Modeling of Selective Area Laser Deposition for Solid Freeform fabrication

The results of a theoretical study of the selective area laser deposition process used for Solid Freeform Fabrication (SFF) from gas phase is presented. We show how the deposition profile of carbon deposited via pyrolytic laser chemical vapor deposition using acetylene as the source gas can be computed by taking into account heat transfer, reaction, and mass transfer processes inside the reactor. The two dimensional representation of the related experimental variables are used to describe the substrate temperature, carbon deposit, and acetylene concentration in the process. The parameters describing these processes are estimated.Mechanical Engineerin

A Preliminary Checklist of the Moths of Butler County, Ohio

Author Institution: Department of Zoology, Miami UniversityUsing a combination of blacklight, mercury vapor light, and sugar bait sampling techniques, we collected moths over a 2-yr period in Butler County, OH, and compiled a list of 392 species. Seventy-eight percent (305) of these species were found to be new county records. A checklist is provided as a baseline catalogue of the moths of Butler County, OH. An analysis of historical county records revealed a bias towards large or colorful species. Although many species we collected are considered common, several infrequently encountered species were discovered. Our effort suggests that biological surveys in fragmented landscapes may reveal unexpected biological diversity

Improvement in the reconstrution method for VAMOS Spectrometer

International audienceThe VAMOS spectrometer operational at GANIL is a large acceptance variable mode spectrometer designed for nuclear reaction studies using radioactive and stable ion beams. The spectrometer coupled with ancillary detectors like EXOGAM has been successfully used in recent experiments on (in)elastic, few nucleon transfer reactions in inverse kinematics and search for nuclei far from stability using deep inelastic transfer reactions In large acceptance spectrometers, the experimental resolution is worsened by aberrations of third and higher orders. Hardware corrections are limited and cannot completely correct the non-linear effects. Thus software reconstruction of trajectories (ray tracing) is essential to obtain the required resolution and identification of the products. A numerical method has been developed for reconstruction of ion trajectories and correction of aberrations in VAMOS. We have devised a procedure to select an optimum subset of closest trajectories for each focal plane event (x, θ, y, ϕ) from the database (generated by an ion-optics calculation). A polynomial fit to the momentum vector of the reaction product in terms of (x, θ, y, ϕ) is made only to this subset. Such an approach is found to give improved resolutions compared to fitting a single polynomial over the entire phase space. Extraction of charge state and angular distributions are rather difficult due to the variation of acceptance over the large phase space. Mass identification of the reaction products and characteristics of the spectrometer acceptance with its variation for different rigidities have been obtained. Applications to 238U+48Ca and 238U+58Ni systems at 5.5 MeV/u will be presented

Mechanical and chemical spinodal instabilities in finite quantum systems

Self consistent quantum approaches are used to study the instabilities of finite nuclear systems. The frequencies of multipole density fluctuations are determined as a function of dilution and temperature, for several isotopes. The spinodal region of the phase diagrams is determined and it appears that instabilities are reduced by finite size effects. The role of surface and volume instabilities is discussed. It is indicated that the important chemical effects associated with mechanical disruption may lead to isospin fractionation.Comment: 4 pages, 4 figure

Low density instability in a nuclear Fermi liquid drop

The instability of a Fermi-liquid drop with respect to bulk density distortions is considered. It is shown that the presence of the surface strongly reduces the growth rate of the bulk instability of the finite Fermi-liquid drop because of the anomalous dispersion term in the dispersion relation. The instability growth rate is reduced due to the Fermi surface distortions and the relaxation processes. The dependence of the bulk instability on the multipolarity of the particle density fluctuations is demonstrated for two nuclei $^{40}Ca$ and $^{208}Pb$.Comment: 12 pages, latex, 3 ps-figures, submitted to Phys. Rev.