29 research outputs found
High-resolution imaging at the SOAR telescope
Bright single and binary stars were observed at the 4.1-m telescope with a
fast electron-multiplication camera in the regime of partial turbulence
correction by the visible-light adaptive optics system. We compare the angular
resolution achieved by simple averaging of AO-corrected images (long-exposure),
selection and re-centering (shift-and-add or "lucky" imaging) and speckle
interferometry. The effect of partial AO correction, vibrations, and image
post-processing on the attained resolution is shown. Potential usefulness of
these techniques is evaluated for reaching the diffraction limit in
ground-based optical imaging. Measurements of 75 binary stars obtained during
these tests are given and objects of special interest are discussed. We report
tentative resolution of the astrometric companion to Zeta Aqr B. A concept of
advanced high-resolution camera is outlined.Comment: Accepted for publication in PASP. 14 pages, 9 figures, 2 tabl
A Comparative In Vitro and In Vivo Study of Osteogenicity by Using Two Biomaterials and Two Human Mesenchymal Stem Cell Subtypes
Background: Bone repair induced by stem cells and biomaterials may represent an alternative to autologous bone grafting. Mesenchymal stromal/stem cells (MSCs), easily accessible in every human, are prototypical cells that can be tested, alone or with a biomaterial, for creating new osteoblasts. The aim of this study was to compare the efficiency of two biomaterialsâbiphasic calcium phosphate (BCP) and bioactive glass (BG)âwhen loaded with either adult bone marrow mesenchymal stem cells (BMMSCs) or newborn nasal ecto-mesenchymal stem cells (NE-MSCs), the latter being collected for further repair of lip cleft-associated bone loss. Materials and Methods: BMMSCs were collected from two adults and NE-MSCs from two newborn infants. An in vitro study was performed in order to determine the best experimental conditions for adhesion, viability, proliferation and osteoblastic differentiation on BCP or BG granules. Bone-associated morphological changes and gene expression modifications were quantified using histological and molecular techniques. The in vivo study was based on the subcutaneous implantation in nude mice of the biomaterials, loaded or not with one of the two cell types. Eight weeks after, bone formation was assessed using histological and electron microscopy techniques. Results: Both cell typesâBMMSC and NE-MSCâdisplay the typical stem cell surface markersâCD73+, CD90+, CD105+, nestin - and exhibit the MSC-associated osteogenic, chondrogenic and adipogenic multipotency. NE-MSCs produce less collagen and alkaline phosphatase than BMMSCs. At the transcript level, NE-MSCs express more abundantly three genes coding for bone sialoprotein, osteocalcin and osteopontin while BMMSCs produce extra copies of RunX2. BMMSCs and NE-MSCs adhere and survive on BCP and BG. In vivo experiments reveal that bone formation is only observed with BMMSCs transplanted on BCP biomaterial. Conclusion: Although belonging to the same superfamily of mesenchymal stem cells, BMMSCs and NE-MSCs exhibit striking differences, in vitro and in vivo . For future clinical applications, the association of BMMSCs with BCP biomaterial seems to be the most promising
Modeling a GLAO system for the Gemini Observatory
NRC publication: Ye
A proposed implementation of a ground layer adaptive optics system on the Gemini Telescope
We describe a simple and cost-effective concept for implementing a Ground Layer Adaptive Optics (GLAO) system on Gemini that will feed all instruments mounted at the Cassegrain focus. The design concept can provide a GLAO correction to any of the current or future seeing-limited optical or near-infrared Gemini instruments. The GLAO design uses an adaptive secondary mirror and provides a significant upgrade to the current telescope acquisition-and-guide system while reusing and building upon the existing telescope facilities and infrastructure. This paper discusses the overall design of the GLAO system including optics, opto-mechanics, laser guide star facilities, natural and laser guide stars wavefront sensors. Such a GLAO system will improve the efficiency of essentially all observations with Gemini and also will help with scheduling since it virtually eliminates poor seeing.NRC publication: Ye
SAXO, the SPHERE extreme AO system: on-sky final performance and future improvements
International audienceThe SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) instrument aims at detecting extremely faint sources (giant extrasolar planets) in the vicinity of bright stars1. Such a challenging goal requires the use of a very-high-order performance Adaptive Optics [AO] system feeding the scientific instruments with a quasi-perfect flat wave front corrected from all the atmospheric turbulence and internal defects. This AO system, called SAXO (Sphere Ao for eXoplanet Observation) is the heart of the instrument, a heart beating 1200 time per second and providing unprecedented image quality for a large ground based telescope at optical/near infrared wavelength. We will present the latest results obtained on-sky, demonstrating its exceptional performance (in terms of correction quality, stability and robustness) and tremendous potentiality for high contrast imaging and more specifically for exoplanet discovery