11 research outputs found
Appearance of dark neurons following anodal polarization in the rat brain.
An anodal direct current of 3.0 microA or 30.0 microA was unilaterally applied for 30 min or 3 h to the surface of the sensorimotor cortex of rats, and the effects of polarization on the morphology of brain cells were examined by light microscopy. After five repeated anodal polarization trials, dark neurons appeared mainly in the polarized neocortex regardless of the intensity and duration of the polarizing currents. Such dark neurons were scarce in the control animals or the animals receiving only one trial of polarization. The dark neurons were most abundant in the second to fourth layers of the ipsilateral superior-lateral convexity of the frontal cortex, but a few were present in the contralateral cortex. The dark neurons began to appear 24 h after the last polarization; thereafter almost all of these neurons gradually reverted to their normal morphological profiles through a transitory state within 1 month of the last trial of repeated polarization. No morphological changes were apparent in any of the brain structures other than the cerebral cortex. These findings indicate that repeated anodal polarization has reversible morphological effects on the cortical neurons, suggesting that the appearance of dark neurons after anodal polarization is an important index for evaluation of cortical plastic change induced by polarization.</p
Photon Upconversion in a Molecular Lanthanide Complex in Anhydrous Solution at Room Temperature
3d-4f-3d trinuclear complexes with di-maltol-polyamine ligands. Solid state structure and solution behaviour
Optimizing Millisecond Time Scale Near-Infrared Emission in Polynuclear Chrome(III)–Lanthanide(III) Complexes
d -> f Energy Transfer in Ir(III)/Eu(III) Dyads: Use of a Naphthyl Spacer as a Spatial and Energetic "Stepping Stone"
A series of luminescent complexes based on {Ir-
(phpy)2} (phpy = cyclometallating anion of 2-phenylpyridine) or
{Ir(F2phpy)2} [F2
phpy = cyclometallating anion of 2-(2′,4′-
difluorophenyl)pyridine] units, with an additional 3-(2-pyridyl)-
pyrazole (pypz) ligand, have been prepared; fluorination of the
phenylpyridine ligands results in a blue-shift of the usual
3MLCT/3LC luminescence of the Ir unit from 477 to 455 nm.
These complexes have pendant from the coordinated pyrazolyl ring
an additional chelating 3-(2-pyridyl)-pyrazole unit, separated via a
flexible chain containing a naphthalene-1,4-diyl or naphthalene-1,5-
diyl spacer. Crystal structures show that the flexibility of the pendant
chain allows the naphthyl group to lie close to the Ir core and participate in a π-stacking interaction with a coordinated phpy or
F2phpy ligand. Luminescence spectra show that, whereas the {Ir(phpy)2(pypz)} complexes show typical Ir-based emission
albeit with lengthened lifetimes because of interaction with the stacked naphthyl groupthe {Ir(F2phpy)2(pypz)} complexes are
nearly quenched. This is because the higher energy of the Ir-based 3MLCT/3LC excited state can now be quenched by the
adjacent naphthyl group to form a long-lived naphthyl-centered triplet (3nap) state which is detectable by transient absorption.
Coordination of an {Eu(hfac)3} unit (hfac = 1,1,1,5,5,5-hexafluoro-pentane-2,4-dionate) to the pendant pypz binding site affords
Ir−naphthyl−Eu triads. For the triads containing a {Ir(phpy)2} core, the unavailability of the 3nap state (not populated by the Irbased
excited state which is too low in energy) means that direct Ir→Eu energy-transfer occurs in the same way as in other
flexible Ir/Eu complexes. However for the triads based on the{Ir(F2phpy)2} core, the initial Ir→3nap energy-transfer step is
followed by a second, slower, 3nap→Eu energy-transfer step: transient absorption measurements clearly show the 3nap state
being sensitized by the Ir center (synchronous Ir-based decay and 3nap rise-time) and then transferring its energy to the Eu
center (synchronous 3nap decay and Eu-based emission rise time). Thus the 3nap state, which is energetically intermediate in the
{Ir(F2phpy)2}−naphthyl−Eu systems, can act as a “stepping stone” for two-step d→f energy-transfer