Techniques for measuring the wetting of leaf surfaces

Different types of plant leaves exhibit a broad spectrum of wetting behaviour because of their different pubescence, wax layer, scales, veins, etc. The wetting tension is used to express the wetting of a leaf with β_sf = σf. cos θ (σf = the surface tension of a liquid and θ= the contact angle of a liquid to the surface of a leaf). Three different methods are used for measuring contact angles: the contact angle goniometer method, the meniscus rise method and the Wilhelmy plate method. All three methods are based on completely independent theories and produce absolutely uniform contact angles on smooth paraffin surfaces. Closed cup systems which could be thermostatted were used for making the measurements. Substantial differences in the contact angles become apparent when contact angle measurements on roughened and smooth firm surfaces are compared, as for example contact angles on smooth and roughened paraffin surfaces. If the figures for the contact angles on a smooth surface are 90° or > 90°, they will be bigger on a roughened surface; if they are <90° on a smooth surface, they will be smaller on a roughened surface. These results obtained with paraffin were confirmed by contact angle measurements made on plant leaves. The contact angles, measured on plant leaves with the help of the three different measuring methods, show a high degree of uniformity.     

Shrimp rearing in biofloc integrated with different mullet stocking densities

This work compared the effects of different densities of Mugil curema integrated in the rearing of Litopenaeus vannamei in a biofloc system on the yield and ecological performance of the system. For that, an experiment lasting 55 days was conducted. Four groups were evaluated as follows: (a) T0: shrimp reared without mullet, (b) T10: shrimp reared with 22 fish per tank, (c) T20: shrimp reared with 43 fish per tank, and (d) T30: shrimp reared with 65 fish per tank, each treatment with four replicates. The sludge:biomass ratio was higher in the T0 treatment, while the T10–T20 treatments were more efficient, producing more biomass and less sludge. The use of water was 17% more efficient in all treatments with mullet. Mullet survival was higher in the T10 and T20 treatments (mean: 84 ± 8%) than in the T30 (61 ± 5%) treatment. The fish final biomass and yield limits of the system were 0.37 kg and 3.7 kg/m³ respectively. Finally, there was no increase in the total nitrogen output of the system up to the T10 density. In conclusion, it is possible to integrate mullet up to 3.7 kg/m³, increasing the yield in 20% and decreasing water use.     

Effect of rapid intravenous administration of 50% dextrose solution on phosphorus homeostasis in postparturient dairy cows

BACKGROUND: Dextrose is commonly administered to postparturient dairy cows, which often have low plasma phosphorus concentration ([P]) as a result of anorexia and sudden onset of lactation. Intravenous (IV) dextrose administration causes hypophosphatemia in other species. HYPOTHESIS: Bolus administration of dextrose to postparturient dairy cows results in a transient decrease in plasma [P]. ANIMALS: Six healthy postparturient dairy cows. METHODS: Using a crossover design, cows were administered 500 mL of 50% dextrose solution IV or a sham treatment. Plasma concentrations of glucose ([glucose]), immunoreactive insulin ([IRI]), and phosphorus were monitored for 12 hours after each treatment. Urine [P], [glucose], and volume and salivary [P] were also determined. RESULTS: Plasma [glucose], [IRI], and [P] were stable during sham treatment. Plasma [P] decreased rapidly after dextrose administration, dropping by 35% in 1 hour and remaining below baseline for 90 minutes. Salivary [P], urine [P], and urine volume per hour remained stable after dextrose administration, but glucose was detected in urine for up to 6 hours. The amount of glucose excreted in urine in 12 hours (11.9+/-4.5 g) was less than 5% of the administered dose. Regression analysis revealed a stronger association between plasma [P] and [IRI] than between plasma [P] and [glucose], suggesting that hyperinsulinemia drove the hypophosphatemia. CONCLUSION AND CLINICAL IMPORTANCE: Results indicate that low plasma [P] should be expected in cows that have received IV dextrose within 1 hour before blood sampling. Caution is advised when administering dextrose solution to cows already at risk of hypophosphatemia.     

Behavioral considerations in the management of working dogs.

This article is not intended as a comprehensive exploration of all issues related to the behavioral management of working dogs or as a survey of all manners of canine employment. Rather, it is one person's perspective into the challenges of managing a behavioral medicine program in a large-scale working dog program environment. The issues presented, however, are those that are commonly encountered when selecting, assessing, diagnosing, and treating working dogs. I hope this article provides insight not only into the author's program but also into some of the unique challenges in working with working dogs as well as some of the commonalities of this kind of behavioral practice with companion animal settings.     

Response of beech and oaks to wounds made at different times of the year

Tree care, especially pruning, is still mostly done in the dormant time. Such treatments expose live inner bark, the vascular cambium, and functioning outer sapwood to harsh external influences followed often by infection of pathogens. Investigations about response reactions of beech and oak to wounding made in different times of the year showed that wound closure was significantly slower for December and February wounds than in April and October. The length of discoloured sapwood was in October and December wounds greater than in February and April. Sapwood reaction expressed by the soluble phenol concentration index indicated however no significant differences among wounding dates. Overall, woundings in the vegetation period will be more effectively compartmentalized than in the dormant season. Consequently, tree care like pruning with many woundings should not be done in the winter period.Presented at the 6th ISA European Conference, 9.-12. June 2004, Maastricht, The Netherlands     

Der pH-Wert und das Vorkommen niedermolekularer Fettsäuren im Naßkern der Buche (Fagus sylvatica L.)

The pH-value and the occurrence of fatty acids in wetwood of European Beech (Fagus sylvatica L.). At the border of the wetwood area pH-value of the capillary liquid was altered from acid to neutral conditions. Fatty acids frequently occurred in wetwood. Probes with pH-values higher than 6.8 often were deeply black stained.     

Zum 100. Jahrgang des Forstwissenschaftlichen Centralblattes

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