Abstract
The GJ 1148 system has two Saturn-mass planets orbiting around an M dwarf star on hierarchical and eccentric orbits, with orbital period ratio of 13 and eccentricities of both planets of ...0.375. The inner planet is in the regime of eccentric warm Jupiters. We perform numerical experiments to study the planet–planet scattering scenario for the origin of this orbital architecture. We consider a third planet of 0.1
M
J
(Jupiter's mass) in the initial GJ 1148 system with initial orbital separations of 3.5, 4, and 4.5 mutual Hill radii and initial semimajor axis of the innermost planet in the range of 0.10–0.50 au. The majority of scattering results in planet–planet collisions, followed by planet ejections, and planet–star close approaches. Among them, only planet ejections produce eccentric and widely separated two-planet systems, with some having similar orbital properties to the GJ 1148 system. We also examine the effects of general relativistic apsidal precession and a higher mass of 0.227
M
J
for the third planet. The simulation results suggest that the GJ 1148 system may have lost a giant planet. We also perform simulations of the general problem of the origin of warm Jupiters by planet–planet scattering. As in the GJ 1148 simulations, a nontrivial number of stable two-planet systems are produced by ejection, which disagrees with the result from a previous study showing that two-planet systems arise exclusively through planet–planet collisions.
Abstract
An increasing number of compact planetary systems with multiple planets in a resonant chain have been detected. The resonant chain must be maintained by convergent migration of the planets ...due to planet–disk interactions if it is formed before the dispersal of the protoplanetary gas disk. For type I migration in an adiabatic disk, we show that an analytic criterion for convergent migration can be developed by requiring that any part of the resonant chain should be convergently migrating toward the remaining part. The criterion depends primarily on the logarithmic gradients
α
and
β
of the surface density and temperature profiles of the disk, respectively, and it is independent of the absolute values of the surface density and temperature. The analytic criterion is applied to the Kepler-60, Kepler-80, Kepler-223, TOI-178, and TRAPPIST-1 systems. Due to the variation of planetary masses within the resonant chains, we find that convergent migration typically requires rather extreme values of (
α
,
β
) that have little or no overlap with common disk models. Finally, we show that there is an empirical relationship between the distance of the innermost planet from the central star and the stellar mass for the observed resonant chain systems, which supports the idea that the resonant chains are formed and maintained by stalling the migration of the innermost planet near the inner edge of the disk truncated by the magnetic fields of the protostar.
The aim of the present study was to assess the neuroprotective effects of pinostrobin (PSB), a dietary bioflavonoid, and its underlying mechanisms in neurotoxin-induced Parkinson’s disease (PD) ...models. First, PSB could attenuate 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced loss of dopaminergic neurons and improve behavior deficiency in zebrafish, supporting its potential neuroprotective actions in vivo. Next, PSB could decreased apoptosis and death in the 1-methyl-4-phenylpyridinium (MPP+)-intoxicated SH-SY5Y cells, evidenced by MTT, LDH, Annexin V-FITC/PI, and DNA fragmentation assay. PSB also blocked MPP+-induced apoptotic cascades, including loss of mitochondrial membrane potential, activation of caspase 3, and reduced ratio of Bcl-2/Bax. In addition, PSB suppressed MPP+-induced oxidative stress but increased antioxidant enzymes, evidenced by decrease of reactive oxygen species generation and lipid peroxidation and up-regulation of GSH-Px, SOD, CAT, GSH/GSSG, and NAD/NADH. Further investigations showed that PSB significantly enhanced Nrf2 expression and nuclear accumulation, improved ARE promoter activity and up-regulated expression of HO-1 and GCLC. Furthermore, Nrf2 knockdown via specific Nrf2 siRNA abolished PSB-induced antioxidative and antiapoptotic effects against MPP+ insults. Interestingly, we then found that PSB promoted phosphorylation of PI3K/AKT and ERK, and pharmacological inhibition of PI3K/AKT or ERK signaling diminished PSB-induced Nrf2/ARE activation and protective actions. In summary, PSB confers neuroprotection against MPTP/MPP+-induced neurotoxicity in PD models. Promoting activation of Nrf2/ARE signaling contributes to PSB-mediated antioxidative and neuroprotective actions, which, in part, is mediated by PI3K/AKT and ERK.
The formation of Pluto's small satellites-Styx, Nix, Keberos, and Hydra-remains a mystery. Their orbits are nearly circular and are near mean-motion resonances and nearly coplanar with Charon's ...orbit. One scenario suggests that they all formed close to their current locations from a disk of debris that was ejected from the Charon-forming impact before the tidal evolution of Charon. The validity of this scenario is tested by performing N-body simulations with the small satellites treated as test particles and Pluto-Charon evolving tidally from an initial orbit at a few Pluto radii with initial eccentricity eC = 0 or 0.2. After tidal evolution, the free eccentricities efree of the test particles are extracted by applying fast Fourier transformation to the distance between the test particles and the center of mass of the system and compared with the current eccentricities of the four small satellites. The only surviving test particles with efree matching the eccentricities of the current satellites are those not affected by mean-motion resonances during the tidal evolution in a model with Pluto's effective tidal dissipation function Q = 100 and an initial eC = 0.2 that is damped down rapidly. However, these test particles do not have any preference to be in or near 4:1, 5:1, and 6:1 resonances with Charon. An alternative scenario may be needed to explain the formation of Pluto's small satellites.
Background/Aims: In the present study, we investigated whether schisantherin A (StA) had anti-inflammatory effects under neuroinflammatory conditions. Methods: The effects of StA and its underlying ...mechanisms were examined in lipopolysaccharide (LPS)-activated BV-2 microglial cells by ELISA, qPCR, EMSA, Western blot, and IHC. Results: Firstly, we found that StA inhibited the inflammatory response in LPS-activated BV-2 microglia. Secondly, we found that StA suppressed LPS-induced activation of NF-κB via interfering with degradation of IκB and phosphorylation of IκB, IKK, PI3K/Akt, JNK, and p38 MAPK. Thirdly, StA conferred indirect antioxidative effects via quenching ROS and promoted expression of antioxidant enzymes, including HO-1 and NQO-1, via stimulating activation of Nrf2 pathways. Finally, we demonstrated that anti-neuroinflammatory actions of StA were dependent on ERK phosphorylation-mediated Nrf2 activation. Conclusion: StA induced ERK phosphorylation-mediated Nrf2 activation, which contributed to its anti-inflammation and anti-oxidation. The anti-neuroinflammatory and anti-oxidative effects of StA may show preventive therapeutic potential for various neuroinflammatory disorders.
Abstract
For grain growth to proceed effectively and lead to planet formation, a number of barriers to growth must be overcome. One such barrier, relevant for compact grains in the inner regions of ...the disc, is the ‘bouncing barrier’ in which large grains (∼mm size) tend to bounce off each other rather than sticking. However, by maintaining a population of small grains, it has been suggested that cm-size particles may grow rapidly by sweeping up these small grains. We present the first numerically resolved investigation into the conditions under which grains may be lucky enough to grow beyond the bouncing barrier by a series of rare collisions leading to growth (so-called ‘breakthrough’). Our models support previous results, and show that in simple models breakthrough requires the mass ratio at which high-velocity collisions transition to growth instead of causing fragmentation to be low, ϕ ≲ 50. However, in models that take into account the dependence of the fragmentation threshold on mass ratio, we find that breakthrough occurs more readily, even if mass transfer is relatively inefficient. This suggests that bouncing may only slow down growth, rather than preventing growth beyond a threshold barrier. However, even when growth beyond the bouncing barrier is possible, radial drift will usually prevent growth to arbitrarily large sizes.
We present a detailed orbital and stability analysis of the HD 59686 binary-star planet system. HD 59686 is a single-lined, moderately close (aB = 13.6 au) eccentric (eB = 0.73) binary, where the ...primary is an evolved K giant with mass M = 1.9 M and the secondary is a star with a minimum mass of mB = 0.53 M . Additionally, on the basis of precise radial velocity (RV) data, a Jovian planet with a minimum mass of mp = 7 MJup, orbiting the primary on a nearly circular S-type orbit with ep = 0.05 and ap = 1.09 au, has recently been announced. We investigate large sets of orbital fits consistent with HD 59686's RV data by applying bootstrap and systematic grid search techniques coupled with self-consistent dynamical fitting. We perform long-term dynamical integrations of these fits to constrain the permitted orbital configurations. We find that if the binary and the planet in this system have prograde and aligned coplanar orbits, there are narrow regions of stable orbital solutions locked in a secular apsidal alignment with the angle between the periapses, Δ , librating about 0°. We also test a large number of mutually inclined dynamical models in an attempt to constrain the three-dimensional orbital architecture. We find that for nearly coplanar and retrograde orbits with mutual inclination 145° Δi ≤ 180°, the system is fully stable for a large range of orbital solutions.
•Danshensu could up-regulate the HO-1 expression via activation of PI3K/Akt/Nrf2 signaling pathways.•Danshensu suppressed 6-OHDA-induced oxidative stress in vitro in PC12 cells.•Danshensu protected ...against 6-hydroxydopamine-induced damage of dopaminergic neurons in zebrafish model.
The overproduction of reactive oxygen species (ROS) has been implicated in the development of neurodegenerative diseases such as Parkinson's disease (PD) and Alzheimer's disease (AD). Previous studies have indicated that danshensu (beta-3,4-dihydroxyphenyl-lactic acid), a main hydrophilic component of the Chinese materia medica Radix Salviae Miltiorrhizae (Danshen, Pharmacopoeia of PR China), has ROS scavenging and antioxidant activities, however its mechanism of action was not clear. In this study, we investigated whether the protective effects of danshensu against neurotoxin 6-hydroxydopamine (6-OHDA)-induced oxidative stress involved the Nrf2/HO-1 pathways. Pretreatment with danshensu in PC12 cells significantly attenuated 6-OHDA-induced cytotoxicity and the production of ROS. Danshensu activated the nuclear translocation of Nrf2 to increase heme oxygenase-1 (HO-1), conferring protection against ROS. Danshensu induced the phosphorylation of Akt, and its cytoprotective effect was abolished by PI3K, Akt and HO-1 inhibitors. These results confirmed the crucial role of PI3K/Akt and HO-1 signaling pathways as the underlying mechanistic action of danshensu. Taken together, the results suggest that danshensu enhances HO-1 expression to suppress 6-OHDA-induced oxidative damage via PI3K/Akt/Nrf2 signaling pathways. Moreover, 6-OHDA-induced dopaminergic neuronal loss in zebrafish could be reduced by danshensu, further supporting the neuroprotective potential of danshensu.
Abstract The K-type star TOI-2525 has an estimated mass of M = 0.849 − 0.033 + 0.024 M ⊙ and radius of R = 0.785 − 0.007 + 0.007 R ⊙ observed by the TESS mission in 22 sectors (within sectors 1 and ...39). The TESS light curves yield significant transit events of two companions, which show strong transit timing variations (TTVs) with a semiamplitude of ∼6 hr. We performed TTV dynamical and photodynamical light-curve analysis of the TESS data combined with radial velocity measurements from FEROS and PFS, and we confirmed the planetary nature of these companions. The TOI-2525 system consists of a transiting pair of planets comparable to Neptune and Jupiter with estimated dynamical masses of m b = 0.088 − 0.004 + 0.005 and m c = 0.709 − 0.033 + 0.034 M Jup , radii of r b = 0.88 − 0.02 + 0.02 and r c = 0.98 − 0.02 + 0.02 R Jup , and orbital periods of P b = 23.288 − 0.002 + 0.001 and P c = 49.260 − 0.001 + 0.001 days for the inner and outer planet, respectively. The period ratio is close to the 2:1 period commensurability, but the dynamical simulations of the system suggest that it is outside the mean-motion resonance (MMR) dynamical configuration. Object TOI-2525 b is among the lowest-density Neptune-mass planets known to date, with an estimated median density of ρ b = 0.174 − 0.015 + 0.016 g cm −3 . The TOI-2525 system is very similar to the other K dwarf systems discovered by TESS, TOI-2202 and TOI-216, which are composed of almost identical K dwarf primaries and two warm giant planets near the 2:1 MMR.
While it has been argued that children with autism spectrum disorders are responsive to robot-like toys, very little research has examined the impact of robot-based intervention on gesture use. These ...children have delayed gestural development. We used a social robot in two phases to teach them to recognize and produce eight pantomime gestures that expressed feelings and needs. Compared to the children in the wait-list control group (N = 6), those in the intervention group (N = 7) were more likely to recognize gestures and to gesture accurately in trained and untrained scenarios. They also generalized the acquired recognition (but not production) skills to human-to-human interaction. The benefits and limitations of robot-based intervention for gestural learning were highlighted.
Implications for Rehabilitation
Compared to typically-developing children, children with autism spectrum disorders have delayed development of gesture comprehension and production.
Robot-based intervention program was developed to teach children with autism spectrum disorders recognition (Phase I) and production (Phase II) of eight pantomime gestures that expressed feelings and needs.
Children in the intervention group (but not in the wait-list control group) were able to recognize more gestures in both trained and untrained scenarios and generalize the acquired gestural recognition skills to human-to-human interaction.
Similar findings were reported for gestural production except that there was no strong evidence showing children in the intervention group could produce gestures accurately in human-to-human interaction.
PDF
