Band-collision gel electrophoresis.

Electrophoretic mobility shift assays are widely used in gel electrophoresis to study binding interactions between different molecular species loaded into the same well. However, shift assays can access only a subset of reaction possibilities that could be otherwise seen if separate bands of reagent species might instead be collisionally reacted. Here, we adapt gel electrophoresis by fabricating two or more wells in the same lane, loading these wells with different reagent species, and applying an electric field, thereby producing collisional reactions between propagating pulse-like bands of these species, which we image optically. For certain pairs of anionic and cationic dyes, propagating bands pass through each other unperturbed; yet, for other pairs, we observe complexing and precipitation reactions, indicating strong attractive interactions. We generalize this band-collision gel electrophoresis (BCGE) approach to other reaction types, including acid-base, ligand exchange, and redox, as well as to colloidal species in passivated large-pore gels

Cycling Willingness: Investigating Distance as a Dependent Variable in Cycling Behavior Among College Students

We present a novel approach to understanding distance as a barrier to cycling and its use as a dependent variable in multinomial logistic regression. In doing so, this study explores distances in relation to spatially and relevant human factors such as gender and propensity to cycle among college students. College students (N = 949) participated in a health survey and stated possible predictors of cycling based on their cycle usage and preferences in the previous 30 days. While utilizing GIS in a bicycle-friendly network, we created geo-statistical GIS-groupings and performed multinomial logistic regression analysis. We examined college students to discover how their demographic and personal characteristics may mediate the deterrent properties of distance when considered as a dependent variable in cycling to a college campus. Age and propensity for cycling for transportation mediate the negative effect of distance on the likelihood of cycling. The findings also suggest that infrastructure improvements could lessen the impact of distance as a barrier to cycling and increase the likelihood of cycling for commuting

Crossover between entropic and interfacial elasticity and osmotic pressure in uniform disordered emulsions

We develop a simple predictive model of the osmotic pressure Π and linear shear elastic modulus G′p of uniform disordered emulsions that includes energetic contributions from entropy and interfacial deformation. This model yields a smooth crossover between an entropically dominated G′p ∼ kBT/a³ for droplet volume fractions ϕ below a jamming threshold for spheres, ϕc, and an interfacially dominated G′p ∼ σ/a for ϕ above ϕc, where a and σ are the undeformed radius and interfacial tension, respectively, of a droplet and T is the temperature. We show that this model reduces to the known ϕ-dependent jamming behavior G′p(ϕ) ∼ (σ/a)ϕ(ϕ − ϕc) as T → 0 for ϕ > ϕc of disordered uniform emulsions, and it also produces the known divergence for disordered hard spheres G′p(ϕ) ∼ (kBT/a³)ϕ/(ϕc − ϕ) for ϕ ϕc when σ → ∞. We compare predictions of this model to data for disordered uniform microscale emulsion droplets, corrected for electrostatic repulsions. The smooth crossover captures the observed trends in G′p and Π below ϕc better than existing analytic models of disordered emulsions, which do not make predictions below ϕc. Moreover, the model predicts that entropic contributions to the shear modulus can become more significant for nanoemulsions as compared to microscale emulsions.LaMnO

Exploring Patterns of Tax Increment Financing Use and Structural Explanations in Missouri’s Major Metropolitan Regions

This article examines tax increment financing (TIF) in Kansas City and St. Louis, two heavy users of the tool under the same statutory authority. Based on a complete database of TIF projects through 2013 (2012 for Kansas City) and numerous interviews with local government officials in both metropolitan areas, we explore the TIF use of these two cities, which have different structural aspects and have gone through sharp policy changes, to examine if central cities that use different strategies beget different outcomes in their suburban areas. We document distinctly different patterns of use in the two central cities. When St. Louis dramatically increased its TIF use under Mayor Francis Slay, the number of projects per year in the suburbs increased. Kansas City suburbs appeared to fill the gap in TIF use when the city sharply decreased its use of TIF under Mayor Mark Funkhouser. More research is needed to determine the factors that drive these mixed effects and if they hold true by context and in other metropolitan areas

Stability of Monomer-Dimer Piles

We measure how strong, localized contact adhesion between grains affects the maximum static critical angle, theta_c, of a dry sand pile. By mixing dimer grains, each consisting of two spheres that have been rigidly bonded together, with simple spherical monomer grains, we create sandpiles that contain strong localized adhesion between a given particle and at most one of its neighbors. We find that tan(theta_c) increases from 0.45 to 1.1 and the grain packing fraction, Phi, decreases from 0.58 to 0.52 as we increase the relative number fraction of dimer particles in the pile, nu_d, from 0 to 1. We attribute the increase in tan(theta_c(nu_d)) to the enhanced stability of dimers on the surface, which reduces the density of monomers that need to be accomodated in the most stable surface traps. A full characterization and geometrical stability analysis of surface traps provides a good quantitative agreement between experiment and theory over a wide range of nu_d, without any fitting parameters.Comment: 11 pages, 12 figures consisting of 21 eps files, submitted to PR