Point-wise mutual information-based video segmentation with high temporal consistency

In this paper, we tackle the problem of temporally consistent boundary detection and hierarchical segmentation in videos. While finding the best high-level reasoning of region assignments in videos is the focus of much recent research, temporal consistency in boundary detection has so far only rarely been tackled. We argue that temporally consistent boundaries are a key component to temporally consistent region assignment. The proposed method is based on the point-wise mutual information (PMI) of spatio-temporal voxels. Temporal consistency is established by an evaluation of PMI-based point affinities in the spectral domain over space and time. Thus, the proposed method is independent of any optical flow computation or previously learned motion models. The proposed low-level video segmentation method outperforms the learning-based state of the art in terms of standard region metrics

Object segmentation in depth maps with one user click and a synthetically trained fully convolutional network

With more and more household objects built on planned obsolescence and consumed by a fast-growing population, hazardous waste recycling has become a critical challenge. Given the large variability of household waste, current recycling platforms mostly rely on human operators to analyze the scene, typically composed of many object instances piled up in bulk. Helping them by robotizing the unitary extraction is a key challenge to speed up this tedious process. Whereas supervised deep learning has proven very efficient for such object-level scene understanding, e.g., generic object detection and segmentation in everyday scenes, it however requires large sets of per-pixel labeled images, that are hardly available for numerous application contexts, including industrial robotics. We thus propose a step towards a practical interactive application for generating an object-oriented robotic grasp, requiring as inputs only one depth map of the scene and one user click on the next object to extract. More precisely, we address in this paper the middle issue of object seg-mentation in top views of piles of bulk objects given a pixel location, namely seed, provided interactively by a human operator. We propose a twofold framework for generating edge-driven instance segments. First, we repurpose a state-of-the-art fully convolutional object contour detector for seed-based instance segmentation by introducing the notion of edge-mask duality with a novel patch-free and contour-oriented loss function. Second, we train one model using only synthetic scenes, instead of manually labeled training data. Our experimental results show that considering edge-mask duality for training an encoder-decoder network, as we suggest, outperforms a state-of-the-art patch-based network in the present application context.Comment: This is a pre-print of an article published in Human Friendly Robotics, 10th International Workshop, Springer Proceedings in Advanced Robotics, vol 7. The final authenticated version is available online at: https://doi.org/10.1007/978-3-319-89327-3\_16, Springer Proceedings in Advanced Robotics, Siciliano Bruno, Khatib Oussama, In press, Human Friendly Robotics, 10th International Workshop,

Osificaciones heterotopicas, en pacientes sometidos a remplazo total de cadera primario mediante abordaje lateral indirecto modificado, en el Hospital Militar Central de Bogotá en los años 2005-2008

La formación de osificaciones heterotópicas peri articulares después de una cirugía de la cadera es un fenómeno bien conocido, su incidencia varia ampliamente desde autores que reportan 6% hasta otros que llegan al 70%. Se han estudiado múltiples factores de riesgo que favorezcan a la aparición de estas, en donde destacan el antecedente de cirugía previa sobre la cadera a operar, la edad y el sexo del paciente así también como la reacción biología ósea de la artrosis que presente el paciente. Como vemos su desarrollo se puede catalogar como multifactorial por lo que es importante tener en cuenta todos estos factores a la hora de intervenir nuestros pacientes y sin dejar a un lado respuesta biológica al trauma o stress quirúrgico que es individual de cada organismo. Las osificaciones heterotópicas posterior a un remplazo de cadera generalmente son asintomáticas y sin repercusión clínica en nuestros pacientes. Nos propusimos estudiar su incidencia en la serie de prótesis totales de cadera primaria de nuestro hospital, y su posible repercusión clínic

Superpixel quality in microscopy images: the impact of noise & denoising

Microscopy is a valuable imaging tool in various biomedical research areas. Recent developments have made high resolution acquisition possible within a relatively short time. State-of-the-art imaging equipment such as serial block-face electron microscopes acquire gigabytes of data in a matter of hours. In order to make these amounts of data manageable, a more data-efficient representation is required. A popular approach for such data efficiency are superpixels which are designed to cluster homogeneous regions without crossing object boundaries. The use of superpixels as a pre-processing step has shown significant improvements in making computationally intensive computer vision analysis algorithms more tractable on large amounts of data. However, microscopy datasets in particular can be degraded by noise and most superpixel algorithms do not take this artifact into account. In this paper, we give a quantitative and qualitative comparison of superpixels generated on original and denoised images. We show that several advanced superpixel techniques are hampered by noise artifacts and require denoising and parameter tuning as a pre-processing step. The evaluation is performed on the Berkeley segmentation dataset as well as on fluorescence and scanning electron microscopy data

Elementos de mecánica matemática

IlustracionesEstas notas de clase surgen con charlas y seminarios dictados por el primer autor a profesores y estudiantes del Departamento de Matemáticas de la Universidad Nacional de Colombia en Bogotá. Fueron complementadas con la visita del primer autor al Departamento y ampliadas con diversas actividades académicas realizadas por los autores en un periodo de tres años. (Texto tomado de la fuente).Incluye apéndices e índice analíticoISBN de la versión impresa 9789587613889Primera edició

Homeostatic Response to Three Years of Experimental Warming Suggests High Intrinsic Natural Resistance in the Páramos to Warming in the Short Term

Páramos, tropical alpine ecosystems, host one of the world s most diverse alpine floras, account for the largest water reservoirs in the Andes, and some of the largest soil carbon pools worldwide. It is of global importance to understand the future of this extremely carbon-rich ecosystem in a warmer world and its role on global climate feedbacks. This study presents the result of the first in situ warming experiment in two Colombian páramos using Open-Top Chambers. We evaluated the response to warming of several ecosystem carbon balance-related processes, including decomposition, soil respiration, photosynthesis, plant productivity, and vegetation structure after 3 years of warming. We found that OTCs are an efficient warming method in the páramo, increasing mean air temperature by 1.7°C and mean daytime temperature by 3.4°C. The maximum air temperature differences between OTC and control was 23.1°C. Soil temperature increased only by 0.1°C. After 3 years of warming using 20 OTC (10 per páramo) in a randomized block design, we found no evidence that warming increased CO2 emissions from soil respiration, nor did it increase decomposition rate, photosynthesis or productivity in the two páramos studied. However, total C and N in the soil and vegetation structure are slowly changing as result of warming and changes are site dependent. In Sumapaz, shrubs, and graminoids cover increased in response to warming while in Matarredonda we observed an increase in lichen cover. Whether this change in vegetation might influence the carbon sequestration potential of the páramo needs to be further evaluated. Our results suggest that páramos ecosystems can resist an increase in temperature with no significant alteration of ecosystem carbon balance related processes in the short term. However, the long-term effect of warming could depend on the vegetation changes and how these changes alter the microbial soil composition and soil processes. The differential response among páramos suggest that the response to warming could be highly dependent on the initial conditions and therefore we urgently need more warming experiments in páramos to understand how specific site characteristics will affect their response to warming and their role in global climate feedbacks. © Copyright © 2021 Lasso, Matheus-Arbeláez, Gallery, Garzón-López, Cruz, Leon-Garcia, Aragón, Ayarza-Páez and Curiel Yuste.Special thanks to David Campos, Fabian Salgado, Luis Fernando Rojas, Ewen Dano, Jorge Acosta, Juliana Portilla, and Michelle Guevara that helped with field and lab work. We would like to thank the Sabogal family for allowing the establishment of the OTC and collection of samples in the p?ramo ?Parque Ecol?gico Matarredonda? and to the Lieutenant Colonel Edgar Riveira, Commander of the High Mountain Battalion No. 1 in Sumapaz and all the commanders that follow him and who provided us with accommodation and food in the battalion as well as logistic support in all our field campaigns. Thanks to all the soldiers who always enthusiastically helped us in the field work in Sumapaz. This research was also supported by the Basque Government through the BERC 2018?2021 program, and by the Spanish Ministry of Science, Innovation and Universities through the BC3 Mar?a de Maeztu excellence accreditation (MDM-2017-0714). Funding. Funding for this research comes from the ?Patrimonio Aut?nomo Fondo Nacional de Financiamiento para la Ciencia, la Tecnolog?a y la Innovaci?n Francisco Jos? de Caldas?Colciencias,? grant number 120471451294, granted by Colciencias (today?s Colombian Ministry of Science, Technology and Innovation), from Eloisa Lasso?s FAPA (Fondo de Apoyo para Profesores Asistentes) grant number P12.160422.001 from the Universidad de los Andes, and from the Research Fund to support faculty programs at the Faculty of Sciences at the Universidad de los Andes grant number INV-2019-84-1805

On the equivalence between hierarchical segmentations and ultrametric watersheds

We study hierarchical segmentation in the framework of edge-weighted graphs. We define ultrametric watersheds as topological watersheds null on the minima. We prove that there exists a bijection between the set of ultrametric watersheds and the set of hierarchical segmentations. We end this paper by showing how to use the proposed framework in practice in the example of constrained connectivity; in particular it allows to compute such a hierarchy following a classical watershed-based morphological scheme, which provides an efficient algorithm to compute the whole hierarchy.Comment: 19 pages, double-colum

Portable, field-based neuroimaging using high-density diffuse optical tomography

Behavioral and cognitive tests in individuals who were malnourished as children have revealed malnutrition-related deficits that persist throughout the lifespan. These findings have motivated recent neuroimaging investigations that use highly portable functional near-infrared spectroscopy (fNIRS) instruments to meet the demands of brain imaging experiments in low-resource environments and enable longitudinal investigations of brain function in the context of long-term malnutrition. However, recent studies in healthy subjects have demonstrated that high-density diffuse optical tomography (HD-DOT) can significantly improve image quality over that obtained with sparse fNIRS imaging arrays. In studies of both task activations and resting state functional connectivity, HD-DOT is beginning to approach the data quality of fMRI for superficial cortical regions. In this work, we developed a customized HD-DOT system for use in malnutrition studies in Cali, Colombia. Our results evaluate the performance of the HD-DOT instrument for assessing brain function in a cohort of malnourished children. In addition to demonstrating portability and wearability, we show the HD-DOT instrument\u27s sensitivity to distributed brain responses using a sensory processing task and measurements of homotopic functional connectivity. Task-evoked responses to the passive word listening task produce activations localized to bilateral superior temporal gyrus, replicating previously published work using this paradigm. Evaluating this localization performance across sparse and dense reconstruction schemes indicates that greater localization consistency is associated with a dense array of overlapping optical measurements. These results provide a foundation for additional avenues of investigation, including identifying and characterizing a child\u27s individual malnutrition burden and eventually contributing to intervention development