20 research outputs found

    Estimación del riesgo por deslizamientos de laderas generados por eventos sismicos en la ciudad de Medellín usando herramientas de la geomática : Caso aplicado a edificaciones urbanas

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    El estudio sobre la estimaci√≥n del riesgo por deslizamientos de laderas accionados por eventos s√≠smicos, se efectu√≥ sobre datos que corresponden al Municipio de Medell√≠n, Rep√ļblica de Colombia, con los cuales se pretende implementar un modelo a partir de herramientas pertenecientes al √°rea de la Geom√°tica, como lo son los Sistemas de Informaci√≥n Geogr√°fica (SIG), con el fin de coadyuvar en la estimaci√≥n y cuantificaci√≥n del riesgo ocasionado por este tipo de desastre en las laderas de la jurisdicci√≥n de estudio, al igual que la proyecci√≥n de un an√°lisis de los costos suscitados por da√Īos en elementos de la infraestructura urbana, para este caso las viviendas del sector de estudio. Esta estimaci√≥n y evaluaci√≥n se llev√≥ a cabo, mediante la adopci√≥n de una metodolog√≠a apoyada en una plataforma SIG, de manera que posibilite la realizaci√≥n de un an√°lisis de comparaci√≥n entre el campo de aceleraciones pico (PGA) que se puede llegar a presentar durante un evento s√≠smico de una magnitud dada, el campo de aceleraci√≥n cr√≠tica y los desplazamientos debidos al evento s√≠smico.The research on the estimate of risk for landslides caused by seismic events, was performed on acquired data corresponding to the Medellin City , Republic of Colombia, with which we intend to implement a model based on tools from the Geomatics area, such as Geographic Information Systems (GIS), to assist in the estimation and quantification of risk caused by this type of disaster on the slopes of the study jurisdiction, like the projection of an analysis of the costs arising from damage to urban infrastructure elements, in this case the houses on the study sector. This assessment and evaluation were carried out by adopting a methodology based on a GIS platform, so it enables the execution of a comparison analysis between the field of peak accelerations (PGA) that can be present during an earthquake of a given magnitude, the critical acceleration field and displacement due to the seismic event.La Maestr√≠a en Geom√°tica es una carrera dependiente de la Facultad de Ciencias Astron√≥micas y Geof√≠sicas y la Facultad de Ingenier√≠a, de la Universidad Nacional de La Plata.Facultad de Ciencias Astron√≥micas y Geof√≠sica

    Effect of the Rainfall Infiltration Processes on the Landslide Hazard Assessment of Unsaturated Soils in Tropical Mountainous Regions

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    Natural disasters caused by meteorological phenomena are affecting countries of the world with increasing frequency, and they are producing severe damage to population and its infrastructure, hampering the economic development of the countries. The rainfall-induced landslides occur almost every year in all mountainous regions, and globally, 14% of economic losses and 0.53% of deaths from disasters caused by natural phenomena are attributed to landslides. For this reason, landslide risk assessment has become more applied in recent years. We present an assessment of the effect of rainfall infiltration on unsaturated soils on slope stability. Initially, a theoretical approach of the problem is presented, and a model of probabilistic analysis is described. Subsequently, an application of the model is carried out in an eastern zone of Medellin, Colombia. The probability of saturation and the landslide hazard are determined and validated considering the effect of a rainfall event registered in November 2010 that caused severe damages in the studied zone. The influence of infiltration under static scenario is evaluated using two different approaches, and the soil parameters for these evaluations are determined by field and laboratory tests. Finally, the effect of the rainfall infiltration processes on the landslide hazard assessment of evaluated unsaturated soils is determined

    Landslide Risk: Economic Valuation in the North-Eastern Zone of Medellin City

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    Natural disasters of a geodynamic nature can cause enormous economic and human losses. The economic costs of a landslide disaster include relocation of communities and physical repair of urban infrastructure. However, when performing a quantitative risk analysis, generally, the indirect economic consequences of such an event are not taken into account. A probabilistic approach methodology that considers several scenarios of hazard and vulnerability to measure the magnitude of the landslide and to quantify the economic costs is proposed. With this approach, it is possible to carry out a quantitative evaluation of the risk by landslides, allowing the calculation of the economic losses before a potential disaster in an objective, standardized and reproducible way, taking into account the uncertainty of the building costs in the study zone. The possibility of comparing different scenarios facilitates the urban planning process, the optimization of interventions to reduce risk to acceptable levels and an assessment of economic losses according to the magnitude of the damage. For the development and explanation of the proposed methodology, a simple case study is presented, located in north-eastern zone of the city of Medellín. This area has particular geomorphological characteristics, and it is also characterized by the presence of several buildings in bad structural conditions. The proposed methodology permits to obtain an estimative of the probable economic losses by earthquake-induced landslides, taking into account the uncertainty of the building costs in the study zone. The obtained estimative shows that the structural intervention of the buildings produces a reduction the order of 21 % in the total landslide risk. © Published under licence by IOP Publishing Ltd

    Variation in neurosurgical management of traumatic brain injury

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    Background: Neurosurgical management of traumatic brain injury (TBI) is challenging, with only low-quality evidence. We aimed to explore differences in neurosurgical strategies for TBI across Europe. Methods: A survey was sent to 68 centers participating in the Collaborative European Neurotrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) study. The questionnaire contained 21 questions, including the decision when to operate (or not) on traumatic acute subdural hematoma (ASDH) and intracerebral hematoma (ICH), and when to perform a decompressive craniectomy (DC) in raised intracranial pressure (ICP). Results: The survey was completed by 68 centers (100%). On average, 10 neurosurgeons work in each trauma center. In all centers, a neurosurgeon was available within 30 min. Forty percent of responders reported a thickness or volume threshold for evacuation of an ASDH. Most responders (78%) decide on a primary DC in evacuating an ASDH during the operation, when swelling is present. For ICH, 3% would perform an evacuation directly to prevent secondary deterioration and 66% only in case of clinical deterioration. Most respondents (91%) reported to consider a DC for refractory high ICP. The reported cut-off ICP for DC in refractory high ICP, however, differed: 60% uses 25 mmHg, 18% 30 mmHg, and 17% 20 mmHg. Treatment strategies varied substantially between regions, specifically for the threshold for ASDH surgery and DC for refractory raised ICP. Also within center variation was present: 31% reported variation within the hospital for inserting an ICP monitor and 43% for evacuating mass lesions. Conclusion: Despite a homogeneous organization, considerable practice variation exists of neurosurgical strategies for TBI in Europe. These results provide an incentive for comparative effectiveness research to determine elements of effective neurosurgical care

    Estimación de atributos estructurales en un fragmento de bosque tropical natural utilizando imágenes de muy alta resolución obtenidas con sistemas aéreos no tripulados

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    Structural attributes are fundamental biophysical parameters of forest, useful for ecological and environmental monitoring and planning. Canopy height is an important input for the estimation of several biophysical parameters as aboveground biomass and carbon stock, and can be related with forest degradation, deforestation, and emission reduction. Thus, an accurate canopy height estimation is a crucial issue in climate change studies and REDD+ initiatives. VHR imagery from unmanned aircraft systems has been studied as a low cost mean for canopy height estimation at local scales, but the accuracy in the estimation is a factor that determines its utility. We evaluated the ability of VHR imagery from unmanned aircraft systems to derive structural attributes, specifically tree-crown area and height, in a natural tropical forest fragment located in the foothills of the Andes Mountains, in the humid tropical forests of the region known as Biogeographic Choc√≥, South America. The region is one of the most biodiverse areas of the world and has a high level of endemism, but it is also at higher risk of natural-resource loss. We used a structure from motion approach to derive canopy height models of the forest fragment, and we applied mean-shift algorithms to identify single tree crowns. The accuracy assessment was performed using reference data derived from field campaigns and visually interpretation of VHR imagery. The estimated root-mean-square error of the population of vertical errors for the canopy height model was 3.6 m. The total accuracy for delineating tree crowns was 73.9%. We found that using VHR imagery, specific trees and canopy gaps can be identified and easily monitored, which is an important step in conservation programs. We also discuss the usefulness of these findings in the context of fragmented forests and the tradeoffs between the price of a LIDAR system and the accuracy of this approach.Los atributos estructurales son par√°metros biof√≠sicos fundamentales de un bosque, √ļtiles para el monitoreo y la planificaci√≥n ecol√≥gica y ambiental. La altura del dosel de un √°rbol es un insumo importante para la estimaci√≥n de varios par√°metros biof√≠sicos como la biomasa a√©rea y las reservas de carbono, y puede relacionarse con la degradaci√≥n forestal, la deforestaci√≥n y la reducci√≥n de emisiones. Por lo tanto, una estimaci√≥n precisa de la altura del dosel es un tema crucial en los estudios de cambio clim√°tico y las iniciativas REDD+. Las im√°genes VHR de sistemas de aeronaves no tripuladas se han estudiado como un medio de bajo costo para la estimaci√≥n de la altura del dosel a escalas locales, pero la precisi√≥n en su estimaci√≥n es un factor que determina su utilidad. Se evalu√≥ la capacidad de las im√°genes VHR de los sistemas de aeronaves no tripuladas para derivar atributos estructurales, espec√≠ficamente el √°rea y la altura de las copas de los √°rboles, en un fragmento de bosque tropical natural ubicado en las estribaciones de la Cordillera de los Andes, en los bosques tropicales h√ļmedos de la regi√≥n conocida como Choc√≥ Biogeogr√°fico, Sudam√©rica. La regi√≥n es una de las √°reas con mayor biodiversidad del mundo y tiene un alto nivel de endemismo, pero tambi√©n tiene el mayor riesgo de p√©rdida de recursos naturales. Se us√≥ un enfoque de estructura a partir de movimiento para derivar modelos de altura del dosel del fragmento de bosque, y se aplicaron algoritmos de desplazamiento medio para identificar las copas de √°rbol. La evaluaci√≥n de la precisi√≥n se realiz√≥ utilizando datos de referencia derivados de campa√Īas de campo e interpretaci√≥n visual de im√°genes VHR. El error cuadr√°tico medio estimado de la poblaci√≥n de errores verticales para el modelo de altura del dosel fue de 3,6 m. La precisi√≥n total para delinear las copas de los √°rboles fue del 73,9%. Se encuentra que utilizando im√°genes VHR, se pueden identificar y monitorear f√°cilmente √°rboles espec√≠ficos y brechas, lo cual es un paso importante en los programas de conservaci√≥n. Tambi√©n se discute la utilidad de estos hallazgos en el contexto de bosques fragmentados y las compensaciones entre el precio de un sistema LIDAR y la precisi√≥n de este enfoque

    Línea base para vivienda de interés social sostenible: caso ciudad de Medellín

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    Lograr la sostenibilidad en las viviendas es una prioridad en la mayor√≠a de los pa√≠ses, como una estrategia para garantizar la calidad de vida de los habitantes, optimizar los recursos, ajustarse a las variaciones de las condiciones ambientales, y reducir el impacto sobre el planeta. La gran mayor√≠a de las alternativas y soluciones propuestas adolecen de un enfoque hol√≠stico que permita enfrentar el problema desde una √≥ptica integradora. La construcci√≥n de una l√≠nea base depende, entre otros factores, de estimaciones confiables de la magnitud y de la discrepancia entre la cantidad de viviendas existentes y la totalidad de la poblaci√≥n de una pa√≠s (d√©ficit cuantitativo), y de la medida en que las viviendas existentes cumplan con ciertos est√°ndares m√≠nimos que permitan ofrecer una calidad de vida adecuada a sus habitantes (d√©ficit cualitativo). A ra√≠z de ello, surge la necesidad de integrar recursos y esfuerzos para implementar una l√≠nea base de construcci√≥n sostenible para VIS mediante la identificaci√≥n de indicadores que combinen los aspectos sociales, econ√≥micos, t√©cnicos, geogr√°ficos y pol√≠ticos, actuales y futuros, con los avances tecnol√≥gicos en las √°reas de los materiales y los servicios p√ļblicos (energ√≠a yagua), y as√≠ poder dise√Īar, construir y comercializar una vivienda digna y accesible para los habitantes de bajos recursos del pa√≠s

    The Use of Lidar Data and VHR Imagery to Estimate the Effects of Tree Roots on Shallow Landslides Assessment

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    The study of geo-hazards has been benefited from the technological advances in the field of Remote Sensing (RS) techniques as the ALS (Airborne Laser Scanners) Systems with Very High Resolution (VHR) cameras. Recently, the LiDAR (Light Detection and Ranging) is an active sensor technique used for a variety of geoscientific applications including slope monitoring to retrieve ground surface displacements at high spatial resolution. Additionally, LiDAR has been widely used in order to collect high-resolution information on forests structure for the determination and characterization of vegetation cover due its ability to capture multiple returns and to reach the ground, even in forested areas, allowing the generation of Digital Terrain Models (DTMs) for the estimation of forest variables. In this paper, a LiDAR dataset and VHR imagery from aerial survey was used in the southwest zone of Medellín City-Colombia where the most frequent landslides are shallow and triggered by rainfall. Slopes with gradients up to 30% on residual soils characterize the study area, having about of 30% of forest cover consisting predominantly of Eucalyptus and Coniferous forests. For the estimation of the tree roots effects on the shallow landslides assessment on a natural slope, interpolation processes were developed from the LiDAR 3D point cloud, obtaining DTMs of 1 m-pixel. Additionally, orthophotos with the same spatial resolution were acquired in the aerial campaign. The proposed workflow was implemented on a GIS platform, and considers the extraction of the tree heights by generating a Canopy Height Model (CHM), while for the delineation of the tree crown a process of image segmentation was developed. Once the vegetation has been characterized using LiDAR products and dendrometric relationships, the Limit Equilibrium Method (LEM) was used to evaluate slope stability considering the effect of vegetation (trees). The results indicate that the proposed workflow allows to obtain adequate stability indicators for the estimation of tree roots contribution and additionally, this RS technique allows saving resources in this kind of analysis. © Published under licence by IOP Publishing Ltd

    Is Re-introducing Major Open and Minimally Invasive Surgery during COVID-19 Safe for Patients and Healthcare Workers?:An International, Multi-centre Cohort Study in the Field of Oesophago-gastric Surgery

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    Introduction: The COVID-19 pandemic has resulted in unparalleled changes to patient care, including the suspension of cancer surgery. Concerns regarding COVID-19-related risks to patients and healthcare workers with the re-introduction of major complex minimally invasive and open surgery have been raised. This study examines the COVID-19 related risks to patients and healthcare workers following the re-introduction of major oesophago-gastric (EG) surgery. Patients and Methods: This was an international, multi-centre, observational study of consecutive patients treated by open and minimally invasive oesophagectomy and gastrectomy for malignant or benign disease. Patients were recruited from nine European centres serving regions with a high population incidence of COVID-19 between 1 May and 1 July 2020. The primary endpoint was 30-day COVID-19-related mortality. All staff involved in the operative care of patients were invited to complete a health-related survey to assess the incidence of COVID-19 in this group. Results: In total, 158 patients were included in the study (71 oesophagectomy, 82 gastrectomy). Overall, 87 patients (57%) underwent MIS (59 oesophagectomy, 28 gastrectomy). A total of 403 staff were eligible for inclusion, of whom 313 (78%) completed the health survey. Approaches to mitigate against the risks of COVID-19 for patients and staff varied amongst centres. No patients developed COVID-19 in the post-operative period. Two healthcare workers developed self-limiting COVID-19. Conclusions: Precautions to minimise the risk of COVID-19 infection have enabled the safe re-introduction of minimally invasive and open EG surgery for both patients and staff. Further studies are necessary to determine the minimum requirements for mitigations against COVID-19

    Is Re-introducing Major Open and Minimally Invasive Surgery during COVID-19 Safe for Patients and Healthcare Workers? An International, Multi-centre Cohort Study in the Field of Oesophago-gastric Surgery

    No full text
    Introduction: The COVID-19 pandemic has resulted in unparalleled changes to patient care, including the suspension of cancer surgery. Concerns regarding COVID-19-related risks to patients and healthcare workers with the re-introduction of major complex minimally invasive and open surgery have been raised. This study examines the COVID-19 related risks to patients and healthcare workers following the re-introduction of major oesophago-gastric (EG) surgery. Patients and Methods: This was an international, multi-centre, observational study of consecutive patients treated by open and minimally invasive oesophagectomy and gastrectomy for malignant or benign disease. Patients were recruited from nine European centres serving regions with a high population incidence of COVID-19 between 1 May and 1 July 2020. The primary endpoint was 30-day COVID-19-related mortality. All staff involved in the operative care of patients were invited to complete a health-related survey to assess the incidence of COVID-19 in this group. Results: In total, 158 patients were included in the study (71 oesophagectomy, 82 gastrectomy). Overall, 87 patients (57%) underwent MIS (59 oesophagectomy, 28 gastrectomy). A total of 403 staff were eligible for inclusion, of whom 313 (78%) completed the health survey. Approaches to mitigate against the risks of COVID-19 for patients and staff varied amongst centres. No patients developed COVID-19 in the post-operative period. Two healthcare workers developed self-limiting COVID-19. Conclusions: Precautions to minimise the risk of COVID-19 infection have enabled the safe re-introduction of minimally invasive and open EG surgery for both patients and staff. Further studies are necessary to determine the minimum requirements for mitigations against COVID-19

    Traumatic brain injury : integrated approaches to improve prevention, clinical care, and research

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    Rahul Raj on työryhmän InTBIR Participants Investigators jäsen.Peer reviewe
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