Weak Plasma Research Articles

Origin of the Weak Plasma Emission Line Detected by Voyager 1 in the Interstellar Medium: Evidence for Suprathermal Electrons

Abstract Recently, a very weak, nearly continuous plasma wave emission line has been discovered in the nearby interstellar medium at the electron plasma frequency. The new observations were made by the plasma wave instrument on the Voyager 1 spacecraft, which crossed into the interstellar medium in 2012 August. Several questions remained unanswered after the initial discovery. Why was the emission line not observed until several years after Voyager 1 entered the interstellar medium, what is the wavelength of the plasma oscillations responsible for the emission line, and what is the origin of the oscillations? Here, we provide answers to these questions. On the most important question, namely the origin of the oscillations, the evidence strongly suggest that the emission is driven by suprathermal electrons that excite plasma oscillations comparable to the quasi-thermal noise (QTN) that is commonly observed by space plasma wave instruments with long, thin electric dipole antennas. These results imply the existence of a relatively dense population of suprathermal electrons that could contribute significantly to the overall pressure in the interstellar medium. Although the similarities to the previous QTN observations are impressive, there is no certainty that the emissions are driven by thermal excitation, and other sources should be explored, such as the possibility that they are driven by pressure fluctuations associated with the short-wavelength cascade of interstellar turbulence.

Reduction of background light by modified voltage waveform in AC plasma display panel

The voltage waveform applied in the reset period has been modified to lower the background light, which is one of the causes of the image quality degradation in the AC plasma display panel. In general, the ramp waveform is used to generate a weak plasma discharge during the reset period, but still considerable background light is generated, which lowers the contrast ratio of the AC PDP. Lowering the slope of the ramp waveform in order to lower the background light takes a lot of reset time. If the reset voltage is lowered, the strength of the write discharge, which is the next step, is weakened and the discharge also fails. In this study, we investigated the timing of discharge generation during the reset period to reduce the background light while maintaining the intensity of the write discharge without increasing the reset time. Thereafter, the application of the ramp waveform was temporarily stopped at the time when the discharge occurred, and the intensity of the discharge was controlled by applying again when the discharge became weak. As a result, the background light could be shortened from 0.71 to 0.52 cd/m2.

Possible Therapeutic Interventions in COVID-19 Induced ARDS by Cotinine as an ACE-2 Promoter and AT-1R Blocker.

In these challenging times of the pandemic, as coronavirus disease 2019 (COVID-19) has taken over the planet, its complications such as acute respiratory distress syndrome (ARDS) have the potential to wipe out a large portion of our population. Whereas a serious lack of ventilators, vaccine being months away makes the condition even worse. That's why promising drug therapy is required. One of them is suggested in this article. It is the angiotensin-converting enzyme-2 (ACE-2) to which the COVID-19 virus binds and upon downregulation of which the pulmonary permeability increases and results in the filling of alveoli by proteinaceous fluids, which finally results in ARDS. ARDS can be assisted by angiotensin-II type-1 receptor (AT-1R) blocker and ACE-2 upregulator. AT-1R blocker will prevent vasoconstriction, the pro-inflammatory effect seen otherwise upon its activation. ACE-2 upregulation will ensure less formation of angiotensin II, vasodilatory effects due to the formation of angiotensin (1-7), increased breakdown of bradykinin at lung level. Overall, decreased vasoconstriction of vessels supplying lungs and decreased vasodilation of lung tissues will ensure decreased pulmonary permeability and eventually relieve ARDS. It should also be considered that all components of the renin-angiotensin-aldosterone system (RAAS) are located in the lung tissues. A drug with the least plasma protein binding is required to ensure its distribution across these lung tissues. Cotinine appears to be a promising candidate for COVID-19- induced ARDS. It acts across the board and acts as both an AT-1R blocker, and ACE-2 upregulator. It also has a weak plasma protein binding that helps to spread through the lung tissues. In this review, we summarized that cotinine, along with COVID-19 virus replication blocker anti-virals, may prove to be a promising therapy for the treatment of COVID-19 induced ARDS.

Imaginary images and Stokes phenomena in the weak plasma lensing of coherent sources

ABSTRACT The study of astrophysical plasma lensing, such as in the case of extreme scattering events, has typically been conducted using the geometric limit of optics, neglecting wave effects. However, for the lensing of coherent sources such as pulsars and fast radio bursts, wave effects can play an important role. Asymptotic methods, such as the so-called Eikonal limit, also known as the stationary phase approximation, have been used to include first-order wave effects; however, these methods are discontinuous at Stokes lines. Stokes lines are generic features of a variety of lens models, and are regions in parameter space where imaginary images begin to contribute to the overall intensity modulation of lensed sources. Using the mathematical framework of Picard–Lefschetz theory to compute diffraction integrals, we argue that these imaginary images contain as much information as their geometric counterparts, and may potentially be observable in data. Thus, weak-lensing events where these imaginary images are present can be as useful for inferring lens parameters as strong-lensing events in which multiple geometric images are present.

Characterization of radical-enhanced atomic layer deposition process based on microwave surface wave generated plasma

A plasma-assisted atomic layer deposition system employing a microwave surfatron plasma was developed and characterized by spatially resolved Langmuir probe diagnostics and optical emission spectroscopy. The deposition process was applied on TiO2 thin films prepared on Si wafers. The surfatron is equipped with a small ring electrode serving as a source of weak radio frequency plasma helping with fast and reliable ignition of the discharge in molecular gas. Results evaluated in the pure argon plasma proved that the plasma potential and the plasma density are homogeneous in the radial direction, while a rapid decrease was observed in the axial direction. Adding up to 30% of nitrogen into the gas mixture led to less homogeneous plasma parameters in the radial direction together with the increase of the electron effective temperature. Optical emission spectra revealed many Ar I lines of neutral atoms with only a few Ar II ions’ lines. The gradual addition of nitrogen causes a systematic decrease in the Ar I line intensity. We expect that excited nitrogen molecules are produced by the inelastic collisions with electrons and by the collisional quenching of metastable Ar(4s) states. On the other hand, oxygen atom and ion lines are detected when oxygen was mixed with argon. Deposited TiO2 thin films are characterized by the anatase phase when the substrate temperature is 250 °C. The anatase phase is observed even for the substrate temperature of 200 °C; however, the microwave power delivered into the surfatrons must be lower in comparison with the prior case.

Ionization of many-electron atoms by the action of two plasma models

The Hartree-Fock equations for many-electron atoms embedded in a plasma medium are solved using two different plasma models: (a) Debye-Hückel screening (DHS) potential and (b) exponential cosine screened Coulomb (ECSC) potential. Roothaan's approach is implemented for these models after solving the inherent difficulties to evaluate integrals where screening appears explicitly. A corresponding computer code was developed using the method of global basis sets (GBS). The reliability of this approach was verified by solving the Hartree-Fock equations through implementation of the finite-differences and finite-element grid methods and applied to two-electron atoms, yielding excellent agreement with the Roothaan-GBS (RGBS) method. The RGBS method was used to study the energy evolution and ionization threshold of several closed- and open-shell many-electron atoms embedded either in weak or strong DHS or ECSC plasma conditions. In all cases, a critical value of the screening length is obtained for which ionization is achieved, being systematically larger for DHS conditions, indicating the effect of a more repulsive ECSC potential. For He-like atoms in the ground state, we report a comprehensive set of accurate total energy data as a function of the screening constant using the Lagrange mesh method, which includes the electron correlation effects. The electron correlation energy is estimated using this data with reference to the RGBS estimates of energy as the Hartree-Fock energy. The variation of correlation energy as a function of screening constant under the different plasma potentials is rationalized in terms of a conjectured comparison theorem. Finally, a discussion on the effect of plasma strength on localization or delocalization of the electronic density derived from the RGBS method is presented in terms of changes in the Shannon entropy, yielding consistent results for delocalization close to the ionization threshold.

Perturbation theory for solitons of the Fokas-Lenells equation: Inverse scattering transform approach

We present perturbation theory based on the inverse scattering transform method for solitons described by an equation with the inverse linear dispersion law ω∼1/k, where ω is the frequency and k is the wave number, and cubic nonlinearity. This equation, first suggested by Davydova and Lashkin for describing dynamics of nonlinear short-wavelength ion-cyclotron waves in plasmas and later known as the Fokas-Lenells equation, arises from the first negative flow of the Kaup-Newell hierarchy. Local and nonlocal integrals of motion, in particular the energy and momentum of nonlinear ion-cyclotron waves, are explicitly expressed in terms of the discrete (solitonic) and continuous (radiative) scattering data. Evolution equations for the scattering data in the presence of a perturbation are presented. Spectral distributions in the wave number domain of the energy emitted by the soliton in the presence of a perturbation are calculated analytically for two cases: (i) linear damping that corresponds to Landau damping of plasma waves, and (ii) multiplicative noise which corresponds to thermodynamic fluctuations of the external magnetic field (thermal noise) and/or the presence of a weak plasma turbulence.

Energetic savings and cardiovascular dynamics of a marine euryhaline fish (Myoxocephalus scorpius) in reduced salinity

Few studies have addressed how reduced water salinity affects cardiovascular and metabolic function in marine euryhaline fishes, despite its relevance for predicting impacts of natural salinity variations and ongoing climate change on marine fish populations. Here, shorthorn sculpin (Myoxocephalus scorpius) were subjected to different durations of reduced water salinity from 33 to 15 ppt. Routine metabolic rate decreased after short-term acclimation (4–9 days) to 15 ppt, which corresponded with similar reductions in cardiac output. Likewise, standard metabolic rate decreased after acute transition (3 h) from 33 to 15 ppt, suggesting a reduced energetic cost of osmoregulation at 15 ppt. Interestingly, gut blood flow remained unchanged across salinities, which contrasts with previous findings in freshwater euryhaline teleosts (e.g., rainbow trout) exposed to different salinities. Although plasma osmolality, [Na+], [Cl−] and [Ca2+] decreased in 15 ppt, there were no signs of cellular osmotic stress as plasma [K+], [hemoglobin] and hematocrit remained unchanged. Taken together, our data suggest that shorthorn sculpin are relatively weak plasma osmoregulators that apply a strategy whereby epithelial ion transport mechanisms are partially maintained across salinities, while plasma composition is allowed to fluctuate within certain ranges. This may have energetic benefits in environments where salinity naturally fluctuates, and could provide shorthorn sculpin with competitive advantages if salinity fluctuations intensify with climate change in the future.

Study of Shock Fronts and Solitary Profiles in a Weak Relativistic Plasma and its Evolution into a Rogue Wave

Study of Shock Fronts and Solitary Profiles in a Weak Relativistic Plasma and its Evolution into a Rogue Wave

Tunable millimeter wave photonic crystal for limiting high power pulses using weakly ionized steady state plasma

We present the transmission characteristics of pulsed 44 GHz millimeter waves (MMWs) through a plasma formed within a photonic crystal. Initially, a low density plasma (ne=0.3×1018m−3) is sustained in a crystal vacancy defect using a continuous wave (cw) MMW power of 0.06 W. This weak plasma does not much attenuate wave transmission, but it does provide seed electrons such that dense plasma forms in response to incoming MMW pulses. The dense plasma formation limits the transmission of high power pulses through the photonic crystal. A high power pulse increases the plasma electron density and shifts the resonant frequency of the crystal vacancy in accordance with the plasma permittivity. A rapid decrease in the transmitted power is observed by following the time-evolution of the plasma. A numerical electromagnetic model estimates electron density and traces the time-evolution of the plasma during MMW pulsing. The plasma-filled photonic crystal is evaluated as a power limiter. As plasma properties are readily tunable, we observe an improved operational bandwidth for incoming pulse frequencies by controlling the cw power and gas pressure of the initial weak plasma.

Solar wind transient currents: statistical properties and impact on Earth’s magnetosphere

Solar wind discontinuities carry intense transient currents and significantly contribute to the turbulent spectrum and plasma heating. The most-investigated characteristics of these discontinuities are the magnetic field configuration and the current density, whereas plasma characteristics attract less attention. In this study, we utilize eight years of ARTEMIS spacecraft observations in the solar wind to investigate plasma density, velocity, and temperature variations across discontinuities. We also consider the role of discontinuities in the development of Earth’s magnetospheric perturbations. We show that observed discontinuities can be separated into two groups: (i) discontinuities with weak plasma density variations and a significant correlation between the solar wind and Alfven velocities, (ii) discontinuities with significant variations of plasma density and temperature. For most discontinuities, observed density variations anti-correlate with temperature variations, but larger density/temperature variations correspond to stronger current densities. Time intervals characterized by increased occurrence rate of solar wind discontinuities correspond to enhanced geomagnetic activity in the Earth’s magnetosphere as characterized by geomagnetic indices.

A sensitive and rapid HPLC-DAD method for the determination of 3-hydroxy-1,2-dimethyl-4-pyridone and its distribution in rats

Purpose: To establish a sensitive and rapid method for the determination of the tissue distribution of 3-hydroxy-1,2-dimethyl-4-pyridone (L1) in vivo, and its plasma protein binding capacity.Methods: This study optimized a reverse-phase HPLC method for specific and sensitive determination of L1 as well as its plasma and tissue distributions. The optimized method was used to determine the plasma protein-binding capacity of L1 in Wistar rats.Results: A rapid, sensitive and simple HPLC-DAD method was established for studying the plasma and tissue distribution of L1. Following TI administration, its liver concentrations peaked at 60 min and 360min, followed 360 min later with peak level in the kidney (second highest). The L1 concentration was significantly lower after 360 min than after 60 min, and values of its mean binding to plasma proteins was 5.2 % at different L1 concentrations.Conclusion: These results indicate that L1 is a drug with rapid-absorption and rapid-elimination thath is distributed widely in vivo in rats. Moreover, the drug has a weak plasma protein-binding capacity.
 Keywords: 3-Hydroxy-1,2-dimethyl-4-pyridone, Distribution, Alzheimer’s disease, Therapy

Analyses of hydrogen release on zirlo alloy anode during plasma electrolytic oxidation

Plasma electrolytic oxidation (PEO) is a complex process, accompanied by spark discharge and intensive gas evolution around metal anode. In this paper, the gas released from Zirlo alloy electrode during PEO process in KF solution and phosphate solution was collected and its composition was analyzed by gas chromatograph (GC). The possibility of H2 evolution from Zirlo alloy anode was evaluated and its formation mechanism was discussed. It was found that the gas released from discharging anode contained H2 and O2. The H2 up to 81.6 vol.% was detected under strong plasma discharge in phosphate solution. Furthermore, a little CO was also detected while the glycerol was added into electrolyte. Hence, a large amount of H2 could be evolved on Zirlo alloy anode during PEO process, which was different from the traditional electrochemical theory and common knowledge of PEO technology for O2 evolution on anode. Relatively less H2 was released in KF solution due to weak plasma discharge. The H2 concentration evolved during PEO process was related to the intensity of plasma discharge. It was believed that the H2 and O2 mainly resulted from the direct thermal decomposition of water vapour in plasma discharge zone, though the electrolyte was also decomposed to form H2, O2 and CO.

Superposition of low-pressure DBD and RF induction discharge for spectroscopic study of dissociative recombination in decaying plasma

The aim of the work was to find the optimal way to set up an experiment for spectroscopic study of the dissociative recombination of molecular ions with electrons in low electron density plasma at low gas pressure. In such an experiment, the influence of inelastic atom–atom collisions on the distribution of the DR flux over the excited atomic levels can be excluded. The first results of an experiment on combining a low-frequency barrier discharge (DBD) in neon at a pressure of less than 1 Torr with a pulsed radio-frequency (RF) induction discharge are presented. To create the plasma, we used DBD in a cylindrical glass tube with an inner diameter of 3.9 cm, which forms the spatial distribution of electron density with a minimum on the axis of the tube. The evolution of such a spatial distribution due to ambipolar diffusion in the initial stage of plasma decay provides an influx of charged particles to the center of the discharge tube, which increases the afterglow duration and helps to overcome the difficulties of detecting weak plasma radiation. The specific features of the DBD also appeared in the ionic composition of the plasma, which contained, in addition to Ne+ and Ne2+, the Ne++ ions, whose recombination with electrons significantly enriched the afterglow spectrum in the short-wavelength region. An RF discharge was used for pulsed heating of electrons in the afterglow. It is shown that, in accordance with the ionic composition, the radiation of a decaying plasma is presented by three groups of spectral lines with characteristic time behavior and the electron temperature dependence. The advantages of the proposed approach for studying the mechanism of dissociative recombination are discussed.

Spectroscopic diagnostics of continuous and transient microplasma formed in a millimeter wave photonic crystal

We present spectroscopic measurements of a microplasma formed within a photonic crystal (PhC) at argon gas pressures up to 750 Torr. Continuous and pulsed millimeter waves (MMW) generate plasma at a vacancy defect within the crystal. Rotational gas temperatures of 300–1050 K and electron densities of 0.3–1.5 × 1020 m−3 are obtained from the CH rotational emission spectrum and from Stark broadening of the atomic transition. Electron density is found to be weakly dependent on MMW power because the plasma expands within the defect volume at higher power. Pulsed MMWs slightly increase the peak electron density compared to continuous waves with the same peak power. With MMW pulses, a rapid decrease of wave transmission through the PhC is observed at the beginning of plasma formation. During plasma ignition two distinct plasmas are formed, one on the conducting wall of the PhC near the optical access port and a second within the center of the PhC defect. With longer periods between pulses, the weak wall plasma is observed to form before the principal plasma in the defect, which aids in initiating the main plasma.

Generalized oscillator strengths for the ground state [formula omitted] of sodium atom embedded in a plasma medium

The dipole and generalized oscillator strengths (DOS and GOS) of the free and confined atomic system are related to the description of several interesting chemical physical properties, e.g. static polarizability, photoionization, and stopping cross section (energy loss), among others. In this work, we show results for the 3s→3p,4p DOS electronic transition, the 3s→4s,5s,6s, and the 3s→3p,4p,5p GOS electronic transition of the sodium atom in the presence of a weak and strong plasma environment describe by a Debye-Hückel (DHS) and an exponential-cosine-screened-Coulomb (ECSC) potentials as a function of the plasma screening length, λ. We solve the time-independent Schrödinger equation implementing a numerical approach using a pseudo-potential model to describe the sodium core electrons. We find that the 3s energy level becomes delocalized due to the screening plasma interaction for lower values of λ~2.43 and ~4.10 a.u., for the DHS and ECSC potentials, respectively. As a consequence, the f3s→3p and f3s→4p DOS transitions for both DHS and ECSC plasma environments are reduced as the screening length is decreased observing clear differences between plasma mediums. Similar behavior is observed for the GOS electronic transitions as a function of the transferred momentum where the ECSC plasma medium decreases the amplitude transition as the screening length reaches the energy delocalization. In the absence of a plasma environment, we compare our DOS and GOS results observing a good agreement in comparison with other theoretical and experimental findings.

ASIC waveform receiver with improved environmental tolerance for probing space plasma waves in environments with high radiation and wide temperature variation

Plasma-wave observations are conducted under conditions of high radiation and wide temperature variation. The electrical characteristics of plasma-wave instruments should therefore be insensitive to these environmental factors. We have developed a new application-specific integrated circuit (ASIC) waveform receiver with a radhard [radiation-hardened] amplifier and a temperature-compensation circuit. The environmental tolerance of the conventional ASIC receiver is unsuitable for probing plasma waves in the range 1 Hz to 10 kHz in harsh space environments. Its weak radiation tolerance under 350 krad results in radiation-induced degradation in noise performance, such that weak plasma waves are lost in the noise floor. With an ambient temperature change of −40° C to +100° C, the gain response of the conventional ASIC receiver varies by more than ±1.0 dB, preventing accurate measurement of plasma waves around the cutoff frequency of 10 kHz. Our new ASIC receiver operates at a total dose rate of 350 krad without degradation in noise performance. Moreover, the temperature dependence of the gain response from −60° C to +100° C dramatically improved by ±0.05 dB due to the addition of a compensation circuit. Our new ASIC receiver can contribute to the measurement of plasma waves in challenging environmental conditions to further the understanding of magnetospheric dynamics.

Shock Fronts and Solitary Profile of Electron Acoustic Wave in Weak Relativistic Plasma at Critical Limit

Shock Fronts and Solitary Profile of Electron Acoustic Wave in Weak Relativistic Plasma at Critical Limit

Investigation of Electron Acoustic (KdV) Solitary Structures in a Weak Relativistic Plasma at the Critical Regime

Investigation of Electron Acoustic (KdV) Solitary Structures in a Weak Relativistic Plasma at the Critical Regime

Shock Fronts and Solitary Profile of Electron Acoustic Wave in Weak Relativistic Plasma at Critical Limit

Shock Fronts and Solitary Profile of Electron Acoustic Wave in Weak Relativistic Plasma at Critical Limit