Browsing by Author "Rebolledo, Rolando"

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    Actas Seminario Interdisciplina en la UC
    (2012) Flores, Luis; Haye, Andrés; Rebolledo, Rolando; Araos, Consuelo; Parra, Catalina de la; Rivera, Daniela; Vergara, Alejandro; San Martín, Ernesto; Min, Wonjung; Funk, regina; Onell, Roberto; Holmes, Robert; García Huidobro, Vicente; Cádiz, Rodrigo; Cuadra, Patricio de la; Sylleros, Álvaro; Hermosilla, Katherine; Vega, Patricia; Ibarra, Macarena; Ramírez, Cecilia; Bonomo, Umberto; Torres, Marisa; Tapia, Rodrigo; Cottet, Pablo; Rojas Lasch, Carolina; Haye M., Andrés
    Publicación de trabajos derivados de un seminario realizado el 14 de diciembre de 2011, patrocinado por la Vicerrectoría de Investigación, la Facultad de Ciencias Sociales y Facultad de Filosofía, con el fin de reunir y poner en diálogo diversas experiencias de interdisciplina en la universidad y así favorecer su reconocimiento como estrategia de conocimiento, reflexionar sus limitaciones y potenciar su crecimiento. Editores: Carolina Rojas y Andrés Haye. Producción y diseño: Laboratorio de Hipermedios, Facultad de Letras PUC, Pablo Chiuminatto, Rodrigo del Río. Corrección de textos: Loreto Fernández. Organización del Seminario: Carolina Rojas, Andrés Haye, Patricio Miranda, Pablo Herraz, Gabriela Rubilar.
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    Algebraic conditions for convergence of a quantum Markov semigroup to a steady state
    (WORLD SCIENTIFIC PUBL CO PTE LTD, 2008) Fagnola, Franco; Rebolledo, Rolando
    Let T be a uniformly continuous quantum Markov semigroup on B(h) with generator represented in a standard GKSL form L(x) = -1/2 Sigma(l)(L-l*L(l)x - 2L(l)*xL(l) + xL(l)*L-l) + i[H, x] and a faithful normal invariant state rho. In this note we give new algebraic conditions for proving that T converges towards a steady state, possibly different from rho. Indeed, we show that this happens whenever the commutator of {H, L-l, L-l*vertical bar l >= 1} (i.e. its fixed point algebra) coincides with the commutator of {L-l, L-l*, delta(H)(L-l), delta(H)(L-l*), ..., delta(n)(H)(L-l), delta(n)(H)(L-l*)vertical bar l >= 1} (where delta(H)(X) = [H,X]) for some n >= 1. As an application we discuss the convergence to the unique invariant state of a spin chain model.
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    AN OPEN-SYSTEM APPROACH TO COMPLEX BIOLOGICAL NETWORKS
    (2019) Rebolledo, Rolando; Navarrete, Sergio A.; Kefi, Sonia; Rojas, Sergio; Marquet, Pablo A.
    Biological diversity is essential for the maintenance of the ecosystem functions that support life on the planet. Inherent to this diversity is the seemingly endless way in which the biological entities of a natural system interact and affect each other at local and regional scales, conforming complex ecological networks permeable to external forcing. Existing approaches to capture and model such complexity typically make unrealistic or excessively restrictive assumptions. Here we use concepts from open dynamical systems and metacommunity theory to develop a framework in which the system dynamics is a function of both interspecific interactions in the focal system (e.g., a local community of coexisting species) and unobserved biotic and abiotic interactions with the local and regional environment (e.g., the metacommunity). Species in the vital system interact through direct exchanges of biomass (i.e., trophic interactions), as well as through altering the acquisition and/or transformation of biomass by other species (nontrophic interactions). Interactions are affected by environmental fluctuations and by migration and emigration processes, which can take place at different time scales and can be modeled by stochastic differential equations driven by a mixture of continuous and discontinuous processes. In this manner, the proposed framework provides a wider and more flexible representation of the complexity of ecological systems, in comparison with the closed-system paradigm that isolates the system from the environment. Because the core model explicitly recognizes the existence of local and regional processes, it is also a natural starting point to examine spatially structured networks.
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    Basic properties of nonlinear stochastic Schrodinger equations driven by Brownian motions
    (INST MATHEMATICAL STATISTICS, 2008) Mora, Carlos M.; Rebolledo, Rolando
    The paper is devoted to the study of nonlinear stochastic Schrodinger equations driven by standard cylindrical Brownian motions (NSSEs) arising from the unraveling of quantum master equations. Under the Born-Markov approximations, this class of stochastic evolutions equations on Hilbert spaces provides characterizations of both continuous quantum measurement processes and the evolution of quantum systems. First, we deal with the existence and uniqueness of regular solutions to NSSEs. Second, we provide two general criteria for the existence of regular invariant measures for NSSEs. We apply our results to a forced and damped quantum oscillator.
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    Can One Validly Use Classical Statistical Inference in Open Quantum Systems?
    (WORLD SCIENTIFIC PUBL CO PTE LTD, 2010) Arenas, Mallen; Rebolledo, Rolando
    A major problem to perform statistical inference in open quantum systems is the perturbation induced by the measurement process. However, at least theoretically, a suitable choice of the measurement process could provide a consistent approach through classical stochastic processes. This work proposes a method to perform statistical inference on open quantum systems represented by quantum Markov semigroups having a suitable classical reduction. The method is based on measurements associated to observables generating invariant abelian algebras.
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    Coexistence, dispersal and spatial structure in metacommunities: a stochastic model approach
    (2021) Tejo, Mauricio; Quininao, Cristobal; Rebolledo, Rolando; Marquet, Pablo A.
    We propose a stochastic model for interacting species in a metacommunity in order to study the factors affecting the intensity of the competition/colonization trade-off as a coexistence mechanism in metacommunities. We particularly focus on the role of the number of local communities and the number of refuges for the inferior competitor. The stochastic component is associated with the dispersal process and is represented by Poisson random measures. Thus, this stochastic model includes two dynamic scales: a continuous one, which refers to the interactions among species, and a low frequency one, referring to dispersal following a Poisson scheme. We show the well-posedness of the model and that it is possible to study its long-term behavior using Lyapunov exponents; the extinction of a species is associated with a negative slope in the time trajectory of the Lyapunov exponent, otherwise, it is equal to zero. We show that the competition/colonization trade-off is a function of the dispersal rate of the inferior competitor, and that it becomes less intense as the number of local communities increases, while the opposite is true with an increase in the number of refuges for the inferior competitor. We also show that under a priority effect type of scenario, dispersal can reverse priority effects and generate coexistence. Our results emphasize the importance of coexistence mechanisms related to the topology of the system of local communities, and its relationship with dispersal, in affecting the result of competition in local communities.
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    Complejidad y Azar
    (2013) Rebolledo, Rolando
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    Development of a Novel Perfusable Solution for ex vivo Preservation: Towards Photosynthetic Oxygenation for Organ Transplantation
    (Frontiers Media SA, 2021) Veloso Gimenez, Valentina; Escamilla, Rosalba; Necuñir, David; Corrales Orovio, Rocio; Riveros, Sergio; Marino, Carlo; Ehrenfeld, Carolina; Guzman, Christian Dani; Boric, Mauricio P.; Rebolledo, Rolando; Egaña, José Tomas
    Oxygen is the key molecule for aerobic metabolism, but no animal cells can produce it, creating an extreme dependency on external supply. In contrast, microalgae are photosynthetic microorganisms, therefore, they are able to produce oxygen as plant cells do. As hypoxia is one of the main issues in organ transplantation, especially during preservation, the main goal of this work was to develop the first generation of perfusable photosynthetic solutions, exploring its feasibility for ex vivo organ preservation. Here, the microalgae Chlamydomonas reinhardtii was incorporated in a standard preservation solution, and key aspects such as alterations in cell size, oxygen production and survival were studied. Osmolarity and rheological features of the photosynthetic solution were comparable to human blood. In terms of functionality, the photosynthetic solution proved to be not harmful and to provide sufficient oxygen to support the metabolic requirement of zebrafish larvae and rat kidney slices. Thereafter, isolated porcine kidneys were perfused, and microalgae reached all renal vasculature, without inducing damage. After perfusion and flushing, no signs of tissue damage were detected, and recovered microalgae survived the process. Altogether, this work proposes the use of photosynthetic microorganisms as vascular oxygen factories to generate and deliver oxygen in isolated organs, representing a novel and promising strategy for organ preservation.
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    Effects of dexmedetomidine and esmolol on systemic hemodynamics and exogenous lactate clearance in early experimental septic shock
    (2016) Hernández P., Glenn; Tapia, Pablo; Alegría, Leyla; Soto, Dagoberto; Jarufe Cassis, Nicolás; Achurra Tirado, Pablo; Rebolledo, Rolando; Bruhn, Alejandro; Castro, Ricardo; Kattan Tala, Eduardo José; Bakker, Jan; Luengo, Cecilia; Gomez, Jussara; Ospina Tascón, Gustavo
    Abstract Background Persistent hyperlactatemia during septic shock is multifactorial. Hypoperfusion-related anaerobic production and adrenergic-driven aerobic generation together with impaired lactate clearance have been implicated. An excessive adrenergic response could contribute to persistent hyperlactatemia and adrenergic modulation might be beneficial. We assessed the effects of dexmedetomidine and esmolol on hemodynamics, lactate generation, and exogenous lactate clearance during endotoxin-induced septic shock. Methods Eighteen anesthetized and mechanically ventilated sheep were subjected to a multimodal hemodynamic/perfusion assessment including hepatic and portal vein catheterizations, total hepatic blood flow, and muscle microdialysis. After monitoring, all received a bolus and continuous infusion of endotoxin. After 1 h they were volume resuscitated, and then randomized to endotoxin-control, endotoxin-dexmedetomidine (sequential doses of 0.5 and 1.0 μg/k/h) or endotoxin-esmolol (titrated to decrease basal heart rate by 20 %) groups. Samples were taken at four time points, and exogenous lactate clearance using an intravenous administration of sodium L-lactate (1 mmol/kg) was performed at the end of the experiments. Results Dexmedetomidine and esmolol were hemodynamically well tolerated. The dexmedetomidine group exhibited lower epinephrine levels, but no difference in muscle lactate. Despite progressive hypotension in all groups, both dexmedetomidine and esmolol were associated with lower arterial and portal vein lactate levels. Exogenous lactate clearance was significantly higher in the dexmedetomidine and esmolol groups. Conclusions Dexmedetomidine and esmolol were associated with lower arterial and portal lactate levels, and less impairment of exogenous lactate clearance in a model of septic shock. The use of dexmedetomidine and esmolol appears to be associated with beneficial effects on gut lactate generation and lactate clearance and exhibits no negative impact on systemic hemodynamics.Abstract Background Persistent hyperlactatemia during septic shock is multifactorial. Hypoperfusion-related anaerobic production and adrenergic-driven aerobic generation together with impaired lactate clearance have been implicated. An excessive adrenergic response could contribute to persistent hyperlactatemia and adrenergic modulation might be beneficial. We assessed the effects of dexmedetomidine and esmolol on hemodynamics, lactate generation, and exogenous lactate clearance during endotoxin-induced septic shock. Methods Eighteen anesthetized and mechanically ventilated sheep were subjected to a multimodal hemodynamic/perfusion assessment including hepatic and portal vein catheterizations, total hepatic blood flow, and muscle microdialysis. After monitoring, all received a bolus and continuous infusion of endotoxin. After 1 h they were volume resuscitated, and then randomized to endotoxin-control, endotoxin-dexmedetomidine (sequential doses of 0.5 and 1.0 μg/k/h) or endotoxin-esmolol (titrated to decrease basal heart rate by 20 %) groups. Samples were taken at four time points, and exogenous lactate clearance using an intravenous administration of sodium L-lactate (1 mmol/kg) was performed at the end of the experiments. Results Dexmedetomidine and esmolol were hemodynamically well tolerated. The dexmedetomidine group exhibited lower epinephrine levels, but no difference in muscle lactate. Despite progressive hypotension in all groups, both dexmedetomidine and esmolol were associated with lower arterial and portal vein lactate levels. Exogenous lactate clearance was significantly higher in the dexmedetomidine and esmolol groups. Conclusions Dexmedetomidine and esmolol were associated with lower arterial and portal lactate levels, and less impairment of exogenous lactate clearance in a model of septic shock. The use of dexmedetomidine and esmolol appears to be associated with beneficial effects on gut lactate generation and lactate clearance and exhibits no negative impact on systemic hemodynamics.
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    Entropy production for quantum Markov semigroups
    (2015) Rebolledo, Rolando
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    Laparoscopic Versus Open Distal Pancreatectomy: Comparative Analysis of Clinical Outcomes at a Single Institution
    (2018) Jarufe, Nicolas; Soto, Pedro; Ahumada, Vanessa; Pacheco, Sergio; Salinas, Jose; Galindo, Jose; Bachler, Jean-Phillipe; Achurra, Pablo; Rebolledo, Rolando; Guerra, Juan F.; Briceno, Eduardo; Martinez, Jorge
    Purpose:Undertake a comparison between laparoscopic distal pancreatectomy (LDP) and open distal pancreatectomy (ODP) for the management of benign and malignant lesions.Methods:A case series study of 93 consecutive patients subjected to a distal pancreatectomy for pancreatic tumors between 2001 and 2015. In each patient, clinical and surgical characteristic, postoperative course, histopathologic examination, and survival were analyzed.Results:LDP was associated with significantly less operative blood loss (50mL vs. 300mL; P<0.01), higher spleen preservation rate (52.6% vs. 19.2%; P<0.01) and shorter hospital stay (5d vs. 8d; P<0.01). In patients with adenocarcinoma, survival at 1 and 5 years were 63.5% and 15.9% in the ODP group versus 66.7% and 33.3% in the LDP group (P=0.43).Conclusions:LDP is a safe and feasible procedure for DP resections. LDP offers advantages over ODP in terms of reduction of operative blood loss, higher spleen preservation rate, and shorter hospital stay.
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    Measurements and Consistent Families of Quantum Channels
    (WORLD SCIENTIFIC PUBL CO PTE LTD, 2011) Le Jan, Yves; Rebolledo, Rolando
    This article introduces the notion of consistent families (Lambda((n))) n >= 1 of quantum channels. These families correspond to simultaneous observation of different copies of a given quantum system. Here, we are primarily interested in the analysis of measurements connected with them. As usual, the measurement of a quantum system requires the construction of a classical dilation of the corresponding quantum channel. In our case, the quantum systems represented by (Lambda((n))) n >= 1 are supposed to interact through the measurement instrument only. That is, we construct a classical probability space which allows to have a common dilation for all the Lambda((n))'s. Doing this, we introduce and solve a quantum version of the moment problem.
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    Microalgae share key features with human erythrocytes and can safely circulate through the vascular system in mice
    (2023) Ehrenfeld, Carolina; Veloso-Giménez, Valentina; Corrales-Orovio, Rocío; Rebolledo, Rolando; Boric, Mauricio P.; Egaña, José Tomás
    As animal cells cannot produce oxygen, erythrocytes are responsible for gas interchange, being able to capture and deliver oxygen upon tissue request. Interestingly, several other cells in nature produce oxygen by photosynthesis, raising the question of whether they could circulate within the vascular networks, acting as an alternative source for oxygen delivery. To address this long-term goal, here some physical and mechanical features of the photosynthetic microalga Chlamydomona reinhardtii were studied and compared with erythrocytes, revealing that both exhibit similar size and rheological properties. Moreover, key biocompatibility aspects of the microalgae were evaluated in vitro and in vivo, showing that C. reinhardtii can be co-cultured with endothelial cells, without affecting each other’s morphology and viability. Moreover, short-term systemic perfusion of the microalgae showed a thoroughly intravascular distribution in mice. Finally, the systemic injection of high numbers of microalgae did not trigger deleterious responses in living mice. Altogether, this work provides key scientific insights to support the notion that photosynthetic oxygenation could be achieved by circulating microalgae, representing another important step towards human photosynthesis.
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    On a Class of Non-Markovian Langevin Equations
    (2013) Rebolledo, Rolando
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    On Completely Positive Non-Markovian Evolution of a d-Level System
    (2008) Kossakowski, Andrzej; Rebolledo, Rolando
    A suffcient condition for non-Markovian master equation which ensures the complete positivity of the resulting time evolution is presented.
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    On non-markovian time evolution in open quantum systems
    (2007) Kossakowski, Andrzej; Rebolledo, Rolando
    Non-Markovian reduced dynamics of an open system is. investigated. In the case when the initial state of the reservoir is the vacuum state, an approximation is introduced which makes it possible to construct a reduced dynamics which is completely positive.
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