The ground state properties of the spin-1/2 transverse Ising chain with periodically varying bonds and fields

Using continued fractions we study the ground state properties of the spin-1/2 Ising chain in a transverse field with periodically varying interaction strengths and external fields. We consider in detail the chain having the period of modulation of interactions equals 2 and compare the results obtained with those corresponding to the spin-1/2 isotropic XY chain in a transverse field. In contrast to the behaviour of the transverse XY chain, the transverse Ising chain does not exhibit a step-like magnetization vs. field dependence caused by the alternation of bonds, its susceptibility exhibits a logarithmic singularity at the field determined by interaction strengths, and it is stable with respect to spin-Peierls dimerization.Comment: 11 pages, latex, 4 figure

Monitoramento da ocorrência de Thaumastocoris peregrinus em plantio de eucalipto.

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Extraction of bioactive compounds from a juçara byproduct.

31st EFFoST. 13 a 16 novembro. Sitges, Spain

Accretion Signatures from Massive Young Stellar Objects

High resolution (lambda / Delta-lambda = 50,000) K-band spectra of massive, embedded, young stellar objects are presented. The present sample consists of four massive young stars located in nascent clusters powering Galactic giant H II regions. Emission in the 2.3 micron 2--0 vibrational--rotational bandhead of CO is observed. A range of velocity broadened profiles seen in three of the objects is consistent with the emission arising from a circumstellar disk seen at various inclination angles. Br gamma spectra of the same spectral and spatial resolution are also presented which support an accretion disk or torus model for massive stars. In the fourth object, Br emission suggesting a rotating torus is observed, but the CO profile is narrow, indicating that there may be different CO emission mechanisms in massive stars and this is consistent with earlier observations of the BN object and MWC 349. To--date, only young massive stars of late O or early B types have been identified with clear accretion disk signatures in such embedded clusters. Often such stars are found in the presence of other more massive stars which are revealed by their photospheric spectra but which exhibit no disk signatures. This suggests the timescale for dissipating their disks is much faster than the less massive OB stars or that the most massive stars do not form with accretion disks.Comment: 28 pages, 10 Figures, accepted for publication in the Astrophysical Journa

Preferência para oviposição e alimentação de Thaumastocoris peregrinus (Hemiptera: Thaumastocoridae) por folhas de Eucalyptus benthamii de diferentes idades.

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Método de criação de Thaumastocoris peregrinus (Hemiptera: Thaumastocoridae) em laboratório.

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Viabilidade dos ovos de Thaumastocoris peregrinus (Hemiptera, Thaumastocoridae) em diferentes substratos.

EVINCI. Resumo

Efeito de Eucalyptus spp na alimentação e excreção de honeydew de Thaumastocoris peregrinus (Hemiptera: Thaumastocoridae).

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