麦秸/聚氨酯复合人造板的工艺对其吸声系数的影响研究

通过变化麦秸和聚氨酯的比例、麦秸/聚氨酯复合人造板的密度、以及发泡温度,研究了麦秸/聚氨酯复合人造板在不同的声波频率下的吸声系数。试验结果表明:在不同的声波频率下,发泡温度的高低对麦秸/聚氨酯复合人造板的吸声系数有不同的影响;麦秸/聚氨酯复合人造板的密度与其吸声系数的大小关系密切;在声波频率为250～4 000Hz区域内,麦秸和聚氨酯的比例对麦秸/聚氨酯复合人造板的吸声系数影响较大。     

Biomass production of Eucalyptus boundary plantations and their effect on crop productivity on Ethiopian highland Vertisols

In recent years, Eucalyptus globulus planted along field boundaries has come to dominate the central highland landscape of Ethiopia. Although evidence is scanty, there is a perception that this practice adversely affects crop productivity. An on-farm trial was conducted on Pellic Vertisol at Ginchi to determine the production potential of eucalypt boundaries and their effect on the productivity of adjacent crops of tef (Eragrostis tef) and wheat (Triticum sp.). The experiment comprised three stand ages, four field aspects and six distances from the tree-crop interface, using a split-split plot design with three replicates. Wood production rates ranged between 168 kg ha⁻¹ y⁻¹ (four years old) and 2901 kg ha⁻¹ y⁻¹ (twelve years). Thus eucalypt boundaries planted on a hectare of land would satisfy 50 to 75% of the annual biomass energy requirement of a rural household of five persons. Significant depression of tef and wheat yields occurred over the first 12m from the tree line: the reduction was 20 to 73% for tef and 20 to 51% for wheat, equivalent to yield losses of 4.4 to 26% and 4.5 to 10% per hectare respectively. Nevertheless, in financial terms, the tree component adequately compensated for crop yield reduction and even generated additional income. Therefore, eucalypt boundaries have great potential to satisfy the rising demand for wood, without requiring a major change in land use on the highland Vertisols. The greater availability of wood will reduce the demand for dung and crop residues for fuel, and thus may contribute to improved soil management on croplands while relieving the increasing pressure on indigenous forest and woodlands.     

异氰酸酯胶麦秆刨花板施胶量的研究

以ＭＤＩ为胶粘剂制备麦秸刨花板，并通过试验确定合理的ＭＤＩ施加量。试验结果证明：①施胶量４％～５ ％可生产出合格的麦秸刨花板；在较佳工艺条件下，施胶量可降低至３％；②施胶量对产品ＴＳ有显著影响，对ＩＢ有影响，而对ＭＯＲ，Ｄ，Ｗ影响不大。     

密山至兴凯湖旅游公路冬季土方施工

本文叙述了冬季土方施工的方法、步骤和要点。     

Winter soil CO2 efflux in two contrasting forest ecosystems on the eastern Tibetan Plateau,China

Significant CO2 fluxes from snow-covered soils occur in cold biomes. However, little is known about winter soil respiration on the eastern Tibetan Plateau of China. We therefore measured winter soil CO...     

改性UF麦秸均质刨花板的工艺研究

通过试验确定了麦秸均质刨花板的主要工艺参数。其结果表明：１０ｍｍ厚麦秸均质刨花板的较优工艺参数为热压温度１５０℃、热压时间８ｍｉｎ、表层麦秸刨花的施胶量为１０％、芯层麦秸刨花的施胶量为８％、板密度０．７５ｇ／ｃｍ３、表芯层刨花比例为３：７。按照以上工艺条件压制的麦秸均质刨花板性能已达到均质刨花板的要求。     

小麦TaCYP78A5基因的克隆及生物信息学分析

细胞色素P450(Cytochromes P450)蛋白家族含有硫羟基和血红素结构域,参与多种生物合成,CYP78A家族成员对籽粒大小形成有重要的功能。利用同源克隆的方法,分别从小麦大粒品系‘P271’和小粒材料‘中国春’中扩增到位于2AS、2BS、2DS上的TaCYP78A5-2A、TaCYP78A5-2B和TaCYP78A5-2D基因,编码534、544、549个氨基酸。通过分析发现在‘P271’和‘中国春’克隆到的TaCYP78A5序列一致,说明TaCYP78A5基因在这2个粒型的小麦中是保守的。CYP78A家族在水稻和拟南芥中具有非自主性细胞表达模式,结合对CYP78A家族的生物进化关系研究发现,CYP78A家族的各个基因在单子叶植物中是保守的。‘P271’和‘中国春’籽粒大小的差异,可能是TaCYP78A5基因在‘P271’中的基因表达量高于‘中国春’,引起种子发育过程中内表皮细胞的增殖,从而促进种子表皮增大,使得‘P271’种子大小和质量增加。     

Responses of glutamine synthetase activity and gene expression to nitrogen levels in winter wheat cultivars with different grain protein content

Glutamine synthetase (GS) plays a central role in plant nitrogen (N) metabolism, which improves crops grain protein content. A pot experiment in field condition was carried out to evaluate GS expression and activity, and grain protein content in high (Wanmai16) and low grain protein (Loumai24) wheat cultivars under two N levels (0.05 and 0.15 g N kg⁻¹ soil). High nitrogen (HN) resulted in significant increases in GS1 and GS2 expression at 10 days after anthesis (DAA), and higher GS activity during the entire grain filling stage. HN also significantly increased yield, grain protein content and protein fraction (except for glutenin of Luomai24) in two wheat cultivars, which indicated that it increased grain yield and protein content by improving nitrogen metabolism. Wanmai16 showed higher grain protein content, gliadin and glutenin content, and had higher expression level of GS2 both in flag leaves and grains at early grain filling stage. However, Luomai24 had greater yield and higher expression level of GS1. The difference expression of GS2 and GS1 genes indicates they had various contributions to the accumulation of protein and starch in wheat grains, respectively. The results suggest that GS2 would be serving as a potential breeding target for improving wheat quality.     

磷肥用量对冬作马铃薯镁素积累与分配特征的影响

以费乌瑞它脱毒种薯为材料,通过大田试验研究4个磷肥水平,即0(P0)、45.0(P1)、90.0(P2)、135.0(P3)kg/hm~2对冬作马铃薯镁积累与分配特征的影响。结果表明:各处理马铃薯整株镁积累量呈先升高后降低变化趋势,齐苗后17~45 d为快速积累期,在齐苗后59 d出现峰值,齐苗后73 d,各处理全株镁积累量表现为:P1P2P3P0;块茎镁积累量呈持续升高趋势,齐苗后73 d,各处理块茎镁积累量表现为:P1P2P3P0,但各处理间并未产生显著差异;各处理镁在叶片中的分配比例均呈逐渐降低趋势;镁在茎中的分配比例整体呈逐渐降低趋势,变幅不大,而在块茎中的分配比例呈持续上升趋势;整个生育期间,镁在各生育阶段各器官的分配比例呈现:叶茎(齐苗后3 d);叶茎块茎(齐苗后17 d);叶块茎茎(齐苗后31~45 d);块茎叶茎(齐苗后59~73 d)的动态变化过程,镁在块茎中的分配率以P1处理最大,为60.38%。供试条件下,磷肥施用量在P1水平下可提高马铃薯镁积累量,P2、P3水平的用量则会降低镁的积累;平均每生产1 000 kg块茎,植株需从土壤中吸收镁0.253 kg.     

Effect of steam explosion on enzymatic hydrolysis and baking quality of wheat bran

In this study, the effect of steam explosion (SE) treatment on microstructure, enzymatic hydrolysis and baking quality of wheat bran was investigated. Coarse and fine bran were treated at different steam temperatures (120–160 °C) and residence times (5 or 10 min) and then hydrolysed with carbohydrase enzymes. The SE treatment increased water extractable arabinoxylan (WEAX) content from 0.75 to 2.06% and reducing sugars from 0.92 to 2.41% for fine bran. The effect was more pronounced with increased SE temperature and residence time. The highest carbohydrate solubilisation was observed in fine bran at SE treatment of 160 °C, 5 min. WEAX content increased to 3.13% when this bran was incubated without enzyme, while WEAX content increased to 9.14% with enzyme addition. Microscopic analysis indicated that cell wall structure of wheat bran was disrupted by severe SE conditions. Supplementation of SE treated (150 °C, 10 min) bran at 20% replacement level decreased the baking quality of bread. However SE followed by enzymatic hydrolysis increased specific volume and decreased crumb hardness (on the day of baking and after three days of storage). Phytic acid content of bread supplemented with SE treated bran was lower than the one supplemented with untreated bran.