Response of soil physical properties to tillage and residue management on two soils in a cool temperate environment

In view of their potential benefits, reduced or no tillage (NT) systems are being advocated worldwide. Concerns about impairment of some soil conditions, however, cast doubt on their unqualified acceptance. We evaluated the effects of 6 years of tillage and residue management on bulk density, penetration resistance, aggregation and infiltration rate of a Black Chernozem at Innisfail (loam, 65 g kg⁻¹ organic matter, Udic Boroll) and a Gray Luvisol at Rimbey (loam, 31 g kg⁻¹ organic matter, Boralf) cropped to monoculture spring barley (Hordeum vulgare L.) in a cool temperate climate in Alberta, Canada. Tillage systems were no tillage and tillage with rototilling (T), and two residue levels were straw removed (−S) and straw retained (+S). Bulk density (BD) of the 0–7.5 and 7.5–15 cm depths was significantly greater under NT (1.13–1.58 Mg m⁻³) than under T (0.99–1.41 Mg m⁻³) in both soils, irrespective of residue management. In both soils, penetration resistance (PR) was greater under NT than under T to 15 cm depth. Residue retention significantly reduced PR of the 0–10 cm soil in NT, but not in T. In the 0–5 cm depth of the Black Chernozem, the >2 mm fraction of dry aggregates was highest under NT + S (72%), and lowest under T − S (50%). The wind-erodible fraction (dry aggregates <1 mm size) was smallest (18%) under NT + S and largest (39%) under T − S. Soil aggregation benefited more from NT than from residue retention. Proportion of wind-erodible aggregates was generally greater in the Gray Luvisol than in the Black Chernozem. In the Black Chernozem, steady-state infiltration rate (IR) was significantly lower (33%) under NT than under T. Residue retention improved IR in both NT and T. In the Gray Luvisol, IR was not significantly affected by tillage and residue management. Despite firmer soil, NT and residue retention are recommended to improve aggregation in the cool temperate region of Western Canada.     

基于聚合分解协调的多水源水资源合理调配研究

为了使南水北调工程能够最大限度地缓解河北省严重缺水状况,更好地发挥工程效益,以南水北调河北段为研究对象,研究南水北调受水区水资源供需平衡问题。在系统分析水资源系统特点基础上,建立一个考虑当地水、南水北调水、中水及地下水等多水源的水资源合理调配模型,采用大系统理论中的聚合分解协调思想进行求解,得到优化调置方案,合理解决了多水源、多用户、多保证率的水资源配置问题,模型计算结果可为受水区水资源可持续利用提供科学依据。     

Tau propagation and its modulation in Alzheimer's disease

The microtubule-associated protein tau plays an important role in maintaining microtubule stabiliza-tion, while the aggregation of hyperphosphorylated tau takes part in the pathophysiology of Alzheimer's disease. Recent studies show that the tau in pathological forms behaves like a prion, which can be propagated between cells and different brain regions. Oligomeric tau clusters in the affected neurons can be released as pathological " seeds" through vesicular and non-vesicular mechanism, then enter the recipient neuron through endocytosis and receptor-mediated uptake. The rate of tau propagation is modulated by the change of β-amyloid, or the activity of neuronal as well as glial cell. With better under-standings on pathological tau propagation, it is hoped that a novel therapy targeting the transmission of tau pathology will be developed for the treatment of Alzheimer's disease.     

我国茶销售市场的空间布局与影响因素研究

对我国茶销售市场进行空间分布特征的研究,有助于茶产业的供需平衡.本文利用地理集中指数和GIS技术,从空间分布类型、均衡性和分布密度3个方面来分析我国茶销售市场空间分布特征.结果表明,我国茶类经营点整体呈集中化分布,但集聚性稍弱,全国范围内高密度核心地区包括广州、南京和郑州等为核心的周边部分城市,而西部等地区大多未形成相...     

凉水实验林场不同类型红松林空间分布格局

以小兴安岭凉水自然保护区不同类型的红松(Pinus koraiensis sie.et Zucc)林作为研究对象,基于10块标准地的样地调查数据,对红松天然林、红松人工纯林、人工红松阔叶混交林和林隙透光抚育后的红松对照林进行对比,采用方差/均值比率法,并结合其它4种聚集度指标,分析和研究了它们的立木空间分布格局。结果表明,林隙透光抚育的红松对照林的空间分布格局为聚集分布,相同立地条件的红松天然林、红松人工纯林和人工红松阔叶混交林的空间分布格局均为随机分布。     

Aggregation behavior of wheat gluten during carboxylic acid deamidation upon hydrothermal treatment

Changes of aggregation behavior of wheat gluten during carboxylic acid deamidation upon hydrothermal treatment were investigated to test the influences of deamidation on the aggregation extent of wheat gluten. Hydrothermal treatment induced that the size of soluble wheat gluten aggregate progressively increased by cross-linking of gliadins and slowly cleaved glutenins. But significant changes in molecular weight distribution, solubility under six denaturing agents’ treatment and Zeta potential of wheat gluten aggregates were observed at 6 min heating time and distinct shift of intra-/inter-molecular interactions of wheat gluten aggregates occurred before and after 6 min heating treatment respectively. Moreover, as heating time increased, the island-like aggregates decreased markedly and the striped aggregates increased notably. To explain the aggregation behavior in this case, we postulated that the extent of aggregation of wheat gluten depended on the balance between intra-/inter-molecular electrostatic repulsion, the non-covalent and disulfide bonds formation in the system. Hence, a scheme was drawn, which appeared to be the mechanism responsible for the aggregation of wheat gluten through thermal cross-linking and opening up of the network structure of wheat gluten aggregates by deamidation.     

宁夏荒漠草原白星花金龟成虫空间分布型的初步研究

通过对白星花金龟(Potosia brevitaris Lewis)成虫空间分布格局的测定,应用聚集度指标法、Taylor幂法则和Iwao回归法对白星花金龟成虫的空间分布型进行分析和检验,以期对该害虫实施预测预报及防治提供科学依据。结果表明:白星花金龟成虫在盐池荒漠草原呈聚集分布,分布的基本单位是个体群,引起聚集的原因主要是白星花金龟成虫自身习性,与环境因素也有一定关系。种群数量动态研究显示白星花金龟种群数量在6个不同样带表现基本一致,除了撂荒2年后形成的以蒙古冰草(Agropyron mongolicum)为优势植物的样带外其他样地也都出现3次高峰。     

Aggregate formation of zein and its structural inversion in aqueous ethanol

Zein is a prolamine of maize. Conventionally, 70–90% aqueous ethanol is used to dissolve zein. When the hydrodynamic radii of zein molecules in aqueous ethanol were monitored with a dynamic light scattering instrument, it was found that zein aggregates in the solvent and the degree of aggregation depends on the composition of the solvent mixture. As the ethanol content of solvent increased from 70% to 90%, the aggregation number of zein molecules decreased from 10,000 until it reached a minimum. The aggregation number then increased abruptly to greater than 10,000 as the ethanol content of the solvent mixture increased to 92%. Since zein has amphiphilic characteristics, this behavior was interpreted as the formation of a micelle-like structure in its solution whereby ca. 90% ethanol that showed minimum aggregation number is regarded as a structural inversion point. This point of view was supported by a simple experiment that showed selective interaction of zein molecules with hydrophilic or hydrophobic particles.     

Spatial distribution of Collembola in presence and absence of a predator

Many Collembola species are characterised by an aggregative behaviour, which is closely related to communication and co-ordination between individuals. In spite of a general heavy predation pressure, a large number of Collembola is found in soil suggesting that they have developed defence strategies against predators.

This study investigates changes in spatial structure of gregarious Collembola species in presence of a predator. It is analysed if the gregarious lifestyle of Collembola populations functions as a defence strategy against predation. In presence of a predator distances between individuals in the Collembola species Folsomia candida and Heteromurus tetrophthalmus became closer, reducing the risk of individuals to be captured by predators. On the contrary, Onychiurus sinensis specimens, which were never caught probably because of the extrusion of repelling fluids by means of their pseudocelli, moved away from each another. Besides being a successful chemical defence against predation, repelling fluid secretion may effectively repel conspecifics, thereby keeping individuals at greater distance.     

桉蝙蛾幼虫空间分布型的研究、

[目的]研究桉蝙蛾幼虫的空间分布型。[方法]通过对广西北流市和陆川县等地的桉树人工林进行幼虫分布调查,共设10块标准地,采用6种不同的聚集度指标和回归模型分析法判断桉蝙蛾幼虫的空间分布格局。[结果]桉蝙蛾幼虫主要分布在1m以下树干基部;按蝙蛾幼虫的空间分布型主体为聚集分布,是环境因素的作用结果。桉蝙蛾幼虫在不同虫口密度下最适抽样数公式n=t2（1.1/m＋0.6744）/D2和序贯抽样决策限模式：T’0（n）,T″0（n）=n±1.332槡n（取m0=1）。[结论]研究结果为桉蝙蛾的调查取样和预测预报工作提供了科学依据。