346 research outputs found
Dust ring and gap formation by gas flow induced by low-mass planets embedded in protoplanetary disks . Steady-state model
Recent high-spatial-resolution observations have revealed dust substructures
in protoplanetary disks such as rings and gaps, which do not always correlate
with gas. Because radial gas flow induced by low-mass, non-gas-gap-opening
planets could affect the radial drift of dust, it potentially forms these dust
substructures in disks. We investigate the potential of gas flow induced by
low-mass planets to sculpt the rings and gaps in the dust profiles. We first
perform three-dimensional hydrodynamical simulations, which resolve the local
gas flow past a planet. We then calculate the trajectories of dust influenced
by the planet-induced gas flow. Finally, we compute the steady-state dust
surface density by incorporating the influences of the planet-induced gas flow
into a one-dimensional dust advection-diffusion model. The outflow of the gas
toward the outside of the planetary orbit inhibits the radial drift of dust,
leading to dust accumulation (the dust ring). The outflow toward the inside of
the planetary orbit enhances the inward drift of dust, causing dust depletion
around the planetary orbit (the dust gap). Under weak turbulence (, where is the turbulence strength
parameter), the gas flow induced by the planet with
(Earth mass) generates the dust ring and gap in the distribution of small dust
grains ( cm) with the radial extent of times gas
scale height around the planetary orbit without creating a gas gap and pressure
bump. The gas flow induced by low-mass, non-gas-gap-opening planets can be
considered a possible origin of the observed dust substructures in disks. Our
results may be helpful to explain the disks whose dust substructures were found
not to correlate with those of the gas.Comment: 25 pages, 20 figures, Accepted for publication in Astronomy and
Astrophysics (A&A
Statistical Mechanics of Self--Gravitating System : Cluster Expansion Method
We study statistical mechanics of the self--gravitating system applying the
cluster expansion method developed in solid state physics. By summing infinite
series of diagrams, we derive a complex free energy whose imaginary part is
related to the relaxation time of the system. Summation of another series
yields two--point correlation function whose correlation length is essentially
given by the Jeans wavelength of the system.Comment: 4 pages including 2 eps figures, RevTe
Effects of culture on PAMPS/PDMAAm double-network gel on chondrogenic differentiation of mouse C3H10T1/2 cells: in vitro experimental study
BACKGROUND: Recently, several animal studies have found that spontaneous hyaline cartilage regeneration can be induced in vivo within a large osteochondral defect by implanting a synthetic double-network (DN) hydrogel, which is composed of poly-(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) and poly-(N,N’-dimethyl acrylamide) (PDMAAm), at the bottom of the defect. However, the effect of hydrogel on hyaline cartilage regeneration remains unexplained. The purpose of this study was to investigate the chondrogenic differentiation of C3H10T1/2 cells on PAMPS/PDMAAm DN gel. METHODS: C3H10T1/2 cells of 1.0 × 10(5) were cultured on PAMPS/PDMAAm DN gel in polystyrene tissue culture dishes or directly on polystyrene tissue culture dishes. We compared cultured cells on PAMPS/PDMAAm DN gel with those on polystyrene dishes by morphology using phase-contrast microscopy, mRNA expression of aggrecan, type I collagen, type II collagen, Sox 9 and osteocalcin using real-time RT-PCR, and local expression of type II collagen using immunocytochemistry. RESULTS: C3H10T1/2 cells cultured on the PAMPS/PDMAAm DN gels formed focal adhesions, aggregated rapidly and developed into large nodules within 7 days, while the cells cultured on the polystyrene surface did not. The mRNA levels of aggrecan, type I collagen, type II collagen, Sox 9 and osteocalcin were significantly greater in cells cultured on the PAMPS/PDMAAm DN gel than in those cultured on polystyrene dishes. In addition, C3H10T1/2 cells cultured on PAMPS/PDMAAm DN gel expressed more type II collagen at the protein level when compared with cells cultured on polystyrene dishes. CONCLUSIONS: The present study showed that PAMPS/PDMAAm DN gel enhanced chondrogenesis of C3H10T1/2 cells, which are functionally similar to mesenchymal stem cells. This suggests that mesenchymal stem cells from the bone marrow contribute to spontaneous hyaline cartilage regeneration in vivo in large osteochondral defects after implantation of PAMPS/PDMAAm DN gels. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/1471-2474-15-320) contains supplementary material, which is available to authorized users
Double-Network Hydrogels Strongly Bondable to Bones by Spontaneous Osteogenesis Penetration
Implanting hydroxyapatite-mineralized tough hydrogel into osteochondral defects of rabbits, osteogenesis spontaneously penetrates into the gel matrix owing to the semi-permeablility of the hydrogel. The gradient layer (around 40 μm thick) contributes quite strong bonding of the gel to bone. This is the first success in realizing the robust osteointegration of tough hydrogels, and the method is simple and feasible for practical use
The nucleotide and deduced amino acid sequences of porcine liver proline-β-naphthylamidase swEvidence for the identity with carboxylesterase
AbstractA cDNA clone for porcine liver proline-β-naphthylamidase was isolated and sequenced. The deduced amino acid sequence of 567 residues was highly homologous with those of carboxylesterases (EC 3.1.1.1) previously reported for other species. In addition, proline-β-naphthylamidase purified from porcine liver was shown to have strong activity towards p-nitrophenylacetate, a representative substrate for carboxylesterases. These results suggest that proline-β-naphthylamidase is identical with carboxylesterase
Low-power display system enabled by combining oxide semiconductor and neural network technologies
An oxide semiconductor (OS)-based field effect transistor (OSFET) exhibits the advantage of having an extremely low off-state current; moreover, the OSFET displays an off-state current that is ten orders of magnitude lower than that of a CMOS-FET [1]. Recently, numerous applications that harness this feature have been reported [2]. For instance, charge leakage from a data retention node of a pixel significantly decreases when the display incorporates OSFETs in its pixel circuit (OS display) [3, 4]. This minimizes degradation in the image quality when the displayed image is static despite using lower refresh rates. Consequently, the consumed power of the display driver circuit can be reduced by a large margin. This driving method is termed idling stop (IDS) driving. The OSFET’s low-leakage can also effectively enable a type of ULSICs that we term OS-large-scale integrated circuits (OSLSI) [5, 6].
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Evidence for Spin–Orbit Alignment in the TRAPPIST-1 System
In an effort to measure the Rossiter–McLaughlin effect for the TRAPPIST-1 system, we performed high-resolution spectroscopy during transits of planets e, f, and b. The spectra were obtained with the InfraRed Doppler spectrograph on the Subaru 8.2 m telescope, and were supplemented with simultaneous photometry obtained with a 1 m telescope of the Las Cumbres Observatory Global Telescope. By analyzing the anomalous radial velocities, we found the projected stellar obliquity to be λ = 1 ± 28° under the assumption that the three planets have coplanar orbits, although we caution that the radial-velocity data show correlated noise of unknown origin. We also sought evidence for the expected deformations of the stellar absorption lines, and thereby detected the "Doppler shadow" of planet b with a false-alarm probability of 1.7%. The joint analysis of the observed residual cross-correlation map including the three transits gave λ = 19_(-15)^(+13)°. These results indicate that the the TRAPPIST-1 star is not strongly misaligned with the common orbital plane of the planets, although further observations are encouraged to verify this conclusion
Planet(esimal)s Around Stars with TESS (PAST) III: A Search for Triplet He I in the Atmospheres of Two 200 Myr-old Planets
We report a search for excess absorption in the 1083.2 nm line of ortho
(triplet) helium during transits of TOI-1807b and TOI-2076b, 1.25 and
2.5R planets on 0.55- and 10.4-day orbits around nearby
200~Myr-old K dwarf stars. We limit the equivalent width of any
transit-associated absorption to 4 and 8 mA, respectively. We limit the
escape of solar-composition atmospheres from TOI-1807b and TOI-2076b to
1 and 0.1M Gyr, respectively,
depending on wind temperature. The absence of a H/He signature for TOI-1807b is
consistent with a measurement of mass indicating a rocky body and the
prediction by a hydrodynamic model that any H-dominated atmosphere would be
unstable and already have been lost. Differential spectra obtained during the
transit of TOI-2076b contain a He I-like feature, but this closely resembles
the stellar line and extends beyond the transit interval. Until additional
transits are observed, we suspect this to be the result of variation in the
stellar He I line produced by rotation of active regions and/or flaring on the
young, active host star. Non-detection of escape could mean that TOI-2076b is
more massive than expected, the star is less EUV-luminous, the models
overestimate escape, or the planet has a H/He-poor atmosphere that is primarily
molecules such as HO. Photochemical models of planetary winds predict a
semi-major axis at which triplet He I observations are most sensitive to mass
loss: TOI-2076b orbits near this optimum. Future surveys could use a distance
criterion to increase the yield of detections.Comment: Accepted to MNRA
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