15,068 research outputs found
Stellar granulation and interferometry
Stars are not smooth. Their photosphere is covered by a granulation pattern
associated with the heat transport by convection. The convection-related
surface structures have different size, depth, and temporal variations with
respect to the stellar type. The related activity (in addition to other
phenomena such as magnetic spots, rotation, dust, etc.) potentially causes bias
in stellar parameters determination, radial velocity, chemical abundances
determinations, and exoplanet transit detections.
The role of long-baseline interferometric observations in this astrophysical
context is crucial to characterize the stellar surface dynamics and correct the
potential biases. In this Chapter, we present how the granulation pattern is
expected for different kind of stellar types ranging from main sequence to
extremely evolved stars of different masses and how interferometric techniques
help to study their photospheric dynamics.Comment: To appear in the Book of the VLTI School 2013, held 9-21 Sep 2013
Barcelonnette (France), "What the highest angular resolution can bring to
stellar astrophysics?", Ed. Millour, Chiavassa, Bigot, Chesneau, Meilland,
Stee, EAS Publications Series (2015
Swept source optical coherence tomography Gabor fusion splicing technique for microscopy of thick samples using a deformable mirror
We present a swept source optical coherence tomography (OCT) system at 1060 nm equipped with a wavefront sensor at 830 nm and a deformable mirror in a closed-loop adaptive optics (AO) system. Due to the AO correction, the confocal profile of the interface optics becomes narrower than the OCT axial range, restricting the part of the B-scan (cross section) with good contrast. By actuating on the deformable mirror, the depth of the focus is changed and the system is used to demonstrate Gabor filtering in order to produce B-scan OCT images with enhanced sensitivity throughout the axial range from a Drosophila larvae. The focus adjustment is achieved by manipulating the curvature of the deformable mirror between two user-defined limits. Particularities of controlling the focus for Gabor filtering using the deformable mirror are presented. © 2015 Society of Photo-Optical Instrumentation Engineers
The ear as a biometric
It is more than 10 years since the first tentative experiments in ear biometrics were conducted and it has now reached the “adolescence” of its development towards a mature biometric. Here we present a timely retrospective of the ensuing research since those early days. Whilst its detailed structure may not be as complex as the iris, we show that the ear has unique security advantages over other biometrics. It is most unusual, even unique, in that it supports not only visual and forensic recognition, but also acoustic recognition at the same time. This, together with its deep three-dimensional structure and its robust resistance to change with age will make it very difficult to counterfeit thus ensuring that the ear will occupy a special place in situations requiring a high degree of protection
The Visegrad Group and the European Union’s ‘Eastern’ Dimension
The 2004 enlargement of the European Union (EU) changed the dynamics of its engagement with the former Soviet Republics which now constitute the Eastern neighbourhood. As well as manifold implications of the eastward shift of the EU
border and ‘acquisition of a shared neighbourhood with Russia, the enlarged EU now incorporated new member states with foreign policy concerns focused mostly on the Eastern neighbours. Four of the new member states – the Czech
Republic, Hungary, Poland and Slovakia – brought into the EU with them their own subregional alliance in the form of the Visegrad Group (VG). Since 2004 the ‘Visegrad 4’ (V4) have been attempting to develop an effective multilateral
contribution to EU ‘Eastern Policy’ and to reform processes in the WNIS. This paper argues that while there has been some evidence of an effective VG multilateral approach, in both inputs to EU Eastern policy and modest support
for broader ‘Europeanisation’ processes in WNIS, so far the VG has failed to achieve a lead role in EU Eastern policy and that a range of obstacles have limited the multilateral approach of the V4 in general
STRATEGY AND INNOVATION IN ORDER TO BE COMPETITIVE IN A GLOBALIZED WORLD; an evolutionary analysis of the emerging wine sector pole of São Francisco Valley (Brazil).
Globalized and fragmented, the wine production sector reconfigures itself. The New World Wine Producers innovate in wine sector management by means of industrial production logics. Brazil faces the challenge of reaching a wider global insertion. The emerging pole of Vale do São Francisco, through a comparative and exploratory multiple case study (2006 to 2010), shows an evolutionary phenomenology with some innovative features. The objective is to analyze the regional innovative strategic positioning and to present proposals to accrued innovative competitiveness
The pre-ZAMS nature of Mol160/IRAS23385+6053 confirmed by Spitzer
Determining the timeline for the formation of massive YSOs requires the
identification and characterisation of all the phases that a massive forming
YSO undergoes. It is of particular interest to verify the observability of the
phase in which the object is rapidly accreting while not yet igniting the
fusion of hydrogen that marks the arrival on the ZAMS. One of the candidate
prototypical objects for this phase is Mol160/IRAS23385+6053, which previous
studies suggest it could be in a pre-Hot Core stage. We further investigate
this issue by means of Spitzer imaging and spectroscopy in the 5-70 micron
range. The dense core of Mol160/IRAS23385+6053, which up to now had only been
detected at submm and mm wavelenghts has been revealed for the first time at 24
and 70 micron by Spitzer. The complete 24 micron -3.4 mm continuum cannot be
fitted with a standard model of a Zero-Age Main-Sequence (ZAMS) star embedded
in an envelope. A simple greybody fit yields a mass of 220 solar masses. The
luminosity is slightly in excess of 3000 solar luminosities, which is a factor
of 5 less than previous estimates when only IRAS fluxes were available between
20 and 100 micron. The source is under-luminous by the same factor with respect
to UCHII regions or Hot-Cores of similar circumstellar mass, and simple models
show that this is compatible with an earlier evolutionary stage. Spectroscopy
between 5 and 40 microns revelas typical PDR/PIR conditions, where the required
UV illumination may be provided by other sources revealed at 24 microns in the
same region, and which can be plausibly modeled as moderately embedded
intermediate-mass ZAMS stars. Our results strengthen the suggestion that the
central core in Mol160/IRAS23385+6053 is a massive YSO actively accreting from
its circumstellar envelope and which did not yet begin hydrogen fusion.Comment: Accepted by A&
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