Observations on parasite fauna of centropomus undecimalis and C. parallelus (perciformes) bred in southern Brazil, and its possible influence on the welfare of fishes.

The metazoan parasite fauna of snooks, Centropomus parallelus and Centropomus undecimalis, cultured in southern Brazil and parasite?s influence on the relative condition factor (Kn), are investigated. Snooks were parasitized by two species of gill monogeneans belonging to Rhabdosynochus (Diplectanidae) genus and by one endoparasitic digenean species Acanthocollaritrema umbilicatum (Acanthocollaritrematidae). Centropomus parallelus and C. undecimalis showed similar prevalence rates of Rhabdosynochus spp., but greater mean intensity and abundance rates were found in C. parallelus. On the other hand, there was no significant difference on prevalence, mean intensity and abundance of A. umbilicatumfor both hosts. The mean abundance of Rhabdosynochusspp. decreased as the hosts´ length and weight increased. Since the most parasitized fish species, C. parallelus, had lower weight than expected (Kn<1.0), the fact suggested that gill monogeneans might alter fish welfare. Current analysis reports a new host and a new locality for A. umbilicatum

Comparing C-60 and C-70 as acceptor in organic solar cells : Influence of the electronic structure and aggregation size on the photovoltaic characteristics

The difference in aggregation size of the C-60 and C-70 fullerenes affect the photovoltaic performance of devices assembled in the so-called bilayer architecture with poly [2,7-(9,9- dioctyl- dibenzosilole)- alt-4,7- bis(thiophen-2-yl)benzo- 2,1,3- thiadiazole] (PSiF-DBT) as the electron donor material. Despite the better performance of the C-70 devices, which is related to the high absorption coefficient in the visible range and the superior charge transport properties, the short-circuit current variation upon annealing treatment at 100 degrees C is approximately twice bigger when the C-60 is the acceptor. We attribute this effect to the tendency of C-60 in form smaller aggregate domains relatively to the C-70. The increased roughness on the polymeric surface after annealing results in an enhanced donor/acceptor contact area and assists the fullerene diffusion deeper inside the polymeric layer. This effect leads to a better mixing between donor and acceptor species and create a interpenetrating layer close to the so-called bulk heterojunction. Since C-60 forms smaller aggregates, this mechanism is more pronounced for this molecule. Therefore, a significant variation in the performance of the C-60 devices is observed after this kind of treatment. Density Functional Theory calculations of the potential energy of interaction between two fullerene molecules and X-Ray measurements gives evidences to support this idea. In addition, combining spectrally resolved external quantum efficiency measurements with optical modeling our results also indicate the occurrence of the bilayer interfacial mixing for PSiF-DBT/C-60.Peer reviewe

Efficient Behavior of Small-World Networks

We introduce the concept of efficiency of a network, measuring how efficiently it exchanges information. By using this simple measure small-world networks are seen as systems that are both globally and locally efficient. This allows to give a clear physical meaning to the concept of small-world, and also to perform a precise quantitative a nalysis of both weighted and unweighted networks. We study neural networks and man-made communication and transportation systems and we show that the underlying general principle of their construction is in fact a small-world principle of high efficiency.Comment: 1 figure, 2 tables. Revised version. Accepted for publication in Phys. Rev. Let

Light-emitting porphyrin derivative obtained from a subproduct of the cashew nut shell liquid: A promising material for OLED applications

In this work, the meso-tetra[4-(2-(3-n-pentadecylphenoxy)ethoxy]phenylporphyrin (H2P), obtained from the cashew nut shell liquid (CNSL), and its zinc (ZnP) and copper (CuP) metallic complexes, were applied as emitting layers in organic light emitting diodes (OLEDs). These compounds were characterized via optical and electrochemical analysis and the electroluminescent properties of the device have been studied. We performed a cyclic voltammetry analysis to determine the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energy levels for the porphyrins, in order to select the proper materials to assemble the device. H2P and ZnP presented fluorescence emission band in the red region, from 601 nm to 718 nm. Moreover, we verified that the introduction of bulky substituents hinders the π-πstacking, favoring the emission in the film. In addition, the strongest emitter, ZnP, presented a threshold voltage of 4 V and the maximum irradiance of 10 μW cm-2 with a current density (J) of 15 mA cm-2 at 10 V. The CuP complex showed to be a favorable material for the design of OLEDs in the infrared. These results suggest that the porphyrins derived from a renewable source, such as CNSL, is a promising material to be used in organic optoelectronic devices such as OLEDs