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Search Results: 1 - 10 of 593335 matches for " L. A. Winslow "
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Simulation of Reactors for Antineutrino Experiments Using DRAGON
L. Winslow
Physics , 2011,
Abstract: From the discovery of the neutrino to the precision neutrino oscillation measurements in KamLAND, nuclear reactors have proven to be an important source of antineutrinos. As their power and our knowledge of neutrino physics has increased, more sensitive measurements have become possible. The next generation of reactor antineutrino experiments require more detailed simulations of the reactor core. Many of the reactor simulation codes are proprietary which makes detailed studies difficult. Here we present the results of the open source DRAGON code and compare it to other industry standards for reactor modeling. We use published data from the Takahama reactor to determine the quality of the simulations. The propagation of the uncertainty to the antineutrino flux is also discussed.
How to formulate membrane potential in a spatially homogeneous myocyte model?
A. J. Tanskanen,E. I. Tanskanen,J. L. Greenstein,R. L. Winslow
Quantitative Biology , 2005,
Abstract: Membrane potential in a mathematical model of a cardiac myocyte can be formulated in different ways. Assuming a spatially homogeneous myocyte that is strictly charge-conservative and electroneutral as a whole, two methods will be compared: (1) the differential formulation dV/dt=-I/C_m of membrane potential used traditionally; and (2) the capacitor formulation, where membrane potential is defined algebraically by the capacitor equation V=Q/C_m. We examine the relationship between the formulations, assumptions under which each formulation is consistent, and show that the capacitor formulation provides a transparent, physically realistic formulation of membrane potential, whereas use of the differential formulation may introduce unintended and undesirable behavior, such as monotonic drift of concentrations. We prove that the drift of concentrations in the differential formulation arises as a compensation for failure to assign all currents in concentrations. As an example of these considerations, we present an electroneutral, explicitly charge-conservative formulation of Winslow et al. model (1999), and extend it to describe membrane potentials between intracellular compartments.
A Reaction-Diffusion Model of ROS-Induced ROS Release in a Mitochondrial Network
Lufang Zhou,Miguel A. Aon,Tabish Almas,Sonia Cortassa,Raimond L. Winslow,Brian O'Rourke
PLOS Computational Biology , 2010, DOI: 10.1371/journal.pcbi.1000657
Abstract: Loss of mitochondrial function is a fundamental determinant of cell injury and death. In heart cells under metabolic stress, we have previously described how the abrupt collapse or oscillation of the mitochondrial energy state is synchronized across the mitochondrial network by local interactions dependent upon reactive oxygen species (ROS). Here, we develop a mathematical model of ROS-induced ROS release (RIRR) based on reaction-diffusion (RD-RIRR) in one- and two-dimensional mitochondrial networks. The nodes of the RD-RIRR network are comprised of models of individual mitochondria that include a mechanism of ROS-dependent oscillation based on the interplay between ROS production, transport, and scavenging; and incorporating the tricarboxylic acid (TCA) cycle, oxidative phosphorylation, and Ca2+ handling. Local mitochondrial interaction is mediated by superoxide (O2.?) diffusion and the O2.?-dependent activation of an inner membrane anion channel (IMAC). In a 2D network composed of 500 mitochondria, model simulations reveal ΔΨm depolarization waves similar to those observed when isolated guinea pig cardiomyocytes are subjected to a localized laser-flash or antioxidant depletion. The sensitivity of the propagation rate of the depolarization wave to O2.? diffusion, production, and scavenging in the reaction-diffusion model is similar to that observed experimentally. In addition, we present novel experimental evidence, obtained in permeabilized cardiomyocytes, confirming that ΔΨm depolarization is mediated specifically by O2.?. The present work demonstrates that the observed emergent macroscopic properties of the mitochondrial network can be reproduced in a reaction-diffusion model of RIRR. Moreover, the findings have uncovered a novel aspect of the synchronization mechanism, which is that clusters of mitochondria that are oscillating can entrain mitochondria that would otherwise display stable dynamics. The work identifies the fundamental mechanisms leading from the failure of individual organelles to the whole cell, thus it has important implications for understanding cell death during the progression of heart disease.
Control and Regulation of Integrated Mitochondrial Function in Metabolic and Transport Networks
Sonia Cortassa,Brian O’Rourke,Raimond L. Winslow,Miguel A. Aon
International Journal of Molecular Sciences , 2009, DOI: 10.3390/ijms10041500
Abstract: The pattern of flux and concentration control coefficients in an integrated mitochondrial energetics model is examined by applying a generalized matrix method of control analysis to calculate control coefficients, as well as response coefficients The computational model of Cortassa et al. encompasses oxidative phosphorylation, the TCA cycle, and Ca2+ dynamics. Control of ATP synthesis, TCA cycle, and ANT fluxes were found to be distributed among various mitochondrial processes. Control is shared by processes associated with ATP/ADP production and transport, as well as by Ca2+ dynamics. The calculation also analyzed the control of the concentrations of key regulatory ions and metabolites (Ca2+, NADH, ADP). The approach we have used demonstrates how properties of integrated systems may be understood through applications of computational modeling and control analysis.
Measuring Directionality in Double-Beta Decay and Neutrino Interactions with Kiloton-Scale Scintillation Detectors
C. Aberle,A. Elagin,H. J. Frisch,M. Wetstein,L. Winslow
Physics , 2013, DOI: 10.1088/1748-0221/9/06/P06012
Abstract: Large liquid-scintillator-based detectors have proven to be exceptionally effective for low energy neutrino measurements due to their good energy resolution and scalability to large volumes. The addition of directional information using Cherenkov light and fast timing would enhance the scientific reach of these detectors, especially for searches for neutrino-less double-beta decay. In this paper, we develop a technique for extracting particle direction using the difference in arrival times for Cherenkov and scintillation light, and evaluate several detector advances in timing, photodetector spectral response, and scintillator emission spectra that could be used to make direction reconstruction a reality in a kiloton-scale detector.
Reactor Simulation for Antineutrino Experiments using DRAGON and MURE
C. L. Jones,A. Bernstein,J. M. Conrad,Z. Djurcic,M. Fallot,L. Giot,G. Keefer,A. Onillon,L. Winslow
Physics , 2011, DOI: 10.1103/PhysRevD.86.012001
Abstract: Rising interest in nuclear reactors as a source of antineutrinos for experiments motivates validated, fast, and accessible simulations to predict reactor fission rates. Here we present results from the DRAGON and MURE simulation codes and compare them to other industry standards for reactor core modeling. We use published data from the Takahama-3 reactor to evaluate the quality of these simulations against the independently measured fuel isotopic composition. The propagation of the uncertainty in the reactor operating parameters to the resulting antineutrino flux predictions is also discussed.
Grand Challenges in Computational Physiology and Medicine
Raimond L. Winslow
Frontiers in Physiology , 2011, DOI: 10.3389/fphys.2011.00079
Abstract:
Systems biology approaches to understanding the cause and treatment of heart, lung, blood, and sleep disorders
Raimond L. Winslow
Frontiers in Physiology , 2014, DOI: 10.3389/fphys.2014.00107
Abstract:
Cyclotrons as Drivers for Precision Neutrino Measurements
A. Adelmann,J. Alonso,W. A. Barletta,J. M. Conrad,M. H. Shaevitz,J. Spitz,M. Toups,L. A. Winslow
Advances in High Energy Physics , 2014, DOI: 10.1155/2014/347097
Abstract: As we enter the age of precision measurement in neutrino physics, improved flux sources are required. These must have a well defined flavor content with energies in ranges where backgrounds are low and cross-section knowledge is high. Very few sources of neutrinos can meet these requirements. However, pion/muon and isotope decay-at-rest sources qualify. The ideal drivers for decay-at-rest sources are cyclotron accelerators, which are compact and relatively inexpensive. This paper describes a scheme to produce decay-at-rest sources driven by such cyclotrons, developed within the DAE ALUS program. Examples of the value of the high precision beams for pursuing Beyond Standard Model interactions are reviewed. New results on a combined DAE ALUS—Hyper-K search for CP violation that achieve errors on the mixing matrix parameter of 4° to 12° are presented. 1. Introduction As we reach the 100th anniversary of the birth of Bruno Pontecorvo, neutrino physics is facing a transition. Neutrino oscillations are well established, albeit in a different form from what Pontecorvo expected [1, 2]. We have a data-driven “Neutrino Standard Model,” ( SM) which, despite questions about its underlying theoretical description, is remarkably predictive. Now, the neutrino community must pivot from “searches” to “precision measurements,” in which we can test the SM. The transition requires new and better tools for these measurements and further calls for original approaches to experiments. The SM is simply described in Figure 1. The three known neutrino flavors mix within three mass states. The separations between the states, or “mass splittings,” are defined as , for The historical name for the smaller splitting ( ) is and the larger mass splitting ( is referred to as , in honor of the solar and atmospheric experiments that established the existence of each. The early solar [3–6] and atmospheric [7–9] experiments have been joined by new results [10–15] to establish this phenomenology [16]. Figure 1: Illustration of the “ SM” showing mass states and mixings. Note that this drawing depicts only one possible mass ordering. There remain many open questions that surround this data-driven picture of neutrinos and oscillations. The mixings are described with a matrix, commonly called the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix, that connects the mass eigenstates ( , , and ) to the flavor eigenstates ( , , and ): where the ranges indicate our knowledge of each of the entries [27]. Together with the mass splittings, the mixing matrix is pictorially represented in Figure 1, in which
Cyclotrons as Drivers for Precision Neutrino Measurements
A. Adelmann,J. Alonso,W. A. Barletta,J. M. Conrad,M. H. Shaevitz,J. Spitz,M. Toups,L. A. Winslow
Physics , 2013,
Abstract: As we enter the age of precision measurement in neutrino physics, improved flux sources are required. These must have a well-defined flavor content with energies in ranges where backgrounds are low and cross section knowledge is high. Very few sources of neutrinos can meet these requirements. However, pion/muon and isotope decay-at-rest sources qualify. The ideal drivers for decay-at-rest sources are cyclotron accelerators, which are compact and relatively inexpensive. This paper describes a scheme to produce decay-at-rest sources driven by such cyclotrons, developed within the DAEdALUS program. Examples of the value of the high precision beams for pursuing Beyond Standard Model interactions are reviewed. New results on a combined DAEdALUS--Hyper-K search for CP-violation that achieve errors on the mixing matrix parameter of 4 degrees to 12 degrees are presented.
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