基于SRTM_DEM的泾河流域特征信息提取研究

流域特征信息的提取对于水文地理信息分析、模拟技术和水文模型建立具有重要意义。基于STRM_DEM数据,在ArcGIS9．3环境下,提取泾河流域坡度、坡向等地形特征,以及河网、流域边界和面积等水文要素,并划分子流域。分析表明,当闽值取5000（40．5km^2）时,生成的流域河网能够较好地反映该地区水系。根据河网分级、低级集水区域生成结果和流域地形特征,可划分为32个子流域,为流域分布式水文模型的构建提供了基础地理信息。SRTM_DEM提取泾河和部分支流流域面积误差均较小,说明提取结果与实际非常接近。结果表明,SRTM_DEM数据和ArcGIS9．3提取流域特征信息方便快捷,具有较高的精度和准确性,应用前景广阔。     

Phosphorus Retention and Release Characteristics of Sewage-Impacted Wetland Sediments

Sediment deposited in traps positioned along a sewage-impacted wetland receiving phosphorus (P)-retaining reactants from natural wetland water was fractionated into different particle sizes, and the amount of P retained in these particle sizes was investigated. Subsamples of the sediments collected from different sites along the wetland system were also equilibrated with water at different water:sediment ratios and equilibration periods to investigate the extent of P released from these sediments under aerobic and anaerobic conditions. Results obtained showed that most of P deposited in sediments is in fine fractions (<16 µm), particularly in sediments collected from confluence sites where water inflow from the natural wetland provides P-retaining reactants and from sites immediately below these confluence sites (postconfluence sites). The extent of P release from sediments depended on the aerobic-anaerobic conditions of the sediments, equilibration period, water:sediment ratio and the position of sites within the wetland. The rate of P released from sediments associated with an increase in equilibration period tended to be higher under aerobic than anaerobic conditions. Water:sediment ratio was found to be a more important factor in controlling the release of P from sediments under anaerobic than aerobic conditions. The amount of P released from the confluence and postconfluence sites was higher than that from other sites over a range of equilibration periods and water:sediment ratios under aerobic and anaerobic conditions.     

Root-growth response of winter barley to subsoiling

Root growth of winter barley was studied on 2 Belgian silt loam soils after subsoiling to 60 cm depth. In the first field (well-drained) rooting depth increased significantly after removal of a plough pan. At the flowering stage, total root weight in the soil layers between 25–50 cm and 50–75 cm was 125% and 325%, respectively, higher on the subsoiled plots than on the control. The P₂O₅ and K₂O concentrations in the roots were significantly increased by 20% and 40%, respectively. In the second field (imperfectly drained) with initially relatively high bulk densities in the subsoil, the influence of subsoiling was negligible. In this study, the clearly-shown root-growth retardation that resulted in a lower yield on the control, seemed to be caused by the high penetration resistance in the plough sole (> 3MPA) rather than poor aeration status induced by the high bulk densities.     

Feeding deterrents from Dictamnus dasycarpus Turcz against two stored-product insects

The screening for insecticidal principles from several Chinese medicinal herbs showed that the root bark of Dictamnus dasycarpus possessed significant feeding deterrence against two stored-product insects (Tribolium castaneum and Sitophilus zeamais). From the methanol extract, two feeding deterrents were isolated by bioassay-guided fractionation. The compounds were identified as fraxinellone and dictamnine from their spectroscopic data. Fraxinellone was demonstrated to possess feeding deterrent activity against adults and larvae of T. castaneum as well as S. zeamais adults with EC50 values of 36.4, 29.1, and 71.2 ppm, respectively. Dictamnine was shown to have feeding deterrent activity against adults and larvae of T. castaneum as well as S. zeamais adults with EC50 values of 57.6, 47.9, and 91.7 ppm, respectively.     

Purification and characterization of hydrolase with chitinase and chitosanase activity from commercial stem bromelain

A hydrolase with chitinase and chitosanase activity was purified from commercial stem bromelain through sequential steps of SP-Sepharose ion-exchange adsorption, HiLoad Superdex 75 gel filtration, HiLoad Q Sepharose ion-exchange chromatography, and Superdex 75 HR gel filtration. The purified hydrolase was homogeneous, as examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme exhibited chitinase activity for hydrolysis of glycol chitin and 4-methylumbelliferyl beta-D-N,N',N' '-triacetylchitotrioside [4-MU-beta-(GlcNAc)(3)] and chitosanase activity for chitosan hydrolysis. For glycol chitin hydrolysis, the enzyme had an optimal pH of 4, an optimal temperature of 60 degrees C, and a K(m) of 0.2 mg/mL. For the 4-MU-beta-(GlcNAc)(3) hydrolysis, the enzyme had an optimal pH of 4 and an optimal temperature of 50 degrees C. For the chitosan hydrolysis, the enzyme had an optimal pH of 3, an optimal temperature of 50 degrees C, and a K(m) of 0.88 mg/mL. For hydrolysis of chitosans with various N-acetyl contents, the enzyme degraded 30-80% deacetylated chitosan most effectively. The enzyme split chitin or chitosan in an endo-manner. The molecular mass of the enzyme estimated by gel filtration was 31.4 kDa, and the isoelectric point estimated by isoelectric focusing electrophoresis was 5.9. Heavy metal ions of Hg(2+) and Ag(+), p-hydroxymercuribenzoic acid, and N-bromosuccinimide significantly inhibited the enzyme activity.     

Evaluation of the simultaneous effects of processing parameters on the iron and zinc solubility of infant sorghum porridge by response surface methodology

The purpose of this study was to improve the micronutrient quality of indigenous African infant flour using traditional techniques available in the region. Response surface methodology was used to study the effect of duration of soaking, germination, and fermentation on phytate and phenolic compounds (PC), pH, viscosity, and the in vitro solubility (IVS) of iron and zinc in infant sorghum flour. The phytate and the PC concentrations of the flour were significantly modified as a result of the duration of germination and fermentation and their mutual interaction. These modifications were accompanied by a significant increase in % IVS Zn after 24 h of sprouting. Except for the interaction of soaking and fermentation, none of the processing parameters exerted a significant effect on the % IVS Fe. The viscosity of the porridge prepared with the flour decreased significantly with the duration of germination, making it possible to produce a porridge with high energy and nutrient density. The use of germination in combination with fermentation is recommended in the processing of cereals for infant feeding in developing countries.     

Influence of storage practices on acrylamide formation during potato frying

A number of parameters linked to storage of potatoes were evaluated with regard to their potential to influence the acrylamide formation in French fries. Acrylamide, which is a potential human carcinogen, is reported to be formed during the frying of potatoes as a result of the reactions between asparagine and reducing sugars. This study was conducted using three potato varieties (Bintje, Ramos, and Saturna) typically used in Belgium, The Netherlands, and the northern part of France for French fry and crisp production. Saturna, mainly used in crisp production, appeared to be the least susceptible for acrylamide formation during frying. Especially storage at low temperatures (4 degrees C) compared to storage at 8 degrees C seemed to enhance acrylamide formation due to a strong increase in reducing sugars caused by low-temperature storage. Because of the reversible nature of this physiological reaction, it was possible to achieve a significant reduction of the reducing sugars after a reconditioning of the cold-stored potatoes for 3 weeks at 15 degrees C. All changes in acrylamide concentrations could mainly be explained by the reducing sugar content of the potato (R2 = 0.84, n = 160). This means that, by ensuring a low reducing sugar content of the potato tuber, the risk for acrylamide formation will largely be reduced. Finally the use of a sprout inhibitor did not influence the composition of the potato, and thus acrylamide formation was not susceptible to this treatment.     

1：25万土壤及地形数据库及指标体系研究

根据土壤及地形(SOTER)数据库基本原理和方法建立1：25万SOTER数据库,重点研究和修正大中比例尺SOTER主地形体划分指标体系,提出海拔高度分组指标、坡度分组指标和地势起伏强度分组指标,并利用上述3个指标组合计算出样区SOTER主地形体组分(中坡度丘陵、低坡度山体台地、山谷、中坡度山体、山前倾斜平原和冲洪积平原),以进一步发展和完善SOTER数据库理论方法体系。同时,SOTER数据库的建立使原有的历次土壤普查、国土资源详查的资料信息化,使之服务于土地资源的评价、管理与保护。     

Development of an indirect competitive ELISA for flumequine residues in raw milk using chicken egg yolk antibodies

To detect flumequine in raw milk, an indirect competitive enzyme-linked immunosorbent assay (ELISA) was developed. By carbodiimide conjugation, flumequine was conjugated to cationized bovine serum albumin (cBSA-flumequine) and to cationized ovalbumin (cOVA-flumequine). For the immunization of chickens, cBSA-flumequine was used, which allowed the isolation of specific chicken egg yolk immunoglobulins (IgY) for flumequine. As the coating antigen in the immunoassay, cOVA-flumequine was used. In the indirect competitive assay, standard flumequine was incubated together with the anti-flumequine antibodies. The antibody by which the lowest concentration of free flumequine that gives 50% inhibition of binding (IC50) was found in aqueous dilution was further tested for the applicability to detect flumequine in raw milk. An IC50 level in milk was reached that was about 5 times lower than in aqueous solution. So flumequine can be detected directly in raw milk at maximum residue level (50 microg/kg). No cross-reactivity was noticed with various related quinolones.     

Effect of moisture content during dry-heating on selected physicochemical and functional properties of dried egg white

This article addresses the effect of moisture content (0.8-9.9%) during dry-heating (80 degrees C) on selected physicochemical (solubility, turbidity, residual denaturation enthalpy, aggregation, surface hydrophobicity, and sulfhydryl content) and functional (foaming ability, foam density, and stability) properties of freeze-dried egg white (FDEW). Moisture content during dry-heating proved to be a parameter determining the functionality of the resulting egg white powder. The degree of conformational changes induced in the egg white proteins by dry-heating was strongly dependent on the amount of water present. Preferentially, dry-heating at 80 degrees C should be performed on egg white powder with a moisture content below 6.8%, as the loss of protein solubility above this value is extensive. In addition to insoluble aggregates, soluble, strongly stabilized aggregates were also formed, especially at higher moisture contents. The decrease in denaturation enthalpy, increase in surface hydrophobicity, and exposure of SH groups previously hidden in the protein core and their subsequent oxidation were more pronounced at prolonged dry-heating times and at higher moisture contents. These conformational changes resulted in improved foaming ability and foams with lower density. No effect of dry-heating on the foam stability was observed.