Galactic globular cluster 47 Tucanae: new ties between the chemical and dynamical evolution of globular clusters?

It is generally accepted today that Galactic globular clusters (GGCs) consist of at least two generations of stars that are different in their chemical composition and perhaps age. However, knowledge about the kinematical properties of these stellar generations, which may provide important information for constraining evolutionary scenarios of the GGCs, is still limited. We therefore study the connections between chemical and kinematical properties of different stellar generations in the Galactic globular cluster 47 Tuc. To achieve this goal, we used abundances of Li, O, and Na determined in 101 main sequence turn-off (TO) stars with the aid of 3D hydrodynamical model atmospheres and NLTE abundance analysis methodology. We divided our sample TO stars into three groups according to their position in the [Li/Na]-[Na/O] plane to study their spatial distribution and kinematical properties. We find that there are statistically significant radial dependencies of lithium and oxygen abundances, A(Li) and A(O), as well as that of [Li/Na] abundance ratio. Our results show that first-generation stars are less centrally concentrated and dynamically hotter than stars belonging to subsequent generations. We also find a significant correlation between the velocity dispersion and O and Na abundance, and between the velocity dispersion and the [Na/O] abundance ratio.Comment: 4 pages, 6 figures, accepted for publication in A&

Atomic interaction effects in the superradiant light scattering from a Bose-Einstein condensate

We investigate the effects of the atomic interaction in the Superradiant Rayleigh scattering from a Bose-Einstein condensate driven by a far-detuned laser beam. We show that for a homogeneous atomic sample the atomic interaction has only a dispersive effect, whereas in the inhomogeneous case it may increase the decay of the matter-wave grating.Comment: 12 pages, 4 figures, presented to the XII International Laser Physics Workshop, August 24-29, Hamburg, to be published in Laser Physic

Survey and Assessment of Laws on the Informal Sector

This study classifies the laws affecting the informal sector and assesses the extent of the empowerment of the sector based on the provisions in the laws that allow for organization, decision making mechanisms and transfer of power from the traditional center to another. Results indicate that, to some extent, four groups within the sector are accorded empowerment through Philippine laws: the agricultural sector, small and medium enterprises, industrial home workers and cooperatives. These groups are allowed to form organizations and to participate in decision making bodies. Decision making is accorded to certain groups among informal sector, which, in some cases, comprise the majority members in decision making bodies. Nowhere among the laws is a shift of power provided from the traditional or government decision makers to the informal sector. However, certain groups within the IS have participated in the institution of some policies and the realization of programs for their own advantage.informal financial sectors, small and medium enterprises

Survey and Assessment of Laws on the Informal Sector

This study classifies the laws affecting the informal sector and assesses the extent of the empowerment of the sector based on the provisions in the laws that allow for organization, decision making mechanisms and transfer of power from the traditional center to another. Results indicate that, to some extent, four groups within the sector are accorded empowerment through Philippine laws: the agricultural sector, small and medium enterprises, industrial home workers and cooperatives. These groups are allowed to form organizations and to participate in decision making bodies. Decision making is accorded to certain groups among informal sector, which, in some cases, comprise the majority members in decision making bodies. Nowhere among the laws is a shift of power provided from the traditional or government decision makers to the informal sector. However, certain groups within the IS have participated in the institution of some policies and the realization of programs for their own advantage.informal financial sectors, small and medium enterprises

Non-LTE abundances of Mg and K in extremely metal-poor stars and the evolution of [O/Mg], [Na/Mg], [Al/Mg] and [K/Mg] in the Milky Way

LTE abundances of light elements in extremely metal-poor (EMP) stars have been previously derived from high quality spectra. New derivations, free from the NLTE effects, will better constrain the models of the Galactic chemical evolution and the yields of the very first supernovae. The NLTE profiles of the magnesium and potassium lines have been computed in a sample of 53 extremely metal-poor stars with a modified version of the program MULTI and adjusted to the observed lines in order to derive the abundances of these elements. The NLTE corrections for magnesium and potassium are in good agreement with the works found in the literature. The abundances are slightly changed, reaching a better precision: the scatter around the mean of the abundance ratios has decreased. Magnesium may be used with confidence as reference element. Together with previously determined NLTE abundances of sodium and aluminum, the new ratios are displayed, for comparison, along the theoretical trends proposed by some models of the chemical evolution of the Galaxy, using different models of supernovae

Up-frequency conversion in a two-resonant-wave high-gain free-electron-laser amplifier

A free-electron laser is able to resonate at two different frequencies, both in free space and in a waveguide. The two waves have positive and negative slippage. We describe the nonlinear interaction between the two waves by a set of partial differential equations which in free space do not require the slowly varying envelope approximation (SVEA). In a waveguide a less restrictive SVEA is applied to each wave. By injecting a small signal at the low frequency, a strong signal and bunching are produced at the high frequency. This effect suggests a new method of generating short wavelength radiation

Lead abundance in the uranium star CS 31082-001

In a previous paper we were able to measure the abundance of uranium and thorium in the very-metal poor halo giant BPS CS 31082-001, but only obtained an upper limit for the abundance of lead (Pb). We have got from ESO 17 hours of additional exposure on this star in order to secure a detection of the minimum amount of lead expected to be present in CS 31082-001, the amount arising from the decay of the original content of Th and U in the star. We report here this successful detection. We find an LTE abundance log(Pb/H)+12=-0.55 \pm 0.15 dex, one dex below the upper limits given by other authors for the similar stars CS 22892-052 and BD +17d3248, also enhanced in r-process elements. From the observed present abundances of Th and U in the star, the expected amount of Pb produced by the decay of 232Th, and 238U alone, over 12-15 Gyr is -0.73\pm 0.17 dex. The decay of 235U is more difficult to estimate, but is probably slightly below the contribution of 238U, making the contribution of the 3 actinides only slightly below, or even equal to, the measured abundance. The contribution from the decay of 234U has was not included, for lack of published data. In this sense our determination is a lower limit to the contribution of actinides to lead production. We comment this result, and we note that if a NLTE analysis, not yet possible, doubles our observed abundance, the decay of the 3 actinides will still represent 50 per cent of the total lead, a proportion higher than the values considered so far in the literature.Comment: 4 pages, LateX, A&A Letters Accepte