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Protocols for conducting in situ transmission electron microscopy (TEM) reactions using an environmental TEM with dry gases have been well established. However, many important reactions that are relevant to catalysis or high-temperature oxidation occur at atmospheric pressure and are influenced by the presence of water vapor. These experiments necessitate using a closed-cell gas reaction TEM holder. We have developed protocols for introducing and controlling water vapor concentrations in experimental gases from 2% at a full atmosphere to 100% at ~17 Torr, while measuring the gas composition using a residual gas analyzer (RGA) on the return side of the in situ gas reactor holder. Initially, as a model system, cube-shaped MgO crystals were used to help develop the protocols for handling the water vapor injection process and confirming that we could successfully inject water vapor into the gas cell. The interaction of water vapor with MgO triggered surface morphological and chemical changes as a result of the formation of Mg(OH)2, later validated with mass spectra obtained with our RGA system with and without water vapor. Integrating an RGA with an in situ scanning/TEM closed-cell gas reaction system can thus provide critical measurements correlating gas composition with dynamic surface restructuring of materials during reactions.
Aberration-corrected STEM has become a standard analytical technique in the field of nanoscience. As “designer materials” have become more in demand in academic circles, verification of a desired product makes atomic-resolutionanalysis mandatory. Industry currently faces the same trend where tailor-made materials are customized for a given application. Here we show several examples where quantifiable atomic-scale manipulation of nanomaterials can have a dramatic impact on structure and, by extension, functionality.
Tight binaries discovered in young nearby associations are ideal targets to provide dynamical mass measurments through orbital monitoring. Coupled with estimated temperatures, surface gravities and luminosities, direct mass measurments provide benchmarks for evolutionary models of low-mass stars (M ≤ 0.5 M๏) and brown dwarfs (M ≤ 0.078 M๏) at young ages (Age ≤ 100 Myrs).
TWA22 AB is likely to be a member of the nearby TW Hydrae association (Age ~ 8 Myr). It was resolved in a tigh binary with a projected separation of a few AU. In this paper we present preliminary results on the companion orbital monitoring and on the spectral characterisation of the system.
In recent years the development of remote microscopy, specifically in electron microscopes, has begun to emerge as a useful research tool rather than simply an educational or teaching aid. Scientists have long been able to work collaboratively at a distance; however, it is often in terms of receiving data or sending some instructions where there may be a delay in receipt of the information. When defining remote control it is important to note that electron microscopy requires instantaneous control and receipt of the feedback (in most cases via images on a screen). Without realtime control it is impossible to conduct high resolution imaging and analysis work. In terms of electron microscopy, there are several reasons for conducting experiments remotely: With sub-Ångström aberration-corrected scanning transmission electron microscopes, the environment within which the microscope itself sits is of utmost importance.
Massive star formation in the central regions of spiral galaxies plays an important role in the dynamical and secular evolution of their hosts. Here, we summarise a number of recent investigations of the star formation history and the physical conditions of the gas in circumnuclear regions, to illustrate not only the detailed results one can achieve, but also the potential of using state-of-the-art spectroscopic and analysis techniques in researching the central regions of galaxies in general. We review how the star formation history of nuclear rings confirms that they are long-lived and stable configurations. Gas flows in from the disk, through the bar, and into the ring, where successive episodes of massive star formation occur. A detailed analysis of the ring in NGC 7742, where we use similar data to determine the physical conditions of the line emitting gas using a combination of ionisation and stellar population modelling, is described in a second poster paper (these proceedings, p. 000; Mazzuca et al. 2006).
Late-type giants (i.e., stars on the red and asymptotic giant branches, RGB/AGB, respectively) are dominant contributors to the overall spectral appearance of intermediate age and old stellar populations, especially in the red/near-infrared part of the spectrum. Being intrinsically bright, they are well suited for probing distant/obscured populations, especially those that can not be studied with their fainter members, like main sequence turn-off stars or subgiants. Late-type giants and supergiants will be the only stellar types accessible in intermediate age and old populations beyond the distances of several Mpc with the future 30-50 m class extremely large telescopes (Olsen et al. 2003). Indeed, proper understanding of their observable properties by means of theoretical models is of key importance for studying the evolution of stellar populations and their host galaxies.
This paper presents the scientific case for a next generation adaptive optics instrument at the VLT, temporarily named “Planet Finder”, that is aimed at detecting and characterizing extrasolar planets through the direct analysis of their emitted photons in the visible and at near-IR wavelengths. We discuss the observational niche of such an instrument to have first light in 2010, in complement to other planet search methods. To improve the efficiency (and consistency) of the search for planets with the PF, the observations will need to be organized in the form of an extensive survey of hundreds of nearby stars, predicted outputs of which are also described here. This summarizes the study phase of the instrument, conducted by two competitive teams and the recent merging of both studies, regarding the scientific impact of Planet Finder.
The space mission PEGASE, proposed to the CNES (Centre National d'Etudes Spatiales = French Space Agency) in the framework of its call for scientific proposals : “formation flying missions”, is a 2-aperture interferometer, composed by 3 free flying satellites (2 siderostats and 1 beam combiner), allowing baselines from 50 to 500 m in both nulling and visibility modes. With an angular resolution of a few mas and a spectral resolution of several tens in the spectral range 2.5-5 microns, PEGASE has several goals:
science : spectroscopy of hot jupiters (Pegasides) and brown dwarves, exploration of the inner part of protoplanetary disks
technology : validation in real space conditions of formation flying, nulling and visibility interferometry concepts.
PEGASE has been studied at a 0-level. In this paper, we summarize the scientific program and associated technological and mission trade-off coming from this 0-level study. We also discuss how PEGASE can be considered as a TPF/DARWIN pathfinder in an international roadmap towards more complex space interferometry missions such as DARWIN/TPF.