Artykuły w czasopismach: „Numerical Ages”

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Geyh, Mebus A. "The handling of numerical ages and their random uncertainties". E&G Quaternary Science Journal 57, nr 1/2 (1.08.2008): 239–52. http://dx.doi.org/10.3285/eg.57.1-2.10.

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Abstract. The correct handling of numerical ages and their standard deviations and a proper introduction to error propagation or propagation of uncertainty and statistical evaluation are important to avoid misleading chronological conclusions and statements even though based on properly determined and reliable numerical dates. The conclusions may also be erroneous if dates were taken from databases without sufficient background information on the origin of the dated material and the applied analytical techniques. This paper is an introduction into the field of mathematical handling and testing of numerical ages. The most common and simple calculations and statistical tests that are needed are described and the steps involved are demonstrated on examples. The problems involved in the visualization of numerical dates in the form of normal histograms and dispersion histograms are discussed.

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Osborn, Gerald, Daniel McCarthy, Aline LaBrie i Randall Burke. "Lichenometric Dating: Science or Pseudo-Science?" Quaternary Research 83, nr 1 (styczeń 2015): 1–12. http://dx.doi.org/10.1016/j.yqres.2014.09.006.

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AbstractThe popular technique of estimating ages of deposits from sizes of lichens continues despite valid criticism, and without agreement on range of utility, treatment of error, and methods of measurement, sampling, and data handling. A major source of error is the assumption that the largest lichen(s) colonized soon after deposition and will survive indefinitely. Recent studies on lichen mortality suggest that this assumption is untenable. Meanwhile, the use of “growth curves” constructed from independently dated substrates is problematic for many reasons, but this has not prevented the publication of baseless claims of accuracy and ages that are extrapolated well beyond data. Experiments indicate that numeric lichenometric ages are not reliable, and in general do not advance the cause of Quaternary science. There are a few studies suggesting reliability, and indeed there may be cases where lichens and growth curves actually provide realistic numerical ages. But it cannot be foretold which lichen assemblages will provide good ages and which bad ages. The logical conclusion is that no assumption of good ages can be made, and that it is folly to assign numerical ages to a deposit on the basis of lichen sizes.

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Siegler, Robert S., i John E. Opfer. "The Development of Numerical Estimation". Psychological Science 14, nr 3 (maj 2003): 237–50. http://dx.doi.org/10.1111/1467-9280.02438.

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We examined children's and adults' numerical estimation and the representations that gave rise to their estimates. The results were inconsistent with two prominent models of numerical representation: the logarithmic-ruler model, which proposes that people of all ages possess a single, logarithmically spaced representation of numbers, and the accumulator model, which proposes that people of all ages represent numbers as linearly increasing magnitudes with scalar variability. Instead, the data indicated that individual children possess multiple numerical representations; that with increasing age and numerical experience, they rely on appropriate representations increasingly often; and that the numerical context influences their choice of representation. The results, obtained with second graders, fourth graders, sixth graders, and adults who performed two estimation tasks in two numerical contexts, strongly suggest that one cause of children's difficulties with estimation is reliance on logarithmic representations of numerical magnitudes in situations in which accurate estimation requires reliance on linear representations.

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Liu, Longlong, Zhaosheng Zhang, Zehua Huangfu i Dahai Huang. "Numerical analysis of concrete temperature stress at different loading ages". Journal of Physics: Conference Series 1732 (styczeń 2021): 012107. http://dx.doi.org/10.1088/1742-6596/1732/1/012107.

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Legendre, Serge, i Bernadette Bachelet. "The numerical ages: A new method of datation applied to Paleogene mammalian localities from Southern France". Newsletters on Stratigraphy 29, nr 3 (19.11.1993): 137–58. http://dx.doi.org/10.1127/nos/29/1993/137.

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Ali. "NUMERICAL PREDICTION MODEL FOR TEMPERATURE DISTRIBUTIONS IN CONCRETE AT EARLY AGES". American Journal of Engineering and Applied Sciences 5, nr 4 (1.04.2012): 282–90. http://dx.doi.org/10.3844/ajeassp.2012.282.290.

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Ali. "NUMERICAL PREDICTION MODEL FOR TEMPERATURE DISTRIBUTIONS IN CONCRETE AT EARLY AGES". American Journal of Engineering and Applied Sciences 7, nr 2 (1.02.2014): 255–65. http://dx.doi.org/10.3844/ajeassp.2014.255.265.

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Odin, G. S. "Concerning the numerical ages proposed for the Jurassic and Cretaceous geochronology". Geological Society, London, Memoirs 10, nr 1 (1985): 196–98. http://dx.doi.org/10.1144/gsl.mem.1985.010.01.16.

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van Breugel, K. "Numerical modelling of volume changes at early ages - Potential, pitfalls and challenges". Materials and Structures 34, nr 239 (27.04.2001): 293–301. http://dx.doi.org/10.1617/13759.

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Jin, Nanguo, Ye Tian i Xianyu Jin. "Numerical simulation of fracture and damage behaviour of concrete at different ages". Computers and Concrete 4, nr 3 (25.06.2007): 221–41. http://dx.doi.org/10.12989/cac.2007.4.3.221.

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van Breugel, K. "Numerical modelling of volume changes at early ages-Potential, pitfalls and challenges". Materials and Structures 34, nr 5 (czerwiec 2001): 293–301. http://dx.doi.org/10.1007/bf02482209.

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Nyland, Kelsey E., Frederick E. Nelson i Paula M. Figueiredo. "Cosmogenic 10Be and 36Cl geochronology of cryoplanation terraces in the Alaskan Yukon-Tanana Upland". Quaternary Research 97 (14.05.2020): 157–66. http://dx.doi.org/10.1017/qua.2020.25.

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ABSTRACTCryoplanation terraces are prominent but enigmatic landforms found in present and past periglacial environments. Geomorphologists have debated for more than a century over processes involved in the formation of these elevated, step-like, bedrock features. Presented here are the first numerical surface exposure ages and scarp retreat rates from cryoplanation terraces in the Yukon-Tanana Upland (YTU) in Alaska, part of unglaciated eastern Beringia, obtained from terrestrial cosmogenic nuclides (TCN) in surface boulders. Ages comprise six 10Be TCN ages from two terrace treads near Eagle Summit and six 36 Cl ages from two treads on Mt. Fairplay. Based on these exposure ages, scarps at both locations were last actively eroding from 49 to 22.4 ka. Both locations exhibit time-transgressive development, particularly near scarp-tread junctions. Boulder exposure ages and distances between sampled boulder locations were used to estimate scarp retreat rates of 0.11 to 0.56 cm/yr. These numerical exposure ages presented here demonstrate that the cryoplanation terraces in the YTU are diachronous surfaces actively eroding during multiple cold intervals. With these results, hypotheses for cryoplanation terrace formation are discussed and evaluated for the YTU, including those based on geologic structure, nivation, and the influence of permafrost.

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Zharov, V. E. "I.I. Smul’skii. New astronomical theory of the ice ages". Вестник Российской академии наук 89, nr 8 (13.08.2019): 878–79. http://dx.doi.org/10.31857/s0869-5873898878-879.

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Riga: Lap Lambert Academic Publishing, 2018. 132 Р. In this book, a new approach to the astronomical theory of climate change is considered, and problems of the orbital and rotational motion of the Earth are solved using the numerical method. The author of the monograph investigated the evolution of the earth’s axis and obtained the periods of its oscillations coinciding with observed oscillations. Calculations that covered 100,000 years showed a significant oscillation of the earth’s axis, which has led to fluctuations in insolation that can explain the changes in the paleoclimate.

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Buczek, Alexandra J., Austin J. W. Hendy, Melanie J. Hopkins i Jocelyn A. Sessa. "On the reconciliation of biostratigraphy and strontium isotope stratigraphy of three southern Californian Plio-Pleistocene formations". GSA Bulletin 133, nr 1-2 (6.05.2020): 100–114. http://dx.doi.org/10.1130/b35488.1.

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Abstract The San Diego Formation, Pico Formation, Careaga Sandstone, and Foxen Mudstone of southern California are thought to be late Pliocene to early Pleistocene; however, numerical ages have not been determined. Following assessment of diagenetic alteration via multiple methods including scanning electron microscopy (SEM), X-ray diffraction (XRD), and minor elemental concentrations, we attempted to use strontium isotope stratigraphy to assign numerical ages. Using aragonitic fossils, we obtained ages of 2.0–1.85 Ma for the Careaga Sandstone and 2.0–1.75 Ma for the uppermost Foxen Mudstone, consistent with biostratigraphic work suggesting a Gelasian age for the Careaga Sandstone. Isotope ratios for aragonitic and calcitic fossils from the Pico Formation were poorly constrained, with the exception of one bed yielding ages of 5.1–4.3 Ma. Isotope ratios from the San Diego Formation were also inconsistent within beds, with the exception of two isolated outcrops that yielded ages of 5.0–4.5 Ma and 4.5–2.8 Ma, respectively. The age estimates for the Pico and San Diego Formations are older than most ages inferred from biostratigraphy. Noting that some aragonitic specimens from the San Diego Formation yielded isotope ratios indicative of ages as old as 19.4 Ma, we propose that some outcrops have been affected by diagenesis caused by groundwater flow through proximal granitic rocks and input from detrital sediment. Although we recommend that strontium isotope results for the Pico and San Diego Formations be interpreted with caution, the ages of the uppermost Foxen Mudstone and Careaga Sandstone can be confidently placed within the early Pleistocene.

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Gadotti, Dimitri A., i Ronaldo E. de Souza. "On the Lengths, Colours and Ages of Bars". Proceedings of the International Astronomical Union 2, S235 (sierpień 2006): 98. http://dx.doi.org/10.1017/s1743921306005333.

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AbstractIn an effort to obtain further observational evidences for secular evolution processes in galaxies, as well as observational constraints to current theoretical models of secular evolution, we have used BVRI and Ks images of a sample of 18 barred galaxies to measure the lengths and colours of bars, create colour maps and estimate global colour gradients. In addition, applying a method we developed in a previous article, we could distinguish for 7 galaxies in our sample those whose bars have been recently formed from the ones with already evolved bars. We estimated an average difference in the optical colours between young and evolved bars that may be translated to an age difference of the order of 10 Gyr, meaning that bars may be long standing structures. Moreover, our results show that, on average, evolved bars are longer than young bars. This seems to indicate that, during its evolution, a bar grows longer by capturing stars from the disk, in agreement with recent numerical and analytical results.

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Ren, Zheng, Lian Zhen Xiao i Wen Chong Shi. "Experimental Study and Numerical Analysis on Chloride Diffusion Coefficient of Concrete with Various Water-Cement Ratios". Key Engineering Materials 726 (styczeń 2017): 547–52. http://dx.doi.org/10.4028/www.scientific.net/kem.726.547.

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A rapid chloride ion diffusion coefficient measurement (RCM) was used in this study. The influence of water-cement ratios of 0.30, 0.35 and 0.40 at various ages (3, 7, 14, 28 and 56 days) on chloride ion diffusion coefficient of the concretes and pastes was studied and analyzed. The results show that, with the increase of curing ages, the chloride ion diffusion coefficient of different water-cement ratio of each specimen is decreased. In the early age, the chloride ion diffusion coefficient of the paste with the water-cement ratio of 0.40 is 2~3 times of the paste with water-cement ratio of 0.30 and 0.35, and with the increase of curing age, this difference is gradually decreased. Additionally, the chloride ion diffusion coefficient of the cement paste is 1~2 times of the concrete with same water-cement ratio at different ages. Based on the actual experiment boundary conditions, the process of chloride ions diffusion and permeability was simulated by COMSOL software, and the simulation result was analyzed to predict the permeability of concrete.

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Luijendijk, Elco. "Beo v1.0: numerical model of heat flow and low-temperature thermochronology in hydrothermal systems". Geoscientific Model Development 12, nr 9 (20.09.2019): 4061–73. http://dx.doi.org/10.5194/gmd-12-4061-2019.

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Abstract. Low-temperature thermochronology can provide records of the thermal history of the upper crust and can be a valuable tool to quantify the history of hydrothermal systems. However, existing model codes of heat flow around hydrothermal systems do not include low-temperature thermochronometer age predictions. Here I present a new model code that simulates thermal history around hydrothermal systems on geological timescales. The modelled thermal histories are used to calculate apatite (U–Th)∕He (AHe) ages, which is a thermochronometer that is sensitive to temperatures up to 70 ∘C. The modelled AHe ages can be compared to measured values in surface outcrops or borehole samples to quantify the history of hydrothermal activity. Heat flux at the land surface is based on equations of latent and sensible heat flux, which allows more realistic land surface and spring temperatures than models that use simplified boundary conditions. Instead of simulating fully coupled fluid and heat flow, the code only simulates advective and conductive heat flow, with the rate of advective fluid flux specified by the user. This relatively simple setup is computationally efficient and allows running larger numbers of models to quantify model sensitivity and uncertainty. Example case studies demonstrate the sensitivity of hot spring temperatures to the depth, width and angle of permeable fault zones, and the effect of hydrothermal activity on AHe ages in surface outcrops and at depth.

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Colman, Steven M., Kenneth L. Pierce i Peter W. Birkeland. "Suggested Terminology for Quaternary Dating Methods". Quaternary Research 28, nr 2 (wrzesień 1987): 314–19. http://dx.doi.org/10.1016/0033-5894(87)90070-6.

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AbstractClassification of Quaternary dating methods should be based on the level of quantitative information and the degree of confidence contained in the age estimates produced by the dating methods. We recommend the use of the terms numerical-age, calibrated-age, relative-age, and correlated-age to describe these levels. We also classify dating methods by type into sideral, isotopic, radiogenic, chemical and biological, geomorphic, and correlation methods. The use of “absolute” is inappropriate for most dating methods, and should be replaced by “numerical.” The use of “date” should be minimized in favor of “age” or “age estimate.” We recommend use of the abbreviations ka and Ma for most ages; calender dates can be used where appropriate and yr B.P. can be used for radiocarbon ages.

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Park, Ki-Bong, Han-Seung Lee i Xiao-Yong Wang. "Prediction of Time-Dependent Chloride Diffusion Coefficients for Slag-Blended Concrete". Advances in Materials Science and Engineering 2017 (2017): 1–10. http://dx.doi.org/10.1155/2017/1901459.

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The chloride diffusion coefficient is considered to be a key factor for evaluating the service life of ground-granulated blast-furnace slag (GGBS) blended concrete. The chloride diffusion coefficient relates to both the concrete mixing proportions and curing ages. Due to the continuous hydration of the binders, the capillary porosity of the concrete decreases and the chloride diffusion coefficient also decreases over time. To date, the dependence of chloride diffusivity on the binder hydration and curing ages of slag-blended concrete has not been considered in detail. To fill this gap, this study presents a numerical procedure to predict time-dependent chloride diffusion coefficients for slag-blended concrete. First, by using a blended cement hydration model, the degree of the binder reaction for hardening concrete can be calculated. The effects of the water to binder ratios and slag replacement ratios on the degree of the binder reaction are considered. Second, by using the degree of the binder reaction, the capillary porosity of the binder paste at different curing ages can be determined. Third, by using the capillary porosity and aggregate volume, the chloride diffusion coefficients of concrete can be calculated. The proposed numerical procedure has been verified using the experimental results of concrete with different water to binder ratios, slag replacement ratios, and curing ages.

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Fabel, Derek, David Fink, Ola Fredin, Jon Harbor, Magnus Land i Arjen P. Stroeven. "Exposure ages from relict lateral moraines overridden by the Fennoscandian ice sheet". Quaternary Research 65, nr 1 (styczeń 2006): 136–46. http://dx.doi.org/10.1016/j.yqres.2005.06.006.

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AbstractLateral moraines constructed along west to east sloping outlet glaciers from mountain centred, pre-last glacial maximum (LGM) ice fields of limited extent remain largely preserved in the northern Swedish landscape despite overriding by continental ice sheets, most recently during the last glacial. From field evidence, including geomorphological relationships and a detailed weathering profile including a buried soil, we have identified seven such lateral moraines that were overridden by the expansion and growth of the Fennoscandian ice sheet. Cosmogenic 10Be and 26Al exposure ages of 19 boulders from the crests of these moraines, combined with the field evidence, are correlated to episodes of moraine stabilisation, Pleistocene surface weathering, and glacial overriding. The last deglaciation event dominates the exposure ages, with 10Be and 26Al data derived from 15 moraine boulders indicating regional deglaciation 9600 ± 200 yr ago. This is the most robust numerical age for the final deglaciation of the Fennoscandian ice sheet. The older apparent exposure ages of the remaining boulders (14,600–26,400 yr) can be explained by cosmogenic nuclide inheritance from previous exposure of the moraine crests during the last glacial cycle. Their potential exposure history, based on local glacial chronologies, indicates that the current moraine morphologies formed at the latest during marine oxygen isotope stage 5. Although numerous deglaciation ages were obtained, this study demonstrates that numerical ages need to be treated with caution and assessed in light of the geomorphological evidence indicating moraines are not necessarily formed by the event that dominates the cosmogenic nuclide data.

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Claoué-Long, J. C., P. J. Jones, J. Roberts i S. Maxwell. "The numerical age of the Devonian-Carboniferous boundary". Geological Magazine 129, nr 3 (maj 1992): 281–91. http://dx.doi.org/10.1017/s0016756800019221.

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AbstractThe SHRIMP ion microprobe has been used to date zircons in a 1 cm thick bentonite located in the Hasselbachtal auxiliary global stratotype section through the Devonian-Carboniferous boundary in Germany, and a tuff located at a similar biostratigraphic level in Australia. Multiple replicate analyses have yielded indistinguishable ages, and indicate 353.2±4.0 Ma (2σ) as the age of the boundary. Obtaining an age for the boundary in the German reference section depended on the ability of SHRIMP to date a small sample and to target small areas of structurally complex zircons. Future refinements of the age of this boundary may depend on re-analysis of this uniquely placed bentonite, and this highlights the value of defining biostratigraphic stratotypes in the vicinity of known dateable horizons.

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Lena, Luis, Rafael López-Martínez, Marina Lescano, Beatriz Aguire-Urreta, Andrea Concheyro, Verónica Vennari, Maximiliano Naipauer i in. "High-precision U–Pb ages in the early Tithonian to early Berriasian and implications for the numerical age of the Jurassic–Cretaceous boundary". Solid Earth 10, nr 1 (8.01.2019): 1–14. http://dx.doi.org/10.5194/se-10-1-2019.

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Abstract. The numerical age of the Jurassic–Cretaceous boundary has been controversial and difficult to determine. In this study, we present high-precision U–Pb geochronological data around the Jurassic–Cretaceous boundary in two distinct sections from different sedimentary basins: the Las Loicas, Neuquén Basin, Argentina, and the Mazatepec, Sierra Madre Oriental, Mexico. These two sections contain primary and secondary fossiliferous markers for the boundary as well as interbedded volcanic ash horizons, allowing researchers to obtain new radioisotopic dates in the late Tithonian and early Berriasian. We also present the first age determinations in the early Tithonian and tentatively propose a minimum duration for the stage as a cross-check for our ages in the early Berriasian. Given our radioisotopic ages in the early Tithonian to early Berriasian, we discuss implications for the numerical age of the boundary.

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AGUIRRE-URRETA, BEATRIZ, MARINA LESCANO, MARK D. SCHMITZ, MAISA TUNIK, ANDREA CONCHEYRO, PETER F. RAWSON i VICTOR A. RAMOS. "Filling the gap: new precise Early Cretaceous radioisotopic ages from the Andes". Geological Magazine 152, nr 3 (26.01.2015): 557–64. http://dx.doi.org/10.1017/s001675681400082x.

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AbstractTwo tuffs in the Lower Cretaceous Agrio Formation, Neuquén Basin, provided U–Pb zircon radioisotopic ages of 129.09±0.16 Ma and 127.42±0.15 Ma. Both horizons are well constrained biostratigraphically by ammonites and nannofossils and can be correlated with the ‘standard’ sequence of the Mediterranean Province. The lower horizon is very close to the base of the Upper Hauterivian and the upper horizon to the Hauterivian/Barremian boundary, indicating that the former lies atc. 129.5 Ma and the latter atc. 127 Ma. These new radioisotopic ages fill a gap of over 8 million years in the numerical calibration of the current global Early Cretaceous geological time scale.

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Lacarriere, Laurie, Alain Sellier, Pierre Souyris, Batian Kolani i Ponleu Chhun. "Numerical prediction of cracking risk of reinforced concrete structures at early age". RILEM Technical Letters 5 (24.09.2020): 41–55. http://dx.doi.org/10.21809/rilemtechlett.2020.106.

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The paper presents a summary of the work concerning the prediction of cracking risk in reinforced concrete structures at early age that has been carried out by our team at the LMDC laboratory during the last ten years. It focuses on the principles that must be taken into account in numerical simulations (evolution of characteristics, behaviour law, numerical implementation, effect of reinforcement, etc.) in order to be able to predict the cracking pattern caused in structures by the thermal loading induced by hydration at early ages

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Kasuya, Masao. "Fission-Track Ages of Tuff Layers Related to the Pliocene-Pleistocene Boundary on the Boso Peninsula, Japan". Quaternary Research 33, nr 1 (styczeń 1990): 86–93. http://dx.doi.org/10.1016/0033-5894(90)90086-z.

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AbstractFission-track ages of zircon crystals from four tuff layers in the late Cenozoic sediment sequence of the Boso Peninsula,.Japan, are 1.6 ± 0.2 myr (the Kurotaki Formation), 5.5 ± 0.6 and 5.2 ± 0.5 myr (the uppermost part of the Amatsu Formation), and 11.5 ± 0.8 myr (the middle part of the Amatsu Formation). These ages provide numerical age constraints on magneto-biostratigraphy. The normal polarity interval in the lower part of the Kiwada Formation corresponds to the Olduvai polarity subzone. The boundary between the Pliocene and Pleistocene lies slightly above the Olduvai polarity subzone.

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Cheung, Pierina, i Mathieu Le Corre. "Parallel individuation supports numerical comparisons in preschoolers". Journal of Numerical Cognition 4, nr 2 (7.09.2018): 380–409. http://dx.doi.org/10.5964/jnc.v4i2.110.

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While the approximate number system (ANS) has been shown to represent relations between numerosities starting in infancy, little is known about whether parallel individuation – a system dedicated to representing objects in small collections – can also be used to represent numerical relations between collections. To test this, we asked preschoolers between the ages of 2 ½ and 4 ½ to compare two arrays of figures that either included exclusively small numerosities (< 4) or exclusively large numerosities (> 4). The ratios of the comparisons were the same in both small and large numerosity conditions. Experiment 1 used a between-subject design, with different groups of preschoolers comparing small and large numerosities, and found that small numerosities are easier to compare than large ones. Experiment 2 replicated this finding with a wider range of set sizes. Experiment 3 further replicated the small-large difference in a within-subject design. We also report tentative evidence that non- and 1-knowers perform better on comparing small numerosities than large numerosities. These results suggest that preschoolers can use parallel individuation to compare numerosities, possibly prior to the onset of number word learning, and thus support previous proposals that there are numerical operations defined over parallel individuation (e.g., Feigenson & Carey, 2003; https://doi.org/10.1111/1467-7687.00313).

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Gómez-Velázquez, Fabiola R., Andrés A. González-Garrido, Ricardo A. Salido-Ruiz, Sulema Torres-Ramos, Aurora Espinoza-Valdez, Israel Román-Godínez i Erwin R. Villuendas-González. "Numerical Comparisons and Sex-Related Brain Connectivity". International Journal of Psychological Studies 13, nr 2 (20.05.2021): 62. http://dx.doi.org/10.5539/ijps.v13n2p62.

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Despite the recent literature on sex-related anatomic, maturational and functional brain differences, the study of significant individual developments in math learning and achievement has scarcely approached this perspective. We aimed to compare the influence of sex in functional brain connectivity and behavioral measures in a numerical comparison task. Therefore, a group of school children with ages from 8 to 11 years old was evaluated during a number comparison task. Even though the behavioral performance was similar across the sexes, males distinctly showed a significant correlation between their math WRAT-4 scores and the number of correct responses in the experimental task and working memory scores. Besides, the analysis of the concurrent EEG during task performance showed that males comparatively had a greater brain left intra-hemispheric connectivity, as well as greater interhemispheric connectivity, particularly in Theta and Alpha bands during task performing -as compared to resting-. In contrast, females showed a significantly different decrement of brain connectivity in the Alpha band from resting to task performing. Present results are interpreted as probably reflecting sex-related maturational dissimilarities in neurodevelopment, along with the progressive development of more efficient cognitive strategies, processes running not necessarily parallel in both sexes. 

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Francis, Julie E., Lawrence L. Loendorf i Ronald I. Dorn. "AMS Radiocarbon and Cation-Ratio Dating of Rock Art in the Bighorn Basin of Wyoming and Montana". American Antiquity 58, nr 4 (październik 1993): 711–37. http://dx.doi.org/10.2307/282204.

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Samples of organic matter and rock varnish from seven rock-art sites in the Bighorn Basin of Wyoming and Montana were collected for dating purposes. Petroglyphs sampled include Dinwoody-style figures, shield-bearing warriors, and other well-known Plains rock-art motifs. Accelerator mass spectrometry (AMS) dating of 10 petroglyphs yielded dates from the Early Archaic to the Protohistoric periods. A strong numerical relation between varnish leaching and time was found for petroglyphs older than 1,000 years, permitting the derivation of a cation-leaching curve (CLC) and calibrated cation-ratio (CR) ages for 15 different petroglyphs. No clear numerical relation between varnish leaching and time was found for petroglyphs less than 1,000 years old, possibly due to historical damage or past environmental conditions. As a result, calibrated CR ages could not be derived for six petroglyphs, and they are considered to be only younger than 1,000 years. Although further research is needed to establish whether one CLC can be used for all petroglyphs in the region, these studies constitute the first numerical chronology for rock art in the Bighorn area. Results indicate the occurrence of spatially discrete, but temporally concurrent styles in the Bighorn Basin during the last 800-900 years.

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Schweinsberg, Avriel D., Jason P. Briner, Joseph M. Licciardi, Ralph R. Shroba i Eric M. Leonard. "Cosmogenic 10Be exposure dating of Bull Lake and Pinedale moraine sequences in the upper Arkansas River valley, Colorado Rocky Mountains, USA". Quaternary Research 97 (27.04.2020): 125–39. http://dx.doi.org/10.1017/qua.2020.21.

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AbstractMany formerly glaciated valleys in the western United States preserve detailed glacial features that span the penultimate glaciation through the last deglaciation; however, numerical age control is limited in many of these systems. We report 35 new cosmogenic 10Be surface exposure ages of moraine boulders in the Sawatch Range, Colorado. Eight ages suggest Bull Lake moraines in Lake Creek (range: 132–120 ka, n = 4) and Clear Creek (range: 187–133 ka, n = 4) valleys may correlate with Marine Isotope Stage 6. In Lake Creek valley, 22 10Be ages from Pinedale end moraines average 20.6 ± 0.6 ka, and 5 10Be ages from a recessional moraine average 15.6 ± 0.7 ka, indicating that glaciers occupied two extended positions at ~21–20 and ~16 ka. The glacial extent dated to ~16 ka was nearly as great as that of the earlier glacial phase, suggesting that climate conditions in the Colorado Rocky Mountains at this time were similar to those of the last glacial maximum. Combining these moraine ages with seven previously published 10Be ages from cirque and valley-bottom bedrock reveals that the Lake Creek paleoglacier lost 82% of its full glacial length in ~1.5 ka and was completely deglaciated by ~14 ka.

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Yang, Zixuan, Bing-Qing Deng i Lian Shen. "Direct numerical simulation of wind turbulence over breaking waves". Journal of Fluid Mechanics 850 (4.07.2018): 120–55. http://dx.doi.org/10.1017/jfm.2018.466.

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We study wind turbulence over breaking waves based on direct numerical simulation (DNS) of two-fluid flows. In the DNS, the air and water are simulated as a coherent system, with the interface captured using the coupled level-set and volume-of-fluid method. Because the wave breaking is an unsteady process, we use ensemble averaging over 100 runs to define turbulence statistics. We focus on analysing the turbulence statistics of the airflow over breaking waves. The effects of wave age and wave steepness are investigated. It is found that before wave breaking, the turbulence statistics are largely influenced by the wave age. The vertical gradient of mean streamwise velocity is positive at small and intermediate wave ages, but it becomes negative near the wave surface at large wave age as the pressure force changes from drag to thrust. Furthermore, wave-coherent motions make increasingly important contributions to the momentum flux and kinetic energy of velocity fluctuations (KE-F) as the wave age increases. During the wave breaking process, spilling breakers do not influence the wind field significantly; in contrast, plunging breakers alter the structures of wind turbulence near the wave surface drastically. It is observed from the DNS results that during wave plunging, a high pressure region occurs ahead of the wave front, which further accelerates the wind in the downstream direction. Meanwhile, a large spanwise vortex is generated, which greatly disturbs the airflow around it, resulting in large magnitudes of Reynolds stress and turbulence kinetic energy (TKE) below the wave crest. Above the crest, the magnitude of KE-F is enhanced during wave plunging at small and large wave ages, but at intermediate wave age, the transient enhancement of KE-F is absent. The effect of wave breaking on the magnitude of KE-F is further investigated through the analysis of the KE-F production. It is discovered that at small wave age, the transient enhancement of KE-F is caused by the appearance of a local maximum in the profile of total momentum flux; but at large wave age, it results from the change in the sign of the KE-F production from negative to positive, due to the sign change in the wave-coherent momentum flux. At intermediate wave age, neither of these two processes is present, and the transient growth of KE-F does not take place.

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ZHANG, Xiaofei, Xin ZHANG, Tao YAN, Yu HUANG, Qian LIU i Xiaoping WANG. "Experimental analysis and numerical calculation on equivalent strength of induced joints of different ages and weakening degrees". Journal of the Ceramic Society of Japan 127, nr 9 (1.09.2019): 642–50. http://dx.doi.org/10.2109/jcersj2.18196.

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BUKRY, DAVID. "Numerical ages of Cenozoic biostratigraphic datum levels: Results of South Atlantic Leg 73 drilling: Discussion and reply". Geological Society of America Bulletin 96, nr 6 (1985): 813. http://dx.doi.org/10.1130/0016-7606(1985)96<813:naocbd>2.0.co;2.

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HSÜ, KENNETH J. "Numerical ages of Cenozoic biostratigraphic datum levels: Results of South Atlantic Leg 73 drilling: Discussion and reply". Geological Society of America Bulletin 96, nr 6 (1985): 814. http://dx.doi.org/10.1130/0016-7606(1985)96<814:naocbd>2.0.co;2.

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COMPSTON, W., M. S. SAMBRIDGE, R. F. REINFRANK, M. MOCZYDEOWSKA, G. VIDAL i S. CLAESSON. "Numerical ages of volcanic rocks and the earliest fauna1 zone within the Late Precambrian of east Poland". Journal of the Geological Society 152, nr 4 (lipiec 1995): 599–611. http://dx.doi.org/10.1144/gsjgs.152.4.0599.

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Balco, Greg, John O. H. Stone i Joseph A. Mason. "Numerical ages for Plio-Pleistocene glacial sediment sequences by 26Al/10Be dating of quartz in buried paleosols". Earth and Planetary Science Letters 232, nr 1-2 (marzec 2005): 179–91. http://dx.doi.org/10.1016/j.epsl.2004.12.013.

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McDougall, I., i R. T. Watkins. "Potassium–argon ages of volcanic rocks from northeast of Lake Turkana, northern Kenya". Geological Magazine 125, nr 1 (styczeń 1988): 15–23. http://dx.doi.org/10.1017/s001675680000933x.

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AbstractThe Asille Group, a 1500 m succession comprising dominantly basaltic lavas but with interbedded sediments and silicic volcanics, lies unconformably upon metamorphosed basement northeast of Lake Turkana. Concordant K–Ar ages on alkali feldspars from pantelleritic units in the succession show that the Langaria Formation erupted 26.9±0.3 Ma ago in late Oligocene time, that Gum Dura Formation volcanism occurred at 15.8±0.2 Ma (early Miocene), and that there was widespread middle Miocene silicic volcanism at 13.0±0.3 Ma. Younger basaltic volcanism producing the flood lavas of the Gombe Group commenced at least 6.16±0.09 Ma ago in late Miocene time. These results, based upon 20 K–Ar age determinations, provide good numerical age control for much of the sequence developed within a little known sector of the Eastern Rift of Africa between the Ethiopian and Kenyan domes.

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Compston, W. "Interpretations of SHRIMP and isotope dilution zircon ages for the geological time-scale: I. The early Ordovician and late Cambrian". Mineralogical Magazine 64, nr 1 (luty 2000): 43–57. http://dx.doi.org/10.1180/002646100549120.

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AbstractIon probe data for zircons from tuffs within the Llfynant flags (Arenig) and the Serw Formation (lower Llanvirn) of north Wales have been revised using better statistical methods for separating detrital ages, making allowance for recently-found variability in radiogenic 206Pb/238U in the reference zircon SL13, and testing the sensitivity of the ages to the secondary ion discrimination slope. The revised ages are options of 469.2 ± 2.1 (σ) or 472.9 ± 2.9 Ma for the Llfynant flags dependent on mixture modelling, and 465.3 ± 1.4 Ma for the Serw Formation. All ages are within error of previous SHRIMP results and the Serw age now has the same numerical value as a previous MSID age for the same sample. It is shown that an MSID age of 483 ± 0.5 Ma with interpreted Pb loss for a late Tremadoc bentonite is dependent on the correction for common Pb, and that a slightly more radiogenic choice for the common Pb composition places nearly all data on Concordia. The latter would indicate that the bentonite might contain two zircon populations: inherited grains at 482 Ma and tuff magmatic grains at 473 Ma, which is more compatible with the SHRIMP Arenig result. Interpretations of other MSID zircon ages from the Ordovician are also sensitive to choice of common Pb, and raise the likelihood that many multigrain ages might be too old owing to admixture with slightly older inherited zircon. A supposed 1–2% technical bias of SHRIMP 206Pb/238U ages relative to MSID is refuted.

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Yang, Di, i Lian Shen. "Direct numerical simulation of scalar transport in turbulent flows over progressive surface waves". Journal of Fluid Mechanics 819 (18.04.2017): 58–103. http://dx.doi.org/10.1017/jfm.2017.164.

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The transport of passive scalars in turbulent flows over progressive water waves is studied using direct numerical simulation. A combined pseudo-spectral and finite-difference scheme on a wave-surface-fitted grid is used to simulate the flow and scalar fields above the wave surface. Three representative wave ages (i.e. wave-to-wind speed ratios) are considered, corresponding to slow, intermediate and fast wind-waves, respectively. For each wave condition, four Schmidt numbers are considered for the scalar transport. The presence of progressive surface waves is found to induce significant wave-phase-correlated variation to the scalar field, with the phase dependence varying with the wave age. The time- and plane-averaged profiles of the scalar over waves of various ages exhibit similar vertical structures as those found in turbulence over a flat wall, but with the von Kármán constant and effective wave surface roughness for the mean scalar profile exhibiting considerable variation with the wave age. The profiles of the root-mean-square scalar fluctuations and the horizontal scalar flux exhibit good scaling in the viscous sublayer that agrees with the scaling laws previously reported for flat-wall turbulence, but with noticeable wave-induced variation in the viscous wall region. The profiles of the vertical scalar flux in the viscous sublayer exhibit apparent discrepancies from the reported scaling law for flat-wall turbulence, due to a negative vertical flux region above the windward face of the wave crest. Direct observation and quadrant-based conditional averages indicate that the wave-dependent distributions of the scalar fluctuations and fluxes are highly correlated with the coherent vortical structures in the turbulence, which exhibit clear wave-dependent characteristics in terms of both shape and preferential location.

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Kobayashi, Lindsay C., i Justin Michael Feldman. "Employment trajectories in midlife and cognitive performance in later life: longitudinal study of older American men and women". Journal of Epidemiology and Community Health 73, nr 3 (23.11.2018): 232–38. http://dx.doi.org/10.1136/jech-2018-211153.

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BackgroundAlthough being employed during midlife is positively associated with cognitive function in later life, little is known with respect to cumulative trajectories or durations of time spent in different kinds of work.MethodsWe investigated the relationships between employment trajectory from ages 31 years to 50 years and cognitive skills at ages 50–78 years among 2521 adults in the US Panel Study of Income Dynamics from 1968 to 2016. Sequence analysis was used to identify prototypical employment trajectories, capturing employment status and high versus lower job skill level at each year of age from 31 years to 50 years. Adjusted and weighted logistic regression was used to estimate relationships between employment trajectory and performance on each of four cognitive tests representing numerical reasoning, verbal reasoning, health literacy and financial literacy. Dose–response relationships between the duration of high-skill employment and cognitive skills were examined.ResultsSeven prototypical employment trajectories were identified, the most common being consistently lower skill employment (44%; 1105/2521). Consistently high-skill and fluctuating skill trajectories were associated with high numerical reasoning scores (OR=1.54, 95% CI 0.99 to 2.40; OR=2.52, 95% CI 1.39 to 4.58, respectively), compared with consistently lower skill employment. There was a dose–response relationship between duration of high-skill employment and numerical reasoning (OR=1.17; 95% CI 1.06 to 1.28), plateauing after approximately 4 years of high-skill employment.ConclusionsSequence analysis of exposure trajectories is a novel method for life course epidemiology that accounts for exposure timing, duration and ordering. Our results using this method indicate that the duration may be more important than the timing of high-skill midlife employment for later-life numerical reasoning skills.

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Rahimzadeh, Neda, Tobias Sprafke, Christine Thiel, Birgit Terhorst i Manfred Frechen. "A comparison of polymineral and K-feldspar post-infrared infrared stimulated luminescence ages of loess from Franconia, southern Germany". E&G Quaternary Science Journal 70, nr 1 (8.02.2021): 53–71. http://dx.doi.org/10.5194/egqsj-70-53-2021.

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Abstract. Loess-paleosol sequences (LPSs) are essential records for reconstructing Quaternary paleoenvironments. No previous study has provided numerical chronologies of loess in Lower Franconia, southern Germany; their chronostratigraphic assumptions have relied mainly on German (pedo)stratigraphic schemes. In this study, we provide for the first time a chronology for LPSs in Lower Franconia based on optically stimulated luminescence (OSL) dating using quartz and a comparison of K-feldspar (63–100 µm) and the polymineral fraction (4–11 µm). Our results show that all obtained ages are in stratigraphic order, ranging from Holocene to late Pleistocene, and in general confirm the former stratigraphical interpretations. A good agreement of the obtained ages is observed between both feldspar grain size fractions; they also agree well with the quartz OSL ages up to ∼50 ka. However, a marked difference between the growth pattern of the dose response curves and consequently different saturation characteristics of fine and coarse grains is found. Even though in our samples the discrepancy in ages is not very significant, we suggest the use of coarse-grained K-feldspar whenever possible in order to not be confronted with unknowns such as the mineral composition of the polymineral fraction.

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Chen, Wei, Yuan Li, Peiliang Shen i Zhonghe Shui. "Microstructural Development of Hydrating Portland Cement Paste at Early Ages Investigated with Non-destructive Methods and Numerical Simulation". Journal of Nondestructive Evaluation 32, nr 3 (2.03.2013): 228–37. http://dx.doi.org/10.1007/s10921-013-0175-y.

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Rinat, Yair, Ari Matmon, Maurice Arnold, Georges Aumaître, Didier Bourlès, Karim Keddadouche, Naomi Porat, Efrat Morin i Robert C. Finkel. "Holocene rockfalls in the southern Negev Desert, Israel and their relation to Dead Sea fault earthquakes". Quaternary Research 81, nr 2 (marzec 2014): 260–73. http://dx.doi.org/10.1016/j.yqres.2013.12.008.

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AbstractRockfall ages in tectonically active regions provide information regarding frequency and magnitude of earthquakes. In the hyper-arid environment of the Dead Sea fault (DSF), southern Israel, rockfalls are most probably triggered by earthquakes. We dated rockfalls along the western margin of the DSF using terrestrial cosmogenic nuclides (TCN). At each rockfall site, samples were collected from simultaneously exposed conjugate boulders and cliff surfaces. Such conjugate samples initially had identical pre-fall (“inherited”) TCN concentrations. After boulder detachment, these surfaces were dosed by different production rates due to differences in post-fall shielding and geometry. However, in our study area, pre-rockfall inheritance and post-rockfall production rates of TCN cannot be evaluated. Therefore, we developed a numerical approach and demonstrated a way to overcome the above-mentioned problems. This approach can be applied in other settings where rockfalls cannot be dated by simple exposure dating. Results suggest rockfall ages between 3.6 ± 0.8 and 4.7 ± 0.7 ka. OSL ages of sediment accumulated behind the boulders range between 0.6 ± 0.1 and 3.4 ± 1.4 ka and support the TCN results. Our ages agree with dated earthquakes determined in paleoseismic studies along the entire length of the DSF and support the observation of intensive earthquake activity around 4–5 ka.

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Bremigan, Elizabeth George. "Activities for Students: Designing the Dynamic Domino Race". Mathematics Teacher 95, nr 7 (październik 2002): 502–8. http://dx.doi.org/10.5951/mt.95.7.0502.

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Students of all ages are enthusiastic about the Olympic Games. Many mathematics teachers use this context as an opportunity for students to examine numerical data while they display and discuss the results of different events and the success of various countries during the Olympic Games. These discussions allow teachers to address several aspects of the Data Analysis and Probability Standard from Principles and Standards for School Mathematics (NCTM 2000).

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Bremigan, Elizabeth George. "Activities for Students: Designing the Dynamic Domino Race". Mathematics Teacher 95, nr 7 (październik 2002): 502–8. http://dx.doi.org/10.5951/mt.95.7.0502.

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Students of all ages are enthusiastic about the Olympic Games. Many mathematics teachers use this context as an opportunity for students to examine numerical data while they display and discuss the results of different events and the success of various countries during the Olympic Games. These discussions allow teachers to address several aspects of the Data Analysis and Probability Standard from Principles and Standards for School Mathematics (NCTM 2000).

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Clauer, Norbert. "How Can Technical Aspects Help Improving K-Ar Isotopic Data of Illite-Rich Clay Materials into Meaningful Ages? The Case of the Dominique Peter Uranium Deposit (Saskatchewan, Canada)". Geosciences 10, nr 8 (27.07.2020): 285. http://dx.doi.org/10.3390/geosciences10080285.

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Previously published K-Ar dating results of <2 μm illite separates from uranium-hosting and associated barren rocks from Dominique Peter district of the Carswell circular structure in the Athabasca Basin (Canada) were considered to trace four distinct tectonic-thermal events at 1447 ± 45, 1282 ± 40 and 1184 ± 15 (all errors at ± 2 Ma, with a younger, less constrained episode at ~900 Ma. Recent analyses of K-Ar ages of additional <0.2 μm illite fractions from a few initial samples demonstrate that the intermediate ages at ~1280 and ~1185 Ma result, in fact, from mixing of two generations of illite that precipitated at ~1450 and ~900 Ma. They have, therefore, no stratigraphic value, while the two tectonic-thermal episodes at 1448 ± 48 and 937 ± 39 Ma appear to be historically sound. In fact, the analytical procedure of isotopic dating clay materials is of more importance than is often stated. For instance, a safe way to evaluate and constrain best numerical isotopic data of clay separates into ages is combining data of two size splits from several samples. If such age data, especially from size fractions of indurated host rocks, are scattered and point towards the higher data of the coarser fractions, they are potentially enriched in earlier crystallized K-rich components, and should consequently be discarded. The occurrence of detrital or early-crystallized components in clay-rich separates becomes a serious concern when comparing ages generated by various isotopic methods on mineral separates of various whole rocks. It is especially verified in very old, metal-rich deposits such as the uranium-rich deposits of the Saskatchewan Basin. These deposits and their host rocks were studied extensively by a large spectrum of isotopic methods on many types of rocks in a widely dispersed area, and for which the numerical statistics became, sometimes, more central in the interpretation than the specificity of the successive events in the host rocks.

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Steuber, Thomas, i Malte Schlüter. "Strontium-isotope stratigraphy of Upper Cretaceous rudist bivalves: Biozones, evolutionary patterns and sea-level change calibrated to numerical ages". Earth-Science Reviews 114, nr 1-2 (sierpień 2012): 42–60. http://dx.doi.org/10.1016/j.earscirev.2012.04.004.

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Wyrzykowski, Mateusz, Julien Sanahuja, Laurent Charpin, Markus Königsberger, Christian Hellmich, Bernhard Pichler, Luca Valentini i in. "Numerical benchmark campaign of COST Action TU1404 – microstructural modelling". RILEM Technical Letters 2 (30.12.2017): 99–107. http://dx.doi.org/10.21809/rilemtechlett.2017.44.

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This paper presents the results of the numerical benchmark campaign on modelling of hydration and microstructure development of cementitious materials. This numerical benchmark was performed in the scope of COST Action TU1404 “Towards the next generation of standards for service life of cement-based materials and structures”. Seven modelling groups took part in the campaign applying different models for prediction of mechanical properties (elastic moduli or compressive strength) in cement pastes and mortars. The simulations were based on published experimental data. The experimental data (both input and results used for validation) were open to the participants. The purpose of the benchmark campaign was to identify the needs of different models in terms of input experimental data, verify predictive potential of the models and finally to provide reference cases for new models in the future. The results of the benchmark show that a relatively high scatter in the predictions can arise between different models, in particular at early ages (e.g. elastic Young’s modulus predicted at 1 d in the range 6-20 GPa), while it reduces at later age, providing relatively good agreement with experimental data. Even though the input data was based on a single experimental dataset, the large differences between the results of the different models were found to be caused by distinct assumed properties for the individual phases at the microstructural level, mainly because of the scatter in the nanoindentation-derived properties of the C-S-H phase.

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Nordström, B., J. Andersen i J. Holmberg. "Evolution of the Galactic Disk from a Local Sample". Proceedings of the International Astronomical Union 2, S235 (sierpień 2006): 126. http://dx.doi.org/10.1017/s1743921306005588.

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AbstractThe Geneva-Copenhagen Survey (Nordström et al., 2004) gives ages, metallicities, velocities, and Galactic orbits for a complete, magnitude-limited sample of 14,000 F and G dwarfs. We have verified the calibrations used in the GCS, improved those of Teff, [Fe/H], distance, and age from uvby β, and checked the effect on the resulting Galactic relations by end- to-end numerical simulations. All the main results of the GCS remain unchanged.

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Ali, Wondwosen, i Girum Urgessa. "Computational Model for Internal Relative Humidity Distributions in Concrete". Journal of Computational Engineering 2014 (9.03.2014): 1–7. http://dx.doi.org/10.1155/2014/539850.

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A computational model is developed for predicting nonuniform internal relative humidity distribution in concrete. Internal relative humidity distribution is known to have a direct effect on the nonuniform drying shrinkage strains. These nonuniform drying shrinkage strains result in the buildup of internal stresses, which may lead to cracking of concrete. This may be particularly true at early ages of concrete since the concrete is relatively weak while the difference in internal relative humidity is probably high. The results obtained from this model can be used by structural and construction engineers to predict critical drying shrinkage stresses induced due to differential internal humidity distribution. The model uses finite elment-finite difference numerical methods. The finite element is used to space discretization while the finite difference is used to obtain transient solutions of the model. The numerical formulations are then programmed in Matlab. The numerical results were compared with experimental results found in the literature and demonstrated very good agreement.

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Colman, Steven M., i Kenneth L. Pierce. "Glacial Sequence Near McCall, Idaho: Weathering Rinds, Soil Development, Morphology, and Other Relative-Age Criteria". Quaternary Research 25, nr 1 (styczeń 1986): 25–42. http://dx.doi.org/10.1016/0033-5894(86)90041-4.

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The sequence of glacial deposits near McCall, Idaho, previously assigned to the Pinedale and Bull Lake glaciations, contains deposits of four different ages. These ages are defined by multiple relative-age criteria, including weathering rinds, soil development, surface-rock weathering, morainal morphology, and loess stratigraphy. The thickness of weathering rinds on basaltic clasts is statistically representative and reproducible and can be used to estimate numerical ages. Following in order of decreasing relation to age are soil development, surface-rock weathering, and moraine morphology. The glacial deposits near McCall appear to correspond to times of high worldwide ice volume indicated by the marine oxygen-isotope record. Pilgrim Cove and McCall deposits, both assigned to the Pinedale glaciation, are late Wisconsin in age, perhaps 14,000 and 20,000 years, respectively. They represent a rare case in which deposits of Pinedale age can be separated by relative-age data. Timber Ridge deposits, assigned to the Bull Lake glaciation, have subdued, but well-preserved morainal morphology; relative-age data indicate that they are pre-Wisconsin in age, probably about 140,000–150,000 years old, although we cannot exclude an older age. Williams Creek deposits are clearly distinct from, and intermediate in age between, McCall and Timber Ridge deposits. Weathering rinds and the inferred ages of the other deposits suggest an early Wisconsin age for Williams Creek deposits.

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