Highlights • CP−/− mice and mice that received FAC had high levels of brain iron. • Brain iron accumulation exacerbated TH-positive neurons apoptosis in MPTP-treated mice. • DFO reduced the neuronal ...damage in MPTP-treated CP−/− mice. • Increased oxidative stress was involved in cell apoptosis exacerbated by the increased brain iron.
Quantum phase transitions (QPTs) are usually associated with many-body systems in the thermodynamic limit when their ground states show abrupt changes at zero temperature with variation of a ...parameter in the Hamiltonian. Recently it has been realized that a QPT can also occur in a system composed of only a two-level atom and a single-mode bosonic field, described by the quantum Rabi model (QRM). Here we report an experimental demonstration of a QPT in the QRM using a
Yb
ion in a Paul trap. We measure the spin-up state population and the average phonon number of the ion as two order parameters and observe clear evidence of the phase transition via adiabatic tuning of the coupling between the ion and its spatial motion. An experimental probe of the phase transition in a fundamental quantum optics model without imposing the thermodynamic limit opens up a window for controlled study of QPTs and quantum critical phenomena.
Abstract
The origin, structure, and propagation characteristics of a switchback are compelling questions posed by Parker Solar Probe (PSP) observations of velocity spikes and magnetic field ...reversals. By assuming interchange reconnection between coronal loop and open magnetic field, we show that this results in the generation of upward (into the heliosphere) and downward complex structures propagating at the fast magnetosonic speed (i.e., the Alfvén speed in the low plasma beta corona) that can have an arbitrary radial magnetic field deflection, including “S-shaped.” We derive the evolution equation for the switchback radial magnetic field as it propagates through the inhomogeneous supersonic solar corona. An analytic solution for arbitrary initial conditions is used to investigate the properties of a switchback propagating from launch ∼6 to ∼35
R
⊙
where PSP observed switchbacks during its first encounter. We provide a detailed comparison to an example event, showing that the magnetic field and plasma solutions are in accord with PSP observations. For a simple single switchback, the model predicts either a single or a double-humped structure; the former corresponding to PSP observing either the main body or the flanks of the switchback. The clustering of switchbacks and their sometimes complicated structure may be due to the formation of multiple closely spaced switchbacks created by interchange reconnection with numerous open and loop magnetic field lines over a short period. We show that their evolution yields a complex, aggregated group of switchbacks that includes “sheaths” with large-amplitude radial magnetic field and velocity fluctuations.
Abstract
We propose a turbulence-driven solar wind model for a fast solar wind flow in an open coronal hole where the solar wind flow and the magnetic field are highly aligned. We compare the ...numerical results of our model with Parker Solar Probe measurements of the fast solar wind flow and find good agreement between them. We find that (1) the majority quasi-2D turbulence is mainly responsible for coronal heating, raising the temperature to about
K within a few solar radii, which leads in turn to the acceleration of the solar wind; (2) the heating rate due to quasi-2D turbulence near the coronal base is larger than that due to nearly incompressible/slab turbulence; (3) the quasi-2D energy in forward-propagating modes decreases with increasing distance, while the nearly incompressible/slab energy in forward-propagating modes increases, reaching a peak value at ∼11.7
before decreasing with increasing heliocentric distance; (4) the correlation length increases with increasing distance from the coronal base; and (5) the variance of the density fluctuations decreases as a function of heliocentric distance.
Abstract
We present the second release of value-added catalogues of the LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC DR2). The catalogues present values of radial velocity Vr, ...atmospheric parameters – effective temperature Teff, surface gravity log g, metallicity Fe/H, α-element to iron (metal) abundance ratio α/Fe (α/M), elemental abundances C/H and N/H and absolute magnitudes MV and $M_{K_{\rm s}}$ deduced from 1.8 million spectra of 1.4 million unique stars targeted by the LSS-GAC since 2011 September until 2014 June. The catalogues also give values of interstellar reddening, distance and orbital parameters determined with a variety of techniques, as well as proper motions and multiband photometry from the far-UV to the mid-IR collected from the literature and various surveys. Accuracies of radial velocities reach 5 km s−1 for the late-type stars, and those of distance estimates range between 10 and 30 per cent, depending on the spectral signal-to-noise ratios. Precisions of Fe/H, C/H and N/H estimates reach 0.1 dex, and those of α/Fe and α/M reach 0.05 dex. The large number of stars, the contiguous sky coverage, the simple yet non-trivial target selection function and the robust estimates of stellar radial velocities and atmospheric parameters, distances and elemental abundances make the catalogues a valuable data set to study the structure and evolution of the Galaxy, especially the solar-neighbourhood and the outer disc.
The 2D + slab superposition model of solar wind turbulence has its theoretical foundations in nearly incompressible magnetohydrodynamics (NI MHD) in the plasma beta ∼1 or <1 regimes. Solar wind ...turbulence measurements show that turbulence in the inertial range is anisotropic, for which the superposition model offers a plausible explanation. We provide a detailed theoretical analysis of the spectral characteristics of the Elsässer variables in the 2D + NI/slab model. We find that (1) the majority 2D component has a power spectrum in perpendicular wavenumber k ; (2) the strongly imbalanced minority NI/slab turbulence has power spectra and , where kz is aligned with the mean magnetic field; (3) NI/slab turbulence can exhibit a double-power-law spectrum, with the steeper part being G*(k) ∼ k−5/3 and corresponding to strong turbulence and the flatter spectrum satisfying G*(k) ∼ k−3/2 and corresponding to weak turbulence; (4) there is a critical balance regime for NI/slab turbulence that satisfies and ; and (5) the forward and backward Elsässer power spectra can have different spectral forms provided that the triple-correlation times for each are different. We use the spectral analysis to compute the total power spectra in frequency parallel to the solar wind flow for the superposition model, showing that strongly imbalanced turbulence yields an f−5/3 spectrum for all angles between the mean flow and magnetic field, and that double power laws are possible when the nonlinear and Alfvén timescales are both finite.
Recent studies of unusual or atypical energetic particle flux events (AEPEs) observed at 1 au show that another mechanism, different from diffusive shock acceleration, can energize particles locally ...in the solar wind. The mechanism proposed by Zank et al. is based on the stochastic energization of charged particles in regions filled with numerous small-scale magnetic islands (SMIs) dynamically contracting or merging and experiencing multiple magnetic reconnection in the super-Alfvénic solar wind flow. A first- and second-order Fermi mechanism results from compression-induced changes in the shape of SMIs and their developing dynamics. Charged particles can also be accelerated by the formation of antireconnection electric fields. Observations show that both processes often coexist in the solar wind. The occurrence of SMIs depends on the presence of strong current sheets like the heliospheric current sheet (HCS), and related AEPEs are found to occur within magnetic cavities formed by stream-stream, stream-HCS, or HCS-shock interactions that are filled with SMIs. Previous case studies comparing observations with theoretical predictions were qualitative. Here we present quantitative theoretical predictions of AEPEs based on several events, including a detailed analysis of the corresponding observations. The study illustrates the necessity of accounting for local processes of particle acceleration in the solar wind.
To evaluate a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and compare it with RT-PCR.
...We designed primers specific to the orf1ab and S genes of SARS-CoV-2. Total viral RNA was extracted using the QIAamp Viral RNA Mini Kit. We optimized the RT-LAMP assay, and evaluated it for its sensitivity and specificity of detection using real-time turbidity monitoring and visual observation.
The primer sets orf1ab-4 and S-123 amplified the genes in the shortest times, the mean (±SD) times were 18 ± 1.32 min and 20 ± 1.80 min, respectively, and 63°C was the optimum reaction temperature. The sensitivities were 2 × 101 copies and 2 × 102 copies per reaction with primer sets orf1ab-4 and S-123, respectively. This assay showed no cross-reactivity with 60 other respiratory pathogens. To describe the availability of this method in clinical diagnosis, we collected 130 specimens from patients with clinically suspected SARS-CoV-2 infection. Among them, 58 were confirmed to be positive and 72 were negative by RT-LAMP. The sensitivity was 100% (95% CI 92.3%–100%), specificity 100% (95% CI 93.7%–100%). This assay detected SARS-CoV-2 in a mean (±SD) time of 26.28 ± 4.48 min and the results can be identified with visual observation.
These results demonstrate that we developed a rapid, simple, specific and sensitive RT-LAMP assay for SARS-CoV-2 detection among clinical samples. It will be a powerful tool for SARS-CoV-2 identification, and for monitoring suspected patients, close contacts and high-risk groups.
We present X-ray timing results of the new black hole candidate MAXI J1535−571 during its 2017 outburst from Hard X-ray Modulation Telescope (Insight-HXMT) observations taken from 2017 September 6 to ...23. Following the definitions given by Belloni, we find that the source exhibits transitions from the low/hard state to the hard intermediate state, and eventually to the soft intermediate state. Quasi-periodic oscillations (QPOs) are found in the intermediate states, which suggest different types of QPOs. With the large effective area of Insight-HXMT at high energies, we are able to present the energy dependence of the QPO amplitude and centroid frequency up to 100 keV, which has rarely been explored by previous satellites. We also find that the phase lag at the type-C QPOs centroid frequency is negative (soft lag) and strongly correlated with the centroid frequency. Assuming a geometrical origin of type-C QPOs, the source is consistent with being a high-inclination system.
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