1,093 research outputs found
Optical turbulence simulations at Mt Graham using the Meso-NH mode
The mesoscale model Meso-NH is used to simulate the optical turbulence at Mt
Graham (Arizona, USA), site of the Large Binocular Telescope. Measurements of
the CN2-profiles obtained with a generalized scidar from 41 nights are used to
calibrate and quantify the model's ability to reconstruct the optical
turbulence. The measurements are distributed over different periods of the
year, permitting us to study the model's performance in different seasons. A
statistical analysis of the simulations is performed for all the most important
astroclimatic parameters: the CN2-profiles, the seeing {\epsilon}, the
isoplanatic angle {\theta}0 and the wavefront coherence time {\tau}0. The model
shows a general good ability in reconstructing the morphology of the optical
turbulence (the shape of the vertical distribution of CN2) as well as the
strength of all the integrated astroclimatic parameters. The relative error
(with respect to measurements) of the averaged seeing on the whole atmosphere
for the whole sample of 41 nights is within 9.0 %. The median value of the
relative error night by night is equal to 18.7 %, so that the model still
maintains very good performances. Comparable percentages are observed in
partial vertical slabs (free atmosphere and boundary layer) and in different
seasons (summer and winter). We prove that the most urgent problem, at present,
is to increase the ability of the model in reconstructing very weak and very
strong turbulence conditions in the high atmosphere. This mainly affects the
model's performances for the isoplanatic angle predictions, for which the
median value of the relative error night by night is equal to 35.1 %. No major
problems are observed for the other astroclimatic parameters. A variant to the
standard calibration method is tested but we find that it does not provide
better results, confirming the solid base of the standard method.Comment: 12 pages, 12 figures. The definitive version can be found at:
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2966.2010.18097.x/abstrac
Mitochondrial cristae revealed with focused light.
Because of the diffraction resolution barrier, optical microscopes have so far failed in visualizing the mitochondrial cristae, that is, the folds of the inner membrane of this 200 to 400 nm diameter sized tubular organelle. Realizing a ∼30 nm isotropic subdiffraction resolution in isoSTED fluorescence nanoscopy, we have visualized these essential structures in the mitochondria of intact cells. We find a pronounced heterogeneity in the cristae arrangements even within individual mitochondrial tubules
Optical turbulence vertical distribution with standard and high resolution at Mt. Graham
A characterization of the optical turbulence vertical distribution (Cn2
profiles) and all the main integrated astroclimatic parameters derived from the
Cn2 and the wind speed profiles above the site of the Large Binocular Telescope
(Mt. Graham, Arizona, US) is presented. The statistic includes measurements
related to 43 nights done with a Generalized Scidar (GS) used in standard
configuration with a vertical resolution Delta(H)~1 km on the whole 20 km and
with the new technique (HVR-GS) in the first kilometer. The latter achieves a
resolution Delta(H)~20-30 m in this region of the atmosphere. Measurements done
in different periods of the year permit us to provide a seasonal variation
analysis of the Cn2. A discretized distribution of Cn2 useful for the Ground
Layer Adaptive Optics (GLAO) simulations is provided and a specific analysis
for the LBT Laser Guide Star system ARGOS (running in GLAO configuration) case
is done including the calculation of the 'gray zones' for J, H and K bands. Mt.
Graham confirms to be an excellent site with median values of the seeing
without dome contribution epsilon = 0.72", the isoplanatic angle theta0 = 2.5"
and the wavefront coherence time tau0= 4.8 msec. We find that the optical
turbulence vertical distribution decreases in a much sharper way than what has
been believed so far in proximity of the ground above astronomical sites. We
find that 50% of the whole turbulence develops in the first 80+/-15 m from the
ground. We finally prove that the error in the normalization of the
scintillation that has been recently put in evidence in the principle of the GS
technique, affects these measurements with an absolutely negligible quantity
(0.04").Comment: 11 figures. MNRAS, accepte
Rare case of clear cell sarcoma in a young female
Clear Cell Sarcoma of Tendon and Aponeuroses (CCTA), also known as Melanoma of soft tissue is a rare and highly malignant soft tissue neoplasm which mostly occurs in young adults A 26-year-old female presented with pain and thickened soft tissue in the popliteal fossa at the posterior aspect of the left knee. Ultrasonography demonstrated a cystic mass with irregular wall and internal debris representing a complex popliteal cyst. Further work-up with MRI demonstrated a cystic mass lateral to the semimembranosus muscle tendon. Excisional biopsy of the mass was consistent with malignant neoplasm with plasmacytoid features. Immunoperoxidase and cytogenic studies supported the diagnosis for Clear Cell Sarcoma arising from the tendon sheath
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