This paper presents a numerical model based on the Lattice Boltzmann Method (LBM), developed for studying dynamic responses of an unsaturated porous medium to periodic imbibition and drainage induced by a cyclic water table movement. The model includes gravity which helps defining an hydraulic head. The model predicted an incremental increase of the overall water content in the medium over each...

Abstract: The processed potato industry is highly vertically coordina ted though the use of production contracts between growers and processors. Contracts in this industry are primarily used to combat market thinness and potato quality requirements. This study uses a two period principle-agent model to describe the incentives inherit in processing potato production contracts. Actual processor p...

Cellular forces generated in the apical domain of epithelial cells reshape tissues. Recent studies highlighted an important role for dynamic actomyosin contractions, called pulses, that change cell and tissue shape. Net cell shape change depends on whether cell shape is stabilized, or ratcheted, between pulses. Whether there are different classes of contractile pulses in wild-type embryos and h...

We present a microfluidic ratchet that exploits the deformation of individual cells through microscale funnel constrictions. The threshold pressure required to transport single cells through such constrictions is greater against the direction of taper than along the direction of taper. This physical asymmetry combined with an oscillatory excitation can enable selective and irreversible transpor...

The conserved protein-conducting channel, referred to as the Sec61 channel in eukaryotes or the SecY channel in eubacteria and archaea, translocates proteins across cellular membranes and integrates proteins containing hydrophobic transmembrane segments into lipid bilayers. Structural studies illustrate how the protein-conducting channel accomplishes these tasks. Three different mechanisms, eac...

The mechanical behavior of soils has been traditionally described using continuum-mechanics-based models. These are empirical relations based on laboratory tests of soil specimens. The investigation of the soils at the grain scale using discrete element models has become possible in recent years. These models have provided valuable understanding of many micromechanical aspects of soil deformati...

Minkowski operators (dilation and erosion of sets in vector spaces) have been extensively used in computer graphics, image processing to analyze the structure of materials, and more recently in molecular dynamics. Here, we apply those mathematical concepts to extend the discrete element method to simulate granular materials with complex-shaped particles. The Voronoi-Minkowski diagrams are intro...

An emerging DNA sequencing technique uses protein or solid-state pores to analyze individual strands as they are driven in single-file order past a nanoscale sensor1–3. However, uncontrolled electrophoresis of DNA through these nanopores is too fast for accurate base reads4. Here, we describe forward and reverse ratcheting of DNA templates through the α-hemolysin nanopore controlled by phi29 DN...

We solve the problem of discrete translocation of a polymer through a pore, driven by the irreversible, random sequential adsorption of particles on one side of the pore. Although the kinetics of the wall motion and the deposition are coupled, we find the exact steady-state distribution for the gap between the wall and the nearest deposited particle. This result enables us to construct the mean...

Using the longest dataset publicly available (The Economist’s index of industrial commodity prices), we analyze the behavior of real commodity prices over the period 1862–1999 and have two main findings. First, while there has been a downward trend in real commodity prices of about 1 percent per year over the last 140 years, little support is found for a break in the long-run trend decline in c...