A field study was conducted in Busia district of Kenya to elucidate the dynamics of ladybirds in mixed stands of maize, beans and cowpeas to determine their efficacy as sole control measures for Aphids. Maize, beans a...A field study was conducted in Busia district of Kenya to elucidate the dynamics of ladybirds in mixed stands of maize, beans and cowpeas to determine their efficacy as sole control measures for Aphids. Maize, beans and cowpeas were intercropped using conventional husbandry practices and the general Coccinellid quantified as follows： Colonies of four Coccinellids, starved for 12 hours to enhance feeding on Aphids were assessed. The effects of weather on the abundance of Coccinellids were also investigated and involved collection of meteorological data from the Busia District Agricultural Office （BDAO） and from Busia Farmers Training Centre （BFTC） and relating them to the abundance and predation values. The predator population was most abundant in the mixed stands of maize and beans （2.33 predators/30 Aphids） as compared to their occurrence in pure stands of cowpeas （0.85 predators/30 Aphids）. The genus Cheilomenes spp. was the most ubiquitous predator with a mean of 4.00 individuals/30 Aphids while Hippodamia variegata was the least abundant predator species with a mean of 0.92 individuals/30 Aphids in all the agro-ecosystems. The larvae of Hippodamia variegata were the most bio-efficient, consuming 32.44 Aphids while their adults were the least bio-efficient, consuming 4.22 individuals for a period of 12 hours. The Coccinellids consumed more Aphids at higher aphid densities （24.05 Aphids） than at lower aphid densities （9.44 Aphids） over the same period of time. Rainfall and relative humidity had significant （F = 3.675; P 〈 0.05） effects on the abundance of Coccinellids. Temperature had significant （F = 3.58; P 〈 0.05） effect on the abundance of Coccinellids though at a lower level. Rainfall （r = -0.162） and relative humidity （r = - 0.084） were both inversely correlated with the abundance of Coccinellids. On the other hand, temperature was positively correlated （r = 0.159） with the prevalence of Coccinellids indicating that warmer and drier conditions favoured their multiplication.展开更多
Strength properties of laboratory scale lime-based samples enhanced with additives such as nanomaterials(nanofibrillated cellulose,nanosilica,nanoclay,expanded graphite),hemp&glass fibres,hemp shiv and polyvinyl a...Strength properties of laboratory scale lime-based samples enhanced with additives such as nanomaterials(nanofibrillated cellulose,nanosilica,nanoclay,expanded graphite),hemp&glass fibres,hemp shiv and polyvinyl acetate(PVAc)are determined.Samples were cured for 26 days in air at 20℃/60%RH after casting before being oven dried for a further two days at 50℃(28 days total).Results show that the nanomaterials on their own had a mixed effect on the strength although nSiO_(2) as a solo additive performed exceptionally well.The combination of fibres in conjunction with PVAc also greatly enhanced the strength due to increased bond between the fibres and the matrix.In addition,Greenhouse Gas emissions(GHG,kgCO_(2)eq)of an arbitrary block was determined for all composites and compared to the GHG of a commonly used lightweight aerated concrete block.Comparison of the normalised compressive strengths to the different loading conditions as outlined in BS EN 8103 shows that a more widespread use of pre-cast lime composites is possible and without unduly increasing GHG emissions.展开更多
文摘A field study was conducted in Busia district of Kenya to elucidate the dynamics of ladybirds in mixed stands of maize, beans and cowpeas to determine their efficacy as sole control measures for Aphids. Maize, beans and cowpeas were intercropped using conventional husbandry practices and the general Coccinellid quantified as follows： Colonies of four Coccinellids, starved for 12 hours to enhance feeding on Aphids were assessed. The effects of weather on the abundance of Coccinellids were also investigated and involved collection of meteorological data from the Busia District Agricultural Office （BDAO） and from Busia Farmers Training Centre （BFTC） and relating them to the abundance and predation values. The predator population was most abundant in the mixed stands of maize and beans （2.33 predators/30 Aphids） as compared to their occurrence in pure stands of cowpeas （0.85 predators/30 Aphids）. The genus Cheilomenes spp. was the most ubiquitous predator with a mean of 4.00 individuals/30 Aphids while Hippodamia variegata was the least abundant predator species with a mean of 0.92 individuals/30 Aphids in all the agro-ecosystems. The larvae of Hippodamia variegata were the most bio-efficient, consuming 32.44 Aphids while their adults were the least bio-efficient, consuming 4.22 individuals for a period of 12 hours. The Coccinellids consumed more Aphids at higher aphid densities （24.05 Aphids） than at lower aphid densities （9.44 Aphids） over the same period of time. Rainfall and relative humidity had significant （F = 3.675; P 〈 0.05） effects on the abundance of Coccinellids. Temperature had significant （F = 3.58; P 〈 0.05） effect on the abundance of Coccinellids though at a lower level. Rainfall （r = -0.162） and relative humidity （r = - 0.084） were both inversely correlated with the abundance of Coccinellids. On the other hand, temperature was positively correlated （r = 0.159） with the prevalence of Coccinellids indicating that warmer and drier conditions favoured their multiplication.
基金supported by the Iraqi Ministry of Higher Education and Scientific Research and Iraqi Cultural Attache in London,who supported the research studies for F.J.Khalaf.
文摘Strength properties of laboratory scale lime-based samples enhanced with additives such as nanomaterials(nanofibrillated cellulose,nanosilica,nanoclay,expanded graphite),hemp&glass fibres,hemp shiv and polyvinyl acetate(PVAc)are determined.Samples were cured for 26 days in air at 20℃/60%RH after casting before being oven dried for a further two days at 50℃(28 days total).Results show that the nanomaterials on their own had a mixed effect on the strength although nSiO_(2) as a solo additive performed exceptionally well.The combination of fibres in conjunction with PVAc also greatly enhanced the strength due to increased bond between the fibres and the matrix.In addition,Greenhouse Gas emissions(GHG,kgCO_(2)eq)of an arbitrary block was determined for all composites and compared to the GHG of a commonly used lightweight aerated concrete block.Comparison of the normalised compressive strengths to the different loading conditions as outlined in BS EN 8103 shows that a more widespread use of pre-cast lime composites is possible and without unduly increasing GHG emissions.
