11 research outputs found
ImpaCT2: pupils' and teachers' perceptions of ICT in the home, school and community
The Strand 2 report of the ImpaCT 2 research describes the results of applying a range of research methods to explore, how pupils use ICT, in particular out of school and what had been gained from this use. ImpaCT2 was a major longitudinal study (1999-2002) involving 60 schools in England, its aims were to: identify the impact of networked technologies on the school and out-of-school environment; determine whether or not this impact affected the educational attainment of pupils aged 8 - 16 years (at Key Stages 2, 3, and 4); and provide information that would assist in the formation of national, local and school policies on the deployment of ICT
ImpaCT2: the impact of information and communication technologies on pupil learning and attainment
The report explores the impact of networked technologies on patterns of use of ICT in English, Mathematics and Science at Key Stages 2, 3 and 4 and the relative gain for high ICT users versus low ICT users in each of these subjects. This publication reports primarily on the outcomes of
Strand 1, but draws on some material from the other
strands of the study. ImpaCT2 was a major longitudinal study (1999-2002) involving 60 schools in England, its aims were to: identify the impact of networked technologies on the school and out-of-school environment; determine whether or not this impact affected the educational attainment of pupils aged 8 - 16 years (at Key Stages 2, 3, and 4); and provide information that would assist in the formation of national, local and school policies on the deployment of ICT
Towards efficient initiators for two-photon induced polymerization: Fine tuning of the donor/acceptor properties
In this work we present the design, synthesis and systematic investigation of the optical properties of symmetric triphenylamine (TPA)-substituted thiophenes. The use of electron-donating (-OMe, -tBu, -Me, -TMS), -neutral (-H) or -withdrawing (-F, -CN, -SO2Me) substituents gives rise to D-A-D based two-photon absorption (2PA) chromophores. The photophysical properties of these compounds, including one-photon absorption and 2PA using two-photon-excited fluorescence, were investigated in different organic solvents with varying polarity. The maximum 2PA cross sections prove to be strongly dependent on the nature of the TPA substituent and range between ~173 GM (Goeppert-Mayer units) and 379 GM. Although most of the investigated substances also exhibit high fluorescence quantum yields, two-photon absorption screening tests of an acrylate monomer formulation revealed the efficiency of these materials as 2PA photoinitiators. These results are supported by quantum chemical calculations of the spin density distribution indicating that the mechanism of polymerization initiation using acrylate monomer is favored by strong localization of the unpaired electrons in the triplet state on the C2 carbon of the thiophene moiety. © 2019 The Royal Society of Chemistry
Revista de educación
Se desarrollan dos tendencias en teoría y práctica educativa: progresismo y tradicionalismo. El tradicionalismo se caracteriza por la necesidad de claridad y autoridad en la presentación del profesor, y por la evaluación objetiva de los resultados de los estudiantes. La sociedad y las instituciones, a través de la escuela y el profesor, son las que deciden qué es lo que hay que aprender, cómo y en qué momento. Sin embargo, los progresistas valoran la elección del alumno y la iniciativa del estudiante. Enfatizan el papel del descubrimiento, donde el trabajo del profesor es proporcionar un ambiente que facilite y provoque la curiosidad intelectual. Se exponen las tres diferencias que hay en la educación: diferencias de lugar, diferencias históricas y diferencias educativas en cuanto al tipo de educación que se cree más apropiado para el desarrollo del niño. Se realiza un repaso de la teoría piagetiana para saber cuáles son las condiciones óptimas de aprendizaje en los distintos niveles. Se destaca la diseminación de la educación en la edad temprana por considerarse uno de los triunfos de la educación. Por último, se hace referencia a la relación entre educación primaria y secundaria junto con algunos problemas relativos a la transferencia.Ministerio Educación CIDEBiblioteca de Educación del Ministerio de Educación, Cultura y Deporte; Calle San Agustín, 5 - 3 Planta; 28014 Madrid; Tel. +34917748000; [email protected]
Le monde des nombres et celui des objets
Lunzer Eric Anthony. Le monde des nombres et celui des objets. In: Bulletin de psychologie, tome 30 n°327, 1977. Hommage à Jean Piaget. pp. 270-276
Solvent tuning of photochemistry upon excited-state symmetry breaking
The nature of the electronic excited state of many symmetric multibranched donor–acceptor molecules varies from delocalized/multipolar to localized/dipolar depending on the environment. Solvent-driven localization breaks the symmetry and traps the exciton in one branch. Using a combination of ultrafast spectroscopies, we investigate how such excited-state symmetry breaking affects the photochemical reactivity of quadrupolar and octupolar A–(π-D)2,3 molecules with photoisomerizable A–π–D branches. Excited-state symmetry breaking is identified by monitoring several spectroscopic signatures of the multipolar delocalized exciton, including the S2 ← S1 electronic transition, whose energy reflects interbranch coupling. It occurs in all but nonpolar solvents. In polar media, it is rapidly followed by an alkyne–allene isomerization of the excited branch. In nonpolar solvents, slow and reversible isomerization corresponding to chemically-driven symmetry breaking, is observed. These findings reveal that the photoreactivity of large conjugated molecules can be tuned by controlling the localization of the excitation
Specific Monitoring of Excited-State Symmetry Breaking by Femtosecond Broadband Fluorescence Upconversion Spectroscopy
Most
quadrupolar molecules designed for large two-photon absorption
cross section have been shown to undergo symmetry breaking upon excitation
to the S<sub>1</sub> state. This was originally deduced from their
strong fluorescence solvatochromism and later visualized in real time
using transient infrared spectroscopy. For molecules not containing
clear IR marker modes, however, a specific real-time observation of
the symmetry breaking process remains lacking. Here we show that this
process can be resolved using broadband fluorescence upconversion
spectroscopy by monitoring the instantaneous emission transition dipole
moment. This approach is illustrated with measurements performed on
two quadrupolar molecules, with only one of them undergoing excited-state
symmetry breaking in polar solvents
Beyond the Threshold: A Study of Chalcogenophene-Based Two-Photon Initiators
A series of nine soluble, symmetric chalcogenophenes bearing hexyl-substituted triphenylamines, indolocarbazoles, or phenylcarbazoles was designed and synthesized as potential two-photon absorption (2PA) initiators. A detailed photophysical analysis of these molecules revealed good 2PA properties of the series and, in particular, a strong influence of selenium on the 2PA cross sections, rendering these materials especially promising new 2PA photoinitiators. Structuring and threshold tests proved the efficiency and broad spectral versatility of two selenium-containing lead compounds as well as their applicability in an acrylate resin formulation. A comparison with commercial photoinitiators Irg369 and BAPO as well as sensitizer ITX showed that the newly designed selenium-based materials TPA-S and TPA-BBS outperform these traditional initiators by far both in terms of reactivity and dose. Moreover, by increasing the ultralow concentration of TPA-BBS, a further reduction of the polymerization threshold can be achieved, revealing the great potential of this series for application in two-photon polymerization (2PP) systems where only low laser power is available.200020-18460
Correction: Towards efficient initiators for two-photon induced polymerization: Fine tuning of the donor/acceptor properties (Molecular Systems Design and Engineering (2019) DOI: 10.1039/c8me00101d)
The authors regret that in the published article, affiliations b and c were inadvertently switched. The correct affiliations are shown here. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers. © The Royal Society of Chemistry 2019
Towards efficient initiators for two-photon induced polymerization: fine tuning of the donor/acceptor properties
In this work we present the design, synthesis and systematic investigation of the optical properties of symmetric triphenylamine (TPA)-substituted thiophenes. The use of electron-donating (–OMe, –tBu, –Me, –TMS), -neutral (–H) or -withdrawing (–F, –CN, –SO2Me) substituents gives rise to D–A–D based two-photon absorption (2PA) chromophores. The photophysical properties of these compounds, including one-photon absorption and 2PA using two-photon-excited fluorescence, were investigated in different organic solvents with varying polarity. The maximum 2PA cross sections prove to be strongly dependent on the nature of the TPA substituent and range between ∼173 GM (Goeppert-Mayer units) and 379 GM. Although most of the investigated substances also exhibit high fluorescence quantum yields, two-photon absorption screening tests of an acrylate monomer formulation revealed the efficiency of these materials as 2PA photoinitiators. These results are supported by quantum chemical calculations of the spin density distribution indicating that the mechanism of polymerization initiation using acrylate monomer is favored by strong localization of the unpaired electrons in the triplet state on the C2 carbon of the thiophene moiety