On the phenomenon of large photoluminescence red shift in GaN nanoparticles

We report on the observation of broad photoluminescence wavelength tunability from n-type gallium nitride nanoparticles (GaN NPs) fabricated using the ultraviolet metal-assisted electroless etching method. Transmission and scanning electron microscopy measurements performed on the nanoparticles revealed large size dispersion ranging from 10 to 100 nm. Nanoparticles with broad tunable emission wavelength from 362 to 440 nm have been achieved by exciting the samples using the excitation power-dependent method. We attribute this large wavelength tunability to the localized potential fluctuations present within the GaN matrix and to vacancy-related surface states. Our results show that GaN NPs fabricated using this technique are promising for tunable-color-temperature white light-emitting diode applications.     

Oswaldocruzia venezuelensis sp. n. (Nematoda:Trichostrongylina, Molineoidea), a parasite of Bufo marinus from Venezuela

A new species of Oswaldocruzia Travassos, 1917, a parasite of Bufo marinus L. from Venezuela, is described. Like most Neotropical Oswaldocruzia, Oswaldocruzia venezuelensis sp. n. is characterized by spicules with three principal branches: blade, shoe and fork, and by a division of the fork within the distal third of the spicule length. O. vaucheri Ben Slimane et Durette-Desset, 1993 is the most closely related species due to its caudal bursa of type II and its cervical alae of the same shape but it differs in the following characters: the position of the papillae of rays 4 situated nearer the papillae of rays 3 rather than rays 5, a higher percentage of the ridges in the oesophageal region, the cervical alae three times longer and sharp and the spicular fork divided less deeply.     

Spectral coded phase bipolar OCDMA technological implementation thanks to low index modulation filters

Telecommunication Systems - Optical code division multiple access (OCDMA) systems are attracting an increasing interest in optical fiber communication. This is due to the various advantages that...     

Atomistic simulations of calcium uranyl(VI) carbonate adsorption on calcite and stepped-calcite surfaces

Adsorption of actinyl ions onto mineral surfaces is one of the main mechanisms that control the migration of these ions in environmental systems. Here, we present computational classical molecular dynamics (MD) simulations to investigate the behavior of U(VI) in contact with different calcite surfaces. The calcium-uranyl-carbonate [Ca(2)UO(2)(CO(3))(3)] species is shown to display both inner- and outer-sphere adsorption to the flat {101?4} and the stepped {314?8} and {31?2?16} planes of calcite. Free energy calculations, using the umbrella sampling method, are employed to simulate adsorption paths of the same uranyl species on the different calcite surfaces under aqueous condition. Outer-sphere adsorption is found to dominate over inner-sphere adsorption because of the high free energy barrier of removing a uranyl-carbonate interaction and replacing it with a new uranyl-surface interaction. An important binding mode is proposed involving a single vicinal water monolayer between the surface and the sorbed complex. From the free energy profiles of the different calcite surfaces, the uranyl complex was also found to adsorb preferentially on the acute-stepped {314?8} face of calcite, in agreement with experiment.