Evolutionary associations between sand seatrout (Cynoscion arenarius) and silver seatrout (C. nothus) inferred from morphological characters, mitochondrial DNA, and microsatellite markers

The evolutionary associations between closely related fish species, both contemporary and historical, are frequently assessed by using molecular markers, such as microsatellites. Here, the presence and variability of microsatellite loci in two closely related species of marine fishes, sand seatrout (Cynoscion arenarius) and silver seatrout (C. nothus), are explored by using heterologous primers from red drum (Sciaenops ocellatus). Data from these loci are used in conjunction with morphological characters and mitochondrial DNA haplotypes to explore the extent of genetic exchange between species offshore of Galveston Bay, TX. Despite seasonal overlap in distribution, low genetic divergence at microsatellite loci, and similar life history parameters of C. arenarius and C. nothus, all three data sets indicated that hybridization between these species does not occur or occurs only rarely and that historical admixture in Galveston Bay after divergence between these species was unlikely. These results shed light upon the evolutionary history of these fishes and highlight the genetic properties of each species that are influenced by their life history and ecology.

Developmental characters of Psettina Iijimae (Jordan and Starks), bothid flat fishes - Pisces

Post larval stages of Psettina Iijimae ranging from 1.8 mm NL to 44.6 mm SL collected during Naga Expedition and International Indian Ocean Expedition (IIOE) are described. The characteristics which help to identify larval stages of Psettina are: the presence of pigmented urohyal appendage in early stages which is progressively reduced during flexion stages and which disappears in later postflexion stages, the meristics, the spines on urohyal and posterior basipterygial processes and the absence of spines on cleithra. The P. iijimae can be distinguished by the presence of spines on the median fin rays which differentiate near the baseosts along the dorsal and ventral body wall much before the fin rays. The larvae of P.iijimae were more abundant in the Gulf of Thailand compared to South China Sea and Indian Ocean.

Notes on the external sex characters of Chanos chanos Forskal spawners

In the present study, no visible differences between the sexes of C. chanos with reference to external features such as colouration, shape of head, snout and operculum, presence of tubercles or nasal pores, length, size and shape as well as any roughness in the various fins, could be found. However, the anal region of the mature milkfish (sabalo) exhibits discernible anatomical differences in the male and female. The male has two main openings visible externally: the anterior anus and the posterior urogenital opening at the tip of the urogenital papilla. The female has three main openings instead of two: the anteriormost anus, followed by the genital pore and the urinary pore located posterior to the genital pore at the tip of the urogenital papilla. Internal examinations were also made on both sexes. In ripe sabalo, it is easier to distinguish the sexes since milk oozes out of the urogenital pore by pressing the abdomen of the ripe male fish. Gravid females are identified by their distended abdomens.

Photovoltaic and electroluminescence characters in hybrid ZnO and conjugated polymer bulk heterojunction devices

We report electroluminescence in hybrid ZnO and conjugated polymer poly[2-methoxy-5-(3', 7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) bulk heterojuriction photovoltaic cells. Photolummescence quenching experimental results indicate that the ultra,fast photoinduced electron transfer occurs from MDMO-PPV to ZnO under illumination. The ultrafast photoinduced electron transfer effect is induced because ZnO has an electron affinity about 1.2 eV greater than that of MDMO-PPV. Electron 'back transfer' can occur if the interfacial barrier between ZnO and MDMO-PPV can be overcome by applying a substantial electric field. Therefore, electroluminescence action due to the fact that the back transfer effect can be observed in the ZnO:MDMO-PPV devices since a forward bias is applied. The photovoltaic and electroluminescence actions in the same ZnO:MDMO-PPV device can be induced by different injection ways: photoinjection and electrical injection. The devices are expected to provide an opportunity for dual functionality devices with photovoltaic effect and electroluminescence character.

X-Ray diffraction determination of the fractions of hexagonal and twinned phases in cubic GaN layers grown on (001)GaAs substrate

Being an established qualitative method for investigating presence of additional phases in single crystal materials, X-ray diffraction has been used widely to characterize their structural qualities and to improve the preparation techniques. Here quantitative X-ray diffraction analysis is described which takes into account diffraction geometry and multiplicity factors. Using double-crystal X-ray four-circle diffractometer, pole figures of cubic (002), {111} and hexagonal {10 (1) over bar0} and reciprocal space mapping were measured to investigate the structural characters of mixed phases and to obtain their diffraction geometry and multiplicity factors. The fractions of cubic twins and hexagonal inclusions were calculated by the integrated intensities of rocking curves of cubic (002), cubic twin {111}, hexagonal {10 (1) over bar0} and hexagonal {10 (1) over bar1}. Without multiplicity factors, the calculated results are portions of mixed phases in only one {111} plane of cubic GaN. Diffraction geometry factor can eliminate the effects of omega and X angles on the irradiated surface areas for different scattered planes. (C) 2001 Elsevier Science B.V. All rights reserved.

Surface roughness and high density of cubic twins and hexagonal inclusions in cubic GaN epilayers

Surface roughness and its correlation with the polarity of internal hexagonal inclusions and cubic twins have been investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The surface roughness resulted from large amount of strips, which prolonged in [1 (1) over bar0] direction with small size in [110] or [110] direction. The sidestep of each strip is just the top of high density of hexagonal inclusions or cubic microtwins. Moreover, XRD shows that the amount of hexagonal inclusions and cubic microtwins measured in [110] direction are twice or more as much as in [110] direction. Therefore, it is hexagonal inclusions, cubic twins and their distributive polarity that is responsible to the surface characteristics of cubic GaN epilayers.