Axial uniformity diagnosis of coaxial surface wave linear plasma by optical emission spectroscopy

The coaxial surface wave linear plasma with preeminent axial uniformity is developed with the 2.45 GHz microwave generator. By optical emission spectroscopy, parameters of the argon linear plasma with a length over 600 mm are diagnosed under gas pressure of 30 Pa and 50 Pa and different microwave powers. The spectral lines of argon and Hβ (486.1 nm) atoms in excited state are observed for estimating electron excitation temperature and electron density. Spectrum bands in 305–310 nm of diatomic OH (A2 Σ+-X2 Πi) radicals are used to determine the molecule rotational temperature. Finally, the axial uniformity of electron density and electron excitation temperature are analyzed emphatically under various conditions. The results prove the distinct optimization of compensation from dual powers input, which can narrow the uniform coefficient of electron density and electron excitation temperature by around 40% and 22% respectively. With the microwave power increasing, the axial uniformity of both electron density and electron excitation temperature performs better. Nevertheless, the fluctuation of electron density along the axial direction appeared with higher gas pressure. The axial uniformity of coaxial surface wave linear plasma could be controlled by pressure and power for a better utilization in material processing.

Characteristic Analysis of Dual-Polarization Weather Radar Echoes of Convective Precipitation and Snowfall in the Mount Everest Region

This paper introduces the X-band weather radar dual-polarization parameters of isolated convective cell precipitation and meso/microscale snowfall on Mount Everest and presents the first precipitation observations based on dual-polarization weather radar in this area. Compared with the Chengdu Plain, Mount Everest experienced convective precipitation on smaller horizontal and vertical scales with a narrower Zdr probability density spectrum (uniformly distributed around approximately 0). The Zh profile on Mount Everest displayed two peaks, unlike that over the plains, and the precipitation at the strong convective core was denser. Furthermore, during winter snowfall on the northern slope of Mount Everest, when the boundary layer exhibited sufficient water vapor and dynamic uplift, due to the low boundary layer temperature (<0 °C), water vapor produced stratiform clouds in the middle and lower layers (approximately 1.5 km above ground level (AGL)). Water vapor condensation at 1.5–2.5 km AGL led to latent heat release, which increased the temperature of regional stratiform clouds with increasing height. Consequently, the temperature at the stratiform cloud top height (2.5 km AGL) unexpectedly exceeded 0 °C. Additionally, the −20 °C isotherm was at approximately 4 km AGL, indicating that the middle- and upper-layer atmospheric temperatures remained low. Therefore, thermal instability occurred between the stratiform cloud top height and the middle/upper atmosphere, forming convective motion. These findings confirm the occurrence of elevated winter snowfall convection above Mount Everest and may have certain reference value for retrieving raindrop size distributions, quantitatively estimating precipitation, and parameterizing cloud microphysical processes in numerical prediction models for the Qinghai-Tibetan Plateau.

Timing and spectral analysis of 2S 1417−624 during its 2018 outburst

We investigate timing and spectral characteristics of the transient X-ray pulsar 2S 1417−624 during its 2018 outburst with NICER follow up observations. We describe the spectra with high-energy cut-off and partial covering fraction absorption (PCFA) model and present flux-dependent spectral changes of the source during the 2018 outburst. Utilizing the correlation-mode switching of the spectral model parameters, we confirm the previously reported sub-critical to critical regime transitions and we argue that secondary transition from the gas-dominated to the radiation pressure-dominated disc do not lead to significant spectral changes below 12 keV. Using the existing accretion theories, we model the spin frequency evolution of 2S 1417−624 and investigate the noise processes of a transient X-ray pulsar for the first time using both polynomial and luminosity-dependent models for the spin frequency evolution. For the first model, the power density spectrum of the torque fluctuations indicate that the source exhibits red noise component (Γ ∼ −2) within the timescales of outburst duration which is typical for disc-fed systems. On the other hand, the noise spectrum tends to be white on longer timescales with high timing noise level that indicates an ongoing accretion process in between outburst episodes. For the second model, most of the red noise component is eliminated and the noise spectrum is found to be consistent with a white noise structure observed in wind-fed systems.

Gravitational waves from preheating in Gauss–Bonnet inflation

We study gravitational wave production in an expanding Universe during the first stages following inflation, and investigate the consequences of the Gauss–Bonnet term on the inflationary parameters for a power-law inflation model with a GB coupling term. Moreover, we perform the analyses on the preheating parameters involving the number of e-folds $$N_{pre}$$ N pre , and the temperature of thermalization $$T_{th},$$ T th , and show that it’s sensitive to the parameters n, and $$\gamma $$ γ , the parameter $$\gamma $$ γ is proposed to connect the density energy at the end of inflation to the preheating energy density. We set a correlation of gravitational wave energy density spectrum with the spectral index $$n_{s}$$ n s detected by the cosmic microwave background experiments. The density spectrum $$\varOmega _{gw}$$ Ω gw shows good consistency with observation for $$\gamma =$$ γ = $$10^{3}$$ 10 3 and $$10^{6}$$ 10 6 . Our findings suggest that the generation of gravitational waves (GWs) during preheating can satisfy the constraints from Planck’s data.

The Investigation of Behavior Change in EEG Signals During Induction of Anesthesia

Anesthesiology aims to make anesthesia safer and increase the precision of prognoses. Correct assessment of the anesthesia depth is crucial to its safety. At present, intraoperative electroencephalogram (EEG) monitoring is the primary mode of anesthesia depth monitoring and judgment. However, most clinical anesthesiologists rely on commercial anesthesia depth monitors to judge anesthesia depth, such as bispectral index (BIS) and patient state index (PSI). This may lack an understanding of associated changes in brain wave quantization. Therefore, this study conducts quantitative analyses of EEG signals during anesthesia induction. EEG signals are processed within specific time windows and extracted brainpower density spectrum arrays with different frequency bands, brain electrical signal spectra, source frequencies and other key indicators. Analysis and comparison of these indicators clarifies patterns of variation in EEG signals during early anesthesia induction. The spectral edge frequencies (SEFs) of EEG signals within different time windows can be modeled accurately, from which the specific time points of EEG signal changes are derived. Furthermore, the relationship between patient age and the effect of anesthetic drugs is preliminarily investigated by analyzing the SEF variations of different age groups. This study quantifies changes in the EEG signals of patients at the initial stage of anesthesia induction and drug-related effects are observed, which opens a way for further exploration of EEG changes in patients under general anesthesia.

Filtered asymmetric dark matter during the Peccei-Quinn phase transition

In this paper, we propose a bubble filtering-out mechanism for an asymmetric dark matter scenario during the Peccei-Quinn (PQ) phase transition. Based on a QCD axion model, extended by extra chiral neutrinos, we show that the PQ phase transition can be first order in the parameter space of the model and regarding the PQ symmetry breaking scale, the mechanism can generate PeV-scale heavy neutrinos as a dark matter candidate. Considering a CP-violating source, during the phase transition, discriminating between the neutrino and antineutrino number density, we find the observed dark matter relic abundance, such that the setup can be applied to the first order phase transition with different strengths. We then calculate effective couplings of the QCD axion addressing the strong CP problem within the model. We also study the energy density spectrum of gravitational waves generated from the first order phase transition and show that the signals can be detected by future ground-based detectors such as Einstein Telescope. In particular, for a visible heavy axion case of the model, it is shown that gravitational waves can be probed by DECIGO and BBO interferometers. Furthermore, we discuss the dark matter-standard model neutrino annihilation process as a source for the creation of PeV-scale neutrinos.

Flattening of the Density Spectrum in Compressible Hall-MHD Simulations

Observations of proton density fluctuations of the solar wind at 1 au have shown the presence of a decade-long transition region of the density spectrum above sub-ion scales, characterized by a flattening of the spectral slope. We use the proton density fluctuations data collected by the BMSW instrument on-board the Spektr-R satellite in order to delimit the plasma parameters under which the transition region can be observed. Under similar plasma conditions to those in observations, we carry out 3D compressible magnetohydrodynamics (MHD) and Hall-MHD numerical simulations and find that Hall physics is necessary to generate the transition region. The analysis of the kω power spectrum in the Hall-MHD simulation indicates that the flattening of the density spectrum is associated with fluctuations having frequencies smaller than the ion cyclotron frequency.

Power Spectral Density Analysis of Nanowire-Anchored Fluctuating Microbead Reveals a Double Lorentzian Distribution

In this work, we investigate the properties of a stochastic model, in which two coupled degrees of freedom are subordinated to viscous, elastic, and also additive random forces. Our model, which builds on previous progress in Brownian motion theory, is designed to describe water-immersed microparticles connected to a cantilever nanowire prepared by polymerization using two-photon direct laser writing (TPP-DLW). The model focuses on insights into nanowires exhibiting viscoelastic behavior, which defines the specific conditions of the microbead. The nanowire bending is described by a three-parameter linear model. The theoretical model is studied from the point of view of the power spectrum density of Brownian fluctuations. Our approach also focuses on the potential energy equipartition, which determines random forcing parametrization. Analytical calculations are provided that result in a double-Lorentzian power density spectrum with two corner frequencies. The proposed model explained our preliminary experimental findings as a result of the use of regression analysis. Furthermore, an a posteriori form of regression efficiency evaluation was designed and applied to three typical spectral regions. The agreement of respective moments obtained by integration of regressed dependences as well as by summing experimental data was confirmed.