Dessulfurização oxidativa do dibenzotiofeno catalisada por V2O5 suportado

A necessidade de redução da emissão de poluentes, visando diminuir os sérios problemas de poluição atmosférica enfrentados atualmente, é hoje uma das principais preocupações mundiais, provocando o surgimento de leis mais rígidas, que restringem o teor de enxofre na gasolina e no diesel. Assim, o desenvolvimento de tecnologias mais eficazes na remoção de enxofre nestes combustíveis tem recebido atenção crescente. Estas tecnologias incluem a extração física com solvente, a adsorção seletiva, processos de redução/oxidação microbiológicos e a dessulfurização oxidativa (ODS). A dessulfurização oxidativa converte os compostos de enxofre em sulfonas que podem ser facilmente separadas por processos físicos. Portanto, a ODS apresenta grande potencial para tornar-se um processo complementar a processo de hidrodessulfurização tradicional na produção de combustíveis altamente dessulfurizados. Neste contexto, este trabalho visou o estudo do desempenho de catalisadores de V2O5 suportados em alumina, sílica e sílica-alumina frente à reação de ODS do dibenzotiofeno em presença do peróxido de hidrogênio, como oxidante, e da acetonitrila, como solvente polar aprótico. Os catalisadores foram preparados por impregnação ao ponto úmido e caracterizados por difração de raios-X (DRX), análise textural, redução à temperatura programada (TPR-H2), dessorção de amônia à temperatura programa (TPD-NH3) e espectroscopia Raman. O efeito de parâmetros reacionais como quantidade de solvente, relação O/S e concentração de catalisador foram investigados, utilizando a alumina como suporte, visando estabelecer as condições reacionais que levassem a maiores valores de conversão do dibenzotiofeno (DBT). Uma vez estabelecidas estas condições, foi analisado o efeito do teor de V2O5 presente no catalisador e, posteriormente, o efeito do suporte catalítico. Os resultados obtidos mostraram a 70 C razão molar H2O2/Sde 16,6, razão carga/solvente igual a 1:1 e 100 mg do catalisador 15 % V2O5/SiO2, a conversão obtida foi de 95%

Heat-stress and light-stress induce different cellular pathologies in the symbiotic dinoflagellate during coral bleaching

Coral bleaching is a significant contributor to the worldwide degradation of coral reefs and is indicative of the termination of symbiosis between the coral host and its symbiotic algae (dinoflagellate; Symbiodinium sp. complex), usually by expulsion or xenophagy (symbiophagy) of its dinoflagellates. Herein, we provide evidence that during the earliest stages of environmentally induced bleaching, heat stress and light stress generate distinctly different pathomorphological changes in the chloroplasts, while a combined heat- and light-stress exposure induces both pathomorphologies; suggesting that these stressors act on the dinoflagellate by different mechanisms. Within the first 48 hours of a heat stress (32°C) under low-light conditions, heat stress induced decomposition of thylakoid structures before observation of extensive oxidative damage; thus it is the disorganization of the thylakoids that creates the conditions allowing photo-oxidative-stress. Conversely, during the first 48 hours of a light stress (2007 µmoles m−2 s−1 PAR) at 25°C, condensation or fusion of multiple thylakoid lamellae occurred coincidently with levels of oxidative damage products, implying that photo-oxidative stress causes the structural membrane damage within the chloroplasts. Exposure to combined heat- and light-stresses induced both pathomorphologies, confirming that these stressors acted on the dinoflagellate via different mechanisms. Within 72 hours of exposure to heat and/or light stresses, homeostatic processes (e.g., heat-shock protein and anti-oxidant enzyme response) were evident in the remaining intact dinoflagellates, regardless of the initiating stressor. Understanding the sequence of events during bleaching when triggered by different environmental stressors is important for predicting both severity and consequences of coral bleaching

Allelopathic mechanism of pyrogallol to Microcystis aeruginosa PCC7806 (Cyanobacteria): From views of gene expression and antioxidant system

Pyrogallol is a potent allelochemical on Microcystis aeruginosa, but its allelopathic mechanism is not fully known. In order to explore this mechanism, gene expressions for prx, mcyB, psbA, recA, grpE, fabZ under pyrogallol stress were studied, and activities of the main antioxidant enzymes were also measured. The results showed that expression of grpE and recA showed no significant change under pyrogallol stress, while psbA and mcyB were up-regulated at 4 mg L-1. Both prx and fabZ were up-regulated even under exposure to 1 mg L-1 pyrogallol concentration. The activities of superoxide dismutase (SOD) and catalase (CAT) were enhanced under pyrogallol stress. Levels of malodialdehyde (MDA) at 2 and 4 mg L-1 pyrogallol were significantly higher than those of the controls. It was concluded that oxidant damage is an important mechanism for the allelopathic effect of pyrogallol on M. aeruginosa. (c) 2009 Elsevier Ltd. All rights reserved.

Growth and antioxidant system of Escherichia coli in response to microcystin-RR

Microcystins are a kind of cyclic hepatoxins produced by many species of cyanobacteria. The toxic effects of microcystins on animals and plants have been well studied. However, the reports about the effects of microcystins on microbial cells are very limited. In present paper, Escherichia coli was undertaken to determine the effect of microcystin-RR. These results suggested that microcystin-RR could prolong the growth of E. coli when exposed to high concentrations of microcystin-RR and cause the accumulation of ROS and induce the oxidant stress for a short time. The antioxidant system protects E. coli from oxidative damage.

Kinetic study of the 2-methyl-3-methoxy-4-phenylbutanoic acid produced by oxidation of microcystin in aqueous solutions

Microcystins (MCs) are a family of related cyclic hepatotoxic heptapeptides, of which more than 70 types have been identified. The chemically unique nature of the C20 beta-amino acid, (2S, 3S, 8S, 9S)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca4,6-dienoic acid (Adda), portion of the MCs has been exploited to develop a strategy to analyze the entirety. Oxidation of MCs causes the cleavage of MC Adda to form 2-methyl-3-methoxy-4-phenylbutanoic acid (MMPB). In the present study, we investigated the kinetics of MMPB produced by oxidation of the most-often-studied MC variant, MC-LR (L = leucine, R = arginine), with permanganate-periodate. This investigation allowed insight regarding the influence of the reaction conditions (concentration of the reactants, temperature, and pH) on the conversion rate. The results indicated that the reaction was second order overall and first order with respect to both permanganate and MC-LR. The second-order rate constant ranged from 0.66 to 1.35 M/s at temperatures from 10 to 30 degrees C, and the activation energy was 24.44 kJ/mol. The rates of MMPB production can be accelerated through increasing reaction temperature and oxidant concentration, and sufficient periodate is necessary for the formation of MMPB. The initial reaction rate under alkaline and neutral conditions is higher than that under acidic conditions, but the former decreases faster than the latter except under weakly acidic conditions. These results provided new insight concerning selection of the permanganate-periodate concentration, pH, and temperature needed for the oxidation of MCs with a high and stable yield of MMPB.

Acute effects of microcystins on the transcription of antioxidant enzyme genes in crucian carp Carassius auratus

Recent evidences suggested that oxidative stress may play a significant role in the pathogenesis of MCs toxicity. In the present study, the acute effects of microcystins on the transcription of antioxidant enzyme genes were investigated in liver of crucian carp i.p.-injected with 50 mu g MC-LReq per kg body weight (BW). We reported the cDNA sequences for four kinds of antioxidant enzyme (GSH-PX, CAT, Cu/Zn SOD, and GR) genes, and evaluated the oxidant stress induced by MCs through analyzing the transcription abundance of antioxidant enzyme genes using real-time PCR method. The time-dependent change of relative transcription abundance and expression of the antioxiclant enzyme genes were determined at 1, 3, 12, 24, and 48 h. The transcription abundance varied among antioxiclant enzymes, with GSH-PX and GR down-regulation, and CAT and SOD significantly upregulation. Based on these data, we tentatively concluded that the oxidant stress was induced by MCs, and caused the different response of the antioxiclant enzyme genes. (c) 2008 Wiley Periodicals, Inc.

Microcystin-RR-induced accumulation of reactive oxygen species and alteration of antioxidant systems in tobacco BY-2 cells

Microcystins are cyclic heptapeptide hepatoxins produced by cyanobacteria. It has been shown that microcystins have adverse effects on animals and on plants as well. Previous researches also indicated that microcystins were capable of inducing oxidative damage in animals both in vivo and in vitro. In this study, tobacco BY-2 suspension cell line was applied to examine the effects of microcystin-RR on plant cells. Cell viability and five biochemical parameters including reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), glutathione peroxide (GPX) and peroxide dismutase (POD) were investigated when cells were exposed to 50 mg/L microcystin-RR. Results showed that microcystin-RR evoked decline of the cell viability to approximately 80% after treating for 144 h. ROS levels, POD and GPX activities of the treated cells were gradually increased with a time dependent manner. Changes of SOD and CAT activities were also detected in BY-2 cells. After 168 h recovery, ROS contents, POD, GPX and CAT activities returned to normal levels. These results suggest that the microcystin-RR can cause the increase of ROS contents in plant cells and these changes led to oxidant stress, at the same time, the plant cells would improve their antioxidant abilities to combat mirocystin-RR induced oxidative injury. (c) 2005 Elsevier Ltd. All rights reserved.

Kinetics of the oxidation of MCRR by potassium permanganate

The occurrence of the microcystins in the water bodies, especially in drinking water resources, has received considerable attentions. In situ chemical oxidation is a promising cost-effective treatment method to remove MC from water body. This research investigated the reaction kinetics of the oxidation of MCRR by permanganate. Experimental results indicate that the reaction is second order overall and first order with respect to both permanganate and MCRR, and has an activation energy of 18.9 kJ/mol. The second-order rate constant ranges from 0.154 to 0.225 l/mg/min at temperature from 15 to 30 degrees C. The MCRR degradation rates can be accelerated through increasing reaction temperature and oxidant concentration. The reaction under acid conditions was slightly faster than under alkaline conditions. The half-life of the reaction was less than 1 min, and more than 99.5% of MCRR was degraded within 10 min. (c) 2005 Elsevier Ltd. All rights reserved.

Responses of antioxidant systems in the hepatocytes of common carp (Cyprinus carpio L.) to the toxicity of microcystin-LR

The freshwater, bloom-forming cyanobacterium (blue-green alga) Microcystis aeruginosa produces a peptide hepatotoxin, which causes the damage of animal liver. Recently, toxic Microcystis blooms frequently occur in the eutrophic Dianchi Lake (300 km(2) and located in the South-Westem of China). Microcystin-LR from Microcystis in Dianchi was isolated and purified by high performance liquid chromatography (HPLC) and its toxicity to mouse and fish liver was studied (Li et al., 2001). In this study, six biochemical parameters (reactive oxygen species, glutathione, superoxide dismutase, catalase, glutathione peroxide and glutathione S-transferase) were determined in common carp hepatocytes when the cells were exposed to 10 mug microcystin-LR per litre. The results showed that reactive oxygen species (ROS) contents increased by more than one-time compared with the control after 6 h exposure to the toxin. In contrast, glutathione (GSH) levels in the hepatocytes exposed to microcystin-LR decreased by 47% compared with the control. The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxide (GSH-Px) increased significantly after 6 h exposure to microcystin-LR, but glutathione S-transferase (GST) activity showed no difference from the control. These results suggested that the toxicity of microcystin-LR caused the increase of ROS contents and the depletion of GSH in hepatocytes exposed to the toxin and these changes led to oxidant shock in hepatocytes. Increases of SOD, CAT and GSH-Px activities revealed that these three kinds of antioxidant enzymes might play important roles in eliminating the excessive ROS. This paper also examined the possible toxicity mechanism of microcystin-LR on the fish hepatocytes and the results were similar to those with mouse hepatocytes. (C) 2003 Elsevier Science Ltd. All rights reserved.

中国沙棘(Hippophae rhamnoides subsp. sinensis)不同种群对干旱胁迫的响应差异与干旱诱导蛋白的分析

沙棘广泛分布于亚欧大陆的温带地区和亚洲亚热带的高海拔地区。沙棘能适应多种生态环境，能耐受多种逆境(如干旱、低温、高温和盐害等)。在中国，沙棘常常被用作植被恢复中的先锋树种而大量栽培。本文以中国沙棘为试验材料，探索沙棘适应干旱机制，以及沙棘对干旱胁迫的适应机制是否存在种群间的差异，同时试图通过分析干旱胁迫下沙棘叶片蛋白质表达变化探索沙棘适应干旱胁迫的分子机理。 对三个分别来自低海拔湿润地区、低海拔干旱地区和高海拔湿润地区的中国沙棘种群进行干旱胁迫处理。干旱胁迫能提高根冠比，比叶面积，降低平均叶面积和总生物量，提高沙棘的抗氧化性酶活性、脯氨酸含量、脱落酸(ABA)含量、降低光合作用，提高长期用水效率。实验中的这两个低海拔种群比高海拔种群抵抗干旱的能力更强,不同的种群采用了不同的策略来耐受干旱胁迫和过氧化胁迫。 在2004 年度的实验中，干旱胁迫处理下，高海拔湿润种群(道孚种群)严重失水，生长也受到更大的抑制，非气孔因素在抑制光合作用方面占支配地位，抗坏血酸含量下降，ABA和脯氨酸含量增加幅度比九寨沟种群的要高，这可能是因为道孚种群严重失水而引起的；而低海拔湿润种群(九寨沟种群)的体内水分状况几乎不受干旱的影响，生长情况也较道孚种群要好。 在2005 年度的试验中，和高海拔湿润地区种群(道孚)相比较，低海拔干旱地区种群(定西)在叶片相对水含量、根冠比、抗氧化酶活性(过氧化氢酶、抗坏血酸过氧化物酶和谷胱甘肽过氧化物酶)、保护性物质(脯氨酸，脱落酸)含量等方面都要高，光能热耗散能力也更强，而且气体交换参数(气孔扩散阻力和胞间CO2浓度等)对干旱也更不敏感。 分析了干旱胁迫下沙棘叶片蛋白质表达的变化。共发现319 个蛋白质，有4 个蛋白在干旱胁迫下消失(Putative ABCtransporter ATP-binding protein 、Hypothetical proteinXP-515578，热激蛋白Hslu219 和一个没得到鉴定的蛋白)，4 个只在干旱胁迫下出现(没命名的蛋白质产物，对甲基苯-丙酮酸双加氧酶，NTrX 和一个没得到鉴定的蛋白)，46 个蛋白质的表达丰度变化显著，包括32 个干旱负调蛋白，14 个干旱正调蛋白(3 个Rubisco 的大亚基、J-type–co-chaperone Hsc20、putative protein DSM3645-2335、putative acyl-COA 脱氢酶、nesprin-2 和两个没有得到鉴定的蛋白质)。这些蛋白质参与了氮代谢调控、抗氧化行物质的合成、脂肪酸β－氧化、核骨架构造、[Fe-S]基团组装、物质跨膜运输、细胞分裂或作为分子伴侣和蛋白质酶起作用。putative ABC transporter ATP-binging protein、NtrX、nesprin-2 和Hslu 是本试验新发现的高等植物蛋白，我们主要从它们的保守结构域或在其他生物中的同源物来猜测它们的功能。实验结果为我们研究植物抗干旱机制提供了新线索和新视野。 Seabuckthorn (Hippophae rhamnoides L.) is widly distributed throughtout the temperatureresiogn of Europe and Asia and sub-tropical plateau zone of Asia. H. rhamnoides can adapatseveral different environments, and can tolerant several envioronmental stresses (e.g, lowtemperature, high temperature, drought and salty). It has been widely used in forest restoration asthe pioneer species in China. In present study, we applied H.rhamnoides subsp. Sinensis asexperimental materials to study its drought-tolerant mechanism, and expected to findpopulational difference in drought-tolerant mechanism that may exist among populations, and tryto get some insight in drought-tolerant mechanism of it at morecular level through analyzing thechange of leaf protein expression. Three populations from high altitude wet zone, low altitude wet zone and low altitude arid znoe,respectively, were applied in our experiment, and were subjected to drought. Drought increasedthe root/shoot ratio(RS), special leaf area, long-term water use efficinency, activity of antioxidantenzymes, proline content and abscisic acid (ABA) content, declined the net photosynthesis rate(A), average leaf area (ALA), total biomass (TB). Both two low altitude populations were moredrought-tolerant than the high altitude population, and different population applied differentstratedgies to tolerant oxidant stress and drought stress. The results of the exprement in 2004 showed that Daofu population was more drought-sensitivethan Jiuzhai population. Under drought conditions, leaf relative water content (RWC) greatlydecreased in Daofu population, but not in Jiuzhai population. The large loss of water in Daofupopulation resulted in a limitation on A mainly caused by non-stomatal factors, severer suppression in growth rate and a significant reduction in ascorbic acid (AsA) content, comparedwith Jiuzhai population. The greater increase in content of ABA and proline in Daofu populationmay be also induced by large loss in water, so that enable plants to cope with sever drought. In the exprement of 2005, drought significantly increased RS, activities of catalase (CAT),peroxidase (POD), glutathione peroxidase (GPX) and ascorbate peroxidase (APX), and alsosignificantly increased ABA and proline contents. On the other hand, compared with Daofupopulation, drought induced larger RS and activities of CAT, GPX and APX, and higher ABAcontent in Dingxi population, whereas gas exchange traits, e.g., stomatal limitation value (LS) andintercellular CO2 concentration (Ci), were less responsive to drought in Dingxi population thanthose in Daofu population. All these factors enable Dingxi population to tolerant drought betterthan Daofu population. The leaf protein profile of seabuchthorn subjected to drought was analyzed. Altogether 319proteins were detected in well-watered sample, four proteins disappeard by drought (putativeABCtransporter ATP-binding protein, hypothetical protein XP-515578, Hslu219and aunidentified protein), four only appeared under drought (a probable nitrogen regulation protein(NtrX), a 4-hydroxyphenylpyruvate dioxygenase , an unnamed protein product and an identified protein), 32 drought down-regulated proteins, and 14 drought up-regulated proteins (nine wereidentified: three large subunits of Rubisco, a hypothetical protein DSM3645-23351, a putativeacyl-COA dehydrogenase, a nesprin-2, a J-type-co-chaperone HSC20 and two unmatchedproteins). These proteins may involve in β-oxidation, cross-membrane transport, cell division,cytoskeleton stabilization, iron-sulfur cluster assembly, nitrogen metabolism regulation andantioxidant substance biosynthesis or function as molecular chaperone or protease. Four proteins(a putative ABC transporter ATP-binging protein, NtrX, nesprin-2, Hslu) were new found in highplants, and their functions were estimated from their conserved domain or their homologues inother organism. Our results provided new clue and new insight for us to study thedrought-tolerant mechanism in plants.

模拟增温与UV-B 辐射增强对云杉种子萌发和幼苗生长的影响

臭氧层损耗导致的地球表面UV-B辐射增强以及温室气体增多引起的气候变暖是当今两大全球环境问题。UV-B辐射增强和气候变暖对陆地植物和生态系统产生深远影响，并已成为全球变化研究的重要议题。作为世界第三极的青藏高原，UV-B 辐射增强以及气候变暖现象尤为突出。本试验所在林区是青藏高原东缘的主要林区，具有大面积的亚高山人工针叶成熟林，在全球变化背景下该森林的天然更新潜力如何是急待回答的重要问题。基于此，本研究围绕森林树种的种子和幼苗这一更新的重要阶段，开展了气候变暖、UV-B辐射增强和联合胁迫对云杉种子萌发及幼苗定居影响的研究，旨在全球变化背景下，探讨全球变暖、UV-B 辐射增强和联合胁迫是否对西南地区大面积人工亚高山针叶林更新的种子萌发和幼苗定居阶段产生影响。 本文以青藏高原东缘亚高山针叶林主要树种云杉为研究对象，研究云杉种子萌发及幼苗的生长和生理对UV-B辐射增强与气候变暖的响应。采用UV-B荧光灯（UV-lamp）来模拟增强的UV-B 辐射，此外，采用开顶式有机玻璃罩（OTCs）来模拟气候变暖。本试验包括四个处理：（1）大气UV-B 辐射+大气温度（C）；（2）大气UV-B 辐射+模拟气候变暖（W）；（3）增强的UV-B辐射+大气温度（U）；（4）增强的UV-B辐射+模拟气候变暖（U+W）。 根据本试验结果，UV-B辐射增强对云杉种子萌发没有显著影响，它对萌发云杉幼苗的影响主要体现在幼叶展开以后。根据两年的试验结果，增强的UV-B辐射降低了云杉幼苗抗氧化酶活性，降低了抗氧化物质的含量，此外，造成了膜质的过氧化，表现为MDA在针叶中的积累。增强的UV-B照射处理萌发云杉幼苗两年后，幼苗的生长受到显著抑制。我们的结果显示，OTCs分别提高了空气（10 cm）和土壤（5 cm）温度1.74℃和0.94 ℃。增温显著地促进了云杉种子提前萌发，提高了萌发速率和萌发比率，而且，明显地促进了幼苗的生长，表现为株高和生物量累积的显著增长。此外增温还有利于云杉幼苗根的伸长生长以及生物量的累积，这可以使云杉幼苗更好地利用土壤中的水分和营养元素。 根据本试验结果，温度升高显著地促进了增强UV-B辐射下云杉萌发幼苗的生长，这说明，温度升高缓解了UV-B辐射增强对云杉萌发幼苗的负面影响。这种缓解作用可能是温度升高对UV-B辐射增强处理下幼苗的抗氧化系统活性改善的结果。温度升高还缓解了高UV-B辐射对云杉幼苗根生长的抑制作用，这也可能是增温缓解伤害的原因之一。此外，根据我们的试验结果，增温与UV-B辐射增强联合作用（U+W）下云杉萌发幼苗的生长状况好于大气温度与大气UV-B辐射联合（C）处理，表现为株高、地径、根长和生物量积累均高于C处理，因此可以推断，UV-B辐射增强与气候变暖同时存在对萌发幼苗在两年之内的生长没有产生抑制作用，也就是说，气候变暖的缓解作用完全弥补了UV-B辐射增强的有害作用。 同样，增强的UV-B辐射显著影响了云杉幼苗的光合作用，表现为净光合速率（Pn）和表观量子效率（Φ）的提高，此外，根据我们的试验结果，它还造成了PSII的光抑制。增强的UV-B辐射显著抑制了云杉幼苗对营养元素的吸收，表现为大量营养元素、碳、钙、镁和锌含量的降低，但是，它却显著促进了铁在植株体内的积累。增温显著地提高了净光合速率，但是，它对光系统II（PSII）的光化学效率影响不大。温度升高缓解了UV-B增强对云杉幼苗光合作用的伤害，表现为净光合速率、表观量子效率以及PSII光化学效率的提高。此外，温度升高还缓解了UV-B辐射增强对离子吸收的抑制作用。 Enhanced UV-B radiation due to the reduction of O3 layer and global warming induced by increased greenhouse gases in the air have become the two pressing aspects of global climate changes. Moreover, enhanced UV-B radiation and warming have profound and long-term impacts on terrestrial plants and ecosystems, and the studies focusing on the two factors have attracted many attentions. Qinghai-Tibetan Plateau is the third in elevation in the world, and enhanced UV-B radiation and climate warming are especially prominent in this region. Our research located in the main forest belt in the eastern Qinghai-Tibetan Plateau where large areas of subalpine coniferous forests distributed. Based on that, we carried out a research to study the effects of enhanced UV-B radiation and climate warming on seed germination and seedlings growth of seedlings which are the important basic stage in forest regeneration. This research was arranged by a complete factorial design and included two factors (UV-B radiation and temperature) with two levels. The UV-lamps were used to manipulate the supplemental UV-B radiation and open-top chambers (OTCs) were adopted to increase temperature. The four treatments were: (1) C, ambient UV-B without warming; (2) U, enhanced UV-B without warming; (3) W, ambient UV-B with OTCs warming; (4) U+W, enhanced UV-B with OTCs warming. The main results were exhibited as follows: 1. Based on our results in this research, OTCs increased temperature on average 1.74℃ in air (10 cm above ground) and 0.92 ℃ in soil (5 cm beneath ground). Furthermore, OTCs also slightly reduced soil moisture and relative air humidity, however, the differences was not statistically significant. 2. Our results showed that enhanced UV-B had no significant effects on the seeds germination of P. asperata. Enhanced UV-B affected sprouts of P. asperata until the needles unfolded. During two years, enhanced UV-B inhibited the efficiency of the antioxidant defense systems, and as a result, it induced oxidant stress and the accumulation of MDA in needles. After two years of exposure to enhanced UV-B, the growth of P. asperata sprouts was markedly restrained compared with those under ambient UV-B radiation and temperature (C). Warming significantly stimulated the germination speed and increased the germination rate of P. asperata seeds. In the next place, it prominently facilitated the growth of P. asperata sprouts, represented as improvements in stem elongation and biomass accumulation. Furthermore, warming also increased root growth of P. asperata sprouts, which could made sprouts more efficient to use water and nutrient elements in soil. In this research, warming alleviated the deleterious effects of enhanced UV-B on P. asperata sprouts. It markedly stimulated the growth of P. asperata sprouts exposed to enhanced UV-B. The ease effects of warming on the abilities of the antioxidant defense systems might account for its amending effects on growth. After two years of exposure to enhanced UV-B radiation and warming, the growth of P. asperata sprouts was better than those under ambient UV-B radiation without warming (C), which could be seen from the higher plant height, basal diameter, root length and total biomass accumulation compared with C. 3. Enhanced UV-B radiation significantly influenced the photosynthesis processes of two-year old P. asperata seedlings. Our results showed that enhanced UV-B reduced the net photosynthetic rate (Pn) and the apparent quantum efficiency (Φ), and induced photoinhibition of photosynthetic system II (PSII). Enhanced UV-B significantly decreased the concentration of nitrogen (N), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg) and zinc (Zn), however, it increased the accumulation of iron (Fe) in the whole plant of P. asperata seedlings. Warming significantly stimulated Pn of P. asperata seedlings but it had no prominent impacts on the photochemical efficiency of PSII. In our research, warming also alleviated the harmful effects of enhanced UV-B on photosynthesis and absorption of ions of P. asperata seedlings. It increased Pn, Φ and the photochemical efficiency of PSII in seedlings exposed to enhanced UV-B. Moreover, warming also increased the absorption of ions of the seedlings exposed to enhanced UV-B radiation.

Catalytic partial oxidation of gasoline to syngas in a dense membrane reactor

In our previous work, it was shown that LiLaNiO/gamma-Al2O3 was an excellent catalyst for partial oxidation of heptane to syngas in a fixed-bed reactor at high temperature and the selectivity of CO was about 93%. However, pure oxygen was used as the oxidant. We have developed a dense oxygen permeation membrane Ba0.5Sr0.5Co0.8Fe0.2O3 that can supply pure oxygen for the reaction. In this work, the membrane was combined with the catalyst LiLaNiO/gamma-Al2O3 in one rector for the partial oxidation of heptane that is typical component of gasoline. A good performance of the membrane reactor has been obtained, with 100% n-heptane conversion and >94% hydrogen selectivity at the optimized reaction conditions. (C) 2004 Elsevier B.V. All rights reserved.

Characterization of metal-containing molecular sieves and their catalytic properties in the selective oxidation of cyclohexane

Three types of metal-containing molecular sieves with AFI, AEL and CHA structures (Me = Co, Mn, Cr and V) were synthesized hydrothermally and characterized by XRD, XRF, TG, TPR, NH3-TPD and FT-IR. It was revealed that metals were incorporated into the framework of molecular sieves and induced the presence of charge centers. Both cobalt and manganese in the framework of AIPO-5, AlPO-11 and SAPO-34 were not reducible before the structure collapse. The redox behaviours of these catalysts in cyclohexane oxidation at 403 K using O-2 as oxidant were examined. CoAPO-11 exhibited best activity and good selectivities for the monofunctional oxidation products (88.5%). Cyclohexanol was the major product over most catalysts, whereas for Cr-containing molecular sieves, high selectivity of cyclohexanone was observed. Investigation of reaction mechanism based on CoAPO-11 and CrAPO-5 catalysts indicated that the decomposition of cyclohexyl hydroperoxide (CHHP), the intermediate in cyclohexane oxidation, followed the pathway: cyclohexanone <-- CHHP --> cyclohexanol -->cyclohexanone. (C) 2004 Elsevier B.V. All rights reserved.

Molybdenum containing surface complex for olefin epoxidation

Silica-supported molybdenum surface complexes were prepared by the reaction between (N=) Mo(OtBu)(3) and silica via displacement of the tert-butoxy ligands for siloxyls from the silica surface. The structure of the surface molybdenum complexes was well defined by in-situ FT-IR, elemental analysis, H-1 NMR and C-13 CP/MAS NMR techniques. The surface complexes could undergo alcoholysis reaction with CD3OD and CH3OH in the same way as free (N =) Mo(OtBu)(3) and they show high catalytic activity and selectivity in olefin epoxidation. Initial rates up to 24.9 mmol epoxide (mmol Mo)(-1) min(-1) were achieved in the epoxidation of cyclohexene using TBHP as oxidant.

Simultaneous synthesis of polyaniline nanotubules and gold nanoplates

This paper describes a facile route for simultaneous synthesis of polyaniline (PANI) nanotubules and gold nanoplates. The inner diameter of PANI nanotubules was less than 10 nm and the length was several micrometers. At the same time, uniform single-crystal gold nanoplates with thicknesses of tens of nanometers were obtained.