Academic literature on the topic 'Topographic heterogeneity'
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Journal articles on the topic "Topographic heterogeneity"
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Blyth, E. M., J. Finch, M. Robinson, and P. Rosier. "Can soil moisture be mapped onto the terrain?" Hydrology and Earth System Sciences 8, no. 5 (2004): 923–30. http://dx.doi.org/10.5194/hess-8-923-2004.
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Abstract. Soil moisture heterogeneity has an effect on the rainfall–runoff characteristics of a landscape. The aggregate effect on the mean water balance over an area can be quantified successfully using models such as the PDM (Moore, 1986) and TOPMODEL (Beven and Kirkby, 1979). These rainfall–runoff models have been embedded in the large-scale land surface schemes used in meteorological models. However, there is also a requirement (e.g. model validation) to identify the spatial structure of the fine-scale soil moisture heterogeneity that makes up these aggregate models. In some types of landscape, this will be dictated by topography, in others by soil characteristics, or by a combination of both. A method to distribute area-average soil moisture according to the likely effect of local topography is presented and tested. The heterogeneity of the soil moisture is described by the Xinanxiang distribution (Zhao et al., 1980), commonly used to describe the natural spatial heterogeneity of the landscape. This distribution is then mapped onto the terrain using a topographic index to locate the wettest and driest areas. Soil moisture data from the Wye catchment in Wales and from the Pang catchment in Berkshire, England, are used to test the method. It is found that soil moisture data from the Wye catchment follow the topographic index reasonably well, whereas data from the quick-draining, chalky Pang catchment do not. The conclusion that topographic index is a useful indicator only in some landscapes applies equally to using this mapping method and those models that use topographic index directly. Keywords: soil moisture, heterogeneity, topographic index, data
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Lange, Y., and M. F. Muraski. "Topographic heterogeneity in cholesterol biosynthesis." Journal of Biological Chemistry 263, no. 19 (1988): 9366–73. http://dx.doi.org/10.1016/s0021-9258(19)76550-8.
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Khan, Mohammad R., Nicola Mordan, Mohamed Parkar, Vehid Salih, Nikolaos Donos, and Peter M. Brett. "Atypical Mesenchymal Stromal Cell Responses to Topographic Modifications of Titanium Biomaterials Indicate Cytoskeletal- and Genetic Plasticity-Based Heterogeneity of Cells." Stem Cells International 2019 (July 1, 2019): 1–16. http://dx.doi.org/10.1155/2019/5214501.
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Titanium (Ti) is widely used as a biomaterial for endosseous implants due to its relatively inert surface oxide layer that enables implanted devices the ability of assembling tissue reparative components that culminate in osseointegration. Topographic modifications in the form of micro- and nanoscaled structures significantly promote osseointegration and enhance the osteogenic differentiation of adult mesenchymal stromal cells (MSCs). While the biological mechanisms central to the differential responses of tissues and cells to Ti surface modifications remain unknown, adhesion and morphological adaptation are amongst the earliest events at the cell-biomaterial interface that are highly influenced by surface topography and profoundly impact the regulation of stem cell fate determination. This study correlated the effects of Ti topographic modifications on adhesion and morphological adaptation of human MSCs with phenotypic change. The results showed that modified Ti topographies precluded the adhesion of a subset of MSCs while incurring distinct morphological constraints on adherent cells. These effects anomalously corresponded with a differential expression of stem cell pluripotency and Wnt signalling-associated markers on both modified surfaces while additionally differing between hydrophobic and hydrophilic surface modifications—though extent of osteogenic differentiation induced by both modified topographies yielded similarly significant higher levels of cellular mineralisation in contrast to polished Ti. These results suggest that in the absence of deposited proteins and soluble factors, both modified topographies incur the selective adhesion of a subpopulation of progenitors with relatively higher cytoskeletal plasticity. While the presence of deposited proteins and soluble factors does not significantly affect adherence of cells, nanotopographic modifications enhance expression of pluripotency markers in proliferative conditions, which are conversely overridden by both modified topographies in osteogenic inductive conditions. Further deciphering the mechanisms underlying cellular selectivity and Ti topographic responsiveness will improve our understanding of stem cell heterogeneity and advance the potential of MSCs in regenerative medicine.
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Revenaugh, Justin, and Hal Mendoza. "Mapping shallow heterogeneity with teleseismic P to Rg scattered waves." Bulletin of the Seismological Society of America 86, no. 4 (1996): 1194–99. http://dx.doi.org/10.1785/bssa0860041194.
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Abstract Over 9000 records of teleseismic P-wave coda from the Southern California Seismic Network are used to map lateral variations in P to Rg scattering strength and the group velocity of scattered Rg. Building on the results of Revenaugh (1995a), we use the correlation of scattering strength and topographic roughness as an indicator of model fit to estimate group-velocity dispersion over five frequency bands between 0 and 3 Hz. Rg group velocity displays normal dispersion, decreasing from 2.7 ± 0.3 km/sec for frequencies between 0 and 0.6 Hz to a low of 2.2 ± 0.4 km/sec for the 2.0 to 3.0 Hz band. Lateral heterogeneity is introduced by assuming Rg velocity is a function of local topographic roughness. Grid-search/migration analysis yields group velocities of 2.2 and 2.85 km/sec for “smooth” and “rough” terrain, respectively, and a 150-m threshold for the local standard deviation of topography distinguishing “smooth” from “rough”. The map of scattering strength approximates topographic roughness throughout southern California, implying that teleseismic P-wave coda duration and relative amplitude level depend strongly on near-surface (<3 km) geology.
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Wang, Lei, Fei-Xue Zhang, Lan-Ping Li, Chun-Jing Wang, and Ji-Zhong Wan. "Effects of Habitat Heterogeneity and Topographic Variation on Insect Pest Risks in Alpine Regions." Land 12, no. 7 (2023): 1314. http://dx.doi.org/10.3390/land12071314.
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Insect pests pose a significant threat to alpine ecosystems, especially under rapid environmental change conditions. Therefore, it is necessary to explore the effects of environmental factors on insect pest risks and provide methods for pest management in alpine regions. Habitat heterogeneity and topographic variation are the indicators of insect pest risks. However, few studies have explored the effects of habitat heterogeneity and topographic variation on insect pest risks in alpine regions. We used species distribution modeling (i.e., maxent modeling) to project the distributions of insect pests in this alpine region based on occurrence records. Then, we delineated the high-risk areas for insect pests based on the species distributions under a conceptual risk framework using Zonation software for different ecoregional types. We determined the alpine conifer and mixed forests of the Nujiang Langcang Gorge, the conifer forests of the Qilian Mountains, and the shrublands and meadows of Southeast Tibet as the key areas requiring monitoring for insect pests in Qinghai province based on the scoring of insect pest risk rank with >0.7. Habitat heterogeneity and topographic variation could be developed as indicators of risk exposure to insect pests in alpine regions. Our study suggests that the prevention and control of insect pests should be conducted in areas with high habitat heterogeneity and topographic roughness in alpine regions. We provided new insights into the application of species distribution modeling based on habitat heterogeneity and topographic variation. The results of our study indicate that habitat heterogeneity and topographic variation should be considered for improving pest management effectiveness in alpine regions.
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Diefenderfer, Heida L., Ian A. Sinks, Shon A. Zimmerman, Valerie I. Cullinan, and Amy B. Borde. "Designing topographic heterogeneity for tidal wetland restoration." Ecological Engineering 123 (November 2018): 212–25. http://dx.doi.org/10.1016/j.ecoleng.2018.07.027.
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Antonio, Anderson Igomar, Junior Admir Cesar de Oliveira, Fabricio Villalobos, and Santiago José Elías Velazco. "Environmental heterogeneity as a determinant of bee diversity patterns in the Atlantic Forest." Frontiers of Biogeography 18 (May 22, 2025): e142410. https://doi.org/10.21425/fob.18.142410.
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The Atlantic Forest encompasses a wide range of environmental and geographical gradients with high endemism and species diversity among several taxonomic groups, including bees. Environmental heterogeneity is a determining factor for species diversity, as environments with greater heterogeneity tend to offer a greater variety of conditions, thus supporting higher species richness. However, bee richness patterns and their relationship with environmental heterogeneity in the Atlantic Forest remain underexplored. In this study, we aimed to describe the bee diversity patterns and investigate how different components of environmental heterogeneity—specifically temperature seasonality, topographic and geomorphic heterogeneity, and stream density—influence species richness, both for the entire biome and within each ecoregion. To do so, we modeled and estimated the distribution of 466 bee species. Relationships between bee species richness and environmental heterogeneity variables were analyzed using Generalized Linear Models, variable importance, and partial dependence curves. We found that the highest richness was in the southwestern regions of the Atlantic Forest, particularly in the Serra do Mar Coastal Forests and Araucaria Moist Forests. The most important variables positively related to species richness were temperature seasonality, followed by topographic and geomorphic heterogeneity, whereas stream density showed the lowest importance. At the ecoregion level, temperature seasonality was the most important variable for 9 of the 11 ecoregions, followed by topographic and geomorphic heterogeneity. In ecoregions with the highest bee richness, environmental heterogeneity showed a low explanatory power. Notably, the relationships between the environmental heterogeneity variables and species richness varied across ecoregions. Our findings highlight the significant role of environmental factors in shaping bee species richness in the Atlantic Forest at multiple scales. Furthermore, the distinct relationship observed between environmental heterogeneity and species richness across ecoregions reinforces the necessity of multi-scale diversity studies to elucidate the unique characteristics of each ecoregion. Highlights Bee species richness in the Atlantic Forest is greatest in the south-west and southern regions. Seasonal temperature was the most important variable for predicting species richness, showing a positive effect in nine of the 11 ecoregions. Topographic and geomorphic heterogeneity contributed significantly to species richness in certain ecoregions. Relationship between species richness and environmental heterogeneity variables varied among ecoregions. Ecoregions with higher richness were poorly explained by environmental heterogeneity, suggesting other influencing factors. Multiscale analysis reveals that different regions may have unique species richness drivers, crucial to understanding species diversity in this biodiversity hotspot.
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Gaffet, Stéphane, and Bernard Massinon. "Far-field seismogram perturbations induced by topographic heterogeneity." Geophysical Research Letters 24, no. 24 (1997): 3313–16. http://dx.doi.org/10.1029/97gl02977.
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Olliff‐Yang, Rachael L., and David D. Ackerly. "Topographic heterogeneity lengthens the duration of pollinator resources." Ecology and Evolution 10, no. 17 (2020): 9301–12. http://dx.doi.org/10.1002/ece3.6617.
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Tesfa, Teklu K., and Lai-Yung Ruby Leung. "Exploring new topography-based subgrid spatial structures for improving land surface modeling." Geoscientific Model Development 10, no. 2 (2017): 873–88. http://dx.doi.org/10.5194/gmd-10-873-2017.
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Abstract. Topography plays an important role in land surface processes through its influence on atmospheric forcing, soil and vegetation properties, and river network topology and drainage area. Land surface models with a spatial structure that captures spatial heterogeneity, which is directly affected by topography, may improve the representation of land surface processes. Previous studies found that land surface modeling, using subbasins instead of structured grids as computational units, improves the scalability of simulated runoff and streamflow processes. In this study, new land surface spatial structures are explored by further dividing subbasins into subgrid structures based on topographic properties, including surface elevation, slope and aspect. Two methods (local and global) of watershed discretization are applied to derive two types of subgrid structures (geo-located and non-geo-located) over the topographically diverse Columbia River basin in the northwestern United States. In the global method, a fixed elevation classification scheme is used to discretize subbasins. The local method utilizes concepts of hypsometric analysis to discretize each subbasin, using different elevation ranges that also naturally account for slope variations. The relative merits of the two methods and subgrid structures are investigated for their ability to capture topographic heterogeneity and the implications of this on representations of atmospheric forcing and land cover spatial patterns. Results showed that the local method reduces the standard deviation (SD) of subgrid surface elevation in the study domain by 17 to 19 % compared to the global method, highlighting the relative advantages of the local method for capturing subgrid topographic variations. The comparison between the two types of subgrid structures showed that the non-geo-located subgrid structures are more consistent across different area threshold values than the geo-located subgrid structures. Overall the local method and non-geo-located subgrid structures effectively and robustly capture topographic, climatic and vegetation variability, which is important for land surface modeling.
Dissertations / Theses on the topic "Topographic heterogeneity"
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Rose, Jonathan Patrick. "The importance of micro-topographic heterogeneity in determining species diversity of alpine plant communities of Glacier National Park, MT." Thesis, University of Iowa, 2010. https://ir.uiowa.edu/etd/731.
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Alpine plant communities can be exceptionally diverse at a fine scale, and they often exhibit fine scale topographic variability. High species diversity is often attributed to spatial and temporal heterogeneity in the environment. The goal of this study was to test for a positive relationship between microtopographic heterogeneity and species diversity of alpine plants. Species diversity of vascular plants was sampled at 8 sites in Glacier National Park, MT during the summer of 2009. Species richness was assessed both within a 1 x 1 m plot and at 100 points spaced 10 cm apart within the plot. To quantify topographic heterogeneity and variability, the relative elevation was measured for all 100 points in the plot as well. Similarity in species composition between study plots was investigated using Non-Metric Multidimensional Scaling. The study plots separated into two groups based on the presence/absence of Dryas octopetala. This difference is most likely due to plots occupying different positions along the mesotopographical gradient and therefore experiencing different moisture regimes. Regression for all 1 m2 plot data found a negative relationship between topographic heterogeneity and species richness, and no relationship between topographic variability and species richness. Quantile regression was used to assess the relationship between point measures of species richness and topographic variability. There is evidence for topographic variability imposing a limit on species richness for all sites grouped together and for sites that do not contain D. octopetala. This limit is most likely due to the interaction of soil disturbance and the productivity of a site.
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Karpytchev, Mikhail. "Geoide et topographie dynamique a grandes longueurs d'onde : influence des heterogeneites lithospheriques." Paris 11, 1997. http://www.theses.fr/1997PA112425.
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Cette these est basee sur une approche maintenant classique qui permet de relier les anomalies de vitesses sismiques aux anomalies de geoide et a la circulation dans le matneau. Les modeles de tomographie fournissent des donnees sur les variations laterales de vitesses sismiques interpretees en terme de variations laterales de densite. La circulation dans le manteau induite par ces contrastes de densite peut etre calculee pour diverses distributions de viscosite. Les anomalies de topographie en surface et les anomalies de geoide, ainsi que les champs de vitesses et de contraintes, predits par les modeles dynamiques sont compares ensuite avec les observations. Ceci permet d'obtenir des renseignements sur la distribution de viscosite, sur la nature des forces qui agissent sur les plaques et sur les processus geophysiques dans la zone de transition. La specificite de cette these est d'incorporer l'effet de la tectonique des plaques et des variations de l'epaisseur des plaques dues au refroidissement de la lithosphere oceanique et a l'existence des racines profondes sous les anciennes provinces continentales. Apres une etude a 2-d sur l'impact de la tectonique des plaques sur les ecoulements mantelliques, un modele a 3-d qui inclut ces variations de structure lithospherique est propose et est compare au modele a viscosite radiale. Une amelioration notable de la prediction du geoide a ete obtenue dans le modele avec variations laterales de viscosite. Le geoide, la topographie dynamique, les contraintes de cisaillement et le champ de vitesse dans le manteau sont fortement influences par les variations laterales d'epaisseur de la lithosphere. Par ailleurs la topographie dynamique predite par les modeles purement a une couche est trois fois superieur a la topographie observee. Ceci suggere l'existence d'anomalies de densite dans la zone de transition qui s'opposent au transfert de matiere entre manteau superieur et manteau inferieur.
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Chevrot, Sébastien. "Les heterogeneites du manteau a toutes les echelles : variations laterales de vitesse et topographie des discontinuites." Paris 7, 1998. http://www.theses.fr/1998PA077030.
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La caracterisation des variations laterales de vitesse des ondes sismiques dans le manteau a petites et moyennes longueurs d'ondes est un enjeu important pour comprendre la dynamique de notre planete. Cette these presente differentes approches pour tenter de progresser dans ce probleme difficile. La premiere partie est consacree a l'etude de l'information contenue dans les modeles tomographiques a differentes echelles, regionales et globales. Un outil nouveau et puissant, le bispectre, est introduit pour aller au dela d'une simple analyse spectrale. La deuxieme partie propose une etude stochastique du champ d'onde diffuse pour en deduire des informations statistiques sur les proprietes du milieu a petite echelle. Cette etude n'est possible que sous l'hypothese de diffusion simple, dans un milieu homogene (milieu dont les proprietes statistiques sont spatialement invariantes). Les discontinuites a 410 et 660 km, qui definissent la zone de transition, montrent egalement des ecarts a la structure radiale. L'epaisseur de la zone de transition est un excellent marqueur geodynamique. Les ondes p converties en ondes s sur ces deux discontinuites permettent de contraindre l'epaisseur de la zone de transition avec une bien meilleure resolution que les precurseurs des ondes ss qui sont utilises habituellement. La troisieme partie est consacree a l'etude globale de ces ondes sous les stations permanentes des reseaux globaux. Le principal resultat de cette etude est la mise en evidence de variations d'epaisseur limitees a 10 km, tres significativement inferieures aux precedentes estimations. De plus, ces ondes peuvent etre utilisees pour localiser en profondeur les regions anisotropes dans le manteau. L'analyse des donnees enregistrees a la station bng (bangui, centrafrique) demontre l'existence d'une couche anisotrope a la base du manteau superieur.
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Åström, Marcus. "Aspects of heterogeneity : effects of clear-cutting and post-harvest extraction of bioenergy on plants in boreal forests." Doctoral thesis, Umeå universitet, Ekologi, miljö och geovetenskap, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-935.
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Abstract. The objectives of this thesis are to evaluate (1) the influence of slope aspect on boreal plant responses to clear-cutting and (2) the effects of post-harvest extraction of bioenergy (logging residues or slash) on plant composition, richness and performance in clear-cuts. Such insight is essential for understanding changes in species composition and richness in response to clear-cutting and application of intensified harvesting systems. The focus is on productive and managed spruce dominated forests and focal organisms are mosses, liverworts (i.e. bryophytes) and vascular plants. Space-for-time substitution studies were performed in south- and north-facing slopes located in 10 forests and 10 adjacent clear-cut stands in central Sweden. Differences between forests and clear-cuts were interpreted as effects of clear-cutting. The results show that the response of all three focal groups differed between aspects. More species were lost in south-facing slopes and clear-cutting reduced species richness of liverworts as well as of bryophytes and vascular plants associated with sheltered habitats. By contrast, clear-cutting caused no reduction in any group and more species were added in north-facing slopes. As a result north-facing clear-cuts generally had higher species richness than their forest counterparts. The disparate patterns in species’ response between aspects were most likely caused by initial microclimatic differences and a greater microclimatic change in south-facing slopes, in response to clear-cutting. A paired comparative study of conventionally harvested (i.e. slash left) and slash-harvested clear-cut stands was performed 5-10 years after clear-cutting in south-central Sweden. Both the species composition and the richness of mosses and liverworts were affected by slash harvest, whereas the composition of vascular plants was not. Slash harvest also reduced richness of mosses and liverworts associated with forests and organic substrates (e.g. dead wood and litter). Species richness of vascular plants and bryophytes associated with inorganic substrates (i.e. mineral soil) was unchanged. Differences between conventionally harvested stands and slash-harvested stands were most likely a result of reduced cover of organic material reducing substrate availability and shelter in the latter. Increased mechanical disturbance in slash-harvested stands that destroys remnant forest vegetation and favours pioneers may also play a role. A bryophyte transplant experiment was performed in seven clear-cuts in central Sweden and monitored over one vegetation period. The results show that logging residues (or slash) and forest edges may shelter ground-dwelling bryophytes by buffering the clear-cut microclimate. In conclusion, both slope aspect and extraction of forest bioenergy affect plant survival in clear-cut boreal forests. As surviving plant populations facilitate re-colonisation, north-facing slopes and conventionally harvested clear-cuts (i.e. slash left) may potentially recover faster than south-facing slopes and slash-harvested clear-cuts.
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Dermisis, Dimitrios Charalampos. "Developing an improved, shock-capturing watershed model for simulating spatially variable runoff and soil erosion processes at the hillslope scale." Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/5930.
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The overarching objective of this study was the development, validation and testing of an improved watershed modeling framework that accounts for the effects of spatial heterogeneity on overland flow and erosion processes and it is computationally sound for shallow, overland flows with shock waves. Most of the existing soil erosion models determine fluxes of water and sediment with the assumption of a homogeneous hill. In these models the physical and biogeochemical properties of the heterogeneous hill are spatially averaged, without considering roughness and longitudinal curvature effects as well as differences in the land use/land cover -LU/LC- and soil properties along the hill. This issue was addressed by improving the Water Erosion Prediction Project (WEPP-Original version 2010.1) soil erosion model at the hillslope scale to account for the physics in terms of spatial heterogeneity in flow using a well-established shock-capturing numerical scheme.
The improved WEPP model, referred to as "WEPP-Improved" model was (i) validated via detailed field experiments within an experimental plot and (ii) tested via generic simulations at the hillslope scale covering a variety of scenarios in terms of topography, LU/LC and soil type. Results showed that the WEPP-Improved model could effectively simulate the unsteadiness of the flow as well as the required time (lag) for the flow rate to reach equilibrium conditions. However, the model provided only a steady-state sediment transport rate and could capture only the equilibrium conditions. Further, the WEPP-Improved model reflected the effects of curvature, LU/LC and soil type on flow, as the model did not treat the hillslope as a homogeneous unit. Based on the generic simulations, landscape variability resulted to differences in the predicted peak runoff rate, Qpeak, between the WEPP-Improved vs. WEPP-Original models ranging ~ 3 - 62 % (avg. 19 %) due to curvature effects only, ~ 17 - 170 % (avg. ~ 66 %) due to added effects of LU/LC variability and ~ 5 % - 200 % (avg. ~ 52 %) due to added effects of soil type variability. The highest reported differences on the predicted Qpeak between the two models were attributed to the formation of the shock waves; these differences were dominant for the low in magnitude storm event and attenuated for the high event.
It is believed that if the physical processes are represented accurately at the hillslope scale using the suggested modeling framework, then by utilizing an appropriate routing scheme of the flow and sediment within the stream network, it will be possible to scale-up the flow/sediment routing from the hillslope to the watershed scale without losing the degree of heterogeneity encapsulated from different hillslopes within the drainage network.
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Puech, Christian. "Détermination des états de surface par télédétection pour caractériser les écoulements des petits bassins versants : application à des bassins en zone méditerranéenne et en zone tropicale sèche." Grenoble 1, 1993. http://www.theses.fr/1993GRE10175.
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La liaison entre la teledetection des etats de surface et l'hydrologie est etudiee sur deux sites, revelant l'importance des problemes d'echelle et la necessite d'informations hydrologiques de type versant. Sur les bassins du real collobrier (var, france) apres des corrections imposees par le fort relief, le traitement de l'imagerie satellitaire conduit a une cartographie des essences forestieres. La part d'ecoulement relative a chaque zone homogene est calculee a des pas de temps annuel, trimestriel, mensuel et sur des episodes. Une liaison coherente entre zones et types d'ecoulement est obtenue mais la signification exacte de zone homogene, et le manque d'observations hydrologiques de versant rendent la validation delicate. Sur des bassins saheliens, un traitement d'image specifique a des zones heterogenes est mis au point, base sur une detection en deux niveaux: paysage, puis etats de surface type du sahel. Le ruissellement elementaire correspondant est agrege sur le bassin versant selon le modele lineaire de l'orstom. Certaines zones non contributives en grand rendent indispensable une approche complementaire a un autre niveau d'echelle
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Laghmach, Rabia. "Modélisation de la cristallisation des élastomères sous sollicitation mécanique par champ de phase." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0061/document.
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La cristallisation induite par déformation des élastomères est un processus cinétique qui conduit à la formation de nano-cristallites thermodynamiquement stables. La présence de ces nano-cristallites au sein de la phase amorphe modifie considérablement les propriétés mécaniques des élastomères cristallisables. Ces élastomères ont en effet la propriété intéressante d'être auto-renforçants. L’objectif de ce travail est de développer un modèle physique capable de décrire localement l’évolution de la microstructure sous l’effet d’un champ de contrainte élastique durant la cristallisation. Dans ce but, un modèle de champ de phase est élaboré et mis en œuvre dans le cadre de la mécanique des milieux continus en couplant thermodynamique et mécanique avec une dynamique de transition de phase d’Allen-Cahn. La description thermodynamique de la cristallisation induite par déformation à petite échelle est basée sur la fonctionnelle d’énergie libre du système amorphe-cristal. Les conséquences du choix de cette formulation sont discutées, on étudie en particulier les effets de contraintes élastiques sur l’équilibre des phases en volumes ainsi que sur la cinétique de croissance des domaines cristallins au sein de l’amorphe. L’introduction de l’élasticité du réseau des contraintes topologiques induite par les enchevêtrements et/ou les nœuds de réticulation dans le modèle de champ de phase a permis de mettre en évidence l’existence d’un état stable de cristallites formées (modèle énergétique) mais aussi des instabilités de croissance (modèle cinétique). Sur la base de ces deux modèles, cinétique et énergétique, nous avons étudié systématiquement l’influence des contraintes topologiques sur la cinétique de croissance et nous montrons que cette cinétique est en effet contrôlée par l’accumulation de contraintes élastiques à l’interface. La prise en compte de l’élasticité du réseau des contraintes topologiques dans l’approche thermodynamique de cristallisation prédit une augmentation de la tension de surface et par conséquent un arrêt du mécanisme de croissance en donnant lieu à la formation de cristallites stables. Enfin, nous avons adopté le modèle énergétique pour modéliser le couplage entre nucléation, croissance et déformation cyclique. Pour valider le modèle local proposé une comparaison entre les résultats des simulations par champ de phase et les données expérimentales issues de la caractérisation d’un caoutchouc naturel réticulé est effectuée et nous montrons qualitativement l’accord entre l’expérience et le modèle<br>Natural rubber NR and more generally elastomer presents unique physical properties that are very important for many engineering applications. Strain induced crystallization of elastomer presents a major interest because it improves considerably the mechanical properties. In fact, the presence of crystallites within the amorphous phase in a polymer network induces a strengthening of this material, giving NR a self-reinforcement character. In this thesis, we develop a mesoscopic model to describe the crystallization of elastomers under strain. In this context, we present a kinetic model using a new physical approach: a phase field model. This model combines the crystallization thermodynamics with the local stress field. The thermodynamic description of the phase transition is based on a Gibbs free energy functional F which contains all energy contributions of the system: the bulk contributions (enthalpy and entropy) and surface tension. To understand the experimental observation of nanometer size crystalites, an explicit account of the topological constraints induced by both entanglements and/or crosslinks is necessary. We investigated two limiting mechanisms, a kinetic limitation of the growth, and an energetic limitation. Based on both the kinetic and the energetic approaches, we have systematically studied the influence of topological constraints on the growth process. We have shown that the growth process is affected by the accumulation of elastic stress at the interface. The kinetic model predicts the existence of instabilities during the growth. These instabilities induce a heterogeneous dynamical growth which leads to the formation of dendrite like structures. On the contrary, the energetic approach predicts an exponential increase of the surface tension during the growth that limits the size of the crystallites very efficiently. In the last part we investigated elastomer crystallization under cyclic deformation. To this end, we coupled the previous energetic model with the nucleation process. Finally the simulation data are compared with experimental measurements
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Du, Preez Cherisse. "Resolving relationships between deep-sea benthic diversity and multi-scale topographic heterogeneity." Thesis, 2014. http://hdl.handle.net/1828/5828.
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Resolving diversity patterns and their underlying drivers has application for both ecological theory and ocean management. Because seafloor characteristics are often used to assess bottom habitat, I examined the relationship between deep-sea benthic (bottom-living) diversity and multi-scale topographic heterogeneity. Most work occurred on the Canadian Pacific continental shelf at Learmonth Bank with additional sites in Strait of Georgia (BC) and Gulf of Maine (Atlantic shelf). High-resolution species distribution and seafloor data were annotated from remotely operated vehicle benthic imagery surveys while large-scale seafloor data were derived from multibeam sonar.
New method development to address problems of current methods and to facilitate comparison among ecosystems is a major outcome. My new MiLS method (microtopographic laser scanning) can profile the deep seafloor at a resolution of ~1-2 cm with high accuracy and precision. I also developed a new ACR (arc-chord ratio) rugosity index as a measure of 3-D topographic heterogeneity that is simple, accurate and highly versatile.
Model systems and scales vary among my studies but results consistently yield a positive relationship between diversity and topographic heterogeneity and identify bottom hydrodynamics as an important underlying driver. Rockfish Sebastes spp. associate with higher seafloor rugosity non-randomly and select for deep-sea corals and sponges over inert substrata alone. Data indicate that degradation of biogenic structures is a long-term detriment to rockfish species. Gorgonian coral- and sponge-dominant biotopes strongly associate with a single substratum type. These relationships were used to map coral and sponge distributions. This work, which collectively adds new information on the ecological relevance and distribution of corals and sponges, is pertinent to the conservation and management of fish stocks and vulnerable marine ecosystems. Epibenthic community variables abundance, richness, and Shannon diversity positively correlated with both the local microtopographic heterogeneity on a scale of 10 m2 and with the surrounding regional large-scale topographic heterogeneity on scales of 25 to 250,000 m2. Relationships were strongest between epibenthic community variables and the largest scale rugosity and were used to generate and test predictive diversity models. Where management strategies rely on surrogate measures in data-poor areas, mapping benthic diversity using ACR rugosity will provide good indicators.
Although bottom hydrodynamics is consistently identified as an underlying driver of epibenthic patterns related to topographic heterogeneity, data suggest the nature of the relationship varies across spatial scales. At small scales, high topographic heterogeneity likely increases diversity by increasing the number of available niches (including hydrodynamic gradients; e.g., the abrupt vertical rugosity created by tall corals and sponges provides rockfish refuge from currents) while at large scales, high topographic heterogeneity increases local diversity less directly through distant hydraulic events that alter bottom flow hydrodynamics.<br>Graduate<br>0329<br>0416<br>0799<br>cdupreez@uvic.ca
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Erlandsson, J., Christopher McQuaid, and V. E. Kostylev. "Contrasting spatial heterogeneity of sessile organisms within mussel (Perna perna L.) beds in relation to topographic variability." 2005. http://hdl.handle.net/10962/d1011979.
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We examined the spatial heterogeneity in three sessile rocky shore organisms, the mussel Perna perna, the barnacle Octomeris angulosa (Sowerby) and the red alga Gelidium pristoides (Turn.) at a range of continuous local scales along horizontal transects within mid- and upper mussel beds of South African shores. We also examined the relationships between variability of organisms and topographic features (rock depressions, slope, aspect), and between mussel, barnacle and algal variability over the same scales. To estimate spatial heterogeneity, we analyzed scaling properties of semivariograms using a fractal approach. Relationships between different variables at the different scales were examined by cross-semivariograms. Spatial dependence of P. perna variability increased with spatial dependence of topographic variability, so that scaling regions of mussel and topographic distributions corresponded well. This relationship often improved with larger local scales (mussel cover increased with depressions, steeper slope and aspect towards waves), while at smaller spatial scales, variability in mussel cover was less well explained by variability in topography. The variability of the barnacle O. angulosa exhibited spatial dependence, even on topographically unstructured shores. In contrast, the distribution of the alga G. pristoides revealed high fractal dimensions, showing spatial independence on topographically unstructured shores. Algae also showed a very strong negative relationship with mussels at most local scales, and a negative relationship with barnacles in upper zones, especially at larger local scales. Barnacles may show clear spatial dependence because of hydrodynamics (at larger local scales) and the need to find a future mate in close proximity (at smaller local scales), while algae may show a strong negative relationship with mussels because of competition for space.
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Peach, Michelle A. "Tussock sedge meadows and topographic heterogeneity ecological patterns underscore the need for experimental approaches to wetland restoration despite the social barriers /." 2005. http://catalog.hathitrust.org/api/volumes/oclc/58538898.html.
Full textBooks on the topic "Topographic heterogeneity"
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Levy, Jonathan I. Evaluating heterogeneity in indoor and outdoor air pollution using land-use regression and constrained factor analysis: With a critique by the HEI Health Review Committee. Health Effects Institute, 2010.
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De Zordo, Ornella, ed. Saggi di anglistica e americanistica. Firenze University Press, 2010. http://dx.doi.org/10.36253/978-88-6453-022-2.
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Saggi brings together the results of the research activity carried out in 2008 on the PhD course in English and American Studies (Department of Modern Philology, University of Florence). The seven contributions relate to the theatre, narrative, poetry, autobiographical writing and correspondence, and range from the Renaissance up to the present day, offering critical perspectives that go from the analysis of the postmodern identity to the phenomenon of rewriting, from reception theories to comparative studies, and from literary topography to computational linguistics. The heterogeneity of the material illustrates the free choice of the young academics who, in the climate of collaboration that was established, decided to address the technical and editorial aspects of the book as a team in the open access editorial workshop of the Department.
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Gao, Yanhong, and Deliang Chen. Modeling of Regional Climate over the Tibetan Plateau. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.591.
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The modeling of climate over the Tibetan Plateau (TP) started with the introduction of Global Climate Models (GCMs) in the 1950s. Since then, GCMs have been developed to simulate atmospheric dynamics and eventually the climate system. As the highest and widest international plateau, the strong orographic forcing caused by the TP and its impact on general circulation rather than regional climate was initially the focus. Later, with growing awareness of the incapability of GCMs to depict regional or local-scale atmospheric processes over the heterogeneous ground, coupled with the importance of this information for local decision-making, regional climate models (RCMs) were established in the 1970s. Dynamic and thermodynamic influences of the TP on the East and South Asia summer monsoon have since been widely investigated by model. Besides the heterogeneity in topography, impacts of land cover heterogeneity and change on regional climate were widely modeled through sensitivity experiments.In recent decades, the TP has experienced a greater warming than the global average and those for similar latitudes. GCMs project a global pattern where the wet gets wetter and the dry gets drier. The climate regime over the TP covers the extreme arid regions from the northwest to the semi-humid region in the southeast. The increased warming over the TP compared to the global average raises a number of questions. What are the regional dryness/wetness changes over the TP? What is the mechanism of the responses of regional changes to global warming? To answer these questions, several dynamical downscaling models (DDMs) using RCMs focusing on the TP have recently been conducted and high-resolution data sets generated. All DDM studies demonstrated that this process-based approach, despite its limitations, can improve understandings of the processes that lead to precipitation on the TP. Observation and global land data assimilation systems both present more wetting in the northwestern arid/semi-arid regions than the southeastern humid/semi-humid regions. The DDM was found to better capture the observed elevation dependent warming over the TP. In addition, the long-term high-resolution climate simulation was found to better capture the spatial pattern of precipitation and P-E (precipitation minus evapotranspiration) changes than the best available global reanalysis. This facilitates new and substantial findings regarding the role of dynamical, thermodynamics, and transient eddies in P-E changes reflected in observed changes in major river basins fed by runoff from the TP. The DDM was found to add value regarding snowfall retrieval, precipitation frequency, and orographic precipitation.Although these advantages in the DDM over the TP are evidenced, there are unavoidable facts to be aware of. Firstly, there are still many discrepancies that exist in the up-to-date models. Any uncertainty in the model’s physics or in the land information from remote sensing and the forcing could result in uncertainties in simulation results. Secondly, the question remains of what is the appropriate resolution for resolving the TP’s heterogeneity. Thirdly, it is a challenge to include human activities in the climate models, although this is deemed necessary for future earth science. All-embracing further efforts are expected to improve regional climate models over the TP.
Book chapters on the topic "Topographic heterogeneity"
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Bin, Yue, Zhigao Wang, Zhangming Wang, Wanhui Ye, Honglin Cao, and Juyu Lian. "The effects of dispersal limitation and topographic heterogeneity on beta diversity and phylobetadiversity in a subtropical forest." In Plant Ecology in China. Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-90-481-9993-8_6.
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Kudo, Yoshihisa, Etsuro Ito, and Akihiko Ogura. "Topographical Heterogeneity of Glutamate Agonist-Induced Calcium Increase in Hippocampus." In Excitatory Amino Acids and Neuronal Plasticity. Springer US, 1990. http://dx.doi.org/10.1007/978-1-4684-5769-8_15.
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Yue, Jiaxin, and Yonggang Shi. "Uncovering Heterogeneity in Alzheimer’s Disease from Graphical Modeling of the Tau Spatiotemporal Topography." In Lecture Notes in Computer Science. Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-43904-9_26.
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Wassef, Marion, Pierre Angaut, Leonor Arsenio-Nunes, Frank Bourrat, and Constantino Sotelo. "Purkinje Cell Heterogeneity: Its Role in Organizing the Topography of the Cerebellar Cortex Connections." In The Cerebellum Revisited. Springer US, 1992. http://dx.doi.org/10.1007/978-1-4612-2840-0_1.
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Parente, Joana, Marj Tonini, Malik Amraoui, and Mário Pareira. "Socioeconomic Impacts and Regional Drivers of Fire Management: The Case of Portugal." In Fire Hazards: Socio-economic and Regional Issues. Springer International Publishing, 2024. http://dx.doi.org/10.1007/978-3-031-50446-4_14.
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AbstractWildfires are uncontrolled and unwanted fires that usually occur in forested/rural areas and burn forests, agricultural areas, and wildlands. Land abandonment, with the consequent growth of the rural–urban interface, increases the exposure and vulnerability of fire-prone regions around the World. In the last two decades, Europe experienced a high number of wildfires causing large burnt areas mainly concentrated in the Mediterranean Basin. This high fire incidence seems to be the result of human activities including land use/land cover changes, but also of climate variability and change. In the present study, we analyse the current situation in Portugal, which is the European country with the highest total number of wildfires and the second-highest total burnt area. The spatial and temporal variability of the wildfires within the country is very heterogeneous, due to the human and biophysical drivers. In this regard, four main aspects are considered and discussed: (1) the spatial and temporal distribution of wildfires in mainland Portugal; (2) the main human and biophysical fire drivers; (3) socioeconomic impacts; and (4) the main strategies for fire risk mapping and management. The main results indicate high spatial heterogeneity of the fire incidence, with higher fire activity in the northern region than the southern region, mainly promoted by a higher irregular topography and significantly different types of climate and land use/land cover characteristics. We highlight how fire incidence is strongly dependent on many biophysical and human factors/drivers and the direct and indirect socioeconomic impacts of wildfires. Methodologies and indexes developed by Portuguese authorities to map fire risk and assess fire danger are described. The elements discussed in this chapter result from research and lessons learned in recent years on the fire regime in Portugal and Europe. These findings can contribute to improving forest, landscape, and fire management, in Mediterranean European countries which share similar characteristics.
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Ritchie, Mark E., and Han Olff. "Resource Partitioning and Biodiversity in Fractal Environments with Applications to Dryland Communities." In Biodiversity in Drylands. Oxford University Press, 2005. http://dx.doi.org/10.1093/oso/9780195139853.003.0018.
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Arid and semiarid ecosystems (drylands) often contain a higher diversity of animals and plants than would be expected from their low productivity. High spatial heterogeneity of resources and physical habitats, exhibited at a wide range of spatial scales (Rundel 1996, Holling 1992, Peterson et al. 1998), may be a major factor explaining such high diversity. For example, at extremely small scales (<10 cm), branched plant material and various soil physical processes can create spatial niches for invertebrates, cyanobacteria, and other cryptogamic organisms (Lightfoot and Whitford 1991). At somewhat larger scales (<10 m), desert shrubs may aggregate water and organic material in “islands of fertility,” yielding a highly patchy heterogeneous distribution of resources (e.g., seeds, water) for other plants and animals (Gibbens and Beck 1988, Halvorson et al. 1997, chapter 13 this volume, chapter 11 this volume). At even larger scales (>100 m), soil erosion patterns create topographic variation that locally concentrates available water and nutrients, yielding a marked heterogeneity in the distribution of productivity across the landscape (Milne 1992). These heterogeneous distributions of physical environments, biotic material, and resources are likely to have strong effects on biodiversity. Ecologists have long associated greater spatial heterogeneity with higher species diversity (MacArthur 1964; Brown 1981; May 1988). Within a particular physical environment (habitat), this association exists presumably because collections of species that use similar resources, or “guilds,” can coexist whenever they can more finely divide up space and different-sized resource “packages” (Hutchinson and MacArthur 1959, Brown 1981, 1995, Morse et al. 1985, Peterson et al. 1998). The partitioning of space and different resource patches may be constrained by the different body sizes of species within guilds (Hutchinson and MacArthur 1959, Morse et al. 1985, Belovsky 1986, 1997, Brown 1995, Siemann et al. 1996). However, the mechanism by which body size and spatial heterogeneity of habitats and resources determine species diversity remains unclear (May 1988, Brown 1995, Siemann et al. 1996, Belovsky 1997). Resource partitioning and spatial heterogeneity therefore may strongly influence diversity in drylands, where, for example, well-known guilds of granivorous vertebrates and invertebrates are structured by competition for different sizes of seeds and seed patches (Brown et al. 1979, Davidson et al. 1980, 1985).
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"The Ecology and Management of Wood in World Rivers." In The Ecology and Management of Wood in World Rivers, edited by LEE BENDA, DANIEL MILLER, JOAN SIAS, et al. American Fisheries Society, 2003. http://dx.doi.org/10.47886/9781888569568.ch3.
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<em>Abstract.</em>—Wood is recruited to rivers by a diversity of processes, including chronic mortality, windstorms, wildfires, bank erosion, landslides, and ice storms. Recruitment, storage, and transport of large wood in streams can be understood in terms of a mass balance, or quantitative wood budget, similar to the study of other material fluxes in watersheds. A wood budgeting framework is presented that includes numerical expressions for punctuated forest mortality by fire, chronic mortality and tree fall, bank erosion, mass wasting, decay, and stream transport. When used with appropriate parameter values derived for specific conditions or regions, the wood budget equations can be used to make predictions on the importance of various landscape processes on wood abundance in streams in any locale. For example, wood budgets can be used to predict how variations in climate (wet – dry), topography (steep – gentle), basin size (small – large), and land management could affect abundance and distribution of large wood in streams. Wood budgets also can be integrated into numerical simulation models for estimating the natural range of variability, specifically temporal fluctuations of wood supply driven by large storms, floods, fires, and mass wasting, and spatial variability driven by topographic heterogeneity and variations in wood transport. Field studies of wood in streams may be enhanced by the use of a wood budget framework. This includes specifying what measurements are required over what length of stream for estimating recruitment rates of all relevant inputs processes, wood loss by decay, and stream transport of wood. Finally, wood budgets can be used to estimate rates of bank erosion, forest mortality, and landsliding, given appropriate field measurements of wood in streams and riparian conditions.
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Ehrlich, Paul R., Ilkka Hanski, and Carol L. Boggs. "What Have We Learned?" In On the Wings of Checkerspots. Oxford University PressNew York, NY, 2004. http://dx.doi.org/10.1093/oso/9780195158274.003.0014.
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Abstract In this chapter we recap the major lessons to be distilled from the work on checkerspots. Some of the lessons are novel; some reinforce previous conclusions by other researchers. The first, and perhaps the most significant lesson relates to the model system approach that we have taken in our research. The diversity of natural populations is so great that model systems may never play quite the same role in population biology as Drosophila in genetics or Caenorhabditis elegans in developmental biology. Nonetheless, the checkerspot system has demonstrated that concentrating research efforts on particular systems will greatly contribute to better understanding of many fundamental issues in ecology, evolution, behavior, and conservation biology. The knowledge gained from the model systems ultimately can be applied to answering questions about less intensively studied species. For instance, if we were now asked to evaluate the conservation status of a little-known endangered insect species, we would first look at its probable metapopulation structure, the topographic heterogeneity of its habitat, and how these will interact with climatic variability. None of this may prove critical in a particular system, but the work on checkerspots tells us that here would be a good place to start.
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Paruelo, José María, and Estebán G. Jobbágy. "The Grasslands and Steppes of Patagonia and the Río de la Plata Plains." In The Physical Geography of South America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195313413.003.0022.
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The Patagonian steppes and the Río de la Plata grasslands occupy a vast proportion of the plains, plateaus, and hills of southern South America, and are characterized by the almost absolute absence of trees. Prairies and steppes (grass and low shrubs) are the dominant physiognomic types, and forests are restricted to some riparian corridors. Savannas become important only in the ecotones of these regions, whereas meadows may be locally important under particular topographic or edaphic conditions. The Río de la Plata grasslands (RPG), one of the most important grassland regions in the world, extend between 28°S and 38°S latitude, covering about 700,000 km2 of eastern Argentina, Uruguay, and southern Brazil. The boundaries of these grasslands include the Atlantic coastline to the east, dry temperate forests to the south and west, and subtropical humid forests to the north. Woody vegetation within the region is restricted to small areas near water bodies, such as the gallery forests along the large Paraná and Uruguay rivers and their tributary streams. The Patagonian steppes occupy the southern tip of the continent from approximately 40°S, and are framed by the Andes to the west and the Atlantic coast to the east and south and cover more than 800,000 km2 of Chile and Argentina. Toward the west, the region displays a sharp ecotone with the subantarctic forests, whereas to the north it grades into a broad zone of Monte scrublands in central Argentina. The RPG and the Patagonian steppes are separated by a wide strip of woody vegetation, the Monte and Espinal phytogeographic units (see chapter 10; Cabrera and Willkins, 1973). In this chapter, we describe the heterogeneity and main characteristics of the dominant ecosystems of the Patagonian steppes and the RPG, focusing on environmental controls and human-induced changes. Although numerous criteria have been applied to describe the internal heterogeneity of both regions, we emphasize here the structural and functional attributes of vegetation as integrators of climate, physiography, and land use.
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Marchesini Ivan, Santangelo Michele, Guzzetti Fausto, Cardinali Mauro, and Bucci Francesco. "Modeling Morpho-Structural Settings Exploiting Bedding Data Obtained Through the Interpretation of Stereoscopic Aerial Photographs." In Geotechnical Safety and Risk V. IOS Press, 2015. https://doi.org/10.3233/978-1-61499-580-7-797.
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Landslide abundance is controlled by multiple factors, including the presence and attitude of beddings, foliation, faults, joints and cleavage systems. Few attempts were made to exploit bedding attitude (BA) data (or data on similar types of rock discontinuities) in statistical or physically based models for regional slope stability analysis. A reason for the lack of applications lays in the complexity of the bedding data, and in the difficulty in the treatment and modelling of circular information. Typically, BA data are collected as point data through field surveys, and suffer from heterogeneity in their spatial distribution. The latter problem is particularly important due to the limited possibility to collect BA data in areas of difficult access. An additional problem lays in the spatial interpolation of the BA data, which are directional data that cannot be interpolated using standard approaches. We build on previous work where we proposed an approach to obtain BA data from bedding traces (BT) i.e., linear signatures of layered rocks on the topographic surface, obtained through the visual interpretation of aerial photographs, and to interpolate the BA data to construct maps showing the geometrical relationship between BA data and slope geometry i.e., maps showing cataclinal, orthoclinal, and anaclinal slopes. In this work, we consider the uncertainties in the definition of the BAs that are used in the production of morpho-structural domain maps, and we investigate the relationships between the morpho-structural domains and landslide abundance in a study area in Umbria, Italy.
Conference papers on the topic "Topographic heterogeneity"
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Kadoya, Takuma, Eizo Moriwaki, and Eiji Okada. "Monte Carlo investigation of separation of two absorbers in topographic image." In European Conference on Biomedical Optics. Optica Publishing Group, 2001. http://dx.doi.org/10.1364/ecbo.2001.4431_176.
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Near infrared topographic imaging is an effective instrument to image brain-cortex activity. The image is reconstructed by changes in light intensity detected with multi-channel source-detector pairs. However, light scattering in tissue prevents us from improving the spatial resolution of the reconstructed image, hence it is important to evaluate the effect of scattering on the spatial resolution of the reconstructed image. In this study, separation of two absorbers in topographic image is investigated by Monte Carlo simulation to evaluate the spatial resolution of topographic imaging. Because of heterogeneity of tissue, especially presence of low scattering CSF layer affects the light propagation in the adult brain. The adult head model consists of three layers including a low scattering medium. In case where the separation of two absorbers is greater than the distance between adjacent measurment points, the two absorbers can be separated in the topographic image.
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Smertina, M. A., E. A. Efremova, and V. A. Marchenko. "DISTRIBUTION OF THE MAIN STRONGYLATA INFECTIONS OF HORSES IN THE PROVINCES OF THE ALTAI REPUBLIC." In THEORY AND PRACTICE OF PARASITIC DISEASE CONTROL. All-Russian Scientific Research Institute for Fundamental and Applied Parasitology of Animals and Plant – a branch of the Federal State Budget Scientific Institution “Federal Scientific Centre VIEV”, 2023. http://dx.doi.org/10.31016/978-5-6048555-6-0.2023.24.447-452.
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The research purpose was to study the distribution of the main Strongylata infections
 of horses in the provinces of the Altai Republic. Infective larvae of strongylates after
 their cultivation were isolated by the Berman-Orlov method and subsequently
 identified taking into account morphometric characteristics. The ubiquitous
 distribution of helminths of the suborder Strongylata with heterogeneity of infection
 in ungulates was detected in the context of administrative districts and provinces.
 In the provinces as a whole and in administrative districts, species of the family
 Trichonematidae predominate, and their infection rate in horses significantly
 exceeds the infection with other strongylates (IP, 64–99%). The infection rate
 of nematodes of the family Strongylidae, including Strongylus, Alfortia and
 Delafondia is 2–4 times smaller and is 31.9, 20.4 and 10.6%, respectively. On the
 farms of the Southeastern Altai (Kosh-Agachsky District), the invasion of ungulates
 with strongylates in general including Trichonema, Alfortia and Delafondia is 2-10
 times lower than in other districts of the Republic and amounts to 59.6, 51.6, 4.8
 and 3.2%, respectively. The sharp difference in the infection of animals in this region in our opinion is mainly associated with the topographic and landscape features of
 the area and is due to the low heat supply and aridity of the climate in most of the
 territory.
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Phukan, Madhujya L., Saad A. Siddiqi, and Matthew J. Robert. "Microporosity of the Shuaiba Formation: The Link Between Depositional Character and Diagenesis in Sharjah, United Arab Emirates." In Abu Dhabi International Petroleum Exhibition & Conference. SPE, 2021. http://dx.doi.org/10.2118/207786-ms.
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Abstract Objectives/Scope This study focuses on assessing the uncertainties related to sedimentological heterogeneity and the diagenetic variability within the gas-condensate reservoirs of the Shuaiba Formation, Sharjah, United Arab Emirates. Methods, Procedures, Process For characterizing the sedimentology of the Shuaiba Formation, a lithofacies scheme has been developed on the basis of Dunham's (1962) and Embry & Klovan classification (1971). The lithofacies are grouped on the basis of their genetic relationships which also correspond to their depositional environment, and are designated as lithofacies associations. A pore-scale fabric/textural investigation was completed using conventional thin-section microscopy and Scanning Electron Microscopy (SEM). Results, Observations, Conclusions The Shuaiba sediments are characterized by skeletal-rich wackestone/packstones to floatstones deposited in an inner ramp setting. The stacking pattern of the inner ramp deposits define broad third order trends observed across the studied field.These trends are relatable to the regional sequence stratigraphic framework of Sharland et al. (2001). In higher order sequences, lateral variations in lithology occur, defining the reservoir heterogeneity, which are most likely forced by topographic/hydrodynamic variation as well as sea level changes. Reservoir quality distribution is controlled by various factors, including the depositional texture and allochem assemblage (abundance, type, and size). Diagenetic alteration of the textures played an important role in determining overall reservoir quality. The pore enhancing phases are defined by dissolution events, where later stage dissolution was the dominant phase to enhance micropores and also to create meso- to macropores which partially to completely negated the effect of previous cementing phases. In these Shuaiba deposits, the porosity comprises common matrix-hosted as well as grain-hosted micropores along with variably distributed intraparticle and rare mouldic meso- to macropores. The measured porosity ranges from very poor to moderate (0.5-17%) while permeability is very low to low (&lt;0.001-1.49 mD). The detailed petrographic analysis highlighted that changes in micritic fabric shows a variation in the reservoir properties. From SEM observations, it was noted that microcrystalline calcite crystals of polyhedral to sub-rounded morphologies with intercrystalline contacts ranging from facial to sub-punctic, which display relatively a good microporosity developement, whereas crystals that show anhedral compact character with coalescent/fused intercrystalline contacts are rarely associated with any microporosity. Novel/Additive Information In addition to SEM characterization, porosity data and elastic properties (e.g., Young's moduli) generated from the interpretation of the well-log data, were used to investigate the prospective relationship between the microporous carbonates and elastic properties. The comparisons highlight that an increase in porosity values results in a decrease of Young's moduli values, thereby reflecting a decrease in the stiffness of the rock. On the other hand, the increase in porosity maybe linked to the evolution of anhedral, compact, micritic fabric to polyhedral/sub-rounded micritic fabric. The understanding of this relationship provides a powerful tool to be utilized in reservoir architecture prediction based on integrating the sedimentological framework and diagenetic overprint.
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Kwon, Gi Hwan, Tae Young Kim, and Sung Jin Kim. "Electrokinetic Microscope for Imaging Three-Dimensional Surface Topography and Heterogeneity." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-62415.
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We introduce the concept of electrokinetic microscope (EKM) which is an imaging technique based on hydrodynamics and electrokinetics. The EKM can provide information of the three-dimensional surface topography and heterogeneity using a syringe pump, pressure sensor, and electrometer. The three-dimensional surface topography is obtained from the relation between the flow impedance and a relative distance of a probe from a specimen, and the surface heterogeneity is obtained by measuring streaming potential or current electrokinetically generated by a surface material. Experimental results show that streaming potential and current depend not only on the relative distance between the probe and specimen, but also on surface materials. The major advantages of the EKM are that it does not need direct physical contact between the probe and specimen, and the surface topography and heterogeneity of the specimen are measured simultaneously. EKM micrographs of microscale patterns with various materials and linewidths are presented. The lateral resolution of the EKM strongly depends on the inner diameter of the probe.
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Artemyev*, Mikhail, Hyoungsu Baek, and Richard L. Gibson. "Fast generalized multiscale FEM for complex media: effortless modeling of topography and heterogeneity." In SEG Technical Program Expanded Abstracts 2015. Society of Exploration Geophysicists, 2015. http://dx.doi.org/10.1190/segam2015-5871574.1.
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Drake, J. M. "Photophysical Studies of DAQ on Silica and Aluminum Oxides. A Molecular Probe of Surface Heterogeneity." In Microphysics of Surfaces, Beams, and Adsorbates. Optica Publishing Group, 1985. http://dx.doi.org/10.1364/msba.1985.mc5.
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The optical features of organic molecules adsorbed to the surface of oxides, such as silica and alumina, can be strongly perturbed by the chemical properties of the surface adsorption sites. The topography of the surface as it relates to the fractal dimension and its relation to the nature and distribution of surface sites is important information if we are to be able to understand the photophysics and photochemistry of surface bound molecules. The work we report here is for the molecule 1,4 dihydroxyanthraquinone (DAQ, Quinizarin). This molecule provides striking evidence of how the surface of silica gel modifies the optical features of DAQ in different ways depending on the nature of the surface adsorption site.
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Hiwiller, Erika, and Kuldeep Singh. "DETERMINING HOW TOPOGRAPHY AND HYDRAULIC HETEROGENEITY CONTROL TÓTH FLOW CHARACTERISTICS AND IMPACT THE TRANSPORT OF ROAD SALT IN AQUIFERS: A GUIDE FOR POLICY AND MANAGEMENT." In GSA Connects 2021 in Portland, Oregon. Geological Society of America, 2021. http://dx.doi.org/10.1130/abs/2021am-367922.
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Bardalaye, Jayanta, Ali Almuntaser, Ibrahim Jaber, Madhujya L. Phukan, Saad A. Siddiqi, and Ishan Raina. "Effects of Diagenesis and Depositional Settings on the Reservoir Quality of the Barremian-Aptian, Kharaib Formation: A Case Study from the Bahrain Field, Kingdom of Bahrain." In ADIPEC. SPE, 2022. http://dx.doi.org/10.2118/211599-ms.
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Abstract The Barremian-Aptian, Kharaib Formation is among the main reservoir units in the Middle-East. The Kharaib Formation is broadly divisible into three main zones: the Upper, Middle and Lower Kharaib, which are defined based on their distinct sedimentological characteristics. The Kharaib interval has been extensively studied across the region; however, the inherent heterogeneity associated with sediments always makes it challenging for interpretation of the depositional facies, stratal geometries, and the prediction of their reservoir properties. This study focuses on the Middle and Upper Kharaib by integrating sedimentological, diagenetic, and pore-scale datasets to provide a better understanding of the depositional framework, diagenesis and its effects on the reservoir properties. Dunham/Embry & Klovan classification (1971) scheme is used to describe the sediments, which determines lithofacies. Lithofacies that are genetically relatable are grouped into larger sets of associations. The lithofacies association represent their sedimentary environments of deposition. The grouping/stacking pattern of the sediments reflects a broad third-order sequence. Higher-order variations/sequences are either from localized topographical changes or energy variations or from sea-level changes, which thereby imparts lateral reservoir heterogeneity. X-ray diffraction (XRD) analysis defines the mineralogical composition, whereas pore-scale fabric/textural characteristics have been defined via conventional light microscopy and scanning electron microscopy (SEM). Sedimentological description of the Kharaib Formation showed varying textures ranging from mudstone to grain-rich floatstone, which are interpreted to be deposited in a broad homoclinal ramp setting. Petrographic evaluation of the sediments from the studied section highlighted the effects of diagenesis on reservoir properties with calcite cementation significantly reducing the reservoir quality (i.e., lower porosity and permeability). In contrast considerable micro and macropore enhancement due to secondary dissolution appears to negate the effects of cementation. In the studied sediments, the porosity comprises considerable abundance of primary and secondary macropores. The measured porosity varies from moderate to very good, while permeability is low to moderately high. Interrogation of conventional core analysis data establishes that the primary control on reservoir quality distribution is sediment texture and composition. The genetically distinct characteristics of lithofacies related to allochem assemblage, their abundance and size aid in defining the associations, which thereby provides the former fabric for the subsequent diagenetic alterations. The abundance of detrital clays in the middle Kharaib appears to be the primary cause of relatively poor reservoir quality. This study shows that both the original depositional texture/composition and diagenesis have had an important impact on shaping reservoir properties. This integrated approach sheds light on the sedimentological make-up, depositional setting, and diagenetic overprint of the Kharaib Formation and their effect on the reservoir quality of various lithofacies. This understanding will further develop work related to pattern prediction of the Kharaib Formation, which may be extrapolated to uncored intervals for reservoir quality correlation and assessment.
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Wang, Xiangzeng, Longjun Zhang, Jiaxuan Song, et al. "AI-Assisted Automation of Well Type Selection and Pad Optimization During Well Placement in Yan'an Tight Gas Reservoir." In SPE Conference at Oman Petroleum & Energy Show. SPE, 2024. http://dx.doi.org/10.2118/218670-ms.
Full textAbstract:
Abstract The Yan'an tight gas field, situated in the Ordos basin in central China, is emblematic of a typical tight gas reservoir. The field's development planning has been confronted with numerous challenges arising from conditions characterized by high geological heterogeneity, low porosity, multiple production formations, low lateral sand continuity, and a complex topography. Among the pivotal tasks in field development that necessitate addressing these challenges are the screening of well types and the optimization of pad locations. The judicious selection of well types, including horizontal, deviated, or vertical wells, in conjunction with the optimization of pad locations, not only facilitates the control of reserves on a larger scale but also significantly diminishes well construction costs. Conventionally, the manual determination of well types and the optimization of well pad locations rely on the analysis of 2D maps depicting sand distribution and other geological properties. This conventional approach heavily depends on individual experience and meticulousness, requiring weeks or even months to reach a final decision, with results that may lack consistency. To address the aforementioned challenges, two algorithms have been developed, harnessing both domain expertise and a state-of-the-art machine learning (ML) algorithm. The first algorithm concentrates on well type selection based on considerations such as well targets, geological conditions, and drilling constraints. A heuristic algorithm, in conjunction with the nearest neighbors method, has been devised to identify optimal combinations of various well types with the least number of wells. The second algorithm focuses on optimizing well pad locations, taking into account surface, drilling, and cost constraints, using a modified K-means clustering method tailored to address real problems under diverse conditions. Through the implementation of these developed algorithms, the planning of hundreds of infill wells in the Yan'an tight gas field has been achieved with minimal human involvement in as little as half a day, in contrast to the traditional timeline of months. The developed algorithms serve to significantly enhance well placement efficiency, reduce operational expenditures, and consistently yield reliable results.
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Griffith, T. M., D. H. Edwards, R. L. Davies, T. J. Harrison, and K. L. Evans. "EDRF AND RESISTANCE VESSELS." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643721.
Full textAbstract:
The influence of endothelium on vasomotionin resistance vessels was studied in an isolated, buffer-perfused rabbit ear preparation using novel microangiographic techniques and haemoglobin as a specific inhibitor of EDRF. In constricted preparations acetylcholine and Substance P, whose action is EDRF-dependent in large vessels, induceddilatation in vessels down to 25um in diameter which was inhibited by haemoglobin. Log (IC50>q) values calculated from diameter changes were the same in the central artery, GO, and its first three generations of branch vessels Gl, G2 and G3 (ie down to 7Oum) being -7.7 and -9.8 respectively. Consistent with this, almost identical valueswere derived from the pressure responses of the intact network. Such spatial homogeneity has not been found when the same vessels are studied in isolation. In contrast,constrictor responses to 5HT or histamine exhibited spatial heterogeneity (in the rank order G0>G1>G2>G3) which was exaggerated by inhibition of basal EDRF activity. Inerms of normalised diameter changes EDRF and its analogue GTN were equipotent in reversing these constrictor responses in GO to G3. Interms of hydraulic resistance however, dilator responses paralleled relative changesn resistance induced by the constrictor agents. EDRF and GTN thus appear more potentin vessels exhibiting high degrees of tone.In control preparations (i.e. in the absence of pharmacological constriction) basal EDRF activity was found to exert maximal influence in vessels in which calculatedshear stress and hydraulic resistance werehighest, and continuously inhibited myogenic tope in Gl and to a lesser extent G2 and G3. In the absence of haemoglobin, diameter and flow were related by the expression QÒaD4+b in GO, Gl and G2 over an 8-fold range of flow rates. In the high-flow limit this implies constancyof pressure gradient and pressure drop inthese vessels so that the energy expended in delivering a given volume of perfusate to the terminal elements of the bed would be effectively independent of flow rate, rather than directly proportional to it as in a rigid tube.Basal EDRF activity also conferred identical flow-related distensibility in G0 through G3 in control and partially constricted preparations over the samerange of flow rates. This implies independence of flow distribution from flowrate. Flow dependent release of EDRF may provide a mechanism which links network topography with vessel function, thus optimising perfusion characteristics.
Reports on the topic "Topographic heterogeneity"
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Oliveto, Julia. Influence of topography and vegetation heterogeneity on wildfire in Earth System Models. Office of Scientific and Technical Information (OSTI), 2021. http://dx.doi.org/10.2172/1768457.
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