Mixture Plasma Research Articles

Accurate diffusion coefficients for dense white dwarf plasma mixtures

ABSTRACT Diffusion coefficients are essential microphysics inputs for modelling white dwarf evolution, as they impact phase separation at crystallization and sedimentary heat sources. Present schemes for computing diffusion coefficients are accurate at weak coupling (Γ ≪ 1), but they have errors up to a factor of 2 in the strongly coupled liquid regime (1 ≲ Γ ≲ 200). With modern molecular dynamics codes, it is possible to accurately determine diffusion coefficients in select systems with per cent-level precision. In this work, we develop a theoretically motivated law for diffusion coefficients that works across the wide range of parameters typical for white dwarf interiors. We perform molecular dynamics simulations of pure systems and two mixtures that respectively model a typical-mass C/O white dwarf and a higher-mass O/Ne white dwarf, and resolve diffusion coefficients for several trace neutron-rich nuclides. We fit the model to the pure systems and propose a physically motivated generalization for mixtures. We show that this model is accurate to roughly 15 per cent when compared to molecular dynamics for many individual elements under conditions typical of white dwarfs, and is straightforward to implement in stellar evolution codes.

Feline Eosinophilic/Proliferative Keratitis: A Retrospective Study (2016-2021)

The medical records of 35 cats (44 eyes) with feline eosinophilic keratitis (FEK) diagnosed between 2016 and 2021 were reviewed. The mean age at the presentation of cases diagnosed with FEK was 4.12 years (3 months-13 years). Domestic shorthair was the dominant breed, accounting for 68.57% of cats (24/35). FEK was unilateral in 74.28% of the cases, and the most frequently affected position was the superotemporal quadrant of the cornea (75% of the eyes). The cytological examination of the cornea and conjunctiva showed a mixture of multiple eosinophils, plasma, and mast cells, confirming the diagnosis of FEK. Eosinophils were found in 86.36% of the corneal and conjunctival scrapings. We performed the polymerase chain reaction test for feline herpes virus type 1 in 12/35 cats. Viral DNA was detected in 20% of these cats. The cats were treated with a subconjunctival corticosteroid, a topical antibiotic-corticosteroid combination, artificial tear drops, and antiviral gel containing ganciclovir. At one to two weeks after the initial examination, the clinical signs markedly improved. The controlled and regular use of topical corticosteroids brought the lesions under control and resolved FEK without recurrence at least for six months.

Maximizing MS/MS Acquisition for Lipidomics Using Capillary Separation and Orbitrap Tribrid Mass Spectrometer.

Liquid chromatography-mass spectrometry (LC-MS) is a typical strategy for lipidomics analysis. Although capillary LC-MS is a common analytical technique for proteomics analysis, its application to lipidomics has been limited. In this study, we aim at improving lipid identifications achieved in a single LC-MS analysis by a 3-fold approach: capillary LC and nanoelectrospray for enhanced ionization, ion trap for higher sensitivity tandem MS, and parallelization of mass analyzers for increased speed of acquisition on an Orbitrap hybrid system. By applying the methods to a complex lipid mixture of human plasma, we identified and performed relative quantification on over 1500 lipids within a 60 min capillary LC-MS analysis.

Ultrasensitive TLC determination of montlukast and loratadine mixture in human plasma utilizing fluorescence detection at dual pH values: Toward attaining separate maximum fluorescence intensity

A novel selective and highly sensitive TLC densitometric method with reflectance/fluorescence detection was developed to separate and quantify montlukast (MONT) and loratadine (LOR). Separation of the studied drugs was performed on precoated silica gel TLC plates using chloroform–ethyl acetate (8 :2 v/v) as a mobile phase. MONT quantification was carried out by measuring emission using 400 nm optical filter after excitation at 340 nm. Enhancement of the week LOR fluorescence was performed through adequate spraying the chromatograms with 0.2 M perchloric acid leading to enhancing sensitivity by 17 folds compared to the reported HPTLC methods with absorbance detection. The scanner was set at 275 nm excitation wavelength and 400 nm optical filter. Detection of both drugs on the same plate separately at different pH conditions was utilized for the first time. Maximum fluorescence was achieved for each of them and this enhances detection sensitivity for both drugs. The linear regression analysis data of the studied drugs produced a good linear relationship with correlation coefficients of 0.996 for MONT and 0.998 for LOR over the concentration range of 6 – 150 ng/band for MONT and 15 – 120 ng/band for LOR. Limit of detection values were 1.7 and 4.5 ng /band for MONT and LOR respectively. The developed method enabled the detection of MONT and LOR in human plasma samples within linear concentrations ranged from 7 to 140 ng/ band and 16 to 50 ng/ band with detection limits of 1.9 and 4.8 ng/band for MONT and LOR respectively.The analytical performance of the proposed method was evaluated according to the International Council for Harmonization (ICH). The method was successfully applied for the analysis of the studied drugs in spiked human plasma and good recovery percentages were obtained indicating that there is no interference from plasma constituents. Therefore the method can be applied for in vivo analysis and pharmacokinetic study.

Effect of oxygen flow rate ratio on crystalline phase and properties of copper oxide films prepared by room-temperature high-power impulse magnetron sputtering

Copper oxide films were prepared at room temperature using high-power impulse magnetron sputtering (HiPIMS). The oxygen flow rate ratio in the Ar/O2 mixture plasma gas is varied from 1.0% to 3.0% and its influences on the plasma radicals, growth mechanism and film properties are systematically investigated. The crystal phase of the film strongly depends on the oxygen flow rate ratio as indicated by the XRD and XPS results. The films consist of mixed (Cu + Cu2O) phase when deposited with an oxygen flow rate ratio of 1.0–2.5%. The Cu2O fraction increases with oxygen flow rate ratio and reaches the greatest value at 2.5%. A n-type to p-type conductivity transition is observed at around 2.0% due to the increasing Cu2O fraction. A phase transition to CuO is observed at a higher oxygen flow rate ratio of 3.0%. The phase transition and conductivity type transition occurred at a much lower oxygen flow rate ratio but similar O2 partial pressure when compared with those reported in literature, implying that the O2 partial pressure is the critical quantity for reactive sputtering rather than the O2 flow rate ratio. Crucially, the film deposited with 2.5% oxygen flow rate ratio exhibits the highest hole mobility of 32 cm2/V·s, the lowest hole concentration of 4.0 × 1015/cm3, the highest transmittance and the largest band gap of 2.62 eV. The film is potential to be used as the channel material of transparent p-type field effect transistors. The results may be helpful for the preparation of copper oxide film by HiPIMS for application in optoelectronic devices.

Diagnostics of Ne–Ar mixture plasma using a fine‐structure resolved collisional radiative model

AbstractA collisional radiative (CR) model has been developed for the diagnostics of Ne–Ar mixture plasma. The 40 fine‐structure resolved energy levels of neon corresponding 2p53s, 2p53p, 2p53d, 2p54s, and 2p54p along with ground state (2p6) and ion state (2p5) have been considered. All the essential population and de‐population channels viz. electron impact excitation‐de‐excitation, ionization, two/three‐body recombination, radiative decay, self‐absorption correction, diffusion, etc., have been considered in the model. The quenching of relatively higher lifetime states 2p53s due to interaction with Ar atoms through associative and Penning ionization is also included in the model. The applicability of the CR model is demonstrated by performing the optical diagnostic of rf induced inductively coupled Ne–Ar mixture plasma. The plasma parameters viz. electron temperature, electron density, and population distribution of levels at various mixture conditions are extracted by coupling the present CR model predictions with emission and absorption measurements by Boffard et al. [J. Phys. D: Appl. Phys., 45, 382001 (2012) and private communication]. The results are also compared with earlier optical models and Langmuir probe measurements. The self‐absorption correction (escape) factors and electron impact excitation rates at various Ne–Ar mixture concentrations are also presented.

Irradiation damage of reduced activation ferritic/martensitic steel CLAM exposed to low-energy high-flux D + He mixture plasma

Irradiation damage behavior of reduced activation ferritic/martensitic steel CLAM exposed to D + He mixture plasma was extensively investigated using the linear plasma facility PSIEC at a sample temperature of ∼800 K with an ion flux of ∼4.0 × 1021 m−2 s−1, an ion fluence of ∼7.0 × 1024 m−2 and an incident ion energy of ∼89 eV. Fiber-like nanostructure fuzz was formed on the irradiated CLAM steel surface. D and He bubbles were observed both inside and under the fuzz structure from cross-sectional TEM characterization. Damage level of the steel surface has been found to gradually increase as increasing He concentration in the mixed plasma. The growth process of fuzz can be described as pinholes (which originated from nano-bubbles) to nano-sphere structures, wavy erosion layers, rods, and eventually develops to nano-fuzz. Tungsten enrichment in the near-surface has been determined after plasma exposure due to preferential sputtering of middle-Z elements of iron and chromium. The measured surface tungsten concentration varied from 1.9 to 4.0 wt.%, depending on He concentration in the plasma. Obtained sputtering yield increased as well with increasing He concentration in the mixed plasma.

Joint meeting of 9th Asia Pacific-Transport Working Group (APTWG) & EU-US Transport Task Force (TTF) workshop

This conference report summarizes the contributions to, and discussions at the joint meeting of the 9th Asia Pacific-Transport Working Group (APTWG) & EU-US Transport Task Force (TTF) workshop held online, hosted by Kyushu University, Japan, during 6–9 July 2021. The topics of the meeting were organized under five main topics: (1) isotope effect on transport and physics on isotope mixture plasma, (2) turbulence spreading and coupling in core-edge-SOL, (3) interplay between magnetohydrodynamic topology/instability and turbulent transport, (4) interaction between energetic particle driven instability and transport, (5) model reduction and experiments for validation.

ANN-LIBS analysis of mixture plasmas: detection of xenon

We developed an artificial neural network method for characterising crucial physical plasma parameters (i.e., temperature, electron density) in a fast and precise manner that mitigates common issues arising in evaluation of LIBS spectra.

Study of the Composition of a Plasma of Dry Air Contaminated by Al<sub>2</sub>O<sub>3</sub>, CO, Fe<sub>2</sub>O<sub>3</sub> and SiO<sub>2</sub>

This paper concerns the calculation of equilibrium composition of plasma mixture Air Fe2O3, SiO2, Al2O3 and CO in temperatures range 1000 K to 6000 K. We supposed that the plasma is at atmospheric pressure and at local thermodynamic equilibrium (ETL). In the Saharan zone, the aerosols are proven from desert dust and biomass fires. They are essentially composed of oxides of silicon, calcium, iron, aluminum and carbonaceous elements from biomass. Thus, air circuit breakers often operate in a polluted environment without specific protection. They can have abnormal behaviors and failures of cuts. We used Gibbs free energy minimization method to access the different numerical densities of chemical species as a function of temperature. These data are very important to calculate thermodynamic properties, transport coefficients and modeling electrical arc in circuit breakers. The results show that the dust brings many particles which have low dissociation and ionization energies. This leads to an increase in metallic elements and a strong increase in the numerical density of electrons which could have a detrimental effect during the current cut-off phase with the increase in the electrical conductivity of the plasma.

Noninvasive Prenatal Test for β-Thalassemia and Sickle Cell Disease Using Probe Capture Enrichment and Next-Generation Sequencing of DNA in Maternal Plasma.

Noninvasive prenatal testing (NIPT) of chromosomal aneuploidies based on next-generation sequencing (NGS) analysis of fetal DNA in maternal plasma is well established, but testing for autosomal recessive disorders remains challenging. NGS libraries prepared by probe capture facilitate the analysis of the short DNA fragments plasma. This system has been applied to the β-hemoglobinopathies to reduce the risk to the fetus. Our probe panel captures >4 kb of the HBB region and 435 single-nucleotide polymorphisms (SNPs) used to estimate fetal fraction. Contrived mixtures of DNA samples, plasma, and whole blood samples from 7 pregnant women with β-thalassemia or sickle cell anemia mutations and samples from the father, sibling, and baby or chorionic villus were analyzed. The fetal genotypes, including point mutations and deletions, were inferred by comparing the observed and expected plasma sequence read ratios, based on fetal fraction, at the mutation site and linked SNPs. Accuracy was increased by removing PCR duplicates and by in silico size selection of plasma sequence reads. A probability was assigned to each of the potential fetal genotypes using a statistical model for the experimental variation, and thresholds were established for assigning clinical status. Using in silico size selection of plasma sequence files, the predicted clinical fetal genotype assignments were correct in 9 of 10 plasma libraries with maternal point mutations, with 1 inconclusive result. For 2 additional plasmas with deletions, the most probable fetal genotype was correct. The β-globin haplotype determined from linked SNPs, when available, was used to infer the fetal genotype at the mutation site. This probe capture NGS assay demonstrates the potential of NIPT for β-hemoglobinopathies.

Study of conditions of gas- discharge synthesis of Zinc oxide nanostructures under automatic UV-irradiation of the substrate by plasma

The spectroscopic characteristics of a bipolar, overstressed discharge of nanosecond duration between zinc electrodes in oxygen at a pressure p(O2) = 13.3 kPa are presented. In the process of microexplosions of inhomogeneities on the working surfaces of the electrodes in a strong electric field, zinc vapor is introduced into the discharge gap. This creates the prerequisites for the formation of zinc oxide molecules and clusters in the plasma and the synthesis of thin island zinc oxide films, which can be deposited on a dielectric substrate installed near the center of the discharge gap. The spectral characteristics of the discharge were investigated from the central part of the discharge gap 2 mm in size. The main excited components of the plasma of a vapor-gas mixture based on zinc and oxygen were established at high values ​​of the parameter E / N (where E is the electric field strength; N is the total concentration of particles in the plasma), which, when deposited outside the discharge plasma, can lead to the formation of fine nanostructured films based on zinc oxide.

In vitro effects of emicizumab on activated clotting time in blood samples from cardiac surgical patients.

Heparin management in hemophilia A (HA) patients with a factor VIII (FVIII) inhibitor can be challenging due to severe activated clotting time (ACT) prolongations. It is important to better understand the impact of emicizumab, a FVIII mimetic on ACT, and tissue factor (TF)-based coagulation assays. Whole blood from 18 patients undergoing cardiopulmonary bypass (CPB) were mixed in vitro with pooled normal plasma, FVIII-deficient or FVIII-inhibitor plasma to affect functional FVIII levels. ACTs and heparin concentration by protamine titration were measured in whole blood mixture with/without emicizumab (50-100μg/ml). Thrombin generation and plasmin generation were measured in the patient's plasma mixed with normal plasma or FVIII-inhibitor plasma to assess the impact of emicizumab under low TF activation. FVIII inhibitors prolonged ACTs by 2.2-fold compared to those in normal plasma mixture at baseline. During CPB, ACTs in normal plasma mixture, and FVIII-deficient mixture were in 400s, but ACTs reached 900s in FVIII-inhibitor mixture. Emicizumab shortened ACTs by up to 100s in normal plasma mixture, and FVIII-deficient mixtures. ACTs remained over 600s in FVIII-inhibitor mixture, despite adding emicizumab at 100μg/ml. Heparin concentration measured by TF-based protamine titration was unaffected. Emicizumab enhanced thrombin peak in the presence of FVIII inhibitors, whereas plasmin generation was mainly affected by thrombin generation, and systemic use of ɛ-aminocaproic acid. FVIII inhibitors extensively prolong ACTs in heparinized whole blood, and clinical levels of emicizumab partially reverse ACT values. Protamine titration should be considered for optimal heparin monitoring in emicizumab-treated patients with FVIII inhibitors.

Thermophysical properties of pure gases and mixtures at temperatures of 300–30 000 K and atmospheric pressure: thermodynamic properties and solution of equilibrium compositions

The equilibrium compositions and thermodynamic properties (density, enthalpy, etc at constant pressure) of plasma of pure gases and mixtures under local thermodynamic nonequilibrium have been calculated in this paper. The homotopy Levenberg–Marquardt algorithm was proposed to accurately solve nonlinear equations with singular Jacobian matrices, and is constructed by the Saha equation and Guldberg–Waage equation combined with mass conservation, the electric neutrality principle and Dalton’s partial pressure law, to solve the problem of dependence on the initial value in the process of iteration calculation. In this research, the equations at a higher temperature were solved and used as the auxiliary equations, and the homotopy control parameters’ sequence of the homotopy equations was selected by equal ratios. For auxiliary equations, the iterative initial value was obtained by assuming that there were only the highest-valence atomic cations and electrons at this temperature, and the plasma equilibrium composition distribution with the required accuracy was ultimately solved under the current conditions employing the Levenberg–Marquardt algorithm. The control parameter sequence was arranged according to the geometric sequence and the homotopy step was gradually shortened to ensure continuity of the homotopy process. Finally, the equilibrium composition and thermodynamic properties of pure N2, Mg(30%)–CO2(70%) and Mg(40%)–CO(50%)–N2(10%) mixture plasma at atmospheric pressure were calculated and the calculation process of some specified temperatures was shown and analyzed. The calculation accuracy of equilibrium composition is higher than other findings in the literature. The results for the thermodynamic properties are in good agreement with data reported by the literature.

Spectral study of argon-methane mixture plasma jet generated by a DC plasmatron

We present the results of studying optical emission spectra of Ar:CH4 plasma produced on a DC plasmatron for graphene synthesis. We have identified the basic set of spectral lines and bands in the obtained spectra and shown that H lines and C2 bands appear due to direct excitation by an electron strike of corresponding neutral particles. C2 molecular bands were also identified in the spectra with intensity considerably lower compared to previous studies where He: C2H2 mixture was used as plasma-forming gas.

Light-emitting p-i-n GaP/GaPAs NW encapsulated in a flexible PDMS membrane

Our work is aimed at the method of fabricating arrays of semiconductor III-V NWs transferred into a flexible polymer membrane made of polydimethylsiloxane. GaP/GaPAs NWs with an axial p-i-n structure were synthesized by molecular beam epitaxy. The synthesized NW arrays on substrates were encapsulated into a silicone membrane by the G-coating method in a swinging-bucket centrifuge. After membranes were treated in a plasma mixture of O2/CF2 gases to open the NWs tops, which ensured the application of conductive transparent contacts - single-walled carbon nanotubes obtained by aerosol chemical method. At the last technological stage, the membranes were separated from substrates by peeling with a razor blade and the second carbon nanotubes contact was formed. The obtained LED NW/silicone membranes were characterized by I-V and the electroluminescence spectroscopy measurements.

Influence of helium incorporation on growth process and properties of aluminum thin films deposited by DC magnetron sputtering

The effect of helium content on the morphology, crystallinity, and composition of aluminum films was investigated by depositing He-loaded Al films onto Si substrates via direct current (DC) magnetron sputtering in different Ar/He plasma mixtures. Three different plasma regimes were identified depending on the percentage of He in the gas phase. For a low He to total gas ratio (ΓHe ≤ 70%), the plasma is dominated by argon, where Ar+ ions contribute to sputter out the target atoms. The films deposited in this regime exhibited the classical dense columnar structure and contain very low amount of He (below 2%). Then, as ΓHe increases, helium ions begin to be formed and more fast He neutrals reach the substrate, affecting the film growth. As He amount increased in the gas phase up to 95%, the proportion of He inserted in the films rised up to ⁓15 at. %. Moreover, bubbles/porosity were formed inside the films; those obtained in pure He plasma presented a highly porous fiberform nanostructure. All results confirmed that the modification of the film characteristics was related to the change of the deposition conditions when Ar was replaced by He and to the insertion/release mechanisms of He during the growth.

Versatilely tuned vertical silicon nanowire arrays by cryogenic reactive ion etching as a lithium-ion battery anode

Production of high-aspect-ratio silicon (Si) nanowire-based anode for lithium ion batteries is challenging particularly in terms of controlling wire property and geometry to improve the battery performance. This report demonstrates tunable optimization of inductively coupled plasma reactive ion etching (ICP-RIE) at cryogenic temperature to fabricate vertically-aligned silicon nanowire array anodes with high verticality, controllable morphology, and good homogeneity. Three different materials [i.e., photoresist, chromium (Cr), and silicon dioxide (SiO2)] were employed as masks during the subsequent photolithography and cryogenic ICP-RIE processes to investigate their effects on the resulting nanowire structures. Silicon nanowire arrays with a high aspect ratio of up to 22 can be achieved by tuning several etching parameters [i.e., temperature, oxygen/sulfur hexafluoride (O2/SF6) gas mixture ratio, chamber pressure, plasma density, and ion energy]. Higher compressive stress was revealed for longer Si wires by means of Raman spectroscopy. Moreover, an anisotropy of lattice stress was found at the top and sidewall of Si nanowire, indicating compressive and tensile stresses, respectively. From electrochemical characterization, half-cell battery integrating ICP-RIE-based silicon nanowire anode exhibits a capacity of 0.25 mAh cm−2 with 16.67% capacity fading until 20 cycles, which has to be improved for application in future energy storage devices.

Characteristics and Parameters of Overstressed Nanosecond Discharge Plasma in Air between an Electrode from Aluminum and Electrode from Chalcopyrite (CuInSe2)

The characteristics and parameters of an overstressed high-current discharge with a duration of 100–150 ns in air, which was ignited between an aluminum electrode and a chalcopyrite electrode (CuInSe2), are presented. The air pressure was 13.3 and 101.3 kPa. In the process of microexplosions of inhomogeneities on the working surfaces of electrodes in a strong electric field, aluminum vapors and chalcopyrite vapors were introduced into the interelectrode gap, which creates the prerequisites for the synthesis of thin films based on quaternary chalcopyrite – CuAlInSe2. The films synthesized from the products of electrode destruction were deposited on a quartz plate at a distance of 2–3 cm from the center of the discharge gap. The current and voltage pulses across the discharge gap of d = 1 mm, as well as the pulse energy input into the discharge, were investigated. The plasma emission spectra were studied, which made it possible to establish the main decay products of the chalcopyrite molecule and the energy states of atoms and singly charged ions of aluminum, copper and indium, which are formed in the discharge. The reference spectral lines of atoms and ions of aluminum, copper, and indium were established, which can be used to control the process of deposition of thin films of quaternary chalcopyrite. Thin films were synthesized from the degradation products of chalcopyrite molecules and aluminum vapors, which may have the composition of the quaternary chalcopyrite CuAlInSe2; the transmission spectra of the synthesized films in the spectral range of 200–800 nm were studied. By the method of numerical simulation of the plasma parameters of an overstressed nanosecond discharge based on aluminum and chalcopyrite vapors in air by solving the Boltzmann kinetic equation for the electron energy distribution function, the temperature and density of electrons, the specific power losses of the discharge for the main electronic processes and their rate constants depending on the value parameter E/N for plasma of vapor-gas mixtures based on air, aluminum vapor and ternary chalcopyrite were modulated.

Etching characteristics of hydrogenated amorphous carbon with different sp2/sp3 hybridization ratios in CF4/O2 plasmas

AbstractAmorphous carbon is used as a hard mask for dielectric etching with a high aspect ratio in the fabrication processes of semiconductor devices. The dependence of the etching characteristics of hydrogenated amorphous carbon (a‐C:H) films on the sp2/sp3 hybridization ratios was studied for CF4/O2 plasma mixtures. The etch rate of sp3‐rich a‐C:H is 33.7 times higher than that of sp2‐rich a‐C:H in a plasma comprising 50% CF4 and 50% O2. The etch rate of the sp2‐rich a‐C:H exhibits a linear correlation with the ion density of CF4/O2 plasma, whereas that of the sp3‐rich a‐C:H exhibits a second‐order exponential correlation with O radical density. A combined etch rate model was suggested to explain the etch rates of a‐C:H. Ion‐enhanced etching is identified as the dominant etching mechanism for the sp2‐rich a‐C:H, whereas spontaneous chemical etching is the main reaction mechanism for the sp3‐rich a‐C:H in CF4/O2 plasmas.