SPINSTARS at low metallicities

The main effect of axial rotation on the evolution of massive PopIII stars is to trigger internal mixing processes which allow stars to produce significant amounts of primary nitrogen 14 and carbon 13. Very metal poor massive stars produce much more primary nitrogen than PopIII stars for a given initial mass and rotation velocity. The very metal poor stars undergo strong mass loss induced by rotation. One can distinguish two types of rotationnaly enhanced stellar winds: 1) Rotationally mechanical winds occurs when the surface velocity reaches the critical velocity at the equator, {\it i.e.} the velocity at which the centrifugal acceleration is equal to the gravity; 2) Rotationally radiatively line driven winds are a consequence of strong internal mixing which brings large amounts of CNO elements at the surface. This enhances the opacity and may trigger strong line driven winds. These effects are important for an initial value of $\upsilon/\upsilon_{\rm crit}$ of 0.54 for a 60 M$_\odot$ at $Z=10^{-8}$, {\it i.e.} for initial values of $\upsilon/\upsilon_{\rm crit}$ higher than the one ($\sim$0.4) corresponding to observations at solar $Z$. These two effects, strong internal mixing leading to the synthesis of large amounts of primary nitrogen and important mass losses induced by rotation, occur for $Z$ between about 10$^{-8}$ and 0.001. For metallicities above 0.001 and for reasonable choice of the rotation velocities, internal mixing is no longer efficient enough to trigger these effects.Comment: 5 pages, 4 figures, to be published in the conference proceedings of First Stars III, Santa Fe, 200

The impact of stellar rotation on the CNO abundance patterns in the Milky Way at low metallicities

We investigate the effect of new stellar models, which take rotation into account, computed for very low metallicities on the chemical evolution of the earliest phases of the Milky Way. We check the impact of these new stellar yields on a model for the halo of the Milky Way that can reproduce the observed halo metallicity distribution. In this way we try to better constrain the ISM enrichment timescale, which was not done in our previous work. The stellar models adopted in this work were computed under the assumption that the ratio of the initial rotation velocity to the critical velocity of stars is roughly constant with metallicity. This naturally leads to faster rotation at lower metallicity, as metal poor stars are more compact than metal rich ones. We find that the new Z = 10-8 stellar yields computed for large rotational velocities have a tremendous impact on the interstellar medium nitrogen enrichment for log(O/H)+12 < 7 (or [Fe/H]< -3). We show that upon the inclusion of the new stellar calculations in a chemical evolution model for the galactic halo with infall and outflow, both high N/O and C/O ratios are obtained in the very-metal poor metallicity range in agreement with observations. Our results give further support to the idea that stars at very low metallicities could have initial rotational velocities of the order of 600-800kms-1. An important contribution to N from AGB stars is still needed in order to explain the observations at intermediate metallicities. One possibility is that AGB stars at very low metallicities also rotate fast. This could be tested in the future, once stellar evolution models for fast rotating AGB stars will be available.Comment: Contribution to Nuclei in the Cosmos IX (Proceedings of Science - 9 pages, 4 figs., accepted) - Version 2: one reference added in the caption of Fig.

Prostate-specific antigen: An unfamiliar protein in the human salivary glands

Objectives: The presence of prostate-specific antigen (PSA) in saliva and salivary glands has been reported. Nevertheless, its release pathway in these glands remains to be elucidated. Here, we showed PSA subcellular distribution focusing on its plausible route in human salivary parenchyma. Materials and Methods: Sections of parotid and submandibular glands were subjected to the immunohistochemical demonstration of PSA by the streptavidin–biotin method revealed by alkaline phosphatase. Moreover, ultrathin sections were collected on nickel grids and processed for immunocytochemical analysis, to visualize the intracellular distribution pattern of PSA through the observation by transmission electron microscopy. Results: By immunohistochemistry, in both parotid and submandibular glands PSA expression was detected in serous secretory acini and striated ducts. By immunocytochemistry, immunoreactivity was retrieved in the cytoplasmic compartment of acinar and ductal cells, often associated with small cytoplasmic vesicles. PSA labeling appeared also on rough endoplasmic reticulum and in the acini's lumen. A negligible PSA labeling appeared in most of the secretory granules of both glands. Conclusions: Our findings clearly support that human parotid and submandibular glands are involved in PSA secretion. Moreover, based on the immunoreactivity pattern, its release in oral cavity would probably occur by minor regulated secretory or constitutive-like secretory pathways

Children's construction task performance and spatial ability: controlling task complexity and predicting mathematics performance.

This paper presents a methodology to control construction task complexity and examined the relationships between construction performance and spatial and mathematical abilities in children. The study included three groups of children (N = 96); ages 7-8, 10-11, and 13-14 years. Each group constructed seven pre-specified objects. The study replicated and extended previous findings that indicated that the extent of component symmetry and variety, and the number of components for each object and available for selection, significantly predicted construction task difficulty. Results showed that this methodology is a valid and reliable technique for assessing and predicting construction play task difficulty. Furthermore, construction play performance predicted mathematical attainment independently of spatial ability

Retarded long-range potentials for the alkali-metal atoms and a perfectly conducting wall

The retarded long-range potentials for hydrogen and alkali-metal atoms in their ground states and a perfectly conducting wall are calculated. The potentials are given over a wide range of atom-wall distances and the validity of the approximations used is established.Comment: RevTeX, epsf, 11 pages, 2 fig

High-precision calculations of dispersion coefficients, static dipole polarizabilities, and atom-wall interaction constants for alkali-metal atoms

The van der Waals coefficients for the alkali-metal atoms from Na to Fr interacting in their ground states, are calculated using relativistic ab initio methods. The accuracy of the calculations is estimated by also evaluating atomic static electric dipole polarizabilities and coefficients for the interaction of the atoms with a perfectly conducting wall. The results are in excellent agreement with the latest data from ultra-cold collisions and from studies of magnetic field induced Feshbach resonances in Na and Rb. For Cs we provide critically needed data for ultra-cold collision studies

The AMANDA Neutrino Telescope and the Indirect Search for Dark Matter

With an effective telescope area of order 10^4 m^2, a threshold of ~50 GeV and a pointing accuracy of 2.5 degrees, the AMANDA detector represents the first of a new generation of high energy neutrino telescopes, reaching a scale envisaged over 25 years ago. We describe its performance, focussing on the capability to detect halo dark matter particles via their annihilation into neutrinos.Comment: Latex2.09, 16 pages, uses epsf.sty to place 15 postscript figures. Talk presented at the 3rd International Symposium on Sources and Detection of Dark Matter in the Universe (DM98), Santa Monica, California, Feb. 199

Deconstructing Decoherence

The study of environmentally induced superselection and of the process of decoherence was originally motivated by the search for the emergence of classical behavior out of the quantum substrate, in the macroscopic limit. This limit, and other simplifying assumptions, have allowed the derivation of several simple results characterizing the onset of environmentally induced superselection; but these results are increasingly often regarded as a complete phenomenological characterization of decoherence in any regime. This is not necessarily the case: The examples presented in this paper counteract this impression by violating several of the simple ``rules of thumb''. This is relevant because decoherence is now beginning to be tested experimentally, and one may anticipate that, in at least some of the proposed applications (e.g., quantum computers), only the basic principle of ``monitoring by the environment'' will survive. The phenomenology of decoherence may turn out to be significantly different.Comment: 13 two-column pages, 3 embedded figure