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J. Boll R. P. G. van Rijn K. W. Weiler J. A. Ewen J. Daliparthy S. J. Herbert T. S. Steenhuis 《Geoderma》1996,70(2-4):117-132
Pollutant transport in sandy soils can be very complex due to the presence of coarse sand lenses. Water flows laterally over the coarse material and, subsequently, breakthrough occurs in concentrated pathways, called fingers. This (funneled) flow process is a form of preferential flow reducing solute travel time and degradation of organic chemicals.
In this paper, we test ground-penetrating radar (GPR) as a tool for detecting layers in the soil. Several GPR transects were established on a fine sandy loam soil throughout the growing season and subsequent fall period to find the best time to reveal layer structures. The effect of the spatially varying moisture content on the radar velocity was determined from actual measurements with soil samples and by using the Common Mid-Point (CMP) technique. The optimal time to find coarse layers with GPR in this soil was at the end of the fall season when the soil was wetted and evaporation had decreased. The depth of layers, as indicated by GPR, was highly sensitive to the soil moisture content and could be in error by as much as ±0.4 m on a depth scale of 1.5 to 2 m if an average propagation velocity was used. A satisfactory depth prediction of textural interfaces was obtained non-destructively by collecting data in both reflection and CMP mode. 相似文献
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The relationship between the spot concentration and the resolution of different components in commercial hexachlorocyclohexane with micro- and macro-thin layer chromatography has been studied. Of the different spot concentrations investigated, only 0.025 μg on micro-t.l.c. and 1.0 μg on macro-t.l.c. gave two clear spots which can be made use of for the rapid semiquantitative estimation of benzene hexachloride in insecticide formulations. The application of this technique has been further investigated on different commercial benzene hexachloride dust formulations and the error ranged between 2 and 5%. 相似文献
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Jayaram Daliparthy Allen V. Barker Shyam S. Mondal 《Journal of plant nutrition》2013,36(11):1859-1886
Potassium (K), a plant nutrient with diverse roles to play in plant metabolism, is required in large amounts by most crops. It interacts with many other plant constituents to affect crop yield and quality. The magnitude of this interaction is high in areas of high cropping intensity, as in the tropics. The interaction of nutrients with K may be in the soil or in plant. Potassium modifies ammonium (NH4 +) ion fixation in soils to restrict nitrogen (N) availability. On the other hand, an antagonistic effect between K and NH4 absorption has been suggested in which K absorption is restricted. Similarly, magnesium (Mg) or calcium (Ca) deficiency occurs from ion antagonism in acid soils following K fertilization and in soils with high exchangeable K. Sulfur (S) has been reported to increase K absorption and productivity of oilseed crops. With increasing levels of applied or soil K, the severity of phosphorus (P)‐induced zinc (Zn) deficiency in corn has been observed to decrease. Application of K decreases manganese (Mn) content and iron (Fe) toxicity in rice. Application of K has been reported to decrease B levels in plants and to increase incidence of boron (B) deficiency. Top‐dressing with K fertilizer was reported to lower the copper (Cu) content of alfalfa forage. In root, sugar‐producing, or fiber‐producing crops, the sodium (Na) and K relationship is important with the specific response to either element depending on which element is in low or high supply. Molybdenum (Mo) stimulated K uptake in alfalfa and com. In intensive agriculture with high‐yielding single crops or with multiple crops per year, farm management must include strategies to maintain substantial K reserves in the soil and to balance K nutrition with other fertilization practices. 相似文献
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Permeation through nanometer pores is important in the design of materials for filtration and separation techniques and because of unusual fundamental behavior arising at the molecular scale. We found that submicrometer-thick membranes made from graphene oxide can be completely impermeable to liquids, vapors, and gases, including helium, but these membranes allow unimpeded permeation of water (H(2)O permeates through the membranes at least 10(10) times faster than He). We attribute these seemingly incompatible observations to a low-friction flow of a monolayer of water through two-dimensional capillaries formed by closely spaced graphene sheets. Diffusion of other molecules is blocked by reversible narrowing of the capillaries in low humidity and/or by their clogging with water. 相似文献
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Mani A Radhakrishnan J Wang H Mani A Mani MA Nelson-Williams C Carew KS Mane S Najmabadi H Wu D Lifton RP 《Science (New York, N.Y.)》2007,315(5816):1278-1282
Coronary artery disease (CAD) is the leading cause of death worldwide and is commonly caused by a constellation of risk factors called the metabolic syndrome. We characterized a family with autosomal dominant early CAD, features of the metabolic syndrome (hyperlipidemia, hypertension, and diabetes), and osteoporosis. These traits showed genetic linkage to a short segment of chromosome 12p, in which we identified a missense mutation in LRP6, which encodes a co-receptor in the Wnt signaling pathway. The mutation, which substitutes cysteine for arginine at a highly conserved residue of an epidermal growth factor-like domain, impairs Wnt signaling in vitro. These results link a single gene defect in Wnt signaling to CAD and multiple cardiovascular risk factors. 相似文献
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Investigations conducted on certain varieties of green leafy vegetables revealed very high BHC residues. The significance of certain common processing techniques in reducing the pesticide residue level on the raw material was investigated. Cooking the material in water for 5 minutes and immersion of the sample in 1% acetic acid solution and subsequent cooking reduced the level of pesticide residue within the permissible limit. 相似文献
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The present investigation was carried out to study the biological parameters and orientation of Sitophilus oryzae (L.) toward wheat cultivar HPW-236 and mixed grains of different cultivars (HPW-155, HPW-236, HPW-249, HPW-349, HPW-360, HS-490, and VL-892). The incubation period, larval period, pupal period, and total life cycle period of S. oryzae was longer when fed on mixed grains as compared to HPW-236. Also, the weevils were more oriented toward HPW-236 and lower germination rates were observed from HPW-236 than mixed cultivars when exposed to S. oryzae. We also evaluated quantitative losses caused by S. oryzae in different cultivars of wheat recommended in the northwestern Himalayas under free-choice conditions. The weevil inflicted greater damage and weight loss in grains of HPW-236 while it was negligible in the case of HPW-360 and HPW-249. HPW-236 which is the most cultivated variety of wheat in northwestern Himalayas proved to be highly susceptible to the weevil and provided a more suitable environment for weevil’s development. Therefore, this particular cultivar can be avoided for prolong storage and the farmers should prefer cultivars such as HPW-360 and HPW-249, which proved to be least affected the weevil. 相似文献
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B Jayaram N M Made Gowda 《Journal of the Association of Official Analytical Chemists》1986,69(1):47-49
Simple titrimetric methods have been developed for determination of the vitamin pyridoxine (PRX) in solution, using aromatic N-haloamines, chloramine-T, bromamine-T, and bromamine-B. The method is based on oxidation of PRX by the N-haloamines; the oxidation involves a 2-electron change. The reaction products, pyridoxal and sulfonamides, were identified. The effects of variables, such as pH of the medium and the presence of foreign ions, and pyridoxal, pyridoxalamine, glycerol, and alcohol, on the rate of oxidation were studied. The methods are useful for determining PRX in pharmaceutical formulations and for assaying its cadmium complex. Statistical evaluation showed that analytical results are accurate to within 1%. 相似文献
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