Aluminium-organic complexation: formation constants and a speciation model for the soil solution

Stability constants describing Al³⁺ combination with soil polycarboxylates were measured using the methods of Gregor et al. (1955) and Tanford (1961). It is suggested that the high stability of such complexes is derived largely from the electrostatic energy associated with the high surface charge of soluble humus acids. Chemically, the affinity of fulvic acids for Al³⁺ appeared to be no greater than that of a weak complexant such as adipic or acetic acid. A species distribution model was constructed showing the proportion of soluble Al that is bound by organic complexes. The model uses certain approximations regarding the degree of dissociation of the humus acids, but from measurements of soluble humus and Al in soil solutions it was suggested that these approximations were reasonably valid. The range of the model falls within conditions likely to occur in agricultural topsoils and demonstrates the importance of organic complexants in limiting Al³⁺ concentrations in natural aqueous systems.     

The relation between the moisture-release curve and the structure of soil

The limit to the precision with which moisture-release data may be related to soil structure is examined. Thin sections in two orthogonal planes were prepared from cores for which moisture release data and saturated conductivity measurements were also collected. Structural parameters are inferred indirectly through estimation of the mass fractal dimension from the moisture-release curve, and directly through measurement of the scaling properties of the pore space and solid matrix from the thin sections using image analysis. Theoretical results are presented which show that, in the absence of additional information, the interpretation of the moisture-release curve is ambiguous for several reasons. A power-law exponent is a consequence of either a fractal pore volume; a fractal solid volume; a fractal pore wall; or a non-fractal, self-similar pore wall, and one cannot infer from the measurement which is the case. Experimental results are presented which confirm that direct measurement of the fractal dimension of the solid matrix is a good predictor of the Brooks–Corey exponent for the soils studied here. Therefore, although a specific structural parameter characterizes the moisture-release curve, the latter cannot be used as a detailed measure of soil structure.     

The effect of a cereal supplement during early lactation on the performance and intake of ewes grazing perennial ryegrass at three stocking rates

A comparison was made of the effect of a cereal supplement during early lactation on the performance and intake of ewes suckling two lambs while rotationally grazing pasture at stocking rates of 20, 17 or 14 ewes per ha. Supplement (S) at the high (H) and medium (M) stocking rates resulted in higher organic matter (OM) intakes (grass + supplement) of 2040 and 2500 g d^-1 respectively, compared with the herbage OM intakes of unsupplemented (U) ewes of 1750 and 2040 g d^-1 respectively. At the low (L) stocking rate the total OM intake of supplemented ewes and the herbage OM intake of unsupplemented ewes was similar at 2250 and 2210 g d^-1 respectively.
Lamb growth rate (g d^-1) to 12 weeks of age was significantly lower on treatment UH (229) compared with those on UM (253) and UL (262). Growth rates on S treatments were similar (SH 248; SM 261; SL 272) and there were no significant differences between S and U within stocking rates. Unsupplemented ewes lost significantly more weight during the period of intake measurement than those receiving supplement. The speed of rotation was faster where supplement was not fed at the medium and high stocking rates and herbage accumulation under UH was less than under SH. Only at the high stocking rate did feeding a supplement give a higher financial output.     

Four season herbicide injection of hardwoods*

Eleven different hardwood species were injected using a hypo-hatchet with eight different lierbicides during the spring, summer, fall and winter seasons. Late spring to fall injections gave maximum efficacy. All the herbicides were effective at the given concentrations and injection of I ml/2.5 cm of stem diameter, Least effect followed winter injections probably due to poor translocation, little active tree metabolism, and high viscosity of some formulations when air temperatures were near freezing. Spring injection tended to allow revegetation by release of lateral buds after apical meristems and leaves had been killed. Multiple clumps of red maple stems were not well controlled by single stem injection. Quatre saisons de traitement herbicide par injection de ligneux à bois dur Onze espéces ligneuses à bois dur ont été traitées par injection en utilisant une hachette spéciale, avec 8 herbicides, au printemps, en été. en automne et en hiver. Les traitements faits de la fin du printemps à l'automne ont donné le maximum d'efficacité. Tous les herbicides ont été actifs aux concentrations données et pour un volume d'injection de 1 ml pour 2,5 cm de diamétre de tige. L'effet plus faible des injections faites en hiver est probablement du à une faible migration, au métabolisme peu actif dans les arbres et à la viscositéélevée de certaines formulations lorsque les températures de I'air avoisinaient le gel. Les injections de printemps ont montré une tendance à un nouveau départ de la végétation par libération de bourgeons latéraux aprés la mort des méristémes apicaux et des feuilles. De nombreux rejets de tiges d'érable n'ont pas été détruits par une injection unique dans la tige. Herbizid-Injektionen bei Laubbdämen in vier Jahreszeiten Mit Hilfe eines Spezialbeils wurden im Frühjahr, Sommer, Herbst’ und Winter Laubbäumen 11 verschiedener Arten acht verschiedene Herbizide injiziert. Injektionen vom späten Frühjahr bis zum Herbst zeigten die beste Wirkung. Mit einer Injektion von 1 ml je 2.5 cm Stammdurchmesser waren alle Herbizide in den gewählten Konzentrationen wirkungsvoll. Den geringsten Effekt zeigten Injektionen im Winter, was wahrschein- lich auf ungenügende Translokation, geringe Stoffwechselaktivität der Bäume im Winter und hohe Viskosität einiger Formulierungen bei Lufttemperaturen in der Nähe des Gefrierpunktes zurückzuführen ist. Injektionen im Frühjajr konnten nach Abtötung von apikalen Meristemen und Blattwerk durch Entwieklung von Seitenknospen zu einem gewissen Austrieb führen. Baumgruppen von Rotahorn liessen sich durch eine einzelne Stamminjektion mit nur mässigem Erfolg bekämpfen.     

Spotlined sardine Sardinops melanostictus listensto 1-kHz sound by using its gas bladder

ABSTRACT:   The auditory characteristics of pelagic fish have received lessattention compared to those of benthic or freshwater fish species,even though underwater sounds are considered to affect their behavior.Audiograms of five spotlined sardines were obtained using the auditorybrainstem response technique in which the evoked potential on theskin covering the head of the fish was measured. The auditory brainstemresponse is a non-invasive electrophysiological method that enablesthe auditory threshold level of fragile species, such as spotlinedsardines, to be measured. The gas bladder of the spotlined sardinehas been considered as possibly contributing to an enhancement intheir hearing. In the test, the sound absorption profile of sardineswas also measured. The frequency at the lowest auditory thresholdlevel (i.e. the most sensitive frequency) and absorption were foundat 1024 Hz and 1040 Hz, respectively. The spotlinedsardine was found to be sensitive to sounds at relatively higherfrequency ranges compared to other seawater fishes and the gas bladderis seen to play a significant role in detecting sound.     

A Comparison of Three Techniques for Closure of Pelvic Flexure Enterotomies in Normal Equine Colon

Six enterotomies 3 cm long, spaced at 3 cm intervals, were made in the antimesenteric border of the pelvic flexure of the ascending colon in five adult horses. Ten incisions each were sutured with a Utrecht pattern (single layer), a full-thickness simple continuous oversewn with a Cushing pattern (two layer), and a mucosal simple continuous with a seromuscular simple continuous oversewn with a Cushing pattern (three layer). In all horses, chromic gut and polyglactin 910 were each used once for each pattern. On day 6, the pelvic flexure was excised and the colonic vessels were injected with a radio-opaque mass. Sections of each enterotomy were studied by light microscopy and high detail radiography. The single-layer closure led to serosa-to-mucosa healing and a thin bowel wall, and the three-layer closure resulted in distortion of the bowel wall by hematoma formation and submucosal contamination with ingesta. The two-layer closure resulted in good alignment and improved healing. There was less inflammatory reaction with polyglactin 910 than with chromic gut.     

Genetic control of two gamma-globulin isoantigenic sites in domestic rabbits

Results of immunochemical analysis of sera from 335 offspring of 81 litters of rabbits are consistent with the hypothesis that the isoantigenic sites, RGG-I and RGG-II, of the gamma-globulins are controlled by a single allelic pair of autosomal genes with both specificities exhibited by the heterozygote. The three genotypes may be designated gamma(I)/gamma(I), gamma(II)/gamma(II), and gamma(I)/gamma(II).     

ASSESSMENT OF THE ACCURACY AND PRECISION OF A PATIENT IMMOBILIZATION DEVICE FOR RADIATION THERAPY IN CANINE HEAD AND NECK TUMORS

The positioning accuracy and precision of a head and neck immobilization device for radiation therapy of tumors in the canine skull was evaluated. Nineteen dogs with a spontaneous tumor of the head were enrolled including 12 with an intracranial mass and seven with an intranasal or maxillary tumor. Three hundred thirty-three pairs of orthogonal digital portal radiographs were analyzed to assess patient displacement in the cranial–caudal, lateral, and dorso-ventral directions. The mean systematic displacement was 0.8, 1, and 0.9 mm. The mean random displacement was 1.9, 1.6, and 1.5 mm. These values resulted in an overall displacement of 2.1 mm in the cranial–caudal direction, 1.8 mm in the lateral direction, and 1.7 mm in the dorsal–ventral direction. The mean displacement value of the three dimensional (3D) vector was 2.4 mm with a standard deviation of 2.1. Ninety-five percent of all vectors were <6.4 mm. This study quantifies the precision and accuracy of this particular positioning device. Knowing the limitations and setup variability of the system being used to set patients up for daily radiotherapy is paramount to planning and delivering appropriate radiation doses, especially as more complex treatment methods are used.