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J. Moeyersons M. Van Den Eeckhaut J. Nyssen Tesfamichael Gebreyohannes J. Van de Wauw J. Hofmeister J. Poesen J. Deckers Haile Mitiku 《CATENA》2008
Mass movement topography characterises the escarpments and piedmont zones of the tabular ridges in the western part of the Mekelle outlier, Tigray, Ethiopia. Several types of mass movements can be distinguished. The first type is rockfall produced by 357 km rocky escarpments and cliffs during the rainy season. In the study area, every current kilometer of Amba Aradam sandstone cliff annually produces 3.7 m3 of rock fragments. However, this is an under-estimation of the actual cliff and escarpment evolution, which is also characterised by debris slides and small rock slides. 相似文献
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S.G. Tesfamichael F. Ahmed J.A.N. van Aardt F. Blakeway 《Forest Ecology and Management》2009,258(7):1188-1199
Estimating stems per hectare (SPHA) for a given forest area from high spatial resolution remotely sensed data usually follows the identification of individual trees. A common method of tree identification is through local maxima filtering, which in the context of a lidar canopy height model (CHM), seeks to locate the highest value within a specified neighbourhood of pixels. Hence, specifying an appropriate window size is a critical consideration. This study investigated the potential of the semi-variogram range towards defining an average window size for a given plot within Eucalyptus species plantations. The analysis also included comparisons of CHMs with three pixel sizes (spatial resolutions) (0.2 m, 0.5 m, and 1 m) at lidar point density of 5 points/m2 and three lidar point densities (1 point/m2, 3 points/m2, and 5 points/m2). These variations were introduced to study the effect of interpolated height surface resolution and lidar point density, respectively, on the identification of trees. Semi-variogram analysis yielded range values that varied distinctly with spatial resolution and point density. Computation of SPHA based on the semi-variogram range values resulted in overall accuracies of 73%, 56%, and 41% for 0.2 m, 0.5 m, and 1 m resolutions, respectively. A comparative approach, that defines window size based on pre-determined tree spacing, yielded corresponding accuracies of 82%, 82%, and 68% at the respective CHM resolutions. Point density comparisons based on interpolated CHM of 0.2 m resolution and the semi-variogram approach resulted in similar results between 5 points/m2 (73%) and 3 points/m2 (70%), whereas 1 point/m2 returned the lowest accuracy (56%). Similar trends with superior accuracies were observed using the pre-determined tree spacing approach from the same resolution CHM: 82% (5 points/m2), 80% (3 points/m2), and 74% (1 point/m2). While all estimates were negatively biased, the CHM with a 0.2 m spatial resolution at a point density of 3 points/m2 resulted in a reasonable level of accuracy, negating the need for high density (>3 points/m2) lidar surveys for this purpose. It was concluded that the semi-variogram approach showed promise for estimation of SPHA, particularly due to its independence from a priori knowledge regarding the tree stocking of the plantation. 相似文献
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Amanda L. Duffy Francisco J. Olea‐Popelka James Eucher Dahlia M. Rice Steven W. Dow 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2010,39(3):302-305
Background: The chemokine monocyte chemoattractant protein‐1 (MCP‐1) is a primary regulator of monocyte mobilization from bone marrow, and increased concentrations of MCP‐1 have been associated with sepsis and other inflammatory disorders in critically ill people. The relationship between MCP‐1 and disease in dogs has not been evaluated previously. Objective: The purpose of this study was to assess serum concentrations of MCP‐1 in healthy dogs, dogs in the postoperative period, and critically ill dogs. We hypothesized that MCP‐1 concentrations would be significantly increased in critically ill dogs compared with postoperative or healthy dogs. Methods: Serum concentrations of MCP‐1 were measured in 26 healthy control dogs, 35 postoperative dogs, and 26 critically ill dogs. Critically ill dogs were further subgrouped into dogs with sepsis, parvovirus gastroenteritis, immune‐mediated hemolytic anemia, and severe trauma (n=26). MCP‐1 concentrations were determined using a commercial canine MCP‐1 ELISA. Associations between MCP‐1 concentrations and disease status were evaluated statistically. Results: MCP‐1 concentration was significantly higher in critically ill dogs (median 578 pg/mL, range 144.7–1723 pg/mL) compared with healthy dogs (median 144 pg/mL, range 4.2–266.8 pg/mL) and postoperative dogs (median 160 pg/mL, range 12.6–560.4 pg/mL) (P<.001). All subgroups of critically ill dogs had increased MCP‐1 concentrations with the highest concentrations occurring in dogs with sepsis. However, differences among the 4 subgroups were not statistically significant. Conclusion: Critically ill dogs had markedly increased serum concentrations of MCP‐1 compared with postoperative and healthy dogs. These results indicate that surgery alone is not sufficient to increase MCP‐1 concentrations; thus, measurement of MCP‐1 may be useful in assessing disease severity in critically ill dogs. 相似文献
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