Nested clade phylogeographic analysis (NCPA) is a widely used method that aims to identify past demographic events that have shaped the history of a population. In an earlier study, NCPA has been fully automated, allowing it to be tested with simulated data sets generated under a null model in which samples simulated from a panmictic population are geographically distributed. It was noted that ...

We shall extend Kingman's coalescent to the geographically structured population model with migration among colonies. It is described by a continuous-time Markov chain, which is proved to be a dual process of the diffusion process of stepping-stone model. We shall derive a system of equations for the spatial distribution of a common ancestor of sampled genes from colonies and the mean time to g...

Informality as a Stepping Stone: Entrepreneurial Entry in a Developing Economy We model decisions with respect to formality or informality for entrepreneurs in a new industry for a developing economy. We show that informality allows a leader to explore, without significant sunk costs, the potential profitability of the industry; that is, informality may be a stepping stone, enabling an entrepre...

A stepping stone arises in risky environments with learning and transferrable human capital. An example is the role played by academic two-year colleges in postsecondary education: Students, as they learn about the uncertain educational outcomes, can drop out or transfer up to harder and more rewarding schools, carrying a fraction of the accumulated human capital. A theory of education is built...

Network attackers frequently use a chain of compromised intermediate nodes to attack a target machine and maintain anonymity. This chain of nodes between the attacker and the target is called a stepping stone chain. Various algorithms have been proposed to detect stepping stones, timing correlation based algorithms being one of them. However, the existing timing based algorithms are susceptible...

Dynamical bipedal walking subject to precise footstep placements is crucial for navigating real world terrain with discrete footholds such as stepping stones, especially as the spacing between the stone locations significantly vary with each step. Here, we present a novel methodology that combines a gait library approach along with control Barrier functions to enforce strict constraints on foot...

Repeated Job Quits: Stepping Stones or Learning about Quality? Despite the fact that worker quits are often associated with wage gains and higher overall job satisfaction, many workers quit once again within one or two years after changing jobs initially. Such repeated job quit behavior may arise as a stepping stone to better quality jobs (Burdett, 1978) or as a response to unexpectedly low job...

In Infrastructure-as-a-Service (IaaS) clouds, stepping-stone attacks via hosted virtual machines (VMs) are critical for the credibility. This type of attack uses compromised VMs as stepping stones for attacking the outside hosts. For self-protection, IaaS clouds should perform active responses against stepping-stone attacks. However, it is difficult to stop only outgoing attacks at edge firewal...

The number of computer break-ins from the outside of an organization has increased with the rapid growth of the Internet. Since many intruders from the outside of an organization employ stepping stones, it is difficult to trace back where the real origin of the attack is. Some research projects have proposed tracing methods for DoS attacks and detecting method of stepping stones. It is still di...