Microscopic basis for pattern formation and anomalous transport in two-dimensional active gels

Active gels are a class of biologically-relevant material containing embedded agents that spontaneously generate forces acting on a sparse filament network. In vitro experiments of protein filaments and molecular motors have revealed a range of non- equilibrium pattern formation resulting from motor motion along filament tracks, and there are a number of hydrodynamic models purporting to describe such systems. Here we present results of extensive simulations designed to elucidate the microscopic basis underpinning macroscopic flow in active gels. Our numerical scheme includes thermal fluctuations in filament positions, excluded volume interactions, and filament elasticity in the form of bending and stretching modes. Motors are represented individually as bipolar springs governed by rate-based rules for attachment, detachment and unidirectional motion of motor heads along the filament contour. We systematically vary motor density and speed, and uncover parameter regions corresponding to unusual statics and dynamics which overlap but do not coincide. The anomalous statics arise at high motor densities and take the form of end-bound localized filament bundles for rapid motors, and extended clusters exhibiting enhanced small-wavenumber density fluctuations and power-law cluster-size distributions for slow, processive motors. Anomalous dynamics arise for slow, processive motors over a range of motor densities, and are most evident as superdiffusive mass transport, which we argue is the consequence of a form of effective self-propulsion resulting from the polar coupling between motors and filaments.Comment: 14 pages, 17 figures. Minor clarifications and updated/additional references. To appear in Soft Matte

Simulating corporate income tax reform proposals with a dynamic CGE model

Opinion leaders and policy makers in the United States have turned their focus to the corporate income tax, which now has the highest statutory rate in the developed world. Using a dynamic computable general equilibrium model (the “NCPA-DCGE Model”), we simulate alternative policies for reducing the U.S. corporate income tax. We find that reductions in the corporate income tax rate result in significant positive impacts on output, investment, capital formation, employment, and household well-being (for almost all deciles). All of the hypothesized reforms also result in a more-streamlined public sector. These results are plausible insofar as the DCGE model from which they are obtained is parameterized by plausible elasticity assumptions, and incorporates the adjustments in prices, output, employment and investment that result from changes in tax policy

A Study of Soteriology: A Commentary, Course, and Conclusion of Brown’s Creek Baptist Church’s Soteriological Beliefs

This thesis identifies a church’s lack of theological awareness of biblical soteriology, investigates the literature for solutions to the ministerial problem, implements the review of literature into a course with curriculum, and the influences on the congregation’s beliefs. The church was a hodgepodge of soteriological beliefs. More specifically, the congregants purported to believe in Calvinism, Arminianism, and Semi-Pelagianism but could not accurately define, adequately describe, or appropriately defend said beliefs. A review of literature led this student to be selective of the soteriological literature known to exist. Simply, the ministerial problem was not because of a lack of literature but because of a lack of application. Surveying the selected literature, this student found several common themes associated with the above soteriological schools. These themes included the historical positions, the theological precepts, the biblical precedents, the exegetical problems, and the contemporary perspectives. These themes, following an exegetical study of Romans 9 for the theological foundation and finding known examples where courses were effective at distributing the information for the theoretical foundation, were implemented with curriculum in a classroom. The course, spanning seven days for an hour each day, presented the review of literature using the themes to distinguish the days. A survey and two identical questionnaires, one given before the course and one given after the course, were used to collect the quantitative and qualitative data. This data revealed that the course was effective at confirming, challenging, and changing the congregation’s soteriological beliefs by bringing theological awareness to biblical soteriology

Distinct viscoelastic scaling for isostatic spring networks of the same fractal dimension

Fractal structure emerges spontaneously from the chemical cross\-linking of monomers into hydrogels, and has been directly linked to power law visco\-elasticity at the gel transition, as recently demonstrated for isostatic (marginally--rigid) spring networks based on the Sierpinski triangle. Here we generalize the Sierpinski triangle generation rules to produce 4 fractals, all with the same dimension $d_{\rm f}=\log 3/\log 2$, with the Sierpinski triangle being one case. We show that spring networks derived from these fractals are all isostatic, but exhibit one of two distinct exponents for their power--law viscoelasticity. We conclude that, even for networks with fixed connectivity, power--law viscoelasticity cannot generally be a function of the fractal dimension alone