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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    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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    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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    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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    Rat donor lung quality deteriorates more after fast than slow brain death induction
    (2020) Van Zanden, J. E.; Rebolledo, Rolando; Hoeksma, D.; Bubberman, J. M.; Burgerhof, J. G.; Breedijk, A.; Yard, B. A.; Erasmus, M. E.; Leuvenink, H. G. D.; Hottenrott, M. C.
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    Reconstructing ecological networks with noisy dynamics
    (ROYAL SOC, 2020) Freilich, Mara A.; Rebolledo, Rolando; Corcoran, Derek; Marquet, Pablo A.
    Ecosystems functioning is based on an intricate web of interactions among living entities. Most of these interactions are difficult to observe, especially when the diversity of interacting entities is large and they are of small size and abundance. To sidestep this limitation, it has become common to infer the network structure of ecosystems from time series of species abundance, but it is not clear how well can networks be reconstructed, especially in the presence of stochasticity that propagates through ecological networks. We evaluate the effects of intrinsic noise and network topology on the performance of different methods of inferring network structure from time-series data. Analysis of seven different four-species motifs using a stochastic model demonstrates that star-shaped motifs are differentially detected by these methods while rings are differentially constructed. The ability to reconstruct the network is unaffected by the magnitude of stochasticity in the population dynamics. Instead, interaction between the stochastic and deterministic parts of the system determines the path that the whole system takes to equilibrium and shapes the species covariance. We highlight the effects of long transients on the path to equilibrium and suggest a path forward for developing more ecologically sound statistical techniques.
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    Regularity of solutions to linear stochastic Schrodinger equations
    (WORLD SCIENTIFIC PUBL CO PTE LTD, 2007) Mora, Carlos M.; Rebolledo, Rolando
    We develop linear stochastic Schrodinger equations driven by standard cylindrical Brownian motions (LSSs) that unravel quantum master equations in Lindblad form into quantum trajectories. More precisely, this paper establishes the existence and uniqueness of the smooth strong solution X-t to a LSS with regular initial condition. Moreover, we obtain that the mean value of the square norm of X-t is constant. We also treat the approximation of LSSs by ordinary stochastic differential equations. We apply our results to:
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    Slow induction of brain death leads to decreased renal function and increased hepatic apoptosis in rats
    (2016) Rebolledo, Rolando; Hoeksma, Dane.; Hottenrott, Christina M. V.; Bodar, Yves J. L.; Ottens, Petra J.; Wiersema Buist, Janneka.; Leuvenink, Henri G. D.
    Abstract Background Donor brain death (BD) is an independent risk factor for graft survival in recipients. While in some patients BD results from a fast increase in intracranial pressure, usually associated with trauma, in others, intracranial pressure increases more slowly. The speed of intracranial pressure increase may be a possible risk factor for renal and hepatic graft dysfunction. This study aims to assess the effect of speed of BD induction on renal and hepatic injury markers. Methods BD induction was performed in 64 mechanically ventilated male Fisher rats by inflating a 4.0F Fogarty catheter in the epidural space. Rats were observed for 0.5, 1, 2 or 4 h following BD induction. Slow induction was achieved by inflating the balloon-catheter at a speed of 0.015 ml/min until confirmation of BD. Fast induction was achieved by inflating the balloon at 0.45 ml/min for 1 min. Plasma, kidney and liver tissue were collected for analysis. Results Slow BD induction led to higher plasma creatinine at all time points compared to fast induction. Furthermore, slow induction led to increased renal mRNA expression of IL-6, and renal MDA values after 4 h of BD compared to fast induction. Hepatic mRNA expression of TNF-α, Bax/Bcl-2, and protein expression of caspase-3 was significantly higher due to slow induction after 4 h of BD compared to fast induction. PMN infiltration was not different between fast and slow induction in both renal and hepatic tissue. Conclusion Slow induction of BD leads to poorer renal function compared to fast induction. Renal inflammatory and oxidative stress markers were increased. Liver function was not affected by speed of BD induction but hepatic inflammatory and apoptosis markers increased significantly due to slow induction compared to fast induction. These results provide initial proof that speed of BD induction influences detrimental renal and hepatic processes which could signify different donor management strategies for patients progressing to BD at different speeds.Abstract Background Donor brain death (BD) is an independent risk factor for graft survival in recipients. While in some patients BD results from a fast increase in intracranial pressure, usually associated with trauma, in others, intracranial pressure increases more slowly. The speed of intracranial pressure increase may be a possible risk factor for renal and hepatic graft dysfunction. This study aims to assess the effect of speed of BD induction on renal and hepatic injury markers. Methods BD induction was performed in 64 mechanically ventilated male Fisher rats by inflating a 4.0F Fogarty catheter in the epidural space. Rats were observed for 0.5, 1, 2 or 4 h following BD induction. Slow induction was achieved by inflating the balloon-catheter at a speed of 0.015 ml/min until confirmation of BD. Fast induction was achieved by inflating the balloon at 0.45 ml/min for 1 min. Plasma, kidney and liver tissue were collected for analysis. Results Slow BD induction led to higher plasma creatinine at all time points compared to fast induction. Furthermore, slow induction led to increased renal mRNA expression of IL-6, and renal MDA values after 4 h of BD compared to fast induction. Hepatic mRNA expression of TNF-α, Bax/Bcl-2, and protein expression of caspase-3 was significantly higher due to slow induction after 4 h of BD compared to fast induction. PMN infiltration was not different between fast and slow induction in both renal and hepatic tissue. Conclusion Slow induction of BD leads to poorer renal function compared to fast induction. Renal inflammatory and oxidative stress markers were increased. Liver function was not affected by speed of BD induction but hepatic inflammatory and apoptosis markers increased significantly due to slow induction compared to fast induction. These results provide initial proof that speed of BD induction influences detrimental renal and hepatic processes which could signify different donor management strategies for patients progressing to BD at different speeds.
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    Stochastic modeling of street lamps operation
    (1996) Rebolledo, Rolando; Ríos Marcuello, Sebastián; Trigo, Rodrigo; Matus Acuña, Marcelo Enrique
    This paper is based on the application of stochastic differential equations in simulating the active power consumption in street lamp operation, both in transient and steady state. The method worked as follows. Firstly, a collection of about 400 street lamps was measured in the laboratory. In addition, a theoretical model for the mean power consumption was derived. This model was expressed by means of a linear stochastic differential equations dependent on two parameter processes. The aforementioned parameters were then estimated from the experimental data and the equations solved numerically leading to a representation of the mean active power by means of a stochastic process.