Bimodality In Size Distribution Research Articles

Correction for adipocyte size and number in the analysis of differences in gene expression in fat tissues.

In gene expression studies of candidate genes related to fat deposition, accounting for differences in cell number using reference genes could be not sufficient when cell transcriptional levels are related to cell size, or the tissues are constituted by different types of cells where candidate genes could be differentially expressed. In these situations, mixed model can be applied giving the possibility to take into account the effects of adipocyte size and number on gene expression. The inclusion in the models of analysis of adipocyte size and number, previously estimated taking into account the possible bimodality of size distribution, reduces the rate of false positives in the expression of candidate genes, although, as expected, more powerful designs are needed to detect true differences. The analysis of cellularity of adipose tissue is recommended to infer differences in the expression of genes related to fat deposition.

The missing middle in developing countries revisited

Purpose The purpose of this paper is to develop a dynamic model to understand the evolution of the firm size distribution in developing countries. Design/methodology/approach Evidence points to the existence of a “missing middle” in the size distribution of firms in developing countries. In the model presented in this paper, the bimodality arises because of agents optimally selecting into a traditional and a modern sector. The key parameter in this model is the mean level of knowledge in the economy. Findings For a low mean, the two sectors co-exist. As the mean rises, the size distribution converges from a bimodal to an unimodal distribution. Originality/value Unlike existing explanations, this model does not rely on frictions to generate the bimodality in size distribution.

Bimodality in the firm size distributions: a kinetic exchange model approach

Firm growth process in the developing economies is known to produce divergence in their growth path giving rise to bimodality in the size distribution. Similar bimodality has been observed in wealth distribution as well. Here, we introduce a modified kinetic exchange model which can reproduce such features. In particular, we will show numerically that a nonlinear retention rate (or savings propensity) causes this bimodality. This model can accommodate binary trading as well as the whole system-side trading thus making it more suitable to explain the non-standard features of wealth distribution as well as firm size distribution.

Bimodality in Size Distributions: The Red Sea Urchin Strongylocentrotus Franciscanus as an Example

We use a model based on the size—structured von Foerster equation to describe how size—dependent growth and mortality rates, pulsed recruitment, and variability in growth affect the shape of a size distribution. The deterministic, equilibrium size distribution with constant recruitment increases with size when the difference between mortality rate and the rate at which growth rate decreases with size is positive (growth dominated), and decreases when it is negative (mortality dominated). Pulsed recruitment causes modes whose relative amplitudes are indicated by the corresponding constant recruitment case. For typical animal growth patterns, the distance between pulses decreases with age. Pulses merge and can be selectively obscured by variability in growth so that their relative amplitudes no longer correspond to the constant recruitment case. We use this information to evaluate why bimodality occurs in size distributions of the red sea urchin, Strongylocentrotus franciscanus, in some habitats, but not others. The mode at larger sizes, which occurs in all habitats, arises because the distribution is mortality dominated and the final sizes of individuals vary. The upper half of a second mode at smaller sizes is caused by higher mortality rates at sizes greater than the peak of that mode. The lower half may be due either to a refuge from predation under the spine canopy of adults or to sampling selectivity.

Parental influence on growth rate, smolting rate and survival in hatchery reared juvenile Atlantic salmon, Salmo salar

The proportion of potential 1‐year smolts, their mean length, the mean length of potential 2‐year smolts, and the mortality rate in four half‐sib families of Atlantic salmon, reared under four contrasted conditions of overhead cover, is shown to be inffuenced primarily by genetic factors (89.9%, 86.1 %, 82.7% and 80.2% of total variance respectively). Variation between families in smolting rate and mortality rate is influenced by both parents, but more by the male than the female. Variation in mean length is influenced almost entirely by the female parent. These results are discussed in relation to previous findings on bimodality of size distribution and inheritance of growth and mortality characteristics in Atlantic salmon.

Bimodal distribution of length of juvenile Atlantic salmon (Salmo salar L.) under artificial rearing conditions

In 52 populations of juvenile Atlantic Salmon, Salmo salar L., from 14 pairings of wild parents, reared at the Almondbank smolt rearing station between 1973 and 1976 in circular radial‐flow tanks, bimodality in the frequency distribution of length and weight has been characteristic by the first autumn of growth, and has become progressively clearer during the following winter.The examination of 13 populations showed the modes did not correspond to separate sexes, from four others it was shown they did not correspond to immature fish and precociously mature males. It is suggested that the two modes correspond to subpopulations smoltifying at ages (t) and (t+1) years. The age‐composition of the smolt‐run originating from individual year‐classes of salmon in four Scottish rivers was found to be consistent with stocks having size‐group segregations, at the time of the first smolt emigration, similar to those found among Almondbank experimental material. It is inferred that bimodality of size distribution is the norm among sibling populations of juvenile Atlantic salmon.