A 3D bacterial swimming model coupled with external fluid mechanics using the immersed boundary method

We introduce a 3D motile rod-shaped bacterial model with a single polar °ag-ellum which is based on the con¯guration of a monotrichous type of bacteria suchas Pseudomonas aeruginosa. The structure of the model bacterial cell consists of acylindrical body together with the °agellar forces produced by the rotation of a helical°agellum. The bacterial cell body is constructed from a set of immersed boundarypoints and elastic links. The helical °agellum is assumed to be rigid and modeledas a set of discrete points along the helical °agellum and °agellar hook. A set of°agellar forces are applied along this rotating helical curve as the °agellum rotates.An additional set of torque balance forces are applied tangentially on the cell bodyto drive the counter-revolution of the body and provide torque balance.The °uid °ow that drives the model bacterial cell is governed by the incompress-ible Navier-Stokes equations with a force density contributed from the elasticity ofthe cell body, the rotation of the °agellum, and the torque balance forces. The modelis based on the immersed boundary method introduced by Peskin to model the °uid°ow of the heart. We solve the Navier-Stokes equations numerically for the °uid ve-locity at each time step by Fast Fourier Transform methods and advect the bacterialcell at the local °uid velocity.This fully 3D model is loosely based on an earlier 2D model for bacterial swimmingintroduced by Dillon, Fauci and Gaver in 1995. Numerical simulations of the bacterialswimming model are presented. We show simulations that demonstrate ¯rst orderconvergence as the numerical mesh is re¯ned. We also show simulations of the modelhelical centroid trajectory, the model behavior in forward and backward swimmingand the hydrodynamic interaction of two or more motile cells from various initialcon¯gurations as well as the hydrodynamic in°uence of walls and tubes on the modelswimming

Leadership, Regulatory Focus and Project Performance

Leadership is one critical factor of effective teamwork, such as information system (IS) projects. The mission of project leaders is to motivate followers and create an effective working environment that allows project teams to effectively meet the predefined goals. However, based on regulatory focus theory, a team may strive to the optional situation (promotion focus) or try to avoid not meeting the minimum requirements (prevention). The aim of this paper is to explore the effect of leadership styles (transformational and transactional) on the regulatory focus of one team (promotion and prevention), and investigate the relationship between regulatory focus and project team performance. Based on data collected from 154 IS professionals, we found that transformational leadership is associated with promotion focus and transactional leadership leads to prevention focus. Furthermore, while promotion focus orientated teams can perform effectively, prevention focus oriented teams are less efficient. Implications toward academia and practitioners are provided

The Development of Dominant Parties and Party Systems – Taiwan as a Case Study

Of the emerging democracies in the 20th century, Taiwan demonstrates itself as a distinguished case as its pre-authoritarian party, the Kuomintang (KMT), was able to prolong its rule in the government after regime transition from authoritarian regime to democracy. According to scholars of dominant parties and party systems, Taiwan's dominant party, the KMT, existed in a dominant party system because it was able to defeat the opposition party, the DPP, until 2000 even after martial law was lifted in 1987. The existing literature investigates the factors of the development of political parties and how it links to the literature which discusses the development of dominant parties and party systems. From the discussion, I argue five factors are the cause of the development of the KMT one-party dominance including 1) social influence from the U.S., 2) the KMT’s ability of crisis management in 1971 event, 3) the development of voting behaviors affected by generational social experiences, 4) the effect of SNTV system on the development of political parties, 5) the effect of the leadership, Lee Teng-Hui, on the KMT’s party internal structure. We found that these five factors confirm our suggesting theorie

An Extended Analytic Solution of Combined Refraction and Diffraction of Long Waves Propagating over Circular Island

An analytic solution of long waves scattering by a cylindrical island mounted on a permeable circular shoal was obtained by solving the linear long wave equation (LWE). The solution is in terms of the Bessel function expressed by complex variables. The present solution is suitable for arbitrary bottom configurations described by a power function with two independent parameters. For the case of the paraboloidal shoal, there exists a singular point (α=2) which can be removed using Frobenius series, where α is a real constant. The present solution is reduced to Yu and Zhang’s (2003) solution for impermeable circular shoal. The numerical results show some special features of the combined effect of wave refraction and diffraction caused by a porous circular island. The effect of key parameters of the island dimension, the shoal slope, and permeability on wave scattering was discussed based on the analytic solution