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This paper is based
on research carried out with children and adults at early childhood education
institutions in Rio de Janeiro, Brazil. The research goals were to identify
interactions between adults and children and to rethink pedagogical practice.
The theoretical-methodological framework was based on language and culture
studies, the sociology of childhood and anthropology. After studying children
and adults in different contexts and early childhood education public policies
and practice, the results present challenges of changing and creating early
education practices in difficult contexts, especially with regard to the
creation and use of spaces intended for children. This is the focus of the text,
which is structured in three sections. Section one presents the theoretical and
methodological issues. The second section analyzes three case studies developed
in public pre-schools situated in different cities in the state of Rio de
Janeiro. Section three presents conclusions and priorities for intervention and
change concerning children, adults and their interactions.
The fluorescence kinetics of 1,6-diphenyl-1,3,5-hexatriene (DPH) dissolved in cyclohexane was investigated as a function of temperature, concentration and 355 nm excitation pulse energy. At concentrations above 2.5 μM and excitation energies above 1 mJ a long-lived, very intense emission, which appears within less than 5 ns and lasts up to 70 ns, is observed. During the first 50 ns the decay does not follow an exponential but rather a linear behaviour. In oxygen saturated solutions the long-lived emission is suppressed and solely short-lived fluorescence with τ < 5 ns can be detected. A kinetic simulation was performed, based on a model whereupon the long-lived emission originates from the S1-state and competes with the formation of DPH-O2 contact charge-transfer complexes and intersystem crossing which both quench the fluorescence. Our investigations show that even the small amount of oxygen dissolved in nitrogen saturated solutions has a distinct influence on the fluorescence kinetics of DPH.