349 research outputs found
Properties of Central Caustics in Planetary Microlensing
To maximize the number of planet detections, current microlensing follow-up
observations are focusing on high-magnification events which have a higher
chance of being perturbed by central caustics. In this paper, we investigate
the properties of central caustics and the perturbations induced by them. We
derive analytic expressions of the location, size, and shape of the central
caustic as a function of the star-planet separation, , and the planet/star
mass ratio, , under the planetary perturbative approximation and compare the
results with those based on numerical computations. While it has been known
that the size of the planetary caustic is \propto \sqrt{q}, we find from this
work that the dependence of the size of the central caustic on is linear,
i.e., \propto q, implying that the central caustic shrinks much more rapidly
with the decrease of compared to the planetary caustic. The central-caustic
size depends also on the star-planet separation. If the size of the caustic is
defined as the separation between the two cusps on the star-planet axis
(horizontal width), we find that the dependence of the central-caustic size on
the separation is \propto (s+1/s). While the size of the central caustic
depends both on and q, its shape defined as the vertical/horizontal width
ratio, R_c, is solely dependent on the planetary separation and we derive an
analytic relation between R_c and s. Due to the smaller size of the central
caustic combined with much more rapid decrease of its size with the decrease of
q, the effect of finite source size on the perturbation induced by the central
caustic is much more severe than the effect on the perturbation induced by the
planetary caustic. Abridged.Comment: 5 pages, 4 figures, ApJ accepte
Microlensing Detections of Planets in Binary Stellar Systems
We demonstrate that microlensing can be used for detecting planets in binary
stellar systems. This is possible because in the geometry of planetary binary
systems where the planet orbits one of the binary component and the other
binary star is located at a large distance, both planet and secondary companion
produce perturbations at a common region around the planet-hosting binary star
and thus the signatures of both planet and binary companion can be detected in
the light curves of high-magnification lensing events. We find that identifying
planets in binary systems is optimized when the secondary is located in a
certain range which depends on the type of the planet. The proposed method can
detect planets with masses down to one tenth of the Jupiter mass in binaries
with separations <~ 100 AU. These ranges of planet mass and binary separation
are not covered by other methods and thus microlensing would be able to make
the planetary binary sample richer.Comment: 5 pages, two figures in JPG forma
Limits of Binaries That Can Be Characterized by Gravitational Microlensing
Due to the high efficiency of planet detections, current microlensing planet
searches focus on high-magnification events. High-magnification events are
sensitive to remote binary companions as well and thus a sample of
wide-separation binaries are expected to be collected as a byproduct. In this
paper, we show that characterizing binaries for a portion of this sample will
be difficult due to the degeneracy of the binary-lensing parameters. This
degeneracy arises because the perturbation induced by the binary companion is
well approximated by the Chang-Refsdal lensing for binaries with separations
greater than a certain limit. For binaries composed of equal mass lenses, we
find that the lens binarity can be noticed up to the separations of
times of the Einstein radius corresponding to the mass of each lens. Among
these binaries, however, we find that the lensing parameters can be determined
only for a portion of binaries with separations less than times of
the Einstein radius.Comment: 5 pages, 3 figures, 1 tabl
Circular Kinks on the Surface of Granular Material Rotated in a Tilted Spinning Bucket
We find that circular kinks form on the surface of granular material when the
axis of rotation is tilted more than the angle of internal friction of the
material. Radius of the kinks is measured as a function of the spinning speed
and the tilting angle. Stability consideration of the surface results in an
explanation that the kink is a boundary between the inner unstable and outer
stable regions. A simple cellular automata model also displays kinks at the
stability boundary
The contribution of myelin to magnetic susceptibility-weighted contrasts in high-field MRI of the brain
T(2)*-weighted gradient-echo MRI images at high field (â„ 7T) have shown rich image contrast within and between brain regions. The source for these contrast variations has been primarily attributed to tissue magnetic susceptibility differences. In this study, the contribution of myelin to both T(2)* and frequency contrasts is investigated using a mouse model of demyelination based on a cuprizone diet. The demyelinated brains showed significantly increased T(2)* in white matter and a substantial reduction in gray-white matter frequency contrast, suggesting that myelin is a primary source for these contrasts. Comparison of in-vivo and in-vitro data showed that, although tissue T(2)* values were reduced by formalin fixation, gray-white matter frequency contrast was relatively unaffected and fixation had a negligible effect on cuprizone-induced changes in T(2)* and frequency contrasts
Akabane viral encephalitis in calves in South Korea
This work was supported by the Brain Korea 21 Project and the Ministry of Agriculture and Forestry (399002-3), Republic of Korea
TonEBP suppresses IL-10-mediated immunomodulation
TonEBP is a key transcriptional activator of M1 phenotype in macrophage, and its high expression is associated with many inflammatory diseases. During the progression of the inflammatory responses, the M1 to M2 phenotypic switch enables the dual role of macrophages in controlling the initiation and resolution of inflammation. Here we report that in human and mouse M1 macrophages TonEBP suppresses IL-10 expression and M2 phenotype. TonEBP knockdown promoted the transcription of the IL-10 gene by enhancing chromatin accessibility and Sp1 recruitment to its promoter. The enhanced expression of M2 genes by TonEBP knockdown was abrogated by antagonism of IL-10 by either neutralizing antibodies or siRNA-mediated silencing. In addition, pharmacological suppression of TonEBP leads to similar upregulation of IL-10 and M2 genes. Thus, TonEBP suppresses M2 phenotype via downregulation of the IL-10 in M1 macrophagesope
Comparative absorption, distribution, and excretion of titanium dioxide and zinc oxide nanoparticles after repeated oral administration
Background
The in vivo kinetics of nanoparticles is an essential to understand the hazard of nanoparticles. Here, the absorption, distribution, and excretion patterns of titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles following oral administration were evaluated.
Methods
Nanoparticles were orally administered to rats for 13Â weeks (7Â days/week). Samples of blood, tissues (liver, kidneys, spleen, and brain), urine, and feces were obtained at necropsy. The level of Ti or Zn in each sample was measured using inductively coupled plasma-mass spectrometry.
Results
TiO2 nanoparticles had extremely low absorption, while ZnO nanoparticles had higher absorption and a clear dose-response curve. Tissue distribution data showed that TiO2 nanoparticles were not significantly increased in sampled organs, even in the group receiving the highest dose (1041.5Â mg/kg body weight). In contrast, Zn concentrations in the liver and kidney were significantly increased compared with the vehicle control. ZnO nanoparticles in the spleen and brain were minimally increased. Ti concentrations were not significantly increased in the urine, while Zn levels were significantly increased in the urine, again with a clear dose-response curve. Very high concentrations of Ti were detected in the feces, while much less Zn was detected in the feces.
Conclusions
Compared with TiO2 nanoparticles, ZnO nanoparticles demonstrated higher absorption and more extensive organ distribution when administered orally. The higher absorption of ZnO than TiO2 nanoparticles might be due to the higher dissolution rate in acidic gastric fluid, although more thorough studies are needed
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