Carbonating magnesia for soil stabilization

This paper investigates the potential for carbonating reactive magnesia (MgO) to serve as a more sustainable soil stabilization method by providing rapid and significant strength development of the stabilized soil through absorbing substantial quantities of CO2. Gaseous CO2 was forced through laboratory-prepared reactive MgO-treated soil samples in a triaxial cell set-up, and their resulting mechanical and microstructural properties were investigated using unconfined compressive strength, X-ray diffraction, and scanning electron microscopy. The results showed that adequately carbonated MgO-treated soils could, in a few hours, reach a similar strength range to corresponding 28 day Portland cement (PC)-stabilized soils. Hydrated magnesium carbonates, namely nesquehonite and hydromagnesite-dypingite, were the main products of the carbonated MgO in the soil, and were responsible for the significant strength development.

EFFECT OF ELEVATED BICARBONATE CONCENTRATION ON GROWTH, CHLOROPHYLL A FLUORESCENCE AND ULTRA-STRUCTURE OF Microcystis aeruginosa (CYANOBACTERIUM)

The influence of bicarbonate (HCO3-) on Microcystis aeruginosa FACHB 905 was assessed in this study. Growth curves, chlorophyll a fluorescence and ultrastructure were measured at two HCO3- concentrations, 2.3 mM and 12.4 mM. A treatment of sodium chloride (NaCl) was also conducted alongside to establish the influence level of sodium. It was found that upon treatment with elevated HCO3- concentrations of 2.3 mM and 12.4 mM, cell densities were 13% and 27% (respectively) higher than controls. In photosynthetic performance, elevated HCO3- concentration initially stimulated Fv/Fm at the prophase of culture and then subsequently inhibited it. The inhibition of 2.3mM was higher than that of 12.4mM HCO3-. The maximum relative electron transport rate (ETRmax) exhibited inhibition at elevated HCO3- concentrations. DI0/CS was decreased at 2.3 mM and increased at 12.4mM. In the case of both treatments. ABS/CSI TR0/CS, ET0/CS, RC/CS0 and RC/CSm were decreased by elevated HCO3- concentrations, which indicated damage to photosynthetic apparati and an inactivation of a fraction of reaction centers. This point was also proven by ultrastructural photos. High HCO3--exposed cells lost the characteristic photosynthetic membrane arrangement compared with the control and high salinity treated samples. At the 2.3mM concentration of HCO3-. damage to photosynthetic apparati caused decreased photosynthetic activity. These findings suggested that elevated HCO3- concentration stimulated the growth and photosynthesis of M. aeruginosa FACHB 905 in a short time. Exposure to high HCO3- concentrations for a longer period of time will damage photosynthetic apparatus. In addition, the ultrastructure indicated that elevated HCO3--concentration lead to photosynthetic apparati damage. In our experiment, it was observed that the inhibition effect of 2.3mM HCO3- was higher than that of 12.4mM HCO3-. We hypothesized that M. aeruginosa FACHB 905 induced a protective mechanism under high concentrations of HCO3-.

Carbon source/sink function of a subtropical, eutrophic lake determined from an overall mass balance and a gas exchange and carbon burial balance

Although studies on carbon burial in lake sediments have shown that lakes are disproportionately important carbon sinks, many studies on gaseous carbon exchange across the water-air interface have demonstrated that lakes are supersaturated with CO2 and CH4 causing a net release of CO2 and CH4 to the atmosphere. In order to more accurately estimate the net carbon source/sink function of lake ecosystems, a more comprehensive carbon budget is needed, especially for gaseous carbon exchange across the water-air interface. Using two methods, overall mass balance and gas exchange and carbon burial balance, we assessed the carbon source/sink function of Lake Donghu, a subtropical, eutrophic take, from April 2003 to March 2004. With the overall mass balance calculations, total carbon input was 14 905 t, total carbon output was 4950 1, and net carbon budget was +9955 t, suggesting that Lake Donghu was a great carbon sink. For the gas exchange and carbon burial balance, gaseous carbon (CO2 and CH4) emission across the water-air interface totaled 752 t while carbon burial in the lake sediment was 9477 t. The ratio of carbon emission into the atmosphere to carbon burial into the sediment was only 0.08. This low ratio indicates that Lake Donghu is a great carbon sink. Results showed good agreement between the two methods with both showing Lake Donghu to be a great carbon sink. This results from the high primary production of Lake Donghu, substantive allochthonous carbon inputs and intensive anthropogenic activity. Gaseous carbon emission accounted for about 15% of the total carbon output, indicating that the total output would be underestimated without including gaseous carbon exchange. (C) 2007 Elsevier Ltd. All rights reserved.

Different tolerances and responses to low temperature and darkness between waterbloom forming cyanobacterium Microcystis and a green alga Scenedesmus

The dynamics of planktonic cyanobacteria in eutrophicated freshwaters play an important role in formation of annual summer blooms, yet overwintering mechanisms of these water bloom forming cyanobacteria remain unknown. The responses to darkness and low temperature of three strains (unicellular Microcystis aeruginosa FACHB-905, colonial M. aeruginosa FACHB-938, and a green alga Scenedesmus quadricauda FACHB-45) were investigated in the present study. After a 30-day incubation under darkness and low temperature, cell morphology, cell numbers, chlorophyll a, photosynthetic activity (ETRmax and I-k), and malodialdehyde (MDA) content exhibited significant changes in Scenedesmus. In contrast, Microcystis aeruginosa cells did not change markedly in morphology, chlorophyll a, photosynthetic activity, and MDA content. The stress caused by low temperature and darkness resulted in an increase of the antioxidative enzyme-catalase (CAT) in all three strains. When the three strains re-grew under routine cultivated condition subjected to darkness and low temperature, specific growth rate of Scenedesmus was lower than that of Microcystis. Flow cytometry (FCM) examination indicated that two distinct types of metabolic response to darkness and low temperature existed in the three strains. The results from the present study reveal that the cyanobacterium Microcystis, especially colonial Microcystis, has greater endurance and adaptation ability to the stress of darkness and low temperature than the green alga Scenedesmus.

Applicability of the MTT assay for measuring viability of cyanobacteria and algae, specifically for Microcystis aeruginosa (Chroococcales, Cyanobacteria)

Several assay methods were screened for viability assessment in cyanobacteria using Microcystis aeruginosa FACHB 905. Compared with fluorescent diacetate (FDA), Evan's Blue and autofluorescence, the 3-[4,5-dimethylthiazol-2-yl]2,5-diphenyl tetrazolium bromide (MTT) assay, which was based on the ability of viable cells to reduce MTT to formazan, was found to be reliable and was selected for further study. MTT concentration, incubation time and temperature were optimized for M. aeruginosa. Improvements to the sensitivity and reproducibility of the MTT assay included performing it in the dark to reduce the effects of formazan light sensitivity when extracted in DMSO. Another improvement involved collecting viability data by cell by counting rather than colourimetrically, which was concluded from the fact that oxidoreductase activity, responsible for MTT reduction, would elevate or decrease under stress conditions. Half-life of oxidoreductase in dead cell was calculated to be 3 h. The MTT assay was also found to be applicable to other cyanobacteria and diatoms, including field samples, but not for algae belonging to Chlorophyta, Euglenophyta, Pyrrophyta or Chrysophyta. Based on the above results, we proposed an optimized procedure for the MTT method on Microcystis strains. The use of this assay may be of importance to better understand the dynamics of bloom and the fate of Microcystis under natural or disturbed conditions.

The adoption of sustainable remediation behaviour in the US and UK: a cross country comparison and determinant analysis.

The sustainable remediation concept, aimed at maximizing the net environmental, social, and economic benefits in contaminated site remediation, is being increasingly recognized by industry, governments, and academia. However, there is limited understanding of actual sustainable behaviour being adopted and the determinants of such sustainable behaviour. The present study identified 27 sustainable practices in remediation. An online questionnaire survey was used to rank and compare them in the US (n=112) and the UK (n=54). The study also rated ten promoting factors, nine barriers, and 17 types of stakeholders' influences. Subsequently, factor analysis and general linear models were used to determine the effects of internal characteristics (i.e. country, organizational characteristics, professional role, personal experience and belief) and external forces (i.e. promoting factors, barriers, and stakeholder influences). It was found that US and UK practitioners adopted many sustainable practices to similar extents. Both US and UK practitioners perceived the most effectively adopted sustainable practices to be reducing the risk to site workers, protecting groundwater and surface water, and reducing the risk to the local community. Comparing the two countries, we found that the US adopted innovative in-situ remediation more effectively; while the UK adopted reuse, recycling, and minimizing material usage more effectively. As for the overall determinants of sustainable remediation, the country of origin was found not to be a significant determinant. Instead, organizational policy was found to be the most important internal characteristic. It had a significant positive effect on reducing distant environmental impact, sustainable resource usage, and reducing remediation cost and time (p<0.01). Customer competitive pressure was found to be the most extensively significant external force. In comparison, perceived stakeholder influence, especially that of primary stakeholders (site owner, regulator, and primary consultant), did not appear to have as extensive a correlation with the adoption of sustainability as one would expect.

太阳能干燥器透光盖层最佳倾角的研究

本文详细讨论了温室型干燥器或集热—温室型干燥器透光盖层最佳倾角的数学物理模型，导出了确定干燥器盖层最佳倾角的计算公式，并通过对北纬20°—40°地区的计算分析，提出了温室型干燥器的设计准则和计算公式。

生物质富氧气化特性的研究

富氧气化是先进的中热值气化方法之一，具有设备体积小、运行稳定等优点。从富氧气化的原理出发，分析氧气浓度、气化当量比等因素对气化结果的影响，并在实验的基础上，分析讨论提高富氧气化经济性和实用性的途径，总结得到循环流化床富氧气化的最佳运行条件：氧气浓度（90±5）%，气化当量比约0.15

黄河河龙区间河流泥沙对相关重大事件与政策的响应

利用径流- 输沙量双累积曲线与单位降雨侵蚀力输沙量(输沙量负荷)的分析表明,河龙区间泥沙变化与相关重大事件与政策密切相关。“大开荒”时期输沙量负荷平均值最大,是输沙量负荷多年平均值的1. 8倍; “大跃进”、“农业学大寨”和“文革”时期的输沙量负荷均值也较大,为输沙量负荷多年平均值的1. 4～1. 5倍。改革开放后,输沙量负荷下降明显,输沙量负荷平均值较改革开放前减少了55. 7% ,特别是在1999年实施“退耕还林(草) ”后,输沙量负荷平均值下降到整个时期的最小值,仅为输沙量负荷多年平均值的33. 3%。

贾第虫的核仁基因组与真核细胞核仁的起源进化

核仁是真核细胞核中最明显的结构，是rRNA转录、加工和核糖体亚基组装的场所。核仁的起源进化无疑是真核细胞起源进化问题的一个极为重要的方面。但迄今为止，这方面的研究很少。本文首先对"不具核仁"的低等单细胞真核生物贾第虫的"核仁"基因及核糖体合成系统的基因群进行了研究，进而对已知的核仁蛋白质组的生物进行了比较基因组研究，从而从基因和基因组的角度对核仁的起源进化问题进行了较为深入的研究。获得了如下结，和结论：1）在"不具核仁"的贾第虫中分离鉴定出了典型真核细胞参与pre-rRNA加工的krr］基因；表明贾第虫中的pre-rRNA加工机制与典型真核细胞的是一致的。在具有核仁结构的典型真核细胞中，krr1基因所编码的KRRIP蛋白是参与Pre一rRNA加工的核仁定位蛋白之一。我们在一度被认为是极为原始的"不具核仁结构"的真核生物－贾弟虫的基因组中分离鉴定出了该基因，并证明该基因在贾第虫中是活跃转录的。同时，还调查发现与KRRIP形成蛋白复合体从而发挥功能的众场，其基因在贾第虫中也是存在的，这提示贾第虫的pre寸RNA加工机制与具有核仁结构的典型真核细胞是一致的。2）对贾第虫核糖体合成系统的基因群／亚基因组进行了全面调查，发现在典型真核生物中所共有的参与核搪体合成的129条保守蛋白基因中有89条在贾第虫基因组具有相应的直系同源基因，包括编码参与rRNA申基化和假尿嗜陡化的蛋白复合体成员以及存在于905、405和605复合体中的蛋白等诸多重要基因。这表明贾第虫的核糖体合成系统与典型的真核生物相似，只是参与的成分相对简单些。以上1）、2）的结果表明贾第虫虽然没有核仁结构，但其核糖体合成机制却与具核仁结构的典型真核细胞一致。这可能意味着真核细胞核仁的核糖体合成功能的起源形成是在核仁结构形成之前，那么核仁结构的形成可能是在此功能之外另有"新意"；另外也可能是由于贾第虫因适应寄生生活而导致核仁"退化"之故，虽然这种可能性偏少，但若果真如此也是生物适应性进化中的一个重要现象，值得深入研究。3）对已知核仁蛋白质组的人、酵母和拟南芥进行了比较基因组学研究。通过搜索KOG直系同源蛋白簇数据库，发现约74％的人的核仁蛋白，约75％的酵母的核仁蛋白以及约84％的拟南芥的核仁蛋白在动物、真菌和植物中都保守。这表明这些高等真核生物的核仁蛋白大都在它们分化之前就已起源形成。进一步的调查发现：共同定位于人和酵母核仁中的同源蛋白中，人有154条蛋白对应于酵母的134条蛋白，其中人的核仁蛋白相对于酵母的有10条蛋白发生了基因重复；同样的分析发现，人的核仁蛋自相对于拟南芥的有21条蛋白发生了基因重复。这些事实表明：随着真核生物的进化，至少在高等真核生物中基因重复是核仁成分复杂化和核仁进化的重要途径。4）用人的442条核仁蛋白（它们在植物和真菌中也都存在同源蛋白，但不一定是核仁蛋白）对原核生物基因组进行了搜索。结果表明，在真细菌和原（古）细菌中都能找到好多同源物，但发现下列重要现象：只在原（古）细菌有同源物的核仁蛋白要比只在真细菌中有同源物的核仁蛋白多得多，包括了RNA修饰蛋白、核糖体蛋自以及参与翻译的相关蛋白等；而只在真细菌中有同源物的核仁蛋白只是RNA螺旋酶和WD重复蛋白。因此，我们认为核仁可能是由真细菌和原细菌复合起源的，但其主体起源于原细菌。

nc-Si／SiN_x超晶格薄膜实现Nd

采用射频磁控反应溅射法制备a—Si／SiN。超晶格薄膜材料，热退火后形成纳米Si晶粒。把nc—Si／SiN，薄膜作为饱和吸收体插入Nd