11 research outputs found
CP and related phenomena in the context of Stellar Evolution
We review the interaction in intermediate and high mass stars between their
evolution and magnetic and chemical properties. We describe the theory of
Ap-star `fossil' fields, before touching on the expected secular diffusive
processes which give rise to evolution of the field. We then present recent
results from a spectropolarimetric survey of Herbig Ae/Be stars, showing that
magnetic fields of the kind seen on the main-sequence already exist during the
pre-main sequence phase, in agreement with fossil field theory, and that the
origin of the slow rotation of Ap/Bp stars also lies early in the pre-main
sequence evolution; we also present results confirming a lack of stars with
fields below a few hundred gauss. We then seek which macroscopic motions
compete with atomic diffusion in determining the surface abundances of AmFm
stars. While turbulent transport and mass loss, in competition with atomic
diffusion, are both able to explain observed surface abundances, the interior
abundance distribution is different enough to potentially lead to a test using
asterosismology. Finally we review progress on the turbulence-driving and
mixing processes in stellar radiative zones.Comment: Proceedings of IAU GA in Rio, JD4 on Ap stars; 10 pages, 7 figure
Blue Straggler Stars in Globular Clusters: a powerful tool to probe the internal dynamical evolution of stellar systems
This chapter presents an overview of the main observational results obtained
to date about Blue Straggler Stars (BSSs) in Galactic Globular Clusters (GCs).
The BSS specific frequency, radial distribution, chemical composition and
rotational properties are presented and discussed in the framework of using
this stellar population as probe of GC internal dynamics. In particular, the
shape of the BSS radial distribution has been found to be a powerful tracer of
the dynamical age of stellar systems, thus allowing the definition of the first
empirical "dynamical clock".Comment: Chapter 5, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
Isolation of Cellulose Nanowhiskers and Their Nanocomposites
Nanocellulose, as a natural polymeric nanomaterial, has been attractive due to its renewability, biodegradability, nontoxicity, high mechanical strength and surface reactivity. The chapter will focus on the isolation and characterization of cellulose nanowhiskers (CNWs). The manufacturing methods including solvent casting, electrospinning, melt blending, and in situ polymerization of cellulose nanowhiskers reinforced polymer nanocomposite will be also reviewed in the chapter