1,088 research outputs found
Asteroseismic detection of latitudinal differential rotation in 13 Sun-like stars
The differentially rotating outer layers of stars are thought to play a role
in driving their magnetic activity, but the underlying mechanisms that generate
and sustain differential rotation are poorly understood. We report the
measurement of latitudinal differential rotation in the convection zones of 40
Sun-like stars using asteroseismology. For the most significant detections, the
stars' equators rotate approximately twice as fast as their mid-latitudes. The
latitudinal shear inferred from asteroseismology is much larger than
predictions from numerical simulations.Comment: 45 pages, 11 figures, 4 tables, published in Scienc
An ecological characterization of Salt River Bay National Historical Park and Ecological Preserve, U.S. Virgin Islands
Salt River Bay National Historical Park and Ecological Preserve (hereafter, SARI or the park) was created in 1992 to preserve, protect, and interpret nationally significant natural, historical, and cultural resources (United States Congress 1992). The diverse ecosystem within it includes a large mangrove forest, a submarine canyon, coral reefs, seagrass beds, coastal forests, and many other natural and developed landscape elements. These ecosystem components are, in turn, utilized by a great diversity of flora and fauna. A comprehensive spatial inventory of these ecosystems is required for successful management. To meet this need, the National Oceanic and Atmospheric Administration (NOAA) Biogeography Program, in consultation with the National Park Service (NPS) and the Government of the Virgin Islands Department of Planning and Natural Resources (VIDPNR), conducted an ecological characterization. The characterization consists of three complementary components: a text report, digital habitat maps, and a collection of historical aerial photographs. This ecological characterization provides managers with a suite of tools that, when coupled with the excellent pre-existing body of work on SARI resources, enables improved research and monitoring activities within the park (see Appendix F for a list of data products)
Complex orbital state in manganites
The -orbital states with complex coefficients of the linear combination
of and are studied for the ferromagnetic state in doped
manganites. Especially the focus is put on the competition among uniform
complex, staggered complex, and real orbital states. As the hole-doping
increases, the real, the canted complex, and the staggered complex orbital
states appears successively. Uniform complex state analoguous to Nagaoka
ferromagnet does not appear. These complex states can be expressed as a
resonating state among the planer orbitals as the orbital liquid, accompanied
by no Jahn-Teller distortion.Comment: 14 pages, 6 figure
Edaravone protects against methylglyoxal-induced barrier damage in human brain endothelial cells
BACKGROUND:
Elevated level of reactive carbonyl species, such as methylglyoxal, triggers carbonyl stress and activates a series of inflammatory responses leading to accelerated vascular damage. Edaravone is the active substance of a Japanese medicine, which aids neurological recovery following acute brain ischemia and subsequent cerebral infarction. Our aim was to test whether edaravone can exert a protective effect on the barrier properties of human brain endothelial cells (hCMEC/D3 cell line) treated with methylglyoxal.
METHODOLOGY:
Cell viability was monitored in real-time by impedance-based cell electronic sensing. The barrier function of the monolayer was characterized by measurement of resistance and flux of permeability markers, and visualized by immunohistochemistry for claudin-5 and ÎČ-catenin. Cell morphology was also examined by holographic phase imaging.
PRINCIPAL FINDINGS:
Methylglyoxal exerted a time- and dose-dependent toxicity on cultured human brain endothelial cells: a concentration of 600 ”M resulted in about 50% toxicity, significantly reduced the integrity and increased the permeability of the barrier. The cell morphology also changed dramatically: the area of cells decreased, their optical height significantly increased. Edaravone (3 mM) provided a complete protection against the toxic effect of methylglyoxal. Co-administration of edaravone restored cell viability, barrier integrity and functions of brain endothelial cells. Similar protection was obtained by the well-known antiglycating molecule, aminoguanidine, our reference compound.
CONCLUSION:
These results indicate for the first time that edaravone is protective in carbonyl stress induced barrier damage. Our data may contribute to the development of compounds to treat brain endothelial dysfunction in carbonyl stress related diseases
Orthorhombic distortion and orbital order in the vanadium spinel FeV2 O4
Using synchrotron and neutron diffraction measurements, we find a low-temperature orthorhombic phase in vanadium spinel FeV2O4. The orbital order of V3+ ions with tetragonal normal modes occurs at 68 K, and this leads to an appearance of the pseudotetragonal phase at a noncollinear ferrimagnetic transition temperature. Below the magnetic transition temperature, unconventional behavior of the orbital state of Fe2+ ions accompanied by the emergence of the orthorhombic phase was observed by using the normal mode analysis. We have also studied the structural properties of orbitally diluted materials. The orthorhombic phase, which is significantly affected by the other ions, is intrinsic in FeV2O4. We suggest the orthorhombic phase is strongly related with the double orbital states of Fe2+ and V3+ ions
Study of KIC 8561221 observed by Kepler: an early red giant showing depressed dipolar modes
The continuous high-precision photometric observations provided by the CoRoT
and Kepler space missions have allowed us to better understand the structure
and dynamics of red giants using asteroseismic techniques. A small fraction of
these stars shows dipole modes with unexpectedly low amplitudes. The reduction
in amplitude is more pronounced for stars with higher frequency of maximum
power. In this work we want to characterize KIC 8561221 in order to confirm
that it is currently the least evolved star among this peculiar subset and to
discuss several hypotheses that could help explain the reduction of the dipole
mode amplitudes. We used Kepler short- and long-cadence data combined with
spectroscopic observations to infer the stellar structure and dynamics of KIC
8561221. We then discussed different scenarios that could contribute to the
reduction of the dipole amplitudes such as a fast rotating interior or the
effect of a magnetic field on the properties of the modes. We also performed a
detailed study of the inertia and damping of the modes. We have been able to
characterize 37 oscillations modes, in particular, a few dipole modes above
nu_max that exhibit nearly normal amplitudes. We have inferred a surface
rotation period of around 91 days and uncovered the existence of a variation in
the surface magnetic activity during the last 4 years. As expected, the
internal regions of the star probed by the l = 2 and 3 modes spin 4 to 8 times
faster than the surface. With our grid of standard models we are able to
properly fit the observed frequencies. Our model calculation of mode inertia
and damping give no explanation for the depressed dipole modes. A fast rotating
core is also ruled out as a possible explanation. Finally, we do not have any
observational evidence of the presence of a strong deep magnetic field inside
the star.Comment: Accepted in A&A. 17 pages, 16 figure
Exploitation of Tolerance of Wheat Kernel Weight and Shape-Related Traits from Aegilops tauschii under Heat and Combined Heat-Drought Stresses
Kernel weight and shape-related traits are inherited stably and increase wheat yield. Narrow genetic diversity limits the progress of wheat breeding. Here, we evaluated kernel weight and shape-related traits and applied genome-wide association analysis to a panel of wheat multiple synthetic derivative (MSD) lines. The MSD lines harbored genomic fragments from Aegilops tauschii. These materials were grown under optimum conditions in Japan, as well as under heat and combined heatâdrought conditions in Sudan. We aimed to explore useful QTLs for kernel weight and shape-related traits under stress conditions. These can be useful for enhancing yield under stress conditions. MSD lines possessed remarkable genetic variation for all traits under all conditions, and some lines showed better performance than the background parent Norin 61. We identified 82 marker trait associations (MTAs) under the three conditions; most of them originated from the D genome. All of the favorable alleles originated from Ae. tauschii. For the first time, we identified markers on chromosome 5D associated with a candidate gene encoding a RING-type E3 ubiquitinâprotein ligase and expected to have a role in regulating wheat seed size. Our study provides important knowledge for the improvement of wheat yield under optimum and stress conditions. The results emphasize the importance of Ae. tauschii as a gene reservoir for wheat breeding
X-ray and optical properties of X-ray sources in the 13hr XMM-Newton/Chandra deep survey
The 13hr XMM-Newton/Chandra deep survey is the first of two extremely deep
XMM-Newton fields observed by the XMM-OM consortium. A 120 ks Chandra mosaic,
covering 0.2 square degrees, provides sensitive, confusion-free point source
detection with sub-arcsecond positions, while the 200 ks XMM-Newton observation
provides high quality X-ray spectroscopy over the same sky area. We have
optical spectroscopic identifications for 70 X-ray sources. Of these, 42 are
broad emission-line AGN with a wide range of redshifts. The optical
counterparts of a further 23 sources are narrow emission line galaxies and
absorption line galaxies. These 23 sources all lie at z < 1 and typically have
lower X-ray luminosities than the broad-line AGN. About half of them show
significant X-ray absorption and are almost certainly intrinsically absorbed
AGN. However some of them have unabsorbed, AGN-like, power-law components in
their X-ray spectra, but do not show broad emission lines in their optical
spectra. These sources may be weak, unobscured AGN in bright galaxies and their
existence at low redshifts could be a consequence of the strong cosmological
evolution of AGN characteristic luminosities.Comment: Proceedings of the "X-ray surveys, in the light of the new
observatories" workshop, Astronomische Nachrichten, in press (4 pages, 4
figures
Can Enhanced Diffusion Improve Helioseismic Agreement for Solar Models with Revised Abundances?
Recent solar photospheric abundance analyses (Asplund et al. 2004, 2005;
Lodders 2003) have revised downward the C, N, O, Ne, and Ar abundances by 0.15
to 0.2 dex compared to previous determinations of Grevesse & Sauval (1998).
With these revisions, the photospheric Z/X decreases to 0.0165 (0.0177
Lodders), and Z to ~0.0122 (0.0133 Lodders). A number of papers report that
solar models evolved with standard opacities and diffusion treatment using
these new abundances give poor agreement with helioseismic inferences. Here we
explore evolved solar models with varying diffusion treatments to reduce the
photospheric abundances while keeping the interior abundances about the same as
earlier standard models. While enhanced diffusion improves agreement with some
helioseismic constraints compared to a solar model evolved with the new
abundances using nominal input physics, the required increases in thermal
diffusion rates are unphysically large, and none of the variations tried
restores the good agreement attained using the earlier abundances. A
combination of modest opacity increases, diffusion enhancements, and abundance
increases near the level of the uncertainties, while somewhat contrived,
remains the most physically plausible means to restore agreement with
helioseismology. The case for enhanced diffusion would be improved if the
inferred convection-zone helium abundance could be reduced; we recommend
reconsidering this derivation in light of new equations of state with modified
abundances and other improvements. We also recommend considering, as a last
resort, diluting the convection zone, which contains only 2.5% of the sun's
mass, by accretion of material depleted in these more volatile elements C, N,
O, Ne, & Ar after the sun arrived on the main sequence.Comment: Version 2: 24 pages, 3 figures; Accepted to ApJ with omission of
g-mode predictions and discussion that are included in this preprin
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