ALBERT

Notes: A plot of relative parallax measurements in a student exercise is proposed for revealing errors in parallax bar readings taken from a stereo-pair of aerial photographs. The sensitivity of the computed heights to measurement error is also evaluated.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméOn propose un tracé graphique des mesures de parallaxe pour mettre en évidence des erreurs de lecture à la barre de parallaxe.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungEs wird eine Auswertung relativer Parallaxenmessungen bei einer studentischen Übung vorgeschlagen, um Fehler der an einem Stereomikrometer vorgenommenen Ablesungen aufzudecken, die an Hand eines Luftbildpaars erfolgten. Der Einfluss des Messfehiers auf den Höhenfehler wird ebenfalls abgeschätzt.

Notes: : Most herbicides applied to crops are adsorbed by plants or transformed (degraded) in the soil, but small fractions are lost from fields and either move to streams in overland runoff, near surface flow, or subsurface drains, or they infiltrate slowly to ground water. Herbicide transformation products (TPs) can be more or less mobile and more or less toxic in the environment than their source herbicides. To obtain information on the concentrations of selected herbicides and TPs in surface waters of the Midwestern United States, 151 water samples were collected from 71 streams and five reservoir outflows in 1998. These samples were analyzed for 13 herbicides and 10 herbicide TPs. Herbicide TPs were found to occur as frequently or more frequently than source herbicides and at concentrations that were often larger than their source herbicides. Most samples contained a mixture of more than 10 different herbicides or TPs. The ratios of TPs to herbicide concentrations can be used to determine the source of herbicides in streams. Results of a two-component mixing model suggest that on average 90 percent or more of the herbicide mass in Midwestern streams during early summer runoff events originates from the runoff and 10 percent or less comes from increased ground water discharge.

Notes: The greenbug [Schizaphis graminum (Rondani)] is an extremely damaging pest of barley (Hordeum vulgare L.), particularly in the southern Great Plains of the USA. Winter barley targeted for production in this region should incorporate resistance to greenbug in the form of the resistance gene Rsg1a (in ‘Post 90′) or Rsg2b (in PI 426756). This study was conducted to fully characterize the resistance profile of these two genes against important greenbug biotypes, and to determine which of the two resistance genes is most effective in protecting barley from the greenbug. Eight barley and four wheat cultivars and germplasms were challenged with six greenbug biotypes and damage ratings were recorded for each combination. In five of the six tests, ‘Post 90’ was significantly more resistant than PI 426756 to greenbug feeding damage. Based on the results presented here, we conclude that the resistance gene, Rsg1a, in ‘Post 90’ is the better choice for use in breeding programmes and will provide better protection than Rsg2b against the greenbug.

Notes: Some naturally occurring and synthetic phenolic antioxidants have been evaluated in a dry model system simulating the exposure of lipids in freeze-dried membranes of whole tissue foods. The system is a linoleic acid monolayer on activated silica gel autoxidized at 80°C in dry air. The system is dry and porous and the demonstrated monolayer adsorption and restricted translational mobility of the lipid present a plausible model of freeze-dried membrane characteristics. Although relative effectiveness of the common antioxidants in this system has some similarities to the reported order in other dry systems, there are notable exceptions. For example, butylated hydroxyanisole is by far the most effective antioxidant in the silica system whereas it is reported to be much less effective than propyl gallate in bulk oils and some other dry systems. Thus, special conditions appear to modify antioxidant effectiveness in the lipid monolayer on silica.

Notes: Roots of sweet potato cultivar Jewel, and two unnamed selections (213 × 228–1, and 2.57 × 255-8) were stored at 5°C or 14°C for 10 wk. Increased discoloration of certain cultivars of chilled sweet potato roots is apparently not due to an increase in the amount of extractable peroxidase or chlorogenic acid oxidase activity. Chilled tissues of 213 ×228–1 discolored and showed an increase in pH and chlorogenic acid. Chilled tissues from roots of 257 × 255-8 exhibited an increase in pH, but did not increase in chlorogenic acid content and were only slightly discolored. Tissues of Jewel changed little in pH or chlorogenic acid content and discolored the least of the three cultivars. Chlorogenic acid discolored under the influence of high pH. The data indicate that differences among cultivars in discoloration resulting from chilling injury may be due to differences in tissue pH and chlorogenic acid content.

Notes: Research is described which evaluates and relates a simple Durometer test of raw potato lots with instrumental texture measurements and sensory panel evaluation of oven-reheated frozen French fried potatoes. Statistical evaluation of the mean data shows no difference between the Idaho and Maine Russet Burbank samples for any of the measurements. Durometer means were significantly correlated with shear press measurements and all shear press values were significantly intercorrelated. The large correlation coefficients between Durometer readings and other measurements indicate that Durometer evaluations can be used to predict from the raw tubers the shear press measurements and overall moistness, crust crispness and internal mealiness of oven-reheated frozen French fried potatoes. Further work is necessary with other source and variety combinations before a general prediction statement can be made.

Notes: Plasma melatonin synthesis in juvenile Atlantic salmon Salmo salar decreased with increasing light intensity. Melatonin profiles reflected accurately the photoperiod under which the salmon were maintained. Groups maintained at 12°C showed significantly higher (P 〈 0·01) levels of dark phase plasma melatonin compared with the groups maintained at 4°C.

Notes: There is increasing public, governmental and commercial interest in the welfare of intensively farmed fish and stocking density has been highlighted as an area of particular concern. Here we draw scientific attention and debate to this emerging research field by reviewing the evidence for effects of density on rainbow trout. Although no explicit reference to ‘welfare’ has been made, there are 43 studies which have examined the effects of density on production and physiological parameters of rainbow trout. Increasing stocking density does not appear to cause prolonged crowding stress in rainbow trout. However, commonly reported effects of increasing density are reductions in food conversion efficiency, nutritional condition and growth, and an increase in fin erosion. Such changes are indicative of a reduced welfare status—although the magnitude of the effects has tended to be dependent upon study-specific conditions. Systematic observations on large scale commercial farms are therefore required, rather than extrapolation of these mainly small-scale experimental findings. There is dispute as to the cause of the observed effects of increasing density, with water quality deterioration and/or an increase in aggressive behaviour being variously proposed. Both causes can theoretically generate the observed effects of increasing density, and the relative contribution of the two causes may depend upon the specific conditions. However, documentation of the relationship between density and the effects of aggressive behaviour at relevant commercial densities is lacking. Consequently only inferential evidence exists that aggressive behaviour generates the observed effects of increasing density, whereas there is direct experimental evidence that water quality degradation is responsible. Nevertheless, there are contradictory recommendations in the literature for key water quality parameters to ensure adequate welfare status. The potential for welfare to be detrimentally affected by non-aggressive behavioural interactions (abrasion, collision, obstruction) and low densities (due to excessive aggressive behaviour and a poor feeding response) have been largely overlooked. Legislation directly limiting stocking density is likely to be unworkable, and a more practical option might be to prescribe acceptable levels of water quality, health, nutritional condition and behavioural indicators.