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Paul Bardunias - One of the best experts on this subject based on the ideXlab platform.
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Two stRategies for optimizing the food Encounter Rate of termite tunnels simulated by a lattice model
Ecological Modelling, 2008Co-Authors: Seungjun Lee, Paul BarduniasAbstract:Abstract The tunneling structure of the Formosan subterranean termite, Coptotermes formosanus Shiraki, was simulated using a lattice model in order to explore a foraging stRategy that optimizes food Encounter Rate. A tunnel was mimicked by algorithms derived from experimental data that determined the movement of a discrete unit of excavation performed by a cadre of termite workers, the tunnel vector cell (TVC). To be consistent with real tunneling behavior, tunnel propagation was terminated when TVCs did not Encounter food particles within a given threshold length L1 (primary tunnel) and L2 (secondary tunnel). The simulations revealed that the length ratio between primary and secondary tunnels, γ (=L2/L1), produced a bimodal distribution of food Encounter Rates. The Encounter Rate was optimized at two values of γ because of either a searching distance effect (SDE), characterized by long primary tunnels with short branches, or a searching area effect (SAE), that balances tunnel length with branch length to cover a broad area. These two stRategies reflect tunnel geometries that subterranean termites may employ in excavating tunnel patterns that optimize the Rate of Encountering food sources.
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Food Encounter Rate of simulated termite tunnels in heterogeneous landscapes
Bio Systems, 2006Co-Authors: S.-h. Lee, Paul BarduniasAbstract:The aim of this study was to explore how a heterogeneous landscape affects food Encounter Rate in the Formosan subterranean termite, Coptotermes formosanus Shiraki. To do this, a lattice model was formulated to simulate the tunneling structure of the termite. The model made use of minimized local rules derived from empirical data. In addition, a landscape structure was geneRated on a lattice space by using a neutral landscape model. Each lattice cell has a value h, representing spatially distributed property of the landscape (e.g., temperature or moisture). The heterogeneity of the landscape was characterized by a parameter, H controlling aggregation of lattice cells with higher values of h. Higher H values correspond to higher aggregation levels. The effect of the landscape heterogeneity on the Encounter Rate was clear in the presence of higher food density than in lower density. The effect was also enhanced by the increase of the number of primary tunnels.
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Food Encounter Rates of simulated termite tunnels with variable food size/distribution pattern and tunnel branch length.
Journal of theoretical biology, 2006Co-Authors: Sanghee Lee, Paul BarduniasAbstract:Subterranean termites excavate tunnels in a search pattern to Encounter food in soil. To investigate the effect of food size, food distribution and the branch length of tunnels on food Encounter Rate we used a lattice gas model to simulate tunnels of the Formosan subterranean termite, Coptotermes formosanus Shiraki. The model made use of minimized local rules derived from empirical data to simulate termite tunnel patterns in featureless soil. Food distributions with three types (uniform, random, and clumped) were defined by using an I-index proposed by Zimmer and Johnson (1985). The food Encounter Rate was higher in a clumped than in non-clumped (uniform and random) distribution of food particles. When food particle size was varied in random distributions of food particles a maximum Encounter Rate was found, with particles of larger or smaller size being Encountered less frequently. We also discussed the relationship between the branch tunnel length and the tunnel search pattern in minimizing the redundancy of overlapping branches.
Jeanette C. Gladstone - One of the best experts on this subject based on the ideXlab platform.
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Stellar Encounter Rate in Galactic Globular Clusters
The Astrophysical Journal, 2013Co-Authors: Arash Bahramian, Craig O. Heinke, Gregory R. Sivakoff, Jeanette C. GladstoneAbstract:The high stellar densities in the cores of globular clusters cause significant stellar interactions. These stellar interactions can produce close binary mass-transferring systems involving compact objects and their progeny, such as X-ray binaries and radio millisecond pulsars. Comparing the numbers of these systems and interaction Rates in different clusters drives our understanding of how cluster parameters affect the production of close binaries. In this paper we estimate stellar Encounter Rates (Gamma) for 124 Galactic globular clusters based on observational data as opposed to the methods previously employed, which assumed "King-model" profiles for all clusters. By deprojecting cluster surface brightness profiles to estimate luminosity density profiles, we treat "King-model" and "core-collapsed" clusters in the same way. In addition, we use Monte-Carlo simulations to investigate the effects of uncertainties in various observational parameters (distance, reddening, surface brightness) on Gamma, producing the first catalog of GC stellar Encounter Rates with estimated errors. Comparing our results with published observations of likely products of stellar interactions (numbers of X-ray binaries, numbers of radio millisecond pulsars, and gamma-ray luminosity) we find both clear correlations and some differences with published results.
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stellar Encounter Rate in galactic globular clusters
The Astrophysical Journal, 2013Co-Authors: Arash Bahramian, Craig O. Heinke, Gregory R. Sivakoff, Jeanette C. GladstoneAbstract:The high stellar densities in the cores of globular clusters cause significant stellar interactions. These stellar interactions can produce close binary mass-transferring systems involving compact objects and their progeny, such as X-ray binaries and radio millisecond pulsars. Comparing the numbers of these systems and interaction Rates in different clusters drives our understanding of how cluster parameters affect the production of close binaries. In this paper we estimate stellar Encounter Rates ({Gamma}) for 124 Galactic globular clusters based on observational data as opposed to the methods previously employed, which assumed 'King-model' profiles for all clusters. By deprojecting cluster surface brightness profiles to estimate luminosity density profiles, we treat 'King-model' and 'core-collapsed' clusters in the same way. In addition, we use Monte Carlo simulations to investigate the effects of uncertainties in various observational parameters (distance, reddening, surface brightness) on {Gamma}, producing the first catalog of globular cluster stellar Encounter Rates with estimated errors. Comparing our results with published observations of likely products of stellar interactions (numbers of X-ray binaries, numbers of radio millisecond pulsars, and {gamma}-ray luminosity) we find both clear correlations and some differences with published results.
Sanghee Lee - One of the best experts on this subject based on the ideXlab platform.
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stRategy for optimizing food Encounter Rate of simulated termite tunnels
Journal of the Korean Physical Society, 2007Co-Authors: Sanghee LeeAbstract:The tunneling structure of the Formosan subterranean termite, Coptotermes formosanus Shiraki, was simulated using a lattice model to study a foraging stRategy that optimizes the food Encounter Rate. In the present study, two possible stRategies for constructing the major feature of the tunnel, the wheel-spoke pattern, were considered: N-stRategy handling the number of primary tunnels, N, and -stRategy controlling the exponent of the distribution of the branch tunnel length, . The simulation results revealed that the food Encounter Rate was more strongly influenced by the -stRategy than by the N-stRategy, and a restricted N was expected in consideration of the search distance defined as the average distance from tunnel tips to the simulated tunnel starting point. Also, the estimated was compared with one derived from empirical data.
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Food Encounter Rates of simulated termite tunnels with variable food size/distribution pattern and tunnel branch length.
Journal of theoretical biology, 2006Co-Authors: Sanghee Lee, Paul BarduniasAbstract:Subterranean termites excavate tunnels in a search pattern to Encounter food in soil. To investigate the effect of food size, food distribution and the branch length of tunnels on food Encounter Rate we used a lattice gas model to simulate tunnels of the Formosan subterranean termite, Coptotermes formosanus Shiraki. The model made use of minimized local rules derived from empirical data to simulate termite tunnel patterns in featureless soil. Food distributions with three types (uniform, random, and clumped) were defined by using an I-index proposed by Zimmer and Johnson (1985). The food Encounter Rate was higher in a clumped than in non-clumped (uniform and random) distribution of food particles. When food particle size was varied in random distributions of food particles a maximum Encounter Rate was found, with particles of larger or smaller size being Encountered less frequently. We also discussed the relationship between the branch tunnel length and the tunnel search pattern in minimizing the redundancy of overlapping branches.
Craig O. Heinke - One of the best experts on this subject based on the ideXlab platform.
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Stellar Encounter Rate in Galactic Globular Clusters
The Astrophysical Journal, 2013Co-Authors: Arash Bahramian, Craig O. Heinke, Gregory R. Sivakoff, Jeanette C. GladstoneAbstract:The high stellar densities in the cores of globular clusters cause significant stellar interactions. These stellar interactions can produce close binary mass-transferring systems involving compact objects and their progeny, such as X-ray binaries and radio millisecond pulsars. Comparing the numbers of these systems and interaction Rates in different clusters drives our understanding of how cluster parameters affect the production of close binaries. In this paper we estimate stellar Encounter Rates (Gamma) for 124 Galactic globular clusters based on observational data as opposed to the methods previously employed, which assumed "King-model" profiles for all clusters. By deprojecting cluster surface brightness profiles to estimate luminosity density profiles, we treat "King-model" and "core-collapsed" clusters in the same way. In addition, we use Monte-Carlo simulations to investigate the effects of uncertainties in various observational parameters (distance, reddening, surface brightness) on Gamma, producing the first catalog of GC stellar Encounter Rates with estimated errors. Comparing our results with published observations of likely products of stellar interactions (numbers of X-ray binaries, numbers of radio millisecond pulsars, and gamma-ray luminosity) we find both clear correlations and some differences with published results.
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stellar Encounter Rate in galactic globular clusters
The Astrophysical Journal, 2013Co-Authors: Arash Bahramian, Craig O. Heinke, Gregory R. Sivakoff, Jeanette C. GladstoneAbstract:The high stellar densities in the cores of globular clusters cause significant stellar interactions. These stellar interactions can produce close binary mass-transferring systems involving compact objects and their progeny, such as X-ray binaries and radio millisecond pulsars. Comparing the numbers of these systems and interaction Rates in different clusters drives our understanding of how cluster parameters affect the production of close binaries. In this paper we estimate stellar Encounter Rates ({Gamma}) for 124 Galactic globular clusters based on observational data as opposed to the methods previously employed, which assumed 'King-model' profiles for all clusters. By deprojecting cluster surface brightness profiles to estimate luminosity density profiles, we treat 'King-model' and 'core-collapsed' clusters in the same way. In addition, we use Monte Carlo simulations to investigate the effects of uncertainties in various observational parameters (distance, reddening, surface brightness) on {Gamma}, producing the first catalog of globular cluster stellar Encounter Rates with estimated errors. Comparing our results with published observations of likely products of stellar interactions (numbers of X-ray binaries, numbers of radio millisecond pulsars, and {gamma}-ray luminosity) we find both clear correlations and some differences with published results.
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X-ray Binaries in the Ultrahigh Encounter Rate Globular Cluster NGC 6388
The Astrophysical Journal, 2012Co-Authors: J. Edward Maxwell, Craig O. Heinke, Phyllis M. Lugger, Haldan N. Cohn, Jonathan E. Grindlay, Sonia A. Budac, Gordon A. Drukier, Charles D. BailynAbstract:We report the results of a joint \chandra-\hst study of the X-ray binary population in the massive, high-density globular cluster NGC 6388. NGC 6388 has one of the highest predicted X-ray binary production Rate of any Galactic cluster. We detected a large population of 61 \chandra sources within the half-mass radius with L$_X > 5 \times 10^{30}$ \ergs. From the X-ray colors, luminosities, (lack of) variability, and spectral fitting, we identify five as likely quiescent low-mass X-ray binaries. Due to the extremely crowded nature of the core of NGC 6388, finding optical identifications to \chandra sources is challenging. We have identified four blue, optically variable counterparts to spectrally hard X-ray sources, evidence that these are bright cataclysmic variables (CVs). One showed variability of 2 magnitudes in V, indicative of a dwarf nova eruption. One other likely CV is identified by its X-ray spectrum (partial covering with high $N_H$) and strong variability, making five likely CVs identified in this cluster. The relatively bright optical magnitudes of these sources put them in the same class as CV1 in M15 and the brightest CVs in 47 Tuc.
Charles D. Bailyn - One of the best experts on this subject based on the ideXlab platform.
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X-ray Binaries in the Ultrahigh Encounter Rate Globular Cluster NGC 6388
The Astrophysical Journal, 2012Co-Authors: J. Edward Maxwell, Craig O. Heinke, Phyllis M. Lugger, Haldan N. Cohn, Jonathan E. Grindlay, Sonia A. Budac, Gordon A. Drukier, Charles D. BailynAbstract:We report the results of a joint \chandra-\hst study of the X-ray binary population in the massive, high-density globular cluster NGC 6388. NGC 6388 has one of the highest predicted X-ray binary production Rate of any Galactic cluster. We detected a large population of 61 \chandra sources within the half-mass radius with L$_X > 5 \times 10^{30}$ \ergs. From the X-ray colors, luminosities, (lack of) variability, and spectral fitting, we identify five as likely quiescent low-mass X-ray binaries. Due to the extremely crowded nature of the core of NGC 6388, finding optical identifications to \chandra sources is challenging. We have identified four blue, optically variable counterparts to spectrally hard X-ray sources, evidence that these are bright cataclysmic variables (CVs). One showed variability of 2 magnitudes in V, indicative of a dwarf nova eruption. One other likely CV is identified by its X-ray spectrum (partial covering with high $N_H$) and strong variability, making five likely CVs identified in this cluster. The relatively bright optical magnitudes of these sources put them in the same class as CV1 in M15 and the brightest CVs in 47 Tuc.
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x ray binaries in the ultrahigh Encounter Rate globular cluster ngc 6388
The Astrophysical Journal, 2012Co-Authors: Edward J Maxwell, Phyllis M. Lugger, Haldan N. Cohn, Jonathan E. Grindlay, Sonia A. Budac, Gordon A. Drukier, C O Heinke, Charles D. BailynAbstract:We report the results of a joint Chandra Hubble Space Telescope study of the X-ray binary (XRB) population in the massive, high-density globular cluster NGC?6388. NGC?6388 has one of the highest predicted XRB production Rates of any Galactic cluster. We detected a large population of 61 Chandra sources within the half-mass radius with LX > 5 ? 1030 erg s?1. From the X-ray colors, luminosities, (lack of) variability, and spectral fitting, we identify five as likely quiescent low-mass X-ray binaries. Due to the extremely crowded nature of the core of NGC?6388, finding optical identifications to Chandra sources is challenging. We have identified four blue, optically variable counterparts to spectrally hard X-ray sources, evidence that these are bright cataclysmic variables (CVs). One showed variability of 2 mag in V, indicative of a dwarf nova eruption. One other likely CV is identified by its X-ray spectrum (partial covering with high N H) and strong variability, making five likely CVs identified in this cluster. The relatively bright optical magnitudes of these sources put them in the same class as CV1 in M15 and the brightest CVs in 47 Tuc.