Dynamics in a discontinuous field: The smooth Fermi piston

In this paper we examine a version of the Fermi piston with a discontinuous, but nonimpulsive, periodic driving force. The dynamics of a particle moving in one spatial dimension are studied using a combination of numerical and analytical techniques. The configuration space of the particle is divided into two regions of constant acceleration that are of equal magnitude and opposite direction. The point of discontinuity F(t) dividing the regions changes periodically in time. The method of surface-of-section is used to study the phase space (phi(n), v(n)), where phi(n) is the phase of the driving function and v(n) is the velocity of the particle at the nth encounter between the particle and boundary. We show that it is not possible to stochastically drive up the energy indefinitely except for the cases where F is discontinuous, or dF/dt is not finite everywhere. In addition, we find a new mechanism, other than KAM tori, for segmenting the phase space. As in the KAM picture, the central cause of the new behavior is resonance between the natural period of the particle and the period of the driving force. The boundaries to diffusion for continuous driving functions result from parabolic fixed points that span the entire phase range.     

Use of Nile Red as a long-wavelength fluorophore in dual-probe studies of ligand-protein interactions

The long-wavelength fluorescence probe, Nile Red, has polarity-dependent fluorescence intensity and wavelength properties that can be used to monitor the binding of drugs and other ligands to plasma proteins such as albumin and -1 acid glycoprotein. This paper shows that it can be used in tandem with another fluorescence probe, 1-anilinonaphthalene-8-sulfonic acid, to study two or more types of ligand binding sites simultaneously. Some ligands displace one or the other probe from the protein/dual-probe complex, other ligands displace both probes. In each case the resulting decrease in fluorescence can be used to estimate the numbers of binding sites and their association constants.     

Precision high-speed neutron activation analysis via very short-lived activities

An automated, highly reproducible fast-transfer system (0.36±0.01 sec) has been developed, an oscillator/multichannel-scaling system has been developed to follow rapidly-changing spectrometer dead-times, the mathematics has been developed, and the data processing steps have been computerized. Three induced activities have been studied in some detail:^207mPb (0.80 sec),^38mCl (0.70 sec) and²⁰F (11.03 sec). Both steady-state and high-intensity pulsed reactor irradiations, with and without a Cd liner, have been used. The dead-time correction method has been carefully checked, and the overall method has been tested by the analysis of two NBS Standard Reference Materials: orchard leaves (for Cl and Pb) and bovine liver (for Cl). This paper represents a portion of the Ph. D. thesis of D. A. MILLER.