Effects of cropping history and phosphorus source on yield and nitrogen fixation in sole and intercropped cowpea–maize systems

Symbiotic N₂-fixation, N uptake efficiency, biomass- and crop production of cowpea and maize as affected by P source, sole- and intercropped, and introduction of break crops were studied on a farmer’s fields in semi-arid Tanzania. Cowpea fixed around 60% of its N from the atmosphere amounting to 70 kg N ha⁻¹ under sole and 36 kg N ha⁻¹ under intercropping as estimated by the ¹⁵N isotope dilution method around peak biomass production. The amount of N₂-fixed was 30–40% higher when P was applied as either TSP or MRP whereas cowpea yield were unaffected. Intercropped maize with 19,000 plant ha⁻¹ accumulated the same amount of N as 38,000 sole cropped maize plants although intercropping reduced the dry matter accumulation by 25%. The N uptake efficiency of the applied ¹⁵N labelled fertiliser was 26%, which equal a total pool of early available plant N of 158 kg N ha⁻¹. Under the N deficient conditions, P application did not increase the grain yield of maize. The LER indicate that sole cropping required 18% more area than intercropping in order to produce the same grain yield, and 35% more land when LER was based on N uptakes. Introduction of break crops in the maize systems, more than doubled accumulation of dry matter and N in the grain compared to continuous maize cropping. During maturation sole crop cowpea shedded leaves containing 41 kg N ha⁻¹. The current findings underline the importance of crop diversity in Sub Saharan Africa agriculture and emphasise the need for including all residues, including shedded leaves, in nutrient balance studies.     

地下水固锰除铁工程设计

地下水固锰除铁工艺中在跌水曝气后过氧化问题一直是该工艺的关键内容,将跌水曝气池、滤池、反冲洗水池合建形成一体化固锰除铁单元,可以根据水量控制曝气强度,防止过曝气,稳定过滤水头,而且可以节约占地,减少滤池面积,并方便运行管理。     

跟骨粉碎骨折的手术治疗

目的评价手术治疗严重粉碎性跟骨骨折的临床疗效。方法对46例粉碎性跟骨骨折给予一期植骨,用可塑形跟骨钛钢板进行开放复位内固定手术治疗。采用Margland Foot Score系统进行术后功能评价。结果46例术后均获随访,时间8～60个月,平均16.6个月。骨折全部愈合。其中优32例,良9例,可4例,差1例,优良率89.1%。结论一期植骨,开放复位可塑形跟骨钛板内固定是治疗粉碎性骨折的良好方法。     

煤燃烧过程中各形态硫析出规律的研究

利用改进的自动测硫仪,以高有机硫北宿烟煤和高黄铁矿硫阳泉无烟煤作为研究对象,在不同温度下对原煤和脱无机硫煤在煤燃烧过程中硫析出特性进行了研究,另外对原煤和脱无机硫煤在热解和燃烧时硫形态的变化进行了研究．实验表明：黄铁矿硫、有机硫、煤中有机硫的分布在不同温度下具有不同的析出能力;煤热解和燃烧过程中各形态硫可以向其它形态转移,使硫的析出变得十分复杂．其结果对研究煤燃烧过程中硫的析出规律及燃中固硫有一定帮助．     

Binocular fixation disparity in single word displays.

It has been claimed that the recognition of words displayed in isolation is affected by the precise location at which they are fixated. However, this putative role for fixation location has yet to be reconciled with the finding from reading research that binocular fixations are often misaligned and, therefore, more than 1 location in a word is often fixated simultaneously. The accuracy and alignment of binocular fixations during single word processing have not been assessed previously. To investigate this issue, words were presented for lexical decision at locations around a central fixation point. Eye-tracking data revealed that participants often fixated inaccurately and that fixations were frequently misaligned, but that this did not affect word recognition. The findings show that binocular fixation disparity is pervasive even in single word displays and a potential source of confound for research into effects of fixation location on word recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

蚕丝丝胶戊二醛固着工艺的研究

本文就戊二醛（ＧＡ法）丝胶固着工艺和减少丝胶固着丝的黄变程度进行了研究，提出了高温短时间浸渍加脱水冷堆的ＧＡ法丝胶固着生产工艺。研究结果表明：在酸性条件下，添加适量稀土元素，采用酸性盐类作ｐＨ调节剂，适当降低固着时的ｐＨ值，能有效地提高丝胶固着牢度和降低固着丝的黄变程度．在弱碱性条件下，添加适当的缓冲稳定剂，能提高丝胶固着牢度和减少黄变现象。     

用于骨折内固定板的可吸收聚合物及其复合材料

综述了骨折内板材料的最新研究进展,阐述了可吸收聚合物（如聚乳酸,聚乙醇酸等）,自增强可吸收聚合物复合材料及碳纤维增强可吸收聚合物复合材料的机械性能及生物相容性,碳纤维增强可吸收聚合物复合材料是最有前途的内固定板材料。     

活性染料与甲壳胺纤维的成键稳定性研究

甲壳胺纤维用乙烯砜型活性染料染色,在中性条件下,其染料 纤维键的耐碱性明显好于碱性条件 下形成的染料 纤维键;成键的稳定性远高于纤维素纤维。其固着机理为:在中性条件下,活性染料与甲壳胺 纤维上的氨基形成共价键结合;在碱性条件下,还会与纤维上的羟基形成共价键结合,但耐碱性较差。双活 性基染料可在甲壳胺纤维大分子间形成交联,其中双侧型双活性基染料空间效应小,交联程度相对较高。     

Nitrogen fixation associated with grasses and cereals: Recent progress and perspectives for the future

Over the last 20 years many new species of N₂-fixing bacteria have been discovered in association with grasses, cereals and other non-nodulating crops. Virtually all of these bacteria are microaerophylic, fixing N₂ only in the presence of low partial pressures of oxygen. Until a few years ago much attention was focussed on members the genusAzospirillum and it was assumed that N₂ fixation was restricted to the rhizosphere or rhizoplane of the host plants. Through the use of N balance and¹⁵N techniques it has been shown that in the case of lowland rice, several tropical pasture grasses and especially sugar cane, the contributions of biological N₂ fixation (BNF) are of agronomic significance.More detailed study of the N₂-fixing bacteria associated with sugar cane (Acetobacter diazotrophicus andHerbaspirillum spp.) has shown that they occur in high numbers not only in roots of this crop but also in the stems, leaves and trash but are rarely found in the soil. Some of these endophytic diazotrophs have now also been found in forage grasses, cereals, sweet potato and cassava, although evidence of significant BNF contributions is still lacking.The identification of these endophytic diazotrophs as the organisms probably responsible for the high contributions of N₂ fixation observed in sugar cane suggests that it may be possible to attain significant BNF contributions in some other gramineae and perhaps root crops.