1,997 research outputs found
The Apollo spacecraft: A chronology volume 4, 21 January 1966 - 13 July 1974
This final volume of the chronology is divided into three parts: (1) preparation for flight, the accident, and investigation; (2) recovery, spacecraft redefinition, and the first manned flight; and (3) man circles the moon, the Eagle lands, and manned space exploration. Congressional documents, official correspondence, government and contractor reports, memoranda, working papers, and minutes of meetings were used as primary sources. A relatively few entries are based on press releases and newspaper and magazine articles
An Extreme-AO Search for Giant Planets around a White Dwarf --VLT/SPHERE performance on a faint target GD 50
CONTEXT. Little is known about the planetary systems around single white
dwarfs although there is strong evidence that they do exist.
AIMS. We performed a pilot study with the extreme-AO system on the
Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) on the Very
Large Telescopes (VLT) to look for giant planets around a young white dwarf, GD
50.
METHODS. We were awarded science verification time on the new ESO instrument
SPHERE. Observations were made with the InfraRed Dual-band Imager and
Spectrograph in classical imaging mode in H band.
RESULTS. Despite the faintness of the target (14.2 mag in R band), the AO
loop was closed and a strehl of 37\% was reached in H band. No objects were
detected around GD 50. We achieved a 5-sigma contrast of 6.2, 8.0 and 8.25 mags
at 0{\farcs}2, 0{\farcs}4 and 0{\farcs}6 and beyond, respectively. We exclude
any substellar objects more massive than 4.0 M at 6.2 AU, 2.9
M at 12.4 AU and 2.8 M at 18.6 AU and beyond. This
rivals the previous upper limit set by Spitzer. We further show that SPHERE is
the most promising instrument available to search for close-in substellar
objects around nearby white dwarfs.Comment: A&A letters, accepte
The Apollo spacecraft: A chronology, volume 3, 1 October 1964 - 20 January 1966
The development of the Apollo spacecraft is traced along with that of Saturn V. Emphasis is placed on the detailed engineering design and exhaustive testing performed to qualify both the command and service modules and the lunar module for manned flight
Interpreting the extended emission around three nearby debris disc host stars
Cool debris discs are a relic of the planetesimal formation process around
their host star, analogous to the solar system's Edgeworth-Kuiper belt. As
such, they can be used as a proxy to probe the origin and formation of
planetary systems like our own. The Herschel Open Time Key Programmes "DUst
around NEarby Stars" (DUNES) and "Disc Emission via a Bias-free Reconnaissance
in the Infrared/Submillimetre" (DEBRIS) observed many nearby, sun-like stars at
far-infrared wavelengths seeking to detect and characterize the emission from
their circumstellar dust. Excess emission attributable to the presence of dust
was identified from around 20% of stars. Herschel's high angular
resolution ( 7" FWHM at 100 m) provided the capacity for resolving
debris belts around nearby stars with radial extents comparable to the solar
system (50 to 100 au). As part of the DUNES and DEBRIS surveys, we obtained
observations of three debris disc stars, HIP 22263 (HD 30495), HIP 62207 (HD
110897), and HIP 72848 (HD 131511), at far-infrared wavelengths with the
Herschel PACS instrument. Combining these new images and photometry with
ancilliary data from the literature, we undertook simultaneous multi-wavelength
modelling of the discs' radial profiles and spectral energy distributions using
three different methodologies: single annulus, modified black body, and a
radiative transfer code. We present the first far-infrared spatially resolved
images of these discs and new single-component debris disc models. We
characterize the capacity of the models to reproduce the disc parameters based
on marginally resolved emission through analysis of two sets of simulated
systems (based on the HIP 22263 and HIP 62207 data) with the noise levels
typical of the Herschel images. We find that the input parameter values are
recovered well at noise levels attained in the observations presented here.Comment: 13 pages, 5 figures, 5 tables, accepted for publication in A&
Using warm dust to constrain unseen planets
Cold outer debris belts orbit a significant fraction of stars, many of which
are planet-hosts. Radiative forces from the star lead to dust particles leaving
the outer belts and spiralling inwards under Poynting-Robertson drag. We
present an empirical model fitted to N-body simulations that allows the fate of
these dust particles when they encounter a planet to be rapidly calculated.
High mass planets eject most particles, whilst dust passes low mass planets
relatively unperturbed. Close-in, high mass planets (hot Jupiters) are best at
accreting dust. The model predicts the accretion rate of dust onto planets
interior to debris belts, with mass accretions rates of up to hundreds of
kilograms per second predicted for hot Jupiters interior to outer debris belts,
when collisional evolution is also taken into account. The model can be used to
infer the presence and likely masses of as yet undetected planets in systems
with outer belts. The non-detection of warm dust with the Large Binocular
Telescope Interferometer (LBTI) around Vega could be explained by the presence
of a single Saturn mass planet, or a chain of lower mass planets. Similarly,
the detection of warm dust in such systems implies the absence of planets above
a quantifiable level, which can be lower than similar limits from direct
imaging. The level of dust detected with LBTI around beta Leo can be used to
rule out the presence of planets more massive than a few Saturn masses outside
of ~5au
489 ANAPHYLATOXINE RECEPTORS AND COMPLEMENT REGULATORY PROTEINS IN TENDON: INTERRELATION WITH IMMUNOREGULATORY CYTOKINES
Cyclin D1-mediated microRNA expression signature predicts breast cancer outcome
Background: Genetic classification of breast cancer based on the coding mRNA suggests the evolution of distinct subtypes. Whether the non-coding genome is altered concordantly with the coding genome and the mechanism by which the cell cycle directly controls the non-coding genome is poorly understood.
Methods: Herein, the miRNA signature maintained by endogenous cyclin D1 in human breast cancer cells was defined. In order to determine the clinical significance of the cyclin D1-mediated miRNA signature, we defined a miRNA expression superset from 459 breast cancer samples. We compared the coding and non-coding genome of breast cancer subtypes.
Results: Hierarchical clustering of human breast cancers defined four distinct miRNA clusters (G1-G4) associated with distinguishable relapse-free survival by Kaplan-Meier analysis. The cyclin D1-regulated miRNA signature included several oncomirs, was conserved in multiple breast cancer cell lines, was associated with the G2 tumor miRNA cluster, ERα+ status, better outcome and activation of the Wnt pathway. The coding and non-coding genome were discordant within breast cancer subtypes. Seed elements for cyclin D1-regulated miRNA were identified in 63 genes of the Wnt signaling pathway including DKK. Cyclin D1 restrained DKK1 via the 3\u27UTR. In vivo studies using inducible transgenics confirmed cyclin D1 induces Wnt-dependent gene expression.
Conclusion: The non-coding genome defines breast cancer subtypes that are discordant with their coding genome subtype suggesting distinct evolutionary drivers within the tumors. Cyclin D1 orchestrates expression of a miRNA signature that induces Wnt/β-catenin signaling, therefore cyclin D1 serves both upstream and downstream of Wnt/β-catenin signaling
<i>Herschel</i> observations of the debris disc around HIP 92043
Context. Typical debris discs are composed of particles ranging from several micron sized dust grains to km sized asteroidal bodies, and their infrared emission peaks at wavelengths 60-100 μm. Recent Herschel DUNES observations have identified several debris discs around nearby Sun-like stars (F, G and K spectral type) with significant excess emission only at 160 μm.
Aims. We observed HIP 92043 (110 Her, HD 173667) at far-infrared and sub-millimetre wavelengths with Herschel PACS and SPIRE. Identification of the presence of excess emission from HIP 92043 and the origin and physical properties of any excess was undertaken through analysis of its spectral energy distribution (SED) and the PACS images.
Methods. The PACS and SPIRE images were produced using the HIPE photProject map maker routine. Fluxes were measured using aperture photometry. A stellar photosphere model was scaled to optical and near infrared photometry and subtracted from the far-infared and sub-mm fluxes to determine the presence of excess emission. Source radial profiles were fitted using a 2D Gaussian and compared to a PSF model based on Herschel observations of α Boo to check for extended emission.
Results. Clear excess emission from HIP 92043 was observed at 70 and 100 μm. Marginal excess was observed at 160 and 250 μm. Analysis of the images reveals that the source is extended at 160 μm. A fit to the source SED is inconsistent with a photosphere and single temperature black body.
Conclusions. The excess emission from HIP 92043 is consistent with the presence of an unresolved circumstellar debris disc at 70 and 100 μm, with low probability of background contamination. The extended 160 μm emission may be interpreted as an additional cold component to the debris disc or as the result of background contamination along the line of sight. The nature of the 160 μm excess cannot be determined absolutely from the available data, but we favour a debris disc interpretation, drawing parallels with previously identified cold disc sources in the DUNES sample
Cyclin D1 integrates G9a-mediated histone methylation.
Lysine methylation of histones and non-histone substrates by the SET domain containing protein lysine methyltransferase (KMT) G9a/EHMT2 governs transcription contributing to apoptosis, aberrant cell growth, and pluripotency. The positioning of chromosomes within the nuclear three-dimensional space involves interactions between nuclear lamina (NL) and the lamina-associated domains (LAD). Contact of individual LADs with the NL are dependent upon H3K9me2 introduced by G9a. The mechanisms governing the recruitment of G9a to distinct subcellular sites, into chromatin or to LAD, is not known. The cyclin D1 gene product encodes the regulatory subunit of the holoenzyme that phosphorylates pRB and NRF1 thereby governing cell-cycle progression and mitochondrial metabolism. Herein, we show that cyclin D1 enhanced H3K9 dimethylation though direct association with G9a. Endogenous cyclin D1 was required for the recruitment of G9a to target genes in chromatin, for G9a-induced H3K9me2 of histones, and for NL-LAD interaction. The finding that cyclin D1 is required for recruitment of G9a to target genes in chromatin and for H3K9 dimethylation, identifies a novel mechanism coordinating protein methylation
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