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Antoine LF Gady Freddy WK Hermans Marion HBJ Van de Wal Eibertus N van Loo Richard GF Visser Christian WB Bachem 《Plant methods》2009,5(1):13-14
Background
The establishment of mutant populations together with the strategies for targeted mutation detection has been applied successfully to a large number of organisms including many species in the plant kingdom. Considerable efforts have been invested into research on tomato as a model for berry-fruit plants. With the progress of the tomato sequencing project, reverse genetics becomes an obvious and achievable goal. 相似文献2.
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Strength properties of thermally modified softwoods and its relation to polymeric structural wood constituents 总被引：3，自引：0，他引：3
Michiel J. Boonstra Joris Van Acker Bôke F. Tjeerdsma Edo V. Kegel 《Annals of Forest Science》2007,64(7):679-690
Thermal modification at relatively high temperatures (ranging from 150 to 260 °C) is an effective method to improve the dimensional stability and resistance against fungal attack. This study was performed to investigate the impact of heat treatment on the mechanical properties of wood. An industrially-used two-stage heat treatment method under relative mild conditions (< 200 °C) was used to treat the boards. Heat treatment revealed a clear effect on the mechanical properties of softwood species. The tensile strength parallel to the grain showed a rather large decrease, whereas the compressive strength parallel to the fibre increased after heat treatment. The bending strength, which is a combination of the tensile stress, compressive stress and shear stress, was lower after heat treatment. This decrease was less than the decrease of only the tensile strength. The impact strength showed a rather large decrease after heat treatment. An increase of the modulus of elasticity during the bending test has been noticed after heat treatment. Changes and/or modifications of the main wood components appear to be involved in the effects of heat treatment on the mechanical properties. The possible effect of degradation and modification of hemicelluloses, degradation and/or crystallization of amorphous cellulose, and polycondensation reactions of lignin on the mechanical properties of heat treated wood have been discussed. The effect of natural defects, such as knots, resin pockets, abnormal slope of grain and reaction wood, on the strength properties of wood appeared to be affected by heat treatment. Nevertheless, heat treated timber shows potential for use in constructions, but it is important to carefully consider the stresses that occur in a construction and some practical consequences when heat treated timber is used. 相似文献
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de Villeneuve VW Dullens RP Aarts DG Groeneveld E Scherff JH Kegel WK Lekkerkerker HN 《Science (New York, N.Y.)》2005,309(5738):1231-1233
Impurities affect the nucleation, growth, and structure of crystals. Here we report the effect of large, spherical, polymethylmethacrylate impurities on the crystal growth of monodisperse, hard, polymethylmethacrylate colloids in a density- and optically matching apolar solvent mixture. Crystal growth, initiated at the bottom of the sample, was studied by imaging sequences of two-dimensional xy slices in the plane of the impurity's center with a laser scanning confocal microscope. Impurities form the center of grain boundaries, and a single fluid particle layer around the impurity persists in all cases. The growth rate sensitively depends on the impurity's size. Crystal growth is inhibited to a greater extent near smaller impurities, pointing to local crystal frustration induced by the curvature of the impurity. 相似文献
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Isolation and pathogenicity of Australian strains of Eimeria praecox and Eimeria mitis 总被引：2，自引：0，他引：2
WK JORGENSEN NP STEWART PJ JESTON JB MOLLOY GW BLIGHT RJ DALGLIESH 《Australian veterinary journal》1997,75(8):592-595
Objective To determine the presence of E praecox and E mitis in Australia, to isolate representative strains of these species from chickens and determine their pathogenicity.
Design Morphological, physiological and cross protection studies were undertaken to confirm the identity of Australian isolates of E praecox and E mitis.
Procedure Oocysts were isolated from a backyard flock at Jimboomba, southeastern Queensland and numbers of E praecox and E mitis enriched by passage in chickens immune to five other species of poultry Eimeria . Oocysts of mean conformation and size of the two species were purified by single oocyst passage. Two isolates that closely matched recorded parameters for E praecox and E mitis were selected and designated JP and JM respectively. The cross protection between the isolates and E acervulina was determined by infection and challenge experiments. The virulence of the two isolates was determined by comparing weight gains of groups of birds inoculated with JP isolate or JM isolate with untreated groups.
Results Isolates JP and JM most closely matched recorded parameters of E praecox and E mitis respectively. Groups of chickens, previously infected with JP and JM isolates, showed no significant protection against infection with E acervulina . In a separate trial, groups of susceptible chickens inoculated with 105 oocysts of JP and JM isolates showed significantly reduced weight gains compared with untreated controls.
Conclusion Isolates JP and JM are E praecox and E mitis respectively, confirming the presence of these species in Australia. These isolates were found capable of causing significant reductions in weight gains in susceptible chickens. 相似文献
Design Morphological, physiological and cross protection studies were undertaken to confirm the identity of Australian isolates of E praecox and E mitis.
Procedure Oocysts were isolated from a backyard flock at Jimboomba, southeastern Queensland and numbers of E praecox and E mitis enriched by passage in chickens immune to five other species of poultry Eimeria . Oocysts of mean conformation and size of the two species were purified by single oocyst passage. Two isolates that closely matched recorded parameters for E praecox and E mitis were selected and designated JP and JM respectively. The cross protection between the isolates and E acervulina was determined by infection and challenge experiments. The virulence of the two isolates was determined by comparing weight gains of groups of birds inoculated with JP isolate or JM isolate with untreated groups.
Results Isolates JP and JM most closely matched recorded parameters of E praecox and E mitis respectively. Groups of chickens, previously infected with JP and JM isolates, showed no significant protection against infection with E acervulina . In a separate trial, groups of susceptible chickens inoculated with 10
Conclusion Isolates JP and JM are E praecox and E mitis respectively, confirming the presence of these species in Australia. These isolates were found capable of causing significant reductions in weight gains in susceptible chickens. 相似文献
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Heat treatment of wood at relatively high temperatures (in the range of 150–280°C) is an effective method to improve biological
durability of wood. This study was performed to investigate the effect of heat treatment process optimisation on the resistance
against fungal attack, including basidiomycetes, molds and blue stain fungi. An industrially used two-stage heat treatment
method under relatively mild conditions (<200°C) was used to treat the boards. Heat treatment of radiata pine sapwood revealed
a clear improvement of the resistance against the brown rot fungi Coniophora puteana and Poria placenta. Increasing process temperature and/or effective process time during the first process stage, the hydro thermolysis, appeared
to affect the resistance against C. puteana attack, but the effect on the resistance against P. placenta was rather limited. Heat treated radiata pine showed a limited resistance against the white rot fungus Coriolus versicolor and process variations during the hydro thermolysis stage appeared not to affect this resistance. A clear difference between
the resistance of heat treated Scots pine sapwood and heartwood against fungal attack is observed. Scots pine heartwood showed
a higher resistance against C. puteana and P. placenta but also against the white rot fungus C. versicolor. Similar results were obtained when heat treated birch was exposed to brown and white rot fungi. Heat treatment showed an
improved resistance against C. puteana attack, especially at higher temperatures during the hydro thermolysis stage. A clear improvement of the durability was also
observed after exposure to the white rot fungus C. versicolor and especially Stereum hirsutum. Increasing the process temperature or process time during the hydro thermolysis stage appeared to have a limited effect
on the resistance against C. versicolor attack. Heat treated radiata pine and Norway spruce were still susceptible to mold growth on the wood surface, probably due
to the formation of hemicelluloses degradation products (e.g. sugars) during heat treatment. Remarkable is the absence of
blue stain fungi on heat treated wood specimen, also because the abandant blue stain fungi were observed on untreated specimen.
Molecular reasons for the resistance of heat treated wood against fungal attack are discussed in detail contributing to a
better understanding of heat treatment methods. 相似文献