Sj Jones
University of Tasmania
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Publication
Featured researches published by Sj Jones.
Journal of Offshore Mechanics and Arctic Engineering-transactions of The Asme | 2007
Jungyong Wang; Ayhan Akinturk; Sj Jones; N Bose; Moon-Chan Kim; Ho-Hwan Chun
With the increase in popularity of podded propulsors and arctic navigation, understanding the interaction between a podded propulsor and ice has become more important. Propeller-ice interaction itself is a complicated process with a high level of uncertainty resulting from the uncertainties associated with the properties of the ice and with the propeller-ice interaction conditions. Model tests provide relatively well-controlled ice properties and interaction conditions to reduce the uncertainties. In order to improve the understanding of this interaction and to develop numerical models of it, a model podded propulsor was used in “Puller” mode, and ice loads were measured on its instrumented blade and propeller shaft. The results of the experiments conducted to simulate the interactions (milling) of the instrumented blade with ice in different operating conditions are reported in this paper. Loads measured during the milling consist of ice milling loads, “inseparable” hydrodynamic loads, and “separable” hydrodynamic loads. The sample results presented here include ice milling and inseparable hydrodynamic loads for various advance coefficients and depths of cut (amount of blade penetration into ice). Some results are compared with existing ice load models. DOI: 10.1115/1.2426993
New Zealand Journal of Crop and Horticultural Science | 2012
Sj Jones; David H. Gent; Sj Pethybridge; Fs Hay
Abstract In Tasmania, Australia, if more than 5% of bean pods are affected by white mould (Sclerotinia sclerotiorum) shipments may be rejected by the processor. This standard dictates prophylactic fungicide application over flowering, although in some instances treatment may not be warranted because of low disease risk. Surveys were conducted to identify relationships among edaphic factors, weather variables, and production practices associated with white mould. Correlations were found between disease incidence and the number of apothecia, fungicide timing, and mean minimum air temperature in the 10- and 30-day periods preceding harvest. Significant differences in disease incidence also were detected among cultivars and bean canopy densities. A nonparametric discriminant analysis model based on the predictor variables of mean minimum air temperature in the 10- and 30-day periods before harvest, cultivar, bean canopy density, and fungicide application correctly predicted presence of white mould on pods in 77% of bean fields. Several factors that can be manipulated to reduce disease risks were identified.
New Zealand Journal of Crop and Horticultural Science | 2015
Sj Jones; S Pilkington; David H. Gent; Fs Hay; Sj Pethybridge
A polymerase chain reaction (PCR) assay was developed that amplified a 170-bp fragment of the intergenic spacer region of Sclerotinia sclerotiorum, the cause of white mould. Sensitivity was 10 S. sclerotiorum ascospores per DNA extraction (0.2 ascospores per PCR reaction). The presence of soil did not affect sensitivity at 50, 100 and 500 ascospores/DNA extraction, but reduced sensitivity at 25 and 10 ascospores/DNA extraction by 10% and 30%, respectively. The assay did not amplify DNA of Botrytis cinerea but detected S. minor and S. trifoliorum. Utility of the test for detection of S. sclerotiorum ascospores in bean fields was demonstrated using rotating impaction samplers over two seasons. The use of the test in combination with an impaction sampler may provide benefits in time, sensitivity and specificity compared with visual identification and enumeration of spores from traps only. This system may provide an opportunity to schedule fungicides during periods of inoculum presence for disease management.
New Zealand Journal of Crop and Horticultural Science | 2011
Sj Jones; Sj Pethybridge; David H. Gent; Fs Hay
White mould caused by Sclerotinia sclerotiorum is one of the most damaging diseases of bean worldwide. High incidence of white mould can lead to complete crop loss through rejection by processors. Since 2004, in Australia, white mould is managed by the prophylactic application of the fungicide, boscalid during flowering. The sensitivity of S. sclerotiorum isolates (n =150) was tested using a mycelial growth assay. The effective concentration of boscalid required to reduce mycelial growth by 50% (EC50) was calculated using probit analysis. The frequency distribution of EC50 values was unimodal and similar to that of 11 non-exposed isolates collected from other crops or obtained from culture collections. No evidence of resistance or reduced sensitivity was found within the tested S. sclerotiorum population from Australian bean fields. This study provides valuable baseline data for monitoring changes in sensitivity to this fungicide.
Plant Disease | 2017
Tamilarasan Thangavel; Cr Wilson; Sj Jones; Jb Scott; H. Voglmayr
© The American Phytopathological Society.Opium poppy (Papaver somniferum) is a highly valuable crop grown for its opiate alkaloid content, primarily morphine, thebaine, and codeine. Australia is the world’s largest producer of licit opiates, cultivating ∼50% of world poppy production, with an estimated farm gate value of
Journal of Phytopathology | 2007
Sj Jones; Sj Pethybridge; Fs Hay; Tim Groom; Cr Wilson
60 million. Downy mildew has been a major constraint to poppy production since it was first recorded in 1996 (Cotterill and Pascoe 1998; Scott et al. 2004). The pathogen was recently reclassified as Peronospora meconopsidis (Voglmayr et al. 2014). This downy mildew species produces vein-delimited, angular, localized necrotic lesions with sparse sporulation on abaxial leaf surfaces. A second downy mildew species, P. somniferi, has been recorded to produce systemic infections, resulting in stunting and deformation of opium poppy in Europe (Voglmayr et al. 2014). In the 2013/14 season, stunted poppy plants with chlorotic distorted leaves, little or no necrosis, and profuse abaxial sporulation were observed within commercial crops in Tasmania, Australia, for the first time. Affected plants also had strongly distorted stems. These symptoms were characteristic of systemic downy mildew infection. In the 2014/15 season, the incidence of plants with systemic downy mildew symptoms was widespread and resulted in complete crop loss in some fields. Pathogen samples were collected from leaves with systemic symptoms. Microscopic examination revealed the presence of hyaline conidiophores and conidia typical of Peronospora. Conidiophores (n = 10) were 290 to 530 μm long, with bifurcating branches. Paired terminal branchlets (n = 24) were 4.2 to 15.9 μm long and straight to slightly curved. Ovoid, hyaline conidia (n = 24) were 17.8 to 23.8 μm long and 14.3 to 17.2 μm wide, with length/width ratios between 1.19 and 1.47. Leaves with systemic symptoms were collected from a commercial field at Gawler in December 2015. Conidial suspensions were collected from leaves by rinsing with sterile deionized water and used to inoculate 6- to 8-week-old poppy seedlings. Seedlings were maintained in a growth chamber (16 to 21°C, 10:14 h dark/light regime; relative humidity 70 to 90%). Systemic symptoms of distorted, chlorotic leaves and stunted plants were observed after 14 to 21 days. Disease development was acropetal, with symptomless lower leaves and obvious symptoms on upper leaves. DNA was extracted from infected leaf tissues and extracts tested by PCR using primers targeting conserved regions of the coxI (Robideau et al. 2011) and coxII (Hudspeth et al. 2000) genes in Peronospora spp. Amplicons of 702 and 603 bp were obtained for the coxI and coxII gene regions, respectively. These were sequenced (GenBank accession nos. KX242325 and KX242326) and compared with published sequences (Voglmayr et al. 2014). Maximum likelihood phylogenetic analysis using a concatenate alignment of these two gene regions confirmed that systemic symptoms on Tasmanian opium poppy crops were caused by P. somniferi. This is the first record of P. somniferi in Australia and represents a major new threat to poppy production in this country.
Plant Pathology | 2008
Sj Pethybridge; Sj Jones; R. G. Shivas; Fs Hay; Cr Wilson; Tim Groom
Plant Pathology | 2011
Sj Jones; David H. Gent; Sj Pethybridge; Fs Hay
Transactions of the Society of Naval Architects and Marine Engineers | 2003
Corwyn Moores; Brian Veitch; N Bose; Sj Jones; Jill Carlton
OMAE 2005 | 2005
Jungyong Wang; Ayhan Akinturk; Sj Jones; N Bose