removal experiments. Calluna vulgaris and Phragmites australis emitted particularly large amounts of CH3Br, the former also emitting substantial CH3Cl. While acknowledging the substantial uncertainties in extrapolating globally, observations from this work suggest that wetlands contribute more CH3Br and CH3Cl to the atmosphere than current World Meteorological Organization estimates.

  12. Gross nitrous oxide production drives net nitrous oxide fluxes across a salt marsh landscape.

    Science.gov (United States)

    Yang, Wendy H; Silver, Whendee L

    2016-06-01

    Sea level rise will change inundation regimes in salt marshes, altering redox dynamics that control nitrification - a potential source of the potent greenhouse gas, nitrous oxide (N2 O) - and denitrification, a major nitrogen (N) loss pathway in coastal ecosystems and both a source and sink of N2 O. Measurements of net N2 O fluxes alone yield little insight into the different effects of redox conditions on N2 O production and consumption. We used in situ measurements of gross N2 O fluxes across a salt marsh elevation gradient to determine how soil N2 O emissions in coastal ecosystems may respond to future sea level rise. Soil redox declined as marsh elevation decreased, with lower soil nitrate and higher ferrous iron in the low marsh compared to the mid and high marshes (P < 0.001 for both). In addition, soil oxygen concentrations were lower in the low and mid-marshes relative to the high marsh (P < 0.001). Net N2 O fluxes differed significantly among marsh zones (P = 0.009), averaging 9.8 ± 5.4 μg N m(-2)  h(-1) , -2.2 ± 0.9 μg N m(-2)  h(-1) , and 0.67 ± 0.57 μg N m(-2)  h(-1) in the low, mid, and high marshes, respectively. Both net N2 O release and uptake were observed in the low and high marshes, but the mid-marsh was consistently a net N2 O sink. Gross N2 O production was highest in the low marsh and lowest in the mid-marsh (P = 0.02), whereas gross N2 O consumption did not differ among marsh zones. Thus, variability in gross N2 O production rates drove the differences in net N2 O flux among marsh zones. Our results suggest that future studies should focus on elucidating controls on the processes producing, rather than consuming, N2 O in salt marshes to improve our predictions of changes in net N2 O fluxes caused by future sea level rise. © 2015 John Wiley & Sons Ltd.

  13. Ozone flux over a Norway spruce forest and correlation with net ecosystem production

    Energy Technology Data Exchange (ETDEWEB)

    Zapletal, Milos, E-mail: milos.zapletal@ekotoxa.cz [Ekotoxa s.r.o. - Centre for Environment and Land Assessment, Oticka 37, 746 01 Opava (Czech Republic); Silesian University at Opava, Faculty of Philosophy and Science, Masarykova 37, 746 01 Opava (Czech Republic); Cudlin, Pavel [Institute of Systems Biology and Ecology of the AS CR, v.v.i., Na Sadkach 7, 37005 Ceske Budejovice (Czech Republic); Chroust, Petr [Ekotoxa s.r.o. - Centre for Environment and Land Assessment, Oticka 37, 746 01 Opava (Czech Republic); Urban, Otmar; Pokorny, Radek [Institute of Systems Biology and Ecology of the AS CR, v.v.i., Porici 3b, 60300 Brno (Czech Republic); Edwards-Jonasova, Magda [Institute of Systems Biology and Ecology of the AS CR, v.v.i., Na Sadkach 7, 37005 Ceske Budejovice (Czech Republic); Czerny, Radek; Janous, Dalibor; Taufarova, Klara [Institute of Systems Biology and Ecology of the AS CR, v.v.i., Porici 3b, 60300 Brno (Czech Republic); Vecera, Zbynek; Mikuska, Pavel [Institute of Analytical Chemistry of the AS CR, v.v.i., Veveri 97, 60200 Brno (Czech Republic); Paoletti, Elena [Institute of Plant Protection, National Research Council of Italy, via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy)

    2011-05-15

    Daily ozone deposition flux to a Norway spruce forest in Czech Republic was measured using the gradient method in July and August 2008. Results were in good agreement with a deposition flux model. The mean daily stomatal uptake of ozone was around 47% of total deposition. Average deposition velocity was 0.39 cm s{sup -1} and 0.36 cm s{sup -1} by the gradient method and the deposition model, respectively. Measured and modelled non-stomatal uptake was around 0.2 cm s{sup -1}. In addition, net ecosystem production (NEP) was measured by using Eddy Covariance and correlations with O{sub 3} concentrations at 15 m a.g.l., total deposition and stomatal uptake were tested. Total deposition and stomatal uptake of ozone significantly decreased NEP, especially by high intensities of solar radiation. - Highlights: > We estimate ozone deposition flux to a Norway spruce forest using the gradient method and model. > The mean stomatal uptake of ozone is approximately 47% of the total deposition. > We measure net ecosystem production (NEP) using Eddy Covariance. > We test whether elevated total deposition and stomatal uptake of O{sub 3} imply a reduction of NEP. > Deposition and stomatal uptake of O{sub 3} decrease NEP, especially by high intensities of solar radiation. - Net ecosystem production of a Norway spruce forest decreases with increasing deposition and stomatal uptake of ozone.

  14. Greenland ice sheet surface mass-balance modelling and freshwater flux for 2007, and in a 1995-2007 perspective

    DEFF Research Database (Denmark)

    Mernild, Sebastian H.; Liston, Glen E.; Hiemstra, Christopher A.

    2009-01-01

    The freshwater flux from the Greenland Ice Sheet (GrIS) to the ocean is of considerable importance to the global eustatic sea level rise. A physical modelling approach using SnowModel, a state-of-the-art snow-evolution modelling system that includes four submodels (MicroMet, EnBal, SnowPack, and ......The freshwater flux from the Greenland Ice Sheet (GrIS) to the ocean is of considerable importance to the global eustatic sea level rise. A physical modelling approach using SnowModel, a state-of-the-art snow-evolution modelling system that includes four submodels (MicroMet, EnBal, Snow......-stations) were used as model inputs. The GrIS minimum surface melt extent of 29% occurred in 1996, while the greatest extent of 51% was present in 2007. The 2007 melt extent was 20% greater than the average for 1995-2006. The year 2007 had the highest GrIS surface runoff (523 km3 y-1) and the lowest SMB (-3 km3...... estimates of GrIS subglacial runoff (from geothermal melt) and GrIS calving to quantify GrIS freshwater flux to the ocean, indicating an average negative mass-balance of 265 (±83) km3 y-1. This study further suggests an average GrIS freshwater flux of approximately 786 km3 y-1 to the ocean, of which 45...

  15. Effect of site of starch digestion on portal nutrient net fluxes in steers.

    Science.gov (United States)

    Nozière, Pierre; Rémond, Didier; Lemosquet, Sophie; Chauveau, Béatrice; Durand, Denys; Poncet, Claude

    2005-08-01

    Processing of maize grain is known to modulate the site of starch digestion, thus the nature and amount of nutrients delivered for absorption. We assessed the effect of site of starch digestion on nutrient net fluxes across portal-drained viscera (PDV). Three steers, fitted with permanent digestive cannulas and blood catheters, successively received two diets containing 35 % starch as dent maize grain. Diets differed according to maize presentation: dry and cracked (by-pass, BP) v. wet and ground (control, C). Ruminal physicochemical parameters were not significantly affected. Between C and BP, the decrease in ruminal starch digestion was compensated by an increase in starch digestion in the small intestine. The amount of glucose and soluble alpha-glucoside reaching the ileum was not affected. The amount of glucose disappearing in the small intestine increased from 238 to 531 g/d between C and BP, but portal net flux of glucose remained unchanged (-97 g/d). The portal O2 consumption and net energy release were not significantly affected, averaging 16 % and 57 % of metabolizable energy intake, respectively. The whole-body glucose appearance rate, measured by jugular infusion of [6,6-2H2]glucose, averaged 916 g/d. The present study shows that the increase in the amount of glucose disappearing in the small intestine of conventionally fed cattle at a moderate intake level induces no change in portal net flux of glucose, reflecting an increase in glucose utilization by PDV. That could contribute to the low response of whole-body glucose appearance rate observed at this moderate level of intestinal glucose supply.

  16. Sustained Magnetorotational Turbulence in Local Simulations of Stratified Disks with Zero Net Magnetic Flux

    DEFF Research Database (Denmark)

    W. Davis, S.; M. Stone, J.; Pessah, Martin Elias

    2010-01-01

    We examine the effects of density stratification on magnetohydrodynamic turbulence driven by the magnetorotational instability in local simulations that adopt the shearing box approximation. Our primary result is that, even in the absence of explicit dissipation, the addition of vertical gravity...... leads to convergence in the turbulent energy densities and stresses as the resolution increases, contrary to results for zero net flux, unstratified boxes. The ratio of total stress to midplane pressure has a mean of ~0.01, although there can be significant fluctuations on long (>~50 orbit) timescales...

  17. Climate model performance and change projection for freshwater fluxes: Comparison for irrigated areas in Central and South Asia

    Directory of Open Access Journals (Sweden)

    Shilpa M. Asokan

    2016-03-01

    New hydrological insights for the region: For precipitation in both regions, model accuracy relative to observations has remained the same or decreased in successive climate model generations until and including CMIP5. No single climate model out-performs other models across all key freshwater variables in any of the investigated basins. Scale effects are not evident from global model application directly to freshwater assessment for the two basins of widely different size. Overall, model results are less accurate and more uncertain for freshwater fluxes than for temperature, and particularly so for model-implied water storage changes. Also, the monsoon-driven runoff seasonality in MRB is not accurately reproduced. Model projections agree on evapotranspiration increase in both regions until the climatic period 2070–2099. This increase is fed by precipitation increase in MRB and by runoff water (thereby decreasing runoff in the Aral Region.

  18. The influence of environmental calcium concentrations on calcium flux, compensatory drinking and epithelial calcium channel expression in a freshwater cartilaginous fish.

    Science.gov (United States)

    Allen, Peter J; Weihrauch, Dirk; Grandmaison, Vanessa; Dasiewicz, Patricia; Peake, Stephan J; Anderson, W Gary

    2011-03-15

    Calcium metabolism and mRNA levels of the epithelial calcium channel (ECaC) were examined in a freshwater cartilaginous fish, the lake sturgeon Acipenser fulvescens. Lake sturgeon were acclimated for ≥2 weeks to 0.1 (low), 0.4 (normal) or 3.3 (high) mmol l(-1) environmental calcium. Whole-body calcium flux was examined using (45)Ca as a radioactive marker. Net calcium flux was inward in all treatment groups; however, calcium influx was greatest in the low calcium environment and lowest in the high calcium environment, whereas efflux had the opposite relationship. A significant difference in the concentration of (45)Ca in the gastrointestinal tract (GIT) of fish in the low calcium environment led to the examination of drinking rate and calcium flux across the anterior-middle (mid) intestine. Drinking rate was not different between treatments; however, calcium influx across the mid-intestine in the low calcium treatment was significantly greater than that in both the normal and high calcium treatments. The lake sturgeon ECaC was 2831 bp in length, with a predicted protein sequence of 683 amino acids that shared a 66% identity with the closest sequenced ECaCs from the vertebrate phyla. ECaC mRNA levels were examined in the gills, kidney, pyloric caeca, mid-intestine and spiral intestine. Expression levels were highest in the gills, then the kidneys, and were orders of magnitude lower in the GIT. Contrary to existing models for calcium uptake in the teleost gill, ECaC expression was greatest in high calcium conditions and kidney ECaC expression was lowest in low calcium conditions, suggesting that cellular transport mechanisms for calcium may be distinctly different in these freshwater cartilaginous fishes.

  19. [Net CO2 exchange and carbon isotope flux in Acacia mangium plantation].

    Science.gov (United States)

    Zou, Lu-Liu; Sun, Gu-Chou; Zhao, Ping; Cai, Xi-An; Zeng, Xiao-Ping; Wang, Quan

    2009-11-01

    By using stable carbon isotope technique, the leaf-level 13C discrimination was integrated to canopy-scale photosynthetic discrimination (Deltacanopy) through weighted the net CO2 assimilation (Anet) of sunlit and shaded leaves and the stand leaf area index (L) in an A. mangium plantation, and the carbon isotope fluxes from photosynthesis and respiration as well as their net exchange flux were obtained. There was an obvious diurnal variation in Deltacanopy, being lower at dawn and at noon time (18.47 per thousand and 19.87 per thousand, respectively) and the highest (21.21 per thousand) at dusk. From the end of November to next May, the Deltacanopy had an increasing trend, with an annual average of (20.37 +/- 0.29) per thousand. The carbon isotope ratios of CO2 from autotrophic respiration (excluding daytime foliar respiration) and heterotrophic respiration were respectively (- 28.70 +/- 0.75) per thousand and (- 26.75 +/- 1.3) per thousand in average. The delta13 C of nighttime ecosystem-respired CO2 in May was the lowest (-30.14 per thousand), while that in November was the highest (-28.01 per thousand). The carbon isotope flux of CO2 between A. mangium forest and atmosphere showed a midday peak of 178.5 and 217 micromol x m(-2) x s(-1) x per thousand in May and July, with the daily average of 638.4 and 873.2 micromol x m(-2) x s(-1) x per thousand, respectively. The carbon isotope flux of CO2 absorbed by canopy leaves was 1.6-2.5 times higher than that of CO2 emitted from respiration, suggesting that a large sum of CO2 was absorbed by A. mangium, which decreased the atmospheric CO2 concentration and improved the environment.

  20. Land Use Effects on Net Greenhouse Gas Fluxes in the US Great Plains: Historical Trends and Model Projections

    Science.gov (United States)

    Del Grosso, S. J.; Parton, W. J.; Ojima, D. S.; Mosier, A. R.; Mosier, A. R.; Paustian, K.; Peterson, G. A.

    2001-12-01

    We present maps showing regional patterns of land use change and soil C levels in the US Great Plains during the 20th century and time series of net greenhouse gas fluxes associated with different land uses. Net greenhouse gas fluxes were calculated by accounting for soil CO2 fluxes, the CO2 equivalents of N2O emissions and CH4 uptake, and the CO2 costs of N fertilizer production. Both historical and modern agriculture in this region have been net sources of greenhouse gases. The primary reason for this, prior to 1950, is that agriculture mined soil C and resulted in net CO2 emissions. When chemical N fertilizer became widely used in the 1950's agricultural soils began to sequester CO2-C but these soils were still net greenhouse gas sources if the effects of increased N2O emissions and decreased CH4 uptake are included. The sensitivity of net greenhouse gas fluxes to conventional and alternative land uses was explored using the DAYCENT ecosystem model. Model projections suggest that conversion to no-till, reduction of the fallow period, and use of nitrification inhibitors can significantly decrease net greenhouse gas emissions in dryland and irrigated systems, while maintaining or increasing crop yields.

  1. Development of an ensemble-adjoint optimization approach to derive uncertainties in net carbon fluxes

    Directory of Open Access Journals (Sweden)

    T. Ziehn

    2011-11-01

    Full Text Available Accurate modelling of the carbon cycle strongly depends on the parametrization of its underlying processes. The Carbon Cycle Data Assimilation System (CCDAS can be used as an estimator algorithm to derive posterior parameter values and uncertainties for the Biosphere Energy Transfer and Hydrology scheme (BETHY. However, the simultaneous optimization of all process parameters can be challenging, due to the complexity and non-linearity of the BETHY model. Therefore, we propose a new concept that uses ensemble runs and the adjoint optimization approach of CCDAS to derive the full probability density function (PDF for posterior soil carbon parameters and the net carbon flux at the global scale. This method allows us to optimize only those parameters that can be constrained best by atmospheric carbon dioxide (CO2 data. The prior uncertainties of the remaining parameters are included in a consistent way through ensemble runs, but are not constrained by data. The final PDF for the optimized parameters and the net carbon flux are then derived by superimposing the individual PDFs for each ensemble member. We find that the optimization with CCDAS converges much faster, due to the smaller number of processes involved. Faster convergence also gives us much increased confidence that we find the global minimum in the reduced parameter space.

  2. Net anthropogenic nitrogen inputs and nitrogen fluxes from Indian watersheds: An initial assessment

    Science.gov (United States)

    Swaney, D. P.; Hong, B.; Paneer Selvam, A.; Howarth, R. W.; Ramesh, R.; Purvaja, R.

    2015-01-01

    In this paper, we apply an established methodology for estimating Net Anthropogenic Nitrogen Inputs (NANI) to India and its major watersheds. Our primary goal here is to provide initial estimates of major nitrogen inputs of NANI for India, at the country level and for major Indian watersheds, including data sources and parameter estimates, making some assumptions as needed in areas of limited data availability. Despite data limitations, we believe that it is clear that the main anthropogenic N source is agricultural fertilizer, which is being produced and applied at a growing rate, followed by N fixation associated with rice, leguminous crops, and sugar cane. While India appears to be a net exporter of N in food/feed as reported elsewhere (Lassaletta et al., 2013b), the balance of N associated with exports and imports of protein in food and feedstuffs is sensitive to protein content and somewhat uncertain. While correlating watershed N inputs with riverine N fluxes is problematic due in part to limited available riverine data, we have assembled some data for comparative purposes. We also suggest possible improvements in methods for future studies, and the potential for estimating riverine N fluxes to coastal waters.

  3. Assessing the Potential to Derive Air-Sea Freshwater Fluxes from Aquarius-Like Observations of Surface Salinity

    Science.gov (United States)

    Zhen, Li; Adamec, David

    2009-01-01

    A state-of-the-art numerical model is used to investigate the possibility of determining freshwater flux fields from temporal changes io sea-surface salinity (SSS), a goal of the satellite salinity-measuring mission, Aquarius/SAC-D. Because the estimated advective temporal scale is usually longer than the Aquarius/SAC-D revisit time, the possibility of producing freshwater flux estimates from temporal salinity changes is first examined by using a correlation analysis. For the mean seasonal cycle, the patterns of the correlations between the freshwater fluxes and surface salinity temporal tendencies are mainly zonally oriented, and are highest where the local precipitation is also relatively high. Nonseasonal (deviations from the monthly mean) correlations are highest along mid-latitude moon tracks and are relatively small in the tropics. The complex correlation patterns presented here suggest that a global retrieval of the difference between evaporation and precipitation (E-P) from salinity changes requires more complex techniques than a simple consideration of local balance with surface forcing.

  4. Nutrient fluxes and net metabolism in a coastal lagoon SW peninsula of Baja California, Mexico

    Directory of Open Access Journals (Sweden)

    Cervantes Duarte, R.

    2016-09-01

    Full Text Available Fluxes of nutrients and net metabolism were estimated in coastal lagoon Magdalena Bay using LOICZ biogeochemical model. In situ data were obtained from 14 sites in the lagoon and also from a fixed site in the adjacent ocean area. Intense upwelling (February to July and faint upwelling (August to January were analyzed from monthly time series. The Temperature, nitrite + nitrate, ammonium and phosphate within the lagoon showed significant differences (p<0.05 between the two periods. Salinity (p=0.408 was more homogeneous (no significantly different due to mixing processes. During the intense upwelling period, nutrients increased in and out of the lagoon due to the influence of Transitional Water and Subartic Water transported by the California Current. However, during the faint upwelling, from August to January, the Transition Water and Subtropical Surface Water were predominant. Magdalena Bay showed denitrification processes of throughout the year as it occurred in other semi-arid coastal lagoons. It also showed a net autotrophic metabolism during intense upwelling and heterotrophic metabolism during faint upwelling. Understanding nutrient flows and net metabolism through simple biogeochemical models can provide tools for better management of the coastal zone.

  5. Net Fluorescein Flux Across Corneal Endothelium Strongly Suggests Fluid Transport is due to Electro-osmosis.

    Science.gov (United States)

    Sanchez, J M; Cacace, V; Kusnier, C F; Nelson, R; Rubashkin, A A; Iserovich, P; Fischbarg, J

    2016-08-01

    We have presented prior evidence suggesting that fluid transport results from electro-osmosis at the intercellular junctions of the corneal endothelium. Such phenomenon ought to drag other extracellular solutes. We have investigated this using fluorescein-Na2 as an extracellular marker. We measured unidirectional fluxes across layers of cultured human corneal endothelial (HCE) cells. SV-40-transformed HCE layers were grown to confluence on permeable membrane inserts. The medium was DMEM with high glucose and no phenol red. Fluorescein-labeled medium was placed either on the basolateral or the apical side of the inserts; the other side carried unlabeled medium. The inserts were held in a CO2 incubator for 1 h (at 37 °C), after which the entire volume of the unlabeled side was collected. After that, label was placed on the opposite side, and the corresponding paired sample was collected after another hour. Fluorescein counts were determined with a (Photon Technology) DeltaScan fluorometer (excitation 380 nm; emission 550 nm; 2 nm bwth). Samples were read for 60 s. The cells utilized are known to transport fluid from the basolateral to the apical side, just as they do in vivo in several species. We used 4 inserts for influx and efflux (total: 20 1-h periods). We found a net flux of fluorescein from the basolateral to the apical side. The flux ratio was 1.104 ± 0.056. That difference was statistically significant (p = 0.00006, t test, paired samples). The endothelium has a definite restriction at the junctions. Hence, an asymmetry in unidirectional fluxes cannot arise from osmosis, and can only point instead to paracellular solvent drag. We suggest, once more, that such drag is due to electro-osmotic coupling at the paracellular junctions.

  6. A Compact, Multi-view Net Flux Radiometer for Future Uranus and Neptune Probes

    Science.gov (United States)

    Aslam, S.; Amato, M.; Atkinson, D. H.; Hewagama, T.; Jennings, D. E.; Nixon, C. A.; Mousis, O.

    2017-01-01

    A Net Flux Radiometer (NFR) is presented that can be included in an atmospheric structure instrument suite for future probe missions to the icy giants Uranus and Neptune. The baseline design has two spectral channels i.e., a solar channel (0.4-to-3.5 m) and a thermal channel (4-to-300 m). The NFR is capable of viewing five distinct viewing angles during the descent. Non-imaging Winston cones with band-pass filters are used for each spectral channel and to define a 5 angular acceptance. Uncooled thermopile detectors are used in each spectral channel and are read out using a custom radiation hard application specific integrated circuit (ASIC). The baseline design can easily be changed to increase the number of detector channels from two to seven.

  7. Quantifying Energy and Mass Fluxes Controlling Godthåbsfjord Freshwater Input in a 5-km Simulation (1991–2012)

    DEFF Research Database (Denmark)

    Langen, P.L.; Mottram, R.H.; Christensen, J.H.

    2015-01-01

    Freshwater runoff to fjords with marine-terminating glaciers along the Greenland Ice Sheet margin has an impact on fjord circulation and potentially ice sheet mass balance through increasing heat transport to the glacier front. Here, the authors use the high-resolution (5.5 km) HIRHAM5 regional...... with observations (typically .0.9), there are biases that impact the results. In particular, overestimated albedo leads to underestimation of melt and runoff at low elevations. In the model simulation (1991–2012), the ice sheet experiences increasing energy input from the surface turbulent heat flux (up...

  8. MetaFluxNet, a program package for metabolic pathway construction and analysis, and its use in large-scale metabolic flux analysis of Escherichia coli.

    Science.gov (United States)

    Lee, Sang Yup; Lee, Dong-Yup; Hong, Soon Ho; Kim, Tae Yong; Yun, Hongsoek; Oh, Young-Gyun; Park, Sunwon

    2003-01-01

    We have developed MetaFluxNet which is a stand-alone program package for the management of metabolic reaction information and quantitative metabolic flux analysis. It allows users to interpret and examine metabolic behavior in response to genetic and/or environmental modifications. As a result, quantitative in silico simulations of metabolic pathways can be carried out to understand the metabolic status and to design the metabolic engineering strategies. The main features of the program include a well-developed model construction environment, user-friendly interface for metabolic flux analysis (MFA), comparative MFA of strains having different genotypes under various environmental conditions, and automated pathway layout creation. The usefulness and functionality of the program are demonstrated by applying to metabolic pathways in E. coli. First, a large-scale in silico E. coli model is constructed using MetaFluxNet, and then the effects of carbon sources on intracellular flux distributions and succinic acid production were investigated on the basis of the uptake and secretion rates of the relevant metabolites. The results indicated that among three carbon sources available, the most reduced substrate is sorbitol which yields efficient succinic acid production. The software can be downloaded from http://mbel.kaist.ac.kr/.

  9. Development of a Net Flux Radiometer for the Hera Saturn Probe Mission

    Science.gov (United States)

    Aslam, Shahid; Amato, Michael; Atkinson, David; Mousis, Olivier; Nixon, Conor; Simon, Amy A.; Hera Probe Mission Team

    2016-10-01

    In situ exploration of all the giant planets in the outer solar system is an imperative and a Saturn probe is the next compelling step beyond Galileo's in situ exploration of Jupiter, the remote investigation of its interior, gravity, and magnetic fields by the Juno mission, and the Cassini spacecraft's similar orbital reconnaissance of Saturn. One such proposed future mission is "HERA: an international atmospheric probe to unveil the depths of Saturn" a nominal configuration is a combined ESA/Class-M probe mission accompanied by a launch vehicle and carrier relay spacecraft provided by NASA. One of the instruments being considered for inclusion on the probe is a Net Flux Radiometer (NFR) to unravel the vertical structure and properties of Saturn's cloud and haze layers. A NFR concept is presented that can be included in an atmospheric structure instrument suite for the Hera mission. The current design has two spectral channels i.e., a solar channel (0.4-to-5 µm) and a thermal channel (4-to-50 µm). The NFR is capable of viewing five distinct viewing angles during the descent. Non-imaging Winston cones with window and filter combinations define the spectral channels with a 5° Field-Of View (FOV). Uncooled thermopile detectors are used in each spectral channel and are read out using a custom designed radiation-hard Application Specific Integrated Circuit (ASIC).

  10. Why and when channelling can decrease pool size at constant net flux in a simple dynamic channel.

    Science.gov (United States)

    Mendes, P; Kell, D B; Westerhoff, H V

    1996-03-15

    Cornish-Bowden and Cárdenas (Cornish-Bowden, A. and Cárdenas M.L. (1993) Eur. J. Biochem. 213, 87-92) have suggested that simulation results peviously published by us (Mendes, P., Kell, D.B. and Westerhoff, H.V. (1992) Eur. J. Biochem. 204, 255-266) which had demonstrated that large reductions of intermediate pool sizes could be accompanied by increasing channel flux in a model metabolic pathway, were an artefact of changes in the pathway's overall flux of the order of 0.0075%, or of inappropriate alterations of enzyme activities. They also asserted to prove that the "channelling of an intermediate cannot affect its free concentration at constant net flux". We consider the co-response of the intermediate metabolite concentration ('pool') and the channel flux to changes in kinetic (or thermodynamic) parameters. Both by analytical proofs and by numerical examples we show that this co-response can be positive, negative or null, depending on the parameter change. In particular, we prove that there is always a number of ways of changing parameters such that the intermediate metabolite concentration decreases with increasing channel flux, whether the total flux varies or is constant. We also show that increased stability of the (dynamic) enzyme-intermediate-enzyme complex, as well as a single parameter change that similarly displays no cross-over effects, can lead to decreased intermediate metabolite concentration and increased channel flux at constant total flux. In general, a non-zero co-response of the intermediate metabolite concentration ('pool') and the channel flux to changes in kinetic (or other) parameters is the rule rather than the exception. More specifically: (i) The algebraic analysis ('general proof') given in Cornish-Bowden and Cárdenas (1993) contains the constraint that the elasticities of various steps to the modulation parameters which were used to vary the channel flux at constant net flux were unity. This is an unfortunate and unnecessary

  11. Eddy covariance flux measurements of net ecosystem carbon dioxide exchange from a lowland peatland flux tower network in England and Wales

    Science.gov (United States)

    Morrison, Ross; Balzter, Heiko; Burden, Annette; Callaghan, Nathan; Cumming, Alenander; Dixon, Simon; Evans, Jonathan; Kaduk, Joerg; Page, Susan; Pan, Gong; Rayment, Mark; Ridley, Luke; Rylett, Daniel; Worrall, Fred; Evans, Christopher

    2016-04-01

    Peatlands store disproportionately large amounts of soil carbon relative to other terrestrial ecosystems. Over recent decades, the large amount of carbon stored as peat has proved vulnerable to a range of land use pressures as well as the increasing impacts of climate change. In temperate Europe and elsewhere, large tracts of lowland peatland have been drained and converted to agricultural land use. Such changes have resulted in widespread losses of lowland peatland habitat, land subsidence across extensive areas and the transfer of historically accumulated soil carbon to the atmosphere as carbon dioxide (CO2). More recently, there has been growth in activities aiming to reduce these impacts through improved land management and peatland restoration. Despite a long history of productive land use and management, the magnitude and controls on greenhouse gas emissions from lowland peatland environments remain poorly quantified. Here, results of surface-atmosphere measurements of net ecosystem CO2 exchange (NEE) from a network of seven eddy covariance (EC) flux towers located at a range of lowland peatland ecosystems across the United Kingdom (UK) are presented. This spatially-dense peatland flux tower network forms part of a wider observation programme aiming to quantify carbon, water and greenhouse gas balances for lowland peatlands across the UK. EC measurements totalling over seventeen site years were obtained at sites exhibiting large differences in vegetation cover, hydrological functioning and land management. The sites in the network show remarkable spatial and temporal variability in NEE. Across sites, annual NEE ranged from a net sink of -194 ±38 g CO2-C m-2 yr-1 to a net source of 784±70 g CO2-C m-2 yr-1. The results suggest that semi-natural sites remain net sinks for atmospheric CO2. Sites that are drained for intensive agricultural production range from a small net sink to the largest observed source for atmospheric CO2 within the flux tower network

  12. Estimation of net ecosystem carbon exchange for the conterminous United States by combining MODIS and AmeriFlux data

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Jingfeng; Zhuang, Qianlai; Baldocchi, Dennis D.; Bolstad, Paul V.; Burns, Sean P.; Chen, Jiquan; Cook, David R.; Curtis, Peter S.; Drake, Bert G.; Foster, David R.; Gu, Lianhong; Hadley, Julian L.; Hollinger, David Y.; Katul, Gabriel G.; Law, Beverly E.; Litvak, Marcy; Ma, Siyan; Martin, Timothy A.; Matamala, Roser; McNulty, Steve; Meyers, Tilden P.; Monson, Russell K.; Munger, J. William; Noormets, Asko; Oechel, Walter C.; Oren, Ram; Richardson, Andrew D.; Schmid, Hans Peter; Scott, Russell L.; Starr, Gregory; Sun, Ge; Suyker, Andrew E.; Torn, Margaret S.; Paw, Kyaw; Verma, Shashi B.; Wharton, Sonia; Wofsy, Steven C.

    2008-10-01

    Eddy covariance flux towers provide continuous measurements of net ecosystem carbon exchange (NEE) for a wide range of climate and biome types. However, these measurements only represent the carbon fluxes at the scale of the tower footprint. To quantify the net exchange of carbon dioxide between the terrestrial biosphere and the atmosphere for regions or continents, flux tower measurements need to be extrapolated to these large areas. Here we used remotely sensed data from the Moderate Resolution Imaging Spectrometer (MODIS) instrument on board the National Aeronautics and Space Administration's (NASA) Terra satellite to scale up AmeriFlux NEE measurements to the continental scale. We first combined MODIS and AmeriFlux data for representative U.S. ecosystems to develop a predictive NEE model using a modified regression tree approach. The predictive model was trained and validated using eddy flux NEE data over the periods 2000-2004 and 2005-2006, respectively. We found that the model predicted NEE well (r = 0.73, p < 0.001). We then applied the model to the continental scale and estimated NEE for each 1 km x 1 km cell across the conterminous U.S. for each 8-day interval in 2005 using spatially explicit MODIS data. The model generally captured the expected spatial and seasonal patterns of NEE as determined from measurements and the literature. Our study demonstrated that our empirical approach is effective for scaling up eddy flux NEE measurements to the continental scale and producing wall-to-wall NEE estimates across multiple biomes. Our estimates may provide an independent dataset from simulations with biogeochemical models and inverse modeling approaches for examining the spatiotemporal patterns of NEE and constraining terrestrial carbon budgets over large areas.

  13. A more accurate formula for calculating the net longwave radiation flux in the Baltic Sea

    Directory of Open Access Journals (Sweden)

    Tomasz Zapadka

    2007-12-01

    Full Text Available A new, more accurate formula for calculating the net longwave radiation fluxLW ↑↓ has been devised for the Baltic Sea region. To this end,the following sets of simultaneously measured data regarding the longwave radiation of the sea andthe atmosphere were used: the temperatures of the sea surface and its contiguous air layer,the water vapour pressure in the air above the water, and the cloud cover.These data were gathered during numerous research cruises in the Baltic in 2000-03 and were supplemented by satellitedata from Karlsson (2001 characterising the cloud cover over the whole Baltic. The formulaestablished for LW ↑↓ can be written in the form of three alternative equations,differing with respect to their cloud cover functions:LW ↑↓ =0.985σT4s - σT4a (0.685+0.00452e{(1 + d n2 average for all cloud types (Z1(1 + din2 separately for low-, mid- and high-level clouds (Z2(1 + dinϒi separately for low-, mid- and high-level clouds (Z3where σ - Stefan-Boltzmann constant; Ts - sea surface temperature [K]; Ta - air temperature [K]; e - water vapour pressure [mbar]; n - total cloud amount [0 - 1]; d - mean empirical dimensionless coefficient, determined for all cloud types or for particular months (see Tables 3 and 4; da - empirical coefficient determined for the quadratic function: d1 = 0.39 for low-level clouds, d2 = 0.305 for mid-level clouds, d3 = 0.22 for high-level clouds; di - empirical coefficient determined as follows: d1 = 0.39 for low-level clouds when γ1 = 1.3, d2 = 0.29 for mid-level clouds when γ2 = 1.1; d3 = 0.17 for high-level clouds when γ3 = 0.96. The improved accuracy of this formula (RMSE ≅ 10 W m-2 is due chiefly to the establishment of functions and coefficients characterising the cloud cover over the Baltic in particular months of the year and their incorporation into it.

  14. Evaluation and uncertainty analysis of regional-scale CLM4.5 net carbon flux estimates

    Science.gov (United States)

    Post, Hanna; Hendricks Franssen, Harrie-Jan; Han, Xujun; Baatz, Roland; Montzka, Carsten; Schmidt, Marius; Vereecken, Harry

    2018-01-01

    Modeling net ecosystem exchange (NEE) at the regional scale with land surface models (LSMs) is relevant for the estimation of regional carbon balances, but studies on it are very limited. Furthermore, it is essential to better understand and quantify the uncertainty of LSMs in order to improve them. An important key variable in this respect is the prognostic leaf area index (LAI), which is very sensitive to forcing data and strongly affects the modeled NEE. We applied the Community Land Model (CLM4.5-BGC) to the Rur catchment in western Germany and compared estimated and default ecological key parameters for modeling carbon fluxes and LAI. The parameter estimates were previously estimated with the Markov chain Monte Carlo (MCMC) approach DREAM(zs) for four of the most widespread plant functional types in the catchment. It was found that the catchment-scale annual NEE was strongly positive with default parameter values but negative (and closer to observations) with the estimated values. Thus, the estimation of CLM parameters with local NEE observations can be highly relevant when determining regional carbon balances. To obtain a more comprehensive picture of model uncertainty, CLM ensembles were set up with perturbed meteorological input and uncertain initial states in addition to uncertain parameters. C3 grass and C3 crops were particularly sensitive to the perturbed meteorological input, which resulted in a strong increase in the standard deviation of the annual NEE sum (σ ∑ NEE) for the different ensemble members from ˜ 2 to 3 g C m-2 yr-1 (with uncertain parameters) to ˜ 45 g C m-2 yr-1 (C3 grass) and ˜ 75 g C m-2 yr-1 (C3 crops) with perturbed forcings. This increase in uncertainty is related to the impact of the meteorological forcings on leaf onset and senescence, and enhanced/reduced drought stress related to perturbation of precipitation. The NEE uncertainty for the forest plant functional type (PFT) was considerably lower (σ ∑ NEE ˜ 4.0-13.5 g C

  15. An experimental investigation of flows from zero-net mass-flux actuators

    Science.gov (United States)

    Holman, Ryan Jay

    Zero-net mass-flux (ZNMF) devices consist of an oscillating driver, a cavity, and a small opening such as a rectangular slot or a circular orifice. The driver produces a series of vortex pairs (or rings) at the slot/orifice which add momentum and circulation to the flow. ZNMF devices are useful tools for flow control applications such as heat transfer, mixing enhancement, and boundary layer separation control. To date much research has been done to qualify and quantify the effects of ZNMF devices in many applications, both experimental and computational. However, a number of issues still remain. First, there is no universally accepted dimensionless parameter space, which makes device characterization and comparison between studies difficult. Second, most experimental studies do not sufficiently quantify the nearfield behavior, which hinders the fundamental understanding of the underlying flow physics. Of particular interest are the regimes of jet formation, and transition from laminar to turbulent-like flow, which are not well understood. Finally, the accuracy of experimental measurements are seldom reported in the literature. This study unifies the experimental and numerical data presented in the literature for ZNMF flowfields exhausting into a quiescent medium. A quantitative experimental database is also generated to completely characterize the topological regions of ZNMF flows over a useful range of the dimensionless parameter space. The database is derived chiefly from two-dimensional velocity field measurements using particle image velocimetry and laser Doppler anemometry. Vorticity, circulation, Reynolds stress, and turbulent kinetic energy is acquired to characterize the resulting flowfield. Significant insight into the behavior of voice coil driven ZNMF devices is uncovered. Design improvements are made by implementing a sinusoidal controller for piston motion and eliminating the need for a sealing membrane in the cavity. It is shown that the proper

  16. Deciphering the components of regional net ecosystem fluxes following a bottom-up approach for the Iberian Peninsula

    Directory of Open Access Journals (Sweden)

    N. Carvalhais

    2010-11-01

    Full Text Available Quantification of ecosystem carbon pools is a fundamental requirement for estimating carbon fluxes and for addressing the dynamics and responses of the terrestrial carbon cycle to environmental drivers. The initial estimates of carbon pools in terrestrial carbon cycle models often rely on the ecosystem steady state assumption, leading to initial equilibrium conditions. In this study, we investigate how trends and inter-annual variability of net ecosystem fluxes are affected by initial non-steady state conditions. Further, we examine how modeled ecosystem responses induced exclusively by the model drivers can be separated from the initial conditions. For this, the Carnegie-Ames-Stanford Approach (CASA model is optimized at set of European eddy covariance sites, which support the parameterization of regional simulations of ecosystem fluxes for the Iberian Peninsula, between 1982 and 2006.

    The presented analysis stands on a credible model performance for a set of sites, that represent generally well the plant functional types and selected descriptors of climate and phenology present in the Iberian region – except for a limited Northwestern area. The effects of initial conditions on inter-annual variability and on trends, results mostly from the recovery of pools to equilibrium conditions; which control most of the inter-annual variability (IAV and both the magnitude and sign of most of the trends. However, by removing the time series of pure model recovery from the time series of the overall fluxes, we are able to retrieve estimates of inter-annual variability and trends in net ecosystem fluxes that are quasi-independent from the initial conditions. This approach reduced the sensitivity of the net fluxes to initial conditions from 47% and 174% to −3% and 7%, for strong initial sink and source conditions, respectively.

    With the aim to identify and improve understanding of the component fluxes that drive the observed trends, the

  17. Estimation of Net Ecosystem Carbon Exchange for the Conterminous UnitedStates by Combining MODIS and AmeriFlux Data

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Jingfeng; Zhuang, Qianlai; Baldocchi, Dennis D.; Law, Beverly E.; Richardson, Andrew D.; Chen, Jiquan; Oren, Ram; Starr, Gregory; Noormets, Asko; Ma, Siyan; Verma, Shashi B.; Wharton, Sonia; Wofsy, Steven C.; Bolstad, Paul V.; Burns, Sean P.; Cook, David R.; Curtis, Peter S.; Drake, Bert G.; Falk, Matthias; Fischer, Marc L.; Foster, David R.; Gu, Lianhong; Hadley, Julian L.; Hollinger, David Y.; Katul, Gabriel G.; Litvak, Marcy; Martin, Timothy A.; Matamala, Roser; McNulty, Steve; Meyers, Tilden P.; Monson, Russell K.; Munger, J. William; Oechel, Walter C.; U, Kyaw Tha Paw; Schmid, Hans Peter; Scott, Russell L.; Sun, Ge; Suyker, Andrew E.; Torn, Margaret S.

    2009-03-06

    Eddy covariance flux towers provide continuous measurements of net ecosystem carbon exchange (NEE) for a wide range of climate and biome types. However, these measurements only represent the carbon fluxes at the scale of the tower footprint. To quantify the net exchange of carbon dioxide between the terrestrial biosphere and the atmosphere for regions or continents, flux tower measurements need to be extrapolated to these large areas. Here we used remotely-sensed data from the Moderate Resolution Imaging Spectrometer (MODIS) instrument on board NASA's Terra satellite to scale up AmeriFlux NEE measurements to the continental scale. We first combined MODIS and AmeriFlux data for representative U.S. ecosystems to develop a predictive NEE model using a regression tree approach. The predictive model was trained and validated using NEE data over the periods 2000-2004 and 2005-2006, respectively. We found that the model predicted NEE reasonably well at the site level. We then applied the model to the continental scale and estimated NEE for each 1 km x 1 km cell across the conterminous U.S. for each 8-day period in 2005 using spatially-explicit MODIS data. The model generally captured the expected spatial and seasonal patterns of NEE. Our study demonstrated that our empirical approach is effective for scaling up eddy flux NEE measurements to the continental scale and producing wall-to-wall NEE estimates across multiple biomes. Our estimates may provide an independent dataset from simulations with biogeochemical models and inverse modeling approaches for examining the spatiotemporal patterns of NEE and constraining terrestrial carbon budgets for large areas.

  18. The influence of cockchafer larvae on net soil methane fluxes under different vegetation types - a mesocosm study

    Science.gov (United States)

    Görres, Carolyn-Monika; Kammann, Claudia; Chesmore, David; Müller, Christoph

    2017-04-01

    The influence of land-use associated pest insects on net soil CH4 fluxes has received little attention thus far, although e.g. soil-dwelling Scarabaeidae larvae are qualitatively known to emit CH4. The project "CH4ScarabDetect" aims to provide the first quantitative estimate of the importance of soil-dwelling larvae of two important European agricultural and forest pest insect species - the common cockchafer (Melolontha melolontha) and the forest cockchafer (M. hippocastani) - for net soil CH4 fluxes. Here we present a mesocosm study within "CH4ScarabDetect" which tests the influence of different abundances of common cockchafer larvae on net soil CH4 fluxes under different vegetation types. In August 2016, 27 PVC boxes with a base area of 50 cm x 50 cm and a height of 40 cm were buried in planting beds previously used for cultivating vegetables. The bottom of each box was filled with a 10 cm thick layer of loam which was then covered with a 25 cm thick layer of loamy sand. The soil was hand-sieved prior to filling the boxes to remove any macrofauna. The mesocosms were planted with either turf, carrots or a combination of both. Of the resulting nine replicates per vegetation type, six were infested with one cockchafer larvae each in November 2016. In three of these infested mesocosms, the larvae abundance will be further increased to three in May 2017. This mesocosm study will continue until October 2017 during which measurements of net soil CH4 fluxes will be conducted with the chamber flux method twice per month. For the in situ separation of gross CH4 production and gross CH4 oxidation, the chamber method will be combined with a 13CH4 isotope pool dilution technique. Methane concentrations and their isotopic signatures in the collected gas samples will be analysed with a state-of-the-art CRDS analyzer (cavity ring-down spectroscopy, G2201-i) equipped with the Small Sample Isotope Module 2 - A0314 (Picarro Inc., USA). Different combinations of larvae abundance and

  19. Methane Bubble Size Distributions, Flux, and Dissolution in a Freshwater Lake.

    Science.gov (United States)

    Delwiche, Kyle B; Hemond, Harold F

    2017-12-05

    The majority of methane produced in many anoxic sediments is released via ebullition. These bubbles are subject to dissolution as they rise, and dissolution rates are strongly influenced by bubble size. Current understanding of natural methane bubble size distributions is limited by the difficulty in measuring bubble sizes over wide spatial or temporal scales. Our custom optical bubble size sensors recorded bubble sizes and release timing at 8 locations in Upper Mystic Lake, MA continuously for 3 months. Bubble size distributions were spatially heterogeneous even over relatively small areas experiencing similar flux, suggesting that localized sediment conditions are important to controlling bubble size. There was no change in bubble size distributions over the 3 month sampling period, but mean bubble size was positively correlated with daily ebullition flux. Bubble data was used to verify the performance of a widely used bubble dissolution model, and the model was then used to estimate that bubble dissolution accounts for approximately 10% of methane accumulated in the hypolimnion during summer stratification, and at most 15% of the diffusive air-water-methane flux from the epilimnion.

  20. Mass flux calculations show strong allochthonous support of freshwater zooplankton production is unlikely.

    Directory of Open Access Journals (Sweden)

    Michael T Brett

    Full Text Available Many studies have concluded terrestrial carbon inputs contribute 20-70% of the carbon supporting zooplankton and fish production in lakes. Conversely, it is also known that terrestrial carbon inputs are of very low nutritional quality and phytoplankton are strongly preferentially utilized by zooplankton. Because of its low quality, substantial terrestrial support of zooplankton production in lakes is only conceivable when terrigenous organic matter inputs are much larger than algal production. We conducted a quantitative analysis of terrestrial carbon mass influx and algal primary production estimates for oligo/mesotrophic lakes (i.e., TP ≤ 20 µg L(-1. In keeping with the principle of mass conservation, only the flux of terrestrial carbon retained within lakes can be utilized by zooplankton. Our field data compilation showed the median (inter-quartile range terrestrial particulate organic carbon (t-POC, available dissolved organic carbon (t-DOC inputs, and in-lake bacterial and algal production were 11 (8-17, 34 (11-78, 74 (37-165, and 253 (115-546 mg C m(-2 d(-1, respectively. Despite the widespread view that terrestrial inputs dominate the carbon flux of many lakes, our analysis indicates algal production is a factor 4-7 greater than the available flux of allochthonous basal resources in low productivity lakes. Lakes with high loading of t-DOC also have high hydraulic flushing rates. Because t-DOC is processed, i.e., mineralized or lost to the sediments, in lakes at ≈ 0.1% d(-1, in systems with the highest t-DOC inputs (i.e., 1000 mg m(-2 d(-1 a median of 98% of the t-DOC flux is advected and therefore is not available to support zooplankton production. Further, advection is the primary fate of t-DOC in lakes with hydraulic retention times <3 years. When taking into account the availability and quality of terrestrial and autochthonous fluxes, this analysis indicates ≈ 95-99% of aquatic herbivore production is supported by in

  1. Mass flux calculations show strong allochthonous support of freshwater zooplankton production is unlikely.

    Science.gov (United States)

    Brett, Michael T; Arhonditsis, George B; Chandra, Sudeep; Kainz, Martin J

    2012-01-01

    Many studies have concluded terrestrial carbon inputs contribute 20-70% of the carbon supporting zooplankton and fish production in lakes. Conversely, it is also known that terrestrial carbon inputs are of very low nutritional quality and phytoplankton are strongly preferentially utilized by zooplankton. Because of its low quality, substantial terrestrial support of zooplankton production in lakes is only conceivable when terrigenous organic matter inputs are much larger than algal production. We conducted a quantitative analysis of terrestrial carbon mass influx and algal primary production estimates for oligo/mesotrophic lakes (i.e., TP ≤ 20 µg L(-1)). In keeping with the principle of mass conservation, only the flux of terrestrial carbon retained within lakes can be utilized by zooplankton. Our field data compilation showed the median (inter-quartile range) terrestrial particulate organic carbon (t-POC), available dissolved organic carbon (t-DOC) inputs, and in-lake bacterial and algal production were 11 (8-17), 34 (11-78), 74 (37-165), and 253 (115-546) mg C m(-2) d(-1), respectively. Despite the widespread view that terrestrial inputs dominate the carbon flux of many lakes, our analysis indicates algal production is a factor 4-7 greater than the available flux of allochthonous basal resources in low productivity lakes. Lakes with high loading of t-DOC also have high hydraulic flushing rates. Because t-DOC is processed, i.e., mineralized or lost to the sediments, in lakes at ≈ 0.1% d(-1), in systems with the highest t-DOC inputs (i.e., 1000 mg m(-2) d(-1)) a median of 98% of the t-DOC flux is advected and therefore is not available to support zooplankton production. Further, advection is the primary fate of t-DOC in lakes with hydraulic retention times <3 years. When taking into account the availability and quality of terrestrial and autochthonous fluxes, this analysis indicates ≈ 95-99% of aquatic herbivore production is supported by in-lake primary

  2. Quantifying the impact of freshwater diatom productivity on silicon isotopes and silicon fluxes: Lake Myvatn, Iceland

    Science.gov (United States)

    Opfergelt, S.; Eiriksdottir, E. S.; Burton, K. W.; Einarsson, A.; Siebert, C.; Gislason, S. R.; Halliday, A. N.

    2011-05-01

    Diatom productivity in the oceans plays a crucial role in the carbon cycle, but is strongly dependent upon the continental silicon supply. However, the relative influence of weathering and biological processes on continental Si fluxes remains poorly constrained. This study aims to quantify the impact of terrestrial diatom productivity on Si fluxes to the ocean. Lake Myvatn in North Iceland is one of the most productive lakes in the Northern Hemisphere, with nutrient-rich waters almost uniquely sourced by groundwater. The primary production is mainly controlled by diatom growth but also by cyanobacteria, and the lake output is via a single river, thereby providing a relatively simple natural laboratory to quantify the impact of diatom growth on the chemistry and Si budget of lake waters. Silicon stable isotopes (δ 30Si) provide a tracer of this biocycling, and have been measured in groundwater inputs to the lake, and in time-series monitoring of waters at the lake outlet. The δ 30Si values at the outlet range from + 0.70 ± 0.08 to + 1.42 ± 0.06‰, which is significantly heavier than the groundwater input (average cold and hot springs: + 0.50 ± 0.17‰, 2SD) and consistent with the preferential uptake of light Si isotopes by diatoms. The δ 30Si value at the outlet increases by up to 0.9‰ in spring and autumn relative to the Si isotope composition of the inflow. These seasonal diatom blooms can be modeled by an open system of Si uptake and affect Si fluxes at the outlet of the lake by up to 79%, or 53% integrated over the year. In the summer a shift to lighter δ 30Si values is correlated with a higher pH, which results in dissolution of diatoms releasing light Si isotopes. From mass balance, this seasonal diatom dissolution affects Si fluxes by up to 33%, but is limited to 3.7% integrated over the year. These results clearly illustrate that biological activity can have a significant impact on both isotope composition and elemental abundance of continental

  3. Inferring CO2 Fluxes from OCO-2 for Assimilation into Land Surface Models to Calculate Net Ecosystem Exchange

    Science.gov (United States)

    Prouty, R.; Radov, A.; Halem, M.; Nearing, G. S.

    2016-12-01

    Investigations of mid to high latitude atmospheric CO2 show a growing seasonal amplitude. Land surface models poorly predict net ecosystem exchange (NEE) and are unable to substantiate these sporadic observations. An investigation of how the biosphere has reacted to changes in atmospheric CO2 is essential to our understanding of potential climate-vegetation feedbacks. A global, seasonal investigation of CO2-flux is then necessary in order to assimilate into land surface models for improving the prediction of annual NEE. The Atmospheric Radiation Measurement program (ARM) of DOE collects CO2-flux measurements (in addition to CO2 concentration and various other meteorological quantities) at several towers located around the globe at half hour temporal frequencies. CO2-fluxes are calculated via the eddy covariance technique, which utilizes CO2-densities and wind velocities to calculate CO2-fluxes. The global coverage of CO2 concentrations as provided by the Orbiting Carbon Observatory (OCO-2) provide satellite-derived CO2 concentrations all over the globe. A framework relating the satellite-inferred CO2 concentrations collocated with the ground-based ARM as well as Ameriflux stations would enable calculations of CO2-fluxes far from the station sites around the entire globe. Regression techniques utilizing deep-learning neural networks may provide such a framework. Additionally, meteorological reanalysis allows for the replacement of the ARM multivariable meteorological variables needed to infer the CO2-fluxes. We present the results of inferring CO2-fluxes from OCO-2 CO2 concentrations for a two year period, Sept. 2014- Sept. 2016 at the ARM station located near Oklahoma City. A feed-forward neural network (FFNN) is used to infer relationships between the following data sets: F([ARM CO2-density], [ARM Meteorological Data]) = [ARM CO2-Flux] F([OCO-2 CO2-density],[ARM Meteorological Data]) = [ARM CO2-Flux] F([ARM CO2-density],[Meteorological Reanalysis]) = [ARM CO2-Flux

  4. Dietary supplementation of branched-chain amino acids increases muscle net amino acid fluxes through elevating their substrate availability and intramuscular catabolism in young pigs.

    Science.gov (United States)

    Zheng, Liufeng; Zuo, Fangrui; Zhao, Shengjun; He, Pingli; Wei, Hongkui; Xiang, Quanhang; Pang, Jiaman; Peng, Jian

    2017-04-01

    Branched-chain amino acids (BCAA) have been clearly demonstrated to have anabolic effects on muscle protein synthesis. However, little is known about their roles in the regulation of net AA fluxes across skeletal muscle in vivo. This study was aimed to investigate the effect and related mechanisms of dietary supplementation of BCAA on muscle net amino acid (AA) fluxes using the hindlimb flux model. In all fourteen 4-week-old barrows were fed reduced-protein diets with or without supplemental BCAA for 28 d. Pigs were implanted with carotid arterial, femoral arterial and venous catheters, and fed once hourly with intraarterial infusion of p-amino hippurate. Arterial and venous plasma and muscle samples were obtained for the measurement of AA, branched-chain α-keto acids (BCKA) and 3-methylhistidine (3-MH). Metabolomes of venous plasma were determined by HPLC-quadrupole time-of-flight-MS. BCAA-supplemented group showed elevated muscle net fluxes of total essential AA, non-essential AA and AA. As for individual AA, muscle net fluxes of each BCAA and their metabolites (alanine, glutamate and glutamine), along with those of histidine, methionine and several functional non-essential AA (glycine, proline and serine), were increased by BCAA supplementation. The elevated muscle net AA fluxes were associated with the increase in arterial and intramuscular concentrations of BCAA and venous metabolites including BCKA and free fatty acids, and were also related to the decrease in the intramuscular concentration of 3-MH. Correlation analysis indicated that muscle net AA fluxes are highly and positively correlated with arterial BCAA concentrations and muscle net BCKA production. In conclusion, supplementing BCAA to reduced-protein diet increases the arterial concentrations and intramuscular catabolism of BCAA, both of which would contribute to an increase of muscle net AA fluxes in young pigs.

  5. Net primary production and seasonal CO2 and CH4 fluxes in a Trapa natans L. meadow

    Directory of Open Access Journals (Sweden)

    Marco BARTOLI

    2010-08-01

    Full Text Available The main hypothesis of this work is that Trapa natans L. and similar floating leaved macrophytes are only temporary sinks of atmospheric carbon dioxide and that they favour water hypoxia and large methane efflux from sediment to the atmosphere, due to their shading effect and scarce ability to transfer oxygen to submerged tissues. For this purpose, from April to August 2005, T. natans production, dissolved O2, CO2 and CH4 concentrations in the water column and CO2 and CH4 fluxes across the wateratmosphere interface were measured in an oxbow lake (Lanca di Po, Northern Italy where a monospecific floating mat of water chestnut develops. Net primary production by T. natans was determined via biomass harvesting while gas fluxes were determined via short-term incubations of light and dark floating chambers. From July onwards, when the water surface of the oxbow lake was entirely colonized by the plant, the dense canopy resulted in a physical barrier for light and water reareation. As a consequence of sediment and plant respiration, persistent hypoxia and often anoxia, and CO2 and CH4 supersaturation occurred in the water column. Net primary production of T. natans, calculated at peak biomass, was 13.05 ± 0.32 mol CO2 m-2. The T. natans mat was a net sink for atmospheric CO2 from mid June to mid August, with an uptake peak measured at the beginning of July (229 mmol m-2 d-1; estimated net ecosystem metabolism was ≤10.09 ± 1.90 mol CO2 m-2. Contextually, during the vegetative period of T. natans, the oxbow lake was a net source of methane (9.52 ± 2.10 mol m-2, and the resulting CH4 to CO2 flux ratio across the water-atmosphere interface was ≥0.94. The large methane release was probably due to the persistent hypoxia and anoxia induced by the T. natans meadow, which uncoupled methane production from methane oxidation.

  6. Net ecosystem exchange and energy fluxes measured with the eddy covariance technique in a western Siberian bog

    Directory of Open Access Journals (Sweden)

    P. Alekseychik

    2017-08-01

    Full Text Available Very few studies of ecosystem–atmosphere exchange involving eddy covariance data have been conducted in Siberia, with none in the western Siberian middle taiga. This work provides the first estimates of carbon dioxide (CO2 and energy budgets in a typical bog of the western Siberian middle taiga based on May–August measurements in 2015. The footprint of measured fluxes consisted of a homogeneous mixture of tree-covered ridges and hollows with the vegetation represented by typical sedges and shrubs. Generally, the surface exchange rates resembled those of pine-covered bogs elsewhere. The surface energy balance closure approached 100 %. Net CO2 uptake was comparatively high, summing up to 202 gC m−2 for the four measurement months, while the Bowen ratio was seasonally stable at 28 %. The ecosystem turned into a net CO2 source during several front passage events in June and July. The periods of heavy rain helped keep the water table at a sustainably high level, preventing a usual drawdown in summer. However, because of the cloudy and rainy weather, the observed fluxes might rather represent the special weather conditions of 2015 than their typical magnitudes.

  7. Forest cockchafer larvae as methane production hotspots in soils and their importance for net soil methane fluxes

    Science.gov (United States)

    Görres, Carolyn-Monika; Kammann, Claudia; Murphy, Paul; Müller, Christoph

    2016-04-01

    Certain groups of soil invertebrates, namely scarab beetles and millipedes, are capable of emitting considerable amounts of methane due to methanogens inhabiting their gut system. It was already pointed out in the early 1990's, that these groups of invertebrates may represent a globally important source of methane. However, apart from termites, the importance of invertebrates for the soil methane budget is still unknown. Here, we present preliminary results of a laboratory soil incubation experiment elucidating the influence of forest cockchafer larvae (Melolontha hippocastani FABRICIUS) on soil methane cycling. In January/February 2016, two soils from two different management systems - one from a pine forest (extensive use) and one from a vegetable field (intensive use) - were incubated for 56 days either with or without beetle larvae. Net soil methane fluxes and larvae methane emissions together with their stable carbon isotope signatures were quantified at regular intervals to estimate gross methane production and gross methane oxidation in the soils. The results of this experiment will contribute to testing the hypothesis of whether methane production hotspots can significantly enhance the methane oxidation capacity of soils. Forest cockchafer larvae are only found in well-aerated sandy soils where one would usually not suspect relevant gross methane production. Thus, besides quantifying their contribution to net soil methane fluxes, they are also ideal organisms to study the effect of methane production hotspots on overall soil methane cycling. Funding support: Reintegration grant of the German Academic Exchange Service (DAAD) (#57185798).

  8. Applying linear programming to estimate fluxes in ecosystems or food webs: An example from the herpetological assemblage of the freshwater Everglades

    Science.gov (United States)

    Diffendorfer, James E.; Richards, Paul M.; Dalrymple, George H.; DeAngelis, Donald L.

    2001-01-01

    We present the application of Linear Programming for estimating biomass fluxes in ecosystem and food web models. We use the herpetological assemblage of the Everglades as an example. We developed food web structures for three common Everglades freshwater habitat types: marsh, prairie, and upland. We obtained a first estimate of the fluxes using field data, literature estimates, and professional judgment. Linear programming was used to obtain a consistent and better estimate of the set of fluxes, while maintaining mass balance and minimizing deviations from point estimates. The results support the view that the Everglades is a spatially heterogeneous system, with changing patterns of energy flux, species composition, and biomasses across the habitat types. We show that a food web/ecosystem perspective, combined with Linear Programming, is a robust method for describing food webs and ecosystems that requires minimal data, produces useful post-solution analyses, and generates hypotheses regarding the structure of energy flow in the system.

  9. Year-round CH4 and CO2 flux dynamics in two contrasting freshwater ecosystems of the subarctic

    Directory of Open Access Journals (Sweden)

    M. Jammet

    2017-11-01

    Full Text Available Lakes and wetlands, common ecosystems of the high northern latitudes, exchange large amounts of the climate-forcing gases methane (CH4 and carbon dioxide (CO2 with the atmosphere. The magnitudes of these fluxes and the processes driving them are still uncertain, particularly for subarctic and Arctic lakes where direct measurements of CH4 and CO2 emissions are often of low temporal resolution and are rarely sustained throughout the entire year. Using the eddy covariance method, we measured surface–atmosphere exchange of CH4 and CO2 during 2.5 years in a thawed fen and a shallow lake of a subarctic peatland complex. Gas exchange at the fen exhibited the expected seasonality of a subarctic wetland with maximum CH4 emissions and CO2 uptake in summer, as well as low but continuous emissions of CH4 and CO2 throughout the snow-covered winter. The seasonality of lake fluxes differed, with maximum CO2 and CH4 flux rates recorded at spring thaw. During the ice-free seasons, we could identify surface CH4 emissions as mostly ebullition events with a seasonal trend in the magnitude of the release, while a net CO2 flux indicated photosynthetic activity. We found correlations between surface CH4 emissions and surface sediment temperature, as well as between diel CO2 uptake and diel solar input. During spring, the breakdown of thermal stratification following ice thaw triggered the degassing of both CH4 and CO2. This spring burst was observed in 2 consecutive years for both gases, with a large inter-annual variability in the magnitude of the CH4 degassing. On the annual scale, spring emissions converted the lake from a small CO2 sink to a CO2 source: 80 % of total annual carbon emissions from the lake were emitted as CO2. The annual total carbon exchange per unit area was highest at the fen, which was an annual sink of carbon with respect to the atmosphere. Continuous respiration during the winter partly counteracted the fen summer sink by accounting for

  10. Year-round CH4 and CO2 flux dynamics in two contrasting freshwater ecosystems of the subarctic

    Science.gov (United States)

    Jammet, Mathilde; Dengel, Sigrid; Kettner, Ernesto; Parmentier, Frans-Jan W.; Wik, Martin; Crill, Patrick; Friborg, Thomas

    2017-11-01

    Lakes and wetlands, common ecosystems of the high northern latitudes, exchange large amounts of the climate-forcing gases methane (CH4) and carbon dioxide (CO2) with the atmosphere. The magnitudes of these fluxes and the processes driving them are still uncertain, particularly for subarctic and Arctic lakes where direct measurements of CH4 and CO2 emissions are often of low temporal resolution and are rarely sustained throughout the entire year. Using the eddy covariance method, we measured surface-atmosphere exchange of CH4 and CO2 during 2.5 years in a thawed fen and a shallow lake of a subarctic peatland complex. Gas exchange at the fen exhibited the expected seasonality of a subarctic wetland with maximum CH4 emissions and CO2 uptake in summer, as well as low but continuous emissions of CH4 and CO2 throughout the snow-covered winter. The seasonality of lake fluxes differed, with maximum CO2 and CH4 flux rates recorded at spring thaw. During the ice-free seasons, we could identify surface CH4 emissions as mostly ebullition events with a seasonal trend in the magnitude of the release, while a net CO2 flux indicated photosynthetic activity. We found correlations between surface CH4 emissions and surface sediment temperature, as well as between diel CO2 uptake and diel solar input. During spring, the breakdown of thermal stratification following ice thaw triggered the degassing of both CH4 and CO2. This spring burst was observed in 2 consecutive years for both gases, with a large inter-annual variability in the magnitude of the CH4 degassing. On the annual scale, spring emissions converted the lake from a small CO2 sink to a CO2 source: 80 % of total annual carbon emissions from the lake were emitted as CO2. The annual total carbon exchange per unit area was highest at the fen, which was an annual sink of carbon with respect to the atmosphere. Continuous respiration during the winter partly counteracted the fen summer sink by accounting for, as both CH4 and CO2, 33

  11. Statistical partitioning of a three-year time series of direct urban net CO2 flux measurements into biogenic and anthropogenic components

    Science.gov (United States)

    Menzer, Olaf; McFadden, Joseph P.

    2017-12-01

    Eddy covariance flux measurements are increasingly used to quantify the net carbon dioxide exchange (FC) in urban areas. FC represents the sum of anthropogenic emissions, biogenic carbon release from plant and soil respiration, and carbon uptake by plant photosynthesis. When FC is measured in natural ecosystems, partitioning into respiration and photosynthesis is a well-established procedure. In contrast, few studies have partitioned FC at urban flux tower sites due to the difficulty of accounting for the temporal and spatial variability of the multiple sources and sinks. Here, we partitioned a three-year time series of flux measurements from a suburban neighborhood of Minneapolis-Saint Paul, Minnesota, USA. We segregated FC into one subset that captured fluxes from a residential neighborhood and into another subset that covered a golf course. For both land use types we modeled anthropogenic flux components based on winter data and extrapolated them to the growing season, to estimate gross primary production (GPP) and ecosystem respiration (Reco) at half-hourly, daily, monthly and annual scales. During the growing season, GPP had the largest magnitude (up to - 9.83 g C m-2 d-1) of any component CO2 flux, biogenic or anthropogenic, and both GPP and Reco were more dynamic seasonally than anthropogenic fluxes. Owing to the balancing of Reco against GPP, and the limitations of the growing season in a cold temperate climate zone, the net biogenic flux was only 1.5%-4.5% of the anthropogenic flux in the dominant residential land use type, and between 25%-31% of the anthropogenic flux in highly managed greenspace. Still, the vegetation sink at our site was stronger than net anthropogenic emissions on 16-20 days over the residential area and on 66-91 days over the recreational area. The reported carbon flux sums and dynamics are a critical step toward developing models of urban CO2 fluxes within and across cities that differ in vegetation cover.

  12. Differential responses in ammonia excretion, sodium fluxes and gill permeability explain different sensitivities to acute high environmental ammonia in three freshwater teleosts.

    Science.gov (United States)

    Liew, Hon Jung; Sinha, Amit Kumar; Nawata, C Michele; Blust, Ronny; Wood, Chris M; De Boeck, Gudrun

    2013-01-15

    We examined the acute physiological responses to high environmental ammonia (HEA), particularly the linkages between branchial ammonia fluxes and unidirectional Na(+) fluxes, as well as urea excretion, cortisol, and indicators of gill permeability in three freshwater teleosts differing in their sensitivities to ammonia; the highly sensitive salmonid Oncorhynchus mykiss (rainbow trout), the less sensitive cyprinid Cyprinus carpio (common carp) and the highly resistant cyprinid Carassius auratus (goldfish). Fish were acutely exposed to two sub-lethal ammonia concentrations (as NH(4)HCO(3)) at pH 7.9: 1 mM for a period of 12 h, identical for all species, and 5 mM for the cyprinids and 1.4 mM for the trout for 3 h. Elevation of plasma cortisol at both levels of HEA was apparent in all species. At 1 mM, ammonia excretion (J(amm)) was inhibited to a greater extent in trout than cyprinids and concurrently a significantly higher plasma ammonia level was evident in trout. However J(amm) was reversed in all species at 5 or 1.4 mM. Goldfish showed a significant increase in urea excretion rate (J(urea)) during HEA exposure. In carp and trout, neither level of HEA elevated J(urea) but urea production was increased as evidenced by a considerable elevation of plasma urea. At 1mM HEA, Na(+) imbalance became progressively more severe in trout and carp due to a stimulation of unidirectional Na(+) efflux (J(out)(Na)) without a concomitant increase in unidirectional Na(+) influx (J(in)(Na)). Additionally, a transient reduction of J(in)(Na) was evident in trout. Goldfish showed an opposite trend for J(out)(Na) with reduced efflux rates and a positive Na(+) balance during the first few hours of HEA. However, after 12 h of exposure, both J(in)(Na) and J(out)(Na) were also increased in both carp and goldfish, whereas only J(out)(Na) was increased in trout, leading to a net Na(+) loss. Na(+) homeostasis was entirely disrupted in all three species when subjected to the 5 or 1.4 mM ammonia

  13. Modulation of Rh glycoproteins, ammonia excretion and Na+ fluxes in three freshwater teleosts when exposed chronically to high environmental ammonia.

    Science.gov (United States)

    Sinha, Amit Kumar; Liew, Hon Jung; Nawata, C Michele; Blust, Ronny; Wood, Chris M; De Boeck, Gudrun

    2013-08-01

    We investigated relationships among branchial unidirectional Na(+) fluxes, ammonia excretion, urea excretion, plasma ammonia, plasma cortisol, and gill transporter expression and function in three freshwater fish differing in their sensitivity to high environmental ammonia (HEA). The highly ammonia-sensitive salmonid Oncorhynchus mykiss (rainbow trout), the less ammonia-sensitive cyprinid Cyprinus carpio (common carp) and the highly ammonia-resistant cyprinid Carassius auratus (goldfish) were exposed chronically (12-168 h) to 1 mmol l(-1) ammonia (as NH4HCO3; pH 7.9). During HEA exposure, carp and goldfish elevated ammonia excretion (JAmm) and Na(+) influx rates ( ) while trout experienced higher plasma ammonia (TAmm) and were only able to restore control rates of JAmm and . All three species exhibited increases in Na(+) efflux rate ( ). At the molecular level, there was evidence for activation of a 'Na(+)/NH4(+) exchange metabolon' probably in response to elevated plasma cortisol and TAmm, though surprisingly, some compensatory responses preceded molecular responses in all three species. Expression of Rhbg, Rhcg (Rhcg-a and Rhcg-b), H(+)-ATPase (V-type, B-subunit) and Na(+)/K(+)-ATPase (NKA) mRNA was upregulated in goldfish, Rhcg-a and NKA in carp, and Rhcg2, NHE-2 (Na(+)/H(+) exchanger) and H(+)-ATPase in trout. Branchial H(+)-ATPase activity was elevated in goldfish and trout, and NKA activity in goldfish and carp, but NKA did not appear to function preferentially as a Na(+)/NH4(+)-ATPase in any species. Goldfish alone increased urea excretion rate during HEA, in concert with elevated urea transporter mRNA expression in gills. Overall, goldfish showed more effective compensatory responses towards HEA than carp, while trout were least effective.

  14. Interannual variability of net ecosystem productivity in forests is explained by carbon flux phenology in autumn

    DEFF Research Database (Denmark)

    Wu, Chaoyang; Chen, Xi Jing; Black, T. Andrew

    2013-01-01

    ) and 13 evergreen needleleaf forests (ENF) across North America and Europe (212 site‐years) were used to explore the relationships between the yearly anomalies of annual NEP and several carbon flux based phenological indicators, including the onset/end of the growing season, onset/end of the carbon uptake...... period, the spring lag (time interval between the onset of growing season and carbon uptake period) and the autumn lag (time interval between the end of the carbon uptake period and the growing season). Meteorological variables, including global shortwave radiation, air temperature, soil temperature...

  15. The Net Carbon Flux due to Deforestation and Forest Re-Growth in the Brazilian Amazon: Analysis using a Process-Based Model

    Science.gov (United States)

    Hirsch, A. I.; Little, W. S.; Houghton, R. A.; Scott, N. A.; White, J. D.

    2004-01-01

    We developed a process-based model of forest growth, carbon cycling, and land cover dynamics named CARLUC (for CARbon and Land Use Change) to estimate the size of terrestrial carbon pools in terra firme (non-flooded) forests across the Brazilian Legal Amazon and the net flux of carbon resulting from forest disturbance and forest recovery from disturbance. Our goal in building the model was to construct a relatively simple ecosystem model that would respond to soil and climatic heterogeneity that allows us to study of the impact of Amazonian deforestation, selective logging, and accidental fire on the global carbon cycle. This paper focuses on the net flux caused by deforestation and forest re-growth over the period from 1970-1998. We calculate that the net flux to the atmosphere during this period reached a maximum of approx. 0.35 PgC/yr (1PgC = 1 x 10(exp I5) gC) in 1990, with a cumulative release of approx. 7 PgC from 1970- 1998. The net flux is higher than predicted by an earlier study by a total of 1 PgC over the period 1989-1 998 mainly because CARLUC predicts relatively high mature forest carbon storage compared to the datasets used in the earlier study. Incorporating the dynamics of litter and soil carbon pools into the model increases the cumulative net flux by approx. 1 PgC from 1970-1998, while different assumptions about land cover dynamics only caused small changes. The uncertainty of the net flux, calculated with a Monte-Carlo approach, is roughly 35% of the mean value (1 SD).

  16. Iron fertilization enhanced net community production but not downward particle flux during the Southern Ocean iron fertilization experiment LOHAFEX

    Science.gov (United States)

    Martin, Patrick; van der Loeff, Michiel Rutgers; Cassar, Nicolas; Vandromme, Pieter; d'Ovidio, Francesco; Stemmann, Lars; Rengarajan, R.; Soares, Melena; González, Humberto E.; Ebersbach, Friederike; Lampitt, Richard S.; Sanders, Richard; Barnett, Bruce A.; Smetacek, Victor; Naqvi, S. Wajih A.

    2013-09-01

    closed eddy core in the Subantarctic Atlantic Ocean was fertilized twice with two tons of iron (as FeSO4), and the 300 km2 fertilized patch was studied for 39 days to test whether fertilization enhances downward particle flux into the deep ocean. Chlorophyll a and primary productivity doubled after fertilization, and photosynthetic quantum yield (FV/FM) increased from 0.33 to ≥0.40. Silicic acid (artificially fertilized bloom with very low diatom biomass. Net community production (NCP) inside the patch, estimated from O2:Ar ratios, averaged 21 mmol POC m-2 d-1, probably ±20%. 234Th profiles implied constant export of 6.3 mmol POC m-2 d-1 in the patch, similar to unfertilized waters. The difference between NCP and 234Th-derived export partly accumulated in the mixed layer and was partly remineralized between the mixed layer and 100 m. Neutrally buoyant sediment traps at 200 and 450 m inside and outside the patch caught mostly fertilization. Our data thus indicate intense flux attenuation between 100 and 200 m, and probably between the mixed layer and 100 m. We attribute the lack of fertilization-induced export to silicon limitation of diatoms and reprocessing of sinking particles by detritus feeders. Our data are consistent with the view that nitrate-rich but silicate-deficient waters are not poised for enhanced particle export upon iron addition.

  17. Effect of resistant starch on net portal-drained viscera flux of glucose, volatile fatty acids, urea, and ammonia in growing pigs

    NARCIS (Netherlands)

    Meulen, van der J.; Bakker, G.C.M.; Bakker, J.G.M.; Visser, de H.; Jongbloed, A.W.; Everts, H.

    1997-01-01

    Net portal-drained viscera (PDV) flux of glucose, VFA, ammonia, and urea was determined in pigs fed diets with or without resistant starch. Diets consisted of 65% cornstarch (diet CS), 32.5% cornstarch and 32.5% raw potato starch (diet CPS), or 65% raw potato starch (diet PS); the remaining 35%

  18. Biogenic carbon fluxes from global agricultural production and consumption: Gridded, annual estimates of net ecosystem carbon exchange

    Science.gov (United States)

    Wolf, J.; West, T. O.; le Page, Y.; Thomson, A. M.

    2014-12-01

    Quantification of biogenic carbon fluxes from agricultural lands is needed to generate globally consistent bottom-up estimates for carbon monitoring and model input. We quantify agricultural carbon fluxes associated with annual (starting in 1961) crop net primary productivity (NPP), harvested biomass, and human and livestock consumption and emissions, with estimates of uncertainty, by applying region- and species-specific carbon parameters to annual crop, livestock, food and trade inventory data, and generate downscaled, gridded (0.05 degree resolution) representations of these fluxes. In 2011, global crop NPP was 5.25 ± 0.46 Pg carbon (excluding root exudates), of which 2.05 ± 0.051 Pg carbon was harvested as primary crops; an additional 0.54 Pg of crop residue carbon was collected for livestock fodder. In 2011, total livestock feed intake was 2.42 ± 0.21 Pg carbon, of which 2.31 ± 0.21 Pg carbon was emitted as carbon dioxide and 0.072 ± 0.005 Pg carbon was emitted as methane. We estimate that livestock grazed 1.18 Pg carbon from non-crop lands in 2011, representing 48.5 % of global total feed intake. In 2009, the latest available data year, we estimate global human food intake (excluding seafood and orchard fruits and nuts) at 0.52 ± 0.03 Pg carbon, with an additional 0.24 ± 0.01 Pg carbon of food supply chain losses. Trends in production and consumption of agricultural carbon between 1961 and recent years, such as increasing dominance of oilcrops and decreasing percent contribution of pasturage to total livestock feed intake, are discussed, and accounting of all agricultural carbon was done for the years 2005 and 2009. Gridded at 0.05 degree resolution, these quantities represent local uptake and release of agricultural biogenic carbon (e.g. biomass production and removal, residue and manure inputs to soils) and may be used with other gridded data to help estimate current and future changes in soil organic carbon.

  19. A Comparison of Three Gap Filling Techniques for Eddy Covariance Net Carbon Fluxes in Short Vegetation Ecosystems

    Directory of Open Access Journals (Sweden)

    Xiaosong Zhao

    2015-01-01

    Full Text Available Missing data is an inevitable problem when measuring CO2, water, and energy fluxes between biosphere and atmosphere by eddy covariance systems. To find the optimum gap-filling method for short vegetations, we review three-methods mean diurnal variation (MDV, look-up tables (LUT, and nonlinear regression (NLR for estimating missing values of net ecosystem CO2 exchange (NEE in eddy covariance time series and evaluate their performance for different artificial gap scenarios based on benchmark datasets from marsh and cropland sites in China. The cumulative errors for three methods have no consistent bias trends, which ranged between −30 and +30 mgCO2 m−2 from May to October at three sites. To reduce sum bias in maximum, combined gap-filling methods were selected for short vegetation. The NLR or LUT method was selected after plant rapidly increasing in spring and before the end of plant growing, and MDV method was used to the other stage. The sum relative error (SRE of optimum method ranged between −2 and +4% for four-gap level at three sites, except for 55% gaps at soybean site, which also obviously reduced standard deviation of error.

  20. In vivo modulation of rat distal tubule net HCO3 flux by VIP, isoproterenol, angiotensin II, and ADH.

    Science.gov (United States)

    Levine, D Z; Iacovitti, M; Buckman, S; Harrison, V

    1994-06-01

    To examine the in vivo effects of agonists reported to influence bicarbonate flux (JtCO2), microperfusion experiments were carried out on distal tubules of normally fed or overnight-fasted rats. As we previously reported, distal tubules from fed rats reabsorbed no bicarbonate, whereas overnight-fasted rats consistently reabsorbed bicarbonate (JtCO2 10 +/- 3 pmol.min-1.mm-1; P < 0.01). Vasoactive intestinal peptide and isoproterenol infused intravenously (7.3 and 4.0 micrograms.kg-1.h-1, respectively) in fasted rats suppressed JtCO2 and, in the case of vasoactive intestinal peptide, elicited net bicarbonate secretion (JtCO2 -10 +/- 2 and -4 +/- 4 pmol.min-1.mm-1, respectively). In fed rats, angiotensin II infused at a rate of 1.2 micrograms.kg-1.h-1 stimulated bicarbonate reabsorption (JtCO2 16 +/- 3 pmol.min-1.mm-1), while antidiuretic hormone infused at 0.024 micrograms.kg-1.h-1 elicited a similar response (17 +/- 4 pmol.min-1.mm-1), both values being significantly different from control. These results, therefore, demonstrate for the first time that these agonists can modulate JtCO2 at the distal tubule site in vivo and therefore may be potential regulators of systemic acid-base balance.

  1. Stability of the Atlantic overturning circulation: competition between Bering Strait freshwater flux and Agulhas heat and salt sources

    NARCIS (Netherlands)

    Weijer, W.; Ruijter, W.P.M. de; Dijkstra, H.A.

    2000-01-01

    In this study we examine the role that is played by interocean fluxes of buoyancy in stabilizing the present-day overturning circulation of the Atlantic Ocean. A 2D model of the Atlantic overturning circulation is used, in which the interocean fluxes of heat and salt (via the Bering Strait, the

  2. Sensitivity of boreal forest regional water flux and net primary production simulations to sub-grid-scale land cover complexity

    Science.gov (United States)

    Kimball, J. S.; Running, S. W.; Saatchi, S. S.

    1999-11-01

    We use a general ecosystem process model (BIOME-BGC) coupled with remote sensing information to evaluate the sensitivity of boreal forest regional evapotranspiration (ET) and net primary production (NPP) to land cover spatial scale. Simulations were conducted over a 3 year period (1994-1996) at spatial scales ranging from 30 to 50 km within the BOREAS southern modeling subarea. Simulated fluxes were spatially complex, ranging from 0.1 to 3.9 Mg C ha-1 yr-1 and from 18 to 29 cm yr-1. Biomass and leaf area index heterogeneity predominantly controlled this complexity, while biophysical differences between deciduous and coniferous vegetation were of secondary importance. Spatial aggregation of land cover characteristics resulted in mean monthly NPP estimation bias from 25 to 48% (0.11-0.20 g C m-2 d-1) and annual estimation errors from 2 to 14% (0.04-0.31 Mg C ha-1 yr-1). Error was reduced at longer time intervals because coarse scale overestimation errors during spring were partially offset by underestimation of fine scale results during summer and winter. ET was relatively insensitive to land cover spatial scale with an average bias of less than 5% (0.04 kg m-2 d-1). Factors responsible for differences in scaling behavior between ET and NPP included compensating errors for ET calculations and boreal forest spatial and temporal NPP complexity. Careful consideration of landscape spatial and temporal heterogeneity is necessary to identify and mitigate potential error sources when using plot scale information to understand regional scale patterns. Remote sensing data integrated within an ecological process model framework provides an efficient mechanism to evaluate scaling behavior, interpret patterns in coarse resolution data, and identify appropriate scales of operation for various processes.

  3. Estimation of Community Land Model parameters for an improved assessment of net carbon fluxes at European sites

    Science.gov (United States)

    Post, Hanna; Vrugt, Jasper A.; Fox, Andrew; Vereecken, Harry; Hendricks Franssen, Harrie-Jan

    2017-03-01

    The Community Land Model (CLM) contains many parameters whose values are uncertain and thus require careful estimation for model application at individual sites. Here we used Bayesian inference with the DiffeRential Evolution Adaptive Metropolis (DREAM(zs)) algorithm to estimate eight CLM v.4.5 ecosystem parameters using 1 year records of half-hourly net ecosystem CO2 exchange (NEE) observations of four central European sites with different plant functional types (PFTs). The posterior CLM parameter distributions of each site were estimated per individual season and on a yearly basis. These estimates were then evaluated using NEE data from an independent evaluation period and data from "nearby" FLUXNET sites at 600 km distance to the original sites. Latent variables (multipliers) were used to treat explicitly uncertainty in the initial carbon-nitrogen pools. The posterior parameter estimates were superior to their default values in their ability to track and explain the measured NEE data of each site. The seasonal parameter values reduced with more than 50% (averaged over all sites) the bias in the simulated NEE values. The most consistent performance of CLM during the evaluation period was found for the posterior parameter values of the forest PFTs, and contrary to the C3-grass and C3-crop sites, the latent variables of the initial pools further enhanced the quality-of-fit. The carbon sink function of the forest PFTs significantly increased with the posterior parameter estimates. We thus conclude that land surface model predictions of carbon stocks and fluxes require careful consideration of uncertain ecological parameters and initial states.

  4. Effects of particle size and dry matter content of a total mixed ration on intraruminal equilibration and net portal flux of volatile fatty acids in lactating dairy cows

    DEFF Research Database (Denmark)

    Storm, Adam Christian; Kristensen, Niels Bastian

    2010-01-01

    ration (44.3 and 53.8%). The feed DM did not affect chewing time, ruminal variables, or net portal flux of VFA. However, decreasing the FPS decreased the overall chewing and rumination times by 151 ± 55 and 135 ± 29 min/d, respectively. No effect of the reduced chewing time was observed on ruminal p...

  5. Interacting effects of elevated temperature and additional water on plant physiology and net ecosystem carbon fluxes in a high Arctic ecosystem

    Science.gov (United States)

    Maseyk, Kadmiel; Seibt, Ulrike; Lett, Céline; Lupascu, Massimo; Czimczik, Claudia; Sullivan, Patrick; Welker, Jeff

    2013-04-01

    Arctic ecosystems are experiencing temperature increases more strongly than the global average, and increases in precipitation are also expected amongst the climate impacts on this region in the future. These changes are expected to strongly influence plant physiology and soil biogeochemistry with subsequent implications for system carbon balance. We have investigated the effects of a long-term (10 years) increase in temperature, soil water and the combination of both on a tundra ecosystem at a field manipulation experiment in NW Greenland. Leaf gas exchange, chlorophyll fluorescence, carbon (C) and nitrogen (N) content and leaf isotopic composition, and leaf morphology were measured on Salix arctica plants in treatment and control plots in June-July 2011, and continuous measurements of net plant and soil fluxes of CO2 and water were made using automatic chambers coupled to a trace gas laser analyzer. Plants in the elevated temperature (T2) treatment had the highest photosynthetic capacity in terms of net CO2 assimilation rates and photosystem II efficiencies, and lowest rates of non-photochemical energy dissipation during photosynthesis. T2 plants also had the highest leaf N content, specific leaf area (SLA) and saturation light level of photosynthesis. It appears that warming increases soil N availability, which the plants direct towards increasing photosynthetic capacity and producing larger thinner leaves. On the other hand, the plants in the plots with both elevated temperatures and additional water (T2W) had the lowest photosystem II efficiencies and the highest rates of non-photochemical energy dissipation, due more to higher levels of constitutive energy dissipation than regulated thermal quenching. Watering, both in combination with higher temperatures and alone (W treatment), also reduced leaf SLA and leaf N relative to control plots. However, net photosynthetic rates remained similar to control plants, due in part to higher stomatal conductance (W) and

  6. Modification of vortex dynamics and transport properties of transitional axisymmetric jets using zero-net-mass-flux actuation

    Energy Technology Data Exchange (ETDEWEB)

    Önder, Asim; Meyers, Johan, E-mail: johan.meyers@mech.kuleuven.be [Department of Mechanical Engineering, KU Leuven, Celestijnenlaan 300A, B3001 Leuven (Belgium)

    2014-07-15

    We study the near field of a zero-net-mass-flux (ZNMF) actuated round jet using direct numerical simulations. The Reynolds number of the jet Re{sub D} = 2000 and three ZNMF actuators are used, evenly distributed over a circle, and directed towards the main jet. The actuators are triggered in phase, and have a relatively low momentum coefficient of C{sub μ} = 0.0049 each. We study four different control frequencies with Strouhal numbers ranging from St{sub D} = 0.165 to St{sub D} = 1.32; next to that, also two uncontrolled baseline cases are included in the study. We find that this type of ZNMF actuation leads to strong deformations of the near-field jet region that are very similar to those observed for non-circular jets. At the end of the jet's potential core (x/D = 5), the jet-column cross section is deformed into a hexagram-like geometry that results from strong modifications of the vortex structures. Two mechanisms lead to these modifications, i.e., (i) self-deformation of the jet's primary vortex rings started by distortions in their azimuthal curvature by the actuation, and (ii) production of side jets by the development and subsequent detachment of secondary streamwise vortex pairs. Further downstream (x/D = 10), the jet transforms into a triangular pattern, as the sharp corner regions of the hexagram entrain fluid and spread. We further investigate the global characteristics of the actuated jets. In particular when using the jet preferred frequency, i.e., St{sub D} = 0.33, parameters such as entrainment, centerline decay rate, and mean turbulent kinetic energy are significantly increased. Furthermore, high frequency actuation, i.e., St{sub D} = 1.32, is found to suppress the mechanisms leading to large scale structure growth and turbulent kinetic energy production. The simulations further include a passive scalar equation, and passive scalar mixing is also quantified and visualized.

  7. A theoretical framework for the net land-to-atmosphere CO2 flux and its implications in the definition of "emissions from land-use change"

    Directory of Open Access Journals (Sweden)

    T. Gasser

    2013-06-01

    Full Text Available We develop a theoretical framework and analysis of the net land-to-atmosphere CO2 flux in order to discuss possible definitions of "emissions from land-use change". The terrestrial biosphere is affected by two perturbations: the perturbation of the global carbon-climate-nitrogen system (CCN with elevated atmospheric CO2, climate change and nitrogen deposition; and the land-use change perturbation (LUC. Here, we progressively establish mathematical definitions of four generic components of the net land-to-atmosphere CO2 flux. The two first components are the fluxes that would be observed if only one perturbation occurred. The two other components are due to the coupling of the CCN and LUC perturbations, which shows the non-linear response of the terrestrial carbon cycle. Thanks to these four components, we introduce three possible definitions of "emissions from land-use change" that are indeed used in the scientific literature, often without clear distinctions, and we draw conclusions as for their absolute and relative behaviors. Thanks to the OSCAR v2 model, we provide quantitative estimates of the differences between the three definitions, and we find that comparing results from studies that do not use the same definition can lead to a bias of up to 20% between estimates of those emissions. After discussion of the limitations of the framework, we conclude on the three major points of this study that should help the community to reconcile modeling and observation of emissions from land-use change. The appendix mainly provides more detailed mathematical expressions of the four components of the net land-to-atmosphere CO2 flux.

  8. A theoretical framework for the net land-to-atmosphere CO2 flux and its implications in the definition of "emissions from land-use change"

    Science.gov (United States)

    Gasser, T.; Ciais, P.

    2013-06-01

    We develop a theoretical framework and analysis of the net land-to-atmosphere CO2 flux in order to discuss possible definitions of "emissions from land-use change". The terrestrial biosphere is affected by two perturbations: the perturbation of the global carbon-climate-nitrogen system (CCN) with elevated atmospheric CO2, climate change and nitrogen deposition; and the land-use change perturbation (LUC). Here, we progressively establish mathematical definitions of four generic components of the net land-to-atmosphere CO2 flux. The two first components are the fluxes that would be observed if only one perturbation occurred. The two other components are due to the coupling of the CCN and LUC perturbations, which shows the non-linear response of the terrestrial carbon cycle. Thanks to these four components, we introduce three possible definitions of "emissions from land-use change" that are indeed used in the scientific literature, often without clear distinctions, and we draw conclusions as for their absolute and relative behaviors. Thanks to the OSCAR v2 model, we provide quantitative estimates of the differences between the three definitions, and we find that comparing results from studies that do not use the same definition can lead to a bias of up to 20% between estimates of those emissions. After discussion of the limitations of the framework, we conclude on the three major points of this study that should help the community to reconcile modeling and observation of emissions from land-use change. The appendix mainly provides more detailed mathematical expressions of the four components of the net land-to-atmosphere CO2 flux.

  9. Impact of Earth's orbit and freshwater fluxes on Holocene climate mean seasonal cycle and ENSO characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Braconnot, P.; Zheng, W. [unite mixte CEA-CNRS-UVSQ, Laboratoire des Sciences du climat et de l' Environnement, Gif-sur-Yvette Cedex (France); Luan, Y. [unite mixte CEA-CNRS-UVSQ, Laboratoire des Sciences du climat et de l' Environnement, Gif-sur-Yvette Cedex (France); Chinese Academy of Sciences (CAS), State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP), Beijing (China); Graduate University of Chinese Academy of Sciences, Beijing (China); Brewer, Simon [University of Wyoming, Department of Botany, Laramie, WY (United States)

    2012-03-15

    We use a state-of-the-art 3-dimensional coupled model to investigate the relative impact of long term variations in the Holocene insolation forcing and of a freshwater release in the North Atlantic. We show that insolation has a greater effect on seasonality and La Nina events and is the major driver of sea surface temperature changes. In contrast, the variations in precipitation reflect changes in El Nino events. The impact of ice-sheet melting may have offset the impact of insolation on El Nino Southern Oscillation variability at the beginning of the Holocene. These simulations provide a coherent framework to refine the interpretation of proxy data and show that changes in seasonality may bias the projection of relationships established between proxy indicators and climate variations in the east Pacific from present day records. (orig.)

  10. Flux

    DEFF Research Database (Denmark)

    Ravn, Ib

    Med udgangspunkt i kompleksistetsforskning og studiet af selvorganiserende systemer beskriver lb Ravn den fysiske og biologiske evolution og menneskets udvikling. Han fortolker begreber som kultur, sprog, frihed, værdier, mening, smerte og det ondes problem i lyset af en procesbaseret ontologi...... kanalisering af den flux eller energi, der strømmer igennem os og giver sig til kende i vore daglige aktiviteter. Skal vores tanker, handlinger, arbejde, samvær og politiske liv organiseres efter stramme og faste regelsæt, uden slinger i valsen? Eller skal de tværtimod forløbe ganske uhindret af regler og bånd...

  11. Proton pump activity is required for active uptake of chloride in isolated amphibian skin exposed to freshwater

    DEFF Research Database (Denmark)

    Jensen, Lars Jørn; Willumsen, Niels J.; Larsen, Erik Hviid

    2002-01-01

    Net proton secretion and unidirectional chloride fluxes were measured in isolated skin of toads (Bufo bufo) and frogs (Rana esculenta) mounted in an Ussing chamber and exposed to a Ringer's solution on the serosal side and a freshwater-like solution (1-3 mM Cl-) on the external side. Active proto...

  12. Effect of climate change on flux of N and C: air-land-freshwater-marine links: synthesis.

    Science.gov (United States)

    Stuanes, Arne O; de Wit, Heleen A; Hole, Lars R; Kaste, Oyvind; Mulder, Jan; Riise, Gunnhild; Wright, Richard F

    2008-02-01

    Projected climate change might increase the deposition of nitrogen by about 10% to seminatural ecosystems in southern Norway. At Storgama, increased precipitation in the growing season increased the fluxes of total organic carbon (TOC) and total organic nitrogen (TON) in proportion to the water flux. In winter, soil temperatures near 0 degrees C, common under a snowpack, induced higher runoff of inorganic nitrogen (N) and lower runoff of TOC. By contrast, soil temperatures below freezing, caused by little snow accumulation (expected in a warmer world), reduced runoff of inorganic N, TON, and TOC. Long-term monitoring data showed that reduced snowpack can cause either decreased or increased N leaching, depending on interactions with N deposition, soil temperature regime, and winter discharge. Seasonal variation in TOC was mainly climatically controlled, whereas deposition of sulfate and nitrate (NO3) explained the long-term TOC increase. Upscaling to the river basin scale showed that the annual flux of NO3 will remain unchanged in response to climate change projections.

  13. Volume eddy-driven heat and freshwater fluxes across 47°N in the Atlantic Ocean

    Science.gov (United States)

    Stendardo, Ilaria; Müller, Vasco; Kieke, Dagmar; Myers, Paul G.; Pennelly, Clark; Rhein, Monika; Steinfeldt, Reiner

    2017-04-01

    The western subpolar North Atlantic between 45°N and 50°N is characterized by the presence of a large amount of eddies and other mesoscale events that play an important role in the local exchange and horizontal mixing of water masses. Eddies trap water with distinguished properties like temperature, salinity, oxygen and nutrients, from the region of their formation. The properties/tracers are then transported with the eddy over longer distances until the eddy gradually dissipates or abruptly decays. Thanks to eddy detection algorithms it has been possible to study the meridional transport of cold and warm water trapped within eddies as they cross 47°N and calculate the temperature fluxes across this line. In order to extend these calculations to full volume fluxes by including a vertical component, high spatial resolution temperature and salinity observations are needed. With the onset of the Argo program the number of salinity and temperature profiles dramatically increased. Although the subpolar North Atlantic is one of the most densest sampled regions in order to cope with the large seasonal to interannual variability and strong mesoscale features, the spatial and temporal coverage is not sufficient to combine each detected eddy with a respective temperature and salinity profile. However a promising method to infer high-resolution salinity and temperature data is the Gravest Empirical Mode (GEM) technique. This technique combined Argo and altimeter data to exploit the relationship between T/S profiles and dynamic height in the North Atlantic. Thanks to this method salinity and temperature time series can be determined from 1993 until nowadays with the same resolution as the altimeter data, that is daily projections onto a 1/4° Cartesian grid. The GEM method in combination with three-dimensional detection of eddies in high resolution models could help to understand the connection between eddy surface signals and the corresponding vertical structure. It also

  14. Adaptive Rule-Based Piece-Wise Regression Models for Estimating Regional Net Ecosystem Exchange in Grassland and Shrubland Ecoregions Using Regional and Flux Tower Data

    Science.gov (United States)

    Fosnight, E. A.; Wylie, B. K.; Zhang, L.

    2005-12-01

    The scientific understanding of the global carbon cycle requires quantitative documentation, monitoring, and projection of carbon stocks and fluxes at various scales across the landscape. The challenge is to develop predictive models using carbon flux towers at site-specific locations, and to extrapolate these models to landscapes and regions. We use remote sensing and national climate and soil databases within data-driven models to estimate carbon fluxes. To accommodate the study of coupled human-environmental relationships and their influences on carbon dynamics, a coherent suite of models is being developed for agricultural, wooded and wetland ecosystems within predominantly grassland and shrubland ecoregions. In previous work, we have mapped carbon fluxes in terms of Net Ecosystem Exchange (NEE), Gross Primary Production (GPP), and Respiration (Re) in the Northern Great Plains, the Sagebrush Steppes and the Kazakh Steppes at 1-km resolution and 10-day time steps. We now extend this work beyond fairly uniform ecological conditions to accommodate more complex spatial mixtures of ecological types within ecoregions. The models need to adapt to both the complexity of the environmental variables and the land cover patterns. Our rule-based models adapt to local climatic, soil and phenology through the definition of piece-wise regression models. A suite of such models is needed to capture the phenologic and climatic variability across the wide range of shrubland and grassland ecoregions that exist. The result is a multi-year time series of 1-km maps of carbon flux that are suitable for trend and anomaly analysis. We seek sensitive models that permit the effective study of localized carbon dynamics while avoiding over-fitting the available carbon flux tower measurement data. Two critical components of the project are (1) sensitivity and cross-validation studies to evaluate the internal consistencies of the models and (2) intercomparison studies to help isolate

  15. Combining tower mixing ratio and community model data to estimate regional-scale net ecosystem carbon exchange by boundary layer inversion over four flux towers in the United States

    Science.gov (United States)

    Xueri Dang; Chun-Ta Lai; David Y. Hollinger; Andrew J. Schauer; Jingfeng Xiao; J. William Munger; Clenton Owensby; James R. Ehleringer

    2011-01-01

    We evaluated an idealized boundary layer (BL) model with simple parameterizations using vertical transport information from community model outputs (NCAR/NCEP Reanalysis and ECMWF Interim Analysis) to estimate regional-scale net CO2 fluxes from 2002 to 2007 at three forest and one grassland flux sites in the United States. The BL modeling...

  16. Sensitivity of the KM3NeT detector to neutrino fluxes from Galactic point-like sources

    NARCIS (Netherlands)

    Trovato, A.; Kooijman, P.; Coniglione, R.; Sapienza, P.

    2014-01-01

    The KM3NeT collaboration has started the implementation of the first phase of a cubic-kilometre-scale neutrino telescope in the Northern hemisphere with an integrated platform for Earth and deep sea sciences. The location in the Mediterranean Sea will allow for surveying a large part of the sky,

  17. Assessing the net effect of long-term drainage on a permafrost ecosystem through year-round eddy-covariance flux measurements

    Science.gov (United States)

    Kittler, F.; Heimann, M.; Goeckede, M.; Zimov, S. A.; Zimov, N.

    2014-12-01

    Permafrost regions in the Northern high latitudes play a key role in the carbon budget of the earth system because of their massive carbon reservoir and the uncertain feedback processes with future climate change. For an improved understanding of mechanisms and drivers dominating permafrost carbon cycling, more observations in high-latitude regions are needed. Particularly the contribution of wintertime fluxes to the annual carbon budget and the impact of disturbances on biogeochemical and biogeophysical ecosystem properties, and the resulting modification of the carbon cycle, have rarely been studied to date. In summer of 2013, we established a new eddy-covariance station for continuous, year-round monitoring of carbon fluxes and their environmental drivers near Cherskii in Northeast Siberia (68.75°N, 161.33°E). Parts of the observation area have been disturbed by drainage since 2004, altering the soil water conditions in a way that is expected for degrading ice-rich permafrost under a warming climate. With two eddy-covariance towers running in parallel over the disturbed (drained) area and a reference area nearby, respectively, we can directly infer the disturbance effect on the carbon cycle budgets and the dominating biogeochemical mechanisms. This study presents findings based on 16 months of continuous eddy-covariance CO2 flux measurements (July 2013 - October 2014) for both observation areas. At both towers, we observed systematic, non-zero flux contributions outside the growing seasons that significantly altered annual CO2 budgets. A direct comparison of fluxes between the two disturbance regimes indicates a net reduction of the sink strength for CO2 in the disturbed area during the growing season, mostly caused by reduced CO2 uptake with low water levels in late summer. Moreover, shifts in soil temperatures and snow cover caused by reduced soil water levels result in lower net CO2 emissions during the winter at the drained area, which is partly

  18. Derivation of Surface Net Radiation at the Valencia Anchor Station from Top of the Atmosphere Gerb Fluxes by Means of Linear Models and Neural Networks

    Science.gov (United States)

    Geraldo Ferreira, A.; Lopez-Baeza, Ernesto; Velazquez Blazquez, Almudena; Soria-Olivas, Emilio; Serrano Lopez, Antonio J.; Gomez Chova, Juan

    2012-07-01

    In this work, Linear Models (LM) and Artificial Neural Networks (ANN) have been developed to estimate net radiation (RN) at the surface. The models have been developed and evaluated by using the synergy between Geostationary Earth Radiation Budget (GERB-1) and Spinning Enhanced Visible and Infrared Imager (SEVIRI) data, both instruments onboard METEOSAT-9, and ``in situ'' measurements. The data used in this work, corresponding to August 2006 and June to August 2007, proceed from Top of the Atmosphere (TOA) broadband fluxes from GERB-1, every 15 min, and from net radiation at the surface measured, every 10 min, at the Valencia Anchor Station (VAS) area, having measured independently the shortwave and the longwave radiation components (downwelling and upwelling) for different land uses and land cover. The adjustment of both temporal resolutions for the satellite and in situ data was achieved by linear interpolation that showed less standard deviation than the cubic one. The LMs were developed and validated by using satellite TOA RN and ground station surface RN measurements, only considering cloudy free days selected from the ground data. The ANN model was developed both for cloudy and cloudy-free conditions using seven input variables selected for the training/validation sets, namely, hour, day, month, surface RN, solar zenith angle and TOA shortwave and longwave fluxes. Both, LMs and ANNs show remarkably good agreement when compared to surface RN measurements. Therefore, this methodology can be successfully applied to estimate RN at surface from GERB/SEVIRI data.

  19. Iron fertilization enhanced net community production but not downward particle flux during the Southern Ocean iron fertilization experiment LOHAFEX

    Digital Repository Service at National Institute of Oceanography (India)

    Martin, P.; Loeff, M.M.R. van der.; Cassar, N.; Vandromme, P.; d'Ovidio, F.; Stemmann, L.; Rengarajan, R.; Soares, M.A.; Gonzalez, H.E.; Ebersbach, F.; Lampitt, R.S.; Sanders, R.; Barnett, B.A.; Smetacek, V.; Naqvi, S.W.A.

    A closed eddy core in the Subantarctic Atlantic Ocean was fertilized twice with two tons of iron (as FeSO4), and the 300 km2 fertilized patch was studied for 39 days to test whether fertilization enhances downward particle flux...

  20. Atmospheric 14CO2 Constraints on and Modeling of Net Carbon Fluxes 06-ERD-031 An LLNL Exploratory Research in the Directorate's Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Guilderson, T P; Cameron-Smith, P; Bergmann, D; Graven, H D; Keeling, R; Boering, K; Caldeira, K

    2009-03-18

    A critical scientific question is: 'what are the present day sources and sinks of carbon dioxide (CO{sub 2}) in the natural environment, and how will these sinks evolve under rising CO{sub 2} concentrations and expected climate change and ecosystem response'? Sources and sinks of carbon dioxide impart their signature on the distribution, concentration, and isotopic composition of CO{sub 2}. Spatial and temporal trends (variability) provide information on the net surface (atmosphere to ocean, atmosphere to terrestrial biosphere) fluxes. The need to establish more reliable estimates of sources and sinks of CO{sub 2} has lead to an expansion of CO{sub 2} measurement programs over the past decade and the development of new methodologies for tracing carbon flows. These methodologies include high-precision pCO{sub 2}, {delta}{sup 13}CO{sub 2}, and [O{sub 2}/N{sub 2}] measurements on atmospheric constituents that, when combined, have allowed estimates of the net terrestrial and oceanic fluxes at decadal timescales. Major gaps in our understanding remain however, and resulting flux estimates have large errors and are comparatively unconstrained. One potentially powerful approach to tracking carbon flows is based on observations of the {sup 14}C/{sup 12}C ratio of atmospheric CO{sub 2}. This ratio can be used to explicitly distinguish fossil-fuel CO{sub 2} from other sources of CO{sub 2} and also provide constraints on the mass and turnover times of carbon in land ecosystems and on exchange rates of CO{sub 2} between air and sea. Here we demonstrated measurement of {sup 14}C/{sup 12}C ratios at 1-2{per_thousand} on archived and currently collected air samples. In parallel we utilized the LLNL-IMPACT global atmospheric chemistry transport model and the TransCom inversion algorithm to utilize these data in inversion estimates of carbon fluxes. This project has laid the foundation for a more expanded effort in the future, involving collaborations with other air

  1. Summer extreme climatic event in the future: impact on the net CO2 and water fluxes of an upland grassland and buffering impact of elevated atmospheric CO2

    Science.gov (United States)

    Roy, Jacques; Ravel, Olivier; Landais, Damien; Piel, Clément; Defossez, Marc; Escape, Christophe; Devidal, Sébastien; Didier, Philippe; Bahn, Michael; Volaire, Florence; Augusti, Angela; Soussana, Jean-François; Picon-Cochard, Catherine

    2013-04-01

    Extreme climatic events are expected to be more frequent and intense in a few decades, but they will also occur in a climatic context different from the current one. In the Montpellier Ecotron, we studied the response of intact grassland monoliths (1m², 60 cm deep) sampled in an upland grassland of the French Massif Central. The first year the grasslands were acclimated to the average climatic conditions of the years around 2050 (+ 4 °C and - 56 mm for summer precipitations). The second year, the same climate was maintained but in half of the experimental units we imposed a summer drought and heat wave (50 % reduction of precipitations for a month and then 100 % precipitation reduction combined with a 3,4 °C increase in temperature for two weeks). A CO2 treatment (520 vs 380 µmol/mol) was crossed with the climatic treatment. Net CO2 fluxes were measured continuously during the second year of the experiment. The extreme climatic event induced a total senescence of the canopy whatever the CO2 treatment. The interactive effect of elevated CO2 with the drought treatment was significant at the onset of the drought and particularly large in the fall after the recovery period, with a net photosynthesis twice as high in the (extreme climate+ CO2) treatment compared to the control. Integrated over the year, elevated CO2 totally buffered the impact of the extreme climatic event on net CO2 exchanges. These results are discussed together with the evapotranspiration and soil humidity data.

  2. Methane Flux

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Methane (CH4) flux is the net rate of methane exchange between an ecosystem and the atmosphere. Data of this variable were generated by the USGS LandCarbon project...

  3. Net sea–air CO2 flux uncertainties in the Bay of Biscay based on the choice of wind speed products and gas transfer parameterizations

    Directory of Open Access Journals (Sweden)

    P. Otero

    2013-05-01

    Full Text Available The estimation of sea–air CO2 fluxes is largely dependent on wind speed through the gas transfer velocity parameterization. In this paper, we quantify uncertainties in the estimation of the CO2 uptake in the Bay of Biscay resulting from the use of different sources of wind speed such as three different global reanalysis meteorological models (NCEP/NCAR 1, NCEP/DOE 2 and ERA-Interim, one high-resolution regional forecast model (HIRLAM-AEMet, winds derived under the Cross-Calibrated Multi-Platform (CCMP project, and QuikSCAT winds in combination with some of the most widely used gas transfer velocity parameterizations. Results show that net CO2 flux estimations during an entire seasonal cycle (September 2002–September 2003 may vary by a factor of ~ 3 depending on the selected wind speed product and the gas exchange parameterization, with the highest impact due to the last one. The comparison of satellite- and model-derived winds with observations at buoys advises against the systematic overestimation of NCEP-2 and the underestimation of NCEP-1. In the coastal region, the presence of land and the time resolution are the main constraints of QuikSCAT, which turns CCMP and ERA-Interim in the preferred options.

  4. Relation of net portal flux of nitrogen compounds with dietary characteristics in ruminants: a meta-analysis approach.

    Science.gov (United States)

    Martineau, R; Sauvant, D; Ouellet, D R; Côrtes, C; Vernet, J; Ortigues-Marty, I; Lapierre, H

    2011-06-01

    Decrease of N intake (NI) with the aim of increasing efficiency of N utilization and decreasing the negative environmental effects of animal production requires assessment of the forms in which N is absorbed. A meta-analysis was conducted on 68 publications (90 experiments and 215 treatments) to study the effect of NI on net portal appearance (NPA) of nitrogenous nutrients [amino acids (AA), ammonia, and urea] in ruminants. In addition, the effect of several dietary energy and protein factors on this relationship was investigated. These factors were: dry matter intake; proportion of concentrate; diet concentrations and intakes of nonfiber carbohydrates and neutral detergent fiber (NDF); diet concentrations of total digestible nutrients (TDN) and crude protein; rumen-degradable protein and rumen-undegradable protein, as percent dry matter or percent crude protein. The effect of species and physiological stage was also investigated. Within-experiment analyses revealed that the NPA of AA-N and ammonia-N increased linearly, whereas the NPA of urea-N decreased (or recycling of urea-N increased) linearly with NI. Besides NI, many significant covariates could be introduced in each NPA model. However, only TDN and neutral detergent fiber intake (NDFi) were common significant covariates of NI in each NPA model. In this database, ruminants converted 60% of incremental NI into NPA of AA-N with no species effect on that slope. However, at similar NI, TDN, and NDFi, sheep absorbed more AA-N than did cattle and dairy cows. On the other hand, species tended to affect the slope of the relationship between NPA of ammonia-N and NI, which varied from 0.19 for the sheep to 0.38 for dairy cows. On average, the equivalent of 11% of incremental NI was recycled as urea-N to the gut through the portal-drained viscera, which excludes salivary contribution, and no species difference was detected. Overall, at similar TDN and NDFi, sheep and cattle increased their NPA of AA-N relative to NI

  5. Using the Synergy Between GERB/SEVIRI and Micrometeorological Data to Study the Relationship Between Surface Net Radiation and Soil Heat Flux at Local and Regional Scales

    Science.gov (United States)

    Ferreira, A. G.; Velázquez Blázquez, A.; Soria, E.; Lopez-Baeza, E.

    2009-04-01

    The surface energy exchange between the land surface and the atmosphere can be described by the energy balance equation Rn - H - LE - G = 0, where Rn represents net radiation, H the sensible heat flux, LE, the latent heat flux and G the soil heat flux. In this work the relationship between Rn and G is studied over vineyard crops, a relative sparse vegetation cover crop where, according to the literature, it is expected that G consumes a significant proportion of Rn. In order to study this relationship at local and regional scales, micrometeorological observations and METEOSAT Second Generation (MSG) satellite data have been used. MSG through the GERB (Geostationary Earth Radiation Budget) and the SEVIRI (Spinning Enhanced Visible and Infrared Imager) sensors can provide estimates of net radiation and required land surface temperature (LST) information with a frequency of 15 min intervals. The necessary micrometeorological parameters, to compare with satellite data, were collected during the full vine growing season of 2007 (May to September) in a field experiment carried out at the Valencia Anchor Station (VAS) site area. The VAS is a robust reference meteorological station which is successfully used preferentially for validation of low spatial resolution satellite data and products. It is located on the natural region of the Utiel-Requena Plateau, at about 80 km west from the city of Valencia, Spain, and represents a reasonable homogeneous area of about 50 km x 50 km dedicated primarily to growing vines. The methodology utilized to study the relationship between Rn and G at local and regional scales, was that proposed by Santanello and Friedel (2002), where surface temperature can be obtained from SEVIRI that provides estimates of LST with unprecedented frequency of 15 min intervals with a spatial resolution of 3.1 km, thus totally covering its diurnal course. The preliminary results show that: 1- the correlation between the ground measurements and SEVIRI LST is

  6. The effect of increasing salinity and forest mortality on soil nitrogen and phosphorus mineralization in tidal freshwater forested wetlands

    Science.gov (United States)

    Noe, Gregory B.; Krauss, Ken W.; Lockaby, B. Graeme; Conner, William H.; Hupp, Cliff R.

    2013-01-01

    Tidal freshwater wetlands are sensitive to sea level rise and increased salinity, although little information is known about the impact of salinification on nutrient biogeochemistry in tidal freshwater forested wetlands. We quantified soil nitrogen (N) and phosphorus (P) mineralization using seasonal in situ incubations of modified resin cores along spatial gradients of chronic salinification (from continuously freshwater tidal forest to salt impacted tidal forest to oligohaline marsh) and in hummocks and hollows of the continuously freshwater tidal forest along the blackwater Waccamaw River and alluvial Savannah River. Salinification increased rates of net N and P mineralization fluxes and turnover in tidal freshwater forested wetland soils, most likely through tree stress and senescence (for N) and conversion to oligohaline marsh (for P). Stimulation of N and P mineralization by chronic salinification was apparently unrelated to inputs of sulfate (for N and P) or direct effects of increased soil conductivity (for N). In addition, the tidal wetland soils of the alluvial river mineralized more P relative to N than the blackwater river. Finally, hummocks had much greater nitrification fluxes than hollows at the continuously freshwater tidal forested wetland sites. These findings add to knowledge of the responses of tidal freshwater ecosystems to sea level rise and salinification that is necessary to predict the consequences of state changes in coastal ecosystem structure and function due to global change, including potential impacts on estuarine eutrophication.

  7. Optimal initial excitations of decadal modification of the Atlantic meridional overturning circulation under the prescribed heat and freshwater flux boundary conditions

    NARCIS (Netherlands)

    Zu, Ziqing; Mu, Mu; Dijkstra, Henk A.

    Within a three-dimensional ocean circulation model, the nonlinear optimal initial perturbations (NOIP) of sea surface salinity (SSS) and sea surface temperature (SST) to excite variability in the Atlantic meridional overturning circulation (AMOC) were obtained under prescribed heat and freshwater

  8. Net transport of suspended matter due to tidal straining

    Science.gov (United States)

    Jones, S. E.; Jago, C. F.; Simpson, J. H.; Rippeth, T. P.

    2003-04-01

    Net transport of suspended particulate matter (SPM) is well-known in tidal regions where there is time-velocity asymmetry due to frictional modification of the tide in shallow water. We present here observations which show a new mechanism for net flux of SPM in response to tidal straining in a region of freshwater influence (ROFI). In situ measurements of the particle size of suspended particulate matter (SPM) and turbulent energy dissipation have been made at a site in Liverpool Bay (Irish Sea) where there is significant resuspension of particles from the muddy sand substrate during spring tides. This is a ROFI where tidal straining dominates the temporal development of turbulence. On a spring tide the water column tries to stratify on the ebb and destratify on the flood, but these tendencies are masked by mixing due to tidal stirring. Nevertheless, there is a marked excess of TKE dissipation rate E on the flood, especially in the upper part of the water column. Resuspension occurs on both flood and ebb, but SPM flux is strongly asymmetric with a net shorewards component. Asymmetry is most pronounced for the larger particles which comprise most of the mass. Enhanced ? on the flood mixes large particles upwards into faster flowing water, which increases the flux. Comparable upwards mixing of large particles does not occur on the ebb where enhanced E is confined to slower bottom waters. The net flux is not seen on neap tides because, although there is more stratification due to tidal straining, there is essentially no resuspension. The net flux on springs is undoubtedly an important component of SPM transport (and any comparable particulates) in coastal regions.

  9. A theoretical framework for the net land-to-atmosphere CO2 flux and its implications in the definition of "emissions from land-use change"

    OpenAIRE

    T. Gasser; Ciais, P

    2013-01-01

    We develop a theoretical framework and analysis of the net land-to-atmosphere CO2 flux in order to discuss possible definitions of "emissions from land-use change". The terrestrial biosphere is affected by two perturbations: the perturbation of the global carbon-climate-nitrogen system (CCN) with elevated atmospheric CO2, climate change and nitrogen deposition; and the land-use change perturbation (LUC). Here, we progressively establish mathematical definitions of four gener...

  10. A theoretical framework for the net land-to-atmosphere CO2 flux and its implications in the definition of "emissions from land-use change"

    OpenAIRE

    T. Gasser; Ciais, P

    2013-01-01

    We develop a theoretical framework and analysis of the net land-to-atmosphere CO2 flux in order to discuss possible definitions of "emissions from land-use change". The terrestrial biosphere is affected by two perturbations: the perturbation of the global Carbon-Climate-Nitrogen system (CCN) with elevated atmospheric CO2, climate change and nitrogen deposition; and the Land-Use Change perturbation (LUC). Here, we progressively establish mathematical definitions of four generic components of t...

  11. The effect of Arctic sea-ice extent on the absorbed (net solar flux at the surface, based on ISCCP-D2 cloud data for 1983–2007

    Directory of Open Access Journals (Sweden)

    C. Matsoukas

    2010-01-01

    Full Text Available We estimate the effect of the Arctic sea ice on the absorbed (net solar flux using a radiative transfer model. Ice and cloud input data to the model come from satellite observations, processed by the International Satellite Cloud Climatology Project (ISCCP and span the period July 1983–June 2007. The sea-ice effect on the solar radiation fluctuates seasonally with the solar flux and decreases interannually in synchronisation with the decreasing sea-ice extent. A disappearance of the Arctic ice cap during the sunlit period of the year would radically reduce the local albedo and cause an annually averaged 19.7 W m−2 increase in absorbed solar flux at the Arctic Ocean surface, or equivalently an annually averaged 0.55 W m−2 increase on the planetary scale. In the clear-sky scenario these numbers increase to 34.9 and 0.97 W m−2, respectively. A meltdown only in September, with all other months unaffected, increases the Arctic annually averaged solar absorption by 0.32 W m−2. We examined the net solar flux trends for the Arctic Ocean and found that the areas absorbing the solar flux more rapidly are the North Chukchi and Kara Seas, Baffin and Hudson Bays, and Davis Strait. The sensitivity of the Arctic absorbed solar flux on sea-ice extent and cloud amount was assessed. Although sea ice and cloud affect jointly the solar flux, we found little evidence of strong non-linearities.

  12. Downward Heat Penetration below Seasonal Thermocline and its Impact on Sea Surface Temperature Variation Affected by Net Heat Flux during Summer Season

    Science.gov (United States)

    Hosoda, S.; Nonaka, M.; Tomita, T.; Taguchi, B.; Tomita, H.; Iwasaka, N.

    2016-02-01

    Oceanic heat capacity of the upper layer is a key of the change in the sea surface temperature (SST) affecting air-sea heat exchange and of the temporal scale of SST variability. In the past, studies of SST variability associated with the air-sea heat exchange have mainly focused on the conditions during the winter, because wintertime deep mixed layer (ML) accumulates a huge amount of heat to the atmosphere. On the contrary, ML during the warming season is thinner than it is during the cooling season, being only a few tens of meters deep at mid- and high- latitudes, bounded by a shallow and sharp seasonal thermocline. Since the ML that directly communicates with the atmosphere is thin, the ocean has been considered to play a passive role in air-sea interactions during the warming season. In this study, we clarified that subsurface ocean plays an important role to seasonal changes of SST and heat capacity during the warming season using observational data of Argo and J-OFURO2, which is net heat flux (Qnet) data from satellites. To clarify the role of upper ocean to the Qnet during summer, we introduce a concept of heat penetration depth (HPD), defined as the depth to which Qnet distinctly penetrates below the seasonal thermocline. Then we assume vertical one dimensional process between Qnet and temporal heat content (HC) change integrating temperature from surface to HPD. The vertical one dimensional process can be assumed in almost mid- and high-latitude NP, and we successfully characterize the heat capacity in terms of the HC above the HPD. The downward heat penetration below the shallow seasonal thermocline is widely found throughout the NP. On the basis of a simple estimation that the amount of heat accumulated by summer Qnet in the NP, about two-thirds of Qnet penetrates below the shallow seasonal thermocline. The effect of heat penetration also makes a magnitude of seasonal change in SST to be smaller, at least a half of that the magnitude under the assumption

  13. Reduced uncertainty of regional scale CLM predictions of net carbon fluxes and leaf area indices with estimated plant-specific parameters

    Science.gov (United States)

    Post, Hanna; Hendricks Franssen, Harrie-Jan; Han, Xujun; Baatz, Roland; Montzka, Carsten; Schmidt, Marius; Vereecken, Harry

    2016-04-01

    Reliable estimates of carbon fluxes and states at regional scales are required to reduce uncertainties in regional carbon balance estimates and to support decision making in environmental politics. In this work the Community Land Model version 4.5 (CLM4.5-BGC) was applied at a high spatial resolution (1 km2) for the Rur catchment in western Germany. In order to improve the model-data consistency of net ecosystem exchange (NEE) and leaf area index (LAI) for this study area, five plant functional type (PFT)-specific CLM4.5-BGC parameters were estimated with time series of half-hourly NEE data for one year in 2011/2012, using the DiffeRential Evolution Adaptive Metropolis (DREAM) algorithm, a Markov Chain Monte Carlo (MCMC) approach. The parameters were estimated separately for four different plant functional types (needleleaf evergreen temperate tree, broadleaf deciduous temperate tree, C3-grass and C3-crop) at four different sites. The four sites are located inside or close to the Rur catchment. We evaluated modeled NEE for one year in 2012/2013 with NEE measured at seven eddy covariance sites in the catchment, including the four parameter estimation sites. Modeled LAI was evaluated by means of LAI derived from remotely sensed RapidEye images of about 18 days in 2011/2012. Performance indices were based on a comparison between measurements and (i) a reference run with CLM default parameters, and (ii) a 60 instance CLM ensemble with parameters sampled from the DREAM posterior probability density functions (pdfs). The difference between the observed and simulated NEE sum reduced 23% if estimated parameters instead of default parameters were used as input. The mean absolute difference between modeled and measured LAI was reduced by 59% on average. Simulated LAI was not only improved in terms of the absolute value but in some cases also in terms of the timing (beginning of vegetation onset), which was directly related to a substantial improvement of the NEE estimates in

  14. The effect of Congo River freshwater discharge on Eastern Equatorial Atlantic climate variability

    Energy Technology Data Exchange (ETDEWEB)

    Materia, Stefano [Centro Euro-Mediterraneo per i Cambiamenti Climatici, Bologna (Italy); Gualdi, Silvio; Navarra, Antonio [Centro Euro-Mediterraneo per i Cambiamenti Climatici, Bologna (Italy); Istituto Nazionale di Geofisica e Vulcanologia, Bologna (Italy); Terray, Laurent [Sciences de l' Univers au CERFACS, URA1875 CERFACS/CNRS, Toulouse (France)

    2012-11-15

    The surface ocean explains a considerable part of the inter-annual Tropical Atlantic variability. The present work makes use of observational datasets to investigate the effect of freshwater flow on sea surface salinity (SSS) and temperature (SST) in the Gulf of Guinea. In particular, the Congo River discharges a huge amount of freshwater into the ocean, affecting SSS in the Eastern Equatorial Atlantic (EEA) and stratifying the surface layers. The hypothesis is that an excess of river runoff emphasize stratification, influencing the ocean temperature. In fact, our findings show that SSTs in the Gulf of Guinea are warmer in summers following an anomalously high Congo spring discharge. Vice versa, when the river discharges low freshwater, a cold anomaly appears in the Gulf. The response of SST is not linear: temperature anomalies are considerable and long-lasting in the event of large freshwater flow, while in dry years they are less remarkable, although still significant. An excess of freshwater seems able to form a barrier layer, which inhibits vertical mixing and the entrainment of the cold thermocline water into the surface. Other processes may contribute to SST variability, among which the net input of atmospheric freshwater falling over EEA. Likewise the case of continental runoff from Congo River, warm anomalies occur after anomalously rainy seasons and low temperatures follow dry seasons, confirming the effect of freshwater on SST. However, the two sources of freshwater anomaly are not in phase, so that it is possible to split between atypical SST following continental freshwater anomalies and rainfall anomalies. Also, variations in air-sea fluxes can produce heating and cooling of the Gulf of Guinea. Nevertheless, atypical SSTs cannot be ascribed to fluxes, since the temperature variation induced by them is not sufficient to explain the SST anomalies appearing in the Gulf after anomalous peak discharges. The interaction processes between river runoff, sea

  15. Modelling daily to seasonal carbon fluxes and annual net ecosystem carbon balance of cereal grain-cropland using DailyDayCent: A model data comparison

    OpenAIRE

    Chabbi, Abad; Smith, Pete

    2018-01-01

    Croplands are important not only for food and fibre, but also for their global climate change mitigation and carbon (C) sequestration potentials. Measurements and modelling of daily C fluxes and annual C balance, which are needed for optimizing such global potentials in croplands, are difficult since many measurements, and the correct simulation of different ecosystem processes are needed. In the present study, a biogeochemical ecosystem model (DailyDayCent) was applied to simulate daily to s...

  16. Comparison of net CO2 fluxes measured with open- and closed-path infrared gas analyzers in an urban complex environment

    DEFF Research Database (Denmark)

    Järvi, L.; Mammarella, I.; Eugster, W.

    2009-01-01

    and their suitability to accurately measure CO2 exchange in such non-ideal landscape. In addition, this study examined the effect of open-path sensor heating on measured fluxes in urban terrain, and these results were compared with similar measurements made above a temperate beech forest in Denmark. The correlation...... improved the performance of the open-path analyzer by reducing discrepancies in NSE at the urban site to 2% and decreasing the difference in NSE from 67% to 7% at the forest site. Overall, the site-specific approach gave the best results at both sites and, if possible, it should be preferred in the sensor...

  17. Aeronet Solar Flux

    Data.gov (United States)

    National Aeronautics and Space Administration — SolRad-Net (Solar Radiation Network) is an established network of ground-based sensors providing high-frequency solar flux measurements in quasi-realtime to the...

  18. Nitrous Oxide Flux

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Nitrous Oxide (N20) flux is the net rate of nitrous oxide exchange between an ecosystem and the atmosphere. Data of this variable were generated by the USGS...

  19. Net Locality

    DEFF Research Database (Denmark)

    de Souza e Silva, Adriana Araujo; Gordon, Eric

    Provides an introduction to the new theory of Net Locality and the profound effect on individuals and societies when everything is located or locatable. Describes net locality as an emerging form of location awareness central to all aspects of digital media, from mobile phones, to Google Maps...... of emerging technologies, from GeoCities to GPS, Wi-Fi, Wiki Me, and Google Android....

  20. Net Neutrality

    DEFF Research Database (Denmark)

    Savin, Andrej

    2017-01-01

    Repealing “net neutrality” in the US will have no bearing on Internet freedom or security there or anywhere else.......Repealing “net neutrality” in the US will have no bearing on Internet freedom or security there or anywhere else....

  1. Net ecosystem exchange from five land-use transitions to bioenergy crops from four locations across the UK - The Ecosystem Land Use Modelling & Soil Carbon GHG Flux Trial (ELUM) project.

    Science.gov (United States)

    Xenakis, Georgios; Perks, Mike; Harris, Zoe M.; McCalmont, Jon; Rylett, Daniel; Brooks, Milo; Evans, Jonathan G.; Finch, Jon; Rowe, Rebecca; Morrison, Ross; Alberti, Giorgio; Donnison, Ian; Siebicke, Lukas; Morison, James; Taylor, Gail; McNamara, Niall P.

    2016-04-01

    A major part of international agreements on combating climate change is the conversion from a fossil fuel economy to a low carbon economy. Bioenergy crops have been proposed as a way to improve energy security while reducing CO2 emissions to help mitigate the effects of climate change. However, the impact of land-use change from a traditional land use (e.g., arable and grassland) to bioenergy cropping systems on greenhouse gas balance (GHG) and carbon stocks are poorly quantified at this time. The Ecosystem Land Use Modelling & Soil Carbon GHG Flux Trial (ELUM) project was commissioned and funded by the Energy Technologies Institute (ETI) to provide scientific evidence within the UK on a range of land-use conversions (LUC) to bioenergy crops. The ELUM network consists of seven partners investigating five LUCs in four locations including Scotland, Wales, North and South England. Transitions included grasslands to short rotation forestry (SRF), to short rotation coppice willow (SRC) and to Miscanthus and arable to SRC and Miscanthus Measurements of net ecosystem exchange (NEE) along with continuous measurements of meteorological conditions were made at seven sub-sites over a two-year period. Results showed that, over two years, two of the land-uses, a grassland in South England and a grassland conversion to Miscanthus in Wales were net sources of carbon. The greatest carbon sink was into the SRF site in Scotland followed by the SRC willow in South England. The annual terrestrial ecosystem respiration (TER) for the SRC willow in North and South Sussex sites were similar, but the annual GPP at the South England site was about 27% higher than that the North England site. Establishing a long term network will allow us to continue monitoring the effects of land use change on whole ecosystem carbon balance, providing an insight into which types of LUC are suitable for bioenergy cropping in the UK.

  2. The impact of storms and stratification on sediment transport in the Rhine region of freshwater influence

    Science.gov (United States)

    Flores, Raúl P.; Rijnsburger, Sabine; Horner-Devine, Alexander R.; Souza, Alejandro J.; Pietrzak, Julie D.

    2017-05-01

    We present measurements of along and across-shore sediment transport in a region of the Dutch coast 10 km north of the Rhine River mouth. This section of the coast is characterized by strong vertical density stratification because it is within the midfield region of the Rhine region of freshwater influence, where processes typical of the far-field, such as tidal straining, are modified by the passage of distinct freshwater lenses at the surface. The experiment captured two storms, and a wide range of wind, wave, tidal and stratification conditions. We focus primarily on the mechanisms leading to cross-shore sediment flux at a mooring location in 12 m of water, which are responsible for the exchange of sediment between the nearshore and the inner shelf. Net transport during storms was directed offshore and influenced by cross-shelf winds, while net transport during spring tides was determined by the mean state of stratification. Tidal straining dominated during neap tides; however, cross-shore transport was negligible due to small sediment concentrations. The passage of freshwater lenses manifested as strong pulses of offshore transport primarily during spring tides. We observe that both barotropic and baroclinic processes are relevant for cross-shore transport at depth and, since transport rates due to these competing processes were similar, the net transport direction will be determined by the frequency and sequencing of these modes of transport. Based on our observations, we find that wind and wave-driven transport during storms tends move fine sediment offshore, while calmer, more stratified conditions move it back onshore.

  3. RESTful NET

    CERN Document Server

    Flanders, Jon

    2008-01-01

    RESTful .NET is the first book that teaches Windows developers to build RESTful web services using the latest Microsoft tools. Written by Windows Communication Foundation (WFC) expert Jon Flanders, this hands-on tutorial demonstrates how you can use WCF and other components of the .NET 3.5 Framework to build, deploy and use REST-based web services in a variety of application scenarios. RESTful architecture offers a simpler approach to building web services than SOAP, SOA, and the cumbersome WS- stack. And WCF has proven to be a flexible technology for building distributed systems not necessa

  4. Tropical Freshwater Biology

    African Journals Online (AJOL)

    Tropical Freshwater Biology promotes the publication of scientific contributions in the field of freshwater biology in the tropical and subtropical regions of the world. One issue is published annually but this number may be increased. Original research papers and short communications on any aspect of tropical freshwater ...

  5. Petri Nets

    Indian Academy of Sciences (India)

    Associate Professor of. Computer Science and. Automation at the Indian. Institute of Science,. Bangalore. His research interests are broadly in the areas of stochastic modeling and scheduling methodologies for future factories; and object oriented modeling. GENERAL I ARTICLE. Petri Nets. 1. Overview and Foundations.

  6. Petri Nets

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 8. Petri Nets - Overview and Foundations. Y Narahari. General Article Volume 4 Issue 8 August 1999 pp ... Author Affiliations. Y Narahari1. Department ot Computer Science and Automation, Indian Institute of Science, Bangalore 560 012, India.

  7. Evaluation of alternative macroinvertebrate sampling techniques for use in a new tropical freshwater bioassessment scheme

    OpenAIRE

    Moore, Isabel Eleanor; Murphy, Kevin Joseph

    2015-01-01

    Aim: The study aimed to determine the effectiveness of benthic macroinvertebrate dredge net sampling procedures as an alternative method to kick net sampling in tropical freshwater systems, specifically as an evaluation of sampling methods used in the Zambian Invertebrate Scoring System (ZISS) river bioassessment scheme. Tropical freshwater ecosystems are sometimes dangerous or inaccessible to sampling teams using traditional kick-sampling methods, so identifying an alternative procedure that...

  8. Responses of Carbon Dynamics to Nitrogen Deposition in Typical Freshwater Wetland of Sanjiang Plain

    Directory of Open Access Journals (Sweden)

    Yang Wang

    2014-01-01

    Full Text Available The effects of nitrogen deposition (N-deposition on the carbon dynamics in typical Calamagrostis angustifolia wetland of Sanjiang Plain were studied by a pot-culture experiment during two continuous plant growing seasons. Elevated atmospheric N-deposition caused significant increases in the aboveground net primary production and root biomass; moreover, a preferential partition of carbon to root was also observed. Different soil carbon fractions gained due to elevated N-deposition and their response intensities followed the sequence of labile carbon > dissolved organic carbon > microbial biomass carbon, and the interaction between N-deposition and flooded condition facilitated the release of different carbon fractions. Positive correlations were found between CO2 and CH4 fluxes and liable carbon contents with N-deposition, and flooded condition also tended to facilitate CH4 fluxes and to inhibit the CO2 fluxes with N-deposition. The increases in soil carbon fractions occurring in the nitrogen treatments were significantly correlated with increases in root, aboveground parts, total biomass, and their carbon uptake. Our results suggested that N-deposition could enhance the contents of active carbon fractions in soil system and carbon accumulation in plant of the freshwater wetlands.

  9. Electron heat flux instability

    Science.gov (United States)

    Saeed, Sundas; Sarfraz, M.; Yoon, P. H.; Lazar, M.; Qureshi, M. N. S.

    2017-02-01

    The heat flux instability is an electromagnetic mode excited by a relative drift between the protons and two-component core-halo electrons. The most prominent application may be in association with the solar wind where drifting electron velocity distributions are observed. The heat flux instability is somewhat analogous to the electrostatic Buneman or ion-acoustic instability driven by the net drift between the protons and bulk electrons, except that the heat flux instability operates in magnetized plasmas and possesses transverse electromagnetic polarization. The heat flux instability is also distinct from the electrostatic counterpart in that it requires two electron species with relative drifts with each other. In the literature, the heat flux instability is often called the 'whistler' heat flux instability, but it is actually polarized in the opposite sense to the whistler wave. This paper elucidates all of these fundamental plasma physical properties associated with the heat flux instability starting from a simple model, and gradually building up more complexity towards a solar wind-like distribution functions. It is found that the essential properties of the instability are already present in the cold counter-streaming electron model, and that the instability is absent if the protons are ignored. These instability characteristics are highly reminiscent of the electron firehose instability driven by excessive parallel temperature anisotropy, propagating in parallel direction with respect to the ambient magnetic field, except that the free energy source for the heat flux instability resides in the effective parallel pressure provided by the counter-streaming electrons.

  10. Freshwater Fungal Infections

    Directory of Open Access Journals (Sweden)

    Dennis J. Baumgardner

    2017-01-01

    Full Text Available Fungal infections as a result of freshwater exposure or trauma are fortunately rare. Etiologic agents are varied, but commonly include filamentous fungi and Candida. This narrative review describes various sources of potential freshwater fungal exposure and the diseases that may result, including fungal keratitis, acute otitis externa and tinea pedis, as well as rare deep soft tissue or bone infections and pulmonary or central nervous system infections following traumatic freshwater exposure during natural disasters or near-drowning episodes. Fungal etiology should be suspected in appropriate scenarios when bacterial cultures or molecular tests are normal or when the infection worsens or fails to resolve with appropriate antibacterial therapy.

  11. Ecological survey of freshwater ecosystems of Ovia, Edo state ...

    African Journals Online (AJOL)

    The survey for freshwater snails in streams, rivers and a lake in Ovia Southwest LGA of Edo State, Nigeria was carried out from June to November, 2013. Samples were collected by using sweep-net and by hand picking of snails within the open water habitat, at marginal areas and on submerged vegetation at edges of the ...

  12. Fish species composition in a tropical lentic freshwater ecosystem ...

    African Journals Online (AJOL)

    Fish species composition of a tropical lentic freshwater ecosystem (Umudike Water Reservoir, Umuahia, Nigeria) belonging to the National Root Crops Research Institute (NRCRI) was investigated from July 2004 to December 2004. The fishes were sampled twice every week using cast nets, traditional baskets traps (drum ...

  13. Tidal and atmospheric forcing of the upper ocean in the Gulf of California. 2: Surface heat flux

    Science.gov (United States)

    Paden, Cynthia A.; Winant, Clinton D.; Abbott, Mark R.

    1993-01-01

    Satellite infrared imagery and coastal meteorological data for March 1984 through February 1985 are used to estimate the net annual surface heat flux for the northern Gulf of California. The average annual surface heat flux for the area north of Guaymas and Santa Rosalia is estimated to be +74 W/sq m for the 1984-1985 time period. This is comparable to the +20-50 W/sq m previously obtained from heat and freshwater transport estimates made with hydrographic surveys from different years and months. The spatial distribution of the net surface heat flux shows a net gain of heat over the whole northern gulf. Except for a local maximum near San Esteban Island, the largest heat gain (+110-120 W/sq m) occurs in the Ballenas and Salsipuedes channels, where strong tidal mixing produces anomalously cold sea surface temperatures (SSTs) over much of the year. The lowest heat gain occurs in the Guayamas Basin (+40-50 W/sq m), where SSTs are consistently warmer. In the relatively shallow northern basin the net surface heat flux is farily uniform, with a net annual gain of approxmately +70 W/sq m. A local minimum in heat gain (approximately +60 W/sq m) is observed over the shelf in the northwest, where spring and summer surface temperatures are particularly high. A similar minimum in heat gain over the shelf was observed in a separate study in which historical SSTs and 7 years (1979-1986) of meteorological data from Puerto Penasco were used to estimate the net surface heat flux for the northern basin. In that study, however, the heat fluxes were higher, with a gain of +100 W/sq m over the shelf and +114 W/sq m in the northern basin. These larger values are directly attributable to the higher humidities in the 1979-1986 study compared to the 1984-1985 satellite study. High humidities reduce evaporation and the associated latent heat loss, promoting a net annual heat gain. In the norther Gulf of California, however, tidal mixing appears to play a key role in the observed gain of

  14. How northern freshwater input can stabilise thermohaline circulation

    Directory of Open Access Journals (Sweden)

    Erwin Lambert

    2016-11-01

    Full Text Available The North Atlantic thermohaline circulation (THC carries heat and salt towards the Arctic. This circulation is partly sustained by buoyancy loss and is generally believed to be inhibited by northern freshwater input as indicated by the ‘box-model’ of Stommel (1961. The inferred freshwater-sensitivity of the THC, however, varies considerably between studies, both quantitatively and qualitatively. The northernmost branch of the Atlantic THC, which forms a double estuarine circulation in the Arctic Mediterranean, is one example where both buoyancy loss and buoyancy gain facilitate circulation. We have built on Stommel's original concept to examine the freshwater-sensitivity of a double estuarine circulation. The net inflow into the double estuary is found to be more sensitive to a change in the distribution of freshwater than to a change in the total freshwater input. A double estuarine circulation is more stable than a single overturning, requiring a larger amount and more localised freshwater input into regions of buoyancy loss to induce a thermohaline ‘collapse’. For the Arctic Mediterranean, these findings imply that the Atlantic inflow may be relatively insensitive to increased freshwater input. Complementing Stommel's thermal and haline flow regimes, the double estuarine circulation allows for a third: the throughflow regime. In this regime, a THC with warm poleward surface flow can be sustained without production of dense water; a decrease in high-latitude dense water formation does therefore not necessarily affect regional surface conditions as strongly as generally thought.

  15. Bjerknes Compensation in Meridional Heat Transport under Freshwater Forcing and the Role of Climate Feedback

    Science.gov (United States)

    Wen, Qin

    2017-04-01

    Using a coupled Earth climate model, freshwater experiments are performed to study the Bjerknes compensation (BJC) between meridional atmosphere heat transport (AHT) and meridional ocean heat transport (OHT). Freshwater hosing in the North Atlantic weakens the Atlantic meridional overturning circulation (AMOC) and thus reduces the northward OHT in the Atlantic significantly, leading to a cooling (warming) in surface layer in the Northern (Southern) Hemisphere. This results in an enhanced Hadley Cell and northward AHT. Meanwhile, the OHT in the Indo-Pacific is increased in response to the Hadley Cell change, partially offsetting the reduced OHT in the Atlantic. Two compensations occur here: compensation between the AHT and the Atlantic OHT, and that between the Indo-Pacific OHT and the Atlantic OHT. The AHT change compensates the OHT change very well in the extratropics, while the former overcompensates the latter in the tropics due to the Indo-Pacific change. The BJC can be understood from the viewpoint of large-scale circulation change. However, the intrinsic mechanism of BJC is related to the climate feedback of Earth system. Our coupled model experiments confirm that the occurrence of BJC is an intrinsic requirement of local energy balance, and local climate feedback determines the extent of BJC, consistent with previous theoretical results. Even during the transient period of climate change in the model, the BJC is well established when the ocean heat storage is slowly varying and its change is weaker than the net heat flux changes at the ocean surface and the top of the atmosphere. The BJC can be deduced from the local climate feedback. Under the freshwater forcing, the overcompensation in the tropics (undercompensation in the extratropics) is mainly caused by the positive longwave feedback related to cloud (negative longwave feedback related to surface temperature change). Different dominant feedbacks determine different BJC scenarios in different regions

  16. Exploring the ecosystem engineering ability of Red Sea shallow benthic habitats using stocks and fluxes in carbon biogeochemistry

    KAUST Repository

    Baldry, Kimberlee

    2017-12-01

    The coastal ocean is a marginal region of the global ocean, but is home to metabolically intense ecosystems which increase the structural complexity of the benthos. These ecosystems have the ability to alter the carbon chemistry of surrounding waters through their metabolism, mainly through processes which directly release or consume carbon dioxide. In this way, coastal habitats can engineer their environment by acting as sources or sinks of carbon dioxide and altering their environmental chemistry from the regional norm. In most coastal water masses, it is difficult to resolve the ecosystem effect on coastal carbon biogeochemistry due to the mixing of multiple offshore end members, complex geography or the influence of variable freshwater inputs. The Red Sea provides a simple environment for the study of ecosystem processes at a coastal scale as it contains only one offshore end-member and negligible freshwater inputs due to the arid climate of adjacent land. This work explores the ability of three Red Sea benthic coastal habitats (coral reefs, seagrass meadows and mangrove forests) to create characteristic ecosystem end-members, which deviate from the biogeochemistry of offshore source waters. This is done by both calculating non-conservative deviations in carbonate stocks collected over each ecosystem, and by quantifying net carbonate fluxes (in seagrass meadows and mangrove forests only) using 24 hour incubations. Results illustrate that carbonate stocks over ecosystems conform to broad ecosystem trends, which are different to the offshore end-member, and are influenced by inherited properties from surrounding ecosystems. Carbonate fluxes also show ecosystem dependent trends and further illustrate the importance of sediment processes in influencing CaCO3 fluxes in blue carbon benthic habitats, which warrants further attention. These findings show the respective advantages of studying both carbonate stocks and fluxes of coastal benthic ecosystems in order to

  17. A model-based study of ice and freshwater transport variability along both sides of Greenland

    Energy Technology Data Exchange (ETDEWEB)

    Lique, Camille; Treguier, Anne Marie [CNRS-Ifremer-UBO-IRD, Laboratoire de Physique des Oceans, Brest (France); Scheinert, Markus [IFM-GEOMAR, Leibniz-Institut fuer Meereswissenshaften, Kiel (Germany); Penduff, Thierry [Laboratoire des Ecoulements Geophysiques et Industriels, Grenoble (France); The Florida State University, Department of Oceanography, Tallahassee, FL (United States)

    2009-10-15

    We investigate some aspects of the variability of the Arctic freshwater content during the 1965-2002 period using the DRAKKAR eddy admitting global ocean/sea-ice model (12 km resolution in the Arctic). A comparison with recent mooring sections shows that the model realistically represents the major advective exchanges with the Arctic basin, through Bering, Fram and Davis Straits, and the Barents Sea. This allows the separate contributions of the inflows and outflows across each section to be quantified. In the model, the Arctic freshwater content variability is explained by the sea-ice flux at Fram and the combined variations of ocean freshwater inflow (at Bering) and outflow (at Fram and Davis). At all routes, except trough Fram Strait, the freshwater transport variability is mainly accounted for by the liquid component, with small contributions from the sea-ice flux. The ocean freshwater transport variability through both Davis and Fram is controlled by the variability of the export branch (Baffin Island Current and East Greenland Current, respectively), the variability of the inflow branches playing a minor role. We examine the respective role of velocity and salinity fluctuations in the variability of the ocean freshwater transport. Fram and Davis Straits offer a striking contrast in this regard. Freshwater transport variations across Davis Strait are completely determined by the variations of the total volume flux (0.91 correlation). On the other hand, the freshwater transport through Fram Strait depends both on variations of volume transport and salinity. As a result, there is no significant correlation between the variability of freshwater flux at Fram and Davis, although the volume transports on each side of Greenland are strongly anti-correlated (-0.84). Contrary to Davis Strait, the salinity of water carried by the East Greenland Current through Fram Strait varies strongly due to the ice-ocean flux north of Greenland. (orig.)

  18. CROATIAN FRESHWATER FISHERY

    Directory of Open Access Journals (Sweden)

    Višnja Knjaz

    2007-07-01

    Full Text Available The basic characteristics of freshwater fishery in Croatia are predominantly negative trend in the past twenty years. Even though the total fish pond area covers more than 12,000 hectares, only 6,200 hectares of carp ponds and 58,700 m2 of trout ponds have been exploited. In 2006 the production of total freshwater fish reached 6,547 tons, out of which the production of consumable fish amounted to 5,067 tons and the juveniles 1,480 tons. The export of freshwater fish to EU countries, Macedonia, Bosnia and Herzegovina, Serbia and Monte Negro shows the positive trend and the Republic of Croatia continuously records a foreign trade surplus (987,000 US$. It must be pointed out, though, that the import of trout from Bosnia and Herzegovina significantly increased in the past three years which resulted in the decrease of the foreign trade surplus in that sector. The freshwater fishery in Croatia has been overly burdened by many problems

  19. NA-NET numerical analysis net

    Energy Technology Data Exchange (ETDEWEB)

    Dongarra, J. [Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science]|[Oak Ridge National Lab., TN (United States); Rosener, B. [Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science

    1991-12-01

    This report describes a facility called NA-NET created to allow numerical analysts (na) an easy method of communicating with one another. The main advantage of the NA-NET is uniformity of addressing. All mail is addressed to the Internet host ``na-net.ornl.gov`` at Oak Ridge National Laboratory. Hence, members of the NA-NET do not need to remember complicated addresses or even where a member is currently located. As long as moving members change their e-mail address in the NA-NET everything works smoothly. The NA-NET system is currently located at Oak Ridge National Laboratory. It is running on the same machine that serves netlib. Netlib is a separate facility that distributes mathematical software via electronic mail. For more information on netlib consult, or send the one-line message ``send index`` to netlib{at}ornl.gov. The following report describes the current NA-NET system from both a user`s perspective and from an implementation perspective. Currently, there are over 2100 members in the NA-NET. An average of 110 mail messages pass through this facility daily.

  20. NA-NET numerical analysis net

    Energy Technology Data Exchange (ETDEWEB)

    Dongarra, J. (Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science Oak Ridge National Lab., TN (United States)); Rosener, B. (Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science)

    1991-12-01

    This report describes a facility called NA-NET created to allow numerical analysts (na) an easy method of communicating with one another. The main advantage of the NA-NET is uniformity of addressing. All mail is addressed to the Internet host na-net.ornl.gov'' at Oak Ridge National Laboratory. Hence, members of the NA-NET do not need to remember complicated addresses or even where a member is currently located. As long as moving members change their e-mail address in the NA-NET everything works smoothly. The NA-NET system is currently located at Oak Ridge National Laboratory. It is running on the same machine that serves netlib. Netlib is a separate facility that distributes mathematical software via electronic mail. For more information on netlib consult, or send the one-line message send index'' to netlib{at}ornl.gov. The following report describes the current NA-NET system from both a user's perspective and from an implementation perspective. Currently, there are over 2100 members in the NA-NET. An average of 110 mail messages pass through this facility daily.

  1. ) Mold Fluxes

    Science.gov (United States)

    Seo, Myung-Duk; Shi, Cheng-Bin; Cho, Jung-Wook; Kim, Seon-Hyo

    2014-10-01

    The effects of basicity (CaO/SiO2), B2O3, and Li2O addition on the crystallization behaviors of lime-silica-based mold fluxes have been investigated by non-isothermal differential scanning calorimetry (DSC), field emission scanning electron microscopy, X-ray diffraction (XRD), and single hot thermocouple technique. It was found that the crystallization temperature of cuspidine increased with increasing the basicity of mold fluxes. The crystallization of wollastonite was suppressed with increasing the mold flux basicity due to the enhancement of cuspidine crystallization. The addition of B2O3 suppresses the crystallization of mold flux. The crystallization temperature of mold flux decreases with Li2O addition. The size of cuspidine increases, while the number of cuspidine decreases with increasing mold flux basicity. The morphology of cuspidine in mold fluxes with lower basicity is largely dendritic. The dendritic cuspidine in mold fluxes is composed of many fine cuspidine crystals. On the contrary, in mold fluxes with higher basicity, the cuspidine crystals are larger in size with mainly faceted morphology. The crystalline phase evolution was also calculated using a thermodynamic database, and compared with the experimental results determined by DSC and XRD. The results of thermodynamic calculation of crystalline phase formation are in accordance with the results determined by DSC and XRD.

  2. Combating freshwater scarcity

    OpenAIRE

    Maheshwari, Ramesh

    2005-01-01

    Pushpangadan et al.1 have 'offered the idea of discovering and exploiting waterfixing/harvesting/synthesizing organisms from desert organisms or thermophilic bacteria' for combating freshwater scarcity in plants. Their idea is based on the false notion that 'certain living organisms (both flora and fauna) grow and thrive well in sand dunes of deserts like Sahara, but certain thermophilic bacteria and some higher forms of life have also been located in the sand dunes'. Further, they write,'Pla...

  3. Professional Enterprise NET

    CERN Document Server

    Arking, Jon

    2010-01-01

    Comprehensive coverage to help experienced .NET developers create flexible, extensible enterprise application code If you're an experienced Microsoft .NET developer, you'll find in this book a road map to the latest enterprise development methodologies. It covers the tools you will use in addition to Visual Studio, including Spring.NET and nUnit, and applies to development with ASP.NET, C#, VB, Office (VBA), and database. You will find comprehensive coverage of the tools and practices that professional .NET developers need to master in order to build enterprise more flexible, testable, and ext

  4. Determination of Energy Fluxes Over Agricultural Surfaces

    Directory of Open Access Journals (Sweden)

    Josefina Argete

    1994-12-01

    Full Text Available An energy budget was conducted over two kinds if surfaces: grass and corn canopy. The net radiative flux and the soil heat flux were directly measured while the latent and sensible heat flux were calculated from the vertical profiles if wet and dry-bulb temperature and wind speed. The crop storage flux was also estimated. Using the gradient or aerodynamic equations, the calculated fluxes when compared to the measured fluxes in the context of an energy budget gave an SEE = 63 Wm-2 over grass and SEE = 81 Wm-2 over corn canopy. The calculated fluxes compared reasonably well with those obtained using the Penman equations.For an energy budget research with limited instrumentation, the aerodynamic method performed satisfactorily in estimating the daytime fluxes, when atmospheric conditions are fully convective, but failed when conditions were stably stratified as during nighttime.

  5. Freshwater and its role in the Arctic Marine System: Sources, disposition, storage, export, and physical and biogeochemical consequences in the Arctic and global oceans

    Science.gov (United States)

    Carmack, E. C.; Yamamoto-Kawai, M.; Haine, T. W. N.; Bacon, S.; Bluhm, B. A.; Lique, C.; Melling, H.; Polyakov, I. V.; Straneo, F.; Timmermans, M.-L.; Williams, W. J.

    2016-03-01

    The Arctic Ocean is a fundamental node in the global hydrological cycle and the ocean's thermohaline circulation. We here assess the system's key functions and processes: (1) the delivery of fresh and low-salinity waters to the Arctic Ocean by river inflow, net precipitation, distillation during the freeze/thaw cycle, and Pacific Ocean inflows; (2) the disposition (e.g., sources, pathways, and storage) of freshwater components within the Arctic Ocean; and (3) the release and export of freshwater components into the bordering convective domains of the North Atlantic. We then examine physical, chemical, or biological processes which are influenced or constrained by the local quantities and geochemical qualities of freshwater; these include stratification and vertical mixing, ocean heat flux, nutrient supply, primary production, ocean acidification, and biogeochemical cycling. Internal to the Arctic the joint effects of sea ice decline and hydrological cycle intensification have strengthened coupling between the ocean and the atmosphere (e.g., wind and ice drift stresses, solar radiation, and heat and moisture exchange), the bordering drainage basins (e.g., river discharge, sediment transport, and erosion), and terrestrial ecosystems (e.g., Arctic greening, dissolved and particulate carbon loading, and altered phenology of biotic components). External to the Arctic freshwater export acts as both a constraint to and a necessary ingredient for deep convection in the bordering subarctic gyres and thus affects the global thermohaline circulation. Geochemical fingerprints attained within the Arctic Ocean are likewise exported into the neighboring subarctic systems and beyond. Finally, we discuss observed and modeled functions and changes in this system on seasonal, annual, and decadal time scales and discuss mechanisms that link the marine system to atmospheric, terrestrial, and cryospheric systems.

  6. Impact of freshwater plumes on intraseasonal upper ocean variability from moored observations in the Bay of Bengal

    Science.gov (United States)

    Prend, C.; Seo, H.; Weller, R. A.; Farrar, J. T.

    2016-12-01

    The Monsoon Intraseasonal Oscillations (MISO) is strongly coupled to upper ocean variability in the Bay of Bengal (BoB). Past studies suggest that net heat flux drives changes in sea surface temperature (SST) in the BoB during the Indian Summer Monsoon (ISM). Here, we use high-resolution mooring observations from the northern BoB (18°N, 90°E) to examine temperature and salinity variability during the 2015 ISM season. The mixed layer heat budget analysis shows that intraseasonal temperature variability deviated greatly from the simple 1-D balance in late summer (August and September). Examination of moored mixed layer salinity and satellite sea surface salinity (SSS) fields suggests that this is due to episodic intrusions of river discharge to the northern BoB driven by southward Ekman drift. Freshwater plumes and associated salinity fronts caused shoaling of the mixed layer to less than 1 meter at times. The presence of this shallow mixed layer led to amplified SST response to MISO-driven surface heat flux. Analysis of satellite SST data and the Price-Weller-Pinkel (PWP) 1-D ocean model are then used to estimate horizontal advection and vertical entrainment, respectively. Accounting for entrainment significantly improved the temperature balance in late summer via barrier layer dynamics, while advection was of secondary importance due to weak lateral SST gradients. Analysis of long-term SSS fields suggests that freshwater plumes arrive to the northern bay in late summer each year, but the exact timing and extent of the individual intrusion event depends highly on synoptic wind conditions. Overall, these results indicate the critical importance of river water intrusions to improved prediction of upper ocean variability and air-sea interaction in the BoB in relation to MISO and ISM rainfall.

  7. Surface renewal method for estimating sensible heat flux | Mengistu ...

    African Journals Online (AJOL)

    For short canopies, latent energy flux may be estimated using a shortened surface energy balance from measurements of sensible and soil heat flux and the net irradiance at the surface. The surface renewal (SR) method for estimating sensible heat, latent energy, and other scalar fluxes has the advantage over other ...

  8. WaveNet

    Science.gov (United States)

    2015-10-30

    Coastal Inlets Research Program WaveNet WaveNet is a web-based, Graphical-User-Interface ( GUI ) data management tool developed for Corps coastal...generates tabular and graphical information for project planning and design documents. The WaveNet is a web-based GUI designed to provide users with a...data from different sources, and employs a combination of Fortran, Python and Matlab codes to process and analyze data for USACE applications

  9. Coloured Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt

    1991-01-01

    This paper describes how Coloured Petri Nets (CP-nets) have been developed — from being a promising theoretical model to being a full-fledged language for the design, specification, simulation, validation and implementation of large software systems (and other systems in which human beings and...... use of CP-nets — because it means that the function representation and the translations (which are a bit mathematically complex) no longer are parts of the basic definition of CP-nets. Instead they are parts of the invariant method (which anyway demands considerable mathematical skills...

  10. Game Coloured Petri Nets

    DEFF Research Database (Denmark)

    Westergaard, Michael

    2006-01-01

    This paper introduces the notion of game coloured Petri nets. This allows the modeler to explicitly model what parts of the model comprise the modeled system and what parts are the environment of the modeled system. We give the formal definition of game coloured Petri nets, a means of reachability...... analysis of this net class, and an application of game coloured Petri nets to automatically generate easy-to-understand visualizations of the model by exploiting the knowledge that some parts of the model are not interesting from a visualization perspective (i.e. they are part of the environment...

  11. Programming NET Web Services

    CERN Document Server

    Ferrara, Alex

    2007-01-01

    Web services are poised to become a key technology for a wide range of Internet-enabled applications, spanning everything from straight B2B systems to mobile devices and proprietary in-house software. While there are several tools and platforms that can be used for building web services, developers are finding a powerful tool in Microsoft's .NET Framework and Visual Studio .NET. Designed from scratch to support the development of web services, the .NET Framework simplifies the process--programmers find that tasks that took an hour using the SOAP Toolkit take just minutes. Programming .NET

  12. Annotating Coloured Petri Nets

    DEFF Research Database (Denmark)

    Lindstrøm, Bo; Wells, Lisa Marie

    2002-01-01

    -net. An example of such auxiliary information is a counter which is associated with a token to be able to do performance analysis. Modifying colour sets and arc inscriptions in a CP-net to support a specific use may lead to creation of several slightly different CP-nets – only to support the different uses...... a method which makes it possible to associate auxiliary information, called annotations, with tokens without modifying the colour sets of the CP-net. Annotations are pieces of information that are not essential for determining the behaviour of the system being modelled, but are rather added to support...

  13. Bistability of mangrove forests and competition with freshwater plants

    Science.gov (United States)

    Jiang, Jiang; Fuller, Douglas O; Teh, Su Yean; Zhai, Lu; Koh, Hock Lye; DeAngelis, Donald L.; Sternberg, L.D.S.L.

    2015-01-01

    Halophytic communities such as mangrove forests and buttonwood hammocks tend to border freshwater plant communities as sharp ecotones. Most studies attribute this purely to underlying physical templates, such as groundwater salinity gradients caused by tidal flux and topography. However, a few recent studies hypothesize that self-reinforcing feedback between vegetation and vadose zone salinity are also involved and create a bistable situation in which either halophytic dominated habitat or freshwater plant communities may dominate as alternative stable states. Here, we revisit the bistability hypothesis and demonstrate the mechanisms that result in bistability. We demonstrate with remote sensing imagery the sharp boundaries between freshwater hardwood hammock communities in southern Florida and halophytic communities such as buttonwood hammocks and mangroves. We further document from the literature how transpiration of mangroves and freshwater plants respond differently to vadose zone salinity, thus altering the salinity through feedback. Using mathematical models, we show how the self-reinforcing feedback, together with physical template, controls the ecotones between halophytic and freshwater communities. Regions of bistability along environmental gradients of salinity have the potential for large-scale vegetation shifts following pulse disturbances such as hurricane tidal surges in Florida, or tsunamis in other regions. The size of the region of bistability can be large for low-lying coastal habitat due to the saline water table, which extends inland due to salinity intrusion. We suggest coupling ecological and hydrologic processes as a framework for future studies.

  14. Characterizing freshwater and nutrient fluxes to West Falmouth Harbor, Massachusetts

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — These data present oceanographic and water-quality observations made at 4 locations in West Falmouth Harbor and 3 in Buzzards Bay, Massachusetts. While both Buzzards...

  15. Marine and freshwater toxins.

    Science.gov (United States)

    Hungerford, James M

    2006-01-01

    In a very busy and exciting year, 2005 included First Action approval of a much needed official method for paralytic shellfish toxins and multiple international toxin symposia highlighted by groundbreaking research. These are the first-year milestones and activities of the Marine and Freshwater Toxins Task Force and Analytical Community. Inaugurated in 2004 and described in detail in last year's General Referee Report (1) this international toxins group has grown to 150 members from many regions and countries. Perhaps most important they are now making important and global contributions to food safety and to providing alternatives to animal-based assays. Official Method 2005.06 was first approved in late 2004 by the Task Force and subsequently Official First Action in 2005 (2) by the Methods Committee on Natural Toxins and Food Allergens and the Official Methods Board. This nonproprietary method (3) is a precolumn oxidation, liquid chromatographic method that makes good use of fluorescence detection to provide high sensitivity detection of the saxitoxins. It has also proven to be rugged enough for regulatory use and the highest level of validation. As pointed out in the report of method principle investigator and Study Director James Lawrence, approval of 2005.06 now provides the first official alternative to the mouse bioassay after many decades of shellfish monitoring. This past year in April 2005 the group also held their first international conference, "Marine and Freshwater Toxins Analysis: Ist Joint Symposium and AOAC Task Force Meeting," in Baiona, Spain. The 4-day conference consisted of research and stakeholder presentations and symposium-integrated subgroup sessions on ciguatoxins, saxitoxin assays and liquid chromatography (LC) methods for saxitoxins and domoic acids, okadaiates and azaspiracids, and yessotoxins. Many of these subgroups were recently formed in 2005 and are working towards their goals of producing officially validated analytical methods

  16. The Zoogeography of North American freshwater fishes

    National Research Council Canada - National Science Library

    Hocutt, Charles H; Wiley, E. O

    1986-01-01

    ..., and Pleistoscene glaciation. The Zoogeography of North American Freshwater Fishes is a comprehensive treatment of the freshwater biogeography of North America, with implications for other disciplines...

  17. Net zero water

    CSIR Research Space (South Africa)

    Lindeque, M

    2013-01-01

    Full Text Available Is it possible to develop a building that uses a net zero amount of water? In recent years it has become evident that it is possible to have buildings that use a net zero amount of electricity. This is possible when the building is taken off...

  18. SolNet

    DEFF Research Database (Denmark)

    Jordan, Ulrike; Vajen, Klaus; Bales, Chris

    2014-01-01

    SolNet, founded in 2006, is the first coordinated International PhD education program on Solar Thermal Engineering. The SolNet network is coordinated by the Institute of Thermal Engineering at Kassel University, Germany. The network offers PhD courses on solar heating and cooling, conference...

  19. Kunstige neurale net

    DEFF Research Database (Denmark)

    Hørning, Annette

    1994-01-01

    Artiklen beskæftiger sig med muligheden for at anvende kunstige neurale net i forbindelse med datamatisk procession af naturligt sprog, specielt automatisk talegenkendelse.......Artiklen beskæftiger sig med muligheden for at anvende kunstige neurale net i forbindelse med datamatisk procession af naturligt sprog, specielt automatisk talegenkendelse....

  20. Net greenhouse gas emissions at Eastmain-1 reservoir, Quebec, Canada

    Energy Technology Data Exchange (ETDEWEB)

    Tremblay, Alain; Bastien, Julie; Bonneville, Marie-Claude; del Giorgio, Paul; Demarty, Maud; Garneau, Michelle; Helie, Jean-Francois; Pelletier, Luc; Prairie, Yves; Roulet, Nigel; Strachan, Ian; Teodoru, Cristian

    2010-09-15

    The growing concern regarding the long-term contribution of freshwater reservoirs to atmospheric greenhouse gases (GHG), led Hydro-Quebec, to study net GHG emissions from Eastmain 1 reservoir, which are the emissions related to the creation of a reservoir minus those that would have been emitted or absorbed by the natural systems over a 100-year period. This large study was realized in collaboration with University du Quebec a Montreal, McGill University and Environnement IIlimite Inc. This is a world premiere and the net GHG emissions of EM-1 will be presented in details.

  1. Are there signs of acidification reversal in freshwaters of the low mountain ranges in Germany?

    Directory of Open Access Journals (Sweden)

    C. Alewell

    2001-01-01

    Full Text Available The reversal of freshwater acidification in the low mountain ranges of Germany is of public, political and scientific concern, because these regions are near natural ecosystems and function as an important drinking water supply. The aim of this study was to evaluate the status and trends of acidification reversal after two decades of reduced anthropogenic deposition in selected freshwaters of the low mountain ranges in the Harz, the Fichtelgebirge, the Bavarian Forest, the Spessart and the Black Forest. In response to decreased sulphate deposition, seven out of nine streams investigated had significantly decreasing sulphate concentrations (all trends were calculated with the Seasonal Kendall Test. The decrease in sulphate concentration was only minor, however, due to the release of previously stored soil sulphur. No increase was found in pH and acid neutralising capacity (defined by Reuss and Johnson, 1986. Aluminum concentrations in the streams did not decrease. Thus, no major acidification reversal can currently be noted in spite of two decades of decreased acid deposition. Nevertheless, the first signs of improvement in water quality were detected as there was a decrease in the level and frequency of extreme values of pH, acid neutralising capacity and aluminium concentrations in streams. With respect to nitrogen, no change was determined for either nitrate or ammonium concentrations in precipitation or stream water. Base cation fluxes indicate increasing net loss of base cations from all ecosystems investigated, which could be interpreted as an increase in soil acidification. The latter was due to a combination of continued high anion leaching and significant reduction of base cation deposition. No major improvement was noted in biological recovery, however, initial signs of recovery were detectable as there was re-occurrence of some single macroinvertebrate species which were formerly extinct. The results of this study have important

  2. Pro NET Best Practices

    CERN Document Server

    Ritchie, Stephen D

    2011-01-01

    Pro .NET Best Practices is a practical reference to the best practices that you can apply to your .NET projects today. You will learn standards, techniques, and conventions that are sharply focused, realistic and helpful for achieving results, steering clear of unproven, idealistic, and impractical recommendations. Pro .NET Best Practices covers a broad range of practices and principles that development experts agree are the right ways to develop software, which includes continuous integration, automated testing, automated deployment, and code analysis. Whether the solution is from a free and

  3. Getting to Net Zero

    Energy Technology Data Exchange (ETDEWEB)

    2016-09-01

    The technology necessary to build net zero energy buildings (NZEBs) is ready and available today, however, building to net zero energy performance levels can be challenging. Energy efficiency measures, onsite energy generation resources, load matching and grid interaction, climatic factors, and local policies vary from location to location and require unique methods of constructing NZEBs. It is recommended that Components start looking into how to construct and operate NZEBs now as there is a learning curve to net zero construction and FY 2020 is just around the corner.

  4. Instant Lucene.NET

    CERN Document Server

    Heydt, Michael

    2013-01-01

    Filled with practical, step-by-step instructions and clear explanations for the most important and useful tasks. A step-by-step guide that helps you to index, search, and retrieve unstructured data with the help of Lucene.NET.Instant Lucene.NET How-to is essential for developers new to Lucene and Lucene.NET who are looking to get an immediate foundational understanding of how to use the library in their application. It's assumed you have programming experience in C# already, but not that you have experience with search techniques such as information retrieval theory (although there will be a l

  5. CO2 and CH4 fluxes across a Nuphar lutea (L. Sm. stand

    Directory of Open Access Journals (Sweden)

    Scott C. Neubauer

    2012-01-01

    Full Text Available Floating-leaved rhizophytes can significantly alter net carbon dioxide (CO2 and methane (CH4 exchanges with the atmosphere in freshwater shallow environments. In particular, CH4 efflux can be enhanced by the aerenchyma-mediated mass flow, while CO2 release from supersaturated waters can be reversed by the plant uptake. Additionally, the floating leaves bed can hamper light penetration and oxygen (O2 diffusion from the atmosphere, thus altering the dissolved gas dynamics in the water column. In this study, net fluxes of CO2 and CH4 were measured seasonally across vegetated [Nuphar lutea (L. Sm.] and free water surfaces in the Busatello wetland (Northern Italy. Concomitantly, dissolved gas concentrations were monitored in the water column and N. lutea leaf production was estimated by means of biomass harvesting. During the vegetative period (May-August, the yellow waterlily stand resulted a net sink for atmospheric carbon (from 97.5 to 110.6 g C-CO2 m-2, while the free water surface was a net carbon source (166.3 g C-CO2 m-2. Both vegetated and plant-free areas acted as CH4 sources, with an overall carbon release comprised between 71.6 and 113.3 g C-CH4 m-2. On the whole, water column chemistry was not affected by the presence of the floating leaves; moreover, no significant differences in CH4 efflux were evidenced between the vegetated and plant-free areas. In general, this study indicates that the colonization of shallow aquatic ecosystems by N. lutea might not have the same drastic effect reported for free-floating macrophytes.

  6. Net Zero Energy Buildings

    DEFF Research Database (Denmark)

    Marszal, Anna Joanna; Bourrelle, Julien S.; Musall, Eike

    2010-01-01

    and identify possible renewable energy supply options which may be considered in calculations. Finally, the gap between the methodology proposed by each organisation and their respective national building code is assessed; providing an overview of the possible changes building codes will need to undergo......The international cooperation project IEA SHC Task 40 / ECBCS Annex 52 “Towards Net Zero Energy Solar Buildings”, attempts to develop a common understanding and to set up the basis for an international definition framework of Net Zero Energy Buildings (Net ZEBs). The understanding of such buildings...... parameters used in the calculations are discussed and the various renewable supply options considered in the methodologies are summarised graphically. Thus, the paper helps to understand different existing approaches to calculate energy balance in Net ZEBs, highlights the importance of variables selection...

  7. PhysioNet

    Data.gov (United States)

    U.S. Department of Health & Human Services — The PhysioNet Resource is intended to stimulate current research and new investigations in the study of complex biomedical and physiologic signals. It offers free...

  8. NetSig

    DEFF Research Database (Denmark)

    Horn, Heiko; Lawrence, Michael S; Chouinard, Candace R

    2018-01-01

    Methods that integrate molecular network information and tumor genome data could complement gene-based statistical tests to identify likely new cancer genes; but such approaches are challenging to validate at scale, and their predictive value remains unclear. We developed a robust statistic (Net......Sig) that integrates protein interaction networks with data from 4,742 tumor exomes. NetSig can accurately classify known driver genes in 60% of tested tumor types and predicts 62 new driver candidates. Using a quantitative experimental framework to determine in vivo tumorigenic potential in mice, we found that Net......Sig candidates induce tumors at rates that are comparable to those of known oncogenes and are ten-fold higher than those of random genes. By reanalyzing nine tumor-inducing NetSig candidates in 242 patients with oncogene-negative lung adenocarcinomas, we find that two (AKT2 and TFDP2) are significantly amplified...

  9. TideNet

    Science.gov (United States)

    2015-10-30

    query tide data sources in a desired geographic region of USA and its territories (Figure 1). Users can select a tide data source through the Google Map ...select data sources according to the desired geographic region. It uses the Google Map interface to display data from different sources. Recent...Coastal Inlets Research Program TideNet The TideNet is a web-based Graphical User Interface (GUI) that provides users with GIS mapping tools to

  10. Building Neural Net Software

    OpenAIRE

    Neto, João Pedro; Costa, José Félix

    1999-01-01

    In a recent paper [Neto et al. 97] we showed that programming languages can be translated on recurrent (analog, rational weighted) neural nets. The goal was not efficiency but simplicity. Indeed we used a number-theoretic approach to machine programming, where (integer) numbers were coded in a unary fashion, introducing a exponential slow down in the computations, with respect to a two-symbol tape Turing machine. Implementation of programming languages in neural nets turns to be not only theo...

  11. Interaction Nets in Russian

    OpenAIRE

    Salikhmetov, Anton

    2013-01-01

    Draft translation to Russian of Chapter 7, Interaction-Based Models of Computation, from Models of Computation: An Introduction to Computability Theory by Maribel Fernandez. "In this chapter, we study interaction nets, a model of computation that can be seen as a representative of a class of models based on the notion of 'computation as interaction'. Interaction nets are a graphical model of computation devised by Yves Lafont in 1990 as a generalisation of the proof structures of linear logic...

  12. Programming NET 35

    CERN Document Server

    Liberty, Jesse

    2009-01-01

    Bestselling author Jesse Liberty and industry expert Alex Horovitz uncover the common threads that unite the .NET 3.5 technologies, so you can benefit from the best practices and architectural patterns baked into the new Microsoft frameworks. The book offers a Grand Tour" of .NET 3.5 that describes how the principal technologies can be used together, with Ajax, to build modern n-tier and service-oriented applications. "

  13. Freshwater Treatment and Test Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Freshwater Treatment and Test Facility, located at SANGB, has direct year-round access to water from Lake St. Clair and has a State of Michigan approved National...

  14. Salting our freshwater lakes

    Science.gov (United States)

    Bartlett, Sarah L.; Burke, Samantha M.; Doubek, Jonathan P.; Krivak-Tetley, Flora E.; Skaff, Nicholas K.; Summers, Jamie C.; Farrell, Kaitlin J.; McCullough, Ian M.; Morales-Williams, Ana M.; Roberts, Derek C.; Ouyang, Zutao; Scordo, Facundo; Hanson, Paul C.; Weathers, Kathleen C.

    2017-01-01

    The highest densities of lakes on Earth are in north temperate ecosystems, where increasing urbanization and associated chloride runoff can salinize freshwaters and threaten lake water quality and the many ecosystem services lakes provide. However, the extent to which lake salinity may be changing at broad spatial scales remains unknown, leading us to first identify spatial patterns and then investigate the drivers of these patterns. Significant decadal trends in lake salinization were identified using a dataset of long-term chloride concentrations from 371 North American lakes. Landscape and climate metrics calculated for each site demonstrated that impervious land cover was a strong predictor of chloride trends in Northeast and Midwest North American lakes. As little as 1% impervious land cover surrounding a lake increased the likelihood of long-term salinization. Considering that 27% of large lakes in the United States have >1% impervious land cover around their perimeters, the potential for steady and long-term salinization of these aquatic systems is high. This study predicts that many lakes will exceed the aquatic life threshold criterion for chronic chloride exposure (230 mg L−1), stipulated by the US Environmental Protection Agency (EPA), in the next 50 y if current trends continue. PMID:28396392

  15. Quantity and quality: unifying food web and ecosystem perspectives on the role of resource subsidies in freshwaters.

    Science.gov (United States)

    Marcarelli, Amy M; Baxter, Colden V; Mineau, Madeleine M; Hall, Robert O

    2011-06-01

    Although the study of resource subsidies has emerged as a key topic in both ecosystem and food web ecology, the dialogue over their role has been limited by separate approaches that emphasize either subsidy quantity or quality. Considering quantity and quality together may provide a simple, but previously unexplored, framework for identifying the mechanisms that govern the importance of subsidies for recipient food webs and ecosystems. Using a literature review of > 90 studies of open-water metabolism in lakes and streams, we show that high-flux, low-quality subsidies can drive freshwater ecosystem dynamics. Because most of these ecosystems are net heterotrophic, allochthonous inputs must subsidize respiration. Second, using a literature review of subsidy quality and use, we demonstrate that animals select for high-quality food resources in proportions greater than would be predicted based on food quantity, and regardless of allochthonous or autochthonous origin. This finding suggests that low-flux, high-quality subsidies may be selected for by animals, and in turn may disproportionately affect food web and ecosystem processes (e.g., animal production, trophic energy or organic matter flow, trophic cascades). We then synthesize and review approaches that evaluate the role of subsidies and explicitly merge ecosystem and food web perspectives by placing food web measurements in the context of ecosystem budgets, by comparing trophic and ecosystem production and fluxes, and by constructing flow food webs. These tools can and should be used to address future questions about subsidies, such as the relative importance of subsidies to different trophic levels and how subsidies may maintain or disrupt ecosystem stability and food web interactions.

  16. Towards more physically constrained freshwater injection and its associated impact on paleoclimate variability

    Science.gov (United States)

    Love, Ryan; Tarasov, Lev; Condron, Alan

    2017-04-01

    Freshwater forcing (or commonly, "hosing") has been proposed as a causal mechanism for the onset of the Younger Dryas period and may play a role in other centennial to millennial climate events outside the last deglacial period. However, paleoclimate modelling experiments attempting to infer the role of freshwater forcing have low confidence due to at least two major issues. First, previous attempts at reproducing the observed variability through freshwater forcing experiments have often utilized unrealistically large freshwater volumes and adhoc injection regions. Second, boundary currents and the associated transport of freshwater sourced from land based ice are to date not resolved (except for a few exceptions) in paleo model experiments. Despite these limitations, freshwater forcing is frequently utilised as a means to induce rapid and large scale changes in simulated paleoclimate. Few studies have examined the effect of using more realistic freshwater distributions and/or a concurrent hierarchy of climate models. To quantify the impact of these freshwater distributions, we sample from the global runoff and calving flux output of the glacial systems model of Tarasov et. al., 2012 as input into our hierarchy of climate models. Furthermore, we address the issue of resolution in part by extracting transport pathways from one of the few experiments that has been conducted at the eddy permitting scale in the global ocean, that of Condron and Winsor, 2012. With these enhancements, we re-examine the role of freshwater forcing in the climate system during glacial conditions. In particular, we quantify the impact of a more realistic freshwater distribution upon the strength of ocean circulation and heat transport to high latitudes.

  17. Natural Air-Sea Flux of CO2 in Simulations of the NASA-GISS Climate Model: Sensitivity to the Physical Ocean Model Formulation

    Science.gov (United States)

    Romanou, A.; Gregg, Watson W.; Romanski, J.; Kelley, M.; Bleck, R.; Healy, R.; Nazarenko, L.; Russell, G.; Schmidt, G. A.; Sun, S.; hide

    2013-01-01

    Results from twin control simulations of the preindustrial CO2 gas exchange (natural flux of CO2) between the ocean and the atmosphere are presented here using the NASA-GISS climate model, in which the same atmospheric component (modelE2) is coupled to two different ocean models, the Russell ocean model and HYCOM. Both incarnations of the GISS climate model are also coupled to the same ocean biogeochemistry module (NOBM) which estimates prognostic distributions for biotic and abiotic fields that influence the air-sea flux of CO2. Model intercomparison is carried out at equilibrium conditions and model differences are contrasted with biases from present day climatologies. Although the models agree on the spatial patterns of the air-sea flux of CO2, they disagree on the strength of the North Atlantic and Southern Ocean sinks mainly because of kinematic (winds) and chemistry (pCO2) differences rather than thermodynamic (SST) ones. Biology/chemistry dissimilarities in the models stem from the different parameterizations of advective and diffusive processes, such as overturning, mixing and horizontal tracer advection and to a lesser degree from parameterizations of biogeochemical processes such as gravitational settling and sinking. The global meridional overturning circulation illustrates much of the different behavior of the biological pump in the two models, together with differences in mixed layer depth which are responsible for different SST, DIC and nutrient distributions in the two models and consequently different atmospheric feedbacks (in the wind, net heat and freshwater fluxes into the ocean).

  18. Natural air-sea flux of CO2 in simulations of the NASA-GISS climate model: Sensitivity to the physical ocean model formulation

    Science.gov (United States)

    Romanou, A.; Gregg, W. W.; Romanski, J.; Kelley, M.; Bleck, R.; Healy, R.; Nazarenko, L.; Russell, G.; Schmidt, G. A.; Sun, S.; Tausnev, N.

    2013-06-01

    Results from twin control simulations of the preindustrial CO2 gas exchange (natural flux of CO2) between the ocean and the atmosphere are presented here using the NASA-GISS climate model, in which the same atmospheric component (modelE2) is coupled to two different ocean models, the Russell ocean model and HYCOM. Both incarnations of the GISS climate model are also coupled to the same ocean biogeochemistry module (NOBM) which estimates prognostic distributions for biotic and abiotic fields that influence the air-sea flux of CO2. Model intercomparison is carried out at equilibrium conditions and model differences are contrasted with biases from present day climatologies. Although the models agree on the spatial patterns of the air-sea flux of CO2, they disagree on the strength of the North Atlantic and Southern Ocean sinks mainly because of kinematic (winds) and chemistry (pCO2) differences rather than thermodynamic (SST) ones. Biology/chemistry dissimilarities in the models stem from the different parameterizations of advective and diffusive processes, such as overturning, mixing and horizontal tracer advection and to a lesser degree from parameterizations of biogeochemical processes such as gravitational settling and sinking. The global meridional overturning circulation illustrates much of the different behavior of the biological pump in the two models, together with differences in mixed layer depth which are responsible for different SST, DIC and nutrient distributions in the two models and consequently different atmospheric feedbacks (in the wind, net heat and freshwater fluxes into the ocean).

  19. La plataforma .NET

    OpenAIRE

    Fornas Estrada, Miquel

    2008-01-01

    L'aparició de la plataforma .NET Framework ha suposat un canvi molt important en la forma de crear i distribuir aplicacions, degut a que incorpora una sèrie d'innovacions tècniques i productives que simplifiquen molt les tasques necessàries per desenvolupar un projecte. La aparición de la plataforma. NET Framework ha supuesto un cambio muy importante en la forma de crear y distribuir aplicaciones, debido a que incorpora una serie de innovaciones técnicas y productivas que simplifican mucho...

  20. Biological Petri Nets

    CERN Document Server

    Wingender, E

    2011-01-01

    It was suggested some years ago that Petri nets might be well suited to modeling metabolic networks, overcoming some of the limitations encountered by the use of systems employing ODEs (ordinary differential equations). Much work has been done since then which confirms this and demonstrates the usefulness of this concept for systems biology. Petri net technology is not only intuitively understood by scientists trained in the life sciences, it also has a robust mathematical foundation and provides the required degree of flexibility. As a result it appears to be a very promising approach to mode

  1. Seasonal patterns in energy partitioning of two freshwater marsh ecosystems in the Florida Everglades

    Science.gov (United States)

    Sparkle L. Malone; Christina L. Staudhammer; Henry W. Loescher; Paulo Olivas; Steven F. Oberbauer; Michael G. Ryan; Jessica Schedlbauer; Gregory Starr

    2014-01-01

    We analyzed energy partitioning in short- and long-hydroperiod freshwater marsh ecosystems in the Florida Everglades by examining energy balance components (eddy covariance derived latent energy (LE) and sensible heat (H) flux). The study period included several wet and dry seasons and variable water levels, allowing us to gain better mechanistic information about the...

  2. On the physical air-sea fluxes for climate modeling

    NARCIS (Netherlands)

    Bonekamp, J.G.

    2001-01-01

    At the sea surface, the atmosphere and the ocean exchange momentum, heat and freshwater. Mechanisms for the exchange are wind stress, turbulent mixing, radiation, evaporation and precipitation. These surface fluxes are characterized by a large spatial and temporal variability and play an

  3. Petri Nets-Applications

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 9. Petri Nets - Applications. Y Narahari. General Article Volume 4 Issue 9 September 1999 pp 44-52. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/004/09/0044-0052. Author Affiliations. Y Narahari ...

  4. Safety nets or straitjackets?

    DEFF Research Database (Denmark)

    Ilsøe, Anna

    2012-01-01

    Does regulation of working hours at national and sector level impose straitjackets, or offer safety nets to employees seeking working time flexibility? This article compares legislation and collective agreements in the metal industries of Denmark, Germany and the USA. The industry has historically...

  5. Coloured Petri Nets

    CERN Document Server

    Jensen, Kurt

    2009-01-01

    Coloured Petri Nets (CPN) is a graphical language for modelling and validating concurrent and distributed systems, and other systems in which concurrency plays a major role. This book introduces the constructs of the CPN modelling language and presents the related analysis methods. It provides a comprehensive road map for the practical use of CPN.

  6. Boom Booom Net Radio

    DEFF Research Database (Denmark)

    Grimshaw, Mark Nicholas; Yong, Louisa; Dobie, Ian

    1999-01-01

    of an existing Internet radio station; Boom Booom Net Radio. Whilst necessity dictates some use of technology-related terminology, wherever possible we have endeavoured to keep such jargon to a minimum and to either explain it in the text or to provide further explanation in the appended glossary....

  7. Game Theory .net.

    Science.gov (United States)

    Shor, Mikhael

    2003-01-01

    States making game theory relevant and accessible to students is challenging. Describes the primary goal of GameTheory.net is to provide interactive teaching tools. Indicates the site strives to unite educators from economics, political and computer science, and ecology by providing a repository of lecture notes and tests for courses using…

  8. Coloured Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt; Kristensen, Lars Michael

    Coloured Petri Nets (CPN) is a graphical language for modelling and validating concurrent and distributed systems, and other systems in which concurrency plays a major role. The development of such systems is particularly challenging because of inherent intricacies like possible nondeterminism...

  9. Thermal Performance Testing of Cryogenic Multilayer Insulation with Silk Net Spacers

    Science.gov (United States)

    Johnson, W. L.; Frank, D. J.; Nast, T. C.; Fesmire, J. E.

    2015-12-01

    Early comprehensive testing of cryogenic multilayer insulation focused on the use of silk netting as a spacer material. Silk netting was used for multiple test campaigns that were designed to provide baseline thermal performance estimates for cryogenic insulation systems. As more focus was put on larger systems, the cost of silk netting became a deterrent and most aerospace insulation firms were using Dacron (or polyester) netting spacers by the early 1970s. In the midst of the switch away from silk netting there was no attempt to understand the difference between silk and polyester netting, though it was widely believed that the silk netting provided slightly better performance. Without any better reference for thermal performance data, the silk netting performance correlations continued to be used. In order to attempt to quantify the difference between the silk netting and polyester netting, a brief test program was developed. The silk netting material was obtained from Lockheed Martin and was tested on the Cryostat-100 instrument in three different configurations, 20 layers with both single and double netting and 10 layers with single netting only. The data show agreement within 15 - 30% with the historical silk netting based correlations and show a substantial performance improvement when compared to previous testing performed using polyester netting and aluminum foil/fiberglass paper multilayer insulation. Additionally, the data further reinforce a recently observed trend that the heat flux is not directly proportional to the number of layers installed on a system.

  10. Alongshore wind stress and heat flux divergence off Visakhapatnam, east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Sadhuram, Y.; Rao, B.P.; Rao, D.P.

    Annual variation of heat flux divergence (Qv) was computed for the coastal waters of Visakhapatnam. The mean values of net heat exchange (Qn) and heat flux divergence (Qv) were found to be 114 and 115 W.m/2 respectively on annual scale. The net heat...

  11. Progress and challenges in freshwater conservation planning

    CSIR Research Space (South Africa)

    Nel, JL

    2009-06-01

    Full Text Available Freshwater ecosystems and their associated biota are among the most endangered in the world. This, combined with escalating human pressure on water resources, demands that urgent measures be taken to conserve freshwater ecosystems and the services...

  12. Native Freshwater Fish and Mussel Species Richness

    Data.gov (United States)

    U.S. Environmental Protection Agency — These data represent predicted current distributions of all native freshwater fish and freshwater mussels in the Middle-Atlantic region. The data are available for...

  13. Inhabitants of the Fresh-Water Community.

    Science.gov (United States)

    Jorgensen, Joseph; Schroeder, Marlene

    This learner's guide is designed to assist middle school students in studying freshwater organisms. Following a brief introduction to freshwater ecology, simple line drawings facilitate the identification of plants and animals common to Florida's freshwater ecosystems. Emphasis of the short text which accompanies each illustration is upon the…

  14. Arctic freshwater export: Status, mechanisms, and prospects

    NARCIS (Netherlands)

    Haine, T.W.N.; Curry, B.; Gerdes, R.; Hansen, E.; Karcher, M.; Lee, C.; Rudels, B.; Spreen, G.; de Steur, L.; Stewart, K.D.; Woodgate, R.

    2015-01-01

    Large freshwater anomalies clearly exist in the Arctic Ocean. For example, liquid freshwater has accumulated in the Beaufort Gyre in the decade of the 2000s compared to 1980–2000, with an extra ˜ 5000 km3 — about 25% — being stored. The sources of freshwater to the Arctic from precipitation and

  15. Food Safety Nets:

    OpenAIRE

    Haggblade, Steven; Diallo, Boubacar; Staatz, John; Theriault, Veronique; Traoré, Abdramane

    2013-01-01

    Food and social safety nets have a history as long as human civilization. In hunter gatherer societies, food sharing is pervasive. Group members who prove unlucky in the short run, hunting or foraging, receive food from other households in anticipation of reciprocal consideration at a later time (Smith 1988). With the emergence of the first large sedentary civilizations in the Middle East, administrative systems developed specifically around food storage and distribution. The ancient Egyptian...

  16. Net technical assessment

    OpenAIRE

    Wegmann, David G.

    1989-01-01

    Approved for public release; distribution is unlimited. The present and near term military balance of power between the U.S. and the Soviet Union can be expressed in a variety of net assessments. One can examine the strategic nuclear balance, the conventional balance in Europe, the maritime balance, and many others. Such assessments are essential not only for policy making but for arms control purposes and future force structure planning. However, to project the future military balance, on...

  17. Estimating daytime ecosystem respiration from eddy-flux data

    DEFF Research Database (Denmark)

    Bruhn, Dan; Mikkelsen, Teis Nørgaard; Herbst, Mathias

    2011-01-01

    To understand what governs the patterns of net ecosystem exchange of CO2, an understanding of factors influencing the component fluxes, ecosystem respiration and gross primary production is needed. In the present paper, we introduce an alternative method for estimating daytime ecosystem respiration...... based on whole ecosystem fluxes from a linear regression of photosynthetic photon flux density data vs. daytime net ecosystem exchange data at forest ecosystem level. This method is based on the principles of the Kok-method applied at leaf level for estimating daytime respiration. We demonstrate...... the method with field data and provide a discussion of the limitations of the method....

  18. Caribbean brackish and freshwater Cyanophyceae

    NARCIS (Netherlands)

    Koster, Joséphine Th.

    1960-01-01

    Among the extensive collections of algae made by Dr P. Wagenaar Hummelinck (Utrecht) in the Antilles and adjacent regions during the years 1930, 1936, 1937, 1948—1949, 1955, a number of chiefly brackish, but also freshwater, Cyanophyceae were incorporated. This collection was kindly committed for

  19. Nearctic freshwater tardigrades: a review

    Directory of Open Access Journals (Sweden)

    Juliana G. HINTON

    2007-09-01

    Full Text Available The distribution and ecology of limno-terrestrial Tardigrada in the Nearctic realm remain poorly known. This is especially true of freshwater tardigrades (i.e., species found in permanently submerged habitats, which have received much less attention than terrestrial species. We reviewed the literature on Nearctic freshwater tardigrades. Of 204 Nearctic limno-terrestrial tardigrade species, 44 have been collected from sediments and aquatic vegetation of streams, rivers, ponds, lakes, groundwater and cryoconite holes. Of these, 17 are hydrophilous species found exclusively or primarily in aquatic environments. Most of the remainder are probably washed in accidentally from terrestrial substrates. Among the hydrophilous species, five are endemic to the Nearctic realm and three cosmopolitan. Hypsibius dujardini is the most widely-distributed hydrophilous species. There are no regional collections of Nearctic freshwater tardigrades comparable to those for terrestrial species. Aquatic tardigrades are benthic, and are found in sediments and on aquatic vegetation. Hypsibius dujardini and other widespread species are found in both substrates, and there is thus no evidence of substrate specificity. Numerically, tardigrades usually comprise a minor component of benthic invertebrate communities. Nothing is known of their trophic relationships or dispersal in these habitats. The density of Nearctic freshwater tardigrade species peaks in the spring and/or fall. Future research should increase the spatial and temporal scale of study, and employ adequate replication.

  20. Methane emission from freshwater marshes

    NARCIS (Netherlands)

    Nat, Frans-Jaco Willy Anthony van der

    2000-01-01

    This thesis describes the results of a four-year study into the CH4 cycle of freshwater marshes dominated by reed and bulrush. This research was conducted in the framework of the research theme carbon and nutrient dynamics in vegetated littoral systems of the department of Littoral Vegetation of

  1. Dissolved organic carbon fluxes by seagrass meadows and macroalgal beds

    Directory of Open Access Journals (Sweden)

    Cristina eBarron

    2014-10-01

    Full Text Available Estimates of dissolved organic carbon (DOC release by marine macrophyte communities (seagrass meadows and macroalgal beds based on in situ benthic chambers from published and unpublished are compiled in this study. The effect of temperature and light availability on DOC release by macrophyte communities was examined. Almost 85 % of the seagrass communities and all of macroalgal communities examined acted as net sources of DOC. Net DOC fluxes in seagrass communities increase positively with water temperature. In macroalgal communities net DOC fluxes under light exceeded those under dark condition, however, this trend was weaker in seagrass communities. Shading of a mixed seagrass meadow in The Philippines led to a significant reduction on the net DOC release when shading was maintained for 6 days compared to only 2 days of shading. Net DOC fluxes increased with increasing community respiration, but were independent of primary production or net community production. The estimated global net DOC flux, and hence export, from marine macrophytes is about 0.158 ± 0.055 Pg C yr-1 or 0.175 ± 0.056 Pg C yr-1 depending on the global extent of seagrass meadows considered.

  2. Using WordNet for Building WordNets

    CERN Document Server

    Farreres, X; Farreres, Xavier; Rodriguez, Horacio; Rigau, German

    1998-01-01

    This paper summarises a set of methodologies and techniques for the fast construction of multilingual WordNets. The English WordNet is used in this approach as a backbone for Catalan and Spanish WordNets and as a lexical knowledge resource for several subtasks.

  3. Proof nets for lingusitic analysis

    NARCIS (Netherlands)

    Moot, R.C.A.

    2002-01-01

    This book investigates the possible linguistic applications of proof nets, redundancy free representations of proofs, which were introduced by Girard for linear logic. We will adapt the notion of proof net to allow the formulation of a proof net calculus which is soundand complete for the

  4. Teaching Tennis for Net Success.

    Science.gov (United States)

    Young, Bryce

    1989-01-01

    A program for teaching tennis to beginners, NET (Net Easy Teaching) is described. The program addresses three common needs shared by tennis students: active involvement in hitting the ball, clearing the net, and positive reinforcement. A sample lesson plan is included. (IAH)

  5. Net4Care Ecosystem Website

    DEFF Research Database (Denmark)

    Christensen, Henrik Bærbak; Hansen, Klaus Marius; Rasmussen, Morten

    2012-01-01

    is a tele-monitoring scenario in which Net4Care clients are deployed in a gateway in private homes. Medical devices then connect to these gateways and transmit their observations to a Net4Care server. In turn the Net4Care server creates valid clinical HL7 documents, stores them in a national XDS repository...

  6. Reciprocal subsidies between freshwater and terrestrial ecosystems structure consumer resource dynamics.

    Science.gov (United States)

    Bartels, Pia; Cucherousset, Julien; Steger, Kristin; Eklöv, Peter; Tranvik, Lars J; Hillebrand, Helmut

    2012-05-01

    Cross-ecosystem movements of material and energy, particularly reciprocal resource fluxes across the freshwater-land interface, have received major attention. Freshwater ecosystems may receive higher amounts of subsidies (i.e., resources produced outside the focal ecosystem) than terrestrial ecosystems, potentially leading to increased secondary production in freshwaters. Here we used a meta-analytic approach to quantify the magnitude and direction of subsidy inputs across the freshwater-land interface and to determine subsequent responses in recipient animals. Terrestrial and freshwater ecosystems differed in the magnitude of subsidies they received, with aquatic ecosystems generally receiving higher subsidies than terrestrial ecosystems. Surprisingly, and despite the large discrepancy in magnitude, the contribution of these subsidies to animal carbon inferred from stable isotope composition did not differ between freshwater and terrestrial ecosystems, likely due to the differences in subsidy quality. The contribution of allochthonous subsidies was highest to primary consumers and predators, suggesting that bottom-up and top-down effects may be affected considerably by the input of allochthonous resources. Future work on subsidies will profit from a food web dynamic approach including indirect trophic interactions and propagating effects.

  7. Dissolved uranium, vanadium and molybdenum behaviours during contrasting freshwater discharges in the Gironde Estuary (SW France)

    Science.gov (United States)

    Strady, Emilie; Blanc, Gérard; Schäfer, Jörg; Coynel, Alexandra; Dabrin, Aymeric

    2009-08-01

    Understanding trace metal behaviour in estuarine environments requires sampling strategies and analytical methods adapted to strong physical and geochemical gradients. In this study, we present a specific sampling strategy covering a wide range of hydrological conditions during nine cruises in 2003-2007 to characterise the behaviour of three dissolved metals (uranium, vanadium and molybdenum) in surface and bottom water along the salinity gradient of the highly turbid macrotidal Gironde Estuary using a solid-liquid extraction. Uranium behaved conservatively whatever the water discharges observed. The slight dissolved U depletion compared to the theoretical dilution line between the fluvial and marine end-members occasionally observed in the low salinity range (0-3) was attributed to the mixing of different water bodies of the Gironde tributaries. In contrast, dissolved V behaviour was largely influenced by the hydrological conditions, showing increasingly pronounced addition with decreasing freshwater discharges, (i.e. increasing residence times of water and particles in the estuary). This addition of dissolved V in the low- to mid-salinity range was attributed to desorption processes observed in the Maximum Turbidity Zone (MTZ). The distribution of dissolved Mo concentrations along the salinity gradient was highly variable. Apparent conservative, and non-conservative behaviours were observed and were related to the concomitance of desorption from SPM, inputs from sediments for additive distribution and biological uptake and removal into sediments for subtractive distribution. Based on the whole database (2003-2007), annual net fluxes to the coastal ocean were estimated for dissolved U (15.5-16.6 t yr -1) and V (31.3-36.7 t yr -1).

  8. Heat in the Barents Sea: transport, storage, and surface fluxes

    Directory of Open Access Journals (Sweden)

    L. H. Smedsrud

    2010-02-01

    Full Text Available A column model is set up for the Barents Sea to explore sensitivity of surface fluxes and heat storage from varying ocean heat transport. Mean monthly ocean transport and atmospheric forcing are synthesised and force the simulations. Results show that by using updated ocean transports of heat and freshwater the vertical mean hydrographic seasonal cycle can be reproduced fairly well.

    Our results indicate that the ~70 TW of heat transported to the Barents Sea by ocean currents is lost in the southern Barents Sea as latent, sensible, and long wave radiation, each contributing 23–39 TW to the total heat loss. Solar radiation adds 26 TW in the south, as there is no significant ice production.

    The northern Barents Sea receives little ocean heat transport. This leads to a mixed layer at the freezing point during winter and significant ice production. There is little net surface heat loss annually in the north. The balance is achieved by a heat loss through long wave radiation all year, removing most of the summer solar heating.

    During the last decade the Barents Sea has experienced an atmospheric warming and an increased ocean heat transport. The Barents Sea responds to such large changes by adjusting temperature and heat loss. Decreasing the ocean heat transport below 50 TW starts a transition towards Arctic conditions. The heat loss in the Barents Sea depend on the effective area for cooling, and an increased heat transport leads to a spreading of warm water further north.

  9. Influence of freshwater input on the skill of decadal forecast of sea ice in the Southern Ocean

    Directory of Open Access Journals (Sweden)

    V. Zunz

    2015-03-01

    Full Text Available Recent studies have investigated the potential link between the freshwater input derived from the melting of the Antarctic ice sheet and the observed recent increase in sea ice extent in the Southern Ocean. In this study, we assess the impact of an additional freshwater flux on the trend in sea ice extent and concentration in simulations with data assimilation, spanning the period 1850–2009, as well as in retrospective forecasts (hindcasts initialised in 1980. In the simulations with data assimilation, the inclusion of an additional freshwater flux that follows an autoregressive process improves the reconstruction of the trend in ice extent and concentration between 1980 and 2009. This is linked to a better efficiency of the data assimilation procedure but can also be due to a better representation of the freshwater cycle in the Southern Ocean. The results of the hindcast simulations show that an adequate initial state, reconstructed thanks to the data assimilation procedure including an additional freshwater flux, can lead to an increase in the sea ice extent spanning several decades that is in agreement with satellite observations. In our hindcast simulations, an increase in sea ice extent is obtained even in the absence of any major change in the freshwater input over the last decades. Therefore, while the additional freshwater flux appears to play a key role in the reconstruction of the evolution of the sea ice in the simulation with data assimilation, it does not seem to be required in the hindcast simulations. The present work thus provides encouraging results for sea ice predictions in the Southern Ocean, as in our simulation the positive trend in ice extent over the last 30 years is largely determined by the state of the system in the late 1970s.

  10. Heat flux viscosity in collisional magnetized plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C., E-mail: cliu@pppl.gov [Princeton University, Princeton, New Jersey 08544 (United States); Fox, W. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Bhattacharjee, A. [Princeton University, Princeton, New Jersey 08544 (United States); Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

    2015-05-15

    Momentum transport in collisional magnetized plasmas due to gradients in the heat flux, a “heat flux viscosity,” is demonstrated. Even though no net particle flux is associated with a heat flux, in a plasma there can still be momentum transport owing to the velocity dependence of the Coulomb collision frequency, analogous to the thermal force. This heat-flux viscosity may play an important role in numerous plasma environments, in particular, in strongly driven high-energy-density plasma, where strong heat flux can dominate over ordinary plasma flows. The heat flux viscosity can influence the dynamics of the magnetic field in plasmas through the generalized Ohm's law and may therefore play an important role as a dissipation mechanism allowing magnetic field line reconnection. The heat flux viscosity is calculated directly using the finite-difference method of Epperlein and Haines [Phys. Fluids 29, 1029 (1986)], which is shown to be more accurate than Braginskii's method [S. I. Braginskii, Rev. Plasma Phys. 1, 205 (1965)], and confirmed with one-dimensional collisional particle-in-cell simulations. The resulting transport coefficients are tabulated for ease of application.

  11. Master Robotic Net

    Directory of Open Access Journals (Sweden)

    Vladimir Lipunov

    2010-01-01

    Full Text Available The main goal of the MASTER-Net project is to produce a unique fast sky survey with all sky observed over a single night down to a limiting magnitude of 19-20. Such a survey will make it possible to address a number of fundamental problems: search for dark energy via the discovery and photometry of supernovae (including SNIa, search for exoplanets, microlensing effects, discovery of minor bodies in the Solar System, and space-junk monitoring. All MASTER telescopes can be guided by alerts, and we plan to observe prompt optical emission from gamma-ray bursts synchronously in several filters and in several polarization planes.

  12. Art/Net/Work

    DEFF Research Database (Denmark)

    Andersen, Christian Ulrik; Lindstrøm, Hanne

    2006-01-01

    The seminar Art|Net|Work deals with two important changes in our culture. On one side, the network has become essential in the latest technological development. The Internet has entered a new phase, Web 2.0, including the occurrence of as ‘Wiki’s’, ‘Peer-2-Peer’ distribution, user controlled...... the praxis of the artist. We see different kinds of interventions and activism (including ‘hacktivism’) using the network as a way of questioning the invisible rules that govern public and semi-public spaces. Who ‘owns’ them? What kind of social relationships do they generate? On what principle...

  13. Photosynthesis drives anomalies in net carbon-exchange of pine forests at different latitudes

    NARCIS (Netherlands)

    Luyssaert, S.; Janssens, I.A.; Sulkava, M.; Papale, D.; Dolman, A.J.; Reichstein, M.; Hollmén, J.; Martin, J.G.; Suni, T.; Vesala, T.; Loustau, D.; Law, B.E.; Moors, E.J.

    2007-01-01

    The growth rate of atmospheric CO2 exhibits large temporal variation that is largely determined by year-to-year fluctuations in land¿atmosphere CO2 fluxes. This land¿atmosphere CO2-flux is driven by large-scale biomass burning and variation in net ecosystem exchange (NEE). Between- and within years,

  14. High-flux water desalination with interfacial salt sieving effect in nanoporous carbon composite membranes

    CERN Document Server

    Chen, Wei; Zhang, Qiang; Fan, Zhongli; Huang, Kuo-Wei; Zhang, Xixiang; Lai, Zhiping; Sheng, Ping

    2016-01-01

    Nanoporous carbon composite membranes, comprising a layer of porous carbon fiber structures with an average channel width of 30-60 nm grown on a porous ceramic substrate, are found to exhibit robust desalination effect with high freshwater flux. In three different membrane processes of vacuum membrane distillation, reverse osmosis and forward osmosis, the carbon composite membrane showed 100% salt rejection with 3.5 to 20 times higher freshwater flux compared to existing polymeric membranes. Thermal accounting experiments found that at least 80% of the freshwater pass through the carbon composite membrane with no phase change. Molecular dynamics simulations revealed a unique salt rejection mechanism. When seawater is interfaced with either vapor or the surface of carbon, one to three interfacial atomic layers contain no salt ions. Below the liquid entry pressure, the salt solution is stopped at the openings to the porous channels and forms a meniscus, while the surface layer of freshwater can feed the surface...

  15. Helminth.net: expansions to Nematode.net and an introduction to Trematode.net

    Science.gov (United States)

    Martin, John; Rosa, Bruce A.; Ozersky, Philip; Hallsworth-Pepin, Kymberlie; Zhang, Xu; Bhonagiri-Palsikar, Veena; Tyagi, Rahul; Wang, Qi; Choi, Young-Jun; Gao, Xin; McNulty, Samantha N.; Brindley, Paul J.; Mitreva, Makedonka

    2015-01-01

    Helminth.net (http://www.helminth.net) is the new moniker for a collection of databases: Nematode.net and Trematode.net. Within this collection we provide services and resources for parasitic roundworms (nematodes) and flatworms (trematodes), collectively known as helminths. For over a decade we have provided resources for studying nematodes via our veteran site Nematode.net (http://nematode.net). In this article, (i) we provide an update on the expansions of Nematode.net that hosts omics data from 84 species and provides advanced search tools to the broad scientific community so that data can be mined in a useful and user-friendly manner and (ii) we introduce Trematode.net, a site dedicated to the dissemination of data from flukes, flatworm parasites of the class Trematoda, phylum Platyhelminthes. Trematode.net is an independent component of Helminth.net and currently hosts data from 16 species, with information ranging from genomic, functional genomic data, enzymatic pathway utilization to microbiome changes associated with helminth infections. The databases’ interface, with a sophisticated query engine as a backbone, is intended to allow users to search for multi-factorial combinations of species’ omics properties. This report describes updates to Nematode.net since its last description in NAR, 2012, and also introduces and presents its new sibling site, Trematode.net. PMID:25392426

  16. Critical flux determination by flux-stepping

    DEFF Research Database (Denmark)

    Beier, Søren; Jonsson, Gunnar Eigil

    2010-01-01

    In membrane filtration related scientific literature, often step-by-step determined critical fluxes are reported. Using a dynamic microfiltration device, it is shown that critical fluxes determined from two different flux-stepping methods are dependent upon operational parameters such as step...... length, step height, and.flux start level. Filtrating 8 kg/m(3) yeast cell suspensions by a vibrating 0.45 x 10(-6) m pore size microfiltration hollow fiber module, critical fluxes from 5.6 x 10(-6) to 1.2 x 10(-5) m/s have been measured using various step lengths from 300 to 1200 seconds. Thus...

  17. Waterscape determinants of net mercury methylation in a tropical wetland.

    Science.gov (United States)

    Lázaro, Wilkinson L; Díez, Sergi; da Silva, Carolina J; Ignácio, Áurea R A; Guimarães, Jean R D

    2016-10-01

    The periphyton associated with freshwater macrophyte roots is the main site of Hg methylation in different wetland environments in the world. The aim of this study was to test the use of connectivity metrics of water bodies, in the context of patches, in a tropical waterscape wetland (Guapore River, Amazonia, Brazil) as a predictor of potential net methylmercury (MeHg) production by periphyton communities. We sampled 15 lakes with different patterns of lateral connectivity with the main river channel, performing net mercury methylation potential tests in incubations with local water and Eichhornia crassipes root-periphyton samples, using (203)HgCl2 as a tracer. Physico-chemical variables, landscape data (morphological characteristics, land use, and lateral connection type of water bodies) using GIS resources and field data were analyzed with Generalized Additive Models (GAM). The net Me(203)Hg production (as % of total added (203)Hg) was expressive (6.2-25.6%) showing that periphyton is an important matrix in MeHg production. The model that best explained the variation in the net Me(203)Hg production (76%) was built by the variables: connection type, total phosphorus and dissolved organic carbon (DOC) in water (AICc=48.324, p=0.001). Connection type factor was the best factor to model fit (r(2)=0.32; p=0.008) and temporarily connected lakes had higher rates of net mercury methylation. Both DOC and total phosphorus showed positive significant covariation with the net methylation rates (r(2)=0.26; p=0.008 and r(2)=0.21; p=0.012 respectively). Our study suggests a strong relationship between rates of net MeHg production in this tropical area and the type of water body and its hydrological connectivity within the waterscape. Copyright © 2016 Elsevier Inc. All rights reserved.

  18. NETS FOR PEACH PROTECTED CULTIVATION

    Directory of Open Access Journals (Sweden)

    Evelia Schettini

    2012-06-01

    Full Text Available The aim of this paper was to investigate the radiometric properties of coloured nets used to protect a peach cultivation. The modifications of the solar spectral distribution, mainly in the R and FR wavelength band, influence plant photomorphogenesis by means of the phytochrome and cryptochrome. The phytochrome response is characterized in terms of radiation rate in the red wavelengths (R, 600-700 nm to that in the farred radiation (FR, 700-800 nm, i.e. the R/FR ratio. The effects of the blue radiation (B, 400-500 nm is investigated by the ratio between the blue radiation and the far-red radiation, i.e. the B/FR ratio. A BLUE net, a RED net, a YELLOW net, a PEARL net, a GREY net and a NEUTRAL net were tested in Bari (Italy, latitude 41° 05’ N. Peach trees were located in pots inside the greenhouses and in open field. The growth of the trees cultivated in open field was lower in comparison to the growth of the trees grown under the nets. The RED, PEARL, YELLOW and GREY nets increased the growth of the trees more than the other nets. The nets positively influenced the fruit characteristics, such as fruit weight and flesh firmness.

  19. The freshwater composition of the Fram Strait outflow derived from a decade of tracer measurements

    DEFF Research Database (Denmark)

    Dodd, Paul A.; Rabe, Benjamin; Hansen, Edmond

    2012-01-01

    The composition of the Fram Strait freshwater outflow is investigated by comparing 10 sections of concurrent salinity, δ18O, nitrate and phosphate measurements collected between 1997 and 2011. The largest inventories of net sea ice meltwater are found in 2009, 2010 and 2011. The 2009–2011 sections...... meltwater inventories, suggesting that meteoric water and brine may be delivered to Fram Strait together from a common source. We find that the freshwater outflow at Fram Strait exhibits a similar meteoric water to net sea ice meltwater ratio as the central Arctic Ocean and Siberian shelves, suggesting...... that much of the sea ice meltwater and meteoric water at Fram Strait may originate from these regions. However, we also find that the ratio of meteoric water to sea ice meltwater inventories at Fram Strait is decreasing with time, due to an increased surface input of sea ice meltwater in recent sections...

  20. Cable Bacteria in Freshwater Sediments

    DEFF Research Database (Denmark)

    Risgaard-Petersen, Nils; Kristiansen, Michael; Frederiksen, Rasmus

    2015-01-01

    In marine sediments cathodic oxygen reduction at the sediment surface can be coupled to anodic sulfide oxidation in deeper anoxic layers through electrical currents mediated by filamentous, multicellular bacteria of the Desulfobulbaceae family, the so-called cable bacteria. Until now, cable...... bacteria have only been reported from marine environments. In this study, we demonstrate that cable bacteria also occur in freshwater sediments. In a first step, homogenized sediment collected from the freshwater stream Giber Å, Denmark, was incubated in the laboratory. After 2 weeks, pH signatures...... marine cable bacteria, with the genus Desulfobulbus as the closest cultured lineage. The results of the present study indicate that electric currents mediated by cable bacteria could be important for the biogeochemistry in many more environments than anticipated thus far and suggest a common evolutionary...

  1. Reviews and syntheses: An empirical spatiotemporal description of the global surface-atmosphere carbon fluxes: opportunities and data limitations

    Science.gov (United States)

    Zscheischler, Jakob; Mahecha, Miguel D.; Avitabile, Valerio; Calle, Leonardo; Carvalhais, Nuno; Ciais, Philippe; Gans, Fabian; Gruber, Nicolas; Hartmann, Jens; Herold, Martin; Ichii, Kazuhito; Jung, Martin; Landschützer, Peter; Laruelle, Goulven G.; Lauerwald, Ronny; Papale, Dario; Peylin, Philippe; Poulter, Benjamin; Ray, Deepak; Regnier, Pierre; Rödenbeck, Christian; Roman-Cuesta, Rosa M.; Schwalm, Christopher; Tramontana, Gianluca; Tyukavina, Alexandra; Valentini, Riccardo; van der Werf, Guido; West, Tristram O.; Wolf, Julie E.; Reichstein, Markus

    2017-08-01

    Understanding the global carbon (C) cycle is of crucial importance to map current and future climate dynamics relative to global environmental change. A full characterization of C cycling requires detailed information on spatiotemporal patterns of surface-atmosphere fluxes. However, relevant C cycle observations are highly variable in their coverage and reporting standards. Especially problematic is the lack of integration of the carbon dioxide (CO2) exchange of the ocean, inland freshwaters and the land surface with the atmosphere. Here we adopt a data-driven approach to synthesize a wide range of observation-based spatially explicit surface-atmosphere CO2 fluxes from 2001 to 2010, to identify the state of today's observational opportunities and data limitations. The considered fluxes include net exchange of open oceans, continental shelves, estuaries, rivers, and lakes, as well as CO2 fluxes related to net ecosystem productivity, fire emissions, loss of tropical aboveground C, harvested wood and crops, as well as fossil fuel and cement emissions. Spatially explicit CO2 fluxes are obtained through geostatistical and/or remote-sensing-based upscaling, thereby minimizing biophysical or biogeochemical assumptions encoded in process-based models. We estimate a bottom-up net C exchange (NCE) between the surface (land, ocean, and coastal areas) and the atmosphere. Though we provide also global estimates, the primary goal of this study is to identify key uncertainties and observational shortcomings that need to be prioritized in the expansion of in situ observatories. Uncertainties for NCE and its components are derived using resampling. In many regions, our NCE estimates agree well with independent estimates from other sources such as process-based models and atmospheric inversions. This holds for Europe (mean ± 1 SD: 0.8 ± 0.1 PgC yr-1, positive numbers are sources to the atmosphere), Russia (0.1 ± 0.4 PgC yr-1), East Asia (1.6 ± 0.3 PgC yr-1), South Asia (0.3 ± 0

  2. The equivalency between logic Petri workflow nets and workflow nets.

    Science.gov (United States)

    Wang, Jing; Yu, ShuXia; Du, YuYue

    2015-01-01

    Logic Petri nets (LPNs) can describe and analyze batch processing functions and passing value indeterminacy in cooperative systems. Logic Petri workflow nets (LPWNs) are proposed based on LPNs in this paper. Process mining is regarded as an important bridge between modeling and analysis of data mining and business process. Workflow nets (WF-nets) are the extension to Petri nets (PNs), and have successfully been used to process mining. Some shortcomings cannot be avoided in process mining, such as duplicate tasks, invisible tasks, and the noise of logs. The online shop in electronic commerce in this paper is modeled to prove the equivalence between LPWNs and WF-nets, and advantages of LPWNs are presented.

  3. The Freshwater Information Platform - an online network supporting freshwater biodiversity research and policy

    Science.gov (United States)

    Schmidt-Kloiber, Astrid; De Wever, Aaike; Bremerich, Vanessa; Strackbein, Jörg; Hering, Daniel; Jähnig, Sonja; Kiesel, Jens; Martens, Koen; Tockner, Klement

    2017-04-01

    Species distribution data is crucial for improving our understanding of biodiversity and its threats. This is especially the case for freshwater environments, which are heavily affected by the global biodiversity crisis. Currently, a huge body of freshwater biodiversity data is often difficult to access, because systematic data publishing practices have not yet been adopted by the freshwater research community. The Freshwater Information Platform (FIP; www.freshwaterplatform.eu) - initiated through the BioFresh project - aims at pooling freshwater related research information from a variety of projects and initiatives to make it easily accessible for scientists, water managers and conservationists as well as the interested public. It consists of several major components, three of which we want to specifically address: (1) The Freshwater Biodiversity Data Portal aims at mobilising freshwater biodiversity data, making them online available Datasets in the portal are described and documented in the (2) Freshwater Metadatabase and published as open access articles in the Freshwater Metadata Journal. The use of collected datasets for large-scale analyses and models is demonstrated in the (3) Global Freshwater Biodiversity Atlas that publishes interactive online maps featuring research results on freshwater biodiversity, resources, threats and conservation priorities. Here we present the main components of the FIP as tools to streamline open access freshwater data publication arguing this will improve the capacity to protect and manage freshwater biodiversity in the face of global change.

  4. Coloured Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt; Kristensen, Lars Michael

    studies that illustrate the practical use of CPN modelling and validation for design, specification, simulation, verification and implementation in various application domains. Their presentation primarily aims at readers interested in the practical use of CPN. Thus all concepts and constructs are first......Coloured Petri Nets (CPN) is a graphical language for modelling and validating concurrent and distributed systems, and other systems in which concurrency plays a major role. The development of such systems is particularly challenging because of inherent intricacies like possible nondeterminism...... and the immense number of possible execution sequences. In this textbook, Jensen and Kristensen introduce the constructs of the CPN modelling language and present the related analysis methods in detail. They also provide a comprehensive road map for the practical use of CPN by showcasing selected industrial case...

  5. Cascade sensitivity studies for KM3NeT

    Directory of Open Access Journals (Sweden)

    Fusco Luigi Antonio

    2016-01-01

    Full Text Available KM3NeT is a future research infrastructure in the deep seas of the Mediterranean housing a large scale neutrino telescope. The first phase of construction of the telescope has started. Next step is an intermediate phase realising a detector volume of about one-third of the final detector volume. We report on calculations of the sensitivity of the KM3NeT detector to showering neutrino events, the strategy to optimise the detector to a cosmic neutrino flux analogous to the one reported by the IceCube Collaboration and the results of this strategy applied to the intermediate phase detector.

  6. Impact of freshwater diversion projects on diversity and activity of methanotrophic communities in freshwater wetlands

    Science.gov (United States)

    Isaac, J.; Schulz, C. J.; Childers, G. W.

    2009-12-01

    Methanotrophic bacteria are key players in the carbon cycle capable of using methane as a sole carbon and energy source. Methanotrophs are ubiquitous in soil environments and play a key role in decreasing methane flux from anaerobic environments to the atmosphere, reducing the concentration of this greenhouse gas. Wetlands are a particularly important source of methane to the atmosphere, even though methanotrophs can consume the majority of the methane produced. Decreases in methanotrophic activity in wetland environments due to disturbance can have negative impacts with regard to greenhouse gas emissions, especially if the impact is widespread. Currently, several freshwater diversion projects are active and/or scheduled to come online in south Louisiana, delivering freshwater, sediments, and nutrients to coastal wetlands en masse to help combat subsidence and coastal erosion. Along with freshwater, these diversions also deliver other components of the Mississippi River including substantial bicarbonate alkalinity, reactive nitrogen, and sulfate. Analogous to the large scale diversion projects are smaller restoration projects that deliver treated wastewater effluent to wetlands. In particular, the Joyce Wildlife Management Area (JWMA) in southeast Louisiana has been the recipient of ~5 million gallons of treated domestic effluent per day since 2006. Both the composition of the marsh receiving the effluent and the effluent itself have similarities to Mississippi River diversions. We collected pre and post JWMA sediment microbial community DNA and created cloned libraries of genes encoding particulate methane monooxygenase (pmoA) as a proxy for methanotrophic community composition. Water chemistry data was also collected. Shifts in methanotrophic community composition were apparent as well as shifts in water chemistry. The most notable shift in water chemistry was pH, which changed from mildly acidic to slightly alkaline conditions, due to the increased alkalinity of

  7. Liquid export of Arctic freshwater components through the Fram Strait 1998–2011

    Directory of Open Access Journals (Sweden)

    G. Kattner

    2013-01-01

    Full Text Available We estimated the magnitude and composition of southward liquid freshwater transports in the East Greenland Current near 79° N in the Western Fram Strait between 1998 and 2011. Previous studies have found this region to be an important pathway for liquid freshwater export from the Arctic Ocean to the Nordic Seas and the North Atlantic subpolar gyre. Our transport estimates are based on six hydrographic surveys between June and September and concurrent data from moored current meters. We combined concentrations of liquid freshwater, meteoric water (river water and precipitation, sea ice melt and brine from sea ice formation, and Pacific Water, presented in Dodd et al. (2012, with volume transport estimates from an inverse model. The average of the monthly snapshots of southward liquid freshwater transports between 10.6° W and 4° E is 100 ± 23 mSv (3160 ± 730 km3 yr−1, relative to a salinity of 34.9. This liquid freshwater transport consists of about 130% water from rivers and precipitation (meteoric water, 30% freshwater from the Pacific, and −60% (freshwater deficit due to a mixture of sea ice melt and brine from sea ice formation. Pacific Water transports showed the highest variation in time, effectively vanishing in some of the surveys. Comparison of our results to the literature indicates that this was due to atmospherically driven variability in the advection of Pacific Water along different pathways through the Arctic Ocean. Variations in most liquid freshwater component transports appear to have been most strongly influenced by changes in the advection of these water masses to the Fram Strait. However, the local dynamics represented by the volume transports influenced the liquid freshwater component transports in individual years, in particular those of sea ice melt and brine from sea ice formation. Our results show a similar ratio of the transports of meteoric water and net sea ice melt as previous studies. However, we observed a

  8. The freshwater reservoir effect in radiocarbon dating

    OpenAIRE

    Philippsen, Bente

    2012-01-01

    The freshwater reservoir effect can result in too high radiocarbon ages of samples from lakes and rivers, including the bones of people whose subsistence was based on freshwater fish, and pottery in which fish was cooked. In my talk, I will explain the causes and consequences of this effect. Two case studies will show the degree of variability of the freshwater reservoir effect over short and long timescales. Radiocarbon dating of recent water samples, aquatic plants and animals, shows that a...

  9. Natural and anthropogenic factors affecting freshwater lenses in coastal dunes of the Adriatic coast

    Science.gov (United States)

    Cozzolino, Davide; Greggio, Nicolas; Antonellini, Marco; Giambastiani, Beatrice Maria Sole

    2017-08-01

    This study characterizes the near-shore portion of the shallow coastal aquifer included in the Ravenna area (Northern Italy) with special attention to the roles of coastal dunes as freshwater reservoirs and their buffer on groundwater salinity. The paper focuses on the presence and evolution of freshwater lenses below coastal dunes and highlights the existing differences between preserved natural dunes and dunes strongly affected by human intervention. The influence that multiple natural and anthropogenic factors, such as land cover, local drainage network, and beach erosion have on the presence, size and evolution of the freshwater lenses in the aquifer is quantified and discussed. The methodology includes multiple seasonal monitoring and sampling campaigns of physical (water level, salinity, and temperature) and chemical (major cations and anions) groundwater parameters. Results indicate that freshwater lenses, where existing, are limited in thickness (about 1-2 m). Proximity to drainage ditches as well as limited dune elevation and size do not allow the formation and permanent storage of large freshwater lenses in the aquifer below the dunes. The pine forest land cover, that replaced the typical bush or sand cover, intensifies evapotranspiration reducing net infiltration and freshwater storage. The cation species distribution in the water shows that a freshening process is ongoing in preserved natural sites with stable or advancing beaches, whereas a salinization process is ongoing in anthropogenic-impacted areas with strongly-fragmented dune systems. Currently, the thin freshwater lenses in the shallow Ravenna coastal aquifer are limited in space and have no relevance for irrigation or any other human activity. The dune-beach system, however, is the recharge zone of the coastal aquifer and its protection is important to reduce water and soil salinization, which in turn control the health of the whole coastal ecosystem.

  10. The freshwater reservoir effect in radiocarbon dating

    DEFF Research Database (Denmark)

    Philippsen, Bente

    2013-01-01

    effect on radiocarbon dating in an estuarine environment is examined. Here, freshwater influence causes reservoir ages to vary between 250 and 700 14C years during the period 5400 BC - AD 700. The examples in this study show clearly that the freshwater reservoir effect can seriously corrupt radiocarbon...... for radiocarbon dating of Mesolithic pottery from inland sites of the Ertebølle culture in Northern Germany. The surprisingly old ages of the earliest pottery most probably are caused by a freshwater reservoir effect. In a sediment core from the Limfjord, northern Denmark, the impact of the freshwater reservoir...

  11. Spatial and Temporal Variability in Carbon Dioxide Fluxes at Three Coastal Marshes Along a Salinity Gradient in the Northern Gulf of Mexico: how Susceptible are Coastal Marshes in the Region to Future Wariming?

    Science.gov (United States)

    Mortazavi, B.; Wilson, B.; Kiene, R. P.

    2014-12-01

    Carbon gas fluxes in tidal marshes vary spatially and temporally because of vegetation cover, subsurface biogeochemical processes, and environmental forcing and predicting the impact of climate change on greenhouse gas fluxes from wetlands remains challenging. We examined how ecosystem carbon gas exchange varies along a salinity gradient (0-32 ppt) in three marshes along an estuary in the northern Gulf of Mexico, USA. Midday net ecosystem exchange (where a negative rate indicates net carbon assimilated through photosynthesis) was greatest at the most freshwater site (4.8 ± 0.3 μmol CO2 m-2 s-1), followed by the saline (2.8 ± 1.0 μmol CO2 m-2 s-1) and brackish (1.4 ± 0.6 μmol CO2 m-2 s-1) sites. However, net ecosystem exchange integrated diurnally revealed each marsh to be a net CO2 source to the atmosphere as a result of high ecosystem respiration with no significant difference across the fresh (105.5 ± 28.9 mmol CO2 m-2 d-1), brackish (100.1 ± 36.5 mmol CO2 m-2 d-1), and salt marsh (78.3 ± 28.6 mmol CO2 m-2 d-1) sites. The large loss of carbon from these ecosystems is suggested to be a contributing factor to the disappearances of marshes in the region. Fifty percent of coastal Alabama wetlands, for examples, have disappeared from 1780 to 1980, and between 1955 and 1979 the percent loss (29%) in the region has exceeded the national average by a factor of three. While future warming is not expected to impact carbon assimilation significantly, our warming simulations suggest that carbon loss in these ecosystems can be enhanced by 12 to 26%, potentially exasperating the loss of marshes in the region.

  12. Geochemical proxies of North American freshwater routing during the Younger Dryas cold event.

    Science.gov (United States)

    Carlson, Anders E; Clark, Peter U; Haley, Brian A; Klinkhammer, Gary P; Simmons, Kathleen; Brook, Edward J; Meissner, Katrin J

    2007-04-17

    The Younger Dryas cold interval represents a time when much of the Northern Hemisphere cooled from approximately 12.9 to 11.5 kiloyears B.P. The cause of this event, which has long been viewed as the canonical example of abrupt climate change, was initially attributed to the routing of freshwater to the St. Lawrence River with an attendant reduction in Atlantic meridional overturning circulation. However, this mechanism has recently been questioned because current proxies and dating techniques have been unable to confirm that eastward routing with an increase in freshwater flux occurred during the Younger Dryas. Here we use new geochemical proxies (DeltaMg/Ca, U/Ca, and (87)Sr/(86)Sr) measured in planktonic foraminifera at the mouth of the St. Lawrence estuary as tracers of freshwater sources to further evaluate this question. Our proxies, combined with planktonic delta(18)O(seawater) and delta(13)C, confirm that routing of runoff from western Canada to the St. Lawrence River occurred at the start of the Younger Dryas, with an attendant increase in freshwater flux of 0.06 +/- 0.02 Sverdrup (1 Sverdrup = 10(6) m(3).s(-1)). This base discharge increase is sufficient to have reduced Atlantic meridional overturning circulation and caused the Younger Dryas cold interval. In addition, our data indicate subsequent fluctuations in the freshwater flux to the St. Lawrence River of approximately 0.06-0.12 Sverdrup, thus explaining the variability in the overturning circulation and climate during the Younger Dryas.

  13. Tentacle structure in freshwater bryozoans.

    Science.gov (United States)

    Tamberg, Yuta; Shunatova, Natalia

    2017-05-01

    Tentacles are the main food-gathering organs of bryozoans. The most common design is a hollow tube of extracellular matrix (ECM), covered with ten columns of epithelial cells on the outside, and a coelothelium on the inside. Nerves follow the ECM, going between the bases of some epidermal cells. The tentacle musculature includes two bundles formed by myoepithelial cells of the coelothelium. The tentacles of freshwater (phylactolaemate) bryozoans, however, differ somewhat in structure from those of marine bryozoans. Here, we describe the tentacles of three species of phylactolaemates, comparing them to gymnolaemates and stenolaemates. Phylactolaemate tentacles tend to be longer, and with more voluminous coeloms. The composition of the frontal cell row and the number of frontal nerves is variable in freshwater bryozoans, but constant in marine groups. Abfrontal cells form a continuous row in Phylactolaemata, but occur intermittently in other two classes. Phylactolaemata lack the microvillar cuticle reported in Gymnolaemata. Abfrontal sensory tufts are always composed of pairs of mono- and/or biciliated cells. This arrangement differs from individual abfrontal ciliary cells of other bryozoans: monociliated in Stenolaemata and monociliated and multiciliated ones in Gymnolaemata. In all three groups, however, ciliated abfrontal cells probably serve as mechanoreceptors. We confirm previously described phylactolemate traits: an unusual arrangement of two-layered coelothelium lining the lateral sides of the tentacle and oral slits in the intertentacular membrane. As previously reported, tentacle movements involved in feeding differ between bryozoan groups, with phylactolaemates tending to have slower movements than both gymnolaemates and stenolaemates, and a narrower behavioral repertoire than gymnolaemates. The morphological and ultrastructural differences between the freshwater species we studied and marine bryozoans may be related to these functional differences. Muscle

  14. Constraining Daily-To-Annual Carbon Budgets in a Brackish Tidal Marsh in the San Francisco Bay Delta: Insights on Methane and Carbon Dioxide Fluxes from Eddy Covariance Measurements

    Science.gov (United States)

    Saraceno, J.; Anderson, F. E.; Knox, S.; Windham-Myers, L.; Bergamaschi, B. A.

    2016-12-01

    Carbon cycling in coastal wetlands is difficult to measure and model due to extremely dynamic atmospheric (vertical) and hydrologic (lateral) fluxes, as well as sensitivities to dynamic land- and ocean-based drivers. Whereas atmospheric carbon is sequestered in accreted carbon stocks over millennia to maintain balance with sea level rise, annual or seasonal carbon fluxes from tidal wetlands can become net negative or net positive, as key drivers of carbon cycling, such as inundation area, soil and air temperature and salinity change over short time periods. Few studies have documented the interannual variability in the net ecosystem carbon balance for tidal-driven ecosystems. Using the eddy covariance technique, we present 2.5 years (March 2014-September 2016) of net ecosystem exchanges (NEE) for CO2 and CH4 from a historic wetland (the National Estuarine Research Reserve's Rush Ranch) in the Suisun Marsh complex of San Francisco Bay, California, where salinity ranges from oligohaline to mesohaline. Preliminary estimates show that daily rates of CO2 NEE were approximately -15 gC m-2 d-1 during the peak growing season in the summer to +10 gC m-2 d-1 during the winter months. CH4 emissions, ranged from 0 to +30 mgC m-2 d-1, a small fraction of observed rates from neighboring freshwater marshes. We have also found that using standard parameters (e.g. temperature and radiation) in an artificial neural network approach to gap-fill missing fluxes and estimate random error uncertainty were insufficient, suggesting that daily and seasonal shifts in salinity, water levels, and plant community phenology may help to reduce uncertainty in estimated values of both CO2 and CH4 fluxes. An additional aspect of this study is to investigate the significance of carbon exported through tidal exchanges, especially considering that regional estimates of carbon accretion in the soils to be only 100 gC m-2. Here we will estimate the aquatic carbon flux using proxies for dissolved

  15. Flux-P: Automating Metabolic Flux Analysis

    Directory of Open Access Journals (Sweden)

    Birgitta E. Ebert

    2012-11-01

    Full Text Available Quantitative knowledge of intracellular fluxes in metabolic networks is invaluable for inferring metabolic system behavior and the design principles of biological systems. However, intracellular reaction rates can not often be calculated directly but have to be estimated; for instance, via 13C-based metabolic flux analysis, a model-based interpretation of stable carbon isotope patterns in intermediates of metabolism. Existing software such as FiatFlux, OpenFLUX or 13CFLUX supports experts in this complex analysis, but requires several steps that have to be carried out manually, hence restricting the use of this software for data interpretation to a rather small number of experiments. In this paper, we present Flux-P as an approach to automate and standardize 13C-based metabolic flux analysis, using the Bio-jETI workflow framework. Exemplarily based on the FiatFlux software, it demonstrates how services can be created that carry out the different analysis steps autonomously and how these can subsequently be assembled into software workflows that perform automated, high-throughput intracellular flux analysis of high quality and reproducibility. Besides significant acceleration and standardization of the data analysis, the agile workflow-based realization supports flexible changes of the analysis workflows on the user level, making it easy to perform custom analyses.

  16. Benthic fluxes in San Francisco Bay

    Science.gov (United States)

    Hammond, Douglas E.; Fuller, C.; Harmon, D.; Hartman, Blayne; Korosec, M.; Miller, L.G.; Rea, R.; Warren, S.; Berelson, W.; Hager, S.W.

    1985-01-01

    Measurements of benthic fluxes have been made on four occasions between February 1980 and February 1981 at a channel station and a shoal station in South San Francisco Bay, using in situ flux chambers. On each occasion replicate measurements of easily measured substances such as radon, oxygen, ammonia, and silica showed a variability (??1??) of 30% or more over distances of a few meters to tens of meters, presumably due to spatial heterogeneity in the benthic community. Fluxes of radon were greater at the shoal station than at the channel station because of greater macrofaunal irrigation at the former, but showed little seasonal variability at either station. At both stations fluxes of oxygen, carbon dioxide, ammonia, and silica were largest following the spring bloom. Fluxes measured during different seasons ranged over factors of 2-3, 3, 4-5, and 3-10 (respectively), due to variations in phytoplankton productivity and temperature. Fluxes of oxygen and carbon dioxide were greater at the shoal station than at the channel station because the net phytoplankton productivity is greater there and the organic matter produced must be rapidly incorporated in the sediment column. Fluxes of silica were greater at the shoal station, probably because of the greater irrigation rates there. N + N (nitrate + nitrite) fluxes were variable in magnitude and in sign. Phosphate fluxes were too small to measure accurately. Alkalinity fluxes were similar at the two stations and are attributed primarily to carbonate dissolution at the shoal station and to sulfate reduction at the channel station. The estimated average fluxes into South Bay, based on results from these two stations over the course of a year, are (in mmol m-2 d-1): O2 = -27 ?? 6; TCO2 = 23 ?? 6; Alkalinity = 9 ?? 2; N + N = -0.3 ?? 0.5; NH3 = 1.4 ?? 0.2; PO4 = 0.1 ?? 0.4; Si = 5.6 ?? 1.1. These fluxes are comparable in magnitude to those in other temperate estuaries with similar productivity, although the seasonal

  17. Linear Logic on Petri Nets

    DEFF Research Database (Denmark)

    Engberg, Uffe Henrik; Winskel, Glynn

    This article shows how individual Petri nets form models of Girard's intuitionistic linear logic. It explores questions of expressiveness and completeness of linear logic with respect to this interpretation. An aim is to use Petri nets to give an understanding of linear logic and give some apprai...

  18. Reference Guide Microsoft.NET

    NARCIS (Netherlands)

    Zee M van der; Verspaij GJ; Rosbergen S; IMP; NMD

    2003-01-01

    Developers, administrators and managers can get more understanding of the .NET technology with this report. They can also make better choices how to use this technology. The report describes the results and conclusions of a study of the usability for the RIVM of this new generation .NET development

  19. Net neutrality and audiovisual services

    NARCIS (Netherlands)

    van Eijk, N.; Nikoltchev, S.

    2011-01-01

    Net neutrality is high on the European agenda. New regulations for the communication sector provide a legal framework for net neutrality and need to be implemented on both a European and a national level. The key element is not just about blocking or slowing down traffic across communication

  20. Methane emissions from a freshwater marsh in response to experimentally simulated global warming and nitrogen enrichment

    DEFF Research Database (Denmark)

    Flury, Sabine; McGinnis, Daniel Frank; Gessner, Mark O.

    2010-01-01

    We determined methane (CH4) emissions in a field enclosure experiment in a littoral freshwater marsh under the influence of experimentally simulated warming and enhanced nitrogen deposition. Methane emissions by ebullition from the marsh composed of Phragmites australis were measured with funnel ...... to the atmosphere, even when they occupy only relatively small littoral areas. More detailed investigations are clearly needed to assess whether global warming and nitrogen deposition can have climate feedbacks by altering methane fluxes from these wetlands.  ...

  1. Freshwater autotrophic picoplankton: a review

    Directory of Open Access Journals (Sweden)

    John G. STOCKNER

    2002-02-01

    Full Text Available Autotrophic picoplankton (APP are distributed worldwide and are ubiquitous in all types of lakes of varying trophic state. APP are major players in carbon production in all aquatic ecosystems, including extreme environments such as cold ice-covered and/or warm tropical lakes and thermal springs. They often form the base of complex microbial food webs, becoming prey for a multitude of protozoan and micro-invertebrate grazers, that effectively channel APP carbon to higher trophic levels including fish. In this review we examine the existing literature on freshwater autotrophic picoplankton, setting recent findings and current ecological issues within an historic framework, and include a description of the occurrence and distribution of both single-cell and colonial APP (picocyanobacteria in different types of lakes. In this review we place considerable emphasis on methodology and ecology, including sampling, counting, preservation, molecular techniques, measurement of photosynthesis, and include extensive comment on their important role in microbial food webs. The model outlined by Stockner of an increase of APP abundance and biomass and a decrease of its relative importance with the increase of phosphorus concentration in lakes has been widely accepted, and only recently confirmed in marine and freshwater ecosystems. Nevertheless the relationship which drives the APP presence and importance in lakes of differing trophic status appears with considerable variation so we must conclude that the success of APP in oligotrophic lakes worldwide is not a certainty but highly probable.

  2. A Small Universal Petri Net

    Directory of Open Access Journals (Sweden)

    Dmitry A. Zaitsev

    2013-09-01

    Full Text Available A universal deterministic inhibitor Petri net with 14 places, 29 transitions and 138 arcs was constructed via simulation of Neary and Woods' weakly universal Turing machine with 2 states and 4 symbols; the total time complexity is exponential in the running time of their weak machine. To simulate the blank words of the weakly universal Turing machine, a couple of dedicated transitions insert their codes when reaching edges of the working zone. To complete a chain of a given Petri net encoding to be executed by the universal Petri net, a translation of a bi-tag system into a Turing machine was constructed. The constructed Petri net is universal in the standard sense; a weaker form of universality for Petri nets was not introduced in this work.

  3. Temporal Variability of Microplastic Concentrations in Freshwater Streams

    Science.gov (United States)

    Watkins, L.; Walter, M. T.

    2016-12-01

    Plastic pollution, specifically the size fraction less than 5mm known as microplastics, is an emerging contaminant in waterways worldwide. The ability of microplastics to adsorb and transport contaminants and microbes, as well as be ingested by organisms, makes them a concern in both freshwater and marine ecosystems. Recent efforts to determine the extent of microplastic pollution are increasingly focused on freshwater systems, but most studies have reported concentrations at a single time-point; few have begun to uncover how plastic concentrations in riverine systems may change through time. We hypothesize the time of day and season of sampling influences the concentrations of microplastics in water samples and more specifically, that daytime stormflow samples contain the highest microplastic concentrations due to maximized runoff and wastewater discharge. In order to test this hypothesis, we sampled in two similar streams in Ithaca, New York using a 333µm mesh net deployed within the thalweg. Repeat samples were collected to identify diurnal patterns as well as monthly variation. Samples were processed in the laboratory following the NOAA wet peroxide oxidation protocol. This work improves our ability to interpret existing single-time-point survey results by providing information on how microplastic concentrations change over time and whether concentrations in existing stream studies are likely representative of their location. Additionally, these results will inform future studies by providing insight into representative sample timing and capturing temporal trends for the purposes of modeling and of developing regulations for microplastic pollution.

  4. Farming of Freshwater Rainbow Trout in Denmark

    DEFF Research Database (Denmark)

    Jokumsen, Alfred; Svendsen, Lars Moeslund

    Textbook on Farming of Freshwater Rainbow Trout in Denmark. Danish edition with the title: Opdræt af regnbueørred i Danmark......Textbook on Farming of Freshwater Rainbow Trout in Denmark. Danish edition with the title: Opdræt af regnbueørred i Danmark...

  5. Freshwater Ecology. LC Science Tracer Bullet.

    Science.gov (United States)

    Niskern, Diana, Comp.

    Freshwater ecosystems include lakes, ponds, streams, rivers, and certain types of wetlands. This literature and resources guide is not intended to be a comprehensive bibliography on freshwater ecology; the guide is designed--as the name of the series implies--to put the reader or student "on target." Other literature guides related to…

  6. Effects of Pollution on Freshwater Fish.

    Science.gov (United States)

    Brungs, W. A.; And Others

    1978-01-01

    Presents a literature review of the effects of pollution on freshwater fish, covering publications of 1976-77. This review includes: (1) water quality; (2) pesticide pollutants; (3) chemical pollutants; (4) miscellaneous pollutants; and (5) physical factors of pollution on freshwater fish. A list of 338 references is also presented. (HM)

  7. Subtropical freshwater storages: a major source of nitrous oxide and methane?

    Science.gov (United States)

    Sturm, Katrin; Grinham, Alistair; Yuan, Zhiguo

    2013-04-01

    Studies of greenhouse gas cycling in subtropical water bodies, particularly in the Southern Hemisphere, are very limited. This represents an important gap in our understanding of global emissions as the higher temperatures experienced in the subtropics will likely accelerate greenhouse gas production and consumption. Critical to understanding the net impact of these accelerated rates are detailed studies of representative systems within this region. In this paper we present a model artificial freshwater storage: Gold Creek Dam in South East Queensland, Australia. Freshwater storages are commonplace for drinking water and irrigation purposes in Australia as unpredictable rainfall patterns make river and ground water sources unreliable. Over 85 % of Australian rivers are modified with weirs and dams providing permanent inundation of previously terrestrial environments. The higher temperatures experienced at these latitudes drive thermal stratification of these systems as well as rapidly deoxygenate bottom waters. High organic matter availability in the sediment zone as well as the anoxic overlying water provide ideal conditions for reduced products (including methane and ammonia) from microbial processing to be formed and diffuse into bottom waters. A mid-water metalimnion is generally associated with large gradients in dissolved oxygen availability and reduced metabolites undergo oxidation prior to their emission from water surface. An intensive field study was undertaken to improve understanding of production and transformation rates of methane and nitrous oxide from the sediments, through the water column and to the atmosphere. Sediment nutrient (ammonia, nitrite/nitrate and filterable reactive phosphorus) and greenhouse gas (methane and nitrous oxide) porewater samples were collected at selected sites. To determine the magnitude of the benthic sediment contribution of methane and nitrous oxide to the water column sediment incubations were conducted in the

  8. The freshwater reservoir effect in radiocarbon dating

    DEFF Research Database (Denmark)

    Philippsen, Bente

    case studies will show the degree of variability of the freshwater reservoir effect over short and long timescales. Radiocarbon dating of recent water samples, aquatic plants and animals, shows that age differences of up to 2000 years can occur within one river. In the Limfjord, freshwater influence......The freshwater reservoir effect can result in too high radiocarbon ages of samples from lakes and rivers, including the bones of people whose subsistence was based on freshwater fish, and pottery in which fish was cooked. In my talk, I will explain the causes and consequences of this effect. Two...... caused reservoir ages to vary between 250 and 700 years during the period 5400 BC - AD 700. Finally, I will discuss the implications of the freshwater reservoir effect for radiocarbon dating of Mesolithic pottery from inland sites of the Ertebølle culture in Northern Germany....

  9. Terrestrial freshwater lenses: Unexplored subterranean oases

    Science.gov (United States)

    Laattoe, Tariq; Werner, Adrian D.; Woods, Juliette A.; Cartwright, Ian

    2017-10-01

    Freshwater lenses are lenticular bodies of fresh (TDS lenses in coastal aquifers, the formation, location and persistence of freshwater lenses in terrestrial settings are poorly understood. This is despite inland aquifers commonly containing saline groundwater, particularly in arid and semi-arid climates, and the local occurrences of freshwater being critical for ecosystems and human endeavour. We identify and classify known terrestrial freshwater lenses (TFLs) using four formation categories, namely topography, geology, groundwater-surface water interaction and recharge mechanisms. The resulting typology highlights the importance of buoyancy in the formation of TFLs in otherwise unlikely situations, implying that TFLs may be more prevalent than previously thought. TFLs represent some of the most vulnerable and precious freshwater resources on Earth that require considerably more research into mechanisms of formation and threats to their existence.

  10. Freshwater to seawater transitions in migratory fishes

    Science.gov (United States)

    Zydlewski, Joseph D.; Michael P. Wilkie,

    2012-01-01

    The transition from freshwater to seawater is integral to the life history of many fishes. Diverse migratory fishes express anadromous, catadromous, and amphidromous life histories, while others make incomplete transits between freshwater and seawater. The physiological mechanisms of osmoregulation are widely conserved among phylogenetically diverse species. Diadromous fishes moving between freshwater and seawater develop osmoregulatory mechanisms for different environmental salinities. Freshwater to seawater transition involves hormonally mediated changes in gill ionocytes and the transport proteins associated with hypoosmoregulation, increased seawater ingestion and water absorption in the intestine, and reduced urinary water losses. Fishes attain salinity tolerance through early development, gradual acclimation, or environmentally or developmentally cued adaptations. This chapter describes adaptations in diverse taxa and the effects of salinity on growth. Identifying common strategies in diadromous fishes moving between freshwater and seawater will reveal the ecological and physiological basis for maintaining homeostasis in different salinities, and inform efforts to conserve and manage migratory euryhaline fishes.

  11. Seasonal effects of irrigation on land-atmosphere latent heat, sensible heat, and carbon fluxes in semiarid basin

    Science.gov (United States)

    Zeng, Yujin; Xie, Zhenghui; Liu, Shuang

    2017-02-01

    Irrigation, which constitutes ˜ 70 % of the total amount of freshwater consumed by the human population, is significantly impacting land-atmosphere fluxes. In this study, using the improved Community Land Model version 4.5 (CLM4.5) with an active crop model, two high-resolution (˜ 1 km) simulations investigating the effects of irrigation on latent heat (LH), sensible heat (SH), and carbon fluxes (or net ecosystem exchange, NEE) from land to atmosphere in the Heihe River basin in northwestern China were conducted using a high-quality irrigation dataset compiled from 1981 to 2013. The model output and measurements from remote sensing demonstrated the capacity of the developed models to reproduce ecological and hydrological processes. The results revealed that the effects of irrigation on LH and SH are strongest during summer, with a LH increase of ˜ 100 W m-2 and a SH decrease of ˜ 60 W m-2 over intensely irrigated areas. However, the reactions are much weaker during spring and autumn when there is much less irrigation. When the irrigation rate is below 5 mm day-1, the LH generally increases, whereas the SH decreases with growing irrigation rates. However, when the irrigation threshold is in excess of 5 mm day-1, there is no accrued effect of irrigation on the LH and SH. Irrigation produces opposite effects to the NEE during spring and summer. During the spring, irrigation yields more discharged carbon from the land to the atmosphere, increasing the NEE value by 0.4-0.8 gC m-2 day-1, while the summer irrigation favors crop fixing of carbon from atmospheric CO2, decreasing the NEE value by ˜ 0.8 gC m-2 day-1. The repercussions of irrigation on land-atmosphere fluxes are not solely linked to the irrigation amount, and other parameters (especially the temperature) also control the effects of irrigation on LH, SH, and NEE.

  12. Flux Analysis in Process Models via Causality

    Directory of Open Access Journals (Sweden)

    Ozan Kahramanoğulları

    2010-02-01

    Full Text Available We present an approach for flux analysis in process algebra models of biological systems. We perceive flux as the flow of resources in stochastic simulations. We resort to an established correspondence between event structures, a broadly recognised model of concurrency, and state transitions of process models, seen as Petri nets. We show that we can this way extract the causal resource dependencies in simulations between individual state transitions as partial orders of events. We propose transformations on the partial orders that provide means for further analysis, and introduce a software tool, which implements these ideas. By means of an example of a published model of the Rho GTP-binding proteins, we argue that this approach can provide the substitute for flux analysis techniques on ordinary differential equation models within the stochastic setting of process algebras.

  13. Clustering of Emerging Flux

    Science.gov (United States)

    Ruzmaikin, A.

    1997-01-01

    Observations show that newly emerging flux tends to appear on the Solar surface at sites where there is flux already. This results in clustering of solar activity. Standard dynamo theories do not predict this effect.

  14. Gap filling strategies for long term energy flux data sets

    DEFF Research Database (Denmark)

    Falge, E.; Baldocchi, D.; Olson, R.

    2001-01-01

    At present a network of over 100 field sites are measuring carbon dioxide, water vapor and sensible heat fluxes between the biosphere and atmosphere, on a nearly continuous basis. Gaps in the long term measurements of evaporation and sensible heat flux must be filled before these data can be used...... for hydrological and meteorological applications. We adapted methods of gap filling for NEE (net ecosystem exchange of carbon) to energy fluxes and applied them to data sets available from the EUROFLUX and AmeriFlux eddy covariance databases. The average data coverage for the sites selected was 69% and 75......% for latent heat (lambdaE) and sensible heat (H). The methods were based on mean diurnal variations (half-hourly binned means of fluxes based on previous and subsequent days, MDV) and look-up tables for fluxes during assorted meteorological conditions (LookUp), and the impact of different gap filling methods...

  15. Evaluation of alternative macroinvertebrate sampling techniques for use in a new tropical freshwater bioassessment scheme

    Directory of Open Access Journals (Sweden)

    Isabel Eleanor Moore

    2015-06-01

    Full Text Available Aim: The study aimed to determine the effectiveness of benthic macroinvertebrate dredge net sampling procedures as an alternative method to kick net sampling in tropical freshwater systems, specifically as an evaluation of sampling methods used in the Zambian Invertebrate Scoring System (ZISS river bioassessment scheme. Tropical freshwater ecosystems are sometimes dangerous or inaccessible to sampling teams using traditional kick-sampling methods, so identifying an alternative procedure that produces similar results is necessary in order to collect data from a wide variety of habitats.MethodsBoth kick and dredge nets were used to collect macroinvertebrate samples at 16 riverine sites in Zambia, ranging from backwaters and floodplain lagoons to fast flowing streams and rivers. The data were used to calculate ZISS, diversity (S: number of taxa present, and Average Score Per Taxon (ASPT scores per site, using the two sampling methods to compare their sampling effectiveness. Environmental parameters, namely pH, conductivity, underwater photosynthetically active radiation (PAR, temperature, alkalinity, flow, and altitude, were also recorded and used in statistical analysis. Invertebrate communities present at the sample sites were determined using multivariate procedures.ResultsAnalysis of the invertebrate community and environmental data suggested that the testing exercise was undertaken in four distinct macroinvertebrate community types, supporting at least two quite different macroinvertebrate assemblages, and showing significant differences in habitat conditions. Significant correlations were found for all three bioassessment score variables between results acquired using the two methods, with dredge-sampling normally producing lower scores than did the kick net procedures. Linear regression models were produced in order to correct each biological variable score collected by a dredge net to a score similar to that of one collected by kick net

  16. High-level Petri Nets

    DEFF Research Database (Denmark)

    High-level Petri nets are now widely used in both theoretical analysis and practical modelling of concurrent systems. The main reason for the success of this class of net models is that they make it possible to obtain much more succinct and manageable descriptions than can be obtained by means...... of low-level Petri nets - while, on the other hand, they still offer a wide range of analysis methods and tools. The step from low-level nets to high-level nets can be compared to the step from assembly languages to modern programming languages with an elaborated type concept. In low-level nets...... there is only one kind of token and this means that the state of a place is described by an integer (and in many cases even by a boolean). In high-level nets each token can carry a complex information/data - which, e.g., may describe the entire state of a process or a data base. Today most practical...

  17. A systematic study of the impact of freshwater pulses with respect to different geographical locations

    Energy Technology Data Exchange (ETDEWEB)

    Roche, Didier M.; Renssen, Hans [Vrije Universiteit Amsterdam, Section Climate Change and Landscape Dynamics, Department of Earth Sciences, Amsterdam (Netherlands); Wiersma, Ane P. [Deltares, Subsurface and Groundwater systems, Utrecht (Netherlands)

    2010-06-15

    The first comparative and systematic climate model study of the sensitivity of the climate response under Last Glacial Maximum (LGM) conditions to freshwater perturbations at various locations that are known to have received significant amounts of freshwater during the LGM (21 kyr BP) climate conditions is presented. A series of ten regions representative of those receiving most of the meltwater from decaying ice-sheets during the deglaciation is defined, comprising the border of LGM ice-sheets, outlets of rivers draining part of the melting ice-sheets and iceberg melt zones. The effect of several given freshwater fluxes applied separately in each of these regions on regional and global climate is subsequently tested. The climate response is then analysed both for the atmosphere and oceans. Amongst the regions defined, it is found that the area close by and dynamically upstream to the main deep water formation zone in the North Atlantic are most sensitive to freshwater pulses, as is expected. However, some important differences between Arctic freshwater forcing and Nordic Seas forcing are found, the former having a longer term response linked to sea-ice formation and advection whereas the latter exhibits more direct influence of direct freshening of the deep water formation sites. Combining the common surface temperature response for each respective zone, we fingerprint the particular surface temperature response obtained by adding freshwater in a particular location. This is done to examine if a surface climate response can be used to determine the origin of a meltwater flux, which is relevant for the interpretation of proxy data. We show that it is indeed possible to generally classify the fingerprints by their origin in terms of sea-ice modification and modification of deep-water formation. Whilst the latter is not an unambiguous characterization of each zone, it nonetheless provides important clues on the physical mechanisms at work. In particular, it is shown

  18. A systematic study of the impact of freshwater pulses with respect to different geographical locations

    Science.gov (United States)

    Roche, Didier M.; Wiersma, Ane P.; Renssen, Hans

    2010-06-01

    The first comparative and systematic climate model study of the sensitivity of the climate response under Last Glacial Maximum (LGM) conditions to freshwater perturbations at various locations that are known to have received significant amounts of freshwater during the LGM (21 kyr BP) climate conditions is presented. A series of ten regions representative of those receiving most of the meltwater from decaying ice-sheets during the deglaciation is defined, comprising the border of LGM ice-sheets, outlets of rivers draining part of the melting ice-sheets and iceberg melt zones. The effect of several given freshwater fluxes applied separately in each of these regions on regional and global climate is subsequently tested. The climate response is then analysed both for the atmosphere and oceans. Amongst the regions defined, it is found that the area close by and dynamically upstream to the main deep water formation zone in the North Atlantic are most sensitive to freshwater pulses, as is expected. However, some important differences between Arctic freshwater forcing and Nordic Seas forcing are found, the former having a longer term response linked to sea-ice formation and advection whereas the latter exhibits more direct influence of direct freshening of the deep water formation sites. Combining the common surface temperature response for each respective zone, we fingerprint the particular surface temperature response obtained by adding freshwater in a particular location. This is done to examine if a surface climate response can be used to determine the origin of a meltwater flux, which is relevant for the interpretation of proxy data. We show that it is indeed possible to generally classify the fingerprints by their origin in terms of sea-ice modification and modification of deep-water formation. Whilst the latter is not an unambiguous characterization of each zone, it nonetheless provides important clues on the physical mechanisms at work. In particular, it is shown

  19. NACP MCI: CO2 Flux from Inversion Modeling, Upper Midwest Region, USA, 2007

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set provides estimates of Net Ecosystem Exchange (NEE) flux for the U.S. Upper Midwest at 0.5-degree resolution for the year 2007. Estimates were...

  20. NACP MCI: CO2 Flux from Inversion Modeling, Upper Midwest Region, USA, 2007

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides estimates of Net Ecosystem Exchange (NEE) flux for the U.S. Upper Midwest at 0.5-degree resolution for the year 2007. Estimates were produced...

  1. LBA-ECO TG-08 Soil Gas Flux after Forest and Pasture Fertilization, Rondonia, Brazil

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides nitric oxide (NO), nitrous oxide (N2O), carbon dioxide (CO2) flux measurements, nitrogen (N) and phosphorus (P) pools, net N mineralization...

  2. CMS: Carbon Fluxes from Global Agricultural Production and Consumption, 2005-2011

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides global estimates of carbon fluxes associate with annual crop net primary production (NPP) and harvested biomass, annual uptake and release by...

  3. NACP VPRM NEE Parameters Optimized to North American Flux Tower Sites, 2000-2006

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides Vegetation Photosynthesis Respiration Model (VPRM) net ecosystem exchange (NEE) parameter values optimized to 65 flux tower sites across North...

  4. LBA-ECO TG-08 Soil Gas Flux after Forest and Pasture Fertilization, Rondonia, Brazil

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set provides nitric oxide (NO), nitrous oxide (N2O), carbon dioxide (CO2) flux measurements, nitrogen (N) and phosphorus (P) pools, net N...

  5. Pro asynchronous programming with .NET

    CERN Document Server

    Blewett, Richard; Ltd, Rock Solid Knowledge

    2014-01-01

    Pro Asynchronous Programming with .NET teaches the essential skill of asynchronous programming in .NET. It answers critical questions in .NET application development, such as: how do I keep my program responding at all times to keep my users happy how do I make the most of the available hardware how can I improve performanceIn the modern world, users expect more and more from their applications and devices, and multi-core hardware has the potential to provide it. But it takes carefully crafted code to turn that potential into responsive, scalable applications.With Pro Asynchronous Programming

  6. Conformal Nets II: Conformal Blocks

    Science.gov (United States)

    Bartels, Arthur; Douglas, Christopher L.; Henriques, André

    2017-08-01

    Conformal nets provide a mathematical formalism for conformal field theory. Associated to a conformal net with finite index, we give a construction of the `bundle of conformal blocks', a representation of the mapping class groupoid of closed topological surfaces into the category of finite-dimensional projective Hilbert spaces. We also construct infinite-dimensional spaces of conformal blocks for topological surfaces with smooth boundary. We prove that the conformal blocks satisfy a factorization formula for gluing surfaces along circles, and an analogous formula for gluing surfaces along intervals. We use this interval factorization property to give a new proof of the modularity of the category of representations of a conformal net.

  7. Stoichiometry and Life-History Interact to Determine the Magnitude of Cross-Ecosystem Element and Biomass Fluxes.

    Science.gov (United States)

    Luhring, Thomas M; DeLong, John P; Semlitsch, Raymond D

    2017-01-01

    Ecosystems are linked through the transfer of materials and energy. Studies examining material fluxes across habitat boundaries frequently quantify unidirectional flows of nutrients and energy. However, material fluxes can be multidirectional, and we lack a conceptual framework to describe how their quantity and stoichiometry influence the net transfer of individual elements between ecosystems. Here we develop a zero net transfer isocline (ZNTI) framework that integrates the relative mass and stoichiometry of fluxes into and out of an ecosystem. We then use case studies with amphibians and salmon to elucidate how life history, ontogenetic shifts in stoichiometry, and trophic interactions shape relative fluxes of nutrients between aquatic and terrestrial ecosystems. Because they increase in both size and Ca content from ova to metamorphs, amphibian life histories strongly bias them toward net Ca export into the terrestrial environment. Because amphibian biomass, C, P, and Ca ZNTIs do not overlap, there is no value of survivorship where the net flux of biomass, C, P, and Ca are simultaneously balanced between terrestrial and aquatic habitats. The degree of iteroparity and semelparity in salmon strongly affects both the magnitude of net biomass and P flux between riverine and marine environments. While the net direction of biomass flux generally remains strongly biased toward import into the riverine system, net P flux can reach net export into the marine environment because of increasing adult breeding survival leading to reduced mass and %P of what they deposit in rivers (e.g., ova vs. whole carcasses). These examples highlight how ontogenetic shifts in body size and stoichiometry result in asymmetric fluxes of elements and biomass that can lead to simultaneous net imports and exports of different elements within the same system. Furthermore, they demonstrate how changes in life-history characteristics and stage-specific survivorship can lead to changes in net

  8. Pathogenic agents in freshwater resources

    Science.gov (United States)

    Geldreich, Edwin E.

    1996-02-01

    Numerous pathogenic agents have been found in freshwaters used as sources for water supplies, recreational bathing and irrigation. These agents include bacterial pathogens, enteric viruses, several protozoans and parasitic worms more common to tropical waters. Although infected humans are a major source of pathogens, farm animals (cattle, sheep, pigs), animal pets (dogs, cats) and wildlife serve as significant reservoirs and should not be ignored. The range of infected individuals within a given warm-blooded animal group (humans included) may range from 1 to 25%. Survival times for pathogens in the water environment may range from a few days to as much as a year (Ascaris, Taenia eggs), with infective dose levels varying from one viable cell for several primary pathogenic agents to many thousands of cells for a given opportunistic pathogen.As pathogen detection in water is complex and not readily incorporated into routine monitoring, a surrogate is necessary. In general, indicators of faecal contamination provide a positive correlation with intestinal pathogen occurrences only when appropriate sample volumes are examined by sensitive methodology.Pathways by which pathogens reach susceptible water users include ingestion of contaminated water, body contact with polluted recreational waters and consumption of salad crops irrigated by polluted freshwaters. Major contributors to the spread of various water-borne pathogens are sewage, polluted surface waters and stormwater runoff. All of these contributions are intensified during periods of major floods. Several water-borne case histories are cited as examples of breakdowns in public health protection related to water supply, recreational waters and the consumption of contaminated salad crops. In the long term, water resource management must focus on pollution prevention from point sources of waste discharges and the spread of pathogens in watershed stormwater runoff.

  9. Quantifying the magnitude and spatiotemporal variation of aquatic CO2 fluxes in a sub-tropical karst catchment, Southwest China

    Science.gov (United States)

    Ding, Hu; Waldron, Susan; Newton, Jason; Garnett, Mark H.

    2017-04-01

    The role played by rivers in regional and global C budgets is receiving increasing attention. A large portion of the carbon transported via inland waters is returned to the atmosphere by carbon dioxide evasion from rivers and lakes. Karst landscapes represent an important C store on land, and are also considered to play an important role in climate regulation by consuming atmospheric CO2 during chemical weathering. However, we cannot be certain how effective this sink is if we do not know how efficiently the rivers draining karst landscapes remobilise weathered C to the atmosphere as CO2. pCO2 in karst waters is generally greater than atmospheric equilibrium, indicating that there can be a net CO2 efflux to the atmosphere. However, measurement confirming this and quantifying flux rates has been rarely conducted. Using a floating chamber method, in 2016 we directly measured CO2 fluxes from spatially distributed freshwaters (springs, sinkholes, streams and reservoirs/ponds) in the Houzhai Catchment, a karst region in SW China. Fluxes ranged from -0.5 to +267.4 μmol CO2 m-2s-1, and most sites showed seasonal variations with higher CO2 efflux rates in the wet (April - September) than dry season (October - March). There was a significant positive relationship between CO2 efflux and flow velocity, indicating that hydraulic controls on CO2 efflux from flowing water are important, while for water with little movement (sinkholes and reservoirs/ponds), pCO2 appears a more important control on efflux rates. Conditions similar to this study area may exist in many sub-tropical rivers that drain karst landscapes in South China. These waters are rich in DIC which can be an order of magnitude greater than some non-karst catchments. The large DIC pool has the potential to be a considerable source of free CO2 to the atmosphere. Considering that carbonate lithology covers a significant part of the Earth's surface, CO2 evasion in fluvial water from these regions is expected to

  10. Arctic freshwater forcing of the Younger Dryas cold reversal.

    Science.gov (United States)

    Tarasov, Lev; Peltier, W R

    2005-06-02

    The last deglaciation was abruptly interrupted by a millennial-scale reversal to glacial conditions, the Younger Dryas cold event. This cold interval has been connected to a decrease in the rate of North Atlantic Deep Water formation and to a resulting weakening of the meridional overturning circulation owing to surface water freshening. In contrast, an earlier input of fresh water (meltwater pulse 1a), whose origin is disputed, apparently did not lead to a reduction of the meridional overturning circulation. Here we analyse an ensemble of simulations of the drainage chronology of the North American ice sheet in order to identify the geographical release points of freshwater forcing during deglaciation. According to the simulations with our calibrated glacial systems model, the North American ice sheet contributed about half the fresh water of meltwater pulse 1a. During the onset of the Younger Dryas, we find that the largest combined meltwater/iceberg discharge was directed into the Arctic Ocean. Given that the only drainage outlet from the Arctic Ocean was via the Fram Strait into the Greenland-Iceland-Norwegian seas, where North Atlantic Deep Water is formed today, we hypothesize that it was this Arctic freshwater flux that triggered the Younger Dryas cold reversal.

  11. Recurrence Analysis of Eddy Covariance Fluxes

    Science.gov (United States)

    Lange, Holger; Flach, Milan; Foken, Thomas; Hauhs, Michael

    2015-04-01

    The eddy covariance (EC) method is one key method to quantify fluxes in biogeochemical cycles in general, and carbon and energy transport across the vegetation-atmosphere boundary layer in particular. EC data from the worldwide net of flux towers (Fluxnet) have also been used to validate biogeochemical models. The high resolution data are usually obtained at 20 Hz sampling rate but are affected by missing values and other restrictions. In this contribution, we investigate the nonlinear dynamics of EC fluxes using Recurrence Analysis (RA). High resolution data from the site DE-Bay (Waldstein-Weidenbrunnen) and fluxes calculated at half-hourly resolution from eight locations (part of the La Thuile dataset) provide a set of very long time series to analyze. After careful quality assessment and Fluxnet standard gapfilling pretreatment, we calculate properties and indicators of the recurrent structure based both on Recurrence Plots as well as Recurrence Networks. Time series of RA measures obtained from windows moving along the time axis are presented. Their interpretation is guided by three different questions: (1) Is RA able to discern periods where the (atmospheric) conditions are particularly suitable to obtain reliable EC fluxes? (2) Is RA capable to detect dynamical transitions (different behavior) beyond those obvious from visual inspection? (3) Does RA contribute to an understanding of the nonlinear synchronization between EC fluxes and atmospheric parameters, which is crucial for both improving carbon flux models as well for reliable interpolation of gaps? (4) Is RA able to recommend an optimal time resolution for measuring EC data and for analyzing EC fluxes? (5) Is it possible to detect non-trivial periodicities with a global RA? We will demonstrate that the answers to all five questions is affirmative, and that RA provides insights into EC dynamics not easily obtained otherwise.

  12. Magnetic properties of two-dimensional Josephson nets with SNS-junctions

    CERN Document Server

    Ishikaev, S M; Ryazanov, V V; Oboznov, V A

    2002-01-01

    The dependence of the magnetic moment of the square (100 x 100) Josephson nets with the SNS-transitions in the Nb-Cu sub 0 sub . sub 9 sub 5 Al sub 0 sub . 0 sub 5 -Nb on the field is studied through the SQUID-magnetometer. Significant difference in the behaviour during the process of the magnetic flux inlet into the net and its outlet from there was identified thereby. The regular periodical dependence with peaks corresponding to the whole and half number of the flux quanta per one cell is observed on the curve branches, where the increase in the field absolute value takes place. At the same time no visible peculiarities are noted by decrease in the field absolute value. The flux quasi-hydrodynamic motion in the net is explained by significant viscosity of the vortices during their passage through the Josephson junction

  13. Novel Synechococcus Genomes Reconstructed from Freshwater Reservoirs

    Science.gov (United States)

    Cabello-Yeves, Pedro J.; Haro-Moreno, Jose M.; Martin-Cuadrado, Ana-Belen; Ghai, Rohit; Picazo, Antonio; Camacho, Antonio; Rodriguez-Valera, Francisco

    2017-01-01

    Freshwater picocyanobacteria including Synechococcus remain poorly studied at the genomic level, compared to their marine representatives. Here, using a metagenomic assembly approach we discovered two novel Synechococcus sp. genomes from two freshwater reservoirs Tous and Lake Lanier, both sharing 96% average nucleotide identity and displaying high abundance levels in these two lakes located at similar altitudes and temperate latitudes. These new genomes have the smallest estimated size (2.2 Mb) and average intergenic spacer length (20 bp) of any previously sequenced freshwater Synechococcus, which may contribute to their success in oligotrophic freshwater systems. Fluorescent in situ hybridization confirmed that Synechococcus sp. Tous comprises small cells (0.987 ± 0.139 μm length, 0.723 ± 0.119 μm width) that amount to 90% of the picocyanobacteria in Tous. They appear together in a phylogenomic tree with Synechococcus sp. RCC307 strain, the main representative of sub-cluster 5.3 that has itself one of the smallest marine Synechococcus genomes. We detected a type II phycobilisome (PBS) gene cluster in both genomes, which suggests that they belong to a phycoerythrin-rich pink low-light ecotype. The decrease of acidic proteins and the higher content of basic transporters and membrane proteins in the novel Synechococcus genomes, compared to marine representatives, support their freshwater specialization. A sulfate Cys transporter which is absent in marine but has been identified in many freshwater cyanobacteria was also detected in Synechococcus sp. Tous. The RuBisCo subunits from this microbe are phylogenetically close to the freshwater amoeba Paulinella chromatophora symbiont, hinting to a freshwater origin of the carboxysome operon of this protist. The novel genomes enlarge the known diversity of freshwater Synechococcus and improve the overall knowledge of the relationships among members of this genus at large. PMID:28680419

  14. Novel Synechococcus Genomes Reconstructed from Freshwater Reservoirs

    Directory of Open Access Journals (Sweden)

    Pedro J. Cabello-Yeves

    2017-06-01

    Full Text Available Freshwater picocyanobacteria including Synechococcus remain poorly studied at the genomic level, compared to their marine representatives. Here, using a metagenomic assembly approach we discovered two novel Synechococcus sp. genomes from two freshwater reservoirs Tous and Lake Lanier, both sharing 96% average nucleotide identity and displaying high abundance levels in these two lakes located at similar altitudes and temperate latitudes. These new genomes have the smallest estimated size (2.2 Mb and average intergenic spacer length (20 bp of any previously sequenced freshwater Synechococcus, which may contribute to their success in oligotrophic freshwater systems. Fluorescent in situ hybridization confirmed that Synechococcus sp. Tous comprises small cells (0.987 ± 0.139 μm length, 0.723 ± 0.119 μm width that amount to 90% of the picocyanobacteria in Tous. They appear together in a phylogenomic tree with Synechococcus sp. RCC307 strain, the main representative of sub-cluster 5.3 that has itself one of the smallest marine Synechococcus genomes. We detected a type II phycobilisome (PBS gene cluster in both genomes, which suggests that they belong to a phycoerythrin-rich pink low-light ecotype. The decrease of acidic proteins and the higher content of basic transporters and membrane proteins in the novel Synechococcus genomes, compared to marine representatives, support their freshwater specialization. A sulfate Cys transporter which is absent in marine but has been identified in many freshwater cyanobacteria was also detected in Synechococcus sp. Tous. The RuBisCo subunits from this microbe are phylogenetically close to the freshwater amoeba Paulinella chromatophora symbiont, hinting to a freshwater origin of the carboxysome operon of this protist. The novel genomes enlarge the known diversity of freshwater Synechococcus and improve the overall knowledge of the relationships among members of this genus at large.

  15. Petri Net Tool Overview 1986

    DEFF Research Database (Denmark)

    Jensen, Kurt; Feldbrugge, Frits

    1987-01-01

    This paper provides an overview of the characteristics of all currently available net based tools. It is a compilation of information provided by tool authors or contact persons. A concise one page overview is provided as well....

  16. Understanding Net Zero Energy Buildings

    DEFF Research Database (Denmark)

    Salom, Jaume; Widén, Joakim; Candanedo, José

    2011-01-01

    Although several alternative definitions exist, a Net-Zero Energy Building (Net ZEB) can be succinctly described as a grid-connected building that generates as much energy as it uses over a year. The “net-zero” balance is attained by applying energy conservation and efficiency measures...... and by incorporating renewable energy systems. While based on annual balances, a complete description of a Net ZEB requires examining the system at smaller time-scales. This assessment should address: (a) the relationship between power generation and building loads and (b) the resulting interaction with the power grid....... This paper presents and categorizes quantitative indicators suitable to describe both aspects of the building’s performance. These indicators, named LMGI - Load Matching and Grid Interaction indicators, are easily quantifiable and could complement the output variables of existing building simulation tools...

  17. PolicyNet Publication System

    Data.gov (United States)

    Social Security Administration — The PolicyNet Publication System project will merge the Oracle-based Policy Repository (POMS) and the SQL-Server CAMP system (MSOM) into a new system with an Oracle...

  18. KM3NeT

    CERN Multimedia

    KM3NeT is a large scale next-generation neutrino telescope located in the deep waters of the Mediterranean Sea, optimized for the discovery of galactic neutrino sources emitting in the TeV energy region.

  19. Net Neutrality: Background and Issues

    National Research Council Canada - National Science Library

    Gilroy, Angele A

    2006-01-01

    .... The move to place restrictions on the owners of the networks that compose and provide access to the Internet, to ensure equal access and nondiscriminatory treatment, is referred to as "net neutrality...

  20. Petri Nets in Cryptographic Protocols

    DEFF Research Database (Denmark)

    Crazzolara, Federico; Winskel, Glynn

    2001-01-01

    A process language for security protocols is presented together with a semantics in terms of sets of events. The denotation of process is a set of events, and as each event specifies a set of pre and postconditions, this denotation can be viewed as a Petri net. By means of an example we illustrate...... how the Petri-net semantics can be used to prove security properties....

  1. The Economics of Net Neutrality

    OpenAIRE

    Hahn, Robert W.; Wallsten, Scott

    2006-01-01

    This essay examines the economics of "net neutrality" and broadband Internet access. We argue that mandating net neutrality would be likely to reduce economic welfare. Instead, the government should focus on creating competition in the broadband market by liberalizing more spectrum and reducing entry barriers created by certain local regulations. In cases where a broadband provider can exercise market power the government should use its antitrust enforcement authority to police anticompetitiv...

  2. Impacts of freshwater changes on Antarctic sea ice in an eddy-permitting sea-ice-ocean model

    Science.gov (United States)

    Haid, Verena; Iovino, Doroteaciro; Masina, Simona

    2017-06-01

    In a warming climate, satellite data indicate that the sea ice extent around Antarctica has increased over the last decades. One of the suggested explanations is the stabilizing effect of increased mass loss of the Antarctic ice sheet. Here, we investigate the sea ice response to changes in both the amount and the spatial distribution of freshwater input to the ocean by comparing a set of numerical sensitivity simulations with additional supply of water at the Antarctic ocean surface. We analyze the short-term response of the sea ice cover and the on-shelf water column to variations in the amount and distribution of the prescribed surface freshwater flux.Our results confirm that enhancing the freshwater input can increase the sea ice extent. Our experiments show a negative development of the sea ice extent only for extreme freshwater additions. We find that the spatial distribution of freshwater is of great influence on sea ice concentration and thickness as it affects sea ice dynamics and thermodynamics. For strong regional contrasts in the freshwater addition the dynamic response dominates the local change in sea ice, which generally opposes the thermodynamic response. Furthermore, we find that additional coastal runoff generally leads to fresher and warmer dense shelf waters.

  3. Net Heterotrophy in the Amazon Continental Shelf Changes Rapidly to a Sink of CO2 in the Outer Amazon Plume

    Directory of Open Access Journals (Sweden)

    Nathalie Lefèvre

    2017-09-01

    Full Text Available The Amazon continental shelf and adjacent oceanic area were sampled for inorganic and organic carbon parameters in order to improve data coverage and understanding of carbon cycling dynamics within this important region. Seasonal coverage of the Amazon plume on the French Guiana continental shelf further north, was provided by CO2 monitoring using a merchant ship sailing from France to French Guiana (2006–2016. Salinity ranged from 1 to 36 (transects in April 2013, and May 2014. At salinity below 10, strong outgassing was observed with fugacity of CO2 (fCO2 over 2,000 μatm. This region displayed net heterotrophy, fueled by organic matter with terrestrial origin, as shown by δ13C and δ15N values of suspended particles. A δ13C cross shelf average of −31% was measured during May 2014, contrasting with oceanic values in excess of −20%. The reactivity of this terrestrial material resulted in the local production of dissolved inorganic and organic carbon as well as fluorescent humic compounds. Further offshore, the dilution of freshwater by ocean waters created a sink for CO2, enhanced by biological activity. The strongest CO2 drawdowns, associated with high chlorophyll a concentrations, were observed on the French Guiana continental shelf in the outer Amazon plume, with fCO2 values below 150 μatm. Here, a CO2 sink was present almost throughout the year, with a seasonal maximum of −9.2 mmol CO2 m−2d−1 observed in June 2015. However, both the CO2 and salinity distributions could vary significantly within a few days, confirming the presence of many eddies in this region. The Amazon continental shelf hence behaved as a transition zone between an inshore source of CO2 to the atmosphere and an offshore sink. Some marine phytoplankton production was detected but occurred mainly close to the French Guiana shelf. A mean net CO2 outgassing of 44 ± 43.6 mmol m−2d−1 was estimated for the area. Quantifying the CO2 flux for the entire Amazon

  4. Global land-water nexus: Agricultural land and freshwater use embodied in worldwide supply chains.

    Science.gov (United States)

    Chen, B; Han, M Y; Peng, K; Zhou, S L; Shao, L; Wu, X F; Wei, W D; Liu, S Y; Li, Z; Li, J S; Chen, G Q

    2018-02-01

    As agricultural land and freshwater inextricably interrelate and interact with each other, the conventional water and land policy in "silos" should give way to nexus thinking when formulating the land and water management strategies. This study constructs a systems multi-regional input-output (MRIO) model to expound global land-water nexus by simultaneously tracking agricultural land and freshwater use flows along the global supply chains. Furthermore, land productivity and irrigation water requirements of 160 crops in different regions are investigated to reflect the land-water linkage. Results show that developed economies (e.g., USA and Japan) and major large developing economies (e.g., mainland China and India) are the overriding drivers of agricultural land and freshwater use globally. In general, significant net transfers of these two resources are identified from resource-rich and less-developed economies to resource-poor and more-developed economies. For some crops, blue water productivity is inversely related to land productivity, indicating that irrigation water consumption is sometimes at odds with land use. The results could stimulus international cooperation for sustainable land and freshwater management targeting on original suppliers and final consumers along the global supply chains. Moreover, crop-specific land-water linkage could provide insights for trade-off decisions on minimizing the environmental impacts on local land and water resources. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. 26 CFR 1.904(f)-3 - Allocation of net operating losses and net capital losses.

    Science.gov (United States)

    2010-04-01

    ... 26 Internal Revenue 9 2010-04-01 2010-04-01 false Allocation of net operating losses and net....904(f)-3 Allocation of net operating losses and net capital losses. For rules relating to the allocation of net operating losses and net capital losses, see § 1.904(g)-3T. ...

  6. 29 CFR 4204.13 - Net income and net tangible assets tests.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 9 2010-07-01 2010-07-01 false Net income and net tangible assets tests. 4204.13 Section....13 Net income and net tangible assets tests. (a) General. The criteria under this section are that either— (1) Net income test. The purchaser's average net income after taxes for its three most recent...

  7. Exotic freshwater planarians currently known from Japan

    NARCIS (Netherlands)

    Sluys, R.; Kawakatsu, M.; Yamamoto, K.

    2010-01-01

    Biogeographical and taxonomic information on the four non-indigenous freshwater planarians of Japan is reviewed, viz. Dugesia austroasiatica Kawakatsu, 1985, Girardia tigrina (Girard, 1850), G. dorotocephala (Woodworth, 1897), and Rhodax evelinae? Marcus, 1947. The occurrence of Girardia

  8. Persistent organochlorine pesticide residues in freshwater systems ...

    African Journals Online (AJOL)

    , heptachlor and endosulfan were determined in water and sediment samples of freshwater systems in the Eastern Cape Province of South Africa that receive runoff from agricultural lands and effluents from industries. The organochlorine ...

  9. Climate changes: effects of secondary salinisation in freshwater organisms

    OpenAIRE

    Leitão, João Luís Vieira

    2011-01-01

    As global climate patterns change, so will freshwater availability. Specially, salinisation of freshwater costal ecosystem is a major point of concern; either by surface flooding or by groundwater intrusions of seawater. This may be potentiated by the decrease of freshwater availability provoked by longer drought periods, evaporation, and increased freshwater extraction (for example for agriculture and other human uses). According, the present work aimed at evaluating how freshwater organi...

  10. Standardized Automated CO2/H2O Flux Systems for Individual Research Groups and Flux Networks

    Science.gov (United States)

    Burba, George; Begashaw, Israel; Fratini, Gerardo; Griessbaum, Frank; Kathilankal, James; Xu, Liukang; Franz, Daniela; Joseph, Everette; Larmanou, Eric; Miller, Scott; Papale, Dario; Sabbatini, Simone; Sachs, Torsten; Sakai, Ricardo; McDermitt, Dayle

    2017-04-01

    In recent years, spatial and temporal flux data coverage improved significantly, and on multiple scales, from a single station to continental networks, due to standardization, automation, and management of data collection, and better handling of the extensive amounts of generated data. With more stations and networks, larger data flows from each station, and smaller operating budgets, modern tools are required to effectively and efficiently handle the entire process. Such tools are needed to maximize time dedicated to authoring publications and answering research questions, and to minimize time and expenses spent on data acquisition, processing, and quality control. Thus, these tools should produce standardized verifiable datasets and provide a way to cross-share the standardized data with external collaborators to leverage available funding, promote data analyses and publications. LI-COR gas analyzers are widely used in past and present flux networks such as AmeriFlux, ICOS, AsiaFlux, OzFlux, NEON, CarboEurope, and FluxNet-Canada, etc. These analyzers have gone through several major improvements over the past 30 years. However, in 2016, a three-prong development was completed to create an automated flux system which can accept multiple sonic anemometer and datalogger models, compute final and complete fluxes on-site, merge final fluxes with supporting weather soil and radiation data, monitor station outputs and send automated alerts to researchers, and allow secure sharing and cross-sharing of the station and data access. Two types of these research systems were developed: open-path (LI-7500RS) and enclosed-path (LI-7200RS). Key developments included: • Improvement of gas analyzer performance • Standardization and automation of final flux calculations onsite, and in real-time • Seamless integration with latest site management and data sharing tools In terms of the gas analyzer performance, the RS analyzers are based on established LI-7500/A and LI-7200

  11. Native Freshwater Fish and Mussel Species Richness

    Science.gov (United States)

    These data represent predicted current distributions of all native freshwater fish and freshwater mussels in the Middle-Atlantic region. The data are available for both 8-digit HUCs and EMAP hexagons and represent total species counts for each spatial unit. More information about these resources, including the variables used in this study, may be found here: https://edg.epa.gov/data/Public/ORD/NERL/ReVA/ReVA_Data.zip.

  12. Metal fluxes in the Mersey Narrows

    Directory of Open Access Journals (Sweden)

    J. A. Cole

    2001-01-01

    Full Text Available Surveys of the Mersey estuary in north-west England were undertaken near the mouth of the estuary in the region known as the Mersey Narrows. Tidal fluxes of suspended and dissolved matter, particularly heavy metals, through the Mersey Narrows were investigated. This paper gives results of conducting four intensive cross-sectional surveys of the Narrows, during which currents, salinities, turbidity and water samples were obtained systematically at numerous positions, throughout selected tidal cycles. Over 300 water samples per survey were analysed to yield suspended and dissolved concentrations of the elements As, Cd, Cr, Cu, Hg, Ni, Pb and Zn, at all states of the tide. Suspended solids, concentrations and salinities were also measured. Suspended particulates account for the majority of each element present, except for cadmium, which was present in roughly equal dissolved and suspended fractions. From the tidal current and water quality data, calculations were made of hour-by-hour fluxes of each component, to show the detailed ebb and flow of heavy metals and the net tidal transport of each component. Although some differences between landward transport on the flood tide and seaward transport on the ebb were not significant, the more definite results consistently showed a seawards net transport. For spring tides of high tidal range, there was an indication of an opposite tendency, reducing the seawards transport or even reversing it, for certain suspended components. Keywords: Mersey estuary, surveys, tidal flux, dissolved metals, particulate metals, salinity, suspended particulate matter, suspended solids

  13. Freshwater Commercial Bycatch: an Understated Conservation Problem

    Energy Technology Data Exchange (ETDEWEB)

    Raby, Graham D.; Colotelo, Alison HA; Blouin-Demers, Gabriel; Cooke, Steven J.

    2011-04-01

    Commercial fisheries bycatch in marine systems has been regarded as a global conservation concern by environmental groups, scientists, government, and the public for decades. Fortunately, some headway has been made to mitigate the negative impacts of bycatch in marine environments. In a survey of the literature, we found that despite freshwater commercial fisheries yields comprising 11% of the global commercial catch, bycatch research focusing on freshwater commercial fisheries represented only {approx}3% of the total bycatch literature. This paucity of research is particularly alarming given that freshwater animals and habitats are some of the world's most imperiled. The limited inland bycatch literature that does exist includes examples of population declines attributed to commercial bycatch (e.g., freshwater dolphins in the Yangtze River in China) and illustrates that in some systems bycatch can be substantial (e.g., lake trout bycatch in the Laurentian Great Lakes). Encouraging results from the marine realm can serve as models for bycatch research in freshwater, and lead to measurable gains in conservation of freshwater ecosystems. We summarize existing work on inland bycatch in an effort to draw attention to this understated and understudied conservation problem.

  14. Ecosystem-scale VOC fluxes during an extreme drought in a ...

    Science.gov (United States)

    Considerable amounts and varieties of biogenic volatile organic compounds (BVOCs) are exchanged between vegetation and the surrounding air. These BVOCs play key ecological and atmospheric roles that must be adequately represented for accurately modeling the coupled biosphere-atmosphere-climate Earth system. One key uncertainty in existing models is the response of BVOC fluxes to an important global change process: drought. We describe the diurnal and seasonal variation in isoprene, monoterpene and methanol fluxes from a temperate forest ecosystem before, during, and after an extreme 2012 drought event in the Ozark region of the central USA. BVOC fluxes were dominated by isoprene, which attained high emission rates of up to 35.4 mg m-2 h-1 at midday. Methanol fluxes were characterized by net deposition in the morning, changing to a net emission flux through the rest of the daylight hours. Net flux of CO2 reached its seasonal maximum approximately a month earlier than isoprenoid fluxes, which highlights the differential response of photosynthesis and isoprenoid emissions to progressing drought conditions. Nevertheless, both processes were strongly suppressed under extreme drought, although isoprene fluxes remained relatively high compared to reported fluxes from other ecosystems. Methanol exchange was less affected by drought throughout the season, confirming the complex processes driving biogenic methanol fluxes. The fraction of daytime (7-17 h) assimilated carbo

  15. Evolution of the Freshwater Eels

    Science.gov (United States)

    Aoyama, Jun; Tsukamoto, Katsumi

    The freshwater anguillid eels have an unusual life history and world-wide distribution. Questions about the phylogenetic relationships of this group and how their long spawning migrations and larval phase may contribute to their global distribution have not been addressed. This paper is first presentation of molecular phylogeny of Anguilla species, and based on this phylogenetic tree we suggest new aspect of the evolution of this group. Namely, ancestral eels originated during the Eocene or earlier, in the western Pacific Ocean near present-day Indonesia. A group derived from this ancestor dispersed westward, probably by larval transport in the global circum-equatorial current through the northern edge of the Tethys Sea. This group split into the ancestor of the European and American eels, which entered into the Atlantic Ocean, and a second group, which dispersed southward and split into the east African species and Australian species. Thus the world-wide distribution of the eel family can be understood from knowledge of continental drift, ocean currents, a specialized larva and evolutionary forces favoring dispersal and speciation of segregated gene pool.

  16. COMMUNITY DEVELOPMENT IN FRESHWATER MICROCOSMS

    Energy Technology Data Exchange (ETDEWEB)

    Rees, John T.

    1978-01-01

    Two cylindrical freshwater microcosms with a volume of 700 {ell} were maintained under controlled laboratory conditions for 190 days. The two microcosms were identical with regard to initial chemical composition and biological inocula, with the exceptions that in one microcosm (designated Tank 2) mosquitofish (Gambusia) and herbivorous catfish (Placostomas) were added. Three distinct communities developed in the tanks: (1) a phytoplankton-zooplankton assemblage and (2) two periphyton-zoobenthos communities associated with the sides and bottom of the tank, respectively. Community development and successional patterns were similar in both tanks. Major differences between the tanks involved timing of succession of the zooplankton and zoobenthos, attributable to predation by fish, principally Gambusia. A major drawback for these microcosms as use for experimental analogs such as lakes was a luxuriant periphyton growth which eventually overwhelmed the biomass of the system. The tanks displayed a degree of successional replicability, a large number of species, and a diversity of community development. Microcosms of this size could find use as experimental systems for higher level trophic manipulation and observation of life cycles not amenable to field studies.

  17. Gear and seasonal bias associated with abundance and size structure estimates for lentic freshwater fishes

    Science.gov (United States)

    Fischer, Jesse R.; Quist, Michael C.

    2014-01-01

    All freshwater fish sampling methods are biased toward particular species, sizes, and sexes and are further influenced by season, habitat, and fish behavior changes over time. However, little is known about gear-specific biases for many common fish species because few multiple-gear comparison studies exist that have incorporated seasonal dynamics. We sampled six lakes and impoundments representing a diversity of trophic and physical conditions in Iowa, USA, using multiple gear types (i.e., standard modified fyke net, mini-modified fyke net, sinking experimental gill net, bag seine, benthic trawl, boat-mounted electrofisher used diurnally and nocturnally) to determine the influence of sampling methodology and season on fisheries assessments. Specifically, we describe the influence of season on catch per unit effort, proportional size distribution, and the number of samples required to obtain 125 stock-length individuals for 12 species of recreational and ecological importance. Mean catch per unit effort generally peaked in the spring and fall as a result of increased sampling effectiveness in shallow areas and seasonal changes in habitat use (e.g., movement offshore during summer). Mean proportional size distribution decreased from spring to fall for white bass Morone chrysops, largemouth bass Micropterus salmoides, bluegill Lepomis macrochirus, and black crappie Pomoxis nigromaculatus, suggesting selectivity for large and presumably sexually mature individuals in the spring and summer. Overall, the mean number of samples required to sample 125 stock-length individuals was minimized in the fall with sinking experimental gill nets, a boat-mounted electrofisher used at night, and standard modified nets for 11 of the 12 species evaluated. Our results provide fisheries scientists with relative comparisons between several recommended standard sampling methods and illustrate the effects of seasonal variation on estimates of population indices that will be critical to

  18. Carbon cycling of Lake Kivu (East Africa: net autotrophy in the epilimnion and emission of CO2 to the atmosphere sustained by geogenic inputs.

    Directory of Open Access Journals (Sweden)

    Alberto V Borges

    Full Text Available We report organic and inorganic carbon distributions and fluxes in a large (>2000 km2 oligotrophic, tropical lake (Lake Kivu, East Africa, acquired during four field surveys, that captured the seasonal variations (March 2007-mid rainy season, September 2007-late dry season, June 2008-early dry season, and April 2009-late rainy season. The partial pressure of CO2 (pCO2 in surface waters of the main basin of Lake Kivu showed modest spatial (coefficient of variation between 3% and 6%, and seasonal variations with an amplitude of 163 ppm (between 579±23 ppm on average in March 2007 and 742±28 ppm on average in September 2007. The most prominent spatial feature of the pCO2 distribution was the very high pCO2 values in Kabuno Bay (a small sub-basin with little connection to the main lake ranging between 11,213 ppm and 14,213 ppm (between 18 and 26 times higher than in the main basin. Surface waters of the main basin of Lake Kivu were a net source of CO2 to the atmosphere at an average rate of 10.8 mmol m(-2 d(-1, which is lower than the global average reported for freshwater, saline, and volcanic lakes. In Kabuno Bay, the CO2 emission to the atmosphere was on average 500.7 mmol m(-2 d(-1 (∼46 times higher than in the main basin. Based on whole-lake mass balance of dissolved inorganic carbon (DIC bulk concentrations and of its stable carbon isotope composition, we show that the epilimnion of Lake Kivu was net autotrophic. This is due to the modest river inputs of organic carbon owing to the small ratio of catchment area to lake surface area (2.15. The carbon budget implies that the CO2 emission to the atmosphere must be sustained by DIC inputs of geogenic origin from deep geothermal springs.

  19. TimeNET Optimization Environment

    Directory of Open Access Journals (Sweden)

    Christoph Bodenstein

    2015-12-01

    Full Text Available In this paper a novel tool for simulation-based optimization and design-space exploration of Stochastic Colored Petri nets (SCPN is introduced. The working title of this tool is TimeNET Optimization Environment (TOE. Targeted users of this tool are people modeling complex systems with SCPNs in TimeNET who want to find parameter sets that are optimal for a certain performance measure (fitness function. It allows users to create and simulate sets of SCPNs and to run different optimization algorithms based on parameter variation. The development of this tool was motivated by the need to automate and speed up tests of heuristic optimization algorithms to be applied for SCPN optimization. A result caching mechanism is used to avoid recalculations.

  20. Influence of Organic Agriculture on the Net Greenhouse Effect in the Red River Valley, Minnesota

    Science.gov (United States)

    Phillips, R. L.

    2004-12-01

    Fluxes for the suite of biologically-produced greenhouse gases (CH4, N2O and CO2) are strongly influenced by agriculture, yet the influence of organic agriculture on all three gases, which comprise the net greenhouse effect (GHE), is not clear in the context of large-scale agricultural production. Greenhouse gas mitigation potential will depend upon the net balance for all three gases [GHE balance (CO2 equiv.)= CO2 flux+ 23CH4flux + 296N2Oflux]. On-farm, field-scale experiments were performed to test the hypothesis that the net GHE at the soil-atmosphere interface is reduced under organic wheat production, compared with conventional, and that effects vary inter-seasonally. Trace gas fluxes were measured at the soil-atmosphere interface for organic and conventional wheat farms in the Red River Valley, Minnesota, one of the most productive agricultural regions in the US. We utilized 40-60 ha field pairs planted with hard red spring wheat (Triticum aestivum L.). Treatment pairs were located 6km apart and consisted of fields continuously cropped for wheat/soybean/sugar beet production for over 20 yr. Ten random, permanent points were generated for each 8.1 ha sub-plot nested inside each field. Each field pair was similar with respect to crop, climate, cultivation history, tillage, rotation, soil texture, pH, macronutrients, bulk density, and water holding capacity. Differences between treatments for the last five years were soil amendments (compost or urea) and herbicide/fungicide application versus mechanical weed control. We collected gas fluxes at each of the 41 points from April (wheat emergence) until the end of July (maturity) to determine the hourly and seasonally integrated net GHE for each management practice, given similar soil/plant/climatic conditions. Moreover, we analyzed inter-seasonal variability to determine the relationship between wheat phenology and flux under field conditions for soil temperature and moisture (water-filled pore space). The net GHE

  1. Methane Fluxes from Subtropical Wetlands

    Science.gov (United States)

    DeLucia, N.; Gomez-Casanovas, N.; Bernacchi, C.

    2013-12-01

    It is well documented that green house gas concentrations have risen at unequivocal rates since the industrial revolution but the disparity between anthropogenic sources and natural sources is uncertain. Wetlands are one example of a natural ecosystem that can be a substantial source or sink for methane (CH4) depending on climate conditions. Due to strict anaerobic conditions required for CH4-generating microorganisms, natural wetlands are one of the main sources for biogenic CH4. Although wetlands occupy less than 5% of total land surface area, they contribute approximately 20% of total CH4 emissions to the atmosphere. The processes regulating CH4 emissions are sensitive to land use and management practices of areas surrounding wetlands. Variation in adjacent vegetation or grazing intensity by livestock can, for example, alter CH4 fluxes from wetland soils by altering nutrient balance, carbon inputs and hydrology. Therefore, understanding how these changes will affect wetland source strength is essential to understand the impact of wetland management practices on the global climate system. In this study we quantify wetland methane fluxes from subtropical wetlands on a working cattle ranch in central Florida near Okeechobee Lake (27o10'52.04'N, 81o21'8.56'W). To determine differences in CH4 fluxes associated with land use and management, a replicated (n = 4) full factorial experiment was designed for wetlands where the surrounding vegetation was (1) grazed or un-grazed and (2) composed of native vegetation or improved pasture. Net exchange of CH4 and CO2 between the land surface and the atmosphere were sampled with a LICOR Li-7700 open path CH4 analyzer and Li-7500A open path CO2/H20 analyzer mounted in a 1-m3 static gas-exchange chamber. Our results showed and verified that CH4 emissions from subtropical wetlands were larger when high soil moisture was coupled with high temperatures. The presence of cattle only amplified these results. These results help quantify

  2. Davis Pond freshwater prediversion biomonitoring study: freshwater fisheries and eagles

    Science.gov (United States)

    Jenkins, Jill A.; Bourgeois, E. Beth; Jeske, Clint W.

    2008-01-01

    In January 2001, the construction of the Davis Pond freshwater diversion structure was completed by the U.S. Army Corps of Engineers. The diversion of freshwater from the Mississippi River is intended to mitigate saltwater intrusion from the Gulf of Mexico and to lessen the concomitant loss of wetland areas. In addition to the freshwater inflow, Barataria Bay basin would receive nutrients, increased flows of sediments, and water-borne and sediment-bound compounds. The purpose of this biomonitoring study was, therefore, to serve as a baseline for prediversion concentrations of selected contaminants in bald eagle (Haliaeetus leucocephalus) nestlings (hereafter referred to as eaglets), representative freshwater fish, and bivalves. Samples were collected from January through June 2001. Two similarly designed postdiversion studies, as described in the biological monitoring program, are planned. Active bald eagle nests targeted for sampling eaglet blood (n = 6) were generally located southwest and south of the diversion structure. The designated sites for aquatic animal sampling were at Lake Salvador, at Lake Cataouatche, at Bayou Couba, and along the Mississippi River. Aquatic animals representative of eagle prey were collected. Fish were from three different trophic levels and have varying feeding strategies and life histories. These included herbivorous striped mullet (Mugil cephalus), omnivorous blue catfish (Ictalurus furcatus), and carnivorous largemouth bass (Micropterus salmoides). Three individuals per species were collected at each of the four sampling sites. Freshwater Atlantic rangia clams (Rangia cuneata) were collected at the downstream marsh sites, and zebra mussels (Dreissena spp.) were collected on the Mississippi River. The U.S. Geological Survey (USGS) Biomonitoring of Environmental Status and Trends (BEST) protocols served as guides for fish sampling and health assessments. Fish are useful for monitoring aquatic ecosystems because they accumulate

  3. Implementing NetScaler VPX

    CERN Document Server

    Sandbu, Marius

    2014-01-01

    An easy-to-follow guide with detailed step-by step-instructions on how to implement the different key components in NetScaler, with real-world examples and sample scenarios.If you are a Citrix or network administrator who needs to implement NetScaler in your virtual environment to gain an insight on its functionality, this book is ideal for you. A basic understanding of networking and familiarity with some of the different Citrix products such as XenApp or XenDesktop is a prerequisite.

  4. Net4Care PHMR Library

    DEFF Research Database (Denmark)

    2014-01-01

    The Net4Care PHMR library contains a) A GreenCDA approach for constructing a data object representing a PHMR document: SimpleClinicalDocument, and b) A Builder which can produce a XML document representing a valid Danish PHMR (following the MedCom profile) document from the SimpleClinicalDocument......The Net4Care PHMR library contains a) A GreenCDA approach for constructing a data object representing a PHMR document: SimpleClinicalDocument, and b) A Builder which can produce a XML document representing a valid Danish PHMR (following the MedCom profile) document from the Simple...

  5. Pro DLR in NET 4

    CERN Document Server

    Wu, Chaur

    2011-01-01

    Microsoft's Dynamic Language Runtime (DLR) is a platform for running dynamic languages such as Ruby and Python on an equal footing with compiled languages such as C#. Furthermore, the runtime is the foundation for many useful software design and architecture techniques you can apply as you develop your .NET applications. Pro DLR in .NET 4 introduces you to the DLR, showing how you can use it to write software that combines dynamic and static languages, letting you choose the right tool for the job. You will learn the core DLR components such as LINQ expressions, call sites, binders, and dynami

  6. Hierarchies in Coloured Petri Nets

    DEFF Research Database (Denmark)

    Huber, Peter; Jensen, Kurt; Shapiro, Robert M.

    1991-01-01

    The paper shows how to extend Coloured Petri Nets with a hierarchy concept. The paper proposes five different hierarchy constructs, which allow the analyst to structure large CP-nets as a set of interrelated subnets (called pages). The paper discusses the properties of the proposed hierarchy...... constructs, and it illustrates them by means of two examples. The hierarchy constructs can be used for theoretical considerations, but their main use is to describe and analyse large real-world systems. All of the hierarchy constructs are supported by the editing and analysis facilities in the CPN Palette...

  7. Rainfall, Plant Communities and Methane Fluxes in the Ka`au Crater Wetland, Oahu, Hawaii

    Science.gov (United States)

    Grand, M.; Gaidos, E.

    2003-12-01

    Tropical wetlands constitute a major source of methane, an atmospheric greenhouse gas. Net methane emission in freshwater settings is the result of organic matter decomposition under anaerobic conditions modulated by aerobic methane oxidation and is thus also an indicator of wetland ecosystem processes. This study is monitoring the methane flux from the Ka`au crater wetland on the island of Oahu (Hawaii) and correlating it with environmental parameters such as precipitation and sunlight. We are obtaining precipitation, Photosynthetic Active Radiation (PAR), and water table level data with data loggers and are correlating these data with static chamber methane flux measurements and measurements of soil methane production potential. Additionally, our research is studying the effects of changes in vegetation type, i.e., of the invasive strawberry guava tree (Psidium Cattleianum) on the wetland methane emissions. Changes in soil chemistry and in the transport of gases by roots that accompany such vegetation change are a potential driver of methane flux modifications that have not been previously examined. Strawberry guava forms dense mats of surface roots that may change soil gas exchange and prolific fruiting may raise the soil organic content. We collected soil samples along a 30 meter transect that extends through two vegetation patterns; the strawberry guava canopy and the sedge meadow (Cladium Leptostachyum). Samples were incubated for 24 hours to estimate their methane generation potential. Our preliminary results show that methane generation potential is greater under the strawberry guava canopy. However, 2 of the 15 samples collected in the sedge meadow section of the transect did not match this pattern. Soil organic carbon content is slightly higher in the strawberry guava than in the sedge. We recorded a 90% decrease in methane generation potential in sedge meadow soils during a dry period relative to a wet period 2 months earlier. We propose that this change

  8. Transient controls on estuarine SPM fluxes: case study in the Dee Estuary, UK.

    Science.gov (United States)

    Amoudry, Laurent; Williams, Megan; Todd, David

    2017-04-01

    Estuaries are a critical interface between land and coastal ocean across which freshwater, suspended particulate matter (SPM), and consequently terrestrial carbon, nutrients and anthropogenic contaminants are exchanged. Suspended particulate matter is closely linked to estuarine turbidity; it affects water quality and estuarine ecology; and it contributes to overall estuarine sediment budgets. However, predicting the response of estuarine ecosystems to climate change and human interventions remains difficult partly due to a lack of comprehensive understanding of SPM concentrations and fluxes across time scales from intratidal to seasonal and interannual variability. We investigate the dynamics of suspended sediment and suspended particulate matter in a hypertidal estuary with a maximum tidal range in excess of 10 m and tidal currents reaching over 1 m/s: the Dee Estuary. This estuary is located in northwest England and outflows in Liverpool Bay, itself in the eastern Irish Sea. The Dee Estuary is a funnel-shaped, coastal plain estuary, which is about 30 km long with a maximum width of 8.5 km at the mouth, and consists of mixed sediments. We focus on field observations, collected during several campaigns in the channels of the Dee Estuary from 2004 to 2009 using acoustic and optical instrumentation, which provide intratidal measurements of flow velocity and suspended sediment, and thus sediment fluxes, over approximately a month. Measurements in February-March 2008 highlight three distinct hydrodynamic regimes: a current dominant regime at neap tides (14-21 February); a combined wave-current regime at spring tides (21-29 February); and a wave dominant regime at neap tide (1-4 March). While analysis of tidal distortion and dominance predicts weak ebb dominant channels, the observations yield flood dominant sediment transport. The net sediment flux exhibits a two-layer structure - import near the bed, export near the surface - that is consistent with the residual

  9. Carbon fluxes in an eutrophic urban lake

    Science.gov (United States)

    Barros, Nathan; Mendonça, Raquel; Huszar, Vera; Roland, Fábio; Kosten, Sarian

    2014-05-01

    Eutrophic lakes have a still unknown net effect on greenhouse gas emission. On one hand, the high photosynthetic rates enhance the freshwater carbon dioxide (CO2) sink. On the other hand, the intense organic matter decomposition may lead to high CO2 release and, when the sediment becomes anoxic, also to more methane (CH4) production. Here, we measured CO2 and CH4 emissions from a highly eutrophic urban lake monthly during summer, autumn and winter, over 24 hour periods. The lake was predominantly a net carbon source to the atmosphere. On the few periods when the lake was a CO2 sink, the magnitude of CO2 influx to the water was small. The CO2 diffusive emission at night was higher than during the day due to daytime CO2 uptake by photosynthesis. The same pattern was not found for CH4 diffusive emission, which was high both during the day and night even though CH4 oxidation reduced the CH4 emission in almost 50%. CH4 emission through bubbles was proven highly dependent on temperature and no bubbles were emitted during colder months. In our study lake, CO2 and CH4 production through mineralization in the water column and in the sediment should be offsetting CO2 fixation by primary production. The greenhouse emission from this system can be even higher considering CO2-equivalents. As conclusion, our data confront the usually accepted idea that eutrophic lakes are carbon sinks.

  10. Estimating the economic impact of climate change on the freshwater sportsfisheries of the Northeastern United States

    Energy Technology Data Exchange (ETDEWEB)

    Pendleton, L. [Univ. of Southern California, Los Angeles, CA (United States). Dept. of Economics; Mendelsohn, R. [Yale Univ., New Haven, CT (United States). School of Forestry and Environmental Studies

    1997-06-06

    This study links models of global climate circulation, ecology, and economic valuation (hedonic travel cost and random utility models) to value the impact of global warming on freshwater sportfishing in the Northeast. An origin-specific linear random utility model (RUM) is introduced. The results of the RUM are shown to be comparable to those of a hedonic travel cost model. A doubling of atmospheric carbon dioxide is predicted to generate between a $4.6 million loss and a $20.5 million net benefit for the Northeastern United States, depending on the climate scenario.

  11. D.NET case study

    International Development Research Centre (IDRC) Digital Library (Canada)

    lremy

    developing products, marketing tools and building capacity of the grass root telecentre workers. D.Net recognized that it had several ideas worth developing into small interventions that would make big differences, but resource constraints were a barrier for scaling-up these initiatives. More demands, limited resources.

  12. Surgery for GEP-NETs

    DEFF Research Database (Denmark)

    Knigge, Ulrich; Hansen, Carsten Palnæs

    2012-01-01

    Surgery is the only treatment that may cure the patient with gastroentero-pancreatic (GEP) neuroendocrine tumours (NET) and neuroendocrine carcinomas (NEC) and should always be considered as first line treatment if R0/R1 resection can be achieved. The surgical and interventional procedures for GEP...

  13. Net Neutrality in the Netherlands

    NARCIS (Netherlands)

    van Eijk, N.

    2014-01-01

    The Netherlands is among the first countries that have put specific net neutrality standards in place. The decision to implement specific regulation was influenced by at least three factors. The first was the prevailing social and academic debate, partly due to developments in the United States. The

  14. Complexity Metrics for Workflow Nets

    DEFF Research Database (Denmark)

    Lassen, Kristian Bisgaard; van der Aalst, Wil M.P.

    2009-01-01

    Process modeling languages such as EPCs, BPMN, flow charts, UML activity diagrams, Petri nets, etc.\\ are used to model business processes and to configure process-aware information systems. It is known that users have problems understanding these diagrams. In fact, even process engineers and system...

  15. Inverse modeling of the terrestrial carbon flux in China with flux covariance among inverted regions

    Science.gov (United States)

    Wang, H.; Jiang, F.; Chen, J. M.; Ju, W.; Wang, H.

    2011-12-01

    Quantitative understanding of the role of ocean and terrestrial biosphere in the global carbon cycle, their response and feedback to climate change is required for the future projection of the global climate. China has the largest amount of anthropogenic CO2 emission, diverse terrestrial ecosystems and an unprecedented rate of urbanization. Thus information on spatial and temporal distributions of the terrestrial carbon flux in China is of great importance in understanding the global carbon cycle. We developed a nested inversion with focus in China. Based on Transcom 22 regions for the globe, we divide China and its neighboring countries into 17 regions, making 39 regions in total for the globe. A Bayesian synthesis inversion is made to estimate the terrestrial carbon flux based on GlobalView CO2 data. In the inversion, GEOS-Chem is used as the transport model to develop the transport matrix. A terrestrial ecosystem model named BEPS is used to produce the prior surface flux to constrain the inversion. However, the sparseness of available observation stations in Asia poses a challenge to the inversion for the 17 small regions. To obtain additional constraint on the inversion, a prior flux covariance matrix is constructed using the BEPS model through analyzing the correlation in the net carbon flux among regions under variable climate conditions. The use of the covariance among different regions in the inversion effectively extends the information content of CO2 observations to more regions. The carbon flux over the 39 land and ocean regions are inverted for the period from 2004 to 2009. In order to investigate the impact of introducing the covariance matrix with non-zero off-diagonal values to the inversion, the inverted terrestrial carbon flux over China is evaluated against ChinaFlux eddy-covariance observations after applying an upscaling methodology.

  16. Eddy Correlation Flux Measurement System Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Cook, D. R. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-01-01

    The eddy correlation (ECOR) flux measurement system provides in situ, half-hour measurements of the surface turbulent fluxes of momentum, sensible heat, latent heat, and carbon dioxide (CO2) (and methane at one Southern Great Plains extended facility (SGP EF) and the North Slope of Alaska Central Facility (NSA CF). The fluxes are obtained with the eddy covariance technique, which involves correlation of the vertical wind component with the horizontal wind component, the air temperature, the water vapor density, and the CO2 concentration. The instruments used are: • a fast-response, three-dimensional (3D) wind sensor (sonic anemometer) to obtain the orthogonal wind components and the speed of sound (SOS) (used to derive the air temperature) • an open-path infrared gas analyzer (IRGA) to obtain the water vapor density and the CO2 concentration, and • an open-path infrared gas analyzer (IRGA) to obtain methane density and methane flux at one SGP EF and at the NSA CF. The ECOR systems are deployed at the locations where other methods for surface flux measurements (e.g., energy balance Bowen ratio [EBBR] systems) are difficult to employ, primarily at the north edge of a field of crops. A Surface Energy Balance System (SEBS) has been installed collocated with each deployed ECOR system in SGP, NSA, Tropical Western Pacific (TWP), ARM Mobile Facility 1 (AMF1), and ARM Mobile Facility 2 (AMF2). The surface energy balance system consists of upwelling and downwelling solar and infrared radiometers within one net radiometer, a wetness sensor, and soil measurements. The SEBS measurements allow the comparison of ECOR sensible and latent heat fluxes with the energy balance determined from the SEBS and provide information on wetting of the sensors for data quality purposes. The SEBS at one SGP and one NSA site also support upwelling and downwelling PAR measurements to qualify those two locations as Ameriflux sites.

  17. High heat flux single phase heat exchanger

    Science.gov (United States)

    Valenzuela, Javier A.; Izenson, Michael G.

    1990-01-01

    This paper presents the results obtained to date in a program to develop a high heat flux, single-phase heat exchanger for spacecraft thermal management. The intended application is a net generation interface heat exchanger to couple the crew module water thermal bus to the two-phase ammonia main thermal bus in the Space Station Freedom. The large size of the interface heat exchanger is dictated by the relatively poor water-side heat transfer characteristics. The objective of this program is to develop a single-phase heat transfer approach which can achieve heat fluxes and heat transfer coefficients comparable to those of the evaporation ammonia side. A new heat exchanger concept has been developed to meet these objecties. The main feature of this heat exchanger is that it can achieve very high heat fluxes with a pressure drop one to two orders of magnitude lower than those of previous microchannel or jet impingement high heat flux heat exchangers. This paper describes proof-of-concept experiments performed in air and water and presents analytical model of the heat exchanger.

  18. Caught in the Net: Perineuronal Nets and Addiction

    Directory of Open Access Journals (Sweden)

    Megan Slaker

    2016-01-01

    Full Text Available Exposure to drugs of abuse induces plasticity in the brain and creates persistent drug-related memories. These changes in plasticity and persistent drug memories are believed to produce aberrant motivation and reinforcement contributing to addiction. Most studies have explored the effect drugs of abuse have on pre- and postsynaptic cells and astrocytes; however, more recently, attention has shifted to explore the effect these drugs have on the extracellular matrix (ECM. Within the ECM are unique structures arranged in a net-like manner, surrounding a subset of neurons called perineuronal nets (PNNs. This review focuses on drug-induced changes in PNNs, the molecules that regulate PNNs, and the expression of PNNs within brain circuitry mediating motivation, reward, and reinforcement as it pertains to addiction.

  19. On the spatial heterogeneity of net ecosystem productivity in complex landscapes

    Science.gov (United States)

    Ryan E. Emanuel; Diego A. Riveros-Iregui; Brian L. McGlynn; Howard E. Epstein

    2011-01-01

    Micrometeorological flux towers provide spatially integrated estimates of net ecosystem production (NEP) of carbon over areas ranging from several hectares to several square kilometers, but they do so at the expense of spatially explicit information within the footprint of the tower. This finer-scale information is crucial for understanding how physical and biological...

  20. Relationships between net primary productivity and forest stand age in U.S. forests

    Science.gov (United States)

    Liming He; Jing M. Chen; Yude Pan; Richard Birdsey; Jens. Kattge

    2012-01-01

    Net primary productivity (NPP) is a key flux in the terrestrial ecosystem carbon balance, as it summarizes the autotrophic input into the system. Forest NPP varies predictably with stand age, and quantitative information on the NPP-age relationship for different regions and forest types is therefore fundamentally important for forest carbon cycle modeling. We used four...

  1. Gap filling strategies for defensible annual sums of net ecosystem exchange

    NARCIS (Netherlands)

    Falge, E.; Baldocchi, D.; Olson, R.; Anthoni, P.; Aubinet, M.; Bernhofer, C.; Burba, G.; Ceulemans, R.; Clement, R.; Dolman, H.; Granier, A.; Gross, P.; Grünwald, T.; Hollinger, D.; Jensen, N.O.; Katul, G.; Keronen, P.; Kowalski, A.; Lai, C.T.; Law, B.E.; Meyers, T.; Moncrieff, J.; Moors, E.J.; Munger, J.W.; Pilegaard, K.; Rebmann, C.; Suyker, A.; Tenhunen, J.; Tu, K.

    2001-01-01

    Heightened awareness of global change issues within both science and political communities has increased interest in using the global network of eddy covariance flux towers to more fully understand the impacts of natural and anthropogenic phenomena on the global carbon balance. Comparisons of net

  2. Army Net Zero Prove Out. Army Net Zero Training Report

    Science.gov (United States)

    2014-11-20

    sensors were strategically placed throughout the installation by magnetically attaching them to water main valve stems. The sensors check sound...Recycle Wrap  Substitutes for Packaging Materials  Re-Use of Textiles and Linens  Setting Printers to Double-Sided Printing Net Zero Waste...can effectively achieve source reduction. Clean and Re-Use Shop Rags - Shop rags represent a large textile waste stream at many installations. As a

  3. Army Net Zero Prove Out. Net Zero Waste Best Practices

    Science.gov (United States)

    2014-11-20

    Anaerobic Digesters – Although anaerobic digestion is not a new technology and has been used on a large-scale basis in wastewater treatment , the...technology and has been used on a large-scale basis in wastewater treatment , the use of the technology should be demonstrated with other...approaches can be used for cardboard and cellulose -based packaging materials. This approach is in line with the Net Zero Waste hierarchy in terms of

  4. Sulfate reduction in freshwater peatlands

    Energy Technology Data Exchange (ETDEWEB)

    Oequist, M.

    1996-12-31

    This text consist of two parts: Part A is a literature review on microbial sulfate reduction with emphasis on freshwater peatlands, and part B presents the results from a study of the relative importance of sulfate reduction and methane formation for the anaerobic decomposition in a boreal peatland. The relative importance of sulfate reduction and methane production for the anaerobic decomposition was studied in a small raised bog situated in the boreal zone of southern Sweden. Depth distribution of sulfate reduction- and methane production rates were measured in peat sampled from three sites (A, B, and C) forming an minerotrophic-ombrotrophic gradient. SO{sub 4}{sup 2-} concentrations in the three profiles were of equal magnitude and ranged from 50 to 150 {mu}M. In contrast, rates of sulfate reduction were vastly different: Maximum rates in the three profiles were obtained at a depth of ca. 20 cm below the water table. In A it was 8 {mu}M h{sup -1} while in B and C they were 1 and 0.05 {mu}M h{sup -1}, respectively. Methane production rates, however, were more uniform across the three nutrient regimes. Maximum rates in A (ca. 1.5 {mu}g d{sup -1} g{sup -1}) were found 10 cm below the water table, in B (ca. 1.0 {mu}g d{sup -1} g{sup -1}) in the vicinity of the water table, and in C (0.75 {mu}g d{sup -1} g{sup -1}) 20 cm below the water table. In all profiles both sulfate reduction and methane production rates were negligible above the water table. The areal estimates of methane production for the profiles were 22.4, 9.0 and 6.4 mmol m{sup -2} d{sup -1}, while the estimates for sulfate reduction were 26.4, 2.5, and 0.1 mmol m{sup -2} d{sup -1}, respectively. The calculated turnover times at the sites were 1.2, 14.2, and 198.7 days, respectively. The study shows that sulfate reducing bacteria are important for the anaerobic degradation in the studied peatland, especially in the minerotrophic sites, while methanogenic bacteria dominate in ombrotrophic sites Examination

  5. CROATIAN FRESHWATER FISHERIES IN 1997

    Directory of Open Access Journals (Sweden)

    Mirko Turk

    1998-10-01

    Full Text Available Data on the production and fish catch according to species, on the surface of the fish ponds, on the means of fish catching and on the distribution of the production and the catch in 1997 is presented. The surface area used for production of fish has decreased for 836 ha or 8.40%. The total fish amount was bigger for 477 tons, or 10,52%. The feeding coefficient is 2.6 kg decreased 35% for in comparison to the bigger compared to the previous year. The amount of the fertilizer used is bigger for 37.30%. The fry carp growing ponds make up 6.50% of the total fish pond surfaces, the young carp ponds 22.04/0, and the ponds with consumption fish 70.31%. The total amount in the carp ponds was 446 kg/ha, and in the trout ponds it was 160.8 tons/ha. The most produced fish species is the carp with 79.32%, followed by the trout with 11.50%, the herbivorous fish with 4.25%, while all the other fish species make up 4.93% of the entire production. In the structure of herbivorous fish the grass carp is leading with 69,23%, followed by the big head carp with 29.74% and the silver carp with 1.03%. Compared to the previous year the production of the carp, grass carp and tench is increased. Fish catch in open waters has decreased by 5.53% in comparison to the previous year. In the production and catch of the total freshwater fish, carp made up 75.34%, herbivorous fish made up 3.89%, trout 10.66%, sheat fish, pike perch and pike 2.70% and all other fish species 7.41%. As far as the distribution of production and catch of fish is concerned, 52,80% were sold on the market, 37.94% were used for reproduction (stocking the fish farms, mortality was 1.43%, and for personal use (sports fishing 7.83%. The number of fisheries workers has decreased for 8.17%, and the production per worker is bigger for 22.25%, compared to the previous year. Average production per worker was 7.17% tons of fish.

  6. [Effects of glyphosate on life histroy characteristics of freshwater rotifer Brachionus calyciflorus].

    Science.gov (United States)

    Chu, Zhaoxia; Yi, Yilong; Xu, Xiaoping; Ge, Yali; Dong, Lili; Chen, Fang

    2005-06-01

    The life table study on the life history characteristics of freshwater rotifer Brachionus calyciflorus under effects of different concentrations glyphosate showed that glyphosate had significant effects on the embryonic developmental time, duration of juvenile and reproductive periods, average lifespan, net reproductive rate, and intrinsic population increasing rate of the rotifer. The embryonic developmental time was significantly lengthened when exposed to 3 and 8 mg x L(-1) glyphosate, the juvenile period began to be lengthened significantly when exposed to 3 mg x L(-1) glyphosate, while the net reproductive rate and intrinsic population increasing rate decreased significantly when the rotifer was exposed to 8.00 and 10.50 mg x L(-1) glyphosate, respectively. Among all the parameters, intrinsic population increasing rate was the most sensitive parameter which could be used in monitoring the effects of glyphosate on the life history characteristics of B. calyciflorus.

  7. Sulfate reduction and methanogenesis at a freshwater

    DEFF Research Database (Denmark)

    Iversen, Vibeke Margrethe Nyvang; Andersen, Martin Søgaard; Jakobsen, Rasmus

    The freshwater-seawater interface was studied in a ~9-m thick anaerobic aquifer located in marine sand and gravel with thin peat lenses. Very limited amounts of iron-oxides are present. Consequently, the dominating redox processes are sulfate reduction and methanogenesis, and the groundwater...... is enriched in dissolved sulfide, methane and bicarbonate. Under normal conditions the seawater-freshwater interface is found at a depth of 4 m at the coastline and reaches the bottom of the aquifer 40 m inland. However, occasional flooding of the area occurs, introducing sulfate to the aquifer. Groundwater...... chemistry was studied in a 120 m transect perpendicular to the coast. Cores were taken for radiotracer rate measurements of sulfate reduction and methanogenesis. In the saline part of the aquifer 35 m inland, sulfate reduction was the dominant process with rates of 0.1-10 mM/year. In the freshwater part 100...

  8. Correction factor to account for dispersion in sharp-interface models of terrestrial freshwater lenses and active seawater intrusion

    Science.gov (United States)

    Werner, Adrian D.

    2017-04-01

    In this paper, a recent analytical solution that describes the steady-state extent of freshwater lenses adjacent to gaining rivers in saline aquifers is improved by applying an empirical correction for dispersive effects. Coastal aquifers experiencing active seawater intrusion (i.e., seawater is flowing inland) are presented as an analogous situation to the terrestrial freshwater lens problem, although the inland boundary in the coastal aquifer situation must represent both a source of freshwater and an outlet of saline groundwater. This condition corresponds to the freshwater river in the terrestrial case. The empirical correction developed in this research applies to situations of flowing saltwater and static freshwater lenses, although freshwater recirculation within the lens is a prominent consequence of dispersive effects, just as seawater recirculates within the stable wedges of coastal aquifers. The correction is a modification of a previous dispersive correction for Ghyben-Herzberg approximations of seawater intrusion (i.e., stable seawater wedges). Comparison between the sharp interface from the modified analytical solution and the 50% saltwater concentration from numerical modelling, using a range of parameter combinations, demonstrates the applicability of both the original analytical solution and its corrected form. The dispersive correction allows for a prediction of the depth to the middle of the mixing zone within about 0.3 m of numerically derived values, at least on average for the cases considered here. It is demonstrated that the uncorrected form of the analytical solution should be used to calculate saltwater flow rates, which closely match those obtained through numerical simulation. Thus, a combination of the unmodified and corrected analytical solutions should be utilized to explore both the saltwater fluxes and lens extent, depending on the dispersiveness of the problem. The new method developed in this paper is simple to apply and offers a

  9. Evaluation of different freshwater forcing scenarios for the 8.2 ka BP event in a coupled climate model

    Energy Technology Data Exchange (ETDEWEB)

    Wiersma, A.P.; Renssen, H. [Vrije Universiteit Amsterdam, Faculty of Earth and Life Sciences, Amsterdam (Netherlands); Goosse, H.; Fichefet, T. [Universite Catholique de Louvain, Institut d' Astronomie et de Geophysique George Lemaitre, Louvain-la-Neuve (Belgium)

    2006-12-15

    To improve our understanding of the mechanism causing the 8.2 ka BP event, we investigated the response of ocean circulation in the ECBilt-CLIO-VECODE (Version 3) model to various freshwater fluxes into the Labrador Sea. Starting from an early Holocene climate state we released freshwater pulses varying in volume and duration based on published estimates. In addition we tested the effect of a baseline flow (0.172 Sv) in the Labrador Sea to account for the background-melting of the Laurentide ice-sheet on the early Holocene climate and on the response of the overturning circulation. Our results imply that the amount of freshwater released is the decisive factor in the response of the ocean, while the release duration only plays a minor role, at least when considering the short release durations (1, 2 and 5 years) of the applied freshwater pulses. Furthermore, the experiments with a baseline flow produce a more realistic early Holocene climate state without Labrador Sea Water formation. Meltwater pulses introduced into this climate state produce a prolonged weakening of the overturning circulation compared to an early Holocene climate without baseline flow, and therefore less freshwater is needed to produce an event of similar duration. (orig.)

  10. Spatial distirbution of Antarctic mass flux due to iceberg transport

    Science.gov (United States)

    Comeau, Darin; Hunke, Elizabeth; Turner, Adrian

    Under a changing climate that sees amplified warming in the polar regions, the stability of the West Antarctic ice sheet and its impact on sea level rise is of great importance. Icebergs are at the interface of the land-ice, ocean, and sea ice systems, and represent approximately half of the mass flux from the Antarctic ice sheet to the ocean. Calved icebergs transport freshwater away from the coast and exchange heat with the ocean, thereby affecting stratification and circulation, with subsequent indirect thermodynamic effects to the sea ice system. Icebergs also dynamically interact with surrounding sea ice pack, as well as serving as nutrient sources for biogeochemical activity. The spatial pattern of these fluxes transported from the continent to the ocean is generally poorly represented in current global climate models. We are implementing an iceberg model into the new Accelerated Climate Model for Energy (ACME) within the MPAS-Seaice model, which uses a variable resolution, unstructured grid framework. This capability will allow for full coupling with the land ice model to inform calving fluxes, and the ocean model for freshwater and heat exchange, giving a complete representation of the iceberg lifecycle and increasing the fidelity of ACME southern cryosphere simulations.

  11. HANPP Collection: Human Appropriation of Net Primary Productivity as a Percentage of Net Primary Productivity

    Data.gov (United States)

    National Aeronautics and Space Administration — The Human Appropriation of Net Primary Productivity (HANPP) as a Percentage of Net Primary Productivity (NPP) portion of the Human Appropriation of Net Primary...

  12. Hydrodynamic characteristics of plane netting used for aquaculture net cages in uniform current

    National Research Council Canada - National Science Library

    DONG, SHUCHUANG; HU, FUXIANG; KUMAZAWA, TAISEI; SIODE, DAISUKE; TOKAI, TADASHI

    2016-01-01

      The hydrodynamic characteristics of polyethylene (PE) netting and chain link wire netting with different types of twine diameter and mesh size for aquaculture net cages were examined by experiments in a flume tank...

  13. Flux in Tallinn

    Index Scriptorium Estoniae

    2004-01-01

    Rahvusvahelise elektroonilise kunsti sümpoosioni ISEA2004 klubiõhtu "Flux in Tallinn" klubis Bon Bon. Eestit esindasid Ropotator, Ars Intel Inc., Urmas Puhkan, Joel Tammik, Taavi Tulev (pseud. Wochtzchee). Klubiõhtu koordinaator Andres Lõo

  14. Freshwater reservoir effect variability in Northern Germany

    OpenAIRE

    Philippsen, Bente; Heinemeier, Jan

    2012-01-01

    The freshwater reservoir effect is a potential problem when radiocarbon dating fishbones, shells, human bones or food crusts on pottery from sites next to rivers or lakes. The reservoir age in rivers containing considerable amounts of dissolved 14C-free carbonates can be up to several thousand years and may be highly variable. For accurate radiocarbon dating of freshwater-based samples, the order of magnitude of the reservoir effect as well as the degree of variability has to be known.The ini...

  15. Residence time control on hot moments of net nitrate production and uptake in the hyporheic zone

    Science.gov (United States)

    Briggs, Martin A.; Lautz, Laura K.; Hare, Danielle K.

    2014-01-01

    The retention capacity for biologically available nitrogen within streams can be influenced by dynamic hyporheic zone exchange, a process that may act as either a net source or net sink of dissolved nitrogen. Over 5 weeks, nine vertical profiles of streambed chemistry (NO3- and NH4+) were collected above two beaver dams along with continuous high-resolution vertical hyporheic flux data. The results indicate a non-linear relation of net NO3- production followed by net uptake in the hyporheic zone as a function of residence time. This Lagrangian-based relation is consistent through time and across varied morphology (bars, pools, glides) above the dams, even though biogeochemical and environmental factors varied. The empirical continuum between net NO3- production and uptake and residence time is useful for identifying two crucial residence time thresholds: the transition to anaerobic respiration, which corresponds to the time of peak net nitrate production, and the net sink threshold, which is defined by a net uptake in NO3- relative to streamwater. Short-term hyporheic residence time variability at specific locations creates hot

  16. Threatened and Endangered Freshwater Fish and Mussel Species Richness

    Data.gov (United States)

    U.S. Environmental Protection Agency — These data represent predicted current distributions of all US listed Threatened and Endangered freshwater fish and freshwater mussels in the Middle-Atlantic region....

  17. Freshwater algae of North America: ecology and classification

    National Research Council Canada - National Science Library

    Wehr, John D; Sheath, R.G; Kociolek, J.P

    2015-01-01

    Freshwater Algae of North America: Ecology and Classification, Second Edition is an authoritative and practical treatise on the classification, biodiversity, and ecology of all known genera of freshwater algae from North America...

  18. Flux Emergence (Theory

    Directory of Open Access Journals (Sweden)

    Mark C. M. Cheung

    2014-07-01

    Full Text Available Magnetic flux emergence from the solar convection zone into the overlying atmosphere is the driver of a diverse range of phenomena associated with solar activity. In this article, we introduce theoretical concepts central to the study of flux emergence and discuss how the inclusion of different physical effects (e.g., magnetic buoyancy, magnetoconvection, reconnection, magnetic twist, interaction with ambient field in models impact the evolution of the emerging field and plasma.

  19. Generic flux coupling analysis

    OpenAIRE

    Reimers, Arne; Goldstein, Y.; Bockmayr, A.

    2015-01-01

    htmlabstractFlux coupling analysis (FCA) has become a useful tool for aiding metabolic reconstructions and guiding genetic manipulations. Originally, it was introduced for constraint-based models of metabolic networks that are based on the steady-state assumption. Recently, we have shown that the steady-state assumption can be replaced by a weaker lattice-theoretic property related to the supports of metabolic fluxes. In this paper, we further extend our approach and develop an efficient algo...

  20. Isolated unit tests in .Net

    OpenAIRE

    Haukilehto, Tero

    2013-01-01

    In this thesis isolation in unit testing is studied to get a precise picture of the isolation frameworks available for .Net environment. At the beginning testing is discussed in theory with the benefits and the problems it may have been linked with. The theory includes software development in general in connection with testing. Theory of isolation is also described before the actual isolation frameworks are represented. Common frameworks are described in more detail and comparable informa...

  1. anNET: a tool for network-embedded thermodynamic analysis of quantitative metabolome data

    Directory of Open Access Journals (Sweden)

    Zamboni Nicola

    2008-04-01

    Full Text Available Abstract Background Compared to other omics techniques, quantitative metabolomics is still at its infancy. Complex sample preparation and analytical procedures render exact quantification extremely difficult. Furthermore, not only the actual measurement but also the subsequent interpretation of quantitative metabolome data to obtain mechanistic insights is still lacking behind the current expectations. Recently, the method of network-embedded thermodynamic (NET analysis was introduced to address some of these open issues. Building upon principles of thermodynamics, this method allows for a quality check of measured metabolite concentrations and enables to spot metabolic reactions where active regulation potentially controls metabolic flux. So far, however, widespread application of NET analysis in metabolomics labs was hindered by the absence of suitable software. Results We have developed in Matlab a generalized software called 'anNET' that affords a user-friendly implementation of the NET analysis algorithm. anNET supports the analysis of any metabolic network for which a stoichiometric model can be compiled. The model size can span from a single reaction to a complete genome-wide network reconstruction including compartments. anNET can (i test quantitative data sets for thermodynamic consistency, (ii predict metabolite concentrations beyond the actually measured data, (iii identify putative sites of active regulation in the metabolic reaction network, and (iv help in localizing errors in data sets that were found to be thermodynamically infeasible. We demonstrate the application of anNET with three published Escherichia coli metabolome data sets. Conclusion Our user-friendly and generalized implementation of the NET analysis method in the software anNET allows users to rapidly integrate quantitative metabolome data obtained from virtually any organism. We envision that use of anNET in labs working on quantitative metabolomics will provide the

  2. CROATIAN FRESHWATER FISHERIES IN 1994

    Directory of Open Access Journals (Sweden)

    Mirko Turk

    1995-09-01

    Full Text Available Data on the production and catch of fish according to species, on the surface of the fish ponds, on the means of fish catching and on the distribution of the product and catch in 1994 is presented. The surface area used for production of fish has decreased by 274 ha or 2,51%. The total amount of fish has decreased by 1.263 tons or 14,78%. The highest production of fish was reached by the fish farm Donji Miholjac with 1.231 kg/ha. The feeding coefficient is 3,10 kg. Only on one fish farm was the feeding coefficient less than 2.0 kg (1,40 and on two large farms this coefficient was greater than 5,00 kg. The main fish food is still wheat followed by corn. The amount of fertilizer used was decreased by 14,40%. The fry carp growing ponds make up 0,92% of the surface area of the entire fish farm, the young carp ponds 21,77% and the culturing ponds for consumption fish 76,55%. The total amount of fish in the carp ponds was 660 kg/ha, and in the trout ponds it was 123.4 tons/ha. The carp is the highest produced fish with 80, 35%, then the herbivorous fish with 5,65 and all other fish make up 14% of the total production. In the structure of herbivorous fish the grass carp is leading with 54, 70%, followed by the big head carp with 25,54% and the silver carp with 19,76%. In comparison with the previous year the production of "all other fish- has significantly increased (287%, and sheat fish 18,90%, while the production of trench has decreased (71%. Fish catch in open waters has increased by 20,57% in comparison to the previous year. Carp made up 78,07% of the total production and catch of freshwater fish, the herbivorous fish made up 5,40%, trout 4,38%, the sheat fish, pike perch and pike 2,86% and all other fish species 9,28%. As far as the distribution of production and catch, 51,60% were sold on the market, 37,54% were used for reproduction (stocking the fish farms , mortalities were 6,35% and for personal use (sports fishing 4,50% was used. The number

  3. Spring Hydrology Determines Summer Net Carbon Uptake in Northern Ecosystems

    Science.gov (United States)

    Yi, Yonghong; Kimball, John; Reichle, Rolf H.

    2014-01-01

    Increased photosynthetic activity and enhanced seasonal CO2 exchange of northern ecosystems have been observed from a variety of sources including satellite vegetation indices (such as the Normalized Difference Vegetation Index; NDVI) and atmospheric CO2 measurements. Most of these changes have been attributed to strong warming trends in the northern high latitudes (greater than or equal to 50N). Here we analyze the interannual variation of summer net carbon uptake derived from atmospheric CO2 measurements and satellite NDVI in relation to surface meteorology from regional observational records. We find that increases in spring precipitation and snow pack promote summer net carbon uptake of northern ecosystems independent of air temperature effects. However, satellite NDVI measurements still show an overall benefit of summer photosynthetic activity from regional warming and limited impact of spring precipitation. This discrepancy is attributed to a similar response of photosynthesis and respiration to warming and thus reduced sensitivity of net ecosystem carbon uptake to temperature. Further analysis of boreal tower eddy covariance CO2 flux measurements indicates that summer net carbon uptake is positively correlated with early growing-season surface soil moisture, which is also strongly affected by spring precipitation and snow pack based on analysis of satellite soil moisture retrievals. This is attributed to strong regulation of spring hydrology on soil respiration in relatively wet boreal and arctic ecosystems. These results document the important role of spring hydrology in determining summer net carbon uptake and contrast with prevailing assumptions of dominant cold temperature limitations to high-latitude ecosystems. Our results indicate potentially stronger coupling of boreal/arctic water and carbon cycles with continued regional warming trends.

  4. Freshwater resources in the insular Caribbean: an environmental perspective

    Science.gov (United States)

    T. Heartsill Scalley

    2012-01-01

    From islands with no permanent flowing streams to those with navigable inland waters, the insular Caribbean contains a great range of conditions regarding the access to freshwater resources. Because of the variation in topography and size, the ability of islands to retain freshwater also varies widely. The usage of freshwater in this region is being led by two major...

  5. Freshwater crayfish invasions in South Africa: past, present and ...

    African Journals Online (AJOL)

    Freshwater crayfish invasions have been studied around the world, but less so in Africa, a continent devoid of native freshwater crayfish. The present study reviews historical and current information on alien freshwater crayfish species introduced into South Africa and aims to indicate which areas are at risk from invasion.

  6. Anthropogenic And Biogenic Carbon Dioxide Fluxes in Urban Houston

    Science.gov (United States)

    Werner, N. D.; Schade, G. W.; Savage, J.; Hale, M.

    2011-12-01

    Approximately 5% of North American land cover is characterized as urban, representing a large source of anthropogenic carbon to the atmosphere but also an unknown sink in urban vegetation and its management. We present measurements of energy and trace gas fluxes from a unique urban research site in Houston, Texas, with a focus on evaluating the anthropogenic and biogenic contributions to the measured net CO2 exchange at this site. Eddy covariance carbon dioxide flux measurements, and CO2 and NOx flux gradient measurements have been operated (with a one-year gap) since mid 2007 from a commercial communications tower north of downtown Houston. In addition, leaf-level and soil CO2 efflux measurements were carried out in the tower's footprint region in 2011. Bottom-up estimates were developed for anthropogenic CO2 fluxes through correlation with CO, traffic count and natural gas use data, and for biogenic CO2 fluxes through modeling soil and plant respiration, and photosynthesis. CO, NO¬x, and CO2 data were strongly correlated during the morning rush hours, and were used to extrapolate CO2 emissions from traffic using measured biweekly to monthly CO (NOx) flux averages. CO emissions from natural gas use were extrapolated from monthly gas consumption data. The results will be compared to a top-down flux estimate that uses quadrant analysis of CO2 fluxes with simultaneously acquired heat and water vapor fluxes to distinguish biogenic (high q'C' correlation) from anthropogenic (high T'C' correlation) carbon flux contributions. First results from both bottom-up and top-down flux estimates will be presented. The successful implementation of this new analysis may allow us to better judge the importance of constantly growing urban areas in the North American carbon cycle. It addresses identified gaps in carbon cycle knowledge and can help in validating inventories and improving estimates of carbon cycling.

  7. Event hierarchies in DanNet

    DEFF Research Database (Denmark)

    Pedersen, Bolette Sandford; Nimb, Sanni

    2008-01-01

    Artiklen omhandler udarbejdelsen af et verbumshierarki i det leksikalsk-semantiske ordnet, DanNet.......Artiklen omhandler udarbejdelsen af et verbumshierarki i det leksikalsk-semantiske ordnet, DanNet....

  8. The Uniframe .Net Web Service Discovery Service

    National Research Council Canada - National Science Library

    Berbeco, Robert W

    2003-01-01

    Microsoft .NET allows the creation of distributed systems in a seamless manner Within NET small, discrete applications, referred to as Web services, are utilized to connect to each other or larger applications...

  9. Long Term RadNet Quality Data

    Data.gov (United States)

    U.S. Environmental Protection Agency — This RadNet Quality Data Asset includes all data since initiation and when ERAMS was expanded to become RadNet, name changed to reflect new mission. This includes...

  10. The flux-flux correlation function for anharmonic barriers

    NARCIS (Netherlands)

    Goussev, Arseni; Schubert, Roman; Waalkens, Holger; Wiggins, Stephen

    2010-01-01

    The flux-flux correlation function formalism is a standard and widely used approach for the computation of reaction rates. In this paper we introduce a method to compute the classical and quantum flux-flux correlation functions for anharmonic barriers essentially analytically through the use of the

  11. Quantal Response Of Freshwater Shrimp ( Desmocaris trispinosa ...

    African Journals Online (AJOL)

    The quantal-response of freshwater shrimp (Desmocaris trispinosa) to the toxicity of five azo dyes was studied. Generally, increase in percentage mortality of the organisms was obtained with increases in concentration of the toxicants and exposure time. The median lethal concentration50 (LC50) and median lethal ...

  12. Methane emission from tidal freshwater marshes

    NARCIS (Netherlands)

    Van der Nat, F.J.; Middelburg, J.J.

    2000-01-01

    In two tidal freshwater marshes, methane emission, production and accumulation in the pore-water have been studied. The two sites differ in their dominant vegetation, i.e., reed and bulrush, and in their heights above sea level. The reed site was elevated in relation to the bulrush site and had

  13. Review: Freshwater conservation planning in South Africa ...

    African Journals Online (AJOL)

    Since the 1970s, at approximately 10-year intervals, 4 national-scale freshwater conservation plans have been developed for South Africa. These 4 plans reflect different but broadly advancing approaches to conservation planning. We provide an overview of 3 historical plans and a more detailed discussion of the most ...

  14. Herbivory on freshwater and marine macrophytes

    NARCIS (Netherlands)

    Bakker, Elisabeth S.; Wood, Kevin A.; Pagès, Jordi F.; Veen, G.F.; Christianen, Marjolijn J.A.; Santamaría, Luis; Nolet, Bart A.; Hilt, Sabine

    2016-01-01

    Until the 1990s, herbivory on aquatic vascular plants was considered to be of minor importance, and the predominant view was that freshwater and marine macrophytes did not take part in the food web: their primary fate was the detritivorous pathway. In the last 25 years, a substantial body of

  15. Petroleum hydrocarbon degrading capability of freshwater ...

    African Journals Online (AJOL)

    Petroleum hydrocarbon degrading capability and growth profile of indigenous filamentous freshwater fungi from four (4) different streams were determined in vitro. The result indicated that the streams under investigation contained an average heterotrophic fungal count of 5.55 0.25x105 cfu ml-1 while the mean count of ...

  16. Effects of Pollution on Freshwater Invertebrates.

    Science.gov (United States)

    Buikema, A. L., Jr.; Herricks, E. E.

    1978-01-01

    Presents a literature review of the effects of pollution on freshwater invertebrates, covering publications of 1976-77. Some of the areas covered are: (1) toxicant effects on invertebrates; (2) microcosm and community effects, and (3) biological control of aquatic life. A list of 123 references is also presented. (HM)

  17. Benthic freshwater nematode community dynamics under conditions ...

    African Journals Online (AJOL)

    Studies of the influence of fish aquaculture on benthic freshwater nematode assemblages are scarce, but could provide a way of gauging environmental effects. The abundance and diversity of nematode assemblages in response to Oreochromis niloticus aquaculture were investigated in Kafr El-Sheikh Governorate, Egypt, ...

  18. Ocean Freshwater Lenses: Prevalence and Persistence

    Science.gov (United States)

    Schanze, Julian; Lagerloef, Gary; Schmitt, Raymond

    2017-04-01

    During the Salinity Processes in the Upper Ocean Regional Study II (SPURS-II), a novel dataset was collected from an underway system sampling seawater at the surface, 2m, 3m and 5m. The surface measurements are performed using a boom-mounted suction hose and a peristaltic pump, as well as a shipboard apparatus with multiple de-bubbling stages. The data collected during this cruise reveal approximately fifty freshwater lenses in the Intertropical Convergence Zone (ITCZ), sampled between August 15 and September 20 under several different wind- and precipitation-regimes. Preliminary analysis shows that that the persistence of oceanic freshwater lenses is strongly dependent on the evolution of wind speed as well as the total amount of precipitated water. The results are analyzed in a number of case studies of different types of freshwater lenses, in which the balance between precipitation and wind-driven mixing is elucidated. While the limited sample size restricts the validity of the findings to the SPURS-II region, centered around 125°W, 10°N, during the late boreal summer of 2016, it has important consequences for modelling of freshwater lenses and their impact on satellite retrievals of salinity.

  19. Thiaminase activity in native freshwater mussels

    Science.gov (United States)

    Blakeslee, Carrie J.; Sweet, Stephanie; Galbraith, Heather S.; Honeyfield, Dale C.

    2015-01-01

    Thiamine (vitamin B1) deficiency in the Great Lakes has been attributed to elevated levels of thiaminase I enzyme activity in invasive prey species; however, few studies have investigated thiaminase activity in native prey species. Some of the highest levels of thiaminase activity have been measured in invasive dreissenid mussels with little understanding of background levels contributed by native freshwater mussels (Bivalvia: Unionidae). In this study, thiaminase activity was measured in two freshwater mussel species, Elliptio complanata and Strophitus undulatus, from the Delaware and Susquehanna River drainage basins located in north eastern United States. Thiaminase activity was also measured in gravid and non-gravid S. undulatus. Average thiaminase activity differed significantly between species (7.2 and 42.4 μmol/g/min, for E. complanata and S. undulatus respectively) with no differences observed between drainage basins. Gravid S. undulatus had significantly lower thiaminase activity (28.0 μmol/g/min) than non-gravid mussels (42.4 μmol/g/min). Our results suggest that a suite of factors may regulate thiaminase activity in freshwater mussels and that native freshwater mussel thiaminase activity is within the range observed for invasive dreissenids. These results add to our understanding of the complexities in identifying the ecological conditions that set the stage for thiamine deficiency.

  20. Impact of blade motion on mass flux to seagrass blade

    Science.gov (United States)

    Lei, J.; Nepf, H. M.

    2016-12-01

    Seagrass and other freshwater macrophytes can acquire nutrients from surrounding water through their blades. This mass flux may depend on the flow velocity (U), which can influence both the posture/motion of flexible blades (reconfiguration) and the thickness of the flux-limiting diffusive layer. Flow over sufficiently pronated, hydraulically-smooth blades resembles flow over a flat-plate, on which a laminar boundary layer develops, producing mass flux that proportionally increases with the square root of the current speed (U0.5). Our laboratory experiments show that a laminar boundary layer condition is appropriate when the blades are sufficiently flexible; however, the model overestimates the flux when the blades are stiff. A meadow-scale analysis suggests that the mass exchange at the blade scale controls the uptake at the meadow scale, so that uptake at the meadow scale should also follow a U0.5 dependence. This is consistent with field measurements under unidirectional current, for which the flux, represented by a transfer velocity (K), exhibits a dependence on velocity of U0.4±0.2. For purely oscillatory flows we anticipate that the mass flux depends on the relative motion between the blade and the water flow. Preliminary flume experiments show that blade motion under wave conditions has two distinct regimes. In the first regime, the blade moves passively with the flow, which diminishes the relative motion and the mass flux. The second regime occurs when the blade is stiff. In this case, the phase lag between the blade and the flow enhances the relative motion, and thus also the mass flux.

  1. PsychoNet: a psycholinguistc commonsense ontology

    OpenAIRE

    Mohtasseb, Haytham; Ahmed, Amr

    2010-01-01

    Ontologies have been widely accepted as the most advanced knowledge representation model. This paper introduces PsychoNet, a new knowledgebase that forms the link between psycholinguistic taxonomy, existing in LIWC, and its semantic textual representation in the form of commonsense semantic ontology, represented by ConceptNet. The integration of LIWC and ConceptNet and the added functionalities facilitate employing ConceptNet in psycholinguistic studies. Furthermore, it simplifies utilization...

  2. A systematic approach for comparing modeled biospheric carbon fluxes across regional scales

    Directory of Open Access Journals (Sweden)

    D. N. Huntzinger

    2011-06-01

    Full Text Available Given the large differences between biospheric model estimates of regional carbon exchange, there is a need to understand and reconcile the predicted spatial variability of fluxes across models. This paper presents a set of quantitative tools that can be applied to systematically compare flux estimates despite the inherent differences in model formulation. The presented methods include variogram analysis, variable selection, and geostatistical regression. These methods are evaluated in terms of their ability to assess and identify differences in spatial variability in flux estimates across North America among a small subset of models, as well as differences in the environmental drivers that best explain the spatial variability of predicted fluxes. The examined models are the Simple Biosphere (SiB 3.0, Carnegie Ames Stanford Approach (CASA, and CASA coupled with the Global Fire Emissions Database (CASA GFEDv2, and the analyses are performed on model-predicted net ecosystem exchange, gross primary production, and ecosystem respiration. Variogram analysis reveals consistent seasonal differences in spatial variability among modeled fluxes at a 1° × 1° spatial resolution. However, significant differences are observed in the overall magnitude of the carbon flux spatial variability across models, in both net ecosystem exchange and component fluxes. Results of the variable selection and geostatistical regression analyses suggest fundamental differences between the models in terms of the factors that explain the spatial variability of predicted flux. For example, carbon flux is more strongly correlated with percent land cover in CASA GFEDv2 than in SiB or CASA. Some of the differences in spatial patterns of estimated flux can be linked back to differences in model formulation, and would have been difficult to identify simply by comparing net fluxes between models. Overall, the systematic approach presented here provides a set of tools for comparing

  3. An intercomparison and validation of satellite-based surface radiative energy flux estimates over the Arctic

    Science.gov (United States)

    Riihelä, Aku; Key, Jeffrey R.; Meirink, Jan Fokke; Kuipers Munneke, Peter; Palo, Timo; Karlsson, Karl-Göran

    2017-05-01

    Accurate determination of radiative energy fluxes over the Arctic is of crucial importance for understanding atmosphere-surface interactions, melt and refreezing cycles of the snow and ice cover, and the role of the Arctic in the global energy budget. Satellite-based estimates can provide comprehensive spatiotemporal coverage, but the accuracy and comparability of the existing data sets must be ascertained to facilitate their use. Here we compare radiative flux estimates from Clouds and the Earth's Radiant Energy System (CERES) Synoptic 1-degree (SYN1deg)/Energy Balanced and Filled, Global Energy and Water Cycle Experiment (GEWEX) surface energy budget, and our own experimental FluxNet / Satellite Application Facility on Climate Monitoring cLoud, Albedo and RAdiation (CLARA) data against in situ observations over Arctic sea ice and the Greenland Ice Sheet during summer of 2007. In general, CERES SYN1deg flux estimates agree best with in situ measurements, although with two particular limitations: (1) over sea ice the upwelling shortwave flux in CERES SYN1deg appears to be underestimated because of an underestimated surface albedo and (2) the CERES SYN1deg upwelling longwave flux over sea ice saturates during midsummer. The Advanced Very High Resolution Radiometer-based GEWEX and FluxNet-CLARA flux estimates generally show a larger range in retrieval errors relative to CERES, with contrasting tendencies relative to each other. The largest source of retrieval error in the FluxNet-CLARA downwelling shortwave flux is shown to be an overestimated cloud optical thickness. The results illustrate that satellite-based flux estimates over the Arctic are not yet homogeneous and that further efforts are necessary to investigate the differences in the surface and cloud properties which lead to disagreements in flux retrievals.

  4. 78 FR 72451 - Net Investment Income Tax

    Science.gov (United States)

    2013-12-02

    ... Revenue Service 26 CFR Part 1 RIN 1545-BL74 Net Investment Income Tax AGENCY: Internal Revenue Service...). These regulations provide guidance on the computation of net investment income. The regulations affect... lesser of: (A) The individual's net investment income for such taxable year, or (B) the excess (if any...

  5. 47 CFR 69.302 - Net investment.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Net investment. 69.302 Section 69.302... Apportionment of Net Investment § 69.302 Net investment. (a) Investment in Accounts 2001, 1220 and Class B Rural...) Investment in Accounts 2002, 2003 and to the extent such inclusions are allowed by this Commission, Account...

  6. 47 CFR 65.450 - Net income.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Net income. 65.450 Section 65.450... OF RETURN PRESCRIPTION PROCEDURES AND METHODOLOGIES Exchange Carriers § 65.450 Net income. (a) Net income shall consist of all revenues derived from the provision of interstate telecommunications services...

  7. 47 CFR 65.500 - Net income.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Net income. 65.500 Section 65.500... OF RETURN PRESCRIPTION PROCEDURES AND METHODOLOGIES Interexchange Carriers § 65.500 Net income. The net income methodology specified in § 65.450 shall be utilized by all interexchange carriers that are...

  8. NetBeans IDE 8 cookbook

    CERN Document Server

    Salter, David

    2014-01-01

    If you're a Java developer of any level using NetBeans and want to learn how to get the most out of NetBeans, then this book is for you. Learning how to utilize NetBeans will provide a firm foundation for your Java application development.

  9. Characterizing behavioural congruences for Petri nets

    DEFF Research Database (Denmark)

    Nielsen, Mogens; Priese, Lutz; Sassone, Vladimiro

    1995-01-01

    We exploit a notion of interface for Petri nets in order to design a set of net combinators. For such a calculus of nets, we focus on the behavioural congruences arising from four simple notions of behaviour, viz., traces, maximal traces, step, and maximal step traces, and from the corresponding...

  10. 27 CFR 4.37 - Net contents.

    Science.gov (United States)

    2010-04-01

    ... the volume of wine within the container, except that the following tolerances shall be allowed: (1... THE TREASURY LIQUORS LABELING AND ADVERTISING OF WINE Labeling Requirements for Wine § 4.37 Net contents. (a) Statement of net contents. The net contents of wine for which a standard of fill is...

  11. Flux Pinning in Superconductors

    CERN Document Server

    Matsushita, Teruo

    2007-01-01

    The book covers the flux pinning mechanisms and properties and the electromagnetic phenomena caused by the flux pinning common for metallic, high-Tc and MgB2 superconductors. The condensation energy interaction known for normal precipitates or grain boundaries and the kinetic energy interaction proposed for artificial Nb pins in Nb-Ti, etc., are introduced for the pinning mechanism. Summation theories to derive the critical current density are discussed in detail. Irreversible magnetization and AC loss caused by the flux pinning are also discussed. The loss originally stems from the ohmic dissipation of normal electrons in the normal core driven by the electric field induced by the flux motion. The readers will learn why the resultant loss is of hysteresis type in spite of such mechanism. The influence of the flux pinning on the vortex phase diagram in high Tc superconductors is discussed, and the dependencies of the irreversibility field are also described on other quantities such as anisotropy of supercondu...

  12. INNOVATIVE HEAT FLUX SENSOR

    Directory of Open Access Journals (Sweden)

    G. N. Lukyanov

    2017-02-01

    Full Text Available Subject of Study.We present a method for heat flux measuring with the use of polarization properties of ferroelectric ceramics. Heat flux innovative sensor is developed on the basis of the proposed method. Its experimental verification is carried out. Method. The measurements are based on maintaining a balance between the processes caused by thermal energy and the energy of the electric field in the ferroelectric ceramics. Main Results. The testing of the proposed heat flux sensor has been organized in two stages. At the first stage the primary calibration has been performed by calibrated sensors ITP MG4.03/x(y “Potok”. At the second stage the testing of heat flux sensor has been carried out for calculating the quantity of heat. The comparison of the results to the readings of serial heat meters VKT-7 and STK-15 has been performed. Experiments have shown that the polarization properties of the ferroelectric ceramics can be used to measure the heat flow. Practical Relevance. The proposed sensor can be recommended as an apartment-level heat meter. The calibration of the proposed heat flux sensor with more accurate measurement tools gives the possibility to include it on the State Register of Measuring Instruments.

  13. Flux pinning in superconductors

    CERN Document Server

    Matsushita, Teruo

    2014-01-01

    The book covers the flux pinning mechanisms and properties and the electromagnetic phenomena caused by the flux pinning common for metallic, high-Tc and MgB2 superconductors. The condensation energy interaction known for normal precipitates or grain boundaries and the kinetic energy interaction proposed for artificial Nb pins in Nb-Ti, etc., are introduced for the pinning mechanism. Summation theories to derive the critical current density are discussed in detail. Irreversible magnetization and AC loss caused by the flux pinning are also discussed. The loss originally stems from the ohmic dissipation of normal electrons in the normal core driven by the electric field induced by the flux motion. The readers will learn why the resultant loss is of hysteresis type in spite of such mechanism. The influence of the flux pinning on the vortex phase diagram in high Tc superconductors is discussed, and the dependencies of the irreversibility field are also described on other quantities such as anisotropy of supercondu...

  14. Flux lenses in the crossing lattices regime of layered superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Cole, D.; Crisan, A.; Bending, S.J.; Tamegai, T.; Beek, K. van der; Konczykowski, M

    2004-05-01

    We report here measurements of flux lensing behaviour which have been performed on Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} single crystals placed on top of linear Hall probe arrays. In the crossing lattices regime we observe significant flux focussing as the in-plane field is swept up with a small constant density of pancake vortices. We also observe a sharp discontinuous lock-in feature in local magnetic induction when the net field is close to the a-b plane.

  15. High Upward Fluxes of Formic Acid from a Boreal Forest Canopy

    Science.gov (United States)

    Schobesberger, Siegfried; Lopez-Hilifiker, Felipe D.; Taipale, Ditte; Millet, Dylan B.; D'Ambro, Emma L.; Rantala, Pekka; Mammarella, Ivan; Zhou, Putian; Wolfe, Glenn M.; Lee, Ben H.; hide

    2016-01-01

    Eddy covariance fluxes of formic acid, HCOOH, were measured over a boreal forest canopy in spring/summer 2014. The HCOOH fluxes were bidirectional but mostly upward during daytime, in contrast to studies elsewhere that reported mostly downward fluxes. Downward flux episodes were explained well by modeled dry deposition rates. The sum of net observed flux and modeled dry deposition yields an upward gross flux of HCOOH, which could not be quantitatively explained by literature estimates of direct vegetative soil emissions nor by efficient chemical production from other volatile organic compounds, suggesting missing or greatly underestimated HCOOH sources in the boreal ecosystem. We implemented a vegetative HCOOH source into the GEOS-Chem chemical transport model to match our derived gross flux and evaluated the updated model against airborne and spaceborne observations. Model biases in the boundary layer were substantially reduced based on this revised treatment, but biases in the free troposphere remain unexplained.

  16. NET 40 Generics Beginner's Guide

    CERN Document Server

    Mukherjee, Sudipta

    2012-01-01

    This is a concise, practical guide that will help you learn Generics in .NET, with lots of real world and fun-to-build examples and clear explanations. It is packed with screenshots to aid your understanding of the process. This book is aimed at beginners in Generics. It assumes some working knowledge of C# , but it isn't mandatory. The following would get the most use out of the book: Newbie C# developers struggling with Generics. Experienced C++ and Java Programmers who are migrating to C# and looking for an alternative to other generic frameworks like STL and JCF would find this book handy.

  17. The Net Reclassification Index (NRI)

    DEFF Research Database (Denmark)

    Pepe, Margaret S.; Fan, Jing; Feng, Ziding

    2015-01-01

    The Net Reclassification Index (NRI) is a very popular measure for evaluating the improvement in prediction performance gained by adding a marker to a set of baseline predictors. However, the statistical properties of this novel measure have not been explored in depth. We demonstrate the alarming...... marker is proven to erroneously yield a positive NRI. Some insight into this phenomenon is provided. Since large values for the NRI statistic may simply be due to use of poorly fitting risk models, we suggest caution in using the NRI as the basis for marker evaluation. Other measures of prediction...

  18. Simulation of atmospherics in KM3NeT

    Energy Technology Data Exchange (ETDEWEB)

    Heid, Thomas [ECAP, FAU Erlangen-Nuernberg, Erlangen (Germany); Collaboration: ANTARES-KM3NeT-Erlangen-Collaboration

    2016-07-01

    With the installation of the first KM3NeT line, a new facility for neutrino astronomy started operation at the end of 2015. KM3NeT detectors are built of several thousands of digital optical modules(DOM) deployed in a three-dimensional grid. The DOMs receive light from particles passing the detector or created in neutrino interactions in the vicinity of the detector. A primary physics goal is to detect point-like neutrino sources. An important step in understanding the signal of astrophysical sources, is to understand the background to the measurement originating in the atmosphere. It consists of muons and neutrinos. Dedicated simulations optimized for KM3NeT have been performed. This contribution describes the simulation chain, starting with an atmospheric air shower simulation and propagating particles from the sea surface to the detector at a depth of 2.5 to 3.5 km. The nature of the background expected to most strongly affect KM3NeT's sensitivity to astrophysical neutrino fluxes is presented, as are methods for dealing with it. Besides their role as background, studying atmospheric particles can improve the understanding of particle creation in the atmosphere, especially the charm production mechanism.

  19. Arctic Ocean Freshwater: How Robust are Model Simulations

    Science.gov (United States)

    Jahn, A.; Aksenov, Y.; deCuevas, B. A.; deSteur, L.; Haekkinen, S.; Hansen, E.; Herbaut, C.; Houssais, M.-N.; Karcher, M.; Kauker, F.; hide

    2012-01-01

    The Arctic freshwater (FW) has been the focus of many modeling studies, due to the potential impact of Arctic FW on the deep water formation in the North Atlantic. A comparison of the hindcasts from ten ocean-sea ice models shows that the simulation of the Arctic FW budget is quite different in the investigated models. While they agree on the general sink and source terms of the Arctic FW budget, the long-term means as well as the variability of the FW export vary among models. The best model-to-model agreement is found for the interannual and seasonal variability of the solid FW export and the solid FW storage, which also agree well with observations. For the interannual and seasonal variability of the liquid FW export, the agreement among models is better for the Canadian Arctic Archipelago (CAA) than for Fram Strait. The reason for this is that models are more consistent in simulating volume flux anomalies than salinity anomalies and volume-flux anomalies dominate the liquid FW export variability in the CAA but not in Fram Strait. The seasonal cycle of the liquid FW export generally shows a better agreement among models than the interannual variability, and compared to observations the models capture the seasonality of the liquid FW export rather well. In order to improve future simulations of the Arctic FW budget, the simulation of the salinity field needs to be improved, so that model results on the variability of the liquid FW export and storage become more robust.

  20. Enhanced Freshwater Production Using Finned-Plate Air Gap Membrane Distillation (AGMD

    Directory of Open Access Journals (Sweden)

    Perves Bappy Mohammad Jabed

    2017-01-01

    Full Text Available Air Gap membrane distillation (AGMD, a special type of energy efficient membrane distillation process, is a technology for producing freshwater from waste water. Having some benefits over other traditional processes, this method has been able to draw attention of researchers working in the field of freshwater production technologies. In this study, a basic AGMD system with flat coolant plate has been modified using a specially designed channelled coolant plate of portable size to observe its effect over the production rate and performance of the system. Attempt has been made to increase the amount of distillate flux by using the “fin effect” of the channelled coolant plate. A finned plate have been used instead of a flat coolant plate and experiments were conducted to compare the effect. Coolant temperature and feed temperature of the system have been varied from 10°C to 25°C and 40°C to 70°C respectively. Comparing the data, around 50% to 58% distillate enhancement has been observed for channelled coolant plate. Also, it was seen that the enhancement was higher for higher feed temperatures and coolant temperatures. With these findings, a better performing AGMD module has been introduced to mitigate the scarcity of freshwater.

  1. The role of hydroclimate and water use on freshwater sustainability over the conterminous US.

    Science.gov (United States)

    Arumugam, S.; Ruhi, A.; Sabo, J. L.; Sinha, T.; Das Bhowmik, R.; Seo, S. B.

    2015-12-01

    A synthesis on freshwater sustainability is investigated across the conterminous US (CONUS). Spatio-temporal variability of potential drivers - hydroclimate and water use - influencing the freshwater sustainability are examined both individually as well as collectively by considering the eco-region and 4-digit Hydrologic Unit Code (HUC-4)as the spatial reference for the analysis. A detailed multivariate analysis relating the potential drivers with downstream flow anomalies indicate that changes in hydroclimate and water use adequately quantify the variability in downstream anomalies, but their signature varies significnatly across various regions of the CONUS. Results from the analysis indicate that both hydroclimatic extremes and mean annual fluxes control, but their signature alos vary across the CONUS. Among the changes in water use, irrigation water use predominantly carries the signature in explaining the downstream flow anomalies. To adequately express the sensitivity of downstream flow anomalies to hydroclimate and water use, we compute the elasticity of downstream flow anomalies to changes in hydroclimate and water use for each HUC8 regions of the US. Differences between the multivariate analysis and the elasticity estimates of freshwater sustainability are also discussed.

  2. Effects of Environmental Conditions on an Urban Wetland's Methane Fluxes

    Science.gov (United States)

    Naor Azrieli, L.; Morin, T. H.; Bohrer, G.; Schafer, K. V.; Brooker, M.; Mitsch, W. J.

    2013-12-01

    Methane emissions from wetlands are the largest natural source of uncertainty in the global methane (CH4) budget. Wetlands are highly productive ecosystems with a large carbon sequestration potential. While wetlands are a net sink for carbon dioxide, they also release methane, a potent greenhouse gas. To effectively develop wetland management techniques, it is important to properly calculate the carbon budget of wetlands by understand the driving factors of methane fluxes. We constructed an eddy flux covariance system in the Olentangy River Wetland Research Park, a series of created and restored wetland in Columbus Ohio. Through the use of high frequency open path infrared gas analyzer (IRGA) sensors, we have continuously monitored the methane fluxes associated with the wetland since May 2011. To account for the heterogeneous landscape surrounding the tower, a footprint analysis was used to isolate data originating from within the wetland. Continuous measurements of the meteorological and environmental conditions at the wetlands coinciding with the flux measurements allow the interactions between methane fluxes and the climate and ecological forcing to be studied. The wintertime daily cycle of methane peaks around midday indicating a typical diurnal pattern in cold months. In the summer, the peak shifts to earlier in the day and also includes a daily peak occurring at approximately 10 AM. We believe this peak is associated with the onset of photosynthesis in Typha latifolia flushing methane from the plant's air filled tissue. Correlations with methane fluxes include latent heat flux, soil temperature, and incoming radiation. The connection to radiation may be further evidence of plant activity as a driver of methane fluxes. Higher methane fluxes corresponding with higher soil temperature indicates that warmer days stimulate the methanogenic consortium. Further analysis will focus on separating the methane fluxes into emissions from different terrain types within

  3. A new approach of surface flux measurements using DTS

    Science.gov (United States)

    van Emmerik, T. H. M.; Wenker, K. J. R.; Rimmer, A.; de Jong, S. A. P.; Lechinsky, Y.; van de Giesen, N. C.

    2012-04-01

    Estimation of surface fluxes is a difficult task, especially over lakes. Determining latent heat flux (evaporation), sensible heat flux and ground heat flux involves measurements and (or calculations) of net radiation, air temperature, water temperature, wind speed and relative humidity. This research presents a new method to measure surface fluxes by means of Distributed Temperature Sensing (DTS). From 0.5 m above lake level to 1.5 m under lake level DTS was applied to measure temperature. Using a PVC hyperboloid construction, a floating standalone measuring device was developed. This new setup distinguished itself by the open construction, so it is almost insensitive to direct radiation. While most of the lake ground heat changes occur very close to the lake surface, most measuring methods only obtain rough results. With this construction it was possible to create a spiral shaped fiber-optic cable setup, with which a vertical spatial resolution of 0.02 m and a temporal resolution of 1 min was obtained. The new method was tested in the deep Lake Kinneret (Israel) from 6 October, 2011 to 11 October, 2011and in the shallow Lake Binaba (Ghana) from 24 October, 2011 to 28 October, 2011. This study shows that with the developed method it is possible to capture the energy fluxes within the top water layer with a high resolution. When the old low resolution method was compared with the new high resolution method, it could be concluded that the impact of the surface fluxes in the upper layer is high on the energy balance on a daily scale. During the measuring period it was possible to use the temperature measured by the DTS to determine the sensible heat flux, the latent heat flux and the ground heat flux of both lakes.

  4. Comparative economic performance and carbon footprint of two farming models for producing atlantic salmon (salmo salar): Land-based closed containment system in freshwater and open pen in seawater

    Science.gov (United States)

    Ocean net pen production of Atlantic salmon is approaching 2 million metric tons (MT) annually and has proven to be cost- and energy- efficient. Recently, with technology improvements, freshwater aquaculture of Atlantic salmon from eggs to harvestable size of 4 -5 kg in land-based closed containmen...

  5. Global Surface Net-Radiation at 5 km from MODIS Terra

    Directory of Open Access Journals (Sweden)

    Manish Verma

    2016-09-01

    Full Text Available Reliable and fine resolution estimates of surface net-radiation are required for estimating latent and sensible heat fluxes between the land surface and the atmosphere. However, currently, fine resolution estimates of net-radiation are not available and consequently it is challenging to develop multi-year estimates of evapotranspiration at scales that can capture land surface heterogeneity and are relevant for policy and decision-making. We developed and evaluated a global net-radiation product at 5 km and 8-day resolution by combining mutually consistent atmosphere and land data from the Moderate Resolution Imaging Spectroradiometer (MODIS on board Terra. Comparison with net-radiation measurements from 154 globally distributed sites (414 site-years from the FLUXNET and Surface Radiation budget network (SURFRAD showed that the net-radiation product agreed well with measurements across seasons and climate types in the extratropics (Wilmott’s index ranged from 0.74 for boreal to 0.63 for Mediterranean sites. Mean absolute deviation between the MODIS and measured net-radiation ranged from 38.0 ± 1.8 W∙m−2 in boreal to 72.0 ± 4.1 W∙m−2 in the tropical climates. The mean bias was small and constituted only 11%, 0.7%, 8.4%, 4.2%, 13.3%, and 5.4% of the mean absolute error in daytime net-radiation in boreal, Mediterranean, temperate-continental, temperate, semi-arid, and tropical climate, respectively. To assess the accuracy of the broader spatiotemporal patterns, we upscaled error-quantified MODIS net-radiation and compared it with the net-radiation estimates from the coarse spatial (1° × 1° but high temporal resolution gridded net-radiation product from the Clouds and Earth’s Radiant Energy System (CERES. Our estimates agreed closely with the net-radiation estimates from the CERES. Difference between the two was less than 10 W·m−2 in 94% of the total land area. MODIS net-radiation product will be a valuable resource for the

  6. To what extent does the salinity flux influence phytoplankton blooms? - Baltic Sea modeling study

    Science.gov (United States)

    Cieszyńska, Agata; Stramska, Małgorzata

    2016-04-01

    This work is focused on numerical modeling of biological-physical interactions and their influence on phytoplankton production and vertical distribution of biomass and its variability in the surface waters of the Baltic Sea. The area of interest is an inland sea with water salinity much smaller than observed in the global ocean (about one fifth of the open ocean value). Vertical distribution of the salinity has a significant influence on water column density stratification, and therefore influences intensity of mixing and the depth of mixed layer. This, in turn, defines environmental conditions for phytoplankton growth. Vertical distribution of water salinity in the basin is controlled by processes such as evaporation/precipitation, freezing/melting of sea ice and runoff of freshwater from land. There are a lot of different phytoplankton species in the area of the Baltic Sea. Every single one has its own characteristics and is sensitive to distinct complex environmental conditions. Biological-physical interactions controlling these microorganisms' life cycles are multiplicitous and because of their complexity difficult to quantify. The best and probably only way to study presented issue is the usage of numerical modeling tool. The results presented here are based on 1D numerical simulations carried out with Princeton Ocean Model (POM, http://www.ccpo.odu.edu/POMWEB/) merged with the Ecological Regional Ecosystem Model (ERGOM, http://ergom.net/) developed for the Baltic Sea research by German scientists from the Leibniz Institute for Baltic Sea Research in Warnemünde. In model simulations surface salinity flux was determined from the difference between the precipitation and evaporation rate at the air-sea interface. Data for parameterization of atmospheric forcing were defined based on data sets from National Centers of Environmental Prediction (NCEP). We carried out systematic calculations using different values of surface fluxes encompassing the range of

  7. Comparing methods for partitioning a decade of carbon dioxide and water vapor fluxes in a temperate forest

    Science.gov (United States)

    Benjamin N. Sulman; Daniel Tyler Roman; Todd M. Scanlon; Lixin Wang; Kimberly A. Novick

    2016-01-01

    The eddy covariance (EC) method is routinely used to measure net ecosystem fluxes of carbon dioxide (CO2) and evapotranspiration (ET) in terrestrial ecosystems. It is often desirable to partition CO2 flux into gross primary production (GPP) and ecosystem respiration (RE), and to partition ET into evaporation and...

  8. Land-ocean gradient in haline stratification and its effects on plankton dynamics and trophic carbon fluxes in Chilean Patagonian fjords (47-50°S)

    Science.gov (United States)

    González, H. E.; Castro, L. R.; Daneri, G.; Iriarte, J. L.; Silva, N.; Tapia, F.; Teca, E.; Vargas, C. A.

    2013-12-01

    Patagonian fjord systems, and in particular the fjords and channels associated with the Baker/Pascua Rivers, are currently under conspicuous natural and anthropogenic perturbations. These systems display very high variability, where limnetic and oceanic features overlap generating strong vertical and horizontal physicochemical gradients. The CIMAR 14-Fiordos cruise was conducted in the Chilean fjords located between 47° and 50°S during the spring (October-November) of 2008. The main objectives were to study vertical and horizontal gradients in physical, chemical and biological characteristics of the water column, and to assess plankton dynamics and trophic carbon fluxes in the fjords and channels of central-south Patagonia. The water column was strongly stratified, with a pycnocline at ca. 20 m depth separating a surface layer of silicic acid-rich freshwater discharged by rivers, from the underlying nitrate- and orthophosphate-rich Subantarctic waters. The outflows from the Baker and Pascua Rivers, which range annually between 500 and 1500 m3 s-1, generate the strong land-ocean gradient in salinity (1-32 psu) and inorganic nutrient concentrations (2-8 and 2-24 μM in nitrate and silicic-acid, respectively) we observed along the Baker Fjord. The POC:chl-a ratio fluctuated from 1087 near the fjord’s head to 175 at its oceanic end in the Penas Gulf. This change was mainly due to an increase in diatom dominance and a concurrent decrease in allochthonous POC towards the ocean. Depth-integrated net primary production (NPP) and bacterial secondary production (BSP) fluctuated between 49 and 1215 and 36 and 150 mg C m-2 d-1, respectively, with higher rates in oceanic waters. At a time series station located close to the Baker River mouth, the average NPP was lower (average 360 mg C m-2 d-1) than at more oceanic stations (average 1063 mg C m-2 d-1), and numerically dominated (45%) by the picoplankton (flux (234 mg m-2 d-1) and high export production (65% of the NPP

  9. Generic flux coupling analysis

    NARCIS (Netherlands)

    A.C. Reimers (Arne); Y. Goldstein; A. Bockmayr

    2015-01-01

    htmlabstractFlux coupling analysis (FCA) has become a useful tool for aiding metabolic reconstructions and guiding genetic manipulations. Originally, it was introduced for constraint-based models of metabolic networks that are based on the steady-state assumption. Recently, we have shown that the

  10. Flux Vacua and Supermanifolds

    CERN Document Server

    Grassi, P A

    2007-01-01

    As been recently pointed out, physically relevant models derived from string theory require the presence of non-vanishing form fluxes besides the usual geometrical constraints. In the case of NS-NS fluxes, the Generalized Complex Geometry encodes these informations in a beautiful geometrical structure. On the other hand, the R-R fluxes call for supergeometry as the underlying mathematical framework. In this context, we analyze the possibility of constructing interesting supermanifolds recasting the geometrical data and RR fluxes. To characterize these supermanifolds we have been guided by the fact topological strings on supermanifolds require the super-Ricci flatness of the target space. This can be achieved by adding to a given bosonic manifold enough anticommuting coordinates and new constraints on the bosonic sub-manifold. We study these constraints at the linear and non-linear level for a pure geometrical setting and in the presence of p-form field strengths. We find that certain spaces admit several supe...

  11. Soluble organic nutrient fluxes

    Science.gov (United States)

    Robert G. Qualls; Bruce L. Haines; Wayne Swank

    2014-01-01

    Our objectives in this study were (i) compare fluxes of the dissolved organic nutrients dissolved organic carbon (DOC), DON, and dissolved organic phosphorus (DOP) in a clearcut area and an adjacent mature reference area. (ii) determine whether concentrations of dissolved organic nutrients or inorganic nutrients were greater in clearcut areas than in reference areas,...

  12. Generic flux coupling analysis.

    Science.gov (United States)

    Reimers, Arne C; Goldstein, Yaron; Bockmayr, Alexander

    2015-04-01

    Flux coupling analysis (FCA) has become a useful tool for aiding metabolic reconstructions and guiding genetic manipulations. Originally, it was introduced for constraint-based models of metabolic networks that are based on the steady-state assumption. Recently, we have shown that the steady-state assumption can be replaced by a weaker lattice-theoretic property related to the supports of metabolic fluxes. In this paper, we further extend our approach and develop an efficient algorithm for generic flux coupling analysis that works with any kind of qualitative pathway model. We illustrate our method by thermodynamic flux coupling analysis (tFCA), which allows studying steady-state metabolic models with loop-law thermodynamic constraints. These models do not satisfy the lattice-theoretic properties required in our previous work. For a selection of genome-scale metabolic network reconstructions, we discuss both theoretically and practically, how thermodynamic constraints strengthen the coupling results that can be obtained with classical FCA. A prototype implementation of tFCA is available at http://hoverboard.io/L4FC. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. Surface Net Solar Radiation Estimated from Satellite Measurements: Comparisons with Tower Observations

    Science.gov (United States)

    Li, Zhanqing; Leighton, H. G.; Cess, Robert D.

    1993-01-01

    A parameterization that relates the reflected solar flux at the top of the atmosphere to the net solar flux at the surface in terms of only the column water vapor amount and the solar zenith angle was tested against surface observations. Net surface fluxes deduced from coincidental collocated satellite-measured radiances and from measurements from towers in Boulder during summer and near Saskatoon in winter have mean differences of about 2 W/sq m, regardless of whether the sky is clear or cloudy. Furthermore, comparisons between the net fluxes deduced from the parameterization and from surface measurements showed equally good agreement when the data were partitioned into morning and afternoon observations. This is in contrast to results from an empirical clear-sky algorithm that is unable to account adequately for the effects of clouds and that shows, at Boulder, a distinct morning to afternoon variation, which is presumably due to the predominance of different cloud types throughout the day. It is also demonstrated that the parameterization may be applied to irradiances at the top of the atmosphere that have been temporally averaged by using the temporally averaged column water vapor amount and the temporally averaged cosine of the solar zenith angle. The good agreement between the results of the parameterization and surface measurements suggests that the algorithm is a useful tool for a variety of climate studies.

  14. Use of CellNetAnalyzer in biotechnology and metabolic engineering.

    Science.gov (United States)

    von Kamp, Axel; Thiele, Sven; Hädicke, Oliver; Klamt, Steffen

    2017-11-10

    Mathematical models of the cellular metabolism have become an essential tool for the optimization of biotechnological processes. They help to obtain a systemic understanding of the metabolic processes in the used microorganisms and to find suitable genetic modifications maximizing the production performance. In particular, methods of stoichiometric and constraint-based modeling are frequently used in the context of metabolic and bioprocess engineering. Since metabolic networks can be complex and comprise hundreds or even thousands of metabolites and reactions, dedicated software tools are required for an efficient analysis. One such software suite is CellNetAnalyzer, a MATLAB package providing, among others, various methods for analyzing stoichiometric and constraint-based metabolic models. CellNetAnalyzer can be used via command-line based operations or via a graphical user interface with embedded network visualizations. Herein we will present key functionalities of CellNetAnalyzer for applications in biotechnology and metabolic engineering and thereby review constraint-based modeling techniques such as metabolic flux analysis, flux balance analysis, flux variability analysis, metabolic pathway analysis (elementary flux modes) and methods for computational strain design. Copyright © 2017 The Author(s). Published by Elsevier B.V. All rights reserved.

  15. Anthropogenic Heat Flux Estimation from Space: Results of the second phase of the URBANFLUXES Project

    Science.gov (United States)

    Chrysoulakis, Nektarios; Marconcini, Mattia; Gastellu-Etchegorry, Jean-Philippe; Grimmond, Sue; Feigenwinter, Christian; Lindberg, Fredrik; Del Frate, Fabio; Klostermann, Judith; Mitraka, Zina; Esch, Thomas; Landier, Lucas; Gabey, Andy; Parlow, Eberhard; Olofson, Frans

    2017-04-01

    The H2020-Space project URBANFLUXES (URBan ANthrpogenic heat FLUX from Earth observation Satellites) investigates the potential of Copernicus Sentinels to retrieve anthropogenic heat flux, as a key component of the Urban Energy Budget (UEB). URBANFLUXES advances the current knowledge of the impacts of UEB fluxes on urban heat island and consequently on energy consumption in cities. In URBANFLUXES, the anthropogenic heat flux is estimated as a residual of UEB. Therefore, the rest UEB components, namely, the net all-wave radiation, the net change in heat storage and the turbulent sensible and latent heat fluxes are independently estimated from Earth Observation (EO), whereas the advection term is included in the error of the anthropogenic heat flux estimation from the UEB closure. The Discrete Anisotropic Radiative Transfer (DART) model is employed to improve the estimation of the net all-wave radiation balance, whereas the Element Surface Temperature Method (ESTM), adjusted to satellite observations is used to improve the estimation the estimation of the net change in heat storage. Furthermore the estimation of the turbulent sensible and latent heat fluxes is based on the Aerodynamic Resistance Method (ARM). Based on these outcomes, QF is estimated by regressing the sum of the turbulent heat fluxes versus the available energy. In-situ flux measurements are used to evaluate URBANFLUXES outcomes, whereas uncertainties are specified and analyzed. URBANFLUXES is expected to prepare the ground for further innovative exploitation of EO in scientific activities (climate variability studies at local and regional scales) and future and emerging applications (sustainable urban planning, mitigation technologies) to benefit climate change mitigation/adaptation. This study presents the results of the second phase of the project and detailed information on URBANFLUXES is available at: http://urbanfluxes.eu

  16. From COS ecosystem fluxes to GPP: integrating soil, branch and ecosystem fluxes.

    Science.gov (United States)

    Kooijmans, L.; Maseyk, K. S.; Vesala, T.; Mammarella, I.; Baker, I. T.; Seibt, U.; Sun, W.; Aalto, J.; Franchin, A.; Kolari, P.; Keskinen, H.; Levula, J.; Chen, H.

    2016-12-01

    The close coupling of Carbonyl Sulfide (COS) and CO2 due to a similar uptake pathway into plant stomata makes COS a promising new tracer that can potentially be used to partition the Net Ecosystem Exchange into gross primary production (GPP) and respiration. Although ecosystem-scale measurements have been made at several sites, the contribution of different ecosystem components to the total COS budget is often unknown. Besides that, the average Leaf Relative Uptake (LRU) ratio needs to be better determined to accurately translate COS ecosystem fluxes into GPP estimates when the simple linear correlation between GPP estimates and COS plant uptake is used. We performed two campaigns in the summer of 2015 and 2016 at the SMEAR II site in Hyytiälä, Finland to provide better constrained COS flux data for boreal forests. A combination of COS measurements were made during both years, i.e. atmospheric profile concentrations up to 125 m, eddy-covariance fluxes and soil chamber fluxes. In addition to these, branch chamber measurements were done in 2016 in an attempt to observe the LRU throughout the whole season. The LRU ratio shows an exponential correlation with photosynthetic active radiation (PAR) but is constant for PAR levels above 500 µmol m-2 s-1. Mid-day LRU values are 1.0 (aspen) and 1.5 (pine). The correlation between LRU and PAR can be explained by the fact that COS is hydrolyzed with the presence of the enzyme carbonic anhydrase, and is not light dependent, whereas the photosynthetic uptake of CO2 is. We observed nighttime fluxes on the order of 25-30 % of the daily maximum COS uptake. Soils are a small sink of COS and contribute to 3 % of the total ecosystem COS flux during daytime. In a comparison between observed and simulated fluxes from the Simple Biosphere (SiB) model, the modelled COS and CO2 ecosystem fluxes are on average 40 % smaller than the observed fluxes, however, the Ecosystem Relative Uptake (ERU) ratios are identical at a value of 1.9 ± 0

  17. Freshwater reservoir effect variability in Northern Germany

    DEFF Research Database (Denmark)

    Philippsen, Bente; Heinemeier, Jan

    2012-01-01

    The freshwater reservoir effect is a potential problem when radiocarbon dating fishbones, shells, human bones or food crusts on pottery from sites next to rivers or lakes. The reservoir age in rivers containing considerable amounts of dissolved 14C-free carbonates can be up to several thousand...... years and may be highly variable. For accurate radiocarbon dating of freshwater-based samples, the order of magnitude of the reservoir effect as well as the degree of variability has to be known. The initial problem in this case was the accurate dating of food crusts on pottery from the Mesolithic sites...... and variability that can also be expected for the past. Water DIC from different seasons, and from the same season in different years, has been dated because it is the carbon source in photosynthesis and thus at the basis of the rivers’ food webs. The radiocarbon ages of underwater plants and different parts...

  18. Freshwater fishes of Tsitsikamma National Park

    Directory of Open Access Journals (Sweden)

    I.A. Russell

    2002-12-01

    Full Text Available This study aimed to determine the distribution and relative abundance of freshwater fishes in the Tsitsikamma National Park. Fish assemblages in six river systems were sampled in 2001, with a total of 323 fish from eight species recorded. Indigenous fish collected included four freshwater species (Pseudobarbus afer, Pseudobarbus tenuis, Sandelia capensis, Anguilla mossambica, three estuarine species (Monodactylus falciformis, Caffrogobius gilchristi, Myxus capensis, and one alien (Micropterus salmoides. One additional indigenous species (Galaxias zebratus and two aliens (Salmo trutta, Oncorhynchus mykiss could potentially occur within the park. The topography and locality of the park presents a unique opportunity to meaningfully conserve the endangered P. tenuis as well as other fish characteristic of the eastern reaches of the Cape Floristic Region. Management action is required to minimise opportunities for further establishment and spread of alien fish species and to conserve indigenous fish assemblages within the park.

  19. Assessing the freshwater distribution of yellow eel

    Directory of Open Access Journals (Sweden)

    Lasne É.

    2009-04-01

    Full Text Available In the global context of the decline in wild species, modeling the distribution of populations is a crucial aspect of ecological management. This can be a major challenge, especially for species, such as the European eel, that have complex life cycles, exhibit cryptic behavior, or migrate over long distances. A review of the literature suggests that eel size data could be used to assess and analyze freshwater distribution of eel. We argue that analyses based on small yellow eels (≤ 300 mm along the longitudinal course of rivers could provide a valuable tool for population monitoring. We propose a standardized catchment recruitment index and a colonization index based on the probability of occurrence (presence/absence data using logistic models for different size classes. The model developed here provides a convenient guide for assessing yellow eel stages in freshwater areas, and should have concrete applications for management of the species.

  20. Three new ascomycetes from freshwater in China.

    Science.gov (United States)

    Hu, Dian-Ming; Cai, Lei; Hyde, Kevin D

    2012-01-01

    Three new freshwater ascomycetes, Diaporthe aquatica sp. nov. (Diaporthaceae), Ophioceras aquaticus sp. nov. (Magnaporthaceae) and Togninia aquatica sp. nov. (Togniniaceae), are described and illustrated based on morphological and molecular data (ITS, 18S, 28S rDNA sequences). Diaporthe aquatica is characterized by globose to subglobose, black ascomata with long necks, broadly cylindrical to obclavate asci, and small, ellipsoidal to fusiform, one-septate, hyaline ascospores; it is unusual among Diaporthe species in the fact that it lacks a stroma and has freshwater habitat. Ophioceras aquaticus is characterized by globose ascomata with a long beak, cylindrical, eight-spored asci with J- subapical rings and 3-5-septate filiform ascospores with slightly acute ends. Togninia aquatica is characterized by globose ascomata with long necks, clavate and truncate asci clustered on distinct ascogenous hyphae, and small, reniform, hyaline ascospores. Differences among the new taxa and similar species are discussed.

  1. Freshwater fish of the Wilderness National Park

    Directory of Open Access Journals (Sweden)

    I.A. Russell

    1999-01-01

    Full Text Available The study aimed to determine the distribution and relative abundance of freshwater fish in the Wilderness National Park. Fish assemblages in the Touw and Duiwe rivers were sampled in 1997 and 1998, with a total of 327 fish from nine species recorded. Indigenous species included two freshwater species (Pseudobarbus afer, Sandelia capensis, two catadromous species (Anguilla mossambicus, Myxus capensis, and two estuarine species (Monodactylusfalciformis, Caffrogobius multifasciatus. Three of the nine recorded species were alien (Micropterus dolomieu, Micropterus salmoides, Gambusia affinis, with the Micropterus spp., in particular, likely to have a substantial negative influence on indigenous species. A further one indigenous species, two translocated indigenous species, and five estuarine species could potentially be recorded in these rivers. River catchment management actions to restore perennial flow to the Duiwe River, to prevent the attenuation of floods, and to prevent further establishment and spread of alien and translocated biota are required to conserve indigenous fish assemblages.

  2. Chesapeake Bay Low Freshwater Inflow Study.

    Science.gov (United States)

    1984-09-01

    and sale: itsI~ (distibution is unlimited. US Army Corps ’c:: gj-n1 contains color of Engineers r: All DTIC reproduct - Ba Eninrs Ti1 be in black and...Cyathurapolita (isopod) food. Changes in freshwater inflow Gammarus daiberi (amphiad) could further reduce this vegetation or Alosa pso ri gs (alewife) prevent...polychaete worm) Cyathura polita (isopod) Gammarus daiberi (amphipod) Alosa sapidissima (Am. shad) A losa pseudoharengus (alewife) Morone saxatilis

  3. Dominance and population structure of freshwater crabs ...

    African Journals Online (AJOL)

    1997-02-06

    Feb 6, 1997 ... E-mail: mjs@m-web.co.za. Despite freshwater crabs of the genus Potamonautes being locally abundant (up .... mm deep, and 10-20 m below the dam wall. At site 2 the river was ca 2 m wide and 400 mm deep and 600 m down- stream from the dam. Crabs were collected from both sites on. 22 October 1993 ...

  4. Effect of riverine freshwater discharge in salinity simulations over the northern Indian Ocean

    Science.gov (United States)

    Kalathupurath Kuttan, Sandeep; Pant, Vimlesh; Devendra Rao, Ambarukhana

    2017-04-01

    Sea surface salinity (SSS) in the north Indian Ocean (NIO) exhibits contrasting spatial distribution, particularly in the two semi-enclosed basins namely the Arabian sea (AS) and Bay of Bengal (BoB). BoB experiences excess amount of freshwater inflow from rivers as well as from the surplus of precipitation over evaporation (E-P) and thus maintains a fresher surface water throughout the year as compared to AS. Major rivers such as Ganges, Brahmaputra, Mahanadi, Godavari, Krishna, and Irrawaddy discharge large amount of freshwater volume to the BoB. The input of relatively less saline waters by the Indonesian Throughflow (ITF) makes the eastern equatorial IO fresher. Substantial change in salinity and temperature due to river runoff results in a change in ambient sea-water density near river mouths in coastal regions. In the present study, we simulate the circulation features of the NIO using a free-surface primitive equation ocean general circulation model 'Regional Ocean Modeling System' (ROMS). The model domain extends from 30°S-30°N, 30°E-120°E with 1/4 x 1/4 degree resolution in the horizontal and 40 vertical terrain following sigma levels. The model is initialized with annual mean climatology of temperature and salinity from World Ocean Atlas 2009 (WOA09) and forced with daily climatological winds from Quikscat and ASCAT and other atmospheric forcing fields from TropFlux. Different numerical experiments were carried out to understand the impact of freshwater forcing on the sea surface salinity (SSS) simulations. Model simulations and available in-situ and satellite observations utilized to understand processes, particularly the contribution of freshwater forcing, controlling the SSS spatial and seasonal variations in various sectors of the Indian Ocean.

  5. Why are freshwater fish so threatened?

    Science.gov (United States)

    Closs, Gerard P.; Angermeier, Paul; Darwall, William R.T.; Balcombe, Stephen R.

    2015-01-01

    The huge diversity of freshwater fishes is concentrated into an area of habitat that covers only about 1% of the Earth's surface, and much of this limited area has already been extensively impacted and intensively managed to meet human needs (Dudgeon et al., 2006). As outlined in Chapter 1, the number and proportions of threatened species tend to rise wherever fish diversity coincides with dense human populations, intensive resource use and development pressure. Of particular concern is the substantial proportion of the global diversity of freshwater fishes concentrated within the Mekong and Amazon Basins and west-central Africa (Berra, 2001; Abell et al., 2008; Dudgeon, 2011; Chapter 1) with extensive exploitation of water resources planned to accelerate in future years (Dudgeon, 2011; Chapter 1). If current trends continue, and the social, political and economic models that have been used to develop industrialised regions of the world over the past two centuries prevail, then the future of a significant proportion of global diversity of freshwater fish species is clearly uncertain.

  6. Monitoring Global Freshwater Resources with GRACE

    Science.gov (United States)

    Rodell, M.; Famiglietti, J. S.; Velicogna, I.; Swenson, S. C.; Chambers, D. P.

    2011-12-01

    Freshwater resources include surface waters, groundwater, and seasonal snowpack. Given adequate ground based measurements, all of these can be monitored effectively, however, outside of the developed world such measurements often are not systematic and the data not centralized, and as a result reports of freshwater availability may be largely anecdotal. Even in the developed world it can be difficult to quantify changes in groundwater storage over large scales. Owing to its global coverage, satellite remote sensing has become a valuable tool for freshwater resources assessment. In particular, the Gravity Recovery and Climate Experiment (GRACE) has demonstrated an unequaled ability to monitor total terrestrial water storage including groundwater at regional to continental scales. In this presentation we will identify apparent trends in terrestrial water storage observed by GRACE over the past nine years and attempt to explain their origins and predict whether they are likely to continue. Trends in certain regions where groundwater extraction has significantly depleted aquifers, including northern India and California's Central Valley, will be discussed in detail.

  7. Evidence for dispersal syndromes in freshwater fishes.

    Science.gov (United States)

    Comte, Lise; Olden, Julian D

    2018-01-31

    Dispersal is a fundamental process defining the distribution of organisms and has long been a topic of inquiry in ecology and evolution. Emerging research points to an interdependency of dispersal with a diverse suite of traits in terrestrial organisms, however the extent to which such dispersal syndromes exist in freshwater species remains uncertain. Here, we test whether dispersal in freshwater fishes (1) is a fixed property of species, and (2) correlates with life-history, morphological, ecological and behavioural traits, using a global dataset of dispersal distances collected from the literature encompassing 116 riverine species and 196 locations. Our meta-analysis revealed a high degree of repeatability and heritability in the dispersal estimates and strong associations with traits related to life-history strategies, energy allocation to reproduction, ecological specialization and swimming skills. Together, these results demonstrate that similar to terrestrial organisms, the multi-dimensional nature of dispersal syndromes in freshwater species offer opportunities for the development of a unifying paradigm of movement ecology that transcend taxonomic and biogeographical realms. The high explanatory power of the models also suggests that trait-based and phylogenetic approaches hold considerable promises to inform conservation efforts in a rapidly changing world. © 2018 The Author(s).

  8. -Net Approach to Sensor -Coverage

    Directory of Open Access Journals (Sweden)

    Fusco Giordano

    2010-01-01

    Full Text Available Wireless sensors rely on battery power, and in many applications it is difficult or prohibitive to replace them. Hence, in order to prolongate the system's lifetime, some sensors can be kept inactive while others perform all the tasks. In this paper, we study the -coverage problem of activating the minimum number of sensors to ensure that every point in the area is covered by at least sensors. This ensures higher fault tolerance, robustness, and improves many operations, among which position detection and intrusion detection. The -coverage problem is trivially NP-complete, and hence we can only provide approximation algorithms. In this paper, we present an algorithm based on an extension of the classical -net technique. This method gives an -approximation, where is the number of sensors in an optimal solution. We do not make any particular assumption on the shape of the areas covered by each sensor, besides that they must be closed, connected, and without holes.

  9. NETS - Danish participation. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Alsen, S. (Grontmij - Carl Bro, Glostrup (Denmark)); Theel, C. (Baltic Sea Solutions, Holeby (Denmark))

    2008-12-15

    Within the NICe-funded project 'Nordic Environmental Technology Solutions (NETS)' a new type of networking at the Nordic level was organized in order to jointly exploit the rapidly growing market potential in the environmental technology sector. The project aimed at increased and professionalized commercialization of Nordic Cleantech in energy and water business segments through 1) closer cooperation and joint marketing activities, 2) a website, 3) cleantech product information via brochures and publications 4) and participating in relevant trade fairs and other industry events. Facilitating business-to-business activities was another core task for the NETS project partners from Norway, Sweden, Finland and Denmark with the aim to encourage total solutions for combined Cleantech system offers. The project has achieved to establish a Cleantech register of 600 Nordic Cleantech companies, a network of 86 member enterprises, produced several publications and brochures for direct technology promotion and a website for direct access to company profiles and contact data. The project partners have attended 14 relevant international Cleantech trade fairs and conferences and facilitated business-to-business contacts added by capacity building offers through two company workshops. The future challenge for the project partners and Nordic Cleantech will be to coordinate the numerous efforts within the Nordic countries in order to reach concerted action and binding of member companies for reliable services, an improved visibility and knowledge exchange. With Cleantech's growing market influence and public awareness, the need to develop total solutions is increasing likewise. Marketing efforts should be encouraged cross-sectional and cross-border among the various levels of involved actors from both the public and the private sector. (au)

  10. SIMULATION OF NET INFILTRATION FOR MODERN AND POTENTIAL FUTURE CLIMATES

    Energy Technology Data Exchange (ETDEWEB)

    J.A. Heveal

    2000-06-16

    detailed representations of the magnitude and distribution of net-infiltration rates that are used to define specified flux upper boundary conditions for the UZ flow and transport model.

  11. Analysis of freshwater flux climatology over the Indian Ocean using the HOAPS data

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Schulz, J.

    to the conventional ship observations. The HOAPS data set is truly representative of both the spatial and temporal scale it represents (in this case, 1C176C21C176 resolution as well as on a monthly scale), unlike the ship observations, which are few in any given 1C176... Traditionally, the evaporation rates over the oceans are estimated by the bulk aerodynamic formula, which makes use of surface wind speed U, specific humidity of air Q a , and sea surface temperature measurements from ship-based standard instruments. The spatial...

  12. Enhanced particle fluxes in Bay of Bengal inducEd. by injection of freshwater

    Digital Repository Service at National Institute of Oceanography (India)

    Ittekkot, V.; Nair, R.R.; Honjo, S.; Ramaswamy, V.; Bartsch, M.; Manganini, S.J.; Desai, B.N.

    deployed three sediment-trap moorings (two traps in each mooring) in the northern, central and southern parts of the Bay of Bengal, respectively. The Bay of Bengal is suitable for such a study, because some of the world's largest rivers supply pulses...

  13. Quantifying aquifer properties and freshwater resource in coastal barriers: a hydrogeophysical approach applied at Sasihithlu (Karnataka state, India

    Directory of Open Access Journals (Sweden)

    J.-M. Vouillamoz

    2012-11-01

    Full Text Available Many human communities living in coastal areas in Africa and Asia rely on thin freshwater lenses for their domestic supply. Population growth together with change in rainfall patterns and sea level will probably impact these vulnerable groundwater resources. Spatial knowledge of the aquifer properties and creation of a groundwater model are required for achieving a sustainable management of the resource. This paper presents a ready-to-use methodology for estimating the key aquifer properties and the freshwater resource based on the joint use of two non-invasive geophysical tools together with common hydrological measurements.

    We applied the proposed methodology in an unconfined aquifer of a coastal sandy barrier in South-Western India. We jointly used magnetic resonance and transient electromagnetic soundings and we monitored rainfall, groundwater level and groundwater electrical conductivity. The combined interpretation of geophysical and hydrological results allowed estimating the aquifer properties and mapping the freshwater lens. Depending on the location and season, we estimate the freshwater reserve to range between 400 and 700 L m−2 of surface area (± 50%. We also estimate the recharge using time lapse geophysical measurements with hydrological monitoring. After a rainy event close to 100% of the rain is reaching the water table, but the net recharge at the end of the monsoon is less than 10% of the rain. Thus, we conclude that a change in rainfall patterns will probably not impact the groundwater resource since most of the rain water recharging the aquifer is flowing towards the sea and the river. However, a change in sea level will impact both the groundwater reserve and net recharge.

  14. Annual net ecosystem exchanges of carbon dioxide and methane from a temperate brackish marsh: should the focus of marsh restoration be on brackish environments?

    Science.gov (United States)

    Windham-Myers, L.; Anderson, F. E.; Bergamaschi, B. A.; Ferner, M. C.; Schile, L. M.; Spinelli, G.

    2015-12-01

    The exchange and transport of carbon in tidally driven, saline marsh ecosystems provide habitat and trophic support for coastal wildlife and fisheries, while potentially accumulating and storing carbon at some of the highest rates compared to other ecosystems. However, due to the predicted rise in sea level over the next century, the preservation and restoration of estuarine habitats is necessary to compensate for their expected decline. In addition, restoration of these marsh systems can also reduce the impacts of global climate change as they assimilate as much carbon as their freshwater counterparts, while emitting less methane due to the higher concentrations of sulfate in seawater. Unfortunately, in brackish marshes, with salinity concentrations less than 18 parts per thousand (ppt), simple relationships between methane production, salinity and sulfate concentrations are not well known. Here we present the net ecosystem exchange (NEE) of carbon dioxide and methane, as calculated by the eddy covariance method, from a brackish marsh ecosystem in the San Francisco Estuary where salinity ranges from oligohaline (0.5-5 ppt) to mesohaline (5-18 ppt) conditions. Daily rates of carbon dioxide and methane NEE ranged from approximately 10 gC-CO2 m-2 d-1 and 0 mgC-CH4 m-2 d-1, during the winter to -15 gC-CO2 m-2 d-1 and 30 mgC-CH4 m-2 d-1, in the summer growing season. A comparison between similar measurements made from freshwater wetlands in the Sacramento-San Joaquin Delta found that the daily rates of carbon dioxide NEE were similar, but daily rates of methane NEE were just a small fraction (0-15%). Our research also shows that the daily fluxes of carbon dioxide and methane at the brackish marsh were highly variable and may be influenced by the tidal exchanges of seawater. Furthermore, the observed decline in methane production from summer to fall may have resulted from a rise in salinity and/or a seasonal decline in water and air temperatures. Our research goals are

  15. Methane and carbon dioxide fluxes over a lake: comparison between eddy covariance, floating chambers and boundary layer method

    Directory of Open Access Journals (Sweden)

    K.-M. Erkkilä

    2018-01-01

    Full Text Available Freshwaters bring a notable contribution to the global carbon budget by emitting both carbon dioxide (CO2 and methane (CH4 to the atmosphere. Global estimates of freshwater emissions traditionally use a wind-speed-based gas transfer velocity, kCC (introduced by Cole and Caraco, 1998, for calculating diffusive flux with the boundary layer method (BLM. We compared CH4 and CO2 fluxes from BLM with kCC and two other gas transfer velocities (kTE and kHE, which include the effects of water-side cooling to the gas transfer besides shear-induced turbulence, with simultaneous eddy covariance (EC and floating chamber (FC fluxes during a 16-day measurement campaign in September 2014 at Lake Kuivajärvi in Finland. The measurements included both lake stratification and water column mixing periods. Results show that BLM fluxes were mainly lower than EC, with the more recent model kTE giving the best fit with EC fluxes, whereas FC measurements resulted in higher fluxes than simultaneous EC measurements. We highly recommend using up-to-date gas transfer models, instead of kCC, for better flux estimates. BLM CO2 flux measurements had clear differences between daytime and night-time fluxes with all gas transfer models during both stratified and mixing periods, whereas EC measurements did not show a diurnal behaviour in CO2 flux. CH4 flux had higher values in daytime than night-time during lake mixing period according to EC measurements, with highest fluxes detected just before sunset. In addition, we found clear differences in daytime and night-time concentration difference between the air and surface water for both CH4 and CO2. This might lead to biased flux estimates, if only daytime values are used in BLM upscaling and flux measurements in general. FC measurements did not detect spatial variation in either CH4 or CO2 flux over Lake Kuivajärvi. EC measurements, on the other hand, did not show any spatial variation in CH4 fluxes but did show a clear difference

  16. Atmospheric lepton fluxes

    Directory of Open Access Journals (Sweden)

    Gaisser Thomas K.

    2015-01-01

    Full Text Available This review of atmospheric muons and neutrinos emphasizes the high energy range relevant for backgrounds to high-energy neutrinos of astrophysical origin. After a brief historical introduction, the main distinguishing features of atmospheric νμ and νe are discussed, along with the implications of the muon charge ratio for the νµ / ν̅µ ratio. Methods to account for effects of the knee in the primary cosmic-ray spectrum and the energy-dependence of hadronic interactions on the neutrino fluxes are discussed and illustrated in the context of recent results from IceCube. A simple numerical/analytic method is proposed for systematic investigation of uncertainties in neutrino fluxes arising from uncertainties in the primary cosmic-ray spectrum/composition and hadronic interactions.

  17. Application and Theory of Petri Nets

    DEFF Research Database (Denmark)

    This volume contains the proceedings of the 13th International Conference onApplication and Theory of Petri Nets, held in Sheffield, England, in June 1992. The aim of the Petri net conferences is to create a forum for discussing progress in the application and theory of Petri nets. Typically....... Balbo and W. Reisig, 18 submitted papers, and seven project papers. The submitted papers and project presentations were selectedby the programme committee and a panel of referees from a large number of submissions....

  18. Are You Neutral About Net Neutrality

    Science.gov (United States)

    2007-06-20

    Information Resources Management College National Defense University Are You Neutral About Net Neutrality ? A presentation for Systems & Software...author uses Verizon FiOS for phone, TV, and internet service 3 Agenda Net Neutrality —Through 2 Lenses Who Are the Players & What Are They Saying...Medical Treatment Mini-Case Studies Updates Closing Thoughts 4 Working Definitions of Net Neutrality "Network Neutrality" is the concept that

  19. Texture Based Image Analysis With Neural Nets

    Science.gov (United States)

    Ilovici, Irina S.; Ong, Hoo-Tee; Ostrander, Kim E.

    1990-03-01

    In this paper, we combine direct image statistics and spatial frequency domain techniques with a neural net model to analyze texture based images. The resultant optimal texture features obtained from the direct and transformed image form the exemplar pattern of the neural net. The proposed approach introduces an automated texture analysis applied to metallography for determining the cooling rate and mechanical working of the materials. The results suggest that the proposed method enhances the practical applications of neural nets and texture extraction features.

  20. Factors associated with mosquito net use by individuals in households owning nets in Ethiopia

    Directory of Open Access Journals (Sweden)

    Graves Patricia M

    2011-12-01

    Full Text Available Abstract Background Ownership of insecticidal mosquito nets has dramatically increased in Ethiopia since 2006, but the proportion of persons with access to such nets who use them has declined. It is important to understand individual level net use factors in the context of the home to modify programmes so as to maximize net use. Methods Generalized linear latent and mixed models (GLLAMM were used to investigate net use using individual level data from people living in net-owning households from two surveys in Ethiopia: baseline 2006 included 12,678 individuals from 2,468 households and a sub-sample of the Malaria Indicator Survey (MIS in 2007 included 14,663 individuals from 3,353 households. Individual factors (age, sex, pregnancy; net factors (condition, age, net density; household factors (number of rooms [2006] or sleeping spaces [2007], IRS, women's knowledge and school attendance [2007 only], wealth, altitude; and cluster level factors (rural or urban were investigated in univariate and multi-variable models for each survey. Results In 2006, increased net use was associated with: age 25-49 years (adjusted (a OR = 1.4, 95% confidence interval (CI 1.2-1.7 compared to children U5; female gender (aOR = 1.4; 95% CI 1.2-1.5; fewer nets with holes (Ptrend = 0.002; and increasing net density (Ptrend [all nets in HH good] = 1.6; 95% CI 1.2-2.1; increasing net density (Ptrend [per additional space] = 0.6, 95% CI 0.5-0.7; more old nets (aOR [all nets in HH older than 12 months] = 0.5; 95% CI 0.3-0.7; and increasing household altitude (Ptrend Conclusion In both surveys, net use was more likely by women, if nets had fewer holes and were at higher net per person density within households. School-age children and young adults were much less likely to use a net. Increasing availability of nets within households (i.e. increasing net density, and improving net condition while focusing on education and promotion of net use, especially in school-age children

  1. Estimation of mercury vapor flux from natural substrate in Nevada.

    Science.gov (United States)

    Zehner, Richard E; Gustin, Mae S

    2002-10-01

    The contribution of mercury to the atmosphere from natural sources is not well-quantified, particularly at the regional scale. This modeling study employed a Geographic Information Systems (GIS) approach to estimate mercury flux from substrate in Nevada, which lies within one of the global belts of geologic Hg enrichment. In situ mercury flux measurements were taken from a variety of substrate types with a wide range of mercury concentrations. This empirical data forms the basis of equations applied to a database of over 71,000 rock and soil samples used in scaling mercury flux for Nevada. The GIS was employed to spatially model estimated flux values according to sample type, geology, presence/absence of hydrothermal alteration, and meteorological conditions. The area average flux calculated for Nevada adjusted for meteorological conditions is 4.2 +/- 1.4 ng m-2 h-1, which corresponds to a approximately 29 kg daily emission of mercury. Areas of hydrothermal alteration emit 12.9 +/- 3.6 ng m-2 h-1, accounts for 22% of net mercury emissions yet represents only 7% of the area of Nevada. Unaltered geologic units have low fluxes (3.5 +/- 1.2 ng m-2 h-1) but, because of their large area, emit 78% of the total mercury.

  2. Combining Eddy Covariance Fluxes, High-Precision Trace Gas Measurements, Chemical Transport Modeling, and Inverse Modeling to Estimate Regional CO2 Fluxes in the Southern Great Plains, USA

    NARCIS (Netherlands)

    Hirsch, A. I.; Fischer, M. L.; Biraud, S. C.; Torn, M. S.; Berry, J. A.; Andrews, A. E.; Peters, W.; Zahorowski, W.; Chambers, S. Z.; Tans, P. P.

    2008-01-01

    We use the radon tracer method to estimate monthly average net ecosystem exchange (NEE) of carbon dioxide in the Southern Great Plains of the USA for the year 2007. These estimates are compared with optimized flux estimates of NEE from NOAA CarbonTracker, sampled with a Lagrangian particle

  3. Effect of land use and groundwater flow path on submarine groundwater discharge nutrient flux

    Directory of Open Access Journals (Sweden)

    James M. Bishop

    2017-06-01

    New hydrological insights for the region: Low nitrate + nitrite (N + N SGD fluxes (24 mols/d were measured where groundwater flowed beneath primarily undeveloped land on transit to the coast. By contrast, of all land use types, sugarcane and pineapple fields contributed the largest amount of N to coastal waters via SGD (3800 mols/d. Despite their much smaller freshwater flux, these SGD sources provide substantially larger N fluxes than the State's largest rivers (avg. 700 mols/d. Septic systems, cesspools, and near coast wastewater injection wells also contribute N + N to groundwater and coastal waters, although in much smaller quantities. This study demonstrates that numerical groundwater modeling combined with geochemical modeling can be used to determine sources and flux of nutrients in SGD and provides a unique, original, and practical framework for studying the effect of land use and its impact on nutrient delivery to coastal waters.

  4. Pro Agile NET Development with Scrum

    CERN Document Server

    Blankenship, Jerrel; Millett, Scott

    2011-01-01

    Pro Agile .NET Development with SCRUM guides you through a real-world ASP.NET project and shows how agile methodology is put into practice. There is plenty of literature on the theory behind agile methodologies, but no book on the market takes the concepts of agile practices and applies these in a practical manner to an end-to-end ASP.NET project, especially the estimating, requirements and management aspects of a project. Pro Agile .NET Development with SCRUM takes you through the initial stages of a project - gathering requirements and setting up an environment - through to the development a

  5. Pro ASP.NET MVC 4

    CERN Document Server

    Freeman, Adam

    2012-01-01

    The ASP.NET MVC 4 Framework is the latest evolution of Microsoft's ASP.NET web platform. It provides a high-productivity programming model that promotes cleaner code architecture, test-driven development, and powerful extensibility, combined with all the benefits of ASP.NET. ASP.NET MVC 4 contains a number of significant advances over previous versions. New mobile and desktop templates (employing adaptive rendering) are included together with support for jQuery Mobile for the first time. New display modes allow your application to select views based on the browser that's making the request whi

  6. Professional Visual Basic 2010 and .NET 4

    CERN Document Server

    Sheldon, Bill; Sharkey, Kent

    2010-01-01

    Intermediate and advanced coverage of Visual Basic 2010 and .NET 4 for professional developers. If you've already covered the basics and want to dive deep into VB and .NET topics that professional programmers use most, this is your book. You'll find a quick review of introductory topics-always helpful-before the author team of experts moves you quickly into such topics as data access with ADO.NET, Language Integrated Query (LINQ), security, ASP.NET web programming with Visual Basic, Windows workflow, threading, and more. You'll explore all the new features of Visual Basic 2010 as well as all t

  7. NASA Net Zero Energy Buildings Roadmap

    Energy Technology Data Exchange (ETDEWEB)

    Pless, S.; Scheib, J.; Torcellini, P.; Hendron, B.; Slovensky, M.

    2014-10-01

    In preparation for the time-phased net zero energy requirement for new federal buildings starting in 2020, set forth in Executive Order 13514, NASA requested that the National Renewable Energy Laboratory (NREL) to develop a roadmap for NASA's compliance. NASA detailed a Statement of Work that requested information on strategic, organizational, and tactical aspects of net zero energy buildings. In response, this document presents a high-level approach to net zero energy planning, design, construction, and operations, based on NREL's first-hand experience procuring net zero energy construction, and based on NREL and other industry research on net zero energy feasibility. The strategic approach to net zero energy starts with an interpretation of the executive order language relating to net zero energy. Specifically, this roadmap defines a net zero energy acquisition process as one that sets an aggressive energy use intensity goal for the building in project planning, meets the reduced demand goal through energy efficiency strategies and technologies, then adds renewable energy in a prioritized manner, using building-associated, emission- free sources first, to offset the annual energy use required at the building; the net zero energy process extends through the life of the building, requiring a balance of energy use and production in each calendar year.

  8. Towards a Standard for Modular Petri Nets

    DEFF Research Database (Denmark)

    Kindler, Ekkart; Petrucci, Laure

    2009-01-01

    When designing complex systems, mechanisms for structuring, composing, and reusing system components are crucial. Today, there are many approaches for equipping Petri nets with such mechanisms. In the context of defining a standard interchange format for Petri nets, modular PNML was defined....... Moreover, we present and discuss some more advanced features of modular Petri nets that could be included in the standard. This way, we provide a formal foundation and a basis for a discussion of features to be included in the upcoming standard of a module concept for Petri nets in general and for high...

  9. Measurements of CO 2 fluxes from the Mexico City urban landscape

    Science.gov (United States)

    Velasco, Erik; Pressley, Shelley; Allwine, Eugene; Westberg, Hal; Lamb, Brian

    In a densely populated section of Mexico City, an eddy covariance (EC) flux system was deployed on a tall urban tower to obtain direct measurements of CO 2 emissions from an urban neighborhood located in a subtropical megacity. The measured fluxes and boundary layer conditions satisfy EC assumptions of stationarity, and cospectral analyses of the turbulence measurements exhibit the required boundary layer patterns for acceptable flux measurements. Results from a field experiment conducted during April 2003 show that the urban surface is a net source of CO 2. The CO 2 flux measurements showed a clear diurnal pattern, with the highest emissions during the morning (up to 1.60 mg m -2 s -1), and the lowest emissions during nighttime. The measured fluxes were closely correlated to traffic patterns in the area. The mean daily flux was 0.41 mg m -2 s -1, which is similar to that observed in European and US cities.

  10. Reviews and syntheses: An empirical spatiotemporal description of the global surface–atmosphere carbon fluxes: opportunities and data limitations

    Directory of Open Access Journals (Sweden)

    J. Zscheischler

    2017-08-01

    Full Text Available Understanding the global carbon (C cycle is of crucial importance to map current and future climate dynamics relative to global environmental change. A full characterization of C cycling requires detailed information on spatiotemporal patterns of surface–atmosphere fluxes. However, relevant C cycle observations are highly variable in their coverage and reporting standards. Especially problematic is the lack of integration of the carbon dioxide (CO2 exchange of the ocean, inland freshwaters and the land surface with the atmosphere. Here we adopt a data-driven approach to synthesize a wide range of observation-based spatially explicit surface–atmosphere CO2 fluxes from 2001 to 2010, to identify the state of today's observational opportunities and data limitations. The considered fluxes include net exchange of open oceans, continental shelves, estuaries, rivers, and lakes, as well as CO2 fluxes related to net ecosystem productivity, fire emissions, loss of tropical aboveground C, harvested wood and crops, as well as fossil fuel and cement emissions. Spatially explicit CO2 fluxes are obtained through geostatistical and/or remote-sensing-based upscaling, thereby minimizing biophysical or biogeochemical assumptions encoded in process-based models. We estimate a bottom-up net C exchange (NCE between the surface (land, ocean, and coastal areas and the atmosphere. Though we provide also global estimates, the primary goal of this study is to identify key uncertainties and observational shortcomings that need to be prioritized in the expansion of in situ observatories. Uncertainties for NCE and its components are derived using resampling. In many regions, our NCE estimates agree well with independent estimates from other sources such as process-based models and atmospheric inversions. This holds for Europe (mean ± 1 SD: 0.8 ± 0.1 PgC yr−1, positive numbers are sources to the atmosphere, Russia (0.1 ± 0.4 PgC yr−1, East Asia

  11. Low-latitude ice cores and freshwater availability

    Science.gov (United States)

    Kehrwald, Natalie Marie

    2009-12-01

    Recent retreat of Tibetan Plateau glaciers affects at least half a billion people. Himalayan glaciers seasonally release meltwater into tributaries of the Indus, Ganges, and Brahmaputra Rivers and supply freshwater necessary to support agricultural and economic practices. Tibetan Plateau glaciers are retreating more rapidly than mountain glaciers elsewhere in the world, and this retreat is accelerating. The Naimona'nyi (30°27'N; 81°91'E, 6050 m a.s.l), Guliya (35°17'N; 81°29'E, 6710 m a.s.l.) and Dasuopu (28°23'N; 85°43'E, 7200 m a.s.l.) ice cores place this recent retreat into a longer time perspective through quantifying climate parameters such as past temperature, aridity, and atmospheric chemistry. Naimona'nyi has not accumulated mass since at least 1950, as evidenced by the virtual lack of radiogenic isotopes (36Cl, 3 H, and beta radioactivity) present in the ice core. These isotopes were produced by U.S. and Soviet atmospheric thermonuclear bomb tests conducted in the 1950s and 1960s and provide independent dating horizons for the ice cores. Lead-210 dates imply that the uppermost preserved glacial ice on Naimona'nyi formed during the 1940s. While this is the highest documented glacial thinning in the world other glaciers at elevations similar to that of Naimona'nyi, such as Kilimanjaro (3°4'S; 37°21'E, 5893 m a.s.l.), are also losing mass at their summits. The global scope of high-elevation glacial thinning suggests that ablation on the Earth's highest ice fields may be more prevalent as global mean temperatures continue to increase. Glacial thinning has not been taken into account in future projections of regional freshwater availability, and the net mass loss indicates that Himalayan glaciers currently store less freshwater than assumed in models. The acceleration of Tibetan Plateau glacial retreat has been hypothesized to be due in part to deposition of black carbon (BC) from biomass burning on to ice fields, thereby lowering the reflectivity of

  12. Experiments and simulation of a net closing mechanism for tether-net capture of space debris

    Science.gov (United States)

    Sharf, Inna; Thomsen, Benjamin; Botta, Eleonora M.; Misra, Arun K.

    2017-10-01

    This research addresses the design and testing of a debris containment system for use in a tether-net approach to space debris removal. The tether-net active debris removal involves the ejection of a net from a spacecraft by applying impulses to masses on the net, subsequent expansion of the net, the envelopment and capture of the debris target, and the de-orbiting of the debris via a tether to the chaser spacecraft. To ensure a debris removal mission's success, it is important that the debris be successfully captured and then, secured within the net. To this end, we present a concept for a net closing mechanism, which we believe will permit consistently successful debris capture via a simple and unobtrusive design. This net closing system functions by extending the main tether connecting the chaser spacecraft and the net vertex to the perimeter and around the perimeter of the net, allowing the tether to actuate closure of the net in a manner similar to a cinch cord. A particular embodiment of the design in a laboratory test-bed is described: the test-bed itself is comprised of a scaled-down tether-net, a supporting frame and a mock-up debris. Experiments conducted with the facility demonstrate the practicality of the net closing system. A model of the net closure concept has been integrated into the previously developed dynamics simulator of the chaser/tether-net/debris system. Simulations under tether tensioning conditions demonstrate the effectiveness of the closure concept for debris containment, in the gravity-free environment of space, for a realistic debris target. The on-ground experimental test-bed is also used to showcase its utility for validating the dynamics simulation of the net deployment, and a full-scale automated setup would make possible a range of validation studies of other aspects of a tether-net debris capture mission.

  13. Diversity-Carbon Flux Relationships in a Northwest Forest

    Directory of Open Access Journals (Sweden)

    Rachael E. Kelm

    2011-12-01

    Full Text Available While aboveground biomass and forest productivity can vary over abiotic gradients (e.g., temperature and moisture gradients, biotic factors such as biodiversity and tree species stand dominance can also strongly influence biomass accumulation. In this study we use a permanent plot network to assess variability in aboveground carbon (C flux in forest tree annual aboveground biomass increment (ABI, tree aboveground net primary productivity (ANPPtree, and net soil CO2 efflux in relation to diversity of coniferous, deciduous, and a nitrogen (N-fixing tree species (Alnus rubra. Four major findings arose: (1 overstory species richness and indices of diversity explained between one third and half of all variation in measured aboveground C flux, and diversity indices were the most robust models predicting measured aboveground C flux; (2 trends suggested decreases in annual tree biomass increment C with increasing stand dominance for four of the five most abundant tree species; (3 the presence of an N-fixing tree species (A. rubra was not related to changes in aboveground C flux, was negatively related to soil CO2 efflux, and showed only a weak negative relationship with aboveground C pools; and (4 stands with higher overstory richness and diversity typically had higher soil CO2 efflux. Interestingly, presence of the N-fixing species was not correlated with soil inorganic N pools, and inorganic N pools were not correlated with any C flux or pool measure. We also did not detect any strong patterns between forest tree diversity and C pools, suggesting potential balancing of increased C flux both into and out of diverse forest stands. These data highlight variability in second-growth forests that may have implications for overstory community drivers of C dynamics.

  14. BOREAS RSS-8 BIOME-BGC Model Simulations at Tower Flux Sites in 1994

    Science.gov (United States)

    Hall, Forrest G. (Editor); Nickeson, Jaime (Editor); Kimball, John

    2000-01-01

    BIOME-BGC is a general ecosystem process model designed to simulate biogeochemical and hydrologic processes across multiple scales (Running and Hunt, 1993). In this investigation, BIOME-BGC was used to estimate daily water and carbon budgets for the BOREAS tower flux sites for 1994. Carbon variables estimated by the model include gross primary production (i.e., net photosynthesis), maintenance and heterotrophic respiration, net primary production, and net ecosystem carbon exchange. Hydrologic variables estimated by the model include snowcover, evaporation, transpiration, evapotranspiration, soil moisture, and outflow. The information provided by the investigation includes input initialization and model output files for various sites in tabular ASCII format.

  15. Measurement of carbon dioxide fluxes in a free-air carbon dioxide enrichment experiment using the closed flux chamber technique

    DEFF Research Database (Denmark)

    Selsted, Merete Bang; Ambus, Per; Michelsen, Anders

    2011-01-01

    Carbon dioxide (CO2) fluxes, composing net ecosystem exchange (NEE), ecosystem respiration (ER), and soil respiration (SR) were measured in a temperate heathland exposed to elevated CO2 by the FACE (free-air carbon enrichment) technique, raising the atmospheric CO2 concentration from c. 380 μmol...... concentration, and the flux also decreased in FACE plots, to 0.79 times that at low concentration. Similar SR in control plots was decreased 0.94 times in control plots and 0.88 times in FACE plots. We found that a useful method to achieve stable and reproducible chamber headspace and soil CO2 concentration...... prior to commencement of flux measurements was to turn off the FACE system at least 10 min in advance. Within 10 min a new equilibrium was established between the soil and atmosphere, apparently due to CO2 degassing from the top soil. The observed increase in SR in response to increased CO2 persisted...

  16. Marginal Ice Zone Flux and Variability

    Science.gov (United States)

    Pfirman, S. L.; Tremblay, B.; Newton, R.; Fowler, C.

    2009-12-01

    Arctic sea ice acts as a conveyor, collecting and transporting material across the central basin, and releasing it in the marginal ice zone (MIZ). Where and when ice with different transport histories melts, has a large impact on the MIZ and is critical for understanding the vulnerability of the Arctic system to climate change. This study focuses on the effects of changing the location and timing of fluxes to the MIZ, as well as the age and origin of ice delivered there. Combining observations and models, we analyze sea ice motion for origin, age, drift path, and flux (both along the drift path and to the MIZ) for past, recent, and future scenarios. We examine temporal and spatial variations in the transport of sea ice and ice-rafted material between different source and melt regions for interannual and seasonal variability, including: a) How the distribution, origin, and age of ice delivered to various MIZs has changed over time, especially during the spring bloom. b) How changes in ice drift related to changes in atmospheric, oceanic, sedimentologic, and ecologic conditions have influenced the delivery of freshwater, sediments, and biological material. c) How changes have varied regionally and with respect to water depth. For example, whether maximum ice melt - and therefore material release - occurs over deep waters or shallow shelves is an important ecological parameter. As the Arctic transitions toward ice free summer conditions, the seasonal ice zone will expand, shifting the location of the marginal ice zone. It is critical to understand processes governing these changes because the MIZ is the most dynamic, most productive, and most vulnerable region in the Arctic.

  17. North American freshwater mussels: natural history, ecology, and conservation

    National Research Council Canada - National Science Library

    Haag, Wendell R

    2012-01-01

    "Synthesizes ecology and natural history of North American freshwater mussels for scientists, natural resource professionals, students and natural history enthusiasts"-- "This well-illustrated book...

  18. HANPP Collection: Human Appropriation of Net Primary Productivity as a Percentage of Net Primary Productivity

    Data.gov (United States)

    National Aeronautics and Space Administration — The Human Appropriation of Net Primary Productivity (HANPP) as a Percentage of Net Primary Product (NPP) portion of the HANPP Collection represents a map identifying...

  19. Turbulent heat and momentum fluxes in the upper ocean under Arctic sea ice

    Science.gov (United States)

    Peterson, Algot K.; Fer, Ilker; McPhee, Miles G.; Randelhoff, Achim

    2017-02-01

    We report observations of heat and momentum fluxes measured in the ice-ocean boundary layer from four drift stations between January and June 2015, covering from the typical Arctic basin conditions in the Nansen Basin to energetic spots of interaction with the warm Atlantic Water branches near the Yermak Plateau and over the North Spitsbergen slope. A wide range of oceanic turbulent heat flux values are observed, reflecting the variations in space and time over the five month duration of the experiment. Oceanic heat flux is weakly positive in winter over the Nansen Basin during quiescent conditions, increasing by an order of magnitude during storm events. An event of local upwelling and mixing in the winter-time Nansen basin highlights the importance of individual events. Spring-time drift is confined to the Yermak Plateau and its slopes, where vertical mixing is enhanced. Wind events cause an approximate doubling of oceanic heat fluxes compared to calm periods. In June, melting conditions near the ice edge lead to heat fluxes of O(100 W m-2). The combination of wind forcing with shallow Atlantic Water layer and proximity to open waters leads to maximum heat fluxes reaching 367 W m-2, concurrent with rapid melting. Observed ocean-to-ice heat fluxes agree well with those estimated from a bulk parameterization except when accumulated freshwater from sea ice melt in spring probably causes the bulk formula to overestimate the oceanic heat flux.

  20. Price smarter on the Net.

    Science.gov (United States)

    Baker, W; Marn, M; Zawada, C

    2001-02-01

    Companies generally have set prices on the Internet in two ways. Many start-ups have offered untenably low prices in a rush to capture first-mover advantage. Many incumbents have simply charged the same prices on-line as they do off-line. Either way, companies are missing a big opportunity. The fundamental value of the Internet lies not in lowering prices or making them consistent but in optimizing them. After all, if it's easy for customers to compare prices on the Internet, it's also easy for companies to track customers' behavior and adjust prices accordingly. The Net lets companies optimize prices in three ways. First, it lets them set and announce prices with greater precision. Different prices can be tested easily, and customers' responses can be collected instantly. Companies can set the most profitable prices, and they can tap into previously hidden customer demand. Second, because it's so easy to change prices on the Internet, companies can adjust prices in response to even small fluctuations in market conditions, customer demand, or competitors' behavior. Third, companies can use the clickstream data and purchase histories that it collects through the Internet to segment customers quickly. Then it can offer segment-specific prices or promotions immediately. By taking full advantage of the unique possibilities afforded by the Internet to set prices with precision, adapt to changing circumstances quickly, and segment customers accurately, companies can get their pricing right. It's one of the ultimate drivers of e-business success.

  1. Multi-year net ecosystem carbon balance at a horticulture-extracted restored peatland

    Science.gov (United States)

    Nugent, Kelly; Strachan, Ian; Strack, Maria

    2017-04-01

    Restoration of previously extracted peatlands is essential to minimize the impact of drainage and peat removal. Best practices restoration methods have been developed that include ditch blocking, site leveling and reintroducing bog vegetation using the moss layer transfer technique. A long term goal of restoration is the return to a peat accumulating ecosystem. Bois-des-Bel is a cool-temperate bog, located in eastern Quebec, Canada, that was vacuum harvested until 1980 and restored in 1999. While several studies have used discrete (chamber) methods to determine the net carbon exchange from rewetted or restored peatlands, ours appears to be the first to have multiple complete years of net ecosystem carbon exchange from a restored northern peatland. An eddy covariance flux tower instrumented with a sonic anemometer and open-path CO2/H2O and CH4 analyzers was operated continuously over three years to produce a robust estimate of net carbon sequestration. Our initial results indicate that this restored peatland was a consistent moderate annual net sink for CO2, a moderate source of CH4 and had low losses of dissolved organic carbon compared to undisturbed northern latitude peatlands. Closed chambers combined with a fast response CO2/H2O/CH4 analyzer were used to investigate ecohydrological controls on net ecosystem exchange of CO2 (NEE) and CH4 flux from the restored fields and remnant ditches at the site. CH4 release was found to be an order of magnitude higher in the ditches compared to the fields, with non-vegetated ditch showing a greater range in flux compared to areas invaded by Typha latifolia. Bubble magnitude and count were highest in the non-vegetated ditch, followed by Typha plots and were undetectable in the restored fields. The latter may be partially attributed to the high cover of Eriophorum vaginatum in the restored fields, plants that have aerenchymous tissue, as well as a much deeper water table level. While the non-vegetated ditch areas were a steady

  2. 78 FR 72393 - Net Investment Income Tax

    Science.gov (United States)

    2013-12-02

    ... Investment Income Tax; Final and Proposed Rules #0;#0;Federal Register / Vol. 78, No. 231 / Monday, December... Parts 1 and 602 RIN 1545-BK44 Net Investment Income Tax AGENCY: Internal Revenue Service (IRS), Treasury... Investment Income Tax and the computation of Net Investment Income. The regulations affect individuals...

  3. 77 FR 72611 - Net Investment Income Tax

    Science.gov (United States)

    2012-12-05

    ... December 5, 2012 Part V Department of the Treasury Internal Revenue Service 26 CFR Part 1 Net Investment... Investment Income Tax AGENCY: Internal Revenue Service (IRS), Treasury. ACTION: Notice of proposed rulemaking...) the individual's net investment income for such taxable year, or (B) the excess (if any) of (i) the...

  4. Net analyte signal based statistical quality control

    NARCIS (Netherlands)

    Skibsted, E.T.S.; Boelens, H.F.M.; Westerhuis, J.A.; Smilde, A.K.; Broad, N.W.; Rees, D.R.; Witte, D.T.

    2005-01-01

    Net analyte signal statistical quality control (NAS-SQC) is a new methodology to perform multivariate product quality monitoring based on the net analyte signal approach. The main advantage of NAS-SQC is that the systematic variation in the product due to the analyte (or property) of interest is

  5. Asynchronous stream processing with S-Net

    NARCIS (Netherlands)

    Grelck, C.; Scholz, S.-B.; Shafarenko, A.

    2010-01-01

    We present the rationale and design of S-Net, a coordination language for asynchronous stream processing. The language achieves a near-complete separation between the application code, written in any conventional programming language, and the coordination/communication code written in S-Net. Our

  6. Using the MVC architecture on . NET platform

    OpenAIRE

    Ježek, David

    2011-01-01

    This thesis deals with usage of MVC (Model View Controller) technology in web development on ASP.NET platform from Microsoft. Mainly it deals with latest version of framework ASP.NET MVC 3. First part describes MVC architecture and the second describes usage of MVC in certain parts of web application an comparing with PHP.

  7. Analysis of Petri Nets and Transition Systems

    Directory of Open Access Journals (Sweden)

    Eike Best

    2015-08-01

    Full Text Available This paper describes a stand-alone, no-frills tool supporting the analysis of (labelled place/transition Petri nets and the synthesis of labelled transition systems into Petri nets. It is implemented as a collection of independent, dedicated algorithms which have been designed to operate modularly, portably, extensibly, and efficiently.

  8. 27 CFR 7.27 - Net contents.

    Science.gov (United States)

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Net contents. 7.27 Section 7.27 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF... the net contents are displayed by having the same blown, branded, or burned in the container in...

  9. Petri nets and other models of concurrency

    DEFF Research Database (Denmark)

    Nielsen, Mogens; Sassone, Vladimiro

    1998-01-01

    This paper retraces, collects, and summarises contributions of the authors - in collaboration with others - on the theme of Petri nets and their categorical relationships to other models of concurrency.......This paper retraces, collects, and summarises contributions of the authors - in collaboration with others - on the theme of Petri nets and their categorical relationships to other models of concurrency....

  10. Delta Semantics Defined By Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt; Kyng, Morten; Madsen, Ole Lehrmann

    This report is identical to an earlier version of May 1978 except that Chapter 5 has been revised. A new paper: "A Petri Net Definition of a System Description Language", DAIMI, April 1979, 20 pages, extends the Petri net model to include a data state representing the program variables. Delta...

  11. Net neutrality and inflation of traffic

    NARCIS (Netherlands)

    Peitz, M.; Schütt, Florian

    Under strict net neutrality Internet service providers (ISPs) are required to carry data without any differentiation and at no cost to the content provider. We provide a simple framework with a monopoly ISP to evaluate the short-run effects of different net neutrality rules. Content differs in its

  12. Net Neutrality and Inflation of Traffic

    NARCIS (Netherlands)

    Peitz, M.; Schütt, F.

    2015-01-01

    Under strict net neutrality Internet service providers (ISPs) are required to carry data without any differentiation and at no cost to the content provider. We provide a simple framework with a monopoly ISP to evaluate different net neutrality rules. Content differs in its sensitivity to delay.

  13. The Net Neutrality Debate: The Basics

    Science.gov (United States)

    Greenfield, Rich

    2006-01-01

    Rich Greenfield examines the basics of today's net neutrality debate that is likely to be an ongoing issue for society. Greenfield states the problems inherent in the definition of "net neutrality" used by Common Cause: "Network neutrality is the principle that Internet users should be able to access any web content they choose and…

  14. Dynamic response of the thermometric net radiometer

    Science.gov (United States)

    J. D. Wilson; W. J. Massman; G. E. Swaters

    2009-01-01

    We computed the dynamic response of an idealized thermometric net radiometer, when driven by an oscillating net longwave radiation intended roughly to simulate rapid fluctuations of the radiative environment such as might be expected during field use of such devices. The study was motivated by curiosity as to whether non-linearity of the surface boundary conditions...

  15. Teaching and Learning with the Net Generation

    Science.gov (United States)

    Barnes, Kassandra; Marateo, Raymond C.; Ferris, S. Pixy

    2007-01-01

    As the Net Generation places increasingly greater demands on educators, students and teachers must jointly consider innovative ways of teaching and learning. In this, educators are supported by the fact that the Net Generation wants to learn. However, these same educators should not fail to realize that this generation learns differently from…

  16. Verification of Timed-Arc Petri Nets

    DEFF Research Database (Denmark)

    Jacobsen, Lasse; Jacobsen, Morten; Møller, Mikael Harkjær

    2011-01-01

    Timed-Arc Petri Nets (TAPN) are an extension of the classical P/T nets with continuous time. Tokens in TAPN carry an age and arcs between places and transitions are labelled with time intervals restricting the age of tokens available for transition firing. The TAPN model posses a number...

  17. A Brief Introduction to Coloured Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt

    1997-01-01

    Coloured Petri Nets (CP-nets or CPN) is a graphical oriented language for design, specification, simulation and verification of systems. It is in particular well- suited for systems in which communication, synchronisation and resource sharing are important. Typical examples of application areas a...

  18. UV sensitivity of planktonic net community production in ocean surface waters

    OpenAIRE

    Regaudie de Gioux, Aurore; Agustí, Susana; Duarte, Carlos M.

    2014-01-01

    The net plankton community metabolism of oceanic surface waters is particularly important as it more directly affects the partial pressure of CO2 in surface waters and thus the air-sea fluxes of CO2. Plankton communities in surface waters are exposed to high irradiance that includes significant ultraviolet blue (UVB, 280-315 nm) radiation. UVB radiation affects both photosynthetic and respiration rates, increase plankton mortality rates, and other metabolic and chemical processes. Here we tes...

  19. Gill net and trammel net selectivity in the northern Aegean Sea, Turkey

    Directory of Open Access Journals (Sweden)

    F. Saadet Karakulak

    2008-09-01

    Full Text Available Fishing trials were carried out with gill nets and trammel nets in the northern Aegean Sea from March 2004 to February 2005. Four different mesh sizes for the gill nets and the inner panel of trammel nets (16, 18, 20 and 22 mm bar length were used. Selectivity parameters for the five most economically important species, bogue (Boops boops, annular sea bream (Diplodus annularis, striped red mullet (Mullus surmuletus, axillary sea bream (Pagellus acarne and blotched picarel (Spicara maena, caught by the two gears were estimated. The SELECT method was used to estimate the selectivity parameters of a variety of models. Catch composition and catch proportion of several species were different in gill and trammel nets. The length frequency distributions of the species caught by the two gears were significantly different. The bi-modal model selectivity curve gave the best fit for gill net and trammel net data, and there was little difference between the modal lengths of these nets. However, a clear difference was found in catching efficiency. The highest catch rates were obtained with the trammel net. Given that many discard species and small fish are caught by gill nets and trammel nets with a mesh size of 16 mm, it is clear that these nets are not appropriate for fisheries. Consequently, the best mesh size for multispecies fisheries is 18 mm. This mesh size will considerably reduce the numbers of small sized individuals and discard species in the catch.

  20. MOLLUSKS IN RADIOECOLOGICAL STUDIES OF FRESHWATER ECOSYSTEMS

    Directory of Open Access Journals (Sweden)

    Д. Гудков

    2012-04-01

    Full Text Available Species-specificity and dynamics of 90Sr, 137Cs and some transuraniс elements accumulation in bivalveand gastropod freshwater molluscs of the Chernobyl exclusion zone during 1998–2010 was analyzed. Theresults of radiation dose as well as chromosome aberration rate estimation and analysis of hemolymphcomposition of molluscs was produced. The radiation absorbed dose rate was registered in the range of 0.3–85.0 μGy h–1. In closed water bodies the heightened chromosome aberration rate (up to 27 % in embryotissues, and also change of haematological indexes for the adult individuals of snails was registered

  1. Monitoring endangered freshwater biodiversity using environmental DNA

    DEFF Research Database (Denmark)

    Thomsen, Philip Francis; Kielgast, Jos; Iversen, Lars Lønsmann

    2012-01-01

    that depend on practical and taxonomic expertise, which is rapidly declining. Here, we show that a diversity of rare and threatened freshwater animals-representing amphibians, fish, mammals, insects and crustaceans-can be detected and quantified based on DNA obtained directly from small water samples of lakes...... of amphibians and fish can be detected by high-throughput sequencing of DNA extracted from pond water. Our findings underpin the ubiquitous nature of DNA traces in the environment and establish environmental DNA as a tool for monitoring rare and threatened species across a wide range of taxonomic groups....

  2. Freshwater reservoir effect variability in Northern Germany

    DEFF Research Database (Denmark)

    Philippsen, B.; Heinemeier, J.

    2013-01-01

    The freshwater reservoir effect is a potential problem when radiocarbon dating fish bones, shells, human bones, or food crusts on pottery from sites near rivers or lakes. The reservoir age in hardwater rivers can be up to several thousand years and may be highly variable. Accurate 14C dating of f...... that can also be expected for the past. This knowledge will be applied to the dating of food crusts on pottery from the Mesolithic sites Kayhude at the Alster River and Schlamersdorf at the Trave River, both in Schleswig-Holstein, northern Germany....

  3. Ion and water fluxes in the ileum of rats.

    Science.gov (United States)

    CURRAN, P F; SOLOMON, A K

    1957-09-20

    Studies have been carried out on the movement of salt and water across the small intestine of the rat. Segments of the ileum of anesthetized rats have been perfused in vivo with unbuffered NaCl solutions or isotonic solutions of NaCl and mannitol. Kinetic analysis of movements of Na(24) and Cl(36) has permitted determination of the efflux and influx of Na and Cl. Net water absorption has been measured using hemoglobin as a reference substance. Water was found to move freely in response to gradients of osmotic pressure. Net water flux from isotonic solutions with varying NaCl concentration was directly dependent on net solute flux. The amount of water absorbed was equivalent to the amount required to maintain the absorbed solute at isotonic concentration. These results have been interpreted as indicating that water movement is a passive process depending on gradients of water activity and on the rate of absorption of solute. The effluxes of Na and Cl are linear functions of concentration in the lumen, but both ions are actively transported by the ileum according to the criterion of Ussing (Acta Physiol. Scand., 1949, 19, 43). The electrical potential difference between the lumen and plasma has been interpreted as a diffusion potential slightly modified by the excess of active Cl flux over active Na flux. The physical properties of the epithelial membrane indicate that it is equivalent to a membrane having negatively charged uniform right circular pores of 36 A radius occupying 0.001 per cent of the surface area.

  4. Global Intercomparison of 12 Land Surface Heat Flux Estimates

    Science.gov (United States)

    Jimenez, C.; Prigent, C.; Mueller, B.; Seneviratne, S. I.; McCabe, M. F.; Wood, E. F.; Rossow, W. B.; Balsamo, G.; Betts, A. K.; Dirmeyer, P. A.; hide

    2011-01-01

    A global intercomparison of 12 monthly mean land surface heat flux products for the period 1993-1995 is presented. The intercomparison includes some of the first emerging global satellite-based products (developed at Paris Observatory, Max Planck Institute for Biogeochemistry, University of California Berkeley, University of Maryland, and Princeton University) and examples of fluxes produced by reanalyses (ERA-Interim, MERRA, NCEP-DOE) and off-line land surface models (GSWP-2, GLDAS CLM/ Mosaic/Noah). An intercomparison of the global latent heat flux (Q(sub le)) annual means shows a spread of approx 20 W/sq m (all-product global average of approx 45 W/sq m). A similar spread is observed for the sensible (Q(sub h)) and net radiative (R(sub n)) fluxes. In general, the products correlate well with each other, helped by the large seasonal variability and common forcing data for some of the products. Expected spatial distributions related to the major climatic regimes and geographical features are reproduced by all products. Nevertheless, large Q(sub le)and Q(sub h) absolute differences are also observed. The fluxes were spatially averaged for 10 vegetation classes. The larger Q(sub le) differences were observed for the rain forest but, when normalized by mean fluxes, the differences were comparable to other classes. In general, the correlations between Q(sub le) and R(sub n) were higher for the satellite-based products compared with the reanalyses and off-line models. The fluxes were also averaged for 10 selected basins. The seasonality was generally well captured by all products, but large differences in the flux partitioning were observed for some products and basins.

  5. Discrete, continuous, and hybrid petri nets

    CERN Document Server

    David, René

    2004-01-01

    Petri nets do not designate a single modeling formalism. In fact, newcomers to the field confess sometimes to be a little puzzled by the diversity of formalisms that are recognized under this "umbrella". Disregarding some extensions to the theoretical modeling capabilities, and looking at the level of abstraction of the formalisms, Condition/Event, Elementary, Place/Transition, Predicate/Transition, Colored, Object Oriented... net systems are frequently encountered in the literature. On the other side, provided with appropriate interpretative extensions, Controled Net Systems, Marking Diagrams (the Petri net generalization of State Diagrams), or the many-many variants in which time can be explicitly incorporated -Time(d), Deterministic, (Generalized) Stochastic, Fuzzy...- are defined. This represents another way to define practical formalisms that can be obtained by the "cro- product" of the two mentioned dimensions. Thus Petri nets constitute a modeling paradigm, understandable in a broad sense as "the total...

  6. Reactor flux calculations

    Energy Technology Data Exchange (ETDEWEB)

    Lhuillier, D. [Commissariat à l' Énergie Atomique et aux Énergies Alternatives, Centre de Saclay, IRFU/SPhN, 91191 Gif-sur-Yvette (France)

    2013-02-15

    The status of the prediction of reactor anti-neutrino spectra is presented. The most accurate method is still the conversion of total β spectra of fissionning isotopes as measured at research reactors. Recent re-evaluations of the conversion process led to an increased predicted flux by few percent and were at the origin of the so-called reactor anomaly. The up to date predictions are presented with their main sources of error. Perspectives are given on the complementary ab-initio predictions and upcoming experimental cross-checks of the predicted spectrum shape.

  7. FLUXNET. Database of fluxes, site characteristics, and flux-community information

    Energy Technology Data Exchange (ETDEWEB)

    Olson, R. J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Holladay, S. K. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cook, R. B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Falge, E. [Univ. Bayreuth, Bayreuth (Germany); Baldocchi, D. [Univ. of California, Berkeley, CA (United States); Gu, L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2004-02-28

    FLUXNET is a “network of regional networks” created by international scientists to coordinate regional and global analysis of observations from micrometeorological tower sites. The flux tower sites use eddy covariance methods to measure the exchanges of carbon dioxide (CO2), water vapor, and energy between terrestrial ecosystems and the atmosphere. FLUXNET’S goals are to aid in understanding the mechanisms controlling the exchanges of CO2, water vapor, and energy across a range of time (0.5 hours to annual periods) and space scales. FLUXNET provides an infrastructure for the synthesis and analysis of world-wide, long-term flux data compiled from various regional flux networks. Information compiled by the FLUXNET project is being used to validate remote sensing products associated with the National Aeronautics and Space Administration (NASA) Terra and Aqua satellites. FLUXNET provides access to ground information for validating estimates of net primary productivity, and energy absorption that are being generated by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors. In addition, this information is also used to develop and validate ecosystem models.

  8. Auxin-driven patterning with unidirectional fluxes

    Science.gov (United States)

    Cieslak, Mikolaj; Runions, Adam; Prusinkiewicz, Przemyslaw

    2015-01-01

    The plant hormone auxin plays an essential role in the patterning of plant structures. Biological hypotheses supported by computational models suggest that auxin may fulfil this role by regulating its own transport, but the plausibility of previously proposed models has been questioned. We applied the notion of unidirectional fluxes and the formalism of Petri nets to show that the key modes of auxin-driven patterning—the formation of convergence points and the formation of canals—can be implemented by biochemically plausible networks, with the fluxes measured by dedicated tally molecules or by efflux and influx carriers themselves. Common elements of these networks include a positive feedback of auxin efflux on the allocation of membrane-bound auxin efflux carriers (PIN proteins), and a modulation of this allocation by auxin in the extracellular space. Auxin concentration in the extracellular space is the only information exchanged by the cells. Canalization patterns are produced when auxin efflux and influx act antagonistically: an increase in auxin influx or concentration in the extracellular space decreases the abundance of efflux carriers in the adjacent segment of the membrane. In contrast, convergence points emerge in networks in which auxin efflux and influx act synergistically. A change in a single reaction rate may result in a dynamic switch between these modes, suggesting plausible molecular implementations of coordinated patterning of organ initials and vascular strands predicted by the dual polarization theory. PMID:26116915

  9. Acoustic neutrino detection investigations within ANTARES and prospects for KM3NeT

    Directory of Open Access Journals (Sweden)

    Lahmann Robert

    2016-01-01

    Full Text Available The acoustic neutrino detection technique is a promising approach for future large-scale detectors with the aim of measuring the small expected flux of cosmogenic neutrinos at energies exceeding 1 EeV. It suggests itself to investigate this technique in the context of underwater Cherenkov neutrino telescopes, in particular KM3NeT, because acoustic sensors are present by design to allow for the calibration of the positions of the optical sensors. For the future, the KM3NeT detector in the Mediterranean Sea will provide an ideal infrastructure for a dedicated array of acoustic sensors. In this presentation results from the acoustic array AMADEUS of the ANTARES detector will be discussed with respect to the potential and implications for acoustic neutrino detection with KM3NeT and beyond.

  10. Freshwater rotifers from Hordaland, western Norway, with a survey of freshwater rotifers previously found in Norway

    Directory of Open Access Journals (Sweden)

    Brit Godske Bjørklund

    2010-01-01

    Full Text Available   Bjørklund BG. 2009. Freshwater rotifers from Hordaland western Norway with a u survey of freshwater rotifers previously found in Norway. Fauna Norvegica29: 11-54. A total of 156 species (or subspecies o rotifers, mostly non-planktonic, have been identified from freshwater or slightly brackish-water localities in the county of Hordaland; 83 are new to Norway and 24 others are new to the county. One hundred of the species were collected from the two valleys of Eksingedalen and Teigdalen in spring and summer 1967. Samples were taken on the shallow shores of lake-like parts of the rivers, and in pools, tarns and small lakes. Forty more or less euryhaline fresh­water rotifers were also collected during studies of slightly brackish-water localities around Bergen in 1963-1969. A number of freshwater rotifers were collected at several localities in and around Bergen in 1968-1970, and on the western part of Hardangervidda. Of those so far identified ,23 are new to Norway and 8 more are new to the county. They are therefore included in the species list. A few additional ones are referred to in the taxonomical notes. All the species are listed with localities and habitat categories, or, in the case of the last-mentioned ones, just the district where they were collected. The paper includes notes, measurements and ,in most cases, figures regarding 44 little known, variable or taxonomically problematical species, especially in the genera Cephalodella and Trichocerca. Comments are given on the distribution , abundance and diversity of the species. The paper presents asurvey of previous investigations on rotifers in Norway, listing 200 previously recorded freshwater (a few euryhaline rotifers, giving other names, the authors who recorded the finds and, in most cases, the counties where the species were collected. 

  11. Pro visual C++/CLI and the net 35 platform

    CERN Document Server

    Fraser, Stephen

    2008-01-01

    Pro Visual C++/CLI and the .NET 3.5 Platform is about writing .NET applications using C++/CLI. While readers are learning the ins and outs of .NET application development, they will also be learning the syntax of C++, both old and new to .NET. Readers will also gain a good understanding of the .NET architecture. This is truly a .NET book applying C++ as its development language not another C++ syntax book that happens to cover .NET.

  12. Combined use of frequency‐domain electromagnetic and electrical resistivity surveys to delineate the freshwater/saltwater interface near saline lakes in the Nebraska Sand Hills, Nebraska, USA

    Science.gov (United States)

    Ong, John T.; White, Eric A.; Lane, John; Halihan, Todd; Zlotnik, Vitaly A; Butler, Dwain K.

    2009-01-01

    We investigate the use of frequency‐domain electromagnetic (FDEM) and electrical resistivity (ER) surveys for rapid and detailed characterization of the direction of lake‐aquifer fluxes and the configuration of salt plumes generated from saline lakes. This methodology was developed and applied at several lakes in the Nebraska Sand Hills, Nebraska, in an area with both freshwater and saline lakes hydraulically connected to the freshwater surficial aquifer. The FDEM survey was conducted by mounting the instrument on a fiberglass cart towed by an all‐terrain vehicle. The towed FDEM surveys covered about 25 km per day and served as a reconnaissance method for choosing locations for the more quantitative and detailed ER surveys. Around the saline lakes, areas with high electrical conductivity are consistent with the regional direction of ground‐water flow. Lower electrical conductivity was measured around the freshwater lakes with anomalies correlating to a paleovalley axis inferred from previous studies. The efficacy of this geophysical approach is attributed to: (1) significant contrast in electrical conductivity between freshwater and saltwater, (2) near‐surface location of the freshwater/saltwater interface, (3) minimal cultural interference, and (4) relative homogeneity of the aquifer materials.

  13. Assessment of the methods for determining net radiation at different time-scales of meteorological variables

    Directory of Open Access Journals (Sweden)

    Ni An

    2017-04-01

    Full Text Available When modeling the soil/atmosphere interaction, it is of paramount importance to determine the net radiation flux. There are two common calculation methods for this purpose. Method 1 relies on use of air temperature, while Method 2 relies on use of both air and soil temperatures. Nowadays, there has been no consensus on the application of these two methods. In this study, the half-hourly data of solar radiation recorded at an experimental embankment are used to calculate the net radiation and long-wave radiation at different time-scales (half-hourly, hourly, and daily using the two methods. The results show that, compared with Method 2 which has been widely adopted in agronomical, geotechnical and geo-environmental applications, Method 1 is more feasible for its simplicity and accuracy at shorter time-scale. Moreover, in case of longer time-scale, daily for instance, less variations of net radiation and long-wave radiation are obtained, suggesting that no detailed soil temperature variations can be obtained. In other words, shorter time-scales are preferred in determining net radiation flux.

  14. Linking valve closure behavior and sodium transport mechanism in freshwater clam Corbicula fluminea in response to copper

    Energy Technology Data Exchange (ETDEWEB)

    Liao, C.-M. [Department of Bioenvironmental Systems Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10617 (China)]. E-mail: cmliao@ntu.edu.tw; Lin, C.-M. [Department of Bioenvironmental Systems Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10617 (China); Jou, L.-J. [Department of Bioenvironmental Systems Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10617 (China); Department of Biomechatronic Engineering, National Ilan University, Ilan, Taiwan 260 (China); Chiang, K.-C. [Department of Bioenvironmental Systems Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10617 (China)

    2007-06-15

    The purpose of this study is to develop a mechanistic model to describe a conceptually new 'flux-biological response' approach based on biotic ligand model (BLM) and Michaelis-Menten (M-M) kinetics to allow the linkage between valve closure behavior and sodium (Na) transport mechanism in freshwater clam Corbicula fluminea in response to waterborne copper (Cu). We test the proposed model against published data regarding Na uptake kinetics in rainbow trout and Na uptake profile in C. fluminea, confirming that the predictive model is robust. Here, we show that the predicted M-M maximum Cu internalization flux in C. fluminea is 0.369 {mu}mol g{sup -1} h{sup -1} with a half-saturation affinity constant of 7.87 x 10{sup -3} {mu}M. Dynamics of Na uptake and valve closure daily rhythm driven by external Cu can also be predicted simultaneously. We suggest that this 'Na transport-valve closure behavior' approach might provide the basis of a future design of biomonitoring tool. - A new flux-biological response model can link valve closure and sodium transport mechanisms in freshwater clam in response to copper.

  15. Assessing the environmental impacts of freshwater thermal pollution from global power generation in LCA.

    Science.gov (United States)

    Raptis, Catherine E; Boucher, Justin M; Pfister, Stephan

    2017-02-15

    Freshwater heat emissions from power plants with once-through cooling systems constitute one of many environmental pressures related to the thermoelectric power industry. The objective of this work was to obtain high resolution, operational characterization factors (CF) for the impact of heat emissions on ecosystem quality, and carry out a comprehensive, spatially, temporally and technologically differentiated damage-based environmental assessment of global freshwater thermal pollution. The aggregation of CFs on a watershed level results in 12.5% lower annual impacts globally and even smaller differences for the most crucial watersheds and months, so watershed level CFs are recommended when the exact emission site within the basin is unknown. Long-range impacts account for almost 90% of the total global impacts. The Great Lakes, several Mississippi subbasins, the Danube, and the Yangtze are among the most thermally impacted watersheds globally, receiving heat emissions from predominantly coal-fuelled and nuclear power plants. Globally, over 80% of the global annual impacts come from power plants constructed during or before the 1980s. While the impact-weighted mean age of the power plants in the Mississippi ranges from 38 to 51years, in Chinese watersheds including the Yangtze, the equivalent range is only 15 to 22years, reflecting a stark contrast in thermal pollution mitigation approaches. With relatively high shares of total capacity from power plants with once-through freshwater cooling, and tracing a large part of the Danube, 1kWh of net electricity mix is the most impactful in Hungary, Bulgaria and Serbia. Monthly CFs are provided on a grid cell level and on a watershed level for use in Life Cycle Assessment. The impacts per generating unit are also provided, as part of our effort to make available a global dataset of thermoelectric power plant emissions and impacts. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Management and the conservation of freshwater ecosystems

    Science.gov (United States)

    Wipfli, Mark S.; Richardson, John S.

    2015-01-01

    Riparian areas are the terrestrial environment adjacent to water that both influences and is influenced by the aquatic feature (Gregory et al., 1991; Naiman et al., 2010). Riparian areas along streams provide shade, sources of wood and organic matter, contribute to bank stability, filter sediments, take up excess nutrients from groundwater inputs, and other key processes that protect freshwaters (e.g. Naiman et al., 2010; Richardson & Danehy, 2007; Figure 9.1). Riparian areas also increase biodiversity through habitat complexity and close juxtaposition of aquatic and terrestrial environments (Quinn et al., 2004; Naiman et al., 2010). Alterations to riparian areas, despite their small area relative to the landscape, have disproportionate effects on habitats and fish communities (Naiman et al., 2010; Wipfli & Baxter, 2010). Key habitat losses and alterations are derived from modification of riparian areas by reducing instream habitat complexity (Bilby & Ward, 1989; Fausch & Northcote, 1992; Naiman et al., 2010), diminishing the productive basis of freshwater food webs (Belsky et al., 1999; Quinn et al., 2004), increasing nutrient, contaminant and sediment intrusion (Muscutt et al., 1993; Daniels & Gilliam, 1996; Nguyen et al., 1998; Waters, 1999).

  17. Reclaiming freshwater sustainability in the Cadillac Desert

    Science.gov (United States)

    Sabo, John L.; Sinha, Tushar; Bowling, Laura C.; Schoups, Gerrit H.W.; Wallender, Wesley W.; Campana, Michael E.; Cherkauer, Keith A.; Fuller, Pam L.; Graf, William L.; Hopmans, Jan W.; Kominoski, John S.; Taylor, Carissa; Trimble, Stanley W.; Webb, Robert H.; Wohl, Ellen E.

    2010-01-01

    Increasing human appropriation of freshwater resources presents a tangible limit to the sustainability of cities, agriculture, and ecosystems in the western United States. Marc Reisner tackles this theme in his 1986 classic Cadillac Desert: The American West and Its Disappearing Water. Reisner's analysis paints a portrait of region-wide hydrologic dysfunction in the western United States, suggesting that the storage capacity of reservoirs will be impaired by sediment infilling, croplands will be rendered infertile by salt, and water scarcity will pit growing desert cities against agribusiness in the face of dwindling water resources. Here we evaluate these claims using the best available data and scientific tools. Our analysis provides strong scientific support for many of Reisner's claims, except the notion that reservoir storage is imminently threatened by sediment. More broadly, we estimate that the equivalent of nearly 76% of streamflow in the Cadillac Desert region is currently appropriated by humans, and this figure could rise to nearly 86% under a doubling of the region's population. Thus, Reisner's incisive journalism led him to the same conclusions as those rendered by copious data, modern scientific tools, and the application of a more genuine scientific method. We close with a prospectus for reclaiming freshwater sustainability in the Cadillac Desert, including a suite of recommendations for reducing region-wide human appropriation of streamflow to a target level of 60%.

  18. Reclaiming freshwater sustainability in the Cadillac Desert

    Science.gov (United States)

    Sabo, John L.; Sinha, Tushar; Bowling, Laura C.; Schoups, Gerrit H. W.; Wallender, Wesley W.; Campana, Michael E.; Cherkauer, Keith A.; Fuller, Pam L.; Graf, William L.; Hopmans, Jan W.; Kominoski, John S.; Taylor, Carissa; Trimble, Stanley W.; Webb, Robert H.; Wohl, Ellen E.

    2010-01-01

    Increasing human appropriation of freshwater resources presents a tangible limit to the sustainability of cities, agriculture, and ecosystems in the western United States. Marc Reisner tackles this theme in his 1986 classic Cadillac Desert: The American West and Its Disappearing Water. Reisner's analysis paints a portrait of region-wide hydrologic dysfunction in the western United States, suggesting that the storage capacity of reservoirs will be impaired by sediment infilling, croplands will be rendered infertile by salt, and water scarcity will pit growing desert cities against agribusiness in the face of dwindling water resources. Here we evaluate these claims using the best available data and scientific tools. Our analysis provides strong scientific support for many of Reisner's claims, except the notion that reservoir storage is imminently threatened by sediment. More broadly, we estimate that the equivalent of nearly 76% of streamflow in the Cadillac Desert region is currently appropriated by humans, and this figure could rise to nearly 86% under a doubling of the region's population. Thus, Reisner's incisive journalism led him to the same conclusions as those rendered by copious data, modern scientific tools, and the application of a more genuine scientific method. We close with a prospectus for reclaiming freshwater sustainability in the Cadillac Desert, including a suite of recommendations for reducing region-wide human appropriation of streamflow to a target level of 60%. PMID:21149727

  19. Persistence of environmental DNA in freshwater ecosystems.

    Directory of Open Access Journals (Sweden)

    Tony Dejean

    Full Text Available The precise knowledge of species distribution is a key step in conservation biology. However, species detection can be extremely difficult in many environments, specific life stages and in populations at very low density. The aim of this study was to improve the knowledge on DNA persistence in water in order to confirm the presence of the focus species in freshwater ecosystems. Aquatic vertebrates (fish: Siberian sturgeon and amphibian: Bullfrog tadpoles were used as target species. In control conditions (tanks and in the field (ponds, the DNA detectability decreases with time after the removal of the species source of DNA. DNA was detectable for less than one month in both conditions. The density of individuals also influences the dynamics of DNA detectability in water samples. The dynamics of detectability reflects the persistence of DNA fragments in freshwater ecosystems. The short time persistence of detectable amounts of DNA opens perspectives in conservation biology, by allowing access to the presence or absence of species e.g. rare, secretive, potentially invasive, or at low density. This knowledge of DNA persistence will greatly influence planning of biodiversity inventories and biosecurity surveys.

  20. Monitoring endangered freshwater biodiversity using environmental DNA.

    Science.gov (United States)

    Thomsen, Philip Francis; Kielgast, Jos; Iversen, Lars L; Wiuf, Carsten; Rasmussen, Morten; Gilbert, M Thomas P; Orlando, Ludovic; Willerslev, Eske

    2012-06-01

    Freshwater ecosystems are among the most endangered habitats on Earth, with thousands of animal species known to be threatened or already extinct. Reliable monitoring of threatened organisms is crucial for data-driven conservation actions but remains a challenge owing to nonstandardized methods that depend on practical and taxonomic expertise, which is rapidly declining. Here, we show that a diversity of rare and threatened freshwater animals--representing amphibians, fish, mammals, insects and crustaceans--can be detected and quantified based on DNA obtained directly from small water samples of lakes, ponds and streams. We successfully validate our findings in a controlled mesocosm experiment and show that DNA becomes undetectable within 2 weeks after removal of animals, indicating that DNA traces are near contemporary with presence of the species. We further demonstrate that entire faunas of amphibians and fish can be detected by high-throughput sequencing of DNA extracted from pond water. Our findings underpin the ubiquitous nature of DNA traces in the environment and establish environmental DNA as a tool for monitoring rare and threatened species across a wide range of taxonomic groups. © 2011 Blackwell Publishing Ltd.

  1. Benchmarking carbon fluxes of the ISIMIP2a biome models

    Science.gov (United States)

    Chang, Jinfeng; Ciais, Philippe; Wang, Xuhui; Piao, Shilong; Asrar, Ghassem; Betts, Richard; Chevallier, Frédéric; Dury, Marie; François, Louis; Frieler, Katja; García Cantú Ros, Anselmo; Henrot, Alexandra-Jane; Hickler, Thomas; Ito, Akihiko; Morfopoulos, Catherine; Munhoven, Guy; Nishina, Kazuya; Ostberg, Sebastian; Pan, Shufen; Peng, Shushi; Rafique, Rashid; Reyer, Christopher; Rödenbeck, Christian; Schaphoff, Sibyll; Steinkamp, Jörg; Tian, Hanqin; Viovy, Nicolas; Yang, Jia; Zeng, Ning; Zhao, Fang

    2017-04-01

    The purpose of this study is to evaluate the eight ISIMIP2a biome models against independent estimates of long-term net carbon fluxes (i.e. Net Biome Productivity, NBP) over terrestrial ecosystems for the recent four decades (1971-2010). We evaluate modeled global NBP against 1) the updated global residual land sink (RLS) plus land use emissions (E LUC) from the Global Carbon Project (GCP), presented as R + L in this study by Le Quéré et al (2015), and 2) the land CO2 fluxes from two atmospheric inversion systems: Jena CarboScope s81_v3.8 and CAMS v15r2, referred to as F Jena and F CAMS respectively. The model ensemble-mean NBP (that includes seven models with land-use change) is higher than but within the uncertainty of R + L, while the simulated positive NBP trend over the last 30 yr is lower than that from R + L and from the two inversion systems. ISIMIP2a biome models well capture the interannual variation of global net terrestrial ecosystem carbon fluxes. Tropical NBP represents 31 ± 17% of global total NBP during the past decades, and the year-to-year variation of tropical NBP contributes most of the interannual variation of global NBP. According to the models, increasing Net Primary Productivity (NPP) was the main cause for the generally increasing NBP. Significant global NBP anomalies from the long-term mean between the two phases of El Niño Southern Oscillation (ENSO) events are simulated by all models (p < 0.05), which is consistent with the R + L estimate (p = 0.06), also mainly attributed to NPP anomalies, rather than to changes in heterotrophic respiration (Rh). The global NPP and NBP anomalies during ENSO events are dominated by their anomalies in tropical regions impacted by tropical climate variability. Multiple regressions between R + L, F Jena and F CAMS interannual variations and tropical climate variations reveal a significant negative response of global net terrestrial ecosystem carbon fluxes to tropical mean annual temperature variation

  2. Soil Trace Gas Flux for Wetland Vegetation Zones in North Dakota Prairie Pothole Basins

    Science.gov (United States)

    Phillips, R. L.; Beeri, O.; Dekaiser, E. S.

    2003-12-01

    Wetland ecosystems are considered a source for radiatively trace gases [methane (CH4), carbon dioxide (CO2), nitrous oxide (N2O)] but flux data for these greenhouse gases are lacking for depressional wetlands that comprise the Prairie Pothole Region. This region is characterized by thousands of small, closed basins that extend along the Missouri Coteau from north central Iowa to central Alberta. Surrounding each body of water are conspicuous zonation patterns given by specific vegetation life-forms and soil properties that are predominately formed by basin hydrology. Basin vegetation zones include deep marsh, shallow marsh, wet meadow, low prairie, and cropland (Stewart and Kantrud,1971). Our primary objective was to determine if net greenhouse gas flux for soils in these wetland basins [mg/m2/day CO2 equivalent (IPCC, 2000)] vary with vegetative zone for prairie pothole ecosystems. These data may then be used to map estimates for total basin greenhouse gas (GHG) flux. Additionally, we aimed to find the relative contribution of each of the 3 trace gases (CO2, CH4 and N2O) to net GHG flux. We hypothesized that flux would be greatest for marsh areas and lowest for upland areas. We selected a semi-permenant prairie pothole research site in Max, ND and mapped respective vegetative zones for 3 adjacent basins. Sample points were randomly selected for each basin and zone using aerial imagery. Samples of soil gases were collected using the static chamber method on August 3, 2003, and these were analyzed using gas chromatography for CO2, CH4 and N2O the following day. Soil moisture, clay content, organic matter, and temperature data were also collected. Net greenhouse gas flux for the cropped zone soils was significantly lower (pwetland zones within these closed basin ecosystems and that CH4 contributes most to net GHG flux for these wetland soils.

  3. Constraints on the Use of 18O in CO2 as a Tracer to Partition Gross Carbon Fluxes

    Science.gov (United States)

    Riley, W. J.; Still, C. J.

    2003-12-01

    Measurements of 18O in atmospheric CO2 can be used to partition measured net CO2 ecosystem fluxes into photosynthesis and respiration. However, uncertainties and temporal variability in the δ 18O value of the soil-surface CO2 flux (δ Fs) and the retro-diffused CO2 flux (δ Fr) can lead to substantial errors in partitioning estimates. We will discuss an integrated isotope and ecosystem model (ISOLSM) that simulates exchanges of 18O in H2O and CO2 in soil and plants, and will apply the model to identify critical factors associated with CO2 flux partitioning. Modeling results, regression analysis of model predictions, and an analysis of characteristic times of relevant processes indicate that, in contrast to previous reports, the δ 18O value of soil water (δ sw) in the top few cm of soil strongly impacts δ Fs. Thus, accurately characterizing near-surface δ sw is critical to the CO2 flux partitioning approach. We also discuss the impact of the soil CO2 source distribution within the column, soil temperature, and the δ 18O value of atmospheric CO2 on predictions of δ Fs. Disequilibrium between CO2 and leaf water, which may be common in C4 grasses, will impact δ Fr and therefore the partitioning of the measured net ecosystem CO2 flux. Finally, temporal variability in δ Fr, in particular, can lead to errors in flux partitioning when measurements of the δ 18O value of leaf water and of 18O in atmospheric CO2 and are not made concurrently. We will present results demonstrating the impact of these factors on partitioning estimates and discuss measurement protocol necessary to accurately partition measured net ecosystem CO2 fluxes into their component gross fluxes. We will also briefly discuss the relative merits of 18O versus 13C as a tracer for partitioning net fluxes.

  4. Freshwater gastropods in the Northern littoral mesoregion of Espírito Santo, Brazil

    Directory of Open Access Journals (Sweden)

    Marco Antônio Andrade de Souza

    2017-09-01

    Full Text Available Studies on the distribution of molluscs in Brazilhave been conducted since the beginning of the twentieth and the knowledge of the species distributed in the country represent important findings, which contribute to the understanding of human diseases and those of veterinary importance, transmitted by them. In order to verify the distribution of freshwater gastropods in Espírito Santo, a malacological surveywas carried out in nine municipalities that comprise the Northern mesoregion of the State, between January 2010 and February 2015. Initially the water collections occurring in the municipality were verified and the lotic systems at different levels of use and conservation were determined. Molluscs were collected monthly using a hand net adapted to a stick steel. An individual sample effort of 30 minutes was applied, by scanning, at about ten meters in each one of the selected habitats. A total of 6,000 specimens were collected, represented by genera Melanoides, Drepanotrema, Physa, Biomphalaria and Pomacea. Among the molluscs, some specimens were positive for flatworm larvae of medical and veterinary importance. The results contributed to the knowledge of the current distribution of freshwater gastropods in the Northern region of Espírito Santo whose the only record for the region dates back to 1983.

  5. The sea level response to ice sheet freshwater forcing in the Community Earth System Model

    Science.gov (United States)

    Slangen, Aimée; Lenaerts, Jan

    2017-04-01

    We show the effect of a realistic ice sheet freshwater forcing on sea-level change in the fully coupled Community Earth System Model (CESM). This not only includes the effect on the ocean density and dynamics, but also the gravitational response to mass redistribution between ice sheets and the ocean. We compare a 'standard' model simulation (NO-FW) to a simulation with a more realistic ice sheet freshwater forcing (FW) for two different climate scenario's (RCP2.6 and RCP8.5) for 1850-2100. We find that the effect on the global mean thermosteric sea-level change is small compared to the total thermosteric change, but on a regional scale the ocean steric/dynamic change shows larger differences in the Southern Ocean, the North Atlantic and the Arctic Ocean (locally over 0.1 m). The gravitational fingerprints of the net sea-level contributions of the ice sheets are computed separately, showing a regional pattern with a magnitude that is similar to the difference between the NO-FW and FW simulations of the ocean steric/dynamic pattern. Our results demonstrate the importance of ice sheet mass loss for regional sea-level projections in light of the projected increasing contribution of ice sheets to future sea-level rise.

  6. Different carbon isotope fractionation patterns during the development of phototrophic freshwater and marine biofilms

    Directory of Open Access Journals (Sweden)

    M. Staal

    2007-08-01

    Full Text Available Natural phototrophic biofilms are influenced by a broad array of abiotic and biotic factors and vary over temporal and spatial scales. Different developmental stages can be distinguished and growth rates will vary due to the thickening of the biofilm, which is expected to lead to a limitation of light or mass transport. This study shows that variation in CO2(aq availability leads to a fractionation shift and thereby affects δ13C signatures during biofilm development. For phototrophic freshwater biofilms it was found that the δ13C value became less negative with the thickening of the biofilm, while the opposite trend was found in marine biofilms. Modeling and pH profiling indicated that the trend in the freshwater system was caused by an increase in CO2(aq limitation resulting in an increase of HCO3 as C-source. The opposite trend in the marine system could be explained by a higher heterotrophic biomass and activity causing a higher carbon recycling and thereby lower δ13C values. We conclude that δ13C was more related to the net areal photosynthesis rate and carbon recycling, rather than to the growth rate of the biofilms.

  7. Use of seasonal freshwater wetlands by fishes in a temperate river floodplain

    Science.gov (United States)

    Henning, Julie A.; Gresswell, Robert E.; Fleming, Ian A.

    2007-01-01

    This study examined the use of freshwater wetland restoration and enhancement projects (i.e. non-estuarine wetlands subject to seasonal drying) by fish populations. To quantify fish use of freshwater emergent wetlands and assess the effect of wetland enhancement (i.e. addition of water control structures), two enhanced and two unenhanced emergent wetlands were compared, as well as two oxbow habitats within the Chehalis River floodplain. Eighteen fish species were captured using fyke nets and emigrant traps from January to the beginning of June, with the most abundant being three-spined stickleback Gasterosteus aculeatus and Olympic mudminnow Novumbra hubbsi. Coho salmon Oncorhynchus kisutch was the dominant salmonid at all sites. Enhanced wetlands, with their extended hydroperiods, had significantly higher abundances of yearling coho salmon than unenhanced wetlands. Both enhanced and unenhanced emergent wetlands yielded higher abundances of non-game native fishes than oxbow habitats. Oxbow habitats, however, were dominated by coho salmon. Fish survival in the wetland habitats was dependent on emigration to the river before dissolved oxygen concentrations decreased and wetlands became isolated and stranding occurred. This study suggests that wetland enhancement projects with an outlet to the river channel appear to provide fishes with important temporary habitats if they have the opportunity to leave the wetland as dissolved oxygen levels deteriorate.

  8. Freshwater nematodes from South Africa. 4. The genus Monhystera ...

    African Journals Online (AJOL)

    During a survey of freshwater nematodes in South Africa, five species of Monhystera Bastian, 1865, were encountered. The ..... in any other South African freshwater Monhystera. Vaginal muscles small and inconspicuous. ... taken from the deep muddy silt together with rotting plant material from the Vaal River and from deep ...

  9. Ammonium transformation in a nitrogen-rich tidal freshwater marsh

    NARCIS (Netherlands)

    Gribsholt, B.; Struyf, E.; Tramper, A.; Andersson, M.G.I.; Brion, N.; de Brabandere, L.; van Damme, S.; Meire, P.; Middelburg, J.J.; Dehairs, F.; Boschker, H.T.S.

    2006-01-01

    The fate and transport of watershed-derived ammonium in a tidal freshwater marsh fringing the nutrient rich Scheldt River, Belgium, was quantified in a whole ecosystem 15N labeling experiment. In late summer (September) we added 15N-NH 4 + to the flood water entering a 3477 m2 tidal freshwater marsh

  10. Greater diversification of freshwater than marine parasites of fish.

    Science.gov (United States)

    Poulin, Robert

    2016-04-01

    The species richness of freshwater environments is disproportionately high compared with that of the oceans, given their respective sizes. If diversification rates are higher in freshwaters because they are isolated and heterogeneous, this should apply to parasites as well. Using 14 large datasets comprising 677 species of freshwater and marine fish, the hypothesis that freshwater parasites experience higher rates of diversification than marine ones is tested by contrasting the relative numbers of species per parasite genus between the regional endohelminth faunas of fish in both environments. The relationship between the number of parasite genera and the number of parasite species per host was well described by a power function, in both environments; although the exponent of this function was slightly lower for freshwater parasite faunas than marine ones, the difference was not significant. However, the ratio between the number of parasite species and the number of parasite genera per host species was significantly higher in freshwater fish than in marine ones. These findings suggest fundamental differences between the way parasite faunas diversify in freshwater versus marine habitats, with the independent evolution of conspecific parasite populations in isolated host populations being a more common phenomenon in freshwater environments. Copyright © 2016 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

  11. Page 1 Tropical Freshwater Biology, 7 (1998) 73 - 80 73 ...

    African Journals Online (AJOL)

    fishes from Europe (Wisniewski, 1932; Arme & Owen, 1968) and mong African freshwater fishes (including among others the cichlids and cyprinid fishes) from. Sudan and East Africa (Paperna, 1980). The present report represents the first of such reports on pleurocercosis from Nigerian freshwater fishes. In the present study ...

  12. Collections of freshwater shrimps along the southern coast of South ...

    African Journals Online (AJOL)

    Collections of freshwater shrimps along the southern coast of South Africa. D.J. Coetzee. Abstract. During the period February 1983 to November 1986 a total of 38 rivers along the south-western, southem and eastern Cape coasts and Ciskei were investigated for the occurrence of freshwater shrimps. Five species were ...

  13. North American freshwater mussels: natural history, ecology, and conservation

    Science.gov (United States)

    Wendell R. Haag

    2012-01-01

    Interest in freshwater mussels is growing for two important reasons. First, freshwater mussels are among the most endangered organisms on Earth, and many species are already extinct or face imminent extinction. Their desperate conservation plight has gained intense interest from natural resource agencies, nongovernmental conservation organizations, academia, and...

  14. Recent changes in the freshwater composition east of Greenland

    NARCIS (Netherlands)

    de Steur, L.; Pickart, R.S.; Torres, D.J.; Valdimarsson, H.

    2015-01-01

    Results from three hydrographic surveys across the East Greenland Current between 2011 and 2013 are presented with focus on the freshwater sources. End-member analysis using salinity, d18O, and nutrient data shows that while meteoric water dominated the freshwater content, a significant amount of

  15. Occurrence of digenean larvae in freshwater snails in the Ruvu ...

    African Journals Online (AJOL)

    Occurrence of digenean larvae in freshwater snails in the Ruvu basin, Tanzania. G Nkwengulila, ESP Kigadye. Abstract. A survey was carried out on digenean larvae infecting freshwater snails in five habitats in Dar es Salaam, Ruvu and Morogoro. 9424 snails belonging to 12 species from five families were examined for ...

  16. The rediscovery of the freshwater shrimp Macrobrachium crenulatum in Jamaica

    NARCIS (Netherlands)

    Hunte, Waine

    1979-01-01

    A record of the freshwater shrimps of Jamaica has been provided by Hart (1961b). His study includes taxonomical comments and notes on the locations at which the various species were caught. Since then Holthuis (1963a) has described a new subterranean freshwater shrimp, Troglocubanus jamaicensis,

  17. Tracking salinity intrusions in a coastal forested freshwater wetland system

    Science.gov (United States)

    Anand D. Jayakaran; Thomas M. Williams; William H. Conner

    2016-01-01

    Coastal forested freshwater wetlands are sentinel sites for salinity intrusions associated with large, tidally influenced, storm-driven or drought-induced incursions of estuarine waters into freshwater ecosystems. These incursions may also be exacerbated by rising sea levels associated with climate change.

  18. Culture of the freshwater rotifer, Brachionus calyciflorus , and its ...

    African Journals Online (AJOL)

    This paper attempts to review the principles and procedures involved in the culture of the freshwater rotifer, Brachionus calyciflorus as starter food for most freshwater fish fry. There are several strains of different sizes of this rotifer, thus making them suitable for fry of a variety of sizes. This rotifer can be isolated, continuously ...

  19. Potential impacts of alien freshwater crayfish in South Africa | de ...

    African Journals Online (AJOL)

    The habitat preferences and life history characteristics of four alien species of freshwater crayfish (Cherax tenuimanus, C. destructor, C. quadricarinatus and Procambarus clarkii) are reviewed. The potential impact of these species on South African freshwater ecosystems is assessed and the desirability of allowing their ...

  20. Short Communications: First record of freshwater fish on the Cape ...

    African Journals Online (AJOL)

    During a non-exhaustive survey of freshwater bodies on five islands of the archipelago, the first presence of a freshwater fish was recorded. Using barcoding sequences, the species was identified as the guppy (Poecilia reticulata), a highly invasive species alien to the Cape Verdean Islands. Key words: Cape Verde, guppy, ...