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Summary. Difficulties of access met with in Britain when applying dalapon to emergent water weeds in drainage channels led to work starting in 1964 on the development of a method of accurate aerial application of aqueous solutions of herbicide. The narrow, sinuous nature of the targets and the proximity of susceptible crops made it necessary to minimize spray drift and maintain a constant height and a slow speed. Nozzles designed to give large droplets were tested for droplet size and distribution. Selected nozzles were then tested from a helicopter in the field and the effect of their spray characteristics on the biological performance of dalapon was assessed. No daman occurred as a result of spray drift and satisfactory control of Phragmites communis, Typha angustifolia and T. latifolia was achieved with a lower dose of dalapon in a lower volume of spray than previously considered necessary for ground applications.
Une nouvelle technique pour l'application précise d'herbicides par voie aérienne sur les canaux de drainage, avec des risques négligeables d'entrainement 相似文献
Une nouvelle technique pour l'application précise d'herbicides par voie aérienne sur les canaux de drainage, avec des risques négligeables d'entrainement 相似文献
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Myelofibrosis has been reported infrequently in dogs. The pathological features of three dogs with this disease are described. All three animals were presented clinically with non-regenerative anaemia. In two dogs, the neoplastic disorder was unaccompanied by other myeloproliferative disease and was characterized histologically by extensive replacement of normal bone marrow elements by proliferating reticulum cells and myeloid metaplasia of the enlarged liver and spleen. In one animal, focal myeloid metaplasia were also present in the lungs. In the third dog, myelofibrosis was accompanied by erythraemic myelosis and in this animal immature erythroid cells were present in blood, bone marrow, liver and spleen. 相似文献
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Testosterone and androstenedione were measured in the plasma of mature tom-cats before, during and after anesthesia with thiopentone, ketamine, xylazine and alphaxolone/alphadolone. Samples were collected via an indwelling jugular catheter at 30 min intervals before anesthesia (5 samples) and during the recovery phase (8 samples), and at intervals of 15 min during anesthesia (7 samples). Thiopentone and ketamine anesthesia significantly depressed testosterone and androstenedione concentrations during and after anesthesia. Xylazine significantly increased testosterone concentrations during anesthesia but they returned to pre-anesthetic concentrations during recovery. Androstenedione concentrations were significantly depressed during the recovery phase from xylazine anesthesia. Alphaxolone/alphadolone anesthesia had no significant effect of testosterone concentrations but significantly increased and androstenedione concentrations during anesthesia and recovery. Testosterone and androstenedione concentrations in cats were significantly altered by these 4 commonly used anesthetics and this must be taken into account if hormone concentrations are measured while cats are anesthetised. 相似文献
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Measurements of scrotal width were strongly correlated with testicular weight in 71 dogs (r = 0–919) and thus provided a convenient index of testicular size and potential sperm production. However, to be useful in trying to predict male fertility this measurement had to be adjusted for bodyweight. A graph is presented which allows estimation of ‘average’ scrotal width and its 95 per cent confidence limits for potentially fertile dogs of bodyweight between 5 and 50 kg. With one exception, dogs with scrotal widths below the 95 per cent confidence limits had very few or no spermatozoa in smears from the cauda epididymidis. 相似文献
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Abstract. Paired subgroups of fish were derived in January from each of two parent sea-cages of Atlantic salmon, Salmo salar L. The proportion of fish which later became sexually mature in each parent group, after one winter (as grilse) and under commercial rearing density, was determined. Maturity rates in the subgroups, reared in sea-cages at lower density, were significantly greater than in the parent groups. Rearing at reduced density was associated with increased growth in some, hut not all, comparisons. Periodic anaesthesia, handling and sampling of blood for steroid hormone determinations did not consistently affect maturation rate or growth among fish in one of each pair of subgroups. Sexual development was assessed by determining levels of the steroid hormones 11-oxotestosterone or 17β-oestradiol in samples of blood serum taken monthly from individually marked fish in one of each pair of subgroups. Between February and April specific growth rates in maturing male grilse were significantly higher than in fish subsequently shown to have remained immature. Growth rates in maturing female grilse differed similarly between March and April. Between July and August, however, growth rates of non-maturing salmon exceeded those of grilse. 相似文献
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Abstract This study aimed to develop and test an electrode array for a resistivity fish counter that could be easily installed in a small river without a weir. An electrode array consisting of three steel cables laid in parallel across the stream channel and connected to a microprocessor-based counter was tested in an Atlantic salmon, Salmo salar L., spawning tributary. The accuracy of the counter was assessed by observing fish movements with closed-circuit television. Most salmon moving upstream were registered correctly (90% overall). Detection of downstream movement was less reliable (60% overall), as a consequence of downstream swimming behaviour. The accuracy of the downstream count was improved by tensioning the cable electrodes, but remained lower than that of the upstream count. Since salmon swam repeatedly up- and downstream, this discrepancy resulted in an overestimate of the net upstream count. The accuracy of the downstream count needs to be improved before a bed-mounted electrode array could be used for routine salmon counting. 相似文献
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