Search

Spatial models where growth is limited to the edge of the expansions have been instrumental to understand the population dynamics and the clone size distribution in growing cellular populations, such as microbial colonies and avascular tumours. A complete characterization of the coalescence process generated by spatial growth is still lacking, limiting our ability to apply classic population genetics inference to spatially growing populations. Here, we start filling this gap by investigating the statistical properties of the cell lineages generated by the two dimensional Eden model, leveraging their physical analogy with directed polymers. Our analysis provides quantitative estimates for population measurements that can easily be assessed via sequencing, such as the average number of segregating sites and the clone size distribution of a subsample of the population. Our results not only reveal remarkable features of the genealogies generated during growth, but also highlight new properties that can be misinterpreted as signs of selection if non-spatial models are inappropriately applied., Comment: orcIDs: Armin Eghdami 0000-0002-2278-5414, Jayson Paulose 0000-0002-4014-9817, Diana Fusco 0000-0002-1505-7160

Galaxies 4(4), 38 (2016). doi:10.3390/galaxies4040038, In the study of relativistic jets one of the key open questions is their interaction with the environment on the microscopic level. Here, we study the initial evolution of both electron–proton ( e$^−$ – p$^+$ ) and electron–positron ( e$^{±}$ ) relativistic jets containing helical magnetic fields, focusing on their interaction with an ambient plasma. We have performed simulations of “global” jets containing helical magnetic fields in order to examine how helical magnetic fields affect kinetic instabilities such as the Weibel instability, the kinetic Kelvin-Helmholtz instability (kKHI) and the Mushroom instability (MI). In our initial simulation study these kinetic instabilities are suppressed and new types of instabilities can grow. In the e$^−$ – p$^+$ jet simulation a recollimation-like instability occurs and jet electrons are strongly perturbed. In the e$^{±}$ jet simulation a recollimation-like instability occurs at early times followed by a kinetic instability and the general structure is similar to a simulation without helical magnetic field. Simulations using much larger systems are required in order to thoroughly follow the evolution of global jets containing helical magnetic fields., Published by MDPI, Basel

U.S. county data for the last 20 or 30 years show that manufacturing employment has been deconcentrating. In contrast, the service sector exhibits concentration in counties with intermediate levels of employment. This paper presents a theory where local sectoral growth is driven by technological diffusion across space. The age of an industry -- measured as the time elapsed since the last major general purpose technology innovation in the sector -- determines the pattern of scale dependence in growth rates. Young industries exhibit non-monotone relationships between employment levels and growth rates, while old industries experience negative scale dependence in growth rates. The model then predicts that the relationship between county employment growth rates and county employment levels in manufacturing at the turn of the 20th century should be similar to the same relationship in services in the last 20 years. We provide evidence consistent with this prediction.

The growth of waves along the direction of motion of viscous compressible liquid sheets in inviscid compressible gas streams was investigated. Gas streams were considered to move at different velocities relative to the liquid sheet. A dispersion relation was derived for the spatial growth of longitudinal waves in the presence of lateral wave modes. The solution of the dispersion relation showed that the incorporation of gas compressibility increases the growth of paraantisymmetric waves. Compressibility in liquid, such as obtained by the dispersion of gas bubbles, has a much lower influence on the growth of paraantisymmetric waves. The presence of lateral wave modes did not influence longitudinal wave growth when the compressibility of liquid and gas was considered in the model. � 2010 The Japan Society of Fluid Mechanics and IOP Publishing Ltd.

The weather of the high concentration of improvement in the inner hemisphere of cities in the developing world is increasingly becoming evident. In Nigeria, and the uncontrolled intensification of homeland use in the inner-city expenses is now an number of serious planning and authority concerns. Governments at various levels are currently struggling with the daunting summons of repressing these urban physical and social problems of almost defied clarification which planners are presently striving to spout with planning-driven strategies. The investment in Akure for this study is because it is an old city and the administrative capital of Ondo State, Nigeria, that has testified immense development and spatial growth, acute traffic volume, industrial and profitable activities with a growing incidence of a dysfunctional city core. This paper examines the inner-city core of Akure using remotely sensed data division of the area. This will assist in generating a compelling and captivating marketing core while representing efficient spatial management toolkits for urban planners, environmental supervisors, learners, and researchers as well as administration and non-governmental regulations.