Macroscopic-Microscopic Mass Models

We discuss recent developments in macroscopic-microscopic mass models, including the 1992 finite-range droplet model, the 1992 extended-Thomas-Fermi Strutinsky-integral model, and the 1994 Thomas-Fermi model, with particular emphasis on how well they extrapolate to new regions of nuclei. We also address what recent developments in macroscopic-microscopic mass models are teaching us about such physically relevant issues as the nuclear curvature energy, a new congruence energy arising from a greater-than-average overlap of neutron and proton wave functions, the nuclear incompressibility coefficient, and the Coulomb redistribution energy arising from a central density depression. We conclude with a brief discussion of the recently discovered rock of metastable superheavy nuclei near 272:110 that had been correctly predicted by macroscopic-microscopic models, along with a possible new tack for reaching an island near 290:110 beyond our present horizon.Comment: 10 pages. LaTeX. Presented at International Conference on Exotic Nuclei and Atomic Masses (ENAM 95), Arles, France, June 19-23, 1995. To be published in conference proceedings by Les Editions Frontieres, Gif sur Yvette, France. Seven figures not included here. PostScript version with figures available at http://t2.lanl.gov/pub/publications/publications.html or by anonymous ftp at ftp://t2.lanl.gov/pub/publications/enam9

Collisions of Deformed Nuclei and Superheavy-Element Production

A detailed understanding of complete fusion cross sections in heavy-ion collisions requires a consideration of the effects of the deformation of the projectile and target. Our aim here is to show that deformation and orientation of the colliding nuclei have a very significant effect on the fusion-barrier height and on the compactness of the touching configuration. To facilitate discussions of fusion configurations of deformed nuclei, we develop a classification scheme and introduce a notation convention for these configurations. We discuss particular deformations and orientations that lead to compact touching configurations and to fusion-barrier heights that correspond to fairly low excitation energies of the compound systems. Such configurations should be the most favorable for producing superheavy elements. We analyse a few projectile-target combinations whose deformations allow favorable entrance-channel configurations and whose proton and neutron numbers lead to compound systems in a part of the superheavy region where alpha half-lives are calculated to be observable, that is, longer than 1 microsecond.Comment: 15 pages. LaTeX with iopconf.sty style file. Presented at 2nd RIKEN/INFN Joint Symposium, Wako-shi, Saitama, Japan, May 22-26, 1995. To be published in symposium proceedings by World Scientific, Singapore. Seven figures not included here. PostScript version with figures available at http://t2.lanl.gov/pub/publications/publications.html or at ftp://t2.lanl.gov/pub/publications/riken9

Evaluating Mutagenicity of Burned Arginine-based Heterocyclic Amines and Anti-mutagenicity Effect of Chinese Medicinal Herbs

From the unexpected finding that cooked grains and meat substitutes elicit a mutagenic response in Salmonella typhimurium TA98, our work has been aimed at deconstructing this finding via a survey of heated binary amino acid combinations, involving arginine, a plant-based amino acid. secondly, our work has looked towards sing phytochemical extracts from traditional Chinese medicinal herbs to inhibit the mutagenic activity of heterocyclic amines (main culprit for mutagenicity in meat). Two fractions from the burned products of arginine and phenylalanine (RF-HCA-06 and -07) were statistically significant inducers of mutagenesis; Scutellaria barbata and Oldenlandia diffusa, both separately and together, were statistically significant inhibitors of PhIP-induced mutagenesis. Further fractionaton of the compounds and herbal extracts may lead to the discovery of the compound(s) responsible for inducing or inhibiting mutagenicity, respectively