超声辅助制备抗冻融大豆分离蛋白工艺优化

为了提高大豆蛋白冻融稳定性,研究了超声波辅助下大豆分离蛋白(soybean protein isolate,SPI)与葡聚糖(dextran,D)发生美拉德反应改性蛋白的方法,以乳化稳定性(emulsion stability index,ESI)和乳析指数(creaming index,CI)为响应值,建立了优化工艺的Box-Behnken模型。验证试验表明,模型具有重现性和可靠性,在SPI质量浓度40 mg/m L、超声温度80℃、比功率5 W/m L条件下,与未改性SPI相比,改性后SPI乳化稳定性提高了43.80%,经1、2、3次冻融循环后乳析指数分别降低了57.76%、75.33%、96.20%。接枝物制备的乳液经冻融循环后粒径维持在50~55μm。红外光谱分析接枝物在1 010 cm-1处的C-N共价键振动增强,说明SPI和葡聚糖是以共价键的方式结合。扫描电镜结果表明,改性后蛋白颗粒更加疏松,分子间聚集程度降低。研究结果为冷冻食品专用大豆分离蛋白的产业化生产提供了理论和技术指导。     

转移矩阵法评价土壤团聚体的稳定性

团聚体稳定性是土壤的基本性质,反映了土壤肥力的高低。在3个合理假设的基础上,通过建立干筛和Yoder法湿筛结果之间的转移矩阵,并通过不同径级团聚体的保存率构造了团聚体稳定性指数。该稳定性指数与文献结果具有良好的一致性,说明了转移矩阵方法可用于土壤团聚体稳定性的评价。同时利用该方法分析了不同径级团聚体抗破裂能力大小,发现降雨模拟、干湿循环(1次)、干湿循环(10次)和Yoder湿筛法影响的团聚体粒径并不相同。>0.25 mm水稳性团聚体含量虽然在整体上与团聚体的稳定性具有良好的相关性,但并不是随着>0.25 mm水稳性团聚体含量的增高,每个径级范围的团聚体稳定性增强。该方法可充分利用团聚体分析所得的信息,为进一步认识土壤团聚体的稳定性提供方法支撑。     

Determination of biological stability in compost: A comparison of methodologies

Biological [dynamic respiration index (DRI); chemical humification indexes: humification index (HI), degree of humification (DH) and humification rate (HR); and thermoanalytical (thermostability index, R₁ and a labile fraction)] indexes were used to assess compost stability of 15 end products. By use of these three techniques independent assessment of compost stability was made possible. Evidence of unstable materials was found where labile, easily biodegradable, and non-humified organic fractions were present. The DRI was used as a reference index for biological stability, and no significant correlation was observed between DRI and the humification indices (HI, DH, HR) and the thermogravimetry index (R₁). On the other hand, significant correlation was observed for DRI vs. non-humified carbon (NHC), which was determined using the chemical method and the labile fraction determined by thermogravimetry, as well as for NHC vs. “labile fraction”. These fractions represent labile, easily biodegradable, and non-humified organic matter. Significant correlations were also observed between the three above mentioned measurements and TEC, suggesting that this fraction is mainly formed of the easily degradable organic fraction. These results suggest that the integrated use of biological, chemical, and thermoanalytical methods could represent a useful tool in differentiating stabilized composts from non-stabilized ones, and it could provide more reliable information for both managerial and sanitary health aspects involved in good agricultural practice.     

反算法在某边坡稳定性评价中的应用

重点探讨了反算法的基本原理、反算的具体方法步骤、反算法建立联立方程的条件,应用边坡稳定性反算分析原理,依据工程实例对边坡滑移面的抗剪强度参数进行反算,给出了抗剪强度参数的建议值。     

Influence of foliar application of manganese on growth,pigment content,and nitrate reductase activity of Vigna radiata (L.) R. Wilczek under salinity

The effect of the micronutrient manganese (Mn) on the physiological performance of green gram [Vigna radiata (L.) R. Wilczek] under saline condition was studied in the present work. Green gram was grown under controlled conditions and treated with different concentrations of sodium chloride (NaCl): 100, 200, and 300 mM. The plant samples were analyzed from 25 to 65 days of plant growth at every 10-day interval. Significant difference was observed in leaf area index, membrane stability index, nitrate reductase enzyme activity, total chlorophyll, and carotenoid content in treated plants. A drastic reduction was recorded at 200 and 300 mM NaCl treated plants in the parameters. The concentration 100 mM resulted in a slight increase of the parameters. Foliar application of Mn as manganese chloride (MnCl₂) was found to improve the physiological parameters in green gram at 200 and 300 mM salinity level and was useful in alleviating the detrimental effects of NaCl.     

子午岭林区典型植被下土壤结构及稳定性指标分析

运用分形理论,研究了子午岭林区5种天然次生植被(以6 a天然恢复弃耕地为对照)下土壤结构特征,分析了土壤水稳性团聚体分维、孔隙分维、平均重量直径等3个指标在描述土壤结构稳定性方面的差异.研究表明,相对于弃耕地,各个植被群落均能明显改善土壤结构,降低土壤水稳性团聚体分形维数,提高孔隙分形维数,增强土壤结构的稳定性.土壤水稳性团聚体分维、孔隙分维q>0.25 mm水稳性团聚体含量、土壤有机碳、容重的相关系数均达到了极显著水平,均能作为评价土壤结构稳定性的指标;而团聚体平均重量直径与土壤有机碳含量、容重相关性不显著,只与>5 mm团聚体含量和>0.25 mm团聚体含量有极显著正相关关系,因此,仅可作为大团聚体含量的评价指标.     

New indices for quantifying the resistance and resilience of soil biota to exogenous disturbances

The stability (resistance and resilience to disturbance) of a soil system is a key factor influencing ecosystem properties and processes. To compare the stability of different systems, it is necessary to have indices that provide a relative quantitative measure of both the resistance and resilience of a response variable in all possible scenarios. However, the indices currently in use are frequently unable to do this, or are difficult to interpret. Here, we present new indices that avoid these problems. We compare our indices with previously published indices of stability, and also test their performance by using a real data set. We show that our indices accurately represent the response of soil properties (e.g. soil microbial biomass) to a disturbance, and that they are capable of determining differences in stability between contrasting soils.     

Differential response of rice seedlings to salt stress in relation to antioxidant enzyme activity and membrane stability index

Three rice genotypes, IR 74802, IR 73104 and IR 72593, along with FL 478 and IR 29 as resistant and susceptible controls, respectively, were subjected to 21 days' salinity stress at the seedling stage in modified yoshida solution with two salt levels (60 and 120 mM NaCl). The results indicated that there was a profound increase in proline and ascorbic acid levels, and in the activity of nitrate reductase and antioxidant enzymes, i.e. catalase, peroxidase and ascorbate peroxidase, as well as malondialdhyde and membrane stability index, which were associated with salt tolerance. Salt stress had a significant and drastic effect on all parameters when the salinity level increased to 120 mM NaCl. The increased enzyme activity was directly related to an increased membrane stability index, as in IR 72593, which is identified as the most tolerant among the genotypes tested. It is clearly confirmed that predicting tolerance at the early seedling stage is the best way to assess the salinity tolerance level by utilizing physiological parameters, especially antioxidant enzyme activities which are found to be closely associated with salinity tolerance. Physiological adaptation of the plant to NaCl salt stress resulted in enhanced activity of stress-related enzymes and low sodium uptake in tolerant genotypes.     

黄土高原小流域重力侵蚀稳定性评价

为评价黄土高原小流域重力侵蚀稳定性,采用有限差分FLAC3D软件对黄土高原王茂沟小流域概化模型进行了研究。对小流域平衡状态时位移场和应力场和塑性屈服区进行数值模拟,并结合Rosen-blueth矩估计方法对流域重力侵蚀破坏概率可靠度进行了分析。结果表明,剪切塑性区域主要分布于坡面和沟坡大部分区域,张拉塑性区域主要分布于梁峁顶和梁峁坡上部;该流域重力侵蚀处于不可接受的风险水平,需采取有效的工程措施以提高其稳定性。Rosenblueth法可有效地将传统安全系数与概率分布相互结合补充,为建立流域稳定性与重力侵蚀可靠度的指标评价体系提供了一种好的方法。     

北京郊区河岸带自然性评价指标体系

河岸带是水陆交错带,是河溪的重要组成部分,对人类的生产、生活具有重要的意义.在分析国内外各种对河流评价方法的基础上,结合安达木河水域特点和野外调查,从结构和功能两方面选取了相互匹配的16个指标,采用层次分析和模糊综合评价相结合的方法,构建了河岸带自然性评价指标体系.综合考虑一个平衡河岸带生态系统的特点以及结构和功能等特点,可以将河岸带的近自然程度分为4个等级:自然状态、近自然状态、退化自然状态和退化状态.并以安达木河为例进行评价,评价结果与实际相符合,可作为北京郊区河岸带评价体系.