The attrition behaviour of oxygen-carriers under inert and reacting conditions

The attrition of two potential oxygen-carriers for chemical-looping, 100. wt% mechanically-mixed, unsupported iron oxide (400-600 μm diameter) and 25. wt% copper oxide impregnated on alumina (600-900 μm diameter), has been studied. The rates of attrition of batches of these particles whilst they were being fluidised and subjected to successive cycles of reduction and oxidation were determined by measuring the rate of production of fine particles elutriated from the bed, as well as progressive changes in the distribution of particle sizes retained in the bed. The ability of the particles to withstand impacts was also investigated by examining the degree of fragmentation of 1. g of reacted particles of known size on projecting them at a target at various velocities. It was found that the mechanical strength of the iron oxide particles deteriorated significantly after repeated cycles of oxidation and reduction. Thus, the rate of elutriation increased ~35-fold between the 1st and 10th cycle. At an impact velocity of 38. m/s, the amount of fragmentation in the impact test, viz. mass fraction of particles after impact having a size less than that before impact, increased from ~2.3. wt% (fresh particles) to 98. wt% after the 10th cycle. The CuO particles, in comparison, were able to withstand repeated reaction: no signs of increased rates of elutriation or fragmentation were observed over ten cycles. These results highlight the importance of selecting a durable support for oxygen-carriers. © 2011 Elsevier Ltd.

SynGAP isoforms exert opposing effects on synaptic strength.

Alternative promoter usage and alternative splicing enable diversification of the transcriptome. Here we demonstrate that the function of Synaptic GTPase-Activating Protein (SynGAP), a key synaptic protein, is determined by the combination of its amino-terminal sequence with its carboxy-terminal sequence. 5' rapid amplification of cDNA ends and primer extension show that different N-terminal protein sequences arise through alternative promoter usage that are regulated by synaptic activity and postnatal age. Heterogeneity in C-terminal protein sequence arises through alternative splicing. Overexpression of SynGAP α1 versus α2 C-termini-containing proteins in hippocampal neurons has opposing effects on synaptic strength, decreasing and increasing miniature excitatory synaptic currents amplitude/frequency, respectively. The magnitude of this C-terminal-dependent effect is modulated by the N-terminal peptide sequence. This is the first demonstration that activity-dependent alternative promoter usage can change the function of a synaptic protein at excitatory synapses. Furthermore, the direction and degree of synaptic modulation exerted by different protein isoforms from a single gene locus is dependent on the combination of differential promoter usage and alternative splicing.

Rapid Electron Beam Reacted Tantalum/Titanium Bilayers on Silicon : Semiconductors and Semiconductor Devices

The electrical and structural characteristics of tantalum-titanium bilayers on silicon reacted by electron beam heating have been investigated over a wide range of temperature and time conditions. The reacted layers exhibit low sheet resistance and stable electrical characteristics up to at least 1100℃. Titanium starts reacting from 750℃ onwards for 100 milliseconds reaction times whereas tantalum starts reacting only above 900℃ for such short reaction times. RBS results confirm that silicon is the major diffusing species and there is no evidence for the formation of ternary silicides. Reactions have also been explored on millisecond time scales by non-isothermal heating.

Attenuated Salmonella Typhimurium lacking the pathogenicity island-2 type 3 secretion system grow to high bacterial numbers inside phagocytes in mice.

Intracellular replication within specialized vacuoles and cell-to-cell spread in the tissue are essential for the virulence of Salmonella enterica. By observing infection dynamics at the single-cell level in vivo, we have discovered that the Salmonella pathogenicity island 2 (SPI-2) type 3 secretory system (T3SS) is dispensable for growth to high intracellular densities. This challenges the concept that intracellular replication absolutely requires proteins delivered by SPI-2 T3SS, which has been derived largely by inference from in vitro cell experiments and from unrefined measurement of net growth in mouse organs. Furthermore, we infer from our data that the SPI-2 T3SS mediates exit from infected cells, with consequent formation of new infection foci resulting in bacterial spread in the tissues. This suggests a new role for SPI-2 in vivo as a mediator of bacterial spread in the body. In addition, we demonstrate that very similar net growth rates of attenuated salmonellae in organs can be derived from very different underlying intracellular growth dynamics.

大兴安岭阿尔山沼泽鼓藻类中国新记录

大兴安岭阿尔山是我国沼泽分布最集中的地区之一,其中鼓藻类植物十分丰富。2004年7月,2005年8月、10月和2006年5月,作者先后4次在该地区采集标本共260号,在对标本鉴定过程中,发现有中国新记录鼓藻10个分类单位,隶属于4个属,包括8种2变种:厚皮鼓藻加厚变种Cosmarium pachydermumvar.incrassatum、穿孔鼓藻C.perforatum、伸长鼓藻C.protractum、具齿角星鼓藻Staurastrum denticulatum、不等角星鼓藻S.dispar、分叉角星

莫氏肾形虫武汉种群的形态学及表膜下纤毛系研究

中国科学院知识创新项目(KSCX2-2-06)资助

黄颡前驼形线虫发生和成熟的季节动态

报道了寄生于黄颡鱼(Pelteobagrus fulvidraco)胃、肠中的黄颡前驼形线虫(Procamallanus fulvidraconis)的成熟和感染丰度的季节动态。从2001年2月到2002年7月的18个月中,对来自于湖北省梁子湖的900尾黄颡鱼进行了调查,结果表明:该线虫的感染率除在2002年1月比较低(32%)外,其他月份都在90%以上,且没有显著的季节性变化(G=16.96F0.01[17,882]=1.98)。在对黄颡前驼形线虫雌虫成虫的三个阶段(成熟期、怀卵期和怀幼期)和雄虫成虫的

东湖螅状独缩虫(纤毛门:寡膜纲)的异质性

以螅状独缩虫(Carchesium polypinumLinne,1785)为研究对象,利用RAPD技术对武汉市南湖、沙湖和东湖3个湖区的螅状独缩虫样本进行了DNA多态性比较分析,以确认种群并期望促进微型生物种群生态学研究。结果如下:(1)从120条随机引物中筛选到31条有清晰扩增条带的,其中20条引物扩增出172条条带清晰、多态性高的条带,片段大小为100~1600bp,而其余11个引物扩增出59条相对多态性差的清晰条带,片段大小为100~1500bp;(2)扩增产物经SPSS12.0与RAPDista

Light absorption in silicon quantum dots embedded in silica

The photon absorption in Si quantum dots (QDs) embedded in SiO2 has been systematically investigated by varying several parameters of the QD synthesis. Plasma-enhanced chemical vapor deposition (PECVD) or magnetron cosputtering (MS) have been used to deposit, upon quartz substrates, single layer, or multilayer structures of Si-rich- SiO2 (SRO) with different Si content (43-46 at. %). SRO samples have been annealed for 1 h in the 450-1250 °C range and characterized by optical absorption measurements, photoluminescence analysis, Rutherford backscattering spectrometry and x-ray Photoelectron Spectroscopy. After annealing up to 900 °C SRO films grown by MS show a higher absorption coefficient and a lower optical bandgap (∼2.0 eV) in comparison with that of PECVD samples, due to the lower density of Si-Si bonds and to the presence of nitrogen in PECVD materials. By increasing the Si content a reduction in the optical bandgap has been recorded, pointing out the role of Si-Si bonds density in the absorption process in small amorphous Si QDs. Both the photon absorption probability and energy threshold in amorphous Si QDs are higher than in bulk amorphous Si, evidencing a quantum confinement effect. For temperatures higher than 900 °C both the materials show an increase in the optical bandgap due to the amorphous-crystalline transition of the Si QDs. Fixed the SRO stoichiometry, no difference in the optical bandgap trend of multilayer or single layer structures is evidenced. These data can be profitably used to better implement Si QDs for future PV technologies. © 2009 American Institute of Physics.

Changes in the Mg profile and in dislocations induced by high temperature annealing of blue LEDs

The efficiency of the injection and recombination processes in InGaN/GaN LEDs is governed by the properties of the active region of the devices, which strongly depend on the conditions used for the growth of the epitaxial material. To improve device quality, it is very important to understand how the high temperatures used during the growth process can modify the quality of the epitaxial material. With this paper we present a study of the modifications in the properties of InGaN/GaN LED structures induced by high temperature annealing: thermal stress tests were carried out at 900 °C, in nitrogen atmosphere, on selected samples. The efficiency and the recombination dynamics were evaluated by photoluminescence measurements (both integrated and time-resolved), while the properties of the epitaxial material were studied by Secondary Ion Mass Spectroscopy (SIMS) and Rutherford Backscattering (RBS) channeling measurements. Results indicate that exposure to high temperatures may lead to: (i) a significant increase in the photoluminescence efficiency of the devices; (ii) a decrease in the parasitic emission bands located between 380 nm and 400 nm; (iii) an increase in carrier lifetime, as detected by time-resolved photoluminescence measurements. The increase in device efficiency is tentatively ascribed to an improvement in the crystallographic quality of the samples. © 2013 SPIE.

Metallothionein-2 gene from the mandarin fish Siniperca chuatsi: cDNA cloning, tissue expression, and immunohistochemical localization

The metallothionein-2 (MT-2) gene was isolated from the mandarin fish, one of the most important industrial aquatic animals in China, by using rapid amplification of cDNA ends (RACE). The deduced amino acid sequence of MT-2 comprised 60 amino acids and showed approximately 62.3% identity to human metallothionein. Its promoter region was amplified by thermal asymmetric interlaced polymerase chain reaction (TAIL-PCR). The MT-2 gene consists of 3 exons and 2 introns, extending approximately 900 bp of genomic sequence. Phylogenetic analysis clearly demonstrated that MT-2 formed a clade with fish metallothionein. The promoter region contained 5 putative metal-regulatory elements (MREs) and 1 TATA box. Real-time quantitative RT-PCR analysis revealed that MT-2 transcripts were significantly increased in the brain and gills and were stable in the muscles, liver, and trunk kidney in Cd2+-stimulated fish. Western blotting analysis demonstrated that the protein of the MT-2 gene was expressed mainly in the gills, liver, heart, trunk kidney, muscle, and intestine; it was weakly detected in the brain and head kidney. Moreover, the MT-2 protein was immunohistochemically detected in the cytoplasm in the liver and trunk kidney. All the above results revealed that the mandarin fish MT-2 would be a useful biomarker for metal pollution. (C) 2008 Published by Elsevier Inc.

Effects of Cd2+ and Pb2+ on the substrate biofilms in the integrated vertical-flow constructed wetland

The effects of single Cd2+ and Pb2+, and combined Cd2+ and Pb2+ on dehydrogenase activity and polysaccharide content of the substrate biofilms in the integrated vertical-flow constructed wetland (IVCW) were studied. Dehydrogenase activities decreased linearly with the increasing concentrations of Cd2+ and Pb2+ at different times (6, 24, 72, and 120 h). The activities at both 6 and 24 h were significantly higher than that at 72 and 120 h in the case of single and combined treatments. The single Cd2+ and Pb2+ treatments significantly inhibited dehydrogenase activities at concentrations in excess of 20 mu mol/L Cd2+ and 80 mu mol/L Pb2+, respectively. The inhibitory effect of Cd2+ was much greater than that of Pb2+. At the same time, the combined treatment of Cd2+ and Pb2+ Significantly inhibited dehydrogenase activities at all five concentrations studied and the lowest combined concentration was 1.25 mu mol/L Cd2+ and 5 mu mol/L Pb2+. A synergistic effect of Cd2+ and Pb2+ was observed. On the other hand, polysaccharide contents varied unpredictably with the increasing concentrations of Cd2+ and Pb2+ and extended experimental time. There were no significant statistical differences within the range of concentration and time studied, whether singly or in combination. These results implied that the effects of heavy metals on biofilms should be a concern for the operation and maintenance of constructed wetlands.

Gene expression profiles in liver of zebrafish treated with microcystin-LR

Microcystin-LR (MC-LR) is the most frequently studied cyclic heptatoxin produced by cyanobacteria, which has tremendous negative impacts on fish, while its molecular mechanism behind remained unclear at present. Here, Affymetrix Zebrafish GeneChip was used to identify alterations in gene expression of zebrafish (Danio rerio) after MC-LR exposure. Among the 14,900 transcripts in the microarray, 273 genes were differentially expressed, in which 243 genes were elevated and 30 were decreased. According to GOstat analysis, MC-LR mainly influenced the cell cycle and mitogen-activated protein kinases (MAPK) signaling pathways. In addition, many immune-related genes were also influenced. These data suggest that MC-LR could promote tumorigenesis and cause immunotoxicity in fish. (C) 2008 Elsevier B.V. All rights reserved.