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Sustainable online communities exhibit distinct hierarchical structures across scales of size.

ABSTRACT: As humans, we are uniquely competent at incorporating ourselves into groups that scale up from a few members to millions of individuals to engage in joint activities in social circles of varying sizes. Yet, the question of how a group's survival depends on its social structure is not well understood. In an analysis of more than 10 122 real-life online communities (with a total of 134 147 members) hosted by a leading platform over periods of more than a decade, we observe a prominent structural difference between stable and unstable communities, enabling the prediction of sustainability up to a decade ahead. We find that communities that fail to maintain a typical hierarchical social structure that preserves cohesiveness across size scales do not survive, while communities that exhibit such balance prevail. This difference is observable in as early as the first 30 days of a community's lifetime, enabling prediction of community sustainability up to 10 years in the future. We theorize that communities comprising distinct social structures that balance global and local factors across scales of sizes are more likely to maintain sustainability.

SUBMITTER: Dover Y

PROVIDER: S-EPMC7426038 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Sustainable online communities exhibit distinct hierarchical structures across scales of size.

Dover Yaniv Y Goldenberg Jacob J Shapira Daniel D

Proceedings. Mathematical, physical, and engineering sciences 20200701 2239

As humans, we are uniquely competent at incorporating ourselves into groups that scale up from a few members to millions of individuals to engage in joint activities in social circles of varying sizes. Yet, the question of how a group's survival depends on its social structure is not well understood. In an analysis of more than 10 122 real-life online communities (with a total of 134 147 members) hosted by a leading platform over periods of more than a decade, we observe a prominent structural d ...[more]

PMID: 32831599

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Project description:Antral follicle size might be a valuable additive predictive marker for IVF outcome. However, while some studies show positive relations between follicle size and reproductive outcome, others have not been successful in establishing this relation. To better understand consequences of antral follicle size for reproductive outcome, we aimed to obtain insight in follicle size-related granulosa cell processes, as granulosa cells play an essential role in follicular development via the production of growth factors, steroids and metabolic intermediates, needed for follicular growth and oocyte development. Using pigs as a model, we compared gene and protein expression in granulosa cells of smaller and larger follicles in the healthy antral follicle pool at the start of the follicular phase of the estrous cycle. In sows, the early antral follicle pool is very heterogeneous when e.g. size and steroid content of the follicular fluid are considered. To which extent this variety contributes to the developmental competence of the follicles is not clear. Therefore, sows with high variation in antral follicle size (HighVAR) as well as sows with low variation in antral follicle size (LowVAR) were used. Granulosa cells of smaller antral follicles in the healthy antral follicle pool show increased cell proliferation, which was accompanied by a metabolic shift towards aerobic glycolysis (i.e. the Warburg effect), similar to other highly proliferating cells. High granulosa cell proliferation rates in smaller follicles might be regulated via increased granulosa cell expression of AR and EGFR which are activated in response to locally produced mitogens. While granulosa cells of smaller follicles in the pool were more proliferative, indicative of higher follicular growth, granulosa cells of larger follicles in the pool showed less proliferation and were more differentiated, as they showed a higher expression of follicular maturation marker IGF1 and ANGPT1. Our results imply that the inclusion of strict criteria of antral follicle size in IVF protocols might improve reproductive outcome. In addition, we have granulosa cell gene expression of healthy follicles to unravel underlying mechanisms of differences in COC morphology. We compared gene expression in sows with low vs. high-COC-health and found a decreased expression of genes involved in ovarian steroidogenesis (e.g. CYP19A1, ADM, SPP1) and higher expression of genes involved in follicular atresia (e.g. GADD45A, INHBB) in sows with low-COC-health. Thereby we have identified several genes which may serve as markers for follicle developmental competence.

Project description:Background and aimsIn eukaryotes, the total kinetochore size (defined as a chromosomal region containing CENH3-positive nucleosomes) per nucleus strongly correlates with genome size, a relationship that has been hypothesized to stem from general intracellular scaling principles. However, if larger chromosomes within a karyotype required larger kinetochores to move properly, it could also be derived from the mechanics of cell division.MethodsWe selected seven species of the plant subfamily Agavoideae whose karyotypes are characterized by the presence of small and very large chromosomes. We visualized the kinetochore regions and chromosomes by immunolabelling with an anti-CENH3 antibody and DAPI (6'-diamidino-2-phenylindole) staining. We then employed 2D widefield and 3D super-resolution microscopy to measure chromosome and kinetochore areas and volumes, respectively. To assess the scaling relationship of kinetochore size to chromosome size inside a karyotype, we log-transformed the data and analysed them with linear mixed models which allowed us to control for the inherent hierarchical structure of the dataset (metaphases within slides and species).Key resultsWe found a positive intra-karyotype relationship between kinetochore and chromosome size. The slope of the regression line of the observed relationship (0.277 for areas, 0.247 for volumes) was very close to the theoretical slope of 0.25 for chromosome width based on the expected physics of chromosome passage through the cytoplasm during cell division. We obtained similar results by reanalysing available data from human and maize.ConclusionsOur findings suggest that the total kinetochore size to genome size scaling observed across eukaryotes may also originate from the mechanics of cell division. Moreover, the potential causal link between kinetochore and chromosome size indicates that evolutionary mechanisms capable of leading kinetochore size changes to fixation, such as centromere drive, could promote the size evolution of entire chromosomes and genomes.

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Sustainable online communities exhibit distinct hierarchical structures across scales of size.

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Sustainable online communities exhibit distinct hierarchical structures across scales of size.

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