Jupiter's tenuous dust ring system is embedded in the planet's inner magnetosphere, and—among other structures—contains a very tenuous protrusion called the Thebe extension. In an attempt to explain ...the existence of this swath of particles beyond Thebe's orbit, Hamilton and Krüger (2008), https://doi.org/10.1038/nature06886 proposed that the dust particle motion is driven by a shadow resonance caused by variable dust charging on the day and night side of Jupiter. However, the model by Divine and Garrett (1983), https://doi.org/10.1029/ja088ia09p06889 together with recent observations by the Juno spacecraft indicates a warm and rather dense inner magnetosphere of Jupiter which implies that the mechanism of the shadow resonance does not work. Instead, we argue that dust grains ejected from Thebe due to micrometeoroid bombardment become the source of dust in the Thebe extension. We show that large (grain radii of a few micrometers up to multi‐micrometers) charged dust grains having significant initial velocities oscillate in the Thebe extension. Smaller charged grains (with sub‐micrometer radii) ejected from Thebe do not spend much time in the Thebe extension and migrate into the Thebe ring. At the same time, if such grains are ejected from larger dust grains in the Thebe extension due to fragmentation, they continue to oscillate within the Thebe extension for years. We argue that fragmentation of large dust grains in the Thebe extensions could be the main source of sub‐micrometer grains detected in the Thebe extension.
Key Points
In Jupiter's warm and dense inner magnetosphere dust grains acquire high negative electric charges
Dust particles ejected from Thebe with sufficient speeds contribute to the formation of the Thebe extension
Instead of shadow resonances as suggested earlier an alternative mechanism is suggested for the formation of the Thebe extension
We investigate the dynamics of dust grains in the Jupiter’s gossamer rings assuming that plasma in the inner magnetosphere is rather warm and dense in accordance with the Divine model. It is shown ...that the well-known mechanism of the shadow resonances attracted previously for the explanation of the gossamer rings formation does not work in the case of warm and dense plasma. Instead two-stage dust delivery together with the dynamics of large and small charged dust grains in the electric and magnetic fields can be responsible for the formation of the Jupiter’s gossamer rings. The suggested mechanism is fast. Large grains released from the surface of the moon (Thebe or Amalthea) provide sufficient radial broadening of dust distribution in one period of their rotation. Possibly some of them are subjected to electrical disruption supplying the gossamer rings with tiny grains.
On accretion in the eclipsing polar BS Tri Kolbin, Alexander I; Borisov, N V; Serebriakova, N A ...
Monthly notices of the Royal Astronomical Society,
02/2022, Letnik:
511, Številka:
1
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
We analyse spectroscopic and photometric observations of the eclipsing polar BS Tri. The polar’s light-curve-shape variations can be interpreted by changing contributions of the accretion ...stream to the integral radiation of the system. Based on the radial-velocity curves of the irradiated part of the secondary, we refine the masses of the system components, M1 = 0.60 ± 0.04 M⊙ and M2 ≈ 0.12 M⊙, and the orbital inclination, i = 85 ± 0.5°. The polar’s spectra reveal cyclotron harmonics forming in an accretion spot with a magnetic field strength of B = 22.7 ± 0.4 MG and an average temperature of T ∼ 10 keV. In addition to the cyclotron harmonics, the BS Tri spectra contain Zeeman components of H α line, which are probably formed in the cool halo near the accretion spot. The orientation of the magnetic dipole and the coordinates of the accretion spot are estimated by modelling the light curves of the polar. We show that for a satisfactory description of the BS Tri light curves we have to take into account the variability of the spot’s optical depth along the line of sight. Doppler maps of BS Tri show a part of the accretion stream with a trajectory close to ballistic near the Lagrange point L1, and another part of the stream moving along the magnetic field lines. The estimate of the stagnation region position found from the Doppler tomograms is consistent with the photometric estimates of the accretion spot position.
Abstract
Context
Metabolic dysfunction–associated fatty liver disease (MAFLD) is highly prevalent among patients with type 2 diabetes mellitus (T2DM); however, there is still no approved ...pharmacological treatment. Sodium-glucose cotransporter 2 (SGLT-2) inhibitors have been suggested to beneficially modify liver-related outcomes in patients with diabetes.
Objective
We aimed to investigate the effects of the SGLT-2 inhibitor canagliflozin on liver-related outcomes in patients with advanced T2DM and high cardiovascular risk.
Methods
We performed a secondary post hoc analysis of 2 large double-blind randomized controlled trials, CANVAS (NCT01032629) and CANVAS-R (NCT01989754), which included patients with T2DM and high cardiovascular risk who were randomized to receive either canagliflozin or placebo once daily. The primary endpoint was a composite of improvement of alanine aminotransferase (ALT) levels >30% or normalization of ALT levels. Secondary endpoints included change in noninvasive tests of fibrosis and weight reduction of >10%.
Results
In total, 10 131 patients were included, with a median follow-up of 2.4 years (mean age 62 years; mean duration of diabetes 13.5 years; 64.2% male). Of those patients, 8967 (88.5%) had MAFLD according to hepatic steatosis index and 2599 (25.7%) exhibited elevated liver biochemistry at baseline. The primary composite endpoint occurred in 35.2% of patients receiving canagliflozin and in 26.4% with placebo (adjusted odds ratio aOR 1.51; 95% CI, 1.38-1.64; P < .001). Canagliflozin led to improvements in some noninvasive tests of fibrosis (NFS, APRI, FNI). Significant weight reduction of >10% (within 6 years) was achieved in 12.7% with canagliflozin compared to 4.1% with placebo (aOR 3.45; 95% CI, 2.91-4.10; P < .001).
Conclusion
In patients with T2DM, treatment with canagliflozin vs placebo resulted in improvements in liver biochemistry and metabolism and might beneficially affect liver fibrosis.
Here we present the spectropolarimetric observations of the radio-loud active galaxy 3C 390.3 in the period 2009–2014 (24 epochs). The galaxy has been observed with the 6-m telescope of Special ...Astrophysical Observatory of the Russian Academy of Science (SAO RAS) using the Spectral Camera with Optical Reducer for Photometric and Interferometric Observations (SCORPIO) spectropolarimeter. We explore the variability and lags in the polarized light of the continuum and broad Hα line. We give the Stokes parameters Q, U, degree of linear polarization P and the position angle of the polarization plane, φ, for 24 epochs.
We find a small lag (10–40 d) between the unpolarized and polarized continuum that is significantly smaller than the estimated lags for the unpolarized broad emission lines (lag(Hα) ∼ 138–186 and lag(Hβ) ∼ 60–79 d). This shows that the region of the variable polarized continuum is significantly smaller than the broad line region, indicating that a part of the polarized continuum is coming from the jet. The lag of the polarized light in the Hα line (89–156 d) indicates an additional component to the disc one that has an outflowing velocity of ∼− 1200 km s−1. This region seems to depolarize the polarized broad Hα line emitted from the disc and scattered in the inner part of the torus.
The low thermal conductivity of paraffin and other organic phase change materials limits their use in thermal energy storage devices. The introduction of components with a high thermal conductivity ...such as graphene into these materials leads to an increase in their thermal conductivity. In this work, we studied the use of inexpensive carbon fillers containing a polycyclic aromatic core, due to them having a structural similarity with graphene, to increase the thermal conductivity of paraffin. As such fillers, technogenic asphaltenes isolated from ethylene tar and their modified derivatives were used. It is shown that the optimal concentration of carbon fillers in the paraffin composite, which contributes to the formation of a structural framework and resistance to sedimentation, is 5 and 30 wt. %, while intermediate concentrations are ineffective, apparently due to the formation of large aggregates, the concentration of which is insufficient to form a strong framework. It has been found that the addition of asphaltenes modified with ammonium persulfate in acetic acid significantly increases the thermal conductivity of paraffin by up to 72%.
The double polarization observable E and the helicity dependent cross sections σ_{1/2} and σ_{3/2} were measured for η photoproduction from quasifree protons and neutrons. The circularly polarized ...tagged photon beam of the A2 experiment at the Mainz MAMI accelerator was used in combination with a longitudinally polarized deuterated butanol target. The almost 4π detector setup of the Crystal Ball and TAPS is ideally suited to detect the recoil nucleons and the decay photons from η→2γ and η→3π^{0}. The results show that the narrow structure previously observed in η photoproduction from the neutron is only apparent in σ_{1/2} and hence, most likely related to a spin-1/2 amplitude. Nucleon resonances that contribute to this partial wave in η production are only N 1/2^{-} (S_{11}) and N 1/2^{+} (P_{11}). Furthermore, the extracted Legendre coefficients of the angular distributions for σ_{1/2} are in good agreement with recent reaction model predictions assuming a narrow resonance in the P_{11} wave as the origin of this structure.
Here, we present an analysis of spectropolarimetric observations of type 1.5 AGN Mrk 6, performed with 6 m telescope of the Special Astrophysical Observatory of Russian Academy of Science in 12 ...epochs (2010-2013). Additionally, the interstellar matter (ISM) polarization has been observed and its contribution to the AGN spectral polarization is taken into account. We measured Stokes parameters and determined the polarization parameters in 12 spectra with and without correction for the ISM polarization. We estimated the time lag between the unpolarized and polarized continuum flux variation of about ∼2 d, which indicates a compact scattering region which contributes to the polarized continuum variability. The polarization in Hα is complex, showing three prominent components in the broad-line region (BLR), one redshifted around +3000 km s−1 that corresponds to the red shoulder in Hα and two blueshifted around −2000 km s−1 and −6000 km s−1. We found that the ISM polarization has a very significant influence on the measured AGN polarization parameters. After correcting the observations for the ISM polarization, we were able to detect the Keplerian motion in the BLR. We give a new method for the black hole mass estimation using spectropolarimetric observation in the line profile, finding the black hole mass in Mrk 6 of M
BH ∼ 1.53 × 108 M, which is in good agreement with reverberation estimates.
We discuss theoretically the excitation of artificial plasma irregularities in the auroral ionosphere by high‐frequency X‐mode radio wave. This is done via a two‐step process. As a first step we ...adopt the thermal self‐focusing instability excited in the F region of the ionosphere under the action of a strong high‐frequency (HF) radio wave. This instability causes the formation of perturbations of the electron temperature and plasma concentration across the magnetic field. In addition, the plasma becomes depleted in the regions of the electron temperature enhancements and vice versa, since the gradients of plasma concentration and the electron temperature have opposite signs. In such conditions the temperature gradient instability comes into play. As a second step we consider plasma and electron temperature inhomogeneities that appear due to this instability to be responsible for the generation of irregularities with transverse sizes smaller than the typical scales of the self‐focusing instability. Alternative mechanisms such as excitation of the gradient‐drift and the current‐convective instabilities, which are often attributed to the generation of plasma irregularities in the F region and can contribute to the formation of artificial irregularities in the case of X‐mode heating, are also discussed.
Key Points
We have investigated F region irregularities produced by high power HF X‐mode radio waves
Plasma instabilities responsible for decametric irregularities in the F region are described via a two‐step process
Our theoretical characteristic time for development of decametric irregularities is of the order of 1 min
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