Since its first edition in 1988,The Arkansas Freedom of Information Acthas become the standard reference for the bench, the bar, and journalists for guidance in interpreting and applying the state's ...open-government law. This sixth edition, published fifty years after the passage of the Act in 1967, builds upon its predecessors, incorporating later legislative enactments, judicial decisions, and Attorney General's opinions to present a synthesis of the law of access to public records and meetings in Arkansas.
The characterization of quasi-hemispherical Pt electrodes of nanometer dimensions (radius 2−150 nm), prepared by electrophoretic coating of etched Pt wires with poly(acrylic acid), is described. The ...goals of these experiments are to estimate the accuracy of using steady-state voltammetric limiting currents (i lim) in determining the true electrode area and to develop new electrochemical methods for rapidly screening individual electrodes for nonideal geometries. Electrochemical active areas were determined by measuring the electrical charge (Q) associated with oxidation of adsorbed bis(2,2‘-bipyridine)chloro(4,4‘-trimethylenedipyridine)osmium(II) in fast-scan voltammetric measurements (scan rate 1000 V/s). Voltammetric peaks corresponding to oxidation of as few as ∼7000 molecules (∼11 zmol) at individual electrodes are reported, allowing precise measurement of electrode areas as small as ∼10-10 cm2. A plot of i lim (for a soluble redox species) versus Q 1/2 (for an adsorbed redox species), constructed from i lim−Q 1/2 data pairs obtained as a function of the electrode radius, is shown to be linear if the electrode geometry is independent of electrode radius; departure of experimental values from the straight-line plot is a diagnostic indicator of a nonideal electrode geometry. The results indicate that ∼50% of the electrodes prepared by the electrophoretic polymer-coating procedure are quasi-hemispherical, the remaining being recessed slightly below the polymer coating. The heterogeneous electron-transfer rate constant for the oxidation of the ferrocenylmethyltrimethylammonium cation in H2O/0.2 M KCl was also determined from steady-state voltammetry using the method of Mirkin and Bard and found to be 4.8 ± 3.2 cm/s with α = 0.64 ± 0.15.
Combinatorics Wilson, Robin; Watkins, John J; Graham, Ronald
2013, 2013-06-27, 2013-06-01
eBook
The history of mathematics is a well-studied and vibrant area of research, with books and scholarly articles published on various aspects of the subject. Yet, the history of combinatorics seems to ...have been largely overlooked. This book goes some way to redress this and serves two main purposes: it constitutes the first book-length survey of the history of combinatorics, and it assembles, for the first time in a single source, researches on the history of combinatorics that would otherwise be inaccessible to the general reader. Individual chapters have been contributed by sixteen experts. The book opens with an introduction to two thousand years of combinatorics. This is followed by seven chapters on early combinatorics, leading from Indian and Chinese writings on permutations to late-Renaissance publications on the arithmetical triangle. The next seven chapters trace the subsequent story, from Euler’s contributions to such wide-ranging topics as partitions, polyhedra, and latin squares to the 20th-century advances in combinatorial set theory, enumeration, and graph theory. The book concludes with some combinatorial reflections.
Across the board Watkins, John J; Watkins, John J
2004., 20110919, 2011, 2004, 2004-01-01
eBook
Across the Board is the definitive work on chessboard problems. It is not simply about chess but the chessboard itself--that simple grid of squares so common to games around the world. And, more ...importantly, the fascinating mathematics behind it. From the Knight's Tour Problem and Queens Domination to their many variations, John Watkins surveys all the well-known problems in this surprisingly fertile area of recreational mathematics. Can a knight follow a path that covers every square once, ending on the starting square? How many queens are needed so that every square is targeted or occupied by one of the queens?
The resistive-pulse method was used to monitor the pressure-driven translocation of multilamellar liposomes with radii between 190 and 450 nm through a single conical nanopore embedded in a glass ...membrane. Liposomes (0% and 5% 1,2-dioleoyl-sn-glycero-3-phospho-l-serine (sodium salt) in 1,2-dilauroyl-sn-glycero-3-phosphocholine or 0%, 5%, and 9% 1,2-dipalmitoyl-sn-glycero-3-phospho(1′-rac-glycerol) (sodium salt) in 1,2-dipalmitoyl-sn-glycero-3-phosphocholine) were prepared by extrusion through a polycarbonate membrane. Liposome translocation through a glass nanopore was studied as a function of nanopore size and the temperature relative to the lipid bilayer transition temperature, T c. All translocation events through pores larger than the liposome, regardless of temperature, show translocation times between 30 and 300 μs and current pulse heights between 0.2% and 15% from the open pore baseline. However, liposomes at temperatures below the T c were captured at the pore orifice when translocation was attempted through pores of smaller dimensions, but squeezed through the same pores when the temperature was raised above T c. The results provide insights into the deformation and translocation of individual liposomes through a porous material.
Advances in the fabrication of nanometer-scaled electrodes during the past decade have created a number of exciting opportunities in both physical chemistry and analytical measurements. This article ...describes how Pt electrodes of nanometer dimensions are synthesized and characterized in a chemical laboratory. A few examples of their applications in fundamental studies of electron-transfer mechanisms and in analytical chemistry are presented. Examples include investigations of the dependence of electron-transfer kinetics and molecular diffusion on interfacial electric fields and electrochemical detection of very small quantities of a redox-active species (zeptomole detection). The concept of comparing the electrode size to the length scales of various microscopic structures (e.g., the double layer) and chemical steps that define electrochemical reactions is emphasized. This approach allows students to understand why new phenomena appear as the electrode size is reduced to the nanometer scale. A brief overview of literature describing electrochemical experimentation with nanometer-scaled electrodes is also included.
The steady-state voltammetric oxidation of hexachloroiridate(III), IrCl6 3- (1−5 mM), in the presence and absence of an excess supporting electrolyte was investigated at disk- and ...hemispherical-shaped Pt electrodes with radii ranging from 48 nm to 12.5 μm. Thermodynamic, kinetic, and transport parameters that define the shape and magnitude of the voltammetric wave exhibit a complex dependence on whether a supporting electrolyte is present in the solution. First, the half-wave potential, E 1/2, for oxidation of IrCl6 3- shifts to more positive potentials in the presence of a supporting electrolyte, a consequence of the relative difference in the strength of ion pairing of IrCl6 3- and IrCl6 2- by the supporting electrolyte cation. E 1/2 increases in the order no electrolyte < n-tetrabutylammonium < Na+ ∼ K+ ∼ Ca2+, but is independent of the supporting electrolyte anion (Cl-, NO3 -, PF6 -). Second, the heterogeneous electron-transfer rate constant for oxidation of IrCl6 3- increases by approximately an order of magnitude in the presence of a supporting electrolyte. Third, in the absence of electrolyte, mass transport limited currents deviate significantly from predicted values based on the Nernst−Planck equation, but only when the electrode radius is smaller than ca. 1 μm. The latter two effects (Frumkin and dynamic diffuse layer effects) result from the dependence of interfacial electrical fields and, thus, the rates of electron-transfer and ion migration, on the supporting electrolyte concentration. We also demonstrate that the theoretical shape of the voltammetric response for oxidation or reduction of a highly charged redox species (e.g., IrCl6 3-) is essentially independent of whether a supporting electrolyte is present in the solution. This finding can greatly simplify the analysis of heterogeneous electron-transfer rates using steady-state voltammetry in low ionic strength solutions.
Latin squares form the basis for the recreational puzzles sudoku and KenKen. In this article we show how useful several ideas from number theory are in solving a KenKen puzzle. For example, the ...simple notion of triangular number is surprisingly effective. We also introduce a variation of KenKen that uses the Gaussian integers in order to illustrate the concept of unique factorization.
