A CONTINGENCY APPROACH TO CHOICE

The moment of choice, when a decision option is identified as being preferred, is a key stage in a decision-making process. Some explicit or implicit mechanism, be it optimising, satisficing or a combination of the two, is required to make a choice. Dependable decision-making requires an appropriate choice mechanism, but the process and criteria by which a choice mechanism is selected are seldom addressed. A contingency approach to choice is proposed in which a choice mechanism is selected according to the characteristics of the information available and the meta-level constraints and objectives of the decision-maker. Information used in the choice is characterised according to the extent and type of uncertainty. The importance in effective decision-making of meta-level requirements, for example for inclusive and transparent mechanisms, is discussed. Normative and fuzzy choice mechanisms are cast within a generic framework of choice mechanisms. A new theory of choice based on interval probabilities is introduced for use in some situations where existing theories of choice are inappropriate.     

EFFECT OF PARTICLE SIZE AND SAMPLE SIZE ON LIPID STABILITY OF MILLED FLAXSEED (Linum usitatissimum L.)

Experiments were conducted to determine the effect of sample size and particle size on lipid oxidation of milled flaxseed. An initial experiment showed that most of the lipid oxidation detected in milled flaxseed samples occurred on the surface that was exposed to the air during storage. In a subsequent experiment, milled flaxseed at 100, 200 and 300 g were stored in the dark in rectangular pans for 8, 24 and 48 days at 50C. Lipid oxidation, as determined by surface lipid content, peroxide value and α-linolenic acid content, was lower in the 300 g samples than in the 100 g samples of milled flaxseed. Large versus small samples had less apparent lipid oxidation because of their inherently lower surface to volume ratio. In a third experiment, oxidation was lower in lipid extracted from coarse ( > 600 µm) than fine particles ( < 600 µm), after 48 days of storage.

PRACTICAL APPLICATIONS

This research has practical applications to the flaxseed milling and food industries. These results show that assessment of lipid oxidation in milled flaxseed needs to consider sample size (collection). Milled flaxseed oxidized predominantly at the sample surface where a polymerized layer of flaxseed particles formed over time. Relatively little oxidation occurred in the interior of the sample. Thus, sampling from the surface or interior of a milled flaxseed sample will end in different results and conclusions. Similarly, results will vary with surface : interior ratio of milled flaxseed. Food manufacturers may want to discard the top layer of milled flaxseed that has been exposed to air. Lipid oxidation was less with coarse than fine particles. Thus it would be prudent not to use milled flaxseed with a finer particle size than is necessary for acceptable end-use quality.     

The Pasterze Glacier,Austria

The remote sensing of foliar biochemical concentration assumes that leaf biochemical absorption features will be manifest in canopy reflectance. This is a reasonable assumption providing the effect of a given change in foliar biochemical concentration has a similar effect on both leaf and canopy reflectance. A comparison between canopy and leaf reflectance was made to determine if canopy effects (composite of leaf area index, biomass, structure, multiple scattering and shadow) could alter the leaf biochemical information in canopy reflectance spectra. Differences in leaf biochemical concentrations and leaf biomass were induced by the application of fertilisers to large plots of slash pine (Pinus elliottii var elliottii) in Florida, U.S.A. The reflectance of plot canopies was measured using the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). The reflectance of samples of leaves drawn from each plot were measured using a laboratory spectrometer. The differences between airborne and laboratory reflectance ratios (fertilised/control spectra) were used to isolate the effects of the canopy in AVIRIS reflectance spectra. From this study it was concluded that the canopy influenced leaf reflectance substantially at wavelengths beyond the water absorption feature at 1400nrn and leaf biochemical information was transmitted virtually unchanged from the leaf to the canopy in near-infrared wavelengths.     

Control of grapevine powdery mildew with mineral oil: an assessment of oil concentration and spray volume

DC Tron, a highly refined mineral oil containing patented additives to prevent UV light induced breakdown, was evaluated in vineyards for control of powdery mildew. DC Tron suppressed development of powdery mildew but was not as effective as the conventional fungicide Topas. Of the oil treatments the 1% rate applied in spray volumes of 1000 L/ha was the most efficient. Poor control was achieved with oil rates less than 1% as well as spray volumes less than 1000 L/ha whereas phytotoxicity developed in many cases at concentrations greater than 1% or spray volumes higher than 1000 L/ha. In all oil treatments, powdery mildew developed less in leaves than on bunches. This difference was attributed to poor spray coverage on bunches compared to leaves.     

Silage from tropical fish 3. Lipid behaviour

Acid silages were prepared from silverbelly ( Leiognathus spp.) at 30°C with 3% (w/w) of 98% formic acid. Lipid oxidation takes place actively during ensilation as demonstrated by changes in fatty acid composition, TBA value and peroxide value. Lipid extraction, with chloroform: methanol or isopropanol, or the addition of an antioxidant before ensilation can limit the build up of lipid oxidation products. Lipid extraction also suppresses the autolysis of proteins in a defatted silage compared with a normal silage when measured by total soluble nitrogen or soluble NPN. The solubilization of collagen appears to be unaffected by lipid extraction perhaps reflecting the non-enzymic nature of this process. The limited autolysis in defatted silages may be beneficial in restricting the release of free amino acids capable of reacting with lipid oxidation products resulting in a lower nutritional value for silage based diets.     

Phosphorous Levels in Peeled and Deveined Shrimp Treated with Sodium Tripolyphosphate

Using volumetric and spectrophotometric methods for the determination of phosphorous, untreated shrimp were shown to have high and variable phosphorous content. When peeled and deveined shrimp were treated with 0.5% and 1.0% sodium tripolyphosphate (STP) solutions, the STP uptake was shown to be low. At these low treatment concentrations the phosphorous content in the treated shrimp did not exceed the range of natural phosphorous found in untreated shrimp. When higher treatment concentrations were used, treated thrimp could be identified. The stability of STP in treated shrimp during frozen storage was investigated using a P³² STP isotope. After 2 wk of frozen storage at –26°C only 12% of the total activity could be attributed to STP. At the same time, pyrophosphate was present at a level of 25% and orthophosphate at 27%. During further frozen storage, the STP concentration remained at approxinately 12%, pyrophosphate dropped down to as low as 2% while orthophosphate gradually increased reaching 45% of total activity at the end of 10 wk storage period.