There is evidence that individuals in animal groups benefit from the presence of knowledgeable group members in different
ways. Experiments and computer simulations have shown that a few individuals within a group can lead others, for a precise
task and at a specific moment. As a group travels, different individuals possessing a particular knowledge may act as temporary
leaders, so that the group will, as a whole, follow their behaviour. In this paper, we use a model to study different factors
influencing group response to temporary leadership. The model is based on four individual behaviours. Three of those, attraction,
repulsion, and alignment, are shared by all individuals. The last one, attraction toward the source of a stimulus, concerns
only a fraction of the group members. We explore the influence of group size, proportion of stimulated individuals, number
of influential neighbours, and intensity of the attraction to the source of the stimulus, on the proportion of the group reaching
this source. Special attention is given to the simulation of large group size, close to those observed in nature. Groups of
100, 400 and 900 individuals are currently simulated, and up to 8,000 in one experiment. We show that more stimulated individuals
and a larger group size both induce the arrival of a larger fraction of the group. The number of influential neighbours and
the intensity of the stimulus have a non-linear influence on the proportion of the group arrival, displaying first a positive
relationship and then, above a given threshold, a negative one. We conclude that an intermediate level of group cohesion provides
optimal transfer information from knowledgeable to naive individuals. 相似文献
Phosphogypsum (PG) is a large hazardous waste from fertiliser and phosphoric acid industries from which useful products including rare-earth elements (REEs) can be recovered depending on the treatment process. Its conversion to calcium sulphide (CaS) which was achieved at 95% followed by the formation of S, CaCO3 and residue is one of the plausible treatment processes leading to economic and environmental benefits. This study aimed at monitoring selected REEs behaviour during the conversion of (PG) to (CaS). The concentrations of REEs in the raw PG, the produced CaS and the obtained residue were determined after digestion (microwave and traditional acid leaching) using ICP-OES. The effect of CO2 and H2S used in the process of forming CaCO3 and S from PG on the concentrations of REEs was also investigated. Microwave digestion proved to be more effective than traditional acid leaching in the recovery of REEs. Microwave digestion using 3 mL HNO3 + 1 mL HCl was more effective than 1 mL HNO3 + 3 mL in REEs recovery. CaS contained the highest amount of Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, La and Y with values of 2646, 476, 2255, 320, 60.5, 376, 79.8, 1.24, 476, 1185 and 318 µg/g respectively. Based on these findings, the residue could be further processed to recover REEs despite less than 40% decrease in concentration for the majority of REEs observed due to the use of H2S and CO2. CO2 was found to be more suitable as fewer REEs were leached as compared to H2S. All things considered, the obtained residue could be a good secondary source of REEs as it is easier to leach, retained good amount of REEs and lesser impurities.
Environmental Science and Pollution Research - Copper (Cu) contamination of soils may alter the functioning and sustainability of vineyard ecosystems. Cultivating Cu-extracting plants in vineyard... 相似文献
Environmental Science and Pollution Research - Regulatory assessment of the effects of chemicals requires the availability of validated tests representing different environments and organisms. In... 相似文献