Digital shearing method for three-dimensional data extraction in holographic particle image velocimetry

We report a new digital shearing method for extracting the three-dimensional displacement vector data from double-exposure holograms. With this method we can manipulate both the phase and the amplitude of the recorded signal, which, like optical correlation analysis, is inherently immune to imaging aberration. However, digital shearing is not a direct digital implementation of optical correlation, and a considerable saving in computation time results. We demonstrate the power of the method by MATLAB simulation and discuss its performance with reference to optical analysis.     

Influence of snail feces and mucus on oviposition and larval behavior ofPherbellia cinerella (Diptera: Sciomyzidae)

Larvae of the sciomyzid flyPherbellia cinerella are voracious predators of terrestrial helicid snails. Eggs are deposited in areas where snails occur and larvae hunt actively for their prey. Snail feces and mucus were tested to determine if they had any kairomone or stimulatory effects onP. cinerella. Adult flies oviposited more frequently on substrates containing fresh snail feces than on substrates containing snail mucus or water (control). However, mucus and feces both stimulated increased search behaviour in first instar larvae. These results are discussed in relation to snail biology, and the potential for augmentation of these flies in areas affected by pest snails.     

Investigating CAL?

Can CAL facilitate discussions and problem solving? Surveys of classroom activities during mathematics lessons in British secondary schools present a rather gloomy picture. Disproportionately large amounts of time are devoted to teacher explanations, and to pupil exercises. Activities such as discussions, practical work, problem solving and investigations happen so rarely that they are collectively referred to as “missing activities”. Can CAL help? Tutorial CAL, of course, reinforces the exposition-imitation mode of teaching. Other kinds of CAL exist, though.An observational study watched 170 mathematics lessons in which the microcomputer was used as a teaching aid. Teachers chose freely from a collection of over 90 programs. The most popular programs, in terms of how often thet were chosen, and how their usefulness was rated by the observers, were investigative in style. This paper describes the lessons which were based on the four most popular programs used (JANE, SUBGAME, EUREKA and VECTOR). Each one facilitated some of the “missing activities”. The role of the microcomputer as an agent of change in teaching style towards more open methods is described and discussed.     

Statistical performance of cascaded linear shift-invariant processing

The cascaded correlator architecture comprises a series of traditional linear correlators separated by nonlinear threshold functions, trained with neural-network techniques. We investigate the shift-invariant classification performance of cascaded correlators in comparison with optimum Bayes classifiers. Inputs are formulated as randomly generated sample members of known statistical class distributions. It is shown that when the separability of true and false classes is varied in both the first and the second orders, the two-stage cascaded correlator shows performance similar to that of the optimum quadratic Bayes classifier throughout the studied range. It is shown that this is due to the similar decision boundaries implemented by the two nonlinear classifiers.     

Encapsulation of Aqueous Components in Solid Fat Beads: Studies of a Model Dye and a Probiotic Culture

Solid fat beads containing aqueous droplets of either a water soluble dye (Brilliant Blue) or a suspension of viable probiotic bacteria (Bifidobacterium animalis ssp lactis) were produced by dropping a water‐in‐molten fat emulsion into cold water or onto a cold plate, respectively. Hydrogenated palm stearin beads containing 20 % dye solution were 4.6 ± 0.2 × 2.7 ± 0.4 mm and the average bead weighed 0.0103 ± 0.0003 g. The dye was completely released into an external aqueous phase after 24 h stirring at temperatures above the melting point of the fat but at temperatures where the fat was solid very little dye was released into an external aqueous phase. When a bacterial suspension was used as the internal phase of 20 % hydrogenated palm stearin/80 % palm kernel oil beads, the beads contained 8.44 log CFU/g. The encapsulated organisms were more resistant to acid stress than an unencapsulated control (loss of 0.7 versus 5.75 log CFU/g). This approach offers a way to protect probiotic bacteria during transit through the stomach. Practical application: by encapsulating bacteria in solid fat they become more resistant to acids. Small beads could be added to foods or swallowed as a pill as a way to deliver viable probiotic organisms to the lower digestive tract.     

On the stability of oil-in-water emulsions to freezing

Oil in water emulsions (40 wt%) were prepared from a homologous series of n-alkanes (C10–C18). The samples were temperature cycled in a differential scanning calorimeter (two cycles of 40 °C to −50 °C to 40 °C at 5 °C min⁻¹) and in bulk (to −20 °C). The emulsions destabilized and phase-separated after freeze–thaw if the droplets were solid at the same time as the continuous phase and were more unstable if a small molecule (SDS or polyoxyethylene sorbitan monolaurate) rather than a protein (whey protein isolate or sodium caseinate) emulsifier was used. The unstable emulsions formed a self-supporting cryo-gel that persisted between the melting of the water and the melting of the hydrocarbon phase. Microscopy provides further evidence of a hydrocarbon continuous network formed during freezing by a mechanism related to partial coalescence which collapses during lipid melting to allow phase separation.     

Stearidonic acid: A plant produced omega‐3 PUFA and a potential alternative for marine oil fatty acids

Omega‐3 (n‐3) fatty acids are widely recognized as being important in regulating many inflammatory disorders in man. However, metabolism of the parent n‐3 fatty acid α‐linolenic acid (ALA, 18:3n‐3) to the highly unsaturated bioactive fatty acids; eicosapentaenoic acid (EPA, 20:5n‐3) and docosahexaenoic acid (DHA, 22:6n‐3), in the body is limited. The first product in the pathway leading to EPA/DHA is the post‐Δ6 desaturase metabolite stearidonic acid (SDA, 18:4n‐3). The activity of the Δ6‐desaturase enzyme is low in man and can be adversely influenced by several environmental factors including dietary fat. SDA has been shown, in several studies, to be rapidly and efficiently converted to EPA which is a probable factor in its bio‐activity. The main source of EPA and DHA in diet is fish oil which, owing to over‐fishing and its extensive use in aquaculture feed, is becoming a scarce resource. There clearly exists a need for a renewable source of a lipid containing the highly unsaturated n‐3 fatty acids EPA, DHA or SDA. Although the highly unsaturated fatty acids (HUFA) have been commercially produced in micro‐organisms neither EPA nor DHA has been shown to exist in any quantity in land‐based plants. SDA is however found in several fungal and algal species and also in a small number of plant seed oils. Plants from the Boraginaceae family notably Echium species are particularly rich in SDA and Echium plantagineum has been grown commercially. Other plants from the Boraginaceae are being investigated and several have been identified that may offer benefits over Echium spp. Transgenic plants containing high levels of SDA have also been reported but engineering EPA or DHA into genetically modified higher plants is proving elusive. SDA‐containing lipids are of great interest in a number of areas such as fortified foods, dietary supplements, medicinal foods, pharmaceuticals and personal‐care products.     

Ultrasonic characterization of lactose dissolution

The ultrasonic properties (at 2.25 MHz) of lactose solutions and suspension of lactose crystals (d ∼ 50 μm) were measured as a function of concentration (0–40 wt.%). Ultrasonic velocity increased linearly with concentration regardless of the state of dissolution of the lactose crystals while ultrasonic attenuation was low and concentration-independent when the lactose was dissolved and increased approximately linearly with the concentration of suspended crystals. Therefore the amount of lactose present and the state of dissolution can be determined simultaneously with single ultrasonic sensor. A sensor based on this principle was applied to a stirred tank and used to measure the time taken to mix powdered lactose into a solution and the time for the added lactose to dissolve.