224 research outputs found
Calibration of quasi-static aberrations in exoplanet direct-imaging instruments with a Zernike phase-mask sensor. II. Concept validation with ZELDA on VLT/SPHERE
Warm or massive gas giant planets, brown dwarfs, and debris disks around
nearby stars are now routinely observed by dedicated high-contrast imaging
instruments on large, ground-based observatories. These facilities include
extreme adaptive optics (ExAO) and state-of-the-art coronagraphy to achieve
unprecedented sensitivities for exoplanet detection and spectral
characterization. However, differential aberrations between the ExAO sensing
path and the science path represent a critical limitation for the detection of
giant planets with a contrast lower than a few at very small
separations (<0.3\as) from their host star. In our previous work, we proposed a
wavefront sensor based on Zernike phase contrast methods to circumvent this
issue and measure these quasi-static aberrations at a nanometric level. We
present the design, manufacturing and testing of ZELDA, a prototype that was
installed on VLT/SPHERE during its reintegration in Chile. Using the internal
light source of the instrument, we performed measurements in the presence of
Zernike or Fourier modes introduced with the deformable mirror. Our
experimental and simulation results are consistent, confirming the ability of
our sensor to measure small aberrations (<50 nm rms) with nanometric accuracy.
We then corrected the long-lived non-common path aberrations in SPHERE based on
ZELDA measurements. We estimated a contrast gain of 10 in the coronagraphic
image at 0.2\as, reaching the raw contrast limit set by the coronagraph in the
instrument. The simplicity of the design and its phase reconstruction algorithm
makes ZELDA an excellent candidate for the on-line measurements of quasi-static
aberrations during the observations. The implementation of a ZELDA-based
sensing path on the current and future facilities (ELTs, future space missions)
could ease the observation of the cold gaseous or massive rocky planets around
nearby stars.Comment: 13 pages, 12 figures, A&A accepted on June 3rd, 2016. v2 after
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Research Activities for the DORIS Contribution to the Next International Terrestrial Reference Frame
For the preparation of ITRF2008, the IDS processed data from 1993 to 2008, including data from TOPEX/Poseidon, the SPOT satellites and Envisat in the weekly solutions. Since the development of ITRF2008, the IDS has been engaged in a number of efforts to try and improve the reference frame solutions. These efforts include (i) assessing the contribution of the new DORIS satellites, Jason-2 and Cryosat2 (2008-2011), (ii) individually analyzing the DORIS satellite contributions to geocenter and scale, and (iii) improving orbit dynamics (atmospheric loading effects, satellite surface force modeling. . . ). We report on the preliminary results from these research activities, review the status of the IDS combination which is now routinely generated from the contributions of the IDS analysis centers, and discuss the prospects for continued improvement in the DORIS contribution to the next international reference frame
Higher-precision radial velocity measurements with the SOPHIE spectrograph using octagonal-section fibers
High-precision spectrographs play a key role in exoplanet searches using the
radial velocity technique. But at the accuracy level of 1 m.s-1, required for
super-Earth characterization, stability of fiber-fed spectrograph performance
is crucial considering variable observing conditions such as seeing, guiding
and centering errors and, telescope vignetting. In fiber-fed spectrographs such
as HARPS or SOPHIE, the fiber link scrambling properties are one of the main
issues. Both the stability of the fiber near-field uniformity at the
spectrograph entrance and of the far-field illumination on the echelle grating
(pupil) are critical for high-precision radial velocity measurements due to the
spectrograph geometrical field and aperture aberrations. We conducted tests on
the SOPHIE spectrograph at the 1.93-m OHP telescope to measure the instrument
sensitivity to the fiber link light feeding conditions: star decentering,
telescope vignetting by the dome,and defocussing.
To significantly improve on current precision, we designed a fiber link
modification considering the spectrograph operational constraints. We have
developed a new link which includes a piece of octagonal-section fiber, having
good scrambling properties, lying inside the former circular-section fiber, and
we tested the concept on a bench to characterize near-field and far-field
scrambling properties.
This modification has been implemented in spring 2011 on the SOPHIE
spectrograph fibers and tested for the first time directly on the sky to
demonstrate the gain compared to the previous fiber link. Scientific validation
for exoplanet search and characterization has been conducted by observing
standard stars.Comment: 12 pages, 9 figures, Proceedings of SPIE 201
APRIL is overexpressed in cancer: link with tumor progression
<p>Abstract</p> <p>Background</p> <p>BAFF and APRIL share two receptors – TACI and BCMA – and BAFF binds to a third receptor, BAFF-R. Increased expression of BAFF and APRIL is noted in hematological malignancies. BAFF and APRIL are essential for the survival of normal and malignant B lymphocytes, and altered expression of BAFF or APRIL or of their receptors (BCMA, TACI, or BAFF-R) have been reported in various B-cell malignancies including B-cell non-Hodgkin's lymphoma, chronic lymphocytic leukemia, Hodgkin's lymphoma, multiple myeloma, and Waldenstrom's macroglobulinemia.</p> <p>Methods</p> <p>We compared the expression of <it>BAFF, APRIL, TACI and BAFF-R </it>gene expression in 40 human tumor types – brain, epithelial, lymphoid, germ cells – to that of their normal tissue counterparts using publicly available gene expression data, including the Oncomine Cancer Microarray database.</p> <p>Results</p> <p>We found significant overexpression of <it>TACI </it>in multiple myeloma and thyroid carcinoma and an association between TACI expression and prognosis in lymphoma. Furthermore, <it>BAFF and APRIL </it>are overexpressed in many cancers and we show that <it>APRIL </it>expression is associated with tumor progression. We also found overexpression of at least one proteoglycan with heparan sulfate chains (HS), which are coreceptors for APRIL and TACI, in tumors where APRIL is either overexpressed or is a prognostic factor. APRIL could induce survival or proliferation directly through HS proteoglycans.</p> <p>Conclusion</p> <p>Taken together, these data suggest that APRIL is a potential prognostic factor for a large array of malignancies.</p
G14A-06- Analysis of the DORIS, GNSS, SLR, VLBI and Gravimetric Time Series at the GGOS Core Sites
Analysis of the time series at the 3-4 multi-technique GGOS sites to analyze and compare the spectral content of the space geodetic and gravity time series. Evaluate the level of agreement between the space geodesy measurements and the physical tie vectors
Implantable photonic neural probes for light-sheet fluorescence brain imaging
Significance: Light-sheet fluorescence microscopy (LSFM) is a powerful technique for highspeed volumetric functional imaging. However, in typical light-sheet microscopes, the illumination and collection optics impose significant constraints upon the imaging of non-transparent brain tissues. We demonstrate that these constraints can be surmounted using a new class of implantable photonic neural probes.Aim: Mass manufacturable, silicon-based light-sheet photonic neural probes can generate planar patterned illumination at arbitrary depths in brain tissues without any additional micro-optic components.Approach: We develop implantable photonic neural probes that generate light sheets in tissue. The probes were fabricated in a photonics foundry on 200-mm-diameter silicon wafers. The light sheets were characterized in fluorescein and in free space. The probe-enabled imaging approach was tested in fixed, in vitro, and in vivo mouse brain tissues. Imaging tests were also performed using fluorescent beads suspended in agarose.Results: The probes had 5 to 10 addressable sheets and average sheet thicknesses Conclusions: The neural probes can lead to new variants of LSFM for deep brain imaging and experiments in freely moving animals
Differential effects of lenalidomide during plasma cell differentiation.
Thalidomide, lenalidomide and pomalidomide have greatly improved the outcome of patients with multiple myeloma. However, their effects on plasma cells, the healthy counterpart of myeloma cells, are unknown. Here, we investigated lenalidomide effects on normal human plasma cell generation using an in vitro model. Lenalidomide inhibited the generation of pre-plasmablasts and early plasma cells, while it moderately affected plasmablast production. It also reduced the expression level of Ikaros, Aiolos, and IRF4 transcription factors, in plasmablasts and early plasma cells. This suggests that their differential sensitivity to lenalidomide is not due to a difference in Ikaros or Aiolos degradation. Lenalidomide also inhibited long-lived plasma cell generation, but did not impair their long-term survival once generated. This last observation is in agreement with the finding that lenalidomide treatment for 3-18 months did not affect the bone marrow healthy plasma cell count in allografted patients with multiple myeloma. Our findings should prompt to investigate whether lenalidomide resistance in patients with multiple myeloma could be associated with the emergence of malignant plasmablasts or long-lived plasma cells that are less sensitive to lenalidomide
Aberrant Expression of Functional BAFF-System Receptors by Malignant B-Cell Precursors Impacts Leukemia Cell Survival
Despite exhibiting oncogenic events, patient's leukemia cells are responsive and dependent on signals from their malignant bone marrow (BM) microenvironment, which modulate their survival, cell cycle progression, trafficking and resistance to chemotherapy. Identification of the signaling pathways mediating this leukemia/microenvironment interplay is critical for the development of novel molecular targeted therapies
Growth factors in multiple myeloma: a comprehensive analysis of their expression in tumor cells and bone marrow environment using Affymetrix microarrays
<p>Abstract</p> <p>Background</p> <p>Multiple myeloma (MM) is characterized by a strong dependence of the tumor cells on their microenvironment, which produces growth factors supporting survival and proliferation of myeloma cells (MMC). In the past few years, many myeloma growth factors (MGF) have been described in the literature. However, their relative importance and the nature of the cells producing MGF remain unidentified for many of them.</p> <p>Methods</p> <p>We have analysed the expression of 51 MGF and 36 MGF receptors (MGFR) using Affymetrix microarrays throughout normal plasma cell differentiation, in MMC and in cells from the bone marrow (BM) microenvironment (CD14, CD3, polymorphonuclear neutrophils, stromal cells and osteoclasts).</p> <p>Results</p> <p>4/51 MGF and 9/36 MGF-receptors genes were significantly overexpressed in plasmablasts (PPC) and BM plasma cell (BMPC) compared to B cells whereas 11 MGF and 11 MGFR genes were overexpressed in BMPC compared to PPC. 3 MGF genes (AREG, NRG3, Wnt5A) and none of the receptors were significantly overexpressed in MMC versus BMPC. Furthermore, 3/51 MGF genes were overexpressed in MMC compared to the the BM microenvironment whereas 22/51 MGF genes were overexpressed in one environment subpopulation compared to MMC.</p> <p>Conclusions</p> <p>Two major messages arise from this analysis 1) The majority of MGF genes is expressed by the bone marrow environment. 2) Several MGF and their receptors are overexpressed throughout normal plasma cell differentiation. This study provides an extensive and comparative analysis of MGF expression in plasma cell differentiation and in MM and gives new insights in the understanding of intercellular communication signals in MM.</p
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