Browsing by Author "Rebolledo, Rolando"

Now showing 1 - 20 of 21
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    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.
  • No Thumbnail Available
    Item
    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.
  • Thumbnail Image
    Item
    Complejidad y Azar
    (2013) Rebolledo, Rolando
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
  • No Thumbnail Available
    Item
    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.
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    On a Class of Non-Markovian Langevin Equations
    (2013) Rebolledo, Rolando
  • No Thumbnail Available
    Item
    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.
  • No Thumbnail Available
    Item
    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.
  • Thumbnail Image
    Item
  • No Thumbnail Available
    Item
    Oxygenation by Intravascular Photosynthesis Reduces Kidney Damage During ex Vivo Preservation
    (2024) Veloso-Gimenez, Valentina; Cardenas-Calderon, Camila; Castillo, Valentina; Carvajal, Felipe; Gallardo-Aguero, Daniela; Gonzalez-Itier, Sergio; Corrales-Orovio, Rocio; Becerra, Daniela; Miranda, Miguel; Rebolledo, Rolando; San Martin, Sebastian; Boric, Mauricio P.; Egana, Jose Tomas
    Several clinical issues are associated with reduced oxygen delivery to tissues due to impaired vascular perfusion; moreover, organs procured for transplantation are subjected to severe hypoxia during preservation. Consequently, alternative tissue oxygenation is an active field in biomedical research where several innovative approaches have been recently proposed. Among these, intravascular photosynthesis represents a promising approach as it relies on the intrinsic capacity of certain microorganisms to produce oxygen upon illumination. In this context, this work aims at the development of photosynthetic perfusable solutions that could be applied to preserve organs for transplantation purposes. Our findings demonstrate that a biocompatible physiological solution containing the photosynthetic microalgae Chlamydomonas reinhardtii can fulfill the metabolic oxygen demand of rat kidney slices in vitro. Furthermore, intravascular administration of this solution does not induce tissue damage in the rat kidneys. Moreover, kidney slices obtained from these algae-perfused organs exhibited significantly improved preservation after 24 h of incubation in hypoxia while exposed to light, resulting in reduced tissue damage and enhanced metabolic status. Overall, the results presented here contribute to the development of alternative strategies for tissue oxygenation, supporting the use of perfusable photosynthetic solutions for organ preservation in transplantation.
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    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.
  • No Thumbnail Available
    Item
    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.