Age spreads in clusters and associations: the lithium test

We report the evidence that several low-mass stars (<~0.4 Msun) of the Orion and Upper Scorpius clusters have lithium abundances well below the interstellar value. Due to time-dependent depletion, our result implies stellar ages greater than ~5 Myr, suggesting that star formation has been proceeding for a long time in these systems.Comment: to appear in IMF@50: The Initial Mass Function 50 years later, eds. E. Corbelli et al. (Kluwer Acad. Press), 2004, in pres

NGC 3603 - a Local Template for Massive Young Clusters

We present a study of the star cluster associated with the massive Galactic HII region NGC3603 based on near-IR broad-- and narrowband observations taken with ISAAC/VLT under excellent seeing conditions (<0.4''). We discuss color-color diagrams and address the impact of the high UV flux on the disk evolution of the low-mass stars.Comment: 3 pages, 3 figures. To appear in the Proceedings of IAU Symposium 207 "Extragalactic Star Clusters", eds. E. Grebel, D. Geisler and D. Minitt

Plant Essential Oils as Biocides in Sustainable Strategies for the Conservation of Cultural Heritage

Biodeterioration is a complex network of interactions between macro/micro-biological systems and organic/inorganic substrates involving physical and chemical alterations, strictly related to their metabolic activities. Concerning microbial deterioration, finding a correct approach to counteract this process is often difficult, requiring an understanding of the kind of alterations and the use of methods that respect artwork and human and environmental health. Specific conservative and remedial methods are used for this aim. They comprise physical, mechanical, and chemical methods, as well as, frequently, synthetic chemical biocides, which have obvious limitations because of their toxicity to operators or because they contain polluting substances that persist in the natural environment. New and alternative research has strongly focused on strategies to replace the use of toxic methods with natural products that do not have undesired effects, as well as implementing safe, novel compounds. Several plants contain natural chemical compounds such as oils, phenols, flavonoids, alkaloids, coumarins, tannins, etc., commonly used as drugs, bioactive molecules, and nutrients. Essential oils extracted from plants can be the correct way to prevent the biodeterioration of cultural heritage in a safe manner. This review aims to summarize the latest research on the use of natural essential oils in restoration procedures for cultural heritage considering them sustainable means with respect to the environment and human health

Conservation of forest biodiversity in Sicily: contribution of the University of Palermo Germplasm Bank (Italy)

Germplasm Banks dedicated to the wild plants seeds conservation play a unique role in integrating the in situ conservation of endemic, rare or endangered plant species. One of the missions of the Seed Bank of the University of Palermo (HBP-Bank) is to support the conservation of biodiversity with particular attention to the spectrum of genetic diversity of plants belonging to Mediterranean habitat. Abies nebrodensis (Lojac.) Mattei is an relict species, consisted of 30 natural individuals, gathered in a small area of the Madonie Natural Park in Sicily (1500 -1600 m above s.l.), recorded on the checklist \u201cTOP 50 Mediterranean Island Plants\u201d. It is also one of eight conifers species critically endangered because of reproductive biology issues. A. nebrodensis species has been monitored in situ in order to evaluate the state of conservation of natural population and to implement the number of individuals. Its preservation has been integrated since 1994 with ex situ conservation of 83 accessions in the HBP-Bank in the long-term conservation conditions. The scientific strength of HBP germplasm collection is supported by the results of several studies on taxonomy, seed biology and genetic diversity. The embryonic loss observed into the seeds produced in natural environment can reduce the genetic variability of germplasm collection. This study, carried out on the A. nebrodensis population, demonstrates that a five-year planning is needed to collect enough seed to represent the genetic variability intra-population. This seed collection scheme can represent a useful tool to apply on other forest endangered species spread in Sicily and in the Mediterranean area

On the Formation of Massive Primordial Stars

We investigate the formation by accretion of massive primordial protostars in the range 10 to 300 Msun. The high accretion rate used in the models (4.4 x 10^{-3} Msun/yr) causes the structure and evolution to differ significantly from those of both present-day protostars and primordial zero-age main sequence stars. After an initial expansion of the radius (for < 12 Msun), the protostar undergoes an extended phase of contraction (up to 60 Msun). The stellar surface is not visible throughout most of the main accretion phase, since a photosphere is formed in the infalling envelope. Also, significant nuclear burning does not take place until a protostellar mass of about 80 Msun. As the interior luminosity approaches the Eddington luminosity, the protostellar radius rapidly expands, reaching a maximum around 100 Msun. Changes in the ionization of the surface layers induce a secondary phase of contraction, followed by a final swelling due to radiation pressure when the stellar mass reaches about 300 Msun. This expansion is likely to signal the end of the main accretion phase, thus setting an upper limit to the protostellar mass formed in these conditions.Comment: 11 pages and 4 figures. ApJL accepte