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Journal articles on the topic 'Isochronie'

Author: Grafiati

Published: 28 June 2021

Last updated: 29 July 2025

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1

Funai, J. T., and M. D. Thames. "Isochronal behavior in left ventricular systolic pressure-wall thickness relations." American Journal of Physiology-Heart and Circulatory Physiology 255, no. 5 (1988): H1136—H1143. http://dx.doi.org/10.1152/ajpheart.1988.255.5.h1136.

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Regional left ventricular systolic pressure-thickness relations have been used to assess regional load-insensitive contractility with the assumption that they possess linear isochrones that are fundamental to the time-varying elastance model of global pressure-volume relations. We examined the shape and time-varying behavior of pressure-thickness isochrones in six open-chest canine preparations. Transmural wall thickening (sonomicrometry) and ventricular pressure were altered by abrupt preload alterations during control, dobutamine, and propranolol. In all dogs and interventions, linear isochr

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2

Krishnamurti, T. N., Anu Simon, Aype Thomas, et al. "Modeling of Forecast Sensitivity on the March of Monsoon Isochrones from Kerala to New Delhi: The First 25 Days." Journal of the Atmospheric Sciences 69, no. 8 (2012): 2465–87. http://dx.doi.org/10.1175/jas-d-11-0170.1.

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Abstract This study addresses observational and modeling sensitivity on the march of the onset isochrones of the Indian summer monsoon. The first 25 days of the passage of the isochrones of monsoon onset is of great scientific interest. Surface and satellite-based datasets are used for high-resolution modeling of the impact of the motion of the onset isochrones from Kerala to New Delhi. These include the asymmetries across the isochrone such as soil moisture and its temporal variability, moistening of the dry soil to the immediate north of the isochrone by nonconvective anvil rains, and format

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3

Schuman, Bertrand. "Une classe d’hamiltoniens polynomiaux isochrones." Canadian Mathematical Bulletin 44, no. 3 (2001): 323–34. http://dx.doi.org/10.4153/cmb-2001-032-9.

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RésuméSoit un hamiltonien isochrone du plan . On met en évidence une classe d’hamiltoniens isochrones qui sont des perturbations polynomiales de H0. On obtient alors une condition nécessaire d’isochronisme, et un critère de choix pour les hamiltoniens isochrones. On voit ce résultat comme étant une généralisation du caractère isochrone des perturbations hamiltoniennes homogènes considérées dans [L], [P], [S].

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4

Wang, Fan, Min Fang, Xiaoting Fu, et al. "Empirical Color Correction to MIST and PARSEC Isochrones on Gaia BR − RP and G − RP with Benchmark Open Clusters." Astrophysical Journal 979, no. 1 (2025): 92. https://doi.org/10.3847/1538-4357/ad960a.

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Abstract Recent literature reports a color deviation between observed Gaia color–magnitude diagrams (CMDs) and theoretical model isochrone predictions, particularly in the very low-mass regime. To assess its impact on cluster age determination via isochrone fitting, we quantified the color deviations for three benchmark clusters, Hyades, Pleiades, and Praesepe, both for the Gaia color (BP − RP) and (G − RP). In general, the (G − RP) color deviations are smaller than the (BP − RP) ones. Empirical color-correction functions based on these benchmarks are derived for the currently available MESA I

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5

Engel, Hugues. "L’Hypothèse d’Isochronie Syllabique Initiale appliquée au français L2." Language, Interaction and Acquisition 11, no. 2 (2020): 268–97. http://dx.doi.org/10.1075/lia.19009.eng.

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Résumé L’objectif principal de cette étude pilote est de tester expérimentalement ce que nous appelons l’Hypothèse d’Isochronie Syllabique Initiale. Selon cette hypothèse, les apprenants de L2 passent par une phase initiale pendant laquelle leurs productions orales présentent les caractéristiques rythmiques des langues dites à isochronie syllabique (telles que l’espagnol et le français). Pour cela, nous analysons des récits oraux d’apprenantes débutantes de français ayant le suédois pour langue maternelle (n = 6). Ces productions sont comparées à celles d’un groupe de locutrices natives du fra

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6

Novico, F., C. Endyana, D. Menier, et al. "The dynamic coastal evidence of Jakarta Bay during Late Pleistocene-Recent." IOP Conference Series: Earth and Environmental Science 930, no. 1 (2021): 012002. http://dx.doi.org/10.1088/1755-1315/930/1/012002.

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Abstract Some significant indication identifying a coastal dynamic during Late Pleistocene to Recent is the evolution of isochrone patterns throughout glacial-interglacial stages. This study aims to identify the sediments stratification of Jakarta Bay during the Late Pleistocene – Recent in the framework of coastal dynamic triggered by the sea-level changes of last prominent climatic stages. The several high-resolution seismic records in Jakarta Bay lines were interpreted to illustrate the different sequences from the top down to the oldest by line-drawing the more robust seismic reflectors as

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7

Engel, Maximilian, and Christian Kuehn. "A Random Dynamical Systems Perspective on Isochronicity for Stochastic Oscillations." Communications in Mathematical Physics 386, no. 3 (2021): 1603–41. http://dx.doi.org/10.1007/s00220-021-04077-z.

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AbstractFor an attracting periodic orbit (limit cycle) of a deterministic dynamical system, one defines the isochron for each point of the orbit as the cross-section with fixed return time under the flow. Equivalently, isochrons can be characterized as stable manifolds foliating neighborhoods of the limit cycle or as level sets of an isochron map. In recent years, there has been a lively discussion in the mathematical physics community on how to define isochrons for stochastic oscillations, i.e. limit cycles or heteroclinic cycles exposed to stochastic noise. The main discussion has concerned

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8

Holeček, Milan. "The Isochronal Map of Individual Road Traffic in the Czech Socialist Republic." Geografie 92, no. 4 (1987): 256–62. http://dx.doi.org/10.37040/geografie1987092040256.

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The paper treats of the method of compilation of an isochronal map depicting the individual motor-car traffic, the irregular bus traffic and the long-distance traffic using the average speed fixed for the four categories of roads and speedways. The isochronal map showing the state of the road network in 1985 is completed with isochrones depicting the anticipated state od road infrastructure in 2010.

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9

Bell, Cameron P. M., Jon M. Rees, Tim Naylor, et al. "Pre-main-sequence isochrones – III. The Cluster Collaboration isochrone server." Monthly Notices of the Royal Astronomical Society 445, no. 4 (2014): 3496–511. http://dx.doi.org/10.1093/mnras/stu1944.

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10

Nereson, Nadine A., and Edwin D. Waddington. "Isochrones and isotherms beneath migrating ice divides." Journal of Glaciology 48, no. 160 (2002): 95–108. http://dx.doi.org/10.3189/172756502781831647.

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AbstractWe use simple numerical and analytical models of ice flow and heat flow to characterize the shape of isochrones and isotherms beneath moving ice divides. Both nonlinear ice flow and reduced accumulation (wind scouring) at a divide can cause reduced downward flow in a region about one ice thickness wide under a divide. Greater downward velocities on the flanks cause isochrones and isotherms to become arched at depth. The magnitudes and shapes of these arches depend on the history of divide position. Arch amplitudes decrease by approximately e−1 for each increase in migration rate of 3–5

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11

Rousseau, C., and B. Toni. "Local Bifurcations of Critical Periods in the Reduced Kukles System." Canadian Journal of Mathematics 49, no. 2 (1997): 338–58. http://dx.doi.org/10.4153/cjm-1997-017-4.

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AbstractIn this paper, we study the local bifurcations of critical periods in the neighborhood of a nondegenerate centre of the reduced Kukles system. We find at the same time the isochronous systems. We show that at most three local critical periods bifurcate from the Christopher-Lloyd centres of finite order, at most two from the linear isochrone and at most one critical period from the nonlinear isochrone. Moreover, in all cases, there exist perturbations which lead to the maximum number of critical periods. We determine the isochrones, using the method of Darboux: the linearizing transform

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12

Li, Yang, and Pieter Vermeesch. "Short communication: Inverse isochron regression for Re–Os, K–Ca and other chronometers." Geochronology 3, no. 2 (2021): 415–20. http://dx.doi.org/10.5194/gchron-3-415-2021.

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Abstract. Conventional Re–Os isochrons are based on mass spectrometric estimates of 187Re/188Os and 187Os/188Os, which often exhibit strong error correlations that may obscure potentially important geological complexity. Using an approach that is widely accepted in 40Ar/39Ar and U–Pb geochronology, we here show that these error correlations are greatly reduced by applying a simple change of variables, using 187Os as a common denominator. Plotting 188Os/187Os vs. 187Re/187Os produces an “inverse isochron”, defining a binary mixing line between an inherited Os component whose 188Os/187Os ratio i

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13

Xi, Yang (Luna), Eric J. Miller, and Shoshanna Saxe. "Exploring the Impact of Different Cut-off Times on Isochrone Measurements of Accessibility." Transportation Research Record: Journal of the Transportation Research Board 2672, no. 49 (2018): 113–24. http://dx.doi.org/10.1177/0361198118783113.

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Isochrone analysis and assessments of cumulative opportunities are a common way to quantify accessibility. However, different time cut-offs have been used by different researchers, with little investigation into what is the ‘best’ cut-off time. Outstanding questions remain concerning the most effective or predictive cut-off time and the potential implications of choosing one time limit over another. The primary objective of this paper is to explore how different cut-off times affect the calculation of isochrone-based accessibility measurements and their potential to predict travel-mode choice.

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14

Ichinose, Natsuhiro, Kazuyuki Aihara, and Kevin Judd. "Extending the Concept of Isochrons from Oscillatory to Excitable Systems for Modeling an Excitable Neuron." International Journal of Bifurcation and Chaos 08, no. 12 (1998): 2375–85. http://dx.doi.org/10.1142/s021812749800190x.

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In this paper, we study an excitable and nonoscillating neuron on the basis of a technique of extending the concept of isochrons from oscillatory to excitable systems. The extended isochrons allow reduction of an excitable system described by possibly high dimensional differential equations to a simpler system. We analytically derive a one-dimensional model of an excitable neuron stimulated by instantaneous pulses with the technique of the extended isochrons and show its similarity to an isochronal map numerically obtained from the FitzHugh–Nagumo model. Response characteristics of the one-dim

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15

Gontcharov, George A., Maxim Yu Khovritchev, and Aleksandr V. Mosenkov. "Isochrone fitting of Galactic globular clusters – II. NGC 6205 (M13)." Monthly Notices of the Royal Astronomical Society 497, no. 3 (2020): 3674–93. http://dx.doi.org/10.1093/mnras/staa1694.

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ABSTRACT We present new isochrone fits to colour–magnitude diagrams of the Galactic globular cluster NGC 6205 (M13). We utilize 34 photometric bands from the ultraviolet to mid-infrared by use of data from the HST, Gaia DR2, SDSS, unWISE, Pan-STARRS DR1, and other photometric sources. In our isochrone fitting we use the PARSEC, MIST, DSEP, BaSTI, and IAC-BaSTI theoretical models and isochrones, both for the solar-scaled and He–α-enhanced abundances, with a metallicity of about [Fe/H] = −1.58 adopted from the literature. The colour–magnitude diagrams, obtained with pairs of filters from differe

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16

Spada, F., P. Demarque, Y. C. Kim, T. S. Boyajian, and J. M. Brewer. "YaPSI: a new database of evolutionary tracks and isochrones." Proceedings of the International Astronomical Union 13, S334 (2017): 362–63. http://dx.doi.org/10.1017/s1743921317007347.

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AbstractThe Yale–Potsdam Stellar Isochrones (YaPSI) cover the low and intermediate stellar mass regime (0.15 to 5.0 M⊙) for a wide range of solar-scaled chemical compositions (metallicity from −0.5 to +0.3; helium mass fraction from 0.25 to 0.37, assigned independently of each other). The tracks are finely spaced in mass, to allow for accurate interpolation. The models feature state-of-the-art input physics relevant to low-mass stars modeling (surface boundary conditions, equation of state), thus updating the faint end of the Yonsei-Yale (YY) isochrones. Utility codes, such as an isochrone int

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17

Jørgensen, B. R., and L. Lindegren. "Determination of stellar ages from isochrones: Bayesian estimation versus isochrone fitting." Astronomy & Astrophysics 436, no. 1 (2005): 127–43. http://dx.doi.org/10.1051/0004-6361:20042185.

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18

Leysinger Vieli, G. J. M. C., R. C. A. Hindmarsh, and M. J. Siegert. "Three-dimensional flow influences on radar layer stratigraphy." Annals of Glaciology 46 (2007): 22–28. http://dx.doi.org/10.3189/172756407782871729.

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AbstractVariations in the depth of radar-detectable englacial layers (isochrones) are commonly used to assess past variability in accumulation rates, but little is known about the effect of internal and basal flow variations on isochrone deflections (e.g. bumps, troughs). In this paper, we show how the isochrones are affected by such variation using a three-dimensional flow model to investigate changes in the flow mode and in increased basal melting. We also investigate how transverse flows with lateral velocity gradients affect the development of isochrones. We use the model to visualize how

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19

Tayar, Jamie, and Meridith Joyce. "Star-crossed Clusters: Asteroseismic Ages for Individual Stars Are in Tension with the Ages of Their Host Clusters." Astrophysical Journal Letters 984, no. 2 (2025): L56. https://doi.org/10.3847/2041-8213/adcd6f.

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Abstract A meta-analysis of seismic ages determined for individual stars in the well-studied open and globular clusters NGC 6819, NGC 6791, M67, M4, M19, M80, and M9 reveals both high variance across measurements and a possible discrepancy with independent, isochrone-based age determinations for the clusters in which these stars reside. The scatter among asteroseismic ages for individual stars in any one of these clusters far surpasses both the absolute age uncertainty computed for reference cluster M92 (5.4%) and the model-to-model systematic uncertainties in isochrones (roughly 10%). This su

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20

Sinisalo, Anna, Aslak Grinsted, and John Moore. "Dynamics of the Scharffenbergbotnen blue-ice area, Dronning Maud Land, Antarctica." Annals of Glaciology 39 (2004): 417–22. http://dx.doi.org/10.3189/172756404781814177.

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AbstractGround-penetrating radar (GPR) surveys in Scharffenbergbotnen valley, Dronning Maud Land, Antarctica, complement earlier, relatively sparse data on the ice-flow dynamics and mass-balance distribution of the area. The negative net surface mass balance in the valley appears to be balanced by the inflow. The flow regime in Scharffenbergbotnen defines four separate mass-balance areas, and about 60 times more ice enters the valley from the northwestern entrance than via the narrow western gate. We formalize and compare three methods of determining both the surface age gradient of the blue i

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Janson, Markus, Stephen Durkan, Mickaël Bonnefoy, et al. "Dynamical masses of M-dwarf binaries in young moving groups." Astronomy & Astrophysics 620 (November 27, 2018): A33. http://dx.doi.org/10.1051/0004-6361/201833375.

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Low-mass stars exhibit substantial pre-main sequence evolution during the first ∼100 Myr of their lives. Thus, young M-type stars are prime targets for isochronal dating, especially in young moving groups (YMGs), which contain large amounts of stars in this mass and age range. If the mass and luminosity of a star can both be directly determined, this allows for a particularly robust isochronal analysis. This motivates in-depth studies of low-mass binaries with spatially resolvable orbits, where dynamical masses can be derived. Here we present the results of an observing campaign dedicated to o

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Claessens, T. E., D. Georgakopoulos, M. Afanasyeva, et al. "Nonlinear isochrones in murine left ventricular pressure-volume loops: how well does the time-varying elastance concept hold?" American Journal of Physiology-Heart and Circulatory Physiology 290, no. 4 (2006): H1474—H1483. http://dx.doi.org/10.1152/ajpheart.00663.2005.

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tThe linear time-varying elastance theory is frequently used to describe the change in ventricular stiffness during the cardiac cycle. The concept assumes that all isochrones (i.e., curves that connect pressure-volume data occurring at the same time) are linear and have a common volume intercept. Of specific interest is the steepest isochrone, the end-systolic pressure-volume relationship (ESPVR), of which the slope serves as an index for cardiac contractile function. Pressure-volume measurements, achieved with a combined pressure-conductance catheter in the left ventricle of 13 open-chest ane

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23

Duchkov, Anton A., and Maarten V. de Hoop. "Extended isochron rays in prestack depth (map) migration." GEOPHYSICS 75, no. 4 (2010): S139—S150. http://dx.doi.org/10.1190/1.3459955.

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Many processes in seismic data analysis and seismic imaging can be identified with solution operators of evolution equations. These include data downward continuation and velocity continuation. We have addressed the question of whether isochrons defined by imaging operators can be identified with wavefronts of solutions to an evolution equation. Rays associated with this equation then would provide a natural way of implementing prestack map migration. Assuming absence of caustics, we have developed constructive proof of the existence of a Hamiltonian describing propagation of isochrons in the

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Alves, Virginia Mello, Eduardo Bica, and Daniela Borges Pavani. "Determination of astrophysical parameters of open clusters using classical and semi-automated isochrone-fitting methods." Proceedings of the International Astronomical Union 5, S266 (2009): 352. http://dx.doi.org/10.1017/s1743921309991268.

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AbstractWhen we use optical isochrone-fitting solutions from the literature to 2mass CMDs, they are often not the best solutions in the infrared domain. We analysed 10 open clusters with 2mass, nine of them previously studied with optical photometry (NGC 1245, NGC 1342, NGC 1502, NGC 2104, NGC 2204, NGC 2243, NGC 2281, NGC 6709 and NGC 744) and one using integrated spectroscopy (BH 132). The study involved the classical (by eye) and a semi-automated method of isochrone fitting. We used the solutions of the first method as input for the second, looking for refined solutions. The semi-automated

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Winter, Anna, Daniel Steinhage, Timothy T. Creyts, Thomas Kleiner, and Olaf Eisen. "Age stratigraphy in the East Antarctic Ice Sheet inferred from radio-echo sounding horizons." Earth System Science Data 11, no. 3 (2019): 1069–81. http://dx.doi.org/10.5194/essd-11-1069-2019.

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Abstract. The East Antarctic Ice Sheet contains a wealth of information that can be extracted from its internal architecture such as distribution of age, past flow features, and surface and basal properties. Airborne radar surveys can sample this stratigraphic archive across broad areas. Here, we identify and trace key horizons across several radar surveys to obtain the stratigraphic information. We transfer the age–depth scales from ice cores to intersecting radar data. We then propagate these age scales across the ice sheet using the high fidelity continuity of the radar horizons. In Dronnin

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Cavitte, Marie G. P., Frédéric Parrenin, Catherine Ritz, et al. "Accumulation patterns around Dome C, East Antarctica, in the last 73 kyr." Cryosphere 12, no. 4 (2018): 1401–14. http://dx.doi.org/10.5194/tc-12-1401-2018.

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Abstract. We reconstruct the pattern of surface accumulation in the region around Dome C, East Antarctica, since the last glacial. We use a set of 18 isochrones spanning all observable depths of the ice column, interpreted from various ice-penetrating radar surveys and a 1-D ice flow model to invert for accumulation rates in the region. The shallowest four isochrones are then used to calculate paleoaccumulation rates between isochrone pairs using a 1-D assumption where horizontal advection is negligible in the time interval of each layer. We observe that the large-scale (100s km) surface accum

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Wanderley, Fábio, Katia Cunha, Diogo Souto, et al. "Stellar Characterization and Radius Inflation of Hyades M-dwarf Stars from the APOGEE Survey." Astrophysical Journal 951, no. 2 (2023): 90. http://dx.doi.org/10.3847/1538-4357/acd4bd.

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Abstract We present a spectroscopic analysis of a sample of 48 M-dwarf stars (0.2 M ⊙ < M < 0.6 M ⊙) from the Hyades open cluster using high-resolution H-band spectra from the Sloan Digital Sky Survey/Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. Our methodology adopts spectrum synthesis with LTE MARCS model atmospheres, along with the APOGEE Data Release 17 line list, to determine effective temperatures, surface gravities, metallicities, and projected rotational velocities. The median metallicity obtained for the Hyades M dwarfs is [M/H] = 0.09 ± 0.03 dex, indi

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Iversen, Einar. "The isochron ray in seismic modeling and imaging." GEOPHYSICS 69, no. 4 (2004): 1053–70. http://dx.doi.org/10.1190/1.1778248.

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The isochron, the name given to a surface of equal two‐way time, has a profound position in seismic imaging. In this paper, I introduce a framework for construction of isochrons for a given velocity model. The basic idea is to let trajectories called isochron rays be associated with iso chrons in an way analogous to the association of conventional rays with wavefronts. In the context of prestack depth migration, an isochron ray based on conventional ray theory represents a simultaneous downward continuation from both source and receiver. The isochron ray is a generalization of the normal ray f

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29

Zhao, Yuan, and Ying Zhou. "Isochrone-Based Accessibility Analysis of Pre-Hospital Emergency Medical Facilities: A Case Study of Central Districts of Beijing." ISPRS International Journal of Geo-Information 13, no. 8 (2024): 288. http://dx.doi.org/10.3390/ijgi13080288.

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Pre-hospital emergency medical service (PHEMS) is critical for the treatment outcomes of life-threatening injuries and time-sensitive illnesses. Response time, influenced by traffic conditions and the site planning of pre-hospital emergency medical facilities (PHEMFs), is the main indicator for evaluating PHEMS. In 2020, the Beijing government released the “Special Plan for Spatial Layout of Pre-hospital Emergency Medical Facilities in Beijing (2020–2022)”. This paper evaluates the functional efficiency and spatial equity of this plan within Beijing’s central six districts using isochrone meas

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Bonfanti, A., and M. Gillon. "MCMCI: A code to fully characterise an exoplanetary system." Astronomy & Astrophysics 635 (February 28, 2020): A6. http://dx.doi.org/10.1051/0004-6361/201936326.

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Context. Useful information can be retrieved by analysing the transit light curve of a planet-hosting star or induced radial velocity oscillations. However, inferring the physical parameters of the planet, such as mass, size, and semi-major axis, requires preliminary knowledge of some parameters of the host star, especially its mass or radius, which are generally inferred through theoretical evolutionary models. Aims. We seek to present and test a whole algorithm devoted to the complete characterisation of an exoplanetary system thanks to the global analysis of photometric or radial velocity t

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Parrenin, F., R. C. A. Hindmarsh, and F. Rémy. "Analytical solutions for the effect of topography, accumulation rate and lateral flow divergence on isochrone layer geometry." Journal of Glaciology 52, no. 177 (2006): 191–202. http://dx.doi.org/10.3189/172756506781828728.

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AbstractThe effect of spatial variations in ice thickness, accumulation rate and lateral flow divergence on radar-detected isochrone geometry in ice sheets is computed using an analytical method, under assumptions of a steady-state ice-sheet geometry, a steady-state accumulation pattern and a horizontally uniform velocity shape function. By using a new coordinate transform, we show that the slope of the isochrones (with a normalized vertical coordinate) depends on three terms: a principal term which determines the sign of the slope, and two scale factors which can modify only the amplitude of

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Esmersoy, Cengiz, and Douglas Miller. "Backprojection versus backpropagation in multidimensional linearized inversion." GEOPHYSICS 54, no. 7 (1989): 921–26. http://dx.doi.org/10.1190/1.1442722.

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Seismic migration can be viewed as either backprojection (diffraction‐stack) or backpropagation (wave‐field extrapolation) (e.g., Gazdag and Sguazzero, 1984). Migration by backprojection was the view supporting the first digital methods—the diffraction and common tangent stacks of what is now called classical or statistical migration (Lindsey and Hermann, 1970; Rockwell, 1971; Schneider, 1971; Johnson and French, 1982). In this approach, each data point is associated with an isochron surface passing through the scattering object. Data values are then interpreted as projections of reflectivity

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NG, Felix, and Edward C. King. "Kinematic waves in polar firn stratigraphy." Journal of Glaciology 57, no. 206 (2011): 1119–34. http://dx.doi.org/10.3189/002214311798843340.

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AbstractRadar studies of firn on the ice sheets have revealed complex folds on its internal layering that form from the interplay of snow accumulation and ice flow. A mathematical theory for these fold structures is presented, for the case where the radar cross section lies along the ice-flow direction and where the accumulation rate and ice-flow velocity are time-invariant. Our model, which accounts for firn densification, shows how ‘information’ (the depth and slope of isochrones) propagates on the radargram to govern its layer undulations. This leads us to discover universal rules behind th

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Armstrong, Richard Lee, and Paul Ramaekers. "Sr isotopic study of Helikian sediment and diabase dikes in the Athabasca Basin, northern Saskatchewan." Canadian Journal of Earth Sciences 22, no. 3 (1985): 399–407. http://dx.doi.org/10.1139/e85-038.

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The Athabasca Group overlies 1.8 Ga or older basement of the Churchill Province and predates uranium mineralization at 1.3 Ga. Cross-cutting diabase dikes have been dated by Rb–Sr mineral isochrons at 1.31 ± 0.07 Ga at Diabase Peninsula, Cree Lake, and 1.16 ± 0.04 Ga at Lazy Edward Bay, Cree Lake. Initial 87Sr/86Sr ratios for these dikes are 0.7040 ± 0.0005 and 0.7036 ± 0.002, respectively. Clastic sedimentary rocks of the Athabasca Group normally show limited variation in Rb/Sr and variable initial 87Sr/86Sr. Sedimentary rocks in two areas near the northern margin of the Athabasca Basin scatt

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Demarque, Pierre. "Isochrones for late-type stars." Proceedings of the International Astronomical Union 4, S258 (2008): 383–94. http://dx.doi.org/10.1017/s1743921309032049.

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AbstractA brief summary of the history of stellar evolution theory and the use of isochrones is given. The present state of the subject is summarized. The major uncertainties in isochrone construction are considered: chemical abundances and color calibrations, and the treatment of turbulent convection in stellar interior and atmosphere models. The treatment of convection affects the modeling of stellar interiors principally in two ways: convective core overshoot which increases evolutionary lifetimes, and the depth of convection zones which determines theoretical radii. Turbulence also modifie

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Ying, Jiaqi (Martin), Brian Chaboyer, Michael Boylan-Kolchin, Daniel R. Weisz, and Rowan Goebel-Bain. "The Absolute Age of Milky Way Globular Clusters." Astrophysical Journal 987, no. 1 (2025): 52. https://doi.org/10.3847/1538-4357/add471.

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Abstract Globular clusters (GCs) provide statistically significant coeval populations of stars spanning various evolutionary stages, allowing robust constraints on stellar evolution model parameters and ages. We analyze eight old Milky Way GCs with metallicities between [Fe/H] = −2.31 and −0.77 by comparing theoretical isochrone sets from the Dartmouth Stellar Evolution Program to Hubble Space Telescope (HST) observations. The theoretical isochrones include uncertainties introduced by 21 stellar evolution parameters such as convective mixing, opacity, diffusion, and nuclear reactions, capturin

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Bergbusch, Peter A., та Don A. VandenBerg. "Models for Old, Metal‐poor Stars with Enhanced α‐Element Abundances. III. Isochrones and Isochrone Population Functions". Astrophysical Journal 556, № 1 (2001): 322–39. http://dx.doi.org/10.1086/321571.

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Parrenin, Frédéric, and Richard Hindmarsh. "Influence of a non-uniform velocity field on isochrone geometry along a steady flowline of an ice sheet." Journal of Glaciology 53, no. 183 (2007): 612–22. http://dx.doi.org/10.3189/002214307784409298.

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The relationship between velocity field and isochrone geometry along a steady flowline of an ice sheet is examined. The method is analytical and based upon the stream function and its vertically normalized form, the normalized stream function (NSF). We show that the slope of the isochrones is the slope of the iso-NSF lines, plus a path term which is the cumulative result of the past trajectory of the ice particles. We illustrate this path term in three different examples: varying basal melting, varying basal sliding (Weertman effect) and varying velocity profile around a divide (Raymond effect

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Casali, G., L. Magrini, E. Tognelli, et al. "The Gaia-ESO survey: Calibrating a relationship between age and the [C/N] abundance ratio with open clusters." Astronomy & Astrophysics 629 (September 2019): A62. http://dx.doi.org/10.1051/0004-6361/201935282.

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Context. In the era of large high-resolution spectroscopic surveys such as Gaia-ESO and APOGEE, high-quality spectra can contribute to our understanding of the Galactic chemical evolution by providing abundances of elements that belong to the different nucleosynthesis channels, and also by providing constraints to one of the most elusive astrophysical quantities: stellar age. Aims. Some abundance ratios, such as [C/N], have been proven to be excellent indicators of stellar ages. We aim at providing an empirical relationship between stellar ages and [C/N] using open star clusters, observed by t

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Barros, Artur Borges, Maria Elisa Leite Costa, and Sérgio Koide. "Performance Analysis of Residential Detention Tanks Based on Spatial Arrangement in an Urbanized Basin in the Federal District, Brazil." Sustainability 17, no. 9 (2025): 4032. https://doi.org/10.3390/su17094032.

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This study evaluated the allocation of residential detention tanks in the Alto da Boa Vista Condominium, Federal District, Brazil, using hydrological and hydraulic modeling using the PCSWMM software (version 7.6.3610). The objective was to investigate the impact of urbanization on local hydrology, considering the occurrence of erosive processes in the area. Critical points in the infrastructure and regions susceptible to flooding were identified. The methodology involved implementing residential detention tanks in different allocation scenarios, including the use of isochrones. Isochrones, whi

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Stevenson, Ross K., P. J. Patchett, and R. F. Martin. "Sm–Nd isochron from a granodiorite–granite complex in the Portman Lake region, Northwest Territories." Canadian Journal of Earth Sciences 26, no. 12 (1989): 2724–29. http://dx.doi.org/10.1139/e89-232.

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Whole-rock samples for a granodiorite–granite intrusion in the Portman Lake area of the Northwest Territories yield an Sm–Nd isochron with an age of 2577 ± 36 Ma. The addition of a garnet analysis results in an age of 2562 ± 21 Ma. An Sm–Nd isochron is rare for granitic samples because of small ranges in 147Sm/144Nd values and variability in the initial Nd isotopic ratios. A wide range in 147Sm/144Nd values among samples in this study is considered a result of garnet fractionation and (or) variable concentrations of titanite in the samples. The εNd values for the initial Nd isotopic ratios of

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Bossini, D., A. Vallenari, A. Bragaglia, et al. "Age determination for 269 Gaia DR2 open clusters." Astronomy & Astrophysics 623 (March 2019): A108. http://dx.doi.org/10.1051/0004-6361/201834693.

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Context. The Gaia Second Data Release provides precise astrometry and photometry for more than 1.3 billion sources. This catalog opens a new era concerning the characterization of open clusters and test stellar models, paving the way for better understanding of the disk properties. Aims. The aim of the paper is to improve the knowledge of cluster parameters, using only the unprecedented quality of the Gaia photometry and astrometry. Methods. We have made use of the membership determination based on the precise Gaia astrometry and photometry. We applied an automated Bayesian tool, BASE-9, to fi

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Martynov, Vasilii, Irina Sazonova, Olga Vasilyeva, Ivan Grekov, and Natalia Sokolova. "Anthropogenic and natural factors shaping the boundaries of the St. Petersburg suburban area." Baltic Region 16, no. 2 (2024): 63–83. https://doi.org/10.5922/2079-8555-2024-2-4.

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The suburban area of St. Petersburg stands out as Russia’s most complex in terms of spatial structure, encompassing districts ranging from the suburban imperial residences of the 18th century to low-rise residential zones and modern multi-storey developments of the 21st century. This study concluded that extensive stretches of the administrative border between St. Petersburg and the Leningrad region divide homogeneous territories. Therefore, it makes little academic or practical sense to confine scholarly efforts solely to suburbs situated on one side of this border. The principal factor

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Vermeesch, Pieter. "Errorchrons and anchored isochrons in IsoplotR." Geochronology 6, no. 3 (2024): 397–407. http://dx.doi.org/10.5194/gchron-6-397-2024.

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Abstract. Isochrons are usually fitted by “York regression”, which uses a weighted least-squares approach that accounts for correlated uncertainties in both variables. Despite its tremendous popularity in modern geochronology, the York algorithm has two important limitations that reduce its utility in several applications. First, it does not provide a satisfactory mechanism to deal with so-called “errorchrons”, i.e. datasets that are overdispersed with respect to the analytical uncertainties. Second, York regression is not readily amenable to anchoring, in which either the slope or the interce

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Bell, Cameron P. M., Eric E. Mamajek, and Tim Naylor. "The Isochronal Age Scale of Young Moving Groups in the Solar Neighbourhood." Proceedings of the International Astronomical Union 10, S314 (2015): 41–48. http://dx.doi.org/10.1017/s1743921315006213.

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AbstractWe present a self-consistent, absolute isochronal age scale for young (≲ 200 Myr), nearby (≲ 100 pc) moving groups, which is consistent with recent lithium depletion boundary ages for both the β Pic and Tucana-Horologium moving groups. This age scale was derived using a set of semi-empirical pre-main-sequence model isochrones that incorporate an empirical colour-Teffrelation and bolometric corrections based on the observed colours of Pleiades members, with theoretical corrections for the dependence on logg. Absolute ages for young, nearby groups are vital as these regions play a crucia

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Artemiev, Dmitry, Robert Krymsky, Boris Belyatsky, and Dmitry Ashikhmin. "The age of mineralization of Mayskoe gold ore deposit (Central Chukotka): results of Re-Os isotopic dating." Journal of Mining Institute 243 (June 10, 2020): 266. http://dx.doi.org/10.31897/pmi.2020.3.266.

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The article presents the results of the sulfide mineralization dating of the Mayskoe gold ore deposit using the Re-Os isotope system and isochron age estimation method of the main sulfide minerals: arsenopyrite, pyrite, and antimonite. The complex multistage formation of the studied sulfides, as well as the close intergrowths of genetically different mineral phases, did not allow obtaining a single rhenium-osmium isochron corresponding to the formation time of sulfide mineralization. Isochrones for single minerals, collected from each sulfide sample, turned out to be the result of isotopically

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Ng, Felix, and Edward C. King. "Formation of RADARSAT backscatter feature and undulating firn stratigraphy at an ice-stream margin." Annals of Glaciology 54, no. 64 (2013): 90–96. http://dx.doi.org/10.3189/2013aog64a202.

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AbstractOn RADARSAT imagery, the southern margin of the onset zone of Bindschadler Ice Stream, West Antarctica, manifests a multi-banded feature, with brightness varying across the bands and oscillating along each band. Ground-based radar profiles across the margin reveal folds in the firn stratigraphy associated with this pattern and provide evidence for correlation between the depth of shallow isochrones and the RADARSAT backscatter intensity on each profile, allowing us to interpret the banded feature for firn-layer geometry in three dimensions. We use a kinematic model of isochrone depth e

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Kostecki, Robert. "Spatial database applications for network analysis: Case study of bicycle accessibility of forested areas in the Poznań Metropolitan Area, Poland." Reports on Geodesy and Geoinformatics 118, no. 1 (2024): 46–52. http://dx.doi.org/10.2478/rgg-2024-0014.

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Abstract The main aim of this paper is to introduce a solution for network analysis based on pgRouting to resolve the bicycle accessibility of forested green spaces. The proposed application uses open-source software tools such as PostgreSQL with PostGIS extension. The solution includes a complete description of how to perform network analysis using a spatial database with SQL and pgRouting. The implemented functionalities consist of solutions for finding the equidistance or isochrone area for any selected point location. The method is tested on case study data drawn from a total of 9,500 km o

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Stone-Martinez, Alexander, Jon A. Holtzman, Julie Imig, Christian Nitschelm, Keivan G. Stassun, and Joel R. Brownstein. "Spectroscopic Distance, Mass, and Age Estimations for APOGEE DR17." Astronomical Journal 167, no. 2 (2024): 73. http://dx.doi.org/10.3847/1538-3881/ad12a6.

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Abstract We derive distances and masses of stars from the Sloan Digital Sky Survey (SDSS) Apache Point Observatory Galactic Evolution Experiment Data Release 17 using simple neural networks. Training data for distances comes from Gaia EDR3, supplemented by literature distances for star clusters. For masses, the network is trained using asteroseismic masses for evolved stars and isochrone masses for main-sequence stars. The models are trained on effective temperature, surface gravity, metallicity, and carbon and nitrogen abundances. We found that our distance predictions have median fractional

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Badawy, W. A., A. L. Tadross, Y. H. M. Hendy, M. N. Ismail, and A. Mouner. "ASTROPHYSICAL STUDIES OF 9 UNSTUDIED OPEN STAR CLUSTERS USING GAIA DR3." Revista Mexicana de Astronomía y Astrofísica 59, no. 2 (2023): 155–69. http://dx.doi.org/10.22201/ia.01851101p.2023.59.02.01.

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Using the Gaia DR3 data sets, this work gives an analysis of nine open clusters: Dolidze 25, Kronberger 13, Kronberger 18, Majaess 99, NGC 7795, Ruprecht 139, Teutsch 55, S1, and FSR 0596, which are close to the Galactic plane of the Milky Way. The number of probable cluster members is found to be 81, 77, 120, 155, 108, 110, 160, and 116 respectively. Radii are determined as 5.40, 5.25, 4.80, 4.20, 4.28, 3.70, 4.30, 4.30, and 3.53 arcmin, respectively. With solar metallicity isochrones log ages of 7.70, 9.00, 8.35, 7.50, 9.00, 8.00, 7.50, 8.50, and 9.5 yr are determined for these clusters. The

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