Electric field effect on the luminescence of KI:Tl

Thermoluminescence of KI:Tl, x- or &#946;-irradiated at T<77°K showed 2 main peaks at 105 and 170°K. They are resp. attributed to the recombination of mobile VK centers with Tl0 centers and to the recombination of thermally released electrons from Tl0 centers with Tl2+ centres. Similar experiments performed under static electric fields (E<40 kV cm-1) show that the intensity of the 2nd glow peak is strongly reduced. The relative intensity variation is anticorrelated with the intensity of glow peaks occurring at >230°K. We suggestthat in the temperature range in which Tl0 centres are thermally ionised, the effect of the electric field favour the retrapping of these electrons on other traps (still unknown). Irradiation doses also play an important role and their effects are studied at 77°K and T=200°K

A Thalamic Reticular Circuit for Head Direction Cell Tuning and Spatial Navigation.

As we navigate in space, external landmarks and internal information guide our movement. Circuit and synaptic mechanisms that integrate these cues with head-direction (HD) signals remain, however, unclear. We identify an excitatory synaptic projection from the presubiculum (PreS) and the multisensory-associative retrosplenial cortex (RSC) to the anterodorsal thalamic reticular nucleus (TRN), so far classically implied in gating sensory information flow. In vitro, projections to TRN involve AMPA/NMDA-type glutamate receptors that initiate TRN cell burst discharge and feedforward inhibition of anterior thalamic nuclei. In vivo, chemogenetic anterodorsal TRN inhibition modulates PreS/RSC-induced anterior thalamic firing dynamics, broadens the tuning of thalamic HD cells, and leads to preferential use of allo- over egocentric search strategies in the Morris water maze. TRN-dependent thalamic inhibition is thus an integral part of limbic navigational circuits wherein it coordinates external sensory and internal HD signals to regulate the choice of search strategies during spatial navigation

Electric field effect on the luminescence of KI:Tl

Thermoluminescence of KI:Tl, x- or &#946;-irradiated at T230°K. We suggestthat in the temperature range in which Tl0 centres are thermally ionised, the effect of the electric field favour the retrapping of these electrons on other traps (still unknown). Irradiation doses also play an important role and their effects are studied at 77°K and T=200°K

Studying changes in the practice of two teachers developing assessment for learning

This paper describes changes in the practice of two teachers, observed over an eighteen month period, who were participating in a study intended to support teachers in developing their use of assessment in support of learning. The design of the intervention allowed each teacher to choose for themselves which aspects of their practice to develop. Analysis of lesson observations, journal entries and interviews indicate that both teachers were keen to change their practice, but were concerned about the disruption to their established routines, and in particular about the potential for loss of control of their classes. Both teachers did effect significant changes in their classrooms, but these tended to be developments of existing preferred ways of working, rather than radical innovations. In conclusion, it is suggested that to be most effective, teacher professional development needs to be structured strongly enough to afford teacher growth, but flexible enough to allow different teachers to take their practice in different ways

Increased Hydrogen Production by Genetic Engineering of Escherichia coli

Escherichia coli is capable of producing hydrogen under anaerobic growth conditions. Formate is converted to hydrogen in the fermenting cell by the formate hydrogenlyase enzyme system. The specific hydrogen yield from glucose was improved by the modification of transcriptional regulators and metabolic enzymes involved in the dissimilation of pyruvate and formate. The engineered E. coli strains ZF1 (ΔfocA; disrupted in a formate transporter gene) and ZF3 (ΔnarL; disrupted in a global transcriptional regulator gene) produced 14.9, and 14.4 µmols of hydrogen/mg of dry cell weight, respectively, compared to 9.8 µmols of hydrogen/mg of dry cell weight generated by wild-type E. coli strain W3110. The molar yield of hydrogen for strain ZF3 was 0.96 mols of hydrogen/mol of glucose, compared to 0.54 mols of hydrogen/mol of glucose for the wild-type E. coli strain. The expression of the global transcriptional regulator protein FNR at levels above natural abundance had a synergistic effect on increasing the hydrogen yield in the ΔfocA genetic background. The modification of global transcriptional regulators to modulate the expression of multiple operons required for the biosynthesis of formate hydrogenlyase represents a practical approach to improve hydrogen production