Digitaria insularis (sourgrass) is a monocotyledon weed of difficult control and high invasive behavior. Atrazine is widely applied in the Americas to control weeds in maize culture, but its efficiency against D. insularis is limited. The incorporation of atrazine into poly(epsilon-caprolactone) nanocapsules increased the herbicidal activity against susceptible weeds; however, the potential of this nanoformulation to control atrazine-tolerant weeds including D. insularis has not yet been tested. Here, we evaluated the post-emergent herbicidal activity of nanoatrazine against D. insularis plants during initial developmental stages. The study was carried out in a greenhouse, using pots filled with clay soil. Plants with two or four expanded leaves were treated with conventional or nanoencapsulated atrazine at 50 or 100% of the recommended dosage (1,000 or 2,000 g ∙ ha−1), followed by the evaluation of physiological, growth, and control parameters of the plants. Compared with conventional herbicide, both dosages of nanoatrazine induced greater and faster inhibition of D. insularis photosystem II activity at both developmental stages. Atrazine nanoencapsulation also improved the control of D. insularis plants, especially in the stage with two expanded leaves. In addition, nanoatrazine led to higher decreases of dry weight of fourleaved plants than atrazine. The use of the half-dosage of nanoatrazine was equally or more efficient in affecting most of the evaluated parameters than the conventional formulation at full dosage. Overall, these results suggest that the nanoencapsulation of atrazine potentiated its post-emergent herbicidal activity against D. insularis plants at initial developmental stages, favoring the control of this atrazine-tolerant weed.
The article presents research aimed at determining the effect of adding rare earth elements to near-eutectic Al-Si and Al-Si-Ni alloys on the microstructure and mechanical properties of the obtained products. Material for the research was prepared using a melt spinner – a device used for rapid crystallization, casting thin ribbons, which were then subjected in subsequent stages to fragmentation, consolidation and plastic working. The ribbons and extruded rods cast were described in terms of their structure and their strength properties were determined at different measurement temperatures. It was shown that the lightweight materials produced from aluminium alloys using the rapid solidification process have an ultra-fine structure and good strength properties.
Analysis under a microscope confirmed that the addition of rare earth alloys Al-Si and Al-Si-Ni causes fragmentation of the microstructure in the tapes produced. The presence of rare earth elements in the alloys tested has an impact on the type and the morphology of the particles of the microstructure’s individual components. In addition to the change in particle morphology, the phenomenon of the separation of numerous nanometric particles of intermetallic phases containing rare earth elements was also observed. The change in microstructure caused by the addition of rare earth elements in the form of a mischmetal increases the mechanical properties.
Three transgenic soybean lines expressing the Cry1Ia5 gene were developed using the Agrobacterium transformation system. The integration of the Cry1Ia5 gene in the genome of the transgenic plants was approved using specific primers for PCR and real time PCR analysis, respectively. The insecticidal activity of three transgenic lines (L1, L2 and L3) against 2nd larval instars Spodoptera littoralis was tested. The data indicate that L2 exhibited the highest mortality percentage 9 days post feeding (60%) followed by L3 (40%) then L1 (20%) while the control showed 0% mortality. The larvae fed transgenic material appeared smaller in size than compared to the control larvae. The reduction in insect size and weight was due to the accumulation of higher phenoloxidase activity in insect tissues. The higher mortality observed in L2 was due to a significant decrease in the acetylcholine esterase activity that leads to accumulation of acetylcholin at higher levels which causes paralysis and death. The developed transgenic line 2 could be used to construct an insect resistant soybean cultivar.
The AlMg10 aluminum alloy reinforced with SiC particles was subjected to friction stir processing (FSP). The composite was made by mechanical mixing and gravity casting. The mass fraction of SiC particles in the composite was about 10%. Evaluation of the effects of FSP treatment was performed by means of light microscopy, scanning electron microscopy, EDS and hardness measurement. It was found that the inhomogeneous distribution of SiC particles and their agglomeration, which were observable in the cast composite, were completely eliminated after FSP modification. The treatment was also accompanied by homogenisation of the material in the mixing zone as well as fragmentation of both the matrix grain of the composite and SiC particles. In the case of SiC particles, a change in their shape was also observed. In the as-cast composite, particles with dimensions from 30 to 60 µm and a sharp-edged polyhedral shape prevailed, while in the material subjected to friction treatment, particles with dimensions from 20 to 40 µm and a more equiangular shape prevailed. Pores and other material discontinuities occurring frequently in the as-cast composite were completely eliminated after friction modification. The recorded changes in the microstructure of the material were accompanied by an increase in the hardness of the composite by nearly 35%. The conducted investigations have shown that FSP modification of the AlMg10/SiC composite made by the casting method leads to favorable microstructural changes in the surface layer and may be an alternative solution to other methods and technologies used in surface engineering.