A coarse-grained biophysical model of sequence evolution and the population size dependence of the speciation rate.

Speciation is fundamental to understanding the huge diversity of life on Earth. Although still controversial, empirical evidence suggests that the rate of speciation is larger for smaller populations. Here, we explore a biophysical model of speciation by developing a simple coarse-grained theory of transcription factor-DNA binding and how their co-evolution in two geographically isolated lineages leads to incompatibilities. To develop a tractable analytical theory, we derive a Smoluchowski equation for the dynamics of binding energy evolution that accounts for the fact that natural selection acts on phenotypes, but variation arises from mutations in sequences; the Smoluchowski equation includes selection due to both gradients in fitness and gradients in sequence entropy, which is the logarithm of the number of sequences that correspond to a particular binding energy. This simple consideration predicts that smaller populations develop incompatibilities more quickly in the weak mutation regime; this trend arises as sequence entropy poises smaller populations closer to incompatible regions of phenotype space. These results suggest that a generic coarse-grained approach to evolutionary stochastic dynamics allows realistic modelling at the phenotypic level

Molecular Dynamics Study of Rotating Nanodroplets: Finite-size Effects and Nonequilibrium Deformation

Noneqiuilibrium dynamics of rotating droplets are studied by molecular dynamics simulations. Small deviations from the theoretical prediction are observed when the size of a droplet is small, and the deviations become smaller as the size of the droplet increases. The characteristic timescale of the deformation is observed, and we find (i) the deformation timescale is almost independent of the rotating velocity with for small frequency and (ii) the deformation timescale becomes shorter as temperature increases. A simple model is proposed to explain the deformation dynamics of droplets.Comment: 14 pages, 8 figure, added references, changed titl

On the Establishment Dynamics in the United States and Japan

This paper compares the establishment-level dynamics of the United States and Japan. I find that there are substantial differences in entry and exit behavior, the average size of establishments, and the amount of job reallocation. First, entry and exit rates are much lower in Japan. Second, the average size of establishments is much smaller in Japan, while the average size of opening/closing establishments are similar in the U.S. and Japan. Third, the amount of job creation and job destruction is much smaller in Japan, especially for continuing establishments. I first examine whether these differences are accounted for by sectoral compositions, and find that the differences in sectoral composition do not explain these facts. Then I construct a general equilibrium industry dynamics model and explore the roles of various frictions in generating these differences. The model experiments suggest that in Japan, there may be important impediments for establishment entry/exit and there may be factors impeding productive establishments from growing larger.Establishment Dynamics, Sectoral Composition, Industry Dynamics Model, Reallocation

Intramolecular vibrational energy redistribution as state space diffusion: Classical-quantum correspondence

We study the intramolecular vibrational energy redistribution (IVR) dynamics of an effective spectroscopic Hamiltonian describing the four coupled high frequency modes of CDBrClF. The IVR dynamics ensuing from nearly isoenergetic zeroth-order states, an edge (overtone) and an interior (combination) state, is studied from a state space diffusion perspective. A wavelet based time-frequency analysis reveals an inhomogeneous phase space due to the trapping of classical trajectories. Consequently the interior state has a smaller effective IVR dimension as compared to the edge state.Comment: 5 pages, 3 figure

A different appetite for sovereignty? Independence movements in subnational island jurisdictions

Local autonomy in a subnational jurisdiction is more likely to be gained, secured or enhanced where there are palpable movements or political parties agitating for independence in these smaller territories. A closer look at the fortunes, operations and dynamics of independence parties from subnational island jurisdictions can offer some interesting insights on the appetite for sovereignty and independence, but also the lack thereof, in the twenty-first century.peer-reviewe