Boson expansion methods applied to a two-level model in the study of multiple giant resonances

We apply boson expansion methods to an extended Lipkin-Meshkov-Glick model including anharmonicities in analogy with previous microscopic calculations. We study the effects of different approximations present in these calculations, among which the truncation of the hamiltonian and of the space, in connection with the study of the properties of two-phonon and three-phonon states. By comparing the approximate results on the spectrum with the exact ones we conclude that the approximations made in the microscopic calculations on two-phonon states are well justified. We find also that a good agreement with the exact results for the three-phonon state is obtained by using a bosonic hamiltonian truncated at the fourth order. This result makes us confident that such approximation can be used in realistic calculations, thus allowing a theoretical study of triple excitations of giant resonances.Comment: 12 pages, 2 figures, Latex with epsfig.st

Conventional and manipulated growth of Cu-Cu(111)

Molecular beam epitaxy of Cu on Cu(111) was studied using thermal energy He scattering, in the temperature range between 100 and 450 K. Three-dimensional growth was observed in the whole temperature range. To determine the onset of various diffusion processes, submonolayer films formed by deposition at low temperature were annealed. Annealing proceeds in two steps. The first step is interpreted as a change in island shape, the second as Ostwald-ripening. A comparison with homoepitaxy on Pt(111) and Ag(111) is made. Growth manipulation was carried out by artificially increasing the island number density via intervention in the nucleation stage of each layer. The procedures applied were temperature reduction during nucleation as well as pulsed ion bombardment. These techniques enabled the convenient growth of good quality films consisting of a large number of monolayers. Finally, the use of oxygen as a surfactant modifying the growth mode was investigated. Under some growth conditions, pre-exposure of the surface to oxygen was found to induce weak He-intensity oscillations during deposition. The quality of the films grown in this way was, however, low

Low-Mass Baryon-Antibaryon Enhancements in B Decays

The nature of low-mass baryon-antibaryon enhancements seen in B decays is explored. Three possibilities include (i) states near threshold as found in a model by Nambu and Jona-Lasinio, (ii) isoscalar states with $J^{PC} = 0^{\pm +}$ coupled to a pair of gluons, and (iii) low-mass enhancements favored by the fragmentation process. Ways of distinguishing these mechanisms using angular distributions and flavor symmetry are proposed.Comment: 8 pages, LaTeX, no figures, to be submitted to Phys. Rev. D. One reference adde

The Ursinus Weekly, December 7, 1936

John Porambo, varsity center, is elected captain of 1937 gridmen by 21 lettermen • Articles by Groff and Yoh are Lantern prize winners • Xmas celebration is two nights • Ursinus rec center to open after Xmas • Y groups to present speaker on cooperative consumers plan • McClure, Sheeder, attend Association of Colleges meeting • Freshman gridders banquet in initial frosh grid fete • Bothell and Garber star in The Dark Tower; record crowd dances to Jan\u27s Tophatters • Dr. Meredith to address physical education group • Interfraternity council issues member list for new students • Students hear economist in talk on natural resources • Debating teams release schedules; women will meet Bucknell this Thursday; men to hold radio debate • Stevens new wrestling coach; good year expected; 27 candidates report for practice • Officials select all-dorm team; five frosh picked • Guest elected soccer captain, bear manager, by 11 lettermen • Costello and Heiges on conference team • Co-ed basketeers participate in new rules exhibition game • Snell\u27s belles end season with six wins, 3 losses • 15 basketballers report; 4 lettermen lead struggle • McAvoy\u27s bears end season in second place, F & M winners in conference; Captain Costello outstanding through season; twelve lettermen leave squadhttps://digitalcommons.ursinus.edu/weekly/1915/thumbnail.jp

The Ursinus Weekly, October 26, 1936

Ursinus amateur, says J.R. Tunis • Fighting grizzlies beat Muhlenberg • Curtain Club tryouts attract large number of students • Sophomore class chooses U ring; Dunn head of committee • The Human Adventure, eight-reel picture reviewing ages of man\u27s past, shown four times to accommodate crowds; Dr. White directs presentation • Hedgerow noted for its Twelfth night rendition • Varsity Club to sponsor annual dance November 7 • Y hobo Halloween party to feature fun for all • Goldberg chosen to head male commuters in recent election • Frosh beat Perkiomen in hard fought game as Kurek, McConnel stage down-field drive • McAvoy\u27s bears to tangle with Albright Lions on Saturday • Bear booters trounced as teachers storm bruin goal • Hockeyites bow to Swarthmore in hard tilt; come back to shatter Beaver\u27s winning streak • Tennis tournament reaches quarter-finals; ends Sunday • Juniors are victorious in inter-class hockey games • Brodbeck leads in dorm football; tie for secondhttps://digitalcommons.ursinus.edu/weekly/1909/thumbnail.jp

Borna disease.

Borna disease virus, a newly classified nonsegmented negative-strand RNA virus with international distribution, infects a broad range of warm-blooded animals from birds to primates. Infection causes movement and behavioral disturbances reminiscent of some neuropsychiatric syndromes. The virus has not been clearly linked to any human disease; however, an association between infection with the virus and selected neuropsychiatric disorders has been suggested. We reviewed recent advances in Borna disease virus research, focusing on evidence of infection in humans

The Influence of Transient Thermal Gradients and Substrate Constraint on Delamination of Thermal Barrier Coatings

A systematic study of factors affecting the delamination energy release rate and mode mix of a thermal barrier coating attached to a substrate is presented accounting for the influence of thermal gradients combined with rapid hot surface cooling. Transient thermal gradients induce stress gradients through the coating and substrate, which produce overall bending if the substrate is not very thick and if it is not constrained. Due to their influences on the coating stresses, substrate thickness and constraint are important aspects of the mechanics of delamination of coating-substrate systems, which must be considered when laboratory tests are designed and for lifetime assessment under in-service conditions. Temperature gradients in the hot state combined with rapid cooling give rise to a maximum energy release rate for delamination that occurs in the early stage of cooling and that can be considerably larger than the driving force for delamination in the cold state. The rates of cooling that give rise to a large early stage energy release rate are identified.Engineering and Applied Science