Pak-Wing Fok

Learn More
Damaged or mismatched bases in DNA can be repaired by base excision repair enzymes (BER) that replace the defective base. Although the detailed molecular structures of many BER enzymes are known, how they colocalize to lesions remains unclear. One hypothesis involves charge transport (CT) along DNA [Yavin et al., Proc. Natl. Acad. Sci. U.S.A. 102, 3546(More)
Plaques are fatty deposits that grow mainly in arteries and develop as a result of a chronic inflammatory response. Plaques are characterized as 'vulnerable' when they have large internal regions of necrosis and are heavily infiltrated by macrophages. The particular composition of a vulnerable plaque renders it susceptible to rupture, which releases(More)
Atherosclerotic plaque can cause severe stenosis in the artery lumen. Blood flow through a substantially narrowed artery may have different flow characteristics and produce different forces acting on the plaque surface and artery wall. The disturbed flow and force fields in the lumen may have serious implications on vascular endothelial cells, smooth muscle(More)
We investigate the dynamics of a one-dimensional asymmetric exclusion process with Langmuir kinetics and a fluctuating wall. At the left-hand boundary, particles are injected onto the lattice; from there, the particles hop to the right. Along the lattice, particles can adsorb or desorb, and the right-hand boundary is defined by a wall particle. The(More)
A moving, solidifying interface that grows by the instantaneous adsorption of a diffusing solute can be described by equations analogous to those of the classical one-sided Stefan problem for solidification. However, the behavior of precipitate growth by material deposition can depend on both surface kinetics and bulk drift of the depositing species. We(More)
A charge transport (CT) mechanism has been proposed in several articles to explain the localization of base excision repair (BER) enzymes to lesions on DNA. The CT mechanism relies on redox reactions of iron-sulfur cofactors that modify the enzyme's binding affinity. These redox reactions are mediated by the DNA strand and involve the exchange of electrons(More)
In this paper, we study the inverse problem of reconstructing the spatially dependent transition rate F (x) of a one-dimensional Broadwell process from exit time distributions. In such a process, an advecting particle is assumed to undergo transitions between states with constant positive (+v) and negative (−v) velocities. The goal is to reconstruct the(More)
In this paper we consider the problem of recovering the drift function of a Brownian motion from its distribution of first passage times, given a fixed starting position. Our approach uses the backward Kolmogorov equation for the probability density function (pdf) of first passage times. By taking Laplace Transforms, we reduce the problem to calculating the(More)
In this paper, we investigate an axisymmetric model of intimal thickening using hyperelasticity theory. Our model describes growth of the arterial intima due to cell proliferation which in turn is driven by the release of a cytokine such as Platelet-Derived Growth Factor (PDGF). With the growth rate tied to both local stress and the local concentration of(More)
— The timing of cellular events is inherently random because of the probabilistic nature of gene expression. Yet cells manage to have precise timing of important events. Here, we study how gene expression could possibly be regulated to precisely schedule timing of an event around a given time. Event timing is modeled as the first–passage time (FPT) for a(More)