Electroluminescence from nano-crystalline Si/SiO2 structures embedded in pn junctions

Phosphorous-doped and boron-doped amorphous Si thin films as well as amorphous SiO2/Si/SiO2 sandwiched structures were prepared in a plasma enhanced chemical vapor deposition system. Then, the p-i-n structures containing nano-crystalline Si/SiO2 sandwiched structures as the intrinsic layer were prepared in situ followed by thermal annealing. Electroluminescence spectra were measured at room temperature under forward bias, and it is found that the electroluminescence intensity is strongly influenced by the types of substrate. The turn-on voltages can be reduced to 3 V for samples prepared on heavily doped p-type Si (p(+)-Si) substrates and the corresponding electroluminescence intensity is more than two orders of magnitude stronger than that on lightly doped p-type Si (p-Si) and ITO glass substrates. The improvements of light emission can be ascribed to enhanced hole injection and the consequent recombination of electron-hole pairs in the luminescent nanocrystalline Si/SiO2 system. (C) 2008 Elsevier Ltd. All rights reserved.

Influence of phosphine flow rate on Si growth rate in gas source molecular beam epitaxy

As reported by other authors, we have also observed that the Si growth rate decreases with increasing phosphine (PH3) flow rate in gas source-Si molecular beam epitaxy using phosphorous (P) as a n-type dopant. Why small quantity PH3 can affect Si growth rate? Up to now, the quantitative characterization of PH3 flow influence on Si growth rate is little known. In this letter, the PH, influence will be analyzed in detail and a model considering strong P surface segregation and its absorption of hydrogen will be proposed to characterize the effect. (C) 2000 Elsevier Science B.V. All rights reserved.

MBE Growth of High Electron Mobility InP Epilayers

The molecular beam epitaxial growth of high quality epilayers on （100） InP substrate using a valve phosphorous cracker cell over a wide range of P/In BEP ratio （2.0-7.0） and growth rate （0.437 and 0. 791μm/h）. Experimental results show that electrical properties exhibit a pronounced dependence on growth parameters,which are growth rate, P/In BEP ratio, cracker zone temperature, and growth temperature. The parameters have been optimized carefully via the results of Hall measurements. For a typical sample, 77K electron mobility of 4.57 × 10^4 cm^2/（V · s） and electron concentration of 1.55×10^15 cm^-3 have been achieved with an epilayer thickness of 2.35μm at a growth temperature of 370℃ by using a cracking zone temperature of 850℃.

岷江上游人工针叶、阔叶林土壤可溶性有机物质特征及其对凋落物分解的响应

土壤可溶性有机物质（Dissolved organic matter，DOM）作为土壤有机质的活性组分，在陆地生态系统物质循环中扮演非常重要的角色。土壤DOM的主要成分可溶性有机碳（Dissolved organic carbon，DOC）和氮（Dissolved organic nitrogen，DON）参与C、N循环过程。为深入揭示全球C、N循环过程机制，在未开展DOC和DON的地区进行相关研究是有必要的。森林土壤（包括枯枝落叶层）DOC、DON动态及调控机理的研究是目前国际上森林生态系统C、N循环研究热点之一。本研究立足于暖温带岷江上游茂县地区人工林植被，对土壤DOC和DON的库容量，季节动态及其与其它养分之间的关系进行了系统研究，旨在了解DOC和DON在该区生态系统中的重要作用，并探讨作为DOM主要来源的叶凋落物对DOC和DON的动态影响，研究有助于更加详细地了解该区生态系统C和N循环过程。本论文主要研究结论如下： 1研究了岷江上游地区两大主要土壤类型（棕壤和褐土）不同植物群落下土壤的DOC和DON含量及特征，结果表明：DOC和DON在两种土壤类型中均有库容量存在，DOC在0-10cm和10-20cm土层的含量幅度分别111.96~159.95 mg kg-1和69.02~100.84 mg kg-1。DON在0-10cm和10-20cm土层的含量幅度分别11.88~23.08 mg kg-1和4.70~10.77 mg kg-1。游离氨基酸在0-10cm和10-20cm土层的含量幅度分别0.84~1.66 mg kg-1和0.39~0.73 mg kg-1。DOC、DON与土壤中的一些养分因子表现出了显著的相关关系，共同反映了土壤的状况和质量，在该区开展DOC和DON的系统研究是有必要的。 2 对油松与连香树林地土壤DOC、DON以及其它化学指标的季节动态进行了研究，结果表明：油松与连香树林地土壤DOC和DON的季节动态变化表现了类似的规律，DOC和DON的含量均以秋季最高。DOC和DON的季节动态变化主要受凋落物生物因素的影响，但其微生物活力的生物因素以及降雨、温度等非生物因素也是控制土壤DOC和DON含量的重要因素。土壤DON在土壤中的行为不同于矿质氮，其季节动态不同于NO3--N和NH4+-N的季节动态，在研究N循环过程中，应考虑DON的变化情况。 3 对油松与连香树林地分解层和表层土壤（0-10cm）氨基酸周转动态进行了研究，结果表明：油松林地和连香树林地均以分解层的氨基酸含量高于矿质表层土壤的含量。每个取样时期，油松林地内各层次的氨基酸含量高于连香树林地内相应层次的含量。两林地各层次无机氮含量均超过了氨基酸的含量，并且室内培养30天后无机N的含量仍然高于氨基酸的含量，所以可以认为该区立地条件下无论是在有机分解层还是矿质土层植物吸收利用的氮素仍是以无机N为主。 4 松林下松针凋落物易于累积，这与松针凋落物分解缓慢有关，从而导致松林内养分周转缓慢。通过用不同性质凋落物和灌丛地土壤构建微生态系统，比较油松、辐射松、连香树、灌丛虎榛子凋落物分解对C、N循环过程的影响，结果显示油松和辐射松针叶凋落物比连香树、虎榛子凋落物分解更慢，减缓了养分循环过程。然而将针叶凋落物与阔叶凋落物混合后，油松和辐射松针叶凋落物的分解加快，C、N元素的循环过程也加速。此结果表明在松林内维持具有高质量凋落物的灌丛植被或在松林内栽植一些阔叶树种如连香树对维持和增进松树人工林的土壤肥力有重大的作用。室内培养的结果还显示添加凋落物后土壤DOC和DON的含量显著增加，表明凋落物是土壤DOM的直接来源。然而不同物种凋落物处理下土壤DOC和DON的含量有所不同，并随时间发生改变。混合凋落物处理下土壤DOC和DON的含量均高于松针凋落物单独处理下土壤DOC和DON的含量。DON是一个主要的水溶性N库，随时间的变化趋势与无机N的变化趋势不同，在土壤N循环过程中起到了中间N库的作用。 As a labile fraction of soil organic matter, dissolved organic matter (DOM) plays a very important role in material cycling of terrestrial ecosystem. The turnover of DOM is now being considered as main components in nutrient cycling. DOM mainly includes dissolved organic carbon (DOC), -nitrogen (DON), -phosphorous (DOP) and –sulfur (DOS). Among these constituents, DOC and DON directly participate in C and N cycling. It is essential to study DOC and DON dynamics and their controlling factors in the areas where no related study has ever been carried out. Study about them can provide data supports on understanding the mechanism of the global C and N cycling. DOC and DON dynamics and their controlling factors have been focused on in the research of C and N cycling of forest ecosystems. Based on forest plantations of Maoxian, Minjiang River in warm temperate zone, soil DOC and DON pool size, their seasonal dynamics, and the correlation between DOC, DON and other nutrients were studied in order to understand the importance of DOC and DON in the study area. Soil DOC and DON dynamics induced by leaf litter decomposition were also studied. The study contributed to comprehensively understanding C and N cycling processes and providing baseline data for including DOC and DON into the indices system of evaluating nutrient conditions. The results were as follows: 1 Several different plant communities under brown soil and Cinnamon soil were chosen as sampling plots. The contents and features of soil DOC and DON were evaluated. The results showed that DOC and DON were present under the two soil types. DOC contents in the top soil (0-10 cm) and the subsoil (10-20 cm) respectively varied from 111.96 mg kg-1to 159.95 mg kg-1, and 69.02 mg kg-1 to 100.84 mg kg-1. DON contents in the top soil (0-10 cm) and the subsoil (10-20 cm) respectively varied from 11.88 mg kg-1to 23.08 mg kg-1, and 4.70 mg kg-1 to 10.77 mg kg-1. Free amino acid contents in the top soil (0-10 cm) and the subsoil (10-20 cm) respectively varied from 0.84 mg kg-1to 1.66 mg kg-1, and 0.39 mg kg-1 to 0.73 mg kg-1. Significant correlations were found between DOC, DON and some nutrient indices, which together reflected soil condition and quality. It was hence essential to study DOC and DON in the study area. 2 Seasonal dynamics of DOC, DON, inorganic N, microbial biomass C and N were studied under Pinus tabulaeformis and Cercidiphyllum japonicum plantation. The results indicated that seasonal dynamics of soil DOC and DON under the two plantations performed similar change pattern, with the highest values in autumn. The seasonal dynamics of soil DOC and DON were mainly influenced by the litterfall. However, biotic factors such as soil microbial activities and abiotic factors such as precipitation and temperature also controlled the dynamics of soil DOC and DON. The seasonal dynamic of DON was different from that of NO3--N and NH4+-N, which showed that the behavioral differences between DON and inorganic nitrogen. And hence, it was proposed to include DON into soil N cycling in the study area. 3 Amino acid dynamics in Oa and topsoil (0-10 cm) under P. tabulaeformis and C. japonicum plantation were studied. The results showed that amino acid content in Oa was significantly higher than that in mineral soil. At each sampling time, significantly higher amino acid contents were found in P. tabulaeformis plantation than in C. japonicum plantation. The content of inorganic nitrogen was much higher than the content of amino acid in each sampling layer at each sampling time. After a 30-days laboratory incubation the content of amino acid was still lower than the content of inorganic nitrogen. The results implicated that the form of N absorbed by plants in these study sites were mainly inorganic nitrogen. 4 Usually needle litter is more resistant to decomposition, which leads to needle litter accumulation in pure coniferous stands and slows down the rate of nutrient circulation. By constructing microcosms with local shrubland soil and containing the four single-species (P. tabulaeformis, P. radiata, C. japonicum, Ostryopsis davidiana) litters, the decomposition rates and related C and N dynamics of needle litters and broadleaved litters during the early stage were compared. The results showed that the decomposition rates of pine needles were lower than those of broadleaved litters, which descended C and N cycling processes. However, the presence of C. japonicum or O. davidiana litter into pine needles increased the decomposition rates of pine needles and also dramatically promoted C and N cycling processes. It should be appropriate for plantation managers to consider C. japonicum as an ameliorative species or remain O. davidiana in pine plantations to improve soil conditions and help maintain soil fertility. The laboratory incubation still showed that DOC and DON contents in all litter-amended treatments were significantly higher than no litter-amended treatment, which proved that litter could be a direct source of DOM in soils. Different species litters induced different soil DOC and DON contents, which correspondingly changed over time. DOC and DON contents in mixed litter treatments were higher than those in pine needle litter treatments. As a major soluble N pool, DON developed a different changing pattern over time compared with inorganic N and played a role of interim N pool in soil N cycling.

九寨沟湖泊湿地植物群落与植物地理研究

九寨沟湖泊湿地在维持九寨沟的生态平衡中起着重要的作用，在旅游产业的发展下，湿地生态系统及生物多样性面临着较大的威胁。尽管九寨沟湿地具有重要的生态价值，但目前对其研究尚比较薄弱。湿地植物群落和植物地理研究可以为湿地资源的可持续利用和监测保护提供科学依据。作者从2004年8月到2007年11月对九寨沟湿地的植物物种组成、地理分布、优势植物群落的结构、生长动态、湿地土壤种子库进行了调查研究。主要结果如下： 1. 九寨沟湿地物种组成、地理分布特点及湿地植物群落特点 九寨沟湿地共有苔藓植物8科13属16种，维管植物为48科107属199种。九寨沟湿地植物的地理成份较为丰富，维管植物在科级水平上有7种地理分布型（变型），在属级水平上有13种地理分布型（变型）， 在种级水平上共有29种地理分布型（变型）。九寨沟湿地植物以温带成份和我国特有成份为主，同时兼有热带、亚热带成份和环极—高山成份。九寨沟湿地植物的分布表现出明显的垂直地带性和水平地带性。湿地植物群落可划分21个群落类型，不同植物群落类型的物种多样性及物种组成存在较大的差异。九寨沟湿地植物的物种多样性和群落多样性以及较高的生产力特征，是维持其湿地生态景观多样性和稳定性的基础。 2. 土壤、水环境、海拔等对湿地植物的分布及生物多样性的影响 九寨沟湿地土壤、水等环境因子存在较大的差异。帕米尔苔草和宽叶香蒲等群落的凋落物较多，土壤有机碳、土壤总磷较高，可能是九寨沟湿地的重要土壤碳库。 九寨沟湿地植物沿水环境梯度的分布规律表现为：沉水植物（轮藻—篦齿眼子菜，水苦荬，杉叶藻）——挺水植物（水木贼，芦苇，宽叶香蒲）——湿生草本（苔草、节节草、披散木贼）——湿生灌木（柳灌丛，小檗灌丛）等。海拔也影响湿地植物的物种组成。 水深对物种多样性有影响，水深与物种丰富度负相关。随着水深的增加，水木贼、芦苇、杉叶藻、宽叶香蒲等群落的物种多样性下降；在长期淹水和季节性淹水的地方，水木贼群落物种多样性存在显著差异。土壤总氮与水木贼群落物种丰富度正相关。 3. 土壤营养元素、水环境对植物生长的影响 水深影响湿地植物生物量的分配。芦苇无性系分株在47 cm水深的环境中单株平均生物量最大；在干滩地中（地面水深0 cm），叶生物量百分比最大，而茎生物量百分比最小，茎的生物量百分比和生长速率随水深的增加而增加；在较干的滩地生境中，开花率、花序的生物量百分比明显大于水较深的生境。 水深与水木贼地上生物量负相关，但水木贼地上生物量在长期淹水和季节性淹水的地方没有显著的差异。在水浅的地方，杉叶藻、水木贼、芦苇等植物群落中，其他伴生物种的生物量占样方总生物量的百分比较大。 土壤有机碳、土壤总氮、土壤总磷等对湿地植物生物量的影响比较大：宽叶香蒲地上生物量与土壤总磷正相关；水木贼地上生物量与土壤总氮正相关；杉叶藻地上生物量与土壤有机碳正相关。 水深、土壤营养成分对湿地植物高度、密度等有影响。水木贼的平均高度在季节性淹水的地方比长期淹水的地方低，平均密度在长期淹水的地方比季节性淹水的地方低；除了5月份，其他观察月份水木贼的密度都与水深负相关，同时与土壤有机碳正相关。另外，芦苇密度与土壤有机碳含量正相关，宽叶香蒲密度与水深负相关，帕米尔苔草高度与土壤有机碳负相关。 4. 优势植物群落的动态变化 在优势植物群落中，优势种的高度、密度、盖度、生物量等在群落中占绝对优势。除五花海，水木贼群落的物种组成、高度、生物量在两年间没有显著的变化。芦苇群落的物种丰富度在近两年有所增加。 湿地植物生长表现为明显的季节动态，生长的峰值大多在7月－8月。优势植物群落的物候与水文周期有关。湿地植物群落的物种组成和密度，可以作为对湿地监测和保护的生物指示。 5. 九寨沟湿地土壤种子库特征及其在湿地生物多样性恢复中的作用 水深和现存植被物种丰富度可以解释湿地土壤种子库的变化。水深可以解释表层物种丰富度45%的变化。现存植被物种丰富度可以分别解释10 cm土层、2－5 cm土层及5－10 cm土层土壤种子库45%、48%和25%的变化。 湿地土壤种子库的密度为0－15945粒m-2, 种子库中共发现23个物种。现存植被优势物种和种子库优势物种不同。各层土壤种子库密度和物种丰富度并不存在显著的差异，但第二层土壤种子库密度最大。海拔、现存植被优势种盖度、土壤总磷、土壤总氮、土壤有机碳对湿地土壤种子库的密度和垂直结构没有影响。土壤种子库物种丰富度小于地上植被物种丰富度。湿地土壤种子库与地上植被的相关性不大。在浅水区域，湿地土壤种子库在湿地植被恢复中有一定作用。但在深水区域，保护现存植被更重要。 The lakeshore wetlands are valuable ecological units of the Jiuzhaigou lakes. Pressure for travel industry development pose a continuing and severe threat to the biodiversity-support function of the wetland system. Despite the ecological importance of wetlands in Jiuzhaigou, they are so far poorly studied. Both general plant communties and biogeographical studies are needed in order to attain basis for sustainable use the wetland resources and adequate protection of these areas. The present study was undertaken to examine aquatic plants distribution and the species compositon, structure and growth dynamics of their communities with variations of environmental factors along altitudes, water depth and soil properities gradients in Jiuzhaigou. Analysis of field survey data collected during August 2004 and November 2007 in lakeshore wetlands in Jiuzhaigou National Nature Reserve, Sichuan, China. The results were as following: (i) Species composition and biogeography in wetland vegetation 8 families, 13 genus, 16 species of moss and 48 families, 107 genus and 199 species of vascular plants in Jiuzhaigou wetlands were found. The floristic compositions were abundunt. Ten geographical distribution types at family level, 13 geographical distributions types at generic level and 29 geographical distribution types at specific level in vascular plants were found. Most species in Jiuzhaigou wetlands are temperate elements and Chinese endemic elements, with a few of tropical and subtropical and some circumarctic elements. And the plant distributions show clear vertical and horizontal patterns. There were 21 major wetland plant community types. Species composition and species richness in different plant communities are different. The species diversity and plant community diversity and their high biomass are the basis for the diversity and stability of wetland landscapes in Jiuzhaigou. (ii) Water depth, soil nutrients and altitudes influence on the species diversity and plant distribution. Total phosphorous and organic cabon in soil were higher in C. pamiernensis and T. latifolia communities, where are important cabon reservoirs in Jiuzhaigou wetlands. Along gradients of water depth, among populations of the dominant plant species present: submerged macrophytes (Chara vulgaris, Potagemonton pectinatus, Veronica anagalis-aquatica，Hippuris vulgaris), emergent macrophytes (Equisetum fluviatile, Phragamites australis, Typha latifolia), helophytes (Carex pamirensis )and shrubs (Salix sp., Berberis sp. ). Altitudes influence on the assemblage of plant communities. Water depth negatively correlated with species richness. Specie richness showed differences between permanently flooded sites and seasonally flooded sites in E. fluvatile communities. And total nitrogen in soil was negatively correlated with species richness in E. fluviatile communities. Altitudes show no significant influence on species richness, but in fact, through our analyses, they do have influence on the assemblage of wetland plants. (iii) Water depth, soil nutrients influence on the plant growth Water depth influences the biomass allocation in Phragmities australis. The average aboveground biomass of a single ramet (4.2 g) was the largest in the habitat with water level 47 cm above the soil surface. At the habitat with water level under soil surface 15 cm (－15 cm), the leaf biomass percentage (of the total ramet biomass) was the largest (46.1%), and the height and percentage of ramose ramets ( with branches on stem )(of the total ramets in a plot) were found obviously different. The deeper in water, the larger the biomass percentage and growth rate of stems were. The flowering rate and biomass of panicles were greater in shallow water than those in deep water. Water depth negatively correlated with aboveground biomass of E. fluviatile. However, above-ground biomass of E. fluviatile showed no significant difference between permanently flooded sites and seasonally flooded sites. But in shallow water, more biomasses of accompanying species were found in dominant plant communities such as H. vulgaris communities, E. fluviatile communities and P. australis communities. Water depth, soil nutrients influence on shoot density and shoot length of wetland plants. The shoot density of E. fluviatile was correlated to water depth in all growth months. Annual average density was significantly lower at permanently flooded sites than at seasonally flooded sites. But the annual average shoot length was significantly lower at seasonally flooded sites than at permanently flooded sites. (iv) Growth dynamics of dominant communities in Jiuzhaigou wetland The shoot length and shoot density, coverage and biomass of domiant species were dominated in plant communities. The species composition increased in P. australis communities in recent two years. The species richness in E. fluviatile communities showed no difference between 2005 and 2007. The above-ground biomass and shoot density in Five－flower Lake from July 2005 to July 2007 were significantly different, while in other sites, the differences were not significant. Shoot height, shoot density and above-ground biomass showed significant seasonal changes in all sites. Growth dynamics correlated with the cycle of water levels in lakes. Most plants growth parameters peaked at July or August. The biomass of T. latifolia peaked in August. But the shoot length of T. latifolia in deeper water peaked in July. The shoot length of E. fluviatile increased significantly from May to August except in seasonally flooded sites in Arrow-bamboo Lake. The species composition of communities and shoot density can be used as bioindicators in Jiuzhaigou wetland. (v) Soil seed bank in Jiuzhaigou wetland and its role in vegetation restoration Seed density in all soil layer samples was negatively correlated to water depth. Water depth can explain 45% variance of species richness in surface layer in sediment. Species richness in extant vegetation can explain 45%, 48%, 25% variance of species richness in total 10 cm and in 2－5 cm and 5－10 cm layer sediment respectively. Mean seed densities in wetlands ranged from 0 to 15945 m–2. A total of 23 species germinated in seed bank. The dominant species in seed bank and extant vegetation showed great difference. The total number of species and seedlings that germinated in different layers was not significantly different. But the second layer had the greatest seed density. In shallow water, seed bank can contribute to vegetation restoration, while in deeper water, protection of extant vegetation may be a better strategy.

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.

Solid-state MAS NMR studies on the hydrothermal stability of the zeolite catalysts for residual oil selective catalytic cracking

By using the solid-state MAS NMR technique, the hydrothermal stabilities (under 100% steam at 1073 K) of HZSM-5 zeolites modified by lanthanum and phosphorus have been studied. They are excellent zeolite catalysts for residual oil selective catalytic cracking (RSCC) processes. It was indicated that the introduction of phosphorus to the zeolite via impregnation with orthophosphoric acid led to dealumination as well as formation of different Al species, which were well distinguished by Al-27 3Q MAS NMR. Meanwhile, the hydrothermal stabilities of the zeolites (P/HZSM-5, La-P/HZSM-5) were enhanced even after the samples were treated under severe conditions for a prolonged time. It was found that the Si-O-Al bonds were broken under hydrothermal conditions, while at the same time the phosphorous compounds would occupy the silicon sites to form (SiO)(x)Al(OP)(4 - x) species. With increasing time, more silicon sites around the tetrahedral coordinated Al in the lattice can be replaced till the aluminum is completely expelled from the framework. The existence of lanthanum can partially restrict the breaking of the Si-O-Al bonds and the replacement of the silicon sites by phosphorus, thus preventing dealumination under hydrothermal conditions. This was also proved by P-31 MAS NMR spectra. (C) 2004 Elsevier Inc. All rights reserved.

黄土高原地区南瓜优质施肥模式研究

安塞试验站2005~2006连续两年采用N、P、K三因素最优设计,田试不同施肥量对南瓜Vc和干物质两项营养品质的影响,探讨南瓜优质的N、P、K肥效反应模式。结果表明,N肥对南瓜Vc含量的影响最大,K肥对干物质含量的影响最大,N与P交互作用和N与K交互作用对南瓜Vc、干物质含量影响显著。筛选出南瓜优质的较佳施肥量为:施氮90~95 kg/hm2,施磷75~80 kg/hm2,施钾25~30 kg/hm2。N∶P2O5∶K2O=1.00∶0.83∶0.28

Synthesis, crystal structure and properties of H-8[P4W14O58Na4 (H2O)(20)] center dot 16H(2)O

A novel heteropoly tungstophosphates, H-8[P4W14O58Na4(H2O)(20)] . 16H(2)O, was synthesized by hydrothermal method and characterized by elemental analysis, IR spectrum and single-crystal X-ray structure analysis. The thermal stability of the compound was investigated by using TG-DTA. The crystal is triclinic system with space group P (1) over bar, a = 1. 137 9(2) nm, b=1. 363 2(3) nm, c=1. 627 1(3) nm; alpha=78. 20(3)degrees, beta=71, 20(3)degrees, gamma= 71. 62(3)degrees; V = 2. 252 5(8) nm(3), Z=1, M-r= 4 374. 38, D-c = 3. 225 mg/cm(3), mu = 18. 007 mm(-1), F(000)=1 972, R=0. 074 2, R-w=0. 200 4. The result of structure analysis shows that the anion of the compound consists of two PW7O29Na2(H2O)(10) subunits and two linked phosphorous atoms. A kind of microporous with size of 0. 661 4 nm X 0. 318 9 nm was formed in the crystal structure.

A new high efficiency green luminescent material - the system Al2O3-B2O3 containing Ce3+ and Tb3+ ions

To obtain high efficiency luminescent materials, the system Al2O3-B2O3 containing Ce3+ and Tb3+ ions with variation of B2O3-content, has been prepared by Al2O3, H3BO3, CeO2 and Tb4O7 under reducing atmosphere at 1250(j)ae. It is notable that the brightness of the sample with appropriate composition is similar to that of commercial phosphorous containing Ce3+ and Tb3+, indicating that a new high efficency green luminescent material was obtained with appropriate B2O3-content.

Synthesis and structure of [NH4](4)H[(PMo8V4V2O42)-V-IV-O-V].24H(2)O

[NH4](4)H[(PMo8V4V2O42)-V-IV-O-V] . 24H(2)O has been hydrothermally synthesized from ammonium vanadate and sodium molybdate in aqueous solution by adding phosphorous acid, and its structure determined by single crystal X-ray analysis. The heteropoly molybdovanadophosphate anion is a bicapped 'pseudo-Keggin' polyanion, two vanadium atoms are distributed at two 'capping' metal atom positions and other four vanadium atoms randomly distributed at eight metal atom positions. (C) 1998 Elsevier Science Ltd. All rights reserved.

The environment effect on fish assemblage structure in waters adjacent to the Changjiang (Yangtze) River estuary (1998-2001)

We collected fish abundance data in the Changjiang (Yangtze River) estuary and adjacent waters in November 1998, May 1999, November 2000, and May 2001. Using the data, we evaluated the characteristics of the fish assemblages at each site and investigated the effect of several environmental factors. We used a multivariate analysis, including community ordination methods such as detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA), and two-way indicator species analysis (TWINSPAN). We analyzed the biological community structure and environmental factors to determine their spatial distributions, temporal dynamics, and seasonal variations. Among the fish species, five exceeded 5% of the total abundance: Harpodon nehereus (42.82%), Benthosema pterotum (13.85%), Setipinna taty (11.64%), Thryssa kammalensis (9.17%) and Apogonichthys lineatus (6.49%). These were separated into four ecological assemblages: hypsithermal-saline, hypsithermal-brackish, hypothermal-brackish, and hypothermal-saline. We evaluated the degree of influence of environmental factors on the fish community. Our analyses suggested that environmental factors including water depth, salinity, turbidity, transparency, nutrient, and suspended matter formed a synthetic spatial gradient between the coastal and pelagic areas. Ecological and environmental factors changed temporally from 1998 to 2001, and drove the fish community succession. The environmental factors driving the fish community structure included bottom temperature, water depth, bottom and surface pH, surface total phosphorous, and bottom dissolved oxygen. This investigation was completed before completion of the Three Gorges Dam; therefore the results of this study provide an important foundation for evaluating the influence of the human activities.

Distribution characteristics of matrix-bound phosphine along the coast of China and possible environmental controls

Matrix-bound phosphine (MBP) concentrations in surface sediments collected from 37 stations along the coast of China in 2006 are reported. MBP was found in all samples and the average concentration was 6.30 ng kg(-1) dry weight (dw). The distribution of MBP showed certain spatial variation characteristics with high MBP concentrations at stations near to the coast. The average concentrations of MBP in the northern Yellow Sea (NYS), the southern Yellow Sea (SYS), the northern area of East China Sea (NECS), the southern area of East China Sea (SECS), and South China Sea (SCS) were 5.57 +/- 3.78, 3.78 +/- 2.81, 5.27 +/- 3.07, 5.48 +/- 4.05 and 13.52 +/- 7.86 ng kg(-1) dw. respectively. The correlations between MBP and influencing factors, such as the sedimentary environmental characteristics (sediment type, the grain size, contents of phosphorous, organic matters and redox potential) and the aquatic environmental characteristics (temperature, salinity, depth and hydrodynamics) were studied. The results indicated that MBP was strongly influenced by various factors, such as total phosphorus (TP), organic phosphorus (OP), organic carbon (OC), the grain size and hydrodynamics, all of which not only offered reasonable interpretations for the distribution characteristics of MBP but also provided evidence to support the viewpoint that phosphine originated from OP decomposition. This work is the first comprehensive study of the distribution of MBP along the coast of China and its relationships with environmental factors which will lead to a better understanding of the phosphorus (P) biogeochemical cycle in the sea. (C) 2008 Elsevier Ltd. All rights reserved.

Preliminary study on different nutrient pools supplies for the phytoplankton growth in the Jiaozhou Bay in China in the fall of 2004

The source and significance. of two mitrients, nitrogen. and phosphorous, were investigated by a modified dilution method performed on seawater samples from the Jiaozhou Bay in autumn 2004. This modified dilution method accounted for the phytoplankton growth rate, microzooplankton grazing mortality rate, the external nutrient pools, as well as nutrient supplied through remineralization by microzooplankton. The results indicated that the phytoplankton net growth rate increased in turn from inside the bay, to outside the bay, to in the Xiaogang Harbor. The phytoplankton, maximum growth rates and microzooplankton grazing mortality rates were 1.14 and 0.92 d(-1) outside the bay, 0.42 and 0.32 d(-1) inside the bay and 0.98 and 0.62 d(-1) in the harbor respectively. Outside the bay, the remineralized nitrogen (K-r = 24.49) had heavy influence on the growth of the phytoplankton. Inside the bay, the remineralized phosphorus(K-r = 3.49) strongly affected the phytoplankton growth. In the harbor, the remineralized phosphorus (K-r = 3.73) was in larger demand by phytoplankton growth. The results demonstrated that the different nutrients pools supplied for phytoplankton growth were greatly in accordance with the phytoplankton community structure, microzooplankton grazing mortality rates and environmental conditions. It is revealed that, nutrient remineralization is much more important for the phytoplankton growth in the Jiaozhou Bay than previously believed.

Tratamento de águas residuais

In this work, it is intended to expose the state of the art relating the use of microalgae in wastewater treatment. Nitrogen and phosphorous removal with microalgae is a common process. Biosorption by microlgae is an alternative to traditional treatment processes of metal ions removal. Neste trabalho pretende-se expor, de uma forma simples, o estado da arte no que diz respeito à utilização de microalgas para tratamento de águas residuais. São abordadas, com algum detalhe, as utilizações das microalgas para remoção de nutrientes e de metais pesadas de águas residuais.