Gas-liquid chromatographic determination of resmethrin in corn, cornmeal, flour, and wheat.

A gas-liquid chromatographic (GLC) method was developed for the determination of residues of resmethrin ((5-benzyl-3-furyl)methyl cis-trans-(+/-)-2,2-dimethyl-3-(2-methylpropenyl)-cyclopropanecarboxylate) in corn, cornmeal, flour, and wheat. The commodity, fortified with resmethrin, was extracted by tumbling with pentane and transferred to acetonitrile, the fat was partitioned off, and the sample was chromatographed with 3% ethyl acetate in pentane on Florisil containing 0.5% water. The resmethrin residue was determined by GLC with a flame ionization detector. The results were compared with known standards that had undergone the same cleanup procedures. The method was sensitive to concentrations of resmethrin to 0.2 ppm, recoveries averaged 83%, and reproducibility was good.     

High-performance liquid chromatographic determination of strychnine in grain baits.l.

A simple and rapid high-performance liquid chromatographic procedure is described for the determination of strychnine. Grain baits containing strychnine alkaloid are ground, mixed, and extracted by shaking with chloroform. Without further cleanup, extract filtrates are injected directly into a liquid chromatograph. Chromatography is complete within 7 min and peak heights are used for quantitation. Separations were made on a 30 cm times 4 mm id stainless steel column packed with mu Porasil (8-12 mum silica). The eluting solvent was methanol-chloroform (10+90) at a flow rate of 2.0 ml/min. Recovery of spiked samples ranged from 91.5 to 95.2%. Confirmation of strychnine from a commercial sample was made by high resolution mass spectrometry with mass agreement to 1.2 ppm.     

The distribution of woodland plant species in some Shropshire hedgewors

A total of 66 samples of roadside hedgerow were examined in a 200 km² area of Shropshire not far from the Welsh border. The mean numbers of vascular plant species in samples of increasing length could be expressed as 17·2 × (length of hedgerow in metres/2)^{0·2 5}. This equation varied somewhat between samples, but not greatly, and the correlation between this variation and the distance to the nearest wood was not significant at the 5% probability level. Association analysis of the floristic data, did, however, provide a fairly clear division into hedgerows with some ‘woodland’ species and hedgerows with few or no ‘woodland’ species, and this difference was not accompanied by any corresponding difference in apparent age of the hedgerow. It is concluded that these ‘woodland’ species do not spread readily throughout the hedgerow network, and that hedgerows do not appear to act as efficient ‘corridors’ for the passage of such plants.     

Europium chelate and fluorescent brightener staining of soil propagules and their photomicrographic counting—I. Methods

A method tor direct visual or photomicrographic enumeration of soil propagules in soil-agar films and soil smears, stained with a mixture ofeuropium(III) ttienoyltrifluoroacetonate and the disodium salt of 4,4¹-bis(4-anilino-6-bis(2-hydroxyethyl)amino-S-triazin-2-ylamino)2,2¹-stilbene disulphonic acid, abbreviated to Eu(TTA)₃ and fluorescent brightener (FB), respectively, is described.Soil-agar suspensions at 55–60°C were introduced into haemocytometer sample chambers of 100 μm and 20 μm depth which gave soil-agar film thicknesses of 25 μm and 12 μm, respectively, after air-drying. Soil smears air-dried on 1.25 cm² and 1.0 cm² areas of glass slide were 5.2–6.0 μm and 6.0–8.0 μm thick, respectively.The Eu(TTA)₃ is best formulated in 50% (v/v) ethanol. The best concentrations of Eu(TTA)3 and FB for staining soil propagules were 2 mM and 25 μM. respectively. A staining period of 18 h for soil-agar films and 90–120 min for soil smears was found to be optimal. The optimum volumes of 50% ethanol for rinsing soil-agar films and soil smears were found to be 12.5 and 5.0 ml. respectively.Lack of in-depth focusing on agar films 25 μm thick resulted in 15–17 per cent error in enumerations. The 12 μm agar films and soil smears required little in-depth focusing and were acceptable for photomicrographic recording of numbers of soil propagules. It is concluded that incident u.v. photomicrographic recording of soil propagule numbers in thin agar films or soil smears is a practical solution to operator fatigue likely to occur during direct microscopy.     

Studies on the ecology of actinomycetes in soil—VIII: Distribution and characteristics of acidophilic actinomycetes

Acidophilic actinomycetes, growing between pH 3.5 and 6.5, were isolated from 17 natural soils and mine wastes. Most isolates were Streptomyces spp. and selected ones were compared with some established neutrophilic species by assessment of overall similarity. Acidophilic and neutrophilic strains clustered separately, differing in a number of cultural and physiological characters, in addition to pH requirements. The possible importance of acidophilic actinomycetes in soil is discussed.     

Clonal depletion in neonatal tolerance

Specific unresponsiveness can be induced in neonatal and adult BALB/c mice by antibody against antigen-specific receptor (antireceptor antibody). When heterologous antireceptor antibody is used in the indirect fluorescence technique, the number of fluorescent cells in these animals is significantly lower than in normal animals. Fluorescent cells appear after a relatively brief incubation of cells from adult-suppressed animals, whereas no fluorescent cells are detected when cells from neonatally treated animals are incubated briefly. Evidently, treating neonatal mice with antireceptor antibody specifically depletes the antigen-responsive clone. In contrast, antireceptor antibody causes reversible blockade of responsive cells in adult-suppressed animals.     

Scaling stride frequency and gait to animal size: mice to horses

The stride frequency at which animals of different size change from one gait to another (walk, trot, gallop) changes in a regular manner with body mass. The speed at the transition from trot to gallop can be used as an equivalent speed for comparing animals of different size. This transition point occurs at lower speeds and higher stride frequencies in smaller animals. Plotting stride frequency at the trot-gallop transition point as a function of body mass in logarithmic coordinates yields a straight line.     

Aerosol and climate: some further considerations

Approximate numerical radiative calculations show that whether added aerosol causes heating or cooling of the earth-atmosphere system is a function not only of its intrinsic absorption-backscatter characteristics but also of its particular location in the atmosphere with respect to the average cloud as well as of both the cloud reflectivity and the underlying surface reflectivity.