Gap junction contributions to the goldfish electroretinogram at the photopic illumination level.

Understanding how the b-wave of the electroretinogram (ERG) is generated by full-field light stimulation is still a challenge in visual neuroscience. To understand more about the origin of the b-wave, we studied the contributions of gap junctions to the ERG b-wave. Many types of retinal neurons are connected to similar and different neighboring neurons through gap junctions. The photopic (cone-dominated) ERG, stimulated by a small light beam, was recorded from goldfish (Carassius auratus) using a corneal electrode. Data were obtained before and after intravitreal injection of agents into the eye under a photopic illumination level. Several agents were used to affect gap junctions, such as dopamine D1 and D2 receptor agonists and antagonists, a nitric oxide (NO) donor, a nitric oxide synthase (NOS) inhibitor, the gap junction blocker meclofenamic acid (MFA), and mixtures of these agents. The ERG b-waves, which were enhanced by MFA, sodium nitroprusside (SNP), SKF 38393, and sulpiride, remained following application of a further injection of a mixture with MFA. The ERG b-waves decreased following N(G)-nitro-L-arginine methyl ester (L-NAME), SCH 23390, and quinpirole administration but were enhanced by further injection of a mixture with MFA. These results indicate that gap junction activity influences b-waves of the ERG related to NO and dopamine actions.

Characterization of pyramidal inversion boundaries in Sb2O3-doped ZnO by using electron back-scattered diffraction (EBSD).

The composition planes of the inversion boundary induced by the addition of Sb2O3 to ZnO ceramics were analyzed crystallographically by the application of electron back-scattered diffraction (EBSD) analysis and stereographic projection techniques. The inversion boundary was determined to consist of three discrete composition planes, {0001}, {1011}, {1010}.

Diffusion, coalescence, and reconstruction of vacancy defects in graphene layers.

Diffusion, coalescence, and reconstruction of vacancy defects in graphene layers are investigated by tight-binding molecular dynamics (TBMD) simulations and by first principles total energy calculations. It is observed in the TBMD simulations that two single vacancies coalesce into a 5-8-5 double vacancy at the temperature of 3000 K, and it is further reconstructed into a new defect structure, the 555-777 defect, by the Stone-Wales type transformation at higher temperatures. First principles calculations confirm that the 555-777 defect is energetically much more stable than two separated single vacancies, and the energy of the 555-777 defect is also slightly lower than that of the 5-8-5 double vacancy. In TBMD simulation, it is also found that the four single vacancies reconstruct into two collective 555-777 defects which is the unit for the hexagonal haeckelite structure proposed by Terrones et al. [Phys. Rev. Lett. 84, 1716 (2000)].

Growth process of the ridge--trough faces of a twinned crystal.

For a twinned face-centered-cubic crystal, the energy barrier for two-dimensional nucleation on a concave trough (or a re-entrant edge) and that for a layer advancing across a convex ridge were calculated. The former was obtained by analyzing the line tension of the trough. The results show that their energy barriers are 39 and 50% compared to that for nucleation on a flat {111} face, respectively. Therefore, the layer advance across the ridge is found to be more difficult than the nucleation on the trough. Based on these results, the morphology of the growing surface is predicted and an alternative growth process by the twin-plane-re-entrant-edge mechanism is suggested.