1,257 research outputs found
The Carnegie Astrometric Planet Search Program
We are undertaking an astrometric search for gas giant planets and brown
dwarfs orbiting nearby low mass dwarf stars with the 2.5-m du Pont telescope at
the Las Campanas Observatory in Chile. We have built two specialized
astrometric cameras, the Carnegie Astrometric Planet Search Cameras (CAPSCam-S
and CAPSCam-N), using two Teledyne Hawaii-2RG HyViSI arrays, with the cameras'
design having been optimized for high accuracy astrometry of M dwarf stars. We
describe two independent CAPSCam data reduction approaches and present a
detailed analysis of the observations to date of one of our target stars, NLTT
48256. Observations of NLTT 48256 taken since July 2007 with CAPSCam-S imply
that astrometric accuracies of around 0.3 milliarcsec per hour are achievable,
sufficient to detect a Jupiter-mass companion orbiting 1 AU from a late M dwarf
10 pc away with a signal-to-noise ratio of about 4. We plan to follow about 100
nearby (primarily within about 10 pc) low mass stars, principally late M, L,
and T dwarfs, for 10 years or more, in order to detect very low mass companions
with orbital periods long enough to permit the existence of habitable,
Earth-like planets on shorter-period orbits. These stars are generally too
faint and red to be included in ground-based Doppler planet surveys, which are
often optimized for FGK dwarfs. The smaller masses of late M dwarfs also yield
correspondingly larger astrometric signals for a given mass planet. Our search
will help to determine whether gas giant planets form primarily by core
accretion or by disk instability around late M dwarf stars.Comment: 48 pages, 9 figures. in press, Publ. Astron. Soc. Pacifi
Hyperglycaemia normalises insulin action on glucose metabolism but not the impaired activation of AKT and glycogen synthase in the skeletal muscle of patients with type 2 diabetes
Magnetic ground state and magnon-phonon interaction in multiferroic h-YMnO
Inelastic neutron scattering has been used to study the magneto-elastic
excitations in the multiferroic manganite hexagonal YMnO. An avoided
crossing is found between magnon and phonon modes close to the Brillouin zone
boundary in the -plane. Neutron polarization analysis reveals that this
mode has mixed magnon-phonon character. An external magnetic field along the
-axis is observed to cause a linear field-induced splitting of one of the
spin wave branches. A theoretical description is performed, using a Heisenberg
model of localized spins, acoustic phonon modes and a magneto-elastic coupling
via the single-ion magnetostriction. The model quantitatively reproduces the
dispersion and intensities of all modes in the full Brillouin zone, describes
the observed magnon-phonon hybridized modes, and quantifies the magneto-elastic
coupling. The combined information, including the field-induced magnon
splitting, allows us to exclude several of the earlier proposed models and
point to the correct magnetic ground state symmetry, and provides an effective
dynamic model relevant for the multiferroic hexagonal manganites.Comment: 12 pages, 10 figure
Ancient manuring of Amazonian Dark Earths as assessed by molecular markers.
Analytical procedures and the applicability of this methods to detect ancient human manuring in those soils, which were as far as we know, not used before in the humid tropics, will be discussed
Nitrogen immobilization in paddy soils as affected by redox conditions and rice straw incorporation
MMTF: The Maryland-Magellan Tunable Filter
This paper describes the Maryland-Magellan Tunable Filter (MMTF) on the
Magellan-Baade 6.5-meter telescope. MMTF is based on a 150-mm clear aperture
Fabry-Perot (FP) etalon that operates in low orders and provides transmission
bandpass and central wavelength adjustable from ~5 to ~15 A and from ~5000 to
over ~9200 A, respectively. It is installed in the Inamori Magellan Areal
Camera and Spectrograph (IMACS) and delivers an image quality of ~0.5" over a
field of view of 27' in diameter (monochromatic over ~10'). This versatile and
easy-to-operate instrument has been used over the past three years for a wide
variety of projects. This paper first reviews the basic principles of FP
tunable filters, then provides a detailed description of the hardware and
software associated with MMTF and the techniques developed to observe with this
instrument and reduce the data. The main lessons learned in the course of the
commissioning and implementation of MMTF are highlighted next, before
concluding with a brief outlook on the future of MMTF and of similar facilities
which are soon coming on line.Comment: 38 pages, 12 figures, 3 tables, now accepted for publication to the
Astronomical Journa
Impaired insulin-induced site-specific phosphorylation of TBC1 domain family, member 4 (TBC1D4) in skeletal muscle of type 2 diabetes patients is restored by endurance exercise-training
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