An evaluation of biological and abiotic controls for grapevine powdery mildew. 2. Vineyard trials

Grapevine powdery mildew ( Erysiphe necator) affects grape yield and fruit quality worldwide. Managers of conventional vineyards rely mainly on synthetic fungicides and sulfur to control powdery mildew, while in organic vineyards sulfur is the main control agent, often in rotation with canola-based oils, bicarbonates and biological control agents. The efficacy of those materials has not been evaluated critically under field conditions in Australia. Accordingly, a range of materials showing most promise in previous greenhouse trials (Crisp et al. 2006 Australian Journal of Grape and Wine Research 12 , pp. 192–202) were assessed via field trials in commercial vineyards. Applications of either milk or whey (alone, or mixed with a canola oil-based product), as well as applications of potassium bicarbonate (commercial formulation), all reduced the severity of powdery mildew compared with untreated vines. Eight applications of a 1:10 dilution of milk, 45 g/L whey powder or programs comprising rotations of potassium bicarbonate plus oil and whey, applied at 10–14 day intervals, reduced the severity of powdery mildew to levels not significantly different from that on vines sprayed with sulfur (wettable powder, 3–6 g/L). However, the relative control of powdery mildew by the test materials in field trials was dependent on the susceptibility of the grapevine cultivar and the extent of spray coverage achieved. In vineyards where highly susceptible cultivars were planted, and spray coverage was compromised, the resultant control of powdery mildew was reduced; and sometimes to commercially unacceptable levels.     

Protoporphyrin-IX as a Substitute for Nitrite in Cured-Meat Color Production

The iron-free heme derivative protoporphyrin-IX, was added to a cooked emulsified beef product to mimic the typical cured-color obtained with nitrite. Although the pigment was stable and could be recovered from the emulsion it imparted a purple hue as noted by visual observation and Hunterlab color values (L,a,b). The possible implications of this pigment as a meat colorant are discussed.     

EFFECT OF CHILLING AND FREEZING ON SURVIVAL OF VIBRIO PARAHAEMOLYTICUS ON FISH FILLETS1

Vibrio parahaemolyticus is a foodborne pathogen isolated from coastal waters of the United States, and from seafoods including fish. No information is available on the viability of V. parahaemolyticus on raw, chilled and frozen fish. A three‐strain mixture of V. parahaemolyticus was inoculated on fish fillets (pH 6.4) to obtain a bacterial load of 10⁴ (high) or 10³ (low) CFU/fillet, and stored at 4C or 8C for 9 days or at – 18C for seven weeks. At 4C and 8C, and at both levels of inoculation, V. parahaemolyticus survived on the fillets for the entire duration of the study. However, there was a significant reduction (P < 0.01) in V. parahaemolyticus population on the fillets by 9 days of storage. In the frozen fillets, there was a sharp decline (P < 0.01) in the population of V. parahaemolyticus by day 5 of storage. Although chilling and freezing significantly (P < 0.01) inactivated high numbers of V. parahaemolyticus on fish, they cannot be relied upon as a method to reduce V. parahaemolyticus on fish, since the time and magnitude of reduction depends on the initial load of the pathogen and the storage temperature.     

Degradation of Wheat Starch in a Single-Screw Extruder: Mechano-Kinetic Breakdown of Cooked Starch

Wheat starch was processed in a 19 mm diameter split-barrel laboratory extruder under varying conditions of barrel temperature (79–121^oC), screw speed (50, 100 rpm) and moisture content (25, 30%). Final product and samples removed from along the barrel length were examined for changes in molecular size by dilute solution viscometry. Final products were also examined for paste viscosity and estimated degree of cook. A mathematical model was developed which relates the residence time of the starch in the barrel, the nominal shear stress acting on the starch and the degree of cook of the product to the extent of molecular degradation of the starch. Solution viscometry was found to be more rapid than gel permeation methods previously used to determine the extent of molecular changes.     

Fracture Intensity Distributions during Compression of Puffed Corn Meal Extrudates: Method for Quantifying Fracturability

The distribution of fracture intensities occurring during compression of puffed corn meal extrudates was described using an exponential function, and parameters from that analysis were used as fracturability indices. Since “jagged” or oscillating stress-strain functions are typical for porous and brittle materials, fracture intensities were determined by measuring the abrupt, sequential reductions in stress produced during compression. Both distribution exponent and cumulative fracture stress correlated strongly with fracturability measured by other techniques, including fractal and Fourier analysis of stress-strain functions. Distribution parameters also indicated textural differences due to process parameters (structural modification through addition of different levels of sucrose) and storage conditions (equilibration at various relative humidities).     

Fracture Induced in Al2O3 Bicrystals by Anisotropic Thermal Expansion

Bicrystals of Al₂O₃ were fabricated to study the effects of thermal expansion anisotropy on fracture in a model system containing one grain boundary. Fractures occurred perpendicular to the directions of maximum tensile stress in bicrystals with thermal expansion coefficient differences as low as 0.31×10⁻⁶⁰C⁻¹ and originated at the boundary, probably in areas of high residual stress associated with pores. Numerical stress analysis of two-dimensional model bicrystal configurations showed that stresses induced by thermal expansion anisotropy are maximal in a region localized along the bicrystal boundary.     

Mixed-Mode Fracture in Soda-Lime Glass Using Indentation Flaws

Mixed-mode failure of soda-lime glass under inert and fatigue test conditions was studied using Knoop indentation flaws. For annealed cracks (residual stress-free) crack extension (catastrophic or subcritical) is by an abrupt transition from the initial crack plane to a noncoplanar crack plane followed by a reorientation of the crack normal to the applied stress. Although fatigue strength of these inclined flaws increased linearly with respect to orientation of the flaws to the applied stress up to an angle of 60°, this increase was considerably less than what was predicted by existing theories. It is believed that subcritical crack growth causes the crack to be realigned perpendicular to the applied stress before failure for all orientations; hence, fatigue strength does not show the dramatic increase at orientation angles as predicted by theory. For as-indented cracks the contact residual stress causes the crack extension to be less inclined to the initial crack plane than for annealed cracks, but in this case also, the crack realigns itself perpendicular to the applied stress. Again, fatigue strength is relatively insensitive to the orientation angle as predicted by theory and subcritical crack growth is believed to play a primary role in determining this strength dependency.     

An investigation of the electrochemical reduction of pentachlorophenol with analysis by HPLC

A study has been made of the electrochemical reduction of pentachlorophenol (PCP) on a lead electrode in both water and propylene carbonate. A combination of voltammetric measurements and analysis of reaction products by high performance liquid chromatography (HPLC) have established that the reduction of PCP in propylene carbonate occurs by two different pathways, depending upon the electrode potential. At -1.9V vs SCE, reduction is mediated by adsorbed hydrogen, whereas at -2.3V vs SCE direct reduction of PCP also occurs. A similar approach has established that the reduction of PCP in water follows only one reaction pathway, namely, direct electron transfer from lead to PCP.     

Making a polynomial Hurwitz-invariant by choice of feedback gains†

An integrated design procedure is developed for a modified Smith predictor and associated controller for linear time-delay systems having transfer functions of the form k ₁, A exp (—sT)/B, where A and B are monic polynomials in s of degree n — l and n, respectively. A is Hurwitz and B has a single right-half-plane root at s = λ. For l=1,2,3, an augmented PI controller guarantees asymptotic stability for λT less than an l-dependent limit. The procedure for l = 3 is extended to l = 4 with the introduction of derivative action into the controller. Design arguments are on root locus topology, and on Nyquist analysis applied to an auxiliary system.