969 research outputs found
The GRAVITY metrology system: modeling a metrology in optical fibers
GRAVITY is the second generation VLT Interferometer (VLTI) instrument for
high-precision narrow-angle astrometry and phase-referenced interferometric
imaging. The laser metrology system of GRAVITY is at the heart of its
astrometric mode, which must measure the distance of 2 stars with a precision
of 10 micro-arcseconds. This means the metrology has to measure the optical
path difference between the two beam combiners of GRAVITY to a level of 5 nm.
The metrology design presents some non-common paths that have consequently to
be stable at a level of 1 nm. Otherwise they would impact the performance of
GRAVITY. The various tests we made in the past on the prototype give us hints
on the components responsible for this error, and on their respective
contribution to the total error. It is however difficult to assess their exact
origin from only OPD measurements, and therefore, to propose a solution to this
problem. In this paper, we present the results of a semi-empirical modeling of
the fibered metrology system, relying on theoretical basis, as well as on
characterisations of key components. The modeling of the metrology system
regarding various effects, e.g., temperature, waveguide heating or mechanical
stress, will help us to understand how the metrology behave. The goals of this
modeling are to 1) model the test set-ups and reproduce the measurements (as a
validation of the modeling), 2) determine the origin of the non-common path
errors, and 3) propose modifications to the current metrology design to reach
the required 1nm stability.Comment: 20 pages, 19 figures. Proceeding of SPIE 9146 "Optical and Infrared
Interferometry IV
Long-term results in malignant pleural mesothelioma treated with neoadjuvant chemotherapy, extrapleural pneumonectomy and intensity-modulated radiotherapy
Introduction: We investigated the clinical outcome and the toxicity of trimodal therapy of malignant pleural mesothelioma (MPM) treated with neoadjuvant chemotherapy, extrapleural pneumonectomy (EPP) and adjuvant intensity-modulated radiotherapy (IMRT). Methods: Chemotherapy regimens included Cisplatin/Pemetrexed, Carboplatin/Pemetrexed and Cisplatin/Gemcitabine, followed by EPP. 62 patients completed the adjuvant radiotherapy. IMRT was carried out in two techniques, either step&shoot or helical tomotherapy. Median target dose was 48 Gy to 54 Gy. Toxicity was scored with the Common Terminology Criteria (CTC) for Adverse Events. We used Kaplan-Meier method to estimate actuarial rate of locoregional control (LRC),distant control (DC) and overall survival (OS),measured from the date of surgery. Rates were compared using the logrank test. For multivariate analysis the Cox proportional hazard model was used. Results: The median OS, LRC and DC times were 20.4, 31.4 and 21.4 months. The 1-,2-,3-year OS rates were 63, 42, 28 %,the LRC rates were 81, 60, 40 %,and the DC rates were 62, 48, 41 %. We observed no CTC grade 4 or grade 5 toxicity. Step&shoot and helical tomotherapy were equivalent both in dosimetric characteristics and clinical outcome. Biphasic tumor histology was associated with worse clinical outcome compared to epitheloid histology. Conclusions: Mature clinical results of trimodal treatment for MPM were presented. They indicate that hemithoracic radiotherapy after EPP can be safely administered by either step&shoot IMRT and tomotherapy. However, the optimal prospective patient selection for this aggressive trimodal therapy approach remains unclear. This study can serve as a benchmark for current and future therapy concepts for MPM
GRAVITY: the Calibration Unit
We present in this paper the design and characterisation of a new sub-system
of the VLTI 2nd generation instrument GRAVITY: the Calibration Unit. The
Calibration Unit provides all functions to test and calibrate the beam combiner
instrument: it creates two artificial stars on four beams, and dispose of four
delay lines with an internal metrology. It also includes artificial stars for
the tip-tilt and pupil guiding systems, as well as four metrology pick-up
diodes, for tests and calibration of the corresponding sub-systems. The
calibration unit also hosts the reference targets to align GRAVITY to the VLTI,
and the safety shutters to avoid the metrology light to propagate in the
VLTI-lab. We present the results of the characterisation and validtion of these
differrent sub-units.Comment: 12 pages, 11 figures. Proceeding of SPIE 9146 "Optical and Infrared
Interferometry IV
A randomized phase II study of radiation induced immune boost in operable non-small cell lung cancer (RadImmune trial)
Background: Lung cancer is the leading cause of cancer deaths worldwide. Surgery, radiotherapy at conventional and high dose and chemotherapy are the mainstay for lung cancer treatment. Insufficient migration and activation of tumour specific effector T cells seem to be important reasons for inadequate host anti-tumour immune response. Ionizing radiation can induce a variety of immune responses. The goal of this randomized trial is to assess if a preoperative single fraction low dose radiation is able to improve anti-tumour immune response in operable early stage lung cancer. Methods/Design: This trial has been designed as an investigator-initiated, prospective, randomized, 2-armed phase II trial. Patients who are candidates for elective resection of early stage non-small cell lung cancer will be randomized into 2 arms. A total of 36 patients will be enrolled. The patients receive either 2 Gy or no radiation prescribed to their primary tumour. Radiation will be delivered by external beam radiotherapy using 3D radiotherapy or intensity-modulated radiation technique (IMRT) 7 days prior to surgical resection. The primary objective is to compare CD8+ T cell counts detected by immunohistochemistry in resected tumours following preoperative radiotherapy versus no radiotherapy. Secondary objectives include the association between CD8+ T cell counts and progression free survival, the correlation of CD8+ T cell counts quantified by immunohistochemistry and flow cytometry, local tumour control and recurrence patterns, survival, radiogenic treatment toxicity and postoperative morbidity and mortality. Further, frequencies of tumour reactive T cells in blood and bone marrow as well as whole blood cell transcriptomics and plasma-proteomics will be correlated with clinical outcome. Discussion: This unique intervention combining preoperative low dose radiation and surgical removal of early stage non-small cell lung cancer is designed to address the problem of inadequate host anti-tumour immune response. If successful, this study may affect the role of radiotherapy in lung cancer treatment. Trial registration: NCT02319408; Registration: December 29, 2014
Investigating the properties of granulation in the red giants observed by Kepler
More than 1000 red giants have been observed by NASA/Kepler mission during a
nearly continuous period of ~ 13 months. The resulting high-frequency
resolution (< 0.03 muHz) allows us to study the granulation parameters of these
stars. The granulation pattern results from the convection motions leading to
upward flows of hot plasma and downward flows of cooler plasma. We fitted
Harvey-like functions to the power spectra, to retrieve the timescale and
amplitude of granulation. We show that there is an anti-correlation between
both of these parameters and the position of maximum power of acoustic modes,
while we also find a correlation with the radius, which agrees with the theory.
We finally compare our results with 3D models of the convection.Comment: 4 pages, 1 figure. To appear in the ASP proceedings of "The 61st
Fujihara seminar: Progress in solar/stellar physics with helio- and
asteroseismology", 13th-17th March 2011, Hakone, Japa
Recommended from our members
Response to Comment on "Ascent of Dinosaurs Linked to an Iridium Anomaly at the Triassic-Jurassic Boundary"
Our recent study on the nature of the ascent of the dinosaurs (1) argued three main points: (i) that a major terrestrial tetrapod mass extinction is concentrated at the palynologically identified Triassic-Jurassic boundary in eastern North America (based on footprints and bones); (ii) that truly large predatory dinosaurs appear immediately after the boundary (based on footprints); and (iii) that both the boundary and the mass extinction level are associated with a modest Ir anomaly and fern spike, plausibly of asteroid or comet impact origin. Although the comment of Thulborn (2) addresses a number of paleontological issues in (1), his only point salient to the conclusions of our paper is his extraordinary claim that very large theropod dinosaurs were already present in the Carnian, some 20 million years or so before the Triassic-Jurassic boundary [in contrast to our assertion in point (ii), above]
Проблемы технической оснащённости России для работы в условиях Арктики
Cytochrome c oxidase is a respiratory enzyme catalysing the energy-conserving reduction of molecular oxygen to water. The crystal structure of the ba(3)-cytochrome c oxidase from Thermus thermophilus has been determined to 2.4 Å resolution using multiple anomalous dispersion (MAD) phasing and led to the discovery of a novel subunit IIa. A structure-based sequence alignment of this phylogenetically very distant oxidase with the other structurally known cytochrome oxidases leads to the identification of sequence motifs and residues that seem to be indispensable for the function of the haem copper oxidases, e.g. a new electron transfer pathway leading directly from Cu(A) to Cu(B). Specific features of the ba(3)-oxidase include an extended oxygen input channel, which leads directly to the active site, the presence of only one oxygen atom (O(2–), OH(–) or H(2)O) as bridging ligand at the active site and the mainly hydrophobic character of the interactions that stabilize the electron transfer complex between this oxidase and its substrate cytochrome c. New aspects of the proton pumping mechanism could be identified
Kepler-68: Three Planets, One With a Density Between That of Earth and Ice Giants
NASA's Kepler Mission has revealed two transiting planets orbiting Kepler-68.
Follow-up Doppler measurements have established the mass of the innermost
planet and revealed a third jovian-mass planet orbiting beyond the two
transiting planets. Kepler-68b, in a 5.4 day orbit has mass 8.3 +/- 2.3 Earth,
radius 2.31 +/- 0.07 Earth radii, and a density of 3.32 +/- 0.92 (cgs), giving
Kepler-68b a density intermediate between that of the ice giants and Earth.
Kepler-68c is Earth-sized with a radius of 0.953 Earth and transits on a 9.6
day orbit; validation of Kepler-68c posed unique challenges. Kepler-68d has an
orbital period of 580 +/- 15 days and minimum mass of Msin(i) = 0.947 Jupiter.
Power spectra of the Kepler photometry at 1-minute cadence exhibit a rich and
strong set of asteroseismic pulsation modes enabling detailed analysis of the
stellar interior. Spectroscopy of the star coupled with asteroseismic modeling
of the multiple pulsation modes yield precise measurements of stellar
properties, notably Teff = 5793 +/- 74 K, M = 1.079 +/- 0.051 Msun, R = 1.243
+/- 0.019 Rsun, and density 0.7903 +/- 0.0054 (cgs), all measured with
fractional uncertainties of only a few percent. Models of Kepler-68b suggest it
is likely composed of rock and water, or has a H and He envelope to yield its
density of about 3 (cgs).Comment: 32 pages, 13 figures, Accepted to Ap
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