Enzymatic method for the estimation of residual organophosphorus compounds in water after treatment with chlorine-containing oxidant

A sensitive method for the estimation of residual organophosphorus compounds in water after treatment with chlorine-containing oxidants has been developed. The method is based on the inhibiting action of organophosphorus compounds towards the enzyme-catalyzed hydrolysis of esters. After the oxidants have been quantitatively destroyed by a mixture of NaHCO₃ and NaNO₂ small amounts of O-ethyl S-(N, N-diisopropylamino)ethyl methylphosphonothioate (MESP), dichlorvos (DDVP) and dimethoate are determined by using horse-serum cholinesterase with 2,6-dichloroindophenyl acetate as the substrate. A linear response range of 2 of 3 orders of magnitude and recovery within 100 ± 5% has been generally obtained.     

A simplified method for the gas-liquid chromatographic determination of methyl mercury in fish and shellfish.

A simple acetone wash of the fish sample which removes lipids and other organic materials replaces the cystein cleanup specified in other methods. Methyl mercury is freed by hydrochloric acid, extracted into benzene, and determined with a gas-liquid chromatograph equipped with an electron capture detector. The method is quantitative for methyl mercury levels as low as 0.10 ppm in fish and shellfish. Ethyl mercury chloride may be used as an internal standard to detect unsuspected error or instrumental parameter variation.     

A new method for the estimation of diffusive resistance of leaves

The measurement of diffusive resistance in leaves is a difficult task, and is frequently accomplished with diffusion porometers. A new energy budget method is shown, where the internal diffusive resistance, the aerodynamic resistance, and the absorbed radiation may be estimated using the temperature of three leaves, the air temperature, and the relative humidity or vapor pressure deficit. Of the three leaves, one is coated with a substance impervious to water, one with water, and one is left uncoated. Absorbed solar irradiances in the 400 to 1100 nm wavelength region for coated leaves were within 2% and 6% of uncoated leaves for adaxial and abaxial surfaces, respectively. The methodology was tested on soybean plants with diffusion porometry used as a reference. The results showed a good correspondence between the two methods, with only as much scatter as reported in inter-porometer comparisons. The method presented here may be developed for automatic unattended operation.     

Simple spectrophotometric method for the estimation of algal polysaccharide concentrations.

A rapid and simple spectrophotometric method is described for the estimation of microgram quantities of algal polysaccharides following the formation of soluble complexes with methylene blue dye. The binding of the dye to algal polysaccharides causes the absorption maximum (664 nm) to decrease, which is almost linear over the range of 0-30 microg for the algal polysaccharides studied. The absorbance at 664 nm can be measured immediately after the mixing of algal polysaccharides and dye solution and is stable over a period of 2 h. No heating, centrifugation, lengthy equilibration, or sophisticated instrumentation, which hamper other methods, is required. The interference due to individual monosaccharides, neutral polysaccharides, bovine serum albumin, sodium dodecyl sulfate, and high concentrations of inorganic salts is discussed.     

A simple method for the estimation of potential primary pasture productivity over Mozambique

Pasture production not only depends on precipitation amount and distribution patterns, but also on soil type and evaporative demand. The simulation model of Rose et al., developed using improved pastures, is one that accounts for these factors and also takes into account the effect of fertilizer levels on production. From this a simplified model is proposed for Mozambique using as inputs annual precipitation, annual potential evapotranspiration and soil moisture storage capacity. The model is applicable only under negligible soil slope and no bush or tree cover, but can be adapted to varying phosphate fertilizer levels. Estimates from this proposed model show close agreement with experimental data from cleared natural pastures in Zimbabwe and with improved pastures of Townsville stylo in Australia under high phosphate fertilizer levels.     

淡水鱼的连续式鱼鳞去除方法

为研究连续式鱼鳞的去除方法,以鲢鱼、鳊鱼、鲤鱼为试验对象,提出了一种以弹簧为主要去鳞结构的去鳞刷,并以弹簧外径、去鳞刷转速与去鳞刷直径等为主要因素,通过自制去鳞试验台研究了其对淡水鱼去鳞率和鱼体损伤的影响,表明弹簧外径、去鳞刷直径对淡水鱼去鳞率有显著影响,对鱼体损伤感官评价得分影响不显著,去鳞刷转速对去鳞率和鱼体损伤感官评价得分均有极显著影响。不同种鱼,其各自适宜的弹簧外径、去鳞刷直径与去鳞刷直径有所不同。确定了白鲢去鳞时弹簧外径、去鳞刷转速、去鳞刷直径的最优参数组合,即弹簧外径21 mm、去鳞刷转速1 120 r/min、去鳞刷直径90 mm。该研究可为连续式去鱼鳞机的研制提供依据。     

Modified method for the analysis of free fatty acids in fish

The objective of this study was the development of a method for the quantification of free fatty acids (FFA) using less aggressive reactants against the handler and the environment than those used in the classic method of Lowry and Tinsley. The modified procedure is a variation of the Lowry and Tinsley method employing cyclohexane in place of benzene. The use of benzene is prohibited in certain work processes and laboratories, and the competent authority in each country is actively promoting research into harmless or less harmful products that could replace benzene. A comparison with the traditional AOCS titration method for oil analysis was performed. FFA content in mackerel frozen at -10 degrees C was measured according to the three methods over a 12 month period. The results showed similar values, and good correlations were obtained.     

A modification of Douglas and Bremner method for colorimetric estimation of urea

Abstract

The use of H₃PO₄ in colorimetric estimation of urea by the method of Douglas and Bremner sometimes leads to wide batch variations. A modification of this method is proposed where H₂SO₄ only is used in place of H₃PO₄. The use of H₂SO₄ increased the linear calibration range almost two‐fold without affecting the precision of the original method. The developed color remains stable for 72 hours in the dark.     

A quantitative lipid extraction method for residue analysis of fish involving nonhalogenated solvents

Numerous intercalibration exercises have indicated that the in Sweden frequently used, so called Jensen extraction method for total lipids and lipophilic pollutants gave satisfactory yields when applied to fatty aquatic organisms. However, a comparison with the classical Bligh and Dyer method and the forerunner, the Folch methods, revealed that in the case of very lean fish (fat content below 1%, e.g., cod), the lipid yields were about 25% too low for the Jensen method; consequently, residue levels quoted on a lipid weight basis were correspondingly too high. To rectify the unacceptably low fat recovery from lean marine organisms, the Jensen extraction method has been modified to give recoveries not significantly different from the Folch and Bligh and Dyer methods. In the modified version, acetone is replaced by 2-propanol and part of the hexane is replaced by diethyl ether. Comparison between the modified Jensen method and the Folch method for cod muscle gave the same recovery of total lipids but slightly lower than that obtained with the Bligh-Dyer method. A possible explanation for this small difference is discussed. It is anticipated that the reported increased yield for cod is due to the superior solubility of phospholipids in 2-propanol as compared to acetone. The possible use of correction factors for previously reported contaminant residual levels of lean and medium fat fish calculated on lipid basis in the future is suggested.     

A simple method for the determination of trace levels of alkylphenolic compounds in fish tissue using pressurized fluid extraction, solid phase cleanup, and high-performance liquid chromatography fluorescence detection

A simple automated extraction method for the determination of alkylphenolic compounds in fish tissue is reported. Pressurized fluid extraction is used to extract ground fish tissue, and the resulting extract is purified on aminopropyl silica (APS) extraction cartridges. With no further sample preparation, nonylphenol (NP) and its ethoxylates, up to nonylphenol pentaethoxylate, are quantitated using normal phase (APS Hypersil) high-performance liquid chromatography with fluorescence detection. The major advantage of this technique is elimination of the conventional gel permeation cleanup step, a lengthy procedure designed to remove fish lipids. Spiked recoveries with lake trout averaged 85% for the six NP and NP ethoxylates that were investigated. Tissue concentrations of NP and NP ethoxylates determined in fish from various locations of the Great Lakes region ranged from 18 to 2075 ng/g, wet weight.     

Rapid NMR method for the quantification of organic compounds in thin stillage

Thin stillage contains organic and inorganic compounds, some of which may be valuable fermentation coproducts. This study describes a thorough analysis of the major solutes present in thin stillage as revealed by NMR and HPLC. The concentration of charged and neutral organic compounds in thin stillage was determined by excitation sculpting NMR methods (double pulse field gradient spin echo). Compounds identified by NMR included isopropanol, ethanol, lactic acid, 1,3-propanediol, acetic acid, succinic acid, glycerophosphorylcholine, betaine, glycerol, and 2-phenylethanol. The concentrations of lactic and acetic acid determined with NMR were comparable to those determined using HPLC. HPLC and NMR were complementary, as more compounds were identified using both methods. NMR analysis revealed that stillage contained the nitrogenous organic compounds betaine and glycerophosphorylcholine, which contributed as much as 24% of the nitrogen present in the stillage. These compounds were not observed by HPLC analysis.     

A new method for the estimation of total dissolved salts in saturation extracts of soils from electrical conductivity

We have determined electrical conductivity (E_e) and total dissolved salts (S) in saturation extracts from 39 soil samples from the Baza basin (Province of Granada, south-east Spain). E_e ranged from 2.8 to 110dS m^?3, and S from 2 to 444 8 dm^?3. The relationship between S and E_e was not linear. When the saturation extracts were diluted with progressively larger quantities of distilled water and their electrical conductivity calculated (E_ec) with the equation where E_d and E_w are the conductivity of the diluted extract and the distilled water and f is the dilution factor, the relationship between S and E_ec tended to become linear. The highest linear correlation coefficient relating S (mg dm^?3) and E_ec (dS m^?1) was reached when E_ec, values were calculated for dilutions with a conductivity (E_d) between 0.1 and 0.3 dS m^?1 (E*_ec). The regression equation was S= 490 E*_ec with r²= 0.999. This relationship can be used in all saturation extracts, regardless of the concentration and type of ions present.     

A new method to determine the carbon content of water-soluble organic compounds in soils

The possibility to use the oxidation rate of different waters by dichromate as measured by photometry for the determination of the organic carbon content in water extracts from the organic horizons of soddy-podzolic soils (in the Republic of Komi) was confirmed. The advantages of the method proposed are discussed.     

基于自监督学习的温室移动机器人位姿跟踪

为实现温室环境下机器人行进过程中的位置及姿态跟踪,该研究提出一种基于时序一致性约束的自监督位姿变换估计模型.模型用软遮罩,处理视频帧间静止造成的位姿预测值收缩现象,进一步用归一化遮罩,解决非刚体场景和目标遮挡问题.设计了一种星型扩张卷积,并基于该卷积,为模型构建自编码器.在采集自种植作物为番茄的日光温室视频数据上开展训...