Low-energy muon-transfer reaction from hydrogen isotopes to helium isotopes

Direct muon transfer in low-energy collisions of the muonic hydrogen H$_\mu$ and helium (He$^{++}$) is considered in a three-body quantum-mechanical framework of coordinate-space integro-differential Faddeev-Hahn-type equations within two- and six-state close coupling approximations. The final-state Coulomb interaction is treated without any approximation employing appropriate Coulomb waves in the final state. The present results agree reasonably well with previous semiclassical calculations.Comment: 4 revtex4 page

An Experimental Study of Evaporites on Titan: Implications for Lake Composition and Future Missions

Titan is the only other planetary body in the solar system with liquid on the surface. With a surface temperature and pressure of 89 – 94 K and 1.5 bar (N2), respectively, Titan’s lakes are comprised of liquid hydrocarbons, predominantly methane and ethane. Over time, Titan’s lakes may evaporate, leaving behind residual deposits (evaporites). The evaporation processes and composition of the evaporites is poorly understood. I address these outstanding questions by experimentally investigating the physical and spectral properties of evaporites at Titan surface conditions using an experimental chamber. Chapter 1 addresses the formation of ethylene evaporites. Ethylene evaporites form more quickly with pure methane, because methane readily evaporates at Titan surface conditions. Ethylene absorption bands at 1.630 and 2.121 μm are redshifted after evaporite formation. These results imply that ethylene is a good candidate for Titan’s evaporites, although they may be restricted to methane-dominated lakes/seas. Chapter 2 addresses the ability to detect the formation of the acetylene-benzene co-crystal using FTIR spectroscopy. The co-crystal is easily identifiable upon formation at ~135 K, as evidenced by drastic spectral band shifts, several new bands in the C-H stretching and combination bands regions, and clear morphological changes of the sample. The co-crystal is stable down to Titan temperatures (90 K). Studying co-crystal formation provides insights into co-condensation in Titan’s atmosphere, and evaporite formation and composition. Chapter 3 investigates the formation of evaporites with acetonitrile. Acetylene and acetonitrile form a co-crystal between 118 – 174 K, which is stable down to 90 K. New bands at 1.676 µm and morphological changes to the sample confirm co-crystal formation. We observe new shapes to NIR absorptions that were not previously present in pure component experiments. These results have implications for astrobiologically relevant co-crystals and where nitrile compounds may accumulate on Titan. Chapter 4 addresses more complex evaporite experiments (“binary” experiments) with two evaporite molecules combined. Acetylene is the most prominent species in these experiments, and the acetylene-acetonitrile co-crystal is stable before, during, and after methane evaporation. These results and future binary experiments can help assess the validity of evaporite models, and represent a more realistic view of evaporite solutions

Failure to infect laboratory rodent hosts with human isolates of Rodentolepis(= Hymenolepis) nana

Confusion exists over the species status and host-specificity of the tapeworm Rodentolepis (= Hymenolepis) nana. It has been described as one species, R. nana, found in both humans and rodents. Others have identified a subspecies; R. nana var. fraterna, describing it as morphologically identical to the human form but only found in rodents. The species present in Australian communities has never been identified with certainty. Fifty one human isolates of Rodentolepis (= Hymenolepis) nana were orally inoculated into Swiss Q, BALB/c, A/J, CBA/CAH and nude (hypothymic) BALB/c mice, Fischer 344 and Wistar rats and specific pathogen free (SPF) hamsters. Twenty four human isolates of R. nana were cross-tested in flour beetles, Tribolium confusum. No adult worms were obtained from mice, rats or hamsters, even when immunosuppressed with cortisone acetate. Only one of the 24 samples developed to the cysticercoid stage in T. confusum; however, when inoculated into laboratory mice the cysticercoids failed to develop into adult worms. The large sample size used in this study, and the range of techniques employed for extraction and preparation of eggs provide a comprehensive test of the hypothesis that the human strain of R. nana is essentially non-infective to rodents