3,091 research outputs found
Radio Galaxy NGC 1265 unveils the Accretion Shock onto the Perseus Galaxy Cluster
We present a consistent 3D model for the head-tail radio galaxy NGC 1265 that
explains the complex radio morphology and spectrum by a past passage of the
galaxy and radio bubble through a shock wave. Using analytical solutions to the
full Riemann problem and hydrodynamical simulations, we study how this passage
transformed the plasma bubble into a toroidal vortex ring. Adiabatic
compression of the aged electron population causes it to be energized and to
emit low-surface brightness and steep-spectrum radio emission. The large infall
velocity of NGC 1265 and the low Faraday rotation measure values and variance
of the jet strongly argue that this transformation was due to the accretion
shock onto Perseus situated roughly at R_200. Estimating the volume change of
the radio bubble enables inferring a shock Mach number of M =
4.2_{-1.2}^{+0.8}, a density jump of 3.4_{-0.4}^{+0.2}, a temperature jump of
6.3_{-2.7}^{+2.5}, and a pressure jump of 21.5 +/- 10.5 while allowing for
uncertainties in the equation of state of the radio plasma and volume of the
torus. Extrapolating X-ray profiles, we obtain upper limits on the gas
temperature and density in the infalling warm-hot intergalactic medium of kT <
0.4 keV and n < 5e-5 / cm^3. The orientation of the ellipsoidally shaped radio
torus in combination with the direction of the galaxy's head and tail in the
plane of the sky is impossible to reconcile with projection effects. Instead,
this argues for post-shock shear flows that have been caused by curvature in
the shock surface with a characteristic radius of 850 kpc. The energy density
of the shear flow corresponds to a turbulent-to-thermal energy density of 14%.
The shock-injected vorticity might be important in generating and amplifying
magnetic fields in galaxy clusters. Future LOFAR observations of head-tail
galaxies can be complementary probes of accretion shocks onto galaxy clusters.Comment: 14 pages, 4 figures, ApJ, in print; v3: typos corrected to match the
published version; v2: improved presentation, added 2D numerical simulations
and exact solution to the 1D Riemann problem of a shock overrunning a
spherical bubble that gets transformed into a vortex rin
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
Effect of rhBMP-2 applied with a 3D-printed titanium implant on new bone formation in rabbit calvarium
Objective: This study sought to compare the biocompatibility of a three-dimensional (3D)-printed titanium implant with a conventional machined titanium product, as well as the effect of such implant applied with recombinant human Bone Morphogenetic Protein Type 2 (rhBMP-2) for guided bone regeneration. Methodology: Disk-shaped titanium specimens fabricated either by the conventional machining technique or by the 3D-printing technique were compared by MC3T3-E1 cells cytotoxicity assay. New bone formation was evaluated using a rapid prototype titanium cap applied to the calvaria of 10 rabbits, which were divided into two groups: one including an atelopeptide collagen plug on one side of the cap (group I) and the other including a plug with rhBMP-2 on the other side (group II). At six and 12 weeks after euthanasia, rabbits calvaria underwent morphometric analysis through radiological and histological examination. Results: Through the cytotoxicity assay, we identified a significantly higher number of MC3T3-E1 cells in the 3D-printed specimen when compared to the machined specimen after 48 hours of culture. Moreover, morphometric analysis indicated significantly greater bone formation at week 12 on the side where rhBMP-2 was applied when evaluating the upper portion immediately below the ca p. Conclusion: The results suggest that 3D-printed titanium implant applied with rhBMP-2 enables new bone formation
STAT1 and Nmi are downstream targets of Ets-1 transcription factor in MCF-7 human breast cancer cell
AbstractEts-1 is a cellular homologue of the product of the viral ets oncogene of the E26 virus, and it functions as a tissue-specific transcription factor. It plays an important role in cell proliferation, differentiation, lymphoid cell development, transformation, angiogenesis, and apoptosis. Ets-1 controls the expression of critical genes involved in these processes by binding to ets binding sites present in the transcriptional regulatory regions. Here, we transiently overexpressed Ets-1 in MCF-7 and comprehensively searched for potential downstream targets of Ets-1 by cDNA microarray analysis. The expressions of several interferon-related genes including STAT1 and Nmi were augmented by the overexpression of Ets-1. RT-PCR and Western blotting confirmed the increase in the levels of STAT1 and Nmi mRNA and protein. In contrast, Ets-1 siRNA decreased the expression of STAT1 and Nmi proteins. As in our transient transfection experiments, stable overexpression of Ets-1, also increased the protein expression of STAT1 and Nmi in MCF-7 cells. Taken together, our results indicate that STAT1 and Nmi are downstream targets of Ets-1 in MCF-7 human breast cancer cells
Flg22-Triggered Immunity Negatively Regulates Key BR Biosynthetic Genes
In plants, activation of growth and activation of immunity are opposing processes that define a trade-off. In the past few years, the growth-promoting hormones brassinosteroids (BR) have emerged as negative regulators of pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI), promoting growth at the expense of defense. The crosstalk between BR and PTI signaling was described as negative and unidirectional, since activation of PTI does not affect several analyzed steps in the BR signaling pathway. In this work, we describe that activation of PTI by the bacterial PAMP flg22 results in the reduced expression of BR biosynthetic genes. This effect does not require BR perception or signaling, and occurs within 15 min of flg22 treatment. Since the described PTI-induced repression of gene expression may result in a reduction in BR biosynthesis, the crosstalk between PTI and BR could actually be negative and bidirectional, a possibility that should be taken into account when considering the interaction between these two pathways
Fabrication of a Microbial Biosensor Based on QD-MWNT Supports by a One-Step Radiation Reaction and Detection of Phenolic Compounds in Red Wines
An Acaligense sp.-immobilized biosensor was fabricated based on QD-MWNT composites as an electron transfer mediator and a microbe immobilization support by a one-step radiation reaction and used for sensing phenolic compounds in commercial red wines. First, a quantum dot-modified multi-wall carbon nanotube (QD-MWNT) composite was prepared in the presence of MWNT by a one-step radiation reaction in an aqueous solution at room temperature. The successful preparation of the QD-MWNT composite was confirmed by XPS, TEM, and elemental analysis. Second, the microbial biosensor was fabricated by immobilization of Acaligense sp. on the surface of the composite thin film of a glassy carbon (GC) electrode, which was prepared by a hand casting method with a mixture of the previously obtained composite and Nafion solution. The sensing ranges of the microbial biosensor based on CdS-MWNT and Cu2S-MWNT supports were 0.5â5.0 mM and 0.7â10 mM for phenol in a phosphate buffer solution, respectively. Total concentration of phenolic compounds contained in commercial red wines was also determined using the prepared microbial immobilized biosensor
Synthesis and Control of the Shell Thickness of Polyaniline and Polypyrrole Half Hollow Spheres Using the Polystyrene Cores
Polyaniline (Pani) and polypyrrole (Ppy) half hollow spheres with different shell thicknesses were successfully synthesized by three steps process using polystyrene (PS) as the core. The PS core was synthesized by emulsion polymerization. Aniline and pyrrole monomers were polymerized on the surface of the PS core. The shells of Pani and Ppy were fabricated by adding different amounts of aniline and pyrrole monomers. PS cores were dissolved and removed from the core shell structure by solvent extraction. The thicknesses of the Pani and Ppy half hollow spheres were observed by FE-SEM and FE-TEM. The chemical structures of the Pani and Ppy half hollow spheres were characterized by FT-IR spectroscopy and UV-Vis spectroscopy. The shell thicknesses of the Pani half hollow spheres were 30.2, 38.0, 42.2, 48.2, and 52.4ânm, while the shell thicknesses of the Ppy half hollow spheres were 16.0, 22.0, 27.0, and 34.0ânm. The shell thicknesses of Pani and Ppy half hollow spheres linearly increased as the amount of the monomer increased. Therefore, the shell thickness of the Pani and Ppy half hollow spheres can be controlled in these ranges
Gravitational Microlensing: A Tool for Detecting and Characterizing Free-Floating Planets
Various methods have been proposed to search for extrasolar planets. Compared
to the other methods, microlensing has unique applicabilities to the detections
of Earth-mass and free-floating planets. However, the microlensing method is
seriously flawed by the fact that the masses of the detected planets cannot be
uniquely determined. Recently, Gould, Gaudi, & Han introduced an observational
setup that enables one to resolve the mass degeneracy of the Earth-mass
planets. The setup requires a modest adjustment to the orbit of an already
proposed Microlensing planet-finder satellite combined with ground-based
observations. In this paper, we show that a similar observational setup can
also be used for the mass determinations of free-floating planets with masses
ranging from ~0.1 M_J to several Jupiter masses. If the proposed observational
setup is realized, the future lensing surveys will play important roles in the
studies of Earth-mass and free-floating planets, which are the populations of
planets that have not been previously probed.Comment: total 8 pages, including 3 figures, ApJ, in press (Mar 1, 2004
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