341 research outputs found
L∞-norm and energy quantization for the planar Lane–Emden problem with large exponent
For any smooth bounded domain (Formula presented.), we consider positive solutions to (Formula presented.)which satisfy the uniform energy bound (Formula presented.)for (Formula presented.). We prove convergence to (Formula presented.) as (Formula presented.) of the (Formula presented.)-norm of any solution. We further deduce quantization of the energy to multiples of (Formula presented.), thus completing the analysis performed in De Marchis et al. (J Fixed Point Theory Appl 19:889–916, 2017)
Analysis of the rotation period of asteroids (1865) Cerberus, (2100) Ra-Shalom, and (3103) Eger - search for the YORP effect
The spin state of small asteroids can change on a long timescale by the
Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, the net torque that arises
from anisotropically scattered sunlight and proper thermal radiation from an
irregularly-shaped asteroid. The secular change in the rotation period caused
by the YORP effect can be detected by analysis of asteroid photometric
lightcurves. We analyzed photometric lightcurves of near-Earth asteroids (1865)
Cerberus, (2100) Ra-Shalom, and (3103) Eger with the aim to detect possible
deviations from the constant rotation caused by the YORP effect. We carried out
new photometric observations of the three asteroids, combined the new
lightcurves with archived data, and used the lightcurve inversion method to
model the asteroid shape, pole direction, and rotation rate. The YORP effect
was modeled as a linear change in the rotation rate in time d\omega /dt. Values
of d\omega/ dt derived from observations were compared with the values
predicted by theory. We derived physical models for all three asteroids. We had
to model Eger as a nonconvex body because the convex model failed to fit the
lightcurves observed at high phase angles. We probably detected the
acceleration of the rotation rate of Eger d\omega / dt = (1.4 +/- 0.6) x
10^{-8} rad/d (3\sigma error), which corresponds to a decrease in the rotation
period by 4.2 ms/yr. The photometry of Cerberus and Ra-Shalom was consistent
with a constant-period model, and no secular change in the spin rate was
detected. We could only constrain maximum values of |d\omega / dt| < 8 x
10^{-9} rad/d for Cerberus, and |d\omega / dt| < 3 x 10^{-8} rad/d for
Ra-Shalom
Predictive value of VEGF gene polymorphisms for metastatic colorectal cancer patients receiving first-line treatment including fluorouracil, irinotecan, and bevacizumab
The aim of this study is to evaluate the influence of germline vascular endothelial growth factor (VEGF) gene polymorphisms (VGPs) on the efficacy of the anti-VEGF antibody bevacizumab (Bev) in metastatic colorectal cancer (MCRC) patients
Triplicity and Physical Characteristics of Asteroid (216) Kleopatra
To take full advantage of the September 2008 opposition passage of the M-type
asteroid (216) Kleopatra, we have used near-infrared adaptive optics (AO)
imaging with the W.M. Keck II telescope to capture unprecedented high
resolution images of this unusual asteroid. Our AO observations with the W.M.
Keck II telescope, combined with Spitzer/IRS spectroscopic observations and
past stellar occultations, confirm the value of its IRAS radiometric radius of
67.5 km as well as its dog-bone shape suggested by earlier radar observations.
Our Keck AO observations revealed the presence of two small satellites in orbit
about Kleopatra (see Marchis et al., 2008). Accurate measurements of the
satellite orbits over a full month enabled us to determine the total mass of
the system to be 4.64+/-0.02 10^18 Kg. This translates into a bulk density of
3.6 +/-0.4 g/cm3, which implies a macroscopic porosity for Kleopatra of ~
30-50%, typical of a rubble-pile asteroid. From these physical characteristics
we measured its specific angular momentum, very close to that of a spinning
equilibrium dumbbell.Comment: 35 pages, 3 Tables, 9 Figures. In press to Icaru
Constraints from deuterium on the formation of icy bodies in the Jovian system and beyond
We consider the role of deuterium as a potential marker of location and
ambient conditions during the formation of small bodies in our Solar system. We
concentrate in particular on the formation of the regular icy satellites of
Jupiter and the other giant planets, but include a discussion of the
implications for the Trojan asteroids and the irregular satellites. We examine
in detail the formation of regular planetary satellites within the paradigm of
a circum-Jovian subnebula. Particular attention is paid to the two extreme
potential subnebulae - "hot" and "cold". In particular, we show that, for the
case of the "hot" subnebula model, the D:H ratio in water ice measured from the
regular satellites would be expected to be near-Solar. In contrast, satellites
which formed in a "cold" subnebula would be expected to display a D:H ratio
that is distinctly over-Solar. We then compare the results obtained with the
enrichment regimes which could be expected for other families of icy small
bodies in the outer Solar system - the Trojan asteroids and the irregular
satellites. In doing so, we demonstrate how measurements by Laplace, the James
Webb Space Telescope, HERSCHEL and ALMA will play an important role in
determining the true formation locations and mechanisms of these objects.Comment: Accepted and shortly to appear in Planetary and Space Science; 11
pages with 5 figure
YSOVAR: Six pre-main-sequence eclipsing binaries in the Orion Nebula Cluster
Eclipsing binaries (EBs) provide critical laboratories for empirically
testing predictions of theoretical models of stellar structure and evolution.
Pre-main-sequence (PMS) EBs are particularly valuable, both due to their rarity
and the highly dynamic nature of PMS evolution, such that a dense grid of PMS
EBs is required to properly calibrate theoretical PMS models. Analyzing
multi-epoch, multi-color light curves for 2400 candidateOrion Nebula Cluster
(ONC) members from our Warm Spitzer Exploration Science Program YSOVAR, we have
identified 12 stars whose light curves show eclipse features. Four of these 12
EBs are previously known. Supplementing our light curves with follow-up optical
and near-infrared spectroscopy, we establish two of the candidates as likely
field EBs lying behind the ONC. We confirm the remaining six candidate systems,
however, as newly identified ONC PMS EBs. These systems increase the number of
known PMS EBs by over 50% and include the highest mass (Theta1 Ori E, for which
we provide a complete set of well-determined parameters including component
masses of 2.807 and 2.797 solar masses) and longest period (ISOY
J053505.71-052354.1, P \sim 20 days) PMS EBs currently known. In two cases
(Theta1 Ori E and ISOY J053526.88-044730.7), enough photometric and
spectroscopic data exist to attempt an orbit solution and derive the system
parameters. For the remaining systems, we combine our data with literature
information to provide a preliminary characterization sufficient to guide
follow-up investigations of these rare, benchmark systems.Comment: Accepted by Ap
Development of a chemically defined medium and discovery of new mitogenic growth factors for mouse hepatocytes: Mitogenic effects of FGF1/2 and PDGF
Chemically defined serum-free media for rat hepatocytes have been useful in identifying EGFR ligands and HGF/MET signaling as direct mitogenic factors for rat hepatocytes. The absence of such media for mouse hepatocytes has prevented screening for discovery of such mitogens for mouse hepatocytes. We present results obtained by designing such a chemically defined medium for mouse hepatocytes and demonstrate that in addition to EGFR ligands and HGF, the growth factors FGF1 and FGF2 are also important mitogenic factors for mouse hepatocytes. Smaller mitogenic response was also noticed for PDGF AB. Mouse hepatocytes are more likely to enter into spontaneous proliferation in primary culture due to activation of cell cycle pathways resulting from collagenase perfusion. These results demonstrate unanticipated fundamental differences in growth biology of hepatocytes between the two rodent species. Copyright: © 2014 Reekie et al
Long-Term Evolution of the Aerosol Debris Cloud Produced by the 2009 Impact on Jupiter
We present a study of the long-term evolution of the cloud of aerosols produced in the atmosphere of Jupiter by the impact of an object on 19 July 2009. The work is based on images obtained during 5 months from the impact to 31 December 2009 taken in visible continuum wavelengths and from 20 July 2009 to 28 May 2010 taken in near-infrared deep hydrogen-methane absorption bands at 2.1-2.3 micron. The impact cloud expanded zonally from approximately 5000 km (July 19) to 225,000 km (29 October, about 180 deg in longitude), remaining meridionally localized within a latitude band from 53.5 deg S to 61.5 deg S planetographic latitude. During the first two months after its formation the site showed heterogeneous structure with 500-1000 km sized embedded spots. Later the reflectivity of the debris field became more homogeneous due to clump mergers. The cloud was mainly dispersed in longitude by the dominant zonal winds and their meridional shear, during the initial stages, localized motions may have been induced by thermal perturbation caused by the impact's energy deposition. The tracking of individual spots within the impact cloud shows that the westward jet at 56.5 deg S latitude increases its eastward velocity with altitude above the tropopause by 5- 10 m/s. The corresponding vertical wind shear is low, about 1 m/s per scale height in agreement with previous thermal wind estimations. We found evidence for discrete localized meridional motions with speeds of 1-2 m/s. Two numerical models are used to simulate the observed cloud dispersion. One is a pure advection of the aerosols by the winds and their shears. The other uses the EPIC code, a nonlinear calculation of the evolution of the potential vorticity field generated by a heat pulse that simulates the impact. Both models reproduce the observed global structure of the cloud and the dominant zonal dispersion of the aerosols, but not the details of the cloud morphology. The reflectivity of the impact cloud decreased exponentially with a characteristic timescale of 15 days; we can explain this behavior with a radiative transfer model of the cloud optical depth coupled to an advection model of the cloud dispersion by the wind shears. The expected sedimentation time in the stratosphere (altitude levels 5-100 mbar) for the small aerosol particles forming the cloud is 45-200 days, thus aerosols were removed vertically over the long term following their zonal dispersion. No evidence of the cloud was detected 10 months after the impact
Identification of the glial cell types containing carnosine-related peptides in the rat brain.
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