36,851 research outputs found
Profiles of near-resonant population-imbalanced trapped Fermi gases
We investigate the density profiles of a partially polarized trapped Fermi
gas in the BCS-BEC crossover region using mean field theory within the local
density approximation. Within this approximation the gas is phase separated
into concentric shells. We describe how the structure of these shells depends
upon the polarization and the interaction strength. A Comparison with
experiments yields insight into the possibility of a polarized superfluid
phase.Comment: 4 pages, 5 Figures, Published versio
Identificação e monitoramento de insetos-praga em bastão-do-imperador (Etlingera elatior) e heliconias no município de Belém, Pará.
Resgate de embriões zigóticos provenientes do cruzamento entre cultivares apirênicas de videira.
Populações de plantas e adubação orgânica em solo degradado na cultura do amendoim
bitstream/CNPA/19705/1/BOLETIM51.pd
Chemical abundances and kinematics of barium stars
In this paper we present an homogeneous analysis of photospheric abundances
based on high-resolution spectroscopy of a sample of 182 barium stars and
candidates. We determined atmospheric parameters, spectroscopic distances,
stellar masses, ages, luminosities and scale height, radial velocities,
abundances of the Na, Al, -elements, iron-peak elements, and s-process
elements Y, Zr, La, Ce, and Nd. We employed the local-thermodynamic-equilibrium
model atmospheres of Kurucz and the spectral analysis code {\sc moog}. We found
that the metallicities, the temperatures and the surface gravities for barium
stars can not be represented by a single gaussian distribution. The abundances
of -elements and iron peak elements are similar to those of field giants
with the same metallicity. Sodium presents some degree of enrichment in more
evolved stars that could be attributed to the NeNa cycle. As expected, the
barium stars show overabundance of the elements created by the s-process. By
measuring the mean heavy-element abundance pattern as given by the ratio
[s/Fe], we found that the barium stars present several degrees of enrichment.
We also obtained the [hs/ls] ratio by measuring the photospheric abundances of
the Ba-peak and the Zr-peak elements. Our results indicated that the [s/Fe] and
the [hs/ls] ratios are strongly anti-correlated with the metallicity. Our
kinematical analysis showed that 90% of the barium stars belong to the thin
disk population. Based on their luminosities, none of the barium stars are
luminous enough to be an AGB star, nor to become self-enriched in the s-process
elements. Finally, we determined that the barium stars also follow an
age-metallicity relation.Comment: 30 pages, 26 figures, 18 tables, accepted for publication in MNRA
Convergent evolution of elaborate nests as structural defences in birds
The pendent nests of some weaverbird and icterid species are among the most complex structures built by any animal, but why they have evolved remains to be explained. The precarious attachments and extended entrance tunnels characteristic of these nests are widely speculated to act as structural defences against invasion by nest predators, particularly tree-climbing snakes, but this hypothesis has yet to be systematically tested. We use phylogenetic comparative methods to investigate the relationship between nest structure and developmental period length, a proxy for offspring mortality, in weaverbirds (Ploceidae) and icterids (Icteridae), two bird families in which highly elaborate pendent nests have independently evolved. We find that more elaborate nests, particularly those with entrance tunnels, are associated with longer developmental periods in both families. This finding is robust to potentially confounding effects of body mass, phylogenetic relationships, nest location and latitude. Our results are consistent with the hypothesis that elaborate nest structures in birds can function as structural defences, resulting in lower offspring mortality and slower development. More generally, our findings suggest that constructing complex, protective structures may buffer against environmental hazards, reducing extrinsic mortality and contributing to the evolution of slower life histories in diverse animal lineages, even humans
Controle de plantas daninhas na cultura do sorgo forrageiro com a mistura Atrazine + Metolachlor em pós-emergência inicial.
Desinfestação de explantes caulinares de umbu-cajazeira por hipoclorito de sódio e bicloreto de mercúrio.
O umbu-cajazeira é uma espécie do gênero Spondias resultante do cruzamento natural entre a cajazeira (Spondias mombin) e o umbuzeiro (Spondias tuberosa). Assim como a cajazeira e o umbuzeiro, é uma fruteira tropical que apresenta grandes perspectivas de inserção no mercado interno e externo de frutas exóticas. A diversidade genética em populações nativas de umbu-cajazeira presentes no Nordeste do Brasil é ampla, porém, encontra-se ameaçada por um processo indiscriminado de exploração das áreas de ocorrência das mesmas, particularmente, pela prática de formação de pastagens, comprometendo a preservação desse patrimônio genético de valor incalculável
Perspectivas da irrigação na cultura algodoeira no nordeste brasileiro.
Potencialidades e disponibilidades hidricas do nordeste - sistema de irrigacao; Perspectivas da lavoura algodoeira irrigada; Principais problemas na lavoura algodoeira irrigada.bitstream/item/33307/1/CNPA-DOCUMENTOS-35-PERSPECTIVAS-DA-IRRIGACAO-NA-CULTURA-ALGODOEIRA-DO-NORDESTE-BRASILEIRO-FL-0290.pd
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