210,989 research outputs found
SHCal13 Southern Hemisphere calibration, 0–50,000 years cal BP
No full textThe Southern Hemisphere SHCal04 radiocarbon calibration curve has been updated with the addition of new data sets extending measurements to 2145 cal BP and including the ANSTO Younger Dryas Huon pine data set. Outside the range of measured data, the curve is based upon the Northern Hemisphere data sets as presented in IntCal13, with an interhemispheric offset averaging 43 ± 23 yr modeled by an autoregressive process to represent the short-term correlations in the offset
CAL evaluation: Future directions
No full textFormal, experimental methods have proved increasingly difficult to implement, and lack the capacity to generate detailed results when evaluating the impact of CAL on teaching and learning. The rigid nature of experimental design restricts the scope of investigations and the conditions in which studies can be conducted It has also consistently failed to account for all influences on learning. In innovative CAL environments, practical and theoretical development depends on the ability fully to investigate the wide range of such influences. Over the past five years, a customizable evaluation framework has been developed specifically for CAL research. The conceptual approach is defined as Situated Evaluation of CAL (SECAL), and the primary focus is on quality of learning outcomes. Two important principles underpin this development. First, the widely accepted need to evaluate in authentic contexts includes examination of the combined effects of CAL with other resources and influential aspects of the learning environment. Secondly, evaluation design is based on a critical approach and qualitative, case‐based research. Positive outcomes from applications of SECAL include the easy satisfaction of practical and situation‐specific requirements and the relatively low cost of evaluation studies. Although there is little scope to produce generalizable results in the short term, the difficulty of doing so in experimental studies suggests that this objective is difficult to achieve in educational research. A more realistic, longer‐term aim is the development of grounded theory based on common findings from individual cases
IntCal04 terrestrial radiocarbon age calibration, 0-26 cal kyr BP
No full textA new calibration curve for the conversion of radiocarbon ages to calibrated (cal) ages has been constructed and internationally ratified to replace ImCal98, which extended from 0-24 cal kyr BP (Before Present, 0 cal BP = AD 1950). The new calibration data set for terrestrial samples extends from 0-26 cal kyr BP, but with much higher resolution beyond 11.4 cal kyr BP than ImCal98. Dendrochronologically-dated tree-ring samples cover the period from 0-12.4 cal kyr BP. Beyond the end of the tree rings, data from marine records (corals and foraminifera) are converted to the atmospheric equivalent with a site-specific marine reservoir correction to provide terrestrial calibration from 12.4-26.0 cal kyr BP. A substantial enhancement relative to ImCal98 is the introduction of a coherent statistical approach based on a random walk model, which takes into account the uncertainty in both the calendar age and the C-14 age to calculate the underlying calibration curve (Buck and Blackwell, this issue). The tree-ring data sets, sources of uncertainty, and regional offsets are discussed here. The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine 04) are discussed in brief, but details are presented in Hughen et al. (this issue a). We do not make a recommendation for calibration beyond 26 cal kyr BP at this time; however, potential calibration data sets are compared in another paper (van der Plicht et al., this issue)
Effective CAL: Theory and practice
No full textThis paper looks at the creation of CAL material in theory and practice through the perspective of a CAL development unit, the Hypertext Support Unit at the University of Kent. With similar units now in place in other institutions, the production of CAL is taking place at a rapid pace, often with the evaluation of the applications disproportionately lagging behind. This inevitably raises questions of whether what we are producing is effective CAL, and what approaches should be taken to use the potential of multimedia in a learning environment
Estabilização do solo da região de São Pedro de Alcântara - SC com cal visando o seu emprego na pavimentação
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico.Neste trabalho foi analisada a melhoria nas características de um solo quando estabilizado com cal, bem como a viabilidade técnica de se utilizar camadas deste novo material em pavimentos urbanos. O solo utilizado no trabalho, para fins de tratamento, localiza-se às margens da Rodovia SC - 407, próximo a Santa Teresa, região metropolitana de Florianópolis/SC. O trabalho teve as seguintes finalidades: realizar um estudo da influência do teor de cal obtido sobre as propriedades físicas e químicas do solo tratado, verificar qual o ganho de resistência com o tempo de cura. O teor ótimo de cal foi identificado pelo método de Hilt e Davidson (Hilt e Davidson, 1960 - LIME FIXATION POINT) como sendo de 7%. Sobre o solo natural e a mistura solo-cal, foram realizados os ensaios de: limites de Atterberg, compactação, CBR, granulometria, permeabilidade, microscopia eletrônica, durabilidade, método das pastilhas MCT, resistência à compressão simples e diametral. Os corpos de prova foram curados em câmara úmida nas idades de 7, 14, 28, 60, 90, 120 e 150 dias. Dos resultados obtidos, concluiu-se: houve, de uma maneira geral, melhora nas características físicas com o acréscimo de cal; houve ganho de resistência com o tempo de cura
On the correspondence between CAL and lagged cohort life expectancy
No full textIt has been established that under certain mortality assumptions, the current value of the Cross-sectional Average length of Life (CAL) is equal to the life expectancy for the cohort currently reaching its life expectancy. This correspondence is important, because the life expectancy for the cohort currently reaching its life expectancy, or lagged cohort life expectancy (LCLE), has been discussed in the tempo literature as a summary mortality measure of substantive interest. In this paper, we build on previous work by evaluating the extent to which the correspondence holds in actual populations. We also discuss the implications of the CAL-LCLE correspondence (or lack thereof) for using CAL as a measure of cohort life expectancy, and for understanding the connection between CAL, LCLE, and underlying period mortality conditions.cohort mortality, life expectancy, mortality measures, tempo effects
Avaliação das melhorias das propriedades físicas e mecânicas de solos originados de rochas sedimentares pela adição de cal para fins de pavimentação
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Civil.Esta dissertação apresenta os resultados de um estudo laboratorial de três amostras de solo expansivo coletadas na Rodovia SC-422, implantada com revestimento primário. Esta rodovia é uma importante rota que liga a cidade de Rio Negrinho à Vila Volta Grande em Santa Catarina, cuja falta de pavimento inibe o desenvolvimento da Vila Volta Grande e região. Os objetivos principais do estudo foram determinar teores de cal para minimizar a expansão e as conseqüentes melhorias das características dos solos, possibilitando seu emprego como camadas de pavimentos rodoviários. As características das amostras de solo e da cal utilizada para mistura foram estudadas através dos ensaios: Limites de Atterberg; granulometria; compactação; ISC; ensaios da metodologia de classificação MCT; ensaio triaxial dinâmico de cargas repetidas; ensaio de difração por raio-X; e análise química das amostras e da cal. Verificou-se o tempo de reação solo-cal por meio do ensaio de LP, provando que as reações de troca de bases são imediatas. Determinaram-se os teores adequados de cal para minimizar a expansão das amostras através dos métodos do Lime Fixation Point (LFP), pH e método das Pastilhas MCT. Este último apresentou teores de cal mais baixos que os outros dois. A adição de teores de cal de 3%, 2% e 3% respectivamente para as amostras AM-01, AM-02 e AM-03 provocou: a aglutinação das partículas mais finas, pequena redução do peso específico aparente seco ( dmáx) e aumento na umidade ótima (wót); e minimizaram a expansão dos solos independentemente da energia de compactação aplicada. Foram também detectados: incrementos nos valores de ISC efetuados 14 dias após a moldagem; pequenos aumentos da resistência à compressão simples em ensaios efetuados até 28 dias depois da moldagem; e aumentos significativos dos módulos resilientes dos solos. Verificou-se através do ensaio da metodologia de classificação MCT e Perda de Massa por imersão que a adição de cal nas amostras tornou-as de comportamento laterítico. Através da análise mecanicista, concluiu-se que pequenas quantidades de cal adicionadas aos solos estudados aumentam a vida de fadiga de pavimentos asfálticos
IntCal09 and Marine09 radiocarbon age calibration curves, 0–50,000 years cal BP
No full textAuthor Posting. © Arizona Board of Regents on behalf of the University of Arizona, 2009. This article is posted here by permission of Dept. of Geosciences, University of Arizona for personal use, not for redistribution. The definitive version was published in Radiocarbon 51 (2009): 1111-1150.The IntCal04 and Marine04 radiocarbon calibration curves have been updated from 12 cal kBP (cal kBP is
here defined as thousands of calibrated years before AD 1950), and extended to 50 cal kBP, utilizing newly available data sets
that meet the IntCal Working Group criteria for pristine corals and other carbonates and for quantification of uncertainty in
both the 14C and calendar timescales as established in 2002. No change was made to the curves from 0–12 cal kBP. The curves
were constructed using a Markov chain Monte Carlo (MCMC) implementation of the random walk model used for IntCal04
and Marine04. The new curves were ratified at the 20th International Radiocarbon Conference in June 2009 and are available
in the Supplemental Material at www.radiocarbon.org.We would like to acknowledge support for this project from the UK Natural Environment Research
Council NE/E018807/1 and IGBP PAGES (Past Global Changes)
INTCAL 09 and MARINE09 aadiocarbon age calibration curves, 0-50,000 years Cal BP
No full textThe IntCal04 and Marine04 radiocarbon calibration curves have been updated from 12 cal kBP (cal kBP is here defined as thousands of calibrated years before AD 1950), and extended to 50 cal kBP, utilizing newly available data sets that meet the IntCal Working Group criteria for pristine corals and other carbonates and for quantification of uncertainty in both the 14C and calendar timescales as established in 2002. No change was made to the curves from 0–12 cal kBP. The curves were constructed using a Markov chain Monte Carlo (MCMC) implementation of the random walk model used for IntCal04 and Marine04. The new curves were ratified at the 20th International Radiocarbon Conference in June 2009 and are available in the Supplemental Material at www.radiocarbon.org
Climate forcing due to the 8200 cal yr BP event observed at Early Neolithic sites in the eastern Mediterranean
No full textWe explore the hypothesis that the abrupt drainage of Laurentide lakes and associated rapid switch of the North Atlantic thermohaline circulation 8200 yr ago had a catastrophic influence on Neolithic civilisation in large parts of southeastern Europe, Anatolia, Cyprus, and the Near East. The event at 8200 cal yr BP is observed in a large number of high-resolution climate proxies in the Northern Hemisphere, and in many cases corresponds to markedly cold and arid conditions. We identify the relevant archaeological levels of major Neolithic settlements in Central Anatolia, Cyprus, Greece and Bulgaria, and examine published stratigraphic, architectural, cultural and geoarchaeological studies for these sites. The specific archaeological events and processes we observe at a number of these sites during the study interval 8400–8000 cal yr BP lead us to refine some previously established Neolithisation models. The introduction of farming to South-East Europe occurs in all study regions (Thrace, Macedonia, Thessaly, Bulgaria) near 8200 cal yr BP. We observe major disruptions of Neolithic cultures in the Levant, North Syria, South-East Anatolia, Central Anatolia and Cyprus, at the same time. We conclude that the 8200 cal yr BP aridity event triggered the spread of early farmers, by different routes, out of West Asia and the Near East into Greece and Bulgaria
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