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The effects of damping on the bending and twisting modes of flax fibre-reinforced polypropylene composites are investigated. The laminate was manufactured by a vacuum bagging process; its dynamic behaviour was then found from the vibration measurements of a beam test specimen using an impulse hammer technique to frequencies of 1 kHz. The frequency response of a sample was measured, and the bending and twisting responses at resonance were used to estimate the natural frequency and loss factor. The single-degree-of-freedom circle-fit method and Newton’s divided differences formula were used to estimate the natural frequencies as well as the loss factors. The damping estimates were also investigated using a “carpet” plot. The results show significant variations in loss factors depending on the type of mode. The loss factor generally lies in the range of 1.7-2.2 % for the bending modes, while 4.8 % on average for the twisting modes. Numerical estimates of the response, and in particular the natural frequencies, were made using a Mechanical APDL (ANSYS parametric design language) finite element model, with the beam being discretised into a number of shell elements. The natural frequencies from the finite element analysis show reasonably good agreement (errors < 5 %) with the measured natural frequencies. 相似文献
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Owen Wally Jayaraman Jayaraj Zamir Punja 《European journal of plant pathology / European Foundation for Plant Pathology》2009,123(3):331-342
Genes encoding an acidic wheat class IV chitinase (383), an acidic wheat β 1,3-glucanase (638) and a rice cationic peroxidase
(POC1) were introduced into ‘Nantes Coreless’ carrot (Daucus carota) by Agrobacterium-mediated transformation. The genes were introduced singly or in various combinations followed by selection imposed by the
herbicide phosphinothricin. Regenerated plantlets were screened for presence and expression of the three transgenes using
PCR, Southern and Northern hybridisations. Eighteen transgenic lines expressing a single transgene and 2 lines each co-expressing
638/383 and 383/POC1 were assessed for resistance to the necrotrophic fungal pathogens Botrytis cinerea and Sclerotinia sclerotiorum. Percentage leaf area diseased was measured 4 and 7 days after inoculation (dai) and compared to non-transformed control
plants. Six lines expressing β-1,3-glucanase 638 alone had no enhanced resistance to B. cinerea at 4 dai and only slight resistance to S. sclerotiorum; there was no effect at 7 dai. Two out of the six lines expressing 383 alone had enhanced tolerance to both pathogens with
a 20–50% reduction in disease development at 7 dai. Two lines co-expressing 638/383 had slight reductions in disease by (10–20%)
similar to that of the lines expressing chitinase 383 alone. Highest levels of disease resistance were seen in transgenic
lines expressing POC1, alone or in combination with chitinase 383. Disease symptoms were slower to develop and symptoms were
reduced by up to 90% for B. cinerea and 70% for S. sclerotiorum. The 383/POC1 co-expressing plants developed disease at levels similar to that of POC1 alone. Petioles of plants over-expressing
POC1 had higher levels of lignin accumulation constitutively compared to control plants, which was greatly enhanced following
inoculation with S. sclerotiorum. These results indicate that peroxidase over-expression can lead to significant disease reduction against necrotrophic pathogens
in transgenic carrot plants. 相似文献
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Paramasivam S. Richards Karen A. Alva A. K. Richards Asha M. Sajwan K. S. Jayaraman K. Heanacho A. Afolabi J. 《Water, air, and soil pollution》2009,203(1-4):229-242
Water, Air, &; Soil Pollution - Leaching of trace metals and greenhouse plant growth (Collard greens; Brassica oleracea var. acephala) response studies were conducted in two types of soils with... 相似文献
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J. Jayaraman L. P. Celino K. H. Lee R. B. Mohamad J. Suns N. Tayaputch Z. Zhang 《Water, air, and soil pollution》1989,45(3-4):371-375
Work done in six nations by seven research groups on Carbofuran metabolism in rice-fish ecosystem is summarized. The following results have been obtained: (a) Soil acts as a sink for the pesticide and there is considerable metabolism in the soil; (b) There is no bioaccumulation/biomagnification by the fish used in the experiments, the residue levels in water being extremely low; and (c) The plants translocate the chemical and even at the time of harvest, the grains show the presence of the pesticide. 相似文献
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The endangered tropical tree, Aquilaria malaccensis, produces agarwood for use in fragrance and medicines. Efforts are currently underway to produce valuable agarwood compoundsn tissue culture. The purpose of this study was to develop an optimal growth medium, specifically, the best hormone combination for callus suspension culture. Using nursery-grown A. malaccensis, sterilized leaf explants were first incubated on basic Murashige and Skoog(MS) gel medium containing 15g/L sucrose and at pH 5.7. Different auxin types including 1-naphthaleneacetic acid(NAA), 2,4-dichlorophenoxyacetic acid(2,4-D), and indole-3-butyric acid(IBA), were tested at various concentrations(0.55, 1.1 and 1.65 μM) using the basic medium. Leaf explants were incubated for 30 days in the dark. Callus induced by 1.1 μM NAA had the highest biomass dry weight(DW) of 17.3 mg; however the callus was of a compact type. This auxin concentration was then combined with either 6-benzylaminopurine(BAP) or kinetin at 0.55, 1.1, 2.2 or 3.3 μM to induce growth of friable callus. The 1.1μM NAA + 2.2μM BAP combination produced friable callus with the highest biomass(93.3mg DW). When testing the different carbon sources and pHs, sucrose at 15g/L and pH at 5.7 yielded highest biomasses at 87.7mg and 83 mg DW, respectively. Microscopic observations revealed the arrangement of the friable cells as loosely packed with relatively large cells, while for the compact callus, the cells were small and densely packed. We concluded that MS medium containing 15 g/L sucrose, 1.1 μM NAA + 2.2 μM BAP hormone combination, and a pH of 5.7 was highly effective for inducing friable callus from leaf explants of A. malaccensis for the purpose of establishing cell suspension culture. 相似文献