36 research outputs found
Influence of severe plastic deformation on the precipitation hardening of a FeSiTi steel
The combined strengthening effects of grain refinement and high precipitated
volume fraction (~6at.%) on the mechanical properties of FeSiTi alloy subjected
to SPD processing prior to aging treatment were investigated by atom probe
tomography and scanning transmission electron microscopy. It was shown that the
refinement of the microstructure affects the precipitation kinetics and the
spatial distribution of the secondary hardening intermetallic phase, which was
observed to nucleate heterogeneously on dislocations and sub-grain boundaries.
It was revealed that alloys successively subjected to these two strengthening
mechanisms exhibit a lower increase in mechanical strength than a simple
estimation based on the summation of the two individual strengthening
mechanisms
Multiple populations in globular clusters. Lessons learned from the Milky Way globular clusters
Recent progress in studies of globular clusters has shown that they are not
simple stellar populations, being rather made of multiple generations. Evidence
stems both from photometry and spectroscopy. A new paradigm is then arising for
the formation of massive star clusters, which includes several episodes of star
formation. While this provides an explanation for several features of globular
clusters, including the second parameter problem, it also opens new
perspectives about the relation between globular clusters and the halo of our
Galaxy, and by extension of all populations with a high specific frequency of
globular clusters, such as, e.g., giant elliptical galaxies. We review progress
in this area, focusing on the most recent studies. Several points remain to be
properly understood, in particular those concerning the nature of the polluters
producing the abundance pattern in the clusters and the typical timescale, the
range of cluster masses where this phenomenon is active, and the relation
between globular clusters and other satellites of our Galaxy.Comment: In press (The Astronomy and Astrophysics Review
Fluctuations in active membranes
Active contributions to fluctuations are a direct consequence of metabolic
energy consumption in living cells. Such metabolic processes continuously
create active forces, which deform the membrane to control motility,
proliferation as well as homeostasis. Membrane fluctuations contain therefore
valuable information on the nature of active forces, but classical analysis of
membrane fluctuations has been primarily centered on purely thermal driving.
This chapter provides an overview of relevant experimental and theoretical
approaches to measure, analyze and model active membrane fluctuations. In the
focus of the discussion remains the intrinsic problem that the sole fluctuation
analysis may not be sufficient to separate active from thermal contributions,
since the presence of activity may modify membrane mechanical properties
themselves. By combining independent measurements of spontaneous fluctuations
and mechanical response, it is possible to directly quantify time and
energy-scales of the active contributions, allowing for a refinement of current
theoretical descriptions of active membranes.Comment: 38 pages, 9 figures, book chapte