Evolution of multivariant microstructures with anisotropic misfit: A phase field study

We study, in two dimensions, the effect of misfit anisotropy on microstructural evolution during precipitation of an ordered beta phase from a disordered alpha matrix; these phases have, respectively, 2- and 6-fold rotation symmetries. Thus, precipitation produces three orientational variants of beta phase particles, and they have an anisotropic (and crystallographically equivalent) misfit strain with the matrix. The anisotropy in misfit is characterized using a parameter t = epsilon(yy)/epsilon(xx), where epsilon(xx) and epsilon(yy) are the principal components of the misfit strain tensor. Our phase field, simulations show that the morphology of beta phase particles is significantly influenced by 1, the level of misfit anisotropy. Particles are circular in systems with dilatational misfit (t = 1), elongated along the direction of lower principal misfit when 0 < t < 1 and elongated along the invariant direction when - 1 <= t <= 0. In the special case of a pure shear misfit strain (t = - 1), the microstructure exhibits star, wedge and checkerboard patterns; these microstructural features are in agreement with those in Ti-Al-Nb alloys.

Instabilities and Waves in Thin Films of Living Fluids

We formulate the thin-film hydrodynamics of a suspension of polar self-driven particles and show that it is prone to several instabilities through the interplay of activity, polarity, and the existence of a free surface. Our approach extends, to self-propelling systems, the work of Ben Amar and Cummings [Phys. Fluids 13 1160 (2001)] on thin-film nematics. Based on our estimates the instabilities should be seen in bacterial suspensions and the lamellipodium, and are potentially relevant to the morphology of biofilms. We suggest several experimental tests of our theory.

Nanocrystalline Janus films of inorganic materials prepared at the liquid-liquid interface

The interface between toluene and water has been employed to prepare ultrathin Janus nanocrystalline films of metal oxides, metal chalcogenides and gold, wherein the surface on the organic-side is hydrophobic and the aqueous-side is hydrophilic. We have changed the nature of the metal precursor or capping agent in the organic layer to increase the hydrophobicity. The strategy employed for this purpose is to increase the length of the alkane chain in the precursor or use a perfluroalkane derivative as precursor or as a capping agent. The hydrophobicity and hydrophilicity of the Janus films have been determined by contact angle measurements. The morphology of hydrophobic and hydrophilic sides of the film have been examined by field emission scanning electron microscopy.

Using lead sulphate instead of lead oxide in flux growth of yttrium iron garnet(YIG) crystals

Crystal growth of YIG from fluxes containing lead sulphate in place of lead oxide in the usual lead oxide-lead fluoride-boron oxide flux system has been tried. Lead sulphate decomposes during crystal growth giving lead oxide and sulphur trioxide. Due to the influence of sulphur trioxide in the system the yield of crystals almost doubles. There is no change either in the morphology of the crystals or their lattice parameter. It is possible that solubility of YIG is different in the new flux and the changed solubility causes the increase in yield of crystals.

Changes in sensory quality of sterile cantaloupe dice stored in controlled atmospheres.

Diced cantaloupe flesh that was microbiologically sterile was prepared in order to study the physiological deterioration of fruit when stored under a range of controlled atmospheres at 4.5°C. Sterile fruit pieces were prepared by boiling whole melons for 3 min, then dicing aseptically. Storage atmospheres were in continuous flow and contained from 0 to 26% CO2 and 3.5 to 17% O2. Sensory assessments were carried out by a highly trained panel at 14-day intervals. Products that were acceptable for up to 28 days were obtained when the following 3 treatments were used: 6% CO2 and 6% O2; 9.5% CO2 and 3.5% O2; and 15% CO2 and 6% O2. Overall, treatment with 0, 19.5 or 26% CO2 (irrespective of O2 concn.) caused significant deterioration in sensory properties.

Robustness of NIR calibrations for soluble solids in intact melon and pineapple

The soluble solids content of intact fruit can be measured non-invasively by near infrared spectroscopy, allowing “sweetness” grading of individual fruit. However, little information is available in the literature with respect to the robustness of such calibrations. We developed calibrations based on a restricted wavelength range (700–1100 nm), suitable for use with low-cost silicon detector systems, using a stepwise multiple linear regression routine. Calibrations for total soluble solids (°Brix) in intact pineapple fruit were not transferable between summer and winter growing seasons. A combined calibration (data of three harvest dates) validated reasonably well against a population set drawn from all harvest dates (r2 = 0.72, SEP = 1.84 °Brix). Calibrations for Brix in melon were transferable between two of the three varieties examined. However, a lack of robustness of calibration was indicated by poor validation within populations of fruit harvested at different times. Further work is planned to investigate the robustness of calibration across varieties, growing districts and seasons.

Activating Mango Fruit Defence to Anthracnose Disease

The fungus causing anthracnose disease in mango, Colletotrichum gloeosporioides, (C g.), infects immature fruit early in the season, then enters a long latent phase. After harvest, when fruit start to ripen, the latency breaks and the fungus ramifies through the peel and pulp tissues causing black disease lesions. The breaking of pathogen latency in ripening mango fruit has been correlated with decreasing concentrations of the endogenous antifungal resorcinol compounds (Droby et al., 1986). The level of these antifungal resorcinols vary among mango cultivars (Droby et a1 , 1986). Controlling diseases by managing natural resistance of fruit to fungal attack could minimize the use of pesticides, which have become of major public concern on health and environmental grounds. The plant resistance activator benzo(l,2,3)thiadiazole-7-carbothioic acid S-methyl ester (trade name Bion®) has been widely reported as an effective inducer of systemic resistance. For example, Bion® was reported to induce pathogenesis-related proteins (PR proteins) and stimulate plant defence in peas (Dann and Deverall, 2000) and roses (Suo and Leung, 2001). However, until now, there is no information about the role of Bion® in activation of mango (cv. Kensington Pride) fruit resistance to anthracnose disease. The aim of this research is to determine the effect of resistance activators on defence responses of mango fruit to anthracnose disease.

Effect of an Ethylene Absorbent on Quality of Tomato Slices

Ethylene production is stimulated during the slicing of fresh cut tomato slices. Experiments were conducted to investigate whether the inclusion of ethylene absorbents in packaging affects the quality of tomato slices cv. Revolution during storage at 5OC. ‘Pink’ maturity stage tomatoes were cut into 7mm thick slices and vertically stacked in closed glass containers for 12 days with or without Purafil® to remove ethylene. The ethylene removal treatment resulted in reduced ethylene, less CO2 accumulation, and firmer slices.

Reducing Browning of Fresh-cut ‘Maha’ Carambola with Chemical Additives and Low-oxygen Atmospheres

The greatest attraction to using carambola (Averrhoa carambola L.) in the fresh-cut market is the star shape that the fruit presents after a transverse cut. Carambola is well-suited for minimal processing, but cut surface browning is a main cause of deterioration. This problem is exacerbated as a result of mechanical injuries occurring during processing and is mainly induced by the leakage of phenolic compounds from the vacuole and subsequent oxidation by polyphenol oxidase (PPO) (Augustin et al., 1985). The use of browning inhibitors in processed fruits is restricted to compounds that are non-toxic, ‘wholesome’, and that do not adversely affect taste and flavour (Gil et al., 1998). In the past, browning was mainly controlled by the action of sulphites, but the use of this compound has declined due to allergic reactions in asthmatics (Weller et al., 1995). The shelf life of fresh-cut products may be extended by a combination of oxygen exclusion and the use of enzymatic browning inhibitors. The objectives of this work were to determine the effects of: (1) post-cutting chemical treatments of ascorbic, citric, oxalic acids, and EDTA-Ca; (2) atmospheric modification; and (3) combinations of the above, on the shelf life of carambola slices based on appearance, colour and polyphenol oxidase activity

Pheromone-mediated mass trapping and population diversion as strategies for suppressing Carpophilus spp. (Coleoptera: Nitidulidae) in Australian stone fruit orchards

1 Five experiments were conducted during 1995-99 in stone fruit orchards on the Central Coast and in inland New South Wales, Australia, on the use of synthetic aggregation pheromones and a coattractant to suppress populations of the ripening fruit pests Carpophilus spp. (Coleoptera: Nitidulidae). 2 Perimeter-based suppression traps baited with pheromone and coattractant placed at 3m intervals around small fruit blocks, caught large numbers of Carpophilus spp. Very small populations of Carpophilus spp. occurred within blocks, and fruit damage was minimal. 3 Carpophilus spp. populations in stone fruit blocks 15-370m from suppression traps were also small and non-damaging, indicating a large zone of pheromone attractivity. 4 Pheromone/coattractant-baited suppression traps appeared to divert Carpophilus spp. from nearby (130 m) ripening stone fruit. Ten metal drums containing decomposing fruit, baited with pheromone and treated with insecticide, attracted Carpophilus spp. and appeared to reduce populations and damage to ripening fruit at distances of 200-500 m. Populations and damage were significantly greater within 200m of the drums and may have been caused by ineffective poisoning or poor quality/overcrowding of fruit resources in the drums. 5 Suppression of Carpophilus spp. populations using synthetic aggregation pheromones and a coattractant appears to be a realistic management option in stone fruit orchards. Pheromone-mediated diversion of beetle populations from ripening fruit may be more practical than perimeter trapping, but more research is needed on the effective range of Carpophilus pheromones and the relative merits of trapping compared to attraction to insecticide-treated areas.

Field evaluation of micropropagated and conventionally propagated ginger in subtropical Queensland

The growth and performance of micropropagated ginger (Zingiber officinale Roscoe) was compared with 'seed'-derived plants in field trials conducted in south-eastern Queensland. In the first generation ex vitro, micropropagated plants had significantly (P<0.01) reduced rhizome yield with smaller knobs and more roots. Micropropagated plants had a greater (P<0.01) shoot: root (rhizome) ratio compared with seed-derived plants. Shoots from micropropagated plants were also significantly (P<0.01) smaller with a greater number of shoots per plant. The unusual shoot morphology of the micropropagated plants did not appear to be related to the presence of benzylaminopurine, a plant growth hormone added to the multiplication medium, as plants subcultured for 3 cycles on a hormone-free medium also exhibited similar characteristics. Seed collected from the micropropagated plants and seed-derived plants was harvested and, despite the micropropagated seed being significantly (P<0.01) smaller, by the second generation ex vitro there were no significant differences between the treatments. Factors that can improve rhizome size, while reducing production costs, need to be identified before micropropagated plants can be recommended for routine use in the ginger industry as a source of disease and pest-free planting material.

The storage stability of passionfruit concentrate

Passionfruit (Passiflora edulis) concentrates (542 g/kg soluble solids) prepared in a wiped-film evaporator were stored for up to 6 months at - 18°, 4° and 20°C. Yeast and mould counts were taken and colour changes noted during storage. When suitable diluted concentrate colour and flavour were acceptable for 1 month at 20°C, 3 months at 4°C and 6 months at -18°C. Commercial short-term storage of concentrate at temperatures above -18°C appears to be feasible. An address presented to the 20th Annual Convention AIFST, Albury NSW, 16th- 20th May, 1987

Fruit maturity and soundness relevant to feeding choice by fruit-piercing moths (Lepidoptera: Noctuidae) in citrus crops in northeast Australia

Fruit-piercing moths are significant pests of a range of fruit crops throughout much of the world's tropics and subtropics. Feeding damage by the adult moths is most widely reported in varieties of citrus. In the years 2003 and 2004, fruit-piercing moth activity was observed regularly at night in citrus crops in northeast Australia, to determine the level of maturity (based on rind colour) and soundness of fruit attacked. 'Navelina' navel and 'Washington' navel orange, grapefruit and mixed citrus crops were assessed, and fruit was rated and placed into five categories: green, colouring, ripe, overripe and damaged. There were no statistical differences in the percentage of fruit attacked in each category across crops. However, within the individual crops significant proportions of green 'Navelina' fruit (58.7%) and green mixed citrus (57.1%) were attacked in 2004. Among all the crops assessed, 25.1% of moth feeding occurred on overripe or damaged fruit. Crops started to be attacked at least 8 weeks before picking, but in two crops there were large influxes of moths (reaching 27 and 35 moths/100 trees, respectively) immediately before harvest. Moth activity was most intense between late February and late March. Eudocima fullonia (Clerck) represented 79.1% of all moths recorded on fruit, with Eudocima materna (L.), Eudocima salaminia (Cramer) and Serrodes campana (Guen.) the only other species observed capable of inflicting primary damage. Our results suggest that growers should monitor moth activity from 8 weeks before harvest and consider remedial action if moth numbers increase substantially as the crop matures or there is a history of moth problems. The number of fruit pickings could be increased to progressively remove ripe fruit or early harvest of the entire crop contemplated if late influxes of moths are known.

Henipaviruses: Emerging Paramyxoviruses Associated with Fruit Bats

Two related, novel, zoonotic paramyxoviruses have been described recently. Hendra virus was first reported in horses and thence humans in Australia in 1994; Nipah virus was first reported in pigs and thence humans in Malaysia in 1998. Human cases of Nipah virus infection, apparently unassociated with infection in livestock, have been reported in Bangladesh since 2001. Species of fruit bats (genus Pteropus ) have been identified as natural hosts of both agents. Anthropogenic changes (habitat loss, hunting) that have impacted the population dynamics of Pteropus species across much of their range are hypothesised to have facilitated emergence. Current strategies for the management of henipaviruses are directed at minimising contact with the natural hosts, monitoring identified intermediate hosts, improving biosecurity on farms, and better disease recognition and diagnosis. Investigation of the emergence and ecology of henipaviruses warrants a broad, cross-disciplinary ecosystem health approach that recognises the critical linkages between human activity, ecological change, and livestock and human health.

Ultraviolet radiation effects on fruit surface respiration and chlorophyll fluorescence

High-value fruit crops are exposed to a range of environmental conditions that can reduce fruit quality. Solar injury (SI) or sunburn is a common disorder in tropical, sub-tropical, and temperate climates and is related to: 1) high fruit surface temperature; 2) high visible light intensity; and, 3) ultraviolet radiation (UV). Positional changes in fruit that are caused by increased weight or abrupt changes that result from summer pruning, limb breakage, or other damage to the canopy can expose fruit to high solar radiation levels, increased fruit surface temperatures, and increased UV exposure that are higher than the conditions to which they are adapted. In our studies, we examined the effects of high fruit surface temperature, saturating photosynthetically-active radiation (PAR), and short-term UV exposure on chlorophyll fluorescence, respiration, and photosynthesis of fruit peel tissues from tropical and temperate fruit in a simulation of these acute environmental changes. All tropical fruits (citrus, macadamia, avocado, pineapple, and custard apple) and the apple cultivars 'Gala', 'Gold Rush', and 'Granny Smith' increased dark respiration (A0) when exposed to UV, suggesting that UV repair mechanisms were induced. The maximum quantum efficiency of photosystem II (Fv/Fm) and the quantum efficiency of photosystem II (ΦII) were unaffected, indicating no adverse effects on photosystem II (PSII). In contrast, 'Braeburn' apple had a reduced Fv/Fm with no increase in A0 on all sampling dates. There was a consistent pattern in all studies. When Fv/Fm was unaffected by UV treatment, A0 increased significantly. Conversely, when Fv/Fm was reduced by UV treatment, then A0 was unaffected. The pattern suggests that when UV repair mechanisms are effective, PSII is adequately protected, and that this protection occurs at the cost of higher respiration. However, when the UV repair mechanisms are ineffective, not only is PSII damaged, but there is additional short-term damage to the repair mechanisms, indicated by a lack of respiration to provide energy.