Lazcano V.,Major University
2016 IEEE International Conference on Automatica, ICA-ACCA 2016 | Year: 2016
Optical flow is defined as the pattern of apparent motion of objects in a image sequence. Optical flow has many applications: control of automatic taking off and landing of an autonomous aircraft, video compression, noise suppression, motion compensation and many more. There are different methods to estimate the optical flow. Variational models are the most frequently used methods to estimate the optical flow. These methods states an energy model to estimate the optical flow and frequently linealizations are used. Theses linearizations causes that the optical flow estimation fails if the motion presents displacements larger than the size of the objects. Optical flow methods generally implies large execution time to be estimated. In this work is presented a method that incorporate, to the classical optical flow's Horn-Schunk method, exhaustive matchings. These exhaustive matchings improve the estimation to handle large displacements. The method was implemented in a Intel i7, 3.5 GHz, GPU GeForce NVidia GTX 980 Ti and also a standard web-cam. Using images of 320 240 pixels the implementation reaches 6 images per second, which means that it is able to run in real time. © 2016 IEEE.
Lazcano V.,Major University
2017 3rd International Conference on Control, Automation and Robotics, ICCAR 2017 | Year: 2017
In this paper we present a method for estimating occlusion of pixels in image sequences. The estimation of the occlusion layer is based on optical flow. In our proposal the optical flow is computed in an exhaustive way by comparing neighborhoods between consecutive images. In order to compute the optical flow we consider three consecutive images (previous, actual and next frame). The optical flow is computed backward (between actual and previous frame) and forward (between actual and next frame). The proposed method considers an energy model which is minimized. The Euler-Lagrange equations let us to compute backward optical flow, forward optical flow and the occlusion layer. The comparison between neighborhoods is stored in a cost volume avoiding computing neighbor comparison repeatedly. © 2017 IEEE.
Rosales-Vera M.,Major University
European Journal of Physics | Year: 2017
In this paper, the one-dimensional motion of a body is studied under the scheme of 'modified Newtonian dynamics' (MOND). Through the asymptotic analysis, approximate analytical expressions for the body movement are found. The asymptotic solutions are compared with the numerical results and with the classical Newtonian dynamics. © 2017 European Physical Society.
Veloso F.A.,Major University
Journal of Theoretical Biology | Year: 2017
Changes in gene expression are thought to regulate the cell differentiation process intrinsically through complex epigenetic mechanisms. In fundamental terms, however, this assumed regulation refers only to the intricate propagation of changes in gene expression or else leads to non-explanatory regresses. The developmental self-regulatory dynamics and evolution of individuated multicellular organisms also lack a unified and falsifiable description. To fill this gap, I computationally analyzed publicly available high-throughput data of histone H3 post-translational modifications and mRNA abundance for different Homo sapiens, Mus musculus, and Drosophila melanogaster cell-type/developmental-period samples. My analysis of genomic regions adjacent to transcription start sites generated a profile from pairwise partial correlations between histone modifications controlling for the respective mRNA levels for each cell-type/developmental-period dataset. I found that these profiles, while explicitly uncorrelated with the respective transcriptional “identities” by construction, associate strongly with cell differentiation states. This association is not expected if cell differentiation is, in effect, regulated by epigenetic mechanisms. Based on these results, I propose a general, falsifiable theory of individuated multicellularity, which relies on the synergistic coupling across the extracellular space of two explicitly uncorrelated “self-organizing” systems constraining histone modification states at the same sites. This theory describes how the simplest multicellular individual—understood as an intrinsic, higher-order constraint—emerges from proliferating undifferentiated cells, and could explain the intrinsic regulation of gene transcriptional changes for cell differentiation and the evolution of individuated multicellular organisms. © 2017 The Authors
Pena M.A.,Major University |
Brenning A.,University of Waterloo |
Sagredo A.,Major University
ISPRS Journal of Photogrammetry and Remote Sensing | Year: 2012
Satellite hyperspectral data were used to construct empirical spectral indices related to the canopy structure of a Cordilleran Cypress (. Austrocedrus chilensis) forest located in the Andes of central Chile. Measurements of tree diameter at breast height (DBH) and tree height (TH) were performed for a set of plots located within a pure and unevenly aged stand of . A. chilensis with moderate cover. Normalized difference vegetation indices (NDIs) related to DBH and TH were constructed from the corresponding hyperspectral data in Hyperion imagery. NDIs construction utilized the original spectral reflectance curve, its first derivative, and the continuum-removed reflectance in a two-step procedure that ranks NDIs based on their Spearman correlation with the response variable while controlling the false discovery rate. Several reflectance-based NDIs as well as a larger group of derivative-based NDIs were significantly related to DBH or TH (. ρ>. 0.70). The NDIs most strongly related to the field variables were based on derivative bands located within the same spectral regions used by the broadband greenness index known as green normalized difference vegetation index. Most other significant NDIs used NIR bands, which are well-known for their sensitivity to foliage amount changes. The results obtained in this exploratory study mostly agreed with the spectral regions expected to be most sensitive to changes in the canopy structure of vegetation. Further research in other . A. chilensis forests subject to different site and environmental conditions is needed in order to assess the applicability of the NDIs over a wider range of this endemic species. © 2012 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS).
Guzman-Venegas R.A.,University of Los Andes, Chile |
Araneda O.F.,University of Los Andes, Chile |
Silvestre R.A.,Major University
Journal of Electromyography and Kinesiology | Year: 2014
Background: Botulinum toxin (BTX) acts on the neuromuscular junction which can be located by the innervation zone (IZ). Clinically, the motor point (MP) is homologous to the IZ and it is used as the injection site of BTX. Differences in the effectiveness of the application of BTX between MP and IZ locations have been determined. Objective: Compare the location of the MP obtained using electrical stimulation and the location of the IZ using a linear surface electrodes array on the biceps brachii muscle. Methods: The biceps brachii muscle of twenty men was assessed. The MP was located using the torque measurement generated by electrical stimulation. The IZ was detected using a linear surface electrodes array. Results: A difference between the MP and the IZ positions (75.8 vs. 86.5. mm, delta 10.7. mm; p=. 0.003, post-hoc power 0.89) was observed. Discussion: The magnitude of the difference between the MP and the IZ may be clinically relevant. The IZ location using surface electromyography as a guide to optimize BTX injection is proposed. © 2014 Elsevier Ltd.
Calixto A.,Pontifical Catholic University of Chile |
Calixto A.,Major University |
Jara J.S.,Pontifical Catholic University of Chile |
Court F.A.,Pontifical Catholic University of Chile |
Court F.A.,NeuroUnion Biomedical Foundation
PLoS Genetics | Year: 2012
Axonal degeneration is a key event in the pathogenesis of neurodegenerative conditions. We show here that mec-4d triggered axonal degeneration of Caenorhabditis elegans neurons and mammalian axons share mechanistical similarities, as both are rescued by inhibition of calcium increase, mitochondrial dysfunction, and NMNAT overexpression. We then explore whether reactive oxygen species (ROS) participate in axonal degeneration and neuronal demise. C. elegans dauers have enhanced anti-ROS systems, and dauer mec-4d worms are completely protected from axonal degeneration and neuronal loss. Mechanistically, downregulation of the Insulin/IGF-1-like signaling (IIS) pathway protects neurons from degenerating in a DAF-16/FOXO-dependent manner and is related to superoxide dismutase and catalase-increased expression. Caloric restriction and systemic antioxidant treatment, which decrease oxidative damage, protect C. elegans axons from mec-4d-mediated degeneration and delay Wallerian degeneration in mice. In summary, we show that the IIS pathway is essential in maintaining neuronal homeostasis under pro-degenerative stimuli and identify ROS as a key intermediate of neuronal degeneration in vivo. Since axonal degeneration represents an early pathological event in neurodegeneration, our work identifies potential targets for therapeutic intervention in several conditions characterized by axonal loss and functional impairment. © 2012 Calixto et al.
Trombert A.,Major University
Beneficial Microbes | Year: 2015
Lactic acid bacteria (LABs) are good candidates for the development of new oral vaccines and are attractive alternatives to attenuated pathogens. This review focuses on the use of wild-type and recombinant lactococci and lactobacilli with emphasis on their molecular design, immunomodulation and treatment of bacterial infections. The majority of studies related to recombinant LABs have focused on Lactococcus lactis, however, molecular tools have been successfully used for Lactobacillus spp. research. Recombinant lactobacilli and lactococci have several health benefits, such as immunomodulation, restoration of the microbiota, synthesis of antimicrobial substances and inhibition of virulence factors. In addition, protective immune responses that are well tolerated are induced by the expression of heterologous antigens from recombinant probiotics. © 2014 Wageningen Academic Publishers.
Calixto A.,Major University
Advances in genetics | Year: 2015
Food availability determines developmental rate, behavior, and survival of animals. Animals that enter diapause or hibernate in response to lack of food have a double advantage: they are able to adapt to environmental and cellular challenges and survive to these challenges for a prolonged time. The metabolic and physiological adaptations that make possible diapause and hibernation also provide a favorable cellular environment for tissue protection. This review highlights the benefits of dormancy on neuronal protection in the model organism Caenorhabditis elegans and small mammals such as squirrels. Additionally, I discuss the link between metabolic restructuring occurring in diapause and changes in gene expression with the increased capacity of diapausing animals to protect neurons from degeneration and potentially foster their regeneration. Copyright © 2015 Elsevier Inc. All rights reserved.
Bustos-Salvagno J.,Major University
Energy Economics | Year: 2015
Contracts in power markets are usually obscure. From recently public auctions of long-term supply contracts we can obtain information on how contract prices are determined. To understand generators' bidding behavior, this paper examines the Chilean experience from 2006 to 2011. Using a divisible good auction model we provide a theoretical framework that explains bidding behavior in terms of expected spot prices and contracting positions. Empirical estimations indicate heterogeneity in the cost of over-contracting depending on incumbency, bringing evidence of significant barriers to entry. © 2015 Elsevier B.V.