On the use of the pseudo-diatomic model for experimental evaluation of stabilization energies of weakly bound molecular complexes

Stabilization energies of weakly bound molecular complexes, relative to the isolated monomers constituents, have been evaluated experimentally using the pseudo-diatomic (PD) model employing a Lennard-Jones 6-12 potential (LJ), here denominated the PD-LJ model. This method uses spectroscopic data to estimate the potential depth of weakly bound species. In this work we report a systematic comparison between high level ab initio stabilization energy values and the respective experimental data available for a series of binary complexes, aiming to assess the efficaciousness of the PD-LJ model

Wintering Ecology of Buff-Breasted Sandpipers (Tryngites subruficollis) in Southern Brazil

Buff-breasted Sandpipers (Tryngites subruficollis) are a medium-sized sandpiper that suffered a steep population decline during the last century. Current estimates of population size are at least one order of magnitude smaller than historical estimates. The continued decline in population size has resulted in Buff-breasted Sandpipers being recognized world-wide as a species of critical conservation concern. Yet, little is known about their ecology at wintering sites and about their population dynamics. In this dissertation, I present results on within- and among-year density trends, life-history strategy, molt, body condition and population dynamics of Buff-breasted Sandpipers wintering in southern Brazil. Additionally, I provide a discriminant function to accurately sex Buffbreasted Sandpipers using morphometric measures. I estimated density trends of Buff-breasted Sandpipers at three wintering sites, Lagoa do Peixe National Park (LPNP), Ilha da Torotama (IT) and Taim Ecological Station (TES). Density was highest at IT, but was closely followed by LPNP. Buff-breasted Sandpipers were absent from TES during most of the study. Because of the consistency of use, and high densities at LPNP and IT, I suggest that these sites be included in any management action directed toward conservation of the species. Results in molt schedule, as well as arrival and departure patterns at LPNP indicated that males and females have different life-history strategies. Males molted wing and tail feathers faster than females, finishing molt approximately ii one month before females. This difference mirrored the difference in departure from the wintering grounds: males depart one month earlier than females. Moreover, sex ratio at LPNP was female biased and males were more prone to leave the site in any given month. The between-sex difference in life-history strategy and female bias at the north end of the wintering range suggest that sexual segregation in Buff-breasted Sandpipers is opposite to what would be predicted by sexual segregation theory: male Buff-breasted Sandpipers winter further south instead of further north as would be predicted. Apparent annual survival of Buff-breasted Sandpipers is equivalent to or higher than survival rates reported for other shorebirds. Additionally, males had lower apparent annual survival and a higher temporary emigration rate than females. Differences in apparent annual survival between sexes may result from the short-term nature of this study and/or higher emigration rate of male Buffbreasted Sandpipers. Therefore, future long-term studies utilizing markrecapture techniques are critical for understanding variation in Buff-breasted Sandpipers annual survival. This study demonstrated that wintering sites provide the best location for estimating annual survival

Magnetic phases evolution in the LaMn1-xFexO3+y system

We have investigated the crystal structure and magnetic properties for polycrystalline samples of LaMn1-xFexO3+y, in the whole range x=0.0 to x=1.0, prepared by solid state reaction in air. All samples show the ORT-2 orthorhombic structure that suppresses the Jahn-Teller distortion, thus favoring a ferromagnetic (FM) superexchange (SE) interaction between Mn^{3+}-O-Mn^{3+}. For x=0.0 the oxygen excess (y ~ 0.09) produces vacancies in the La and Mn sites and generates a fraction around 18% of Mn^{4+} ions and 82% of the usual Mn^{3+} ions, with possible double exchange interaction between them. The Fe doping in this system is known to produce only stable Fe^{3+} ions. We find an evolution from a fairly strong FM phase with a Curie temperature T_{C} ~ 160 K, for x=0.0, to an antiferromagnetic (AFM) phase with T_{N} = 790 K, for x=1.0, accompanied by clear signatures of a cluster-glass behavior. For intermediate Fe contents a mixed-phase state occurs, with a gradual decrease (increase) of the FM (AFM) phase, accompanied by a systematic transition broadening for 0.2 < x < 0.7. A model based on the expected exchange interaction among the various magnetic-ion types, accounts very well for the saturation-magnetization dependence on Fe doping.Comment: 27 pages, 9 figure