1,721,090 research outputs found
A new beach topography-based method for shoreline identification
Full text linkThe definition of shoreline is not the same for all contexts, and it is often a subjective matter. Various methods exist that are based on the use of different instruments that can determine and highlight a shoreline. In recent years, numerous studies have employed photogrammetric methods, based on different colours, to map the boundary between water and land. These works use images acquired by satellites, drones, or cameras, and differ mainly in terms of resolution. Such methods can identify a shoreline by means of automatic, semi-automatic, or manual procedures. The aim of this work is to find and promote a new and valid beach topography-based algorithm, able to identify the shoreline. We apply the Structure from Motion (SfM) techniques to reconstruct a high-resolution Digital Elevation Model by means of a drone for image acquisition. The algorithm is based on the variation of the topographic beach profile caused by the transition from water to sand. The SfM technique is not efficient when applied to reflecting surfaces like sea water resulting in a very irregular and unnatural profile over the sea. Taking advantage of this fact, the algorithm searches for the point in the space where a beach profile changes from irregular to regular, causing a transition from water to land. The algorithm is promoted by the release of a QGIS v3.x plugin, which allows the easy application and extraction of other shorelines
Rimodellamento dei vasi epicardici nell’iperteso: relazioni con ipertensione arteriosa e massa ventricolare sinistra, e implicazioni per la suscettibilità dell’ischemia da sforzo
No full textRat pial microvascular responses to melatonin during bilateral common carotid artery occlusion and reperfusion
No full textThe present study assessed the in vivo rat pial microvascular responses induced by melatonin during brain hypoperfusion and reperfusion (RE) injury. Pial microcirculation of male Wistar rats was visualized by fluorescence microscopy through a closed cranial window. Hypoperfusion was induced by bilateral common carotid artery occlusion (BCCAO, 30 min); thereafter, pial microcirculation was observed for 60 min. Arteriolar diameter, permeability increase, leukocyte adhesion to venular walls, perfused capillary length (PCL), and capillary red blood cell velocity (V(RBC)) were investigated by computerized methods. Melatonin (0.5, 1, 2 mg/kg b.w.) was intravenously administered 10 min before BCCAO and at the beginning of RE. Pial arterioles were classified in five orders according to diameter, length, and branchings. In control group, BCCAO caused decrease in order 2 arteriole diameter (by 17.5 +/- 3.0% of baseline) that was reduced by 11.8 +/- 1.2% of baseline at the end of RE, accompanied by marked leakage and leukocyte adhesion. PCL and capillary VRBC decreased. At the end of BCCAO, melatonin highest dosage caused order 2 arteriole diameter reduction by 4.6 +/- 2.0% of baseline. At RE, melatonin at the lower dosages caused different arteriolar responses. The highest dosage caused dilation in order 2 arteriole by 8.0 +/- 1.5% of baseline, preventing leakage and leukocyte adhesion, while PCL and VRBC increased. Luzindole (4 mg/kg b.w.) prior to melatonin caused order 2 arteriole constriction by 12.0 +/- 1.5% of baseline at RE, while leakage, leukocyte adhesion, PCL and VRBC were not affected. Prazosin (1 mg/kg b.w.) prior to melatonin did not significantly change melatonin's effects. In conclusion, melatonin caused different responses during hypoperfusion and RE, modulating pial arteriolar tone likely by MT1 and MT2 melatonin receptors while preventing blood-brain barrier changes through its free radical scavenging action
Rat pial microvascular responses to melatonin during bilateral common carotid artery occlusion and reperfusion
No full textThe present study assessed the in vivo rat pial microvascular responses induced by melatonin during brain hypoperfusion and reperfusion (RE) injury. Pial microcirculation of male Wistar rats was visualized by fluorescence microscopy through a closed cranial window. Hypoperfusion was induced by bilateral common carotid artery occlusion (BCCAO, 30 min); thereafter, pial microcirculation was observed for 60 min. Arteriolar diameter, permeability increase, leukocyte adhesion to venular walls, perfused capillary length (PCL), and capillary red blood cell velocity (V(RBC) ) were investigated by computerized methods. Melatonin (0.5, 1, 2 mg/kg b.w.) was intravenously administered 10 min before BCCAO and at the beginning of RE. Pial arterioles were classified in five orders according to diameter, length, and branchings. In control group, BCCAO caused decrease in order 2 arteriole diameter (by 17.5 ± 3.0% of baseline) that was reduced by 11.8 ± 1.2% of baseline at the end of RE, accompanied by marked leakage and leukocyte adhesion. PCL and capillary V(RBC) decreased. At the end of BCCAO, melatonin highest dosage caused order 2 arteriole diameter reduction by 4.6 ± 2.0% of baseline. At RE, melatonin at the lower dosages caused different arteriolar responses. The highest dosage caused dilation in order 2 arteriole by 8.0 ± 1.5% of baseline, preventing leakage and leukocyte adhesion, while PCL and V(RBC) increased. Luzindole (4 mg/kg b.w.) prior to melatonin caused order 2 arteriole constriction by 12.0 ± 1.5% of baseline at RE, while leakage, leukocyte adhesion, PCL and V(RBC) were not affected. Prazosin (1 mg/kg b.w.) prior to melatonin did not significantly change melatonin's effects. In conclusion, melatonin caused different responses during hypoperfusion and RE, modulating pial arteriolar tone likely by MT1 and MT2 melatonin receptors while preventing blood-brain barrier changes through its free radical scavenging action
The first order absolute moment in contour tracking
No full textA procedure to outline contours automatically in temporal sequences of cardiovascular images is presented. The contour determined on the nth frame of the sequence is used as the starting contour to determine the contour on the (n+1)th frame. When given a starting contour, standard edge detectors can efficiently locate only ideal discontinuities with step shape. First and second Gaussian derivatives, computed at points pi of the starting contour, directly provide amplitude and direction of the vectors which join pi to the respective points of the final contour. Conversely, if the discontinuity does not show an ideal profile with step shape, the computation of the Gaussian derivatives must be carried out at all points between the starting and the final contour. In the paper, a property of the first order absolute moment is exploited to develop a robust and efficient iterative procedure which can be used to locate discontinuities that do not show an ideal step profile
The first order absolute moment in contour tracking of large arteries echo images: perspectives for quantification of arterial distenibility
No full textEpicardial vessel remodeling associated to endurance training in middle-age normal subjects
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Contour tracking over image sequences
No full textAn automatic contour tracking procedure is illustrated over sequences of x-ray and echo images. The entire procedure is based on two main steps: (i) a furrow of suitable width is obtained at the image luminance variations by filtering the images with a first order derivative filter and (U) the "true" contour is obtained by dropping an approximate starting contour to the bottom of the furrow. Once the contour is determined on the first image it is used as starting contour to determine the contour on the subsequent image and so on. Therefore, when an approximate starting contour is given on the first image, every contour of the sequence is automatically outlined. As the gradient of Gaussian (GoG) provides a reduced output at two-dimensional discontinuities, a novel first order derivative filter is used to produce the furrow maps. The filter is obtained from the generalization of the first order absolute moment
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