Dilute Plasma Research Articles

The Classical Binary and Triplet Distribution Functions for Dilute Relativistic Plasma

The aim of this paper is to calculate the binary and triplet distribution functions for dilute relativistic plasma in terms of the thermal parameter μ where , is the mass of charge; c is the speed of light; k is the Boltzmann’s constant; and T is the absolute temperature. Our calculations are based on the relativistic Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy. We obtain classical binary and triplet distribution functions for one- and two-component plasmas. The excess free energy and pressure are represented in the forms of a convergent series expansions in terms of the thermal parameter μ.

Coupling of an average-atom model with a collisional-radiative equilibrium model

We present a method to combine a collisional-radiative equilibrium model and an average-atom model to calculate bound and free electron wavefunctions in hot dense plasmas by taking into account screening. This approach allows us to calculate electrical resistivity and thermal conductivity as well as pressure in non local thermodynamic equilibrium plasmas. Illustrations of the method are presented for dilute titanium plasma.

The effect of cosmic rays on the stability of hot dilute plasmas

Many factors are considered in instability analysis, such as self-gravity, differential rotation, and magnetic field. Cosmic rays (CRs) are another factor that have been recently considered and shown to play a dynamic role. However, the effect of CRs on the stability of hot dilute plasma systems has not yet been considered. This type of plasma is believed to be found in the intracluster medium of galaxy clusters and inefficient radiation accretion flows around black holes. Here, we study the dynamic effects of CRs on instability modes in such systems. We discuss analytically some special cases and work out general cases numerically. We show that the growth rate of some unstable modes such as magnetothermal instability (MTI), gyroviscous magnetorotational instability, and convective instability which depend on the ratio of CR pressure to gas pressure (βcr), the ratio of the radial gradient of CR pressure to the radial gradient of gas pressure (Φ), and CR diffusion coefficient. CRs can alter MTI criterion. In this paper, we show that a plasma which is stable in ideal MTI criterion, i.e. dT/dR > 0, such as cooling flow clusters, can be unstable in the presence of CRs if |Φ| > 1.

Channeling the electrical breakdown of air by optically heated plasma filaments

Femtosecond laser pulses with sufficiently high peak power leave tracks of dilute plasma in their wakes. Potential use of this plasma for channeling electrical discharges in the atmosphere has been discussed and demonstrated in laboratory-scale experiments. However, the electron density in femtosecond laser-generated plasma decays rapidly on the nanosecond time scale, due to recombination and electron attachment to air molecules. The finite plasma lifetime limits the maximum extent of the guided electrical breakdown to a few meters. Here, we experimentally demonstrate that the limitation associated with the short plasma lifetime can be overcome though optical heating of the plasma filaments by an auxiliary energetic laser pulse with a duration in the nanosecond range. We show that the breakdown electric field can be reduced by up to a factor of 4 with a heater fluence of about 1 kJ/cm2. This approach could have applications in channeling long-range electrical discharges in the atmosphere and, potentially, in channeling lightning strikes.

The effect of plasma background on the instability of two non-parallel quantum plasma shells in whole K space

In this paper, quantum fluid equations together with Maxwell's equations are used to study the stability problem of non-parallel and non-relativistic plasma shells colliding over a “background plasma” at arbitrary angle, as a first step towards a microscopic understanding of the collision shocks. The calculations have been performed for all magnitude and directions of wave vectors. The colliding plasma shells in the vacuum region have been investigated in the previous works as a counter-streaming model. While, in the presence of background plasma (more realistic system), the colliding shells are mainly non-paralleled. The obtained results show that the presence of background plasma often suppresses the maximum growth rate of instabilities (in particular case, this behavior is contrary). It is also found that the largest maximum growth rate occurs for the two-stream instability of the configuration consisting of counter-streaming currents in a very dilute plasma background. The results derived in this study can be used to analyze the systems of three colliding plasma slabs, provided that the used coordinate system is stationary relative to the one of the particle slabs. The present analytical investigations can be applied to describe the quantum violent astrophysical phenomena such as white dwarf stars collision with other dense astrophysical bodies or supernova remnants. Moreover, at the limit of ℏ→0, the obtained results described the classical (sufficiently dilute) events of colliding plasma shells such as gamma-ray bursts and flares in the solar winds.

Temporal induction of immunoregulatory processes coincides with age-dependent resistance to viral-induced type 1 diabetes

The dilute plasma cytokine milieu associated with Type 1 diabetes (T1D), while difficult to measure directly, is sufficient to drive transcription in a bioassay that uses healthy leukocytes as reporters. Previously, we reported disease-associated, partially IL-1 dependent, transcriptional signatures in both T1D patients and the BioBreeding (BB) rat model. Here we examine temporal signatures in congenic BBDR.lyp/lyp rats that develop spontaneous T1D, and BBDR rats where T1D progresses only after immunological perturbation in young animals. After weaning, the BBDR temporal signature showed early coincident induction of transcription related to innate inflammation as well as IL-10- and TGF-β-mediated regulation. BBDR plasma cytokine levels mirrored the signatures showing early inflammation, followed by induction of a regulated state that correlated with failure of virus to induce T1D in older rats. In contrast, the BBDR.lyp/lyp temporal signature exhibited asynchronous dynamics, with delayed induction of inflammatory transcription and later, weaker induction of regulatory transcription, consistent with their deficiency in regulatory T cells. Through longitudinal analyses of plasma induced signatures in BB rats and a human T1D progressor, we have identified changes in immunoregulatory processes that attenuate a preexisting innate inflammatory state in BBDR rats, suggesting a mechanism underlying the decline in T1D susceptibility with age.

Abstract 73: Atrial Fibrillation-induced Changes in Left Atrial Hemodynamics Directly Impact the Thrombotic Potential of Human Primary Endothelial Cell Cultures

Thrombus formation in the left atrial appendage (LAA) of the heart is a source of stroke risk in patients with atrial fibrillation (Afib). Strategies to prevent thromboembolism from the LAA via restoration of normal rhythm or prevention of clot formation are limited by lack of adequate human surrogate systems that recapitulate the biology ex vivo. Endothelial cell phenotype and function in blood vessels and chambers of the heart are regulated in part by regional hemodynamics. Blood flow shear forces in the LAA are substantially altered during Afib. Thus, we hypothesized that Afib-induced alterations in hemodynamics directly impacts the thrombotic potential of the endothelium in the LAA. To test this, human primary aortic endothelial cell cultures were primed under hemodynamic shear forces simulating the human LAA during normal sinus rhythm for 24 hrs and continued under sinus rhythm or switched to simulate Afib for an additional 24 hrs. Compared to sustained sinus rhythm, Afib hemodynamics suppressed genes (qRTPCR) that define a healthy/quiescent endothelial cell phenotype (e.g. KLF2 and NOS3/eNOS) while inducing the pro-thrombotic gene F3 (tissue factor) and suppressing ADAMSTS13, MMP14 and TIMP2. To determine whether the observed molecular response produced a functional prothrombotic phenotype, hemodynamic primed aortic endothelial cells were exposed to dilute (~27% final concentration) human platelet-free plasma supplemented with Alexa488-labeled human fibrinogen, corn trypsin inhibitor and calcium. Cleavage of fibrinogen to fibrin and concomitant deposition on the endothelium was measured by quantitative confocal microscopy. When exposed to Afib hemodynamics, endothelial cells supported significant fibrin deposition that extended to greater depth (i.e., thicker) on the endothelium compared to sinus rhythm hemodynamics. In conclusion, we show for the first time a direct mechanistic link between changes in LAA hemodynamics associated with development of Afib and functional alterations in the thrombotic potential of the endothelium. This study produced a novel insight enabled by studying potential triggers of thrombosis in a context that more closely mimics the normal and pathological human in vivo environment.

Coulomb expansion: Analytical solutions

Exact and approximate analytical solutions are presented, describing expansion of a cloud of charged particles in one, two, and three dimensions (assuming the planar, axial, and spherical symmetries, respectively). The expansion occurs in a gas or dilute plasma, where the screening is unimportant, so that particles interact with each other via Coulomb repulsive forces. It is shown that, irrespective of dimensionality, the density distribution remains homogeneous across the cloud and the velocity increases linearly towards the cloud boundary. The density evolution obeys a universal dependence, asymptotically decreasing with time as t(-1). It is also shown that in the presence of an inhomogeneous external field the interparticle repulsion becomes negligible at an early stage of expansion and then the density decreases with time exponentially.

Imaging the evolution of an ultracold strontium Rydberg gas

Clouds of ultracold strontium $5s48s\phantom{\rule{4pt}{0ex}}{}^{1}{S}_{0}$ or $5s47d\phantom{\rule{4pt}{0ex}}{}^{1}{D}_{2}$ Rydberg atoms are created by two-photon excitation of laser-cooled $5{s}^{2}\phantom{\rule{4pt}{0ex}}{}^{1}{S}_{0}$ atoms. The spontaneous evolution of the cloud of low orbital angular momentum (low-$\ensuremath{\ell}$) Rydberg states towards an ultracold neutral plasma is observed by imaging resonant light scattered from core ions, a technique that provides both spatial and temporal resolution. Evolution is observed to be faster for the $S$ states, which display isotropic attractive interactions, than for the $D$ states, which exhibit anisotropic, principally repulsive interactions. Immersion of the atoms in a dilute ultracold neutral plasma speeds up the evolution and allows the number of Rydberg atoms initially created to be determined.

Negative Refraction in Chiral Plasma Media

Negative refraction is currently achieved by driving the magnetic permeability and electrical permittivity simultaneously negative. It is studied an alternative route to negative refraction without manipulating these parameters ( εand μ) on a chiral magnetized plasma. By adding chirality to the plasma, we obtain windows where the refraction is negative. The size of these windows depends on parameters such as: chirality degree, external magnetic field and the angle of incidence of the electromagnetic wave. The present study demonstrates that the condition for negative phase-velocity propagation can be satisfied by non dissipative Faraday chiral medium such as a very dilute magnetized space plasma.

Seeded optically driven avalanche ionization in molecular and noble gases

We report experimental and numerical results on the dual laser-pulse plasma excitation in molecular and noble gases at atmospheric pressure. Dilute plasma channels generated through filamentation of ultraintense femtosecond laser pulses in air, argon, and helium are densified through the application of multijoule nanosecond heater pulses. Plasma densification in molecular gases is always accompanied by the fragmentation of the plasma channels into discrete bubbles, while in atomic gases, under certain conditions, the densified channels remain smooth and continuous. The densification effect in atomic gases persists through considerably longer delays between the femtosecond and nanosecond pulses compared to that in molecular gases. Using rate equations we trace this difference in the temporal dynamics of densification to the different cooling mechanisms operative in atomic and molecular cases.

Extreme ultraviolet spectroscopy and modeling of Cu on the SSPX Spheromak and laser plasma “Sparky”

Impurities play a critical role in magnetic fusion research. In large quantities, impurities can cool and dilute plasma creating problems for achieving ignition and burn; however in smaller amounts the impurities could provide valuable information about several plasma parameters through the use of spectroscopy. Many impurity ions radiate within the extreme ultraviolet (EUV) range. Here, we report on spectra from the silver flat field spectrometer, which was implemented at the Sustained Spheromak Physics experiment (SSPX) to monitor ion impurity emissions. The chamber within the SSPX was made of Cu, which makes M-shell Cu a prominent impurity signature. The Spect3D spectral analysis code was utilized to identify spectral features in the range of 115-315 Å and to more fully understand the plasma conditions. A second set of experiments was carried out on the compact laser-plasma x-ray∕EUV facility "Sparky" at UNR, with Cu flat targets used. The EUV spectra were recorded between 40-300 Å and compared with results from SSPX.

Particle chains in a dilute dusty plasma with subsonic ion flow

Chains of charged dust particles are observed aligned with a subsonic ion flow. These chains are found in dilute regions, near the midplane of a parallel-plate radio-frequency plasma under microgravity conditions. The argon ion flow speed near these chains was estimated to be of order 10(2) m/s, corresponding to an ion acoustic Mach number M<0.1. The chains were observed to be stable in both the longitudinal and transverse directions. This stability suggests that there is a transverse restoring force. The transverse components of the ion-drag force or electrostatic wake-field forces could provide such a stabilizing effect. The chain appears to terminate with a final dust particle that is located in a dilute region; this observation suggests a possible attractive force in the longitudinal direction in the presence of a subsonic ion flow.

Ultralow Fouling Polyacrylamide on Gold Surfaces via Surface-Initiated Atom Transfer Radical Polymerization

In this work, polyacrylamide is investigated as an ultralow fouling surface coating to highly resist protein adsorption, cell adhesion, and bacterial attachment. Polyacrylamide was grafted on gold surfaces via surface-initiated atom transfer radical polymerization (ATRP). Protein adsorption from a wide range of biological media, including single protein solutions of fibrinogen, bovine serum albumin, and lysozyme, dilute and undiluted human blood serum, and dilute and undiluted human blood plasma, was studied by surface plasmon resonance (SPR). Dependence of the protein resistance on polyacrylamide film thickness was examined. With the optimal film thickness, the adsorption amount of all three single proteins on polyacrylamide-grafted surfaces was <3 pg/mm(2), close to the detection limit of SPR. The average nonspecific adsorptions from 10% plasma, 10% serum, 100% plasma, and 100% serum onto the polyacrylamide-grafted surfaces were 5, 6.5, 17, and 28 pg/mm(2), respectively, comparable (if not better) than the adsorption levels on poly(ethylene glycol) (PEG) and zwitterionic poly(sulfobetaine methacrylate) surfaces, the best antifouling materials known to date. The polyacrylamide-grafted surfaces were also shown strongly resistant to adhesion from bovine aortic endothelial cells and two bacterial species, Gram-positive Staphylococcus epidermidis ( S. epidermidis ) and Gram-negative Pseudomonas aeruginosa ( P. aeruginosa ). Strong hydrogen bond with water is considered the key attribute for the ultralow fouling properties of polyacrylamide. This is the first work to graft gold surfaces with polyacrylamide brushes via ATRP to achieve ultralow fouling surfaces, demonstrating that polyacrylamide is a promising alternative to traditional PEG-based antifouling materials.

Opacity and Transport Measurements Reveal That Dilute Plasma Models of Sonoluminescence Are Not Valid

A strong interaction between a nanosecond laser and a 70μm radius sonoluminescing plasma is achieved. The overall response of the system results in a factor of 2 increase in temperature as determined by its spectrum. Images of the interaction reveal that light energy is absorbed and trapped in a region smaller than the sonoluminescence emitting region of the bubble for over 100ns. We interpret this opacity and transport measurement as demonstrating that sonoluminescencing bubbles can be 1000 times more opaque than what follows from the Saha equation of statistical mechanics in the ideal plasma limit. To address this discrepancy, we suggest that the effects of strong Coulomb interactions are an essential component of a first principles theory of sonoluminescence.

Immune responses against domain I of β2-glycoprotein I are driven by conformational changes: Domain I of β2-glycoprotein I harbors a cryptic immunogenic epitope

The presence of autoantibodies against a cryptic epitope in domain I of β(2)-glycoprotein I (β(2)GPI) is strongly associated with thrombotic events in patients with the antiphospholipid syndrome. We hypothesized that a conformational change could be a trigger for the formation of antibodies against domain I of β(2)GPI. Therefore, we investigated whether immune responses against β(2)GPI are related to its conformation. Conformational changes in β(2)GPI were studied using various techniques, either upon binding to cardiolipin or after disruption of the internal disulfide bonds. The immunogenicity of β(2)GPI in different conformations as well as the individual domains of β(2)GPI were studied in vivo by monitoring the generation of antibodies after intravenous administration of β(2)GPI to mice. Furthermore, plasma samples from these mice were assessed for lupus anticoagulant activity and thrombin-antithrombin complex levels. We observed that the interaction of β(2)GPI with cardiolipin induced a conformational change in β(2)GPI: electron microscopy revealed that β(2)GPI assembled into polymeric meshworks. We next investigated the immunogenicity of both human and murine β(2)GPI in mice. Both human and murine β(2)GPI combined with cardiolipin and misfolded β(2)GPI triggered antibody formation against the native protein as well as against domain I of β(2)GPI, while native β(2)GPI was not immunogenic. In addition, we observed that anti-domain I antibodies developed in mice injected with domain I of β(2)GPI, and that antibodies did not develop in mice injected with domains II-V. The induced anti-domain I antibodies prolonged the dilute Russell's viper venom plasma clotting time. The plasma of mice with anti-domain I antibodies had increased levels of circulating thrombin-antithrombin complexes. The results of our studies indicate that the exposure of cryptic epitopes due to conformational changes in β(2)GPI can induce autoantibody formation.

Optical breakdown of air triggered by femtosecond laser filaments

We report experiments on the generation of dense plasma channels in ambient air using a dual laser pulse excitation scheme. The dilute plasma produced through the filamentation of an ultraintense femtosecond laser pulse is densified via avalanche ionization driven by a co-propagating multi-Joule nanosecond pulse.

Global solutions to the relativistic Landau–Maxwell system in the whole space

The relativistic Landau–Maxwell system is one of the most fundamental models for description of the dynamics of dilute cold plasma in which particles interact through the Coulomb collision in the self-consistent electro-magnetic field. By constructing the compensating functions to this system and by using the structure of the equations, we obtain the global existence of classical solutions to this system in the whole space. For a simpler model, that is, the relativistic Landau–Poisson system, the analysis yields the optimal convergence rate in time to the equilibrium.

Factors influencing the activity of thrombin preparations.

Summary The nature of the relationship between thrombin concentration and clotting time is discussed. The rectilinear log:log relationship holds good generally. The effect of temperature on the rate of reaction in dilute plasma is found to be in agreement with the Arrhenius equation and a value for the “activation energy” is calculated. The temperature optimum for thrombin in plasma appears to be between 40° and 45° C. The general retarding effect of salts is noted, and the specific effect of calcium, barium, manganous and nickelous salts is noted and discussed. 5 The activity of thrombin in plasma may show complex dependence on the species of origin. 6 Glycerol retards coagulation, and arabinic acid accelerates it. There is a very marked interaction between the latter and calcium salts.

Two component relativistic acceleration and polarized radiation of the parsec-scale AGN jet

AbstractWe perform axisymmetric simulations of two-component jet acceleration using the special relativistic MHD code PLUTO (Mignone et al., 2007). The inner, thermally driven component constitutes a dilute relativistic plasma originating in a high enthalpy central corona. The second component is a Poynting-dominated wind driven by a global current system. Once a near-stationary state is reached, we solve the polarized Synchrotron radiation transport incorporating self-absorption and (internal) Faraday rotation. With this approach we obtain high-resolution radio maps and spectra that can help in the interpretation of observational data from nearby active galactic nuclei by predicting spine-sheath polarization structures and Faraday rotation gradients.