Determination of the zeta potential for highly charged colloidal suspensions

We compute the electrostatic potential at the surface, or zeta potential $\zeta$, of a charged particle embedded in a colloidal suspension using a hybrid mesoscopic model. We show that for weakly perturbing electric fields, the value of $\zeta$ obtained at steady state during electrophoresis is statistically indistinguishable from $\zeta$ in thermodynamic equilibrium. We quantify the effect of counterions concentration on $\zeta$. We also evaluate the relevance of the lattice resolution for the calculation of $\zeta$ and discuss how to identify the effective electrostatic radius.Comment: 8 pages, 3 figures with 2 panel

Effect of Salt Concentration on the Electrophoretic Speed of a Polyelectrolyte through a Nanopore

In a previous paper [S. Ghosal, Phys. Rev. E 74, 041901 (2006)] a hydrodynamic model for determining the electrophoretic speed of a polyelectrolyte through an axially symmetric slowly varying nanopore was presented in the limit of a vanishingly small Debye length. Here the case of a finite Debye layer thickness is considered while restricting the pore geometry to that of a cylinder of length much larger than the diameter. Further, the possibility of a uniform surface charge on the walls of the nanopore is taken into account. It is thereby shown that the calculated transit times are consistent with recent measurements in silicon nanopores.Comment: 4 pages, 2 figure

Slaves for Sale: Abolitionist Art and the American Slave Trade

Visual Representations of Slavery Maurie McInnis, an art professor at the University of Virginia has written a rare book. In the first instance she has thrown fresh light on slavery and abolition, two much-studied topics. Secondly, she has produced a book that deserves considerable atte...

Ante Bellum Studies in Slavery, Politics, and the Railroads

Ante Bellum Studies in Slavery, Politics, and the Railroads By Robert R. Russel Professor and Head, Department of History Western Michigan University Series of Articles: What Was the Compromise of 1850? Reprinted from The Journal of Southern History, XXII (August 1956), 292-309. The Economic History of Negro Slavery in the United States. Reprinted from Agricultural History, XI (October 1937), 308-21. The General Effects of Slavery Upon Southern Economic Progress. Reprinted from The Journal of Southern History, IV (February 1938), 34-54. The Effects of Slavery upon Nonslaveholders in the Ante Bellum South. Reprinted from Agricultural History, XV (April 1941), 112-26. A Revaluation of the Period before the Civil War: Railroads. Reprinted from The Mississippi Valley Historical Review, XV (December 1928), 341-54. The Pacific Railway Issue in Politics Prior to the Civil War. Reprinted from The Mississippi Valley Historical Review, XII (September 1925), 187-201. Bibliography of the Works of Robert R. Russe

Forecasting Grain Equipment Sales

The purpose of the study was to identify and discuss variables that have an effect on the sale of grain handling equipment. A case study format was used to present the analysis. The problem addressed in the study is the inability of the case study company to forecast sales. It was hypothesized that sales could be predicted using data from previous years. Multiple regression was preformed using two independent variables: the number of acres of corn harvested for grain, and the government loan rates for on farm storage facilities, with past sales of the company being the dependent variable. Other variables were discussed but not included in the actual statistical analysis. The study was limited to the state of Iowa for two variables: equipment sales in Iowa and acres of corn harvested from grain in Iowa. This limitation was places on the study until the practicality of further study was apparent. The findings of the study were that the interest rate variable was not a good indicator of sales and the number of acres harvested was just as good of an indicator by itself as when included with the interest rate variable. The conclusion was drawn that more variables were needed to improve the worth of regression equation

A Long-Lived Accretion Disk Around a Lithium-Depleted Binary T Tauri Star

We present a high dispersion optical spectrum of St 34 and identify the system as a spectroscopic binary with components of similar luminosity and temperature (both M3+/-0.5). Based on kinematics, signatures of accretion, and location on an H-R diagram, we conclude that St 34 is a classical T Tauri star belonging to the Taurus-Auriga T Association. Surprisingly, however, neither component of the binary shows LiI 6708 A, absorption, the most universally accepted criterion for establishing stellar youth. In this uniquely known instance, the accretion disk appears to have survived longer than the lithium depletion timescale. We speculate that the long-lived accretion disk is a consequence of the sub-AU separation companion tidally inhibiting, though not preventing, circumstellar accretion. Comparisons with pre-main sequence evolutionary models imply, for each component of St 34, a mass of 0.37+/-0.08 Msun and an isochronal age of 8+/-3 Myr, which is much younger than the predicted lithium depletion timescale of ~ 25 Myr. Although a distance 38% closer than that of Taurus-Auriga or a hotter temperature scale could reconcile this discrepancy at 21-25 Myr, similar discrepancies in other systems and the implications of an extremely old accreting Taurus-Auriga member suggest instead a possible problem with evolutionary models. Regardless, the older age implied by St 34's depleted lithium abundance is the first compelling evidence for a substantial age spread in this region. Additionally, since St 34's coeval co-members with early M spectral types would likewise fail the lithium test for youth, current membership lists may be incomplete.Comment: 4 pages, including 2 figures. Accepted for publication in ApJ Let