Photoluminescence emission from nanostructured porous preparations of CdS–ZnTiO3 assembled nanoparticles

This study reports the structural and optical properties of CdS/ZnTiO₃ nanocomposites prepared using a chemical bath and different titanate concentrations. Commercial ZnTiO₃ nanoparticles were introduced into a chemical bath that had been used to produce CdS semiconductor nanoparticles (NPs). Here, the growing CdS crystallites precipitated onto the suspended zinc titanate NPs. X‐ray diffraction patterns revealed that samples of CdS/ZnTiO₃ nanopowders were made of cubic ZnTiO₃ and hexagonal CdS wurtzite. The morphology of the particles was studied using transmission electron microscopy and scanning electron microscopy images. These images demonstrated the different characteristics of the CdS/ZnTiO₃ nanocomposites and their dependence on titanate concentration when placed into the CdS‐growing solution. Photoluminescence spectra showed three main emission bands for the electron transitions in the CdS/ZnTiO₃ composite. This composite produced three photoluminescence bands, the intensities of which depended on composite shape, which in turn depended on the relative concentrations of CdS and ZnTiO₃.     

Two new trochids of the genus <Emphasis Type="Italic">Antimargarita</Emphasis> (Gastropoda: Vetigastropoda: Trochidae) from the Bellingshausen Sea and South Shetland Islands,Antarctica

Two new trochids of the genus Antimargarita, A. powelli and A. bentarti, from the Antarctic waters are described here. A. powelli, from the Bellingshausen Sea, is distinguished by its rounded whorls, numerous spiral cords, a radula with seven lateral teeth at each side of the rachidian, and an epipodium with eight pairs of tentacles. A. bentarti, from the South Shetland Islands, is characterized by having a shell outline gradated by prominent primary spiral cords, a radula with five lateral teeth at each side of the rachidian and an epipodium with six tentacles on the left side. The diagnostic features for Antimargarita are redefined considering both shell and anatomical features and its suprageneric placement is discussed.     

Transcriptomic response to differentiation induction

Background  

Microarrays used for gene expression studies yield large amounts of data. The processing of such data typically leads to lists of differentially-regulated genes. A common terminal data analysis step is to map pathways of potentially interrelated genes.     

Distribution and dynamics of bacterioplankton production in a polymictic tropical lake (Lago Xolotlán,Nicaragua)

From 1988 to 1993 we assessed the variability of bacterioplankton production and biomass in Lake Xolotlán (L. Managua), Nicaragua via [3H]thymidine incorporation into DNA and cell counting. Bacterial production ranged from 3 to 8 μg C l-1 h-1, and since production was equal throughout the water column, areal production was high (≈ 600–1200 mg C m-2 d-1). Bacterial abundance in Lake Managua was extremely high, 7–30 × 109 cells l-1. Thus, specific rates of bacterial production were low. There was a strong correlation between production and number and the specific rate of bacterial production was constant. Comparable measurements of production via [3H]leucine incorporation into proteins indicated that bacteria were experiencing ‘balanced growth’. We conclude that bacterioplankton in Lake Xolotlán had reached its carrying capacity and a significant correlation between bacterial production and concentration of phaeophytin implied that dead or dying algae was the limiting substrate for bacterioplankton. The majority of bacterial number and most of bacterial production (up to 75%) were associated with particles in the >3-μm fraction, probably lysing algal cells to which bacterioplankton were ‘attached’. Grazing on bacterioplankton must be low and bacteria should be a ‘sink’ for organic matter in Lake Xolotlán. This revised version was published online in July 2006 with corrections to the Cover Date.     

SO2 污染油菜对桃蚜的影响

ＳＯ_２污染油菜对桃蚜的影响龚佩瑜,吴坤君,李秀珍（中国科学院动物研究所北京１０００８０）ＳＯ２是我国大气污染的主要成分,它是一种对生物影响很大的污染物。ｓｏ。曾被用作熏蒸剂来防治害虫,但只有在浓度很高时才有效。更多的观察表明,ｓｏ：污染有利于蚜虫的?..