L. David Roper

Nucleon-alpha elastic scattering analyses: (I). Low-energy n-α and p-α analyses

Abstract Energy-dependent phase-shift analyses of low-energy n-α and p-α elastic scattering data were performed. Effective range parameters were obtained using the least number of parameters, and data up to the lowest energy necessary to give good fits. Fits to data up to 5 MeV for p-α scattering and up to 3 MeV for n-α scattering, with 7 parameters used in each case, were chosen as the optimum low-energy solutions. Examples of observables which can be calculated from these solutions are presented.

Nucleon-alpha elastic scattering analyses: (II). 0 to 21 MeV energy-dependent n-α analysis

Abstract An energy-dependent phase-shift analysis of 0–21 MeV n-α scattering is presented and compared to the previous 0–23 MeV p-α analysis. The error matrix and inverse error matrix for both the n-α and the p-α analyses are given.

An Exact Constant-Field Solution for a Simple Membrane

We show that the exact steady-state solution to the electrodiffusion equations for a simple membrane is the constant electric field solution when the ion environment is electroneutral on both sides of the membrane and the total numbers of ions of the same valence on both sides are equal.

Electroneutral approximate solutions of steady-state electrodiffusion equations for a simple membrane.

Abstract Electroneutral approximate solutions for steady-state electrodiffusion of ions across a simple membrane are derived for general bionic environments and a restricted class of ion environments with more than two ion types, and a criterion is given for the electroneutral solution to be a good approximate solution.

A fit to nerve membrane rectification curves with a double-dipole-layer membrane model

Following Weis suggestion that nerve stimulation and conduction properties are due to dipole layers at the two membrane surfaces (Wei, 1969), we have done steady-state electro-diffusion calculations in the constant field approximation for a simple double-dipole-layer model. We are thereby able to quantitatively fit the recent potassium iso-osmotic rectification curves of Gilbert and Ehrenstein for the squid giant axon membrane. For the squid axon membrane in a natural ion environment, only the outside dipole layer is present in the fit to the data.

Numerical Solution of Steady-State Electrodiffusion Equations for a Simple Membrane

A technique is given for obtaining numerical solutions to the steady-state electrodiffusion equations for a simple membrane. Solutions are given for several membrane boundary conditions in terms of ratios of current density to mobility for each ion type.

Numerical solution of time dependent electrodiffusion equations for a simple membrane

Abstract A technique is given for obtaining numerical solutions to the time-dependent electrodiffusion equations for a simple membrane. Voltage-clamp current densities are given as functions of time for several membrane boundary conditions and ion mobilities.

Quantitative comparison of dipole models for steady-state currents in excitable membranes

The dipole models for steady-state currents in excitable membranes of Arndt, Bond and Roper and of Hamel and Zimmerman are compared by fitting the equations to the data of Gilbert and Ehrenstein. The more complex Hammel and Zimmerman model does not fit the data as well as does the simpler Arndt, Bond and Reper model. When fitting the data, the Hammel and Zimmerman current equation reduces to the Arndt, Bond and Roper current equation because of the values assumed by the parameters. An interpretation is given for the parameter values obtained with the Arndt, Bond and Roper model.

Production-history projections of fuels and some crucial metals in the United States

The production-history projection method of the authors is refined to determine the earliest date at which reasonably well determined depletion parameters can be ascertained. The method is applied to the United States production data for silver, crude oil, natural gas, coal, iron ore and uranium ore.

A multichannel look at the available partial-wave analyses of the K̄N system in the region 0–1400 MeV/c

The available partial-wave analyses on the KN scattering data, the majority of which are single-channel analyses over limited momentum ranges, are studied with a view to facilitate a multichannel partial wave analysis over an extended momentum range (0–1400 MeV/c). The high-energy behaviour of the KN scattering amplitudes is examined by making energy-dependent multichannel M-matrix fits to the best sets of partial-wave scattering amplitudes over the entire momentum range under consideration. Finally, the same fits are repeated on the low-momentum (0–500 MeV/c) scattering amplitudes, and the parameters obtained can be used as starting points in a multichannel partial-wave analysis on the KN scattering data.