Nuclear binding energies and liquid drop parameters in the extended Thomas-Fermi approximation

Using the extended Thomas-Fermi model, we calculate average nuclear binding energies with Skyrme type effective interactions. The total energy is minimized with respect to variations of the nucleon densities without the use of wave functions or adjustable parameters. We obtain binding energies only ～2–7 MeV higher than self consistenly averaged Hartree-Fock energies. By least-square fits we determine the liquid drop parameters of different effective interactions very accurately. Shell effects are added perturbatively and lead to total energies within 5–10 MeV of the exact Hartree-Fock results.     

Spin-orbit splitting in theN-Δ spectra and the deformed baryon model

The absence of appreciable spin-orbit splitting in the low-lying even and odd parity states of the nucleon and delta is puzzling in conventional quark models. A constitutent quark model, in which the quarks interact through gluon as well as pion exchange, and the baryon is allowed to deform in the excited states, may provide a solution to the problem.     

Surface barrier structure analysis using leed

Using a modified image surface potential energy barrier model we have calculated intensity profiles for Cu(001) and Ni(001) which show surface barrier resonance features. These features correlate well with experimental features suggesting that the modified image barrier is an appropriate one-dimensional phenomenological model for the real surface potential energy barrier. From the available experimental data the two parameters in the model locating the origin with respect to the top row of atoms at the surface and the height of the barrier are determined for each surface.     

An electronic audio delay system

It is frequently desirable to be able to delay audio frequencies by times ranging from several milliseconds to hundreds of milliseconds. Although several methods have been developed to achieve this, most of them employ electromechanical delay systems. The article describes an all-electronic technique of delaying acoustic signals; experimental work on the system has established its feasibility.     

Surface-catalyzed growth of polymethylene-rich copolymer films on gold

We report the preparation of a new class of copolymer films that consist of polymethylene (PM) with a low percentage ( approximately 1-4%) of randomly distributed ethyl ester side groups, consistent with poly(methylene-co-ethyl acetate). The films are prepared through a surface-catalyzed polymerization on gold surfaces upon exposure to a dilute solution of diazomethane (DM) and ethyl diazoacetate (EDA) in ether at 0 degrees C. While EDA alone does not polymerize at gold surfaces but DM does decompose on gold to grow PM films, the combined presence of EDA and DM results in dramatic enhancements in film growth and promotes an alternative mechanism for propagation as compared with that for the PM homopolymerization. The rate of copolymer film growth is constant over a approximately 24 h period, consistent with a controlled polymerization in which chain terminations are minimized. Carefully controlled experiments indicate that chain propagation does not occur at the outer film-solvent interface, but more likely, at the film-metal interface, suggesting a catalyzed insertion mechanism that extends the chain and pushes the outer chain termini further away from the metal-polymer interface. The results also suggest that adsorbed intermediates of EDA function as co-catalysts to promote the propagation reaction. Of particular importance for materials modification is that the ester side chains of these copolymer films can be hydrolyzed to carboxylate groups that exhibit pH-dependent wettability.