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Sample records for catchment network perspective

  1. Collaborative knowledge in catchment research networks

    NASA Astrophysics Data System (ADS)

    Macleod, Christopher Kit

    2015-04-01

    There is a need to improve the production, sharing and use of collaborative knowledge of catchment systems through networks of researchers, policy makers and practitioners. This requires greater levels of systems based integrative research. In parallel to the growing realization that greater levels of collaborative knowledge in scientific research networks are required, a digital revolution has been taking place. This has been driven primarily by the emergence of distributed networks of computers and standards-based interoperability. The objective of this paper is to present the status and research needs for greater levels of systems based integrative research for the production, sharing and use of collaborative knowledge in catchment research networks. To enable increased levels of integrative research depends on development and application of digital technologies to improve collection, use and sharing of data and devise new knowledge infrastructures. This paper focuses on the requirements for catchment observatories that integrate existing and novel physical, social and digital networks of knowledge infrastructures. To support this focus, I present three leading international examples of collaborative networks of catchment researchers and their development of catchment observatories. In particular, the digital infrastructures they have developed to support collaborative knowledge in catchment research networks. These examples are from North America (NSF funded CUAHSI HIS) and from Europe (UK NERC funded EVOp and the German Helmholtz Association Centers funded TERENO/TEODOOR). These exemplars all supported advancing collaborative knowledge in catchment research networks through the development of catchment observatories. I will conclude by discussing the future research directions required for greater levels of production, sharing and use of collaborative knowledge in catchment research networks based on catchment systems science.

  2. Creating a catchment perspective for river restoration

    NASA Astrophysics Data System (ADS)

    Benda, L.; Miller, D.; Barquín, J.

    2011-03-01

    One of the major challenges in river restoration is to identify the natural fluvial landscape in catchments with a long history of river control. Intensive land use on valley floors often predates the earliest remote sensing: levees, dikes, dams, and other structures alter valley-floor morphology, river channels and flow regimes. Consequently, morphological patterns indicative of the fluvial landscape including multiple channels, extensive floodplains, wetlands, and fluvial-riparian and tributary-confluence dynamics can be obscured, and information to develop appropriate and cost effective river restoration strategies can be unavailable. This is the case in the Pas River catchment in northern Spain (650 km2), in which land use and development have obscured the natural fluvial landscape in many parts of the basin. To address this issue we coupled general principles of hydro-geomorphic processes with computer tools to characterize the fluvial landscape. Using a 5-m digital elevation model, valley-floor surfaces were mapped according to elevation above the channel and proximity to key geomorphic processes. The predicted fluvial landscape is patchily distributed according to topography, valley morphology, river network structure, and fan and terrace landforms. The vast majority of the fluvial landscape in the main segments of the Pas River catchment is presently masked by human infrastructure, with only 15% not impacted by river control structures and development. The reconstructed fluvial landscape provides a catchment scale context to support restoration planning, in which areas of potential ecological productivity and diversity could be targeted for in-channel, floodplain and riparian restoration projects.

  3. Catchments network on badlands around Mediterranean area (RESOBAM)

    NASA Astrophysics Data System (ADS)

    Copard, Yoann; Lebouteiller, Caroline; Regues-Munoz, David; Latron, Jerome; Solé-Benet, Albert; Canton, Yolanda; Nadal-Romero, Estela; Della Seta, Marta; Rossi, Mauro; Capolongo, Domenico; Maquaire, Olivier; Forey, Estelle; Di-Giovanni, Christian; Gallart, Francesc; Delmonte, Maurizio; Vergari, Francesca; Massei, Nicolas; Torri, Dino

    2016-04-01

    Between 2013 and 2014, a network funded by MISTRALS-ENVIMED institution, was born around some instrumented catchments developing a badland-type morphology. This network has grouped 3 countries (France, Spain and Italy) with 12 scientific labs. RESOBAM has concerned two sites in France (Draix-Bléone and Vaches Noires), three in Spain (Vallcebre, Araguas and El Cautivo) and some sites in Italy (Tuscany, Basilicata). Main goal of this network was to federate the research around badlands at the European scale, by proposing some scientific topics as: sediment and water transports / budget, (bio)geochemical cycles, agricultural (farming), education, restoration, cultural heritage, soil conservation / biodiversity, climatic change etc. Other main interests were also to propose some common scientific projects and the development of students exchanges. This communication presents the synthesis of our four meetings held at Draix, Zaragoza, Almeriá and Rouen and some perspectives to continue this network.

  4. Creating a catchment scale perspective for river restoration

    NASA Astrophysics Data System (ADS)

    Benda, L.; Miller, D.; Barquín, J.

    2011-09-01

    One of the major challenges in river restoration is to identify the natural fluvial landscape in catchments with a long history of river control. Intensive land use on valley floors often predates the earliest remote sensing: levees, dikes, dams, and other structures alter valley-floor morphology, river channels and flow regimes. Consequently, morphological patterns indicative of the fluvial landscape including multiple channels, extensive floodplains, wetlands, and fluvial-riparian and tributary-confluence dynamics can be obscured, and information to develop appropriate and cost effective river restoration strategies can be unavailable. This is the case in the Pas River catchment in northern Spain (650 km2), in which land use and development have obscured the natural fluvial landscape in many parts of the basin. To address this issue we used computer tools to examine the spatial patterns of fluvial landscapes that are associated with five domains of hydro-geomorphic processes and landforms. Using a 5-m digital elevation model, valley-floor surfaces were mapped according to elevation above the channel and proximity to key geomorphic processes. The predicted fluvial landscape is patchily distributed according to hillslope and valley topography, river network structure, and channel elevation profiles. The vast majority of the fluvial landscape in the main segments of the Pas River catchment is presently masked by human infrastructure, with only 15% not impacted by river control structures and development. The reconstructed fluvial landscape provides a catchment scale context to support restoration planning, in which areas of potential ecological productivity and diversity could be targeted for in-channel, floodplain and riparian restoration projects.

  5. Neural networks forecast in small catchments with transfer of network parameters

    NASA Astrophysics Data System (ADS)

    Maca, P.; Havlicek, V.; Hermanovsky, M.; Horacek, S.; Pech, P.

    2009-04-01

    This contribution deals with neural network approach for short term forecast on small catchments. The applied methodology is based on theory of multilayer perceptron (MLP), feed forward neural network with back propagation optimization procedure was tested in order to explore the possibilities to transfer parameters between different catchments. Supervised optimization of network parameters and structure was investigated. A software tool was created for these research and operative purposes. The hourly discharges and rainfall data of real flood events served as an input to MLP. Seven catchments with areas, which range from 10 to 250 square kilometres and which are situated in the east part of the Czech Republic, were selected. The input data were normalized by parametric method. Variable configuration of neural network was tested in number of modes represented by different combination of learning and testing data sets. The analysis focuses on ability of the model to forecast the flood event with different peak discharge magnitudes. This should be achieved in both application steps - MLP learning and testing within given catchment and in step of parameter transfer of well learned network to another catchment. The length of prediction ranged from one hour to six hours ahead. The results showed that the model is capable to provide satisfying short term discharge forecast for the most of studied cases, including successful parameter transfer among different catchments. This was accomplished by using optimization of parameters which determine not only the structure and behaviour of applied network but also the transformation of input data.

  6. Collaborative Catchment-Scale Water Quality Management using Integrated Wireless Sensor Networks

    NASA Astrophysics Data System (ADS)

    Zia, Huma; Harris, Nick; Merrett, Geoff

    2013-04-01

    collaborative information sharing can have a direct influence on agricultural practice. We apply a nutrient management scheme to a model of an example catchment with several individual networks. The networks are able to correlate catchment events to events within their zone of influence, allowing them to adapt their monitoring and control strategy in light of wider changes across the catchment. Results indicate that this can lead to significant reductions in nutrient losses (up to 50%) and better reutilization of nutrients amongst farms, having a positive impact on catchment scale water quality and fertilizer costs. 1. EC, E.C., Directive 2000/60/EC establishing a framework for Community action in the field of water policy, 2000. 2. Rivers, M., K. Smettem, and P. Davies. Estimating future scenarios for farm-watershed nutrient fluxes using dynamic simulation modelling-Can on-farm BMPs really do the job at the watershed scale? in Proc.29th Int.Conf System Dynamics Society, 2011. 2010. Washington 3. Liu, C., et al., On-farm evaluation of winter wheat yield response to residual soil nitrate-N in North China Plain. Agronomy Journal, 2008. 100(6): p. 1527-1534. 4. Kotamäki, N., et al., Wireless in-situ sensor network for agriculture and water monitoring on a river basin scale in Southern Finland: Evaluation from a data user's perspective. Sensors, 2009. 9(4): p. 2862-2883.

  7. Controls of catchments` sub-storage contributions to dynamic water quality patterns in the stream network

    NASA Astrophysics Data System (ADS)

    Schuetz, Tobias; Maike Hegenauer, Anja

    2016-04-01

    Water quality is usually observed either continuously at a few stations within a catchment or with few snapshot sampling campaigns throughout the whole stream network. Although we know that the depletion of catchment sub-storages can vary throughout the stream network according to their actual water content (spatial variability of actual storage conditions can be caused amongst others by unevenly distributed rainfall, storage size or spatial differences in soil characteristics and land use), we know little about the impact of this process on spatial water quality patterns. For summer low flow recession periods, when stream water composition can be crucial for aquatic ecosystem conditions and the exceedance of water quality thresholds, knowledge on the controls of the dynamic interplay of catchment storages and stream water composition might improve water quality management and the implementation of corresponding mitigation measures. We studied this process throughout the stream network of a first-order agricultural headwater catchment in south-western Germany during two summer low flow recession periods. The underlying geology of the study area is a deep layer of aeolian loess, whilst the dominating soil is a silty calcaric regosol with gleizations in the colluvium. The land use in the catchment is dominated by viniculture (63 %) and arable crops (18 %). Due to the dense drainpipe network within the catchment we could identify 12 sub-catchments contributing during summer low flow recession periods to total stream discharge. We continuously observed discharge, electrical conductivity and water temperatures for 8 of the sub-catchments and at the catchment outlet. This data set was accomplished by 10 snapshot campaigns where we sampled for water temperatures, electrical conductivity, major ions, pH and O2 throughout the stream network. Using either discharge concentration relationships or time dependent functions, we derived continuous export rates for all measures in

  8. Connectivity of overland flow by drainage network expansion in a rain forest catchment

    NASA Astrophysics Data System (ADS)

    Zimmermann, Beate; Zimmermann, Alexander; Turner, Benjamin L.; Francke, Till; Elsenbeer, Helmut

    2014-02-01

    Soils in various places of the Panama Canal Watershed feature a low saturated hydraulic conductivity (Ks) at shallow depth, which promotes overland-flow generation and associated flashy catchment responses. In undisturbed forests of these areas, overland flow is concentrated in flow lines that extend the channel network and provide hydrological connectivity between hillslopes and streams. To understand the dynamics of overland-flow connectivity, as well as the impact of connectivity on catchment response, we studied an undisturbed headwater catchment by monitoring overland-flow occurrence in all flow lines and discharge, suspended sediment, and total phosphorus at the catchment outlet. We find that connectivity is strongly influenced by seasonal variation in antecedent wetness and can develop even under light rainfall conditions. Connectivity increased rapidly as rainfall frequency increased, eventually leading to full connectivity and surficial drainage of entire hillslopes. Connectivity was nonlinearly related to catchment response. However, additional information on factors such as overland-flow volume would be required to constrain relationships between connectivity, stormflow, and the export of suspended sediment and phosphorus. The effort to monitor those factors would be substantial, so we advocate applying the established links between rain event characteristics, drainage network expansion by flow lines, and catchment response for predictive modeling and catchment classification in forests of the Panama Canal Watershed and in similar regions elsewhere.

  9. Establishment of a hydrological monitoring network in a tropical African catchment: An integrated participatory approach

    NASA Astrophysics Data System (ADS)

    Gomani, M. C.; Dietrich, O.; Lischeid, G.; Mahoo, H.; Mahay, F.; Mbilinyi, B.; Sarmett, J.

    Sound decision making for water resources management has to be based on good knowledge of the dominant hydrological processes of a catchment. This information can only be obtained through establishing suitable hydrological monitoring networks. Research catchments are typically established without involving the key stakeholders, which results in instruments being installed at inappropriate places as well as at high risk of theft and vandalism. This paper presents an integrated participatory approach for establishing a hydrological monitoring network. We propose a framework with six steps beginning with (i) inception of idea; (ii) stakeholder identification; (iii) defining the scope of the network; (iv) installation; (v) monitoring; and (vi) feedback mechanism integrated within the participatory framework. The approach is illustrated using an example of the Ngerengere catchment in Tanzania. In applying the approach, the concept of establishing the Ngerengere catchment monitoring network was initiated in 2008 within the Resilient Agro-landscapes to Climate Change in Tanzania (ReACCT) research program. The main stakeholders included: local communities; Sokoine University of Agriculture; Wami Ruvu Basin Water Office and the ReACCT Research team. The scope of the network was based on expert experience in similar projects and lessons learnt from literature review of similar projects from elsewhere integrated with local expert knowledge. The installations involved reconnaissance surveys, detailed surveys, and expert consultations to identify best sites. First, a Digital Elevation Model, land use, and soil maps were used to identify potential monitoring sites. Local and expert knowledge was collected on flow regimes, indicators of shallow groundwater plant species, precipitation pattern, vegetation, and soil types. This information was integrated and used to select sites for installation of an automatic weather station, automatic rain gauges, river flow gauging stations

  10. Predictive optimal control of sewer networks using CORAL tool: application to Riera Blanca catchment in Barcelona.

    PubMed

    Puig, V; Cembrano, G; Romera, J; Quevedo, J; Aznar, B; Ramón, G; Cabot, J

    2009-01-01

    This paper deals with the global control of the Riera Blanca catchment in the Barcelona sewer network using a predictive optimal control approach. This catchment has been modelled using a conceptual modelling approach based on decomposing the catchments in subcatchments and representing them as virtual tanks. This conceptual modelling approach allows real-time model calibration and control of the sewer network. The global control problem of the Riera Blanca catchment is solved using a optimal/predictive control algorithm. To implement the predictive optimal control of the Riera Blanca catchment, a software tool named CORAL is used. The on-line control is simulated by interfacing CORAL with a high fidelity simulator of sewer networks (MOUSE). CORAL interchanges readings from the limnimeters and gate commands with MOUSE as if it was connected with the real SCADA system. Finally, the global control results obtained using the predictive optimal control are presented and compared against the results obtained using current local control system. The results obtained using the global control are very satisfactory compared to those obtained using the local control. PMID:19700825

  11. Why Network? Theoretical Perspectives on Networking

    ERIC Educational Resources Information Center

    Muijs, Daniel; West, Mel; Ainscow, Mel

    2010-01-01

    In recent years, networking and collaboration have become increasingly popular in education. However, there is at present a lack of attention to the theoretical basis of networking, which could illuminate when and when not to network and under what conditions networks are likely to be successful. In this paper, we will attempt to sketch the…

  12. Catchment sediment flux: a lake sediment perspective on the onset of the Anthropocene?

    NASA Astrophysics Data System (ADS)

    Chiverrell, Richard

    2014-05-01

    Definitions of the Anthropocene are varied but from a geomorphological perspective broadly can be described as the interval of recent Earth history during which 'humans have had an 'overwhelming' effect on the Earth system' (Brown et al., 2013). Identifying the switch to a human-dominated geomorphic process regime is actually a challenging process, with in the 'Old World' ramping up of human populations and impacts on earth surface processes since the Neolithic/Mesolithic transition and the onset of agriculture. In the terrestrial realm lakes offer a unique window on changes in human forcing of earth surface processes from a sedimentary flux perspective, because unlike alluvial and hill-slope systems sedimentation is broadly continuous and uninterrupted. Dearing and Jones (2003) showed for a global dataset of lakes a 5-10 fold increase in sediment delivery comparing pre- and post-anthropogenic disturbance. Here sediment records from several lakes in lowland agricultural landscapes are presented to examine the changes in the flux and composition of materials delivered from their catchments. By definition the lakes record the switch to a human dominated system, but not necessary in accelerated sediment accumulation rates with changes in sediment composition equally important. Data from Crose, Hatch and Peckforton Meres, in lowland northwest England are interrogated producing quantitative land-cover reconstructions from pollen spectra calculated using the REVEALS model (Sugita, 2007), geochemical evidence for changes sediment provenance and flux, and 14C and stable Pb pollutant based chronological models detecting changes in sediment accumulation rate. The lake sediment geochemistry points to several phases of heightened human impact within these small agricultural catchments. Following small-in-scale forest cover reductions and limited impacts in terms of sediment flux during the Neolithic, the Bronze to Iron Age saw the first substantial reductions in forest cover

  13. Characteristics of nitrogen retention along the river network of upper Xin'anjiang catchment in China

    NASA Astrophysics Data System (ADS)

    Wang, A.; Yang, D.; Tang, L.

    2014-12-01

    Nitrogen (N) originates mainly from the non-point source (NPS) in the headwaters of many rivers. Understanding the nitrogen retention characteristics along the river network is important for land management in order to implement water resources protection. This study employs a geomorphology based non-point source pollution (GBNP) model to simulate the hillslope hydrological processes, sediment and pollutants transportation in the upper Xin'anjiang catchment in recent 10 years from 2001 to 2010. Calibration and validation of the GBNP model are carried out carefully using the observed discharge, sediment and total nitrogen (TN) concentrations at several hydrological gauges, and then the simulated results of the whole catchment are used to analyze the spatial and temporal distribution of nitrogen along the river networks with emphasis on its retention characteristics. The simulated results indicate that annual TN loaded from the hillslopes in the study catchment ranges from nearly 4000 ton to 11,000 ton and relatively higher TN load occurred in spring and summer. Average TN loads from hillslopes have significant positive correlation with the irrigated-cropland area (correlation coefficient =0.820), and significant negative correlation with the area of forest and grassland (correlation coefficient =-0.427 and -0.246). Seasonal nitrogen retention ratio in the river networks of study catchment in last 10 years varies from 0%-81%, and the streams of order 1 in the Horton-Strahler ordering system has the highest retention ratio and is followed by order 2, order 3 and order 4. The results also indicate that nitrogen retention ratio has positive correlation with river length and negative correlation with discharge and velocity. Scenario analysis of fertilizer application demonstrates that the nitrogen retention ratio increases logarithmically with the TN load and reach a maximum value rapidly.

  14. Estimation of regional recharge in the HOBE catchment using data from a distributed soil moisture network

    NASA Astrophysics Data System (ADS)

    Andreasen, M.; Andreasen, L. A.; Bircher, S.; Sonnenborg, T.; Jensen, K. H.

    2012-12-01

    The regional variation of recharge of ground water is dependent on a larger number of variables and conditions and is therefore difficult to quantify. In this study we have estimated regional recharge using data from a distributed network of soil moisture stations within the HOBE catchment. The network has been designed in an arrangement of three clusters along a long-term precipitation gradient and the stations have been distributed according to respective fractions of classes combining the prevailing land use, top- and subsoil conditions. At each of the 30 stations water content has been measured at three depths (0-5cm, 20-25cm and 50-55cm) for the period 2009-2011 at a temporal resolution of 30 minutes. The 1D soil-plant-atmosphere system model DAISY has been applied to each of the field locations to simulate the water balance of the root zone and the associated components of evapotranspiration and recharge. The 30 models have been formulated and parameterized using specific information on local climate, soil texture, land use and management. Each model was calibrated to the measured soil water content from the distributed network using the PEST (Parameter ESTimation) software. The calibrated parameters were saturated hydraulic conductivity Ks and van Genuchten parameter n as they were found most sensitive. The 30 sets of results were averaged to represent the mean conditions of the catchment. An effective parameterization was also determined by calibration against mean soil moisture and compared to the results obtained by using effective parameters using various averaging methods. The regional variation in groundwater recharge, actual evapotranspiration and soil water content in the catchment was dependent on land use. The simulated results showed that the largest recharge was found at the agricultural sites (554 mm/yr) and the lowest at the forested sites (257 mm/yr). Correspondingly, the highest actual evapotranspiration was found at the forested sites (614

  15. A social network approach to analyzing water governance: The case of the Mkindo catchment, Tanzania

    NASA Astrophysics Data System (ADS)

    Stein, C.; Ernstson, H.; Barron, J.

    The governance dimension of water resources management is just as complex and interconnected as the hydrological processes it aims to influence. There is an increasing need (i) to understand the multi-stakeholder governance arrangements that emerge from the cross-scale nature and multifunctional role of water; and (ii) to develop appropriate research tools to analyze them. In this study we demonstrate how social network analysis (SNA), a well-established technique from sociology and organizational research, can be used to empirically map collaborative social networks between actors that either directly or indirectly influence water flows in the Mkindo catchment in Tanzania. We assess how these collaborative social networks affect the capacity to govern water in this particular catchment and explore how knowledge about such networks can be used to facilitate more effective or adaptive water resources management. The study is novel as it applies social network analysis not only to organizations influencing blue water (the liquid water in rivers, lakes and aquifers) but also green water (the soil moisture used by plants). Using a questionnaire and semi-structured interviews, we generated social network data of 70 organizations, ranging from local resource users and village leaders, to higher-level governmental agencies, universities and NGOs. Results show that there is no organization that coordinates the various land and water related activities at the catchment scale. Furthermore, an important result is that village leader play a crucial role linking otherwise disconnected actors, but that they are not adequately integrated into the formal water governance system. Water user associations (WUAs) are in the process of establishment and could bring together actors currently not part of the formal governance system. However, the establishment of WUAs seems to follow a top-down approach not considering the existing informal organization of water users that are revealed

  16. Catchment organisation, free energy dynamics and network control on critical zone water flows

    NASA Astrophysics Data System (ADS)

    Zehe, E.; Ehret, U.; Kleidon, A.; Jackisch, C.; Scherer, U.; Blume, T.

    2012-04-01

    From a functional point of view the catchment system is compiled by patterns of permeable and less permeable textural elements - soils and mother rock. Theses textural elements provide a mechanical stabile matrix for growth of terrestrial biota and soil formation. They furthermore organize subsurface storage of water against gravity, dissolved nutrients and heat. Storage against gravity is only possible because water acts as wetting fluid and is thus attracted by capillary forces in the pores space. Capillarity increases non-linearly with decreasing pore size and is zero at local saturation. The pore size distribution of a soil is thus characteristic of its capability to store water against losses such as drainage, evaporation and root extraction and at the same time a fingerprint of the work that has been performed by physical, chemical and biological processes to weather solid mother rock and form a soil. A strong spatial covariance of soil hydraulic properties within the same soil type is due to a fingerprint of strong spatial organization at small scales. Spatial organization at the hillslope scale implies the existence of a typical soil catena i.e. that hillslopes exhibit the same/ downslope sequence of different soils types. Textural storage elements are separated by strikingly self-similar network like structures, we name them flow structures. These flow structures are created in a self-reinforcing manner by work performed either by biota like earth worms and plant roots or by dissipative processes such as soil cracking and water/fluvial erosion. Regardless of their different origin connected flow structures exhibit a highly similar functioning and similar characteristics: they allow for high mass flows at small driving potential gradients because specific flow resistance along the network is continuously very small. This implies temporal stability even during small extremes, due to the small amount of local momentum dissipation per unit mass flow, as well

  17. Influence of catchment vegetation on mercury accumulation in lake sediments from a long-term perspective.

    PubMed

    Rydberg, Johan; Rösch, Manfred; Heinz, Emanuel; Biester, Harald

    2015-12-15

    Organic matter (OM) cycling has a large impact on the cycling of mercury (Hg) in the environment. Hence, it is important to have a thorough understanding on how changes in, e.g., catchment vegetation - through its effect on OM cycling - affect the behavior of Hg. To test whether shifts in vegetation had an effect on Hg-transport to lakes we investigated a sediment record from Herrenwieser See (Southern Germany). This lake has a well-defined Holocene vegetation history: at ~8700years BP Corylus avellana (hazel) was replaced by Quercus robur (oak), which was replaced by Abies alba (fir) and Fagus sylvatica (beech) ~5700years BP). We were particularly interested in testing if coniferous vegetation leads to a larger export of Hg to aquatic systems than deciduous vegetation. When hazel was replaced by oak, reduced soil erosion and increased transport of DOM-bound mercury from the catchment resulted in increases in both Hg-concentrations and accumulation rates (61ngg(-1) and 5.5ngcm(-2)yr.(-)(1) to 118ngg(-1) and 8.5ngcm(-2)yr.(-)(1)). However, even if Hg-concentrations increased also in association with the introduction of fir and beech (173ngg(-1)), as a result of higher Hg:C, there was no increase in Hg-accumulation rates (7.6ngcm(-2)yr.(-)(1)), because of a decreased input of OM. At around 2500years BP Hg-accumulation rates and Hg-concentration indicated an additional input of Hg to the sediment (316ngg(-1) and 10.3ngcm(-2)yr.(-)(1)), which might be due to increased human activities in the area, e.g., forest burning or mining. Our results contrast those of several paired-catchment studies that suggest a higher release of Hg from coniferous than deciduous forest, and there is a need for studies with a long-term perspective to increase our understanding of the effects of slow and gradual processes on mercury cycling. PMID:26363145

  18. Effects of a network of sand-storage dams on the hydrology on catchment scale

    NASA Astrophysics Data System (ADS)

    Ertsen, Maurits; Strohschein, Paul; Onencan, Abby; van de Giesen, Nick

    2015-04-01

    Water conservation is a high priority in the drier areas of sub-Saharan Africa. Storage of water from the rainy season to the dry season, or even from wet years to dry years is highly important. Small multi-purpose sub-surface water reservoirs recharged through infiltration are used to provide water for humans, livestock and crops in the Kitui region in Kenya. The groundwater dams obstruct the natural flow of water in wet seasons or periods, and provide storage of water during dry seasons or periods. This paper links the hydrology of the sand-storage dams to human agency. When is a dam a success in hydrological terms? When it provides water every year? Every two years? How many months? What happens in very dry years? Obviously, water use will decrease the water volume and thus the water level upstream of the dam, but to what extent typically depends on the amounts used compared to the size of the dam and the water use itself. Longer-term effects on groundwater levels to be expected depend strongly on the way the water is used. Household water use and river banks infiltration increasing seasonal storage can go hand in hand. However, when water in dams is used for higher water demanding activities such as (motorized) irrigation, the infiltration effect into banks may be minimal. A dam can also be "too effective" and decrease water availability for water users further downstream. It is unlikely, however, that an individual farmer will effect on the downstream users of the resources he/she is tapping, but a network of dams as in Kitui may have considerable effect. Measurements indicate that only about 2% to 3% of the total yearly runoff within the catchment directly associated with a single dam is stored in its reservoir. Therefore only this small percentage of the total flow of a seasonal river with dams is blocked. The paper will detail these general concepts with a case study of the Kiindu catchment. The hydrology of the Kiindu catchment is dependent on different

  19. Applying the Fuzzy ARTMAP neural network for mapping erosive status in the Ria Formosa catchment (Portugal)

    NASA Astrophysics Data System (ADS)

    Granja Martins, F. M.; Neto Paixão, H. M.; Jordán, A.; Zavala, L. M.; Bellinfante, N.

    2012-04-01

    The study of the soil erosion risk is the starting point for development and sustainable land management. The intensity of soil erosion risk is conditioned by soil erodibility, slope, land use and vegetation cover. The objective of this work is mapping the erosive status of the Ria Formosa catchment using "Fuzzy ARTMAP" neural network. The study area is the catchment of Ria Formosa, which includes a shallow coastal lagoon with an area of about 16000 ha located in Algarve (southern Portugal). It is protected by EU and national laws, and is classified as a wetland of international importance under the RAMSAR convention. Previously to the construction of the artificial neuronal network model, it was necessary to establish the training areas (< 1% of total study area) in order to get information about lithofacies, land use, slope and the percentage of vegetation cover. These variables were assessed by supervised classification. Five classes of erosive status were obtained by the artificial neuronal network. These classes were compared with the map of erosive status elaborated with the methodology proposed by the Priority Action Plan/Regional Activity Centre (PAP/RAC, 1997). The differences between both methods were about 1% of the total area. Both maps were validated with field observations and analysis of aerial photographs.

  20. Psychology and social networks: a dynamic network theory perspective.

    PubMed

    Westaby, James D; Pfaff, Danielle L; Redding, Nicholas

    2014-04-01

    Research on social networks has grown exponentially in recent years. However, despite its relevance, the field of psychology has been relatively slow to explain the underlying goal pursuit and resistance processes influencing social networks in the first place. In this vein, this article aims to demonstrate how a dynamic network theory perspective explains the way in which social networks influence these processes and related outcomes, such as goal achievement, performance, learning, and emotional contagion at the interpersonal level of analysis. The theory integrates goal pursuit, motivation, and conflict conceptualizations from psychology with social network concepts from sociology and organizational science to provide a taxonomy of social network role behaviors, such as goal striving, system supporting, goal preventing, system negating, and observing. This theoretical perspective provides psychologists with new tools to map social networks (e.g., dynamic network charts), which can help inform the development of change interventions. Implications for social, industrial-organizational, and counseling psychology as well as conflict resolution are discussed, and new opportunities for research are highlighted, such as those related to dynamic network intelligence (also known as cognitive accuracy), levels of analysis, methodological/ethical issues, and the need to theoretically broaden the study of social networking and social media behavior. (PsycINFO Database Record (c) 2014 APA, all rights reserved). PMID:24750076

  1. Catchment organisation, free energy dynamics and network control on critical zone water flows

    NASA Astrophysics Data System (ADS)

    Zehe, E.; Ehret, U.; Kleidon, A.; Jackisch, C.; Scherer, U.; Blume, T.

    2012-04-01

    From a functional point of view the catchment system is compiled by patterns of permeable and less permeable textural elements - soils and mother rock. Theses textural elements provide a mechanical stabile matrix for growth of terrestrial biota and soil formation. They furthermore organize subsurface storage of water against gravity, dissolved nutrients and heat. Storage against gravity is only possible because water acts as wetting fluid and is thus attracted by capillary forces in the pores space. Capillarity increases non-linearly with decreasing pore size and is zero at local saturation. The pore size distribution of a soil is thus characteristic of its capability to store water against losses such as drainage, evaporation and root extraction and at the same time a fingerprint of the work that has been performed by physical, chemical and biological processes to weather solid mother rock and form a soil. A strong spatial covariance of soil hydraulic properties within the same soil type is due to a fingerprint of strong spatial organization at small scales. Spatial organization at the hillslope scale implies the existence of a typical soil catena i.e. that hillslopes exhibit the same/ downslope sequence of different soils types. Textural storage elements are separated by strikingly self-similar network like structures, we name them flow structures. These flow structures are created in a self-reinforcing manner by work performed either by biota like earth worms and plant roots or by dissipative processes such as soil cracking and water/fluvial erosion. Regardless of their different origin connected flow structures exhibit a highly similar functioning and similar characteristics: they allow for high mass flows at small driving potential gradients because specific flow resistance along the network is continuously very small. This implies temporal stability even during small extremes, due to the small amount of local momentum dissipation per unit mass flow, as well

  2. From natural to human-dominated floodplains - A Holocene perspective for the Dijle catchment, Belgium

    NASA Astrophysics Data System (ADS)

    Broothaerts, Nils; Verstraeten, Gert; Kasse, Cornelis; Bohncke, Sjoerd; Notebaert, Bastiaan; Vandenberghe, Jef

    2015-04-01

    Floodplain systems underwent important changes in many West and Central European catchments through the late Holocene. To better understand the relation between these landscape changes and human disturbances, geomorphic fieldwork needs to be complemented by quantitative measures of human impact in the landscape. In this study, we provide an holistic discussion in which we combine detailed data on floodplain changes with detailed data on human impact for the Dijle catchment (758 km²), Belgium. Human impact in the catchment was quantified based on statistical analysis of pollen data of six alluvial study sites. The results show that during the Neolithic Period, human impact was nearly absent and floodplains consisted of a strongly vegetated marshy environment where organic material accumulated, which is considered as the natural state of the floodplain. From the Bronze Age onwards, human impact increased and caused an increase in soil erosion and hillslope-floodplain connectivity. Consequently, sediment input in the floodplain system increased and floodplain geoecology changed towards an open floodplain dominated by clastic overbank deposits, mainly as the indirect result of an intensification of agricultural activities. Based on these data, a generalized model of floodplain development is presented: At the scale of the entire Dijle catchment, the gradual changes in floodplain morphology coincided with the gradually increasing human impact in the catchment, which suggests a linearity between the external forcing (human impact) and geomorphic response (floodplain change). However, at the narrow floodplains in the headwaters, the gradual increase in human impact contrasts with the abrupt change in floodplain geoecology, only triggered when human impact reached a threshold. Observed differences at catchment scale in time-lags and in the process-response model are attributed to differences in hillslope-floodplain connectivity, the location within the catchment and to

  3. Design and performance of a wireless sensor network for catchment-scale snow and soil moisture measurements

    NASA Astrophysics Data System (ADS)

    Kerkez, Branko; Glaser, Steven D.; Bales, Roger C.; Meadows, Matthew W.

    2012-09-01

    A wireless sensor network (WSN) was deployed as part of a water balance instrument cluster across a forested 1 km2headwater catchment in the southern Sierra Nevada of California. The network, which integrates readings from over 300 sensors, provides spatially representative measurements of snow depth, solar radiation, relative humidity, soil moisture, and matric potential. The ability of this densely instrumented watershed to capture catchment-scale snow depth and soil moisture distributions is investigated through comparison with three comprehensive gridded surveys and 1 day of detailed lidar snow data. Statistical analysis shows that the network effectively characterized catchment-wide distributions of snow depth, while offering a cost-effective, reliable, and energy-efficient means for collecting distributed data in real time. A temporal analysis of snow depth variability reveals that canopy cover is the major explanatory variable of snow depth and that under-canopy measurements persistently show higher variability compared to those in open terrain. An analysis of soil moisture shows lower variability at deeper soil depth and a correlation between mean soil moisture and variability for shallow soils. A three-phase design procedure was used to optimize the WSN deployment. First, as off-the-shelf performance of current WSN platforms for large-scale, long-term deployments cannot be guaranteed, statistics from a prototype deployment were analyzed. Two indicators of network performance, the packet delivery ratio and received signal strength indicator, showed that for our site conditions, a conservative 50 m node-to-node spacing would ensure low-power, reliable, and robust network communications. Second, results from the prototype were used to refine hardware specifications and to guide the layout of the full 57-node wireless network. Of these nodes, 23 were used actively for sensing, while the remaining 34 nodes were used as signal repeaters to ensure proper spatial

  4. Karst catchments exhibited higher degradation stress from climate change than the non-karst catchments in southwest China: An ecohydrological perspective

    NASA Astrophysics Data System (ADS)

    Liu, Meixian; Xu, Xianli; Wang, Dingbao; Sun, Alexander Y.; Wang, Kelin

    2016-04-01

    Karst landform represents about 10% of the continental area and plays key roles in water supplies for almost a quarter of the global population. Knowledge of ecohydrological responses of karst landform to climate change is critical for both water resources management and ecological protection in these regions. This study investigated the effects of karst landform on the elasticity of actual evapotranspiration (derived by the Budyko equation), estimated the contribution of climate change and evaluated the implications, on the basis of 13 typical catchments that have different karst landform coverages in southwest China. Catchment properties, including the vegetation coverage, portion of karst landform (POK), drainage area, surface roughness, mean topographic wetness index, mean slope, and mean aspect, were selected to test the influencing factors for the elasticity of actual evapotranspiration. Results indicate that POK is the most influencing factor for the elasticity of actual evapotranspiration in this region. Moreover, the actual evapotranspiration in karst catchments is more sensitive to precipitation change and less sensitive to the potential evapotranspiration change than that in the non-karst catchments. On the other hand, the contribution of climate change to actual evapotranspiration was generally negative in this region. Furthermore, relatively large negative contributions mainly occurred in the karst-dominated catchments, suggesting that the karst catchments were exposed to higher degradation stress brought by the climate change than that in non-karst catchments.

  5. Calibration of a catchment scale cosmic-ray probe network: A comparison of three parameterization methods

    NASA Astrophysics Data System (ADS)

    Baatz, R.; Bogena, H. R.; Hendricks Franssen, H.-J.; Huisman, J. A.; Qu, W.; Montzka, C.; Vereecken, H.

    2014-08-01

    The objective of this work was to assess the accuracy of soil water content determination from neutron flux measured by cosmic-ray probes under humid climate conditions. Ten cosmic-ray probes were set up in the Rur catchment located in western Germany, and calibrated by gravimetric soil sampling campaigns. Aboveground biomass was estimated at the sites to investigate the role of vegetation cover on the neutron flux and the calibration procedure. Three parameterization methods were used to generate site-specific neutron flux - soil water content calibration curves: (i) the N0-method, (ii) the hydrogen molar fraction method (hmf-method), and (iii) the COSMIC-method. At five locations, calibration measurements were repeated to evaluate site-specific calibration parameters obtained in two different sampling campaigns. At two locations, soil water content determined by cosmic-ray probes was evaluated with horizontally and vertically weighted soil water content measurements of two distributed in situ soil water content sensor networks. All three methods were successfully calibrated to determine field scale soil water content continuously at the ten sites. The hmf-method and the COSMIC-method had more similar calibration curves than the N0-method. The three methods performed similarly well in the validation and errors were within the uncertainty of neutron flux measurements despite observed differences in the calibration curves and variable model complexity. In addition, we found that the obtained calibration parameters NCOSMIC, N0 and NS showed a strong correlation with aboveground biomass.

  6. Malaria transmission modelling: a network perspective

    PubMed Central

    2012-01-01

    Malaria transmission can be affected by multiple or even hidden factors, making it difficult to timely and accurately predict the impact of elimination and eradication programs that have been undertaken and the potential resurgence and spread that may continue to emerge. One approach at the moment is to develop and deploy surveillance systems in an attempt to identify them as timely as possible and thus to enable policy makers to modify and implement strategies for further preventing the transmission. Most of the surveillance data will be of temporal and spatial nature. From an interdisciplinary point of view, it would be interesting to ask the following important as well as challenging question: Based on the available surveillance data in temporal and spatial forms, how can we build a more effective surveillance mechanism for monitoring and early detecting the relative prevalence and transmission patterns of malaria? What we can note from the existing clustering-based surveillance software systems is that they do not infer the underlying transmission networks of malaria. However, such networks can be quite informative and insightful as they characterize how malaria transmits from one place to another. They can also in turn allow public health policy makers and researchers to uncover the hidden and interacting factors such as environment, genetics and ecology and to discover/predict malaria transmission patterns/trends. The network perspective further extends the present approaches to modelling malaria transmission based on a set of chosen factors. In this article, we survey the related work on transmission network inference, discuss how such an approach can be utilized in developing an effective computational means for inferring malaria transmission networks based on partial surveillance data, and what methodological steps and issues may be involved in its formulation and validation. PMID:23849949

  7. What makes catchment management groups "tick"?

    PubMed

    Oliver, P

    2001-01-01

    The work of catchment management groups throughout Australia represents a significant economic and social investment in natural resource management. Institutional structures and policies, the role of on-ground coordinators, facilitation processes, citizen participation and social capital are critical factors influencing the success of catchment management groups. From a participant-researcher viewpoint, this paper signposts research directions and themes that are being pursued from the participant/coordinator, catchment group, and lead government/non-government agency perspective on the influence of these factors on the success of a catchment management group in the Pumicestone Region of Southeast Queensland, Australia. Research directions, themes and discussion/reflection points for practitioners include--the importance of understanding milieu; motivation; success; having fun; "networking networks"; involvement of "nontraditional" stakeholders; development of stakeholder/participant partnerships; learning from other practitioners; methods of stakeholder/participant representation; evaluation; the need for guiding principles or philosophy; the equivalence of planning, implementation, evaluation, and resourcing; catchments as fundamental units of Nature; continuity of support for groups; recognising a new role for government; working with existing networks; and the need for an eclectic approach to natural resource management. PMID:11424936

  8. Dominant mechanisms for the delivery of fine sediment and phosphorus to fluvial networks draining grassland dominated headwater catchments.

    PubMed

    Perks, M T; Owen, G J; Benskin, C McW H; Jonczyk, J; Deasy, C; Burke, S; Reaney, S M; Haygarth, P M

    2015-08-01

    Recent advances in monitoring technology have enabled high frequency, in-situ measurements of total phosphorus and total reactive phosphorus to be undertaken with high precision, whilst turbidity can provide an excellent surrogate for suspended sediment. Despite these measurements being fundamental to understanding the mechanisms and flow paths that deliver these constituents to river networks, there is a paucity of such data for headwater agricultural catchments. The aim of this paper is to deduce the dominant mechanisms for the delivery of fine sediment and phosphorus to an upland river network in the UK through characterisation of the temporal variability of hydrological fluxes, and associated soluble and particulate concentrations for the period spanning March 2012-February 2013. An assessment of the factors producing constituent hysteresis is undertaken following factor analysis (FA) on a suite of measured environmental variables representing the fluvial and wider catchment conditions prior to, and during catchment-wide hydrological events. Analysis indicates that suspended sediment is delivered to the fluvial system predominantly via rapidly responding pathways driven by event hydrology. However, evidence of complex, figure-of-eight hysteresis is observed following periods of hydrological quiescence, highlighting the importance of preparatory processes. Sediment delivery via a slow moving, probably sub-surface pathway does occur, albeit infrequently and during low magnitude events at the catchment outlet. Phosphorus is revealed to have a distinct hysteretic response to that of suspended sediment, with sub-surface pathways dominating. However, high magnitude events were observed to exhibit threshold-like behaviour, whereby activation and connection of usually disconnected depositional zones to the fluvial networks results in the movement of vast phosphorus fluxes. Multiple pathways are observed for particulate and soluble constituents, highlighting the

  9. Linking the levels: network and relational perspectives for community psychology.

    PubMed

    Neal, Jennifer Watling; Christens, Brian D

    2014-06-01

    In this article, we assert that relationships and networks are of paramount importance for understanding and improving settings, neighborhoods, communities, and larger social systems. Despite previous acknowledgements of their relevance, relational and social network perspectives and analyses remain underrepresented in community psychological research and action. Here, we claim that network and relational perspectives can provide conceptual and empirical 'links' between levels of analysis, more fully reflecting a transactional view. We also describe some of the sophisticated methodologies that can be employed in empirical studies drawing on these perspectives. Additionally, we contend that core concepts in community psychology such as health promotion, empowerment, coalition building, and dissemination and implementation can be better understood when employing relational and network perspectives. As an introduction to this special issue of American Journal of Community Psychology, we draw out themes and key points from the articles in the issue, and offer recommendations for future advancement of these perspectives in the field. PMID:24752731

  10. Untangling hydrological pathways and nitrate sources by chemical appraisal in a stream network of a reservoir catchment

    NASA Astrophysics Data System (ADS)

    Yevenes, M. A.; Mannaerts, C. M.

    2012-03-01

    The knowledge of water source contributions to streamflow is important for understanding chemical contamination origins and the status of biogeochemical cycling in stream networks of catchments. In this study, we evaluated whether a limited number of spatially distributed geochemical tracer data sampled during different hydrological seasons were sufficient to quantify water flow pathways and nitrate sources in a catchment. Six geochemical water constituents (δ2H, δ18O, Cl-, SO2-4, Na+, NO-3 and K+) of precipitation, stream water, alluvial sediment pore water and shallow groundwater of a 352 km2 agricultural catchment in the Alentejo region of Portugal were analysed. Exploratory data analysis and end-member mixing analysis (EMMA) were performed to estimate the water source mixing proportions. Residual analysis of principal components was used to identify the appropriate geochemical tracers and the number of end-members (water sources and flow paths), and their proportional contributions to streamflow were quantified. Spearman's rank correlation analysis was further used to identify nitrate origins in the streamflow. Results showed that, when using data from both wet and dry seasons, streamflow chemistry was strongly influenced by shallow groundwater. When only wet season data were modelled, streamflow chemistry was controlled and generated by three end-members: shallow groundwater, alluvial sediment pore water and precipitation. Isotope signatures of stream water were located mostly below the local meteoric water line (LMWL) and plotted along a local evaporation line (LEL), reflecting the permanence in the streamflow of shallow groundwater subjected to prior evaporation. Interpretation of isotope signatures during summer showed an isotopic enrichment in both streamflow and shallow groundwater. Measured and historical stream nitrate concentrations appeared to be strongly related to shallow groundwater. In addition, two hydrochemical data outliers for almost every

  11. Flow simulation and erosion assessment in a ditch network of a drained peatland forest catchment in Eastern Finland

    NASA Astrophysics Data System (ADS)

    Haahti, Kersti; Koivusalo, Harri; Younis, Bassam; Stenberg, Leena

    2014-05-01

    One third of the land area in Finland is covered by peatlands and today 4.5 million ha of peatlands are drained for forestry purposes. In order to sustain forest productivity, ditch networks are maintained annually on an area of approximately 60 000 ha. The suspended solid (SS) load from drained peatland forest sites after ditch network maintenance causes one of the largest strains on the water system by forestry in Finland. Understanding the hydraulic processes in newly maintained ditch networks is necessary for quantifying the SS load generation and transport in the source areas. In this study we developed a hydraulic unsteady-flow model to predict the behavior of flow in a drainage network in a boreal forested peatland site. The input to this model was in the form of a discharge hydrograph that was produced by a hydrological model (FEMMA). The simulations were performed using the algorithm of Zhu et al. (2011) for unsteady flows in a network of channels. In this iterative procedure, the Saint-Venant equations that govern the flow in each of the network channels were solved separately, and the flow depths at the junction-points were corrected using the method of characteristics. The algorithm was programmed using the numeric computing environment MATLAB by MathWorks. Based on the hydraulic conditions produced by the model, erosion risk within the network was evaluated. The model was applied to a peatland catchment drained for forestry in Koivupuro in Eastern Finland (63°53' N, 28°40' E). In August 2011, most of the Koivupuro catchment ditch network was maintained creating simultaneously a smaller nested catchment (area 5.2 ha) which was the focus of this study. The ditch network consisted of 15 branches, altogether 1.6 km in length, and 8 junctions. The model performance was evaluated against flow depth measurements at 5 locations in the network. The simulations in the small ditches of Koivupuro with mostly very low flow rate (< 0.05 m3/s) introduced its

  12. Theoretical perspectives of terrorist enemies as networks.

    SciTech Connect

    Spulak, Robert George, Jr.; Glicken, Jessica

    2005-08-01

    This perspective of terrorist enemies as networks by two distinguished associate fellows of the Joint Special Operations University (JSOU) follows as a result of its recent initiative to support USSOCOM strategic planning for the Global War on Terrorism. The paper is a manifestation of JSOU's goals for contributing products that will advance SOF strategic art and generating strategic outreach to the military, civilian, and academic communities to enrich those products. Dr. Robert Spulak and Dr. Jessica Glicken Turnley presented the findings of this paper to assembled strategic planners from USSOCOM, other combatant commands, and interagency players at the Center for Special Operations plan development conference, September 2005, in Tampa, Florida. At that meeting, the authors put forward a number of helpful planning concepts based on their professional studies in science and the humanities and their experiences in government and business. The JSOU Strategic Studies Department is pleased to facilitate the association of USSOCOM strategic planners with civilian expertise and insights that can broaden military thought and encourage planning decisions directly relevant to the changing global environment. Through JSOU's strategic outreach initiative, experts in many professional disciplines have signaled their willingness to support the Nation's counterterrorism efforts. In that spirit, JSOU is proud to commend this paper to SOF readers and appreciates the support of Dr. Spulak and Dr. Turnley.

  13. Water quality in the Scottish uplands: a hydrological perspective on catchment hydrochemistry.

    PubMed

    Soulsby, C; Gibbins, C; Wade, A J; Smart, R; Helliwell, R

    2002-07-22

    Land above 300 m covers approximately 75% of the surface of Scotland and most of the nation's major river systems have their headwaters in this upland environment. The hydrological characteristics of the uplands exert an important influence on the hydrochemistry of both headwater streams and downstream river systems. Thus, many of the spatial and temporal patterns in the chemical quality of surface waters are mediated by hydrological processes that route precipitation through upland catchments. These hydrological pathways also have an important influence on how the hydrochemistry of upland streams is responding to increasing pressures from environmental changes at the global and regional scales. At the present time, atmospheric deposition remains an issue in many parts of the Scottish uplands, where critical loads of acidity are exceeded, particularly in areas affected by increasing N deposition. Moreover, climatic change forecasts predict increasingly wetter, warmer and more seasonal conditions, which may modify the hydrochemical regimes of many river systems, particularly those with a strong snowmelt component. On a more localised scale, land management practices, including felling of commercial forests, expansion of native woodlands, agricultural decline and moorland management all have implications for the freshwater environment. Moreover, increasing public access to upland areas for a range of recreational activities have implications for water quality. Understanding the hydrology of the uplands, through integrated field and modelling studies, particularly of the hydrological pathways that regulate chemical transfers to streamwaters, will remain an important research frontier for the foreseeable future. PMID:12169013

  14. The logic of participation: critical perspectives on the 'participatory turn' in river and catchment management

    NASA Astrophysics Data System (ADS)

    Lane, Stuart

    2014-05-01

    Both academic research and catchment management practice have now placed considerable emphasis upon the ways in which participation might be used with the objective of improving water management. It is often predicated upon the observation that, historically, water management decisions have been dominated by those who hold certain kinds of expertise, to the detriment of the expertise of others. Participation, then, is a means of opening up decision-making to capture a greater range of those implicated in water management. Scholars of Science Technology Studies have traditionally advocated participation as involving a diversified set of ideals and approaches, ones that are sensitive to the context within which they are practiced and the logics that surround them. But, STS scholars have also argued that as soon as participation, notably participation in a particular form, becomes proscribed, it loses its very raison d'être, that is as a space within which slightly different understandings of a problem may form, grow and take on meaning oustide of the institutional systems of decision-making that all to often dominate our lives. Here I argue that this implies a need to think through what can be called a 'logic of participation' in water management, that is why certain individuals or institutions advocate it, and under what conditions, for whom and with what end. In short, we need a political science analysis of who participation in water management might serve. This paper is motivated by one element of such an analysis linked to the observation that many models of how participation in water management might be done have developed without sufficient attention to the sometimes sophisticated and advanced levels of participation that already exist in many water management systems. Interventions to improve participation in such cases may be as much about displacing and replacing existing participatory systems, whether: intentional, because of concerns held by authorities

  15. Neoformation of clay in lateral root catchments of mallee eucalypts: a chemical perspective

    PubMed Central

    Verboom, William H.; Pate, John S.; Aspandiar, Mehrooz

    2010-01-01

    Background and Aims A previous paper (Annals of Botany 103: 673–685) described formation of clayey pavements in lateral root catchments of eucalypts colonizing a recently formed sand dune in south-west Western Australia. Here chemical and morphological aspects of their formation at the site are studied. Methods Chemical and physical examinations of soil cores through pavements and sand under adjacent heath assessed build-up of salts, clay and pH changes in or below pavements. Relationships of root morphology to clay deposition were examined and deposits subjected to scanning electron microscopy and energy-dispersive X-ray analysis. Xylem transport of mineral elements in eucalypt and non-eucalypt species was studied by analysis of xylem (tracheal) sap from lateral roots. Key Results The columns of which pavements are composed develop exclusively on lower-tier lateral roots. Such sites show intimate associations of fine roots, fungal filaments, microbiota and clay deposits rich in Si, Al and Fe. Time scales for construction of pavements by eucalypts were assessed. Cores through columns of pavemented profiles showed gross elevations of bulk density, Al, Fe and Si in columns and related increases in pH, Mg and Ca status in lower profiles. A cutting through the dune exhibited pronounced alkalinity (pH 7–10) under mallee woodland versus acidity (pH 5–6·5) under proteaceous heath. Xylem sap analyses showed unusually high concentrations of Al, Fe, Mg and Si in dry-season samples from column-bearing roots. Conclusions Deposition of Al–Fe–Si-rich clay is pivotal to pavement construction by eucalypts and leads to profound chemical and physical changes in relevant soil profiles. Microbial associates of roots are likely to be involved in clay genesis, with parent eucalypts supplying the required key mineral elements and carbon sources. Acquisition of the Al and Fe incorporated into clay derives principally from hydraulic uplift from ground water via deeply

  16. Web-based modelling of energy, water and matter fluxes to support decision making in mesoscale catchments??the integrative perspective of GLOWA-Danube

    NASA Astrophysics Data System (ADS)

    Ludwig, R.; Mauser, W.; Niemeyer, S.; Colgan, A.; Stolz, R.; Escher-Vetter, H.; Kuhn, M.; Reichstein, M.; Tenhunen, J.; Kraus, A.; Ludwig, M.; Barth, M.; Hennicker, R.

    The GLOWA-initiative (Global Change of the water cycle), funded by the German Ministry of Research and Education (BMBF), has been established to address the manifold consequences of Global Change on regional water resources in a variety of catchment areas with different natural and cultural characteristics. Within this framework, the GLOWA-Danube project is dealing with the Upper Danube watershed as a representative mesoscale test site (∼75.000 km 2) for mountain-foreland regions in the temperate mid-latitudes. The principle objective is to identify, examine and develop new techniques of coupled distributed modelling for the integration of natural and socio-economic sciences. The transdisciplinary research in GLOWA-Danube develops an integrated decision support system, called DANUBIA, to investigate the sustainability of future water use. GLOWA-Danube, which is scheduled for a total run-time of eight years to operationally implement and establish DANUBIA, comprises a university-based network of experts with water-related competence in the fields of engineering, natural and social sciences. Co-operation with a network of stakeholders in water resources management of the Upper Danube catchment ensures that practical issues and future problems in the water sector of the region can be addressed. In order to synthesize a common understanding between the project partners, a standardized notation of parameters and functions and a platform-independent structure of computational methods and interfaces has been established, by making use of the unified modelling language, an industry standard for the structuring and co-ordination of large projects in software development [Booch et al., The Unified Modelling Language User Guide, Addison-Wesley, Reading, 1999]. DANUBIA is object-oriented, spatially distributed and raster-based at its core. It applies the concept of “proxels” (process pixels) as its basic objects, which have different dimensions depending on the viewing

  17. The logic of participation: critical perspectives on the 'participatory turn' in river and catchment management

    NASA Astrophysics Data System (ADS)

    Lane, Stuart

    2014-05-01

    Both academic research and catchment management practice have now placed considerable emphasis upon the ways in which participation might be used with the objective of improving water management. It is often predicated upon the observation that, historically, water management decisions have been dominated by those who hold certain kinds of expertise, to the detriment of the expertise of others. Participation, then, is a means of opening up decision-making to capture a greater range of those implicated in water management. Scholars of Science Technology Studies have traditionally advocated participation as involving a diversified set of ideals and approaches, ones that are sensitive to the context within which they are practiced and the logics that surround them. But, STS scholars have also argued that as soon as participation, notably participation in a particular form, becomes proscribed, it loses its very raison d'être, that is as a space within which slightly different understandings of a problem may form, grow and take on meaning oustide of the institutional systems of decision-making that all to often dominate our lives. Here I argue that this implies a need to think through what can be called a 'logic of participation' in water management, that is why certain individuals or institutions advocate it, and under what conditions, for whom and with what end. In short, we need a political science analysis of who participation in water management might serve. This paper is motivated by one element of such an analysis linked to the observation that many models of how participation in water management might be done have developed without sufficient attention to the sometimes sophisticated and advanced levels of participation that already exist in many water management systems. Interventions to improve participation in such cases may be as much about displacing and replacing existing participatory systems, whether: intentional, because of concerns held by authorities

  18. Integration of Volterra model with artificial neural networks for rainfall-runoff simulation in forested catchment of northern Iran

    NASA Astrophysics Data System (ADS)

    Kashani, Mahsa H.; Ghorbani, Mohammad Ali; Dinpashoh, Yagob; Shahmorad, Sedaghat

    2016-09-01

    Rainfall-runoff simulation is an important task in water resources management. In this study, an integrated Volterra model with artificial neural networks (IVANN) was presented to simulate the rainfall-runoff process. The proposed integrated model includes the semi-distributed forms of the Volterra and ANN models which can explore spatial variation in rainfall-runoff process without requiring physical characteristic parameters of the catchments, while taking advantage of the potential of Volterra and ANNs models in nonlinear mapping. The IVANN model was developed using hourly rainfall and runoff data pertaining to thirteen storms to study short-term responses of a forest catchment in northern Iran; and its performance was compared with that of semi-distributed integrated ANN (IANN) model and lumped Volterra model. The Volterra model was applied as a nonlinear model (second-order Volterra (SOV) model) and solved using the ordinary least square (OLS) method. The models performance were evaluated and compared using five performance criteria namely coefficient of efficiency, root mean square error, error of total volume, relative error of peak discharge and error of time for peak to arrive. Results showed that the IVANN model performs well than the other semi-distributed and lumped models to simulate the rainfall-runoff process. Comparing to the integrated models, the lumped SOV model has lower precision to simulate the rainfall-runoff process.

  19. Temporal Change in Discharge Response in Unregulated Swedish Catchments - Quantifying Potential Effects of Anthropogenic Modifications in Stream Network Properties on Flow Time Distributions

    NASA Astrophysics Data System (ADS)

    Worman, A. L. E.; Åkesson, A. M.; Riml, J.; Seibert, J.

    2015-12-01

    Fourier spectral analysis of daily discharge time-series with a duration of 55-110 years in 79 unregulated catchments revealed that the discharge power spectrum slope has gradually increased (statistically significant at the 99% confidence level) over time. For the locations for which historical meteorological observations is available (the 41 southernmost catchments), the evaluation theoretically accounted for fluctuation in the precipitation power spectrum. The results indicate that (local) land-use changes within the catchments may have a relatively more important role (than climate change) for the temporal changes shown in the discharge power spectra. With a basis in stream network maps from present day in two different resolutions as well as a historical map from the 1880's, anthropogenic modifications, in terms of the flow paths within the stream networks, were identified for an agricultural catchment in southern Sweden. Through scenario modelling using a 1-D distributed routing model, the influence of common anthropogenic activities such as e.g. straightening of flowpaths, widening of stream channels to avoid damming and excavation to eliminate thresholds in the stream bottom topography, on the travel time distributions within a stream network were quantified. The map studies showed that the average flow path length had decreased over the last century. The study also shows that all of the studied anthropogenic factors can potentially have a substantial impact on the travel times through the stream networks - by decreasing the average travel time as well as by decreasing the variance. These types of temporal changes in stream network properties leads to a diminished possibility to attenuate peakflows, and are expected to have a substantial influence on discharge hydrographs. This study verifies the hypothesis that anthropogenic impacts of stream networks can influence the hydrological response in catchments, and that land-use changes on a local scale may be

  20. Information theory perspective on network robustness

    NASA Astrophysics Data System (ADS)

    Schieber, Tiago A.; Carpi, Laura; Frery, Alejandro C.; Rosso, Osvaldo A.; Pardalos, Panos M.; Ravetti, Martín G.

    2016-01-01

    A crucial challenge in network theory is the study of the robustness of a network when facing a sequence of failures. In this work, we propose a dynamical definition of network robustness based on Information Theory, that considers measurements of the structural changes caused by failures of the network's components. Failures are defined here as a temporal process defined in a sequence. Robustness is then evaluated by measuring dissimilarities between topologies after each time step of the sequence, providing a dynamical information about the topological damage. We thoroughly analyze the efficiency of the method in capturing small perturbations by considering different probability distributions on networks. In particular, we find that distributions based on distances are more consistent in capturing network structural deviations, as better reflect the consequences of the failures. Theoretical examples and real networks are used to study the performance of this methodology.

  1. Propagation and stability in software: A complex network perspective

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Wang, Ping

    2015-09-01

    In this paper, we attempt to understand the propagation and stability feature of large-scale complex software from the perspective of complex networks. Specifically, we introduced the concept of "propagation scope" to investigate the problem of change propagation in complex software. Although many complex software networks exhibit clear "small-world" and "scale-free" features, we found that the propagation scope of complex software networks is much lower than that of small-world networks and scale-free networks. Furthermore, because the design of complex software always obeys the principles of software engineering, we introduced the concept of "edge instability" to quantify the structural difference among complex software networks, small-world networks and scale-free networks. We discovered that the edge instability distribution of complex software networks is different from that of small-world networks and scale-free networks. We also found a typical structure that contributes to the edge instability distribution of complex software networks. Finally, we uncovered the correlation between propagation scope and edge instability in complex networks by eliminating the edges with different instability ranges.

  2. Consciousness, cognition and brain networks: New perspectives.

    PubMed

    Aldana, E M; Valverde, J L; Fábregas, N

    2016-10-01

    A detailed analysis of the literature on consciousness and cognition mechanisms based on the neural networks theory is presented. The immune and inflammatory response to the anesthetic-surgical procedure induces modulation of neuronal plasticity by influencing higher cognitive functions. Anesthetic drugs can cause unconsciousness, producing a functional disruption of cortical and thalamic cortical integration complex. The external and internal perceptions are processed through an intricate network of neural connections, involving the higher nervous activity centers, especially the cerebral cortex. This requires an integrated model, formed by neural networks and their interactions with highly specialized regions, through large-scale networks, which are distributed throughout the brain collecting information flow of these perceptions. Functional and effective connectivity between large-scale networks, are essential for consciousness, unconsciousness and cognition. It is what is called the "human connectome" or map neural networks. PMID:26143337

  3. Untangling hydrological pathways and nitrate diffusive sources by chemical appraisal in a stream network of a reservoir catchment

    NASA Astrophysics Data System (ADS)

    Yevenes-Burgos, M. A.; Mannaerts, C. M.

    2011-03-01

    Stable water isotopes and water hydrochemistry of a catchment in the Alentejo region, south Portugal, were analysed to investigate source origins of water and nitrate flows towards a reservoir. The 353 km2 headwater catchment of Roxo river, is strongly influenced by agricultural impacts, and high variations in water and chemical inflows into an important drinking and irrigation water supply (108 m3) are observed. This leads to regular disputes on water quantity and quality amongst local authorities and population. Three sampling campaigns in different seasons were used to address the temporal and spatial variations in stream and groundwater hydrochemistry and water isotopic signatures. A total of 27 sampling points from the stream network, shallow groundwater and reservoir were used. Isotopic signatures and chemistry of precipitation were obtained from local data of the Global Network of Isotopes in Precipitation (GNIP) and the Global Atmosphere Watch (GAWSIS) network. Other meteorological, hydrological and environmental datasets were obtained from local authorities. The stable water isotopes deuterium (δ2H), oxygen-18 (δ18O) together with chloride (Cl-) and sulphate (SO42-) were used as environmental tracers in the hydrological pathways. Water pathways were then related with nitrate concentrations to elucidate potential relationships between the water and nutrient sources. Interpretation of isotope signatures showed a high degree of isotope enrichment in both surface (stream flow) and shallow groundwater. For the entire period, most of stream waters were located right of the global meteoric water line or GMWL and plotted along a local evaporation line (LEL) established for the study area. The LEL showed slopes similar to stream systems in other dry environments. Monthly stream flow and precipitation, seasonal isotope compositions and major ion chemistry data were used for an evaluation of the relative contribution of water sources using an end-member mixing

  4. Viewing Attractiveness Socialization from a Social Network Perspective.

    ERIC Educational Resources Information Center

    Downs, A. Chris

    Providing a framework for a symposium exploring the influence of physical attractiveness on the socialization process, this paper (1) offers a working definition of physical attractiveness, (2) reviews stereotypes associated with attractiveness, and (3) discusses a social network perspective on the influence of attractiveness. Physical…

  5. Water level and response time of rivers during flash floods derived from a nested network in the Claduègne Mediterranean catchment (43 km2)

    NASA Astrophysics Data System (ADS)

    Gonzalez-Sosa, Enrique; Braud, Isabelle; Molinié, Gilles; Nord, Guillaume; Vandervaere, Jean-Pierre; Uber, Magdalana

    2016-04-01

    Flash floods are natural hazards that affect the Mediterranean region. They are caused by intense rainfall events but catchments characteristics are also influential on the hydrological response. In order to study the respective roles of rainfall, land use, geology and soil moisture on this hydrological response at various scales, a high space-time resolution hydrometeorological experimental monitoring system was set in the Mediterranean Claduègne catchment (43 km2), located in the Ardèche catchment, south-east France between 2011 and 2014 (Braud et al., 2014; Nord et al., in prep). Rainfall was monitored using a high resolution rainfall network (Hpiconet) composed of 21 rain gauges with 1 min time step covering an area of about 100 km2. The monitoring of surface hydrology include water level measurements at the outlet of 10 subcatchments ranging from 0.2 to 2.2 km2 and hydrometric measurements (water level, discharge) at the outlet of 3 catchments (Gazel: 3.4 km², SJ1: 12 km² and Claduègne: 43 km²). The 10 subcatchments as well as the Gazel and SJ1 catchments are all embedded within the Claduègne catchments. The location of the 10 subcatchments was chosen to sample different combinations of geology, land use and pedology within the Claduègne catchment. In particular, 4 of these subcathments are located within the Gazel catchment and 2 are located within the SJ1 catchment. Soil moisture data with a 20 minutes time step at depths 10cm, 20-25 and 30-50 cm is also available at nine locations, sampling different combinations of land use and geology. Catchment rainfall was computed from the Hpiconet data for each sub-catchment and all rainfall events using the Thiessen polygons method. The corresponding hydrological response was extracted for the whole data sets. For each event, rainfall characteristics describing rainfall amount and intensity, antecedent rainfall (and thus initial soil moisture) were computed. When a hydrological response was observed, reaction

  6. Animal welfare: a social networks perspective.

    PubMed

    Kleinhappel, Tanja K; John, Elizabeth A; Pike, Thomas W; Wilkinson, Anna; Burman, Oliver H P

    2016-01-01

    Social network theory provides a useful tool to study complex social relationships in animals. The possibility to look beyond dyadic interactions by considering whole networks of social relationships allows researchers the opportunity to study social groups in more natural ways. As such, network-based analyses provide an informative way to investigate the factors influencing the social environment of group-living animals, and so has direct application to animal welfare. For example, animal groups in captivity are frequently disrupted by separations, reintroductions and/or mixing with unfamiliar individuals and this can lead to social stress and associated aggression. Social network analysis ofanimal groups can help identify the underlying causes of these socially-derived animal welfare concerns. In this review we discuss how this approach can be applied, and how it could be used to identify potential interventions and solutions in the area of animal welfare. PMID:27120815

  7. A mountain environmental virtual observatory (Mountain-EVO) to support participatory monitoring in a network of Andean catchments

    NASA Astrophysics Data System (ADS)

    Buytaert, Wouter; Ochoa Tocachi, Boris; De Bievre, Bert; Zulkafli, Zed

    2015-04-01

    The tropical Andes are a hotspot of environmental change. The combination of dramatic land-use change with global climate change, demographic growth, and increasing water demand is causing extreme pressures on water resources. This is of particular concern to rural upland communities. They are facing a double challenge of maintaining their own livelihoods with dwindling natural resources, and at the same time supporting downstream ecosystem services such as a well buffered stream flow and good water quality. This challenge is complicated further by the acute lack of data on the hydrological functioning of Andean catchments. The factors controlling their hydrological response are extremely variable in space and time, including meteorological forcing, land cover types, soil properties and geology. This makes it very difficult to predict accurately the impact of human activities such as land use, ecosystem management, and watershed investments. Such predictions are essential for policy-making and sustainable ecosystem management. To tackle the issue of hydrological data scarcity in the tropical Andes, an initiative was set up to implement a network of hydrological monitoring of upland catchments in a pairwise fashion. Using a trading-space-for-time approach, the initiative intends to use these data to improve predictions about the impact of land-use changes and other ecosystem management practices on the hydrological response. Currently, over 25 catchments are being monitored for precipitation and streamflow in 9 sites located in Bolivia, Peru, Ecuador, and Venezuela. The sites are supported by local stakeholders and communities in a participatory monitoring scheme that otherwise would be impractical or prohibitively expensive. To overcome the technical challenges of monitoring hydrological variables in remote mountain areas, the initiative has set up a web-based infrastructure to support local technicians and stakeholders. Additionally, using open data standards such

  8. Link Prediction in Complex Networks: A Mutual Information Perspective

    PubMed Central

    Tan, Fei; Xia, Yongxiang; Zhu, Boyao

    2014-01-01

    Topological properties of networks are widely applied to study the link-prediction problem recently. Common Neighbors, for example, is a natural yet efficient framework. Many variants of Common Neighbors have been thus proposed to further boost the discriminative resolution of candidate links. In this paper, we reexamine the role of network topology in predicting missing links from the perspective of information theory, and present a practical approach based on the mutual information of network structures. It not only can improve the prediction accuracy substantially, but also experiences reasonable computing complexity. PMID:25207920

  9. Some Perspectives on Network Modeling in Therapeutic Target Prediction

    PubMed Central

    Albert, Reka; DasGupta, Bhaskar; Mobasheri, Nasim

    2013-01-01

    Drug target identification is of significant commercial interest to pharmaceutical companies, and there is a vast amount of research done related to the topic of therapeutic target identification. Interdisciplinary research in this area involves both the biological network community and the graph algorithms community. Key steps of a typical therapeutic target identification problem include synthesizing or inferring the complex network of interactions relevant to the disease, connecting this network to the disease-specific behavior, and predicting which components are key mediators of the behavior. All of these steps involve graph theoretical or graph algorithmic aspects. In this perspective, we provide modelling and algorithmic perspectives for therapeutic target identification and highlight a number of algorithmic advances, which have gotten relatively little attention so far, with the hope of strengthening the ties between these two research communities. PMID:25288898

  10. Modelling dendritic ecological networks in space: anintegrated network perspective

    USGS Publications Warehouse

    Peterson, Erin E.; Ver Hoef, Jay M.; Isaak, Dan J.; Falke, Jeffrey A.; Fortin, Marie-Josée; Jordon, Chris E.; McNyset, Kristina; Monestiez, Pascal; Ruesch, Aaron S.; Sengupta, Aritra; Som, Nicholas; Steel, E. Ashley; Theobald, David M.; Torgersen, Christian E.; Wenger, Seth J.

    2013-01-01

    the context of stream ecology. Within this context, we summarise the key innovations of a new family of spatial statistical models that describe spatial relationships in DENs. Finally, we discuss how different network analyses may be combined to address more complex and novel research questions. While our main focus is streams, the taxonomy of network analyses is also relevant anywhere spatial patterns in both network and 2-D space can be used to explore the influence of multi-scale processes on biota and their habitat (e.g. plant morphology and pest infestation, or preferential migration along stream or road corridors).

  11. A Topological Perspective of Neural Network Structure

    NASA Astrophysics Data System (ADS)

    Sizemore, Ann; Giusti, Chad; Cieslak, Matthew; Grafton, Scott; Bassett, Danielle

    The wiring patterns of white matter tracts between brain regions inform functional capabilities of the neural network. Indeed, densely connected and cyclically arranged cognitive systems may communicate and thus perform distinctly. However, previously employed graph theoretical statistics are local in nature and thus insensitive to such global structure. Here we present an investigation of the structural neural network in eight healthy individuals using persistent homology. An extension of homology to weighted networks, persistent homology records both circuits and cliques (all-to-all connected subgraphs) through a repetitive thresholding process, thus perceiving structural motifs. We report structural features found across patients and discuss brain regions responsible for these patterns, finally considering the implications of such motifs in relation to cognitive function.

  12. A Network of Networks Perspective on Global Trade.

    PubMed

    Maluck, Julian; Donner, Reik V

    2015-01-01

    Mutually intertwined supply chains in contemporary economy result in a complex network of trade relationships with a highly non-trivial topology that varies with time. In order to understand the complex interrelationships among different countries and economic sectors, as well as their dynamics, a holistic view on the underlying structural properties of this network is necessary. This study employs multi-regional input-output data to decompose 186 national economies into 26 industry sectors and utilizes the approach of interdependent networks to analyze the substructure of the resulting international trade network for the years 1990-2011. The partition of the network into national economies is observed to be compatible with the notion of communities in the sense of complex network theory. By studying internal versus cross-subgraph contributions to established complex network metrics, new insights into the architecture of global trade are obtained, which allow to identify key elements of global economy. Specifically, financial services and business activities dominate domestic trade whereas electrical and machinery industries dominate foreign trade. In order to further specify each national sector's role individually, (cross-)clustering coefficients and cross-betweenness are obtained for different pairs of subgraphs. The corresponding analysis reveals that specific industrial sectors tend to favor distinct directionality patterns and that the cross-clustering coefficient for geographically close country pairs is remarkably high, indicating that spatial factors are still of paramount importance for the organization of trade patterns in modern economy. Regarding the evolution of the trade network's substructure, globalization is well-expressed by trends of several structural characteristics (e.g., link density and node strength) in the interacting network framework. Extreme events, such as the financial crisis 2008/2009, are manifested as anomalies superimposed to

  13. A Network of Networks Perspective on Global Trade

    PubMed Central

    Maluck, Julian; Donner, Reik V.

    2015-01-01

    Mutually intertwined supply chains in contemporary economy result in a complex network of trade relationships with a highly non-trivial topology that varies with time. In order to understand the complex interrelationships among different countries and economic sectors, as well as their dynamics, a holistic view on the underlying structural properties of this network is necessary. This study employs multi-regional input-output data to decompose 186 national economies into 26 industry sectors and utilizes the approach of interdependent networks to analyze the substructure of the resulting international trade network for the years 1990–2011. The partition of the network into national economies is observed to be compatible with the notion of communities in the sense of complex network theory. By studying internal versus cross-subgraph contributions to established complex network metrics, new insights into the architecture of global trade are obtained, which allow to identify key elements of global economy. Specifically, financial services and business activities dominate domestic trade whereas electrical and machinery industries dominate foreign trade. In order to further specify each national sector’s role individually, (cross-)clustering coefficients and cross-betweenness are obtained for different pairs of subgraphs. The corresponding analysis reveals that specific industrial sectors tend to favor distinct directionality patterns and that the cross-clustering coefficient for geographically close country pairs is remarkably high, indicating that spatial factors are still of paramount importance for the organization of trade patterns in modern economy. Regarding the evolution of the trade network’s substructure, globalization is well-expressed by trends of several structural characteristics (e.g., link density and node strength) in the interacting network framework. Extreme events, such as the financial crisis 2008/2009, are manifested as anomalies superimposed

  14. Network analysis of sediment cascades derived from digital geomorphological maps - a comparative study of three catchments in the Austrian and Swiss Alps

    NASA Astrophysics Data System (ADS)

    Heckmann, Tobias; Hilger, Ludwig; Meßenzehl, Karoline; Hoffmann, Thomas; Schwanghart, Wolfgang; Götz, Joachim; Buckel, Johannes

    2014-05-01

    Sediment fluxes in alpine environments are strongly conditioned by sediment storage, resulting in non-linear feedbacks between sediment input and output. Recently, geomorphological mapping in alpine regions has focused on the static distribution of sediment storage units, neglecting the dynamic links of geomorphic processes units along the sediment pathways. Here we present an approach i) to analyse the sediment connectivity of a catchment based on coupling relationships of neighbouring storage units, and ii) to re-evaluate existing geomorphological maps in terms of the network structure. The approach is applied in three catchments in the European Alps, which were mapped in previous geomorphological studies: i) the Gradenbach catchment (Upper Tauern, Carinthia, Austria), ii) the (upper) Kaunertal (Ötztal Mountains, Tyrolia, Austria) and the Val Müschauns (Engadine, Switzerland). While the morphology of all study areas is predominantly controlled by former glaciations, only the two Austrian areas feature recent glaciers. The available geomorphic maps consist of non-overlapping polygons representing geomorphic process units of erosion, sediment transport and deposition. Mapping was conducted in the field, and supported by digital orthophotos and derivatives of LiDAR-based digital elevation models (slope, curvature, aspect, shaded relief, etc.). Based on the observation of diagnostic features, the geomorphic coupling state of every pair of adjacent landforms, i.e. the existence of sediment transfer across their common boundary, was assessed and mapped. Taking the landforms as nodes, and the inferred coupling relationships as edges, a graph model of the sediment transfer system is established. Graph theory offers a versatile toolbox for the analysis of the spatial structure of sediment cascades in different ways: Nodes are analysed for the number of incoming and outgoing edges, and classified as sediment source, sink, or link. Depending on the spatial and functional

  15. Hospital network performance: a survey of hospital stakeholders' perspectives.

    PubMed

    Bravi, F; Gibertoni, D; Marcon, A; Sicotte, C; Minvielle, E; Rucci, P; Angelastro, A; Carradori, T; Fantini, M P

    2013-02-01

    Hospital networks are an emerging organizational form designed to face the new challenges of public health systems. Although the benefits introduced by network models in terms of rationalization of resources are known, evidence about stakeholders' perspectives on hospital network performance from the literature is scanty. Using the Competing Values Framework of organizational effectiveness and its subsequent adaptation by Minvielle et al., we conducted in 2009 a survey in five hospitals of an Italian network for oncological care to examine and compare the views on hospital network performance of internal stakeholders (physicians, nurses and the administrative staff). 329 questionnaires exploring stakeholders' perspectives were completed, with a response rate of 65.8%. Using exploratory factor analysis of the 66 items of the questionnaire, we identified 4 factors, i.e. Centrality of relationships, Quality of care, Attractiveness/Reputation and Staff empowerment and Protection of workers' rights. 42 items were retained in the analysis. Factor scores proved to be high (mean score>8 on a 10-item scale), except for Attractiveness/Reputation (mean score 6.79), indicating that stakeholders attach a higher importance to relational and health care aspects. Comparison of factor scores among stakeholders did not reveal significant differences, suggesting a broadly shared view on hospital network performance. PMID:23201189

  16. Perspective: network-guided pattern formation of neural dynamics.

    PubMed

    Hütt, Marc-Thorsten; Kaiser, Marcus; Hilgetag, Claus C

    2014-10-01

    The understanding of neural activity patterns is fundamentally linked to an understanding of how the brain's network architecture shapes dynamical processes. Established approaches rely mostly on deviations of a given network from certain classes of random graphs. Hypotheses about the supposed role of prominent topological features (for instance, the roles of modularity, network motifs or hierarchical network organization) are derived from these deviations. An alternative strategy could be to study deviations of network architectures from regular graphs (rings and lattices) and consider the implications of such deviations for self-organized dynamic patterns on the network. Following this strategy, we draw on the theory of spatio-temporal pattern formation and propose a novel perspective for analysing dynamics on networks, by evaluating how the self-organized dynamics are confined by network architecture to a small set of permissible collective states. In particular, we discuss the role of prominent topological features of brain connectivity, such as hubs, modules and hierarchy, in shaping activity patterns. We illustrate the notion of network-guided pattern formation with numerical simulations and outline how it can facilitate the understanding of neural dynamics. PMID:25180302

  17. Youth, friendship, and gaming: a network perspective.

    PubMed

    De Grove, Frederik

    2014-09-01

    With digital games being part of the leisure of a multitude of young people, it is important to understand to what extent gaming-related practices such as talking about games or playing games together are associated with the quality of friendship relations with players and nonplayers. Based on 100 friendship networks, this study explored to what extent those practices permeated the everyday life of youngsters and whether they could be considered as a part of doing friendship. Results indicated that gaming as a conversational topic was widespread within and between networks. Furthermore, regardless of gender, this was significantly associated with friendship quality in almost all of the networks. When considering playing games together, a somewhat different picture emerged. In contrast to conversational practices, playing together was less widespread. Moreover, both the occurrence and the effect of co-play and friendship quality was gendered. The findings of this study show that a focus on gaming-related practices yields a fruitful starting point when considering the role of digital games in a social context that is not limited to people playing (online) games. Furthermore, they also feed into the ongoing debate of possible effects of digital games in that it shows that the way in which games influence the lives of young people goes beyond a direct effects approach. PMID:25127060

  18. Network planning from telecom provider's perspective

    NASA Astrophysics Data System (ADS)

    Zhou, Minli; Chen, Ziqing

    2005-11-01

    The network planner of the incumbent telecom service provider faces a series of challenges following technology developments, riding demand changes and utilizing existing resources. It is believed that the telecom planning that was started from the early time for PSTN deployment has been contributed to the foundation for the telecom planning but does not provide enough methodologies to help today's planning activities. The planning work for the provider must make innovation for adapting to the dynamic environment and supporting business development. In this paper, the situations and trends faced by the telecom service provider are first reviewed, the planning system restructure and planning methodologies innovation for meeting present situations are then presented, and the issues and directions are finally summarized.

  19. Comparative analyses of factors determining soil erosion rates based on network of Mediterranean monitored catchments for the innovative, adaptive and resilient agriculture of the future

    NASA Astrophysics Data System (ADS)

    Smetanová, Anna; Le Bissonnais, Yves; Raclot, Damien; Perdo Nunes, João; Licciardello, Feliciana; Mathys, Nicolle; Latron, Jérôme; Rodríguez Caballero, Emilio; Le Bouteiller, Caroline; Klotz, Sébastien; Mekki, Insaf; Gallart, Francesc; Solé Benet, Albert; Pérez Gallego, Nuria; Andrieux, Patrick; Jantzi, Hugo; Moussa, Roger; Planchon, Olivier; Marisa Santos, Juliana

    2015-04-01

    In order to project the soil erosion response to climate change in the fragile Mediterranean region it is inevitable to understand its existing patterns. Soil erosion monitoring on a catchment scale enables to analyse temporal and spatial variability of soil erosion and sediment delivery, while the integrating study of different catchments is often undertaken to depicther the general patterns. In this study, eight small catchments (with area up to 1,32 km2), representative for the western part of the Mediterranean region (according to climate, bedrock, soils and main type of land use) were compared. These catchments, grouped in the R-OS Med Network were situated in France (3), Spain (2), Portugal (1), Italy (1) and Tunisia (1). The average precipitation ranged between 236 to 1303 mm·a-1 and mean annual sediment yield varied 7.5 to 6900 Mg·km-2·a-1. The complex databes was based on more than 120 years of hydrological and sediment data, with series between 3 and 29 years long. The variability of sediment data was described on annual and monthly basis. The relationship between the sediment yield and more than 35 factors influencing the sediment yield including the characteristics of climate, topography, rainfall, runoff, land use, vegetation and soil cover, connectivity and dominant geomorphic processes, was studied. The preliminary results confirmed the differences in rainfall, runoff and sediment response, and revealed both the similarities and differences in soil erosion responses of the catchments. They are further dependent on the variability of factors themselves, with important contribution of the state of soil properties, vegetation cover and land use. Anna Smetanová has received the support of the European Union, in the framework of the Marie-Curie FP7 COFUND People Programme, through the award of an AgreenSkills' fellowship (under grant agreement n° 267196)

  20. Inter-generational Contact From a Network Perspective

    PubMed Central

    Marcum, Christopher Steven; Koehly, Laura M.

    2015-01-01

    Pathways for resource—or other—exchanges within families have long been known to be dependent on the structure of relations between generations (Silverstein, 2011; Fuller-Thomson et al., 1997; Agree et al., 2005; Treas and Marcum, 2011). Much life course research has theorized models of inter-generational exchange— including, the ‘sandwich generation’ (Miller, 1981) and the ‘skipped generation’ pathways (Chalfie, 1994)—but there is little work relating these theories to relevant network mechanisms such as liaison brokerage (Gould and Fernandez, 1989) and other triadic configurations (Davis and Leinhardt, 1972; Wasserman and Faust, 1994). To address this, a survey of models of resource allocation between members of inter-generational households from a network perspective is introduced in this paper. Exemplary data come from health discussion networks among Mexican-origin multi-generational households. PMID:26047986

  1. Inter-generational contact from a network perspective.

    PubMed

    Marcum, Christopher Steven; Koehly, Laura M

    2015-06-01

    Pathways for resource--or other--exchanges within families have long been known to be dependent on the structure of relations between generations (Agree et al., 2005; Fuller-Thomson et al., 1997; Silverstein, 2011; Treas & Marcum, 2011). Much life course research has theorized models of inter-generational exchange--including, the 'sandwich generation' (Miller, 1981) and the 'skipped generation' pathways (Chalfie, 1994)--but there is little work relating these theories to relevant network mechanisms such as liaison brokerage (Gould & Fernandez, 1989) and other triadic configurations (Davis & Leinhardt, 1972; Wasserman & Faust, 1994). To address this, a survey of models of resource allocation between members of inter-generational households from a network perspective is introduced in this paper. Exemplary data come from health discussion networks among Mexican-origin multi-generational households. PMID:26047986

  2. Evaporation over a Heterogeneous Mixed Savanna-Agricultural Catchment using a Distributed Wireless Sensor Network

    NASA Astrophysics Data System (ADS)

    Ceperley, N. C.; Mande, T.; Barrenetxea, G.; Vetterli, M.; Yacouba, H.; Repetti, A.; Parlange, M. B.

    2010-12-01

    Small scale rain fed agriculture is the primary livelihood for a large part of the population of Burkina Faso. Regional climate change means that this population is becoming increasingly vulnerable. Additionally, as natural savanna is converted for agriculture, hydrological systems are observed to become less stable as infiltration is decreased and rapid runoff is increased to the detriment of crop productivity, downstream populations and local water sources. The majority of the Singou River Basin, located in South East Burkina Faso is managed by hunting reserves, geared to maintaining high populations of wild game; however, residents surrounding the protected areas have been forced to intensify agriculture that has resulted in soil degradation as well as increases in the frequency and severity of flooding and droughts. Agroforestry, or planting trees in cultivated fields, has been proposed as a solution to help buffer these negative consequences, however the specific hydrologic behavior of the watershed land cover is unknown. We have installed a distributed sensor network of 17 Sensorscope wireless meteorological stations. These stations are dispersed across cultivated rice and millet fields, natural savanna, fallow fields, and around agroforestry fields. Sensorscope routes data through the network of stations to be delivered by a GPRS connection to a main server. This multi hop network allows data to be gathered over a large area and quickly adapts to changes in station performance. Data are available in real time via a website that can be accessed by a mobile phone. The stations are powered autonomously by small photovoltaic panels. This deployment is the first time that these meteorological stations have been used on the African continent. Initial calibration with measures from 2 eddy covariance stations allows us to calculate the energy balance at each of the Sensorscope stations. Thus, we can observe variation in evaporation over the various land cover in the

  3. Ukrainian network of permanent geodynamic stations: Current status and perspective

    NASA Astrophysics Data System (ADS)

    Yatskiv, Y.; Bolotin, S.; Bolotina, O.; Khoda, O.; Medvedsky, M.; Sydorenko, G.; Stopkhay, Y.; Volvach, O.

    Current status and perspective of establishing the Ukrainian network of permanent geodynamic stations (UKRGEONETWORK) is reviewed in connection with Integrated Space Geodetic Systems project. The UKRGEONETWORK consists of several stations which form GPS, SLR, and VLBI subnetworks as well as Gravimetry subsystem. Some information concerned with current activity of the UKRGEONETWORK in particular precise orbit determination in software complex Kiev-Geodynamic, ionospheric modelling in Klio program, and EOP determination on SteelBreeze software is given. Plan for upgrading the hardware of stations and for increasing the number of collocation sites is considered.

  4. Network analysis of sediment cascades derived from a digital geomorphological map - an example from the Gradenbach catchment (Schober Mountains, Austrian Alps)

    NASA Astrophysics Data System (ADS)

    Götz, Joachim; Heckmann, Tobias; Schrott, Lothar

    2013-04-01

    A detailed geomorphological map of the Gradenbach catchment (32 km², Schober Mountains, Austrian Alps) is presented that focuses on the sediment transfer system. Data were acquired in the field and by the interpretation of orthophotos, LIDAR data and derivatives (slope, curvature, aspect, shaded relief). The resulting digital geomorphological map contains polygon representations of landforms together with their morphometric parameters and an assessment of recent geomorphic activity. Special attention was paid to landform coupling, i.e. an additional table was constructed that indicates recently observable coupling between specific landforms (based on their ID in the database). From these data, we can obtain sediment cascades as a succession of coupled landforms along which sediment transfer occurs through the activity of various geomorphic processes. Based on this digital landform inventory the sediment transfer system is analysed using graph theory. As a rather new approach in geomorphology (already established within several disciplines; e.g. hydrology, biogeography), graph theory provides a promising framework for connectivity analysis in geomorphologic systems and powerful tools to visualise and analyse catchment-wide sediment transfer networks. Since the concept is arbitrarily scalable it can be applied to discrete land surface units (e.g. mapped landforms) or to continuous surface data (e.g. grid cells). In combination with geomorphological mapping, the concept allows for the (abstracted) visualisation of complex coupling relationships between multiple sediment storage landforms. Graph networks can be analysed at the level of nodes (e.g. the number of incoming and/or outgoing edges and their character as sediment source, sink or link), edges (e.g. importance within the network as conveyors of sediment from different sources), pathways (e.g. edge sequences leading to the catchment outlet or to storage landforms; these can be termed sediment cascades), or the

  5. Collective arrangements and social networks: Coping strategies for the poor households in the Great Ruaha Catchment in Tanzania

    NASA Astrophysics Data System (ADS)

    Kadigi, Reuben M. J.; Mdoe, N. S. Y.; Ashimogo, G. C.

    Access to water and land resources underpins the socio-economic fabric of many societies in the Southern Africa region, which is characterized broadly as underdeveloped with widespread food insecurity, exacerbated by persistent droughts, erratic rainfalls and increasing human populations. The availability of land and water resources is increasingly diminishing and becoming a stumbling block to the development of the agrarian societies in the region. The poor households have in turn adopted new livelihood coping mechanisms but little research has been done to assess the effectiveness of these ‘instruments’. Consequently, the concepts of sustainable water resources management and agricultural development have remained elusive and poorly understood by policy makers as well as by water resources planners and managers. Recognizing this, a study was conducted between 2002 and 2005 under the RIPARWIN (Raising Irrigation Productivity and Releasing Water for Intersectoral Needs) project to assess the spatial dynamics of livelihood capital, vulnerability and coping strategies for the poor agrarian households in the Upper Great Ruaha River Catchment (GRRC) in Tanzania. The results of analysis showed an array of livelihood platforms and institutional contexts that act to shape the existing livelihood typologies in the GRRC. In addition, the results showed a gradual increase in household vulnerability from upstream to downstream, particularly in terms of access to physical and natural assets. Vulnerability was found to be directly associated with the number of dependants. The female-headed households were relatively more likely to be vulnerable than the male-headed households (cf. probabilities of 27% and 21%, respectively). The value of collective arrangements and drawing on social networks crosscut all social strata and ranked as the most common livelihood strategy. This suggests that the scope for reducing vulnerability among the poor households in the GRRC critically

  6. Incorporating community and multiple perspectives in the development of acceptable drinking water source protection policy in catchments facing recreation demands.

    PubMed

    Syme, Geoffrey J; Nancarrow, Blair E

    2013-11-15

    The protection of catchment areas for drinking water quality has become an increasingly disputed issue in Australia and internationally. This is particularly the case in regard to the growing demand for nature based and rural recreation. Currently the policy for the protection of drinking water in Western Australia is to enforce a 2 km exclusion zone with a much larger surrounding area with limited and prescribed access to recreators. The debate between recreators and water management agencies has been lively, culminating in a recent state government enquiry. This paper describes the second phase of a three phase study to develop a methodology for defensible policy formulation which accounts for the points of view of all stakeholders. We examine general community, active recreators and professionals' views on the current policy of catchment protection and five proposed alternatives using a social judgement theory approach. Key attitudinal determinants of the preferences for policies were identified. Overall the recreators did not support the current policy despite strong support from both the general community and the professional group. Nevertheless, it was evident that there was some support by the community for policies that would enable a slight relaxation of current recreational exclusion. It was also evident that there was a significant proportion of the general community who were dissatisfied with current recreational opportunities and that, in future, it may be less easy to police exclusion zones even if current policy is maintained. The potential for future integration of recreational and water source protection is discussed as well as the benefits of community research in understanding policy preferences in this regard. PMID:23911764

  7. A groundwater recharge perspective on locating tree plantations within low-rainfall catchments to limit water resource losses

    NASA Astrophysics Data System (ADS)

    Dean, J. F.; Webb, J. A.; Jacobsen, G. E.; Chisari, R.; Dresel, P. E.

    2015-02-01

    Despite the many studies that consider the impacts of plantation forestry on groundwater recharge, and others that explore the spatial heterogeneity of recharge in low-rainfall regions, there is little marriage of the two subjects in forestry management guidelines and legislation. Here we carry out an in-depth analysis of the impact of reforestation on groundwater recharge in a low-rainfall (< 700 mm annually), high-evapotranspiration paired catchment characterized by ephemeral streams. Water table fluctuation (WTF) estimates of modern recharge indicate that little groundwater recharge occurs along the topographic highs of the catchments (average 18 mm yr-1); instead the steeper slopes in these areas direct runoff downslope to the lowland areas, where most recharge occurs (average 78 mm yr-1). Recharge estimates using the chloride mass balance (CMB) method were corrected by replacing the rainfall input Cl- value with that for streamflow, because most recharge occurs from infiltration of runoff through the streambed and adjacent low gradient slopes. The calculated CMB recharge values (average 10 mm yr-1) are lower than the WTF recharge values (average 47 mm yr-1), because they are representative of groundwater that was mostly recharged prior to European land clearance (> BP 200 years). The tree plantation has caused a progressive drawdown in groundwater levels due to tree water use; the decline is less in the upland areas. The results of this study show that spatial variations in recharge are important considerations for locating tree plantations. To conserve water resources for downstream users in low-rainfall, high-evapotranspiration regions, tree planting should be avoided in the dominant zone of recharge, i.e. the topographically low areas and along the drainage lines, and should be concentrated on the upper slopes, although this may negatively impact the economic viability of the plantation.

  8. Oncogenes and tumor suppressor genes: comparative genomics and network perspectives

    PubMed Central

    2015-01-01

    Background Defective tumor suppressor genes (TSGs) and hyperactive oncogenes (OCGs) heavily contribute to cell proliferation and apoptosis during cancer development through genetic variations such as somatic mutations and deletions. Moreover, they usually do not perform their cellular functions individually but rather execute jointly. Therefore, a comprehensive comparison of their mutation patterns and network properties may provide a deeper understanding of their roles in the cancer development and provide some clues for identification of novel targets. Results In this study, we performed a comprehensive survey of TSGs and OCGs from the perspectives of somatic mutations and network properties. For comparative purposes, we choose five gene sets: TSGs, OCGs, cancer drug target genes, essential genes, and other genes. Based on the data from Pan-Cancer project, we found that TSGs had the highest mutation frequency in most tumor types and the OCGs second. The essential genes had the lowest mutation frequency in all tumor types. For the network properties in the human protein-protein interaction (PPI) network, we found that, relative to target proteins, essential proteins, and other proteins, the TSG proteins and OCG proteins both tended to have higher degrees, higher betweenness, lower clustering coefficients, and shorter shortest-path distances. Moreover, the TSG proteins and OCG proteins tended to have direct interactions with cancer drug target proteins. To further explore their relationship, we generated a TSG-OCG network and found that TSGs and OCGs connected strongly with each other. The integration of the mutation frequency with the TSG-OCG network offered a network view of TSGs, OCGs, and their interactions, which may provide new insights into how the TSGs and OCGs jointly contribute to the cancer development. Conclusions Our study first discovered that the OCGs and TSGs had different mutation patterns, but had similar and stronger protein

  9. An Explicit Representation of High Resolution River Networks using a Catchment-based Land Surface Model with the NHDPlus dataset for California Region

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Kim, H.; Famiglietti, J. S.

    2011-12-01

    The main motivation of this study is to characterize how accurately we can estimate river discharge, river depth and inundation extent using an explicit representation of the river network with a catchment-based hydrological and routing modeling system (CHARMS) framework. Here we present a macroscale implementation of CHARMS over California. There are two main components in CHARMS: a land surface model based on National Center Atmospheric Research Community Land Model (CLM) 4.0, which is modified for implementation on a catchment template; and a river routing model that considers the water transport of each river reach. The river network is upscaled from the National Hydrography Dataset Plus (NHDPlus) to the Hydrologic Unit Code (HUC8) river basins. Both long-term monthly and daily streamflow simulation are generated and show reasonable results compared with gage observations. With river cross-section profile information derived from empirical relationships between channel dimensions and drainage area, river depth and floodplain extent associated with each river reach are also explicitly represented. Results have implications for assimilation of surface water altimetry and for implementation of the approach at the continental scale.

  10. Virtual water trade and country vulnerability: A network perspective

    NASA Astrophysics Data System (ADS)

    Sartori, Martina; Schiavo, Stefano

    2015-04-01

    This work investigates the relationship between countries' participation in virtual water trade and their vulnerability to external shocks from a network perspective. In particular, we investigate whether (i) possible sources of local national crises may interact with the system, propagating through the network and affecting the other countries involved; (ii) the topological characteristics of the international agricultural trade network, translated into virtual water-equivalent flows, may favor countries' vulnerability to external crises. Our work contributes to the debate on the potential merits and risks associated with openness to trade in agricultural and food products. On the one hand, trade helps to ensure that even countries with limited water (and other relevant) resources have access to sufficient food and contribute to the global saving of water. On the other hand, there are fears that openness may increase the vulnerability to external shocks and thus make countries worse off. Here we abstract from political considerations about food sovereignty and independence from imports and focus instead on investigating whether the increased participation in global trade that the world has witnessed in the last 30 years has made the system more susceptible to large shocks. Our analysis reveals that: (i) the probability of larger supply shocks has not increased over time; (ii) the topological characteristics of the VW network are not such as to favor the systemic risk associated with shock propagation; and (iii) higher-order interconnections may reveal further important information about the structure of a network. Regarding the first result, fluctuations in output volumes, among the sources of shock analyzed here, are more likely to generate some instability. The first implication is that, on one side, past national or regional economic crises were not necessarily brought about or strengthened by global trade. The second, more remarkable, implication is that, on

  11. Community, Collective or Movement? Evaluating Theoretical Perspectives on Network Building

    NASA Astrophysics Data System (ADS)

    Spitzer, W.

    2015-12-01

    Since 2007, the New England Aquarium has led a national effort to increase the capacity of informal science venues to effectively communicate about climate change. We are now leading the NSF-funded National Network for Ocean and Climate Change Interpretation (NNOCCI), partnering with the Association of Zoos and Aquariums, FrameWorks Institute, Woods Hole Oceanographic Institution, Monterey Bay Aquarium, and National Aquarium, with evaluation conducted by the New Knowledge Organization, Pennsylvania State University, and Ohio State University. NNOCCI enables teams of informal science interpreters across the country to serve as "communication strategists" - beyond merely conveying information they can influence public perceptions, given their high level of commitment, knowledge, public trust, social networks, and visitor contact. We provide in-depth training as well as an alumni network for ongoing learning, implementation support, leadership development, and coalition building. Our goals are to achieve a systemic national impact, embed our work within multiple ongoing regional and national climate change education networks, and leave an enduring legacy. What is the most useful theoretical model for conceptualizing the work of the NNOCCI community? This presentation will examine the pros and cons of three perspectives -- community of practice, collective impact, and social movements. The community of practice approach emphasizes use of common tools, support for practice, social learning, and organic development of leadership. A collective impact model focuses on defining common outcomes, aligning activities toward a common goal, structured collaboration. A social movement emphasizes building group identity and creating a sense of group efficacy. This presentation will address how these models compare in terms of their utility in program planning and evaluation, their fit with the unique characteristics of the NNOCCI community, and their relevance to our program goals.

  12. Promotores' perspectives on a male-to-male peer network.

    PubMed

    Macia, Laura; Ruiz, Hector Camilo; Boyzo, Roberto; Documet, Patricia Isabel

    2016-06-01

    Little documentation exists about male community health workers (promotores) networks. The experiences of promotores can provide input on how to attract, train, supervise and maintain male promotores in CHW programs. We present the experience and perspectives of promotores who participated in a male promotores network assisting Latino immigrant men in an emerging Latino community. All promotores in this community-based participatory study received payment for work 10 hours a week. We conducted qualitative interviews with all promotores starting the program, after 5 and 13 months. Three main themes emerged: 1) Men decided to become promotores to help others, yet appreciated being paid. 2) Promotores' learning experience was ongoing and was facilitated by a cooperative dynamic among them. Learning how to listen was crucial for promotores 3) Promotores experienced difficulty separating their personal lives form their role as a promotor We conclude that paying promotores facilitates the fulfillment of their drive to serve the community. Enhancing listening abilities needs to be part of promotores' training curricula. Finally, it is advisable to build a project with many opportunities for promotores and project staff to share professional and non-professional time and discuss their challenges. PMID:27102810

  13. Parkinson’s disease dementia: a neural networks perspective

    PubMed Central

    Jahanshahi, Marjan; Foltynie, Thomas

    2015-01-01

    In the long-term, with progression of the illness, Parkinson’s disease dementia affects up to 90% of patients with Parkinson’s disease. With increasing life expectancy in western countries, Parkinson’s disease dementia is set to become even more prevalent in the future. However, current treatments only give modest symptomatic benefit at best. New treatments are slow in development because unlike the pathological processes underlying the motor deficits of Parkinson’s disease, the neural mechanisms underlying the dementing process and its associated cognitive deficits are still poorly understood. Recent insights from neuroscience research have begun to unravel the heterogeneous involvement of several distinct neural networks underlying the cognitive deficits in Parkinson’s disease dementia, and their modulation by both dopaminergic and non-dopaminergic transmitter systems in the brain. In this review we collate emerging evidence regarding these distinct brain networks to give a novel perspective on the pathological mechanisms underlying Parkinson’s disease dementia, and discuss how this may offer new therapeutic opportunities. PMID:25888551

  14. Toward next-generation optical networks: a network operator perspective based on experimental tests and economic analysis

    NASA Astrophysics Data System (ADS)

    Xiao, Xiaojun; Du, Chunsheng; Zhou, Rongsheng

    2004-04-01

    As a result of data traffic"s exponential growth, network is currently evolving from fixed circuit switched services to dynamic packet switched services, which has brought unprecedented changes to the existing transport infrastructure. It is generally agreed that automatic switched optical network (ASON) is one of the promising solutions for the next generation optical networks. In this paper, we present the results of our experimental tests and economic analysis on ASON. The intention of this paper is to present our perspective, in terms of evolution strategy toward ASON, on next generation optical networks. It is shown through experimental tests that the performance of current Pre-standard ASON enabled equipments satisfies the basic requirements of network operators and is ready for initial deployment. The results of the economic analysis show that network operators can be benefit from the deployment of ASON from three sides. Firstly, ASON can reduce the CAPEX for network expanding by integrating multiple ADM & DCS into one box. Secondly, ASON can reduce the OPEX for network operation by introducing automatic resource control scheme. Finally, ASON can increase margin revenue by providing new optical network services such as Bandwidth on Demand, optical VPN etc. Finally, the evolution strategy is proposed as our perspective toward next generation optical networks. We hope the evolution strategy introduced may be helpful for the network operators to gracefully migrate their fixed ring based legacy networks to next generation dynamic mesh based network.

  15. Beyond the Labor Market Paradigm: A Social Network Perspective on Teacher Recruitment and Retention

    ERIC Educational Resources Information Center

    Baker-Doyle, Kira

    2010-01-01

    This article identifies limits of the dominant labor market perspective (LMP) in research on teacher recruitment and retention and describes how research that incorporates a social network perspective (SNP) can contribute to the knowledge base and development of teacher education, staffing, and professional development approaches. A discussion of…

  16. Molecular signatures of ovarian diseases: Insights from network medicine perspective.

    PubMed

    Kori, Medi; Gov, Esra; Arga, Kazim Yalcin

    2016-08-01

    Dysfunctions and disorders in the ovary lead to a host of diseases including ovarian cancer, ovarian endometriosis, and polycystic ovarian syndrome (PCOS). Understanding the molecular mechanisms behind ovarian diseases is a great challenge. In the present study, we performed a meta-analysis of transcriptome data for ovarian cancer, ovarian endometriosis, and PCOS, and integrated the information gained from statistical analysis with genome-scale biological networks (protein-protein interaction, transcriptional regulatory, and metabolic). Comparative and integrative analyses yielded reporter biomolecules (genes, proteins, metabolites, transcription factors, and micro-RNAs), and unique or common signatures at protein, metabolism, and transcription regulation levels, which might be beneficial to uncovering the underlying biological mechanisms behind the diseases. These signatures were mostly associated with formation or initiation of cancer development, and pointed out the potential tendency of PCOS and endometriosis to tumorigenesis. Molecules and pathways related to MAPK signaling, cell cycle, and apoptosis were the mutual determinants in the pathogenesis of all three diseases. To our knowledge, this is the first report that screens these diseases from a network medicine perspective. This study provides signatures which could be considered as potential therapeutic targets and/or as medical prognostic biomarkers in further experimental and clinical studies. Abbreviations DAVID: Database for Annotation, Visualization and Integrated Discovery; DEGs: differentially expressed genes; GEO: Gene Expression Omnibus; KEGG: Kyoto Encyclopedia of Genes and Genomes; LIMMA: Linear Models for Microarray Data; MBRole: Metabolite Biological Role; miRNA: micro-RNA; PCOS: polycystic ovarian syndrome; PPI: protein-protein interaction; RMA: Robust Multi-Array Average; TF: transcription factor. PMID:27341345

  17. Origin of the Valley Networks On Mars: A Hydrological Perspective

    NASA Technical Reports Server (NTRS)

    Gulick, Virginia C.

    2000-01-01

    The geomorphology of the Martian valley networks is examined from a hydrological perspective for their compatibility with an origin by rainfall, globally higher heat flow, and localized hydrothermal systems. Comparison of morphology and spatial distribution of valleys on geologic surfaces with terrestrial fluvial valleys suggests that most Martian valleys are probably not indicative of a rainfall origin, nor are they indicative of formation by an early global uniformly higher heat flow. In general, valleys are not uniformly distributed within geologic surface units as are terrestrial fluvial valleys. Valleys tend to form either as isolated systems or in clusters on a geologic surface unit leaving large expanses of the unit virtually untouched by erosion. With the exception of fluvial valleys on some volcanoes, most Martian valleys exhibit a sapping morphology and do not appear to have formed along with those that exhibit a runoff morphology. In contrast, terrestrial sapping valleys form from and along with runoff valleys. The isolated or clustered distribution of valleys suggests localized water sources were important in drainage development. Persistent ground-water outflow driven by localized, but vigorous hydrothermal circulation associated with magmatism, volcanism, impacts, or tectonism is, however, consistent with valley morphology and distribution. Snowfall from sublimating ice-covered lakes or seas may have provided an atmospheric water source for the formation of some valleys in regions where the surface is easily eroded and where localized geothermal/hydrothermal activity is sufficient to melt accumulated snowpacks.

  18. Integrated observation and modelling of runoff and sediments across different compartments of semi-arid catchments and channel networks

    NASA Astrophysics Data System (ADS)

    Bronstert, Axel; Ramon, Batalla; Araújo José C., De; da Costa Alexandre, Cunha; Till, Francke; Andreas, Güntner; Jose, Lopez-Tarazon; George, Mamede; Müller Eva, N.

    2010-05-01

    About one-third of the global population currently lives in countries which experience conditions of water stress. Such regions, often located within dryland ecosystems, are exposed to the hazard that the available freshwater resources fail to meet the water demand in domestic, agricultural and industrial sectors. Water availability often relies on the retention of river runoff in artificial lakes and reservoirs. However, the water storage in reservoirs is often adversely affected by sedimentation as a result of soil erosion. Erosion of the land surface due to natural or anthropogenic reasons and deposition of the eroded material in reservoirs threatens the reliability of reservoirs as a source of water supply. To sustain future water supply, a quantification of the sediment export from large dryland catchments becomes indispensable. A comprehensive modelling framework for water and sediment transport at the meso-scale, with a particular focus on dryland regions, has been developed from a German, Catalonian and Brazilian team during the last decade. It includes novel components for erosion from erosion-prone hillslopes, sediment transfer, retention and re-mobilization through the river system and sediment distribution, trapping and transfer through a reservoir. The parameterisation for pilot catchments is based on field monitoring campaigns of water and sediment fluxes, the analysis of land-use patterns, and the identification of the sediment hot spots through remotely sensed data. We present results of erosion-prone landscape units, the role of sediment transport in the river system, and the sedimentation processes in reservoirs. The modelling studies demonstrate the wide range of environmental problems where the model may be employed to develop sustainable management strategies for land and water resources. Evaluation of scenarios (land use, climate change) combined with an integrated assessment of options in reservoir management opens the opportunity to address

  19. Friendship Networks, Social Capital and Ethnic Identity: Researching the Perspectives of Caribbean Young People in Britain

    ERIC Educational Resources Information Center

    Reynolds, Tracey

    2007-01-01

    This article examines the perspectives of Caribbean young people in Britain in order to examine the issue of friendship networks. The research shows that the young people interviewed have a vast array of friendship networks across diverse ethnic groups. However, the majority of the Caribbean young people in the study acknowledged that their three…

  20. Let's put this in perspective: using dynamic simulation modelling to assess the impacts of farm-scale land management change on catchment-scale water quality

    NASA Astrophysics Data System (ADS)

    Rivers, Mark; Clarendon, Simon; Coles, Neil

    2013-04-01

    Natural Resource Management and Agri-industry development groups in Australia have invested considerable resources into the investigation of the economic, social and, particularly, environmental impacts of varying farming activities in a "catchment context". This research has resulted in the development of a much-improved understanding of the likely impacts of changed management practices at the farm-scale as well as the development of a number of conceptual models which place farming within this broader catchment context. The project discussed in this paper transformed a conceptual model of dairy farm phosphorus (P) management and transport processes into a more temporally and spatially dynamic model. This was then loaded with catchment-specific data and used as a "policy support tool" to allow the Australian dairy industry to examine the potential farm and catchment-scale impacts of varying dairy farm management practices within some key dairy farming regions. Models were developed, validated and calibrated using "STELLA©" dynamic modelling software for three catchments in which dairy is perceived as a significant land use. The models describe P movement and cycling within and through dairy farms in great detail and also estimate P transport through major source, sink and flow sectors of the catchments. A series of scenarios were executed for all three catchments which examined three main "groups" of tests: changes to farm P input rates; implementation of perceived environmental "Best Management Practices" (BMPs), and; changes to land use mosaics. Modifications to actual P input rates into dairy farms (not surprisingly) had a major effect on nutrient transport within and from the farms with a significant rise in nutrient loss rates at all scales with increasing fertiliser use. More surprisingly, however, even extensive environmental BMP implementation did not have marked effects on off-farm nutrient loss rates. On and off-farm riparian management implemented

  1. Unfolding Perspectives on Networked Professional Learning: Exploring Ties and Time

    ERIC Educational Resources Information Center

    de Laat, Maarten; Strijbos, Jan-Willem

    2014-01-01

    Networked learning and learning networks are commonplace concepts in most contemporary discourse on learning in the 21st century. This special issue provides a collection of studies that address the need for a growing body of empirical work to extent the limited understanding of the use and benefits of networks in relation to learning and…

  2. Broadcast Networks and the Outsiders: Legal Responsibility from Two Perspectives.

    ERIC Educational Resources Information Center

    Deming, Caren J.

    This paper examines the legal responsibility of networks to fairly represent outsiders in network employment and programming. The outsiders--women, racial and ethnic minorities, homosexuals, older people, members of minor political parties--have been using legal avenues provided by the Federal Communications Commission (FCC) and the Equal…

  3. Schools, Groups and Networks: A Political Perspective. Revised Version.

    ERIC Educational Resources Information Center

    Peterson, Paul E.

    Network theory has recently been suggested as providing a useful framework for developing a change strategy by which the federal government can induce educational reform. In this paper the potential contributions of network theory are assessed by showing its close relationship to group theory. Then three critiques of group theory and…

  4. Ocean-atmosphere coupling from a climate network perspective

    NASA Astrophysics Data System (ADS)

    Wiedermann, Marc; Donges, Jonathan F.; Donner, Reik V.; Kurths, Jürgen

    2014-05-01

    In recent years extensive studies on the climate system have been carried out making use of advanced complex network statistics. However, most previous studies have been characterized by two conceptual restrictions: First, in most cases network measures have been computed without taking into account the topology of the discrete grid, regular or irregular, that climate data is typically stored on. To overcome this problem, the concept of node splitting invariant network measures has been introduced considering individual node weights, for example according to the surface area a node represents, when computing network measures [1]. Second, the great majority of recent studies have been focussing on single climatological fields located on surfaces parallel to or directly on the Earth's surface. A recent work introduced a methodology for quantifying interaction structures between geopotential height fields at different isobaric surfaces by proposing general definitions for network measures dealing with a network of networks composed from distinct subnetworks [2]. In this work, we combine both, the node-weighting scheme as well as the interacting network measure approach. For this purpose, we invent new node-weighted cross-network measures that provide a general tool for quantifying interaction structures in multilayer networks that is applicable to many fields beyond the study of the climate system, such as communication, social or trade networks. Our new approach is utilized for studying ocean-atmosphere coupling in the northern hemisphere. Specifically, we construct 18 coupled climate networks based on monthly data from the ERA 40 reanalysis, each consisting of two subnetworks. In all cases, one subnetwork represents sea-surface temperature (SST) anomalies while the other is based on the geopotential height (HGT) of isobaric surfaces at different pressure levels. By investigating the connectivity of the resulting interdependent network structures, we identify a

  5. Evolution based on chromosome affinity from a network perspective

    NASA Astrophysics Data System (ADS)

    Monteiro, R. L. S.; Fontoura, J. R. A.; Carneiro, T. K. G.; Moret, M. A.; Pereira, H. B. B.

    2014-06-01

    Recent studies have focused on models to simulate the complex phenomenon of evolution of species. Several studies have been performed with theoretical models based on Darwin's theories to associate them with the actual evolution of species. However, none of the existing models include the affinity between individuals using network properties. In this paper, we present a new model based on the concept of affinity. The model is used to simulate the evolution of species in an ecosystem composed of individuals and their relationships. We propose an evolutive algorithm that incorporates the degree centrality and efficiency network properties to perform the crossover process and to obtain the network topology objective, respectively. Using a real network as a starting point, we simulate its evolution and compare its results with the results of 5788 computer-generated networks.

  6. Towards catchment classification by means of environmental tracers and landscape analysis: The Attert catchment in Luxembourg

    NASA Astrophysics Data System (ADS)

    Wrede, S.; Pfister, L.; Krein, A.; Fenicia, F.; Bogaard, T. A.; Uhlenbrook, S.; Savenije, H. H. G.

    2010-05-01

    Until recently hydrological research has been mainly focusing on detailed investigations at small spatial scales, resulting in a set of more and more complex physically-based and spatially distributed hydrologic models. While much of the research effort today is targeted to advance these hydrological model predictions at the catchment scale, shortcomings remain to adequately capture the dominating hydrological processes across a range of scales that translate into the rainfall-runoff response of a catchment. Thus, studies addressing the fundamental relations between catchment structure and function are urgently needed, as they help catchment classification by advancing our knowledge about suitable catchment signatures and controls at different spatial and temporal scales. In our study in the nested Attert catchment in the Grand-Duchy of Luxembourg (Europe) we investigate how environmental tracer dynamics, hydrological response behavior and landscape analysis can help to identify such dominating controls on runoff generation across multiple scales. Techniques to characterize landscape structure and hydrological processes are complementary applied to identify scales in which shifts of the dominant hydrological processes occur. These dominating controls in turn provide a more integrated perspective of catchment structure and functioning that can be used for catchment classification based on functional response.

  7. Social Network Perspectives Reveal Strength of Academic Developers as Weak Ties

    ERIC Educational Resources Information Center

    Matthews, Kelly E.; Crampton, Andrea; Hill, Matthew; Johnson, Elizabeth D.; Sharma, Manjula D.; Varsavsky, Cristina

    2015-01-01

    Social network perspectives acknowledge the influence of disciplinary cultures on academics' teaching beliefs and practices with implications for academic developers. The contribution of academic developers in 18 scholarship of teaching and learning (SoTL) projects situated in the sciences are explored by drawing on data from a two-year national…

  8. Reducing Readmissions to Detoxification: An Interorganizational Network Perspective

    PubMed Central

    Spear, Suzanne E.

    2014-01-01

    Background The high cost of detoxification (detox) services and health risks associated with continued substance abuse make readmission to detox an important indicator of poor performance for substance use disorder treatment systems. This study examined the extent to which the structure of local networks available to detox programs affects patients’ odds of readmission to detox within 1 year. Methods Administrative data from 32 counties in California in 2008–2009 were used to map network ties between programs based on patient transfers. Social network analysis was employed to measure structural features of detox program networks. Contextual predictors included efficiency (proportion of ties within a network that are non-redundant) and out-degree (number of outgoing ties to other programs). A binary mixed model was used to predict the odds of readmission among detox patients in residential (non-hospital) facilities (N =18,278). Results After adjusting for patient-level covariates and continuity of service from detox to outpatient or residential treatment, network efficiency was associated with lower odds of readmission. Conclusion The impact of network structure on detox readmissions suggests that the interorganizational context in which detox programs operate may be important for improving continuity of service within substance use disorder treatment systems. Implications for future research are discussed. PMID:24529966

  9. The network perspective: an integration of attachment and family systems theories.

    PubMed

    Kozlowska, Kasia; Hanney, Lesley

    2002-01-01

    In this article we discuss the network paradigm as a useful base from which to integrate attachment and family systems theories. The network perspective refers to the application of general systems theory to living systems, and provides a framework that conceptualizes the dyadic and family systems as simultaneously distinct and interconnected. Network thinking requires that the clinician holds multiple perspectives in mind, considers each system level as both a part and a whole, and shifts the focus of attention between levels as required. Key epistemological issues that have hindered the integration of the theories are discussed. These include inconsistencies within attachment theory itself and confusion surrounding the theoretical conceptualizations of the relationship between attachment and family systems theories. Detailed information about attachment categories is provided using the Dynamic Maturational model. Case vignettes illustrating work with young children and their families explore the clinical implications of integrating attachment data into family therapy practice. PMID:12395561

  10. Evolution After Whole-Genome Duplication: A Network Perspective

    PubMed Central

    Zhu, Yun; Lin, Zhenguo; Nakhleh, Luay

    2013-01-01

    Gene duplication plays an important role in the evolution of genomes and interactomes. Elucidating how evolution after gene duplication interplays at the sequence and network level is of great interest. In this work, we analyze a data set of gene pairs that arose through whole-genome duplication (WGD) in yeast. All these pairs have the same duplication time, making them ideal for evolutionary investigation. We investigated the interplay between evolution after WGD at the sequence and network levels and correlated these two levels of divergence with gene expression and fitness data. We find that molecular interactions involving WGD genes evolve at rates that are three orders of magnitude slower than the rates of evolution of the corresponding sequences. Furthermore, we find that divergence of WGD pairs correlates strongly with gene expression and fitness data. Because of the role of gene duplication in determining redundancy in biological systems and particularly at the network level, we investigated the role of interaction networks in elucidating the evolutionary fate of duplicated genes. We find that gene neighborhoods in interaction networks provide a mechanism for inferring these fates, and we developed an algorithm for achieving this task. Further epistasis analysis of WGD pairs categorized by their inferred evolutionary fates demonstrated the utility of these techniques. Finally, we find that WGD pairs and other pairs of paralogous genes of small-scale duplication origin share similar properties, giving good support for generalizing our results from WGD pairs to evolution after gene duplication in general. PMID:24048644

  11. The geometry of chaotic dynamics — a complex network perspective

    NASA Astrophysics Data System (ADS)

    Donner, R. V.; Heitzig, J.; Donges, J. F.; Zou, Y.; Marwan, N.; Kurths, J.

    2011-12-01

    Recently, several complex network approaches to time series analysis have been developed and applied to study a wide range of model systems as well as real-world data, e.g., geophysical or financial time series. Among these techniques, recurrence-based concepts and prominently ɛ-recurrence networks, most faithfully represent the geometrical fine structure of the attractors underlying chaotic (and less interestingly non-chaotic) time series. In this paper we demonstrate that the well known graph theoretical properties local clustering coefficient and global (network) transitivity can meaningfully be exploited to define two new local and two new global measures of dimension in phase space: local upper and lower clustering dimension as well as global upper and lower transitivity dimension. Rigorous analytical as well as numerical results for self-similar sets and simple chaotic model systems suggest that these measures are well-behaved in most non-pathological situations and that they can be estimated reasonably well using ɛ-recurrence networks constructed from relatively short time series. Moreover, we study the relationship between clustering and transitivity dimensions on the one hand, and traditional measures like pointwise dimension or local Lyapunov dimension on the other hand. We also provide further evidence that the local clustering coefficients, or equivalently the local clustering dimensions, are useful for identifying unstable periodic orbits and other dynamically invariant objects from time series. Our results demonstrate that ɛ-recurrence networks exhibit an important link between dynamical systems and graph theory.

  12. Persistent brain network homology from the perspective of dendrogram.

    PubMed

    Lee, Hyekyoung; Kang, Hyejin; Chung, Moo K; Kim, Bung-Nyun; Lee, Dong Soo

    2012-12-01

    The brain network is usually constructed by estimating the connectivity matrix and thresholding it at an arbitrary level. The problem with this standard method is that we do not have any generally accepted criteria for determining a proper threshold. Thus, we propose a novel multiscale framework that models all brain networks generated over every possible threshold. Our approach is based on persistent homology and its various representations such as the Rips filtration, barcodes, and dendrograms. This new persistent homological framework enables us to quantify various persistent topological features at different scales in a coherent manner. The barcode is used to quantify and visualize the evolutionary changes of topological features such as the Betti numbers over different scales. By incorporating additional geometric information to the barcode, we obtain a single linkage dendrogram that shows the overall evolution of the network. The difference between the two networks is then measured by the Gromov-Hausdorff distance over the dendrograms. As an illustration, we modeled and differentiated the FDG-PET based functional brain networks of 24 attention-deficit hyperactivity disorder children, 26 autism spectrum disorder children, and 11 pediatric control subjects. PMID:23008247

  13. Network Perspectives on the Mechanisms of Deep Brain Stimulation

    PubMed Central

    McIntyre, Cameron C.; Hahn, Philip J.

    2009-01-01

    Deep brain stimulation (DBS) is an established medical therapy for the treatment of movement disorders and shows great promise for several other neurological disorders. However, after decades of clinical utility the underlying therapeutic mechanisms remain undefined. Early attempts to explain the mechanisms of DBS focused on hypotheses that mimicked an ablative lesion to the stimulated brain region. More recent scientific efforts have explored the wide-spread changes in neural activity generated throughout the stimulated brain network. In turn, new theories on the mechanisms of DBS have taken a systems-level approach to begin to decipher the network activity. This review provides an introduction to some of the network based theories on the function and pathophysiology of the cortico-basal-ganglia-thalamo-cortical loops commonly targeted by DBS. We then analyze some recent results on the effects of DBS on these networks, with a focus on subthalamic DBS for the treatment of Parkinson's disease. Finally we attempt to summarize how DBS could be achieving its therapeutic effects by overriding pathological network activity. PMID:19804831

  14. The Immatsiak network of groundwater wells in a small catchment basin in the discontinuous permafrost zone of Northern Quebec, Canada: A unique opportunity for monitoring the impacts of climate change on groundwater (Invited)

    NASA Astrophysics Data System (ADS)

    Fortier, R.; Lemieux, J.; Molson, J. W.; Therrien, R.; Ouellet, M.; Bart, J.

    2013-12-01

    During a summer drilling campaign in 2012, a network of nine groundwater monitoring wells was installed in a small catchment basin in a zone of discontinuous permafrost near the Inuit community of Umiujaq in Northern Quebec, Canada. This network, named Immatsiak, is part of a provincial network of groundwater monitoring wells to monitor the impacts of climate change on groundwater resources. It provides a unique opportunity to study cold region groundwater dynamics in permafrost environments and to assess the impacts of permafrost degradation on groundwater quality and availability as a potential source of drinking water. Using the borehole logs from the drilling campaign and other information from previous investigations, an interpretative cryo-hydrogeological cross-section of the catchment basin was produced which identified the Quaternary deposit thickness and extent, the depth to bedrock, the location of permafrost, one superficial aquifer located in a sand deposit, and another deep aquifer in fluvio-glacial sediments and till. In the summer of 2013, data were recovered from water level and barometric loggers which were installed in the wells in August 2012. Although the wells were drilled in unfrozen zones, the groundwater temperature is very low, near 0.4 °C, with an annual variability of a few tenths of a degree Celsius at a depth of 35 m. The hydraulic head in the wells varied as much as 6 m over the last year. Pumping tests performed in the wells showed a very high hydraulic conductivity of the deep aquifer. Groundwater in the wells and surface water in small thermokarst lakes and at the catchment outlet were sampled for geochemical analysis (inorganic parameters, stable isotopes of oxygen (δ18O) and hydrogen (δ2H), and radioactive isotopes of carbon (δ14C), hydrogen (tritium δ3H) and helium (δ3He)) to assess groundwater quality and origin. Preliminary results show that the signature of melt water from permafrost thawing is observed in the

  15. A financial network perspective of financial institutions' systemic risk contributions

    NASA Astrophysics Data System (ADS)

    Huang, Wei-Qiang; Zhuang, Xin-Tian; Yao, Shuang; Uryasev, Stan

    2016-08-01

    This study considers the effects of the financial institutions' local topology structure in the financial network on their systemic risk contribution using data from the Chinese stock market. We first measure the systemic risk contribution with the Conditional Value-at-Risk (CoVaR) which is estimated by applying dynamic conditional correlation multivariate GARCH model (DCC-MVGARCH). Financial networks are constructed from dynamic conditional correlations (DCC) with graph filtering method of minimum spanning trees (MSTs). Then we investigate dynamics of systemic risk contributions of financial institution. Also we study dynamics of financial institution's local topology structure in the financial network. Finally, we analyze the quantitative relationships between the local topology structure and systemic risk contribution with panel data regression analysis. We find that financial institutions with greater node strength, larger node betweenness centrality, larger node closeness centrality and larger node clustering coefficient tend to be associated with larger systemic risk contributions.

  16. Default Network and Aging: Beyond the Task-Negative Perspective.

    PubMed

    Maillet, David; Schacter, Daniel L

    2016-09-01

    During cognitive tasks requiring externally directed attention, activation in the default-network (DN) typically decreases below baseline levels ('deactivation'). Healthy aging is associated with reduced deactivation, which is usually attributed to a failure to suppress DN processes. Recent evidence instead suggests that older adults may be more reliant on DN than young adults when performing these tasks. PMID:27282744

  17. A Network Perspective on Dropout Prevention in Two Cities

    ERIC Educational Resources Information Center

    Wells, Rebecca; Gifford, Elizabeth; Bai, Yu; Corra, Ashley

    2015-01-01

    Purpose: This exploratory case study examines how school systems and other local organizations have been working within two major U.S. cities to improve high school graduation rates. Systematically assessing active interorganizational dropout prevention networks may reveal characteristics affecting communities' capacity to support school…

  18. The CE3R Network: current status and future perspectives

    NASA Astrophysics Data System (ADS)

    Lenhardt, Wolfgang; Pesaresi, Damiano; Živčić, Mladen; Costa, Giovanni; Kuk, Kresimir; Bondár, István; Duni, Llambro; Spacek, Petr

    2016-04-01

    In order to improve the monitoring of seismic activities in the border regions and to enhance the collaboration between countries and seismological institutions in Central Europe, the Environment Agency of the Slovenian Republic (ARSO), the Italian National Institute for Oceanography and Experimental Geophysics (OGS), the University of Trieste (UniTS) and the Austrian Central Institute for Meteorology and Geodynamics (ZAMG) established in 2001 the "South Eastern Alps Transfrontier Seismological Network". In May 2014 ARSO, OGS, UniTS and ZAMG agreed to formalize the transfrontier network, to name it "Central and East European Earthquake Research Network", (CE3RN or CE3R Network) in order to locate it geographically since cross-border networks can be established in other areas of the world and to expand their cooperation, including institutions in other countries. The University of Zagreb (UniZG) joined CE3RN in October 2014. The Kövesligethy Radó Seismological Observatory (KRSZO) of the Hungarian Academy of Sciences joined CE3RN in October 2015. The Institute of Geosciences, Energy, Water and Environment (IGEWE) of the Polytechnic University of Tirana joined CE3RN in November 2015. The Institute of Physics of the Earth (IPE) of the Masaryk University in Brno joined CE3RN in November 2015. CE3RN Parties intend to formalize and possibly extend their ongoing cooperation in the field of seismological data acquisition, exchange and use for seismological and earthquake engineering and civil protection purposes. The purpose of this cooperation is to retain and expand the existing cross-border network, specify the rules of conduct in the network management, improvements, extensions and enlargements, enhance seismological research in the region, and support civil protection activities. Since the formal establishment of CE3RN, several common projects have been completed, like the SeismoSAT project for the seismic data center connection over satellite funded by the Interreg

  19. Mechanics of composite actin networks: in vitro and cellular perspectives

    NASA Astrophysics Data System (ADS)

    Upadhyaya, Arpita

    2014-03-01

    Actin filaments and associated actin binding proteins play an essential role in governing the mechanical properties of eukaryotic cells. Even though cells have multiple actin binding proteins (ABPs) that exist simultaneously to maintain the structural and mechanical integrity of the cellular cytoskeleton, how these proteins work together to determine the properties of actin networks is not well understood. The ABP, palladin, is essential for the integrity of cell morphology and movement during development. Palladin coexists with alpha-actinin in stress fibers and focal adhesions and binds to both actin and alpha-actinin. To obtain insight into how mutually interacting actin crosslinking proteins modulate the properties of actin networks, we have characterized the micro-structure and mechanics of actin networks crosslinked with palladin and alpha-actinin. Our studies on composite networks of alpha-actinin/palladin/actin show that palladin and alpha-actinin synergistically determine network viscoelasticity. We have further examined the role of palladin in cellular force generation and mechanosensing. Traction force microscopy revealed that TAFs are sensitive to substrate stiffness as they generate larger forces on substrates of increased stiffness. Contrary to expectations, knocking down palladin increased the forces generated by cells, and also inhibited the ability to sense substrate stiffness for very stiff gels. This was accompanied by significant differences in the actin organization and adhesion dynamics of palladin knock down cells. Perturbation experiments also suggest altered myosin activity in palladin KD cells. Our results suggest that the actin crosslinkers such as palladin and myosin motors coordinate for optimal cell function and to prevent aberrant behavior as in cancer metastasis.

  20. Charting gene regulatory networks: strategies, challenges and perspectives

    PubMed Central

    2004-01-01

    One of the foremost challenges in the post-genomic era will be to chart the gene regulatory networks of cells, including aspects such as genome annotation, identification of cis-regulatory elements and transcription factors, information on protein–DNA and protein–protein interactions, and data mining and integration. Some of these broad sets of data have already been assembled for building networks of gene regulation. Even though these datasets are still far from comprehensive, and the approach faces many important and difficult challenges, some strategies have begun to make connections between disparate regulatory events and to foster new hypotheses. In this article we review several different genomics and proteomics technologies, and present bioinformatics methods for exploring these data in order to make novel discoveries. PMID:15080794

  1. Employment, Social Networks and Undocumented Migrants: The Employer Perspective

    PubMed Central

    Bloch, Alice; McKay, Sonia

    2015-01-01

    This article draws on data from qualitative interviews with ethnic enclave and ethnic economy business entrepreneurs from Chinese, Bangladeshi and Turkish-speaking communities in London. Routes into business and worker recruitment practices are explored, demonstrating the centrality of social capital in the form of family and other social networks within these processes. The article investigates what employers consider the desirable characteristics of workers: trust, kinship, gender, social networks, language compatibility and the needs of the business intersect with racialised notions of workers’ strengths and characteristics. Finally, we consider changing practices in relation to the employment of undocumented migrants, in the context of an increasingly punitive legislative regime. The complex and variable impact of policy alongside the ways in which other obligations and positions outweigh the fear and risks of sanctions associated with non-compliance is revealed. PMID:25866421

  2. Relational correlates of interpersonal citizenship behavior: a social network perspective.

    PubMed

    Bowler, Wm Matthew; Brass, Daniel J

    2006-01-01

    This study examines the role of social network ties in the performance and receipt of interpersonal citizenship behavior (ICB), one form of organizational citizenship behavior (OCB). A field study involving 141 employees of a manufacturing firm provided evidence that social network ties are related to the performance and receipt of ICB. Results support hypothesized relationships, which are based on social exchange theory, suggesting strength of friendship is related to performance and receipt of ICB. Support was also found for impression management-based hypotheses suggesting that asymmetric influence and 3rd-party influence are related to the performance and receipt of ICB. These relationships were significant when controlling for job satisfaction, commitment, procedural justice, hierarchical level, demographic similarity, and job similarity. Implications and directions for future research are addressed. PMID:16435939

  3. Understanding Crowd-Powered Search Groups: A Social Network Perspective

    PubMed Central

    Zhang, Qingpeng; Wang, Fei-Yue; Zeng, Daniel; Wang, Tao

    2012-01-01

    Background Crowd-powered search is a new form of search and problem solving scheme that involves collaboration among a potentially large number of voluntary Web users. Human flesh search (HFS), a particular form of crowd-powered search originated in China, has seen tremendous growth since its inception in 2001. HFS presents a valuable test-bed for scientists to validate existing and new theories in social computing, sociology, behavioral sciences, and so forth. Methodology In this research, we construct an aggregated HFS group, consisting of the participants and their relationships in a comprehensive set of identified HFS episodes. We study the topological properties and the evolution of the aggregated network and different sub-groups in the network. We also identify the key HFS participants according to a variety of measures. Conclusions We found that, as compared with other online social networks, HFS participant network shares the power-law degree distribution and small-world property, but with a looser and more distributed organizational structure, leading to the diversity, decentralization, and independence of HFS participants. In addition, the HFS group has been becoming increasingly decentralized. The comparisons of different HFS sub-groups reveal that HFS participants collaborated more often when they conducted the searches in local platforms or the searches requiring a certain level of professional knowledge background. On the contrary, HFS participants did not collaborate much when they performed the search task in national platforms or the searches with general topics that did not require specific information and learning. We also observed that the key HFS information contributors, carriers, and transmitters came from different groups of HFS participants. PMID:22761888

  4. A physical layer perspective on access network sharing

    NASA Astrophysics Data System (ADS)

    Pfeiffer, Thomas

    2015-12-01

    Unlike in copper or wireless networks, there is no sharing of resources in fiber access networks yet, other than bit stream access or cable sharing, in which the fibers of a cable are let to one or multiple operators. Sharing optical resources on a single fiber among multiple operators or different services has not yet been applied. While this would allow for a better exploitation of installed infrastructures, there are operational issues which still need to be resolved, before this sharing model can be implemented in networks. Operating multiple optical systems and services over a common fiber plant, autonomously and independently from each other, can result in mutual distortions on the physical layer. These distortions will degrade the performance of the involved systems, unless precautions are taken in the infrastructure hardware to eliminate or to reduce them to an acceptable level. Moreover, the infrastructure needs to be designed such as to support different system technologies and to ensure a guaranteed quality of the end-to-end connections. In this paper, suitable means are proposed to be introduced in fiber access infrastructures that will allow for shared utilization of the fibers while safeguarding the operational needs and business interests of the involved parties.

  5. The Major Transitions of Life from a Network Perspective

    PubMed Central

    Suki, Béla

    2012-01-01

    Many attempts have been made to understand the origin of life and biological complexity both at the experimental and theoretical levels but neither is fully explained. In an influential work, Maynard Smith and Szathmáry (1995) argued that the majority of the increase in complexity is not gradual, but it is associated with a few so-called major transitions along the way of the evolution of life. For each major transition, they identified specific mechanisms that could account for the change in complexity related to information transmission across generations. In this work, I propose that the sudden and unexpected improvement in the functionality of an organism that followed a major transition was enabled by a phase transition in the network structure associated with that function. The increase in complexity following a major transition is therefore directly linked to the emergence of a novel structure–function relation which altered the course of evolution. As a consequence, emergent phenomena arising from these network phase transitions can serve as a common organizing principle for understanding the major transitions. As specific examples, I analyze the emergence of life, the emergence of the genetic apparatus, the rise of the eukaryotic cells, the evolution of movement and mechanosensitivity, and the emergence of consciousness. Finally, I discuss the implications of network associated phase transitions to issues that bear relevance to the history, the immediate present and perhaps the future, of life. PMID:22514542

  6. Feigenbaum graphs: a complex network perspective of chaos.

    PubMed

    Luque, Bartolo; Lacasa, Lucas; Ballesteros, Fernando J; Robledo, Alberto

    2011-01-01

    The recently formulated theory of horizontal visibility graphs transforms time series into graphs and allows the possibility of studying dynamical systems through the characterization of their associated networks. This method leads to a natural graph-theoretical description of nonlinear systems with qualities in the spirit of symbolic dynamics. We support our claim via the case study of the period-doubling and band-splitting attractor cascades that characterize unimodal maps. We provide a universal analytical description of this classic scenario in terms of the horizontal visibility graphs associated with the dynamics within the attractors, that we call Feigenbaum graphs, independent of map nonlinearity or other particulars. We derive exact results for their degree distribution and related quantities, recast them in the context of the renormalization group and find that its fixed points coincide with those of network entropy optimization. Furthermore, we show that the network entropy mimics the Lyapunov exponent of the map independently of its sign, hinting at a Pesin-like relation equally valid out of chaos. PMID:21915254

  7. Feigenbaum Graphs: A Complex Network Perspective of Chaos

    PubMed Central

    Luque, Bartolo; Lacasa, Lucas; Ballesteros, Fernando J.; Robledo, Alberto

    2011-01-01

    The recently formulated theory of horizontal visibility graphs transforms time series into graphs and allows the possibility of studying dynamical systems through the characterization of their associated networks. This method leads to a natural graph-theoretical description of nonlinear systems with qualities in the spirit of symbolic dynamics. We support our claim via the case study of the period-doubling and band-splitting attractor cascades that characterize unimodal maps. We provide a universal analytical description of this classic scenario in terms of the horizontal visibility graphs associated with the dynamics within the attractors, that we call Feigenbaum graphs, independent of map nonlinearity or other particulars. We derive exact results for their degree distribution and related quantities, recast them in the context of the renormalization group and find that its fixed points coincide with those of network entropy optimization. Furthermore, we show that the network entropy mimics the Lyapunov exponent of the map independently of its sign, hinting at a Pesin-like relation equally valid out of chaos. PMID:21915254

  8. Incorporating flood event analyses and catchment structures into model development

    NASA Astrophysics Data System (ADS)

    Oppel, Henning; Schumann, Andreas

    2016-04-01

    The space-time variability in catchment response results from several hydrological processes which differ in their relevance in an event-specific way. An approach to characterise this variance consists in comparisons between flood events in a catchment and between flood responses of several sub-basins in such an event. In analytical frameworks the impact of space and time variability of rainfall on runoff generation due to rainfall excess can be characterised. Moreover the effect of hillslope and channel network routing on runoff timing can be specified. Hence, a modelling approach is needed to specify the runoff generation and formation. Knowing the space-time variability of rainfall and the (spatial averaged) response of a catchment it seems worthwhile to develop new models based on event and catchment analyses. The consideration of spatial order and the distribution of catchment characteristics in their spatial variability and interaction with the space-time variability of rainfall provides additional knowledge about hydrological processes at the basin scale. For this purpose a new procedure to characterise the spatial heterogeneity of catchments characteristics in their succession along the flow distance (differentiated between river network and hillslopes) was developed. It was applied to study of flood responses at a set of nested catchments in a river basin in eastern Germany. In this study the highest observed rainfall-runoff events were analysed, beginning at the catchment outlet and moving upstream. With regard to the spatial heterogeneities of catchment characteristics, sub-basins were separated by new algorithms to attribute runoff-generation, hillslope and river network processes. With this procedure the cumulative runoff response at the outlet can be decomposed and individual runoff features can be assigned to individual aspects of the catchment. Through comparative analysis between the sub-catchments and the assigned effects on runoff dynamics new

  9. Foundational perspectives on causality in large-scale brain networks.

    PubMed

    Mannino, Michael; Bressler, Steven L

    2015-12-01

    A profusion of recent work in cognitive neuroscience has been concerned with the endeavor to uncover causal influences in large-scale brain networks. However, despite the fact that many papers give a nod to the important theoretical challenges posed by the concept of causality, this explosion of research has generally not been accompanied by a rigorous conceptual analysis of the nature of causality in the brain. This review provides both a descriptive and prescriptive account of the nature of causality as found within and between large-scale brain networks. In short, it seeks to clarify the concept of causality in large-scale brain networks both philosophically and scientifically. This is accomplished by briefly reviewing the rich philosophical history of work on causality, especially focusing on contributions by David Hume, Immanuel Kant, Bertrand Russell, and Christopher Hitchcock. We go on to discuss the impact that various interpretations of modern physics have had on our understanding of causality. Throughout all this, a central focus is the distinction between theories of deterministic causality (DC), whereby causes uniquely determine their effects, and probabilistic causality (PC), whereby causes change the probability of occurrence of their effects. We argue that, given the topological complexity of its large-scale connectivity, the brain should be considered as a complex system and its causal influences treated as probabilistic in nature. We conclude that PC is well suited for explaining causality in the brain for three reasons: (1) brain causality is often mutual; (2) connectional convergence dictates that only rarely is the activity of one neuronal population uniquely determined by another one; and (3) the causal influences exerted between neuronal populations may not have observable effects. A number of different techniques are currently available to characterize causal influence in the brain. Typically, these techniques quantify the statistical

  10. Estimation with Wireless Sensor Networks: Censoring and Quantization Perspectives

    NASA Astrophysics Data System (ADS)

    Msechu, Eric James

    In the last decade there has been an increase in application areas for wireless sensor networks (WSNs), which can be attributed to the advances in the enabling sensor technology. These advances include integrated circuit miniaturization and mass-production of highly-reliable hardware for sensing, processing, and data storage at a lower cost. In many emerging applications, massive amounts of data are acquired by a large number of low-cost sensing devices. The design of signal processing algorithms for these WSNs, unlike in wireless networks designed for communications, face a different set of challenges due to resource constraints sensor nodes must adhere to. These include: (i) limited on-board memory for storage; (ii) limited energy source, typically based on irreplaceable battery cells; (iii) radios with limited transmission range; and (iv) stringent data rates either due to a need to save energy or due to limited radio-frequency bandwidth allocated to sensor networks. This work addresses distributed data-reduction at sensor nodes using a combination of measurement-censoring and measurement quantization. The WSN is envisioned for decentralized estimation of either a vector of unknown parameters in a maximum likelihood framework, or, for decentralized estimation of a random signal using Bayesian optimality criteria. Early research effort in data-reduction methods involved using a centralized computation platform directing selection of the most informative data and focusing computational and communication resources toward the selected data only. Robustness against failure of the central computation unit, as well as the need for iterative data-selection and data-gathering in some applications (e.g., real-time navigation systems), motivates a rethinking of the centralized data-selection approach. Recently, research focus has been on collaborative signal processing in sensor neighborhoods for the data-reduction step. It is in this spirit that investigation of methods

  11. Foundational perspectives on causality in large-scale brain networks

    NASA Astrophysics Data System (ADS)

    Mannino, Michael; Bressler, Steven L.

    2015-12-01

    A profusion of recent work in cognitive neuroscience has been concerned with the endeavor to uncover causal influences in large-scale brain networks. However, despite the fact that many papers give a nod to the important theoretical challenges posed by the concept of causality, this explosion of research has generally not been accompanied by a rigorous conceptual analysis of the nature of causality in the brain. This review provides both a descriptive and prescriptive account of the nature of causality as found within and between large-scale brain networks. In short, it seeks to clarify the concept of causality in large-scale brain networks both philosophically and scientifically. This is accomplished by briefly reviewing the rich philosophical history of work on causality, especially focusing on contributions by David Hume, Immanuel Kant, Bertrand Russell, and Christopher Hitchcock. We go on to discuss the impact that various interpretations of modern physics have had on our understanding of causality. Throughout all this, a central focus is the distinction between theories of deterministic causality (DC), whereby causes uniquely determine their effects, and probabilistic causality (PC), whereby causes change the probability of occurrence of their effects. We argue that, given the topological complexity of its large-scale connectivity, the brain should be considered as a complex system and its causal influences treated as probabilistic in nature. We conclude that PC is well suited for explaining causality in the brain for three reasons: (1) brain causality is often mutual; (2) connectional convergence dictates that only rarely is the activity of one neuronal population uniquely determined by another one; and (3) the causal influences exerted between neuronal populations may not have observable effects. A number of different techniques are currently available to characterize causal influence in the brain. Typically, these techniques quantify the statistical

  12. Operating a global seismic network - perspectives from the USGS GSN

    NASA Astrophysics Data System (ADS)

    Gee, L. S.; Derr, J. S.; Hutt, C. R.; Bolton, H.; Ford, D.; Gyure, G. S.; Storm, T.; Leith, W.

    2007-05-01

    The Global Seismographic Network (GSN) is a permanent digital network of state-of-the-art seismological and geophysical sensors connected by a global telecommunications network, serving as a multi-use scientific facility used for seismic monitoring for response applications, basic and applied research in solid earthquake geophysics, and earth science education. A joint program of the U.S. Geological Survey (USGS), the National Science Foundation, and Incorporated Research Institutions in Seismology (IRIS), the GSN provides near- uniform, worldwide monitoring of the Earth through 144 modern, globally distributed seismic stations. The USGS currently operates 90 GSN or GSN-affiliate stations. As a US government program, the USGS GSN is evaluated on several performance measures including data availability, data latency, and cost effectiveness. The USGS-component of the GSN, like the GSN as a whole, is in transition from a period of rapid growth to steady- state operations. The program faces challenges of aging equipment and increased operating costs at the same time that national and international earthquake and tsunami monitoring agencies place an increased reliance on GSN data. Data acquisition of the USGS GSN is based on the Quanterra Q680 datalogger, a workhorse system that is approaching twenty years in the field, often in harsh environments. An IRIS instrumentation committee recently selected the Quanterra Q330 HR as the "next generation" GSN data acquisition system, and the USGS will begin deploying the new equipment in the middle of 2007. These new systems will address many of the issues associated with the ageing Q680 while providing a platform for interoperability across the GSN.. In order to address the challenge of increasing operational costs, the USGS employs several tools. First, the USGS benefits from the contributions of local host institutions. The station operators are the first line of defense when a station experiences problems, changing boards

  13. Evolution and Controllability of Cancer Networks: A Boolean Perspective.

    PubMed

    Srihari, Sriganesh; Raman, Venkatesh; Leong, Hon Wai; Ragan, Mark A

    2014-01-01

    Cancer forms a robust system capable of maintaining stable functioning (cell sustenance and proliferation) despite perturbations. Cancer progresses as stages over time typically with increasing aggressiveness and worsening prognosis. Characterizing these stages and identifying the genes driving transitions between them is critical to understand cancer progression and to develop effective anti-cancer therapies. In this work, we propose a novel model for the `cancer system' as a Boolean state space in which a Boolean network, built from protein-interaction and gene-expression data from different stages of cancer, transits between Boolean satisfiability states by "editing" interactions and "flipping" genes. Edits reflect rewiring of the PPI network while flipping of genes reflect activation or silencing of genes between stages. We formulate a minimization problem min flip to identify these genes driving the transitions. The application of our model (called BoolSpace) on three case studies-pancreatic and breast tumours in human and post spinal-cord injury (SCI) in rats-reveals valuable insights into the phenomenon of cancer progression: (i) interactions involved in core cell-cycle and DNA-damage repair pathways are significantly rewired in tumours, indicating significant impact to key genome-stabilizing mechanisms; (ii) several of the genes flipped are serine/threonine kinases which act as biological switches, reflecting cellular switching mechanisms between stages; and (iii) different sets of genes are flipped during the initial and final stages indicating a pattern to tumour progression. Based on these results, we hypothesize that robustness of cancer partly stems from "passing of the baton" between genes at different stages-genes from different biological processes and/or cellular components are involved in different stages of tumour progression thereby allowing tumour cells to evade targeted therapy, and therefore an effective therapy should target a "cover set" of

  14. A differential equation for specific catchment area

    NASA Astrophysics Data System (ADS)

    Gallant, John C.; Hutchinson, Michael F.

    2011-05-01

    Analysis of the behavior of specific catchment area in a stream tube leads to a simple nonlinear differential equation describing the rate of change of specific catchment area along a flow path. The differential equation can be integrated numerically along a flow path to calculate specific catchment area at any point on a digital elevation model without requiring the usual estimates of catchment area and width. The method is more computationally intensive than most grid-based methods for calculating specific catchment area, so its main application is as a reference against which conventional methods can be tested. This is the first method that provides a benchmark for more approximate methods in complex terrain with both convergent and divergent areas, not just on simple surfaces for which analytical solutions are known. Preliminary evaluation of the D8, M8, digital elevation model networks (DEMON), and D∞ methods indicate that the D∞ method is the best of those methods for estimating specific catchment area, but all methods overestimate in divergent terrain.

  15. Spectral Analysis in Catchment Hydrology and Geochemistry

    NASA Astrophysics Data System (ADS)

    Kirchner, J. W.; Feng, X.; Renshaw, C. E.; Neal, C.

    2001-12-01

    Spectral analysis of chemical tracer time series can be used to probe the internal workings of catchments. It has recently been shown that catchments act as fractal filters for inert chemical tracers like chloride, converting "white noise" rainfall chemistry inputs into fractal "1/f noise" runoff chemistry time series (Kirchner et al., 2000). This implies that catchments have long-tailed travel time distributions, and thus retain soluble contaminants for unexpectedly long timespans. Long-term monitoring data from North America, Britain, and Scandinavia show that this fractal behavior characterizes a wide array of catchments. How can this fractal scaling arise in such diverse settings? One can show that advection and dispersion of spatially distributed rainfall tracer inputs will generate fractal tracer time series, as long as the flow system is highly dispersive (Kirchner et al., in press). This implies that subsurface flow in small catchments is dominated by large conductivity contrasts, such as arise from macropores, fracture networks, and similar large-scale heterogeneities in subsurface conductivity. One can also use spectral methods to analyze long-term time series of water fluxes in rainfall and streamflow. Spectral analysis of hydrologic time series measures the downslope propagation of the hydraulic potential waves that mobilize runoff, whereas spectral analysis of tracer time series clocks the propagation of water itself through the catchment. Water fluxes in streamflow exhibit non-fractal scaling, instead of the fractal 1/f scaling shown by chemical tracers. These observations imply that hydrologic signals are transmitted downslope more rapidly, and with much less dispersion, than chemical tracer signals are. Thus small upland catchments transmit hydraulic potentials (which drive runoff) much less dispersively than they transport water itself. These observations provide important constraints for theoretical models of subsurface flow and transport in

  16. Research on Single Nucleotide Polymorphisms Interaction Detection from Network Perspective

    PubMed Central

    Su, Lingtao; Liu, Guixia; Wang, Han; Tian, Yuan; Zhou, Zhihui; Han, Liang; Yan, Lun

    2015-01-01

    Single Nucleotide Polymorphisms (SNPs) found in Genome-Wide Association Study (GWAS) mainly influence the susceptibility of complex diseases, but they still could not comprehensively explain the relationships between mutations and diseases. Interactions between SNPs are considered so important for deeply understanding of those relationships that several strategies have been proposed to explore such interactions. However, part of those methods perform poorly when marginal effects of disease loci are weak or absent, others may lack of considering high-order SNPs interactions, few methods have achieved the requirements in both performance and accuracy. Considering the above reasons, not only low-order, but also high-order SNP interactions as well as main-effect SNPs, should be taken into account in detection methods under an acceptable computational complexity. In this paper, a new pairwise (or low-order) interaction detection method IG (Interaction Gain) is introduced, in which disease models are not required and parallel computing is utilized. Furthermore, high-order SNP interactions were proposed to be detected by finding closely connected function modules of the network constructed from IG detection results. Tested by a wide range of simulated datasets and four WTCCC real datasets, the proposed methods accurately detected both low-order and high-order SNP interactions as well as disease-associated main-effect SNPS and it surpasses all competitors in performances. The research will advance complex diseases research by providing more reliable SNP interactions. PMID:25763929

  17. Research on single nucleotide polymorphisms interaction detection from network perspective.

    PubMed

    Su, Lingtao; Liu, Guixia; Wang, Han; Tian, Yuan; Zhou, Zhihui; Han, Liang; Yan, Lun

    2015-01-01

    Single Nucleotide Polymorphisms (SNPs) found in Genome-Wide Association Study (GWAS) mainly influence the susceptibility of complex diseases, but they still could not comprehensively explain the relationships between mutations and diseases. Interactions between SNPs are considered so important for deeply understanding of those relationships that several strategies have been proposed to explore such interactions. However, part of those methods perform poorly when marginal effects of disease loci are weak or absent, others may lack of considering high-order SNPs interactions, few methods have achieved the requirements in both performance and accuracy. Considering the above reasons, not only low-order, but also high-order SNP interactions as well as main-effect SNPs, should be taken into account in detection methods under an acceptable computational complexity. In this paper, a new pairwise (or low-order) interaction detection method IG (Interaction Gain) is introduced, in which disease models are not required and parallel computing is utilized. Furthermore, high-order SNP interactions were proposed to be detected by finding closely connected function modules of the network constructed from IG detection results. Tested by a wide range of simulated datasets and four WTCCC real datasets, the proposed methods accurately detected both low-order and high-order SNP interactions as well as disease-associated main-effect SNPS and it surpasses all competitors in performances. The research will advance complex diseases research by providing more reliable SNP interactions. PMID:25763929

  18. Measuring the default risk of sovereign debt from the perspective of network

    NASA Astrophysics Data System (ADS)

    Chuang, Hongwei; Ho, Hwai-Chung

    2013-05-01

    Recently, there has been a growing interest in network research, especially in the fields of biology, computer science, and sociology. It is natural to address complex financial issues such as the European sovereign debt crisis from the perspective of network. In this article, we construct a network model according to the debt-credit relations instead of using the conventional methodology to measure the default risk. Based on the model, a risk index is examined using the quarterly report of consolidated foreign claims from the Bank for International Settlements (BIS) and debt/GDP ratios among these reporting countries. The empirical results show that this index can help the regulators and practitioners not only to determine the status of interconnectivity but also to point out the degree of the sovereign debt default risk. Our approach sheds new light on the investigation of quantifying the systemic risk.

  19. Photonic Network R&D Activities in Japan-Current Activities and Future Perspectives

    NASA Astrophysics Data System (ADS)

    Kitayama, Ken-Ichi; Miki, Tetsuya; Morioka, Toshio; Tsushima, Hideaki; Koga, Masafumi; Mori, Kazuyuki; Araki, Soichiro; Sato, Ken-Ichi; Onaka, Hiroshi; Namiki, Shu; Aoyama, Tomonori

    2005-10-01

    R&D activities on photonic networks in Japan are presented. First, milestones in current ongoing R&D programs supported by Japanese government agencies are introduced, including long-distance and wavelength division multiplexing (WDM) fiber transmission, wavelength routing, optical burst switching (OBS), and control-plane technology for IP backbone networks. Their goal was set to evolve a legacy telecommunications network to IP-over-WDM networks by introducing technologies for WDM and wavelength routing. We then discuss the perspectives of so-called PHASE II R&D programs for photonic networks over the next 5 years until 2010, by focusing on the report that has been recently issued by the Photonic Internet Forum (PIF), a consortium that has major carriers, telecom vendors, and Japanese academics as members. The PHASE II R&D programs should serve to establish a photonic platform to provide abundant bandwidth on demand, at any time on a real-time basis, through the customer's initiative to promote bandwidth-rich applications, such as grid computing, real-time digital-cinema streaming, medical and educational applications, and network storage in e-commerce.

  20. Resistance and Security Index of Networks: Structural Information Perspective of Network Security

    NASA Astrophysics Data System (ADS)

    Li, Angsheng; Hu, Qifu; Liu, Jun; Pan, Yicheng

    2016-06-01

    Recently, Li and Pan defined the metric of the K-dimensional structure entropy of a structured noisy dataset G to be the information that controls the formation of the K-dimensional structure of G that is evolved by the rules, order and laws of G, excluding the random variations that occur in G. Here, we propose the notion of resistance of networks based on the one- and two-dimensional structural information of graphs. Given a graph G, we define the resistance of G, written , as the greatest overall number of bits required to determine the code of the module that is accessible via random walks with stationary distribution in G, from which the random walks cannot escape. We show that the resistance of networks follows the resistance law of networks, that is, for a network G, the resistance of G is , where and are the one- and two-dimensional structure entropies of G, respectively. Based on the resistance law, we define the security index of a network G to be the normalised resistance of G, that is, . We show that the resistance and security index are both well-defined measures for the security of the networks.

  1. Resistance and Security Index of Networks: Structural Information Perspective of Network Security

    PubMed Central

    Li, Angsheng; Hu, Qifu; Liu, Jun; Pan, Yicheng

    2016-01-01

    Recently, Li and Pan defined the metric of the K-dimensional structure entropy of a structured noisy dataset G to be the information that controls the formation of the K-dimensional structure of G that is evolved by the rules, order and laws of G, excluding the random variations that occur in G. Here, we propose the notion of resistance of networks based on the one- and two-dimensional structural information of graphs. Given a graph G, we define the resistance of G, written , as the greatest overall number of bits required to determine the code of the module that is accessible via random walks with stationary distribution in G, from which the random walks cannot escape. We show that the resistance of networks follows the resistance law of networks, that is, for a network G, the resistance of G is , where and are the one- and two-dimensional structure entropies of G, respectively. Based on the resistance law, we define the security index of a network G to be the normalised resistance of G, that is, . We show that the resistance and security index are both well-defined measures for the security of the networks. PMID:27255783

  2. Resistance and Security Index of Networks: Structural Information Perspective of Network Security.

    PubMed

    Li, Angsheng; Hu, Qifu; Liu, Jun; Pan, Yicheng

    2016-01-01

    Recently, Li and Pan defined the metric of the K-dimensional structure entropy of a structured noisy dataset G to be the information that controls the formation of the K-dimensional structure of G that is evolved by the rules, order and laws of G, excluding the random variations that occur in G. Here, we propose the notion of resistance of networks based on the one- and two-dimensional structural information of graphs. Given a graph G, we define the resistance of G, written , as the greatest overall number of bits required to determine the code of the module that is accessible via random walks with stationary distribution in G, from which the random walks cannot escape. We show that the resistance of networks follows the resistance law of networks, that is, for a network G, the resistance of G is , where and are the one- and two-dimensional structure entropies of G, respectively. Based on the resistance law, we define the security index of a network G to be the normalised resistance of G, that is, . We show that the resistance and security index are both well-defined measures for the security of the networks. PMID:27255783

  3. The California Integrated Seismic Network:status and perspectives

    NASA Astrophysics Data System (ADS)

    CISN,

    2001-12-01

    The California Integrated Seismic Network (CISN) is a consortium of federal, state and academic institutions engaged in earthquake monitoring in California. The CISN represents California as a designated region of the Advanced National Seismic System (ANSS). The CISN is governed by a Steering Committee representing institutions actively involved in earthquake monitoring in California (currently USGS, CDMG, UCB and Caltech) and the California OES. Current members of the CISN Steering Committee are Barbara Romanowicz (chair) and Lind Gee (both at UCB), David Oppenheimer and Mary-Lou Zoback (both at USGS/Menlo Park), Egill Hauksson and Robert Clayton (both at Caltech), Jim Davis and Tony Shakal (both at CDMG), Lucy Jones (vice-chair) and David Wald (both at USGS/Pasadena), Rich Eisner (OES) and Chris Poland (Degenkolb Engineers; head of the CISN Advisory Committee). A major goal of the CISN is to ensure a more uniform system for earthquake monitoring, through the improvement of seismic infrastructure in northern California and continued maintenance of the TriNet system in southern California. Another major goal is to integrate the earthquake monitoring and reporting efforts in California, utilizing compatible softrware and creating a single catalog. In particular, we will work to improve the robustness of statewide rapid notification and work with the California OES and other emergency responders to maximize the use and benefit of this real time seismic information. In the coming year, with new support from the State of California through the Office of Emergency Services, and from the ANSS program of the USGS, more than 50 new strong-motion stations will be installed, with a focus in the San Francisco Bay Area, in order to improve coverage for ShakeMap and 2 new broadband stations will be deployed in northern California to enhance earthquake reporting. CISN is also contributing to structural monitoring. The CISN is also focusing on data distribution and plans to

  4. Ocean Research - Perspectives from an international Ocean Research Coordination Network

    NASA Astrophysics Data System (ADS)

    Pearlman, Jay; Williams, Albert, III

    2013-04-01

    The need for improved coordination in ocean observations is more urgent now given the issues of climate change, sustainable food sources and increased need for energy. Ocean researchers must work across disciplines to provide policy makers with clear and understandable assessments of the state of the ocean. With advances in technology, not only in observation, but also communication and computer science, we are in a new era where we can answer questions asked over the last 100 years at the time and space scales that are relevant. Programs like GLOBEC moved us forward but we are still challenged by the disciplinary divide. Interdisciplinary problem solving must be addressed not only by the exchange of data between the many sides, but through levels where questions require day-to-day collaboration. A National Science Foundation-funded Research Coordination Network (RCN) is addressing approaches for improving interdisciplinary research capabilities in the ocean sciences. During the last year, the RCN had a working group for Open Data led by John Orcutt, Peter Pissierssens and Albert Williams III. The teams has focused on three areas: 1. Data and Information formats and standards; 2. Data access models (including IPR, business models for open data, data policies,...); 3. Data publishing, data citation. There has been a significant trend toward free and open access to data in the last few years. In 2007, the US announced that Landsat data would be available at no charge. Float data from the US (NDBC), JCOMM and OceanSites offer web-based access. The IODE is developing its Ocean Data Portal giving immediate and free access to ocean data. However, from the aspect of long-term collaborations across communities, this global trend is less robust than might appear at the surface. While there are many standard data formats for data exchange, there is not yet widespread uniformity in their adoption. Use of standard data formats can be encouraged in several ways: sponsors of

  5. Water Catchment and Storage Monitoring

    NASA Astrophysics Data System (ADS)

    Bruenig, Michael; Dunbabin, Matt; Moore, Darren

    2010-05-01

    Sensors and Sensor Networks technologies provide the means for comprehensive understanding of natural processes in the environment by radically increasing the availability of empirical data about the natural world. This step change is achieved through a dramatic reduction in the cost of data acquisition and many orders of magnitude increase in the spatial and temporal granularity of measurements. Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) is undertaking a strategic research program developing wireless sensor network technology for environmental monitoring. As part of this research initiative, we are engaging with government agencies to densely monitor water catchments and storages, thereby enhancing understanding of the environmental processes that affect water quality. In the Gold Coast hinterland in Queensland, Australia, we are building sensor networks to monitor restoration of rainforest within the catchment, and to monitor methane flux release and water quality in the water storages. This poster will present our ongoing work in this region of eastern Australia. The Springbrook plateau in the Gold Coast hinterland lies within a World Heritage listed area, has uniquely high rainfall, hosts a wide range of environmental gradients, and forms part of the catchment for Gold Coast's water storages. Parts of the plateau are being restored from agricultural grassland to native rainforest vegetation. Since April 2008, we have had a 10-node, multi-hop sensor network deployed there to monitor microclimate variables. This network will be expanded to 50-nodes in February 2010, and to around 200-nodes and 1000 sensors by mid-2011, spread over an area of approximately 0.8 square kilometers. The extremely dense microclimate sensing will enhance knowledge of the environmental factors that enhance or inhibit the regeneration of native rainforest. The final network will also include nodes with acoustic and image sensing capability for

  6. Real Time Semantic Interoperability in AD HOC Networks of Geospatial Data Sources: Challenges, Achievements and Perspectives

    NASA Astrophysics Data System (ADS)

    Mostafavi, M. A.; Bakillah, M.

    2012-07-01

    Recent advances in geospatial technologies have made available large amount of geospatial data. Meanwhile, new developments in Internet and communication technologies created a shift from isolated geospatial databases to ad hoc networks of geospatial data sources, where data sources can join or leave the network, and form groups to share data and services. However, effective integration and sharing of geospatial data among these data sources and their users are hampered by semantic heterogeneities. These heterogeneities affect the spatial, temporal and thematic aspects of geospatial concepts. There have been many efforts to address semantic interoperability issues in the geospatial domain. These efforts were mainly focused on resolving heterogeneities caused by different and implicit representations of the concepts. However, many approaches have focused on the thematic aspects, leaving aside the explicit representation of spatial and temporal aspects. Also, most semantic interoperability approaches for networks have focused on automating the semantic mapping process. However, the ad hoc network structure is continuously modified by source addition or removal, formation of groups, etc. This dynamic aspect is often neglected in those approaches. This paper proposes a conceptual framework for real time semantic interoperability in ad hoc networks of geospatial data sources. The conceptual framework presents the fundamental elements of real time semantic interoperability through a hierarchy of interrelated semantic states and processes. Then, we use the conceptual framework to set the discussion on the achievements that have already been made, the challenges that remain to be addressed and perspectives with respect to these challenges.

  7. Competing endogenous RNA networks in human cancer: hypothesis, validation, and perspectives

    PubMed Central

    Jin, Yinji; Wang, Dong; Wang, Tianzhen; Li, Xiaobo

    2016-01-01

    Non-coding RNAs represent a majority of the human transcriptome. However, less is known about the functions and regulatory mechanisms of most non-coding species. Moreover, little is known about the potential non-coding functions of coding RNAs. The competing endogenous RNAs (ceRNAs) hypothesis is proposed recently. This hypothesis describes potential communication networks among all transcript RNA species mediated by miRNAs and miRNA-recognizing elements (MREs) within RNA transcripts. Here we review the evolution of the ceRNA hypothesis, summarize the validation experiments and discusses the significance and perspectives of this hypothesis in human cancer. PMID:26872371

  8. Catchment scale multi-objective flood management

    NASA Astrophysics Data System (ADS)

    Rose, Steve; Worrall, Peter; Rosolova, Zdenka; Hammond, Gene

    2010-05-01

    Rural land management is known to affect both the generation and propagation of flooding at the local scale, but there is still a general lack of good evidence that this impact is still significant at the larger catchment scale given the complexity of physical interactions and climatic variability taking place at this level. The National Trust, in partnership with the Environment Agency, are managing an innovative project on the Holnicote Estate in south west England to demonstrate the benefits of using good rural land management practices to reduce flood risk at the both the catchment and sub-catchment scales. The Holnicote Estate is owned by the National Trust and comprises about 5,000 hectares of land, from the uplands of Exmoor to the sea, incorporating most of the catchments of the river Horner and Aller Water. There are nearly 100 houses across three villages that are at risk from flooding which could potentially benefit from changes in land management practices in the surrounding catchment providing a more sustainable flood attenuation function. In addition to the contribution being made to flood risk management there are a range of other ecosystems services that will be enhanced through these targeted land management changes. Alterations in land management will create new opportunities for wildlife and habitats and help to improve the local surface water quality. Such improvements will not only create additional wildlife resources locally but also serve the landscape response to climate change effects by creating and enhancing wildlife networks within the region. Land management changes will also restore and sustain landscape heritage resources and provide opportunities for amenity, recreation and tourism. The project delivery team is working with the National Trust from source to sea across the entire Holnicote Estate, to identify and subsequently implement suitable land management techniques to manage local flood risk within the catchments. These

  9. [Opportunity for the integration of the gender perspective in health research and innovation in Europe: COST Network genderSTE].

    PubMed

    Sánchez de Madariaga, Inés; Ruiz Cantero, María Teresa

    2014-01-01

    The European Commission supports several routes for incorporating the gender perspective. The Commission currently supports the new Horizon 2020 program, and also funds projects such as "gendered innovations", which show how gender innovations increase the quality of research and professional practice for health and welfare. One of the policy instruments is the Recommendation on Gender, Science and Innovation. Against this background, the international European Cooperation in Science and Technology (COST) network genderSTE (Gender, Science, Technology and Environment) was created, which seeks to: 1) promote structural changes in institutions to increase the number of women researchers; 2) identify the gender dimensions relevant to the environment; and 3) improve the integration of a gender perspective in research and technology. COST GenderSTE supports networking and the dissemination of knowledge with a gender perspective. All these tools provide an opportunity to incorporate a gender perspective in research in Europe. PMID:24852090

  10. Understanding Urban Traffic Flow Characteristics from the Network Centrality Perspective at Different Granularities

    NASA Astrophysics Data System (ADS)

    Zhao, P. X.; Zhao, S. M.

    2016-06-01

    In this study, we analyze urban traffic flow using taxi trajectory data to understand the characteristics of traffic flow from the network centrality perspective at point (intersection), line (road), and area (community) granularities. The entire analysis process comprises three steps. The first step utilizes the taxi trajectory data to evaluate traffic flow at different granularities. Second, the centrality indices are calculated based on research units at different granularities. Third, correlation analysis between the centrality indices and corresponding urban traffic flow is performed. Experimental results indicate that urbaxperimental results indicate that urbaxperimental results indicate that urban traffic flow is relatively influenced by the road network structure. However, urban traffic flow also depends on the research unit size. Traditional centralities and traffic flow exhibit a low correlation at point granularity but exhibit a high correlation at line and area granularities. Furthermore, the conclusions of this study reflect the universality of the modifiable areal unit problem.

  11. The network and the remodeling theories of aging: historical background and new perspectives.

    PubMed

    Franceschi, C; Valensin, S; Bonafè, M; Paolisso, G; Yashin, A I; Monti, D; De Benedictis, G

    2000-09-01

    Two general theories, i.e. "the network theory of aging" (1989) and "the remodeling theory of aging" (1995), as well as their implications, new developments, and perspectives are reviewed and discussed. Particular attention has been paid to illustrate: (i) how the network theory of aging fits with recent data on aging and longevity in unicellular organisms (yeast), multicellular organisms (worms), and mammals (mice and humans); (ii) the evolutionary and experimental basis of the remodeling theory of aging (immunological, genetic, and metabolic data in healthy centenarians, and studies on the evolution of the immune response, stress and inflammation) and its recent development (the concepts of "immunological space" and "inflamm-aging"); (iii) the profound relationship between these two theories and the data which suggest that aging and longevity are related, in a complex way, to the capability to cope with a variety of stressors. PMID:11053678

  12. A Faculty Peer Network for Integrating Consumer Health Solutions in Nursing Education: Contextual Influences and Perspectives.

    PubMed

    Doyle, Glynda

    2016-01-01

    The Canadian Association of Schools of Nursing and Canada Health Infoway recently launched a national project to facilitate the integration of digital and consumer health solutions into undergraduate nursing programs across Canada. Led by eleven nursing faculty members with expertise in informatics, the Digital Health Nursing Faculty Peer Network provided a forum for mentorship and support to other nursing faculty (72) across Canada and facilitated the development of a number of strategies to advance the incorporation of digital health content into undergraduate nursing curricula (e.g., the creation of a Faculty Toolkit for teaching Consumer Health Solutions). In this panel presentation, contextual and regional influences as well as specific perspectives related to the experience of each of the panelists within the Faculty Peer Network project will be outlined and discussed. PMID:27332275

  13. Exploring links between tectonics, catchment morphology and hydrographs across Europe

    NASA Astrophysics Data System (ADS)

    Vanmaercke, Matthias; Campforts, Benjamin; Van Ruyskensvelde, Glenn; Poesen, Jean

    2016-04-01

    A growing number of studies show that contemporary catchment sediment yields (SY, [t/km²/y]) are strongly correlated to patterns of seismic activity at regional to continental scales. Nonetheless, the mechanisms explaining these correlations are still poorly understood. Seismicity may increase SY by triggering landslides or weakening the surface lithology. On the other hand seismicity can be considered as a proxy for tectonic movements, while there is a growing consensus that tectonics exert an important influence on catchment morphology. This morphology influences the properties of runoff events (e.g. peak discharge, stream power). Given the large influence of large runoff events on annual SY, it is therefore possible that observed correlations between SY and seismicity are (at least partly) attributable to tectonic influences on catchment morphology. We test this hypothesis by investigating links between runoff hydrographs and patterns in catchment properties at a European scale using numerous catchment indices such as the slope, channel steepness, circularity, drainage length, river network topology, etc. From DEMs with a resolution of ca. 100m we randomly delineated over 5000 catchments across Europe with an area of 90 to 100 km². For each of these catchments, we simulated a runoff hydrograph, using a simple Hortonian runoff model that routes water through the catchment based on previously proposed flow velocity equations. We made abstraction of rainfall patterns, lithology, land use and all factors other than topography. Hence, the hydrographs only reflect the influence of the morphological properties of the catchments and allow for comparisons. First results show that, apart from average catchment slope, there are very few regional patterns in catchment morphological properties that may significantly affect hydrographs. In some tectonically active regions, channel slopes are slightly steeper compared to catchments with the same average catchment slope in

  14. Local Community Mining on Distributed and Dynamic Networks From a Multiagent Perspective.

    PubMed

    Bu, Zhan; Wu, Zhiang; Cao, Jie; Jiang, Yichuan

    2016-04-01

    Distributed and dynamic networks are ubiquitous in many real-world applications. Due to the huge-scale, decentralized, and dynamic characteristics, the global topological view is either too hard to obtain or even not available. So, most existing community detection methods working on the global view fail to handle such decentralized and dynamic large networks. In this paper, we propose a novel autonomy-oriented computing-based method for community mining (AOCCM) from the multiagent perspective in the distributed environment. In particular, AOCCM utilizes reactive agents to pick the neighborhood node with the largest structural similarity as the candidate node, and thus determine whether it should be added into local community based on the modularity gain. We further improve AOCCM to a more efficient incremental version named AOCCM-i for mining communities from dynamic networks. AOCCM and AOCCM-i can be easily expanded to detect both nonoverlapping and overlapping global community structures. Experimental results on real-life networks demonstrate that the proposed methods can reduce the computational cost by avoiding repeated structural similarity calculation and can still obtain the high-quality communities. PMID:26087512

  15. Constructing networks from a dynamical system perspective for multivariate nonlinear time series

    NASA Astrophysics Data System (ADS)

    Nakamura, Tomomichi; Tanizawa, Toshihiro; Small, Michael

    2016-03-01

    We describe a method for constructing networks for multivariate nonlinear time series. We approach the interaction between the various scalar time series from a deterministic dynamical system perspective and provide a generic and algorithmic test for whether the interaction between two measured time series is statistically significant. The method can be applied even when the data exhibit no obvious qualitative similarity: a situation in which the naive method utilizing the cross correlation function directly cannot correctly identify connectivity. To establish the connectivity between nodes we apply the previously proposed small-shuffle surrogate (SSS) method, which can investigate whether there are correlation structures in short-term variabilities (irregular fluctuations) between two data sets from the viewpoint of deterministic dynamical systems. The procedure to construct networks based on this idea is composed of three steps: (i) each time series is considered as a basic node of a network, (ii) the SSS method is applied to verify the connectivity between each pair of time series taken from the whole multivariate time series, and (iii) the pair of nodes is connected with an undirected edge when the null hypothesis cannot be rejected. The network constructed by the proposed method indicates the intrinsic (essential) connectivity of the elements included in the system or the underlying (assumed) system. The method is demonstrated for numerical data sets generated by known systems and applied to several experimental time series.

  16. A flexible multi-model framework for catchment-specific calibration, and application to diverse European catchments

    NASA Astrophysics Data System (ADS)

    Kavetski, Dmitri; Fenicia, Fabrizio; Savenije, Hubert H. G.

    2010-05-01

    If one accepts that a single model structure cannot accommodate the wide spectrum of catchment dynamics encountered in practice, the need for flexible hydrological models becomes evident. Here, we present SUPERFLEX, a hydrological modelling system that represent the catchment as a network of conceptual elements, including nonlinear reservoirs and routing components, with connectivity, constitutive relations and parameterizations specified by the Hydrologist using a priori insights into the catchment of interest, and refined based on calibration results. The model equations are implemented using robust numerical approaches, and the entire SUPERFLEX system is integrated into a Bayesian inference suite, permitting hypotheses regarding forcing/response data to be evaluated and refined as part of the model inference. The application of the SUPERFLEX approach to a range of European catchments is presented, demonstrating how the ability to adjust the model structure to specific catchments allows improved representatation of its key hydrological processes, and consequently improved model performance.

  17. Understanding Online Health Groups for Depression: Social Network and Linguistic Perspectives

    PubMed Central

    2016-01-01

    Background Mental health problems have become increasingly prevalent in the past decade. With the advance of Web 2.0 technologies, social media present a novel platform for Web users to form online health groups. Members of online health groups discuss health-related issues and mutually help one another by anonymously revealing their mental conditions, sharing personal experiences, exchanging health information, and providing suggestions and support. The conversations in online health groups contain valuable information to facilitate the understanding of their mutual help behaviors and their mental health problems. Objective We aimed to characterize the conversations in a major online health group for major depressive disorder (MDD) patients in a popular Chinese social media platform. In particular, we intended to explain how Web users discuss depression-related issues from the perspective of the social networks and linguistic patterns revealed by the members’ conversations. Methods Social network analysis and linguistic analysis were employed to characterize the social structure and linguistic patterns, respectively. Furthermore, we integrated both perspectives to exploit the hidden relations between them. Results We found an intensive use of self-focus words and negative affect words. In general, group members used a higher proportion of negative affect words than positive affect words. The social network of the MDD group for depression possessed small-world and scale-free properties, with a much higher reciprocity ratio and clustering coefficient value as compared to the networks of other social media platforms and classic network models. We observed a number of interesting relationships, either strong correlations or convergent trends, between the topological properties and linguistic properties of the MDD group members. Conclusions (1) The MDD group members have the characteristics of self-preoccupation and negative thought content, according to Beck

  18. What determines social capital in a social-ecological system? Insights from a network perspective.

    PubMed

    Barnes-Mauthe, Michele; Gray, Steven Allen; Arita, Shawn; Lynham, John; Leung, PingSun

    2015-02-01

    Social capital is an important resource that can be mobilized for purposive action or competitive gain. The distribution of social capital in social-ecological systems can determine who is more productive at extracting ecological resources and who emerges as influential in guiding their management, thereby empowering some while disempowering others. Despite its importance, the factors that contribute to variation in social capital among individuals have not been widely studied. We adopt a network perspective to examine what determines social capital among individuals in social-ecological systems. We begin by identifying network measures of social capital relevant for individuals in this context, and review existing evidence concerning their determinants. Using a complete social network dataset from Hawaii's longline fishery, we employ social network analysis and other statistical methods to empirically estimate these measures and determine the extent to which individual stakeholder attributes explain variation within them. We find that ethnicity is the strongest predictor of social capital. Measures of human capital (i.e., education, experience), years living in the community, and information-sharing attitudes are also important. Surprisingly, we find that when controlling for other factors, industry leaders and formal fishery representatives are generally not well connected. Our results offer new quantitative insights on the relationship between stakeholder diversity, social networks, and social capital in a coupled social-ecological system, which can aid in identifying barriers and opportunities for action to overcome resource management problems. Our results also have implications for achieving resource governance that is not only ecologically and economically sustainable, but also equitable. PMID:25376745

  19. What Determines Social Capital in a Social-Ecological System? Insights from a Network Perspective

    NASA Astrophysics Data System (ADS)

    Barnes-Mauthe, Michele; Gray, Steven Allen; Arita, Shawn; Lynham, John; Leung, PingSun

    2015-02-01

    Social capital is an important resource that can be mobilized for purposive action or competitive gain. The distribution of social capital in social-ecological systems can determine who is more productive at extracting ecological resources and who emerges as influential in guiding their management, thereby empowering some while disempowering others. Despite its importance, the factors that contribute to variation in social capital among individuals have not been widely studied. We adopt a network perspective to examine what determines social capital among individuals in social-ecological systems. We begin by identifying network measures of social capital relevant for individuals in this context, and review existing evidence concerning their determinants. Using a complete social network dataset from Hawaii's longline fishery, we employ social network analysis and other statistical methods to empirically estimate these measures and determine the extent to which individual stakeholder attributes explain variation within them. We find that ethnicity is the strongest predictor of social capital. Measures of human capital (i.e., education, experience), years living in the community, and information-sharing attitudes are also important. Surprisingly, we find that when controlling for other factors, industry leaders and formal fishery representatives are generally not well connected. Our results offer new quantitative insights on the relationship between stakeholder diversity, social networks, and social capital in a coupled social-ecological system, which can aid in identifying barriers and opportunities for action to overcome resource management problems. Our results also have implications for achieving resource governance that is not only ecologically and economically sustainable, but also equitable.

  20. Characterizing streamflow generation in Alpine catchments

    NASA Astrophysics Data System (ADS)

    Chiogna, Gabriele; Cano Paoli, Karina; Bellin, Alberto

    2016-04-01

    Developing effective hydrological models for streamflow generation in Alpine catchments is challenging due to the inherent complexity of the intertwined processes controlling water transfer from hillslopes to streams and along the river network. With water discharge as the sole observational variable it is impossible to differentiate between different streamflow sources, and modelling activity is often limited to simplified phenomenological rainfall-runoff models. This study focuses on quantifying streamflow sources at different temporal scales and the associated uncertainty by using natural tracer data (electrical conductivity, oxygen and hydrogen stable isotopes ratios) as observational variables supplementing streamflow measurements. We determine the spatial and temporal hydrological behavior and the mean residence time of water in the Vermigliana catchment, North-Eastern Italy and we separate contributions to streamflow originating from Presena and Presanella glaciers, both exerting a strong control on the hydrologic budget of the study site. Furthermore, we identify a seasonal control on the effect of storm events. The catchment responded rapidly to precipitation events in early autumn, it was unaffected by precipitation events in early spring, while runoff generation was enhanced by snow melting in late autumn. Air temperature is identified as the main controlling parameter, in addition to precipitation. Two-component mixing analysis showed that the relative contribution of new water, which can contribute up to 75% of total streamflow, is very rapid. Only two hours time-lag was observed between the beginning of the precipitation event and the emergence of a significant contribution of new water. These results evidence the relevance of mixing between pre-event and event water in the Vermigliana catchment, and in similar high elevation Alpine catchments. This study provides new insights on the dynamics of streamflow generation in Alpine catchments and a

  1. Pharmacy Faculty Members' Perspectives on the Student/Faculty Relationship in Online Social Networks

    PubMed Central

    Finley, Kristen N.; Ulbrich, Timothy R.; McAuley, James W.

    2010-01-01

    Objective To describe pharmacy faculty members' use of the online social network Facebook and compare the perspectives of faculty members with and without Facebook profiles regarding student/faculty relationships. Methods An electronic survey instrument was sent to full-time faculty members (n = 183) at 4 colleges of pharmacy in Ohio seeking their opinions on student/faculty relationships on Facebook. If respondents answered “yes” to having a Facebook profile, they were asked 14 questions on aspects of being “friends” with students. If respondents answered “no,” they were asked 4 questions. Results Of the 95 respondents (52%) to the survey instrument, 44 faculty members (46%) had a Facebook profile, while 51 faculty members (54%) did not. Those who had a profile had been faculty members for an average of 8.6 years, versus 11.4 years for those who did not have a Facebook profile. Seventy-nine percent of faculty members who used Facebook were not “friends” with their students. The majority of respondents reported that they would decline/ignore a “friend” request from a student, or decline until after the student graduated. Although a limited number of faculty members had used Facebook for online discussions, teaching purposes, or student organizations, the majority of universities did not have policies on the use of social networking sites. Conclusion Online social network sites are used widely by students and faculty members, which may raise questions regarding professionalism and appropriate faculty/student relationships. Further research should address the student/preceptor relationship, other online social networking sites, and whether students are interested in using these sites within the classroom and/or professional organizations. PMID:21436929

  2. Catchments of general practice in different countries– a literature review

    PubMed Central

    2014-01-01

    The purpose of this paper is to review the current research on catchment areas of private general practices in different developed countries because healthcare reform, including primary health care, has featured prominently as an important political issue in a number of developed countries. The debates around health reform have had a significant health geographic focus. Conceptually, GP catchments describe the distribution, composition and profile of patients who access a general practitioner or a general practice (i.e. a site or facility comprising one or more general practitioners). Therefore, GP catchments provide important information into the geographic variation of access rates, utilisation of services and health outcomes by all of the population or different population groups in a defined area or aggregated area. This review highlights a wide range of diversity in the literature as to how GP catchments can be described, the indicators and measures used to frame the scale of catchments. Patient access to general practice health care services should be considered from a range of locational concepts, and not necessarily constrained by their place of residence. An analysis of catchment patterns of general practitioners should be considered as dynamic and multi-perspective. Geographic information systems provide opportunities to contribute valuable methodologies to study these relationships. However, researchers acknowledge that a conceptual framework for the analysis of GP catchments requires access to real world data. Recent studies have shown promising developments in the use of real world data, especially from studies in the UK. Understanding the catchment profiles of individual GP surgeries is important if governments are serious about patient choice being a key part of proposed primary health reforms. Future health planning should incorporate models of GP catchments as planning tools, at the micro level as well as the macro level, to assist policies on the

  3. A network perspective on the calamity, induced inaccessibility of communities and the robustness of centralized, landbound relief efforts

    NASA Astrophysics Data System (ADS)

    Valenzuela, Jesus Felix; Legara, Erika Fille; Fu, Xiuju; Goh, Rick Siow Mong; de Souza, Robert; Monterola, Christopher

    2014-04-01

    We examine the robustness of centralized, landbound relief operations' capability to promptly reach areas affected by a disaster event from a network perspective. We initially look at two idealized road networks: a two-dimensional grid and a scale-free network, and compare them to an actual road network obtained from OpenStreetMap. We show that, from a node designated as the center for relief operations (a "relief center"), damage to a road network causes a substantial fraction of the other nodes (about 20% in the three networks we examined) to become initially inaccessible from any relief effort, although the remaining majority can still be reached readily. Furthermore, we show the presence of a threshold in the two idealized road networks but not in the real one. Below this threshold, all nodes can robustly be reached in a short span of time, and above it, not only the partitioning mentioned above sets in, but also the time needed to reach the nodes becomes susceptible to the amount of damage sustained by the road network. Under damage sustained by random segments of the network, this threshold is higher in the scale-free network compared to the grid, due to the robustness of the former against random attacks. Our results may be of importance in formulating contingency plans for the logistics of disaster relief operations.

  4. State of the Art of Network Security Perspectives in Cloud Computing

    NASA Astrophysics Data System (ADS)

    Oh, Tae Hwan; Lim, Shinyoung; Choi, Young B.; Park, Kwang-Roh; Lee, Heejo; Choi, Hyunsang

    Cloud computing is now regarded as one of social phenomenon that satisfy customers' needs. It is possible that the customers' needs and the primary principle of economy - gain maximum benefits from minimum investment - reflects realization of cloud computing. We are living in the connected society with flood of information and without connected computers to the Internet, our activities and work of daily living will be impossible. Cloud computing is able to provide customers with custom-tailored features of application software and user's environment based on the customer's needs by adopting on-demand outsourcing of computing resources through the Internet. It also provides cloud computing users with high-end computing power and expensive application software package, and accordingly the users will access their data and the application software where they are located at the remote system. As the cloud computing system is connected to the Internet, network security issues of cloud computing are considered as mandatory prior to real world service. In this paper, survey and issues on the network security in cloud computing are discussed from the perspective of real world service environments.

  5. Terrain representation impact on periurban catchment morphological properties

    NASA Astrophysics Data System (ADS)

    Rodriguez, F.; Bocher, E.; Chancibault, K.

    2013-04-01

    SummaryModelling the hydrological behaviour of suburban catchments requires an estimation of environmental features, including land use and hydrographic networks. Suburban areas display a highly heterogeneous composition and encompass many anthropogenic elements that affect water flow paths, such as ditches, sewers, culverts and embankments. The geographical data available, either raster or vector data, may be of various origins and resolutions. Urban databases often offer very detailed data for sewer networks and 3D streets, yet the data covering rural zones may be coarser. This study is intended to highlight the sensitivity of geographical data as well as the data discretisation method used on the essential features of a periurban catchment, i.e. the catchment border and the drainage network. Three methods are implemented for this purpose. The first is the DEM (for digital elevation model) treatment method, which has traditionally been applied in the field of catchment hydrology. The second is based on urban database analysis and focuses on vector data, i.e. polygons and segments. The third method is a TIN (or triangular irregular network), which provides a consistent description of flow directions from an accurate representation of slope. It is assumed herein that the width function is representative of the catchment's hydrological response. The periurban Chézine catchment, located within the Nantes metropolitan area in western France, serves as the case study. The determination of both the main morphological features and the hydrological response of a suburban catchment varies significantly according to the discretization method employed, especially on upstream rural areas. Vector- and TIN-based methods allow representing the higher drainage density of urban areas, and consequently reveal the impact of these areas on the width function, since the DEM method fails. TINs seem to be more appropriate to take streets into account, because it allows a finer

  6. A catchment scale water balance model for FIFE

    NASA Technical Reports Server (NTRS)

    Famiglietti, J. S.; Wood, E. F.; Sivapalan, M.; Thongs, D. J.

    1992-01-01

    A catchment scale water balance model is presented and used to predict evaporation from the King's Creek catchment at the First ISLSCP Field Experiment site on the Konza Prairie, Kansas. The model incorporates spatial variability in topography, soils, and precipitation to compute the land surface hydrologic fluxes. A network of 20 rain gages was employed to measure rainfall across the catchment in the summer of 1987. These data were spatially interpolated and used to drive the model during storm periods. During interstorm periods the model was driven by the estimated potential evaporation, which was calculated using net radiation data collected at site 2. Model-computed evaporation is compared to that observed, both at site 2 (grid location 1916-BRS) and the catchment scale, for the simulation period from June 1 to October 9, 1987.

  7. Design and development of a wireless sensor network to monitor snow depth in multiple catchments in the American River basin, California: hardware selection and sensor placement techniques

    NASA Astrophysics Data System (ADS)

    Kerkez, B.; Rice, R.; Glaser, S. D.; Bales, R. C.; Saksa, P. C.

    2010-12-01

    A 100-node wireless sensor network (WSN) was designed for the purpose of monitoring snow depth in two watersheds, spanning 3 km2 in the American River basin, in the central Sierra Nevada of California. The network will be deployed as a prototype project that will become a core element of a larger water information system for the Sierra Nevada. The site conditions range from mid-elevation forested areas to sub-alpine terrain with light forest cover. Extreme temperature and humidity fluctuations, along with heavy rain and snowfall events, create particularly challenging conditions for wireless communications. We show how statistics gathered from a previously deployed 60-node WSN, located in the Southern Sierra Critical Zone Observatory, were used to inform design. We adapted robust network hardware, manufactured by Dust Networks for highly demanding industrial monitoring, and added linear amplifiers to the radios to improve transmission distances. We also designed a custom data-logging board to interface the WSN hardware with snow-depth sensors. Due to the large distance between sensing locations, and complexity of terrain, we analyzed network statistics to select the location of repeater nodes, to create a redundant and reliable mesh. This optimized network topology will maximize transmission distances, while ensuring power-efficient network operations throughout harsh winter conditions. At least 30 of the 100 nodes will actively sense snow depth, while the remainder will act as sensor-ready repeaters in the mesh. Data from a previously conducted snow survey was used to create a Gaussian Process model of snow depth; variance estimates produced by this model were used to suggest near-optimal locations for snow-depth sensors to measure the variability across a 1 km2 grid. We compare the locations selected by the sensor placement algorithm to those made through expert opinion, and offer explanations for differences resulting from each approach.

  8. A methodological comparison of catchment storages in mountainous catchments

    NASA Astrophysics Data System (ADS)

    Weiler, Markus; Staudinger, Maria; Stölzle, Michael; Seeger, Stefan; Seibert, Jan; Stahl, Kerstin

    2015-04-01

    One of the most important functions of catchments is the temporary storage of water, which directly influences runoff dynamics, rainfall-runoff transformation, partitioning of evaporation and runoff fluxes, and accessibility of water to plants. Generally, a large catchment storage is considered beneficial and in particular increases the transit times and hence the buffer functioning related to water quality. Many different methods have been developed to assess catchment storage, however, there are hardly any direct comparisons of several of these methods. One challenge is the definition of water storage, while some methods allow estimation of the entire water storage in a catchment, other methods quantify only the dynamic storage. In addition, most studies focused more on lowland catchments with rain-dominated runoff regimes and observed groundwater fluctuations. Furthermore, these studies often focus on one or two catchments, but do not consider the influence of different climates on the relevance of water storage in the catchment. We applied a range of different methods to assess catchment storage characteristics in 18 catchments in the Swiss Alps, ranging from 500 to 2000m of mean elevation and hence from rainfall- to snowmelt dominated runoff regimes. The first method use only discharge information during recession periods and with varying approaches to extract discharge and storage changes between high flow and low flow, the dynamic catchment storage can be derived. In the next methods the conceptual hydrological model HBV is calibrated to the runoff dynamics and the dynamic and total catchment storages of the different compartments are being evaluated. The last methods are based on stable water isotope data analysis. We use the model TRANSEP to derive the dynamic storage as well as the total water storage of the catchment based on the transit times using several years of fortnightly isotope data in streamflow. The results show that the derived catchment

  9. Perspectives.

    ERIC Educational Resources Information Center

    Robertson, Shari; Camerini, Michael

    2001-01-01

    Provides background information on the U.S. Immigration and Naturalization Service Asylum office. Uses the perspective of two movie producers as they filmed a documentary film, "Well-founded Fear", about asylum and refugee protection. Includes information on how to order a classroom aid and the film. (CMK)

  10. Perspectives

    ERIC Educational Resources Information Center

    Tarone, Elaine

    2013-01-01

    The topic of this "Perspectives" column is "Requiring a Proficiency Level as a Requirement for U.S. K-12 Teacher Licensure." In 1998, the American Council of Teachers of Foreign Languages (ACTFL) began to work with the National Council for Accreditation of Teacher Education (NCATE), which accredits teacher education programs…

  11. Catchment controls on solute export

    NASA Astrophysics Data System (ADS)

    Musolff, Andreas; Schmidt, Christian; Selle, Benny; Fleckenstein, Jan H.

    2015-12-01

    Dynamics of solute export from catchments can be classified in terms of chemostatic and chemodynamic export regimes by an analysis of concentration-discharge relationships. Previous studies hypothesized that distinct export regimes emerge from the presence of solute mass stores within the catchment and their connectivity to the stream. However, so far a direct link of solute export to identifiable catchment characteristics is missing. Here we investigate long-term time series of stream water quality and quantity of nine neighboring catchments in Central Germany ranging from relatively pristine mountain catchments to agriculturally dominated lowland catchments, spanning large gradients in land use, geology, and climatic conditions. Given the strong collinearity of catchment characteristics we used partial least square regression analysis to quantify the predictive power of these characteristics for median concentrations and the metrics of export regime. We can show that median concentrations and metrics of the export regimes of major ions and nutrients can indeed be inferred from catchment characteristics. Strongest predictors for median concentrations were the share of arable land, discharge per area, runoff coefficient and available water capacity in the root zone of the catchments. The available water capacity in the root zone, the share of arable land being artificially drained and the topographic gradient were found to be the most relevant predictors for the metrics of export regime. These catchment characteristics can represent the size of solute mass store such as the fraction of arable land being a measure for the store of nitrate. On the other hand, catchment characteristics can be a measure for the connectivity of these solute stores to the stream such as the fraction of tile drained land in the catchments. This study demonstrates the potential of data-driven, top down analyses using simple metrics to classify and better understand dominant controls of

  12. An approach for aggregating upstream catchment information to support research and management of fluvial systems across large landscapes.

    PubMed

    Tsang, Yin-Phan; Wieferich, Daniel; Fung, Kuolin; Infante, Dana M; Cooper, Arthur R

    2014-01-01

    The growing quality and availability of spatial map layers (e.g., climate, geology, and land use) allow stream studies, which historically have occurred over small areas like a single watershed or stream reach, to increasingly explore questions from a landscape perspective. This large-scale perspective for fluvial studies depends on the ability to characterize influences on streams resulting from throughout entire upstream networks or catchments. While acquiring upstream information for a single reach is relatively straight-forward, this process becomes demanding when attempting to obtain summaries for all streams throughout a stream network and across large basins. Additionally, the complex nature of stream networks, including braided streams, adds to the challenge of accurately generating upstream summaries. This paper outlines an approach to solve these challenges by building a database and applying an algorithm to gather upstream landscape information for digitized stream networks. This approach avoids the need to directly use spatial data files in computation, and efficiently and accurately acquires various types of upstream summaries of landscape information across large regions using tabular processing. In particular, this approach is not limited to the use of any specific database software or programming language, and its flexibility allows it to be adapted to any digitized stream network as long as it meets a few minimum requirements. This efficient approach facilitates the growing demand of acquiring upstream summaries at large geographic scales and helps to support the use of landscape information in assisting management and decision-making across large regions. PMID:25392769

  13. Colorectal cancer prevention: Perspectives of key players from social networks in a low-income rural US region.

    PubMed

    Schoenberg, Nancy E; Eddens, Kathryn; Jonas, Adam; Snell-Rood, Claire; Studts, Christina R; Broder-Oldach, Benjamin; Katz, Mira L

    2016-01-01

    Social networks influence health behavior and health status. Within social networks, "key players" often influence those around them, particularly in traditionally underserved areas like the Appalachian region in the USA. From a total sample of 787 Appalachian residents, we identified and interviewed 10 key players in complex networks, asking them what comprises a key player, their role in their network and community, and ideas to overcome and increase colorectal cancer (CRC) screening. Key players emphasized their communication skills, resourcefulness, and special occupational and educational status in the community. Barriers to CRC screening included negative perceptions of the colonoscopy screening procedure, discomfort with the medical system, and misinformed perspectives on screening. Ideas to improve screening focused on increasing awareness of women's susceptibility to CRC, providing information on different screening tests, improving access, and the key role of health-care providers and key players themselves. We provide recommendations to leverage these vital community resources. PMID:26905402

  14. Colorectal cancer prevention: Perspectives of key players from social networks in a low-income rural US region

    PubMed Central

    Schoenberg, Nancy E.; Eddens, Kathryn; Jonas, Adam; Snell-Rood, Claire; Studts, Christina R.; Broder-Oldach, Benjamin; Katz, Mira L.

    2016-01-01

    Social networks influence health behavior and health status. Within social networks, “key players” often influence those around them, particularly in traditionally underserved areas like the Appalachian region in the USA. From a total sample of 787 Appalachian residents, we identified and interviewed 10 key players in complex networks, asking them what comprises a key player, their role in their network and community, and ideas to overcome and increase colorectal cancer (CRC) screening. Key players emphasized their communication skills, resourcefulness, and special occupational and educational status in the community. Barriers to CRC screening included negative perceptions of the colonoscopy screening procedure, discomfort with the medical system, and misinformed perspectives on screening. Ideas to improve screening focused on increasing awareness of women's susceptibility to CRC, providing information on different screening tests, improving access, and the key role of health-care providers and key players themselves. We provide recommendations to leverage these vital community resources. PMID:26905402

  15. The application of GEOtop for catchment scale hydrology in Ireland

    NASA Astrophysics Data System (ADS)

    Lewis, C.; Xu, X.; Albertson, J.; Kiely, G.

    2009-04-01

    GEOtop represents the new generation of distributed hydrological model driven by geospatial data (e.g. topography, soils, vegetation, land cover). It estimates rainfall-runoff, evapotranspiration and provides spatially distributed outputs as well as routing water and sediment flows through stream and river networks. The original version of GEOtop designed in Italy, includes a rigorous treatment of the core hydrological processes (e.g. unsaturated and saturated flow and transport, surface energy balances, and streamflow generation/routing). Recently GEOtop was extended to include treatment of shallow landslides. The GEOtop model is built on an open-source programming framework, which makes it well suited for adaptation and extension. GEOtop has been run very successfully in a number of alpine catchments (such as Brenta) but has not been used on Irish catchments before. The cell size used for the spatially distributed inputs varies from catchment to catchment. In smaller catchments (less than 2000ha) 50 by 50m cells have been used and 200 by 200 for larger catchments. Smaller cell sizes have been found to significantly increase the computational time so a larger cell size is used providing it does not significantly affect the performance of the model. Digital elevation model, drainage direction, landuse and soil type maps are the minimum spatial requirements with precipitation, radiation, temperature, atmospheric pressure and wind speed been the minimum meteorological requirements for a successful run. The soil type maps must also contain information regarding texture and hydraulic conductivity. The first trial of GEOtop in Ireland was on a small 1524 ha catchment in the south of Ireland. The catchment ranges from 50 to just over 200m, the land use is predominately agricultural grassland and it receives on average 1400mm of rain per year. Within this catchment there is a meteorological tower which provides the meteorological inputs, soil moisture is also recorded at

  16. Quantifying human impacts on catchment sediment yield: A continental approach

    NASA Astrophysics Data System (ADS)

    Vanmaercke, Matthias; Poesen, Jean; Govers, Gerard; Verstraeten, Gert

    2015-07-01

    Both from a scientific and environmental management perspective, there is a large need to assess the magnitude and controlling factors of human impacts on catchment sediment yield. Quantifying this impact is difficult, since it requires knowing both the actual sediment yield (SYa, [t km- 2 y- 1]) as well as the corresponding "pristine" value of a catchment (SYp, [t km- 2 y- 1]; i.e. the sediment yield that can be expected if the catchment was not affected by humans). Here we address this problem by comparing measured SYa values for 165 European catchments that were unaffected by dams or reservoirs with their corresponding SYp, which were predicted using a recently developed regression model. The ratio between these two values is expected to reflect the degree of human impact on catchment sediment yield (HIF). Correlation and partial correlation analyses showed that spatial variability in HIF is mainly explained by differences in land use (i.e. the fraction of arable land) and catchment area. The effect of these two factors was clearly linked in western and central Europe: whereas SYa can be easily 40 times higher than SYp in intensively cultivated small (≤ 1 km2) catchments, the difference is negligible for large (> 1000 km2) catchments with the same land use. While, this concurs with our knowledge that the effects of land use (change) on erosion rates can be buffered at the catchment scale, this study provides a first robust quantification of this effect. Apart from a potential climatic effect (i.e. a correlation between HIF and the average annual air temperature) no other factors could be identified that are significant in explaining observed differences in HIF. This indicates that HIF is mainly controlled by catchment scale and land use, while other factors may be only of secondary importance at an intra-continental scale. Nonetheless, more accurate quantifications of these HIF values and more refined characterizations of the catchments in terms of (historical

  17. Investigation of rotated PCA from the perspective of network communities applied to climate data

    NASA Astrophysics Data System (ADS)

    Hartman, David; Hlinka, Jaroslav; Vejmelka, Martin; Palus, Milan

    2013-04-01

    , seasonality, and persistence of low-frequency atmospheric circulation patterns. Monthly Weather Review 115:1083-1126. Feldstein, SB (2000) The timescale, power spectra, and climate noise properties of teleconnection patterns. Journal of Climate 13(24), 4430-4440. Fortunato, S (2010) Community detection in graphs. Physics Report-Review Section of Physics Letters 486(3-5), 75-174. Kistler, R and Coauthors (2001) The NCEP-NCAR 50-Year Reanalysis: Monthly means CD-ROM and documentation. Bulletin of American Meteorological Society 82, 247-267. Hlinka J, Hartman D, Vejmelka M, Novotna D and Palus M. Non-linear dependence and teleconnections in climate data: sources, relevance, nonstationarity. Submitted preprint, available at arXiv:1211.6688. Girvan, M ; Newman, MEJ (2002) Community structure in social and biological networks. Proceedings of the National Academy of Science of the United State of America 99(12), 7821-7826. Newman, MEJ and Girvan N (2004) Finding and evaluating community structure in networks. Physical Review E 69(2), 026113. Tsonis, AA; Swanson, KL (2012) On the origins of decadal climate variability: a network perspective. Nonlinear Processes in Geophysics 19(5), 559-568. Tsonis, AA; Wang, G; Swanson, KL ; Rodrigues, FA; Costa, LD (2011) Community structure and dynamics in climate networks. Climate Dynamics 37(5-6), 933-940.

  18. Field Study of all GSM and WiFi Networks in Amman City from Geospatial Perspective

    NASA Astrophysics Data System (ADS)

    Hawarey, Mosab; Alibrahim, Mustafa; Jetto, Hamza; Salah Mahmoud, Firas

    2016-04-01

    A thorough field study over multiple months has been conducted in the streets of Amman, the capital city of Jordan, in order to collect massive amounts of GSM and WiFi data and analyze them from geospatial perspective. Some interesting realities have been detected; e.g. the North and West of Amman are much better served by GSM operators than the East, South, and Center. Also, the security measures taken to protect WiFi networks in the North and West are much better than those in the East, South, and Center. This has led to the recognition of an interesting pattern that groups the North and West together, while the East, South, and Center constitute another group. Extremely interesting finding was found; the GSM signals are so strong at certain locations that they constitute direct lethal threat to human health; it is scientifically documented that such strengths would lead to certain human cell mutations and cancer. The exact locations and contributors of such hazards will be disclosed in this paper for the first time. Many tabular and graphical presentations of the data will be presented.

  19. Urban Poverty and Neighborhood Effects on Crime: Incorporating Spatial and Network Perspectives

    PubMed Central

    Graif, Corina; Gladfelter, Andrew S.; Matthews, Stephen A.

    2015-01-01

    Research on neighborhoods and crime is on a remarkable growth trajectory. In this article, we survey important recent developments in the scholarship on neighborhood effects and the spatial stratification of poverty and urban crime. We advance the case that, in understanding the impact of neighborhoods and poverty on crime, sociological and criminological research would benefit from expanding the analytical focus from residential neighborhoods to the network of neighborhoods individuals are exposed to during their daily routine activities. This perspective is supported by reemerging scholarship on activity spaces and macro-level research on inter-neighborhood connections. We highlight work indicating that non-residential contexts add variation in criminogenic exposure, which in turn influence offending behavior and victimization risk. Also, we draw on recent insights from research on gang violence, social and institutional connections, and spatial mismatch, and call for advancements in the scholarship on urban poverty that investigates the salience of inter-neighborhood connections in evaluating the spatial stratification of criminogenic risk for individuals and communities. PMID:27375773

  20. Moments of catchment storm area

    NASA Technical Reports Server (NTRS)

    Eagleson, P. S.; Wang, Q.

    1985-01-01

    The portion of a catchment covered by a stationary rainstorm is modeled by the common area of two overlapping circles. Given that rain occurs within the catchment and conditioned by fixed storm and catchment sizes, the first two moments of the distribution of the common area are derived from purely geometrical considerations. The variance of the wetted fraction is shown to peak when the catchment size is equal to the size of the predominant storm. The conditioning on storm size is removed by assuming a probability distribution based upon the observed fractal behavior of cloud and rainstorm areas.

  1. Internally Drained Supraglacial River Catchments on the Southwest Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Yang, K.; Smith, L. C.; Chu, V. W.; Pitcher, L. H.; Gleason, C. J.

    2015-12-01

    Internally drained catchments are the hydrologic units on the Greenland ice sheet (GrIS) surface that collect and drain meltwater into moulins or supraglacial lakes without out flows. Understanding the spatial pattern of these internal catchments is critical, which can provide key information about how supraglacial meltwater is transported and released on the ice surface. This study proposed an automatic approach to detect supraglacial hydrologic features (rivers, lakes, moulins, and internal catchments) located at southwest GrIS from Landsat-8 OLI panchromatic imagery. A total of 800 internal catchments are delineated and the average catchment size (river network length) is found to increase with elevations. In addition, moulins are the prime way to drain internal catchments and the average moulin densities decrease with elevations. Adaptive depression area thresholds are calculated to achieve optimal match between DEM-modeled and image-detected internal catchment patterns. The pattern of these image-detected internal catchments also indicates that: 1) not all the DEM-modeled topographic depressions act as meltwater sinks; 2) moulin distribution greatly impacts the internal catchment patterns; and 3) topographic depressions can be connected downstream without being fully filled, changing the fragmentary of the internal catchments.

  2. Analysis of Rainfall Variability Over Subtropical South America Considering a Complex Network Perspective

    NASA Astrophysics Data System (ADS)

    Martín, V.; Barreiro, M.

    2013-05-01

    Subtropical South America presents large rainfall variability from interannual to interdecadal time scales that has significant agricultural, environmental, energy and economic impacts. Several studies have shown that the tropical Pacific, Atlantic and Indian oceans influence rainfall variability in the subtropics through different mechanisms. Moreover, these oceans interact among them forcing sea surface temperatures in remote basins through atmospheric and oceanic teleconnections. However, it is not clear to date how the SST anomalies in different basins interact to induce rainfall anomalies. In this study we consider the interaction among oceans and their influence on rainfall over subtropical South America from a complex network perspective. The network is defined with indices that characterize the regions of the tropical oceans that influence rainfall, that is, Nino3.4 (El Niño/Southern Oscillation (ENSO), the Tropical North Atlantic (TNA, (60W-30W;10N-30N)), the Indian Ocean Dipole (IOD, (50E-70E;10S-10N)-(90E-110E;10S-0N)) and the Equatorial Atlantic (ATL3, (3N- 3S;170W-120W)) as well as an index that characterizes precipitation over different regions of the subtropics. We investigate the collective behavior of the network focusing on the detection of synchronization events in order to know more about the dynamics that characterize their interaction. We use two different measures of synchronization, that is the mean distance and the root mean square of the cross-correlation. For comparison we consider the Hadley Center Sea Surface Temperature (HadSST), the Extended Reconstructed Sea Surface Temperature (ERSSTv3b) and the Precipitation Climatology datasets from the Global Precipitation Climatological Center (GPCCv5) in the period 1901-2006. The synchronization is characterized by interdecadal variability in most of the seasons considered during 20th century. There are differences between the results of the two datasets (HadSST and ERSSTv3b) particularly in

  3. Investigating dominant processes on small poorly gauged catchments: an inter-comparison approach for catchment similarity study

    NASA Astrophysics Data System (ADS)

    Crabit, Armand; Colin, François; Moussa, Roger; Lagacherie, Philippe

    2010-05-01

    's density and water depth. Results show that the use of roughness coefficient values presented in the literature often induces overestimation in flow velocities calculation. This could be mainly explained by effective roughness which depends on the relative submergence of vegetation. Hydrological indicators were derived from estimated discharges: runoff coefficient, rising time, lag-time, peak runoff, runoff threshold. In spite of the associated uncertainty, indicators allow to discriminate catchments according to functions of partition, release and storage. The second step was to evaluate the efficiency of a catchment classification based on similarity assumptions. The classification highlights an obvious spatial hydrological variability on the studied region. This new approach shows the appeal to use a catchment network, even when poorly gauged, to gain understanding of processes driving hydrological responses.

  4. Revisiting topological properties and models of protein-protein interaction networks from the perspective of dataset evolution.

    PubMed

    Shao, Mingyu; Zhou, Shuigeng; Guan, Jihong

    2015-08-01

    Protein-protein interaction (PPI) networks are crucial for organisms. Many research efforts have thus been devoted to the study on the topological properties and models of PPI networks. However, existing studies did not always report consistent results on the topological properties of PPI networks. Although a number of PPI network models have been introduced, yet in the literature there is no convincing conclusion on which model is best for describing PPI networks. This situation is primarily caused by the incompleteness of current PPI datasets. To solve this problem, in this study, the authors propose to revisit the topological properties and models of PPI networks from the perspective of PPI dataset evolution. Concretely, they used 12 PPI datasets of Arabidopsis thaliana and 10 PPI datasets of Saccharomyces cerevisiae from different Biological General Repository for Interaction Datasets (BioGRID) database versions, and compared the topological properties of these datasets and the fitting capabilities of five typical PPI network models over these datasets. PMID:26243826

  5. Hydrological Catchment Similarity Assessment in Geum River Catchments, Korea

    NASA Astrophysics Data System (ADS)

    Ko, Ara; Park, Kisoon; Lee, Hyosang

    2013-04-01

    Similarity measure of catchments is essential for regionalization studies, which provide in depth analysis in hydrological response and flood estimations at ungauged catchments. However, this similarity measure is often biased to the selected catchments and is notclearly explained in hydrological sense. This study applied a type of hydrological similarity distance measure-Flood Estimation Handbook to 25 Geum river catchments, Korea. Three Catchment Characteristics, Area (A)-Annual precipitation (SAAR)-SCS Curve Number (CN), are used in Euclidian distance measures. Furthermore, six index of Flow Duration Curve (ILow:Q275/Q185, IDrought:Q355/Q185, IFlood:Qmax/Q185, IAbundant:Q95/Q185, IFloodDuration:Q10/Q355 and IRiverRegime:Qmax/Qmin) are applied to clustering analysis of SPSS. The catchments' grouping of hydrological similarity measures suggests three groups: H1 (Cheongseong, Gidae, Bukil, Oksan, Seockhwa, Habgang and Sangyeogyo), H2 (Cheongju, Guryong, Ugon, Boksu, Useong and Seokdong) and H3 (Muju, Yangganggyo and YongdamDam). The four catchments (Cheoncheon, Donghyang, DaecheongDam and Indong) are not grouped in this study. The clustering analysis of FDC provides four Groups; CFDC1 (Muju, YongdamDam, Yangganggyo, DaecheongDam, Cheongseong, Gidae, Seokhwa, Bukil, Habgang, Cheongju, Oksan, Yuseong and Guryong), CFDC2 (Cheoncheon, Donghyang, Boksu, Indong, Nonsan, Seokdong, Ugon, Simcheon, Useong and Sangyeogyo), CFDC3 (Songcheon) and CFDC4 (Tanbu). The six catchments (out of seven) of H1 are grouped in CFDC1, while Sangyeogyo is grouped in CFDC2. The four catchments (out of six) of H2 are also grouped in CFDC2, while Cheongju and Guryong are grouped in CFDC1. The catchments of H3 are categorized in CFDC1. The authors examine the results (H1, H2 and H3) of similarity measure based on catchment physical descriptors with results (CFDC1 and CFDC2) of clustering based on catchment hydrological response. The results of hydrological similarity measures are supported by

  6. Algorithmic Perspectives of Network Transitive Reduction Problems and their Applications to Synthesis and Analysis of Biological Networks

    PubMed Central

    Aditya, Satabdi; DasGupta, Bhaskar; Karpinski, Marek

    2013-01-01

    In this survey paper, we will present a number of core algorithmic questions concerning several transitive reduction problems on network that have applications in network synthesis and analysis involving cellular processes. Our starting point will be the so-called minimum equivalent digraph problem, a classic computational problem in combinatorial algorithms. We will subsequently consider a few non-trivial extensions or generalizations of this problem motivated by applications in systems biology. We will then discuss the applications of these algorithmic methodologies in the context of three major biological research questions: synthesizing and simplifying signal transduction networks, analyzing disease networks, and measuring redundancy of biological networks. PMID:24833332

  7. Groundwater recharge from point to catchment scale

    NASA Astrophysics Data System (ADS)

    Leterme, Bertrand; Di Ciacca, Antoine; Laloy, Eric; Jacques, Diederik

    2016-04-01

    Accurate estimation of groundwater recharge is a challenging task as only a few devices (if any) can measure it directly. In this study, we discuss how groundwater recharge can be calculated at different temporal and spatial scales in the Kleine Nete catchment (Belgium). A small monitoring network is being installed, that is aimed to monitor the changes in dominant processes and to address data availability as one goes from the point to the catchment scale. At the point scale, groundwater recharge is estimated using inversion of soil moisture and/or water potential data and stable isotope concentrations (Koeniger et al. 2015). At the plot scale, it is proposed to monitor the discharge of a small drainage ditch in order to calculate the field groundwater recharge. Electrical conductivity measurements are necessary to separate shallow from deeper groundwater contribution to the ditch discharge (see Di Ciacca et al. poster in session HS8.3.4). At this scale, two or three-dimensional process-based vadose zone models will be used to model subsurface flow. At the catchment scale though, using a mechanistic, process-based model to estimate groundwater recharge is debatable (because of, e.g., the presence of numerous drainage ditches, mixed land use pixels, etc.). We therefore investigate to which extent various types of surrogate models can be used to make the necessary upscaling from the plot scale to the scale of the whole Kleine Nete catchment. Ref. Koeniger P, Gaj M, Beyer M, Himmelsbach T (2015) Review on soil water isotope based groundwater recharge estimations. Hydrological Processes, DOI: 10.1002/hyp.10775

  8. A Washington Perspective on Women and Networking: The Power and the Pitfalls.

    ERIC Educational Resources Information Center

    Green, Madeleine F.

    1982-01-01

    Describes two successful, institutionalized networking programs of the American Council on Education. Discusses the potential benefits and pitfalls of networking especially as they apply to women. (RC)

  9. New Perspectives on Spontaneous Brain Activity: Dynamic Networks and Energy Matter

    PubMed Central

    Tozzi, Arturo; Zare, Marzieh; Benasich, April A.

    2016-01-01

    Spontaneous brain activity has received increasing attention as demonstrated by the exponential rise in the number of published article on this topic over the last 30 years. Such “intrinsic” brain activity, generated in the absence of an explicit task, is frequently associated with resting-state or default-mode networks (DMN)s. The focus on characterizing spontaneous brain activity promises to shed new light on questions concerning the structural and functional architecture of the brain and how they are related to “mind”. However, many critical questions have yet to be addressed. In this review, we focus on a scarcely explored area, specifically the energetic requirements and constraints of spontaneous activity, taking into account both thermodynamical and informational perspectives. We argue that the “classical” definitions of spontaneous activity do not take into account an important feature, that is, the critical thermodynamic energetic differences between spontaneous and evoked brain activity. Spontaneous brain activity is associated with slower oscillations compared with evoked, task-related activity, hence it exhibits lower levels of enthalpy and “free-energy” (i.e., the energy that can be converted to do work), thus supporting noteworthy thermodynamic energetic differences between spontaneous and evoked brain activity. Increased spike frequency during evoked activity has a significant metabolic cost, consequently, brain functions traditionally associated with spontaneous activity, such as mind wandering, require less energy that other nervous activities. We also review recent empirical observations in neuroscience, in order to capture how spontaneous brain dynamics and mental function can be embedded in a non-linear dynamical framework, which considers nervous activity in terms of phase spaces, particle trajectories, random walks, attractors and/or paths at the edge of the chaos. This takes us from the thermodynamic free-energy, to the realm

  10. New Perspectives on Spontaneous Brain Activity: Dynamic Networks and Energy Matter.

    PubMed

    Tozzi, Arturo; Zare, Marzieh; Benasich, April A

    2016-01-01

    Spontaneous brain activity has received increasing attention as demonstrated by the exponential rise in the number of published article on this topic over the last 30 years. Such "intrinsic" brain activity, generated in the absence of an explicit task, is frequently associated with resting-state or default-mode networks (DMN)s. The focus on characterizing spontaneous brain activity promises to shed new light on questions concerning the structural and functional architecture of the brain and how they are related to "mind". However, many critical questions have yet to be addressed. In this review, we focus on a scarcely explored area, specifically the energetic requirements and constraints of spontaneous activity, taking into account both thermodynamical and informational perspectives. We argue that the "classical" definitions of spontaneous activity do not take into account an important feature, that is, the critical thermodynamic energetic differences between spontaneous and evoked brain activity. Spontaneous brain activity is associated with slower oscillations compared with evoked, task-related activity, hence it exhibits lower levels of enthalpy and "free-energy" (i.e., the energy that can be converted to do work), thus supporting noteworthy thermodynamic energetic differences between spontaneous and evoked brain activity. Increased spike frequency during evoked activity has a significant metabolic cost, consequently, brain functions traditionally associated with spontaneous activity, such as mind wandering, require less energy that other nervous activities. We also review recent empirical observations in neuroscience, in order to capture how spontaneous brain dynamics and mental function can be embedded in a non-linear dynamical framework, which considers nervous activity in terms of phase spaces, particle trajectories, random walks, attractors and/or paths at the edge of the chaos. This takes us from the thermodynamic free-energy, to the realm of "variational

  11. Environmental care in agricultural catchments: Toward the communicative catchment

    NASA Astrophysics Data System (ADS)

    Martin, Peter

    1991-11-01

    Substantial land degradation of agricultural catchments in Australia has resulted from the importation of European farming methods and the large-scale clearing of land. Rural communities are now being encouraged by government to take responsibility for environmental care. The importance of community involvement is supported by the view that environmental problems are a function of interactions between people and their environment. It is suggested that the commonly held view that community groups cannot care for their resources is due to inappropriate social institutions rather that any inherent disability in people. The communicative catchment is developed as a vision for environmental care into the future. This concept emerges from a critique of resource management through the catchment metaphors of the reduced, mechanical, and the complex, evolving catchment, which reflect the development of systemic and people-centered approaches to environmental care. The communicative catchment is one where both community and resource managers participate collaboratively in environmental care. A methodology based on action research and systemic thinking (systemic action research) is proposed as a way of moving towards the communicative catchment of the future. Action research is a way of taking action in organizations and communities that is participative and informed by theory, while systemic thinking takes into account the interconnections and relationships between social and natural worlds. The proposed vision, methodology, and practical operating principles stem from involvement in an action research project looking at extension strategies for the implementation of total catchment management in the Hunter Valley, New South Wales.

  12. Temporal and Spatial Patterns of Preferential Flow Occurrence in the Shale Hills Catchment: From the Hillslope to the Catchment Scales

    NASA Astrophysics Data System (ADS)

    Liu, H.; Lin, H.

    2013-12-01

    Understanding temporal and spatial patterns of preferential flow (PF) occurrence is important in revealing hillslope and catchment hydrologic and biogeochemical processes. Quantitative assessment of the frequency and control of PF occurrence in the field, however, has been limited, especially at the landscape scale of hillslope and catchment. By using 5.5-years' (2007-2012) real-time soil moisture at 10 sites response to 323 precipitation events, we tested the temporal consistency of PF occurrence at the hillslope scale in the forested Shale Hills Catchment; and by using 25 additional sites with at least 1-year data (2011-2012), we evaluated the spatial patterns of PF occurrence across the catchment. To explore the potential effects of PF occurrence on catchment hydrology, wavelet analysis was performed on the recorded time series of hydrological signals (i.e., precipitation, soil moisture, catchment discharge). Considerable temporal consistence was observed in both the frequency and the main controls of PF occurrence at the hillslope scale, which was attributed largely to the statistical stability of precipitation pattern over the monitoring period and the relatively stable subsurface preferential pathways. Preferential flow tended to occur more often in response to intense rainfall events, and favored the conditions at dry hilltop or wet valley floor sites. When upscaling to the entire catchment, topographic control on the PF occurrence was amplified remarkably, leading to the identification of a subsurface PF network in the catchment. Higher frequency of PF occurrence was observed at the valley floor (average 48%), hilltop (average 46%), and swales/hillslopes near the stream (average 40%), while the hillslopes in the eastern part of the catchment were least likely to experience PF (0-20%). No clear relationship, however, was observed between terrain attributes and PF occurrence, because the initiation and persistency of PF in this catchment was controlled

  13. A simple model to assess nitrogen and phosphorus contamination in ungauged surface drainage networks: application to the Massaciuccoli Lake Catchment, Italy.

    PubMed

    Pistocchi, C; Silvestri, N; Rossetto, R; Sabbatini, T; Guidi, M; Baneschi, I; Bonari, E; Trevisan, D

    2012-01-01

    Modeling is a common practice to evaluate factors affecting water quality in environmental systems impaired by point and nonpoint losses of N and P. Nevertheless, in situations with inadequate information, such as ungauged basins, a balance between model complexity and data availability is necessary. In this paper, we applied a simplified analytical model to an artificially drained floodplain in central-western Italy to evaluate the importance of different nutrient sources and in-stream retention processes and to identify critical source areas. We first considered only a set of chemical concentrations in water measured from February through May 2008 and from November 2008 through February 2009. We then broadened available data to include water discharge and hydraulic-head measurements to construct a hydrogeological model using MODFLOW-2000 and to evaluate the reliability of the simplified method. The simplified model provided acceptable estimates of discharge (ranging from 0.03-0.75 m s) and diffuse nutrient inputs from water table discharge and in-stream retention phenomena. Estimates of PO-P and total P retention (ranging from 1.0 to 0.6 μg m s and from 1.18 to 0.95 μg m s for PO-P and total P, respectively) were consistent with the range of variability in literature data. In contrast, the higher temporal variability of nitrate concentrations decreased model accuracy, suggesting the need for more intensive monitoring. The model also separated the dynamics of different reaches of the drainage network and identified zones considered critical source areas and buffer zones where pollutant transport is reduced. PMID:22370417

  14. Dynamic processes in the mountain catchment

    NASA Astrophysics Data System (ADS)

    Trifonova, Tatiana; Arakelian, Sergei

    2015-04-01

    The process of the river cftchment foundation and the mechanisms being in the basis of its development are not clear at present. Principal phenomena determining the dynamics of formation of the river catchment are under our study in this paper for the case of the mountain basin as an example. The methodology of this monitoring includes the space image recognition and computer data processing of the images for the Maliy Caucasus Mountains. Mountain river catchment formation on the slope of the ridge can be considered as a self-organizing staged process of its evolution passing through several non-equilibrium but steady-state conditions. We consider a system of tributaries in the mountain river catchment as a system of cracks, which are formed on the slope of the mountain massif. In other words, the formation of river networks should be the result of development of several processes, among of which the mechanisms of crack development should play a dominant role. The principal results, discussed in the present report, can be formulated as follow. (1) The mountain catchment (litho-watershed) formation takes place under conditions of the confined states of a mountain massif: on the one hand it is bounded by the surface of the slope; but on the other hand, - by a primary cracks density occurrence (as a spatial distribution 3D-crack net). (2) The development in time of the river catchment takes place by several stages. Each stage specifies a definite energetic state of the system in the mountain massif. (3) The overhead river streams arise not only due to surface water, but and namely due to rising of water from underground water horizons over the watercourse cracks penetrating deeply into the underground. (4) The 3D-river catchment structure results in concept in behavior of the unit as an open nonlinear dynamic system with a spatially distributed feedback. The energetic (endogen) processes of formation, rising and bifurcation for cracks are the consequence of relaxation

  15. Proximate and ultimate controls on carbon and nutrient dynamics of small agricultural catchments

    NASA Astrophysics Data System (ADS)

    Thomas, Z.; Abbott, B. W.; Troccaz, O.; Baudry, J.; Pinay, G.

    2015-09-01

    Direct and indirect effects from agriculture, urbanization, and resource extraction have dramatically increased nutrient loading to aquatic inland and estuarine ecosystems. The capacity of a watershed to remove or retain nutrients is a function of biotic and abiotic conditions across the terrestrial-aquatic gradient including soil, groundwater, riparian zone, and surface water. The goal of this study was to identify proximate and ultimate controls on dissolved organic carbon and nutrient dynamics in small agricultural catchments. We analysed a five-year, high frequency water chemistry dataset from 3 catchments ranging from 2.3 to 10.8 km2 in northwestern France. Catchments differed in the relationship between hydrology and solute concentrations, associated with catchment characteristics such as hedgerow density, agricultural activity, and geology. The catchment with thicker soil and higher surface roughness appeared to have greater transient storage and residence time, buffering the catchment to fluctuations in water chemistry, reflected in relatively invariant carbon and nutrient chemistry across hydrologic conditions. Conversely, the catchments with smoother, thinner soils responded to both intra- and inter-annual hydrologic variation with high concentrations of PO43- and NH4+ during low flow conditions and strong increases in DOC, sediment, and particulate organic matter during high flows. Despite contrasting agricultural activity between catchments, the physical context (geology, topography, and land use) appeared to be the most important determinant of catchment solute dynamics based on principle components analysis. The influence of geology and accompanying topographic and geomorphological factors on elemental fluxes is both direct and indirect because the distribution of agricultural activity in these catchments is largely a consequence of the geologic and topographic context. This link between inherent catchment buffering capacity and probability of human

  16. The catchment based approach using catchment system engineering

    NASA Astrophysics Data System (ADS)

    Jonczyk, Jennine; Quinn, Paul; Barber, Nicholas; Wilkinson, Mark

    2015-04-01

    The catchment based approach (CaBa) has been championed as a potential mechanism for delivery of environmental directives such as the Water Framework Directive in the UK. However, since its launch in 2013, there has been only limited progress towards achieving sustainable, holistic management, with only a few of examples of good practice ( e.g. from the Tyne Rivers trust). Common issues with developing catchment plans over a national scale include limited data and resources to identify issues and source of those issues, how to systematically identify suitable locations for measures or suites of measures that will have the biggest downstream impact and how to overcome barriers for implementing solutions. Catchment System Engineering (CSE) is an interventionist approach to altering the catchment scale runoff regime through the manipulation of hydrological flow pathways throughout the catchment. A significant component of the runoff generation can be managed by targeting hydrological flow pathways at source, such as overland flow, field drain and ditch function, greatly reducing erosive soil losses. Coupled with management of farm nutrients at source, many runoff attenuation features or measures can be co-located to achieve benefits for water quality and biodiversity. A catchment, community-led mitigation measures plan using the CSE approach will be presented from a catchment in Northumberland, Northern England that demonstrate a generic framework for identification of multi-purpose features that slow, store and filter runoff at strategic locations in the landscape. Measures include within-field barriers, edge of field traps and within-ditch measures. Progress on the implementation of measures will be reported alongside potential impacts on the runoff regime at both local and catchment scale and costs.

  17. Carbon redistribution by erosion processes in an intensively disturbed catchment

    NASA Astrophysics Data System (ADS)

    Boix-Fayos, Carolina; Martínez-Mena, María; Pérez Cutillas, Pedro; de Vente, Joris; Barberá, Gonzalo G.; Mosch, Wouter; Navarro Cano, Jose Antonio; Gaspar, Leticia; Navas, Ana

    2016-04-01

    Understanding how organic carbon moves with sediments along the fluvial system is crucial to close catchment scale carbon budgets. Especially challenging is the analysis of organic carbon dynamics during fluvial transport in heterogeneous, fragile and disturbed environments with ephemeral and intense hydrological pulses, typical of Mediterranean conditions. This paper explores the catchment scale organic carbon redistribution by lateral flows in extreme Mediterranean environmental conditions from a geomorphological perspective. The study area is a catchment (Cárcavo) in SE Spain with a semiarid climate, erodible lithologies, shallow soils, and highly disturbed by agricultural terraces, land levelling, reforestations and construction of check-dams. To increase understanding of erosion induced catchment scale organic carbon redistribution, we studied the subcatchments of 8 check-dams distributed along the catchment main channel in detail. We determined 137Cs, physicochemical characteristics and organic carbon pools of soils and sediments deposited behind each check-dam, performed spatial analysis of properties of the catchment and buffer areas around check-dams, and carried out geomorphological analysis of the slope-channel connections. Soils showed very low Total Organic Carbon (TOC) values oscillating between 15.2 and 4.4 g Kg-1 for forest and agricultural soils, respectively. Sediments mobilized by erosion were poor in TOC compared to the eroded (forest) soils (6.6±0.7 g Kg-1), and the redistribution of organic carbon through the catchment, especially of the Mineral Associated Organic Carbon (MAC) pool, showed the same pattern as clay particles and 137Cs. The TOC erosion rates (0.031±0.03 Mg ha-1 y-1) were comparable to others reported for subhumid Mediterranean catchments and to those modelled worldwide for pasture land. Those lateral fluxes were equivalent to 10.4 % of the TOC stock from the topsoil at the moment of the check-dam construction and

  18. Dispersion mechanisms and the effect of parameter uncertainty on hydrologic response in urban catchments

    NASA Astrophysics Data System (ADS)

    Cantone, Joshua; Schmidt, Arthur

    2011-05-01

    The link between river network structure and hydrologic response for natural watersheds has been the subject of ongoing research for the past 30 years. In this paper we investigate the link between sewer network structure and hydrologic response in urban catchments. It has been shown in natural watersheds that there are dispersion mechanisms that contribute to the impulse response function of the catchment: hydrodynamic dispersion, geomorphologic dispersion, and hydrodynamic dispersion. We introduce a fourth dispersion mechanism, intrastate dispersion, which accounts for the variance in conduit (e.g., slope, length, diameter, etc.) and overland region input parameters (e.g., slope, area, imperviousness, etc.) within an order. This dispersion mechanism is found to be the second largest contributor to the total dispersion in the urban catchments analyzed, contributing less than hydrodynamic dispersion but more than kinematic and geomorphologic dispersion. This is primarily a result of the shorter network travel times observed in urban catchment. The dispersion mechanisms are incorporated in the Illinois Urban Hydrologic Model, which is a recently developed probabilistic approach for predicting the hydrologic response in highly urbanized catchments. Furthermore, an analysis is performed to help better understand the uncertainty in the predicted hydrologic response that is introduced by spatial variation in conduit and overland input parameters. It is identified that conduit slope and length are the greatest sources of uncertainty in the predicted direct runoff hydrograph for the CDS-51 catchment in the village of Dolton, Illinois, and the CDS-36 catchment in the city of Chicago, Illinois.

  19. Quantifying the effects of human impact on sediment yield for European catchments

    NASA Astrophysics Data System (ADS)

    Vanmaercke, M.; Poesen, J.; Govers, G.; Verstraeten, G.; Kettner, A.; Van Den Eeckhaut, M.

    2012-04-01

    Both from a scientific and environmental management perspective, there is a great need to better assess the magnitude of human impacts on catchment sediment yield (SY, t/km2/y) and to identify the factors that control this magnitude. Quantification of these impacts is generally impeded by the lack of reliable SY data under "pristine" conditions, i.e. before the catchment was affected by humans in terms of land use or reservoirs. Based on a dataset with SY-measurements from 146 mainly forested catchments in Europe that were not affected by reservoirs, a regression model was developed. This model allows estimating pristine SY, based on the catchment topography, lithology and the degree of seismic activity (as indicated on earthquake hazard maps). Validation of this model indicated that this model is fairly robust, while 95% of the predicted SY-values deviate less than one order of magnitude from their measured SY-value. Hence, the application of this model to a large (> 400) number of European catchments for which measured actual, i.e. "disturbed", SY-data were available allowed to quantify the effects of human impact on SY and their controlling factors. It was found that catchment area has a strong control on catchment sensitivity to human impact. Whereas in small (< 1 km2) disturbed catchments actual SY can be up to 100 times higher than their modeled pristine SY-value, a clear human impact is generally difficult to detect for catchments > 100 km2. Furthermore, a clear positive relationship between the degree of SY disturbance (i.e. the ratio between the actual and the pristine SY) and the fraction of disturbed land use in the catchment was noted. Catchments with a high fraction of arable land (> 50%) also showed a more distinctive decrease in the degree of disturbance with increasing catchment area. However, the form of this relationship is also controlled by other factors, such as catchment lithology. The relation between the degree of disturbance and the

  20. On the value of data for catchment modelling.

    NASA Astrophysics Data System (ADS)

    Fenicia, F.; McDonnell, J. J.; Savenije, H. H.; Pfister, L.

    2006-12-01

    The dialogue between experimentalist and modeller in catchment hydrology continues to be minimal, despite the clear need for this to quantify and reduce uncertainty in our predictions. Experimentalists often instrument catchments to measure key diagnostic properties and variables that, from their perspective, characterize catchment behaviour. Typically, after some years, the research switches to the hands of the catchment modeller who uses these data to support model development or to constrain a model's degrees of freedom. Often there is frustration on the part of the modeller because only a small part of the collected information can be actually used for the set-up, calibration and evaluation of the hydrological model. Much of the field data turns out to be of little use for modelling, for problems that may be related to the disparity between the scale of measurements and the scale of model components. This happens not only because of a lack of communication between modellers and experimentalists, but also because the information requirements of a model are seldom treated as a scientific issue. We use the well-studied Maimai catchment to explore what types of measurements, what length of time series and what resolution in time and space is best suited for modellers, in a way that it can be processed into simple, integrative evaluative data that constrain the model so as to represent the hydrological processes realistically. We discuss the marginal value of different data sources and the tradeoffs between time spent completing time series for a few variables and locations to spatially distributed snapshots of different variables aimed at increasing data complementarity. A first direct application of this study will be to orientate future field research on the experimental catchments operating in the Grand Duchy of Luxembourg.

  1. Characterizing Runoff and Water Yield from Headwater Catchments in the Southern Sierra Nevada

    NASA Astrophysics Data System (ADS)

    Safeeq, M.; Hunsaker, C. T.

    2015-12-01

    In a mediterranean climate where much of the annual precipitation falls during winter, the snow-capped Sierra Nevada serves as the primary source of dry season runoff that supports agriculture, industries, urban, and other ecosystems. Increased warming has led to significant reductions in mountain snowpack accumulation and earlier snowmelt throughout the western United States where most of the snow accumulates at temperatures near the freezing point. As a result, declines in dry season runoff magnitude, earlier runoff timing, and altered flood risk have been reported across the region. An important question in this context is, how to best manage forested catchments for water and other ecosystem services? We depict the differences in hydrologic response of ten catchments in the Kings River Experimental Watersheds (KREW) research project using continuous precipitation, snow, and runoff data during 2004-2014. The size of these catchments ranges from 50 to 475 ha, and they span a 600-m elevation range in the rain snow transitional zone. In terms of soil, Shaver and Gerle-Cagwin dominate the lower elevation Providence catchments, and Cagwin soils dominate the higher elevation Bull catchments. The majority of these catchments have southwest aspect, moderate average slope (i.e. <25%), and a well-developed drainage network with drainage density ranging from 4.6 to 10.1 km/km2. Bull catchments, on average, have higher runoff than the Providence catchments across all hydrologic signatures extracted from daily hydrographs. Mean annual runoff ranges between 281 to 408 mm in Providence and 436 to 656 mm in Bull catchments despite no significant difference in precipitation among KREW's four meteorological stations. However, high elevation Bull catchments receive significantly more precipitation as snow than the low elevation Providence catchments. The average runoff ratio ranges from 18% to as high as 43% among different catchments, indicating that the catchment

  2. Is the subarctic landscape still a carbon sink? Evidence from a detailed catchment balance

    NASA Astrophysics Data System (ADS)

    Lundin, Erik J.; Klaminder, Jonatan; Giesler, Reiner; Persson, Andreas; Olefeldt, David; Heliasz, Michal; Christensen, Torben R.; Karlsson, Jan

    2016-03-01

    Climate warming raises the question whether high-latitude landscape still function as net carbon (C) sinks. By compiling an integrated C balance for an intensely studied subarctic catchment, we show that this catchment's C balance is not likely to be a strong current sink of C, a commonly held assumption. In fact, it is more plausible (71% probability) that the studied catchment functions as a C source (-11 ± 20 g C m-2 yr-1). Analyses of individual fluxes indicate that soil and aquatic C losses offset C sequestering in other landscape components (e.g., peatlands and aboveground forest biomass). Our results stress the importance of fully integrated catchment C balance estimates and highlight the importance of upland soils and their interaction with the aquatic network for the catchment C balance.

  3. Comparison of subsurface connectivity in Alpine headwater catchments

    NASA Astrophysics Data System (ADS)

    Zuecco, Giulia; Rinderer, Michael; van Meerveld, Ilja; Penna, Daniele; Borga, Marco

    2016-04-01

    Saturation at the soil-bedrock interface or the rise of shallow groundwater into more permeable soil layers results in subsurface stormflow and can lead to hillslope-stream connectivity. Despite the importance of subsurface connectivity for streamflow and streamwater chemistry, the factors controlling its spatial and temporal variability are still poorly understood. This study takes advantage of networks of spatially-distributed piezometers in five small (<14 ha) headwater catchments in the Italian Dolomites and the Swiss pre-Alps to i) quantify and compare the spatial and temporal variability of subsurface connectivity and its relation to streamflow, and ii) assess whether the differences in connectivity between the catchments are related to climatological or morphological characteristics of the catchments (e.g. the presence of a riparian zone). Shallow groundwater levels were measured for two years from spring to fall in 16 and 12 piezometers in the 14 and 3.3 ha catchments in the Italian Dolomites, and for four years from spring to fall in 7-8 piezometers in three <1 ha Swiss pre-alpine catchments. Subsurface connectivity was quantified by a graph-theory approach, considering linear connections (edges) between the piezometers (nodes). A node was considered to be connected to the stream when shallow groundwater was observed in the piezometer and it was connected by the edges to the stream. Weights were given to each piezometer based on Thiessen polygons to determine the area of the catchment that was connected to the stream. For the Swiss pre-alpine catchments the duration that nodes were connected to the stream was significantly correlated to the local and upslope site characteristics, such as the topographic wetness index, local slope and curvature. For the dolomitic catchment with the largest riparian zone, the time that nodes were connected to the stream was correlated with downslope site characteristics, such as the vertical distance to the nearest stream

  4. A Network-Based Approach for Modeling Water, Sediment, and Nutrient Dynamics: Guiding Watershed Management Through a Systems Perspective

    NASA Astrophysics Data System (ADS)

    Czuba, J. A.; Foufoula-Georgiou, E.; T Hansen, A.; Finlay, J. C.; Wilcock, P. R.

    2015-12-01

    River networks form the arteries of a landscape, efficiently conveying water, sediment, and nutrients through a small fraction of a watershed. Yet this small fraction, which comprises the river network, dictates the watershed-scale response. Thus, by incorporating the dominant transport, storage, and transformation processes of a given flux into a river-network context, one can reveal the large-scale system functioning and the emergence of vulnerabilities and "hotspots" of change. We apply such a network-modeling framework by (1) decomposing the landscape into a connected network of elements including river channels, lakes, wetlands, etc., (2) spatially and temporally distributing inputs of water, sediment, and nutrients, and (3) tracking these inputs through individual landscape elements using process-based time delays and transformations. We suggest that landscapes are too complex to be modeled with fully distributed deterministic models that consider all the small-scale physics and interactions, due to large and unavoidable uncertainties. Besides, changes in climate, land use, and water management impose non-stationary conditions, and also nonlinearities in the system make it sensitive to small perturbations. Instead, the aim of this framework is to combine the system connectivity and most important processes in an effort to guide watershed-management decisions in a simple, physically-based way. We will describe the application of this framework to bed-material sediment, nitrogen, and streamflow. Specifically, we will use the framework to identify channel-migration and nitrate hotspots, and explore various management strategies for hotspot reduction. Also, we will show, through the network perspective offered by this framework, how simple questions about where to manage for peak-flow reduction can be answered. This framework offers a simple approach for gaining systems-level understanding that can be applied in route to more complex watershed modeling.

  5. Process scales in catchment science: a new synthesis

    NASA Astrophysics Data System (ADS)

    Price, K.; Dennedy-frank, P.; Harman, C. J.; Purucker, T.; Jackson, C. R.; Sidle, R. C.

    2013-12-01

    Concerns surrounding data resolution, choice of spatial and temporal scales in research design, and problems with extrapolation of processes across spatial and temporal scales differ greatly between scientific process-elucidation research and scenario exploration for watershed management and policy. This is true whether the underlying watershed models are statistical or process-based. Watershed scientists understand that we lack the knowledge and tools to extrapolate this detailed understanding from the smallest scales of observations to larger, more heterogeneous watershed systems over larger timescales, while it is at these larger scales where our most pressing questions of water availability lie, creating a conundrum that has stymied watershed science for several decades. As a scientific community, catchment scientists clearly understand the potential problems associated with up- and down-scaling in hydrology and related processes, but we suggest that the community lacks a cohesive perspective on how to deal with these issues. Having been nearly two decades since the last major review of this topic, we offer a new synthesis on the topic of scaling in catchment science with the results of four main objectives: 1) to identify a community definition of management and policy scales and their relationship to catchment process scales, 2) to synthesize legacy perspectives on scaling in hydrology, 3) to identify known scale-dependent and scale-invariant catchment processes , and 4) to suggest methods and conceptualizations for removal of scaling barriers in future research. Suggested approaches will incorporate trans-disciplinary perspectives on scaling, and will cover: thresholds for scale-dependence, the role of the representative elementary watershed in conceptualizing scaling, existing and potential use of scaling algorithms, strengths and weaknesses of cross-scale process-based modeling, and statistical approaches for maximizing observed information and

  6. Proximate and ultimate controls on carbon and nutrient dynamics of small agricultural catchments

    NASA Astrophysics Data System (ADS)

    Thomas, Zahra; Abbott, Benjamin W.; Troccaz, Olivier; Baudry, Jacques; Pinay, Gilles

    2016-03-01

    catchment buffering capacity and the probability of human disturbance provides a useful perspective for evaluating vulnerability of aquatic ecosystems and for managing systems to maintain agricultural production while minimizing leakage of nutrients.

  7. Deriving N-year discharges in small catchments

    NASA Astrophysics Data System (ADS)

    Ledvinka, Ondrej; Bohac, Milon

    2016-04-01

    Maximum discharges with the return period of 100 years (Q100) belong to basic hydrological data that are derived and provided for any profile of the river network by the Czech Hydrometeorological Institute (CHMI). However, as regards small catchments, the determination of these characteristics is largely subjective and thus it is rather performed by comparing the results of several methods. The first approach is to extrapolate the three parameters of maximum peak discharges (average Qmax, coefficient of variation Cvmax, Q100) from water-gauging stations to selected unobserved profiles (using regression relationships and regularities at the confluence points). For this purpose, the so-called program Budsez is utilized. During this process, the physical-geographical (PG) features, rainfall data and other information about catchments are considered, based on which the parameters of theoretical distributions of N-year discharges are optimized. For smaller catchments the relationships between the 100-year specific runoff q100 and the catchment area and other PG characteristics are used that are determined in a GIS environment with the extension AGPosudek. In this innovative method, besides many other PG characteristics, especially the average value of CN and N-year maximum daily precipitation are taken into account when computing Q100. In the older methodologies, Q100 is based on the average slope of the stream and the average slope of the catchment. The values of Q100 are then corrected according to the percentage of forested areas and the catchment shape. Hydrologists compare the values of Q100 coming from different approaches in a logarithmic graph (q100 against area) for the particular catchment or its analogon. The final value is determined with respect to experience and previously issued values. The remaining N-year discharges are usually assessed through the ratio QN/Q100 from the nearest water-gauging station or the closest profile where these ratios were

  8. Does Human Migration Affect International Trade? A Complex-Network Perspective

    PubMed Central

    Fagiolo, Giorgio; Mastrorillo, Marina

    2014-01-01

    This paper explores the relationships between international human migration and merchandise trade using a complex-network approach. We firstly compare the topological structure of worldwide networks of human migration and bilateral trade over the period 1960–2000. Next, we ask whether pairs of countries that are more central in the migration network trade more. We show that: (i) the networks of international migration and trade are strongly correlated, and such correlation can be mostly explained by country economic/demographic size and geographical distance; (ii) centrality in the international-migration network boosts bilateral trade; (iii) intensive forms of country centrality are more trade enhancing than their extensive counterparts. Our findings suggest that bilateral trade between any two countries is not only affected by the presence of migrants from either countries, but also by their relative embeddedness in the complex web of corridors making up the network of international human migration. PMID:24828376

  9. Influence of Rainfall Data Resolution and Catchment Subdivision on Runoff Modelling

    NASA Astrophysics Data System (ADS)

    Puttaraksa Mapiam, Punpim; Chauysuk, Suttiched

    2016-04-01

    Precipitation and catchment characteristics are significant factors for runoff modelling. This study demonstrates the relative benefits offered by the application of alternate rainfall products to several scales of catchment subdivision for simulation of the runoff hydrograph in the upper Ping river basin, northern Thailand. Two point locations at the runoff stations in the upper Ping river basin were selected for model calibration over the period of 2004-2005. Rain gauge and radar rainfall products were specified as inputs to the semi-distributed hydrological URBS model at each runoff station with five catchment subdivision schemes for runoff simulation. Point rainfall from the sparse rain gauge network and estimated radar rainfall at each radar pixel were spatially averaged over each sub-catchment using Thiessen polygons and arithmetic averaging approaches, respectively. Results for using high resolution of radar rainfall input appear that the accuracy of runoff estimates is affected appreciably by a number of sub-catchments, and the accuracy of runoff estimates tends to obviously increase with an increase of the number of sub-catchments. On the other hand, there is no significant improvement with an increasing number of sub-catchments while the coarse resolution of rain gauge rainfall input is used. The comparison on runoff accuracy among different scenarios indicates that the use of radar rainfall together with the largest number of sub-catchments gives the highest accuracy of runoff estimates.

  10. Catchment systems science and management: from evidence to resilient landscapes

    NASA Astrophysics Data System (ADS)

    Quinn, Paul

    2014-05-01

    There is an urgent need to reassess both the scientific understanding and the policy making approaches taken to manage flooding, water scarcity and pollution in intensively utilised catchments. Many European catchments have been heavily modified and natural systems have largely disappeared. However, working with natural processes must still be at the core of any future management strategy. Many catchments have greatly reduced infiltration rates and buffering capacity and this process needs to be reversed. An interventionist and holistic approach to managing water quantity and quality at the catchment scale is urgently required through the active manipulation of natural flow processes. Both quantitative (field experiments and modelling) and qualitative evidence (local knowledge) is required to demonstrate that catchment have become 'unhealthy'. For example, dense networks of low cost instrumentation could provide this multiscale evidence and, coupled with stakeholder knowledge, build a comprehensive understanding of whole system function. Proactive Catchment System Management is an interventionist approach to altering the catchment scale runoff regime through the manipulation of landscape scale hydrological flow pathways. Many of the changes to hydrological processes cannot be detected at the catchment scale as the primary causes of flooding and pollution. Evidence shows it is the land cover and the soil that are paramount to any change. Local evidence shows us that intense agricultural practices reduce the infiltration capacity through soil degradation. The intrinsic buffering capacity has also been lost across the landscape. The emerging hydrological process is one in which the whole system responds too quickly (driven by near surface and overland flow processes). The bulk of the soil matrix is bypassed during storm events and there is little or no buffering capacity in the riparian areas or in headwater catchments. The prospect of lower intensity farming rates is

  11. Productive Tensions in a Cross-Cultural Peer Mentoring Women's Network: A Social Capital Perspective

    ERIC Educational Resources Information Center

    Esnard, Talia; Cobb-Roberts, Deirdre; Agosto, Vonzell; Karanxha, Zorka; Beck, Makini; Wu, Ke; Unterreiner, Ann

    2015-01-01

    A growing body of researchers documents the unique barriers women face in their academic career progression and the significance of mentoring networks for advancement of their academic trajectories as faculty. However, few researchers explore the embedded tensions and conflicts in the social processes and relations of mentoring networks, and the…

  12. Research on spatial economic structure for different economic sectors from a perspective of a complex network

    NASA Astrophysics Data System (ADS)

    Hu, Sen; Yang, Hualei; Cai, Boliang; Yang, Chunxia

    2013-09-01

    The economy system is a complex system, and the complex network is a powerful tool to study its complexity. Here we calculate the economic distance matrices based on annual GDP of nine economic sectors from 1995-2010 in 31 Chinese provinces and autonomous regions,1 then build several spatial economic networks through the threshold method and the Minimal Spanning Tree method. After the analysis on the structure of the networks and the influence of geographic distance, some conclusions are drawn. First, connectivity distribution of a spatial economic network does not follow the power law. Second, according to the network structure, nine economic sectors could be divided into two groups, and there is significant discrepancy of network structure between these two groups. Moreover, the influence of the geographic distance plays an important role on the structure of a spatial economic network, network parameters are changed with the influence of the geographic distance. At last, 2000 km is the critical value for geographic distance: for real estate and finance, the spearman’s rho with l<2000 is bigger than that with l>2000, and the case is opposite for other economic sectors.

  13. Repetitive Behaviors in Autism and Obsessive-Compulsive Disorder: New Perspectives from a Network Analysis

    ERIC Educational Resources Information Center

    Ruzzano, Laura; Borsboom, Denny; Geurts, Hilde M.

    2015-01-01

    The association between autism and obsessive-compulsive disorder (OCD) seems largely dependent upon observed similarities in the repetitive behaviors that manifest in both disorders. The aim of this study was to use a network approach to explore the interactions between these behaviors. We constructed a network based on clinician's…

  14. Efficacy of Online Social Networks on Language Teaching: A Bangladeshi Perspective

    ERIC Educational Resources Information Center

    Shams, Shaila

    2014-01-01

    It is now an established fact that the use of technology facilitates teaching and learning in language classrooms. With the advancement of technology, social networking websites have emerged too. Social networking sites have been quite popular among various age group users particularly the young users since their invention. Also, they are…

  15. Home-Based Peer Social Networks of Young Children with Down Syndrome: A Developmental Perspective

    ERIC Educational Resources Information Center

    Guralnick, Michael J.; Connor, Robert T.; Johnson, L. Clark

    2009-01-01

    Numerous dimensions of the peer social networks of children with Down syndrome were examined within a developmental framework. Results revealed that for many key measures, particularly involvement in play, linkages to other settings, and control of play, children with Down syndrome have less well-developed peer networks even in comparison to a…

  16. The STIN in the Tale: A Socio-Technical Interaction Perspective on Networked Learning

    ERIC Educational Resources Information Center

    Walker, Steve; Creanor, Linda

    2009-01-01

    In this paper, we go beyond what have been described as "mechanistic" accounts of e-learning to explore the complexity of relationships between people and technology as encountered in cases of networked learning. We introduce from the social informatics literature the concept of sociotechnical interaction networks which focus on the interplay…

  17. A Social Network Perspective on Teacher Collaboration in Schools: Theory, Methodology, and Applications

    ERIC Educational Resources Information Center

    Moolenaar, Nienke M.

    2012-01-01

    An emerging trend in educational research is the use of social network theory and methodology to understand how teacher collaboration can support or constrain teaching, learning, and educational change. This article provides a critical synthesis of educational literature on school social networks among educators to advance our understanding of the…

  18. Added-value from a multi-criteria selection of donor catchments in the prediction of continuous streamflow series at ungauged pollution control-sites

    NASA Astrophysics Data System (ADS)

    Drogue, Gilles; Ben Khediri, Wiem; Conan, Céline

    2016-05-01

    We explore the potential of a multi-criteria selection of donor catchments in the prediction of continuous streamflow series by the spatial proximity method. Three criteria have been used: (1) spatial proximity; (2) physical similarity; (3) stream gauging network topology. An extensive assessment of our spatial proximity method variant is made on a 149 catchment-data set located in the Rhine-Meuse catchment. The competitiveness of the method is evaluated against spatial interpolation of catchment model parameters with ordinary kriging. We found that the spatial proximity approach is more efficient than ordinary kriging. When distance to upstream/downstream stream gauge stations is considered as a second order criterion in the selection of donor catchments, an unprecedented level of efficiency is reached for nested catchments. Nevertheless, the spatial proximity method does not take advantage from physical similarity between donor catchments and receiver catchments because catchments that are the most hydrologically similar to each catchment poorly match with the catchments that are the most physically similar to each catchment.

  19. Consensus group sessions: a useful method to reconcile stakeholders’ perspectives about network performance evaluation

    PubMed Central

    Lamontagne, Marie-Eve; Swaine, Bonnie R; Lavoie, André; Champagne, François; Marcotte, Anne-Claire

    2010-01-01

    Background Having a common vision among network stakeholders is an important ingredient to developing a performance evaluation process. Consensus methods may be a viable means to reconcile the perceptions of different stakeholders about the dimensions to include in a performance evaluation framework. Objectives To determine whether individual organizations within traumatic brain injury (TBI) networks differ in perceptions about the importance of performance dimensions for the evaluation of TBI networks and to explore the extent to which group consensus sessions could reconcile these perceptions. Methods We used TRIAGE, a consensus technique that combines an individual and a group data collection phase to explore the perceptions of network stakeholders and to reach a consensus within structured group discussions. Results One hundred and thirty-nine professionals from 43 organizations within eight TBI networks participated in the individual data collection; 62 professionals from these same organisations contributed to the group data collection. The extent of consensus based on questionnaire results (e.g. individual data collection) was low, however, 100% agreement was obtained for each network during the consensus group sessions. The median importance scores and mean ranks attributed to the dimensions by individuals compared to groups did not differ greatly. Group discussions were found useful in understanding the reasons motivating the scoring, for resolving differences among participants, and for harmonizing their values. Conclusion Group discussions, as part of a consensus technique, appear to be a useful process to reconcile diverging perceptions of network performance among stakeholders. PMID:21289996

  20. Durability of Kinase-Directed Therapies--A Network Perspective on Response and Resistance.

    PubMed

    Murray, Brion W; Miller, Nichol

    2015-09-01

    Protein kinase-directed cancer therapies yield impressive initial clinical responses, but the benefits are typically transient. Enhancing the durability of clinical response is dependent upon patient selection, using drugs with more effective pharmacology, anticipating mechanisms of drug resistance, and applying concerted drug combinations. Achieving these tenets requires an understanding of the targeted kinase's role in signaling networks, how the network responds to drug perturbation, and patient-to-patient network variations. Protein kinases create sophisticated, malleable signaling networks with fidelity coded into the processes that regulate their presence and function. Robust and reliable signaling is facilitated through network processes (e.g., feedback regulation, and compensatory signaling). The routine use of kinase-directed therapies and advancements in both genomic analysis and tumor cell biology are illuminating the complexity of tumor network biology and its capacity to respond to perturbations. Drug efficacy is attenuated by alterations of the drug target (e.g., steric interference, compensatory activity, and conformational changes), compensatory signaling (bypass mechanisms and phenotype switching), and engagement of other oncogenic capabilities (polygenic disease). Factors influencing anticancer drug response and resistance are examined to define the behavior of kinases in network signaling, mechanisms of drug resistance, drug combinations necessary for durable clinical responses, and strategies to identify mechanisms of drug resistance. PMID:26264276

  1. The importance of social networks on smoking: perspectives of women who quit smoking during pregnancy.

    PubMed

    Nguyen, Stephanie N; Von Kohorn, Isabelle; Schulman-Green, Dena; Colson, Eve R

    2012-08-01

    While up to 45% of women quit smoking during pregnancy, nearly 80% return to smoking within a year after delivery. Interventions to prevent relapse have had limited success. The study objective was to understand what influences return to smoking after pregnancy among women who quit smoking during pregnancy, with a focus on the role of social networks. We conducted in-depth, semi-structured interviews during the postpartum hospital stay with women who quit smoking while pregnant. Over 300 pages of transcripts were analyzed using qualitative methods to identify common themes. Respondents [n = 24] were predominately white (63%), had at least some college education (54%) and a mean age of 26 years (range = 18-36). When reflecting on the experience of being a smoker who quit smoking during pregnancy, all participants emphasized the importance of their relationships with other smokers and the changes in these relationships that ensued once they quit smoking. Three common themes were: (1) being enmeshed in social networks with prominent smoking norms (2) being tempted to smoke by members of their social networks, and (3) changing relationships with the smokers in their social networks as a result of their non-smoking status. We found that women who quit smoking during pregnancy found themselves confronted by a change in their social network since most of those in their social network were smokers. For this reason, smoking cessation interventions may be most successful if they help women consider restructuring or reframing their social network. PMID:21989676

  2. A STUDY OF PERSPECTIVE OF ROAD TRANSPORTATION RELIABILITY ON THE NETWORK LEVEL AND ITS EVALUATION

    NASA Astrophysics Data System (ADS)

    Nakayama, Sho-Ichiro

    In this paper, road transportation reliability on th e network level is considered . First, previous studies of connectivity reliability and vuln erability are reviewed. Next, stocha stic network equilibrium models, whose flows and travel times are stochastic, and simu lation techniques are classified, and their future works are pointed out. Th en, transportation policies and network design problems which increase or optimize the reliability are re viewed. Finally, a method of unified travel time and connectivity reliability assessment is proposed based on the review of this paper.

  3. Brain Functional Effects of Psychopharmacological Treatments in Schizophrenia: A Network-based Functional Perspective Beyond Neurotransmitter Systems

    PubMed Central

    De Rossi, Pietro; Chiapponi, Chiara; Spalletta, Gianfranco

    2015-01-01

    Psychopharmacological treatments for schizophrenia have always been a matter of debate and a very important issue in public health given the chronic, relapsing and disabling nature of the disorder. A thorough understanding of the pros and cons of currently available pharmacological treatments for schizophrenia is critical to better capture the features of treatment-refractory clinical pictures and plan the developing of new treatment strategies. This review focuses on brain functional changes induced by antipsychotic drugs as assessed by modern functional neuroimaging techniques (i.e. fMRI, PET, SPECT, MRI spectroscopy). The most important papers on this topic are reviewed in order to draw an ideal map of the main functional changes occurring in the brain during antipsychotic treatment. This supports the hypothesis that a network-based perspective and a functional connectivity approach are needed to fill the currently existing gap of knowledge in the field of psychotropic drugs and their mechanisms of action beyond neurotransmitter systems. PMID:26412063

  4. Brain Functional Effects of Psychopharmacological Treatments in Schizophrenia: A Network-based Functional Perspective Beyond Neurotransmitter Systems.

    PubMed

    De Rossi, Pietro; Chiapponi, Chiara; Spalletta, Gianfranco

    2015-01-01

    Psychopharmacological treatments for schizophrenia have always been a matter of debate and a very important issue in public health given the chronic, relapsing and disabling nature of the disorder. A thorough understanding of the pros and cons of currently available pharmacological treatments for schizophrenia is critical to better capture the features of treatment-refractory clinical pictures and plan the developing of new treatment strategies. This review focuses on brain functional changes induced by antipsychotic drugs as assessed by modern functional neuroimaging techniques (i.e. fMRI, PET, SPECT, MRI spectroscopy). The most important papers on this topic are reviewed in order to draw an ideal map of the main functional changes occurring in the brain during antipsychotic treatment. This supports the hypothesis that a network-based perspective and a functional connectivity approach are needed to fill the currently existing gap of knowledge in the field of psychotropic drugs and their mechanisms of action beyond neurotransmitter systems. PMID:26412063

  5. Modeling epidemics on adaptively evolving networks: A data-mining perspective.

    PubMed

    Kattis, Assimakis A; Holiday, Alexander; Stoica, Ana-Andreea; Kevrekidis, Ioannis G

    2016-02-17

    The exploration of epidemic dynamics on dynamically evolving ("adaptive") networks poses nontrivial challenges to the modeler, such as the determination of a small number of informative statistics of the detailed network state (that is, a few "good observables") that usefully summarize the overall (macroscopic, systems-level) behavior. Obtaining reduced, small size accurate models in terms of these few statistical observables - that is, trying to coarse-grain the full network epidemic model to a small but useful macroscopic one - is even more daunting. Here we describe a data-based approach to solving the first challenge: the detection of a few informative collective observables of the detailed epidemic dynamics. This is accomplished through Diffusion Maps (DMAPS), a recently developed data-mining technique. We illustrate the approach through simulations of a simple mathematical model of epidemics on a network: a model known to exhibit complex temporal dynamics. We discuss potential extensions of the approach, as well as possible shortcomings. PMID:26695450

  6. Architecture and biological applications of artificial neural networks: a tuberculosis perspective.

    PubMed

    Darsey, Jerry A; Griffin, William O; Joginipelli, Sravanthi; Melapu, Venkata Kiran

    2015-01-01

    Advancement of science and technology has prompted researchers to develop new intelligent systems that can solve a variety of problems such as pattern recognition, prediction, and optimization. The ability of the human brain to learn in a fashion that tolerates noise and error has attracted many researchers and provided the starting point for the development of artificial neural networks: the intelligent systems. Intelligent systems can acclimatize to the environment or data and can maximize the chances of success or improve the efficiency of a search. Due to massive parallelism with large numbers of interconnected processers and their ability to learn from the data, neural networks can solve a variety of challenging computational problems. Neural networks have the ability to derive meaning from complicated and imprecise data; they are used in detecting patterns, and trends that are too complex for humans, or other computer systems. Solutions to the toughest problems will not be found through one narrow specialization; therefore we need to combine interdisciplinary approaches to discover the solutions to a variety of problems. Many researchers in different disciplines such as medicine, bioinformatics, molecular biology, and pharmacology have successfully applied artificial neural networks. This chapter helps the reader in understanding the basics of artificial neural networks, their applications, and methodology; it also outlines the network learning process and architecture. We present a brief outline of the application of neural networks to medical diagnosis, drug discovery, gene identification, and protein structure prediction. We conclude with a summary of the results from our study on tuberculosis data using neural networks, in diagnosing active tuberculosis, and predicting chronic vs. infiltrative forms of tuberculosis. PMID:25502388

  7. How people make friends in social networking sites—A microscopic perspective

    NASA Astrophysics Data System (ADS)

    Hu, Haibo; Wang, Xiaofan

    2012-02-01

    We study the detailed growth of a social networking site with full temporal information by examining the creation process of each friendship relation that can collectively lead to the macroscopic properties of the network. We first study the reciprocal behavior of users, and find that link requests are quickly responded to and that the distribution of reciprocation intervals decays in an exponential form. The degrees of inviters/accepters are slightly negatively correlative with reciprocation time. In addition, the temporal feature of the online community shows that the distributions of intervals of user behaviors, such as sending or accepting link requests, follow a power law with a universal exponent, and peaks emerge for intervals of an integral day. We finally study the preferential selection and linking phenomena of the social networking site and find that, for the former, a linear preference holds for preferential sending and reception, and for the latter, a linear preference also holds for preferential acceptance, creation, and attachment. Based on the linearly preferential linking, we put forward an analyzable network model which can reproduce the degree distribution of the network. The research framework presented in the paper could provide a potential insight into how the micro-motives of users lead to the global structure of online social networks.

  8. Sediment connectivity evolution on an alpine catchment undergoing glacier retreat

    NASA Astrophysics Data System (ADS)

    Goldin, Beatrice; Rudaz, Benjamin; Bardou, Eric

    2014-05-01

    Climate changes can result in a wide range of variations of natural environment including retreating glaciers. Melting from glaciers will have a significant impact on the sediment transport characteristics of glacierized alpine catchments that can affect downstream channel network. Sediment connectivity assessment, i.e. the degree of connections that controls sediment fluxes between different segments of a landscape, can be useful in order to address management activity on sediment fluxes changes of alpine streams. Through the spatial characterization of the connectivity patterns of a catchment and its potential evolution it is possible to both define sediment transport pathways and estimate different contributions of the sub-catchment as sediment sources. In this study, a topography based index (Cavalli et al., 2013) has been applied to assess spatial sediment connectivity in the Navisence catchment (35 km2), an alpine basin located in the southern Walliser Alps (Switzerland) characterized by a complex glacier system with well-developed lateral moraines on glacier margins already crossed by several lateral channels. Glacier retreat of the main glacial edifice will provide a new connectivity pattern. At present the glacier disconnects lateral slopes from the main talweg: it is expected that its retreat will experience an increased connectivity. In order to study this evolution, two high resolution (2 m) digital terrain models (DTMs) describing respectively the terrain before and after glacier retreat have been analyzed. The current DTM was obtained from high resolution photogrammetry (2 m resolution). The future DTM was derived from application of the sloping local base level (SLBL) routine (Jaboyedoff et al., 2004) on the current glacier system, allowing to remove the ice body by reconstituting a U-shaped polynomial bedrock surface. From this new surface a coherent river network was drawn and slight random noise was added. Finally the river network was burned into

  9. A catchment-scale model of mountain stream channel morphologies in southeast Australia

    NASA Astrophysics Data System (ADS)

    Thompson, Chris; Croke, Jacky; Takken, Ingrid

    2008-03-01

    The position of mountain streams high in the channel network and their proportional dominance mean that channel modifications and adjustments within these systems will have important implications for downstream processes and linkages. This study develops an analysis framework for examining the catchment-scale distribution of reach morphologies, and the relationship among reach type, catchment lithology and flow competence in southeast Australian mountain streams. The analysis framework is applied to three catchments which have contrasting proportions of the two dominant lithologies of the region, Devonian granites and Ordovician metasediments. The model successfully delineated 68% of reach types, and the resultant spatial maps allowed the effects of stream network position and catchment specific controls on channel morphology to be evaluated. Maximum lengths of the majority of reach morphology types were in second-order streams and the maximum number of morphology types (six) was present in third-order streams, with dramatic reductions in reach type variability as the network expands. The position of catchment lithology within the channel network structure was recognized as more important than the aerial extent of a particular lithology on the distribution and abundance of reach morphologies. The model provides an important tool in the management of channel networks for the protection or restoration of ecological diversity, by identifying river segments and tributaries with high morphological diversity.

  10. Crossing thresholds: Analysis of hazardous tipping points in alpine catchments

    NASA Astrophysics Data System (ADS)

    Lutzmann, Silke; Sass, Oliver

    2016-04-01

    Steep mountain channels or torrents in small alpine catchments are characterized by high geomorphic activity with sediment dynamics being inherently nonlinear and threshold-mediated. Localized, high intensity rainstorms can drive torrential systems past a tipping point resulting in a sudden onset of hazardous events like (flash-) flooding, heavy bedload transport or debris flows. Such responses exhibit an abrupt switch in the fluvial system's mode (e.g. transport / supply limited). Changes in functional connectivity may persist beyond the tipping point. Torrential hazards cause costly damage in the densely populated Alpine Region. Thus, there is a rising interest in potential effects of climate change on torrential sediment dynamics. Understanding critical conditions close to tipping points is important to reduce uncertainty in predicting sediment fluxes. In this study we aim at (i) establishing threshold precipitation characteristics for the Eastern Alps of Austria. Precipitation is hypothesized to be the main forcing factor of torrential events. (ii) How do thresholds vary in space and time? (iii) The effect of external triggers is strongly mediated by the internal disposition of catchments to respond. Which internal conditions are critical for susceptibility? (iv) Is there a change in magnitude or frequency in the recent past and what can be expected for the future? The 71 km2 catchment of the river Schöttlbach in the East Alpine Region of Styria (Austria) is monitored since a heavy precipitation event resulted in a catastrophic flood in July 2011. Sediment mobilization from slopes as well as within-channel storage and bedload transport are regularly measured using photogrammetric methods and sediment impact sensors. Thus, detailed knowledge exists on magnitude and spatial propagation of sediment waves through the catchment. The associated hydro-meteorological (pre-) conditions can be inferred from a dense station network. Changing bedload transport rates and

  11. Understanding the relationship between sediment connectivity and spatio-temporal landscape changes in two small catchments

    NASA Astrophysics Data System (ADS)

    Giuseppina Persichillo, Maria; Meisina, Claudia; Cavalli, Marco; Crema, Stefano; Bordoni, Massimiliano

    2016-04-01

    The degree of linkage between the sediments sources and downstream areas (i.e., sediment connectivity) is one of the most important properties controlling landscape evolution. Many factors have been found to affect sediment connectivity, especially at the catchment scale. In particular, the degree of linkage between different areas within a catchment depends largely on the morphological complexity of the catchment (relief, terrain roughness, stream network density and catchment shape) and the combined effects of vegetation, such as land use changes and land abandonment. Moreover, the analysis of the spatial distribution of sediment connectivity and its temporal evolution can be also useful for the characterization of sediment source areas. Specifically, these areas represent sites of instability and their connectivity influences the probability that a local on-site effect could propagate within a multiple-events feedback system. Within this framework, the aim of this study is to apply a geomorphometric approach to analyze the linkage between landscape complexity and the sediment connectivity at the catchment scale. Moreover, to assess sediment delivery, the index of connectivity (IC) proposed by Cavalli et al. (2013) was used to evaluate the potential connection of sediment source areas with the main channel network. To better understand the relationship between morphological complexity of the catchment's landscape and the sediment spatial distribution and mobilization, two catchments with different size and geomorphological and land use characteristics were analysed: the Rio Frate and Versa catchments (Oltrepo Pavese, Southern Lombardy, Italy). Several shallow landslides, which represents the main sediment source area type in the catchments, were triggered especially in the period from 2009 to 2013. Moreover, relevant modification of land use and drainage system during last decades, especially related to land abandonment, have conditioned the sediment connectivity

  12. Shareholding relationships in the Euro Area banking market: A network perspective

    NASA Astrophysics Data System (ADS)

    Pecora, Nicolò; Spelta, Alessandro

    2015-09-01

    In this paper we analyze the topological properties of the network of the Euro Area banking market network, with the primary aim of assessing the importance of a bank in the financial system with respect to ownership and control of other credit institutions. The network displays power law distributions in both binary and weighted degree metrics indicating a robust yet fragile structure and a direct link between an increase of control diversification and a rise in the market power. Therefore while in good time the network is seemingly robust, in bad times many banks can simultaneously go into distress. This behavior paves the way for Central bank's actions. In particular we investigate whether the Single Supervisory Mechanism introduced by the European Central Banks and based on banks' total asset is a good proxy to quantify their systemic importance. Results indicate that not all the financial institutions with high valued total assets are systemically important but only few of them. Moreover the network structure reveals that control is highly concentrated, with few important shareholders approximately controlling a separate subset of banks.

  13. Global Spatio-Temporal Patterns in Human Migration: A Complex Network Perspective

    PubMed Central

    Davis, Kyle F.; D'Odorico, Paolo; Laio, Francesco; Ridolfi, Luca

    2013-01-01

    Migration is a powerful adaptive strategy for humans to navigate hardship and pursue a better quality of life. As a universal vehicle facilitating exchanges of ideas, culture, money and goods, international migration is a major contributor to globalization. Consisting of countries linked by multiple connections of human movements, global migration constitutes a network. Despite the important role of human migration in connecting various communities in different parts of the world, the topology and behavior of the international migration network and its changes through time remain poorly understood. Here we show that the global human migration network became more interconnected during the latter half of the twentieth century and that migrant destination choice partly reflects colonial and postcolonial histories, language, religion, and distances. From 1960 to 2000 we found a steady increase in network transitivity (i.e. connectivity between nodes connected to the same node), a decrease in average path length and an upward shift in degree distribution, all of which strengthened the ‘small-world’ behavior of the migration network. Furthermore, we found that distinct groups of countries preferentially interact to form migration communities based largely on historical, cultural and economic factors. PMID:23372664

  14. The sound of emotions-Towards a unifying neural network perspective of affective sound processing.

    PubMed

    Frühholz, Sascha; Trost, Wiebke; Kotz, Sonja A

    2016-09-01

    Affective sounds are an integral part of the natural and social environment that shape and influence behavior across a multitude of species. In human primates, these affective sounds span a repertoire of environmental and human sounds when we vocalize or produce music. In terms of neural processing, cortical and subcortical brain areas constitute a distributed network that supports our listening experience to these affective sounds. Taking an exhaustive cross-domain view, we accordingly suggest a common neural network that facilitates the decoding of the emotional meaning from a wide source of sounds rather than a traditional view that postulates distinct neural systems for specific affective sound types. This new integrative neural network view unifies the decoding of affective valence in sounds, and ascribes differential as well as complementary functional roles to specific nodes within a common neural network. It also highlights the importance of an extended brain network beyond the central limbic and auditory brain systems engaged in the processing of affective sounds. PMID:27189782

  15. Climate change impacts on urban wildfire and flooding policy in Idaho: a comparative policy network perspective

    NASA Astrophysics Data System (ADS)

    Lindquist, E.; Pierce, J. L.

    2013-12-01

    Numerous frameworks and models exist for understanding the dynamics of the public policy process. A policy network approach considers how and why stakeholders and interests pay attention to and engage in policy problems, such as flood control or developing resilient and fire resistant landscapes. Variables considered in this approach include what the relationships are between these stakeholders, how they influence the process and outcomes, communication patterns within and between policy networks, and how networks change as a result of new information, science, or public interest and involvement with the problem. This approach is useful in understanding the creation of natural hazards policy as new information or situations, such as projected climate change impacts, influence and disrupt the policy process and networks. Two significant natural hazard policy networks exist in the semi-arid Treasure Valley region of Southwest Idaho, which includes the capitol city of Boise and the surrounding metropolitan area. Boise is situated along the Boise River and adjacent to steep foothills; this physiographic setting makes Boise vulnerable to both wildfires at the wildland-urban interface (WUI) and flooding. Both of these natural hazards have devastated the community in the past and floods and fires are projected to occur with more frequency in the future as a result of projected climate change impacts in the region. While both hazards are fairly well defined problems, there are stark differences lending themselves to comparisons across their respective networks. The WUI wildfire network is large and well developed, includes stakeholders from all levels of government, the private sector and property owner organizations, has well defined objectives, and conducts promotional and educational activities as part of its interaction with the public in order to increase awareness and garner support for its policies. The flood control policy network, however, is less defined

  16. A dynamic evolutionary clustering perspective: Community detection in signed networks by reconstructing neighbor sets

    NASA Astrophysics Data System (ADS)

    Chen, Jianrui; Wang, Hua; Wang, Lina; Liu, Weiwei

    2016-04-01

    Community detection in social networks has been intensively studied in recent years. In this paper, a novel similarity measurement is defined according to social balance theory for signed networks. Inter-community positive links are found and deleted due to their low similarity. The positive neighbor sets are reconstructed by this method. Then, differential equations are proposed to imitate the constantly changing states of nodes. Each node will update its state based on the difference between its state and average state of its positive neighbors. Nodes in the same community will evolve together with time and nodes in the different communities will evolve far away. Communities are detected ultimately when states of nodes are stable. Experiments on real world and synthetic networks are implemented to verify detection performance. The thorough comparisons demonstrate the presented method is more efficient than two acknowledged better algorithms.

  17. Striking the balance: Challenges and perspectives for the protected areas network in northeastern European Russia.

    PubMed

    Degteva, Svetlana V; Ponomarev, Vasily I; Eisenman, Sasha W; Dushenkov, Vyacheslav

    2015-10-01

    Increasing anthropogenic pressure on the largest remaining tracts of old-growth boreal forest in Europe necessitates additional conservation of ecosystems and biodiversity in northeastern European Russia. In a regional network comprising 8 % of the Nenets Autonomous District and 13.5 % of the Komi Republic, 248 areas have varying protected statuses as state nature reserves (zapovedniks), national parks, reserves/sanctuaries (zakazniks), or natural monuments. Due to increased natural resource extraction in this relatively pristine area, designation of additional protected areas is critical for the protection of key ecological sites. The history of ecological preservation in these regions is herein described, and recent recommendations for incorporating additional ecologically representative areas into the regional network are presented. If the protected area network can be expanded, the overall environmental stability in these globally significant ecosystems may remain intact, and can help Russia meet the 2020 Aichi conservation targets, as set forth by the Convention of Biological Diversity. PMID:25663528

  18. Modeling of matters removal from swampy catchment

    NASA Astrophysics Data System (ADS)

    Inishev, N. G.; Inisheva, L. I.

    2010-05-01

    This work shows the results of fixed study of geochemical conditions in the system of landscape oligotrophic profile at Vasyugan mire spurs, and also we make an approach to processes modelling of compounds removal from swampy catchment. During investigation of symbolic model of chemical matters removal from the surface of a catchment basin and their movement along the channel network it was taken into account that removal of chemical elements during the period of spring flood and rain high waters occur mainly with overland flow. During calculation of dissolved matters movement the following admissions take place: 1. The problem is solved at one-dimension set-up. Concentration of investigated components is taken as averaged one along the flow cross section or effective area of slope cross-section for overland runoff, i.e. it changes only lengthways and in time. 2. It is considered that dissolved matters spread due to movement of water and together with its particles. 3. Processes of water self-clarification are not considered. The model is calculated on the basis of discharge of the investigated ingredient, i.e. matter mass moving through the given flow cross-section into time unit. This is the peculiarity of the model. Matter removal together with water flow is determined if necessary. Everyday impurity consumptions and its concentration can be estimated at the outlet at the moment of time according to convolution integral. Estimation of overland runoff and water inflow into the channel network is based on the mathematic model of outflow formation from peatland areas which considers basic processes carrying out at catchment and basin channel network. Stored moisture estimation of snow cover is taken according to snow survey data before snow melting. Everyday water supply to the surface of water collection was determined according to the results of snow melt intensity estimation by the methods of temperature coefficient and water yield from snow (A.G. Kovzel). All

  19. Comparison of Multi-Scale Digital Elevation Models for Defining Waterways and Catchments Over Large Areas

    NASA Astrophysics Data System (ADS)

    Harris, B.; McDougall, K.; Barry, M.

    2012-07-01

    Digital Elevation Models (DEMs) allow for the efficient and consistent creation of waterways and catchment boundaries over large areas. Studies of waterway delineation from DEMs are usually undertaken over small or single catchment areas due to the nature of the problems being investigated. Improvements in Geographic Information Systems (GIS) techniques, software, hardware and data allow for analysis of larger data sets and also facilitate a consistent tool for the creation and analysis of waterways over extensive areas. However, rarely are they developed over large regional areas because of the lack of available raw data sets and the amount of work required to create the underlying DEMs. This paper examines definition of waterways and catchments over an area of approximately 25,000 km2 to establish the optimal DEM scale required for waterway delineation over large regional projects. The comparative study analysed multi-scale DEMs over two test areas (Wivenhoe catchment, 543 km2 and a detailed 13 km2 within the Wivenhoe catchment) including various data types, scales, quality, and variable catchment input parameters. Historic and available DEM data was compared to high resolution Lidar based DEMs to assess variations in the formation of stream networks. The results identified that, particularly in areas of high elevation change, DEMs at 20 m cell size created from broad scale 1:25,000 data (combined with more detailed data or manual delineation in flat areas) are adequate for the creation of waterways and catchments at a regional scale.

  20. Magnets and Seekers: A Network Perspective on Academic Integration inside Two Residential Communities

    ERIC Educational Resources Information Center

    Smith, Rachel A.

    2015-01-01

    Residential learning communities aim to foster increased academic and social integration, ideally leading to greater student success. However, the concept of academic integration is often conceptualized and measured at the individual level, rather than the theoretically more consistent community level. Network analysis provides a paradigm and…

  1. A diffusion perspective on temporal networks: A case study on a supermarket

    NASA Astrophysics Data System (ADS)

    Deng, Shiguo; Qiu, Lu; Yang, Yue; Yang, Huijie

    2016-01-01

    From a large amount of records, one can extract behavioral characteristics of a social system at different scales. Theoretically, it can help us to know how the global behavior of a social system is formed from individual activities. Practically, it can be used to optimize and even to control the social system. Complicated relationships between the individuals form a network, which evolves with time. The behavior of the system can be accordingly understood in the framework of temporal network. In the present paper, instead of focusing on microscopic structures, we develop a framework to investigate temporal networks from the viewpoint of diffusion process, in which each snapshot network is divided into groups and the ID number of the group a node belongs to is used to measure its state. By this way trajectories of the nodes form an ensemble of realizations of a stochastic process. As an illustration, we investigate the diffusion behavior of a supermarket. One can find that with the increase of time the customers cluster and separate into different groups. Meanwhile, the system evolves in a significant order way, instead of a complete random one.

  2. Social Networking in an Intensive English Program Classroom: A Language Socialization Perspective

    ERIC Educational Resources Information Center

    Reinhardt, Jonathon; Zander, Victoria

    2011-01-01

    This ongoing project seeks to investigate the impact, inside and outside of class, of instruction focused on developing learner awareness of social-networking site (SNS) use in an American Intensive English Program (IEP). With language socialization as an interpretative framework (Duff, in press; Ochs, 1988; Watson-Gegeo, 2004), the project uses a…

  3. Foregrounding the Role of Relationships in Reform: A Social Network Perspective on Leadership and Change

    ERIC Educational Resources Information Center

    Liou, Yi-Hwa; Daly, Alan J.; Brown, Chris; del Fresno, Miguel

    2015-01-01

    Purpose: The role of relationships in the process of leadership and change is central, yet the social aspect of the work of reform is often background in favor of more technical approaches to improvement. Therefore, the purpose of this paper is to argue that social network theory and analysis provides a useful theory and set of tools to unpack the…

  4. Culture, Role and Group Work: A Social Network Analysis Perspective on an Online Collaborative Course

    ERIC Educational Resources Information Center

    Stepanyan, Karen; Mather, Richard; Dalrymple, Roger

    2014-01-01

    This paper discusses the patterns of network dynamics within a multicultural online collaborative learning environment. It analyses the interaction of participants (both students and facilitators) within a discussion board that was established as part of a 3-month online collaborative course. The study employs longitudinal probabilistic social…

  5. Relational Networks, Social Trust, and Norms: A Social Capital Perspective on Students' Chances of Academic Success.

    ERIC Educational Resources Information Center

    Goddard, Roger D.

    2003-01-01

    Elaborated a theoretical rationale for relational networks, norms, and trust as structural and functional norms of social capital that facilitate student achievement. Results of hierarchical generalized linear modeling show that the odds of fourth graders passing state-mandated assessments are modestly increased in urban schools (n=49)…

  6. Japanese Language Proficiency, Social Networking, and Language Use during Study Abroad: Learners' Perspectives

    ERIC Educational Resources Information Center

    Dewey, Dan P.; Bown, Jennifer; Eggett, Dennis

    2012-01-01

    This study examines the self-perceived speaking proficiency development of 204 learners of Japanese who studied abroad in Japan and analyzes connections between self-reported social network development, language use, and speaking development. Learners perceived that they gained the most in areas associated with the intermediate and advanced levels…

  7. Principal Perspectives on Social Networking and the Disruptive Effects of Cyberbullying

    ERIC Educational Resources Information Center

    Welker, Heidi Stevenson

    2010-01-01

    Cyberbullying on social networking sites such as MySpace and Facebook has had negative effects on children at school. Cyberbullying disruption during the school day adds to the complexity of maintaining school operations, safety, and academic achievement. With the advancement of technology, there is a gap in the literature on the disruption in…

  8. The Flow of International Students from a Macro Perspective: A Network Analysis

    ERIC Educational Resources Information Center

    Barnett, George A.; Lee, Moosung; Jiang, Ke; Park, Han Woo

    2016-01-01

    This paper provides a network analysis of the international flow of students among 210 countries and the factors determining the structure of this flow. Among these factors, bilateral hyperlink connections between countries and the number of telephone minutes (communication variables) are the most important predictors of the flow's structure,…

  9. Getting Ideas into Action: Building Networked Improvement Communities in Education. Carnegie Perspectives

    ERIC Educational Resources Information Center

    Bryk, Anthony S.; Gomez, Louis M.; Grunow, Alicia

    2010-01-01

    In this Carnegie essay by Anthony Bryk, Louis Gomez and Alicia Grunow, the authors argue that the social organization of the research enterprise is badly broken and a very different alternative is needed. They instead support a science of improvement research and introduce the idea of a networked improvement community that creates the purposeful…

  10. Critical Adult Learning of Asian Immigrant Workers: A Social Network Perspective

    ERIC Educational Resources Information Center

    Lee, Mosung; Madyun, Na'im

    2008-01-01

    This study reveals how the social networks of immigrant workers play a key role in mediating critical learning towards a particular political attitude. Theoretical relationships between critical learning and political attitudes were set up and four types of political attitudes were identified. A "resistant political attitude" was conceptually…

  11. Networking and the Role of the Academic Systems Librarian: An Evolutionary Perspective.

    ERIC Educational Resources Information Center

    Lavagnino, Merri Beth

    1997-01-01

    This paper examines the role of academic systems librarians, focusing on the effect of networking technologies. Outlines stages in the evolution of the field derived from the literature and surveys, discusses new administrative and professional tasks and trends resulting from technological change, and speculates about the future of academic…

  12. Parents and Peers as Providers of Support in Adolescents' Social Network: A Developmental Perspective

    ERIC Educational Resources Information Center

    del Valle, Jorge F.; Bravo, Amaia; Lopez, Monica

    2010-01-01

    The authors carried out an assessment of social support networks with a sample of 884 Spanish adolescents aged 12 to 17. The main goal was to analyze the development of the figures of parents and peers as providers of social support in the two basic dimensions of emotional and instrumental support. In peers, they distinguished between the contexts…

  13. Monitoring Scientific Developments from a Dynamic Perspective: Self-Organized Structuring To Map Neural Network Research.

    ERIC Educational Resources Information Center

    Noyons, E. C. M.; van Raan, A. F. J.

    1998-01-01

    Using bibliometric mapping techniques, authors developed a methodology of self-organized structuring of scientific fields which was applied to neural network research. Explores the evolution of a data generated field structure by monitoring the interrelationships between subfields, the internal structure of subfields, and the dynamic features of…

  14. Learners' Perspectives on Networked Collaborative Interaction with Native Speakers of Spanish in the US

    ERIC Educational Resources Information Center

    Lee, Lina

    2004-01-01

    In this paper, I discuss a network-based collaborative project that focused on the learning conditions non-native speakers (NNSs) of Spanish perceived to be necessary to satisfactoraly communicate with native speakers (NSs). Data from online discussions, end-of-semester surveys, and final oral interviews are presented and discussed. The results of…

  15. Tutorial on neural network applications in high energy physics: A 1992 perspective

    SciTech Connect

    Denby, B.

    1992-04-01

    Feed forward and recurrent neural networks are introduced and related to standard data analysis tools. Tips are given on applications of neural nets to various areas of high energy physics. A review of applications within high energy physics and a summary of neural net hardware status are given.

  16. Creativity of Student Information System Projects: From the Perspective of Network Embeddedness

    ERIC Educational Resources Information Center

    Yang, Heng-Li; Cheng, Hsiu-Hua

    2010-01-01

    Many companies have pursued innovation to obtain a competitive edge. Thus, educational reform focuses mainly on training creative students. This study adopted the concept of an affiliated network of projects to investigate how project embeddedness influences project team creativity. This work surveys 60 projects in a Management Information Systems…

  17. Social Networks and Workplace Risk: Classroom Scenarios from a U.S. and EU Perspective

    ERIC Educational Resources Information Center

    Binder, Perry; Mansfield, Nancy R.

    2013-01-01

    The explosion of social networks and the growing concern over privacy in the digital age--both in the United States and Europe--have provided an opportunity to introduce students to the legal risks of using social media in the workplace. This article builds on the authors' classroom experiences and provides social media scenarios and projects that…

  18. Virtual war, military revolutions, and networks: a guide through the concepts from an Australian perspective

    NASA Astrophysics Data System (ADS)

    Bowley, Dean K.; Gaertner, Paul S.

    2003-07-01

    In this paper the argument is made that the offensive fire support organisation and doctrine, born of the "indirect fire revolution" of the first world war, is the start point for distributed sensors, shooters and deciders that may be transferred to a joint force; that the culture of directive control and mission orders developed by the German Army in 1918 and then adopted by most western armies is the start point for the culture required to achieve "self synchronisation" and that the network developed for the air defence of carrier battle groups is the start point for developing a networked ground manoeuvre force. We discuss the strategic expectations of network centric warfare, a "virtual war" scenario and the inherent vulnerabilities. The current level of understanding and implementation in specific areas is analysed and lessons for general application are developed and the potential payoff identified. Three broad operational domains are investigated, networked platform versus platform warfare between states, guerrilla/counter-insurfence operations and the emerging domain of "netwars" (terror organisations and criminal gangs).

  19. The Key Roles in the Informal Organization: A Network Analysis Perspective

    ERIC Educational Resources Information Center

    de Toni, Alberto F.; Nonino, Fabio

    2010-01-01

    Purpose: The purpose of this paper is to identify the key roles embedded in the informal organizational structure (informal networks) and to outline their contribution in the companies' performance. A major objective of the research is to find and characterize a new key informal role that synthesises problem solving, expertise, and accessibility…

  20. Infotainment and road safety service support in vehicular networking: From a communication perspective

    NASA Astrophysics Data System (ADS)

    Cheng, Ho Ting; Shan, Hangguan; Zhuang, Weihua

    2011-08-01

    Vehicular ad hoc networking is an emerging technology for future on-the-road communications. Due to the virtue of vehicle-to-vehicle and vehicle-to-infrastructure communications, vehicular ad hoc networks (VANETs) are expected to enable a plethora of communication-based automotive applications including diverse in-vehicle infotainment applications and road safety services. Even though vehicles are organized mostly in an ad hoc manner in the network topology, directly applying the existing communication approaches designed for traditional mobile ad hoc networks to large-scale VANETs with fast-moving vehicles can be ineffective and inefficient. To achieve success in a vehicular environment, VANET-specific communication solutions are imperative. In this paper, we provide a comprehensive overview of various radio channel access protocols and resource management approaches, and discuss their suitability for infotainment and safety service support in VANETs. Further, we present recent research activities and related projects on vehicular communications. Potential challenges and open research issues are also discussed.

  1. When People See News from a Non-Western Perspective: Cable News Network's "World Report."

    ERIC Educational Resources Information Center

    Stewart, Robert K.

    Much of what Americans "see" of the world is focused through the prism of the American news media. Broadcast journalists, in particular, provide the images that help shape viewers' ideas of the world. The recent introduction on U.S. television of Cable News Network's (CNN) "World Report" now provides the opportunity for American viewers to watch…

  2. Coevolution of volcanic catchments in Japan

    NASA Astrophysics Data System (ADS)

    Yoshida, Takeo; Troch, Peter A.

    2016-03-01

    Present-day landscapes have evolved over time through interactions between the prevailing climates and geological settings. Understanding the linkage between spatial patterns of landforms, soils, and vegetation in landscapes and their hydrological response is critical to make quantitative predictions in ungaged basins. Catchment coevolution is a theoretical framework that seeks to formulate hypotheses about the mechanisms and conditions that determine the historical development of catchments and how such evolution affects their hydrological response. In this study, we selected 14 volcanic catchments of different ages (from 0.225 to 82.2 Ma) in Japan. We derived indices of landscape properties (drainage density and slope-area relationship) as well as hydrological response (annual water balance, baseflow index, and flow-duration curves) and examined their relation with catchment age and climate (through the aridity index). We found a significant correlation between drainage density and baseflow index with age, but not with climate. The intra-annual flow variability was also significantly related to catchments age. Younger catchments tended to have lower peak flows and higher low flows, while older catchments exhibited more flashy runoff. The decrease in baseflow with catchment age is consistent with the existing hypothesis that in volcanic landscapes the major flow pathways change over time from deep groundwater flow to shallow subsurface flow. The drainage density of our catchments decreased with age, contrary to previous findings in a set of similar, but younger volcanic catchments in the Oregon Cascades, in which drainage density increased with age. In that case, older catchments were thought to show more landscape incision due to increasing near-surface lateral flow paths. Our results suggests two competing hypotheses on the evolution of drainage density in mature catchments. One is that as catchments continue to age, the hydrologically active channels retreat

  3. Wireless in-situ Sensor Network for Agriculture and Water Monitoring on a River Basin Scale in Southern Finland: Evaluation from a Data User’s Perspective

    PubMed Central

    Kotamäki, Niina; Thessler, Sirpa; Koskiaho, Jari; Hannukkala, Asko O.; Huitu, Hanna; Huttula, Timo; Havento, Jukka; Järvenpää, Markku

    2009-01-01

    Sensor networks are increasingly being implemented for environmental monitoring and agriculture to provide spatially accurate and continuous environmental information and (near) real-time applications. These networks provide a large amount of data which poses challenges for ensuring data quality and extracting relevant information. In the present paper we describe a river basin scale wireless sensor network for agriculture and water monitoring. The network, called SoilWeather, is unique and the first of this type in Finland. The performance of the network is assessed from the user and maintainer perspectives, concentrating on data quality, network maintenance and applications. The results showed that the SoilWeather network has been functioning in a relatively reliable way, but also that the maintenance and data quality assurance by automatic algorithms and calibration samples requires a lot of effort, especially in continuous water monitoring over large areas. We see great benefits on sensor networks enabling continuous, real-time monitoring, while data quality control and maintenance efforts highlight the need for tight collaboration between sensor and sensor network owners to decrease costs and increase the quality of the sensor data in large scale applications. PMID:22574050

  4. Examining the Use of Peer-to-Peer Networks from an Activity Perspective

    NASA Astrophysics Data System (ADS)

    de Boever, Jorn; de Grooff, Dirk

    Since the introduction of Napster in 1999, millions of Internet users have exchanged massive amounts of files via P2P (Peer-to-Peer) filesharing networks. Notwithstanding the widespread penetration of these systems among Internet consumers, little is known about the usage process. Therefore, the aim of this chapter is to examine the usage of "illegal" P2P networks by means of an exploratory, qualitative study. The main findings revealed significant differences between the uses of various systems. Bittorrent clients were mainly used to download large files such as video, movies, and complete albums, while Gnutella clients were particularly utilized for small files such as single songs. The results indicate that the type of content, the characteristics of the client, the omnipresence of fake files and malware, the users' motivations, the users' lifestyles and the presence of bandwidth caps had an impact on how the participants utilized P2P systems.

  5. Home-Based Peer Social Networks of Young Children With Down Syndrome: A Developmental Perspective

    PubMed Central

    Guralnick, Michael J.; Connor, Robert T.; Johnson, L. Clark

    2010-01-01

    Numerous dimensions of the peer social networks of children with Down syndrome were examined within a developmental framework. Results revealed that for many key measures, particularly involvement in play, linkages to other settings, and control of play, children with Down syndrome have less well-developed peer networks even in comparison to a mental age matched group of typically developing children. This suggests both an absence of any social advantage in the peer context for children with Down syndrome and the existence of unusual difficulties that may be traced to underlying problems in peer-related social competence. The need for future observational studies of peer interactions for this group of children was emphasized. PMID:19928016

  6. Interprofessional Student Perspectives of Online Social Networks in Health and Business Education.

    PubMed

    Doyle, Glynda; Jones, Cyri; Currie, Leanne

    2016-01-01

    The education sector is experiencing unprecedented change with the increasing use by students of mobile devices, social networks and e-portfolios as they prepare for future positions in the workforce. The purpose of this study was to examine student's preferences around these technologies. A mixed methods research strategy was used with an initial online survey using 29 Likert scale style questions to students from the School of Health Sciences and the School of Business at the British Columbia Institute of Technology (BCIT). Descriptive statistics and ANOVAs were performed to examine if there were any differences between groups regarding their overall responses to the survey questions. Content analysis was used for qualitative focus group data. Overall, students (n = 260) were enthusiastic about technology but wary of cost, lack of choice, increased workload and faculty involvement in their online social networks. Of note, students see significant value in face-to-face classroom time. PMID:27332207

  7. Anthropogenic impacts on tropical forest biodiversity: a network structure and ecosystem functioning perspective

    PubMed Central

    Morris, Rebecca J.

    2010-01-01

    Huge areas of diverse tropical forest are lost or degraded every year with dramatic consequences for biodiversity. Deforestation and fragmentation, over-exploitation, invasive species and climate change are the main drivers of tropical forest biodiversity loss. Most studies investigating these threats have focused on changes in species richness or species diversity. However, if we are to understand the absolute and long-term effects of anthropogenic impacts on tropical forests, we should also consider the interactions between species, how those species are organized in networks, and the function that those species perform. I discuss our current knowledge of network structure and ecosystem functioning, highlighting empirical examples of their response to anthropogenic impacts. I consider the future prospects for tropical forest biodiversity, focusing on biodiversity and ecosystem functioning in secondary forest. Finally, I propose directions for future research to help us better understand the effects of anthropogenic impacts on tropical forest biodiversity. PMID:20980318

  8. Data governance requirements for distributed clinical research networks: triangulating perspectives of diverse stakeholders

    PubMed Central

    Kim, Katherine K; Browe, Dennis K; Logan, Holly C; Holm, Roberta; Hack, Lori; Ohno-Machado, Lucila

    2014-01-01

    There is currently limited information on best practices for the development of governance requirements for distributed research networks (DRNs), an emerging model that promotes clinical data reuse and improves timeliness of comparative effectiveness research. Much of the existing information is based on a single type of stakeholder such as researchers or administrators. This paper reports on a triangulated approach to developing DRN data governance requirements based on a combination of policy analysis with experts, interviews with institutional leaders, and patient focus groups. This approach is illustrated with an example from the Scalable National Network for Effectiveness Research, which resulted in 91 requirements. These requirements were analyzed against the Fair Information Practice Principles (FIPPs) and Health Insurance Portability and Accountability Act (HIPAA) protected versus non-protected health information. The requirements addressed all FIPPs, showing how a DRN's technical infrastructure is able to fulfill HIPAA regulations, protect privacy, and provide a trustworthy platform for research. PMID:24302285

  9. Anthropogenic impacts on tropical forest biodiversity: a network structure and ecosystem functioning perspective.

    PubMed

    Morris, Rebecca J

    2010-11-27

    Huge areas of diverse tropical forest are lost or degraded every year with dramatic consequences for biodiversity. Deforestation and fragmentation, over-exploitation, invasive species and climate change are the main drivers of tropical forest biodiversity loss. Most studies investigating these threats have focused on changes in species richness or species diversity. However, if we are to understand the absolute and long-term effects of anthropogenic impacts on tropical forests, we should also consider the interactions between species, how those species are organized in networks, and the function that those species perform. I discuss our current knowledge of network structure and ecosystem functioning, highlighting empirical examples of their response to anthropogenic impacts. I consider the future prospects for tropical forest biodiversity, focusing on biodiversity and ecosystem functioning in secondary forest. Finally, I propose directions for future research to help us better understand the effects of anthropogenic impacts on tropical forest biodiversity. PMID:20980318

  10. The impact of information technology and networks: new perspectives for scientific, technical and medical (STM) publishing

    NASA Astrophysics Data System (ADS)

    De Kemp, Arnoud

    This contribution is a strongly abbreviated notation of a much longer presentation at the Workshop on Strategies and Techniques of Information for Astronomy, organized by the European Science Foundation in Strasbourg on 21/22 June 1996. The process of publishing will undergo dramatic changes due to the influences of information technology and networks. The publishing business as a whole will shift from traditional print- and paper-based organisations to a fully digital workflow from author to end-user. Electronic publishing has moved from pre-print activities to digital preprints on a variety of servers, but still most scientific documentation is printed and not only for archival purposes. In this short contribution, a plea is made for new rules in scientific communication that authors, editors, publishers, societies, libraries and users can recognize. In addition, in the electronic age we need more security for copyright, transactions over networks and against misuse in general.

  11. Data governance requirements for distributed clinical research networks: triangulating perspectives of diverse stakeholders.

    PubMed

    Kim, Katherine K; Browe, Dennis K; Logan, Holly C; Holm, Roberta; Hack, Lori; Ohno-Machado, Lucila

    2014-01-01

    There is currently limited information on best practices for the development of governance requirements for distributed research networks (DRNs), an emerging model that promotes clinical data reuse and improves timeliness of comparative effectiveness research. Much of the existing information is based on a single type of stakeholder such as researchers or administrators. This paper reports on a triangulated approach to developing DRN data governance requirements based on a combination of policy analysis with experts, interviews with institutional leaders, and patient focus groups. This approach is illustrated with an example from the Scalable National Network for Effectiveness Research, which resulted in 91 requirements. These requirements were analyzed against the Fair Information Practice Principles (FIPPs) and Health Insurance Portability and Accountability Act (HIPAA) protected versus non-protected health information. The requirements addressed all FIPPs, showing how a DRN's technical infrastructure is able to fulfill HIPAA regulations, protect privacy, and provide a trustworthy platform for research. PMID:24302285

  12. Ionic nanoparticle networks: development and perspectives in the landscape of ionic liquid based materials.

    PubMed

    Neouze, Marie-Alexandra; Kronstein, Martin; Tielens, Frederik

    2014-09-28

    This feature article gives an overview of the research performed on ionic nanoparticle networks (INNs). These INNs are hybrid materials consisting of inorganic nanoparticles and ionic linkers, such as imidazolium, bisimidazolium or pyridinium. The synthesis and properties of INNs, for catalysis or sensorics, are presented. At each step INN materials are compared to other hybrid materials of similar composition such as ionogels or suspensions of imidazolium modified nanoparticles. PMID:24968952

  13. Integrated Carbon Observation System (ICOS) ecosystem network: current state and future perspectives

    NASA Astrophysics Data System (ADS)

    Gielen, B.; Op de Beeck, M.; Ceulemans, R.; Janssens, I.; Loustau, D.; Valentini, R.; Papale, D.

    2013-12-01

    Atmospheric concentrations of greenhouse gases (GHG) such as carbon dioxide (CO2) and methane (CH4) are increasing due to emissions related to human activity, affecting the global climate. Natural sinks remove a fraction of the GHG anthropogenic excess at the global level. The characterization of greenhouse gases atmospheric burden and fluxes, both anthropogenic and natural, are needed at the global and regional scale, making use of all available information in an integrated framework. The Integrated Carbon Observation System (ICOS) research infrastructure will address this issue by providing the community with systematic measurements of a suite of atmospheric, terrestrial ecosystem and oceanic measurements. The ecosystem network comprises three station classes, for which variables are collected with different intensity. These stations are well distributed among the major European ecosystem types and cover most climatic zones in Europe. The Ecosystem Thematic Center (ETC) is coordinating the ICOS ecosystem network providing assistance with instruments and methods, testing and developing new measurement techniques and associated processing algorithms; also ensuring a high level of data standardization, uncertainty analysis and database services in coordination with the ICOS carbon portal. The ETC is also coordinating the drafting of the protocols describing in detail how measurements will be collected at all ecosystem stations, in order to guarantee inter comparability. This is done in close collaboration with experts in the field and with the other existing ecological and meteorological networks (NEON, Ameriflux, ICP -forests, MWO, TERN, ...). This presentation will focus on the current state of the ICOS ecosystem network, on the data products and the potential user community.

  14. Geomorphometric assessment of spatial sediment connectivity in small Alpine catchments

    NASA Astrophysics Data System (ADS)

    Cavalli, Marco; Trevisani, Sebastiano; Comiti, Francesco; Marchi, Lorenzo

    2013-04-01

    Complex and rugged topography induces large variations in erosion and sediment delivery in the headwaters of alpine catchments. An effective connection of hillslopes with the channel network results in highly efficient sediment transfer processes, such as debris flows. In contrast, morphological conditions producing decoupling of hillslopes from channels (e.g. glacial cirques) may exclude large areas of the catchment from sediment delivery to its lower parts. Moreover, an efficient connection between hillslopes and channel network does not always ensure an effective downstream transfer of sediment. Low-slope channel reaches (e.g. in hanging valleys) cause sediment deposition, which often results in changes of the sediment transport processes, typically from debris flow to streamflow with low bedload and suspended load rates. The availability of high-resolution digital terrain models, such as those derived from aerial LiDAR, improves our capability to quantify the topographic controls on sediment connectivity. A geomorphometric index, based on the approach by Borselli et al. (2008), was developed and applied to assess spatial sediment connectivity in two small catchments of the Italian Alps featuring contrasting morphological characteristics. The results of the geomorphometric analysis were checked against field evidences, showing good performance and thus potential usefulness of the index.

  15. The telematic network of referee hospital "V. Monaldi" in Naples: state of the art and perspectives.

    PubMed

    Pepino, A; Colasanate, A; Rossi, A

    2001-01-01

    The new advances in I.T. both in Hardware (wideband network) and in Software are rapidly changing the Health Information Systems scenario. In many hospitals of Campania Region this leads in many case to rebuild, starting from zero, both infrastructure and applications. Ericsson Enterprise has recently developed for the A.O. Monaldi and Integrated information System which consists of an advanced LAN (Local Area Network), a number of software infrastructures and some application systems as WEB site, Dicom PACS, E-mail server, Streaming Video from Operating Theatres, Internal TV Network. This integrated system represents the starting point for modern health information systems, which is compliant with new standards. The start-up of such systems represents always a problem for the organization and management point of view, therefore a number of problems concerning: training, education, security, privacy, operative procedures, co-ordination with existing applications, system management at the start-up and after. This paper deals with the technical aspects of this information system and discusses the problem met in introducing these IT products in a big and important hospital of Campania Region in Italy, in order to suggest a model, useful for other similar experiences. PMID:11604837

  16. Words Analysis of Online Chinese News Headlines about Trending Events: A Complex Network Perspective

    PubMed Central

    Li, Huajiao; Fang, Wei; An, Haizhong; Huang, Xuan

    2015-01-01

    Because the volume of information available online is growing at breakneck speed, keeping up with meaning and information communicated by the media and netizens is a new challenge both for scholars and for companies who must address public relations crises. Most current theories and tools are directed at identifying one website or one piece of online news and do not attempt to develop a rapid understanding of all websites and all news covering one topic. This paper represents an effort to integrate statistics, word segmentation, complex networks and visualization to analyze headlines’ keywords and words relationships in online Chinese news using two samples: the 2011 Bohai Bay oil spill and the 2010 Gulf of Mexico oil spill. We gathered all the news headlines concerning the two trending events in the search results from Baidu, the most popular Chinese search engine. We used Simple Chinese Word Segmentation to segment all the headlines into words and then took words as nodes and considered adjacent relations as edges to construct word networks both using the whole sample and at the monthly level. Finally, we develop an integrated mechanism to analyze the features of words’ networks based on news headlines that can account for all the keywords in the news about a particular event and therefore track the evolution of news deeply and rapidly. PMID:25807376

  17. Words analysis of online Chinese news headlines about trending events: a complex network perspective.

    PubMed

    Li, Huajiao; Fang, Wei; An, Haizhong; Huang, Xuan

    2015-01-01

    Because the volume of information available online is growing at breakneck speed, keeping up with meaning and information communicated by the media and netizens is a new challenge both for scholars and for companies who must address public relations crises. Most current theories and tools are directed at identifying one website or one piece of online news and do not attempt to develop a rapid understanding of all websites and all news covering one topic. This paper represents an effort to integrate statistics, word segmentation, complex networks and visualization to analyze headlines' keywords and words relationships in online Chinese news using two samples: the 2011 Bohai Bay oil spill and the 2010 Gulf of Mexico oil spill. We gathered all the news headlines concerning the two trending events in the search results from Baidu, the most popular Chinese search engine. We used Simple Chinese Word Segmentation to segment all the headlines into words and then took words as nodes and considered adjacent relations as edges to construct word networks both using the whole sample and at the monthly level. Finally, we develop an integrated mechanism to analyze the features of words' networks based on news headlines that can account for all the keywords in the news about a particular event and therefore track the evolution of news deeply and rapidly. PMID:25807376

  18. European Competence Network on Mastocytosis (ECNM): 10-year jubilee, update, and future perspectives.

    PubMed

    Valent, Peter; Arock, Michel; Bonadonna, Patrizia; Brockow, Knut; Broesby-Olsen, Sigurd; Escribano, Luis; Gleixner, Karoline V; Grattan, Clive; Hadzijusufovic, Emir; Hägglund, Hans; Hermine, Olivier; Horny, Hans-Peter; Kluin-Nelemans, Hanneke C; Maurer, Marcus; Niedoszytko, Marek; Nedoszytko, Boguslaw; Nilsson, Gunnar; Oude-Elberink, Hanneke N G; Orfao, Alberto; Radia, Deepti; Reiter, Andreas; Siebenhaar, Frank; Sotlar, Karl; Sperr, Wolfgang R; Triggiani, Massimo; VanDoormaal, Jaap J; Várkonyi, Judit; Yavuz, Selim; Hartmann, Karin

    2012-12-01

    The European Competence Network on Mastocytosis (ECNM) was initiated in 2002 as a multidisciplinary and multinational cooperative approach to increase awareness and to improve diagnosis and therapy of mastocytosis. The network is composed of local centers, physicians, and scientists who have dedicated their work to patients with mastocytosis. A strategic goal of the ECNM is to provide the best available information about the disease to patients and physicians. During the past 10 years, the ECNM has expanded to various countries and contributed successfully to the development of markers, definitions, and standards in the field of mastocytosis. Members of the ECNM organized Annual Meetings in Europe and two Working Conferences on Mastocytosis in Vienna (in 2005 and 2010), and initiated and supported several preclinical and clinical trials. In all these activities, representatives of the ECNM cooperate closely with their US colleagues, with patient-organizations in Europe and in the USA, and with other scientific networks. The ECNM also launched a mastocytosis registry that has been activated in 2012. Using the central database of this registry, cooperative multicenter studies, which should include sufficient numbers of patients and robust evaluations, will be conducted. These studies will increase our knowledge about optimal management and therapy of patients with mastocytosis in the future. PMID:23179435

  19. Trade Integration and Trade Imbalances in the European Union: A Network Perspective

    PubMed Central

    Krings, Gautier M.; Carpantier, Jean-François; Delvenne, Jean-Charles

    2014-01-01

    We study the ever more integrated and ever more unbalanced trade relationships between European countries. To better capture the complexity of economic networks, we propose two global measures that assess the trade integration and the trade imbalances of the European countries. These measures are the network (or indirect) counterparts to traditional (or direct) measures such as the trade-to-GDP (Gross Domestic Product) and trade deficit-to-GDP ratios. Our indirect tools account for the European inter-country trade structure and follow (i) a decomposition of the global trade flow into elementary flows that highlight the long-range dependencies between exporting and importing economies and (ii) the commute-time distance for trade integration, which measures the impact of a perturbation in the economy of a country on another country, possibly through intermediate partners by domino effect. Our application addresses the impact of the launch of the Euro. We find that the indirect imbalance measures better identify the countries ultimately bearing deficits and surpluses, by neutralizing the impact of trade transit countries, such as the Netherlands. Among others, we find that ultimate surpluses of Germany are quite concentrated in only three partners. We also show that for some countries, the direct and indirect measures of trade integration diverge, thereby revealing that these countries (e.g. Greece and Portugal) trade to a smaller extent with countries considered as central in the European Union network. PMID:24465381

  20. Multivariate analysis of a small pleistocene catchment: tracing hydrological change

    NASA Astrophysics Data System (ADS)

    Boettcher, Steven; Merz, Christoph; Dannowski, Ralf

    2013-04-01

    The water budget of catchments in north-east Germany has decreased considerably over the last decades. Especially small catchments are affected due to the small amount of water stored within. Climate projections for the next decades hint to even more negative impacts on the water budgets of these catchments. Therefore, a new concept of water resource management for this region must be developed, including counter measures to extreme events such as low and high flow conditions. In order to manage a hydrological system one needs to know the typical behavior and be able to effectively counteract if needed. Within the network activity INKA-BB (Inovationsnetzwerk Klimaanpassung Brandenburg Berlin) dealing with possible adaptation measures to climate change in the Brandenburg and Berlin region, this study aims at identifying the typical hydraulic behavior of the Fredersdorfer Mühlenfließ catchment located north-east of Berlin as a basis for a sustainable water resource management concept. Established schemes are followed, including the application of numerical geochemical and hydraulic models as well as chemical graphical interpretation approaches. A common problem is the sparse spatial as well as temporal resolution of the data at hand. Here, these schemes are too inflexible and vague with respect to analyzing and parameterization of complex features used for identifying operative hydraulic-geochemical processes including intensive non-linear interactions. Hence, methods must be applied that are able to effectively utilize the limited information available. Ordination methods such as the Principle Component Analysis (PCA) or the non-linear Isometric Feature Mapping (Isomap) can provide such a tool. Ordination methods are used in order to derive a meaningful low-dimensional representation of a high-dimensional input data set. The approach is based on the hypothesis, that the amount of processes which explain the variance of the data is relative low although the

  1. Integrated monitoring of nitrogen dynamics in contrasting catchments

    NASA Astrophysics Data System (ADS)

    Schwientek, M.; Fleischer, M.

    2012-04-01

    The research institute WESS (Water & Earth System Science) is monitoring three adjacent meso-scale catchments (72 - 140 km2) in southwest Germany with respect to water quantity and quality. Due to their spatial proximity, the studied catchments are similar regarding climatic conditions and water balance. Geology is characterized by sedimentary rocks which are partly karstified. The catchments contrast strongly in land use and show a range from predominantly agriculture to almost exclusively forestry. In this context, a special focus of our research is the distinction of matter coming from the catchment area versus substances stemming from urban point sources. One important compound representing inputs from the catchment area is nitrogen. Nitrogen is an essential nutrient governing plant growth. If available in excess it leads to eutrophication and is therefore one of the globally most widespread contaminants in aquatic ecosystems. Transport of human-derived nitrogen through landscapes including urban areas to the oceans predominantly occurs via river network systems. Hence, monitoring of nitrogen fluxes in streams and rivers reveals mechanisms and dynamics of its transport and gives also insight into hydrologic processes which influence the mobilization of nitrogen. Presently, the catchments are equipped with online probes enabling high resolution monitoring of nitrate concentrations and other parameters. We found that average nitrate concentrations in stream water perfectly reflect the portion of fertilized arable land. The dynamics of N transport, however, largely depends on the hydrologic system and is driven by the dominating runoff generation processes. The interplay between different hydrological storages, which eventually also act as N pools, turns out to be decisive for the temporal variability of N concentrations in stream discharge. Inversely, the study of N transport dynamics can be used to infer the hydrologic mechanisms responsible for N mobilization

  2. Hydrological Controls on Nutrient Concentrations and Fluxes in Agricultural Catchments

    NASA Astrophysics Data System (ADS)

    Petry, J.; Soulsby, C.

    2002-12-01

    strips can reduce the delivery of NH3-N and PO4-P by overland flow to stream channels during storm events, the management of N-rich storm runoff as NO3 via sub-surface drains would require significant interference with the drainage network. This could have a negative impact on agricultural production in the catchment.

  3. The Idiosyncrasies of Storage and Implications for Catchment Runoff (Invited)

    NASA Astrophysics Data System (ADS)

    Spence, C.

    2010-12-01

    Because water goes into storage when it rains, perhaps the entire concept of a direct rainfall-runoff process is erroneous and misleading. Perhaps the runoff generation process is merely the conversion of storage to runoff. Using this perspective as a foundation, it then becomes important to understand how catchments retain water, where this storage is distributed and what controls the distribution of this storage. There is a growing body of observational evidence that the idiosyncrasies of storage in the catchment are crucial for runoff generation. These idiosyncrasies are important enough that some hydrologists are questioning assumptions of steady state, linearity, and topographic control in existing theories and algorithms of runoff generation. For instance, thresholds that control the release of water have been identified at many scales and in many landscapes. Hysteresis in storage-runoff relationships at all scales manifest because of these thresholds. Because storage thresholds at a range of scales are now known to be important for runoff response, connectivity has become an important concept crucial to interpreting catchment runoff response. There appears to be growing acceptance of such ideas as thresholds, hysteresis and connectivity in the hydrological literature. Theoretical development and model parameterization have begun, but there remains much work to resolve these field observations. In particular, our community should strive to investigate the relevance of storage-runoff relationships partly through innovative measurement techniques and the development of model structures appropriate for the requisite testing of these theories in a diversity of landscapes.

  4. The Role of Geoethics in Geohazards Mitigation: A YES Network Perspective

    NASA Astrophysics Data System (ADS)

    wang, Meng; Barich, Amel; Peppoloni, Silvia

    2013-04-01

    The YES Network is an international group of early career geoscientists from universities, geosciences organizations and companies, with over 3000 members from 121 countries. It has been founded in 2008 during the International Year of Planet Earth with the vision of "Promoting the Geosciences for Society". Until now, 42 National Chapters have been set up. The YES Network aims to build communication bridges between geologists, Policy makers, and Society in order to develop Geological Projects for sustainable development, international scientific collaborations, to bridge the ages between the geoscientists' generations, promote equity in the professional development of young and early career earth-scientists, etc. Concerning the Geoethics field, recently introduced into the Geosciences domain, the YES Network would like to raise the following ideas: The L'Aquila trial is a case for geoscientists to think about their freedom on research, their responsibility toward the society and their relationship with the public policy and medias. These points are crucial for the professional development of the young and early-career earth-scientists around the world. The YES Network is, therefore, setting up an open forum to collect ideas from all young and early-career scientists around the world on this topic in order to spread awareness among this growing part of the scientific community and help them act like an efficient part of it. There have been for a long time many debates about natural hazards both at regional and global level. It is the duty of the scientific community with the collaboration of policy makers to help mitigate the consequences of the natural disasters around the world. The YES Network is currently developing projects about these issues notably about in coastal Countries including geological mapping, Geohazards Reduction Scenarios, teaching programs for local populations. Earth sciences Education is slowing down in developed countries and growing very

  5. CAOS: the nested catchment soil-vegetation-atmosphere observation platform

    NASA Astrophysics Data System (ADS)

    Weiler, Markus; Blume, Theresa

    2016-04-01

    Most catchment based observations linking hydrometeorology, ecohydrology, soil hydrology and hydrogeology are typically not integrated with each other and lack a consistent and appropriate spatial-temporal resolution. Within the research network CAOS (Catchments As Organized Systems), we have initiated and developed a novel and integrated observation platform in several catchments in Luxembourg. In 20 nested catchments covering three distinct geologies the subscale processes at the bedrock-soil-vegetation-atmosphere interface are being monitored at 46 sensor cluster locations. Each sensor cluster is designed to observe a variety of different fluxes and state variables above and below ground, in the saturated and unsaturated zone. The numbers of sensors are chosen to capture the spatial variability as well the average dynamics. At each of these sensor clusters three soil moisture profiles with sensors at different depths, four soil temperature profiles as well as matric potential, air temperature, relative humidity, global radiation, rainfall/throughfall, sapflow and shallow groundwater and stream water levels are measured continuously. In addition, most sensors also measure temperature (water, soil, atmosphere) and electrical conductivity. This setup allows us to determine the local water and energy balance at each of these sites. The discharge gauging sites in the nested catchments are also equipped with automatic water samplers to monitor water quality and water stable isotopes continuously. Furthermore, water temperature and electrical conductivity observations are extended to over 120 locations distributed across the entire stream network to capture the energy exchange between the groundwater, stream water and atmosphere. The measurements at the sensor clusters are complemented by hydrometeorological observations (rain radar, network of distrometers and dense network of precipitation gauges) and linked with high resolution meteorological models. In this

  6. Building learning catchments for integrated catchment managing: designing learning systems based on experiences in the UK and South Africa.

    PubMed

    Collins, Kevin; Colvin, John; Ison, Ray

    2009-01-01

    We examine challenges and opportunities for developing 'learning systems' for integrated catchment managing (ICMg) drawing on our experiences in two contexts: UK and South Africa (SA). Our research question is: what is it that we would have to experience to claim that a catchment was a learning catchment? We suggest that any valid answer to this question will arise in social relations in context-determined ways. From this perspective ICMg is an emergent 'performance' of stakeholders engaged in mutual action, or social learning (SL), in which understandings and practices are transformed in situation improving ways. These questions are relevant given recent reviews suggesting that implementation of the European Water Framework Directive (WFD) is not nurturing adaptive management. Our European and SA experiences demonstrate that it is possible to invest in social learning as a governance mechanism for water managing, but key constraints exist. Our SA work based on (i) appreciating the situation, especially the history, and (ii) contextual appreciation and design of learning systems (as a result of (i)) is described in response to these constraints. We conclude that more attention on developing an effective praxis for ICMg is required. PMID:19237762

  7. Global monitoring of influenza: potential contribution of national networks from a French perspective.

    PubMed

    Flahault, Antoine

    2006-06-01

    The aim of global monitoring of influenza is to help decision making in regular seasonal influenza and in the case of a new pandemic. FluNet is the main tool for information sharing among the WHO Global Influenza Surveillance Network, as well as the public. It allows 112 WHO National Influenza Centers in 83 countries access to remote data entry. Weekly information on recent isolates and epidemiological situations are available to the public through many functionalities, for example, maps (animated or static), charts and raw data are embedded in the system for data display. Thus far, FluNet has collected weekly influenza surveillance data from up to 1997. A major outcome of this global network is the influenza vaccine composition, which is proposed twice a year (i.e., for both hemispheres) on the basis of the collected data. However, FluNet is far from performing comprehensive monitoring of influenza at a global level; 109 WHO member states still do not participate in the network and participating national influenza centers have only limited resources, which do not allow them to implement a reliable, accurate and real-time epidemiology of influenza in the areas they deserve. By following the time and space dynamics of an influenza strain, an epidemiologically valid system would make assessment of decisions after adopting preventive measures (e.g., closing schools, travel restriction, use of antivirals or of protective masks and mass immunization) possible. This international cooperation in public health fields must be considerably reinforced in the future, and should encourage database linkage with environmental information, allowing for the evaluation of the role of climate change, animal behavior or pollution involvement in disease. PMID:16771616

  8. Cosmetic surgery intent among generation Y consumers: a social network perspective.

    PubMed

    Voelker, Troy A; Pentina, Iryna

    2011-01-01

    This article details research examining attitudes towards, and utilization of, cosmetic augmentation procedures among Generation Y individuals. Cosmetic augmentation is defined as the utilization of advanced technologies to augment the appearance of otherwise healthy individuals. Examples of cosmetic augmentation include plastic surgery and laser surgical procedures. A social exchange framework is advanced, suggesting that an individual's access to others who have utilized cosmetic augmentation increases the positive attitude towards cosmetic procedures. Findings support a social exchange model for intention to utilize laser cosmetic procedures as well as a positive relationship between the diversity of a subject's ego network and access to others who have utilized some form of cosmetic augmentation. PMID:21347941

  9. A physically-based Distributed Hydrologic Model for Tropical Catchments

    NASA Astrophysics Data System (ADS)

    Abebe, N. A.; Ogden, F. L.

    2010-12-01

    Hydrological models are mathematical formulations intended to represent observed hydrological processes in a watershed. Simulated watersheds in turn vary in their nature based on their geographic location, altitude, climatic variables and geology and soil formation. Due to these variations, available hydrologic models vary in process formulation, spatial and temporal resolution and data demand. Many tropical watersheds are characterized by extensive and persistent biological activity and a large amount of rain. The Agua Salud catchments located within the Panama Canal Watershed, Panama, are such catchments identified by steep rolling topography, deep soils derived from weathered bedrock, and limited exposed bedrock. Tropical soils are highly affected by soil cracks, decayed tree roots and earthworm burrows forming a network of preferential flow paths that drain to a perched water table, which forms at a depth where the vertical hydraulic conductivity is significantly reduced near the bottom of the bioturbation layer. We have developed a physics-based, spatially distributed, multi-layered hydrologic model to simulate the dominant processes in these tropical watersheds. The model incorporates the major flow processes including overland flow, channel flow, matrix and non-Richards film flow infiltration, lateral downslope saturated matrix and non-Darcian pipe flow in the bioturbation layer, and deep saturated groundwater flow. Emphasis is given to the modeling of subsurface unsaturated zone soil moisture dynamics and the saturated preferential lateral flow from the network of macrospores. Preliminary results indicate that the model has the capability to simulate the complex hydrological processes in the catchment and will be a useful tool in the ongoing comprehensive ecohydrological studies in tropical catchments, and help improve our understanding of the hydrological effects of deforestation and aforestation.

  10. Social network analysis in the study of nonhuman primates: A historical perspective

    PubMed Central

    Brent, Lauren J.N.; Lehmann, Julia; Ramos-Fernández, Gabriel

    2011-01-01

    Advances over the last fifteen years have made social network analysis (SNA) a powerful tool for the study of nonhuman primate social behavior. Although many SNA-based techniques have been only very recently adopted in primatological research, others have been commonly used by primatologists for decades. The roots of SNA also stem from some of the same conceptual frameworks as the majority of nonhuman primate behavioral research. The rapid development of SNA in recent years has led to questions within the primatological community of where and how SNA fits within this field. We aim to address these questions by providing an overview of the historical relationship between SNA and the study of nonhuman primates. We begin with a brief history of the development of SNA, followed by a detailed description of the network-based visualization techniques, analytical methods and conceptual frameworks which have been employed by primatologists since as early as the 1960s. We also introduce some of the latest advances to SNA, thereby demonstrating that this approach contains novel tools for study of nonhuman primate social behavior which may be used to shed light on questions that cannot be addressed fully using more conventional methods. PMID:21433047

  11. Physical states in the canonical tensor model from the perspective of random tensor networks

    NASA Astrophysics Data System (ADS)

    Narain, Gaurav; Sasakura, Naoki; Sato, Yuki

    2015-01-01

    Tensor models, generalization of matrix models, are studied aiming for quantum gravity in dimensions larger than two. Among them, the canonical tensor model is formulated as a totally constrained system with first-class constraints, the algebra of which resembles the Dirac algebra of general relativity. When quantized, the physical states are defined to be vanished by the quantized constraints. In explicit representations, the constraint equations are a set of partial differential equations for the physical wave-functions, which do not seem straightforward to be solved due to their non-linear character. In this paper, after providing some explicit solutions for N = 2 , 3, we show that certain scale-free integration of partition functions of statistical systems on random networks (or random tensor networks more generally) provides a series of solutions for general N. Then, by generalizing this form, we also obtain various solutions for general N. Moreover, we show that the solutions for the cases with a cosmological constant can be obtained from those with no cosmological constant for increased N. This would imply the interesting possibility that a cosmological constant can always be absorbed into the dynamics and is not an input parameter in the canonical tensor model. We also observe the possibility of symmetry enhancement in N = 3, and comment on an extension of Airy function related to the solutions.

  12. The dynamics of friendships and victimization in adolescence: a longitudinal social network perspective.

    PubMed

    Sentse, Miranda; Dijkstra, Jan Kornelis; Salmivalli, Christina; Cillessen, Antonius H N

    2013-01-01

    This study investigated the development of relational and physical victimization in adolescent friendship networks over time. Using longitudinal social network analysis (SIENA) it was simultaneously tested whether similarity in victimization contributed to friendship formation (selection effects) and whether victimization of friends contributed to changes in victimization (influence effects). This was done for peer-reported relational and physical victimization separately in two middle schools (total N = 480; N = 220, 47% girls, in School 1; N = 260, 52% girls, in School 2) across three time points (Grades 6 through 8; M ages 11.5-13.5). Gender, ethnicity, and baseline aggression were controlled as individual predictors of victimization. Similarity in physical victimization predicted friendship formation, whereas physical victimization was not influenced by friends' victimization but rather by adolescents' own physical aggression. Peer influence effects existed for relational victimization, in that adolescents with victimized friends were more likely to increase in victimization over time as well, over and above the effect of adolescents' own relational aggression. These selection and influence effects were not further qualified by gender. The results suggested that both selection and influence processes as well as individual characteristics play a role in the co-evolution of friendships and victimization, but that these processes are specific for different types of victimization. PMID:23446945

  13. Applying a GIS-based geomorphological routing model in urban catchments

    NASA Astrophysics Data System (ADS)

    Lhomme, Julien; Bouvier, Christophe; Perrin, Jean-Louis

    2004-12-01

    This paper discusses using a GIS-based geomorphological routing model to simulate urban stormwater runoff as an alternative to physically based routing models. Hydrological measurements have been carried out (1982-1984) in the urban catchment El Batan (52 km 2), which forms part of the city of Quito (Ecuador). As detailed data on the drainage network were available, a first attempt was made using, on the one hand, complete Barré de Saint-Venant equations in the network and, on the other, the linear reservoir model for the sub-catchments. Knowing both the geometry and hydraulics of the network was proved to achieve accurate simulations. However, collecting the network data and building the whole topology (reaches, nodes, sub-catchments) of this large urban catchment is very time-consuming work. Thus, grosser representations of the network to simulate runoff were tested, but it was found that the estimation of the concentration time becomes predominant, and may result in a significant loss of accuracy. Using a GIS-based geomorphological routing model is shown to be an efficient alternative: first, physical velocities in the reaches can be derived from slopes and upstream areas; second, the integration of these velocities in a distributed lag and route model produces flood simulations that are equivalent to the physically based routing model; third, Digital Elevation Models avoid most of the tedious preliminary tasks in building the catchment topology. Further investigation is required in order to evaluate variations in the lag parameter from one catchment to another.

  14. Multi-OMICs and Genome Editing Perspectives on Liver Cancer Signaling Networks.

    PubMed

    Lin, Shengda; Yin, Yi A; Jiang, Xiaoqian; Sahni, Nidhi; Yi, Song

    2016-01-01

    The advent of the human genome sequence and the resulting ~20,000 genes provide a crucial framework for a transition from traditional biology to an integrative "OMICs" arena (Lander et al., 2001; Venter et al., 2001; Kitano, 2002). This brings in a revolution for cancer research, which now enters a big data era. In the past decade, with the facilitation by next-generation sequencing, there have been a huge number of large-scale sequencing efforts, such as The Cancer Genome Atlas (TCGA), the HapMap, and the 1000 genomes project. As a result, a deluge of genomic information becomes available from patients stricken by a variety of cancer types. The list of cancer-associated genes is ever expanding. New discoveries are made on how frequent and highly penetrant mutations, such as those in the telomerase reverse transcriptase (TERT) and TP53, function in cancer initiation, progression, and metastasis. Most genes with relatively frequent but weakly penetrant cancer mutations still remain to be characterized. In addition, genes that harbor rare but highly penetrant cancer-associated mutations continue to emerge. Here, we review recent advances related to cancer genomics, proteomics, and systems biology and suggest new perspectives in targeted therapy and precision medicine. PMID:27403431

  15. Multi-OMICs and Genome Editing Perspectives on Liver Cancer Signaling Networks

    PubMed Central

    Lin, Shengda; Yin, Yi A.; Jiang, Xiaoqian; Sahni, Nidhi; Yi, Song

    2016-01-01

    The advent of the human genome sequence and the resulting ~20,000 genes provide a crucial framework for a transition from traditional biology to an integrative “OMICs” arena (Lander et al., 2001; Venter et al., 2001; Kitano, 2002). This brings in a revolution for cancer research, which now enters a big data era. In the past decade, with the facilitation by next-generation sequencing, there have been a huge number of large-scale sequencing efforts, such as The Cancer Genome Atlas (TCGA), the HapMap, and the 1000 genomes project. As a result, a deluge of genomic information becomes available from patients stricken by a variety of cancer types. The list of cancer-associated genes is ever expanding. New discoveries are made on how frequent and highly penetrant mutations, such as those in the telomerase reverse transcriptase (TERT) and TP53, function in cancer initiation, progression, and metastasis. Most genes with relatively frequent but weakly penetrant cancer mutations still remain to be characterized. In addition, genes that harbor rare but highly penetrant cancer-associated mutations continue to emerge. Here, we review recent advances related to cancer genomics, proteomics, and systems biology and suggest new perspectives in targeted therapy and precision medicine. PMID:27403431

  16. How tritium illuminates catchment structure

    NASA Astrophysics Data System (ADS)

    Stewart, M.; Morgenstern, U.; McDonnell, J.

    2012-04-01

    Streams contain water which has taken widely-varying times to pass through catchments, and the distribution of ages is likely to change with the flow. Part of the water has 'runoff' straight to the stream with little delay, other parts are more delayed and some has taken years (in some cases decades) to traverse the deeper regolith or bedrock of the catchment. This work aims to establish the significance of the last component, which is important because it can cause catchments to have long memories of contaminant inputs (e.g. nitrate). Results of tritium studies on streams world-wide were accessed from the scientific literature. Most of the studies assumed that there were just two age-components present in the streams (i.e. young and old). The mean ages and proportions of the components were found by fitting simulations to tritium data. It was found that the old component in streams was substantial (average was 50% of the annual runoff) and had considerable age (average mean age was 10 years) (Stewart et al., 2010). Use of oxygen-18 or chloride variations to estimate streamflow mean age usually does not reveal the age or size of this old component, because these methods cannot detect water older than about four years. Consequently, the use of tritium has shown that substantial parts of streamflow in headwater catchments are older than expected, and that deep groundwater plays an active and sometimes even a dominant role in runoff generation. Difficulties with interpretation of tritium in streams in recent years due to interference from tritium due to nuclear weapons testing are becoming less serious, because very accurate tritium measurements can be made and there is now little bomb-tritium remaining in the atmosphere. Mean ages can often be estimated from single tritium measurements in the Southern Hemisphere, because there was much less bomb-tritium in the atmosphere. This may also be possible for some locations in the Northern Hemisphere. Age determination on

  17. Perspectives on Advanced Learning Technologies and Learning Networks and Future Aerospace Workforce Environments

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K. (Compiler)

    2003-01-01

    An overview of the advanced learning technologies is given in this presentation along with a brief description of their impact on future aerospace workforce development. The presentation is divided into five parts (see Figure 1). In the first part, a brief historical account of the evolution of learning technologies is given. The second part describes the current learning activities. The third part describes some of the future aerospace systems, as examples of high-tech engineering systems, and lists their enabling technologies. The fourth part focuses on future aerospace research, learning and design environments. The fifth part lists the objectives of the workshop and some of the sources of information on learning technologies and learning networks.

  18. Relationships between predicted moonlighting proteins, human diseases, and comorbidities from a network perspective

    PubMed Central

    Zanzoni, Andreas; Chapple, Charles E.; Brun, Christine

    2015-01-01

    Moonlighting proteins are a subset of multifunctional proteins characterized by their multiple, independent, and unrelated biological functions. We recently set up a large-scale identification of moonlighting proteins using a protein-protein interaction (PPI) network approach. We established that 3% of the current human interactome is composed of predicted moonlighting proteins. We found that disease-related genes are over-represented among those candidates. Here, by comparing moonlighting candidates to non-candidates as groups, we further show that (i) they are significantly involved in more than one disease, (ii) they contribute to complex rather than monogenic diseases, (iii) the diseases in which they are involved are phenotypically different according to their annotations, finally, (iv) they are enriched for diseases pairs showing statistically significant comorbidity patterns based on Medicare records. Altogether, our results suggest that some observed comorbidities between phenotypically different diseases could be due to a shared protein involved in unrelated biological processes. PMID:26157390

  19. How does competition structure affect industry merger waves? A network analysis perspective

    NASA Astrophysics Data System (ADS)

    Hou, Rui; Yang, Jianmei; Yao, Canzhong; McKelvey, Bill

    2015-07-01

    By taking China's beer industry as an example, this paper establishes a series of industrial competition-pressure networks and examines the correlation between competition structure and merger actions. We present a cascade dynamic-merger agent-based computational model driven by competition pressure diffusion to describe the forming process of industry merger wave. The empirical analyses and agent-based computational simulation results show that the competition structure among rivals has a strong effect on the scale, the duration time, and the stability of industry merger wave. We also give explanations on why there are different simulation results between in single market competition environment and in multi-market competition environment, as well as discuss the management implications for the industry-merger policy makers and the merger-tactics decision makers that are involved in merger wave.

  20. Performance of the primary seismic array stations of the IMS network for the year 2015 Part II): An Analyst's perspective

    NASA Astrophysics Data System (ADS)

    Jonathan, Ezekiel; Kebede, Fekadu

    2016-04-01

    Verification of the CTBT is partly dependent on the ability of the automatic system to detect and present correct attributes for all phases that are detected at the stations. This helps in building of more accurate automatic event solutions and thus reducing the work load and time for interactive analysis whilst increasing the quality of bulletins issued out to member states so that they can decide if there are any treaty violations. During interactive analysis automatic event solutions are refined and/or re-estimated by checking the correctness of the associated phase identity, phase arrival time, azimuth and slowness using raw waveform data. This refinement procedure leads analysts to rename, associate, disassociate and manually add seismic arrivals. The final event solution is accepted or rejected based on the existing rules, guidelines and procedures. In addition, new event solutions are built using unassociated signal detections and the raw waveform data during scanning. In this study differences between seismic phases associated to automatically produced SEL3 bulletin and the Late Event Bulletin (LEB) obtained through interactive analysis are investigated using data from all primary seismic array stations of the International Monitoring System (IMS) network during the year 2015. The performance of the network is evaluated from an analyst's perspective by looking at the number of phases that are renamed, manually added, associated, and disassociated by analysts during interactive analysis. The observed differences do shed some light on analysts workload as well as the performance of the primary seismic array of the IMS network. For example, the results indicate that for the Waramunga array station in Australia (WRA) out of a total of 41175 detections associated to saved events in 2015, 13305 (32.3%) of them were renamed during interactive analysis and 7667 were automatic detections that were associated to events by analysts. 1174 detections were manually added

  1. Hydrologic connectivity between landscapes and streams: Transferring reach- and plot-scale understanding to the catchment scale

    USGS Publications Warehouse

    Jencso, K.G.; McGlynn, B.L.; Gooseff, M.N.; Wondzell, S.M.; Bencala, K.E.; Marshall, L.A.

    2009-01-01

    The relationship between catchment structure and runoff characteristics is poorly understood. In steep headwater catchments with shallow soils the accumulation of hillslope area (upslope accumulated area (UAA)) is a hypothesized first-order control on the distribution of soil water and groundwater. Hillslope-riparian water table connectivity represents the linkage between the dominant catchment landscape elements (hillslopes and riparian zones) and the channel network. Hydrologic connectivity between hillslope-riparian-stream (HRS) landscape elements is heterogeneous in space and often temporally transient. We sought to test the relationship between UAA and the existence and longevity of HRS shallow groundwater connectivity. We quantified water table connectivity based on 84 recording wells distributed across 24 HRS transects within the Tenderfoot Creek Experimental Forest (U.S. Forest Service), northern Rocky Mountains, Montana. Correlations were observed between the longevity of HRS water table connectivity and the size of each transect's UAA (r2 = 0.91). We applied this relationship to the entire stream network to quantify landscape-scale connectivity through time and ascertain its relationship to catchment-scale runoff dynamics. We found that the shape of the estimated annual landscape connectivity duration curve was highly related to the catchment flow duration curve (r2 = 0.95). This research suggests internal catchment landscape structure (topography and topology) as a first-order control on runoff source area and whole catchment response characteristics. Copyright 2009 by the American Geophysical Union.

  2. Networks.

    ERIC Educational Resources Information Center

    Maughan, George R.; Petitto, Karen R.; McLaughlin, Don

    2001-01-01

    Describes the connectivity features and options of modern campus communication and information system networks, including signal transmission (wire-based and wireless), signal switching, convergence of networks, and network assessment variables, to enable campus leaders to make sound future-oriented decisions. (EV)

  3. Map correlation method: Selection of a reference streamgage to estimate daily streamflow at ungaged catchments.

    USGS Publications Warehouse

    Archfield, Stacey A.; Vogel, Richard M.

    2010-01-01

    Daily streamflow time series are critical to a very broad range of hydrologic problems. Whereas daily streamflow time series are readily obtained from gaged catchments, streamflow information is commonly needed at catchments for which no measured streamflow information exists. At ungaged catchments, methods to estimate daily streamflow time series typically require the use of a reference streamgage, which transfers properties of the streamflow time series at a reference streamgage to the ungaged catchment. Therefore, the selection of a reference streamgage is one of the central challenges associated with estimation of daily streamflow at ungaged basins. The reference streamgage is typically selected by choosing the nearest streamgage; however, this paper shows that selection of the nearest streamgage does not provide a consistent selection criterion. We introduce a new method, termed the map-correlation method, which selects the reference streamgage whose daily streamflows are most correlated with an ungaged catchment. When applied to the estimation of daily streamflow at 28 streamgages across southern New England, daily streamflows estimated by a reference streamgage selected using the map-correlation method generally provides improved estimates of daily streamflow time series over streamflows estimated by the selection and use of the nearest streamgage. The map correlation method could have potential for many other applications including identifying redundancy and uniqueness in a streamgage network, calibration of rainfall runoff models at ungaged sites, as well as for use in catchment classification.

  4. Catchment classification by means of hydrological models

    NASA Astrophysics Data System (ADS)

    Hellebrand, Hugo; Ley, Rita; Casper, Markus

    2013-04-01

    An important hydrological objective is catchment classification that will serve as a basis for the regionalisation of discharge parameters or model parameters. The main task of this study is the development and assessment of two classification approaches with respect to their efficiency in catchment classification. The study area in western Germany comprises about 80 catchments that range in size from 8 km2 up to 1500 km2, covering a wide range of geological substrata, soils, landscapes and mean annual precipitation. In a first approach Self Organising Maps (SOMs) use discharge characteristics or catchment characteristics to classify the catchments of the study area. Next, a reference hydrological model calibrates the catchments of the study area and tests the possibilities of parameter transfer. Compared to the transfer of parameters outside a class, for most catchments the model performance improves when parameters within a class are transferred. Thus, it should be possible to distinguish catchment classes by means of a hydrological model. The classification results of the SOM are compared to the classification results of the reference hydrological model in order to determine the latter validity. The second approach builds on the first approach in such a way that it uses the Superflex Modelling Framework instead of only one reference model. Within this framework multiple conceptual model structures can be calibrated and adapted. Input data for each calibration of a catchment are hourly time series of runoff, precipitation and evaporation for at least eight years. The calibration of multiple models for each catchment and their comparison allows for the assessment of the influence of different model structures on model performance. Learning loops analyse model performance and adapt model structures accordingly with a view to performance improvement. The result of the modelling exercise is a best performing model structure for each catchment that serves as a basis

  5. Coarse-Grained Models Reveal Functional Dynamics - I. Elastic Network Models – Theories, Comparisons and Perspectives

    PubMed Central

    Yang, Lee-Wei; Chng, Choon-Peng

    2008-01-01

    In this review, we summarize the progress on coarse-grained elastic network models (CG-ENMs) in the past decade. Theories were formulated to allow study of conformational dynamics in time/space frames of biological interest. Several highlighted models and their underlined hypotheses are introduced in physical depth. Important ENM offshoots, motivated to reproduce experimental data as well as to address the slow-mode-encoded configurational transitions, are also introduced. With the theoretical developments, computational cost is significantly reduced due to simplified potentials and coarse-grained schemes. Accumulating wealth of data suggest that ENMs agree equally well with experiment in describing equilibrium dynamics despite their distinct potentials and levels of coarse-graining. They however do differ in the slowest motional components that are essential to address large conformational changes of functional significance. The difference stems from the dissimilar curvatures of the harmonic energy wells described for each model. We also provide our views on the predictability of ‘open to close’ (open→close) transitions of biomolecules on the basis of conformational selection theory. Lastly, we address the limitations of the ENM formalism which are partially alleviated by the complementary CG-MD approach, to be introduced in the second paper of this two-part series. PMID:19812764

  6. The Informatics Challenges Facing Biobanks: A Perspective from a United Kingdom Biobanking Network

    PubMed Central

    Groves, Martin; Jordan, Lee B.; Stobart, Hilary; Purdie, Colin A.; Thompson, Alastair M

    2015-01-01

    The challenges facing biobanks are changing from simple collections of materials to quality-assured fit-for-purpose clinically annotated samples. As a result, informatics awareness and capabilities of a biobank are now intrinsically related to quality. A biobank may be considered a data repository, in the form of raw data (the unprocessed samples), data surrounding the samples (processing and storage conditions), supplementary data (such as clinical annotations), and an increasing ethical requirement for biobanks to have a mechanism for researchers to return their data. The informatics capabilities of a biobank are no longer simply knowing sample locations; instead the capabilities will become a distinguishing factor in the ability of a biobank to provide appropriate samples. There is an increasing requirement for biobanking systems (whether in-house or commercially sourced) to ensure the informatics systems stay apace with the changes being experienced by the biobanking community. In turn, there is a requirement for the biobanks to have a clear informatics policy and directive that is embedded into the wider decision making process. As an example, the Breast Cancer Campaign Tissue Bank in the UK was a collaboration between four individual and diverse biobanks in the UK, and an informatics platform has been developed to address the challenges of running a distributed network. From developing such a system there are key observations about what can or cannot be achieved by informatics in isolation. This article will highlight some of the lessons learned during this development process. PMID:26418270

  7. Can We Recognize an Innovation? Perspective from an Evolving Network Model

    NASA Astrophysics Data System (ADS)

    Jain, Sanjay; Krishna, Sandeep

    "Innovations" are central to the evolution of societies and the evolution of life. But what constitutes an innovation? We can often agree after the event, when its consequences and impact over a long term are known, whether something was an innovation, and whether it was a "big" innovation or a "minor" one. But can we recognize an innovation "on the fly" as it appears? Successful entrepreneurs often can. Is it possible to formalize that intuition? We discuss this question in the setting of a mathematical model of evolving networks. The model exhibits self-organization , growth, stasis, and collapse of a complex system with many interacting components, reminiscent of real-world phenomena. A notion of "innovation" is formulated in terms of graph-theoretic constructs and other dynamical variables of the model. A new node in the graph gives rise to an innovation, provided it links up "appropriately" with existing nodes; in this view innovation necessarily depends upon the existing context. We show that innovations, as defined by us, play a major role in the birth, growth, and destruction of organizational structures. Furthermore, innovations can be categorized in terms of their graph-theoretic structure as they appear. Different structural classes of innovation have potentially different qualitative consequences for the future evolution of the system, some minor and some major. Possible general lessons from this specific model are briefly discussed.

  8. Broadband local service offerings using free-space optical links: a network business perspective

    NASA Astrophysics Data System (ADS)

    Britz, David M.; Dodley, J. P.; Barnickel, D. J.

    2001-02-01

    12 This paper describes a promising optical wireless broadband technology that will provide low cost broadband services to the local access `last mile' market. This paper examines the application, advantages and limitations of utilizing Free Space Optical Communications (FSOC) systems for broadband access markets. The service markets that would fully utilize FSOC technologies include metropolitan areas, BLECs (multi- tenant dwellings/business apartments), campuses, industrial parks and `pole-to-hole' neighborhood deployments. This paper will identify weather dependent link availability as being the primary consideration in defining and selecting suitable locations for FSOC-based systems. Link availability in turn determines link range, type of service, and the need for transmission diversity. This paper will describe the implications of telecom `five nines' last-mile access availability and its effect on the transparent integration of FSOC technologies into the existing fiber optic networks. This paper will also describe propagation losses and link budget requirements for broadband FSOC-based local service. During adverse weather conditions, stand-alone, FSOC-based optical wireless links typically offer path lengths of less than 200 meters while still meeting the `five nines' availability criteria. This paper will also consider `availability limited' services. These services may prove to be attractive to customers who are willing to accept broadband service on an `as available basis'. The use of availability-enhancing transmission diversity and the use of intelligent `roof-top' routing and optical wireless cross connects between buildings will also be discussed.

  9. The Human Frontal Lobes and Frontal Network Systems: An Evolutionary, Clinical, and Treatment Perspective

    PubMed Central

    Hoffmann, Michael

    2013-01-01

    Frontal lobe syndromes, better termed as frontal network systems, are relatively unique in that they may manifest from almost any brain region, due to their widespread connectivity. The understandings of the manifold expressions seen clinically are helped by considering evolutionary origins, the contribution of the state-dependent ascending monoaminergic neurotransmitter systems, and cerebral connectivity. Hence, the so-called networktopathies may be a better term for the syndromes encountered clinically. An increasing array of metric tests are becoming available that complement that long standing history of qualitative bedside assessments pioneered by Alexander Luria, for example. An understanding of the vast panoply of frontal systems' syndromes has been pivotal in understanding and diagnosing the most common dementia syndrome under the age of 60, for example, frontotemporal lobe degeneration. New treatment options are also progressively becoming available, with recent evidence of dopaminergic augmentation, for example, being helpful in traumatic brain injury. The latter include not only psychopharmacological options but also device-based therapies including mirror visual feedback therapy. PMID:23577266

  10. The Informatics Challenges Facing Biobanks: A Perspective from a United Kingdom Biobanking Network.

    PubMed

    Quinlan, Philip R; Groves, Martin; Jordan, Lee B; Stobart, Hilary; Purdie, Colin A; Thompson, Alastair M

    2015-10-01

    The challenges facing biobanks are changing from simple collections of materials to quality-assured fit-for-purpose clinically annotated samples. As a result, informatics awareness and capabilities of a biobank are now intrinsically related to quality. A biobank may be considered a data repository, in the form of raw data (the unprocessed samples), data surrounding the samples (processing and storage conditions), supplementary data (such as clinical annotations), and an increasing ethical requirement for biobanks to have a mechanism for researchers to return their data. The informatics capabilities of a biobank are no longer simply knowing sample locations; instead the capabilities will become a distinguishing factor in the ability of a biobank to provide appropriate samples. There is an increasing requirement for biobanking systems (whether in-house or commercially sourced) to ensure the informatics systems stay apace with the changes being experienced by the biobanking community. In turn, there is a requirement for the biobanks to have a clear informatics policy and directive that is embedded into the wider decision making process. As an example, the Breast Cancer Campaign Tissue Bank in the UK was a collaboration between four individual and diverse biobanks in the UK, and an informatics platform has been developed to address the challenges of running a distributed network. From developing such a system there are key observations about what can or cannot be achieved by informatics in isolation. This article will highlight some of the lessons learned during this development process. PMID:26418270

  11. Reconceptualizing anhedonia: novel perspectives on balancing the pleasure networks in the human brain

    PubMed Central

    Rømer Thomsen, Kristine; Whybrow, Peter C.; Kringelbach, Morten L.

    2015-01-01

    Anhedonia, the lack of pleasure, has been shown to be a critical feature of a range of psychiatric disorders. Yet, it is currently measured primarily through subjective self-reports and as such has been difficult to submit to rigorous scientific analysis. New insights from affective neuroscience hold considerable promise in improving our understanding of anhedonia and for providing useful objective behavioral measures to complement traditional self-report measures, potentially leading to better diagnoses and novel treatments. Here, we review the state-of-the-art of hedonia research and specifically the established mechanisms of wanting, liking, and learning. Based on this framework we propose to conceptualize anhedonia as impairments in some or all of these processes, thereby departing from the longstanding view of anhedonia as solely reduced subjective experience of pleasure. We discuss how deficits in each of the reward components can lead to different expressions, or subtypes, of anhedonia affording novel ways of measurement. Specifically, we review evidence suggesting that patients suffering from depression and schizophrenia show impairments in wanting and learning, while some aspects of conscious liking seem surprisingly intact. Furthermore, the evidence suggests that anhedonia is heterogeneous across psychiatric disorders, depending on which parts of the pleasure networks are most affected. This in turn has implications for diagnosis and treatment of anhedonia. PMID:25814941

  12. Multilevel functional genomics data integration as a tool for understanding physiology: a network biology perspective.

    PubMed

    Davidsen, Peter K; Turan, Nil; Egginton, Stuart; Falciani, Francesco

    2016-02-01

    The overall aim of physiological research is to understand how living systems function in an integrative manner. Consequently, the discipline of physiology has since its infancy attempted to link multiple levels of biological organization. Increasingly this has involved mathematical and computational approaches, typically to model a small number of components spanning several levels of biological organization. With the advent of "omics" technologies, which can characterize the molecular state of a cell or tissue (intended as the level of expression and/or activity of its molecular components), the number of molecular components we can quantify has increased exponentially. Paradoxically, the unprecedented amount of experimental data has made it more difficult to derive conceptual models underlying essential mechanisms regulating mammalian physiology. We present an overview of state-of-the-art methods currently used to identifying biological networks underlying genomewide responses. These are based on a data-driven approach that relies on advanced computational methods designed to "learn" biology from observational data. In this review, we illustrate an application of these computational methodologies using a case study integrating an in vivo model representing the transcriptional state of hypoxic skeletal muscle with a clinical study representing muscle wasting in chronic obstructive pulmonary disease patients. The broader application of these approaches to modeling multiple levels of biological data in the context of modern physiology is discussed. PMID:26542523

  13. Reconceptualizing anhedonia: novel perspectives on balancing the pleasure networks in the human brain.

    PubMed

    Rømer Thomsen, Kristine; Whybrow, Peter C; Kringelbach, Morten L

    2015-01-01

    Anhedonia, the lack of pleasure, has been shown to be a critical feature of a range of psychiatric disorders. Yet, it is currently measured primarily through subjective self-reports and as such has been difficult to submit to rigorous scientific analysis. New insights from affective neuroscience hold considerable promise in improving our understanding of anhedonia and for providing useful objective behavioral measures to complement traditional self-report measures, potentially leading to better diagnoses and novel treatments. Here, we review the state-of-the-art of hedonia research and specifically the established mechanisms of wanting, liking, and learning. Based on this framework we propose to conceptualize anhedonia as impairments in some or all of these processes, thereby departing from the longstanding view of anhedonia as solely reduced subjective experience of pleasure. We discuss how deficits in each of the reward components can lead to different expressions, or subtypes, of anhedonia affording novel ways of measurement. Specifically, we review evidence suggesting that patients suffering from depression and schizophrenia show impairments in wanting and learning, while some aspects of conscious liking seem surprisingly intact. Furthermore, the evidence suggests that anhedonia is heterogeneous across psychiatric disorders, depending on which parts of the pleasure networks are most affected. This in turn has implications for diagnosis and treatment of anhedonia. PMID:25814941

  14. A large-scale perspective on stress-induced alterations in resting-state networks.

    PubMed

    Maron-Katz, Adi; Vaisvaser, Sharon; Lin, Tamar; Hendler, Talma; Shamir, Ron

    2016-01-01

    Stress is known to induce large-scale neural modulations. However, its neural effect once the stressor is removed and how it relates to subjective experience are not fully understood. Here we used a statistically sound data-driven approach to investigate alterations in large-scale resting-state functional connectivity (rsFC) induced by acute social stress. We compared rsfMRI profiles of 57 healthy male subjects before and after stress induction. Using a parcellation-based univariate statistical analysis, we identified a large-scale rsFC change, involving 490 parcel-pairs. Aiming to characterize this change, we employed statistical enrichment analysis, identifying anatomic structures that were significantly interconnected by these pairs. This analysis revealed strengthening of thalamo-cortical connectivity and weakening of cross-hemispheral parieto-temporal connectivity. These alterations were further found to be associated with change in subjective stress reports. Integrating report-based information on stress sustainment 20 minutes post induction, revealed a single significant rsFC change between the right amygdala and the precuneus, which inversely correlated with the level of subjective recovery. Our study demonstrates the value of enrichment analysis for exploring large-scale network reorganization patterns, and provides new insight on stress-induced neural modulations and their relation to subjective experience. PMID:26898227

  15. A large-scale perspective on stress-induced alterations in resting-state networks

    PubMed Central

    Maron-Katz, Adi; Vaisvaser, Sharon; Lin, Tamar; Hendler, Talma; Shamir, Ron

    2016-01-01

    Stress is known to induce large-scale neural modulations. However, its neural effect once the stressor is removed and how it relates to subjective experience are not fully understood. Here we used a statistically sound data-driven approach to investigate alterations in large-scale resting-state functional connectivity (rsFC) induced by acute social stress. We compared rsfMRI profiles of 57 healthy male subjects before and after stress induction. Using a parcellation-based univariate statistical analysis, we identified a large-scale rsFC change, involving 490 parcel-pairs. Aiming to characterize this change, we employed statistical enrichment analysis, identifying anatomic structures that were significantly interconnected by these pairs. This analysis revealed strengthening of thalamo-cortical connectivity and weakening of cross-hemispheral parieto-temporal connectivity. These alterations were further found to be associated with change in subjective stress reports. Integrating report-based information on stress sustainment 20 minutes post induction, revealed a single significant rsFC change between the right amygdala and the precuneus, which inversely correlated with the level of subjective recovery. Our study demonstrates the value of enrichment analysis for exploring large-scale network reorganization patterns, and provides new insight on stress-induced neural modulations and their relation to subjective experience. PMID:26898227

  16. Network environ perspective for urban metabolism and carbon emissions: a case study of Vienna, Austria.

    PubMed

    Chen, Shaoqing; Chen, Bin

    2012-04-17

    Cities are considered major contributors to global warming, where carbon emissions are highly embedded in the overall urban metabolism. To examine urban metabolic processes and emission trajectories we developed a carbon flux model based on Network Environ Analysis (NEA). The mutual interactions and control situation within the urban ecosystem of Vienna were examined, and the system-level properties of the city's carbon metabolism were assessed. Regulatory strategies to minimize carbon emissions were identified through the tracking of the possible pathways that affect these emission trajectories. Our findings suggest that indirect flows have a strong bearing on the mutual and control relationships between urban sectors. The metabolism of a city is considered self-mutualistic and sustainable only when the local and distal environments are embraced. Energy production and construction were found to be two factors with a major impact on carbon emissions, and whose regulation is only effective via ad-hoc pathways. In comparison with the original life-cycle tracking, the application of NEA was better at revealing details from a mechanistic aspect, which is crucial for informed sustainable urban management. PMID:22424579

  17. Runoff generation in a Mediterranean semi-arid landscape: Thresholds, scale, rainfall and catchment characteristics

    NASA Astrophysics Data System (ADS)

    Ries, Fabian; Schmidt, Sebastian; Sauter, Martin; Lange, Jens

    2016-04-01

    Surface runoff acts as an integrated response of catchment characteristics and hydrological processes. In the Eastern Mediterranean region, a lack of runoff data has hindered a better understanding of runoff generation processes on the catchment scale, despite the importance of surface runoff as a water resource or flood hazard. Our main aim was to identify and explain differences in catchment runoff reactions across a variety of scales. Over a period of five years, we observed runoff in ephemeral streams of seven watersheds with sizes between 3 and 129 km2. Landuse and surface cover types (share of vegetation, bare soil and rock outcrops) were derived from aerial images by objective classification techniques. Using data from a dense rainfall network we analysed the effects of scale, catchment properties and aridity on runoff generation. Thereby we extracted rainfall and corresponding runoff events from our time-series to calculate event based rainfall characteristics and catchment runoff coefficients. Soil moisture observations provided additional information on antecedent moisture conditions, infiltration characteristics and the evolution of saturated areas. In contrast to the prevailing opinion that the proportion of Hortonian overland flow increases with aridity, we found that in our area the largest share (> 95 %) of runoff is generated by saturation excess overland flow in response to long lasting, rainfall events of high amount. This was supported by a strong correlation between event runoff and precipitation totals. Similar rainfall thresholds (50 mm) for runoff generation were observed in all investigated catchments. No scale effects on runoff coefficients were found; instead we identified up to three-fold runoff coefficients in catchments with larger extension of arid areas, higher percentage of rock outcrops and urbanization. Comparing two headwater catchments with noticeable differences in extent of olive orchards, no difference in runoff generation was

  18. Trend analysis of nutrient loadings in the South Saskatchewan River catchment

    NASA Astrophysics Data System (ADS)

    Morales-Marin, L. A.; Chun, K. P.; Wheater, H. S.; Lindenschmidt, K. E.

    2015-12-01

    Nutrient loadings in river catchments have increased in the past years as a consequence of rapid expansion of agricultural areas, new urban developments and industries, and population growth. Nutrient enrichment of water bodies has intensified eutrophication conditions that degrade water quality and ecosystem health. In large-scale catchments, the assessment of temporal and spatial variability of nutrient loads imply challenges due to climate, land use and geology heterogeneity, and to anthropogenic changes. In this study we carried out a trend analysis of total phosphorus and total nitrogen loads in the South Saskatchewan River (SSR) catchment. This catchment is located in the Canadian Prairie Provinces of Alberta and Saskatchewan. The eastern and central areas of the catchment consist mostly of croplands, pasture lands and livestock farms, whereas the western parts are located on the Rocky Mountains that are the source of most of the catchment's streamflows. The trend analysis was performed applying a novel approach to analyse nutrient time series recorded at long-term water quality stations along the main stems of the SSR river network. Since water quality is taken infrequently, in the proposed approach the time series were complemented using regression analysis methods based on streamflow data recorded at the nearest gauge stations. The time series were subsequently pre-whitened in order to remove the autocorrelation, and then subjected to non-parametric statistical test to detect trends. Seasonal analysis of trends at each of the water quality stations were performed in order to determine the relationships between annual flow regimes and nutrient loads in the catchment, in particular, the influence of the high spring runoff on nutrient export. Decadal analysis was also performed to determine the long-tern relationships of nutrients with anthropogenic changes in the catchment. In particular, the capacity of reservoirs to trap nutrients and the effects of the

  19. Hydropedological insights when considering catchment classification

    NASA Astrophysics Data System (ADS)

    Bouma, J.; Droogers, P.; Sonneveld, M. P. W.; Ritsema, C. J.; Hunink, J. E.; Immerzeel, W. W.; Kauffman, S.

    2011-06-01

    Soil classification systems are analysed to explore the potential of developing classification systems for catchments. Soil classifications are useful to create systematic order in the overwhelming quantity of different soils in the world and to extrapolate data available for a given soil type to soils elsewhere with identical classifications. This principle also applies to catchments. However, to be useful, soil classifications have to be based on permanent characteristics as formed by the soil forming factors over often very long periods of time. When defining permanent catchment characteristics, discharge data would therefore appear to be less suitable. But permanent soil characteristics do not necessarily match with characteristics and parameters needed for functional soil characterization focusing, for example, on catchment hydrology. Hydropedology has made contributions towards the required functional characterization of soils as is illustrated for three recent hydrological catchment studies. However, much still needs to be learned about the physical behaviour of anisotropic, heterogeneous soils with varying soil structures during the year and about spatial and temporal variability. The suggestion is made therefore to first focus on improving simulation of catchment hydrology, possibly incorporating hydropedological expertise, before embarking on a catchment classification effort which involves major input of time and involves the risk of distraction. In doing so, we suggest to also define other characteristics for catchment performance than the traditionally measured discharge rates. Such characteristics may well be derived from societal issues being studied, as is illustrated for the Green Water Credits program.

  20. Coupling catchment hydrology and landscape evolution: Interactive effects on hydrograph and basin shape

    NASA Astrophysics Data System (ADS)

    Vivoni, E. R.; Istanbulluoglu, E.; Bras, R. L.

    2003-12-01

    The catchment hydrologic response to rainfall and the evolution of the river basin network and landscape morphology are closely linked phenomena, albeit active over different temporal scales. While the relation between hydrograph shape and catchment form has long been hypothesized, little is yet understood about the evolution of the basin hydrologic response with catchment age or geomorphic condition. Similarly, the long-term morphologic changes and feedbacks associated with a spatially-variable, evolving runoff response are still unknown. Understanding the complex interaction between basin hydrology and geomorphology was an important pursuit during Michael J. Kirkby's scientific career. In this study, we describe the interactive effects and feedbacks between the basin hydrograph (hydrologic response) and shape (geomorphic response) utilizing two state-of-the-art models: the Channel-Hillslope Integrated Landscape Development (CHILD) and the TIN-based Real-time Integrated Basin Simulator (tRIBS). We first illustrate the changes occurring in the basin hydrograph, variable source area and channel network as the catchment evolves. We then describe how the spatially-explicit hydrologic response from various mechanisms and its associated moisture field directly impacts the erosion and subsequently the basin shape. Quantitative comparisons are then made between a set of interactive and non-interactive simulations for idealized conditions. Our ultimate goal is to highlight the need for coupling distributed simulations of catchment hydrology and geomorphology for investigating the interaction between basin and hydrograph shape.

  1. Hydrological relation between two small catchments in central Poland - Zwolenka vs Zagozdzonka rivers

    NASA Astrophysics Data System (ADS)

    Nestorowicz, Anna; Banasik, Kazimierz; Gładecki, Jacek

    2010-05-01

    Hydrological relation between two small catchments in central Poland - Zwolenka vs Zagozdzonka rivers. Key words: long time hydrological data, Nature 2000 network, hydrological relation Since 1992 the European Union is implementing the European Ecological Natura 2000 Network. The main purpose of creation of Natura 2000, is to protect the natural endangered habitats and species of plants and animals across Europe characteristic to 9 regions. In Poland there are only two regions: continental and alpine. Many Nature 2000 areas are in a way connected with water and often covers small not hydrologically investigated catchments and rivers. Since, 2008 the Department of Hydraulic Engineering and Environmental Restoration, Warsaw University of Life Sciences has started a hydrological investigation in Zwoleńka river catchment which valley is a protected Nature 2000 area. One of the most important species in this area is a pond turtle which prefer the wet habitats. There is no precise hydrological data for the Zwoleńka river, however, the other Zagożdżonka river catchment which border on Zwoleńka is investigated since 1963. The main purpose of this investigation is the find the relation between this two river catchment: protected Nature 2000 with no data and carefully investigated Zagożdżonka, with long time hydrological data set.

  2. Dominant controls on catchment hydrological functions: what can we learn from biological and isotopic tracers?

    NASA Astrophysics Data System (ADS)

    Pfister, L.; Klaus, J.; Wetzel, C. E.; Stewart, M. K.; McDonnell, J.; Martinez Carreras, N.

    2014-12-01

    One emerging and important control on catchment hydrological functions of water storage, mixing and release is bedrock geology. Until today, catchment-based work has been limited by small ranges of rock types in adjacent basins. Moreover, conventional hydrological tracer approaches suffer from limitations inherent to the large storages related to certain bedrock types (e.g. the damping of stable isotope tracer signatures in deep storage catchments and obliteration of output signals at larger spatial scales). Here, we show how a multi-tracer approach, based on terrestrial diatoms and different stable and radioactive isotopic tracers can help refining our understanding of the dominant controls on catchment hydrological functions, especially the role of bedrock geology. We present new data and results from a nested catchment set-up, located in the Alzette River basin in Luxembourg (Europe). These 16 catchments (with sizes ranging from 0.47 to 285 km2) are characterized by clean and mixed assemblages of geology and land use. We have monitored these systems since 2002, including meteorological variables (precipitation, air temperature, etc.), as well as 15 minute discharge. Additional parameters have been monitored bi-weekly and at the event time scale, including geochemical and isotopic (3H, D, 18O) tracers, as well as terrestrial diatom communities in streamwater. Our results show that water balance derived dynamic storage significantly differs across the 16 catchments and scales. Catchment mixing potential inferred from standard deviations in stream baseflow ∂D (as a proxy for the damping of isotopic signatures in precipitation), as well as tritium-derived baseflow transit times, both exhibit a significant spatial variability, but strong correlation to bedrock pemeability. Terrestrial diatom assemblages in streamwater, as a proxy for rapid flow pathway connectedness to the stream network, are highly variable across the study catchments but also show strong

  3. Comparing runoff on 11 poorly-gauged headwater catchments using a soft monitoring approach

    NASA Astrophysics Data System (ADS)

    Colin, F.; Crabit, A.; Moussa, R.

    2012-04-01

    used to compare the runoff of 11 small catchments with ephemeral streams (0,1-0,6 km2) with the given uncertainty at both the event and the annual scale (Crabit et al., in Hydrological Processes 25 (18), 2011). The results indicate significant variability between the catchment's responses. This variability allows for classification in spite of all the uncertainty associated with runoff estimation. This study highlights the potential of using a network of poorly gauged catchments. From almost no catchment understanding the proposed methodology allows to compare poorly gauged catchments and highlights similarity/dissimilarity between catchment responses.

  4. Using Wildlife Water Developments to Measure Precipitation and Estimate Runoff in Remote Catchments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In Nevada, available data on precipitation and runoff in remote catchments is extremely limited. The National Weather Service’s Cooperative Observer Network (COOP) includes 178 weather stations, most of which collect precipitation data and qualitative weather observations. Most of these stations a...

  5. Instrumenting Wildlife Water Developments to Measure Precipitation and Estimate Runoff in Remote Catchments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In Nevada, available data on precipitation and runoff in remote catchments are extremely limited. The National Weather Service’s Cooperative Observer Network (COOP) includes 178 weather stations, most of which collect precipitation data and qualitative weather observations. Most of these stations ar...

  6. Restoring Landform Geodiversity in Modified Rivers and Catchments

    NASA Astrophysics Data System (ADS)

    Smith, Ben; Clifford, Nicholas

    2014-05-01

    also undertaken to show landform position within catchments and the wider river network. We conclude that river restoration could play an important role in the assessment and improvement of geodiversity within heavily-modified European catchments

  7. Global Genome Biodiversity Network: saving a blueprint of the Tree of Life – a botanical perspective

    PubMed Central

    Seberg, O.; Droege, G.; Barker, K.; Coddington, J. A.; Funk, V.; Gostel, M.; Petersen, G.; Smith, P. P.

    2016-01-01

    Background Genomic research depends upon access to DNA or tissue collected and preserved according to high-quality standards. At present, the collections in most natural history museums do not sufficiently address these standards, making them often hard or impossible to use for whole-genome sequencing or transcriptomics. In response to these challenges, natural history museums, herbaria, botanical gardens and other stakeholders have started to build high-quality biodiversity biobanks. Unfortunately, information about these collections remains fragmented, scattered and largely inaccessible. Without a central registry or even an overview of relevant institutions, it is difficult and time-consuming to locate the needed samples. Scope The Global Genome Biodiversity Network (GGBN) was created to fill this vacuum by establishing a one-stop access point for locating samples meeting quality standards for genome-scale applications, while complying with national and international legislations and conventions. Increased accessibility to genomic samples will further genomic research and development, conserve genetic resources, help train the next generation of genome researchers and raise the visibility of biodiversity collections. Additionally, the availability of a data-sharing platform will facilitate identification of gaps in the collections, thereby empowering targeted sampling efforts, increasing the breadth and depth of preservation of genetic diversity. The GGBN is rapidly growing and currently has 41 members. The GGBN covers all branches of the Tree of Life, except humans, but here the focus is on a pilot project with emphasis on ‘harvesting’ the Tree of Life for vascular plant taxa to enable genome-level studies. Conclusion While current efforts are centred on getting the existing samples of all GGBN members online, a pilot project, GGI-Gardens, has been launched as proof of concept. Over the next 6 years GGI-Gardens aims to add to the GGBN high-quality genetic

  8. Process type identification in torrential catchments

    NASA Astrophysics Data System (ADS)

    Heiser, Micha; Scheidl, Christian; Eisl, Julia; Spangl, Bernhard; Hübl, Johannes

    2015-04-01

    The classification of torrential processes takes place according to factors like sediment concentration and flow behavior and ranges from fluvial process types, including water floods and fluvial sediment transport processes, to fluvial mass movements such as debris flows. This study hypothises a context between basic geomorphological disposition parameters and potential dominant flow process types in steep headwater catchments. Thus, examined catchments were selected based on a historical event documentation of torrential events in the Austrian Alps. In total, 84 catchments could be analysed, and 11 different morphometric parameters were considered. To predict the dominant torrential process type within a catchment, a naive Bayes classifier, a decision tree model, and a multinomial regression model was trained against the compiled geomorphological disposition parameters. All models as well as their combination were compared, based on bootstrapping and complexity. The presented classification model with the lowest prediction error for our data might help to identify the most likely torrential process within a considered catchment.

  9. Catchment-scale biogeography of riverine bacterioplankton.

    PubMed

    Read, Daniel S; Gweon, Hyun S; Bowes, Michael J; Newbold, Lindsay K; Field, Dawn; Bailey, Mark J; Griffiths, Robert I

    2015-02-01

    Lotic ecosystems such as rivers and streams are unique in that they represent a continuum of both space and time during the transition from headwaters to the river mouth. As microbes have very different controls over their ecology, distribution and dispersion compared with macrobiota, we wished to explore biogeographical patterns within a river catchment and uncover the major drivers structuring bacterioplankton communities. Water samples collected across the River Thames Basin, UK, covering the transition from headwater tributaries to the lower reaches of the main river channel were characterised using 16S rRNA gene pyrosequencing. This approach revealed an ecological succession in the bacterial community composition along the river continuum, moving from a community dominated by Bacteroidetes in the headwaters to Actinobacteria-dominated downstream. Location of the sampling point in the river network (measured as the cumulative water channel distance upstream) was found to be the most predictive spatial feature; inferring that ecological processes pertaining to temporal community succession are of prime importance in driving the assemblages of riverine bacterioplankton communities. A decrease in bacterial activity rates and an increase in the abundance of low nucleic acid bacteria relative to high nucleic acid bacteria were found to correspond with these downstream changes in community structure, suggesting corresponding functional changes. Our findings show that bacterial communities across the Thames basin exhibit an ecological succession along the river continuum, and that this is primarily driven by water residence time rather than the physico-chemical status of the river. PMID:25238398

  10. Catchment-scale biogeography of riverine bacterioplankton

    PubMed Central

    Read, Daniel S; Gweon, Hyun S; Bowes, Michael J; Newbold, Lindsay K; Field, Dawn; Bailey, Mark J; Griffiths, Robert I

    2015-01-01

    Lotic ecosystems such as rivers and streams are unique in that they represent a continuum of both space and time during the transition from headwaters to the river mouth. As microbes have very different controls over their ecology, distribution and dispersion compared with macrobiota, we wished to explore biogeographical patterns within a river catchment and uncover the major drivers structuring bacterioplankton communities. Water samples collected across the River Thames Basin, UK, covering the transition from headwater tributaries to the lower reaches of the main river channel were characterised using 16S rRNA gene pyrosequencing. This approach revealed an ecological succession in the bacterial community composition along the river continuum, moving from a community dominated by Bacteroidetes in the headwaters to Actinobacteria-dominated downstream. Location of the sampling point in the river network (measured as the cumulative water channel distance upstream) was found to be the most predictive spatial feature; inferring that ecological processes pertaining to temporal community succession are of prime importance in driving the assemblages of riverine bacterioplankton communities. A decrease in bacterial activity rates and an increase in the abundance of low nucleic acid bacteria relative to high nucleic acid bacteria were found to correspond with these downstream changes in community structure, suggesting corresponding functional changes. Our findings show that bacterial communities across the Thames basin exhibit an ecological succession along the river continuum, and that this is primarily driven by water residence time rather than the physico-chemical status of the river. PMID:25238398

  11. Morphometric properties of the trans-Himalayan river catchments: Clues towards a relative chronology of orogen-wide drainage integration

    NASA Astrophysics Data System (ADS)

    Ghosh, Parthasarathi; Sinha, Sayan; Misra, Arindam

    2015-03-01

    The geomorphological evolution of the Himalayan mountain belt both in terms of crustal deformation and concomitant erosion by surface processes has been suggested to have a profound influence on a number of earth system processes and has been extensively researched through a number of different techniques. The huge catchments of the trans-Himalayan rivers are the product of long-term fluvial erosion of the landscape. This work attempts to understand their evolution through a study of drainage network, morphology, and internal organization of the smaller watersheds nested within each catchment. Using morphometric techniques applied to an orogen-wide digital elevation data grid, we characterized the drainage network structure and catchment of all the 18 trans-Himalayan rivers situated between the exits of the Indus and Brahmaputra rivers and constructed rectangular approximations of the catchment geometries. With the help of catchment dimensions measured transverse and parallel to the strike of the orogen, and by analyzing the dimension and spatial dispositions of the rectangular approximations, we demonstrate that the trans-Himalayan catchment shapes cannot be explained only as a product of the headward enlargement of drainage networks on a topographic slope, or orogenic taper. Within individual catchments we identified the existence of drainage components (watersheds) that are organized in a systematic manner with respect to the first-order physiographic features of the Himalayas, formed at different periods of geological time. Each of them shows distinct morphometric characteristics that are indicative of differences in processes and / or time scale involved in their formation. The hypsometric properties of the watersheds occupying the upper part of the catchments suggest that they are the remnants of pre-orogenic drainage that became confined to the leeward side of the Himalayas before the advent of monsoon circulation. The shape and organization of the

  12. Modelling herbicide transfers from land to water in the Upper Cherwell catchment UK

    NASA Astrophysics Data System (ADS)

    Whelan, Mick; Tediosi, Alice; Gandolfi, Claudio; Rienzner, Michele; Rushton, Ken; Pullan, Stephanie

    2013-04-01

    Pesticide losses from land to water can present problems for environmental management, particularly in catchments where surface waters are abstracted for drinking water. Here, we describe a model to predict chemical transfers from land to water at the catchment scale. The model was used to describe the behaviour of two herbicides, propyzamide and carbetamide, in the 199 km2 Upper Cherwell catchment, UK, which is used as a municipal water supply. The model operates at two spatial scales: (1) the hillslope scale and (2) the catchment scale. At the hillslope scale pesticide is assumed to diffuse into the majority of the water filled pore volume in a shallow soil layer after application, where it partitions between the dissolved and sorbed phases. A fraction of the dissolved phase pesticide mass in a "mobile" pore water fraction is then displaced by rainfall and is transported to field drains, if present. The hillslope-scale model was tested in a 15.5 ha headwater sub-catchment of the Cherwell, dominated by under-drained heavy clay soil. Significant transfers of both herbicides to the drain network occurred soon after application. Peak concentration coincided with peak drain flow and concentrations then decreased gradually in a quasi-exponential fashion, mirroring the receding hydrograph. Observed carbetamide concentrations were about an order of magnitude higher that those observed for propyzamide due to a combination of a higher application rate and lower KOC. For propyzamide, total observed loss over the study period was estimated to be 1.1% of the applied mass and for carbetamide the loss was estimated to be 8.6%. At the catchment scale, hillslope contributions are integrated using a convolution of the network width function (link frequency distribution), assuming a constant kinematic wave celerity and allowing for the spatial distribution of hillslope contributions from different soil types throughout the network. Two soil types dominate: heavy soils which are

  13. Physical and biological controls on reach to catchment scale nutrient retention and streamwater composition

    NASA Astrophysics Data System (ADS)

    Covino, T. P.; McGlynn, B. L.; Wohl, E.

    2014-12-01

    Physical and biological processes occurring within fluvial networks can have strong influence on catchment scale retention of water and nutrients. Quantifying the physical (i.e., hydrologic exchange) and biological (i.e., nutrient uptake) contributions to total retention and deciphering how they relate to catchment morphology remains a central challenge in the hydrologic and biogeo-sciences. Here we present examples from our research that highlight the interactions between biology, physical hydrology, and geomorphology and how they combine to influence nutrient retention and streamwater compositions. Biological nutrient uptake in streams can have substantial influence on downstream fluxes and induce nutrient transformation along stream networks. Additionally, hydrologic loss of water and associated nutrients from streams to surrounding groundwater systems can greatly elongate water and nutrient retention times. While in-stream nutrient uptake is often associated with hyporheic exchanges that occur at sub-meter scales, these are nested within a larger framework of fluvial exchanges (100s - 1000s of meters). Larger scale exchanges can lead to strong shifts in streamwater composition over relatively short spatial scales (~1km) and are often very pronounced along geomorphic transitions (e.g., mountain to valley) and/or catchment retention zones (e.g., alluvial aquifers, wetlands, lakes). In fact, 50 - 80% of the water in the channel can be exchanged and replaced by different water (i.e., groundwater) along geomorphic transitions/catchment retention zones that are ~1 km in scale. These features can enhance geochemical processing through extended interactions between water, sediment, and nutrients. Accordingly, we suggest that although catchment retention features may be limited in spatial extent (~1km) and frequency they have the capacity to play a disproportionately large role in controlling catchment retention dynamics and setting fluvial network streamwater

  14. Networking.

    ERIC Educational Resources Information Center

    Duvall, Betty

    Networking is an information giving and receiving system, a support system, and a means whereby women can get ahead in careers--either in new jobs or in current positions. Networking information can create many opportunities: women can talk about how other women handle situations and tasks, and previously established contacts can be used in…

  15. Does the simple dynamical systems approach provide useful information about catchment hydrological functioning in a Mediterranean context? Application to the Ardèche catchment (France)

    NASA Astrophysics Data System (ADS)

    Adamovic, M.; Braud, I.; Branger, F.; Kirchner, J. W.

    2014-09-01

    This study explores how catchment heterogeneity and variability can be summarized in simplified models, representing the dominant hydrological processes. It focuses on Mediterranean catchments, characterized by heterogeneous geology, pedology, and land use, as well as steep topography and a rainfall regime in which summer droughts contrast with high-rainfall periods in autumn. The Ardèche catchment (south-east France), typical of this environment, is chosen to explore the following questions: (1) can such a Mediterranean catchment be adequately characterized by simple dynamical systems approach and what are the limits of the method under such conditions? (2) What information about dominant predictors of hydrological variability can be retrieved from this analysis in such catchments? In this work we apply the data-driven approach of Kirchner (WRR, 2009) to estimate discharge sensitivity functions that summarize the behavior of four sub-catchments of the Ardèche, using non-vegetation periods (November-March) from 9 years of data (2000-2008) from operational networks. The relevance of the inferred sensitivity function is assessed through hydrograph simulations, and through estimating precipitation rates from discharge fluctuations. We find that the discharge-sensitivity function is downward-curving in double-logarithmic space, thus allowing further simulation of discharge and non-divergence of the model, only during non-vegetation periods. The analysis is complemented by a Monte-Carlo sensitivity analysis showing how the parameters summarizing the discharge sensitivity function impact the simulated hydrographs. The resulting discharge simulation results are good for granite catchments, found to be predominantly characterized by saturation excess runoff and sub-surface flow processes. The simple dynamical system hypothesis works especially well in wet conditions (peaks and recessions are well modeled). On the other hand, poor model performance is associated with

  16. Doing hydrology backwards in tropical humid catchments

    NASA Astrophysics Data System (ADS)

    Real Rangel, R.; Brena-Naranjo, J. A.; Pedrozo-Acuña, A.

    2015-12-01

    Top-down approaches in hydrology offer the possibility to predict water fluxes at the catchment scale based on the interpretation of the observed hydrological response at the catchment itself. Doing hydrology backwards (inferring precipitation and evapotranspiration rates at the catchment scale from streamflow measurements, see Kirchner (2009)) can be a useful methodology for estimating water fluxes at the catchment and regional scales. Previous studies using this inverse modeling approach have been performed in regions (UK, Switzerland, France, Eastern US) where energy-limited (in winter and early spring) and water-limited conditions (in summer) prevail during a large period of the year. However, such approach has not been tested in regions characterized by a quasi-constant supply of water and energy (e.g. humid tropics). The objective of this work is to infer annual rates of precipitation and evapotranspiration over the last decade in 10 catchments located in Mexico's tropical humid regions. Hourly discharge measurements during recession periods were analyzed and parameters for the nonlinear storage-discharge relationship of each catchment were derived. Results showed large variability in both catchment-scale precipitation and evapotranspiration rates among the selected study sites. Finally, a comparison was done between such estimates and those obtained from remotely-sensed data (TRMM for precipitation and MOD16 for evapotranspiration).

  17. Catchment water storage: Models vs Measurements

    NASA Astrophysics Data System (ADS)

    McMillan, Hilary

    2016-04-01

    Recent years have seen a great deal of progress in development of hydrological models that can simulate both the dynamic streamflow response and the hydrochemical flux response of a catchment. In general terms, streamflow response is driven by water deficit in the catchment, whereas hydrochemical response is driven by water storage. Therefore, models that can simultaneously predict both responses must succeed in representing these two related, but different, quantities. This presentation will consider how much information we can gain from field studies to quantify the joint deficit/storage state of a catchment. In particular, examples from two New Zealand experimental catchments in lowland and high country locations will be used to link typical measurements available with the information required by hydrological - hydrochemical models. I will then use the example catchments to assess how well the structure of a typical hydrological-hydrochemical model is supported by field measurements. In particular, can we quantify catchment storage and link this to flow response? Can we incorporate our knowledge of plant water use into such a model, including timing and depth of water withdrawn by the plant? What can field measurements tell us about spatial variability in hydrological-hydrochemical response and can this be represented in the model? I will conclude by discussing what we can learn from field data about the major challenges ahead in catchment storage modelling.

  18. Catchments as heterogeneous and multi-species reactors: An integral approach for identifying biogeochemical hot-spots at the catchment scale

    NASA Astrophysics Data System (ADS)

    Weyer, Christina; Peiffer, Stefan; Schulze, Kerstin; Borken, Werner; Lischeid, Gunnar

    2014-11-01

    From a biogeochemical perspective, catchments can be regarded as reactors that transform the input of various substances via precipitation or deposition as they pass through soils and aquifers towards draining streams. Understanding and modeling the variability of solute concentrations in catchment waters require the identification of the prevailing processes, determining their respective contribution to the observed transformation of substances, and the localization of "hot spots", that is, the most reactive areas of catchments. For this study, we applied a non-linear variant of the Principle Component Analysis, the Isometric Feature Mapping (Isomap), to a data set composed of 1686 soil solution, groundwater and stream water samples and 16 variables (Al, Ca, Cl, Fe, K, Mg, Mn, Na, NH4, NO3, SO4, total S, Si, DOC, electric conductivity and pH values) from the Lehstenbach catchment in Germany. The aim was (i) to assess the contribution of the prevailing biogeochemical processes to the variability of solute concentrations in water samples taken from soils, in groundwater and in stream water in a catchment and (ii) to identify hot spots at the catchment scale with respect to 16 solutes along different flow paths. The first three dimensions of the Isomap analysis explained 48%, 30% and 11%, respectively, i.e. 89% of the variance in the data set. Scores of the first three dimensions could be ascribed to three predominating bundles of biogeochemical processes: (i) redox processes, (ii) acid-induced podzolization, and (iii) weathering processes. In general, the upper 1 m topsoil layer could be considered as hot spots along flow paths from upslope soils and in the wetland, although with varying extents for the different prevailing biogeochemical processes. Nearly 67% and 97% of the variance with respect to redox processes and acid induced podzolization could be traced back to hot spots, respectively, representing less than 2% of the total spatial volume of the catchment

  19. Improved understanding and prediction of the hydrologic response of highly urbanized catchments through development of the Illinois Urban Hydrologic Model

    NASA Astrophysics Data System (ADS)

    Cantone, Joshua; Schmidt, Arthur

    2011-08-01

    What happens to the rain in highly urbanized catchments? That is the question that urban hydrologists must ask themselves when trying to integrate the hydrologic and hydraulic processes that affect the hydrologic response of urban catchments. The Illinois Urban Hydrologic Model (IUHM) has been developed to help answer this question and improve understanding and prediction of hydrologic response in highly urbanized catchments. Urban catchments are significantly different than natural watersheds, but there are similarities that allow features of the pioneering geomorphologic instantaneous unit hydrograph concept developed for natural watersheds to be adapted to the urban setting. This probabilistically based approach is a marked departure from the traditional deterministic models used to design and simulate urban sewer systems and does not have the burdensome input data requirements that detailed deterministic models possess. Application of IUHM to the CDS-51 catchment located in the village of Dolton, Illinois, highlights the model's ability to predict the hydrologic response of the catchment as well as the widely accepted SWMM model and is in accordance with observed data recorded by the United States Geological Survey. In addition, the unique structure and organization of urban sewer networks make it possible to characterize a set of ratios for urban catchments that allow IUHM to be applied when detailed input data are not available.

  20. Sources of sediment in catchments and its eutrophication potential

    NASA Astrophysics Data System (ADS)

    Krasa, Josef; Dostal, Tomas; Bauer, Miroslav; Janotova, Barbora; Rosendorf, Pavel

    2013-04-01

    To help the implementation of Water Framework Directive in the Czech Republic the four-year project was set-up to assess eutrophication factors in endangered catchments. The assessed area covers approximately 40% of the area of the Czech Republic (almost 31 500 km2). The erosion phosphorus loads are modeled by WATEM/SEDEM model adapted for the purpose. For each catchment the sediment transport maps are delivered. Database of 20 477 reservoirs (spatial information taken from DIBAVOD) within CR has been built up during the project and all available information on volumes and flow rates in the reservoirs is collected. From these, 9 890 reservoirs lay in the target area and to estimate the sediment trapping efficiency their volumes and average annual flow rates have to be assessed. The official databases offer less than 10% data coverage so especially for smaller reservoirs the volumes and flow rates have to be derived by analogy using pond area and catchments specific runoff. Brune curves method readjusted by Dendy (1978) is then used for sediment trap efficiency estimation. WATEM/SEDEM model had to be further adapted for modeling phosphorus fluxes within catchments. The ratio of nutrient concentration in eroded sediment to that in the original soil (the enrichment ratio, ER) commonly drops down with raising the soil loss. We used the dependence proposed by Sharply (1995). The soil erodibility factor of WATEM/SEDEM (K-factor) is then replaced by phosphorus erodibility potential. Finally the erosion phosphorus transport is computed getting also phosphorus retention in all reservoirs in target watersheds. In 2012 sediment transport was modeled in all catchments. Assessment of silting of thousands or reservoirs within the stream network of the target catchments is important "side output" of the project Balancing phosphorus sources with attempt to find the importance of erosion for eutrophication is a complicated task. The regular monthly monitoring network in streams and

  1. Geological controls on isotopic signatures of streamflow: results from a nested catchment experiment in Luxembourg (Europe)

    NASA Astrophysics Data System (ADS)

    Pfister, Laurent; McDonnell, Jeffrey J.; Hissler, Christophe; Martinez-Carreras, Nuria; Gourdol, Laurent; Klaus, Julian; François Iffly, Jean; Barnich, François; Stewart, Mike K.

    2014-05-01

    Controls of geology and topography on hydrological metrics, like summer low flow (Grant and Tague, 2004) or dynamic storage (Sayama et al., 2011), have been identified in nested catchment experiments. However, most tracer-based studies on streamflow generation have been carried out in small (10 km2) homogenous catchments (Klaus and McDonnell, 2013). The controlling effects of catchment physiography on how catchments store and release water, and how this eventually controls stream isotope behaviour over a large range of scale are poorly understood. Here, we present results from a nested catchment analysis in the Alzette River basin (Luxembourg, Europe). Our hydro-climatological network consists of 16 recording streamgauges and 21 pluviographs. Catchment areas range from 0.47 to 285 km2, with clean and mixed combinations of distinct geologies ranging from schists to marls, sandstone, dolomite and limestone. Our objective was to identify geological controls on (i) winter runoff ratios, (ii) maximum storage and (iii) isotopic signatures in streamflow. For each catchment we determined average runoff ratios from winter season precipitation-discharge double-mass curves. Maximum catchment storage was based on the dynamic storage change approach of Sayama et al. (2011). Changes in isotopic signatures of streamflow were documented along individual catchment flow duration curves. We found strong correlations between average winter runoff ratios, maximum storage and the prevailing geological settings. Catchments with impermeable bedrock (e.g. marls or schists) were characterised by small storage potential and high average filling ratios. As a consequence, these catchments also exhibited the highest average runoff ratios. In catchments underlain by permeable bedrock (e.g. sandstone), storage potential was significantly higher and runoff ratios were considerably smaller. The isotopic signatures of streamflow showed large differences between catchments. In catchments dominated by

  2. Applying different spatial distribution and modelling concepts in three nested mesoscale catchments of Germany

    NASA Astrophysics Data System (ADS)

    Bongartz, K.

    Distributed, physically based river basin models are receiving increasing importance in integrated water resources management (IWRM) in Germany and in Europe, especially after the release of the new European Water Framework Directive (WFD). Applications in mesoscale catchments require an appropriate approach to represent the spatial distribution of related catchment properties such as land use, soil physics and topography by utilizing techniques of remote sensing and GIS analyses. The challenge is to delineate scale independent homogeneous modelling entities which, on the one hand may represent the dynamics of the dominant hydrological processes and, on the other hand can be derived from spatially distributed physiographical catchment properties. This scaling problem is tackled in this regional modelling study by applying the concept of hydrological response units (HRUs). In a nested catchment approach three different modelling conceptualisations are used to describe the runoff processes: (i) the topographic stream-segment-based HRU delineation proposed by Leavesley et al. [Precipitation-Runoff-Modelling-System, User’s Manual, Water Resource Investigations Report 83-4238, US Geological Survey, 1983]; (ii) the process based physiographic HRU-concept introduced by Flügel [Hydrol. Process. 9 (1995) 423] and (iii) an advanced HRU-concept adapted from (ii), which included the topographic topology of HRU-areas and the river network developed by Staudenraush [Eco Regio 8 (2000) 121]. The influence of different boundary conditions associated with changing the landuse classes, the temporal data resolution and the landuse scenarios were investigated. The mesoscale catchment of the river Ilm ( A∼895 km 2) in Thuringia, Germany, and the Precipitation-Runoff-Modelling-System (PRMS) were selected for this study. Simulations show that the physiographic based concept is a reliable method for modelling basin dynamics in catchments up to 200 km 2 whereas in larger catchments

  3. Relict rock glaciers as groundwater storage in alpine catchments - the example of the Seckauer Tauern Range

    NASA Astrophysics Data System (ADS)

    Wagner, Thomas; Pauritsch, Marcus; Winkler, Gerfried

    2015-04-01

    Debris accumulations like relict rock glaciers (RRG) might act as groundwater storages in alpine catchments influencing the discharge dynamics of mountain streams. The degree of influence is related to the hydrometeorological conditions and changes seasonally. Especially during drought and flood events, the storage/buffer abilities of RRGs have an impact on the downstream river network. Stream flow could be assured during low flow periods and peak flows might be dampened during storm events. The assessment of the impact is investigated in the Seckauer Tauern Range, the easternmost subunit of the Niedere Tauern Range. In more detail, the discharge of a spring (Schöneben spring) emerging at the front of a RRG draining a catchment of 0.67 km² and discharges at gauging stations Finsterliesing and Unterwald further downstream with areal extents of 7.26 and 44.10 km² respectively are used as input for a lumped-parameter rainfall-runoff model, a modified version of the GR4J (Perrin et al., 2003). The Schöneben spring is 100% influenced by the RRG groundwater storage, as the whole catchment drains through the RRG. The flow dynamics of the other catchments are influenced only partially by RRGs with 15 and 12% as only headwater sections of it are drained by RRGs. The areal extend of the RRG (sub-) catchments, vegetation, debris in general and bare rock are compared to the storage parameters (routing and production store) of the rainfall-runoff model. As such, the influence of RRGs can be identified even in the overall catchment. It can be concluded that RRGs, due to their storage and buffer capabilities and abundance in the Seckauer Tauern Range are important for stream basin management and as a water resource for the sensitive ecosystem in alpine catchments. References: Perrin, C., Michel, C., Andréassian, V. (2003): Improvement of a parsimonious model for streamflow simulation. Journal of Hydrology 279, 275-289.

  4. Plot and Catchment Scale Hydrological Impacts of Agricultural Field Boundary Features

    NASA Astrophysics Data System (ADS)

    Coates, Victoria; Pattison, Ian

    2015-04-01

    Natural flood management aims to reduce downstream flow levels by delaying the movement of water through a catchment and increasing the amount of soil infiltration. Field boundary features such as hedgerows and dry stone walls are common features in the rural landscape. It is hypothesised that there presence could reduce runoff connectivity and change the soil moisture levels by altering the soil structure and porosity. The use of larger agricultural machinery has resulted in the removal of field boundaries and the subsequent increase in field sizes over the 20th Century. This change in the rural landscape is likely to have changed the partitioning of rainfall into runoff and the hydrological pathways throughout the catchment. However, the link between field boundaries and catchment scale flood risk has not yet been proven. We aim to address this need for evidence to support natural flood management by focussing on these widespread features in the rural landscape. Firstly, we quantify the change in the density of field boundaries over the past 120 years for the Skell catchment, Northern England using historical OS maps. The analysis has shown that field size has approximately doubled in the Skell catchment since 1892, due to the removal of field boundaries. Secondly, we assess the effect of field boundaries on local soil characteristics and hydrological processes through plot scale continuous monitoring of the hydrological processes along a 20m transect through the linear boundary features. For the summer period results show that soil moisture levels are lower immediately next to the hedgerow compared to distances greater than 1m from the hedgerow. Finally, we use this data to parameterise and validate a catchment scale hydrological model. The model is then applied to test the impact of a network of field boundaries on river flow extremes at the catchment scale.

  5. Pseudo Paired Catchments Analysis to Assess the Impact of Urbanization on Catchment Hydrology

    NASA Astrophysics Data System (ADS)

    Salavati, B.; Oudin, L.; Furusho, C.; Ribstein, P.

    2014-12-01

    Paired catchments analysis provides a robust approach to assess the impact of land use changes on catchment's hydrological response. This approach is limited by the availability of data for two neighbor catchments with and without land use changes under similar climate conditions. Thus, hydrological modelling approaches are also very popular since they do not depend on data of a reference catchment. In the present study, 70 urbanized and non-urbanized paired catchments were selected in the United States. Unit housing density maps over the 1940-2010 time period were used to reconstruct historic impervious area extents with aproximatly the same resolution as the National Land Cover Database (NLCD) maps. Two approaches were compared to assess the impact of urbanization on catchment-scale hydrology: the classical paired catchments approach using observed flow time series and an alternative paired catchments approach involving hydrological modeling that allows to simulate a virtual control catchment. To this aim, the GR4J model, a conceptual daily 4-parameter hydrological model, was used. The parameters of the model calibrated on the pre urbanization period were used to predict the streamflow that would have occurred in the urban catchment if the urbanization had not taken place. Then, classical statistical methods involving ANCOVA were used to detect the significance and to quantify the change on the hydrological responses due to land use changes. Results show that the two approaches lead to similar conclusions on the impact of urbanization on catchment hydrology. Thus, the modelling approach provides a relevant alternative for case studies where data of reference catchments are not available.

  6. Use of natural tracers to identify spatial and temporal variation in runoff sources in a complex, mountainous mesoscale catchment

    NASA Astrophysics Data System (ADS)

    Soulsby, C.; Rodgers, P.; Petry, J.; Dunn, S.

    2003-04-01

    Natural tracers (18O, Si and alkalinity) were used to assess the spatial and temporal variation in runoff sources within the 230 km^2 Feshie catchment in the Cairngorm Mountains of Scotland as part of the UK Catchment Hydrology And Sustainable Management (CHASM) initiative. The elevation of the mesoscale catchment ranges between 230--1110 m and snowfall comprises, on average, ca. 30% of annual precipitation. Tracer behavior was monitored by routine sampling in gauged, nested subcatchments ranging from 3--90 km^2 over a hydrological year. In addition, extensive surveys sampled the spatial variation in tracer concentrations throughout the catchment river network at low, moderate and high flows at sampling intensities of 1 per 1 km^2. Use of tracer data and GIS-based assessment indicated that catchment characteristics, rather than scale, accounted for the major differences in contributions from contrasting hydrological sources in nested subcatchments. Most notably, geology and the distribution of soil types exerted a strong control on the partitioning of runoff sources and groundwater contributions to flow (which mixing analysis showed range between 25 and 52% of annual flow in different subcatchments). Coverage of organic peat soils and thin montane podzols strongly influenced the storm runoff response of different subcatchments (with average runoff coefficients ranging from 0.75 to 0.4 for different sub-catchments) and dominated stream hydrochemistry at high flows. Despite the dominant influence of catchment characteristics at the sub-catchment scale, as spatial scale increased beyond 100 km^2 within the mesoscale catchment, the influence of significant alluvial aquifers on hydrological response became apparent. Neverthless, at scales >3 km^2, preliminary analysis of weekly 18O data indicated that mean residence times are similar, though it is reasonable to expect that residence time distributions would vary if high resolution tracer samples (ie daily or sub

  7. Hydrogeomorphological and water quality impacts of oil palm conversion and logging in Sabah, Malaysian Borneo: a multi-catchment approach

    NASA Astrophysics Data System (ADS)

    Walsh, Rory; Nainar, Anand; Bidin, Kawi; Higton, Sam; Annammala, Kogilavani; Blake, William; Luke, Sarah; Murphy, Laura; Perryman, Emily; Wall, Katy; Hanapi, Jamil

    2016-04-01

    The last three decades have seen a combination of logging and land-use change across most of the rainforest tropics. This has involved conversion to oil palm across large parts of SE Asia. Although much is now known about the hydrological and sediment transport impacts of logging, relatively little is known about how impacts of oil palm conversion compare with those of logging. Furthermore little is known about the impacts of both on river morphology and water quality. This paper reports some findings of the first phase of a ten-year large-scale manipulative multi-catchment experiment (part of the SAFE - Stability of Altered Forest Ecosystems - Project), based in the upper part of the Brantian Catchment in Sabah, Malaysian Borneo; the project is designed to assess the degree to which adverse impacts of oil palm conversion (on erosion, downstream channel change, water quality and river ecology) might be reduced by retaining buffer zones of riparian forest of varying width from zero to 120 metres. Ten 2 km2 catchments of contrasting land use history have been instrumented since 2011 to record discharge, turbidity, conductivity and water temperature at 5-minute intervals. These comprise 6 repeat-logged catchments being subjected in 2015-16 to conversion to oil palm with varying riparian forest widths; a repeat-logged 'control' catchment; an old regrowth catchment; an oil palm catchment; and a primary forest catchment. In addition, (1) monthly water samples from the catchments have been analysed for nitrates and phosphates, (2) channel cross-sectional change along each stream has been monitored at six-monthly intervals and (3) supplementary surveys have been made of downstream bankfull channel cross-sectional size and water chemistry at a wider range of catchment sites, and (4) sediment cores have been taken and contemporary deposition monitored at a hierarchical network of sites in the large Brantian catchment for geochemical analysis and dating to establish the

  8. Linking the field to the stream: soil erosion and sediment yield in a rural catchment, NW Spain

    NASA Astrophysics Data System (ADS)

    Rodriguez-Blanco, M. L.; Taboada-Castro, M. M.; Palleiro-Suarez, L.; Taboada-Castro, M. T.

    2009-04-01

    Quantifying the linkages between field erosion, fluvial response and catchment sediment yield remains problematic, among other reasons, because of the re-deposition of eroded sediment within the catchment, which is controlled by the spatial organization of the land use and the connectivity between sediment sources and the stream network. This paper presents the results of an integrated study that considered the relationship between erosion and stream sediment yield in an agroforestry catchment (16 km2) in NW Spain. The geology consists of basic metamorphic schist. The relieve of the area is steeper, the mean slope is approximately 19%. Main soil types are classified as Umbrisol and Cambisol. Soils are acidic and rich in organic matter. The soil texture is silt and silt-loam. Land cover consists of a mixture of forest (65%) and agricultural fields (mainly grassland, pasture and maize). The study combined measurements of soil erosion by concentrate flow and sediment deposition at field scale with sediment yield measured at the catchment outlet. The hydrological data and water samples were obtained at the catchment outlet. Stream water level was monitored continuously and converted to discharge using a rating curve. The sampling for suspended sediments was supplemented by an automatic sampler. Suspended sediment load was calculated from the suspended sediment concentrations and discharge data. Eroded volume was calculated from cross-sections (measured at specific points, where the section changed abruptly) and length of the channel segments. The total sediment delivered to stream was determined as the difference between all erosion features (rills and gullies) and the sediment volumes that were deposited on the fields. The results showed that in the catchment during the period winter 2007/08 soil erosion by concentrate flow, i.e. rills and ephemeral gullies, occurred on unprotected crop field. Erosion by concentrate flow was highly discontinuous within the catchment

  9. Natural flood risk management in flashy headwater catchments: managing runoff peaks, timing, water quality and sediment regimes

    NASA Astrophysics Data System (ADS)

    Wilkinson, Mark; Addy, Steve; Ghimire, Sohan; Kenyon, Wendy; Nicholson, Alex; Quinn, Paul; Stutter, Marc; Watson, Helen

    2013-04-01

    catchments are known for their rapid runoff generation and have downstream local communities at risk of flash flooding. In Bowmont, NFM measures are currently being put in place to restore river bars and to store water more effectively on the flood plains during these flashy events. For example, Apex engineered wood structure in the river channel and riparian zones are designed to trap sediment and log bank protection structures are being installed to stop bank erosion. Tree planting in the catchment is also taking place. In the Belford catchment storage ponds and woody debris have been installed over the past five years to help to reduce the flood risk to the village of Belford. A dense instrumentation network has provided data for analysis and modelling which shows evidence of local scale flood peak reductions along with the collection of large amounts of sediment. A modelling study carried out (using a pond network model) during an intense summer storm showed that 30 small scale pond features used in sequence could reduce the flood peak by ~35% at the local scale. Findings show that managing surface runoff and local ditch flow at local scale headwater catchments is a cost effective way of managing flashy catchment for flood risk and sediment control. Working with catchment stakeholders is vital. Information given by the local community post flooding has been useful in placing NFM measures throughout the catchments. Involving the local communities in these projects and giving them access to the data and model outputs has helped to develop these projects further.

  10. Hillslopes to hollows to first order channels: identification of transitions and characteristics of process domains in headwater catchments

    NASA Astrophysics Data System (ADS)

    Williams, K.; Locke, W. W.

    2009-12-01

    Where hillslopes end and hollows and first order channels begin continues to be a relevant question for landscape evolution and development of channel networks. In this work, we test a technique using LIDAR-derived topographic indices to define the transition from hillslopes to unchannelized (zero order) hollows, and from hollows to first order channels in four small (<4 km2 ) headwater catchments in mountainous regions of central and southwest Montana. Commonly used channel network delineation methods rely on global criteria such as area and slope thresholds, and can yield widely varying drainage patterns and density outcomes. Local curvature and an aspect-derived parameter were used to identify the spatial extent of hillslopes, hollows, and first order channels in ArcMap. The spatial patterns of frequency-magnitude plots of the local parameters were used to identify thresholds or transition zones between process domains, and indicate the degree of self-organization. Analytically-derived thresholds were verified against field mapping of channel heads and hollows. Results show that the power law portions of the frequency-magnitude relationships were successfully used to locate domain transitions. The transition zones of hillslope to hollow and hollow to channel were identified, for continuous and discontinuous headwater channels of 0.5 to 1 meter in width. Incisive flow alternates downstream with diffusive flow resulting in a discontinuous headwater channel network. The degree of network evolution and self organization of the networks was also evaluated using frequency-magnitude relationships of the topographic indices and total energy dissipation of each catchment. The southwest Montana catchments exhibited more advanced landscape evolution based upon the extent of self organization and optimality, as evidenced by minimum total catchment energy dissipation. The network development of the central Montana catchments appears constrained by debris flow lag deposit in

  11. Social integration and suicide-related ideation from a social network perspective: a longitudinal study among inner-city African Americans.

    PubMed

    Kuramoto, S Janet; Wilcox, Holly C; Latkin, Carl A

    2013-08-01

    Social network density, as measured by the extent to which network members know each other, was examined to determine whether it is associated with suicide-related ideation and plan approximately 3 years later. Eight hundred and nineteen African Americans were interviewed at Wave 1 (1997-1999) and Wave 4 (2001-2003) of the Self-Help In Eliminating Life-Threatening Diseases (SHIELD) study, a HIV preventive intervention study in Baltimore, MD. Multinomial logistic regression models were used to compare risks of suicide-related ideation and plan at Wave 4 by Wave 1 density. Even after adjusting for baseline sociodemographic characteristics and depressive symptoms, individuals with a lower level of density were three times more likely to report suicide-related ideation and plan in the past year at Wave 4. The findings reinforce the importance of social integration among inner-city African Americans from a social network perspective. Future research should examine the mechanisms associated with this relationship and other social network constructs. PMID:23530665

  12. Topic: Catchment system dynamics: Processes and feedbacks

    NASA Astrophysics Data System (ADS)

    Keesstra, Saskia

    2015-04-01

    In this meeting we can talk about my main expertise: the focus of my research ocus revolves around understanding catchment system dynamics in a holistic way by incorporating both processes on hillslopes as well as in the river channel. Process knowledge enables explanation of the impact of natural and human drivers on the catchment systems and which consequences these drivers have for water and sediment connectivity. Improved understanding of the catchment sediment and water dynamics will empower sustainable land and river management and mitigate soil threats like erosion and off-side water and sediment accumulation with the help of nature's forces. To be able to understand the system dynamics of a catchment, you need to study the catchment system in a holistic way. In many studies only the hillslopes or even plots are studied; or only the channel. However, these systems are connected and should be evaluated together. When studying a catchment system any intervention to the system will create both on- as well as off sites effects, which should especially be taken into account when transferring science into policy regulations or management decisions.

  13. Problematization of perspectives on health promotion and empowerment in mental health nursing--within the research network "MeHNuRse" and the Horatio conference, 2012.

    PubMed

    Jönsson, Patrik D; Nunstedt, Håkan; Berglund, Inger J; Ahlström, Britt H; Hedelin, Birgitta; Skärsäter, Ingela; Jormfeldt, Henrika

    2014-01-01

    Mental illness is increasing worldwide, while society's response seems to be a trend toward narrower and more specialized mental health care. This development is creating great demands on mental health nurses to include a health promotion perspective in care and support of persons with mental illness. A health promotion perspective emphasizes cooperation and communication with people who suffer from long-term mental illness, focusing on their independence and health. From a health perspective, every human being is an actor in his/her own life, with an inherent ability to make his/her own choices. However, persons who suffer from long-term mental illness are at risk of losing power and control over areas of their lives and their health. Mental health nurses are in a position to support these individuals in promoting health and in maintaining or regaining control over their lives. The emphasis of this paper is to problematize mental health nurses' responsibility to provide health-promoting nursing care in relation to empowerment by means of emancipation, self-efficacy, and self-management. We argue that mental health nurses can work from a health-promoting perspective by using these concepts and that this challenges some of the traditional ideas of health promotion in mental health nursing. The theoretical background discussions in this paper have their origin in the research network "Mental Health Nursing Research in Scandinavia" (MeHNuRse) and from the professional discussions developed during a 2012 workshop that included mental health nurses and researchers at the European Horatio Festival in Stockholm. PMID:24717267

  14. A perspective on the advancement of natural language processing tasks via topological analysis of complex networks. Comment on "Approaching human language with complex networks" by Cong and Liu

    NASA Astrophysics Data System (ADS)

    Amancio, Diego Raphael

    2014-12-01

    Concepts and methods of complex networks have been applied to probe the properties of a myriad of real systems [1]. The finding that written texts modeled as graphs share several properties of other completely different real systems has inspired the study of language as a complex system [2]. Actually, language can be represented as a complex network in its several levels of complexity. As a consequence, morphological, syntactical and semantical properties have been employed in the construction of linguistic networks [3]. Even the character level has been useful to unfold particular patterns [4,5]. In the review by Cong and Liu [6], the authors emphasize the need to use the topological information of complex networks modeling the various spheres of the language to better understand its origins, evolution and organization. In addition, the authors cite the use of networks in applications aiming at holistic typology and stylistic variations. In this context, I will discuss some possible directions that could be followed in future research directed towards the understanding of language via topological characterization of complex linguistic networks. In addition, I will comment the use of network models for language processing applications. Additional prospects for future practical research lines will also be discussed in this comment.

  15. Connectivity influences on nutrient and sediment migration in the Wartburg catchment, KwaZulu-Natal Province, South Africa

    NASA Astrophysics Data System (ADS)

    Kollongei, Kipkemboi J.; Lorentz, Simon A.

    Non-point-source (NPS) pollution of surface and groundwater by sediment and nutrient loads emanating from agricultural catchments is a prominent environmental issue, with major consequences on water supply and aquatic ecosystem quality. The concept of connectivity has proved invaluable in understanding migration of NPS pollutants in catchments. Observations of sediments or suspended solids (SS), nitrate (NO3) and phosphorous (P) fluxes alongside stable water isotope sampling were made on a nested basis at field and catchment (41 km2) scales for a series of events in the Wartburg catchment, South Africa. The nested catchment scale sampling was focused on control features in the stream network, including road crossings, farm dams and wetland zones. The analyzed stable water (δ18O and δ2H) isotopes results were used to interpret the connectivity of the contributing land forms and the stream network. The results reveal the dominant influences of farm dams and wetlands in limiting the downstream migration of sediment and nutrients for all but the most intense events. Certain events resulted in mixing in the dams and larger resultant outflow than inflow loads. These occurrences appear to be as a result of combinations of reservoir status, catchment antecedent conditions and rainfall depth and intensity. The nutrients loads between Bridge 1 and Bridge 2 stations reflect the bedrock control, where contributions from sugar cane hillslopes between these stations are not retained, even in the short wetland upstream of Bridge 2. Isotope analyses reveal that the headwaters, comprising 70% of the catchment area, contribute as little as 29% of the total catchment discharge, due to impoundments in this area. However, this contribution varies significantly for different events, reaching a maximum of 78% of the catchment discharge. It can therefore be concluded that nutrients and sediment migration in the Wartburg catchment is greatly influenced by connectivity. The δ18O and δ2H

  16. Inductive machine learning for improved estimation of catchment-scale snow water equivalent

    NASA Astrophysics Data System (ADS)

    Buckingham, David; Skalka, Christian; Bongard, Josh

    2015-05-01

    Infrastructure for the automatic collection of single-point measurements of snow water equivalent (SWE) is well-established. However, because SWE varies significantly over space, the estimation of SWE at the catchment scale based on a single-point measurement is error-prone. We propose low-cost, lightweight methods for near-real-time estimation of mean catchment-wide SWE using existing infrastructure, wireless sensor networks, and machine learning algorithms. Because snowpack distribution is highly nonlinear, we focus on Genetic Programming (GP), a nonlinear, white-box, inductive machine learning algorithm. Because we did not have access to near-real-time catchment-scale SWE data, we used available data as ground truth for machine learning in a set of experiments that are successive approximations of our goal of catchment-wide SWE estimation. First, we used a history of maritime snowpack data collected by manual snow courses. Second, we used distributed snow depth (HS) data collected automatically by wireless sensor networks. We compared the performance of GP against linear regression (LR), binary regression trees (BT), and a widely used basic method (BM) that naively assumes non-variable snowpack. In the first experiment set, GP and LR models predicted SWE with lower error than BM. In the second experiment set, GP had lower error than LR, but outperformed BT only when we applied a technique that specifically mitigated the possibility of over-fitting.

  17. Modeling of Visuospatial Perspectives Processing and Modulation of the Fronto-Parietal Network Activity during Action Imitation

    PubMed Central

    Oh, Hyuk; Gentili, Rodolphe J.; Reggia, James A.; Contreras-Vidal, José L.

    2013-01-01

    It has been suggested that the human mirror neuron system (MNS) plays a critical role in action observation and imitation. However, the transformation of perspective between the observed (allocentric) and the imitated (egocentric) actions has received little attention. We expand a previously proposed biologically plausible MNS model by incorporating general spatial transformation capabilities that are assumed to be encoded by the intraparietal sulcus (IPS) and the superior parietal lobule (SPL) as well as investigating their interactions with the inferior frontal gyrus and the inferior parietal lobule. The results reveal that the IPS/SPL could process the frame of reference and the viewpoint transformations, and provide invariant visual representations for the temporo-parieto-frontal circuit. This allows the imitator to imitate the action performed by a demonstrator under various perspectives while replicating results from the literatures. Our results confirm and extend the importance of perspective transformation processing during action observation and imitation. PMID:23366445

  18. Shale to Regolith Evolution: The Controls on Catchment Solute Fluxes

    NASA Astrophysics Data System (ADS)

    Sullivan, Pamela; Goddéris, Yves; Shi, Yuning; Singha, Kamini; Clarke, Brian; Schott, Jacques; Duff, Chritopher; Brantley, Susan

    2014-05-01

    Understanding the factors that control the formation of regolith and the evolution of pore space within regolith as it is moves upward to the surface is of global importance. Unfortunately, both access and high costs have been prohibitive in gathering information about the bedrock-regolith boundary. Recognizing the need for data at depth, the Critical Zone Observatory (CZO) network initiated the "Drill the Ridge" project. The goal of this project is to investigate fresh bedrock at each CZO and then to perform an array of downhole geophysical survey and geochemical analyses to understand regolith formation. In response to this call, several ridgetop boreholes were drilled at the Susquehanna Shale Hills CZO in 2012 and 2013. Here we present the optical televiewer and gamma logs of these boreholes, along with downcore bulk geochemical analysis to shed light on the geochemical and lithological controls on the evolution of the watershed. Observations of catchment hydrology are also being used with estimates of hydrologic parameters to quantify near-surface geologic evolution and geochemical fluxes associated with weathering at depth. To quantify the contribution of weathering fluxes from the mobile regolith, we then link the meteorological forcing from the North American Land Data Assimilation System (NLDAS-2), the fully-coupled land-surface Penn State Integrated Hydrologic Model (Flux-PIHM), and the geochemical box model WITCH. With this cascade of models, solute fluxes for the CZO are being simulated. At depth, the bulk geochemical analysis of ridgetop sediments indicates that pyrite had the deepest depletion front, which was concurrent with the regional water table position. Hydrologic data together with detailed borehole and bulk soil/rock geochemical analysis elucidated an eastern to western progression in lithology across the SSHCZO catchment controls fracture distribution and thus groundwater flow. Where shale and mudstone underlie the eastern portion of

  19. Assessing the simple dynamical systems approach in a Mediterranean context: application to the Ardeche catchment (France)

    NASA Astrophysics Data System (ADS)

    Adamovic, M.; Braud, I.; Branger, F.; Kirchner, J. W.

    2015-05-01

    This study explores how catchment heterogeneity and variability can be summarized in simplified models, representing the dominant hydrological processes. It focuses on Mediterranean catchments, characterized by heterogeneous geology, pedology and land use, as well as steep topography and a rainfall regime in which summer droughts contrast with high-rainfall periods in autumn. The Ardeche catchment (Southeast France), typical of this environment, is chosen to explore the following questions: (1) can such a Mediterranean catchment be adequately characterized by a simple dynamical systems approach and what are the limits of the method under such conditions? (2) what information about dominant predictors of hydrological variability can be retrieved from this analysis in such catchments? In this work we apply the data-driven approach of Kirchner (2009) to estimate discharge sensitivity functions that summarize the behaviour of four sub-catchments of the Ardeche, using low-vegetation periods (November-March) from 9 years of measurements (2000-2008) from operational networks. The relevance of the inferred sensitivity function is assessed through hydrograph simulations, and through estimating precipitation rates from discharge fluctuations. We find that the discharge sensitivity function is downward-curving in double-logarithmic space, thus allowing further simulation of discharge and non-divergence of the model, only during low-vegetation periods. The analysis is complemented by a Monte Carlo sensitivity analysis showing how the parameters summarizing the discharge sensitivity function impact the simulated hydrographs. The resulting discharge simulation results are good for granite catchments, which are likely to be characterized by shallow subsurface flow at the interface between soil and bedrock. The simple dynamical system hypothesis works especially well in wet conditions (peaks and recessions are well modelled). On the other hand, poor model performance is associated

  20. Transport of cyazofamid and kresoxim methyl in runoff at the plot and catchment scales

    NASA Astrophysics Data System (ADS)

    Lefrancq, Marie; Joaquín García Verdú, Antonio; Maillard, Elodie; Imfeld, Gwenaël; Payraudeau, Sylvain

    2013-04-01

    Surface runoff and erosion during the course of rainfall events represent major processes of pesticides transport from agricultural land to aquatic ecosystem. In general, field and catchment studies on pesticide transfer are carried out separately. A study at both scales may enable to improve the understanding of scale effects on processes involved in pesticides transport and to give clues on the source areas within an agricultural catchment. In this study, the transport in runoff of two widely used fungicides, i.e. kresoxim methyl (KM) and cyazofamid (CY) was assessed in a 43 ha vineyard catchment and the relative contribution of the total fungicides export from one representative plot was evaluated. During an entire period of fungicide application, from May to August 2011, the discharge and loads of dissolved and particle-laden KM and CY were monitored at the plot and catchment scales. The results showed larger export coefficient of KM and CY from catchment (0.064 and 0.041‰ for KM and CY respectively) than from the studied plot (0.009 and 0.023 ‰ for KM and CY respectively). It suggests that the plot margins especially the road network contributed as well to the fungicide loads. This result underlines the impact of fungicide drift on non-target areas. Furthermore, a larger rainfall threshold is necessary at the plot scale to trigger runoff and mobilise pesticides than on the road network. At the plot scale, a rapid dissipation of the both fungicides in the top soil was observed. It highlights that the risky period encompasses the first rainfall events triggering runoff after the applications. At both scales, KM and CY were not detected in suspended solids (i.e. > 0.7 µm). However their partitioning in runoff water differed. 64.1 and 91.8% of the KM load was detected in the dissolved phase (i.e. < 0.22 µm) at the plot and catchment scales respectively, whereas 98.7 and 100% of the CY load was detected in the particulate phase (i.e. between 0.22 and 0.7 µm

  1. Quantifying in-stream retention of nitrate at catchment scales using a practical mass balance approach.

    PubMed

    Schwientek, Marc; Selle, Benny

    2016-02-01

    As field data on in-stream nitrate retention is scarce at catchment scales, this study aimed at quantifying net retention of nitrate within the entire river network of a fourth-order stream. For this purpose, a practical mass balance approach combined with a Lagrangian sampling scheme was applied and seasonally repeated to estimate daily in-stream net retention of nitrate for a 17.4 km long, agriculturally influenced, segment of the Steinlach River in southwestern Germany. This river segment represents approximately 70% of the length of the main stem and about 32% of the streambed area of the entire river network. Sampling days in spring and summer were biogeochemically more active than in autumn and winter. Results obtained for the main stem of Steinlach River were subsequently extrapolated to the stream network in the catchment. It was demonstrated that, for baseflow conditions in spring and summer, in-stream nitrate retention could sum up to a relevant term of the catchment's nitrogen balance if the entire stream network was considered. PMID:26801154

  2. Primary Care Clinicians' Perspectives on Management of Skin and Soft Tissue Infections: An Iowa Research Network Study

    ERIC Educational Resources Information Center

    Daly, Jeanette M.; Ely, John W.; Levy, Barcey T.; Smith, Tara C.; Merchant, Mary L.; Bergus, George R.; Jogerst, Gerald J.

    2011-01-01

    An estimated 95,000 people developed methicillin-resistant "Staphylococcus aureus" (MRSA) infections during 2005 of which 14% were community-associated and 85% were hospital or other health setting associated, and 19,000 Americans died from these infections that year. Purpose: To explore health care providers' perspectives on management of skin…

  3. The RAFT Telemedicine Network: Lessons Learnt and Perspectives from a Decade of Educational and Clinical Services in Low- and Middle-Incomes Countries

    PubMed Central

    Bediang, Georges; Perrin, Caroline; Ruiz de Castañeda, Rafael; Kamga, Yannick; Sawadogo, Alexandre; Bagayoko, Cheick Oumar; Geissbuhler, Antoine

    2014-01-01

    Background: The objectives of this paper are to (i) provide an overview of the educational and clinical experiences of the Réseau en Afrique Francophone pour la Télémédecine (RAFT) network, (ii) analyze key challenges and lessons learnt throughout a decade of activity, and (iii) draw a vision and perspectives of its sustainability. Methods: The study was carried out following three main stages: (i) a literature review, (ii) the analysis of key documents, and (iii) discussions with key collaborators of the RAFT. Results: Réseau en Afrique Francophone pour la Télémédecine has been offering an important quantity of educational, clinical, and public health activities during the last decade. The educational activities include the weekly delivery of video-lectures for continuing and post-graduate medical education, the use of virtual patients for training in clinical decision making, research training activities using ICTs and other e-learning activities. The clinical and public health activities include tele-expertise to support health professionals in the management of difficult clinical cases, the implementation of clinical information systems in African hospitals, the deployment of mHealth projects, etc. Since 2010, the RAFT has been extended to the Altiplano in Bolivia and Nepal (in progress). Lessons Learnt and Perspectives: Important lessons have been learnt from the accumulated experiences throughout these years. These lessons concern: social and organization, human resources, technologies and data security, policy and legislation, and economy and financing. Also, given the increase of the activities and the integration of eHealth and telemedicine in the health system of most of the countries, the RAFT network faces many other challenges and perspectives such as learning throughout life, recognition, and valorization of teaching or learning activities, the impact evaluation of interventions, and the scaling up and transferability out of Africa of RAFT

  4. Informing Hydrological Drought Response in Headwater Catchments Using Water Storage Estimated From GRACE: Storage-Flow Dynamics

    NASA Astrophysics Data System (ADS)

    Gaffney, R.; Tyler, S. W.; Harpold, A. A.; Volk, J. M.

    2015-12-01

    Quantifying the relationship between subsurface water storage and streamflow is challenging due to heterogeneity of surface-groundwater interactions in space and time. Hence, point measurements of storage from wells are insufficient to characterize the storage across a catchment, especially in mountainous environments with complex geology. Here, we present a novel approach to quantify the storage-flow relationship for catchments in the Sierra Nevada Mountains. For 23 gages in the Hydro-Climatic Data Network, the 7-day average annual minimum flow (drought flow) was computed for years 2003 to 2015. We then aggregated, for each gage, the associated storage time-series dataset from 1o gridded measurements of monthly Terrestrial Water Storage (TWS) derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. Despite the significant mismatch between the spatial scales and temporal resolution, we found a strong empirical correlation between TWS and drought flow. From these relationships, we examined how physical characteristics of each catchment (such as size and geology) impact the observed nonlinear relationship between TWS and drought flow. Furthermore, we show how physical characteristics, such as geology/storage capacity, of catchments affect the sensitivity of decreasing flows to multi-year droughts. This research has the potential to help better quantify the streamflow-storage relationship in small mountainous catchments, as well as, classify catchments that may be more vulnerable to decreasing flows with multi-year droughts.

  5. Hydropedological insights when considering catchment classification

    NASA Astrophysics Data System (ADS)

    Bouma, J.; Droogers, P.; Sonneveld, M. P. W.; Ritsema, C. J.; Hunink, J. E.; Immerzeel, W. W.; Kauffman, S.

    2011-02-01

    Soil classification systems are analysed in relation to the functioning and characterisation of catchments. Soil classifications are useful to create systematic order in the overwhelming quantity of different soils in the world and to extrapolate data available for a given soil type to soils elsewhere with identical classifications. However, such classifications are based on permanent characteristics as formed by the soil forming factors over often very long periods of time and this does not necessarily match with characteristics and parameters needed for functional soil characterization focusing, for example, on catchment hydrology. Hydropedology has made contributions towards functional characterization of soils as is illustrated for recent hydrological catchment studies. However, much still needs to be learned about the physical behaviour of anisotropic, heterogeneous field soils with varying soil structures during the year and the suggestion is made to first focus on improving simulation of catchment hydrology, incorporating hydropedological expertise, before embarking on a classification effort which involves major input of time and involves the risk of distraction. In doing so, we advise to also define other characteristics for catchment performance than the traditionally measured discharge rates.

  6. Flood Nowcasting With Linear Catchment Models, Radar and Kalman Filters

    NASA Astrophysics Data System (ADS)

    Pegram, Geoff; Sinclair, Scott

    A pilot study using real time rainfall data as input to a parsimonious linear distributed flood forecasting model is presented. The aim of the study is to deliver an operational system capable of producing flood forecasts, in real time, for the Mgeni and Mlazi catchments near the city of Durban in South Africa. The forecasts can be made at time steps which are of the order of a fraction of the catchment response time. To this end, the model is formulated in Finite Difference form in an equation similar to an Auto Regressive Moving Average (ARMA) model; it is this formulation which provides the required computational efficiency. The ARMA equation is a discretely coincident form of the State-Space equations that govern the response of an arrangement of linear reservoirs. This results in a functional relationship between the reservoir response con- stants and the ARMA coefficients, which guarantees stationarity of the ARMA model. Input to the model is a combined "Best Estimate" spatial rainfall field, derived from a combination of weather RADAR and Satellite rainfield estimates with point rain- fall given by a network of telemetering raingauges. Several strategies are employed to overcome the uncertainties associated with forecasting. Principle among these are the use of optimal (double Kalman) filtering techniques to update the model states and parameters in response to current streamflow observations and the application of short term forecasting techniques to provide future estimates of the rainfield as input to the model.

  7. Evidence of the impact of urbanization on the hydrological regime of a medium-sized periurban catchment in France

    NASA Astrophysics Data System (ADS)

    Braud, I.; Breil, P.; Thollet, F.; Lagouy, M.; Branger, F.; Jacqueminet, C.; Kermadi, S.; Michel, K.

    2013-04-01

    SummaryIn this paper we explore several indicators to evidence the impact of land use change, and particularly of urbanization/artificialization on discharge series of periurban catchments. A first set of indicators is derived from the literature and describes the monthly and annual hydrological regime, low flows and high flows, and flow components. Statistical tests are also applied to assess the existence of trends/ruptures on the longest time series. In addition, new indicators, especially built to show the impact of sewer overflow devices (SODs) and infiltration into sewer networks are proposed. The method is applied to the Yzeron (150 km2) catchment, located close to Lyon city (France) where various discharge gauges with a variable time step are available on sub-catchments ranging from a few to 130 km2 (some of them nested), with a large variety of land uses (forest, agricultural land, artificialized areas). In addition, discharge is also measured in a SOD and a combined sewer network so that the relevance of the new proposed indicators can be assessed. In the largest sub-catchments, the results show a decrease of specific discharge from upstream to downstream corresponding to an increase of artificialized areas, except for high flows. When a SOD is present, the specific discharge is increased for frequencies larger than 50%, and the frequency of zero daily discharge is decreased. Waste water can be the only source of water in autumn month in a 4.1 km2 sub-catchment. Base flow is also decreased for the most urbanized catchments. Our results confirm the impact of SODs on the modification of the flood regime, with an increase of frequent floods, but a marginal impact on the largest floods, mainly governed by saturation of the rural parts of the catchments. The decomposition of the sewer discharge shows that, on an annual basis, infiltration in the sewer network accounts for 30% of the total discharge and runoff due to rainwater to about 40% (the remaining being

  8. What can we learn from the hydrological modeling of small-scale catchments for the discharge and water balance modeling of mesoscale catchments?

    NASA Astrophysics Data System (ADS)

    Cornelissen, Thomas; Diekkrüger, Bernd; Bogena, Heye

    2015-04-01

    The application of 3D hydrological models remains a challenge both in research and application studies because the parameterization not only depends on the amount and quality of data available for calibration and validation but also on the spatial and temporal model resolution. In recent years, the model parameterization has improved with the availability of high resolution data (e.g. eddy-covariance, wireless soil sensor networks). Unfortunately, these high resolution data are typically only available for small scale research test sites. This study aims to upscale the parameterization from a highly equipped, small-scale catchment to a mesoscale catchment in order to reduce the parameterization uncertainty at that scale. The two nested catchments chosen for the study are the 0.38 km² large spruce covered Wüstebach catchment and the 42 km² large Erkensruhr catchment characterized by a mixture of spruce and beech forest and grassland vegetation. The 3D hydrogeological model HydroGeoSphere (HGS) has already been setup for the Wüstebach catchment in a previous study with a focus on the simulation performance of soil water dynamics and patterns. Thus, the parameterization process did not only optimize the water balance components but the catchment's wireless soil sensor network data were utilized to calibrate porosities in order to improve the simulation of soil moisture dynamics. In this study we compared different HGS model realizations for the Erkensruhr catchment with different input data. For the first model realization, the catchment is treated heterogeneous in terms of soil properties and topography but homogeneous with respect to land use, precipitation and potential evapotranspiration. For this case, the spruce forest parameterization and the climate input data were taken directly from the small-scale Wüstebach model realization. Next, the calibrated soil porosity for the Wüstebach catchment is applied to the Erkensruhr. Further model realizations

  9. Contrasting Patterns of Fine Fluvial Sediment Delivery in Two Adjacent Upland Catchments

    NASA Astrophysics Data System (ADS)

    Perks, M.; Bracken, L.; Warburton, J.

    2010-12-01

    Quantifying patterns of fine suspended sediment transfer in UK upland rivers is of vital importance in combating the damaging effects of elevated fluxes of suspended sediment, and sediment associated transport of contaminants, on in-stream biota. In many catchments of the UK there is still a lack of catchment-wide understanding of both the spatial patterns and temporal variation in fine sediment delivery. This poster describes the spatial and temporal distribution of in-stream fine sediment delivery from a network of 44 time-integrated mass flux samplers (TIMs) in two adjacent upland catchments. The two catchments are the Esk (210 km2) and Upper Derwent (236 km2) which drain the North York Moors National Park. Annual suspended sediment loads in the Upper Derwent are 1273 t, whereas in the Esk catchment they are greater at 1778 t. Maximum yields of 22 t km-2 yr -1 were measured in the headwater tributaries of the Rye River (Derwent), whereas peak yields in the Esk are four times greater (98 t km-2 yr-1) on the Butter Beck subcatchment. Analysis of the within-storm sediment dynamics, indicates that the sediment sources within the Upper Derwent catchment are from distal locations possibly mobilised by hillslope runoff processes, whereas in the Esk, sediment sources are more proximal to the channel e.g. within channel stores or bank failures. These estimates of suspended sediment flux are compared with the diffuse pollution potential generated by a risk-based model of sediment transfer (SCIMAP) in order to assess the similarity between the model predictions and observed fluxes.

  10. Digital divide 2.0: the role of social networking sites in seeking health information online from a longitudinal perspective.

    PubMed

    Feng, Yang; Xie, Wenjing

    2015-01-01

    Adopting a longitudinal angle, this study analyzed data from the Pew Internet's Health Tracking Survey in 2006, 2008, and 2010 to identify potential communication inequalities in social networking site use. Results showed that with the growing role of social networking site use in predicting people's likelihood of seeking health information online, the socioeconomic and demographic factors that contributed to the disparities in social networking site use could also lead to disparities in seeking health information online. Also, results indicated that people are more likely to seek heath-related information online if they or their close family or friends have a chronic disease situation. PMID:25119019

  11. The many levels of causal brain network discovery. Comment on "Foundational perspectives on causality in large-scale brain networks" by M. Mannino and S.L. Bressler

    NASA Astrophysics Data System (ADS)

    Valdes-Sosa, Pedro A.

    2015-12-01

    Unraveling the dynamically changing networks of the brain is probably the single most important current task for the neurosciences. I wish to commend the authors on this refreshing and provocative paper [1], which not only recapitulates some of the longstanding philosophical difficulties involved in the analysis of causality in the sciences, but also summarizes current work on statistical methods for determining causal networks in the brain. I fully concur with several of the opinions defended by the authors: The most fruitful level of analysis for systems neuroscience is that of neural masses, each comprising thousands of neurons. This is what is known as the mesoscopic scale.

  12. Before and After Integrated Catchment Management in a Headwater Catchment: Changes in Water Quality

    NASA Astrophysics Data System (ADS)

    Hughes, Andrew O.; Quinn, John M.

    2014-12-01

    Few studies have comprehensively measured the effect on water quality of catchment rehabilitation measures in comparison with baseline conditions. Here we have analyzed water clarity and nutrient concentrations and loads for a 13-year period in a headwater catchment within the western Waikato region, New Zealand. For the first 6 years, the entire catchment was used for hill-country cattle and sheep grazing. An integrated catchment management plan was implemented whereby cattle were excluded from riparian areas, the most degraded land was planted in Pinus radiata, channel banks were planted with poplar trees and the beef cattle enterprise was modified. The removal of cattle from riparian areas without additional riparian planting had a positive and rapid effect on stream water clarity. In contrast, the water clarity decreased in those sub-catchments where livestock was excluded but riparian areas were planted with trees and shrubs. We attribute the decrease in water clarity to a reduction in groundcover vegetation that armors stream banks against preparatory erosion processes. Increases in concentrations of forms of P and N were recorded. These increases were attributed to: (i) the reduction of instream nutrient uptake by macrophytes and periphyton due to increased riparian shading; (ii) uncontrolled growth of a nitrogen fixing weed (gorse) in some parts of the catchment, and (iii) the reduction in the nutrient attenuation capacity of seepage wetlands due to the decrease in their areal coverage in response to afforestation. Our findings highlight the complex nature of the water quality response to catchment rehabilitation measures.

  13. How old is upland catchment water?

    NASA Astrophysics Data System (ADS)

    Hofmann, Harald; Cartwright, Ian; Morgenstern, Uwe; Gilfedder, Benjamin

    2014-05-01

    Understanding the dynamics of water supply catchments is an essential part of water management. Upland catchments provide a continuous, reliable source of high quality water not only for some of the world's biggest cities, but also for agriculture and industry. Headwater streams control river flow in lowland agricultural basins as the majority of river discharge emerges from upland catchments. Many rivers are perennial and flow throughout the year, even during droughts. However, it is still unclear how reliable and continuous upland catchment water resources really are. Despite many efforts in upland catchment research, there is still little known about where the water is stored and how long it takes to travel through upper catchments. Resolving these questions is crucial to ensure that this resource is protected from changing land use and to estimate potential impacts from a changing climate. Previous research in this important area has been limited by existing measurement techniques. Knowledge to date has relied heavily on the use of variation in stable isotope signals to estimate the age and origin of water from upland catchments. The problem with relying on these measures is that as the water residence time increases, the variation in the stable isotope signal decreases. After a maximum period of four years, no variation can be detected This means that to date, the residence time in upland catchments is likely to have been vastly underestimated. Consequently, the proportion of water flow out of upland river catchments to the total river flow is also underestimated. Tritium (3H) combines directly with water molecules and enters the flow paths with the infiltrating water. Its half-life (12.32 years) makes it ideal to describe residence times in upper catchment reservoirs as it can theoretically measure water up to about 150 years old. The bomb pulse peak in the southern hemisphere was several orders of magnitude lower than in the northern hemisphere. Hence the

  14. Validation of Pacific Northwest hydrologic landscapes at the catchment scale

    EPA Science Inventory

    The interaction between the physical properties of a catchment (form) and climatic forcing of precipitation and energy control how water is partitioned, stored, and conveyed through a catchment (function). Hydrologic Landscapes (HLs) were previously developed across Oregon and de...

  15. Terrestrial and in-stream influences on the spatial variability of nitrate in a forested headwater catchment

    NASA Astrophysics Data System (ADS)

    Scanlon, Todd M.; Ingram, Spencer M.; Riscassi, Ami L.

    2010-06-01

    A vast majority of monitoring programs designed to assess nutrient fluxes from headwater systems rely upon temporally intensive sampling at a single position within the stream network, essentially measuring the integrated response of the catchment. Missing from such an approach is spatial information related to how nutrient availability varies throughout the network, where freshwater biota live and where biogeochemical processes ultimately shape the downstream water chemistry. Here, we examine the spatial distribution of nitrate (NO3-) concentrations within the Paine Run catchment, a forested headwater catchment in Shenandoah National Park, Virginia. Nitrate concentrations throughout the stream network were measured as part of synoptic surveys conducted in 1992-1994, in the aftermath of region-wide gypsy moth defoliation that caused dramatic increases in stream water NO3- concentrations. A follow-up synoptic survey was conducted in 2007, when the stream water NO3- concentrations had returned to predefoliation levels. Common to each of the eight synoptic surveys were observations of multiple-fold declines in NO3- concentration along the main stem of the stream network from the headwaters to the catchment outlet. A portion of this decline was caused by dilution, as water input by tributaries at the lower elevations of the catchment tended to have lower NO3- concentrations. A stream network model was applied to determine the relative contributions of terrestrial versus in-stream processes to the spatial variability of the NO3- concentrations. Model results suggest that even though nitrate removal within the stream network can be substantial, terrestrial factors that determine the NO3- inputs to streams account for the vast majority of the spatial variability in stream water NO3- concentrations.

  16. Tracking multiple sediment cascades at the river network scale identifies controls and emerging patterns of sediment connectivity

    NASA Astrophysics Data System (ADS)

    Schmitt, Rafael J. P.; Bizzi, Simone; Castelletti, Andrea

    2016-05-01

    Sediment connectivity in fluvial networks results from the transfer of sediment between multiple sources and sinks. Connectivity scales differently between all sources and sinks as a function of distance, source grain size and sediment supply, network topology and topography, and hydrologic forcing. In this paper, we address the challenge of quantifying sediment connectivity and its controls at the network scale. We expand the concept of a single, catchment-scale sediment cascade toward representing sediment transport from each source as a suite of individual cascading processes. We implement this approach in the herein presented CAtchment Sediment Connectivity And DElivery (CASCADE) modeling framework. In CASCADE, each sediment cascade establishes connectivity between a specific source and its multiple sinks. From a source perspective, the fate of sediment is controlled by its detachment and downstream transport capacity, resulting in a specific trajectory of transfer and deposition. From a sink perspective, the assemblage of incoming cascades defines provenance, sorting, and magnitude of sediment deliveries. At the network scale, this information reveals emerging patterns of connectivity and the location of bottlenecks, where disconnectivity occurs. In this paper, we apply CASCADE to quantitatively analyze the sediment connectivity of a major river system in SE Asia. The approach provides a screening model that can support analyses of large, poorly monitored river systems. We test the sensitivity of CASCADE to various parameters and identify the distribution of energy between the multiple, simultaneously active sediment cascades as key control behind network sediment connectivity. To conclude, CASCADE enables a quantitative, spatially explicit analysis of network sediment connectivity with potential applications in both river science and management.

  17. Assessment of suspended matter transport in a large agricultural catchment using the MOHID water modelling system

    NASA Astrophysics Data System (ADS)

    David, Bailly; David, Brito; Chantha, Oeurng; Ramiro, Neves; Sabine, Sauvage; Sánchez-Pérez, José-Miguel

    2010-05-01

    Suspended sediment transport from agricultural catchments to stream networks is responsible for impaired water quality, reservoir sedimentation and the transport of sediment-bound pollutants (pesticides, particulate nutrients, metals and other adsorbed toxic substances). The dynamic of pollutants adsorbed on sediment and associated with particulate organic carbon, from land areas into stream network arises mainly from erosion and sedimentation processes. It is known that up to 90% of suspended sediment is transported during flood event and therefore quick flood events have a major impact on pollutant transport. This study - part of the EU AguaFlash (http://www.aguaflash-sudoe.eu/) project - examined and quantified suspended sediment dynamics from catchment to river (erosion, transport, deposition on hillside and in the river). Semi-distributed, physics-based watershed or reservoir models are generally used to simulate sediment dynamics. One of the limitations of this kind of modelling is that transport along agricultural field and the possibility of deposition of suspended sediments in hillslopes are not considered. Consequently, all sediments eroded are assumed to be accumulated in the river and the sediment and associated pollutant dynamics are over- or under-estimated. In our approach, the mechanistic physics-based water modelling system MOHID (http://www.mohid.com) was used to quantify soil erosion and sediment transport processes at the local and macroscopic scale. This paper present the erosion and transport mathematical model and modelling strategy used and compares our initial results with filed data obtained on an 1100 km² intensive agricultural catchment (Save catchment, South-west France) during 2007-2009 and with simulation data produced using SWAT (Soil and Water Assessment Tool, 2005 version). The contribution of the MOHID model compared with that of the semi-distributed SWAT model is discussed. Keywords: Erosion, suspended sediment, transport

  18. Identification of internal flow dynamics in two experimental catchments

    USGS Publications Warehouse

    Hansen, D.P.; Jakeman, A.J.; Kendall, C.; Weizu, G.

    1997-01-01

    Identification of the internal flow dynamics in catchments is difficult because of the lack of information in precipitation -stream discharge time series alone. Two experimental catchments, Hydrohill and Nandadish, near Nanjing in China, have been set up to monitor internal flows reaching the catchment stream at various depths, from the surface runoff to the bedrock. With analysis of the precipitation against these internal discharges, it is possible to quantify the time constants and volumes associated with various flowpaths in both catchments.

  19. Picturing and modelling catchments by representative hillslopes

    NASA Astrophysics Data System (ADS)

    Loritz, Ralf; Hassler, Sibylle; Jackisch, Conrad; Zehe, Erwin

    2016-04-01

    Hydrological modelling studies often start with a qualitative sketch of the hydrological processes of a catchment. These so-called perceptual models are often pictured as hillslopes and are generalizations displaying only the dominant and relevant processes of a catchment or hillslope. The problem with these models is that they are prone to become too much predetermined by the designer's background and experience. Moreover it is difficult to know if that picture is correct and contains enough complexity to represent the system under study. Nevertheless, because of their qualitative form, perceptual models are easy to understand and can be an excellent tool for multidisciplinary exchange between researchers with different backgrounds, helping to identify the dominant structures and processes in a catchment. In our study we explore whether a perceptual model built upon an intensive field campaign may serve as a blueprint for setting up representative hillslopes in a hydrological model to reproduce the functioning of two distinctly different catchments. We use a physically-based 2D hillslope model which has proven capable to be driven by measured soil-hydrological parameters. A key asset of our approach is that the model structure itself remains a picture of the perceptual model, which is benchmarked against a) geo-physical images of the subsurface and b) observed dynamics of discharge, distributed state variables and fluxes (soil moisture, matric potential and sap flow). Within this approach we are able to set up two behavioral model structures which allow the simulation of the most important hydrological fluxes and state variables in good accordance with available observations within the 19.4 km2 large Colpach catchment and the 4.5 km2 large Wollefsbach catchment in Luxembourg without the necessity of calibration. This corroborates, contrary to the widespread opinion, that a) lower mesoscale catchments may be modelled by representative hillslopes and b) physically

  20. Development of regionalisation procedures using a multi-model approach for flow simulation in an ungauged catchment

    NASA Astrophysics Data System (ADS)

    Goswami, M.; O'Connor, K. M.; Bhattarai, K. P.

    2007-02-01

    SummaryFlow simulation in ungauged catchments is presently regarded as one of the most challenging tasks in surface water hydrology. Many of the ungauged catchments are located in the headwaters of rivers in mountainous regions of the world having enormous potential for sustainable water resource development. However, due to inaccessibility, rugged and inhospitable terrain, and historical lack of foresight concerning the need to have these headwaters adequately gauged, their potential is not readily realizable. Many downstream sites also suffer from non-availability of site-specific data as even in countries having extensive networks of gauged stations data may not be available at sites where these are most needed. As predictive tools for water resources, water quality, natural hazard mitigation and water availability assessment are generally data-driven, the lack of adequate hydrometric records poses difficult problems for planners, engineers, managers, and stake-holders alike. In this study, a methodology is developed for flow simulation in ungauged catchments using a regionalisation and multi-model approach involving a suite of rainfall-runoff models and combination techniques. Daily observed hydrometeorological data for 12 French catchments are used for illustrating the procedures. Following a preliminary investigation of the regional homogeneity of that group of catchments, three regional flow simulation techniques are applied. Although all 12 catchments are gauged, initially each catchment is successively considered as being ungauged for the purpose of flow simulation in that catchment, their actual discharges being subsequently used for evaluating the performance of the flow estimation procedures for the catchment. The Nash-Sutcliffe efficiency index ( R2) is used for assessing and ranking the relative performances of the regionalisation-model couples to identify the most appropriate couple for the region. The final step of applying that couple to a truly

  1. Paleofluvial landscape inheritance for Jakobshavn Isbræ catchment, Greenland

    NASA Astrophysics Data System (ADS)

    Cooper, M. A.; Michaelides, K.; Siegert, M. J.; Bamber, J. L.

    2016-06-01

    Subglacial topography exerts strong controls on glacier dynamics, influencing the orientation and velocity of ice flow, as well as modulating the distribution of basal waters and sediment. Bed geometry can also provide a long-term record of geomorphic processes, allowing insight into landscape evolution, the origin of which may predate ice sheet inception. Here we present evidence from ice-penetrating radar data for a large dendritic drainage network, radiating inland from Jakobshavn Isbræ, Greenland's largest outlet glacier. The size of the drainage basin is ˜450,000 km2 and accounts for about 20% of the total land area of Greenland. Topographic and basin morphometric analyses of an isostatically uplifted (ice-free) bedrock topography suggests that this catchment predates ice sheet initiation and has likely been instrumental in controlling the location and form of the Jakobshavn ice stream, and ice flow from the deep interior to the margin, now and over several glacial cycles.

  2. Parsimonious hydrological modeling of urban sewer and river catchments

    NASA Astrophysics Data System (ADS)

    Coutu, Sylvain; Del Giudice, Dario; Rossi, Luca; Barry, D. A.

    2012-09-01

    SummaryA parsimonious model of flow capable of simulating flow in natural/engineered catchments and at WWTP (Wastewater Treatment Plant) inlets was developed. The model considers three interacting, dynamic storages that account for transfer of water within the system. One storage describes the “flashy” response of impervious surfaces, another pervious areas and finally one storage describes subsurface flow. The sewerage pipe network is considered as an impervious surface and is thus included in the impervious surface storage. In addition, the model assumes that water discharged from several CSOs (combined sewer overflows) can be accounted for using a single, characteristic CSO. The model was calibrated on, and validated for, the Vidy Bay WWTP, which receives effluent from Lausanne, Switzerland (population about 200,000), as well as for an overlapping urban river basin. The results indicate that a relatively simple approach is suitable for predicting the responses of interacting engineered and natural hydrosystems.

  3. Trends in floods in West Africa: analysis based on 11 catchments in the region

    NASA Astrophysics Data System (ADS)

    Nka, B. N.; Oudin, L.; Karambiri, H.; Paturel, J. E.; Ribstein, P.

    2015-11-01

    After the drought of the 1970s in West Africa, the variability in rainfall and land use changes mostly affected flow, and recently flooding has been said to be an increasingly common occurrence throughout the whole of West Africa. These changes have raised many questions about the impact of climate change on the flood regimes in West African countries. This paper investigates whether floods are becoming more frequent or more severe and to what extent climate patterns have been responsible for these changes. We analyzed the trends in the floods occurring in 11 catchments within West Africa's main climate zones. The methodology includes two methods for sampling flood events, namely the AM (annual maximum) method and the POT (peak over threshold), and two perspectives of analysis are presented: long-term analysis based on two long flood time series and a regional perspective involving 11 catchments with shorter series. The Mann-Kendall trend test and the Pettitt break test were used to detect nonstationarities in the time series. The trends detected in flood time series were compared to the rainfall index trends and vegetation indices using contingency tables in order to identify the main driver of change in flood magnitude and flood frequency. The relation between the flood index and the physiographic index was evaluated through a success criterion and the Cramer criterion calculated from the contingency tables. The results show the existence of trends in flood magnitude and flood frequency time series, with two main patterns. Sahelian floods show increasing flood trends and one Sudanian. catchment presents decreasing flood trends. For the overall catchments studied, trends in the maximum 5-day consecutive rainfall index (R5d) show good coherence with trends in flood, while the trends in normalized difference vegetation indices (NDVIs) do not show a significant agreement with flood trends, meaning that this index has possibly no impact on the behavior of floods in

  4. Integrating structural and functional connectivity to characterize sediment dynamics in a small Alpine catchment

    NASA Astrophysics Data System (ADS)

    Cavalli, Marco; Crema, Stefano; Blok, Michiel; Lucía, Ana; Comiti, Francesco; Marchi, Lorenzo; Keesstra, Saskia

    2016-04-01

    Sediment connectivity can be regarded as a descriptor of the internal linkages between different landscape components within a catchment. The recent focus of the scientific community on connectivity related topics, both concerning hydrological and sediment connectivity, stresses the importance of understanding the main active pathways for a better estimation of energy and matter transfer at catchment scale. This task can be addressed using topography-based indices that analyse the linkages between landscape units. This approach to characterize connectivity is known as structural connectivity. The main limitation of structural connectivity is that it does not account for the processes driving sediment and energy fluxes (i.e., functional connectivity). In this work the integration between structural and functional approaches is proposed for characterizing sediment connectivity in mountain catchments. The structural approach, based on a topography-based sediment connectivity index, was used for assessing hillslope-to-channel connectivity. Since field data on processes driving sediment transport along the channel network are available, a functional approach has been devised to estimate within-channel connectivity. An index of unit stream power computed from the hydraulic properties of the channel (i.e., discharge, slope and channel width) has been compared with the critical unit stream power computed from incipient motion thresholds derived from field data to identify the cells of the Digital Terrain Model (DTM) in which sediment can be mobilized under near-bankfull conditions. The index expressing the within-channel connectivity is given by the length of the reaches consisting of contiguous cells that exceed the critical unit stream power. During high-magnitude floods, when unit stream power values exceed the threshold for incipient motion, channels experience an increase in both hydrological and sediment connectivity. The proposed index characterizes those sections

  5. Modeling daily streamflow at ungauged catchments: What information is necessary?

    NASA Astrophysics Data System (ADS)

    Patil, S.; Stieglitz, M.

    2011-12-01

    Streamflow modeling at ungauged catchments involves transfer of information (viz., model structure and parameters) from gauged to ungauged catchments that are judged to be hydrologically similar. In this study, we focus on identifying: (1) what constitutes the critical information that needs to be transferred among hydrologically similar catchments to achieve good predictability using models at ungauged sites, and (2) which is the best approach for transferring this information from gauged to ungauged catchments. We develop a simple hydrologic model with minimal calibration requirement and implement it over 756 catchments located across the continental United States. The model computes water balance at a daily time-step and conceptualizes subsurface runoff through a storage-dependent exponential decline in saturated hydraulic conductivity. Snow accumulation and melt are modeled using the thermal degree-day concept. The calibrated model performs better in humid runoff-dominated regions than in the drier evapotranspiration-dominated regions. Results show that within a region, transfer of hydrograph recession information alone is sufficient for reliable streamflow predictions at ungauged catchments. Information transfer from spatially proximate gauged catchments provides better streamflow predictability at ungauged catchments than transfer from catchments identified as physically similar. When considering spatially proximate catchments, information transfer from multiple donor catchments is preferable to transfer from a single donor catchment.

  6. How agricultural landscape features control the transfer of nutrient and eutrophication risk in headwater catchments?

    NASA Astrophysics Data System (ADS)

    Dupas, Rémi; Delmas, Magalie; Dorioz, Jean-Marcel; Garnier, Josette; Moatar, Florentina; Gascuel-Odoux, Chantal

    2014-05-01

    The degradation of surface water quality due to nitrogen and phosphorus pollution is a major concern for drinking water quality and ecosystems health. Numerous studies have demonstrated that headwater catchments are large contributors of nutrient loads to downstream waters bodies. In terms of scientific understanding of the processes controlling nutrient transfers, headwater catchments are relevant spatial units to study the role of landscape features because of the relatively low contribution of point sources and in-stream processes compared to larger river networks. This paper presents an analysis of the variability in space and time of observed N and P loads for a dataset of 160 headwater catchments at a national level (France). A multivariate statistical analysis was performed to relate observed N and P loads to spatial attributes describing agricultural landscapes and the physical characteristics of the catchments: climate, topography, soils, etc. We identified factors controlling N and P loads and N:P:Si ratios in freshwaters; and specifically spatially described factors, by considering river corridors and interaction between soils and land use attributes. The same catchment dataset is used to calibrate the Nutting model, i.e. a statistical model developed to estimate nutrient emission to surface water, using readily available data in France (Dupas et al., 2013). Nutting is a statistical model linking N/P sources and catchment land and river attributes to estimate mean interannual nitrate-N, total-N, dissolved-P and total-P loads. It allows to extrapolate nutrient loads in unmonitored catchments at a national level and to estimate the risk of eutrophication in freshwaters considering Redfield's (1963) N:P:Si ratios. Results show that N is in excess over silica in 93% of French headwater bodies, and that phosphorus is in excess over silica in 26%-65% of French headwater catchments. This means that between 26% and 63% of French headwaters are at risk of

  7. The artifcial catchment Chicken Creek as a tool to study initial ecosystem development

    NASA Astrophysics Data System (ADS)

    Schaaf, W.; Elmer, M.; Fischer, A.; Gerwin, W.; Nenov, R.

    2011-12-01

    areas with evolving terrestrial or aquatic characteristics and from a very episodic to a more permanent stream network and discharge, together with the observed vegetation dynamics increased site diversity and heterogeneity with respect to water and nutrient availability and transformation processes compared to the more homogenous conditions at point zero. We expect that these more permanent structures and patterns established after five years will greatly influence the future development of the catchment with respect to e.g. input and accumulation of soil organic matter, nitrogen input and availability by symbiotic microbial N-fixation, development of root systems and soil food webs, weathering and soil formation, element cycling, and the water and element budget at the catchment scale.

  8. Estimation of groundwater contribution in runoff from small agricultural dominated catchments

    NASA Astrophysics Data System (ADS)

    Deelstra, Johannes; Jansons, Viesturs; Lagzdiņš, Ainis

    2013-04-01

    Latvia. Each set consisted of a field providing both surface and subsurface runoff located within the catchment. Different filters were tested but the one developed by Chapman & Maxwell (1996) was selected. An improved filter parameter value was obtained, resulting in more realistic values for BFI in Norwegian catchments, being in the order of 10%. The values for the Latvian catchments were slightly higher, the main reason for this being soil types and geological settings. The results indicate that care should be taken in selecting the digital filter value for catchments having flashy runoff behaviour. This might lead to wrong estimates of baseflow contribution which can have negative effects on modelling hydrology, pollutant transport and the selection of mitigation measures at the scale of small agricultural catchments. References Chapman, T.G., Maxwell, A.I . 1996. Baseflow separation - comparison of numerical methods with tracer experiments. Institute Engineers Australia National Conference. Publ. 96/05, 539-545 Deelstra, J., Eggestad, H.O., Iital, A., Jansons, V. and Barkved, L.J. (2010), "Time resolution and hydrological characteristics in agricultural catchments", in Hermann, A. and Schumann, S. (Eds), Status and Perspectives of Hydrology in Small Basins, Vol. 336, IAHS Publication, pp. 138 - 143.

  9. The hydrological and economic impacts of changing water allocations in political regions within the peri-urban South Creek catchment in Western Sydney II: Scenarios

    NASA Astrophysics Data System (ADS)

    Davidson, Brian; Malano, Hector; Nawarathna, Bandara; Maheshwari, Basant

    2013-08-01

    The aim in this paper is to assess the hydrological and economic impacts of deploying water in the political jurisdictions of the peri-urban South Creek catchment of Western Sydney. This catchment has been identified as the region in which the city of Sydney will grow into in the future, with a plan to move an extra one million people into the catchment in the next 25-30 years. In conjunction with this expansion, a plan exists to augment the existing water supply by treating waste water effluent, harvesting stormwater and improving irrigation efficiency, along with a strategy for saving water on farms. Water in this catchment is operated by and in the interests of society, where decisions on its allocation have a political perspective to them. However, the growth within this catchment and the water augmentation strategies are not split evenly amongst the political entities within this catchment, namely the Local Government Authorities. An integrated hydro-economic model segregated according to the political entities in the catchment is used in this study to address a range of water saving scenarios raised by stakeholders. The trade-offs inherent in all water allocation decisions on a regional basis are made transparent in this model and its political ramifications, defined as the impacts on different political regions, are identified. In analysing the measures designed to save water across the catchment, none resulted in a positive Net Present Value. Even just expanding the system to accommodate one million extra people resulted in significant economic losses. In addition, the impact of each measure in each political region was markedly different. The purpose of this study is to provide stakeholders in individual local government regions with evidence of the costs and impacts of rational decisions to change the management of water resources in South Creek catchment.

  10. Influence of urbanization pattern on stream flow of a peri-urban catchment under Mediterranean climate

    NASA Astrophysics Data System (ADS)

    Ferreira, Carla S. S.; Walsh, Rory P. D.; Ferreira, António J. D.; Steenhuis, Tammo S.; Coelho, Celeste A. O.

    2015-04-01

    . Percentage impermeable surface seems to control streamflow particularly during dry periods. Winter runoff was 2-4 times higher than total river flow in the summer dry season in highly urbanized areas, but was 21-fold higher in winter in the least urbanized sub-catchment, denoting greater flow connectivity enhanced by increased soil moisture. Although impermeable surfaces are prone to generate overland flow, the proximity to the stream network is an important parameter determining their hydrological impacts. During the monitoring period, the enlargement of 2% of the urban area at downslope locations in the Covões sub-catchment, led to a 6% increase in the runoff coefficient. In contrast, the urban area increase from 9 to 25% mainly in upslope parts of the Quinta sub-catchment did not increase the peak streamflow due to downslope infiltration and surface retention opportunities. Despite impermeable surfaces enhance overland flow, some urban features (e.g. walls and road embankments) promote surface water retention. The presence of artificial drainage systems, on the other hand, enhances flow connectivity, leading to increasing peak flow and quicker response times (~10 minutes versus 40-50 minutes) as in the Covões sub-catchment. Urbanization impact on streamflow responses may be minimized through planning the land-use mosaic so as to maximize infiltration opportunities. Knowledge of the influence of distinct urban mosaics on flow connectivity and stream discharge is therefore important to landscape managers and should guide urban planning in order to minimize flood hazards.

  11. Global investigation of vegetation impact on mean annual catchment evapotranspiration

    NASA Astrophysics Data System (ADS)

    Peel, Murray C.; McMahon, Thomas A.; Finlayson, Brian L.

    2010-05-01

    Historically, relationships between catchment vegetation type, evapotranspiration and runoff have been assessed primarily through paired catchment studies. The literature contains results from over 200 of these studies from around the world but two factors limit the applicability of the results to the wider domain. Firstly, catchment areas are generally small (<10 km2). Secondly, the range of climate types is narrow, with temperate (Köppen C) and cold (Köppen D) climate types in the majority. Here we present results from a global assessment of the impact of vegetation type on mean annual catchment evapotranspiration for a large, spatially and climatically diverse dataset of 699 catchments. This assessment is based on analysis of areal precipitation, temperature, runoff, and land cover information from each catchment, which differs from the paired catchment methodology where streamflow responses to a controlled land cover change are assessed. When catchments are grouped by vegetation type, any evidence of differing vegetation impact on actual evapotranspiration will be observed through differences in mean annual actual evapotranspiration, defined as precipitation minus runoff. Stratifying catchments by climate type was observed to be important when assessing the vegetation impact on evapotranspiration. Tropical and temperate forested catchments had significantly higher median evapotranspiration (~170mm and ~130mm, respectively) than non-forested catchments. Cold forested catchments unexpectedly had significantly lower median evapotranspiration (~90mm) than non-forested catchments. No significant difference in median evapotranspiration was found between temperate evergreen and deciduous forested catchments, though sample sizes were small. Temperate evergreen needleleaf forested catchments had significantly higher median evapotranspiration than evergreen broadleaf forested catchments, though again sample sizes were small. The significant difference in median

  12. Hydrologic predictions on ungauged catchments using deterministic distributed modelling system

    NASA Astrophysics Data System (ADS)

    Tachecí, Pavel; Kimlová, Martina

    2010-05-01

    simulation. Back-calculation of initial conditions using regular observation network data is applied to minimize errors of water balance. Scaled values of simulated deficit of water content in unsaturated zone, aggregated over user-defined areas, were chosen as flash-flood danger indicator. User - defined templates for presentation of results are available. The advantage of this approach sustains in a fact, that it uses three different types of input data. Further on, it may give results for user-defined areas, which are not necessarily connected to on-line flow gauging station profiles. This means, that it is capable to give flash-flood danger maps also for upper catchments and small tributaries, which are not included in the network of main warning profiles.

  13. Morphotectonic interpretation of the Makuyuni catchment in Northern Tanzania using DEM and SAR data

    NASA Astrophysics Data System (ADS)

    Flores-Prieto, Elio; Quénéhervé, Geraldine; Bachofer, Felix; Shahzad, Faisal; Maerker, Michael

    2015-11-01

    Landscapes in the East African Rift System are formed by complex effects of the active continental extension zone. These effects are caused by the Somalian micro-plate's eastward drift away from the Nubian plate, as well as by volcanic, erosional and depositional processes. Tectonic processes in this region have significantly contributed to the formation of the current drainage systems and landforms. This study focuses on the morphotectonics of the Makuyuni catchment with an analysis of topography, drainage networks, stream longitudinal profiles and lineaments. This analysis reveals a morphostructural control with an N-S trend for the uplifted Masai Block, as well as tectonic deformation in the Makuyuni catchment area (NE of Lake Manyara). Whereas basin asymmetry analysis shows basin tilting associated with active faulting and uplifting near the Essimingor volcanic cone, in this catchment the steepness and concavity indices, coupled with lineaments obtained from interpretations of Synthetic Aperture Radar satellite scenes, show an uplifting along micro-faults. Hypsometry curves reveal that subcatchments on the right side of the Makuyuni River are in a mature equilibrium phase, whereas those at the left side are in a younger stage of maturity. An investigation of base level and statistical moments of the hypsometric curves provides evidences for the spatial distribution of gully erosion phenomena. Such erosion processes are due to tectonic deformation in the northern parts of the Makuyuni catchment. These results of regional tectonic instability suggest that tectonic processes are a significant factor for the current landscape evolution in the Lake Manyara basin.

  14. Non-linearities in hydrological connectivity and microbiological flux in nested catchments - implications of environmental change

    NASA Astrophysics Data System (ADS)

    Tetzlaff, D.; Soulsby, C.; Birkel, C.; Capell, R.; Speed, M.

    2009-12-01

    The non-linearities of catchment hydrological behaviour are strongly influenced by the connectivity of hillslopes and channel networks, particularly where overland flow is an important runoff mechanism. Such surface connectivity also controls the flux of microbiological pollutants (coliform bacteria) from areas of live stock grazing which can have serious health implications for potable water supplies. We report a nested catchment study where hydrological and tracer monitoring over a two year period has been coupled with regular sampling for faecal indicator organisms (FIOs). The study has been based in catchments with mixed landuse where FIOs are derived from livestock (sheep and cows) in agricultural land and wild animals (red deer) on moorlands. At all scales (3-1800km2), high levels of FIO were transient and episodic and strongly correlated with periods of high hydrological connectivity. We show how this non-linearity in connectivity can be captured within a dynamic hydrological model. The model was used, along with climate change predictions, to assess possible scenarios of change in connectivity and microbiological contamination in catchments with different land use.

  15. Assessing the applicability of the Revised Universal Soil Loss Equation (RUSLE) to Irish Catchments

    NASA Astrophysics Data System (ADS)

    Rymszewicz, A.; Mockler, E.; O'Sullivan, J.; Bruen, M.; Turner, J.; Conroy, E.; Kelly-Quinn, M.; Harrington, J.; Lawler, D.

    2015-03-01

    Elevated suspended sediment concentrations in fluvial environments have important implications for system ecology and even small concentrations may have serious consequences for sensitive ecosystems or organisms, such as freshwater pearl mussels (Margaritifera margaritifera). Informed decision making is therefore required for land managers to understand and control soil erosion and sediment delivery to the river network. However, given that monitoring of sediment fluxes requires financial and human resources which are often limited at a national scale, sediment mobilisation and delivery models are commonly used for sediment yield estimation and management. The Revised Universal Soil Loss Equation (RUSLE) is the most widely used model for overland flow erosion and can, when combined with a sediment delivery ratio (SDR), provide reasonable sediment load estimations for a catchment. This paper presents RUSLE factors established from extant GIS and rainfall datasets that are incorporated into a flexible catchment modelling approach. We believe that this is the first time that results from a RUSLE application at a national scale are tested against measured sediment yield values available from Ireland. An initial assessment of RUSLE applied to Irish conditions indicates an overestimation of modelled sediment yield values for most of the selected catchments. Improved methods for model and SDR factors estimation are needed to account for Irish conditions and catchment characteristics. Nonetheless, validation and testing of the model in this study using observed values is an important step towards more effective sediment yield modelling tools for nationwide applications.

  16. Geomorphic connectivity within abandoned small catchments (Stołowe Mts, SW Poland)

    NASA Astrophysics Data System (ADS)

    Latocha, Agnieszka

    2014-05-01

    Studying 5 small catchments (0.6-2.7 km2) located in the central part of the Stołowe Mountains (SW Poland), which are partly or totally abandoned, has revealed the substantial changes of connectivity within the catchments. Field investigation (geomorphic mapping, morphometric analyses) and GIS based analyses of historical data show that slope-channel coupling is much less efficient than in the past, mainly due to the decrease of unpaved road network, especially roads linked directly with streams. Also land-use change with considerable loss of arable land does not support erosion from slopes. The general direction of geomorphic change due to depopulation and lack of maintenance of anthropogenic features tends towards higher stability and lower efficiency of morphological processes, connected with a sustained decrease in slope-channel coupling. This tendency is evidenced by relict landscape features (e.g. road gullies, abandoned roads) formed in the period of more intensive land use, for which higher dynamics of the morphogenetic system may be inferred. The evidence of contemporary erosion and mineral material transport is very local and spatially limited to a few roads which are still in use. Sediment transfer is additionally slowed down by the presence of numerous anthropogenic barriers within slope and valley-floor domains. Even though their total impact may seem only local and negligible at the catchment scale, their contribution to increase the diversity of morphological processes is significant. Especially the neglect of hydrotechnical constructions enhances trapping of material within the catchments.

  17. Feedbacks between structures and processes during initial ecosystem development in an artificial catchment

    NASA Astrophysics Data System (ADS)

    Schaaf, Wolfgang; Elemer, Michael; Gerwin, Werner; Fischer, Anton; Zaplata, Markus; Neneov, Rossen

    2013-04-01

    We studied the role of strutures and processes and their feedbacks during initial ecosystem development in the artificial catchment Chicken Creek. During the first seven years, considerable changes within the catchment were observed. Both internal and external factors could be identified as driving forces for the formation of structures and patterns in the artificial catchment. Initial structures formed by the construction process and initial substrate characteristics were decisive for the distribution and flow of water. External factors like episodic events triggered erosion and dissection during this initial phase, promoted by the low vegetation cover and the unconsolidated sandy substrate. The transformation of the initial geo-system into areas with evolving terrestrial or aquatic characteristics and from a very episodic to a more permanent stream network and discharge, together with the observed vegetation dynamics increased site diversity and heterogeneity with respect to water and nutrient availability and transformation processes compared to the more homogenous conditions at point zero. The processes and feedback mechanisms in the initial development of a new landscape may deviate in rates, intensity and dominance from those known from mature ecosystems. It is therefore crucial to understand these early phases of ecosystem development and to disentangle the increasingly complex interactions between the evolving terrestrial and aquatic, biotic and abiotic compartments of the system. Artificially created catchments could be a suitable tool to study these initial developments at the landscape scale under known, designed and defined boundary conditions.

  18. Variability of rainfall over Lake Kariba catchment area in the Zambezi river basin, Zimbabwe

    NASA Astrophysics Data System (ADS)

    Muchuru, Shepherd; Botai, Joel O.; Botai, Christina M.; Landman, Willem A.; Adeola, Abiodun M.

    2016-04-01

    In this study, average monthly and annual rainfall totals recorded for the period 1970 to 2010 from a network of 13 stations across the Lake Kariba catchment area of the Zambezi river basin were analyzed in order to characterize the spatial-temporal variability of rainfall across the catchment area. In the analysis, the data were subjected to intervention and homogeneity analysis using the Cumulative Summation (CUSUM) technique and step change analysis using rank-sum test. Furthermore, rainfall variability was characterized by trend analysis using the non-parametric Mann-Kendall statistic. Additionally, the rainfall series were decomposed and the spectral characteristics derived using Cross Wavelet Transform (CWT) and Wavelet Coherence (WC) analysis. The advantage of using the wavelet-based parameters is that they vary in time and can therefore be used to quantitatively detect time-scale-dependent correlations and phase shifts between rainfall time series at various localized time-frequency scales. The annual and seasonal rainfall series were homogeneous and demonstrated no apparent significant shifts. According to the inhomogeneity classification, the rainfall series recorded across the Lake Kariba catchment area belonged to category A (useful) and B (doubtful), i.e., there were zero to one and two absolute tests rejecting the null hypothesis (at 5 % significance level), respectively. Lastly, the long-term variability of the rainfall series across the Lake Kariba catchment area exhibited non-significant positive and negative trends with coherent oscillatory modes that are constantly locked in phase in the Morlet wavelet space.

  19. Identifying sediment sources in a gullied catchment using natural and anthropogenic radioactivity

    NASA Astrophysics Data System (ADS)

    Olley, J. M.; Murray, A. S.; MacKenzie, D. H.; Edwards, K.

    1993-04-01

    The ratio of the lithogenic nuclides 226Ra and 232Th indicates that the major source of sediment in transport in a gullied catchment, located in the head waters of Whiteheads Creek, New South Wales, Australia, is the gully itself. This observation is supported by 7Be and 137Cs concentrations which indicate that the sediment is derived from erosion of either gully floor or gully wall material. While subcatchment 7Be and 137Cs data show sheet, rill, and gully erosion are occurring in the upstream catchments, sediment from these sources is either being trapped before entering the gully, or the volume of sediment is small compared to that derived from the gully itself. The differences in the 226Ra to 232Th ratio between the suspended solids collected on the rising stage and samples of sediment deposited during the falling stage at the outlet of the catchment, indicate a change in the source of sediment during storm events. The results presented here demonstrate the applicability of radionuclide tracers in providing quantitative estimates of the relative contributions of individual catchments to the sediment moving within a drainage network, and in determining whether or not the sediments are mainly derived from subsoil or topsoil sources.

  20. Characterizing long-term hydrologic-response and sediment-transport for the R-5 catchment.

    PubMed

    Heppner, Christopher S; Loague, Keith

    2008-01-01

    Recently there have been several calls to establish long-term data collection networks to monitor near-surface hydrologic response and landscape evolution. The focus of this paper is a long-term dataset from the International Hydrologic Decade (1965-1974). The small upland catchment, known as R-5, located near Chickasha, Olahoma, has been the subject of considerable attention within the event-based hydrologic modeling community for more than 30 yr. Here, for the first time, 8 yr of continuous near-surface hydrologic-response and sediment-transport data are analyzed to show trends in the catchment's long-term behavior. The datasets include precipitation, temperature, solar radiation, soil-water content, infiltration, water discharge, and sediment discharge. Potential and actual evapotranspiration rates were estimated and used to calculate an average annual water balance for the catchment. Findings include, for example, that rainfall intensity rarely exceeds the threshold for Horton-type runoff, soil-water content is both spatially and temporally variable, and the water and sediment discharge rates are positively correlated. The R-5 data provide a unique opportunity to test (and refine) process-based models of continuous hydrologic response and sediment transport at the catchment scale for applications in the emerging fields of hydroecology and hydrogeomorphology. PMID:18948471

  1. Co-evolution of volcanic catchments in Japan

    NASA Astrophysics Data System (ADS)

    Yoshida, T.; Troch, P. A.

    2015-09-01

    Present day landscapes have evolved over time through interactions between the prevailing climates and geological settings. Understanding the linkage between spatial patterns of landforms, soils, and vegetation in landscapes and their hydrological response is critical to make quantitative predictions in ungaged basins. Catchment co-evolution is a theoretical framework that seeks to formulate hypotheses about the mechanisms and conditions that determine the historical development of catchments and how such evolution affects their hydrological response. In this study, we selected 14 volcanic catchments of different ages (from 0.225 to 82.2 Ma) in Japan. We derived indices of landscape properties (drainage density) as well as hydrological response (annual water balance, baseflow index, and flow duration curves) and examined their relation with catchment age and climate (through the aridity index). We found significant correlation between drainage density and baseflow index with age, but not with climate. The age of the catchments was also significantly related to intra-annual flow variability. Younger catchments tend to have lower peak flows and higher low flows, while older catchments exhibit more flashy runoff. The decrease of baseflow with catchment age confirms previous studies that hypothesized that in volcanic landscapes the major flow pathways have changed over time, from deep groundwater flow to shallow subsurface flow. The drainage density of our catchments decreased with age, contrary to previous findings in similar volcanic catchments but of significant younger age than the ones explored here. In these younger catchments, an increase in drainage density with age was observed, and it was hypothesized that this was because of more landscape incision due to increasing near-surface lateral flow paths in more mature catchments. Our results suggests two hypotheses on the evolution of drainage density in matured catchments. One is that as catchments further evolve

  2. Ecosystem Services Derived from Headwater Catchments

    EPA Science Inventory

    We used data from the USEPA’s wadeable streams assessment (WSA), US Forest Service’s forest inventory and analysis (FIA), and select USFS experimental forests (EF) to investigate potential ecosystems services derived from headwater catchments. C, N, and P inputs to these catchmen...

  3. Geomorphic histories for river and catchment management.

    PubMed

    Wasson, R J

    2012-05-13

    River and catchment management usually proceeds from the identification of an undesirable state (e.g. pollution, sedimentation, excessive water extraction, dams, invasion by exotic species) to a strategy for reaching a desirable state described as a target. Desirable states are usually determined from community values, economic assessments and ecosystem functions, or a combination of these. Where a catchment is highly disturbed, the target is usually not a natural state, as that cannot be achieved while maintaining human uses, and a history is needed to document the disturbance, understand its cause and define the 'existence space', that is, the range of natural states that have occurred in the past. Where a catchment is less disturbed, a former natural state could provide a target for management. But which of the many natural (equilibrium) states that have occurred in the past should be the target? The paper reviews what is known of the quantitative difference between pre- and post-disturbance states, searches for the presence or otherwise of equilibrium and comments on the utility of this information for catchment management. The focus is on erosion and sediment transport. PMID:22474683

  4. Measuring winter precipitation in a mountain catchment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Measuring winter precipitation (principally snowfall) in a mountain catchment is difficult. The magnitude of gauge under catch is affected by variable density during deposition, wind speed and direction, and site conditions such as vegetation and topography. Though numerous studies have been condu...

  5. Catchment management and the Great Barrier Reef.

    PubMed

    Brodie, J; Christie, C; Devlin, M; Haynes, D; Morris, S; Ramsay, M; Waterhouse, J; Yorkston, H

    2001-01-01

    Pollution of coastal regions of the Great Barrier Reef is dominated by runoff from the adjacent catchment. Catchment land-use is dominated by beef grazing and cropping, largely sugarcane cultivation, with relatively minor urban development. Runoff of sediment, nutrients and pesticides is increasing and for nitrogen is now four times the natural amount discharged 150 years ago. Significant effects and potential threats are now evident on inshore reefs, seagrasses and marine animals. There is no effective legislation or processes in place to manage agricultural pollution. The Great Barrier Reef Marine Park Act does not provide effective jurisdiction on the catchment. Queensland legislation relies on voluntary codes and there is no assessment of the effectiveness of the codes. Integrated catchment management strategies, also voluntary, provide some positive outcomes but are of limited success. Pollutant loads are predicted to continue to increase and it is unlikely that current management regimes will prevent this. New mechanisms to prevent continued degradation of inshore ecosystems of the Great Barrier Reef World Heritage Area are urgently needed. PMID:11419129

  6. Catchment scale afforestation for mitigating flooding

    NASA Astrophysics Data System (ADS)

    Barnes, Mhari; Quinn, Paul; Bathurst, James; Birkinshaw, Stephen

    2016-04-01

    After the 2013-14 floods in the UK there were calls to 'forest the uplands' as a solution to reducing flood risk across the nation. At present, 1 in 6 homes in Britain are at risk of flooding and current EU legislation demands a sustainable, 'nature-based solution'. However, the role of forests as a natural flood management technique remains highly controversial, due to a distinct lack of robust evidence into its effectiveness in reducing flood risk during extreme events. SHETRAN, physically-based spatially-distributed hydrological models of the Irthing catchment and Wark forest sub-catchments (northern England) have been developed in order to test the hypothesis of the effect trees have on flood magnitude. The advanced physically-based models have been designed to model scale-related responses from 1, through 10, to 100km2, a first study of the extent to which afforestation and woody debris runoff attenuation features (RAFs) may help to mitigate floods at the full catchment scale (100-1000 km2) and on a national basis. Furthermore, there is a need to analyse the extent to which land management practices, and the installation of nature-based RAFs, such as woody debris dams, in headwater catchments can attenuate flood-wave movement, and potentially reduce downstream flood risk. The impacts of riparian planting and the benefits of adding large woody debris of several designs and on differing sizes of channels has also been simulated using advanced hydrodynamic (HiPIMS) and hydrological modelling (SHETRAN). With the aim of determining the effect forestry may have on flood frequency, 1000 years of generated rainfall data representative of current conditions has been used to determine the difference between current land-cover, different distributions of forest cover and the defining scenarios - complete forest removal and complete afforestation of the catchment. The simulations show the percentage of forestry required to have a significant impact on mitigating

  7. Mother Tongue Maintenance in a Chinese Community School in Newcastle Upon Tyne: Developing a Social Network Perspective.

    ERIC Educational Resources Information Center

    Wei, Li

    1993-01-01

    A group of 20 British-born Chinese children aged 12 to 14 were examined in terms of ability to use their mother tongue and of social network structures. One finding is that, to make community language education more effective, parents and children should be brought closer together socially. (Contains 46 references.) (Author/LB)

  8. Cooperative VET in Training Networks: Analysing the Free-Rider Problem in a Sociology-of-Conventions Perspective

    ERIC Educational Resources Information Center

    Leemann, Regula Julia; Imdorf, Christian

    2015-01-01

    In training networks, particularly small and medium-sized enterprises pool their resources to train apprentices within the framework of the dual VET system, while an intermediary organisation is tasked with managing operations. Over the course of their apprenticeship, the apprentices switch from one training company to another on a (half-) yearly…

  9. Thinking Management and Leadership within Colleges and Schools Somewhat Differently: A Practice-Based, Actor-Network Theory Perspective

    ERIC Educational Resources Information Center

    Mulcahy, Dianne; Perillo, Suzanne

    2011-01-01

    This article examines the significance of materiality for management and leadership in education using resources provided by actor-network theory (ANT). Espousing the idea that human interactions are mediated by material objects and that these objects participate in the production of practices, ANT affords thinking management and leadership in a…

  10. Inferring the effect of catchment complexity on mesoscale hydrologic response

    NASA Astrophysics Data System (ADS)

    FröHlich, Holger L.; Breuer, Lutz; Vaché, Kellie B.; Frede, Hans-Georg

    2008-09-01

    The effect of catchment complexity on hydrologic and hydrochemical catchment response was characterized in the mesoscale Dill catchment (692 km2), Germany. This analysis was developed using multivariate daily stream concentration and discharge data at the basin outlet, in connection with less frequently sampled catchment-wide end-member chemistries. The link between catchment-wide runoff sources and basin output was observed through a combination of concentration-discharge (C-Q) analysis and multivariate end-member projection. Subsurface stormflow, various groundwater and wastewater sources, as well as urban surface runoff emerged in catchment output chemistry. Despite the identification of multiple sources, several runoff sources observed within the catchment failed to display consistent links with the output chemistry. This failure to associate known source chemistry with outlet chemistry may have resulted from a lack of hydraulic connectivity between sources and basin outlet, from different arrival times of subbasin-scale runoff contributions, and also from an overlap of source chemistries that subsumed discrete runoff sources in catchment output. This combination of catchment heterogeneity and complexity simply suggests that the internal spatial organization of the catchment impeded the application of lumped mixing calculations at the 692 km2 outlet. Given these challenges, we suggest that in mesoscale catchment research, the potential effects of spatial organization should be included in any interpretation of highly integrated response signals, or when using those signals to evaluate numerical rainfall-runoff models.

  11. Predicting nutrient responses to mitigation at catchment to national scale: the UK research platform (Invited)

    NASA Astrophysics Data System (ADS)

    Johnes, P.

    2013-12-01

    Nutrient enrichment of waters from land-based and atmospheric sources presents a significant management challenge, requiring effective stakeholder engagement and policy development, properly underpinned by robust scientific evidence. The challenge is complex, raising significant questions about the specific sources, apportionment and pathways that determine nutrient enrichment and the key priorities for effective management and policy intervention. This paper presents outputs from 4 major UK research programmes: the Defra Demonstration Test Catchments programme (DTC), the Environment Agency's Catchment Sensitive Farming monitoring and evaluation programme (CSF), Natural Resources Wales Welsh Catchment Initiative (WCI) and the NERC Environmental Virtual Observatory programme (EVOp). Funded to meet this challenge, they are delivering new understanding of the rates and sources of pollutant fluxes from land to water, their impacts on ecosystem goods and services, and likely trends under future climate and land use change from field to national scale. DTC, a 12m investment by the UK Government, has set up long-term, high resolution research platforms equipped with novel telemetered sensor networks to monitor stream ecosystem responses to on-farm mitigation measures at a representative scale for catchment management. Ecosystem structural and functional responses and bulk hydrochemistry are also being monitored using standard protocols. CSF has set up long-term, enhanced monitoring in 8 priority catchments, with monthly monitoring in a further 72 English catchments and 6 Welsh priority catchments, to identify shifts in pollutant flux to waters resulting from mitigation measures in priority areas and farming sectors. CSF and WCI have contributed to >50 million of targeted farm improvements to date, representing a significant shift in farming practice. Each programme has generated detailed evidence on stream ecosystem responses to targeted mitigation. However, to provide

  12. Catchment rehabilitation and hydro-geomorphic characteristics of mountain streams in the western Rift Valley escarpment of Northern Ethiopia

    NASA Astrophysics Data System (ADS)

    Ghebreyohannes Asfaha, Tesfaalem; Frankl, Amaury; Haile, Mitiku; Nyssen, Jan

    2013-04-01

    The catchments in the western Rift Valley escarpment of Northern Ethiopia are highly responsive in terms of hydro-geomorphic changes. With rapid deforestation in the first half of the 20th century, dense gully and scar networks developed, exporting huge amounts of runoff and sediment down to the fertile and densely populated Raya Valley. Consequently, threatening the environment and the livelihoods of the people both in the upstream and downstream areas. To reverse this problem, catchment-scale rehabilitation activities were initiated in the mid-1980s. In this study, we examine the hydro-geomorphic response of streams after catchment rehabilitation. Scar density was digitized from Google Earth imagery (2005) in 20 adjacent catchments and was explained in terms of its corresponding Normalized Difference Vegetation Index (NDVI) and slope gradient. This was accompanied by analysis of incidental repeat photographs and field observations. As evidenced by the series of repeat photographs, the vegetation cover of the catchments decreased up to 1975 and rapid reforestation occurred thereafter. A multiple regression analysis (R2=0.53, P<0.01) showed that scar density is negatively correlated with NDVI and positively with average gradient of very steep slopes (>60%). Moreover, due to reduction in discharge and sediment flow from the rehabilitated catchments, stream adjustments were observed in the field: previously braided stream channels have changed to single-thread streams, many lateral bars are stabilized and covered by vegetation, stream channels are incising due to clear water effect and the size of boulder deposits decreases. Therefore, the study shows that, land degradation activities in the upper catchments resulted in changes in hydro-geomorphic characteristics of the streams and reduction in runoff and sediment transport to the Raya Valley. Key words: scar density; NDVI; stream incision; soil and water conservation; stream adjustment; land use change.

  13. Controls on Nitrate Spatial Variability in Paine Run Catchment of Shenandoah National Park

    NASA Astrophysics Data System (ADS)

    Ingram, S. M.; Scanlon, T. M.

    2007-12-01

    This research examines the catchment-scale controls on in-stream nitrate concentrations by (1) quantifying nitrate spatial variability in a headwater catchment and (2) determining the biophysical processes underlying this variability. The Shenandoah Watershed Study (SWAS) established thirty-eight stream sampling sites in the Paine Run catchment to collect field data on stream chemistry, discharge and transient storage. An evaluation of SWAS data at these sites from the early 1990s to 2007 reveals spatial and temporal variability in nitrate concentrations following the gypsy moth defoliation. We observed high in-stream nitrate concentrations with elevation and an apparent dilution at lower elevations. Main topographic descriptors related to the spatial distribution of nitrate, elevation and contributing area, are associated with differing biophysical factors such as soil residence time, bacterial denitrification, vegetation and mineralization. Previous studies have demonstrated that the physical properties of hyporheic zones can strongly influence denitrification rates. We examined this in the Paine Run catchment with tracer tests to evaluate dilution effects and predict stream outflow and inflow from hyporheic zones responsible for denitrification. We then looked for biophysical processes responsible for higher nitrate levels at higher elevation by using the OTIS model for transient storage to evaluate hyporhiec zones in Paine Run. We also established a method to evaluate soil parameters for depth and permeability. By identifying the controls on nitrate inputs, transport and denitrification, we isolated a set of criteria applied to a quantitative model for nitrate spatial variability. This research has important implications for defining nutrient availability both within the stream network and at the outlet of forested headwater catchments.

  14. Minimizing uncertainty of daily rainfall interpolation over large catchments through realistic sampling of anisotropic correlogram parameters

    NASA Astrophysics Data System (ADS)

    Gyasi-Agyei, Yeboah

    2016-04-01

    It has been established that daily rainfall gauged network density is not adequate for the level of hydrological modelling required of large catchments involving pollutant and sediment transport, such as the catchments draining the coastal regions of Queensland, Australia, to the sensitive Great Barrier Reef. This paper seeks to establish a link between the spatial structure of radar and gauge rainfall for improved interpolation of the limited gauged data over a grid or functional units of catchments in regions with or without radar records. The study area is within Mt. Stapylton weather radar station range, a 128 km square region for calibration and validation, and the Brisbane river catchment for validation only. Two time periods (2000-01-01 to 2008-12-31 and 2009-01-01 to 2015-06-30) were considered, the later period for calibration when radar records were available and both time periods for validation without regard to radar information. Anisotropic correlograms of both the gauged and radar data were developed and used to establish the linkage required for areas without radar records. The maximum daily temperature significantly influenced the distributional parameters of the linkage. While the gauged, radar and sampled correlogram parameters reproduced the mean estimates similarly using leave-one-out cross-validation of Ordinary Kriging, the gauged parameters overestimated the standard deviation (SD) which reflects uncertainty by over 91% of cases compared with the radar or the sampled parameter sets. However, the distribution of the SD generated by the radar and the sampled correlogram parameters could not be distinguished, with a Kolmogorov-Smirnov test p-value of 0.52. For the validation case with the catchment, the percentage overestimation of SD by the gauged parameter sets decreased to 81.2% and 87.1% for the earlier and later time periods, respectively. It is observed that the extreme wet days' parameters and statistics were fairly widely distributed

  15. Overland flow and sediment transport in an agricultural lowland catchments: a focus on tile drain export

    NASA Astrophysics Data System (ADS)

    Vandromme, Rosalie; Grangeon, Thomas; Cerdan, Olivier; Manière, Louis; Salvador Blanes, Sébastien; Foucher, Anthony; Chapalain, Marion; Evrard, Olivier; Le Gall, Marion

    2016-04-01

    Rural landscapes have been extensively modified by human activities in Western Europe since the beginning of the 20th century in order to intensify agricultural production. Cultivated areas often expanded at the expense of grassland and wetlands located in lowland areas (de Groot et al., 2002). Therefore, large modifications were made to the agricultural landscapes: stream redesign, land consolidation, removal of hedges, and installation of tile drainage networks to drain the hydromorphic soils. These changes modified sediment processes and resulted in large morphological alterations (e.g. channel bed incision, deposition of fine sediment, channel bank erosion). Accordingly, these alterations threaten water quality and prevent to meet the requirements of the European directives. Improving water quality requires a clear understanding of the hydrosedimentary dynamics in these lowland cultivated catchments. However, few studies were conducted in drained environments. To fill this research gap, a pilot study was started in cultivated catchment of the Loire River basin, France, where tile drain densities are very high (> 1.5 km/km²). Six hydro-sedimentary monitoring stations were installed in the Louroux catchment (24 km²). One of them was specifically dedicated to measuring water/sediment fluxes from tile drains. Water level and turbidity were continuously monitored and sediments were sampled during floods and low stage periods. Samples were measured for particle size distribution, and sediment tracing studies are currently being developed to quantify the contribution of potential sources (e.g. surface vs subsurface, lithologies) to river sediment. Hydro-sedimentary fluxes were quantified and modelled for some selected events. The catchment hydrosedimentary fluxes and their properties were shown to be impacted by tile drain sediment transport, especially regarding particle size distribution, with the dominant export of very fine particles (< 2 μm) from tile drains

  16. A bioinformatics analysis of Lamin-A regulatory network: a perspective on epigenetic involvement in Hutchinson-Gilford progeria syndrome.

    PubMed

    Arancio, Walter

    2012-04-01

    Hutchinson-Gilford progeria syndrome (HGPS) is a rare human genetic disease that leads to premature aging. HGPS is caused by mutation in the Lamin-A (LMNA) gene that leads, in affected young individuals, to the accumulation of the progerin protein, usually present only in aging differentiated cells. Bioinformatics analyses of the network of interactions of the LMNA gene and transcripts are presented. The LMNA gene network has been analyzed using the BioGRID database (http://thebiogrid.org/) and related analysis tools such as Osprey (http://biodata.mshri.on.ca/osprey/servlet/Index) and GeneMANIA ( http://genemania.org/). The network of interaction of LMNA transcripts has been further analyzed following the competing endogenous (ceRNA) hypotheses (RNA cross-talk via microRNAs [miRNAs]) and using the miRWalk database and tools (www.ma.uni-heidelberg.de/apps/zmf/mirwalk/). These analyses suggest particular relevance of epigenetic modifiers (via acetylase complexes and specifically HTATIP histone acetylase) and adenosine triphosphate (ATP)-dependent chromatin remodelers (via pBAF, BAF, and SWI/SNF complexes). PMID:22533413

  17. Inverse distributed hydrological modelling of alpine catchments

    NASA Astrophysics Data System (ADS)

    Kunstmann, H.; Krause, J.; Mayr, S.

    2005-12-01

    Even in physically based distributed hydrological models, various remaining parameters must be estimated for each sub-catchment. This can involve tremendous effort, especially when the number of sub-catchments is large and the applied hydrological model is computationally expensive. Automatic parameter estimation tools can significantly facilitate the calibration process. Hence, we combined the nonlinear parameter estimation tool PEST with the distributed hydrological model WaSiM. PEST is based on the Gauss-Marquardt-Levenberg method, a gradient-based nonlinear parameter estimation algorithm. WaSiM is a fully distributed hydrological model using physically based algorithms for most of the process descriptions. WaSiM was applied to the alpine/prealpine Ammer River catchment (southern Germany, 710 km2) in a 100×100 m2 horizontal resolution. The catchment is heterogeneous in terms of geology, pedology and land use and shows a complex orography (the difference of elevation is around 1600 m). Using the developed PEST-WaSiM interface, the hydrological model was calibrated by comparing simulated and observed runoff at eight gauges for the hydrologic year 1997 and validated for the hydrologic year 1993. For each sub-catchment four parameters had to be calibrated: the recession constants of direct runoff and interflow, the drainage density, and the hydraulic conductivity of the uppermost aquifer. Additionally, five snowmelt specific parameters were adjusted for the entire catchment. Altogether, 37 parameters had to be calibrated. Additional a priori information (e.g. from flood hydrograph analysis) narrowed the parameter space of the solutions and improved the non-uniqueness of the fitted values. A reasonable quality of fit was achieved. Discrepancies between modelled and observed runoff were also due to the small number of meteorological stations and corresponding interpolation artefacts in the orographically complex terrain. A detailed covariance analysis was performed

  18. Inverse distributed hydrological modelling of Alpine catchments

    NASA Astrophysics Data System (ADS)

    Kunstmann, H.; Krause, J.; Mayr, S.

    2006-06-01

    Even in physically based distributed hydrological models, various remaining parameters must be estimated for each sub-catchment. This can involve tremendous effort, especially when the number of sub-catchments is large and the applied hydrological model is computationally expensive. Automatic parameter estimation tools can significantly facilitate the calibration process. Hence, we combined the nonlinear parameter estimation tool PEST with the distributed hydrological model WaSiM. PEST is based on the Gauss-Marquardt-Levenberg method, a gradient-based nonlinear parameter estimation algorithm. WaSiM is a fully distributed hydrological model using physically based algorithms for most of the process descriptions. WaSiM was applied to the alpine/prealpine Ammer River catchment (southern Germany, 710 km2 in a 100×100 m2 horizontal resolution. The catchment is heterogeneous in terms of geology, pedology and land use and shows a complex orography (the difference of elevation is around 1600 m). Using the developed PEST-WaSiM interface, the hydrological model was calibrated by comparing simulated and observed runoff at eight gauges for the hydrologic year 1997 and validated for the hydrologic year 1993. For each sub-catchment four parameters had to be calibrated: the recession constants of direct runoff and interflow, the drainage density, and the hydraulic conductivity of the uppermost aquifer. Additionally, five snowmelt specific parameters were adjusted for the entire catchment. Altogether, 37 parameters had to be calibrated. Additional a priori information (e.g. from flood hydrograph analysis) narrowed the parameter space of the solutions and improved the non-uniqueness of the fitted values. A reasonable quality of fit was achieved. Discrepancies between modelled and observed runoff were also due to the small number of meteorological stations and corresponding interpolation artefacts in the orographically complex terrain. Application of a 2-dimensional numerical

  19. Establishing a connection between hydrologic model parameters and physical catchment signatures for improved hierarchical Bayesian modeling in ungauged catchments

    NASA Astrophysics Data System (ADS)

    Marshall, L. A.; Weber, K.; Smith, T. J.; Greenwood, M. C.; Sharma, A.

    2012-12-01

    In an effort to improve hydrologic analysis in areas with limited data, hydrologists often seek to link catchments where little to no data collection occurs to catchments that are gauged. Various metrics and methods have been proposed to identify such relationships, in the hope that "surrogate" catchments might provide information for those catchments that are hydrologically similar. In this study we present a statistical analysis of over 150 catchments located in southeast Australia to examine the relationship between a hydrological model and certain catchment metrics. A conceptual rainfall-runoff model is optimized for each of the catchments and hierarchical clustering is performed to link catchments based on their calibrated model parameters. Clustering has been used in recent hydrologic studies but catchments are often clustered based on physical characteristics alone. Usually there is little evidence to suggest that such "surrogate" data approaches provide sufficiently similar model predictions. Beginning with model parameters and working backwards, we hope to establish if there is a relationship between the model parameters and physical characteristics for improved model predictions in the ungauged catchment. To analyze relationships, permutational multivariate analysis of variance tests are used that suggest which hydrologic metrics are most appropriate for discriminating between calibrated catchment clusters. Additional analysis is performed to determine which cluster pairs show significant differences for various metrics. We further examine the extent to which these results may be insightful for a hierarchical Bayesian modeling approach that is aimed at generating model predictions at an ungauged site. The method, known as Bayes Empirical Bayes (BEB) works to pool information from similar catchments to generate informed probability distributions for each model parameter at a data-limited catchment of interest. We demonstrate the effect of selecting

  20. Implementing a Catchment-Based, National-Scale Land Surface and River Routing Model

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Famiglietti, J. S.; Kim, H.

    2012-12-01

    In this study we characterize how accurately we can estimate river discharge, river depth and inundation extent using a catchment-based hydrological and routing modeling system (CHARMS) with an explicit representation of the river network. Here we present a national- scale implementation of CHARMS that includes an explicit representation of the river network upscaled from the NHDPlus dataset. HUC8 (Hydrologic Unit Code) is chosen as the average catchment size (~3900 km2), and the main river channel in each catchment is extracted using the Strahler Stream Oder from NHDPlus. We also derive empirical relationships between channel dimensions and drainage area to describe the river cross- sectional profile for several large regions of the country. The modeled daily streamflow shows reasonable agreement with gage observations. River depth and floodplain extent associated with each river reach are also explicitly simulated. Results have implications for capturing the seasonal-to-interannual dynamics of surface water in climate models, and for assimilation of surface water altimetry, e.g. from the upcoming NASA SWOT mission.

  1. Application of continuum- and hybrid models in karst spring catchments

    NASA Astrophysics Data System (ADS)

    Rehrl, Christoph; Birk, Steffen

    2010-05-01

    Flow in karst aquifers is concentrated along highly permeable solution conduits embedded in the much less permeable fissured system of the surrounding rock. This complex and heterogeneous flow regime can be conceptualized as dual flow systems composed of slow, laminar flow in the fractured porous matrix as opposed to rapid, often turbulent flow in solution conduits. Flow in the fractured porous rock can be treated as a continuous flow field (continuum model), whereas flow in the conduit system is spatially localized and can be modelled by a discrete pipe network model. Hybrid models couple both flow systems and have frequently been employed in basic research, e.g., to simulate and analyse the mechanism of speleogenesis. In many practical applications, however, continuum models are employed. In these models the two flow components are lumped together and the conduits are represented by highly permeable cells (smeared conduit approach). Standard groundwater models imply that conduit flow is represented by a Darcian approach, thus ignoring potential effects of turbulent flow. On this account the USGS has recently released a MODFLOW-2005 Conduit Flow Process (CFP), which makes it possible to account for turbulent flow in the continuum approach (CFP mode 2). Additionally a discrete pipe network model can be coupled to MODFLOW. This hybrid model (CFP mode 1) employs the Darcy-Weisbach equation to represent turbulent flow in the karst conduits. In this work, it is attempted to simulate the discharge hydrographs of a hypothetical karst spring catchment in which conduit systems are embedded in fissured porous rock using both the single-continuum approach (CFP mode 2) and the hybrid model (CFP mode 1). This study shows that the hydraulic response of the spring signal is influenced by the flow conditions in the conduit, i.e. the shape of the spring hydrograph predicted by a model that accounts for turbulent flow differs from that obtained with a laminar flow model. This

  2. Groundwater Contributions to Intermittent Streamflow in a Headwater Catchment: How do Geoclimatic Controls Influence Downstream Water Quality?

    NASA Astrophysics Data System (ADS)

    Smull, E. M.; Gooseff, M. N.; Singha, K.

    2014-12-01

    Hydrologic connectivity of headwater catchments affects surface water yield and quality of downstream drinking water supplies. Lower Gordon Gulch, a 2.75 km2 catchment, is part of the Boulder Creek watershed - the primary drinking water supply for the city of Boulder, Colorado. We hypothesize that the geologic and climatic environment within the catchment controls the magnitude, timing, and duration of hydrologic connection between the landscape and the stream, and thus the distribution of major ions to the surface water. Specifically, bedrock patterns, vegetation type and density, and snowpack dynamics influence how precipitation inputs move from the hillslopes to the catchment outlet. Preliminary results suggest that north-facing hillslopes with steeper slopes, deeper weathering of bedrock, denser vegetation stands, and a seasonal snowpack, provide consistently greater groundwater inputs to the stream compared to the south-facing hillslopes. We believe that this is in part due to subsurface bedrock patterns forcing a dominate cross-valley gradient. Through an extensive observation network of hillslope wells, periodic stream water balance measurements, and synoptic chemistry samples, we plan to continue our assessment of the spatio-temporal connectivity dynamics throughout the seasonal dry down (late summer through winter), during which streamflow can be intermittent. Results will help to guide landuse practices of upland catchments with respect to their role in Boulder's drinking water supply.

  3. Effect of Agricultural Practices on Hydrology and Water Chemistry in a Small Irrigated Catchment, Yakima River Basin, Washington

    USGS Publications Warehouse

    McCarthy, Kathleen A.; Johnson, Henry M.

    2009-01-01

    The role of irrigation and artificial drainage in the hydrologic cycle and the transport of solutes in a small agricultural catchment in central Washington's Yakima Valley were explored using hydrologic, chemical, isotopic, age-dating, and mineralogical data from several environmental compartments, including stream water, ground water, overland flow, and streambed pore water. A conceptual understanding of catchment hydrology and solute transport was developed and an inverse end-member mixing analysis was used to further explore the effects of agriculture in this small catchment. The median concentrations of major solutes and nitrates were similar for the single field site and for the catchment outflow site, indicating that the net effects of transport processes for these constituents were similar at both scales. However, concentrations of nutrients were different at the two sites, suggesting that field-scale variations in agricultural practices as well as nearstream and instream biochemical processes are important components of agricultural chemical transformation and transport in this catchment. This work indicates that irrigation coupled with artificial drainage networks may exacerbate the ecological effects of agricultural runoff by increasing direct connectivity between fields and streams and minimizing potentially mitigating effects (denitrification and dilution, for example) of longer subsurface pathways.

  4. Spatial and temporal occurrence of preferential flow in a forested headwater catchment

    NASA Astrophysics Data System (ADS)

    Wiekenkamp, I.; Huisman, J. A.; Bogena, H. R.; Lin, H. S.; Vereecken, H.

    2016-03-01

    The highly dynamic nature of preferential flow in time and space makes it challenging to identify and analyze its occurrence at the catchment scale. Novel analysis methods using soil moisture sensor response times offer an opportunity to investigate catchment-wide controls on preferential flow. The aim of this study was to identify factors that control preferential flow occurrence based on 3-year soil moisture monitoring using a wireless sensor network in the Wüstebach catchment, Germany. At 101 locations, the sensor response times at three depths (5, 20, and 50 cm) were classified into one of four classes: (1) non-sequential preferential flow, (2) velocity-based preferential flow, (3) sequential flow, and (4) no response. A conceptual model, postulating that preferential flow in the Wüstebach catchment is dominated by differences in soil type, landscape position, and rainfall input, was proposed for hypothesis testing. To test the conceptual model, the classification results were combined with spatial and event-based data to understand and identify controlling factors. Spatial parameters consisted of hydrological, topographical, and soil physical and chemical parameters. Temporal factors included precipitation characteristics and antecedent soil moisture conditions. The conceptual model as proposed could only be partly confirmed. Event-based occurrence of preferential flow was highly affected by precipitation amount, with a nearly catchment-wide preferential response during large storm events. During intermediate events, preferential flow was controlled by small-scale heterogeneity, instead of showing catchment-wide patterns. The effect of antecedent catchment wetness on the occurrence of preferential flow was generally less profound, although a clear negative relationship was found for precipitation events with more than 25 mm. It was found that spatial occurrence of preferential flow was however governed by small-scale soil and biological features and local

  5. Physically based modeling in catchment hydrology at 50: Survey and outlook

    NASA Astrophysics Data System (ADS)

    Paniconi, Claudio; Putti, Mario

    2015-09-01

    Integrated, process-based numerical models in hydrology are rapidly evolving, spurred by novel theories in mathematical physics, advances in computational methods, insights from laboratory and field experiments, and the need to better understand and predict the potential impacts of population, land use, and climate change on our water resources. At the catchment scale, these simulation models are commonly based on conservation principles for surface and subsurface water flow and solute transport (e.g., the Richards, shallow water, and advection-dispersion equations), and they require robust numerical techniques for their resolution. Traditional (and still open) challenges in developing reliable and efficient models are associated with heterogeneity and variability in parameters and state variables; nonlinearities and scale effects in process dynamics; and complex or poorly known boundary conditions and initial system states. As catchment modeling enters a highly interdisciplinary era, new challenges arise from the need to maintain physical and numerical consistency in the description of multiple processes that interact over a range of scales and across different compartments of an overall system. This paper first gives an historical overview (past 50 years) of some of the key developments in physically based hydrological modeling, emphasizing how the interplay between theory, experiments, and modeling has contributed to advancing the state of the art. The second part of the paper examines some outstanding problems in integrated catchment modeling from the perspective of recent developments in mathematical and computational science.

  6. Runoff generation mechanism at two distinct headwater catchments - isotopic evidence

    NASA Astrophysics Data System (ADS)

    Dohnal, Michal; Votrubová, Jana; Šanda, Martin; Tesař, Miroslav; Vogel, Tomáš; Dušek, Jaromír

    2016-04-01

    Data from two headwater catchments indicate considerably different runoff formation mechanisms. The contributions of different surface and subsurface runoff mechanisms to the catchment discharge formation at these two small forested headwater catchments are studied with help of the natural isotopic signatures of the observed fluxes. The Uhlirska catchment (1.78 sq. km, Jizera Mts., Czech Republic) is situated in headwater area of Cerna Nisa stream. Deluviofluvial granitic sediments in the valley bottom areas (riparian zones/wetlands) are surrounded by gentle hillslopes with shallow soils developed on crystalline bedrock. The Liz catchment (0.99 sq. km, Bohemian Forest, Czech Republic) belongs to hillslope-type catchments without riparian zones situated in headwater area of Volynka River. The soil at Liz is developed on biotite paragneiss bedrock. Autocorrelation analysis of the measured catchment discharge rates reveals different hydrograph characteristics for each of the two catchments. Estimated autocorrelation lengths differ by an order of magnitude. Variations of oxygen-18 isotope concentrations in precipitation, groundwater and streamflow were analyzed. Several significant rainfall-runoff events at each of the two catchments were analyzed in detail. These events exhibit substantial difference in isotopic compositions of event and pre-event water, which facilitates hydrograph separation. Clockwise and counterclockwise hysteretic relationships between the stream discharge and its isotope concentration were identified. Results were confronted with the previously published concepts of the runoff formation at the catchments under study. The research was funded by the Czech Science Foundation, project No. 14-15201J.

  7. Downward approach at the catchment scale or at the catchment set scale?

    NASA Astrophysics Data System (ADS)

    Perrin, C.; Andréassian, V.; Le Moine, N.

    2009-04-01

    The downward approach that learns from observations the main features of the catchment hydrological response has long been recognized as a way to develop hydrological models for the catchment scale (Klemes, 1983). In this approach, a link is made between rainfall inputs and flow outputs using the mathematical tools found the most efficient to reproduce catchment behaviour. This approach received recently more attention, as some limitations of the upward approach were identified (Sivapalan et al., 2003). However model structures developed with this downward approach at the catchment scale are often difficult to generalize, i.e. difficult to transpose to other catchments. Indeed they are often over-adapted to the specific features of the catchment on which they were developed. Generalization is a major problem in current hydrological modelling (Sivakumar, 2008). This is potentially a major drawback for the application of such models to the case of ungauged catchments. We argue that a better way to develop the structure of hydrological models following a downward approach is to place model development at the level of large set of catchments and not only at the level of a single catchment. This way of developing models will force them to be general, i.e. more transposable in space. They will capture the essential features of the rainfall-runoff transformation common between catchments. This way of developing models also gives the opportunity to analyse the spatial patterns of model failures, therefore providing more robust sources of explanations and more convincing ways to improve models. We do not believe that we could develop a single model that fit all conditions, but models developed with this approach are likely to be better starting points to get general models. Then we have to find ways to make them more appropriate to specific conditions without losing their generality. We will illustrate the advantages (and possible limitations) of this approach using

  8. Co-evolution of volcanic catchments in Japan

    NASA Astrophysics Data System (ADS)

    Yoshida, T.; Troch, P. A. A.

    2015-12-01

    Present day landscapes have evolved over time through interactions between the prevailing climates and geological settings. Understanding the linkage between spatial patterns of landforms, soils, and vegetation in landscapes and their hydrological response is critical to make quantitative predictions in ungaged basins. Catchment co-evolution is a theoretical framework that seeks to formulate hypotheses about the mechanisms and conditions that determine the historical development of catchments and how such evolution affects their hydrological response. In this study, we selected 14 volcanic catchments of different ages (from 0.22 to 82Ma) in Japan. We derived indices of landscape properties (drainage density) as well as hydrological response (annual water balance, baseow index, and flow duration curves) and examined their relation with catchment age and climate (through the aridity index). We found signicant correlation between drainage density and baseow index with age, but not with climate. The age of the catchments was also signicantly related to intra-annual flow variability. Younger catchments tend to have lower peak flows and higher low flows, while older catchments exhibit more flashy runoff. The decrease of baseflow with catchment age confirms previous studies that hypothesized that in volcanic landscapes the major flow pathways have changed over time, from deep groundwater flow to shallow subsurface flow. The drainage density of our catchments decreased with age, contrary to previous findings in similar volcanic catchments but of signicant younger age than the ones explored here. In these younger catchments, an increase in drainage density with age was observed, and it was hypothesized that this was because of more landscape incision due to increasing near-surface lateral flow paths in more mature catchments. Our results suggest that as catchments further evolve, hydrologically active channels retreat as less recharge leads to lower average aquifer levels

  9. Catchment Engineering: A New Paradigm in Water Management

    NASA Astrophysics Data System (ADS)

    Quinn, P. F.; Burke, S.; O'Donnell, G. M.; Wilkinson, M.; Jonczyk, J.; Barber, N.; Nicholson, A.; Proactive Team

    2011-12-01

    Recent catchment initiatives have highlighted the need for new holistic approaches to sustainable water management. Here, a catchment engineering approach seeks to describe catchment 'function' (or role) as the principal driver for evaluating how it should be managed in the future. Catchment engineering does not seek to re-establish a natural system but seeks to work with natural processes in order to engineer landscapes so that multiple benefits accrue. This approach involves quantifying and assessing catchment change and impacts but most importantly suggests an urgent and proactive agenda for future planning. In particular, an interventionist approach to managing hydrological flow pathways across scale is proposed. It is already accepted that future management will require a range of scientific expertise and full engagement with stakeholders, namely the general public and policy makers. This inclusive concept under a catchment engineering agenda forces any consortia to commit to actively changing and perturbing the catchment system and thus learn, in situ, how to manage the environment for collective benefits. The shared cost, the design, the implementation, the evaluation and any subsequent modifications should involve all relevant parties in the consortia. This joint ownership of a 'hands on' interventionist agenda to catchment change is at the core of catchment engineering. In this paper we show a range of catchment engineering projects from the UK that have addressed multi-disciplinary approaches to flooding, pollution and ecosystem management whilst maintaining economic food production. Local scale demonstration activities, led by local champions, have proven to be an effective means of encouraging wider uptake. Catchment engineering is a concept that relies on all relevant parties within a catchment to take responsibility for the water quantity and quality that arises from the catchment. Further, any holistic solution requires a bottom up, problem solving

  10. Similarity and scale in catchment storm response

    NASA Technical Reports Server (NTRS)

    Wood, Eric F.; Sivapalan, Murugesu; Beven, Keith

    1993-01-01

    Until recently, very little progress had been made in understanding the relationship between small-scale variability of topography, soil, and rainfalls and the storm response seen at the catchment scale. The work reviewed here represents the first attempt at a systematic theoretical framework for such understanding in the context of surface runoff generation by different processes. The parameterization of hydrological processes over a range of scales is examined, and the concept of the 'representative elementary area' (REA) is introduced. The REA is a fundamental scale for catchment modeling at which continuum assumptions can be applied for the spatially variable controls and parameters, and spatial patterns no longer have to be considered explicitly. The investigation of scale leads into the concept of hydrologic similarity in which the effects of the environmental controls on runoff generation and flood frequency response be investigated independently of catchment scale. The paper reviews the authors' initial results and hopefully will motivate others to also investigate the issues of hydrologic scale and similarity.

  11. Modeling of facade leaching in urban catchments

    NASA Astrophysics Data System (ADS)

    Coutu, S.; Del Giudice, D.; Rossi, L.; Barry, D. A.

    2012-12-01

    Building facades are protected from microbial attack by incorporation of biocides within them. Flow over facades leaches these biocides and transports them to the urban environment. A parsimonious water quantity/quality model applicable for engineered urban watersheds was developed to compute biocide release from facades and their transport at the urban basin scale. The model couples two lumped submodels applicable at the basin scale, and a local model of biocide leaching at the facade scale. For the facade leaching, an existing model applicable at the individual wall scale was utilized. The two lumped models describe urban hydrodynamics and leachate transport. The integrated model allows prediction of biocide concentrations in urban rivers. It was applied to a 15 km2urban hydrosystem in western Switzerland, the Vuachère river basin, to study three facade biocides (terbutryn, carbendazim, diuron). The water quality simulated by the model matched well most of the pollutographs at the outlet of the Vuachère watershed. The model was then used to estimate possible ecotoxicological impacts of facade leachates. To this end, exceedance probabilities and cumulative pollutant loads from the catchment were estimated. Results showed that the considered biocides rarely exceeded the relevant predicted no-effect concentrations for the riverine system. Despite the heterogeneities and complexity of (engineered) urban catchments, the model application demonstrated that a computationally "light" model can be employed to simulate the hydrograph and pollutograph response within them. It thus allows catchment-scale assessment of the potential ecotoxicological impact of biocides on receiving waters.

  12. Climate change influence on catchment sediment yield

    NASA Astrophysics Data System (ADS)

    Rulli, Maria Cristina; Grossi, Giovanna

    2010-05-01

    The effects of a change in climate are expected to be recognizable in many environmental aspects even at small spatial scales: atmospheric carbon dioxide concentration, air temperature, precipitation pattern (days of snowfall translate in days of rainfall), rainfall intensity and erosivity. As a consequence, strong modifications may affect the rate of evapo-transpiration, infiltration and plant biomass production, but also of the soil erosion. To which extent climate change may affect runoff production, soil erosion and sediment transport in upland catchments is investigated here by combining data of long term precipitation, sediment yield and future climate change provided by Global Circulation Models (GCMs) with a spatially distributed modeling approach to flow generation and surface erosion. The model accounts for changes in the structure and properties of soil and vegetation cover by combining the tube-flux approach to the topographic watershed partitioning through a parsimonious parametrization of the main hydrological processes. This model is used to predict hydrological and sediment fluxes for three small catchments in Saint Gabriel mountains of Southern California under control and climate change conditions. Simulation runs using a 45 years long record of hourly precipitation, both observed and referred to a future scenario, show that climate change may induce a significant modification in the catchment response to storms, with major effects on erosion and flood flows.

  13. Water quality in sugar catchments of Queensland.

    PubMed

    Rayment, G E

    2003-01-01

    Water quality condition and trend are important indicators of the impact of land use on the environment, as degraded water quality causes unwelcome changes to ecosystem composition and health. These concerns extend to the sea, where discharges of nutrients, sediments and toxicants above natural levels are unwelcome, particularly when they drain to the Great Barrier Reef World Heritage Area and other coastal waters of Queensland. Sugarcane is grown in 26 major river catchments in Queensland, most in environmentally sensitive areas. This puts pressure on the Queensland Sugar Industry to manage the land in ways that have minimum adverse off-site impacts. Sugar researchers including CRC Sugar have been associated with water quality studies in North Queensland. These include investigations and reviews to assess the role of groundwater as a pathway for nitrate loss from canelands in the Herbert Catchment, to find causes of oxygen depletion in water (including irrigation runoff) from Ingham to Mackay, to use residues of superseded pesticides as indicators of sediment loss to the sea, and to assemble information on water quality pressure and status in sugar catchments. Key findings, plus information on input pressures are described in this paper, and areas of concern and opportunities discussed. PMID:14653632

  14. New Perspectives on the “Silo Effect”: Initial Comparisons of Network Structures Across Public Health Collaboratives

    PubMed Central

    H. Retrum, Jessica; M. Varda, Danielle

    2015-01-01

    Objectives. We explored to what extent “silos” (preferential partnering) persist in interorganizational boundaries despite advances in working across boundaries. We focused on organizational homophily and resulting silo effects within networks that might both facilitate and impede success in public health collaboratives (PHCs). Methods. We analyzed data from 162 PHCs with a series of exponential random graph models to determine the influence of uniform and differential homophily among organizations and to identify the propensity for partnerships with similar organizations. Results. The results demonstrated a low presence (8%) of uniform homophily among networks, whereas a greater number (30%) of PHCs contained varying levels of differential homophily by 1 or more types of organization. We noted that the higher frequency among law enforcement, nonprofits, and public health organizations demonstrated a partner preference with similar organizations. Conclusions. Although we identified only a modest occurrence of partner preference in PHCs, overall success in efforts to work across boundaries might be problematic when public health members (often leaders of PHCs) exhibit the tendency to form silos. PMID:25689195

  15. Challenges in initiating and conducting personalized cancer therapy trials: perspectives from WINTHER, a Worldwide Innovative Network (WIN) Consortium trial

    PubMed Central

    Rodon, J.; Soria, J. C.; Berger, R.; Batist, G.; Tsimberidou, A.; Bresson, C.; Lee, J. J.; Rubin, E.; Onn, A.; Schilsky, R. L.; Miller, W. H.; Eggermont, A. M.; Mendelsohn, J.; Lazar, V.; Kurzrock, R.

    2015-01-01

    Advances in ‘omics’ technology and targeted therapeutic molecules are together driving the incorporation of molecular-based diagnostics into the care of patients with cancer. There is an urgent need to assess the efficacy of therapy determined by molecular matching of patients with particular targeted therapies. WINTHER is a clinical trial that uses cutting edge genomic and transcriptomic assays to guide treatment decisions. Through the lens of this ambitious multinational trial (five countries, six sites) coordinated by the Worldwide Innovative Networking Consortium for personalized cancer therapy, we discovered key challenges in initiation and conduct of a prospective, omically driven study. To date, the time from study concept to activation has varied between 19 months at Gustave Roussy Cancer Campus in France to 30 months at the Segal Cancer Center, McGill University (Canada). It took 3+ years to be able to activate US sites due to national regulatory hurdles. Access to medications proposed by the molecular analysis remains a major challenge, since their availability through active clinical trials is highly variable over time within sites and across the network. Rules regarding the off-label use of drugs, or drugs not yet approved at all in some countries, pose a further challenge, and many biopharmaceutical companies lack a simple internal mechanism to supply the drugs even if they wish to do so. These various obstacles should be addressed to test and then implement precision medicine in cancer. PMID:25908602

  16. Challenges in initiating and conducting personalized cancer therapy trials: perspectives from WINTHER, a Worldwide Innovative Network (WIN) Consortium trial.

    PubMed

    Rodon, J; Soria, J C; Berger, R; Batist, G; Tsimberidou, A; Bresson, C; Lee, J J; Rubin, E; Onn, A; Schilsky, R L; Miller, W H; Eggermont, A M; Mendelsohn, J; Lazar, V; Kurzrock, R

    2015-08-01

    Advances in 'omics' technology and targeted therapeutic molecules are together driving the incorporation of molecular-based diagnostics into the care of patients with cancer. There is an urgent need to assess the efficacy of therapy determined by molecular matching of patients with particular targeted therapies. WINTHER is a clinical trial that uses cutting edge genomic and transcriptomic assays to guide treatment decisions. Through the lens of this ambitious multinational trial (five countries, six sites) coordinated by the Worldwide Innovative Networking Consortium for personalized cancer therapy, we discovered key challenges in initiation and conduct of a prospective, omically driven study. To date, the time from study concept to activation has varied between 19 months at Gustave Roussy Cancer Campus in France to 30 months at the Segal Cancer Center, McGill University (Canada). It took 3+ years to be able to activate US sites due to national regulatory hurdles. Access to medications proposed by the molecular analysis remains a major challenge, since their availability through active clinical trials is highly variable over time within sites and across the network. Rules regarding the off-label use of drugs, or drugs not yet approved at all in some countries, pose a further challenge, and many biopharmaceutical companies lack a simple internal mechanism to supply the drugs even if they wish to do so. These various obstacles should be addressed to test and then implement precision medicine in cancer. PMID:25908602

  17. Exploring Individual Creativity from Network Structure Perspective: Comparison of Task Force Team and R&D Team

    NASA Astrophysics Data System (ADS)

    Lee, Kun Chang; Chae, Seong Wook; Seo, Young Wook

    The objectives of this paper are to empirically investigate the fact that the factors affecting individual creativity differ depending on team characteristics and the fact that its practical implications are plentiful, especially for those who are concerned with how to design team network structures with a bid to motivate individual creativity. From previous studies, this paper suggests crucial factors for facilitating individual creativity: intrinsic motivation, organizational learning culture, and network structure. To maximize practical implications, we divide team characteristics into two types: task force teams and R&D teams. A task force team is organized with a clear mission to be completed within a rather short period. In contrast, an R&D team exists for a long time with numerous projects to finish with various terms and conditions. Empirical results reveal that individual creativity in the task force team should be controlled by adjusting the organizational learning culture and degree centrality, while individual creativity in the R&D team must be administered in a way that the individual's intrinsic motivation is stimulated and encouraged through the use of a structural hole through which external information from outside team is available.

  18. Pragmatism, persistence and patience: a user perspective on strategies for data collection using popular online social networks.

    PubMed

    Mannix, Judy; Wilkes, Lesley; Daly, John

    2014-01-01

    The increasing pervasiveness of the internet and social networking globally presents new opportunities and challenges for empirical social science researchers including those in nursing. Developments in computer-mediated communication are not static and there is potential for further advances and innovation in research methods embracing this technology. The aim of this paper is to present a reflexive account and critique of the use of social media as a means of data collection in a study that sought to explore the aesthetics of clinical leadership in contemporary nursing. In doing so, comparisons are drawn from using Twitter, Facebook and e-learning announcements as methods of recruitment and subsequent data collection via an online survey. The pragmatics of the internet and online social networks as vehicles for data collection are discussed. While questions remain about best practice to safeguard the scientific integrity of these approaches and the researchers and research participants who choose to participate, the potential exists for researchers to enhance and expand research methods without compromising rigour and validity. In the interests of sharpening thinking about this means of data collection dialogue and debate are needed on a range of research aspects including but not limited to pragmatics, new requirements in research training and development, legal and ethical guidelines and strengths and limitations encountered. PMID:25109211

  19. Assessment of contaminant fate in catchments using a novel integrated hydrobiogeochemical-multimedia fate model.

    PubMed

    Nizzetto, Luca; Butterfield, Dan; Futter, Martyn; Lin, Yan; Allan, Ian; Larssen, Thorjørn

    2016-02-15

    Models for pollution exposure assessment typically adopt an overly simplistic representation of geography, climate and biogeochemical processes. This strategy is unsatisfactory when high temporal resolution simulations for sub-regional spatial domains are performed, in which parameters defining scenarios can vary interdependently in space and time. This is, for example, the case when assessing the influence of biogeochemical processing on contaminant fate. Here we present INCA-Contaminants, the Integrated Catchments model for Contaminants; a new model that simultaneously and realistically solves mass balances of water, carbon, sediments and contaminants in the soil-stream-sediment system of catchments and their river networks as a function of climate, land use/management and contaminant properties. When forced with realistic climate and contaminant input data, the model was able to predict polychlorinated biphenyls (PCBs) concentrations in multiple segments of a river network in a complex landscape. We analyzed model output sensitivity to a number of hydro-biogeochemical parameters. The rate of soil organic matter mineralization was the most sensitive parameter controlling PCBs levels in river water, supporting the hypothesis that organic matter turnover rates will influence re-mobilization of previously deposited PCBs which had accumulated in soil organic matrix. The model was also used to project the long term fate of PCB 101 under two climate scenarios. Catchment diffuse run-off and riverine transport were the major pathways of contaminant re-mobilization. Simulations show that during the next decade the investigated boreal catchment will shift from being a net atmospheric PCB sink to a net source for air and water, with future climate perturbation having little influence on this trend. Our results highlight the importance of using credible hydro-biogeochemical simulations when modeling the fate of hydrophobic contaminants. PMID:26674684

  20. PAI-OFF: A new proposal for online flood forecasting in flash flood prone catchments

    NASA Astrophysics Data System (ADS)

    Schmitz, G. H.; Cullmann, J.

    2008-10-01

    SummaryThe Process Modelling and Artificial Intelligence for Online Flood Forecasting (PAI-OFF) methodology combines the reliability of physically based, hydrologic/hydraulic modelling with the operational advantages of artificial intelligence. These operational advantages are extremely low computation times and straightforward operation. The basic principle of the methodology is to portray process models by means of ANN. We propose to train ANN flood forecasting models with synthetic data that reflects the possible range of storm events. To this end, establishing PAI-OFF requires first setting up a physically based hydrologic model of the considered catchment and - optionally, if backwater effects have a significant impact on the flow regime - a hydrodynamic flood routing model of the river reach in question. Both models are subsequently used for simulating all meaningful and flood relevant storm scenarios which are obtained from a catchment specific meteorological data analysis. This provides a database of corresponding input/output vectors which is then completed by generally available hydrological and meteorological data for characterizing the catchment state prior to each storm event. This database subsequently serves for training both a polynomial neural network (PoNN) - portraying the rainfall-runoff process - and a multilayer neural network (MLFN), which mirrors the hydrodynamic flood wave propagation in the river. These two ANN models replace the hydrological and hydrodynamic model in the operational mode. After presenting the theory, we apply PAI-OFF - essentially consisting of the coupled "hydrologic" PoNN and "hydrodynamic" MLFN - to the Freiberger Mulde catchment in the Erzgebirge (Ore-mountains) in East Germany (3000 km 2). Both the demonstrated computational efficiency and the prediction reliability underline the potential of the new PAI-OFF methodology for online flood forecasting.

  1. Sensitivity maps for impacts of land management on an extreme flood in the Hodder catchment, UK

    NASA Astrophysics Data System (ADS)

    O'Donnell, G.; Ewen, J.; O'Connell, P. E.

    It is increasingly recognised that the management of land and the management of water are strongly interdependent, and that integrated management approaches are needed. There is evidence that modern land management practices have an effect on runoff generation in rural upland areas, so there is the potential to use land management control as a tool in flood risk mitigation programmes. Flooding from historical extreme rainfall events must be considered when designing mitigation programmes, especially if the designs have to take into account the possibility that such events will become more frequent in the future. The largest 90 min rainfall ever recorded in the UK was 117 mm, recorded in 1967 in the Dunsop tributary (25 km 2) of the Hodder catchment, northwest England. Extensive land management changes have recently been made in the catchment, including peat restoration, tree planting and reductions in sheep stocking density, and the analysis of the flooding in 1967 has been undertaken as part of a wider study on the potential impact of the recent changes. A method is demonstrated in which maps of sensitivity are plotted which show how peak flows for extreme events are affected by spatial patterns of changes in runoff generation. This method uses a gridded model for runoff generation containing an embedded hydraulic model of the river network which can calculate sensitivities efficiently and accurately using reverse algorithmic differentiation. The modelling examines the sensitivity of the hydrograph peak at the catchment outlet to changes in flashy runoff generation, which can be affected by land management practices including the blocking of open drainage channels in peat moorland. It is concluded that, as a result of hydraulic and geomorphologic dispersion in the network, changes in land management that affect the flashiness of runoff generation at small scales would probably have had only a relatively minor effect on the flow peaks at the outlet from the

  2. Spatial interpolation of daily rainfall at catchment scale: a case study of the Ourthe and Ambleve catchments, Belgium

    NASA Astrophysics Data System (ADS)

    Ly, S.; Charles, C.; Degré, A.

    2010-09-01

    Spatial interpolation of precipitation data is of great importance for hydrological modelling. Geostatistical methods (krigings) are widely used in spatial interpolation from point measurement to continuous surfaces. However, the majority of existing geostatistical algorithms are available only for single-moment data. The first step in kriging computation is the semi-variogram modelling which usually uses only one variogram model for all-moment data. The objective of this paper was to develop different algorithms of spatial interpolation for daily rainfall on 1 km2 regular grids in the catchment area and to compare the results of geostatistical and deterministic approaches. In this study, we used daily rainfall data from 70 raingages in the hilly landscape of the Ourthe and Ambleve catchments in Belgium (2908 km2). This area lies between 35 and 693 m in elevation and consists of river networks, which are tributaries of the Meuse River. For geostatistical algorithms, Cressie's Approximate Weighted Least Squares method was used to fit seven semi-variogram models (logarithmic, power, exponential, Gaussian, rational quadratic, spherical and penta-spherical) to daily sample semi-variogram on a daily basis. Seven selected raingages were used to compare the interpolation performance of these algorithms applied to many degenerated-raingage cases. Spatial interpolation with the geostatistical and Inverse Distance Weighting (IDW) algorithms outperformed considerably interpolation with the Thiessen polygon that is commonly used in various hydrological models. Kriging with an External Drift (KED) and Ordinary Cokriging (OCK) presented the highest Root Mean Square Error (RMSE) between the geostatistical and IDW methods. Ordinary Kriging (ORK) and IDW were considered to be the best methods, as they provided smallest RMSE value for nearly all cases.

  3. The regime of sediment transport in the Soloneţ Catchment (Romania): quantification of the controlling factors

    NASA Astrophysics Data System (ADS)

    Niga, Bogdan; Obreja, Florin; Robu, Delia; Rǎdoane, Maria

    2016-04-01

    This paper focuses on the regime of sediment transportation to the river mouth of a catchment of 206 km2, located on the easternmost side of the Eastern Carpathians (NE Romania). The primary aim of the paper is to attempt a quantification of the catchment controlling factors of the sediment volume transited through the drainage network and their annual and multi-annual distribution. Among these factors we will focus on the role of sediment sources and human interventions in the mobilization of sediments towards rivers. The data employed in this study were obtained from the Parhauti gauging station (1973 to 2014), located at a distance of about 1.7 km from the confluence of the Solonet River with the Suceava River. These are represented of measurements of water discharge, suspended sediment discharge (hourly or daily measurements during flash flood intervals) and monthly values. The data were correlated with records on rainfall, local slope and morphological characteristics of the river crosssection. For a more detailed analysis we introduced a further comparison with records obtained at other gauging stations, located within the same physical-geographical settings, in neighboring catchments. Regarding our study catchment, investigations were performed on all variables that control flow formation and sediment load of water flows, i.e. geologic substrate, landforms, catchment morphometry, characteristics of the drainage network, land use, types of human interventions in the catchment area and on the river network. The average drainage network density equals ca. 2.5 km / km2, ranging from less than 1 km / km2 at the watershed, to the maximum of over 4 km / km2 recorded at the cuesta frontslopes. The multi-annual average amount of suspended sediment transport is 3.06 kg / s. Suspended sediment transport occurs most intensely during summer (months VI-VIII), (59.8%) as a result of floods which enhance the power of the river. During winter months (XII-II), sediment

  4. Understanding sediment sources in a peri-urban Mediterranean catchment using geochemical tracers

    NASA Astrophysics Data System (ADS)

    Ferreira, Carla; Walsh, Rory; Kikuchi, Ryunosuke; Blake, Will

    2016-04-01

    different particle size fractions (0.125-2.000mm, 0.063-0.125mm and <0.063mm). Seventeen stream sites were sampled plus a sample of sediment from a road surface immediately it entered the stream network. The elemental composition (40 elements) of each size fraction was assessed using a Niton X-ray fluorescence elemental analyser. Results show that rock type has a profound influence on the geochemical properties of bed-sediments. Catchment outlet sediment collected after the summer and a storm of high rainfall intensity following dry weather displayed geochemical properties closer to those of sediment from sandstone sub-catchments, and in particularly sediment from the enterprise park under construction. After the storm that followed very wet weather, however, limestone areas became of much greater significance as sediment sources, probably because of the high soil saturation. At limestone stream sites receiving runoff from the newly constructed road, fine bed-sediment geochemistry was found to be similar to that of road sediment, indicating a high contribution of this source. These results are supported by spatio-temporal differences in streamflow and suspended sediment concentrations at instrumented monitoring stations. It is concluded that this methodology represents a potentially useful tool to enable river managers to detect and assess sediment sources in urbanized and partly urbanized catchments, and to supporting them in designing and implementing effective land-use mosaics and site-specific measures to mitigate erosion.

  5. Using network analysis to explore if professional opinions on Japanese encephalitis risk factors in Nepal reflect a socio-ecological system perspective.

    PubMed

    Hecker, Kent; El Kurdi, Syliva; Joshi, Durgadatt; Stephen, Craig

    2013-12-01

    Japanese encephalitis (JE) is the leading cause of viral encephalitis in Asia and a significant public health problem in Nepal. Its epidemiology is influenced by factors affecting its amplifying hosts (pigs), vectors (mosquitoes), and dead-end hosts (including people). While most control efforts target reduced susceptibility to infection either by vaccination of people or pigs or by reduced exposure to mosquitoes; the economic reality of Nepal makes it challenging to implement standard JE control measures. An ecohealth approach has been nominated as a way to assist in finding and prioritizing locally relevant strategies for JE control that may be viable, feasible, and acceptable. We sought to understand if Nepalese experts responsible for JE management conceived of its epidemiology in terms of a socio-ecological system to determine if they would consider ecohealth approaches. Network analysis suggested that they did not conceive JE risk as a product of a socio-ecological system. Traditional proximal risk factors of pigs, mosquitoes, and vaccination predominated experts' conception of JE risk. People seeking to encourage an ecohealth approach or social change models to JE management in Nepal may benefit from adopting social marketing concepts to encourage and empower local experts to examine JE from a socio-ecological perspective. PMID:24052266

  6. The European Marine Observing Network and the development of an Integrated European Ocean Observing System. An EuroGOOS perspective

    NASA Astrophysics Data System (ADS)

    Fernandez, Vicente; Gorringe, Patrick; Nolan, Glenn

    2016-04-01

    The ocean benefits many sectors of society, being the biggest reservoir of heat, water, carbon and oxygen and playing a fundamental role regulating the earth's climate. We rely on the oceans for food, transport, energy and recreation. Therefore, a sustained marine observation network is crucial to further our understanding of the oceanic environment and to supply scientific data to meet society's need. Marine data and observations in Europe, collected primarily by state governmental agencies, is offered via five Regional Operational Oceanographic Systems (ROOS) within the context of EuroGOOS (http://www.eurogos.eu), an International Non-Profit Association of national governmental agencies and research organizations (40 members from 19 member states) committed to European-scale operational oceanography within the context of the Intergovernmental Global Ocean Observing System (GOOS). Strong cooperation within these regions, enabling the involvement of additional partners and countries, forms the basis of EuroGOOS work. Ocean data collected from different type of sensors (e.g. moored buoys, tide gauges, Ferrybox systems, High Frequency radars, gliders and profiling floats) is accessible to scientist and other end users through data portals and initiatives such as the European Marine Observations and Data Network (EMODnet) (www.emodnet.eu) and the Copernicus Marine Service Copernicus (www.copernicus.eu). Although a relatively mature European ocean observing capability already exists and its well-coordinated at European level, some gaps have been identified, for example the demand for ecosystem products and services, or the case that biogeochemical observations are still relatively sparse particularly in coastal and shelf seas. Assessing gaps based on the capacity of the observing system to answer key societal challenges e.g. site suitability for aquaculture and ocean energy, oil spill response and contextual oceanographic products for fisheries and ecosystems is still

  7. Leaching of nitrogen from forested catchments in Finland

    NASA Astrophysics Data System (ADS)

    Kortelainen, Pirkko; Saukkonen, Sari; Mattsson, Tuija

    1997-12-01

    This study provides an assessment on the spatial variability of the long-term leaching (8-23 years) of nitrogen and organic carbon from 22 forested catchments (0.69-56 km2). The catchments are located throughout Finland excluding the northernmost regions. The Kruunuoja catchment is located in a national park; the other catchments represent typical Finnish forestry land. The leaching from the 21 forestry land catchments can be considered to represent average leaching from Finnish forestry land since the most important forestry practices (ditching, clear-cutting, scarification, and fertilization) since the 1960s have affected about 2.4% of the catchment area per year (compare 2.5% in the entire country in 1980 and 2% in 1991). Moreover, the mean annual runoff from the catchments, 230-420 mm yr-1, agree with the mean annual runoff from Finland (301 mm yr-1 from 1931 to 1990). The major part of the nitrogen transported from the catchments consisted of organic nitrogen (on average 79%). The average inorganic nitrogen proportion ((NO3-N + NH4-N)/Ntot) was lowest (7.3%) in the Kruunuoja catchment and was highest (54%) in the southernmost Teeressuonoja catchment located in the highest anthropogenic nitrogen deposition area. The median C/N ratio in the study streams was high, ranging from 34 to 66. Nitrate leaching from the catchments varied between 2.8 (Kruunuoja) and 100 kg km-2 yr-1 (Teeressuonoja) and was negatively related to C/N ratio in stream water and latitude. The stepwise multiple regression model selected C/N ratio and nitrogen deposition which together explained 72% of the variation in NO3-N leaching. Retention of NO3-N deposition (calculated as ((input-output)/input) was high in all catchments, ranging from 0.99 in Kruunuoja to 0.67 in Teeressuonoja.

  8. Perspectives for a better understanding of the metabolic integration of photorespiration within a complex plant primary metabolism network.

    PubMed

    Hodges, Michael; Dellero, Younès; Keech, Olivier; Betti, Marco; Raghavendra, Agepati S; Sage, Rowan; Zhu, Xin-Guang; Allen, Doug K; Weber, Andreas P M

    2016-05-01

    Photorespiration is an essential high flux metabolic pathway that is found in all oxygen-producing photosynthetic organisms. It is often viewed as a closed metabolic repair pathway that serves to detoxify 2-phosphoglycolic acid and to recycle carbon to fuel the Calvin-Benson cycle. However, this view is too simplistic since the photorespiratory cycle is known to interact with several primary metabolic pathways, including photosynthesis, nitrate assimilation, amino acid metabolism, C1 metabolism and the Krebs (TCA) cycle. Here we will review recent advances in photorespiration research and discuss future priorities to better understand (i) the metabolic integration of the photorespiratory cycle within the complex network of plant primary metabolism and (ii) the importance of photorespiration in response to abiotic and biotic stresses. PMID:27053720

  9. A critical review of the allocentric spatial representation and its neural underpinnings: toward a network-based perspective

    PubMed Central

    Ekstrom, Arne D.; Arnold, Aiden E. G. F.; Iaria, Giuseppe

    2014-01-01

    While the widely studied allocentric spatial representation holds a special status in neuroscience research, its exact nature and neural underpinnings continue to be the topic of debate, particularly in humans. Here, based on a review of human behavioral research, we argue that allocentric representations do not provide the kind of map-like, metric representation one might expect based on past theoretical work. Instead, we suggest that almost all tasks used in past studies involve a combination of egocentric and allocentric representation, complicating both the investigation of the cognitive basis of an allocentric representation and the task of identifying a brain region specifically dedicated to it. Indeed, as we discuss in detail, past studies suggest numerous brain regions important to allocentric spatial memory in addition to the hippocampus, including parahippocampal, retrosplenial, and prefrontal cortices. We thus argue that although allocentric computations will often require the hippocampus, particularly those involving extracting details across temporally specific routes, the hippocampus is not necessary for all allocentric computations. We instead suggest that a non-aggregate network process involving multiple interacting brain areas, including hippocampus and extra-hippocampal areas such as parahippocampal, retrosplenial, prefrontal, and parietal cortices, better characterizes the neural basis of spatial representation during navigation. According to this model, an allocentric representation does not emerge from the computations of a single brain region (i.e., hippocampus) nor is it readily decomposable into additive computations performed by separate brain regions. Instead, an allocentric representation emerges from computations partially shared across numerous interacting brain regions. We discuss our non-aggregate network model in light of existing data and provide several key predictions for future experiments. PMID:25346679

  10. Assessing Wetland Effects on Nitrogen Reduction within a Fluvial Network Perspective: A Combined Field and Modeling Approach

    NASA Astrophysics Data System (ADS)

    T Hansen, A.; Finlay, J. C.; Czuba, J. A.; Dolph, C.; Foufoula-Georgiou, E.

    2015-12-01

    Agriculturally-derived excess nitrogen in Midwestern US streams and rivers has contributed to water quality impairments at the local, regional, and continental scales, such as the dead zone in the northern Gulf of Mexico. Rates of biogeochemical processing of nitrogen, through denitrification and assimilation, vary throughout space and time and are dependent on factors such as carbon and nitrogen availability, temperature and water residence time. Through an extensive field sampling campaign in the Minnesota River Basin, a 44,000 km2 agricultural basin in the upper Midwest, we investigated the spatial and temporal variability of nitrate concentrations throughout the river network and found that wetlands and lakes, characterized by long residence time and vegetative flow paths, behave as hot spots of nitrogen reduction. We documented that during the critical high loading period of late spring, nitrate concentrations were dependent on the fraction of lakes and wetlands composing the drainage area and that this dependency held even after controlling for the fraction of drainage area in crops. Variability in N uptake within wetlands was characterized through a separate field sampling effort in order to determine first order controls on denitrification and assimilation rates. These observational results were used to develop a spatially explicit, reduced complexity fluvial network model of nitrate transport and uptake which, together with the field measurements, highlights the disproportionately large contribution of wetlands and lakes to nitrate reduction and thus affirms the need to strategically conserve wetlands in intensively managed agricultural landscapes. Ultimately, this effort can guide wetland restoration and management by quantifying critical locations and wetland specifications for achieving desired nitrate reductions within a basin.

  11. Coarse-grained models reveal functional dynamics--I. Elastic network models--theories, comparisons and perspectives.

    PubMed

    Yang, Lee-Wei; Chng, Choon-Peng

    2008-01-01

    In this review, we summarize the progress on coarse-grained elastic network models (CG-ENMs) in the past decade. Theories were formulated to allow study of conformational dynamics in time/space frames of biological interest. Several highlighted models and their underlined hypotheses are introduced in physical depth. Important ENM offshoots, motivated to reproduce experimental data as well as to address the slow-mode-encoded configurational transitions, are also introduced. With the theoretical developments, computational cost is significantly reduced due to simplified potentials and coarse-grained schemes. Accumulating wealth of data suggest that ENMs agree equally well with experiment in describing equilibrium dynamics despite their distinct potentials and levels of coarse-graining. They however do differ in the slowest motional components that are essential to address large conformational changes of functional significance. The difference stems from the dissimilar curvatures of the harmonic energy wells described for each model. We also provide our views on the predictability of 'open to close' (open-->close) transitions of biomolecules on the basis of conformational selection theory. Lastly, we address the limitations of the ENM formalism which are partially alleviated by the complementary CG-MD approach, to be introduced in the second paper of this two-part series. PMID:19812764

  12. Effects of financial crisis on the industry sector of Chinese stock market — from a perspective of complex network

    NASA Astrophysics Data System (ADS)

    Yang, Chunxia; Chen, Yanhua; Hao, Weiwei; Shen, Ying; Tang, Minxuan; Niu, Lei

    2014-05-01

    In this paper, we use mutual information to measure the statistical interdependence between 23 industry sectors of Shanghai stock market and construct corresponding correlation network to analyze the shock of 2008 financial crisis on industry sectors. The obtained meaningful facts are as follows. First, such crisis has only a limited impact on leading industries such as Manufacturing, Commercial trade and Machinery & Equipment, which still play an important role in Chinese economy. Second, the crisis badly attacks China's export industries like Electronics, Wood & Furniture and Textile & Clothing. The damage further hurts other industries, and then export industries' influence becomes larger. Third, the crisis adversely impacts the import industries like Petrochemical, Metal & Nonmetal and Pharmaceutical Biotechnology. While due to the stimulation of macroeconomic policies, the influence of crisis on import industries is limited. Similarly, due to relatively strict capital control and the macroeconomic policies stimulating the domestic demand, those industries like Construction, Real Estate and Financial Services are slightly wounded. All these findings suggest that Chinese government should transform from the external demand to the domestic consumption to sustain economic growth.

  13. Behavioral risk assessment in HIV Vaccine Trials Network (HVTN) clinical trials: A qualitative study exploring HVTN staff perspectives

    PubMed Central

    Andrasik, Michele Peake; Karuna, Shelly T.; Nebergall, Michelle; Koblin, Beryl A.; Kublin, Jim G.

    2013-01-01

    In HIV vaccine trials, the collection and analysis of participant behavior data associated with risk of acquiring HIV-infection is important for a number of reasons. Although the rationale for behavioral risk assessment in HIV vaccine clinical trials is clear, consistent collection of behavioral data over time and across protocols has been challenging for the HIV Vaccine Trials Network (HVTN). Integrating biomedical and behavioral research within the same preventive vaccine clinical trial has proven difficult. The HVTN conducted an internal landscape analysis to: (1) evaluate the challenges of behavioral risk assessment in HIV vaccine trials and observational studies; (2) explore the impact of the Step Study on behavioral risk assessment measures; and (3) identify strategies to overcome existing challenges and improve the quality of data resulting from behavioral risk analysis. These analyses of behavioral risk within the HVTN revealed several challenges and recommendations for improved behavioral risk data collection in future protocols. The recommendations for improvement include: (1) establishment of protocol-specific behavioral risk working groups that include social and behavioral experts; (2) provision of behavioral rationale and objectives to the development team; (3) creation of a template for geographic- and population-specific assessment of low and high risk behaviors; and (4) pilot testing of behavioral risk assessments. Results also underscored the need for routinely conducted analyses of behavioral data. PMID:23859840

  14. A numerical solution to define channel heads and hillslope parameters from digital topography of glacially conditioned catchments

    NASA Astrophysics Data System (ADS)

    Salcher, Bernhard; Baumann, Sebastian; Kober, Florian; Robl, Jörg; Heiniger, Lukas

    2016-04-01

    The analysis of the slope-area relationship in bedrock streams is a common way for discriminating the channel from the hillslope domain and associated landscape processes. Spatial variations of these domains are important indicators of landscape change. In fluvial catchments, this relationship is a function of contributing drainage area, channel slope and the threshold drainage area for fluvial erosion. The resulting pattern is related to climate, tectonic and underlying bedrock. These factors may become secondary in catchments affected by glacial erosion, as it is the case in many mid- to high-latitude mountain belts. The perturbation (i.e. the destruction) of an initial steady state fluvial bedrock morphology (where uplift is balanced by surface lowering rates) will tend to become successively larger if the repeated action of glacial processes exceeds the potential of fluvial readjustment during deglaciated periods. Topographic change is associated with a decrease and fragmentation of the channel network and an extension of the hillslope domain. In case of glacially conditioned catchments discrimination of the two domains remains problematic and a discrimination inconsistent. A definition is therefore highly needed considering that (i) a spatial shift in the domains affect the process and rate of erosion and (ii) topographic classifications of alpine catchments often base on channel and hillslope parameters (i.e.channel or hillslope relief). Here we propose a novel numerical approach to topographically define channel heads from digital topography in glacially conditioned mountain range catchments in order to discriminate the channel from the hillslope domain. We analyzed the topography of the southern European Central Alps, a region which (i) has been glaciated multiple times during the Quaternary, shows (ii) little lithological variations, is (iii) home of very low erodible rocks and is (iv) known as a region were tectonic processes have largely ceased. The

  15. Topological and canonical kriging for design flood prediction in ungauged catchments: an improvement over a traditional regional regression approach?

    NASA Astrophysics Data System (ADS)

    Archfield, S. A.; Pugliese, A.; Castellarin, A.; Skøien, J. O.; Kiang, J. E.

    2013-04-01

    In the United States, estimation of flood frequency quantiles at ungauged locations has been largely based on regional regression techniques that relate measurable catchment descriptors to flood quantiles. More recently, spatial interpolation techniques of point data have been shown to be effective for predicting streamflow statistics (i.e., flood flows and low-flow indices) in ungauged catchments. Literature reports successful applications of two techniques, canonical kriging, CK (or physiographical-space-based interpolation, PSBI), and topological kriging, TK (or top-kriging). CK performs the spatial interpolation of the streamflow statistic of interest in the two-dimensional space of catchment descriptors. TK predicts the streamflow statistic along river networks taking both the catchment area and nested nature of catchments into account. It is of interest to understand how these spatial interpolation methods compare with generalized least squares (GLS) regression, one of the most common approaches to estimate flood quantiles at ungauged locations. By means of a leave-one-out cross-validation procedure, the performance of CK and TK was compared to GLS regression equations developed for the prediction of 10, 50, 100 and 500 yr floods for 61 streamgauges in the southeast United States. TK substantially outperforms GLS and CK for the study area, particularly for large catchments. The performance of TK over GLS highlights an important distinction between the treatments of spatial correlation when using regression-based or spatial interpolation methods to estimate flood quantiles at ungauged locations. The analysis also shows that coupling TK with CK slightly improves the performance of TK; however, the improvement is marginal when compared to the improvement in performance over GLS.

  16. Topological and canonical kriging for design flood prediction in ungauged catchments: an improvement over a traditional regional regression approach?

    USGS Publications Warehouse

    Archfield, Stacey A.; Pugliese, Alessio; Castellarin, Attilio; Skøien, Jon O.; Kiang, Julie E.

    2013-01-01

    In the United States, estimation of flood frequency quantiles at ungauged locations has been largely based on regional regression techniques that relate measurable catchment descriptors to flood quantiles. More recently, spatial interpolation techniques of point data have been shown to be effective for predicting streamflow statistics (i.e., flood flows and low-flow indices) in ungauged catchments. Literature reports successful applications of two techniques, canonical kriging, CK (or physiographical-space-based interpolation, PSBI), and topological kriging, TK (or top-kriging). CK performs the spatial interpolation of the streamflow statistic of interest in the two-dimensional space of catchment descriptors. TK predicts the streamflow statistic along river networks taking both the catchment area and nested nature of catchments into account. It is of interest to understand how these spatial interpolation methods compare with generalized least squares (GLS) regression, one of the most common approaches to estimate flood quantiles at ungauged locations. By means of a leave-one-out cross-validation procedure, the performance of CK and TK was compared to GLS regression equations developed for the prediction of 10, 50, 100 and 500 yr floods for 61 streamgauges in the southeast United States. TK substantially outperforms GLS and CK for the study area, particularly for large catchments. The performance of TK over GLS highlights an important distinction between the treatments of spatial correlation when using regression-based or spatial interpolation methods to estimate flood quantiles at ungauged locations. The analysis also shows that coupling TK with CK slightly improves the performance of TK; however, the improvement is marginal when compared to the improvement in performance over GLS.

  17. The hydrological response of a small catchment after the abandonment of terrace cultivation. A study case in northwestern Spain

    NASA Astrophysics Data System (ADS)

    Llorente-Adán, Jose A.; Lana-Renault, Noemí; Galilea, Ianire; Ruiz-Flaño, Purificacion

    2015-04-01

    Terrace construction for cultivation results in a complete transformation of the hillslopes to a series of flat sectors and almost vertical steps. This strategy, which involves a redistribution of soils and a re-organization of the drainage network, provides fertile soil over steep slopes, improves infiltration and controls overland flow under conditions of intense rainstorms. In Camero Viejo (north-western Iberian ranges) most of the hillslopes are occupied by terraced fields. During the XXth century, rural population declined and agricultural practices were abandoned. In this area, a small catchment (1.9 km2) was monitored in 2012 for studying how the abandonment of agricultural terraces affect water and sediment transfer from the hillslopes to the channels. Terraces occupy 40% of the catchment and are covered by sparse grass and shrubs. The equipment installed in the catchment registers continuously meteorological data, discharge and water table fluctuations. Data on suspended sediment transport is obtained by means of a rising-stage sampler. Here we present the hydrological results corresponding to the years 2012-13 and 2013-14. The hydrological response of the catchment was moderate (annual runoff coefficient < 0.20), which could be in part explained by the high evapotranspiration rates reported in the area. Lows flows were recorded in summer and autumn, when the water reserves of the catchment were dry, and high flows occurred from January, when the catchment became wetter. The shape of the hydrographs, with slow response times, moderate peakflows and long recession limbs suggested a large contribution of subsurface flow, probably favored by deep and well structured soils in the bench terraces. Soil saturation areas were not observed during the study period, suggesting that soil infiltration processes and subsurface flow are important, and that the drainage system of the terraces is probably well maintained. No suspended sediment has been collected so far

  18. Snowcover interaction with climate, topography & vegetation in mountain catchments in catchments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mountainous regions in the semi-arid Western US are snow-dominated with little or no summer precipitation. Wind and topographic structure control snow deposition, causing tremendous spatial heterogeneity in the distribution of the snowcover and the delivery of melt water across mountain catchments....

  19. Modeling relationships between catchment attributes and river water quality in southern catchments of the Caspian Sea.

    PubMed

    Hasani Sangani, Mohammad; Jabbarian Amiri, Bahman; Alizadeh Shabani, Afshin; Sakieh, Yousef; Ashrafi, Sohrab

    2015-04-01

    Increasing land utilization through diverse forms of human activities, such as agriculture, forestry, urban growth, and industrial development, has led to negative impacts on the water quality of rivers. To find out how catchment attributes, such as land use, hydrologic soil groups, and lithology, can affect water quality variables (Ca(2+), Mg(2+), Na(+), Cl(-), HCO 3 (-) , pH, TDS, EC, SAR), a spatio-statistical approach was applied to 23 catchments in southern basins of the Caspian Sea. All input data layers (digital maps of land use, soil, and lithology) were prepared using geographic information system (GIS) and spatial analysis. Relationships between water quality variables and catchment attributes were then examined by Spearman rank correlation tests and multiple linear regression. Stepwise approach-based multiple linear regressions were developed to examine the relationship between catchment attributes and water quality variables. The areas (%) of marl, tuff, or diorite, as well as those of good-quality rangeland and bare land had negative effects on all water quality variables, while those of basalt, forest land cover were found to contribute to improved river water quality. Moreover, lithological variables showed the greatest most potential for predicting the mean concentration values of water quality variables, and noting that measure of EC and TDS have inversely associated with area (%) of urban land use. PMID:25395322

  20. Validation of Pacific Northwest Hydrologic Landscapes at the Catchment Scale

    NASA Astrophysics Data System (ADS)

    Sawicz, K. A.; Leibowitz, S. G.; Comeleo, R. L.; Wigington, P. J., Jr.

    2014-12-01

    The interaction between the physical properties of a catchment (form) and climatic forcing of precipitation and energy control how water is partitioned, stored, and conveyed through a catchment (function). Hydrologic Landscapes (HLs) were previously developed across Oregon and describe climatic and physical properties for over 5000 assessment units. This approach was then extended to the three Pacific Northwest states of Washington, Oregon and Idaho (PNW HL). The HLs were developed using the National Hydrography Dataset's WBD HU12 scale and are comprised of classification components describing climate, climate seasonality, aquifer permeability, terrain, and soil permeability. To compare the PNW HL classification to catchment hydrologic behavior, HLs were aggregated to catchment scale to compare against the input/output of water in the catchment. HL aggregation must preserve information on the location of the HL within the catchment outlet (upstream vs. downstream) and properties of that HL (i.e. water source vs. sink). Catchment function was investigated by use of hydrologic signatures, which are attributes of long-term time series of water into and out of the catchment. Signatures include Runoff Ratio, Baseflow Index, Snow Ratio, and Recession Coefficients. This study has three primary objectives: 1) derivation of hydrologic signatures to capture the hydrologic behavior for catchments in the Pacific Northwest: 2) development of methodology to aggregate HLs to the catchment scale; and 3) statistical analysis of signature values and trends with respect to aggregated HL classification. We hypothesize that we will find: 1) strong relationships between aggregated HLs and hydrologic signatures; 2) signatures related to water balance are explained by climatic conditions; and 3) signatures describing flow paths are predicted by terrain, soil, and aquifer permeability. This study examined 230 catchments to achieve objectives and test hypotheses stated.

  1. Lithogenic and cosmogenic tracers in catchment hydrology

    SciTech Connect

    Nimz, G.J.

    1995-01-01

    A variety of physical processes affect solute concentrations within catchment waters. The isotopic compositions of the solutes can indicate which processes have determined the observed concentrations. These processes together constitute the physical history of the water, which is one of the primary concerns in hydrology. Many groundwater solutes are derived as a result of interaction between the water and the rock and/or soil within the system. These are termed {open_quotes}lithogenic{close_quotes} solutes. The isotopic compositions of these solutes provide information regarding rock-water interactions. Many other solutes have their isotopic compositions determined both internally and externally to the catchment system. Important members of this group include solutes that have isotopic compositions produced by atomic particle interactions with other nuclides. The source of the atomic particles can be cosmic radiation (producing {open_quotes}cosmogenic{close_quotes} nuclides in the atmosphere and land surface), anthropogenic nuclear reactions (producing {open_quotes}thermonuclear{close_quotes} nuclides), or radioactive and fission decay of naturally-occurring elements, such as U and Th (producing {open_quotes}in-situ{close_quotes} lithogenic nuclides in the deep subsurface). Current language usage often combines all of the atomic particle-produced nuclides under the heading {open_quotes}cosmogenic nuclides{close_quotes}, and for simplicity we will often follow that usage, although always clearly indicating which variety is being discussed. This paper addresses the processes that affect the lithogenic and cosmogenic solute compositions in groundwater, and how these compositions can therefore be used in integrative ways to understand the physical history of groundwater within a catchment system.

  2. Describing Ecosystem Complexity through Integrated Catchment Modeling

    NASA Astrophysics Data System (ADS)

    Shope, C. L.; Tenhunen, J. D.; Peiffer, S.

    2011-12-01

    Land use and climate change have been implicated in reduced ecosystem services (ie: high quality water yield, biodiversity, and agricultural yield. The prediction of ecosystem services expected under future land use decisions and changing climate conditions has become increasingly important. Complex policy and management decisions require the integration of physical, economic, and social data over several scales to assess effects on water resources and ecology. Field-based meteorology, hydrology, soil physics, plant production, solute and sediment transport, economic, and social behavior data were measured in a South Korean catchment. A variety of models are being used to simulate plot and field scale experiments within the catchment. Results from each of the local-scale models provide identification of sensitive, local-scale parameters which are then used as inputs into a large-scale watershed model. We used the spatially distributed SWAT model to synthesize the experimental field data throughout the catchment. The approach of our study was that the range in local-scale model parameter results can be used to define the sensitivity and uncertainty in the large-scale watershed model. Further, this example shows how research can be structured for scientific results describing complex ecosystems and landscapes where cross-disciplinary linkages benefit the end result. The field-based and modeling framework described is being used to develop scenarios to examine spatial and temporal changes in land use practices and climatic effects on water quantity, water quality, and sediment transport. Development of accurate modeling scenarios requires understanding the social relationship between individual and policy driven land management practices and the value of sustainable resources to all shareholders.

  3. Evaluation of TOPLATS on three Mediterranean catchments

    NASA Astrophysics Data System (ADS)

    Loizu, Javier; Álvarez-Mozos, Jesús; Casalí, Javier; Goñi, Mikel

    2016-08-01

    Physically based hydrological models are complex tools that provide a complete description of the different processes occurring on a catchment. The TOPMODEL-based Land-Atmosphere Transfer Scheme (TOPLATS) simulates water and energy balances at different time steps, in both lumped and distributed modes. In order to gain insight on the behavior of TOPLATS and its applicability in different conditions a detailed evaluation needs to be carried out. This study aimed to develop a complete evaluation of TOPLATS including: (1) a detailed review of previous research works using this model; (2) a sensitivity analysis (SA) of the model with two contrasted methods (Morris and Sobol) of different complexity; (3) a 4-step calibration strategy based on a multi-start Powell optimization algorithm; and (4) an analysis of the influence of simulation time step (hourly vs. daily). The model was applied on three catchments of varying size (La Tejeria, Cidacos and Arga), located in Navarre (Northern Spain), and characterized by different levels of Mediterranean climate influence. Both Morris and Sobol methods showed very similar results that identified Brooks-Corey Pore Size distribution Index (B), Bubbling pressure (ψc) and Hydraulic conductivity decay (f) as the three overall most influential parameters in TOPLATS. After calibration and validation, adequate streamflow simulations were obtained in the two wettest catchments, but the driest (Cidacos) gave poor results in validation, due to the large climatic variability between calibration and validation periods. To overcome this issue, an alternative random and discontinuous method of cal/val period selection was implemented, improving model results.

  4. Equitable water allocation in a heavily committed international catchment area: the case of the Komati Catchment

    NASA Astrophysics Data System (ADS)

    Nkomo, Sakhiwe; van der Zaag, Pieter

    This paper investigates water availability and use in the Komati catchment. The Komati catchment is shared by Swaziland and South Africa and forms part of the Incomati basin, with Mozambique as the third riparian country. In 2002 the three countries reached agreement about how the scarce water should be allocated, based on the principle of equitable and sustainable utilization, as stipulated by the SADC Protocol. The Komati catchment has five main water uses: afforestation, irrigation, the environment, urban/industrial/mining (UIM), and interbasin water transfers (for industrial use). In addition, South Africa and Swaziland have committed themselves to satisfy a certain cross border flow to downstream Mozambique. Frequently, debate has arisen between users and riparian countries on the direction that water resources development has taken in the catchment. Downstream farmers have often complained about interbasin transfers taking place in the upstream portions of the catchment. There has also been animosity about effecting environmental flow releases. A relatively simple, spreadsheet-based water resources model (Waflex) was developed to analyse water availability and use under current and future scenarios. The results were then compared to results obtained from another model that was used in a joint study by Mozambique, South Africa and Swaziland. The Waflex model showed a high degree of consistency with the one used for comparison, especially in terms of trends. It was found that the recent completion of two new dams has improved water supply to irrigation in the two countries. Future water demands will result in appreciable shortages for irrigation and domestic use. The agreed maximum development levels will soon outstrip the ability of the catchment’s supply. The paper shows that a combination of measures will be required to ensure equitable and sustainable water utilisation in the Komati catchment. These will have to be agreed by the riparian countries

  5. Analysis of the protein network of cholesterol homeostasis in different brain regions: an age and sex dependent perspective.

    PubMed

    Segatto, Marco; Di Giovanni, Annalaura; Marino, Maria; Pallottini, Valentina

    2013-07-01

    Although a great knowledge about the patho-physiological roles of cholesterol metabolism perturbation in several organs has been reached, scarce information is available on the regulation of cholesterol homeostasis in the brain where this lipid is involved in the maintenance of several of neuronal processes. Currently, no study is available in literature dealing how and if sex and age may modulate the major proteins involved in the regulatory network of cholesterol levels in different brain regions. Here, we investigated the behavior of 3-hydroxy 3-methylglutaryl coenzyme A reductase (HMGR) and low-density lipoprotein receptor (LDLr) in adult (3-month-old) and aged (12-month-old) male and female rats. The analyses were performed in four different brain regions: cortex, brain stem, hippocampus, and cerebellum which represent brain areas characterized by different neuronal cell types, metabolism, cytoarchitecture and white matter composition. The results show that in hippocampus HMGR is lower (30%) in adult female rats than in age-matched males. Differences in LDLr expression are also observable in old females with respect to age-matched males: the protein levels increase (40%) in hippocampus and decrease (20%) in cortex, displaying different mechanisms of regulation. The mechanism underlying the observed modifications are ascribable to Insig-1 and SREBP-1 modulation. The obtained data demonstrate that age- and sex-related differences in cholesterol homeostasis maintenance exist among brain regions, such as the hippocampus and the prefrontal cortex, important for learning, memory and affection. Some of these differences could be at the root of marked gender disparities observed in clinical disease incidence, manifestation, and prognosis. PMID:23280554

  6. Brain Stimulation Therapy for Central Post-Stroke Pain from a Perspective of Interhemispheric Neural Network Remodeling

    PubMed Central

    Morishita, Takashi; Inoue, Tooru

    2016-01-01

    Central post-stroke pain (CPSP) is a debilitating, severe disorder affecting patient quality of life. Since CPSP is refractory to medication, various treatment modalities have been tried with marginal results. Following the first report of epidural motor cortex (M1) stimulation (MCS) for CPSP, many researchers have investigated the mechanisms of electrical stimulation of the M1. CPSP is currently considered to be a maladapted network reorganization problem following stroke, and recent studies have revealed that the activities of the impaired hemisphere after stroke may be inhibited by the contralesional hemisphere. Even though this interhemispheric inhibition (IHI) theory was originally proposed to explain the motor recovery process in stroke patients, we considered that IHI may also contribute to the CPSP mechanism. Based on the IHI theory and the fact that electrical stimulation of the M1 suppresses CPSP, we hypothesized that the inhibitory signals from the contralesional hemisphere may suppress the activities of the M1 in the ipsilesional hemisphere, and therefore pain suppression mechanisms may be malfunctioning in CPSP patients. In this context, transcranial direct current stimulation (tDCS) was considered to be a reasonable procedure to address the interhemispheric imbalance, as the bilateral M1 can be simultaneously stimulated using an anode (excitatory) and cathode (inhibitory). In this article, we review the potential mechanisms and propose a new model of CPSP. We also report two cases where CPSP was addressed with tDCS, discuss the potential roles of tDCS in the treatment of CPSP, and make recommendations for future studies. PMID:27148019

  7. Investigating the impact of data uncertainty on the estimation of catchment nutrient fluxes.

    NASA Astrophysics Data System (ADS)

    Lloyd, Charlotte; Freer, Jim; Collins, Adrian; Johnes, Penny; Coxon, Gemma

    2014-05-01

    Changing climate and a growing population are increasing pressures on the world's water bodies. Maintaining food security has resulted in changes in agricultural practices, leading to adverse impacts on water quality. To address this problem robust evidence is needed to determine which on-farm mitigation strategies are likely to be most effective in reducing pollutant impacts. The introduction of in-situ quasi-continuous monitoring of water quality provides the means to improve the characterisation of pollutant behaviour and gain new and more robust understanding of hydrological and biogeochemical flux behaviours in catchments. Here we analyse a suite of high temporal resolution data sets generated from in-situ sensor networks within an uncertainty framework to provide robust estimates of nutrient fluxes from catchments impacted by intensive agricultural production practices. Previous research into nutrient flux estimation has focused on assessing the uncertainty associated with the use of different load models to interpolate or extrapolate nutrient data where daily or sub-daily discharge data are generally available and used with lower resolution nutrient concentrations. In such studies examples of datasets where paired discharge and nutrient concentrations are available are used as a benchmark of 'truth' against which the other data models or sample resolutions are tested. This work illustrates that even given high temporal-resolution paired datasets, where no load model is necessary, there will still be significant uncertainties and therefore demonstrates the importance of analysing such data within an uncertainty framework to obtain robust estimates of catchment nutrient loads. This study uses 15-minute resolution paired velocity and stage height data, in order to calculate river discharge, along with high temporal resolution (15 or 30 minute) nutrient data from four field sites collected as part of the Hampshire Avon Demonstration Test Catchment project

  8. Catchment controls and human disturbances on the geomorphology of small Mediterranean estuarine systems

    NASA Astrophysics Data System (ADS)

    Estrany, Joan; Grimalt, Miquel

    2014-10-01

    Geographic signatures are physical and human-induced characteristics or processes that identify comparable or unique features of estuaries along latitudinal gradients. In Mediterranean areas, the microtidal regime and the strong seasonal and inter-annual contrasts cause an alternation between relatively high runoff and arid conditions. Furthermore, the long history of human settlement also increases the complexity in the study of these estuarine systems. This study investigates these signatures of the estuaries located within the Mallorcan eastern coast, which are geomorphologically homogeneous because of a similar bedrock geology and Holocene history. A multi-method approach focused on the integration of geomorphometry, hydraulics, historical sources and statistics was used. We explore the role played by catchment morphometric parameters, severe flash flood events and human disturbances in controlling the geomorphology of 10 beach-barrier enclosed, fluvial incised lagoons. Most of the lagoons discharge into 'calas', ranging in size from 1345 to 17,537 m2 and their related catchments are representative of the Mediterranean hydrological systems. Multiple regression models illustrate that the size, slope and drainage network development of the catchments explain the variance in length (r2 = 0.67), volume (r2 = 0.49), area (r2 = 0.64), circularity (r2 = 0.72) and average width (r2 = 0.81) of the lagoons. Depending on these catchment morphometric variables, the shape of the lagoons is also determined by the occurrence of catastrophic flash floods, which cause scouring and dredging, whereas the ordinary flood events and sea storms promote refilling and sedimentation. A historical analysis since 1850 documented 18 flood events, 5 of which were catastrophic with destructive effects along the catchments and large morphological changes in coastal lagoons. High intensity rainfall (up to 200 mm in 2 h), the geomorphometry of the catchments and the massive construction of

  9. Catchment Restoration in the Tweed UNESCO-IHP HELP Basin - Eddleston Water

    NASA Astrophysics Data System (ADS)

    Spray, Christopher

    2013-04-01

    initial characterisation of the catchment; the identification of potential key locations and types of intervention to improve ecological status and flood risk reduction; the setting up of the monitoring networks, the engagement with local communities and land managers; initial habitat modifications and the early results of the study. We situate this within the wider context of priorities for restoration and the UNESCO IHP-HELP programme.

  10. Effects of impervious pavements on reducing runoff in an arid urban catchment

    NASA Astrophysics Data System (ADS)

    Epshtein, O.; Turnbull, L.; Earl, S.

    2011-12-01

    from 5 mm to 25 mm. Model testing shows total event discharge simulated well, although low Nash-Sutcliffe coefficients for events indicate a poor fit between the shape and timing of the modeled and monitored hydrograph, which we attribute to poor characterization of friction factors in urban catchments. Scenario-based model analysis tested catchment response to substitution of pervious for conventional pavement by percent and pavement-function scenarios. Results are consistent with previous findings in that short duration-high intensity storms trigger threshold infiltration capacity, past which pervious pavement damping of runoff volume levels off, approaching conventional levels. However at the modeled catchment scale, this initial damping represents a significant reduction in volume, peak flow velocity, and contaminant loading potential. Urban surface drainage networks concentrate and channel flow along roads: the capacity of pervious pavements to simultaneously increase infiltration directly at location of greatest runoff and mitigate inflow effects from remote points has compelling potential as a hydrologic and urban systems engineering tool.

  11. An Eco-hydrologic Assessment of Small Experimental Catchments with Various Land Uses within the Panama Canal Watershed: Agua Salud Project

    NASA Astrophysics Data System (ADS)

    Crouch, T. D.; Ogden, F. L.; Stallard, R. F.; Smithsonian Tropical Research Institute, Panama Canal Watershed Experiment, Agua Salud Project

    2010-12-01

    Hydrological processes in the humid tropics are poorly understood and an important topic when it comes to water management in the seasonal tropics. The Smithsonian Tropical Research Institute, Panama Canal Watershed Experiment, Agua Salud Project, seeks to understand these processes and quantify the long-term effects of different land cover and uses across the Panama Canal Watershed. One of the project’s main objectives is to understand how reforestation effects seasonal stream flows. To meet this objective, a baseline characterization of hydrology on the small catchment scale is being assessed across different land uses typical in rural Panama. The small experimental catchments are found within Panama’s protected Soberania National Park and the adjacent headwaters of the Agua Salud and Mendoza Rivers, all of which are part of the greater Panama Canal Watershed. The land uses being monitored include a variety of control catchments as well as treated pasture sites. The catchments used for this study include a mature old regrowth forest, a 50% deforested or mosaic regrowth site, an active pasture and a monoculture invasive grass site (saccharum spontaneum) as experimental controls and two treated catchments that were recently abandoned pastures converted to teak and native species timber plantations. Installed instrumentation includes a network of rain gauges, v-notched weirs, atmometers, an eddy covariance system and an assortment of meteorological and automated geochemical sampling systems. Spatial, rainfall, runoff and ET data across these six geologically and topographically similar catchments are available from 2009 and 2010. Classic water balance and paired catchment techniques were used to compare the catchments on an annual, seasonal, and event basis. This study sets the stage for hydrologic modeling and for better understanding the effects of vegetation and land-use history on rainfall-runoff processes for the Agua Salud P