AGGREGATION,EMERGENCE AND IMMERGENCE IN HIERARCHICALLY ORGANIZED SYSTEMS

Abstract

The aim of this work is to show that couplings between fast micro-dynamics and slow macro-dynamics can make emerge global properties. Emergence corresponds to a bottom-up coupling, that is to the effect exerted by a micro-level at a macro-level. Immergence corresponds to the inverse process, that is to an up-down coupling. As an example, we present a prey-predator model with different time scales in a heterogeneous environment. A fast time scale is associated to the migration process on spatial patches and a slow time scale is associated to growth and interactions between the populations. Preys go on spatial patches where resources are located and where predators can attack them. The efficiency of predators is patch-dependent. Perturbation theory is used in order to aggregate the initial system of ordinary differential equations for patch sub-populations into a macro-system of two differential equations governing total populations. First, we study a case of density-independent migrations, for which no emergence occurs. Then, we study some examples of density-dependent migrations. In this case, emerging properties appear at the population level.     

EFFECT OF HOST DEFENSE CHEMICALS ON CLONAL DISTRIBUTION AND PERFORMANCE OF DIFFERENT GENOTYPES OF THE CEREAL APHID <Emphasis Type="Italic">Sitobion avenae</Emphasis>

Five microsatellite loci were used to study the genetic variability and population structure of Sitobion avenae (Hemiptera: Aphididae) on some of its host plants. Individuals were collected in Chile from different cultivated and wild Poaceae. Forty-four multilocus genotypes were found among the 1052 aphids analyzed, of which four represented nearly 90% of the sample. No specialist genotypes were found, although some preferred hosts endowed with chemical defenses, i.e., hydroxamic acids (Hx), while others preferred comparatively undefended hosts. Performances of some predominant and some rare genotypes were evaluated on plants differing in their Hx levels. Significant differences in performance were found among clones, the two most common genotypes showing no differences in performance among all hosts tested, and the rare genotypes showing enhanced performance on the host with highest Hx level. A hypothesis is proposed whereby the appearance of rarer genotypes is in part related to the presence of Hx.     

Liposomes as Proteinase Carriers for the Accelerated Ripening of Saint-Paulin Type Cheese

The possibility of accelerated cheese ripening through addition of liposome entrapped proteinase to milk was investigated. Both enzyme encapsulation rate in liposomes and their retention in cheese were evaluated with multilamellar vesicles (MLV) and reverse-phase evaporation vesicles (REV). Using REV in Saint-Paulin type curd, no nitrogen loss was observed to the whey due to the added enzymes in liposomes. In cheese, REV produced a more progressive proteolysis during ripening than MLV did. REV addition did not lead to texture defects. Bitterness development, a critical defect in enzyme added cheese, could be delayed and minimized using REV.     

LASER-DOPPLER ANEMOMETRY IN A BAFFLED MIXING TANK

Experiments were conducted for extremely high turbulent mixing operations in a baffled mixing lank. Three components of the mean and root-mean-square velocities were measured using a laser-Doppler anemometer. The impeller rotation rate, the impeller type, and the impeller location were considered.

Due to the complexity of flow in a baffled mixing tank, there are still several fundamental modeling and computational difficulties in simulating the flow, Thus, these experimental data based on the sophisticated and extensive measurements may improve fundamental modeling methods.

The results show that the flow patterns depend on the impeller type. The effect of the impeller location on flow was small. The axial direction of the How was caused by the baffles. The flow was three-dimensional, rotational periodic, and statistically random. This information successfully characterizes the flow in the baffled mixing tank.