68 research outputs found

    Teaching Story without Struggle: Using Graded Readers and Their Audio Packs in the EFL Classroom

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    In recent years the support for extensive reading (ER) in English as a second or foreign language (ESL/EFL) programs has been compelling. When practicing extensive reading, the learner reads a wide variety of texts for pleasure and achieves a general understanding of the content while deciphering unknown words through context. This approach contrasts with intensive reading, a more traditional approach based on a slow, careful reading of a text, with goals of complete comprehension and the identification of specific details and information

    The Eurasian Modern Pollen Database (EMPD), version 2

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    The Eurasian (née European) Modern Pollen Database (EMPD) was established in 2013 to provide a public database of high-quality modern pollen surface samples to help support studies of past climate, land cover, and land use using fossil pollen. The EMPD is part of, and complementary to, the European Pollen Database (EPD) which contains data on fossil pollen found in Late Quaternary sedimentary archives throughout the Eurasian region. The EPD is in turn part of the rapidly growing Neotoma database, which is now the primary home for global palaeoecological data. This paper describes version 2 of the EMPD in which the number of samples held in the database has been increased by 60 % from 4826 to 8134. Much of the improvement in data coverage has come from northern Asia, and the database has consequently been renamed the Eurasian Modern Pollen Database to reflect this geographical enlargement. The EMPD can be viewed online using a dedicated map-based viewer at https://empd2.github.io and downloaded in a variety of file formats at https://doi.pangaea.de/10.1594/PANGAEA.909130 (Chevalier et al., 2019)Swiss National Science Foundation | Ref. 200021_16959

    The Eurasian Modern Pollen Database (EMPD), version 2

    Get PDF
    The Eurasian (nee European) Modern Pollen Database (EMPD) was established in 2013 to provide a public database of high-quality modern pollen surface samples to help support studies of past climate, land cover, and land use using fossil pollen. The EMPD is part of, and complementary to, the European Pollen Database (EPD) which contains data on fossil pollen found in Late Quaternary sedimentary archives throughout the Eurasian region. The EPD is in turn part of the rapidly growing Neotoma database, which is now the primary home for global palaeoecological data. This paper describes version 2 of the EMPD in which the number of samples held in the database has been increased by 60% from 4826 to 8134. Much of the improvement in data coverage has come from northern Asia, and the database has consequently been renamed the Eurasian Modern Pollen Database to reflect this geographical enlargement. The EMPD can be viewed online using a dedicated map-based viewer at https://empd2.github.io and downloaded in a variety of file formats at https://doi.pangaea.de/10.1594/PANGAEA.909130 (Chevalier et al., 2019).Peer reviewe

    Equilibration between three different excited states in a bichromophoric copper(I) polypyridine complex

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    Fast reversible energy transfer and intersystem crossing conspire to permit excited-state equilibration between three excited states in a copper(I) phenanthroline complex. Introduction of multiple quasi-isoenergetic excited states in a planned fashion represents a new strategy to prolong luminescence lifetimes of copper phenanthroline complexes (e.g., 1.2 μs compared with 70 ns for the parent complex)

    Equilibration between three different excited states in a bichromophoric copper(I) polypyridine complex

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    Fast reversible energy transfer and intersystem crossing conspire to permit excited-state equilibration between three excited states in a copper(I) phenanthroline complex. Introduction of multiple quasi-isoenergetic excited states in a planned fashion represents a new strategy to prolong luminescence lifetimes of copper phenanthroline complexes (e.g., 1.2 μs compared with 70 ns for the parent complex)

    Improving the photophysical properties of copper(I) bis(phenanthroline) complexes

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    Homoleptic copper(I) bis(2,9-dialkyl-1,10-phenanthroline) units, as well as a range of related heteroleptic species, represent popular choices for building blocks in the construction of supramolecular edifices and photo- and electroactive devices. The photophysical properties of these traditionally underperforming luminescent complexes can be dramatically modified in a qualitatively predictable fashion through ligand design, the use of bichromophoric ligands, and by reconstitution of the primary coordination sphere. An overview of key excited-state processes established in these complexes is presented, with particular emphasis on recent developments and insights, as well as ramifications for developing successful strategies to prolong luminescence lifetimes and increase quantum yields

    Impact of water on the cis-trans photoisomerization of hydroxychalcones.

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    The photochromism of a 2-hydroxychalcone has been studied in CH3CN and H2O/CH3OH (1/1, v/v), as well as in analogous deuterated solvents using steady-state (UV-vis absorption, (1)H and (13)C NMR) and time-resolved (ultrafast transient absorption and nanosecond flow flash photolysis) spectroscopies. Whereas the irradiation of trans-chalcone (Ct) under neutral pH conditions leads to the formation of the same final chromene derivative (B) in both media, two distinct photochemical mechanisms are proposed in agreement with thermodynamic and kinetic properties of the chemical reaction network at the ground state. Following light excitation, the first steps are identical in acetonitrile and aqueous solution: the Franck-Condon excited state rapidly populates the trans-chalcone singlet excited state (1)Ct* (LE), which evolves into a twisted state (1)P*. This excited state is directly responsible for the photochemistry in acetonitrile in the nanosecond time scale (16 ns) leading to the formation of cis-chalcone (Cc) through a simple isomerization process. The resulting cis-chalcone evolves into the chromene B through a tautomerization process in the ground state (τ = 10 ms). Unlike in acetonitrile, in H2O/CH3OH (1/1, v/v), the P* state becomes unstable and evolves into a new state attributed to the tautomer (1)Q*. This state directly evolves into B in one photochemical step through a consecutive ultrafast tautomerization process followed by electrocyclization. This last case represents a new hypothesis in the photochromism of 2-hydroxychalcone derivatives

    Impact of Water on the Cis–Trans Photoisomerization of Hydroxychalcones

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    The photochromism of a 2-hydroxychalcone has been studied in CH<sub>3</sub>CN and H<sub>2</sub>O/CH<sub>3</sub>OH (1/1, v/v), as well as in analogous deuterated solvents using steady-state (UV–vis absorption, <sup>1</sup>H and <sup>13</sup>C NMR) and time-resolved (ultrafast transient absorption and nanosecond flow flash photolysis) spectroscopies. Whereas the irradiation of <i>trans</i>-chalcone (<b>Ct</b>) under neutral pH conditions leads to the formation of the same final chromene derivative (<b>B</b>) in both media, two distinct photochemical mechanisms are proposed in agreement with thermodynamic and kinetic properties of the chemical reaction network at the ground state. Following light excitation, the first steps are identical in acetonitrile and aqueous solution: the Franck–Condon excited state rapidly populates the <i>trans</i>-chalcone singlet excited state <sup>1</sup><b>Ct</b>* (LE), which evolves into a twisted state <sup>1</sup><b>P</b>*. This excited state is directly responsible for the photochemistry in acetonitrile in the nanosecond time scale (16 ns) leading to the formation of <i>cis</i>-chalcone (<b>Cc</b>) through a simple isomerization process. The resulting <i>cis</i>-chalcone evolves into the chromene <b>B</b> through a tautomerization process in the ground state (τ = 10 ms). Unlike in acetonitrile, in H<sub>2</sub>O/CH<sub>3</sub>OH (1/1, v/v), the <b>P</b>* state becomes unstable and evolves into a new state attributed to the tautomer <sup>1</sup><b>Q</b>*. This state directly evolves into <b>B</b> in one photochemical step through a consecutive ultrafast tautomerization process followed by electrocyclization. This last case represents a new hypothesis in the photochromism of 2-hydroxychalcone derivatives
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