U–Pb zircon geochronology of two granite intrusions containing bluish‑tint K-feldspars and two biotite-hornblende gneisses in the Kagasawa area, situated at the center part of the Hida metamorphic ...complex, southwest Japan, reveals the early Triassic low P/T metamorphism in the Hida metamorphic complex (251–247Ma). The granite intrusions into the Hida gneiss occurred at two different stages (235.4±1.6Ma and 183.6±1.8Ma) and thermally affected the Hida gneiss. In the Unazuki area, situated at the northeast margin of the Hida metamorphic complex, a quartzo-feldspathic schist and a biotite granite containing a quartzo-feldspathic schist as xenolith yielded U–Pb zircon ages of 258.0±2.3Ma and 253.0±1.9Ma, respectively, which indicates that the medium P/T metamorphism in the Unazuki area occurred in late Permian. The similarity between the geochemical compositions in whole rocks and zircons of the quartzo-feldspathic schist and the granite suggests that felsic volcanics were deposited on basement rocks at 258Ma and, after affecting the medium P/T metamorphism, residual felsic magma was exhumed while taking the Unazuki schists as a xenolith at 253Ma. Although the time interval between protolith formation and post-peak regional metamorphism in the Unazuki area (0.8–9.2Ma) is similar to that in the Kagasawa area (1–8.6Ma), the different timing of the regional metamorphism indicates that the protolith of the Unazuki metasediments was deposited not on the proximal Hida metamorphic complex but on ancient rocks containing Eoarchean-Paleoproterozoic components of the North China Craton.
•U–Pbzircon geochronology applied to the Kagasawa area and the Unazuki, situated inthe Hida metamorphic complex, Japan.•Low P/T metamorphism of the Hida metamorphic complex in the Kagasawa area occurred in the early Triassic (251-247Ma).•Medium P/T metamorphism in the Unazuki area occurred in the late Permian (258-253Ma).•Durationof the metamorphism in the Unazuki area (~9.2Ma) and in the Kagasawa area (~8.6Ma) suggests rapid process.ml>•Protolith of the Unazuki metasediments was deposited on ancient rocks containing Eoarchean-Paleoproterozoic components.
Earth's atmosphere and surface ocean were pervasively and mildly oxygenated after the ca. 2.4 Ga Great Oxidation Event (GOE), which induced dramatic environmental and biological changes. Positive ...nitrogen isotopic compositions of Paleoproterozoic marine deposits reveal aerobic nitrogen cycling and the widespread availability of bioavailable nitrate, but the nature of nitrogen cycling in freshwater environment remains unclear. To elucidate the redox conditions and bioavailability of nitrogen, redox-sensitive element and nitrogen isotopic compositions, as well as the depositional age, were determined for black shales of the late Paleoproterozoic Embury Lake Formation, Flin Flon belt, Canada. This formation accumulated in a sulfate-poor freshwater basin isolated from the open ocean, as indicated by its low total‑sulfur/total-organic‑carbon ratio of ∼0.05. Our U-Pb ages for detrital zircons show that the formation is younger than 1862.2 ± 2.6 Ma. Redox-sensitive elements (V and U) in the black shales show positive correlation with detrital tracers Al and Ti. Low enrichment factors for V and U indicate minor authigenic accumulations of the two elements. Moreover, the black shales are depleted in Mn, suggesting deposition under suboxic to anoxic conditions. δ15N values of the black shales are generally < +1‰, indicating a nitrate-limited environment, and are distinct from those of previously reported coeval marine deposits. It is proposed that the nitrate was exhausted by nitrogen-loss processes such as denitrification in the freshwater basin, but was available for nitrate-assimilating organisms in the ocean during the late Paleoproterozoic.
Digital‐first assessments: A security framework LaFlair, Geoffrey T.; Langenfeld, Thomas; Baig, Basim ...
Journal of computer assisted learning,
August 2022, 2022-08-00, 20220801, Letnik:
38, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Background
Digital‐first assessments leverage the affordances of technology in all elements of the assessment process: from design and development to score reporting and evaluation to create test ...taker‐centric assessments.
Objectives
The goal of this paper is to describe the engineering, machine learning, and psychometric processes and technologies of a test security framework (part of a larger ecosystem; Burstein et al., 2021) that can be used to create systems that protect the integrity of test scores.
Methods
We use the Duolingo English Test to exemplify the processes and technologies that are presented. This includes methods for actively detecting and deterring malicious behaviour (e.g., a custom desktop app). It also includes methods for passively detecting and deterring malicious behaviour (e.g., a large item bank created through automatic generation methods). We describe the certification process that each test administration undergoes, which includes both automated and human review. Additionally, we describe our quality assurance dashboard which leverages psychometric data mining techniques to monitor test quality and inform decisions about item pool maintenance.
Results and Conclusions
As assessment developers transition to online delivery and to a design approach that places the test taker at the centre, it becomes increasingly important to take advantage of the tools and methodological advances in different fields (e.g., engineering, machine learning, psychometrics). These tools and methods are essential to maintaining the security of assessments so that the score reliability is sustained and the interpretations and uses of test scores remain valid.
Lay Description
What is known about this topic?
As more and more testing programmes transition to test taker‐centric administrations, effective measures to prevent cheating and protect content are critical to ensure the validity and integrity of scores.
Two of the most common forms of cheating in online testing are (a) having someone other than the person who has registered take the test, and (b) stealing content and providing it to others to assist them in achieving a higher score.
What does this paper add?
In designing a test taker‐centric digital‐first assessment, a test security framework must inform decisions from end‐to‐end (i.e., registration, onboarding, communications regarding test taker behaviours, test preparation and practice, test administration, and post‐administrative activities including scoring).
Security is safeguarded through active and passive design methods; active methods include having test takers attest that they will follow the rules governing testing and informing them that they will be videoed during testing; passive methods include a computer adaptive design that limits item exposure and test overlap rates, development of a large item pool using automated item generation, and applying artificial intelligence to review test administration videos to flag unauthorized behaviours for human review.
Implications:
With more educational and assessment programmes transitioning to online digital models, the paper presents a comprehensive review of security issues and identifies an integrated approach for preventing cheating and other unauthorized behaviours.
The Quaternary Kurobegawa Granite, central Japan, is not only the youngest known granitic pluton exposed on the Earth's surface, it is one of few localities where both Quaternary volcanics and ...related plutons are well exposed. Here, we present new zircon U-Pb ages together with whole rock and mineral geochemical data, revealing that the Kurobegawa Granite is a resurgent pluton that was emplaced following the caldera-forming eruption of the Jiigatake Volcanics at 1.55 ± 0.09 Ma. Following the eruption, the remnant magma chamber progressively cooled forming the voluminous Kurobegawa pluton in the upper crust (~ 6 km depth) until ~ 0.7 Ma when resurgence caused rapid uplift and erosion in the region. This is the first study to document the detailed spatiotemporal evolution of resurgent pluton for a Quaternary caldera system. Our new findings may contribute significantly to understanding the fate of active caldera systems that can produce supereruptions.
Abstract
Background and Aims
Hybridization is the main driver of plant diversification, and gene flow via hybridization has multifaceted effects on plant evolution. Carex angustisquama is an ...extremophyte that grows on soils heavily acidified by volcanism. Despite its habitat distinct from that of other species, this species is known to form interspecific hybrids, implying interspecific gene flow. It is crucial to verify the extent and direction of interspecific gene flow between C. angustisquama and closely related species to understand the evolutionary process of an extremophyte in solfatara fields.
Methods
In this study, expressed sequence tag–simple sequence repeat markers were utilized to infer the extent and direction of interspecific gene flow between C. angustisquama and closely related species.
Key Results
Bayesian clustering and simulation analyses revealed that all individuals of the three hybrid species were classified into the first hybrid generation or first backcross to C. angustisquama; therefore, current interspecific gene flow is limited. Moreover, in the Bayesian inference of historical gene flow based on multispecies samples, the model that assumed no interspecific gene flow was the most strongly supported across all species pairs, including phylogenetically close but ecologically distinctive species pairs.
Conclusions
Our results revealed that interspecific gene flow between C. angustisquama and its related species has been limited both currently and historically. Moreover, our results of Bayesian inference of historical gene flow indicated that extrinsic, rather than intrinsic, factors probably act as isolating barriers between Carex species, with hybrid breakdown via microhabitat segregation being the probable potential barrier. Overall, our findings provide insights into the evolutionary process of an extremophyte in solfatara fields and offer an important example of the mechanisms of diversification of the speciose genus Carex.
► We reassessed Archaean metasedimentary sequences of the Western Dharwar Craton. ► Progressive change of metamorphic conditions within schist belt is recognized. ► Depositional age of 3.14–2.63Ga is ...constrained from SHRIMP zircon U–Pb dating. ► Composite age-metamorphic record implies some discontinuity within schist belt. ► Our data give clue to the formation of deep to shallow Archaean crust.
Archaean metasedimentary sequences of the Chitradurga Schist Belt in Western Dharwar Craton were reassessed in terms of their protoliths, potential timing of deposition and metamorphic events along with metamorphic conditions. Existing geological and stratigraphic constraints and our field observations suggest that the oldest supracrustal sequence of the Sargur Group, which occurs as enclaves in Peninsular Gneiss, is overlain by the Dharwar Supergroup consisting of lower Bababudan and upper Chitradurga Groups. In the Chitradurga Schist Belt, the metamorphic conditions of each stratigraphic unit are distinct, with most prominent difference observed in the Chitradurga Group. The lower unit of this group are metamorphosed under biotite-muscovite grade, whereas the upper unit at chlorite-muscovite grade. Detrital zircon U–Pb dates obtained by ion microprobe analyses suggest 3.14Ga and 3.22–2.92Ga for the youngest protolith's magmatic ages, which constrain the oldest age limit of deposition of Bababudan Group and Lower Unit of Chitradurga Group, respectively. The depositional age of Upper Unit of Chitradurga Schist Belt can be bracketed by 2.68Ga magmatic zircon ages from meta-rhyolite and 2.63Ga magmatic detrital zircon age of the overlying sandstone that are significantly younger than the Lower Unit. Monazite U–Th–Pb ages are similar for both Lower and Upper Units of the Chitradurga Group (∼c. 2.4Ga) but are significantly younger than those of the underlying Bababudan and Sargur Groups (∼c. 3.1Ga). Combined zircon and monazite data imply that the continuous or composite Mesoarchaean-Neoarchaean supracrustal sequences of the Chitradurga Group are metamorphosed together at the latest Archaean-early Proterozoic. These regional metamorphic ages are not detected in the underlying Bababudan and Sargur Groups, as well as the basement Peninsular Gneiss. Contrasting depositional and metamorphic history in coherent Mesoarchaean and Neoarchaean strata in the Chitradurga Schist Belt have important implications for the comparison with the well-established sedimentary sequences of similar ages in the Pilbara and Kaapvaal cratons. The protolith and metamorphic ages of the Dharwar Supergroup, when compared with available similar information from the surrounding Archaean cratons in India, Madagascar, and East Antarctica, testify the probable Archaean connection, and give clues to the formation of deep to shallow Archaean crust.
To understand the chemical durability of highly radioactive cesium-rich microparticles (CsMPs) released from the Fukushima Daiichi Nuclear Power Plant in March 2011, we have, for the first time, ...performed systematic dissolution experiments with CsMPs isolated from Fukushima soils (one sample with 108 Bq and one sample with 57.8 Bq of 137Cs) using three types of solutions: simulated lung fluid, ultrapure water, and artificial sea water, at 25 and 37 °C for 1–63 days. The 137Cs was released rapidly within three days and then steady-state dissolution was achieved for each solution type. The steady-state 137Cs release rate at 25 °C was determined to be 4.7 × 103, 1.3 × 103, and 1. 3 × 103 Bq·m−2 s−1 for simulated lung fluid, ultrapure water, and artificial sea water, respectively. This indicates that the simulated lung fluid promotes the dissolution of CsMPs. The dissolution of CsMPs is similar to that of Si-based glass and is affected by the surface moisture conditions. In addition, the Cs release from the CsMPs is constrained by the rate-limiting dissolution of silicate matrix. Based on our results, CsMPs with ∼2 Bq, which can be potentially inhaled and deposited in the alveolar region, are completely dissolved after >35 years. Further, CsMPs could remain in the environment for several decades; as such, CsMPs are important factors contributing to the long-term impacts of radioactive Cs in the environment.
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•We report chemical durability of Cs-rich microparticle from Fukushima Daiichi.•The dissolution rate was estimated for various solution composition.•Cs-rich microparticles can remain in lung and environments for several decades.
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